Bronchial airway epithelial cell damage following exposure to cigarette smoke includes disassembly of tight junction components mediated by the extracellular signal-regulated kinase 1/2 pathway.
BACKGROUND
Through a variety of biochemical mechanisms, cigarette smoke (CS) may damage airway epithelium, altering its normal structure and function. Injury to epithelium may include changes in tight junction (TJ) integrity with impairment of epithelial barrier function.


RESULTS
To study the effect of the exposure to CS condensate (CSC) on TJ integrity, two human bronchial epithelial cell lines (HBECs), BEAS-2B and 16HBE14o-, were used. Exposure of the two HBECs to CSC resulted in a time-dependent and concentration-dependent disassembly of TJs, which were already detectable at 24 h at all the CSC concentrations tested (5%, 10%, and 20%), associated with changes in cell shape, suggesting cell damage. However, a significant inhibition of cell growth and an increase in DNA fragmentation were detected only at the highest CSC concentration tested (20%) at 48 and 72 h, respectively. The involvement of epidermal growth factor receptor (EGFR)-extracellular signal-regulated kinase (ERK) 1/2 cascade in CSC-induced damage was shown by the observation that exposure to CSC (5%) induced a marked phosphorylation of ERK1/2, already detectable after 5-min incubation and confirmed by the demonstration that not only ERK1/2 phosphorylation but also CSC-induced TJ disassembly and DNA fragmentation were partially inhibited by a mitogen-activated protein kinase kinase inhibitor (U0126) and completely blocked by a EGFR inhibitor (AG1478).


CONCLUSIONS
CSC-induced damage to airway epithelium includes disassembly of TJs, modulated through the EGFR-ERK1/2 signaling pathway.
Petecchia
Loredana
L
Pulmonary Disease Unit, G. Gaslini Institute, Genoa, Italy. Electronic address: loredanapetecchia@ospedale-gaslini.ge.it.
Sabatini
Federica
F
Pulmonary Disease Unit, G. Gaslini Institute, Genoa, Italy.
Varesio
Luigi
L
Molecular Biology Laboratory, G. Gaslini Institute, Genoa, Italy.
Camoirano
Anna
A
Department of Health Sciences, University of Genoa, Genoa, Italy.
Usai
Cesare
C
Institute of Biophysics, National Research Council, Genoa, Italy.
Pezzolo
Annalisa
A
Oncology and Pathology Laboratory, G. Gaslini Institute, Genoa, Italy.
Rossi
Giovanni A
GA
Pulmonary Disease Unit, G. Gaslini Institute, Genoa, Italy.
D001980:Bronchi / Q000166:cytology; D049109:Cell Proliferation; D002478:Cells, Cultured; D004249:DNA Damage; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects*; D066246:ErbB Receptors; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D018613:Microscopy, Confocal; D019950:Mitogen-Activated Protein Kinase 1 / Q000187:drug effects / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000187:drug effects / Q000378:metabolism*; D011336:Probability; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D012906:Smoke / Q000009:adverse effects*; D018709:Statistics, Nonparametric; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism*
D012906:Smoke; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3