Background: Beside their role as the main energy source in the colonic mucosa, short chain fatty acids were found to act as potent antiproliferative and differentiation agents in various cancer cell lines. It has recently been shown that butyrate also induces TGF-beta 1 mRNA in human keratinocytes, suggesting that TGF-beta 1 may play a role in butyrate induced cell differentiation.
Aim of the study: The objective of our study was to investigate the possible role of exogenous and endogenous TGF-beta on butyrate induced differentiation of intestinal epithelium.
Methods: Studies were performed in Caco-2 cells, a cell line resembling functionally normal enterocytes. Cells, cultured in standard medium were studied over a 15-day period. Sodium butyrate (5 mM), TGF-beta 1 (2 ng/ml) or butyrate (5 mM) + anti-human TGF-beta 1 antibody (30 micrograms/ml) were added to the medium. At day 4, 8, 11 and 15 total protein content, alkaline phosphatase activity, lactate dehydrogenase activity and transepithelial resistance were measured.
Results: Under culture conditions both, butyrate and TGF-beta 1 inhibited growth accompanied by an induction of cell differentiation approved by increased alkaline phosphatase activity and transepithelial resistance. The differentiating effect of butyrate was accompanied by an increased endogenous TGF-beta 1, but not TGF-beta 2 expression in Caco-2 cells. Co-incubation of butyrate with anti-human TGF-beta 1 antibody suppressed at least in part the differentiating effects of butyrate.
Conclusions: Our results directly implicate that the TGF-beta isoform TGF-beta 1 is necessary for butyrate-induced Caco-2 cell differentiation, but other molecular mechanisms may also play a role in the differentiation of this cell line.