Bone cancer pain (BCP) is a serious clinical problem that affects the quality of life of cancer patients. However, the current treatment methods for this condition are still unsatisfactory. This study investigated whether intrathecal injection of rosiglitazone modulates the noxious behaviors associated with BCP, and the possible mechanisms related to this effect were explored. We found that rosiglitazone treatment relieved bone cancer-induced mechanical hyperalgesia in a dose-dependent manner, promoted the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) in spinal cord neurons, and inhibited the activation of the nuclear factor-kappa B (NF-κB)/nod-like receptor protein 3 (NLRP3) inflammatory axis induced by BCP. However, concurrent administration of the PPAR-γ antagonist GW9662 reversed these effects. The results show that rosiglitazone inhibits the NF-κB/NLRP3 inflammation axis by activating PPAR-γ in spinal neurons, thereby alleviating BCP. Therefore, the PPAR-γ/NF-κB/NLRP3 signaling pathway may be a potential target for the treatment of BCP in the future.

Supplemental Digital Content is Available in the Text.LncRNA71132 works as a miRNA sponge in miR-143-5p–mediated posttranscriptional modulation of GPR85 expression in bone cancer pain.

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Chronic, inflammatory pain is an international health concern that severely diminishes individuals’ quality of life. Catalpol is an iridoid glycoside derived from the roots of Rehmannia glutinosa that possesses anti-inflammatory, antioxidant, and neuroprotective properties for the treating multiple kinds of disorders. Nevertheless, catalpol’s impacts on inflammatory pain and its potential methods of action are still unclear. The purpose of this investigation is to determine the mechanism of catalpol to reduce the inflammatory pain behaviors in a rat model with complete Freund’s adjuvant (CFA). Catwalk, Von-Frey, and open field testing were performed for behavioral assessment. Western blot analysis and real-time quantitative PCR (RT-PCR) were employed to identify variations in molecular expression, while immunofluorescence was utilized to identify cellular localization. Catalpol effectively reduced CFA-induced mechanical allodynia and thermal hyperalgesia when injected intrathecally. Moreover, catalpol can regulate the HDAC4/PPAR-γ-signaling pathway in CFA rat spinal cord neurons. Meanwhile catalpol significantly decreased the expression of the NF-κB/NLRP3 inflammatory axis in the spinal cord of CFA rats. In addition, both in vivo and in vitro research revealed that catalpol treatment inhibited astrocyte activation and increase inflammatory factor expression. Interestingly, we also found that catalpol could alleviate peripheral pain by inhibiting tissue inflammation. Taken together, the findings declared that catalpol may inhibit inflammatory pain in CFA rats by targeting spinal cord and peripheral inflammation.

Bone cancer pain (BCP) is a clinically intractable mixed pain, involving inflammation and neuropathic pain, and its mechanisms remain unclear. CXC chemokine receptor 1 (CXCR1, IL-8RA) and 2 (CXCR2, IL-8RB) are high-affinity receptors for interleukin 8 (IL8). According to previous studies, CXCR2 plays a crucial role in BCP between astrocytes and neurons, while the role of CXCR1 remains unclear. The objective of this study was to investigate the role of CXCR1 in BCP. We found that CXCR1 expression increased in the spinal dorsal horn. Intrathecal injection of CXCR1 siRNA effectively attenuated mechanical allodynia and pain-related behaviors in rats. It was found that CXCR1 was predominantly co-localized with neurons. Intrathecal injection of CXCR1-siRNA reduced phosphorylated JAK2/STAT3 protein levels and the NLRP3 inflammasome (NLRP3, caspase1, and IL-1β) levels. Furthermore, in vitro cytological experiments confirmed this conclusion. The study results suggest that the spinal chemokine receptor CXCR1 activation mediates BCP through JAK2/STAT3 signaling pathway and NLRP3 inflammasome (NLRP3, caspase1, and IL-1β).

Background: Noncoding microRNAs have emerged as critical players of gene expression in the nervous system, where they contribute to regulating nervous disease. As stated in previous research, the miR-155-5p upregulation happens in the spinal cord at the nociceptive state. It was unclear if miR-155-5p is linked to bone cancer pain (BCP). Herein, we aimed at investigating the miR-155-5p functional regulatory function in BCP process and delineating the underlying mechanism. Methods: The miRNA-155-5p levels and cellular distribution were determined by RNA sequencing, fluorescent in situ hybridization (FISH), and quantitative real-time PCR (qPCR). Immunoblotting, qPCR, dual-luciferase reporter gene assays, immunofluorescence, recombinant overexpression adeno-associated virus, small interfering RNA, intraspinal administration, and behavioral tests were utilized for exploring the downstream signaling pathway. Results: The miR-155-5p high expression in spinal neurons contributes to BCP maintenance. The miR-155-5p blockage via the intrathecal injection of miR-155-5p antagomir alleviated the pain behavior; in contrast, upregulating miR-155-5p by agomir induced pain hypersensitivity. The miR-155-5p bounds directly to TCF4 mRNA’s 3′ UTR. BCP significantly reduced protein expression of TCF4 versus the Sham group. The miR-155-5p inhibition relieved the spinal TCF4 protein’s down-expression level, while miR-155-5p upregulation by miR-155-5p agomir intrathecal injection decreased TCF4 protein expression in naïve rats. Additionally, TCF4 overexpression in BCP rats could increase Kv1.1. Moreover, TCF4 knockdown inhibited Kv1.1 expression in BCP rats. Indeed, TCF4 and Kv1.1 were co-expressed in BCP spinal cord neurons. Conclusion: The study findings stated the miR-155-5p pivotal role in regulating BCP by directly targeting TCF4 in spinal neurons and suggested that miR-155 could be a promising target in treating BCP.

Notch signal plays an important role in regulating cell–cell interactions with the adjacent cells. However, it remains unknown whether Jagged1 (JAG‐1) mediated Notch signaling regulates bone cancer pain (BCP) via the spinal cell interactions mechanism. Here, we showed that intramedullary injection of Walker 256 breast cancer cells increased the expression of JAG‐1 in spinal astrocytes and knockdown of JAG‐1 reduced BCP. The supplementation of exogenous JAG‐1 to the spinal cord induced BCP‐like behavior and promoted expression of c‐Fos and hairy and enhancer of split homolog‐1 (Hes‐1) in the spinal cord of the naïve rats. These effects were reversed when the rats were administered intrathecal injections of N‐[N‐(3,5‐difluorophenacetyl)‐l‐alanyl]‐S‐phenylglycine t‐butyl ester (DAPT). The intrathecal injection of DAPT reduced BCP and inhibited Hes‐1 and c‐Fos expression in the spinal cord. Furthermore, our results showed that JAG‐1 up‐regulated Hes‐1 expression by inducing the recruitment of Notch intracellular domain (NICD) to the RBP‐J/CSL‐binding site located within the Hes‐1 promoter sequence. Finally, the intrathecal injection of c‐Fos‐antisense oligonucleotides (c‐Fos‐ASO) and administration of sh‐Hes‐1 to the spinal dorsal horn also alleviated BCP. The study indicates that inhibition of the JAG‐1/Notch signaling axis may be a potential strategy for the treatment of BCP.image

Background Recent studies have shown that interactions between astrocytes and neurons in the spinal cord are involved in chronic pain. In this study, we investigated whether the Jagged-1(JAG-1) /Notch signaling pathway regulates bone cancer pain (BCP) via the astrocyte-neuron mechanism. Methods Walker256 breast cancer cells were injected into the tibia bone marrow of the female rat to establish a stable BCP rat model. The molecular mechanism of hyperalgesia mediated by the JAG-1/Notch signal pathway was determined by western blotting, immunofluorescence, real-time quantitative polymerase chain reaction, dual-luciferase reporter gene, and chromatin immunoprecipitation assays. Von-Frey test, catwalk gait analysis, open field test, and conditioned place aversion test were used to study changes in pain behavior in rats. In addition, the effect of the JAG-1/Notch signal pathway on neuronal excitability was also investigated. Results The intramedullary injection of Walker256 breast cancer cells induces persistent hyperalgesia and increased the expression of JAG-1, Notch intracellular domain (NICD), and c-Fos in the spinal cord. The expression of JAG-1 was exclusively observed in astrocytes and Notch-1 was expressed only in neuronal cells. Astrocyte activation increased JAG-1 expression, and knockdown of JAG-1 in the spinal cord reduced BCP. The supplementation of exogenous JAG-1 to the spinal cord induced BCP-like behavior and promoted expression of c-Fos and hairy and enhancer of split homolog-1 (Hes-1) in the spinal cord of the naïve rats. These effects were reversed when the rats were administered intrathecal injections of DAPT, an inhibitor of notch signaling. The intrathecal injection of DAPT reduced BCP and inhibited Hes-1 and c-Fos expression in the spinal cord. Furthermore, our results showed that JAG-1 regulated neural excitability via the Notch signaling pathway. JAG-1 upregulated Hes-1 expression by inducing the recruitment of NICD to the RBP-J/CSL binding site located within the Hes-1 promoter sequence. Finally, the intrathecal injection of c-Fos-ASO and administration of sh-Hes-1 to the spinal dorsal horn also alleviated BCP. Conclusion JAG-1/Notch signaling axis mediated interaction of astrocyte-neuron contributes to the maintenance of bone cancer-induced pain hypersensitivity. The inhibition of the crosstalk between astrocytic JAG-1 and neuronal Notch-1 may serve as a potential strategy for the treatment of BCP.