神经型一氧化氮合酶调控谷氨酰胺转氨酶2抑制心力衰竭模型大鼠心脏收缩功能的作用机制

The mechanism of transglutaminase 2 regulated by neuronal nitric oxide synthase inhibiting systolic function in rats heart failure model

[目的]探讨神经型一氧化氮合酶(nNOS)调控谷氨酰胺转氨酶2(TG2)抑制心力衰竭心脏收缩功能的作用机制.[方法]向渗透压泵储药仓内注入血管紧张素Ⅱ后植入于大鼠背部颈后皮下组织,灌注速度为125 ng/(min·kg),制作高血压诱导的心力衰竭模型.假手术组进行同样的手术,但不植入胶囊渗透压泵.[结果]与假手术组比较,心力衰竭组左心室射血分数LVEF(P=0.03)与左心室缩短分数(P=0.04)均明显降低,心肌细胞收缩时肌节缩短长度明显降低(P<0.001),TG2活性及三磷酸腺苷含量均明显降低(P<0.01).应用TG2活性抑制剂(Cystamine,500μmol/L)后,假手术组的心肌细胞收缩时肌节缩短长度明显下降(P<0.05);心力衰竭组nNOS蛋白表达水平升高,心肌细胞内TG2-SNO/TG2比值升高(P<0.05),给予nNOS抑制剂SMTC后恢复至正常水平(P<0.05).使用SMTC或L-VNIO(100μmol/L)抑制假手术组及心力衰竭组细胞内nNOS活性后,心肌细胞内TG2活性升高(对照组分别与SMTC、L-VNIO比较,P<0.05),先应用L-VNIO(100μmol/L)抑制心力衰竭组心肌细胞中nNOS活性,心肌细胞的肌节收缩幅度增加(P<0.05),再追加TG2活性抑制剂(Cystamine,500μmol/L)抑制心肌细胞中TG2活性,结果显示心肌细胞的肌节收缩幅度被抑制(P<0.05);相反,先应用Cystamine再追加L-VNIO时心肌细胞的肌节长度未发生改变(Cystamine,P>0.05;Cystamine+L-VNIO,P>0.05).[结论]心力衰竭模型大鼠心肌细胞内nNOS增多可抑制TG2活性,从而导致心肌细胞肌节缩短长度降低,认为其可能是导致心功能降低的原因.

OBJECTIVE To investigate the mechanism of transglutaminase 2(TG2)regulated by neuronal nitric oxide synthase(nNOS)inhibiting cardiac systolic function in heart failure.METHODS AngiotensinⅡwas injected into the drug storage chamber of the osmotic pump,then the osmotic pump was implanted into the subcutaneous tissue of the posterior neck of rat at the infusion rate of 125 ng/(min·kg)to make the hypertension-induced heart failure model.The sham operation group was performed the same operation,but did not implant the osmotic pump capsule.RESULTS Compared with the sham operation group,left ventricular ejection fraction(P=0.03)and left ventricular shortening fraction(P=0.04)were significantly decreased,and the length of sarcomere shortening was significantly decreased during the contraction of cardiomyocytes(P<0.001),TG2 activity and adenosine triphosphate content were significantly lower(P<0.01)in the heart failure group.After the application of TG2 activity inhibitor(Cystamine,500μmol/L),the length of sarcomere shortening was significantly decreased during the contraction of cardiomyocytes in the sham operation group(P<0.05),the level of nNOS was increased in the heart failure group,and the ratio of TG2-SNO/TG2 in cardiomyocytes was increased(P<0.05)and returned to the normal level after administration of the nNOS inhibitor SMTC(P<0.05).After the use of SMTC or L-VNIO(100μmol/L)in the sham operation group and heart failure group to inhibit the activity of intracellular nNOS,the activity of TG2 in cardiomyocytes was increased(control group vs.SMTC and L-VNIO respectively,P<0.05).First,L-VNIO(100μmol/L)was applied to inhibit the nNOS activity of cardiomyocytes in the heart failure group,and the sarcomere contraction amplitude of cardiomyocytes was increased(P<0.05),then,the TG2 inhibitor(Cystamine,500μmol/L)was added to inhibit TG2 activity in cardiomyocytes,the results showed that the sarcomere contraction amplitude of cardiomyocytes was inhibited(P<0.05).On the contrary,the sarcomere length of cardiomyocytes did not change when Cystamine was firstly applied and L-VNIO was added(Cystamine,P>0.05,Cystamine+L-VNIO,P>0.05).CONCLUSION The increase of nNOS in cardiomyocytes could inhibit TG2 activity in rat heart failure model,resulting in the reduction of sarcomere shortening length of cardiomyocytes,which may be the cause of the decrease of cardiac function.