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

Oral nicotine pouches with an aftertaste? Part 2: in vitro toxicity in human gingival fibroblasts

Nicotine pouches contain fewer characteristic toxicants than conventional tobacco products. However, the associated risks in terms of toxicity and addiction potential are still unclear. Therefore, endpoints of toxicity and contents of flavoring substances were investigated in this study. The in vitro toxicity of five different nicotine pouches and the reference snus CRP1.1 were studied in human gingival fibroblasts (HGF-1). Cells were exposed to product extracts (nicotine contents: 0.03-1.34 mg/mL) and sampled at different time points. Cytotoxicity, total cellular reactive oxygen species (ROS) levels, and changes in the expression levels of inflammatory and oxidative stress genes were assessed. Flavor compounds used in the nicotine pouches were identified by GC-MS. Cytotoxicity was observed in two nicotine pouches. Gene expression of interleukin 6 (IL6) and heme oxygenase 1 (HMOX1) was upregulated by one and three pouches, respectively. ROS production was either increased or decreased, by one pouch each. CRP1.1 caused an upregulation of IL6 and elevated ROS production. Toxicity was not directly dependent on nicotine concentration and osmolarity. A total of 56 flavorings were detected in the five nicotine pouches. Seven flavorings were classified according to the harmonized hazard classification system as laid down in the European Classification, Labelling and Packaging regulation. Nine flavorings are known cytotoxins. Cytotoxicity, inflammation, and oxidative stress responses indicate that adverse effects such as local lesions in the buccal mucosa may occur after chronic product use. In conclusion, flavorings used in nicotine pouches likely contribute to the toxicity of nicotine pouches.

Use of Conventional Cigarette Smoking and E-Cigarette Vaping for Experimental Stroke Studies in Mice

Cigarette smoking is a major prodromal factor for the onset of many adverse health effects that may occur in the short run and is the leading cause of preventable disease, disability, and death in the United States. Moreover, it is well established that chronic smoking is associated with vascular endothelial dysfunction in a causative and dose-dependent manner primarily related to the release of reactive oxygen species (ROS), nicotine, and the induction of oxidative stress (OS)-driven inflammation. Preclinical studies have also shown that nicotine (the principal e-liquid ingredient used in e-cigarettes) can also cause OS, exacerbating cerebral ischemia and secondary brain injury. Likewise, chronic e-Cig vaping could be prodromal to cerebrovascular impairment and promote cerebrovascular conditions favoring stroke onset and worsening post-ischemic brain injury. Therefore, using mouse models is crucial to understand how xenobiotics such as those released by conventional and/or e-cigs can impact the onset and severity of stroke as well as post-stroke recovery. To appropriately model human-like smoking/vaping behavior in mice, however, the exposure to these xenobiotics must be standardized and undertaken in a controlled environment. This chapter describes a well-validated protocol to reproduce standardized chronic tobacco smoke or e-cigarette vape exposure in mice in the setting of a mouse transient ischemic stroke model.

Flavor Classification/Categorization and Differential Toxicity of Oral Nicotine Pouches (ONPs) in Oral Gingival Epithelial Cells and Bronchial Epithelial Cells

Oral nicotine pouches (ONPs) are a modern form of smokeless tobacco products sold by several brands in the U.S., which comprise a significant portion of non-combustible nicotine-containing product (NCNP) sales to date. ONPs are available in various flavors and may contain either tobacco-derived nicotine (TDN) or tobacco-free nicotine (TFN). The growth in popularity of these products has raised concerns that flavored ONPs may cause adverse oral health effects and promote systemic toxic effects due to nicotine and other ONP by-products being absorbed into the circulatory system through oral mucosa. We hypothesized that flavored ONPs are unsafe and likely to cause oral and pulmonary inflammation in oral and respiratory epithelial cells. Before analyzing the effects of ONPs, we first classified ONPs sold in the U.S. based on their flavor and the flavor category to which they belonged using a wheel diagram. Human gingival epithelial cells (HGEP) were treated with flavored ONP extracts of tobacco (original, smooth), menthol (wintergreen and cool cider), and fruit flavor (americana and citrus), each from the TDN and TFN groups. The levels of ONP-induced inflammatory cytokine release (TNF-α, IL-6, and IL-8) by ELISA, cellular reactive oxygen species (ROS) production by CellRox Green, and cytotoxicity by lactate dehydrogenase (LDH) release assay in HGEP cells were assessed. Flavored ONP extracts elicited differential toxicities in a dose- and extract-dependent manner in HGEP cells 24 h post-treatment. Both fruit TDN and TFN extracts resulted in the greatest cytotoxicity. Tobacco- and fruit-flavored, but not menthol-flavored, ONPs resulted in increased ROS production 4 h post-treatment. Flavored ONPs led to differential cytokine release (TNF-α, IL-6, and IL-8) which varied by flavor (menthol, tobacco, or fruit) and nicotine (TDN vs. TFN) 24 h post-treatment. Menthol-flavored ONPs led to the most significant TNF-α release; fruit TFN resulted in the most significant IL-6 release; and fruit TDN and tobacco TFN led to the highest release of IL-8. Subsequently, human bronchial epithelial cells (16-HBE and BEAS-2B) were also treated with flavored ONP extracts, and similar assays were evaluated. Here, the lowest concentration treatments displayed increased cytotoxicity. The most striking response was observed among cells treated with spearmint and tobacco flavored ONPs. Our data suggest that flavored ONPs are unsafe and likely to cause systemic and local toxicological responses during chronic usage.

Tobacco Use and Periodontal Disease-The Role of Microvascular Dysfunction

Periodontal disease consists in highly prevalent wide-ranging inflammatory conditions that affect the supporting apparatus of teeth. Tobacco use is the most important risk factor for periodontal disease as it increases disease severity and periodontal surgery complications. Tobacco use is harmful for the vasculature by causing microvascular dysfunction, which is known to negatively affect periodontal disease. To the author's knowledge this paper is the first comprehensive review on the mechanisms by which tobacco use affects oral microcirculation and impacts the pathophysiology of periodontal disease. In healthy subjects, acute nicotine administration or tobacco use (smoking/smokeless forms) increases the blood flow in the oral mucosa due to local irritation and increased blood pressure, which overcome neural- and endocrine-mediated vasoconstriction. Chronic tobacco smokers display an increased gingival microvascular density, which is attributed to an increased capillary recruitment, however, these microcirculatory units show higher tortuosity and lower caliber. These morphological changes, together with the repetitive vasoconstrictive insults, contribute to lower gingival perfusion in chronic smokers and do not completely regress upon smoking cessation. In periodontal disease there is considerable gingival inflammation and angiogenesis in non-smokers which, in chronic smokers, are considerably suppressed, in part due to local immune suppression and oxidative stress. Tobacco exposure, irrespective of the form of use, causes long-term microvascular dysfunction that increases the risk of complications due to the natural disease course or secondary therapeutic strategies.