Cardioprotection And Mechanisms Of Selectively Stimulating β1-Adrenergic Receptor During Rat Myocardial Ischemia/Reperfusion Injury

Objectives:1. To investigate whether dobutamine, a selective β1-adrenergic receptor agonist, attenuates myocardial ischemia/reperfusion (I/R) injury in rats2. To investigate whether dobutamine could inhibit HMGB1release via β1-adrenergic receptor-mediated HO-1induction during myocardial ischemia and reperfusion (I/R) in rats.3. To investigate whether the regulation of β1-ARs-mediated Nrf-2-HO-1-HMGB1axis exsits in Hypoxia/Reoxygenation (H/R)-induced neonatal rat cardiomyocytes.4. To investigate whether the PI3K/p38MAPK involves the regulation of β1-ARs-mediated Nrf-2-HO-1-HMGB1axis in Hypoxia/Reoxygenation (H/R)-induced neonatal rat cardiomyocytes.Methods:1. Anesthetized male rats were pretreated with dobutamine (5or10μg. Kg-1. min-1, intravenous) before ischemia in the absence and/or presence of LY294002(0.3mg/Kg), a phosphatidylinositol3-kinase (PI3K)<inhibitor; SB203580(1mg/Kg), a p38mitogen-activated-protein kinase (P38mitogen-activated-protein kinase [p38MAPK]) inhibitor, and zinc protoporphyrin IX ([ZnPPIX],10mg/Kg), a HO-1inhibitor, respectively, and then subjected to ischemia for30min followed by reperfusion for4h. The myocardial I/R injury and oxidative stress were assessed. Likewise, the expressions of HO-1protein, nuclear factor kappa B (NF-kB) p65, and HMGB1were measured by Western blot analysis.2. The neonatal cultured cardiomyocytes were concentration-dependently pretreated by dobutamine in the absence and/or presence of LY294002, SB203580, Nrf2siRNA and HO-1siRNA, respectively, and then the neonatal rat cardiomyocytes were induced by Hypoxia/Reoxygenation (H/R). These mechanisms contribute to their actions were further measured by Western blot analysis.Results:1. Dobutamine significantly and dose-dependently attenuated myocardial I/R injury, reduced oxidative stress (all P﹤0.05), and caused the induction of HO-1(P﹤0.05), the reduction of NF-kB activation (P﹤0.05) and HMGB1over expression (all P﹤0.05). However, all the effects caused by dobutamine were significantly reversed by the presence of LY294002, SB203580, and ZnPPIX, respectively (all P﹤0.05).2. Dobutamine concentration-dependently induced HO-1(all P﹤0.05) via Nrf-2translocation (all P﹤0.05) in cardiomyocytes of neonatal rat and concentration-dependently inhibited the release of HMGB1in a concentration-dependent manner in H/R-induced cardiomyocytes (all P﹤0.05). Dobutamine failed to induce HO-1expression when Nrf2expression was suppressed by Nrf2siRNA (P﹤0.05). Meanwhile, Dobutamine failed to inhibit HMGB1release when HO-1expression was suppressed by HO-1siRNA (P﹤0.05). Likewise, LY294002and SB203580significantly inhibited these effects of HO-1induction and anti-HMGB1release by dobutamine (all P﹤0.05). In addition, dobutamine significantly inhibited NF-kB activity in H/R-induced cardiomyocytes (all P﹤0.05).Conclusions:1. Dobutamine, a selective β1-adrenergic receptor agonist significantly attenuates myocardial ischemia/reperfusion (I/R) injury in rats2. Dobutamine could inhibit HMGB1release via β1-adrenergic receptor-mediated HO-1induction during myocardial ischemia and reperfusion (I/R) in rats.3. The regulation of β1-ARs-mediated Nrf-2-HO-1-HMGB1axis exsits in Hypoxia/Reoxygenation (H/R)-induced neonatal rat cardiomyocytes.4. The PI3K/p38MAPK involves the regulation of β1-ARs-mediated Nrf-2-HO-1-HMGB1axis in Hypoxia/Reoxygenation (H/R)-induced neonatal rat cardiomyocytes.