title: Role of ERK1/2 and p38 mitogen-activated protein kinases in the regulation of thrombospondin-1 by TGF-beta1 in rat proximal tubular cells and mouse fibroblasts.
abstract: Thrombospondin-1 (TSP-1) inhibits angiogenesis and activates latent TGF-beta1, both of which are strongly associated with progression of renal disease. Recently, it was reported that Smad2 but not Smad3 regulates TSP-1 expression in response to TGF-beta1 in rat tubular epithelial cells as well as in mouse fibroblasts. This study investigated the role of ERK1/2 and p38 mitogen-activated protein kinases (MAPK). TGF-beta1 activated both ERK1/2 and p38 in the rat proximal tubular cell line NRK52E. Blocking ERK1/2 and p38 inhibited TGF-beta1-induced TSP-1 mRNA and protein expression. Next, the cross-talk between Smad2 and ERK1/2 or p38 was examined. Whereas blocking of ERK1/2 or p38 failed to inhibit TGF-beta1-induced Smad2 activation, inhibition of Smad2 by Smad7 overexpression inhibited the phosphorylation of ERK1/2 but not p38 in response to TGF-beta1. Similar results were observed using mouse fibroblasts from Smad2 knockout embryos, in that TGF-beta1 was able to activate p38 but not ERK1/2 in this cell line. In conclusion, TSP-1 expression is regulated by both ERK1/2 and p38 MAPK in rat proximal tubular cells and mouse fibroblasts in response to TGF-beta1. The ERK1/2 activation is dependent on Smad2 activation, whereas the p38 activation occurs independent of Smad2. Because TSP-1 is a major antiangiogenic molecule and an activator of TGF-beta1, this provides an important insight to the mechanism by which TGF-beta1 may mediate interstitial fibrosis and progressive renal disease.
authors.affiliation: Division of Nephrology, Hypertension and Transplantation, University of Florida, P.O. Box 100224, Gainesville, FL 32610-0224, USA. nakagt@medicine.ufl.edu
authors.forename: Takahiko
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Hui Y
authors.initials: HY
authors.lastname: Lan
authors.forename: Olena
authors.initials: O
authors.lastname: Glushakova
authors.forename: Hong J
authors.initials: HJ
authors.lastname: Zhu
authors.forename: Duk-Hee
authors.initials: DH
authors.lastname: Kang
authors.forename: George F
authors.initials: GF
authors.lastname: Schreiner
authors.forename: Erwin P
authors.initials: EP
authors.lastname: Böttinger
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Johnson
authors.forename: Yuri Y
authors.initials: YY
authors.lastname: Sautin
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000502:physiology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D051899:Smad2 Protein; D019700:Thrombospondin 1 / Q000096:biosynthesis / Q000378:metabolism*; D015534:Trans-Activators / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1; D048051:p38 Mitogen-Activated Protein Kinases / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; C497784:Smad2 protein, rat; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D019700:Thrombospondin 1; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases