CAJ | 학술논문

我们前期研究表明胰岛素可激活细胞内信号转导机制如磷脂酰肌醇3-激酶-蛋白激酶B-内皮型一氧化氮合酶-一氧化氮(PI3-K-Akt-eNOS-NO)信号通路,减轻心肌缺血/再灌注(ischemia/reperfusion,I/R)损伤,改善缺血后心肌功能恢复.然而c-Jun氨基末端激酶(c-Jun NH2-terminal kinase,JNK)信号通路在胰岛素保护I/R心肌中的作用尚不清楚,本研究旨在探讨JNK信号通路在胰岛素保护I/R心肌中的作用及其与PI3-K/Akt信号通路间的相互关系.离体Sprague-Dawley大鼠心脏缺血30 min后施行2 h或4 h的再灌注,缺血前用LY294002(15 mmol/L)和SP600125(10 mmol/L)灌注15 min,分别阻断PI3-K/Akt和磷酸化JNK(phosphorylated-JNK,p-JNK)活化,观测心脏功能、心肌梗死、细胞凋亡和蛋白磷酸化水平.与对照组相比,胰岛素再灌注2 h后,心率、左心室发展压和左心室收缩/舒张最大速率均明显增加,梗死面积减少约16.1%[(28.9±2.0)%vs(45.0±4.0)%,n=6,P＜0.01],细胞凋亡指数从(27.6±1.3)%减少到(16.0±0.7)%(n=6,P＜0.01),Akt的活性增加1.7倍(n=6,P＜0.05),同时JNK活性增加1.5倍(n=6,P＜0.05).用LY294002处理后,胰岛素对I/R心肌的保护作用消失;而用SP600125处理可增强胰岛素的保护作用,且可部分逆转LY294002的抑制作用.进一步观察发现SP600125减弱了Akt的磷酸化(n=6,P＜0.05).上述结果表明,在I/R心肌中,胰岛素可同时激活PI3-K/Akt及JNK信号通路,且通过后者进一步增加Akt活化,从而减轻I/R损伤,改善心肌功能.这种PI3-K/Akt与JNK信号通路交互机制对胰岛素保护I/R心肌有重要意义.
아문전기연구표명이도소가격활세포내신호전도궤제여린지선기순3-격매-단백격매B-내피형일양화담합매-일양화담(PI3-K-Akt-eNOS-NO)신호통로,감경심기결혈/재관주(ischemia/reperfusion,I/R)손상,개선결혈후심기공능회복.연이c-Jun안기말단격매(c-Jun NH2-terminal kinase,JNK)신호통로재이도소보호I/R심기중적작용상불청초,본연구지재탐토JNK신호통로재이도소보호I/R심기중적작용급기여PI3-K/Akt신호통로간적상호관계.리체Sprague-Dawley대서심장결혈30 min후시행2 h혹4 h적재관주,결혈전용LY294002(15 mmol/L)화SP600125(10 mmol/L)관주15 min,분별조단PI3-K/Akt화린산화JNK(phosphorylated-JNK,p-JNK)활화,관측심장공능、심기경사、세포조망화단백린산화수평.여대조조상비,이도소재관주2 h후,심솔、좌심실발전압화좌심실수축/서장최대속솔균명현증가,경사면적감소약16.1%[(28.9±2.0)%vs(45.0±4.0)%,n=6,P＜0.01],세포조망지수종(27.6±1.3)%감소도(16.0±0.7)%(n=6,P＜0.01),Akt적활성증가1.7배(n=6,P＜0.05),동시JNK활성증가1.5배(n=6,P＜0.05).용LY294002처리후,이도소대I/R심기적보호작용소실;이용SP600125처리가증강이도소적보호작용,차가부분역전LY294002적억제작용.진일보관찰발현SP600125감약료Akt적린산화(n=6,P＜0.05).상술결과표명,재I/R심기중,이도소가동시격활PI3-K/Akt급JNK신호통로,차통과후자진일보증가Akt활화,종이감경I/R손상,개선심기공능.저충PI3-K/Akt여JNK신호통로교호궤제대이도소보호I/R심기유중요의의.
Our previous results have demonstrated that insulin reduces myocardial ischemia/reperfusion (MI/R) injury and increases the postischemic myocardial functions via activating the cellular survival signaling, i.e., phosphatidylinositol 3-kinase (PI3-K)-Akt-endothelial nitric oxide synthase (eNOS)-nitric oxide (NO) cascade. However, it remains largely controversial whether c-Jun NH2-terminal kinase (JNK) is involved in the effects of insulin on MI/R injury. Therefore, the aims of the present study were to investigate the role of JNK, especially the cross-talk between JNK and previously expatiated Akt signaling, in the protective effect of insulin on I/R myocardium. Isolated hearts from adult Sprague-Dawley rats were subjected to 30 min of regional ischemia and followed by 2 or 4 h of reperfusion (n=6). The hearts were pretreated with PI3-K inhibitor LY294002, or phosphorylated-JNK inhibitor SP600125,respectively, then perfused retrogradely with insulin, and the mechanical functions of hearts, including the heart rate (HR), left ventricular developed pressure (LVDP) and instantaneous first derivation of left ventricular pressure (±LVdp/dtmax) were measured. At the end of reperfusion, the infarct size (IS) and apoptotic index (AI) were examined. MI/R caused significant cardiac dysfunction and myocardial apoptosis (strong TUNEL-positive staining). Compared with the control group, insulin treatment in MI/R rats exerted protective effects as evidenced by reduced myocardial IS [(28.9±2.0)% vs (45.0±4.0)%, n=6, P＜0.01 ], inhibited cardiomyocyte apoptosis [decreased AI: (16.0±0.7)% vs (27.6±1.3)%, n=6, P＜0.01] and improved recovery of cardiac systolic/diastolic function (including LVDP and ±LVdp/dtmax) at the end of reperfusion. Moreover, insulin resulted in 1.7-fold and 1.5-fold increases in Akt and JNK phosphorylation in I/R myocardium, respectively (n=6, P＜0.05). Inhibition of Akt activation with LY294002 abolished, and inhibition of JNK activation with SP600125 enhanced the cardioprotection by insulin, respectively. And the abolishment by LY294002could be partly converted by SP600125 pretreatment. In addition, SP600125 also decreased the Akt phosphorylation (n=6, P＜0.05).These results demonstrate that insulin simultaneously activates both Akt and JNK, and the latter further increases the phosphorylation of Akt which attenuates MI/R injury and improves heart function; this cross-talk between Akt and JNK in the insulin signaling is involved in insulin-induced cardioprotective effect.