Cardioplegic Solution Provides Myocardial Protection via Activation of NRF2

Abstract

Open heart surgery is often an unavoidable procedure for treatment of cardiovascular disease. Myocardial Ischemia-Reperfusion Injury (MIRI) can occur as a result of cardiopulmonary bypass which is required in open heart surgery. The multifaceted mechanisms of MIRI involve the generation of pro-inflammatory mediators and increase in reactive oxygen species (ROS), resulting in damage to proteins, lipids, and DNA, ultimately impacting postoperative cardiac performance and complications. Nf-E2 related factor-2 (NRF2), a basic leucine zipper transcription factor, is regarded as one of the most important regulators in antioxidant pathways. NRF2 binds to and activates the Antioxidant Response Element (ARE) in the promoters of many antioxidant and detoxification genes. Mechanism of NRF2 activation involves de novo protein translation, or protein stabilization due to dissociation from KEAP1 and other alternative mechanisms. We addressed whether or not cardioplegic solutions induce the activation of NRF2, therefore serving to protect the myocardium from MIRI. We next investigated the specific components of cardioplegic solution playing critical roles in NRF2 activation and the precise underlying mechanism. We used adult cardiomyocytes in culture to test whether or not five different types of cardioplegic solutions and their key ingredients induce NRF2. We tested routine laboratory cell culture at 37C. Our data showed that Del Nido and High K cardioplegic solution caused increases in NRF2 protein levels under cell culture. We found that the combination of K+ and Ca2+ included in those cardioplegic solutions play an essential role in induction of NRF2. ARE luciferase reporter assay confirmed NRF2 activation as a transcription factor by the cardioplegic solutions and K+ in the presence of Ca2+. Our data supports that cardioplegic solutions can be cardiac protective via the activation of NRF2 and the results also indicate among cardioplegic solution compositions, K+ and Ca2+ play an essential role in activation of NRF2.