Shuyan Zhao,Tiankun Liang,Tao Zhou,Dongqi Li,Bohui Wang,Jingjing Zhan,Lifen Liu
Perfluorooctane sulfonamide (FOSA) is an important perfluorooctane sulfonate (PFOS) precursor used for commercial applications. In order to investigate the transformation and responses of selected antioxidant and degradation enzymes of FOSA in the plants, in vivo exposure of soybean ( Glycine max L. Merrill) and pumpkin ( Cucurbita maxima L.) were conducted in the solution-plant microcosms. FOSA was readily taken up by soybean and pumpkin roots and translocated to shoots, and metabolized to PFOS, perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). Although morphological and biomass effects were not visible, significant changes in oxidative stress response were observed except for thiobarbituric acid reactive substances (TBARS). Superoxide dismutase (SOD) and peroxidase (POD) activities were significantly increased by 19.2–30.8% and 19.2–20.7% in soybean (8–12 d) respectively, and increased by 39.2–92.8% and 21.1–37.6% in pumpkin (3–12 d) respectively, suggesting an activation of the antioxidant defense system in the plants exposed to FOSA. Glutathione-S-transferase (GST) activities were decreased in soybean (2–12 d) with 9.0–36.1% inhibition and increased in pumpkin (3–12 d) with 22.5–47.3% activation respectively; cytochrome P450 (CYP450) activities were increased markedly in soybean and pumpkin with 13.2–53.6% and 26.7–50.2% activation respectively, giving indirect evidences on the involvement of CYP450 and GST in degradation of FOSA in plants.
Shuyan Zhao,Bohui Wang,Lingyan Zhu,Tiankun Liang,Meng Chen,Liping Yang,Jingping Lv,Lifen Liu
N-ethyl perfluorooctane sulfonamide (N-EtFOSA) is commonly known as the active ingredient of sulfluramid. It can be degraded to perfluorooctane sulfonic acid (PFOS) in biota and environment. Earthworms ( Eisenia fetida ) were exposed with N-EtFOSA to examine the bioaccumulation, elimination and metabolism of N-EtFOSA by the earthworms after in vivo and in vitro exposure. N-EtFOSA could be biodegraded in quartz sands to perfluorooctane sulfonamide (FOSA) and PFOS. In the in vivo tests, in addition to parent N-EtFOSA, three metabolites, including perfluorooctane sulfonamide acetate (FOSAA), FOSA and PFOS also accumulated in earthworms as a result of N-EtFOSA biotransformation , with FOSA as the predominant metabolite. The bioaccumulation factor (BAF) and uptake rate coefficient ( k u ) of N-EtFOSA from sand were 20.4 and 2.41·d −1 , respectively. The elimination rate constants ( k e ) decreased in the order FOSAA (0.130·d −1 ) > N-EtFOSA (0.118·d −1 ) > FOSA (0.073·d −1 ) > PFOS (0.051·d −1 ). The biotransformation of N-EtFOSA in earthworm was further confirmed by the in vitro test involving incubation of earthworm homogenates with N-EtFOSA. This work provides evidence on the accumulation and transformation of N-EtFOSA in terrestrial invertebrates and will be helpful to explore the indirect sources of FOSA and PFOS in environmental biota.
Perfluorooctane sulfonamide (FOSA) is known as a key intermediate of perfluorooctane sulfonic acid (PFOS) precursors, which can be frequently detected in the environment and biota. FOSA could be bioaccumulated in earthworms from soil, but the contributions of enzymes and gut microbes involved in the biotransformation of FOSA in earthworms have not been identified. Therefore, the effects of enzyme inhibitors and intestinal microflora on biotransformation of FOSA in earthworms were investigated in the present study. FOSA was biotransformed to form PFOS by earthworms obtained from in vivo and in vitro tests. The addition of FOSA had significantly positive effects on cytolchrome P450 (CYP450) and glutathione- s -transferase (GST) activities, suggesting CYP450 and GST are likely involved in the enzymatic transformation. In addition, both 1-Aminobenzotriazole (ABT) and ezatiostat hydrochloride (TLK199), which were selected to inhibit the CYP and GST enzymes, respectively, demonstrated inhibition effects on biotransformation of FOSA in earthworms with a dose-dependent relationship. However, the concentrations of FOSA weren't changed by the bacteria isolated from worm gut, suggesting that gut bacteria did not contribute to FOSA biotransformation in earthworms. The results of this study confirm that the transformation of FOSA in earthworms is mediated mainly by enzymes rather than by gut microbes.
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