Protective Mechanism Of Adiponectin On Apoptosis In Palimitate Induced Cardiomyocyte

Part I The mechanisms of apoptosis in palmitate-induced H9c2cellsBackgroud and Objective:Cardiomyocyte apoptosis is an important factor causing myocardial dysfunction, heart failure and other cardiovascular diseases. Cardiac myocytes undergo apoptosis under condition of high free fatty acid concentrations such as palmitate, which is implicated in lipotoxic cardiomyopathy. However, such a high concentration of saturated fatty acids result in cardiomyocyte apoptosis molecular mechanism is not clear. In this section, we use high concentrations of palmitate to induce cardiomyocyte, establishment of cardiomyocye apoptosis model induced by high palmitate model, observed palmitate-induced apoptosis of cardiomyocyte, and to investigate the possible molecular mechanisms of cardiomyocyte apoptosis induced by palmitate.Methods:H9c2cells were exposed to palmitate for12h. The effect on the cell viability of H9c2cells was evaluated using MTT assay, and cell apoptosis was determined by Hoechst33342staining. The level of intracellular ROS was determined using a peroxide-sensitive fluorescent probe (DCFH-DA). Protein expression was measured using the western blot method.Results:After treatment with palmitate for12h, H9c2cells apoptosis was evidenced an increasing brightly condensed chromatin or unclear fragments by staining with Hoechst33342, which was associated with increasing the level of active caspase-3and cleaved PARP. In this model of treatment with palmitate, H9c2cells apoptosis was associated with increasing the level of p53and Bax expression, and reducing the level of Bcl-2expression. Meanwhile, palmitate-induced apoptosis increased the level of intracellular ROS production, the level of p-ERK1/2, and decreased the level of p-Akt significantly. In line with these results, palmitate-induced apoptosis can be attenuated by ERK1/2inhibitor U0126through partial reducing the intracellular ROS generation.Conclusions:Taken together, these results suggest that palmitate-induced apoptosis in H9c2cells through activation of ERK1/2signaling pathway, reducing the activity of the Akt signaling pathway, increased intracellular ROS production that caused oxidative stress, and leading to the apoptosis-related proteins activation of caspase-3and PARRIn this study, the results clearly that ERK1/2signaling pathway and ROS-mediated oxidative stress mechanism in palmitate induced lipotoxicity cardiomyopathy, and would provide an experimental basic for lipotoxicity cardiomyopathy study. Part II Protective Mechanism of globular adiponectin on apoptosis in palimitate-induced H9c2cellsBackground and Objective:Adiponectin, a protein of hormone, is a major secreted by fat tissue, and has a variety of biological effects. Studies have shown that myocardial apoptosis is an important factor of myocardial dysfunction and heart failure, and prevent the myocardial apoptosis can be significantly improved myocardial function. Excessive accumulation of lipids in the heart would cause cardiac dysfunction and heart failure. Research indicated that free saturated fatty acids levels were significantly increased in the patients with myocardial dysfunction and heart failure. Adiponectin has a protection and resistance to the effects of myocardial apoptosis. However, the effects of protection and its mechanism on adiponctin are no clear. In this section, we use high palmitate to induce cardiomyocyte apoptosis, and to investigate whether adiponectin can block palmitate-induced apoptosis and the underlying biochemical mechanism in H9c2cells.Methods:H9c2cells were treated with palmitate presence or absence of2.5μg/ml globular adiponectin. The effect on the cell viability of H9c2cells was evaluated using MTT assay, and cell apoptosis was determined by Hoechst33342staining. The level of intracellular ROS was determined using a peroxide-sensitive fluorescent probe (DCFH-DA). The inflammation-related factors IL6, CRP, and ICAM mRNA expression were detected by RT-PCR. Protein expression was measured using the western blot method.Results:Our results showed that the palmitate treatment induced apoptosis in H9c2cells, which was associated with significantly increasing the level of cleaved caspase-3, cleaved PARP, and intracellular ROS. The inflammation-ralated factor IL6, CRP and mRNA expression levels were significantly inreased in the palmitate treatment. Meanwhile, palmitate-induced apoptosis increased the protein level of p-ERK1/2, and decreased the protein level of p-Akt significantly. However, levels of both of these proteins were restored to the normal when pretreated with adiponectin, and followed with the decrease of cleaved caspase-3, cleaved PARP, and levels of intracellular ROS. IL6, CRP and ICAM mRNA expression levels were significantly decreased in palmitate combined with adiponectin treament than in palmitate treament. In line with these results, the protective effect of adiponectin can be blocked by PI3K/Akt inhibitor LY294002, and palmitate-induced apoptosis can be attenuated by ERK1/2inhibitor U0126.Conclusions:Taken together, the present study demonstrated that adiponectin protects H9c2cells from palmitate-induced apoptosis via PI3K/Akt and ERK1/2signaling pathways. Our results reveal a link between adiponectin and cardiomyocytes apoptosis, suggesting that adioponectin may be a promising therapeutic for the treatment of lipotoxicity cardiomyopathy.