Equol Inhibits LPS-Induced Oxidative Stress and Enhances the Immune Response in Chicken HD11 Macrophages

Background/aims: There has been increasing recent attention on the antioxidative capacity of equol. This study tested the effect of equol on oxidative stress induced by lipopolysaccharide (LPS) and regulation of immunity in chicken macrophages.

Methods: Chicken HD11 macrophages were challenged with LPS (100 ng/mL) alone or with LPS (100 ng/mL) and (±)equol (10, 20, 40, 80, 160 μmol/L) together for 24h. Evaluated responses included the contents of malondialdehyde (MDA) and reduced glutathione (GSH), activities of total superoxide dismutase (T-SOD) and inducible nitric oxide synthase (iNOS), transcript abundance of superoxide dismutase 2 (SOD2), catalase (CAT), glutathione transferase (GST), Toll-like receptor 4 (TLR4), tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β), and contents of the cytokines TNFα, IL-1β, interleukin-2 (IL-2) and interferon beta (IFNβ).

Results: Exposure to LPS induced oxidative stress as contents of MDA increased and GSH decreased in LPS-treated cells (P < 0.05) compared to those in control cells. Compared to LPS alone, co-treatment with equol (20 μmol/L, 40 μmol/L or 80 μmol/L) reduced contents of MDA and increased those of GSH (both P < 0.05). Activity of T-SOD increased (P < 0.05) in cells treated with the higher contentration of equol (80 μmol/L or 160 μmol/L), however, all concentrations (20 μmol/L to 160 μmol/L) increased activity of iNOS (P < 0.05). The highest concentration of equol (160 μmol/L) increased SOD2 and GST transcripts (P < 0.05). Equol treatment increased transcripts of TLR4, TNFα and IL-1β (P < 0.05). And there were similar changes in contents of IL-1β, IL-2, IFNβ and TNFα in the cells (P < 0.05).

Conclusions: It concluded that equol can protect chicken HD11 macrophages from oxidative stress induced by LPS through reducing lipid peroxidation products and enhancing contents of antioxidants, and activities of relevant antioxidase enzymes; effects were also seen in gene expression related to the immune response and increased contents of cytokines. The optimal concentration of equol on antioxidation and immune enhancement in chicken macrophages was 40 μmol/L.