title: Tumor necrosis factor-alpha (TNF-alpha) enhances functional thermal and chemical responses of TRP cation channels in human synoviocytes.
abstract: BACKGROUND
  We have shown functional expression of several TRP channels on human synovial cells, proposing significance in known calcium dependent proliferative and secretory responses in joint inflammation. The present study further characterizes synoviocyte TRP expression and activation responses to thermal and osmotic stimuli after pre-treatment with proinflammatory mediator tumor necrosis factor alpha (TNF-alpha, EC50 1.3221 x 10(-10) g/L).
  
  
  RESULTS
  Fluorescent imaging of Fura-2 loaded human SW982 synoviocytes reveals immediate and delayed cytosolic calcium oscillations elicited by (1) TRPV1 agonists capsaicin and resiniferatoxin (20-40% of cells), (2) moderate and noxious temperature change, and (3) osmotic stress TRPV4 activation (11.5% of cells). TNF-alpha pre-treatment (1 ng/ml, 8-16 hr) significantly increases (doubles) capsaicin responsive cell numbers and [Ca2+]i spike frequency, as well as enhances average amplitude of temperature induced [Ca2+]i responses. With TNF-alpha pre-treatment for 8, 12, and 16 hr, activation with 36 or 45 degree bath solution induces bimodal [Ca2+]i increase (temperature controlled chamber). Initial temperature induced rapid transient spikes and subsequent slower rise reflect TRPV1 and TRPV4 channel activation, respectively. Only after prolonged TNF-alpha exposure (12 and 16 hr) is recruitment of synoviocytes observed with sensitized TRPV4 responses to hypoosmolarity (3-4 fold increase). TNF-alpha increases TRPV1 (8 hr peak) and TRPV4 (12 hr peak) immunostaining, mRNA and protein expression, with a TRPV1 shift to membrane fractions.
  
  
  CONCLUSIONS
  TNF-alpha provides differentially enhanced synoviocyte TRPV1 and TRPV4 expression and [Ca2+]i response dependent on the TRP stimulus and time after exposure. Augmented relevance of TRPV1 and TRPV4 as inflammatory conditions persist would provide calcium mediated cell signaling required for pathophysiological responses of synoviocytes in inflammatory pain states.
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas, USA. mykochuk@utmb.edu
authors.forename: Mikhail Y
authors.initials: MY
authors.lastname: Kochukov
authors.forename: Terry A
authors.initials: TA
authors.lastname: McNearney
authors.forename: Huaizhi
authors.initials: H
authors.lastname: Yin
authors.forename: Liping
authors.initials: L
authors.lastname: Zhang
authors.forename: Fei
authors.initials: F
authors.lastname: Ma
authors.forename: Larissa
authors.initials: L
authors.lastname: Ponomareva
authors.forename: Sarah
authors.initials: S
authors.lastname: Abshire
authors.forename: Karin N
authors.initials: KN
authors.lastname: Westlund
mesh_terms: D002211:Capsaicin / Q000494:pharmacology; D002460:Cell Line; D004224:Diterpenes / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D009997:Osmotic Pressure / Q000187:drug effects; D018689:Sensory System Agents / Q000494:pharmacology; D013583:Synovial Membrane / Q000166:cytology* / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D050051:Transient Receptor Potential Channels / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D004224:Diterpenes; D018689:Sensory System Agents; D050916:TRPV Cation Channels; D050051:Transient Receptor Potential Channels; D014409:Tumor Necrosis Factor-alpha; C024353:resiniferatoxin; D002211:Capsaicin
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