6PPD and 6PPD-Q Induce Mitochondrial Dysfunction in Saccharomyces cerevisiae.

N-(1,3-dimethylbutyl)-N'phenyl-p-phenylenediamine, more commonly known as 6PPD, is a tire antiozonant used to prevent rubber oxidation and degradation. When 6PPD reacts with ozone, it becomes 6PPD-Quinone (6PPD-Q). Stormwater road runoff facilitates the transport of phenylenediamines (PPDs) into the environment. In recent years, 6PPD-Q has been identified as an acute environmental toxicant causing major disruptions to aquatic life. To aid in the growing body of knowledge on the mechanism of action of PPD and potentially support environmental regulations, this study aims to elucidate the toxic effects of 6PPD and 6PPD-Q in Saccharomyces cerevisiae. To accomplish this, a growth assay, RNA sequencing, mitochondrial staining, and RT-qPCR were performed. The results suggest that 6PPD and 6PPD-Q impact growth and gene regulation by dysregulating Complex III, IV, and V of the oxidative phosphorylation pathway. Additionally, 6PPD and 6PPD-Q are, seemingly, agglomerated at different pHs and in various media. The agglomeration of 6PPD-Q may inhibit cellular uptake, leading to fewer discernible toxic effects. Taken together, we can posit that 6PPD and 6PPD-Q both induce oxidative stress upon exposure to budding yeast, but 6PPD seems to be more toxic than 6PPD-Q.