RESUMEN
Neuropathic pain is a clinical manifestation of nerve injury difficult to treat even with potent analgesic compounds. Here, we used different lines of genetically modified mice to clarify the role played by CB(2) cannabinoid receptors in the regulation of the central immune responses leading to the development of neuropathic pain. CB(2) knock-out mice and wild-type littermates were exposed to sciatic nerve injury, and both genotypes developed a similar hyperalgesia and allodynia in the ipsilateral paw. Most strikingly, knock-outs also developed a contralateral mirror image pain, associated with an enhanced microglial and astrocytic expression in the contralateral spinal horn. In agreement, hyperalgesia, allodynia, and microglial and astrocytic activation induced by sciatic nerve injury were attenuated in transgenic mice overexpressing CB(2) receptors. These results demonstrate the crucial role of CB(2) cannabinoid receptor in modulating glial activation in response to nerve injury. The enhanced manifestations of neuropathic pain were replicated in irradiated wild-type mice reconstituted with bone marrow cells from CB(2) knock-outs, thus demonstrating the implication of the CB(2) receptor expressed in hematopoietic cells in the development of neuropathic pain at the spinal cord.
Asunto(s)
Neuralgia/inmunología , Enfermedades del Sistema Nervioso Periférico/inmunología , Receptor Cannabinoide CB2/inmunología , Médula Espinal/inmunología , Animales , Astrocitos/inmunología , Astrocitos/metabolismo , Trasplante de Médula Ósea , Modelos Animales de Enfermedad , Femenino , Gliosis/inmunología , Gliosis/metabolismo , Gliosis/fisiopatología , Células Madre Hematopoyéticas/inmunología , Hiperalgesia/inmunología , Hiperalgesia/metabolismo , Hiperalgesia/fisiopatología , Masculino , Ratones , Ratones Noqueados , Microglía/inmunología , Microglía/metabolismo , Neuralgia/metabolismo , Neuralgia/fisiopatología , Enfermedades del Sistema Nervioso Periférico/metabolismo , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Células del Asta Posterior/inmunología , Células del Asta Posterior/patología , Células del Asta Posterior/fisiopatología , Receptor Cannabinoide CB2/genética , Receptor Cannabinoide CB2/metabolismo , Neuropatía Ciática/inmunología , Neuropatía Ciática/metabolismo , Neuropatía Ciática/fisiopatología , Médula Espinal/metabolismo , Médula Espinal/fisiopatologíaRESUMEN
Nerve injuries often lead to neuropathic pain syndrome. The mechanisms contributing to this syndrome involve local inflammatory responses, activation of glia cells, and changes in the plasticity of neuronal nociceptive pathways. Cannabinoid CB(2) receptors contribute to the local containment of neuropathic pain by modulating glial activation in response to nerve injury. Thus, neuropathic pain spreads in mice lacking CB(2) receptors beyond the site of nerve injury. To further investigate the mechanisms leading to the enhanced manifestation of neuropathic pain, we have established expression profiles of spinal cord tissues from wild-type and CB(2)-deficient mice after nerve injury. An enhanced interferon-gamma (IFN-gamma) response was revealed in the absence of CB(2) signaling. Immunofluorescence stainings demonstrated an IFN-gamma production by astrocytes and neurons ispilateral to the nerve injury in wild-type animals. In contrast, CB(2)-deficient mice showed neuronal and astrocytic IFN-gamma immunoreactivity also in the contralateral region, thus matching the pattern of nociceptive hypersensitivity in these animals. Experiments in BV-2 microglia cells revealed that transcriptional changes induced by IFN-gamma in two key elements for neuropathic pain development, iNOS (inducible nitric oxide synthase) and CCR2, are modulated by CB(2) receptor signaling. The most direct support for a functional involvement of IFN-gamma as a mediator of CB(2) signaling was obtained with a double knock-out mouse strain deficient in CB(2) receptors and IFN-gamma. These animals no longer show the enhanced manifestations of neuropathic pain observed in CB(2) knock-outs. These data clearly demonstrate that the CB(2) receptor-mediated control of neuropathic pain is IFN-gamma dependent.
Asunto(s)
Interferón gamma/inmunología , Neuralgia/inmunología , Enfermedades del Sistema Nervioso Periférico/inmunología , Receptor Cannabinoide CB2/inmunología , Transducción de Señal/inmunología , Médula Espinal/inmunología , Animales , Astrocitos/inmunología , Células Cultivadas , Técnicas de Inactivación de Genes/métodos , Hiperalgesia/inmunología , Hiperalgesia/fisiopatología , Interferón gamma/genética , Interferón gamma/metabolismo , Masculino , Ratones , Ratones Noqueados , Microglía/efectos de los fármacos , Microglía/inmunología , Microglía/metabolismo , Neuralgia/genética , Neuralgia/metabolismo , Neuronas/inmunología , Óxido Nítrico Sintasa de Tipo II/inmunología , Óxido Nítrico Sintasa de Tipo II/metabolismo , Traumatismos de los Nervios Periféricos , Nervios Periféricos/inmunología , Nervios Periféricos/fisiopatología , Enfermedades del Sistema Nervioso Periférico/genética , Enfermedades del Sistema Nervioso Periférico/metabolismo , Receptor Cannabinoide CB2/genética , Receptor Cannabinoide CB2/metabolismo , Receptores CCR2/inmunología , Receptores CCR2/metabolismo , Transducción de Señal/genética , Médula Espinal/metabolismo , Médula Espinal/fisiopatología , Regulación hacia Arriba/inmunologíaRESUMEN
Allergic contact dermatitis affects about 5% of men and 11% of women in industrialized countries and is one of the leading causes for occupational diseases. In an animal model for cutaneous contact hypersensitivity, we show that mice lacking both known cannabinoid receptors display exacerbated allergic inflammation. In contrast, fatty acid amide hydrolase-deficient mice, which have increased levels of the endocannabinoid anandamide, displayed reduced allergic responses in the skin. Cannabinoid receptor antagonists exacerbated allergic inflammation, whereas receptor agonists attenuated inflammation. These results demonstrate a protective role of the endocannabinoid system in contact allergy in the skin and suggest a target for therapeutic intervention.
Asunto(s)
Moduladores de Receptores de Cannabinoides/fisiología , Dermatitis Alérgica por Contacto/fisiopatología , Endocannabinoides , Receptor Cannabinoide CB1/fisiología , Receptor Cannabinoide CB2/fisiología , Piel/metabolismo , Animales , Ácidos Araquidónicos/metabolismo , Canfanos/administración & dosificación , Canfanos/farmacología , Cannabinoides/administración & dosificación , Cannabinoides/farmacología , Quimiocinas/fisiología , Dermatitis Alérgica por Contacto/patología , Dinitrofluorobenceno , Modelos Animales de Enfermedad , Regulación hacia Abajo , Dronabinol/administración & dosificación , Dronabinol/farmacología , Femenino , Glicéridos/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Análisis de Secuencia por Matrices de Oligonucleótidos , Piperidinas/administración & dosificación , Piperidinas/farmacología , Alcamidas Poliinsaturadas/metabolismo , Pirazoles/administración & dosificación , Pirazoles/farmacología , Receptor Cannabinoide CB1/agonistas , Receptor Cannabinoide CB1/antagonistas & inhibidores , Receptor Cannabinoide CB1/genética , Receptor Cannabinoide CB2/agonistas , Receptor Cannabinoide CB2/antagonistas & inhibidores , Receptor Cannabinoide CB2/genética , Rimonabant , Piel/patología , Regulación hacia ArribaRESUMEN
The effect of tumor necrosis factor alpha (TNF-alpha) on rabies virus (RV) infection of the mouse central nervous system (CNS) was studied, using recombinant RV engineered to express either soluble TNF-alpha [SPBN-TNF-alpha+] or insoluble membrane-bound TNF-alpha [SPBN-TNF-alpha(MEM)]. Growth curves derived from infections of mouse neuroblastoma NA cells revealed significantly less spread and production of SPBN-TNF-alpha+ than of SPBN-TNF-alpha(MEM) or SPBN-TNF-alpha-, which carries an inactivated TNF-alpha gene. The expression of soluble or membrane-bound TNF-alpha was not associated with increased cell death or induction of alpha/beta interferons. Brains of mice infected intranasally with SPBN-TNF-alpha+ showed significantly less virus spread than did mouse brains after SPBN-TNF-alpha- infection, and none of the SPBN-TNF-alpha+-infected mice succumbed to RV infection, whereas 80% of SPBN-TNF-alpha- -infected mice died. Reduced virus spread in SPBN-TNF-alpha+-infected mouse brains was paralleled by enhanced CNS inflammation, including T-cell infiltration and microglial activation. These data suggest that TNF-alpha exerts its protective activity in the brain directly through an as yet unknown antiviral mechanism and indirectly through the induction of inflammatory processes in the CNS.