Illustration of an owl monkey. These animals possess a fusion gene, TRIMCyp, that is able to block HIV-1 infection. The gene was created by retrotransposition of the cDNA encoding an HIV-1 capsid-binding protein, cyclophilin A, into the antiretroviral gene TRIM5. Following the example of the owl monkey, Neagu and colleagues designed a human TRIM5-cyclophilin fusion protein and show that it is an ideal candidate for anti–HIV-1 gene therapy (page 3035).
IIlustration by Bruce Worden.
Physicians in the United States have a unique appreciation of the tremendous successes and even greater potential of our health care system, yet we also endure firsthand its woeful deficiencies. In the ongoing debate about how to improve the current health care structure in the United States, our individual voices have been all too quiet. No single health care organization, nor its spokesmen, speaks for the broad range of physicians’ opinions. Rather, doctors must make every effort, and indeed have an obligation, to speak forcefully as informed participants in this important process.
Jonathan A. Epstein, Laurence A. Turka, Morris Birnbaum, Gary Koretzky
Eric G. Neilson
Jeffrey S. Flier
C. Ronald Kahn
Sepsis is characterized by a severe inflammatory response to infection, and its complications, including acute kidney injury, can be fatal. Animal models that correctly mimic human disease are extremely valuable because they hasten the development of clinically useful therapeutics. Too often, however, animal models do not properly mimic human disease. In this Review, we outline a bedside-to-bench-to-bedside approach that has resulted in improved animal models for the study of sepsis — a complex disease for which preventive and therapeutic strategies are unfortunately lacking. We also highlight a few of the promising avenues for therapeutic advances and biomarkers for sepsis and sepsis-induced acute kidney injury. Finally, we review how the study of drug targets and biomarkers are affected by and in turn have influenced these evolving animal models.
Kent Doi, Asada Leelahavanichkul, Peter S.T. Yuen, Robert A. Star
When Brian J. Druker was a boy, he wanted to be a baseball player; Nicholas B. Lydon had his sights set on flying jets; Charles L. Sawyers knew early on that he wanted to practice medicine. Decades later, this trio (Figure 1) would collaborate to revolutionize the treatment of chronic myelogenous leukemia (CML). On September 14, the Albert and Mary Lasker Foundation announced that they will recognize these researchers with the 2009 Lasker-DeBakey Clinical Medical Research Award for research that led to the development of drugs, including imatinib (Gleevec) and dasatinib (Sprycel), which have converted CML from a fatal cancer to a manageable condition. Notably, imatinib was the first successful, molecularly targeted, small-molecule drug approved for cancer therapy. The winners spoke with the JCI about their success story.
Bone undergoes a continuous cycle of renewal, and osteoclasts — the cells responsible for bone resorption — play a pivotal role in bone homeostasis. This resorption is largely mediated by inflammatory cytokines such as TNF-α. In this issue of the JCI, Yao et al. demonstrate that the NF-κB precursor protein NF-κB2 (p100) acts as a negative regulator of osteoclastogenesis (see the related article beginning on page 3024). TNF-α induced a sustained accumulation of p100 in osteoclast precursors, and TNF-α–induced osteoclast formation was markedly increased in Nfkb2–/– mice. They also found that TNF receptor–associated factor 3 (TRAF3) is involved in the posttranslational regulation of p100 expression. These results suggest that blockade of the processing of p100 is a novel strategy to treat TNF-α–related bone diseases such as RA.
Sakae Tanaka, Hiroyasu Nakano
The role of B cells and autoimmunity as contributing factors to poor neurological outcomes following spinal cord injury (SCI) is poorly understood. The study by Ankeny et al., in this issue of the JCI, identifies a new immunopathological mechanism arising after SCI in mice (see the related article beginning on page 2990). The study shows that B cells produce pathogenic antibodies that impair lesion repair, resulting in worse neurological outcome. This new understanding of SCI disease pathogenesis, if confirmed in humans, reveals potential avenues for the development of novel neuroprotective immunotherapies.
Gregory A. Dekaban, Sakina Thawer
The aging process affects all aspects of the immune system, particularly the T cells. The immune system in older individuals is often characterized by lower T cell numbers, lower naive/memory T cell ratios, and lower T cell diversity. Most measures of inflammation increase with age. Why this happens, and why there is so much person-to-person variability in these changes, is not known. In this issue of the JCI, Sauce and colleagues show that removal of the thymus during infancy results in premature onset of many of these age-associated changes to the immune system (see the related article beginning on page 3070). The effect of thymectomy was particularly notable in those individuals who acquired CMV infection. Data from this study, as well as data from other observational settings, suggest that reduced thymic function and persistent viral infections combine to accelerate a decline in immunologic function.
Ronald E. Gress, Steven G. Deeks
Secondary hyperparathyroidism often occurs in chronic kidney disease (CKD) and vitamin D deficiency, resulting in increased fractures and mortality. Understanding factors that stimulate parathyroid hormone (PTH) synthesis is important for devising methods to treat this condition. Previous work has demonstrated that murine Pth mRNA levels are regulated by proteins that bind AU-rich elements (AREs) within the 3′ UTR region of Pth mRNA and influence Pth mRNA stability. In this issue of the JCI, Nechama et al. demonstrate that in murine secondary hyperparathyroidism associated with CKD or Ca deficiency, the activity of Pin1, a peptidyl-prolyl isomerase, is reduced (see the related article beginning on page 3102). Reduced Pin1 activity resulted in the phosphorylation and degradation of an ARE-binding protein, K-homology splicing regulator protein (KSRP), which normally enhances the degradation of Pth mRNA. The activity of other ARE-binding proteins, such as AU-rich binding factor 1 (AUF1), that increase Pth mRNA stability, was increased, thereby increasing PTH synthesis. This work suggests new ways by which to regulate PTH synthesis in secondary hyperparathyroidism.
Inflammation-associated lung injury is a major cause of morbidity and mortality for patients in intensive care units. Although the cellular and molecular events that initiate lung inflammation are now well understood, the mechanisms that promote its resolution remain poorly defined. In this issue of the JCI, D’Alessio et al. show in a mouse model that recovery from acute lung injury is not simply a passive process, but involves Tregs in an active resolution program (see the related article beginning on page 2898).
Anthony Pietropaoli, Steve N. Georas
Individuals carrying a mutation in the breast cancer 1, early onset gene (BRCA1) are at increased risk of breast or ovarian cancer and thus are candidates for risk reduction strategies such as oophorectomy and mastectomy. A recurring problem in the clinic is that many detectable changes within the BRCA1 gene produce subtle alterations to the protein that are not easily recognized as either harmful (loss-of-function) alleles or harmless and thus inconsequential polymorphisms. In this issue of the JCI, Chang, Sharan, and colleagues describe a novel system to evaluate human BRCA1 alleles for in vivo function using BACs containing human BRCA1 vectors in mouse cells and embryos (see the related article beginning on page 3160). This strategy should provide new avenues for clinicians to interpret results of genetic testing of BRCA1 variants and for researchers to study the basic molecular mechanisms of BRCA1 function in in vivo model systems.
Susan M. Domchek, Roger A. Greenberg
Acute lung injury (ALI) is characterized by rapid alveolar injury, inflammation, cytokine induction, and neutrophil accumulation. Although early events in the pathogenesis of ALI have been defined, the mechanisms underlying resolution are unknown. As a model of ALI, we administered intratracheal (i.t.) LPS to mice and observed peak lung injury 4 days after the challenge, with resolution by day 10. Numbers of alveolar lymphocytes increased as injury resolved. To examine the role of lymphocytes in this response, lymphocyte-deficient Rag-1–/– and C57BL/6 WT mice were exposed to i.t. LPS. The extent of injury was similar between the groups of mice through day 4, but recovery was markedly impaired in the Rag-1–/– mice. Adoptive transfer studies revealed that infusion of CD4+CD25+Foxp3+ Tregs as late as 24 hours after i.t. LPS normalized resolution in Rag-1–/– mice. Similarly, Treg depletion in WT mice delayed recovery. Treg transfer into i.t. LPS–exposed Rag-1–/– mice also corrected the elevated levels of alveolar proinflammatory cytokines and increased the diminished levels of alveolar TGF-β and neutrophil apoptosis. Mechanistically, Treg-mediated resolution of lung injury was abrogated by TGF-β inhibition. Moreover, BAL of patients with ALI revealed dynamic changes in CD3+CD4+CD25hiCD127loFoxp3+ cells. These results indicate that Tregs modify innate immune responses during resolution of lung injury and suggest potential targets for treating ALI, for which there are no specific therapies currently available.
Franco R. D’Alessio, Kenji Tsushima, Neil R. Aggarwal, Erin E. West, Matthew H. Willett, Martin F. Britos, Matthew R. Pipeling, Roy G. Brower, Rubin M. Tuder, John F. McDyer, Landon S. King
Various acute and chronic inflammatory stimuli increase the number and activity of pulmonary mucus-producing goblet cells, and goblet cell hyperplasia and excess mucus production are central to the pathogenesis of chronic pulmonary diseases. However, little is known about the transcriptional programs that regulate goblet cell differentiation. Here, we show that SAM-pointed domain–containing Ets-like factor (SPDEF) controls a transcriptional program critical for pulmonary goblet cell differentiation in mice. Initial cell-lineage–tracing analysis identified nonciliated secretory epithelial cells, known as Clara cells, as the progenitors of goblet cells induced by pulmonary allergen exposure in vivo. Furthermore, in vivo expression of SPDEF in Clara cells caused rapid and reversible goblet cell differentiation in the absence of cell proliferation. This was associated with enhanced expression of genes regulating goblet cell differentiation and protein glycosylation, including forkhead box A3 (Foxa3), anterior gradient 2 (Agr2), and glucosaminyl (N-acetyl) transferase 3, mucin type (Gcnt3). Consistent with these findings, levels of SPDEF and FOXA3 were increased in mouse goblet cells after sensitization with pulmonary allergen, and the proteins were colocalized in goblet cells lining the airways of patients with chronic lung diseases. Deletion of the mouse Spdef gene resulted in the absence of goblet cells in tracheal/laryngeal submucosal glands and in the conducting airway epithelium after pulmonary allergen exposure in vivo. These data show that SPDEF plays a critical role in regulating a transcriptional network mediating the goblet cell differentiation and mucus hyperproduction associated with chronic pulmonary disorders.
Gang Chen, Thomas R. Korfhagen, Yan Xu, Joseph Kitzmiller, Susan E. Wert, Yutaka Maeda, Alexander Gregorieff, Hans Clevers, Jeffrey A. Whitsett
ER stress–induced apoptosis is implicated in various pathological conditions, but the mechanisms linking ER stress–mediated signaling to downstream apoptotic pathways remain unclear. Using human and mouse cell culture and in vivo mouse models of ER stress–induced apoptosis, we have shown that cytosolic calcium resulting from ER stress induces expression of the Fas death receptor through a pathway involving calcium/calmodulin-dependent protein kinase IIγ (CaMKIIγ) and JNK. Remarkably, CaMKIIγ was also responsible for processes involved in mitochondrial-dependent apoptosis, including release of mitochondrial cytochrome c and loss of mitochondrial membrane potential. CaMKII-dependent apoptosis was also observed in a number of cultured human and mouse cells relevant to ER stress–induced pathology, including cultured macrophages, endothelial cells, and neuronal cells subjected to proapoptotic ER stress. Moreover, WT mice subjected to systemic ER stress showed evidence of macrophage mitochondrial dysfunction and apoptosis, renal epithelial cell apoptosis, and renal dysfunction, and these effects were markedly reduced in CaMKIIγ-deficient mice. These data support an integrated model in which CaMKII serves as a unifying link between ER stress and the Fas and mitochondrial apoptotic pathways. Our study also revealed what we believe to be a novel proapoptotic function for CaMKII, namely, promotion of mitochondrial calcium uptake. These findings raise the possibility that CaMKII inhibitors could be useful in preventing apoptosis in pathological settings involving ER stress–induced apoptosis.
Jenelle M. Timmins, Lale Ozcan, Tracie A. Seimon, Gang Li, Cristina Malagelada, Johannes Backs, Thea Backs, Rhonda Bassel-Duby, Eric N. Olson, Mark E. Anderson, Ira Tabas
Protein S (ProS) is a blood anticoagulant encoded by the Pros1 gene, and ProS deficiencies are associated with venous thrombosis, stroke, and autoimmunity. These associations notwithstanding, the relative risk that reduced ProS expression confers in different disease settings has been difficult to assess without an animal model. We have now described a mouse model of ProS deficiency and shown that all Pros1–/– mice die in utero, from a fulminant coagulopathy and associated hemorrhages. Although ProS is known to act as a cofactor for activated Protein C (aPC), plasma from Pros1+/– heterozygous mice exhibited accelerated thrombin generation independent of aPC, and Pros1 mutants displayed defects in vessel development and function not seen in mice lacking protein C. Similar vascular defects appeared in mice in which Pros1 was conditionally deleted in vascular smooth muscle cells. Mutants in which Pros1 was deleted specifically in hepatocytes, which are thought to be the major source of ProS in the blood, were viable as adults and displayed less-severe coagulopathy without vascular dysgenesis. Finally, analysis of mutants in which Pros1 was deleted in endothelial cells indicated that these cells make a substantial contribution to circulating ProS. These results demonstrate that ProS is a pleiotropic anticoagulant with aPC-independent activities and highlight new roles for ProS in vascular development and homeostasis.
Tal Burstyn-Cohen, Mary Jo Heeb, Greg Lemke
Inflammation is associated with blood vessel and lymphatic vessel proliferation and remodeling. The microvasculature of the mouse trachea provides an ideal opportunity to study this process, as Mycoplasma pulmonis infection of mouse airways induces widespread and sustained vessel remodeling, including enlargement of capillaries into venules and lymphangiogenesis. Although the mediators responsible for these vascular changes in mice have not been identified, VEGF-A is known not to be involved. Here, we sought to determine whether TNF-α drives the changes in blood vessels and lymphatics in M. pulmonis–infected mice. The endothelial cells, but not pericytes, of blood vessels, but not lymphatics, were immunoreactive for TNF receptor 1 (TNF-R1) and lymphotoxin B receptors. Most TNF-R2 immunoreactivity was on leukocytes. Infection resulted in a large and sustained increase in TNF-α expression, as measured by real-time quantitative RT-PCR, and smaller increases in lymphotoxins and TNF receptors that preceded vessel remodeling. Substantially less vessel remodeling and lymphangiogenesis occurred when TNF-α signaling was inhibited by a blocking antibody or was silenced in Tnfr1–/– mice. When administered after infection was established, the TNF-α–specific antibody slowed but did not reverse blood vessel remodeling and lymphangiogenesis. The action of TNF-α on blood vessels is probably mediated through direct effects on endothelial cells, but its effects on lymphangiogenesis may require inflammatory mediators from recruited leukocytes. We conclude that TNF-α is a strong candidate for a mediator that drives blood vessel remodeling and lymphangiogenesis in inflammation.
Peter Baluk, Li-Chin Yao, Jennifer Feng, Talia Romano, Sonia S. Jung, Jessica L. Schreiter, Li Yan, David J. Shealy, Donald M. McDonald
Viruses that infect T cells, including those of the lentivirus genus, such as HIV-1, modulate the responsiveness of infected T cells to stimulation by interacting APCs in a manner that renders the T cells more permissive for viral replication. HIV-1 and other primate lentiviruses use their Nef proteins to manipulate the T cell/APC contact zone, the immunological synapse (IS). It is known that primate lentiviral Nef proteins differ substantially in their ability to modulate cell surface expression of the TCR-CD3 and CD28 receptors critical for the formation and function of the IS. However, the impact of these differences in Nef function on the interaction and communication between virally infected T cells and primary APCs has not been investigated. Here we have used primary human cells to show that Nef proteins encoded by HIV-2 and most SIVs, which downmodulate cell surface expression of TCR-CD3, disrupt formation of the IS between infected T cells and Ag-presenting macrophages or DCs. In contrast, nef alleles from HIV-1 and its simian precursor SIVcpz failed to suppress synapse formation and events downstream of TCR signaling. Our data suggest that most primate lentiviruses disrupt communication between virally infected CD4+ Th cells and APCs, whereas HIV-1 and its SIV precursor have largely lost this capability. The resulting differences in the levels of T cell activation and apoptosis may play a role in the pathogenesis of AIDS.
Nathalie Arhel, Martin Lehmann, Karen Clauß, G. Ulrich Nienhaus, Vincent Piguet, Frank Kirchhoff
X-linked lymphoproliferative disease (XLP) is a rare congenital immunodeficiency that leads to an extreme, usually fatal increase in the number of lymphocytes upon infection with EBV. It is most commonly defined molecularly by loss of expression of SLAM-associated protein (SAP). Despite this, there is little understanding of how SAP deficiency causes lymphocytosis following EBV infection. Here we show that T cells from individuals with XLP are specifically resistant to apoptosis mediated by TCR restimulation, a process that normally constrains T cell expansion during immune responses. Expression of SAP and the SLAM family receptor NK, T, and B cell antigen (NTB-A) were required for TCR-induced upregulation of key pro-apoptotic molecules and subsequent apoptosis. Further, SAP/NTB-A signaling augmented the strength of the proximal TCR signal to achieve the threshold required for restimulation-induced cell death (RICD). Strikingly, TCR ligation in activated T cells triggered increased recruitment of SAP to NTB-A, dissociation of the phosphatase SHP-1, and colocalization of NTB-A with CD3 aggregates. In contrast, NTB-A and SHP-1 contributed to RICD resistance in XLP T cells. Our results reveal what we believe to be novel roles for NTB-A and SAP in regulating T cell homeostasis through apoptosis and provide mechanistic insight into the pathogenesis of lymphoproliferative disease in XLP.
Andrew L. Snow, Rebecca A. Marsh, Scott M. Krummey, Philip Roehrs, Lisa R. Young, Kejian Zhang, Jack van Hoff, Deepali Dhar, Kim E. Nichols, Alexandra H. Filipovich, Helen C. Su, Jack J. Bleesing, Michael J. Lenardo
Traumatic injury to the mammalian spinal cord activates B cells, which culminates in the synthesis of autoantibodies. The functional significance of this immune response is unclear. Here, we show that locomotor recovery was improved and lesion pathology was reduced after spinal cord injury (SCI) in mice lacking B cells. After SCI, antibody-secreting B cells and Igs were present in the cerebrospinal fluid and/or injured spinal cord of WT mice but not mice lacking B cells. In mice with normal B cell function, large deposits of antibody and complement component 1q (C1q) accumulated at sites of axon pathology and demyelination. Antibodies produced after SCI caused pathology, in part by activating intraspinal complement and cells bearing Fc receptors. These data indicate that B cells, through the production of antibodies, affect pathology in SCI. One or more components of this pathologic immune response could be considered as novel therapeutic targets for minimizing tissue injury and/or promoting repair after SCI.
Daniel P. Ankeny, Zhen Guan, Phillip G. Popovich
EGFR is a major anticancer drug target in human epithelial tumors. One effective class of agents is the tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib. These drugs induce dramatic responses in individuals with lung adenocarcinomas characterized by mutations in exons encoding the EGFR tyrosine kinase domain, but disease progression invariably occurs. A major reason for such acquired resistance is the outgrowth of tumor cells with additional TKI-resistant EGFR mutations. Here we used relevant transgenic mouse lung tumor models to evaluate strategies to overcome the most common EGFR TKI resistance mutation, T790M. We treated mice bearing tumors harboring EGFR mutations with a variety of anticancer agents, including a new irreversible EGFR TKI that is under development (BIBW-2992) and the EGFR-specific antibody cetuximab. Surprisingly, we found that only the combination of both agents together induced dramatic shrinkage of erlotinib-resistant tumors harboring the T790M mutation, because together they efficiently depleted both phosphorylated and total EGFR. We suggest that these studies have immediate therapeutic implications for lung cancer patients, as dual targeting with cetuximab and a second-generation EGFR TKI may be an effective strategy to overcome T790M-mediated drug resistance. Moreover, this approach could serve as an important model for targeting other receptor tyrosine kinases activated in human cancers.
Lucia Regales, Yixuan Gong, Ronglai Shen, Elisa de Stanchina, Igor Vivanco, Aviva Goel, Jason A. Koutcher, Maria Spassova, Ouathek Ouerfelli, Ingo K. Mellinghoff, Maureen F. Zakowski, Katerina A. Politi, William Pao
Cytokines orchestrate the tumor-promoting interplay between malignant cells and the immune system. In many experimental and human cancers, the cytokine TNF-α is an important component of this interplay, but its effects are pleiotropic and therefore remain to be completely defined. Using a mouse model of ovarian cancer in which either TNF receptor 1 (TNFR1) signaling was manipulated in different leukocyte populations or TNF-α was neutralized by antibody treatment, we found that this inflammatory cytokine maintained TNFR1-dependent IL-17 production by CD4+ cells and that this led to myeloid cell recruitment into the tumor microenvironment and enhanced tumor growth. Consistent with this, in patients with advanced cancer, treatment with the TNF-α–specific antibody infliximab substantially reduced plasma IL-17 levels. Furthermore, expression of IL-1R and IL-23R was downregulated in CD4+CD25– cells isolated from ascites of ovarian cancer patients treated with infliximab. We have also shown that genes ascribed to the Th17 pathway map closely with the TNF-α signaling pathway in ovarian cancer biopsy samples, showing particularly high levels of expression of genes encoding IL-23, components of the NF-κB system, TGF-β1, and proteins involved in neutrophil activation. We conclude that chronic production of TNF-α in the tumor microenvironment increases myeloid cell recruitment in an IL-17–dependent manner that contributes to the tumor-promoting action of this proinflammatory cytokine.
Kellie A. Charles, Hagen Kulbe, Robin Soper, Monica Escorcio-Correia, Toby Lawrence, Anne Schultheis, Probir Chakravarty, Richard G. Thompson, George Kollias, John F. Smyth, Frances R. Balkwill, Thorsten Hagemann
TNF and RANKL mediate bone destruction in common bone diseases, including osteoarthritis and RA. They activate NF-κB canonical signaling directly in osteoclast precursors (OCPs) to induce osteoclast formation in vitro. However, unlike RANKL, TNF does not activate the alternative NF-κB pathway efficiently to process the IκB protein NF-κB p100 to NF-κB p52, nor does it appear to induce osteoclast formation in vivo in the absence of RANKL. Here, we show that TNF limits RANKL- and TNF-induced osteoclast formation in vitro and in vivo by increasing NF-κB p100 protein accumulation in OCPs. In contrast, TNF induced robust osteoclast formation in vivo in mice lacking RANKL or RANK when the mice also lacked NF-κB p100, and TNF-Tg mice lacking NF-κB p100 had more severe joint erosion and inflammation than did TNF-Tg littermates. TNF, but not RANKL, increased OCP expression of TNF receptor–associated factor 3 (TRAF3), an adapter protein that regulates NF-κB p100 levels in B cells. TRAF3 siRNA prevented TNF-induced NF-κB p100 accumulation and inhibition of osteoclastogenesis. These findings suggest that upregulation of TRAF3 or NF-κB p100 expression or inhibition of NF-κB p100 degradation in OCPs could limit bone destruction and inflammation-induced bone loss in common bone diseases.
Zhenqiang Yao, Lianping Xing, Brendan F. Boyce
New World monkeys of the genus Aotus synthesize a fusion protein (AoT5Cyp) containing tripartite motif-containing 5 (TRIM5) and cyclophilin A (CypA) that potently blocks HIV-1 infection. We attempted to generate a human HIV-1 inhibitor modeled after AoT5Cyp, by fusing human CypA to human TRIM5 (hT5Cyp). Of 13 constructs, 3 showed substantial HIV-1–inhibitory activity when expressed in human cell lines. This activity required capsid binding by CypA and correlated with CypA linkage to the TRIM5a capsid-specificity determinant and the ability to form cytoplasmic bodies. CXCR4- and CCR5-tropic HIV-1 clones and primary isolates were inhibited from infecting multiple human macrophage and T cell lines and primary cells by hT5Cyp, as were HIV-2ROD, SIVAGMtan, FIVPET, and a circulating HIV-1 isolate previously reported to be AoT5Cyp resistant. The anti–HIV-1 activity of hT5Cyp was surprisingly more effective than that of the well-characterized rhesus TRIM5α, especially in T cells. hT5Cyp also blocked HIV-1 infection of primary CD4+ T cells and macrophages and conferred a survival advantage to these cells without disrupting their function. Extensive attempts to elicit HIV-1 resistance to hT5Cyp were unsuccessful. Finally, Rag2–/–γc–/– mice were engrafted with human CD4+ T cells that had been transduced by optimized lentiviral vectors bearing hT5Cyp. Upon challenge with HIV-1, these mice showed decreased viremia and productive infection in lymphoid organs and preserved numbers of human CD4+ T cells. We conclude that hT5Cyp is an extraordinarily robust inhibitor of HIV-1 replication and a promising anti–HIV-1 gene therapy candidate.
Martha R. Neagu, Patrick Ziegler, Thomas Pertel, Caterina Strambio-De-Castillia, Christian Grütter, Gladys Martinetti, Luca Mazzucchelli, Markus Grütter, Markus G. Manz, Jeremy Luban
Although many self-reactive T cells are eliminated by negative selection in the thymus, some of these cells escape into the periphery, where they must be controlled by additional mechanisms. However, the molecular mechanisms underlying peripheral T cell tolerance and its maintenance remain largely undefined. In this study, we report that sirtuin 1 (Sirt1), a type III histone deacetylase, negatively regulates T cell activation and plays a major role in clonal T cell anergy in mice. In vivo, we found that loss of Sirt1 function resulted in abnormally increased T cell activation and a breakdown of CD4+ T cell tolerance. Conversely, upregulation of Sirt1 expression led to T cell anergy, in which the activity of the transcription factor AP-1 was substantially diminished. Furthermore, Sirt1 interacted with and deacetylated c-Jun, yielding an inactive AP-1 factor. In addition, Sirt1-deficient mice were unable to maintain T cell tolerance and developed severe experimental allergic encephalomyelitis as well as spontaneous autoimmunity. These findings provide insight into the molecular mechanisms of T cell activation and anergy, and we suggest that activators of Sirt1 may be useful as therapeutic agents for the treatment and/or prevention of autoimmune diseases.
Jinping Zhang, Sang-Myeong Lee, Stephen Shannon, Beixue Gao, Weimin Chen, An Chen, Rohit Divekar, Michael W. McBurney, Helen Braley-Mullen, Habib Zaghouani, Deyu Fang
Muscle wasting is associated with a number of pathophysiologic conditions, including metabolic acidosis, diabetes, sepsis, and high angiotensin II levels. Under these conditions, activation of muscle protein degradation requires endogenous glucocorticoids. As the mechanism(s) underlying this dependence on glucocorticoids have not been identified, we analyzed the effects of glucocorticoids on muscle wasting in a mouse model of acute diabetes. Adrenalectomized, acutely diabetic mice given a physiologic dose of glucocorticoids exhibited decreased IRS-1–associated PI3K activity in muscle and progressive muscle atrophy. These responses were related to increased association of PI3K with the glucocorticoid receptor (GR). In mice with muscle-specific GR deletion (referred to as MGRKO mice), acute diabetes minimally suppressed IRS-1–associated PI3K activity in muscle and did not cause muscle atrophy. However, when a physiologic dose of glucocorticoids was given to mice with muscle-specific IR deletion, muscle protein degradation was accelerated. Fluorescence resonance energy transfer and an in vitro competition assay revealed that activated GRs competed for PI3K, reducing its association with IRS-1. Reexpression of WT GRs or those with a mutation in the nuclear localization signal in the muscle of MGRKO mice indicated that competition for PI3K was a prominent mechanism underlying reduced IRS-1–associated PI3K activity. This nongenomic influence of the GR contributes to activation of muscle protein degradation. We therefore conclude that stimulation of muscle proteolysis requires 2 events, increased glucocorticoid levels and impaired insulin signaling.
Zhaoyong Hu, Huiling Wang, In Hee Lee, Jie Du, William E. Mitch
While the thymus is known to be essential for the initial production of T cells during early life, its contribution to immune development remains a matter of debate. In fact, during cardiac surgery in newborns, the thymus is completely resected to enable better access to the heart to correct congenital heart defects, suggesting that it may be dispensable during childhood and adulthood. Here, we show that young adults thymectomized during early childhood exhibit an altered T cell compartment. Specifically, absolute CD4+ and CD8+ T cell counts were decreased, and these T cell populations showed substantial loss of naive cells and accumulation of oligoclonal memory cells. A subgroup of these young patients (22 years old) exhibited a particularly altered T cell profile that is usually seen in elderly individuals (more than 75 years old). This condition was directly related to CMV infection and the induction of strong CMV-specific T cell responses, which may exhaust the naive T cell pool in the absence of adequate T cell renewal from the thymus. Together, these marked immunological alterations are reminiscent of the immune risk phenotype, which is defined by a cluster of immune markers predictive of increased mortality in the elderly. Overall, our data highlight the importance of the thymus in maintaining the integrity of T cell immunity during adult life.
Delphine Sauce, Martin Larsen, Solène Fastenackels, Anne Duperrier, Michael Keller, Beatrix Grubeck-Loebenstein, Christophe Ferrand, Patrice Debré, Daniel Sidi, Victor Appay
To improve contractile function, the myocardium undergoes hypertrophic growth without myocyte proliferation in response to both pathologic and physiologic stimulation. Various membrane-bound receptors and intermediate signal transduction pathways regulate the induction of cardiac hypertrophy, but the cardioprotective regulatory pathways or effectors that antagonize cardiac hypertrophy remain poorly understood. Here we identify the small GTPase Cdc42 as a signaling intermediate that restrained the cardiac growth response to physiologic and pathologic stimuli. Cdc42 was specifically activated in the heart after pressure overload and in cultured cardiomyocytes by multiple agonists. Mice with a heart-specific deletion of Cdc42 developed greater cardiac hypertrophy at 2 and 8 weeks of stimulation and transitioned more quickly into heart failure than did wild-type controls. These mice also displayed greater cardiac hypertrophy in response to neuroendocrine agonist infusion for 2 weeks and, more remarkably, enhanced exercise-induced hypertrophy and sudden death. These pathologies were associated with an inability to activate JNK following stimulation through a MEKK1/MKK4/MKK7 pathway, resulting in greater cardiac nuclear factor of activated T cells (NFAT) activity. Restoration of cardiac JNK signaling with an Mkk7 heart-specific transgene reversed the enhanced growth effect. These results identify what we believe to be a novel antihypertrophic and protective cardiac signaling pathway, whereby Cdc42-dependent JNK activation antagonizes calcineurin-NFAT activity to reduce hypertrophy and prevent transition to heart failure.
Marjorie Maillet, Jeffrey M. Lynch, Bastiano Sanna, Allen J. York, Yi Zheng, Jeffery D. Molkentin
Cyclin I is an atypical cyclin because it is most abundant in postmitotic cells. We previously showed that cyclin I does not regulate proliferation, but rather controls survival of podocytes, terminally differentiated epithelial cells that are essential for the structural and functional integrity of kidney glomeruli. Here, we investigated the mechanism by which cyclin I safeguards against apoptosis and found that cyclin I bound and activated cyclin-dependent kinase 5 (Cdk5) in isolated mouse podocytes and neurons. Cdk5 activity was reduced in glomeruli and brain lysates from cyclin I–deficient mice, and inhibition of Cdk5 increased in vitro the susceptibility to apoptosis in response to cellular damage. In addition, levels of the prosurvival proteins Bcl-2 and Bcl-XL were reduced in podocytes and neurons from cyclin I–deficient mice, and restoration of Bcl-2 or Bcl-XL expression prevented injury-induced apoptosis. Furthermore, we found that levels of phosphorylated MEK1/2 and ERK1/2 were decreased in cyclin I–deficient podocytes and that inhibition of MEK1/2 restored Bcl2 and Bcl-XL protein levels. Of interest, this pathway was also defective in mice with experimental glomerulonephritis. Taken together, these data suggest that a cyclin I–Cdk5 complex forms a critical antiapoptotic factor in terminally differentiated cells that functions via MAPK signaling to modulate levels of the prosurvival proteins Bcl-2 and Bcl-XL.
Paul T. Brinkkoetter, Paul Olivier, Jimmy S. Wu, Scott Henderson, Ronald D. Krofft, Jeffrey W. Pippin, David Hockenbery, James M. Roberts, Stuart J. Shankland
Secondary hyperparathyroidism is a major complication of chronic kidney disease (CKD). In experimental models of secondary hyperparathyroidism induced by hypocalcemia or CKD, parathyroid hormone (PTH) mRNA levels increase due to increased PTH mRNA stability. K-homology splicing regulator protein (KSRP) decreases the stability of PTH mRNA upon binding a cis-acting element in the PTH mRNA 3′ UTR region. As the peptidyl-prolyl isomerase (PPIase) Pin1 has recently been shown to regulate the turnover of multiple cytokine mRNAs, we investigated the role of Pin1 in regulating PTH mRNA stability in rat parathyroids and transfected cells. The data generated were consistent with Pin1 being a PTH mRNA destabilizing protein. Initial analysis indicated that Pin1 activity was decreased in parathyroid protein extracts from both hypocalcemic and CKD rats and that pharmacologic inhibition of Pin1 increased PTH mRNA levels posttranscriptionally in rat parathyroid and in transfected cells. Pin1 mediated its effects via interaction with KSRP, which led to KSRP dephosphorylation and activation. In the rat parathyroid, Pin1 inhibition decreased KSRP–PTH mRNA interactions, increasing PTH mRNA levels. Furthermore, Pin1–/– mice displayed increased serum PTH and PTH mRNA levels, suggesting that Pin1 determines basal PTH expression in vivo. These results demonstrate that Pin1 is a key mediator of PTH mRNA stability and indicate a role for Pin1 in the pathogenesis of secondary hyperparathyroidism in individuals with CKD.
Morris Nechama, Takafumi Uchida, Irit Mor Yosef-Levi, Justin Silver, Tally Naveh-Many
X-linked nephrogenic diabetes insipidus (XNDI) is a severe kidney disease caused by inactivating mutations in the V2 vasopressin receptor (V2R) gene that result in the loss of renal urine-concentrating ability. At present, no specific pharmacological therapy has been developed for XNDI, primarily due to the lack of suitable animal models. To develop what we believe to be the first viable animal model of XNDI, we generated mice in which the V2R gene could be conditionally deleted during adulthood by administration of 4-OH-tamoxifen. Radioligand-binding studies confirmed the lack of V2R-binding sites in kidneys following 4-OH-tamoxifen treatment, and further analysis indicated that upon V2R deletion, adult mice displayed all characteristic symptoms of XNDI, including polyuria, polydipsia, and resistance to the antidiuretic actions of vasopressin. Gene expression analysis suggested that activation of renal EP4 PGE2 receptors might compensate for the lack of renal V2R activity in XNDI mice. Strikingly, both acute and chronic treatment of the mutant mice with a selective EP4 receptor agonist greatly reduced all major manifestations of XNDI, including changes in renal morphology. These physiological improvements were most likely due to a direct action on EP4 receptors expressed on collecting duct cells. These findings illustrate the usefulness of the newly generated V2R mutant mice for elucidating and testing new strategies for the potential treatment of humans with XNDI.
Jian Hua Li, Chung-Lin Chou, Bo Li, Oksana Gavrilova, Christoph Eisner, Jürgen Schnermann, Stasia A. Anderson, Chu-Xia Deng, Mark A. Knepper, Jürgen Wess
Seborrheic keratoses (SKs) are common, benign epithelial tumors of the skin that do not, or very rarely, progress into malignancy, for reasons that are not understood. We investigated this by gene expression profiling of human SKs and cutaneous squamous cell carcinomas (SCCs) and found that several genes previously connected with keratinocyte tumor development were similarly modulated in SKs and SCCs, whereas the expression of others differed by only a few fold. In contrast, the tyrosine kinase receptor FGF receptor–3 (FGFR3) and the transcription factor forkhead box N1 (FOXN1) were highly expressed in SKs, and close to undetectable in SCCs. We also showed that increased FGFR3 activity was sufficient to induce FOXN1 expression, counteract the inhibitory effect of EGFR signaling on FOXN1 expression and differentiation, and induce differentiation in a FOXN1-dependent manner. Knockdown of FOXN1 expression in primary human keratinocytes cooperated with oncogenic RAS in the induction of SCC-like tumors, whereas increased FOXN1 expression triggered the SCC cells to shift to a benign SK-like tumor phenotype, which included increased FGFR3 expression. Thus, we have uncovered a positive regulatory loop between FGFR3 and FOXN1 that underlies a benign versus malignant skin tumor phenotype.
Anna Mandinova, Vihren Kolev, Victor Neel, Bing Hu, Wesley Stonely, Jocelyn Lieb, Xunwei Wu, Claudia Colli, Rong Han, Mike Pazin, Paola Ostano, Reinhard Dummer, Janice L. Brissette, G. Paolo Dotto
As most metabolic studies are conducted in male animals, understanding the sex specificity of the underlying molecular pathways has been broadly neglected; for example, whether PPARs elicit sex-dependent responses has not been determined. Here we show that in mice, PPARα has broad female-dependent repressive actions on hepatic genes involved in steroid metabolism and immunity. In male mice, this effect was reproduced by the administration of a synthetic PPARα ligand. Using the steroid oxysterol 7α-hydroxylase cytochrome P450 7b1 (Cyp7b1) gene as a model, we elucidated the molecular mechanism of this sex-specific PPARα-dependent repression. Initial sumoylation of the ligand-binding domain of PPARα triggered the interaction of PPARα with GA-binding protein α (GABPα) bound to the target Cyp7b1 promoter. Histone deacetylase and DNA and histone methylases were then recruited, and the adjacent Sp1-binding site and histones were methylated. These events resulted in loss of Sp1-stimulated expression and thus downregulation of Cyp7b1. Physiologically, this repression conferred on female mice protection against estrogen-induced intrahepatic cholestasis, the most common hepatic disease during pregnancy, suggesting a therapeutic target for prevention of this disease.
Nicolas Leuenberger, Sylvain Pradervand, Walter Wahli
The B cell lymphoma 2 (Bcl-2) family member Bcl-xL has a well-characterized antiapoptotic function in lymphoid cells. However, its functions in other cells — including osteoclasts, which are of hematopoietic origin — and other cellular processes remain unknown. Here we report an unexpected function of Bcl-xL in attenuating the bone-resorbing activity of osteoclasts in mice. To investigate the role of Bcl-xL in osteoclasts, we generated mice with osteoclast-specific conditional deletion of Bcl-x (referred to herein as Bcl-x cKO mice) by mating Bcl-xfl/fl mice with mice in which the gene encoding the Cre recombinase has been knocked into the cathepsin K locus and specifically expressed in mature osteoclasts. Although the Bcl-x cKO mice grew normally with no apparent morphological abnormalities, they developed substantial osteopenia at 1 year of age, which was caused by increased bone resorption. Bcl-x deficiency increased the bone-resorbing activity of osteoclasts despite their high susceptibility to apoptosis, whereas Bcl-xL overexpression produced the opposite effect. In addition, Bcl-x cKO osteoclasts displayed increased c-Src activity, which was linked to increased levels of vitronectin and fibronectin expression. These results suggest that Bcl-xL attenuates osteoclastic bone-resorbing activity through the decreased production of ECM proteins, such as vitronectin and fibronectin, and thus provide evidence for what we believe to be a novel cellular function of Bcl-xL.
Mitsuyasu Iwasawa, Tsuyoshi Miyazaki, Yuichi Nagase, Toru Akiyama, Yuho Kadono, Masaki Nakamura, Yasushi Oshima, Tetsuro Yasui, Takumi Matsumoto, Takashi Nakamura, Shigeaki Kato, Lothar Hennighausen, Kozo Nakamura, Sakae Tanaka
To date, inheritance of a mutant BRCA1 or BRCA2 gene is the best-established indicator of an increased risk of developing breast cancer. Sequence analysis of these genes is being used to identify BRCA1/2 mutation carriers, though these efforts are hampered by the high frequency of variants of unknown clinical significance (VUSs). Functional evaluation of such variants has been restricted due to lack of a physiologically relevant assay. In this study we developed a functional assay using mouse ES cells to study variants of BRCA1. We introduced BAC clones with human wild-type BRCA1 or variants into Brca1-null ES cells and confirmed that only wild-type and a known neutral variant rescued cell lethality. The same neutral variant was also able to rescue embryogenesis in Brca1-null mice. A test of several BRCT domain mutants revealed all to be deleterious, including a VUS. Furthermore, we used this assay to determine the effects of BRCA1 variants on cell cycle regulation, differentiation, and genomic stability. Importantly, we discovered that ES cells rescued by S1497A BRCA1 exhibited significant hypersensitivity after γ-irradiation. Our results demonstrate that this ES cell–based assay is a powerful and reliable method for analyzing the functional impact of BRCA1 variants, which we believe could be used to determine which patients may require preventative treatments.
Suhwan Chang, Kajal Biswas, Betty K. Martin, Stacey Stauffer, Shyam K. Sharan
The presence of circulating tumor cells (CTCs) in the peripheral blood is associated with short survival, making the detection of CTCs clinically useful as a prognostic factor of disease outcome and/or a surrogate marker of treatment response. Recent technical advances in immunocytometric analysis and quantitative real-time PCR have made it possible to detect a few CTCs in the blood; however, there is no sensitive assay to specifically detect viable CTCs. Here, we report what we believe to be a new approach to visually detect live human CTCs among millions of peripheral blood leukocytes, using a telomerase-specific replication-selective adenovirus expressing GFP. First, we constructed a GFP-expressing attenuated adenovirus, in which the telomerase promoter regulates viral replication (OBP-401; TelomeScan). We then used OBP-401 to establish a simple ex vivo method that was able to detect viable human CTCs in the peripheral blood. The detection method involved a 3-step procedure, including the lysis of rbc, the subsequent addition of OBP-401 to the cell pellets, and an automated scan using fluorescence microscopy. OBP-401 infection increased the signal-to-background ratio as a tumor-specific probe, because the fluorescent signal was amplified only in viable, infected human tumor cells, by viral replication. This GFP-expressing virus-based method is remarkably simple and allows precise enumeration of CTCs.
Toru Kojima, Yuuri Hashimoto, Yuichi Watanabe, Shunsuke Kagawa, Futoshi Uno, Shinji Kuroda, Hiroshi Tazawa, Satoru Kyo, Hiroyuki Mizuguchi, Yasuo Urata, Noriaki Tanaka, Toshiyoshi Fujiwara
William Y. Kim, Samanthi Perera, Bing Zhou, Julian Carretero, Jen Jen Yeh, Samuel A. Heathcote, Autumn L. Jackson, Petros Nikolinakos, Beatriz Ospina, George N. Naumov, Kathleyn A. Brandstetter, Victor J. Weigman, Sara Zaghlul, D. Neil Hayes, Robert F. Padera, John V. Heymach, Andrew L. Kung, Norman E. Sharpless, William G. Kaelin Jr., Kwok-Kin Wong