ABSTRACT
There is accumulating evidence to implicate the importance of EphBs receptors and ephrinBs ligands were involved in modulation of spinal nociceptive information. However, the downstream mechanisms that control this process are not well understood. In the present study, we investigated whether phosphatidylinositol 3-kinase (PI3K), as the downstream effectors, participates in modulation of spinal nociceptive information related to ephrinBs/EphBs. Intrathecal injection of ephrinB1-Fc produced a dose- and time-dependent thermal and mechanical hyperalgesia, accompanied by the increase of spinal PI3K-p110γ, phosphorylation of AKT (p-AKT) and c-Fos expression. Pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented activation of spinal AKT induced by ephrinB1-Fc. Inhibition of spinal PI3K signaling dose-dependently prevented and reversed pain behaviors and spinal c-Fos protein expression induced by intrathecal injection of ephrinB1-Fc. Inhibition of EphBs receptors by intrathecal injection of EphB1-Fc reduced formalin-induced inflammation and chronic constrictive injury-induced neuropathic pain behaviors accompanied by decreased expression of spinal PI3K,p-AKT and c-Fos protein. Furthermore, pre-treatment with PI3K inhibitor wortmannin or LY294002 prevented ephrinB1-Fc-induced ERK activation in spinal. These data demonstrated that PI3K and PI3K crosstalk to ERK signaling contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs.
Subject(s)
Ephrin-B1/pharmacology , Nociception , Phosphatidylinositol 3-Kinase/metabolism , Receptors, Eph Family/metabolism , Spinal Cord/enzymology , Spinal Cord/pathology , Animals , Disease Models, Animal , Enzyme Activation/drug effects , Ephrin-B1/administration & dosage , Ephrin-B1/therapeutic use , Extracellular Signal-Regulated MAP Kinases/metabolism , Humans , Hyperalgesia/complications , Hyperalgesia/drug therapy , Hyperalgesia/enzymology , Hyperalgesia/pathology , Inflammation/complications , Inflammation/drug therapy , Inflammation/enzymology , Inflammation/pathology , Injections, Spinal , Male , Mice , Neuralgia/complications , Neuralgia/drug therapy , Neuralgia/enzymology , Neuralgia/pathology , Nociception/drug effects , Phosphoinositide-3 Kinase Inhibitors , Phosphorylation/drug effects , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-fos/metabolism , Spinal Cord/drug effects , Time FactorsABSTRACT
BACKGROUND: Our previous studies have demonstrated that EphBs receptors and ephrinBs ligands were involved in modulation of spinal nociceptive information. However, the downstream mechanisms that control this process are not well understood. The aim of this study was to further investigate whether mitogen-activated protein kinases (MAPKs), as the downstream effectors, participate in modulation of spinal nociceptive information related to ephrinBs/EphBs. METHODS: Thermal hyperalgesia and mechanical allodynia were measured using radiant heat and von Frey filaments test. Immunofluorescence staining was used to detect the expression of p-MAPKs and of p-MAPKs/neuronal nuclei, or p-MAPKs/glial fibrillary acidic protein double label. C-Fos expression was determined by immunohistochemistry. The expression of p-MAPKs was also determined by Western blot assay. RESULTS: Intrathecal injection of ephrinB1-Fc produced a dose- and time-dependent thermal and mechanical hyperalgesia, accompanied by the increase of spinal p-MAPKs and c-Fos expression. Immunofluorescence staining revealed that p-MAPKs colocalized with the neuronal marker (neuronal nuclei) and the astrocyte marker (glial fibrillary acidic protein). Inhibition of MAPKs prevented and reversed pain behaviors and the increase of spinal c-Fos expression induced by intrathecal injection of ephrinB1-Fc. Inhibition of EphBs receptors by intrathecal injection of EphB1-Fc reduced formalin-induced inflammation and chronic constrictive injury-induced neuropathic pain behaviors accompanied by decreased expression of spinal p-MAPKs and c-Fos protein. Furthermore, pretreatment with MK-801, an N-methyl-d-aspartate receptor antagonist, prevented behavioral hyperalgesia and activation of spinal MAPKs induced by intrathecal injection of ephrinB1-Fc. CONCLUSIONS: These results demonstrated that activation of MAPKs contributed to modulation of spinal nociceptive information related to ephrinBs/EphBs.
