Histone modifications and Sp1 promote GPR160 expression in bone cancer pain within rodent models.

Bone cancer pain (BCP) affects ~70% of patients in advanced stages, primarily due to bone metastasis, presenting a substantial therapeutic challenge. Here, we profile orphan G protein-coupled receptors in the dorsal root ganglia (DRG) following tumor infiltration, and observe a notable increase in GPR160 expression. Elevated Gpr160 mRNA and protein levels persist from postoperative day 6 for over 18 days in the affected DRG, predominantly in small-diameter C-fiber type neurons specific to the tibia. Targeted interventions, including DRG microinjection of siRNA or AAV delivery, mitigate mechanical allodynia, cold, and heat hyperalgesia induced by the tumor. Tumor infiltration increases DRG neuron excitability in wild-type mice, but not in Gpr160 gene knockout mice. Tumor infiltration results in reduced H3K27me3 and increased H3K27ac modifications, enhanced binding of the transcription activator Sp1 to the Gpr160 gene promoter region, and induction of GPR160 expression. Modulating histone-modifying enzymes effectively alleviated pain behavior. Our study delineates a novel mechanism wherein elevated Sp1 levels facilitate Gpr160 gene transcription in nociceptive DRG neurons during BCP in rodents.

miR-155-5p in the spinal cord regulates hypersensitivity in a rat model of bone cancer pain.

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-155-5p could be a promising target in treating BCP.

CXCR1 participates in bone cancer pain induced by Walker 256 breast cancer cells in female rats.

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-1ß) 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-1ß).

The role of orphan G protein-coupled receptors in pain.

G protein-coupled receptors (GPCRs), which form the largest family of membrane protein receptors in humans, are highly complex signaling systems with intricate structures and dynamic conformations and locations. Among these receptors, a specific subset is referred to as orphan GPCRs (oGPCRs) and has garnered significant interest in pain research due to their role in both central and peripheral nervous system function. The diversity of GPCR functions is attributed to multiple factors, including allosteric modulators, signaling bias, oligomerization, constitutive signaling, and compartmentalized signaling. This review primarily focuses on the recent advances in oGPCR research on pain mechanisms, discussing the role of specific oGPCRs including GPR34, GPR37, GPR65, GPR83, GPR84, GPR85, GPR132, GPR151, GPR160, GPR171, GPR177, and GPR183. The orphan receptors among these receptors associated with central nervous system diseases are also briefly described. Understanding the functions of these oGPCRs can contribute not only to a deeper understanding of pain mechanisms but also offer a reference for discovering new targets for pain treatment.

LncRNA 51325 Alleviates Bone Cancer Induced Hyperalgesia Through Inhibition of Pum2.

Background: Bone cancer pain (BCP) represents one of the most challenging comorbidities associated with cancer metastasis. Long non-coding RNAs (lncRNAs) have garnered attention as potential therapeutic agents in managing neuropathic pain. However, their role in the regulation of nociceptive information processing remains poorly understood. In this study, we observed a significant down-regulation of the spinal lncRNA ENSRNOG00000051325 (lncRNA51325) in a rat model of bone cancer pain. Our study sought to elucidate the potential involvement of lncRNA51325 in the development of BCP by modulating the expression of molecules associated with pain modulation. Methods: We established the BCP model by injecting Walker 256 cells into the tibial plateau of rats. We conducted tests on the pain behaviors and anxiety-like responses of rats through von-Frey test, Gait analysis, and Open Field Test. Spinal lumbar expansion was harvested for molecular biology experiments to explore the relationship between lncRNA51325 and Pumilio RNA binding family member 2 (Pum2). Results: Notably, the overexpression of lncRNA51325 effectively attenuated mechanical allodynia in rats afflicted with BCP, whereas the knockdown of lncRNA51325 induced pain behaviors and anxiety-like responses in naïve rats. Additionally, we observed a time-dependent increase in the expression of Pum2 in BCP-afflicted rats, and intrathecal injection of Pum2-siRNA alleviated hyperalgesia. Furthermore, our investigations revealed that lncRNA51325 exerts a negative modulatory effect on Pum2 expression. The overexpression of lncRNA51325 significantly suppressed Pum2 expression in BCP rats, while the knockdown of lncRNA51325 led to elevated Pum2 protein levels in the spinal cord of naïve rats. Subsequent treatment with Pum2-siRNA mitigated the downregulation of lncRNA51325-induced mechanical allodynia in naïve rats. Conclusion: Our findings indicate that lncRNA51325 plays a role in regulating bone cancer pain by inhibiting Pum2 expression, offering a promising avenue for novel treatments targeting nociceptive hypersensitivity induced by bone metastatic cancer.

Efficacy and Safety of Crisugabalin (HSK16149) in Adults with Postherpetic Neuralgia: A Phase 3 Randomized Clinical Trial.

Importance: China carries a heavy burden of postherpetic neuralgia, with an unmet need for novel drugs with greater efficacy and less prominent neurotoxic effects than existing calcium channel ligands. Objective: To investigate the efficacy and safety of crisugabalin, an oral calcium channel α2δ-1 subunit ligand, for postherpetic neuralgia. Design, Setting, and Participants: This randomized clinical trial, carried out between November 9, 2021, and January 5, 2023, at 48 tertiary care centers across China had 2 parts. Part 1 was a phase 3, multicenter, randomized, double-blind, placebo-controlled, parallel-group study consisting of a 2-week screening period, a 7-day run-in period, and a 12-week double-blind treatment period. Part 2 was a 14-week open-label extension study. Investigators, statisticians, trial clinicians, and patients were blinded to trial group assignments. Participants included adults with postherpetic neuralgia with an average daily pain score (ADPS) of at least 4 on the 11-point Numeric Pain Rating Scale over the preceding week, with the exclusion of patients with pain not controlled by prior therapy with pregabalin (≥300 mg/d) or gabapentin (≥1200 mg/d). Interventions: Patients were randomized 1:1:1 to receive crisugabalin, 20 mg twice daily (ie, 40 mg/d), and crisugabalin, 40 mg twice daily (ie, 80 mg/d), or placebo for 12 weeks. Eligible patients received crisugabalin, 40 mg, twice daily during extension. Main Outcome and Measure: The primary efficacy end point was the change from baseline in ADPS at week 12. Results: The study enrolled 366 patients (121 patients receiving crisugabalin, 40 mg/d; 121 patients receiving crisugabalin, 80 mg/d; 124 patients receiving placebo; median [IQR] age, 63.0 [56.0-69.0] years; 193 men [52.7%]). At week 12, the least squares mean (SD) change from baseline in ADPS was -2.2 (0.2) for crisugabalin, 40 mg/d, and -2.6 (0.2) for crisugabalin, 80 mg/d, vs -1.1 (0.2) for placebo, with a least squares mean difference of -1.1 (95% CI, -1.6 to -0.7; P < .001) and -1.5 (-95% CI, -2.0 to -1.0; P < .001) vs placebo, respectively. No new safety concerns emerged. Conclusions and Relevance: Crisugabalin, 40 mg/d, or crisugabalin, 80 mg/d, was well tolerated and demonstrated a statistically significant improvement in ADPS over placebo. Trial Registration: ClinicalTrials.gov Identifier: NCT05140863.

The Diagnosis and Therapy of Degenerative Knee Joint Disease: Expert Consensus from the Chinese Pain Medicine Panel.

At present, there are many constantly updated guidelines and consensuses on the diagnosis and treatment of osteoarthritis both at home and abroad. The recommendations established using methods of evidence-based medicine has experienced strict research on controlling bias and promoting reproduction rate. As a result, the previous evidence was reevaluated, and a lot of changes were provoked in the diagnosis and treatment concept of osteoarthritis. However, several methods not recommended by foreign guidelines are still in use in the current clinical practice in China. On the one hand, Chinese experts have not reached extensive consensus on whether it is necessary to make changes according to foreign guidelines. On the other hand, almost all the current relevant guidelines are on osteoarthritis, but the lesions around knee joints which, as a whole, bear the largest weight in human body, cannot be ignored. For this purpose, Chinese Association for the Study of Pain (CASP) organized some leading experts to formulate this Chinese Pain Specialist Consensus on the diagnosis and treatment of degenerative knee osteoarthritis (DKOA) in combination with the guidelines in foreign countries and the expert experience of clinical practice in China. The consensus, which includes the definition, pathophysiology, epidemiology, clinical manifestation, diagnostic criteria, and treatments of DKOA, is intended to be used by first-line doctors, including pain physicians to manage patients with DKOA.

Sevoflurane exposure in postnatal rats induced long-term cognitive impairment through upregulating caspase-3/cleaved-poly (ADP-ribose) polymerase pathway.

The association of anesthetic exposure in infants or young children with the long-term impairment of neurologic functions has been reported previously; however, the underlying mechanisms remain largely unknown. In order to identify dysregulated gene expression underlying long-term cognitive impairment caused by sevoflurane exposure at the postnatal stage, the present study initially performed behavioral tests on adult Wistar rats, which received 3% sevoflurane at postnatal day 7 (P7) for different time course. Subsequently, transcriptome profiling of hippocampal tissues from experimental and control rats was performed. Significant impairment of the working memory was observed in adult rats with sevoflurane exposure for 4-6 h, when compared with the control rats. The results indicated that a total of 264 genes were aberrantly expressed (51 downregulated and 213 upregulated; fold change >2.0; P<0.05; false discovery rate <0.05) in the hippocampus of experimental adult rats compared with those from control rats. Particularly, the expression of caspase-3 gene (CASP3), encoding caspase-3 protein, presented the most significant upregulation, which was further validated by quantitative polymerase chain reaction and immunohistochemical analysis. Further analysis revealed that CASP3 expression level was negatively correlated with the rats' spatial working memory performance, as indicated by the Y-maze test. The level of cleaved-poly (ADP-ribose) polymerase (PARP), a substrate of caspase-3, was also increased in the hippocampus of experimental adult rats. Thus, the present study revealed that upregulation of caspase-3/cleaved-PARP may be involved in long-term cognitive impairment caused by sevoflurane exposure in infants, which may be useful for the clinical prevention of cognitive impairment.