Inhaled asbestos exacerbates atherosclerosis in apolipoprotein E-deficient mice via CD4+ T cells

Abstract

Background: Associations between air pollution and morbidity/mortality from cardiovascular disease are recognized in epidemiologic and clinical studies, but the mechanisms by which inhaled fibers or particles mediate the exacerbation of atherosclerosis are unclear. Objective and Methods: To determine whether lung inflammation after inhalation of a well-characterized pathogenic particulate, chrysotile asbestos, is directly linked to exacerbation of atherosclerosis and the mechanisms involved, we exposed apolipoprotein E-deficient (ApoE-/-) mice and ApoE-/- mice crossed with CD4-/- mice to ambient air, NIEHS (National Institute of Environmental Health Sciences) reference sample of chrysotile asbestos, or fine titanium dioxide (TiO2), a nonpathogenic control particle, for 3, 9, or 30 days. Results: ApoE-/- mice exposed to inhaled asbestos fibers had approximately 3-fold larger atherosclerotic lesions than did TiO2-exposed ApoE-/- mice or asbestos-exposed ApoE-/-/CD4-/- double-knockout (DKO) mice. Lung inflammation and the magnitude of lung fibrosis assessed histologically were similar in asbestos-exposed ApoE-/- and DKO mice. Monocyte chemoattractant protein-1 (MCP-1) levels were increased in bronchoalveolar lavage fluid and plasma, and plasma concentrations correlated with lesion size (p < 0.04) in asbestos-exposed ApoE-/- mice. At 9 days, activator protein-1 (AP-1) and nuclear factor-κB (NF-κB), transcription factors linked to inflammation and found in the promoter region of the MCP-1 gene, were increased in aortas of asbestos-exposed ApoE-/- but not DKO mice. Conclusion: Our findings show that the degree of lung inflammation and fibrosis does not correlate directly with cardiovascular effects of inhaled asbestos fibers and support a critical role of CD4+ T cells in linking fiber-induced pulmonary signaling to consequent activation of AP-1- and NF-κB-regulated genes in atherogenesis.