A Study On The Toxic Effect Of PFOS On Perinereis Nuntia

Perfluorooctane sulfonate(PFOS)is an emerging persistent organic pollutant that has global distribution,but there was no report focused on the potential toxicity of PFOS to Perinereis nuntia which could assess the ecological risk both of ocean and intertidal zone as an important biomonitor.In this study,the Periereis nuntia was used to detect the potential effects of PFOS on the marine deposit-feeding invertebrates from the view of molecule level.The study not only enriched the data on sandworms biological monitoring,but also provided the scientific basis for the PFOS toxic effect and early warning.This study evaluated the toxic effect of oxidative stress,DNA damage and detoxification system response in P.nuntia exposed to 3 different concentrations(1/4,1/8,1/16 of 96 h-LC50)of PFOS for 14 days and 5 days after recovery period.The results are listed below point by point:1.The acute toxicity.The 96 h-LC50 of PFOS on P.nuntia was 64 mg·L-1 which belongs to moderate toxicity.The P.nuntia showed tolerance to PFOS.2.Oxidative stress: P.nuntia antioxidant defense system biomarkers include superoxide dismutase(SOD),glutathione reducatase(GR)that are sensitive to low concentration and glutathione peroxidase(GSH-PX),glutathione S-transferase(GST)that mainly react during late exposure.Also,malondialdehyde(MDA)content and the ratio of reduced glutathione(GSH)and oxidized glutathione(GSSG)could respond to environmental pollutant properly.3.DNA damage: The mechanism of PFOS-induced DNA damage may be associated with the oxidative stress and showed time-and does-dependent manner clearly.The DNA damage could be repaired by sandworms to some extent.DNA damage of P.nuntia could be used as early warning for environmental PFOS biomonitoring.4.Detoxification system: this paper studied the combine response of genes transcription and enzymes activity of cytochrome P450(CYP),glutathione S-transferase(GST)in nereis,P.nuntia.The PFOS-induced inhibition of EROD showed a time-dependent relationship clearly.The P.nuntia CYP431A1(CYP2 clan)m RNA was sensitively expressed to PFOS exposure with a clear dose-dependent relationship and showed the highest inducibility on day 14.The transcription levels of CYP424A1,a CYP4 clan gene,in 4 and 8 mg·L-1 treatments all positively correlated with the PFOS exposure time.As one of phase II detoxification enzymes,the GSTenzyme and GST omega gene both decreased first and upregulated then with the prolong of PFOS exposure.P.nuntia still could accelerate metabolism under the serious exposure and showed its tolerance for PFOS.During recovery period,all the observed indexes showed a tendency to recover to the control level.In conclusion,the response of gene transcription and enzyme activity showed that CYPs and GST of P.nuntia played important roles in the PFOS detoxification and these indexes of P.nuntia would have great potentials as biomarkers to detect the PFOS pollution in marine intertidal zone.5.Mechanism of toxication: As exposure of PFOS,a series of metabolites were produced.First,the PFOS disturbed the receptor of CYP pathway and triggered the detoxification system I.Then,with the accumulation of ROS which indicated by some obvious oxidative stress,e.g.lipid peroxidation in this study,the response of antioxidative enzyme systems(SOD,CAT,GSH,GR,GSH-PX)were induced.Finally,The detoxification system II was respond and caused serious DNA damage.