Changes of blood endocannabinoids during anaesthesia: a special case for fatty acid amide hydrolase inhibition by propofol?

The Basic Science of Cannabinoids

The cannabis plant has been used for centuries to manage the symptoms of various ailments including pain. Hundreds of chemical compounds have been identified and isolated from the plant and elicit a variety of physiological responses by binding to specific receptors and interacting with numerous other proteins. In addition, the body makes its own cannabinoid-like compounds that are integrally involved in modulating normal and pathophysiological processes. As the legal cannabis landscape continues to evolve within the United States and throughout the world, it is important to understand the rich science behind the effects of the plant and the implications for providers and patients. This narrative review aims to provide an overview of the basic science of the cannabinoids by describing the discovery and function of the endocannabinoid system, pharmacology of cannabinoids, and areas for future research and therapeutic development as they relate to perioperative and chronic pain medicine.

Long-term molecular differences between resilient and susceptible mice after a single traumatic exposure

BACKGROUND AND PURPOSE

PTSD is a heterogeneous disorder induced by trauma, resulting in severe long-term impairments of an individual's mental health. Interestingly, PTSD does not develop in every individual; thus, some individuals are more resilient than others. However, the underlying molecular mechanisms are poorly understood. Here, we aimed at shedding light on these processes.

EXPERIMENTAL APPROACH

We used a single-trauma PTSD model in mice to induce long-term maladaptive behaviours and profiled the mice four weeks post-trauma into resilient or susceptible individuals. The phenotype's classification was based on their individual responses in different behavioural experiments. We analysed microbiome, circulating endocannabinoids, and long-term changes in brain phospholipid and transcript levels.

KEY RESULTS

We found a plethora of molecular differences between resilient and susceptible individuals across multiple molecular domains, including lipidome, transcriptome, and gut microbiome. Some of these differences were stable even several weeks after the trauma, indicating the long-term impact of traumatic stimuli on the organism's physiology. Furthermore, the integration of these multi-layered molecular data revealed that resilient and susceptible individuals have very distinct molecular signatures across various physiological systems.

CONCLUSIONS AND IMPLICATIONS

We showed that trauma induces individual-specific behavioural responses that, in combination with a longitudinal characterization of mice, can be used to identify distinct sub-phenotypes within the trauma-exposed group. These groups differ significantly not only in their behaviour but also in specific molecular aspects across a variety of tissues and brain regions. This approach may reveal new targets and predictive biomarkers for the pharmacological treatment and prognosis of stress-related disorders.

Intrathecal morphine administration reduces postoperative pain and peripheral endocannabinoid levels in total knee arthroplasty patients: a randomized clinical trial

Background

The primary goal of this study was to determine whether administration of intrathecal morphine reduces postoperative pain. The secondary goal was to determine the effect of intrathecal morphine upon circulating levels of the weakly analgesic endocannabinoids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and the related lipids palmitoylethanolamide (PEA) and oleoylethanolamide (OEA).

Methods

Forty two total knee arthroplasty (TKA) patients were enrolled in a prospective, double-blinded, randomized study. The intervention consisted of intrathecal morphine (200 μg) or placebo administered at the time of the spinal anesthesia. Postoperative pain was measured during the first 4 h after surgery while serum levels of AEA, 2-AG, PEA, OEA, and cortisol were measured at baseline and 4 h after surgery.

Results

Administration of intrathecal morphine reduced postoperative pain 4 h after TKA surgery compared to placebo (p = 0.005) and reduced postoperative systemic opioid consumption (p = 0.001). At baseline, intrathecal morphine led to a significant reduction in AEA, 2-AG, and OEA levels but did not affect PEA or cortisol levels. In patients administered intrathecal placebo, 2-AG levels were elevated 4 h after surgery; whereas patients receiving intrathecal morphine showed reductions in AEA, PEA, and OEA when compared to placebo. At 4 h after TKA surgery cortisol levels were significantly elevated in the placebo group and reduced in those receiving morphine.

Conclusions

These results indicate that intrathecal morphine reduces postoperative pain in TKA patients. Furthermore, activation of central opioid receptors negatively modulates the endocannabinoid tone, suggesting that potent analgesics may reduce the stimulus for production of peripheral endocannabinoids. This study is the first to document the existence of rapid communication between the central opioid and peripheral endocannabinoid systems in humans.

Trial registration

This trial was registered retrospectively. Trial registry: NCT02620631. Study to Examine Pain Relief With Supplemental Intrathecal Morphine in TKA Patients, NCT02620631, 12/03/2015.

Circulating Endocannabinoids: From Whence Do They Come and Where are They Going?

The goal of this review is to summarize studies in which concentrations of circulating endocannabinoids in humans have been examined in relationship to physiological measurements and pathological status. The roles of endocannabinoids in the regulation of energy intake and storage have been well studied and the data obtained consistently support the hypothesis that endocannabinoid signaling is associated with increased consumption and storage of energy. Physical exercise mobilizes endocannabinoids, which could contribute to refilling of energy stores and also to the analgesic and mood-elevating effects of exercise. Circulating concentrations of 2-arachidonoylglycerol are very significantly circadian and dysregulated when sleep is disrupted. Other conditions under which circulating endocannabinoids are altered include inflammation and pain. A second important role for endocannabinoid signaling is to restore homeostasis following stress. Circulating endocannabinoids are stress-responsive and there is evidence that their concentrations are altered in disorders associated with excessive stress, including post-traumatic stress disorder. Although determination of circulating endocannabinoids can provide important information about the state of endocannabinoid signaling and thus allow for hypotheses to be defined and tested, the large number of physiological factors that contribute to their circulating concentrations makes it difficult to use them in isolation as a biomarker for a specific disorder.

Activation of Endocannabinoid Receptor 2 as a Mechanism of Propofol Pretreatment-Induced Cardioprotection against Ischemia-Reperfusion Injury in Rats

Propofol pretreatment before reperfusion, or propofol conditioning, has been shown to be cardioprotective, while its mechanism is unclear. The current study investigated the roles of endocannabinoid signaling in propofol cardioprotection in an in vivo model of myocardial ischemia/reperfusion (I/R) injury and in in vitro primary cardiomyocyte hypoxia/reoxygenation (H/R) injury. The results showed that propofol conditioning increased both serum and cell culture media concentrations of endocannabinoids including anandamide (AEA) and 2-arachidonoylglycerol (2-AG) detected by LC-MS/MS. The reductions of myocardial infarct size in vivo and cardiomyocyte apoptosis and death in vitro were accompanied with attenuations of oxidative injuries manifested as decreased reactive oxygen species (ROS), malonaldehyde (MDA), and MPO (myeloperoxidase) and increased superoxide dismutase (SOD) production. These effects were mimicked by either URB597, a selective endocannabinoids degradation inhibitor, or VDM11, a selective endocannabinoids reuptake inhibitor. In vivo study further validated that the cardioprotective and antioxidative effects of propofol were reversed by selective CB2 receptor antagonist AM630 but not CB1 receptor antagonist AM251. We concluded that enhancing endogenous endocannabinoid release and subsequent activation of CB2 receptor signaling represent a major mechanism whereby propofol conditioning confers antioxidative and cardioprotective effects against myocardial I/R injury.

Endocannabinoid Mechanisms Influencing Nausea

One of the first recognized medical uses of Δ(9)-tetrahydrocannabinol was treatment of chemotherapy-induced nausea and vomiting. Although vomiting is well controlled with the currently available non-cannabinoid antiemetics, nausea continues to be a distressing side effect of chemotherapy and other disorders. Indeed, when nausea becomes conditionally elicited by the cues associated with chemotherapy treatment, known as anticipatory nausea (AN), currently available antiemetics are largely ineffective. Considerable evidence demonstrates that the endocannabinoid system regulates nausea in humans and other animals. In this review, we describe recent evidence suggesting that cannabinoids and manipulations that enhance the functioning of the natural endocannabinoid system are promising treatments for both acute nausea and AN.

Analysis of eicosanoids by LC-MS/MS and GC-MS/MS: a historical retrospect and a discussion

Eicosanoids are a large family that derives from arachidonic acid, i.e., eicosatetraenoic acid. Prominent members include prostaglandins, thromboxane and leukotrienes. They are biologically highly active lipid mediators and play multiple physiological roles. GC-MS/MS has played a pivotal role in the identification and quantification of eicosanoids in biological samples. This technology generated a solid knowledge of their analytical chemistry, biochemistry, physiology and pharmacology. Since about a decade, GC-MS and GC-MS/MS are increasingly displaced by the seemingly more simple, rapid and powerful LC-MS/MS in the area of instrumental analysis of physiological substances, drugs and their metabolites. In this article, we review and discuss LC-MS/MS methods published over the last decade from the perspective of the GC-MS/MS user. Our analysis revealed that the shift from the adult GC-MS/MS to the youthful emerging LC-MS/MS technology in eicosanoid analysis is associated with several important challenges. Known pitfalls and problematic issues discovered by eicosanoid pioneers by using GC-MS/MS are often ignored by LC-MS/MS users. Established reference values and intervals provided by GC-MS-based methods are not considered properly in developing and validating LC-MS/MS methods. Virtually, there is a belief in the unlimited capability of the LC-MS/MS technique in eicosanoid analysis, a thought that simulates analytical certainty. LC-MS/MS users should profit from the plethora of solid knowledge acquired from the use of GC-MS/MS in eicosanoid analysis in basic and clinical research.

The effect of mifepristone (RU486) on the endocannabinoid system in human plasma and first-trimester trophoblast of women undergoing termination of pregnancy

INTRODUCTION

High anandamide (AEA) concentrations are detrimental for implantation and early pregnancy. Progesterone, essential for pregnancy, may keep AEA levels low by increasing fatty acid amide hydrolase (FAAH) expression. Here the effect of RU486, a P4 antagonist used to initiate medical termination of pregnancy (MTOP), on plasma AEA concentrations and the endocannabinoid system (ECS) in trophoblasts was examined.

OBJECTIVE

Quantification of the endocannabinoid concentrations and expression of the ECS in trophoblast tissue of MTOP women and women undergoing surgical termination of pregnancy (STOP).

DESIGN AND SETTING

A prospective study at the University Hospitals of Leicester National Health Service Trust.

PATIENTS AND METHODS

AEA, N-oleoylethanolamine (OEA), and N-palmitolylethanolamine (PEA) concentrations in trophoblast tissues and blood samples from 68 MTOP and 15 STOP were analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry. ECS expression was determined by immunohistochemistry, quantitative RT-PCR, and Western blotting.

RESULTS

Concentrations of AEA, OEA, and PEA were significantly higher in MTOP than STOP trophoblasts (P = .0062, P = .016, and P = .0029, respectively), whereas no significant differences in plasma AEA, OEA, and PEA concentrations were observed even though plasma AEA and PEA concentrations were significantly (P = .005 and P = .025, respectively) increased the day after RU486 administration in women undergoing MTOP. Changes in the immunohistochemical densities of the AEA modifying enzymes N-acylphophatidylethanolamine-phospholipase D (NAPE-PLD) and FAAH, and the cannabinoid receptors (CB1 and CB2) were observed with increased NAPE-PLD, FAAH, and CB1 expression seen in the trophoblast of MTOP patients.

CONCLUSIONS

Trophoblast after MTOP demonstrated high AEA concentrations with increased expression of NAPE-PLD, FAAH, and CB1.

Monoacylglycerol lipase - a target for drug development?

The endocannabinoid (eCB) system is involved in processes as diverse as control of appetite, perception of pain and the limitation of cancer cell growth and invasion. The enzymes responsible for eCB breakdown are attractive pharmacological targets, and fatty acid amide hydrolase inhibitors, which potentiate the levels of the eCB anandamide, are now undergoing pharmaceutical development. 'Drugable' selective inhibitors of monoacylglycerol lipase, a key enzyme regulating the levels of the other main eCB, 2-arachidonoylglycerol, were however not identified until very recently. Their availability has resulted in a large expansion of our knowledge concerning the pharmacological consequences of monoacylglycerol lipase inhibition and hence the role(s) played by the enzyme in the body. In this review, the pharmacology of monoacylglycerol lipase will be discussed, together with an analysis of the therapeutic potential of monoacylglycerol lipase inhibitors as analgesics and anticancer agents.