ABSTRACT
Bone cancer pain (BCP) is a clinical pathology that urgently needs to be solved, but research on the mechanism of BCP has so far achieved limited success. Nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2) has been shown to be involved in pain, but its involvement in BCP and the specific mechanism have yet to be examined. This study aimed to test the hypothesis that BCP induces the transfer of Nrf2 from the cytoplasm to the nucleus and further promotes nuclear transcription to activate heme oxygenase-1 (HO-1) and inhibit the activation of nuclear factor-kappa B (NF-κB) signalling, ultimately regulating the neuroinflammatory response. Von-Frey was used for behavioural analysis in rats with BCP, whereas western blotting, real-time quantitative PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect molecular expression changes, and immunofluorescence was used to detect cellular localization. We demonstrated that BCP induced increased Nrf2 nuclear protein expression with decreased cytoplasmic protein expression in the spinal cord. Further increases in Nrf2 nuclear protein expression can alleviate hyperalgesia and activate HO-1 to inhibit the expression of NF-κB nuclear protein and inflammatory factors. Strikingly, intrathecal administration of the corresponding siRNA reversed the above effects. In addition, the results of double immune labelling revealed that Nrf2 and NF-κB were coexpressed in spinal cord neurons of rats with BCP. In summary, these findings suggest that the entry of Nrf2 into the nucleus promotes the expression of HO-1, inhibiting activation of the NF-κB signalling pathway, reducing neuroinflammation and ultimately exerting an anti-nociceptive effect.
Subject(s)
Bone Neoplasms/metabolism , Cancer Pain/metabolism , Hyperalgesia/metabolism , NF-E2-Related Factor 2/biosynthesis , NF-kappa B/metabolism , Spinal Cord/metabolism , Active Transport, Cell Nucleus/physiology , Animals , Bone Neoplasms/pathology , Cancer Pain/pathology , Cell Line, Tumor , Cell Nucleus/metabolism , Female , Hyperalgesia/pathology , NF-kappa B/antagonists & inhibitors , Neurons/metabolism , Neurons/pathology , Rats , Rats, Sprague-Dawley , Spinal Cord/pathologyABSTRACT
The pathogenesis of cancer induced bone pain (CIBP) is extremely complex, and glutamate receptor dysfunction plays an important role in the formation of CIBP. Synapse-associated protein 102 (SAP102) anchors glutamate receptors in the postsynaptic membrane. However, its effect on hyperalgesia formation in CIBP has not been clarified. This study investigated the role of SAP102 in the formation of hyperalgesia in rats with CIBP SAP102 is present in spinal dorsal horn neurons, but not in astrocytes or microglia. NMDAR-NR2B is localized with neurons. In addition, SAP102 and NMDAR-NR2B expression levels in spinal dorsal horn tissues were detected by Western blot and co-immunoprecipitation. Intrathecal injection of lentiviral vector of RNAi to knockdown SAP102 expression in the spinal dorsal horn significantly attenuated abnormal mechanic pain when compared to non-coding lentiviral vector. These findings indicate that SAP102 can anchor NMDA receptors to affect hyperalgesia formation in bone cancer pain.
Subject(s)
Bone Neoplasms/complications , Cancer Pain/genetics , Carcinoma 256, Walker/complications , Hyperalgesia/genetics , Neuropeptides/genetics , Receptors, N-Methyl-D-Aspartate/metabolism , Tibia , Animals , Bone Neoplasms/secondary , Cancer Pain/etiology , Cancer Pain/metabolism , Carcinoma 256, Walker/secondary , Female , Gene Knockdown Techniques , Hyperalgesia/etiology , Hyperalgesia/metabolism , Neuropeptides/metabolism , Posterior Horn Cells/metabolism , Rats , Spinal Cord Dorsal Horn/metabolismABSTRACT
Treatment of cancerinduced bone pain (CIBP) is challenging in clinical settings. Oxycodone (OXY) is used to treat CIBP; however, a lack of understanding of the mechanisms underlying CIBP limits the application of OXY. In the present study, all rats were randomly divided into three groups: The sham group, the CIBP group, and the OXY group. Then, a rat model of CIBP was established by inoculation of Walker 256 tumor cells from rat tibia. Phosphoproteomic profiling of the OXYtreated spinal dorsal cords of rats with CIBP was performed, and 1,679 phosphorylated proteins were identified, of which 160 proteins were significantly different between the CIBP and sham groups, and 113 proteins were significantly different between the CIBP and OXY groups. Gene Ontology analysis revealed that these proteins mainly clustered as synapticassociated cellular components; among these, disks large homolog 3 expression was markedly increased in rats with CIBP and was reversed by OXY treatment. Subsequent domain analysis of the differential proteins revealed several significant synapticassociated domains. In conclusion, synapticassociated cellular components may be critical in OXYinduced analgesia in rats with CIBP.