Treatment with anti-TGF-β antibody ameliorates chronic progressive nephritis by inhibiting Smad/TGF-β signaling

Treatment with anti-TGF-β antibody ameliorates chronic progressive nephritis by inhibiting Smad/TGF-β signaling. Background Although short-term treatment with anti-transforming growth factor-β (TGF-β) antibody (αT) has been shown to prevent early glomerular lesions, its long-term effects and molecular mechanisms, including intracellular signaling, remain poorly understood. We examined whether αT treatment induces prevention of renal insufficiency and fibrosis, and affects the TGF-β/Smad signaling pathway in rats with chronic progressive anti-thymocyte serum (ATS) nephritis induced by repeated ATS injections on days 0 and 7. Methods Nephritic and non-nephritic rats were treated with either αT or control immunoglobulin (Ig)G twice weekly for 4weeks from days 7 to 35 (each group, N = 21). Renal lesions and cortical expression of TGF-β1, TGF-β2, TGF-β3, type II TGF-β receptor (TβRII), Smads, type I collagen, and plasminogen activator inhibitor-1 were examined by immunohistochemistry, Western blot, and/or real-time reverse transcription polymerase chain reaction (RT-PCR). The binding of Smad3 in renal cortical cell nuclei to the Smad-binding element (SBE) was investigated by the electrophoretic mobility shift assay. Results Nephritic rats developed heavy proteinuria, renal insufficiency, and increased extracellular matrix deposition resulting in renal fibrosis. Cortical expression levels of TGF-β1, TGF-β2, TβRII, and Smad2, but not TGF-β3, Smad3, and Smad4 were increased. Expression and preferential localization of phosphorylated Smad2/3 in the glomerular and tubular cell nuclei, and Smad3-SBE complex-forming activity were also increased. Four-week αT treatment resulted in marked amelioration of chronic progressive ATS nephritis at 8weeks. Conclusion In chronic progressive ATS nephritis, the TGF-β/Smad signaling was up-regulated. TGF-β blockade by αT suppressed the progression of renal scarring, at least in part, via inhibition of activated TGF-β/Smad signaling.