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Abstract
Glucagon, a hormone released from pancreatic α-cells, plays a key role in maintaining euglycemia. New insights into the signaling pathways that control glucagon secretion may stimulate the development of novel therapeutic agents. In this study, we investigated the potential regulation of α-cell function by G proteins of the Gq family. The use of a chemogenetic strategy allowed us to selectively activate Gq signaling in mouse α-cells in vitro and in vivo. Acute stimulation of α-cell Gq signaling led to elevated plasma glucagon levels, accompanied by increased insulin release and improved glucose tolerance. Moreover, chronic activation of this pathway greatly improved glucose tolerance in obese mice. We also identified an endogenous Gq-coupled receptor (vasopressin 1b receptor; V1bR) that is enriched in mouse and human α-cells. Agonist-induced activation of the V1bR strongly stimulated glucagon release in a Gq-dependent fashion. In vivo studies indicated that V1bR-mediated glucagon release plays a key role in the counter-regulatory hyperglucagonemia under hypoglycemic and glucopenic conditions. These data indicate that α-cell Gq signaling represents an important regulator of glucagon secretion, resulting in multiple beneficial metabolic effects. Thus, drugs that target α-cell enriched Gq-coupled receptors may prove useful to restore euglycemia in various pathophysiological conditions.
Authors
Liu Liu, Diptadip Dattaroy, Katherine F. Simpson, Luiz F. Barella, Yinghong Cui, Yan Xiong, Jian Jin, Gabriele M. König, Evi Kostenis, Jefferey C. Roman, Klaus H. Kaestner, Nicolai M. Doliba, Jürgen Wess
Abstract
The PD-1: PD-L1 is a potent inhibitory pathway involved in immune regulation and a potential therapeutic target in transplantation. In this study, we show that overexpression of PD-1 (PD-1 Tg) on T cells promotes allograft tolerance in a fully MHC-mismatched cardiac transplant model when combined with costimulation blockade (CTLA-4-Ig). PD-1 overexpression on T cells also protected against chronic rejection in a single MHC II mismatched cardiac transplant model, while it still allowed the generation of an effective immune response against an Influenza A virus. Notably, Treg cells from PD-1 Tg mice were required for tolerance induction and presented higher ICOS expression than those from wild-type mice. Survival benefit of PD-1 Tg recipients required ICOS signaling and donor PD-L1 expression. These results indicate that modulation of PD-1 expression, in combination with a costimulation blockade, is a promising therapeutic target to promote transplant tolerance.
Authors
Thiago J. Borges, Naoka Murakami, Isadora T. Lape, Rodrigo B. Gassen, Kaifeng Liu, Songjie Cai, Joe Daccache, Kassem Safa, Tetsunosuke Shimizu, Shunsuke Ohori, Alison M. Paterson, Paolo Cravedi, Jamil Azzi, Peter Sage, Arlene Sharpe, Xian C. Li, Leonardo V. Riella
Abstract
Severe respiratory coronavirus 2 (SARS-CoV-2) promotes an imbalanced host response which underlies the development and severity of COVID-19. Infections with viruses are known to modulate transposable elements (TEs) which can exert downstream effects by modulating host gene expression, innate immune sensing, or activities encoded by their protein products. We investigated the impact of SARS-CoV-2 infection on TE expression using RNA-seq data from cell lines and from primary patient samples. Using a bioinformatic tool, Telescope, we showed that SARS-CoV-2 infection led to up- or down-regulation of TE transcripts, a subset of which differed from cells infected with SARS, MERS, RSV, HPIV3 or IAV. Differential expression of key retroelements specifically identified distinct virus families such as coronaviridae, with unique retroelement expression subdividing viral species. Analysis of ChIP-seq data shows that TEs differentially expressed in SARS-CoV-2 infection are enriched for binding sites for TFs involved in immune responses and for pioneer transcription factors. In COVID-19 patient samples, there was a significant TE overexpression in bronchoalveolar lavage fluid and downregulation in peripheral blood mononuclear cells. Thus, while the host gene transcriptome is altered by infection with SARS-CoV-2, the retrotranscriptome may contain the most distinctive features of the cellular response to SARS-CoV-2 infection.
Authors
Jez L. Marston, Matthew Greenig, Manvendra Singh, Matthew L. Bendall, Rodrigo R.R. Duarte, Cédric Feschotte, Luis P. Iñiguez, Douglas F. Nixon
Abstract
Nociceptors, the high-threshold primary sensory neurons that trigger pain, interact with immune cells in the periphery to modulate innate immune responses. Whether they also participate in adaptive and humoral immunity is, however, not known. In this study, we probed if nociceptors have a role in distinct airway and skin models of allergic inflammation. In both models, the genetic ablation and pharmacological silencing of nociceptors substantially reduced inflammatory cell infiltration to the affected tissue. Moreover, we also found a profound and specific deficit in IgE production in these models of allergic inflammation. Mechanistically, we discovered that the nociceptor-released neuropeptide Substance P help triggered the formation of antibody secreting cells and their release of IgE. Our findings suggest that nociceptors, in addition to their contributions to innate immunity, play a key role in modulating the adaptive immune response, particularly B cell antibody class switching to IgE.
Authors
Shreya Mathur, Jo-Chiao Wang, Corey R. Seehus, Florence Poirier, Theo Crosson, Yu-Chen Hsieh, Benjamin Doyle, Seungkyu Lee, Clifford J. Woolf, Simmie L. Foster, Sebastien Talbot
Abstract
Leukemia stem cells (LSCs) promote the disease and seem resistant to therapy and immune control. Why LSCs are selectively resistant against elimination by cytotoxic CD8+ T cells (CTLs) is still unknown. In this study, we demonstrate that LSCs in chronic myeloid leukemia (CML) can be recognized and killed by CD8+ CTLs in vitro. However, Tregs, which preferentially localized close to CD8+ CTLs in CML bone marrow (BM), protected LSCs from MHC-class I dependent CD8+ CTL-mediated elimination in vivo. BM Tregs in CML were characterized by the selective expression of tumor necrosis factor receptor 4 (Tnfrsf4). Stimulation of Tnfrsf4-signaling did not deplete Tregs but reduced the capacity of Tregs to protect LSCs from CD8+ CTL-mediated killing. In the BM of newly diagnosed CML patients, TNFRSF4 mRNA levels were significantly increased and correlated with the expression of the Treg-restricted transcription factor FOXP3. Overall, these results identify Tregs as key regulator of immune escape of LSCs and TNFRSF4 as a potential target to reduce the function of Tregs and boost anti-leukemic immunity in CML.
Authors
Magdalena Hinterbrandner, Viviana Rubino, Carina Stoll, Stefan Forster, Noah Schnüriger, Ramin Radpour, Gabriela M. Baerlocher, Adrian F. Ochsenbein, Carsten Riether
Abstract
Osteoarthritis is the most prevalent joint disease worldwide and a leading source of pain and disability. To date, this disease lacks curative treatment as underlying molecular mechanisms remain largely unknown. The histone methyltransferase DOT1L protects against osteoarthritis, and DOT1L-mediated H3K79 methylation is reduced in human and mouse osteoarthritic joints. Thus, restoring DOT1L function seems to be critical to preserve joint health. However, DOT1L-regulating molecules and networks remain elusive, in the joint and beyond. Here, we identify transcription factors and networks that regulate DOT1L gene expression using a novel bioinformatics pipeline. Thereby, we unravel an undiscovered link between the hypoxia pathway and DOT1L. We provide unprecedented evidence that hypoxia enhances DOT1L expression and H3K79 methylation via Hypoxia-inducible factor-1 alpha (HIF1A). Importantly, we demonstrate that DOT1L contributes to the protective effects of hypoxia in articular cartilage and osteoarthritis. Intra-articular treatment with a selective hypoxia mimetic in mice after surgical induction of osteoarthritis restores DOT1L function and stalls disease progression. Collectively, our data unravel a novel molecular mechanism that protects against osteoarthritis with hypoxia inducing DOT1L transcription in cartilage. Local treatment with a selective hypoxia mimetic in the joint restores DOT1L function and could be an attractive therapeutic strategy for osteoarthritis.
Authors
Astrid De Roover, Ana Escribano Núñez, Frederique M.F. Cornelis, Chahrazad Cherifi, Leire Casas-Fraile, An Sermon, Frederic Cailotto, Rik J. Lories, Silvia Monteagudo
Abstract
Bacterial cancer therapy (BCT) shows great promise for treatment of solid tumors, yet basic mechanisms of bacterial-induced tumor suppression remain undefined. Attenuated strains of Salmonella enterica serovar Typhimurium (STm) have commonly been used in mouse models of BCT in xenograft and orthotopic transplant cancer models. We aimed to better understand the tumor epithelium-targeted mechanisms of BCT by using autochthonous mouse models of intestinal cancer and tumor organoid cultures to assess the effectiveness and consequences of oral treatment with aromatase A-deficient STm (STm∆aroA). STm∆aroA delivered by oral gavage significantly reduced tumor burden and tumor load in both a colitis-associated colon cancer model (CAC) and in a spontaneous Apcmin/+ intestinal cancer model. STm∆aroA colonization of tumors caused alterations in transcription of mRNAs associated with tumor stemness, epithelial–mesenchymal transition and cell cycle. Metabolomic analysis of tumors demonstrated alteration in the metabolic environment of STm∆aroA-treated tumors, suggesting STm∆aroA imposes metabolic competition on the tumor. Use of tumor organoid cultures in vitro recapitulated effects seen on tumor stemness, mesenchymal markers and altered metabolome. Furthermore, live STm∆aroA was required, demonstrating active mechanisms including metabolite usage. We demonstrate that BCT is efficacious in autochthonous intestinal cancer models, that BCT imposes metabolic competition, and that BCT has direct effects on the tumor epithelium affecting tumor stem cells.
Authors
Gillian M. Mackie, Alastair Copland, Masumi Takahashi, Yumiko Nakanishi, Isabel Everard, Tamotsu Kato, Hirotsugu Oda, Takashi Kanaya, Hiroshi Ohno, Kendle M. Maslowski
Abstract
Mechanistically driven therapies for atrial fibrillation (AF), the most common cardiac arrhythmia, are urgently needed, the development of which require improved understanding of the cellular signaling pathways that facilitate the structural and electrophysiological remodeling that occurs in the atria. Similar to humans, increased persistent Na+ current leads to the development of an atrial myopathy and spontaneous and long-lasting episodes of AF in mice. How increased persistent Na+ current causes both structural and electrophysiological remodeling in the atria is unknown. We cross-bred mice expressing human F1759A-NaV1.5 channels with mice expressing human mitochondrial catalase (mCAT). Increased expression of mitochondrial catalase attenuated mitochondrial and cellular reactive oxygen species (ROS), and the structural remodeling that was induced by persistent F1759A-Na+ current. Despite the heterogeneously prolonged atrial action potential, which was unaffected by the reduction in ROS, the incidence of both spontaneous AF and pacing-induced after-depolarizations and AF was substantially reduced. Expression of mitochondrial catalase markedly reduced persistent Na+ current induced ryanodine receptor oxidation and dysfunction. In summary, increased persistent Na+ current in atrial cardiomyocytes, which is observed in patients with AF, induces atrial enlargement, fibrosis, mitochondrial dysmorphology, early after-depolarizations and AF, all of which can be attenuated by resolving mitochondrial oxidative stress.
Authors
Uma Mahesh R. Avula, Haikel Dridi, Bi-xing Chen, Qi Yuan, Alexander N. Katchman, Steven R. Reiken, Amar D. Desai, Samantha Parsons, Haajra Baksh, Elaine Ma, Parmanand Dasrat, Ruiping Ji, Yejun Lin, Christine Sison, W. Jonathan Lederer, Humberto C. Joca, Christopher Ward, Maura Greiser, Andrew R. Marks, Steven O. Marx, Elaine Y. Wan
Abstract
Oral conditions are relatively common in patients with inflammatory bowel disease (IBD). However, the contribution of oral maladies to gut inflammation remains unexplored. Here, we investigated the impact of periodontitis on disease phenotypes of IBD patients. In all, 60 IBD patients (42 with ulcerative colitis [UC] and 18 with Crohn’s disease [CD]) and 45 non-IBD healthy controls (HCs) were recruited for this clinical investigation. The effects of incipient periodontitis on the oral and gut microbiome, IBD characteristics were examined. In addition, patients were prospectively monitored up to 12 months after enrollment. We found that in both UC and CD patients, the gut microbiome was significantly more similar to the oral microbiome than in HCs, suggesting that ectopic gut colonization by oral bacteria is increased in IBD patients. Incipient periodontitis did not further enhance gut colonization by oral bacteria. The presence of incipient periodontitis did not significantly affect the clinical outcomes of UC and CD patients. However, the short Crohn’s disease activity index increased in CD patients with incipient periodontitis but declined or unchanged during the study period in patients without periodontitis. Thus, early periodontitis may associate with worse clinically symptoms in some patients with CD.
Authors
Jin Imai, Hitoshi Ichikawa, Sho Kitamoto, Jonathan L. Golob, Motoki Kaneko, Junko Nagata, Miho Takahashi, Merritt G. Gillilland, Rika Tanaka, Hiroko Nagao-Kitamoto, Atsushi Hayashi, Kohei Sugihara, Shrinivas Bishu, Shingo Tsuda, Hiroyuki Ito, Seiichiro Kojima, Kazunari Karakida, Masashi Matsushima, Takayoshi Suzuki, Katsuto Hozumi, Norihito Watanabe, William V. Giannobile, Takayuki Shirai, Hidekazu Suzuki, Nobuhiko Kamada
Abstract
Understanding viral rebound in pediatric HIV-1 infection may inform the development of alternatives to lifelong antiretroviral therapy (ART) to achieve viral remission. We thus investigated viral rebound after analytical treatment interruption (ATI) in 10 infant macaques orally infected with SHIV.C.CH505 and treated with long-term ART. Rebound viremia was detected within 7-35 days of ATI in 9/10 animals, with post-treatment control of viremia seen in 5/5 Mamu-A*01+ macaques. Single-genome sequencing revealed initial rebound virus was similar to viral DNA present in CD4+ T cells from blood, rectum, and lymph nodes before ATI. We assessed the earliest sites of viral reactivation immediately following ATI using ImmunoPET imaging. The largest increase in signal that preceded detectable viral RNA in plasma was found in the gastrointestinal (GI) tract, a site with relatively high SHIV RNA/DNA ratios in CD4+ T cells prior to ATI. Thus, the GI tract may be an initial source of rebound virus but as ATI progresses, viral reactivation in other tissues likely contributes to the composition of plasma virus. Our study provides novel insight into the features of viral rebound in pediatric infection and highlights the application of a non-invasive technique to monitor areas of HIV-1 expression in children.
Authors
Veronica Obregon-Perko, Katherine M. Bricker, Gloria Mensah, Ferzan Uddin, Laura Rotolo, Daryll Vanover, Yesha Desai, Philip J. Santangelo, Sherrie Jean, Jennifer S. Wood, Fawn C. Connor-Stroud, Stephanie Ehnert, Stella J. Berendam, Shan Liang, Thomas H. Vanderford, Katharine J. Bar, George M. Shaw, Guido Silvestri, Amit Kumar, Genevieve G. Fouda, Sallie R. Permar, Ann Chahroudi
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