H2O2-mediated oxidative stress activates NF-κB in lens epithelial cells

In the mammalian lens, intracellular oxidants produced by photo-oxidative processes and exposure to toxic chemicals constitute stresses that produce cellular oxidative damage, result in changes in gene expression, and are causally related to cataract formation. Currently, it is believed that H2O2 is the major oxidant to which the lens is exposed. In this report, we examine the activation and regulation of the oxidant-sensitive transcription factor, NF-kappaB, by H2O2-mediated oxidative stress in lens epithelial cells. Lens epithelial cells treated with H2O2 demonstrated at 1 h a strong activation of NF-kappaB which returned to basal levels by 2 h. Under proteasome inhibition using both MG132 and lactacystin, H2O2-mediated activation of NF-kappaB was prevented, implicating the involvement of proteasome degradation Of I kappaB proteins as being necessary for this activation. However, Western blot analysis demonstrated no degradation of I kappaB-alpha, -beta, or -epsilon associated with H2O2-mediated NF-kappaB activation. In comparison, when cells were treated with the cytokine TNF-alpha, NF-kappaB was strongly activated and degradation of both I kappaB-alpha and -beta was observed. These results clearly demonstrate that H2O2-mediated oxidative stress activates NF-kappaB in lens epithelial cells, which may subsequently lead to changes in gene expression. The results also reveal that different signaling pathways in the activation of NF-kappaB in lens epithelial cells are utilized by H2O2 and TNF-alpha. These different pathways of NF-kappaB activation may be required to effect specific NF-kappaB-dependent gene expression in response to these different stimuli. (C) 2001 Elsevier Science Inc.