Al. True et al., Activation of NF-kappa B induced by H2O2 and TNF-alpha and its effects on ICAM-1 expression in endothelial cells, AM J P-LUNG, 279(2), 2000, pp. L302-L311
Citations number
48
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY
Reactive oxygen species have been proposed to signal the activation of the
transcription factor nuclear factor (NF)-kappa B in response to tumor necro
sis factor (TNF)-alpha challenge. In the present study, we investigated the
effects of H2O2 and TNF-alpha in mediating activation of NF-kappa B and tr
anscription of the intercellular adhesion molecule (ICAM)-1 gene. Northern
blot analysis showed that TNF-alpha exposure of human dermal microvascular
endothelial cells (HMEC-1) induced marked increases in ICAM-1 mRNA and cell
surface protein expression. In contrast, H2O2 added at subcytolytic concen
trations failed to activate ICAM-1 expression. Challenge with H2O2 also fai
led to induce NF-kappa B-driven reporter gene expression in the transduced
HMEC-1 cells, whereas TNF-alpha increased the NF-kappa B-driven gene expres
sion similar to 10-fold. Gel supershift assay revealed the presence of p65
(Rel A), p50, and c-Rel in both H2O2- and TNF-alpha-induced NF-kappa B comp
lexes bound to the ICAM-1 promoter, with the binding of the p65 subunit bei
ng the most prominent. In vivo phosphorylation studies, however, showed tha
t TNF-alpha exposure induced marked phosphorylation of NF-kappa B p65 in HM
EC-1 cells, whereas H2O2 had no effect. These results suggest that reactive
oxygen species generation in endothelial cells mediates the binding of NF-
kappa B to nuclear DNA, whereas TNF-alpha generates additional signals that
induce phosphorylation of the bound NF-kappa B p65 and confer transcriptio
nal competency to NF-kappa B.