PRIOR INDUCTION OF HEAT SHOCK PROTEINS BY A NITRIC OXIDE DONOR ATTENUATES CARDIAC ISCHEMIA/REPERFUSION INJURY IN THE RAT1

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Abstract
Recent studies have demonstrated that nitric oxide (NO) releasers considerably increase heat shock proteins (HSPs) in the in vitro cell system, providing resistance to oxidant damage. This study was designed to examine the cellular responses of HSPs induced by prior administration of an NO releaser, FK409 (FK), in an in vivo transplantation model. Lewis rats received either saline or FK solution intravenously administered at different time points before graft harvesting (10 μmol/kg) or for 15 min during reperfusion (0.66 μmol/kg/min). Tissue specimens were taken to determine HSP70 and heme oxygenase-1/HSP32 (HO-1) expression, and glutathione content. After 24-hr preservation with University of Wisconsin solution, heterotopic cardiac transplantations were performed, and graft survival was determined at 14 days. Tissue samples for end labeling of nuclear DNA fragments (TdT-mediated d-uridine triphosphate biotin nick end labeling; TUNEL) and propidium iodide staining were taken 15 min after reperfusion. The gene and protein expression of HSP70 after FK administration peaked at 12 min and 60–90 min, whereas those of HO-1 peaked at 6 min and 90 min, respectively. Then, representative cardiac grafts taken 60 min after FK treatment were examined for further assay. Localization of induced HSP70 and HO-1 molecules were observed in the myocardium and vascular endothelium, respectively. Prior treatment of FK was effective in preventing the reduction of tissue glutathione contents compared with control (P <0.05). Fewer TUNEL and propidium iodide-positive cells were also observed in the FK group (P <0.0005, vs. control). The graft survival rate was higher in the FK group (9/10 vs. 1/10 of control;P <0.001), whereas the groups either harvested 10 min after FK pretreatment or continuously infused for 15 min during reperfusion were inferior, similar to that of control. Prior induction of HSP70 and HO-1 with a relatively low dose of FK administration attenuates ischemia and reperfusion injury, which was due to antioxidant and antiapoptotic activities augmented by such stress proteins. Thus, NO releasers as a pharmacological maneuver may provide an innovative approach for the prevention of ischemia and reperfusion injury.