d-609 and 1-6-bis(cyclohexyloximinocarbonyl)hexane

Recently, we reported that intracerebroventricularly (i.c.v.) administered histamine evokes the secretion of noradrenaline and adrenaline from adrenal medulla by brain cyclooxygenase-1- and thromboxane A2-mediated mechanisms in rats. These results suggest the involvement of brain arachidonic acid cascade in the histamine-induced activation of the central adrenomedullary outflow. Arachidonic acid is released mainly by phospholipase A2 (PLA2)-dependent pathway or phospholipase C (PLC)/diacylglycerol lipase-dependent pathway. In the present study, histamine (27 nmol/animal, i.c.v.) -induced elevation of plasma noradrenaline and adrenaline was dose-dependently reduced by U-73122 (PLC inhibitor) (10 and 100 nmol/animal, i.c.v.), ET-18-OCH3 (phosphatidylinositol-specific PLC inhibitor) (10 and 30 nmol/animal, i.c.v.) and RHC-80267 (diacylglycerol lipase inhibitor) (1.3 and 2.6 micromol/animal, i.c.v.). However, mepacrine (PLA2 inhibitor) (1.1 and 2.2 micromol/animal, i.c.v.) and D609 (phosphatidylcholine-specific PLC inhibitor) (30, 100 and 300 nmol/animal, i.c.v.) had no effect. These results suggest the involvement of brain phosphatidylinositol-specific PLC and diacylglycerol lipase in the centrally administered histamine-induced activation of the adrenomedullary outflow in rats.

Topics: Adrenal Medulla; Animals; Arachidonic Acid; Brain; Bridged-Ring Compounds; Cyclohexanones; Dose-Response Relationship, Drug; Enzyme Inhibitors; Epinephrine; Estrenes; Histamine; Injections, Intraventricular; Lipoprotein Lipase; Male; Norbornanes; Norepinephrine; Phosphatidylinositol Diacylglycerol-Lyase; Phosphoinositide Phospholipase C; Phospholipases A; Phospholipases A2; Phospholipid Ethers; Pyrrolidinones; Quinacrine; Rats; Rats, Wistar; Signal Transduction; Thiocarbamates; Thiones; Time Factors

We have undertaken a study to characterize the lipolytic pathway responsible for the generation of free fatty acids (FFA) during Fas/CD95-induced apoptosis in Jurkat cells. It was initially shown that the cellular lipid fraction that suffered the major quantitative decrease during Fas-induced apoptosis was that of phosphatidylcholine (PC). In addition, the secretion of palmitic acid-derived FFA was largely prevented by D609, an inhibitor of PC-specific phospholipase C (PC-PLC) and also by the diacylglycerol lipase (DAGL) inhibitor RHC-80267, suggesting that the secretion of these FFA during Fas-induced apoptosis is mediated by the generation of DAG by a PC-PLC activity and, sequentially, by a 1-DAGL activity which generates the FFA from its sn-1 position. The endocannabinoid 2-arachidonoyl glycerol (2-AG) should be generated as a sub-product of this pathway, but it did not accumulate inside the cells nor was secreted into the supernatant. Interestingly, the complete inhibition of free AA secretion during Fas-induced apoptosis was only achieved by using the AA trifluoromethylketone, which not only inhibits all types of phospholipase-A(2) (PLA(2)) activities, but also the described lytic activities on 2-AG. Using a combination of RHC-80267 and the iPLA(2)-specific inhibitor bromoenol lactone, it was shown that the DAGL pathway also cooperates with iPLA(2) in the generation of free arachidonate.

Topics: Apoptosis; Arachidonic Acids; Bridged-Ring Compounds; Cyclohexanones; Endocannabinoids; Enzyme Inhibitors; fas Receptor; Fatty Acids, Nonesterified; Glycerides; Humans; Jurkat Cells; Ketones; Lipid Metabolism; Lipolysis; Lipoprotein Lipase; Models, Biological; Norbornanes; Palmitic Acid; Phosphatidic Acids; Phosphatidylcholines; Thiocarbamates; Thiones; Type C Phospholipases