HO-1 Activation Can Attenuate Cardiomyocytic Apoptosis via Inhibition of NF-κB and AP-1 Translocation Following Cardiac Global Ischemia and Reperfusion

Background: NF-κB and AP-1 play important roles in regulation of inflammatory responses that lead to cardiomyocytic injury following cardiopulmonary bypass (CPB) and cardiac global ischemia and reperfusion. It has been reported that heme oxygenase-1 (HO-1) can block those responses. Our aim was to determine whether HO-1 activation could decrease myocardial ischemia-reperfusion injury with cardioplegia during CPB and attenuate apoptosis of cardiomyocytes. Materials and Methods: Rabbits (10 in each group) were randomized to receive either bypass only (Group 1), CPB plus intravenous normal saline (Group 2), hemin (HO-1 inducer; Group 3), SnPP (HO-1 inhibitor; Group 4), or hemin + SnPP (Group 5) 2 d before CPB. In all groups except Group 1, cold (4°C) antegrade intermittent crystalloid cardioplegia was delivered every 20 min for a total of 60 min of cardiac arrest, after CPB was established. Rabbits were weaned from CPB and reperfused for 4 h. Blood was sampled at various time points. The reperfused hearts were harvested for Western blotting and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) experiments. Results: The postoperative elevation of serum levels of IL-10, IL-6, and TNF-α were significantly decreased in Group 3, but HO-1 inhibitor abolished this effect (Group 4). Moreover in Group 3, the number of apoptotic cardiomyocytes, level of apoptosis-related activated fragments of caspase-3 and Akt, and level of nuclear NF-κB and AP-1 translocation were significantly decreased. Conclusions: HO-1 activation can dampen the surge of inflammation-related cytokines during CPB and decrease the occurrence of cardiomyocytic apoptosis via inhibition of NF-κB and AP-1 translocation.