Nrf-2 Activation by Palm Fruit Bioactives

PURPOSE: Overexposure to reactive oxygen species has been implicated in the pathogenesis of a wide range of chronic conditions, including cardiovascular disease, cancer, and the aging process (e.g. “free radical theory of aging”). While some early studies have shown the benefits of “direct” antioxidants (e.g. vitamins A, C, E) in reducing oxidative cellular damage, more recent evidence suggests that mega-doses of antioxidants (e.g. E, beta-carotene, resveratrol) may interfere with internal cellular protection pathways, disrupt redox balance, and suppress several important exercise-induced adaptations. In contrast, up-regulation of endogenous “indirect” antioxidant pathways has been proposed as a mechanism for optimizing redox balance. Activation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a transcriptional regulator of phase II antioxidant enzymes, has been suggested as an important step in attenuating oxidative stress. A number of natural phytonutrients have been shown to activate Nrf2, including turmeric and green tea. Palm Fruit Bioactives (PFB), a standardized 5-polyphenol blend, has been shown to exhibit anti-hypertensive, anti-atherogenic, anti-diabetic, and chemo-preventive effects in animal models. The purpose of this study was to evaluate the effect of palm fruit bioactives (PFB) on activation of the Nrf2 pathway in cell culture as one potential mechanism of action for PFB’s health effects. METHODS: AREc32 cells (MCF-7 cell line stably transfected with a vector containing firefly luciferase under the control of the Antioxidant Response Element, ARE) were cultured in RPMI 1640 culture medium with L-glutamine and supplemented with 10% fetal bovine serum and antibiotic/antimycotic. AREc32 cells were seeded at a density of 500 cells/well and exposed to PFB at varying concentrations from 0.125% to 20% for 6-24h. RESULTS: PFB increased cell viability at 6h (0.125% and 3.3%) and 24h (2% and 3.3%). At both time points, PFB increased Nrf2-activation expression over untreated controls by a factor of 9-20 fold (0.25% and 7.5% at 6h; 0.125% and 5% at 24h). CONCLUSIONS: These data demonstrate potent Nrf2-activation by PFB which may provide a potential mechanism of attenuating oxidative stress and explaining previously observed cardiovascular, metabolic, and cell-protection effects.