Staphylococcus xylosus is an opportunistic pathogen that causes infection in humans and cow mastitis. And S. xylosus possesses a strong ability to form biofilms in vitro. As biofilm formation facilitates resistance to antimicrobial agents, the discovery of new medicinal properties for classic drugs is highly desired. Aspirin, which is the most common active component of non-steroidal anti-inflammatory compounds, affects the biofilm-forming capacity of various bacterial species. We have found that aspirin effectively inhibits biofilm formation of S. xylosus by Crystal violet (CV) staining and scanning electron microscopy analyses. The present study sought to elucidate possible targets of aspirin in suppressing S. xylosus biofilm formation. Based on an isobaric tag for relative and absolute quantitation (iTRAQ) fold-change of >1.2 or <0.8 (P-value < 0.05), 178 differentially expressed proteins, 111 down-regulated and 67 up-regulated, were identified after application of aspirin to cells at a 1/2 minimal inhibitory concentration. Gene ontology analysis indicated enrichment in metabolic processes for the majority of the differentially expressed proteins. We then used the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database to analyze a large number of differentially expressed proteins and identified genes involved in biosynthesis of amino acids pathway, carbon metabolism (pentose phosphate and glycolytic pathways, tricarboxylic acid cycle) and nitrogen metabolism (histidine metabolism). These novel proteins represent candidate targets in aspirin-mediated inhibition of S. xylosus biofilm formation at sub-MIC levels. The findings lay the foundation for further studies to identify potential aspirin targets.
The imidazole glycerophosphate dehydratase (IGPD) protein is a therapeutic target for herbicide discovery. It is also regarded as a possible target in Staphylococcus xylosus (S. xylosus) for solving mastitis in the dairy cow. The 3D structure of IGPD protein is essential for discovering novel inhibitors during high-throughput virtual screening. However, to date, the 3D structure of IGPD protein of S. xylosus has not been solved. In this study, a series of computational techniques including homology modeling, Ramachandran Plots, and Verify 3D were performed in order to construct an appropriate 3D model of IGPD protein of S. xylosus. Nine hits were identified from 2,500 compounds by docking studies. Then, these nine compounds were first tested in vitro in S. xylosus biofilm formation using crystal violet staining. One of the potential compounds, baicalin was shown to significantly inhibit S. xylosus biofilm formation. Finally, the baicalin was further evaluated, which showed better inhibition of biofilm formation capability in S. xylosus by scanning electron microscopy. Hence, we have predicted the structure of IGPD protein of S. xylosus using computational techniques. We further discovered the IGPD protein was targeted by baicalin compound which inhibited the biofilm formation in S. xylosus. Our findings here would provide implications for the further development of novel IGPD inhibitors for the treatment of dairy mastitis.
This study investigated the effects of forsythiaside on the acute inflammatory response induced by Escherichia coli lipopolysaccharide (LPS) in liver of broiler chickens. Fifteen-day-old chickens were randomly assigned to three groups (n = 20 for each group, orally treated with 0, 30, or 60 mg/kg BW of forsythiaside) for 7 days. At 21 days of age, the chickens were intravenously injected with either LPS (200 μg/kg BW) or sterile saline (200 μg/kg BW, control group). All the chickens were humanely euthanized by cervical dislocation 2 h after the LPS injection. The results showed that the injection of LPS induced some indexes, including total proteins, nitric oxide (NO), interleukin-1beta (IL-1β), interleukin-6 (IL-6), and interleukin-17 (IL-17) production (P < 0.05) and increased the mRNA expression of LPS-induced tumor necrosis factor-alpha (LITAF), IL-1β, IL-17, IL-6, and inducible nitric oxide synthase (iNOS) (P < 0.05). Forsythiaside supplementation alleviated the LPS-induced inflammatory response by inhibiting the production of total proteins, NO, LITAF, IL-1β, IL-17, and IL-6 and down-regulating the mRNA expression of pro-inflammatory cytokines and iNOS. In conclusion, forsythiaside is a potential treatment for LPS-induced liver acute inflammation in chicken.
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