Synthesis, molecular modelling studies and biological evaluation of new oxoeicosanoid receptor 1 agonists.

The oxoeicosanoid receptor 1 (OXER1) is a member of the G-protein coupled receptors (GPCR) family, and is involved in inflammatory processes and oncogenesis. As such it is an attractive target for pharmacological intervention. The present study aimed to shed light on the molecular fundaments of OXER1 modulation using chemical probes structurally related to the natural agonist 5-oxo-ETE. In a first step, 5-oxo-ETE and its closely related derivatives (5-oxo-EPE and 4-oxo-DHA) were obtained by conducting concise and high-yielding syntheses. The biological activity of obtained compounds was assessed in terms of potency (EC50) and efficacy (Emax) for arrestin recruitment. Finally, molecular modelling and simulation were used to explore binding characteristics of 5-oxo-ETE and derivatives with the aim to rationalize biological activity. Our data suggest that the tested 5-oxo-ETE derivatives (i) insert quickly into the membrane, (ii) access the receptor via transmembrane helices (TMs) 5 and 6 from the membrane side and (iii) drive potency and efficacy by differential interaction with TM5 and 7. Most importantly, we found that the methyl ester of 5-oxo-ETE (1a) showed even a higher maximum response than the natural agonist (1). In contrast, shifting the 5-oxo group into position 4 results in inactive compounds (4-oxo DHA compounds (3) and (3a)). All in all, our study provides relevant structural data that help understanding better OXER1 functionality and its modulation. The structural information presented herein will be useful for designing new lead compounds with desired signalling profiles.

2-Arachidonoylglycerol: A signaling lipid with manifold actions in the brain.

2-Arachidonoylglycerol (2-AG) is a signaling lipid in the central nervous system that is a key regulator of neurotransmitter release. 2-AG is an endocannabinoid that activates the cannabinoid CB1 receptor. It is involved in a wide array of (patho)physiological functions, such as emotion, cognition, energy balance, pain sensation and neuroinflammation. In this review, we describe the biosynthetic and metabolic pathways of 2-AG and how chemical and genetic perturbation of these pathways has led to insight in the biological role of this signaling lipid. Finally, we discuss the potential therapeutic benefits of modulating 2-AG levels in the brain.

On the cellular metabolism of the click chemistry probe 19-alkyne arachidonic acid.

Alkyne and azide analogs of natural compounds that can be coupled to sensitive tags by click chemistry are powerful tools to study biological processes. Arachidonic acid (AA) is a FA precursor to biologically active compounds. 19-Alkyne-AA (AA-alk) is a sensitive clickable AA analog; however, its use as a surrogate to study AA metabolism requires further evaluation. In this study, AA-alk metabolism was compared with that of AA in human cells. Jurkat cell uptake of AA was 2-fold greater than that of AA-alk, but significantly more AA-Alk was elongated to 22:4. AA and AA-alk incorporation into and remodeling between phospholipid (PL) classes was identical indicating equivalent CoA-independent AA-PL remodeling. Platelets stimulated in the pre-sence of AA-alk synthesized significantly less 12-lipoxygenase (12-LOX) and cyclooxygenase products than in the presence of AA. Ionophore-stimulated neutrophils produced significantly more 5-LOX products in the presence of AA-alk than AA. Neutrophils stimulated with only exogenous AA-alk produced significantly less 5-LOX products compared with AA, and leukotriene B4 (LTB4)-alk was 12-fold less potent at stimulating neutrophil migration than LTB4, collectively indicative of weaker leukotriene B4 receptor 1 agonist activity of LTB4-alk. Overall, these results suggest that the use of AA-alk as a surrogate for the study of AA metabolism should be carried out with caution.

Asymmetric synthesis of novel N-(1-phenyl-2,3-dihydroxypropyl)arachidonylamides and evaluation of their anti-inflammatory activity.

AIMS: To design and synthesize novel N-(1-phenyl-2,3-dihydroxypropyl)arachidonylamides and evaluate their analgesic and anti-inflammatory potential. MAIN METHODS: The murine macrophage cell line RAW 264.7 has been widely used as a model for inflammatory responses in vitro. Our model consists of cultured monolayers of RAW 264.7 cells in which media concentrations of 15-deoxy-Δ(13,14)-PGJ2 (PGJ) are measured by ELISA following LPS (10ng/ml) stimulation and treatment with 0.1, 0.3, 1.0, 3.0 and 10µM concentrations of the compounds. KEY FINDINGS: Our data indicate that several of our compounds have the capacity to increase production of PGJ and may also increase the occurrence of programmed cell death (apoptosis). SIGNIFICANCE: Thus these agents are potential candidates for the therapy of conditions characterized by ongoing (chronic) inflammation and its associated pain.

4-Aminocyclopentane-1,3-diols as platforms for diversity: synthesis of anandamide analogs.

Starting from cyclopentadiene, two racemic mixtures of 4-aminocyclopentane-1,3-diols were prepared in 8 steps and characterized. Structure determination proved the anticipated trans-orientation of the two oxygen atoms with respect to the plane of the ring. The fragment-like new compounds are small and hydrophilic, devoid of rotatable bonds, and offer stereochemically defined attachment points for substituents. Thus, these platforms for diversity are suitable starting points for the construction of combinatorial libraries of lead-like 4-amidocyclopentane-1,3-diols or natural product analogs. As a proof of concept, cyclopentanoid anandamide analogs were prepared using these molecular platforms and evaluated as tools for the investigation of unresolved issues in the molecular biology of anandamide.

Resorcinol-sn-glycerol derivatives: novel 2-arachidonoylglycerol mimetics endowed with high affinity and selectivity for cannabinoid type 1 receptor.

Since the discovery of the endocannabinoid system, evidence has been progressively accumulating to suggest that 2-arachidonoylglycerol (2-AG) rather than anandamide (AEA) is the endogenous ligand for both cannabinoid (CB) receptors. Moreover, other studies have shown that another lipid molecule, 2-arachidonyl-glycerol ether (2-AGE, noladin ether), which acts as a full agonist at cannabinoid receptors, might occur in tissues. Having previously designed a resorcinol-AEA hybrid model, in this paper we have explored the cannabinoid receptor binding properties, the CB1 functional activity, and the stability to plasma esterases of a novel series of compounds characterized by the conversion of the amide head into the glycerol-ester or glycerol-ether head, typical of 2-AG or the "putative" endocannabinoid 2-AGE, respectively. Glyceryl esters 39 and 41 displayed greater potency for CB1 (Ki in the nanomolar range) than for CB2 receptors plus the potential to be exploited as useful hits for the development of novel 2-AG mimetics.

Development of endocannabinoid-based chemical probes for the study of cannabinoid receptors.

We report the synthesis of new chemical probes (1a,b, 2a-c, 3a-c) based on the structure of the main endocannabinoids for their use in biological systems directly or via click chemistry. As proof of concept, 2-arachidonyl glyceryl ether based biotinylated 3b enables direct visualization of CB(1) receptor in cells. These results represent the starting point for the development of advanced small molecule chemical probes able to generate valuable information about the cannabinoid receptors.

17(R),18(S)-epoxyeicosatetraenoic acid, a potent eicosapentaenoic acid (EPA) derived regulator of cardiomyocyte contraction: structure-activity relationships and stable analogues.

17(R),18(S)-epoxyeicosatetraenoic acid [17(R),18(S)-EETeTr], a cytochrome P450 epoxygenase metabolite of eicosapentaenoic acid (EPA), exerts negative chronotropic effects and protects neonatal rat cardiomyocytes against Ca(2+)-overload with EC(50) ≈ 1-2 nM. Structure-activity studies revealed that a cis-Δ(11,12)- or Δ(14,15)-olefin and a 17(R),18(S)-epoxide are minimal structural elements for antiarrhythmic activity whereas antagonist activity was often associated with the combination of a Δ(14,15)-olefin and a 17(S),18(R)-epoxide. Compared with natural material, the agonist and antagonist analogues are chemically and metabolically more robust and several show promise as templates for future development of clinical candidates.

6-Methylnitroarachidonate: a novel esterified nitroalkene that potently inhibits platelet aggregation and exerts cGMP-mediated vascular relaxation.

Nitro-fatty acids represent endogenously occurring products of oxidant-induced nitration reactions. We have previously synthesized a mixture of four isomers of nitroarachidonic acid, a novel anti-inflammatory signaling mediator. In this study, we synthesized and chemically and biologically characterized for the first time an esterified nitroalkene derived from the nitration of methylarachidonate (AAMet): 6-methylnitroarachidonate (6-AAMetNO(2)). Synthesis was performed by reacting AAMet with sodium nitrite under acidic conditions. Analysis by mass spectrometry (positive-ion ESI-MS) showed an [M+H](+) ion of m/z 364, characteristic of AAMetNO(2). Fragmentation of this ion yielded a daughter ion at m/z 317, corresponding to the neutral loss of the nitro group ([M+H-HNO(2)](+)). Furthermore, IR signal at 1378 cm(-1) and NMR data confirmed the structure of a 6-nitro-positional isomer. This novel esterified nitroalkene was capable of promoting vascular protective actions including: (a) the induction of vasorelaxation via endothelium-independent mechanisms, associated with an increase in smooth muscle cell cGMP levels, and (b) a potent dose-dependent inhibition of human platelet aggregation. We postulate that 6-AAMetNO(2) could be a potential drug for the prevention of vascular and inflammatory diseases, and the presence of the methyl group may increase its pharmacological potential.

Synthesis, binding studies and molecular modeling of novel cannabinoid receptor ligands.

In the present work, we report upon the design, synthesis and biological evaluation of new anandamide derivatives obtained by modifications of the fatty acyl chain and/or of the ethanolamide 'tail'. The compounds are of the general formula: 6-(substituted-phenyl)/naphthyl-4-oxohex-5-enoic acid N-substituted amide and 7-naphthyl-5-oxohept-6-enoicacid N-substituted amide. The novel compounds had been evaluated for their binding affinity to CB1/CB2 cannabinoid receptors, binding studies showed that some of the newly developed compounds have measurable affinity and selectivity for the CB2 receptor. Compounds XI and XVIII showed the highest binding affinity for CB2 receptor. None of the compounds exhibited inhibitory activity towards anandamide hydrolysis, thus arguing in favor of their enzymatic stability. The structure-activity relationship has been extensively studied through a tailor-made homological model using constrained docking in addition to pharmacophore analysis, both feature and field based.

The role of iodine and delta-iodolactone in growth and apoptosis of malignant thyroid epithelial cells and breast cancer cells.

OBJECTIVE: As we previously demonstrated, the inhibitory effect of iodine on thyroid cell growth is mediated by iodolactones, especially 6-iodo-5-hydroxy-eicosatrienoic acid (delta-iodolactone). In this communication we compare the effect of iodide, molecular iodine and delta-iodolactone on growth inhibition and apoptosis on three human thyroid carcinoma cell lines (B-CPAP cells, FTC-133 cells and 8505C cells) as well as on human breast cancer cells (MCF 7). METHODS: Thyroid carcinoma cells were cultured in Dulbecco's modified Eagle's medium (DMEM) and MCF 7 cells in Rowswell Park Memorial Institute (RPMI) culture medium, both containing 10% (v/v) Fetal Calf Serum (FCS), until they were confluent. Around 2000 cells were then distributed in 12-well plates and grown for 48 h in either DMEM (thyroid cancer cells) or in RPMI medium (MCF 7 cells) both containing 5% FCS. Thereafter, different concentrations of iodide, iodine or delta-iodolactone were added for 24 h. Growth rate was estimated by cell counting in a Coulter Counter adapted for epithelial cells. Apoptosis was determined by a mitochondrial potential assay. RESULTS: The growth rate of B-CPAP cells was unaffected by iodide, but was reduced by high concentreations of molecular iodine (100 and 500 microM). However, delta-iodolactone significantly reduced cell proliferation already with low concentrations (5 microM and 10 microM) and further in a dose-dependent manner up to 82%. FTC-133 and 8505C cells were unaffected by iodide, iodine or delta-iodolactone. In contrast, in MCF 7 cells, molecular iodine (100 microM) inhibited growth from 100% to 83% but delta-iodolactone (1, 5 and 10 microM) dose-dependently decreased growth rate from 100% to 82% and 62%, respectively. The inhibition of growth was through apoptosis, and not necrosis, as the amount of apoptotic cells corresponded to the growth inhibition. CONCLUSION: delta-Iotaodolactone seems to be the main iodocompound which can inhibit growth and induce apoptosis in B-CPAP cells as well as in MCF 7 breast cancer cells.

Design and synthesis of (13S)-methyl-substituted arachidonic acid analogues: templates for novel endocannabinoids.

Two novel methyl-substituted arachidonic acid derivatives were prepared in an enantioselective manner from commercially available chiral building blocks, and were found to be excellent templates for the development of (13S)-methyl-substituted anandamide analogues. One of the compounds synthesized, namely, (13S,5Z,8Z,11Z,14Z)-13-methyl-eicosa-5,8,11,14-tetraenoic acid N-(2-hydroxyethyl)amide, is an endocannabinoid analogue with remarkably high affinity for the CB1 cannabinoid receptor.

Characterization of an AM404 analogue, N-(3-hydroxyphenyl)arachidonoylamide, as a substrate and inactivator of prostaglandin endoperoxide synthase.

N-(4-Hydroxyphenyl)arachidonoylamide (AM404) is an inhibitor of endocannabinoid inactivation that has been used in cellular and animal studies. AM404 is a derivative of arachidonic acid and has been reported to inhibit arachidonate oxygenation by prostaglandin endoperoxide synthase-1 and -2 (PGHS-1 and -2, respectively). While examining the structural requirements for inhibition of PGHS, we discovered that the meta isomer of AM404, N-(3-hydroxyphenyl)arachidonoylamide (3-HPAA), is a substrate for purified PGHS. PGHS-2 efficiently oxygenated 3-HPAA to prostaglandin and hydroxyeicosatetraenoate products. No oxidation of the phenolamide moiety was observed. 3-HPAA appeared to be converted by PGHS-1 in a similar manner; however, conversion was less efficient than that by PGHS-2. PGHS-2 was selectively, dose-dependently, and irreversibly inactivated in the presence of 3-HPAA. Complete inactivation of PGHS-2 was achieved with 10 muM 3-HPAA. Preliminary characterization revealed that 3-HPAA inactivation did not result from covalent modification of PGHS-2 or damage to the heme moiety. These studies provide additional insight into the structural requirements for substrate metabolism and inactivation of PGHS and report the first metabolism-dependent, selective inactivator of PGHS-2.

Synthesis and pharmacological evaluation of sulfamide-based analogues of anandamide.

Arachidonyl and linoleyl sulfamide derivatives have been synthesized and their potential cannabimimetic properties evaluated in in vitro functional and binding assays. Replacement of the ethanolamide moiety of anandamide by -CH(2)NHSO(2)NH-R considerably reduces the CB1 receptor activity and only some of the compounds showed modest cannabinoid properties in binding assays. The new compounds were also tested as inhibitors of the FAAH enzyme but were inactive.

Synthesis, in vitro and in vivo evaluation, and radiolabeling of aryl anandamide analogues as candidate radioligands for in vivo imaging of fatty acid amide hydrolase in the brain.

Fatty acid amide hydrolyase (FAAH) is one of the main enzymes responsible for terminating the signaling of endocannabinoids in the brain. Imaging FAAH in vivo using PET or SPECT is important to deeper understanding of its role in neuropsychiatric disorders. However, at present, no radioligand is available for mapping the enzyme in vivo. Here, we synthesized 18 aryl analogues of anandamide, FAAH's endogenous substrate, and in vitro evaluated their potential as metabolic trapping tracers. Interaction studies with recombinant FAAH revealed good to very good interaction of the methoxy substituted aryl anandamide analogues 17, 18, 19, and 20 with FAAH and they were identified as competing substrates. Compounds 17 and 18 did not display significant binding to CB1 and CB2 cannabinoid receptors and stand out as potential candidate metabolic trapping tracers. They were successfully labeled with 11C in good yields and high radiochemical purity and displayed brain uptake in C57BL/6J mice. Radioligands [11C]-17 and [11C]-18 merit further investigation in vivo.

[Endocannabinoid 2-arachidonoylglycerol: 1,3-dinitrates of cyclooxygenase metabolites, synthesis and properties].

Glycerol esters 1,3-dinitrates of the cyclooxygenase metabolites of natural prostaglandin 2-arachidonoylglycerol, an endogenous ligand of cannabinoid receptors, were synthesized for the first time. Four methods of synthesis of these esters were developed via the activation of a carboxyl group and their chemical and pharmacological properties were investigated. The esters exhibit a more selective pharmacological spectrum of activities in comparison with the corresponding natural prostaglandins: some types of myotropic activity were enhanced, while others were loosened. 1,3-dinitroglycerol esters act as vasodilators, whereas the majority of natural prostaglandins act as vasoconstrictors. The observed changes result from the introduction of an NO-releasing fragment into prostaglandin molecule.

New resorcinol-anandamide "hybrids" as potent cannabinoid receptor ligands endowed with antinociceptive activity in vivo.

Bearing in mind the pharmacophoric requirements of both (-)-trans-Delta(9)-tetrahydrocannabinol (THC) and anandamide (AEA), we designed a novel pharmacophore consisting of both a rigid aromatic backbone and a flexible chain with the aim to develop a series of stable and potent ligands of cannabinoid receptors. In this paper we report the synthesis, docking studies, and structure-activity relationships of new resorcinol-anandamide "hybrids" differing in the side chain group. Compounds bearing a 2-methyloctan-2-yl group at position 5 showed a significantly higher affinity for cannabinoid (CB) receptors, in particular when an alkyloxy chain of 7 or 10 carbon atoms was also present at position 1. Derivative 32 was a potent CB(1) and CB(2) ligand, with K(i) values similar to that of WIN 55-212 and potent antinociceptive activity in vivo. Moreover, derivative 38, although less potent, proved to be the most selective ligand for CB(2) receptor (K(i)(CB(1)) = 1 muM, K(i)(CB(2)) = 35 nM).

Total synthesis of photoactivatable or fluorescent anandamide probes: novel bioactive compounds with angiogenic activity.

Endocannabinoids are endogenous polyunsaturated fatty acids involved in a multitude of health and disease processes. Recently, several lines of evidence suggest the presence of a novel non-CB1/CB2 anandamide receptor in endothelial cells. Thus, we synthesized two types of photoaffinity probes that contain either an arylazide group or a diazirin moiety, together with a fluorescent analogue. The key steps rely on selective hydrogenation of skipped tetrayne backbones and on copper-mediated cross-coupling reactions between diynic precursors. Three synthetic routes were investigated. In biological functional assays, we found that both the arylazide and the fluorescent probes induced robust increases in matrix metalloprotease activity and produced positive angiogenic responses in in vitro endothelial cell tube formation assays. Irradiation of the arylazide probe nicely enhanced this effect in both HUVEC and CB1-KO HUVEC. These results suggest that the arylazide and the fluorescent probes can be used to identify "non-CB1/CB2 anandamide receptor" from endothelial cells.

Chemical synthesis, pharmacological characterization, and possible formation in unicellular fungi of 3-hydroxy-anandamide.

The fungal pathogen Candida albicans transforms arachidonic acid (AA) into 3-hydroxyarachidonic acid [3R-HETE], and we investigated if its nonpathogenic and 3R-HETE-producing close relative, Dipodascopsis uninucleata, could similarly transform the endocannabinoid/endovanilloid anandamide into 3-hydroxyanandamide (3-HAEA). We found that D. uninucleata converts anandamide into 3-HAEA, and we therefore developed an enantiodivergent synthesis for this compound to study its pharmacological activity. Both enantiomers of 3-HAEA were as active as anandamide at elevating intracellular Ca2+ via TRPV1 receptors overexpressed in HEK-293 cells, while a approximately 70-90-fold and approximately 45-60-fold lower affinity at cannabinoid CB1 and CB2 receptors was instead observed. Patch clamp recordings showed that 3R-HAEA activates a TRPV1-like current in TRPV1-expressing HEK-293 cells. Thus, 3R-HETE-producing yeasts might convert anandamide released by host cells at the site of infection into 3R-HAEA, and this event might contribute to the inflammatory and algogenous responses associated to fungal diseases.

New analgesics synthetically derived from the paracetamol metabolite N-(4-hydroxyphenyl)-(5Z,8Z,11Z,14Z)-icosatetra-5,8,11,14-enamide.

N-(4-hydroxyphenyl)-(5Z,8Z,11Z,14Z)-icosatetra-5,8,11,14-enamide (AM404) is a metabolite of the well-known analgesic paracetamol. AM404 inhibits endocannabinoid cellular uptake, binds weakly to CB1 and CB2 cannabinoid receptors, and is formed by fatty acid amide hydrolase (FAAH) in vivo. We prepared three derivatives of this new (endo)cannabinoid using bioisosteric replacement (1), homology (2), and derivatization (3) of the 4-aminophenol moiety in AM404 and tested them against CB1, CB2, and FAAH. We found affinities toward both cannabinoid receptors equal to or greater than that of AM404. Shortening the acyl chain from C20 to C2 led to three new paracetamol analogues: N-(1H-indazol-5-yl)acetamide (5), N-(4-hydroxybenzyl)acetamide (6), and N-(4-hydroxy-3-methoxyphenyl)acetamide (7). Again, 5, 6, and 7 were tested against CB1, CB2, and FAAH without significant activity. However, 5 and 7 behaved like inhibitors of cyclooxygenases in whole blood assays. Finally, 5 (50 mg/kg) and 6 (275 mg/kg) displayed analgesic activities comparable to paracetamol (200 mg/kg) in the mouse formalin test.