title: CXCL12 induces connective tissue growth factor expression in human lung fibroblasts through the Rac1/ERK, JNK, and AP-1 pathways.
abstract: CXCL12 (stromal cell-derived factor-1, SDF-1) is a potent chemokine for homing of CXCR4+ fibrocytes to injury sites of lung tissue, which contributes to pulmonary fibrosis. Overexpression of connective tissue growth factor (CTGF) plays a critical role in pulmonary fibrosis. In this study, we investigated the roles of Rac1, extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and activator protein-1 (AP-1) in CXCL12-induced CTGF expression in human lung fibroblasts. CXCL12 caused concentration- and time-dependent increases in CTGF expression and CTGF-luciferase activity. CXCL12-induced CTGF expression was inhibited by a CXCR4 antagonist (AMD3100), small interfering RNA of CXCR4 (CXCR4 siRNA), a dominant negative mutant of Rac1 (RacN17), a mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor (PD98059), a JNK inhibitor (SP600125), a p21-activated kinase inhibitor (PAK18), c-Jun siRNA, and an AP-1 inhibitor (curcumin). Treatment of cells with CXCL12 caused activations of Rac1, Rho, ERK, and c-Jun. The CXCL12-induced increase in ERK phosphorylation was inhibited by RacN17. Treatment of cells with PD98059 and SP600125 both inhibited CXCL12-induced c-Jun phosphorylation. CXCL12 caused the recruitment of c-Jun and c-Fos binding to the CTGF promoter. Furthermore, CXCL12 induced an increase in α-smooth muscle actin (α-SMA) expression, a myofibroblastic phenotype, and actin stress fiber formation. CXCL12-induced actin stress fiber formation and α-SMA expression were respectively inhibited by AMD3100 and CTGF siRNA. Taken together, our results suggest that CXCL12, acting through CXCR4, activates the Rac/ERK and JNK signaling pathways, which in turn initiates c-Jun phosphorylation, and recruits c-Jun and c-Fos to the CTGF promoter and ultimately induces CTGF expression in human lung fibroblasts. Moreover, overexpression of CTGF mediates CXCL12-induced α-SMA expression.
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chien-Huang
authors.initials: CH
authors.lastname: Lin
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan; Division of Pulmonary Medicine, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Chung-Huang
authors.initials: CH
authors.lastname: Shih
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chih-Chieh
authors.initials: CC
authors.lastname: Tseng
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Chung-Chi
authors.initials: CC
authors.lastname: Yu
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yuan-Jhih
authors.initials: YJ
authors.lastname: Tsai
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan; Division of Pulmonary Medicine, Department of Internal Medicine, Taipei Medical University Hospital, Taipei, Taiwan.
authors.forename: Mauo-Ying
authors.initials: MY
authors.lastname: Bien
authors.affiliation: School of Respiratory Therapy, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Bing-Chang
authors.initials: BC
authors.lastname: Chen
mesh_terms: D000199:Actins / Q000378:metabolism; D001483:Base Sequence; D002460:Cell Line; D054377:Chemokine CXCL12 / Q000502:physiology*; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D008168:Lung / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D019718:Receptors, CXCR4 / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; C515255:CXCL12 protein, human; C527276:CXCR4 protein, human; D054377:Chemokine CXCL12; D017931:DNA Primers; D019718:Receptors, CXCR4; D018808:Transcription Factor AP-1; D055513:Connective Tissue Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases; D048670:MAP Kinase Kinase 4; D020744:rac GTP-Binding Proteins