Does the electronic-cigarette aerosol impact rat brain lipid profile?

The lack of tobacco combustion, the most attractive feature of electronic cigarettes (e-cigs), has quickly made these new devices become the most sought-after alternative to the traditional cigarettes, contributing also to its widespread safety perception. Contrary to the general belief that the electronic nicotine-delivery systems avoid the release of harmful chemicals, the high temperature reached by e-cig solutions can actually generate dozens of toxic compounds, some of which are listed as known human carcinogens. Male Sprague Dawley rats, at 8 weeks of age, were housed under a 12h-light/12h-dark cycle, 22°C, 60% humidity, and fed ad libitum. After 5 days’ adaptation, the rats were randomly split into two groups of 10 animals each (non-exposed (control group) and exposed). Animals were whole-body exposed to 11 cycles/day, in order to consume 1 mL/day of e-liquid containing 18 mg/mL of nicotine. At the end of each cycle, the animals were transferred to a clean chamber to begin the next one. Animals were treated 5 days/week for 4 consecutive weeks. Rats were fasted 16 h prior to sacrifice. Animals were anesthetized by administering Zoletil 100 (100 mg/kg b.w.) and then sacrificed by decapitation according to the approved Ministerial procedures. The rats’ brains were isolated and their lipid matter was subjected to the analysis of total fatty acids, sterols and oxysterols composition. The e-cig aerosol exposure decreased the total lipid content in rat brain. A slight increase of saturated fatty acids and n-6 long-chain polyunsaturated fatty acids (LC-PUFA) was detected, while n-3 LC-PUFA dropped. A reduction of total cholesterol content and its oxidation products was also observed; in fact, the levels of 7alfa-hydroxycholesterol, alfa/beta-epoxycholesterol isomers and triol were lower compared to those found in the control group. The present research study revealed how e-cigs aerosol could disrupt the lipid and cholesterol homeostasis in rat brain, which could contribute to the new occurrence of some neurodegenerative diseases. A deeper investigation is needed to assess the harmful health impact of e-cigs, particularly after long-term exposure.