CYTOTOXICITY AND APOPTOSIS PRODUCED BY ARACHIDONIC-ACID IN HEPG2 CELLS OVEREXPRESSING HUMAN CYTOCHROME P-4502E1

The goal of the current study was to evaluate the effects of arachidon ic acid, as a representative polyunsaturated fatty acid, on the viabil ity of a HepG2 cell line, which has been transduced to express human c ytochrome P4502E1 (CYP2E1). Arachidonic acid produced a concentration- and time-dependent toxicity to HepG2-MV2E1-9 cells, which express CYP 2E1, but little or no toxicity was found with control cells. in contra st to arachidonic acid, oleic acid was not toxic to the HepG2-MV2E1-9 cells. The cytotoxicity of arachidonic acid involved a lipid peroxidat ion type of mechanism since toxicity was enhanced after depletion of c ellular glutathione; formation of malondialdehyde and 4-hydroxy-2-none nal was markedly elevated in the cells expressing CYP2E1, and toxicity was prevented by antioxidants and the iron chelator desferrioxamine. The CYP2E1-dependent arachidonic acid toxicity appeared to involve apo ptosis, as demonstrated by terminal deoxynucleotidyltransferase-mediat ed dUTP nick end labeling and DNA laddering experiments. Trolox, which prevented toxicity of arachidonic acid, also prevented the apoptosis. Transfection with a plasmid containing bcl-2 resulted in complete pro tection against the CYP2E1-dependent arachidonic acid toxicity. It is proposed that elevated production of reactive oxygen intermediates by cells expressing CYP2E1 can cause lipid peroxidation, which subsequent ly promotes apoptosis and cell toxicity when the cells are enriched wi th polyunsaturated fatty acids such as arachidonic acid.