Dietary soyasaponin attenuates 2,4-dinitrofluorobenzene-induced contact hypersensitivity via gut microbiota in mice

Abstract

Soyasaponins (SSs) are abundant in soybeans and display inhibitory activity against contact hypersensitivity (CHS), which is often used as a mouse model for allergic contact dermatitis (ACD); however, their therapeutic mechanisms remain unknown. Here, we attempted to clarify the role of gut microbiota in the inhibition of CHS by dietary soyasaponins. For antibiotic treatment, mice were administered a mixture of ciprofloxacin and metronidazole or vancomycin. These antibiotics and SSs were given to mice via drinking water 3-weeks prior to CHS induction with 2,4-dinitrofluorobenzene, and the mice were analysed for ear swelling, tissue oedema, infiltration of Gr-1-positive immune cells, the composition of faecal microbiota and regulatory T (T ) cells. The soyasaponin diets attenuated ear swelling and tissue oedema, and reduced the number of Gr-1-positive cells infiltrating ear tissues. CHS caused changes in the structure of the gut microbiota, but dietary SSs blocked the changes in the microbiota composition. Ciprofloxacin and metronidazole treatments significantly enhanced the severity of CHS symptoms, whereas vancomycin treatment blocked the suppressive effect of dietary SSs on CHS. These antibiotic treatments differed in their effects on the gut microbiota composition. T cells in auricular lymph node and spleen increased under SS-enriched diets, but this increase was blocked by vancomycin treatment. These results suggest that dietary SSs exert their inhibitory activity on CHS via the gut microbiota in mice, suggesting that dietary supplementation with SSs may have beneficial effects on ACD patients, but that the gut microbiota is a critical determinant of the therapeutic value of dietary SSs.

Effect of a diet containing a mixture of soybean isoflavones and soyasaponins on contact hypersensitivity and gut microbiota in mice

“…Bacteria were recovered from the lysates of fecal samples using a FastDNA Spin Kit for Soil (MP Biomedicals). Polymerase chain reaction and sequencing were performed using the Illumina MiSeq platform (Illumina, San Diego), as described previously (Nagano et al., 2019c). Taxonomic analysis of the 16S rDNA sequences was conducted by the TechnoSuruga Laboratory (Shizuoka, Japan) based on the Ribosomal Database Project using Metagenome@Kin analysis software (World Fusion, Tokyo).…”

“…This antibiotic treatment reduced the number of regulatory T (T reg ) cells in auricular lymph nodes and spleen, and completely altered the gut microbiota composition in the SS‐treated mice. These results indicated that the observed reduction in CHS‐inhibitory activity was likely due to an altered gut microbiota composition that resulted in a reduction in T reg cells (Nagano et al., 2019c). However, the CHS‐inhibitory effects of diets containing a mixture of SIs and SSs and the role of the intestinal microbiota are unknown.…”

“…Consumption of soybean milk has CHS‐suppressive effects and reduced changes due to CHS induction in the composition of gut microbiota (Nagano et al., 2019b). We also used antibiotics to elucidate the role of gut microbiota in the CHS‐inhibitory activity of dietary SSs and found that this activity was absent after vancomycin treatment (Nagano et al., 2019c). This antibiotic treatment reduced the number of regulatory T (T reg ) cells in auricular lymph nodes and spleen, and completely altered the gut microbiota composition in the SS‐treated mice.…”

Soy Saponin Improves Egg-Laying Performance and Immune Function of Laying Hens

“…Additionally, there were no negative effects on its performance, intestinal morphology and organ index with SS supplementation to the diet of mice [26]. SS alleviated 2,4-dinitro uoro benzene (DNFB)-induced intestinal micro ora imbalance in mice [31]. Most of these studies were concentrated in the medical eld.…”

“…Studies showed that the proliferation of Staphylococcus aureus and Escherichia coli were inhibited by SS [9; 16]. SS could also alleviate allergic skin reactions in mice via improving the intestinal micro ora [31]. Besides, some scholars tried to ferment soybean meal with Lactobacillus pentosus, and nally detected the production of soyasaponol and genistein.…”