Dietary Phytoestrogens Have Anti-Inflammatory Activity in a Guinea Pig Model of Asthma

Abstract

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 phytoestrogen isoflavones, genistin and daidzin, would alter the antigen-induced cellular infiltration, particularly eosinophilia, characteristic of a guinea pig model of asthma. Throughout the duration of the study, guinea pigs were maintained on a control diet (standard guinea pig chow) or the same diet enriched in isoflavones. The animals were placed on the diet 2 weeks prior to active sensitization with ovalbumin (OA). Three weeks after sensitization, animals were challenged with OA aerosol. The cellular infiltration into the lung and protein and red blood cells (RBC) in the bronchoalveolar lavage fluid (BAL) were determined 17 hr later. In animals maintained on the control diet, OA aerosol challenge resulted in the expected increase in eosinophils 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 contrast, in animals maintained on the isoflavone diet, the OA-induced eosinophilia in the lung tissue was significantly attenuated. In addition, OA challenge caused a greater increase in BAL protein in animals maintained on the isoflavone diet compared with animals on the control diet. Our results indicated that a diet enriched in isoflavones results in reduced antigen-induced eosinophilia in the lung in the guinea pig model of asthma. However, this beneficial anti-inflammatory effect of dietary phytoestrogens is accompanied by a potentially detrimental increase in antigen-induced leakage of protein into the airspace.

Obesity is associated with increased risk of allergy in Vietnamese adolescents

“…In our study, BMI showed a tendency towards higher risk of allergy in girls but not boys, but we observed no difference between boys and girls with %BF as indicator. There is also some evidence of an anti-inflammatory effect of isoflavones, a phytoestrogen with estrogenic activity that is processed in a manner similar to estradiol (Kuiper et al, 1998;Regal et al, 2000).…”

Endocrine disrupters – potential modulators of the immune system and allergic response

“…Studies on an guinea-pig model of asthma demonstrated that genistein, contrary to daidzein, which has no inhibitory activity against tyrosine kinases, effectively reduced acute bronchoconstriction, pulmonary eosinophilia, and AHR induced by ovalbumine (OVA), but not histamine or metacholine (79). However, other results show that the reduction of antigen-induced eosinophilia in the lung of the asthmatic guinea-pigs being on a diet enriched with isoflavones is accompanied by a potentially detrimental increase in antigen-induced leakage of protein into the airspace (78).…”

“…In mice, injection of genistein caused a decrease in relative percentages of both thymic CD4(+)CD8()) and CD4(+)CD8(+) thymocytes (39,45). As genistein is an inhibitor of tyrosine kinase -an enzyme playing a pivotal role in the activation of inflammatory cells, it has been proposed that soy isoflavones have immunosuppressive and antiinflammatory properties (78)(79)(80). However, a few experimental data does not correspond with this assumption.…”

Phytoestrogens

“…Although licorice contains bioactive triterpenes and chalcones, the isoflavonoid licoricidin was recently shown to inhibit lyso-platelet activating factor (PAF) acetyltransferase, making it a strong candidate for the active antiallergenic principle (21). An isoflavone phytoestrogen-rich diet has also been shown to reduce inflammatory markers in a guinea pig model of asthma, although this was accompanied by potentially detrimental leakage of protein into the airspace of the lungs following challenge with an aerosol containing ovalbumin, to which the guinea pigs had been previously sensitized (155).…”