CD36-Dependent 7-Ketocholesterol Accumulation in Macrophages Mediates Progression of Atherosclerosis in Response to Chronic Air Pollution Exposure
Rationale: Air pollution exposure has been shown to potentiate plaque progression in humans and animals. Our previous studies have suggested a role for oxidized lipids in mediating adverse vascular effect of air pollution. However, the types of oxidized lipids formed in response to air pollutants and how this occurs and their relevance to atherosclerosis is not fully understood.
Objective: To investigate the mechanisms by which particulate matter <2.5μm (PM2.5) induces progression of atherosclerosis.
Methods and Results: Atherosclerosis-prone ApoE-/- or LDLR-/- mice were exposed to filtered air or concentrated ambient PM2.5 using a versatile aerosol concentrator enrichment system for 6 months. PM2.5 increased 7-ketocholesterol (7-KCh), an oxidatively modified form of cholesterol, in plasma IDL/LDL fraction and in aortic plaque concomitant with progression of atherosclerosis and increased CD36 expression in plaque-macrophages from PM2.5-exposed mice. Macrophages isolated from PM2.5-exposed mice displayed increased uptake of oxidized lipids without alterations in their efflux capacity. Consistent with these finding, CD36-positive macrophages displayed a heightened capacity for oxidized lipid uptake. Deficiency of CD36 on hematopoietic cells diminished the effect of air pollution on 7-KCh accumulation, foam cell formation, and atherosclerosis.
Conclusions: Our results suggest a potential role for CD36-mediated abnormal accumulations of oxidized lipids such as 7-KCh in air pollution induced atherosclerosis progression.
- particulate matter
- air pollution
- lipid metabolites
- foam cells
- Received June 22, 2014.
- Revision received September 2, 2014.
- Accepted September 3, 2014.