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Systemic Toxicity of Smokeless Tobacco Products in Mice
Marina V Malovichko1, Iris Zeller1, Tatiana V Krivokhizhina1
1American Heart Association-Tobacco Regulation and Addiction Center, Institute of Molecular Cardiology, and Diabetes and Obesity Center, University of Louisville, Louisville, KY.
Introduction:
Smokeless tobacco products such as snuff and snus are used worldwide. However, little is known about the systemic and cardiovascular toxicity of smokeless tobacco exposure.
Methods:
Biomarkers of endothelial activation and injury, immune functions, platelet activation and insulin resistance were measured in 8-week old male C57BL/6 mice exposed to commercial snuff, CRP-2 reference snuff, commercial snus, CRP-1 reference snus, and nicotine in drinking water (100 µg/mL) for 4, 12, and 24 weeks.
Results:
Twenty-four weeks of exposure to smokeless tobacco products or nicotine significantly decreased the levels of circulating Flk+/Sca+ endothelial progenitor cells. Twelve and 24 weeks of exposure to all the smokeless tobacco products and nicotine significantly decreased the levels of circulating CD19+ B cells, CD4+ T cells, CD8+ T cells, and CD11b+ monocytes, whereas 4 weeks of exposure to Camel snus and Copenhagen snuff significantly depleted the levels of peripheral blood CD19+ B cells and CD11b+ monocytes. Twenty-four weeks of exposure to smokeless tobacco products or nicotine significantly decreased plasma IFNγ levels. However, plasma TNFα levels were significantly increased in mice exposed to Copenhagen snuff or nicotine for 24 weeks. This was accompanied by a five to sevenfold increase in the hepatic expression of TNFα. Neither smokeless products nor nicotine affected plasma lipoproteins, platelet activation, or systemic insulin sensitivity.
Conclusions:
Chronic exposure to snuff and snus suppresses circulating levels of EPCs, endothelial microparticles and immune cells, but increases plasma TNF-α levels. These effects of smokeless tobacco products are attributable, at least in part, to nicotine.
Implications:
Exposure to smokeless tobacco products results in the depletion of endothelial progenitor cells, which may impair the endothelium repair. Suppression of the circulating levels of immune cells upon exposure to smokeless tobacco products may increase the susceptibility to secondary infection. Increased formation of proinflammatory cytokines such as TNFα by nicotine or Copenhagen snuff may lead to vascular inflammation and thereby exacerbate atherogenesis.
Insights
Smokeless tobacco use, including snuff and snus, significantly reduces endothelial progenitor cells and immune cells while increasing TNF-α. These adverse cardiovascular effects are largely due to nicotine content.
Area of Science:
- Cardiovascular Toxicology
- Immunotoxicology
- Pharmacology
Background:
- Smokeless tobacco products (snuff, snus) are widely used globally.
- Systemic and cardiovascular toxicity associated with smokeless tobacco exposure remains poorly understood.
Purpose of the Study:
- To investigate the systemic and cardiovascular toxicity of smokeless tobacco exposure in a mouse model.
- To determine the role of nicotine in the observed toxic effects.
Main Methods:
- Mice were exposed to various smokeless tobacco products (snuff, snus) and nicotine for 4, 12, and 24 weeks.
- Biomarkers of endothelial activation, immune function, platelet activation, and insulin resistance were measured.
Main Results:
- Chronic exposure decreased endothelial progenitor cells (EPCs) and immune cells (B cells, T cells, monocytes).
- Plasma levels of TNF-α increased significantly, particularly with Copenhagen snuff and nicotine exposure.
- Nicotine was identified as a key contributor to the observed toxic effects.
Conclusions:
- Smokeless tobacco exposure suppresses circulating EPCs and immune cells, potentially impairing vascular repair and increasing infection susceptibility.
- Increased TNF-α levels contribute to vascular inflammation and may exacerbate atherogenesis.
- Nicotine is a significant factor in the toxicity of smokeless tobacco products.
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