The protective effect of zeaxanthin on human limbal and conjunctival epithelial cells against UV-induced cell death and oxidative stress

Abstract

● AIM: To explore the protective effect of zeaxanthin on human limbal and conjunctival epithelial cells against UV-radiation and excessive oxidative stress. ● METHODS: Human limbal and conjunctival epithelial cells were isolated from cadaver and cultured in vitro. They were challenged with UVB radiation and H 2 O 2 with and without zeaxanthin pretreatment. Cell viability, p38 and c-JUN NH(2)-terminal kinase (JNK) phosphorylation, IL-6, IL-8 and MCP-1 secretion and malondialdehyde (MDA) content were measured. ● RESULTS: Zeaxanthin had no measurable cytotoxicity on limbal or conjunctival epithelial cells when used at concentrations of 5 µg/mL and below. At 30 mJ/cm 2 UVB, the pretreatment of zeaxanthin increased the percentage of live cells from 50% to 69% (P=0.01) and from 66% to 75% (P=0.05) for limbal and conjunctival epithelial cells, respectively. The concentrations of IL-6, IL-8 and MCP-1 in the culture medium reduced to 66% (for IL-6 and MCP-1) and 56% (for IL-8) of the levels without zeaxanthin. This was accompanied by reduced p38 and JNK protein phosphorylation. Pretreatment of zeaxanthin also reduced intracellular MDA content caused by H 2 O 2 stimulation from 0.86 µmol/L to 0.52 µmol/L (P=0.02) in limbal epithelial cells and from 0.96 µmol/L to 0.56 µmol/L in conjunctival epithelial cells (P=0.03). However, zeaxanthin did not have significant effect on H 2 O 2 -induced cell death in limbal or conjunctival epithelial cells. ● CONCLUSION: Zeaxanthin is an effective reagent in reducing the detrimental effect of UV-radiation and oxidative stress on ocular surface epithelial cells.