(252) Modulations of proinflammatory cytokines by NF-kap-. paB and JNK in HAPI cells treated with a new TLR4 agonist. KDO2. X Zheng, W Zheng, S Liu, and S ...
Abstracts
The Journal of Pain
S39
D. Molecular and Cellular Biology
(254) Targeting of spinal GluA2-lacking AMPA receptors inhibits morphine induced hyperalgesia
D01 Immune Mediators
~ero Ferri, Y Xia, Z Melyan, A Baker, S Zhou, G Hargett, S Carlton, D Caban and J Moron-Concepcion; Columbia University Medical Center, New York, NY
(252) Modulations of proinflammatory cytokines by NF-kappaB and JNK in HAPI cells treated with a new TLR4 agonist KDO2
Non-medical use of prescription opioids is a major and emerging problem. The increase in pain sensitivity (hyperalgesia) observed after cessation of opioid administration could lengthen the treatment and increase opioid abuse liability. Since spinal cord AMPA receptors (AMPAR) participate in pain transmission, we decided to investigate their role in morphine-induced hyperalgesia in mice. Biochemical studies show that hyperalgesia is associated with alterations in expression and subunit composition of AMPAR in the spinal cord dorsal horn, suggesting a postsynaptic increase in Ca2+-permeable AMPAR consisting of GluA4 homomers. Immunohistochemical analyses further confirm this finding by localizing the increase in GluA4-containing AMPAR in dorsal horn laminae III-V. Whole cell patch-clamp recordings from spinal cord slices show an insertion of Ca2+-permeable AMPARs in these laminae. Moreover, we find that intrathecal administration of a Ca2+-permeable AMPAR blocker disrupts morphine-induced mechanical hyperalgesia. Current experiments are being performed to investigate the molecular mechanisms underlying the increased trafficking and clustering of GluA4-containing AMPAR in dorsal horn synapses. These results highlight the role of Ca2+-permeable AMPAR as a potential target to prevent pain sensitivity after discontinuation of morphine treatment. This work was supported by NIH grants DA027460 to J.A.M. and S.M.C. and DA025036 to J.A.M.
X Zheng, W Zheng, S Liu, and S Hao; University of Miami Miller School of Medicine, Miami, FL Recent evidence shows that activation of microglia releases various proinflammatory cytokines and neurotoxic mediators, which plays an important role in the pathogenesis of chronic pain. Toll-like receptor 4 (TLR4) on the microglia is the main receptor on the cell membrane for the Gram-negative bacteria cell-wall component. Both nuclear factor kappa B (NF-kB) and mitogen activated protein kinases (MAPkinases) mediate production of proinflammatory cytokines in many types of cells, however, the signal pathways and relationship in details are not very clear in microglia. Here, we investigated the effects of KDO2 (a new TLR4 agonist) on the highly aggressively proliferating immortalized (HAPI) cells that had been enriched for microglia. KDO2 treatment significantly induced the phosphorylation of c-Jun N-terminal kinase (JNK) and NF-kB, but not p38, and released TNFa and IL-1b. The knockdown of TLR4 with TLR4 siRNA significantly reduced the expression of phosphorylation of JNK (pJNK) and phosphorylation of NF-kB (pNF-kB), TNFa, and IL-1b. Inhibition of JNK reduced the release of TNFa, but not phosphorylation of NF-kB. Inhibition of NF-kB reduced the release of IL-1b; unexpectedly, inhibition of NF-kB enhanced pJNK and release of TNFa. These findings showed that TNFa induced by KDO2 was JNK-dependent, and that NF-kB negatively modulated both pJNK and TNFa in the cultured microglial cells. The current study may provide a new insight in the modulation of cytokines in the microglial cells.
D02 Mechanisms of Opioid Action
D03 Neurotrophins
(253) Activation of the spinal NR2B NMDA receptors-p38 pathway by the mu-opioid receptor agonist fentanyl; implication in a rat model of post-operative pain
(255) 4-Methylcatechol ameliorates chronic pain concurrent with mood disorder by inducing brain-derived neurotrophic factor
C Rivat, M Xu, R Koopmans, A Cahana, and P Richebe; University of Washington, Seattle, WA
T Ishikawa, K Ishikawa, S Yasuda, Y Kishishita, and A Masuzawa; Yamaguchi University, Ube, Yamaguchi, Japan
Pre-clinical and clinical studies demonstrated that opioid may worsen pain especially after surgery. This phenomenon is NMDA receptor-dependent. However, little is known about the contribution of central sensitization in the paradoxical effects of opioids. Here we investigated whether activation of the spinal MAPK kinase p38, known to be implicated in spinal sensitization initiated by chronic pain, is also triggered by systemic fentanyl administration in rat with or without post-operative pain. Rats received 4 fentanyl (4x80 mg/kg, s.c.) or saline injections administered at 15 min intervals. After the second injection, some animals underwent incision on the left hindpaw. Thermal and mechanical sensory hypersensitivities were evaluated after the surgery. In animals without incision, fentanyl induced analgesia followed by sensory hypersensitivity, as previously described. Fentanyl also enhanced plantar incision-induced pain hypersensitivity. On D1, increased activity of the dorsal horn neurons (DHN) in response to mechanical stimulation was recorded in incision and fentanyl groups as compared to saline animals. DHN activity was dramatically enhanced in fentanyl-incisioned animals. In rats with or without incision, an increased p-p38 immunoreactivity was observed in the spinal dorsal horn of fentanyl-treated animals as compared to saline or incision-treated animals, alone. The intrathecal injection of p38 inhibitor SB 203580 (10 mg) reduced p-p38 immunoreactivity and mechanical pain hypersensitivity observed in fentanyl-treated rats with or without incision. It also reduced DHN hyperexcitability measured in fentanyl-incisioned animals. Similar effects were observed with the NMDA receptor antagonist ketamine (10 mg/kg, s.c.) injected at the time of surgery. NMDA receptor activation was confirmed by the increased phosphorylation of the NR2B subunit observed in incision group and more extensively in fentanyl groups as compared to saline animals. These data indicate that the NR2B NMDA receptors-p38 pathway mediates fentanyl enhancement of surgery-induced pain hypersensitivity suggesting common cellular pathways between opioid and chronic injury-induced hyperalgesia.
Neuropathic pain with mood disorder after nerve injury is serious problems that affects the quality of life. Recent studies have suggested that a lack of brain-derived neurotrophic factor (BDNF) may cause pain-emotion. BDNF is induced in cultured neurons by 4-methylcatechol (4-MC), but the role in painemotion is poorly understood. Thus, we aimed to investigate the involvement of BDNF and its related BDNF in pain with mood disorder. In addition, we examined whether icv. 4-MC prevents chronic pain and an anti-depressant effect. SD rats implanted icv. with a PE-10 were subjected to chronic constriction injury (CCI). Hyperalgesia was assessed by a reduction in paw withdrawal latency (PWL). We also employed a forced swimming testing (FST: time of immobility) chronic stage after CCI. Modulation by PD0325901 (PD: a MEK1/2 inhibitor) and 4-MC administered for 3 days after CCI. To block these effects, anti-BDNF or K252a (a TrkB receptor inhibitor) was injected in combination with 4-MC. To ensure analgesic and anti-depressant effects of 4-MC, either anti-BDNF or K252a was injected. After completion of experiment and were perfused with 4% paraformaldehyde for fixation for immunohistochemistry (pERK). The rats showed a decrease in PWL associated with extension of the FST after CCI. PD and 4-MC reduced the decrease in PWL and the increased FST. 4-MC attenuated the CCI-induced increases of pERK in regions related to pain pathway and limbic system. The PD reduced decreased PWL and increased FST. With 4-MC, decreased PWL and increased FST were reduced and these effects were reversed by anti-BDNF or K252a. Based on these results, we suggest that a lack of BDNF and activation of ERK in the pain-emotion network may be involved in depression during chronic pain. 4-MC ameliorates abnormal via induction of BDNF and normalization of pERK activities.
