Issue published January 2, 2015 Previous issue | Next issue
On the cover: TALENs for cervical cancer
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Reviews
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Abstract
Autophagy (“self-eating”) constitutes one of the most spectacular yet subtly regulated phenomena in cell biology. Similarly to cell division, differentiation, and death, autophagy is perturbed in multiple diseases, in that excessive or deficient autophagy may contribute to pathogenesis. Numerous attempts have been launched to identify specific inducers or inhibitors of autophagy and to use them for the therapeutic correction of its deregulation. At present, several major disease categories (including but not limited to age-related, cardiovascular, infectious, neoplastic, neurodegenerative, and metabolic pathologies) are being investigated for pathogenic aberrations in autophagy and their pharmacologic rectification. Driven by promising preclinical results, several clinical trials are exploring autophagy as a therapeutic target.
Authors
Guido Kroemer
×Abstract
Autophagy is an important intracellular catabolic mechanism critically involved in regulating tissue homeostasis. The implication of autophagy in human diseases and the need to understand its regulatory mechanisms in mammalian cells have stimulated research efforts that led to the development of high-throughput screening protocols and small-molecule modulators that can activate or inhibit autophagy. Herein we review the current landscape in the development of screening technology as well as the molecules and pharmacologic agents targeting the regulatory mechanisms of autophagy. We also evaluate the potential therapeutic application of these compounds in different human pathologies.
Authors
Helin Vakifahmetoglu-Norberg, Hong-guang Xia, Junying Yuan
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Defects in autophagy have been linked to a wide range of medical illnesses, including cancer as well as infectious, neurodegenerative, inflammatory, and metabolic diseases. These observations have led to the hypothesis that autophagy inducers may prevent or treat certain clinical conditions. Lifestyle and nutritional factors, such as exercise and caloric restriction, may exert their known health benefits through the autophagy pathway. Several currently available FDA-approved drugs have been shown to enhance autophagy, and this autophagy-enhancing action may be repurposed for use in novel clinical indications. The development of new drugs that are designed to be more selective inducers of autophagy function in target organs is expected to maximize clinical benefits while minimizing toxicity. This Review summarizes the rationale and current approaches for developing autophagy inducers in medicine, the factors to be considered in defining disease targets for such therapy, and the potential benefits of such treatment for human health.
Authors
Beth Levine, Milton Packer, Patrice Codogno
×Abstract
mTOR, a serine/threonine kinase, is a master regulator of cellular metabolism. mTOR regulates cell growth and proliferation in response to a wide range of cues, and its signaling pathway is deregulated in many human diseases. mTOR also plays a crucial role in regulating autophagy. This Review provides an overview of the mTOR signaling pathway, the mechanisms of mTOR in autophagy regulation, and the clinical implications of mTOR inhibitors in disease treatment.
Authors
Young Chul Kim, Kun-Liang Guan
×Abstract
Autophagy is a well-conserved catabolic process essential for cellular homeostasis. First described in yeast as an adaptive response to starvation, this pathway is also present in higher eukaryotes, where it is triggered by stress signals such as damaged organelles or pathogen infection. Autophagy is characterized at the cellular level by the engulfment of portions of the cytoplasm in double-membrane structures called autophagosomes. Autophagosomes fuse with lysosomes, resulting in degradation of the inner autophagosomal membrane and luminal content. This process is coordinated by complex molecular systems, including the ATG8 ubiquitin–like conjugation system and the ATG4 cysteine proteases, which are implicated in the formation, elongation, and fusion of these autophagic vesicles. In this Review, we focus on the diverse functional roles of the autophagins, a protease family formed by the four mammalian orthologs of yeast Atg4. We also address the dysfunctional expression of these proteases in several pathologic conditions such as cancer and inflammation and discuss potential therapies based on their modulation.
Authors
Álvaro F. Fernández, Carlos López-Otín
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Autophagy is a survival-promoting pathway that captures, degrades, and recycles intracellular proteins and organelles in lysosomes. Autophagy preserves organelle function, prevents the toxic buildup of cellular waste products, and provides substrates to sustain metabolism in starvation. Although in some contexts autophagy suppresses tumorigenesis, in most contexts autophagy facilitates tumorigenesis. Cancers can upregulate autophagy to survive microenvironmental stress and to increase growth and aggressiveness. Mechanisms by which autophagy promotes cancer include suppressing induction of the p53 tumor suppressor protein and maintaining metabolic function of mitochondria. Efforts to inhibit autophagy to improve cancer therapy have thereby attracted great interest.
Authors
Eileen White
×Abstract
Autophagy is a catabolic process mediated by incorporation of cellular material into cytosolic membrane vesicles for lysosomal degradation. It is crucial for maintaining cell viability and homeostasis in response to numerous stressful conditions. In this Review, the role of autophagy in both normal biology and disease is discussed. Emphasis is given to the interplay of autophagy with nutrient signaling through the ULK1 autophagy pre-initiation complex. Furthermore, related cellular processes utilizing components of the canonical autophagy pathway are discussed due to their potential roles in nutrient scavenging. Finally, the role of autophagy in cancer and its potential as a cancer therapeutic target are considered.
Authors
Xuejun Jiang, Michael Overholtzer, Craig B. Thompson
×Abstract
Cardiovascular disease is the leading cause of death worldwide. As such, there is great interest in identifying novel mechanisms that govern the cardiovascular response to disease-related stress. First described in failing hearts, autophagy within the cardiovascular system has been widely characterized in cardiomyocytes, cardiac fibroblasts, endothelial cells, vascular smooth muscle cells, and macrophages. In all cases, a window of optimal autophagic activity appears to be critical to the maintenance of cardiovascular homeostasis and function; excessive or insufficient levels of autophagic flux can each contribute to heart disease pathogenesis. In this Review, we discuss the potential for targeting autophagy therapeutically and our vision for where this exciting biology may lead in the future.
Authors
Sergio Lavandero, Mario Chiong, Beverly A. Rothermel, Joseph A. Hill
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Most neurodegenerative diseases that afflict humans are associated with the intracytoplasmic deposition of aggregate-prone proteins in neurons. Autophagy is a powerful process for removing such proteins. In this Review, we consider how certain neurodegenerative diseases may be associated with impaired autophagy and how this may affect pathology. We also discuss how autophagy induction may be a plausible therapeutic strategy for some conditions and review studies in various models that support this hypothesis. Finally, we briefly describe some of the signaling pathways that may be amenable to therapeutic targeting for these goals.
Authors
Rebecca A. Frake, Thomas Ricketts, Fiona M. Menzies, David C. Rubinsztein
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The broad immunologic roles of autophagy span innate and adaptive immunity and are often manifested in inflammatory diseases. The immune effects of autophagy partially overlap with its roles in metabolism and cytoplasmic quality control but typically expand further afield to encompass unique immunologic adaptations. One of the best-appreciated manifestations of autophagy is protection against microbial invasion, but this is by no means limited to direct elimination of intracellular pathogens and includes a stratified array of nearly all principal immunologic processes. This Review summarizes the broad immunologic roles of autophagy. Furthermore, it uses the autophagic control of
Mycobacterium tuberculosis as a paradigm to illustrate the breadth and complexity of the immune effects of autophagy.Authors
Vojo Deretic, Tomonori Kimura, Graham Timmins, Pope Moseley, Santosh Chauhan, Michael Mandell
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Life and health span can be prolonged by calorie limitation or by pharmacologic agents that mimic the effects of caloric restriction. Both starvation and the genetic inactivation of nutrient signaling converge on the induction of autophagy, a cytoplasmic recycling process that counteracts the age-associated accumulation of damaged organelles and proteins as it improves the metabolic fitness of cells. Here we review experimental findings indicating that inhibition of the major nutrient and growth-related signaling pathways as well as the upregulation of anti-aging pathways mediate life span extension via the induction of autophagy. Furthermore, we discuss mounting evidence suggesting that autophagy is not only necessary but, at least in some cases, also sufficient for increasing longevity.
Authors
Frank Madeo, Andreas Zimmermann, Maria Chiara Maiuri, Guido Kroemer
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Commentaries
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Abstract
Patients with type 1 diabetes (T1D) rapidly lose β cell function and/or mass, leading to a life-long dependence on insulin therapy. β Cell destruction is mediated by aberrant immune responses; therefore, immune modulation has potential to ameliorate disease. While immune intervention in animal models of diabetes has shown promising results, treatment of patients with T1D with the same agents has not been as successful. In this issue of the
JCI , Haller and colleagues present data from a small clinical trial that tested the efficacy of a combination of immunomodulatory agents, anti-thymocyte globulin and pegylated granulocyte CSF, neither of which have shown benefit for T1D as single treatment agents. Many patients that received combination therapy maintained β cell function at baseline levels up to a year after treatment. The results from this study challenge current trial design paradigm that for combined therapy to be successful individual agents should show benefit.Authors
Jay S. Skyler
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Hepatitis C virus (HCV) is a leading cause of chronic liver disease, and efforts to develop therapeutic vaccine strategies have been limited by immune escape due to HCV variants that are resistant to current vaccines or HCV variants that rapidly acquire new resistance-conferring mutations. Recently, the crystal structure of the viral envelope protein E2 region was resolved as well as how E2 docks to the host CD81 protein; therefore, antibodies that block this interaction should prevent viral entry into host cells. In this issue of the
JCI , Bailey and colleagues show that immune escape of HCV can occur by naturally occurring polymorphisms in E2 that are distinct from those at mapped sites of antibody binding. These data reveal alternative mechanisms of resistance that need to be considered in both natural viral escape as well as in rationale vaccine design against HCV.Authors
Jay K. Kolls, Gyongyi Szabo
×Abstract
Mutations in
SCN5A , which encodes the α subunit of the major cardiac sodium channel NaV1.5, are associated with multiple cardiac arrhythmias, including Brugada syndrome. It is not clear why mutations inSCN5A result in such a variety of cardiac phenotypes, and introduction of analogousScn5a mutations into small-animal models has not recapitulated alterations in cardiac physiology associated with human disease. In this issue of theJCI , Park and colleagues present a pig model of cardiac sodium channelopathy that was generated by introducing a human Brugada syndrome–associatedSCN5A allele. This large-animal model exhibits many phenotypes seen in patients withSCN5A loss-of-function mutations and has the potential to provide important insight into sodium channelopathies.Authors
Arthur A.M. Wilde, Pieter G. Postema
×Abstract
Systemic lupus erythematosus (SLE) is a severe autoimmune disease characterized by the presence of nucleic acid– and protein-targeting autoantibodies and an aberrant type I IFN expression signature. Aicardi-Goutières syndrome (AGS) is an autosomal-recessive encephalopathy in children that is characterized by mutations in numerous nucleic acid repair enzymes and elevated IFN levels. Phenotypically, patients with AGS and SLE share many similarities. Ribonuclease H2 (RNase H2) is a nucleic acid repair enzyme that removes unwanted ribonucleotides from DNA. In this issue of the
JCI , Günther and colleagues provide an in-depth investigation of the mechanisms underlying the link between defective removal of ribonucleotides in AGS and SLE, and these findings will likely serve as a strong springboard to provide novel therapeutic inroads.Authors
William F. Pendergraft III, Terry K. Means
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Research Articles
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Abstract
Alternative splicing of nucleoredoxin-like 1 (
Nxnl1 ) results in 2 isoforms of the rod-derived cone viability factor. The truncated form (RdCVF) is a thioredoxin-like protein secreted by rods that promotes cone survival, while the full-length isoform (RdCVFL), which contains a thioredoxin fold, is involved in oxidative signaling and protection against hyperoxia. Here, we evaluated the effects of these different isoforms in 2 murine models of rod-cone dystrophy. We used adeno-associated virus (AAV) to express these isoforms in mice and found that both systemic and intravitreal injection of engineered AAV vectors resulted in RdCVF and RdCVFL expression in the eye. Systemic delivery of AAV92YF vectors in neonates resulted in earlier onset of RdCVF and RdCVFL expression compared with that observed with intraocular injection using the same vectors at P14. We also evaluated the efficacy of intravitreal injection using a recently developed photoreceptor-transducing AAV variant (7m8) at P14. Systemic administration of AAV92YF-RdCVF improved cone function and delayed cone loss, while AAV92YF-RdCVFL increased rhodopsin mRNA and reduced oxidative stress by-products. Intravitreal 7m8-RdCVF slowed the rate of cone cell death and increased the amplitude of the photopic electroretinogram. Together, these results indicate different functions forNxnl1 isoforms in the retina and suggest that RdCVF gene therapy has potential for treating retinal degenerative disease.Authors
Leah C. Byrne, Deniz Dalkara, Gabriel Luna, Steven K. Fisher, Emmanuelle Clérin, Jose-Alain Sahel, Thierry Léveillard, John G. Flannery
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The epithelial Na+ channel (ENaC) is essential for Na+ homeostasis, and dysregulation of this channel underlies many forms of hypertension. Recent studies suggest that mTOR regulates phosphorylation and activation of serum/glucocorticoid regulated kinase 1 (SGK1), which is known to inhibit ENaC internalization and degradation; however, it is not clear whether mTOR contributes to the regulation of renal tubule ion transport. Here, we evaluated the effect of selective mTOR inhibitors on kidney tubule Na+ and K+ transport in WT and
Sgk1–/– mice, as well as in isolated collecting tubules. We found that 2 structurally distinct competitive inhibitors (PP242 and AZD8055), both of which prevent all mTOR-dependent phosphorylation, including that of SGK1, caused substantial natriuresis, but not kaliuresis, in WT mice, which indicates that mTOR preferentially influences ENaC function. PP242 also substantially inhibited Na+ currents in isolated perfused cortical collecting tubules. Accordingly, patch clamp studies on cortical tubule apical membranes revealed that mTOR inhibition markedly reduces ENaC activity, but does not alter activity of K+ inwardly rectifying channels (ROMK channels). Together, these results demonstrate that mTOR regulates kidney tubule ion handling and suggest that mTOR regulates Na+ homeostasis through SGK1-dependent modulation of ENaC activity.Authors
Catherine E. Gleason, Gustavo Frindt, Chih-Jen Cheng, Michael Ng, Atif Kidwai, Priyanka Rashmi, Florian Lang, Michel Baum, Lawrence G. Palmer, David Pearce
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Podoplanin (PDPN, also known as Gp38) is highly expressed on the surface of lymphatic endothelial cells, where it regulates development of lymphatic vessels. We have recently observed that PDPN is also expressed on effector T cells that infiltrate target tissues during autoimmune inflammation; however, the function of PDPN in T cells is largely unclear. Here, we demonstrated that global deletion of
Pdpn results in exaggerated T cell responses and spontaneous experimental autoimmune encephalomyelitis (EAE) in mice with a susceptible genetic background. In contrast, T cell–specific overexpression of PDPN resulted in profound defects in IL-7–mediated T cell expansion and survival. Consequently, these animals exhibited a more rapid resolution of CNS inflammation, characterized by a reduced effector CD4+ T cell population in the CNS. Mice harboring a T cell–specific deletion ofPdpn developed exacerbated EAE, with increased accumulation of effector CD4+ T cells in the CNS. Transcriptional profiling of naturally occurring PDPN+ effector T cells in the CNS revealed increased expression of other inhibitory receptors, such asPd1 andTim3 , and decreased expression of prosurvival factors, includingIl7ra . Together, our data suggest that PDPN functions as an inhibitory molecule on T cells, thereby promoting tissue tolerance by limiting long-term survival and maintenance of CD4+ effector T cells in target organs.Authors
Anneli Peters, Patrick R. Burkett, Raymond A. Sobel, Christopher D. Buckley, Steve P. Watson, Estelle Bettelli, Vijay K. Kuchroo
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MicroRNA-21 (miR-21) contributes to the pathogenesis of fibrogenic diseases in multiple organs, including the kidneys, potentially by silencing metabolic pathways that are critical for cellular ATP generation, ROS production, and inflammatory signaling. Here, we developed highly specific oligonucleotides that distribute to the kidney and inhibit miR-21 function when administered subcutaneously and evaluated the therapeutic potential of these anti–miR-21 oligonucleotides in chronic kidney disease. In a murine model of Alport nephropathy, miR-21 silencing did not produce any adverse effects and resulted in substantially milder kidney disease, with minimal albuminuria and dysfunction, compared with vehicle-treated mice. miR-21 silencing dramatically improved survival of Alport mice and reduced histological end points, including glomerulosclerosis, interstitial fibrosis, tubular injury, and inflammation. Anti–miR-21 enhanced PPARα/retinoid X receptor (PPARα/RXR) activity and downstream signaling pathways in glomerular, tubular, and interstitial cells. Moreover, miR-21 silencing enhanced mitochondrial function, which reduced mitochondrial ROS production and thus preserved tubular functions. Inhibition of miR-21 was protective against TGF-β–induced fibrogenesis and inflammation in glomerular and interstitial cells, likely as the result of enhanced PPARα/RXR activity and improved mitochondrial function. Together, these results demonstrate that inhibition of miR-21 represents a potential therapeutic strategy for chronic kidney diseases including Alport nephropathy.
Authors
Ivan G. Gomez, Deidre A. MacKenna, Bryce G. Johnson, Vivek Kaimal, Allie M. Roach, Shuyu Ren, Naoki Nakagawa, Cuiyan Xin, Rick Newitt, Shweta Pandya, Tai-He Xia, Xueqing Liu, Dorin-Bogdan Borza, Monica Grafals, Stuart J. Shankland, Jonathan Himmelfarb, Didier Portilla, Shiguang Liu, B. Nelson Chau, Jeremy S. Duffield
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Survivin is a tumor-associated antigen (TAA) that inhibits apoptosis and is widely overexpressed in cancer cells; therefore, survivin has potential as a target for cancer immunotherapy. Application of HLA-A2–restricted survivin-specific T cell receptors (TCRs) isolated from allogeneic HLA–mismatched TCR repertoires has, however, been impeded by the inability of these TCRs to distinguish healthy cells expressing low levels of survivin from cancer cells with high survivin expression levels. Here, we identified an HLA-A2–restricted survivin-specific TCR isolated from autologous TCR repertoires that targets tumor cells in vitro and in vivo but does not cause fratricidal toxicity. Molecular modeling of the TCR-peptide-HLA ternary complexes and alanine scanning revealed that the autologously derived TCRs had tighter interactions with the survivin peptide than did fratricidal TCRs. Similar recognition patterns were observed among 7 additional TAA-specific TCRs isolated from allogeneic versus autologous repertoires. Together, the results from this study indicate that maximal peptide recognition is key for TCR selectivity and likely critical for reducing unwanted off-target toxicities. Moreover, isolating TCRs from autologous repertoires to maximize TCR selectivity has potential as a useful strategy to identify and select other shared tumor- and self-antigen–specific TCRs and ensure selective antitumor activity.
Authors
Caroline Arber, Xiang Feng, Harshal Abhyankar, Errika Romero, Meng-Fen Wu, Helen E. Heslop, Patrick Barth, Gianpietro Dotti, Barbara Savoldo
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Unlike other picornaviruses, hepatitis A virus (HAV) is cloaked in host membranes when released from cells, providing protection from neutralizing antibodies and facilitating spread in the liver. Acute HAV infection is typified by minimal type I IFN responses; therefore, we questioned whether plasmacytoid dendritic cells (pDCs), which produce IFN when activated, are capable of sensing enveloped virions (eHAV). Although concentrated nonenveloped virus failed to activate freshly isolated human pDCs, these cells produced substantial amounts of IFN-α via TLR7 signaling when cocultured with infected cells. pDCs required either close contact with infected cells or exposure to concentrated culture supernatants for IFN-α production. In isopycnic and rate-zonal gradients, pDC-activating material cosedimented with eHAV but not membrane-bound acetylcholinesterase, suggesting that eHAV, and not viral RNA exosomes, is responsible for IFN-α induction. pDC activation did not require virus replication and was associated with efficient eHAV uptake, which was facilitated by phosphatidylserine receptors on pDCs. In chimpanzees, pDCs were transiently recruited to the liver early in infection, during or shortly before maximal intrahepatic IFN-stimulated gene expression, but disappeared prior to inflammation onset. Our data reveal that, while membrane envelopment protects HAV against neutralizing antibody, it also facilitates an early but limited detection of HAV infection by pDCs.
Authors
Zongdi Feng, You Li, Kevin L. McKnight, Lucinda Hensley, Robert E. Lanford, Christopher M. Walker, Stanley M. Lemon
×Abstract
Hematopoietic stem cell (HSC) function is regulated by activation of receptor tyrosine kinases (RTKs). Receptor protein tyrosine phosphatases (PTPs) counterbalance RTK signaling; however, the functions of receptor PTPs in HSCs remain incompletely understood. We found that a receptor PTP, PTPσ, was substantially overexpressed in mouse and human HSCs compared with more mature hematopoietic cells. Competitive transplantation of bone marrow cells from PTPσ-deficient mice revealed that the loss of PTPσ substantially increased long-term HSC-repopulating capacity compared with BM cells from control mice. While HSCs from PTPσ-deficient mice had no apparent alterations in cell-cycle status, apoptosis, or homing capacity, these HSCs exhibited increased levels of activated RAC1, a RhoGTPase that regulates HSC engraftment capacity. shRNA-mediated silencing of PTPσ also increased activated RAC1 levels in wild-type HSCs. Functionally, PTPσ-deficient BM cells displayed increased cobblestone area–forming cell (CAFC) capacity and augmented transendothelial migration capacity, which was abrogated by RAC inhibition. Specific selection of human cord blood CD34+CD38–CD45RA–lin– PTPσ– cells substantially increased the repopulating capacity of human HSCs compared with CD34+CD38–CD45RA–lin– cells and CD34+CD38–CD45RA–lin–PTPσ+ cells. Our results demonstrate that PTPσ regulates HSC functional capacity via RAC1 inhibition and suggest that selecting for PTPσ-negative human HSCs may be an effective strategy for enriching human HSCs for transplantation.
Authors
Mamle Quarmyne, Phuong L. Doan, Heather A. Himburg, Xiao Yan, Mai Nakamura, Liman Zhao, Nelson J. Chao, John P. Chute
×Abstract
Inflammation in response to excess low-density lipoproteins in the blood is an important driver of atherosclerosis development. Due to its ability to enhance ATP–binding cassette A1–dependent (ABCA1-dependent) reverse cholesterol transport (RCT), liver X receptor (LXR) is an attractive target for the treatment of atherosclerosis. However, LXR also upregulates the expression of sterol regulatory element–binding protein 1c (SREBP-1c), leading to increased hepatic triglyceride synthesis, an independent risk factor for atherosclerosis. Here, we developed a strategy to separate the favorable and unfavorable effects of LXR by exploiting the specificity of the coactivator thyroid hormone receptor–associated protein 80 (TRAP80). Using human hepatic cell lines, we determined that TRAP80 selectively promotes the transcription of
SREBP-1c but notABCA1 . Adenovirus-mediated expression of shTRAP80 inhibited LXR-dependent SREBP-1c expression and RNA polymerase II recruitment to the LXR responsive element (LXRE) ofSREBP-1c , but not to the LXRE ofABCA1 . In murine models, liver-specific knockdown of TRAP80 ameliorated liver steatosis and hypertriglyceridemia induced by LXR activation and maintained RCT stimulation by the LXR ligand. Together, these data indicate that TRAP80 is a selective regulator of hepatic lipogenesis and is required for LXR-dependentSREBP-1c activation. Moreover, targeting the interaction between TRAP80 and LXR should facilitate the development of potential LXR agonists that effectively prevent atherosclerosis.Authors
Geun Hyang Kim, Gyun-Sik Oh, Jin Yoon, Gang Gu Lee, Ki-Up Lee, Seung-Whan Kim
×Abstract
Activation of CD4+ T cells results in rapid proliferation and differentiation into effector and regulatory subsets. CD4+ effector T cell (Teff) (Th1 and Th17) and Treg subsets are metabolically distinct, yet the specific metabolic differences that modify T cell populations are uncertain. Here, we evaluated CD4+ T cell populations in murine models and determined that inflammatory Teffs maintain high expression of glycolytic genes and rely on high glycolytic rates, while Tregs are oxidative and require mitochondrial electron transport to proliferate, differentiate, and survive. Metabolic profiling revealed that pyruvate dehydrogenase (PDH) is a key bifurcation point between T cell glycolytic and oxidative metabolism. PDH function is inhibited by PDH kinases (PDHKs). PDHK1 was expressed in Th17 cells, but not Th1 cells, and at low levels in Tregs, and inhibition or knockdown of PDHK1 selectively suppressed Th17 cells and increased Tregs. This alteration in the CD4+ T cell populations was mediated in part through ROS, as
N -acetyl cysteine (NAC) treatment restored Th17 cell generation. Moreover, inhibition of PDHK1 modulated immunity and protected animals against experimental autoimmune encephalomyelitis, decreasing Th17 cells and increasing Tregs. Together, these data show that CD4+ subsets utilize and require distinct metabolic programs that can be targeted to control specific T cell populations in autoimmune and inflammatory diseases.Authors
Valerie A. Gerriets, Rigel J. Kishton, Amanda G. Nichols, Andrew N. Macintyre, Makoto Inoue, Olga Ilkayeva, Peter S. Winter, Xiaojing Liu, Bhavana Priyadharshini, Marta E. Slawinska, Lea Haeberli, Catherine Huck, Laurence A. Turka, Kris C. Wood, Laura P. Hale, Paul A. Smith, Martin A. Schneider, Nancie J. MacIver, Jason W. Locasale, Christopher B. Newgard, Mari L. Shinohara, Jeffrey C. Rathmell
×Abstract
Fibrosis underlies the loss of renal function in patients with chronic kidney disease (CKD) and in kidney transplant recipients with chronic allograft nephropathy (CAN). Here, we studied the effect of an intronic SNP in
SHROOM3 , which has previously been linked to CKD, on the development of CAN in a prospective cohort of renal allograft recipients. The presence of the rs17319721 allele at theSHROOM3 locus in the donor correlated with increasedSHROOM3 expression in the allograft. In vitro, we determined that the sequence containing the risk allele at rs17319721 is a transcription factor 7–like 2–dependent (TCF7L2-dependent) enhancer element that functions to increaseSHROOM3 transcription. In renal tubular cells, TGF-β1 administration upregulatedSHROOM3 expression in a β-catenin/TCF7L2–mediated manner, while SHROOM3 in turn facilitated canonical TGF-β1 signaling and increased α1 collagen (COL1A1 ) expression. Inducible and tubular cell–specific knockdown ofShroom3 markedly abrogated interstitial fibrosis in mice with unilateral ureteric obstruction. Moreover,SHROOM3 expression in allografts at 3 months after transplant and the presence of theSHROOM3 risk allele in the donor correlated with increased allograft fibrosis and with reduced estimated glomerular filtration rate at 12 months after transplant. Our findings suggest that rs17319721 functions as acis -acting expression quantitative trait locus ofSHROOM3 that facilitates TGF-β1 signaling and contributes to allograft injury.Authors
Madhav C. Menon, Peter Y. Chuang, Zhengzhe Li, Chengguo Wei, Weijia Zhang, Yi Luan, Zhengzi Yi, Huabao Xiong, Christopher Woytovich, Ilana Greene, Jessica Overbey, Ivy Rosales, Emilia Bagiella, Rong Chen, Meng Ma, Li Li, Wei Ding, Arjang Djamali, Millagros Saminego, Philip J. O’Connell, Lorenzo Gallon, Robert Colvin, Bernd Schroppel, John Cijiang He, Barbara Murphy
×Abstract
The
KRAS gene is commonly mutated in human cancers, rendering the encoded small GTPase constitutively active and oncogenic. This gene has the unusual feature of being enriched for rare codons, which limit protein expression. Here, to determine the effect of the rare codon bias of theKRAS gene on de novo tumorigenesis, we introduced synonymous mutations that converted rare codons into common codons in exon 3 of theKras gene in mice. Compared with control animals, mice with at least 1 copy of thisKrasex3op allele had fewer tumors following carcinogen exposure, and this allele was mutated less often, with weaker oncogenic mutations in these tumors. This reduction in tumorigenesis was attributable to higher expression of theKrasex3op allele, which induced growth arrest when oncogenic and exhibited tumor-suppressive activity when not mutated. Together, our data indicate that the inherent rare codon bias ofKRAS plays an integral role in tumorigenesis.Authors
Nicole L.K. Pershing, Benjamin L. Lampson, Jason A. Belsky, Erin Kaltenbrun, David M. MacAlpine, Christopher M. Counter
×Abstract
Long-term potentiation (LTP) of synaptic strength between hippocampal neurons is associated with learning and memory, and LTP dysfunction is thought to underlie memory loss. LTP can be temporally and mechanistically classified into decaying (early-phase) LTP and nondecaying (late-phase) LTP. While the nondecaying nature of LTP is thought to depend on protein synthesis and contribute to memory maintenance, little is known about the mechanisms and roles of decaying LTP. Here, we demonstrated that inhibiting endocytosis of postsynaptic α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid receptors (AMPARs) prevents LTP decay, thereby converting it into nondecaying LTP. Conversely, restoration of AMPAR endocytosis by inhibiting protein kinase Mζ (PKMζ) converted nondecaying LTP into decaying LTP. Similarly, inhibition of AMPAR endocytosis prolonged memory retention in normal animals and reduced memory loss in a murine model of Alzheimer’s disease. These results strongly suggest that an active process that involves AMPAR endocytosis mediates the decay of LTP and that inhibition of this process can prolong the longevity of LTP as well as memory under both physiological and pathological conditions.
Authors
Zhifang Dong, Huili Han, Hongjie Li, Yanrui Bai, Wei Wang, Man Tu, Yan Peng, Limin Zhou, Wenting He, Xiaobin Wu, Tao Tan, Mingjing Liu, Xiaoyan Wu, Weihui Zhou, Wuyang Jin, Shu Zhang, Todd Charlton Sacktor, Tingyu Li, Weihong Song, Yu Tian Wang
×Abstract
BACKGROUND . Roux-en-Y gastric bypass (RYGB) surgery causes profound weight loss and improves insulin sensitivity (SI) in obese patients. Regular exercise can also improve SI in obese individuals; however, it is unknown whether exercise and RYGB surgery–induced weight loss would additively improve SI and other cardiometabolic factors.METHODS . We conducted a single-blind, prospective, randomized trial with 128 men and women who recently underwent RYGB surgery (within 1–3 months). Participants were randomized to either a 6-month semi-supervised moderate exercise protocol (EX,n = 66) or a health education control (CON;n = 62) intervention. Main outcomes measured included SI and glucose effectiveness (SG), which were determined from an intravenous glucose tolerance test and minimal modeling. Secondary outcomes measured were cardiorespiratory fitness (VO2 peak) and body composition. Data were analyzed using an intention-to-treat (ITT) and per-protocol (PP) approach to assess the efficacy of the exercise intervention (>120 min of exercise/week).RESULTS . 119 (93%) participants completed the interventions, 95% for CON and 91% for EX. There was a significant decrease in body weight and fat mass for both groups (P < 0.001 for time effect). SI improved in both groups following the intervention (ITT: CON vs. EX; +1.64 vs. +2.24 min–1/μU/ml,P = 0.18 for Δ,P < 0.001 for time effect). A PP analysis revealed that exercise produced an additive SI improvement (PP: CON vs. EX; +1.57 vs. +2.69 min–1/μU/ml,P = 0.019) above that of surgery. Exercise also improved SG (ITT: CON vs. EX; +0.0023 vs. +0.0063 min–1,P = 0.009) compared with the CON group. Exercise improved cardiorespiratory fitness (VO2 peak) compared with the CON group.CONCLUSION . Moderate exercise following RYGB surgery provides additional improvements in SI, SG, and cardiorespiratory fitness compared with a sedentary lifestyle during similar weight loss.TRIAL REGISTRATION . clinicaltrials.gov identifier: NCT00692367.FUNDING . This study was funded by the NIH/National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK078192) and an NIH/National Center for Research Resources/Clinical and Translational Science Award (UL1 RR024153).Authors
Paul M. Coen, Charles J. Tanner, Nicole L. Helbling, Gabriel S. Dubis, Kazanna C. Hames, Hui Xie, George M. Eid, Maja Stefanovic-Racic, Frederico G.S. Toledo, John M. Jakicic, Joseph A. Houmard, Bret H. Goodpaster
×Abstract
Premature ovarian failure (POF) is a genetically and phenotypically heterogeneous disorder that includes individuals with manifestations ranging from primary amenorrhea to loss of menstrual function prior to age 40. POF presents as hypergonadotropic hypogonadism and can be part of a syndrome or occur in isolation. Here, we studied 3 sisters with primary amenorrhea, hypothyroidism, and hypergonadotropic hypogonadism. The sisters were born to parents who are first cousins. SNP analysis and whole-exome sequencing revealed the presence of a pathogenic variant of the minichromosome maintenance 8 gene (
MCM8 , c.446C>G; p.P149R) located within a region of homozygosity that was present in the affected daughters but not in their unaffected sisters. Because MCM8 participates in homologous recombination and dsDNA break repair, we tested fibroblasts from the affected sisters for hypersensitivity to chromosomal breaks. Compared with fibroblasts from unaffected daughters, chromosomal break repair was deficient in fibroblasts from the affected individuals, likely due to inhibited recruitment of MCM8 p.P149R to sites of DNA damage. Our study identifies an autosomal recessive disorder caused by anMCM8 mutation that manifests with endocrine dysfunction and genomic instability.Authors
Saleh AlAsiri, Sulman Basit, Michelle A. Wood-Trageser, Svetlana A. Yatsenko, Elizabeth P. Jeffries, Urvashi Surti, Deborah M. Ketterer, Sibtain Afzal, Khushnooda Ramzan, Muhammad Faiyaz-Ul Haque, Huaiyang Jiang, Michael A. Trakselis, Aleksandar Rajkovic
×Abstract
Spinocerebellar ataxia type 28 (SCA28) is a neurodegenerative disease caused by mutations of the mitochondrial protease AFG3L2. The SCA28 mouse model, which is haploinsufficient for
Afg3l2 , exhibits a progressive decline in motor function and displays dark degeneration of Purkinje cells (PC-DCD) of mitochondrial origin. Here, we determined that mitochondria in culturedAfg3l2 -deficient PCs ineffectively buffer evoked Ca2+ peaks, resulting in enhanced cytoplasmic Ca2+ concentrations, which subsequently triggers PC-DCD. This Ca2+-handling defect is the result of negative synergism between mitochondrial depolarization and altered organelle trafficking to PC dendrites inAfg3l2 -mutant cells. In SCA28 mice, partial genetic silencing of the metabotropic glutamate receptor mGluR1 decreased Ca2+ influx in PCs and reversed the ataxic phenotype. Moreover, administration of the β-lactam antibiotic ceftriaxone, which promotes synaptic glutamate clearance, thereby reducing Ca2+ influx, improved ataxia-associated phenotypes in SCA28 mice when given either prior to or after symptom onset. Together, the results of this study indicate that ineffective mitochondrial Ca2+ handling in PCs underlies SCA28 pathogenesis and suggest that strategies that lower glutamate stimulation of PCs should be further explored as a potential treatment for SCA28 patients.Authors
Francesca Maltecca, Elisa Baseggio, Francesco Consolato, Davide Mazza, Paola Podini, Samuel M. Young Jr., Ilaria Drago, Ben A. Bahr, Aldamaria Puliti, Franca Codazzi, Angelo Quattrini, Giorgio Casari
×Abstract
Polymorphisms within
HLA gene loci are strongly associated with susceptibility to autoimmune disorders; however, it is not clear how genetic variations in these loci confer a disease risk. Here, we devised a cell-surface MHC expression assay to detect allelic differences in the intrinsic stability of HLA-DQ proteins. We found extreme variation in cell-surface MHC density amongHLA-DQ alleles, indicating a dynamic allelic hierarchy in the intrinsic stability of HLA-DQ proteins. Using the case-control data for type 1 diabetes (T1D) for the Swedish and Japanese populations, we determined that T1D risk–associatedHLA-DQ haplotypes, which also increase risk for autoimmune endocrinopathies and other autoimmune disorders, encode unstable proteins, whereas the T1D–protective haplotypes encode the most stable HLA-DQ proteins. Among the amino acid variants ofHLA-DQ , alterations in 47α, the residue that is located on the outside of the peptide-binding groove and acts as a key stability regulator, showed strong association with T1D. Evolutionary analysis suggested that 47α variants have been the target of positive diversifying selection. Our study demonstrates a steep allelic hierarchy in the intrinsic stability of HLA-DQ that is associated with T1D risk and protection, suggesting that HLA instability mediates the development of autoimmune disorders.Authors
Hiroko Miyadera, Jun Ohashi, Åke Lernmark, Toshio Kitamura, Katsushi Tokunaga
×Abstract
The strong genetic association between particular HLA alleles and type 1 diabetes (T1D) indicates a key role for CD4+ T cells in disease; however, the differentiation state of the responsible T cells is unclear. T cell differentiation originally was considered a dichotomy between Th1 and Th2 cells, with Th1 cells deemed culpable for autoimmune islet destruction. Now, multiple additional T cell differentiation fates are recognized with distinct roles. Here, we used a transgenic mouse model of diabetes to probe the gene expression profile of islet-specific T cells by microarray and identified a clear follicular helper T (Tfh) cell differentiation signature. Introduction of T cells with a Tfh cell phenotype from diabetic animals efficiently transferred diabetes to recipient animals. Furthermore, memory T cells from patients with T1D expressed elevated levels of Tfh cell markers, including
CXCR5 ,ICOS ,PDCD1 ,BCL6 , andIL21 . Defects in the IL-2 pathway are associated with T1D, and IL-2 inhibits Tfh cell differentiation in mice. Consistent with these previous observations, we found that IL-2 inhibited human Tfh cell differentiation and identified a relationship between IL-2 sensitivity in T cells from patients with T1D and acquisition of a Tfh cell phenotype. Together, these findings identify a Tfh cell signature in autoimmune diabetes and suggest that this population could be used as a biomarker and potentially targeted for T1D interventions.Authors
Rupert Kenefeck, Chun Jing Wang, Tauseef Kapadi, Lukasz Wardzinski, Kesley Attridge, Louise E. Clough, Frank Heuts, Alexandros Kogimtzis, Sapna Patel, Miranda Rosenthal, Masahiro Ono, David M. Sansom, Parth Narendran, Lucy S.K. Walker
×Abstract
Epstein-Barr virus (EBV) infection transforms B cells in vitro and is associated with human B cell lymphomas. The major EBV oncoprotein, latent membrane protein 1 (LMP1), mimics constitutively active CD40 and is essential for outgrowth of EBV-transformed B cells in vitro; however, EBV-positive diffuse large B cell lymphomas and Burkitt lymphomas often express little or no LMP1. Thus, EBV may contribute to the development and maintenance of human lymphomas even in the absence of LMP1. Here, we found that i.p. injection of human cord blood mononuclear cells infected with a LMP1-deficient EBV into immunodeficient mice induces B cell lymphomas. In this model, lymphoma development required the presence of CD4+ T cells in cord blood and was inhibited by CD40-blocking Abs. In contrast, LMP1-deficient EBV established persistent latency but did not induce lymphomas when directly injected into mice engrafted with human fetal CD34+ cells and human thymus. WT EBV induced lymphomas in both mouse models and did not require coinjected T cells in the cord blood model. Together, these results demonstrate that LMP1 is not essential for EBV-induced lymphomas in vivo and suggest that T cells supply signals that substitute for LMP1 in EBV-positive B cell lymphomagenesis.
Authors
Shi-Dong Ma, Xuequn Xu, Julie Plowshay, Erik A. Ranheim, William J. Burlingham, Jeffrey L. Jensen, Fotis Asimakopoulos, Weihua Tang, Margaret L. Gulley, Ethel Cesarman, Jenny E. Gumperz, Shannon C. Kenney
×Abstract
Posttranslationally modified proteins serve as autoimmunogenic targets in a wide spectrum of autoimmune diseases. Here, we identified a posttranslationally modified paraprotein target (paratargs) in monoclonal gammopathies of undetermined significance (MGUS), multiple myelomas (MM), and Waldenstrom’s macroglobulinemias (WM) using protein macroarrays that were sumoylated and screened for reactivity with paraproteins from MGUS, MM, and WM patients. We found that paraproteins from a proportion of European, African-American, and Japanese patients specifically reacted with the sumoylated heat-shock protein 90 β isoform-α (HSP90-SUMO1, where SUMO indicates
s mallu biquitin-likemo difier), while no reactivity with HSP90-SUMO1 was detected in over 800 controls. HSP90-SUMO1 was present in blood cells from all patients with HSP90-SUMO1–binding paraproteins. We determined that the HSP90-SUMO1 carrier state is autosomal-dominantly inherited and caused by the inability of SUMO peptidase sentrin/SUMO-specific protease 2 (SENP2) to desumoylate HSP90-SUMO1. HSP90-SUMO1 was detected in a small percentage of healthy individuals from all backgrounds; however, only MGUS, MM, and WM patients who were HSP90-SUMO1 carriers produced HSP90-SUMO1–specific paraproteins, suggesting that sumoylated HSP90 promotes pathogenesis of these diseases through chronic antigenic stimulation. This study demonstrates that harboring HSP90-SUMO1 identifies healthy individuals at risk for plasma cell dyscrasias and that dominant inheritance of posttranslationally modified autoantigenic paratargs is one of the strongest molecular defined risk factors for MGUS, MM, and WM.Authors
Klaus-Dieter Preuss, Michael Pfreundschuh, Natalie Fadle, Evi Regitz, Boris Kubuschok
×Abstract
As the central pacemaker, the suprachiasmatic nucleus (SCN) has long been considered the primary regulator of blood pressure circadian rhythm; however, this dogma has been challenged by the discovery that each of the clock genes present in the SCN is also expressed and functions in peripheral tissues. The involvement and contribution of these peripheral clock genes in the circadian rhythm of blood pressure remains uncertain. Here, we demonstrate that selective deletion of the circadian clock transcriptional activator aryl hydrocarbon receptor nuclear translocator–like (
Bmal1 ) from smooth muscle, but not from cardiomyocytes, compromised blood pressure circadian rhythm and decreased blood pressure without affecting SCN-controlled locomotor activity in murine models. In mesenteric arteries, BMAL1 bound to the promoter of and activated the transcription of Rho-kinase 2 (Rock2 ), andBmal1 deletion abolished the time-of-day variations in response to agonist-induced vasoconstriction, myosin phosphorylation, and ROCK2 activation. Together, these data indicate that peripheral inputs contribute to the daily control of vasoconstriction and blood pressure and suggest that clock gene expression outside of the SCN should be further evaluated to elucidate pathogenic mechanisms of diseases involving blood pressure circadian rhythm disruption.Authors
Zhongwen Xie, Wen Su, Shu Liu, Guogang Zhao, Karyn Esser, Elizabeth A. Schroder, Mellani Lefta, Harald M. Stauss, Zhenheng Guo, Ming Cui Gong
×Abstract
The brain relies on a constant supply of glucose, its primary fuel, for optimal function. A taste-independent mechanism within the CNS that promotes glucose delivery to the brain has been postulated to maintain glucose homeostasis; however, evidence for such a mechanism is lacking. Here, we determined that glucokinase activity within the hypothalamic arcuate nucleus is involved in regulation of dietary glucose intake. In fasted rats, glucokinase activity was specifically increased in the arcuate nucleus but not other regions of the hypothalamus. Moreover, pharmacologic and genetic activation of glucokinase in the arcuate nucleus of rodent models increased glucose ingestion, while decreased arcuate nucleus glucokinase activity reduced glucose intake. Pharmacologic targeting of potential downstream glucokinase effectors revealed that ATP-sensitive potassium channel and P/Q calcium channel activity are required for glucokinase-mediated glucose intake. Additionally, altered glucokinase activity affected release of the orexigenic neurotransmitter neuropeptide Y in response to glucose. Together, our results suggest that glucokinase activity in the arcuate nucleus specifically regulates glucose intake and that appetite for glucose is an important driver of overall food intake. Arcuate nucleus glucokinase activation may represent a CNS mechanism that underlies the oft-described phenomena of the “sweet tooth” and carbohydrate craving.
Authors
Syed Hussain, Errol Richardson, Yue Ma, Christopher Holton, Ivan De Backer, Niki Buckley, Waljit Dhillo, Gavin Bewick, Shuai Zhang, David Carling, Steve Bloom, James Gardiner
×Abstract
Microglia, the innate immune cells of the CNS, perform critical inflammatory and noninflammatory functions that maintain normal neural function. For example, microglia clear misfolded proteins, elaborate trophic factors, and regulate and terminate toxic inflammation. In Alzheimer’s disease (AD), however, beneficial microglial functions become impaired, accelerating synaptic and neuronal loss. Better understanding of the molecular mechanisms that contribute to microglial dysfunction is an important objective for identifying potential strategies to delay progression to AD. The inflammatory cyclooxygenase/prostaglandin E2 (COX/PGE2) pathway has been implicated in preclinical AD development, both in human epidemiology studies and in transgenic rodent models of AD. Here, we evaluated murine models that recapitulate microglial responses to Aβ peptides and determined that microglia-specific deletion of the gene encoding the PGE2 receptor EP2 restores microglial chemotaxis and Aβ clearance, suppresses toxic inflammation, increases cytoprotective insulin-like growth factor 1 (IGF1) signaling, and prevents synaptic injury and memory deficits. Our findings indicate that EP2 signaling suppresses beneficial microglia functions that falter during AD development and suggest that inhibition of the COX/PGE2/EP2 immune pathway has potential as a strategy to restore healthy microglial function and prevent progression to AD.
Authors
Jenny U. Johansson, Nathaniel S. Woodling, Qian Wang, Maharshi Panchal, Xibin Liang, Angel Trueba-Saiz, Holden D. Brown, Siddhita D. Mhatre, Taylor Loui, Katrin I. Andreasson
×Abstract
Chemokines are important modulators of neuroinflammation and neurodegeneration. In the brains of Alzheimer’s disease (AD) patients and in AD animal models, the chemokine CXCL10 is found in high concentrations, suggesting a pathogenic role for this chemokine and its receptor, CXCR3. Recent studies aimed at addressing the role of CXCR3 in neurological diseases indicate potent, but diverse, functions for CXCR3. Here, we examined the impact of CXCR3 in the amyloid precursor protein (APP)/presenilin 1 (PS1) transgenic mouse model of AD. We found that, compared with control APP/PSI animals, plaque burden and Aβ levels were strongly reduced in CXCR3-deficient APP/PS1 mice. Analysis of microglial phagocytosis in vitro and in vivo demonstrated that CXCR3 deficiency increased the microglial uptake of Aβ. Application of a CXCR3 antagonist increased microglial Aβ phagocytosis, which was associated with reduced TNF-α secretion. Moreover, in CXCR3-deficient APP/PS1 mice, microglia exhibited morphological activation and reduced plaque association, and brain tissue from APP/PS1 animals lacking CXCR3 had reduced concentrations of proinflammatory cytokines compared with controls. Further, loss of CXCR3 attenuated the behavioral deficits observed in APP/PS1 mice. Together, our data indicate that CXCR3 signaling mediates development of AD-like pathology in APP/PS1 mice and suggest that CXCR3 has potential as a therapeutic target for AD.
Authors
Marius Krauthausen, Markus P. Kummer, Julian Zimmermann, Elisabet Reyes-Irisarri, Dick Terwel, Bruno Bulic, Michael T. Heneka, Marcus Müller
×Abstract
Glucagon-like peptide-1–based (GLP-1–based) therapies improve glycemic control in patients with type 2 diabetes. While these agents augment insulin secretion, they do not mimic the physiological meal-related rise and fall of GLP-1 concentrations. Here, we tested the hypothesis that increasing the number of intestinal L cells, which produce GLP-1, is an alternative strategy to augment insulin responses and improve glucose tolerance. Blocking the NOTCH signaling pathway with the γ-secretase inhibitor dibenzazepine increased the number of L cells in intestinal organoid–based mouse and human culture systems and augmented glucose-stimulated GLP-1 secretion. In a high-fat diet–fed mouse model of impaired glucose tolerance and type 2 diabetes, dibenzazepine administration increased L cell numbers in the intestine, improved the early insulin response to glucose, and restored glucose tolerance. Dibenzazepine also increased K cell numbers, resulting in increased gastric inhibitory polypeptide (GIP) secretion. Using a GLP-1 receptor antagonist, we determined that the insulinotropic effect of dibenzazepine was mediated through an increase in GLP-1 signaling. Together, our data indicate that modulation of the development of incretin-producing cells in the intestine has potential as a therapeutic strategy to improve glycemic control.
Authors
Natalia Petersen, Frank Reimann, Johan H. van Es, Bernard M. van den Berg, Chantal Kroone, Ramona Pais, Erik Jansen, Hans Clevers, Fiona M. Gribble, Eelco J.P. de Koning
×Abstract
Nonalcoholic fatty liver disease (NAFLD) is a major worldwide health problem. Recent studies suggest that the gut microbiota influences NAFLD pathogenesis. Here, a murine model of high-fat diet–induced (HFD-induced) NAFLD was used, and the effects of alterations in the gut microbiota on NAFLD were determined. Mice treated with antibiotics or tempol exhibited altered bile acid composition, with a notable increase in conjugated bile acid metabolites that inhibited intestinal farnesoid X receptor (FXR) signaling. Compared with control mice, animals with intestine-specific
Fxr disruption had reduced hepatic triglyceride accumulation in response to a HFD. The decrease in hepatic triglyceride accumulation was mainly due to fewer circulating ceramides, which was in part the result of lower expression of ceramide synthesis genes. The reduction of ceramide levels in the ileum and serum in tempol- or antibiotic-treated mice fed a HFD resulted in downregulation of hepatic SREBP1C and decreased de novo lipogenesis. Administration of C16:0 ceramide to antibiotic-treated mice fed a HFD reversed hepatic steatosis. These studies demonstrate that inhibition of an intestinal FXR/ceramide axis mediates gut microbiota–associated NAFLD development, linking the microbiome, nuclear receptor signaling, and NAFLD. This work suggests that inhibition of intestinal FXR is a potential therapeutic target for NAFLD treatment.Authors
Changtao Jiang, Cen Xie, Fei Li, Limin Zhang, Robert G. Nichols, Kristopher W. Krausz, Jingwei Cai, Yunpeng Qi, Zhong-Ze Fang, Shogo Takahashi, Naoki Tanaka, Dhimant Desai, Shantu G. Amin, Istvan Albert, Andrew D. Patterson, Frank J. Gonzalez
×Abstract
SCN5A encodes the α subunit of the major cardiac sodium channel NaV1.5. Mutations inSCN5A are associated with conduction disease and ventricular fibrillation (VF); however, the mechanisms that link loss of sodium channel function to arrhythmic instability remain unresolved. Here, we generated a large-animal model of a human cardiac sodium channelopathy in pigs, which have cardiac structure and function similar to humans, to better define the arrhythmic substrate. We introduced a nonsense mutation originally identified in a child with Brugada syndrome into the orthologous position (E558X) in the pigSCN5A gene.SCN5AE558X/+ pigs exhibited conduction abnormalities in the absence of cardiac structural defects. Sudden cardiac death was not observed in young pigs; however, Langendorff-perfusedSCN5AE558X/+ hearts had an increased propensity for pacing-induced or spontaneous VF initiated by short-coupled ventricular premature beats. Optical mapping during VF showed that activity often began as an organized focal source or broad wavefront on the right ventricular (RV) free wall. Together, the results from this study demonstrate that theSCN5AE558X/+ pig model accurately phenocopies many aspects of human cardiac sodium channelopathy, including conduction slowing and increased susceptibility to ventricular arrhythmias.Authors
David S. Park, Marina Cerrone, Gregory Morley, Carolina Vasquez, Steven Fowler, Nian Liu, Scott A. Bernstein, Fang-Yu Liu, Jie Zhang, Christopher S. Rogers, Silvia G. Priori, Larry A. Chinitz, Glenn I. Fishman
×Abstract
Genome integrity is continuously challenged by the DNA damage that arises during normal cell metabolism. Biallelic mutations in the genes encoding the genome surveillance enzyme ribonuclease H2 (RNase H2) cause Aicardi-Goutières syndrome (AGS), a pediatric disorder that shares features with the autoimmune disease systemic lupus erythematosus (SLE). Here we determined that heterozygous parents of AGS patients exhibit an intermediate autoimmune phenotype and demonstrated a genetic association between rare
RNASEH2 sequence variants and SLE. Evaluation of patient cells revealed that SLE- and AGS-associated mutations impair RNase H2 function and result in accumulation of ribonucleotides in genomic DNA. The ensuing chronic low level of DNA damage triggered a DNA damage response characterized by constitutive p53 phosphorylation and senescence. Patient fibroblasts exhibited constitutive upregulation of IFN-stimulated genes and an enhanced type I IFN response to the immunostimulatory nucleic acid polyinosinic:polycytidylic acid and UV light irradiation, linking RNase H2 deficiency to potentiation of innate immune signaling. Moreover, UV-induced cyclobutane pyrimidine dimer formation was markedly enhanced in ribonucleotide-containing DNA, providing a mechanism for photosensitivity in RNase H2–associated SLE. Collectively, our findings implicate RNase H2 in the pathogenesis of SLE and suggest a role of DNA damage–associated pathways in the initiation of autoimmunity.Authors
Claudia Günther, Barbara Kind, Martin A.M. Reijns, Nicole Berndt, Manuel Martinez-Bueno, Christine Wolf, Victoria Tüngler, Osvaldo Chara, Young Ae Lee, Norbert Hübner, Louise Bicknell, Sophia Blum, Claudia Krug, Franziska Schmidt, Stefanie Kretschmer, Sarah Koss, Katy R. Astell, Georgia Ramantani, Anja Bauerfeind, David L. Morris, Deborah S. Cunninghame Graham, Doryen Bubeck, Andrea Leitch, Stuart H. Ralston, Elizabeth A. Blackburn, Manfred Gahr, Torsten Witte, Timothy J. Vyse, Inga Melchers, Elisabeth Mangold, Markus M. Nöthen, Martin Aringer, Annegret Kuhn, Kirsten Lüthke, Leonore Unger, Annette Bley, Alice Lorenzi, John D. Isaacs, Dimitra Alexopoulou, Karsten Conrad, Andreas Dahl, Axel Roers, Marta E. Alarcon-Riquelme, Andrew P. Jackson, Min Ae Lee-Kirsch
×Abstract
Persistent HPV infection is recognized as the main etiologic factor for cervical cancer. HPV expresses the oncoproteins E6 and E7, both of which play key roles in maintaining viral infection and promoting carcinogenesis. While siRNA-mediated targeting of
E6 andE7 transcripts temporarily induces apoptosis in HPV-positive cells, it does not eliminate viral DNA within the host genome, which can harbor escape mutants. Here, we demonstrated that specifically targetingE6 andE7 within host DNA with transcription activator–like effector nucleases (TALENs) induces apoptosis, inhibits growth, and reduces tumorigenicity in HPV-positive cell lines. TALEN treatment efficiently disruptedE6 andE7 oncogenes, leading to the restoration of host tumor suppressors p53 and retinoblastoma 1 (RB1), which are targeted by E6 and E7, respectively. In the K14-HPV16 transgenic mouse model of HPV-driven neoplasms, direct cervical application of HPV16-E7 –targeted TALENs effectively mutated theE7 oncogene, reduced viral DNA load, and restored RB1 function and downstream targets transcription factor E2F1 and cycling-dependent kinase 2 (CDK2), thereby reversing the malignant phenotype. Together, the results from our study suggest that TALENs have potential as a therapeutic strategy for HPV infection and related cervical malignancy.Authors
Zheng Hu, Wencheng Ding, Da Zhu, Lan Yu, Xiaohui Jiang, Xiaoli Wang, Changlin Zhang, Liming Wang, Teng Ji, Dan Liu, Dan He, Xi Xia, Tao Zhu, Juncheng Wei, Peng Wu, Changyu Wang, Ling Xi, Qinglei Gao, Gang Chen, Rong Liu, Kezhen Li, Shuang Li, Shixuan Wang, Jianfeng Zhou, Ding Ma, Hui Wang
×Abstract
For hepatitis C virus (HCV) and other highly variable viruses, broadly neutralizing mAbs are an important guide for vaccine development. The development of resistance to anti-HCV mAbs is poorly understood, in part due to a lack of neutralization testing against diverse, representative panels of HCV variants. Here, we developed a neutralization panel expressing diverse, naturally occurring HCV envelopes (E1E2s) and used this panel to characterize neutralizing breadth and resistance mechanisms of 18 previously described broadly neutralizing anti-HCV human mAbs. The observed mAb resistance could not be attributed to polymorphisms in E1E2 at known mAb-binding residues. Additionally, hierarchical clustering analysis of neutralization resistance patterns revealed relationships between mAbs that were not predicted by prior epitope mapping, identifying 3 distinct neutralization clusters. Using this clustering analysis and envelope sequence data, we identified polymorphisms in E2 that confer resistance to multiple broadly neutralizing mAbs. These polymorphisms, which are not at mAb contact residues, also conferred resistance to neutralization by plasma from HCV-infected subjects. Together, our method of neutralization clustering with sequence analysis reveals that polymorphisms at noncontact residues may be a major immune evasion mechanism for HCV, facilitating viral persistence and presenting a challenge for HCV vaccine development.
Authors
Justin R. Bailey, Lisa N. Wasilewski, Anna E. Snider, Ramy El-Diwany, William O. Osburn, Zhenyong Keck, Steven K.H. Foung, Stuart C. Ray
×Abstract
BACKGROUND. Previous efforts to preserve β cell function in individuals with type 1 diabetes (T1D) have focused largely on the use of single immunomodulatory agents administered within 100 days of diagnosis. Based on human and preclinical studies, we hypothesized that a combination of low-dose anti-thymocyte globulin (ATG) and pegylated granulocyte CSF (G-CSF) would preserve β cell function in patients with established T1D (duration of T1D >4 months and <2 years).METHODS. A randomized, single-blinded, placebo-controlled trial was performed on 25 subjects: 17 subjects received ATG (2.5 mg/kg intravenously) followed by pegylated G-CSF (6 mg subcutaneously every 2 weeks for 6 doses) and 8 subjects received placebo. The primary outcome was the 1-year change in AUC C-peptide following a 2-hour mixed-meal tolerance test (MMTT). At baseline, the age (mean ± SD) was 24.6 ± 10 years; mean BMI was 25.4 ± 5.2 kg/m2; mean A1c was 6.5% ± 1.1%; insulin use was 0.31 ± 0.22 units/kg/d; and length of diagnosis was 1 ± 0.5 years.RESULTS. Combination ATG/G-CSF treatment tended to preserve β cell function in patients with established T1D. The mean difference in MMTT-stimulated AUC C-peptide between treated and placebo subjects was 0.28 nmol/l/min (95% CI 0.001–0.552,P = 0.050). A1c was lower in ATG/G-CSF–treated subjects at the 6-month study visit. ATG/G-CSF therapy was associated with relative preservation of Tregs.CONCLUSIONS. Patients with established T1D may benefit from combination immunotherapy approaches to preserve β cell function. Further studies are needed to determine whether such approaches may prevent or delay the onset of the disease.TRIAL REGISTRATION. Clinicaltrials.gov NCT01106157.FUNDING. The Leona M. and Harry B. Helmsley Charitable Trust and Sanofi.Authors
Michael J. Haller, Stephen E. Gitelman, Peter A. Gottlieb, Aaron W. Michels, Stephen M. Rosenthal, Jonathan J. Shuster, Baiming Zou, Todd M. Brusko, Maigan A. Hulme, Clive H. Wasserfall, Clayton E. Mathews, Mark A. Atkinson, Desmond A. Schatz
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Corrigenda
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Abstract
Authors
Michaela Yuen, Sarah A. Sandaradura, James J. Dowling, Alla S. Kostyukova, Natalia Moroz, Kate G. Quinlan, Vilma-Lotta Lehtokari, Gianina Ravenscroft, Emily J. Todd, Ozge Ceyhan-Birsoy, David S. Gokhin, Jérome Maluenda, Monkol Lek, Flora Nolent, Christopher T. Pappas, Stefanie M. Novak, Adele D’Amico, Edoardo Malfatti, Brett P. Thomas, Stacey B. Gabriel, Namrata Gupta, Mark J. Daly, Biljana Ilkovski, Peter J. Houweling, Ann E. Davidson, Lindsay C. Swanson, Catherine A. Brownstein, Vandana A. Gupta, Livija Medne, Patrick Shannon, Nicole Martin, David P. Bick, Anders Flisberg, Eva Holmberg, Peter Van den Bergh, Pablo Lapunzina, Leigh B. Waddell, Darcée D. Sloboda, Enrico Bertini, David Chitayat, William R. Telfer, Annie Laquerrière, Carol C. Gregorio, Coen A.C. Ottenheijm, Carsten G. Bönnemann, Katarina Pelin, Alan H. Beggs, Yukiko K. Hayashi, Norma B. Romero, Nigel G. Laing, Ichizo Nishino, Carina Wallgren-Pettersson, Judith Melki, Velia M. Fowler, Daniel G. MacArthur, Kathryn N. North, Nigel F. Clarke
×Abstract
Authors
Brice Emanuelli, Sara G. Vienberg, Graham Smyth, Christine Cheng, Kristin I. Stanford, Manimozhiyan Arumugam, Mervyn D. Michael, Andrew C. Adams, Alexei Kharitonenkov, C. Ronald Kahn
Copyright © 2024 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)