Objective To investigate the impacts of matrine on the balance of helper T cell 17(Th17)/regulatory T cell(Treg)and the Ras homolog gene family member A(RhoA)-Rho-associated coiled-coil forming protein kinase(ROCK)signaling pathway in coronary heart disease(CHD)rats.Methods A model of coronary heart disease was established.Rats were grouped into control group,model group(CHD group),low-dose matrine(50 mg·kg-1,Matrine-L)group,high-dose matrine(200 mg·kg-1,Matrine-H)group,and Matrine-H+LPA(200 mg·kg-1 matrine+10 mg·kg-1 LPA)group.Echocardiography was applied to detect cardiac function.Enzyme linked immunosorbent assay(ELISA)method was used to detect interleukin-17(IL-17)and transforming growth factor(TGF-β).The quantity of Th17,Treg and Th17/Treg ratio were detected by flow cytometry.Immunohistochemistry was applied to detect the protein expressions of endothelial nitric oxide synthase(eNOS)and endothelin 1(ET-1).Masson staining was carried out to observe the pathological changes of myocardial tissue.The myocardial infarction in each group of rats was observed by TCC staining.TUNEL staining was performed to detect cell apoptosis in myocardial tissue.Additionally,RhoA activity was detected by assay kit.Western Blot method was applied to detect the protein expressions levels of B-cell lymphoma factor 2(Bcl-2),Bcl-2 associated X protein(Bax),cysteine aspartate proteinase-3(Caspase-3),RhoA,ROCK1 and ROCK2.Results Compared with the control group,a large amount of blue collagen fiber deposition was observed in the myocardial tissue of CHD group.The expression levels of left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),IL-17,Th17,Th17/Treg,ET-1,infarct size,cell apoptosis rate,TUNEL positive rate,Bax,Caspase-3,RhoA activity,RhoA,ROCK1,ROCK2 were obviously increased.The expression levels of left ventricular ejection fraction(LVEF),left ventricular shortening fraction(LVFS),TGF-β,Treg,eNOS,and Bcl-2 were obviously reduced(P＜0.05).Compared with the CHD group,blue collagen fibers in myocardial tissue of Matrine-L and Matrine-H groups gradually decreased.The expression levels of LVEDV,LVESV,IL-17,Th17,Th17/Treg,ET-1,infarct size,cell apoptosis rate,TUNEL positive rate,Bax,Caspase-3,RhoA activity,RhoA,ROCK1 and ROCK2 were obviously reduced in sequence.The expression levels of LVEF,LVFS,TGF-β,Treg,eNOS,and Bcl-2 were also obviously increased in sequence(P＜0.05).Compared with the Matrine-H group,blue collagen fibers in myocardial tissue of Matrine-H+LPA group increased.The expression levels of LVEDV,LVESV,IL-17,Th17,Th17/Treg,ET-1,infarct size,cell apoptosis rate,TUNEL positive rate,Bax,Caspase-3,RhoA activity,RhoA,ROCK1,ROCK2 were obviously increased,while the expression levels of LVEF,LVFS,TGF-β,Treg,eNOS and Bcl-2 were obviously reduced(P＜0.05).Conclusion Matrine regulates Th17/Treg cell balance and improves myocardial injury in rats with CHD by inhibiting the RhoA-ROCK signaling pathway.