Acute exposure to a Mn/Zn ethylene-bis-dithiocarbamate fungicide leads to mitochondrial dysfunction and increased reactive oxygen species production in Caenorhabditis elegans

• Published in: Neurotoxicology (Park Forest South) Vol. 57; pp. 112 - 120
• Main Authors: Todt, Callie E., Bailey, Denise C., Pressley, Aireal S., Orfield, Sarah E., Denney, Rachel D., Snapp, Isaac B., Negga, Rekek, Bailey, Andrew C., Montgomery, Kara M., Traynor, Wendy L., Fitsanakis, Vanessa A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2016; Elsevier BV
• Subjects: Adenosine Triphosphate - metabolism; Animals; Animals, Genetically Modified; C. elegans; Caenorhabditis elegans; Caenorhabditis elegans Proteins - genetics; Caenorhabditis elegans Proteins - metabolism; Disease Models, Animal; Ethylene; Exposure; Fungi; Fungicides; Fungicides, Industrial - toxicity; Glutathione Transferase - metabolism; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Hydrogen peroxide; Hydrogen Peroxide - metabolism; Hydroxyl radicals; Inhibition; Mancozeb; Manganese; Manzate; Mitochondria; Mitochondrial Diseases - chemically induced; Mitochondrial Diseases - metabolism; Mitochondrial inhibition; Multienzyme Complexes - metabolism; Nematodes; Neurodegeneration; Neurodegenerative diseases; Neurological diseases; Oxygen; Oxygen consumption; Oxygen Consumption - drug effects; Pesticides; Reactive oxygen species; Reactive Oxygen Species - metabolism; Statistical analysis; Statistical significance; Superoxide; Superoxides - metabolism; Up-Regulation - drug effects; Zinc; DHE; Reactive oxygen species; O2; Hydrogen peroxide; DMSO; TMRE; H2O2; GFP; Mitochondrial inhibition; ANOVA; OH; E. coli; CGC; Manzate; NBT; C. elegans; Mancozeb; DAB; EDTA; MZ; EGTA; Mn/Zn-EBDC; PD; Δψ; NGM; ROS; SEM
• ISSN: 0161-813X; 1872-9711
• DOI: 10.1016/j.neuro.2016.09.011

•C. elegans acutely treated with manzate show reduced ATP levels.•The decreased ATP may be attributed to Complex III inhibition.•Mitochondrial inhibition is associated with increased hydrogen peroxide levels.•Increased glutathione-S-transferase levels correlate with oxidative stress.•Mitochondrial inhibition and oxidative stress may be mechanisms of manzate toxicity. Mn/Zn ethylene-bis-dithiocarbamate (Mn/Zn-EBDC) fungicides are among some the most widely-used fungicides in the world. Although they have been available for over 50 years, little is known about their mechanism of action in fungi, or their potentially toxic mechanisms in humans. To determine if exposure of Caenorhabditis elegans (C. elegans) to a representative fungicide (Manzate; MZ) from this group inhibits mitochondria or produces reactive oxygen species (ROS), we acutely (30min) exposed worms to various MZ concentrations. Initial oxygen consumption studies showed an overall statistically significant decrease in oxygen consumption associated with addition of Complex I- and/or II-substrate in treatment groups compared to controls (*p<0.05). In order to better characterize the individual complex activity, further studies were completed that specifically assessed Complex II or Complex IV. Data indicated that neither of these two complexes were targets of MZ treatment. Results from tetramethylrhodamine ethyl ester (proton gradient) and ATP assays showed statistically significant reductions in both endpoints (*p<0.05, **p<0.01, respectively). Additional studies were completed to determine if MZ treatment also resulted in increased ROS production. These assays provided evidence that hydrogen peroxide, but not superoxide or hydroxyl radical levels were statistically significantly increased (*p<0.05). Taken together, these data indicate exposure of C. elegans to MZ concentrations to which humans are exposed leads to mitochondrial inhibition and concomitant hydrogen peroxide production. Since mitochondrial inhibition and increased ROS are associated with numerous neurodegenerative diseases, we suggest further studies to determine if MZ catalyzes similar toxic processes in mammals.