Vascular endothelial function is impaired by aerosol from a single IQOS HeatStick to the same extent as by cigarette smoke

Abstract

Background: Heated tobacco products (also called 'heat-not-burn' products) heat tobacco at temperatures below that of combustion, causing nicotine and other compounds to aerosolise. One such product, IQOS from Philip Morris International, is being marketed internationally with claims of harm reduction. We sought to determine whether exposure to IQOS aerosol impairs arterial flow-mediated dilation (FMD), a measure of vascular endothelial function that is impaired by tobacco smoke.

Methods: We exposed anaesthetised rats (n=8/group) via nose cone to IQOS aerosol from single HeatSticks, mainstream smoke from single Marlboro Red cigarettes or clean air for a series of consecutive 30 s cycles over 1.5-5 min. Each cycle consisted of 15 or 5 s of exposure followed by removal from the nose cone. We measured pre-exposure and postexposure FMD, and postexposure serum nicotine and cotinine.

Results: FMD was impaired comparably by ten 15 s exposures and ten 5 s exposures to IQOS aerosol and to cigarette smoke, but not by clean air. Serum nicotine levels were similar to plasma levels after humans have smoked one cigarette, confirming that exposure conditions had real-world relevance. Postexposure nicotine levels were ~4.5-fold higher in rats exposed to IQOS than to cigarettes, despite nicotine being measured in the IQOS aerosol at ~63% the amount measured in smoke. When IQOS exposure was briefer, leading to comparable serum nicotine levels to the cigarette group, FMD was still comparably impaired.

Conclusions: Acute exposures to IQOS aerosol impairs FMD in rats. IQOS use does not necessarily avoid the adverse cardiovascular effects of smoking cigarettes.

Keywords: electronic nicotine delivery devices; harm reduction; nicotine; non-cigarette tobacco products; smoking caused disease.

Figure 1

IQOS. IQOS is composed of three main parts: HeatStick, holder and pocket charger. HeatSticks are inserted in the holder, which contains an electronic heating blade to heat tobacco and release aerosol. HeatSticks contain strips of processed and reformed tobacco. Photos by MLS and PN.

Figure 2

Aerosol generation and exposure systems. (A) Manual exposure system. (B) Analytical vaping machine made by Gram Research. (C) IQOS aerosol coming out of nose cone. (D) Rat’s nose placed in the nose cone. Photos in A, C and D by PN; photo in B from Gram Research with permission.

Figure 3

Arterial flow-mediated dilation was impaired by mainstream cigarette smoke and IQOS aerosol. (A) Ultrasound imaging of rat femoral artery. (B) FMD experimental design: FMD was measured pre-exposure and postexposure in each rat. (C) FMD after 10 cycles of 15 s exposure +15 s break. (D) FMD after 10 cycles of 5 s exposure +25 s break. Coloured lines denote individual rats pre-exposure and postexposure; bars denote group means; p values are derived from paired 2-tailed t-tests. FMD, flow-mediated dilation.

Figure 4

Serum nicotine and cotinine levels immediately and 20 min postexposure. Samples were taken after 10 cycles of 5 s exposure +25 s break. P values are derived from two-tailed Student’s t-tests. IQOS x10, 10 IQOS exposure cycles; cigarette x10, 10 cigarette exposure cycles; air x10, 10 air exposure cycles; IQOS x3, three IQOS exposure cycles; BLQ, below level of quantification.

Figure 5

Reduced IQOS exposure to match nicotine absorption level of the cigarette group still impairs FMD to a comparable extent. Coloured lines denote individual rats pre-exposure and postexposure; bars denote group means; p values are derived from paired two-tailed t-tests. Exposure conditions were three cycles of 5 s exposure +25 s break. FMD, flow-mediated dilation.