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Cannabinoids and Neuro-Inflammation: Regulation of Brain Immune Response
Abstract and Figures
Background:
Cannabinoid receptors are involved in the neuro-pathogenic mechanisms of inflammatory conditions of the central nervous system and their expression can be modulated during diseases.
Methods:
In this manuscript we highlight the function of cannabinoid receptors, their signalling and expression at peripheral and central levels in order to understand their implication in neuro-inflammation and review the effects of cannabinoids in neuro-inflammatory disorders.
Results:
Brain inflammatory processes are characterized by infiltration of numerous types of cells: both peripheral and brain resident immune cells and other neuronal cells. The disruption of the blood brain barrier favours cell infiltration in the central nervous system with consequent neuronal damage, a common event in many neuro-inflammatory diseases. Cannabinoids affect brain adaptive and immune response, regulate inflammatory mediators and can exert a role in blood brain barrier damage prevention.
Conclusion:
Various patents describe the beneficial properties of cannabinoids in numerous neurodegenerative diseases with inflammatory components and overall effects support the therapeutic application of cannabinoids.
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... Cannabinoids, endogenous, synthetic, and natural types have been generally associated with anti-neuroinflammation by downregulating pro-inflammatory and/or upregulating anti-inflammatory cytokines typically through CB2Rs [93][94][95]. However, there is growing evidence demonstrating that natural and synthetic cannabinoids can indeed upregulate pro-inflammatory cytokines and thus possibly induce neuroinflammation and/or depression. ...
... Cannabinoids, endogenous, synthetic, and natural types have been generally associated with anti-neuroinflammation by downregulating pro-inflammatory and/or upregulating anti-inflammatory cytokines typically through CB 2 Rs [93][94][95]. However, there is growing evidence demonstrating that natural and synthetic cannabinoids can indeed upregulate pro-inflammatory cytokines and thus possibly induce neuroinflammation and/or depression. ...
Substance use/abuse is one of the main causes of depressive symptoms. Cannabis and synthetic cannabinoids in particular gained significant popularity in the past years. There is an increasing amount of clinical data associating such compounds with the inflammatory component of depression, indicated by the up-regulation of pro-inflammatory cytokines. Pro-inflammatory cytokines are also well-known to regulate the enzymes of the kynurenine pathway (KP), which is responsible for metabolizing tryptophan, a precursor in serotonin synthesis. Enhanced pro-inflammatory cytokine levels may over-activate the KP, leading to tryptophan depletion and reduced serotonin levels, which can subsequently precipitate depressive symptoms. Therefore, such mechanism might represent a possible link between the endocannabinoid system (ECS) and the KP in depression, via the inflammatory and dysregulated serotonergic component of the disorder. This review will summarize the data regarding those natural and synthetic cannabinoids that increase pro-inflammatory cytokines. Furthermore, the data on such cytokines associated with KP activation will be further reviewed accordingly. The interaction of the ECS and the KP has been postulated and demonstrated in some studies previously. This review will further contribute to this yet less explored connection and propose the KP to be the missing link between cannabinoid-induced inflammation and depressive symptoms.
... In this regard, CB1Rs and CB2Rs are present in both microglia and astrocytes (Navarrete and Araque, 2008;Stella, 2010), and their expression depends on the microglial activation profile. Further evidence supports the antiinflammatory role of endogenous, natural, and synthetic cannabinoids, which can downregulate inflammatory and upregulate antiinflammatory cytokines acting at CB2Rs (Klein et al., 2000;Massi et al., 2006;Ranieri et al., 2016). ...
... In this regard, CB1Rs and CB2Rs are present in both microglia and astrocytes [15,16], and their expression depends on the microglial activation pro le. Further evidence supports the anti-in ammatory role of endogenous, natural, and synthetic cannabinoids, which can downregulate in ammatory and upregulate antiin ammatory cytokines acting at CB2Rs [17][18][19]. ...
Background
The misuse of synthetic cannabinoid receptor agonists (SCRAs) poses major psychiatric risks. We previously showed that repeated exposure to the prototypical SCRA JWH-018 induces alterations in dopamine (DA) transmission, abnormalities in the emotional state, and glial cell activation in the mesocorticolimbic DA circuits of rats. Despite growing evidence suggesting the relationship between drugs of abuse and neuroinflammation, little is known about the impact of SCRA on the neuroimmune system. Here, we investigated whether repeated JWH-018 exposure altered neuroimmune signaling, which could be correlated with previously reported central effects.
Methods
Adult male Sprague‒Dawley rats were exposed to JWH-018 (0.25 mg/kg, i.p.) for fourteen consecutive days, and the expression of cytokines, chemokines, and growth factors was measured seven days after treatment discontinuation in the striatum, cortex, and hippocampus. Moreover, microglial (ionized calcium binding adaptor molecule 1, IBA-1) and astrocyte (glial fibrillary acidic protein, GFAP) activation markers were evaluated in the caudate-putamen (CPu).
Results
Repeated JWH-018 exposure induces a perturbation of neuroimmune signaling specifically in the striatum, as shown by increased levels of cytokines [interleukins (IL) -2, -4, -12p70, -13, interferon (IFN) γ], chemokines [macrophage inflammatory protein (MIP) -1α, -3α], and growth factors [macrophage colony-stimulating factor (M-CSF), vascular endothelial growth factor (VEGF)], together with increased IBA-1 and GFAP expression in the CPu.
Conclusions
JWH-018 exposure induces enduring brain region-specific immune alterations, which may contribute to the behavioral and neurochemical dysregulations in striatal areas that play a role in reward and reward-related processes, such as addictive behaviors.
... Both CB1 and CB2 receptors are known for their anti-inflammatory and antinociceptive properties. [5][6][7][8] Our ligand design followed a traditional SAR approach and was supported by molecular modeling studies of the reported X-ay structures of NAAA. 50 Several inhibitors were evaluated in stability assays and demonstrated very good plasma stability (t 1/2 > 120 min; human and rodents), but rather moderate microsomal stability (t 1/ 2~5 -15 min) in human and rodent liver microsomal preparations. ...
N-acylethanolamine acid amidase (NAAA) inhibition represents an exciting novel approach to treat inflammation and pain. NAAA is a cysteine amidase which preferentially hydrolyzes the endogenous biolipids palmitoylethanolamide (PEA) and oleoylethanolamide (OEA). PEA is an endogenous agonist of the nuclear peroxisome proliferator-activated receptor-α (PPAR-α), which is a key regulator of inflammation and pain. Thus, blocking the degradation of PEA with NAAA inhibitors results in augmentation of the PEA/PPAR-α signaling pathway and regulation of inflammatory and pain processes. We have prepared a new series of NAAA inhibitors exploring the azetidine-nitrile (cyanamide) pharmacophore that led to the discovery of highly potent and selective compounds. Key analogs demonstrated single-digit nanomolar potency for hNAAA and showed >100-fold selectivity against serine hydrolases FAAH, MGL and ABHD6, and cysteine protease cathepsin K. Additionally, we have identified potent and selective dual NAAA-FAAH inhibitors to investigate a potential synergism between two distinct anti-inflammatory molecular pathways, the PEA/PPAR-α anti-inflammatory signaling pathway,1-4 and the cannabinoid receptors CB1 and CB2 pathways which are known for their antiinflammatory and antinociceptive properties.5-8 Our ligand design strategy followed a traditional structure-activity relationship (SAR) approach and was supported by molecular modeling studies of reported X-ray structures of hNAAA. Several inhibitors were evaluated in stability assays and demonstrated very good plasma stability (t1/2 > 2 h; human and rodents). The disclosed cyanamides represent promising new pharmacological tools to investigate the potential role of NAAA inhibitors and dual NAAA-FAAH inhibitors as therapeutic agents for the treatment of inflammation and pain.
... It has been suggested the abnormal brain connectivity seen in children with ASD could be due to lack of CB1 axon guidance (Schultz and Gould, 2016;Schultz, 2010;McFadden and Minshew, 2013). The cannabinoid receptors2 (CB2) are abundant in immune and microglial cells and primarily play a role in immune system regulation (Ranieri et al., 2016). Siniscalco et al. demonstrated that CB2, but not CB1, is upregulated in peripheral blood mononuclear cells of children affected by ASD compared to controls (Siniscalco et al., 2013). ...
Background:
The non-prescription medication paracetamol (acetaminophen, APAP) is currently recommended as a safe pain and fever treatment during pregnancy. However, recent studies suggest a possible association between APAP use in pregnancy and offspring neurodevelopment.
Objectives:
To conduct a review of publications reporting associations between prenatal APAP use and offspring neurodevelopmental outcomes.
Methods:
Relevant sources were identified through a key word search of multiple databases (Medline, CINAHL, OVID and TOXNET) in September 2016. All English language observational studies of pregnancy APAP and three classes of neurodevelopmental outcomes (autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and intelligence quotient (IQ)) were included. One reviewer (AZB) independently screened all titles and abstracts, extracted and analyzed the data.
Results:
64 studies were retrieved and 55 were ineligible. Nine prospective cohort studies fulfilled all inclusion criteria. Data pooling was not appropriate due to heterogeneity in outcomes. All included studies suggested an association between prenatal APAP exposure and the neurodevelopmental outcomes; ADHD, ASD, or lower IQ. Longer duration of APAP use was associated with increased risk. Associations were strongest for hyperactivity and attention-related outcomes. Little modification of associations by indication for use was reported.
Conclusions:
Together, these nine studies suggest an increased risk of adverse neurodevelopmental outcomes following prenatal APAP exposure. Further studies are urgently needed with; precise indication of use and exposure assessment of use both in utero and in early life. Given the current findings, pregnant women should be cautioned against indiscriminate use of APAP. These results have substantial public health implications.
Dysfunction of the blood-brain barrier (BBB) is closely related to neuroinflammation-mediated neurodegenerative disorders. Lipopolysaccharide (LPS), an endotoxin, can cause inflammation by impairing the brain endothelial barrier function and increasing the BBB permeability. Although Taraxacum coreanum NAKAI extract (TC), a traditional medicine widely used in Korea, has antioxidant and anti-inflammatory properties, the protective effects on neuroinflammation and BBB dysfunction are not fully understood. In the present study, bEnd.3 cerebral vascular endothelial cells were treated with TC followed by LPS exposure, and the effects on transendothelial electrical resistance (TEER) values, pro-inflammatory cytokine production, and expression of proteins related to inflammatory responses and tight junction integrity were assessed. The TC-treated group exhibited elevated TEER values in bEnd.3 monolayer compared to LPS-only treated group. In addition, TC treatment increased the expression of proteins involved in the tight junctions, such as ZO-1, claudin-5, and occludin. Furthermore, the TC-treated group suppressed the proteins expression-related to nuclear factor-κB (NF-κB) pathway. Taken together, TC attenuates LPS-induced neuroinflammatory responses by regulating NF-κB activation, which may contribute to protecting against BBB disruption. These findings suggest that TC may have the potential to be used as a material for functional foods to prevent neuroinflammation-related brain diseases.
Drug addiction is a chronic and debilitating disease that is considered a global health problem. Various cell types in the brain are involved in the progression of drug addiction. Recently, the xenobiotic hypothesis has been proposed, which frames substances of abuse as exogenous molecules that are responded to by the immune system as foreign "invaders", thus triggering protective inflammatory responses. An emerging body of literature reveals that microglia, the primary resident immune cells in the brain, play an important role in the progression of addiction. Repeated cycles of drug administration cause a progressive, persistent induction of neuroinflammation by releasing microglial proinflammatory cytokines and their metabolic products. This contributes to drug addiction via modulation of neuronal function. In this review, we focus on the role of microglia in the etiology of drug addiction. Then, we discuss the dynamic states of microglia and the correlative and causal evidence linking microglia to drug addiction. Finally, possible mechanisms of how microglia sense drug-related stimuli and modulate the addiction state and how microglia-targeted anti-inflammation therapies affect addiction are reviewed. Understanding the role of microglia in drug addiction may help develop new treatment strategies to fight this devastating societal challenge.
This review summarizes the pharmacological properties of tetrahydrocannabinol (THC) and cannabidiol (CBD), cannabinoid components of several species of herbal cannabis. The pharmacological effects of the phytocannabinoids have been extensively investigated and the importance of the cannabinoid receptors (CB1 and CB2) on immune cells has provided important information on the intracellular targets for these molecules. In addition to the phytocannabinoids, endogenous cannabinoids also exist in the form of anadramide and 2-srodolylglycerol (2-AG). These, together with their synthesizing and metabolizing enzymes, form the cannabinoid system. Since the discovery of the endocannabinoid system and the role that neuroinflammation plays in neurological and psychiatric illness, the potential therapeutic importance of this system has been of growing interest. In addition, the need to develop drugs which specifically target the CB1 and CB2 receptors has been stimulated by the pharmacological complexity of both THC and CBD. This review briefly summarizes the therapeutic potential of the naturally occurring and the synthetic cannabinoids which will need to be developed, if such drugs are to fulfill the therapeutic promise which the cannabinoids offer.
Inflammation in the central nervous system (CNS) contributes to disease pathologies by disrupting the integrity of the blood–brain barrier (BBB). Tight junctions (TJ) are a key component of the BBB. Following hypoxic–ischaemic or mechanical injury to the brain, inflammatory mediators are released such as cytokines, chemokines, and growth factors. Simultaneously, matrix metalloproteinases (MMPs) are released which can degrade TJ proteins. Subsequently, the function and morphology of the BBB are disrupted, which allows immune cells an opportunity to enter into the brain parenchyma. This review summarises the information on the role of TJ protein families in the BBB and provides a comprehensive summary of the mechanisms whereby inflammation breaks down the BBB by increasing degradation of TJ proteins.
Tumor necrosis factor superfamily (TNFSF) molecules play an important role in the activation, proliferation, differentiation, and migration of immune cells into the central nervous system (CNS). Several TNF superfamily molecules are known to control alloimmunity, autoimmunity, and immunity. Development of transgenic and gene knockout animals, and monoclonal antibodies against TNFSF molecules have increased our understanding of individual receptor–ligand interactions, and their intracellular signaling during homeostasis and neuroinflammation. A strong clinical association has been observed between TNFSF members and CNS autoimmunity such as multiple sclerosis and also in its animal model experimental autoimmune encephalomyelitis. Therefore, they are promising targets for alternative therapeutic options to control autoimmunity. Although, TNFSF ligands are widely distributed and have diverse functions, we have restricted the discussions in this review to TNFSF receptor–ligand interactions and their role in the pathogenesis of neuroinflammation and CNS autoimmunity.
It is well known that systemic infections cause flare-ups of disease in individuals with asthma and rheumatoid arthritis, and that relapses in multiple sclerosis can often be associated with upper respiratory-tract infections. Here we review evidence to support our hypothesis that in chronic neurodegenerative diseases such as Alzheimer's disease, with an ongoing innate immune response in the brain, systemic infections and inflammation can cause acute exacerbations of symptoms and drive the progression of neurodegeneration.
Alpha/beta-hydrolase domain 6 (ABHD6) is a novel 2-arachidonoylglycerol (2-AG) hydrolytic enzyme, that can fine-tune the endocannabinoid signaling in the central nervous system. Recently we and others have demonstrated the protective effect of ABHD6 inhibition in the animal models of traumatic brain injury and epileptic seizures. In this study, we investigated the role of targeting ABHD6 in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). Post-symptom treatment with an ABHD6 inhibitor WWL70 increased the brain levels of 2-AG and ameliorated the clinical signs of EAE, T cells infiltration, microglia activation and the expression of activated leukocyte cell adhesion molecules. The production of iNOS, COX-2, TNF-α and IL-1β and the phosphorylation of NF-κB were also significantly reduced by WWL70 treatment. The neuroprotective effect of WWL70 was demonstrated by increased survival of mature oligodendrocytes, reduced demyelination and axonal loss in WWL70 treated EAE mouse spinal cord. The therapeutic effect of WWL70 on EAE was absent by co-administration of CB2 receptor antagonist, but not CB1 receptor antagonist. Consistently, WWL70 did not afford any protection in CB2 receptor knockout mice after EAE induction. Given the increased expression of ABHD6 in microglia/macrophages, but not in T cells, we speculated that inhibition of ABHD6 might enhance 2-AG signaling particularly in microglia/macrophages to exert anti-inflammatory effects via activation of CB2 receptors. These results suggest that inhibition of ABHD6 might be used as an ideal strategy for the treatment of MS and other neurodegenerative diseases.
Copyright © 2015. Published by Elsevier Ltd.
The blood-brain barrier (BBB) limits entry of blood-derived products, pathogens, and cells into the brain that is essential for normal neuronal functioning and information processing. Post-mortem tissue analysis indicates BBB damage in Alzheimer's disease (AD). The timing of BBB breakdown remains, however, elusive. Using an advanced dynamic contrast-enhanced MRI protocol with high spatial and temporal resolutions to quantify regional BBB permeability in the living human brain, we show an age-dependent BBB breakdown in the hippocampus, a region critical for learning and memory that is affected early in AD. The BBB breakdown in the hippocampus and its CA1 and dentate gyrus subdivisions worsened with mild cognitive impairment that correlated with injury to BBB-associated pericytes, as shown by the cerebrospinal fluid analysis. Our data suggest that BBB breakdown is an early event in the aging human brain that begins in the hippocampus and may contribute to cognitive impairment.
Copyright © 2015 Elsevier Inc. All rights reserved.