The Roles And Molecular Mechanisms Of Growth Differentiation Factor 15 In Acute Myocardial Infarction.

Acute myocardial infarction is characterized with severe chest pain,electrocardiogram and dynamic changes of myocardial enzymes,which is caused by sudden complete occlusion of coronary artery inducing myocardial ischemia,injury and necrosis.In recent years,there has been an obvious upward trend in China,with at least nearly 10 million cases.According to the development of acute myocardial infarction,the course of the disease can be divided into three stages: acute inflammation stage,wound healing stage,and ventricular remodeling stage.We know that ventricular remodeling is a remodeling process of cardiac structure,metabolism and function,which is triggered by the alteration of cell level,such as myocardial cell,non cardiac muscle cell and e?tracellular matri?.Ventricular remodeling is a pathophysiological basis for heart failure and cardiac dysfunction after acute myocardial infarction or chronic myocardial ischemia,which seriously threatens the life of patients and affects the quality of life.Growth differentiation factor 15 was first isolated from a c DNA library enriched for macrophage-associated genes obtained from the U937 cell line.It was described as a divergent member of the human transforming growth factor ? superfamily.Transforming growth factor ? and other inflammatory factors are also a fibroblast promoting factor,although it can promote wound healing in the early stage of myocardial infarction,but long-term sustained effect leads to ventricular remodeling.A large number of reports have shown that the roles of GDF-15 in cardiovascular disease is multiple.GDF-15 can regulate lipid metabolism,stable endothelial cells,inhibit inflammation and myocardial apoptosis,and promote healing infarct area in the e?perimental model.Nevertheless,high level of GDF-15 is closely related with the poor prognosis of patients with cardiovascular disease,indicates the higher death rate and poor quality of life.There are obvious contradictions.We hypothesize that after acute myocardial infarction,the level of GDF-15 in the myocardium increases sharply,and GDF-15 as anti-inflammatory factor inhibits the apoptosis of cardiac myocytes,and activates cardiac fibroblasts.It can help wound healing in the early stage of myocardial infarction,however,aggravates ventricular remodeling and leads to heart failure at the later stage.According to the hypothesis,we carried out the following researchs: 1)Firstly collecting the serum of 30 patients,using ELISA to analyze the correlation between GDF-15 and classic adverse prognostic indicators.Then primary isolate neonatal SD rat cardiac fibroblasts and myocytes were subjected to hypo?ia,and we use q RT-PCR,ELISA,Western Blot to study the origin of GDF-15.2)By making use of the primary isolated SD rat cardiac fibroblasts and cardiomyocytes stimulated with GDF-15,we confirmed the effect in different cells in the heart.Then GDF-15 knockout mices were used to construct an acute myocardial infarction model and divided into three groups.Recombinant GDF-15 was subcutaneously injected to observe the different roles of GDF-15 in the development of acute myocardial infarction.3)By making use of i TRAQ,q RT-PCR,WB,and laser confocal,we studied molecular mechanisms of activation of cardiac fibroblast phenotype transformation by regulation of NF-?B pathway.Through the above research,we obtained the following results: 1)In Chinese population,GDF-15 was closely related to the poor prognosis of acute myocardial infarction;In the case of acute myocardial infarction,serum GDF-15 is secreted by cardiac fibroblasts mainly.2)In vitro,GDF-15 inhibited myocardial cell apoptosis in hypo?ia and promotes cardiac fibroblast cells transforming phenotype in acute myocardial infarction;in vitro,GDF-15 inhibited the apoptosis of myocardial cells induced by hypo?ia,and promoted cardiac fibroblast cells transforming phenotype;By constructing GDF-15 knockout mice models of acute myocardial infarction we confirmed the biological function of GDF-15 in different stages of acute myocardial infarction: in the acute inflammation stage and healing stage GDF-15 inhibited myocardial cell apoptosis,promoted wound healing and promoted the left ventricular remodeling in remodeling stage,leading to heart failure.3)The results of protein quantitative analysis and analysis show that upregulation of NF-?B was one of the pathways of GDF-15 activation of cardiac fibroblasts.We found that GDF-15 upregulated NF-?B signaling pathway in three ways: GDF-15 degraded I?B?,promoted nuclear import of NF-?B dimer p65/p50,and then activated NF-?B pathway;in addition,GDF-15 inhibited p50 production to reduce the competitive occupancy of p50/p50 dimer in the nucleus,and then promoted the binding of transcriptionally active p65/p50 dimer to DNA.GDF-15 reduced the e?pression of histone deacetylase and reduces the deacetylation of p65 Nucleation,and further promoted the transcriptional activity of NF-?B.Our results suggested that cardiac fibroblasts secreted GDF-15 when myocardial infarction occurs.GDF-15 can activate cardiac fibroblasts to secrete collagen through the NF-?B pathway in an autocrine or paracrine manner;Activated cardiac fibroblasts and secreted collagen can help to heal the myocardial infarction in the acute phase,but it leads to ventricular remodeling and induces heart failure during the remodeling phase.This study firstly demonstrated the roles of GDF-15 in the development of myocardial infarction from the perspective of cardiac fibroblasts,and clarified that GDF-15 is an important molecule that can cause ventricular remodeling after myocardial infarction.This study provided the treatment of ischemic cardiomyopathy induced by myocardial infarction and developed a theoretical foundation for therapeutic drugs for ischemic heart disease by targeting GDF-15 signaling pathway.