| Ionic liquids (ILs) have been applied in many fields, due to its excellent solubility, well thermal stability, negligible vapor pressure and other unique properties. With wide application, the biological toxicity and poor biodegradability of ionic liquids attracts more and more attention. Current studies have mainly focused on the lethal toxicity of ionic liquids. However, studies on the hormesis effect of ionic liquids are rarely. In this work, we investigated the hormetic effects of imidazolium-based bromide ionic liquids on Caenorhabditis elegans, and explored the possible underlying mechanisms.The effects of different alkyl chain length and concentrations of imidazolium-based bromide ionic liquid on the lifespan, thermotolerance, body length, reproductive ability and neurotoxicity of nematodes were examined to explore whether there is a hormetic effect. Our results show that the effects are not consistant for different endpoints in Caenorhabditis elegans. Hormetic effects were found on the lifespan, thermotolerance, body length and neurotoxicity of the worms, however the effective concentrations were different for the ILs with different alkyl chain length. No hormetic effect was found on the repodcutive ability.The lifespan of nematodes were prolonged when exposed to 0.01 mg/L of ILs, and the ILs with longer alkyl chain showed more obvious effects. To investigate the possible underlying mechanism, nematodes were exposed to the three ILs at 0.01 mg/L for 2,5,7,9 and 11 days. Levels of reactive oxygen species (ROS), lipofuscin accumulation and expression of sod-5, daf-16 genes of nematodes were measured. ROS production and lipofuscin accumulation in C. elegans increased significantly when treated for a short term and then gradually declined as time went on. The expression of oxidative stress related gene sod-5 and aging related gene daf-16 was slightly up-regulated with exposure for 2,5 and 7 days, and significantly up-regulated after 9 days exposure. Therefore, we proposed that low concentration ILs extend the lifespan of C. elegans by removing ROS and up-regulating the associated genes and removing ROS. The hormetic effect induced by ILs could be an overcompensation response.Mortality is the most basic and commonly used endpoint in C. elegans to study the acute and chronic toxicity, lifespan and heat resistance. While traditional lethality detection method is time-consuming, and may cause mechanical damage to the nematodes. In this work, we developed a rapid and simple method to detect the mortality of worms. This method contains two steps:image acquisition and software analysis. A charge coupled device (CCD) digital camera was installed on a stereo microscope and connected to a computer. The movement of nematodes under the irradiation of blue light was recorded using software Toupview on the microscope. A software named Nematode Count was designed to analyze the travel path of the worms and the live worms were marked with a bright yellow color. The number of bright yellow area was defined as the number of live worms, and the mortality would be obtained. |
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