[The oxidative stress enhanced adenoviral E1A-involved transactivation of nuclear factor-kappaB]

The relationship between latent adenovirus infection and airway inflammation have not been well documented. The aim of this study is to illustrate the roles of adenovirus E1A protein on the level of glutathione (GSH) in response to oxidative stress and the effect of the oxidant/antioxidant imbalance upon the transactivation of NF-kappaB triggered by E1A protein.

Rat alveolar epithelial cell stably expressing adenoviral E1A or control plasmid were developed. For isolation of nuclear extracts, 5 x 10(5) cells were plated and grown overnight in 60 mm dishes. Experiments were repeated three times. The cell model of stably expressing adenoviral E1A was stimulated by H2O2. The level of GSH were measured. E1A positive clone was stimulated by LPS or TNF-alpha and treated with L-Buthionine-sulfoximine (BSO). The expression of NF-kappaB was measured by Western blot. Differences between groups were assessed for significance by Student' t test; multiple comparisons by the one-way ANOVA.

There is no difference of GSH level without stimulation between E1A-positive clones and E1A-negative clones. For E1A-positive clones, the level of GSH did not increase in response to H2O2 as E1A-negative clones. The quantitation by densitometry of the NF-kappaB expression in E1A-positive clones were (79.3 +/- 4.6), (80.3 +/- 3.8) respectively without treatment and were (81.8 +/- 3.9) - (89.9 +/- 1.6) and (94.1 +/- 1.9) - (99.8 +/- 1.6) respectively under LPS or TNF-alpha stimulation, which were significantly higher than that of the control group (68.3 +/- 3.8), (69.4 +/- 4.3) respectively without stimulation and (70.1 +/- 2.8) - (80.8 +/- 3.6), (73.4 +/- 4.9) - (83.2 +/- 6.7) respectively under stimulation. The quantitation by densitometry of the NF-kappaB expression in E1A-negative clones were (1.25 +/- 0.18) and (1.69 +/- 0.19) respectively under LPS and TNF-alpha-stimulation and (1.22 +/- 0.16) and (1.75 +/- 0.13) respectively upon treatment for LPS and TNF-alpha with BSO preincubation. There did not show difference upon treatment with LPS or TNF-alpha with or without BSO in E1A-negative cell clone. The quantitation by densitometry of the NF-kappaB expression in E1A-positive clone were (1.75 +/- 0.10) and (2.26 +/- 0.21) respectively upon treatment for LPS and TNF-alpha with BSO preincubation which were significantly higher than that of LPS or TNF-alpha-stimulation alone (1.35 +/- 0.12), (1.80 +/- 0.14) respectively.

These results indicate that E1A protein decreased GSH levels in oxidant stress and upregulated NF-kappaB transcription activity. The oxidant/antioxidant imbalance in rat alveolar epithelial cells enhances E1A-modulated transcriptional activation of NF-kappaB. The mechanism underlying transactivation of NF-kappaB involved by E1A may be related to oxidative stress.