Cardiovascular Depression in Rats Exposed to Inhaled Particulate Matter and Ozone: Effects of Diet-Induced Metabolic Syndrome

Background: High ambient levels of ozone (O(3)) and fine particulate matter (PM(2.5)) are associated with cardiovascular morbidity and mortality, especially in people with preexisting cardiopulmonary diseases. Enhanced susceptibility to the toxicity of air pollutants may include individuals with metabolic syndrome (MetS). Objective: We tested the hypothesis that cardiovascular responses to O(3) and PM(2.5) will be enhanced in rats with diet-induced MetS. Methods: Male Sprague-Dawley rats were fed a high-fructose diet (HFrD) to induce MetS and then exposed to O(3), concentrated ambient PM(2.5), or the combination of O(3) plus PM(2.5) for 9 days. Data related to heart rate (HR), HR variability (HRV), and blood pressure (BP) were collected. Results: Consistent with MetS, HFrD rats were hypertensive and insulin resistant, and had elevated fasting levels of blood glucose and triglycerides. Decreases in HR and BP, which were found in all exposure groups, were greater and more persistent in HFrD rats compared with those fed a normal diet (ND). Coexposure to O(3) plus PM(2.5) induced acute drops in HR and BP in all rats, but only ND rats adapted after 2 days. HFrD rats had little exposure-related changes in HRV, whereas ND rats had increased HRV during O(3) exposure, modest decreases with PM(2.5), and dramatic decreases during O(3) plus PM(2.5) coexposures. Conclusions: Cardiovascular depression in O(3)- and PM(2.5)-exposed rats was enhanced and prolonged in rats with HFrD-induced MetS. These results in rodents suggest that people with MetS may be prone to similar exaggerated BP and HR responses to inhaled air pollutants. Citation: Wagner JG, Allen K, Yang HY, Nan B, Morishita M, Mukherjee B, Dvonch JT, Spino C, Fink GD, Rajagopalan S, Sun Q, Brook RD, Harkema JR. 2014. Cardiovascular depression in rats exposed to inhaled particulate matter and ozone: effects of diet-induced metabolic syndrome. Environ Health Perspect 122:27–33; http://dx.doi.org/10.1289/ehp.1307085