Project Summary (2000-2005)

The primary objective of this project is to define the cellular and molecular mechanisms responsible for changes in vascular cell phenotype and proliferation following exposure to low levels of arsenite. These changes promote occlusive cardiovascular disease. The hypothesis is that arsenite causes vascular disease by stimulating oxidant-mediated signaling in endothelial and smooth muscle cells. In addition, the oxidants caused by arsenite exposure may deprive the vasculature of nitric oxide required for vasodilation and suppression of smooth muscle cell proliferation. Previous studies made the distinction between oxidant-sensitive cell regulation and oxidant stress in response to increasing amounts of arsenite. Low, environmentally relevant levels of arsenite and oxidants were shown to be regulatory and proliferative, while high levels activate stress pathways and cell death. Focus is now being placed on the signal cascades that initiate superoxide production by nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase. Dominant negative strategies, with highly expressed adenoviral vectors, will demonstrate the role of the monomeric guanosine triphosphatase (GTPase), Racl (a small GTPase), in initiating this activity and in promoting the activation NF-kB, an oxidant-sensitive transcription factor that promotes expression of cytoprotective genes and cell proliferation. Finally, mice are being chronically exposed to low levels of arsenite to test the hypothesis that arsenite decreases vasodilator-induced nitric oxide release and promotes NF-kB-dependent thickening of brain blood vessels. In vivo electron paramagnetic resonance (epr) spectroscopy and an adenoviral construct that suppresses NF-kB activation are facilitating these studies.