ERK1/2 signaling pathway modulates the airway smooth muscle cell phenotype in the rat model of chronic asthma.
BACKGROUND
It has been demonstrated that the phenotypic modulation of airway smooth muscle cells (ASMCs) is important to the pathogenesis of airway remodeling in chronic asthma. The extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway is one of the most important transduction pathways involved in the process of asthma; however, its role in the phenotypic transition of ASMCs remains unclear.


OBJECTIVE
To examine the role of ERK1/2 in the phenotypic modulation of ASMCs in the rat model of chronic asthma.


METHODS
Bronchial smooth muscle strips were cultured in vitro in the presence of the ERK1/2 agonist epidermal growth factor or/and the MEK inhibitor PD98059. The phenotype of ASMCs was determined by observing these cells under an electron microscope and analyzing expression of phenotypic markers (smooth muscle alpha-actin for the contractile phenotype and osteopontin for the synthetic) by using Western blot and reverse-transcriptase polymerase chain reaction, respectively.


RESULTS
The phenotype of the ASMCs from the chronic asthmatic rats changed from the contractile type to the synthetic type with synthetic organelles abundantly gathered around the nucleus and altered expression of phenotypic markers. ERK1/2 was strongly expressed in the ASMCs of the chronic asthmatic rats and its activation by epidermal growth factor excessively promoted the synthetic function of ASMCs; the MEK inhibitor PD98059, however, reversed this phenotypic change in the ASMCs.


CONCLUSIONS
Our results reveal a key role of the ERK1/2 signaling pathway in the phenotypic modulation of ASMCs in chronic asthmatic rats, indicating that specific inhibition of ERK1/2 in ASMCs may be therapeutically valuable in the control of airway remodeling in chronic asthma.
Xie
Min
M
Department of Respiratory Medicine, Tongji Hospital Affiliated to Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Liu
Xian-Sheng
XS
Xu
Yong-Jian
YJ
Zhang
Zhen-Xiang
ZX
Bai
Jing
J
Ni
Wang
W
Chen
Shi-Xin
SX
D000818:Animals; D001249:Asthma / Q000235:genetics* / Q000378:metabolism*; D015153:Blotting, Western; D002908:Chronic Disease; D004195:Disease Models, Animal; D015870:Gene Expression; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism* / Q000648:ultrastructure; D010641:Phenotype; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values
D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3