Exogenous delta⁹-tetrahydrocannabinol influences circulating endogenous cannabinoids in humans

Dose-dependent effects of oral cannabidiol and delta-9-tetrahydrocannabinol on serum anandamide and related N-acylethanolamines in healthy volunteers

BACKGROUND

The mental health benefits of cannabidiol (CBD) are promising but can be inconsistent, in part due to challenges in defining an individual's effective dosage. In schizophrenia, alterations in anandamide (AEA) concentrations, an endocannabinoid (eCB) agonist of the eCB system, reflect positively on treatment with CBD. Here, we expanded this assessment to include eCBs alongside AEA congeners, comparing phytocannabinoids and dosage in a clinical setting.

METHODS

Liquid chromatography-tandem mass spectrometry quantified changes in serum levels of AEA, 2-arachidonoylglycerol (2-AG), alongside AEA-related compounds oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), which were attained from two independent, parallel-designed, clinical trials investigating single, oral CBD (600 or 800 mg), delta-9-tetrahydrocannabinol (Δ9-THC, 10 or 20 mg) and combination administration (CBD|800 mg+Δ9-THC|20 mg) in healthy volunteers (HVs, n=75). Concentrations were measured at baseline (t=0), 65 and 160 min post administration.

RESULTS

CBD-led increases in AEA (1.6-fold), OEA and PEA (1.4-fold) were observed following a single 800 mg (pcorr<0.05) but not 600 mg dosage. Declining AEA was observed with Δ9-THC at 10 mg (-1.3-fold) and 20 mg (-1.4-fold) but restored to baseline levels by 160 min. CBD+Δ9-THC yielded the highest increases in AEA (2.1-fold), OEA (1.9-fold) and PEA (1.8-fold) without reaching a maximal response.

CONCLUSION

CBD-administered effects towards AEA, OEA and PEA are consistent with phase II trials reporting clinical improvement for acute schizophrenia (CBD≥800 mg). Including Δ9-THC appears to enhance the CBD-induced response towards AEA and its congeners. Our results warrant further investigations into the potential of these lipid-derived mediators as metabolic measures for CBD dose prescription and co-cannabinoid administration.

Peripheral endocannabinoids in major depressive disorder and alcohol use disorder: a systematic review

BACKGROUND

Major Depressive Disorder (MDD) and Alcohol Use Disorder (AUD) are two high-prevalent conditions where the Endocannabinoid system (ECS) is believed to play an important role. The ECS regulates how different neurotransmitters interact in both disorders, which is crucial for controlling emotions and responses to stress and reward stimuli. Measuring peripheral endocannabinoids (eCBs) in human serum and plasma can help overcome the limitations of detecting endocannabinoid levels in the brain. This systematic review aims to identify levels of peripheral eCBs in patients with MDD and/or AUD and find eCBs to use as diagnostic, prognostic biomarkers, and potential therapeutic targets.

METHODS

We conducted a systematic literature search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines from the earliest manuscript until October 22, 2023, in three electronic databases. We included studies of human adults who had a current diagnosis of AUD and/or MDD and evaluated plasma or serum endocannabinoids. We carefully considered known variables that may affect endocannabinoid levels.

RESULTS

We included 17 articles in this systematic review, which measured peripheral eCBs in 170 AUD and 359 MDD patients. Stressors increase peripheral 2-arachidonyl-glycerol (2-AG) concentrations, and 2-AG may be a particular feature of depression severity and chronicity. Anxiety symptoms are negatively correlated with anandamide (AEA) concentrations, and AEA significantly increases during early abstinence in AUD. Studies suggest a negative correlation between Oleoylethanolamide (OEA) and length of abstinence in AUD patients. They also show a significant negative correlation between peripheral levels of AEA and OEA and fatty acid amide hydrolase (FAAH) activity. Eicosapentaenoylethanolamide (EPEA) is correlated to clinical remission rates in depression. Included studies show known variables such as gender, chronicity, symptom severity, comorbid psychiatric symptoms, length of abstinence in the case of AUD, and stress-inducibility that can affect peripheral eCBs.

CONCLUSIONS

This systematic review highlights the important role that the ECS plays in MDD and AUD. Peripheral eCBs appear to be useful biomarkers for these disorders, and further research may identify potential therapeutic targets. Using accessible biological samples such as blood in well-designed clinical studies is crucial to develop novel therapies for these disorders.

Effects of Cannabidiol and Delta-9-Tetrahydrocannabinol on Plasma Endocannabinoid Levels in Healthy Volunteers: A Randomized Double-Blind Four-Arm Crossover Study

Background: The effects of cannabis are thought to be mediated by interactions between its constituents and the endocannabinoid system. Delta-9-tetrahydrocannabinol (THC) binds to central cannabinoid receptors, while cannabidiol (CBD) may influence endocannabinoid function without directly acting on cannabinoid receptors. We examined the effects of THC coadministered with different doses of CBD on plasma levels of endocannabinoids in healthy volunteers. Methods: In a randomized, double-blind, four-arm crossover study, healthy volunteers (n=46) inhaled cannabis vapor containing 10 mg THC plus either 0, 10, 20, or 30 mg CBD, in four experimental sessions. The median time between sessions was 14 days (IQR=20). Blood samples were taken precannabis inhalation and at 0-, 5-, 15-, and 90-min postinhalation. Plasma concentrations of THC, CBD, anandamide, 2-arachidonoylglycerol (2-AG), and related noncannabinoid lipids were measured using liquid chromatography-mass spectrometry. Results: Administration of cannabis induced acute increases in plasma concentrations of anandamide (+18.0%, 0.042 ng/mL [95%CI: 0.023-0.062]), and the noncannabinoid ethanolamides, docosatetraenylethanolamide (DEA; +35.8%, 0.012 ng/mL [95%CI: 0.008-0.016]), oleoylethanolamide (+16.1%, 0.184 ng/mL [95%CI: 0.076-0.293]), and N-arachidonoyl-L-serine (+25.1%, 0.011 ng/mL [95%CI: 0.004-0.017]) (p<0.05). CBD had no significant effect on the plasma concentration of anandamide, 2-AG or related noncannabinoid lipids at any of three doses used. Over the four sessions, there were progressive decreases in the preinhalation concentrations of anandamide and DEA, from 0.254 ng/mL [95%CI: 0.223-0.286] to 0.194 ng/mL [95%CI: 0.163-0.226], and from 0.039 ng/mL [95%CI: 0.032-0.045] to 0.027 ng/mL [95%CI: 0.020-0.034] (p<0.05), respectively. Discussion: THC induced acute increases in plasma levels of anandamide and noncannabinoid ethanolamides, but there was no evidence that these effects were influenced by the coadministration of CBD. It is possible that such effects may be evident with higher doses of CBD or after chronic administration. The progressive reduction in pretreatment anandamide and DEA levels across sessions may be related to repeated exposure to THC or participants becoming less anxious about the testing procedure and requires further investigation. The study was registered on clinicaltrials.gov (NCT05170217).

A Sensitive Ultrahigh-Performance Liquid Chromatography/Tandem Mass Spectrometry Method for the Simultaneous Analysis of Phytocannabinoids and Endocannabinoids in Plasma and Brain

Introduction: Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are major chemical constituents of cannabis, which may interact either directly or indirectly with the endocannabinoid and endocannabinoid-like ("paracannabinoid") systems, two lipid-based signaling complexes that play important roles in physiology. Legislative changes emphasize the need to understand how THC and CBD might impact endocannabinoid and paracannabinoid signaling, and to develop analytical approaches to study such impact. In this study, we describe a sensitive and accurate method for the simultaneous quantification of THC, its main oxidative metabolites [11-hydroxy-Δ9-THC (11-OH-THC) and 11-nor-9-carboxy-Δ9-THC (11-COOH-THC)], CBD, and a representative set of endocannabinoid [anandamide and 2-arachidonoyl-sn-glycerol (2-AG)] and paracannabinoid [palmitoylethanolamide (PEA) and oleoylethanolamide (OEA)] compounds. Analyte separation relies on the temperature-dependent shape selectivity properties of polymerically bonded C18 stationary phases. Materials and Methods: Analytes are extracted from tissues using acetonitrile precipitation followed by phospholipid removal. The ultrahigh-performance liquid chromatography/tandem mass spectrometry protocol utilizes a commercially available C18 polymeric-bonded phase column and a simple gradient elution system. Results: Ten-point calibration curves show excellent linearity (R2>0.99) over a wide range of analyte concentrations (0.02-500 ng/mL). Lowest limits of quantification are 0.05 ng/mL for anandamide, 0.1 ng/mL for 11-OH-THC and OEA, 0.2 ng/mL for THC and CBD, 0.5 ng/mL for 11-COOH-THC, 1.0 ng/mL for 2-AG, and 2.0 ng/mL for PEA. The lowest limits of detection are 0.02 ng/mL for anandamide, 0.05 ng/mL for 11-OH-THC and OEA, 0.1 ng/mL for THC and CBD, 0.2 ng/mL for 11-COOH-THC, 0.5 ng/mL for 2-AG, and 1.0 ng/mL for PEA. Conclusions: An application of the method is presented, which showed that phytocannabinoid administration elevates endocannabinoid levels in plasma and brain of adolescent male and female mice.

The Relationship Between Circulating Endogenous Cannabinoids and the Effects of Smoked Cannabis

Background: The endogenous cannabinoid system (ECS), including the endocannabinoids (eCBs), anandamide (AEA), and 2-arachidonoylglycerol (2-AG), plays an integral role in psychophysiological functions. Although frequent cannabis use is associated with adaptations in the ECS, the impact of acute smoked cannabis administration on circulating eCBs, and the relationship between cannabis effects and circulating eCBs are poorly understood. Methods: This study measured the plasma levels of AEA, 2-AG, and Δ-9-tetrahydrocannabinol (THC), subjective drug-effects ratings, and cardiovascular measures at baseline and 15-180 min after cannabis users (n=26) smoked 70% of a cannabis cigarette (5.6% THC). Results: Cannabis administration increased the ratings of intoxication, heart rate, and plasma THC levels relative to baseline. Although cannabis administration did not affect eCB levels relative to baseline, there was a significant positive correlation between baseline AEA levels and peak ratings of "High" and "Good Drug Effect." Further, baseline 2-AG levels negatively correlated with frequency of cannabis use (mean days/week) and with baseline THC metabolite levels. Conclusions: In a subset of heavy cannabis smokers: (1) more frequent cannabis use was associated with lower baseline 2-AG, and (2) those with lower AEA got less intoxicated after smoking cannabis. These findings contribute to a sparse literature on the interaction between endo- and phyto-cannabinoids. Future studies in participants with varied cannabis use patterns are needed to clarify the association between circulating eCBs and the abuse-related effects of cannabis, and to test whether baseline eCBs predict the intoxicating effects of cannabis and are a potential biomarker of cannabis tolerance.

Sex differences in endocannabinoid tone in a pilot study of cannabis use disorder and acute cannabis abstinence

Cannabis use disorder (CUD) presents differently in men and women, particularly in symptoms of cannabis withdrawal. Novel pharmacotherapeutic interventions for CUD, such as those that target the endocannabinoid (eCB) system, must be developed in a manner consistent with these sex differences. The present pilot study sought to prospectively assess sex differences in cannabis withdrawal in a small sample of adults with moderate-to-severe CUD and to determine if withdrawal was associated with peripheral eCB and eCB congener tone. Men and women (n = 5/sex) completed 2 weeks of study participation separated by 1 month; in the latter week, participants abstained from cannabis use. Each week, participants attended in-person laboratory visits during which blood was drawn repeatedly to assess plasma eCB and eCB congener tone. Participants also completed multiple daily ambulatory assessments to assess cannabis use and withdrawal symptoms. As anticipated, women reported a greater increase in withdrawal symptoms during the abstinent week [Δ = 9.4 (SE = 1.1); p < 0.001] than men [Δ = 1.2 (SE = 1.2); p = 0.35]. Sex differences in levels of the eCB N-arachidonoylethanolamide (AEA), as well as the eCB congeners stearoylethanolamide (SEA) and linoleylethanolamide (LEA), were evident during abstinence at the morning time point only (p's < 0.05). LEA was associated with withdrawal symptom expression in both sexes [β = 0.16 (SE = 0.09)] and palmitoylethanolamide (PEA) [β = 0.22 (SE = 0.13)] and 2-arachidonoylglycerol (2-AG) [β = 0.32 (SE = 0.15)] were associated with withdrawal symptoms in women only. Pharmacotherapeutic development for CUD should consider evident sex differences in eCB and eCB congener tone during abstinence and their associations with cannabis withdrawal, as eCB-based interventions may produce differential effects by sex.

Circulating Endocannabinoids and N-Acylethanolamines in Individuals with Cannabis Use Disorder-Preliminary Findings

BACKGROUND

Endocannabinoids and related N-acylethanolamines (NAEs) are bioactive lipids with important physiological functions and putative roles in mental health and addictions. Although chronic cannabis use is associated with endocannabinoid system changes, the status of circulating endocannabinoids and related NAEs in people with cannabis use disorder (CUD) is uncertain.

METHODS

Eleven individuals with CUD and 54 healthy non-cannabis using control participants (HC) provided plasma for measurement by high-performance liquid chromatography-mass spectrometry of endocannabinoids (2-arachidonoylglycerol (2-AG) and N-arachidonoylethanolamine (AEA)) and related NAE fatty acids (N-docosahexaenoylethanolamine (DHEA) and N-oleoylethanolamine (OEA)). Participants were genotyped for the functional gene variant of FAAH (rs324420, C385A) which may affect concentrations of AEA as well as other NAEs (OEA, DHEA).

RESULTS

In overnight abstinent CUD, AEA, OEA and DHEA concentrations were significantly higher (31-40%; p < 0.05) and concentrations of the endocannabinoid 2-AG were marginally elevated (55%, p = 0.13) relative to HC. There were no significant correlations between endocannabinoids/NAE concentrations and cannabis analytes, self-reported cannabis use frequency or withdrawal symptoms. DHEA concentration was inversely related with marijuana craving (r = -0.86; p = 0.001). Genotype had no significant effect on plasma endocannabinoids/NAE concentrations.

CONCLUSIONS

Our preliminary findings, requiring replication, might suggest that activity of the endocannabinoid system is elevated in chronic cannabis users. It is unclear whether this elevation is a compensatory response or a predating state. Studies examining endocannabinoids and NAEs during prolonged abstinence as well as the potential role of DHEA in craving are warranted.

The Inflammatory Signals Associated with Psychosis: Impact of Comorbid Drug Abuse

Psychosis and substance use disorders are two diagnostic categories whose association has been studied for decades. In addition, both psychosis spectrum disorders and drug abuse have recently been linked to multiple pro-inflammatory changes in the central nervous system. We have carried out a narrative review of the literature through a holistic approach. We used PubMed as our search engine. We included in the review all relevant studies looking at pro-inflammatory changes in psychotic disorders and substance use disorders. We found that there are multiple studies that relate various pro-inflammatory lipids and proteins with psychosis and substance use disorders, with an overlap between the two. The main findings involve inflammatory mediators such as cytokines, chemokines, endocannabinoids, eicosanoids, lysophospholipds and/or bacterial products. Many of these findings are present in different phases of psychosis and in substance use disorders such as cannabis, cocaine, methamphetamines, alcohol and nicotine. Psychosis and substance use disorders may have a common origin in an abnormal neurodevelopment caused, among other factors, by a neuroinflammatory process. A possible convergent pathway is that which interrelates the transcriptional factors NFκB and PPARγ. This may have future clinical implications.

Herbal Cannabis Use Is Not Associated with Changes in Levels of Endocannabinoids and Metabolic Profile Alterations among Older Adults

Simple Summary

The endocannabinoid system is a complex cell-signaling system that has numerous effects on the human body, including on the heart, blood vessels, and metabolism. In this study, we aimed to assess the effects of exogenous herbal medical cannabis use on the components of the endocannabinoid system among older adults with a diagnosis of hypertension. Medical cannabis is a product containing cannabinoids used for medical purposes. Herbal cannabis contains many types of cannabinoids, the most well-known of which are Δ⁹-tetrahydrocannabinol and cannabidiol. We followed people aged 60 years and older and conducted a number of tests, including endocannabinoids levels, before they started using cannabis and following three months of daily cannabis treatment. Fifteen patients (53.3% male; mean age, 69.5 years) underwent complete evaluations. We found positive correlations between the components of the endocannabinoid system and blood lipids, markers of inflammation, and blood pressure. On average, cannabis treatment for 3 months does not result in a significant change in the levels of endogenous cannabinoids and thus has a safe metabolic risk profile. This study provides additional evidence for the safety of medical cannabis use among older adults.

Abstract

Activation of the endocannabinoid system has various cardiovascular and metabolic expressions, including increased lipogenesis, decreased blood pressure, increased heart rate, and changes in cholesterol levels. There is a scarcity of data on the metabolic effects of exogenous cannabis in older adults; therefore, we aimed to assess the effect of exogenous cannabis on endocannabinoid levels and the association with changes in 24 h ambulatory blood pressure and lipid levels. We conducted a prospective study of patients aged 60 years or more with hypertension treated with a new prescription of herbal cannabis. We assessed changes in endocannabinoids, blood pressure, and metabolic parameters prior to and following three months of cannabis use. Fifteen patients with a mean age of 69.47 ± 5.83 years (53.3% male) underwent complete evaluations. Changes in 2-arachidonoylglycerol, an endocannabinoid, were significantly positively correlated with changes in triglycerides. Changes in arachidonic acid levels were significantly positively correlated with changes in C-reactive protein and with changes in mean diastolic blood pressure. Exogenous consumption of cannabidiol was negatively correlated with endogenous levels of palmitoylethanolamide and oleoylethanolamide. On average, cannabis treatment for 3 months does not result in a significant change in the levels of endogenous cannabinoids and thus has a safe metabolic risk profile.

Biomarkers of the Endocannabinoid System in Substance Use Disorders

Despite substance use disorders (SUD) being one of the leading causes of disability and mortality globally, available therapeutic approaches remain ineffective. The difficulty in accurately characterizing the neurobiological mechanisms involved with a purely qualitative diagnosis is an obstacle to improving the classification and treatment of SUD. In this regard, identifying central and peripheral biomarkers is essential to diagnosing the severity of drug dependence, monitoring therapeutic efficacy, predicting treatment response, and enhancing the development of safer and more effective pharmacological tools. In recent years, the crucial role that the endocannabinoid system (ECS) plays in regulating the reinforcing and motivational properties of drugs of abuse has been described. This has led to studies characterizing ECS alterations after exposure to various substances to identify biomarkers with potential diagnostic, prognostic, or therapeutic utility. This review aims to compile the primary evidence available from rodent and clinical studies on how the ECS components are modified in the context of different substance-related disorders, gathering data from genetic, molecular, functional, and neuroimaging experimental approaches. Finally, this report concludes that additional translational research is needed to further characterize the modifications of the ECS in the context of SUD, and their potential usefulness in the necessary search for biomarkers.

Sphingolipid and Endocannabinoid Profiles in Adult Attention Deficit Hyperactivity Disorder

Genes encoding endocannabinoid and sphingolipid metabolism pathways were suggested to contribute to the genetic risk towards attention deficit hyperactivity disorder (ADHD). The present pilot study assessed plasma concentrations of candidate endocannabinoids, sphingolipids and ceramides in individuals with adult ADHD in comparison with healthy controls and patients with affective disorders. Targeted lipid analyses of 23 different lipid species were performed in 71 mental disorder patients and 98 healthy controls (HC). The patients were diagnosed with adult ADHD (n = 12), affective disorder (major depression, MD n = 16 or bipolar disorder, BD n = 6) or adult ADHD with comorbid affective disorders (n = 37). Canonical discriminant analysis and CHAID analyses were used to identify major components that predicted the diagnostic group. ADHD patients had increased plasma concentrations of sphingosine-1-phosphate (S1P d18:1) and sphinganine-1-phosphate (S1P d18:0). In addition, the endocannabinoids, anandamide (AEA) and arachidonoylglycerol were increased. MD/BD patients had increased long chain ceramides, most prominently Cer22:0, but low endocannabinoids in contrast to ADHD patients. Patients with ADHD and comorbid affective disorders displayed increased S1P d18:1 and increased Cer22:0, but the individual lipid levels were lower than in the non-comorbid disorders. Sphingolipid profiles differ between patients suffering from ADHD and affective disorders, with overlapping patterns in comorbid patients. The S1P d18:1 to Cer22:0 ratio may constitute a diagnostic or prognostic tool.

Spatio-temporal effects of acute alcohol intoxication on endocannabinoid system in rat brain and blood

The endocannabinoid system (ECS) has been shown to play a critical role in the regulation of alcohol intake and alcohol-related behaviors. However, there are discrepancies between studies examining the interaction of the ECS and alcohol administration due to different experimental procedures. The present study aims at clarifying the time course effects of acute alcohol consumption on the ECS in the peripheral circulatory systems and central nervous systems of the same cohort of subjects. We have closely monitored the critical indicators reflecting changes of the ECS during the entire process from alcohol absorption to its metabolization, after acute alcohol (4.5 g/kg) intake by intragastric administration, including two key endocannabinoids (arachidonoylethanolamide and 2-arachidonoylglycerol) and their hydrolytic enzymes (fatty acid amide hydrolase and monoacylglycerol lipase) in blood and three brain regions, as well as a crucial and abundant receptor (cannabinoid 1 receptor) of the ECS in the three brain regions. Our results indicate that acute alcohol consumption inhibits endocannabinoid (eCB) production in the blood and in the prefrontal cortex of the brain, whereas the reverse was observed in the brain regions of the hippocampus and striatum. The variation between levels of two hydrolytic enzymes in the blood and in the three brain regions failed to reach statistical significance. After acute alcohol consumption, CB1R levels in striatum, hippocampus, and prefrontal cortex showed a similar trend of increasing, while the significant changes occurred at different time points. The present findings reveal different ligand-receptor changing patterns in the blood and in different brain regions, supporting the notion that the ECS plays a vital role in acute alcohol intoxication. Additionally, the temporal effects of alcohol on key elements of the ECS of blood and different brain nuclei were different. Our investigation may lead to a deeper understanding of the effect of acute alcohol consumption on the ECS.

Delta-9-tetrahydrocannabinol reduces the performance in sensory delayed discrimination tasks. A pharmacological-fMRI study in healthy volunteers

BACKGROUND

Cannabis proofed to be effective in pain relief, but one major side effect is its influence on memory in humans. Therefore, the role of memory on central processing of nociceptive information was investigated in healthy volunteers.

METHODS

In a placebo-controlled cross-over study including 22 healthy subjects, the effect of 20 mg oral Δ9-tetrahydrocannabinol (THC) on memory involving nociceptive sensations was studied, using a delayed stimulus discrimination task (DSDT). To control for nociceptive specificity, a similar DSDT-based study was performed in a subgroup of thirteen subjects, using visual stimuli.

RESULTS

For each nociceptive stimulus pair, the second stimulus was associated with stronger and more extended brain activations than the first stimulus. These differences disappeared after THC administration. The THC effects were mainly located in two clusters comprising the insula and inferior frontal cortex in the right hemisphere, and the caudate nucleus and putamen bilaterally. These cerebral effects were accompanied in the DSDT by a significant reduction of correct ratings from 41.61% to 37.05% after THC administration (rm-ANOVA interaction "drug" by "measurement": F (1,21) = 4.685, p = 0.042). Rating performance was also reduced for the visual DSDT (69.87% to 54.35%; rm-ANOVA interaction of "drug" by "measurement": F (1,12) = 13.478, p = 0.003) and reflected in a reduction of stimulus-related brain deactivations in the bilateral angular gyrus.

CONCLUSIONS

Results suggest that part of the effect of THC on pain may be related to memory effects. THC reduced the performance in DSDT of nociceptive and visual stimuli, which was accompanied by significant effects on brain activations. However, a pain specificity of these effects cannot be deduced from the data presented.

A systematic review of phytocannabinoid exposure on the endocannabinoid system: Implications for psychosis

Cannabis, the most widely used illicit drug worldwide, produces psychoactive effects through its component cannabinoids, which act on the endocannabinoid system. Research on how cannabinoid exposure affects the endocannabinoid system is limited. Substantial evidence indicates cannabis use as a risk factor for psychosis, and the mechanism(s) by which this is occurring is/are currently unknown. Here, we conduct the first review of the effects of exogenous cannabinoids on the endocannabinoid system in humans with and without psychotic disorders. The most well established finding is the down-regulation of cannabinoid CB1 receptors (CB1R) after chronic and recent cannabis exposure, but it remains uncertain whether this effect is present in cannabis users with schizophrenia. We highlight where cannabis exposure affects the endocannabinoid system in a pattern that may mirror what is seen in psychosis, and how further research can push this field forward. In these times of changing cannabis legislation, research highlighting the biological effects of cannabinoids is greatly needed.

Anti-stress neuropharmacological mechanisms and targets for addiction treatment: A translational framework

Stress-related substance use is a major challenge for treating substance use disorders. This selective review focuses on emerging pharmacotherapies with potential for reducing stress-potentiated seeking and consumption of nicotine, alcohol, marijuana, cocaine, and opioids (i.e., key phenotypes for the most commonly abused substances). I evaluate neuropharmacological mechanisms in experimental models of drug-maintenance and relapse, which translate more readily to individuals presenting for treatment (who have initiated and progressed). An affective/motivational systems model (three dimensions: valence, arousal, control) is mapped onto a systems biology of addiction approach for addressing this problem. Based on quality of evidence to date, promising first-tier neurochemical receptor targets include: noradrenergic (α1 and β antagonist, α2 agonist), kappa-opioid antagonist, nociceptin antagonist, orexin-1 antagonist, and endocannabinoid modulation (e.g., cannabidiol, FAAH inhibition); second-tier candidates may include corticotropin releasing factor-1 antagonists, serotonergic agents (e.g., 5-HT reuptake inhibitors, 5-HT3 antagonists), glutamatergic agents (e.g., mGluR2/3 agonist/positive allosteric modulator, mGluR5 antagonist/negative allosteric modulator), GABA-promoters (e.g., pregabalin, tiagabine), vasopressin 1b antagonist, NK-1 antagonist, and PPAR-γ agonist (e.g., pioglitazone). To address affective/motivational mechanisms of stress-related substance use, it may be advisable to combine agents with actions at complementary targets for greater efficacy but systematic studies are lacking except for interactions with the noradrenergic system. I note clinically-relevant factors that could mediate/moderate the efficacy of anti-stress therapeutics and identify research gaps that should be pursued. Finally, progress in developing anti-stress medications will depend on use of reliable CNS biomarkers to validate exposure-response relationships.

Sex difference in brain CB1 receptor availability in man

The endocannabinoid system (ECS) has a widespread neuromodulatory function in the central nervous system and is involved in important aspects of brain function including brain development, cortical rhythms, plasticity, reward, and stress sensitivity. Many of these effects are mediated via the cannabinoid CB1 receptor (CB1R) subtype. Animal studies convincingly show an interaction between the ECS and sex hormones, as well as a sex difference of higher brain CB1R in males. Human in vivo studies of sex difference have yielded discrepant findings. Gender differences in CB1R availability were investigated in vivo in 11 male and 11 female healthy volunteers using a specific CB1R tracer [¹⁸F]FMPEP-d2 and positron emission tomography (PET). Regional [¹⁸F]FMPEP-d2 distribution volume was used as a proxy for CB1R availability. In addition, we explored whether CB1R availability is linked to neuropsychological functioning. Relative to females, CB1R availability was on average 41% higher in males (p = 0.002) with a regionally specific effect larger in the posterior cingulate and retrosplenial cortices (p = 0.001). Inter-subject variability in CB1R availability was similar in both groups. Voxel-based analyses revealed an inverse association between CB1R availability and visuospatial working memory task performance in both groups (p < 0.001). A CB1R sex difference with a large effect size was observed and should be considered in the design of CB1R-related studies on neuropsychiatric disorders. The behavioural correlates and clinical significance of this difference remain to be further elucidated, but our studies suggest an association between CB1R availability and working memory.

Δ9-Tetrahydrocannabinol induces endocannabinoid accumulation in mouse hepatocytes: antagonism by Fabp1 gene ablation

Phytocannabinoids, such as Δ9-tetrahydrocannabinol (THC), bind and activate cannabinoid (CB) receptors, thereby "piggy-backing" on the same pathway's endogenous endocannabinoids (ECs). The recent discovery that liver fatty acid binding protein-1 (FABP1) is the major cytosolic "chaperone" protein with high affinity for both Δ9-THC and ECs suggests that Δ9-THC may alter hepatic EC levels. Therefore, the impact of Δ9-THC or EC treatment on the levels of endogenous ECs, such as N-arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG), was examined in cultured primary mouse hepatocytes from WT and Fabp1 gene-ablated (LKO) mice. Δ9-THC alone or 2-AG alone significantly increased AEA and especially 2-AG levels in WT hepatocytes. LKO alone markedly increased AEA and 2-AG levels. However, LKO blocked/diminished the ability of Δ9-THC to further increase both AEA and 2-AG. In contrast, LKO potentiated the ability of exogenous 2-AG to increase the hepatocyte level of AEA and 2-AG. These and other data suggest that Δ9-THC increases hepatocyte EC levels, at least in part, by upregulating endogenous AEA and 2-AG levels. This may arise from Δ9-THC competing with AEA and 2-AG binding to FABP1, thereby decreasing targeting of bound AEA and 2-AG to the degradative enzymes, fatty acid amide hydrolase and monoacylglyceride lipase, to decrease hydrolysis within hepatocytes.

Current evidence of cannabinoid-based analgesia obtained in preclinical and human experimental settings

Cannabinoids have a long record of recreational and medical use and become increasingly approved for pain therapy. This development is based on preclinical and human experimental research summarized in this review. Cannabinoid CB₁ receptors are widely expressed throughout the nociceptive system. Their activation by endogenous or exogenous cannabinoids modulates the release of neurotransmitters. This is reflected in antinociceptive effects of cannabinoids in preclinical models of inflammatory, cancer and neuropathic pain, and by nociceptive hypersensitivity of cannabinoid receptor-deficient mice. Cannabis-based medications available for humans mainly comprise Δ⁹ -tetrahydrocannabinol (THC), cannabidiol (CBD) and nabilone. During the last 10 years, six controlled studies assessing analgesic effects of cannabinoid-based drugs in human experimental settings were reported. An effect on nociceptive processing could be translated to the human setting in functional magnetic resonance imaging studies that pointed at a reduced connectivity within the pain matrix of the brain. However, cannabinoid-based drugs heterogeneously influenced the perception of experimentally induced pain including a reduction in only the affective but not the sensory perception of pain, only moderate analgesic effects, or occasional hyperalgesic effects. This extends to the clinical setting. While controlled studies showed a lack of robust analgesic effects, cannabis was nearly always associated with analgesia in open-label or retrospective reports, possibly indicating an effect on well-being or mood, rather than on sensory pain. Thus, while preclinical evidence supports cannabinoid-based analgesics, human evidence presently provides only reluctant support for a broad clinical use of cannabinoid-based medications in pain therapy.

SIGNIFICANCE

Cannabinoids consistently produced antinociceptive effects in preclinical models, whereas they heterogeneously influenced the perception of experimentally induced pain in humans and did not provide robust clinical analgesia, which jeopardizes the translation of preclinical research on cannabinoid-mediated antinociception into the human setting.

Effects of oral Δ9-tetrahydrocannabinol on the cerebral processing of olfactory input in healthy non-addicted subjects

BACKGROUND

Considering the increasing acknowledgment of the human sense of smell as a significant component of the quality of life, olfactory drug effects gain potential clinical importance. A recent observation in a human experimental context indicated that Δ⁹-tetrahydrocannabinol (THC) impaired the subject's performance in olfactory tests. To further analyze the role of THC in human olfaction, the present report addresses its effects on the central processing of olfactory stimuli.

METHODS

Employing a placebo-controlled randomized crossover design, an oral dose of 20 mg THC was administered in 15 healthy volunteers. The central processing of olfactory input, consisting of short pulses of gaseous vanillin or hydrogen sulfide, and for comparison, of non-odorous but painful carbon dioxide, were investigated before and after administration of THC or placebo in a pharmacological functional magnet resonance imaging study.

RESULTS

Following THC administration, the vanillin stimuli lost their pleasantness and became hedonically inert. This observation had its functional correlate in reduced stimulus-associated brain activations located in the left amygdala, the hippocampus and superior temporal pole (peak MNI coordinates x = - 27, y = - 1, z = - 26 mm p = 0.039). Differences in amygdala activations were significantly correlated with the corresponding differences in vanillin pleasantness (p = 0.025). By contrast, no effects were observed on the perception of processing of H₂S stimuli.

CONCLUSIONS

The results support that THC induced a modulation of the central processing of olfactory input. The THC-induced reduction in the pleasantness of a pleasurable odor was accompanied by reduced activations in the limbic system. Results agree with previous observation of negative effects of cannabinoids on the human sense of smell and strengthen the evidence that THC-based medications will be among drugs with olfactory side effects.

Brain Mapping-Based Model of Δ(9)-Tetrahydrocannabinol Effects on Connectivity in the Pain Matrix

Cannabinoids receive increasing interest as analgesic treatments. However, the clinical use of Δ(9)-tetrahydrocannabinol (Δ(9)-THC) has progressed with justified caution, which also owes to the incomplete mechanistic understanding of its analgesic effects, in particular its interference with the processing of sensory or affective components of pain. The present placebo-controlled crossover study therefore focused on the effects of 20 mg oral THC on the connectivity between brain areas of the pain matrix following experimental stimulation of trigeminal nocisensors in 15 non-addicted healthy volunteers. A general linear model (GLM) analysis identified reduced activations in the hippocampus and the anterior insula following THC administration. However, assessment of psychophysiological interaction (PPI) revealed that the effects of THC first consisted in a weakening of the interaction between the thalamus and the secondary somatosensory cortex (S2). From there, dynamic causal modeling (DCM) was employed to infer that THC attenuated the connections to the hippocampus and to the anterior insula, suggesting that the reduced activations in these regions are secondary to a reduction of the connectivity from somatosensory regions by THC. These findings may have consequences for the way THC effects are currently interpreted: as cannabinoids are increasingly considered in pain treatment, present results provide relevant information about how THC interferes with the affective component of pain. Specifically, the present experiment suggests that THC does not selectively affect limbic regions, but rather interferes with sensory processing which in turn reduces sensory-limbic connectivity, leading to deactivation of affective regions.

Circulating Endocannabinoids and Insulin Resistance in Patients with Obstructive Sleep Apnea

Objectives. The purpose of this study is to investigate the relationship between plasma endocannabinoids and insulin resistance (IR) in patients with obstructive sleep apnea (OSA). Methods. A population of 64 with OSA and 24 control subjects was recruited. Body mass index (BMI), waist circumference, lipids, blood glucose and insulin, homeostasis model of assessment for insulin resistance index (HOMA-IR), anandamide (AEA), 1/2-arachidonoylglycerol (1/2-AG), and apnea-hypopnea index (AHI) were analyzed. Results. Fasting blood insulin (22.9 ± 7.8 mIU/L versus 18.5 ± 7.2 mIU/L, P < 0.05), HOMA-IR (2.9 ± 1.0 versus 2.4 ± 0.9, P < 0.01), AEA (3.2 ± 0.7 nmol/L versus 2.5 ± 0.6 nmol/L, P < 0.01), and 1/2-AG (40.8 ± 5.7 nmol/L versus 34.3 ± 7.7 nmol/L, P < 0.01) were higher in OSA group than those in control group. In OSA group, AEA, 1/2-AG, and HOMA-IR increase with the OSA severity. The correlation analysis showed significant positive correlation between HOMA-IR and AHI (r = 0.44, P < 0.01), AEA and AHI (r = 0.52, P < 0.01), AEA and HOMA-IR (r = 0.62, P < 0.01), and 1/2-AG and HOMA-IR (r = 0.33, P < 0.01). Further analysis showed that only AEA was significantly correlated with AHI and HOMA-IR after adjusting for confounding factors. Conclusions. The present study indicated that plasma endocannabinoids levels, especially AEA, were associated with IR and AHI in patients with OSA.

Effects of 20 mg oral Δ(9) -tetrahydrocannabinol on the olfactory function of healthy volunteers

AIMS

Olfactory loss impairs the patient's quality of life. In individualized therapies, olfactory drug effects gain clinical importance. Molecular evidence suggests that among drugs with potential olfactory effects is Δ(9) -tetrahydrocannabinol (THC), which is approved for several indications, including neuropathic pain or analgesia in cancer patients. The present study aimed at assessing the olfactory effects of THC to be expected during analgesic treatment.

METHODS

The effects of 20 mg oral THC on olfaction were assessed in a placebo-controlled, randomized cross-over study in healthy volunteers. Using an established olfactory test (Sniffin' Sticks), olfactory thresholds, odour discrimination and odour identification were assessed in 15 subjects at baseline and 2 h after THC administration.

RESULTS

Δ(9) -Tetrahydrocannabinol impaired the performance of subjects (n = 15) in the olfactory test. Specifically, olfactory thresholds were increased and odour discrimination performance was reduced. This resulted in a significant drop in composite threshold, discrimination, identification (TDI) olfactory score by 5.5 points (from 37.7 ± 4.2 to 32.2 ± 5.6, 95% confidence interval for differences THC vs. placebo, -7.8 to -2.0, P = 0.003), which is known to be a subjectively perceptible impairment of olfactory function.

CONCLUSIONS

Considering the resurgence of THC in medical use for several pathological conditions, the present results indicate that THC-based analgesics may be accompanied by subjectively noticeable reductions in olfactory acuity. In particular, for patients relying on their sense of smell, this might be relevant information for personalized therapy strategies.

Fatty acid-binding proteins (FABPs) are intracellular carriers for Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD)

Δ(9)-Tetrahydrocannabinol (THC) and cannabidiol (CBD) occur naturally in marijuana (Cannabis) and may be formulated, individually or in combination in pharmaceuticals such as Marinol or Sativex. Although it is known that these hydrophobic compounds can be transported in blood by albumin or lipoproteins, the intracellular carrier has not been identified. Recent reports suggest that CBD and THC elevate the levels of the endocannabinoid anandamide (AEA) when administered to humans, suggesting that phytocannabinoids target cellular proteins involved in endocannabinoid clearance. Fatty acid-binding proteins (FABPs) are intracellular proteins that mediate AEA transport to its catabolic enzyme fatty acid amide hydrolase (FAAH). By computational analysis and ligand displacement assays, we show that at least three human FABPs bind THC and CBD and demonstrate that THC and CBD inhibit the cellular uptake and catabolism of AEA by targeting FABPs. Furthermore, we show that in contrast to rodent FAAH, CBD does not inhibit the enzymatic actions of human FAAH, and thus FAAH inhibition cannot account for the observed increase in circulating AEA in humans following CBD consumption. Using computational molecular docking and site-directed mutagenesis we identify key residues within the active site of FAAH that confer the species-specific sensitivity to inhibition by CBD. Competition for FABPs may in part or wholly explain the increased circulating levels of endocannabinoids reported after consumption of cannabinoids. These data shed light on the mechanism of action of CBD in modulating the endocannabinoid tone in vivo and may explain, in part, its reported efficacy toward epilepsy and other neurological disorders.

Disrupted gamma-band neural oscillations during coherent motion perception in heavy cannabis users

Previous work in animals and humans has shown that exogenous cannabinoids disrupt time-locked, evoked gamma oscillations (30-80 Hz). However, no studies to date have examined the effect of cannabis on non-time-locked, induced gamma oscillations during more complex Gestalt perception. The current study therefore utilized electroencephalography (EEG) to examine gamma oscillations during coherent motion perception in heavy cannabis users and controls. Chronic cannabis users (n = 24; 12 h abstinence before study; positive 11-nor-9-carboxy-delta-9-tetrahydrocannabinol urine levels) and cannabis-naive controls (n = 23) were evaluated. Stimuli consisted of random dot kinetograms (RDKs) that subjects passively viewed during three different conditions: coherent motion, incoherent motion, and static. Time × frequency analysis on EEG data was performed using Fourier-based mean trial power (MTP). Transient event-related potentials (ERPs) to stimulus onset (visual N100 and P200 components) were also evaluated. The results showed that the coherent motion condition produced a robust increase in neural activity in the gamma range (induced power from 40 to 59 Hz) as compared with the incoherent motion and static conditions. As predicted, the cannabis group showed significant reductions in induced gamma power in the coherent condition relative to healthy controls. No differences were observed between the groups in the N100 or P200 components, indicating intact primary sensory processing. Finally, cannabis users showed a trend toward increased scores on the Chapman Perceptual Aberration Scale (PAS) that was positively correlated with total years of active cannabis use. These data suggest that cannabis use may interfere with the generation of induced gamma-band neural oscillations that could in part mediate the perceptual-altering effects of exogenous cannabinoids.

Regulation of circulating endocannabinoids associated with cancer and metastases in mice and humans

BACKGROUND AND AIMS

Endocannabinoids may modify cancer development, progression and associated pain. We determined whether cancer-evoked dysregulations in this system become manifest in altered tissue and plasma endocannabinoids.

METHODS

Endocannabinoid changes due to cancer were explored in a local and metastatic syngeneic mouse melanoma model. Endocannabinoid stratification in human cancer was cross-sectionally assessed in the plasma of 304 patients (147 men, 157 women, aged 32 - 87 years) suffering from several types of cancer at Roman Numeral Staging between I and IVc, mostly IV (n = 220), and compared with endocannabinoids of healthy controls.

RESULTS

In mice with local tumor growth, ethanolamide endocannabinoids, i.e., anandamide (AEA), palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) were downregulated, whereas 2-arachidonoylglycerol (2-AG) was increased. Upon spreading of the cancer cells particularly 2-AG steadily increased in parallel to disease progression while OEA modulated cell migration. Results translated into humans, in whom cancer was associated with a decreased AEA, increased 2-AG and increased OEA correlating with the number of metastases.

CONCLUSIONS

The endocannabinoid system was subject to cancer-associated regulations to an extent that led to measurable changes in circulating endocannabinoid levels, emphasizing the importance of the endocannabinoid system in the pathophysiology of cancer.