Abstract
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‐κB) within the human lens epithelium, since NF‐κB 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‐1β (IL‐1β) and NF‐κB activation was measured by electrophoretic shift assay (EMSA). Phosphorylation of IκB 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‐κB, 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‐κB. UVAR‐induced NF‐κB 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‐κB inhibitory protein, IκB, revealed that UVAR activates NF‐κB via a mechanism involving the phosphorylation of IκB‐α; this effect was dose‐dependent. Supershift analysis demonstrated that UVAR and IL‐1β activate the transcriptionally active p65/p50 NF‐κB dimer. These studies demonstrate that UVAR activates NF‐κB in HLE cells in a time‐ and dose‐dependent manner via signaling through IκB‐α. The activation of NF‐κB in HLE cells by UVAR may have implications for the development and progression of cataract and other related ocular disorders.© 2003 Wiley Periodicals, Inc. J Biochem Mol Toxicol 17:108–113, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10067