Study On The Toxicity Correlation And Mechanism Of Pesticides And Other Organic Pollutants To Different Organisms,Cell And Mitochondria Based On Modes Of Action

With the rapid development of economy,pesticides,fungicides,herbicides,nitrobenzenes,phenols,anilines and other types of organic pollutants are more and more widely used in industry and agriculture.These different types of organic pollutants are very easy to cause the pollution of estuaries and offshore waters,worsen the aquatic ecological environment,and make serious harm to the whole ecosystem even to the human health.In recent years,researches on the ecological risks of different types of organic substances,such as pesticides,have received extensive attention from the academic community.Toxicity value is an important indicator for evaluating the environmental risk of organic pollutants,and reflects the environmental safety of organics to a certain extent.At present,limited researches were carried on the toxicity of different types of organic pollutants to non-target aquatic organisms and a few studies were performed on the relationships between the molecular structures of compounds and different non-target organisms,the interspecies toxicity correlation of different species,toxic modes of action and the water quality criteria.In response to the above issues,acute toxicity(log 1/LC₅₀,mol/L)of three important organisms in aquatic ecosystems were measured,including amphibians（tadpoles,Rana chensinensis）,swimming organisms（fish,Danio rerio）and benthics organisms（worms,Limnodrilus hoffmeisteri）.At the same time,the acute and chronic toxicity values of more than a thousand compounds have been collected from database such as TOX21,ECOTOX,PAN and published literature.The molecular descriptors were calculated from computational softwares（such as MOPAC and Algorithm Builder）for these compounds.The aims of this thesis are:to explore the interspecies toxicity correlation of the tadpoles-fish,tadpoles-worms,fish-cytotoxicity and cytotoxicity-mitochondrial toxicity;to distinguish the modes of action（MOAs）of different types of organic pollutants on different organisms from the toxicity ratio（TR）method;to establish quantitative structure-activity correlation（QSAR）models of tadpoles,worms,cytotoxicity and mitochondrial toxicity and investigate toxicity-related factors;to extrapolate the water quality criteria（WQC）from the acute and chronic species sensitivity distribution（SSD）curve of the compounds and the 5%hazard concentration（HC₅）.At the same time,effect of neonicotinoid insecticides on the oxidative stress effect of worms and the mechanism of the sublethal effect of pendimethalin on zebrafish embryos/larvae were ingestigated.This thesis applied a combination of chemical analysis and biological analysis to explore the toxic effect or mechanisms of different types of organic pollutants from three levels（acute toxicity,bioconcentration and oxidative stress）,which is valuable for the early detection indicators of compounds to aquatic organisms and their ecological risk assessment.The main research results are summarized as follows:（1）Comparison of the toxicity values between tadpoles and fish revealed that there were no significant differences for the overlapping compounds（AR=0.29）.Tadpole toxicity is significantly related to worm toxicity for overlapping compounds,but tadpoles are more sensitive than worms.QSAR showed that toxicity to tadpoles is closely related to the log K_OW,E_LUMOand NHDA,representing the bio-uptake potential in tadpoles,the electrophilicity and hydrogen bonding capacity with target site（s）,respectively.Classification of MOAs for the class-based compounds based on the excess toxicity calculated from toxicity ratio suggested that baseline,less inert compounds and some reactive or specifically-acting compounds share same MOAs between tadpoles and fish.Regression analysis revealed that the toxicity of inert or baseline compounds is linearly related to hydrophobicity for both the tadpoles and worms and the two baseline models are parallel,suggesting that these inert compounds share the same MOA between the two species.Analysis of the excess toxicity suggested that phenols and anilines can be classified as less inert compounds,aminophenols and resorcinols can be classified as reactive compounds,and insecticides and fungicides can be classified as specifically-acting compounds for tadpoles and worms.（2）Results showed that fish toxicity was well correlated to cytotoxicity,with overall fish toxicity relatively greater than the cytotoxicity.The excess toxicity calculated from toxicity ratio（TR）shows that specifically-acting compounds in cytotoxicity,such as insecticides,fungicides,herbicides,dyes and medications used to treat cancer,depression,heart failure and blood pressure,are active compounds in mitochondrial toxicity.However,the less inert compounds identified in fish and cell toxicity exhibit greatly mitochondrial toxicity.QSAR models reveal that fish or cell toxicity is closely related to the chemical hydrophobicity,ionization,energy of lowest unoccupied molecular orbital,hydrogen bonding potential and stability.On the other hand,binomial model reveals that mitochondrial toxicity is closely related to the chemical hydrophobicity and polarizability/dipolarity,indicating bio-uptake and Van der Waals interaction play key roles in mitochondrial toxicity.Cytotoxicity can serve as a surrogate for fish toxicity and be used in the safety evaluation of organic pollutants in aqueous environment,but not mitochondrial toxicity,although some compounds share same modes of action between fish or cell toxicity and mitochondrial toxicity.（3）The acute and chronic SSDs curves of methoxyacrylate fungicides were established,and the acute and chronic HC₅values were calculated,so as to deduce the WQC of four fungicides.The acute HC₅values were 96.21,44.93,0.96 and 14.14μg/L,and the chronic HC₅values were 3.52,12.81,0.29 and 2.78μg/L for azoxystrobin,kresoxim-methyl pyraclostrobin and trifloxystrobin,respectively.SSDs revealed that aquatic animals were relatively sensitive species and aquatic plants are insensitive species for the four methoxyacrylate fungicides.There was very close interspecies correlation between two fish toxicity because they have same physiological structure and share same MOA for the four fungicides.Principal component analysis of HC₅values revealed that water flea and algae were far away from the fish and amphibians,indicating different MOA to different species.According to toxicity correlation and principal component analysis,the kresoxim-methyl toxicity was very close to trifloxystrobin as compared with azoxystrobin and pyraclostrobin.QSAR revealed that toxicity of strobilurin fungicides was dependent both on chemical hydrophobicity and hydrogen bond basicity.（4）Embryos at～6 hours post-fertilization（hpf）were exposed to either a solvent control（0.1%DMSO,v/v）,embryo rearing medium（ERM）,or one dose of either 1,2.5,5,or 25μM pendimethalin for up to 7-days post fertilization depending on the bioassay.The toxicological endpoints such as measured mortality,developmental abnormalities,oxidative respiration,reactive oxygen species,gene expression,and locomotor activity were quantified.Exposure to25μM pendimethalin resulted in high prevalence of spinal curvature,tail deformity,pericardial edema,and yolk sac edema at 4 dpf,while exposure to 5μM pendimethalin induced pericardial edema and lordosis in the fish exposed for 7 dpf.Although no effect of pendimethalin on oxidative respiration and reactive oxygen species was observed,transcripts related to oxidative respiration and damage response were observed,with increased expression of cox1 m RNA and decreased expression of cox5a1 and sod2 m RNA.When exposed to low concentration,pendimethalin can reduce the motor activity of larvae in the dark.