RESUMO
Sensing acidosis is an important somatosensory function in responses to ischemia, inflammation, and metabolic alteration. Accumulating evidence has shown that acidosis is an effective factor for pain induction and that many intractable chronic pain diseases are associated with acidosis signaling. Various receptors have been known to detect extracellular acidosis and all express in the somatosensory neurons, such as acid sensing ion channels (ASIC), transient receptor potential (TRP) channels and proton-sensing G-protein coupled receptors. In addition to sense noxious acidic stimulation, these proton-sensing receptors also play a vital role in pain processing. For example, ASICs and TRPs are involved in not only nociceptive activation but also anti-nociceptive effects as well as some other non-nociceptive pathways. Herein, we review recent progress in probing the roles of proton-sensing receptors in preclinical pain research and their clinical relevance. We also propose a new concept of sngception to address the specific somatosensory function of acid sensation. This review aims to connect these acid-sensing receptors with basic pain research and clinical pain diseases, thus helping with better understanding the acid-related pain pathogenesis and their potential therapeutic roles via the mechanism of acid-mediated antinociception.
Assuntos
Acidose , Dor Crônica , Humanos , Dor Crônica/tratamento farmacológico , Prótons , Canais Iônicos Sensíveis a Ácido/metabolismo , Transdução de Sinais/fisiologia , Acidose/tratamento farmacológico , Acidose/complicaçõesRESUMO
Rheumatoid arthritis (RA), an autoimmune disease, is characterized by chronic joint inflammation and pain. We previously found that the deletion of T-cell death-associated gene 8 (TDAG8) significantly reduces disease severity and pain in RA mice. Whether it is by modulating gut microbiota remains unclear. In this study, 64 intestinal samples of feces, cecal content, and cecal mucus from the complete Freund's adjuvant-induced arthritis mouse models were compared. The α- and ß-diversity indices of the microbiome were significantly lower in RA mice. Cecal mucus showed a higher ratio of Firmicutes to Bacteroidetes in RA than healthy mice, suggesting the ratio could serve as an RA indicator. Four core genera, Eubacterium_Ventriosum, Alloprevotella, Rikenella, and Treponema, were reduced in content in both feces and mucus RA samples, and could serve microbial markers representing RA progression. TDAG8 deficiency decreased the abundance of proinflammation-related Eubacterium_Xylanophilum, Clostridia, Ruminococcus, Paraprevotella, and Rikenellaceae, which reduced local mucosal inflammation to relieve RA disease severity and pain. The pharmacological block of the TDAG8 function by a salicylanilide derivative partly restored the RA microbiome to a healthy composition. These findings provide a further understanding of specific bacteria interactions with host gut mucus in the RA model. The modulation by TDAG8 on particular bacteria can facilitate microbiota-based therapy.
Assuntos
Artrite Reumatoide , Microbioma Gastrointestinal , Microbiota , Animais , Bactérias/genética , Microbioma Gastrointestinal/genética , Inflamação , Camundongos , Dor , SalicilanilidasRESUMO
Neuropathic pain is one type of chronic pain that occurs as a result of a lesion or disease to the somatosensory nervous system. Chronic excessive inflammatory response after nerve injury may contribute to the maintenance of persistent pain. Although the role of inflammatory mediators and cytokines in mediating allodynia and hyperalgesia has been extensively studied, the detailed mechanisms of persistent pain or whether the interactions between neurons, glia and immune cells are essential for maintenance of the chronic state have not been completely elucidated. ASIC3, a voltage-insensitive, proton-gated cation channel, is the most essential pH sensor for pain perception. ASIC3 gene expression is increased in dorsal root ganglion neurons after inflammation and nerve injury and ASIC3 is involved in macrophage maturation. ASIC currents are increased after nerve injury. However, whether prolonged hyperalgesia induced by the nerve injury requires ASIC3 and whether ASIC3 regulates neurons, immune cells or glial cells to modulate neuropathic pain remains unknown. We established a model of chronic constriction injury of the sciatic nerve (CCI) in mice. CCI mice showed long-lasting mechanical allodynia and thermal hyperalgesia. CCI also caused long-term inflammation at the sciatic nerve and primary sensory neuron degeneration as well as increased satellite glial expression and ATF3 expression. ASIC3 deficiency shortened mechanical allodynia and attenuated thermal hyperalgesia. ASIC3 gene deletion shifted ATF3 expression from large to small neurons and altered the M1/M2 macrophage ratio, thereby preventing small neuron degeneration and relieved pain.
Assuntos
Canais Iônicos Sensíveis a Ácido/deficiência , Deleção de Genes , Degeneração Neural/etiologia , Degeneração Neural/metabolismo , Regeneração Nervosa , Neuralgia/etiologia , Neuralgia/metabolismo , Neurônios/metabolismo , Fator 3 Ativador da Transcrição/metabolismo , Animais , Biomarcadores , Modelos Animais de Doenças , Hiperalgesia/etiologia , Hiperalgesia/metabolismo , Imunofenotipagem , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/patologia , Masculino , Camundongos , Neuralgia/diagnóstico , Neuroglia/metabolismo , Neuroglia/patologiaRESUMO
Mind-body interventions (MBIs) have many health benefits, such as reducing stress, modulating blood pressure, and improving sleep and life quality. The long-term practice of Tai chi, an MBI, also increases the number of CD34+ cells, which are surface markers of hematopoietic stem cells, so prolonged Tai chi practice may have antiaging effects. We developed the day easy exercise (DEE), an innovative MBI, that is easy to learn and requires only a small exercise area and a short practice time. The aim of this study was to explore whether DEE, like Tai chi, has antiaging effects after short-term practice. Total 44 individuals (25 to 62 years old) with or without 3-month DEE practice were divided into young- and middle-aged groups (≤30 and >30 years old) and peripheral blood was collected at 0, 1, 2, and 3 months for analysis of CD34+ cells. The number of CD34+ cells in peripheral blood remained unchanged in control young- and middle-aged groups. After DEE, the number of CD34+ cells in peripheral blood was increased over time in both young- and middle-aged groups. For young-aged adults, the cell number was markedly increased by threefold at 3 months after DEE, and for middle-aged adults, the increase was significant from the first month. DEE practice indeed increased the number of CD34+ cells in peripheral blood and the increase was more significant for older people in a shorter time. This is the first study to provide evidence that the DEE may have antiaging effects and could be beneficial for older people.
Assuntos
Antígenos CD34/metabolismo , Exercício Físico/fisiologia , Terapias Mente-Corpo , Adulto , Linfócitos B/citologia , Contagem de Células , Feminino , Humanos , Lipídeos/sangue , Masculino , Pessoa de Meia-Idade , Placebos , Linfócitos T/citologiaRESUMO
BACKGROUND: The autoimmune disease rheumatoid arthritis (RA) affects approximately 1% of the global population. RA is characterized with chronic joint inflammation and often associated with chronic pain. The imbalance of pro-inflammatory and anti-inflammatory macrophages is a feature of RA progression. Glial cells affecting neuronal sensitivity at both peripheral and central levels may also be important for RA progression and associated pain. Genetic variants in the T cell death-associated gene 8 (TDAG8) locus are found to associate with spondyloarthritis. TDAG8 was also found involved in RA disease progression and associated hyperalgesia in the RA mouse model. However, its modulation in RA remains unclear. METHODS: To address this question, we intra-articularly injected complete Freund's adjuvant (CFA) into TDAG8+/+, TDAG8-/- or wild-type mice, followed by pain behavioral tests. Joints and dorsal root ganglia were taken, sectioned, and stained with antibodies to observe the number of immune cells, macrophages, and satellite glial cells (SGCs). For compound treatments, compounds were intraperitoneally or orally administered weekly for 9 consecutive weeks after CFA injection. RESULTS: We demonstrated that TDAG8 deletion slightly reduced RA pain in the early phase but dramatically attenuated RA progression and pain in the chronic phase (> 7 weeks). TDAG8 deletion inhibited an increase in SGC number and inhibition of SGC function attenuated chronic phase of RA pain, so TDAG8 could regulate SGC number to control chronic pain. TDAG8 deletion also reduced M1 pro-inflammatory macrophage number at 12 weeks, contributing to the attenuation of chronic RA pain. Such results were further confirmed by using salicylanilide derivatives, CCL-2d or LCC-09, to suppress TDAG8 expression and function. CONCLUSIONS: This study demonstrates that TDAG8 deletion reduced SGC and M1 macrophage number to relieve RA disease severity and associated chronic pain. M1 macrophages are critical for the development and maintenance of RA disease and pain, but glial activation is also required for the chronic phase of RA pain.
Assuntos
Artrite Reumatoide/metabolismo , Macrófagos/imunologia , Neuroglia/imunologia , Animais , Artrite Experimental/imunologia , Artrite Experimental/metabolismo , Artrite Experimental/patologia , Artrite Reumatoide/imunologia , Artrite Reumatoide/patologia , Dor Crônica/imunologia , Dor Crônica/metabolismo , Gânglios Espinais/metabolismo , Gânglios Espinais/patologia , Camundongos , Receptores Acoplados a Proteínas G/metabolismoRESUMO
Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of synovial joints and often associated with chronic pain. Chronic joint inflammation is attributed to severe proliferation of synoviocytes and resident macrophages and infiltration of immune cells. These cells secrete pro-inflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and IL-17 to overcome actions of anti-inflammatory cytokines, thereby maintaining chronic inflammation and pain. The imbalance between pro-inflammatory cytokines (produced by M1 macrophages) and anti-inflammatory cytokines (produced by M2 macrophages) is a feature of RA progression, but the switch time of M1/M2 polarization and which receptor regulates the switch remain unsolved. Here we used an established RA mouse model to demonstrate that TNF-α expression was responsible for the initial acute stage of inflammation and pain (1-4 weeks), IL-17 expression the transition stage (4-12 weeks), and IL-6 expression the later maintenance stage (> 12 weeks). The switch time of M1/M2 polarization occurred at 4-8 weeks. We also identified a potential compound, anthra[2,1-c][1,2,5] thiadiazole-6,11-dione (NSC745885), that specifically inhibited T-cell death-associated gene 8 (TDAG8) function and expression. NSC745885 decreased joint inflammation and destruction and attenuated pain by reducing cytokine production and regulating the M1/M2 polarization switch. TDAG8 may participate in regulating the M1/M2 polarization and temporal expression of distinct cytokines to control RA progression.
Assuntos
Artrite Reumatoide/imunologia , Citocinas/genética , Macrófagos/metabolismo , Animais , Anti-Inflamatórios/farmacologia , Artrite Reumatoide/metabolismo , Artrite Reumatoide/patologia , Células Cultivadas , Citocinas/metabolismo , Expressão Gênica/genética , Inflamação/metabolismo , Interleucina-17/metabolismo , Interleucina-6/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos ICR , Dor/genética , Dor/metabolismo , Sinoviócitos/metabolismo , Transcriptoma/genética , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
INTRODUCTION: Systemic lupus erythematosus (SLE) is a chronic and complex autoimmune disease with a wide range of clinical manifestations that affects multiple organs and tissues. Therefore the differential expression of proteins in the serum/plasma have potential clinical applications when treating SLE. METHODS: We have compared the plasma/serum protein expression patterns of nineteen active SLE patients with those of twelve age-matched and gender-matched healthy controls by proteomic analysis. To investigate the differentially expressed proteins among SLE and controls, a 2-dimensional gel electrophoresis coupled with high-resolution liquid chromatography tandem mass spectrometry was performed. To further understand the molecular and biological functions of the identified proteins, PANTHER and Gene Ontology (GO) analyses were employed. RESULTS: A total of 14 significantly expressed (p < 0.05, p < 0.01) proteins were identified, and of these nine were up-regulated and five down-regulated in the SLE patients. The functional enrichment analysis assigned the majority of the identified proteins including alpha 2 macroglobulin, complement C4, complement factor H, fibrinogen beta chain, and alpha-1-antitrypsin were part of the complement/coagulation cascade, which is an important pathway that plays a crucial role in SLE pathogenesis. In addition to these proteins the differential expressions of ceruloplasmin, transthyretin, and haptoglobin play a potential role in the renal system abnormalities of SLE. CONCLUSION: Therefore, the identified differentially expressed proteins are relevant to SLE patient's cohort. Most importantly the up-regulated proteins might be the potential candidates for renal system involvement in SLE disease pathogenesis. In order to confirm the diagnostic/therapeutic potential of the identified proteins, future validation studies are required.
Assuntos
Biomarcadores/sangue , Proteínas Sanguíneas/metabolismo , Lúpus Eritematoso Sistêmico/sangue , Lúpus Eritematoso Sistêmico/metabolismo , Proteômica/métodos , Adulto , Estudos de Coortes , Feminino , Ontologia Genética , Humanos , Lúpus Eritematoso Sistêmico/diagnóstico , Masculino , Pessoa de Meia-Idade , alfa 1-Antitripsina/sangueRESUMO
Rheumatoid arthritis (RA), characterized by chronic inflammation of synovial joints, is often associated with ongoing pain and increased pain sensitivity. Chronic pain that comes with RA turns independent, essentially becoming its own disease. It could partly explain that a significant number (50%) of RA patients fail to respond to current RA therapies that focus mainly on suppression of joint inflammation. The acute phase of pain seems to associate with joint inflammation in early RA. In established RA, the chronic phase of pain could be linked to inflammatory components of neuron-immune interactions and noninflammatory components. Accumulating evidence suggests that the initial inflammation and autoimmunity in RA (preclinical RA) begin outside of the joint and may originate at mucosal sites and alterations in the composition of microbiota located at mucosal sites could be essential for mucosal inflammation, triggering joint inflammation. Fibroblast-like synoviocytes in the inflamed joint respond to cytokines to release acidic components, lowering pH in synovial fluid. Extracellular proton binds to proton-sensing ion channels, and G-protein-coupled receptors in joint nociceptive fibers may contribute to sensory transduction and release of neurotransmitters, leading to pain and hyperalgesia. Activation of peripheral sensory neurons or nociceptors further modulates inflammation, resulting in neuroinflammation or neurogenic inflammation. Peripheral and central nerves work with non-neuronal cells (such as immune cells, glial cells) in concert to contribute to the chronic phase of RA-associated pain. This review will discuss actions of proton-sensing receptors on neurons or non-neuronal cells that modulate RA pathology and associated chronic pain, and it will be beneficial for the development of future therapeutic treatments.
Assuntos
Artrite Reumatoide/fisiopatologia , Canais Iônicos/fisiologia , Nociceptores/fisiologia , Dor/fisiopatologia , Receptores Acoplados a Proteínas G/fisiologia , Humanos , Concentração de Íons de Hidrogênio , Hiperalgesia/fisiopatologia , Prótons , Líquido Sinovial/químicaRESUMO
Advillin is a sensory neuron-specific actin-binding protein expressed at high levels in all types of somatosensory neurons in early development. However, the precise role of advillin in adulthood is largely unknown. Here we reveal advillin expression restricted to isolectin B4-positive (IB4+) neurons in the adult dorsal root ganglia (DRG). Advillin knockout (KO) specifically impaired axonal regeneration in adult IB4+ DRG neurons. During axon regeneration, advillin was expressed at the very tips of filopodia and modulated growth cone formation by interacting with and regulating focal-adhesion-related proteins. The advillin-containing focal-adhesion protein complex was shed from neurite tips during neurite retraction and was detectable in cerebrospinal fluid in experimental autoimmune encephalomyelitis, oxaliplatin-induced peripheral neuropathy, and chronic constriction injury of the sciatic nerve. In addition, advillin KO disturbed experimental autoimmune encephalomyelitis-induced neural plasticity in the spinal-cord dorsal horn and aggravated neuropathic pain. Our study highlights a role for advillin in growth cone formation, axon regeneration, and neuropathic pain associated with IB4+ DRG neurons in adulthood.
Assuntos
Gânglios Espinais/fisiologia , Cones de Crescimento/fisiologia , Proteínas dos Microfilamentos/metabolismo , Regeneração/fisiologia , Animais , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/metabolismo , Adesões Focais/genética , Adesões Focais/metabolismo , Camundongos , Camundongos Knockout , Proteínas dos Microfilamentos/genética , Síndromes de Compressão Nervosa/genética , Síndromes de Compressão Nervosa/metabolismo , Neuralgia/genética , Neuralgia/metabolismo , Doenças do Sistema Nervoso Periférico/genética , Doenças do Sistema Nervoso Periférico/metabolismo , Pseudópodes/genética , Pseudópodes/metabolismo , Neuropatia Ciática/genética , Neuropatia Ciática/metabolismoRESUMO
CONTEXT: Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease with unknown etiology. OBJECTIVE: Human plasma is comprised of over 10 orders of magnitude concentration of proteins and tissue leakages. The changes in the abundance of these proteins have played an important role in various human diseases. Therefore, the research objective of this study is to identify the significantly altered expression levels of plasma proteins from SLE patients compared with healthy controls using proteomic analysis. The plasma proteome profiles of both SLE patients and controls were compared. METHODS: A total of 19 active SLE patients and 12 healthy controls plasma samples were analyzed using high-resolution electrospray ionization liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) followed by label-free quantification. RESULTS: A total of 19 proteins showed a significant level of expression in the comparative LC-ESI-MS/MS triplicate analysis; among these, 14 proteins had >1.5- to three-fold up-regulation and five had <0.2- to 0.6-fold down-regulation. Gene ontology and DAVID (Database Annotation Visualization, and Integrated Discovery) functional enrichment analysis revealed that these proteins are involved in several important biological processes including acute phase inflammatory responses, complement activation, hemostasis, and immune system regulation. CONCLUSION: Our study identified a group of differentially expressed proteins in the plasma of SLE patients that are involved in the imbalance of the immune system and inflammatory responses. Therefore, these findings may have the potential to be used as prognostic/diagnostic markers for SLE disease assessment or disease monitoring.
RESUMO
Tissue injury, pathogen infection, and diseases are often accompanied by inflammation to release mediators that sensitize nociceptors and further recruit immune cells, which can lead to chronic hyperalgesia and inflammation. Tissue acidosis, occurring at the inflammatory site, is a major factor contributing to pain and hyperalgesia. The receptor G2 accumulation (G2A), expressed in neurons and immune cells, responds to protons or oxidized free fatty acids such as 9-hydroxyoctadecadienoic acid produced by injured cells or oxidative stresses. We previously found increased G2A expression in mouse dorsal root ganglia (DRG) at 90 min after complete Freund's adjuvant (CFA)-induced inflammatory pain, but whether G2A is involved in the inflammation or hyperalgesia remained unclear. In this study, we overexpressed or knocked-down G2A gene expression in DRG to explore the roles of G2A. G2A overexpression reduced the infiltration of acute immune cells (granulocytes) and attenuated hyperalgesia at 90 to 240 min after CFA injection. G2A knockdown increased the number of immune cells before CFA injection and prolonged the inflammatory hyperalgesia after CFA injection. G2A may serve as a threshold regulator in neurons to attenuate the initial nociceptive and inflammatory signals, modulating the chronic state of hyperalgesia.
Assuntos
Proteínas de Ciclo Celular/genética , Hiperalgesia/genética , Limiar da Dor , Receptores Acoplados a Proteínas G/genética , Animais , Proteínas de Ciclo Celular/metabolismo , Feminino , Gânglios Espinais/citologia , Gânglios Espinais/metabolismo , Gânglios Espinais/fisiologia , Granulócitos/metabolismo , Hiperalgesia/metabolismo , Hiperalgesia/fisiopatologia , Masculino , Camundongos , Camundongos Endogâmicos ICR , Neurônios/metabolismo , Receptores Acoplados a Proteínas G/metabolismoRESUMO
Mirror-image pain (MIP), which occurs along with complex regional pain syndrome, rheumatoid arthritis and chronic migraine, is characterized by increased pain sensitivity of healthy body regions other than the actual injured or inflamed sites. A high level of peripheral inflammation may activate central or peripheral glia, triggering mirror-image pain. However, which receptors mediate inflammatory signals to contribute glial activation remains unclear. Intraplantarly injecting mice with 5-hydroxytryptamine (5-HT) or acidic buffer (proton) caused only unilateral hyperalgesia, but co-injection of 5-HT/acid induced bilateral hyperalgesia (MIP). Blocking 5-HT3 or acid-sensing ion channel 3 (ASIC3) abolished satellite glial activation, inhibiting MIP. Interestingly, intraplantar administration of a 5-HT3 agonist induced MIP, and 5-HT3-mediated MIP can be reversed by a 5-HT3 antagonist or an ASIC3 blocker. Similar results were found using a ASIC3 agonist. Furthermore, 5-HT3 was observed to co-localize with ASIC3 in DRG neurons; 5-HT3 activation-induced an increase in intracellular calcium that was inhibited by an ASIC3 blocker and vice versa. A cross-talk between 5-HT3 and ASIC3 mediates satellite glial activation, thereby triggering mirror-image pain.
Assuntos
Canais Iônicos Sensíveis a Ácido/metabolismo , Hiperalgesia/metabolismo , Receptores 5-HT3 de Serotonina/metabolismo , Bloqueadores do Canal Iônico Sensível a Ácido/farmacologia , Animais , Dinoprostona/farmacologia , Modelos Animais de Doenças , Gânglios Espinais/metabolismo , Gânglios Espinais/patologia , Células HEK293 , Humanos , Inflamação/metabolismo , Inflamação/patologia , Masculino , Camundongos , Camundongos Endogâmicos ICR , Serotonina/farmacologia , Agonistas do Receptor 5-HT2 de Serotonina/farmacologia , Antagonistas do Receptor 5-HT3 de Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologiaRESUMO
Rheumatoid arthritis (RA), characterized by chronic inflammation of synovial joints, is often associated with ongoing pain and increased pain sensitivity. High hydrogen ion concentration (acidosis) found in synovial fluid in RA patients is associated with disease severity. Acidosis signaling acting on proton-sensing receptors may contribute to inflammation and pain. Previous studies focused on the early phase of arthritis (<5 weeks) and used different arthritis models, so elucidating the roles of different proton-sensing receptors in the chronic phase of arthritis is difficult. We intra-articularly injected complete Freund's adjuvant into mice once a week for 4 weeks to establish chronic RA pain. Mice with knockout of acid-sensing ion channel 3 (ASIC3) or transient receptor potential/vanilloid receptor subtype 1 (TRPV1) showed attenuated chronic phase (>6 weeks) of RA pain. Mice with T-cell death-associated gene 8 (TDAG8) knockout showed attenuated acute and chronic phases of RA pain. TDAG8 likely participates in the initiation of RA pain, but all three genes, TDAG8, TRPV1, and ASIC3, are essential to establish hyperalgesic priming to regulate the chronic phase of RA pain.
Assuntos
Canais Iônicos Sensíveis a Ácido/genética , Artrite Reumatoide/complicações , Artrite Reumatoide/genética , Hiperalgesia/etiologia , Hiperalgesia/fisiopatologia , Canais de Cátion TRPV/genética , Canais Iônicos Sensíveis a Ácido/metabolismo , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação Mielomonocítica/metabolismo , Artralgia/etiologia , Artralgia/fisiopatologia , Artrite Experimental , Artrite Reumatoide/patologia , Biomarcadores , Citocinas/sangue , Citocinas/metabolismo , Modelos Animais de Doenças , Feminino , Expressão Gênica , Imuno-Histoquímica , Macrófagos/imunologia , Macrófagos/metabolismo , Macrófagos/patologia , Masculino , Camundongos , Camundongos Knockout , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Canais de Cátion TRPV/metabolismoRESUMO
Chronic pain, resulting from injury, arthritis, and cancer, is often accompanied by inflammation. High concentrations of protons found in inflamed tissues results in tissue acidosis, a major cause of pain and hyperalgesia. Acidosis signals may mediate a transition from acute to chronic hyperalgesia (hyperalgesic priming) via proton-sensing G-protein-coupled receptors (GPCRs). The expression of T-cell death-associated gene 8 (TDAG8), a proton-sensing GPCR, is increased during inflammatory hyperalgesia. Attenuating TDAG8 expression in the spinal cord inhibits bone cancer pain, but whether TDAG8 is involved in inflammatory hyperalgesia or hyperalgesic priming remains unclear. In this study, we used TDAG8-knockout or -knockdown to explore the role of TDAG8 in pain. Suppressed TDAG8 expression delayed the onset of inflammatory hyperalgesia and shortened hyperalgesic time in mice. In a dual acid-injection model (acid [pH 5.0] injected twice, 5 days apart), shRNA inhibition of TDAG8 shortened the duration of the second hyperalgesia. Similar results were found in TDAG8-deficient mice. The dual administration of TDAG8 agonist also confirmed that TDAG8 is involved in hyperalgsic priming. Accordingly, TDAG8 may mediate acidosis signals to initiate inflammatory hyperalgesia and establish hyperalgesic priming.
Assuntos
Hiperalgesia/metabolismo , Hiperalgesia/patologia , Inflamação/metabolismo , Inflamação/patologia , Animais , Cálcio/metabolismo , Sinalização do Cálcio , Carragenina , AMP Cíclico/metabolismo , Adjuvante de Freund , Deleção de Genes , Técnicas de Silenciamento de Genes , Células HEK293 , Humanos , Concentração de Íons de Hidrogênio , Espaço Intracelular/metabolismo , Camundongos Endogâmicos ICR , RNA Interferente Pequeno/metabolismo , Receptores Acoplados a Proteínas G/agonistas , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismoRESUMO
Itch and pain are closely related but are distinct sensations. Intradermal injection of acid generates pain in both rodents and humans; however, few studies have addressed the intriguing question of whether acid (protons) can evoke itch like other algogens by spatial contrast activation of single nociceptors. Here, we report that (i) citric acid (0.2 mol/L) pH-dependently induced a scratching response in mice when applied intradermally to nape or cheek skin, (ii) acidified buffer elevated intracellular calcium levels in dorsal root ganglion pruriceptors, and (iii) injection of intradermal citric acid (pH 3.0) into the nape induced a pruritogen-like but not algogen-like c-Fos immunoreactivity pattern in the cervical spinal cord. Using pharmacological and genetic approaches, we identified potential acid-sensing channels/receptors involved in acidic citrate-evoked itch. Results indicate that TRPV1, but neither ASIC3 nor TRPA1, is involved in the acidic citrate-induced scratching response. Furthermore, one of the proton-sensing G-protein-coupled receptors, TDAG8, was highly (â¼71%) expressed in Nppb+ dorsal root ganglion pruriceptors. Itch induced by acidic citrate, but not α-methyl-5-hydroxytryptamine, chloroquine, compound 48/80, or bile acid, was markedly decreased in TDAG8-/- mice. In a heterologous expression system, TDAG8 potentiated the acid-induced calcium response by regulating TRPV1. Thus, protons could evoke pruriception by acting on TDAG8 to regulate TRPV1 activation with its mechanism of future therapeutic relevance.
Assuntos
Acidose/metabolismo , Formiatos/farmacologia , Prurido/metabolismo , Canais de Cátion TRPV/metabolismo , Acidose/genética , Análise de Variância , Animais , Comportamento Animal , Modelos Animais de Doenças , Injeções Intradérmicas , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Nociceptividade/efeitos dos fármacos , Prurido/induzido quimicamente , Prurido/patologia , Distribuição Aleatória , Reação em Cadeia da Polimerase em Tempo Real/métodos , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Estatísticas não Paramétricas , Canais de Cátion TRPV/genéticaRESUMO
A series of 1-amino-4-(phenylamino)anthraquinone-2-sulfonate sodium derivatives was synthesized and evaluated for osteoclast inhibition using a TRAP-staining assay. Among them, two compounds, LCCY-13 and LCCY-15, dose-dependently suppressed receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation. Moreover, the cytotoxicity assay on RAW264.7 cells suggested that the inhibition of osteoclastic bone resorption by these compounds was not a result of their cytotoxicity. Further, the inhibitory activities of compounds LCCY-13 and LCCY-15 were further confirmed by including specific inhibition of NFATc1 expression levels in nuclei using an immunofluorescent analysis. In addition, LCCY-13 and LCCY-15 also significantly attenuated the bone resorption activity of osteoclasts according to a pit formation assay. Thus, a new class of 1-amino-4-(phenylamino)anthraquinone-2-sulfonate sodium compounds might be considered as an essential lead structure for the further development of anti-resorptive agents.
Assuntos
Antraquinonas/síntese química , Antraquinonas/farmacologia , Osteogênese/efeitos dos fármacos , Ligante RANK/antagonistas & inibidores , Animais , Reabsorção Óssea , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Relação Dose-Resposta a Droga , Camundongos , Fatores de Transcrição NFATC/biossíntese , Osteoclastos/efeitos dos fármacos , Ligante RANK/metabolismoRESUMO
Proton-sensing G-protein-coupled receptors (GPCRs; OGR1, GPR4, G2A, TDAG8), with full activation at pH 6.4 â¼ 6.8, are important to pH homeostasis, immune responses and acid-induced pain. Although G2A mediates the G13-Rho pathway in response to acid, whether G2A activates Gs, Gi or Gq proteins remains debated. In this study, we examined the response of this fluorescence protein-tagged OGR1 family to acid stimulation in HEK293T cells. G2A did not generate detectable intracellular calcium or cAMP signals or show apparent receptor redistribution with moderate acid (pH ≥ 6.0) stimulation but reduced cAMP accumulation under strong acid stimulation (pH ≤ 5.5). Surprisingly, coexpression of OGR1- and G2A-enhanced proton sensitivity and proton-induced calcium signals. This alteration is attributed to oligomerization of OGR1 and G2A. The oligomeric potential locates receptors at a specific site, which leads to enhanced proton-induced calcium signals through channels.
Assuntos
Sinalização do Cálcio/genética , Proteínas de Ciclo Celular/química , Prótons , Receptores Acoplados a Proteínas G/química , Ácidos/química , Cálcio/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , AMP Cíclico/química , Regulação da Expressão Gênica , Células HEK293 , Humanos , Concentração de Íons de Hidrogênio , Multimerização Proteica , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismoRESUMO
Serotonin [5-hydroxytryptamine (5-HT)], an inflammatory mediator, contributes to inflammatory pain. The presence of multiple 5-HT subtype receptors on peripheral and central nociceptors complicates the role of 5-HT in pain. Previously, we found that 5-HT2B/2C antagonist could block 5-HT-induced mechanical hyperalgesia. However, the types of neurons or circuits underlying this effect remained unsolved. Here, we demonstrate that the Gq/11-phospholipase Cß-protein kinase Cε (PKCε) pathway mediated by 5-HT2B is involved in 5-HT-induced mechanical hyperalgesia in mice. Administration of a transient receptor potential vanilloid 1 (TRPV1) antagonist inhibited the 5-HT-induced mechanical hyperalgesia. 5-HT injection enhanced 5-HT- and capsaicin-evoked calcium signals specifically in isolectin B4 (IB4)-negative neurons; signals were inhibited by a 5-HT2B/2C antagonist and PKCε blocker. Thus, 5-HT2B mediates 5-HT-induced mechanical hyperalgesia by regulating TRPV1 function.
Assuntos
Hiperalgesia/metabolismo , Receptor 5-HT2B de Serotonina/metabolismo , Canais de Cátion TRPV/metabolismo , Animais , Sinalização do Cálcio , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP/metabolismo , Lectinas/genética , Lectinas/metabolismo , Masculino , Camundongos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosfolipase C beta/metabolismo , Proteína Quinase C-épsilon/antagonistas & inibidores , Proteína Quinase C-épsilon/metabolismo , Serotonina/farmacologia , Canais de Cátion TRPV/antagonistas & inibidoresRESUMO
Chronic inflammatory pain, when not effectively treated, is a costly health problem and has a harmful effect on all aspects of health-related quality of life. Previous studies suggested that in male Sprague Dawley rats, prostaglandin E2 (PGE2)-induced short-term hyperalgesia depends on protein kinase A (PKA) activity, whereas long-lasting hyperalgesia induced by PGE2 with carrageenan pre-injection, requires protein kinase Cε (PKCε). However, the mechanism underlying the kinase switch with short- to long-term hyperalgesia remains unclear. In this study, we used the inflammatory agents carrageenan or complete Freund's adjuvant (CFA) to induce long-term hyperalgesia, and examined PKA and PKCε dependence and switching time. Hyperalgesia induced by both agents depended on PKA/PKCε and Gs/Gi-proteins, and the switching time from PKA to PKCε and from Gs to Gi was about 3 to 4 h after inflammation induction. Among the single inflammatory mediators tested, PGE2 and 5-HT induced transient hyperalgesia, which depended on PKA and PKCε, respectively. Only acidic solution-induced hyperalgesia required Gs-PKA and Gi-PKCε, and the switch time for kinase dependency matched inflammatory hyperalgesia, in approximately 2 to 4 h. Thus, acidosis in inflamed tissues may be a decisive factor to regulate switching of PKA and PKCε dependence via proton-sensing G-protein-coupled receptors.
Assuntos
Acidose/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/metabolismo , Subunidades alfa Gs de Proteínas de Ligação ao GTP/metabolismo , Hiperalgesia/metabolismo , Inflamação/metabolismo , Proteína Quinase C-épsilon/metabolismo , Animais , Carragenina , Adjuvante de Freund , Concentração de Íons de Hidrogênio , Hiperalgesia/etiologia , Inflamação/complicações , Camundongos , Inibidores de Proteínas Quinases/farmacologia , Transporte Proteico/efeitos dos fármacos , Receptores Acoplados a Proteínas G/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Advanced gene targeting technology and related tools in mice have been incorporated into studies of acid-sensing ion channels (ASICs). A single ASIC subtype can be knocked out specifically and screened thoroughly for expression in the nervous system at the cellular level. Mapping studies have further shed light on the initiation and identification of related behavioral phenotypes. Here we review studies involving genetically engineered mouse models used to investigate the physiological function of individual ASIC subtypes: ASIC1 (and ASIC1a), ASIC2, ASIC3 and ASIC4. We discuss the detailed expression studies and significant phenotypes revealed with gene knockout for most known Asic subtypes. Each strategy designed to manipulate mouse genetics has advantages and disadvantages. We discuss the limitations of these Asic-knockout models and propose future directions to solve the genetic issues. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.