Assessment of the exposure to selected smoke constituents in adult smokers using in-market heated tobacco products: a randomized, controlled study

A Randomized Control Study in Healthy Adult Smokers to Assess Reduced Exposure to Selected Cigarette Smoke Constituents in Switching to the Novel Heated Tobacco Product DT3.0a

This was a randomized, controlled, open-label, confinement study to assess change in exposure to selected cigarette smoke constituents in healthy adult cigarette smokers who switched to using a novel heated tobacco product (direct heating tobacco system, platform 3, generation 3, version a [DT3.0a]). Sixty nonmenthol cigarette smokers were randomized into 1 of the 4 study groups in which subjects switched to a nonmenthol type of tobacco stick used with DT3.0a, switched to a nonmenthol tobacco stick used with an in-market heated tobacco product device (THS), continued to smoke nonmenthol cigarettes, or stopped smoking. Furthermore, 30 menthol cigarette smokers were randomized into 1 of the 2 study groups in which subjects switched to a menthol tobacco stick used with DT3.0a (mDT3.0a) or continued to smoke menthol cigarettes. Fifteen biomarkers of exposure to selected harmful and potentially harmful constituents (HPHCs) were measured during the 5-day exposure period, followed by assessment of nicotine pharmacokinetics with the assigned product. Results indicated that switching to DT3.0a, THS, and mDT3.0a showed significant exposure reductions in most of the selected HPHCs as compared to continuing smoking cigarettes, with reductions being similar in magnitude to reductions observed with smoking cessation. For DT3.0a and mDT3.0a, nicotine pharmacokinetic parameters were not remarkably different from those obtained for cigarettes and the THS except that a longer time to maximum concentration was obtained following use of the mDT3.0a. In conclusion, switching from smoking cigarettes to DT3.0a or THS use reduced exposure to most of the selected HPHCs, and no remarkable differences were observed for the measurements obtained from different flavors of DT3.0a stick.

Effects of aerosols from heated tobacco products with flavors on the discoloration of bovine tooth enamel

OBJECTIVES

This in vitro study assessed the potential of tooth discoloration by aerosols generated from three heated tobacco products (HTPs) with different specifications: in-direct heating tobacco system platform 1.0a (IT1.0a), in-direct heating tobacco system platform 2.0a (IT2.0a), and direct heating tobacco system platform 3.0a (DT3.0a). In addition, three flavor types (regular, menthol, and berry menthol) were selected for each HTP to characterize the effect of flavor types on tooth discoloration.

MATERIAL AND METHODS

Six bovine tooth samples were exposed directly to aerosols generated from one pack of each HTP: 350 puffs for IT1.0a, 325 puffs for IT2.0a, and 220 puffs for DT3.0a. Six bovine tooth samples were also exposed to air (350 puffs) and smoke generated from one pack of cigarettes (160 puffs) as negative and positive controls, respectively. The color of each tooth sample was measured before and after exposure. The overall color changes were assessed using overall color differences (ΔE) calculated according to the Commission International de I'Eclairage color system. A one-way analysis of variance followed by Tukey's post hoc test was used to compare ΔE among bovine tooth samples exposed to air, cigarette smoke, and aerosols generated from each HTP.

RESULTS

ΔE values for tooth samples exposed to air and aerosols generated from the three HTPs (IT1.0a, IT2.0a, and DT3.0a) were significantly lower than ΔE value for tooth samples exposed to cigarette smoke. ΔE values obtained with DT3.0a were significantly higher than those obtained with air-exposed control samples. However, ΔE values obtained with IT1.0a and IT2.0a were not significantly different from that obtained with air-exposed control samples. No HTPs showed significant differences in ΔE values among the three flavor types.

CONCLUSIONS

This study showed that HTP aerosols reduce tooth discoloration potential compared with cigarette smoke, regardless of flavor types, and the tooth discoloration potential of the product may depend on product specifications.

Effects of heated tobacco product aerosol extracts on DNA methylation and gene transcription in lung epithelial cells

AIMS

Smoking causes DNA methylation (DNAm) alterations that lead to lung cancer development. Although the use of heated tobacco products (HTPs) has recently increased, their impact on health remains unclear. This study aimed to evaluate the effects of HTPs on DNAm and gene transcription in human lung epithelial cells in vitro.

MAIN METHODS

Human lung adenocarcinoma (A549) cells with type II alveolar epithelial characteristics were treated with aerosol extracts of two HTPs or a smoke extract of combustible reference cigarette (RC). Global 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) levels were quantified using dot blot analysis. Furthermore, reduced representation of bisulfite sequencing, DNA microarray, and quantitative PCR analyses were performed to determine CpG methylation and gene transcription changes induced by HTP and RC.

KEY FINDINGS

Global 5-mC and 5-hmC levels were decreased by the RC extract but not the HTP extracts. However, an HTP extract altered the CpG methylation pattern, and Gene Ontology enrichment analysis of the differentially methylated regions of the RC and HTP groups showed a similar pattern. The HTP extract affected gene expression, albeit to a lesser extent than the RC extract. In particular, the HTP extract markedly affected the mRNA expression and promoter methylation of cytochrome P450 family 1 subfamily A member 1 (CYP1A1), which is associated with carcinogenic risk.

SIGNIFICANCE

The study results suggest that HTPs as well as conventional combustible cigarettes can alter CpG methylation and gene transcription in lung epithelial cells.