Gastroenterology
Abstract
Bruton tyrosine kinase (BTK) is present in a wide variety of cells and may thus have important non-B cell functions. Here we explored the function of this kinase in macrophages with studies of its regulation of the NLRP3 inflammasome. We found that bone marrow-derived macrophages (BMDMs) from BTK-deficient mice or monocytes from X-linked agammaglobulinemia patients exhibit increased NLRP3 inflammasome activity; this was also the case with BMDMs exposed to low doses of BTK inhibitor such as ibrutinib and monocytes from chronic lymphocytic leukemia patients being treated with ibrutinib. In mechanistic studies, we found that BTK binds to NLRP3 during the priming phase of inflammasome activation and in doing so inhibits LPS/nigericin-induced assembly of the NLRP3 inflammasome during the activation phase of inflammasome activation. This inhibitory effect was caused by BTK inhibition of PP2A-mediated dephosphorylation of Ser5 in the pyrin domain of NLRP3. Finally, we showed that BTK-deficient mice are subject to severe experimental colitis and such colitis is normalized by administration of anti-IL-β or an inhibitor of IL-1β signaling, anakinra. Together, these studies strongly suggest that BTK functions as a physiologic inhibitor of NLRP3 inflammasome activation; they thereby explain the fact that XLA patients are prone to develop Crohn’s disease.
Authors
Liming Mao, Atsushi Kitani, Eitaro Hiejima, Kim Montgomery-Recht, Wenchang Zhou, Ivan Fuss, Adrian Wiestner, Warren Strober
Abstract
An excess of fecal bile acids (BAs) is thought to be one of the mechanisms for diarrhea-predominant irritable bowel syndrome (IBS-D). However, the factors causing excessive BA excretion remain incompletely studied. Given the importance of gut microbiota in BA metabolism, we hypothesized that gut dysbiosis might contribute to excessive BA excretion in IBS-D. By performing BA-related metabolic and metagenomic analyses in 290 IBS-D patients and 89 healthy volunteers, we found that 24.5% of IBS-D patients exhibited excessive excretion of total BAs and alteration of BA-transforming bacteria in feces. Notably, the increase in Clostridia bacteria (e.g., C. scindens) was positively associated with the levels of fecal BAs and serum 7α-hydroxy-4-cholesten-3-one (C4), but negatively correlated with serum fibroblast growth factor 19 (FGF19) concentration. Furthermore, colonization with Clostridia-rich IBS-D fecal microbiota or C. scindens individually enhanced serum C4 and hepatic conjugated BAs but reduced ileal FGF19 expression in mice. Inhibition of Clostridium species with vancomycin yielded opposite results. Clostridia-derived BAs suppressed the intestinal FGF19 expression in vitro and in vivo. In conclusion, this study demonstrates that the Clostridia-rich microbiota contributes to excessive BA excretion in IBS-D patients, which provides a mechanistic hypothesis with testable clinical implications.
Authors
Ling Zhao, Wei Yang, Yang Chen, Fengjie Huang, Lin Lu, Chengyuan Lin, Tao Huang, Ziwan Ning, Lixiang Zhai, Linda L.D. Zhong, Waiching Lam, Zhen Yang, Xuan Zhang, Chungwah Cheng, Lijuan Han, Qinwei Qiu, Xiaoxiao Shang, Runyue Huang, Haitao Xiao, Zhenxing Ren, Dongfeng Chen, Silong Sun, Hani El-Nezami, Zongwei Cai, Aiping Lu, Xiaodong Fang, Wei Jia, Zhaoxiang Bian
Abstract
Authors
John M. Carethers
Abstract
Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with rising incidence. Diseased tissues are heavily vascularized. Surprisingly, the pathogenic impact of the vasculature in IBD and the underlying regulatory mechanisms remain largely unknown. IFN-γ is a major cytokine in IBD pathogenesis, but in the context of the disease, it is almost exclusively its immune-modulatory and epithelial cell–directed functions that have been considered. Recent studies by our group demonstrated that IFN-γ also exerts potent effects on blood vessels. Based on these considerations, we analyzed the vessel-directed pathogenic functions of IFN-γ and found that it drives IBD pathogenesis through vascular barrier disruption. Specifically, we show that inhibition of the IFN-γ response in vessels by endothelial-specific knockout of IFN-γ receptor 2 ameliorates experimentally induced colitis in mice. IFN-γ acts pathogenic by causing a breakdown of the vascular barrier through disruption of the adherens junction protein VE-cadherin. Notably, intestinal vascular barrier dysfunction was also confirmed in human IBD patients, supporting the clinical relevance of our findings. Treatment with imatinib restored VE-cadherin/adherens junctions, inhibited vascular permeability, and significantly reduced colonic inflammation in experimental colitis. Our findings inaugurate the pathogenic impact of IFN-γ–mediated intestinal vessel activation in IBD and open new avenues for vascular-directed treatment of this disease.
Authors
Victoria Langer, Eugenia Vivi, Daniela Regensburger, Thomas H. Winkler, Maximilian J. Waldner, Timo Rath, Benjamin Schmid, Lisa Skottke, Somin Lee, Noo Li Jeon, Thomas Wohlfahrt, Viktoria Kramer, Philipp Tripal, Michael Schumann, Stephan Kersting, Claudia Handtrack, Carol I. Geppert, Karina Suchowski, Ralf H. Adams, Christoph Becker, Andreas Ramming, Elisabeth Naschberger, Nathalie Britzen-Laurent, Michael Stürzl
Abstract
Currently, an effective targeted therapy for pancreatitis is still lacking. Hereditary pancreatitis (HP) is a heritable, autosomal-dominant disorder with recurrent acute pancreatitis (AP) progressing to chronic pancreatitis (CP) and a markedly increased risk of pancreatic cancer. In 1996, mutations in PRSS1 were linked to the development of HP. Here, we developed a mouse model by inserting a full-length human PRSS1R122Hgene, the most commonly mutated gene in human HP, into mice. Expression of PRSS1R122H protein in the pancreas markedly increased stress signaling pathways and exacerbated AP. After the attack of AP, all PRSS1R122H mice had disease progression to CP, with similar histologic features as those observed in human HP. By comparing PRSS1R122H mice with PRSS1WT mice as well as enzymatically inactivated Dead-PRSS1R122H mice, we unraveled that increased trypsin activity is the mechanism for R122H mutation to sensitize mice to the development of pancreatitis. We further discovered that trypsin inhibition, in combination with anti-coagulation therapy, synergistically prevented the progression to CP in PRSS1R122H mice. These animal models help us better understand the complex nature of this disease and provide powerful tools for developing and testing novel therapeutics for human pancreatitis.
Authors
Fu Gui, Yuebo Zhang, Jianhua Wan, Xianbao Zhan, Yao Yao, Yinghua Li, Ashley N. Haddock, Ji Shi, Jia Guo, Jiaxiang Chen, Xiaohui Zhu, Brandy H. Edenfield, Lu Zhuang, Cheng Hu, Ying Wang, Debabrata Mukhopadhyay, Evette S. Radisky, Lizhi Zhang, Aurelia Lugea, Stephen J. Pandol, Yan Bi, Baoan Ji
Abstract
Clostridioides difficile infection (CDI) accounts for a substantial proportion of deaths attributable to antibiotic-resistant bacteria in the United States. Although C. difficile can be an asymptomatic colonizer, its pathogenic potential is most commonly manifested in patients with antibiotic-modified intestinal microbiomes. In a cohort of 186 hospitalized patients, we showed that host and microbe-associated shifts in fecal metabolomes had the potential to distinguish patients with CDI from those with non–C. difficile diarrhea and C. difficile colonization. Patients with CDI exhibited a chemical signature of Stickland amino acid fermentation that was distinct from those of uncolonized controls. This signature suggested that C. difficile preferentially catabolizes branched chain amino acids during CDI. Unexpectedly, we also identified a series of noncanonical, unsaturated bile acids that were depleted in patients with CDI. These bile acids may derive from an extended host-microbiome dehydroxylation network in uninfected patients. Bile acid composition and leucine fermentation defined a prototype metabolomic model with potential to distinguish clinical CDI from asymptomatic C. difficile colonization.
Authors
John I. Robinson, William H. Weir, Jan R. Crowley, Tiffany Hink, Kimberly A. Reske, Jennie H. Kwon, Carey-Ann D. Burnham, Erik R. Dubberke, Peter J. Mucha, Jeffrey P. Henderson
Abstract
While improvements in genetic analysis have greatly enhanced our understanding of the mechanisms behind pancreatitis, it continues to afflict many families for whom the hereditary factors remain unknown. Recent evaluation of a patient with a strong family history of pancreatitis sparked us to reexamine a large kindred originally reported over 50 years ago with an autosomal dominant inheritance pattern of chronic pancreatitis, diabetes and pancreatic adenocarcinoma. Whole exome sequencing analysis identified a rare missense mutation in the gene encoding pancreas-specific protease Elastase 3B (CELA3B) that cosegregates with disease. Studies of the mutant protein in vitro, in cell lines and in CRISPR-Cas9 engineered mice indicate that this mutation causes translational upregulation of CELA3B, which upon secretion and activation by trypsin leads to uncontrolled proteolysis and recurrent pancreatitis. Although lesions in several other pancreatitic proteases have been previously linked to hereditary pancreatitis, this is the first known instance of a mutation in CELA3B and a defect in translational control contributing to this disease.
Authors
Paul C. Moore, Jessica T. Cortez, Chester E. Chamberlain, Diana Alba, Amy C. Berger, Zoe Quandt, Alice Chan, Mickie H. Cheng, Jhoanne L. Bautista, Justin Peng, Michael S. German, Mark Anderson, Scott A. Oakes
Abstract
Epithelial barrier dysfunction is a significant factor in many allergic diseases, including eosinophilic esophagitis (EoE). Infiltrating leukocytes and tissue adaptations increase metabolic demands and decrease oxygen availability at barrier surfaces. Understanding of how these processes impact barrier is limited, particularly in allergy. Here, we identified a regulatory axis whereby the oxygen-sensing transcription factor HIF-1α orchestrated epithelial barrier integrity, selectively controlling tight junction CLDN1 (claudin-1). Prolonged experimental hypoxia or HIF1A knockdown suppressed HIF-1α–dependent claudin-1 expression and epithelial barrier function, as documented in 3D organotypic epithelial cultures. L2-IL5OXA mice with EoE-relevant allergic inflammation displayed localized eosinophil oxygen metabolism, tissue hypoxia, and impaired claudin-1 barrier via repression of HIF-1α/claudin-1 signaling, which was restored by transgenic expression of esophageal epithelial-targeted stabilized HIF-1α. EoE patient biopsy analysis identified a repressed HIF-1α/claudin-1 axis, which was restored via pharmacologic HIF-1α stabilization ex vivo. Collectively, these studies reveal HIF-1α’s critical role in maintaining barrier and highlight the HIF-1α/claudin-1 axis as a potential therapeutic target for EoE.
Authors
Joanne C. Masterson, Kathryn A. Biette, Juliet A. Hammer, Nathalie Nguyen, Kelley E. Capocelli, Bejan J. Saeedi, Rachel F. Harris, Shahan D. Fernando, Lindsay B. Hosford, Caleb J. Kelly, Eric L. Campbell, Stefan F. Ehrentraut, Faria N. Ahmed, Hiroshi Nakagawa, James J. Lee, Eóin N. McNamee, Louise E. Glover, Sean P. Colgan, Glenn T. Furuta
Abstract
Resident microbiota activate regulatory cells that modulate intestinal inflammation and promote and maintain intestinal homeostasis. IL-10 is a key mediator of immune regulatory function. Our studies described the functional importance and mechanisms by which gut microbiota and specific microbial components influenced the development of intestinal IL-10-producing B cells. We used fecal transplant to germ-free (GF) Il10+/EGFP reporter and Il10-/- mice to demonstrate that microbiota from specific pathogen-free mice primarily stimulated IL-10-producing colon-specific B cells and T regulatory-1 cells in ex-GF mice. IL-10 in turn down-regulated microbiota-activated mucosal inflammatory cytokines. TLR2/9 ligands and enteric bacterial lysates preferentially induced IL-10 production and regulatory capacity of intestinal B cells. Analysis of Il10+/EGFP mice crossed with additional gene-deficient strains and B cell co-transfer studies demonstrated that microbiota-induced IL-10-producing intestinal B cells ameliorated chronic T cell-mediated colitis in a TLR2, MyD88 and PI3K-dependent fashion. In vitro studies implicated PI3Kp110δ and AKT downstream signaling. These studies demonstrated that resident enteric bacteria activated intestinal IL-10-producing B cells through TLR2, MyD88 and PI3K pathways. These B cells reduced colonic T cell activation and maintained mucosal homeostasis in response to intestinal microbiota.
Authors
Yoshiyuki Mishima, Akihiko Oka, Bo Liu, Jeremy W. Herzog, Chang Soo Eun, Ting-Jia Fan, Emily Bulik-Sullivan, Ian M. Carroll, Jonathan J. Hansen, Liang Chen, Justin E. Wilson, Nancy C. Fisher, Jenny P. Y. Ting, Tomonori Nochi, Angela Wahl, J. Victor Garcia, Christopher L. Karp, R. Balfour Sartor
Abstract
Impaired intestinal epithelial barrier (IEB) function with loss of desmosomal junctional protein desmoglein 2 (DSG2) is a hallmark in the pathogenesis of inflammatory bowel disease (IBD). While previous studies have reported that glial cell line–derived neurotrophic factor (GDNF) promotes IEB function, the mechanisms are poorly understood. We hypothesized that GDNF is involved in the loss of DSG2, resulting in impaired IEB function as seen in IBD. In the inflamed intestine of patients with IBD, there was a decrease in GDNF concentrations accompanied by a loss of DSG2, changes of the intermediate filament system, and increased phosphorylation of p38 MAPK and cytokeratins. DSG2-deficient and RET-deficient Caco2 cells revealed that GDNF specifically recruits DSG2 to the cell borders, resulting in increased DSG2-mediated intercellular adhesion via the RET receptor. Challenge of Caco2 cells and enteroids with proinflammatory cytokines as well as dextran sulfate sodium–induced (DSS-induced) colitis in C57Bl/6 mice led to impaired IEB function with reduced DSG2 mediated by p38 MAPK–dependent phosphorylation of cytokeratins. GDNF blocked all inflammation-induced changes in the IEB. GDNF attenuates inflammation-induced impairment of IEB function caused by the loss of DSG2 through p38 MAPK–dependent phosphorylation of cytokeratin. The reduced GDNF in patients with IBD indicates a disease-relevant contribution to the development of IEB dysfunction.
Authors
Michael Meir, Natalie Burkard, Hanna Ungewiß, Markus Diefenbacher, Sven Flemming, Felix Kannapin, Christoph-Thomas Germer, Matthias Schweinlin, Marco Metzger, Jens Waschke, Nicolas Schlegel
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)