Inhibitors of Fatty Acid Amide Hydrolase and Monoacylglycerol Lipase: New Targets for Future Antidepressants.

“Cannabis and analogs of Δ9-tetrahydrocannabinol have been used for therapeutic purposes…

Endogenous cannabinoids have been discovered, and dysregulation of endocannabinoid signaling is implicated in the pathophysiology of major depressive disorder (MDD).

Recently, endocannabinoid hydrolytic enzymes such as fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) have become new therapeutic targets in the treatment of MDD.

Several FAAH or MAGL inhibitors are reported to have no cannabimimetic side effects and, therefore, are new potential therapeutic options for patients with MDD who are resistant to first-line antidepressants (selective serotonin and serotonin-norepinephrine reuptake inhibitors).

In this review, we focus on the possible relationships between MDD and the endocannabinoid system as well as the inhibitors’ therapeutic potential.

MAGL inhibitors may reduce inflammatory responses through activation of cannabinoid receptor type 2.

In the hypothalamic-pituitary-adrenal axis, repeated FAAH inhibitor administration may be beneficial for reducing circulating glucocorticoid levels. Both FAAH and MAGL inhibitors may contribute to dopaminergic system regulation. Recently, several new inhibitors have been developed with strong potency and selectivity. FAAH inhibitor, MAGL inhibitor, or dual blocker use would be promising new treatments for MDD. Further pre-clinical studies and clinical trials using these inhibitors are warranted.”

http://www.ncbi.nlm.nih.gov/pubmed/26630956

Endocannabinoid signaling mediates oxytocin-driven social reward.

Image result for Proc Natl Acad Sci U S A.

“Marijuana exerts profound effects on human social behavior, but the neural substrates underlying such effects are unknown. Here we report that social contact increases, whereas isolation decreases, the mobilization of the endogenous marijuana-like neurotransmitter, anandamide, in the mouse nucleus accumbens (NAc), a brain structure that regulates motivated behavior. The results indicate that anandamide-mediated signaling at CB1 receptors, driven by oxytocin, controls social reward. Deficits in this signaling mechanism may contribute to social impairment in autism spectrum disorders and might offer an avenue to treat these conditions.”  http://www.ncbi.nlm.nih.gov/pubmed/26504214

“In conclusion, our results illuminate a mechanism underlying the prosocial actions of oxytocin, and provide unexpected insights on possible neural substrates involved in the social facilitation caused by marijuana. Pharmacological modulation of oxytocin-driven anandamide signaling (by using, for example, FAAH inhibitors) might open new avenues to treat social impairment in autism spectrum disorders.”  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4653148/

Genetic Manipulation of the Endocannabinoid System.

“The physiological and pathophysiological functions of the endocannabinoid system have been studied extensively using transgenic and targeted knockout mouse models.

The first gene deletions of the cannabinoid CB1 receptor were described in the late 1990s, soon followed by CB2 and FAAH mutations in early 2000.

These mouse models helped to elucidate the fundamental role of endocannabinoids as retrograde transmitters in the CNS and in the discovery of many unexpected endocannabinoid functions, for example, in the skin, bone and liver.

We now have knockout mouse models for almost every receptor and enzyme of the endocannabinoid system.

Conditional mutant mice were mostly developed for the CB1 receptor, which is widely expressed on many different neurons, astrocytes and microglia, as well as on many cells outside the CNS.

These mouse strains include “floxed” CB1 alleles and mice with a conditional re-expression of CB1. The availability of these mice made it possible to decipher the function of CB1 in specific neuronal circuits and cell populations or to discriminate between central and peripheral effects.

Many of the genetic mouse models were also used in combination with viral expression systems.

The purpose of this review is to provide a comprehensive overview of the existing genetic models and to summarize some of the most important discoveries that were made with these animals.”

http://www.ncbi.nlm.nih.gov/pubmed/26408160

Potential Therapeutic Value of a Novel FAAH Inhibitor for the Treatment of Anxiety.

“Anxiety disorders are among the most prevalent psychiatric diseases with high personal costs and a remarkable socio-economic burden. However, current treatment of anxiety is far from satisfactory.

Novel pharmacological targets have emerged in the recent years, and attention has focused on the endocannabinoid (eCB) system, given the increasing evidence that supports its central role in emotion, coping with stress and anxiety.

In the management of anxiety disorders, drug development strategies have left apart the direct activation of type-1 cannabinoid receptors to indirectly enhance eCB signalling through the inhibition of eCB deactivation, that is, the inhibition of the fatty acid amide hydrolase (FAAH) enzyme.

In the present study, we provide evidence for the anxiolytic-like properties of a novel, potent and selective reversible inhibitor of FAAH, ST4070, orally administered to rodents.

Altogether, ST4070 offers a promising anxiolytic-like profile in preclinical studies, although further studies are warranted to clearly demonstrate its efficacy in the clinic management of anxiety disorders.”

http://www.ncbi.nlm.nih.gov/pubmed/26360704

Cannabinoid-based drugs targeting CB1 and TRPV1, the sympathetic nervous system, and arthritis.

“Chronic inflammation in rheumatoid arthritis (RA) is accompanied by activation of the sympathetic nervous system, which can support the immune system to perpetuate inflammation. Several animal models of arthritis already demonstrated a profound influence of adrenergic signaling on the course of RA.

Peripheral norepinephrine release from sympathetic terminals is controlled by cannabinoid receptor type 1 (CB1), which is activated by two major endocannabinoids (ECs), arachidonylethanolamine (anandamide) and 2-arachidonylglycerol.

These ECs also modulate function of transient receptor potential channels (TRPs) located on sensory nerve fibers, which are abundant in arthritic synovial tissue. TRPs not only induce the sensation of pain but also support inflammation via secretion of pro-inflammatory neuropeptides.

In addition, many cell types in synovial tissue express CB1 and TRPs.

In this review, we focus on CB1 and transient receptor potential vanilloid 1 (TRPV1)-mediated effects on RA since most anti-inflammatory mechanisms induced by cannabinoids are attributed to cannabinoid receptor type 2 (CB2) activation.

We demonstrate how CB1 agonism or antagonism can modulate arthritic disease.

The concept of functional antagonism with continuous CB1 activation is discussed.

Since fatty acid amide hydrolase (FAAH) is a major EC-degrading enzyme, the therapeutic possibility of FAAH inhibition is studied.

Finally, the therapeutic potential of ECs is examined since they interact with cannabinoid receptors and TRPs but do not produce central side effects.”

http://www.ncbi.nlm.nih.gov/pubmed/26343051

Enhancement of endocannabinoid signaling protects against cocaine-induced neurotoxicity.

“Cocaine is an addictive substance with a potential to cause deleterious effects in the brain. The strategies for treating its neurotoxicity, however, are limited.

Evidence suggests that the endocannabinoid system exerts neuroprotective functions against various stimuli. Thus, we hypothesized that inhibition of fatty acid amide hydrolase (FAAH), the main enzyme responsible for terminating the actions of the endocannabinoid anandamide, reduces seizures and cell death in the hippocampus in a model of cocaine intoxication…

In conclusion, the pharmacological facilitation of the anandamide/CB1/PI3K signaling protects the brain against cocaine intoxication in experimental models. This strategy may be further explored in the development of treatments for drug-induced neurotoxicity.”

http://www.ncbi.nlm.nih.gov/pubmed/25933444

Full FAAH inhibition combined with partial monoacylglycerol lipase inhibition: Augmented and sustained antinociceptive effects with negligible cannabimimetic side effects in mice.

“Inhibition of fatty acid amide hydrolase (FAAH) or monoacylglycerol lipase (MAGL), the primary hydrolytic enzymes for the respective endocannabinoids, N-arachidonoylethanolamine (AEA) and 2-arachidonylglycerol (2-AG), produces antinociception, but with minimal cannabimimetic side effects.

Although selective inhibitors of either enzyme often show partial efficacy in various nociceptive models, their combined blockade elicits augmented antinociceptive effects, but side effects emerge. Moreover, complete and prolonged MAGL blockade leads to CB1 receptor functional tolerance, which represents another challenge in this potential therapeutic strategy.

Therefore, the present study tested whether full FAAH inhibition, combined with partial MAGL inhibition, would produce sustained antinociceptive effects with minimal cannabimimetic side effects…

Thus, full FAAH inhibition combined with partial MAGL inhibition reduces neuropathic and inflammatory pain states, with minimal cannabimimetic effects.”

Enhancement of endocannabinoid signalling protects against cocaine-induced neurotoxicity.

“Cocaine is an addictive substance with a potential to cause deleterious effects in the brain. The strategies for treating its neurotoxicity, however, are limited.

Evidence suggest that the endocannabinoid system exerts neuroprotective functions against various stimuli. Thus, we hypothesized that inhibition of fatty acid amide hydrolase (FAAH), the main enzyme responsible for terminating the actions of the endocannabinoid anandamide, reduces seizures and cell death in the hippocampus in a model of cocaine intoxication…

In conclusion, the pharmacological facilitation of the anandamide/CB1/PI3K signalling protects the brain against cocaine intoxication in experimental models. This strategy may be further explored in the development of treatments for drug-induced neurotoxicity.”

Inhibition of FAAH reduces nitroglycerin-induced migraine-like pain and trigeminal neuronal hyperactivity in mice.

“There is evidence to suggest that a dysregulation of endocannabinoid signaling may contribute to the etiology and pathophysiology of migraine.

Thus, patients suffering from chronic migraine or medication overuse headache showed alterations in the activity of the arachidonoylethanolamide (AEA) degrading enzyme fatty acid amide hydrolase (FAAH) and a specific AEA membrane transporter, alongside with changes in AEA levels.

The precise role of different endocannabinoid system components is, however, not clear. We have therefore investigated mice with a genetic deletion of the two main cannabinoid receptors CB1 and CB2, or the main endocannabinoid degrading enzymes, FAAH and monoacylglycerol lipase (MAGL), which degrades 2-arachidonoylglycerol (2-AG), in a nitroglycerine-induced animal model of migraine.

The effects of the genetic deletion of pharmacological blockade of FAAH are mediated by CB1 receptors, because they were completely disrupted with the CB1 antagonist rimonabant.

These results identify FAAH as a target for migraine pharmacotherapy.”

http://www.ncbi.nlm.nih.gov/pubmed/25910421

http://www.thctotalhealthcare.com/category/headachemigraine/

Pharmacological blockade of the fatty acid amide hydrolase (FAAH) alters neural proliferation, apoptosis and gliosis in the rat hippocampus, hypothalamus and striatum in a negative energy context.

“Endocannabinoids participate in the control of neurogenesis, neural cell death and gliosis.

The pharmacological effect of the fatty acid amide hydrolase (FAAH) inhibitor URB597, which limits the endocannabinoid degradation, was investigated in the present study…

Main results indicated that FAAH inhibitor URB597 decreased neural proliferation, glia and apoptosis in a brain region-dependent manner, which were coupled to local changes in Faah and/or Cnr1 expression and a negative energy context.”

http://www.ncbi.nlm.nih.gov/pubmed/25870539