Experimental study
Particulate air pollution induces progression of atherosclerosis

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Abstract

Objectives

We sought to determine the effect of exposure to air pollution particulate matter <10 μm (PM10) on the progression of atherosclerosis in rabbits.

Background

Epidemiologic studies have associated exposure to ambient PM10with increased cardiovascular morbidity and mortality. We have previously shown that PM10exposure induces a systemic inflammatory response that includes marrow stimulation, and we hypothesized that this response accelerates atherosclerosis.

Methods

Watanabe heritable hyperlipidemic rabbits were exposed to PM10(n = 10) or vehicle (n = 6) for four weeks, and bone marrow stimulation was measured. Quantitative histologic methods were used to determine the morphologic features of the atherosclerotic lesions.

Results

Exposure to PM10caused an increase in circulating polymorphonuclear leukocytes (PMN) band cell counts (day 15: 24.6 ± 3.0 vs. 11.5 ± 2.7 × 107/l [PM10vs. vehicle], p < 0.01) and an increase in the size of the bone marrow mitotic pool of PMNs. Exposure to PM10also caused progression of atherosclerotic lesions toward a more advanced phenotype. The volume fraction (vol/vol) of the coronary atherosclerotic lesions was increased by PM10exposure (33.3 ± 4.6% vs. 19.5 ± 3.1% [PM10vs. vehicle], p < 0.05). The vol/vol of atherosclerotic lesions correlated with the number of alveolar macrophages that phagocytosed PM10(coronary arteries: r = 0.53, p < 0.05; aorta: r = 0.51, p < 0.05). Exposure to PM10also caused an increase in plaque cell turnover and extracellular lipid pools in coronary and aortic lesions, as well as in the total amount of lipids in aortic lesions.

Conclusions

Progression of atherosclerosis and increased vulnerability to plaque rupture may underlie the relationship between particulate air pollution and excess cardiovascular death.

Abbreviations

BrdU
5"-bromo-2"-deoxyuridine
HDL
high-density lipoprotein
LAD
left anterior descending coronary artery
LCx
left circumflex coronary artery
LDL
low-density lipoprotein
LMCA
left main coronary artery
MCP-1
monocyte chemoattractant protein-1
PM10
particulate matter <10 μm
PMN
polymorphonuclear leukocyte
RCA
right coronary artery
TC
total cholesterol
vol/vol
volume fraction
WHHL
Watanabe heritable hyperlipidemic

Cited by (0)

This study was supported by grant no. 4219 from the Canadian Institute of Health Research and by the Toxic Substance Research Initiative. Dr. van Eeden is a recipient of a Career Investigators Award from the American Lung Association.