Effects On Antioxidant System And Apoptosis Induction Of Perfluorooctane Sulfonate(PFOS) To Hyriopsis Cumingii

Perfluorooctane sulfonate(PFOS) is a typical persistent organic pollutant(POPs), which is widely spread in the environment because of its high water solubility, bioavailability and ability of bioaccumulation. At the same time, it has a wide range of biological toxicity. High levels of PFOS have been detected in environmental samples and tissues of wild life and humans. Environmental water bodies are considered to be the most common carriers of PFOS, but the high water/sediment distribution coefficient makes sediments becoming the destination of PFOS. Thus the benthonic organism may have more chance to expose to PFOS, and it plays an important role in the transferring of environmental PFOS to the biosphere. However, few studies have focused on the toxicity mechanism of PFOS on aquatic benthic animals.Hyriopsis cumingii is a traditional fresh water pearl mussel of China and have a great distribution in the environmental water systems. In this study, we explored the toxic effects of different concentrations(0.1, 1.0 and 5.0 mg?L-1) of PFOS to Hyriopsis cumingii by monitoring the activation of the biological detoxification system and antioxidant defense system. The research focused on the Gills and hepatopancreas, the GSH concentration, activity of glutathione S-transferase(GST), glutathione peroxidase(GPx), glutathione reductase(GR), acid phosphatase(ACP), alkaline phosphatase(AKP), superoxide dismutase(SOD), catalase(CAT), Alanine transaminase(ALT), Aspartate Transaminase(AST) and the MDA concentration were tested. To explore the mechanism of the toxicity, we also tested the activity of caspase-3 and caspase-9. Finally, TUNEL assays were analyzed to show the apoptosis in situ for both organs.1. During the 30d’s PFOS stressing test, the GSH concentration of gills was significantly inhibited, followed by the induction of SOD activity and MDA concentration, suggesting that PFOS can cause an obvious oxidative stress in gill and intensify the lipid peroxidation. In the period of restoration, GSH and MDA concentration have recovered to the level of control group, but a increase of variability was detected in all the PFOS treated group, indicating the receding of the environmental suitability.2. During the 30d’s PFOS stressing test, the GSH concentration, the activity of SOD, GST ALT and AST of the lower concentration(0.1mg/L) group were generally induced by PFOS on a significant level versus the control group. In contrast, different patterns for the above indicators shifting from induction to inhibition were found in the 1.0mg/L and 5.0mg/L group. Almost all the transitions were detected around 4d, indicating that 4d may be the key period of dysfunction and tissue injury. The significant increase of MDA could be another evidence of oxidative stress and the damage of cellular structure. Besides, a positive correlation was found between GSH concentration and GST activity of same group, it reach the significant level in the 5.0 mg?L-1 group, suggesting that the cellular detoxification system was highly motivated and more GSH were used to combine and transfer PFOS than elimination of reactive oxygen species in the high concentration group. Finally the activity of ALT and AST shows the dysfunction of PFOS treated group, it may be the reason of the inhibition of antioxidant enzymes activities. During the restoration period, most of the indicators did not recover to the normal level, but the tendencies indicating that a longer period was need for Hyriopsis cumingii to repair the damage of PFOS stress.3. The clue of this section was the transitions period of the indicators in the second section. More biomarkers were tested in the section to describe the organic internal environment, and the TUNEL assays were did to show the apoptosis of the organs. After 4d’s PFOS stress experiment, the GSH concentration of gill decreased significantly, followed by the induction of GST and the inhibition of GPx, suggesting that the ability of combining and transferring PFOS increased drastically, but the function of ROS elimination was weakening. The hepatopancreas shows a same result on GST and GPx activities, but GSH concentration was induced significantly in all PFOS treated group, and GR was activated significantly in 5.0mg/L group. It may relate to the initiative transferring of PFOS from other organs to hepatopancreas. The activation of CAT and increase of MDA concentration indicate the oxidant stess and cellular damage of both gill and hepatopancreas. ACP and AKP activities were obviously changed in gill of 5.0mg/L group. It shows the increase risk of metabolism disturbance and cytolysis. The caspase-3 and caspase-9 were drastically activated in hepatopancreas of 1.0mg/L and 5.0mg/L group(P<0.05), but only caspase-9 was significantly induced in gills of 5.0mg/L group. Finally we detected a great quantity of apoptotic cells through the TUNEL assay both in gill and hepatopancreas in all PFOS treated groups.In summary, PFOS can rapidly motivate the cellular detoxification system and cause a obvious oxidant stress which is significantly surpass the antioxidant ability both in gill and hepatopancreas, along with the explosion of lipid peroxidant. Then the signaling proteins of apoptosis were activated and finally lead to a wide range of apoptosis.