title: Bradykinin-induced expression of alpha-smooth muscle actin in human mesenchymal stem cells.
abstract: Phenotypic expression of alpha-smooth muscle actin (alpha-SMA), a smooth muscle marker, has been implicated in vascular diseases, fibrosis, wound healing, and tissue remodeling. Bradykinin (BK), a vasoactive peptide produced during tissue injury, plays a key role in inflammatory and vascular responses associated with tissue injury. In the present study, we demonstrated for the first time that BK treatment increased alpha-SMA expression in human adipose tissue-derived mesenchymal stem cells (hADSCs). This BK-induced alpha-SMA expression was abrogated by small interfering RNA (siRNA)-mediated depletion of endogenous myocardin, a transcription factor involved in smooth muscle differentiation. BK also increased the intracellular calcium concentration ([Ca(2+)](i)), a response that was completely blocked by treatment with a BK B2 receptor-specific antagonist (HOE 140), suggesting that the BK B2 receptor was participating in BK-induced cellular responses. In addition, BK induced the secretion of transforming growth factor-beta1 (TGF-beta1) and autocrine activation of Smad2. Pretreatment with a TGF-beta type I receptor kinase inhibitor (SB-431542), small interfering RNA-mediated depletion of endogenous Smad2, or adenoviral expression of Smad7 (an inhibitory Smad isoform) all blocked BK-induced alpha-SMA expression and Smad2 phosphorylation. Furthermore, a MEK-specific inhibitor (U0126) abrogated BK-induced TGF-beta1 secretion, Smad2 phosphorylation, and alpha-SMA expression. These results suggest that BK induced expression of alpha-SMA in hADSCs through ERK-dependent activation of the autocrine TGF-beta1-Smad2 crosstalk pathway.
authors.affiliation: Department of Physiology, School of Medicine, Pusan National University, Busan 602-739, Republic of Korea.
authors.forename: Young Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Eun Su
authors.initials: ES
authors.lastname: Jeon
authors.forename: Mi Ra
authors.initials: MR
authors.lastname: Kim
authors.forename: Jung Sub
authors.initials: JS
authors.lastname: Lee
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000199:Actins / Q000378:metabolism*; D000273:Adipose Tissue / Q000166:cytology; D019898:Autocrine Communication / Q000187:drug effects; D001920:Bradykinin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D043782:Receptor, Bradykinin B2 / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D000099251:Myocardin
chemical_list: D000199:Actins; D001920:Bradykinin; D002118:Calcium; D048049:Extracellular Signal-Regulated MAP Kinases; D009687:Nuclear Proteins; D043782:Receptor, Bradykinin B2; D051899:Smad2 Protein; D015534:Trans-Activators; D053773:Transforming Growth Factor beta1; D000099251:Myocardin; C497782:SMAD2 protein, human