Molecular Pain最新文献

Depression is commonly observed in individuals suffering from chronic pain, but the exact molecular mechanisms behind these symptoms are still not fully understood. This study highlights the important role of the TRIM14-NF-κB pathway in the anterior cingulate cortex (ACC) in regulating comorbid depressive symptoms associated with chronic pain. Our results show that the CFA model induces both chronic pain and depression-like behaviors in mice, with significant activation of the ACC brain regions. Specifically, the protein expression of TRIM14 was notably elevated in the ACC of CFA mice. Furthermore, reducing TRIM14 expression alleviated both chronic pain and depression-like behaviors in these mice. In addition, we also discovered that NF-κB may act as a downstream target of TRIM14, as silencing TRIM14 expression led to a reduction in the levels of phosphorylated NF-κB. Notably, inhibiting NF-κB produced similar improvements in chronic pain and depression-like behaviors, mirroring the effects observed with TRIM14 knockdown. In summary, our findings emphasize the critical role of the TRIM14-NF-κB pathway in regulating chronic pain and depression-like behaviors in the CFA mouse model. These insights provide a foundation for further exploration of the molecular mechanisms underlying chronic pain and depression, and may guide the development of targeted therapeutic strategies.

Depression is a common comorbidity of chronic pain. The comorbidity of pain and depression causes longer symptoms and poorer patient prognosis. Periaqueductal gray (PAG) is the key region for the regulation of pain and depression. Puerarin (Pue) is a natural isoflavone compound that has a neuroprotective effect, but the mechanisms on the comorbidity of chronic pain and depression remain unclear. In this study, the spared nerve injury (SNI) produced mechanical allodynia and depressive-like behaviors and elevated the neurological damage in ventrolateral (vl) PAG. Meanwhile, at the eight weeks following injury, mitochondrial dysfunctions including the dysregulated protein levels, the decreased Mn-SOD activity and the reduced ATP contents were observed in vlPAG of SNI model mice. Pue administration improved mechanical pain, motor coordination, and depression-like behaviors, decreased the neuronal activity and neuroinflammation, and elevated the mitochondrial function in vlPAG. Database analysis and experimental assay showed that Pue bound with Bax at the affinity of 2.4 ± 0.1 μM via D102 residue, and decreased Bax level in vlPAG of mice and in primary astrocytic cells. In addition, Pue also recovered levels of mitochondrial membrane potential and reactive oxygen species, and decreased inflammation in primary astrocytic cells. These results suggest that Pue improves the comorbidity of chronic pain and depression by targeting Bax and reducing mitochondrial dysfunction in vlPAG. This study may provide a theoretical basis for Pue application in improving the comorbidity of chronic pain and depression.

Neuropathic pain is still a clinical challenge. Inflammatory responses and autophagy in the spinal cord are important mechanisms for the occurrence and maintain of neuropathic pain. PDCD4 is an important molecule that regulates inflammation and autophagy. However, the regulatory role of PDCD4 is unknown in pain modulation. In this study we found that the expression of PDCD4 in the spinal cord of CCI mice was increased. Inhibition of PDCD4 by intrathecal injection of adeno-associated virus alleviated neuropathic pain hypersensitivity and enhanced autophagy in CCI mice, and inhibited the activation of MAPKs, as well as the expression of inflammatory factors. Intrathecal injection of autophagy inhibitor 3-MA reversed PDCD4 inhibition induced pain relief and change of autophagy. Our results indicate that spinal cord inhibition of PDCD4 alleviates pain sensitization in neuropathic pain mice, and PDCD4 may be developed into a therapeutic target of neuropathic pain treatment.

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.

Migraine is a chronic episodic neurological disorder. However, its diagnosis and management remain unclear. The pathogenesis of migraine is intricately linked to the dysfunction of mitochondria, and aberrant trigeminal neuronal activity. Here, we established a murine migraine model via intraperitoneal administration of nitroglycerin (NTG) to examine alterations in mitochondria-associated proteins and calcium signaling patterns within trigeminal neurons, while also investigating the underlying mechanisms. NTG-treated mice exhibited marked periorbital allodynia, decreased crossing of the central area, and decreased time spent in the central area in the open field test compared to Veh treated animals. Furthermore, increased calcium signaling in response to adenosine triphosphate (ATP) stimulation was observed in the trigeminal ganglion (TG) of mice with migraine. Meanwhile, mRNA levels of genes including nuclear respiratory factor-1 (Nrf1), nuclear respiratory factor-2 (Nrf2) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc-1) were decreased in the TG. Pharmacological regulation of the mitochondrial function affected NTG-induced migraine chronic pain symptoms. TG mitochondria dysfunctions is implicated in the regulation of mechanical hyperalgesia through the modulation of calcium signaling in an NTG-induced migraine animal model.

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes. Half of DPN patients experience sensory deficits including loss of sensation and pain. Loss of sensation increases the risk of unnoticed foot injuries which combined with poor circulation and healing lead to amputation. Type 2 diabetes accounts for 50% of foot amputation highlighting the significant impact sensory loss can have on patients' quality of life. However, the cellular basis underlying sensory loss in DPN remains unclear. We characterised diabetes-induced neuronal loss and damage in dorsal root ganglia (DRG) in the db/db mouse model of type 2 diabetes. Morphometric characterisation was carried out on two neuronal populations in lumbar DRGs of 32-week diabetic (db/db) mice. These are the N200-positive neurons, a marker for low and high-threshold mechanosensitive sensory and proprioceptive neurons, and peripherin (PRPH)-positive neurons, a marker for pain sensing neurons. In diabetic mice, N200-positive neurons were reduced by 30%. Furthermore, diabetes increased the percentage of N200-positive neurons with cytoplasmic vacuoles, a sign of damage and stress, by 2.44 fold. In addition, the average number of vacuoles was 1.6 fold higher in diabetic mice. Therapies aimed at reducing this loss could help patients better protect their limbs from injuries and thus reduce amputations.

Preclinical studies addressing the peripheral effects of cancer perineural invasion report severe neuronal availability and excitability changes. Oral cell squamous cell carcinoma perineural invasion (MOC2-PNI) shows similar effects, modulating the afferent's sensibility (tactile desensitization with concurrent nociceptive sensitization) and demyelination without inducing spontaneous activity (see Part 1.). The current study addresses the electrical status (normal or abnormal) of both active (low threshold mechano receptors (LT) and high threshold mechano receptors (HT)) and inactive (F-type and S-type) afferents. Concurrently, we have also evaluated changes in the genetic landscape that may help to understand the physiological dynamics behind MOC2-PNI-induced functional disruption of the peripheral sensory system. We have observed that the altered cell distribution and mechanical sensibility of the animal's somatosensory system cannot be explained by cellular electrical dysfunction or MOC2-PNI-induced apoptosis. Although PNI does modify the expression of several genes related to cellular hypersensitivity, these changes are insufficient to explain the MOC2-PNI-induced aberrant neuronal excitability state. Our results indicate that genetic markers provide limited information about the functional hyperexcitable state of the peripheral system. Importantly, our results also highlight the emerging role of plasma membrane Ca²⁺-ATPase activity (PMCA) in explaining several aspects of the observed gender-specific neuronal plasticity and the reported cellular distribution switch generated by MOC2-PNI.

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.

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.

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.