Therapeutic potential of monoacylglycerol lipase inhibitors

JZL184, A Monoacylglycerol Lipase Inhibitor, Induces Bone Loss in a Multiple Myeloma Model of Immunocompetent Mice

Multiple myeloma (MM) patients develop osteolysis characterised by excessive osteoclastic bone destruction and lack of osteoblast bone formation. Pharmacological manipulation of monoacylglycerol lipase (MAGL), an enzyme responsible for the degradation of the endocannabinoid 2-arachidonoyl glycerol (2-AG), reduced skeletal tumour burden and osteolysis associated with osteosarcoma and advanced breast and prostate cancers. MM and hematopoietic, immune and bone marrow cells express high levels of type 2 cannabinoid receptor and osteoblasts secrete 2-AG. However, the effects of MAGL manipulation on MM have not been investigated. Here, we report that treatment of pre-osteoclasts with non-cytotoxic concentrations of JZL184, a verified MAGL inhibitor, enhanced MM- and RANKL-induced osteoclast formation and size in vitro. Exposure of osteoblasts to JZL184 in the presence of MM cell-derived factors reduced osteoblast growth but had no effect on the ability of these cells to mature or form bone nodules. In vivo, administration of JZL184 induced a modest, yet significant, bone loss at both trabecular and cortical compartments of long bones of immunocompetent mice inoculated with the syngeneic 5TGM1-GFP MM cells. Notably, JZL184 failed to inhibit the in vitro growth of a panel of mouse and human MM cell lines, or reduce tumour burden in mice. Thus, MAGL inhibitors such as JZL184 can exacerbate MM-induced bone loss.

Lipase Inhibitors for Obesity: A Review

With the rapid increase in the population of obese individuals, obesity has become a global problem. Many kinds of chronic metabolic diseases easily caused by obesity have received increasing attention from researchers. People are also striving to find various safe and effective treatment methods as well as anti-obesity medicines. Pancreatic lipase (PL) inhibitors have received substantial attention from researchers in recent years, and PL inhibitors from natural products have attracted much attention due to their structural diversity, low toxicity and wide range of sources. They have been used in the intestinal tract, blood, and the central nervous system with no side effects, and these advantages could lead to a new generation of diet pills or health care products with great development potential. This article is mainly aimed at discussing the research of obesity drug treatment with PL inhibitors and offers a brief review of related properties and the use of PL inhibitors in the field of weight loss.

Dysregulated expression of monoacylglycerol lipase is a marker for anti-diabetic drug metformin-targeted therapy to correct impaired neurogenesis and spatial memory in Alzheimer's disease

Rationale: Monoacylglycerol lipase (Mgll), a hydrolase that breaks down the endocannabinoid 2-arachidonoyl glycerol (2-AG) to produce arachidonic acid (ARA), is a potential target for neurodegenerative diseases, such as Alzheimer's disease (AD). Increasing evidence shows that impairment of adult neurogenesis by perturbed lipid metabolism predisposes patients to AD. However, it remains unknown what causes aberrant expression of Mgll in AD and how Mgll-regulated lipid metabolism impacts adult neurogenesis, thus predisposing to AD during aging. Here, we identify Mgll as an aging-induced factor that impairs adult neurogenesis and spatial memory in AD, and show that metformin, an FDA-approved anti-diabetic drug, can reduce the expression of Mgll to reverse impaired adult neurogenesis, prevent spatial memory decline and reduce β-amyloid accumulation.

Methods: Mgll expression was assessed in both human AD patient post-mortem hippocampal tissues and 3xTg-AD mouse model. In addition, we used both the 3xTg-AD animal model and the CbpS436A genetic knock-in mouse model to identify that elevated Mgll expression is caused by the attenuation of the aPKC-CBP pathway, involving atypical protein kinase C (aPKC)-stimulated Ser436 phosphorylation of histone acetyltransferase CBP through biochemical methods. Furthermore, we performed in vivo adult neurogenesis assay with BrdU/EdU labelling and Morris water maze task in both animal models following pharmacological treatments to show the key role of Mgll in metformin-corrected neurogenesis and spatial memory deficits of AD through reactivating the aPKC-CBP pathway. Finally, we performed in vitro adult neurosphere assays using both animal models to study the role of the aPKC-CBP mediated Mgll repression in determining adult neural stem/progenitor cell (NPC) fate.

Results: Here, we demonstrate that aging-dependent induction of Mgll is observed in the 3xTg-AD model and human AD patient post-mortem hippocampal tissues. Importantly, we discover that elevated Mgll expression is caused by the attenuation of the aPKC-CBP pathway. The accumulation of Mgll in the 3xTg-AD mice reduces the genesis of newborn neurons and perturbs spatial memory. However, we find that metformin-stimulated aPKC-CBP pathway decreases Mgll expression to recover these deficits in 3xTg-AD. In addition, we reveal that elevated Mgll levels in cultured adult NPCs from both 3xTg-AD and CbpS436A animal models are responsible for their NPC neuronal differentiation deficits.

Conclusion: Our findings set the stage for development of a clinical protocol where Mgll would serve as a biomarker in early stages of AD to identify potential metformin-responsive AD patients to restore their neurogenesis and spatial memory.

A Guide to Targeting the Endocannabinoid System in Drug Design

The endocannabinoid system (ECS) is one of the most crucial systems in the human organism, exhibiting multi-purpose regulatory character. It is engaged in a vast array of physiological processes, including nociception, mood regulation, cognitive functions, neurogenesis and neuroprotection, appetite, lipid metabolism, as well as cell growth and proliferation. Thus, ECS proteins, including cannabinoid receptors and their endogenous ligands’ synthesizing and degrading enzymes, are promising therapeutic targets. Their modulation has been employed in or extensively studied as a treatment of multiple diseases. However, due to a complex nature of ECS and its crosstalk with other biological systems, the development of novel drugs turned out to be a challenging task. In this review, we summarize potential therapeutic applications for ECS-targeting drugs, especially focusing on promising synthetic compounds and preclinical studies. We put emphasis on modulation of specific proteins of ECS in different pathophysiological areas. In addition, we stress possible difficulties and risks and highlight proposed solutions. By presenting this review, we point out information pivotal in the spotlight of ECS-targeting drug design, as well as provide an overview of the current state of knowledge on ECS-related pharmacodynamics and show possible directions for needed research.

Lipid accumulation and oxidation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common and lethal primary malignant brain tumor in adults. Despite the multimodal standard treatments for GBM, the median survival is still about one year. Analysis of brain tissues from GBM patients shows that lipid droplets are highly enriched in tumor tissues while undetectable in normal brain tissues, yet the identity and functions of lipid species in GBM are not well understood. The aims of the present work are to determine how GBM utilizes fatty acids, and assess their roles in GBM proliferation. Treatment of U138 GBM cells with a monounsaturated fatty acid, oleic acid, induces accumulation of perilipin 2-coated lipid droplets containing triglycerides enriched in C18:1 fatty acid, and increases fatty acid oxidation. Interestingly, oleic acid also increases glucose utilization and proliferation of GBM cells. In contrast, pharmacologic inhibition of monoacylglycerol lipase attenuates GBM proliferation. Our findings demonstrate that monounsaturated fatty acids promote GBM proliferation via triglyceride metabolism, suggesting a novel lipid droplet-mediated pathway which may be targeted for GBM treatment.

Pharmacologic Characterization of JNJ-42226314, [1-(4-Fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone, a Reversible, Selective, and Potent Monoacylglycerol Lipase Inhibitor

The serine hydrolase monoacylglycerol lipase (MAGL) is the rate-limiting enzyme responsible for the degradation of the endocannabinoid 2-arachidonoylglycerol (2-AG) into arachidonic acid and glycerol. Inhibition of 2-AG degradation leads to elevation of 2-AG, the most abundant endogenous agonist of the cannabinoid receptors (CBs) CB1 and CB2. Activation of these receptors has demonstrated beneficial effects on mood, appetite, pain, and inflammation. Therefore, MAGL inhibitors have the potential to produce therapeutic effects in a vast array of complex human diseases. The present report describes the pharmacologic characterization of [1-(4-fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone (JNJ-42226314), a reversible and highly selective MAGL inhibitor. JNJ-42226314 inhibits MAGL in a competitive mode with respect to the 2-AG substrate. In rodent brain, the compound time- and dose-dependently bound to MAGL, indirectly led to CB1 occupancy by raising 2-AG levels, and raised norepinephrine levels in cortex. In vivo, the compound exhibited antinociceptive efficacy in both the rat complete Freund's adjuvant-induced radiant heat hypersensitivity and chronic constriction injury-induced cold hypersensitivity models of inflammatory and neuropathic pain, respectively. Though 30 mg/kg induced hippocampal synaptic depression, altered sleep onset, and decreased electroencephalogram gamma power, 3 mg/kg still provided approximately 80% enzyme occupancy, significantly increased 2-AG and norepinephrine levels, and produced neuropathic antinociception without synaptic depression or decreased gamma power. Thus, it is anticipated that the profile exhibited by this compound will allow for precise modulation of 2-AG levels in vivo, supporting potential therapeutic application in several central nervous system disorders. SIGNIFICANCE STATEMENT: Potentiation of endocannabinoid signaling activity via inhibition of the serine hydrolase monoacylglycerol lipase (MAGL) is an appealing strategy in the development of treatments for several disorders, including ones related to mood, pain, and inflammation. [1-(4-Fluorophenyl)indol-5-yl]-[3-[4-(thiazole-2-carbonyl)piperazin-1-yl]azetidin-1-yl]methanone is presented in this report to be a novel, potent, selective, and reversible noncovalent MAGL inhibitor that demonstrates dose-dependent enhancement of the major endocannabinoid 2-arachidonoylglycerol as well as efficacy in models of neuropathic and inflammatory pain.

Activity-based protein profiling of the human failing ischemic heart reveals alterations in hydrolase activities involving the endocannabinoid system

AIM

Acute myocardial infarction and subsequent post-infarction heart failure are among the leading causes of mortality worldwide. The endocannabinoid system has emerged as an important modulator of cardiovascular disease, however the role of endocannabinoid metabolic enzymes in heart failure is still elusive. Herein, we investigated the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls.

METHODS AND RESULTS

Quantitative real-time PCR, targeted lipidomics, and activity-based protein profiling (ABPP) enabled assessment of the endocannabinoids and their metabolic enzymes in ischemic end-stage failing human hearts and non-failing controls. Based on lipidomic analysis, two subgroups were identified within the ischemic heart failure group; the first similar to control hearts and the second with decreased levels of the endocannabinoid 2-arachidonoyl-glycerol (2-AG) and drastically increased levels of the endocannabinoid anandamide (AEA), other N-acylethanolamines (NAEs) and free fatty acids. The altered lipid profile was accompanied by strong reductions in the activity of 13 hydrolases, including the 2-AG hydrolytic enzyme monoacylglycerol lipase (MGLL).

CONCLUSIONS

Our findings suggest the presence of different biological states within the ischemic heart failure group, based on alterations in the lipid and hydrolase activity profiles. In addition, this study demonstrates that ABPP is a valuable tool to rapidly analyze enzyme activity in clinical samples with potential for novel drug and biomarker discovery.

The Metabolic Profiles in Hematological Malignancies

Leukemia is one of the most aggressive hematological malignancies. Leukemia stem cells account for the poor prognosis and relapse of the disease. Decades of investigations have been performed to figure out how to eradicate the leukemia stem cells. It has also been known that cancer cells especially solid cancer cells use energy differently than most of the cell types. The same thing happens to leukemia. Since there are metabolic differences between the hematopoietic stem cells and their immediate descendants, we aim at manipulating the energy sources with which that could have an effect on leukemia stem cells while sparing the normal blood cells. In this review we summarize the metabolic characteristics of distinct leukemias such as acute myeloid leukemia, chronic myeloid leukemia, T cell lymphoblastic leukemia, B-cell lymphoblastic leukemia, chronic lymphocytic leukemia and other leukemia associated hematological malignancies such as multiple myeloma and myelodysplastic syndrome. A better understanding of the metabolic profiles in distinct leukemias might provide novel perspectives and shed light on novel metabolic targeting strategies towards the clinical treatment of leukemias.

ω-Quinazolinonylalkyl aryl ureas as reversible inhibitors of monoacylglycerol lipase

The serine hydrolase monoacylglycerol lipase (MAGL) is involved in a plethora of pathological conditions, in particular pain and inflammation, various types of cancer, metabolic, neurological and cardiovascular disorders, and is therefore a promising target for drug development. Although a large number of irreversible-acting MAGL inhibitors have been discovered over the past years, there are only few compounds known so far which inhibit the enzyme in a reversible manner. Therefore, much effort is put into the development of novel chemical entities showing reversible inhibitory behavior, which is thought to cause less undesired side effects. To explore a wide range of chemical structures as MAGL binders, we have applied a virtual screening approach by docking small molecules into the crystal structure of human MAGL (hMAGL) and envisaged a library of 45 selected compounds which were then synthesized. Biochemical investigations included the determination of the inhibitory potency on hMAGL and two related hydrolases, i.e. human fatty acid amide hydrolase (hFAAH) and murine cholesterol esterase (mCEase). The most promising candidates from theses analyses, i.e. three ω-quinazolinonylalkyl aryl ureas bearing alkyl spacers of three to five methylene groups, exhibited IC₅₀ values of 20-41 µM and reversible, detergent-insensitive behavior towards hMAGL. Among these compounds, the inhibitor 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-(4-oxo-3,4-dihydroquinazolin-2-yl)butyl)urea (96) was selected for further kinetic characterization, yielding a dissociation constant K_i = 15.4 µM and a mixed-type inhibition with a pronounced competitive component (α = 8.94). This mode of inhibition was further supported by a docking experiment, which suggested that the inhibitor occupies the substrate binding pocket of hMAGL.

Regulating membrane lipid levels at the synapse by small-molecule inhibitors of monoacylglycerol lipase: new developments in therapeutic and PET imaging applications

Monoacylglycerol lipase (MAGL) is a major endocannabinoid hydrolyzing enzyme and can be regulated to control endogenous lipid levels in the brain. This review highlights the pharmacological roles and in vivo PET imaging of MAGL in brain.

Bones and Joints: The Effects of Cannabinoids on the Skeleton

CONTEXT

The endocannabinoid system uses tissue-specific lipid ligands and G protein‒coupled transmembrane receptors to regulate neurologic, metabolic, and immune responses. Recent studies demonstrate that the endocannabinoid system influences bone metabolism. With the increasing use of endocannabinoid mimetics (e.g., tetrahydrocannabinol and cannabidiol), the involvement of endocannabinoids in bone growth and remodeling has become clinically relevant.

EVIDENCE ACQUISITION

This literature review is based on a search of PubMed and Google Scholar databases as of June 2019 for all English-language publications relating to cannabinoids and bone. We evaluated retrieved articles for relevance, experimental design, data acquisition, statistical analysis, and conclusions.

EVIDENCE SYNTHESIS

Preclinical studies establish a role for endocannabinoids in bone metabolism. These studies yield complex and often contradictory results attributed to differences in the specific experimental model examined. Studies using human cells or subjects are limited.

CONCLUSIONS

In vitro and animal models document that endocannabinoids are involved in bone biology. The relevance of these observations to humans is not clear. The increasing long-term use of medical and recreational cannabis underscores the need to better understand the role of endocannabinoids in human bone metabolism. Moreover, it is important to evaluate the role of endocannabinoids as a therapeutic target to prevent and treat disorders associated with bone loss.

Potential of Cannabinoid Receptor Ligands as Treatment for Substance Use Disorders

Substance use disorder (SUD) is a major public health crisis worldwide, and effective treatment options are limited. During the past 2 decades, researchers have investigated the impact of a variety of pharmacological approaches to treat SUD, one of which is the use of medical cannabis or cannabinoids. Significant progress was made with the discovery of rimonabant, a selective CB1 receptor (CB1R) antagonist (also an inverse agonist), as a promising therapeutic for SUDs and obesity. However, serious adverse effects such as depression and suicidality led to the withdrawal of rimonabant (and almost all other CB1R antagonists/inverse agonists) from clinical trials worldwide in 2008. Since then, much research interest has shifted to other cannabinoid-based strategies, such as peripheral CB1R antagonists/inverse agonists, neutral CB1R antagonists, allosteric CB1R modulators, CB2R agonists, fatty acid amide hydrolase (FAAH) inhibitors, monoacylglycerol lipase (MAGL) inhibitors, fatty acid binding protein (FABP) inhibitors, or nonaddictive phytocannabinoids with CB1R or CB2R-binding profiles, as new therapeutics for SUDs. In this article, we first review recent progress in research regarding the endocannabinoid systems, cannabis reward versus aversion, and the underlying receptor mechanisms. We then review recent progress in cannabinoid-based medication development for the treatment of SUDs. As evidence continues to accumulate, neutral CB1R antagonists (such as AM4113), CB2R agonists (JWH133, Xie2-64), and nonselective phytocannabinoids (cannabidiol, β-caryophyllene, ∆9-tetrahydrocannabivarin) have shown great therapeutic potential for SUDs, as shown in experimental animals. Several cannabinoid-based medications (e.g., dronabinol, nabilone, PF-04457845) that entered clinical trials have shown promising results in reducing withdrawal symptoms in cannabis and opioid users.

Design, Synthesis, and Evaluation of 18F-Labeled Monoacylglycerol Lipase Inhibitors as Novel Positron Emission Tomography Probes

Dysfunction of monoacylglycerol lipase (MAGL) is associated with several psychopathological disorders, including drug addiction and neurodegenerative diseases. Herein we design, synthesize, and evaluate several irreversible fluorine-containing MAGL inhibitors for positron emission tomography (PET) ligand development. Compound 6 (identified from a therapeutic agent) was advanced for ¹⁸F-labeling via a novel spirocyclic iodonium ylide (SCIDY) strategy, which demonstrated high brain permeability and excellent specific binding. This work supports further development of novel ¹⁸F-labeled MAGL PET probes.

Identification and Development of an Irreversible Monoacylglycerol Lipase (MAGL) Positron Emission Tomography (PET) Radioligand with High Specificity

Monoacylglycerol lipase (MAGL), a serine hydrolase extensively expressed throughout the brain, serves as a key gatekeeper regulating the tone of endocannabinoid signaling. Preclinically, inhibition of MAGL is known to provide therapeutic benefits for a number of neurological disorders. The availability of a MAGL-specific positron emission tomography (PET) ligand would considerably facilitate the development and clinical characterization of MAGL inhibitors via noninvasive and quantitative PET imaging. Herein, we report the identification of the potent and selective irreversible MAGL inhibitor 7 (PF-06809247) as a suitable radioligand lead, which upon radiolabeling was found to exhibit a high level of MAGL specificity; this enabled cross-species measurement of MAGL brain expression (B_max), assessment of in vivo binding in the rat, and nonhuman primate PET imaging.

Monoacylglycerol lipase inhibition as potential treatment for interstitial cystitis

Interstitial cystitis is a chronic inflammatory condition of the urinary bladder with an unclear etiology. Currently, there are no widely accepted long-term treatment options available for patients with IC, with the European Association of Urology (EAU, 2017 guidelines), American Urology Association (AUA, 2014 guidelines), and the Royal College of Obstetricians and Gynaecologists (RCOG, 2016 guidelines) all suggesting various different conservative, pharmacological, intravesical, and surgical interventions. The endocannabinoid system represents a potential target for IC treatment and management. Activation of cannabinoid receptor 2 (CBR2) with various agonists has previously been shown to reduce leukocyte differentiation and migration, in addition to inhibiting the release of pro-inflammatory cytokines at the site of inflammation. These receptors have been identified in the detrusor and sensory nerves of the urothelium in various mammalian species, including humans. We hypothesize that by inhibiting the enzymes responsible for the catabolism of endogenous cannabinoids locally, bladder concentrations of CBR2 agonists will increase, particularly 2-arachidonyl glycerol, resulting in a diminished inflammatory response.

Multi-target-directed-ligands acting as enzyme inhibitors and receptor ligands

In this review, we present the latest advances in the field of multi-target-directed ligand (MTDL) design for the treatment of various complex pathologies of multifactorial origin. In particular, latest findings in the field of MTDL design targeting both an enzyme and a receptor are presented for different diseases such as Alzheimer's disease (AD), depression, addiction, glaucoma, non-alcoholic steatohepatitis and pain and inflammation. The ethology of the diseases is briefly described, with special emphasis on how the MTDL can evolve into novel therapies that replace the classic pharmacological dogma "one target one disease". Considering the current needs for therapy adherence improvement, it is exposed as from the medicinal chemistry, different molecular scaffolds are studied. With the use of structure activity relationship studies and molecular optimization, new hybrid molecules are generated with improved biological properties acting at two biologically very distinct targets.

Radiosynthesis and evaluation of a novel monoacylglycerol lipase radiotracer: 1,1,1,3,3,3-hexafluoropropan-2-yl-3-(1-benzyl-1H-pyrazol-3-yl)azetidine-1-[11C]carboxylate

Monoacylglycerol lipase (MAGL) is a major serine hydrolase that hydrolyses 2-arachidonoylglycerol (2-AG) into arachidonic acid (AA) and glycerol in the brain. Because 2-AG and AA are endogenous biologically active ligands in the brain, the inhibition of MAGL is an attractive therapeutic target for neurodegenerative diseases. In this study, to visualize MAGL via positron emission tomography (PET), we report a new carbon-11-labeled radiotracer, namely 1,1,1,3,3,3-hexafluoropropan-2-yl-3-(1-benzyl-1H-pyrazol-3-yl)azetidine-1-[¹¹C]carboxylate ([¹¹C]6). Compound 6 exhibited high in vitro binding affinity (IC₅₀ = 0.41 nM) to MAGL in the brain with a suitable lipophilicity (cLogD = 3.29). [¹¹C]6 was synthesized by reacting 1,1,1,3,3,3-hexafluoropropanol (7) with [¹¹C]phosgene ([¹¹C]COCl₂), followed by a reaction with 3-(1-benzyl-1H-pyrazol-3-yl)azetidine hydrochloride (8), which resulted in a 15.0 ± 6.8% radiochemical yield (decay-corrected, n = 7) based on [¹¹C]CO₂ and a 45 min synthesis time from the end of bombardment. A biodistribution study in mice showed high uptake of radioactivity in MAGL-rich organs, including the lungs, heart, and kidneys. More than 90% of the total radioactivity was irreversibly bound in the brain homogenate of rats 5 min and 30 min after the radiotracer injection. PET summation images of rat brains showed high radioactivity in all brain regions. Pretreatment with 6 or MAGL-selective inhibitor JW642 significantly reduced the uptake of radioactivity in the brain. [¹¹C]6 is a promising PET tracer which offers in vivo specific binding and selectivity for MAGL in rodent brains.

Paradoxical effects of JZL184, an inhibitor of monoacylglycerol lipase, on bone remodelling in healthy and cancer-bearing mice

BACKGROUND

Cancer-associated bone disease is a serious complication in bone sarcomas and metastatic carcinomas of breast and prostate origin. Monoacylglycerol lipase (MAGL) is an enzyme of the endocannabinoid system, and is responsible for the degradation of the most abundant endocannabinoid in bone, 2-arachidonoyl glycerol (2AG).

METHODS

The effects of the verified MAGL inhibitor on bone remodelling were assessed in healthy mice and in mouse models of bone disease caused by prostate and breast cancers and osteosarcoma.

FINDINGS

JZL184 reduced osteolytic bone metastasis in mouse models of breast and prostate cancers, and inhibited skeletal tumour growth, metastasis and the formation of ectopic bone in models of osteosarcoma. Additionally, JZL184 suppressed cachexia and prolonged survival in mice injected with metastatic osteosarcoma and osteotropic cancer cells. Functional and histological analysis revealed that the osteoprotective action of JZL184 in cancer models is predominately due to inhibition of tumour growth and metastasis. In the absence of cancer, however, exposure to JZL184 exerts a paradoxical reduction of bone volume via an effect that is mediated by both Cnr1 and Cnr2 cannabinoid receptors.

INTERPRETATION

MAGL inhibitors such as JZL184, or its novel analogues, may be of value in the treatment of bone disease caused by primary bone cancer and bone metastasis, however, activation of the skeletal endocannabinoid system may limit their usefulness as osteoprotective agents.

Aberrant lipid metabolism as a therapeutic target in liver cancer

INTRODUCTION

Hepatocellular carcinoma (HCC) is one of the most common and lethal cancers. Progress has been made in treatment of HCC; however, improved outcomes are much needed. The increased metabolic needs of cancer cells underscore the importance of metabolic pathways in cancer cell survival. Lipid metabolism has a role in HCC development; aberrant overexpression of several key enzymes is seen in many solid human tumors. Areas covered: We discuss aberrant lipid metabolism and the promise of multiple targets, in particular related to HCC treatment. We searched PubMed and clinicaltrials.gov for published and unpublished studies from 2000 to 2019. These terms were used: lipids, fatty acid metabolism, lipid metabolism, liver cancer, HCC, de novo fatty acid synthesis, ATP citrate lyase, stearoyl CoA denaturase, fatty acid synthase, acetyl coenzyme A carboxylase, CD147, KLF4, monoglyceride lipase, AMP activated protein kinase. Expert opinion: The importance of dysregulation of fatty acid synthesis in cancer is a growing area of research. HCC demonstrates significant alteration in lipid metabolism, representing great potential as a target for novel therapeutics. Various agents have demonstrated promising anti-neoplastic activity. This strategy deserves further development for improved outcomes.

Development of Thiazole-5-carboxylate Derivatives as Selective Inhibitors of Monoacylglycerol Lipase as Target in Cancer

INTRODUCTION

The signalling function of 2-arachidonoylglycerol (2-AG) in endocannabinoid system is delineated by Monoacylglycerol lipase (MAGL). MAGL readdresses the lipid stores in the direction of pro-tumorigenic signalling lipids in cancer cells. Selective as well as potent MAGL inhibitors are limited in number hence their continuous development may lead to a breakthrough invention in the field of MAGL inhibitors. In succession of the above, we have synthesised 2-amino-4- methylthiazole-5-carboxylate derivatives and characterised them by collective use of IR, 1H-NMR, 13C-NMR, Mass spectral data and elemental analysis.

METHODOLOGY

Thirteen compounds (3c-g, 4c, 4e, 4f and 6b-f) inhibited MAGL with IC50 value 0.037- 9.60 µM. Two compounds (3g and 4c) were found to be most potent with IC50 values 0.037 and 0.063µM, respectively. Thirty synthesised compounds were sent to NCI for anticancer screening, out of which nine compounds were selected for one dose anticancer assay. Compounds 3g (NSC:788170) and 4c (NSC:788176)were found to be the most potent during one dose anticancer screening and fulfilled the specified threshold for growth inhibition criteria of NCI and were further selected for full panel five dose assay at 10-fold dilutions of five different concentrations.

CONCLUSION

Compound 3g displayed GI50 value 0.865 μM against EKVX (Non-Small Cell Lung Cancer cell line), and 1.20 µM against MDA-MB-468 (Breast Cancer cell Line), while (4c) showed GI50 value 0.34 and 0.96 µM against HOP-92 and EKVX (Non-Small Cell Lung Cancer cell line) and 1.08 µM against MDA-MB-231/ATCC(Breast Cancer cell Line). In addition, molecular docking studies of the said MAGL inhibitors have also been presented in this article.

Design, Synthesis, and Evaluation of Reversible and Irreversible Monoacylglycerol Lipase Positron Emission Tomography (PET) Tracers Using a "Tail Switching" Strategy on a Piperazinyl Azetidine Skeleton

Monoacylglycerol lipase (MAGL) is a serine hydrolase that degrades 2-arachidonoylglycerol (2-AG) in the endocannabinoid system (eCB). Selective inhibition of MAGL has emerged as a potential therapeutic approach for the treatment of diverse pathological conditions, including chronic pain, inflammation, cancer, and neurodegeneration. Herein, we disclose a novel array of reversible and irreversible MAGL inhibitors by means of "tail switching" on a piperazinyl azetidine scaffold. We developed a lead irreversible-binding MAGL inhibitor 8 and reversible-binding compounds 17 and 37, which are amenable for radiolabeling with ¹¹C or ¹⁸F. [¹¹C]8 ([¹¹C]MAGL-2-11) exhibited high brain uptake and excellent binding specificity in the brain toward MAGL. Reversible radioligands [¹¹C]17 ([¹¹C]PAD) and [¹⁸F]37 ([¹⁸F]MAGL-4-11) also demonstrated excellent in vivo binding specificity toward MAGL in peripheral organs. This work may pave the way for the development of MAGL-targeted positron emission tomography tracers with tunability in reversible and irreversible binding mechanisms.

N-Acyl pyrazoles: Effective and tunable inhibitors of serine hydrolases

A series of N-acyl pyrazoles was examined as candidate serine hydrolase inhibitors in which the active site acylating reactivity and the leaving group ability of the pyrazole could be tuned not only through the nature of the acyl group (reactivity: amide > carbamate > urea), but also through pyrazole C4 substitution with electron-withdrawing or electron-donating substituents. Their impact on enzyme inhibitory activity displayed pronounced effects with the activity improving substantially as one alters both the nature of the reacting carbonyl group (urea > carbamate > amide) and the pyrazole C4 substituent (CN > H > Me). It was further demonstrated that the acyl chain of the N-acyl pyrazole ureas can be used to tailor the potency and selectivity of the inhibitor class to a targeted serine hydrolase. Thus, elaboration of the acyl chain of pyrazole-based ureas provided remarkably potent, irreversible inhibitors of fatty acid amide hydrolase (FAAH, apparent K_i = 100-200 pM), dual inhibitors of FAAH and monoacylglycerol hydrolase (MGLL), or selective inhibitors of MGLL (IC₅₀ = 10-20 nM) while simultaneously minimizing off-target activity (e.g., ABHD6 and KIAA1363).

Inhibition of endocannabinoid degradation rectifies motivational and dopaminergic deficits in the Q175 mouse model of Huntington's disease

Prominent motor deficits (e.g., chorea) that typify Huntington's disease (HD) arise following a prolonged prodromal stage characterized by psychiatric disturbances. Apathy, a disorder of motivation characterized by diminished goal-directed behavior, is one of the earliest and most common psychiatric symptoms in HD, but the underlying neurobiology is unclear and treatment options are limited. Alterations in the endocannabinoid (eCB) and dopamine systems represent prominent pathophysiological markers in HD that-similar to motivational deficits-present early and decline across disease progression. Whether changes in dopamine and eCB systems are associated with specific behavioral impairments in HD and whether these deficits are amenable to viable treatments is unknown. Here, we show that dopaminergic encoding of effortful drive progressively declines with age in an HD mouse model, and is restored by elevating tissue levels of the eCB 2-arachidonoylglycerol (2-AG) through targeted inhibition of its enzymatic degradation. This work supports aberrant dopaminergic encoding of reward as a neurobiological correlate of apathy in HD, and indicates that cannabinoid receptor-based therapies may benefit neuropsychiatric care for HD.

Endocannabinoids in Body Weight Control

Maintenance of body weight is fundamental to maintain one's health and to promote longevity. Nevertheless, it appears that the global obesity epidemic is still constantly increasing. Endocannabinoids (eCBs) are lipid messengers that are involved in overall body weight control by interfering with manifold central and peripheral regulatory circuits that orchestrate energy homeostasis. Initially, blocking of eCB signaling by first generation cannabinoid type 1 receptor (CB1) inverse agonists such as rimonabant revealed body weight-reducing effects in laboratory animals and men. Unfortunately, rimonabant also induced severe psychiatric side effects. At this point, it became clear that future cannabinoid research has to decipher more precisely the underlying central and peripheral mechanisms behind eCB-driven control of feeding behavior and whole body energy metabolism. Here, we will summarize the most recent advances in understanding how central eCBs interfere with circuits in the brain that control food intake and energy expenditure. Next, we will focus on how peripheral eCBs affect food digestion, nutrient transformation and energy expenditure by interfering with signaling cascades in the gastrointestinal tract, liver, pancreas, fat depots and endocrine glands. To finally outline the safe future potential of cannabinoids as medicines, our overall goal is to address the molecular, cellular and pharmacological logic behind central and peripheral eCB-mediated body weight control, and to figure out how these precise mechanistic insights are currently transferred into the development of next generation cannabinoid medicines displaying clearly improved safety profiles, such as significantly reduced side effects.

Elevated levels of 2-arachidonoylglycerol promote atherogenesis in ApoE-/- mice

BACKGROUND

The endocannabinoid (eCB) 2-arachidonoylglycerol (2-AG) is a known modulator of inflammation and ligand to both, pro-inflammatory cannabinoid receptor 1 (CB1) and anti-inflammatory CB2. While the role of both receptors in atherogenesis has been studied extensively, the significance of 2-AG for atherogenesis is less well characterized.

METHODS

The impact of 2-AG on atherogenesis was studied in two treatment groups of ApoE-/- mice. One group received the monoacylglycerol lipase (MAGL)-inhibitor JZL184 [5 mg/kg i.p.], which impairs 2-AG degradation and thus causes elevated 2-AG levels, the other group received vehicle for four weeks. Simultaneously, both groups were fed a high-cholesterol diet. The atherosclerotic plaque burden was assessed in frozen sections through the aortic sinus following oil red O staining and infiltrating macrophages were detected by immunofluorescence targeting CD68. In vitro, the effect of 2-AG on B6MCL macrophage migration was assessed by Boyden chamber experiments. Transcription of adhesion molecules and chemokine receptors in macrophages was assessed by qPCR.

RESULTS

As expected, application of the MAGL-inhibitor JZL184 resulted in a significant increase in 2-AG levels in vascular tissue (98.2 ± 16.1 nmol/g vs. 27.3 ± 4.5 nmol/g; n = 14-16; p < 0.001). ApoE-/- mice with elevated 2-AG levels displayed a significantly increased plaque burden compared to vehicle treated controls (0.44 ± 0.03 vs. 0.31 ± 0.04; n = 14; p = 0.0117). This was accompanied by a significant increase in infiltrating macrophages within the atherosclerotic vessel wall (0.33 ± 0.02 vs. 0.27 ± 0.01; n = 13-14; p = 0.0076). While there was no alteration to the white blood counts of JZL184-treated animals, 2-AG enhanced macrophage migration in vitro by 1.8 ± 0.2 -fold (n = 4-6; p = 0.0393) compared to vehicle, which was completely abolished by co-administration of either CB1- or CB2-receptor-antagonists. qPCR analyses of 2-AG-stimulated macrophages showed an enhanced transcription of the chemokine CCL5 (1.59 ± 0.23 -fold; n = 5-6; p = 0.0589) and its corresponding receptors CCR1 (2.04 ± 0.46 -fold; n = 10-11; p = 0.0472) and CCR5 (2.45 ± 0.62 -fold; n = 5-6; p = 0.0554).

CONCLUSION

Taken together, elevated 2-AG levels appear to promote atherogenesis in vivo. Our data suggest that 2-AG promotes macrophage migration, possibly by the CCL5-CCR5/CCR1 axis, and thereby contributes to vascular inflammation. Thus, decreasing vascular 2-AG levels might represent a promising therapeutic strategy in patients suffering from atherosclerosis and coronary heart disease.

Enhanced endocannabinoid tone as a potential target of pharmacotherapy

The endocannabinoid system is up-regulated in numerous pathophysiological states such as inflammatory, neurodegenerative, gastrointestinal, metabolic and cardiovascular diseases, pain, and cancer. It has been suggested that this phenomenon primarily serves an autoprotective role in inhibiting disease progression and/or diminishing signs and symptoms. Accordingly, enhancement of endogenous endocannabinoid tone by inhibition of endocannabinoid degradation represents a promising therapeutic approach for the treatment of many diseases. Importantly, this allows for the avoidance of unwanted psychotropic side effects that accompany exogenously administered cannabinoids. The effects of endocannabinoid metabolic pathway modulation are complex, as endocannabinoids can exert their actions directly or via numerous metabolites. The two main strategies for blocking endocannabinoid degradation are inhibition of endocannabinoid-degrading enzymes and inhibition of endocannabinoid cellular uptake. To date, the most investigated compounds are inhibitors of fatty acid amide hydrolase (FAAH), an enzyme that degrades the endocannabinoid anandamide. However, application of FAAH inhibitors (and consequently other endocannabinoid degradation inhibitors) in medicine became questionable due to a lack of therapeutic efficacy in clinical trials and serious adverse effects evoked by one specific compound. In this paper, we discuss multiple pathways of endocannabinoid metabolism, changes in endocannabinoid levels across numerous human diseases and corresponding experimental models, pharmacological strategies for enhancing endocannabinoid tone and potential therapeutic applications including multi-target drugs with additional targets outside of the endocannabinoid system (cyclooxygenase-2, cholinesterase, TRPV1, and PGF_2α-EA receptors), and currently used medicines or medicinal herbs that additionally enhance endocannabinoid levels. Ultimately, further clinical and preclinical studies are warranted to develop medicines for enhancing endocannabinoid tone.

In Vitro and in Vivo Evaluation of 11C-Labeled Azetidinecarboxylates for Imaging Monoacylglycerol Lipase by PET Imaging Studies

Monoacylglycerol lipase (MAGL) is the principle enzyme for metabolizing endogenous cannabinoid ligand 2-arachidonoyglycerol (2-AG). Blockade of MAGL increases 2-AG levels, resulting in subsequent activation of the endocannabinoid system, and has emerged as a novel therapeutic strategy to treat drug addiction, inflammation, and neurodegenerative diseases. Herein we report a new series of MAGL inhibitors, which were radiolabeled by site-specific labeling technologies, including 11C-carbonylation and spirocyclic iodonium ylide (SCIDY) radiofluorination. The lead compound [11C]10 (MAGL-0519) demonstrated high specific binding and selectivity in vitro and in vivo. We also observed unexpected washout kinetics with these irreversible radiotracers, in which in vivo evidence for turnover of the covalent residue was unveiled between MAGL and azetidine carboxylates. This work may lead to new directions for drug discovery and PET tracer development based on azetidine carboxylate inhibitor scaffold.

Effects of Distal Mutations on the Structure, Dynamics and Catalysis of Human Monoacylglycerol Lipase

An understanding of how conformational dynamics modulates function and catalysis of human monoacylglycerol lipase (hMGL), an important pharmaceutical target, can facilitate the development of novel ligands with potential therapeutic value. Here, we report the discovery and characterization of an allosteric, regulatory hMGL site comprised of residues Trp-289 and Leu-232 that reside over 18 Å away from the catalytic triad. These residues were identified as critical mediators of long-range communication and as important contributors to the integrity of the hMGL structure. Nonconservative replacements of Trp-289 or Leu-232 triggered concerted motions of structurally distinct regions with a significant conformational shift toward inactive states and dramatic loss in catalytic efficiency of the enzyme. Using a multimethod approach, we show that the dynamically relevant Trp-289 and Leu-232 residues serve as communication hubs within an allosteric protein network that controls signal propagation to the active site, and thus, regulates active-inactive interconversion of hMGL. Our findings provide new insights into the mechanism of allosteric regulation of lipase activity, in general, and may provide alternative drug design possibilities.

Rational Development of MAGL Inhibitors

Hit identification and hit-to-lead optimization are key steps of the early drug discovery program. Starting from the X-ray crystal structure of the human monoacylglycerol lipase (hMAGL), we herein describe the computational and experimental procedures that we applied for identifying and optimizing a new active inhibitor of this target enzyme. A receptor-based virtual screening method is reported in details, together with enzymatic assays and a first round of hit optimization.

The Endocannabinoid System and Heart Disease: The Role of Cannabinoid Receptor Type 2

Decades of research has provided evidence for the role of the endocannabinoid system in human health and disease. This versatile system, consisting of two receptors (CB1 and CB2), their endogenous ligands (endocannabinoids), and metabolic enzymes has been implicated in a wide variety of disease states, ranging from neurological disorders to cancer. CB2 has gained much interest for its beneficial immunomodulatory role that can be obtained without eliciting psychotropic effects through CB1. Recent studies have shed light on a protective role of CB2 in cardiovascular disease, an ailment which currently takes more lives each year in Western countries than any other disease or injury. By use of CB2 knockout mice and CB2-selective ligands, knowledge of how CB2 signaling affects atherosclerosis and ischemia has been acquired, providing a major stepping stone between basic science and translational clinical research. Here, we summarize the current understanding of the endocannabinoid system in human pathologies and provide a review of the results from preclinical studies examining its function in cardiovascular disease, with a particular emphasis on possible CB2-targeted therapeutic interventions to alleviate atherosclerosis.

Expression of monoacylglycerol lipase as a marker of tumour invasion and progression in malignant melanoma

BACKGROUND

Accumulating evidence suggests that the lipid lytic enzyme monoacylglycerol lipase (MAGL) promotes tumour invasion and metastasis through up-regulation of pro-tumorigenic signalling lipids in several tumour cell lines. However, the expression status of MAGL in clinical melanoma tissues and its clinicopathological significance remain unclear.

OBJECTIVE

To correlate the tumour expression status of MAGL with the clinicopathological information of patients with malignant melanoma.

METHODS

Polymerase chain reaction (PCR) array screening was performed, and the results were validated using immunocytochemical analysis of tumour and non-tumour melanocytic cell lines. Immunohistochemical staining for MAGL was performed for 74 melanoma samples, including 48 primary and 26 metastatic tumours, in which the expression of MAGL was determined by evaluating the percentage of MAGL-positive tumour cells and the MAGL staining intensity. Finally, we analysed the association of MAGL expression status with tumour progression, tumour thickness and vascular invasion of the primary lesion.

RESULTS

Immunocytochemical analysis revealed that MAGL was expressed in all 12 melanoma cell lines, but not in normal human epidermal melanocytes. In the immunohistochemical analysis, positive staining for MAGL was noted in 32 of 48 (64.5%) primary lesions, 14 of 17 (82.4%) lymph node metastatic lesions and 7 of 9 (77.8%) skin metastatic lesions. Metastatic tumours had a significantly higher staining intensity (P = 0.033 for lymph node, P = 0.010 for skin). In the analysis of primary lesions, higher MAGL expression correlated with greater tumour thickness (P = 0.015) and the presence of vascular invasion (P = 0.017). On further evaluation of MAGL-positive primary lesions, staining intensity of MAGL tended to be higher in deeper areas of the tumour mass.

CONCLUSIONS

The expression of MAGL in tumour cells reflects the aggressiveness of melanoma cells and may serve as a marker of tumour progression.

Development of terphenyl-2-methyloxazol-5(4H)-one derivatives as selective reversible MAGL inhibitors

Monoacylglycerol lipase is a serine hydrolase that plays a major role in the degradation of the endocannabinoid neurotransmitter 2-arachidonoylglycerol. A wide number of MAGL inhibitors are reported in literature; however, many of them are characterised by an irreversible mechanism of action and this behavior determines an unwanted chronic MAGL inactivation, which acquires a functional antagonism of the endocannabinoid system. The possible use of reversible MAGL inhibitors has only recently been explored, due to the lack of known compounds possessing efficient reversible inhibitory activities. In this work, we report a new series of terphenyl-2-methyloxazol-5(4H)-one derivatives characterised by a reversible MAGL-inhibition mechanism. Among them, compound 20b showed to be a potent MAGL reversible inhibitor (IC₅₀ = 348 nM) with a good MAGL/FAAH selectivity. Furthermore, this compound showed antiproliferative activities against two different cancer cell lines that overexpress MAGL.

Inhibition of monoacylglycerol lipase: Another signalling pathway for potential therapeutic targets in migraine?

Background

Drugs that modulate endocannabinoid signalling are effective in reducing nociception in animal models of pain and may be of value in the treatment of migraine.

Methods

We investigated the anti-nociceptive effects of inhibition of monoacylglycerol lipase (MGL), a key enzyme in the hydrolysis of the 2-arachidonoylglycerol, in a rat model of migraine based on nitroglycerin (NTG) administration. We evaluated c-fos expression in specific brain areas and nociceptive behavior in trigeminal and extra-trigeminal body areas.

Results

URB602, a reversible MGL inhibitor, did not show any analgesic effect in the tail flick test, but it inhibited NTG-induced hyperalgesia in both the tail flick test and the formalin test applied to the hind paw or to the orofacial area. Quite unexpectedly, URB602 potentiated formalin-induced hyperalgesia in the trigeminal area when used alone. The latter result was also confirmed using a structurally distinct, irreversible MGL inhibitor, JZL184. URB602 did not induce neuronal activation in the area of interest, but significantly reduced the NTG-induced neuronal activation in the ventrolateral column of the periaqueductal grey and the nucleus trigeminalis caudalis.

Conclusions

These findings support the hypothesis that modulation of the endocannabinoid system may be a valuable approach for the treatment of migraine. The topographically segregated effect of MGL inhibition in trigeminal/extra-trigeminal areas calls for further mechanistic research.

Mechanism of dexamethasone in the context of Toxoplasma gondii infection

Toxoplasmosis is a serious zoonoses disease and opportunistic, and can be life-threatening. Dexamethasone (DEX) is widely used in the clinic for treatment of inflammatory and autoimmune diseases. However, long-term use of DEX is often easy to lead to acute toxoplasmosis in patients, and the potential molecular mechanism is still not very clear. The aims of this study were to investigate the effect of DEX on proliferation of Toxoplasma and its molecular mechanisms, and to establish the corresponding control measures. All the results showed that dexamethasone could enhance the proliferation of Toxoplasma gondii tachyzoites. After 72 h of DEX treatment, 566 (±7) tachyzoites were found in 100 host cells, while only 86 (±8) tachyzoites were counted from the non-treated control cells (P < 0·01). Gas chromatography (GC) analysis showed changes in level and composition of fatty acids in DEX-treated host cells, and T. gondii. Fish oil was added as a modulator of lipid metabolism in experimental mice. It was found that mice fed with fish oil did not develop the disease after infection with T. gondii, and the structure of fatty acids in plasma changed significantly. The metabolism of fatty acid in the parasites was limited, and the desaturase gene expression was downregulated. These results indicate that the molecular mechanism of dexamethasone to promote the proliferation of T. gondii may be that dexamethasone induces the change of fatty acids composition of tachyzoites and host cells. Therefore, we recommend supplementation of fatty acid in immunosuppressive and immunocompromised patients in order to inhibit toxoplasmosis.

Cannabinoids for treating inflammatory bowel diseases: where are we and where do we go?

Fifty years after the discovery of Δ⁹-tetrahydrocannabinol (THC) as the psychoactive component of Cannabis, we are assessing the possibility of translating this herb into clinical treatment of inflammatory bowel diseases (IBDs). Here, a discussion on the problems associated with a potential treatment is given. From first surveys and small clinical studies in patients with IBD we have learned that Cannabis is frequently used to alleviate diarrhea, abdominal pain, and loss of appetite. Single ingredients from Cannabis, such as THC and cannabidiol, commonly described as cannabinoids, are responsible for these effects. Synthetic cannabinoid receptor agonists are also termed cannabinoids, some of which, like dronabinol and nabilone, are already available with a narcotic prescription. Areas covered: Recent data on the effects of Cannabis/cannabinoids in experimental models of IBD and in clinical trials with IBD patients have been reviewed using a PubMed database search. A short background on the endocannabinoid system is also provided. Expert commentary: Cannabinoids could be helpful for certain symptoms of IBD, but there is still a lack of clinical studies to prove efficacy, tolerability and safety of cannabinoid-based medication for IBD patients, leaving medical professionals without evidence and guidelines.