Molecular Pain最新文献

Background: Pancreatic neuropathy occurs during the development of pancreatic ductal adenocarcinoma (PDAC), with changes correlating to pancreatic neuropathic pain and increased expression of nociceptive genes in sensory ganglia. Emerging evidence suggests that sphingosine-1-phosphate receptor 1 (S1PR1) plays critical roles in the onset and maintenance of pain. However, whether S1PR1 in sensory ganglia contributes to PDAC-associated neuropathic pain remains unclear.

Methods: We collected histopathological sections and pain-related data from patients who underwent surgical resection and were pathologically confirmed as having PDAC. S1PR1 levels in intrapancreatic nerves were measured using immunohistochemistry. A mouse model of PDAC-associated pain was established in C57BL/6J mice via orthotopic transplantation of MT5 cells. Pain behaviors were evaluated through abdominal mechanical hyperalgesia, hunch score, and open-field tests. The changes and subcellular localization of S1PR1 in dorsal root ganglia (DRGs) were observed. Subsequently, the S1PR1 antagonists W146 and FTY720 were administered to investigate the underlying molecular mechanisms. We further assessed the analgesic efficacy and its impact on tumor progression of the S1PR1 antagonist FTY720.

Results: S1PR1 levels in nerves from PDAC patients experiencing cancer-associated pain were significantly higher compared to those without such pain. In the DRGs of a PDAC mouse model, S1PR1 expression was upregulated and colocalized with neurons and satellite glial cells. Intrathecal injection of S1PR1 antagonists W146 and FTY720 effectively alleviated PDAC-induced neuropathic pain hypersensitivity and suppressed the upregulation of transient receptor potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP). Additionally, FTY720 alleviated pancreatic cancer-related neuropathic pain and demonstrated partial anti-tumor effects.

Conclusions: Our findings indicate that S1PR1 in DRGs plays a pivotal role in PDAC-associated neuropathic pain. Inhibition of S1PR1 signaling may alleviate PDAC-related neuropathic pain, and targeting S1PR1 represents a promising strategy for adjuvant management of pancreatic cancer-related pain.

Short-chain free fatty acids (SCFAs) are generated by gut microbiota through anaerobic fermentation of dietary fibers. Although gut microbiota-derived SCFAs modulate voltage-gated Ca²⁺ channels via G-protein-coupled receptor 41 (GPR41) in isolated sympathetic ganglion neurons, the influence of SCFAs, specifically propionic acid (PA), on the excitability of nociceptive neurons under in vivo conditions has yet to be ascertained. In the current study we assessed whether systemic PA administration diminishes the excitability of nociceptive trigeminal spinal nucleus caudalis (SpVc) wide-dynamic range neurons responding to mechanical stimulation. Extracellular single-unit recordings from SpVc wide-dynamic range neurons were performed in anesthetized rats after mechanical stimulation of the orofacial region. PA significantly and reversibly inhibited the mean firing frequency of SpVc neurons in response to both non-noxious and noxious mechanical stimuli in a dose-dependent manner. Simultaneous administration of a GPR41 inhibitor abolished the PA-induced inhibited firing rate of SpVc neurons, indicating that systemic PA decreased the excitability of nociceptive secondary trigeminal neurons by activating GPR41 signaling-mediated inhibition of voltage-gated Ca²⁺ channels in the central terminals of the SpVc. Modulation of trigeminal nociception by systemic SCFA administration indicates that gut microbiota-derived SCFAs could be effective analgesic agents for relieving trigeminal pain, creating a new therapeutic strategy for the management of trigeminal pain, including clinical pain.

μ-opioid receptor (MOP) plays a critical role in mediating opioid analgesic effects. Genetic variations, particularly those in the MOP gene (Oprm1), significantly influence individual variations in opioid efficacy and side effects across species, highlighting the need for pharmacogenomic research in human and veterinary contexts. This study aimed to identify single-nucleotide variations (SNVs) within Oprm1 in 100 cats of various breeds. Oprm1 spans over 170 kb and consists of five exons that combine to yield three splice variants in the cat Ensembl database. Among these variants, Oprm1-202 is an ortholog of the MOR-1 transcript, which is the most abundant in humans and mice. Oprm1-202 shares 92% and 87% coding sequences (CDS) and 96% and 94% amino acid sequence identity with human and mouse MOR-1, respectively. Phylogenetic trees were constructed from the CDS and amino acid sequences of nine species, including humans, cats, and mice. Both the CDS and amino acid sequences of MOP in cats showed phylogenetic development closer to that of primates than of rodents. Four SNVs were identified in the CDS of Oprm1. One SNV was located in exon 1 and the other three in exon 2 of Oprm1, all of which were synonymous substitutions. Although synonymous mutations generally have a limited functional impact, they may influence splicing and receptor expression. Further research is required to assess the effects of these SNVs on opioid efficacy, receptor expression, and analgesic responses across breeds, considering the potential breed-specific genetic factors in cat species.

Inflammatory pain presents a significant clinical challenge. AMP-activated protein kinase (AMPK) is recognized for its capacity to alleviate inflammation by inhibiting transcription factors such as nuclear factor kappa B (NF-κB) and signal transducer and activator of transcription (STAT). Our prior research demonstrated that AMPK reduces inflammatory pain by inhibiting NF-κB activation and interleukin-1 beta (IL-1β) expression. However, the role of AMPK in regulating reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS) by modulating STAT3 phosphorylation in inflammatory pain remains inadequately understood. This study aims to investigate the role of AMPK in modulating STAT3 phosphorylation in the macrophages of inflamed tissues to mitigate inflammatory pain. A Complete Freund's Adjuvant (CFA)-induced inflammatory pain model was established by subcutaneous injection into the plantar surface of the left hindpaw of adult male mice. Behavioral tests of mechanical allodynia and thermal latency were used to determine nociceptive behavior. Immunoblotting quantified p-AMPK and iNOS expression levels. Nuclear translocation of p-STAT3(Ser727) and STAT3 in macrophages was assessed by western blot and immunofluorescence. ROS accumulation and mitochondrial damage in NR8383 macrophages were detected by flow cytometry. Lentivirus infection cells experiment was performed to transfect vectors encoding the STAT3 S727D mutants. Treatment with the AMPK activator AICAR alleviated CFA-induced inflammatory pain, enhanced AMPK phosphorylation, and reduced iNOS expression in inflamed skin tissues. AICAR effectively prevented STAT3 nuclear translocation while promoting the phosphorylation of STAT3 (Ser727) in the cytoplasm. In vitro studies with CFA-stimulated NR8383 macrophages revealed that AICAR increased STAT3(Ser727) phosphorylation, curtailed iNOS expression, and attenuated ROS accumulation and mitochondrial damage. Furthermore, the S727D mutation, which enhances STAT3 phosphorylation, replicated the protective effects of AICAR against CFA-induced oxidative stress and mitochondrial dysfunction. Our study shows that the AMPK acitvation downregulates iNOS expression by inhibiting the STAT3 nuclear translocation and promotes cytoplasmic STAT3(Ser727) phosphorylation, which reduces ROS expression and mitochondrial dysfunction, thereby alleviating inflammatory pain. These findings underscore the therapeutic potential of targeting AMPK and STAT3 pathways in inflammatory pain management.

Introduction: Meninges surrounding the brain and spinal cord house a variety of immune cell types including macrophages that express the CD206 mannose receptor. Here, we investigated whether CD206⁺ macrophages in the meninges play a role in regulating nociception and pain hypersensitivity.

Methods: We selectively depleted CD206⁺ macrophages in the meninges around the lumbar spinal cord by intrathecal administration of anti-CD206 coupled to saporin, and determined the effects of CD206⁺ macrophage depletion on responses in naïve rats and in those that had received a skin incision to the upper hindlimb. In addition, we used RNAseq to investigate transcriptional changes in lumbar meninges and dorsal root ganglia. Experiments were done in both male and female rats.

Results: Depleting CD206⁺ meningeal macrophages did not alter basal responses in naïve animals of either sex. By contrast depleting these cells after skin injury induced mechanical hypersensitivity in male rats, without changes in thermal sensitivity but had no effect in females. In male rats with skin incision injury, we found that the mechanical hypersensitivity induced by depleting CD206⁺ meningeal macrophages was reversed by administering the NMDAR antagonist, APV. In addition, the hypersensitivity was reversed by an enhancer of KCC2 function, CLP290. Unexpectedly, skin incision caused significant transcriptional changes in the meninges, but only in male rats.

Conclusions: Taken together, our results indicate that while CD206⁺ meningeal macrophages do not regulate basal nociception in naïve rats, after skin incision injury, these cells mask mechanical hypersensitivity in male rats only. Thus, we conclude that in a sex-dependent manner CD206⁺ meningeal macrophages prevent the spread of pain hypersensitivity after a minor injury. Importantly, the skin incision we used was comparable to that used in "sham" controls in numerous rodent studies of neuropathic pain. Our findings have, therefore, potentially broad implications for re-interpreting results from previous neuropathic pain research.

Post-COVID syndrome (PCS) may manifest as chronic pain and fibromyalgia-like symptoms, but the specific risk factors contributing to these outcomes remain poorly understood. We conducted a prospective cohort study using data from the ongoing "Post-Acute Sequelae of SARS-CoV-2 Infection (PASC)" study to identify predictors of chronic pain and fibromyalgia-related phenotypes among previously hospitalized COVID-19 patients. Participants were adults (n = 756, mean age 55, 47% female) hospitalized between March and August 2020 at the University of São Paulo Medical School. Clinical and demographic data from hospitalization, along with psychological, functional, and cognitive assessments at 3-11 months post-discharge (phase 1), were used to predict chronic pain, chronic widespread pain (CWP), fibromyalgia-like symptoms (FLS), and probable fibromyalgia (FM) at a 2-3 year follow-up (phase 2). Multivariate logistic regression analyses revealed that higher anxiety/depression severity (OR 1.35; 95% CI 1.09-1.69; p = 0.008) and reduced left handgrip strength (OR 0.95; 95% CI 0.92-0.98; p < 0.001) at phase 1 significantly predicted chronic pain at phase 2. For fibromyalgia-related phenotypes, greater left-side pain, insomnia severity, and weaker left handgrip strength were consistently associated with increased risk across all outcomes (CWP, FLS, FM), with statistically significant odds ratios ranging from 1.07 to 1.44. These findings highlight key modifiable risk factors - particularly psychological distress, sleep disruption, and muscle weakness - that may contribute to the development of chronic pain and fibromyalgia symptoms following COVID-19 hospitalization. Early identification and targeted intervention on these domains could improve long-term outcomes in PCS populations.

Patients with cancer perineural invasion (PNI) report greater spontaneous pain and mechanical allodynia. Here, we examine the impact of the disease on the peripheral sensory system, the excitability changes induced by PNI at the dorsal root ganglia, and the potential protective role of the absence of Tumor Necrosis Factor-α Receptor 1 (TNFR1). To study these effects, we use a murine model generated by injecting mouse oral cancer squamous cell carcinoma (MOC2) into the sciatic nerve (MOC2-PNI) in both male and female mice. We found that MOC2-PNI induces a profound change in the somatosensory landscape by deactivating/blocking the peripheral inputs while modulating the afferent's sensibility (tactile desensitization with concurrent nociceptive sensitization) and demyelination without inducing spontaneous activity. All these changes caused by MOC2-PNI are unmitigated by the absence of TNFR1. We conclude that MOC2-PNI induces an aberrant neuronal excitability state and triggers extreme gender-specific neuronal plasticity. These data allow us to speculate on the role of such plasticity as a powerful defense mechanism to prevent terminal sensory dysfunction, the rise of chronic pain, and extend animals' survivability.

Background: Myofascial trigger points (MTrPs) for abnormal skeletal muscle contraction are the cause of myofascial pain. The G protein-coupled receptor family and tyrosine kinase receptor family regulate the contraction of vascular smooth muscle through the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway. Phosphorylated myosin light chain (p-MLC) is associated with skeletal muscle contraction. The aim of the current study was to explore the effect and mechanism of the PI3K/AKT/MLC signalling pathway on myofascial pain in rats.

Methods: A rat model of myofascial pain was established by a blunt strike to the gastrocnemius muscle combined with centrifugal exercise for 8 weeks, followed by recovery for 4 weeks. Different concentrations of the PI3K inhibitor LY294002 (0.01, 0.1, or 1 mg/ml) were subsequently injected into the MTrPs of rats with myofascial pain to observe the effects on the mechanical tenderness threshold at the MTrPs.

Results: LY294002 (0.1 mg/ml) inhibited myofascial pain at 0.5, 1 and 2 h after injection, and LY294002 (1 mg/ml) inhibited myofascial pain at 0.5, 1, 2 and 4 h after injection. The expression of PI3K increased on the enlarged muscle fibre membrane at MTrPs. LY294002 (1 mg/ml) inhibited the expression of PI3K, p-AKT, and p-MLC and the abnormal contraction of muscle fibres at MTrPs and alleviated nerve fibre compression at MTrPs. Moreover, LY294002 inhibited the expression of Fos in the spinal dorsal horn of rats with myofascial pain.

Conclusions: These findings suggested that the increased expression of PI3K/p-AKT/p-MLC was related to myofascial pain in rats and that the PI3K inhibitor LY294002 might alleviate myofascial pain in rats by inhibiting abnormal contraction at MTrPs.

Aim: To investigate the efficacy of medicinal plant bioactive secondary metabolites as inhibitors of voltage-gated sodium channels (Nav1.7, Nav1.8, and Nav1.9) in managing painful states of dental pulps.

Methodology: Molecular docking, ADME prediction, toxicity profiling, and pharmacophore modeling were used to assess the binding affinities, pharmacokinetic properties, toxicological profiles, and active pharmacophores of the selected bioactive compounds.

Results: Three compounds (Sepaconitine, Lappaconitine, and Ranaconitine) showed binding affinities (ΔG = -8.95 kcal/mol, -7.77 kcal/mol, and -7.44 kcal/mol, respectively) with all three Nav1.7, Nav1.8, and Nav1.9 sodium channels. The sepaconitine amine group formed hydrophobic interactions with key residues. The Lappaconitine benzene ring contributed to hydrophobic interactions and hydrogen bond acceptor interactions. The hydrophobic interactions of the ranaconitine amine group play a critical role with specific residues on Nav1.8 and Nav1.9.

Conclusion: The natural fusicoccane diterpenoid derivatives Sepaconitine, Lappaconitine, and Ranaconitine are potential lead compounds for the development of novel analgesics as selective antihyperalgesic drugs, which will provide a new dental pharmacological intervention for managing painful dental pulp conditions. Further experimental validation and clinical studies that confirm the efficacy and safety of these compounds will strengthen their applicability in dental practice.

Fibromyalgia (FM) is a complex disorder characterized by chronic pain, fatigue, and functional impairments, with unclear pathological mechanisms. Gut microbiota and plasma metabolites have been implicated in FM, but their causal relationships remain unexplored. This study aims to assess the causal relationships between gut microbiota, plasma metabolites, and FM using Mendelian randomization (MR) analysis and to explore potential mediating mechanisms. Public genome-wide association study data were analyzed using bidirectional MR. Associations between gut microbiota, plasma metabolites, and FM were evaluated, and multivariable MR identified mediating metabolites. Results were validated with inverse variance weighted, MR-Egger, and weighted median methods, with metabolic pathway enrichment analysis for further insights. MR identified protective associations between FM and four taxa (family Enterobacteriaceae, genus Butyricicoccus, genus Coprococcus1, and order Enterobacteriales) and risk associations with genus Eggerthella and genus Ruminococcaceae UCG005. Additionally, 82 plasma metabolites linked to pathways such as caffeine metabolism, α-linolenic acid metabolism, GLP-1, and incretin regulation were associated with FM. Mediation analysis revealed Enterobacteriaceae and Enterobacteriales influenced FM risk through 2,3-dihydroxypyridine and palmitoylcholine. Personalized dietary interventions, such as limiting caffeine intake, increasing omega-3 fatty acid consumption, adopting a low glycemic index diet, and reducing the intake of high-oxalate foods, may effectively alleviate FM-related symptoms by modulating metabolic pathways, reducing inflammation, and mitigating oxidative stress. This study highlights the intricate interactions between the gut microbiota and metabolic pathways, providing critical scientific evidence and actionable targets for clinical interventions, dietary management, and precision medicine approaches in FM treatment.