Vascular effects of ambient pollutant particles and metals.

Exposure to ambient pollutant particle (APP) is associated with increased cardiovascular morbidity and mortality. Recent evidence indicates that APP-induced vasoconstriction may be an important mechanism. APP constricts systemic arteries and increases blood pressure in human. APP decreases the diameter of pulmonary arterioles in animals. Intratracheal instillation of APP increases pulmonary artery resistance in isolated buffer-perfused lungs, and APP constricts isolated arterial rings. APP-induced vasoconstriction may be secondary to the release of inflammatory mediators from lung cells, which then activate vascular endothelial and smooth muscle cells. The vasoconstriction may also be caused by alterations in autonomic nervous system balance. Some soluble metals (e.g., vanadium) can produce acute vasoconstriction in in vitro and in vivo systems, and contribute to the systemic health effects of APP since they can more easily permeate the alveolar-capillary membrane than the whole particle. Both APP and its associated metals have been shown to enhance the release of endothelin 1 and reactive oxygen species, activate epithelial growth factor receptor and mitogen-activated protein kinases, and inhibit nitric oxide vasodilator activity. The vasoactive properties of APP and metals raised the possibility that patients with vascular diseases may be more susceptible to APP-induced adverse health effects, and that people who are regularly exposed to high amount of metals, e.g., vanadium contained in certain dietary and muscle-building regimens or in the air of boiler making plants, may have increased risk for vascular diseases. Understanding how metals induce vasoconstriction may lead to the development of novel vasodilator therapies for vascular diseases.