Cellular Mechanisms of 1,3-Dimethylamylamine (1,3-DMAA)-Induced Toxicity

Abstract

Background: 1,3-Dimethylamylamine (1,3-DMAA) is a chiral sympathomimetic amine formerly used as a nasal decongestant until its withdrawal in the 1980s due to adverse effects such as headaches, nervousness, psychomotor agitation, and tremors [1]. In 2005, it re-emerged in dietary supplements marketed for weight loss, performance enhancement, and recreational purposes [2]. Despite regulatory bans, 1,3-DMAA continues to be detected in doping controls and dietary supplements, raising toxicological concerns. The cellular mechanisms underlying its neurotoxic potential remain incompletely characterized [3]. Objective: This study aimed to investigate the cytotoxic mechanisms induced by 1,3-DMAA in a human neuronal cell model (SH-SY5Y), contributing to a better understanding of its toxicodynamics. Methods: SH-SY5Y cells were exposed for 48h to 1,3-DMAA (1.3×10⁻⁴ to 1.5×10¹ mM; n=5); mitochondrial metabolic activity was assessed using the MTT assay and the lysosomal integrity through the neutral red uptake (NR) assay. Based on the MTT results, cells were subsequently exposed to the EC₂₀ (4.21 mM), EC₄₀ (4.91 mM), and EC₆₀ (5.59 mM), and changes in intracellular reactive oxygen species (ROS) production and mitochondrial membrane potential (ΔΨm) assessed using fluorometric probes. Autophagic features were evaluated using acridine orange (AO) staining to detect acidic vesicular organelles. Results: 1,3-DMAA induced concentration-dependent cytotoxicity, with a greater impact on mitochondrial function than lysosomal integrity, as evidenced by lower EC₅₀ values in the MTT assay compared to the NR assay (5.24 mM versus 6.36 mM, respectively). 1,3-DMAA induced a concentration-dependent increase in intracellular ROS levels from EC₂₀ (236.67%; p<0.001) and EC₄₀ (211.87%; p<0.01) and peaking at EC₆₀ (272.05%; p<0.0001). In contrast, ΔΨm remained unchanged at lower concentrations, with a significant increase observed at EC₆₀ (317.32%; p<0.0001). AO staining showed increased acidic vesicular organelles at higher concentrations. Conclusions: The concomitant increase in ROS and hyperpolarization of ΔΨm indicate a pro-oxidant state. The AO assay demonstrated progression to autophagy and/or apoptosis. These findings consolidate and provide a mechanistic basis for future studies.