title: Novel interactions between TGF-{beta}1 actions and the 12/15-lipoxygenase pathway in mesangial cells.
abstract: Diabetic nephropathy (DN) is characterized by mesangial cell (MC) hypertrophy and progressive accumulation of glomerular extracellular matrix (ECM). It was reported recently that 12/15-lipoxygenase (12/15-LO) expression is increased in high-glucose (HG)-stimulated MC and in experimental DN. 12-LO products could also directly induce MC hypertrophy and ECM expression and mediate growth factor effects, thus implicating the 12/15-LO pathway in DN. Because TGF-beta is a major player in the pathogenesis of DN, whether there is an interplay between the TGF-beta and 12/15-LO pathways in MC was evaluated. Treatment of rat MC (RMC) with TGF-beta significantly increased levels of the 12/15-LO product 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] and also 12/15-LO mRNA and protein expression. HG-induced TGF-beta mRNA expression in RMC was inhibited by a specific ribozyme and siRNA targeted to knockdown rat 12/15-LO. It is interesting that direct treatment of RMC with 12(S)-HETE increased TGF-beta mRNA and protein levels, as well as p-Smad2/3, which are TGF-beta-specific target transcription factors. 12(S)-HETE also increased transcription from a minimal TGF-beta promoter. Furthermore, TGF-beta expression and p-Smad2/3 levels were lower in MC from 12/15-LO knockout mice relative to control mice. Reciprocally, mouse MC stably overexpressing 12/15-LO had greater TGF-beta mRNA and also nuclear p-Smad2/3 relative to mock-transfected cells. 12/15-LO and TGF-beta could functionally signal and increase ECM expression via the p38 mitogen-activated protein kinase signaling pathway. These results indicate for the first time that the 12/15-LO and TGF-beta pathways can cross-talk and activate each other. These novel interactions may amplify the signal transduction cascades and molecular events that lead to DN.
authors.affiliation: Gonda Diabetes Research Center, Beckman Research Institute of the City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA.
authors.forename: Young-Sook
authors.initials: YS
authors.lastname: Kim
authors.forename: Zhong-Gao
authors.initials: ZG
authors.lastname: Xu
authors.forename: Marpadga A
authors.initials: MA
authors.lastname: Reddy
authors.forename: Shu-Lian
authors.initials: SL
authors.lastname: Li
authors.forename: Linda
authors.initials: L
authors.lastname: Lanting
authors.forename: Kumar
authors.initials: K
authors.lastname: Sharma
authors.forename: Sharon G
authors.initials: SG
authors.lastname: Adler
authors.forename: Rama
authors.initials: R
authors.lastname: Natarajan
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000187:drug effects / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000187:drug effects / Q000378:metabolism*; D001483:Base Sequence; D015153:Blotting, Western; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D005920:Glomerular Mesangium / Q000166:cytology* / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
chemical_list: C475064:12-15-lipoxygenase; D012333:RNA, Messenger; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase