Gastroenterology
Abstract
N-formyl peptide receptors (FPRs) are critical regulators of host defense in phagocytes and are also expressed in epithelia. FPR signaling and function have been extensively studied in phagocytes, yet their functional biology in epithelia is poorly understood. We describe a novel intestinal epithelial FPR signaling pathway that is activated by an endogenous FPR ligand, annexin A1 (ANXA1), and its cleavage product Ac2-26, which mediate activation of ROS by an epithelial NADPH oxidase, NOX1. We show that epithelial cell migration was regulated by this signaling cascade through oxidative inactivation of the regulatory phosphatases PTEN and PTP-PEST, with consequent activation of focal adhesion kinase (FAK) and paxillin. In vivo studies using intestinal epithelial specific Nox1–/–IEC and AnxA1–/– mice demonstrated defects in intestinal mucosal wound repair, while systemic administration of ANXA1 promoted wound recovery in a NOX1-dependent fashion. Additionally, increased ANXA1 expression was observed in the intestinal epithelium and infiltrating leukocytes in the mucosa of ulcerative colitis patients compared with normal intestinal mucosa. Our findings delineate a novel epithelial FPR1/NOX1-dependent redox signaling pathway that promotes mucosal wound repair.
Authors
Giovanna Leoni, Ashfaqul Alam, Philipp-Alexander Neumann, J. David Lambeth, Guangjie Cheng, James McCoy, Roland S. Hilgarth, Kousik Kundu, Niren Murthy, Dennis Kusters, Chris Reutelingsperger, Mauro Perretti, Charles A. Parkos, Andrew S. Neish, Asma Nusrat
Abstract
Intestinal barrier function requires intricate cooperation between intestinal epithelial cells and immune cells. Enteropathogens are able to invade the intestinal lymphoid tissue known as Peyer’s patches (PPs) and disrupt the integrity of the intestinal barrier. However, the underlying molecular mechanisms of this process are poorly understood. In mice infected with Yersinia pseudotuberculosis, we found that PP barrier dysfunction is dependent on the Yersinia virulence plasmid and the expression of TLR-2 by hematopoietic cells, but not by intestinal epithelial cells. Upon TLR-2 stimulation, Y. pseudotuberculosis–infected monocytes activated caspase-1 and produced IL-1β. In turn, IL-1β increased NF-κB and myosin light chain kinase activation in intestinal epithelial cells, thus disrupting the intestinal barrier by opening the tight junctions. Therefore, Y. pseudotuberculosis subverts intestinal barrier function by altering the interplay between immune and epithelial cells during infection.
Authors
Camille Jung, Ulrich Meinzer, Nicolas Montcuquet, Elodie Thachil, Danielle Château, Raphaële Thiébaut, Maryline Roy, Ziad Alnabhani, Dominique Berrebi, Monique Dussaillant, Eric Pedruzzi, Sophie Thenet, Nadine Cerf-Bensussan, Jean-Pierre Hugot, Frederick Barreau
Abstract
Radiation gastrointestinal (GI) syndrome is a major lethal toxicity that may occur after a radiation/nuclear incident. Currently, there are no prophylactic countermeasures against radiation GI syndrome lethality for first responders, military personnel, or remediation workers entering a contaminated area. The pathophysiology of this syndrome requires depletion of stem cell clonogens (SCCs) within the crypts of Lieberkühn, which are a subset of cells necessary for postinjury regeneration of gut epithelium. Recent evidence indicates that SCC depletion is not exclusively a result of DNA damage but is critically coupled to ceramide-induced endothelial cell apoptosis within the mucosal microvascular network. Here we show that ceramide generated on the surface of endothelium coalesces to form ceramide-rich platforms that transmit an apoptotic signal. Moreover, we report the generation of 2A2, an anti-ceramide monoclonal antibody that binds to ceramide to prevent platform formation on the surface of irradiated endothelial cells of the murine GI tract. Consequently, we found that 2A2 protected against endothelial apoptosis in the small intestinal lamina propria and facilitated recovery of crypt SCCs, preventing the death of mice from radiation GI syndrome after high radiation doses. As such, we suggest that 2A2 represents a prototype of a new class of anti-ceramide therapeutics and an effective countermeasure against radiation GI syndrome mortality.
Authors
Jimmy Rotolo, Branka Stancevic, Jianjun Zhang, Guoqiang Hua, John Fuller, Xianglei Yin, Adriana Haimovitz-Friedman, Kisu Kim, Ming Qian, Marina Cardó-Vila, Zvi Fuks, Renata Pasqualini, Wadih Arap, Richard Kolesnick
Abstract
The constant self renewal and differentiation of adult intestinal stem cells maintains a functional intestinal mucosa for a lifetime. However, the molecular mechanisms that regulate intestinal stem cell division and epithelial homeostasis are largely undefined. We report here that the small GTPases Cdc42 and Rab8a are critical regulators of these processes in mice. Conditional ablation of Cdc42 in the mouse intestinal epithelium resulted in the formation of large intracellular vacuolar structures containing microvilli (microvillus inclusion bodies) in epithelial enterocytes, a phenotype reminiscent of human microvillus inclusion disease (MVID), a devastating congenital intestinal disorder that results in severe nutrient deprivation. Further analysis revealed that Cdc42-deficient stem cells had cell division defects, reduced capacity for clonal expansion and differentiation into Paneth cells, and increased apoptosis. Cdc42 deficiency impaired Rab8a activation and its association with multiple effectors, and prevented trafficking of Rab8a vesicles to the midbody. This impeded cytokinesis, triggering crypt apoptosis and disrupting epithelial morphogenesis. Rab8a was also required for Cdc42-GTP activity in the intestinal epithelium, where continued cell division takes place. Furthermore, mice haploinsufficient for both Cdc42 and Rab8a in the intestine demonstrated abnormal crypt morphogenesis and epithelial transporter physiology, further supporting their functional interaction. These data suggest that defects of the stem cell niche can cause MVID. This hypothesis represents a conceptual departure from the conventional view of this disease, which has focused on the affected enterocytes, and suggests stem cell–based approaches could be beneficial to infants with this often lethal condition.
Authors
Ryotaro Sakamori, Soumyashree Das, Shiyan Yu, Shanshan Feng, Ewa Stypulkowski, Yinzheng Guan, Veronique Douard, Waixing Tang, Ronaldo P. Ferraris, Akihiro Harada, Cord Brakebusch, Wei Guo, Nan Gao
Abstract
Biliary atresia (BA) is a destructive cholangiopathy of childhood in which Th1 immunity has been mechanistically linked to the bile duct inflammation and obstruction that culminate in liver injury. Based on reports of decreased Th1 cytokines in some patients and the development of BA in mice lacking CD4+ T cells, we hypothesized that Th1-independent mechanisms can also activate effector cells and induce BA. Here, we tested this hypothesis using Stat1–/– mice, which lack the ability to mount Th1 immune responses. Infection of Stat1–/– mice with rhesus rotavirus type A (RRV) on postnatal day 1 induced a prominent Th2 response, duct epithelial injury and obstruction within 7 days, and atresia shortly thereafter. A high degree of phosphorylation of the Th2 transcription factor Stat6 was observed; however, concurrent inactivation of Stat1 and Stat6 in mice did not prevent BA after RRV infection. In contrast, depletion of macrophages or combined loss of Il13 and Stat1 reduced tissue infiltration by lymphocytes and myeloid cells, maintained epithelial integrity, and prevented duct obstruction. In concordance with our mouse model, humans at the time of BA diagnosis exhibited differential hepatic expression of Th2 genes and serum Th2 cytokines. These findings demonstrate compatibility between Th2 commitment and the pathogenesis of BA, and suggest that patient subgrouping in future clinical trials should account for differences in Th2 status.
Authors
Jun Li, Kazuhiko Bessho, Pranavkumar Shivakumar, Reena Mourya, Sujit Kumar Mohanty, Jorge L. dos Santos, Irene K. Miura, Gilda Porta, Jorge A. Bezerra
Abstract
While there is evidence that specific T cell populations can promote the growth of established tumors, instances where T cell activity causes neoplasms to arise de novo are infrequent. Here, we employed two conditional mutagenesis systems to delete the TGF-β signaling pathway component Smad4 in T cells and observed the spontaneous development of massive polyps within the gastroduodenal regions of mice. The epithelial lesions contained increased levels of transcripts encoding IL-11, IL-6, TGF-β, IL-1β, and TNF-α, and lamina propria cells isolated from lesions contained abundant IL-17A+CD4+ T cells. Furthermore, we found that Smad4 deficiency attenuated TGF-β–mediated in vitro polarization of FoxP3+CD4+ T cells, but not IL-17A+CD4+ T cells, suggesting that the epithelial lesions may have arisen as a consequence of unchecked Th17 cell activity. Proinflammatory cytokine production likely accounted for the raised levels of IL-11, a cytokine known to promote gastric epithelial cell survival and hyperplasia. Consistent with IL-11 having a pathogenic role in this model, we found evidence of Stat3 activation in the gastric polyps. Thus, our data indicate that a chronic increase in gut Th17 cell activity can be associated with the development of premalignant lesions of the gastroduodenal region.
Authors
Jennifer Nancy Hahn, Vincent George Falck, Frank Robert Jirik
Abstract
Hirschsprung (HSCR) disease is a complex genetic disorder attributed to a failure of the enteric neural crest cells (ENCCs) to form ganglia in the hindgut. Hedgehog and Notch are implicated in mediating proliferation and differentiation of ENCCs. Nevertheless, how these signaling molecules may interact to mediate gut colonization by ENCCs and contribute to a primary etiology for HSCR are not known. Here, we report our pathway-based epistasis analysis of data generated by a genome-wide association study on HSCR disease, which indicates that specific genotype constellations of Patched (PTCH1) (which encodes a receptor for Hedgehog) and delta-like 3 (DLL3) (which encodes a receptor for Notch) SNPs confer higher risk to HSCR. Importantly, deletion of Ptch1 in mouse ENCCs induced robust Dll1 expression and activation of the Notch pathway, leading to premature gliogenesis and reduction of ENCC progenitors in mutant bowels. Dll1 integrated Hedgehog and Notch pathways to coordinate neuronal and glial cell differentiation during enteric nervous system development. In addition, Hedgehog-mediated gliogenesis was found to be highly conserved, such that Hedgehog was consistently able to promote gliogenesis of human neural crest–related precursors. Collectively, we defined PTCH1 and DLL3 as HSCR susceptibility genes and suggest that Hedgehog/Notch-induced premature gliogenesis may represent a new disease mechanism for HSCR.
Authors
Elly Sau-Wai Ngan, Maria-Mercè Garcia-Barceló, Benjamin Hon-Kei Yip, Hiu-Ching Poon, Sin-Ting Lau, Carmen Ka-Man Kwok, Eric Sat, Mai-Har Sham, Kenneth Kak-Yuen Wong, Brandon J. Wainwright, Stacey S. Cherny, Chi-Chung Hui, Pak Chung Sham, Vincent Chi-Hang Lui, Paul Kwong-Hang Tam
Abstract
Expression of the transmembrane glycoprotein CD98 (encoded by SLC3A2) is increased in intestinal inflammatory conditions, such as inflammatory bowel disease (IBD), and in various carcinomas, yet its pathogenetic role remains unknown. By generating gain- and loss-of-function mouse models with genetically manipulated CD98 expression specifically in intestinal epithelial cells (IECs), we explored the role of CD98 in intestinal homeostasis, inflammation, and colitis-associated tumorigenesis. IEC-specific CD98 overexpression induced gut homeostatic defects and increased inflammatory responses to DSS-induced colitis, promoting colitis-associated tumorigenesis in mice. Further analysis indicated that the ability of IEC-specific CD98 overexpression to induce tumorigenesis was linked to its capacity to induce barrier dysfunction and to stimulate cell proliferation and production of proinflammatory mediators. To validate these results, we constructed mice carrying conditional floxed Slc3a2 alleles and crossed them with Villin-Cre mice such that CD98 was downregulated only in IECs. These mice exhibited attenuated inflammatory responses and resistance to both DSS-induced colitis and colitis-associated tumorigenesis. Together, our data show that intestinal CD98 expression has a crucial role in controlling homeostatic and innate immune responses in the gut. Modulation of CD98 expression in IECs therefore represents a promising therapeutic strategy for the treatment and prevention of inflammatory intestinal diseases, such as IBD and colitis-associated cancer.
Authors
Hang Thi Thu Nguyen, Guillaume Dalmasso, Leif Torkvist, Jonas Halfvarson, Yutao Yan, Hamed Laroui, Doron Shmerling, Tiziano Tallone, Mauro D’Amato, Shanthi V. Sitaraman, Didier Merlin
Abstract
Intestinal epithelial cell (IEC) apoptosis contributes to the development of ulcerative colitis (UC), an inflammatory bowel disease (IBD) that affects the colon and rectum. Therapies that target the inflammatory cytokine TNF have been found to inhibit IEC apoptosis in patients with IBD, although the mechanism of IEC apoptosis remains unclear. We therefore investigated the role of p53-upregulated modulator of apoptosis (PUMA), a p53 target and proapoptotic BH3-only protein, in colitis and IEC apoptosis, using patient samples and mouse models of UC. In UC patient samples, PUMA expression was elevated in colitis tissues relative to that in uninvolved tissues, and the degree of elevation of PUMA expression correlated with the severity of colitis and the degree of apoptosis induction. In mice, PUMA was markedly induced in colonic epithelial cells following induction of colitis by either dextran sulfate sodium salt (DSS) or 2,4,6-trinitrobenzene sulfonic acid (TNBS). The induction of PUMA was p53-independent but required NF-κB. Absence of PUMA, but neither absence of p53 nor that of another BH3-only protein (Bid), relieved DSS- and TNBS-induced colitis and inhibited IEC apoptosis. Furthermore, treating mice with infliximab (Remicade), a clinically used TNF-specific antibody, suppressed DSS- and TNBS-induced PUMA expression and colitis. These results indicate that PUMA induction contributes to the pathogenesis of colitis by promoting IEC apoptosis and suggest that PUMA inhibition may be an effective strategy to promote mucosal healing in patients with UC.
Authors
Wei Qiu, Bin Wu, Xinwei Wang, Monica E. Buchanan, Miguel D. Regueiro, Douglas J. Hartman, Robert E. Schoen, Jian Yu, Lin Zhang
Abstract
Mucin-type O-linked oligosaccharides (O-glycans) are primary components of the intestinal mucins that form the mucus gel layer overlying the gut epithelium. Impaired expression of intestinal O-glycans has been observed in patients with ulcerative colitis (UC), but its role in the etiology of this disease is unknown. Here, we report that mice with intestinal epithelial cell–specific deficiency of core 1–derived O-glycans, the predominant form of O-glycans, developed spontaneous colitis that resembled human UC, including massive myeloid infiltrates and crypt abscesses. The colitis manifested in these mice was also characterized by TNF-producing myeloid infiltrates in colon mucosa in the absence of lymphocytes, supporting an essential role for myeloid cells in colitis initiation. Furthermore, induced deletion of intestinal core 1–derived O-glycans caused spontaneous colitis in adult mice. These data indicate a causal role for the loss of core 1–derived O-glycans in colitis. Finally, we detected a biosynthetic intermediate typically exposed in the absence of core 1 O-glycan, Tn antigen, in the colon epithelium of a subset of UC patients. Somatic mutations in the X-linked gene that encodes core 1 β1,3-galactosyltransferase–specific chaperone 1 (C1GALT1C1, also known as Cosmc), which is essential for core 1 O-glycosylation, were found in Tn-positive epithelia. These data suggest what we believe to be a new molecular mechanism for the pathogenesis of UC.
Authors
Jianxin Fu, Bo Wei, Tao Wen, Malin E.V. Johansson, Xiaowei Liu, Emily Bradford, Kristina A. Thomsson, Samuel McGee, Lilah Mansour, Maomeng Tong, J. Michael McDaniel, Thomas J. Sferra, Jerrold Turner, Hong Chen, Gunnar C. Hansson, Jonathan Braun, Lijun Xia
Copyright © 2021 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)