ABSTRACT
The effects of hypoxia on the level of reactive oxygen species (ROS), IkappaBalpha tyrosine phosphorylation, transcription of P65 mRNA and NF-kappaB activation in isolated rat peritoneal macrophages were investigated by DCFH-DA fluorescence spectrophotometry, Western blotting and RT-PCR. The results obtained are as follows. (1) During hypoxia, the levels of intracellular ROS began to increase at 1 h, then reached a peak at 2 h, and began to decrease after 3 h. IkappaBalpha tyrosine phosphorylation began to rise after 2 h hypoxia and was the highest after 3 h hypoxia. After 4 h hypoxia it decreased gradually. NF-kappaB activation began to increase after 3 h hypoxia, and reached a peak after 4 h hypoxia. (2) When antioxidant NAC (500 mmol/L) was added into the medium, the level of IkappaBalpha phosphorylation showed no significant changes during hypoxia. After adding protein tyrosine kinase inhibitor genistein (200 micromol/L), NF-kappaB activation induced by hypoxia was blocked significantly. (3) The expression of p65 mRNA was also elevated markedly during hypoxia. These results suggest that hypoxia may lead to IkappaBalpha phosphorylation and NF-kappaB activation through intracellular ROS, and that the regulation of NF-kappaB activity may involve IkappaBalpha phosphorylation and the expressions of each subunit gene of NF-kappaB.