Inhibitor of fatty acid amide hydrolase normalizes cardiovascular function in hypertension without adverse metabolic effects

Protective role of cannabinoid CB1 receptors and vascular effects of chronic administration of FAAH inhibitor URB597 in DOCA-salt hypertensive rats

AIMS

This study examined whether the fall in blood pressure (BP) induced by the chronic inhibition of fatty acid amide hydrolase (FAAH) by URB597 in deoxycorticosterone acetate (DOCA-salt) hypertensive rats correlates with endocannabinoid-mediated vascular changes.

MAIN METHODS

Functional studies were performed in isolated endothelium-intact aortas and small mesenteric arteries (sMAs) using organ bath technique and wire myography, respectively.

KEY FINDINGS

In the DOCA-salt rats, methanandamide-stimulated relaxation was enhanced in sMAs or diminished in aortas. Its vasorelaxant effect in sMAs was sensitive to the antagonist of the Transient Receptor Potential Vanilloid type 1 (TRPV1), capsazepine, in normo- and hypertensive animals and to the antagonist of the cannabinoid CB1 receptors, AM6545, only in DOCA-salt rats. Cannabinoid CB1 receptors were up-regulated merely in DOCA-salt sMAs. URB597 decreased elevated BP in DOCA-salt rats, medial hypertrophy in DOCA-salt aortas. In sMAs it reduced FAAH expression and restored the augmented phenylephrine-induced contraction in the DOCA-salt rats to the level obtained in normotensive controls. In normotensive rats it diminished endothelium-dependent relaxation and increased phenylephrine-induced contraction.

SIGNIFICANCE

The study showed the protective role of cannabinoid CB1 receptors in DOCA-salt sMAs. Reduction in BP after chronic administration of the FAAH inhibitor URB597 in DOCA-salt hypertensive rats only partially correlates with structural and functional changes in conductance and resistance vessels, respectively. Caution should be taken in studying cannabinoids and FAAH inhibitors as potential therapeutics, because of their vessel- and model-specific activities, and side effects connected with off-target response and activation of alternative pathways of anandamide metabolism.

The novel, orally available and peripherally restricted selective cannabinoid CB2 receptor agonist LEI-101 prevents cisplatin-induced nephrotoxicity

BACKGROUND AND PURPOSE

Here, we have characterized 3-cyclopropyl-1-(4-(6-((1,1-dioxidothiomorpholino)methyl)-5-fluoropyridin-2-yl)benzyl)imidazolidine-2,4-dione hydrochloride (LEI-101) as a novel, peripherally restricted cannabinoid CB2 receptor agonist, using both in vitro and in vivo models.

EXPERIMENTAL APPROACH

We investigated the effects of LEI-101 on binding and functional activity. We assessed its in vitro and in vivo selectivity. Efficacy of LEI-101 was determined in a mouse model of cisplatin-induced nephrotoxicity.

KEY RESULTS

LEI-101 behaved as a partial agonist at CB2 receptors using β-arrestin and GTPγS assays and was ~100-fold selective in CB2 /CB1 receptor-binding assays. It did not display any activity on endocannabinoid hydrolases and nor did it react with serine hydrolases in an activity-based protein profiling assay. In mice, LEI-101 had excellent oral bioavailability reaching high concentrations in the kidney and liver with minimal penetration into the brain. LEI-101 up to a dose of 60 mg·kg(-1) (p.o.) did not exert any CNS-mediated effects in the tetrad assay, in mice. LEI-101 (p.o. or i.p.) at 3 or 10 mg·kg(-1) dose-dependently prevented kidney dysfunction and/or morphological damage induced by cisplatin in mice. These protective effects were associated with improved renal histopathology, attenuated oxidative stress and inflammation in the kidney. These effects were absent in CB2 receptor knockout mice.

CONCLUSION AND IMPLICATIONS

These results indicate that LEI-101 is a selective, largely peripherally restricted, orally available CB2 receptor agonist with therapeutic potential in diseases that are associated with inflammation and/or oxidative stress, including kidney disease.

Enhanced vasorelaxation effect of endogenous anandamide on thoracic aorta in renal vascular hypertension rats

Emerging evidence has indicated that anandamide (AEA) is able to stimulate vasorelaxation in both spontaneously hypertensive rats (SHRs) and L-NAME-induced hypertensive rats. Yet it remains unknown whether AEA modulates vasomotion of the aorta in renovascular hypertensive (RVH) rats. The aim of present study is to explore the effect of AEA on the relaxation of thoracic aortas in two-kidney one-clip (2K1C)-induced RVH rats. It is demonstrated that AEA stimulates a pronounced relaxation in the aortas of 2K1C rats compared with sham rats. The enhanced relaxation caused by AEA in aortas from 2K1C rats was diminished in the presence of the cannabinoid receptor-1 (CB₁ ) antagonist AM251 and the CB₂ receptor antagonist AM630. Likewise, the vasodilation action of AEA was blocked in L-NAME-treated or endothelium-denuded aortas. The Western blot results revealed that the expression of CB₁ and CB₂ receptors was increased in the 2K1C rat aortas compared with sham rats. The phosphorylation of endothelial nitric oxide synthase (p-eNOS) at the activation site Ser1177 was enhanced in AEA-treated rings from 2K1C rats in both time-dependent and dose-dependent manners. The augmented p-eNOS expression was inhibited by the co-treatment with AM251 or AM630. Taken together, the present study demonstrated that AEA enhanced endothelium-dependent aortic relaxation through activation of both CB₁ and CB₂ receptors and P-eNOS/NO pathway in 2K1C rats.

Enhanced function of inhibitory presynaptic cannabinoid CB1 receptors on sympathetic nerves of DOCA-salt hypertensive rats

AIMS

This study was performed to examine whether hypertension affects the sympathetic transmission to resistance vessels of pithed rats via inhibitory presynaptic cannabinoid CB1 receptors and whether endocannabinoids are involved in this response.

MATERIALS AND METHODS

We compared uninephrectomised rats rendered hypertensive by high salt diet and deoxycorticosterone acetate (DOCA) injections with normotensive animals (uninephrectomy only). Experiments were performed on vagotomised and pithed animals. Increases in diastolic blood pressure (DBP) were induced four times (S1-S4) by electrical stimulation or phenylephrine injection.

KEY FINDINGS

Electrical stimulation (0.75Hz, 1ms, 50V, 5 impulses) of the preganglionic sympathetic nerve fibres innervating the blood vessels more strongly increased DBP in normotensive than in DOCA-salt rats. Phenylephrine (0.01μmol/kg) induced similar increases in DBP in both groups. The cannabinoid receptor agonist CP55940 (0.01-1μmol/kg) did not modify the rises in DBP induced by phenylephrine. However, it inhibited the electrically stimulated increases in DBP, more strongly in DOCA-salt than in normotensive animals (maximally by 50 and 30%, respectively). The effect of CP55940 was attenuated by the CB1 antagonist AM251 (3μmol/kg). AM251 enhanced the neurogenic vasopressor response during S4 by itself in hypertensive rats only. URB597 (3μmol/kg), which inhibits degradation of the endocannabinoid anandamide, did not modify the electrically stimulated increases in DBP.

SIGNIFICANCE

The function of inhibitory presynaptic CB1 receptors on sympathetic nerves is enhanced in DOCA-salt hypertensive rats. Thus, the CB1 receptor-mediated inhibition of noradrenaline release from the sympathetic nerve fibres innervating the resistance vessels might play a protective role in hypertension.

Sulfonyl fluorides as privileged warheads in chemical biology

The use of sulfonyl fluoride probes in chemical biology is reviewed.

Sulfonyl fluoride electrophiles have found significant utility as reactive probes in chemical biology and molecular pharmacology. As warheads they possess the right balance of biocompatibility (including aqueous stability) and protein reactivity. Their functionality is privileged in this regard as they are known to modify not only reactive serines (resulting in their common use as protease inhibitors), but also context-specific threonine, lysine, tyrosine, cysteine and histidine residues. This review describes the application of sulfonyl fluoride probes across various areas of research and explores new approaches that could further enhance the chemical biology toolkit. We believe that sulfonyl fluoride probes will find greater utility in areas such as covalent enzyme inhibition, target identification and validation, and the mapping of enzyme binding sites, substrates and protein–protein interactions.

Investigational drugs under development for the treatment of PTSD

INTRODUCTION

Posttraumatic stress disorder (PTSD) is a prevalent, chronic and disabling anxiety disorder that may develop following exposure to a traumatic event. There is currently no effective pharmacotherapy for PTSD and therefore the discovery of novel, evidence-based treatments is particularly important. This review of potential novel treatments could act as a catalyst for further drug investigation.

AREAS COVERED

In this review, the authors discuss the heterogeneity of PTSD and why this provides a challenge for discovering effective treatments for this disorder. By searching for the neurobiological systems that are disrupted in individuals with PTSD and their correlation with different symptoms, the authors propose potential pharmacological treatments that could target these symptoms. They discuss drugs such as nabilone, d-cycloserine, nor-BNI, 7,8-dihydroxyflavone and oxytocin (OT) to target systems such as cannabinoids, glutamate, opioids, brain-derived neurotrophic factor and the OT receptor, respectively. While not conclusive, the authors believe that these brain systems include promising targets for drug discovery. Finally, the authors review animal studies, proof-of-concept studies and case studies that support our proposed treatments.

EXPERT OPINION

A mechanism-based approach utilizing techniques such as in vivo neuroimaging will allow for the determination of treatments. Due to the heterogeneity of the PTSD phenotype, focusing on symptomology rather than a categorical diagnosis will allow for more personalized treatment. Furthermore, there appears to be a promise in drugs as cognitive enhancers, the use of drug cocktails and novel compounds that target specific pathways linked to the etiology of PTSD.

Inhibitors of Fatty Acid Amide Hydrolase and Monoacylglycerol Lipase: New Targets for Future Antidepressants

Cannabis and analogs of Δ⁹-tetrahydrocannabinol have been used for therapeutic purposes, but their therapeutic use remains limited because of various adverse effects. Endogenous cannabinoids have been discovered, and dysregulation of endocannabinoid signaling is implicated in the pathophysiology of major depressive disorder (MDD). Recently, endocannabinoid hydrolytic enzymes such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) have become new therapeutic targets in the treatment of MDD. Several FAAH or MAGL inhibitors are reported to have no cannabimimetic side effects and, therefore, are new potential therapeutic options for patients with MDD who are resistant to first-line antidepressants (selective serotonin and serotonin-norepinephrine reuptake inhibitors). In this review, we focus on the possible relationships between MDD and the endocannabinoid system as well as the inhibitors' therapeutic potential. MAGL inhibitors may reduce inflammatory responses through activation of cannabinoid receptor type 2. In the hypothalamic-pituitary-adrenal axis, repeated FAAH inhibitor administration may be beneficial for reducing circulating glucocorticoid levels. Both FAAH and MAGL inhibitors may contribute to dopaminergic system regulation. Recently, several new inhibitors have been developed with strong potency and selectivity. FAAH inhibitor, MAGL inhibitor, or dual blocker use would be promising new treatments for MDD. Further pre-clinical studies and clinical trials using these inhibitors are warranted.

Cannabinoids alter endothelial function in the Zucker rat model of type 2 diabetes

Circulating levels of anandamide are increased in diabetes, and cannabidiol ameliorates a number of pathologies associated with diabetes. The aim of the present study was to examine how exposure to anandamide or cannabidiol might affect endothelial dysfunction associated with Zucker Diabetic Fatty rats. Age-matched Zucker Diabetic Fatty and Zucker lean rats were killed by cervical dislocation and their arteries mounted on a myograph at 37 °C. Arteries were incubated for 2h with anandamide, cannabidiol or vehicle, contracted, and cumulative concentration-response curves to acetylcholine were constructed. Anandamide (10 µM, 2h) significantly improved the vasorelaxant responses to acetylcholine in aortae and femoral arteries from Zucker Diabetic Fatty rats but not Zucker lean rats. By contrast, anandamide (1 µM, 2h) significantly blunted acetylcholine-induced vasorelaxation in third-order mesenteric arteries (G3) from Zucker Diabetic Fatty rats. Cannabidiol incubation (10 µM, 2h) improved acetylcholine responses in the arteries of Zucker Diabetic Fatty rats (aorta and femoral) and Zucker lean (aorta, femoral and G3 mesenteric), and this effect was greater in the Zucker Diabetic Fatty rat. These studies suggest that increased circulating endocannabinoids may alter vascular function both positively and negatively in type 2 diabetes, and that part of the beneficial effect of cannabidiol in diabetes may be due to improved endothelium-dependent vasorelaxation.

Monounsaturated fatty acids generated via stearoyl CoA desaturase-1 are endogenous inhibitors of fatty acid amide hydrolase

High-fat diet (HFD)-induced obesity and insulin resistance are associated with increased activity of the endocannabinoid/CB1 receptor (CB1R) system that promotes the hepatic expression of lipogenic genes, including stearoyl-CoA desaturase-1 (SCD1). Mice deficient in CB1R or SCD1 remain lean and insulin-sensitive on an HFD, suggesting a functional link between the two systems. The HFD-induced increase in the hepatic levels of the endocannabinoid anandamide [i.e., arachidonoylethanolamide (AEA)] has been attributed to reduced activity of the AEA-degrading enzyme fatty acid amide hydrolase (FAAH). Here we show that HFD-induced increased hepatic AEA levels and decreased FAAH activity are absent in SCD1(-/-) mice, and the monounsaturated fatty acid (MUFA) products of SCD1, palmitoleic and oleic acid, inhibit FAAH activity in vitro at low micromolar concentrations. HFD markedly increases hepatic SCD1 activity in WT mice as well as in CB1R(-/-) mice with transgenic reexpression of CB1R in hepatocytes, but not in global CB1R(-/-) mice. Treatment of HFD-fed mice with the SCD1 inhibitor A939572 prevents the diet-induced reduction of hepatic FAAH activity, normalizes hepatic AEA levels, and improves insulin sensitivity. SCD1(-/-) mice on an HFD remain insulin-sensitive, but develop glucose intolerance and insulin resistance in response to chronic treatment with the FAAH inhibitor URB597. An HFD rich in MUFA or feeding mice pure oleic acid fail to inhibit hepatic FAAH activity. We conclude that MUFAs generated via SCD1 activity, but not diet-derived MUFAs, function as endogenous FAAH inhibitors mediating the HFD-induced increase in hepatic AEA, which then activates hepatic CB1R to induce insulin resistance.

Amygdala FAAH and anandamide: mediating protection and recovery from stress

A long-standing literature linking endocannabinoids (ECBs) to stress, fear, and anxiety has led to growing interest in developing novel anxiolytics targeting the ECB system. Following rapid on-demand biosynthesis and degradation upon neuronal activation, the ECB N-arachidonoylethanolamide (anandamide, AEA) is actively degraded by the serine hydrolase enzyme, fatty acid amide hydrolase (FAAH). Exposure to stress rapidly mobilizes FAAH to deplete the signaling pool of AEA and increase neuronal excitability in a key anxiety-mediating region--the basolateral amygdala (BLA). Gene deletion or pharmacological inhibition of FAAH prevents stress-induced reductions in AEA and associated increases in BLA dendritic hypertrophy and anxiety-like behavior. Additionally, inhibition of FAAH facilitates long-term fear extinction and rescues deficient fear extinction in rodent models by enhancing AEA-CB1 (cannabinoid type 1) receptor signaling and synaptic plasticity in the BLA. These preclinical findings propose restoring deficient BLA AEA levels by pharmacologically inhibiting FAAH as a mechanism to therapeutically mitigate the effects of traumatic stress.

Elevating endocannabinoid levels: pharmacological strategies and potential therapeutic applications

The endocannabinoid system consists of cannabinoid CB1 and CB2 receptors, of endogenous agonists for these receptors known as ‘endocannabinoids’, and of processes responsible for endocannabinoid biosynthesis, cellular uptake and metabolism. There is strong evidence first, that this system up-regulates in certain disorders as indicated by an increased release of endocannabinoids onto their receptors and/or by increases in the expression levels or coupling efficiency of these receptors, and second, that this up-regulation often appears to reduce or abolish unwanted effects of these disorders or to slow their progression. This discovery has raised the possibility of developing a medicine that enhances up-regulation of the endocannabinoid system associated with these disorders by inhibiting the cellular uptake or intracellular metabolism of an endocannabinoid following its ‘autoprotective’ endogenous release. For inhibition of endocannabinoid metabolism, research has focused particularly on two highly investigated endocannabinoids, anandamide and 2-arachidonoyl glycerol, and hence on inhibitors of the main anandamide-metabolising enzyme, fatty acid amide hydrolase (FAAH), and of the main 2-arachidonoyl glycerol-metabolising enzyme, monoacylglycerol (MAG) lipase. The resulting data have provided strong preclinical evidence that selective FAAH and MAG lipase inhibitors would ameliorate the unwanted effects of several disorders, when administered alone or with a cyclooxygenase inhibitor, and that the benefit-to-risk ratio of a FAAH inhibitor would exceed that of a MAG lipase inhibitor or dual inhibitor of FAAH and MAG lipase. Promising preclinical data have also been obtained with inhibitors of endocannabinoid cellular uptake. There is now an urgent need for clinical research with these enzyme and uptake inhibitors.

Activation of the Nlrp3 inflammasome in infiltrating macrophages by endocannabinoids mediates beta cell loss in type 2 diabetes

Type 2 diabetes mellitus (T2DM) progresses from compensated insulin resistance to beta cell failure resulting in uncompensated hyperglycemia, a process replicated in the Zucker diabetic fatty (ZDF) rat. The Nlrp3 inflammasome has been implicated in obesity-induced insulin resistance and beta cell failure. Endocannabinoids contribute to insulin resistance through activation of peripheral CB1 receptors (CB₁Rs) and also promote beta cell failure. Here we show that beta cell failure in adult ZDF rats is not associated with CB₁R signaling in beta cells, but rather in M1 macrophages infiltrating into pancreatic islets, and that this leads to activation of the Nlrp3-ASC inflammasome in the macrophages. These effects are replicated in vitro by incubating wild-type human or rodent macrophages, but not macrophages from CB₁R-deficient (Cnr1(-/-)) or Nlrp3(-/-) mice, with the endocannabinoid anandamide. Peripheral CB₁R blockade, in vivo depletion of macrophages or macrophage-specific knockdown of CB₁R reverses or prevents these changes and restores normoglycemia and glucose-induced insulin secretion. These findings implicate endocannabinoids and inflammasome activation in beta cell failure and identify macrophage-expressed CB₁R as a therapeutic target in T2DM.

Convergent translational evidence of a role for anandamide in amygdala-mediated fear extinction, threat processing and stress-reactivity

Endocannabinoids are released 'on-demand' on the basis of physiological need, and can be pharmacologically augmented by inhibiting their catabolic degradation. The endocannabinoid anandamide is degraded by the catabolic enzyme fatty acid amide hydrolase (FAAH). Anandamide is implicated in the mediation of fear behaviors, including fear extinction, suggesting that selectively elevating brain anandamide could modulate plastic changes in fear. Here we first tested this hypothesis with preclinical experiments employing a novel, potent and selective FAAH inhibitor, AM3506 (5-(4-hydroxyphenyl)pentanesulfonyl fluoride). Systemic AM3506 administration before extinction decreased fear during a retrieval test in a mouse model of impaired extinction. AM3506 had no effects on fear in the absence of extinction training, or on various non-fear-related measures. Anandamide levels in the basolateral amygdala were increased by extinction training and augmented by systemic AM3506, whereas application of AM3506 to amygdala slices promoted long-term depression of inhibitory transmission, a form of synaptic plasticity linked to extinction. Further supporting the amygdala as effect-locus, the fear-reducing effects of systemic AM3506 were blocked by intra-amygdala infusion of a CB1 receptor antagonist and were fully recapitulated by intra-amygdala infusion of AM3506. On the basis of these preclinical findings, we hypothesized that variation in the human FAAH gene would predict individual differences in amygdala threat-processing and stress-coping traits. Consistent with this, carriers of a low-expressing FAAH variant (385A allele; rs324420) exhibited quicker habituation of amygdala reactivity to threat, and had lower scores on the personality trait of stress-reactivity. Our findings show that augmenting amygdala anandamide enables extinction-driven reductions in fear in mouse and may promote stress-coping in humans.

Modulating the endocannabinoid system in human health and disease--successes and failures

The discovery of the endocannabinoid system, comprising the G-protein coupled cannabinoid 1 and 2 receptors (CB1/2), their endogenous lipid ligands or endocannabinoids, and synthetic and metabolizing enzymes, has triggered an avalanche of experimental studies implicating the endocannabinoid system in a growing number of physiological/pathological functions. These studies have also suggested that modulating the activity of the endocannabinoid system holds therapeutic promise for a broad range of diseases, including neurodegenerative, cardiovascular and inflammatory disorders; obesity/metabolic syndrome; cachexia; chemotherapy-induced nausea and vomiting; and tissue injury and pain, amongst others. However, clinical trials with globally acting CB1 antagonists in obesity/metabolic syndrome, and other studies with peripherally-restricted CB1/2 agonists and inhibitors of the endocannabinoid metabolizing enzyme in pain, have introduced unexpected complexities, suggesting that a better understanding of the pathophysiological role of the endocannabinoid system is required to devise clinically successful treatment strategies.

Chemical probes of endocannabinoid metabolism

The endocannabinoid signaling system regulates diverse physiologic processes and has attracted considerable attention as a potential pharmaceutical target for treating diseases, such as pain, anxiety/depression, and metabolic disorders. The principal ligands of the endocannabinoid system are the lipid transmitters N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG), which activate the two major cannabinoid receptors, CB1 and CB2. Anandamide and 2-AG signaling pathways in the nervous system are terminated by enzymatic hydrolysis mediated primarily by the serine hydrolases fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively. In this review, we will discuss the development of FAAH and MAGL inhibitors and their pharmacological application to investigate the function of anandamide and 2-AG signaling pathways in preclinical models of neurobehavioral processes, such as pain, anxiety, and addiction. We will place emphasis on how these studies are beginning to discern the different roles played by anandamide and 2-AG in the nervous system and the resulting implications for advancing endocannabinoid hydrolase inhibitors as next-generation therapeutics.

Modulation by 17β-estradiol of anandamide vasorelaxation in normotensive and hypertensive rats: a role for TRPV1 but not fatty acid amide hydrolase

Recent studies suggest that endocannabinoid signaling is modulated by 17β-estradiol (17Eβ) however it is unclear if this applies to the cardiovascular actions of anandamide, a major endocannabinoid. This study examined the in vitro effects of 17Eβ on vasorelaxation to anandamide in myograph-mounted small mesenteric arteries obtained from Wistar rats and Spontaneously Hypertensive Rats (SHRs) of both sexes. Treatment with 1μM 17Eβ but not its enantiomer 17Eα significantly enhanced relaxation to anandamide in male Wistar rats. This effect was independent of a functional endothelium but was blocked by the Transient Receptor Potential Vanilloid type 1 (TRPV1) receptor antagonist SB366791 (2μM) or prolonged treatment with the TRPV1 agonist capsaicin (10μM). A TRPV1-dependent potentiation by 17Eβ was also observed in male SHRs, but not in female Wistar rats or female SHRs. Whilst inhibition of anandamide hydrolysis by 1μM URB597 (an inhibitor of fatty acid amide hydrolase; FAAH) similarly augmented anandamide relaxation in male, but not female, Wistar rats and SHRs, URB597 did not affect the 17Eβ-induced potentiation. Female SHRs displayed a larger maximal relaxation to anandamide; however sex difference was not found in Wistar rats. We conclude that pharmacological levels of 17Eβ potentiate mesenteric relaxation to anandamide through mechanisms dependent on TRPV1 receptors but not FAAH-mediated hydrolysis in male Wistar rats and male SHRs. Sexual dimorphism was observed in the modulatory effects of 17Eβ and URB597, which does not necessarily lead to a greater anandamide response in female rats.

Inhibition of FAAH and activation of PPAR: new approaches to the treatment of cognitive dysfunction and drug addiction

Enhancing the effects of endogenously-released cannabinoid ligands in the brain might provide therapeutic effects more safely and effectively than administering drugs that act directly at the cannabinoid receptor. Inhibitors of fatty acid amide hydrolase (FAAH) prevent the breakdown of endogenous ligands for cannabinoid receptors and peroxisome proliferator-activated receptors (PPAR), prolonging and enhancing the effects of these ligands when they are naturally released. This review considers recent research on the effects of FAAH inhibitors and PPAR activators in animal models of addiction and cognition (specifically learning and memory). These studies show that FAAH inhibitors can produce potentially therapeutic effects, some through cannabinoid receptors and some through PPAR. These effects include enhancing certain forms of learning, counteracting the rewarding effects of nicotine and alcohol, relieving symptoms of withdrawal from cannabis and other drugs, and protecting against relapse-like reinstatement of drug self-administration. Since FAAH inhibition might have a wide range of therapeutic actions but might also share some of the adverse effects of cannabis, it is noteworthy that at least one FAAH-inhibiting drug (URB597) has been found to have potentially beneficial effects but no indication of liability for abuse or dependence. Although these areas of research are new, the preliminary evidence indicates that they might lead to improved therapeutic interventions and a better understanding of the brain mechanisms underlying addiction and memory.

Sulfonyl fluoride inhibitors of fatty acid amide hydrolase

Sulfonyl fluorides are known to inhibit esterases. Early work from our laboratory has identified hexadecyl sulfonylfluoride (AM374) as a potent in vitro and in vivo inhibitor of fatty acid amide hydrolase (FAAH). We now report on later generation sulfonyl fluoride analogs that exhibit potent and selective inhibition of FAAH. Using recombinant rat and human FAAH, we show that 5-(4-hydroxyphenyl)pentanesulfonyl fluoride (AM3506) has similar inhibitory activity for both the rat and the human enzyme, while rapid dilution assays and mass spectrometry analysis suggest that the compound is a covalent modifier for FAAH and inhibits its action in an irreversible manner. Our SAR results are highlighted by molecular docking of key analogs.

Peripheral cannabinoid-1 receptor inverse agonism reduces obesity by reversing leptin resistance

Obesity-related leptin resistance manifests in loss of leptin's ability to reduce appetite and increase energy expenditure. Obesity is also associated with increased activity of the endocannabinoid system, and CB(1) receptor (CB(1)R) inverse agonists reduce body weight and the associated metabolic complications, although adverse neuropsychiatric effects halted their therapeutic development. Here we show that in mice with diet-induced obesity (DIO), the peripherally restricted CB(1)R inverse agonist JD5037 is equieffective with its brain-penetrant parent compound in reducing appetite, body weight, hepatic steatosis, and insulin resistance, even though it does not occupy central CB(1)R or induce related behaviors. Appetite and weight reduction by JD5037 are mediated by resensitizing DIO mice to endogenous leptin through reversing the hyperleptinemia by decreasing leptin expression and secretion by adipocytes and increasing leptin clearance via the kidney. Thus, inverse agonism at peripheral CB(1)R not only improves cardiometabolic risk in obesity but has antiobesity effects by reversing leptin resistance.

Triphasic blood pressure responses to cannabinoids: do we understand the mechanism?

The cannabinoids comprise three major classes of substances, including compounds derived from the cannabis plant (e.g. Δ(9) -tetrahydrocannabinol and the chemically related substances CP55940 and HU210), endogenously formed (e.g. anandamide) and synthetic compounds (e.g. WIN55212-2). Beyond their psychotropic effects, cannabinoids have complex effects on blood pressure, including biphasic changes of Δ(9) -tetrahydrocannabinol and WIN55212-2 and an even triphasic effect of anandamide. The differing pattern of blood pressure changes displayed by the three types of compounds is not really surprising since, although they share an agonistic effect at cannabinoid CB(1) and CB(2) receptors, some compounds have additional effects. In particular, anandamide is known for its pleiotropic effects, and there is overwhelming evidence that anandamide influences blood pressure via (i) CB(1) receptors, (ii) TRPV1 receptors, (iii) endothelial cannabinoid receptors and (iv) degradation products. This review is dedicated to the description of the effects of externally added cannabinoids on cardiovascular parameters in vivo. First, the cardiovascular effects of cannabinoids in anaesthetized animals will be highlighted since most data have been generated in experiments of that type. The text will follow the three phases of anandamide on blood pressure, and we will check to which extent cardiovascular changes elicited by other cannabinoids show overlap with those effects or differ. The second part will be dedicated to the cardiovascular effects of the cannabinoids in conscious animals. In the third part, cardiovascular effects in humans will be discussed, and similarities and differences with respect to the data from animals will be examined.

Inhibiting fatty acid amide hydrolase normalizes endotoxin-induced enhanced gastrointestinal motility in mice

BACKGROUND AND PURPOSE

Gastrointestinal (GI) motility is regulated in part by fatty acid ethanolamides (FAEs), including the endocannabinoid (EC) anandamide (AEA). The actions of FAEs are terminated by fatty acid amide hydrolase (FAAH). We investigated the actions of the novel FAAH inhibitor AM3506 on normal and enhanced GI motility.

EXPERIMENTAL APPROACH

We examined the effect of AM3506 on electrically-evoked contractility in vitro and GI transit and colonic faecal output in vivo, in normal and FAAH-deficient mice treated with saline or LPS (100 µg·kg(-1), i.p.), in the presence and absence of cannabinoid (CB) receptor antagonists. mRNA expression was measured by quantitative real time-PCR, EC levels by liquid chromatography-MS and FAAH activity by the conversion of [(3)H]-AEA to [(3)H]-ethanolamine in intestinal extracts. FAAH expression was examined by immunohistochemistry.

KEY RESULTS

FAAH was dominantly expressed in the enteric nervous system; its mRNA levels were higher in the ileum than the colon. LPS enhanced ileal contractility in the absence of overt inflammation. AM3506 reversed the enhanced electrically-evoked contractions of the ileum through CB(1) and CB(2) receptors. LPS increased the rate of upper GI transit and faecal output. AM3506 normalized the enhanced GI transit through CB(1) and CB(2) receptors and faecal output through CB(1) receptors. LPS did not increase GI transit in FAAH-deficient mice.

CONCLUSIONS AND IMPLICATIONS

Inhibiting FAAH normalizes various parameters of GI dysmotility in intestinal pathophysiology. Inhibition of FAAH represents a new approach to the treatment of disordered intestinal motility.

Phytoestrogens enhance the vascular actions of the endocannabinoid anandamide in mesenteric beds of female rats

In rat isolated mesenteric beds that were contracted with NA as an in vitro model of the vascular adrenergic hyperactivity that usually precedes the onset of primary hypertension, the oral administration (3 daily doses) of either 10 mg/kg genistein or 20 mg/kg daidzein potentiated the anandamide-induced reduction of contractility to NA in female but not in male rats. Oral treatment with phytoestrogens also restored the vascular effects of anandamide as well as the mesenteric content of calcitonin gene-related peptide (CGRP) that were reduced after ovariectomy. The enhancement of anandamide effects caused by phytoestrogens was prevented by the concomitant administration of the estrogen receptor antagonist fulvestrant (2.5 mg/kg, s.c., 3 daily doses). It is concluded that, in the vasculature of female rats, phytoestrogens produced an estrogen-receptor-dependent enhancement of the anandamide-vascular actions that involves the modulation of CGRP levels and appears to be relevant whenever an adrenergic hyperactivity occurs.

Approximating protein flexibility through dynamic pharmacophore models: application to fatty acid amide hydrolase (FAAH)

A structure-based drug discovery method is described that incorporates target flexibility through the use of an ensemble of protein conformations. The approach was applied to fatty acid amide hydrolase (FAAH), a key deactivating enzyme in the endocannabinoid system. The resultant dynamic pharmacophore models are rapidly able to identify known FAAH inhibitors over drug-like decoys. Different sources of FAAH conformational ensembles were explored, with both snapshots from molecular dynamics simulations and a group of X-ray structures performing well. Results were compared to those from docking and pharmacophore models generated from a single X-ray structure. Increasing conformational sampling consistently improved the pharmacophore models, emphasizing the importance of incorporating target flexibility in structure-based drug design.

The endocannabinoid 2-arachidonoylglycerol mediates D1 and D2 receptor cooperative enhancement of rat nucleus accumbens core neuron firing

Many motivated and addiction-related behaviors are sustained by activity of both dopamine D1- and D2-type receptors (D1Rs and D2Rs) as well as CB1 receptors (CB1Rs) in the nucleus accumbens (NAc). Here, we use in vitro whole-cell patch-clamp electrophysiology to describe an endocannabinoid (eCB)-dopamine receptor interaction in adult rat NAc core neurons. D1R and D2R agonists in combination enhanced firing, with no effect of a D1R or D2R agonist alone. This D1R+D2R-mediated firing increase required CB1Rs, since it was prevented by the CB1R antagonists AM251 and Rimonabant. The D1R+D2R firing increase also required phospholipase C (PLC), the major synthesis pathway for the eCB 2-arachidonoylglycerol (2-AG) and one of several pathways for anandamide. Further, inhibition of 2-AG hydrolysis with the monoglyceride lipase (MGL) inhibitor JZL184 allowed subthreshold levels of D1R+D2R receptor agonists to enhance firing, while inhibition of anandamide hydrolysis with the fatty acid amide hydrolase (FAAH) inhibitors URB597 or AM3506 did not. Filling the postsynaptic neuron with 2-AG enabled subthreshold D1R+D2R agonists to increase firing, and the 2AG+D1R+D2R increase in firing was prevented by a CB1R antagonist. Also, the metabotropic glutamate receptor 5 (mGluR5) blocker MPEP prevented the ability of JZL184 to promote subthreshold D1R+D2R enhancement of firing, while the 2-AG+D1R+D2R increase in firing was not prevented by the mGluR5 blocker, suggesting that mGluR5s acted upstream of 2-AG production. Thus, our results taken together are consistent with the hypothesis that NAc core eCBs mediate dopamine receptor (DAR) enhancement of firing, perhaps providing a cellular mechanism underlying the central role of NAc core D1Rs, D2Rs, CB1Rs, and mGluR5s during many drug-seeking behaviors.