title: Role of the extracellular signal-regulated kinase 1/2 signaling pathway in regulating the secretion of bronchial smooth muscle cells in a rat model of chronic asthma.
abstract: BACKGROUND
  Although it is recognized that bronchial smooth muscle cells (BSMCs) play a key role in airway remodeling during chronic asthma, it is not well understood how BSMCs exert their inflammatory functions. The extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway is an important signaling pathway in chronic asthma, but its influence on secretion by BSMCs has not been well-studied. We investigated the impact of ERK1/2 signaling pathway on secretion by BSMCs in a rat model of chronic asthma in this study.
  
  
  METHODS
  To create a rat model of chronic asthma, Wistar rats underwent ovalbumim (OVA) injection and eight weeks of inhalation. BSMCs were isolated and cultured in vitro. Epidermal growth factor, PD98059 and ERK1/2 antisense oligonucleotide were used to explore the role of ERK1/2 signaling pathway. The expression of P-ERK1/2 (phospho-ERK1/2) in BSMCs was analyzed by Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR). Secretion of BSMCs was detected by enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  Phospho-ERK1/2 expression was increased in BSMCs of chronic asthmatic rats compared with the controls. PD98059 inhibited expression of phospho-ERK1/2 protein, while treatment with an antisense oligonucleotide inhibited the expression of P-ERK1/2 mRNA and protein. BSMCs obtained from the chronic asthma group secreted significantly greater quantities of growth factors (transforming growth factor (TGF)-beta(1), vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF)), cytokines (regulated upon activation, normal T cell-expressed and secreted (RANTES) and eotaxin), and extracellular matrix (fibronectin and collagen I) compared with normal controls. Epidermal growth factor stimulated secretion in both groups, but the response of the chronic asthma group was more intense. Both PD98059 and antisense oligonucleotide suppressed secretion by BSMCs in chronic ashmatic rats. Antisense oligonucleotide reduced the level of RANTES nearly to that of normal controls, while PD98059 could not.
  
  
  CONCLUSIONS
  These results suggest that ERK1/2 signaling pathway may play an important role in the augmented secretion of BSMCs in chronic asthmatic rats, and ERK1/2 antisense oligonucleotide effectively inhibits the process.
authors.affiliation: Department of Respiratory Medicine, Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, China.
authors.forename: Min
authors.initials: M
authors.lastname: Xie
authors.forename: Xian-sheng
authors.initials: XS
authors.lastname: Liu
authors.forename: Yong-jian
authors.initials: YJ
authors.lastname: Xu
authors.forename: Zhen-xiang
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Bai
authors.forename: Wang
authors.initials: W
authors.lastname: Ni
authors.forename: Shi-xin
authors.initials: SX
authors.lastname: Chen
mesh_terms: D000818:Animals; D001249:Asthma / Q000378:metabolism*; D001980:Bronchi / Q000378:metabolism*; D018946:Chemokine CCL5 / Q000378:metabolism; D002908:Chronic Disease; D004195:Disease Models, Animal; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D018946:Chemokine CCL5; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3