Role And Mechanism Of MCPIP In Cardiomyocyte Death In Age-related Atrial Fibrillation

Objective:Monocyte chemotactic protein-1 induced protein(MCPIP),a zinc finger protein with transcriptional activity induced by MCP-1 binding to its receptor CCR2,is closely related to apoptosis of cardiomyocyte and cardiofibroblasts,as well as inflammatory angiogenesis.Aging is an independent risk factor of atrial fibrillation(AF)and it can aggravate inflammatory process which plays a role in AF,thus accelerate the process of AF by inducing the expression of inflammatory factors such as MCP-1.Therefore,to study the expression of MCPIP in the process of AF at different ages is helpful to clarify the mechanism of AF and to provide a new idea for the treatment of AF.The subjects of this research include:(1)Comparison of MCPIP expression in peripheral blood of patients with atrial fibrillation of different ages and control subjects without atrial fibrillation,and the correlations between MCPIP level and fibrosis biomarkers.(2)Dog AF models at different ages were built and the electrophysiological properties,atrial structure changes and MCPIP expression of AF dogs and control dogs were compared in order to explore the relationship between MCPIP expression and cardiac myocyte death.(3)H9c2 cells were cultured with administration of CCR2 antagonists and/or MCP-1 to investigate the effects of MCP-1 and CCR2 antagonists on apoptosis and autophagy.Methods:Part 1?542 patients with AF and 542 control people matched by age and sex were selected and their medical data and blood samples were collected to compare the history of disease,echocardiography and medication history of different ages.ELISA was used to detect the expression of MCPIP,TGF-?1,PIIINP and ICTP in serum,for the comparison of the correlation between MCPIP and these two biomarkers.Part 2: 24 beagle dogs were divided into aged AF group,adult AF group,aged control group and adult control group according to their age.After 8 weeks,the effective refractory period,effective refractory period dispersion and corrected sinus node recovery time were measured,and the induction of atrial fibrillation was compared.Changes in cardiac structure were measured by echocardiography,and changes in atrial tissue structure in dogs were compared by tissue section staining.The peripheral blood was collected and the change of MCPIP level during the modeling process was compared by ELISA.Immunohistochemical staining,RT-PCR and Western blot were used to detect the level of MCPIP and cell death related indexes in canine atrial tissue.Part 3: H9c2 cells were cultured and CCR2 antagonist and/or MCP-1 were added separately.After 72 hours,cells were collected for detection.The apoptosis index was measured by flow cytometry and TUNEL staining,and the expression of MCP-1,MCPIP,cell death related biomarkers and signaling pathway proteins were detected by immunofluorescence staining and western blot.Results:(1)The expression of MCPIP in aged AF patients was higher than that in adult AF patients and aged control group.There was no significant difference in the expression of adult AF patients and aged controls.The expression of MCPIP and PIIINP were positively correlated in the aged AF group,adult AF group and aged control group.The expression of MCPIP and ICTP was also positively correlated in the three groups,and was highly correlated in the adult AF group.(2)The MCPIP level in peripheral blood of aged AF dogs was higher than that in adult AF group.And the expression of Caspase-3 and autophagy-related protein Rubicon in peripheral blood and myocardial tissue of aged AF group were higher than those in adult AF group and aged control group.Also,the expression of key enzyme IRE1 of endoplasmic reticulum stress in atrial tissue of aged AF group was up-regulated.(3)After the administration of MCP-1,the apoptosis index increased significantly,and the apoptosis index decreased after the administration of CCR2 antagonist.MCPIP expression was significantly increased in MCP-1 group,while CCR2 antagonist was effective in inhibiting the expression of MCPIP.The expression of Caspase-3 and IRE1 were similar to that of MCPIP,and their expression were increased by the induction of MCP-1,and the administration of CCR2 antagonist could decrease their expression.The expression of PPAR-? was decreased in the MCP-1 group,but those of CEBP-? and NF-?B were significantly increased.However,the impacts of MCP-1 were reversed after dealing with CCR2 antagonist.Conclusion:(1)The expression of MCPIP was increased in peripheral blood of aged AF patients,and it was related to the fibrosis after AF.(2)The expression of MCPIP was more common in aged AF dogs,and the trend was consistent with myocardial apoptosis.Then the expression and intergroup differences of MCPIP in peripheral blood and atrial tissues were the same as those of apoptosis and autophagy biomarkers,and endoplasmic reticulum stress played a key role.(3)Increased expression of MCP-1 could cause a decrease in cardiomyocyte survival and increased apoptosis,which worked by MCPIP;Moreover,MCP-1/MCPIP could cause cardiomyocyte apoptosis or autophagy,and endoplasmic reticulum stress occurred.All these changes functioned through CEBP? and PPAR-? pathways.