Alloantibodies in presensitized transplant candidates deposit complement membrane attack complexes (MACs) on graft endothelial cells (ECs), increasing risk of CD8+ T cell–mediated acute rejection. We recently showed that human ECs endocytose MACs into Rab5+ endosomes, creating a signaling platform that stabilizes NF-κB–inducing kinase (NIK) protein. Endosomal NIK activates both noncanonical NF-κB signaling to synthesize pro–IL-1β and an NLRP3 inflammasome to process and secrete active IL-1β. IL-1β activates ECs, increasing recruitment and activation of alloreactive effector memory CD4+ T (Tem) cells. Here, we report that IFN-γ priming induced nuclear expression of IL-15/IL-15Rα complexes in cultured human ECs and that MAC-induced IL-1β stimulated translocation of IL-15/IL-15Rα complexes to the EC surface in a canonical NF-κB–dependent process in which IL-15/IL-15Rα transpresentation increased activation and maturation of alloreactive CD8+ Tem cells. Blocking NLRP3 inflammasome assembly, IL-1 receptor, or IL-15 on ECs inhibited the augmented CD8+ Tem cell responses, indicating that this pathway is not redundant. Adoptively transferred alloantibody and mouse complement deposition induced IL-15/IL-15Rα expression by human ECs lining human coronary artery grafts in immunodeficient mice, and enhanced intimal CD8+ T cell infiltration, which was markedly reduced by inflammasome inhibition, linking alloantibody to acute rejection. Inhibiting MAC signaling may similarly limit other complement-mediated pathologies.
Catherine B. Xie, Bo Jiang, Lingfeng Qin, George Tellides, Nancy C. Kirkiles-Smith, Dan Jane-wit, Jordan S. Pober
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
Maximilian F. Konig, Mike Powell, Verena Staedtke, Ren-Yuan Bai, David L. Thomas, Nicole Fischer, Sakibul Huq, Adham M. Khalafallah, Allison Koenecke, Ruoxuan Xiong, Brett Mensh, Nickolas Papadopoulos, Kenneth W. Kinzler, Bert Vogelstein, Joshua T. Vogelstein, Susan Athey, Shibin Zhou, Chetan Bettegowda
Plasmacytoid DCs (pDCs), the major producers of type I interferon, are principally recognized as key mediators of antiviral immunity. However, their role in tumor immunity is less clear. Depending on the context, pDCs can promote or suppress antitumor immune responses. In this study, we identified a naturally occurring pDC subset expressing high levels of OX40 (OX40+ pDC) enriched in the tumor microenvironment (TME) of head and neck squamous cell carcinoma. OX40+ pDCs were distinguished by a distinct immunostimulatory phenotype, cytolytic function, and ability to synergize with conventional DCs (cDCs) in generating potent tumor antigen–specific CD8+ T cell responses. Transcriptomically, we found that they selectively utilized EIF2 signaling and oxidative phosphorylation pathways. Moreover, depletion of pDCs in the murine OX40+ pDC–rich tumor model accelerated tumor growth. Collectively, we present evidence of a pDC subset in the TME that favors antitumor immunity.
Kate Poropatich, Donye Dominguez, Wen-Ching Chan, Jorge Andrade, Yuanyuan Zha, Brian Wray, Jason Miska, Lei Qin, Lisa Cole, Sydney Coates, Urjeet Patel, Sandeep Samant, Bin Zhang
Vaccination is a mainstay in preventive medicine, reducing morbidity and mortality from infection, largely by generating pathogen-specific neutralizing antibodies. However, standard immunization strategies are insufficient with increasing age due to immunological impediments, including defects in T follicular helper (Tfh) cells. Here, we found that Tfh generation is inversely linked to the expression of the ecto-NTPDase CD39 that modifies purinergic signaling. The lineage-determining transcription factor BCL6 inhibited CD39 expression, while increased Tfh frequencies were found in individuals with a germline polymorphism preventing transcription of ENTPD1, encoding CD39. In in vitro human and in vivo mouse studies, Tfh generation and germinal center responses were enhanced by reducing CD39 expression through the inhibition of the cAMP/PKA/p-CREB pathway, or by blocking adenosine signaling downstream of CD39 using the selective adenosine A2a receptor antagonist istradefylline. Thus, purinergic signaling in differentiating T cells can be targeted to improve vaccine responses, in particular in older individuals who have increased CD39 expression.
Wenqiang Cao, Fengqin Fang, Timothy Gould, Xuanying Li, Chulwoo Kim, Claire Gustafson, Simon Lambert, Cornelia M. Weyand, Jörg J. Goronzy
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
Phosphoglycerate dehydrogenase (PHGDH), the first rate-limiting enzyme of serine synthesis, is frequently overexpressed in human cancer. PHGDH overexpression activates serine synthesis to promote cancer progression. Currently, PHGDH regulation in normal cells and cancer is not well understood. Parkin, an E3 ubiquitin ligase involved in Parkinson’s disease, is a tumor suppressor. Parkin expression is frequently downregulated in many types of cancer, and its tumor-suppressive mechanism is poorly defined. Here, we show that PHGDH is a substrate for Parkin-mediated ubiquitination and degradation. Parkin interacted with PHGDH and ubiquitinated PHGDH at lysine 330, leading to PHGDH degradation to suppress serine synthesis. Parkin deficiency in cancer cells stabilized PHGDH and activated serine synthesis to promote cell proliferation and tumorigenesis, which was largely abolished by targeting PHGDH with RNA interference, CRISPR/Cas9 KO, or small-molecule PHGDH inhibitors. Furthermore, Parkin expression was inversely correlated with PHGDH expression in human breast cancer and lung cancer. Our results revealed PHGDH ubiquitination by Parkin as a crucial mechanism for PHGDH regulation that contributes to the tumor-suppressive function of Parkin and identified Parkin downregulation as a critical mechanism underlying PHGDH overexpression in cancer.
Juan Liu, Cen Zhang, Hao Wu, Xiao-Xin Sun, Yanchen Li, Shan Huang, Xuetian Yue, Shou-En Lu, Zhiyuan Shen, Xiaoyang Su, Eileen White, Bruce G. Haffty, Wenwei Hu, Zhaohui Feng
Despite widespread use of taxanes, mechanisms of action and resistance in vivo remain to be established, and there is no way of predicting who will respond to therapy. This study examined prostate cancer (PCa) xenografts and patient samples to identify in vivo mechanisms of taxane action and resistance. Docetaxel drug-target engagement was assessed by confocal anti-tubulin immunofluorescence to quantify microtubule bundling in interphase cells and aberrant mitoses. Tumor biopsies from metastatic PCa patients obtained 2 to 5 days after their first dose of docetaxel or cabazitaxel were processed to assess microtubule bundling, which correlated with clinical response. Microtubule bundling was evident in PCa xenografts 2 to 3 days after docetaxel treatment but was decreased or lost with acquired resistance. Biopsies after treatment with leuprolide plus docetaxel showed extensive microtubule bundling as did biopsies obtained 2 to 3 days after initiation of docetaxel or cabazitaxel in 2 patients with castration-resistant PCa with clinical responses. In contrast, microtubule bundling in biopsies 2 to 3 days after the first dose of docetaxel was markedly lower in 4 nonresponding patients. These findings indicate that taxanes target both mitotic and interphase cells in vivo and that resistance is through mechanisms that impair drug-target engagement. Moreover, the findings suggest that microtubule bundling after initial taxane treatment may be a predictive biomarker for clinical response.
Ada Gjyrezi, Fang Xie, Olga Voznesensky, Prateek Khanna, Carla Calagua, Yang Bai, Justin Kung, Jim Wu, Eva Corey, Bruce Montgomery, Sandrine Mace, Diego A. Gianolio, Glenn J. Bubley, Steven P. Balk, Paraskevi Giannakakou, Rupal S. Bhatt
The critical role of suppressive myeloid cells in immune regulation has come to the forefront in cancer research, with myeloid-derived suppressor cells (MDSCs) as a main oncology immunotherapeutic target. Recent improvement and standardization of criteria classifying tumor-induced MDSCs have led to unified descriptions and also promoted MDSC research in tuberculosis (TB) and AIDS. Despite convincing evidence on the induction of MDSCs by pathogen-derived molecules and inflammatory mediators in TB and AIDS, very little attention has been given to their therapeutic modulation or roles in vaccination in these diseases. Clinical manifestations in TB are consequences of complex host-pathogen interactions and are substantially affected by HIV infection. Here we summarize the current understanding and knowledge gaps regarding the role of MDSCs in HIV and Mycobacterium tuberculosis (co)infections. We discuss key scientific priorities to enable application of this knowledge to the development of novel strategies to improve vaccine efficacy and/or implementation of enhanced treatment approaches. Building on recent findings and potential for cross-fertilization between oncology and infection biology, we highlight current challenges and untapped opportunities for translating new advances in MDSC research into clinical applications for TB and AIDS.
Anca Dorhoi, Leigh A. Kotzé, Jay A. Berzofsky, Yongjun Sui, Dmitry I. Gabrilovich, Ankita Garg, Richard Hafner, Shabaana A. Khader, Ulrich E. Schaible, Stefan H.E. Kaufmann, Gerhard Walzl, Manfred B. Lutz, Robert N. Mahon, Suzanne Ostrand-Rosenberg, William Bishai, Nelita du Plessis
Treatment for hepatitis C virus (HCV) with direct-acting antivirals (DAAs) in hepatitis B virus (HBV) coinfection can result in HBV reactivation. In this issue of the JCI, Cheng and colleagues explored the role of interferon signaling in the complex interaction between HBV and HCV using cell lines, mouse models, and samples from people with coinfection. Notably, HCV enhanced interferon signaling, as measured by interferon-stimulated gene (ISG) expression, and decreased HBV transcription and replication. Blockade of interferon signaling reversed the effects on HBV replication. Further, pharmacologic inhibition of HCV replication in vitro and in coinfected humanized mice also reduced interferon signaling and, correspondingly, increased HBV replication. Intriguingly, baseline serum levels of the ISG CXCL10 predicted HBV reactivation in a cohort of coinfected people taking DAAs. Determining how interferon signaling silences HBV transcription and whether serum CXCL10 predicts HBV reactivation in a clinical setting are questions that warrant further investigation.
Ashwin Balagopal, Chloe L. Thio
Phosphoglycerate dehydrogenase (PHGDH) catalyzes the first step in the synthesis of the amino acid serine, important for protein synthesis, one-carbon metabolism, lipid production, redox homeostasis, and other key processes of normal and cancer metabolism. While PHGDH is often overexpressed in cancer cells, how it is regulated has been unclear. In this issue of the JCI, Liu and colleagues describe a new aspect of PHGDH regulation, demonstrating that the Parkinson disease gene and tumor suppressor Parkin bound and ubiquitinated PHGDH. Parkin promoted PHGDH degradation, suppressed serine synthesis, and inhibited tumor growth in human cancer cell line xenografts. Conversely, inactivation of Parkin not only accelerated tumor growth, but also sensitized tumors to small molecule inhibitors of PHGDH. These results offer a new link between Parkin and the serine synthesis pathway, and they bear translational potential that warrants further study in Parkin-deficient human cancers.
W. Brian Dalton
BACKGROUND Insulin is a key regulator of metabolic function. The effects of excess adiposity, insulin resistance, and hepatic steatosis on the complex integration of insulin secretion and hepatic and extrahepatic tissue extraction are not clear.METHODS A hyperinsulinemic-euglycemic clamp and a 3-hour oral glucose tolerance test were performed to evaluate insulin sensitivity and insulin kinetics after glucose ingestion in 3 groups: (a) lean subjects with normal intrahepatic triglyceride (IHTG) and glucose tolerance (lean-NL; n = 14), (b) obese subjects with normal IHTG and glucose tolerance (obese-NL; n = 24), and (c) obese subjects with nonalcoholic fatty liver disease (NAFLD) and prediabetes (obese-NAFLD; n = 22).RESULTS Insulin sensitivity progressively decreased and insulin secretion progressively increased from the lean-NL to the obese-NL to the obese-NAFLD groups. Fractional hepatic insulin extraction progressively decreased from the lean-NL to the obese-NL to the obese-NAFLD groups, whereas total hepatic insulin extraction (molar amount removed) was greater in the obese-NL and obese-NAFLD subjects than in the lean-NL subjects. Insulin appearance in the systemic circulation and extrahepatic insulin extraction progressively increased from the lean-NL to the obese-NL to the obese-NAFLD groups. Total hepatic insulin extraction plateaued at high rates of insulin delivery, whereas the relationship between systemic insulin appearance and total extrahepatic extraction was linear.CONCLUSION Hyperinsulinemia after glucose ingestion in obese-NL and obese-NAFLD is due to an increase in insulin secretion, without a decrease in total hepatic or extrahepatic insulin extraction. However, the liver’s maximum capacity to remove insulin is limited because of a saturable extraction process. The increase in insulin delivery to the liver and extrahepatic tissues in obese-NAFLD is unable to compensate for the increase in insulin resistance, resulting in impaired glucose homeostasis.TRIAL REGISTRATION ClinicalTrials.gov NCT02706262.FUNDING NIH grants DK56341 (Nutrition Obesity Research Center), DK052574 (Digestive Disease Research Center), RR024992 (Clinical and Translational Science Award), and T32 DK007120 (a T32 Ruth L. Kirschstein National Research Service Award); the American Diabetes Foundation (1-18-ICTS-119); Janssen Research & Development; and the Pershing Square Foundation.
Gordon I. Smith, David C. Polidori, Mihoko Yoshino, Monica L. Kearney, Bruce W. Patterson, Bettina Mittendorfer, Samuel Klein