Mechanisms of protection against ischemic damage in the heart

Heart disease including ischemic heart disease is the highest contributor to death and morbidity in the western world. The studies presented were conducted to determine possible pathways of protection of the heart against ischemia/reperfusion. We employed adenovirus mediated over-expression of Methionine sulfoxide reductase A (MsrA) in primary neonatal rat cardiac myocytes to determine the effect of this enzyme in protecting against hypoxia/reoxygenation. Cells transfected with MsrA encoding adenovirus and subjected to hypoxia/reoxygenation exhibited a 45% decrease in apoptosis as compared to controls. Likewise total cell death as determined by levels of Lactate Dehydrogenase (LDH) release was dramatically decreased by MsrA overexpression. The initial hypothesis that led to our testing sulindac was based on the fact that the S epimer of sulindac was a substrate for MsrA and that this compound might function as a catalytic anti-oxidant based on a reaction cycle that involved reductio n to sulindac sulfide followed by oxidation back to sulindac. To test this we examined the protective effect of sulindac in hypoxia re-oxygenation in both cardiac myocytes in culture and using a Langendorff model of myocardial ischemia. Using this model of myocardial ischemia we showed that pre-incubation of hearts with sulindac, or the S and R epimers of sulindac resulted in protection against cell death. We present several lines of evidence that the protective effect of sulindac is not dependent on the Msr enzyme system nor does it involve the well established role of sulindac as a Cyclooxygenase (COX) inhibitor. Numerous signaling pathways have been implicated in myocardial protective mechanisms, many of which require fluctuations in ROS levels as initiators or mediators.