[Effects of chronic ethanol ingestion on intercellular junction proteins and barrier function of airway epithelium in the endotoxemic rat].
OBJECTIVE
To investigate the effects of chronic ethanol ingestion and lipopolysaccharide (LPS) on airway epithelium barrier function and the expression of tight junction protein occludin and adherens junction protein E-cadherin.


METHODS
Forty Sprague-Dawley (SD) rats were assigned to control, ethanol, LPS and ethanol+LPS groups. The bronchoalveolar epithelial permeability was assessed by the bronchoalveolar lavage fluid (BALF): serum fluorescein isothiocyanate (FITC)-dextran (FD(4)) fluorescence ratio. Protein localization and expression of occludin and E-cadherin in airway epithelium of rats lung were examined by immunofluorescence. The protein, messenger RNA expression of occludin and E-cadherin in the lung were examined by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR).


RESULTS
The bronchoalveolar epithelial permeability in the ethanol group and LPS group were approximately 2-fold higher than those in the control group (both P<0.05). The permeability in the ethanol+LPS group was increased further (P<0.01). Occludin and E-cadherin appeared as a continuous and uniform expression in the airway epithelium of control rats. In ethanol group and LPS group partial breakdown of membrane staining and decreased cytoplasm staining of occludin and E-cadherin were seen in the airway epithelium. In ethanol plus LPS group, there was breakdown of epithelial membrane and obvious disappearance of cytoplasm staining pattern of occludin and E-cadherin. Western blotting and RT-PCR showed that both in ethanol and LPS groups protein levels of occludin and E-cadherin were depressed in lung. Treatment with ethanol together with LPS further depressed the protein and mRNA levels of occludin and E-cadherin in lung. RT-PCR showed that messenger RNA levels of occludin and E-cadherin in ethanol group and LPS group were lower than those in the control group (both P< 0.05). Treatment with ethanol plus LPS had the greatest depressive effect on these messenger RNA levels (ethanol+LPS group vs. the other groups, all P<0.01).


CONCLUSIONS
These data suggest that chronic ethanol ingestion impairs the airway epithelial barrier function through down-regulation the messenger RNA expression and disruption of membrane localization of occludin and E-cadherin. Those deterioration of occludin and E-cadherin predisposes to acute lung injury induced by LPS.
Zhang
Yuan-Li
YL
Division of Intensive Care Unit, Affiliated Hospital of Guangdong Medical College, Zhanjiang 524001, Guangdong, China.
Li
Qing-Quan
QQ
Guo
Wei
W
Huang
Yi
Y
Yang
Jiong
J
D055371:Acute Lung Injury / Q000139:chemically induced / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D004195:Disease Models, Animal; D004731:Endotoxins / Q000633:toxicity; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D000431:Ethanol / Q000494:pharmacology*; D007365:Intercellular Junctions / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D062793:Occludin; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014132:Trachea / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology
D015820:Cadherins; D004731:Endotoxins; D008565:Membrane Proteins; D062793:Occludin; C568987:Ocln protein, rat; D000431:Ethanol