Objective: The relationship between latent adenvorius infection and airway inflammation has not been well documented. The aim of this study is to illustrate the roles of adenovirus E1A protein on the inflammation mediator expression in response to lipopolysaccharide and tumor necrosis factor alpha (TNF-alpha) in rat alveolar epithelial cells.
Methods: An eukaryotic expression vector for expressing adenovirus E1A protein was constructed and transfected into CCL149 cells. Cells stably expressing E1A protein were selected by G418 resistance. The inflammatory mediator intercellular adhesion molecule-1 (ICAM-1) expression in response to lipopolysaccharide and TNF-alpha was compared between adenovirus E1A-positive clones, control clones and CCL149 cells. Messenger RNA of ICAM-1 was measured by RT-PCR, and proteins quantified by flow cytometry. The nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1) activity were measured by LUC report system and electrophoretic mobility shift assay (EMSA).
Results: ICAM-1 messenger RNA and protein were increased in E1A-positive cells exposed to 10 ng/ml TNF-alpha and 10 microg/ml lipopolysaccharide. The luciferase activity drived by NF-kappaB and AP-1 elements were increased in E1A-positive cells compared with control with or without lipopolysaccharide and TNF-alpha stimulation. EMSA showed that only NF-kappaB activity increased in E1A-positive cells. This increase was not observed in AP1 element drived EMSA.
Conclusions: The results indicate that E1A upregulates ICAM-1 expression induced by lipopolysaccharide and TNF-alpha in rat alveolar epithelial cells. E1A enhances the expression of inflammatory mediator by triggering NF-kappaB activity. It is suggested that E1A amplified inflammatory response may contribute to the pathogenesis of chronic obstructive pulmonary disease.