Doxorubicin induces ceramide and diacylglycerol accumulation in rat hepatocytes through independent routes

Doxorubicin (DOX) is a potent anticancer drug, whose clinical use is limited due to its toxicity. This toxicity has been associated with free radicals generated during the drug metabolism. We previously found that DOX increased the intracellular diacylglycerol (DAG) levels at 1 h in isolated rat hepatocytes, probably by mobilizing choline-enriched phospholipids. In this work, we studied the effects of DOX on oxidative stress markers, and the possible contribution of ceramide metabolism to DAG accumulation. Other possible routes of DAG production, such as impairment of triacylglycerol (TAG) synthesis, and their connection with oxidative stress were also investigated. Time-course experiments revealed that DOX decreased intracellular GSH at 2 h, but did not affect cell viability, ATP or malondialdehyde (MDA) levels at any time. DOX did not modify the intracellular levels of [3H]-ceramide during the first 90 min of exposure, but increased it significantly at 2 h. [3H]-Sphingomyelin remained unchanged during the whole period. These results indicate that ceramide metabolism is not involved in the early DAG response to DOX. The drug markedly increased the incorporation of [3H]-oleate into intracellular DAG from 60 min. In contrast, DOX reduced the incorporation of [3H]-oleate into intracellular phospholipids and TAG. DOX inhibited TAG synthesis at the DAG acyltransferase step. These results suggest that DOX increases the intracellular levels of the lipid messengers, ceramide and DAG, by independent mechanisms. Activation of the de novo synthesis of ceramide is probably involved in the sphingolipid accumulation, while inhibition of TAG synthesis contributes to DAG accumulation, this response being independent of oxidative damage.