The abnormalities in cerebellar circuit function within the Crus I/II lobules in autism spectrum disorder (ASD) are widely recognized as critical contributors to impairments in motor behavior and social interaction. We here investigated the impact of prenatal valproic acid (VPA) exposure on facial stimulation-evoked synaptic plasticity at cerebellar mossy fiber-granule cell (MF-GC) synapses in urethane-anesthetized offspring mice invivo. When the GABAA receptor was blocked, 20 Hz facial stimulation induced MF-GC LTP in control mice, whereas the same stimulation paradigm triggered MF-GC LTD in VPA-treated offspring. Blockade of N-methyl-D-aspartate receptors abolished LTP in control mice while unmasking LTD in VPA-treated offspring. Notably, the facial stimulation-induced LTD observed in VPA-treated offspring was abolished by blocking group I metabotropic glutamate receptors, but not by the selective blockade of either mGluR1 or mGluR5 alone. Blockade of cannabinoid receptor 1 (CB1) or inhibition of diacylglycerol lipase (DGL) prevented the induction of LTD. Pharmacologically activating mGluR1/5 or CB1 produced MF-GC LTD and overwhelmed the facial stimulation-induced LTD in VPA-treated offspring mice. Conversely, mGluR1/5 activation failed to induce LTD in control mice. Moreover, 20 Hz facial stimulation induced MF-GC LTP in the absence of mGluR1/5 or CB1 receptor activity in VPA-treated offspring mice. Immunohistochemical analyses revealed that the expression levels of mGluR1/5 were significantly higher in the cerebellar GCs of VPA-treated offspring compared to those of control mice. These results indicate that 20 Hz facial stimulation induces MF-GC LTD by enhancing the mGluR1/5-DGL-CB1 receptor signaling cascade, thereby resulting in impairment of MF-GC LTP in VPA-treated offspring mice.

The principle endocannabinoids are 2-acylglycerol esters, such as 2-arachidonoylglycerol (2-AG), and N-acylethanolamines, such as anandamide (N-arachidonoylethanolamine, AEA). The glycerol esters and ethanolamides are synthesised and hydrolysed by parallel, independent pathways. Mechanisms for release and re-uptake of endocannabinoids are unclear, although potent and selective inhibitors of facilitated diffusion of endocannabinoids across cell membranes have been developed [32]. FABP5 (Q01469) has been suggested to act as a canonical intracellular endocannabinoid transporter in vivo [19]. For the generation of 2-arachidonoylglycerol, the key enzyme involved is diacylglycerol lipase (DAGL), whilst several routes for anandamide synthesis have been described, the best characterized of which involves N-acylphosphatidylethanolamine-phospholipase D (NAPE-PLD, [79]). A transacylation enzyme which forms N-acylphosphatidylethanolamines has been identified as a cytosolic enzyme, PLA2G4E (Q3MJ16) [70]. In vitro experiments indicate that the endocannabinoids are also substrates for oxidative metabolism via cyclooxygenase, lipoxygenase and cytochrome P450 enzyme activities [6, 26, 81].

The ventrolateral periaqueductal gray (vlPAG) plays a critical role in pain modulation. GABAergic neurotransmission within the vlPAG regulates the descending pain pathway. This study investigates the mechanisms through which corticosterone (CORT) modulates GABA release in the vlPAG via putative membrane-associated glucocorticoid receptors (mbGRs). Superfusion of CORT decreases evoked inhibitory postsynaptic currents in a mbGR- and CB1 cannabinoid receptor (CB1R)-dependent manner. Using a depolarization-induced suppression of inhibition protocol to test the effects of CORT on the endocannabinoid system, we find that CORT-mediated signaling enhances 2-arachidonoylglycerol synthesis that is inhibited by the diacylglycerol lipase inhibitor, DO34. CORT prolongs CB1R activation through a Gαs and protein kinase A-dependent pathway, whereas early depolarization-induced suppression of inhibition-initiated endocannabinoid activation of CB1Rs is independent of protein kinase A. These results highlight the critical role of CORT in the vlPAG in engaging endocannabinoid pathways to inhibit GABA release. The results indicate that CORT activation of putative mbGRs promote activation of the descending pain modulatory pathway through CB1R-mediated inhibition of GABA release in the vlPAG. SIGNIFICANCE STATEMENT: This study provides evidence that corticosterone activates putative membrane glucocorticoid receptors to increase levels of 2-arachidonoylglycerol to activate presynaptic CB1 cannabinoid receptors. These findings reveal mechanisms by which stress modulates the ventrolateral periaqueductal gray and the descending pain circuit.

The endocannabinoid (eCB) signaling system is robustly expressed in the cerebellum from embryonic developmental stages to adulthood. It plays a key role in regulating cerebellar synaptic plasticity and excitability, suggesting that impaired eCB signaling could lead to deficits in cerebellar adjustments of ongoing behaviors and cerebellar learning. Indeed, human mutations in DAGLα are associated with neurodevelopmental disorders. In this study, we show that selective deletion of the eCB synthesizing enzyme diacylglycerol lipase alpha (Daglα) from mouse cerebellar Purkinje cells (PCs) alters motor and social behaviors, disrupts short-term synaptic plasticity in both excitatory and inhibitory synapses, and reduces PC activity during social exploration. Our results provide the first evidence for cerebellar-specific eCB regulation of social behaviors and implicate eCB regulation of synaptic plasticity and PC activity as the neural substrates contributing to these deficits.

We report here that microglia exert a surprisingly discrete but functionally critical influence on synaptic plasticity in the mouse hippocampus. Treatment of adult male mice with colony-stimulating factor 1 receptor antagonist PLX5622 (PLX), with resultant depletion of forebrain microglia, did not disturb basal synaptic transmission at four synaptic connections in the hippocampus. Long-term potentiation (LTP) was also intact for three of these sites, but the singular, endocannabinoid-dependent form of LTP expressed by lateral perforant path (LPP) input to the dentate gyrus (DG) was severely impaired. The LPP-LTP defect occurred in conjunction with a pronounced increase in DG (but not neocortical) levels of 2-arachidonoylglycerol (2-AG), the retrograde (spine-to-terminal) endocannabinoid messenger that initiates LPP-LTP. Despite this, concentrations of the 2-AG synthetic enzyme diacylglycerol lipase were not affected by PLX treatment. Synaptic levels of the cannabinoid type 1 receptor, which mediates 2-AG effects on LPP-LTP, were similarly unaffected. Prior work has implicated the LPP in episodic memory. We determined that the LPP-LTP impairment in PLX-treated mice was accompanied by a failure to acquire the three basic elements of an episode: the identities, locations, and presentation order for a collection of olfactory cues. Treatment with JZL184, which inhibits the 2-AG degradative enzyme monoglyceride lipase, restored both LPP-LTP and episodic "What" encoding in PLX-treated mice. We conclude that microglia selectively regulate endocannabinoid transmission at the LPP→DG synapse and thereby potently influence synaptic plasticity at the initial stage of a corticohippocampal circuit that is critical for episodic memory.

Acetaminophen inhibits diacylglycerol lipase synthesis of 2-arachidonoyl glycerol: Implications for nociception

Acetaminophen (APAP) is commonly used as a pain and fever reliever, but its mechanisms remain unclear. Conflicting evidence implicates the endocannabinoid system in the effects of APAP. We tested the hypothesis that the analgesic effects of APAP were dependent upon both CB1 cannabinoid receptors and diacylglycerol lipase (DAGL), an enzyme which catalyzes formation of the endocannabinoid 2-arachidonoylglycerol. We examined the impact of APAP, administered in the presence and absence of DAGL inhibitors, on mechanical hypersensitivity in mice using models of inflammatory (induced by intraplantar injection of complete Freunds adjuvant (CFA)) and post-surgical (induced by incisional injury) pain. Pharmacological specificity was assessed using global (Rimonabant, AM251) and peripherally restricted (AM6545) CB1 antagonists. APAP produced a dose-dependent attenuation of inflammation-induced mechanical hypersensitivity, but did not alter peripheral edema in the CFA-injected paw. APAP also attenuated mechanical hypersensitivity in mice with incisional injury. The DAGL inhibitors, RHC-80267 or DO34, attenuated the anti-allodynic effects of APAP in both models of pain. CB1 receptor antagonists (Rimonabant and/or AM251) suppressed the antinociceptive effect of APAP in both pain models. The peripherally-restricted CB1 antagonist AM6545 did not alter the anti-allodynic effects of APAP. We also assessed the impact of APAP on tail-flick antinociception, locomotor behavior, and body temperature. APAP produced hypothermia and hypolocomotion at the highest dose, but these effects were not blocked by RHC-80267 or AM251. APAP did not produce tail flick antinociception. Our studies demonstrate that the analgesic effects of APAP observed in mouse models of pathological pain require both DAGL and CB1 activation. Our findings support a potential mechanism of APAP-induced analgesic action involving the enzyme DAGL and CB1 receptors.

The emerging role of endocannabinoid system modulation in human fibroblast-like synoviocytes: Exploring new biomarkers and potential therapeutic targets.

Hereditary factors play a significant role in the development of Parkinson's disease and the identification of causative genes is ongoing. Biallelic variants in Diacylglycerol lipase β (DAGLB) are related to early-onset Parkinson's disease (EOPD) in the Chinese population, and have also been identified in an Algerian case. To date, no EOPD cases with DAGLB variants have been reported among Japanese patients. This study was conducted to clarify the occurrence of DAGLB variants among Japanese EOPD patients. We screened 270 patients with sporadic EOPD (male: female ratio, 1.37:1; mean age at onset ± standard deviation, 37.32 ± 7.91 years), and 276 patients with suspected autosomal recessive Parkinson's disease (ARPD, male: female ratio, 0.75:1; mean age at onset ± standard deviation, 58.86 ± 14.67 years). Genetic screening of all coding exons and flanking splicing regions was performed by Sanger sequencing. We identified two rare biallelic variants in two patients, both from consanguineous families. One variant was a homozygous frameshift variant (c.1770_1771del, p.Tyr591ProfsTer26), which was predicted to be pathogenic. The other was a missense variant (c.1444T > C, p.Tyr482His) and was predicted to be benign, with co-segregation ruled out for this variant. We identified a pathogenic variant in the DAGLB gene. Together with previous reports, these findings provide further evidence that loss-of-function variants in DAGLB are involved in EOPD in the Japanese population.

While it is known that endocannabinoids (eCB) modulate multiple neuronal functions, the molecular mechanism governing their release and transport remains elusive. Here, we propose an "on-demand release" model, wherein the formation of microvesicles, a specific group of extracellular vesicles (EVs) containing the eCB, 2-arachidonoylglycerol (2-AG), is an important step. A coculture model system that combines a reporter cell line expressing the fluorescent eCB sensor, G protein-coupled receptor-based (GRAB)eCB2.0, and neuronal cells revealed that neurons release EVs containing 2-AG, but not anandamide, in a stimulus-dependent process regulated by protein kinase C, Diacylglycerol lipase, Adenosinediphosphate (ADP) ribosylation factor 6 (Arf6), and which was sensitive to inhibitors of eCB facilitated diffusion. A vesicle contained approximately 2,000 2-AG molecules. Accordingly, hippocampal eCB-mediated synaptic plasticity was modulated by Arf6 and transport inhibitors. The "on-demand release" model, supported by mathematical analysis, offers a cohesive framework for understanding eCB trafficking at the molecular level and suggests that microvesicles carrying signaling lipids in their membrane regulate neuronal functions in parallel to canonical synaptic vesicles.

The endocannabinoid system's significance in maintaining blood-brain barrier (BBB) integrity under physiological and pathological conditions is suggested by several reports, but the underlying molecular mechanisms are not well understood. In this paper, we investigated the effects of depletion of 2-arachidonoylglycerol (2-AG), one of the main endocannabinoids in the central nervous system, on BBB integrity using pharmacological tools. Female Sprague-Dawley rats were injected with the diacylglycerol lipase α (DAGLα) inhibitor LEI-106 (40mg/kg, i.p.), followed by assessment of BBB integrity via in situ brain perfusion. Liquid chromatography-mass spectrometry, western immunoblotting, light transmittance experiments and pressure myography were also used to further examine the results of DAGLα blockade on the BBB and vascular reactivity. We found that DAGLα inhibition caused BBB opening in cortical brain areas, manifesting as increased sucrose transport measured by in situ brain perfusion. This was accompanied by reduced levels of 2-AG and decreased detection of the tight junction protein zonula occludens-1 (ZO-1). The protein level in cortical areas of neuronal PAS domain protein 4 (NPAS4), encoded by an activity-dependent immediate early gene, was increased without the presence of cortical spreading depression after LEI-106 administration. We also observed a significant increase in pressure-induced constriction within the parenchymal microcirculation after inhibition of DAGLα, possibly altering shear stress in the microcirculation. These results support the role of endogenous 2-AG in maintaining normal tight junction function. This improved understanding of the molecular mechanisms of endocannabinoid system function at the neurovascular unit can help to unlock the therapeutic potentials of cannabinoids in central nervous system disorders associated with BBB dysfunction. KEY POINTS: The administration of the diacylglycerol lipase α (DAGLα) inhibitor LEI-106 (40mg/kg, i.p.) induced blood-brain barrier (BBB) opening of cortical brain areas in female Sprague-Dawley rats. This BBB disruption was accompanied by reduced levels of 2-arachidonoylglycerol (2-AG) and decreased detection of the tight junction protein zonula occludens-1 (ZO-1). The protein level in cortical areas of neuronal PAS domain protein 4 (NPAS4), encoded by an activity-dependent immediate early gene, was increased without the presence of cortical spreading depression after LEI-106 administration. A significant increase in pressure-induced constriction within the parenchymal microcirculation was also observed after inhibition of DAGLα, possibly altering shear stress. These results support the role of endogenous 2-AG in maintaining normal tight junction function.

Background/Objectives: Omega-3 long-chain polyunsaturated fatty acids (PUFAs) support brain cell membrane integrity and help mitigate synaptic plasticity deficits. The endocannabinoid system (ECS) is integral to synaptic plasticity and regulates various brain functions. While PUFAs influence the ECS, the effects of omega-3 on the ECS, cognition, and behavior in a healthy brain remain unclear. Methods and Results: Here, we demonstrate that hippocampal synaptosomes from male mice fed an omega-3-rich diet exhibit increased levels of cannabinoid CB1 receptors (~30%), phospholipase C β1 (PLCβ1, ~30%), monoacylglycerol lipase (MAGL, ~30%), and cannabinoid receptor-interacting protein 1a (Crip1a, ~60%). Conversely, these synaptosomes show decreased levels of diacylglycerol lipase α (DAGLα, ~40%), synaptosomal-associated protein 25kDa (SNAP-25, ~30%), and postsynaptic density protein 95 (PSD-95, ~40%). Omega-3 intake also reduces Gαo and Gαi3 levels, though receptor-stimulated [35S]GTPγS binding remains unaffected. Stimulation of the medial perforant path (MPP) induced long-term potentiation (LTP) in omega-3-fed mice. This LTP was dependent on group I metabotropic glutamate receptors (mGluR), 2 arachidonoylglycerol (2-AG), CB1 receptors, N-type Ca2+ channels, and actin filaments. Behaviorally, omega-3-fed mice displayed reduced exploratory behavior and significantly improved object discrimination in the novel object recognition test (NORT). They also spent more time in open arms and exhibited reduced freezing time in the elevated plus maze (EPM), indicative of reduced anxiety-like behavior. Conclusions: Our findings suggest that omega-3 leverages the ECS to enhance brain function under normal conditions.

Extra-cerebral manifestations of Alzheimer's disease (AD) develop in the retina, which is, therefore, considered a "window to the brain". Recent studies demonstrated the dysregulation of the endocannabinoid (eCB) system (ECS) in AD brain. Here, we explored the possible alterations of ECS and the onset of gliosis in the retina of AD-like mice. Tg2576 (TG) mice overexpressing the amyloid precursor protein (APP) were used at the age of 12 months, when hippocampal β-amyloid plaques had not been developed yet. Analysis of retinal gliosis showed a significant increase in the number of IBA1 (+) microglia cells in TG versus wild type (WT). Gliosis was not associated with retinal β-amyloid plaques, evident retinal degenerative signatures, or excitotoxicity; instead, oxidative stress burden was observed as increased acrolein levels. Analysis of the ECS (receptors/metabolic enzymes) through western blotting (WB) revealed the up-regulation of cannabinoid receptor 2 (CB2) and monoacylglycerol lipase (MAGL), the enzyme responsible for the degradation of 2-arachidonoylglycerol (2-AG), in TG retinas. Fluorescence intensity analysis of anti-CB2 and anti-MAGL immuno-stained cryosections was consistent with WB, showing their up-regulation throughout the retinal layers. No statistically significant differences were found for the other enzymes/receptors of the ECS under study. However, linear regression analysis for individual animals showed a significant correlation between CB2 and fatty acid amide hydrolase (FAAH), diacylglycerol lipase α/β (DAGLα/β), and APP; instead, a significant negative correlation was found between MAGL and APP. Finally, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) demonstrated a significant reduction of 2-AG in TG retinas (~0.34 ng/mg) compared to WT (~1.70 ng/mg), while a trend toward increase was found for the other eCB anandamide (AEA). Overall, our data indicate that gliosis and ECS dysregulation-in particular of CB2, MAGL and 2-AG-occur in the retina of AD-like mice before retinal degeneration and development of hippocampal β-amyloid plaques.

Acute myeloid leukemia (AML) is a highly heterogeneous hematological malignancy. The key problem lies in the complexity of the genome, so that drug resistance and relapse have become the main problems. Recent studies have found an association between synaptotagmin-like 4 (SYTL4) and drug resistance in triple-negative breast cancer and its high expression is correlated with poor prognosis; however, it is unclear whether this gene is associated with the prognosis of AML. This study aimed to investigate the role and action mechanism of SYTL4 in AML. We downloaded gene expression profiles and corresponding clinical data from The Cancer Genome Atlas (TCGA) public database and conducted differential and survival analyses using the Limma and survival packages in R. The receiver operating characteristic (ROC) curve, univariate COX, and multivariate COX were used for gene prediction analysis. Co-expression analysis of SYTL4 was performed using Limma, and enrichment analysis of differentially expressed genes in the SYTL4 high- and low-expression groups was conducted. We performed immune cell infiltration using the CIBERSORTx algorithm. The expression level of SYTL4 was highest in the poor prognosis group, and lowest in the good prognosis group. Survival was better in the SYTL4 low expression group than that in the high expression group. The areas under the ROC curve for TCGA-Acute Myeloid Leukemia (TCGA-LAML) at 1, 3, and 5 years were 0.725, 0.683, and 0.787, respectively. Sushi repeat protein X-linked 2 (SRPX2), caveolae associated protein 2 (CAVIN2), and other genes were identified as positive regulators of SYTL4 expression, whereas lactoperoxidase (LPO), diacylglycerol lipase beta (DAGLB), and other genes were identified as negative regulators. Differentially expressed genes in the SYTL4 high- and low-expression groups were enriched in pathways such as the embryonic skeletal system and platelet alpha granules. Differences were observed in follicular helper T cells, Tregs, monocytes, and M2 macrophages between SYTL4 high- and low-expression groups. SYTL4 expression negatively correlates with AML prognosis and may be associated with exosome secretion in AML.

BackgroundDepression is a chronic psychiatric disease of multifactorial etiology, and its pathophysiology is not fully understood. Stress and other chronic inflammatory pathologies are shared risk factors for psychiatric diseases, and comorbidities are features of major depression. Epidemiological evidence suggests that periodontitis, as a source of low-grade chronic systemic inflammation, may be associated with depression, but the underlying mechanisms are not well understood.MethodsPeriodontitis (P) was induced in Wistar: Han rats through oral gavage with the pathogenic bacteria Porphyromonas gingivalis and Fusobacterium nucleatum for 12 weeks, followed by 3 weeks of chronic mild stress (CMS) to induce depressive-like behavior. The following four groups were established (n = 12 rats/group): periodontitis and CMS (P + CMS+), periodontitis without CMS, CMS without periodontitis, and control. The morphology and inflammatory phenotype of microglia in the frontal cortex (FC) were studied using immunofluorescence and bioinformatics tools. The endocannabinoid (EC) signaling and proteins related to synaptic plasticity were analyzed in FC samples using biochemical and immunohistochemical techniques.ResultsUltrastructural and fractal analyses of FC revealed a significant increase in the complexity and heterogeneity of Iba1 + parenchymal microglia in the combined experimental model (P + CMS+) and increased expression of the proinflammatory marker inducible nitric oxide synthase (iNOS), while there were no changes in the expression of cannabinoid receptor 2 (CB2). In the FC protein extracts of the P + CMS + animals, there was a decrease in the levels of the EC metabolic enzymes N-acyl phosphatidylethanolamine-specific phospholipase D (NAPE-PLD), diacylglycerol lipase (DAGL), and monoacylglycerol lipase (MAGL) compared to those in the controls, which extended to protein expression in neurons and in FC extracts of cannabinoid receptor 1 (CB1) and to the intracellular signaling molecules phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt) and extracellular signal-regulated kinase 1/2 (ERK1/2). The protein levels of brain-derived neurotrophic factor (BDNF) and synaptophysin were also lower in P + CMS + animals than in controls.ConclusionsThe combined effects on microglial morphology and inflammatory phenotype, the EC signaling, and proteins related to synaptic plasticity in P + CMS + animals may represent relevant mechanisms explaining the association between periodontitis and depression. These findings highlight potential therapeutic targets that warrant further investigation.Graphical

ABSTRACTThe endocannabinoid (eCB) signaling system is robustly expressed in the cerebellum starting from the embryonic developmental stages to adulthood. There it plays a key role in regulating cerebellar synaptic plasticity and excitability, suggesting that impaired eCB signaling will lead to deficits in cerebellar adjustments of ongoing behaviors and cerebellar learning. Indeed, human mutations inDAGLαare associated with neurodevelopmental disorders. In this study, we show that selective deletion of the eCB synthesizing enzyme diacylglycerol lipase alpha (Daglα) from mouse cerebellar Purkinje cells (PCs) alters motor and social behaviors, disrupts short-term synaptic plasticity in both excitatory and inhibitory synapses, and reduces Purkinje cell activity during social exploration. Our results provide the first evidence for cerebellar-specific eCB regulation of social behaviors and implicate eCB regulation of synaptic plasticity and PC activity as the neural substrates contributing to these deficits.Abstract FigureGraphical abstract.Cerebellar anatomy, morphology of Purkinje cells, localization, density, and spontaneous activity of excitatory and inhibitory synapses are normal in cerebellar-Purkinje-cell-specific Daglα KOs. However, endocannabinoid-dependent short-term synaptic plasticity (DSE and DSI) and activity of Purkinje cells in lobe VI during social exploration are dramatically reduced, and the KO mice exhibit alterations in sensorimotor coordination, deceased social preference, and increased anxiety.

Cyclooxygenase-2 converts arachidonic acid to prostaglandins (PGs) and the endocannabinoid, 2-arachidonoylglycerol (2-AG), to PG glyceryl esters (PG-Gs). The physiological function of PG biosynthesis has been extensively studied, but the importance of the more recently discovered PG-G synthetic pathway remains incompletely defined. This disparity is due in part to a lack of knowledge of the physiological conditions under which PG-G biosynthesis occurs. We have discovered that RAW264.7 macrophages stimulated with Kdo2-lipid A (KLA) produce primarily PGs within the first 12 h followed by robust PG-G synthesis between 12 h and 24 h. We suggest that the amount of PG-Gs quantified is less than actually synthesized, because PG-Gs are subject to a significant level of hydrolysis during the time course of synthesis. Inhibition of cytosolic phospholipase A2 by giripladib does not accelerate PG-G synthesis, suggesting the differential time course of PG and PG-G synthesis is not due to the competition between arachidonic acid and 2-AG. The late-phase PG-G formation is accompanied by an increase in the level of 2-AG and a concomitant decrease in 18:0-20:4 diacylglycerol (DAG). Inhibition of DAG lipases by KT-172 decreases the levels of 2-AG and PG-Gs, indicating that the DAG-lipase pathway is involved in delayed 2-AG metabolism/PG-G synthesis. These results demonstrate that physiologically significant levels of PG-Gs are produced by activated RAW264.7 macrophages well after the production of PGs plateaus.

2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid (EC), acting as a full agonist at both CB1 and CB2 cannabinoid receptors. It is synthesized on demand in postsynaptic membranes through the sequential action of phosphoinositide-specific phospholipase Cβ1 (PLCβ1) and diacylglycerol lipase α (DAGLα), contributing to retrograde signaling upon interaction with presynaptic CB1. However, 2-AG production might also involve various combinations of PLC and DAGL isoforms, as well as additional intracellular pathways implying other enzymes and substrates. Three other alternative pathways of 2-AG synthesis rest on the extracellular cleavage of 2-arachidonoyl-lysophospholipids by three different hydrolases: glycerophosphodiesterase 3 (GDE3), lipid phosphate phosphatases (LPPs), and two members of ecto-nucleotide pyrophosphatase/phosphodiesterases (ENPP6-7). We propose the names of AlterAG-1, -2, and -3 for three pathways sharing an ectocellular localization, allowing them to convert extracellular lysophospholipid mediators into 2-AG, thus inducing typical signaling switches between various G-protein-coupled receptors (GPCRs). This implies the critical importance of the regioisomerism of both lysophospholipid (LPLs) and 2-AG, which is the object of deep analysis within this review. The precise functional roles of AlterAGs are still poorly understood and will require gene invalidation approaches, knowing that both 2-AG and its related lysophospholipids are involved in numerous aspects of physiology and pathology, including cancer, inflammation, immune defenses, obesity, bone development, neurodegeneration, or psychiatric disorders.

Neonatal dysregulation of 2-arachidonoylglycerol induces impaired brain function in adult mice

Arachidonic acid (AA), an important polyunsaturated fatty acid in the brain, is hydrolyzed by a direct action of phospholipase A2(PLA2) or through the combined action of phospholipase C and diacylglycerol lipase, and released into the cytoplasm. Various derivatives of AA can be synthesized mainly through the cyclooxygenase (COX), lipoxygenase (LOX) and cytochrome P450 (P450) enzyme pathways. AA and its metabolic enzymes and metabolites play important roles in a variety of neurophysiological activities. The abnormal metabolites and their catalytic enzymes in the AA cascade are related to the pathogenesis of various central nervous system (CNS) diseases, including epilepsy. Here, we systematically reviewed literatures in PubMed about the latest randomized controlled trials, animal studies and clinical studies concerning the known features of AA, its metabolic enzymes and metabolites, and their roles in epilepsy. The exclusion criteria include non-original studies and articles not in English.