Shihab F S, Yi H, Bennett W M, Andoh T F
Divisions of Nephrology, University of Utah Health Sciences Center, Salt Lake City, Utah, USA.
Kidney Int. 2000 Sep;58(3):1174-85. doi: 10.1046/j.1523-1755.2000.00273.x.
Chronic cyclosporine (CsA) nephrotoxicity is characterized by interstitial fibrosis and afferent arteriolar hyalinosis. L-arginine (L-Arg), the substrate for nitric oxide (NO) synthase and N-nitro-L-arginine-methyl ester (L-NAME), the NO synthase inhibitor, were shown to modulate acute CsA nephrotoxicity. However, the mechanism of fibrosis in chronic CsA nephrotoxicity remains unclear. Thus, we examined the effect of NO modulation on fibrosis and the expression of transforming growth factor-beta1 (TGF-beta1) and matrix proteins in chronic CsA nephrotoxicity.
Rats were administered CsA (7.5 mg/kg), CsA + L-Arg (1.7 g/kg), CsA + L-NAME (3.5 mg/kg), vehicle (VH), VH + L-Arg, and VH + L-NAME, and were sacrificed at 7 or 28 days. NO production, physiologic parameters, and histology were studied in addition to the mRNA expression of TGF-beta1, plasminogen activator inhibitor-1 (PAI-1) and the matrix proteins biglycan and collagens type I and IV by Northern and the protein expression of PAI-1 and fibronectin by enzyme-linked immunosorbent assay.
While L-NAME strikingly reduced NO biosynthesis and worsened the glomerular filtration rate and CsA-induced fibrosis, L-Arg had the opposite beneficial effect. In addition, the CsA-induced up-regulated expression of TGF-beta1, PAI-1, and the matrix proteins biglycan, fibronectin, and collagen I was significantly increased with L-NAME and strikingly improved with L-Arg. Collagen IV expression was not affected. Also, NO modulation did not affect VH-treated rats.
Chronic CsA nephrotoxicity can be aggravated by NO blockade and ameliorated by NO enhancement, suggesting that NO maintains a protective function. NO modulation was associated with a change in TGF-beta1 expression, which, in turn, was associated with alterations in matrix deposition and matrix degradation through its effect on PAI-1.
慢性环孢素（CsA）肾毒性的特征为间质纤维化和入球小动脉玻璃样变。L-精氨酸（L-Arg）作为一氧化氮（NO）合酶的底物，以及NO合酶抑制剂N-硝基-L-精氨酸甲酯（L-NAME），已被证明可调节急性CsA肾毒性。然而，慢性CsA肾毒性中纤维化的机制仍不清楚。因此，我们研究了NO调节对慢性CsA肾毒性中纤维化以及转化生长因子-β1（TGF-β1）和基质蛋白表达的影响。
给大鼠分别注射CsA（7.5mg/kg）、CsA + L-Arg（1.7g/kg）、CsA + L-NAME（3.5mg/kg）、赋形剂（VH）、VH + L-Arg和VH + L-NAME，并在7天或28天时处死。除了通过Northern印迹法研究TGF-β1、纤溶酶原激活物抑制剂-1（PAI-1）以及基质蛋白双糖链蛋白聚糖和I型及IV型胶原的mRNA表达，通过酶联免疫吸附测定法研究PAI-1和纤连蛋白的蛋白表达外，还研究了NO生成、生理参数和组织学情况。
L-NAME显著降低NO生物合成，并使肾小球滤过率和CsA诱导的纤维化恶化，而L-Arg则具有相反的有益作用。此外，L-NAME使CsA诱导的TGF-β1、PAI-1以及基质蛋白双糖链蛋白聚糖、纤连蛋白和I型胶原的表达上调显著增加，而L-Arg则使其显著改善。IV型胶原表达未受影响。而且，NO调节对VH处理的大鼠没有影响。
慢性CsA肾毒性可因NO阻断而加重，因NO增强而改善，这表明NO具有保护作用。NO调节与TGF-β1表达的变化相关，而TGF-β1表达的变化又通过其对PAI-1的作用与基质沉积和基质降解的改变相关。
