The role of mitochondrial dysfunction and calcium dysregulation in 2C-I and 25I-NBOMe-induced neurotoxicity

New psychoactive substances (NPS) are designed to evade legal regulation while mimicking the effects of classic illicit drugs such as 3,4-methylenedioxymethamphetamine (MDMA). This category includes phenethylamine derivatives, such as the psychedelic 2C and NBOMe drugs. Given the lack of data regarding the toxicological profile of these substances, the goal of this study was to evaluate the neurotoxicity of 2C-I and 25I-NBOMe and explore their neurotoxic pathways. Lower EC₅₀ values, in both NR uptake and MTT reduction assays in differentiated SH-SY5Y cells and primary rat cortical cultures, revealed that 25I-NBOMe is significantly more cytotoxic than 2C-I, likely due to its higher lipophilicity. Both drugs triggered severe mitochondrial dysfunction, characterized by decreased intracellular ATP levels and mitochondrial membrane depolarization, although no significant changes in intracellular ROS/RNS levels were observed. Additionally, 25I-NBOMe increased the intracellular Ca²⁺ levels. Apoptosis was an observed mechanism of cell death for both drugs, as demonstrated by a significant increase in the number of cells undergoing early apoptosis (AnV⁺/PI⁻) and late apoptosis/necrosis (AnV⁺/PI⁺). However, only 2C-I induced autophagy and strongly triggered caspase-3 activation. This suggests that 2C-I induces caspase-3-dependent apoptosis, whereas 25I-NBOMe may also induce apoptosis through a caspase-3-independent pathway, possibly involving increased intracellular Ca²⁺ levels and direct mitochondrial damage.

These findings underscore the complex interplay between mitochondrial dysfunction, calcium dysregulation, and cell death pathways, highlighting the central role of mitochondria in the cytotoxicity of 2C-I and 25I-NBOMe.