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Flagellin is required for salmonella-induced expression of heat shock protein Hsp25 in intestinal epithelium

¹Section of Infectious Disease and ²Martin Boyer Laboratories and IBD Research Center, Department of Medicine, ³Department of Pathology, and ⁴Section of Neonatology, Department of Pediatrics, The University of Chicago, Chicago, Illinois; and ⁵Department of Pathology, Emory University, Atlanta, Georgia

Submitted 9 August 2007 ; accepted in final form 16 January 2008

Flagellin is a bacterial protein responsible for activation of Toll-like receptor 5 (TLR5), which we hypothesize is involved in Salmonella's induction of cytoprotective heat shock proteins in intestinal epithelial cells. Flagellin induces the cytoprotective heat shock protein Hsp25 in different intestinal epithelial cell lines and in mouse intestine. Flagellin induces Hsp25 expression in a time-dependent manner in vitro. This effect is transcriptional, as confirmed by luciferase reporter assays and actinomycin D treatment. In addition, Hsp25 induction requires p38 MAPK activation and is only observed when flagellin is added to the basolateral side of polarized intestinal epithelial cells, consistent with the known location of TLR5. Flagellin-mediated Hsp25 induction is associated with increased protective effects against oxidant stress, an effect that is at least partially mediated by p38 MAPK. Use of small interfering RNA against Hsp25 demonstrates that flagellin-mediated protection against oxidant stress is to some degree mediated through Hsp25 induction. This suggests that, by protecting against oxidant injury, the induction of Hsp25 expression by flagellin may contribute to intestinal homeostasis. In a coculture cell model and in a mouse model of Salmonella enterica Serovar Typhimurium infection, not only does infection with wild-type and a flagellin-deletion mutant strain of Salmonella show that flagellin induces Hsp25 in vivo, but it also demonstrates that in the case of live Salmonella infection, flagellin serves as a major stimulus for the induction of Hsp25 expression. These data provide evidence that flagellin is required for Salmonella-mediated induction of Hsp25 expression in intestinal epithelium.

intestinal epithelial cells; oxidant stress; innate immunity; Toll-like receptors

This article has been cited by other articles:

				M. Lopez, N. Li, J. Kataria, M. Russell, and J. Neu Live and Ultraviolet-Inactivated Lactobacillus Rhamnosus GG Decrease Flagellin-Induced Interleukin-8 Production in Caco-2 Cells J. Nutr., November 1, 2008; 138(11): 2264 - 2268. [Abstract] [Full Text] [PDF]