Reactive oxygen species (ROS) are critical in tissue responses to ischemia-reperfusion. The enzyme methionine sulfoxide reductase-A (MsrA) is capable of protecting cells against oxidative damage by reversing damage to proteins caused by methionine oxidation or by decreasing ROS through a scavenger mechanism. The current study employed adenovirus mediated over-expression of MsrA in primary neonatal rat cardiac myocytes to determine the effect of this enzyme in protecting against hypoxia/reoxygenation in this tissue. Cells were transduced with MsrA encoding adenovirus and subjected to hypoxia/reoxygenation. Apoptotic cell death was decreased by greater than 45% in cells over-expressing MsrA relative to cells transduced with a control virus. Likewise total cell death as determined by levels of LDH release was dramatically decreased by MsrA over-expression. These observations indicate that MsrA is protective against hypoxia/ reoxygenation stress in cardiac myocytes and point to MsrA as an important therapeutic target for ischemic heart disease. (c) 2007 Elsevier Inc. All rights reserved.