Cytotoxicity and cytoprotective effects of citrus flavonoids on insulin-secreting cells BRIN-BD11: beneficial synergic effects.

Flavonoids, in general, have potent antioxidant activity and they can be used in treating chronic diseases involving oxidative stress, such as diabetes mellitus. The purpose of this study was to evaluate the cytotoxicity and cytoprotective effects of citrus flavonoids on the functionality of BRIN-BD11 cells. The assessment of cytotoxic and cytoprotective flavonoid tested was performed using the MTT reduction assay. The flavonoids did not show cytotoxic effects in any of the tested concentrations (5-20 µM) and also negative insulinotropic effects were not observed. To cytoprotective assay, the IC50 of H2O2 in treatment of 2 h (acute oxidative stress) was measured (350 µM). Moreover, under acute oxidative stress, the isolated flavonoids (10 µM) had no cytoprotective effects. Besides an antioxidant role of the flavonoids was only observed when using in association. Thus future experiments are needed, varying the experimental condition, to better evaluate the possible mechanisms of action of these flavonoids.

Cholesterol induces fetal rat enterocyte death in culture.

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 microM 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 microM cholesterol reduced enterocyte proliferation as early as 6 h of culture. Reduction of enterocyte proliferation by 28 and 41% was observed after 24 h of culture in the presence and absence of 10% 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% at 40 microM and by 20.8% at 80 microM. 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% for 40 microM and 84.3% for 80 microM. Chromatin condensation of IEC-6 cells was observed after treatment with cholesterol even at 20 microM. 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.

Cholesterol induces fetal rat enterocyte death in culture

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.

Ranking the toxicity of fatty acids on Jurkat and Raji cells by flow cytometric analysis.

The fatty acids have an important role in the control of leukocyte metabolism and function. Higher concentrations of certain fatty acids, particularly polyunsaturated fatty acids (PUFAs) and volatile fatty acids, can cause cell death via apoptosis or, when concentrations are greater, necrosis. In this study, we determined the highest concentrations of various fatty acids that are non-toxic to two human leukemic cell lines, Jurkat (T-lymphocyte) and Raji (B-lymphocyte). Toxicity was evaluated by either loss of membrane integrity and/or DNA fragmentation using flow cytometric analysis. There were no remarkable differences for the toxicity of the fatty acids between B and T cell lines. The cytotoxicity of the fatty acids was related to the carbon chain length and number of double bonds: docosahexaenoic acid=eicosapentaenoic acid=arachidonic acid=gamma-linolenic acid=stearic acid=palmitic acid > linoleic acid=palmitoleic acid > vacenic acid=lauric acid > oleic acid > elaidic acid > capric acid > butyric acid > caprylic acid=caproic acid=propionic acid. The proportion of cells undergoing apoptosis or necrosis, induced by the fatty acids tested, remains to be investigated.