The sensory nerve was recently identified as being involved in regulation of bone mass accrual. We previously discovered that prostaglandin E2 (PGE2) secreted by osteoblasts could activate sensory nerve EP4 receptor to promote bone formation by inhibiting sympathetic activity. However, the fundamental units of bone formation are active osteoblasts, which originate from mesenchymal stromal/stem cells (MSCs). Here, we found that after sensory denervation, knockout of the EP4 receptor in sensory nerves, or knockout of COX-2 in osteoblasts, could significantly promote adipogenesis and inhibit osteogenesis in adult mice. Furthermore, injection of SW033291 (a small molecule that locally increases the PGE2 level) or propranolol (a beta blocker) significantly promoted osteogenesis and inhibited adipogenesis. This effect of SW033291, but not propranolol, was abolished in conditional EP4-KO mice under normal conditions or in the bone repair process. We conclude that the PGE2/EP4 sensory nerve axis could regulate MSC differentiation in bone marrow of adult mice.
Bo Hu, Xiao Lv, Hao Chen, Peng Xue, Bo Gao, Xiao Wang, Gehua Zhen, Janet L. Crane, Dayu Pan, Shen Liu, Shuangfei Ni, Panfeng Wu, Weiping Su, Xiaonan Liu, Zemin Ling, Mi Yang, Ruoxian Deng, Yusheng Li, Lei Wang, Ying Zhang, Mei Wan, Zengwu Shao, Huajiang Chen, Wen Yuan, Xu Cao
Multiple sclerosis (MS) is an inflammatory demyelinating disorder of the CNS. Bile acids are cholesterol metabolites that can signal through receptors on cells throughout the body, including in the CNS and the immune system. Whether bile acid metabolism is abnormal in MS is unknown. Using global and targeted metabolomic profiling, we identified lower levels of circulating bile acid metabolites in multiple cohorts of adult and pediatric patients with MS compared with controls. In white matter lesions from MS brain tissue, we noted the presence of bile acid receptors on immune and glial cells. To mechanistically examine the implications of lower levels of bile acids in MS, we studied the in vitro effects of an endogenous bile acid, tauroursodeoxycholic acid (TUDCA), on astrocyte and microglial polarization. TUDCA prevented neurotoxic (A1) polarization of astrocytes and proinflammatory polarization of microglia in a dose-dependent manner. TUDCA supplementation in experimental autoimmune encephalomyelitis reduced the severity of disease through its effects on G protein–coupled bile acid receptor 1 (GPBAR1). We demonstrate that bile acid metabolism was altered in MS and that bile acid supplementation prevented polarization of astrocytes and microglia to neurotoxic phenotypes and ameliorated neuropathology in an animal model of MS. These findings identify dysregulated bile acid metabolism as a potential therapeutic target in MS.
Pavan Bhargava, Matthew D. Smith, Leah Mische, Emily Harrington, Kathryn C. Fitzgerald, Kyle Martin, Sol Kim, Arthur Anthony Reyes, Jaime Gonzalez-Cardona, Christina Volsko, Ajai Tripathi, Sonal Singh, Kesava Varanasi, Hannah-Noelle Lord, Keya Meyers, Michelle Taylor, Marjan Gharagozloo, Elias S. Sotirchos, Bardia Nourbakhsh, Ranjan Dutta, Ellen M. Mowry, Emmanuelle Waubant, Peter A. Calabresi
Since it was shown in the early 1950s that it is possible to induce transplantation tolerance in neonates, immune tolerance strategies have been actively pursued. It was found that T cells play a critical role in graft rejection, but can also be major players in mediating transplantation tolerance. Consequently, many experimental systems focused on T cells, often with a complete exclusion of B cells from in vivo animal models. It is now becoming clear that in addition to T cells, B cells can mediate graft rejection and transplantation tolerance. In this issue of the JCI, Khiew et al. investigated the contribution of alloreactive B cells to transplantation tolerance using a mouse cardiac transplantation model. The authors revealed a distinct tolerant B cell phenotype possessing the ability to suppress naive B cells. These data lead to a better understanding of B cell contributions to transplantation tolerance, and may inform the development of future immune tolerance protocols.
AMPK is a heterotrimeric complex that serves as a major sensor of energy status in eukaryotic cells. Accumulating evidence depicts a complex role of dysregulated AMPK signaling in Alzheimer’s disease (AD). In this issue of the JCI, Zimmermann et al. report on their investigation of AD-specific differential expression of AMPKα1 and AMPKα2 isoforms of the catalytic subunit and demonstrate that genetic reduction of AMPKα1, but not AMPKα2, rescued cognitive decline in AD mouse models. These findings reveal an isoform-specific role of AMPKα in the pathogenesis of AD, which likely provides a more precise target for future therapeutic development.
Fanpeng Zhao, Chunyu Wang, Xiongwei Zhu
AMPK is a key regulator at the molecular level for maintaining energy metabolism homeostasis. Mammalian AMPK is a heterotrimeric complex, and its catalytic α subunit exists in 2 isoforms: AMPKα1 and AMPKα2. Recent studies suggest a role of AMPKα overactivation in Alzheimer’s disease–associated (AD-associated) synaptic failure. However, whether AD-associated dementia can be improved by targeting AMPK remains unclear, and roles of AMPKα isoforms in AD pathophysiology are not understood. Here, we showed distinct disruption of hippocampal AMPKα isoform expression patterns in postmortem human AD patients and AD model mice. We further investigated the effects of brain- and isoform-specific AMPKα repression on AD pathophysiology. We found that repression of AMPKα1 alleviated cognitive deficits and synaptic failure displayed in 2 separate lines of AD model mice. In contrast, AMPKα2 suppression did not alter AD pathophysiology. Using unbiased mass spectrometry–based proteomics analysis, we identified distinct patterns of protein expression associated with specific AMPKα isoform suppression in AD model mice. Further, AD-associated hyperphosphorylation of eukaryotic elongation factor 2 (eEF2) was blunted with selective AMPKα1 inhibition. Our findings reveal isoform-specific roles of AMPKα in AD pathophysiology, thus providing insights into potential therapeutic strategies for AD and related dementia syndromes.
Helena R. Zimmermann, Wenzhong Yang, Nicole P. Kasica, Xueyan Zhou, Xin Wang, Brenna C. Beckelman, Jingyun Lee, Cristina M. Furdui, C. Dirk Keene, Tao Ma
β Cell apoptosis and dedifferentiation are 2 hotly debated mechanisms underlying β cell loss in type 2 diabetes; however, the molecular drivers underlying such events remain largely unclear. Here, we performed a side-by-side comparison of mice carrying β cell–specific deletion of ER-associated degradation (ERAD) and autophagy. We reported that, while autophagy was necessary for β cell survival, the highly conserved Sel1L-Hrd1 ERAD protein complex was required for the maintenance of β cell maturation and identity. Using single-cell RNA-Seq, we demonstrated that Sel1L deficiency was not associated with β cell loss, but rather loss of β cell identity. Sel1L-Hrd1 ERAD controlled β cell identity via TGF-β signaling, in part by mediating the degradation of TGF-β receptor 1. Inhibition of TGF-β signaling in Sel1L-deficient β cells augmented the expression of β cell maturation markers and increased the total insulin content. Our data revealed distinct pathogenic effects of 2 major proteolytic pathways in β cells, providing a framework for therapies targeting distinct mechanisms of protein quality control.
Neha Shrestha, Tongyu Liu, Yewei Ji, Rachel B. Reinert, Mauricio Torres, Xin Li, Maria Zhang, Chih-Hang Anthony Tang, Chih-Chi Andrew Hu, Chengyang Liu, Ali Naji, Ming Liu, Jiandie D. Lin, Sander Kersten, Peter Arvan, Ling Qi
The absence of alloantibodies is a feature of transplantation tolerance. Although the lack of T cell help has been evoked to explain this absence, herein we provide evidence for B cell–intrinsic tolerance mechanisms. Using a murine model of heart tolerance, we showed that alloreactive B cells were not deleted but rapidly lost their ability to differentiate into germinal center B cells and secrete donor-specific antibodies. We inferred that tolerant alloreactive B cells retained their ability to sense alloantigen because they continued to drive T cell maturation into CXCR5+PD-1+ T follicular helper cells. Unexpectedly, dysfunctional alloreactive B cells acquired the ability to inhibit antibody production by new naive B cells in an antigen-specific manner. Thus, tolerant alloreactive B cells contribute to transplantation tolerance by foregoing germinal center responses while retaining their ability to function as antigen-presenting cells and by actively suppressing de novo alloreactive B cell responses.
Stella H.W. Khiew, Dharmendra Jain, Jianjun Chen, Jinghui Yang, Dengping Yin, James S. Young, Alexander Dent, Roger Sciammas, Maria-Luisa Alegre, Anita S. Chong
Mark Donowitz, Jerrold R. Turner, Alan S. Verkman, Nicholas Constantine Zachos
Barney S. Graham, Kizzmekia S. Corbett
This Viewpoint calls on investigators that are developing and testing therapeutic and prophylactic approaches for COVID-19 to design studies that are inclusive of male-female differences.
Evelyne Bischof, Jeannette Wolfe, Sabra L. Klein
The Warburg effect is a tumor related phenomenon that may be targeted therapeutically. Here, we showed that glioblastoma cultures and patient tumors harbored super-enhancers in several genes related to the Warburg effect. By conducting a transcriptome analysis followed by chromatin immunoprecipitation (CHIP) sequencing coupled with a comprehensive metabolite analysis in GBM models, we unraveled that FDA-approved global (panobinostat, vorinostat) and selective (romidepsin) histone-deacetylase (HDAC) inhibitors elicited metabolic reprogramming in concert with disruption of several Warburg-effect related super-enhancers. Extracellular flux and carbon tracing analyses revealed that HDAC inhibitors blunted glycolysis in a c-Myc dependent manner accompanied by lower ATP levels. This resulted in engagement of oxidative phosphorylation (OXPHOS) driven by elevated fatty acid oxidation (FAO), rendering GBM cells dependent on these pathways. Mechanistically, interference with HDAC1/2 elicited a suppression of c-Myc protein levels and a concomitant increase of two transcriptional drivers of oxidative metabolism, PGC1A and PPARD, suggesting an inverse relationship. Rescue and CHIP experiments indicated that c-Myc bound to the promoter regions of PGC1A and PPARD to counteract their up-regulation driven by HDAC1/2 inhibition. Finally, we demonstrated that the combination treatment of HDAC and FAO inhibitors extended animal survival in patient-derived xenograft (PDX) model systems in vivo more potently than single treatments in the absence of toxicity.
Trang Nguyen, Yiru Zhang, Enyuan Shang, Chang Shu, Consuelo Torrini, Junfei Zhao, Elena Bianchetti, Angeliki Mela, Nelson Humala, Aayushi Mahajan, Arif O. Harmanci, Zhengdeng Lei, Mark Maienschein-Cline, Catarina Maria Quinzii, Mike-Andrew Westhoff, Georg Karpel-Massler, Jeffrey N. Bruce, Peter Canoll, Markus D. Siegelin
Unchecked inflammation is a hallmark of inflammatory tissue injury in diseases such as acute respiratory distress syndrome (ARDS). Yet the mechanisms of inflammatory lung injury remain largely unknown. Here we showed that bacterial endotoxin lipopolysaccharide (LPS) and cecal ligation and puncture (CLP)-induced polymicrobial sepsis decreased the expression of transcription factor cAMP Response Element Binding (CREB) in lung endothelial cells. We demonstrated that endothelial CREB was crucial for VE-cadherin transcription and the formation of the normal restrictive endothelial adherens junctions. The inflammatory cytokine IL-1β reduced cAMP generation and CREB-mediated transcription of VE-cadherin. Furthermore, endothelial cell-specific deletion of CREB induced lung vascular injury whereas ectopic expression of CREB in the endothelium prevented the injury. We also observed that rolipram, which inhibits PDE4-mediated hydrolysis of cAMP, prevented endotoxemia-induced lung vascular injury since it preserved CREB-mediated VE-cadherin expression. These data demonstrate the fundamental role of endothelial cAMP-CREB axis in promoting lung vascular integrity and suppressing inflammatory injury. Therefore, strategies aimed at enhancing endothelial CREB-mediated VE-cadherin transcription are potentially useful in preventing sepsis-induced lung vascular injury in ARDS.
Shiqin Xiong, Zhigang Hong, Long Shuang Huang, Yoshikazu Tsukasaki, Saroj Nepal, Anke Di, Ming Zhong, Wei Wu, Zhiming Ye, XiaoPei Gao, Gadiparthi Rao, Dolly Mehta, Jalees Rehman, Asrar B. Malik
Microbial ingestion by a macrophage results in the formation of an acidic phagolysosome but the host cell has no information on the pH susceptibility of the ingested organism. This poses a problem for the macrophage and raises the fundamental question of how the phagocytic cell optimizes the acidification process to prevail. We analyzed the dynamical distribution of phagolysosomal pH in murine and human macrophages that had ingested live or dead Cryptococcus neoformans cells, or inert beads. Phagolysosomal acidification produced a range of pH values that approximated normal distributions, but these differed from normality depending on ingested particle type. Analysis of the increments of pH reduction revealed no forbidden ordinal patterns, implying that phagosomal acidification process was a stochastic dynamical system. Using simulation modeling, we determined that by stochastically acidifying a phagolysosome to a pH within the observed distribution, macrophages sacrificed a small amount of overall fitness to reduce their overall variation in fitness. Hence, chance in the final phagosomal pH introduces unpredictability to the outcome of the macrophage-microbe, which implies a bet-hedging strategy that benefits the macrophage. While bet hedging is common in biological systems at the organism level, our results show its use at the organelle and cellular level.
Quigly Dragotakes, Kaitlin M. Stouffer, Man Shun Fu, Yehonatan Sella, Christine Youn, Olivia Insun Yoon, Carlos M. De Leon-Rodriguez, Joudeh Freij, Aviv Bergman, Arturo Casadevall
Ischemic acute kidney injury (AKI), a complication that frequently occurs in hospital settings, is often associated with hemodynamic compromise, sepsis, cardiac surgery or exposure to nephrotoxicants. Here, using a murine renal ischemia-reperfusion injury (IRI) model we show that intercalated cells (ICs) rapidly adopted a pro-inflammatory phenotype post-IRI. During the early phase of AKI, we demonstrate that either blocking the pro-inflammatory P2Y14 receptor located on the apical membrane of ICs, or ablation of the gene encoding the P2Y14 receptor in ICs: 1) inhibited IRI-induced chemokine expression increase in ICs; 2) reduced neutrophil and monocyte renal infiltration; 3) reduced the extent of kidney dysfunction; and 4) attenuated proximal tubule (PT) damage. These observations indicate that the P2Y14 receptor participates in the very first inflammatory steps associated with ischemic AKI. In addition, we show that the concentration of the P2Y14 receptor ligand, uridine diphosphate-glucose (UDP-Glc), was higher in urine samples from intensive care unit patients who developed AKI compared to patients without AKI. In particular, we observed a strong correlation between UDP-Glc concentration and the development of AKI in cardiac surgery patients. Our study identifies the UDP-Glc/P2Y14 receptor axis as a potential target for the prevention and/or attenuation of ischemic-AKI.
Maria Agustina Battistone, Alexandra C. Mendelsohn, Raul German Spallanzani, Andrew S. Allegretti, Rachel N. Liberman, Juliana Sesma, Sahir Kalim, Susan M. Wall, Joseph V. Bonventre, Eduardo R. Lazarowski, Dennis Brown, Sylvie Breton
BACKGROUND Novel therapeutic approaches are critically needed for Staphylococcus aureus bloodstream infections (BSI), particularly for methicillin-resistant S. aureus (MRSA). Exebacase, a first-in-class antistaphylococcal lysin, is a direct lytic agent that is rapidly bacteriolytic, eradicates biofilms, and synergizes with antibiotics. METHODS In this superiority-design study, we randomly assigned 121 patients with S. aureus BSI/endocarditis to receive a single dose of exebacase or placebo. All patients received standard-of-care antibiotics. The primary efficacy endpoint was clinical outcome (responder rate) at Day 14. RESULTS Clinical responder rates at Day 14 were 70.4% and 60.0% in the exebacase + antibiotics and antibiotics alone groups, respectively (difference=10.4, 90% CI [-6.3, 27.2], p-value=0.31), and were 42.8 percentage points higher in the pre-specified exploratory MRSA subgroup (74.1% vs. 31.3%, difference=42.8, 90% CI [14.3, 71.4], ad hoc p value=0.01). Rates of adverse events (AEs) were similar in both groups. No AEs of hypersensitivity to exebacase were reported. Thirty-day all-cause mortality rates were 9.7% and 12.8% in the exebacase + antibiotics and antibiotics alone groups, respectively, with a notable difference in MRSA (3.7% vs. 25.0%, difference= –21.3, 90% CI [-45.1, 2.5], ad hoc p-value=0.06). Among MRSA patients in the United States, median length-of-stay was 4-days shorter and 30-day hospital readmission rates were 48 percentage points lower in the exebacase-treated group compared with antibiotics alone. CONCLUSIONS This study establishes proof-of-concept for exebacase and direct lytic agents as potential therapeutics and supports conduct of a confirmatory study focused on exebacase to treat MRSA BSI.
Vance G. Fowler, Jr., Anita F. Das, Joy Lipka-Diamond, Raymond Schuch, Roger Pomerantz, Luis Jáuregui-Peredo, Adam Bressler, David C. Evans, Gregory J. Moran, Mark E. Rupp, Robert A. Wise, G. Ralph Corey, Marcus Zervos, Pamela S. Douglas, Cara Cassino
Food allergies are a major clinical problem and are driven by IgE antibodies specific for food antigens. T follicular regulatory (TFR) cells are a specialized subset of Foxp3+ T cells that modulate antibody responses. Here we analyzed the role of TFR cells in regulating antigen-specific IgE using a peanut-based food allergy model in mice. Peanut-specific IgE titers and anaphylaxis responses were significantly blunted in TFR cell-deficient Foxp3-cre Bcl6-fl/fl mice. Loss of TFR cells led to greatly increased non-specific IgE levels, showing that TFR cells have both helper and suppressor functions on IgE production in the GC that work together to facilitate the production of antigen-specific IgE. Foxp3-cre Pten-fl/fl mice with augmented TFR cell responses had markedly higher levels of peanut-specific IgE, revealing an active helper function by TFR cells on antigen-specific IgE. The helper function of TFR cells for IgE production involves IL-10, and the loss of IL-10 signaling by B cells led to a severely curtailed peanut-specific IgE response, decreased GC B cell survival and loss of GC dark zone B cells after peanut sensitization. We thus reveal that TFR cells have an unexpected helper role in promoting food allergy and are a novel target for drug development.
Markus M. Xie, Qiang Chen, Hong Liu, Kai Yang, Byunghee Koh, Hao Wu, Soheila J. Maleki, Barry K. Hurlburt, Joan Cook-Mills, Mark H. Kaplan, Alexander L. Dent
Hidradenitis suppurativa (HS) is a chronic, relapsing, inflammatory skin disease. HS appears to be a primary abnormality in the pilosebaceous-apocrine unit. In this work, we characterized hair follicle stem cells isolated from HS patients and more precisely the Outer Root Sheath Cells (ORS). We show that hair follicles from HS patients have an increased number of proliferating progenitor cells and lose quiescent stem cells. Remarkably, we also show that the progression of replication forks is altered in HS-ORS and activates the ATR-CHK1 pathway. These alterations are associated with an increased number of micronuclei and with the presence of cytoplasmic ssDNA, leading to the activation of IFI16-STING pathway and the production of type I IFNs. This mechanistic analysis of the etiology of HS in the hair follicle stem cells compartment establishes a formal link between the genetic predisposition and skin inflammation observed in HS.
Cindy Orvain, Yea-Lih Lin, Francette Jean-Louis, Hakim Hocini, Barbara Hersant, Yamina Bennasser, Nicolas Ortonne, Claire Hotz, Pierre Wolkenstein, Michele Boniotto, Pascaline Tisserand, Cecile Lefebvre, Jean-Daniel Lelievre, Monsef Benkirane, Philippe Pasero, Yves Levy, Sophie Hue
A common variant in the RAB27A gene in adults was recently found to be associated with the fractional exhaled nitric oxide level, a marker of eosinophilic airway inflammation. The small GTPase, Rab27, is known to regulate intracellular vesicle traffic, although its role in allergic responses is unclear. We demonstrated that exophilin-5, a Rab27 binding protein, was predominantly expressed in both the major IL-33 producers, lung epithelial cells, and the specialized IL-5 and IL-13 producers in CD44highCXCR3lowCD62Llow pathogenic T helper 2 (Th2) cell population in mice. Exophilin-5 deficiency increased stimulant-dependent damages and IL-33 secretion of lung epithelial cells. Moreover, it enhanced IL-5 and IL-13 production in response to TCR and IL-33 stimulation from a specific subset of pathogenic Th2 cells that expresses a high level of IL-33 receptor, which exacerbated allergic airway inflammation in a mouse model of asthma. Mechanistically, exophilin-5 regulates extracellular superoxide release, intracellular ROS production, and phosphoinositide 3-kinase activity by controlling intracellular traffic of Nox2-containing vesicles, which seems to prevent the overactivation of pathogenic Th2 cells mediated by IL-33. This is the first report to establish the significance of Rab27-related protein exophilin-5 in the development of allergic airway inflammation, and provides new insights into the pathophysiology of asthma.
Katsuhide Okunishi, Hao Wang, Maho Suzukawa, Ray Ishizaki, Eri Kobayashi, Miho Kihara, Takaya Abe, Jun-ichi Miyazaki, Masafumi Horie, Akira Saito, Hirohisa Saito, Susumu Nakae, Tetsuro Izumi