Impairment of endothelial function by cigarette smoke and e-cigarette aerosol requires RAGE

Introduction: Although e-cigarette is known to cause detrimental physiological alterations in the cardiovascular system, the molecular mechanism of e-cigarette-induced vascular impairment is relatively unexplored. We investigated whether the inhibition of RAGE prevents impairment of vasomotor function from acute and chronic e-cigarette exposure. 

Hypothesis: RAGE is required to cause e-cigarette-induced impairment of endothelial vasodilation.

Methods: In both exposure settings, anaesthetized rats (n=8/group) were exposed to aerosols from flavorless tank-style e-cigarettes with and without freebase nicotine (12 mg/mL) or air. For acute exposure, exposure was done in a singles session of 10 cycles of pulsatile 5s exposure over 5 minutes using a Gram REsearch analytical vaping machine drawing 55ml. All rats received RAGEi or DMSO i.p. 1h pre-exposure. FMD was measured pre-exposure and 10 minutes after the end of the exposure. For sub-acute exposure, the exposure consisted of a single session of 120 cycles of pulsatile 5s exposure over 1h/day for 2 weeks. All the rats received RAGEi or DMSO i.p. 1h pre-exposure daily during acclimation and exposure (total of 3 weeks). Echocardiography was conducted one day before the end of the experiment. FMD was measured before and after the exposure on the last day of the experiment. 

Results: Exposure to e-cigarette aerosol with and without nicotine impaired FMD in vehicle groups in both acute and subacute exposures with no change in air control. As expected, the positive control of cigarette exposure impaired FMD in the vehicle group in acute settings. However, FPS-ZM1 prevented the FMD impairment in e-cigarette aerosol exposures and cigarette exposures in both acute and subacute exposures with no changes in air control.

Conclusions: RAGE plays a role in mediating e-cigarette-induced acute and sub-acute impairment of endothelial vasodilatory function.

Methods
For femoral artery diameter data, raw ultrasound data were collected by a Vevo 3100LT micro-ultrasound system (VisualSonics Inc., Toronto, Canada). Ultrasound images were processed and femoral artery diameter was measured by an automated system (Brachial Analyzer, Medical Imaging Applications, Coralville, IA). 

For cardiac function data, raw echocardiograms was collected by a Vevo 3100LT micro-ultrasound system (VisualSonics Inc., Toronto, Canada) and echocardiographic parameters were measured by a VevoLab software (VisualSonics Inc., Toronto, Canada).

引言：尽管已知电子烟会引发心血管系统出现有害生理改变，但电子烟诱导血管损伤的分子机制仍有待深入探索。本研究旨在探讨晚期糖基化终末产物受体（RAGE）的抑制作用，能否阻断急性与慢性电子烟暴露所导致的血管舒缩功能损伤。

假说：晚期糖基化终末产物受体（RAGE）是介导电子烟诱导的内皮血管舒张功能损伤的必要因子。

方法：在两种暴露模型中，均采用每组8只麻醉大鼠，分别暴露于无调味罐式电子烟产生的气溶胶（含/不含12mg/mL游离碱尼古丁）或洁净空气。急性暴露方案：使用Gram Research公司的分析型电子烟抽吸装置（抽吸体积55mL），在5分钟内完成10次脉冲式5秒暴露，单次完成。所有大鼠于暴露前1小时接受腹腔注射RAGE抑制剂（RAGEi）或二甲基亚砜（DMSO）。分别于暴露前及暴露结束后10分钟测量血流介导的血管舒张（FMD）。亚急性暴露方案：每日1小时内完成120次脉冲式5秒暴露，持续2周。所有大鼠在适应期与暴露期每日暴露前1小时接受腹腔注射RAGEi或DMSO（总时长共3周）。实验结束前1天进行超声心动图检测。实验最后一日分别于暴露前后测量血流介导的血管舒张（FMD）。

结果：在急性与亚急性暴露模型中，溶剂对照组大鼠暴露于含/不含尼古丁的电子烟气溶胶后，血流介导的血管舒张（FMD）均出现损伤，而空气对照组无明显变化。正如预期，急性暴露模型中香烟暴露的阳性对照可使溶剂对照组大鼠的FMD出现损伤。然而，FPS-ZM1可阻断电子烟气溶胶及香烟暴露所导致的FMD损伤，空气对照组无明显变化。

结论：晚期糖基化终末产物受体（RAGE）参与介导电子烟诱导的急性与亚急性内皮血管舒张功能损伤。

补充方法：
股动脉直径数据：采用Vevo 3100LT微型超声系统（加拿大多伦多VisualSonics公司）采集原始超声数据，通过自动化分析系统（Brachial Analyzer，美国爱荷华州科勒尔维尔医学成像应用公司）处理超声图像并测量股动脉直径。
心脏功能数据：采用Vevo 3100LT微型超声系统（加拿大多伦多VisualSonics公司）采集原始超声心动图数据，通过VevoLab软件（加拿大多伦多VisualSonics公司）分析超声心动图参数。