Monoacylglycerol Lipase Inhibitor Research Articles

MAGL blockade alleviates steroid-induced femoral head osteonecrosis by reprogramming BMSC fate in rat

The leading cause of steroid-induced femoral head osteonecrosis (ONFH) is the imbalance of bone homeostasis. Bone marrow-derived mesenchymal stem cell (BMSC) differentiation and fate are closely associated with bone homeostasis imbalance. Blocking monoacylglycerol lipase (MAGL) could effectively ameliorate ONFH by mitigating oxidative stress and apoptosis in BMSCs induced by glucocorticoids (GC). Nevertheless, whether MAGL inhibition can modulate the balance during BMSC differentiation, and therefore improve ONFH, remains elusive. Our study indicates that MAGL inhibition can effectively rescue the enhanced BMSC adipogenic differentiation caused by GC and promote their differentiation toward osteogenic lineages. Cannabinoid receptor 2 (CB2) is the direct downstream target of MAGL in BMSCs, rather than cannabinoid receptor 1(CB1). Using RNA sequencing analyses and a series of in vitro experiments, we confirm that the MAGL blockade-induced enhancement of BMSC osteogenic differentiation is primarily mediated by the phosphoinositide 3-kinases (PI3K)/ the serine/threonine kinase (AKT)/ (glycogen synthase kinase-3 beta) GSK3β pathway. Additionally, MAGL blockade can also reduce GC-induced bone resorption by directly suppressing osteoclastogenesis and indirectly reducing the expression of receptor activator of nuclear factor kappa-Β ligand (RANKL) in BMSCs. Thus, our study proposes that the therapeutic effect of MAGL blockade on ONFH is partly mediated by restoring the balance of bone homeostasis and MAGL may be an effective therapeutic target for ONFH.

Modulation of chemotherapy-induced peripheral neuropathy by JZL195 through glia and the endocannabinoid system

Chemotherapy-induced peripheral neuropathy (CIPN) used to treat cancer, is a significant side effect with a complex pathophysiology, and its mechanisms remain unclear. Recent research highlights neuroinflammation, which is modulated by the endocannabinoid system (ECS) and associated with glial activation, and the role of toll-like receptor 4 (TLR4) in CIPN. This study aimed to investigate the effects of JZL195, an inhibitor of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), and explore the connection between cannabinoid receptors and TLR4 in glial cells. A CIPN animal model was developed using cisplatin-injected male C57BL/6 mice. Mechanical and cold allodynia were assessed through von Frey and acetone tests. Western blot analysis was used to examine the expression of catabolic enzymes, cannabinoid receptors, glial cells, and neuroinflammatory factors in the dorsal root ganglia (DRGs) and spinal cord. Immunohistochemistry was used to investigate the colocalization of cannabinoid receptors and TLR4 in glial cells. JZL195 alleviated pain by inhibiting FAAH/MAGL, modulating the ECS and neuroinflammatory factors, and suppressing glial cell activity. Additionally, cannabinoid receptors and TLR4 colocalized with astrocytes and microglia in the spinal cord. This study highlights the therapeutic potential of JZL195 in modulating the ECS and suggests a correlation between cannabinoid receptors and TLR4 in spinal glial cells, providing insight into alleviating pain and neuroinflammation in CIPN.

Synergistic effect and mechanism of monoacylglycerol lipase inhibitor and Icaritin in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic, relapsing nonspecific intestinal inflammatory disease. It is difficult for a single drug to treat UC effectively and maintain long-term efficacy. There is an urgent need to find new drugs and treatment strategies. MAGL11 is a new kind of single acylglycerol lipase (MAGL) inhibitor. Icaritin (Y003) is the major metabolite of icariin in vivo. Several studies have confirmed the role of MAGL inhibitors and icariin in anti-inflammatory and regulation of intestinal stability. Therefore, this study adopted a new strategy of combining MAGL inhibitor with Icaritin to further explore the role and mechanism of drugs in the treatment of UC. Enzyme-linked immunosorbent assay (ELISA), hematoxylin-eosin staining (HE), immunohistochemical (IHC) and Western blot were used to detect the synergistic protective effects of MAGL11 and Y003 on intestinal pathological injury, intestinal mucosal permeability and inflammation in UC mice. 16S rDNA sequencing was used to detect the synergistic effect of MAGL11 and Y003 on gut microbiota. The effects of MAGL11 and Y003 combined therapy on serum and fecal metabolism of UC mice were analyzed by untargeted metabolomics. Proteomics method was applied to investigate the molecular mechanisms underlying MAGL11 and Y003 synergy in the treatment of UC. The results showed that MAGL11 and Y003 could synergistically improve the clinical symptoms, reduce intestinal inflammation and pathological damage, and improve intestinal mucosal permeability in UC mice. The mechanism study found that MAGL11 and Y003 could synergistically inhibit Toll-like receptors 4 (TLR4) / Myeloid differentiation primary response gene (Myd88)/Nuclear factor kappa-B (NF-κB) pathway and further regulate gut microbiota imbalance and metabolic disorders to treat UC.

Identifying Potential Human Monoacylglycerol Lipase Inhibitors from the Phytoconstituents of Morinda Citrifolia L. Fruits by in silico Pharmacology and in vitro Study.

Human monoacylglycerol lipase (MGL) is accountable for the hydrolysis of 2-arachidonoylglycerol (2-AG), thus contributing pivotally to neuroprotection because 2-AG is the main source of arachidonic acid, the precursor of prostaglandins production. Inhibiting MGL reduces inflammatory damage in the ischemic brain and enhances cerebral blood flow. Plants have been reported for their neuroprotective effect, such as Morinda citrifolia on pentylenetetrazol (PTZ)-induced kindling seizures in mice, by reducing the seizures and restoring behavioral and biochemical changes, although the mechanism is not described. To evaluate the binding affinity and stability of phytoconstituents in M. citrifolia fruits toward human MGL (PDB ID 3PE6), compared to the known MGL inhibitors (JZL195 and ZYH). The in silico pharmacology study was validated by an in vitro study of the phytosterols and the ethanol extract of M. citrifolia fruits (EEMC) towards MGL. Initially, nine phytoconstituents of M. citrifolia fruits were docked to the catalytic pocket of human MGL (PDB ID: 3PE6), and compounds with the best affinity were subjected to a molecular dynamic (MD) simulation. The in vitro study was performed using the MGL inhibitor screening assay kit. The best binding affinity and stability toward human MGL were shown by stigmasterol and beta-sitosterol, and the MM-PBSA total binding energy of stigmasterol and beta-sitosterol to MGL is stronger than that of JZL195 and ZYH. Moreover, beta-sitosterol and EEMC inhibit MGL with an IC50 value of, respectively, 8.10μg/mL and 196.20μg/mL, while JZL195 shows an IC50 of 0.028μg/mL. Beta-sitosterol of Morinda citrifolia fruits may have the potential to protect human neurons by occupying the catalytic site of human MGL, thus competitively inhibiting the substrate of the enzyme. However, the inhibitory activity towards human MGL is lower than JZL195.

Seeing through the Haze: Monoacylglycerol Lipase Inhibitors As Analgesics.

Seeing through the Haze: Monoacylglycerol Lipase Inhibitors As Analgesics.

Structure-Activity Relationship Studies of Aryl Sulfoxides as Reversible Monoacylglycerol Lipase Inhibitors.

Monoacylglycerol lipase (MAGL) is the key enzyme for the hydrolysis of endocannabinoid 2-arachidonoylglycerol (2-AG). The central role of MAGL in the metabolism of 2-AG makes it an attractive therapeutic target for a variety of disorders, including inflammation-induced tissue injury, pain, multiple sclerosis, and cancer. Previously, we reported LEI-515, an aryl sulfoxide, as a peripherally restricted, covalent reversible MAGL inhibitor that reduced neuropathic pain and inflammation in preclinical models. Here, we describe the structure-activity relationship (SAR) of aryl sulfoxides as MAGL inhibitors that led to the identification of LEI-515. Optimization of the potency of high-throughput screening (HTS) hit 1 yielded compound ±43. However, ±43 was not metabolically stable due to its ester moiety. Replacing the ester group with α-CF2 ketone led to the identification of compound ±73 (LEI-515) as a metabolically stable MAGL inhibitor with subnanomolar potency. LEI-515 is a promising compound to harness the therapeutic potential of MAGL inhibition.

Design, synthesis and biological evaluation of naphthyl amide derivatives as reversible monoacylglycerol lipase (MAGL) inhibitors

Monoacylglycerol lipase (MAGL) is a key enzyme responsible for the metabolism of the endocannabinoid 2-arachidonoylglycerol (2-AG), and has attracted great interest due to its involvement in various physiological and pathological processes, such as cancer progression. In the past, a number of covalent irreversible inhibitors have been reported for MAGL, however, experimental evidence highlighted some drawbacks associated with the use of these irreversible agents. Therefore, efforts were mainly focused on the development of reversible MAGL inhibitor in recent years. Here, we designed and synthesized a series of naphthyl amide derivatives (12–39) as another type of reversible MAGL inhibitors, exemplified by ± 34, which displayed good MAGL inhibition with a pIC50 of 7.1, and the potency and selectivity against endogenous MAGL were further demonstrated by competitive ABPP. Moreover, the compound showed appreciable antiproliferative activities against several cancer cells, including H460, HT29, CT-26, Huh7 and HCCLM-3. The investigations culminated in the discovery of the naphthyl amide derivative ± 34, and it may represent as a new scaffold for MAGL inhibitor development, particularly for the reversible ones.

A carrier free delivery system of a MAGL inhibitor is effective on ovarian cancer

Monoacylglycerol lipase (MAGL) is a promising target for cancer therapy due to its involvement in lipid metabolism and its impact on cancer hallmarks like cell proliferation, migration, and tumor progression. A potent reversible MAGL inhibitor, MAGL23, has been recently developed by our group, demonstrating promising anticancer activities. To enhance its pharmacological properties, a nanoformulation using nanocrystals coated with albumin was prepared (MAGL23AF). In a previous work, the formulated inhibitor showed potency in ovarian and colon cancer cell lines in terms of IC50, and was tested on mice in order to assess its biocompatibility, organs biodistribution and toxicity. In the present work, we expanded the investigation to assess the potential in vivo application of MAGL23AF. Stability assays in serum and in human derived microsomes showed a good structural stability in physiological conditions of MAGL23AF. The antitumor efficacy tested on mice bearing ovarian cancer tumor xenografts demonstrated that MAGL23AF is more potent than the non-formulated drug, leading to necrosis-driven cancer cell death. In vivo studies revealed that albumin-complexed nanocrystals improved the therapeutic window of MAGL23, exhibiting a favorable biodistribution with slightly increased accumulation in the tumor. In conclusion, the MAGL23AF showed increased in vitro stability in conditions mirroring the bloodstream environment and hepatic metabolism coupled with an optimal antitumor efficacy in vivo. These results not only validates the efficacy of our formulation but also positions it as a promising strategy for addressing challenges related to the solubility of drugs in body fluids.

Disrupted stress-induced analgesia in a neuropathic pain state is rescued by the endocannabinoid degradation inhibitor JZL195.

Acute stress normally engages descending brain pathways to produce an antinociceptive response, known as stress-induced analgesia. Paradoxically, these descending pain modulatory pathways are also involved in the maintenance of the abnormal pain associated with chronic neuropathic pain. It remains unclear how stress-induced analgesia is affected by neuropathic pain states. We therefore examined the impact of a chronic constriction nerve-injury (CCI) model of neuropathic pain on restraint stress-induced analgesia in C57BL/6 mice. Thirty minutes of restraint stress produced analgesia in the hotplate thermal nociceptive assay that was less in CCI compared to control mice who underwent a sham-surgery. In sham but not CCI mice, stress-induced analgesia was reduced by the opioid receptor antagonist naltrexone. The cannabinoid CB1 receptor antagonist AM281 did not affect stress-induced analgesia in either sham or CCI mice. Low-dose pre-treatment with the dual fatty acid amide hydrolase and monoacylglycerol lipase inhibitor JZL195 increased stress-induced analgesia in CCI but not sham mice. The JZL195 enhancement of stress-induced analgesia in CCI mice was abolished by AM281 but was unaffected by naltrexone. These findings indicate that the acute opioid-mediated analgesic response to a psychological stressor is disrupted in a nerve-injury model of neuropathic pain. Importantly, this impairment of stress-induced analgesia was rescued by blockade of endocannabinoid breakdown via a cannabinoid CB1 receptor dependent mechanism. These findings suggest that subthreshold treatment with endocannabinoid degradation blockers could be used to alleviate the disruption of endogenous pain control systems in a neuropathic pain state.

Watermelon: setup and validation of an in silico fragment-based approach

We present a new computational approach, named Watermelon, designed for the development of pharmacophore models based on receptor structures. The methodology involves the sampling of potential hotspots for ligand interactions within a protein target’s binding site, utilising molecular fragments as probes. By employing docking and molecular dynamics (MD) simulations, the most significant interactions formed by these probes within distinct regions of the binding site are identified. These interactions are subsequently transformed into pharmacophore features that delineates key anchoring sites for potential ligands. The reliability of the approach was experimentally validated using the monoacylglycerol lipase (MAGL) enzyme. The generated pharmacophore model captured features representing ligand-MAGL interactions observed in various X-ray co-crystal structures and was employed to screen a database of commercially available compounds, in combination with consensus docking and MD simulations. The screening successfully identified two new MAGL inhibitors with micromolar potency, thus confirming the reliability of the Watermelon approach.

Endocannabinoid Hydrolase Inhibitors: Potential Novel Anxiolytic Drugs.

Over the past decade, the idea of targeting the endocannabinoid system to treat anxiety disorders has received increasing attention. Previous studies focused more on developing cannabinoid receptor agonists or supplementing exogenous cannabinoids, which are prone to various adverse effects due to their strong pharmacological activity and poor receptor selectivity, limiting their application in clinical research. Endocannabinoid hydrolase inhibitors are considered to be the most promising development strategies for the treatment of anxiety disorders. More recent effortshave emphasized that inhibition of two major endogenous cannabinoid hydrolases, monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), indirectly activates cannabinoid receptors by increasing endogenous cannabinoid levels in the synaptic gap, circumventing receptor desensitization resulting from direct enhancement of endogenous cannabinoid signaling. In this review, we comprehensively summarize the anxiolytic effects of MAGL and FAAH inhibitors and their potential pharmacological mechanisms, highlight reported novel inhibitors or natural products, and provide an outlook on future directions in this field.

A helping HAND: therapeutic potential of MAGL inhibition against HIV-1-associated neuroinflammation.

Human immunodeficiency virus (HIV) affects nearly 40 million people globally, with roughly 80% of all people living with HIV receiving antiretroviral therapy. Antiretroviral treatment suppresses viral load in peripheral tissues but does not effectively penetrate the blood-brain barrier. Thus, viral reservoirs persist in the central nervous system and continue to produce low levels of inflammatory factors and early viral proteins, including the transactivator of transcription (Tat). HIV Tat is known to contribute to chronic neuroinflammation and synaptodendritic damage, which is associated with the development of cognitive, motor, and/or mood problems, collectively known as HIV-associated neurocognitive disorders (HAND). Cannabinoid anti-inflammatory effects are well documented, but therapeutic utility of cannabis remains limited due to its psychotropic effects, including alterations within brain regions encoding reward processing and motivation, such as the nucleus accumbens. Alternatively, inhibiting monoacylglycerol lipase (MAGL) has demonstrated therapeutic potential through interactions with the endocannabinoid system. The present study utilized a reward-related operant behavioral task to quantify motivated behavior in female Tat transgenic mice treated with vehicle or MAGL inhibitor MJN110 (1 mg/kg). Brain tissue was collected to assess dendritic injury and neuroinflammatory profiles, including dendritic microtubule-associated protein (MAP2ab) intensity, microglia density, microglia morphology, astrocyte density, astrocytic interleukin-1ß (IL-1ß) colocalization, and various lipid mediators. No significant behavioral differences were observed; however, MJN110 protected against Tat-induced dendritic injury by significantly upregulating MAP2ab intensity in the nucleus accumbens and in the infralimbic cortex of Tat(+) mice. No or only minor effects were noted for Iba-1+ microglia density and/or microglia morphology. Further, Tat increased GFAP+ astrocyte density in the infralimbic cortex and GFAP+ astrocytic IL-1ß colocalization in the nucleus accumbens, with MJN110 significantly reducing these measures in Tat(+) subjects. Lastly, selected HETE-related inflammatory lipid mediators in the striatum were downregulated by chronic MJN110 treatment. These findings demonstrate anti-inflammatory and neuroprotective properties of MJN110 without cannabimimetic behavioral effects and suggest a promising alternative to cannabis for managing neuroinflammation.

Improvement of lower urinary tract dysfunction by a monoacylglycerol lipase inhibitor in mice with spinal cord injury.

Activation of the endocannabinoid system by monoacylglycerol lipase (MAGL) blockade may affect the lower urinary tract function. We investigated the effect of an MAGL inhibitor, MJN110, on neurogenic lower urinary tract dysfunction (LUTD) in the mouse model of spinal cord injury (SCI). Female C57BL/6 mice that underwent spinal cord transection at T8-10 level were divided into three groups consisting of (1) vehicle-treated SCI mice, (2) 5 mg/kg, or (3) 10 mg/kg of MJN110-treated SCI mice. MJN110 and vehicle were administered intraperitoneally for 7 days from 4 weeks after spinal cord transection. We then conducted awake cystometrograms and compared urodynamic parameters between three groups. The expression of cannabinoid (CB) receptors, TRP receptors, and inflammatory cytokines in L6-S1 dorsal root ganglia (DRG) or the bladder mucosa were evaluated and compared among three groups. Changes in the level of serum 2-arachidonoylglycerol (2-AG) and bladder MAGL were also evaluated. In the cystometrogram, detrusor overactivity (DO) parameters, such as the number of nonvoiding contraction (NVC), a ratio of time to the 1st NVC to intercontraction interval (ICI), and NVC integrals were improved by MJN110 treatment, and some effects were dose dependent. Although MJN110 did not improve voiding efficiency, it decreased bladder capacity, ICI, and residual urine volume compared to vehicle injection. MJN110 treatment groups had lower CB2, TRPV1, TRPA1, and inflammatory cytokines mRNA levels in DRG and bladder mucosa. Serum 2-AG was increased,and bladder MAGL was decreased after MAGL inhibitor treatment. MAGL inhibition improved LUTD including attenuation of DO after SCI. Thus, MAGL can be a therapeutic target for neurogenic LUTD after SCI.

Inhibition of MAGL attenuates Intervertebral Disc Degeneration by Delaying nucleus pulposus senescence through STING

Intervertebral disc degeneration (IVDD) stands as the primary cause of low back pain (LBP). A significant contributor to IVDD is nucleus pulposus cell (NPC) senescence. However, the precise mechanisms underlying NPC senescence remain unclear. Monoacylglycerol lipase (MAGL) serves as the primary enzyme responsible for the hydrolysis of 2-arachidonoylglycerol (2-AG), breaking down monoglycerides into glycerol and fatty acids. It plays a crucial role in various pathological processes, including pain, inflammation, and oxidative stress. In this study, we utilized a lipopolysaccharide (LPS)-induced NPC senescence model and a rat acupuncture-induced IVDD model to investigate the role of MAGL in IVDD both in vitro and in vivo. Initially, our results showed that MAGL expression was increased 2.41-fold and 1.52-fold within NP tissues from IVDD patients and rats induced with acupuncture, respectively. This increase in MAGL expression was accompanied by elevated expression of p16INK4α. Following this, it was noted that the suppression of MAGL resulted in a notable decrease in the quantity of SA-β-gal-positive cells and hindered the manifestation of p16INK4α and the inflammatory factor IL-1β in NPCs. MAGL inhibition promotes type II collagen (Col-2) expression and inhibits matrix metalloproteinase 13 (MMP13), thereby restoring the balance of extracellular matrix (ECM) metabolism both in vitro and in vivo. A significant role for STING has also been demonstrated in the regulation of NPC senescence by MAGL. The expression of the STING protein was reduced by 57% upon the inhibition of MAGL. STING activation can replicate the effects of MAGL and substantially increase LPS-induced inflammation while accelerating the senescence of NPCs. These results strongly indicate that the inhibition of MAGL can significantly suppress nucleus pulposus senescence via its interaction with STING, consequently restoring the balance of ECM metabolism. This insight provides new perspectives for potential treatments for IVDD.

Discovery of a novel class of reversible monoacylglycerol lipase inhibitors for potential treatment of depression

Biological studies on the endocannabinoid system (ECS) have suggested that monoacylglycerol lipase (MAGL), an essential enzyme responsible for the hydrolysis of 2-arachidonoylglycerol (2-AG), is a novel target for developing antidepressants. A decrease of 2-AG levels in the hippocampus of the brain has been observed in depressive-like models induced by chronic stress. Herein, employing a structure-based approach, we designed and synthesized a new class of (piperazine-1-carbonyl) quinolin-2(1H)-one derivatives as potent, reversible and selective MAGL inhibitors. And detailed structure-activity relationships (SAR) studies were discussed. Compound 27 (IC50 = 10.3 nM) exhibited high bioavailability (92.7%) and 2-AG elevation effect in vivo. Additionally, compound 27 exerted rapid antidepressant effects caused by chronic restraint stress (CRS) and didn't show signs of addictive properties in the conditioned place preference (CPP) assays. Our study is the first to report that reversible MAGL inhibitors can treat chronic stress-induced depression effectively, which may provide a new potential therapeutic strategy for the discovery of an original class of safe, rapid antidepressant drugs.

Acute Effects of Monoacylglycerol Lipase Inhibitor ABX1431 on Neuronal Hyperexcitability, Nociception, Locomotion, and the Endocannabinoid System in HIV-1 Tat Male Mice.

Background: Evidence suggests that monoacylglycerol lipase (MAGL) inhibitors can potentially treat HIV symptoms by increasing the concentration of 2-arachidonoylglycerol (2-AG). We examined a selective MAGL inhibitor ABX1431 in the context of neuroHIV. Methods: To assess the effects of ABX1431, we conducted in vitro and in vivo studies. In vitro calcium imaging on frontal cortex neuronal cultures was performed to evaluate the role of ABX1431 (10, 30, 100 nM) on transactivator of transcription (Tat)-induced neuronal hyperexcitability. Following in vitro experiments, in vivo experiments were performed using Tat transgenic male mice. Mice were treated with 4 mg/kg ABX1431 and assessed for antinociception using tail-flick and hot plate assays followed by locomotor activity. After the behavioral experiments, their brains were harvested to quantify endocannabinoids (eCB) and related lipids through mass spectrometry, and cannabinoid type-1 and -2 receptors (CB1R and CB2R) were quantified through western blot. Results: In vitro studies revealed that adding Tat directly to the neuronal cultures significantly increased intracellular calcium concentration, which ABX1431 completely reversed at all concentrations. Preincubating the cultures with CB1R and CB2R antagonists showed that ABX1431 exhibited its effects partially through CB1R. In vivo studies demonstrated that acute ABX1431 increased overall total distance traveled and speed of mice regardless of their genotype. Mass spectrometry and western blot analyses revealed differential effects on the eCB system based on Tat expression. The 2-AG levels were significantly upregulated following ABX1431 treatment in the striatum and spinal cord. Arachidonic acid (AA) was also upregulated in the striatum of vehicle-treated Tat(+) mice. No changes were noted in CB1R expression levels; however, CB2R levels were increased in ABX1431-treated Tat(-) mice only. Conclusion: Findings indicate that ABX1431 has potential neuroprotective effects in vitro partially mediated through CB1R. Acute treatment of ABX1431 in vivo shows antinociceptive effects, and seems to alter locomotor activity, with upregulating 2-AG levels in the striatum and spinal cord.

Effects of Repeated Treatment with the Monoacylglycerol Lipase Inhibitor MJN110 on Pain-Related Depression of Nesting and Cannabinoid 1 Receptor Function in Male and Female Mice.

MJN110 inhibits the enzyme monoacylglycerol lipase (MAGL) to increase levels of the endocannabinoid 2-arachidonoylglycerol , an endogenous high-efficacy agonist of cannabinoid 1 and 2 receptors (CB1/2R). MAGL inhibitors are under consideration as candidate analgesics, and we reported previously that acute MJN110 produced partial antinociception in an assay of pain-related behavioral depression in mice. Given the need for repeated analgesic administration in many pain patients and the potential for analgesic tolerance during repeated treatment, this study examined antinociceptive effects of repeated MJN110 on pain-related behavioral depression and CB1R-mediated G-protein function. Male and female ICR mice were treated daily for 7 days in a 2 × 2 design with (a) 1.0 mg/kg/d MJN110 or its vehicle followed by (b) intraperitoneal injection of dilute lactic acid (IP acid) or its vehicle as a visceral noxious stimulus to depress nesting behavior. After behavioral testing, G-protein activity was assessed in lumbar spinal cord (LSC) and five brain regions using an assay of CP55,940-stimulated [35S]GTPɣS activation. As reported previously, acute MJN110 produced partial but significant relief of IP acid-induced nesting depression on day 1. After 7 days, MJN110 continued to produce significant but partial antinociception in males, while antinociceptive tolerance developed in females. Repeated MJN110 also produced modest decreases in maximum levels of CP55,940-induced [35S]GTPɣS binding in spinal cord and most brain regions. These results indicate that repeated treatment with a relatively low antinociceptive MJN110 dose produces only partial and sex-dependent transient antinociception associated with the emergence of CB1R desensitization in this model of IP acid-induced nesting depression. SIGNIFICANCE STATEMENT: The drug MJN110 inhibits monoacylglycerol lipase (MAGL) to increase levels of the endogenous cannabinoid 2-arachidonoylglycerol and produce potentially useful therapeutic effects including analgesia. This study used an assay of pain-related behavioral depression in mice to show that repeated MJN110 treatment produced (1) weak but sustained antinociception in male mice, (2) antinociceptive tolerance in females, and (3) modest cannabinoid-receptor desensitization that varied by region and sex. Antinociceptive tolerance may limit the utility of MJN110 for treatment of pain.

Development of Potent and Selective Monoacylglycerol Lipase Inhibitors. SARs, Structural Analysis, and Biological Characterization.

New potent, selective monoacylglycerol lipase (MAGL) inhibitors based on the azetidin-2-one scaffold ((±)-5a-v, (±)-6a-j, and (±)-7a-d) were developed as irreversible ligands, as demonstrated by enzymatic and crystallographic studies for (±)-5d, (±)-5l, and (±)-5r. X-ray analyses combined with extensive computational studies allowed us to clarify the binding mode of the compounds. 5v was identified as selective for MAGL when compared with other serine hydrolases. Solubility, in vitro metabolic stability, cytotoxicity, and absence of mutagenicity were determined for selected analogues. The most promising compounds ((±)-5c, (±)-5d, and (±)-5v) were used for in vivo studies in mice, showing a decrease in MAGL activity and increased 2-arachidonoyl-sn-glycerol levels in forebrain tissue. In particular, 5v is characterized by a high eudysmic ratio and (3R,4S)-5v is one of the most potent irreversible inhibitors of h/mMAGL identified thus far. These results suggest that the new MAGL inhibitors have therapeutic potential for different central and peripheral pathologies.

Function of Presynaptic Inhibitory Cannabinoid CB1 Receptors in Spontaneously Hypertensive Rats and Its Modification by Enhanced Endocannabinoid Tone.

We studied whether the function of presynaptic inhibitory cannabinoid CB1 receptors on the sympathetic nerve fibres innervating resistance vessels is increased in spontaneously hypertensive rats (SHR) like in deoxycorticosterone (DOCA)-salt hypertension. An increase in diastolic blood pressure (DBP) was induced by electrical stimulation of the preganglionic sympathetic neurons or by phenylephrine injection in pithed SHR and normotensive Wistar-Kyoto rats (WKY). The electrically (but not the phenylephrine) induced increase in DBP was inhibited by the cannabinoid receptor agonist CP55940, similarly in both groups, and by the endocannabinoid reuptake inhibitor AM404 in SHR only. The effect of CP55940 was abolished/reduced by the CB1 receptor antagonist AM251 (in both groups) and in WKY by endocannabinoid degradation blockade, i.e., the monoacylglycerol lipase (MAGL) inhibitor MJN110 and the dual fatty acid amide hydrolase (FAAH)/MAGL inhibitor JZL195 but not the FAAH inhibitor URB597. MJN110 and JZL195 tended to enhance the effect of CP55940 in SHR. In conclusion, the function of presynaptic inhibitory CB1 receptors depends on the hypertension model. Although no differences occurred between SHR and WKY under basal experimental conditions, the CB1 receptor function was better preserved in SHR when the endocannabinoid tone was increased by the inhibition of MAGL or the endocannabinoid transporter.

β-Caryophyllene Inhibits Monoacylglycerol Lipase Activity and Increases 2-Arachidonoyl Glycerol Levels In Vivo: A New Mechanism of Endocannabinoid-Mediated Analgesia?

The mechanisms of β-caryophyllene (BCP)-induced analgesia are not well studied. Here, we tested the efficacy of BCP in an acute postsurgical pain model and evaluated its effect on the endocannabinoid system. Rats were treated with vehicle and 10, 25, 50, and 75 mg/kg BCP. Paw withdrawal responses to mechanical stimuli were evaluated using an electronic von Frey anesthesiometer. Endocannabinoids, including 2-arachidonoylglycerol (2-AG), were also evaluated in plasma and tissues using high-performance liquid chromatography-tandem mass spectrometry. Monoacylglycerol lipase (MAGL) activity was evaluated in vitro as well as ex vivo. We observed a dose-dependent and time-dependent alleviation of hyperalgesia in incised paws up to 85% of the baseline value at 30 minutes after administration of BCP. We also observed dose-dependent increases in the 2-AG levels of about threefold after administration of BCP as compared with vehicle controls. Incubations of spinal cord tissue homogenates from BCP-treated rats with isotope-labeled 2-arachidonoylglycerol-d8 revealed a reduced formation of the isotope-labeled MAGL product 2-AG-d8 as compared with vehicle controls, indicating MAGL enzyme inhibition. In vitro MAGL enzyme activity assessment using 2-AG as the substrate revealed an IC50 of 15.8 µM for MAGL inhibition using BCP. These data showed that BCP inhibits MAGL activity in vitro and in vivo, causing 2-AG levels to rise. Since the endocannabinoid 2-AG is a CB1 and CB2 receptor agonist, we propose that 2-AG-mediated cannabinoid receptor activation contributes to BCP's mechanism of analgesia. SIGNIFICANCE STATEMENT: β-Caryophyllene (BCP) consumption is relatively safe and is approved by the Food and Drug Administration as a flavoring agent, which can be used in cosmetic and food additives. BCP is a potent anti-inflammatory agent that showed substantial antihyperalgesic properties in this study of acute pain suggesting that BCP might be an alternative to opioids. This study shows an additive mechanism (monoacylglycerol lipase inhibition) by which BCP might indirectly alter CB1 and CB2 receptor activity and exhibit its pharmacological properties.