Diluted aqueous extract of heat-not-burn tobacco product smoke causes less oxidative damage in fibroblasts than conventional cigarette

Research progress and prospect on the safety of heated tobacco products

In recent years, Heated tobacco products (HTP) have gradually entered the market and become more and more popular with consumers because of their low risk (compared with traditional cigarette). With the increasing popularity and proportion of HTP in the international market, people pay more and more attention to the safety evaluation of HTP, but there is still a lack of systematic review of HTP safety research. In this review, the harmful components of HTP, multi-organ functional programming effects (including respiratory system, cardiovascular system, etc.), and mechanism of the effect generation (including oxidative stress, inflammatory response, etc.) were systematically reviewed, the safety effects of HTP and traditional cigarettes were compared in detail, and the shortcomings and future research directions in the field of HTP safety were discussed. In summary, this review conforms to the general trend of contemporary "tobacco and health", helps people to understand and evaluate HTP more systematically, and provides a strong theoretical support and literature basis for the tobacco industry to carry out HTP risk assessment and exposure improvement.

Role of reactive carbonyls and superoxide radicals in protein damage by cigarette smoke extracts: Comparison of Heat-not-Burn e-cigarettes to conventional cigarettes

Oxidative protein damage involving carbonylation of respiratory tract proteins typically accompanies exposure to tobacco smoke. Such damage can arise via multiple mechanisms, including direct amino acid oxidation by reactive oxygen species or protein adduction by electrophilic aldehydes. This study investigated the relative importance of these pathways during exposure of a model protein to fresh cigarette emission extracts. Briefly, protein carbonyl adducts were estimated in bovine serum albumin following incubation in buffered solutions with whole cigarette emissions extracts prepared from either a single 1R6F research cigarette or a single "Heat-not-Burn" e-cigarette. Although both extracts caused concentration-dependent protein carbonylation, conventional cigarette extracts produced higher adduct yields than e-cigarette extracts. Superoxide radical generation by conventional and e-cigarette emissions was assessed by monitoring nitro blue tetrazolium reduction and was considerably lower in extracts made from "Heat-Not-Burn" e-cigarettes. The superoxide dismutase/catalase mimic EUK-134 strongly suppressed radical production by whole smoke extracts from conventional cigarettes, however, it did not diminish protein carbonyl adduction when incubating smoke extracts with the model protein. In contrast, edaravone, a neuroprotective drug with strong carbonyl-trapping properties, strongly suppressed protein damage without inhibiting superoxide formation. Although these findings require extension to appropriate cell-based and in vivo systems, they suggest reactive aldehydes in tobacco smoke make greater contributions to oxidative protein damage than smoke phase radicals.

Association of conventional cigarette smoking, heated tobacco product use, and dual use with hearing loss: A working population-based study

INTRODUCTION

Although conventional cigarette smoking has been linked to an increased risk of hearing loss, the association between heated tobacco products (HTPs) and hearing loss is unknown. The objective of this study was to investigate the association between cigarette and HTP use and hearing loss.

METHODS

This cross-sectional study examined the data of 7769 employees from five companies (Study I) and 34404 employees from a large company (Study II), all participants in the Japan Epidemiology Collaboration on Occupational Health Study. The participants were categorized into five groups based on their self-reported tobacco use: never smokers, former smokers, exclusive cigarette smokers, exclusive users of HTPs, and those who used both cigarettes and HTPs. Hearing levels were measured using pure-tone audiometry at 1 and 4 kHz frequencies. Separate analyses were carried out for each study, and the results were then combined using fixed-effect models to pool the estimates.

RESULTS

The analysis included 42173 participants, with a prevalence of 12.9% for exclusive cigarette smoking, 9.8% for exclusive HTP use, and 5.5% for dual use. The pooled adjusted odds ratios with 95% confidence intervals for unilateral hearing loss at 4 kHz were 1.21 (95% CI: 1.10-1.33) for former smokers, 1.83 (95% CI: 1.64-2.05) for exclusive cigarette smokers,1.46 (95% CI: 1.28-1.67) for exclusive HTP users, and 1.66 (95% CI: 1.41-1.96) for dual users, compared to never smokers. Additionally, the adjusted odds ratios for hearing loss at 4 kHz among exclusive cigarette smokers, exclusive HTP users, and dual users increased with the intensity of cigarette/HTP consumption (all p for trend <0.001). No significant associations were found between exclusive HTP use, dual use, and hearing loss at 1 kHz, apart from exclusive cigarette smoking.

CONCLUSIONS

In this cross-sectional study, associations were found between exclusive cigarette smoking, exclusive HTP use, dual use, and hearing loss, particularly at 4 kHz. Further research is needed to confirm these findings.

The Product Science of Electrically Heated Tobacco Products: An Updated Narrative Review of the Scientific Literature

Heated tobacco products represent a novel category of tobacco products in which a tobacco consumable is heated to a temperature that releases nicotine from the tobacco leaf but not to a temperature sufficient to cause combustion. Heated tobacco products may therefore have the potential to be a less harmful alternative for adult smokers who would otherwise continue to smoke cigarettes, as their use should result in exposure to substantially fewer and lower levels of toxicants. This update represents a two-year extension to our previous narrative review, which covered peer-reviewed journal articles published up to August 31, 2021. The scientific evidence published between 2021 and 2023 continues to indicate that aerosols produced from heated tobacco products contain fewer and substantially lower levels of harmful and potentially harmful constituents and that these observed reductions consistently translate to reduced biological effects in both in vitro and in vivo toxicological studies. Biomarker and clinical data from studies in which product use is controlled within a clinical setting continue to suggest changes in levels of biomarkers of exposure, biomarkers of potential harm, and clinical endpoints indicating the potential for reduced harm with switching to exclusive use of heated tobacco products in adult smokers. Overall, the available peer-reviewed scientific evidence continues to indicate that heated tobacco products offer promise as a potentially less harmful alternative to cigarettes, and as such, the conclusions of our original narrative review remain valid.

Effect of heated tobacco products and traditional cigarettes on pulmonary toxicity and SARS-CoV-2-induced lung injury

Cigarette smoke (CS) significantly contributes to the development of chronic obstructive pulmonary disease (COPD). Heated tobacco products (HTPs), newly developed cigarette products, have been proposed as an alternative for safe cigarette smoking. Although it is plausible to think that replacing traditional cigarettes with HTPs would lower the risks of COPD, this notion requires confirmation by further investigations from sources independent of the tobacco industry. COPD is characterized by an ongoing inflammatory process in the lungs, and the renin-angiotensin system (RAS) has been implicated in the pathogenesis of COPD. Angiotensin-converting enzyme-2 (ACE2) functions as a negative regulator of RAS and has been suggested as a cellular receptor for the causative agent of SARS-CoV-2. It has been shown that smoking is most likely associated with the negative progression and adverse outcomes of SARS-CoV-2. In this study, we found that cigarette smoke extracts from traditional cigarettes (CSE) caused higher cytotoxicity and higher oxidative stress levels than extracts from HTPs (HTPE) in two lung cell lines (Calu-3 and Beas-2B). CSE and HTPE induced RAS activation, MAPK activation, and NF-kB inflammatory pathway activation, resulting in the production of inflammatory cytokines. Furthermore, CSE and a high dose of HTPE reduced tight junction proteins, including claudin 1, E-cadherin, and ZO-1, and disrupted lung epidermal tight junctions at the air-liquid interface (ALI). Finally, CSE and HTPE enhanced the spike protein S1-induced lung injury response. Together, these results suggest that HTPE induced similar lung pathogenesis relevant to COPD and SARS-CoV-2-induced lung injury caused by CSE.