Differential Effects of Paraquat, Rotenone, and MPTP on Cellular Bioenergetics of Undifferentiated and Differentiated Human Neuroblastoma Cells

Abstract

Paraquat (PQ), rotenone (RO), and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) are neurotoxicants that can damage human health. Exposure to these neurotoxicants has been linked to neurodegeneration, particularly Parkinson’s disease. However, their mechanisms of action have not been fully elucidated, nor has the relative vulnerability of neuronal subtypes to their exposures. To address this, the current study investigated the cytotoxic effects of PQ, RO, and MPTP and their relative effects on cellular bioenergetics and oxidative stress on undifferentiated human neuroblastoma (SH-SY5Y) cells and those differentiated to dopaminergic (DA) or cholinergic (CH) phenotypes. The tested neurotoxicants were all cytotoxic to the three cell phenotypes that correlated with both concentration and exposure duration. At half-maximal effective concentrations (EC50s), there were significant reductions in cellular ATP levels and reduced activity of the mitochondrial complexes I and III, with a parallel increase in lactate production. PQ at 10 µM significantly decreased ATP production and mitochondrial complex III activity only in DA cells. RO was the most potent inhibitor of mitochondrial complex 1 and did not inhibit mitochondrial complex III even at concentrations that induced a 50% loss of cell viability. MPTP was the most potent toxicant in undifferentiated cells. All neurotoxicants significantly increased reactive oxygen species, lipid peroxidation, and nuclear expression of Nrf2, with a corresponding inhibition of the antioxidant enzymes catalase and superoxide dismutase. At a 10 µM exposure to PQ or RO, oxidative stress biomarkers were significant in DA cells. Collectively, this study underscores the importance of mitochondrial dysfunction and oxidative stress in PQ, RO, and MPTP-induced cytotoxicity and that neuronal phenotypes display differential vulnerability to these neurotoxicants.

Alcohol Triggers the Accumulation of Oxidatively Damaged Proteins in Neuronal Cells and Tissues

“…Surprisingly, IC 50 values were higher for differentiated cells (Table 1), indicative that differentiation was protective against alcohol. This contrasts with the effects of some toxic agents, such as organophosphate and carbamate pesticides, which are more toxic to differentiated SH-SY5Y cells [46] but not to other neurotoxicants, such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [62], an agent that can induce Parkinsonian phenotypes in animals [63,64].…”

An In Silico and In Vitro Assessment of the Neurotoxicity of Mefloquine

“…After two hours of incubation at 37 °C, the media was removed from the plates and replaced with DMSO, before the absorbance was read at 570 nm using a Varioskan™ LUX multimode microplate reader (ThermoFisher Scientific, Waltham, MA, USA) to quantify the formation of formazan. At these cell seeding and growth conditions, the MTT signal displays linearity [ 26 ]. The viability of vehicle control treated cells was set at 100%.…”

Exploring the Neuroprotective Potential of Desmodium Species: Insights into Radical Scavenging Capacity and Mechanisms against 6-OHDA-Induced Neurotoxicity

“…Following exposure to 6-OHDA (25 µM) or rotenone (1 µM) for 24 h [33,50], the viability of the cells was evaluated using the MTT assay in accordance with our previous protocols [31]. To assess the protective effects of the methanolic extracts from three Desmodium plant species, namely D. pulchellum, D. sequax, and D. motorium, on the SH-SY5Y cells, a 15 min treatment was administered prior to the addition of 6-OHDA or rotenone.…”