Secondhand Smoke Exposure Impairs Ion Channel Function and Contractility of Mesenteric Arteries

Cigarette smoke, including secondhand smoke (SHS), has significant detrimental vascular effects, but its effects on myogenic tone of small resistance arteries and the underlying mechanisms are understudied. Although it is apparent that SHS contributes to endothelial dysfunction, much less is known about how this toxicant alters arterial myocyte contraction, leading to alterations in myogenic tone. The study's goal is to determine the effects of SHS on mesenteric arterial myocyte contractility and excitability. C57BL/6J male mice were randomly assigned to either filtered air (FA) or SHS (6 h/d, 5 d/wk) exposed groups for a 4, 8, or 12-weeks period. Third and fourth-order mesenteric arteries and arterial myocytes were acutely isolated and evaluated with pressure myography and patch clamp electrophysiology, respectively. Myogenic tone was found to be elevated in mesenteric arteries from mice exposed to SHS for 12 wk but not for 4 or 8 wk. These results were correlated with an increase in L-type Ca2+ channel activity in mesenteric arterial myocytes after 12 wk of SHS exposure. Moreover, 12 wk SHS exposed arterial myocytes have reduced total potassium channel current density, which correlates with a depolarized membrane potential (Vm). These results suggest that SHS exposure induces alterations in key ionic conductances that modulate arterial myocyte contractility and myogenic tone. Thus, chronic exposure to an environmentally relevant concentration of SHS impairs mesenteric arterial myocyte electrophysiology and myogenic tone, which may contribute to increased blood pressure and risks of developing vascular complications due to passive exposure to cigarette smoke.

Effects of E-Cigarette Vapor on the Pulmonary Immune System

E-cigarettes are nicotine delivery devices that have rapidly gained popularity in recent years. It is not well understood how the use of these devices impact the pulmonary immune system and its ability to defend against respiratory viral infection. To this end, BALB/c mice were exposed to e-cigarette aerosols for 3 hours per day, 5 days per week for 2 weeks. Lung tissue and serum were collected following 1, 3, 5 and 10 days of exposure. Average serum nicotine and cotinine concentrations during the 10-day exposure were 133 ± 46 ng/mL and 712 ± 302 ng/mL, respectively, which is consistent with levels found in active tobacco smokers. Compared to filtered air controls, e-cigarette exposure significantly increased total cells and macrophages in bronchoalveolar lavage fluid on days 1 and 5, and significantly decreased neutrophils on day 1, suggesting that e-cigarette vapor may change the cellular infiltrate of the lungs. mRNA expression of IL-1β, IL-6, TNFα and IL-10 in right lung tissue was significantly decreased at all timepoints, suggesting possible dampening of the pulmonary immune response. To investigate how these cellular changes may effect the response to viral stimuli, human Type II epithelial cells were treated with e-cigarette conditioned media 24 hours prior to poly(I:C) stimulation. Compared to controls, e-cigarette treatment of type II epithelial cells resulted in significantly decreased expression of the critical interferon pathway genes IRF3, IFNα, and IL-1β following poly(I:C) stimulation. E-cigarette media alone was able to significantly decrease the expression of IRF3 in these cells, suggesting e-cigarette vapor may impair key genes necessary for the recognition of and sufficient response to respiratory viruses.