Particulate matter exposure induces persistent lung inflammation and endothelial dysfunction

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Abstract
Epidemiologic and animal studies have shown that exposure to particulate matter air pollution (PM) is a risk factor for the development of atherosclerosis. Whether PM-induced lung and systemic inflammation is involved in this process is not clear. We hypothesized that PM exposure causes lung and systemic inflammation, which in turn leads to vascular endothelial dysfunction, a key step in the initiation and progression of atherosclerosis. New Zealand White rabbits were exposed for 5 days (acute, total dose 8 mg) and 4 wk (chronic, total dose 16 mg) to either PM smaller than 10 μm (PM10) or saline intratracheally. Lung inflammation was quantified by morphometry; systemic inflammation was assessed by white blood cell and platelet counts and serum interleukin (IL)-6, nitric oxide, and endothelin levels. Endothelial dysfunction was assessed by vascular response to acetylcholine (ACh) and sodium nitroprusside (SNP). PM10 exposure increased lung macrophages ( P < 0.02), macrophages containing particles ( P < 0.001), and activated macrophages ( P < 0.006). PM10 increased serum IL-6 levels in the first 2 wk of exposure ( P < 0.05) but not in weeks 3 or 4. PM10 exposure reduced ACh-related relaxation of the carotid artery with both acute and chronic exposure, with no effect on SNP-induced vasodilatation. Serum IL-6 levels correlated with macrophages containing particles ( P = 0.043) and ACh-induced vasodilatation ( P = 0.014 at week 1, P = 0.021 at week 2). Exposure to PM10 caused lung and systemic inflammation that were both associated with vascular endothelial dysfunction. This suggests that PM-induced lung and systemic inflammatory responses contribute to the adverse vascular events associated with exposure to air pollution.