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D Piomelli

Publications and source records attributed to D Piomelli.

At least 55 records · Page 3Linked to original sources
PubMed1997

Functional role of high-affinity anandamide transport, as revealed by selective inhibition.

Anandamide, an endogenous ligand for central cannabinoid receptors, is released from neurons on depolarization and rapidly inactivated. Anandamide inactivation is not completely understood, but it may occur by transport into cells or by enzymatic hydrolysis. The compound N-(4-hydroxyphenyl)arachidonylamide (AM404) was shown to inhibit high-affinity anandamide accumulation in rat neurons and astrocytes in vitro, an indication that this accumulation resulted from carrier-mediated transport. Although AM404 did not activate cannabinoid receptors or inhibit anandamide hydrolysis, it enhanced receptor-mediated anandamide responses in vitro and in vivo. The data indicate that carrier-mediated transport may be essential for termination of the biological effects of anandamide, and may represent a potential drug target.

Analgesics↗
PubMed1997

A second endogenous cannabinoid that modulates long-term potentiation.

Cannabinoid receptors are molecular targets for marijuana and hashish, the widespread drugs of abuse. These receptors are expressed in areas of the central nervous system that contribute in important ways to the control of memory, cognition, movement and pain perception. Indeed, such functions can be strongly influenced by cannabinoid drugs, with consequences that include euphoria, analgesia, sedation and memory impairment. Although the pharmacology of cannabinoid drugs is now beginning to be understood, we still lack essential information on the endogenous signalling system(s) by which cannabinoid receptors are normally engaged. An endogenous ligand for cannabinoid receptors, anandamide, has been described. Here we report that sn-2 arachidonylglycerol (2-AG), a cannabinoid ligand isolated from intestinal tissue, is present in brain in amounts 170 times greater than anandamide. 2-AG is produced in hippocampal slices by stimulation of the Schaffer collaterals, an excitatory fibre tract that projects from CA3 to CA1 neurons. Formation of 2-AG is calcium dependent and is mediated by the enzymes phospholipase C and diacylglycerol lipase. 2-AG activates neuronal cannabinoid receptors as a full agonist, and prevents the induction of long-term potentiation at CA3-CA1 synapses. Our results indicate that 2-AG is a second endogenous cannabinoid ligand in the central nervous system.

Animals↗
PubMed1997

Interleukin-1 enhances the ATP-evoked release of arachidonic acid from mouse astrocytes.

During neuropathological states associated with inflammation, the levels of cytokines such as interleukin-1beta (IL-1beta) are increased. Several studies have suggested that the neuronal damage observed in pathogenesis implicating IL-1beta are caused by an alteration in the neurochemical interactions between neurons and astrocytes. We report here that treating striatal astrocytes in primary culture with IL-1beta for 22-24 hr enhances the ATP-evoked release of arachidonic acid (AA) with no effect on the ATP-induced accumulation of inositol phosphates. The molecular mechanism responsible for this effect involves the expression of P2Y2 receptors (a subtype of purinoceptor activated by ATP) and cytosolic phospholipase A2 (cPLA2, an enzyme that mediates AA release). Indeed, P2Y2 antisense oligonucleotides reduce the ATP-evoked release of AA only from IL-1beta-treated astrocytes. Further, both the amount of cPLA2 (as assessed by Western blotting) and the release of AA resulting from direct activation of cPLA2 increased fourfold in cells treated with IL-1beta. We also report evidence indicating that the coupling of newly expressed P2Y2 receptors to cPLA2 is dependent on PKC activity. These results suggest that during inflammatory conditions, IL-1beta reveals a functional P2Y2 signaling pathway in astrocytes that results in a dramatic increase in the levels of free AA. This pathway may thus contribute to the neuronal loss associated with cerebral ischemia or traumatic brain injury.

Adenosine Triphosphate↗
PubMed1997

Inhibition of anandamide hydrolysis in rat brain tissue by (E)-6-(bromomethylene) tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one.

Anandamide, an endogenous canabinoid substance, is hydrolyzed by an amidohydrolase activity present in rat brain and liver. We report that the bromoenol lactone, (E)-6-(bromomethylene) tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one (BTNP), is a potent inhibitor of this enzyme activity. BTNP prevented anandamide hydrolysis in rat brain microsomes with an IC50 of 0.8 +/- 0.3 microM. Kinetic and dialysis experiments indicated that this effect was non-competitive and irreversible. After chromatographic fractionation of the enzyme activity, BTNP was still effective, suggesting that it interacts directly with the enzyme. Anandamide hydrolysis was 12-fold greater in rat cortical neurons (1.94 +/- 0.1 pmol/min/mg protein) than in cortical astrocytes (0.16 +/- 0.01 pmol/min/mg protein) and, in either cell type, it was inhibited by BTNP (IC50 = 0.1 microM in neurons). These results suggest that BTNP may provide a useful lead for the development of novel inhibitors of anandamide hydrolysis.

Amidohydrolases↗
PubMed1997

Occurrence and biosynthesis of endogenous cannabinoid precursor, N-arachidonoyl phosphatidylethanolamine, in rat brain.

It has been suggested that anandamide (N-arachidonoylethanolamine), an endogenous cannabinoid substance, may be produced through Ca2+-stimulated hydrolysis of the phosphatidylethanolamine (PE) derivative N-arachidonoyl PE. The presence of N-arachidonoyl PE in adult brain tissue and the enzyme pathways that underlie its biosynthesis are, however, still undetermined. We report here that rat brain tissue contains both anandamide (11 +/- 7 pmol/gm wet tissue) and N-arachidonoyl PE (22 +/- 16 pmol/gm), as assessed by gas chromatography/mass spectrometry. We describe a N-acyltransferase activity in brain that catalyzes the biosynthesis of N-arachidonoyl PE by transferring an arachidonate group from the sn-1 carbon of phospholipids to the amino group of PE. We also show that sn-1 arachidonoyl phospholipids are present in brain, where they constitute approximately 0.5% of total phospholipids. N-acyltransferase activity is Ca2+ dependent and is enriched in brain and testis. Within the brain, N-acyltransferase activity is highest in brainstem; intermediate in cortex, striatum, hippocampus, medulla, and cerebellum; and lowest in thalamus, hypothalamus, and olfactory bulb. Pharmacological inhibition of N-acyltransferase activity in primary cultures of cortical neurons prevents Ca2+-stimulated N-arachidonoyl PE biosynthesis. Our results demonstrate, therefore, that rat brain tissue contains the complement of enzymatic activity and lipid substrates necessary for the biosynthesis of the anandamide precursor N-arachidonoyl PE. They also suggest that biosynthesis of N-arachidonoyl PE and formation of anandamide are tightly coupled processes, which may concomitantly be stimulated by elevations in intracellular Ca2+ occurring during neural activity.

Acyltransferases↗
PubMed1997

Medicinal plants for the treatment of urogenital tract pathologies according to Dioscorides' De Materia Medica.

The De Materia Medica of the Greek Dioscorides reports about 200 plants used for the treatment of pathologies of the urogenital tract during the 1st century AD. On the basis of explicit and implicit affirmations by Dioscorides, a theoretical system concerning the specific properties of these plants has been attempted. Comparison of the species reported by Dioscorides and Pliny the Elder for renal affections does not support the thesis of a close relationship between De Materia Medica and the Naturalis Historia.

Female Urogenital Diseases↗
PubMed1996

Biosynthesis of an endogenous cannabinoid precursor in neurons and its control by calcium and cAMP.

Understanding the mechanisms involved in the biogenesis of N-arachidonoylethanolamine (anandamide) and N-palmitoylethanolamine is important in view of the possible role of these lipids as endogenous cannabinoid substances. Anandamide (which activates cannabinoid CB1 receptors) and N-palmitoylethanolamine (which activates a CB2-like receptor subtype in mast cells) may both derive from cleavage of precursor phospholipid, N-acylphosphatidylethanolamine (NAPE), catalyzed by Ca(2+)-activated D-type phosphodiesterase activity. We report here that the de novo biosynthesis of NAPE is enhanced in a Ca(2+)-dependent manner when rat cortical neurons are stimulated with the Ca(2+)-ionophore ionomycin or with membrane-depolarizing agents such as veratridine and kainate. This reaction is likely to be mediated by a neuronal N-acyltransferase activity, which catalyzes the transfer of an acyl group from phosphatidylcholine to the ethanolamine moiety of phosphatidylethanolamine. In addition, we show that Ca2+-dependent NAPE biosynthesis is potentiated by agents that increase cAMP levels, including forskolin and vasoactive intestinal peptide. Our results thus indicate that NAPE levels in cortical neurons are controlled by Ca2+ ions and cAMP. Such regulatory effect may participate in maintaining a supply of cannabimimetic N-acylethanolamines during synaptic activity, and prime target neurons for release of these bioactive lipids.

Amides↗
PubMed1996

Membrane localization of N-acylphosphatidylethanolamine in central neurons: studies with exogenous phospholipases.

We studied the localization of N-acyl phosphatidylethanolamine (NAPE), a putative cannabinoid precursor, in primary cultures of striatal and cortical neurons from the rat brain. We probed intact neurons with various exogenous phospholipases, including S. chromofuscus phospholipase D (PLD). S. chromofuscus PLD does not penetrate into neurons (as demonstrated by a lack of internalization of 125I-labeled PLD), and does not cause gross damage to the neuronal membrane (as demonstrated by a lack of effect of PLD on [3H]gamma-aminobutyric acid release). When neurons, labeled to isotopic equilibrium with [3H]ethanolamine, were incubated for 10 min with S. chromofuscus PLD, approximately 50% of neuronal NAPE was hydrolysed. This hydrolysis was accompanied by the release of a family of N-acyl ethanolamines (NAE) (assessed by high performance liquid chromatography), which included the cannabinoid receptor agonist, anandamide. Exogenous phospholipase A2 (PLA2) (Apis mellifera) and PLC (B. cereus) mobilized [3H]arachidonate and [3H]diacylglycerol, respectively, but had no effect on NAE formation under these conditions. These experiments indicate that approximately 50% of neuronal NAPE is localized in a compartment that is easily accessible to extracellular PLD, possibly the plasmalemma, where it would also be easily hydrolyzed upon stimulation to produce NAE.

Animals↗
PubMed1996

Arachidonate 5-lipoxygenase and its activating protein: prominent hippocampal expression and role in somatostatin signaling.

5-Lipoxygenase-activating protein (FLAP) is an 18-kDa integral membrane protein required, in peripheral cells, for the activation of 5-lipoxygenase (5-LO) and for the resulting synthesis of leukotrienes from arachidonic acid. In the brain, the leukotrienes have been implicated in several pathophysiological events and in the electrophysiological effect of somatostatin, yet the cellular origin and role of these messenger molecules are still poorly understood. In the present study, we used reverse transcriptase-polymerase chain reaction, in situ hybridization, and immunohistochemistry to demonstrate that 5-LO and FLAP are expressed in various regions of the rat brain, including hippocampus, cerebellum, primary olfactory cortex, superficial neocortex, thalamus, hypothalamus, and brainstem. Highest levels of expression were observed in cerebellum and hippocampus. In the latter we demonstrate the colocalization of 5-LO and FLAP in CA1 pyramidal neurons. Moreover, electrophysiological experiments show that selective inhibition of FLAP with the compound MK-886 (0.25-1 microM) prevents the somatostatin-induced augmentation of the hippocampal K+ M-current. Our results provide necessary evidence for the presence and signaling role of 5-LO and FLAP in central neurons and strongly support their proposed participation in somatostatin-receptor transmembrane signaling.

5-Lipoxygenase-Activating Proteins↗
PubMed1995

Inhibition by anandamide of gap junctions and intercellular calcium signalling in striatal astrocytes.

Anandamide, an endogenous arachidonic acid derivative that is released from neurons and activates cannabinoid receptors, may act as a transcellular cannabimimetic messenger in the central nervous system. The biological actions of anandamide and the identity of its target cells are, however, still poorly documented. Here we show that anandamide is a potent inhibitor of gap-junction conductance and dye permeability in striatal astrocytes. This inhibitory effect is specific for anandamide as compared to co-released congeners or structural analogues, is sensitive to pertussis toxin and to protein-alkylating agents, and is neither mimicked by cannabinoid-receptor agonists nor prevented by a cannabinoid-receptor antagonist. Glutamate released from neurons evokes calcium waves in astrocytes that propagate via gap junctions, and may, in turn, activate neurons distant from their initiation sites in astrocytes. We find that anandamide blocks the propagation of astrocyte calcium waves generated by either mechanical stimulation or local glutamate application. Thus, by regulating gap-junction permeability, anandamide may control intercellular communication in astrocytes and therefore neuron-glial interactions.

Animals↗
PubMed1995

Anandamide amidohydrolase activity in rat brain microsomes. Identification and partial characterization.

An amidohydrolase activity present in rat brain microsomes catalyzes the hydrolysis of N-arachidonoyl-[3H]ethanolamine ([3H]anandamide), an endogenous cannabimimetic substance, forming [3H]ethanolamine and arachidonic acid. Amidohydrolase activity is maximal at pH 6 and 8, is independent of divalent cations, has an apparent Km for [3H]anandamide of 12.7 +/- 1.8 microM, and has a Vmax of 5630 +/- 200 pmol/min/mg of protein. Phenylmethylsulfonyl fluoride, a serine protease inhibitor, and p-bromophenacyl bromide, a histidine-alkylating reagent, inhibit the activity, whereas N-ethylmaleimide and various nonselective peptidase inhibitors (EDTA, o-phenanthroline, bacitracin) have no effect. Brain amidohydrolase activity exhibits high substrate specificity for [3H]anandamide; N-gamma-linolenoyl-, N-homo-gamma-linolenoyl-, and N-11,14-eicosadienoyl- are hydrolyzed at markedly slower rates. Moreover, N-11-eicosaenoyl- and N-palmitoyl-[3H]ethanolamine are not hydrolyzed. [3H]Anandamide hydrolysis is inhibited competitively by nonradioactive anandamide and by other N-acylethanolamines with the following rank order of potency: anandamide > N-linoleoyl- = N-cis-linolenoyl- = N-gamma-linolenoyl- = N- homo-gamma-linolenoyl- > N-11,14-eicosadienoyl- > N-oleoyl- > N- docosahexaenoyl- > N-docosatetraenoyl > N-linoelaidoyl- > N-eicosaenoyl- > N- palmitoyl > or = N-elaidoyl- = N-eicosanoyl-ethanolamine = no effect. Amidohydrolase activity is high in liver and brain and low in heart, kidney, intestine, stomach, lung, spleen, and skeletal muscle. Within the central nervous system, highest activity is found in globus pallidus and hippocampus, two regions rich in cannabinoid receptors, and lowest activity is found in brainstem and medulla, where cannabinoid receptors are sparse. The results, showing that brain amidohydrolase activity is selective for anandamide and enriched in areas of the central nervous system with high density of cannabinoid receptors, suggest that this activity may participate in the inactivation of anandamide at its sites of action.

Amidohydrolases↗
PubMed1995

Analysis of anandamide, an endogenous cannabinoid substance, and of other natural N-acylethanolamines.

Recent reports have suggested that N-arachidonoylethanolamine (anandamide) acts as an endogenous ligand for cannabinoid receptors in mammalian brain. Here we describe methods for the extraction, purification and analysis of anandamide and related N-fatty acyl-ethanolamines (NAEs). Liquid-phase extraction, silica gel G column chromatography and thin-layer chromatography (TLC) were employed for sample fractionation. Three analytical high-performance liquid chromatography (HPLC) methods for purification of NAEs were developed. Finally, analyses of NAEs by gas chromatography/mass spectrometry (GC/MS) are described. The applications of these analytical methods to the identification of anandamide and related NAEs in cell cultures as well as of artifacts in biosynthetic studies are described.

Animals↗
PubMed1995

Dopamine D2 receptors potentiate arachidonate release via activation of cytosolic, arachidonate-specific phospholipase A2.

Several G(i)-linked neurotransmitter receptors, including dopamine D2 receptors, act synergistically with Ca(2+)-mobilizing stimuli to potentiate release of arachidonic acid (AA) from membrane phospholipids. In brain, AA and its metabolites are thought to act as intracellular second messengers, suggesting that receptor-dependent potentiation of AA release may participate in neuronal transmembrane signaling. To study the molecular mechanisms underlying this modulatory response, we have now used Chinese hamster ovary cells transfected with rat D2-receptor cDNA, CHO(D2). Two antisense oligodeoxynucleotides corresponding to distinct cDNA sequences of cytosolic, AA-specific phospholipase A2 (cPLA2) were synthesized and added to cultures of CHO(D2) cells. Incubation with antisense oligodeoxynucleotides inhibited D2 receptor-dependent release of AA but had no effect on D2-receptor binding or D2 inhibition of cyclic AMP accumulation. In addition, pharmacological experiments showed that D2 receptor-dependent AA release was prevented by nonselective phospholipase inhibitors (such as mepacrine) but not by inhibitors of membrane-bound, non-AA-specific PLA2 (such as p-bromophenacyl bromide). cPLA2 is expressed in brain tissue. The results, showing that cPLA2 participates in receptor-dependent potentiation of AA release in CHO(D2) cells, suggest that this phospholipase may serve a similar signaling function in brain.

Adenosine Triphosphate↗
PubMed1994

Formation and inactivation of endogenous cannabinoid anandamide in central neurons.

Anandamide (N-arachidonoyl-ethanolamine) was recently identified as a brain arachidonate derivative that binds to and activates cannabinoid receptors, yet the mechanisms underlying formation, release and inactivation of this putative messenger molecule are still unclear. Here we report that anandamide is produced in and released from cultured brain neurons in a calcium ion-dependent manner when the neurons are stimulated with membrane-depolarizing agents. Anandamide formation occurs through phosphodiesterase-mediated cleavage of a novel phospholipid precursor, N-arachidonoyl-phosphatidylethanolamine. A similar mechanism also governs the formation of a family of anandamide congeners, whose possible roles in neuronal signalling remain unknown. Our results and those of others indicate therefore that multiple biochemical pathways may participate in anandamide formation in brain tissue. The life span of extracellular anandamide is limited by a rapid and selective process of cellular uptake, which is accompanied by hydrolytic degradation to ethanolamine and arachidonate. Our results thus strongly support the proposed role of anandamide as an endogenous neuronal messenger.

Animals↗
PubMed1994

A study in Renaissance psychotropic plant ointments.

Various historical sources from the Renaissance--including transcripts of trials for witchcraft, writings on demonology and textbooks of pharmaceutical botany--describe vegetal ointments prepared by women accused of witchcraft and endowed with marked psychoactive properties. Here, we examine the botanical composition and the possible pharmacological actions of these ointments. The results of our study suggest that recipes for narcotic and mind-altering salves were known to Renaissance folk healers, and were in part distinct from homologous preparations of educated medicine. In addition, our study reveals an unexpected connection of these vegetal psychotropes with archaic chtonic beliefs, confirming the tight association between rituals and cults entered on the Underworld and the image of the Medieval witch.

Europe↗
PubMed1994

Eicosanoids in synaptic transmission.

Arachidonic acid is released from membrane phospholipids in a receptor-dependent manner when neurons or glial cells are stimulated with neurotransmitters, hormones, or growth factors. The released fatty acid can be metabolized in brain tissue by three enzymatic pathways--cyclooxygenase, lipoxygenase, and cytochrome P450--giving rise to a series of biologically active products, the eicosanoids. Intracellular actions of these lipids include regulation of membrane ion channels, protein kinases, and ion pumps, thus suggesting a role as neuronal second messengers. In addition, the eicosanoids may be released into the extracellular space and interact with high affinity, G protein-coupled receptors on neurons and glial cells. Acting through these two distinct and complementary modes of action, the eicosanoids may participate in several forms of neuromodulation and synaptic plasticity.

Animals↗