[Expression of toll-like receptor 4 in human alveolar epithelial cells and its role in cellular inflammation].
OBJECTIVE
To investigate if type II alveolar epithelial cells express Toll-like receptor 4 (TLR4) and to investigate the role of TLR4 in airway inflammation of chronic obstructive pulmonary diseases (COPD).


METHODS
A549, the line of human type II alveolar epithelial cells were cultured and divided into 3 groups: normal control group, E1A(+) group transfected with adenovirus E1A plasmid, E1A(-) group transferred with blank plasmid without adenovirus E1A. Lipopolysaccharide (LPS) of the concentrations of 0, 0.1, 1, and 10 microg/ml, IL-1 beta of the concentrations of 0, and 0.1 ng/ml, and cigarette smoking extract (CSE) of the concentrations of 0, 10%, 20%, and 40% were used to stimulated the A549 cells for 12 and 24 h. Reverse transcription polymerase chain reaction was used to detect the mRNA expression of IL-8 and TLR4. Western blotting was used to detect the protein expression of nuclear factor kappaB (NF-kappaB) subunit P65.


RESULTS
Twenty-four hours after the stimulation of 10 microg/ml LPS, 0.1 ng/ml IL-1beta, and 20% CSE, the IL-8 mRNA expression of the E1A(+) group was 2.82, 1.87, and 4.70 respectively, all significantly higher than those of the normal control group (0.95, 0.78, and 1.02 respectively, all P < 0.05) and those of the E1A(-) group (0.97, 0.81, and 1.12 respectively, all P < 0.05). Twelve and twenty-four hours after the stimulation of 10 microg/ml of LPS, the TLR4 mRNA expression of the E1A+ group were 4.52 and 7.99, both significantly higher than those of the normal control group (1.91 and 3.81 respectively, both P < 0.05) and those of the E1A(-) group (2.00 and 3.88 respectively, both P < 0.05). IL-1beta increased the expression of TLR4 mRNA too, but CSE did not change the expression of TLR4 mRNA in all these groups. LPS, IL-1beta, and CSE all increased the expression levels of NF-kappaB subunit P65 protein.


CONCLUSIONS
Pulmonary type II epithelial cells express TLR4. LPS and IL-1beta up-regulate the release of IL-8 which may be mediated via the activation of NF-kappaB induced by TLR4.
Zhou
Min
M
Department of Respiratory Disease, Ruijin Hospital, Shanghai Jiaotong University, Shanghai 200025, China.
Wan
Huan-Ying
HY
Huang
Shao-Guang
SG
Li
Biao
B
Li
Min
M
D017500:Adenovirus E1A Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D053583:Interleukin-1beta / Q000494:pharmacology; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D010936:Plant Extracts / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000473:pathology*; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014026:Nicotiana / Q000737:chemistry; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D014162:Transfection
D017500:Adenovirus E1A Proteins; D053583:Interleukin-1beta; D016209:Interleukin-8; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010936:Plant Extracts; D051197:Toll-Like Receptor 4