Atherosclerosis lesion progression during inhalation exposure to environmental tobacco smoke: A comparison to concentrated ambient air fine particles exposure

Abstract

Environmental tobacco smoke (ETS) and ambient air fine particulate matter (PM_2.5) are both complex mixtures that have important adverse effects on the cardiovascular system. Although exposures to these complex mixtures have been studied individually, direct comparisons between the two has not been performed. In this study, the authors employed a novel, noninvasive ultrasound biomicroscopy method (UBM) to assess the effects of long-term, low-concentration inhalations of side-stream smoke (SS) and concentrated ambient PM_2.5 (CAPs) on plaque progression. ApoE^−/− mice (n = 8/group) on high-fat chow (HFC), or normal chow (NC), were exposed to SS (PM = 450 µg/m³) or filtered air (FA) for 6 h/day, 5 days/week, for 6 months; CAPs exposure was at 134 µg/m³ (NC only). Mortality during the SS exposure was greater in the HFC than in the NC, and SS significantly enhanced the effects of diet. No mortality was observed in CAPs-exposed mice. At 4 and 6 months, SS produced the greatest change in plaque area in the left common carotid artery (CCA) in HFC as compared to FA or NC, but not in the brachiocephalic artery. In contrast, CAPs exposure significantly enhanced plaque areas in brachiocephalic and left CCA at 3 and 6 months of exposure. The effect of SS was comparable in magnitude to that produced by CAPs at an average PM_2.5 mass concentration that was only 30% as high. In light of the employment of the same animal model, uniform inhalation exposure protocols, time schedules, a noninvasive monitoring protocol, and a parallel study design, these findings have broad applicability.

Keywords::

• Concentrated ambient particles
• environmental tobacco smoke
• cardiovascular disease
• atherosclerosis ultrasound imaging

Acknowledgments

The authors are also grateful to Dr. Lippmann for his review of the manuscript and to Ken Magar for his technical assistance.

Declaration of interest

The authors acknowledge the support they received from a NIEHS Center Grant ES 00260 (Lippmann and Chen), a NIEHS research grant R01ES015495 (Chen), a research grant supporting the CAPs exposures from the Health Effects Institute NPACT Initiative (Lippmann and Chen), and a research grant from the Philip Morris External Research Program that supported the SS smoke exposures. Dr. Sun was supported by NIEHS grant ES016588.