Soybean Agglutinin Alters the Gut Microbiota and Promotes Inflammation in Lupus-Prone MRL/lpr Mice

Certain foods can trigger flares in patients with systemic lupus erythematosus. Lectins in edible plants have been reported to increase inflammation. This study aimed to determine the effects of 1-time intake of soybean agglutinin (SBA) on the gut microbiota and immune response in lupus-prone MRL/MpJ (MRL)/lpr mice. MRL/MpJ-Faslpr/J (MRL/lpr) and MRL mice were randomly assigned into 4 groups (8 mice/group): MRL mice + phosphate-buffered saline (PBS) (CON), MRL mice + SBA (CS), MRL/lpr mice + PBS (LPR), and MRL/lpr + SBA (LS). PBS and SBA were orally administered at 16 wk of age, and all mice were killed 24 h after oral challenge. The disease phenotype, levels of proinflammatory cytokines, and composition of the intestinal microbiota were determined. Interferon-gamma (IFN-γ) in the serum was significantly higher, whereas the level of serum IL-10 was significantly lower in LS mice than in LPR mice [fold change (FC) = 1.31 and FC = 0.36, respectively]. The expression levels of IL-6 and TNF-α in the spleen of LS mice were significantly higher than those in LPR mice (FC = 1.66 and FC = 1.96, respectively). The expression levels of IL-6, TNF-α, and IL-1β in the kidney were also significantly higher in LS mice than in LPR mice (FC = 2.89, FC = 3.78, and FC = 2.02, respectively). The relative abundances of Erysipelotrichaceae and Turicibacter in LS mice were significantly higher than those in LPR mice (FC = 1.73 and FC = 1.74, respectively). The percentage of Breg cells in the mesenteric lymph nodes was significantly lower in LS mice than in LPR mice (FC = 0.53) (P < 0.05). No change was found between SBA treatment or not in the control (MRL) mice. One-time intake of SBA can promote the secretion of proinflammatory cytokines, downregulate Breg cells, and alter the intestinal flora in MRL/lpr mice within 24 h of oral challenge, which may contribute to exacerbation of lupus.