title: Collagen regulates transforming growth factor-β receptors of HL-1 cardiomyocytes through activation of stretch and integrin signaling.
abstract: The extracellular matrix (ECM) and transforming growth factor-β (TGF)-β are important in cardiac fibrosis, however, the effects of the ECM on TGF‑β signaling remain to be fully elucidated. The aims of the present study were to evaluate the role of collagen in TGF‑β signaling and examine the underlying mechanisms. In the present study, western blot analysis was used to examine TGF‑β signaling in HL‑1 cells treated with and without (control) type I collagen (10 µg/ml), which was co‑administered with either an anti‑β1 integrin antibody (10 µg/ml) or a stretch‑activated channel inhibitor (gadolinium; 50 µM). Cell proliferation and adhesion assays were used to investigate the roles of integrin, mechanical stretch and mitogen‑activated protein kinases (MAPKs) on cell proliferation and adhesion. The type I collagen (10 µg/ml)‑treated HL‑1 cells were incubated with or without anti‑β1 integrin antibody (10 µg/ml), gadolinium (50 µM) or inhibitors of p38 (SB203580; 3 µM), extracellular signal‑regulated kinase (ERK; PD98059; 50 µM) and c‑Jun N‑terminal kinase (JNK; SP600125; 50 µM). Compared with the control cells, the collagen‑treated HL‑1 cells had lower expression levels of type I and type II TGF‑β receptors (TGFβRI and TGFβRII), with an increase in phosphorylated focal adhesion kinase (FAK), p38 and ERK1/2, and a decrease in JNK. Incubation with the anti‑β1 integrin antibody reversed the collagen‑induced downregulation of the expression of TGFβRII and phosphorylated FAK. Gadolinium downregulated the expression levels of TGFβRI and small mothers against decapentaplegic (Smad)2/3, and decreased the levels of phosphorylated p38, ERK1/2 and JNK. In addition, gadolinium reversed the collagen‑induced activation of p38 and ERK1/2. In the presence of gadolinium and anti‑β1 integrin antibody, collagen regulated the expression levels of TGFβRI, TGFβRII and Smad2/3, but did not alter the phosphorylation of p38, ERK1/2 or JNK. In addition, collagen increased cell proliferation and adhesion, and this collagen‑induced cell proliferation was inhibited by the anti‑β1 integrin antibody and ERK inhibitor. Taken together, the data obtained suggested that collagen differentially regulated the expression levels of TGFβRI and TGFβRII, and modulated the phosphorylation of MAPKs through integrin‑ or stretch‑dependent and ‑independent signaling pathways.
authors: Division of Cardiology, Department of Internal Medicine, Sijhih Cathay General Hospital, New Taipei City 221, Taiwan, R.O.C.
authors: Yen-Yu
authors: YY
authors: Lu
authors: Division of Cardiology, Department of Internal Medicine, School of Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan, R.O.C.
authors: Yung-Kuo
authors: YK
authors: Lin
authors: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei 110, Taiwan, R.O.C.
authors: Yu-Hsun
authors: YH
authors: Kao
authors: Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei 116, Taiwan, R.O.C.
authors: Cheng-Chih
authors: CC
authors: Chung
authors: Cardiovascular Division, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Tao‑Yuan 333, Taiwan, R.O.C.
authors: Yung-Hsin
authors: YH
authors: Yeh
authors: School of Medicine, National Yang-Ming University, Taipei 112, Taiwan, R.O.C.
authors: Shih-Ann
authors: SA
authors: Chen
authors: Division of Cardiovascular Medicine, Department of Internal Medicine, Wan Fang Hospital, Taipei Medical University, Taipei 116, Taiwan, R.O.C.
authors: Yi-Jen
authors: YJ
authors: Chen
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D003094:Collagen / Q000378:metabolism*; D019012:Integrin beta1 / Q000378:metabolism*; D051379:Mice; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051785:Smad Proteins / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D019012:Integrin beta1; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II