Although there has been much research focused on the cardiovascular effects of particulate matter (PM) exposure, we know very little about the possible cardiovascular effects of the oxidant gaseous pollutant, ozone. We hypothesize that ozone exposure delivers an oxidative burden to the lung and to the vascular endothelium, via lipid peroxidation and secondary reactive oxygen and nitrogen species (ROS). This increased ROS burden depletes nitric oxide (NO) via chemical inactivation and reduced formation, altering vascular function in both the pulmonary and systemic circulations. Further, subjects with genetic polymorphisms conferring reduced function in glutathione transferase M1 (GSTM1) or nuclear factor erythroid 2- related factor 2 (Nrf2), key regulators of antioxidant defenses, will show increased susceptibility.
In Aim #1, healthy nonsmoking subjects with and without genetic susceptibility will undergo 3 exposures: air, 0.1 ppm ozone, and 0.2 ppm ozone for 3 hours with intermittent exercise. The primary outcomes will be change in pulmonary and systemic vascular function, NO vascular bioavailability and transport, cardiac function, and platelet and microparticle activation. Airway inflammation and pulmonary function responses will also be assessed.
Aim #2 will provide a new and innovative approach to the clinical study in Aim #1, determining the personal and ambient pollutant exposures of the subjects during their involvement in the study. We will incorporate personal monitoring of ozone and NO2, and data from central monitors on multiple pollutants, to assess subjects'exposures for 3 days prior, during, and 2 days after their experimental exposures. Analytical models will determine the influence of ambient pollutant exposures on the responses to the experimental exposures, and will incorporate both ambient and experimental exposures in an overall assessment of pollutant-related effects. We expect that subjects with the selected genetic polymorphisms in GSTM1 and Nrf2 will have increased systemic oxidative stress, reduced pulmonary capillary blood volume, and reduced peripheral vascular responsiveness and tissue perfusion in response to ozone exposure, and that these changes will correlate with the degree of airway inflammation. These studies will identify pathways and mechanisms for the cardiovascular effects of ozone exposure, identify determinants of susceptibility, and assist in establishing adequately protective ambient air quality standards. Confirmation of our hypothesis that subjects with impaired antioxidant defense are at increased risk will set the stage for future studies examining the effectiveness of preventive measures, such as dietary antioxidant supplementation.
Increases in air pollution are associated with increases in deaths from cardiovascular disease, but we know little about how ozone air pollution affects the cardiovascular system. Our proposed studies will determine the effects of ozone on blood vessel and heart function that could worsen illness in people with underlying heart disease. This will be accomplished by studying healthy volunteers who inhale ozone in a controlled clinical study, and also by studying their exposure to ozone and other pollutants during their normal daily activities. We will study volunteers who may be at increased risk for the effects of ozone because of genetic susceptibility. Understanding the effects of ozone on the heart and circulation can help establish appropriate air pollution standards, and provide strategies to protect the most susceptible people.
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