RESUMEN
Sigma-1 receptors (σ1Rs) are implicated in nociception, including pain sensitization, and inflammation. We assessed the role of σ1Rs on acute colitis-associated hypersensitivity using both genetic (constitutive knockout) and pharmacological blockade of the receptor. Colitis was induced in CD1 wild-type (WT) and σ1R KO mice (exposure to dextran sodium sulfate, 3%). A von Frey test was used to assess referred mechanosensitivity (abdominal and plantar withdrawal responses). The effects of the selective σ1R antagonists BD1063 and E-52862 were also assessed in WT animals. The expression of immune and sensory-related markers (RT-qPCR, Western blot) was assessed in the colon and lumbosacral spinal cord. The genetic ablation or pharmacological blockade of σ1Rs attenuated acute colonic inflammation in a similar manner. Mechanosensitivity was similar in WT and σ1R KO mice before colitis. In WT mice, but not in σ1R KO, colitis was associated with the development of referred mechanical hypersensitivity, manifested as a reduction in the withdrawal thresholds to mechanical probing (paw and abdominal wall). In WT mice, BD1063 and E-52862 blocked colitis-associated hypersensitivity. A genotype- and treatment-related differential regulation of sensory-related markers was detected locally (colon) and within the spinal cord. σ1Rs are involved in the development of acute intestinal inflammation and its associated referred mechanical hypersensitivity. The selective modulation of sensory-related pathways within the colon and spinal cord might be part of the underlying mechanisms. These observations support the pharmacological use of σ1R antagonists for the treatment of intestinal inflammation-induced hypersensitivity.
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Mice lacking the σ1 receptor chaperone (σ1R-/-) are resilient to depressive-like behaviors secondary to neuropathic pain. Examining the resilience's brain mechanisms could help develop conceptually novel therapeutic strategies. We explored the diminished motivation for a natural reinforcer (white chocolate) in the partial sciatic nerve ligation (PSNL) model in wild-type (WT) and σ1R-/- mice. In the same mice, we performed a comprehensive reverse transcription quantitative PCR (qPCR) analysis across ten brain regions of seven genes implicated in pain regulation and associated affective disorders, such as anxiety and depression. PSNL induced anhedonic-like behavior in WT but not in σ1R-/- mice. In WT mice, PSNL up-regulated dopamine transporter (DAT) and its rate-limiting enzyme, tyrosine hydroxylase (Th), in the ventral tegmental area (VTA) and periaqueductal gray (PAG) as well as the serotonin transporters (SERT) and its rate-limiting enzyme tryptophan hydroxylase 2 (Tph2) in VTA. In addition, µ-opioid receptor (MOR) and σ1R were up-regulated in PAG, and MOR was also elevated in the somatosensory cortex (SS) but down-regulated in the striatum (STR). Finally, increased BDNF was found in the medial prefrontal cortex (mPFC) and hypothalamus (HPT). Sham surgery also produced PSNL-like expression changes in VTA, HPT, and STR. Genetic deletion of the σ1R in mice submitted to PSNL or sham surgery prevented changes in the expression of most of these genes. σ1R is critically involved in the supraspinal gene expression changes produced by PSNL and sham surgery. The changes in gene expression observed in WT mice may be related to pain-related depression, and the absence of these changes observed in σ1R-/- mice may be related to resilience.
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Depresión , Neuralgia , Ratones , Animales , Depresión/genética , Depresión/tratamiento farmacológico , Ratones Noqueados , Encéfalo/metabolismo , Neuralgia/tratamiento farmacológicoRESUMEN
Chronic pain remains a major health problem and is currently facing slow drug innovation. New drug treatments should address not only the sensory-discriminative but also functional and motivational-affective components of chronic pain. In a mouse model of neuropathic pain induced by partial sciatic nerve ligation (PSNL), we analyzed sensory and functional-like outcomes by hindpaw mechanical stimulation and automated gait analysis (CatWalk). We characterized over time a reward-seeking task based on diminished motivation for natural reinforcers (anhedonic-like behavior). To differentiate the appetitive ("wanting") and consummatory ("liking") aspects of motivational behavior, we quantified the latency and number of approaches to eat white chocolate, as well as the eating duration and amount consumed. We explored a putative chronic pain-induced dysregulation of monoamine function by measuring monoamine levels in the nucleus accumbens (NAc), a well-known brain reward area. Finally, we investigated the role of sigma-1 receptor (σ1R) modulation, a nonopioid target, in these multiple dimensions by genetic deletion and pharmacological dose-response studies. After 6 weeks, PSNL increased the approach latency and reduced the consumption of white chocolate in 20-25% of the mice, while around 50-60% had one or the other parameter affected independently. After 10 weeks, sham-operated mice also displayed anhedonic-like behavior. PSNL was associated with reduced extracellular baseline dopamine and increased norepinephrine in the NAc and with a suppression of increased dopamine and serotonin efflux in response to the rewarding stimulus. Genetic and pharmacological blockade of σ1R relieved these multiple alterations in nerve-injured mice. We comprehensively describe sensory, functional, and depression-like impairment of key components of motivated behavior associated with nerve injury. We provide a neurochemical substrate for the depressed mesocorticolimbic reward processing in chronic pain, with a potentially increased translational value. Our results also highlight σ1R for the therapeutic intervention of neuropathic pain.
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Sigma-1 receptors (σ1R) have been implicated in several pain pathways. We assessed the implication of σ1Rs in the development of intestinal inflammation and inflammation-associated referred hypersensitivity in a model of colitis in σ1R knockout (KO) mice. Colitis was induced with dextran sulfate sodium (DSS) in wild type (WT) and σ1R KO mice. The development of referred mechanical hypersensitivity (von Frey test) was assessed. Colonic and spinal changes in expression of immune- and sensory-related markers were also investigated (RT-qPCR/Western blot). Absence of σ1Rs had little impact in colitis generation and progression, although during the chronic phase a reduction in edema and a down-regulation of iNOS gene expression was observed. In σ1R KO mice, inflammation-associated hypersensitivity was significantly attenuated (paw) or completely prevented (abdomen). During colitis, in WT mice, changes in the colonic expression of nociceptive markers were observed during the acute and chronic phases of inflammation. Although σ1R KO mice showed similar regulation in the acute phase, an attenuated response was observed during the chronic phase of colitis. These differences were especially relevant for CB2 and TRPV1 receptors, which could play an important role in σ1-mediated regulation of sensitivity. No changes were detected on ERK phosphorylation at the level of the lumbosacral spinal cord. In summary, intestinal inflammation-associated referred hyperalgesia was reduced (paw) or absent (abdomen) in σ1R KO mice, thus confirming an important role for σ1R in the development of colitis-associated hypersensitivity. These results identify σ1Rs as a possible therapeutic target for the treatment of hypersensitivity associated to intestinal inflammation.
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Colitis/metabolismo , Colon/metabolismo , Hiperalgesia/prevención & control , Umbral del Dolor , Receptores sigma/deficiencia , Médula Espinal/metabolismo , Animales , Colitis/inducido químicamente , Colitis/genética , Colitis/fisiopatología , Colon/inervación , Sulfato de Dextran , Modelos Animales de Enfermedad , Hiperalgesia/genética , Hiperalgesia/metabolismo , Hiperalgesia/fisiopatología , Mediadores de Inflamación/metabolismo , Masculino , Ratones Endogámicos C57BL , Ratones Noqueados , Receptores sigma/genética , Transducción de Señal , Médula Espinal/fisiopatología , Receptor Sigma-1RESUMEN
The synthesis and pharmacological activity of a new series of pyrazoles that led to the identification of 1-(4-(2-((1-(3,4-difluorophenyl)-1H-pyrazol-3-yl)methoxy)ethyl)piperazin-1-yl)ethanone (9k, EST64454) as a σ1 receptor (σ1R) antagonist clinical candidate for the treatment of pain are reported. The compound 9k is easily obtained through a five-step synthesis suitable for the production scale and shows an outstanding aqueous solubility, which together with its high permeability in Caco-2 cells will allow its classification as a BCS class I compound. It also shows high metabolic stability in all species, linked to an adequate pharmacokinetic profile in rodents, and antinociceptive properties in the capsaicin and partial sciatic nerve ligation models in mice.
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Analgésicos/uso terapéutico , Dolor/tratamiento farmacológico , Piperazinas/uso terapéutico , Pirazoles/uso terapéutico , Receptores sigma/antagonistas & inhibidores , Analgésicos/síntesis química , Analgésicos/farmacocinética , Animales , Células CACO-2 , Humanos , Ratones , Estructura Molecular , Piperazinas/síntesis química , Piperazinas/farmacocinética , Pirazoles/síntesis química , Pirazoles/farmacocinética , Ratas Wistar , Relación Estructura-Actividad , Receptor Sigma-1RESUMEN
Pain encompasses both sensory and affective dimensions which can be differentially modulated by drugs. Here, we compare the pharmacological sensitivity of the sensory and affective responses using acetic acid-induced abdominal writhings (sensory-reflexive outcome) and acetic acid-induced depression of reward seeking behaviour (RSB, affective-nonreflexive outcome) to a highly palatable food in mice. We found that the expression of RSB critically depends on factors such as sex and previous knowledge and type of the food stimulus. Intraperitoneal administration of acetic acid (iAA) produced a long-lasting (beyond the resolution of writhing behaviour) and concentration-dependent decrease on both appetitive-approach and consummatory dimensions of RSB. Ibuprofen and diclofenac were much more potent in reversing AA-induced changes in RSB: latency to eat (ED50 = 2 and 0.005 mg/kg, intraperinoneally, respectively) and amount consumed (ED50 = 11 and 0.1 mg/kg) than in AA-induced writhing (ED50 = 123 and 60 mg/kg). Morphine and duloxetine inhibited the writhing response (ED50 = 0.8 and 6 mg/kg, respectively) but not the AA-induced changes in RSB. Caffeine was ineffective in both AA-induced writhing and RSB changes. Overall, this study characterized a preclinical mouse model of hedonic deficits induced by pain that can be used to assess affective responses as well as complementary classic reflexive approaches in the evaluation of candidate analgesics.
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Analgésicos/farmacología , Conducta Apetitiva/efectos de los fármacos , Conducta Consumatoria/efectos de los fármacos , Reflejo/efectos de los fármacos , Dolor Visceral/fisiopatología , Ácido Acético/farmacología , Animales , Condicionamiento Clásico/efectos de los fármacos , Diclofenaco/farmacología , Clorhidrato de Duloxetina/farmacología , Femenino , Ibuprofeno/farmacología , Masculino , Ratones , Morfina/farmacología , RecompensaRESUMEN
Reflex-based procedures are important measures in preclinical pain studies that evaluate stimulated behaviors. These procedures, however, are insufficient to capture the complexity of the pain experience, which is often associated with the depression of several innate behaviors. While recent studies have made efforts to evidence the suppression of some positively motivated behaviors in certain pain models, they are still far from being routinely used as readouts for analgesic screening. Here, we characterized and compared the effect of the analgesic ibuprofen (Ibu) and the stimulant, caffeine, in assays of acute pain-stimulated and pain-depressed behavior. Intraperitoneal injection of acetic acid (AA) served as a noxious stimulus to stimulate a writhing response or depress saccharin preference and locomotor activity (LMA) in mice. AA injection caused the maximum number of writhes between 5 and 20 minutes after administration, and writhing almost disappeared 1 hour later. AA-treated mice showed signs of depression-like behaviors after writhing resolution, as evidenced by reduced locomotion and saccharin preference for at least 4 and 6 hours, respectively. Depression-like behaviors resolved within 24 hours after AA administration. A dose of Ibu (40 mg/kg) - inactive to reduce AA-induced abdominal writhing - administered before or after AA injection significantly reverted pain-induced saccharin preference deficit. The same dose of Ibu also significantly reverted the AA-depressed LMA, but only when it was administered after AA injection. Caffeine restored locomotion - but not saccharin preference - in AA-treated mice, thus suggesting that the reduction in saccharin preference - but not in locomotion - was specifically sensitive to analgesics. In conclusion, AA-induced acute pain attenuated saccharin preference and LMA beyond the resolution of writhing behavior, and the changes in the expression of hedonic behavior, such as sweet taste preference, can be used as a more sensitive and translational model to evaluate analgesics.
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While opioids are potent analgesics widely used in the management of pain, a number of well-known adverse effects limit their use. The sigma-1 receptor is a ligand-regulated molecular chaperone involved in pain processing, including modulation of opioid antinociception. However, data supporting the potential use of sigma-1 receptor ligands as suitable opioid adjuvants are based on studies that use non selective ligands. Also, safety issues derived from combination therapy are poorly addressed. In this study we used the new selective sigma-1 receptor antagonist S1RA (E-52862) to characterize the effect of selective sigma-1 receptor blockade on opioid-induced efficacy- and safety-related outcomes in mice. S1RA (40 mg/kg) had no effect in the tail-flick test but did enhance the antinociceptive potency of several opioids by a factor between 2 and 3.3. The potentiating effect of S1RA on morphine antinociception did not occur in sigma-1 receptor knockout mice, which supports the selective involvement of the sigma-1 receptor. Interestingly, S1RA co-administration restored morphine antinociception in tolerant mice and reverted the reward effects of morphine in the conditioned place preference paradigm. In addition, enhancement of antinociception was not accompanied by potentiation of other opioid-induced effects, such as the development of morphine analgesic tolerance, physical dependence, inhibition of gastrointestinal transit, or mydriasis. The use of sigma-1 receptor antagonists as opioid adjuvants could represent a promising pharmacological strategy to enhance opioid potency and, most importantly, to increase the safety margin of opioids. S1RA is currently in phase II clinical trials for the treatment of several pain conditions.
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Analgésicos Opioides/efectos adversos , Analgésicos Opioides/farmacología , Receptores sigma/antagonistas & inhibidores , Animales , Conducta Animal/efectos de los fármacos , Quimioterapia Adyuvante , Condicionamiento Psicológico/efectos de los fármacos , Sinergismo Farmacológico , Tolerancia a Medicamentos , Tránsito Gastrointestinal/efectos de los fármacos , Técnicas de Inactivación de Genes , Intestinos/efectos de los fármacos , Intestinos/fisiología , Masculino , Ratones , Morfina/efectos adversos , Morfina/farmacología , Midriasis/inducido químicamente , Naloxona/farmacología , Receptores sigma/deficiencia , Receptores sigma/genética , Recompensa , Conducta Espacial/efectos de los fármacos , Receptor Sigma-1RESUMEN
RATIONALE: Oxidative stress is involved in the skeletal muscle dysfunction observed in patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that the diaphragms of such patients might generate greater levels of oxidants than those neutralized by antioxidants. OBJECTIVES: To assess the levels of both oxidative and nitrosative stress and different antioxidants in the diaphragms of those patients, and to analyze potential relationships with lung and respiratory muscle dysfunctions. METHODS AND MEASUREMENTS: We conducted a case-control study in which reactive carbonyl groups, hydroxynonenal-protein adducts, antioxidant enzyme levels, nitric oxide synthases, and 3-nitrotyrosine formation were detected using immunoblotting and immunhistochemistry in diaphragm specimens (thoracotomy) obtained from six patients with severe COPD, six patients with moderate COPD, and seven control subjects. MAIN RESULTS: Diaphragms of patients with severe COPD showed both higher protein carbonyl groups and hydroxynonenal-protein adducts than control subjects. When only considering patients with COPD, negative correlations were found between carbonyl groups and airway obstruction, and between hydroxynonenal-protein adducts and respiratory muscle strength. Although diaphragmatic neuronal nitric oxide synthase did not differ among the three groups and no inducible nitric oxide synthase was detected in any muscle, muscle endothelial nitric oxide synthase was lower in patients with severe COPD than in control subjects. Muscle nitrotyrosine levels were similar in both patients with severe COPD and control subjects. CONCLUSIONS: This study shows that oxidative stress rather than nitric oxide is likely to be involved in the respiratory muscle dysfunction in severe COPD.
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Diafragma/metabolismo , Diafragma/fisiopatología , Estrés Oxidativo , Enfermedad Pulmonar Obstructiva Crónica/metabolismo , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Anciano , Antioxidantes/metabolismo , Estudios de Casos y Controles , Diafragma/patología , Humanos , Masculino , Fibras Musculares Esqueléticas/citología , Fibras Musculares Esqueléticas/patología , Óxido Nítrico/metabolismo , Proteínas/metabolismo , Enfermedad Pulmonar Obstructiva Crónica/patología , Valores de Referencia , Pruebas de Función Respiratoria , Tirosina/metabolismoRESUMEN
Reactive oxygen and nitrogen species (ROS and RNS) have been proposed as mechanisms of cancer-induced cachexia. In this study, we assessed using Western blot analysis the levels of total protein carbonylation (2,4-dinitrophenylhydrazine assay), both malondialdehyde- (MDA-) and 2-hydroxy-4-nonenal- (HNE-) protein adducts, Mn-superoxide dismutase (Mn-SOD), catalase, heme oxygenase-1 (HO-1) and 3-nitrotyrosine formation in gastrocnemius muscles of rats bearing the Yoshida AH-130 hepatoma. In the muscles of the tumour-bearing animals, protein carbonylation as measured by total levels of carbonyl group formation and both HNE and MDA-protein adducts, and protein tyrosine nitration were significantly greater than in control muscles. Protein levels of the antioxidant enzymes Mn-SOD, catalase, and HO-1 were not significantly modified in the rat cachectic muscles compared to controls. The inefficiency of the antioxidant enzymes in neutralizing excessive ROS production may account for elevated markers of protein oxidation and be responsible for the development of both oxidative and nitrosative stress in cancer-induced cachexia.