Immunotoxicity and hepatotoxicity of PFOS and PFOA in tilapia (Oreochromis niloticus)

Perfluorinated organic compounds (PFOCs) are emerging persistent organic pollutants (POPs) widely distributed in the environment, wildlife and human. We studied the toxicology of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) on immunotoxicity and hepatotoxicity in primarily cultured hepatocytes of freshwater tilapia (Oreochromis niloticus). Cultured hepatocytes were exposed to PFOS or PFOA (0, 10, 20 and 30 mg/L) for 24, 48, 72, 96, 120 and 144 hours, respectively. Oral doses of these compounds that induce significantly detectable immunotoxicity and hepatotoxicity were employed in the study. In response to PFOS, the leukocytes, B cells, granulocytes, and macrophages among the isolation of intrahepatic immune cells (IHIC) from PFOS-treated tilapia produced significant levels of immune cells compared with that of the control group. The numbers of leukocytes, B cells, granulocytes, and macrophages for PFOS-treated tilapia increased with the incremental exposure concentration. Moreover, similar to the findings in PFOA toxicity effects, the erythropoietin levels in tilapia increased with the increase of the PFOS and PFOA concentrations. The lowest doses (10 mg/L) of PFOS exposure led to a marked inhibition in the hepatocyte viability in tilapia. Similarly, tilapia exposed to PFOA demonstrated a similar pattern, and a dose-dependent decrease in the hepatocyte viability was observed in the following treatment of PFOA. In the 72 h exposures, ethoxy-resorufin-O-deethylase (EROD) activity was significantly induced with the increase concentrations in tilapia liver (p<0.05). Tilapia showed a strong EROD induction in livers, and significantly difference in EROD activity was observed between control, PFOS and PFOA-exposed tilapias. The liver glycogen content showed that PFOS and PFOA exposure caused significant changes in the liver glycogen content, which depended on the duration of exposure. And it appeared that the decrease in blood glucose level during the acclimation was followed by significant increase in liver glycogen content in tilapia.