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ARTICLES

Impairment of coronary endothelial cell ET_B receptor function after short-term inhalation exposure to whole diesel emissions

¹Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center and ²Department of Toxicology, Lovelace Respiratory Research Institute, Albuquerque, New Mexico

Submitted 3 November 2008 ; accepted in final form 12 June 2009

Air pollutant levels positively correlate with increases in both acute and chronic cardiovascular disease. The pollutant diesel exhaust (DE) increases endothelin (ET) levels, suggesting that this peptide may contribute to DE-induced cardiovascular disease. We hypothesized that acute exposure to DE also enhances ET-1-mediated coronary artery constrictor sensitivity. Constrictor responses to KCl, U-46619, and ET-1 were recorded by videomicroscopy in pressurized intraseptal coronary arteries from rats exposed for 5 h to DE (300 µg/m³) or filtered air (Air). ET-1 constriction was augmented in arteries from DE-exposed rats. Nitric oxide synthase (NOS) inhibition [N-nitro-L-arginine (L-NNA), 100 µM] and endothelium inactivation augmented ET-1 responses in arteries from Air but not DE rats so that after either treatment responses were not different between groups. DE exposure did not affect KCl and U-46619 constrictor responses, while NOS inhibition augmented KCl constriction equally in both groups. Thus basal NOS activity does not appear to be affected by DE exposure. The endothelin type B (ET_B) receptor antagonist BQ-788 (10 µM) inhibited ET-1 constriction in DE but not Air arteries, and constriction in the presence of the antagonist was not different between groups. Cytokine levels were not different in plasma from DE and AIR rats, suggesting that acute exposure to DE does not cause an immediate inflammatory response. In summary, a 5-h DE exposure selectively increases constrictor sensitivity to ET-1. This augmentation is endothelium-, NOS-, and ET_B receptor dependent. These data suggest that DE exposure diminishes ET_B receptor activation of endothelial NOS and augments ET_B-dependent vasoconstriction. This augmented coronary vasoreactivity to ET-1 after DE, coupled with previous reports that DE induces production of ET-1, suggests that ET-1 may contribute to the increased incidence of cardiac events during acute increases in air pollution levels.

nitric oxide synthase; exhaust; N-nitro-L-arginine; arteries; rat