Glaesserella parasuis (G. parasuis) causes serious inflammation and meningitis in piglets. Quercetin has anti-inflammatory and anti-bacterial activities; however, whether quercetin can alleviate brain inflammation and provide protective effects during G. parasuis infection has not been studied. Here, we established a mouse model of G. parasuis infection in vivo and in vitro to investigate transcriptome changes in the mouse cerebrum and determine the protective effects of quercetin on brain inflammation and blood–brain barrier (BBB) integrity during G. parasuis infection. The results showed that G. parasuis induced brain inflammation, destroyed BBB integrity, and suppressed PI3K/Akt/Erk signaling-pathway activation in mice. Quercetin decreased the expression of inflammatory cytokines (Il-18, Il-6, Il-8, and Tnf-α) and BBB-permeability marker genes (Mmp9, Vegf, Ang-2, and Et-1), increased the expression of angiogenetic genes (Sema4D and PlexinB1), reduced G. parasuis-induced tight junction disruption, and reactivated G. parasuis-induced suppression of the PI3K/Akt/Erk signaling pathway in vitro. Thus, we concluded that quercetin may protect BBB integrity via the PI3K/Akt/Erk signaling pathway during G. parasuis infection. This was the first attempt to explore the protective effects of quercetin on brain inflammation and BBB integrity in a G. parasuis-infected mouse model. Our findings indicated that quercetin is a promising natural agent for the prevention and treatment of G. parasuis infection.

Although porcine liver contributes to their growth and development by nutrition production and energy supply, oxidative stress-induced hepatocyte damage is inevitable during metabolism. N-glycosylation is a common modification in oxidation; nevertheless, the effects of N-glycosylation on pig liver oxidative reactions remain undefined. In this study, liver proteins with N-glycosylation were detected in Wuzhishan (WZS) pigs between 4 and 8 months old and Large White (LW) pigs at 4 months old based on LC-MS/MS. The results showed that the number of differentially expressed proteins (DEPs) was larger between different pig cultivars than that between WZS pigs at various growth periods. The enriched pathways of DEPs were mainly related to oxidative reactions, and 10 proteins were finally selected that primarily consisted of CYPs, GSTs and HSPs with expressions significantly correlating to liver size and weight. The oxidative genes shared N-glycosylation-modified models of N-x-S and N-G. Five out of 10 proteins were upregulated in WZS pigs compared to LW pigs at 4 months old, while five proteins increased in WZS pigs from 4 to 8 months old. In conclusion, this research provides valuable information on the N-glycosylation motifs in liver oxidation genes of WZS pigs.