DJ-1 upregulates anti-oxidant enzymes and attenuates hypoxia/re-oxygenation-induced oxidative stress by activation of the nuclear factor erythroid 2-like 2 signaling pathway

DJ-1 protein, as a multifunctional intracellular protein, has an important role in transcriptional regulation and anti-oxidant stress. A recent study by our group showed that DJ-1 can regulate the expression of certain anti-oxidant enzymes and attenuate hypoxia/re-oxygenation (H/R)-induced oxidative stress in the cardiomyocyte cell line H9c2; however, the detailed molecular mechanisms have remained to be elucidated. Nuclear factor erythroid 2-like 2 (Nrf2) is an essential transcription factor that regulates the expression of several anti-oxidant genes via binding to the anti-oxidant response element (ARE). The present study investigated whether activation of the Nrf2 pathway is responsible for the induction of anti-oxidative enzymes by DJ-1 and contributes to the protective functions of DJ-1 against H/R-induced oxidative stress in H9c2 cells. The results demonstrated that DJ-1-overexpressing H9c2 cells exhibited anti-oxidant enzymes, including manganese superoxide dismutase, catalase and glutathione peroxidase, to a greater extent and were more resistant to H/R-induced oxidative stress compared with native cells, whereas DJ-1 knockdown suppressed the induction of these enzymes and further augmented the oxidative stress injury. Determination of the importance of Nrf2 in DJ-1-mediated anti-oxidant enzymes induction and cytoprotection against oxidative stress induced by H/R showed that overexpression of DJ-1 promoted the dissociation of Nrf2 from its cytoplasmic inhibitor Keap1, resulting in enhanced levels of nuclear translocation, ARE-binding and transcriptional activity of Nrf2. Of note, Nrf2 knockdown abolished the DJ-1-mediated induction of anti-oxidant enzymes and cytoprotection against oxidative stress induced by H/R. In conclusion, these findings indicated that activation of the Nrf2 pathway is a critical mechanism by which DJ-1 upregulates anti-oxidative enzymes and attenuates H/R-induced oxidative stress in H9c2 cells.