Cholesterol induces fetal rat enterocyte death in culture

RESUMO

The effect of cholesterol on fetal rat enterocytes and IEC-6 cells (line originated from normal rat small intestine) was examined. Both cells were cultured in the presence of 20 to 80 æM cholesterol for up to 72 h. Apoptosis was determined by flow cytometric analysis and fluorescence microscopy. The expression of HMG-CoA reductase and peroxisome proliferator-activated receptor gamma (PPARgamma) was measured by RT-PCR. The addition of 20 æM cholesterol reduced enterocyte proliferation as early as 6 h of culture. Reduction of enterocyte proliferation by 28 and 41 percent was observed after 24 h of culture in the presence and absence of 10 percent fetal calf serum, respectively, with the effect lasting up to 72 h. Treatment of IEC-6 cells with cholesterol for 24 h raised the proportion of cells with fragmented DNA by 9.7 percent at 40 æM and by 20.8 percent at 80 æM. When the culture period was extended to 48 h, the effect of cholesterol was still more pronounced, with the percent of cells with fragmented DNA reaching 53.5 percent for 40 æM and 84.3 percent for 80 æM. Chromatin condensation of IEC-6 cells was observed after treatment with cholesterol even at 20 æM. Cholesterol did not affect HMG-CoA reductase expression. A dose-dependent increase in PPARgamma expression in fetal rat enterocytes was observed. The expression of PPAR-gamma was raised by 7- and 40-fold, in the presence and absence of fetal calf serum, respectively, with cholesterol at 80 mM. The apoptotic effect of cholesterol on enterocytes was possibly due to an increase in PPARgamma expression.