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Xanthophylls and alpha-tocopherol decrease UVB-induced lipid peroxidation and stress signaling in human lens
Chureeporn Chitchumroonchokchai1, Joshua A Bomser, Jayme E Glamm
1Ohio State University Interdisciplinary PhD Program in Nutrition, Ohio State University, Columbus, OH 43210, USA.
The Journal of Nutrition
|December 1, 2004
Summary
Dietary xanthophylls, lutein (LUT) and zeaxanthin (ZEA), protect human lens cells from UVB damage by reducing lipid peroxidation and stress signaling. These carotenoids are more potent than alpha-tocopherol (alpha-TC) in preventing UVB-induced cellular injury.
Area of Science:
- Ophthalmology and Vision Science
- Photobiology
- Cellular and Molecular Biology
Background:
- Age-related cataract is a leading cause of vision loss, with epidemiological studies linking reduced risk to dietary xanthophylls: lutein (LUT) and zeaxanthin (ZEA).
- LUT and ZEA are the sole dietary carotenoids found in the human lens, yet direct evidence of their photoprotective role in this organ is lacking.
- Ultraviolet B (UVB) radiation is a significant environmental stressor implicated in ocular damage.
Purpose of the Study:
- To investigate the protective effects of xanthophylls (LUT, ZEA) and alpha-tocopherol (alpha-TC) against UVB-induced damage in human lens epithelial (HLE) cells.
- To assess the impact of these compounds on lipid peroxidation and stress signaling pathways (JNK, p38) following UVB exposure.
- To compare the relative potencies of xanthophylls and alpha-TC in protecting HLE cells from UVB insult.
Main Methods:
- Human lens epithelial (HLE) cells were treated with lutein (LUT), zeaxanthin (ZEA), astaxanthin (AST), or alpha-tocopherol (alpha-TC) using methyl-beta-cyclodextrin complexes.
- Cells were exposed to 300 J/m(2) UVB radiation after pretreatment with varying concentrations of the compounds.
- Lipid peroxidation levels and the activation of mitogen-activated protein kinase pathways (c-JUN NH(2)-terminal kinase [JNK] and p38) were measured.
Main Results:
- HLE cells accumulated LUT, ZEA, and AST in a concentration- and time-dependent manner, with higher uptake of LUT compared to ZEA and AST.
- Pretreatment with 2 micromol/L xanthophylls or 10 micromol/L alpha-TC significantly reduced UVB-induced lipid peroxidation by 47-57%.
- Xanthophylls and alpha-TC inhibited UVB-induced JNK activation by 50-60% and p38 activation by 25-32%.
- Significantly lower cellular concentrations of xanthophylls (<0.20 nmol/mg) compared to alpha-TC (>2.3 nmol/mg) were required to inhibit UVB-induced stress signaling.
Conclusions:
- Xanthophylls (LUT and ZEA) demonstrate significant photoprotective effects against UVB radiation in human lens epithelial cells.
- These carotenoids effectively reduce UVB-induced lipid peroxidation and mitigate stress signaling pathway activation.
- Xanthophylls are more potent than alpha-tocopherol in protecting lens cells from UVB damage, suggesting their crucial role in preventing age-related cataract.