H2O2-mediated oxidative stress activates NF-kappa B in lens epithelial cells

In the mammalian lens, intracellular oxidants produced by photo-oxidative p rocesses and exposure to toxic chemicals constitute stresses that produce c ellular oxidative damage, result in changes in gene expression, and are cau sally 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 facto r, NF-kappaB, by H2O2-mediated oxidative stress in lens epithelial cells. L ens epithelial cells treated with H2O2 demonstrated at 1 h a strong activat ion of NF-kappaB which returned to basal levels by 2 h. Under proteasome in hibition using both MG132 and lactacystin, H2O2-mediated activation of NF-k appaB was prevented, implicating the involvement of proteasome degradation Of I kappaB proteins as being necessary for this activation. However, Weste rn 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. T hese results clearly demonstrate that H2O2-mediated oxidative stress activa tes NF-kappaB in lens epithelial cells, which may subsequently lead to chan ges in gene expression. The results also reveal that different signaling pa thways in the activation of NF-kappaB in lens epithelial cells are utilized by H2O2 and TNF-alpha. These different pathways of NF-kappaB activation ma y be required to effect specific NF-kappaB-dependent gene expression in res ponse to these different stimuli. (C) 2001 Elsevier Science Inc.