Ayahuasca is a psychoactive brew traditionally used in religious rituals by indigenous Amazonian populations and South American syncretic religions such as Santo Daime and União do Vegetal. Its psychoactive effects are primarily due to N,N-dimethyltryptamine (DMT), while harmine (HRE), a β-carboline alkaloid, inhibits monoamine oxidase (MAO), enabling DMT's oral bioavailability. Recent studies demonstrate Ayahuasca's therapeutic potential in treating substance use disorders, including cocaine use disorder, which involves neurotoxic effects. However, no in vitro studies to date have evaluated the neuroprotective potential of Ayahuasca compounds in this context. This study investigated the effects of DMT and HRE, isolated and combined, on cocaine-induced toxicity in human SH-SY5Y neuroblastoma cells. Cells were exposed for 48 h to various concentrations of DMT and HRE (0.1-1000 µM), cocaine (0.5-5 mM), and DMT:HRE combinations (10:10 to 10:100 µM). The non-toxic concentrations of DMT (10 µM) and HRE (10 µM), both isolated and combined (10:20 µM DMT:HRE), were co-incubated with the lethal concentration 50 (LC) of cocaine (2.5 mM) to assess neuroprotection. Cell viability was evaluated by MTT assay, apoptosis by flow cytometry using annexin-V/propidium iodide staining, and protein expression of apoptosis-related markers (Bax, Bcl-2, and caspase-8) by western blot. The results showed increased cell viability in co-treatment groups (cocaine + DMT and/or HRE) when compared to cocaine-only groups. Flow cytometry revealed partial to complete protection against apoptosis in co-treated cells. Western blot demonstrated reduced caspase-8 expression in cells treated with Ayahuasca compounds plus cocaine versus cocaine alone. In conclusion, DMT and HRE-isolated and combined-provided partial neuroprotection against cocaine-induced toxicity in SH-SY5Y cells. These findings support Ayahuasca-derived alkaloids as candidates for further investigation in neuroprotection and substance use disorder treatment. 50
Psychedelic Science