Cardioprotective Role of Sphingosine 1-Phosphate Receptor Agonist Fingolimod (FTY720) in Global Ischemia-Reperfusion Models

Background and purpose: Ischemic Heart Diseases (IHD) are the most common cause of morbidity and mortality. Incidence and prevalence is continuously growing. There is an escalating risk for revascularization or resuscitation in patients with IHD. Recently, it has been reported that sphingosine 1-phosphate receptor agonist plays anti-apoptotic and anti-inflammatory role in ischemia-reperfusion injury. The aim of our study is to investigate the cardioprotective effects of sphingosine 1-phosphate receptor agonist fingolimod (FTY720) in global ischemia-reperfusion injury related to the cardiac arrest, cardiopulmonary bypass, and heart transplantation. Methods: In all the three experimental studies, global ischemia-reperfusion was achieved by cardiac arrest either by Ventricular fibrillation or cardioplegia (CPB HT) in anesthetized (sodium pentobarbital, 60 mg/ml/kg i.v) and ventilated male Sprague-Dawley rats (300 - 350 g). The global ischemic period lasted 10 min in the cardiac arrest and cardioplegic arrest, but in transplantation, ischemia time was 60 min while reperfusion times were maintained for either 60 min or 24 hours. Where applicable, monitoring was done using electrocardiogram and hemodynamic data recorded at baseline, 1 hour and 24 hours of reperfusion. The level of high energy phosphates was measured. Apoptotic, inflammatory and oxidative markers were analyzed. The statistical significance was considered as p ≤ 0.05. Experimental design: In all the above mentioned protocols, 10 animals were used in each of the control and treated groups. The first study examined the cardioprotective potential of fingolimod using the following treatment strategy, treatment administered (post ischemia) immediately at the early phase of reperfusion (fingolimod 1mg/kg i.v) compared to saline controls (0.9% saline). In next two experimental models, treatment administration was done 15 min before ischemic phase (fingolimod 1mg/kg i.v.) compared to controls (0.9% saline), followed by 10 min ischemia and 60 min reperfusion in cardioplegic arrest while 60 min ischemic phase remained from heart explantation to reperfusion, and reperfusion phase lasted for 24 hours following blood and tissue collection Results: Three experimental models demonstrated significant myocardial protection in Fingolimod treated groups as compared to control groups. Hemodynamic assessment showed improved cardiac function at late phase. Reduced frequency of apoptotic cells and inflammatory mediators were found in the treated group. High energy phosphates were preserved in the treated as compared to control groups. Reactive Oxygen Species (ROS) were also attenuated in the fingolimod-treated group. Increased phosphorylation of Akt and Erk1/2 signaling pathways found in fingolimod treated group as compared to control, these are important part of Reperfusion Injury Salvage Kinase (RISK) and Survivor Activating Factor Enhancement(SAFE) pathways. Conclusions: The intravenous administration of fingolimod in global ischemia-reperfusion was cardioprotective. Fingolimod cardioprotection appears to be mediated through preservation of high energy phosphates, reduction in oxidative stress, inhibition of apoptosis and inflammation leading to preserved cardiac functions. In summary, targeting sphingosine 1-phosphate receptors modulation may offer a new potential therapeutic cardioprotective agent to attenuate myocardial damage during global myocardial ischemia and reperfusion.