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Background: Interaction of CD200 with its receptor CD200R has an immunoregulatory role and attenuates various types of neuroinflammatory diseases., Methods: Immunofluorescence staining, western blot analysis, and RT-PCR were used to investigate the modulatory effects of CD200 fusion protein (CD200Fc) on activation of microglia and astrocytes as well as synthesis of pro- (TNF, IL-1β, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines in the L4-L5 spinal cord segments in relation to behavioral signs of neuropathic pain after unilateral sterile chronic constriction injury (sCCI) of the sciatic nerve. Withdrawal thresholds for mechanical hypersensitivity and latencies for thermal hypersensitivity were measured in hind paws 1 day before operation; 1, 3, and 7 days after sCCI operation; and then 5 and 24 h after intrathecal application of artificial cerebrospinal fluid or CD200Fc., Results: Seven days from sCCI operation and 5 h from intrathecal application, CD200Fc reduced mechanical and thermal hypersensitivity when compared with control animals. Simultaneously, CD200Fc attenuated activation of glial cells and decreased proinflammatory and increased anti-inflammatory cytokine messenger RNA (mRNA) levels. Administration of CD200Fc also diminished elevation of CD200 and CD200R proteins as a concomitant reaction of the modulatory system to increased neuroinflammatory reactions after nerve injury. The anti-inflammatory effect of CD200Fc dropped at 24 h after intrathecal application., Conclusions: Intrathecal administration of the CD200R1 agonist CD200Fc induces very rapid suppression of neuroinflammatory reactions associated with glial activation and neuropathic pain development. This may constitute a promising and novel therapeutic approach for the treatment of neuropathic pain.

The central nervous system (CNS) innate immune response includes an arsenal of molecules and receptors expressed by professional phagocytes, glial cells and neurons that is involved in host defence and clearance of toxic and dangerous cell debris. However, any uncontrolled innate immune responses within the CNS are widely recognized as playing a major role in the development of autoimmune disorders and neurodegeneration, with multiple sclerosis (MS) Alzheimer's disease (AD) being primary examples. Hence, it is important to identify the key regulatory mechanisms involved in the control of CNS innate immunity and which could be harnessed to explore novel therapeutic avenues. Neuroimmune regulatory proteins (NIReg) such as CD95L, CD200, CD47, sialic acid, complement regulatory proteins (CD55, CD46, fH, C3a), HMGB1, may control the adverse immune responses in health and diseases. In the absence of these regulators, when neurons die by apoptosis, become infected or damaged, microglia and infiltrating immune cells are free to cause injury as well as an adverse inflammatory response in acute and chronic settings. We will herein provide new emphasis on the role of the pair CD200-CD200R in MS and its experimental models: experimental autoimmune encephalomyelitis (EAE) and Theiler's virus induced demyelinating disease (TMEV-IDD). The interest of the cannabinoid system as inhibitor of inflammation prompt us to introduce our findings about the role of endocannabinoids (eCBs) in promoting CD200-CD200 receptor (CD200R) interaction and the benefits caused in TMEV-IDD. Finally, we also review the current data on CD200-CD200R interaction in AD, as well as, in the aging brain.

Microglia-neuron interaction is a complex process involving a plethora of ligands and receptors. The outcome of this intricate process will depend on the prevailing signals (i.e., whether the microglial cells will produce pro-inflammatory cytokines and/or phagocyte a dying neuron or whether it will produce neurotrophic factors and support neuronal growth, among other possible scenarios). In order to study this complex process, several tools have been developed, ranging from in vivo models (knockout and knock-in mice, conditional transgenic mice, imaging techniques) to in vitro models (microglia-neuron cocultures, transwell cell cultures). Here we describe a protocol for primary microglia-neuron coculture. this coculture allows to combine neurons and microglial cells coming from wild-type and KO mice, making this coculture a useful method to study in vitro the interaction of different sets of ligand-receptor.

The endocannabinoid anandamide (AEA) is released by macrophages and microglia on pathological neuroinflammatory conditions such as multiple sclerosis (MS). CD200 is a membrane glycoprotein expressed in neurons that suppresses immune activity via its receptor (CD200R) mainly located in macrophages/microglia. CD200-CD200R interactions contribute to the brain immune privileged status. In this study, we show that AEA protects neurons from microglia-induced neurotoxicity via CD200-CD200R interaction. AEA increases the expression of CD200R1 in LPS/IFN-γ activated microglia through the activation of CB(2) receptors. The neuroprotective effect of AEA disappears when microglial cells derive from CD200R1(-/-) mice. We also show that engagement of CD200R1 by CD200Fc decreased the production of the proinflammatory cytokines IL-1β and IL-6, but increased IL-10 in activated microglia. In the chronic phases of Theiler's virus-induced demyelinating disease (TMEV-IDD) the expression of CD200 and CD200R1 was reduced in the spinal cord. AEA-treated animals up-regulated the expression of CD200 and CD200R1, restoring levels found in sham animals together with increased expression of IL-10 and reduced expression of IL-1β and IL-6. Treated animals also improved their motor behavior. Because AEA up-regulated the expression of CD200R1 in microglia, but failed to enhance CD200 in neurons we suggest that AEA-induced up-regulation of CD200 in TMEV-IDD is likely due to IL-10 as this cytokine increases CD200 in neurons. Our findings provide a new mechanism of action of AEA to limit immune response in the inflamed brain., (Copyright © 2012 Wiley Periodicals, Inc.)

Tissue plasminogen activator (tPA) is the only available treatment for acute stroke. In addition to its vascular fibrinolytic action, tPA exerts various effects within the brain, ranging from synaptic plasticity to control of cell fate. To date, the influence of tPA in the ischemic brain has only been investigated on neuronal, microglial, and endothelial fate. We addressed the mechanism of action of tPA on oligodendrocyte (OL) survival and on the extent of white matter lesions in stroke. We also investigated the impact of aging on these processes. We observed that, in parallel to reduced levels of tPA in OLs, white matter gets more susceptible to ischemia in old mice. Interestingly, tPA protects murine and human OLs from apoptosis through an unexpected cytokine-like effect by the virtue of its epidermal growth factor-like domain. When injected into aged animals, tPA, although toxic to the gray matter, rescues white matter from ischemia independently of its proteolytic activity. These studies reveal a novel mechanism of action of tPA and unveil OL as a target cell for cytokine effects of tPA in brain diseases. They show overall that tPA protects white matter from stroke-induced lesions, an effect which may contribute to the global benefit of tPA-based stroke treatment.

The endocannabinoid system represents a novel therapeutic target for autoimmune and chronic inflammatory diseases. IL-12 and IL-23 are functionally related heterodimeric cytokines that play a crucial role in the pathogenesis of multiple sclerosis (MS). In the present study we investigated the effects of the endocannabinoid anandamide (AEA) on the inducible expression of the biologically active cytokines IL-12p70 and IL-23, and their forming subunits, in activated microglial cells. We also studied the signalling pathways involved in the regulation of IL-12p70/IL-23 expression and addressed the possible interactions of AEA with these pathways. Here, we show that AEA was capable to inhibit the production of biologically active IL-12p70 and IL-23, and their subunits, by activated human and murine microglial cultures. Treatment of activated microglial cells with inhibitors of several mitogen-activated protein kinase (MAPK) reveals that AEA acts through the ERK1/2 and JNK pathways to down-regulate IL-12p70 and IL-23. These effects were partially mediated by CB2 receptor activation. Together, our results provide the first demonstration of a role of AEA in inhibiting IL-12p70/IL-23 axis in human and murine microglial cells via the CB2 receptor and suggest that the pharmacological manipulation of the endocannabinoid system is a potential tool for treating brain inflammatory and autoimmune diseases, like MS.

Background: Cannabinoids have been shown to exert beneficial actions in different animal models of multiple sclerosis (MS). However, the use of cannabinoids compounds in human therapy is greatly limited by their psychoactivity. Thus, new hopes in MS therapy have arisen from the evidence for a cannabinoid receptor, termed CB2, which is devoid of psychoactive effects in animal models., Objective: This review discusses the different mechanisms by which CB2 activation could induce therapeutic actions in MS., Methods: Particular focus is given to the potential effects on inflammation/autoimmunity, remyelination and neuroprotection., Conclusion: This review discusses the importance of glial cells in sustaining these effects, as well as the putative secondary effects that would limit the use of CB2 agonists in the treatment of MS.

Inflammation, autoimmune response, demyelination and axonal damage are thought to participate in the pathogenesis of multiple sclerosis (MS). Understanding whether axonal damage causes or originates from demyelination is a crucial issue. Excitotoxic processes may be responsible for white matter and axonal damage. Experimental and clinical studies indicate that cannabinoids could prove efficient in the treatment of MS. Using a chronic model of MS in mice, we show here that clinical signs and axonal damage in the spinal cord were reduced by the AMPA antagonist, NBQX. Amelioration of symptomatology by the synthetic cannabinoid HU210 was also accompanied by a reduction of axonal damage in this model. Moreover, HU210 reduced AMPA-induced excitotoxicity both in vivo and in vitro through the obligatory activation of both CB1 and CB2 cannabinoid receptors. Together, these data underline the implication of excitotoxic processes in demyelinating pathologies such as MS and the potential therapeutic properties of cannabinoids.

There is a growing amount of evidence suggesting that cannabinoids may be neuroprotective in central nervous system inflammatory conditions. Advances in the understanding of the physiology and pharmacology of the cannabinoid system have potentiated the interest in cannabinoids as potential therapeutic targets. Here our aim was to update the actions of cannabinoids on immune system and glial cells and their implications on multiple sclerosis. We also show our results on the modulation of cytokines of the IL-12 family by cannabinoids in macrophages and brain microglia. We used murine primary cultures of macrophage and microglia activated by lipopolysaccharide/IFN-gamma and Theiler's virus to study the effects of cannabinoids on the regulation of IL-12 and IL-23 mRNA and protein IL-12p40, evaluated by RT-PCR and ELISA, respectively. Cannabinoids negatively regulate the production of these cytokines by microglial cells in part due to the activation of CB(2) receptors. The effects of cannabinoids on cytokine brain work and on the regulation of neuroinflammatory processes may affect chronic inflammatory demyelinating diseases such as multiple sclerosis., (Copyright 2007 S. Karger AG, Basel.)