肥厚心肌左心室重构进展中生存信号通路表达的变化

The Effects of Survival Signaling Pathways in Pressure Overload-induced Cardiomyopathy and Heart Failure in Mice

目的探讨生存信号通路细胞外信号调节激酶1/2(ERK1/2)、磷脂酰肌醇3激酶/蛋白激酶B(PI3K/Akt)在压力超负荷诱导的肥厚心肌从代偿到失代偿心力衰竭转变中的动态表达变化及意义。方法 12周龄C57/BL小鼠通过主动脉弓缩窄(TAC)建立心肌肥厚模型,在1、4、8、12、16周时进行高频心脏超声、血流动力学、组织质量检测,RT-PCR半定量测定心房利钠肽(ANP)、B型利钠肽(BNP)、α肌球蛋白重链(α-MHC)、β肌球蛋白重链(β-MHC),Westernblot法检测ERK1/2、Akt、GSK-3β蛋白表达的变化。结果①与对照组比较,缩窄组左心室收缩期、舒张期前壁、后壁厚度、左心室收缩末期、舒张末期内径于术后呈逐渐增加趋势;左心室短轴缩短率于术后12周显著降低(P<0.05)。左心室收缩压及左心室压力上升和下降最大速率于术后4周明显增加,8～12周保持稳定,16周明显下降;左心室舒张末压于术后8周持续增加(均P<0.05);显示心肌由左心室肥厚最终发展为心力衰竭。②与对照组比较,缩窄组心肌组织ANP、β-MHC术后1～16周表达持续增加;而α-MHCmRNA表达持续降低;缩窄组心肌组织磷酸化ERK1/2蛋白水平于术后1～4周明显增加,随后下降(均P<0.05);磷酸化Akt从第8周开始下降,磷酸化GSK-3β从1～8周增加,随后开始下降(均P<0.05);总ERK1/2、Akt、GSK-3β蛋白水平无明显变化。结论 ERK1/2、Akt及GSK3β蛋白下调是压力负荷诱导心肌肥厚向心力衰竭转变发生发展过程中重要的分子机制。

Objective To explore the changes of extracellular signal regulated protein kinase (ERK1/2) and phosphatidylinositol-3-kinase-Akt(PI3K-Akt)which exist in survival signaling pathways happening in the hypertrophic myocardium induced by pressure overload at different time courses and to determine the molecular mechanism in the myocardium from hypertrophy to heart failure. Methods C57/BL wild mice,aged 12 weeks old,were subjected to sham-operation (SH) or transversing aortic constriction (TAC) to establish models of left ventricular hypertrophy. Echocardiographic assessments,hemodynamic determination,organ weight measurement,morphological and histological examination were performed at 1,4,8,12 and 16 weeks after surgery. At the meanwhile mRNA levels of atrial natriuretic peptide (ANP),brain natriuretic peptide (BNP),α-myosin heavy chain (α-MHC),β-myosin heavy chain (β-MHC)were determined by RT-PCR and ERK1/2,Akt and GSK3β levels were detected by Weatern blot. The animals in SH group were given the same tests and then sacrificed at 16 weeks. Results①Compared with those in SH group,LVESd,LVEDd,Awsth,Awdth,Pwsth and Pwdth in TAC group were progressively increased. Meanwhile,Shortening Fraction (FS) significantly decreased at 12-week (P<0.05). LVSP,dp/dtmaxand dp/dtmin in TAC group progressively increased after 4 wks. From 8-12 weeks these parameters maintained stable and then sharply decreased at 16 weeks (all P<0.05). However LVEDP was increased at 8 weeks and there arose significant difference (P<0.05). These echocardiographic and hemodynamic changes indicated a development of LVH eventually progressing towards to heart failure. ② Compared with those in SH group,mRNA levels of ANP and β-MHC were time-dependently increased while α-MHC were time-dependently decreased. Phosphorylation of ERK1/2 was increased at 4 weeks,and then decreased with age of TAC(P<0.05). Phosphorylation of Akt was decresed from 8 weeks(P<0.05). Phosphorylation ofGSK3β was increased from 1-8 weeks,and then decreased from week 12 after TAC(P<0.05). No changes of the levels of total ERK1/2,Akt,GSK-3β were observed. Conclusion Downregulation of ERK1/2,Akt and GSK3β were implicated as important mechanisms in the transition from compensated hypertrophy to heart failure.