Bellini Maria H, Coutinho Enia L, Filgueiras Thelma C, Maciel Thiago T, Schor Nestor
Division of Nephrology, Department of Medicine, Universidade Federal de São Paulo, São Paulo, Brazil.
Nephrology (Carlton). 2007 Oct;12(5):459-65. doi: 10.1111/j.1440-1797.2007.00850.x.
Renal ischaemia-hypoxia is a leading cause of acute renal failure, a clinical condition associated with rapid loss of renal function and high rates of mortality. Renal proximal tubular cells are the most severely injured during renal ischaemia, caused by the breakdown of the extracellular matrix of the tubular basement membrane. Endostatin is the C-terminal fragment of collagen XVIII generated by proteolytic cleavage and it is well-known as being an inhibitor of angiogenesis. In vitro, endostatin inhibits endothelial cell proliferation and migration, as well as tubule formation. In vivo, it has a potent inhibitory effect on tumour growth. In this study, we analysed endostatin gene expression in C57BL/6 mouse kidneys subjected to ischaemia/reperfusion.
Ischaemic renal failure was induced via 45 min of bilateral occlusion of the renal artery and vein, followed by 12 h or 24 h of reperfusion. Whole-kidney homogenate and total RNA were extracted for examination by western blot analysis and quantitative polymerase chain reaction. The immunohistological examination revealed increased endostatin expression in injured kidney, mainly in the proximal tubule and collecting ducts.
Endostatin/collagen XVIII mRNA and protein expression increased during ischaemia and within 12 h of reperfusion. In the western blot assay, we identified increased expression of the 30 kDa endostatin-related fragment and of matrix metalloproteinase-9. CD31 was significantly expressed during reperfusion (P < 0.05). Immunohistological examination revealed glomerular and tubulointerstitial expression of endostatin.
These data suggest the local synthesis of a 30 kDa endostatin-related fragment following acute renal failure and suggest its role in the modulation of renal capillary density.
肾缺血缺氧是急性肾衰竭的主要原因，急性肾衰竭是一种与肾功能迅速丧失和高死亡率相关的临床病症。肾近端小管细胞在肾缺血期间受损伤最为严重，这是由肾小管基底膜细胞外基质的破坏所致。内皮抑素是通过蛋白水解裂解产生的胶原蛋白 XVIII 的 C 末端片段，它是众所周知的血管生成抑制剂。在体外，内皮抑素抑制内皮细胞增殖、迁移以及小管形成。在体内，它对肿瘤生长具有强大的抑制作用。在本研究中，我们分析了 C57BL/6 小鼠肾脏在缺血/再灌注后的内皮抑素基因表达。
通过双侧肾动脉和静脉闭塞 45 分钟诱导缺血性肾衰竭，随后再灌注 12 小时或 24 小时。提取全肾匀浆和总 RNA，通过蛋白质印迹分析和定量聚合酶链反应进行检测。免疫组织学检查显示，损伤肾脏中内皮抑素表达增加，主要在近端小管和集合管中。
内皮抑素/胶原蛋白 XVIII 的 mRNA 和蛋白表达在缺血期间以及再灌注 12 小时内增加。在蛋白质印迹分析中，我们鉴定出 30 kDa 内皮抑素相关片段和基质金属蛋白酶 -9 的表达增加。CD31 在再灌注期间显著表达（P < 0.05）。免疫组织学检查显示内皮抑素在肾小球和肾小管间质表达。
这些数据表明急性肾衰竭后局部合成了 30 kDa 内皮抑素相关片段，并提示其在调节肾毛细血管密度中的作用。
