High mobility group box 1 protein binding to lipopolysaccharide facilitates transfer of lipopolysaccharide to CD14 and enhances lipopolysaccharide-mediated TNF-alpha production in human monocytes.
LPS-binding protein (LBP) is a central mediator that transfers LPS to CD14 to initiate TLR4-mediated proinflammatory response. However, a possibility of another LPS transfer molecule has been suggested because LBP-deficient mice showed almost normal inflammatory response after LPS injection. In this study, we describe the novel finding that high mobility group box 1 protein (HMGB1) recently identified as a mediator of sepsis has a function of LPS transfer for a proinflammatory response. We used ELISA and surface plasmon resonance to show that HMGB1 binds LPS in a concentration-dependent manner and that the binding is stronger to lipid A moiety than to the polysaccharide moiety of LPS. This binding was inhibited by LBP and polymyxin B. Using native PAGE and fluorescence-based LPS transfer analyses, we show that HMGB1 can catalytically disaggregate and transfer LPS to both soluble CD14 protein and to human PBMCs in a dose-dependent manner. However, this effect was dramatically reduced to the baseline level when HMGB1 was heat inactivated. Furthermore, a mixture of HMGB1 and LPS treatment results in a higher increase in TNF-alpha production in human PBMCs and peripheral blood monocytes than LPS or HMGB1 treatment alone or their summation. Thus, we propose that HMGB1 plays an important role in Gram-negative sepsis by catalyzing movement of LPS monomers from LPS aggregates to CD14 to initiate a TLR4-mediated proinflammatory response.
Youn
Ju Ho
JH
Department of Microbiology, Brain Korea 21 Project for Medical Science, National Core Research Center for Nanomedical Technology, Yonsei University College of Medicine, Seoul, Republic of Korea.
Oh
Young Joo
YJ
Kim
Eun Sook
ES
Choi
Ji Eun
JE
Shin
Jeon-Soo
JS
D000818:Animals; D016466:CHO Cells; D002384:Catalysis; D006224:Cricetinae; D003412:Cricetulus; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008823:Micelles; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism*; D011485:Protein Binding; D012995:Solubility; D020349:Surface Plasmon Resonance; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D024243:HMGB1 Protein; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008823:Micelles; D014409:Tumor Necrosis Factor-alpha