Lipopolysaccharide induced apoptosis and necrosis of human umbilical venous endothelial cells in a time-dependent manner. Lipopolysaccharide (1 microgram/ml)-induced apoptosis was maximal after 18 h, whereas necrosis occurred after prolonged incubation for more than 24 h. The increase in apoptosis correlated with a reduction in Bcl-2, a potent cell death inhibitor. Furthermore, lipopolysaccharide treatment upregulated Bax, which heterodimerizes with and thereby inhibits Bcl-2. Both the antioxidant N-acetylcysteine and the combination of vitamin C and E (10 microM) completely inhibited lipopolysaccharide-induced apoptosis, whereas vitamin C or E alone was less effective. The reduction of lipopolysaccharide-induced apoptosis by vitamin C and E was paralleled by an increase in Bcl-2 and a decrease in Bax protein levels. Thus, vitamin C and E seem to interfere with the Bcl-2 family of apoptosis regulators in human umbilical venous endothelial cells.