A single exposure to eucalyptus smoke sensitizes rats to the postprandial cardiovascular effects of a high carbohydrate oral load

Objective: Previous studies have shown that air pollution exposure primes the body to heightened responses to everyday stressors of the cardiovascular system. The purpose of this study was to examine the utility of postprandial responses to a high carbohydrate oral load, a cardiometabolic stressor long used to predict cardiovascular risk, in assessing the impacts of exposure to eucalyptus smoke (ES), a contributor to wildland fire air pollution in the Western coast of the United States.

Materials and methods: Three-month-old male Sprague Dawley rats were exposed once (1 h) to filtered air (FA) or ES (700 µg/m³ fine particulate matter), generated by burning eucalyptus in a tube furnace. Rats were then fasted for six hours the following morning, and subsequently administered an oral gavage of either water or a HC suspension (70 kcal% from carbohydrate), mimicking a HC meal. Two hours post gavage, cardiovascular ultrasound, cardiac pressure-volume (PV), and baroreceptor sensitivity assessments were made, and pulmonary and systemic markers assessed.

Results: ES inhalation alone increased serum interleukin (IL)-4 and nasal airway levels of gamma glutamyl transferase. HC gavage alone increased blood glucose, blood pressure, and serum IL-6 and IL-13 compared to water vehicle. By contrast, only ES-exposed and HC-challenged animals had increased PV loop measures of cardiac output, ejection fraction %, dP/dt _max, dP/dt _min, and stroke work compared to ES exposure alone and/or HC challenge alone.

Discussion and conclusions: Exposure to a model wildfire air pollution source modifies cardiovascular responses to HC challenge, suggesting air pollution sensitizes the body to systemic triggers.

Keywords: Air pollution; cardiovascular; eucalyptus smoke; high carbohydrate meal; inhalation; postprandial; wildland fires.