Procyanidin B2 has anti- and pro-oxidant effects on metal-mediated DNA damage

Abstract

Procyanidin B2 (epicatechin-(4β-8)-epicatechin), which is present in grape seeds, apples, and cacao beans, has antioxidant properties. We investigated the mechanism of preventive action of procyanidin B2 against oxidative DNA damage in human cultured cells and isolated DNA. Procyanidin B2 inhibited the formation of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in the human leukemia cell line HL-60 treated with an H 2O 2-generating system. In contrast, a high concentration of procyanidin B2 increased the formation of 8-oxodG in HL-60 cells. Experiments with calf thymus DNA also revealed that procyanidin B2 decreased 8-oxodG formation by Fe(II)/H 2O 2, whereas procyanidin B2 induced DNA damage in the presence of Cu(II), and H 2O 2 extensively enhanced it. An electron spin resonance spin trapping study utilizing 3,3,5,5-tetramethyl-1-pyrroline- N-oxide (M 4PO) demonstrated that procyanidin B2 decreased the signal of M 4PO–OH from H 2O 2 and Fe(II), whereas procyanidin B2 enhanced the signal from H 2O 2 and Cu(II). As an antioxidant mechanism, UV–visible spectroscopy showed that procyanidin B2 chelated Fe(II) at equivalent concentrations. As a pro-oxidant property, we examined DNA damage induced by procyanidin B2, using 32P-labeled DNA fragments obtained from genes relevant to human cancer. Our results raise the possibility that procyanidin B2 exerts both antioxidant and pro-oxidant properties by interacting with H 2O 2 and metal ions.