Implementation and validation of a UHPLC-MS/MS method for quantification of the endocannabinoids AEA and 2-AG in cerebral interstitial fluid and plasma

Endogenous endocannabinoids such as N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) are involved in the patho-biochemistry of several neurological diseases and have been associated with mood-enhancing phenomena. Although they have been intensively studied in recent years, accurate and reliable quantification of these analytes in cerebral interstitial fluid (cISF) to elucidate their neuro-modulatory role is still challenging. Moreover, there is a need for an analytical method that can analyze plasma in addition to cISF and is thus able to address research questions in both preclinical and clinical studies. Aim was to implement a method for simultaneous quantification of AEA and 2-AG in cISF and plasma, to validate it by taking the requirements of the U.S. Food and Drug Administration into account, and to test its usability in three different case studies. A UHPLC-MS/MS method with preceding liquid-liquid extraction to determine AEA and 2-AG in cISF and plasma was successfully implemented, and the parameters selectivity, specificity, linearity, accuracy, precision, sensitivity, carry-over and stability met the validation criteria. The usability of the analytical method was demonstrated in an in vitro study with cerebral open flow microperfusion (cOFM), an in vivo cOFM study in rats, and a clinical study in human plasma. The developed method allowed quantification of AEA and 2-AG in the biologically relevant concentration ranges in cISF and plasma. The availability of a reliable, complementary, time-resolved dataset of endocannabinoid concentrations in both matrices can be of considerable future importance for the evaluation of drug efficacy.

Longitudinal course of endocannabinoids and N-acylethanolamines in hair of mothers and their children in the first year postpartum: investigating the relevance of maternal childhood maltreatment experiences

BACKGROUND

Childhood maltreatment (CM) exerts long-lasting psychological and biological alterations in affected individuals and might also affect the endocannabinoid (eCB) system which modulates inflammation and the endocrine stress response. Here, we investigated the eCB system of women with and without CM and their infants using hair samples representing eCB levels accumulated during the last trimester of pregnancy and 10-12 months postpartum.

METHODS

CM exposure was assessed with the Childhood Trauma Questionnaire. At both timepoints, 3 cm hair strands were collected from mothers and children (N = 170 resp. 150) to measure anandamide (AEA), 2/1-arachidonoylglycerol (2-AG/1-AG), stearoylethanolamide (SEA), oleoylethanolamide (OEA), and palmitoylethanolamide (PEA).

RESULTS

Maternal hair levels of 2-AG/1-AG increased and SEA levels decreased from late pregnancy to one year postpartum. Maternal CM was associated with lower SEA levels in late pregnancy, but not one year later. In the children's hair, levels of 2-AG/1-AG increased while levels of SEA, OEA, and PEA decreased from late pregnancy to one year later. Maternal CM was not consistently associated with the eCB levels measured in children's hair.

CONCLUSIONS

We provide first evidence for longitudinal change in the eCB system of mothers and infants from pregnancy to one year later. While maternal CM influenced the maternal eCB system, we found no consistent intergenerational effects on early regulation of the eCB system in children. Longitudinal research on the importance of the eCB system for the course and immunoregulation of pregnancy as well as for the children's development.

Endocannabinoid signaling in the central nervous system

It is hard to overestimate the influence of the endocannabinoid signaling (ECS) system on central nervous system (CNS) function. In the 40 years since cannabinoids were found to trigger specific cell signaling cascades, studies of the ECS system continue to cause amazement, surprise, and confusion! CB1 cannabinoid receptors are expressed widely in the CNS and regulate cell-cell communication via effects on the release of both neurotransmitters and gliotransmitters. CB2 cannabinoid receptors are difficult to detect in the CNS but seem to "punch above their weight" as compounds targeting these receptors have significant effects on inflammatory state and behavior. Positive and negative allosteric modulators for both receptors have been identified and examined in preclinical studies. Concentrations of the endocannabinoid ligands, N-arachidonoylethanolamine and 2-arachidonoylglycerol (2-AG), are regulated by a combination of enzymatic synthesis and degradation and inhibitors of these processes are available and making their way into clinical trials. Importantly, ECS regulates many essential brain functions, including regulation of reward, anxiety, inflammation, motor control, and cellular development. While the field is on the cusp of preclinical discoveries providing impactful clinical and therapeutic insights into many CNS disorders, there is still much to be learned about this remarkable and versatile modulatory system.

Quantification of Endocannabinoids in Human Plasma

The determination of the concentration of endocannabinoids and related compounds in human plasma has become a matter of interest due to their implication in physiological processes and, thus, their possible relation with physiological conditions or illnesses. The analysis of these compounds though has to be carefully designed as they are found in very low concentrations, and some of them degrade easily once blood is collected. In this chapter, a simple method based on a liquid-liquid extraction and analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) is described to determine the concentration of eight of the most relevant endocannabinoids in plasma.

Loneliness, Circulating Endocannabinoid Concentrations, and Grief Trajectories in Bereaved Older Adults: A Longitudinal Study

Background: Loneliness is one of the most distressing grief symptoms and is associated with adverse mental health in bereaved older adults. The endocannabinoid signaling (ECS) system is stress-responsive and circulating endocannabinoid (eCB) concentrations are elevated following bereavement. This study examined the association between loneliness and circulating eCB concentrations in grieving older adults and explored the role of eCBs on the association between baseline loneliness and grief symptom trajectories. Methods: A total of 64 adults [grief with high loneliness: n = 18; grief with low loneliness: n = 26; and healthy comparison (HC): n = 20] completed baseline clinical assessments for the UCLA loneliness scale. In grief participants, longitudinal clinical assessments, including the Inventory of Complicated Grief and 17-item Hamilton Depression Rating scales, were collected over 6 months. Baseline circulating eCB [N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG)] concentrations were quantified in the serum using isotope dilution, liquid chromatography-mass spectrometry; cortisol concentrations were measured in the same samples using radioimmunoassay. Results: Circulating AEA concentrations were higher in severely lonely grieving elders than in HC group; cortisol concentrations were not different among the groups. Cross-sectionally, loneliness scores were positively associated with AEA concentrations in grievers; this finding was not significant after accounting for depressive symptom severity. Grieving individuals who endorsed high loneliness and had higher 2-AG concentrations at baseline showed faster grief symptom resolution. Conclusions: These novel findings suggest that in lonely, bereaved elders, increased circulating eCBs, a reflection of an efficient ECS system, are associated with better adaptation to bereavement. Circulating eCBs as potential moderators and mediators of the loneliness-grief trajectory associations should be investigated.

Meet Your Stress Management Professionals: The Endocannabinoids

The endocannabinoid signaling system (ECSS) is altered by exposure to stress and mediates and modulates the effects of stress on the brain. Considerable preclinical data support critical roles for the endocannabinoids and their target, the CB1 cannabinoid receptor, in the adaptation of the brain to repeated stress exposure. Chronic stress exposure increases vulnerability to mental illness, so the ECSS has attracted attention as a potential therapeutic target for the prevention and treatment of stress-related psychopathology. We discuss human genetic studies indicating that the ECSS contributes to risk for mental illness in those exposed to severe stress and trauma early in life, and we explore the potential difficulties in pharmacological manipulation of the ECSS.

Lower circulating endocannabinoid levels in children with autism spectrum disorder

Background

The endocannabinoid system (ECS) is a major regulator of synaptic plasticity and neuromodulation. Alterations of the ECS have been demonstrated in several animal models of autism spectrum disorder (ASD). In some of these models, activating the ECS rescued the social deficits. Evidence for dysregulations of the ECS in human ASD are emerging, but comprehensive assessments and correlations with disease characteristics have not been reported yet.

Methods

Serum levels of the main endocannabinoids, N-arachidonoylethanolamine (AEA or anandamide) and 2-arachidonoylglycerol (2-AG), and their related endogenous compounds, arachidonic acid (AA), N-palmitoylethanolamine (PEA), and N-oleoylethanolamine (OEA), were analyzed by liquid chromatography/tandem mass spectrometry in 93 children with ASD (age = 13.1 ± 4.1, range 6–21; 79% boys) and 93 age- and gender-matched neurotypical children (age = 11.8 ± 4.3, range 5.5–21; 79% boys). Results were associated with gender and use of medications, and were correlated with age, BMI, and adaptive functioning of ASD participants as reflected by scores of Autism Diagnostic Observation Schedule (ADOS-2), Vineland Adaptive Behavior Scale-II (VABS-II), and Social Responsiveness Scale-II (SRS-2).

Results

Children with ASD had lower levels (pmol/mL, mean ± SEM) of AEA (0.722 ± 0.045 vs. 1.252 ± 0.072, P < 0.0001, effect size 0.91), OEA (17.3 ± 0.80 vs. 27.8 ± 1.44, P < 0.0001, effect size 0.94), and PEA (4.93 ± 0.32 vs. 7.15 ± 0.37, P < 0.0001, effect size 0.65), but not AA and 2-AG. Serum levels of AEA, OEA, and PEA were not significantly associated or correlated with age, gender, BMI, medications, and adaptive functioning of ASD participants. In children with ASD, but not in the control group, younger age and lower BMI tended to correlate with lower AEA levels. However, these correlations were not statistically significant after a correction for multiple comparisons.

Conclusions

We found lower serum levels of AEA, PEA, and OEA in children with ASD. Further studies are needed to determine whether circulating endocannabinoid levels can be used as stratification biomarkers that identify clinically significant subgroups within the autism spectrum and if they reflect lower endocannabinoid “tone” in the brain, as found in animal models of ASD.

Electronic supplementary material

The online version of this article (10.1186/s13229-019-0256-6) contains supplementary material, which is available to authorized users.

Endocannabinoid Transport Proteins: Discovery of Tools to Study Sterol Carrier Protein-2

The endocannabinoid (eCB) neurotransmitter system regulates diverse neurological functions including stress and anxiety, pain, mood, and reward. Understanding the mechanisms underlying eCB regulation is critical for developing targeted pharmacotherapies to treat these and other neurologic disorders. Cellular studies suggest that the arachidonate eCBs, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), are substrates for intracellular binding and transport proteins, and several candidate proteins have been identified. Initial evidence from our laboratory indicates that the lipid transport protein, sterol carrier protein 2 (SCP-2), binds to the eCBs and can regulate their cellular concentrations. Here, we present methods for evaluating SCP-2 binding of eCBs and their application to the discovery of the first inhibitor lead molecules. Using a fluorescent probe displacement assay, we found SCP-2 binds the eCBs, AEA (Ki=0.68±0.05μM) and 2-AG (Ki=0.37±0.02μM), with moderate affinity. A series of structurally diverse arachidonate analogues also bind SCP-2 with Ki values between 0.82 and 2.95μM, suggesting a high degree of tolerance for arachidonic acid head group modifications in this region of the protein. We also report initial structure-activity relationships surrounding previously reported inhibitors of Aedis aegypti SCP-2, and the results of an in silico high-throughput screen that identified structurally novel SCP-2 inhibitor leads. The methods and results reported here provide the basis for a robust probe discovery effort to fully elucidate the role of facilitated transport mediated by SCP-2 in eCB regulation and function.

Cannabinoid receptor signaling in progenitor/stem cell proliferation and differentiation

Cannabinoids, the active components of cannabis (Cannabis sativa) extracts, have attracted the attention of human civilizations for centuries, much earlier than the discovery and characterization of their substrate of action, the endocannabinoid system (ECS). The latter is an ensemble of endogenous lipids, their receptors [in particular type-1 (CB1) and type-2 (CB2) cannabinoid receptors] and metabolic enzymes. Cannabinoid signaling regulates cell proliferation, differentiation and survival, with different outcomes depending on the molecular targets and cellular context involved. Cannabinoid receptors are expressed and functional from the very early developmental stages, when they regulate embryonic and trophoblast stem cell survival and differentiation, and thus may affect the formation of manifold adult specialized tissues derived from the three different germ layers (ectoderm, mesoderm and endoderm). In the ectoderm-derived nervous system, both CB1 and CB2 receptors are present in neural progenitor/stem cells and control their self-renewal, proliferation and differentiation. CB1 and CB2 show opposite patterns of expression, the former increasing and the latter decreasing along neuronal differentiation. Recently, endocannabinoid (eCB) signaling has also been shown to regulate proliferation and differentiation of mesoderm-derived hematopoietic and mesenchymal stem cells, with a key role in determining the formation of several cell types in peripheral tissues, including blood cells, adipocytes, osteoblasts/osteoclasts and epithelial cells. Here, we will review these new findings, which unveil the involvement of eCB signaling in the regulation of progenitor/stem cell fate in the nervous system and in the periphery. The developmental regulation of cannabinoid receptor expression and cellular/subcellular localization, together with their role in progenitor/stem cell biology, may have important implications in human health and disease.

Lipid signaling cascades of orexin/hypocretin receptors

Orexins - orexin-A and orexin-B - are neuropeptides with significant role in regulation of fundamental physiological processes such as sleep-wakefulness cycle. Orexins act via G-protein-coupled OX1 and OX2 receptors, which are found, in addition to the central nervous system, also in a number of peripheral organs. Orexin receptors show high degree of signaling promiscuity. One particularly prominent way of signaling for these receptors is via phospholipase cascades, including the phospholipase C, phospholipase D and phospholipase A2 cascades, and also diacylglycerol lipase and phosphoinositide-3-kinase pathways. Most analyses have been performed in recombinant cells; there are indications of some of these cascades in native cells while the significance of other cascades remains to be shown. In this review, I present these pathways, their activation mechanisms and their physiological significance.