Mechanisms behind the neurotoxicity of 2C-I and 25I-NBOMe drugs

Abstract

Background: New Psychoactive Substances (NPS) pose significant health and legal risks worldwide. At the end of 2021, the European Monitoring Centre for Drugs and Drug Addiction was monitoring 886 NPS, 106 of them phenethylamines [1]. Phenethylamine derivatives include 2,5-dimethoxyphenethylamine-based (2C) and N-benzylphenethylamine-based (NBOMe) drugs, widely known for their psychedelic effects. However, their toxicological profile remains poorly characterized [2,3]. Objective: To address this gap, 2C-I (2-(4-iodo-2,5-dimethoxyphenyl)ethanamine) and its corresponding NBOMe derivative (2-(4-iodo-2,5-dimethoxyphenyl)-N-[(2-methoxyphenyl)methyl]ethanamine) were synthesized and their neurotoxic profile evaluated, elucidating potential mechanistic pathways involved in drug-induced cytotoxicity. Methods: 2C-I and 25I-NBOMe were synthesized and structurally characterized by nuclear magnetic resonance and mass spectrometry techniques. Neuronal SH-SY5Y cells differentiated into a dopaminergic phenotype and primary rat cortical neurons, which were exposed to the drugs for 24 hours, were used for the in vitro experiments. Drugs’ neurotoxicity and the impact of MAO-mediated inhibition on drug-induced cytotoxicity were evaluated using the neutral red uptake assay. The capacity of the drugs to generate free radicals was estimated using the DCFH-DA probe and their impact on the intracellular GSH and ATP levels were assessed using the DTNB-reductase-recycling and the ATP bioluminescence assays, respectively. Changes in the mitochondrial membrane potential were investigated using the JC-1 probe. The chromatographic hydrophobicity index (CHI) of the drugs was also evaluated by Fast-Gradient RP-HPLC. Results: Both drugs exhibited a concentration-dependent neurotoxic effect, with 25I-NBOMe being more cytotoxic than its counterpart, which supports the drugs’ lipophilicity data. MAO inhibition had no significant impact on drug-induced cytotoxicity. No significant changes in ROS production were observed for both drugs, but a significant decrease in intracellular GSH and ATP levels, and significant mitochondrial membrane depolarization was detected. Conclusions: The introduction of a NBOMe substituent significantly increased all the evaluated neurotoxic effects, demonstrating the high potential of these drugs to induce severe adverse reactions.