title: Nerve growth factor increases MMP9 activity in annulus fibrosus cells by upregulating lipocalin 2 expression.
abstract: OBJECTIVE
  Nerve growth factor (NGF) expression and activity is important in chronic lower back pain but may also act as a pro-catabolic factor in the pathogenesis of intervertebral disc (IVD) degeneration. Lipocalin 2 (Lcn2) expression in IVD was upregulated by NGF stimulation in our previous study. The current study was undertaken to identify potential mechanisms of the latter effect including potential interactions between Lcn2 and matrix metalloproteinase 9 (MMP9).
  
  
  METHODS
  Rat annulus fibrosus (AF) cells were stimulated by NGF and subjected to microarray analysis, subsequent real-time PCR, western immunoblotting, and immunofluorescence. Cells were treated with NGF in the absence or presence of the NGF inhibitor Ro 08-2750. Zymography and functional MMP9 assays were used to determine MMP9 activity, whilst the dimethyl-methylene blue assay was used to quantify the release of glycosaminoglycans (GAGs) reflecting catabolic effects following NGF treatment. Immunoprecipitation with immunoblotting was used to identify interactions between MMP9 and Lcn2.
  
  
  RESULTS
  Increased expression of Lcn2 gene and protein following NGF stimulation was confirmed by microarray analysis, real-time PCR, western blot and immunofluorescence. Zymography showed that NGF enhanced 125-kDa gelatinase activity, identified as a Lcn2/MMP9 complex by immunoprecipitation and immunoblotting. Functional assays showed increased MMP9 activity and GAG release in the presence of NGF. The effects of NGF were neutralized by the presence of Ro 08-2750.
  
  
  CONCLUSIONS
  NGF upregulates Lcn2 expression and increases MMP9 activity in AF cells; processes which are likely to potentiate degeneration of AF tissue in vivo. Anti-NGF treatment may have benefit for management of pain relief and slowing down progression of AF tissue degeneration.
authors.affiliation: Graduate Institute of Medical Science, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors.forename: Ting-Hsien
authors.initials: TH
authors.lastname: Kao
authors.forename: Yi-Jen
authors.initials: YJ
authors.lastname: Peng
authors.forename: Donald M
authors.initials: DM
authors.lastname: Salter
authors.forename: Herng-Sheng
authors.initials: HS
authors.lastname: Lee
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005415:Flavins; D007403:Intervertebral Disc / Q000187:drug effects* / Q000378:metabolism; D055959:Intervertebral Disc Degeneration; D000071068:Lipocalin-2; D054834:Lipocalins / Q000187:drug effects* / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D020932:Nerve Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011621:Pteridines / Q000494:pharmacology; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: C412503:2,3,4,10-tetrahydro-7,10-dimethyl-2,4-dioxobenzo(g)pteridine; D005415:Flavins; C097278:Lcn2 protein, rat; D000071068:Lipocalin-2; D054834:Lipocalins; D011621:Pteridines; D020932:Nerve Growth Factor; D020780:Matrix Metalloproteinase 9; C572337:Mmp9 protein, rat