2400 7 br Materials and methods br Results br
Materials and methods
Discussion I/R injury is characterized by myocardial damage triggered by the ischemic insult followed by reperfusion injury. While the primary insult depends mainly on the severity and duration of blood flow restriction and the breakdown of ATP-dependent 2400 7 systems, reperfusion injury is the consequence of a set of more complex and intertwined mechanisms, some of which are not yet fully understood (Kalogeris et al., 2012). Reperfusion injury has been linked to cytosolic calcium overload, the overproduction of ROS, inflammatory processes (e.g., neutrophil invasion), mitochondrial swelling and dysfunction, necrosis, necroptosis, and endothelial dysfunction characterized by diminished NO availability (Kalogeris et al., 2012: Baines, 2009, Baines, 2011). Up to 50% of the is attributed to reperfusion injury (Murry et al., 1986). Multiple studies have been implemented using novel pharmacological agents to limit the magnitude of reperfusion injury yielding disappointing results (Perricone and Vander Heide, 2014; Hausenloy and Yellon, 2013; Ibáñez et al., 2015; Yamazaki et al., 2010). Epidemiological evidence indicates that a moderate amount of dark chocolate consumption is associated with reduced cardiometabolic risk, including improved outcomes after myocardial infarction and a reduced incidence of heart failure. Such effects are attributed to the EPI content present in cocoa products. We previously reported on the capacity of EPI to reduce infarct size and preserve cardiac hemodynamics in rats undergoing either I/R injury or a permanent coronary occlusion (Schnorr et al., 2008: Yamazaki et al., 2010). EPI decreased I/R-induced myocardial damage by 52% 48h after I/R and by 33% at 3 weeks (Yamazaki et al., 2010). In a separate study, animals that received EPI (10mg/kg) IV 15min prior to reperfusion led to a 27% reduction in infarct size at 48h and a 28% at 3 weeks while a second dose decreased infarct size by ~80% at 48h and by 52% at 3 weeks (Yamazaki et al., 2014). EPI induced inhibition of Ar activity as noted in the present study provides evidence for possible mechanisms that may account for cardioprotection. Other nutraceuticals such as the red wine polyphenol resveratrol, are capable of attenuating endothelial dysfunction through the modulation of Ar expression, although at concentrations higher than those for EPI. The cytosolic form of Ar (Ar 1) is expressed in the liver and in select other tissues and hydrolyzes L-arginine to ornithine and urea (Dal-Ros et al., 2012). Ar 2 is a mitochondrial enzyme that is expressed in tissues such as kidney, prostate, small intestine, secreting mammary gland, brain, monocytes and macrophages (Munder, 2009; Cederbaum et al., 2004). In addition to their primary function in the urea cycle, they appear to be involved in wound healing, angiogenesis, immune responses and cardiovascular function (Das et al., 2010). S-nitrosylation is a reversible chemical reaction in which a cysteine thiol reacts with NO to form an S-NO bond to regulate protein expression and activity. Under certain pathological conditions, the process can become irreversible and has been associated with events such as mitochondrial dysfunction, cell stress and death (Nakamura et al., 2013;Gaston et al., 2003). Results from this study reveal increases in Ar 1 and 2 protein levels as well as in their nitrosylated forms in ischemic myocardium. We assume that nitrosylated Ar 1 and Ar 2 levels reflect the activity levels of both enzymes (Santhanam et al., 2007;Dunn et al., 2011). Pre-treatment of rats with 1mg/kg oral EPI prevented these increases possibly contributing to the maintenance of NO availability in injured myocardium. We believed that these effects are induced by conformational changes in arginase as a result of Epi presence. We based this assumption in the docking analysis since, in Epi presence the interaction of L-arginine with Gly142 And ASP 138 (hydrogen bonds) residues disappears and the interaction (attractive changes) with ASP124, Asp 128 and His126 residues appears suggesting differential interaction in the enzyme´s pocket active site resulting in changes in activation and activity.