Exposure to the Tire Rubber-Derived Contaminant 6PPD-Quinone Causes Mitochondrial Dysfunction In Vitro

Abstract

N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediaminequinone (6PPD-quinone), a rubber tire oxidation product found in road runoff, is highly and acutely toxic to selected salmonids including coho salmon, brook trout, and rainbow trout but not other fish species and invertebrates studied to date. Sensitive species displayed increased ventilation and gasping, suggesting a possible impact on respiration. Here, adherent cell lines RTL-W1 and RTgill-W1 were exposed to 5− 80 μg/L 6PPD-quinone, and cytotoxicity, oxygen consumption rate (OCR), and biotransformation of 6PPD-quinone were measured to assess the ability of 6PPD-quinone to uncouple mitochondrial respiration in vitro. RTL-W1 cells were not sensitive to 6PPD-quinone, and exposure did not result in significant impacts on cytotoxicity or OCR. In contrast, RTgill-W1 cells demonstrated decreased cell viability at 80 μg/L and a 2-fold increase in OCR at 20 μg/L. Effects appear to be partly driven by toxicokinetic differences where incubation of RTL-W1 cells with 6PPD-quinone led to almost quantitative conversion of 6PPD-quinone into a suspected hydroxy-metabolite, which was not observed in RTgill-W1 cells. Exposure studies with primary cultures of rainbow trout gill cells indicated that 6PPD-quinone increased OCR by uncoupling the mitochondrial electron transport chain. Together, these findings suggest that 6PPD-quinone toxicity might be driven by a tissue-specific disruption of mitochondrial respiration.

The Tire-Derived Chemical 6PPD-quinone Is Lethally Toxic to the White-Spotted Char Salvelinus leucomaenis pluvius but Not to Two Other Salmonid Species

“…The suspected monohydroxylated metabolite was detected in all exposure samples (Figure ), indicating the ability to metabolize 6PPD-Q by brain and gill in three tested species. This observation is inconsistent with the previous study demonstrating no detectable monohydroxylated metabolite in rainbow trout gill cells (RTgill-W1) exposed to 6PPD-Q . The reasons for the inconsistency are unknown but might be related to the difference between in vivo and in vitro systems .…”

“…The recovery ratios of 6PPD-Q during the extraction were estimated to be 96 ± 14% (brain) and 102 ± 11% (gill) using wet tissue taken from a clean culture spiked with 0.1 μg of 6PPD-Q per sample ( n = 3; mean ± standard deviation). Also, the suspected monohydroxylated metabolite of 6PPD-Q was semiquantified on the basis of the transition from m / z 315 to 231 according to a recent study for selected samples (i.e., the highest and second highest concentrations for S. leucomaenis pluvius and all concentrations for the other two). The semiquantification assumed the response was equal to that of 6PPD-Q due to the unavailability of the analytical standards.…”

“…These species were selected as they are taxonomically close to the species that have been reported to be sensitive to 6PPD-Q and are culturally, commercially, and ecologically important in Japan. In addition to acute lethality, accumulation of 6PPD-Q in fish brain and gill, which are considered 6PPD-Q target tissues, , was examined to determine whether toxicokinetic differences contributed to species sensitivity differences. Also, the accumulation in liver and muscle was examined for selected individuals to obtain preliminary data on the tissue distribution of 6PPD-Q.…”

First Report on the Occurrence of N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and 6PPD-Quinone as Pervasive Pollutants in Human Urine from South China

“…Given that a portion of 6PPD and 6PPD-Q may also be excreted through feces and exhaled air like some other pollutants, , the actual exposure dose of 6PPD and 6PPD-Q may even be higher than our estimates. Although the dose is unlikely to exceed a proposed reference dose (RfD) of 26000 (ng/kg bw)/day calculated for 6PPD, the potential health risk posed by long-term exposure to 6PPD-Q requires considerable attention, as 6PPD-Q has been proven to be more toxic to aquatic organisms than 6PPD from the individual species to the tissue levels. − ,, In future studies, additional biomonitoring investigations on 6PPD and 6PPD-Q are needed to better elucidate their internal exposure in humans. More toxicological and epidemiological studies of 6PPD and 6PPD-Q are also recommended to shed light on their potential health risks.…”

Rubber Antioxidants and Their Transformation Products: Environmental Occurrence and Potential Impact

“…Mahoney et al also found that 6PPD-quinone might disrupt mitochondrial respiration of rainbow trout gill cells (RTgill-W1). The oxygen consumption rate was increased rapidly in 15 min in RTgill-W1 cell after being exposed to 5–80 μg/L 6PPD-quinone, implying the tissue-specific toxicity of 6PPD-quinone [ 55 ]. 6PPD-quinone was also observed to be highly toxic to silver salmon with an LC 50 of 0.79 ± 0.16 μg/L, which is almost three orders of magnitude lower than that of 6PPD [ 7 ].…”