Homologues and analogues of palmitoylethanolamide : templates for agents affecting the metabolism of endocannabinoids without direct effects upon cannabinoid receptors

The endogenous ligands of cannabinoid receptors (i.e. the endocannabinoids) exhibit multiple interesting pharmacological properties. Unfortunately, these compounds are rapidly inactivated by enzymatic hydrolysis which prevents their effective medical use. The design of inhibitors of the proteins responsible of endocannabinoids degradation is thus a necessary step of the development of endocannabinoids-based therapteutics, and was the main aim of the work. Starting from the template of palmitoylethanolamide (PEA), an endogenous substance related to endocannabinoids devoid of cannabinoid receptors affinity, we demonstrated here that analogues and homologues of palmitoylethanolamide (PEA) constitute a interesting pool of selective agents interfering with the endocannabinoid anandamide (AEA) metabolism. Among the multiple derivatives of PEA which were synthesized, palmitoylcyclohexamide was picked out as a selective inhibitor of AEA transporter in C6 and RBL-2H3 cells. Palmitoylisopropylamide was a mixed inhibitor capable of acting on the same time on FAAH and AEA transporter. Oleoylethylamide, N-(1-oxohexadecyl)glycine mehyl ester and N-(2-acetoxyacetyl)pentadecylamine exhibited selective FAAH inhibition. Lauroylethanolamide was a mixed agent which induced moderate FAAH inhibition and enhancement of VR-1 activation by AEA. Palmitoylmorpholinamide and palmitoyldiethylamide were selective VR-1 activation enhancers that increased VR-1 activation by AEA without affecting FAAH nor AEA transporter. Two analogues of PEA were also distinguished for their selectivity to N-palmitoylethanolamine selective acid amidase (NPAA) which preferentially hydrolyzes PEA. Cyclohexylpalmitate and N-cyclohexanecarbonylpentadecylamine are selective inhibitors of NPAA. The selectivity exhibited by the last has allowed its use as pharmacological tool to distinguish NPAA from FAAH in RBL-1 cells. Our approach allowed the discovery of an antinociceptive agent, namely oleoylethylamide (OEt), effective in normal and neuropathic conditions, and capable of modulating AEA, 2-arachidonoylglycerol (2-AG) and oleoylethanolamide (OEA) endogenous tones without any changes in PEA content. We provided further evidence to the hypothesis that manipulation of endocannabinoid tones in vivo with FAAH inhibitors is possible, and can be used to induce some therapeutically useful cannabimimetic effects, without the adverse effects accompanying exogenous cannabinoids like delta9-THC.Doctorat en sciences (sciences chimiques) (CHIM 3)--UCL, 200

Gros plan sur les endocannabinoïdes, de nouveaux agents thérapeutiques

The endogenous ligands of cannabinoid receptors (i.e.the endocannabinoids) exhibit multiple interesting pharmacologicalproperties. Unfortunately, these compounds are rapidly inactivatedby enzymatic hydrolysis which prevents their effective medical use.The design of inhibitors of the proteins involved in endocannabi-noids degradation is thus a necessary step of the development ofendocannabinoids-based therapeutics. The purpose of this article isto present the recent data which confirm the therapeutic potential ofthe endocannabinoids, and the strategy that we chose to design inhi-bitors of the enzymes responsible of their degradation

Anticonvulsant activity of N-palmitoylethanolamide, a putative endocannabinoid, in mice

Purpose: The purpose of this study was to evaluate in mice the antieonvulsant potential of N-palmitoylethanolamide, a putative endocannabinoid that accumulates in the body during inflammatory processes. Methods: N-palmitoylethanolamide was injected intraperitoneally (i.p.) in mice and evaluated for anticonvulsant activity [in maximal electroshock seizure (MES) and chemical-induced convulsions] and for neurologic impairment (rotorod). It was compared with anandamide and with different palmitic acid analogues as well as with reference anticonvulsants (AEDs) injected under the same conditions. Results: The MES test showed, after i.p. administration to mice, that N- palmitoylethanolamide had an median effective dose (ED50) value comparable to that of phenytoin (PHT; 8.9 and 9.2 mg/kg, respectively). In the subcutaneous pentylenetetrazol test and in the 3-mercaptropropionic acid test, it was effective only against tonic convulsions. N-palmitoylethanolamide was devoid of neurologic impairment ≤250 mg/kg, yielding a high protective index. Conclusions: N-palmitoylethanolamide, an endogenous compound with antiinflammatory and analgesic activities, is a potent AED in mice. Its precise mechanism of action remains to be elucidated.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effects of homologues and analogues of palmitoylethanolamide upon the inactivation of the endocannabinoid anandamide

1. The ability of a series of homologues and analogues of palmitoylethanolamide to inhibit the uptake and fatty acid amidohydrolase (FAAH)-catalysed hydrolysis of [(3)H]-anandamide ([(3)H]-AEA) has been investigated. 2. Palmitoylethanolamide and homologues with chain lengths from 12–18 carbon atoms inhibited rat brain [(3)H]-AEA metabolism with pI(50) values of ∼5. Homologues with chain lengths ⩽eight carbon atoms gave <20% inhibition at 100 μM. 3. R-palmitoyl-(2-methyl)ethanolamide, palmitoylisopropylamide and oleoylethanolamide inhibited [(3)H]-AEA metabolism with pI(50) values of 5.39 (competitive inhibition), 4.89 (mixed type inhibition) and 5.33 (mixed type inhibition), respectively. 4. With the exception of oleoylethanolamide, the compounds did not produce dramatic inhibition of [(3)H]-WIN 55,212-2 binding to human CB(2) receptors expressed on CHO cells. Palmitoylethanolamide, palmitoylisopropylamide and R-palmitoyl-(2-methyl)ethanolamide had modest effects upon [(3)H]-CP 55,940 binding to human CB(1) receptors expressed on CHO cells. 5. Most of the compounds had little effect upon the uptake of [(3)H]-AEA into C6 and/or RBL-2H3 cells. However, palmitoylcyclohexamide (100 μM) and palmitoylisopropylamide (30 and 100 μM) produced more inhibition of [(3)H]-AEA uptake than expected to result from inhibition of [(3)H]-AEA metabolism alone. 6. In intact C6 cells, palmitoylisopropylamide and oleoylethanolamide inhibited formation of [(3)H]-ethanolamine from [(3)H]-AEA to a similar extent as AM404, whereas palmitoylethanolamide, palmitoylcyclohexamide and R-palmitoyl-(2-methyl)ethanolamide were less effective. 7. These data provide useful information upon the ability of palmitoylethanolamide analogues to act as ‘entourage' compounds. Palmitoylisopropylamide may prove useful as a template for design of compounds that reduce the cellular accumulation and metabolism of AEA without affecting either CB(1) or CB(2) receptors

AM404 and VDM 11 non-specifically inhibit C6 glioma cell proliferation at concentrations used to block the cellular accumulation of the endocannabinoid anandamide

AM404 [N-(4-hydroxyphenyl)arachidonylamide] and VDM 11 [(5Z,8Z,11Z,14Z)-N-(4-hydroxy-2-methylphenyl)-5,8,11,14-eicosatetraenamide] are commonly used to prevent the cellular accumulation of the endocannabinoid anandamide, and thereby to potentiate its actions. However, it has been reported that AM404 can produce an influx of calcium into cells, which might be expected to have deleterious effects on cell proliferation. In the present study, AM404 and VDM 11 were found to reduce C6 glioma cell proliferation with IC50 values of 4.9 and 2.7 muM, respectively. The inhibition of cell proliferation following a 96-h exposure was not accompanied by dramatic caspase activation, and was not prevented by either a combination of cannabinoid and vanilloid receptor antagonists, or by the antioxidant alpha-tocopherol, suggestive of a non-specific mode of action. Similar results were seen with palmitoylisopropylamide, although this compound only produced significant inhibition of cell proliferation at 30 muM concentrations. AM404 (1 muM), VDM 11 (1 muM) and palmitoylisopropylamide (3-30 muM), i.e. concentrations producing relatively modest effects on cell proliferation per se, reduced the vanilloid receptor-mediated antiproliferative effects of anandamide, as would be expected for compounds preventing the cellular accumulation of anandamide (and thereby access to its binding site on the vanilloid receptor). It is concluded that concentrations of AM404 and VDM 11 that are generally used to reduce the cellular accumulation of anandamide have deleterious effects upon cell proliferation, and that lower concentrations of these compounds may be more appropriate to use in vitro