血管紧张素Ⅱ诱导肾小球IQGAP1表达改变及细胞凋亡

AngiotensinⅡ promotes the expression of glomerular IQGAP1 and apoptosis of glomerular cells

目的研究血管紧张素Ⅱ（AngⅡ）输注对大鼠肾小球rasGTP酶活化蛋白（IQGAP1）表达及细胞凋亡的影响，探讨IQGAP1在AngⅡ诱导肾小球细胞凋亡中的作用。方法36只雄性Wistar大鼠按随机数字法分为正常对照组、生理盐水输注组和AngⅡ输注组，每隔7d测量大鼠血压及尿蛋白量。分别于实验第14天、第28天处死动物取。肾，PAS染色观察肾组织病理学改变；免疫组化、免疫荧光法观察IQGAP1在肾小球的表达及分布；Western印迹法检测。肾组织IQGAP1、半胱氨酸蛋白酶3（caspase．3）及细胞外调节蛋白激酶1／2（ERK1／2）蛋白表达；TUNEL法检测肾小球细胞凋亡。结果AngⅡ输注组大鼠血压升高，实验第14天达峰值并维持在较高水平；第7天出现蛋白尿，且随时间的延长尿蛋白量持续增加，与对照组比较，差异有统计学意义（P〈0．05）。AngⅡ输注组出现轻度系膜细胞增殖和系膜基质增加，生理盐水输注组和正常对照组均未见明显病理改变。TUNEL检测结果显示，AngⅡ输注后肾小球细胞凋亡显著增加；Western印迹发现，AngⅡ输注组大鼠肾小球caspase．3活化明显增加，与对照组比较，差异有统计学意义（P〈0．05）。正常对照组IQGAP1呈低水平表达并沿毛细血管袢线性分布，AngⅡ输注后IQGAP1表达量显著增加（P〈0．05），且其蛋白表达量与caspase-3活化量呈正相关（r=0．689，P〈0．05）。与对照组比较，AngⅡ输注组磷酸化的ERK1／2（p-ERK1／2）表达量显著增加（P〈0．05），且与IQGAP1蛋白表达呈正相关（r=0．658，P〈0．05）。结论IQGAP1表达上调可能通过激活ERK1/2信号通路参与AngⅡ诱导肾小球细胞凋亡的病理过程。

Objective To evaluate the effects of Ang Ⅱ on the expression of IQ domain GTPase- activating proteinl （IQGAP1） and apoptosis of glomerular cells, and to explore the role of IQGAP1 in Ang Ⅱ - induced apoptosis of glomerular cells. Methods Thirty - six male Wistar rats were randomIy assigned to receive either saline or Ang Ⅱ by osmotic mini-pump, or be used as normal control. The systolic blood pressure and proteinuria were measured at day 7, 14, 21, 28. After the animals were sacrificed at day 14, 28 respectively, the kidneys were collected. Renal pathological change, glomerular cell apoptosis were observed. The expression of glomerular IQGAP1 was assessed by immunohistochemistry, immunofluorescence and Western blotting. The activation of caspase-3 andphosphorylation of extracellular regulated protein kinases 1 and 2 （ERK1/2） were determined by Western blotting. Results Ang Ⅱ-infused rats developed significant hypertension and marked proteinuria. Mild glomerular mesangial cell proliferation and mesangial matrix increase were also observed in Ang Ⅱ- infused rats. The number of apoptotic glomernlar cells in Ang Ⅱ -infused rats was significantly more than that in normal control （P 〈 0.05）. The expression of IQGAP1 in glomernli distributed linearly along the capillary loops. Ang Ⅱ infusion up-regulated the expression of glomerular IQGAP1, which had an siguificantly positive correlation with activation of caspase-3（r = 0.689, P 〈 0.05） and phosphorylation of ERK1/2 （r = 0.658, P 〈 0.05）. Conclusion The enhanced expression of IQGAPI may be involved in Ang Ⅱ -induced glomerular cells apoptosis via activation of ERK1/2 signaling pathway.