H11 kinase/Hsp22 (H11K) is a small heat shock protein (hsp) which is upregulated in ischemic heart disease, both in animal models and in patients. Cardiac-specific overexpression of H11K in a transgenic (TG) mouse provides protection against ischemic damage that is equivalent to ischemic preconditioning (IPC). Because studies in mice can not always be translated to patients, we examined the role of H11K in mediating cardiomyopathy in a swine model. An adenovirus harboring the H11K sequence, or a LacZ control, was injected in the potential area-at-risk (AAR) perfused by the left circumflex coronary artery (CA) in chronically instrumented swine (n=5/group). Three days after injection, CA occlusion (O) for 60 min, followed by 3 days of reperfusion (R), induced myocardial infarction. Although the AAR was similar between groups, the MI/AAR was reduced significantly (P<0.05) in the H11K-injected group (32±5%) compared to the LacZ group (50±5%). Three days following reperfusion, regional wall thickening in the ischemic region was reduced by 58±2% of baseline in H11K group vs. 82±7% in LacZ (P<0.05). Compared to LacZ, H11K-injected myocardium showed a significant (P<0.05) 4-fold increase in H11K, and a 2- to 4-fold increase in the expression of the inducible form of nitric oxide synthase (NOS), a key mediator of IPC. To substantiate a role of NOS, the effects of CAO/CAR were examined in H11K-injected pigs (n=4) after pretreatment with 35 mg/kg of the NOS inhibitor L-NNA. In these pigs, the cardioprotection of H11K was abolished, i.e., MI/AAR was 67±6% (NS vs. LacZ control). These results were further substantiated in the TG mouse, pretreated or not with L-NNA for 2 days. After 45 min no-flow ischemia followed by 6h reperfusion, the MI/AAR was 5.0±0.4% in non-treated TG and 36±6% in L-NNA-treated TG mice (P<0.01). Therefore, overexpression of H11K in a large mammalian model of ischemic heart disease induces significant cardioprotection. The mechanism involves upregulation of iNOS, since cardioprotection is no longer evident in the presence of NOS inhibition with L-NNA.
Role of Coronary Vasoconstriction in Ischemic Heart Disease and Search for Novel Therapeutic Targets
