Toxicity of glutathione depletion in mesencephalic cultures: a role for arachidonic acid and its lipoxygenase metabolites.

Abstract

The contribution of arachidonic acid (AA) release and metabolism to the toxicity that results from glutathione (GSH) depletion was studied in rat mesencephalic cultures treated with the GSH synthesis inhibitor l-buthionine sulfoximine. Our data show that GSH depletion is accompanied by increased release of AA, which is phosholipase A2 (PLA2) dependent. Exogenous AA is toxic to GSH-depleted cells. This toxicity is prevented by inhibition of lipoxygenase activity, suggesting participation of toxic byproducts of AA metabolism. Hydroxyperoxyeicosatetraenoic acid (HPETE), one of the primary products of AA metabolism by lipoxygenase is also toxic to GSH-depleted cells, whereas hydroeicosatetraenoic acid (HETE) is not. Cell death caused by GSH depletion is prevented by: (i) replenishment of GSH levels with GSH-ethyl ester; (ii) inhibition of PLA2 activity; (iii) inhibition of lipoxygenase activity; and (iv), treatment with ascorbic acid. These data suggest that the following events likely contribute to cell death when GSH levels become depleted. Loss of GSH results in increased release of AA, which is PLA2 dependent. Metabolism of arachidonic acid via the lipoxygenase pathway results in generation of oxygen free radicals possibly produced during conversion of HPETE to HETE, which contribute to cellular damage and death. Our study suggests that limiting AA release and metabolism may provide benefit in conditions with an existing depletion of GSH, such as Parkinson's disease.