TLR2 and TLR4 agonists synergistically up-regulate SR-A in RAW264.7 through p38.
It is known that macrophage scavenger receptor A (SR-A) can protect mice from endotoxemia. In addition, Escherichia coli O111:B4 LPS from Sigma (sLPS), which contains both TLR4 and TLR2 agonists, was previously reported to be able to induce SR-A expression on murine macrophage cell line RAW264.7. However, the relative role of both TLR4 and TLR2 agonists from Sigma (sLPS) in the up-regulation of SR-A on RAW264.7 is still undefined. Here, we found that sLPS could only slightly up-regulate SR-A on RAW264.7 following removing its TLR4 and TLR2 agonists, respectively. In contrast, the combination of TLR4 agonist uLPS (re-extracted sLPS) and TLR2 agonist Pam3CSK4 dramatically induced SR-A expression, and synergistically promoted RAW264.7 to bind and internalize FITC-LPS specifically through SR-A. The combination had no such effect either on TLR2 or TLR4 expression, and incubation with IL-6, IL-10, IL-12 or TNF-alpha alone could not induce SR-A expression on RAW264.7. In addition, treatment with a NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC) could only weakly suppress the up-regulation of SR-A by the combination. However, the combination synergistically promoted MAPK p38 phosphorylation, and p38 specific inhibitor SB203580 completely suppressed its inducible effect on SR-A expression. Hence, we demonstrated that up-regulation of SR-A by sLPS was resulted from the cooperation of its TLR4 and TLR2 agonists through p38, and we also presented a novel synergy effect of TLR2 and TLR4 agonists.
Xu
Wen-Yue
WY
Institute of Immunology, The Third Military Medical University, 30 Gaotanyan Street, Shapingba District, Chongqing 400038, China.
Wang
Li
L
Wang
Hui-Ming
HM
Wang
Yi-Qin
YQ
Liang
Yun-Fei
YF
Zhao
Ting-Ting
TT
Wu
Yu-Zhang
YZ
D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004357:Drug Synergism; D004705:Endocytosis / Q000187:drug effects; D016650:Fluorescein-5-isothiocyanate; D006801:Humans; D055666:Lipopeptides; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D011112:Polymyxin B / Q000494:pharmacology; D051117:Scavenger Receptors, Class A / Q000235:genetics / Q000378:metabolism*; D051195:Toll-Like Receptor 2 / Q000819:agonists*; D051197:Toll-Like Receptor 4 / Q000819:agonists*; D015854:Up-Regulation / Q000235:genetics*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D016207:Cytokines; D055666:Lipopeptides; D008070:Lipopolysaccharides; D016328:NF-kappa B; C508075:Pam(3)CSK(4) peptide; D010455:Peptides; D051117:Scavenger Receptors, Class A; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D048051:p38 Mitogen-Activated Protein Kinases; D016650:Fluorescein-5-isothiocyanate; D011112:Polymyxin B