血管紧张素Ⅱ与其介导的蛋白质酪氨酸激酶JAK2信号通路在缺血再灌注肾损伤时小管上皮细胞逆向分化中的作用

Role of angiotensin Ⅱ and JAK2 signal pathway in transdifferentation of renal tubular cells in mice after acute ischemic followed by reperfusion

目的探讨血管紧张素（Ang）Ⅱ与其介导的蛋白酪氨酸激酶JAK2信号通路在急性缺血再灌注肾损伤模型中发生的肾小管上皮细胞逆向分化的作用机制。方法（1）建立Wistar大鼠急性缺血再灌注肾损伤模型，采用放射免疫法检测肾脏局部AngⅡ的水平变化，采用免疫组织化学ABC法和RT—PCR，观察间充质细胞表面标记α-平滑肌肌动蛋白（α-SMA）的表达。（2）模拟高、中、低浓度的肾素-血管紧张素系统（RAS）环境，体外观察培养的肾小管上皮细胞（NRK-52E）逆向分化的情况。（3）先后阻断AngⅡ受体（AT2R）及其介导的AngⅡ信号转导通路的JAK2，研究AngⅡ与JAK2通路对肾小管上皮细胞逆向分化的影响。结果（1）肾脏缺血再灌注损伤后0、24、48、72、96、120h，局部AngⅡ含量持续增高，分别为（406．7±106．1）、（463．0±112．9）、（526．6±128．3）、（649．5±131．5）、（875．g±150．2）、（980．8±155．2）ng／L，P〈0．05。（2）缺血再灌注后48h，肾小管上皮细胞开始表达α-SMA mRNA及蛋白质。（3）高浓度（10^-7mol／L）AngⅡ刺激可诱导体外培养的肾小管上皮细胞表达α—SMA，且呈剂量和时间依赖性。10^-9mol／L浓度AngⅡ刺激30min时，α-SMA表达水平最高。无论是阻断AT2R抑或JAK2信号通路，肾小管上皮细胞表达α-SMA均明显受到抑制。结论急性缺血再灌注损伤时肾小管上皮细胞可向间充质细胞逆向分化，局部RAS启动与其密切相关。AngⅡ可能通过AT2R及其介导的JAK2信号通路促发肾小管细胞的逆向分化。

Objective To investigate the effect of angiotensin （Ang） Ⅱ and its Janns-aetivated kinase-2 （JAK2） signal pathway in transdifferentiation of renal tubular cells under the challenge of acute ischemie reperfusion injury. Methods Models of acute isehemie repeffusion injury were established and the level of local Ang Ⅱ , a key element of renin-angiotensin system （RAS）, in kidney was measured using radioimmunity technique. The expression of or-smooth muscle aetin （ α-SMA）, a phenotype of mesenehymal cells, was detected by RT-PCR and immunohistoehemistry methods. Renal tubule cells （NRK-52E）were cultured with various concentration of Ang Ⅱ, followed by blocking of PD123319, Ang Ⅱ receptor 2 antagonist, and AG490, an inhibitor of JAK2 signal pathway. Results Ang Ⅱ of kidney tissue increased immediately after acute isehemie-repeefusion injury, in time dependent fashion. Expression of α-SMA in renal tubule cells was found at 48 hours after isehemic-reperfasion injury and in NRK-52E cells treated by high concentration of Ang Ⅱ and was dose and time dependent. The peak of α-SMA expression was seen after 30 minute treatment at the dose of 10^-9 tool/L, which was interrupted by both of PD123319 and AG490. Conclusions Transdifferentiation of renal tubular epithelial cells occurs under acute isehemieeperfusion injury. Local renin-angiotensin system may play a role in the transdifferentiation of TEC through AT2 receptor and its JAK2 signal pathway.