Protection of the myocardium against ischemia/reperfusion injury by punicalagin through an SIRT1-NRF-2-HO-1-dependent mechanism

Punicalagin has been found to exert cardiac protective effects against myocardial ischemia/reperfusion (MI/R) injury, although the detailed mechanisms remain largely unknown. This experiment was performed to explore the potential involvement of silent information regulator 1 (SIRT1)-NFE2-related factor 2 (NRF-2)-heme oxygenase-1 (HO-1) pathway in the cardiac protective actions of punicalagin. Sprague-Dawley (SD) rats were subjected to MI/R operation with or without punicalagin treatment (40 mg kg(-1)d(-1)). We showed that punicalagin-treated group exhibited enhanced cardiac function, reduced myocardial infarction and decreased cleaved caspase-3 level. Furthermore, myocardial oxidative/nitrosative stress was ameliorated by punicalagin as evidenced by suppressed superoxide generation, gp91(phox) and iNOS expressions, NO metabolites as well as myocardial nitrotyrosine level. Additionally, punicalagin decreased myocardial IL-6, TNF-alpha and the levels of ICAM-1, VCAM-1 and IKK-beta expressions as well as I kappa B-alpha phosphorylation and NF-kappa B nuclear translocation. However, these effects were abolished by EX527 (5 mg kg(-1)d(-1), a selective SIRT1 inhibitor). We further found that punicalagin dose-dependently enhanced SIRT1 nuclear distribution and NRF-2-HO-1 signaling. While EX527 treatment not only reduced SIRT1 activity, but also reversed the activation of NRF-2-HO-1 pathway. Collectively, these results revealed that punicalagin reduced cardiac oxidative/nitrosative stress and inflammatory response induced by MI/R operation through SIRT1-mediated activation of NRF-2-HO-1 signaling.