N-butyrate increases heat shock protein 70 through heat shock factor 1 and AMP-activated protein kinase pathways in human intestinal Caco-2 cells.

Impaired integrity of the intestinal epithelium is a cause of intestinal and extraintestinal diseases. Heat shock protein 70 (HSP70), a cytoprotective protein, plays an important role in maintaining intestinal homeostasis. The intestinal expression of HSP70 is linked with the local microbiota. The present study investigated the molecular mechanisms underlying the upregulation of HSP70 by n-butyrate, a major metabolite of the intestinal microbiota in human intestinal Caco-2 cells. Treatment of Caco-2 cells with n-butyrate upregulated HSP70 protein and mRNA levels in a dose-dependent manner. Using luciferase reporter assay, it was found that n-butyrate enhanced the transcriptional activity of HSP70. These effects were sensitive to the inhibition of heat shock factor 1 (HSF1), a transcription factor, and AMP-activated protein kinase (AMPK). N-butyrate increased the phosphorylation (activity) of HSF1 and AMPK. Taken together, this study shows that n-butyrate is partly involved in the microbiota-dependent intestinal expression of HSP70, and the effect is exerted through the HSF1 and AMPK pathways.

Fermentable fibers upregulate suppressor of cytokine signaling1 in the colon of mice and intestinal Caco-2 cells through butyrate production.

Short chain fatty acids (SCFAs), the microbial metabolites of fermentable dietary fibers exert multiple beneficial effects on mammals including humans. We examined the effects of fermentable dietary fibers on suppressor of cytokine signaling 1 (SOCS1), a negative regulator of inflammatory signaling, on the intestinal epithelial cells of the mouse colon and human intestinal Caco-2 cells, specifically focusing on the role of SCFAs. Feeding fermentable fibers, guar gum (GG) and partially hydrolyzed GG (PHGG) increased SOCS1 expression in the colon and the cecal pool of some SCFAs including acetate, propionate, and butyrate. The antibiotic administration abolished the GG-mediated SOCS1 expression in the colon. In Caco-2 cells, butyrate, but not other SCFAs, increased SOCS1 expression. Taken together, fermentable fibers such as GG and PHGG upregulate the colonic SOCS1 expression, possibly through the increased production of butyrate in mice and can be a potential tool in the fight against inflammatory diseases. Abbreviations: GG: Guar gum; GPR: G protein-coupled receptor; IL: Interleukin; JAK: Janus kinase; NF- κB: Nuclear factor-kappa B; PHGG: Partially hydrolyzed guar gum; SCFA: Short chain fatty acid; SOCS: Suppressor of cytokine signaling; STAT: Signal transducer and activator of transcription; TLR: Toll-like receptor.

Propionate and Dietary Fermentable Fibers Upregulate Intestinal Heat Shock protein70 in Intestinal Caco-2 Cells and Mouse Colon.

Short-chain fatty acids (SCFAs), including propionate, are major metabolites of intestinal microorganisms and play an essential role in regulating intestinal epithelial integrity. Heat shock proteins (HSPs) promote cellular homeostasis under physiological and stressed conditions. This study aimed to investigate the regulation of intestinal HSP70 by propionate in human intestinal Caco-2 cells and the colon of fermentable dietary fiber (DF)-fed mice and germ-free mice. The results showed that propionate increased Hspa1a (HSP70 mRNA) level in Caco-2 cells, upregulated HSP70 protein, and phosphorylation of heat shock factor 1; however, the latter two were reduced by mitogen-activated protein kinases and the mechanistic target of rapamycin inhibitors. Feeding fermentable DFs, such as guar gum (GG) and partially hydrolyzed GG, increased both cecal SCFAs and colonic HSP70 expression, both of which were reduced in germ-free mice than in specific-pathogen-free mice. Collectively, the propionate-induced HSP70 expression was shown to be possibly involved in intestinal homeostasis.