Biomarkers of Chronic Acrolein Inhalation Exposure in Mice: Implications for Tobacco Product-Induced Toxicity

Abstract

Exposure to tobacco smoke, which contains several harmful and potentially harmful constituents such as acrolein increases cardiovascular disease (CVD) risk. Although high acrolein levels induce pervasive cardiovascular injury, the effects of low-level exposure remain unknown and sensitive biomarkers of acrolein toxicity have not been identified. Identification of such biomarkers is essential to assess the toxicity of acrolein present at low levels in the ambient air or in new tobacco products such as e-cigarettes. Hence, we examined the systemic effects of chronic (12 weeks) acrolein exposure at concentrations similar to those found in tobacco smoke (0.5 or 1 ppm). Acrolein exposure in mice led to a 2- to 3-fold increase in its urinary metabolite 3-hydroxypropyl mercapturic acid (3-HPMA) with an attendant increase in pulmonary levels of the acrolein-metabolizing enzymes, glutathione S-transferase P and aldose reductase, as well as several Nrf2-regulated antioxidant proteins. Markers of pulmonary endoplasmic reticulum stress and inflammation were unchanged. Exposure to acrolein suppressed circulating levels of endothelial progenitor cells (EPCs) and specific leukocyte subsets (eg, GR-1+ cells, CD19+ B-cells, CD4+ T-cells; CD11b+ monocytes) whilst other subsets (eg, CD8+ cells, NK1.1+ cells, Ly6C+ monocytes) were unchanged. Chronic acrolein exposure did not affect systemic glucose tolerance, platelet-leukocyte aggregates or microparticles in blood. These findings suggest that circulating levels of EPCs and specific leukocyte populations are sensitive biomarkers of inhaled acrolein injury and that low-level (<0.5 ppm) acrolein exposure (eg, in secondhand smoke, vehicle exhaust, e-cigarettes) could increase CVD risk by diminishing endothelium repair or by suppressing immune cells or both.

Electronic cigarette-generated aldehydes: The contribution of e-liquid components to their formation and the use of urinary aldehyde metabolites as biomarkers of exposure

“…This is supported by associations between 3HPMA (primary urine acrolein metabolite) and cardiovascular disease risk (DeJarnett et al 2014). Moreover, mice exposed acutely or chronically to acrolein alone have altered cardiovascular biomarkers of harm (Conklin et al 2017; Wheat et al 2011). We used a state-of-the-art carbonyl trapping system that allowed us to quantify individual aldehydes such as acrolein and crotonaldehyde to quite low levels (0.003 ng/puff) that are otherwise missed in studies using dinitrophenylhydrazine (DNPH) cartridges (El-Hellani et al 2016).…”

“…On day 2, the same mice were exposed to aerosols of KY Reference cigarette mainstream smoke (3R4F cigarettes: 12 cigarettes/6 h) or an e-cig (blu®; Classic Tobacco, CT; Magnificent Menthol, MM; 13–16 mg nicotine; 4h) and then placed singly per metabolic cage with glucose/saccharin solution to collect urine (without food) in 1 h increments over the 3 h post-exposure followed by an overnight (O/N; with food) urine collection. Urine samples were collected, decanted, and stored at −80 ° C (Conklin et al 2017).…”

Formaldehyde Induces Mesenteric Artery Relaxation via a Sensitive Transient Receptor Potential Ankyrin-1 (TRPA1) and Endothelium-Dependent Mechanism: Potential Role in Postprandial Hyperemia

“…Urine samples were collected, centrifuged (2,500 RPM, 10 min, 4°C), decanted, and stored at –80 ° C until analysis (Conklin et al, 2017). Each mouse was briefly and manually (<5 s) exposed on the mouth with a water bottle filled with D-glucose/saccharin solution (w/v; 3.0%/0.125%; Sigma) immediately prior to a 6 h fast.…”

“…In total, mice were fasted for 9-h. After fasted urine collection, mice were provided food and glucose/saccharin solution ab libitum for overnight urine collection (O/N). Urine samples were collected, centrifuged, decanted, and stored at –80 ° C (Conklin et al, 2017).…”

Comprehensive, robust, and sensitive UPLC-MS/MS analysis of free biogenic monoamines and their metabolites in urine

“…For each model, the percent change (and 95% confidence interval) was calculated for comparing smokers vs. non-smokers. Smoking status was confirmed using urinary cotinine levels, as described by Conklin et al [55]. All statistical analyses were performed using SAS, version 9.4, software (SAS Institute, Inc., Cary, North Carolina) and GraphPad Prism, version 7 (GraphPad Software, La Jolla, California).…”