Abstract
Natural polyphenols are promising anti-aging compounds not only for their antioxidant activity, but also their ability to activate specific cellular pathways mediating the aging process. Avenanthramide C (Avn C), found exclusively in oats, is a natural antioxidant associated with free radical scavenging; however, it is how this compound elicits other protective effects. We investigated the intracellular antioxidant activity of Avn C and other cytoprotective potential in normal human skin fibroblasts exposed to extracellular stress. Avn C reduced H2O2-induced oxidative stress by reducing intracellular free radical levels and antioxidant gene transcripts. Avn C also resulted in decreased levels of gene transcripts encoding pro-inflammatory cytokines in response to H2O2 or tumor necrosis factor-α (TNF-α). This reduction in cytokine gene transcription occurred concomitantly with reduced phosphorylated nuclear factor-κB (NF-κB) p65, and decreased NF-κB DNA binding. Avn C further induced heme oxygense-1 (HO-1) expression through increased Nrf2 DNA binding activity, demonstrating a second mechanism by which Avn C attenuates cellular stress. Collectively, our findings indicate that Avn C protects normal human skin fibroblasts against oxidative stress and inflammatory response through NF-κB inhibition and Nrf2/HO-1 activation.
Highlights
Oats (Avena sativa L.) have many scientifically verified health-promoting effects, making them one of the best grains for human consumption[1,2]
As we observed that Avenanthramide C (Avn C) showed cytoprotective effect against H2O2-induced oxidative stress in 2DD normal human skin fibroblasts, we evaluated if Avn C can reduce H2O2-induced pro-inflammatory signaling in 2DD cells
Given that Avn C showed protective effect against H2O2-induced oxidative stress through free radical scavenging which decreased H2O2-induced antioxidant gene transcription, we further investigated if Avn C could exert protective effects by activating other protective pathways in untransformed fibroblasts. 2DD cells were treated with Avn C for 48 h and RNA was extracted, converted to cDNA and evaluated by qRT-PCR to examine if there was any antioxidant enzyme that was up-regulated by Avn C treatment
Summary
Oats (Avena sativa L.) have many scientifically verified health-promoting effects, making them one of the best grains for human consumption[1,2]. Several studies have indicated that both oat phenolic-rich extract and pure Avns had anti-inflammatory activity by reducing the expression of pro-inflammatory cytokines and repressing NF-κB function[15,16,17,18] These studies document the anti-inflammatory response in cancer cell lines and; it remains unclear if Avn C is able to supress pro-inflammatory signals in normal cells/tissues. Avn C has been demonstrated to activate the nuclear factor erythroid 2-krupple-like 2 (Nrf-2) signalling in immortalized kidney cells[26]; a factor associated with pro-longevity These studies have indicated anti-oxidant, anti-inflammatory, anti-genotoxic and anti-proliferation mechanisms/cellular pathways, which could cooperate and lead to overall increases in health and lifespan[27,28]. We demonstrate that Avn C attenuated the effects of H2O2 and TNF-α through Nrf2/HO-1 activation and NF-κB inhibition as well as anti-proliferative effect in human skin fibroblasts
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