Lipoteichoic acid from an clinical strain promotes TNF-α expression through the NF-κB and p38 MAPK signaling pathways in differentiated THP-1 macrophages.

To study the immune-inflammatory response and signaling mechanism of macrophages to purified () lipoteichoic acid (LTA), intact LTA was obtained from an clinical 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 of , and were 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. LTA induced the gene expression of and whilst it downregulated , suggesting a -dependent and -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, LTA stimulated the expression of TNF-α in macrophages possibly through the NF-κB and p38 pathways.