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- Title
Enhanced TGF-b/Smad signaling in the early stage of diabetic nephropathy is independent of the AT1a receptor.
- Authors
Okazaki, Yuko; Yamasaki, Yasushi; Uchida, Haruhito A.; Okamoto, Kazunori; Satoh, Minoru; Maruyama, Keisuke; Maeshima, Yohei; Sugiyama, Hitoshi; Sugaya, Takeshi; Kashihara, Naoki; Makino, Hirofumi
- Abstract
Angiotensin II (AII) and transforming growth factor-β (TGF-β) are closely involved in the pathogenesis of diabetic nephropathy (DN). AII is known to induce TGF-β production in resident renal cells, including glomerular mesangial cells and tubular epithelial cells. TGF-β receptor types I and II (TGF-βRI, II) are up-regulated in the diabetic kidney. The aim of this study was to clarify the role of AII in the regulation of the TGF-β system in the early stage of DN using AII type1a receptor-deficient(AT1a−/−) mice. We investigated the expression of TGF-β1, TGF-βRI, II, and Smad signaling in AT1a−/− mice with streptozotocin (STZ)-induced DN. Mice were killed 10 and 20 days after the induction of hyperglycemia. The expression of TGF-β receptors was analyzed by immunohistochemical staining and reverse transcriptase–polymerase chain reaction (RT–PCR). TGF-β-specific Smad signaling was analyzed by electrophoretic mobility shift assay and Western blotting. The expression of both TGF-βRI and RII was up-regulated in the glomerular tufts and vasculature in diabetic AT1a+/+ mice kidney by immunohistochemistry. RT–PCR revealed that mRNAs for TGF-βRI and RII were also up-regulated. Smad2 and 4 protein levels were reduced in the renal cortex after the induction of diabetes, with an increase of Smad 3/4 complex in the nucleus. The expression of TGF-β receptors increased in both diabetic AT1a−/− and AT1a+/+ mice. Smad signaling in AT1a−/− mice was also enhanced. Our results suggest that the complete blockade of the AT1a-mediated pathway has a minimal effect on the enhanced TGF-β/Smad signaling in the early stage of DN, at least in the AT1a−/− model.
- Subjects
DIABETIC nephropathies; TRANSFORMING growth factors; ANGIOTENSIN II; STREPTOZOTOCIN; EPITHELIAL cells
- Publication
Clinical & Experimental Nephrology, 2007, Vol 11, Issue 1, p77
- ISSN
1342-1751
- Publication type
Article
- DOI
10.1007/s10157-006-0456-1