Selective Fatty Acid Amide Hydrolase Inhibitors as Potential Novel Antiepileptic Agents

Endocannabinoid involvement in beneficial effects of caloric restriction in a rodent model of comorbid depression and epilepsy

Clinically, patients with depression are at a heightened risk for developing epilepsy, and vice versa, suggesting shared mechanisms for this bidirectional comorbidity. Unfortunately, comorbid depression and epilepsy is associated with worsened quality of life and treatment refractoriness, highlighting the need for novel treatment targets and nonpharmacologic supplements to existing therapies. The present study used the Swim-Low Active rat, a well-validated model of depression and epilepsy comorbidity that was selectively bred based on forced swim test behavior, to assess the safety and efficacy of caloric restriction in treating this comorbidity. The study also investigated the role of endocannabinoids in the effects of caloric restriction on the behavioral endpoints and to determine whether there were any sex differences in these effects. Male rats restricted to approximately 80 % of their daily food intake for an acute 24-h period showed elevated struggling behavior in the Porsolt (Forced) Swim Test and increased latency to pilocarpine-induced seizure; this same caloric restriction yielded a significant increase in hippocampal anandamide levels compared to ad lib rats. These effects were not seen in female rats, although female rats did show anticonvulsant effects of chronic caloric restriction. Administration of 1 mg/kg SR141716 alongside an acute caloric restriction in male rats blocked the antidepressant-like effects of caloric restriction but did not affect seizure responses. Combined, these results suggest caloric restriction may be both safe and modestly effective in benefitting depression- and epilepsy-related behaviors in male SwLo rats, and that the endocannabinoid system may be a promising target for treating this comorbidity.

Lipid metabolism: Novel approaches for managing idiopathic epilepsy

Epilepsy is a common neurological condition characterized by abnormal neuronal activity, often leading to cellular damage and death. There is evidence to suggest that lipid imbalances resulting in cellular death play a key role in the development of epilepsy, including changes in triglycerides, cholesterol, sphingolipids, phospholipids, lipid droplets, and bile acids (BAs). Disrupted lipid metabolism acts as a crucial pathological mechanism in epilepsy, potentially linked to processes such as cellular ferroptosis, lipophagy, and immune modulation of gut microbiota (thus influencing the gut-brain axis). Understanding these mechanisms could open up new avenues for epilepsy treatment. This study investigates the association between disturbances in lipid metabolism and the onset of epilepsy.

Targeting Relevant HDACs to Support the Survival of Cone Photoreceptors in Inherited Retinal Diseases: Identification of a Potent Pharmacological Tool with In Vitro and In Vivo Efficacy

Inherited retinal diseases, which include retinitis pigmentosa, are a family of genetic disorders characterized by gradual rod-cone degeneration and vision loss, without effective pharmacological treatments. Experimental approaches aim to delay disease progression, supporting cones' survival, crucial for human vision. Histone deacetylases (HDACs) mediate the activation of epigenetic and nonepigenetic pathways that modulate cone degeneration in RP mouse models. We developed new HDAC inhibitors (5a-p), typified by a tetrahydro-γ-carboline scaffold, characterized by high HDAC6 inhibition potency with balanced physicochemical properties for in vivo studies. Compound 5d (repistat, IC50 HDAC6 = 6.32 nM) increased the levels of acetylated α-tubulin compared to histone H3 in ARPE-19 and 661W cells. 5d promoted vision rescue in the atp6v0e1-/- zebrafish model of photoreceptor dysfunction. A single intravitreal injection of 5d in the rd10 mouse model of RP supported morphological and functional preservation of cone cells and maintenance of the retinal pigment epithelium array.

The State of Synthetic Cannabinoid Medications for the Treatment of Pain

Synthetic cannabinoids are compounds made in the laboratory to structurally and functionally mimic phytocannabinoids from the Cannabis sativa L. plant, including delta-9-tetrahydrocannabinol (THC). Synthetic cannabinoids (SCs) can signal via the classical endogenous cannabinoid system (ECS) and the greater endocannabidiome network, highlighting their signalling complexity and far-reaching effects. Dronabinol and nabilone, which mimic THC signalling, have been approved by the Food and Drug Administration (FDA) for treating nausea associated with cancer chemotherapy and/or acquired immunodeficiency syndrome (AIDS). However, there is ongoing interest in these two drugs as potential analgesics for a variety of other clinical conditions, including neuropathic pain, spasticity-related pain, and nociplastic pain syndromes including fibromyalgia, osteoarthritis, and postoperative pain, among others. In this review, we highlight the signalling mechanisms of FDA-approved synthetic cannabinoids, discuss key clinical trials that investigate their analgesic potential, and illustrate challenges faced when bringing synthetic cannabinoids to the clinic.

Amyotrophic Lateral Sclerosis and Pain: A Narrative Review from Pain Assessment to Therapy

Amyotrophic lateral sclerosis (ALS) is the most frequent neurodegenerative disease of the motor system that affects upper and lower motor neurons, leading to progressive muscle weakness, spasticity, atrophy, and respiratory failure, with a life expectancy of 2-5 years after symptom onset. In addition to motor symptoms, patients with ALS have a multitude of nonmotor symptoms; in fact, it is currently considered a multisystem disease. The purpose of our narrative review is to evaluate the different types of pain, the correlation between pain and the disease's stages, the pain assessment tools in ALS patients, and the available therapies focusing above all on the benefits of cannabis use. Pain is an underestimated and undertreated symptom that, in the last few years, has received more attention from research because it has a strong impact on the quality of life of these patients. The prevalence of pain is between 15% and 85% of ALS patients, and the studies on the type and intensity of pain are controversial. The absence of pain assessment tools validated in the ALS population and the dissimilar study designs influence the knowledge of ALS pain and consequently the pharmacological therapy. Several studies suggest that ALS is associated with changes in the endocannabinoid system, and the use of cannabis could slow the disease progression due to its neuroprotective action and act on pain, spasticity, cramps, sialorrhea, and depression. Our research has shown high patients' satisfaction with the use of cannabis for the treatment of spasticity and related pain. However, especially due to the ethical problems and the lack of interest of pharmaceutical companies, further studies are needed to ensure the most appropriate care for ALS patients.

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.

Pioneering first-in-class FAAH-HDAC inhibitors as potential multitarget neuroprotective agents

Aiming to simultaneously modulate the endocannabinoid system (ECS) functions and the epigenetic machinery, we selected the fatty acid amide hydrolase (FAAH) and histone deacetylase (HDAC) enzymes as desired targets to develop potential neuroprotective multitarget-directed ligands (MTDLs), expecting to achieve an additive or synergistic therapeutic effect in oxidative stress-related conditions. We herein report the design, synthesis, and biological evaluation of the first-in-class FAAH-HDAC multitarget inhibitors. A pharmacophore merging strategy was applied, yielding 1-phenylpyrrole-based compounds 4a-j. The best-performing compounds (4c, 4f, and 4h) were tested for their neuroprotective properties in oxidative stress models, employing 1321N1 human astrocytoma cells and SHSY5 human neuronal cells. In our preliminary studies, compound 4h stood out, showing a balanced nanomolar inhibitory activity against the selected targets and outperforming the standard antioxidant N-acetylcysteine in vitro. Together with 4f, 4h was also able to protect 1321N1 cells from tert-butyl hydroperoxide or glutamate insult. Our study may provide the basis for the development of novel MTDLs targeting the ECS and epigenetic enzymes.

FAAH rs324420 Polymorphism: Biological Pathways, Impact on Elite Athletic Performance and Insights for Sport Medicine

Gene variation linked to physiological functions is recognised to affect elite athletic performance by modulating training and competition-enabling behaviour. The fatty acid amide hydrolase (FAAH) has been investigated as a good candidate for drug targeting, and recently, its single-nucleotide polymorphism (SNP) rs324420 was reported to be associated with athletic performance. Given the implications, the biological pathways of this genetic polymorphism linked to elite athletic performance, considering sport type, psychological traits and sports injuries, need to be dissected. Thus, a narrative review of the literature concerning the biological mechanisms of this SNP was undertaken. In addition to its role in athletic performance, FAAH rs324420 is also involved in important mechanisms underlying human psychopathologies, including substance abuse and neural dysfunctions. However, cumulative evidence concerning the C385A variant is inconsistent. Therefore, validation studies considering homogeneous sports modalities are required to better define the role of this SNP in elite athletic performance and its impact on stress coping, pain regulation and inflammation control.

The study of rs324420 (C385A) polymorphism of the FAAH gene of the endocannabinoid system in patients with epilepsy and ADHD

The endocannabinoid (eCB) system regulates many physiological functions in the central nervous system. Fatty acid amide hydrolase (FAAH) is an essential enzyme in the eCB system, degrading anandamide. Single nucleotide polymorphism (SNP) rs324420 is a common genetic polymorphism of the FAAH gene and has been associated with susceptibility to neurological conditions. This study examined whether the SNP rs324420 (C385A) is associated with epilepsy and attention deficit hyperactivity disorder (ADHD). This study consists of two case-control parts. The first part comprises 250 epilepsy subjects and 250 healthy individuals as controls. The second one comprises 157 cases with ADHD and 136 healthy individuals as controls. Genotyping was carried out using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) technique. Interestingly, the FAAH C384A genotype (OR 1.755, 95 % CI 1.124-2.742, p = 0.013) and allele (OR 1.462, 95 % CI 1.006-2.124, p = 0.046) distribution showed an association with generalized epilepsy. On the other hand, this SNP was not associated with the risk of ADHD. To our knowledge, there was no study on the association between rs324420 (C385A) polymorphism and the risks of ADHD or epilepsy. This study provided the first evidence of an association between generalized epilepsy and rs324420 (C385A) of FAAH. Larger sample sizes and functional studies are warranted to explore the clinical utility of FAAH genotyping as a possible marker for increased generalized epilepsy risk.

Development of potent and selective FAAH inhibitors with improved drug-like properties as potential tools to treat neuroinflammatory conditions

The neuroprotective performance against neuroinflammation of the endocannabinoid system (ECS) can be remarkably improved by indirect stimulation mediated by the pharmacological inhibition of the key ECS catabolic enzyme fatty acid amide hydrolase (FAAH). Based on our previous works and aiming to discover new selective FAAH inhibitors , we herein reported a new series of carbamate-based FAAH inhibitors (4a-t) which showed improved drug disposition properties compared to the previously reported analogues 2a-b. The introduction of ionizable functions allowed us to obtain new FAAH inhibitors of nanomolar potency characterized by good water solubility and chemical stability at physiological pH. Interesting structure-activity relationships (SARs), deeply analyzed by molecular docking and molecular dynamic (MD) simulations, were obtained. All the newly developed inhibitors showed an excellent selectivity profile evaluated against monoacylglycerol lipase and cannabinoid receptors. The reversible mechanism of action was determined by a rapid dilution assay. Absence of toxicity was confirmed in mouse fibroblasts NIH3T3 (for compounds 4e, 4g, 4n-o, and 4s) and in human astrocytes cell line 1321N1 (for compounds 4e, 4n, and 4s). The absence of undesired cardiac effects was also confirmed for compound 4n. Selected analogues (compounds 4e, 4g, 4n, and 4s) were able to reduce oxidative stress in 1321N1 astrocytes and exhibited notable neuroprotective effects when tested in an ex vivo model of neuroinflammation.

Radiometric Assay of FAAH Activity

Fatty acid amide hydrolase (FAAH) is an intracellular enzyme responsible for the hydrolysis of endogenous anandamide (AEA), a reaction that terminates the biological effects of this lipid mediator. The final products of AEA cleavage are arachidonic acid and ethanolamine. In the method described herein, FAAH activity is measured through the use of the radioactive substrate [¹⁴C-ethanolamine]-AEA and subsequent quantification of the reaction product [¹⁴C]-ethanolamine.

Inhibition of FAAH suppresses RANKL-induced osteoclastogenesis and attenuates ovariectomy-induced bone loss partially through repressing the IL17 pathway

Fatty amide hydrolase (FAAH) is a key degradation enzyme of the endocannabinoid system, mainly responsible for the hydrolysis of arachidonic acid ethanolamine (AEA). Previous investigations have shown that FAAH is involved in a series of biological processes, such as inflammation, immune regulation, and transmembrane signal transduction of neurons. Endogenous cannabinoids and cannabinoid receptors have been reported to participate in the regulation of bone homeostasis by regulating the differentiation of osteoblasts and osteoclasts. We hypothesized that FAAH may play an important role in osteoclastogenesis based on the above evidence. The present study found that the FAAH expression was increased at both mRNA and protein levels during RANKL-induced osteoclastogenesis. Pharmacological and genetic inhibition of FAAH in bone marrow-derived macrophages (BMMs) inhibited osteoclastogenesis, F-actin ring formation, bone resorption, and osteoclast-specific gene expression in vitro. Moreover, intragastric administration of the FAAH inhibitor PF-04457845(PF) ameliorated ovariectomy (OVX)-induced bone loss in mice. Further investigation revealed that nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways were inhibited by PF treatment and FAAH knockdown. RNAseq indicated that the IL17 pathway was blocked by PF, and administration of recombinant murine IL17 protein could partially restore osteoclastogenesis and activate NF-κB and MAPK pathways. To sum up, our findings demonstrate that targeting FAAH could be a promising candidate strategy for treating osteoclast-related diseases, especially osteoporosis.

Synthesis of Unsymmetrical Squaramides as Allosteric GSK-3β Inhibitors Promoting β-Catenin-Mediated Transcription of TCF/LEF in Retinal Pigment Epithelial Cells

The glycogen synthase kinase 3β (GSK-3β) is a ubiquitous enzyme that is a validated target for the development of potential therapeutics useful in several diseases including retinal degeneration. Aiming at developing an innovative class of allosteric inhibitors of GSK-3β potentially useful for retinal degeneration, we explored the class of squaramides. The developed compounds (6 a-l) were obtained through a nontoxic one-pot synthetic protocol, which employs low-cost goods and avoids any purification step. Ethanol was used as the reaction solvent, simultaneously allowing the pure reaction products' recovery (by precipitation). Out of this set of squaramides, 6 j stood out, from computational and enzymatic converging data, as an ATP non-competitive inhibitor of GSK-3β of micromolar potency. When engaged in cellular studies using retinal pigment epithelial cells (ARPE-19) transfected with a luciferase reporter gene under the control of T-cell factor/lymphoid enhancer factor (TCF/LEF) binding sites, 6 j was able to dose-dependently induce β-catenin nuclear accumulation, as shown by the increased luciferase activity at a concentration of 2.5 μM.

Design and synthesis of multifunctional microtubule targeting agents endowed with dual pro-apoptotic and anti-autophagic efficacy

Autophagy is a lysosome dependent cell survival mechanism and is central to the maintenance of organismal homeostasis in both physiological and pathological situations. Targeting autophagy in cancer therapy attracted considerable attention in the past as stress-induced autophagy has been demonstrated to contribute to both drug resistance and malignant progression and recently interest in this area has re-emerged. Unlocking the therapeutic potential of autophagy modulation could be a valuable strategy for designing innovative tools for cancer treatment. Microtubule-targeting agents (MTAs) are some of the most successful anti-cancer drugs used in the clinic to date. Scaling up our efforts to develop new anti-cancer agents, we rationally designed multifunctional agents 5a-l with improved potency and safety that combine tubulin depolymerising efficacy with autophagic flux inhibitory activity. Through a combination of computational, biological, biochemical, pharmacokinetic-safety, metabolic studies and SAR analyses we identified the hits 5i,k. These MTAs were characterised as potent pro-apoptotic agents and also demonstrated autophagy inhibition efficacy. To measure their efficacy at inhibiting autophagy, we investigated their effects on basal and starvation-mediated autophagic flux by quantifying the expression of LC3II/LC3I and p62 proteins in oral squamous cell carcinoma and human leukaemia through western blotting and by immunofluorescence study of LC3 and LAMP1 in a cervical carcinoma cell line. Analogues 5i and 5k, endowed with pro-apoptotic activity on a range of hematological cancer cells (including ex-vivo chronic lymphocytic leukaemia (CLL) cells) and several solid tumor cell lines, also behaved as late-stage autophagy inhibitors by impairing autophagosome-lysosome fusion.

Polypharmacological Approaches for CNS Diseases: Focus on Endocannabinoid Degradation Inhibition

Polypharmacology breaks up the classical paradigm of “one-drug, one target, one disease” electing multitarget compounds as potential therapeutic tools suitable for the treatment of complex diseases, such as metabolic syndrome, psychiatric or degenerative central nervous system (CNS) disorders, and cancer. These diseases often require a combination therapy which may result in positive but also negative synergistic effects. The endocannabinoid system (ECS) is emerging as a particularly attractive therapeutic target in CNS disorders and neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), Huntington’s disease (HD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), stroke, traumatic brain injury (TBI), pain, and epilepsy. ECS is an organized neuromodulatory network, composed by endogenous cannabinoids, cannabinoid receptors type 1 and type 2 (CB₁ and CB₂), and the main catabolic enzymes involved in the endocannabinoid inactivation such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). The multiple connections of the ECS with other signaling pathways in the CNS allows the consideration of the ECS as an optimal source of inspiration in the development of innovative polypharmacological compounds. In this review, we focused our attention on the reported polypharmacological examples in which FAAH and MAGL inhibitors are involved.

Commonalities for comorbidity: Overlapping features of the endocannabinoid system in depression and epilepsy

A wealth of clinical and pre-clinical data supports a bidirectional comorbidity between depression and epilepsy. This suggests commonalities in underlying mechanisms that may serve as targets for more effective treatment strategies. Unfortunately, many patients with this comorbidity are highly refractory to current treatment strategies, while others experience a worsening of one arm of the comorbidity when treating the other arm. This highlights the need for novel pharmaceutical targets that may provide safe and effective relief for both depression and epilepsy symptoms. The endocannabinoid system (ECS) of the brain has become an area of intense interest for possible roles in depression and epilepsy. Several existing literature reviews have provided in-depth analysis of the involvement of various aspects of the ECS in depression or epilepsy separately, while others have addressed the effectiveness of different treatment strategies targeting the ECS in either condition individually. However, there is not currently a review that considers the ECS when both conditions are comorbid. This mini-review will address areas of common overlap between the ECS in depression and in epilepsy, such as commonalities in endocannabinoids themselves, their receptors, and degradative enzymes. These areas of overlap will be discussed alongside their implications for treatment of this challenging comorbidity.