title: High systemic levels of the cytokine-inducing HMGB1 isoform secreted in severe macrophage activation syndrome.
abstract: Macrophage activation syndrome (MAS) is a potentially fatal complication of systemic inflammation. High mobility group box 1 (HMGB1) is a nuclear protein extensively leaked extracellularly during necrotic cell death or actively secreted by natural killer (NK) cells, macrophages and additional cells during infection or sterile injury. Extracellular HMGB1 orchestrates key events in inflammation as a prototypic alarmin. The redox states of its three cysteines render the molecule mutually exclusive functions: fully reduced "all-thiol HMGB1" exerts chemotactic activity; "disulfide HMGB1" has cytokine-inducing, toll-like receptor 4 (TLR4)-mediated effects—while terminally oxidized "sulfonyl HMGB1" lacks inflammatory activity. This study examines the kinetic pattern of systemic HMGB1 isoform expression during therapy in four children with severe MAS. Three of the four patients with underlying systemic rheumatic diseases were treated with biologics and two suffered from triggering herpes virus infections at the onset of MAS. All patients required intensive care unit therapy due to life-threatening illness. Tandem mass-spectrometric analysis revealed dramatically increased systemic levels of the cytokine-inducing HMGB1 isoform during early MAS. Disease control coincided with supplementary etoposide therapy initiated to boost apoptotic cell death, when systemic HMGB1 levels drastically declined and the molecule emerged mainly in its oxidized, noninflammatory isoform. Systemic interferon (IFN)-γ and ferritin peaked concomitantly with HMGB1, whereas interleukin (IL)-18 and monocyte chemotactic protein (MCP)-1 levels developed differently. In conclusion, this work provides new insights in HMGB1 biology, suggesting that the molecule is not merely a biomarker of inflammation, but most likely also contributes to the pathogenesis of MAS. These observations encourage further studies of disulfide HMGB1 antagonists to improve outcome of MAS.
authors.affiliation: Unit of Pediatric Rheumatology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Palmblad
authors.affiliation: Unit of Pediatric Rheumatology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Schierbeck
authors.affiliation: Unit of Pediatric Rheumatology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Sundberg
authors.affiliation: Unit of Pediatric Rheumatology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Horne
authors.affiliation: Rheumatology Unit, Department of Medicine, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Helena Erlandsson
authors.initials: HE
authors.lastname: Harris
authors.affiliation: Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jan-Inge
authors.initials: JI
authors.lastname: Henter
authors.affiliation: Medical Research Council Centre for Drug Safety Science, Department of Molecular and Clinical Pharmacology, University of Liverpool, United Kingdom.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Antoine
authors.affiliation: Unit of Pediatric Rheumatology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ulf
authors.initials: U
authors.lastname: Andersson
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood; D002648:Child; D002675:Child, Preschool; D016207:Cytokines / Q000097:blood; D005047:Etoposide / Q000627:therapeutic use; D005260:Female; D005293:Ferritins / Q000097:blood; D024243:HMGB1 Protein / Q000097:blood*; D006801:Humans; D055501:Macrophage Activation Syndrome / Q000097:blood* / Q000188:drug therapy; D008297:Male; D020033:Protein Isoforms / Q000097:blood
chemical_list: D015415:Biomarkers; D016207:Cytokines; D024243:HMGB1 Protein; C585491:HMGB1 protein, human; D020033:Protein Isoforms; D005047:Etoposide; D005293:Ferritins