title: Genomic analysis and differential expression of HMG and S100A family in human arthritis: upregulated expression of chemokines, IL-8 and nitric oxide by HMGB1.
abstract: We applied global gene expression arrays, quantitative real-time PCR, immunostaining, and functional assays to untangle the role of High Mobility Groups proteins (HMGs) in human osteoarthritis (OA)-affected cartilage. Bioinformatics analysis showed increased mRNA expression of Damage-Associated Molecular Patterns (DAMPs): HMGA, HMGB, HMGN, SRY, LEF1, HMGB1, MMPs, and HMG/RAGE-interacting molecules (spondins and S100A4, S100A10, and S100A11) in human OA-affected cartilage as compared with normal cartilage. HMGB2 was down-regulated in human OA-affected cartilage. Immunohistological staining identified HMGB1 in chondrocytes in the superficial cartilage. Cells of the deep cartilage and subchondral bone showed increased expression of HMGB1 in OA-affected cartilage. HMGB1 was expressed in the nucleus, cytosol, and extracellular milieu of chondrocytes in cartilage. Furthermore, HMGB1 was spontaneously released from human OA-affected cartilage in ex vivo conditions. The effects of recombinant HMGB1 was tested on human cartilage and chondrocytes in vitro. HMGB1 stimulated mRNA of 2 NFκB gene enhancers (NFκB1 and NFκB2), 16 CC and CXC chemokines (IL-8, CCL2, CCL20, CCL3, CCL3L1, CCL3L3, CCL4, CCL4L1, CCL4L2, CCL5, CCL8, CXCL1, CXCL10, CXCL2, CXCL3, and CXCL6) by ≥10-fold. Furthermore, HMGB1 and IL-1β and/or tumor necrosis factor α (but not HMGI/Y) also significantly induced inducible nitric oxide synthase, NO, and interleukin (IL)-8 production in human cartilage and chondrocytes. The recombinant HMGB1 utilized in this study shows properties that are similar to disulfide-HMGB1. The differential, stage and/or tissue-specific expression of HMGB1, HMGB2, and S100A in cartilage was associated with regions of pathology and/or cartilage homeostasis in human OA-affected cartilage. Noteworthy similarities in the expression of mouse and human HMGB1 and HMGB2 were conserved in normal and arthritis-affected cartilage. The multifunctional forms of HMGB1 and S100A could perpetuate damage-induced cartilage inflammation in late-stage OA-affected joints similar to sterile inflammation. The paracrine effects of HMGB1 can induce chemokines and NO that are perceived to change cartilage homeostasis in human OA-affected cartilage.
authors.affiliation: 1 Department of Bio-Medical Engineering, Virginia Tech and Virginia College of Osteopathic Medicine , RheuMatrix, Inc., Blacksburg, Virginia.
authors.forename: Ashok R
authors.initials: AR
authors.lastname: Amin
authors.forename: Abul B M M K
authors.initials: AB
authors.lastname: Islam
mesh_terms: D002356:Cartilage / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D018925:Chemokines / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D015894:Genome, Human; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism*; D019899:Paracrine Communication; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome; D015854:Up-Regulation
chemical_list: D018925:Chemokines; D024243:HMGB1 Protein; C585491:HMGB1 protein, human; D016209:Interleukin-8; D009418:S100 Proteins; D009569:Nitric Oxide; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II