Particulate Pollution and Endothelial Function

Agrowing body of epidemiological data implicates particulate matter air pollution (PM) as yet another factor in the pathogenesis of cardiovascular disease.1 PM influences susceptibility to hard events and may be particularly harmful to high-risk groups such as people with diabetes, people with hypertension, and people who smoke.2 The synergistic impact of PM in diabetes mellitus is internally consistent with previous observations, demonstrating that risk factors such as hypertension, diabetes, and smoking may potentiate atherosclerosis. Thus, if one were to predict likely pathological mechanisms, recapitulation of some the previously well-characterized pathways through which risk factors such as smoking or diabetes modulate atherosclerosis may be equally applicable to PM-mediated atherogenicity.See p 2913 In this issue of Circulation , O’Neill and colleagues demonstrate that antecedent 6-day moving average levels of PM were negatively associated with endothelium-dependent flow-mediated dilation and nitroglycerin-mediated dilation in 269 subjects with diabetes mellitus (type 1, n=45; type 2, n=182) or subjects at risk for developing diabetes (n=42).3 Although the results of the study represent pooled data from 4 trials, the clinical and environmental variables were merged by date to provide startling insights between variations in vasomotor tone and preceding ambient PM levels. The negative association in the type 2 diabetes population (the majority) was striking and, not surprisingly, drove the results of the study. These results are consistent with the recurring observation of impaired large-vessel endothelial function in people with type 2 diabetes.4 Another notable finding in the present study was the effect of PM on nitroglycerin-mediated dilation. These results are similar to previous studies that noted the impact of risk factors such as diabetes on smooth muscle function and could potentially implicate abnormalities in guanylate cyclase–cyclic guanosine monophosphate signaling pathways to PM.4Of the 4 metrics of PM measured in the study …