Research Article
VAMP8 is the v-SNARE that mediates basolateral exocytosis in a mouse model of alcoholic pancreatitis
Abstract
In rodents and humans, alcohol exposure has been shown to predispose the pancreas to cholinergic or viral induction of pancreatitis. We previously developed a rodent model in which exposure to an ethanol (EtOH) diet, followed by carbachol (Cch) stimulation, redirects exocytosis from the apical to the basolateral plasma membrane of acinar cells, resulting in ectopic zymogen enzyme activation and pancreatitis. This redirection of exocytosis involves a soluble NSF attachment receptor (SNARE) complex consisting of syntaxin-4 and synapse-associated protein of 23 kDa (SNAP-23). Here, we investigated the role of the zymogen granule (ZG) SNARE vesicle-associated membrane protein 8 (VAMP8) in mediating basolateral exocytosis. In WT mice, in vitro EtOH exposure or EtOH diet reduced Cch-stimulated amylase release by redirecting apical exocytosis to the basolateral membrane, leading to alcoholic pancreatitis. Further reduction of zymogen secretion, caused by blockade of both apical and basolateral exocytosis and resulting in a more mild induction of alcoholic pancreatitis, was observed in Vamp8–/– mice in response to these treatments. In addition, although ZGs accumulated in Vamp8–/– acinar cells, ZG-ZG fusions were reduced compared with those in WT acinar cells, as visualized by electron microscopy. This reduction in ZG fusion may account for reduced efficiency of apical exocytosis in Vamp8–/– acini. These findings indicate that VAMP8 is the ZG-SNARE that mediates basolateral exocytosis in alcoholic pancreatitis and that VAMP8 is critical for ZG-ZG homotypic fusion.
Authors
Laura I. Cosen-Binker, Marcelo G. Binker, Cheng-Chun Wang, Wanjin Hong, Herbert Y. Gaisano
Abstract
The proinflammatory cytokine IL-6 seems to have an important role in the intestinal inflammation that characterizes inflammatory bowel diseases (IBDs) such as Crohn disease and ulcerative colitis. However, little is known about the molecular mechanisms regulating IL-6 production in IBD. Here, we assessed the role of the transcriptional regulator IFN regulatory factor–4 (IRF4) in this process. Patients with either Crohn disease or ulcerative colitis exhibited increased IRF4 expression in lamina propria CD3+ T cells as compared with control patients. Consistent with IRF4 having a regulatory function in T cells, in a mouse model of IBD whereby colitis is induced in RAG-deficient mice by transplantation with CD4+CD45RBhi T cells, adoptive transfer of wild-type but not IRF4-deficient T cells resulted in severe colitis. Furthermore, IRF4-deficient mice were protected from T cell–dependent chronic intestinal inflammation in trinitrobenzene sulfonic acid– and oxazolone-induced colitis. In addition, IRF4-deficient mice with induced colitis had reduced mucosal IL-6 production, and IRF4 was required for IL-6 production by mucosal CD90+ T cells, which it protected from apoptosis. Finally, the protective effect of IRF4 deficiency could be abrogated by systemic administration of either recombinant IL-6 or a combination of soluble IL-6 receptor (sIL-6R) plus IL-6 (hyper–IL-6). Taken together, our data identify IRF4 as a key regulator of mucosal IL-6 production in T cell–dependent experimental colitis and suggest that IRF4 might provide a therapeutic target for IBDs.
Authors
Jonas Mudter, Lioubov Amoussina, Mirjam Schenk, Jingling Yu, Anne Brüstle, Benno Weigmann, Raja Atreya, Stefan Wirtz, Christoph Becker, Arthur Hoffman, Imke Atreya, Stefan Biesterfeld, Peter R. Galle, Hans A. Lehr, Stefan Rose-John, Christoph Mueller, Michael Lohoff, Markus F. Neurath
Abstract
Huntingtin interacting protein 1 related (Hip1r) is an F-actin– and clathrin-binding protein involved in vesicular trafficking. In this study, we demonstrate that Hip1r is abundantly expressed in the gastric parietal cell, predominantly localizing with F-actin to canalicular membranes. Hip1r may provide a critical function in vivo, as demonstrated by extensive changes to parietal cells and the gastric epithelium in Hip1r-deficient mice. Electron microscopy revealed abnormal apical canalicular membranes and loss of tubulovesicles in mutant parietal cells, suggesting that Hip1r is necessary for the normal trafficking of these secretory membranes. Accordingly, acid secretory dynamics were altered in mutant parietal cells, with enhanced activation and acid trapping, as measured in isolated gastric glands. At the whole-organ level, gastric acidity was reduced in Hip1r-deficient mice, and the gastric mucosa was grossly transformed, with fewer parietal cells due to enhanced apoptotic cell death and glandular hypertrophy associated with cellular transformation. Hip1r-deficient mice had increased expression of the gastric growth factor gastrin, and mice mutant for both gastrin and Hip1r exhibited normalization of both proliferation and gland height. Taken together, these studies demonstrate that Hip1r plays a significant role in gastric physiology, mucosal architecture, and secretory membrane dynamics in parietal cells.
Authors
Renu N. Jain, Asma A. Al-Menhali, Theresa M. Keeley, Jianhua Ren, Mohammed El-Zaatari, Xunsheng Chen, Juanita L. Merchant, Theodora S. Ross, Catherine S. Chew, Linda C. Samuelson
Abstract
Identifying the genetic variants that regulate fasting glucose concentrations may further our understanding of the pathogenesis of diabetes. We therefore investigated the association of fasting glucose levels with SNPs in 2 genome-wide scans including a total of 5,088 nondiabetic individuals from Finland and Sardinia. We found a significant association between the SNP rs563694 and fasting glucose concentrations (P = 3.5 × 10–7). This association was further investigated in an additional 18,436 nondiabetic individuals of mixed European descent from 7 different studies. The combined P value for association in these follow-up samples was 6.9 × 10–26, and combining results from all studies resulted in an overall P value for association of 6.4 × 10–33. Across these studies, fasting glucose concentrations increased 0.01–0.16 mM with each copy of the major allele, accounting for approximately 1% of the total variation in fasting glucose. The rs563694 SNP is located between the genes glucose-6-phosphatase catalytic subunit 2 (G6PC2) and ATP-binding cassette, subfamily B (MDR/TAP), member 11 (ABCB11). Our results in combination with data reported in the literature suggest that G6PC2, a glucose-6-phosphatase almost exclusively expressed in pancreatic islet cells, may underlie variation in fasting glucose, though it is possible that ABCB11, which is expressed primarily in liver, may also contribute to such variation.
Authors
Wei-Min Chen, Michael R. Erdos, Anne U. Jackson, Richa Saxena, Serena Sanna, Kristi D. Silver, Nicholas J. Timpson, Torben Hansen, Marco Orrù, Maria Grazia Piras, Lori L. Bonnycastle, Cristen J. Willer, Valeriya Lyssenko, Haiqing Shen, Johanna Kuusisto, Shah Ebrahim, Natascia Sestu, William L. Duren, Maria Cristina Spada, Heather M. Stringham, Laura J. Scott, Nazario Olla, Amy J. Swift, Samer Najjar, Braxton D. Mitchell, Debbie A. Lawlor, George Davey Smith, Yoav Ben-Shlomo, Gitte Andersen, Knut Borch-Johnsen, Torben Jørgensen, Jouko Saramies, Timo T. Valle, Thomas A. Buchanan, Alan R. Shuldiner, Edward Lakatta, Richard N. Bergman, Manuela Uda, Jaakko Tuomilehto, Oluf Pedersen, Antonio Cao, Leif Groop, Karen L. Mohlke, Markku Laakso, David Schlessinger, Francis S. Collins, David Altshuler, Gonçalo R. Abecasis, Michael Boehnke, Angelo Scuteri, Richard M. Watanabe
Abstract
To meet tissue requirements for oxygen, capillaries must be properly distributed without excess or shortage. In this process, tissue oxygen concentration is well known to determine capillary density via the hypoxia-induced cascade, in which HIFs and VEGF play key roles. However, some additional mechanisms modulating this cascade are suggested to be involved in precise capillary network formation. Here, we showed that leukemia inhibitory factor (LIF) was predominantly expressed in developing endothelium, while its receptor was expressed in surrounding cells such as retinal astrocytes. The retinas of Lif–/– mice displayed increased microvessel density accompanied by sustained tip cell activity, due to increased VEGF expression by astrocytes in the vascularized area. Lif–/– mice resisted hyperoxygen insult in the oxygen-induced retinopathy model, whereas they paradoxically had increased numbers of neovascular tufts. In an in vitro study, LIF inhibited hypoxia-induced VEGF expression and proliferation in cultured astrocytes. Lif–/– mice also exhibited similarly increased microvessel density and upregulated VEGF in various tissues outside the retina. Together, these findings suggest that tissues and advancing vasculature communicate to ensure adequate vascularization using LIF as well as oxygen, which suggests a new strategy for antiangiogenic therapy in human diseases such as diabetic retinopathy and cancer.
Authors
Yoshiaki Kubota, Masanori Hirashima, Kazuo Kishi, Colin L. Stewart, Toshio Suda
Abstract
Hereditary sensory and autonomic neuropathy type II (HSANII) is an early-onset autosomal recessive disorder characterized by loss of perception to pain, touch, and heat due to a loss of peripheral sensory nerves. Mutations in hereditary sensory neuropathy type II (HSN2), a single-exon ORF originally identified in affected families in Quebec and Newfoundland, Canada, were found to cause HSANII. We report here that HSN2 is a nervous system–specific exon of the with-no-lysine(K)–1 (WNK1) gene. WNK1 mutations have previously been reported to cause pseudohypoaldosteronism type II but have not been studied in the nervous system. Given the high degree of conservation of WNK1 between mice and humans, we characterized the structure and expression patterns of this isoform in mice. Immunodetections indicated that this Wnk1/Hsn2 isoform was expressed in sensory components of the peripheral nervous system and CNS associated with relaying sensory and nociceptive signals, including satellite cells, Schwann cells, and sensory neurons. We also demonstrate that the novel protein product of Wnk1/Hsn2 was more abundant in sensory neurons than motor neurons. The characteristics of WNK1/HSN2 point to a possible role for this gene in the peripheral sensory perception deficits characterizing HSANII.
Authors
Masoud Shekarabi, Nathalie Girard, Jean-Baptiste Rivière, Patrick Dion, Martin Houle, André Toulouse, Ronald G. Lafrenière, Freya Vercauteren, Pascale Hince, Janet Laganiere, Daniel Rochefort, Laurence Faivre, Mark Samuels, Guy A. Rouleau
Abstract
Dysfunctional Tregs have been identified in individuals with psoriasis. However, their role in the pathogenesis of the disease remains unclear. Here we explored the effect of diminished CD18 (β2 integrin) expression on the function of CD4+CD25+CD127– Tregs using the Cd18 hypomorphic (Cd18hypo) PL/J mouse model of psoriasis that closely resembles the human disease. We found that reduced CD18 expression impaired cell-cell contact between Tregs and DCs. This led to dysfunctional Tregs, which both failed to suppress the pathogenic T cells and promoted the onset and severity of the disease. This failure was TGF-β–dependent, as Tregs derived from Cd18hypo PL/J mice had diminished TGF-β1 expression. Adoptive transfer of Tregs expressing wild-type levels of CD18 into affected Cd18hypo PL/J mice resulted in a substantial improvement of the psoriasiform skin disease, which did not occur upon coinjection of the cells with TGF-β–specific neutralizing antibody. Our data indicate a primary dysfunction of Cd18hypo Tregs, allowing subsequent hyperproliferation of pathogenic T cells in the Cd18hypo PL/J mouse model of psoriasis. This study may provide a step forward in our understanding of the unique role of CD18 expression levels in avoiding autoimmunity.
Authors
Honglin Wang, Thorsten Peters, Anca Sindrilaru, Daniel Kess, Tsvetelina Oreshkova, Xue-Zhong Yu, Anne Maria Seier, Heike Schreiber, Meinhard Wlaschek, Robert Blakytny, Jan Röhrbein, Guido Schulz, Johannes M. Weiss, Karin Scharffetter-Kochanek
Abstract
Recent evidence indicates that small noncoding RNA molecules known as microRNAs (miRNAs) can function as tumor suppressors and oncogenes. Mutation, misexpression, and altered mature miRNA processing are implicated in carcinogenesis and tumor progression. Because SNPs in pre-miRNAs could alter miRNA processing, expression, and/or binding to target mRNA, we conducted a systematic survey of common pre-miRNA SNPs and their surrounding regions and evaluated in detail the association of 4 of these SNPs with the survival of individuals with non–small cell lung cancer (NSCLC). When we assumed that disease susceptibility was inherited as a recessive phenotype, we found that the rs11614913 SNP in hsa-mir-196a2 was associated with survival in individuals with NSCLC. Specifically, survival was significantly decreased in individuals who were homozygous CC at SNP rs11614913. In the genotype-phenotype correlation analysis of 23 human lung cancer tissue samples, rs11614913 CC was associated with a statistically significant increase in mature hsa-mir-196a expression but not with changes in levels of the precursor, suggesting enhanced processing of the pre-miRNA to its mature form. Furthermore, binding assays revealed that the rs11614913 SNP can affect binding of mature hsa-mir-196a2-3p to its target mRNA. Therefore, the rs11614913 SNP in hsa-mir-196a2 may be a prognostic biomarker for NSCLC. Further characterization of miRNA SNPs may open new avenues for the study of cancer and therapeutic interventions.
Authors
Zhibin Hu, Jiaping Chen, Tian Tian, Xiaoyi Zhou, Haiyong Gu, Lin Xu, Yi Zeng, Ruifen Miao, Guangfu Jin, Hongxia Ma, Yijiang Chen, Hongbing Shen
Abstract
Chronic inflammation increases cancer risk. While it is clear that cell signaling elicited by inflammatory cytokines promotes tumor development, the impact of DNA damage production resulting from inflammation-associated reactive oxygen and nitrogen species (RONS) on tumor development has not been directly tested. RONS induce DNA damage that can be recognized by alkyladenine DNA glycosylase (Aag) to initiate base excision repair. Using a mouse model of episodic inflammatory bowel disease by repeated administration of dextran sulfate sodium in the drinking water, we show that Aag-mediated DNA repair prevents colonic epithelial damage and reduces the severity of dextran sulfate sodium–induced colon tumorigenesis. Importantly, DNA base lesions expected to be induced by RONS and recognized by Aag accumulated to higher levels in Aag-deficient animals following stimulation of colonic inflammation. Finally, as a test of the generality of this effect we show that Aag-deficient animals display more severe gastric lesions that are precursors of gastric cancer after chronic infection with Helicobacter pylori. These data demonstrate that the repair of DNA lesions formed by RONS during chronic inflammation is important for protection against colon carcinogenesis.
Authors
Lisiane B. Meira, James M. Bugni, Stephanie L. Green, Chung-Wei Lee, Bo Pang, Diana Borenshtein, Barry H. Rickman, Arlin B. Rogers, Catherine A. Moroski-Erkul, Jose L. McFaline, David B. Schauer, Peter C. Dedon, James G. Fox, Leona D. Samson
Abstract
Increased retinal vasopermeability contributes to diabetic retinopathy, the leading cause of blindness in working-age adults. Despite clinical progress, effective therapy remains a major need. Vasoinhibins, a family of peptides derived from the protein hormone prolactin (and inclusive of the 16-kDa fragment of prolactin), antagonize the proangiogenic effects of VEGF, a primary mediator of retinal vasopermeability. Here, we demonstrate what we believe to be a novel function of vasoinhibins as inhibitors of the increased retinal vasopermeability associated with diabetic retinopathy. Vasoinhibins inhibited VEGF-induced vasopermeability in bovine aortic and rat retinal capillary endothelial cells in vitro. In vivo, vasoinhibins blocked retinal vasopermeability in diabetic rats and in response to intravitreous injection of VEGF or of vitreous from patients with diabetic retinopathy. Inhibition by vasoinhibins was similar to that achieved following immunodepletion of VEGF from human diabetic retinopathy vitreous or blockage of NO synthesis, suggesting that vasoinhibins inhibit VEGF-induced NOS activation. We further showed that vasoinhibins activate protein phosphatase 2A (PP2A), leading to eNOS dephosphorylation at Ser1179 and, thereby, eNOS inactivation. Moreover, intravitreous injection of okadaic acid, a PP2A inhibitor, blocked the vasoinhibin effect on endothelial cell permeability and retinal vasopermeability. These results suggest that vasoinhibins have the potential to be developed as new therapeutic agents to control the excessive retinal vasopermeability observed in diabetic retinopathy and other vasoproliferative retinopathies.
Authors
Celina García, Jorge Aranda, Edith Arnold, Stéphanie Thébault, Yazmín Macotela, Fernando López-Casillas, Valentín Mendoza, Hugo Quiroz-Mercado, Hebert Luis Hernández-Montiel, Sue-Hwa Lin, Gonzalo Martínez de la Escalera, Carmen Clapp
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