Dietary phytoestrogens have anti-inflammatory activity in a guinea pig model of asthma

Phytoestrogens are a normal constituent of soy protein and have been shown to have anti-inflammatory activity in various in vitro and in vivo models. The present study was designed to determine if a diet enriched in the phyto estrogen isoflavones, genistin and daidzin, would alter the antigen-induced cellular Infiltration, particularly eosinophilia, characteristic of a guin ea pig model of asthma. Throughout the duration of the study, guinea pigs w ere maintained on a control diet (standard guinea pig chow) or the same, di et enriched in isoflavones. The animals were placed on the diet 2 weeks pri or to active sensitization with ovalbumin (OA). Three weeks after sensitiza tion, animals were challenged with OA aerosol. The cellular Infiltration in to the lung and protein and red blood cells (RBC) in the bronchoalveolar la vage fluid (BAL) were determined 17 hr later. In animals maintained on the control diet, OA aerosol challenge resulted in the expected increase in eos inophils in both the BAL and the lung tissue, an increase in neutrophils in the BAL, and an increase in protein and the number of RBC in the BAL. in c ontrast, in animals maintained on the isoflavone diet, the OA-induced eosin ophilia in the lung tissue was significantly attenuated. In addition, OA ch allenge caused a greater increase In BAL protein In animals maintained on t he isoflavone diet compared with animals an the control diet. Our results i ndicated that a diet enriched in isoflavones results in reduced antigen-ind uced eosinophilia in the lung in the guinea pig model of asthma. However, t his beneficial anti-inflammatory effect of dietary phytoestrogens is accomp anied by a potentially detrimental increase in antigen-induced leakage of p rotein into the airspace.