Original article Overexpression of glutaredoxin-2 reduces myocardial cell death by preventing both apoptosis and necrosis Norbert Nagy a,b , Gautam Malik b , Arpad Tosaki b , Ye-Shih Ho c , Nilanjana Maulik a , Dipak K. Das a, ⁎ ,1 a Cardiovascular Research Center, University of Connecticut, School of Medicine, Farmington, CT 06030-1110, USA b Department of Pharmacology, Faculty of Pharmacy, Health Science Center, University of Debrecen, Debrecen, Hungary c Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, USA Received 26 July 2007; received in revised form 21 August 2007; accepted 23 August 2007 Available online 14 September 2007 Abstract Mitochondrial glutaredoxin-2 (Glrx2) has been recognized as an important redox regulator in mammalian organs including heart. To date no investigations have addressed the potential role of Glrx2 in cardiac disorders. The present study examined if myocardial overexpression of Glrx2 in the heart could rescue the cardiac cells from apoptosis and necrosis induced by ischemia and reperfusion. The human Glrx2 transgene was created by placing a full-length cDNA fragment encoding human mitochondrial Glrx2 downstream to the 5′ flanking sequence and promoter of the mouse α-myosin heavy chain gene. The isolated hearts from Glrx2 transgenic mice and non-transgenic (wild type) littermates [on c57BL/ 6×C3H hybrid background] were subjected to 30 min of global ischemia followed by 2 h of reperfusion via working mode. The hearts from Glrx2 transgenic mice displayed significantly improved contractile performance and reduced myocardial infarct size and cardiomyocyte apoptosis. There was a reduction in cytochrome c release and activation of caspase 3 and caspase 9. Glrx2 overexpression also reduced the ischemia/reperfusion- mediated loss of mitochondrial cardiolipin, decreased the activities of reactive oxygen species (ROS) and preserved GSH/GSSG ratio. Glrx2 mediated survival signal appeared to be stemmed from PI-3-kinase-Akt survival signaling pathway and involved the activation of redox sensitive transcription factor NFκB and antiapoptotic protein Bcl-2. The results indicated a crucial role of mitochondrial Glrx2 in cardioprotection. © 2007 Elsevier Inc. All rights reserved. Keywords: Heart; Glutaredoxin-2; Redox signaling; Reactive oxygen species; Transgenic mice 1. Introduction A growing body of evidence supports a crucial role of mito- chondria in cell signaling and regulation of survival and death of heart cells. For example, protooncogene product Bcl-2 located in mitochondria functions as a suppressor of apoptosis while the proapoptotic protein Bax readily translocated into the mitochon- drial membrane after a death signal [1,2]. Bcl-2 prevents the release of many apoptogenic proteins from mitochondria to the cytosol thereby inhibiting apoptosis [3]. In heart cells, the ratio of Bcl-2 and Bax predicts whether these cells would survive or destined to die. When Bcl-2/Bax ratio is reduced, such as during ischemia/reperfusion, cytochrome c is released in the cytosol, which triggers the formation of apoptosome complex leading to the activation of caspases, the end effectors of apoptosis [4]. Ischemia/reperfusion changes the intracellular environment of the hearts into the oxidizing condition due to the reduction of intracellular antioxidant reserve and excessive production of the reactive oxygen species (ROS) [5]. Mitochondria are the major intracellular source of ROS, which are produced by complex I and complex III during mitochondrial respiration [6]. Redox environment of the mitochondria is controlled by a variety of redox regulating systems that include Mn-superoxide dismutase (MnSOD), glutathione peroxidase (Gpx), thioredoxin (Trx)-2, thioredoxin reductase-2, glutaredoxin (Grx)-2 and peroxiredoxin III. Among these proteins, thioredoxin-2 and glutaredoxin-2 are responsible for the maintenance of reduced intracellular redox Available online at www.sciencedirect.com Journal of Molecular and Cellular Cardiology 44 (2008) 252 – 260 www.elsevier.com/locate/yjmcc ⁎ Corresponding author. Fax: +1 860 679 4606. E-mail address: DDAS@NEURON.UCHC.EDU (D.K. Das). 1 Current address: Department of Pharmacology, Faculty of Pharmacy, Health Science Center, University of Debrecen, Debrecen, Hungary. 0022-2828/$ - see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.yjmcc.2007.08.021 RETRACTED