Responses of human lens epithelial cells to quercetin and DMSO

Oxidative stress is an initiating factor in the development of maturity-onset cataract. Diet has a significant impact on cataract development, and individual dietary components responsible for the protective effect include flavonoids, of which quercetin is the most important. The purpose of this study was to investigate the protective effect of quercetin and its toxicity for human lens epithelial cells (HLECs).

HLECs in culture were incubated for 48 hours with either 1% (vol/vol) dimethyl sulfoxide (DMSO) alone or with this concentration of DMSO and between 0.1 and 100 microM of quercetin. Nonstimulated cells served as control cultures. The viability of HLECs was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay. Gene expression was assessed with reverse transcription-polymerase chain reaction (RT-PCR). Cellular apoptosis was examined by in situ immunocytochemistry using terminal deoxynucleotidyl transferase-mediated biotin-dUTP nicked labeling (TUNEL) and by flow cytometry, using annexin V-FITC apoptosis detection.

DMSO (1% vol/vol) decreased cell viability, increased cellular apoptosis, and upregulated Bax in these cells; 0.1 microM quercetin inhibited these effects and protected HLECs from the toxicity of DMSO. Higher concentrations of quercetin the viability of HLECs decreased. In a dose-dependent response to quercetin, cellular apoptosis increased and the change correlated with upregulation of Bax and decreased cell viability.

Quercetin, at a low concentration (0.1 microM), protects HLECs and reverses the toxic effects of DMSO (1% vol/vol). However, at higher concentrations, quercetin is toxic to HLECs with an LD(50) of 90.85 microM. Quercetin induced apoptosis and upregulates apoptotic genes in HLECs in a dose-dependent manner.