title: Delta-opioid receptors attenuate TNF-α-induced MMP-2 secretion from human ONH astrocytes.
abstract: OBJECTIVE
  We examined the signaling mechanisms involved in δ-opioid-receptor agonist, SNC-121-mediated attenuation of TNF-α-induced matrix metalloproteinase-2 (MMP-2) secretion from human optic nerve head (ONH) astrocytes.
  
  
  METHODS
  Human ONH astrocytes were treated with SNC-121 (1 μmol/L) for 15 minutes followed by TNF-α (25 ng/mL) treatment for 6 or 24 hours. Cells were pretreated with inhibitors of p38 mitogen-activated protein (MAP) kinase (SB-203580) or NF-κB (Helenalin) prior to TNF-α treatment. Changes in phosphorylation and expression of p38 MAP kinase, IκBα, NF-κB, and MMP-2 were measured by Western blotting. Translocation of NF-κB was determined by immunocytochemistry.
  
  
  RESULTS
  TNF-α treatment increased MMP-2 secretion from ONH astrocytes to 236% ± 17% and 142% ± 8% at 6 and 24 hours, respectively; while SNC-121 treatment reduced MMP-2 secretion to 149% ± 11% and 108% ± 7% at 6 and 24 hours, respectively. The SNC-121-mediated inhibitory response was blocked by the δ-opioid-receptor antagonist naltrindole. TNF-α treatment resulted in a sustained phosphorylation of p38 MAP kinase up to 24 hours (226% ± 15% over control levels), which was reduced to 150% ± 20% by SNC-121 treatment. TNF-α treatment increased the expression of NF-κB to 179% ± 21% and 139% ± 6% at 6 and 24 hours, respectively, which was significantly blocked by SNC-121 treatment. Furthermore, TNF-α-induced MMP-2 secretion was blocked by 100% and 78% in the presence of SB-203580 and Helenalin, respectively.
  
  
  CONCLUSIONS
  Evidence is provided that SNC-121 attenuated TNF-α-induced MMP-2 secretion from ONH astrocytes. Data also supported the idea that p38 MAP kinase and NF-κB played central roles in TNF-α-induced MMP-2 secretion, and both were negatively regulated by SNC-121.
authors.affiliation: Hewitt Laboratory of the Ola B. Williams Glaucoma Center, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina.
authors.forename: Naseem
authors.initials: N
authors.lastname: Akhter
authors.forename: Melissa
authors.initials: M
authors.lastname: Nix
authors.forename: Yasir
authors.initials: Y
authors.lastname: Abdul
authors.forename: Sudha
authors.initials: S
authors.lastname: Singh
authors.forename: Shahid
authors.initials: S
authors.lastname: Husain
mesh_terms: D000704:Analysis of Variance; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D001549:Benzamides / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D009898:Optic Disk / Q000187:drug effects* / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D017465:Receptors, Opioid, delta / Q000819:agonists*; D012717:Sesquiterpenes / Q000494:pharmacology; D045789:Sesquiterpenes, Guaiane; D015398:Signal Transduction / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D001549:Benzamides; D004791:Enzyme Inhibitors; D016328:NF-kappa B; D010879:Piperazines; D017465:Receptors, Opioid, delta; D012717:Sesquiterpenes; D045789:Sesquiterpenes, Guaiane; D014409:Tumor Necrosis Factor-alpha; C102990:SNC 121; C001329:helenalin; D048051:p38 Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2
keywords: astrocytes; glaucoma; matrix metalloproteinases; opioids; optic nerve head
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