The in vitro toxicology of Swedish snus

Key Challenges for In Vitro Testing of Tobacco Products for Regulatory Applications: Recommendations for the In Vitro Mouse Lymphoma Assay

The Institute for In Vitro Sciences (IIVS) is sponsoring a series of workshops to develop recommendations for optimal scientific and technical approaches for conducting in vitro assays to assess potential toxicity within and across traditional tobacco and various tobacco and nicotine next-generation products (NGPs), including Heated Tobacco Products (HTPs) and Electronic Nicotine Delivery Systems (ENDS). This report was developed by a working group composed of attendees of the seventh IIVS workshop, 'Approaches and recommendations for conducting the mouse lymphoma gene mutation assay (MLA) and introduction to in vitro disease models', which was held virtually on 21-23 June 2022. This publication provides a background overview of the MLA, and includes the description of assay conduct and data interpretation, key challenges and recommended best practices for evaluating tobacco and nicotine products, with a focus on the evaluation of NGPs, and a summary of how the assay has been used to evaluate and compare tobacco and nicotine products.

Classification, Perception, and Toxicity of Emerging Flavored Oral Nicotine Pouches

INTRODUCTION

Oral Nicotine Pouches (ONPs) are the new form of nicotine pouches that have become a type of emerging smokeless tobacco product sold by various tobacco companies. These smokeless tobacco products are marketed for usage all over as snus containing tobacco-derived nicotine (natural) or as tobacco-free nicotine (synthetic) as substitutes for other tobacco products. Based on perception and socio-behavioral aspects, ONPs have become popular tobacco products among adolescents/young adults, and over 50% of young adult users of ONP use flavored ONPs, such as menthol/mint, tobacco, dessert/candy, and fruity, which are the most popular flavors. Various new ONP flavors are currently popular locally as well as in the online market. Tobacco, menthol, and fruit-flavored ONPs could motivate cigarette smokers to change to ONPs.

METHODS

We expanded our knowledge on natural/synthetic ONP flavor wheels to available data on ONPs, describing, in detail, their flavors and brands (US and Europe) in both natural and synthetic ONP categories. We classified over 152 snus and 228 synthetic ONPs into the following flavor categories: "Tobacco", "Menthol/Mint", "Fruity", "Candy/Deserts", "Drink", "Aroma", "Spices", and "Mixed Flavors".

RESULTS

Based on total numbers, we found the most popular ONP flavors, sold as tobacco and menthol, to be among natural ONPs; among synthetic ONPs, fruity and menthol are the most prominent flavors, with varying concentrations of nicotine and other flavoring chemicals, including coolant WS-23. We also showed possible molecular targets and toxicities, due to exposure to ONPs, activating several signaling cascades such as AKT and NF-kappaB, which might possibly lead to apoptosis and epithelial mesenchymal transition (EMT).

CONCLUSIONS

Considering the marketing of ONP products with various flavor profiles and with most of these products containing tobacco/menthol/fruit flavor, it is likely to have regulation and a marketing disclaimer on some of these products. Further, it would be logical to determine how the market reacts in terms of compliance and non-compliance with flavor restrictions by the regulatory agencies.

Effects of smokeless tobacco on cell viability, reactive oxygen species, apoptosis, and inflammatory cytokines in human umbilical vein endothelial cells

Smokeless tobacco products provide an alternative to cigarettes; however, smokeless tobacco is carcinogenic and harmful to human health. This study evaluated the toxicological effects of snus extracts and cigarette smoke total particulate matter (TPM) on human umbilical vein endothelial cells (HUVECs). Treated cells were examined for cell viability, reactive oxygen species (ROS), apoptosis, and inflammatory cytokines. Moreover, we explored the mechanism of programmed cell death induced by snus. The results showed that snus extracts significantly inhibited cell viability in a dose-dependent manner. ROS was significantly increased in treatment groups, and anti-oxidant treatment could not prevent snus extract-induced cell death. Snus extracts induced apoptosis, DNA damage, activation and cleavage of caspase-3 and caspase-8, pathway-related gene change, and interleukin (IL)-6 and IL-8 release in HUVECs. Snus extracts exposure may induce cytotoxicity, ROS generation, inflammatory cytokines release, and apoptosis or DNA damage through intrinsic and extrinsic pathways in HUVECs.

An approach for the extract generation and toxicological assessment of tobacco-free 'modern' oral nicotine pouches

Tobacco-free 'modern' oral nicotine pouches (MOPs), are similar in appearance and use to Swedish-style snus, but without tobacco. There are few identified methods to create test samples for toxicologically assessment of MOPs in vitro. In this study we present a simple method for the extraction of pouch material in cell culture media, providing consistent nicotine concentration and easy in vitro assessment. A series of contemporary in vitro screening assays (viability, cell health markers, oxidative stress and genotoxicity) using human oral fibroblasts (HGF) and human lung epithelial cells (H292) were employed. Extracts were generated from LYFT and compared to snus (CRP1.1) and cigarette (1R6F) reference products. MOP and CRP1.1 extracts were generated by incubating one pouch in 20 ml of cell culture media, while 1R6F AqE was prepared by smoking 1 cigarette into 20 ml of cell culture media. 1R6F demonstrated toxicological responses in most assays; CRP1.1 had minimal to moderate effects while MOP demonstrated little or no response in all assays. This study demonstrated the generation of MOPs extracts and their toxicological evaluation using in vitro screening approaches. Future product usage, pharmacokinetics and clinical studies will further substantiate the reduced risk potential of MOPs.

Adult interest in using a hypothetical modified risk tobacco product: findings from wave 1 of the Population Assessment of Tobacco and Health Study (2013-14)

BACKGROUND AND AIMS

The US Family Smoking Prevention and Tobacco Control Act provides a pathway for manufacturers to market a modified risk tobacco product (MRTP). This study examines socio-demographic and tobacco use correlates of interest in a hypothetical MRTP in a nationally representative sample of US adults.

DESIGN

Cross sectional wave 1 data from the 2013-14 Population Assessment of Tobacco and Health (PATH) Study.

SETTING

Household Audio-Computer Assisted Self-Interviews of US adults conducted in 2013-14.

PARTICIPANTS

A total of 32 320 civilian, non-institutionalized adults in the United States.

MEASUREMENTS

Interest in using a hypothetical MRTP ('If a tobacco product made a claim that it was less harmful to health than other tobacco products, how likely would you be to use that product?'), socio-demographics, tobacco use history and mental health and substance use problems. All estimates were weighted.

FINDINGS

Overall, 16.7% [95% confidence interval (CI) = 16.28, 17.18] of US adults reported interest in a hypothetical MRTP. Tobacco use was associated significantly with interest in a hypothetical MRTP, with interest most common among current established smokers (54.4%; 95% CI = 53.31, 55.39) and least common among never tobacco users (3.0%; 95% CI = 2.49, 3.55). Interest in a hypothetical MRTP was associated with experimental e-cigarette use among current experimental, current established and former smokers. Among non-smokers, race, age, education and substance use were associated with interest in using a hypothetical MRTP.

CONCLUSIONS

Among adults in the United States, interest in using a hypothetical modified risk tobacco product is low overall, and highest among current experimental and established smokers. A small percentage of non-smokers are interested in using a hypothetical hypothetical modified risk tobacco product.

In vitro cytotoxicity of Nicotiana gossei leaves, used in the Australian Aboriginal smokeless tobacco known as pituri or mingkulpa

The Aboriginal population of Central Australia use endemic Nicotiana species to make a smokeless tobacco product known usually as pituri or mingkulpa. Nicotiana leaves are masticated with wood ash into a 'quid' that is chewed/sucked for absorption of nicotine. In addition to nicotine, smokeless tobacco products contain a spectrum of biologically active compounds that may contribute to effects on health. The objective of this study was to quantify nicotine, and related alkaloids and tobacco specific nitrosamines (TSNAs), in Nicotiana leaves used in pituri, and compare in vitro toxicity of pure nicotine with Nicotiana leaf extract at the same concentration of nicotine. An aqueous extract of dry leaves of Nicotiana gossei and a reference smokeless tobacco (CORESTA CRP2) were quantified for major pyridine alkaloids and TSNAs using HPLC-UV and LC-MS/MS. A range of extract concentrations and corresponding concentrations of nicotine standard were tested using an MTS assay to measure human lung epithelium cell (A549) survival. Cells treated for 24h with the maximum concentration of 1.5mg/ml of nicotine resulted in 77% viability. In contrast, extracts from N. gossei leaves and CRP2 containing a similar concentration of nicotine (1.3mg/ml) resulted in remarkably lower viability of 1.5 and 6%, respectively. Comparison of cytotoxicity of pure nicotine with that of the extracts revealed that nicotine was not the source of their cytotoxicity. Other biologically active compounds such as the known carcinogens NNK and NNN, derived from nicotine and nornicotine and found to be present in the smokeless tobacco extracts, may be responsible.

A critical assessment of the scientific basis, and implementation, of regulations for the safety assessment and marketing of innovative tobacco-related products

Our scientific, logistical, ethical and animal welfare-related concerns about the latest US Food and Drug Administration (FDA) regulations for existing and so-called 'new' tobacco products, aimed at reducing harmful exposures, are explained. Such claims for sales in the USA now have to be based on a wide range of information, a key part of which will increasingly be data on safety and risk. One of the pathways to achieve marketing authorisation is to demonstrate substantial equivalence (SE) with benchmark products, called predicates. However, the regulations are insufficiently transparent with regard to: a) a rationale for the cut-off date for 'old' and 'new' products, and for exempting the former from regulation; b) the scientific validity and operation of SE; c) options for product labelling to circumvent SE; d) the experimental data required to support, and criteria to judge, a claim; and e) a strategy for risk assessment/management. Scientific problems related to the traditional animal methods used in respiratory disease and inhalation toxicology, and the use of quantitative comparators of toxicity, such as the No Observed Adverse Effect Level, are discussed. We review the advantages of relevant in vitro, mechanism-based, target tissue-oriented technologies, which an advisory report of the Institute of Medicine of the US National Academy of Sciences largely overlooked. These benefits include: a) the availability, for every major site in the respiratory tract, of organotypic human cell-based tissue culture systems, many of which are already being used by the industry; b) the accurate determination of concentrations of test materials received by target cells; c) methods for exposure to particulate and vapour phases of smoke, separately or combined; d) the ability to study tissue-specific biotransformation; and e) the use of modern, human-focused methodologies, unaffected by species differences. How data extrapolation, for risk assessment, from tissue culture to the whole animal, could be addressed, is also discussed. A cost (to animal welfare)-benefit (to society, including industry and consumers) analysis was conducted, taking into account the above information; the potential for animal suffering; the extensive data already available; the existence of other, less hazardous forms of nicotine delivery; the fact that much data will be generated solely for benchmarking; and that many smokers (especially nicotine-dependents) ignore health warnings. It is concluded that, in common with policies of several tobacco companies and countries, the use of laboratory animals for tobacco testing is very difficult, if not impossible, to justify. Instead, we propose and argue for an integrated testing scheme, starting with extensive chemical analysis of the ingredients and by-products associated with the use of tobacco products and their toxicity, followed by use of in vitro systems and early clinical studies (involving specific biomarkers) with weight-of-evidence assessments at each stage. Appropriate adjustment factors could be developed to enable concentration-response data obtained in vitro, with the other information generated by the strategy, to enable the FDA to meet its objectives. It is hoped that our intentionally provocative ideas will stimulate further debate on this contentious area of regulatory testing and public safety.

Toxicity assessment of tobacco products in vitro

Driven by new regulatory demands to demonstrate risk reduction, the toxicity assessment of tobacco products increasingly employs innovative in vitro methods, including biphasic cell and tissue cultures exposed to whole cigarette smoke at the air-liquid interface, cell transformation assays, and genomic analyses. At the same time, novel tobacco products are increasingly compared to traditional cigarettes. This overview of in vitro toxicology studies of tobacco products reported in the last five years provides evidence to support the prioritisation of in vitro over in vivo methods by industry and their recommendation by regulatory authorities.

Non-cigarette tobacco and the lung

Cigarette smoking is known to cause a wide range of damaging health outcomes; however, the effects of non-cigarette tobacco products are either unknown or perceived as less harmful than cigarettes. Smokeless tobacco, cigar smoking, and waterpipe smoking have increased in usage over the past few decades. Some experts believe that their use is reaching epidemic proportions. Factors such as a perception of harm reduction, targeted advertising, and unrecognized addiction may drive the increased consumption of non-cigarette tobacco products. In particular, the need for social acceptance, enjoyment of communal smoking activities, and exotic nature of waterpipe smoking fuels, in part, its popularity. The public is looking for "safer" alternatives to smoking cigarettes, and some groups advertise products such as smokeless tobacco and electronic cigarettes as the alternatives they seek. Though it is clear that cigar and waterpipe tobacco smoking are probably as dangerous to health as cigarette smoking, there is an opinion among users that the health risks are less compared to cigarette smoking. This is particularly true in younger age groups. In the cases of smokeless tobacco and electronic cigarettes, the risks to health are less clear and there may be evidence of a harm reduction compared to cigarettes. In this article, we discuss commonly used forms of non-cigarette tobacco products, their impacts on lung health, and relevant controversies surrounding their use.

Toxicity of gutkha, a smokeless tobacco product gone global: is there more to the toxicity than nicotine?

The popularity of smokeless tobacco (ST) is growing rapidly and its prevalence of use is rising globally. Consumption of Gutkha, an addictive form of ST, is particularly common amongst South Asian communities throughout the World. This includes within the US, following large-scale immigration into the country. However, there exists a lack of knowledge concerning these alternative tobacco products. To this end, a study was carried out to determine the toxicity of gutkha, and what role, if any, nicotine contributes to the effects. Adult male mice were treated daily for 3-week (5 day/week, once/day), via the oral mucosa, with equal volumes (50 μL) of either sterile water (control), a solution of nicotine dissolved in water (0.24 mg of nicotine), or a solution of lyophilized guthka dissolved in water (21 mg lyophilized gutkha). Serum cotinine, measured weekly, was 36 and 48 ng/mL in gutkha- and nicotine-treated mice, respectively. Results demonstrated that exposure to nicotine and gutkha reduced heart weight, while exposure to gutkha, but not nicotine, decreased liver weight, body weight, and serum testosterone levels (compared to controls). These findings suggest that short-term guhtka use adversely impacts growth and circulating testosterone levels, and that gutkha toxicity may be driven by components other than nicotine. As use of guthka increases worldwide, future studies are needed to further delineate toxicological implications such that appropriate policy decisions can be made.

Mutagenicity of smoke condensates from Canadian cigarettes with different design features

There is currently limited knowledge regarding the impact of different cigarette designs on the toxicological properties of cigarette smoke condensate (CSC). This study used the Salmonella Mutagenicity Assay to examine the mutagenic activity of mainstream CSCs from 11 commercial Canadian cigarette brands with different design features or tobacco blend. The brands were selected to include design features that are common for cigarettes sold in the Canadian market, as well as cigarettes with alternate filters (charcoal or MicroBlue™), the super slim design, and cigarettes containing mixed blends of different tobacco types. CSCs were obtained using the International Organization for Standardization (ISO) and Health Canada Intense (HCI) smoking regimes, and mutagenic activity was assessed using Salmonella strains TA98, YG1041 and YG5185. Comparisons of the commercial brands to the Kentucky 3R4F, the Canadian Monitor 8 reference and a Canadian best seller revealed no significant reduction in CSC mutagenicity for cigarettes with alternate filters. However, the super slim design did afford some reduction in mutagenic potency. Nevertheless, since the study did not attempt to evaluate the impact of the cigarette designs on human health at the individual or population level, the super slim cigarettes cannot be considered 'reduced-harm' cigarettes.