title: Proinflammatory cytokines oppose opioid-induced acute and chronic analgesia.
abstract: Spinal proinflammatory cytokines are powerful pain-enhancing signals that contribute to pain following peripheral nerve injury (neuropathic pain). Recently, one proinflammatory cytokine, interleukin-1, was also implicated in the loss of analgesia upon repeated morphine exposure (tolerance). In contrast to prior literature, we demonstrate that the action of several spinal proinflammatory cytokines oppose systemic and intrathecal opioid analgesia, causing reduced pain suppression. In vitro morphine exposure of lumbar dorsal spinal cord caused significant increases in proinflammatory cytokine and chemokine release. Opposition of analgesia by proinflammatory cytokines is rapid, occurring < or =5 min after intrathecal (perispinal) opioid administration. We document that opposition of analgesia by proinflammatory cytokines cannot be accounted for by an alteration in spinal morphine concentrations. The acute anti-analgesic effects of proinflammatory cytokines occur in a p38 mitogen-activated protein kinase and nitric oxide dependent fashion. Chronic intrathecal morphine or methadone significantly increased spinal glial activation (toll-like receptor 4 mRNA and protein) and the expression of multiple chemokines and cytokines, combined with development of analgesic tolerance and pain enhancement (hyperalgesia, allodynia). Statistical analysis demonstrated that a cluster of cytokines and chemokines was linked with pain-related behavioral changes. Moreover, blockade of spinal proinflammatory cytokines during a stringent morphine regimen previously associated with altered neuronal function also attenuated enhanced pain, supportive that proinflammatory cytokines are importantly involved in tolerance induced by such regimens. These data implicate multiple opioid-induced spinal proinflammatory cytokines in opposing both acute and chronic opioid analgesia, and provide a novel mechanism for the opposition of acute opioid analgesia.
authors.affiliation: Department of Psychology and The Center for Neuroscience, Campus Box 345, University of Colorado at Boulder, Boulder, CO 80309-0345, USA.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Hutchinson
authors.forename: Benjamen D
authors.initials: BD
authors.lastname: Coats
authors.forename: Susannah S
authors.initials: SS
authors.lastname: Lewis
authors.forename: Yingning
authors.initials: Y
authors.lastname: Zhang
authors.forename: David B
authors.initials: DB
authors.lastname: Sprunger
authors.forename: Niloofar
authors.initials: N
authors.lastname: Rezvani
authors.forename: Eric M
authors.initials: EM
authors.lastname: Baker
authors.forename: Brian M
authors.initials: BM
authors.lastname: Jekich
authors.forename: Julie L
authors.initials: JL
authors.lastname: Wieseler
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Somogyi
authors.forename: David
authors.initials: D
authors.lastname: Martin
authors.forename: Stephen
authors.initials: S
authors.lastname: Poole
authors.forename: Charles M
authors.initials: CM
authors.lastname: Judd
authors.forename: Steven F
authors.initials: SF
authors.lastname: Maier
authors.forename: Linda R
authors.initials: LR
authors.lastname: Watkins
mesh_terms: D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D002408:Catheters, Indwelling; D054428:Chemokine CX3CL1 / Q000276:immunology; D016207:Cytokines / Q000134:cerebrospinal fluid / Q000378:metabolism*; D006930:Hyperalgesia / Q000188:drug therapy; D007278:Injections, Spinal; D053590:Interleukin 1 Receptor Antagonist Protein / Q000494:pharmacology; D007375:Interleukin-1 / Q000276:immunology; D008297:Male; D008691:Methadone / Q000494:pharmacology; D009020:Morphine / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy / Q000276:immunology* / Q000378:metabolism; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013116:Spinal Cord / Q000276:immunology / Q000378:metabolism; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D054428:Chemokine CX3CL1; D016207:Cytokines; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D012333:RNA, Messenger; D047888:Receptors, Tumor Necrosis Factor, Type I; D009020:Morphine; D008691:Methadone