Citation:

Thompson, L., Y. Kim, B. Martin, A. Ledbetter, J. Dye, M. Hazari, Ian Gilmour, AND A. Farraj. Pulmonary Exposure to Peat Smoke Extracts in Rats Decreases Expiratory Time and Increases Left Heart End Systolic Volume. INHALATION TOXICOLOGY. Taylor & Francis, Inc., Philadelphia, PA, 30(11-12):439-447, (2019). https://doi.org/10.1080/08958378.2018.1551443

Impact/Purpose:

this study provides evidence that exposure to peat smoke constituents can influence the regulation of left ventricular volumes and pulmonary artery hemodynamics, which could be linked to early pulmonary irritation responses. Though our findings are indicative of subclinical endpoints that may be transient in nature, they were still detectable without the use of experimental challenges. As such, diminished physiological feedback regulation of parameters like left ventricular volume could promote increased vulnerability to non-specific physiological stressors and exacerbation of disease. Given that environmental conditions may continue to favor the occurrence of peat fires and other wildland fires, these findings may increase appreciation for the potential public health consequences from exposure.

Description:

Exposure to wildland fire-related particulate matter (PM) causes adverse health outcomes. However, the impacts of specific biomass sources remain unclear. The purpose of this study was to investigate cardiopulmonary responses in rats following exposure to PM extracts collected from peat fire smoke. We hypothesized that peat smoke PM would dose-dependently alter cardiopulmonary function. Male Sprague–Dawley rats (n = 8/group) were exposed to 35 µg (Lo PM) or 350 µg (Hi PM) of peat smoke PM extracts suspended in saline, or saline alone (Vehicle) via oropharyngeal aspiration (OA). Ventilatory expiration times, measured in whole-body plethysmographs immediately after OA, were the lowest in Hi PM exposed subjects at 6 min into recovery (p = .01 vs. Lo PM, p = .08 vs. Vehicle) and resolved shortly afterwards. The next day, we evaluated cardiovascular function in the same subjects via cardiac ultrasound under isoflurane anesthesia. Compared to Vehicle, Hi PM had 45% higher end systolic volume (p = .03) and 17% higher pulmonary artery blood flow acceleration/ejection time ratios, and both endpoints expressed significant increasing linear trends by dose (p = .01 and .02, respectively). In addition, linear trend analyses across doses detected an increase for end diastolic volume and decreases for ejection fraction and fractional shortening. These data suggest that exposure to peat smoke constituents modulates regulation of ventricular ejection and filling volumes, which could be related to altered blood flow in the pulmonary circulation. Moreover, early pulmonary responses to peat smoke PM point to irritant/autonomic mechanisms as potential drivers of later cardiovascular responses.

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