Embryonic exposure to PFOS induces immunosuppression in the Fish larvae of marine medaka
In this study, the larvae of marine medaka (Oryzias melastigma) were evaluated for postnatal immune toxicity after embryonic exposure to PFOS (0, 1, 4 and 16 mg/L) from 2 days post fertilization (dpf). The physiological indices, survival rates, PFOS elimination kinetics, liver histology and gene transcription in the fish larvae were examined after depuration. The elimination rate constant (ke) of PFOS in the fish larvae ranged from 0.047±0.00 to 0.077±0.01 d−1. Embryonic exposure to PFOS severely compromised the postnatal survival of fish larvae after depuration. The survival rate and body width decreased in a concentration dependent manner. PFOS impaired the liver structure in the fish larvae by enlarging the cell nuclei and damaging the cell structure. To explore the toxic mechanisms that affect the immune responses, fish larvae at 27 days post hatch (dph) were exposed to lipopolysaccharides (LPS) to elicit an inflammatory response. The inflammatory response and immune-related genes were generally up-regulated in the fish larvae following embryonic exposure to 0 mg/L PFOS. In contrast, the genes were all markedly down-regulated in the fish larvae following embryonic exposure to 1 and 4 mg/L PFOS. These results suggest that early life exposure to PFOS could alter immunoregulation functions, leading to functional dysfunction or weakness of the immune system in fish larvae.
