Impact of e-cigarette refill liquid exposure on rat kidney.

Electronic-cigarettes (e-cigarette), the alternative to classic cigarettes are becoming extremely popular but their safety is not still established. Recent studies have showed cytotoxic effects of the electronic cigarette and its recharge e-liquid, in vitro. The present study was designed to evaluate e-cigarette liquid nephrotoxicity in rats. For this purpose, 32 rats were treated for 28 days as follows: Control group was injected intraperitoneally with NaCl 9 g/l; e-cigarette 0% treated group received an intraperitoneal injection of e-liquid without nicotine diluted in NaCl 9 g/l, e-cigarette treated group, received an intraperitoneal injection of e-liquid containing 0.5 mg of nicotine/kg of body weight/day diluted in NaCl 9 g/l and nicotine-treated group received an intraperitoneal injection of 0.5 mg of nicotine/kg of body weight/day diluted in NaCl 9 g/l. In nicotine group, creatinine level was increased, whereas urea and acid uric levels were decreased. In e-liquid-exposed groups, levels of uric acid and mainly urea were lower. Interestingly, after e-liquid exposure, oxidative stress status showed increased total protein and sulfhydril content, whereas superoxide dismutase and catalase activities were decreased. However, the levels of lipid peroxides were not increased after e-liquid exposure. Histological studies identified excess of cells with reduced and dark nuclei exclusively located in the renal collecting ducts. Thus, e-liquid seems to alter anti-oxidant defense and to promote minor changes in renal function parameters. This preliminary study raises some flags about possible nephrotoxicity of e-cigarette liquids in rats. As some features observed in rats may not be observed in human smokers, additional studies are needed to further qualify conclusions that might be applicable to actual users of e-cigarettes.

Neurobehavioral assessment following e-cigarette refill liquid exposure in adult rats.

The present study was conducted to assess the toxic effect of e-cigarette refill liquid on cognitive and motor functions in adult rats. Animals were administered 28 µl/kg of body weight of e-liquid with/without a dose of 0.5 mg of nicotine/kg of body weight, using the intraperitoneally route for a period of 4 weeks. They were then evaluated by novel object recognition test (NORT) and spontaneous alternation T-maze test for cognitive functions. Results indicated that e-liquid without nicotine induced, in the NORT, a decrease in time exploring the novel object during the test session and lower discrimination and recognition indexes compared to control and e-liquid with nicotine treated rats. Furthermore, short-term spatial memory was affected after e-liquid treatment in the spontaneous alternation T-maze test, identifying recognition memory impairments. However, none of the treatments altered motor functions assessed by inclined plane test, Kondziela's inverted screen test and weights test. Cell cytotoxicity assessment following e-liquid exposure showed a significant decrease in hippocampal cell viability, but no change in cortical cell viability. Thereby, e-liquid without nicotine causes cognitive impairments, especially on the hippocampus. Based on these results, more extensive assessments on e-cigarettes must be carried out.