The mitochondrial permeability transition pore (mPTP) opening has been proposed to play an important role in myocardial ischemia/reperfusion injury (Suleiman et al., 2001;Weiss et al., 2003). (cGMP)/protein kinase G (PKG) pathway. Resveratrol translocated GSK-3 from cytosol to mitochondria via the cGMP/PKG pathway. Further studies showed that mitochondrial GSK-3 was co-immunoprecipitated with cyclophilin D but not with VDAC (voltage dependent anion channel) or ANT (adenine nucleotide translocator). These data suggest that resveratrol prevents myocardial reperfusion injury presumably by targeting the mPTP through translocation of GSK-3 from cytosol to mitochondria. Translocated GSK-3 may ultimately interact with cyclophilin D to modulate the mPTP opening. Keywords:Resveratrol, Reperfusion injury, Glycogen synthase kinase 3, Mitochondrial permeability transition pore == 1. Introduction == First isolated from the roots of white hellebore in 1940, resveratrol (3,5,4-trihydroxystilbene) is a polyphenolic product found abundantly in grapes and red Emodin-8-glucoside wines. Studies have shown that resveratrol exerts numerous biological effects including antioxidant (Frankel et al., 1993), anti-cancer (Jang et al., 1997), anti-ageing (Wood et al., 2004), and anti-inflammation (Birrell et al., 2005). Recent studies have demonstrated that resveratrol can protect the heart from ischemia/reperfusion injury by eliciting pharmacological preconditioning (Bradamante et al., 2003;Das et al., 2005a;Hattori et al., 2002). Nitric oxide (NO) (Hattori et al., 2002;Hung et al., 2004;Imamura et al., 2002), adenosine receptors (Das et al., 2005a,b), PI3 kinase (Das et al., 2006a,b), and mitogen-activated protein kinase (MAPK) (Das et al., 2006a,b) have been proposed to mediate the cardioprotective effect of resveratrol-induced pharmacological preconditioning. While preconditioning can effectively protect the heart from ischemia/reperfusion injury, it can hardly be applied in the clinical setting of acute myocardial infarction because of the requirement for pretreatment. In Emodin-8-glucoside addition, restoration of blood flow after ischemia also causes myocardial damage, so called reperfusion injury (Braunwald and Kloner, 1985). Thus, it is important to determine if resveratrol applied at reperfusion can also protect the heart from ischemia/reperfusion injury. If resveratrol is protective when given at reperfusion, it is interesting to define the potential cellular and molecular mechanisms underlying the protection. The mitochondrial permeability transition pore (mPTP) opening has been proposed to play an important role in Emodin-8-glucoside myocardial ischemia/reperfusion injury (Suleiman et al., 2001;Weiss et al., 2003). The mPTP remains closed during ischemia but opens at the onset of reperfusion (Griffiths and Halestrap, 1995), and modulation of the mPTP opening at early reperfusion can protect the heart from reperfusion injury (Argaud et al., 2005a,b;Halestrap et al., 2004;Hausenloy et al., 2003,2002). Since resveratrol protects the heart through a NO-dependent mechanism (Hattori et al., 2002;Hung et al., 2004) and NO has been demonstrated to prevent the mPTP opening (Wang et al., 2005), it is possible that resveratrol could modulate the mPTP opening at reperfusion. Identified as a regulator of glycogen metabolism, glycogen synthase kinase 3 (GSK-3) is now a well established Emodin-8-glucoside component contributing to cell signaling, protein synthesis, cell proliferation, cell differentiation, cell adhesion, and apoptosis (Frame and Cohen, 2001). Studies have shown that GSK-3 plays a role in ischemic preconditioning (Tong et al., 2002) and in morphine-induced cardioprotection at reperfusion (Gross et al., 2004). In addition, a recent study has shown that GSK-3 plays a central role in pharmacological TNFSF10 preconditioning induced modulation of the mPTP opening (Juhaszova et al., 2004). Importantly, we have recently demonstrated that bradykinin (Park et al., 2006b) and IB-MECA (Park et al., 2006a) given at reperfusion protect the heart by targeting the mPTP through inhibition of GSK-3. Furthermore, resveratrol can activate the PI3K/Akt (Das et al., 2006a) and mitogen-activated protein kinase (Das et al., 2006b) and these signaling kinases have been demonstrated to negatively regulate GSK-3. Therefore, it isintriguing to determine whether GSK-3 is involved in the action of resveratrol, if resveratrol protects the heart at reperfusion by targeting the mPTP. In this study, we first examined if resveratrol applied at reperfusion could Emodin-8-glucoside reduce infarct size in rat hearts. Then, we determined whether resveratrol protects the heart by targeting the mPTP through inhibition of GSK-3. Lastly, we investigated the mechanism by which GSK-3 inhibition leads to inhibition of the mPTP opening. == 2. Materials and methods == This study conforms to the NIH Guide for the Care and Use of Laboratory Animals (NIH publication NO. 85-23, revised 1996). == 2.1. Chemicals and antibodies == Resveratrol was purchased from Sigma Chemical (St..
The mitochondrial permeability transition pore (mPTP) opening has been proposed to play an important role in myocardial ischemia/reperfusion injury (Suleiman et al