REGULATION OF TGF-β AND ITS SIGNAL MOLECULE, SMAD, FOR ATTENUATION OF GLOEMRULAR DISEASE.

TGF-β1在包括肾小球硬化和肾纤维化的纤维化疾病中起病理作用。Smads已被确定为TGF-β细胞内信号传导的关键成分。本研究探讨了TGF-β1对大鼠系膜细胞Smad活性的影响。在系膜细胞中，TGF-β1而不是BMP-7诱导Smad 2磷酸化。相反，BMP-7，而不是TGF-β1，诱导BMP相关Smads的磷酸化。TGF-β1以剂量和时间依赖的方式刺激Smad 2的磷酸化。腺病毒介导的基因转移、Smad 2和Smad 4的双重过表达诱导了TGF-β1刺激的纤溶酶原激活物抑制剂-1（派-1）的表达。Smad 7（Smad 6）的过表达可阻断TGF-β1诱导的派-1表达，并通过抑制Smad 2磷酸化逆转TGF-β1抑制的细胞增殖。在使用Thy-1肾炎的实验性肾小球肾炎中，Smad 2磷酸化以与肾小球基质扩张相似的方式瞬时显著增加。在受损的肾小球中观察到磷酸化的Smad 2。这些结果提示，Smad蛋白在体内外肾小球系膜细胞中均存在，并作为TGF-β的信号分子发挥作用。我们的研究结果表明，Smad活性的调节可能会减弱肾小球硬化和纤维化的发展

TGF-β1 plays a pathological role in fibrotic diseases including glomerulosclerosis and renal fibrosis. Smads have been identified as pivotal components in TGF-β intracellular signaling. The present study was carried out to investigate TGF-β1-induced Smad activation in cultured mesangial cells and experimental mesangioproliferative glomerulonephritis in rats. In mesangial cells, TGF-β1, but not BMP-7, induced phosphorylation of Smad2. In contrast, BMP-7, but not TGF-β1, induced phosphorylation of BMP-related Smads. TGF-β1 stimulated the phosphorylation of Smad2 in a dose- and time-dependent manner. Gene transfer using Adenovirus-vector, double-overexpression of Smad2 and Smad4 induced TGF-β1-stimulated plasminogen activator inhibitor-1 (PAI-1) expression more than overexpression of each Smad alone. Furthermore, overexpression of Smad7, one of inhibitory Smads, but not Smd6, blocked TGF-β1-induced PAI-1 expression and reversed TGF-β1-inhibited cell proliferation by inhibiting Smad2 phosphorylation. In experimental glomerulonephritis using Thy-1 nephritis, Smad2 phosphorylation increased transiently and significantly in a similar manner to glomerular matrix expansion. Phosphorylated Smad2 was observed in the damaged glomeruli. These results suggested that Smad proteins are present and act as signaling molecule of TGF-β in mesangial cells in vitro and in vivo. Our results indicate the possibility that modulation of Smad activity may attenuate the development of glomerulosclerosis and fibrosis