Cytotoxicity, metabolism, and isozyme mapping of the synthetic cannabinoids JWH-200, A-796260, and 5F-EMB-PINACA studied by means of in vitro systems

Metabolism and cytotoxicity studies of the two hallucinogens 1cP-LSD and 4-AcO-DET in human liver and zebrafish larvae models using LC-HRMS/MS and a high-content screening assay

The continuous emergence of new psychoactive substances (NPS) attracted a great deal of attention within recent years. Lately, the two hallucinogenic NPS 1cP-LSD and 4-AcO-DET have appeared on the global market. Knowledge about their metabolism to identify potential metabolic targets for analysis and their cytotoxic properties is lacking. The aim of this work was thus to study their in vitro and in vivo metabolism in pooled human liver S9 fraction (pHLS9) and in zebrafish larvae (ZL) by means of liquid chromatography-high-resolution tandem mass spectrometry. Monooxygenases involved in the initial metabolic steps were elucidated using recombinant human isozymes. Investigations on their cytotoxicity were performed on the human hepatoma cell line HepG2 using a multiparametric, fluorescence-based high-content screening assay. This included measurement of CYP-enzyme mediated effects by means of the unspecific CYP inhibitor 1-aminbenzotriazole (ABT). Several phase I metabolites of both compounds and two phase II metabolites of 4-AcO-DET were produced in vitro and in vivo. After microinjection of 1cP-LSD into the caudal vein of ZL, three out of seven metabolites formed in pHLS9 were also detected in ZL. Twelve 4-AcO-DET metabolites were identified in ZL after exposure via immersion bath and five of them were found in pHLS9 incubations. Notably, unique metabolites of 4-AcO-DET were only produced by ZL, whereas 1cP-LSD specific metabolites were found both in ZL and in pHLS9. No toxic effects were observed for 1cP-LSD and 4-AcO-DET in HepG2 cells, however, two parameters were altered in incubations containing 4-AcO-DET together with ABT compared with incubations without ABT but in concentrations far above expected in vivo concentration. Further investigations should be done with other hepatic cell lines expressing higher levels of CYP enzymes.

Exposure to Synthetic Psychoactive Substances: A Potential Cause for Increased Human Hepatotoxicity Markers

BACKGROUND

Approximately 30 million people worldwide consume new psychoactive substances (NPS), creating a serious public health issue due to their toxicity and potency. Drug-induced liver injury is the leading cause of liver disease, responsible for 4% of global deaths each year.

CONTENT

A systematic literature search revealed 64 case reports, in vitro and in vivo studies on NPS hepatotoxicity. Maximum elevated concentrations of aspartate aminotransferase (136 to 15 632 U/L), alanine transaminase (121.5 to 9162 U/L), total bilirubin (0.7 to 702 mg/dL; 0.04 to 39.03 mmol/L), direct (0.2-15.1 mg/dL; 0.01-0.84 mmol/L) and indirect (5.3 mg/dL; 0.29 mmol/L) bilirubin, alkaline phosphatase (79-260 U/L), and gamma-glutamyltransferase (260 U/L) were observed as biochemical markers of liver damage, with acute and fulminant liver failure the major toxic effects described in the NPS case reports. In vitro laboratory studies and subsequent in vivo NPS exposure studies on rats and mice provide data on potential mechanisms of toxicity. Oxidative stress, plasma membrane stability, and cellular energy changes led to apoptosis and cell death. Experimental studies of human liver microsome incubation with synthetic NPS, with and without specific cytochrome P450 inhibitors, highlighted specific enzyme inhibitions and potential drug-drug interactions leading to hepatotoxicity.

SUMMARY

Mild to severe hepatotoxic effects following synthetic NPS exposure were described in case reports. In diagnosing the etiology of liver damage, synthetic NPS exposure should be considered as part of the differential diagnosis. Identification of NPS toxicity is important for educating patients on the dangers of NPS consumption and to suggest promising treatments for observed hepatotoxicity.

Synthetic Cannabinoids: A Pharmacological and Toxicological Overview

Synthetic cannabinoids (SCs) are a chemically diverse group of new psychoactive substances (NPSs) that target the endocannabinoid system, triggering a plethora of actions (e.g., elevated mood sensation, relaxation, appetite stimulation) that resemble, but are more intense than, those induced by cannabis. Although some of these effects have been explored for therapeutic applications, anticipated stronger psychoactive effects than cannabis and reduced risk perception have increased the recreational use of SCs, which have dominated the NPS market in the United States and Europe over the past decade. However, rising SC-related intoxications and deaths represent a major public health concern and embody a major challenge for policy makers. Here, we review the pharmacology and toxicology of SCs. A thorough characterization of SCs' pharmacodynamics and toxicodynamics is important to better understand the main mechanisms underlying acute and chronic effects of SCs, interpret the clinical/pathological findings related to SC use, and improve SC risk awareness.

A simplified strategy to assess the cytotoxicity of new psychoactive substances in HepG2 cells using a high content screening assay - Exemplified for nine compounds

New psychoactive substances (NPS) are an issue of global concern posing a serious threat to the healthcare systems. Consumption of some NPS has been associated with toxic effects on the liver amongst others. However, data concerning their (cyto-)toxicity are usually not available. For a straightforward assessment of their cytotoxic potential, a simplified strategy measuring six different cytotoxicity indicating parameters simultaneously by a high content screening assay (HCSA) was developed. Its applicability was further investigated using nine NPS from heterogeneous chemical classes. HepG2 cells were incubated with NPS for 48 h at a low and high concentration (7.81 and 125 µM), respectively. To study metabolism-mediated effects on their cytotoxicity, cells were additionally incubated with the unspecific cytochrome (CYP) P450 inhibitor 1-aminobenzotriazole. Four fluorescence dyes were used to monitor cell count, nuclear size, and nuclear intensity (all Hoechst33342), mitochondrial membrane potential (TMRM), cytoplasmic calcium levels (CAL-520), and plasma membrane integrity (TOTO-3). Amongst the investigated NPS, ephylone, CUMYL-CBMICA, and dibutylone showed a strong cytotoxic potential, affecting two parameters at 7.81 µM. 5-MeO-MiPT showed moderate effects by impairing one parameter at 7.81 and one at 125 µM. Furthermore, at the high concentration of 5-MeO-MiPT, an effect of metabolism on cytotoxicity was observed. The HCSA confirmed the cytotoxic potential of ephylone and 5-MeO-MiPT, as the investigated concentrations were in the range of their published blood concentrations which induced liver damages after intake. The mitochondrial membrane potential was the parameter with the highest sensitivity and thus considered as suitable "cytobiomarker". In turn, parameters showing a high variability or unexpected effects such as cytosolic calcium levels and plasma membrane integrity might be omitted in the future. Even though 5-MeO-MiPT showed metabolism-based effects, HepG2 are known to have limited metabolic activity compared to cell lines such as HepaRG. Therefore, in further experiments cell lines with higher CYP-expression needs to be included and findings compared. Nevertheless, the simplified HCSA-based strategy allowed to screen NPS from diverse chemical groups for a first assessment of the cytotoxic properties of the parent compound. This information is crucial for a thorough risk assessment of NPS not only for public health authorities.