Medicinal chemistry of cannabinoids Vemuri, V Kiran; Makriyannis, A
Clinical pharmacology and therapeutics,
June 2015, Letnik:
97, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The endocannabinoid system comprises the two well characterized Gi/o‐protein coupled receptors (cannabinoid receptor 1 (CB1) and CB2), their endogenous lipid ligands, and the enzymes involved in ...their biosynthesis and biotransformation. Drug discovery efforts relating to the endocannabinoid system have been focused mainly on the two cannabinoid receptors and the two endocannabinoid deactivating enzymes fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). This review provides an overview of cannabinergic agents used in drug research and those being explored clinically.
Endocannabinoids are released 'on-demand' on the basis of physiological need, and can be pharmacologically augmented by inhibiting their catabolic degradation. The endocannabinoid anandamide is ...degraded by the catabolic enzyme fatty acid amide hydrolase (FAAH). Anandamide is implicated in the mediation of fear behaviors, including fear extinction, suggesting that selectively elevating brain anandamide could modulate plastic changes in fear. Here we first tested this hypothesis with preclinical experiments employing a novel, potent and selective FAAH inhibitor, AM3506 (5-(4-hydroxyphenyl)pentanesulfonyl fluoride). Systemic AM3506 administration before extinction decreased fear during a retrieval test in a mouse model of impaired extinction. AM3506 had no effects on fear in the absence of extinction training, or on various non-fear-related measures. Anandamide levels in the basolateral amygdala were increased by extinction training and augmented by systemic AM3506, whereas application of AM3506 to amygdala slices promoted long-term depression of inhibitory transmission, a form of synaptic plasticity linked to extinction. Further supporting the amygdala as effect-locus, the fear-reducing effects of systemic AM3506 were blocked by intra-amygdala infusion of a CB1 receptor antagonist and were fully recapitulated by intra-amygdala infusion of AM3506. On the basis of these preclinical findings, we hypothesized that variation in the human FAAH gene would predict individual differences in amygdala threat-processing and stress-coping traits. Consistent with this, carriers of a low-expressing FAAH variant (385A allele; rs324420) exhibited quicker habituation of amygdala reactivity to threat, and had lower scores on the personality trait of stress-reactivity. Our findings show that augmenting amygdala anandamide enables extinction-driven reductions in fear in mouse and may promote stress-coping in humans.
Background and purpose:
The ability of cannabinoids to suppress mechanical hypersensitivity (mechanical allodynia) induced by treatment with the chemotherapeutic agent vincristine was evaluated in ...rats. Sites of action were subsequently identified.
Experimental approach:
Mechanical hypersensitivity developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same times. Effects of the CB
1
/CB
2
receptor agonist WIN55,212‐2, the receptor‐inactive enantiomer WIN55,212‐3, the CB
2
‐selective agonist (R,S)‐AM1241, the opiate agonist morphine and vehicle on chemotherapy‐induced neuropathy were evaluated. WIN55,212‐2 was administered intrathecally (i.t.) or locally in the hindpaw to identify sites of action. Pharmacological specificity was established using competitive antagonists for CB
1
(SR141716) or CB
2
receptors (SR144528).
Key results:
Systemic administration of WIN55,212‐2, but not WIN55,212‐3, suppressed vincristine‐evoked mechanical allodynia. A leftward shift in the dose‐response curve was observed following WIN55,212‐2 relative to morphine treatment. The CB
1
(SR141716) and CB
2
(SR144528) antagonists blocked the anti‐allodynic effects of WIN55,212‐2. (R,S)‐AM1241 suppressed vincristine‐induced mechanical hypersensitivity through a CB
2
mechanism. Both cannabinoid agonists suppressed vincristine‐induced mechanical hypersensitivity without inducing catalepsy. Spinal sites of action are implicated in cannabinoid modulation of chemotherapy‐induced neuropathy. WIN55,212‐2, but not WIN55,212‐3, administered i.t. suppressed vincristine‐evoked mechanical hypersensitivity at doses that were inactive following local hindpaw administration. Spinal coadministration of both the CB
1
and CB
2
antagonists blocked the anti‐allodynic effects of WIN55,212‐2.
Conclusions and implications:
Cannabinoids suppress the maintenance of vincristine‐induced mechanical allodynia through activation of CB
1
and CB
2
receptors. These anti‐allodynic effects are mediated, at least in part, at the level of the spinal cord.
British Journal of Pharmacology
(2007)
152
, 765–777; doi:
10.1038/sj.bjp.0707333
; published online 18 June 2007
Background and purpose:
The ability of cannabinoids to suppress mechanical hypersensitivity (mechanical allodynia) induced by treatment with the chemotherapeutic agent vincristine was evaluated in ...rats. Sites of action were subsequently identified.
Experimental approach:
Mechanical hypersensitivity developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same times. Effects of the CB1/CB2 receptor agonist WIN55,212‐2, the receptor‐inactive enantiomer WIN55,212‐3, the CB2‐selective agonist (R,S)‐AM1241, the opiate agonist morphine and vehicle on chemotherapy‐induced neuropathy were evaluated. WIN55,212‐2 was administered intrathecally (i.t.) or locally in the hindpaw to identify sites of action. Pharmacological specificity was established using competitive antagonists for CB1 (SR141716) or CB2 receptors (SR144528).
Key results:
Systemic administration of WIN55,212‐2, but not WIN55,212‐3, suppressed vincristine‐evoked mechanical allodynia. A leftward shift in the dose‐response curve was observed following WIN55,212‐2 relative to morphine treatment. The CB1 (SR141716) and CB2 (SR144528) antagonists blocked the anti‐allodynic effects of WIN55,212‐2. (R,S)‐AM1241 suppressed vincristine‐induced mechanical hypersensitivity through a CB2 mechanism. Both cannabinoid agonists suppressed vincristine‐induced mechanical hypersensitivity without inducing catalepsy. Spinal sites of action are implicated in cannabinoid modulation of chemotherapy‐induced neuropathy. WIN55,212‐2, but not WIN55,212‐3, administered i.t. suppressed vincristine‐evoked mechanical hypersensitivity at doses that were inactive following local hindpaw administration. Spinal coadministration of both the CB1 and CB2 antagonists blocked the anti‐allodynic effects of WIN55,212‐2.
Conclusions and implications:
Cannabinoids suppress the maintenance of vincristine‐induced mechanical allodynia through activation of CB1 and CB2 receptors. These anti‐allodynic effects are mediated, at least in part, at the level of the spinal cord.
British Journal of Pharmacology (2007) 152, 765–777; doi:10.1038/sj.bjp.0707333; published online 18 June 2007
Background and Purpose
The HIV‐envelope glycoprotein Gp120 is involved in neuronal injury and is associated with neuro‐AIDS pathogenesis in the brain. Endocannabinoids are important lipid ligands in ...the CNS regulating neural functions, and their degeneration is controlled by hydrolysing enzymes such as the fatty acid amide hydrolase (FAAH). Here, we examined whether in vivo genetic deletion of Faah gene prevents HIV‐1 Gp120‐mediated effects on neurogenesis.
Experimental Approach
We generated new GFAP/Gp120 transgenic (Tg) mice that have genetic deletion of Faah gene by mating glial fribillary acidic protein (GFAP)/Gp120 Tg mice with Faah−/− mice. Neurogenesis and cell death were assessed by immunocytochemical analysis.
Key Results
Endocannabinoid levels in the brain of the double GFAP/Gp120//Faah−/− mice were similar to those observed in Faah−/− mice. However, unlike the impaired neurogenesis observed in GFAP/Gp120 Tg mice and Faah−/− mice, these GFAP/Gp120//Faah‐/ mice showed significantly improved neurogenesis in the hippocampus, indicated by a significant increase in neuroblasts and neuronal cells, an increase in BrdU+ cells and doublecortin positive cells (DCX+), and an increase in the number of PCNA. Furthermore, a significant decrease in astrogliosis and gliogenesis was observed in GFAP/Gp120//Faah−/−mice and neurogenesis was stimulated by neural progenitor cells (NPCs) and/or the newly formed NPC niches characterized by increased COX‐2 expression and elevated levels of PGE2.
Conclusions and Implications
In vivo genetic ablation of Faah, resulted in enhanced neurogenesis through modulation of the newly generated NPC niches in GFAP/Gp120//Faah−/− mice. This suggests a novel approach of using FAAH inhibitors to enhance neurogenesis in HIV‐1 infected brain.
Background and Purpose
The endocannabinoid (EC) system has been implicated in the pathogenesis of diabetic nephropathy (DN). We investigated the effects of peripheral blockade of the cannabinoid CB1 ...receptor as an add‐on treatment to ACE‐inhibition in type 1 diabetic mice (DM) with established albuminuria.
Experimental Approach
Renal functional parameters (albumin excretion rate, creatinine clearance), tubular injury, renal structure, both EC and CB receptor levels and markers of podocyte dysfunction, fibrosis and inflammation were studied in streptozotocin‐induced DM treated for 14 weeks with vehicle, the ACE‐inhibitor perindopril (2 mg·kg−1·day−1), peripherally‐restricted CB1 receptor antagonist AM6545 (10 mg·kg−1·day−1) or both. Treatments began at 8 weeks after diabetes onset, when early DN is established.
Key Results
CB1 receptors were overexpressed in DM and neither perindopril nor AM6545 altered this effect, while both drugs abolished diabetes‐induced overexpression of angiotensin AT1 receptors. Single treatment with either AM6545 or perindopril significantly reduced progression of albuminuria, down‐regulation of nephrin and podocin, inflammation and expression of markers of fibrosis. However, reversal of albuminuria was only observed in mice administered both treatments. The ability of the combination therapy to completely abolish slit diaphragm protein loss, monocyte infiltration, overexpression of inflammatory markers and favour macrophage polarization towards an M2 phenotype may explain this greater efficacy. In vitro experiments confirmed that CB1 receptor activation directly inhibits retinoic acid‐induced nephrin expression in podocytes and IL‐4‐induced M2 polarization in macrophages.
Conclusion and Implications
Peripheral CB1 receptor blockade used as add‐on treatment to ACE‐inhibition reverses albuminuria, nephrin loss and inflammation in DM.
Background and Purpose
Endocannabinoids such as anandamide (AEA) are important lipid ligands regulating cell proliferation, differentiation and apoptosis. Their levels are regulated by hydrolase ...enzymes, the fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MGL). Here, we investigated whether FAAH or AEA are involved in NF (erythroid‐derived 2)‐like 2 (Nrf2)/antioxidant responsive element (ARE) pathway.
Experimental Approach
The aim of this study was to analyse the effects of AEA or FAAH inhibition by the URB597 inhibitor or FAAH/siRNA on the activation of Nrf2‐ARE signalling pathway and heme oxygenase‐1 (HO‐1) induction and transcription.
Key Results
Endogenous AEA was detected in the immortalized human mammary epithelial MCF‐10A cells (0.034 ng per 106 cells) but not in MCF‐7 or MDA‐MB‐231 breast cancer cells. Because breast tumour cells express FAAH abundantly, we examined the effects of FAAH on Nrf2/antioxidant pathway. We found that inhibition of FAAH by the URB597 inhibitor induced antioxidant HO‐1 in breast cancer cells and MCF‐10A cells. RNAi‐mediated knockdown of FAAH or treatment with AEA‐activated ARE‐containing reporter induced HO‐1 mRNA and protein expression, independent of the cannabinoid receptors, CB1, CB2 or TRPV1. Furthermore, URB597, AEA and siRNA‐FAAH treatments induced the nuclear translocation of Nrf2, while siRNA‐Nrf2 treatment and Keap1 expression blocked AEA, URB597 and si‐FAAH from activation of ARE reporter and HO‐1 induction. siRNA‐HO‐1 treatment decreased the viability of breast cancer cells and MCF‐10A cells.
Conclusions and Implications
These data uncovered a novel mechanism by which inhibition of FAAH or exposure to AEA induced HO‐1 transcripts and implicating AEA and FAAH as direct modifiers in signalling mediated activation of Nrf2‐HO‐1 pathway, independent of cannabinoid receptors.
The endogenous cannabinoid anandamide is removed from the synaptic space by a high-affinity transport system present in neurons and astrocytes, which is inhibited by ...N-(4-hydroxyphenyl)-arachidonamide (AM404). After internalization, anandamide is hydrolyzed by fatty-acid amide hydrolase (FAAH), an intracellular membrane-bound enzyme that also cleaves AM404. Based on kinetic evidence, it has recently been suggested that anandamide internalization may be mediated by passive diffusion driven by FAAH activity. To test this possibility, in the present study, we have investigated anandamide internalization in wild-type and FAAH-deficient ( FAAH-/-) mice. Cortical neurons from either mouse strain internalized 3H anandamide through a similar mechanism, i.e., via a rapid temperature-sensitive and saturable process, which was blocked by AM404. Moreover, systemic administration of AM404 to either wild-type or FAAH-/-mice enhanced the hypothermic effects of exogenous anandamide, a response that was prevented by the CB1cannabinoid antagonist rimonabant (SR141716A). The results indicate that anandamide internalization in mouse brain neurons is independent of FAAH activity. In further support of this conclusion, the compound N-(5Z, 8Z, 11Z, 14Z eicosatetraenyl)-4-hydroxybenzamide (AM1172) blocked 3Hanandamide internalization in rodent cortical neurons and human astrocytoma cells without acting as a FAAH substrate or inhibitor. AM1172 may serve as a prototype for novel anandamide transport inhibitors with increased metabolic stability.
BACKGROUND AND PURPOSE Cannabinoid CB1 receptor antagonists reduce food intake and body weight, but clinical use in humans is limited by effects on the CNS. We have evaluated a novel cannabinoid ...antagonist (AM6545) designed to have limited CNS penetration, to see if it would inhibit food intake in rodents, without aversive effects.
EXPERIMENTAL APPROACH Cannabinoid receptor binding studies, cAMP assays, brain penetration studies and gastrointestinal motility studies were carried out to assess the activity profile of AM6545. The potential for AM6545 to induce malaise in rats and the actions of AM6545 on food intake and body weight were also investigated.
KEY RESULTS AM6545 binds to CB1 receptors with a Ki of 1.7 nM and CB2 receptors with a Ki of 523 nM. AM6545 is a neutral antagonist, having no effect on cAMP levels in transfected cells and was less centrally penetrant than AM4113, a comparable CB1 receptor antagonist. AM6545 reversed the effects of WIN55212‐2 in an assay of colonic motility. In contrast to AM251, AM6545 did not produce conditioned gaping or conditioned taste avoidance in rats. In rats and mice, AM6545 dose‐dependently reduced food intake and induced a sustained reduction in body weight. The effect on food intake was maintained in rats with a complete subdiaphragmatic vagotomy. AM6545 inhibited food intake in CB1 receptor gene‐deficient mice, but not in CB1/CB2 receptor double knockout mice.
CONCLUSIONS AND IMPLICATIONS Peripherally active, cannabinoid receptor antagonists with limited brain penetration may be useful agents for the treatment of obesity and its complications.
Background and Purpose:
Effects of locally administered agonists and antagonists for cannabinoid CB
1
and CB
2
receptors on mechanical and thermal hypersensitivity were compared after the ...establishment of chronic inflammation.
Experimental approach:
Carrageenan was administered unilaterally to the rat hindpaw on day 1. Prophylactic efficacy of locally administered CB
1
‐ and CB
2
‐selective agonists −arachidonyl‐2‐chloroethylamide (ACEA) and (R,S)‐(2‐iodo‐5‐nitro‐phenyl)‐l‐(l‐methyl‐piperidin‐2‐ylmethyl)‐l
H
‐ubdik‐3‐yl‐methanone ((R,S)‐AM1241), respectively− on mechanical and thermal hypersensitivity were compared on day 2. Pharmacological specificity was evaluated using locally administered CB
1
and CB
2
‐selective antagonists −
N
‐(piperidin‐1‐yl)‐5‐(4‐chlorophenyl)‐1‐(2,4‐dichlorophenyl)‐4‐methyl‐1
H
‐pyrazole‐3‐carboxamidehydrochloride (SR141716A) and
N‐
(1S)‐endo‐1,3,3‐trimethyl bicycle 2.2.1 heptan‐2‐yl‐5‐(4‐chloro‐3‐methylphenyl)‐1‐(4‐methylbenzyl)‐pyrazole‐3‐carboxamide (SR144528), respectively.
Key Results:
Administration of either ACEA or AM1241 to the inflamed but not noninflamed paw suppressed the maintenance of carrageenan‐evoked mechanical hyperalgesia and tactile allodynia and attenuated thermal hyperalgesia. The ACEA‐induced suppression of mechanical and thermal hypersensitivity was blocked by local injection of SR141716A but not SR144528. AM1241 suppressed mechanical hypersensitivity with the reverse pharmacological specificity. The AM1241‐induced suppression of thermal hyperalgesia was blocked by SR144528 and to a lesser extent by SR14176A. Co‐administration of ACEA with AM1241 in the inflamed paw increased the magnitude but not the duration of thermal antihyperalgesia compared to intraplantar administration of either agonist alone.
Conclusions and Implications:
Cannabinoids act locally through distinct CB
1
and CB
2
mechanisms to suppress mechanical hypersensitivity after the establishment of chronic inflammation, at doses that produced modest changes in thermal hyperalgesia. Additive antihyperalgesic effects were observed following prophylactic co‐administration of the CB
1
‐ and CB
2
‐selective agonists. Our results suggest that peripheral cannabinoid antihyperalgesic actions may be exploited for treatment of inflammatory pain states.
British Journal of Pharmacology
(2007)
150
, 153–163. doi:
10.1038/sj.bjp.0706984
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