Abstract
Procyanidins, polymers of flavan-3-ol units, have been reported to exhibit many beneficial health effects such as antioxidant and anti-carcinogenic effects. In this study, we investigated the cancer chemopreventive properties of procyanidins from wild grape (Vitis amurensis) seeds in particular their roles in inducing phase II detoxifying/antioxidant enzymes as well as in modulating the upstream kinases. Ethanolic extract of V. amurensis seeds was fractionated with a series of organic solvents and finally separated into six fractions, F1–F6. Chemical properties of the procyanidins were analyzed by vanillin assay, BuOH-HCl test, and depolymerization with phloroglucinol followed by LC/MS analysis. The F5 had the highest procyanidin content among all the fractions and strongly induced the reporter activity of antioxidant response element as well as the protein expression of nuclear factor E2-related factor (Nrf2) in HepG2 human hepatocarcinoma cells. The procyanidin-rich F5 also strongly induced the expression of the phase II detoxifying and antioxidant enzymes such as NAD(P)H:quinone oxidoreductase1 and hemeoxygenase1. Phosphorylations of the upstream kinases such as MAPKs and PI3K/Akt were significantly increased by treatment with procyanidin fraction. In addition, the procyanidin-mediated Nrf2 expression was partly attenuated by PI3K inhibitor LY294002, and almost completely by p38 inhibitor SB202190, but neither by JNK inhibitor SP600125 nor by MEK1/2 inhibitor U0126. Taken together, the procyanidins from wild grape seeds could be used as a potential natural chemopreventive agent through Nrf2/ARE-mediated phase II detoxifying/antioxidant enzymes induction via p38 and PI3K/Akt pathway.
Highlights
Chemoprevention is a cancer preventive approach using naturally occurring or synthetic chemical agents to block or reverse carcinogenesis [1]
Many studies have demonstrated that the molecular mechanisms and signaling pathway regulating the activation of NF-E2-related factor (Nrf2) as part of a cytoprotective mechanism are driven from its anti-carcinogenic activities [3,34,35]
The presence of monomeric flavan-3-ols in Fraction 4 (F4) might be responsible for the strong antioxidant activity and nuclear factor E2-related factor (Nrf2)/anti-oxidant response element (ARE) inducing ability of F4
Summary
Chemoprevention is a cancer preventive approach using naturally occurring or synthetic chemical agents to block or reverse carcinogenesis [1]. Mattito et al have recently demonstrated the efficacy of diverse grape procyanidin fractions against oxidative damage induced by UVA and UVB radiation on human keratinocytes and epidermis [19] These effects have been confirmed by many animal studies, in which procyanidin inhibited tumorigenesis in tissues including skin [20,21], colon [21,22,23], breast [24] and prostate [25]. The active compounds and molecular mechanism underlying the cancer preventive effects of wild grape seed has not been elucidated completely, several hypotheses have been proposed. Many studies have demonstrated that the molecular mechanisms and signaling pathway regulating the activation of NF-E2-related factor (Nrf2) as part of a cytoprotective mechanism are driven from its anti-carcinogenic activities [3,34,35].
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