Persistent endothelial dysfunction in humans after diesel exhaust inhalation

Rationale: Exposure to combustion-derived air pollution is associated with an early (1-2 h) and sustained (24 h) rise in cardiovascular morbidity and mortality. We have previously demonstrated that inhalation of diesel exhaust causes an immediate (within 2 h) impairment of vascular and enclothelial function in humans. Objectives: To investigate the vascular and systemic effects of diesel exhaust in humans 24 hours after inhalation. Methods: Fifteen healthy men were exposed to diesel exhaust (particulate concentration, 300 mu g/m(3)) or filtered air for 1 hour in a double-blind, randomized, crossover study. Twenty-four hours after exposure, bilateral forearm blood flow, and inflammatory and fibrinolytic markers were measured before and during unilateral intrabrachial bradykinin (100-1,000 pmol/min), acetylcholine (520 mu g/min), sodium nitroprusside (2-8 mu g/min), and verapamil (10-100 mu g/min) infusions. Measurements and Main Results: Resting forearm blood flow, blood pressure, and basal fibrinolytic markers were similar 24 hours after either exposure. Diesel exhaust increased plasma cytokine concentrations (tumor necrosis factor-a and interleukin-6, p < 0.05 for both) but appeared to reduce acetylcholine (p = 0.01), and bradykinin (p = 0.08) induced forearm vasodilatation. In contrast, there were no differences in either endothelium-independent (sodium nitroprusside and verapamil) vasoclilatation or bradykinin-induced acute plasma tissue plasminogen activator release. Conclusions: Twenty-four hours after diesel exposure, there is a selective and persistent impairment of endothelium-dependent vasodilatation that occurs in the presence of mild systemic inflammation. These findings suggest that combustion -derived air pollution may have important systemic and adverse vascular effects for at least 24 hours after exposure.