Role and regulation of ferritin H in rotenone-mediated mitochondrial oxidative stress.

Tight regulation of intracellular iron levels in response to mitochondrial dysfunction is an important mechanism that prevents oxidative stress, thereby limiting cellular damage. Here, we describe a cytoprotective response involving transcriptional activation of the ferritin H gene in response to the mitochondrial complex I inhibitor and neurotoxic compound rotenone. Rotenone exposure increased ferritin H mRNA and protein synthesis in NIH3T3 fibroblasts and SH-SY5Y neuroblastoma cells. Transient transfection of a ferritin H promoter-luciferase reporter into NIH3T3 cells showed that ferritin H was transcriptionally activated by rotenone through an antioxidant-responsive element (ARE). Chromatin immunoprecipitation assays showed that rotenone treatment enhanced binding of Nrf2 and JunD transcription factors to the ARE. In addition, rotenone induced production of reactive oxygen species (ROS), and pretreatment with N-acetylcysteine abrogated ferritin H mRNA induction by rotenone, suggesting that this response is oxidative stress-mediated. Furthermore, reduced ferritin H expression by siRNA sensitized cells to rotenone-induced apoptosis with increased ROS production and annexin V-positive cells. Taken together, these results suggest that ferritin H transcription is activated by rotenone via an oxidative stress-mediated pathway leading to ARE activation and may be critically important to protect cells from mitochondrial dysfunction and oxidative stress.