On page 315, Sukhai and colleagues demonstrate that lysosome-disrupting compounds preferentially target acute myeloid leukemia (AML) for destruction. Based on a drug screen, the researchers found that the antimalarial agent mefloquine selectively kills AML cells and AML progenitors by directly permeabilizing lysosomal membranes and releasing cathepsins into the cytosol. Their work suggests that lysosomal disruption is a potential therapeutic strategy for treating AML.
Image credit: Lyndsay Stephenson.
Cardiovascular research is progressing on many fronts, as highlighted in the collection of Reviews in this issue of the
The management of cardiovascular risk through lifestyle modification and pharmacotherapy is paramount to the prevention of cardiovascular disease. Epidemiological studies have identified obesity, dyslipidemia, diabetes, and hypertension as interrelated factors that negatively affect cardiovascular health. Recently, genetic and pharmacological evidence in model systems has implicated microRNAs as dynamic modifiers of disease pathogenesis. An expanded understanding of the function of microRNAs in gene regulatory networks associated with cardiovascular risk will enable identification of novel genetic mechanisms of disease and inform the development of innovative therapeutic strategies.
Genetic mutations account for a significant percentage of cardiomyopathies, which are a leading cause of congestive heart failure. In hypertrophic cardiomyopathy (HCM), cardiac output is limited by the thickened myocardium through impaired filling and outflow. Mutations in the genes encoding the thick filament components myosin heavy chain and myosin binding protein C (
Many remarkable advances have improved our understanding of the cellular and molecular events in the pathogenesis of atherosclerosis. Chief among these is the accumulating knowledge of how the immune system contributes to all phases of atherogenesis, including well-known inflammatory reactions consequent to intimal trapping and oxidation of LDL. Advances in our understanding of the innate and adaptive responses to these events have helped to clarify the role of inflammation in atherogenesis and suggested new diagnostic modalities and novel therapeutic targets. Here we focus on recent advances in understanding how adaptive immunity affects atherogenesis.
Cardiovascular disease is the number one cause of mortality in the Western world. The heart responds to many cardiopathological conditions with hypertrophic growth by enlarging individual myocytes to augment cardiac pump function and decrease ventricular wall tension. Initially, such cardiac hypertrophic growth is often compensatory, but as time progresses these changes become maladaptive. Cardiac hypertrophy is the strongest predictor for the development of heart failure, arrhythmia, and sudden death. Here we discuss therapeutic avenues emerging from molecular and genetic studies of cardiovascular disease in animal models. The majority of these are based on intracellular signaling pathways considered central to pathologic cardiac remodeling and hypertrophy, which then leads to heart failure. We focus our discussion on selected therapeutic targets that have more recently emerged and have a tangible translational potential given the available pharmacologic agents that could be readily evaluated in human clinical trials.
Ca2+-dependent signaling is highly regulated in cardiomyocytes and determines the force of cardiac muscle contraction. Ca2+ cycling refers to the release and reuptake of intracellular Ca2+ that drives muscle contraction and relaxation. In failing hearts, Ca2+ cycling is profoundly altered, resulting in impaired contractility and fatal cardiac arrhythmias. The key defects in Ca2+ cycling occur at the level of the sarcoplasmic reticulum (SR), a Ca2+ storage organelle in muscle. Defects in the regulation of Ca2+ cycling proteins including the ryanodine receptor 2, cardiac (RyR2)/Ca2+ release channel macromolecular complexes and the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a)/phospholamban complex contribute to heart failure. RyR2s are oxidized, nitrosylated, and PKA hyperphosphorylated, resulting in “leaky” channels in failing hearts. These leaky RyR2s contribute to depletion of Ca2+ from the SR, and the leaking Ca2+ depolarizes cardiomyocytes and triggers fatal arrhythmias. SERCA2a is downregulated and phospholamban is hypophosphorylated in failing hearts, resulting in impaired SR Ca2+ reuptake that conspires with leaky RyR2 to deplete SR Ca2+. Two new therapeutic strategies for heart failure (HF) are now being tested in clinical trials: (a) fixing the leak in RyR2 channels with a novel class of Ca2+-release channel stabilizers called Rycals and (b) increasing expression of SERCA2a to improve SR Ca2+ reuptake with viral-mediated gene therapy. There are many potential opportunities for additional mechanism-based therapeutics involving the machinery that regulates Ca2+ cycling in the heart.
Advances in understanding the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, make gene-based therapy a promising treatment option for heart conditions. Cardiovascular gene therapy has benefitted from recent advancements in vector technology, design, and delivery modalities. There is a critical need to explore new therapeutic approaches in heart failure, and gene therapy has emerged as a viable alternative. Advances in understanding of the molecular basis of myocardial dysfunction, together with the development of increasingly efficient gene transfer technology, has placed heart failure within reach of gene-based therapy. The recent successful and safe completion of a phase 2 trial targeting the cardiac sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump (SERCA2a) has the potential to open a new era for gene therapy for heart failure.
This article discusses current understanding of myocardial biology, emphasizing the regeneration potential of the adult human heart and the mechanisms involved. In the last decade, a novel conceptual view has emerged. The heart is no longer considered a postmitotic organ, but is viewed as a self-renewing organ characterized by a resident stem cell compartment responsible for tissue homeostasis and cardiac repair following injury. Additionally, HSCs possess the ability to transdifferentiate and acquire the cardiomyocyte, vascular endothelial, and smooth muscle cell lineages. Both cardiac and hematopoietic stem cells may be used therapeutically in an attempt to reverse the devastating consequences of chronic heart failure of ischemic and nonischemic origin.
Despite many innovative advances in cardiology over the past 50 years, heart disease remains a major killer. The steady progress that continues to be made in diagnostics and therapeutics is offset by the cardiovascular consequences of the growing epidemics of obesity and diabetes. Truly innovative approaches on the horizon have been greatly influenced by new insights in cardiovascular development. In particular, research in stem cell biology, the cardiomyocyte lineage, and the interactions of the myocardium and epicardium have opened the door to new approaches for healing the injured heart.
The abrupt cessation of effective cardiac function due to an aberrant heart rhythm can cause sudden and unexpected death at any age, a syndrome called sudden cardiac death (SCD). Annually, more than 300,000 cases of SCD occur in the United States alone, making this a major public health concern. Our current understanding of the mechanisms responsible for SCD has emerged from decades of basic science investigation into the normal electrophysiology of the heart, the molecular physiology of cardiac ion channels, fundamental cellular and tissue events associated with cardiac arrhythmias, and the molecular genetics of monogenic disorders of heart rhythm. This knowledge has helped shape the current diagnosis and treatment of inherited arrhythmia susceptibility syndromes associated with SCD and has provided a pathophysiological framework for understanding more complex conditions predisposing to this tragic event. This Review presents an overview of the molecular basis of SCD, with a focus on monogenic arrhythmia syndromes.
The discovery of the genetic basis of inherited arrhythmias has paved the way for an improved understanding of arrhythmogenesis in a wide spectrum of life-threatening conditions. In vitro expression of mutations and transgenic animal models have been instrumental in enhancing this understanding, but the applicability of results to the human heart remains unknown. The ability to differentiate induced pluripotent stem cells (iPSs) into cardiomyocytes enables the potential to generate patient-specific myocytes, which could be used to recapitulate the features of inherited arrhythmias in the context of the patient’s genetic background. Few studies have been reported on iPS-derived myocytes obtained from patients with heritable arrhythmias, but they have demonstrated the applicability of this innovative approach to the study of inherited arrhythmias. Here we review the results achieved by iPS investigations in arrhythmogenic syndromes and discuss the existing challenges to be addressed before the use of iPS-derived myocytes can become a part of personalized management of inherited arrhythmias.
Acute myocardial infarction (MI) is a major cause of death and disability worldwide. In patients with MI, the treatment of choice for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PPCI). However, the process of reperfusion can itself induce cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. A number of new therapeutic strategies currently under investigation for preventing myocardial reperfusion injury have the potential to improve clinical outcomes in patients with acute MI treated with PPCI.
Delivery of oxygen to tissues is the primary function of the cardiovascular system. NO, a gasotransmitter that signals predominantly through protein
Angiotensin I–converting enzyme (ACE, or DCP1) is a zinc metallopeptidase that converts angiotensin I into the vasoactive and aldosterone-stimulating peptide angiotensin II and cleaves bradykinin into inactive peptides. Plasma ACE measurement is widely used for the diagnosis of sarcoidosis. While enzyme concentrations are highly stable in an individual, there is a high level of interindividual variability. In 1990, we identified an insertion/deletion polymorphism in
Clinical vignette: A 38-year-old man consults you in the GI clinic because of frequent episodes of epigastric pain, nausea, and tiredness. His blood count shows signs of mild iron deficiency anemia. Upper GI endoscopy was normal, but antral and corpus biopsy specimens show evidence of gastric atrophy and
In response to feeding, insulin promotes the uptake of sugar in peripheral tissues and suppresses the production of sugar, a process called gluconeogenesis, in the liver. Recent research has shown that chronic inflammation promotes insulin resistance, and in turn, chronically high glucose levels can drive inflammation. In this issue of the
Thyroid hormone is a well-known regulator of metabolic and cardiovascular functions, and signaling through thyroid receptors has differential effects on cells depending on the receptor isoform that they express. In this issue of the
The pathophysiology of the E150K mutation in the rod opsin gene associated with autosomal recessive retinitis pigmentosa (arRP) has yet to be determined. We generated knock-in mice carrying a single nucleotide change in exon 2 of the rod opsin gene resulting in the E150K mutation. This novel mouse model displayed severe retinal degeneration affecting rhodopsin’s stabilization of rod outer segments (ROS). Homozygous E150K (KK) mice exhibited early-onset retinal degeneration, with disorganized ROS structures, autofluorescent deposits in the subretinal space, and aberrant photoreceptor phagocytosis. Heterozygous (EK) mice displayed a delayed-onset milder retinal degeneration. Further, mutant receptors were mislocalized to the inner segments and perinuclear region. Though KK mouse rods displayed markedly decreased phototransduction, biochemical studies of the mutant rhodopsin revealed only minimally affected chromophore binding and G protein activation. Ablation of the chromophore by crossing KK mice with mice lacking the critical visual cycle protein LRAT slowed retinal degeneration, whereas blocking phototransduction by crossing KK mice with GNAT1-deficient mice slightly accelerated this process. This study highlights the importance of proper higher-order organization of rhodopsin in the native tissue and provides information about the signaling properties of this mutant rhodopsin. Additionally, these results suggest that patients heterozygous for the E150K mutation should be periodically reevaluated for delayed-onset retinal degeneration.
Acute respiratory infections are responsible for more than 4 million deaths each year. Neutrophils play an essential role in the innate immune response to lung infection. These cells have an armamentarium of pattern recognition molecules and antimicrobial agents that identify and eliminate pathogens. In the setting of infection, neutrophil triggering receptor expressed on myeloid cells 1 (TREM-1) amplifies inflammatory signaling. Here we demonstrate for the first time that TREM-1 also plays an important role in transepithelial migration of neutrophils into the airspace. We developed a TREM-1/3–deficient mouse model of pneumonia and found that absence of TREM-1/3 markedly increased mortality following
Late-stage breast cancer metastasis is driven by dysregulated TGF-β signaling, but the underlying molecular mechanisms have not been fully elucidated. We attempted to recapitulate tumor and metastatic microenvironments via the use of biomechanically compliant or rigid 3D organotypic cultures and combined them with global microRNA (miR) profiling analyses to identify miRs that were upregulated in metastatic breast cancer cells by TGF-β. Here we establish miR-181a as a TGF-β–regulated “metastamir” that enhanced the metastatic potential of breast cancers by promoting epithelial-mesenchymal transition, migratory, and invasive phenotypes. Mechanistically, inactivation of miR-181a elevated the expression of the proapoptotic molecule Bim, which sensitized metastatic cells to anoikis. Along these lines, miR-181a expression was essential in driving pulmonary micrometastatic outgrowth and enhancing the lethality of late-stage mammary tumors in mice. Finally, miR-181a expression was dramatically and selectively upregulated in metastatic breast tumors, particularly triple-negative breast cancers, and was highly predictive for decreased overall survival in human breast cancer patients. Collectively, our findings strongly implicate miR-181a as a predictive biomarker for breast cancer metastasis and patient survival, and consequently, as a potential therapeutic target in metastatic breast cancer.
Bacterial LPS (endotoxin) has been implicated in the pathogenesis of acute liver disease through its induction of the proinflammatory cytokine TNF-α. TNF-α is a key determinant of the outcome in a well-established mouse model of acute liver failure during septic shock. One possible mechanism for regulating TNF-α expression is through the control of protein elongation during translation, which would allow rapid cell adaptation to physiological changes. However, the regulation of translational elongation is poorly understood. We found that expression of p38γ/δ MAPK proteins is required for the elongation of nascent TNF-α protein in macrophages. The MKK3/6-p38γ/δ pathway mediated an inhibitory phosphorylation of eukaryotic elongation factor 2 (eEF2) kinase, which in turn promoted eEF2 activation (dephosphorylation) and subsequent TNF-α elongation. These results identify a new signaling pathway that regulates TNF-α production in LPS-induced liver damage and suggest potential cell-specific therapeutic targets for liver diseases in which TNF-α production is involved.
TLR activation on CD11c+ DCs triggers DC maturation, which is critical for T cell activation. Given the expansion of CD11c+ DCs during the progression of atherosclerosis and the key role of T cell activation in atherogenesis, we sought to understand the role of TLR signaling in CD11c+ DCs in atherosclerosis. To this end, we used a mouse model in which a key TLR adaptor involved in DC maturation, MYD88, is deleted in CD11c+ DCs. We transplanted bone marrow containing
Metastasis involves critical interactions between cancer and stromal cells. Intratumoral hypoxia promotes metastasis through activation of hypoxia-inducible factors (HIFs). We demonstrate that HIFs mediate paracrine signaling between breast cancer cells (BCCs) and mesenchymal stem cells (MSCs) to promote metastasis. In a mouse orthotopic implantation model, MSCs were recruited to primary breast tumors and promoted BCC metastasis to LNs and lungs in a HIF-dependent manner. Coculture of MSCs with BCCs augmented HIF activity in BCCs. Additionally, coculture induced expression of the chemokine CXCL10 in MSCs and the cognate receptor CXCR3 in BCCs, which was augmented by hypoxia.
Influenza causes substantial morbidity and mortality, and highly pathogenic and drug-resistant strains are likely to emerge in the future. Protease-activated receptor 1 (PAR1) is a thrombin-activated receptor that contributes to inflammatory responses at mucosal surfaces. The role of PAR1 in pathogenesis of virus infections is unknown. Here, we demonstrate that PAR1 contributed to the deleterious inflammatory response after influenza virus infection in mice. Activating PAR1 by administering the agonist TFLLR-NH2 decreased survival and increased lung inflammation after influenza infection. Importantly, both administration of a PAR1 antagonist and PAR1 deficiency protected mice from infection with influenza A viruses (IAVs). Treatment with the PAR1 agonist did not alter survival of mice deficient in plasminogen (PLG), which suggests that PLG permits and/or interacts with a PAR1 function in this model. PAR1 antagonists are in human trials for other indications. Our findings suggest that PAR1 antagonism might be explored as a treatment for influenza, including that caused by highly pathogenic H5N1 and oseltamivir-resistant H1N1 viruses.
Brown adipose tissue (BAT) is known to function in the dissipation of chemical energy in response to cold or excess feeding, and also has the capacity to modulate energy balance. To test the hypothesis that BAT is fundamental to the regulation of glucose homeostasis, we transplanted BAT from male donor mice into the visceral cavity of age- and sex-matched recipient mice. By 8–12 weeks following transplantation, recipient mice had improved glucose tolerance, increased insulin sensitivity, lower body weight, decreased fat mass, and a complete reversal of high-fat diet–induced insulin resistance. Increasing the quantity of BAT transplanted into recipient mice further improved the metabolic effects of transplantation. BAT transplantation increased insulin-stimulated glucose uptake in vivo into endogenous BAT, white adipose tissue (WAT), and heart muscle but, surprisingly, not skeletal muscle. The improved metabolic profile was lost when the BAT used for transplantation was obtained from
Deposition of amyloid β protein (Aβ) to form neuritic plaques in the brain is the pathological hallmark of Alzheimer’s disease (AD). Aβ is generated from sequential cleavages of the β-amyloid precursor protein (APP) by the β- and γ-secretases, and β-site APP-cleaving enzyme 1 (BACE1) is the β-secretase essential for Aβ generation. Previous studies have indicated that glycogen synthase kinase 3 (GSK3) may play a role in APP processing by modulating γ-secretase activity, thereby facilitating Aβ production. There are two highly conserved isoforms of GSK3: GSK3α and GSK3β. We now report that specific inhibition of GSK3β, but not GSK3α, reduced BACE1-mediated cleavage of APP and Aβ production by decreasing
Nephrocalcinosis, acute calcium oxalate (CaOx) nephropathy, and renal stone disease can lead to inflammation and subsequent renal failure, but the underlying pathological mechanisms remain elusive. Other crystallopathies, such as gout, atherosclerosis, and asbestosis, trigger inflammation and tissue remodeling by inducing IL-1β secretion, leading us to hypothesize that CaOx crystals may induce inflammation in a similar manner. In mice, intrarenal CaOx deposition induced tubular damage, cytokine expression, neutrophil recruitment, and renal failure. We found that CaOx crystals activated murine renal DCs to secrete IL-1β through a pathway that included NLRP3, ASC, and caspase-1. Despite a similar amount of crystal deposits, intrarenal inflammation, tubular damage, and renal dysfunction were abrogated in mice deficient in MyD88; NLRP3, ASC, and caspase-1; IL-1R; or IL-18. Nephropathy was attenuated by DC depletion, ATP depletion, or therapeutic IL-1 antagonism. These data demonstrated that CaOx crystals trigger IL-1β–dependent innate immunity via the NLRP3/ASC/caspase-1 axis in intrarenal mononuclear phagocytes and directly damage tubular cells, leading to the release of the NLRP3 agonist ATP. Furthermore, these results suggest that IL-1β blockade may prevent renal damage in nephrocalcinosis.
IL-17–producing CD8+ T (Tc17) cells are detectible in multiple sclerosis (MS) lesions; however, their contribution to the disease is unknown. To identify functions of Tc17 cells, we induced EAE, a murine model of MS, in mice lacking IFN regulatory factor 4 (IRF4). IRF4-deficient mice failed to generate Tc17 and Th17 cells and were resistant to EAE. After adoptive transfer of WT CD8+ T cells and subsequent immunization for EAE induction in these mice, the CD8+ T cells developed a Tc17 phenotype in the periphery but could not infiltrate the CNS. Similarly, transfer of small numbers of WT CD4+ T cells alone did not evoke EAE, but when transferred together with CD8+ T cells, IL-17–producing CD4+ (Th17) T cells accumulated in the CNS and mice developed severe disease. Th17 accumulation and development of EAE required IL-17A production by CD8+ T cells, suggesting that Tc17 cells are required to promote CD4+ T cell–mediated induction of EAE. Accordingly, patients with early-stage MS harbored a greater number of Tc17 cells in the cerebrospinal fluid than in peripheral blood. Our results reveal that Tc17 cells contribute to the initiation of CNS autoimmunity in mice and humans by supporting Th17 cell pathogenicity.
Hyperglycemia is a result of impaired insulin action on glucose production and disposal, and a major target of antidiabetic therapies. The study of insulin-independent regulatory mechanisms of glucose metabolism may identify new strategies to lower blood sugar levels. Here we demonstrate an unexpected metabolic function for IL-13 in the control of hepatic glucose production. IL-13 is a Th2 cytokine known to mediate macrophage alternative activation. Genetic ablation of
A cell-based therapy for the replacement of dopaminergic neurons has been a long-term goal in Parkinson’s disease research. Here, we show that autologous engraftment of A9 dopaminergic neuron-like cells induced from mesenchymal stem cells (MSCs) leads to long-term survival of the cells and restoration of motor function in hemiparkinsonian macaques. Differentiated MSCs expressed markers of A9 dopaminergic neurons and released dopamine after depolarization in vitro. The differentiated autologous cells were engrafted in the affected portion of the striatum. Animals that received transplants showed modest and gradual improvements in motor behaviors. Positron emission tomography (PET) using [11C]-CFT, a ligand for the dopamine transporter (DAT), revealed a dramatic increase in DAT expression, with a subsequent exponential decline over a period of 7 months. Kinetic analysis of the PET findings revealed that DAT expression remained above baseline levels for over 7 months. Immunohistochemical evaluations at 9 months consistently demonstrated the existence of cells positive for DAT and other A9 dopaminergic neuron markers in the engrafted striatum. These data suggest that transplantation of differentiated autologous MSCs may represent a safe and effective cell therapy for Parkinson’s disease.
MicroRNAs (miRNAs) and methionine adenosyltransferase 1A (
Aberrant expression of the homeodomain transcription factor CDX2 occurs in most cases of acute myeloid leukemia (AML) and promotes leukemogenesis, making CDX2, in principle, an attractive therapeutic target. Conversely, CDX2 acts as a tumor suppressor in colonic epithelium. The effectors mediating the leukemogenic activity of CDX2 and the mechanism underlying its context-dependent properties are poorly characterized, and strategies for interfering with CDX2 function in AML remain elusive. We report data implicating repression of the transcription factor KLF4 as important for the oncogenic activity of CDX2, and demonstrate that CDX2 differentially regulates KLF4 in AML versus colon cancer cells through a mechanism that involves tissue-specific patterns of promoter binding and epigenetic modifications. Furthermore, we identified deregulation of the PPARγ signaling pathway as a feature of CDX2-associated AML and observed that PPARγ agonists derepressed KLF4 and were preferentially toxic to CDX2+ leukemic cells. These data delineate transcriptional programs associated with CDX2 expression in hematopoietic cells, provide insight into the antagonistic duality of CDX2 function in AML versus colon cancer, and suggest reactivation of KLF4 expression, through modulation of PPARγ signaling, as a therapeutic modality in a large proportion of AML patients.
Despite efforts to understand and treat acute myeloid leukemia (AML), there remains a need for more comprehensive therapies to prevent AML-associated relapses. To identify new therapeutic strategies for AML, we screened a library of on- and off-patent drugs and identified the antimalarial agent mefloquine as a compound that selectively kills AML cells and AML stem cells in a panel of leukemia cell lines and in mice. Using a yeast genome-wide functional screen for mefloquine sensitizers, we identified genes associated with the yeast vacuole, the homolog of the mammalian lysosome. Consistent with this, we determined that mefloquine disrupts lysosomes, directly permeabilizes the lysosome membrane, and releases cathepsins into the cytosol. Knockdown of the lysosomal membrane proteins LAMP1 and LAMP2 resulted in decreased cell viability, as did treatment of AML cells with known lysosome disrupters. Highlighting a potential therapeutic rationale for this strategy, leukemic cells had significantly larger lysosomes compared with normal cells, and leukemia-initiating cells overexpressed lysosomal biogenesis genes. These results demonstrate that lysosomal disruption preferentially targets AML cells and AML progenitor cells, providing a rationale for testing lysosomal disruption as a novel therapeutic strategy for AML.
Neurofibromatosis type 1 (NF1) predisposes individuals to the development of juvenile myelomonocytic leukemia (JMML), a fatal myeloproliferative disease (MPD). In genetically engineered murine models, nullizygosity of
Children with neurofibromatosis type 1 (NF1) are predisposed to juvenile myelomonocytic leukemia (JMML), an aggressive myeloproliferative neoplasm (MPN) that is refractory to conventional chemotherapy. Conditional inactivation of the
Neurofibromatosis type 1 (NF1) patients develop benign neurofibromas and malignant peripheral nerve sheath tumors (MPNST). These incurable peripheral nerve tumors result from loss of
Down syndrome (DS) patients exhibit abnormalities of hippocampal-dependent explicit memory, a feature that is replicated in relevant mouse models of the disease. Adult hippocampal neurogenesis, which is impaired in DS and other neuropsychiatric diseases, plays a key role in hippocampal circuit plasticity and has been implicated in learning and memory. However, it remains unknown whether increasing adult neurogenesis improves hippocampal plasticity and behavioral performance in the multifactorial context of DS. We report that, in the Ts65Dn mouse model of DS, chronic administration of lithium, a clinically used mood stabilizer, promoted the proliferation of neuronal precursor cells through the pharmacological activation of the Wnt/β-catenin pathway and restored adult neurogenesis in the hippocampal dentate gyrus (DG) to physiological levels. The restoration of adult neurogenesis completely rescued the synaptic plasticity of newborn neurons in the DG and led to the full recovery of behavioral performance in fear conditioning, object location, and novel object recognition tests. These findings indicate that reestablishing a functional population of hippocampal newborn neurons in adult DS mice rescues hippocampal plasticity and memory and implicate adult neurogenesis as a promising therapeutic target to alleviate cognitive deficits in DS patients.
Low-grade chronic inflammation is a major characteristic of obesity and results from deregulated white adipose tissue function. Consequently, there is interest in identifying the underlying regulatory mechanisms and components that drive adipocyte inflammation. Here, we report that expression of the transcriptional corepressor complex subunits GPS2 and SMRT was significantly reduced in obese adipose tissue, inversely correlated to inflammatory status, and was restored upon gastric bypass surgery–induced weight loss in morbid obesity. These alterations correlated with reduced occupancy of the corepressor complex at inflammatory promoters, providing a mechanistic explanation for elevated inflammatory transcription. In support of these correlations, RNAi-mediated depletion of GPS2 and SMRT from cultured human adipocytes promoted derepression of inflammatory transcription and elevation of obesity-associated inflammatory markers, such as IL-6 and MCP-1. Furthermore, we identified a regulatory cascade containing PPARγ and TWIST1 that controlled the expression of GPS2 and SMRT in human adipocytes. These findings were clinically relevant, because treatment of diabetic obese patients with pioglitazone, an antidiabetic and antiinflammatory PPARγ agonist, restored expression of TWIST1, GPS2, and SMRT in adipose tissue. Collectively, our findings identify alterations in a regulatory transcriptional network in adipocytes involving the dysregulation of a specific corepressor complex as among the initiating events promoting adipose tissue inflammation in human obesity.
HIV-1 accumulates mutations in and around reactive epitopes to escape recognition and killing by CD8+ T cells. Measurements of HIV-1 time to escape should therefore provide information on which parameters are most important for T cell–mediated in vivo control of HIV-1. Primary HIV-1–specific T cell responses were fully mapped in 17 individuals, and the time to virus escape, which ranged from days to years, was measured for each epitope. While higher magnitude of an individual T cell response was associated with more rapid escape, the most significant T cell measure was its relative immunodominance measured in acute infection. This identified subject-level or “vertical” immunodominance as the primary determinant of in vivo CD8+ T cell pressure in HIV-1 infection. Conversely, escape was slowed significantly by lower population variability, or entropy, of the epitope targeted. Immunodominance and epitope entropy combined to explain half of all the variability in time to escape. These data explain how CD8+ T cells can exert significant and sustained HIV-1 pressure even when escape is very slow and that within an individual, the impacts of other T cell factors on HIV-1 escape should be considered in the context of immunodominance.
The detection of estrogen receptor-α (ERα) in osteoblasts and osteoclasts over 20 years ago suggested that direct effects of estrogens on both of these cell types are responsible for their beneficial effects on the skeleton, but the role of ERα in osteoblast lineage cells has remained elusive. In addition, estrogen activation of ERα in osteoclasts can only account for the protective effect of estrogens on the cancellous, but not the cortical, bone compartment that represents 80% of the entire skeleton. Here, we deleted
High-grade gliomas (HGGs) are incurable brain tumors that are characterized by the presence of glioma-initiating cells (GICs). GICs are essential to tumor aggressiveness and retain the capacity for self-renewal and multilineage differentiation as long as they reside in the perivascular niche. ID proteins are master regulators of stemness and anchorage to the extracellular niche microenvironment, suggesting that they may play a role in maintaining GICs. Here, we modeled the probable therapeutic impact of ID inactivation in HGG by selective ablation of
Little is known about the transcriptional regulation of tumor angiogenesis, and tumor ECs (tECs) remain poorly characterized. Here, we studied the expression pattern of the transcription factor
Primary immune thrombocytopenia (ITP) is a disorder caused by autoantibody-mediated platelet destruction and decreased platelet production. Rituximab, a B cell–depleting agent, has become the first-line treatment for ITP; however, patients with refractory disease usually require splenectomy. We identified antibody-secreting cells as the major splenic B cell population that is resistant to rituximab. The phenotype, antibody specificity, and gene expression profile of these cells were characterized and compared to those of antibody-secreting cells from untreated ITP spleens and from healthy tissues. Antiplatelet-specific plasma cells (PC) were detected in the spleens of patients with ITP up to 6 months after rituximab treatment, and the PC population displayed a long-lived program similar to the one of bone marrow PC, thus explaining for most of these patients the absence of response to rituximab and the response to splenectomy. When analyzed by multiplex PCR at the single-cell level, normal splenic PC showed a markedly different gene expression profile, with an intermediate signature, including genes characteristic of both long-lived PC and proliferating plasmablasts. Surprisingly, long-lived PC were not detected in untreated ITP spleens. These results suggest that the milieu generated by B cell depletion promotes the differentiation and settlement of long-lived PC in the spleen.
Postprandially, the liver experiences an extensive metabolic reprogramming that is required for the switch from glucose production to glucose assimilation. Upon refeeding, the unfolded protein response (UPR) is rapidly, though only transiently, activated. Activation of the UPR results in a cessation of protein translation, increased chaperone expression, and increased ER-mediated protein degradation, but it is not clear how the UPR is involved in the postprandial switch to alternate fuel sources. Activation of the inositol-requiring enzyme 1 (IRE1) branch of the UPR signaling pathway triggers expression of the transcription factor Xbp1s. Using a mouse model with liver-specific inducible Xbp1s expression, we demonstrate that Xbp1s is sufficient to provoke a metabolic switch characteristic of the postprandial state, even in the absence of caloric influx. Mechanistically, we identified UDP-galactose-4-epimerase (GalE) as a direct transcriptional target of Xbp1s and as the key mediator of this effect. Our results provide evidence that the Xbp1s/GalE pathway functions as a novel regulatory nexus connecting the UPR to the characteristic postprandial metabolic changes in hepatocytes.
The scaffold protein p62 (sequestosome 1; SQSTM1) is an emerging key molecular link among the metabolic, immune, and proliferative processes of the cell. Here, we report that adipocyte-specific, but not CNS-, liver-, muscle-, or myeloid-specific
Gastric adenocarcinoma is strongly associated with
Cyclin D1b is a splice variant of the cell cycle regulator cyclin D1 and is known to harbor divergent and highly oncogenic functions in human cancer. While cyclin D1b is induced during disease progression in many cancer types, the mechanisms underlying cyclin D1b function remain poorly understood. Herein, cell and human tumor xenograft models of prostate cancer were utilized to resolve the downstream pathways that are required for the protumorigenic functions of cyclin D1b. Specifically, cyclin D1b was found to modulate the expression of a large transcriptional network that cooperates with androgen receptor (AR) signaling to enhance tumor cell growth and invasive potential. Notably, cyclin D1b promoted AR-dependent activation of genes associated with metastatic phenotypes. Further exploration determined that transcriptional induction of
Thyroid hormone is well known for its profound direct effects on cardiovascular function and metabolism. Recent evidence, however, suggests that the hormone also regulates these systems indirectly through the central nervous system. While some of the molecular mechanisms underlying the hormone’s central control of metabolism have been identified, its actions in the central cardiovascular control have remained enigmatic. Here, we describe a previously unknown population of parvalbuminergic neurons in the anterior hypothalamus that requires thyroid hormone receptor signaling for proper development. Specific stereotaxic ablation of these cells in the mouse resulted in hypertension and temperature-dependent tachycardia, indicating a role in the central autonomic control of blood pressure and heart rate. Moreover, the neurons exhibited intrinsic temperature sensitivity in patch-clamping experiments, providing a new connection between cardiovascular function and core temperature. Thus, the data identify what we believe to be a novel hypothalamic cell population potentially important for understanding hypertension and indicate developmental hypothyroidism as an epigenetic risk factor for cardiovascular disorders. Furthermore, the findings may be beneficial for treatment of the recently identified patients that have a mutation in thyroid hormone receptor α1.
Because of the high risk of recurrence in high-grade serous ovarian carcinoma (HGS-OvCa), the development of outcome predictors could be valuable for patient stratification. Using the catalog of The Cancer Genome Atlas (TCGA), we developed subtype and survival gene expression signatures, which, when combined, provide a prognostic model of HGS-OvCa classification, named “
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