P5393Myonectin/CTRP15 protects against myocardial ischemia-reperfusion injury

Abstract

bility in revascularization after unpredicted ischemic events. The protective mechanism is independent of Akt, Erk and STAT-3 phosphorylation and the protective effect of XE991 seems to involve Kv7.4 subchannels. Background: SelenoproteinP (SeP), a secretory protein produced primarily in the liver, functions as a selenium supply protein. SeP has been reported to be associated with insulin resistance in humans through serial analysis of gene expression. Recently Sep also inhibits vascular endothelial growth factor-stimulated cell proliferation in human umbilical vein endothelial cells and impairs angiogene-sis in mice hind limb model. It remains unknown whether inhibition of SeP protects the heart during ischemia/reperfusion (I/R) injury. Objective: In this study, we investigates the role of SeP in I/R injury. Method and results: We found serum SeP levels were increased in patients with coronary artery disease compared to patients without coronary artery disease (3.72±0.14 versus 3.00±0.32 μg/ml, p<0.05). SeP knock out (KO) and lit-termate wild type (WT) mice were subjected to 30 minutes myocardial ischemia and 24 hours reperfusion. Myocardial infarction/area at risk (MI/AAR) evaluated by evans bule and triphenyltetrazolium chloride staining was significantly smaller in SeP KO mice than in WT mice (21.58±2.02 versus 32.24±4.33%, p<0.05). My-ocardial damage was also assessed the serum levels of lactate dehydrogenase (LDH) by ELISA kits. Serum level of LDH was significantly lower in Sep KO than in WT (985.2±70.1 versus 1906.3±334.2 U/L, p<0.05). The number of TUNEL-positive nuclei, evaluated by terminal deoxynucleotidyl transferase dUTP nick end labelling staining, was significantly lower in SeP KO than in WT mice (0.82±0.11 versus 2.09±0.47%, p<0.05). In addition, caspase-3 activation in SeP KO was reduced compared to WT mice. Furthermore, we examined phosphoinositide 3-kinase/Akt and Erk as the reperfusion injury salvage kinase (RISK) pathway. Interestingly , SeP KO was significantly increased the phosphorylation of IGF-1, Akt and Erk compared to the WT mice after I/R. Conclusions: These results suggest that inhibition of SeP protects the heart from I/R injury through upregulation of the RISK pathway. Background: Post-conditioning (Post-Co) has been proposed to limit infarct size by reducing ischemia and reperfusion (I/R) injury. However, the molecular mechanisms by which Post-Co affords cardio-protection remain unclear. Purpose: We hypothesized that a systems biology approach could be of help to identify an integrated group of proteins with different functions involved in Post-Co induced cardio-protection. Methods: We induced myocardial ischemia (1.5h) by balloon occlusion of the left anterior descending coronary artery (LAD) in a swine model of closed-chest my-ocardial infarction (MI; N=20). Post-Co was achieved by 6 cycles of 20 seconds of reperfusion and 20 seconds of re-occlusion. Benefits of Post-Co were measured by clinical and morphological evaluation of heart function and infarct size reduction after 2.5 hours of reperfusion. Samples of the myocardium were obtained and processed for proteomic analysis. Proof-of-concept studies were run in a mice MI model (N=26). Results: Among the identified proteins in the myocardial proteome, 28% were associated to the mitochondrial-dysfunction pathway. I/R induced a decrease in 15 mitochondrial-related proteins, whereas Post-Co rescued over 47% of those changes and induced a 10% recovery in cardiac performance. Post-Co protected the heart DJ-1 levels against the decrease induced by unprotected reperfusion. Recombinant DJ-1 was then administered to mice 1h before the induction of MI by LAD-ligation. DJ-1 administration significantly reduced infarct size (75%) by diminishing apoptosis through a multigenic response in the myocardium involving the Gαq-signaling pathway and the oxidative stress-related iNOS pathway. Conclusions: Post-Co coordinately prevents the pro-oxidant mitochondrial-related changes that occur during reperfusion by protecting DJ-1 function in the myocardium. Raising DJ-1 levels may protect against myocardial injury without the need of mechanical Post-Co due to its direct cardioprotective effect. Background: Endurance exercise training is associated with reduction of cardio-vascular risk. Skeletal muscle secretes a variety of bioactive molecules, referred to as myokines, which directly affect nearby or remote organs. Here, we sought to identify an exercise-regulated myokine and investigated whether this factor modulates acute ischemic injury in the heart. Method and results: Wild-type (WT) mice were run on a treadmill for 6 weeks and subjected to 60 minutes of myocardial ischemia and 24 hours of reperfu-sion (I/R). Treadmill running significantly reduces myocardial infarct size, apopto-sis and expression of inflammatory mediators following I/R. By microarray analysis of gene expression profiles of skeletal muscle in sedentary versus exercised mice, we identified myonectin/CTRP15 (C1q/TNF-related protein 15) as a myokine that is upregulated by treadmill exercise. Myonectin-knockout (KO) mice showed increased myocardial infarct size, following I/R compared with WT mice. Myonectin-KO mice also exhibited increased apoptotic activity and expression of pro-inflammatory mediators in ischemic heart compared with WT mice. In cultured cardiomyocytes, myonectin protein suppressed hypoxia/reoxygenation-induced apoptosis. Myonectin enhanced the phosphorylation of Akt in cardiomy-ocytes, and blockade of Akt activity reversed the inhibitory effects of myonectin on cardiomyocyte apoptosis. Treatment of cultured macrophages with myonectin led to suppression of LPS-induced expression of pro-inflammatory genes, which was reversed by inactivation of Akt. Treatment of cardiomyocytes or macrophages with myonectin resulted in increased production of cAMP. Pharmacological inhibition of adenylyl cyclase reversed myonectin-induced suppression of cardiomyocyte apoptosis and macrophage inflammatory response. Conclusion: Myonectin functions as an exercise-induced myokine that ameliorates acute ischemic injury in the heart by suppressing apoptosis and inflammation through the cAMP-dependent activation of Akt.