Advances in targeted liquid chromatography-tandem mass spectrometry methods for endocannabinoid and N-acylethanolamine quantification in biological matrices: A systematic review

Liquid chromatography paired with tandem mass spectrometry (LC-MS/MS) is the gold standard in measurement of endocannabinoid concentrations in biomatrices. We conducted a systematic review of literature to identify advances in targeted LC-MS/MS methods in the period 2017-2024. We found that LC-MS/MS methods for endocannabinoid quantification are relatively consistent both across time and across biomatrices. Recent advances have primarily been in three areas: (1) sample preparation techniques, specific to the chosen biomatrix; (2) the range of biomatrices tested, recently favoring blood matrices; and (3) the breadth of endocannabinoid and endocannabinoid-like analytes incorporated into assays. This review provides a summary of the recent literature and a guide for researchers looking to establish the best methods for quantifying endocannabinoids in a range of biomatrices.

Hair and Saliva Endocannabinoid and Steroid Hormone Analysis by Liquid Chromatography Paired with Tandem Mass Spectrometry

Endocannabinoids are lipid neurotransmitters that play an important part in human health. Recent methods have found that quantification of endocannabinoids in hair and saliva samples is possible using liquid chromatography paired with tandem mass spectrometry (LC-MS/MS). This chapter describes two simple sample preparation methods that can be used to prepare hair and saliva samples for analysis using LC-MS/MS. Our LC-MS/MS method can be applied to both hair and saliva samples and is sufficiently sensitive for endocannabinoid, as well as steroid hormone, quantification in both of these sample matrices. This chapter provides a comprehensive description of how this can be achieved and provides tips and tricks for troubleshooting problems users may experience.

Hair endocannabinoids predict physiological fear conditioning and salivary endocannabinoids predict subjective stress reactivity in humans

On the basis of substantial preclinical evidence, the endogenous cannabinoid system has been proposed to be closely involved in stress reactivity and extinction of fear. Existing human research supports this proposal to some extent, but existing studies have used only a narrow range of tools and biomatrices to measure endocannabinoids during stress and fear experiments. In the present study we collected hair and saliva samples from 99 healthy participants who completed a fear conditioning and intrusive memory task. Subjective, physiological and biological stress reactivity to a trauma film, which later served as unconditional stimulus during fear conditioning, was also measured. We found that salivary endocannabinoid concentrations predicted subjective responses to stress, but not cortisol stress reactivity, and replicated previous findings demonstrating a sex dimorphism in hair and salivary endocannabinoid levels. Hair 2-arachidonoyl glycerol levels were significantly associated with better retention of safety learning during extinction and renewal phases of fear conditioning, while hair concentrations of oleoylethanolamide and palmitoylethanolamide were associated with overall physiological arousal, but not conditional learning, during fear conditioning. This study is the first to test the relationship between hair and salivary endocannabinoids and these important psychological processes. Our results suggest that these measures may serve as biomarkers of dysregulation in human fear memory and stress.

Reduced Endocannabinoid Tone in Saliva of Chronic Orofacial Pain Patients

Background: the endocannabinoid system (ECS) participates in many physiological and pathological processes including pain generation, modulation, and sensation. Its involvement in chronic orofacial pain (OFP) in general, and the reflection of its involvement in OFP in salivary endocannabinoid (eCBs) levels in particular, has not been examined. Objectives: to evaluate the association between salivary (eCBs) levels and chronic OFP. Methods: salivary levels of 2 eCBs, anandamide (AEA), 2-arachidonoylglycerol (2-AG), 2 endocannabinoid-like compoundsN-palmitoylethanolamine (PEA), N-oleoylethanolamine (OEA), and their endogenous precursor and breakdown product, arachidonic acid (AA), were analyzed using liquid chromatography/tandem mass spectrometry in 83 chronic OFP patients and 43 pain-free controls. The chronic OFP patients were divided according to diagnosis into musculoskeletal, neurovascular/migraine, and neuropathic pain types. Results: chronic OFP patients had lower levels of OEA (p = 0.02) and 2-AG (p = 0.01). Analyzing specific pain types revealed lower levels of AEA and OEA in the neurovascular group (p = 0.04, 0.02, respectively), and 2-AG in the neuropathic group compared to controls (p = 0.05). No significant differences were found between the musculoskeletal pain group and controls. Higher pain intensity was accompanied by lower levels of AA (p = 0.028), in neuropathic group. Conclusions: lower levels of eCBs were found in the saliva of chronic OFP patients compared to controls, specifically those with neurovascular/migraine, and neuropathic pain. The detection of changes in salivary endocannabinoids levels related to OFP adds a new dimension to our understanding of OFP mechanisms, and may have diagnostic as well as therapeutic implications for pain.

Owens J, Barbian ME, Jones RM, R. Naudin C. At the heart of microbial conversations: endocannabinoids and the microbiome in cardiometabolic risk

Cardiometabolic syndrome encompasses intertwined risk factors such as hypertension, dyslipidemia, elevated triglycerides, abdominal obesity, and other maladaptive metabolic and inflammatory aberrations. As the molecular mechanisms linking cardiovascular disease and metabolic disorders are investigated, endocannabinoids have emerged as molecules of interest. The endocannabinoid system (ECS) of biologically active lipids has been implicated in several conditions, including chronic liver disease, osteoporosis, and more recently in cardiovascular diseases. The gut microbiome is a major regulator of inflammatory and metabolic signaling in the host, and if disrupted, has the potential to drive metabolic and cardiovascular diseases. Extensive studies have unraveled the impact of the gut microbiome on host physiology, with recent reports showing that gut microbes exquisitely control the ECS, with significant influences on host metabolic and cardiac health. In this review, we outline how modulation of the gut microbiome affects host metabolism and cardiovascular health via the ECS, and how these findings could be exploited as novel therapeutic targets for various metabolic and cardiac diseases.

Synthesis and molecular targets of N-13-hydroxy-octadienoyl-ethanolamine, a novel endogenous bioactive 15-lipoxygenase-derived metabolite of N-linoleoyl-ethanolamine found in the skin and saliva

N-Arachidonoyl-ethanolamine (AEA) is an endocannabinoid (eCB) and endogenous lipid mimicking many of the effects of Δ9-tetrahydrocannabinol, notably on brain functions, appetite, pain and inflammation. The eCBs and eCB-like compounds contain fatty acids, the main classes being the monoacylglycerols and the N-acyl-ethanolamines (NAEs). Thus, each long chain fatty acid likely exists under the form of a monoacylglycerol and NAE, as it is the case for arachidonic acid (AA) and linoleic acid (LA). Following their biosynthesis, AA and AEA can be further metabolized into additional eicosanoids, notably by the 15-lipoxygenase pathway. Thus, we postulated that NAEs possessing a 1Z,4Z-pentadiene motif, near their omega end, would be transformed into their 15-lipoxygenase metabolites. As a proof of concept, we investigated N-linoleoyl-ethanolamine (LAE). We successfully synthesized LEA and LEA-d4 as well as their 15-lipoxygenase-derived derivatives, namely 13-hydroxy-9Z,11E-octadecadienoyl-N-ethanolamine (13-HODE-EA) and 13-HODE-EA-d4, using Novozyme 435 immobilized on acrylic resin and soybean lipoxygenase respectively. We also show that both human 15-lipoxygenase-1 and -2 can biosynthesize 13-HODE-EA. Co-incubation of LEA and LA with either human 15-lipoxygenase led to the biosynthesis of 13-HODE-EA and 13-HODE in a ratio equal to or greater than 3:1, indicating that LEA is preferred to LA by these enzymes. Finally, we show that 13-HODE-EA is found in human saliva and skin and is a weak although selective TRPV1 agonist. The full biological importance of 13-HODE-EA remains to be explored.

Role of the Endocannabinoid System in the Adipose Tissue with Focus on Energy Metabolism

The endocannabinoid system is involved in a wide range of processes including the control of energy acquisition and expenditure. Endocannabinoids and their receptors are present in the central nervous system but also in peripheral tissues, notably the adipose tissues. The endocannabinoid system interacts with two main hormones regulating appetite, namely leptin and ghrelin. The inhibitory effect of the cannabinoid receptor 1 (CB₁) antagonist rimonabant on fat mass suggested that the endocannabinoid system can also have a peripheral action in addition to its effect on appetite reduction. Thus, several investigations have focused on the peripheral role of the endocannabinoid system in the regulation of metabolism. The white adipose tissue stores energy as triglycerides while the brown adipose tissue helps to dissipate energy as heat. The endocannabinoid system regulates several functions of the adipose tissues to favor energy accumulation. In this review we will describe the presence of the endocannabinoid system in the adipose tissue. We will survey the role of the endocannabinoid system in the regulation of white and brown adipose tissue metabolism and how the eCB system participates in obesity and metabolic diseases.

Endocannabinoid reactivity to acute stress: Investigation of the relationship between salivary and plasma levels

The endogenous cannabinoid (eCB) system has been shown in animal models to regulate the initiation and termination of central nervous responses to stress. In human studies, the role of peripherally measured eCBs is much less clear and the effect in salivary eCBs has not been studied. In this study, we use a novel method to quantify cortisol and eCBs arachidonoyl ethanolamide (AEA) and 2-arachidonoyl glycerol (2-AG) in human saliva, as well as in plasma samples. Forty-five females and 32 males completed a mixed physiological/psychosocial stress-induction study where saliva, and blood samples in males, were collected at baseline, immediately following, 30-minutes following, and 45-minutes following stress induction. Cortisol significantly increased after stress, but there were sex differences in the cortisol response to stress, with females having higher cortisol after stress compared to males. There was a significant increase in salivary levels of 2-AG immediately following stress induction, but no effect of AEA. Salivary AEA was higher in males compared to females. Surprisingly, there was no effect of stress on plasma AEA or 2-AG levels in the male cohort, though small effect sizes for 2-AG were observed, which is consistent with most other human literature. This study is the first to show that the eCB system is active in human saliva and is responsive to acute stress, possibly as part of the sympathetic nervous system response.

Endocannabinoids, endocannabinoid-like molecules and their precursors in human small intestinal lumen and plasma: does diet affect them?

PURPOSE

To determine the small intestinal concentration of endocannabinoids (ECs), N-acylethanolamines (NAEs) and their precursors N-acylphosphatidylethanolamines (NAPEs) in humans. To identify relationships between those concentrations and habitual diet composition as well as individual inflammatory status.

METHODS

An observational study was performed involving 35 participants with an ileostomy (18W/17M, aged 18-70 years, BMI 17-40 kg/m²). Overnight fasting samples of ileal fluid and plasma were collected and ECs, NAEs and NAPEs concentrations were determined by LC-HRMS. Dietary data were estimated from self-reported 4-day food diaries.

RESULTS

Regarding ECs, N-arachidonoylethanolamide (AEA) was not detected in ileal fluids while 2-arachidonoylglycerol (2-AG) was identified in samples from two participants with a maximum concentration of 129.3 µg/mL. In contrast, mean plasma concentration of AEA was 2.1 ± 0.06 ng/mL and 2-AG was 4.9 ± 1.05 ng/mL. NAEs concentrations were in the range 0.72-17.6 µg/mL in ileal fluids and 0.014-0.039 µg/mL in plasma. NAPEs concentrations were in the range 0.3-71.5 µg/mL in ileal fluids and 0.19-1.24 µg/mL in plasma being more abundant in participants with obesity than normal weight and overweight. Significant correlations between the concentrations of AEA, OEA and LEA in biological fluids with habitual energy or fat intakes were identified. Plasma PEA positively correlated with serum C-reactive protein.

CONCLUSION

We quantified ECs, NAEs and NAPEs in the intestinal lumen. Fat and energy intake may influence plasma and intestinal concentrations of these compounds. The luminal concentrations reported would allow modulation of the homeostatic control of food intake via activation of GPR119 receptors located on the gastro-intestinal mucosa.

CLINICAL TRIAL REGISTRY NUMBER AND WEBSITE

NCT04143139; www.clinicaltrials.gov .

Simultaneous quantification of endocannabinoids, oleoylethanolamide and steroid hormones in human plasma and saliva

Endogenous cannabinoids are an increasingly intriguing target for biological research, given the changing legal status of medicinal cannabinoid-based products throughout the world. However, studying the endogenous cannabinoid system is a relatively new field, with few research teams attempting to develop quantitative methods for these important modulatory analytes in human matrices, other than blood. Here we develop and validate simultaneous methods for quantifying arachidonoyl-ethanolamide, 2-arachidonoyl glycerol, oleoylethanolamide, cortisol and progesterone in human plasma and saliva using liquid-liquid extraction combined with ultra-high performance liquid chromatography coupled to tandem mass spectrometry. The method was fully validated over the linear concentration range 1-20 ng/mL for each analyte in plasma (R² = 0.98-0.99) and saliva (R² = 0.99). We find that salivary endogenous cannabinoids and cortisol are acutely responsive to exercise, suggesting that targeting the saliva system may present a convenient way for future research of endogenous cannabinoids. This finding also encourages a broader understanding of the endogenous cannabinoid system during stress responses, and our method may consequently lead to a better understanding of the role of endogenous cannabinoids in peripheral tissues.

N-Acylphosphatidylethanolamines and N-acylethanolamines increase in saliva upon food mastication: the influence of the individual nutritional status and fat type in food

This study aimed to evaluate the influence of the individual nutritional status on the salivary concentration of N-acylethanolamines (NAEs), including linoleoylethanolamide (LEA), oleoylethanolamide (OEA), and palmitoylethanolamide (PEA), and their precursors N-acylphosphatidylethanolamines (NAPEs) upon mastication of biscuits containing different fats. Three types of biscuits were formulated with 10% extra-virgin olive oil (EVOB), 10% palm oil (PALMB) or 10% paraffin oil (0% lipids, CONB). Twenty-five healthy subjects, 12 normal weight (NW, 9 F, 30.4 ± 8.7 years) and 13 obese (OB, 8 F, 35.5 ± 10.7 years) participated in a randomized crossover study. Fasting subjects collected unstimulated saliva (US) and stimulated saliva by masticating a parafilm piece (PP), and CONB, EVOB and PALMB. NAPEs, LEA, OEA and PEA were quantified in saliva samples by liquid chromatography-high-resolution mass spectrometry. The results showed that salivary NAPE and NAE concentrations in OB were higher than in NW in both US (NAPEs: 280.0 ± 45.4 ng mL-1vs. 121.8 ± 24.4 ng mL-1, p = 0.015; NAEs: 10.8 ± 1.4 ng mL-1vs. 4.8 ± 0.8 ng mL-1, p = 0.002, respectively) and PP (NAPEs: 259.8 ± 47.1 ng mL-1vs. 121.7 ± 16.9 ng mL-1, p = 0.049; NAEs: 6.1 ± 0.8 ng mL-1vs. 3.8 ± 0.4 ng mL-1, p = 0.03, respectively). NAPE and LEA levels were similar in US and PP, while the levels of OEA and PEA were lower in PP vs. US. Compared to PP, biscuit mastication increased the salivary NAPEs, LEA, OEA and overall NAEs in NW and OB. NAPEs increased in the order of EVOB = CONB > PALMB in NW and EVOB > CONB = PALMB in OB. LEA, OEA and overall NAEs increased similarly with all the biscuits in NW and in the order of EVOB > PALMB > CONB in OB. In contrast, the PEA concentration did not vary in saliva upon biscuit mastication in NW and neither with EVOB in OB, while it lowered with CONB and PALMB in OB. In conclusion, OB showed higher salivary levels of NAPEs and NAEs than NW. Mastication itself did not vary salivary NAPEs and LEA but reduced OEA, PEA and overall NAEs. Biscuit mastication increased salivary NAPEs and all NAEs, but PEA. Altogether, the data suggested that NAPEs and NAEs were released in saliva from biscuits at levels influenced by the individual nutritional status and biscuit type. These findings may have implications in molecular mechanisms underpinning gustatory processes in humans.

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram-positive and Gram-negative bacteria

In this study, the endogenous lipid signalling molecules, N-myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂S NPs are spherical in shape with a size of 5-30 and 8-30 nm, respectively. AgNPs and Ag₂S NPs exhibit antimicrobial activity against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.

The endocannabinoid system: Novel targets for treating cancer induced bone pain

Treating Cancer-induced bone pain (CIBP) continues to be a major clinical challenge and underlying mechanisms of CIBP remain unclear. Recently, emerging body of evidence suggested the endocannabinoid system (ECS) may play essential roles in CIBP. Here, we summarized the current understanding of the antinociceptive mechanisms of endocannabinoids in CIBP and discussed the beneficial effects of endocannabinoid for CIBP treatment. Targeting non-selective cannabinoid 1 receptors or selective cannabinoid 2 receptors, and modulation of peripheral AEA and 2-AG, as well as the inhibition the function of fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL) have produced analgesic effects in animal models of CIBP. Management of ECS therefore appears to be a promising way for the treatment of CIBP in terms of efficacy and safety. Further clinical studies are encouraged to confirm the possible translation to humans of the very promising results already obtained in the preclinical studies.

Food database of N-acyl-phosphatidylethanolamines, N-acylethanolamines and endocannabinoids and daily intake from a Western, a Mediterranean and a vegetarian diet

The contents of N-acylphosphatidylethanolamines (NAPEs), N-acylethanolamines (NAEs) and endocannabinoids (ECs) in 43 food products were assessed and daily intakes, based on consumption of Mediterranean, vegetarian and Western diets, were simulated. NAPEs and NAEs were more abundant in plant-based foods than in animal food products; NAPEs were in the ranges 0-4032 vs 4-398 µg/g dw and NAEs were in the ranges 0-35 vs 0.1-0.7 µg/g dw, respectively while ECs were in the range 0-0.1 vs 0-34 µg/g dw. Daily intakes of NAPEs and NAEs were higher from Mediterranean (263 and 0.25 mg/day) and vegetarian (242 and 0.28 mg/day) diets than the Western diet (163 and 0.08 mg/day). Conversely, ECs intakes were higher from Western and Mediterranean diets (0.17 mg/day) than the vegetarian diet (0.01 mg/day). Future studies will evaluate the physiological role of dietary NAPEs, NAEs and ECs in humans.