Apoptotic process in the monkey small intestinal epithelium: 2. Possible role of oxidative stress

Recent findings suggest that intracellular oxidants are involved in the ind uction of apoptosis and this type of cell death can be inhibited by various antioxidants. In our accompanying paper, we have shown apoptosis in the vi llus tip cells of the monkey small intestinal epithelium. The aim of the pr esent study was to evaluate the possible relationship between oxidative str ess, antioxidant levels and the apoptotic process in the monkey small intes tinal epithelium. Monkey small intestinal epithelial cells were isolated in to different fractions consisting of villus, middle and crypt cells. Mitoch ondrial function was assessed by the reduction of the tetrazolium dye, 3-(4 ,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), with and wi thout succinate. The extent of lipid peroxidation was assessed by measuring the formation of conjugated diene, depletion of polyunsaturated fatty acid s and a-tocopherol. Level of antioxidant enzymes like, superoxide dismutase (SOD), catalase, glutathione S-transferase (GST), glutathione peroxidase ( GPx) and glutathione reductase were also quantitated in various cell fracti ons. MTT reduction was significantly decreased in villus cells as compared to the cells from other fractions and this was evident even in presence of the respiratory substrate, succinate. Increased formation of conjugated die ne and depletion of polyunsaturated fatty acids were seen in villus and cry pt cells as compared to middle fraction cells. The a-tocopherol level was d ecreased in both villus and crypt cells as compared to cells from middle re gion. Significant decrease of SOD activity was seen in the villus tip cells and a slight decrease was seen in the crypt fractions. Glutathione depende nt enzymes like GST, GPx and GSH reductase showed higher activity in the vi llus fractions. A similar observation was also seen in the catalase activit y. This study has shown that although oxidative stress is seen in both vill us and crypt cells, decreased mitochondrial function was seen in villus tip cells which may be responsible for apoptotic process in the intestinal epi thelium. (C) 1998 Elsevier Science Inc.