High-mobility group box-1 gene, a potent proinflammatory mediators, is upregulated in more degenerated human discs in vivo and its receptor upregulated by TNF-α exposure in vitro.
Mechanisms which control and enhance proinflammatory cytokine expression during human disc degeneration are still poorly understood. The high-mobility group box-1 gene (HMGB1) produces a protein which can itself act as a cytokine, or can function as a potent proinflammatory mediator. Little is known about expression of HMGB1 in the human disc. Since proinflammatory cytokines increase significantly during human disc degeneration, in this work we hypothesized that HMGB1 may show upregulation with advancing stages of degeneration, and upregulation in cells exposed to TNF-α. Immunohistochemistry was performed to confirm the presence of HMGB1 in the human disc, and human annulus cells were cultured and challenged with 10(3)pM TNF-α for 14days in 3D culture. Cells with positive HMGB1 immunolocalization were abundant in the outer annulus. Molecular analysis of cultured cells showed an 8-fold significant increase in HMGB1 expression in more degenerated Thompson grade V discs compared to healthier grade I/II discs (p=0.033). Human disc tissue was assessed in molecular studies. Herniated specimens showed a 6.3-fold significantly greater expression level than that seen in control specimens (p=0.001). In culture experiments, expression of the receptor to HMGB1, toll-like receptor 2, showed a 24-fold upregulation in vitro in cells exposed to TNF-α vs. controls (p=0.0003).
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA. Electronic address: helen.gruber@carolinashealthcare.org.
Helen E
HE
Gruber
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA.
Gretchen L
GL
Hoelscher
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA.
Synthia
S
Bethea
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA.
Jane
J
Ingram
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA.
Michael
M
Cox
Department of Orthopaedic Surgery, Carolinas Medical Center, P.O. Box 32861, Charlotte, NC, USA.
Edward N
EN
Hanley
D000328:Adult; D000368:Aged; D002478:Cells, Cultured; D005260:Female; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007403:Intervertebral Disc / Q000187:drug effects / Q000378:metabolism*; D055959:Intervertebral Disc Degeneration / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
D024243:HMGB1 Protein; C585491:HMGB1 protein, human; D051195:Toll-Like Receptor 2; D014409:Tumor Necrosis Factor-alpha
Disc degeneration; HMGB1; Proinflammatory cytokines; TNF-α