Attenuation of Na/K-ATPase/Src/ROS amplification signal pathway with pNaktide ameliorates myocardial ischemia-reperfusion injury

Oxidative stress plays an important role in myocardial ischemia-reperfusion (I/R) injury. And pNaKtide is known to inhibit Na/K-ATPase/Src/reactive oxygen species (ROS) amplification signaling. Accordingly, we aimed to investigate the effect of pNaKtide on myocardial I/R injury. We first determine the effect of pNaKtide on hypoxia- or cobalt chloride-induced injury in embryonic heart-derived H9c2 cells via measuring lactate dehydrogenase (LDH) level and trypan blue stain assay. In addition, TUNEL stain assay and western blot analysis of cleaved-PARP and cleaved-caspase3 were performed to detect apoptosis level. Meanwhile, ROS accumulation was assessed by dichlorofluorescin diacetate (DCFH-DA) assay. Then we conducted cell counting kit-8 (CCK-8) and flow cytometry to examine cell proliferation and cell cycle respectively. We next generated rat I/R model and determined the effect of pNaKtide by measuring serum LDH and evaluating heart pathology. At last, the activities of Src and ERK1/2 were examined via western blot to clarify molecular mechanism. In vitro, pNaKtide exposure significantly attenuated the H9c2 cells death and ROS accumulation induced by hypoxia or cobalt chloride. And no significant effect was detected on cell cycle and proliferation upon pNaKtide administration. In vivo, pNaKtide distinctly decreased serum LDH level and ameliorated I/R induced myocardial injury in the rats. Western blot analysis revealed pNaKtide decreased Src and ERK1/2 activities robustly. The results provided evidence that pNaKtide exhibited cardioprotective effect against hypoxia-induced injury in vitro and in vivo. And pNaKtide might be a potential molecular for therapy of I/R related heart disease.