RESUMO
Sexual dimorphism among mammals includes variations in the pain threshold. These differences are influenced by hormonal fluctuations in females during the estrous and menstrual cycles of rodents and humans, respectively. These physiological conditions display various phases, including proestrus and diestrus in rodents and follicular and luteal phases in humans, distinctly characterized by varying estrogen levels. In this study, we evaluated the capsaicin responses in male and female mice at different estrous cycle phases, using two murine acute pain models. Our findings indicate that the capsaicin-induced pain threshold was lower in the proestrus phase than in the other three phases in both pain assays. We also found that male mice exhibited a higher pain threshold than females in the proestrus phase, although it was similar to females in the other cycle phases. We also assessed the mRNA and protein levels of TRPV1 in the dorsal root and trigeminal ganglia of mice. Our results showed higher TRPV1 protein levels during proestrus compared to diestrus and male mice. Unexpectedly, we observed that the diestrus phase was associated with higher TRPV1 mRNA levels than those in both proestrus and male mice. These results underscore the hormonal influence on TRPV1 expression regulation and highlight the role of sex steroids in capsaicin-induced pain.
Assuntos
Capsaicina , Dor , Canais de Cátion TRPV , Animais , Canais de Cátion TRPV/metabolismo , Canais de Cátion TRPV/genética , Capsaicina/farmacologia , Masculino , Feminino , Camundongos , Dor/metabolismo , Dor/genética , Hormônios Esteroides Gonadais/metabolismo , Ciclo Estral/efeitos dos fármacos , Limiar da Dor/efeitos dos fármacos , Gânglios Espinais/metabolismo , Gânglios Espinais/efeitos dos fármacos , Gânglio Trigeminal/metabolismo , Gânglio Trigeminal/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Caracteres Sexuais , RNA Mensageiro/metabolismo , RNA Mensageiro/genéticaRESUMO
Noradrenaline (NA) and serotonin (5-HT) induce nociception and antinociception. This antagonistic effect can be explained by the dose and type of activated receptors. We investigated the existence of synergism between the noradrenergic and serotonergic systems during peripheral antinociception. The paw pressure test was performed in mice that had increased sensitivity by intraplantar injection of prostaglandin E2 (PGE2). Noradrenaline (80 ng) administered intraplantarly induced an antinociceptive effect, that was reversed by the administration of selective antagonists of serotoninergic receptors 5-HT1B isamoltan, 5-HT1D BRL15572, 5-HT2A ketanserin, 5-HT3 ondansetron, but not by selective receptor antagonist 5-HT7 SB-269970. The administration of escitalopram, a serotonin reuptake inhibitor, potentiated the antinociceptive effect at a submaximal dose of NA. These results, indicate the existence of synergism between the noradrenergic and serotonergic systems in peripheral antinociception in mice.
Assuntos
Norepinefrina , Receptores de Serotonina , Antagonistas da Serotonina , Serotonina , Animais , Camundongos , Norepinefrina/metabolismo , Serotonina/metabolismo , Antagonistas da Serotonina/farmacologia , Masculino , Receptores de Serotonina/metabolismo , Dinoprostona/metabolismo , Citalopram/farmacologia , Nociceptividade/efeitos dos fármacos , Analgésicos/farmacologia , Ondansetron/farmacologia , Ketanserina/farmacologia , Dor/tratamento farmacológico , Dor/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/farmacologiaRESUMO
BACKGROUND AND PURPOSE: Fibromyalgia is a complex clinical disorder with an unknown aetiology, characterized by generalized pain and co-morbid symptoms such as anxiety and depression. An imbalance of oxidants and antioxidants is proposed to play a pivotal role in the pathogenesis of fibromyalgia symptoms. However, the precise mechanisms by which oxidative stress contributes to fibromyalgia-induced pain remain unclear. The transient receptor potential ankyrin 1 (TRPA1) channel, known as both a pain sensor and an oxidative stress sensor, has been implicated in various painful conditions. EXPERIMENTAL APPROACH: The feed-forward mechanism that implicates reactive oxygen species (ROS) driven by TRPA1 was investigated in a reserpine-induced fibromyalgia model in C57BL/6J mice employing pharmacological interventions and genetic approaches. KEY RESULTS: Reserpine-treated mice developed pain-like behaviours (mechanical/cold hypersensitivity) and early anxiety-depressive-like disorders, accompanied by increased levels of oxidative stress markers in the sciatic nerve tissues. These effects were not observed upon pharmacological blockade or global genetic deletion of the TRPA1 channel and macrophage depletion. Furthermore, we demonstrated that selective silencing of TRPA1 in Schwann cells reduced reserpine-induced neuroinflammation (NADPH oxidase 1-dependent ROS generation and macrophage increase in the sciatic nerve) and attenuated fibromyalgia-like behaviours. CONCLUSION AND IMPLICATIONS: Activated Schwann cells expressing TRPA1 promote an intracellular pathway culminating in the release of ROS and recruitment of macrophages in the mouse sciatic nerve. These cellular and molecular events sustain mechanical and cold hypersensitivity in the reserpine-evoked fibromyalgia model. Targeting TRPA1 channels on Schwann cells could offer a novel therapeutic approach for managing fibromyalgia-related behaviours.
Assuntos
Fibromialgia , Camundongos Endogâmicos C57BL , Estresse Oxidativo , Espécies Reativas de Oxigênio , Reserpina , Células de Schwann , Canal de Cátion TRPA1 , Animais , Reserpina/farmacologia , Fibromialgia/induzido quimicamente , Fibromialgia/metabolismo , Canal de Cátion TRPA1/metabolismo , Canal de Cátion TRPA1/antagonistas & inibidores , Canal de Cátion TRPA1/genética , Estresse Oxidativo/efeitos dos fármacos , Células de Schwann/metabolismo , Células de Schwann/efeitos dos fármacos , Masculino , Camundongos , Espécies Reativas de Oxigênio/metabolismo , Dor/metabolismo , Dor/induzido quimicamente , Nervo Isquiático/metabolismo , Modelos Animais de Doenças , Camundongos Knockout , Canais de Potencial de Receptor Transitório/metabolismo , Canais de Potencial de Receptor Transitório/antagonistas & inibidores , Canais de Potencial de Receptor Transitório/genéticaRESUMO
OBJECTIVE AND DESIGN: Our aim was to determine an age-dependent role of Nav1.8 and ASIC3 in dorsal root ganglion (DRG) neurons in a rat pre-clinical model of long-term inflammatory pain. METHODS: We compared 6 and 24 months-old female Wistar rats after cutaneous inflammation. We used behavioral pain assessments over time, qPCR, quantitative immunohistochemistry, selective pharmacological manipulation, ELISA and in vitro treatment with cytokines. RESULTS: Older rats exhibited delayed recovery from mechanical allodynia and earlier onset of spontaneous pain than younger rats after inflammation. Moreover, the expression patterns of Nav1.8 and ASIC3 were time and age-dependent and ASIC3 levels remained elevated only in aged rats. In vivo, selective blockade of Nav1.8 with A803467 or of ASIC3 with APETx2 alleviated mechanical and cold allodynia and also spontaneous pain in both age groups with slightly different potency. Furthermore, in vitro IL-1ß up-regulated Nav1.8 expression in DRG neurons cultured from young but not old rats. We also found that while TNF-α up-regulated ASIC3 expression in both age groups, IL-6 and IL-1ß had this effect only on young and aged neurons, respectively. CONCLUSION: Inflammation-associated mechanical allodynia and spontaneous pain in the elderly can be more effectively treated by inhibiting ASIC3 than Nav1.8.
Assuntos
Canais Iônicos Sensíveis a Ácido , Hiperalgesia , Canal de Sódio Disparado por Voltagem NAV1.8 , Dor , Animais , Feminino , Ratos , Canais Iônicos Sensíveis a Ácido/genética , Canais Iônicos Sensíveis a Ácido/metabolismo , Canais Iônicos Sensíveis a Ácido/farmacologia , Analgésicos/uso terapêutico , Gânglios Espinais , Hiperalgesia/tratamento farmacológico , Hiperalgesia/metabolismo , Inflamação/metabolismo , Dor/tratamento farmacológico , Dor/metabolismo , Ratos Sprague-Dawley , Ratos Wistar , Células Receptoras Sensoriais/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.8/metabolismoRESUMO
In the 1990s, the identification of a non-selective ion channel, especially responsive to capsaicin, revolutionized the studies of somatosensation and pain that were to follow. The TRPV1 channel is expressed mainly in neuronal cells, more specifically, in sensory neurons responsible for the perception of noxious stimuli. However, its presence has also been detected in other non-neuronal cells, such as immune cells, ß- pancreatic cells, muscle cells and adipocytes. Activation of the channel occurs in response to a wide range of stimuli, such as noxious heat, low pH, gasses, toxins, endocannabinoids, lipid-derived endovanilloid, and chemical agents, such as capsaicin and resiniferatoxin. This activation results in an influx of cations through the channel pore, especially calcium. Intracellular calcium triggers different responses in sensory neurons. Dephosphorylation of the TRPV1 channel leads to its desensitization, which disrupts its function, while its phosphorylation increases the channel's sensitization and contributes to the channel's rehabilitation after desensitization. Kinases, phosphoinositides, and calmodulin are the main signaling pathways responsible for the channel's regulation. Thus, in this review we provide an overview of TRPV1 discovery, its tissue expression as well as on the mechanisms by which TRPV1 activation (directly or indirectly) induces pain in different disease models.
Assuntos
Neuroimunomodulação , Dor , Canais de Cátion TRPV , Humanos , Cálcio/metabolismo , Capsaicina/farmacologia , Dor/metabolismo , Canais de Cátion TRPV/metabolismo , AnimaisRESUMO
Pain is characterized by the unpleasant sensory and emotional sensation associated with actual or potential tissue damage, whereas nociception refers to the mechanism by which noxious stimuli are transmitted from the periphery to the CNS. The main drugs used to treat pain are nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics, which have side effects that limit their use. Therefore, in the search for new drugs with potential antinociceptive effects, essential oils have been studied, whose constituents (monoterpenes) are emerging as a new therapeutic possibility. Among them, linalool and its metabolites stand out. The present study aims to investigate the antinociceptive potential of linalool and its metabolites through a screening using an in silico approach. Molecular docking was used to evaluate possible interactions with important targets involved in antinociceptive activity, such as α2-adrenergic, GABAergic, muscarinic, opioid, adenosinergic, transient potential, and glutamatergic receptors. The compounds in the investigated series obtained negative energies for all enzymes, representing satisfactory interactions with the targets and highlighting the multi-target potential of the L4 metabolite. Linalool and its metabolites have a high likelihood of modulatory activity against the targets involved in nociception and are potential candidates for future drugs.
Assuntos
Monoterpenos Acíclicos , Analgésicos , Simulação de Acoplamento Molecular , Monoterpenos Acíclicos/química , Monoterpenos Acíclicos/farmacologia , Monoterpenos Acíclicos/metabolismo , Analgésicos/química , Analgésicos/farmacologia , Analgésicos/metabolismo , Humanos , Simulação por Computador , Animais , Dor/tratamento farmacológico , Dor/metabolismo , Monoterpenos/química , Monoterpenos/farmacologiaRESUMO
BACKGROUND: The aim of this in vivo study was to quantitatively evaluate pain after rapid maxillary expansion (RME) in young rats by analyzing the activation of nociception-related structures, that is, the caudalis, interpolaris, and oralis subnuclei, according to the Fos expression. METHODS: A total of 65 Wistar rats were assigned to three groups: control group (n = 15) with no treatment, positive control group (n = 25), and experimental group (n = 25) with RME. The experimental animals were euthanized at 6, 12, 24, 48, and 72 hours after RME, and the brain was later carefully collected. Coronal sections through the spinal trigeminal caudalis, spinal trigeminal interpolaris, and spinal trigeminal oralis were cut (thickness of 40 µm) on a cryostat and processed for Fos immunohistochemistry. Images from the sections were captured under light microscopy, and ImageJ software was used to count Fos-like immunoreactive neurons. The Analysis of variance (ANOVA) and Tukey test were used for statistical analysis, and the significance level was set at 5%. RESULTS: RME induced incisor distalization and opening of the midpalatal suture, as well as neuronal activation of the spinal trigeminal nucleus. The experimental group demonstrated significantly more Fos-positive neurons in subnuclei caudalis and subnuclei interpolaris 6 hours after the maxillary expansion. The Fos immunoreactivity significantly decreased at 12 hours and increased again at 24 and 48 hours (P < 0.001). CONCLUSIONS: The RME increases the neural activation of brain regions involved in the nociception region, as determined by the Fos expression. The most intense Fos-like immunoreactive expression was detected in the brain 6 hours after the start of the palatal expansion.
Assuntos
Técnica de Expansão Palatina , Núcleo Espinal do Trigêmeo , Ratos , Animais , Ratos Wistar , Núcleo Espinal do Trigêmeo/metabolismo , Encéfalo/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Dor/metabolismoRESUMO
The perception of noxious environmental stimuli by nociceptive sensory neurons is an essential mechanism for the prevention of tissue damage. Etv4 is a transcriptional factor expressed in most nociceptors in dorsal root ganglia (DRG) during the embryonic development. However, its physiological role remains unclear. Here, we show that Etv4 ablation results in defects in the development of the peripheral peptidergic projections in vivo, and in deficits in axonal elongation and growth cone morphology in cultured sensory neurons in response to NGF. From a mechanistic point of view, our findings reveal that NGF regulates Etv4-dependent gene expression of molecules involved in extracellular matrix (ECM) remodeling. Etv4-null mice were less sensitive to noxious heat stimuli and chemical pain, and this behavioral phenotype correlates with a significant reduction in the expression of the pain-transducing ion channel TRPV1 in mutant mice. Together, our data demonstrate that Etv4 is required for the correct innervation and function of peptidergic sensory neurons, regulating a transcriptional program that involves molecules associated with axonal growth and pain transduction.
Assuntos
Fator de Crescimento Neural , Nociceptividade , Proteínas Proto-Oncogênicas c-ets/metabolismo , Animais , Gânglios Espinais/metabolismo , Camundongos , Fator de Crescimento Neural/genética , Nociceptividade/fisiologia , Dor/metabolismo , Células Receptoras Sensoriais/metabolismoRESUMO
Chronic pain is a major health issue, and the search for new analgesics has become increasingly important because of the addictive properties and unwanted side effects of opioids. To explore potentially new drug targets, we investigated mutations in the NTRK1 gene found in individuals with congenital insensitivity to pain with anhidrosis (CIPA). NTRK1 encodes tropomyosin receptor kinase A (TrkA), the receptor for nerve growth factor (NGF) and that contributes to nociception. Molecular modeling and biochemical analysis identified mutations that decreased the interaction between TrkA and one of its substrates and signaling effectors, phospholipase Cγ (PLCγ). We developed a cell-permeable phosphopeptide derived from TrkA (TAT-pQYP) that bound the Src homology domain 2 (SH2) of PLCγ. In HEK-293T cells, TAT-pQYP inhibited the binding of heterologously expressed TrkA to PLCγ and decreased NGF-induced, TrkA-mediated PLCγ activation and signaling. In mice, intraplantar administration of TAT-pQYP decreased mechanical sensitivity in an inflammatory pain model, suggesting that targeting this interaction may be analgesic. The findings demonstrate a strategy to identify new targets for pain relief by analyzing the signaling pathways that are perturbed in CIPA.
Assuntos
Hipo-Hidrose , Mutação , Insensibilidade Congênita à Dor , Fosfolipase C gama , Receptor trkA , Analgésicos/farmacologia , Animais , Canalopatias/genética , Canalopatias/metabolismo , Células HEK293 , Humanos , Hipo-Hidrose/genética , Hipo-Hidrose/metabolismo , Camundongos , Fator de Crescimento Neural/genética , Fator de Crescimento Neural/farmacologia , Dor/genética , Dor/metabolismo , Insensibilidade Congênita à Dor/genética , Insensibilidade Congênita à Dor/metabolismo , Fosfolipase C gama/genética , Fosfolipase C gama/metabolismo , Receptor trkA/genética , Receptor trkA/metabolismoRESUMO
The zebrafish has been considered an ideal model for studies of complex behaviors since its behavioral repertoire is well described. Therefore, this study evaluated the perceived pain through behavioral changes in zebrafish larvae. Here we investigated the Acetic Acid (AA) effects on zebrafish larvae exposed in a short-time period (60 s) and the preventive effect from routinely used compounds, Dimethyl Sulfoxide (DMSO), Ethanol (EtOH), Ibuprofen (IBP), and Paracetamol (PAR). In addition, the effect of P2×7 antagonist, A740003, and pannexin channel 1 (PANX-1) inhibitor Probenecid (PROB) on AA-induced behavioral changes were evaluated. AA impaired the distance covered, acceleration, movement, and latency to the first entry in the center from 5 dpf exposed larvae. At 0.050% AA, PAR prevented alterations from the distance covered, acceleration, and movement. Surprisingly, 0.3% DMSO prevented behavioral changes induced by AA. However, the effects from 0.2% DMSO were not prominent. We used 0.2% DMSO as a PROB diluent. PROB prevented the changes in distance and movement observed at both AA concentrations (0.0025% and 0.05%) tested. Since EtOH had no analgesic properties, we used it as an A740003 vehicle to observe the analgesic effects of this compound. As noted, A740003 did not prevent the behavioral changes in the AA-induced pain model. In contrast, 0.2% DMSO and PROB prevented AA-induced behavioral changes. These data enforce that zebrafish could be used in translational studies since this species has behavioral responses related to pain in the early stages of development and responses to analgesics similar to observed in mammals.