Effects of menadione, hydrogen peroxide, and quercetin on apoptosis and delayed luminescence of human leukemia Jurkat T-cells.

Menadione (MD) is an effective cytotoxic drug able to produce intracellularly large amounts of superoxide anion. Quercetin (QC), a widely distributed bioflavonoid, can exert both antioxidant and pro-oxidant effects and is known to specifically inhibit cell proliferation and induce apoptosis in different cancer cell types. We have investigated the relation between delayed luminescence (DL) induced by UV-laser excitation and the effects of MD, hydrogen peroxide, and QC on apoptosis and cell cycle in human leukemia Jurkat T-cells.

A two-gate model for the ryanodine receptor with allosteric modulation by caffeine and quercetin.

We have developed a model of the tetrameric ryanodine receptor--the calcium channel of the sarcoplasmic reticulum. The model accurately describes published experimental data on channel activity at various concentrations of Ca2+, caffeine and quercetin. The proposed mechanisms involve allosteric regulation of Ca2+ affinity by both caffeine and quercetin, and the existence of two independent, A- and I-gates controlled by Ca2+ binding to an activating and an inhibitory module of the receptor.