title: The analgesic effect of rolipram is associated with the inhibition of the activation of the spinal astrocytic JNK/CCL2 pathway in bone cancer pain.
abstract: Bone cancer pain (BCP) is one of the most difficult and intractable tasks for pain management, which is associated with spinal 'neuron-astrocytic' activation. The activation of the c-Jun N-terminal kinase (JNK)/chemokine (C-C motif) ligand (CCL2) signaling pathway has been reported to be critical for neuropathic pain. Rolipram (ROL), a selective phosphodiesterase 4 inhibitor, possesses potent anti-inflammatory and anti-nociceptive activities. The present study aimed to investigate whether the intrathecal administration of ROL has an analgesic effect on BCP in rats, and to assess whether the inhibition of spinal JNK/CCL2 pathway and astrocytic activation are involved in the analgesic effects of ROL. The analgesic effects of ROL were evaluated using the Von Frey and Hargreaves tests. Immunofluorescence staining was used to determine the number of c-Fos immunoreactive neurons, and the expression of spinal astrocytes and microglial activation on day 14 after tumor cell inoculation. Enzyme‑linked immunosorbent assay (ELISA) was used to detect the expression of pro-inflammatory cytokines [interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α] and chemokines (CCL2), and western blot analysis was then used to examine the spinal phosphodiesterase 4 (PDE4), ionized calcium binding adapter molecule-1 (IBA-1) and JNK levels on day 14 after tumor cell inoculation. The results revealed that ROL exerted a short-term analgesic effect in a dose-dependent manner, and consecutive daily injections of ROL exerted continuous analgesic effects. In addition, spinal 'neuron‑astrocytic' activation was suppressed and was associated with the downregulation of spinal IL-1β, IL-6 and TNF-α expression, and the inhibition of PDE4B and JNK levels in the spine was also observed. In addition, the level of CCL2 was decreased in the rats with BCP. The JNK inhibitor, SP600125, decreased CCL2 expression and attenuated pain behavior. Following co-treatment with ROL and SP600125, no significant increases in thermal hyperalgesia and CCL2 expression were observed compared with the ROL group. Thus, our findings suggest that the analgesic effects of ROL in BCP are mainly mediated through the inhibition of 'neuron‑astrocytic' activation, which occurs via the suppression of spinal JNK/CCL2 signaling.
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China.
authors.forename: Chi-Hua
authors.initials: CH
authors.lastname: Guo
authors.affiliation: Department of Medical Imaging, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China.
authors.forename: Lu
authors.initials: L
authors.lastname: Bai
authors.affiliation: Department of Anesthesiology, Fuzhou General Hospital of Nanjing Military Region, Fuzhou, Fujian 350025, P.R. China.
authors.forename: Huang-Hui
authors.initials: HH
authors.lastname: Wu
authors.affiliation: Institute of Neuroscience, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310027, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Neurobiology and Collaborative Innovation Center for Brain Science, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Guo-Hong
authors.initials: GH
authors.lastname: Cai
authors.affiliation: Department of Neurobiology and Collaborative Innovation Center for Brain Science, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Neurobiology and Collaborative Innovation Center for Brain Science, The Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China.
authors.forename: Sheng-Xi
authors.initials: SX
authors.lastname: Wu
authors.affiliation: Department of Orthopedics, The First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Ma
mesh_terms: D000700:Analgesics / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D001859:Bone Neoplasms / Q000150:complications / Q000188:drug therapy*; D000072716:Cancer Pain / Q000188:drug therapy* / Q000201:enzymology / Q000209:etiology; D018932:Chemokine CCL2 / Q000378:metabolism*; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006930:Hyperalgesia / Q000150:complications / Q000188:drug therapy / Q000201:enzymology; D018836:Inflammation Mediators / Q000378:metabolism; D007278:Injections, Spinal; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D017207:Rats, Sprague-Dawley; D020889:Rolipram / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D015398:Signal Transduction / Q000187:drug effects; D013116:Spinal Cord / Q000473:pathology*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000700:Analgesics; D000873:Anthracenes; D018932:Chemokine CCL2; D016207:Cytokines; D018836:Inflammation Mediators; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C546993:PDE4B protein, rat; D020889:Rolipram