Submitted on October 24, 2006
Accepted on January 30, 2007
REDOX REGULATION OF ISCHEMIC PRECONDITIONING IS MEDIATED BY THE DIFFERENTIAL ACTIVATION OF CAVEOLINS AND THEIR ASSOCIATION WITH eNOS AND GLUT-4
Srikanth Koneru1, SureshVarma Penumathsa1, Mahesh Thirunavukkarasu1, Samson Mathews Samuel1, Lijun Zhan1, Zhihua Han2, Gautam Maulik3, Dipak K. Das4, and Nilanjana Maulik5*
1 Surgery, University of Connecticut Medical center, Farmington, Connecticut, United States
2 College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States
3 Thoracic Surgery, Harvard Medical School, Boston, Massachusetts, United States
4 Department of Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, United States
5 Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, United States
* To whom correspondence should be addressed. E-mail: nmaulik{at}neuron.uchc.edu.
Reactive oxygen species (ROS) generated during ischemia (I)/reperfusion (R) enhance myocardial injury, but brief periods of myocardial ischemia followed by reperfusion (ischemic preconditioning, IP) induce cardioprotection. Ischemia is reported to stimulate glucose uptake through the translocation of Glut-4 from the intracellular vesicles to sarcolemma. In the present study we demonstrated involvement of ROS in IP mediated Glut-4 translocation along with increased expression of caveolin-3, p-eNOS, p-Akt and decreased expression of caveolin-1. The rats were divided into: Control Sham, NAC Sham (NS) [N=n-acetyl cysteine (NAC), free radical scavenger], IR, IP + I/R (IP), IPN. IP was performed by 4 cycles of 4 min I and 4 min R followed by 30 min of ischemia and 3, 24, 48 hrs of R depending on protocol. Increased mRNA expression of Glut-4 and caveolin-3 was observed after 3h of R in IP compared to other groups. IP increased expression of Glut-4, caveolin-3, p-eNOS, p-AKT and decreased expression of caveolin-1 in the isolated membrane fractions as compared to IR. Co-immunoprecipitation demonstrated decreased association of cav-1 / eNOS in IP group as compared to IR. Significant Glut-4 & caveolin-3 association was also observed in IP group. This association was disrupted when NAC was used in conjunction with IP. It clearly documents significant role of ROS signaling in Akt/eNOS/caveolin-3 mediated Glut-4 translocation and association in IP myocardium. In conclusion, we demonstrated a novel redox mechanism in IP induced eNOS and Glut-4 translocation and the role of caveolar paradox in making the heart euglycemic during the process of ischemia leading to myocardial protection in a clinically relevant rat ischemic model.
