| Myocardial infarction(MI)is one of the major diseases that endangers people's health.At present,clinical use of thrombolytics or interventional treatment can improve the heart function to a certain extent,however,they could also trigger ischemia-reperfusion injury(I/R).Therefore,there is an urgent need to find suitable targets for the treatment of myocardial infarction.Adult myocardial damage cannot be regenerated due to its unique biological feature.The tissue damage repair mainly depends on the removal of necrotic cells and formation of scar tissues.Sixty percent of the cardiac tissue is composed of myocardial fibroblasts.By secreting extracellular matrix proteins,they are involved in tissue damage repair,scar formation and post-injury remodeling,thus playing important roles in the repair processes and maintenance of cardiac functions.Non-metastatic melanoma glycoprotein(Gpnmb)is a type I transmembrane glycoprotein that is expressed in a variety of tissues and cells.Studies have shown that,after liver injury in rats,Gpnmb expression were increased,preventing liver fibrosis.Suggesting that Gpnmb may be involved in tissue repair by adjusting the degree of fibrosis.In mouse with myocarditis,the dendritic cell(DCs)markers(OX-62)were highly expressed in the myocardium,and the expression of Gpnmb was also up-regulated.It has been reported that the number DCs are increased in myocardium in rats after AMI.As Gpnmb is also expressed on DCs cells,suggesting that DCs may promote tissue repair by Gpnmb.However,the role of Gpnmb in myocardial repair has not been elucidated.Histone acetylation is a common feature of gene regulation,and the expression Gpnmb can also be modulated by histone acetylation level.Trichostatin A(TSA)is a broad spectrum histone deacetylase inhibitor(HDACi),which can increase acetylation level of histone,affecting the regulation of gene expression.Our previous experiments have shown that TSA can reduce myocardial infarct size and protect against myocardial schemic injury.But it is still unclear whether Gpnmb is involved in tissue repair by TSA.Objectives:In this study,we will investigated whether TSA protects the myocardium by regulating Gpbmb expression,thus uncover the detailed mechanism by which TSA exerts such effects.Methods:In this study,healthy adult Wista male rats were used as the research subjects.The myocardial infarction model was established by ligating the left anterior descending coronary artery.The myocardial infarct size was measured by TTC staining.The expression of CK-MB and c Tn T were monitored by ELISA to clarify the protective effects of TSA on myocardial ischemic injury.Western blotting was used to detect the timely expression of Gpnmb,?-SMA,TGF-?1and CTGF.The acetylation level of H3 and H4 at the promoter region of Gpnmb were detected by Chromatin-immunoprecipitation assay.The effect of TSA on collagen expression in infarcted myocardium was detected by Sirius scarlet staining.The expression of Gpnmb and its co-localization with infiltrated dendritic cell marker OX-62 were visualized by immunofluorescence staining.Results:Compared with the control group,the myocardial infarct size was significantly increased time-dependently at 1,3,7,14,21 and 28 days after myocardial infarction(P <0.01).Compared with the model group,the infarct size was significantly reduced by TSA treatment(P <0.05).Compared with the control group,the expression of CK-MB and c Tn T in the serum were increased after MI and peaked at day 1 and day 3 respectively.The expression of CK-MB and c Tn T in TSA group was significantly lower than that in model group(P <0.05).Western blot results showed that Gpnmb expression was significantly increased in the infarcted myocardium of the model group(P <0.05)and peaked at day 21.The expression of Gpnmb in TSA group was further up-regulated compared with the model group(P <0.05).Immunofluorescence analysis of Gpnmb protein revealed its expression in TSA group was significantly higher than that of model group(P <0.05).The Ch IP results showed that the H3 and H4 acetylation levels at Gpnmb promoter region in the model group were higher than those in the control group(P <0.05),and were further increased by TSA treatment(P <0.05).Compared with the model group,the expression of collagen fibers in the myocardial tissue treated were further increased by TSA(P<0.05).Pearson correlation analysis showed that there is a positive correlation between expression of Gpnmb and collagen in the model group(r=0.803,P<0.05)as well as in TSA group(r=0.795,P<0.05).After treatment with TSA,TGF-?1 that regulates myofibroblasts transformation,and its downstream CTGF as well as myofibroblast differentiation marker ?-SMA were increased.The co-immunostaining showed that Gpnmb were partially expressed on OX-62+ DCs.Conclusions:TSA up-regulates Gpnmb expression by increasing H3 and H4 acetylation at gpnmb promoter region.Meanwhile,TSA up-regulates the expression of collagen,and the expression of TGF-?1 and its downstream CTGF which regulates myofibroblast differentiation,as well as the expression of myofibroblast differentiation marker ?-SMA were regulated by TSA,suggesting that TSA may be involved in tissue damage repair by regulating Gpnmb.Our study provides new ideas for the regulation of myocardial repair after myocardial infarction,and provides a new experimental basis for improving the quality of life of patients with myocardial infarction. |
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