Ultrastructural changes in atherosclerotic plaques following the instillation of airborne particulate matter into the lungs of rabbits.
BACKGROUND
Epidemiological studies have established that cardiovascular events account for the greatest number of air pollution-related deaths. However, the underlying structural changes are still unknown.


OBJECTIVE
To investigate changes in the ultrastructure of atherosclerotic plaques in Watanabe heritable hyperlipidemic (WHHL) rabbits following the instillation of ambient particulate matter air pollution (particles smaller than 10 µm in diameter) into the lungs.


METHODS
WHHL rabbits (n=8) exposed to 5 mg of ambient particles (Environmental Health Centre - 1993 [EHC-93]; suspended in saline and instilled in the airway) twice per week for four weeks were compared with control WHHL rabbits (n=8) treated with saline alone.


RESULTS
All abdominal aortic plaques were examined using light and electron microscopy, which showed the following: increased accumulation of macrophage-derived foam cells immediately below the endothelial plaque surface (P=0.04); increased contact between these foam cells and the dense subendothelial extracellular matrix (P<0.005) with reduction (P<0.0001) and fragmentation (P<0.0001) of this matrix; and emigration of macrophage- derived foam cells from the plaques in exposed rabbits. In addition, immunohistochemistry verified the presence of type IV collagen in the thickened extracellular matrix material subtending the endothelium.


CONCLUSIONS
The ultrastructure of atherosclerotic plaques in EHC-93- instilled rabbits differed from the ultrastructure observed in rabbits that did not receive EHC-93. These ultrastructural differences are consistent with greater endothelial instability in the plaques of atherosclerosis-prone rabbits.
Tranfield
Erin M
EM
St Paul's Hospital, University of British Columbia, Vancouver.
van Eeden
Stephan F
SF
Yatera
Kazuhiro
K
Hogg
James C
JC
Walker
David C
DC
D000818:Animals; D001012:Aorta, Abdominal / Q000648:ultrastructure*; D050197:Atherosclerosis / Q000473:pathology*; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000648:ultrastructure; D006938:Hyperlipoproteinemia Type II / Q000473:pathology*; D007958:Leukocyte Count; D008168:Lung / Q000473:pathology / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009000:Monocytes / Q000648:ultrastructure*; D052638:Particulate Matter / Q000633:toxicity*; D011817:Rabbits; D012016:Reference Values
D052638:Particulate Matter