Luminal bacterial flora determines physiological expression of intestinal epithelial cytoprotective heat shock proteins 25 and 72

Abstract

and 72 are expressed normally by surface colonocytes but not by small intestinal enterocytes. We hypothesized that luminal commensal microflora maintain the observed colonocyte HSP expression. The ability of the small intestine to respond to bacteria and their products and modulate HSPs has not been determined. The effects of luminal bacterial flora in surgically created midjejunal self-filling (SFL) vs. self-emptying (SEL) small-bowel blind loops on epithelial HSP expression were studied. HSP25 and HSP72 expression were assessed by immunoblot and immunohistochemistry. SFL were chronically colonized, whereas SEL contained levels of bacteria normal for the proximal small intestine. SFL creation significantly increased HSP25 and HSP72 expression relative to corresponding sections from SEL. Metronidazole treatment, which primarily affects anaerobic bacteria as well as a diet lacking fermentable fiber, significantly decreased SFL HSP expression. Small bowel incubation with butyrate ex vivo induced a sustained and significant upregulation of HSP25 and altered HSP72 expression, confirming the role of short-chain fatty acids. To determine whether HSPs induction altered responses to an injury, effects of the oxidant, monochloramine, on epithelial resistance and short-circuit current (I sc) responses to carbachol and glucose were compared. Increased SFL HSP expression was associated with protection against oxidant-induced decreases in transmural resistance and I sc responses to glucose, but not secretory responses to carbachol. In conclusion, luminal microflora and their metabolic byproducts direct expression of HSPs in gut epithelial cells, an effect that contributes to preservation of epithelial cell viability under conditions of stress.

From the gut to the peripheral tissues: the multiple effects of butyrate

“…Thus, cell protection is possibly enhanced because of chaperone activity, mostly ascribed to HSP70 family members (193) . It was shown that HSP25/27 need SCFA for basal expression in epithelial cells of the colon and in the distal small intestine in vivo in the rat (194,195) , which is in agreement with the results obtained in the calf (8) . In vitro, SCFA enhance the expression of HSP25/27 in a dose-and time-dependent manner, an effect that is transcriptionally regulated (196) , and protect rat intestinal epithelial cells from injury (194) .…”

Heat shock protein 70 is upregulated in the intestine of intrauterine growth retardation piglets

“…The distribution of Hsp70 may be related to the protection function of molecular chaperones (Arvans et al 2005;Yu et al 2008). Immunolabeling showed that the Hsp70 protein was predominantly localized in the cytoplasm of epithelial cell.…”

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

“…In small intestine, there is normally very low basal expression of inducible heat shock protein, and blind-loop studies have shown that heat shock protein expression increases in the presence of bacteria (1). When blind loops crafted from small intestine are surgically attached to the colon so that they self-empty with peristalsis into the colon, they do not become colonized with bacteria and heat shock protein expression remains low.…”

“…Presence of bacteria appears to upregulate expression of inducible heat shock proteins (1), and both TLR signaling and the induction of heat shock proteins by luminal bacteria are thought to play important roles in intestinal homeostasis (19). There are vast numbers of flagellated bacteria in the normal enteric flora of the intestine, and hence there are large quantities of flagellin circulating in the gut luminal contents, and yet the relative contribution and role of flagellin in intestinal homeostasis remains largely unknown.…”