Intestinal barrier function is compromised in inflammatory, infectious, ischemic, and immune-mediated intestinal disease. In the previous cycle we studied mechanisms and impact of tumor necrosis factor- (TNF-) induced barrier loss using in vitro and in vivo models to: i) define TNF-induced, myosin light chain kinase- (MLCK-) dependent tight junction regulation;ii) show that MLCK is required for TNF-induced diarrhea;iii) identify and characterize the human MLCK promoter;iv) document MLCK activation in human inflammatory bowel disease (IBD);and v) show that chronic epithelial MLCK activation stimulates mucosal immune cells and sensitizes mice to experimental IBD. We have now begun to define the mechanisms by which TNF specifically activates MLCK1, a long MLCK splice variant, to trigger endocytosis of the tight junction protein occludin. This creates tight junction 'leaks'that allow paracellular flux of large macromolecules without affecting ion selectivity. Our preliminary data show that expression of constitutively-active MLCK in vivo increases flux across the 'leak'pathway. Moreover, unlike in vitro MLCK activation, chronic in vivo MLCK activation alters ion selectivity of the paracellular barrier. This is due to increased mucosal IL-13 production, which induces epithelial claudin-2 expression to create small, cation-selective 'pores'that allow Na+, but not large macromolecules, to traverse the paracellular pathway. This in vivo result emphasizes the presence of, as well as interactions between, two distinct pathways across the tight junction;a high capacity 'pore'pathway that allows small uncharged solutes and specific ions to pass and a low capacity 'leak'pathway that is permeable to larger, uncharged macromolecules but is not ion selective. The fact that 'pore'and 'leak'pathways interact through the mucosal immune system, i.e. IL-13 production, suggests that these pathways may make distinct contributions to disease pathogenesis. These and other data have led to the central hypothesis that at least two mechanisms of regulation modulate unique paracellular pathways, i.e. 'pore'and 'leak,'to differentially impact mucosal homeostasis and disease pathogenesis.
The aims of this application are to i) define the mechanisms by which TNF triggers MLCK1 perijunctional trafficking and enzymatic activation to enhance flux across the tight junction 'leak'pathway;ii) identify the mechanisms that regulate claudin-2 expression and 'pore'pathway flux;and iii) determine the impact of MLCK, occludin, and claudin-2 expression on 'pore'and 'leak'pathway function as well as initiation and progression of chronic intestinal disease. As a whole, these studies will define the relative roles of specific epithelial regulatory processes and immune signaling in modulation of 'pore'and 'leak'pathway paracellular flux and disease pathogenesis. The data, which will provide new understanding of the mechanisms by which intestinal barrier function contributes to human health and disease, will lay the foundation necessary for development of novel therapeutic strategies to correct barrier dysfunction.
The intestinal lining (epithelium) must maintain a barrier that keeps the intestinal contents separate from the remainder of the body. This function is frequently compromised in intestinal disease and has been implicated as an early step in disease development. The proposed studies will advance mechanistic understanding of barrier regulation and dysregulation and, therefore, lead to development of novel therapeutic approaches to improve human health.
|Sallis, Benjamin F; Erkert, Lena; Moñino-Romero, Sherezade et al. (2018) An algorithm for the classification of mRNA patterns in eosinophilic esophagitis: Integration of machine learning. J Allergy Clin Immunol 141:1354-1364.e9|
|Almansour, Khaled; Taverner, Alistair; Turner, Jerrold R et al. (2018) An intestinal paracellular pathway biased toward positively-charged macromolecules. J Control Release 288:111-125|
|Hu, Madeleine D; Ethridge, Alexander D; Lipstein, Rebecca et al. (2018) Epithelial IL-15 Is a Critical Regulator of ?? Intraepithelial Lymphocyte Motility within the Intestinal Mucosa. J Immunol 201:747-756|
|Hou, Qihang; Ye, Lulu; Liu, Haofei et al. (2018) Lactobacillus accelerates ISCs regeneration to protect the integrity of intestinal mucosa through activation of STAT3 signaling pathway induced by LPLs secretion of IL-22. Cell Death Differ 25:1657-1670|
|Krug, S M; Bojarski, C; Fromm, A et al. (2018) Tricellulin is regulated via interleukin-13-receptor ?2, affects macromolecule uptake, and is decreased in ulcerative colitis. Mucosal Immunol 11:345-356|
|Odenwald, Matthew A; Choi, Wangsun; Kuo, Wei-Ting et al. (2018) The scaffolding protein ZO-1 coordinates actomyosin and epithelial apical specializations in vitro and in vivo. J Biol Chem 293:17317-17335|
|Buckley, Aaron; Turner, Jerrold R (2018) Cell Biology of Tight Junction Barrier Regulation and Mucosal Disease. Cold Spring Harb Perspect Biol 10:|
|Syed, Sana; Yeruva, Sunil; Herrmann, Jeremy et al. (2018) Environmental Enteropathy in Undernourished Pakistani Children: Clinical and Histomorphometric Analyses. Am J Trop Med Hyg 98:1577-1584|
|Drolia, Rishi; Tenguria, Shivendra; Durkes, Abigail C et al. (2018) Listeria Adhesion Protein Induces Intestinal Epithelial Barrier Dysfunction for Bacterial Translocation. Cell Host Microbe 23:470-484.e7|
|Edelblum, Karen L; Sharon, Gil; Singh, Gurminder et al. (2017) The Microbiome Activates CD4 T-cell-mediated Immunity to Compensate for Increased Intestinal Permeability. Cell Mol Gastroenterol Hepatol 4:285-297|
Showing the most recent 10 out of 103 publications