Cannabinoid receptor and N-acyl phosphatidylethanolamine phospholipase D--evidence for altered expression in multiple sclerosis

Cannabinoids' Role in Modulating Central and Peripheral Immunity in Neurodegenerative Diseases

Cannabinoids (the endocannabinoids, the synthetic cannabinoids, and the phytocannabinoids) are well known for their various pharmacological properties, including neuroprotective and anti-inflammatory features, which are fundamentally important for the treatment of neurodegenerative diseases. The aging of the global population is causing an increase in these diseases that require the development of effective drugs to be even more urgent. Taking into account the unavailability of effective drugs for neurodegenerative diseases, it seems appropriate to consider the role of cannabinoids in the treatment of these diseases. To our knowledge, few reviews are devoted to cannabinoids' impact on modulating central and peripheral immunity in neurodegenerative diseases. The objective of this review is to provide the best possible information about the cannabinoid receptors and immuno-modulation features, peripheral immune modulation by cannabinoids, cannabinoid-based therapies for the treatment of neurological disorders, and the future development prospects of making cannabinoids versatile tools in the pursuit of effective drugs.

Design and Synthesis of Highly Potent and Specific ABHD6 Inhibitors

Fine-tuning than complete disruption of 2-arachidonoylglycerol (2-AG) metabolism in the brain represents a promising pharmacological approach to limit potential untoward effects associated with complete blockade of monoacylglycerol lipase (MGL), the primary hydrolase of 2-AG. This could be achieved through a/b-hydrolase domain containing 6 (ABHD6) inhibition, which will provide a smaller and safer contribution to 2-AG regulation in the brain. Pharmacological studies with ABHD6 inhibitors have recently been reported, where modulation of ABHD6 activity either through CB1R-dependent or CB1R-independent processes showed promise in preclinical models of epilepsy, neuropathic pain and inflammation. Furthermore in the periphery, ABHD6 modulates 2-AG and other fatty acid monoacylglycerols (MAGs) and is implicated in Type-2 diabetes, metabolic syndrome and potentially other diseases. Herein, we report the discovery of single-digit nanomolar potent and highly specific ABHD6 inhibitors with >1000-fold selectivity against MGL and FAAH. The new ABHD6 inhibitors provide early leads to develop therapeutics for neuroprotection and the treatment of inflammation and diabetes.

Endocannabinoid signaling in astrocytes

The study of the astrocytic contribution to brain functions has been growing in popularity in the neuroscience field. In the last years, and especially since the demonstration of the involvement of astrocytes in synaptic functions, the astrocyte field has revealed multiple functions of these cells that seemed inconceivable not long ago. In parallel, cannabinoid investigation has also identified different ways by which cannabinoids are able to interact with these cells, modify their functions, alter their communication with neurons and impact behavior. In this review, we will describe the expression of different endocannabinoid system members in astrocytes. Moreover, we will relate the latest findings regarding cannabinoid modulation of some of the most relevant astroglial functions, namely calcium (Ca²⁺ ) dynamics, gliotransmission, metabolism, and inflammation.

Pharmacognosy and Effects of Cannabinoids in the Vascular System

Understanding the pharmacodynamics of cannabinoids is an essential subject due to the recent increasing global acceptance of cannabis and its derivation for recreational and therapeutic purposes. Elucidating the interaction between cannabinoids and the vascular system is critical to exploring cannabinoids as a prospective therapeutic agent for treating vascular-associated clinical conditions. This review aims to examine the effect of cannabinoids on the vascular system and further discuss the fundamental pharmacological properties and mechanisms of action of cannabinoids in the vascular system. Data from literature revealed a substantial interaction between endocannabinoids, phytocannabinoids, and synthetic cannabinoids within the vasculature of both humans and animal models. However, the mechanisms and the ensuing functional response is blood vessels and species-dependent. The current understanding of classical cannabinoid receptor subtypes and the recently discovered atypical cannabinoid receptors and the development of new synthetic analogs have further enhanced the pharmacological characterization of the vascular cannabinoid receptors. Compelling evidence also suggest that cannabinoids represent a formidable therapeutic candidate for vascular-associated conditions. Nonetheless, explanations of the mechanisms underlining these processes are complex and paradoxical based on the heterogeneity of receptors and signaling pathways. Further insight from studies that uncover the mechanisms underlining the therapeutic effect of cannabinoids in the treatment of vascular-associated conditions is required to determine whether the known benefits of cannabinoids thus currently outweigh the known/unknown risks.

Microglial Inflammatory-Metabolic Pathways and Their Potential Therapeutic Implication in Major Depressive Disorder

Increasing evidence supports the notion that neuroinflammation plays a critical role in the etiology of major depressive disorder (MDD), at least in a subset of patients. By virtue of their capacity to transform into reactive states in response to inflammatory insults, microglia, the brain's resident immune cells, play a pivotal role in the induction of neuroinflammation. Experimental studies have demonstrated the ability of microglia to recognize pathogens or damaged cells, leading to the activation of a cytotoxic response that exacerbates damage to brain cells. However, microglia display a wide range of responses to injury and may also promote resolution stages of inflammation and tissue regeneration. MDD has been associated with chronic priming of microglia. Recent studies suggest that altered microglial morphology and function, caused either by intense inflammatory activation or by senescence, may contribute to depression and associated impairments in neuroplasticity. In this context, modifying microglia phenotype by tuning inflammatory pathways might have important translational relevance to harness neuroinflammation in MDD. Interestingly, it was recently shown that different microglial phenotypes are associated with distinct metabolic pathways and analysis of the underlying molecular mechanisms points to an instrumental role for energy metabolism in shaping microglial functions. Here, we review various canonical pro-inflammatory, anti-inflammatory and metabolic pathways in microglia that may provide new therapeutic opportunities to control neuroinflammation in brain disorders, with a strong focus on MDD.

Glial Cells and Their Contribution to the Mechanisms of Action of Cannabidiol in Neuropsychiatric Disorders

Cannabidiol (CBD) is a phytocannabinoid with a broad-range of therapeutic potential in several conditions, including neurological (epilepsy, neurodegenerative diseases, traumatic and ischemic brain injuries) and psychiatric disorders (schizophrenia, addiction, major depressive disorder, and anxiety). The pharmacological mechanisms responsible for these effects are still unclear, and more than 60 potential molecular targets have been described. Regarding neuropsychiatric disorders, most studies investigating these mechanisms have focused on neuronal cells. However, glial cells (astrocytes, oligodendrocytes, microglia) also play a crucial role in keeping the homeostasis of the central nervous system. Changes in glial functions have been associated with neuropathological conditions, including those for which CBD is proposed to be useful. Mostly in vitro studies have indicated that CBD modulate the activation of proinflammatory pathways, energy metabolism, calcium homeostasis, and the proliferative rate of glial cells. Likewise, some of the molecular targets proposed for CBD actions are f expressed in glial cells, including pharmacological receptors such as CB1, CB2, PPAR-γ, and 5-HT1A. In the present review, we discuss the currently available evidence suggesting that part of the CBD effects are mediated by interference with glial cell function. We also propose additional studies that need to be performed to unveil the contribution of glial cells to CBD effects in neuropsychiatric disorders.

Drug-Resistant Temporal Lobe Epilepsy Alters the Expression and Functional Coupling to Gαi/o Proteins of CB1 and CB2 Receptors in the Microvasculature of the Human Brain

Cannabinoid receptors 1 and 2 (CB1 and CB2, respectively) play an important role in maintaining the integrity of the blood–brain barrier (BBB). On the other hand, BBB dysfunction is a common feature in drug-resistant epilepsy. The focus of the present study was to characterize protein expression levels and Gαi/o protein-induced activation by CB1 and CB2 receptors in the microvascular endothelial cells (MECs) isolated from the brain of patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). MECs were isolated from the hippocampus and temporal neocortex of 12 patients with DR-MTLE and 12 non-epileptic autopsies. Immunofluorescence experiments were carried out to determine the localization of CB1 and CB2 receptors in the different cell elements of MECs. Protein expression levels of CB1 and CB2 receptors were determined by Western blot experiments. [³⁵S]-GTPγS binding assay was used to evaluate the Gαi/o protein activation induced by specific agonists. Immunofluorescent double-labeling showed that CB1 and CB2 receptors colocalize with tight junction proteins (claudin-5, occludin, and zonula occludens-1), glial fibrillary acidic protein and platelet-derived growth factor receptor-β. These results support that CB1 and CB2 receptors are expressed in the human isolated microvessels fragments consisting of MECs, astrocyte end feet, and pericytes. The hippocampal microvasculature of patients with DR-MTLE presented lower protein expression of CB1 and CB2 receptors (66 and 43%, respectively; p < 0.001). However, its Gαi/o protein activation was with high efficiency (CB1, 251%, p < 0.0008; CB2, 255%, p < 0.0001). Microvasculature of temporal neocortex presented protein overexpression of CB1 and CB2 receptors (35 and 41%, respectively; p < 0.01). Their coupled Gαi/o protein activation was with higher efficiency for CB1 receptors (103%, p < 0.006), but lower potency (p < 0.004) for CB2 receptors. The present study revealed opposite changes in the protein expression of CB1 and CB2 receptors when hippocampus (diminished expression of CB1 and CB2) and temporal neocortex (increased expression of CB1 and CB2) were compared. However, the exposure to specific CB1 and CB2 agonists results in high efficiency for activation of coupled Gαi/o proteins in the brain microvasculature of patients with DR-MTLE. CB1 and CB2 receptors with high efficiency could represent a therapeutic target to maintain the integrity of the BBB in patients with DR-MTLE.

Expression of endocannabinoid system components in human airway epithelial cells: impact of sex and chronic respiratory disease status

Cannabis smoking is the dominant route of delivery, with the airway epithelium functioning as the site of first contact. The endocannabinoid system is responsible for mediating the physiological effects of inhaled phytocannabinoids. The expression of the endocannabinoid system in the airway epithelium and contribution to normal physiological responses remains to be defined. To begin to address this knowledge gap, a curated dataset of 1090 unique human bronchial brushing gene expression profiles was created. The dataset included 616 healthy subjects, 136 subjects with asthma, and 338 subjects with COPD. A 32-gene endocannabinoid signature was analysed across all samples with sex and disease-specific analyses performed. Immunohistochemistry and immunoblots were performed to probe in situ and in vitro protein expression. CB₁, CB₂, and TRPV1 protein signal is detectable in human airway epithelial cells in situ and in vitro, justifying examining the downstream endocannabinoid pathway. Sex status was associated with differential expression of 7 of 32 genes. In contrast, disease status was associated with differential expression of 21 of 32 genes in people with asthma and 26 of 32 genes in people with COPD. We confirm at the protein level that TRPV1, the most differentially expressed candidate in our analyses, was upregulated in airway epithelial cells from people with asthma relative to healthy subjects. Our data demonstrate that the endocannabinoid system is expressed in human airway epithelial cells with expression impacted by disease status and minimally by sex. The data suggest that cannabis consumers may have differential physiological responses in the respiratory mucosa.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Druggable targets of the endocannabinoid system: Implications for the treatment of HIV-associated neurocognitive disorder

HIV-associated neurocognitive disorder (HAND) affects nearly half of all HIV-infected individuals. Synaptodendritic damage correlates with neurocognitive decline in HAND, and many studies have demonstrated that HIV-induced neuronal injury results from excitotoxic and inflammatory mechanisms. The endocannabinoid (eCB) system provides on-demand protection against excitotoxicity and neuroinflammation. Here, we discuss evidence of the neuroprotective and anti-inflammatory properties of the eCB system from in vitro and in vivo studies. We examine the pharmacology of the eCB system and evaluate the therapeutic potential of drugs that modulate eCB signaling to treat HAND. Finally, we provide perspective on the need for additional studies to clarify the role of the eCB system in HIV neurotoxicity and speculate that strategies that enhance eCB signaling might slow cognitive decline in HAND.

Neuroprotection in Oxidative Stress-Related Neurodegenerative Diseases: Role of Endocannabinoid System Modulation

SIGNIFICANCE

Redox imbalance may lead to overproduction of reactive oxygen and nitrogen species (ROS/RNS) and subsequent oxidative tissue damage, which is a critical event in the course of neurodegenerative diseases. It is still not fully elucidated, however, whether oxidative stress is the primary trigger or a consequence in the process of neurodegeneration. Recent Advances: Increasing evidence suggests that oxidative stress is involved in the propagation of neuronal injury and consequent inflammatory response, which in concert promote development of pathological alterations characteristic of most common neurodegenerative diseases.

CRITICAL ISSUES

Accumulating recent evidence also suggests that there is an important interplay between the lipid endocannabinoid system [ECS; comprising the main cannabinoid 1 and 2 receptors (CB1 and CB2), endocannabinoids, and their synthetic and metabolizing enzymes] and various key inflammatory and redox-dependent processes.

FUTURE DIRECTIONS

Targeting the ECS to modulate redox state-dependent cell death and to decrease consequent or preceding inflammatory response holds therapeutic potential in a multitude of oxidative stress-related acute or chronic neurodegenerative disorders from stroke and traumatic brain injury to Alzheimer's and Parkinson's diseases and multiple sclerosis, just to name a few, which will be discussed in this overview. Antioxid. Redox Signal. 29, 75-108.

Interaction between interleukin-1β and type-1 cannabinoid receptor is involved in anxiety-like behavior in experimental autoimmune encephalomyelitis

Background

Mood disorders, including anxiety and depression, are frequently diagnosed in multiple sclerosis (MS) patients, even independently of the disabling symptoms associated with the disease. Anatomical, biochemical, and pharmacological evidence indicates that type-1 cannabinoid receptor (CB1R) is implicated in the control of emotional behavior and is modulated during inflammatory neurodegenerative diseases such as MS and experimental autoimmune encephalomyelitis (EAE).

Methods

We investigated whether CB1R could exert a role in anxiety-like behavior in mice with EAE. We performed behavioral, pharmacological, and electrophysiological experiments to explore the link between central inflammation, mood, and CB1R function in EAE.

Results

We observed that EAE-induced anxiety was associated with the downregulation of CB1R-mediated control of striatal GABA synaptic transmission and was exacerbated in mice lacking CB1R (CB1R-KO mice). Central blockade of interleukin-1β (IL-1β) reversed the anxiety-like phenotype of EAE mice, an effect associated with the concomitant rescue of dopamine (DA)-regulated spontaneous behavior, and DA-CB1R neurotransmission, leading to the rescue of striatal CB1R sensitivity.

Conclusions

Overall, results of the present investigation indicate that synaptic dysfunction linked to CB1R is involved in EAE-related anxiety and motivation-based behavior and contribute to clarify the complex neurobiological mechanisms underlying mood disorders associated to MS.

Endocannabinoids in cerebrovascular regulation

The cerebral blood flow is tightly regulated by myogenic, endothelial, metabolic, and neural mechanisms under physiological conditions, and a large body of recent evidence indicates that inflammatory pathways have a major influence on the cerebral blood perfusion in certain central nervous system disorders, like hemorrhagic and ischemic stroke, traumatic brain injury, and vascular dementia. All major cell types involved in cerebrovascular control pathways (i.e., smooth muscle, endothelium, neurons, astrocytes, pericytes, microglia, and leukocytes) are capable of synthesizing endocannabinoids and/or express some or several of their target proteins [i.e., the cannabinoid 1 and 2 (CB1 and CB2) receptors and the transient receptor potential vanilloid type 1 ion channel]. Therefore, the endocannabinoid system may importantly modulate the regulation of cerebral circulation under physiological and pathophysiological conditions in a very complex manner. Experimental data accumulated since the late 1990s indicate that the direct effect of cannabinoids on cerebral vessels is vasodilation mediated, at least in part, by CB1 receptors. Cannabinoid-induced cerebrovascular relaxation involves both a direct inhibition of smooth muscle contractility and a release of vasodilator mediator(s) from the endothelium. However, under stress conditions (e.g., in conscious restrained animals or during hypoxia and hypercapnia), cannabinoid receptor activation was shown to induce a reduction of the cerebral blood flow, probably via inhibition of the electrical and/or metabolic activity of neurons. Finally, in certain cerebrovascular pathologies (e.g., subarachnoid hemorrhage, as well as traumatic and ischemic brain injury), activation of CB2 (and probably yet unidentified non-CB1/non-CB2) receptors appear to improve the blood perfusion of the brain via attenuating vascular inflammation.

Isolevuglandin adducts in disease

SIGNIFICANCE

A diverse family of lipid-derived levulinaldehydes, isolevuglandins (isoLGs), is produced by rearrangement of endoperoxide intermediates generated through both cyclooxygenase (COX) and free radical-induced cyclooxygenation of polyunsaturated fatty acids and their phospholipid esters. The formation and reactions of isoLGs with other biomolecules has been linked to alcoholic liver disease, Alzheimer's disease, age-related macular degeneration, atherosclerosis, cardiac arythmias, cancer, end-stage renal disease, glaucoma, inflammation of allergies and infection, mitochondrial dysfunction, multiple sclerosis, and thrombosis. This review chronicles progress in understanding the chemistry of isoLGs, detecting their production in vivo and understanding their biological consequences.

CRITICAL ISSUES

IsoLGs have never been isolated from biological sources, because they form adducts with primary amino groups of other biomolecules within seconds. Chemical synthesis enabled investigation of isoLG chemistry and detection of isoLG adducts present in vivo.

RECENT ADVANCES

The first peptide mapping and sequencing of an isoLG-modified protein present in human retina identified the modification of a specific lysyl residue of the sterol C27-hydroxylase Cyp27A1. This residue is preferentially modified by iso[4]LGE2 in vitro, causing loss of function. Adduction of less than one equivalent of isoLG can induce COX-associated oligomerization of the amyloid peptide Aβ1-42. Adduction of isoLGE2 to phosphatidylethanolamines causes gain of function, converting them into proinflammatory isoLGE2-PE agonists that foster monocyte adhesion to endothelial cells.

FUTURE DIRECTIONS

Among the remaining questions on the biochemistry of isoLGs are the dependence of biological activity on isoLG isomer structure, the structures and mechanism of isoLG-derived protein-protein and DNA-protein cross-link formation, and its biological consequences.

Endocannabinoids modulate human blood-brain barrier permeability in vitro

Background and Purpose

Endocannabinoids alter permeability at various epithelial barriers, and cannabinoid receptors and endocannabinoid levels are elevated by stroke, with potential neuroprotective effects. We therefore explored the role of endocannabinoids in modulating blood–brain barrier (BBB) permeability in normal conditions and in an ischaemia/reperfusion model.

Experimental Approach

Human brain microvascular endothelial cell and astrocyte co-cultures modelled the BBB. Ischaemia was modelled by oxygen-glucose deprivation (OGD) and permeability was measured by transepithelial electrical resistance. Endocannabinoids or endocannabinoid-like compounds were assessed for their ability to modulate baseline permeability or OGD-induced hyperpermeability. Target sites of action were investigated using receptor antagonists and subsequently identified with real-time PCR.

Key Results

Anandamide (10 μM) and oleoylethanolamide (OEA, 10 μM) decreased BBB permeability (i.e. increased resistance). This was mediated by cannabinoid CB₂ receptors, transient receptor potential vanilloid 1 (TRPV1) channels, calcitonin gene-regulated peptide (CGRP) receptor (anandamide only) and PPARα (OEA only). Application of OEA, palmitoylethanolamide (both PPARα mediated) or virodhamine (all 10 μM) decreased the OGD-induced increase in permeability during reperfusion. 2-Arachidonoyl glycerol, noladin ether and oleamide did not affect BBB permeability in normal or OGD conditions. N-arachidonoyl-dopamine increased permeability through a cytotoxic mechanism. PPARα and γ, CB₁ receptors, TRPV1 channels and CGRP receptors were expressed in both cell types, but mRNA for CB₂ receptors was only present in astrocytes.

Conclusion and Implication

The endocannabinoids may play an important modulatory role in normal BBB physiology, and also afford protection to the BBB during ischaemic stroke, through a number of target sites.

Functions of the CB1 and CB 2 receptors in neuroprotection at the level of the blood-brain barrier

The cannabinoid (CB) receptors are the main targets of the cannabinoids, which include plant cannabinoids, endocannabinoids and synthetic cannabinoids. Over the last few years, accumulated evidence has suggested a role of the CB receptors in neuroprotection. The blood-brain barrier (BBB) is an important brain structure that is essential for neuroprotection. A link between the CB receptors and the BBB is thus likely, but this possible connection has only recently gained attention. Cannabinoids and the BBB share the same mechanisms of neuroprotection and both protect against excitotoxicity (CB1), cell death (CB1), inflammation (CB2) and oxidative stress (possibly CB independent)-all processes that also damage the BBB. Several examples of CB-mediated protection of the BBB have been found, such as inhibition of leukocyte influx and induction of amyloid beta efflux across the BBB. Moreover, the CB receptors were shown to improve BBB integrity, particularly by restoring the tightness of the tight junctions. This review demonstrated that both CB receptors are able to restore the BBB and neuroprotection, but much uncertainty about the underlying signaling cascades still exists and further investigation is needed.

Radiofluorination and biological evaluation of N-aryl-oxadiazolyl-propionamides as potential radioligands for PET imaging of cannabinoid CB2 receptors

Background

The level of expression of cannabinoid receptor type 2 (CB₂R) in healthy and diseased brain has not been fully elucidated. Therefore, there is a growing interest to assess the regional expression of CB₂R in the brain. Positron emission tomography (PET) is an imaging technique, which allows quantitative monitoring of very low amounts of radiolabelled compounds in living organisms at high temporal and spatial resolution and, thus, has been widely used as a diagnostic tool in nuclear medicine. Here, we report on the radiofluorination of N-aryl-oxadiazolyl-propionamides at two different positions in the lead structure and on the biological evaluation of the potential of the two tracers [¹⁸F]1 and [¹⁸F]2 as CB₂ receptor PET imaging agents.

Results

High binding affinity and specificity towards CB₂ receptors of the lead structure remained unaffected by the structural changes such as the insertion of the aliphatic and aromatic fluorine in the selected labelling sites of 1 and 2. Aliphatic and aromatic radiofluorinations were optimized, and [¹⁸F]1 and [¹⁸F]2 were achieved in radiochemical yields of ≥30% with radiochemical purities of ≥98% and specific activities of 250 to 450 GBq/μmol. Organ distribution studies in female CD1 mice revealed that both radiotracers cross the blood–brain barrier (BBB) but undergo strong peripheral metabolism. At 30 min after injection, unmetabolized [¹⁸F]1 and [¹⁸F]2 accounted for 60% and 2% as well as 68% and 88% of the total activity in the plasma and brain, respectively. The main radiometabolite of [¹⁸F]2 could be identified as the free acid [¹⁸F]10, which has no affinity towards the CB₁ and CB₂ receptors but can cross the BBB.

Conclusions

N-aryl-oxadiazolyl-propionamides can successfully be radiolabelled with ¹⁸F at different positions. Fluorine substitution at these positions did not affect affinity and specificity towards CB₂R. Despite a promising in vitro behavior, a rather rapid peripheral metabolism of [¹⁸F]1 and [¹⁸F]2 in mice and the generation of brain permeable radiometabolites hamper the application of these radiotracers in vivo. However, it is expected that future synthetic modification aiming at a replacement of metabolically susceptible structural elements of [¹⁸F]1 and [¹⁸F]2 will help to elucidate the potential of this class of compounds for CB₂R PET studies.

Isolevuglandin-modified phosphatidylethanolamine is metabolized by NAPE-hydrolyzing phospholipase D

Lipid aldehydes including isolevuglandins (IsoLGs) and 4-hydroxynonenal modify phosphatidylethanolamine (PE) to form proinflammatory and cytotoxic adducts. Therefore, cells may have evolved mechanisms to degrade and prevent accumulation of these potentially harmful compounds. To test if cells could degrade isolevuglandin-modified phosphatidylethanolamine (IsoLG-PE), we generated IsoLG-PE in human embryonic kidney 293 (HEK293) cells and human umbilical cord endothelial cells and measured its stability over time. We found that IsoLG-PE levels decreased more than 75% after 6 h, suggesting that IsoLG-PE was indeed degraded. Because N-acyl phosphatidylethanolamine-hydrolyzing phospholipase D (NAPE-PLD) has been described as a key enzyme in the hydrolysis of N-acyl phosphatidylethanoamine (NAPE) and both NAPE and IsoLG-PE have large aliphatic headgroups, we considered the possibility that this enzyme might also hydrolyze IsoLG-PE. We found that knockdown of NAPE-PLD expression using small interfering RNA (siRNA) significantly increased the persistence of IsoLG-PE in HEK293 cells. IsoLG-PE competed with NAPE for hydrolysis by recombinant mouse NAPE-PLD, with the catalytic efficiency (V(max)/K(m)) for hydrolysis of IsoLG-PE being 30% of that for hydrolysis of NAPE. LC-MS/MS analysis confirmed that recombinant NAPE-PLD hydrolyzed IsoLG-PE to IsoLG-ethanolamine. These results demonstrate that NAPE-PLD contributes to the degradation of IsoLG-PE and suggest that a major physiological role of NAPE-PLD may be to degrade aldehyde-modified PE, thereby preventing the accumulation of these harmful compounds.

Differential migratory properties of monocytes isolated from human subjects naïve and non-naïve to Cannabis

This study evaluates the migratory potential of monocytes isolated from two groups of human subjects: naïve and non-naïve to Cannabis. Phytocannabinoids (pCB), the bioactive agents produced by the plant Cannabis, regulate the phenotype and function of immune cells by interacting with CB1 and CB2 receptors. It has been shown that agents influencing the phenotype of circulating monocytes influence the phenotype of macrophages and the outcome of immune responses. To date, nothing is known about the acute and long-term effects of pCB on human circulating monocytes. Healthy subjects were recruited for a single blood draw. Monocytes were isolated, fluorescently labeled and their migration quantified using a validated assay that employs near infrared fluorescence and modified Boyden chambers. CB1 and CB2 receptor mRNA expression was quantified by qPCR. Monocytes from all subjects (n = 10) responded to chemokine (c-c motif) ligand 2 (CCL2) and human serum stimuli. Acute application of pCB significantly inhibited both the basal and CCL2-stimulated migration of monocytes, but only in subjects non-naïve to Cannabis. qPCR analysis indicates that monocytes from subjects non-naïve to Cannabis express significantly more CB1 mRNA. The phenotype of monocytes isolated from subjects non-naïve to Cannabis is significantly different from monocytes isolated from subjects naïve to Cannabis. Only monocytes from subjects non-naïve to Cannabis respond to acute exposure to pCB by reducing their overall migratory capacity. Our study suggests that chronic exposure to Cannabis affects the phenotype of circulating monocytes and accordingly could influence outcome of inflammatory responses occurring in injured tissues.

Site-specific and time-dependent activation of the endocannabinoid system after transection of long-range projections

Background

After focal neuronal injury the endocannabinioid system becomes activated and protects or harms neurons depending on cannabinoid derivates and receptor subtypes. Endocannabinoids (eCBs) play a central role in controlling local responses and influencing neural plasticity and survival. However, little is known about the functional relevance of eCBs in long-range projection damage as observed in stroke or spinal cord injury (SCI).

Methods

In rat organotypic entorhino-hippocampal slice cultures (OHSC) as a relevant and suitable model for investigating projection fibers in the CNS we performed perforant pathway transection (PPT) and subsequently analyzed the spatial and temporal dynamics of eCB levels. This approach allows proper distinction of responses in originating neurons (entorhinal cortex), areas of deafferentiation/anterograde axonal degeneration (dentate gyrus) and putative changes in more distant but synaptically connected subfields (cornu ammonis (CA) 1 region).

Results

Using LC-MS/MS, we measured a strong increase in arachidonoylethanolamide (AEA), oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) levels in the denervation zone (dentate gyrus) 24 hours post lesion (hpl), whereas entorhinal cortex and CA1 region exhibited little if any changes. NAPE-PLD, responsible for biosynthesis of eCBs, was increased early, whereas FAAH, a catabolizing enzyme, was up-regulated 48hpl.

Conclusion

Neuronal damage as assessed by transection of long-range projections apparently provides a strong time-dependent and area-confined signal for de novo synthesis of eCB, presumably to restrict neuronal damage. The present data underlines the importance of activation of the eCB system in CNS pathologies and identifies a novel site-specific intrinsic regulation of eCBs after long-range projection damage.

Anandamide inhibits Theiler's virus induced VCAM-1 in brain endothelial cells and reduces leukocyte transmigration in a model of blood brain barrier by activation of CB(1) receptors

Background

VCAM-1 represents one of the most important adhesion molecule involved in the transmigration of blood leukocytes across the blood-brain barrier (BBB) that is an essential step in the pathogenesis of MS. Several evidences have suggested the potential therapeutic value of cannabinoids (CBs) in the treatment of MS and their experimental models. However, the effects of endocannabinoids on VCAM-1 regulation are poorly understood. In the present study we investigated the effects of anandamide (AEA) in the regulation of VCAM-1 expression induced by Theiler's virus (TMEV) infection of brain endothelial cells using in vitro and in vivo approaches.

Methods

i) in vitro: VCAM-1 was measured by ELISA in supernatants of brain endothelial cells infected with TMEV and subjected to AEA and/or cannabinoid receptors antagonist treatment. To evaluate the functional effect of VCAM-1 modulation we developed a blood brain barrier model based on a system of astrocytes and brain endothelial cells co-culture. ii) in vivo: CB₁ receptor deficient mice (Cnr1^-/-) infected with TMEV were treated with the AEA uptake inhibitor UCM-707 for three days. VCAM-1 expression and microglial reactivity were evaluated by immunohistochemistry.

Results

Anandamide-induced inhibition of VCAM-1 expression in brain endothelial cell cultures was mediated by activation of CB₁ receptors. The study of leukocyte transmigration confirmed the functional relevance of VCAM-1 inhibition by AEA. In vivo approaches also showed that the inhibition of AEA uptake reduced the expression of brain VCAM-1 in response to TMEV infection. Although a decreased expression of VCAM-1 by UCM-707 was observed in both, wild type and CB₁ receptor deficient mice (Cnr1^-/-), the magnitude of VCAM-1 inhibition was significantly higher in the wild type mice. Interestingly, Cnr1^-/- mice showed enhanced microglial reactivity and VCAM-1 expression following TMEV infection, indicating that the lack of CB₁ receptor exacerbated neuroinflammation.

Conclusions

Our results suggest that CB₁ receptor dependent VCAM-1 inhibition is a novel mechanism for AEA-reduced leukocyte transmigration and contribute to a better understanding of the mechanisms underlying the beneficial role of endocannabinoid system in the Theiler's virus model of MS.