Cell-specific activation profile of extracellular signal-regulated kinase 1/2, Jun N-terminal kinase, and p38 mitogen-activated protein kinases in asthmatic airways.
BACKGROUND
Many airway cells manifest signs of chronic activation in asthma. The mechanism of this chronic activation is unknown.


OBJECTIVE
We sought to study the activation of the mitogen-activated protein kinase (MAPK) signaling pathway in airway cells.


METHODS
Endobronchial biopsy specimens from patients with severe and mild asthma (n = 17 in each group) and healthy control subjects (n = 15) were analyzed for the phosphorylated MAPKs extracellular signal-regulated kinase (ERK) 1/2, p38, and Jun N-terminal kinase (JNK) and their downstream effectors by means of immunofluorescence staining. Airway epithelial activation of ERK1/2 and p38 was studied by using Western blotting. Epithelial function was studied by means of real-time PCR, ELISA, and the thymidine incorporation assay.


RESULTS
We detected strong phospho-ERK1/2 staining in airway epithelium and smooth muscle cells in biopsy specimens from asthmatic patients. Fluorescent areas per image, as well as mean fluorescence intensity, were significantly (P < .0001) different among the 3 study groups (patients with severe asthma, patients with mild asthma, and healthy control subjects). Patients with severe asthma also demonstrated strong phospho-p38 staining, mostly in epithelial cells, which was significantly different from that in patients with mild asthma (P = .0001) and healthy control subjects (P = .02). Phospho-JNK primarily stained airway smooth muscle cells. Healthy subjects showed the highest intensity of phospho-JNK staining compared with that seen in patients with severe (P = .004) and mild asthma (P = .003). Inhibition of ERK1/2 and p38 in primary airway epithelial cells blocked their proliferation and expression of select, but not all, chemokines.


CONCLUSIONS
Significant phosphorylation of ERK1/2 and p38 and their correlation with disease severity suggests that the foregoing signaling pathways play an important role in asthma. The ERK1/2 and p38 pathways regulate epithelial cell secretory function and proliferation.
Liu
Weimin
W
Division of Allergy and Immunology, Department of Medicine, National Jewish Medical and Research Center, Denver, CO 80206, USA.
Liang
Qiaoling
Q
Balzar
Silvana
S
Wenzel
Sally
S
Gorska
Magdalena
M
Alam
Rafeul
R
D000328:Adult; D001249:Asthma / Q000201:enzymology* / Q000473:pathology; D001980:Bronchi / Q000201:enzymology* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D018925:Chemokines / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism; D004789:Enzyme Activation / Q000276:immunology; D004790:Enzyme Induction / Q000276:immunology; D005260:Female; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology
D018925:Chemokines; D047428:Protein Kinase Inhibitors; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases