Cannabinoids ameliorate disease progression in a model of multiple sclerosis in mice, acting preferentially through CB₁ receptor-mediated anti-inflammatory effects

Eva de Lago^a^,^b^,^c,
Miguel Moreno-Martet^a^,^b^,^c,
Ana Cabranes^a^,¹,
José A. Ramos^a^,^b^,^c,
Javier Fernández-Ruiz^a^,^b^,^c^,^,

^a Departamento de Bioquímica y Biología Molecular, Instituto Universitario de Investigación en Neuroquímica, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain
^b Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain
^c Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain

Received 29 October 2011. Revised 26 January 2012. Accepted 30 January 2012. Available online 8 February 2012.

http://dx.doi.org/10.1016/j.neuropharm.2012.01.030, How to Cite or Link Using DOI

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1. Introduction

2. Materials and methods

3. Results

4. Discussion

Acknowledgments

References

Abstract

Multiple sclerosis (MS) is an autoimmune disease that affects the CNS and it is characterized by inflammation, demyelination, remyelination, gliosis and axonal damage that occur mainly in the spinal cord. Cannabinoids have been proposed as promising therapeutic agents in MS given their capability to alleviate specific MS symptoms (e.g., spasticity, pain). Although MS has been considered mainly an inflammatory disorder, recent evidence, however, revealed the importance of neurodegenerative events, opening the possibility that cannabinoid agonists, given their cytoprotective properties, may also serve to

reduce oligodendrocyte death and axonal damage in MS. Thus, the treatment with WIN55,512-2, a potent CB₁ and CB₂ agonist, was reported to be effective to ameliorate tremor and spasticity in mice with chronic relapsing experimental autoimmune encephalomyelitis, a murine model of MS, but also to delay disease progression in this and other murine models of MS. The purpose of this investigation was to further explore the mechanism(s) underlying the amelioration in disease progression caused by WIN55,212-2. We have particularly focused on anti-glutamatergic and anti-inflammatory effects of this cannabinoid agonist. In this study, we used mice treated with myelin oligodendrocyte glycoprotein (MOG) that induces a progressive pattern of EAE and conducted the pharmacological experiments in early stages of the disease. As expected, the administration of WIN55,512-2 (5 mg/kg, i.p) had a positive effect in reducing neurological disability and improving motor coordination of EAE mice. Levels of glutamate and GABA in the spinal cord and also in the brainstem of EAE mice were similar to control animals, and, accordingly, they were not altered by the treatment with WIN55,212-2. However, EAE mice showed some subtle alterations in mRNA levels for the glutamate transporter GLT1 and, to a lesser extent, GLAST too, changes that were altered by the treatment with WIN55,212-2 in the spinal cord, but not in the brainstem. Regarding to inflammatory responses, EAE mice showed a marked up-regulation in mRNA levels for COX-2, inducible NOS and TNF-α in the spinal cord and the brainstem, these responses being attenuated after the treatment with WIN55,212-2. We also observed the presence of cell aggregates in the spinal cord of EAE mice that were significantly attenuated by the treatment with WIN55,212-2. Immunohistochemical analysis (with Iba-1 and Cd11b) of these aggregates indicated that they corresponded to microglia (resident macrophages) and peripheral macrophages. Lastly, experiments conducted with selective antagonists for the CB₁ (e.g. rimonabant) or CB₂ (e.g. AM-630) receptors revealed that WIN55,212-2 effects in EAE mice were mediated by the activation of CB₁ but not CB₂ receptors, as reflected the reversion of positive effects of this cannabinoid on neurological decline, TNF-α generation and accumulation of cell aggregates in the spinal cord with rimonabant, but not with AM-630. This was concordant with the lack of positive effects on neurological decline observed in EAE mice when they received HU-308, a selective CB₂ receptor agonist, instead WIN55,212-2. In summary, the treatment of EAE mice with the cannabinoid agonist WIN55,512-2 reduced their neurological disability and the progression of the disease. This effect was exerted through the activation of CB₁ receptors, which would exert a positive influence in the reduction of inflammatory events linked to the pathogenesis of this disease.

Highlights

► Treatment with WIN55,212-2 improved neurological deficits in EAE mice. ► WIN55,212-2 effects are related to a reduction in some proinflammatory mediators. ► WIN55,212-2 effects are produced by the participation of CB₁ but not CB₂ receptors.