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George Kunos

Publications and source records attributed to George Kunos.

At least 19 recordsLinked to original sources
PubMed2006

A biosynthetic pathway for anandamide.

The endocannabinoid arachidonoyl ethanolamine (anandamide) is a lipid transmitter synthesized and released "on demand" by neurons in the brain. Anandamide is also generated by macrophages where its endotoxin (LPS)-induced synthesis has been implicated in the hypotension of septic shock and advanced liver cirrhosis. Anandamide can be generated from its membrane precursor, N-arachidonoyl phosphatidylethanolamine (NAPE) through cleavage by a phospholipase D (NAPE-PLD). Here we document a biosynthetic pathway for anandamide in mouse brain and RAW264.7 macrophages that involves the phospholipase C (PLC)-catalyzed cleavage of NAPE to generate a lipid, phosphoanandamide, which is subsequently dephosphorylated by phosphatases, including PTPN22, previously described as a protein tyrosine phosphatase. Bacterial endotoxin (LPS)-induced synthesis of anandamide in macrophages is mediated exclusively by the PLC/phosphatase pathway, which is up-regulated by LPS, whereas NAPE-PLD is down-regulated by LPS and functions as a salvage pathway of anandamide synthesis when the PLC/phosphatase pathway is compromised. Both PTPN22 and endocannabinoids have been implicated in autoimmune diseases, suggesting that the PLC/phosphatase pathway of anandamide synthesis may be a pharmacotherapeutic target.

Animals↗
PubMed2006

Genetic impairment of frontocortical endocannabinoid degradation and high alcohol preference.

Endocannabinoid signaling has recently been implicated in ethanol-seeking behavior. We analyzed the expression of endocannabinoid-related genes in key brain regions of reward and dependence, and compared them between the alcohol-preferring AA (Alko Alcohol) and nonpreferring ANA (Alko Non-Alcohol) rat lines. A decreased expression of fatty acid amidohydrolase (FAAH), the main endocannabinoid-degrading enzyme, was found in prefrontal cortex (PFC) of AA rats, and was accompanied by decreased enzyme activity in this region. Binding of the endocannabinoid-cannabinoid 1 (CB1) receptor ligand (3)[H]SR141716A, and [35S]GTPgammaS incorporation stimulated by the CB1 agonist WIN 55,212-2 were downregulated in the same area. Together, this suggests an overactive endocannabinoid transmission in the PFC of AA animals, and a compensatory downregulation of CB1 signaling. The functional role of impaired FAAH function for alcohol self-administration was validated in two independent ways. The CB1 antagonist SR141716A potently and dose-dependently suppressed self-administration in AA rats when given systemically, or locally into the PFC, but not in the striatum. Conversely, intra-PFC injections of the competitive FAAH inhibitor URB597 increased ethanol self-administration in nonselected Wistar rats. These results show for the first time that impaired FAAH function may confer a phenotype of high voluntary alcohol intake, and point to a FAAH both as a potential susceptibility factor and a therapeutic target.

Alcohol Drinking↗
PubMed2006

N-arachidonoyl L-serine, an endocannabinoid-like brain constituent with vasodilatory properties.

The endocannabinoid N-arachidonoyl ethanolamine (anandamide), found both in the CNS and in the periphery, plays a role in numerous physiological systems. One might expect that the chemically related N-arachidonoyl-L-serine (ARA-S) could also be formed alongside anandamide. We have now isolated ARA-S from bovine brain and elucidated its structure by comparison with synthetic ARA-S. Contrary to anandamide, ARA-S binds very weakly to cannabinoid CB1 and CB2 or vanilloid TRPV1 (transient receptor potential vanilloid 1) receptors. However, it produces endothelium-dependent vasodilation of rat isolated mesenteric arteries and abdominal aorta and stimulates phosphorylation of p44/42 mitogen-activated protein (MAP) kinase and protein kinase B/Akt in cultured endothelial cells. ARA-S also suppresses LPS-induced formation of TNF-alpha in a murine macrophage cell line and in wild-type mice, as well as in mice deficient in CB1 or CB2 receptors. Many of these effects parallel those reported for abnormal cannabidiol (Abn-CBD), a synthetic agonist of a putative novel cannabinoid-type receptor. Hence, ARA-S may represent an endogenous agonist for this receptor.

Animals↗
PubMed2006

The endocannabinoid system as an emerging target of pharmacotherapy.

The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson's and Huntington's disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients' need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.

Animals↗
PubMed2005

Cocaine- and amphetamine-related transcript is involved in the orexigenic effect of endogenous anandamide.

Endocannabinoids acting at CB1 cannabinoid receptors (CB1) increase appetite. In view of the predominant presynaptic localization of CB1 in the brain, we tested the hypothesis that the orexigenic effect of endocannabinoids involves inhibition of the release of a tonically active anorexigenic mediator, such as the peptide product of the cocaine- and amphetamine-related transcript (CART). The CB1 antagonist rimonabant inhibited food intake in food-restricted wild-type mice, but not in their CART-deficient littermates. Mice deficient in fatty acid amide hydrolase (FAAH), the enzyme responsible for the in vivo metabolism of the endocannabinoid anandamide, have reduced levels of CART-immunoreactive nerve fibers and terminals in several brain regions implicated in appetite control, including the arcuate, dorsomedial and periventricular nuclei of the hypothalamus, the amygdala, the bed nucleus of the stria terminalis and the nucleus accumbens, and treatment of FAAH(-/-) mice with rimonabant, 3 mg/kg/day for 7 days, increased CART levels toward those seen in FAAH(+/+) wild-type controls. In contrast, no difference in the density of CART-immunoreactive fibers was observed in the median eminence and the paraventricular nucleus of FAAH(+/+) and FAAH(-/-) mice. Acute treatment of wild-type mice with the cannabinoid agonist HU-210 resulted in elevated CART levels in the dorsomedial nucleus and the shell portion of the nucleus accumbens. These observations are compatible with CART being a downstream mediator of the CB1-mediated orexigenic effect of endogenous anandamide.

Animals↗
PubMed2005

Low doses of alcohol substantially decrease glucose metabolism in the human brain.

Moderate doses of alcohol decrease glucose metabolism in the human brain, which has been interpreted to reflect alcohol-induced decreases in brain activity. Here, we measure the effects of two relatively low doses of alcohol (0.25 g/kg and 0.5 g/kg, or 5 to 10 mM in total body H2O) on glucose metabolism in the human brain. Twenty healthy control subjects were tested using positron emission tomography (PET) and FDG after placebo and after acute oral administration of either 0.25 g/kg, or 0.5 g/kg of alcohol, administered over 40 min. Both doses of alcohol significantly decreased whole-brain glucose metabolism (10% and 23% respectively). The responses differed between doses; whereas the 0.25 g/kg dose predominantly reduced metabolism in cortical regions, the 0.5 g/kg dose reduced metabolism in cortical as well as subcortical regions (i.e. cerebellum, mesencephalon, basal ganglia and thalamus). These doses of alcohol did not significantly change the scores in cognitive performance, which contrasts with our previous results showing that a 13% reduction in brain metabolism by lorazepam was associated with significant impairment in performance on the same battery of cognitive tests. This seemingly paradoxical finding raises the possibility that the large brain metabolic decrements during alcohol intoxication could reflect a shift in the substrate for energy utilization, particularly in light of new evidence that blood-borne acetate, which is markedly increased during intoxication, is a substrate for energy production by the brain.

Adult↗
PubMed2005

Hemodynamic profile, responsiveness to anandamide, and baroreflex sensitivity of mice lacking fatty acid amide hydrolase.

The endocannabinoid anandamide exerts neurobehavioral, cardiovascular, and immune-regulatory effects through cannabinoid receptors (CB). Fatty acid amide hydrolase (FAAH) is an enzyme responsible for the in vivo degradation of anandamide. Recent experimental studies have suggested that targeting the endocannabinergic system by FAAH inhibitors is a promising novel approach for the treatment of anxiety, inflammation, and hypertension. In this study, we compared the cardiac performance of FAAH knockout (FAAH-/-) mice and their wild-type (FAAH+/+) littermates and analyzed the hemodynamic effects of anandamide using the Millar pressure-volume conductance catheter system. Baseline cardiovascular parameters, systolic and diastolic function at different preloads, and baroreflex sensitivity were similar in FAAH-/- and FAAH+/+ mice. FAAH-/- mice displayed increased sensitivity to anandamide-induced, CB1-mediated hypotension and decreased cardiac contractility compared with FAAH(+/+) littermates. In contrast, the hypotensive potency of synthetic CB1 agonist HU-210 and the level of expression of myocardial CB1 were similar in the two strains. The myocardial levels of anandamide and oleoylethanolamide, but not 2-arachidonylglycerol, were increased in FAAH-/- mice compared with FAAH+/+ mice. These results indicate that mice lacking FAAH have a normal hemodynamic profile, and their increased responsiveness to anandamide-induced hypotension and cardiodepression is due to the decreased degradation of anandamide rather than an increase in target organ sensitivity to CB1 agonists.

Amidohydrolases↗
PubMed2005

Blood pressure regulation by endocannabinoids and their receptors.

Cannabinoids and their endogenous and synthetic analogs exert powerful hypotensive and cardiodepressor effects by complex mechanisms involving direct and indirect effects on myocardium and vasculature. On the one hand, endocannabinoids and cannabinoid receptors have been implicated in the hypotensive state associated with hemorrhagic, endotoxic and cardiogenic shock, and advanced liver cirrhosis. On the other hand, there is emerging evidence suggesting that the endocannabinergic system plays an important role in the cardiovascular regulation in hypertension. This review is aimed to discuss the in vivo hypotensive and cardiodepressant effects of cannabinoids mediated by cannabinoid and TRPV(1) receptors, and focuses on the novel therapeutical strategies offered by targeting the endocannabinoid system in the treatment of hypertension.

Animals↗
PubMed2005

Evidence for novel cannabinoid receptors.

Cannabinoids, including the bioactive constituents of the marijuana plant, their synthetic analogs, and endogenous lipids with cannabinoid-like activity, produce their biological effects by interacting with specific receptors. To date, two G protein-coupled cannabinoid receptors have been identified by molecular cloning, CB1 receptors mainly expressed in the brain and mediating most of the neurobehavioral effects of cannabinoids and CB2 receptors expressed by immune and hematopoietic tissues. Recent findings indicate that some cannabinoid effects are not mediated by either CB1 or CB2 receptors, and in some cases there is compelling evidence to implicate additional receptors in these actions. These include transient receptor potential vanilloid 1 (TRPV1) receptors and as-yet-unidentified receptors implicated in the endothelium-dependent vasodilator effect of certain cannabinoids and in the presynaptic inhibition of glutamatergic neurotransmission in the hippocampus. The case for these additional receptors is being reviewed here.

Animals↗
PubMed2005

Coronary vasodilator effects of endogenous cannabinoids in vasopressin-preconstricted unpaced rat isolated hearts.

The mechanisms by which cannabinoids alter coronary vascular tone and cardiac performance are controversial. We investigated the effects of various cannabinoids in spontaneously beating Langendorff-perfused rat hearts. Bolus injections of anandamide (0.1-1 micromol) caused no change in coronary flow (CF) or left ventricular systolic pressure (LVSP). In hearts preperfused with vasopressin to induce vasoconstrictor tone, anandamide or the selective CB1 receptor agonist ACEA (1-100 nmol) dose-dependently increased CF by up to 267% and LVSP by 20 mm Hg. The metabolically stable endocannabinoid derivatives, R-methanandamide and noladin ether, displayed similar effects. In contrast, Delta-THC (10-100 nmol), the major psychoactive ingredient of cannabis, strongly decreased CF and LVSP. The CB2 receptor agonist JWH-133 (10-100 nmol) elicited vasodilator and positive inotropic effects only at higher doses. The CB1 antagonists SR141716A and AM-251 as well as the potassium channel inhibitors tetraethylammonium and iberiotoxin blocked the anandamide-induced increases in CF and LVSP, whereas the CB2 antagonist SR144528 and the putative "CB3 antagonist" O-1918 did not have an inhibitory effect. Immunohistochemistry revealed the presence of cardiac CB1 but no CB2 receptors. Anandamide and 2-arachidonoylglycerol were detected in heart tissue. However, combined application of fatty acid amidohydrolase inhibitors and the transport inhibitor AM-404 to augment tissue levels of endocannabinoids was without effect on CF or LVSP. We conclude that in the rat isolated heart with reestablished vasoconstrictor tone, cannabinoids including anandamide elicit coronary vasodilation and a secondary increase in contractility via CB1 receptors and potassium channels.

Animals↗
PubMed2005

Endocannabinoid activation at hepatic CB1 receptors stimulates fatty acid synthesis and contributes to diet-induced obesity.

Endogenous cannabinoids acting at CB(1) receptors stimulate appetite, and CB(1) antagonists show promise in the treatment of obesity. CB(1) (-/-) mice are resistant to diet-induced obesity even though their caloric intake is similar to that of wild-type mice, suggesting that endocannabinoids also regulate fat metabolism. Here, we investigated the possible role of endocannabinoids in the regulation of hepatic lipogenesis. Activation of CB(1) in mice increases the hepatic gene expression of the lipogenic transcription factor SREBP-1c and its targets acetyl-CoA carboxylase-1 and fatty acid synthase (FAS). Treatment with a CB(1) agonist also increases de novo fatty acid synthesis in the liver or in isolated hepatocytes, which express CB(1). High-fat diet increases hepatic levels of the endocannabinoid anandamide (arachidonoyl ethanolamide), CB(1) density, and basal rates of fatty acid synthesis, and the latter is reduced by CB(1) blockade. In the hypothalamus, where FAS inhibitors elicit anorexia, SREBP-1c and FAS expression are similarly affected by CB(1) ligands. We conclude that anandamide acting at hepatic CB(1) contributes to diet-induced obesity and that the FAS pathway may be a common molecular target for central appetitive and peripheral metabolic regulation.

Animals↗
PubMed2004

Endocannabinoids acting at cannabinoid-1 receptors regulate cardiovascular function in hypertension.

BACKGROUND: Endocannabinoids are novel lipid mediators with hypotensive and cardiodepressor activity. Here, we examined the possible role of the endocannabinergic system in cardiovascular regulation in hypertension. METHODS AND RESULTS: In spontaneously hypertensive rats (SHR), cannabinoid-1 receptor (CB1) antagonists increase blood pressure and left ventricular contractile performance. Conversely, preventing the degradation of the endocannabinoid anandamide by an inhibitor of fatty acid amidohydrolase reduces blood pressure, cardiac contractility, and vascular resistance to levels in normotensive rats, and these effects are prevented by CB1 antagonists. Similar changes are observed in 2 additional models of hypertension, whereas in normotensive control rats, the same parameters remain unaffected by any of these treatments. CB1 agonists lower blood pressure much more in SHR than in normotensive Wistar-Kyoto rats, and the expression of CB1 is increased in heart and aortic endothelium of SHR compared with Wistar-Kyoto rats. CONCLUSIONS: We conclude that endocannabinoids tonically suppress cardiac contractility in hypertension and that enhancing the CB1-mediated cardiodepressor and vasodilator effects of endogenous anandamide by blocking its hydrolysis can normalize blood pressure. Targeting the endocannabinoid system offers novel therapeutic strategies in the treatment of hypertension.

Amidohydrolases↗
PubMed2004

Haemodynamic profile and responsiveness to anandamide of TRPV1 receptor knock-out mice.

The endocannabinoid anandamide and cannabinoid (CB) receptors have been implicated in the hypotension in various forms of shock and in advanced liver cirrhosis. Anandamide also activates vanilloid TRPV(1) receptors on sensory nerve terminals, triggering the release of calcitonin gene-related peptide which elicits vasorelaxation in isolated blood vessels in vitro. However, the contribution of TRPV(1) receptors to the in vivo hypotensive effect of anandamide is equivocal. We compared the cardiac performance of anaesthetized TRPV(1) knockout (TRPV(1)(-/-)) mice and their wild-type (TRPV(1)(+/+)) littermates and analysed in detail the haemodynamic effects of anandamide using the Millar pressure-volume conductance catheter system. Baseline cardiovascular parameters and systolic and diastolic function at different preloads were similar in TRPV(1)(-/-) and TRPV(1)(+/+) mice. The predominant hypotensive response to bolus intravenous injections of anandamide and the associated decrease in cardiac contractility and total peripheral resistance (TPR) were similar in TRPV(1)(+/+) and TRPV(1)(-/-) mice, as was the ability of the CB(1) receptor antagonist SR141716 to completely block these effects. In TRPV(1)(+/+) mice, this hypotensive response was preceded by a transient, profound drop in cardiac contractility and heart rate and an increase in TPR, followed by a brief pressor response, effects which were unaffected by SR141716 and were absent in TRPV(1)(-/-) mice. These results indicate that mice lacking TRPV(1) receptors have a normal cardiovascular profile and their predominant cardiovascular depressor response to anandamide is mediated through CB(1) receptors. The role of TRPV(1) receptors is limited to the transient activation of the Bezold-Jarisch reflex by very high initial plasma concentrations of anandamide.

Animals↗
PubMed2004

Atypical cannabinoid stimulates endothelial cell migration via a Gi/Go-coupled receptor distinct from CB1, CB2 or EDG-1.

The endothelium-dependent mesenteric vasorelaxant effect of anandamide has been attributed to stimulation of a Gi/Go-coupled receptor, for which the nonpsychoactive analog abnormal cannabidiol (abn-cbd, (-)-4-(3-3,4-trans-p-menthadien-[1,8]-yl)olivetol) is a selective agonist and the compound O-1918 ((-)-4-(3-3,4-trans-p-menthadien-(1,8)-yl)-orcinol) is a selective antagonist. In human umbilical vein endothelial cells abn-cbd was reported to increase the phosphorylation of p44/42 mitogen activated protein kinase (MAPK) and protein kinase B/Akt, and these effects could be inhibited by pertussis toxin, by phosphatidylinositol 3-kinase (PI3K) inhibitors or by O-1918 [Mol. Pharmacol. 63 (2003) 699]. In the present experiments, abn-cbd caused a concentration-dependent increase in human umbilical vein endothelial cell migration, as quantified in a transwell chamber. This effect was antagonized by O-1918, by the PI3K inhibitor wortmannin, and by pertussis toxin, but not by the cannabinoid CB1 receptor antagonist AM251 or the cannabinoid CB2 receptor antagonist SR144528. The EDG-1 receptor agonist sphingosine-1-phosphate also increased human umbilical vein endothelial cell migration, but this response was unaffected by O-1918. In Chinese hamster ovary cells stably transfected with the gene encoding the EDG-1 receptor, p44/42 MAPK phosphorylation was unaffected by abn-cbd, but strongly induced by sphingosine-1-phosphate. These results indicate that an abn-cbd-sensitive endothelial receptor distinct from cannabinoid CB1, CB2 or EDG-1 receptors mediates not only vasorelaxation but also endothelial cell migration.

Androstadienes↗
PubMed2004

Cannabinoid antagonist SR-141716 inhibits endotoxic hypotension by a cardiac mechanism not involving CB1 or CB2 receptors.

Endocannabinoids and CB1 receptors have been implicated in endotoxin (LPS)-induced hypotension: LPS stimulates the synthesis of anandamide in macrophages, and the CB1 antagonist SR-141716 inhibits the hypotension induced by treatment of rats with LPS or LPS-treated macrophages. Recent evidence indicates the existence of cannabinoid receptors distinct from CB1 or CB2 that are inhibited by SR-141716 but not by other CB1 antagonists such as AM251. In pentobarbital-anesthetized rats, intravenous injection of 10 mg/kg LPS elicited hypotension associated with profound decreases in cardiac contractility, moderate tachycardia, and an increase in lower body vascular resistance. Pretreatment with 3 mg/kg SR-141716 prevented the hypotension and decrease in cardiac contractility, slightly attenuated the increase in peripheral resistance, and had no effect on the tachycardia caused by LPS, whereas pretreatment with 3 mg/kg AM251 did not affect any of these responses. SR-141716 also elicited an acute reversal of the hypotension and decreased contractility when administered after the response to LPS had fully developed. The LPS-induced hypotension and its inhibition by SR-141716 were similar in pentobarbital-anesthetized wild-type, CB1(-/-), and CB1(-/-)/CB2(-/-) mice. We conclude that SR-141716 inhibits the acute hemodynamic effects of LPS by interacting with a cardiac receptor distinct from CB1 or CB2 that mediates negative inotropy and may be activated by anandamide or a related endocannabinoid released during endotoxemia.

Animals↗