Epigallocatechin gallate protects the human lens epithelial cell survival against UVB irradiation through AIF/endo G signalling pathways in vitro

Abstract

Objective Oxidative stress has been recognised as an important mediator of apoptosis in lens epithelial cells. It also plays an important role in the pathogenesis of cataracts. It is reported that (-)-Epigallocatechin gallate (EGCG), the most abundant component in green tea, exhibits potent antioxidant activity against oxidative stress. This study aimed to investigate the protective effect of EGCG against Ultraviolet B (UVB) induced apoptotic death and the underlying mechanism in human lens epithelial cells (HLECs). Methods HLECs were exposed to various concentrations of EGCG under UVB (30 mJ/cm2), and cell viability was monitored by the MTT assay. Next, mitochondrial membrane potential (Δψm), reactive oxygen species (ROS) and apoptosis were detected by flow cytometry. Meanwhile, the total antioxigenic capacity (T-AOC) was determined by enzyme standard instrument, and the expression of apoptosis inducing factor (AIF) and endonuclease G (Endo G) was measured by quantitative PCR (Q-PCR) and western blotting, respectively. Moreover, the localisation of AIF and Endo G within cells was further detected by confocal optical microscopy. Results The results indicated that EGCG could enhance the cell viability and protect against cell apoptosis caused by UVB irradiation in HLECs. EGCG could also decrease the UVB-induced generation of ROS and collapse of Δψm, increase the T-AOC level. In addition, EGCG could also inhibit the UVB-stimulated increase of AIF and Endo G expression at mRNA and protein levels and ameliorate the UVB-induced mitochondria-nuclear translocation of AIF and Endo G. Conclusions UVB irradiation could damage HLECs viability, while EGCG exhibits antioxidant effect and inhibits UVB-induced apoptosis in HLECs through AIF/Endo G signalling pathways. Our findings reveal the underlying mechanism of EGCG against UVB-induced oxidative stress in HLECs.