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Salmonella typhimurium (S. t.) is one of the main pathogens that causes acute gastroenteritis. To evaluate the anti-inflammatory mechanism of Astragalus polysaccharide (APS) in vivo and its influence on the intestinal flora, BALB/c mice were infected with S. t. to establish a model of diarrhea. The disease activity index (DAI) scores showed that APS attenuated S. t.-induced weight loss and diarrhea in mice. APS significantly reduced the index of the liver and spleen as well as the ALT and AST levels in serum (P < 0.05). Hematoxylin and eosin (H&E) results indicated that APS significantly increased jejunum villus height and crypt depth and reduced the infiltration of inflammatory cells (P < 0.05). Additionally, APS increased the tight junction (TJ) proteins expression levels of ZO-1, Occludin and Claudin-1 in the jejunum. The results of 16S rDNA showed that APS significantly increased the number of Lactobacillus and Bifidobacterium spp. to normal levels (compared with the control group). In addition, APS significantly decreased the mRNA expression levels of the proinflammatory cytokines TNF-α, IL-1β, IL-6 and IL-17 in the jejunum (P < 0.01) as well as the proteins expression levels of COX-2 and iNOS (P < 0.05). Western blot confirmed that prefeeding with APS inhibited S. t.-induced expression of TLR4 and MyD88 in the jejunum and further inhibited nuclear factor-κB (NF-κB) activation, including the nuclear translocation of the p65 NF-κB subunit and the phosphorylation and degradation of IκB-α. This was the key to APS inhibition of the production of inflammatory factors and inflammatory mediators in the jejunum., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Salmonella typhimurium is one of the main causes of intestinal diseases, affecting the health of humans and livestock. Ethyl pyruvate (EP), which is ordinarily an edible spice, has been indicated to exert anti-inflammatory effects and preserve intestinal barrier function. In this study, intestinal immune function and signaling pathways activated by EP were investigated in vivo in S. typhimurium-challenged BALB/c mice and in vitro in RAW264.7 cells. EP improved body weight loss and the organ index of the liver and spleen (p < 0.05). Serum IgA and IgM levels were significantly increased in EP-treated mice (p < 0.05). According to histopathological and immunohistochemical staining, EP significantly increased the villus height, reduced edema in the jejunum and increased the levels of claudin-1, occludin-1 and ZO-1 proteins compared to the Salmonella-treated group (p < 0.05). In addition, EP decreased the levels of the IL-6, IL-1β and TNF-α mRNA levels in jejunum, liver, spleen and RAW264.7 cells (p < 0.05). EP decreased the levels of TLR4, phosphorylated p38MAPK and ERK1/2 in mice infected with S. typhimurium (p < 0.05). In conclusion, EP effectively protected BALB/c mice from an intestinal S. typhimurium infection by improving the activity of the humoral immune system, reducing intestinal barrier damage, and inhibiting proinflammatory cytokine production in the jejunum by modulating the TLR4/MAPK signaling pathway. Based on these findings, EP has the potential to inhibit inflammation or to serve as an immune-enhancing adjuvant., (Copyright © 2019 Elsevier B.V. All rights reserved.)