Thirdhand smoke exposure causes replication stress and impaired transcription in human lung cells

Policy-relevant differences between secondhand and thirdhand smoke: strengthening protections from involuntary exposure to tobacco smoke pollutants

Starting in the 1970s, individuals, businesses and the public have increasingly benefited from policies prohibiting smoking indoors, saving thousands of lives and billions of dollars in healthcare expenditures. Smokefree policies to protect against secondhand smoke exposure, however, do not fully protect the public from the persistent and toxic chemical residues from tobacco smoke (also known as thirdhand smoke) that linger in indoor environments for years after smoking stops. Nor do these policies address the economic costs that individuals, businesses and the public bear in their attempts to remediate this toxic residue. We discuss policy-relevant differences between secondhand smoke and thirdhand smoke exposure: persistent pollutant reservoirs, pollutant transport, routes of exposure, the time gap between initial cause and effect, and remediation and disposal. We examine four policy considerations to better protect the public from involuntary exposure to tobacco smoke pollutants from all sources. We call for (a) redefining smokefree as free of tobacco smoke pollutants from secondhand and thirdhand smoke; (b) eliminating exemptions to comprehensive smoking bans; (c) identifying indoor environments with significant thirdhand smoke reservoirs; and (d) remediating thirdhand smoke. We use the case of California as an example of how secondhand smoke-protective laws may be strengthened to encompass thirdhand smoke protections. The health risks and economic costs of thirdhand smoke require that smokefree policies, environmental protections, real estate and rental disclosure policies, tenant protections, and consumer protection laws be strengthened to ensure that the public is fully protected from and informed about the risks of thirdhand smoke exposure.

Thirdhand smoke exposure promotes gastric tumor development in mouse and human

The pollution of indoor environments and the consequent health risks associated with thirdhand smoke (THS) are increasingly recognized in recent years. However, the carcinogenic potential of THS and its underlying mechanisms have yet to be thoroughly explored. In this study, we examined the effects of short-term THS exposure on the development of gastric cancer (GC) in vitro and in vivo. In a mouse model of spontaneous GC, CC036, we observed a significant increase in gastric tumor incidence and a decrease in tumor-free survival upon THS exposure as compared to control. RNA sequencing of primary gastric epithelial cells derived from CC036 mice showed that THS exposure increased expression of genes related to the extracellular matrix and cytoskeletal protein structure. We then identified a THS exposure-induced 91-gene expression signature in CC036 and a homologous 84-gene signature in human GC patients that predicted the prognosis, with secreted phosphoprotein 1 (SPP1) and tribbles pseudokinase 3 (TRIB3) emerging as potential targets through which THS may promote gastric carcinogenesis. We also treated human GC cell lines in vitro with media containing various concentrations of THS, which, in some exposure dose range, significantly increased their proliferation, invasion, and migration. We showed that THS exposure could activate the epithelial-mesenchymal transition (EMT) pathway at the transcript and protein level. We conclude that short-term exposure to THS is associated with an increased risk of GC and that activation of the EMT program could be one potential mechanism. Increased understanding of the cancer risk associated with THS exposure will help identify new preventive and therapeutic strategies for tobacco-related disease as well as provide scientific evidence and rationale for policy decisions related to THS pollution control to protect vulnerable subpopulations such as children.

Impact of indoor air pollution on DNA damage and chromosome stability: a systematic review

Indoor air pollution is becoming a rising public health problem and is largely resulting from the burning of solid fuels and heating in households. Burning these fuels produces harmful compounds, such as particulate matter regarded as a major health risk, particularly affecting the onset and exacerbation of respiratory diseases. As exposure to polluted indoor air can cause DNA damage including DNA sd breaks as well as chromosomal damage, in this paper, we aim to provide an overview of the impact of indoor air pollution on DNA damage and genome stability by reviewing the scientific papers that have used the comet, micronucleus, and γ-H2AX assays. These methods are valuable tools in human biomonitoring and for studying the mechanisms of action of various pollutants, and are readily used for the assessment of primary DNA damage and genome instability induced by air pollutants by measuring different aspects of DNA and chromosomal damage. Based on our search, in selected studies (in vitro, animal models, and human biomonitoring), we found generally higher levels of DNA strand breaks and chromosomal damage due to indoor air pollutants compared to matched control or unexposed groups. In summary, our systematic review reveals the importance of the comet, micronucleus, and γ-H2AX assays as sensitive tools for the evaluation of DNA and genome damaging potential of different indoor air pollutants. Additionally, research in this particular direction is warranted since little is still known about the level of indoor air pollution in households or public buildings and its impact on genetic material. Future studies should focus on research investigating the possible impact of indoor air pollutants in complex mixtures on the genome and relate pollutants to possible health outcomes.

Machine Learning Reveals Impacts of Smoking on Gene Profiles of Different Cell Types in Lung

Smoking significantly elevates the risk of lung diseases such as chronic obstructive pulmonary disease (COPD) and lung cancer. This risk is attributed to the harmful chemicals in tobacco smoke that damage lung tissue and impair lung function. Current research on the impact of smoking on gene expression in specific lung cells is limited. This study addresses this gap by analyzing gene expression profiles at the single-cell level from 43,539 lung endothelial cells, 234,349 lung epithelial cells, 189,843 lung immune cells, and 16,031 lung stromal cells using advanced machine learning techniques. The data, categorized by different lung cell types, were classified into three smoking states: active smoker, former smoker, and never smoker. Each cell sample encompassed 28,024 feature genes. Employing an incremental feature selection method within a computational framework, several specific genes have been identified as potential markers of smoking status in different lung cell types. These include B2M, EEF1A1, and TPT1 in lung endothelial cells; FTL and MT-ATP8 in lung epithelial cells; HLA-B and HLA-C in lung immune cells; and HSP90B1 and LCN2 in lung stroma cells. Additionally, this study developed quantitative rules for representing the gene expression patterns related to smoking. This research highlights the potential of machine learning in oncology, enhancing our molecular understanding of smoking's harm and laying the groundwork for future mechanism-based studies.

Dermal thirdhand smoke exposure induced epidermal alterations in human keratinocyte cells through oxidative damage and MMP-1 expression

Thirdhand smoke (THS) is the residual cigarette smoke that settles on indoor surface fabrics, dust and can accumulate in the environment. Therefore, it can be a risk factor for individuals who have frequent dermal contact with THS-contaminated surfaces. In the present study, it was aimed to elucidate the toxicity of dermal THS exposure in HaCaT human keratinocytes. The THS was extracted from terrycloth exposed to 3R4F research cigarette smoke in a closed chamber and the adverse outcomes induced by THS were determined through assessment of cytotoxicity tests (MTT and NRU), intracellular GSH level, total SOD activity, matrix metalloproteinase-1 (MMP-1) and IL-6 levels. The wound healing capacity of THS-exposed keratinocytes was evaluated via scratch assay. A potent antioxidant isothiocyanate compound, sulforaphane (SFN), was used as a negative control. THS was dose-dependently cytotoxic (12.5%-100%, v/v) to the HaCaT cells through mitochondrial cell dysfunction (p < 0.01), which was ameliorated by SFN (0.62 μM) pre-treatment. In parallel, THS exposure significantly decreased the intracellular GSH deposits and T-SOD activity in keratinocytes. Collagen degradation through elevated MMP-1 expression was observed in THS-exposed cells in parallel with the delay of wound healing and increased pro-inflammatory response in a dose-dependent manner (p < 0.05). The findings are expected to raise awareness about THS as an environmental pollutant for skin, particularly in the highest-ranked countries in cigarette consumption. To conclude, these results might contribute to the studies on the importance of dermal exposure to THS in the pathogenesis of epidermal alterations and the other skin diseases.

Thirdhand tobacco smoke exposure increases the genetic background-dependent risk of pan-tumor development in Collaborative Cross mice

Increasing evidence has shown that thirdhand smoke (THS) exposure is likely to induce adverse health effects. An important knowledge gap remains in our understanding of THS exposure related to cancer risk in the human population. Population-based animal models are useful and powerful in investigating the interplay between host genetics and THS exposure on cancer risk. Here, we used the Collaborative Cross (CC) mouse population-based model system, which recapitulates the genetic and phenotypic diversity observed in the human population, to assess cancer risk after a short period of exposure, between 4 and 9 weeks of age. Eight CC strains (CC001, CC019, CC026, CC036, CC037, CC041, CC042 and CC051) were included in our study. We quantified pan-tumor incidence, tumor burden per mouse, organ tumor spectrum and tumor-free survival until 18 months of age. At the population level, we observed a significantly increased pan-tumor incidence and tumor burden per mouse in THS-treated mice as compared to the control (p = 3.04E-06). Lung and liver tissues exhibited the largest risk of undergoing tumorigenesis after THS exposure. Tumor-free survival was significantly reduced in THS-treated mice compared to control (p = 0.044). At the individual strain level, we observed a large variation in tumor incidence across the 8 CC strains. CC036 and CC041 exhibited a significant increase in pan-tumor incidence (p = 0.0084 and p = 0.000066, respectively) after THS exposure compared to control. We conclude that early-life THS exposure increases tumor development in CC mice and that host genetic background plays an important role in individual susceptibility to THS-induced tumorigenesis. Genetic background is an important factor that should be taken into account when determining human cancer risk of THS exposure.

Replication stress drives chromosomal instability in fibroblasts of childhood cancer survivors with second primary neoplasms

New development and optimization of oncologic strategies are steadily increasing the number of long-term cancer survivors being at risk of developing second primary neoplasms (SPNs) as a late consequence of genotoxic cancer therapies with the highest risk among former childhood cancer patients. Since risk factors and predictive biomarkers for therapy-associated SPN remain unknown, we examined the sensitivity to mild replication stress as a driver of genomic instability and carcinogenesis in fibroblasts from 23 long-term survivors of a pediatric first primary neoplasm (FPN), 22 patients with the same FPN and a subsequent SPN, and 22 controls with no neoplasm (NN) using the cytokinesis-block micronucleus (CBMN) assay. Mild replication stress was induced with the DNA-polymerase inhibitor aphidicolin (APH). Fibroblasts from patients with the DNA repair deficiency syndromes Bloom, Seckel, and Fanconi anemia served as positive controls and for validation of the CBMN assay supplemented by analysis of chromosomal aberrations, DNA repair foci (γH2AX/53BP1), and cell cycle regulation. APH treatment resulted in G2/M arrest and underestimation of cytogenetic damage beyond G2, which could be overcome by inhibition of Chk1. Basal micronuclei were significantly increased in DNA repair deficiency syndromes but comparable between NN, FPN, and SPN donors. After APH-induced replication stress, the average yield of micronuclei was significantly elevated in SPN donors compared to FPN (p = 0.013) as well as NN (p = 0.03) donors but substantially lower than for DNA repair deficiency syndromes. Our findings suggest that mild impairment of the response to replication stress induced by genotoxic impacts of DNA-damaging cancer therapies promotes genomic instability in a subset of long-term cancer survivors and may drive the development of an SPN. Our study provides a basis for detailed mechanistic studies as well as predictive bioassays for clinical surveillance, to identify cancer patients at high risk for SPNs at first diagnosis.

Tobacco-specific nitrosamine 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA) causes DNA damage and impaired replication/transcription in human lung cells

Thirdhand smoke (THS) is a newly described health hazard composed of toxicants, mutagens and carcinogens, including nicotine-derived tobacco specific nitrosamines (TSNAs), one of which is 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA). Although TSNAs are generally potent carcinogens, the risk of NNA, which is specific to THS, is poorly understood. We recently reported that THS exposure-induced adverse impact on DNA replication and transcription with implications in the development of cancer and other diseases. Here, we investigated the role of NNA in THS exposure-induced harmful effects on fundamental cellular processes. We exposed cultured human lung epithelial BEAS-2B cells to NNA. The formation of DNA base damages was assessed by Long Amplicon QPCR (LA-QPCR); DNA double-strand breaks (DSBs) and NNA effects on replication and transcription by immunofluorescence (IF); and genomic instability by micronuclei (MN) formation. We found increased accumulation of oxidative DNA damage and DSBs as well as activation of DNA damage response pathway, after exposure of cells to NNA. Impaired S phase progression was also evident. Consistent with these results, we found increased MN formation, a marker of genomic instability, in NNA-exposed cells. Furthermore, ongoing RNA synthesis was significantly reduced by NNA exposure, however, RNA synthesis resumed fully after a 24h recovery period only in wild-type cells but not in those deficient in transcription-coupled nucleotide excision repair (TC-NER). Importantly, these cellular effects are common with the THS-exposure induced effects. Our findings suggest that NNA in THS could be a contributing factor for THS exposure-induced adverse health effect.

Differential associations of hand nicotine and urinary cotinine with children's exposure to tobacco smoke and clinical outcomes

BACKGROUND

Children's overall tobacco smoke exposure (TSE) consists of both inhalation of secondhand smoke (SHS) and ingestion, dermal uptake, and inhalation of thirdhand smoke (THS) residue from dust and surfaces in their environments.

OBJECTIVES

Our objective was to compare the different roles of urinary cotinine as a biomarker of recent overall TSE and hand nicotine as a marker of children's contact with nicotine pollution in their environments. We explored the differential associations of these markers with sociodemographics, parental smoking, child TSE, and clinical diagnoses.

METHODS

Data were collected from 276 pediatric emergency department patients (Median age = 4.0 years) who lived with a cigarette smoker. Children's hand nicotine and urinary cotinine levels were determined using LC-MS/MS. Parents reported tobacco use and child TSE. Medical records were reviewed to assess discharge diagnoses.

RESULTS

All children had detectable hand nicotine (GeoM = 89.7ng/wipe; 95 % CI = [78.9; 102.0]) and detectable urinary cotinine (GeoM = 10.4 ng/ml; 95%CI = [8.5; 12.6]). Although hand nicotine and urinary cotinine were highly correlated (r = 0.62, p < 0.001), urinary cotinine geometric means differed between racial groups and were higher for children with lower family income (p < 0.05), unlike hand nicotine. Independent of urinary cotinine, age, race, and ethnicity, children with higher hand nicotine levels were at increased risk to have discharge diagnoses of viral/other infectious illness (aOR = 7.49; 95%CI = [2.06; 27.24], p = 0.002), pulmonary illness (aOR = 6.56; 95%CI = [1.76; 24.43], p = 0.005), and bacterial infection (aOR = 5.45; 95%CI = [1.50; 19.85], p = 0.03). In contrast, urinary cotinine levels showed no associations with diagnosis independent of child hand nicotine levels and demographics.

DISCUSSION

The distinct associations of hand nicotine and urinary cotinine suggest the two markers reflect different exposure profiles that contribute differentially to pediatric illness. Because THS in a child's environment directly contributes to hand nicotine, additional studies of children of smokers and nonsmokers are warranted to determine the role of hand nicotine as a marker of THS exposure and its potential role in the development of tobacco-related pediatric illnesses.

The effects of thirdhand smoke on reproductive health

Tobacco smoke is an environmental pollutant that can cause follicle destruction and oocyte dysfunction. Thirdhand smoke (THS) is residual tobacco smoke existing in the environment long after cigarettes have been extinguished, which can react with other environmental compounds to produce secondary pollutants. THS contains a variety of toxic and harmful chemicals, such as nicotine and 1-(N-methyl-N-nitrosamino)-1-(3-pyridinyl)-4-butanal (NNA), a logical biomarker of THS exposure. The health hazards of THS exposure and its components have been researched in recent years. In this review, we have summarized research progress on the effects of THS exposure on organs in mice and humans especially on the reproductive system. This review may help evaluate the health risks of THS, in particular reproduction and offspring health. We hope this review will guide public health education on the dangers of THS exposure and promotion of healthy living habits.

Genetic background influences the effect of thirdhand smoke exposure on anxiety and memory in Collaborative Cross mice

Growing evidence indicates that thirdhand smoke (THS) exposure induces many adverse health effects. However, it is unclear how THS exposure affects behavior and how host genetic background modulates phenotypic changes. Here we used the Collaborative Cross (CC) mouse population-based model to assess behavioral alterations immediately after THS exposure from 4 to 9 weeks of age. We first measured anxiety-like behavior in six strains using light/dark box combined with a custom multivariate mouse tracking system. We developed an anxiety risk scoring system based on anxiety-related traits and then evaluated the THS impact on them. THS exposure significantly decreased anxiety risk in CC019 (P = 0.002) and CC051 (P = 0.009), but increased anxiety risk in CC036 (P < 0.001), while the other three strains did not show significant changes in anxiety-related traits. Such differences were driven by female mice for the six measures of anxiety-like behavior. Memory potential was measured in the same cohort of mice using the passive avoidance assay. Both THS-exposed male and female CC019 mice displayed significant memory loss compared to controls while no significant changes were found in the other five strains. This study provides strong evidence that THS exposure leads to strain-dependent changes in anxiety-like behavior and memory, suggesting that host genetic variations play a critical role in individual susceptibility to THS-induced effects.

Household Rules regarding Cannabis Use and Tobacco Smoking in Denver Airbnb Venues

Cannabis legalization threatens to undermine clean indoor air norms. We investigated the prevalence and nature of tobacco and cannabis use rules in Airbnb venues in Denver, Colorado, where recreational cannabis was legalized in 2014. The study used publicly available Inside Airbnb data for all Denver listings (N = 4,511) collected on 06/29/2019. We analyzed reported tobacco smoking and cannabis use house rules. Tobacco smoking with or without conditions was allowed in 9.7% of venues. Of all venues, 23.7% included details about cannabis use. Of these, 75.9% allowed cannabis use without or with conditions. Of the venues that allowed cannabis use, 30.5% also allowed tobacco smoking. Of the venues that did not allow cannabis use, 0.4% allowed tobacco smoking. Additional multilevel regression models revealed that venues in higher income neighborhoods were less likely to allow cannabis and tobacco use. A substantial number of Airbnb listings in Denver, Colorado permit cannabis use and venues permitting cannabis use may be more likely to also permit tobacco smoking. Findings support the idea that cannabis legalization threatens clean indoor air norms. Airbnb should consider including cannabis use in house rules in jurisdictions that have legalized cannabis to help guests identify spaces with clean air.