Toxic Effects Of Chronic Exposure To Imidazolium-based Ionic Liquids On Caenorhabditis Elegans And Its Detoxification

Because of their unique physicochemical properties,ionic liquids(ILs)have been extensively used in various areas such as catalysis,materials and electrochemistry.With their extensive usage,more and more attention has been gradually paid to their toxicities.Although acute toxicities of ILs have been reported by many researchers,few studies focus on their chronic toxicities.In this article,Caenorhabditis elegans(C.elegans)was employed to evaluate the chronic effects of 1-tetradecyl-3-methyl imidazolium bromide,an imidazolium-based IL,and the possible detoxification processes of ILs were further examined.First,the effects of acute and prolonged exposure on lethality,body length,locomotive behaviors,reproduction and development in C.elegans were studied.LC50 values are 59.1 mg/L and 15.4 mg/L in the acute and prolonged exposure system,respectively,which indicates that the prolonged exposure system has high sensitivity compared to the acute exposure system.Little effects on body length,locomotive behaviors and reproduction were displayed in the acute exposure system.In contract,adverse effects on the growth,locomotive behaviors and development were induced after the prolonged exposure to 5 and 10 mg/L of ILs.These results together show that the prolonged exposure system would be more suitable for the toxicity assessment of low toxic pollutants.Second,toxicity mechanisms of ILs were exploded in the prolonged system.After the prolonged exposure,the lipofuscin content,reactive oxygen species(ROS)level and the expressions of superoxide dismutase(SOD)were examined,and the results indicate that the lipofuscin content,ROS level and the expressions of SOD did not show significant changes except that the expression of.sod-5 was reduced following the treatment of 10 mg/L ILs,suggesting that oxidative stress may not be responsible for the adverse physiological effects induced by imidazolium-based ILs.Third,detoxification processes of ILs were investigated in C.elegans and some important detoxifying genes were discovered.The gene expressions of phase I detoxification enzyme cytochrome P450(CYP),phase ? detoxification enzyme UDP-glucuronosyltransferase(UGT)and ATP-binding cassette(ABC)transporter P-glycoprotein(PGP)show highly significant changes after the prolonged exposure,and pgp-13 RNAi worms showed significant decreases in body length.These results demonstrate that CYP,UGT and PGP may be involved in the detoxification of ILs.