Neuroprotective Effect Is Driven Through the Upregulation of CB1 Receptor in Experimental Autoimmune Encephalomyelitis

Enhancing axonal myelination in seniors: A review exploring the potential impact cannabis has on myelination in the aged brain

Consumption of cannabis is on the rise as public opinion trends toward acceptance and its consequent legalization. Specifically, the senior population is one of the demographics increasing their use of cannabis the fastest, but research aimed at understanding cannabis' impact on the aged brain is still scarce. Aging is characterized by many brain changes that slowly alter cognitive ability. One process that is greatly impacted during aging is axonal myelination. The slow degradation and loss of myelin (i.e., demyelination) in the brain with age has been shown to associate with cognitive decline and, furthermore, is a common characteristic of numerous neurological diseases experienced in aging. It is currently not known what causes this age-dependent degradation, but it is likely due to numerous confounding factors (i.e., heightened inflammation, reduced blood flow, cellular senescence) that impact the many cells responsible for maintaining overall homeostasis and myelin integrity. Importantly, animal studies using non-human primates and rodents have also revealed demyelination with age, providing a reliable model for researchers to try and understand the cellular mechanisms at play. In rodents, cannabis was recently shown to modulate the myelination process. Furthermore, studies looking at the direct modulatory impact cannabis has on microglia, astrocytes and oligodendrocyte lineage cells hint at potential mechanisms to prevent some of the more damaging activities performed by these cells that contribute to demyelination in aging. However, research focusing on how cannabis impacts myelination in the aged brain is lacking. Therefore, this review will explore the evidence thus far accumulated to show how cannabis impacts myelination and will extrapolate what this knowledge may mean for the aged brain.

Treadmill Exercise Prevents Cognitive Impairments in Adolescent Intermittent Ethanol Rats by Reducing the Excessive Activation of Microglia Cell in the Hippocampus

The excessive activation of microglia cell induced by adolescent intermittent ethanol (AIE) leads to neuroinflammation in the hippocampus. The endocannabinoid system plays a key role in the modulation of microglia activation. Accumulating evidence suggests that regular exercise improves learning and memory deficits in AIE models. The purpose of this study was to explore the effects of treadmill exercise intervention on the cognitive performance, activation of microglia cells and the expression of monoacylglycerol lipase (MAGL), cannabinoid receptor type 1 (CB1R) and cannabinoid receptor type 2 (CB2R) in the hippocampus of AIE rats. Here, we show that AIE rats exhibited cognitive impairments, whereas the treadmill exercise improves the cognitive performance in AIE rats. In order to explore the possible mechanisms for the exercise-induced attenuation of cognitive disorder, we examined the neuroinflammation in the hippocampus. We found that treadmill exercise led to the decrease in the level of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and the increase in the level of anti-inflammatory cytokine (IL-10). In addition, we found that treadmill exercise reduced the excessive activation of the microglia cell in the hippocampus of AIE rats. Finally, we found that AIE led to a decrease in the expression of CB1R and CB2R in the hippocampus; however, the treadmill exercise further decreased the expression of CB2R in the hippocampus of AIE rats. Our results suggest that treadmill exercise attenuates AIE-induced neuroinflammation and the excessive activation of hippocampus microglial cells, which may contribute to the exercise-induced improvement of cognitive performance in AIE rats.

Inducible Nitric Oxide Synthase Inhibition in the Medial Prefrontal Cortex Attenuates the Anxiogenic-Like Effect of Acute Restraint Stress via CB1 Receptors

Stress exposure can result in several proinflammatory alterations in the brain, including overexpression of the inducible isoform of nitric oxide synthase (iNOS) in the medial prefrontal cortex (mPFC). These changes may be involved in the development of many psychiatric conditions. However, it is unknown if iNOS in mPFC plays a significant role in stress-induced behavioral changes. The endocannabinoid (ECB) system is also influenced by stress. Its activation seems to be a counter regulatory mechanism to prevent or decrease the stress-mediated neuroinflammatory consequences. However, it is unclear if the ECB system and iNOS interact to influence stress consequences. This study aimed to test the hypothesis that the anti-stress effect of iNOS inhibition in mPFC involves the local ECB system, particularly the CB₁ cannabinoid receptors. Male Wistar rats with guide cannula aimed at the mPFC were submitted to acute restraint stress (RS) for 2 h. In the following morning, rats received bilateral microinjections of vehicle, AM251 (CB₁ antagonist; 100 pmol), and/or 1400W (iNOS selective inhibitor; 10^-4, 10^-3, or 10^-2 nmol) into the prelimbic area of mPFC (PL-mPFC) before being tested in the elevated plus-maze (EPM). iNOS inhibition by 1400W prevented the anxiogenic-like effect observed in animals submitted to RS. The drug did not promote behavior changes in naive animals, demonstrating a stress-dependent effect. The 1400W-anti-stress effect was prevented by local pretreatment with AM251. Our data suggest that iNOS inhibition may facilitate the local endocannabinoid signaling, attenuating stress effects.

Selective Endocannabinoid Reuptake Inhibitor WOBE437 Reduces Disease Progression in a Mouse Model of Multiple Sclerosis

The modulation of the endocannabinoid system (ECS) has shown positive results in animal models of multiple sclerosis (MS) and immune and inflammatory disorders. However, chronic administration of CB1 receptor agonists and degrading enzyme inhibitors can lead to CB1 receptor desensitization and sedation. WOBE437 is the prototype of a new class of ECS modulators named selective endocannabinoid reuptake inhibitors (SERIs), which mildly and selectively increase central endocannabinoid levels with a self-limiting mode of action. In previous studies, WOBE437 demonstrated analgesic, anxiolytic, and anti-inflammatory effects. Here, we tested the therapeutic potential of WOBE437 in a clinically relevant mouse model of MS (experimental autoimmune encephalomyelitis). C57BL/6 mice were administered WOBE437 (10 mg/kg, 20 days) or vehicle using two therapeutic options: (1) starting the treatment at the disease onset or (2) before reaching the peak of the disease. In both strategies, WOBE437 significantly reduced disease severity and accelerated recovery through CB1 and CB2 receptor-dependent mechanisms. At the peak of the disease, WOBE437 increased endocannabinoid levels in the cerebellum, concurring with a reduction of central nervous system (CNS)-infiltrating immune cells and lower microglial proliferation. At the end of treatment, endocannabinoid levels were mildly increased in brain, cerebellum, and plasma of WOBE437-treated mice, without desensitization of CB1 receptor in the brain and cerebellum. In a mouse model of spasticity (Straub test), WOBE437 (10 mg/kg) induced significant muscle relaxation without eliciting the typical sedative effects associated with muscle relaxants or CB1 receptor agonists. Collectively, our results show that WOBE437 (and SERIs) may represent a novel therapeutic strategy for slowing MS progression and control major symptoms.

Hemopressin as a breakthrough for the cannabinoid field

Hemopressin (PVNFKFLSH in rats, and PVNFKLLSH in humans and mice), a fragment derived from the α-chain of hemoglobin, was the first peptide described to have type 1 cannabinoid receptor activity. While hemopressin was shown to have inverse agonist/antagonistic activity, extended forms of hemopressin (i.e. RVD-hemopressin, also called pepcan-12) exhibit type 1 and type 2 cannabinoid receptor agonistic/allosteric activity, and recent studies suggest that they can activate intracellular mitochondrial cannabinoid receptors. Therefore, hemopressin and hemopressin-related peptides could have location-specific and biased pharmacological action, which would increase the possibilities for fine-tunning and broadening cannabinoid receptor signal transduction. Consistent with this, hemopressins were shown to play a role in a number of physiological processes including antinociceptive and anti-inflammatory activity, regulation of food intake, learning and memory. The shortest active hemopressin fragment, NFKF, delays the first seizure induced by pilocarpine, and prevents neurodegeneration in an experimental model of autoimmune encephalomyelitis. These functions of hemopressins could be due to engagement of both cannabinoid and non-cannabinoid receptor systems. Self-assembled nanofibrils of hemopressin have pH-sensitive switchable surface-active properties, and show potential as inflammation and cancer targeted drug-delivery systems. Upon disruption of the self-assembled hemopressin nanofibril emulsion, the intrinsic analgesic and anti-inflammatory properties of hemopressin could help bolster the therapeutic effect of anti-inflammatory or anti-cancer formulations. In this article, we briefly review the molecular and behavioral pharmacological properties of hemopressins, and summarize studies on the intricate and unique mode of generation and binding of these peptides to cannabinoid receptors. Thus, the review provides a window into the current status of hemopressins in expanding the repertoire of signaling and activity by the endocannabinoid system, in addition to their new potential for pharmaceutic formulations.

Role of cannabinoids in alcohol-induced neuroinflammation

Alcohol is a psychoactive substance highly used worldwide, whose harmful use might cause a broad range of mental and behavioural disorders. Underlying brain impact, the neuroinflammatory response induced by alcohol is recognised as a key contributing factor in the progression of other neuropathological processes, such as neurodegeneration. These sequels are determined by multiple factors, including age of exposure. Strikingly, it seems that the endocannabinoid system modulation could regulate the alcohol-induced neuroinflammation. Although direct CB1 activation can worsen alcohol consequences, targeting other components of the expanded endocannabinoid system may counterbalance the pro-inflammatory response. Indeed, specific modulations of the expanded endocannabinoid system have been proved to exert anti-inflammatory effects, primarily through the CB2 and PPARγ signalling. Among them, some endo- and exogeneous cannabinoids can block certain pro-inflammatory mediators, such as NF-κB, thereby neutralizing the neuroinflammatory intracellular cascades. Furthermore, a number of cannabinoids are able to activate complementary anti-inflammatory pathways, which are necessary for the transition from chronically overactivated microglia to a regenerative microglial phenotype. Thus, cannabinoid modulation provides cooperative anti-inflammatory mechanisms that may be advantageous to resolve a pathological neuroinflammation in an alcohol-dependent context.

Endocannabinoid Modulation of Microglial Phenotypes in Neuropathology

Microglia, the resident immune cells of the central nervous system, mediate brain homeostasis by controlling neuronal proliferation/differentiation and synaptic activity. In response to external signals from neuropathological conditions, homeostatic (M0) microglia can adopt one of two activation states: the classical (M1) activation state, which secretes mediators of the proinflammatory response, and the alternative (M2) activation state, which presumably mediates the resolution of neuroinflammation and tissue repair/remodeling. Since chronic inflammatory activation of microglia is correlated with several neurodegenerative diseases, functional modulation of microglial phenotypes has been considered as a potential therapeutic strategy. The endocannabinoid (eCB) system, composed of cannabinoid receptors and ligands and their metabolic/biosynthetic enzymes, has been shown to activate anti-inflammatory signaling pathways that modulate immune cell functions. Growing evidence has demonstrated that endogenous, synthetic, and plant-derived eCB agonists possess therapeutic effects on several neuropathologies; however, the molecular mechanisms that mediate the anti-inflammatory effects have not yet been identified. Over the last decade, it has been revealed that the eCB system modulates microglial activation and population. In this review, we thoroughly examine recent studies on microglial phenotype modulation by eCB in neuroinflammatory and neurodegenerative disease conditions. We hypothesize that cannabinoid 2 receptor (CB2R) signaling shifts the balance of expression between neuroinflammatory (M1-type) genes, neuroprotective (M2-type) genes, and homeostatic (M0-type) genes toward the latter two gene expressions, by which microglia acquire therapeutic functionality.

Inflammatory biomarkers in children with cerebral palsy: A systematic review

BACKGROUND

An exacerbated systemic inflammatory response has been associated with the occurrence of central nervous system injuries that may determine, in long term, motor, sensorial and cognitive disabilities. Persistence of this exacerbated inflammatory response seems to be involved in the pathophysiology of cerebral palsy (CP).

METHODS

A systematic search was conducted in Bireme, Embase, PubMed and Scopus including studies that were published until August 2019. The key words used were "cerebral palsy", "brain injury", "inflammation", "oxidative stress", "cytokines", "chemokines", "neuropsychomotor development", "neurodevelopment outcomes" and "child". The quality of the eligible studies was determined according to the criteria suggested by the Newcastle-Ottawa Scale (NOS).

RESULTS

Fourteen eligible studies aimed to investigate the association between peripheral inflammatory molecules and neurodevelopment in infants. The studies differed regarding CP-related risk factors and its classification. Inflammatory proteins were measured in blood, plasma, serum, cerebrospinal fluid or urine. In ten studies, higher circulating levels of cytokines, including IL-1β, IL-6, TNF and CXCL8/IL-8, were associated with abnormal neurological findings.

CONCLUSION

The investigation of the potential association between inflammatory molecules and neurological development in children with CP requires further original studies in order to clarify the influence of prenatal and perinatal inflammation on neurological outcomes.

Mdivi-1, a mitochondrial fission inhibitor, modulates T helper cells and suppresses the development of experimental autoimmune encephalomyelitis

Background

Unrestrained activation of Th1 and Th17 cells is associated with the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). While inactivation of dynamin-related protein 1 (Drp1), a GTPase that regulates mitochondrial fission, can reduce EAE severity by protecting myelin from demyelination, its effect on immune responses in EAE has not yet been studied.

Methods

We investigated the effect of Mdivi-1, a small molecule inhibitor of Drp1, on EAE. Clinical scores, inflammation, demyelination and Drp1 activation in the central nervous system (CNS), and T cell responses in both CNS and periphery were determined.

Results

Mdivi-1 effectively suppressed EAE severity by reducing demyelination and cellular infiltration in the CNS. Mdivi-1 treatment decreased the phosphorylation of Drp1 (ser616) on CD4⁺ T cells, reduced the numbers of Th1 and Th17 cells, and increased Foxp3⁺ regulatory T cells in the CNS. Moreover, Mdivi-1 treatment effectively inhibited IFN-γ⁺, IL-17⁺, and GM-CSF⁺ CD4⁺ T cells, while it induced CD4⁺ Foxp3⁺ regulatory T cells in splenocytes by flow cytometry.

Conclusions

Together, our results demonstrate that Mdivi-1 has therapeutic potential in EAE by modulating the balance between Th1/Th17 and regulatory T cells.

Gut microbiota, cannabinoid system and neuroimmune interactions: New perspectives in multiple sclerosis

The gut microbiota plays a fundamental role on the education and function of the host immune system. Immunological dysregulation is the cause of numerous human disorders such as autoimmune diseases and metabolic disorders frequently associated with inflammatory processes therefore is critical to explore novel mechanisms involved in maintaining the immune system homeostasis. The cannabinoid system and related bioactive lipids participate in multiple central and peripheral physiological processes that affect metabolic, gastrointestinal and neuroimmune regulatory mechanisms displaying a modulatory role and contributing to the maintenance of the organism's homeostasis. In this review, we gather the knowledge on the gut microbiota-endocannabinoids interactions and their impact on autoimmune disorders such as inflammatory bowel disease, rheumatoid arthritis and particularly, multiple sclerosis (MS) as the best example of a CNS autoimmune disorder. Furthermore, we contribute to this field with new data on changes in many elements of the cannabinoid system in a viral model of MS after gut microbiota manipulation by both antibiotics and probiotics. Finally, we highlight new therapeutic opportunities, under an integrative view, targeting the eCBS and the commensal microbiota in the context of neuroinflammation and MS.

The inhibition of CB1 receptor accelerates the onset and development of EAE possibly by regulating microglia/macrophages polarization

Cannabinoid 1 receptor (CB₁R) regulates the neuro-inflammatory and neurodegenerative damages of experimental autoimmune encephalomyelitis (EAE) and of multiple sclerosis (MS). The mechanism by which CB₁R inhibition exerts inflammatory effects is still unclear. Here, we explored the cellular and molecular mechanisms of CB₁R in the treatment of EAE by using a specific and selective CB₁R antagonist SR141716A. Our study demonstrated that SR141716A accelerated the clinical onset and development of EAE, accompanied by body weight loss. SR141716A significantly up-regulated the expression of toll like receptor-4 (TLR-4) and nuclear factor-kappaB/p65 (NF-κB/p65) on microglia/macrophages of EAE mice as well as levels of inflammatory factors (TNF-α, IL-1β, IL-6) and chemokines (MCP-1, CX3CL1), accompanied by the shifts of cytokines from Th2 (IL-4, IL-10) to Th1 (IFN-γ)/Th17 (IL-17) in the spinal cords of EAE mice. Similar changes happened on splenic mononuclear cells (MNCs) except chemokine CX3CL1. Consistently, SR141716A promoted BV-2 microglia to release inflammatory factors (TNF-α, IL-1β, IL-6) while inhibited the production of IL-10 and chemokines (MCP-1, CX3CL1). Furthermore, when splenic CD4⁺ T cells co-cultured with SR141716A-administered BV-2 microglia, the levels of IL-4 and IL-10 were decreased while production of IL-17 and IFN-γ increased significantly. Our research indicated that inhibition of CB₁R induced M1 phenotype-Th17 axis changed of microglia/macrophages through TLR-4 and NF-κB/p65 which accelerated the onset and development of EAE. Therefore, CB₁R may be a promising target for the treatment of MS/EAE, but its complexity remains to be carefully considered and studied in further clinical application.

Impact of aging immune system on neurodegeneration and potential immunotherapies

The interaction between the nervous and immune systems during aging is an area of avid interest, but many aspects remain unclear. This is due, not only to the complexity of the aging process, but also to a mutual dependency and reciprocal causation of alterations and diseases between both the nervous and immune systems. Aging of the brain drives whole body systemic aging, including aging-related changes of the immune system. In turn, the immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution that are sources of chronic inflammation in the elderly (termed inflammaging), potentially induces brain aging and memory loss in a reciprocal manner. Therefore, immunotherapeutics including modulation of inflammation, vaccination, cellular immune therapies and "protective autoimmunity" provide promising approaches to rejuvenate neuroinflammatory disorders and repair brain injury. In this review, we summarize recent discoveries linking the aging immune system with the development of neurodegeneration. Additionally, we discuss potential rejuvenation strategies, focusing aimed at targeting the aging immune system in an effort to prevent acute brain injury and chronic neurodegeneration during aging.

Toll-like receptor signalling as a cannabinoid target in Multiple Sclerosis

Toll-like receptors (TLRs) are the sensors of pathogen-associated molecules that trigger tailored innate immune intracellular signalling responses to initiate innate immune reactions. Data from the experimental autoimmune encephalomyelitis (EAE) model indicates that TLR signalling machinery is a pivotal player in the development of murine EAE. To compound this, data from human studies indicate that complex interplay exists between TLR signalling and Multiple Sclerosis (MS) pathogenesis. Cannabis-based therapies are in clinical development for the management of a variety of medical conditions, including MS. In particular Sativex^®, a combination of plant-derived cannabinoids, is an oromucosal spray with efficacy in MS patients, particularly those with neuropathic pain and spasticity. Despite this, the precise cellular and molecular mechanisms of action of Sativex^® in MS patients remains unclear. This review will highlight evidence that novel interplay exists between the TLR and cannabinoid systems, both centrally and peripherally, with relevance to the pathogenesis of MS. This article is part of the Special Issue entitled 'Lipid Sensing G Protein-Coupled Receptors in the CNS'.