The involvement of autophagic flux in the development and recovery of doxorubicin-induced neurotoxicity

Abstract

Doxorubicin (Dox) is an effective anti-cancer agent, whose clinical use is limited by the cytotoxicity in non-target tissues, especially the heart and brain. The drug-induced neuronal damage is primarily mediated by oxidative stress, in which autophagy plays a central role. Although numerous studies indicate the involvement of autophagy in neurodegenerative diseases and brain injury, the evidence concerning autophagic process in Dox-induced neuronal death is limited. We found that repeated Dox administration induced the protein expression of LC3II and P62 and impaired autophagic flux with enhanced autophagasome accumulation in rat hippocampus, whereas two weeks after the cessation of Dox treatment, the autophagic process was restored, even stimulated, with normalized protein levels of LC3II and P62 and enhanced expression of Becline-1, indicating a compensatory response in the recovery state. Likewise, while repeated Dox exposure inhibited the hippocampal expression of lysosomal-associated membrane protein 2 (LAMP2) and cathepsin D (CTSD), and suppressed CTSD activity, the Dox-induced impaired autophagy-lysosome pathway was also restored in rats following two weeks of recovery. To further verify the role of autophagy, the autophagy inhibitor, 3-methyladenine (3-MA), was administrated daily for the two weeks of recovery period. Our data demonstrated that while the animals in the recovery state showed a significant trend to decreased oxidative damage, normalized antioxidative system and ameliorated endoplasmic reticulum (ER) stress compared with Dox-induced toxic model, 3-MA treatment abrogated the recovering process, resulting in sustained oxidative and ER stress and neuronal apoptosis. Collectively, the present study firstly provided the evidence for the involvement of autophagy in both development and recovery of Dox-induced neurotoxicity, highlighting a novel target for mitigating the chemotherapy-induced neuronal damage.

Keywords: Autophagy; Doxorubicin; Neurotoxicity; Oxidative stress.