Role of Oxidative Stress and Glutathione in Busulfan Toxicity in Cultured Murine Hepatocytes

Unlabelled: This study examines busulfan metabolism. Busulfan given in vivo or in vitro decreased hepatocyte glutathione (GSH) by 60 and 50%, respectively. In vitro, busulfan toxicity was prevented by glutathione S-transferase inhibitors or by antioxidants and led to increased production of oxidized GSH and thiobarbituric acid reactive substances. 'Rescue' from toxicity by GSH precursors was prevented by N,N-bis(2-chloroethyl)-N-nitrosourea (BCNU). Depletion of GSH exacerbated toxicity. In GSH-depleted hepatocytes, busulfan decreased GSH by 95% and BCNU did not prevent rescue by GSH precursors.

Conclusions: (1) In hepatocytes with normal GSH: busulfan toxicity requires GSH conjugation, does not cause profound GSH depletion and is mediated by oxidative stress. We postulate that a GSH conjugate promotes oxidative stress. (2) In GSH-depleted hepatocytes: busulfan profoundly depletes GSH; toxicity is mediated by oxidative stress and is prevented by restoring GSH levels; cell death may be due to unopposed endogenous oxidative stress.