Effect Of Ionic Liquids On Oxidative Stress, Swimming Behavior And Reproductive System Of Zebrafish

Ionic liquids are gaining growing attentions due to their special physical and chemical properties. They are concerned as “green solution” which are environmentally friendly so they have been widely used in industries. However, the biological safety of ionic liquids and the unexpected health impacts to humans become interesting points of researches. The current study choosed the model animal zebrafish(Danio rerio) to determine the molecular mechanism leading to cytotoxic and genotoxic of [BMIM]BF4 and the main results are summarized as follows:1. After different concentrations of the ionic liquid [BMIM]BF4 exposure for 10, 20 and 30 days, the contents of MDA and hydroxyl radicalthe and activities of antioxidant enzymes(superoxide dismutase and catalase) were changed in livers. This study indicated that after[BMIM]BF4 exposure, concentration of reactive oxygen species increased, the lipid were injured in liver cells and hepatic antioxidant defense were activated. These results suggested that zebrafish had adaptable response to environmental stress to adapt it.2. Using the behavioural analysis system to assess swimming behavior of larval zebrafish,the results showed that the total distance decreased in a dose and time dependent manner.Expressions of proteins essential for excitation-contraction(EC) coupling in muscle, ryanodine receptor, related genes Ry Rs showed a decreasing trend. Accessory proteins related genes like CK and SPEN1 were down regulated significantly. After [BMIM]BF4 exposure, energy supplied for muscle contraction in larval zebrafish decreased and release/reflux of Ca2+ were inhibited,which result in decline of muscle contraction degree and frequency and decrease of swimming ability.3. To further determine the toxicity of [BMIM]BF4 to reproductive system of zebrafish, a systematic study involving the assessment of testosterone(T) and estradiol(E2)contents and expressions of hypothalamic-pituitary-gonadal axis related genes in both male and female zebrafish was performed. After adult zebrafish exposure to [BMIM]BF4 for 30 days, thecontents of T and E2 decreased in dose dependent manner, which suggested that [BMIM]BF4might affect the reproductive system in adult fishes. The following study showed expressions of gonadotrophin releasing hormone and its receptors related genes up-regulated in both females and males brains which were consistent with the decrease of estradiol and testostrone in blood.Expressions of proteins which are important in hormone synthesis process related genes such like cyp11 a and star were down regulated. This might be the reason for the decrease of sex hormone. The expressions of hypothalamic-pituitary-gonadal axis related genes disordered after exposure to [BMIM]BF4 and the reproductive system in both female and male zebrafish were adversely affected.In summary, ionic liquid [BMIM]BF4 could cause the oxidative damage to fishes, decline the larval swimming ability significantly and disrupt the reproductive system. This study enriched toxic data of ionic liquids to freshwater organisms, recognized toxic and molecular mechanisms of ionic liquids to zebrafish comprehensively and also could provide data and theory for establishment of environmental security assessment to ionic liquids.