title: N-Acetyl-seryl-aspartyl-lysyl-proline inhibits TGF-beta-mediated plasminogen activator inhibitor-1 expression via inhibition of Smad pathway in human mesangial cells.
abstract: Recent large clinical trials indicate that angiotensin-converting enzyme inhibitors (ACE-I) attenuate the detrimental outcome of progressive renal disease. The hemoregulatory tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP, AcSDKP) is hydrolyzed by ACE, and plasma Ac-SDKP level is increased by fivefold after treatment with ACE-I. Ac-SDKP was found to ameliorate cardiac and renal fibrosis in hypertensive animal models. However, the molecular mechanisms by which Ac-SDKP mediates anti-fibrotic effects remain unclear. This study is an examination of the interaction between Ac-SDKP and transforming growth factor-beta (TGF-beta), one of the key cytokines in the progression of renal disease, in human mesangial cells. Ac-SDKP inhibited TGF-beta1-induced plasminogen activator inhibitor-1 (PAI-1) and alpha2 (I) collagen mRNA. Ac-SDKP suppressed not only TGF-beta1-induced Smad2 phosphorylation at Ser-465/467 in a dose-dependent manner, but also the nuclear accumulation of receptor-regulated Smads (R-Smad), Smad2 and Smad3. As expected, Ac-SDKP inhibited TGF-beta-responsive Smad-dependent luciferase reporters, 3TP-luc and 4xSBE-luc. Immunofluorescence analysis revealed that the inhibitory Smad, Smad7, was exported to the cytoplasm from the nucleus by the treatment with Ac-SDKP. These findings provide novel evidence that Ac-SDKP inhibits TGF-beta signal transduction through the suppression of R-Smad activation via nuclear export of Smad7, highlighting an alternative mechanism involved in the reno-protective efficacy of ACE-I.
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Keizo
authors.initials: K
authors.lastname: Kanasaki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koya
authors.forename: Toshiro
authors.initials: T
authors.lastname: Sugimoto
authors.forename: Motohide
authors.initials: M
authors.lastname: Isono
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kashiwagi
authors.forename: Masakazu
authors.initials: M
authors.lastname: Haneda
mesh_terms: D018929:Cell Culture Techniques; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005355:Fibrosis; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology*; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D051785:Smad Proteins; D051906:Smad7 Protein; D015534:Trans-Activators / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D006131:Growth Inhibitors; D009842:Oligopeptides; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; C497806:SMAD7 protein, human; D051785:Smad Proteins; D051906:Smad7 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; C058504:goralatide