Control of tobacco-specific nitrosamines by the Bacillus siamensis: Strain isolation, genome sequencing, mechanism analysis and genetic engineering

Nitrosamines are considered carcinogens that threaten human health and environment. Especially, high contents of Tobacco-specific nitrosamines (TSNAs) are generated during the fermentation process of cigar tobacco. To control the accumulation of TSNAs, one novel strain WD-32 was isolated by comprehensively evaluating the reduction characteristics of nitrate, nitrite, and TSNAs, and this strain was identified as Bacillus siamensis by 16 S rRNA gene analysis and MALDI-TOF MS evaluation. Subsequently, whole genome sequencing of B. siamensis WD-32 was carried out to excavate important genes and enzymes involved, and the possible reduction mechanism of TSNAs was explored. More importantly, the reduction of TSNAs by B. siamensis was significantly promoted by knockout of narG gene. During the practical agricultural fermentation process of the cigar tobacco leaves, the treatment by the WD-32∆narG cells resulted in a 60% reduction of the total TSNAs content compared with the control, and the concentrations of the NNN and NNK were decreased by 69% and 59%, respectively. In summary, this study offers efficient strains for reduction of the TSNAs in cigar tobacco, and provides new insights into the reduction mechanism of TSNAs, which will promote the application of microbial methods in control of TSNAs and nitrite.

Specific biomarker comparison in current smokers, e-cigarette users, and non-smokers

INTRODUCTION

This study aims to address the existing gap in the literature, while adding evidence, by comparing tobacco-specific biomarkers (cotinine and nitrosamines: NNK, NNAL, NNN), and other biomarkers of e-cigarette use (humectants: glycerol, 1,2-PD, 1,3-PD) according to five study groups.

METHODS

A pooling analysis including two different studies was conducted. In both analyses, we took saliva samples from smokers (n = 409) and non-smokers (n = 154), dual tobacco and e-cig users (n = 92), exclusive e-cig user with nicotine (n = 158), and exclusive e-cig users without nicotine (n = 38). We analyzed and compared the geometric means (GM) and geometric standard deviations (GSD) of the concentration of tobacco-specific biomarkers, and e-cigarette biomarkers among groups. We used log-linear models adjusted for sex and age to model the change percentage and their 95% confidence intervals.

RESULTS

Cotinine was significantly higher in nicotine consumers and in e-cigarette users without nicotine when compared to non-smokers. TSNAs were generally significantly lower in non-smokers and higher in nicotine consumers. NNN and NNAL were lower in e-cigarette users with nicotine comparted to smokers, and NNN was higher in e-cigarette users without nicotine when compared to non-smokers. No differences were found in humectant biomarkers between e-cigarette groups.

CONCLUSIONS

Although there was a reduction in TSNAs in e-cigarette exclusive users compared to smokers, and a reduction of cotinine concentrations in e-cigarette exclusive users without nicotine compared to smokers, there are still high levels of these biomarkers when compared to non-smokers, which may be a clue towards the harmful effect of e-cigarettes.

Hand nicotine as an independent marker of thirdhand smoke pollution in children's environments

BACKGROUND

Hand nicotine (HN) levels measure children's exposure to tobacco smoke pollutants from thirdhand and secondhand smoke. HN is associated with urinary and salivary cotinine, but the associations of HN with other tobacco smoke exposure (TSE) markers remain unknown.

OBJECTIVES

We compared levels of HN and four urinary TSE biomarkers: cotinine, trans-3'-hydroxycotinine (3HC), nicotelline N-oxides, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), and children's sociodemographic and TSE patterns. We also examined if HN is a plausible pathway for children's exposure to active smoking.

METHODS

Data were collected from 175 non-smoking patients (Mean (SD) age = 5.4 (3.4) years) who lived with ≥1 cigarette smoker(s). HN and TSE biomarker levels were determined using LC-MS/MS. Multivariate and multivariable regression analyses were conducted to examine associations between TSE markers and parent-reported measures, controlling for sociodemographics.

RESULTS

Of the five markers of TSE, cotinine (R² = 0.221; p = 0.003) and HN (R² = 0.247; p = 0.001) showed the strongest overall associations. Of the five markers, only cotinine showed significantly higher levels among Black children (β^=0.307,p<0.05) independent of age, reported exposure, and home smoking bans. Cotinine (β^=0.010,p<0.05), NNAL (β^=0.012,p<0.05), and HN (β^=0.011,p<0.05) showed significant positive associations with reported exposure independent of race, age, and home smoking bans. NNAL (β^=-0.285,p<0.05) and HN (β^=-0.336,p<0.05), but not cotinine, 3HC, and N-oxides, showed significantly lower levels among children who lived in homes with smoking bans. Child age, hand surface area, home smoking ban, and reported exposure independently accounted for 21 % of the variance in HN levels (p = 0.002). HN accounted for 30 % of the variance in cotinine independent of child race and child age.

DISCUSSION

HN levels were associated with modifiable tobacco-related behaviors and shows promise as a marker of sources of THS pollution in a child's environment not captured by measurement of urinary cotinine alone. HN levels provide additional information about TSE, complementing other biomarkers when assessing children's overall TSE.

Indoor Secondary Pollutants Cannot Be Ignored: Third-Hand Smoke

Smoking has been recognized by the World Health Organization (WHO) as the fifth highest threat to humanity. Smoking, a leading disease promoter, is a major risk factor for non-communicable diseases (NCDs) such as cancer, cardiovascular disease, diabetes, and chronic respiratory diseases. NCDs account for 63% of all deaths worldwide. Passive smoking is also a health risk. Globally, more than a third of all people are regularly exposed to harmful smoke. Air pollution is a common global problem in which pollutants emitted into the atmosphere undergo a series of physical or chemical reactions to produce various oxidation products, which are often referred to as secondary pollutants. Secondary pollutants include ozone (O₃), sulfur trioxide (SO₃), nitrogen dioxide (NO₂), and respirable particulate matter (PM). It is worth mentioning that third-hand smoke (THS), formed by the reaction of nicotine with second-hand smoke (SHS) caused by indoor O₃ or nitrous acid (HONO), is a major indoor secondary pollutant that cannot be ignored. As a form of indoor air pollution that is relatively difficult to avoid, THS exists in any corner of the environment where smokers live. In this paper, we summarize the important research progress on the main components, detection, and toxicity of THS and look forward to future research directions. Scientific understanding of THS and its hazards will facilitate smoking bans in indoor and public places and raise public concern for how to prevent and remove THS.

Microorganisms: crucial players of smokeless tobacco for several health attributes

Global consumption of smokeless tobacco (SLT) reached 300 million users worldwide majorly from middle-income countries. More than 4000 chemical compounds represent it as one of the noxious consumable products by humans. Besides toxicants/carcinogens, the heavy microbial load on smokeless tobacco further keeps human health at higher risk. Several of these inhabitant microbes participate in biofilm formation and secrete endotoxin/mycotoxins and proinflammatory-like molecules, leading to several oral diseases. Tobacco-associated bacteria exhibit their role in tobacco-specific nitrosamines (TSNAs) formation and acetaldehyde production; both are well-documented carcinogens. Moreover, tobacco exhibits the potential to alter the oral microbiome and induce dysbiotic conditions that lead to the onset of several oral and systemic diseases. Traditional cultivation approaches of microbiology provide partial information of microbial communities of a habitat; therefore, microbiomics has now been employed to study the metagenomes of entire microbial communities. In the past 5 years, few NGS-based investigations have revealed that SLT harbors four dominant phyla (Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes) dominating Bacillus spp. and/or Pseudomonas spp. However, functional characterization of their genetic elements will be a more informative attribute to understand the correlation between inhabitant microbial diversity and their relatedness concerning abundance and diseases. This review provides an update on the microbial diversity of SLT and its associated attributes in human health. KEY POINTS: • Heavy microbial load on smokeless tobacco alarms for poor oral hygiene. • Inhabitant microorganisms of SLT participate in TSNA and biofilm formation. • SLTs alter the oral microbiome and causes oral dysbiosis.

Comparison of TSNAs concentration in saliva according to type of tobacco smoked

OBJECTIVE

To compare tobacco-specific nitrosamines (TSNAs) measured in saliva according to different types of tobacco smoked in a sample of smokers of the city of Barcelona (Spain).

METHODS

We used data from a cross-sectional study of a sample of the adult smoking population of Barcelona, Spain in 2013-2014 (n = 165). We classified smokers in five groups according to the type of tobacco smoked: a) manufactured cigarettes only, b) roll-your-own (RYO) cigarettes only, c) dual smokers (both manufactured and RYO cigarettes), d) manufactured plus other types of tobacco products different from RYO and e) other types of tobacco products different from manufactured and RYO cigarettes. We calculated the geometric mean (GM) and geometric standard deviation (GSD) of TSNAs concentration in saliva (pg/mL), including N'-nitroaonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) according to the five tobacco groups. We also described all TSNAs concentration in each tobacco group stratified by the number of cigarettes smoked per day.

RESULTS

Smokers from the RYO cigarette group had higher TSNAs concentration than smokers from the manufactured cigarette group: 13 pg/mL vs 4.9 pg/mL of NNN, 1.9 pg/mL vs 1.7 pg/mL in NNK and 1.1 pg/mL vs 0.9 pg/mL of NNAL. There were significant differences in NNN concentrations between smokers of RYO vs manufactured cigarettes. The higher the number of cigarettes smoked, the higher the TSNAs concentrations. After adjusted by number of cigarettes smoked, there were not statistically significant differences in TSNAs between RYO and manufactured cigarettes.

CONCLUSIONS

Our data shows that RYO cigarette is at least as hazardous as manufactured cigarettes. Regulating RYO tobacco prices could be an effective strategy to control tobacco use.

Electronic cigarette: A recent update of its toxic effects on humans

Electronic cigarettes (e-cigarettes), battery-powered and liquid-vaporizing devices, were invented to replace the conventional cigarette (c-cigarette) smoking for the sake of reducing the adverse effects on multiple organ systems that c-cigarettes have induced. Although some of the identified harmful components in e-cigarettes were alleged to be measured in lower quantity than those in c-cigarettes, researchers unveiled that the toxic effects of e-cigarettes should not be understated. This review is sought for an attempt to throw light on several typical types of e-cigarette components (tobacco-specific nitrosamines, carbonyl compounds, and volatile organic compounds) by revealing their possible impacts on human bodies through different action mechanisms characterized by alteration of specific biomarkers on cellular and molecular levels. In addition, this review is intended to draw the limelight that like c-cigarettes, e-cigarettes could also be accompanied with toxic effects on whole human body, which are especially apparent on respiratory system. From head to foot, from physical aspect to chemical aspect, from genotype to phenotype, potential alterations will take place upon the intake of the liquid aerosol.

Chemical and toxicological characteristics of conventional and low-TSNA moist snuff tobacco products

Use of smokeless tobacco products (STPs) is associated with oral cavity cancer and other health risks. Comprehensive analysis for chemical composition and toxicity is needed to compare conventional and newer STPs with lower tobacco-specific nitrosamines (TSNAs) yields. Seven conventional and 12 low-TSNA moist snuff products purchased in the U.S., Sweden, and South Africa were analyzed for 18 chemical constituents (International Agency for Research on Cancer classified carcinogens), pH, nicotine, and free nicotine. Chemicals were compared in each product using Wilcoxon rank-sum test and principle component analysis (PCA). Conventional compared to low-TSNA moist snuff products had higher ammonia, benzo[a]pyrene, cadmium, nickel, nicotine, nitrate, and TSNAs and had lower arsenic in dry weight content and per mg nicotine. Lead and chromium were significantly higher in low-TSNA moist snuff products. PCA showed a clear difference for constituents between conventional and low-TSNA moist snuff products. Differences among products were reduced when considered on a per mg nicotine basis. As one way to contextualize differences in constituent levels, probabilistic lifetime cancer risk was estimated for chemicals included in The University of California's carcinogenic potency database (CPDB). Estimated probabilistic cancer risks were 3.77-fold or 3-fold higher in conventional compared to low-TSNA moist snuff products under dry weight or under per mg nicotine content, respectively. In vitro testing for the STPs indicated low level toxicity and no substantial differences. The comprehensive chemical characterization of both conventional and low-TSNA moist snuff products from this study provides a broader assessment of understanding differences in carcinogenic potential of the products. In addition, the high levels and probabilistic cancer risk estimates for certain chemical constituents of smokeless tobacco products will further inform regulatory decision makers and aid them in their efforts to reduce carcinogen exposure in smokeless tobacco products.

The interaction of a cobalt porphyrin with cancer-associated nitrosamines

A cobalt porphyrin (CY-B) was presented, and its interaction with tobacco-specific nitrosamines (TSNAs) was investigated by UV-Vis spectroscopy and high-resolution mass spectrometry. The results revealed that the stoichiometry of the host-guest interaction was 1:2 and that the binding constant between CY-B and TSNAs was within the range of 0.78×10(8)-7.83×10(8)M(-2). The coordination strength between CY-B and TSNAs decreased in the sequence of NNN>NAB>NAT>NNK based on the binding constant. The interaction mechanism of CY-B with TSNAs involved a coordination interaction, and the π-π interaction between the porphyrin macrocycle and the aromatic frame of the TSNAs pyridines may also have been a driving force. The measured thermodynamic properties demonstrated that the reaction of CY-B with TSNAs was spontaneous and that the driving force for the interaction was a change in enthalpy. The reaction was exothermic, and an increasing temperature inhibited the interaction. The IR spectrum of the complex revealed that the NNO group of TSNAs and the metal cobalt of CY-B formed the six-coordinate complex.

Risk for oral cancer from smokeless tobacco

Tobacco products which are used in a way other than smoking are known as smokeless tobacco. The most common smokeless tobaccos are chewing tobacco, naswar, snuff, snus, gutka, and topical tobacco paste. Any product which contains tobacco is not safe for human health. There are more than twenty-five compounds in smokeless tobacco which have cancer causing activity. Use of smokeless tobacco has been linked with risk of oral cancer. Smokeless tobacco contains tobacco-specific nitrosamines (TSNAs), polonium, formaldehyde, cadmium, lead, and benzo[a]pyrene, which are carcinogenic agents. Although there is presence of some compounds, carotenoids and phenolic compounds, that have cancer inhibiting properties, they are in low concentrations. Dry snuff use is linked with higher relative risks, while the use of other smokeless tobacco is of intermediate risk. Moist snuff and chewing tobacco have a very low risk for oral cancer. Therefore, from this review article, it was concluded that smokeless tobacco has risk for oral cancer - either low, medium or high depending on the balance between cancer causing agents and cancer inhibiting agents.