Induction of apoptosis by arachidonic acid in human retinoblastoma Y79 cells: Involvement of oxidative stress

Arachidonic acid administration caused apoptosis in Y79 cells, as shown by typical morphological changes, phosphatidylserine externalization, chromati n condensation, processing and activation of caspase-3 and cleavage of the endogenous caspase substrate poly-(ADP-ribose)-polymerase. Arachidonic acid also caused lamin B cleavage, suggesting caspase-6 activation. Arachidonic acid treatment was accompanied by increased formation of the lipid peroxid ation end products malondialdehyde and 4-hydroxy-2-nonenal, lowering in red uced glutathione content and in mitochondrial membrane potential. Inhibitin g glutathione synthesis sensitized Y79 cells to apoptosis-inducing stimuli, whilst replenishing reduced glutathione attenuated arachidonic acid toxici ty. Similar findings were obtained using hydroperoxyeicosatetranoic acids ( oxygenated metabolites of arachidonic acid which deplete the reduced glutat hione pool) and nordihydroguaretic acid, a general inhibitor of lipooxygena se pathway, which may also trigger rapid depletion of reduced glutathione. Melittin, which is known to activate phospholipase A2, also potently induce d apoptosis. Arachidonic acid toxicity was inversely related to cell densit y. This could depend on an increased production of molecules with antiapopt otic effect: insulin-like growth factors could most likely be one of these molecules. These results propose a role for oxidative stress in the cytotox icity induced by arachidonic acid in Y79 cells and suggest that these cells could be protected from such toxicity as long as sufficient levels of redu ced glutathione and survival factors are present. (C) 2000 Academic Press.