Lipoteichoic acid ofEnterococcus faecalisinduces the expression of chemokines via TLR2 and PAFR signaling pathways

Abstract

Enterococcus faecalis is one of the most common opportunistic pathogens responsible for nosocomial infections, and its LTA is known as an important virulence factor causing inflammatory responses. As chemokines play a key role in inflammatory diseases by triggering leukocyte infiltration into the infection site, we purified EfLTA and investigated its effect on the expression of chemokines, IP-10, MIP-1α, and MCP-1, in murine macrophages. EfLTA induced the expression of these chemokines at the mRNA and protein levels. TLR2, CD14, and MyD88 were involved in the EfLTA-induced chemokine expression, as the expression was reduced remarkably in macrophages derived from TLR2-, CD14-, or MyD88-deficient mice. EfLTA induced phosphorylation of MAPKs and enhanced the DNA-binding activity of NF-κB, AP-1, and NF-IL6 transcription factors. The induction of IP-10 required ERK, JNK, p38 MAPK, PKC, PTK, PI3K, and ROS. We noticed that all of these signaling molecules, except p38 MAPK and ROS, were indispensable for the induction of MCP-1 and MIP-1α. Interestingly, the EfLTA-induced chemokine expression was mediated through PAFR/JAK/STAT1 signaling pathways without IFN-β involvement, which is different from LPS-induced chemokine expression requiring IFN-β/JAK/STAT1 signaling pathways. Furthermore, the culture supernatant of EfLTA-treated RAW 264.7 cells promoted the platelet aggregation, and exogenous PAF induced the chemokine expression in macrophages derived from WT and TLR2-deficient mice. These results suggest that EfLTA induces the expression of chemokines via signaling pathways requiring TLR2 and PAFR, which is distinct from that of LPS-induced chemokine expression.

The protective effect of CDDO-Me on lipopolysaccharide-induced acute lung injury in mice

“…It is recently accepted that Rac1 plays an important role in modulating PI3K/Akt/IKK/NF-κB signalings [41]. Meanwhile, evidence has been published to show that JAK/STAT pathway is associated with the regulation of Akt/NF-κB cascade and MAPKs [42,43].…”

New Insights into the Antimicrobial Effect of Mast Cells against Enterococcus faecalis

“…TLR2 signaling has been reported to be critically involved in the control of other pathogens, like Francisella tularensis, by MCs (50). Furthermore, it has been demonstrated that lipoteichoic acid of E. faecalis induces the expression of chemokines in macrophages, mainly via the TLR2/PAFR signaling pathway (51). Also, the involvement of other TLRs in the immune response to enterococci has been demonstrated in recent studies involving the recognition of enterococcal nucleic acids by the endosomal TLR7 and TLR9 in macrophages (52).…”

Lipopolysaccharide of Aggregatibacter actinomycetemcomitans induces the expression of chemokines MCP-1, MIP-1α, and IP-10 via similar but distinct signaling pathways in murine macrophages

“…TLR4-and MyD88-deficient mice with C57BL/6 background were kindly provided by Dr. Shizuo Akira (Osaka University, Osaka, Japan). BMMs were prepared as described previously (Park et al, 2013).…”

“…In a separate experiment, RAW 264.7 cells were pretreated with MAP kinase inhibitors for 1 h and then stimulated with 0.1 g/ml of AaLPS for 3 h. The mRNA expression of IFN-␤ and ␤-actin was determined by RT-PCR as described previously (Park et al, 2013) with the following primers: IFN-␤: forward 5 -TCCAAGAAAGGACGAACATTCG-3 and reverse 5 -TGAGGACATCTCCCACGTCAA-3 , and ␤-actin: Western blotting RAW 264.7 cells were stimulated with 0.1 g/ml AaLPS for the indicated time periods. Cell lysates were prepared, separated by 10% SDS-PAGE, and transferred to PVDF membrane as described previously (Park et al, 2013). The membrane was then blocked with 5% bovine serum albumin at room temperature for 1 h and incubated with primary antibodies specific to p38 MAP kinase, phospho-p38 MAP kinase (p-p38), JNK, phospho-JNK (p-JNK), ERK, phospho-ERK (p-ERK), STAT1, or phospho-STAT1 (p-STAT1) at 4 • C overnight.…”