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Exebacase for Staphylococcus aureus bloodstream infection and endocarditis

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Abstract

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.

Authors

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

T follicular regulatory cells and IL-10 promote food antigen-specific IgE

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Abstract

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.

Authors

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

Notch signaling licenses allergic airway inflammation by promoting Th2 cell lymph node egress

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Abstract

Allergic asthma is mediated by T helper 2 (Th2) responses to inhaled allergens. Although previous experiments indicated that Notch signaling activates expression of the key Th2 transcription factor Gata3, it remains controversial how Notch promotes allergic airway inflammation. Here we show that T cell-specific Notch deficiency in mice prevented house dust mite-driven eosinophilic airway inflammation and significantly reduced Th2 cytokine production, serum IgE levels and airway hyperreactivity. However, transgenic Gata3 overexpression in Notch-deficient T cells only partially rescued this phenotype. We found that Notch signaling was not required for T cell proliferation or Th2 polarization. Instead, Notch-deficient in vitro polarized Th2 cells showed reduced accumulation in the lungs upon in vivo transfer and allergen challenge, as Notch-deficient Th2 cells were retained in the lung draining lymph nodes. Transcriptome analyses and sequential adoptive transfer experiments revealed that while Notch-deficient lymph node Th2 cells established competence for lung migration, they failed to upregulate the sphingosine 1-phosphate receptor (S1PR1) and its critical upstream transcriptional activator Krüppel-like factor 2 (KLF2). As this KLF2-S1PR1 axis represents the essential cell-intrinsic regulator of T cell lymph node egress, we conclude that the druggable Notch signaling pathway licenses the Th2 response in allergic airway inflammation via promoting lymph node egress.

Authors

Irma Tindemans, Anne van Schoonhoven, Alex KleinJan, Marjolein J.W. de Bruijn, Melanie Lukkes, Menno van Nimwegen, Anouk van den Branden, Ingrid M. Bergen, Odilia B. J. Corneth, Wilfred F.J. van IJcken, Ralph Stadhouders, Rudi W. Hendriks

Deployment of convalescent plasma for the prevention and treatment of COVID-19

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Abstract

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease (COVID-19), has spurred a global health crisis. To date, there are no proven options for prophylaxis for those who have been exposed to SARS-CoV-2, nor therapy for those who develop COVID-19. Immune (i.e. “convalescent”) plasma refers to plasma that is collected from individuals, following resolution of infection and development of antibodies. Passive antibody administration through transfusion of convalescent plasma may offer the only short-term strategy to confer immediate immunity to susceptible individuals. There are numerous examples, where convalescent plasma has been used successfully as post-exposure prophylaxis and/or treatment of infectious diseases, including other outbreaks of coronaviruses (e.g., SARS-1, Middle East Respiratory Syndrome [MERS]). Convalescent plasma has also been used in the COVID-19 pandemic; limited data from China suggest clinical benefit, including radiological resolution, reduction in viral loads and improved survival. Globally, blood centers have robust infrastructure to undertake collections and construct inventories of convalescent plasma to meet the growing demand. Nonetheless, there are nuanced challenges, both regulatory and logistical, spanning donor eligibility, donor recruitment, collections and transfusion itself. Data from rigorously controlled clinical trials of convalescent plasma are also few, underscoring the need to evaluate its use objectively for a range of indications (e.g., prevention vs treatment) and patient populations (e.g., age, comorbid disease). We provide an overview of convalescent plasma, from evidence of benefit, regulatory considerations, logistical work flow and proposed clinical trials, as scale up is brought underway to mobilize this critical resource.

Authors

Evan M. Bloch, Shmuel Shoham, Arturo Casadevall, Bruce S. Sachais, Beth Shaz, Jeffrey L. Winters, Camille van Buskirk, Brenda J. Grossman, Michael Joyner, Jeffrey P. Henderson, Andrew Pekosz, Bryan Lau, Amy Wesolowski, Louis Katz, Hua Shan, Paul G. Auwaerter, David Thomas, David J. Sullivan, Nigel Paneth, Eric Gehrie, Steven Spitalnik, Eldad Hod, Lewis Pollack, Wayne T. Nicholson, Liise-anne Pirofski, Jeffrey A. Bailey, Aaron A.R. Tobian

Kidney diseases in the time of COVID-19: major challenges to patient care

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The current COVID-19 pandemic has affected everyone, but presents profound consequences for patients with kidney disease, health care providers, and biomedical researchers. In this Viewpoint, I will discuss a number of kidney-specific aspects of COVID-19 infection, noting therapeutic and basic research opportunities.

Authors

Hamid Rabb

The COVID-19 pandemic and research shutdown: staying safe and productive

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This viewpoint addresses the major impact of the COVID-19 pandemic on biomedical research, the challenges created by the COVID-19 pandemic for research-intensive institutions, and what investigators can do to maintain some level of research activity while keeping their coworkers and trainees safe and engaged.

Authors

M. Bishr Omary, Jeetendra R. Eswaraka, S. David Kimball, Prabhas V. Moghe, Reynold A. Panettieri, Jr., Kathleen W. Scotto

Exophilin-5 regulates allergic airway inflammation by controlling IL-33-mediated Th2 responses

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Abstract

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.

Authors

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

Hair follicle stem cell replication stress drives IFI16/STING-dependent inflammation in hidradenitis suppurativa

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Abstract

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.

Authors

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

Serine-threonine kinase, ROCK2, regulates germinal center B cell positioning and cholesterol biosynthesis

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Abstract

Germinal center (GC) responses require B cells to respond to a dynamic set of intercellular and microenvironmental signals that instruct B cell positioning, differentiation, and metabolic reprogramming. ROCK2, a serine-threonine kinase that can be therapeutically targeted by ROCK inhibitors or statins, is a key downstream effector of RHOA-GTPases. While RHOA-mediated pathways are emerging as critical regulators of GC responses, the role of ROCK2 in B cells is unknown. Here, we find that ROCK2 was activated in response to key T cell signals like CD40 and IL21 and that it regulated GC formation and maintenance. RNA-seq analyses revealed that ROCK2 controlled a unique transcriptional program in GC B cells that promoted optimal GC polarization and cholesterol biosynthesis. ROCK2 regulated this program by restraining AKT activation and subsequently enhancing FOXO1 activity. ATAC-seq and biochemical analyses revealed that the effects of ROCK2 on cholesterol biosynthesis were instead mediated via a novel mechanism. ROCK2 directly phosphorylated IRF8, a crucial mediator of GC responses, and promoted its interaction with SREBP2 at key regulatory regions controlling the expression of cholesterol biosynthetic enzymes, resulting in optimal recruitment of SREBP2 at these sites. These findings thus uncover ROCK2 as a multifaceted and therapeutically targetable regulator of GC responses.

Authors

Edd Ricker, Yurii Chinenov, Tania Pannellini, Danny M. Flores Castro, Chao Ye, Sanjay Gupta, Michela Manni, James K. Liao, Alessandra Pernis

Microenvironmental Th9– and Th17– lymphocytes induce metastatic spreading in lung cancer

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Abstract

Immune microenvironment plays a critical role in lung cancer control versus progression and metastasis. In this investigation, we explored the impact of tumor-infiltrating-lymphocyte subpopulations on lung cancer biology by studying in vitro co-cultures, in vivo mouse models and human lung cancer tissue. Lymphocyte conditioned media-(CM) induced epithelial-mesenchymal-transition (EMT), and migration in both primary human lung cancer cells and cell lines. Correspondingly, major accumulation of Th9 and Th17 cells was detected in human lung cancer tissue, and correlated with poor survival. Co-culturing lung cancer cells with Th9/Th17 cells or exposing them to the respective-CM induced-EMT in cancer cells and modulated the expression profile of genes implicated in EMT and metastasis. These features were reproduced by the signatory cytokines IL–9 and IL–17, with gene regulatory profiles evoked by these cytokines partly overlapping and partly complementary. Co-injection of Th9 and/or Th17 cells with tumor cells in wildtype, Rag1-/-, Il9r-/- and Il17ra-/- mice altered tumor growth and metastasis. Accordingly, inhibition of IL–9 or IL–17 cytokines by neutralizing antibodies decreased EMT and slowed lung cancer progression and metastasis. In conclusion, Th9 and Th17 lymphocytes induce lung cancer cell EMT, thereby promoting migration, and metastatic spreading and offering for novel therapeutic strategies.

Authors

Ylia Salazar, Xiang Zheng, David Brunn, Hartmann Raifer, Felix S.R. Picard, Yajuan Zhang, Hauke Winter, Stefan Günther, Andreas Weigert, Benno Weigmann, Laure Dumoutier, Jean-Christophe Renauld, Ari Waisman, Anja Schmall, Amanda Tufman, Ludger Fink, Bernhard Brüne, Tobias Bopp, Friedrich Grimminger, Werner Seeger, Soni Savai Pullamsetti, Magdalena Huber, Rajkumar Savai

COVID-19 threatens health systems in sub-Saharan Africa: the eye of the crocodile

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Abstract

The threat of Coronavirus Disease 2019 (COVID-19) to health systems in sub-Saharan Africa (SSA) can be compared metaphorically to a lake in Africa infested with a bask of crocodiles and the saying: “the eye of the crocodile.” In the lake, only the eyes of the crocodile appear on the surface while the rest of the body is submerged in water. In this Viewpoint, the eyes and the body of the crocodile represent the public health preparedness and health systems, respectively, in SSA.

Authors

Elijah Paintsil

Clinical and immunologic features in severe and moderate Coronavirus Disease 2019

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Abstract

BACKGROUND. Since December 2019, an outbreak of Coronavirus Disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in Wuhan, and is now becoming a global threat. We aimed to delineate and compare the immunologic features of severe and moderate COVID-19. METHODS. In this retrospective study, the clinical and immunologic characteristics of 21 patients (17 male and 4 female) with COVID-19 were analyzed. These patients were classified as severe (11 cases) and moderate (10 cases) according to the Guidelines released by the National Health Commission of China. RESULTS. The median age of severe and moderate cases was 61.0 and 52.0 years, respectively. Common clinical manifestations included fever, cough and fatigue. Compared to moderate cases, severe cases more frequently had dyspnea, lymphopenia, and hypoalbuminemia, with higher levels of alanine aminotransferase, lactate dehydrogenase, C-reactive protein, ferritin and D-dimer as well as markedly higher levels of IL-2R, IL-6, IL-10, and TNF-α. Absolute number of T lymphocytes, CD4+T and CD8+T cells decreased in nearly all the patients, and were markedly lower in severe cases (294.0, 177.5 and 89.0 × 106/L) than moderate cases (640.5, 381.5 and 254.0 × 106/L). The expressions of IFN-γ by CD4+T cells tended to be lower in severe cases (14.1%) than moderate cases (22.8%). CONCLUSION. The SARS-CoV-2 infection may affect primarily T lymphocytes particularly CD4+T and CD8+ T cells, resulting in decrease in numbers as well as IFN-γ production. These potential immunological markers may be of importance due to their correlation with disease severity in COVID-19.

Authors

Guang Chen, Di Wu, Wei Guo, Yong Cao, Da Huang, Hongwu Wang, Tao Wang, Xiaoyun Zhang, Huilong Chen, Haijing Yu, Xiaoping Zhang, Minxia Zhang, Shiji Wu, Jianxin Song, Tao Chen, Meifang Han, Shusheng Li, Xiaoping Luo, Jianping Zhao, Qin Ning

SARS-CoV-2: A Storm is Raging

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Abstract

The pandemic coronavirus infectious disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is rapidly spreading across the globe. In this issue of the JCI, Chen and colleagues compared the clinical and immunologic characteristics between moderate versus severe COVID-19. The authors found that respiratory distress on admission is associated with unfavorable outcomes. Increased cytokine levels (IL-6, IL-10 and TNFα), lymphopenia (in CD4+ and CD8+ T cells), and decreased IFNγ expression in CD4+ T cells are associated with severe COVID-19. Overall, this study characterized the cytokine storm in severe COVID-19 and provides insights into immune therapeutics and vaccine design.

Authors

Savannah F. Pedersen, Ya-Chi Ho

Brain-specific repression of AMPKα1 alleviates pathophysiology in Alzheimer’s model mice

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Abstract

AMP-activated protein kinase (AMPK) is a key regulator at the molecular level to maintain energy metabolism homeostasis. Mammalian AMPK is a heterotrimeric complex and its catalytic α subunit exists in two isoforms: AMPKα1 and AMPKα2. Recent studies suggest a role of AMPKα over-activation in 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 post mortem 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 two 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 hyper-phosphorylation 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 strategy for AD and related dementia syndromes.

Authors

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

Sensory nerves regulate mesenchymal stromal cell lineage commitment by tuning sympathetic tones

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Abstract

Sensory nerve was recently identified as being involved in regulation of bone mass accrual. We previously discovered that PGE2 secreted by osteoblastic cells 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 skeletal stem cells. Here, we found that after sensory denervation, knockout of the EP4 receptor in sensory nerves, or knockout of cyclooxygenase-2 (COX2) in osteoblasts could significantly promote adipogenesis and inhibit osteogenesis in adult mice. Furthermore, injection of SW033291 (a small molecule that locally increases 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 knockout mice under normal conditions or in the bone repair process. We conclude that the PGE2-EP4 sensory nerve axis could regulate skeletal stem cell differentiation in bone marrow of adult mice.

Authors

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

Complement activated interferon-γ-primed human endothelium transpresents interleukin-15 to CD8+ T cells

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Abstract

Alloantibodies in pre-sensitized transplant candidates deposit complement membrane attack complexes (MAC) on graft endothelial cells (ECs), increasing risk of CD8+ T cell-mediated acute rejection. We recently showed (a) human ECs endocytose MAC into Rab5+ endosomes, creating a signaling platform that stabilizes NF-κB–inducing kinase (NIK) protein; (b) endosomal NIK activates both non-canonical NF-κB signaling to synthesize pro-IL-1β and an NLRP3 inflammasome to process and secrete active IL-1β; and (c) IL-1β activates ECs, increasing recruitment and activation of alloreactive effector memory CD4+ T (TEM) cells. Here, we report 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, where IL-15/IL-15Rα transpresentation increased activation and maturation of alloreactive CD8+ TEM. Blocking NLRP3 inflammasome assembly, IL-1 receptor or IL-15 on ECs inhibited the augmented CD8+ TEM responses, indicating this pathway was 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.

Authors

Catherine B. Xie, Bo Jiang, Lingfeng Qin, George Tellides, Nancy C. Kirkiles-Smith, Dan Jane-wit, Jordan S. Pober

B cell-intrinsic TLR9 expression is protective in murine lupus

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Toll-like receptor 9 (TLR9) is a regulator of disease pathogenesis in systemic lupus erythematosus (SLE). Why TLR9 represses disease while TLR7 and MyD88 have the opposite effect remains undefined. To begin to address this question, we created two novel alleles to manipulate TLR9 expression, allowing for either selective deletion or overexpression. We used these to test cell type-specific effects of Tlr9 expression on the regulation of SLE pathogenesis. Notably, Tlr9 deficiency in B cells was sufficient to exacerbate nephritis while extinguishing anti-nucleosome antibodies, whereas Tlr9 deficiency in dendritic cells (DCs), plasmacytoid DCs, and neutrophils had no discernable effect on disease. Thus, B cell-specific Tlr9 deficiency unlinked disease from autoantibody production. Critically, B cell-specific Tlr9 overexpression resulted in ameliorated nephritis, opposite of the effect of deleting Tlr9. Our findings highlight the non-redundant role of B cell-expressed TLR9 in regulating lupus and suggests therapeutic potential in modulating and perhaps even enhancing TLR9 signals in B cells.

Authors

Jeremy S. Tilstra, Shinu John, Rachael A. Gordon, Claire Leibler, Michael Kashgarian, Sheldon Bastacky, Kevin M. Nickerson, Mark J. Shlomchik

Semaphorin 3F signaling actively retains neutrophils at sites of inflammation

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Neutrophilic inflammation is central to disease pathogenesis, e.g. in chronic obstructive pulmonary disease, yet the mechanisms retaining neutrophils within tissues remain poorly understood. With emerging evidence that axon guidance factors can regulate myeloid recruitment and that neutrophils can regulate expression of a class 3 Semaphorin, SEMA3F, we investigated the role of SEMA3F in inflammatory cell retention within inflamed tissues. We observed that neutrophils upregulate SEMA3F in response to pro-inflammatory mediators and following recruitment to the inflamed lung. In both zebrafish tail injury and murine acute lung injury models of neutrophilic inflammation, overexpression of SEMA3F delayed inflammation resolution with slower neutrophil migratory speeds and retention of neutrophils within the tissues. Conversely, constitutive loss of sema3f accelerated egress of neutrophils from the tail injury site in fish, whilst neutrophil specific deletion of Sema3f in mice resulted in more rapid neutrophil transit through the airways, and significantly reduced time to resolution of the neutrophilic response. Study of filamentous- (F-) actin subsequently showed SEMA3F mediated retention is associated with F-actin disassembly. In conclusion, SEMA3F signaling actively regulates neutrophil retention within the injured tissues with consequences for neutrophil clearance and inflammation resolution.

Authors

Tracie Plant, Suttida Eamsamarng, Manuel A. Sanchez-Garcia, Leila Reyes, Stephen A. Renshaw, Patricia Coelho, Ananda S. Mirchandani, Jessie-May Morgan, Felix E. Ellett, Tyler Morrison, Duncan Humphries, Emily R. Watts, Fiona Murphy, Ximena L. Raffo-Iraolagoitia, Ailiang Zhang, Jenna L. Cash, Catherine Loynes, Philip M. Elks, Freek Van Eeden, Leo M. Carlin, Andrew J. W. Furley, Moira K. B. Whyte, Sarah R. Walmsley

c-Rel gain in B cells drives germinal center reactions and autoantibody production

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Single nucleotide polymorphisms and locus amplification link the NF-κB transcription factor c-Rel to human autoimmune diseases and B cell lymphomas, respectively. However, the functional consequences of enhanced c-Rel levels remain enigmatic. Here, we overexpressed c-Rel specifically in mouse B cells from BAC-transgenic gene loci and demonstrate that c-Rel protein levels linearly dictated expansion of germinal center (GC) B cells and isotype-switched plasma cells. c-Rel expression in B cells of otherwise c-Rel-deficient mice fully rescued terminal B cell differentiation, underscoring its critical B cell-intrinsic roles. Unexpectedly, in GCB cells transcription-independent regulation produced the highest c-Rel protein levels amongst B cell subsets. In c-Rel overexpressing GCB cells this caused enhanced nuclear translocation, a profoundly altered transcriptional program and increased proliferation. Finally, we provide a link between c-Rel gain and autoimmunity by showing that c-Rel overexpression in B cells caused autoantibody production and renal immune complex deposition.

Authors

Maike Kober-Hasslacher, Hyunju Oh-Strauß, Dilip Kumar, Valeria Soberón, Carina Diehl, Maciej Lech, Thomas Engleitner, Eslam Katab, Vanesa Fernandez Saiz, Guido Piontek, Hongwei Li, Björn Menze, Christoph Ziegenhain, Wolfgang Enard, Roland Rad, Jan P. Böttcher, Hans-Joachim Anders, Martina Rudelius, Marc Schmidt-Supprian

Influence of adiposity, insulin resistance and intrahepatic triglyceride content on insulin kinetics

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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 used to evaluate insulin sensitivity and insulin kinetics after glucose ingestion in three groups: i) lean with normal intrahepatic triglyceride (IHTG) and glucose tolerance (Lean-NL; n=14); ii) obese with normal IHTG and glucose tolerance (Obese-NL; n=24); and iii) obese with hepatic steatosis and prediabetes (Obese-NAFLD; n=22). Results. Insulin sensitivity progressively decreased and insulin secretion progressively increased from Lean-NL to Obese-NL to Obese-NAFLD. Fractional hepatic insulin extraction progressively decreased from Lean-NL to Obese-NL to Obese-NAFLD, whereas total hepatic insulin extraction (molar amount removed) was greater in Obese-NL and Obese-NAFLD than Lean-NL. Insulin appearance in the systemic circulation and extrahepatic insulin extraction progressively increased from Lean-NL to Obese-NL to Obese-NAFLD. 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.

Authors

Gordon I. Smith, David C. Polidori, Mihoko Yoshino, Monica L. Kearney, Bruce W. Patterson, Bettina Mittendorfer, Samuel Klein