Ultraviolet radiation modulates nuclear factor kappa B activation in human lens epithelial cells

Exposure to ultraviolet radiation (UVR) is a known risk factor for cataract, but the molecular mechanisms involved have not been elucidated. We hypothesized that exposure to UVR would modulate the activation of nuclear factor kappa-B (NF-kappaB) within the human lens epithelium, since NF-kappaB is a key regulator of cellular responses to UVR stress in other cell types. Human lens epithelial (HLE) cells were exposed to acute physiological doses of ultraviolet A (UVAR), B (UVBR), C (UVCR) radiation, or interleukin-1beta (IL-1beta) and NF-kappaB activation was measured by electrophoretic shift assay (EMSA). Phosphorylation of IkappaB in response to UVAR was measured by Western blotting. Irradiation of HLE cells with UVAR (0-1100 J/m(2)) did not reduce cell survival, while UVBR (400-1600 J/m(2)) and UVCR (300-900 J/m(2)) significantly reduced HLE cell survival. EMSA analysis of HLE nuclear proteins indicated activation of NF-kappaB, but not activator protein-1 (AP-1), by UVAR. The effects of UVBR and UVCR were less pronounced. Exposure of HLE cells to UVAR (0-900 J/m(2)) followed by a 30-min incubation resulted in a dose-dependent activation of NF-kappaB. UVAR-induced NF-kappaB activation in HLE cells was evident 10 min postirradiation, maximal at 60 min and returned to control levels by 120 min. Western blot analysis of phosphorylation of the NF-kappaB inhibitory protein, IkappaB, revealed that UVAR activates NF-kappaB via a mechanism involving the phosphorylation Of IkappaB-alpha; this effect was dose-dependent. Supershift analysis demonstrated that UVAR and IL-1beta activate the transcriptionally active p65/p50 NF-kappaB dimer. These studies demonstrate that UVAR activates NF-kappaB in HLE cells in a time- and dose-dependent manner via signaling through IkappaB-alpha. The activation of NF-kappaB in HLE cells by UVAR may have implications for the development and progression of cataract and other related ocular disorders. (C) 2003 Wiley Periodicals, Inc.