title: The alarmin HMGB1 acts in synergy with endogenous and exogenous danger signals to promote inflammation.
abstract: The nuclear protein HMGB1 has previously been demonstrated to act as an alarmin and to promote inflammation upon extracellular release, yet its mode of action is still not well defined. Access to highly purified HMGB1 preparations from prokaryotic and eukaryotic sources enabled studies of activation of human PBMC or synovial fibroblast cultures in response to HMGB1 alone or after binding to cofactors. HMGB1 on its own could not induce detectable IL-6 production. However, strong enhancing effects on induction of proinflammatory cytokine production occurred when the protein associated with each of the separate proinflammatory molecules, rhIL-1beta, the TLR4 ligand LPS, the TLR9 ligand CpG-ODN, or the TLR1-TLR2 ligand Pam3CSK4. The bioactivities were recorded in cocultures with preformed HMGB1 complexes but not after sequential or simultaneous addition of HMGB1 and the individual ligands. Individual A-box and B-box domains of HMGB1 had the ability to bind LPS and enhance IL-6 production. Heat denaturation of HMGB1 eliminated this enhancement. Cocultures with HMGB1 and other proinflammatory molecules such as TNF, RANKL, or IL-18 did not induce enhancement. HMGB1 thus acts broadly with many but not all immunostimulatory molecules to amplify their activity in a synergistic manner.
authors: Department of Medicine, Rheumatology Research Unit, Karolinska Hospital, Karolinska Institutet, S-171 76 Stockholm, Sweden.
authors: Hulda Sigridur
authors: HS
authors: Hreggvidsdottir
authors: Therese
authors: T
authors: Ostberg
authors: Heidi
authors: H
authors: Wähämaa
authors: Hanna
authors: H
authors: Schierbeck
authors: Ann-Charlotte
authors: AC
authors: Aveberger
authors: Lena
authors: L
authors: Klevenvall
authors: Karin
authors: K
authors: Palmblad
authors: Lars
authors: L
authors: Ottosson
authors: Ulf
authors: U
authors: Andersson
authors: Helena Erlandsson
authors: HE
authors: Harris
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000473:pathology; D019921:Biotinylation; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D016207:Cytokines / Q000032:analysis; D005347:Fibroblasts / Q000276:immunology / Q000378:metabolism; D024243:HMGB1 Protein / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D007249:Inflammation / Q000276:immunology*; D018836:Inflammation Mediators / Q000276:immunology*; D053583:Interleukin-1beta / Q000276:immunology; D015850:Interleukin-6 / Q000096:biosynthesis; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology; D008024:Ligands; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D009838:Oligodeoxyribonucleotides / Q000276:immunology; D051381:Rats; D011994:Recombinant Proteins / Q000276:immunology / Q000302:isolation & purification / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology*; D013583:Synovial Membrane / Q000276:immunology / Q000378:metabolism; D051194:Toll-Like Receptor 1 / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000276:immunology
chemical_list: C408982:CPG-oligonucleotide; D016207:Cytokines; D024243:HMGB1 Protein; D018836:Inflammation Mediators; D053583:Interleukin-1beta; D015850:Interleukin-6; D008024:Ligands; D008070:Lipopolysaccharides; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051217:Toll-Like Receptor 9