钙调神经磷酸酶在L-精氨酸抗心肌肥厚中的作用

目的研究L-精氨酸抗右心室心肌肥厚作用及其与钙调神经磷酸酶(calcineurin,CaN)信号通路的关系。方法利用野百合碱(monocrotaline,MCT)诱导大鼠右心室心肌肥厚模型和前列腺素F2α(prostaglandin F2α,PGF2α)诱导心肌细胞肥大模型,分别以右心室肥厚指数(right ventricle hypertro-phy index,RVHI,即右心室/左心室+室间隔)、心肌细胞直径、蛋白含量和心房利钠肽(atrial natriuretic peptide,ANP)mRNA表达为心肌肥厚指标。用RT-PCR法检测mRNA的表达;Western blot法检测蛋白表达;荧光法检测细胞内钙Ca2+]i的变化情况。结果L-精氨酸200mg.kg-1.d-1预防和治疗给药均明显抑制MCT诱导的大鼠心肌肥厚,降低MCT所致心肌CaN mRNA和蛋白及其下游因子NFAT3及GATA4蛋白表达的增加。L-精氨酸1mmol.L-1也明显抑制PGF2α100nmol.L-1诱导的大鼠心肌细胞肥大和Ca2+]i升高,阻遏其诱导的CaN mRNA及CaN-,NFAT3-,GATA4-蛋白表达升高。在体和离体实验中一氧化氮合成酶抑制剂NG-硝基-L-精氨酸-甲酯均可完全阻断L-精氨酸的作用。结论L-精氨酸可能通过降低Ca2+]i,从而抑制CaN信号转导通路而产生抗右心室心肌肥厚作用。

Role of calcineurin signal transduction pathway in the inhibition of cardiac hypertrophy by L-arginine in vivo and in vitro

Aim To study the role of calcineurin signal transduction pathway in the anti-hypertrophic effect of L-arginine in vivo and in vitro.Methods The hypertrophic effects was assayed by calculating the right ventricular hypertrophy index(RVHI=right ventricle weight/left ventricle and septum weight),and atrial natriuretic peptide(ANP)mRNA expression in rat right ventricle hypertrophy model induced by monocrotaline(MCT) or by measuring the cell diameter,protein content,and ANP mRNA expression in hypertrophic cardiomyocyte induced by prostaglandin F2α(PGF2α).For mechanism studies,the intracellular free calcium concentration(Ca2+]i) in cultured cardiomyocytes was measured by using Fura 2/AM as a fluorescent indicator.ANP and CaN mRNA expressions,and expressions of CaN and its downstream effectors,NFAT3 and GATA4 proteins were assayed by RT-PCR and Western blot,respectively,in vivo and in vitro.Results In MCT-hypertrophic model,prevention-and treatment-administration of L-arginine,a nitric oxide(NO) precursor,200 mg·kg-1·d-1,could obviously inhibit the elevated RVHI and ANP mRNA expression;similar to that found in vivo.Addition of L-arginine 1 mmol·L-1 could markedly inhibit the increased cell diameter,protein content and the expression of ANP mRNA in the hypertrophic cardiomyocyte induced by PGF2α 100 nmol·L-1,and it could also decrease the elevated Ca2+]i in vitro;notably,the above dose or concentration of L-arginine could blunt the elevated expressions of calcineurin mRNA and the calcineurin-,NFAT3-,GATA4-proteins induced by MCT or by PGF2α.These effects of L-arginine were blocked by NG-nitro-L-arginine-methyl ester,a NO synthase inhibitor,in vivo and in vitro.Conclusion These results suggest that calcineurin signal transduction pathway may play an important role in the NO-induced inhibition of cardiac hypertrophy.The anti-hypertrophic effects of L-arginine may involve the decrease of Ca2+]i,and then inhibit the activated calcineurin pathway,through the release of NO.