title: Angiotensin II-dependent Src and Smad1 signaling pathway is crucial for the development of diabetic nephropathy.
abstract: Angiotensin II (Ang II) is known to play a pivotal role in the development of diabetic nephropathy. However, the precise mechanism of Ang II-mediated effects on diabetic nephropathy is still unknown. We have reported that Smad1 plays a key role in diabetic mesangial matrix expansion and directly regulates the transcription of type IV collagen (Col4) in vitro and in vivo. Here we examined the effect of Ang II on the expression of Smad1 and mesangial matrix expansion in streptozotocin (STZ)-induced diabetic rats in vivo, using Ang II type 1 receptor blocker, olmesartan. We also examined the signaling mechanism by which Ang II induces mesangial matrix expansion in vitro. Treatment of diabetic rats with low-dose olmesartan for 20 weeks reduced albuminuria and hyperfiltration without affecting blood pressure and inhibited mesangial matrix expansive changes and the expression of Col4 and smooth muscle alpha actin compared with those in untreated rats. Immunohistochemical staining and Western blotting showed that the increased expression of Smad1, phospho-Smad1, and phospho-Src was inhibited by olmesartan. Ang II induced Col4 synthesis and increased expression of phospho-Src and phospho-Smad1 in cultured mesangial cells, which was blocked by olmesartan. PP2, a Src tyrosine kinase inhibitor, and overexpression of dominant negative Src also reduced the phosphorylation of Smad1. Moreover, addition of small-interfering RNA against Src significantly reduced the phosphorylation of Smad1 and synthesis of Col4. Taken together, these results indicate that Ang II can regulate the development of mesangial matrix expansion in the early phase of diabetic nephropathy through Src and Smad1.
authors.affiliation: Department of Nephrology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Mima
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsubara
authors.forename: Hidenori
authors.initials: H
authors.lastname: Arai
authors.forename: Hideharu
authors.initials: H
authors.lastname: Abe
authors.forename: Kojiro
authors.initials: K
authors.lastname: Nagai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kanamori
authors.forename: Eriko
authors.initials: E
authors.lastname: Sumi
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Takahashi
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Iehara
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukatsu
authors.forename: Toru
authors.initials: T
authors.lastname: Kita
authors.forename: Toshio
authors.initials: T
authors.lastname: Doi
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers; D000818:Animals; D002070:Butadienes; D002460:Cell Line; D024141:Collagen Type IV / Q000096:biosynthesis; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D003928:Diabetic Nephropathies / Q000378:metabolism*; D015870:Gene Expression; D005920:Glomerular Mesangium / Q000378:metabolism; D007093:Imidazoles; D008297:Male; D050527:Mesangial Cells / Q000378:metabolism*; D009570:Nitriles; D010766:Phosphorylation; D011743:Pyrimidines; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D051898:Smad1 Protein / Q000378:metabolism*; D013777:Tetrazoles; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: C412373:AG 1879; D047228:Angiotensin II Type 1 Receptor Blockers; D002070:Butadienes; D024141:Collagen Type IV; D007093:Imidazoles; D009570:Nitriles; D011743:Pyrimidines; D034741:RNA, Small Interfering; D051898:Smad1 Protein; C497400:Smad1 protein, rat; D013777:Tetrazoles; C113580:U 0126; D000804:Angiotensin II; C437965:olmesartan; D019061:src-Family Kinases