The lymphatic vasculature revisited

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Abstract

Lymphatic vessels constitute a ubiquitous countercurrent system to the blood vasculature that returns interstitial fluid, salts, small molecules, resorbed fat, and cells to the bloodstream. They serve as conduits to lymph nodes and are essential for multiple physiologic activities. However, they are also hijacked by cancer cells to establish initial lymph node metastases, as well as by infectious agents and parasites. Despite these obvious important functions in human pathologies, a more detailed understanding of the molecular mechanisms involved in the regulation of the lymphatic vasculature has trailed that of the blood vasculature for many years, mainly because critical specific characteristics of lymphatic endothelial cells were discovered only recently. In this Review series, several major aspects of the active and passive involvement of the lymphatic vasculature in human disease and physiology are presented, with a focus on translational findings.

Authors

Dontscho Kerjaschki

Lymphangiogenic factors, mechanisms, and applications

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Abstract

Lymphangiogenesis, the growth of lymphatic vessels, is essential in embryonic development. In adults, it is involved in many pathological processes such as lymphedema, inflammatory diseases, and tumor metastasis. Advances during the past decade have dramatically increased the knowledge of the mechanisms of lymphangiogenesis, including the roles of transcription factors, lymphangiogenic growth factors and their receptors, and intercellular and intracellular signaling cascades. Strategies based on these mechanisms are being tested in the treatment of various human diseases such as cancer, lymphedema, and tissue allograft rejection. This Review summarizes the recent progress on lymphangiogenic mechanisms and their applications in disease treatment.

Authors

Wei Zheng, Aleksanteri Aspelund, Kari Alitalo

Development of the mammalian lymphatic vasculature

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Abstract

The two vascular systems of our body are the blood and lymphatic vasculature. Our understanding of the cellular and molecular processes controlling the development of the lymphatic vasculature has progressed significantly in the last decade. In mammals, this is a stepwise process that starts in the embryonic veins, where lymphatic EC (LEC) progenitors are initially specified. The differentiation and maturation of these progenitors continues as they bud from the veins to produce scattered primitive lymph sacs, from which most of the lymphatic vasculature is derived. Here, we summarize our current understanding of the key steps leading to the formation of a functional lymphatic vasculature.

Authors

Ying Yang, Guillermo Oliver

Genetics of lymphatic anomalies

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Abstract

Lymphatic anomalies include a variety of developmental and/or functional defects affecting the lymphatic vessels: sporadic and familial forms of primary lymphedema, secondary lymphedema, chylothorax and chylous ascites, lymphatic malformations, and overgrowth syndromes with a lymphatic component. Germline mutations have been identified in at least 20 genes that encode proteins acting around VEGFR-3 signaling but also downstream of other tyrosine kinase receptors. These mutations exert their effects via the RAS/MAPK and the PI3K/AKT pathways and explain more than a quarter of the incidence of primary lymphedema, mostly of inherited forms. More common forms may also result from multigenic effects or post-zygotic mutations. Most of the corresponding murine knockouts are homozygous lethal, while heterozygotes are healthy, which suggests differences in human and murine physiology and the influence of other factors.

Authors

Pascal Brouillard, Laurence Boon, Miikka Vikkula

Emerging lymphatic imaging technologies for mouse and man

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Abstract

The lymphatic circulatory system has diverse functions in lipid absorption, fluid homeostasis, and immune surveillance and responds dynamically when presented with infection, inflammation, altered hemodynamics, and cancer. Visualization of these dynamic processes in human disease and animal models of disease is key to understanding the contributory role of the lymphatic circulatory system in disease and to devising effective therapeutic strategies. Longitudinal, non-destructive, and repeated imaging is necessary to expand our understanding of disease progression and regression in basic science and clinical investigations. Herein we summarize recent advances in in vivo lymphatic imaging employing magnetic resonance, computed tomography, lymphoscintigraphy, and emerging optical techniques with respect to their contributory roles in both basic science and clinical research investigations.

Authors

Eva M. Sevick-Muraca, Sunkuk Kwon, John C. Rasmussen

New developments in clinical aspects of lymphatic disease

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Abstract

The lymphatic system is fundamentally important to cardiovascular disease, infection and immunity, cancer, and probably obesity — the four major challenges in healthcare in the 21st century. This Review will consider the manner in which new knowledge of lymphatic genes and molecular mechanisms has demonstrated that lymphatic dysfunction should no longer be considered a passive bystander in disease but rather an active player in many pathological processes and, therefore, a genuine target for future therapeutic developments. The specific roles of the lymphatic system in edema, genetic aspects of primary lymphedema, infection (cellulitis/erysipelas), Crohn’s disease, obesity, cancer, and cancer-related lymphedema are highlighted.

Authors

Peter S. Mortimer, Stanley G. Rockson

Mechanisms of lymphatic metastasis

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Abstract

Malignant tumors release growth factors such as VEGF-C to induce lymphatic vessel expansion (lymphangiogenesis) in primary tumors and in draining sentinel LNs, thereby promoting LN metastasis. Surprising recent evidence suggests that lymphatic vessels do not merely represent passive channels for tumor spread, but that they may actively promote tumor cell recruitment to LNs, cancer stem cell survival, and immune modulation. New imaging approaches allow the sensitive visualization of the earliest LN metastases and the quantitative, noninvasive measurement of the function of tumor-draining lymphatic vessels, with potential applications in the development of biomarkers for prognosis and measurement of therapeutic response.

Authors

Sinem Karaman, Michael Detmar

Lymphatic transport of high-density lipoproteins and chylomicrons

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Abstract

The life cycles of VLDLs and most LDLs occur within plasma. By contrast, the role of HDLs in cholesterol transport from cells requires that they readily gain access to and function within interstitial fluid. Studies of lymph derived from skin, connective tissue, and adipose tissue have demonstrated that particles as large as HDLs require transport through lymphatics to return to the bloodstream during reverse cholesterol transport. Targeting HDL for therapeutic purposes will require understanding its biology in the extravascular compartment, within the interstitium and lymph, in health and disease, and we herein review the processes that mediate the transport of HDLs and chylomicrons through the lymphatic vasculature.

Authors

Gwendalyn J. Randolph, Norman E. Miller

Inflammation-associated lymphangiogenesis: a double-edged sword?

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Abstract

Lymphangiogenesis and lymphatic vessel remodeling are complex biological processes frequently observed during inflammation. Accumulating evidence indicates that inflammation-associated lymphangiogenesis (IAL) is not merely an endpoint event, but actually a phenomenon actively involved in the pathophysiology of various inflammatory disorders. The VEGF-C/VEGFR-3 and VEGF-A/VEGF-R2 signaling pathways are two of the best-studied pathways in IAL. Methods targeting these molecules, such as prolymphangiogenic or antilymphatic treatments, were found to be beneficial in various preclinical and/or clinical studies. This Review focuses on the most recent achievements in the fields of lymphatic biology relevant to inflammatory conditions. Additionally, preclinical and clinical therapies that modulate IAL are summarized.

Authors

Honsoul Kim, Raghu P. Kataru, Gou Young Koh

Emerging roles of lymphatic endothelium in regulating adaptive immunity

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Abstract

Emerging research on the roles of stromal cells in modulating adaptive immune responses has included a new focus on lymphatic endothelial cells (LECs). LECs are presumably the first cells that come into direct contact with peripheral antigens, cytokines, danger signals, and immune cells travelling from peripheral tissues to lymph nodes. LECs can modulate dendritic cell function, present antigens to T cells on MHC class I and MHC class II molecules, and express immunomodulatory cytokines and receptors, which suggests that their roles in adaptive immunity are far more extensive than previously realized. This Review summarizes the emergent evidence that LECs are important in maintaining peripheral tolerance, limiting and resolving effector T cell responses, and modulating leukocyte function.

Authors

Catherine M. Card, Shann S. Yu, Melody A. Swartz

Lymphatic vessels and tertiary lymphoid organs

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Abstract

Tertiary lymphoid organs (TLOs) are accumulations of lymphoid cells in chronic inflammation that resemble LNs in their cellular content and organization, high endothelial venules, and lymphatic vessels (LVs). Although acute inflammation can result in defective LVs, TLO LVs appear to function normally in that they drain fluid and transport cells that respond to chemokines and sphingosine-1-phosphate (S1P) gradients. Molecular regulation of TLO LVs differs from lymphangiogenesis in ontogeny with a dependence on cytokines and hematopoietic cells. Ongoing work to elucidate the function and molecular regulation of LVs in TLOs is providing insight into therapies for conditions as diverse as lymphedema, autoimmunity, and cancer.

Authors

Nancy H. Ruddle

NRF2 mitigates radiation-induced hematopoietic death

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Abstract

Fractionated, high-dose total body irradiation (TBI) is used therapeutically to myeloablate and immune suppress patients undergoing hematopoietic stem cell (HSC) transplantation. Acute exposure to ionizing radiation can have fatal effects on the hematopoietic and immune systems. Currently, therapies aimed at ameliorating ionizing radiation–associated toxicities are limited. In the February 2014 issue of the JCI, Kim and colleagues demonstrated that induction of nuclear factor erythroid 2–related factor 2 (NRF2) enhances HSC regeneration and increases survival following ionizing radiation exposure in mice. The results of this study suggest that NRF2 is a novel potential target for the development of therapeutics aimed at mitigating the toxicities of ionizing radiation exposure.

Authors

John P. Chute

Fanning the flames to regenerate the heart

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Abstract

Damage to the adult mammalian heart is irreversible, and lost cells are not replaced through regeneration. In neonatal mice, prior to P7, heart tissue can be regenerated after injury; however, the factors that facilitate cardiac regeneration in the neonatal heart are not known. In this issue of the JCI, Aurora and colleagues evaluated the immune response following myocardial infarction in P1 mice compared with that in P14 mice, which have lost their regenerative capacity, and identified a population of macrophages as mediators of cardiac repair. Further understanding of the immune modulators that promote the regenerative properties of this macrophage subset could potentially be exploited to recapitulate regenerative function in the adult heart.

Authors

Paul R. Riley

Translational enhancers of EAAT2: therapeutic implications for neurodegenerative disease

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Abstract

Glutamate excitotoxicity contributes to the neuronal injury and death associated with many neurodegenerative diseases. The glutamate transporter EAAT2, which is primarily localized on astrocytic processes, facilitates glutamate clearance from synapses, thus preventing neuronal damage. In this issue of the JCI, Kong et al. characterize a compound that upregulates EAAT2 translation, thereby increasing glutamate uptake by glial cells. Furthermore, this strategy for alleviating excitotoxicity was found to be beneficial in mouse models of both amyotrophic lateral sclerosis (ALS) and epilepsy, suggesting that future development in this chemical series may lead to much-needed treatments for these disorders.

Authors

Allison S. Limpert, Nicholas D.P. Cosford

Working toward immune tolerance in lung transplantation

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Abstract

Long-term allograft survival is a major challenge facing solid organ transplantation. Recent studies have shown a negative correlation between infiltration of memory T cells and allograft survival. Furthermore, blockade of leukocyte activation increases acceptance of transplanted organs, including heart, liver, and kidney. Lung allografts are associated with high rates of rejection, and therapies that increase acceptance of other transplanted organs have not translated into the lung. In this issue of the JCI, Krupnick and colleagues demonstrate in a murine model that lung allograft acceptance requires infiltration of a specific T cell population into the graft. This study highlights the unique immunobiology of the lung and the complexity of lung transplant tolerance.

Authors

Xinguo Jiang, Mark R. Nicolls

Neurogenesis or non-neurogenesis: that is the question

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Abstract

Neural stem/precursor cells (NPCs) that reside within germinal niches of the adult CNS have more complex roles than previously expected. In addition to their well-documented neurogenic functions, emerging evidence indicates that NPCs exert non-neurogenic functions that contribute to the regulation and preservation of tissue homeostasis under both physiological and pathological conditions. In this issue of the JCI, Mohammad et al. found that DCs efficiently patrol the CNS only when the germinal niche of the subventricular zone functions properly. Indeed, DCs traveled from the ventricles along the rostral migratory stream to the olfactory bulb (a cervical lymph node access point) to dampen anti-CNS immune responses. The authors’ findings further support a non-neurogenic role for NPCs in maintaining tissue homeostasis and promoting tissue protection in the adult brain.

Authors

Gianvito Martino, Erica Butti, Marco Bacigaluppi

Dangerous liaisons: flirtations between oncogenic BRAF and GRP78 in drug-resistant melanomas

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Abstract

BRAF mutations in aggressive melanomas result in kinase activation. BRAF inhibitors reduce BRAF^V600E tumors, but rapid resistance follows. In this issue of the JCI, Ma and colleagues report that vemurafenib activates ER stress and autophagy in BRAF^V600E melanoma cells, through sequestration of the ER chaperone GRP78 by the mutant BRAF and subsequent PERK activation. In preclinical studies, treating vemurafenib-resistant melanoma with a combination of vemurafenib and an autophagy inhibitor reduced tumor load. Further work is needed to establish clinical relevance of this resistance mechanism and demonstrate efficacy of autophagy and kinase inhibitor combinations in melanoma treatment.

Authors

Shirish Shenolikar

Dynamin 2 the rescue for centronuclear myopathy

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Abstract

Centronuclear myopathy is a lethal muscle disease. The most severe form of the disease, X-linked centronuclear myopathy, is due to mutations in the gene encoding myotubularin (MTM1), while mutations in dynamin 2 (DNM2) and amphiphysin 2/BIN1 (AMPH2) cause milder forms of myopathy. MTM1 is a lipid phosphatase, and mutations that disrupt this activity cause severe muscle wasting. In this issue of the JCI, Cowling and colleagues report on their finding of increased DNM2 levels in human and mouse muscle with MTM1 mutations. Partial reduction of Dnm2 in mice harboring Mtm1 mutations remarkably rescued muscle wasting and lethality, and this effect was muscle specific. DNM2 regulates membrane trafficking through vesicular scission, and it is presumed that reducing this activity accounts for improved outcome in X-linked centronuclear myopathy.

Authors

Alexis R. Demonbreun, Elizabeth M. McNally

PPARγ in emphysema: blunts the damage and triggers repair?

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Abstract

Cigarette smoke is the most common cause of pulmonary emphysema, which results in an irreversible loss of lung structure and function. Th1 and Th17 immune responses have been implicated in emphysema pathogenesis; however, the drivers of emphysema-associated immune dysfunction are not fully understood. In this issue of the JCI, Shan and colleagues found that peroxisome proliferator–activated receptor γ (PPARγ) is downregulated in APCs isolated from the lungs of emphysematous chronic smokers and mice exposed to cigarette smoke. Furthermore, treatment with a PPARγ agonist prevented emphysema development and appeared to reduce emphysema-associated lung volume expansion in mice exposed to cigarette smoke. Further work will need to be done to evaluate the potential of PPARγ agonists to restore lung capacity in emphysematous patients.

Authors

Neil J. Kelly, Steven D. Shapiro

TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction

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Abstract

The olfactory bulb (OB) receives odor information from the olfactory epithelium and relays this to the olfactory cortex. Using a mouse model, we found that development and maturation of OB interneurons depends on the zinc finger homeodomain factor teashirt zinc finger family member 1 (TSHZ1). In mice lacking TSHZ1, neuroblasts exhibited a normal tangential migration to the OB; however, upon arrival to the OB, the neuroblasts were distributed aberrantly within the radial dimension, and many immature neuroblasts failed to exit the rostral migratory stream. Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits. We therefore investigated olfaction in human subjects from families with congenital aural atresia that were heterozygous for TSHZ1 loss-of-function mutations. These individuals displayed hyposmia, which is characterized by impaired odor discrimination and reduced olfactory sensitivity. Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein–coupled receptor essential for OB development. Mutations in PROKR2 lead to Kallmann syndrome, characterized by anosmia and hypogonadotrophic hypogonadism. Our data indicate that TSHZ1 is a key regulator of mammalian OB development and function and controls the expression of molecules involved in human Kallmann syndrome.

Authors

Daniela Ragancokova, Elena Rocca, Anne M.M. Oonk, Herbert Schulz, Elvira Rohde, Jan Bednarsch, Ilse Feenstra, Ronald J.E. Pennings, Hagen Wende, Alistair N. Garratt

ALS-associated mutation FUS-R521C causes DNA damage and RNA splicing defects

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Abstract

Autosomal dominant mutations of the RNA/DNA binding protein FUS are linked to familial amyotrophic lateral sclerosis (FALS); however, it is not clear how FUS mutations cause neurodegeneration. Using transgenic mice expressing a common FALS-associated FUS mutation (FUS-R521C mice), we found that mutant FUS proteins formed a stable complex with WT FUS proteins and interfered with the normal interactions between FUS and histone deacetylase 1 (HDAC1). Consequently, FUS-R521C mice exhibited evidence of DNA damage as well as profound dendritic and synaptic phenotypes in brain and spinal cord. To provide insights into these defects, we screened neural genes for nucleotide oxidation and identified brain-derived neurotrophic factor (Bdnf) as a target of FUS-R521C–associated DNA damage and RNA splicing defects in mice. Compared with WT FUS, mutant FUS-R521C proteins formed a more stable complex with Bdnf RNA in electrophoretic mobility shift assays. Stabilization of the FUS/Bdnf RNA complex contributed to Bdnf splicing defects and impaired BDNF signaling through receptor TrkB. Exogenous BDNF only partially restored dendrite phenotype in FUS-R521C neurons, suggesting that BDNF-independent mechanisms may contribute to the defects in these neurons. Indeed, RNA-seq analyses of FUS-R521C spinal cords revealed additional transcription and splicing defects in genes that regulate dendritic growth and synaptic functions. Together, our results provide insight into how gain-of-function FUS mutations affect critical neuronal functions.

Authors

Haiyan Qiu, Sebum Lee, Yulei Shang, Wen-Yuan Wang, Kin Fai Au, Sherry Kamiya, Sami J. Barmada, Steven Finkbeiner, Hansen Lui, Caitlin E. Carlton, Amy A. Tang, Michael C. Oldham, Hejia Wang, James Shorter, Anthony J. Filiano, Erik D. Roberson, Warren G. Tourtellotte, Bin Chen, Li-Huei Tsai, Eric J. Huang

Angiotensin-converting enzyme overexpression in myelomonocytes prevents Alzheimer’s-like cognitive decline

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Abstract

Cognitive decline in patients with Alzheimer’s disease (AD) is associated with elevated brain levels of amyloid β protein (Aβ), particularly neurotoxic Aβ_1–42. Angiotensin-converting enzyme (ACE) can degrade Aβ_1–42, and ACE overexpression in myelomonocytic cells enhances their immune function. To examine the effect of targeted ACE overexpression on AD, we crossed ACE^10/10 mice, which overexpress ACE in myelomonocytes using the c-fms promoter, with the transgenic APP_SWE/PS1_ΔE9 mouse model of AD (AD⁺). Evaluation of brain tissue from these AD⁺ACE^10/10 mice at 7 and 13 months revealed that levels of both soluble and insoluble brain Aβ_1–42 were reduced compared with those in AD⁺ mice. Furthermore, both plaque burden and astrogliosis were drastically reduced. Administration of the ACE inhibitor ramipril increased Aβ levels in AD⁺ACE^10/10 mice compared with the levels induced by the ACE-independent vasodilator hydralazine. Overall, AD⁺ACE^10/10 mice had less brain-infiltrating cells, consistent with reduced AD-associated pathology, though ACE-overexpressing macrophages were abundant around and engulfing Aβ plaques. At 11 and 12 months of age, the AD⁺ACE^10/WT and AD⁺ACE^10/10 mice were virtually equivalent to non-AD mice in cognitive ability, as assessed by maze-based behavioral tests. Our data demonstrate that an enhanced immune response, coupled with increased myelomonocytic expression of catalytically active ACE, prevents cognitive decline in a murine model of AD.

Authors

Kenneth E. Bernstein, Yosef Koronyo, Brenda C. Salumbides, Julia Sheyn, Lindsey Pelissier, Dahabada H.J. Lopes, Kandarp H. Shah, Ellen A. Bernstein, Dieu-Trang Fuchs, Jeff J.-Y. Yu, Michael Pham, Keith L. Black, Xiao Z. Shen, Sebastien Fuchs, Maya Koronyo-Hamaoui

IL-15 regulates memory CD8⁺ T cell O-glycan synthesis and affects trafficking

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Abstract

Memory and naive CD8⁺ T cells exhibit distinct trafficking patterns. Specifically, memory but not naive CD8⁺ T cells are recruited to inflamed tissues in an antigen-independent manner. However, the molecular mechanisms that regulate memory CD8⁺ T cell trafficking are largely unknown. Here, using murine models of infection and T cell transfer, we found that memory but not naive CD8⁺ T cells dynamically regulate expression of core 2 O-glycans, which interact with P- and E-selectins to modulate trafficking to inflamed tissues. Following infection, antigen-specific effector CD8⁺ T cells strongly expressed core 2 O-glycans, but this glycosylation pattern was lost by most memory CD8⁺ T cells. After unrelated infection or inflammatory challenge, memory CD8⁺ T cells synthesized core 2 O-glycans independently of antigen restimulation. The presence of core 2 O-glycans subsequently directed these cells to inflamed tissue. Memory and naive CD8⁺ T cells exhibited the opposite pattern of epigenetic modifications at the Gcnt1 locus, which encodes the enzyme that initiates core 2 O-glycan synthesis. The open chromatin configuration in memory CD8⁺ T cells permitted de novo generation of core 2 O-glycans in a TCR-independent, but IL-15–dependent, manner. Thus, IL-15 stimulation promotes antigen-experienced memory CD8⁺ T cells to generate core 2 O-glycans, which subsequently localize them to inflamed tissues. These findings suggest that CD8⁺ memory T cell trafficking potentially can be manipulated to improve host defense and immunotherapy.

Authors

Jeffrey C. Nolz, John T. Harty

Memory regulatory T cells reside in human skin

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Abstract

Regulatory T cells (Tregs), which are characterized by expression of the transcription factor Foxp3, are a dynamic and heterogeneous population of cells that control immune responses and prevent autoimmunity. We recently identified a subset of Tregs in murine skin with properties typical of memory cells and defined this population as memory Tregs (mTregs). Due to the importance of these cells in regulating tissue inflammation in mice, we analyzed this cell population in humans and found that almost all Tregs in normal skin had an activated memory phenotype. Compared with mTregs in peripheral blood, cutaneous mTregs had unique cell surface marker expression and cytokine production. In normal human skin, mTregs preferentially localized to hair follicles and were more abundant in skin with high hair density. Sequence comparison of TCRs from conventional memory T helper cells and mTregs isolated from skin revealed little homology between the two cell populations, suggesting that they recognize different antigens. Under steady-state conditions, mTregs were nonmigratory and relatively unresponsive; however, in inflamed skin from psoriasis patients, mTregs expanded, were highly proliferative, and produced low levels of IL-17. Taken together, these results identify a subset of Tregs that stably resides in human skin and suggest that these cells are qualitatively defective in inflammatory skin disease.

Authors

Robert Sanchez Rodriguez, Mariela L. Pauli, Isaac M. Neuhaus, Siegrid S. Yu, Sarah T. Arron, Hobart W. Harris, Sara Hsin-Yi Yang, Bryan A. Anthony, Francis M. Sverdrup, Elisabeth Krow-Lucal, Tippi C. MacKenzie, David S. Johnson, Everett H. Meyer, Andrea Löhr, Andro Hsu, John Koo, Wilson Liao, Rishu Gupta, Maya G. Debbaneh, Daniel Butler, Monica Huynh, Ethan C. Levin, Argentina Leon, William Y. Hoffman, Mary H. McGrath, Michael D. Alvarado, Connor H. Ludwig, Hong-An Truong, Megan M. Maurano, Iris K. Gratz, Abul K. Abbas, Michael D. Rosenblum

Metformin interferes with bile acid homeostasis through AMPK-FXR crosstalk

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Abstract

The nuclear bile acid receptor farnesoid X receptor (FXR) is an important transcriptional regulator of bile acid, lipid, and glucose metabolism. FXR is highly expressed in the liver and intestine and controls the synthesis and enterohepatic circulation of bile acids. However, little is known about FXR-associated proteins that contribute to metabolic regulation. Here, we performed a mass spectrometry–based search for FXR-interacting proteins in human hepatoma cells and identified AMPK as a coregulator of FXR. FXR interacted with the nutrient-sensitive kinase AMPK in the cytoplasm of target cells and was phosphorylated in its hinge domain. In cultured human and murine hepatocytes and enterocytes, pharmacological activation of AMPK inhibited FXR transcriptional activity and prevented FXR coactivator recruitment to promoters of FXR-regulated genes. Furthermore, treatment with AMPK activators, including the antidiabetic biguanide metformin, inhibited FXR agonist induction of FXR target genes in mouse liver and intestine. In a mouse model of intrahepatic cholestasis, metformin treatment induced FXR phosphorylation, perturbed bile acid homeostasis, and worsened liver injury. Together, our data indicate that AMPK directly phosphorylates and regulates FXR transcriptional activity to precipitate liver injury under conditions favoring cholestasis.

Authors

Fleur Lien, Alexandre Berthier, Emmanuel Bouchaert, Céline Gheeraert, Jeremy Alexandre, Geoffrey Porez, Janne Prawitt, Hélène Dehondt, Maheul Ploton, Sophie Colin, Anthony Lucas, Alexandre Patrice, François Pattou, Hélène Diemer, Alain Van Dorsselaer, Christophe Rachez, Jelena Kamilic, Albert K. Groen, Bart Staels, Philippe Lefebvre

B cells mediate chronic allograft rejection independently of antibody production

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Abstract

Chronic rejection is the primary cause of long-term failure of transplanted organs and is often viewed as an antibody-dependent process. Chronic rejection, however, is also observed in mice and humans with no detectable circulating alloantibodies, suggesting that antibody-independent pathways may also contribute to pathogenesis of transplant rejection. Here, we have provided direct evidence that chronic rejection of vascularized heart allografts occurs in the complete absence of antibodies, but requires the presence of B cells. Mice that were deficient for antibodies but not B cells experienced the same chronic allograft vasculopathy (CAV), which is a pathognomonic feature of chronic rejection, as WT mice; however, mice that were deficient for both B cells and antibodies were protected from CAV. B cells contributed to CAV by supporting splenic lymphoid architecture, T cell cytokine production, and infiltration of T cells into graft vessels. In chimeric mice, in which B cells were present but could not present antigen, both T cell responses and CAV were markedly reduced. These findings establish that chronic rejection can occur in the complete absence of antibodies and that B cells contribute to this process by supporting T cell responses through antigen presentation and maintenance of lymphoid architecture.

Authors

Qiang Zeng, Yue-Harn Ng, Tripti Singh, Ke Jiang, Khaleefathullah A. Sheriff, Renee Ippolito, Salwa Zahalka, Qi Li, Parmjeet Randhawa, Rosemary A. Hoffman, Balathiripurasundari Ramaswami, Frances E. Lund, Geetha Chalasani

Lipotoxic disruption of NHE1 interaction with PI(4,5)P2 expedites proximal tubule apoptosis

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Abstract

Chronic kidney disease progression can be predicted based on the degree of tubular atrophy, which is the result of proximal tubule apoptosis. The Na⁺/H⁺ exchanger NHE1 regulates proximal tubule cell survival through interaction with phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], but pathophysiologic triggers for NHE1 inactivation are unknown. Because glomerular injury permits proximal tubule luminal exposure and reabsorption of fatty acid/albumin complexes, we hypothesized that accumulation of amphipathic, long-chain acyl-CoA (LC-CoA) metabolites stimulates lipoapoptosis by competing with the structurally similar PI(4,5)P2 for NHE1 binding. Kidneys from mouse models of progressive, albuminuric kidney disease exhibited increased fatty acids, LC-CoAs, and caspase-2–dependent proximal tubule lipoapoptosis. LC-CoAs and the cytosolic domain of NHE1 directly interacted, with an affinity comparable to that of the PI(4,5)P2-NHE1 interaction, and competing LC-CoAs disrupted binding of the NHE1 cytosolic tail to PI(4,5)P2. Inhibition of LC-CoA catabolism reduced NHE1 activity and enhanced apoptosis, whereas inhibition of proximal tubule LC-CoA generation preserved NHE1 activity and protected against apoptosis. Our data indicate that albuminuria/lipiduria enhances lipotoxin delivery to the proximal tubule and accumulation of LC-CoAs contributes to tubular atrophy by severing the NHE1-PI(4,5)P2 interaction, thereby lowering the apoptotic threshold. Furthermore, these data suggest that NHE1 functions as a metabolic sensor for lipotoxicity.

Authors

Shenaz Khan, Bassam G. Abu Jawdeh, Monu Goel, William P. Schilling, Mark D. Parker, Michelle A. Puchowicz, Satya P. Yadav, Raymond C. Harris, Ashraf El-Meanawy, Malcolm Hoshi, Krekwit Shinlapawittayatorn, Isabelle Deschênes, Eckhard Ficker, Jeffrey R. Schelling

Mutant p53–associated myosin-X upregulation promotes breast cancer invasion and metastasis

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Abstract

Mutations of the tumor suppressor TP53 are present in many forms of human cancer and are associated with increased tumor cell invasion and metastasis. Several mechanisms have been identified for promoting dissemination of cancer cells with TP53 mutations, including increased targeting of integrins to the plasma membrane. Here, we demonstrate a role for the filopodia-inducing motor protein Myosin-X (Myo10) in mutant p53–driven cancer invasion. Analysis of gene expression profiles from 2 breast cancer data sets revealed that MYO10 was highly expressed in aggressive cancer subtypes. Myo10 was required for breast cancer cell invasion and dissemination in multiple cancer cell lines and murine models of cancer metastasis. Evaluation of a Myo10 mutant without the integrin-binding domain revealed that the ability of Myo10 to transport β₁ integrins to the filopodia tip is required for invasion. Introduction of mutant p53 promoted Myo10 expression in cancer cells and pancreatic ductal adenocarcinoma in mice, whereas suppression of endogenous mutant p53 attenuated Myo10 levels and cell invasion. In clinical breast carcinomas, Myo10 was predominantly expressed at the invasive edges and correlated with the presence of TP53 mutations and poor prognosis. These data indicate that Myo10 upregulation in mutant p53–driven cancers is necessary for invasion and that plasma-membrane protrusions, such as filopodia, may serve as specialized metastatic engines.

Authors

Antti Arjonen, Riina Kaukonen, Elina Mattila, Pegah Rouhi, Gunilla Högnäs, Harri Sihto, Bryan W. Miller, Jennifer P. Morton, Elmar Bucher, Pekka Taimen, Reetta Virtakoivu, Yihai Cao, Owen J. Sansom, Heikki Joensuu, Johanna Ivaska

Cyclin-dependent kinase inhibitor 2B regulates efferocytosis and atherosclerosis

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Abstract

Genetic variation at the chromosome 9p21 risk locus promotes cardiovascular disease; however, it is unclear how or which proteins encoded at this locus contribute to disease. We have previously demonstrated that loss of one candidate gene at this locus, cyclin-dependent kinase inhibitor 2B (Cdkn2b), in mice promotes vascular SMC apoptosis and aneurysm progression. Here, we investigated the role of Cdnk2b in atherogenesis and found that in a mouse model of atherosclerosis, deletion of Cdnk2b promoted advanced development of atherosclerotic plaques composed of large necrotic cores. Furthermore, human carriers of the 9p21 risk allele had reduced expression of CDKN2B in atherosclerotic plaques, which was associated with impaired expression of calreticulin, a ligand required for activation of engulfment receptors on phagocytic cells. As a result of decreased calreticulin, CDKN2B-deficient apoptotic bodies were resistant to efferocytosis and not efficiently cleared by neighboring macrophages. These uncleared SMCs elicited a series of proatherogenic juxtacrine responses associated with increased foam cell formation and inflammatory cytokine elaboration. The addition of exogenous calreticulin reversed defects associated with loss of Cdkn2b and normalized engulfment of Cdkn2b-deficient cells. Together, these data suggest that loss of CDKN2B promotes atherosclerosis by increasing the size and complexity of the lipid-laden necrotic core through impaired efferocytosis.

Authors

Yoko Kojima, Kelly Downing, Ramendra Kundu, Clint Miller, Frederick Dewey, Hope Lancero, Uwe Raaz, Ljubica Perisic, Ulf Hedin, Eric Schadt, Lars Maegdefessel, Tom Quertermous, Nicholas J. Leeper

Podocyte-associated talin1 is critical for glomerular filtration barrier maintenance

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Abstract

Podocytes are specialized actin-rich epithelial cells that line the kidney glomerular filtration barrier. The interface between the podocyte and the glomerular basement membrane requires integrins, and defects in either α₃ or β₁ integrin, or the α₃β₁ ligand laminin result in nephrotic syndrome in murine models. The large cytoskeletal protein talin1 is not only pivotal for integrin activation, but also directly links integrins to the actin cytoskeleton. Here, we found that mice lacking talin1 specifically in podocytes display severe proteinuria, foot process effacement, and kidney failure. Loss of talin1 in podocytes caused only a modest reduction in β₁ integrin activation, podocyte cell adhesion, and cell spreading; however, the actin cytoskeleton of podocytes was profoundly altered by the loss of talin1. Evaluation of murine models of glomerular injury and patients with nephrotic syndrome revealed that calpain-induced talin1 cleavage in podocytes might promote pathogenesis of nephrotic syndrome. Furthermore, pharmacologic inhibition of calpain activity following glomerular injury substantially reduced talin1 cleavage, albuminuria, and foot process effacement. Collectively, these findings indicate that podocyte talin1 is critical for maintaining the integrity of the glomerular filtration barrier and provide insight into the pathogenesis of nephrotic syndrome.

Authors

Xuefei Tian, Jin Ju Kim, Susan M. Monkley, Nanami Gotoh, Ramiro Nandez, Keita Soda, Kazunori Inoue, Daniel M. Balkin, Hossam Hassan, Sung Hyun Son, Yashang Lee, Gilbert Moeckel, David A. Calderwood, Lawrence B. Holzman, David R. Critchley, Roy Zent, Jochen Reiser, Shuta Ishibe

Optogenetic stimulation of the auditory pathway

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Abstract

Auditory prostheses can partially restore speech comprehension when hearing fails. Sound coding with current prostheses is based on electrical stimulation of auditory neurons and has limited frequency resolution due to broad current spread within the cochlea. In contrast, optical stimulation can be spatially confined, which may improve frequency resolution. Here, we used animal models to characterize optogenetic stimulation, which is the optical stimulation of neurons genetically engineered to express the light-gated ion channel channelrhodopsin-2 (ChR2). Optogenetic stimulation of spiral ganglion neurons (SGNs) activated the auditory pathway, as demonstrated by recordings of single neuron and neuronal population responses. Furthermore, optogenetic stimulation of SGNs restored auditory activity in deaf mice. Approximation of the spatial spread of cochlear excitation by recording local field potentials (LFPs) in the inferior colliculus in response to suprathreshold optical, acoustic, and electrical stimuli indicated that optogenetic stimulation achieves better frequency resolution than monopolar electrical stimulation. Virus-mediated expression of a ChR2 variant with greater light sensitivity in SGNs reduced the amount of light required for responses and allowed neuronal spiking following stimulation up to 60 Hz. Our study demonstrates a strategy for optogenetic stimulation of the auditory pathway in rodents and lays the groundwork for future applications of cochlear optogenetics in auditory research and prosthetics.

Authors

Victor H. Hernandez, Anna Gehrt, Kirsten Reuter, Zhizi Jing, Marcus Jeschke, Alejandro Mendoza Schulz, Gerhard Hoch, Matthias Bartels, Gerhard Vogt, Carolyn W. Garnham, Hiromu Yawo, Yugo Fukazawa, George J. Augustine, Ernst Bamberg, Sebastian Kügler, Tim Salditt, Livia de Hoz, Nicola Strenzke, Tobias Moser

Central memory CD8⁺ T lymphocytes mediate lung allograft acceptance

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Abstract

Memory T lymphocytes are commonly viewed as a major barrier for long-term survival of organ allografts and are thought to accelerate rejection responses due to their rapid infiltration into allografts, low threshold for activation, and ability to produce inflammatory mediators. Because memory T cells are usually associated with rejection, preclinical protocols have been developed to target this population in transplant recipients. Here, using a murine model, we found that costimulatory blockade–mediated lung allograft acceptance depended on the rapid infiltration of the graft by central memory CD8⁺ T cells (CD44^hiCD62L^hiCCR7⁺). Chemokine receptor signaling and alloantigen recognition were required for trafficking of these memory T cells to lung allografts. Intravital 2-photon imaging revealed that CCR7 expression on CD8⁺ T cells was critical for formation of stable synapses with antigen-presenting cells, resulting in IFN-γ production, which induced NO and downregulated alloimmune responses. Thus, we describe a critical role for CD8⁺ central memory T cells in lung allograft acceptance and highlight the need for tailored approaches for tolerance induction in the lung.

Authors

Alexander Sasha Krupnick, Xue Lin, Wenjun Li, Ryuiji Higashikubo, Bernd H. Zinselmeyer, Hollyce Hartzler, Kelsey Toth, Jon H. Ritter, Mikhail Y. Berezin, Steven T. Wang, Mark J. Miller, Andrew E. Gelman, Daniel Kreisel

Chemical chaperone ameliorates pathological protein aggregation in plectin-deficient muscle

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Abstract

The ubiquitously expressed multifunctional cytolinker protein plectin is essential for muscle fiber integrity and myofiber cytoarchitecture. Patients suffering from plectinopathy-associated epidermolysis bullosa simplex with muscular dystrophy (EBS-MD) and mice lacking plectin in skeletal muscle display pathological desmin-positive protein aggregation and misalignment of Z-disks, which are hallmarks of myofibrillar myopathies (MFMs). Here, we developed immortalized murine myoblast cell lines to examine the pathogenesis of plectinopathies at the molecular and single cell level. Plectin-deficient myotubes, derived from myoblasts, were fully functional and mirrored the pathological features of EBS-MD myofibers, including the presence of desmin-positive protein aggregates and a concurrent disarrangement of the myofibrillar apparatus. Using this cell model, we demonstrated that plectin deficiency leads to increased intermediate filament network and sarcomere dynamics, marked upregulation of HSPs, and reduced myotube resilience following mechanical stretch. Currently, no specific therapy or treatment is available to improve plectin-related or other forms of MFMs; therefore, we assessed the therapeutic potential of chemical chaperones to relieve plectinopathies. Treatment with 4-phenylbutyrate resulted in remarkable amelioration of the pathological phenotypes in plectin-deficient myotubes as well as in plectin-deficient mice. Together, these data demonstrate the biological relevance of the MFM cell model and suggest that this model has potential use for the development of therapeutic approaches for EBS-MD.

Authors

Lilli Winter, Ilona Staszewska, Eva Mihailovska, Irmgard Fischer, Wolfgang H. Goldmann, Rolf Schröder, Gerhard Wiche

HSC commitment–associated epigenetic signature is prognostic in acute myeloid leukemia

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Abstract

Acute myeloid leukemia (AML) is characterized by disruption of HSC and progenitor cell differentiation. Frequently, AML is associated with mutations in genes encoding epigenetic modifiers. We hypothesized that analysis of alterations in DNA methylation patterns during healthy HSC commitment and differentiation would yield epigenetic signatures that could be used to identify stage-specific prognostic subgroups of AML. We performed a nano HpaII-tiny-fragment-enrichment-by-ligation-mediated-PCR (nanoHELP) assay to compare genome-wide cytosine methylation profiles between highly purified human long-term HSC, short-term HSC, common myeloid progenitors, and megakaryocyte-erythrocyte progenitors. We observed that the most striking epigenetic changes occurred during the commitment of short-term HSC to common myeloid progenitors and these alterations were predominantly characterized by loss of methylation. We developed a metric of the HSC commitment–associated methylation pattern that proved to be highly prognostic of overall survival in 3 independent large AML patient cohorts, regardless of patient treatment and epigenetic mutations. Application of the epigenetic signature metric for AML prognosis was superior to evaluation of commitment-based gene expression signatures. Together, our data define a stem cell commitment–associated methylome that is independently prognostic of poorer overall survival in AML.

Authors

Boris Bartholdy, Maximilian Christopeit, Britta Will, Yongkai Mo, Laura Barreyro, Yiting Yu, Tushar D. Bhagat, Ujunwa C. Okoye-Okafor, Tihomira I. Todorova, John M. Greally, Ross L. Levine, Ari Melnick, Amit Verma, Ulrich Steidl

T cell repertoire following autologous stem cell transplantation for multiple sclerosis

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Abstract

Autologous hematopoietic stem cell transplantation (HSCT) is commonly employed for hematologic and non-hematologic malignancies. In clinical trials, HSCT has been evaluated for severe autoimmunity as a method to “reset” the immune system and produce a new, non-autoimmune repertoire. While the feasibility of eliminating the vast majority of mature T cells is well established, accurate and quantitative determination of the relationship of regenerated T cells to the baseline repertoire has been difficult to assess. Here, in a phase II study of HSCT for poor-prognosis multiple sclerosis, we used high-throughput deep TCRβ chain sequencing to assess millions of individual TCRs per patient sample. We found that HSCT has distinctive effects on CD4⁺ and CD8⁺ T cell repertoires. In CD4⁺ T cells, dominant TCR clones present before treatment were undetectable following reconstitution, and patients largely developed a new repertoire. In contrast, dominant CD8⁺ clones were not effectively removed, and the reconstituted CD8⁺ T cell repertoire was created by clonal expansion of cells present before treatment. Importantly, patients who failed to respond to treatment had less diversity in their T cell repertoire early during the reconstitution process. These results demonstrate that TCR characterization during immunomodulatory treatment is both feasible and informative, and may enable monitoring of pathogenic or protective T cell clones following HSCT and cellular therapies.

Authors

Paolo A. Muraro, Harlan Robins, Sachin Malhotra, Michael Howell, Deborah Phippard, Cindy Desmarais, Alessandra de Paula Alves Sousa, Linda M. Griffith, Noha Lim, Richard A. Nash, Laurence A. Turka

Extracellular caspase-6 drives murine inflammatory pain via microglial TNF-α secretion

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Abstract

Increasing evidence indicates that the pathogenesis of neuropathic pain is mediated through spinal cord microglia activation. The intracellular protease caspase-6 (CASP6) is known to regulate neuronal apoptosis and axonal degeneration; however, the contribution of microglia and CASP6 in modulating synaptic transmission and pain is unclear. Here, we found that CASP6 is expressed specifically in C-fiber axonal terminals in the superficial spinal cord dorsal horn. Animals exposed to intraplantar formalin or bradykinin injection exhibited CASP6 activation in the dorsal horn. Casp6-null mice had normal baseline pain, but impaired inflammatory pain responses. Furthermore, formalin-induced second-phase pain was suppressed by spinal injection of CASP6 inhibitor or CASP6-neutralizing antibody, as well as perisciatic nerve injection of CASP6 siRNA. Recombinant CASP6 (rCASP6) induced marked TNF-α release in microglial cultures, and most microglia within the spinal cord expressed Tnfa. Spinal injection of rCASP6 elicited TNF-α production and microglia-dependent pain hypersensitivity. Evaluation of excitatory postsynaptic currents (EPSCs) revealed that rCASP6 rapidly increased synaptic transmission in spinal cord slices via TNF-α release. Interestingly, the microglial inhibitor minocycline suppressed rCASP6 but not TNF-α–induced synaptic potentiation. Finally, rCASP6-activated microglial culture medium increased EPSCs in spinal cord slices via TNF-α. Together, these data suggest that CASP6 released from axonal terminals regulates microglial TNF-α secretion, synaptic plasticity, and inflammatory pain.

Authors

Temugin Berta, Chul-Kyu Park, Zhen-Zhong Xu, Ruo-Gang Xie, Tong Liu, Ning Lü, Yen-Chin Liu, Ru-Rong Ji

Serum IgE clearance is facilitated by human FcεRI internalization

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Abstract

The high-affinity IgE receptor FcεRI is constitutively expressed in mast cells and basophils and is required for transmitting stimulatory signals upon engagement of IgE-bound allergens. FcεRI is also constitutively expressed in dendritic cells (DCs) and monocytes in humans; however, the specific functions of the FcεRI expressed by these cells are not completely understood. Here, we found that FcεRI expressed by human blood DC antigen 1–positive (BDCA1⁺) DCs and monocytes, but not basophils, traffics to endolysosomal compartments under steady-state conditions. Furthermore, IgE bound to FcεRI on BDCA1⁺ DCs was rapidly endocytosed, transported to the lysosomes, and degraded in vitro. IgE injected into mice expressing human FcεRIα (FCER1A-Tg mice) was endocytosed by conventional DCs and monocytes, and endocytosis was associated with rapid clearance of circulating IgE from these mice. Importantly, this rapid IgE clearance was dependent on monocytes or DCs but not basophils. These findings strongly suggest that constitutive internalization of human FcεRI by DCs and monocytes distinctively contributes to serum IgE clearance.

Authors

Alexandra M. Greer, Nan Wu, Amy L. Putnam, Prescott G. Woodruff, Paul Wolters, Jean-Pierre Kinet, Jeoung-Sook Shin

Conjugation of a brain-penetrant peptide with neurotensin provides antinociceptive properties

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Abstract

Neurotensin (NT) has emerged as an important modulator of nociceptive transmission and exerts its biological effects through interactions with 2 distinct GPCRs, NTS1 and NTS2. NT provides strong analgesia when administered directly into the brain; however, the blood-brain barrier (BBB) is a major obstacle for effective delivery of potential analgesics to the brain. To overcome this challenge, we synthesized chemical conjugates that are transported across the BBB via receptor-mediated transcytosis using the brain-penetrant peptide Angiopep-2 (An2), which targets LDL receptor–related protein-1 (LRP1). Using in situ brain perfusion in mice, we found that the compound ANG2002, a conjugate of An2 and NT, was transported at least 10 times more efficiently across the BBB than native NT. In vitro, ANG2002 bound NTS1 and NTS2 receptors and maintained NT-associated biological activity. In rats, i.v. ANG2002 induced a dose-dependent analgesia in the formalin model of persistent pain. At a dose of 0.05 mg/kg, ANG2002 effectively reversed pain behaviors induced by the development of neuropathic and bone cancer pain in animal models. The analgesic properties of ANG2002 demonstrated in this study suggest that this compound is effective for clinical management of persistent and chronic pain and establish the benefits of this technology for the development of neurotherapeutics.

Authors

Michel Demeule, Nicolas Beaudet, Anthony Régina, Élie Besserer-Offroy, Alexandre Murza, Pascal Tétreault, Karine Belleville, Christian Ché, Alain Larocque, Carine Thiot, Richard Béliveau, Jean-Michel Longpré, Éric Marsault, Richard Leduc, Jean E. Lachowicz, Steven L. Gonias, Jean-Paul Castaigne, Philippe Sarret

Immune cell trafficking from the brain maintains CNS immune tolerance

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Abstract

In the CNS, no pathway dedicated to immune surveillance has been characterized for preventing the anti-CNS immune responses that develop in autoimmune neuroinflammatory disease. Here, we identified a pathway for immune cells to traffic from the brain that is associated with the rostral migratory stream (RMS), which is a forebrain source of newly generated neurons. Evaluation of fluorescently labeled leukocyte migration in mice revealed that DCs travel via the RMS from the CNS to the cervical LNs (CxLNs), where they present antigen to T cells. Pharmacologic interruption of immune cell traffic with the mononuclear cell-sequestering drug fingolimod influenced anti-CNS T cell responses in the CxLNs and modulated experimental autoimmune encephalomyelitis (EAE) severity in a mouse model of multiple sclerosis (MS). Fingolimod treatment also induced EAE in a disease-resistant transgenic mouse strain by altering DC-mediated Treg functions in CxLNs and disrupting CNS immune tolerance. These data describe an immune cell pathway that originates in the CNS and is capable of dampening anti-CNS immune responses in the periphery. Furthermore, these data provide insight into how fingolimod treatment might exacerbate CNS neuroinflammation in some cases and suggest that focal therapeutic interventions, outside the CNS have the potential to selectively modify anti-CNS immunity.

Authors

Mohammad G. Mohammad, Vicky W.W. Tsai, Marc J. Ruitenberg, Masoud Hassanpour, Hui Li, Prue H. Hart, Samuel N. Breit, Paul E. Sawchenko, David A. Brown

Cell-specific translational profiling in acute kidney injury

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Abstract

Acute kidney injury (AKI) promotes an abrupt loss of kidney function that results in substantial morbidity and mortality. Considerable effort has gone toward identification of diagnostic biomarkers and analysis of AKI-associated molecular events; however, most studies have adopted organ-wide approaches and have not elucidated the interplay among different cell types involved in AKI pathophysiology. To better characterize AKI-associated molecular and cellular events, we developed a mouse line that enables the identification of translational profiles in specific cell types. This strategy relies on CRE recombinase–dependent activation of an EGFP-tagged L10a ribosomal protein subunit, which allows translating ribosome affinity purification (TRAP) of mRNA populations in CRE-expressing cells. Combining this mouse line with cell type–specific CRE-driver lines, we identified distinct cellular responses in an ischemia reperfusion injury (IRI) model of AKI. Twenty-four hours following IRI, distinct translational signatures were identified in the nephron, kidney interstitial cell populations, vascular endothelium, and macrophages/monocytes. Furthermore, TRAP captured known IRI-associated markers, validating this approach. Biological function annotation, canonical pathway analysis, and in situ analysis of identified response genes provided insight into cell-specific injury signatures. Our study provides a deep, cell-based view of early injury-associated molecular events in AKI and documents a versatile, genetic tool to monitor cell-specific and temporal-specific biological processes in disease modeling.

Authors

Jing Liu, A. Michaela Krautzberger, Shannan H. Sui, Oliver M. Hofmann, Ying Chen, Manfred Baetscher, Ivica Grgic, Sanjeev Kumar, Benjamin Humphreys, Winston A. Hide, Andrew P. McMahon

Small-molecule activator of glutamate transporter EAAT2 translation provides neuroprotection

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Abstract

Glial glutamate transporter EAAT2 plays a major role in glutamate clearance in synaptic clefts. Several lines of evidence indicate that strategies designed to increase EAAT2 expression have potential for preventing excitotoxicity, which contributes to neuronal injury and death in neurodegenerative diseases. We previously discovered several classes of compounds that can increase EAAT2 expression through translational activation. Here, we present efficacy studies of the compound LDN/OSU-0212320, which is a pyridazine derivative from one of our lead series. In a murine model, LDN/OSU-0212320 had good potency, adequate pharmacokinetic properties, no observed toxicity at the doses examined, and low side effect/toxicity potential. Additionally, LDN/OSU-0212320 protected cultured neurons from glutamate-mediated excitotoxic injury and death via EAAT2 activation. Importantly, LDN/OSU-0212320 markedly delayed motor function decline and extended lifespan in an animal model of amyotrophic lateral sclerosis (ALS). We also found that LDN/OSU-0212320 substantially reduced mortality, neuronal death, and spontaneous recurrent seizures in a pilocarpine-induced temporal lobe epilepsy model. Moreover, our study demonstrated that LDN/OSU-0212320 treatment results in activation of PKC and subsequent Y-box–binding protein 1 (YB-1) activation, which regulates activation of EAAT2 translation. Our data indicate that the use of small molecules to enhance EAAT2 translation may be a therapeutic strategy for the treatment of neurodegenerative diseases.

Authors

Qiongman Kong, Ling-Chu Chang, Kou Takahashi, Qibing Liu, Delanie A. Schulte, Liching Lai, Brian Ibabao, Yuchen Lin, Nathan Stouffer, Chitra Das Mukhopadhyay, Xuechao Xing, Kathleen I. Seyb, Gregory D. Cuny, Marcie A. Glicksman, Chien-Liang Glenn Lin

CXCL5-secreting pulmonary epithelial cells drive destructive neutrophilic inflammation in tuberculosis

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Abstract

Successful host defense against numerous pulmonary infections depends on bacterial clearance by polymorphonuclear leukocytes (PMNs); however, excessive PMN accumulation can result in life-threatening lung injury. Local expression of CXC chemokines is critical for PMN recruitment. The impact of chemokine-dependent PMN recruitment during pulmonary Mycobacterium tuberculosis infection is not fully understood. Here, we analyzed expression of genes encoding CXC chemokines in M. tuberculosis–infected murine lung tissue and found that M. tuberculosis infection promotes upregulation of Cxcr2 and its ligand Cxcl5. To determine the contribution of CXCL5 in pulmonary PMN recruitment, we generated Cxcl5^–/– mice and analyzed their immune response against M. tuberculosis. Both Cxcr2^–/– mice and Cxcl5^–/– mice, which are deficient for only one of numerous CXCR2 ligands, exhibited enhanced survival compared with that of WT mice following high-dose M. tuberculosis infection. The resistance of Cxcl5^–/– mice to M. tuberculosis infection was not due to heightened M. tuberculosis clearance but was the result of impaired PMN recruitment, which reduced pulmonary inflammation. Lung epithelial cells were the main source of CXCL5 upon M. tuberculosis infection, and secretion of CXCL5 was reduced by blocking TLR2 signaling. Together, our data indicate that TLR2-induced epithelial-derived CXCL5 is critical for PMN-driven destructive inflammation in pulmonary tuberculosis.

Authors

Geraldine Nouailles, Anca Dorhoi, Markus Koch, Jens Zerrahn, January Weiner 3rd, Kellen C. Faé, Frida Arrey, Stefanie Kuhlmann, Silke Bandermann, Delia Loewe, Hans-Joachim Mollenkopf, Alexis Vogelzang, Catherine Meyer-Schwesinger, Hans-Willi Mittrücker, Gayle McEwen, Stefan H.E. Kaufmann

Long-lived intestinal tuft cells serve as colon cancer–initiating cells

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Abstract

Doublecortin-like kinase 1 protein (DCLK1) is a gastrointestinal tuft cell marker that has been proposed to identify quiescent and tumor growth–sustaining stem cells. DCLK1⁺ tuft cells are increased in inflammation-induced carcinogenesis; however, the role of these cells within the gastrointestinal epithelium and their potential as cancer-initiating cells are poorly understood. Here, using a BAC-CreERT–dependent genetic lineage–tracing strategy, we determined that a subpopulation of DCLK1⁺ cells is extremely long lived and possesses rare stem cell abilities. Moreover, genetic ablation of Dclk1 revealed that DCLK1⁺ tuft cells contribute to recovery following intestinal and colonic injury. Surprisingly, conditional knockdown of the Wnt regulator APC in DCLK1⁺ cells was not sufficient to drive colonic carcinogenesis under normal conditions; however, dextran sodium sulfate–induced (DSS-induced) colitis promoted the development of poorly differentiated colonic adenocarcinoma in mice lacking APC in DCLK1⁺ cells. Importantly, colonic tumor formation occurred even when colitis onset was delayed for up to 3 months after induced APC loss in DCLK1⁺ cells. Thus, our data define an intestinal DCLK1⁺ tuft cell population that is long lived, quiescent, and important for intestinal homeostasis and regeneration. Long-lived DCLK1⁺ cells maintain quiescence even following oncogenic mutation, but are activated by tissue injury and can serve to initiate colon cancer.

Authors

C. Benedikt Westphalen, Samuel Asfaha, Yoku Hayakawa, Yoshihiro Takemoto, Dana J. Lukin, Andreas H. Nuber, Anna Brandtner, Wanda Setlik, Helen Remotti, Ashlesha Muley, Xiaowei Chen, Randal May, Courtney W. Houchen, James G. Fox, Michael D. Gershon, Michael Quante, Timothy C. Wang

An AXL/LRP-1/RANBP9 complex mediates DC efferocytosis and antigen cross-presentation in vivo

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Abstract

The phagocytosis of apoptotic cells (ACs), or efferocytosis, by DCs is critical for self-tolerance and host defense. Although many efferocytosis-associated receptors have been described in vitro, the functionality of these receptors in vivo has not been explored in depth. Using a spleen efferocytosis assay and targeted genetic deletion in mice, we identified a multiprotein complex — composed of the receptor tyrosine kinase AXL, LDL receptor–related protein–1 (LRP-1), and RAN-binding protein 9 (RANBP9) — that mediates DC efferocytosis and antigen cross-presentation. We found that AXL bound ACs, but required LRP-1 to trigger internalization, in murine CD8α⁺ DCs and human-derived DCs. AXL and LRP-1 did not interact directly, but relied on RANBP9, which bound both AXL and LRP-1, to form the complex. In a coculture model of antigen presentation, the AXL/LRP-1/RANBP9 complex was used by DCs to cross-present AC-associated antigens to T cells. Furthermore, in a murine model of herpes simplex virus–1 infection, mice lacking DC-specific LRP-1, AXL, or RANBP9 had increased AC accumulation, defective viral antigen-specific CD8⁺ T cell activation, enhanced viral load, and decreased survival. The discovery of this multiprotein complex that mediates functionally important DC efferocytosis in vivo may have implications for future studies related to host defense and DC-based vaccines.

Authors

Manikandan Subramanian, Crystal D. Hayes, Joseph J. Thome, Edward Thorp, Glenn K. Matsushima, Joachim Herz, Donna L. Farber, Kang Liu, Madepalli Lakshmana, Ira Tabas

Hyaluronan digestion controls DC migration from the skin

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Abstract

The breakdown and release of hyaluronan (HA) from the extracellular matrix has been hypothesized to act as an endogenous signal of injury. To test this hypothesis, we generated mice that conditionally overexpressed human hyaluronidase 1 (HYAL1). Mice expressing HYAL1 in skin either during early development or by inducible transient expression exhibited extensive HA degradation, yet displayed no evidence of spontaneous inflammation. Further, HYAL1 expression activated migration and promoted loss of DCs from the skin. We subsequently determined that induction of HYAL1 expression prior to topical antigen application resulted in a lack of an antigenic response due to the depletion of DCs from the skin. In contrast, induction of HYAL1 expression concurrent with antigen exposure accelerated allergic sensitization. Administration of HA tetrasaccharides, before or simultaneously with antigen application, recapitulated phenotypes observed in HYAL1-expressing animals, suggesting that the generation of small HA fragments, rather than the loss of large HA molecules, promotes DC migration and subsequent modification of allergic responses. Furthermore, mice lacking TLR4 did not exhibit HA-associated phenotypes, indicating that TLR4 mediates these responses. This study provides direct evidence that HA breakdown controls the capacity of the skin to present antigen. These events may influence DC function in injury or disease and have potential to be exploited therapeutically for modification of allergic responses.

Authors

Jun Muto, Yasuhide Morioka, Kenshi Yamasaki, Margaret Kim, Andrea Garcia, Aaron F. Carlin, Ajit Varki, Richard L. Gallo

Relative acidic compartment volume as a lysosomal storage disorder–associated biomarker

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Abstract

Lysosomal storage disorders (LSDs) occur at a frequency of 1 in every 5,000 live births and are a common cause of pediatric neurodegenerative disease. The relatively small number of patients with LSDs and lack of validated biomarkers are substantial challenges for clinical trial design. Here, we evaluated the use of a commercially available fluorescent probe, Lysotracker, that can be used to measure the relative acidic compartment volume of circulating B cells as a potentially universal biomarker for LSDs. We validated this metric in a mouse model of the LSD Niemann-Pick type C1 disease (NPC1) and in a prospective 5-year international study of NPC patients. Pediatric NPC subjects had elevated acidic compartment volume that correlated with age-adjusted clinical severity and was reduced in response to therapy with miglustat, a European Medicines Agency–approved drug that has been shown to reduce NPC1-associated neuropathology. Measurement of relative acidic compartment volume was also useful for monitoring therapeutic responses of an NPC2 patient after bone marrow transplantation. Furthermore, this metric identified a potential adverse event in NPC1 patients receiving i.v. cyclodextrin therapy. Our data indicate that relative acidic compartment volume may be a useful biomarker to aid diagnosis, clinical monitoring, and evaluation of therapeutic responses in patients with lysosomal disorders.

Authors

Danielle te Vruchte, Anneliese O. Speak, Kerri L. Wallom, Nada Al Eisa, David A. Smith, Christian J. Hendriksz, Louise Simmons, Robin H. Lachmann, Alison Cousins, Ralf Hartung, Eugen Mengel, Heiko Runz, Michael Beck, Yasmina Amraoui, Jackie Imrie, Elizabeth Jacklin, Kate Riddick, Nicole M. Yanjanin, Christopher A. Wassif, Arndt Rolfs, Florian Rimmele, Naomi Wright, Clare Taylor, Uma Ramaswami, Timothy M. Cox, Caroline Hastings, Xuntian Jiang, Rohini Sidhu, Daniel S. Ory, Begona Arias, Mylvaganam Jeyakumar, Daniel J. Sillence, James E. Wraith, Forbes D. Porter, Mario Cortina-Borja, Frances M. Platt

Abnormal muscle mechanosignaling triggers cardiomyopathy in mice with Marfan syndrome

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Abstract

Patients with Marfan syndrome (MFS), a multisystem disorder caused by mutations in the gene encoding the extracellular matrix (ECM) protein fibrillin 1, are unusually vulnerable to stress-induced cardiac dysfunction. The prevailing view is that MFS-associated cardiac dysfunction is the result of aortic and/or valvular disease. Here, we determined that dilated cardiomyopathy (DCM) in fibrillin 1–deficient mice is a primary manifestation resulting from ECM-induced abnormal mechanosignaling by cardiomyocytes. MFS mice displayed spontaneous emergence of an enlarged and dysfunctional heart, altered physical properties of myocardial tissue, and biochemical evidence of chronic mechanical stress, including increased angiotensin II type I receptor (AT1R) signaling and abated focal adhesion kinase (FAK) activity. Partial fibrillin 1 gene inactivation in cardiomyocytes was sufficient to precipitate DCM in otherwise phenotypically normal mice. Consistent with abnormal mechanosignaling, normal cardiac size and function were restored in MFS mice treated with an AT1R antagonist and in MFS mice lacking AT1R or β-arrestin 2, but not in MFS mice treated with an angiotensin-converting enzyme inhibitor or lacking angiotensinogen. Conversely, DCM associated with abnormal AT1R and FAK signaling was the sole abnormality in mice that were haploinsufficient for both fibrillin 1 and β1 integrin. Collectively, these findings implicate fibrillin 1 in the physiological adaptation of cardiac muscle to elevated workload.

Authors

Jason R. Cook, Luca Carta, Ludovic Bénard, Elie R. Chemaly, Emily Chiu, Satish K. Rao, Thomas G. Hampton, Peter Yurchenco, Kevin D. Costa, Roger J. Hajjar, Francesco Ramirez

Serotonergic mechanisms responsible for levodopa-induced dyskinesias in Parkinson’s disease patients

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Abstract

Levodopa-induced dyskinesias (LIDs) are the most common and disabling adverse motor effect of therapy in Parkinson’s disease (PD) patients. In this study, we investigated serotonergic mechanisms in LIDs development in PD patients using ¹¹C-DASB PET to evaluate serotonin terminal function and ¹¹C-raclopride PET to evaluate dopamine release. PD patients with LIDs showed relative preservation of serotonergic terminals throughout their disease. Identical levodopa doses induced markedly higher striatal synaptic dopamine concentrations in PD patients with LIDs compared with PD patients with stable responses to levodopa. Oral administration of the serotonin receptor type 1A agonist buspirone prior to levodopa reduced levodopa-evoked striatal synaptic dopamine increases and attenuated LIDs. PD patients with LIDs that exhibited greater decreases in synaptic dopamine after buspirone pretreatment had higher levels of serotonergic terminal functional integrity. Buspirone-associated modulation of dopamine levels was greater in PD patients with mild LIDs compared with those with more severe LIDs. These findings indicate that striatal serotonergic terminals contribute to LIDs pathophysiology via aberrant processing of exogenous levodopa and release of dopamine as false neurotransmitter in the denervated striatum of PD patients with LIDs. Our results also support the development of selective serotonin receptor type 1A agonists for use as antidyskinetic agents in PD.

Authors

Marios Politis, Kit Wu, Clare Loane, David J. Brooks, Lorenzo Kiferle, Federico E. Turkheimer, Peter Bain, Sophie Molloy, Paola Piccini

Reducing dynamin 2 expression rescues X-linked centronuclear myopathy

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Abstract

Centronuclear myopathies (CNM) are congenital disorders associated with muscle weakness and abnormally located nuclei in skeletal muscle. An autosomal dominant form of CNM results from mutations in the gene encoding dynamin 2 (DNM2), and loss-of-function mutations in the gene encoding myotubularin (MTM1) result in X-linked CNM (XLCNM, also called myotubular myopathy), which promotes severe neonatal hypotonia and early death. Currently, no effective treatments exist for XLCNM. Here, we found increased DNM2 levels in XLCNM patients and a mouse model of XLCNM (Mtm1^–/y). Generation of Mtm1^–/y mice that were heterozygous for Dnm2 revealed that reduction of DNM2 in XLCNM mice restored life span, whole-body strength, and diaphragm function and increased muscle strength. Additionally, classic CNM-associated histological features, including fiber atrophy and nuclei mispositioning, were absent or reduced. Ultrastructural analysis revealed improvement of sarcomere organization and triad structures. Skeletal muscle–specific decrease of Dnm2 during embryogenesis or in young mice after disease onset revealed that the rescue associated with downregulation of Dnm2 is cell autonomous and is able to stop and potentially revert XLCNM progression. These data indicate that MTM1 and DNM2 regulate muscle organization and force through a common pathway. Furthermore, despite DNM2 being a key mechanoenzyme, its reduction is beneficial for XLCNM and represents a potential therapeutic approach for patients.

Authors

Belinda S. Cowling, Thierry Chevremont, Ivana Prokic, Christine Kretz, Arnaud Ferry, Catherine Coirault, Olga Koutsopoulos, Vincent Laugel, Norma B. Romero, Jocelyn Laporte

5′RNA-Seq identifies Fhl1 as a genetic modifier in cardiomyopathy

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Abstract

The transcriptome is subject to multiple changes during pathogenesis, including the use of alternate 5′ start-sites that can affect transcription levels and output. Current RNA sequencing techniques can assess mRNA levels, but do not robustly detect changes in 5′ start-site use. Here, we developed a transcriptome sequencing strategy that detects genome-wide changes in start-site usage (5′RNA-Seq) and applied this methodology to identify regulatory events that occur in hypertrophic cardiomyopathy (HCM). Compared with transcripts from WT mice, 92 genes had altered start-site usage in a mouse model of HCM, including four-and-a-half LIM domains protein 1 (Fhl1). HCM-induced altered transcriptional regulation of Fhl1 resulted in robust myocyte expression of a distinct protein isoform, a response that was conserved in humans with genetic or acquired cardiomyopathies. Genetic ablation of Fhl1 in HCM mice was deleterious, which suggests that Fhl1 transcriptional changes provide salutary effects on stressed myocytes in this disease. Because Fhl1 is a chromosome X–encoded gene, stress-induced changes in its transcription may contribute to gender differences in the clinical severity of HCM. Our findings indicate that 5′RNA-Seq has the potential to identify genome-wide changes in 5′ start-site usage that are associated with pathogenic phenotypes.

Authors

Danos C. Christodoulou, Hiroko Wakimoto, Kenji Onoue, Seda Eminaga, Joshua M. Gorham, Steve R. DePalma, Daniel S. Herman, Polakit Teekakirikul, David A. Conner, David M. McKean, Andrea A. Domenighetti, Anton Aboukhalil, Stephen Chang, Gyan Srivastava, Barbara McDonough, Philip L. De Jager, Ju Chen, Martha L. Bulyk, Jochen D. Muehlschlegel, Christine E. Seidman, J.G. Seidman

Agonistic induction of PPARγ reverses cigarette smoke–induced emphysema

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Abstract

The development of emphysema in humans and mice exposed to cigarette smoke is promoted by activation of an adaptive immune response. Lung myeloid dendritic cells (mDCs) derived from cigarette smokers activate autoreactive Th1 and Th17 cells. mDC-dependent activation of T cell subsets requires expression of the SPP1 gene, which encodes osteopontin (OPN), a pleiotropic cytokine implicated in autoimmune responses. The upstream molecular events that promote SPP1 expression and activate mDCs in response to smoke remain unknown. Here, we show that peroxisome proliferator–activated receptor γ (PPARG/Pparg) expression was downregulated in mDCs of smokers with emphysema and mice exposed to chronic smoke. Conditional knockout of PPARγ in APCs using Cd11c-Cre Pparg^flox/flox mice led to spontaneous lung inflammation and emphysema that resembled the phenotype of smoke-exposed mice. The inflammatory phenotype of Cd11c-Cre Pparg^flox/flox mice required OPN, suggesting an antiinflammatory mechanism in which PPARγ negatively regulates Spp1 expression in the lung. A 2-month treatment with a PPARγ agonist reversed emphysema in WT mice despite continual smoke exposure. Furthermore, endogenous PPARγ agonists were reduced in the plasma of smokers with emphysema. These findings reveal a proinflammatory pathway, in which reduced PPARγ activity promotes emphysema, and suggest that targeting this pathway in smokers could prevent and reverse emphysema.

Authors

Ming Shan, Ran You, Xiaoyi Yuan, Michael V. Frazier, Paul Porter, Alexander Seryshev, Jeong-Soo Hong, Li-zhen Song, Yiqun Zhang, Susan Hilsenbeck, Lawrence Whitehead, Nazanin Zarinkamar, Sarah Perusich, David B. Corry, Farrah Kheradmand

Macrophages are required for neonatal heart regeneration

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Abstract

Myocardial infarction (MI) leads to cardiomyocyte death, which triggers an immune response that clears debris and restores tissue integrity. In the adult heart, the immune system facilitates scar formation, which repairs the damaged myocardium but compromises cardiac function. In neonatal mice, the heart can regenerate fully without scarring following MI; however, this regenerative capacity is lost by P7. The signals that govern neonatal heart regeneration are unknown. By comparing the immune response to MI in mice at P1 and P14, we identified differences in the magnitude and kinetics of monocyte and macrophage responses to injury. Using a cell-depletion model, we determined that heart regeneration and neoangiogenesis following MI depends on neonatal macrophages. Neonates depleted of macrophages were unable to regenerate myocardia and formed fibrotic scars, resulting in reduced cardiac function and angiogenesis. Immunophenotyping and gene expression profiling of cardiac macrophages from regenerating and nonregenerating hearts indicated that regenerative macrophages have a unique polarization phenotype and secrete numerous soluble factors that may facilitate the formation of new myocardium. Our findings suggest that macrophages provide necessary signals to drive angiogenesis and regeneration of the neonatal mouse heart. Modulating inflammation may provide a key therapeutic strategy to support heart regeneration.

Authors

Arin B. Aurora, Enzo R. Porrello, Wei Tan, Ahmed I. Mahmoud, Joseph A. Hill, Rhonda Bassel-Duby, Hesham A. Sadek, Eric N. Olson

Bitter and sweet taste receptors regulate human upper respiratory innate immunity

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Abstract

Bitter taste receptors (T2Rs) in the human airway detect harmful compounds, including secreted bacterial products. Here, using human primary sinonasal air-liquid interface cultures and tissue explants, we determined that activation of a subset of airway T2Rs expressed in nasal solitary chemosensory cells activates a calcium wave that propagates through gap junctions to the surrounding respiratory epithelial cells. The T2R-dependent calcium wave stimulated robust secretion of antimicrobial peptides into the mucus that was capable of killing a variety of respiratory pathogens. Furthermore, sweet taste receptor (T1R2/3) activation suppressed T2R-mediated antimicrobial peptide secretion, suggesting that T1R2/3-mediated inhibition of T2Rs prevents full antimicrobial peptide release during times of relative health. In contrast, during acute bacterial infection, T1R2/3 is likely deactivated in response to bacterial consumption of airway surface liquid glucose, alleviating T2R inhibition and resulting in antimicrobial peptide secretion. We found that patients with chronic rhinosinusitis have elevated glucose concentrations in their nasal secretions, and other reports have shown that patients with hyperglycemia likewise have elevated nasal glucose levels. These data suggest that increased glucose in respiratory secretions in pathologic states, such as chronic rhinosinusitis or hyperglycemia, promotes tonic activation of T1R2/3 and suppresses T2R-mediated innate defense. Furthermore, targeting T1R2/3-dependent suppression of T2Rs may have therapeutic potential for upper respiratory tract infections.

Authors

Robert J. Lee, Jennifer M. Kofonow, Philip L. Rosen, Adam P. Siebert, Bei Chen, Laurel Doghramji, Guoxiang Xiong, Nithin D. Adappa, James N. Palmer, David W. Kennedy, James L. Kreindler, Robert F. Margolskee, Noam A. Cohen

Targeting ER stress–induced autophagy overcomes BRAF inhibitor resistance in melanoma

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Abstract

Melanomas that result from mutations in the gene encoding BRAF often become resistant to BRAF inhibition (BRAFi), with multiple mechanisms contributing to resistance. While therapy-induced autophagy promotes resistance to a number of therapies, especially those that target PI3K/mTOR signaling, its role as an adaptive resistance mechanism to BRAFi is not well characterized. Using tumor biopsies from BRAF^V600E melanoma patients treated either with BRAFi or with combined BRAF and MEK inhibition, we found that BRAFi-resistant tumors had increased levels of autophagy compared with baseline. Patients with higher levels of therapy-induced autophagy had drastically lower response rates to BRAFi and a shorter duration of progression-free survival. In BRAF^V600E melanoma cell lines, BRAFi or BRAF/MEK inhibition induced cytoprotective autophagy, and autophagy inhibition enhanced BRAFi-induced cell death. Shortly after BRAF inhibitor treatment in melanoma cell lines, mutant BRAF bound the ER stress gatekeeper GRP78, which rapidly expanded the ER. Disassociation of GRP78 from the PKR-like ER-kinase (PERK) promoted a PERK-dependent ER stress response that subsequently activated cytoprotective autophagy. Combined BRAF and autophagy inhibition promoted tumor regression in BRAFi-resistant xenografts. These data identify a molecular pathway for drug resistance connecting BRAFi, the ER stress response, and autophagy and provide a rationale for combination approaches targeting this resistance pathway.

Authors

Xiao-Hong Ma, Sheng-Fu Piao, Souvik Dey, Quentin Mcafee, Giorgos Karakousis, Jessie Villanueva, Lori S. Hart, Samuel Levi, Janice Hu, Gao Zhang, Rossitza Lazova, Vincent Klump, John M. Pawelek, Xiaowei Xu, Wei Xu, Lynn M. Schuchter, Michael A. Davies, Meenhard Herlyn, Jeffrey Winkler, Constantinos Koumenis, Ravi K. Amaravadi

A microRNA-dependent program controls p53-independent survival and chemosensitivity in human and murine squamous cell carcinoma

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Abstract

Authors

Benjamin Ory, Matthew R. Ramsey, Catherine Wilson, Douangsone D. Vadysirisack, Nicole Forster, James W. Rocco, S. Michael Rothenberg, Leif W. Ellisen

RSK3/4 mediate resistance to PI3K pathway inhibitors in breast cancer

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Abstract

Authors

Violeta Serra, Pieter J.A. Eichhorn, Celina García-García, Yasir H. Ibrahim, Ludmila Prudkin, Gertrudis Sánchez, Olga Rodríguez, Pilar Antón, Josep-Lluís Parra, Sara Marlow, Maurizio Scaltriti, José Pérez-Garcia, Aleix Prat, Joaquín Arribas, William C. Hahn, So Young Kim, José Baselga

Cancer epigenetics drug discovery and development: the challenge of hitting the mark

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Abstract

Authors

Robert M. Campbell, Peter J. Tummino