Metal Ion Periplasmic-Binding Protein YfeA of Glaesserella parasuis Induces the Secretion of Pro-Inflammatory Cytokines of Macrophages via MAPK and NF-κB Signaling through TLR2 and TLR4

Abstract

The YfeA gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system Yfe, encodes the substrate-binding subunit of the iron, zinc, and manganese transport system in bacteria. As a potential vaccine candidate in Glaesserella parasuis, the functional mechanisms of YfeA in the infection process remain obscure. In this study, vaccination with YfeA effectively protected the C56BL6 mouse against the G. parasuis SC1401 challenge. Bioinformatics analysis suggests that YfeA is highly conserved in G. parasuis, and its metal-binding sites have been strictly conserved throughout evolution. Stimulation of RAW 264.7 macrophages with YfeA verified that toll-like receptors (TLR) 2 and 4 participated in the positive transcription and expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. The activation of TLR2 and TLR4 utilized the MyD88/MAL and TRIF/TRAM pairs to initiate TLRs signaling. Furthermore, YfeA was shown to stimulate nuclear translocation of NF-κB and activated diverse mitogen-activated protein (MAP) kinase signaling cascades, which are specific to the secretion of particular cytokine(s) in murine macrophages. Separate blocking TLR2, TLR4, MAPK, and RelA (p65) pathways significantly decreased YfeA-induced pro-inflammatory cytokine production. In addition, YfeA-stimulated RAW 264.7 produces the pro-inflammatory hallmark, reactive oxygen species (ROS). In conclusion, our findings indicate that YfeA is a novel pro-inflammatory mediator in G. parasuis and induces TLR2 and TLR4-dependent pro-inflammatory activity in RAW 264.7 macrophages through P38, JNK-MAPK, and NF-κB signaling pathways.

Quercetin Protects Blood–Brain Barrier Integrity via the PI3K/Akt/Erk Signaling Pathway in a Mouse Model of Meningitis Induced by Glaesserella parasuis

“…Studies have demonstrated that in piglets infected with G. parasuis , mononuclear phagocytes increase the gene expression levels of the inflammatory cytokines IL-6 , IL-8 , and IL-10 via the NF-κB signaling pathway [ 32 ]. G. parasuis infection also triggers the upregulation of inflammatory cytokines, IL-1α, IL-1β, IL-6, IL-8, and TNF-α, in porcine alveolar macrophages by activating NF-κB and MAPK signaling pathways [ 33 , 34 ]. Moreover, G. parasuis elevated the expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α in mice through the P38 and JNK-MAPK signaling pathways [ 35 ].…”

EspP2 Regulates the Adhesion of Glaesserella parasuis via Rap1 Signaling Pathway

“…The Western blotting assay was performed as described previously to detect the claudin-1 and occludin expression levels [49]. PK15 cells were plated into 6-well plates at a density of a 1 × 10 6 cells/well and stimulated with EspP2 (50 µg mL −1 ) for different lengths of time.…”