Studies On Inhibiting Effects And Mechanism Of Taurine On Myocardial Fibrosis

Myocardial fibrosis is the important pathological manifestation of left ventricular hypertrophy(LVH) and plays a pivotal role in the transition from compensation to decompensation. It is well documented that abnormal proliferation and collagen synthesis of cardiac fibroblast (CFb) contribute to the pathogenesis of cardiac fibrosis.CFb play a crucial role in the development of cardiac fibrosis due to their over-proliferation. Therefore, it is an important strategy for antifibrosis to inhibit the proliferation of CFb. Taurine(Tau)is a conditionally-essential amino acid. First discovered as a component of ox bile in 1827, it was not until 1975 that the significance of taurine in human nutrition was identified .Tau possesses many bioeffects which include: detoxification, membrane stabilization ,osmoregulation , and modulation of cellular calcium levels.Our previous work showed that Tau can inhibit the proliferation of cultured CFb,but the signaling mechanism is not well understood.Reinin-angiotensin-aldosterone system (RAAS) plays pivotal role in multiple factor leading myocardial fibrosis.In order to elucidate the inhibiting effect of taurine(Tau) on myocardial fibrosis and its possible signal transduction pathway so as to provide valuable insight into mechanism of the etiology and find a new way to treatment of myocardial fibrosis , the study built the model of myocardial fibrosis in rats by subcutaneous injection of isoprel(Iso) in vivo and angiotensinⅡ(AngⅡ) inducing the proliferation of the cultured neonatal rat cardiac fibroblast(CFb) in vitro ,accompanied the use of protein kinase Cα(PKCα)inhibitor (che).The study applied many kinds of methods such as enzymology index (LDH,SOD,MDA,NO) detection in serum,HE staining, ultramicrostructure observe in myocardium tissue, the thiazole blue (MTT)colorimetric assay, enzyme linked immunosorbent assay(ELISA), immunocytochemical staining,flow cytometry,nitric acid reductase method,spectrophotometry,immunofluorescence staining and western blot technology.Experiments results in vivo showed that the content of hydroxyproline were decreased in Tau(160 , 320mg·kg -1·d -1) groups as compared with model group(P<0.01 or P<0.001). HE staining results indicated that myocardium fiber appeared hyperplastic and were arranged disorder and kytoplasm swelled in model group .Through increasing the activity of SOD and reducing the content of MDA in tissue and LDH and CK in serum ,Tau could relieve the damage of myocardium induced by Iso . At the same time , Tau could inhibited the protein express of PKCa to membrane in myocardium . In vitro ,CFb proliferation rate and the content of TGF-β1 and collagenⅠand collagenⅢwere greatly declined when CFb was treated with Tau at concentrations of 40, 80 and 160 mmol·L-1 for 24h (P<0.05 or P<0.01). In the flow cytometry analysis, it was found that Tau could block CFb in the G0/Gl phase from entering the S phase, resulting in more cells in the G0/G1 phase and fewer in the S phase. The percentage of the cells in the G0/G1 phase and the S phase at the dosage of 40,80,160mmol·L-1 were significantly different in comparison to the model group (P<0.05 or P<0.01). CFb expressed cell cycle regulatory protein cyclin D1 and p27. Tau induced p27 expression and had no effect on cyclin D1 expression. Tau significantly increased iNOS-NO system activity and inhibited the nuclear translocation of NF-kB in CFb(P<0.05或P<0.01). Tau abolished the translocation of PKCa from cytosol to membrane (P<0.05, P<0.01) and Che improve the protective effect of Tau.Based on the above results in vivo and in vitro, we can take a conclusion that Tau protected the cardiac fibroblast from proliferation probably owning to reducing free radical production and abolish the translocation of PKCa from cytosol to membrane in cardiac fibroblast in a concentration dependent manner, then upregulation the protein expression of iNOS and inducing the production of NO; then prompting p27 expression and block CFb in the G0/Gl phase;then inhibition the nuclear translocation of NF-kB p65. Ultimatly suppressing the myocardial fibrosis occurance.