Antioxidant effect of a phytoestrogen equol on cultured muscle cells of embryonic broilers

Abstract

Previous studies have shown that the in ovo injection of equol can markedly improve the water-holding capacity of muscles of broilers chickens at 7wk of age through promotion of the antioxidant status. We aimed to investigate directly the antioxidant effects of equol on muscle cells in broilers. Muscle cells were separated from leg muscle of embryos on the 11th day of incubation and treated with equol and H(2)O(2), either alone or together. Cells were pretreated with medium containing 1, 10, or 100μM equol for 1h prior to the addition of 1mM H(2)O(2) for a further 1h. Photomicrographs of cells were obtained. Cell viability, malondialdehyde (MDA) content, and L-lactate dehydrogenase (LDH) activity in the cell supernatant, as well as intracellular total superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-Px) activities were determined. Treatment with 1mM H(2)O(2) caused serious damage to cells, indicated by comets with no clear head region but a very apparent tail of DNA fragments. Pretreatment with low (1μM) but not high concentrations of equol (10μM) inhibited cell damage, while 100μM equol caused more serious damage than H(2)O(2) alone. Pretreatment with 1μM equol had no effect on cell viability, while pretreatment with 10 and 100μM equol significantly decreased cell viability in a dose-dependent manner. Compared with H(2)O(2) alone, pretreatment with low-dosage equol markedly decreased LDH activity and MDA production in the supernatant, significantly increased intracellular T-SOD activity (P < 0.05) and tended to increase intracellular GSH-Px activity (0.05 < P < 0.1). Pretreatment with high-dosage equol (10 and 100μM) significantly enhanced LDH activity, but had no effect on MDA content, T-SOD or GSH-Px activity induced by H(2)O(2,) except for an obvious increase in GSH-Px activity caused by 10μM equol. These results indicate that equol at low dosage can prevent skeletal muscle cell damage induced by H(2)O(2), while pretreatment with high-dosage equol shows a synergistic effect with H(2)O(2) in inducing cell damage.