Effects of simulated maternal transfer of perfluorooctane sulfonate (PFOS) on oxidative stress levels in rainbow trout eggs

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Abstract
Extensive use of per- and polyfluoroalkyl substances (PFAS) has led to their widespread contamination of the Great Lakes. Due to their resilient carbon-fluorine bonds, some PFAS bioaccumulate, biomagnify, and cause toxic effects in biota. In wild-caught Lake Michigan salmonids, perfluorooctane sulfonate (PFOS) concentrations were higher in eggs than in muscle tissue, suggesting maternal offloading. We evaluated PFOS exposure effects through egg development in rainbow trout, an introduced salmonid now important to the Great Lakes. We simulated maternal offloading of PFOS in vitro (0, 0.03, 0.3, 3, and 30 ppm) based on previous literature. Eggs were exposed for three hours, fertilized, and incubated until hatching to alevins. Samples were taken at various timepoints from egg to alevin and assessed for key markers of oxidative stress: lipid peroxidation, superoxide dismutase (SOD) activity and glutathione (GSH) abundance. PFOS accumulation in eggs was also analyzed at various development stages. At time zero, internal PFOS concentrations in eggs ranged from 1.02–44.1% of exposure solution concentrations, declining further through development. Oxidative stress indicators fluctuated through development. Lipid peroxidation levels generally decreased throughout treatments in alevins, with no significant difference observed in embryos. SOD activity varied throughout development; notably, embryo SOD levels in the 0.3 ppm treatment were lower than control at week four. GSH levels were above control in embryos at week four and generally fell below control in alevins. Overall, markers of oxidative stress showed varying trends (positive/negative) in eggs exposed to PFOS, which raises concerns for fish embryonic development and broader environmental impacts.

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