Nrf2-regulated antioxidant response is activated by protein kinase C in postconditioned rat hearts

• Postconditioning activates the Nrf2 signaling pathway in an in vivo protocol.
• PKC activation is required for Nrf2 transcriptional activation under these conditions.
• PKC/Nrf2 signaling activation is essential for postconditioning cardioprotection.

Postconditioning (PostC) activates endogenous protective mechanisms that contend against reperfusion injury. Nevertheless, although PostC efficiency in both experimental studies and clinical trials has been demonstrated, a complete picture of the interacting mechanisms, particularly the relationship between kinase signaling and redox maintenance, is still lacking. To unravel such association, in this work we focus on the participation of protein kinase C (PKC) and the transcription factor nuclear factor E2-related factor 2 (Nrf2) in the cardioprotective response elicited by PostC. PostC was performed in an in vivo rat model by applying three repetitive cycles of ischemia and reperfusion (10 s each), followed by evaluation of heart function and infarct size measurements. PKC activation and Nrf2 phosphorylation were evaluated after 10 min of reperfusion, whereas Nrf2 activity and the content and activities of Nrf2-regulated antioxidant proteins were evaluated after 60 min of reperfusion in PostC hearts. Maintenance of heart function and diminution in infarct size concurred with PKC activation and Nrf2 phosphorylation. PKC inhibition diminished Nrf2 phosphorylation and transcriptional activity in association with diminished levels and activities of Nrf2-regulated antioxidant proteins. In conclusion, this study proposes that the novel pathway PKC/Nrf2 participates in the long-term protective mechanisms induced by PostC application by maintaining the antioxidant defense system.

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