MLCK regulation of claudin 3 expression contributes to IL1β mediated weakening of colonic epithelial tight junctions (1113.1)

Abstract

Interleukin 1β (IL1β) is an inflammatory cytokine well recognized for its role in autoinflammatory diseases including multiple sclerosis and ulcerative colitis, both associated with increased endothelial and epithelial barrier dysfunction respectively. Epithelial barrier integrity is maintained, in part, by expression of tight junction proteins such as occludin, zonula occludens, and claudin family of proteins. The major claudins involved in colonic epithelial barrier function are claudin 2, claudin 3, and claudin 4. In addition to structural components of tight junctions, kinases play a role in mediating signaling events that can affect gene expression. Recently, myosin light chain kinase (MLCK) has been shown to play a role in IL1β mediated abrogation of epithelial tight junctions, however the manner in which MLCK contributes to this dysfunction is not known. Our studies show that IL1β downregulated claudin 3, a sealing claudin, in young adult mouse epithelial (YAMC) and CACO 2 cells. In addition, we show that the MLCK inhibitor ML7 attenuated IL1β induced claudin 3 downregulation, and improved barrier function as measured by electric cell‐substrate impedance sensing (ECIS). Moreover, the role of MLCK mediated downregulation of claudin 3 was further characterized by immunocytochemistry. These results suggest that MLCK plays a critical gene regulatory role in addition to its known place in epithelial cell contractility in response to inflammation.Grant Funding Source: Supported by VA Merit Review 5101BX000799, the NIH grants HL96640, HL61507 and HL70752