Preliminary study on the E-liquid and aerosol on the neurobehavior of C. elegans.

E-cigarettes, also known as electronic nicotine delivery systems (ENDS), are mainly used among adolescents and young adults. Similar to traditional cigarettes, different concentrations of nicotine are also added to E-cigarette's liquid (E-liquid), but due to the supplementation of chemicals such as propylene glycol (PG), vegetable glycerin (VG) and flavors, it is difficult to determine the risk after using E-cigarettes. And given to the specificity of the aerosol particle composition and atomization process of E-cigarettes, it is necessary to assess the neurotoxic effects of long-term E-cigarettes use. In this study, two commercial nicotine-containing (5%) and nicotine-free E-liquids were diluted to investigate the neurobehavioral changes and addictive tendencies of developing C. elegans after sub-chronic exposure to E-liquid. The results showed that sub-chronic exposure of E-liquid could lead to impaired growth and development of nematodes, abnormal general neuromotor behavior and advanced learning and memory behavior, and nicotine-containing E-liquid could also lead to increased addiction tendency of nematodes. Although the damage effect of nicotine free E-liquid is smaller than that of the nicotine-containing group, its toxic effect cannot be ignored. Further analysis of the neurotoxicity mechanism found that redox imbalance-mediated mitochondrial stress and aging may be important causes of E-liquid-induced biological damage. The biosafety of e-cigarette aerosols was also included in the assessment. The study found that the heated atomization process did not alter the E-liquid components, and E-cigarette aerosols still have the effect of interfering with the growth and development of nematodes and neurobehavior, and its addictive nature is also of concern. This study can provide new ideas for future studies on the neurotoxic effects and safety assessment of the E-cigarettes, and provide theoretical reference for the study on the injury mechanism of E-cigarettes.

Microplastics induce neurotoxicity in aquatic animals at environmentally realistic concentrations: A meta-analysis.

Microplastics (MPs) draw international attention owing to their widespread distribution in water ecosystems, but whether MPs cause neurotoxic effects in aquatic animals at environmentally realistic concentrations is still controversial. This meta-analysis recompiled 35 studies to determine whether MPs could change the levels of brain (in vivo) neurotransmitters in aquatic animals at environmentally realistic concentrations (≤1 mg/L, median = 0.100 mg/L). Then, a group comparison was conducted to compare the effects of different factors on the effect size and to explore the significant factors affecting the neurotoxicity of MPs. The results demonstrated that MP exposure could considerably decrease the levels of acetylcholinesterase (AchE) in the brain of aquatic animals by 16.2%. However, the effects of MPs on cholinesterase (CHE), acetylcholine (ACh), dopamine (DA) and γ-aminobutyric acid (GABA) were not statistically significant due to the small number of studies and samples. The neurotoxicity of MPs was closely linked with particle size and exposure time but independent of animal species, MP compositions, MP morphology and MP concentrations. Further literatures review indicated that MP-induced neurotoxicity and behavioral changes are related with multiple biological processes, including nerve damage, oxidative stress, intestinal flora disturbance and metabolic disorder. Furthermore, some factors influencing MP neurotoxicity in the real environment (e.g. the aging of MPs, the release of MP additives, and the co-exposure of MPs and pollutants) were discussed. Overall, this study preliminarily explored whether MPs induced changes in neurotoxicity-related indicators in aquatic animals through meta-analysis and provided scientific evidence for evaluating the health risks and neurotoxicity of MPs at the environmental level.

Toxicity of electronic cigarettes: A general review of the origins, health hazards, and toxicity mechanisms.

Electronic cigarettes (E-cigarette) are an alternative for traditional cigarette smokers to quit smoking. Based on the current understanding, electronic cigarettes have rapidly become popular among existing smokers and former non-smokers. However, increasing research at different levels reveals that e-cigarettes are unsafe. This review provides an overview of the toxicology of e-cigarettes based on existing in vivo and in vitro studies and compares their toxicity with that of traditional cigarettes. Moreover, we describe the associated toxicity components in e-cigarettes, as well as the potential mechanism by which e-cigarettes exert toxic effects. As is known to all, the nicotine in traditional cigarettes and e-cigarettes has certain toxicity. Besides, a few studies have shown that propylene glycol and vegetable glycerin mixture and flavoring agents in e-cigarettes also are the key components causing adverse effects in animals or cells. There is insufficient scientific evidence on the toxicity of e-cigarettes due to the lack of standardized research methods, prompting the need to conduct a comprehensive toxicity assessment of e-cigarette toxicity to elucidate the safety issues of e-cigarettes. Eventually, a basis for decision-making on whether people use e-cigarettes will be obtained.