Enhanced permeability of intestinal epithelium is a key mechanism of inflammatory diseases of the gut. Such intestinal leakiness exposes internal organs to luminal microbial products, therefore exaggerating mucosal inflammation and increasing the risk of systemic inflammatory responses. Breakdown of the intestinal barrier is caused by disassembly of specialized epithelial structures, tight junctions (TJs) and adherens junctions (AJs). Many inflammatory mediators, including cytokines, nitric oxide and reactive oxygen species, are known to disrupt AJ and TJ structure. Understanding mechanisms of epithelial junctional disassembly during intestinal inflammation represents the major goal of the proposed study. An emerging view is that TJs and AJs undergo a continuous remodeling consisting of the removal of aging junctional components from the plasma membrane by endocytosis and delivery of new TJ/AJ proteins via exocytosis. A central innovative hypothesis of this proposal implies that intestinal inflammation interrupts a steady-state remodeling of epithelial AJs and TJs by blocking vesicle-mediated exocytosis of junctional proteins. This suppression of AJ/TJ exocytosis occurs via inhibition of expression and/or activity of proteins regulating vesicle fusion with the plasma membrane, namely the N-ethylmaleimide sensitive factor (NSF), soluble NSF receptors (SNAREs) and NSF- attachment protein (1SNAP). Dysfunction of SNARE/NSF/1SNAP-mediated trafficking of junctional proteins is likely to eventuate in the defective AJ/TJ structure and increased intestinal barrier permeability. We will test this hypothesis in the following Aims: (1): to investigate the involvement of SNARE-mediated exocytosis in regulation of epithelial junctional structure and functions in vitro and in vivo;(2) to determine the role of oxidative modification of NSF in free-radical induced disassembly of epithelial junctions;3) to analyze the role of 1SNAP in disassembly and recovery of epithelial junctions during mucosal damage and restitution.
These aims will be accomplished using in vitro intestinal epithelial cell monolayers exposed to proinflammatory mediators as well as in vivo murine models of intestinal inflammation. Vesicle fusion machinery will be analyzed by a combination of biochemical (biotinylation, immunoprecipitation, affinity chromatography), immunocytochemical and genetic (siRNA knock-down of SNARE proteins, overexpression of NSF and 1SNAP mutants) approaches. Significance: the proposed study will provide new insights into fundamental mechanisms of intestinal mucosal injury during inflammation. Understanding these mechanisms will potentially provide new therapeutic targets to prevent breakdown of the intestinal barrier in patients with digestive diseases.
The proposed research is aimed to understand mechanisms underlying disruption and restoration of the intestinal epithelial barrier. The barrier breakdown is a common manifestation of different gastroenterological disorders including ulcerative colitis, Chron's disease, celiac diseases and infectious colitis. Furthermore, dysfunctions of the gut barrier contribute to the development of other diseases such as septic shock, alcoholic liver disease and type I diabetes. This project will provide new insights into understanding the pathogenesis of gastrointestinal disorders by exploring a novel epithelium-related mechanism involving in initiation and/or exaggeration of mucosal inflammation. Furthermore, it may provide novel targets for pharmacological prevention of the intestinal barrier breakdown and for accelerated healing of the injured gut mucosa. This may result in decreased morbidity and mortality of a large cohort of patients with inflammatory disorders.
|Naydenov, Nayden G; Feygin, Alex; Wang, Dongdong et al. (2016) Nonmuscle Myosin IIA Regulates Intestinal Epithelial Barrier in vivo and Plays a Protective Role During Experimental Colitis. Sci Rep 6:24161|
|Wang, Dongdong; Naydenov, Nayden G; Feygin, Alex et al. (2016) Actin-Depolymerizing Factor and Cofilin-1 Have Unique and Overlapping Functions in Regulating Intestinal Epithelial Junctions and Mucosal Inflammation. Am J Pathol 186:844-58|
|Miller, Kelly A; Chaand, Mudit; Gregoire, Stacy et al. (2016) Characterization of V. cholerae T3SS-dependent cytotoxicity in cultured intestinal epithelial cells. Cell Microbiol 18:1857-1870|
|Wang, Dongdong; Chadha, Gibran K; Feygin, Alex et al. (2015) F-actin binding protein, anillin, regulates integrity of intercellular junctions in human epithelial cells. Cell Mol Life Sci 72:3185-200|
|Lechuga, Susana; Baranwal, Somesh; Ivanov, Andrei I (2015) Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions. Am J Physiol Gastrointest Liver Physiol 308:G745-56|
|Ivanov, Andrei I (2014) Pharmacological inhibitors of exocytosis and endocytosis: novel bullets for old targets. Methods Mol Biol 1174:3-18|
|Lechuga, Susana; Baranwal, Somesh; Li, Chao et al. (2014) Loss of Î³-cytoplasmic actin triggers myofibroblast transition of human epithelial cells. Mol Biol Cell 25:3133-46|
|Naydenov, Nayden G; Feygin, Alex; Wang, Lifu et al. (2014) N-ethylmaleimide-sensitive factor attachment protein Î± (Î±SNAP) regulates matrix adhesion and integrin processing in human epithelial cells. J Biol Chem 289:2424-39|
|Kuo, I-Hsin; Carpenter-Mendini, Amanda; Yoshida, Takeshi et al. (2013) Activation of epidermal toll-like receptor 2 enhances tight junction function: implications for atopic dermatitis and skin barrier repair. J Invest Dermatol 133:988-98|
|Ghatak, Sayak; Reveiller, Marie; Toia, Liana et al. (2013) Bile acid at low pH reduces squamous differentiation and activates EGFR signaling in esophageal squamous cells in 3-D culture. J Gastrointest Surg 17:1723-31|
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