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.
Cadas
H
H
The Neurosciences Institute, San Diego, California 92121, USA.
di Tomaso
E
E
Piomelli
D
D
D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002186:Cannabinoids / Q000378:metabolism*; D063388:Endocannabinoids; D004798:Enzymes / Q000378:metabolism; D050356:Lipid Metabolism; D008297:Male; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D053284:Polyunsaturated Alkamides; D011355:Prodrugs / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution
D001095:Arachidonic Acids; D002186:Cannabinoids; D063388:Endocannabinoids; D004798:Enzymes; C109143:N-arachidonylphosphatidylethanolamine; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D053284:Polyunsaturated Alkamides; D011355:Prodrugs; D000217:Acyltransferases; C078814:anandamide