The Role Of TRPV4 Channel In Diabetic Myocardial Fibrosis In Rats

Objective To investigate the role of TRPV4 channel in diabetic myocardial fibrosis and its possible mechanism.Methods(1)Healthy male Sprague-Dawley rats(6 weeks)were randomly assigned to control,diabetes mellitus(DM),and DM treated with TRPV4 antagonist HC067047(DM+HC)groups.Diabetes was induced by a single intraperitoneal(i.p.)injection of streptozotocin(STZ)at 60 mg/kg.Rats in DM+HC group were treated with HC067047 at8 weeks after STZ injection till 12 weeks.The expression level of TRPV4 gene was analyzed using the quantitative reverse transcription polymerase chain reaction.Western blotting was used to determine the protein expression of TRPV4,collagen Ι,TGF-β1,P-Smad3 and Smad3 in myocardium in rats.The heart weight/body weight ratio was measured.Masson’s trichrome staining was used to determine the degree of myocardial fibrosis.(2)Cardiac fibroblasts extracted from neonatal SD rat were incubated in either normal glucose(5.5 m M)or high glucose(30 m M)medium in the presence or absence of a TRPV4 antagonist.CCK-8 assay was used to determine the proliferation of cardiac fibroblasts.Western blotting was used to determine the protein expression of collagen Ι,TGF-β1,P-Smad3 and Smad3 in cardiac fibroblasts.Results(1)Compared to controls,the expression of TRPV4 protein and the expression of TRPV4 m RNA in myocardium of diabetic rats increased significantly at 3days,4,8 and 12 weeks after successful modeling(P<0.05);(2)Consistent with results in vivo,the expression of TRPV4 protein in the high glucose medium was up-regulated compared to normal glucose(P<0.01).(3)Compared with normal glucose,the proliferation of cardiac fibroblasts increased in high glucose,while cardiac fibroblasts proliferation induced by high glucose was inhibited by the TRPV4 antagonist HC067047(P<0.01).(4)Compared with the control group,the heart weight/body weight ratio increased in DM group(P<0.001),and diabetic rats revealed clear myocardial fibrosis(P<0.01),while TRPPV4 antagonist reversed this phenomenon.(5)Compared to normal glucose group,the expression of collagen Ι,TGF-β1,and P-Smad3 increased in cardiac fibroblasts cultured in high glucose medium,whereas TRPV4 antagonist inhibited the expression of collagen Ι,TGF-β1,and P-Smad3 induced by high glucose(P<0.05).In addition,the TRPV4 antagonist inhibited the expression of collagen Ι,TGF-β1 and P-Smad3 protein in diabetic myocardium(P<0.05).Conclusion TRPV4 induces diabetic myocardial fibrosis through TGF-β1/Smad3 signaling pathway.