Sirtuin 1 ( SIRT 1 ) Activation Mediates Sildenafil Induced Delayed Cardioprotection against Ischemia-Reperfusion Injury in Mice

Background: It has been well documented that phosphodiesterase-5 inhibitor, sildenafil (SIL) protects against myocardial ischemia/reperfusion (I-R) injury. SIRT1 is part of the class III Sirtuin family of histone deacetylases that deacetylates proteins involved in cellular stress response including those related to I-R injury. Objective/Hypothesis: We tested the hypothesis that SIL-induced cardioprotection may be mediated through activation of SIRT1. Methods: Adult male ICR mice were treated with SIL (0.7 mg/kg, i.p.), Resveratrol (RSV, 5 mg/kg, a putative activator of SIRT1 used as the positive control), or saline (0.2 mL). The hearts were harvested 24 hours later and homogenized for SIRT1 activity analysis. Results: Both SILand RSV-treated mice had increased cardiac SIRT1 activity (P,0.001) as compared to the saline-treated controls 24 hours after drug treatment. In isolated ventricular cardiomyocytes, pretreatment with SIL (1 mM) or RSV (1 mM) for one hour in vitro also upregulated SIRT1 activity (P,0.05). We further examined the causative relationship between SIRT1 activation and SIL-induced late cardioprotection. Pretreatment with SIL (or RSV) 24 hours prior to 30 min ischemia and 24 hours of reperfusion significantly reduced infarct size, which was associated with a significant increase in SIRT1 activity (P,0.05). Moreover, sirtinol (a SIRT1 inhibitor, 5 mg/kg, i.p.) given 30 min before I-R blunted the infarct-limiting effect of SIL and RSV (P,0.001). Conclusion: Our study shows that activation of SIRT1 following SIL treatment plays an essential role in mediating the SILinduced cardioprotection against I-R injury. This newly identified SIRT1-activating property of SIL may have enormous therapeutic implications. Citation: Shalwala M, Zhu S-G, Das A, Salloum FN, Xi L, et al. (2014) Sirtuin 1 (SIRT1) Activation Mediates Sildenafil Induced Delayed Cardioprotection against Ischemia-Reperfusion Injury in Mice. PLoS ONE 9(1): e86977. doi:10.1371/journal.pone. 0086977 Editor: Dinender K. Singla, University of Central Florida, United States of America Received August 28, 2013; Accepted December 18, 2013; Published January 22, 2014 Copyright: 2014 Shalwala et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: [This study was supported in part by research grants from the National Institutes of Health (HL51045, HL79424, HL118808 to Dr. R.C. Kukreja) and from the American Heart Association (National Scientist Development Grants 10SDG3770011 to Dr. F.N. Salloum and 0530157N to Dr. L. Xi; Mid-Atlantic Beginning Grant-in-Aid 0765273U to Dr. A. Das) and from the Health Ministry of Guangdong Province, China (Medical Research Grant A2013320 to Dr. S.G. Zhu). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors declare that all of the co-authors including Rakesh Kukreja, Anindita Das and Fadi Salloum are PLOS ONE Editorial Board members. Also, the authors confirm that this does not alter their adherence to all the PLOS ONE policies on sharing data and materials. * E-mail: rakesh@vcu.edu