Haraguchi M, Border W A, Huang Y, Noble N A
Fibrosis Research Laboratory, Division of Nephrology, University of Utah, Salt Lake City, Utah 84108, USA.
Kidney Int. 2001 Jun;59(6):2146-55. doi: 10.1046/j.1523-1755.2001.00729.x.
In addition to its well-known role in degrading fibrin, recent evidence suggests that plasmin degrades matrix proteins and activates prometalloproteinases. Plasmin is generated from plasminogen by tissue plasminogen activator (t-PA). We hypothesized that t-PA treatment increases plasmin generation in nephritic glomeruli and degrades pathological matrix leading to a therapeutic reduction in matrix accumulation.
Anti-Thy-1 nephritis was induced by injection of OX-7 antibody. Rats were given twice daily intravenous injections of saline (disease control group) or human recombinant t-PA (rt-PA; 1 mg/kg body weight) on days 3 through 5. Proteinuria, glomerular matrix protein staining, and glomerular mRNA levels for transforming growth factor-beta 1 (TGF-beta 1), fibronectin, and plasminogen activator inhibitor type 1 (PAI-1) were evaluated at day 6. Localization of rt-PA, plasmin generation by glomeruli in vitro, and glomerular production and content of active TGF-beta1 were also investigated.
Compared with disease control animals, proteinuria and staining score for periodic acid-Schiff (2.75 +/- 0.17 vs. 1.41 +/- 0.09), fibronectin-EDA+ (19 +/- 2 vs. 14 +/- 1), laminin (35 +/- 2 vs. 25 +/- 2), type I collagen (33 +/- 1 vs. 21 +/- 3), and type IV collagen (27 +/- 2 vs. 23 +/- 1) were significantly reduced in treated rats (P < 0.01). Glomerular TGF-beta 1, fibronectin, and PAI-1 mRNA levels were unchanged. rt-PA colocalized with fibrin along glomerular capillary walls and in the mesangium. Nephritic glomeruli in vitro had decreased plasmin activity, which was elevated by an in vivo presacrifice injection of rt-PA. Glomerular production and content of active TGF-beta 1 were unchanged by the rt-PA injection.
: These results show that injected rt-PA binds to fibrin in nephritic glomeruli, thus increasing plasmin generation and promoting pathological matrix degradation without activating latent TGF-beta. Agents that increase plasmin generation, such as t-PA, may have potential as antifibrotic therapies.
除了其在降解纤维蛋白方面的知名作用外，最近的证据表明纤溶酶还能降解基质蛋白并激活前基质金属蛋白酶。纤溶酶由组织纤溶酶原激活物（t-PA）从纤溶酶原生成。我们推测t-PA治疗可增加肾炎性肾小球中的纤溶酶生成，并降解病理性基质，从而导致基质积聚的治疗性减少。
通过注射OX-7抗体诱导抗Thy-1肾炎。在第3至5天，大鼠每天接受两次静脉注射生理盐水（疾病对照组）或人重组t-PA（rt-PA；1mg/kg体重）。在第6天评估蛋白尿、肾小球基质蛋白染色以及转化生长因子-β1（TGF-β1）、纤连蛋白和纤溶酶原激活物抑制剂1型（PAI-1）的肾小球mRNA水平。还研究了rt-PA的定位、体外肾小球的纤溶酶生成以及活性TGF-β1的肾小球产生和含量。
与疾病对照动物相比，治疗组大鼠的蛋白尿和高碘酸-希夫染色评分（2.75±0.17对1.41±0.09）、纤连蛋白-EDA+（19±2对14±1）、层粘连蛋白（35±2对25±2）、I型胶原（33±1对21±3）和IV型胶原（27±2对23±1）显著降低（P<0.01）。肾小球TGF-β1、纤连蛋白和PAI-1 mRNA水平未改变。rt-PA与纤维蛋白在肾小球毛细血管壁和系膜中共定位。体外肾炎性肾小球的纤溶酶活性降低，而体内注射rt-PA进行预处死可提高该活性。rt-PA注射后，活性TGF-β-1的肾小球产生和含量未改变。
这些结果表明，注射的rt-PA与肾炎性肾小球中的纤维蛋白结合，从而增加纤溶酶生成并促进病理性基质降解，而不激活潜伏的TGF-β。增加纤溶酶生成的药物，如t-PA，可能具有作为抗纤维化疗法的潜力。
