Heme oxygenase‐1 related carbon monoxide production and ventricular fibrillation in isolated ischemic/reperfused mouse myocardium

Abstract

Heme oxygenase-1 (HO-1)-dependent carbon monoxide (CO) production related to reperfusioninduced ventricular fibrillation (VF) was studied in HO-1 wild-type (+/+), heterozygous (+/−), and homozygous (−/−) isolated ischemic/reperfused mouse heart. In HO-1 homozygous myocardium, under aerobic conditions, HO-1 enzyme activity, HO-1 mRNA, and protein expression were not detected in comparison with aerobically perfused wild-type and heterozygous myocardium. In wild-type, HO-1 hetero-and homozygous hearts subjected to 20 min ischemia followed by 2 h of reperfusion, the expression of HO-1 mRNA, protein, and HO-1 enzyme activity was detected in various degrees. A reduction in the expression of HO-1 mRNA, protein, and enzyme activity in fibrillated wild-type and heterozygous myocardium was observed. In reperfused/nonfibrillated wild-type and heterozygous hearts, a reduction in HO-1 mRNA, protein expression, and HO-1 enzyme activity was not observed, indicating that changes in HO-1 mRNA, protein, and enzyme activity could be related to the development of VF. These changes were reflected in the HO-1-related endogenous CO production measured by gas chromatography. In HO-1 knockout ischemic/reperfused myocardium, all hearts showed VF, and no detection in HO-1 mRNA, protein, and enzyme activity was observed. Thus, interventions that are able to increase endogenous CO may prevent the development of VF.Key words: heme oxygenase-1 expression • ischemia/reperfusion • HO-1 knockout mouse hearts t has been proposed that most cases of sudden cardiac death may result from ischemia and/or reperfusion-induced ventricular fibrillation (VF; 1-3). Interest in the development and pharmacological control of reperfusion-induced VF has been stimulated by the realization that such arrhythmias may occur under a number of pathological and clinical circumstances, including the spontaneous relief of coronary artery spasm (4). There is considerable controversy over the mechanisms responsible for the induction of these arrhythmias, and a number of I different mechanisms have been suggested (5), but the two major factors proposed and generally accepted to explain reperfusion-induced injury and VF are 1) calcium overload and 2) free radical formation. Examples of oxidative stress-related diseases include reperfusion-induced injury occurring after tissue ischemia or stroke and inflammatory processes, such as arthritis (6). Heme oxygenase (HO) catalyzes the rate-limiting step in the oxidative degradation of heme to biliverdin and carbon monoxide (CO; ref 7). Three isozymes of HO have been identified and cloned; HO-1, an inducible form, HO-2, and HO-3 constitutive forms (8). Studies demonstrate that HO-1 is induced in response to various interventions causing oxidative stress, including ultraviolet irradiation, hypoxia, and ischemia (6,(9)(10)(11)(12).In previous studies, we observed a reduction in HO-1 mRNA expression, its protein, and enzyme activity in ischemic/reperfused fibrillated myocardium but not in nonfibrillated ischemic/reperfused hear...

Carbon Monoxide: Endogenous Production, Physiological Functions, and Pharmacological Applications

“…After exposure to ischemia/reperfusion damage, the isolated hearts from HO-1 homozygous knockout mice developed VF. The same damage to the hearts from wildtype mice leads to significant increase in endogenous CO production and HO-1 up-regulation, which protected the hearts from the reperfusion-induced VF (Bak et al, 2003).…”

Carbon monoxide inhibits inward rectifier potassium channels in cardiomyocytes

“…Myocardial expression of Hmox1 is upregulated in a rat experimental myocardial infarction model 7 . In mice lacking Hmox1 undergoing ischaemic/reperfusion, all the hearts examined exhibited VF 8 . The mechanism of ischaemia/ reperfusion-induced VF involves the downregulation of Hmox1 mRNA and a reduction in Hmox activity 9 , however, the mechanism by which CO may act to prevent this remains unknown.…”

Cardioprotective mechanisms ofPrunus cerasus(sour cherry) seed extract against ischemia-reperfusion-induced damage in isolated rat hearts

“…In the search of the mechanisms of ischemiareperfusion-induced pathways that may be amenable to manipulation, a number of potential candidates have been identified and have been the subject of many investigations. It is highly probable that a number of interaction mechanisms combine to determine the damage caused by ischemia-reperfusion in the myocardium, and a variety of such triggers have been postulated, including ionic disturbances and ion channels (30,69), fatty acid metabolism (35), ␣-and ␤-adrenergic receptors (67), various gene expression (53,60,64), platelet-activating factor (6), endothelin (50), nitric oxide (24), heme oxygenase-1 and carbon monoxide (5,61), and free radicals (15,30). It has been also shown that ischemia and reperfusion of the myocardium result in an activation of various pathways including caspase cascade, and it is hypothesized that a degree of caspase inhibition could be related to the recovery of postischemic cardiac function (4,31,57,62,66).…”