title: Lipoteichoic acid from anEnterococcus faecalisclinical strain promotes TNF-α expression through the NF-κB and p38 MAPK signaling pathways in differentiated THP-1 macrophages.
abstract: To study the immune-inflammatory response and signaling mechanism of macrophages to purifiedEnterococcus faecalis(E. faecalis) lipoteichoic acid (LTA), intact LTA was obtained from anE. faecalisclinical strain P25RC using the butanol method and hydrophobic interaction chromatography purification. The fractions containing LTA were determined using phosphate detection. Contaminations with lipopolysaccharide and proteins were excluded using the Limulus amoebocyte lysate assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively. LTA was analyzed using nuclear magnetic resonance. Prior to LTA stimulation assays, THP-1 monocytes were pretreated with phorbol 12-myristate 13-acetate to differentiate into macrophages. Macrophages were treated with LTA in concentration gradients and cells without LTA treatment as the control. Gene expression ofTLR2,CD14andMyD88were evaluated by quantitative polymerase chain reaction. Tumor necrosis factor-α (TNF-α) and interleukin (IL)-10 were quantified using ELISA. The activated and total nuclear factor-κB (NF-κB) p65 and three mitogen-activated protein kinases (p38, ERK1/2 and JNK) were assessed using western blot analysis.E. faecalisLTA induced the gene expression ofTLR2andMyD88whilst it downregulatedCD14, suggesting aTLR2-dependent andCD14-independent immune-inflammatory activity. LTA stimulated the expression of pro-inflammatory cytokine TNF-α (P<0.05), but not the anti-inflammatory cytokine IL-10. In conclusion,E. faecalisLTA stimulated the expression of TNF-α in macrophages possibly through the NF-κB and p38 pathways.
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Wang
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China ; School of Stomatology, Capital Medical University, Beijing 100050, P.R. China.
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
authors.affiliation: Faculty of Dentistry, National University of Singapore, Singapore 119074, Singapore.
authors.forename: Chaminda Jayampath
authors.initials: CJ
authors.lastname: Seneviratne
authors.affiliation: Faculty of Chemistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Xuechen
authors.initials: X
authors.lastname: Li
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Gary Shun Pan
authors.initials: GS
authors.lastname: Cheung
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Lijian
authors.initials: L
authors.lastname: Jin
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Chun Hung
authors.initials: CH
authors.lastname: Chu
authors.affiliation: Faculty of Dentistry, University of Hong Kong, Hong Kong, SAR 999077, P.R. China.
authors.forename: Chengfei
authors.initials: C
authors.lastname: Zhang
keywords: Enterococcus faecalis; innate immune response; lipoteichoic acid; root canal infection; signaling pathways; tumor necrosis factor-α