Xanthophylls and α-tocopherol decrease UVB-induced lipid peroxidation and stress signaling in human lens epithelial cells

Abstract

Epidemiological studies suggest that consumption of vegetables rich in the xanthophylls lutein (LUT) and zeaxanthin (ZEA) reduces the risk for developing age-related cataract, a leading cause of vision loss. Although LUT and ZEA are the only dietary carotenoids present in the lens, direct evidence for their photoprotective effect in this organ is not available. The present study examined the effects of xanthophylls and α-tocopherol (α-TC) on lipid peroxidation and the mitogen-activated stress signaling pathways in human lens epithelial (HLE) cells following ultraviolet B light (UVB) irradiation. When presented with LUT, ZEA, astaxanthin (AST), and α-TC as methyl-β-cyclodextrin complexes, HLE cells accumulated the lipophiles in a concentration- and time-dependent manner with uptake of LUT exceeding that of ZEA and AST. Pretreatment of cultures with either 2 μmol/L xanthophyll or 10 μmol/L α-TC for 4 h before exposure to 300 J/m2 UVB radiation decreased lipid peroxidation by 47-57% compared with UVB-treated control HLE cells. Pretreatment with the xanthophylls and α-TC also inhibited UVB-induced activation of c-JUN NH2-terminal kinase (JNK) and p38 by 50-60 and 25-32%, respectively. There was substantial inhibition of UVB-induced JNK and p38 activation for cells containing <0.20 and ∼0.30 nmol xanthophylls/mg, respectively, whereas >2.3 nmol α-TC/mg protein was required to significantly decrease UVB-induced stress signaling. These data suggest that xanthophylls are more potent than α-TC for protecting human lens epithelial cells against UVB insult.