title: Nerve Growth Factor Is Regulated by Toll-Like Receptor 2 in Human Intervertebral Discs.
abstract: Nerve growth factor (NGF) contributes to the development of chronic pain associated with degenerative connective tissue pathologies, such as intervertebral disc degeneration and osteoarthritis. However, surprisingly little is known about the regulation of NGF in these conditions. Toll-like receptors (TLR) are pattern recognition receptors classically associated with innate immunity but more recently were found to be activated by endogenous alarmins such as fragmented extracellular matrix proteins found in degenerating discs or cartilage. In this study we investigated if TLR activation regulates NGF and which signaling mechanisms control this response in intervertebral discs. TLR2 agonists, TLR4 agonists, or IL-1β (control) treatment increased NGF, brain-derived neurotrophic factor (BDNF), and IL-1β gene expression in human disc cells isolated from healthy, pain-free organ donors. However, only TLR2 activation or IL-1β treatment increased NGF protein secretion. TLR2 activation increased p38, ERK1/2, and p65 activity and increased p65 translocation to the cell nucleus. JNK activity was not affected by TLR2 activation. Inhibition of NF-κB, and to a lesser extent p38, but not ERK1/2 activity, blocked TLR2-driven NGF up-regulation at both the transcript and protein levels. These results provide a novel mechanism of NGF regulation in the intervertebral disc and potentially other pathogenic connective tissues. TLR2 and NF-κB signaling are known to increase cytokines and proteases, which accelerate matrix degradation. Therefore, TLR2 or NF-κB inhibition may both attenuate chronic pain and slow the degenerative progress in vivo.
authors.affiliation: From the Orthopeadic Research Laboratory, Faculty of Medicine, Alan Edwards Centre for Research on Pain, McGill Scoliosis and Spine Research Group.
authors.forename: Emerson
authors.initials: E
authors.lastname: Krock
authors.affiliation: From the Orthopeadic Research Laboratory, Faculty of Medicine.
authors.forename: J Brooke
authors.initials: JB
authors.lastname: Currie
authors.affiliation: McGill Scoliosis and Spine Research Group.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Weber
authors.affiliation: Alan Edwards Centre for Research on Pain, McGill Scoliosis and Spine Research Group.
authors.forename: Jean A
authors.initials: JA
authors.lastname: Ouellet
authors.affiliation: Alan Edwards Centre for Research on Pain, McGill Scoliosis and Spine Research Group, Integrated Program in Neuroscience, Departments of Anesthesiology, Pharmacology, and Therapeutics, Faculty of Medicine, and Faculty of Dentistry, McGill University, Montreal Quebec H3G 1A4, Canada.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Stone
authors.affiliation: From the Orthopeadic Research Laboratory, Faculty of Medicine, McGill Scoliosis and Spine Research Group.
authors.forename: Derek H
authors.initials: DH
authors.lastname: Rosenzweig
authors.affiliation: From the Orthopeadic Research Laboratory, Faculty of Medicine, McGill Scoliosis and Spine Research Group, lisbet.haglund@mcgill.ca.
authors.forename: Lisbet
authors.initials: L
authors.lastname: Haglund
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000293:Adolescent; D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D057134:Antibodies, Neutralizing / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D053583:Interleukin-1beta / Q000037:antagonists & inhibitors / Q000378:metabolism; D007403:Intervertebral Disc / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008024:Ligands; D008159:Lumbar Vertebrae; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D020932:Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014019:Tissue Donors; D051195:Toll-Like Receptor 2 / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors / Q000378:metabolism; D055815:Young Adult
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D057134:Antibodies, Neutralizing; C508585:IL1B protein, human; D053583:Interleukin-1beta; D008024:Ligands; C502240:NGF protein, human; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; D011498:Protein Precursors; C498143:RELA protein, human; D011994:Recombinant Proteins; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051996:Transcription Factor RelA; C061397:pro-nerve growth factor, human; D020932:Nerve Growth Factor
keywords: NF-κB (NF-KB); intervertebral disc; low back pain; nerve growth factor; neurotrophin; nucleus pulposus; pain; toll-like receptor (TLR)