Protective Effect Of Ginsenoside Re On ET-1 Induced Hypertrophy And Fibrosis In Isolated Beating Rat Atria

BackgroundEndothelin 1(ET-1)is a most potent vasoconstrictor in the human cardiovascular system.In the heart,ET-1 increases intracellular calcium concentration in a voltage-independent mechanism through its A and B receptors(ETRA & ETRB),resulting in positive inotropic and chronotropic effects in cardiomyocytes.However,abnormal increase in ET-1 is associated with the occurrence of cardiovascular diseases such as myocardial hypertrophy,fibrosis,heart failure and pulmonary hypertension.Therefore,interfering with ET-1 is one of the effective strategies for treatment of ET-1-related cardiovascular diseases.Ginsenoside Re(G-Re)is one of the main active ingredients of ginsenosides widely used in the treatment of cardiovascular diseases.G-Re improves blood circulation,regulates blood pressure and lipid metabolism,protects the heart to against ischemic injury.It is also improves myocardial remodeling and fibrosis,relieves myocardial ischemia/reperfusion injury,arrhythmia,and promotes angiogenesis.However,the effect of G-Re on ET-1-induced atrial muscle hypertrophy and fibrosis is still unclear.ObjectiveThis study was to investigate the effect and the mechanism of G-Re on ET-1-induced hypertrophy and fibrosis in isolated beating rat atria.MethodsThe 18 weeks old specefic pathogen free rats(weighing 200-250 g,male or female)were used.The rats were randomly divided into 6 groups(6 rats in each group): control group,ET-1 group,G-Re group,G-Re+ET-1 group,Bosentan(Bo,non-selective antagonist of ET receptors)+ET-1 group and GLX351322(GLX,NOX4inhibitor)+ ET-1 group.1.Preparation of isolated beating rat atrial model and puls pressure measurement:an isolated perfused beating rat atrial model was used,and the atrial pulse pressure was recorded by a physiograph in real time base;2.The content of atrial natriuretic peptide(ANP)was measured by radioimmunoassay;3.The levels of m RNA of ETRA and ETRB were detected by quantitative real-time PCR(q-PCR);4.Western blotting was used to detect ETRA and ETRB,cytoplasmic phospholipase A2(c PLA2),nicotinamide adenine dinucleotide phosphate oxidases 4(NOX4),p38 mitogen-activated protein kinase(p38),protein kinase B(Akt);hypertrophic and fibrotic factors,such as nuclear factor kappa-B(NF-κB),transforming growth factor β1(TGF-β1),collagen 1(Coll 1),matrix metalloproteinase 2(MMP2);and marker of cardiac hypertrophy,such as β-myosin heavy chain(β-MHC)and ANP expression.5.The fibrotic changes in atria induced by ET-1 were observed by Masson staining.Results1.ET-1(7 nmol/L)significantly increased atrial pulse pressure and ANP secretion in isolated perfused beating rat atria,which was completely blocked by bosentan and G-Re;2.ET-1 significantly increase the levels of m RNA and protein expression of atrial ETRA and ETRB,leading to increased the levels of phosphorylated c PLA2 and expression of NOX4;3.ET-1-induced NOX4 activated NF-κB through phosphorylation of p38 and Akt,thereby increasing the expression of TGF-β1 and Coll 1,MMP2,β-MHC and ANP;4.Result of the Masson staining showed that ET-1 significantly increased the deposition of interstitial collagen;5.G-Re completely blocked the effect of ET-1-induced upregulation of m RNA levels and protein expression of ET receptors,concomitantly with abolition of the upregulation of p-p38,p-Akt,NOX4,p-NF-κB,NOX4,TGF-β1,Coll 1,MMP2,β-MHC and ANP induced by ET-1.The ET-1-increased deposition of interstitial collagen in atria was also dramatically attenuated by G-Re.Conclusions1.G-Re resists ET-1-induced hyper mechanical dynamics and ANP secretion in isolated beating rat atria;2.G-Re alleviates ET-1-induced atrial hypertrophy and fibrosis through inhibition of ETRA and ETRB.