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ABSTRACT: Rodents and human studies indicate that the hippocampus, a brain region necessary for memory processing, responds to noxious stimuli. However, the hippocampus has yet to be considered a key brain region directly involved in the human pain experience. One approach to answer this question is to perform quantitative sensory testing on patients with hippocampal damage-ie, medial temporal lobe epilepsy. Some case studies and case series have performed such tests in a handful of patients with various types of epilepsy and have reported mixed results. Here, we aimed to determine whether mechanical pain sensitivity was altered in patients diagnosed with temporal lobe epilepsy. We first investigated whether mechanical pain sensitivity in patients with temporal lobe epilepsy differs from that of healthy individuals. Next, in patients with temporal lobe epilepsy, we evaluated whether the degree of pain sensitivity is associated with the degree of hippocampal integrity. Structural integrity was based on hippocampal volume, and functional integrity was based on verbal and visuospatial memory scores. Our findings show that patients with temporal lobe epilepsy have lower mechanical pain sensitivity than healthy individuals. Only left hippocampal volume was positively associated with mechanical pain sensitivity-the greater the hippocampal damage, the lower the sensitivity to mechanical pain. Hippocampal measures of functional integrity were not significantly associated with mechanical pain sensitivity, suggesting that the mechanisms of hippocampal pain processing may be different than its memory functions. Future studies are necessary to determine the mechanisms of pain processing in the hippocampus.
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Epilepsia del Lóbulo Temporal , Hipocampo , Imagen por Resonancia Magnética , Umbral del Dolor , Humanos , Hipocampo/diagnóstico por imagen , Hipocampo/patología , Hipocampo/fisiopatología , Masculino , Femenino , Adulto , Epilepsia del Lóbulo Temporal/fisiopatología , Epilepsia del Lóbulo Temporal/patología , Epilepsia del Lóbulo Temporal/diagnóstico por imagen , Epilepsia del Lóbulo Temporal/complicaciones , Umbral del Dolor/fisiología , Persona de Mediana Edad , Dimensión del Dolor/métodos , Adulto Joven , Hiperalgesia/fisiopatología , Hiperalgesia/patología , Dolor/fisiopatología , Dolor/patología , Dolor/diagnóstico por imagen , Estimulación FísicaRESUMEN
Neuroactive steroids (NASs) directly affect neuronal excitability. Despite their role in the nervous system is intimately linked to pain control, knowledge is currently limited. This study investigates the peripheral involvement of NASs in chronic ischemic pain by targeting the cytochrome P450 side-chain cleavage enzyme (P450scc). Using a rat model of hind limb thrombus-induced ischemic pain (TIIP), we observed an increase in P450scc expression in the ischemic hind paw skin. Inhibiting P450scc with intraplantar aminoglutethimide (AMG) administration from post-operative day 0 to 3 significantly reduced the development of mechanical allodynia. However, AMG administration from post-operative day 3 to 6 did not affect established mechanical allodynia. In addition, we explored the role of the peripheral sigma-1 receptor (Sig-1R) by co-administering PRE-084 (PRE), a Sig-1R agonist, with AMG. PRE reversed the analgesic effects of AMG during the induction phase. These findings indicate that inhibiting steroidogenesis with AMG alleviates peripheral ischemic pain during the induction phase via Sig-1Rs.
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Modelos Animales de Enfermedad , Hiperalgesia , Isquemia , Ratas Sprague-Dawley , Receptores sigma , Animales , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/patología , Hiperalgesia/complicaciones , Masculino , Isquemia/complicaciones , Isquemia/patología , Receptores sigma/antagonistas & inhibidores , Receptores sigma/metabolismo , Receptor Sigma-1 , Dolor/tratamiento farmacológico , Dolor/complicaciones , Dolor/etiología , Dolor/patología , Miembro Posterior/efectos de los fármacos , Ratas , Sistema Enzimático del Citocromo P-450/metabolismoRESUMEN
INTRODUCTION: Following amputation, peripheral nerves lack distal targets for regeneration, often resulting in symptomatic neuromas and debilitating neuropathic pain. Animal models can establish a practical method for symptomatic neuroma formation for better understanding of neuropathic pain pathophysiology through behavioral and histological assessments. We created a clinically translatable animal model of symptomatic neuroma to mimic neuropathic pain in patients and assess sexual differences in pain behaviors. METHODS: Twenty-two male and female rats were randomly assigned to one of two experimental groups: (1) neuroma surgery, or (2) sham surgery. For the neuroma experimental group, the tibial nerve was transected in the thigh, and the proximal segment was placed under the skin for mechanical testing at the site of neuroma. For the sham surgery, rats underwent tibial nerve isolation without transection. Behavioral testing consisted of neuroma-site pain, mechanical allodynia, cold allodynia, and thermal hyperalgesia at baseline, and then weekly over 8 weeks. RESULTS: Male and female neuroma rats demonstrated significantly higher neuroma-site pain response compared to sham groups starting at weeks 3 and 4, indicating symptomatic neuroma formation. Weekly assessment of mechanical and cold allodynia among neuroma groups showed a significant difference in pain behavior compared to sham groups (p < 0.001). Overall, males and females did not display significant differences in their pain responses. Histology revealed a characteristic neuroma bulb at week 8, including disorganized axons, fibrotic tissue, Schwann cell displacement, and immune cell infiltration. CONCLUSION: This novel animal model is a useful tool to investigate underlying mechanisms of neuroma formation and neuropathic pain.
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Modelos Animales de Enfermedad , Hiperalgesia , Neuralgia , Neuroma , Animales , Masculino , Neuroma/patología , Neuralgia/fisiopatología , Neuralgia/patología , Neuralgia/etiología , Femenino , Hiperalgesia/fisiopatología , Hiperalgesia/patología , Ratas Sprague-Dawley , Ratas , Nervio Tibial/patología , Nervio Tibial/fisiopatología , Dimensión del Dolor/métodosRESUMEN
BACKGROUND: Painful diabetic neuropathy (PDN) is closely linked to inflammation, which has been demonstrated to be associated with pyroptosis. Emerging evidence has implicated TANK-binding kinase 1 (TBK1) in various inflammatory diseases. However, it remains unknown whether activated TBK1 causes hyperalgesia via pyroptosis. METHODS: PDN mice model of type 1 or type 2 diabetic was induced by C57BL/6J or BKS-DB mice with Lepr gene mutation. For type 2 diabetes PDN model, TBK1-siRNA, Caspase-1 inhibitor Ac-YVAD-cmk or TBK1 inhibitor amlexanox (AMX) were delivered by intrathecal injection or intragastric administration. The pain threshold and plantar skin blood perfusion were evaluated through animal experiments. The assessments of spinal cord, dorsal root ganglion, sciatic nerve, plantar skin and serum included western blotting, immunofluorescence, ELISA, and transmission electron microscopy. RESULTS: In the PDN mouse model, we found that TBK1 was significantly activated in the spinal dorsal horn (SDH) and mainly located in microglia, and intrathecal injection of chemically modified TBK1-siRNA could improve hyperalgesia. Herein, we described the mechanism that TBK1 could activate the noncanonical nuclear factor κB (NF-κB) pathway, mediate the activation of NLRP3 inflammasome, trigger microglia pyroptosis, and ultimately induce PDN, which could be reversed following TBK1-siRNA injection. We also found that systemic administration of AMX, a TBK1 inhibitor, could effectively improve peripheral nerve injury. These results revealed the key role of TBK1 in PDN and that TBK1 inhibitor AMX could be a potential strategy for treating PDN. CONCLUSIONS: Our findings revealed a novel causal role of TBK1 in pathogenesis of PDN, which raises the possibility of applying amlexanox to selectively target TBK1 as a potential therapeutic strategy for PDN.
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Neuropatías Diabéticas , Microglía , Proteínas Serina-Treonina Quinasas , Piroptosis , Animales , Masculino , Ratones , Aminopiridinas/farmacología , Aminopiridinas/uso terapéutico , Neuropatías Diabéticas/patología , Modelos Animales de Enfermedad , Hiperalgesia/patología , Ratones Endogámicos C57BL , Microglía/metabolismo , Microglía/patología , Microglía/efectos de los fármacos , FN-kappa B/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/metabolismo , Proteína con Dominio Pirina 3 de la Familia NLR/genética , Proteína con Dominio Pirina 3 de la Familia NLR/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Serina-Treonina Quinasas/genética , Piroptosis/efectos de los fármacos , ARN Interferente Pequeño/metabolismo , ARN Interferente Pequeño/genéticaRESUMEN
We report that diazepam binding inhibitor (DBI) is a glial messenger mediating crosstalk between satellite glial cells (SGCs) and sensory neurons in the dorsal root ganglion (DRG). DBI is highly expressed in SGCs of mice, rats, and humans, but not in sensory neurons or most other DRG-resident cells. Knockdown of DBI results in a robust mechanical hypersensitivity without major effects on other sensory modalities. In vivo overexpression of DBI in SGCs reduces sensitivity to mechanical stimulation and alleviates mechanical allodynia in neuropathic and inflammatory pain models. We further show that DBI acts as an unconventional agonist and positive allosteric modulator at the neuronal GABAA receptors, particularly strongly affecting those with a high-affinity benzodiazepine binding site. Such receptors are selectively expressed by a subpopulation of mechanosensitive DRG neurons, and these are also more enwrapped with DBI-expressing glia, as compared with other DRG neurons, suggesting a mechanism for a specific effect of DBI on mechanosensation. These findings identified a communication mechanism between peripheral neurons and SGCs. This communication modulates pain signaling and can be targeted therapeutically.
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Inhibidor de la Unión a Diazepam , Ganglios Espinales , Neuroglía , Animales , Ganglios Espinales/metabolismo , Neuroglía/metabolismo , Ratones , Ratas , Humanos , Inhibidor de la Unión a Diazepam/metabolismo , Inhibidor de la Unión a Diazepam/genética , Masculino , Células Receptoras Sensoriales/metabolismo , Receptores de GABA-A/metabolismo , Receptores de GABA-A/genética , Hiperalgesia/metabolismo , Hiperalgesia/genética , Hiperalgesia/patología , Ratas Sprague-Dawley , Mecanotransducción Celular , Ratones Endogámicos C57BLRESUMEN
BACKGROUND: The periaqueductal gray (PAG) plays a well-established pivotal role in the descending pain modulatory circuit. The objective of this study was to investigate morphological changes in the astroglia in models that are commonly used in pain and itch studies. METHODS: Five different mouse models of pain, as well as two models of chronic itch, were established using complete Freund's adjuvant (CFA), spared nerve injury (SNI), bone cancer pain (BCP), cisplatin (CIS), and paclitaxel (PTX) for pain, and diphenylcyclopropenone (DCP) and acetone and diethyl ether followed by water (AEW) for chronic itch. von Frey tests and video recordings were employed to assess pain and itching behaviors. The immunofluorescence of S100ß, pSTAT3, and glial fibrillary acidic protein (GFAP) was examined. Two- and three-dimensional studies were used to evaluate changes in astrocyte morphology. RESULTS: Significant scratching was caused by DCP and AEW, whereas the administration of CFA, SNI, BCP, CIS, and PTX produced clear mechanical allodynia. The expression of GFAP in the lPAG/vlPAG was upregulated in CFA, SNI, BCP, CIS, PTX, and DCP mice but decreased in AEW mice. According to Sholl analysis, CFA, SNI, PTX, and BCP mice showed substantially higher astrocyte intersections in the vlPAG, whereas CFA, SNI, BCP, CIS, and DCP mice presented longer peak lengths. In three-dimensional analysis, CFA, SNI, PTX, and DCP mice showed increased astrocyte surface areas, while CIS and AEW mice showed both reduced surface areas and/or volumes of astrocytes. CONCLUSION: The findings showed that different pain and itching conditions have different astrocyte morphologies, and these variations in morphological changes help to explain the pathophysiology of these conditions.
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Astrocitos , Modelos Animales de Enfermedad , Dolor , Sustancia Gris Periacueductal , Prurito , Animales , Astrocitos/patología , Astrocitos/metabolismo , Sustancia Gris Periacueductal/metabolismo , Sustancia Gris Periacueductal/patología , Prurito/patología , Prurito/fisiopatología , Masculino , Dolor/patología , Dolor/fisiopatología , Dolor/metabolismo , Ratones , Proteína Ácida Fibrilar de la Glía/metabolismo , Ratones Endogámicos C57BL , Hiperalgesia/patología , Hiperalgesia/fisiopatologíaRESUMEN
Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain accompanied by fatigue and muscle atrophy. Although its etiology is not known, studies have shown that FM patients exhibit altered function of the sympathetic nervous system (SNS), which regulates nociception and muscle plasticity. Nevertheless, the precise SNS-mediated mechanisms governing hyperalgesia and skeletal muscle atrophy in FM remain unclear. Thus, we employed two distinct FM-like pain models, involving intramuscular injections of acidic saline (pH 4.0) or carrageenan in prepubertal female rats, and evaluated the catecholamine content, adrenergic signaling and overall muscle proteolysis. Subsequently, we assessed the contribution of the SNS to the development of hyperalgesia and muscle atrophy in acidic saline-injected rats treated with clenbuterol (a selective ß2-adrenergic receptor agonist) and in animals maintained under baseline conditions and subjected to epinephrine depletion through adrenodemedullation (ADM). Seven days after inducing an FM-like model with acidic saline or carrageenan, we observed widespread mechanical hyperalgesia along with loss of strength and/or muscle mass. These changes were associated with reduced catecholamine content, suggesting a common underlying mechanism. Notably, treatment with a ß2-agonist alleviated hyperalgesia and prevented muscle atrophy in acidic saline-induced FM-like pain, while epinephrine depletion induced mechanical hyperalgesia and increased muscle proteolysis in animals under baseline conditions. Together, the results suggest that reduced sympathetic activity is involved in the development of pain and muscle atrophy in the murine model of FM analyzed.
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Clenbuterol , Modelos Animales de Enfermedad , Fibromialgia , Hiperalgesia , Atrofia Muscular , Sistema Nervioso Simpático , Animales , Femenino , Fibromialgia/patología , Fibromialgia/fisiopatología , Atrofia Muscular/patología , Atrofia Muscular/fisiopatología , Hiperalgesia/fisiopatología , Hiperalgesia/patología , Sistema Nervioso Simpático/fisiopatología , Sistema Nervioso Simpático/efectos de los fármacos , Sistema Nervioso Simpático/patología , Clenbuterol/farmacología , Ratas , Carragenina/toxicidad , Ratas Sprague-Dawley , Dolor/patología , Dolor/fisiopatología , Epinefrina , Músculo Esquelético/patología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/fisiopatología , Catecolaminas/metabolismo , Agonistas Adrenérgicos beta/farmacologíaRESUMEN
Methylene blue (MB) has been shown to reduce mortality and morbidity in vasoplegic patients after cardiac surgery. Though MB is considered to be safe, extravasation of MB leading to cutaneous toxicity has been reported. In this study, we sought to characterize MB-induced cutaneous toxicity and investigate the underlying mechanisms. To induce MB-induced cutaneous toxicity, we injected 64 adult male Sprague-Dawley rates with 200 µL saline (vehicle) or 1%, 0.1%, or 0.01% MB in the plantar hind paws. Paw swelling, skin histologic changes, and heat and mechanical hyperalgesia were measured. Injection of 1%, but not 0.1% or 0.01% MB, produced significant paw swelling compared to saline. Injection of 1% MB produced heat hyperalgesia but not mechanical hyperalgesia. Pain behaviors were unchanged following injections of 0.1% or 0.01% MB. Global transcriptomic analysis by RNAseq identified 117 differentially expressed genes (111 upregulated, 6 downregulated). Ingenuity Pathway Analysis showed an increased quantity of leukocytes, increased lipids, and decreased apoptosis of myeloid cells and phagocytes with activation of IL-1ß and Fos as the two major regulatory hubs. qPCR showed a 16-fold increase in IL-6 mRNA. Thus, using a novel rat model of MB-induced cutaneous toxicity, we show that infiltration of 1% MB into cutaneous tissue causes a dose-dependent pro-inflammatory response, highlighting potential roles of IL-6, IL-1ß, and Fos. Thus, anesthesiologists should administer dilute MB intravenously through peripheral venous catheters. Higher concentrations of MB (1%) should be administered through a central venous catheter to minimize the risk of cutaneous toxicity.
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Modelos Animales de Enfermedad , Hiperalgesia , Inflamación , Azul de Metileno , Ratas Sprague-Dawley , Piel , Animales , Masculino , Azul de Metileno/farmacología , Azul de Metileno/administración & dosificación , Hiperalgesia/patología , Hiperalgesia/inducido químicamente , Inflamación/patología , Inflamación/inducido químicamente , Piel/efectos de los fármacos , Piel/patología , Relación Dosis-Respuesta a Droga , Calor , Ratas , Interleucina-1beta/metabolismo , Interleucina-1beta/genéticaRESUMEN
Chronic pain is associated with alterations in fundamental cellular processes. Here, we investigate whether Beclin 1, a protein essential for initiating the cellular process of autophagy, is involved in pain processing and is targetable for pain relief. We find that monoallelic deletion of Becn1 increases inflammation-induced mechanical hypersensitivity in male mice. However, in females, loss of Becn1 does not affect inflammation-induced mechanical hypersensitivity. In males, intrathecal delivery of a Beclin 1 activator, tat-beclin 1, reverses inflammation- and nerve injury-induced mechanical hypersensitivity and prevents mechanical hypersensitivity induced by brain-derived neurotrophic factor (BDNF), a mediator of inflammatory and neuropathic pain. Pain signaling pathways converge on the enhancement of N-methyl-D-aspartate receptors (NMDARs) in spinal dorsal horn neurons. The loss of Becn1 upregulates synaptic NMDAR-mediated currents in dorsal horn neurons from males but not females. We conclude that inhibition of Beclin 1 in the dorsal horn is critical in mediating inflammatory and neuropathic pain signaling pathways in males.
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Autofagia , Beclina-1 , Animales , Beclina-1/metabolismo , Masculino , Femenino , Ratones , Hiperalgesia/metabolismo , Hiperalgesia/patología , Receptores de N-Metil-D-Aspartato/metabolismo , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Neuralgia/metabolismo , Neuralgia/patología , Ratones Endogámicos C57BL , Inflamación/metabolismo , Inflamación/patología , Transducción de Señal , Células del Asta Posterior/metabolismo , Células del Asta Posterior/patologíaRESUMEN
Satellite glial cells (SGCs) of dorsal root ganglia (DRGs) are activated in a variety of chronic pain conditions; however, their mediation roles in pain remain elusive. Here, we take advantage of proteolipid protein (PLP)/creERT-driven recombination in the periphery mainly occurring in SGCs of DRGs to assess the role of SGCs in the regulation of chronic mechanical hypersensitivity and pain-like responses in two organs, the distal colon and hindpaw, to test generality. We show that PLP/creERT-driven hM3Dq activation increases, and PLP/creERT-driven TrkB.T1 deletion attenuates, colon and hindpaw chronic mechanical hypersensitivity, positively associating with calcitonin gene-related peptide (CGRP) expression in DRGs and phospho-cAMP response element-binding protein (CREB) expression in the dorsal horn of the spinal cord. Activation of Plp1+ DRG cells also increases the number of small DRG neurons expressing Piezo2 and acquiring mechanosensitivity and leads to peripheral organ neurogenic inflammation. These findings unravel a role and mechanism of Plp1+ cells, mainly SGCs, in the facilitation of chronic mechanical pain and suggest therapeutic targets for pain mitigation.
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Dolor Crónico , Ganglios Espinales , Canales Iónicos , Neuronas , Regulación hacia Arriba , Animales , Ganglios Espinales/metabolismo , Dolor Crónico/metabolismo , Dolor Crónico/patología , Dolor Crónico/genética , Neuronas/metabolismo , Ratones , Canales Iónicos/metabolismo , Canales Iónicos/genética , Colon/metabolismo , Colon/patología , Masculino , Hiperalgesia/metabolismo , Hiperalgesia/patología , Proteína Proteolipídica de la Mielina/metabolismo , Proteína Proteolipídica de la Mielina/genética , Neuroglía/metabolismoRESUMEN
BACKGROUND: Tactile and mechanical pain are crucial to our interaction with the environment, yet the underpinning molecular mechanism is still elusive. Endophilin A2 (EndoA2) is an evolutionarily conserved protein that is documented in the endocytosis pathway. However, the role of EndoA2 in the regulation of mechanical sensitivity and its underlying mechanisms are currently unclear. METHODS: Male and female C57BL/6 mice (8-12 weeks) and male cynomolgus monkeys (7-10 years old) were used in our experiments. Nerve injury-, inflammatory-, and chemotherapy-induced pathological pain models were established for this study. Behavioral tests of touch, mechanical pain, heat pain, and cold pain were performed in mice and nonhuman primates. Western blotting, immunostaining, co-immunoprecipitation, proximity ligation and patch-clamp recordings were performed to gain insight into the mechanisms. RESULTS: The results showed that EndoA2 was primarily distributed in neurofilament-200-positive (NF200+) medium-to-large diameter dorsal root ganglion (DRG) neurons of mice and humans. Loss of EndoA2 in mouse NF200+ DRG neurons selectively impaired the tactile and mechanical allodynia. Furthermore, EndoA2 interacted with the mechanically sensitive ion channel Piezo2 and promoted the membrane trafficking of Piezo2 in DRG neurons. Moreover, as an adaptor protein, EndoA2 also bound to kinesin family member 5B (KIF5B), which was involved in the EndoA2-mediated membrane trafficking process of Piezo2. Loss of EndoA2 in mouse DRG neurons damaged Piezo2-mediated rapidly adapting mechanically activated currents, and re-expression of EndoA2 rescued the MA currents. In addition, interference with EndoA2 also suppressed touch sensitivity and mechanical hypersensitivity in nonhuman primates. CONCLUSIONS: Our data reveal that the KIF5B/EndoA2/Piezo2 complex is essential for Piezo2 trafficking and for sustaining transmission of touch and mechanical hypersensitivity signals. EndoA2 regulates touch and mechanical allodynia via kinesin-mediated Piezo2 trafficking in sensory neurons. Our findings identify a potential new target for the treatment of mechanical pain.
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Aciltransferasas , Hiperalgesia , Canales Iónicos , Tacto , Animales , Femenino , Masculino , Ratones , Hiperalgesia/patología , Canales Iónicos/metabolismo , Cinesinas/metabolismo , Mecanotransducción Celular/fisiología , Ratones Endogámicos C57BL , Dolor , Primates , Tacto/fisiología , Aciltransferasas/metabolismoRESUMEN
BACKGROUND: Pannexin1 (Panx1) is a membrane channel expressed in different cells of the nervous system and is involved in several pathological conditions, including pain and inflammation. At the central nervous system, the role of Panx1 is already well-established. However, in the periphery, there is a lack of information regarding the participation of Panx1 in neuronal sensitization. The dorsal root ganglion (DRG) is a critical structure for pain processing and modulation. For this reason, understanding the molecular mechanism in the DRG associated with neuronal hypersensitivity has become highly relevant to discovering new possibilities for pain treatment. Here, we aimed to investigate the role of Panx1 in acute nociception and peripheral inflammatory and neuropathic pain by using two different approaches. METHODS: Rats were treated with a selective Panx1 blocker peptide (10Panx) into L5-DRG, followed by ipsilateral intraplantar injection of carrageenan, formalin, or capsaicin. DRG neuronal cells were pre-treated with 10Panx and stimulated by capsaicin to evaluate calcium influx. Panx1 knockout mice (Panx1-KO) received carrageenan or capsaicin into the paw and paclitaxel intraperitoneally. The von Frey test was performed to measure the mechanical threshold of rats' and mice's paws before and after each treatment. RESULTS: Pharmacological blockade of Panx1 in the DRG of rats resulted in a dose-dependent decrease of mechanical allodynia triggered by carrageenan, and nociception decreased in the second phase of formalin. Nociceptive behavior response induced by capsaicin was significantly lower in rats treated with Panx1 blockade into DRG. Neuronal cells with Panx1 blockage showed lower intracellular calcium response than untreated cells after capsaicin administration. Accordingly, Panx1-KO mice showed a robust reduction in mechanical allodynia after carrageenan and a lower nociceptive response to capsaicin. A single dose of paclitaxel promoted acute mechanical pain in wildtype (WT) but not in Panx1-KO mice. Four doses of chemotherapy promoted chronic mechanical allodynia in both genotypes, although Panx1-KO mice had significant ablation in the first eight days. CONCLUSION: Our findings suggest that Panx1 is critical for developing peripheral inflammatory pain and acute nociception involving transient receptor potential vanilloid subtype 1 (TRPV1) but is not essential for neuropathic pain chronicity.
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Hiperalgesia , Neuralgia , Ratas , Ratones , Animales , Hiperalgesia/inducido químicamente , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/patología , Capsaicina/farmacología , Capsaicina/uso terapéutico , Paclitaxel/efectos adversos , Carragenina/efectos adversos , Calcio , Neuralgia/inducido químicamente , Neuralgia/tratamiento farmacológico , Formaldehído/efectos adversos , Ganglios Espinales , Proteínas del Tejido Nervioso , Conexinas/genética , Conexinas/uso terapéuticoRESUMEN
During tendinopathy, prolonged inflammation results in fibrosis and the adherence of tendons to the adjacent tissues, causing discomfort and movement disorders. As a natural compound, noscapine has several anti-inflammatory and anti-fibrotic properties. Therefore, we aimed to investigate the effects of noscapine against a rat model of tendinopathy. We created a surgical rat model of Achilles tendon damage to emulate tendinopathy. Briefly, an incision was made on the Achilles tendon, and it was then sutured using an absorbable surgical thread. Immediately, the injured area was topically treated with the vehicle, noscapine (0.2, 0.6, and 1.8 mg/kg), or dexamethasone (0.1 mg/kg) as a positive control. During the 19-day follow-up period, animals were assessed for weight, behavior, pain, and motor coordination testing. On day 20th, the rats were sacrificed, and the tendon tissue was isolated for macroscopic scoring, microscopic (H&E, Masson's trichrome, Ki67, p53) analyses, and cytokine secretion levels. The levels of macroscopic parameters, including thermal hyperalgesia, mechanical and cold allodynia, deterioration of motor coordination, tendon adhesion score, and microscopic indices, namely histological adhesion, vascular prominence and angiogenesis, and Ki67 and p53 levels, as well as fibrotic and inflammatory biomarkers (IL-6, TNF-α, TGF-ß, VEGF) were significantly increased in the vehicle group compared to the sham group (P < 0.05-0.001 for all cases). In contrast, the administration of noscapine (0.2, 0.6, and 1.8 mg/kg) attenuated the pain, fibrosis, and inflammatory indices in a dose-dependent manner compared to the vehicle group (P < 0.05-0.001). Histological research indicated that noscapine 0.6 and 1.8 mg/kg had the most remarkable healing effects. Interestingly, two higher doses of noscapine had impacts similar to those of the positive control group in both clinical and paraclinical assessments. Taken together, our findings suggested that noscapine could be a promising medicine for treating tendinopathies.
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Tendón Calcáneo , Noscapina , Tendinopatía , Ratas , Animales , Tendinopatía/tratamiento farmacológico , Tendón Calcáneo/patología , Antígeno Ki-67 , Proteína p53 Supresora de Tumor , Antiinflamatorios/uso terapéutico , Dolor/patología , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/patología , FibrosisRESUMEN
BACKGROUND: Complex regional pain syndrome (CRPS) develops after injury and is characterized by disproportionate pain, oedema, and functional loss. CRPS has clinical signs of neuropathy as well as neurogenic inflammation. Here, we asked whether skin biopsies could be used to differentiate the contribution of these two systems to ultimately guide therapy. To this end, the cutaneous sensory system including nerve fibres and the recently described nociceptive Schwann cells as well as the cutaneous immune system were analysed. METHODS: We systematically deep-phenotyped CRPS patients and immunolabelled glabrous skin biopsies from the affected ipsilateral and non-affected contralateral finger of 19 acute (< 12 months) and 6 chronic (> 12 months after trauma) CRPS patients as well as 25 sex- and age-matched healthy controls (HC). Murine foot pads harvested one week after sham or chronic constriction injury were immunolabelled to assess intraepidermal Schwann cells. RESULTS: Intraepidermal Schwann cells were detected in human skin of the finger-but their density was much lower compared to mice. Acute and chronic CRPS patients suffered from moderate to severe CRPS symptoms and corresponding pain. Most patients had CRPS type I in the warm category. Their cutaneous neuroglial complex was completely unaffected despite sensory plus signs, e.g. allodynia and hyperalgesia. Cutaneous innate sentinel immune cells, e.g. mast cells and Langerhans cells, infiltrated or proliferated ipsilaterally independently of each other-but only in acute CRPS. No additional adaptive immune cells, e.g. T cells and plasma cells, infiltrated the skin. CONCLUSIONS: Diagnostic skin punch biopsies could be used to diagnose individual pathophysiology in a very heterogenous disease like acute CRPS to guide tailored treatment in the future. Since numbers of inflammatory cells and pain did not necessarily correlate, more in-depth analysis of individual patients is necessary.
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Síndromes de Dolor Regional Complejo , Distrofia Simpática Refleja , Humanos , Animales , Ratones , Síndromes de Dolor Regional Complejo/patología , Piel/patología , Hiperalgesia/etiología , Hiperalgesia/patología , Dolor/patología , Células de Schwann/patologíaRESUMEN
Oxaliplatin, a platinum-based anticancer drug, is associated with peripheral neuropathy (oxaliplatin-induced peripheral neuropathy, OIPN), which can lead to worsening of quality of life and treatment interruption. The endothelial glycocalyx, a fragile carbohydrate-rich layer covering the luminal surface of endothelial cells, acts as an endothelial gatekeeper and has been suggested to protect nerves, astrocytes, and other cells from toxins and substances released from the capillary vessels. Mechanisms underlying OIPN and the role of the glycocalyx remain unclear. This study aimed to define changes in the three-dimensional ultrastructure of capillary endothelial glycocalyx near nerve fibers in the hind paws of mice with OIPN. The mouse model of OPIN revealed disruption of the endothelial glycocalyx in the peripheral nerve compartment, accompanied by vascular permeability, edema, and damage to the peripheral nerves. To investigate the potential treatment interventions, nafamostat mesilate, a glycocalyx protective agent was used in tumor-bearing male mice. Nafamostat mesilate suppressed mechanical allodynia associated with neuropathy. It also prevented intra-epidermal nerve fiber loss and improved vascular permeability in the peripheral paws. The disruption of endothelial glycocalyx in the capillaries that lie within peripheral nerve bundles is a novel finding in OPIN. Furthermore, these findings point toward the potential of a new treatment strategy targeting endothelial glycocalyx to prevent vascular injury as an effective treatment of neuropathy as well as of many other diseases. PERSPECTIVE: OIPN damages the endothelial glycocalyx in the peripheral capillaries, increasing vascular permeability. In order to prevent OIPN, this work offers a novel therapy approach that targets endothelial glycocalyx.
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Antineoplásicos , Glicocálix , Oxaliplatino , Animales , Glicocálix/efectos de los fármacos , Glicocálix/metabolismo , Glicocálix/patología , Oxaliplatino/toxicidad , Ratones , Masculino , Antineoplásicos/farmacología , Enfermedades del Sistema Nervioso Periférico/inducido químicamente , Enfermedades del Sistema Nervioso Periférico/patología , Capilares/efectos de los fármacos , Capilares/patología , Modelos Animales de Enfermedad , Hiperalgesia/inducido químicamente , Hiperalgesia/patología , Permeabilidad Capilar/efectos de los fármacos , Permeabilidad Capilar/fisiología , Ratones Endogámicos C57BLRESUMEN
Cold injury or frostbite is a common medical condition that causes serious clinical complications including sensory abnormalities and chronic pain ultimately affecting overall well-being. Opioids are the first-choice drug for the treatment of frostbite-induced chronic pain; however, their notable side effects, including sedation, motor incoordination, respiratory depression, and drug addiction, present substantial obstacle to their clinical utility. To address this challenge, we have exploited peripheral mu-opioid receptors as potential target for the treatment of frostbite-induced chronic pain. In this study, we investigated the effect of dermorphin [D-Arg2, Lys4] (1-4) amide (DALDA), a peripheral mu-opioid receptor agonist, on frostbite injury and hypersensitivity induced by deep freeze magnet exposure in rats. Animals with frostbite injury displayed significant hypersensitivity to mechanical, thermal, and cold stimuli which was significant ameliorated on treatment with different doses of DALDA (1, 3, and 10 mg/kg) and ibuprofen (100 mg/kg). Further, molecular biology investigations unveiled heightened oxido-nitrosative stress, coupled with a notable upregulation in the expression of TRP channels (TRPA1, TRPV1, and TRPM8), glial cell activation, and neuroinflammation (TNF-α, IL-1ß) in the sciatic nerve, dorsal root ganglion (DRG), and spinal cord of frostbite-injured rats. Treatment with DALDA leads to substantial reduction in TRP channels, microglial activation, and suppression of the inflammatory cascade in the ipsilateral L4-L5 DRG and spinal cord of rats. Overall, findings from the present study suggest that activation of peripheral mu-opioid receptors mitigates chronic pain in rats by modulating the expression of TRP channels and suppressing glial cell activation and neuroinflammation.
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Congelación de Extremidades , Microglía , Enfermedades Neuroinflamatorias , Péptidos Opioides , Ratas Sprague-Dawley , Animales , Masculino , Ratas , Congelación de Extremidades/tratamiento farmacológico , Congelación de Extremidades/complicaciones , Congelación de Extremidades/patología , Hiperalgesia/tratamiento farmacológico , Hiperalgesia/patología , Hiperalgesia/metabolismo , Microglía/efectos de los fármacos , Microglía/metabolismo , Microglía/patología , Enfermedades Neuroinflamatorias/tratamiento farmacológico , Enfermedades Neuroinflamatorias/metabolismo , Péptidos Opioides/metabolismo , Péptidos Opioides/farmacología , Péptidos Opioides/uso terapéutico , Dolor/tratamiento farmacológico , Dolor/metabolismo , Dolor/patología , Receptores Opioides mu/metabolismo , Receptores Opioides mu/agonistas , Canales de Potencial de Receptor Transitorio/metabolismoRESUMEN
Pathological pain imposes a huge burden on the economy and the lives of patients. At present, drugs used for the treatment of pathological pain have only modest efficacy and are also plagued by adverse effects and risk for misuse and abuse. Therefore, understanding the mechanisms of pathological pain is essential for the development of novel analgesics. Several lines of evidence indicate that interleukin-17 (IL-17) is upregulated in rodent models of pathological pain in the periphery and central nervous system. Besides, the administration of IL-17 antibody alleviated pathological pain. Moreover, IL-17 administration led to mechanical allodynia which was alleviated by the IL-17 antibody. In this review, we summarized and discussed the therapeutic potential of targeting IL-17 for pathological pain. The upregulation of IL-17 promoted the development of pathological pain by promoting neuroinflammation, enhancing the excitability of dorsal root ganglion neurons, and promoting the communication of glial cells and neurons in the spinal cord. In general, the existing research shows that IL-17 is an attractive therapeutic target for pathologic pain, but the underlying mechanisms still need to be investigated.
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Interleucina-17 , Dolor , Ratas , Animales , Humanos , Ratas Sprague-Dawley , Dolor/tratamiento farmacológico , Dolor/patología , Hiperalgesia/patología , Neuroglía/patologíaRESUMEN
Previous studies have shown that the C-C motif chemokine ligand 2 (CCL2) is widely expressed in the nervous system and involved in regulating the development of chronic pain and related anxiety-like behaviors, but its precise mechanism is still unclear. This paper provides an in-depth examination of the involvement of CCL2-CCR2 signaling in the anterior cingulate cortex (ACC) in intraplantar injection of complete Freund's adjuvant (CFA) leading to inflammatory pain and its concomitant anxiety-like behaviors by modulation of glutamatergic N-methyl-D-aspartate receptor (NMDAR). Our findings suggest that local bilateral injection of CCR2 antagonist in the ACC inhibits CFA-induced inflammatory pain and anxiety-like behavior. Meanwhile, the expression of CCR2 and CCL2 was significantly increased in ACC after 14 days of intraplantar injection of CFA, and CCR2 was mainly expressed in excitatory neurons. Whole-cell patch-clamp recordings showed that the CCR2 inhibitor RS504393 reduced the frequency of miniature excitatory postsynaptic currents (mEPSC) in ACC, and CCL2 was involved in the regulation of NMDAR-induced current in ACC neurons in the pathological state. In addition, local injection of the NR2B inhibitor of NMDAR subunits, Ro 25-6981, attenuated the effects of CCL2-induced hyperalgesia and anxiety-like behavior in the ACC. In summary, CCL2 acts on CCR2 in ACC excitatory neurons and participates in the regulation of CFA-induced pain and related anxiety-like behaviors through upregulation of NR2B. CCR2 in the ACC neuron may be a potential target for the treatment of chronic inflammatory pain and pain-related anxiety.
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Ansiedad , Quimiocina CCL2 , Giro del Cíngulo , Inflamación , N-Metilaspartato , Dolor , Receptores CCR2 , Receptores de N-Metil-D-Aspartato , Transducción de Señal , Animales , Giro del Cíngulo/metabolismo , Giro del Cíngulo/efectos de los fármacos , Inflamación/patología , Inflamación/metabolismo , Masculino , Ansiedad/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Quimiocina CCL2/metabolismo , Receptores CCR2/metabolismo , Receptores CCR2/antagonistas & inhibidores , Dolor/metabolismo , Dolor/patología , Transducción de Señal/efectos de los fármacos , Potenciales Postsinápticos Excitadores/efectos de los fármacos , Adyuvante de Freund/toxicidad , Ratones Endogámicos C57BL , Neuronas/metabolismo , Neuronas/efectos de los fármacos , Conducta Animal , Hiperalgesia/metabolismo , Hiperalgesia/patología , Compuestos de Espiro , BenzoxazinasRESUMEN
Immune cells play a critical role in promoting neuroinflammation and the development of neuropathic pain. However, some subsets of immune cells are essential for pain resolution. Among them are regulatory T cells (Tregs), a specialised subpopulation of T cells that limit excessive immune responses and preserve immune homeostasis. In this study, we utilised intrathecal adoptive transfer of activated Tregs in male and female mice after peripheral nerve injury to investigate Treg migration and whether Treg-mediated suppression of pain behaviours is associated with changes in peripheral immune cell populations in lymphoid and meningeal tissues and spinal microglial and astrocyte reactivity and phenotypes. Treatment with Tregs suppressed mechanical pain hypersensitivity and improved changes in exploratory behaviours after chronic constriction injury (CCI) of the sciatic nerve in both male and female mice. The injected Treg cells were detected in the choroid plexus and the pia mater and in peripheral lymphoid organs in both male and female recipient mice. Nonetheless, Treg treatment resulted in differential changes in meningeal and lymph node immune cell profiles in male and female mice. Moreover, in male mice, adoptive transfer of Tregs ameliorated the CCI-induced increase in microglia reactivity and inflammatory phenotypic shift, increasing M2-like phenotypic markers and attenuating astrocyte reactivity and neurotoxic astrocytes. Contrastingly, in CCI female mice, Treg injection increased astrocyte reactivity and neuroprotective astrocytes. These findings show that the adoptive transfer of Tregs modulates meningeal and peripheral immunity, as well as spinal glial populations, and alleviates neuropathic pain, potentially through different mechanisms in males and females.
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Neuralgia , Linfocitos T Reguladores , Ratones , Masculino , Femenino , Animales , Hiperalgesia/patología , Neuralgia/terapia , Neuralgia/patología , Médula Espinal/patología , MeningesRESUMEN
This study aimed to examine the effects of luteolin (LUT) on chronic neuropathic pain (NP)-induced mood disorders (i.e., anxiety and depression) by regulating oxidative stress, neurotrophic factors (NFs), and neuroinflammation. Chronic constrictive injury (CCI) was used to induce NP in the animals. Animals in the treatment groups received LUT in three doses of 10, 25, and 50 mg/kg for 21 days. The severity of pain and mood disorders were examined. Finally, animals were sacrificed, and their brain tissue was used for molecular and histopathological studies. CCI led to cold allodynia and thermal hyperalgesia. Mood alterations were proven in the CCI group, according to the behavioral tests. Levels of glial cell-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), B-cell lymphoma-2 (Bcl2), superoxide dismutase (SOD), catalase (CAT), and nuclear factor erythroid-2-related factor 2 (Nrf2) were reduced in the hippocampus (HPC) and prefrontal cortex (PFC). Furthermore, the levels of MDA, Bcl-2-associated X protein (Bax), and inflammatory markers, including nuclear factor kappa B (NF-κB), NLR family pyrin domain containing 3 (NLRP3), interleukin-1ß (IL-1ß), IL-18, IL-6, and tumor necrosis factor-α (TNF-α) significantly increased in the HPC and PFC following CCI induction. LUT treatment reversed the behavioral alterations via regulation of oxidative stress, neurotrophines, and inflammatory mediators in the HPC and PFC. Findings confirmed the potency of LUT in the improvement of chronic pain-induced anxiety- and depressive-like symptoms, probably through antioxidant, anti-inflammatory, and neuroprotective properties in the HPC and PFC.