RHC 80267

RHC 80267 is a potent and selective inhibitor of diacylglycerol lipase [1].

Diacylglycerol lipase is a key enzyme in the biosynthesis of the endocannabinoid 2-arachidonoylglycerol and catalyzes the hydrolysis of diacylglycerol.

RHC 80267 is a potent and selective diacylglycerol lipase inhibitor. RHC 80267 inhibited canine platelet diglyceride lipase with IC50 value of 4 μM. RHC 80267 inhibited diacylglycerol lipase released from rat and dog platelets. Also, RHC 80267 induced diglyceride accumulation and inhibited fatty acid accumulation [1]. In smooth muscle isolated from the guinea-pig gastric antrum, RHC-80267 (0.3-1 μM) increased slow potential frequency and reduced the refractory period for slow potentials generation evoked by depolarizing stimuli from 8 s to 5 s. Also, RHC-80267 enhanced the frequency of slow potentials increased by acetylcholine (ACh). RHC 80267 increased diacylglycerol accumulation, which then activated PKC. PKC was involved in regulating the frequency of slow potentials [2]. In rat mesenteric artery contracted with either KCl or noradrenaline, RHC-80267 (0.1-10 μM) enhanced acetylcholine-evoked relaxation. In brain homogenate, RHC-80267 inhibited cholinesterase activity with IC50 value of 4 μM in a concentration-dependent way. These results suggested that the enhancement of acetylcholine-evoked responses by RHC-80267 was caused by the inhibition of the cholinesterase activity [3].

References:
[1].  Sutherland CA, Amin D. Relative activities of rat and dog platelet phospholipase A2 and diglyceride lipase. Selective inhibition of diglyceride lipase by RHC 80267. J Biol Chem, 1982, 257(23): 14006-14010.
[2].  Suzuki H, Kito Y, Fukuta H, et al. Effects of RHC-80267, an inhibitor of diacylglycerol lipase, on excitation of circular smooth muscle of the guinea-pig gastric antrum. J Smooth Muscle Res, 2002, 38(6): 153-164.
[3].  Ghisdal P, Vandenberg G, Hamaide MC, et al. The diacylglycerol lipase inhibitor RHC-80267 potentiates the relaxation to acetylcholine in rat mesenteric artery by anti-cholinesterase action. Eur J Pharmacol, 2005, 517(1-2): 97-102.

The diacylglycerol lipase inhibitor RHC-80267 potentiates the relaxation to acetylcholine in rat mesenteric artery by anti-cholinesterase action.[Pubmed:15958263]

Eur J Pharmacol. 2005 Jul 4;517(1-2):97-102.

The diacylglycerol lipase inhibitor 1,6-bis(cyclohexyloximinocarbonylamino) hexane (RHC-80267) was tested for its effect on acetylcholine-evoked relaxation in rat mesenteric artery. In artery contracted with either noradrenaline or KCl, RHC-80267 (0.1-10 muM) potentiated the relaxation evoked by acetylcholine. The effect of RHC-80267 was not affected by nitric oxide synthase inhibition or by inhibitors of protein kinase C or of phospholipase A(2). The diacylglycerol analogue 1-oleoyl-2-acetyl-sn-glycerol did not change the relaxation to acetylcholine. RHC-80267 did not affect the relaxation evoked by carbachol, by the nitric oxide donor SNAP (S-nitroso-N-acetylpenicillamine) or by the K(+) channel opener cromakalim. Neostigmine, a cholinesterase inhibitor, produced the same effect as RHC-80267 on acetylcholine-evoked relaxation. When tested on cholinesterase in brain homogenate, RHC-80267 concentration-dependently inhibited cholinesterase activity with an IC(50) of 4 muM. These results indicate that the potentiation of acetylcholine-evoked responses by RHC-80267 in rat mesenteric artery is caused by the inhibition of the cholinesterase activity in the vascular wall.

Effects of RHC-80267, an inhibitor of diacylglycerol lipase, on excitation of circular smooth muscle of the guinea-pig gastric antrum.[Pubmed:12713022]

J Smooth Muscle Res. 2002 Dec;38(6):153-64.

In small segments of circular smooth muscle isolated from the guinea-pig gastric antrum, the effects of RHC-80267, an inhibitor of diacylglycerol lipase, were investigated both on regenerative slow potentials (either occurring spontaneously or as the result of a depolarizing intracellular current injection) and on the actions of acetylcholine (ACh). As diacylglycerol is a known activator of protein kinase C (PKC), it would therefore be expected that RHC-80267 would activate PKC indirectly. In circular smooth muscle bundles, spontaneously generating slow potentials recorded simultaneously from two given cells were synchronized, indicating that these two cells were electrically coupled. RHC-80267 (0.3-1 microM) increased the frequency of slow potential generation, with no alteration to the amplitude of either the slow potentials or the resting membrane potential. Synchronous electrical activity in a given pair of cells was also unchanged by RHC-80267, indicating that intercellular electrical coupling was not altered. The input resistance of smooth muscle cells calculated from the amplitude of electrotonic potentials produced by injection of current was not significantly altered by RHC-80267. The refractory period for the generation of slow potentials evoked by depolarizing stimuli was about 8 s, and it was decreased to about 5 s by RHC-80267, with no significant alteration to the amplitude of spontaneous or evoked slow potentials. ACh (0.5 microM) depolarized the membrane by about 5 mV and increased the amplitude and frequency of slow potentials. The actions of ACh on the frequency of slow potentials were enhanced by RHC-80267, with no alteration to the amplitudes of both the ACh-induced depolarization and slow potentials. These results support the idea that PKC is involved in determining the frequency of slow potentials, by shortening the refractory period for excitation of gastric smooth muscle cells.

Nordihydroguaiaretic acid and RHC 80267 potentiate astroglial injury during combined glucose-oxygen deprivation.[Pubmed:7546017]

Mol Chem Neuropathol. 1995 May;25(1):35-49.

Membrane phospholipid degradation has been proposed to play a key role in hypoxic-ischemic brain injury. We tested the hypotheses that both nordihydroguaiaretic acid, a phospholipase A2 and lipoxygenase inhibitor, and RHC 80267, a diacylglycerol lipase inhibitor, would decrease the release of [3H]arachidonic acid metabolites from prelabeled cultures of astroglia subjected to combined glucose-oxygen deprivation and that these inhibitors would also decrease astroglial injury during combined glucose-oxygen deprivation. Both nordihydroguaiaretic acid and RHC 80267 significantly inhibited the release of [3H]arachidonic acid metabolites during combined glucose-oxygen deprivation. This suggests that two separate enzymic pathways, the phospholipase A2 pathway and the phospholipase C/diacylglycerol lipase pathway, contribute to the release of astroglial [3H]arachidonic acid metabolites during combined glucose-oxygen deprivation. However, both of these lipase inhibitors increased astroglial cell death during combined glucose-oxygen deprivation, probably due to inhibition of arachidonic acid release. We speculate that arachidonic acid release may be a mechanism of astroglial self-preservation during combined glucose-oxygen deprivation.

Inhibition of glucose-induced insulin secretion by the diacylglycerol lipase inhibitor RHC 80267 and the phospholipase A2 inhibitor ACA through stimulation of K+ permeability without diminution by exogenous arachidonic acid.[Pubmed:9175712]

Biochem Pharmacol. 1997 Apr 25;53(8):1077-86.

The effects of the diacylglycerol lipase inhibitor 1,6-bis-(cyclohexyloximinocarbonyl-amino)-hexane (RHC 80267) and the phospholipase A2 inhibitor N-(p-amylcinnamoyl)anthranilic acid (ACA) on insulin secretion and 86Rb+ efflux in mouse pancreatic islets were studied. RHC 80267 (35 microM) and ACA (100 microM) inhibited glucose (16.7 mM)-induced insulin secretion, but did not inhibit insulin secretion induced by K+ (40 mM) or the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA; 0.16 microM). K+ (40 mM) or TPA (0.16 microM) potentiated glucose (16.7 mM)-induced insulin secretion, and prevented inhibition of glucose (16.7 mM)-induced insulin secretion by RHC 80267 and ACA. In comparison, potentiation of glucose-induced insulin secretion by albumin-bound arachidonic acid (AA; 200 microM total; 10 microM free unbound) failed to counteract inhibition of glucose-induced insulin secretion by RHC 80267 or ACA, suggesting that inhibition of insulin secretion by these agents was not mediated by a decrease in AA accumulation in islets. Determination of 86Rb+ efflux, a marker of K+ channel activity, revealed that both RHC 80267 and ACA stimulated K+ efflux from islets. These effects of RHC 80267 and ACA were observed at both 3.3 and 16.7 mM glucose and persisted in Ca2+-free medium, suggesting that they may represent an opening of ATP-sensitive K+ channels. RHC 80267-mediated stimulation of 86Rb+ efflux was not mimicked by the diacylglycerol analog TPA (0.16 microM) and was not prevented by the diacylglycerol kinase inhibitor R 59022 (50 microM), suggesting that stimulation of 86Rb+ efflux did not reflect a conditional increase in diacylglycerol or in phosphatidic acid upon inhibition of diacylglycerol lipase. In contrast, TPA (0.16 microM) attenuated RHC 80267 and ACA stimulation of 86Rb+ efflux. Addition of AA (200 microM total; 10 microM free unbound) stimulated 86Rb+ efflux, suggesting that stimulation of 86Rb+ efflux by RHC 80267 and ACA was not due to a decrease in AA accumulation. This stimulation by AA was not dependent on AA metabolism because it persisted in the presence of the lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA; 50 microM) or the cyclooxygenase inhibitor indomethacin (50 microM). In contrast to RHC 80267 and ACA, AA stimulation of 86Rb+ efflux was attenuated in Ca2+-free medium, probably implicating Ca2+-sensitive K+ channels in AA regulation of 86Rb+ efflux. Parallel experiments with diazoxide (100 microM) revealed that RHC 80267 and ACA mimicked the effects of diazoxide, a specific activator of ATP-sensitive K+ channels in islets, on both insulin secretion and 86Rb+ efflux. In conclusion, it is suggested that RHC 80267 and ACA, independently of their action on AA release, may inhibit glucose-induced insulin secretion by the opening of ATP-sensitive K+ channels in islets.

RHC 80267 (U-57908) is a potent and selective inhibitor of diacylglycerol lipase (DAGL) (with IC50 of 4 μM in canine platelets). RHC-80267 inhibits cholinesterase activity with an IC50 of 4 μM, thereby enhancing the relaxation evoked by acetylcholine. RHC 80267 also inhibits COX and the hydrolysis of phosphatidylcholine (PC).

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