title: Insulin-like growth factor-I enhances transforming growth factor-beta-induced extracellular matrix protein production through the P38/activating transcription factor-2 signaling pathway in keloid fibroblasts.
abstract: Keloids are benign dermal tumors, characterized by invasive growth of fibroblasts and concomitant increased biosynthesis of extracellular matrix components, with unclear etiology. We previously demonstrated that keloid fibroblasts overexpress insulin-like growth factor-I receptor. In investigating the role of insulin-like growth factor-I receptor overexpression, insulin-like growth factor-I and transforming growth factor-beta interaction was examined in relation to extracellular matrix protein production in cultured human and mouse fibroblasts. Western blotting revealed that collagen type I was expressed in keloid and normal fibroblasts, and its expression was increased by transforming growth factor-beta stimulation more significantly in keloid rather than in normal fibroblasts. Insulin-like growth factor-I and transforming growth factor-beta1 costimulation markedly increased extracellular matrix proteins (collagen type I, fibronectin, and plasminogen activator inhibitor-1) compared with cultures with transforming growth factor-beta1 alone. Insulin-like growth factor-I treatment alone had no stimulatory effect. Real-time reverse transcription-polymerase chain reaction confirmed parallel collagen type I messenger RNA level changes. Luciferase assays were conducted to investigate intracellular signaling pathways in this synergistic stimulation using a mouse fibroblast cell line. Transforming growth factor-beta1 (1 or 10 ng per ml) increased the specific signaling activity approximately 10-fold, whereas the increase with insulin-like growth factor-I (100 ng per ml) was less than 2-fold compared with basal activity; however, the combination of transforming growth factor-beta1 and insulin-like growth factor-I resulted in an approximately 25-fold increase. Insulin-like growth factor-I markedly enhanced transforming growth factor-beta-induced phosphorylation of p38 mitogen-activated protein kinase and activating transcription factor-2. Luciferase assay showed that this synergistic effect was attenuated by the p38 mitogen-activated protein kinase specific inhibitor SB203580 or phosphatidylinositol 3-kinase inhibitor wortmannin, but not by the mitogen-activated protein kinase/extracellular-signal-regulated protein kinase kinase inhibitor PD98059. These results indicate that insulin-like growth factor-I enhances transforming growth factor-beta-induced keloid formation through transforming growth factor-beta postreceptor signal cross-talk, mainly via the p38 mitogen-activated protein kinase/activating transcription factor-2 pathway.
authors.affiliation: Department of Plastic and Reconstructive Surgery, Atomic Bomb Disease Institute, Nagasaki University Graduate School of Biomedical Sciences, 1-12-4, Sakamoto, Nagasaki 852-8523, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Daian
authors.forename: Akira
authors.initials: A
authors.lastname: Ohtsuru
authors.forename: Tatiana
authors.initials: T
authors.lastname: Rogounovitch
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishihara
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Hirano
authors.forename: Yuri
authors.initials: Y
authors.lastname: Akiyama-Uchida
authors.forename: Vladimir
authors.initials: V
authors.lastname: Saenko
authors.forename: Tohru
authors.initials: T
authors.lastname: Fujii
authors.forename: Shunichi
authors.initials: S
authors.lastname: Yamashita
mesh_terms: D016475:3T3 Cells; D051698:Activating Transcription Factor 2; D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002478:Cells, Cultured; D002648:Child; D024042:Collagen Type I / Q000235:genetics; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D020405:Dermis / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007627:Keloid / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D024042:Collagen Type I; D017362:Cyclic AMP Response Element-Binding Protein; D016326:Extracellular Matrix Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases