Barbara Cserepes

Expression and Protective Role of Heme Oxygenase-1 in Delayed Myocardial Preconditioning

Abstract:  In the study the authors aimed to demonstrate the expression and protective effect of heme oxygenase‐1 (HO‐1) in the delayed preconditioning (PC) on cultured myocardiac cells. Neonatal rat cardiac myocytes were exposed to ischemic (ischemic medium [IM] for 20 min) and pharmacological (adenosine, epinephrine, opioid) PC. Twenty‐four hours later cells were subjected to a simulated ischemia (SI )—culturing for 3 h in IM, followed by 2‐h reperfusion in normal medium‐–and then lactate dehydrogenase (LDH), live/death ratio, and apoptosis were measured. For demonstrating the protective role of HO‐1, its enzymatic activity was competitively inhibited by administration of zinc protoporphyrin IX (ZnPPIX), and HO‐1 synthesis was blocked with HO‐1 siRNA. Cells in control group were cultured under normoxic conditions. In SI group, cells underwent only an SI without PC. HO‐1 expression in all of the groups was demonstrated with immunostaining. Our results showed a significant decrease of LDH release, apoptosis, and cell death in PC groups versus SI group, which has been risen in ZnPPIX‐ and HO‐1 siRNA‐treated groups. HO‐1 immunostaining showed an appreciable HO‐1 expression in PC groups, which was abolished with HO‐1 siRNA administration, but not in ZnPPIX group. The results therefore suggest that HO‐1 expression increases in both ischemic and pharmacological PC, and HO‐1 has cellular protective effect against cell death and apoptosis in ischemia‐reperfusion‐induced oxidative injury.

Effect of acetylsalicylic acid on nuclear factor-kappaB activation and on late preconditioning against infarction in the myocardium.

Nuclear factor-κB (NF-κB) plays an essential role in the intracellular signal transduction of the second window of protection (SWOP). Acetylsalicylic acid (ASA) blocks NF-κB-dependent gene activation in leukocytes and endothelial cells through preventing phosphorylation and subsequent degradation of the inhibitor IκB-α. This study investigated the effect of ASA on the late phase of ischemic preconditioning (PC) against myocardial infarction and on the activation of NF-κB in the preconditioned myocardium. Conscious rabbits were subjected to 4 cycles of 5 minutes of coronary occlusion and 5 minutes of reperfusion together with 3 different doses of ASA (5 mg/kg; 25 mg/kg; 130 mg/kg). After 30 minutes of reperfusion we determined the activation of NF-κB with an electrophoretic mobility shift assay (EMSA). Twenty-four hours later, after 30 minutes of test ischemia, we performed infarct size analysis using triphenyltetrazolium-chloride (TTC) staining. Neither 5 mg/kg (antithrombotic dose) nor 25 mg/kg (analgesic/antipyretic dose) of ASA interfered with the NF-κB activation and the protective effect of late preconditioning against myocardial infarction. In contrast, NF-kB activation and late PC effect were completely abrogated by 130 mg/kg of ASA. Our results suggest that nonselective doses of NSAIDs should be used with caution in patients with atherosclerotic cardiovascular disease because they may deprive the heart of its innate defensive response.

Cardioprotective action of urocortin in early pre- and postconditioning

Abstract:  Pre‐ and postconditioning are powerful endogenous adaptive phenomenon of the organism whereby different stimuli enhance the tolerance against various types of stress. Urocortin (Ucn), member of the corticotropin‐releasing factor (CRF) family has potent effects on the cardiovascular system. The aim of this article was to investigate the action of Ucn on cultured cardiomyocytes in the process of pre‐ and postconditioning. Isolated neonatal rat ventricular myocytes were preconditioned with adenosine, simulated ischemia, and Ucn (10‐min treatment followed by 10‐min reperfusion/recovery). For detecting the effect of alternative types of preconditioning, necrosis enzyme (lactate dehydrogenase [LDH]) release, vital staining (trypan blue), and ratio of apoptosis/necrosis were examined after cardiac cells were exposed to 3‐h sustained ischemia and 2‐h reperfusion. Same parameters were measured in the postconditioned groups (30‐ or 60‐min ischemia followed by postconditioning with 10‐min ischemic stimulus or Ucn and 2‐h reperfusion). Cells exposed to 3‐h ischemia followed by 2‐h reperfusion were shown as control. Our results show that LDH release a number of trypan blue‐stained dead cells and the ratio of apoptotized and necrotized cells was decreased in all preconditioned groups compared with control group. In postconditioned groups LDH content of culture medium, trypan blue‐positive cardiomyocytes, and the rate of apoptotic/necrotic cells was reduced contrasted with non‐postconditioned group. We can conclude that preconditioning with Ucn induced such a powerful cell protective effect as adenosine and ischemia. Furthermore, postconditioning with Ucn after 60‐min ischemia was more cardioprotective than ischemic postconditioning.