Arsenic is a prevalent toxin in ground water and soil around areas with extractive industries. Exposure to arsenic is linked to several developmental defects in the nervous system and limbs, pregnancy complications and miscarriage. Vascular defects are often the underlying basis for limb deformations and developmental anomalies in other systems and vascular abnormalities often form the basis for placentation defects linked to miscarriage. The overall goal of this project is to define the developmental mechanisms for how arsenic toxicity causes developmental defects and miscarriage, and to characterize the molecular mechanisms for arsenic mediated alteration of endothelial cell physiology. Our preliminary data suggest that arsenic and arsenic-metal mixtures dramatically alter endothelial cell physiology. We hypothesize that arsenite toxicity causes defects in vascular development, predisposing the embryo to other developmental anomalies and miscarriage. The following aims have been designed to test this hypothesis: (1) Characterize the molecular mechanisms for arsenic-mediated alteration of endothelial cell physiology. Cultured endotheiial cells will be exposed to arsenic and analyzed for alterations in the molecular regulatory pathways for vascular development. (2) Define the developmental mechanisms for how arsenic toxicity causes developmental defects. The effects of arsenic toxicity on angiogenesis and vasculogenesis will be assessed using quail-chick chimeras with arsenic-treated tissue transplants. The resulting growth and development of the quail angioblasts through vasculogenesis and angiogenesis will be analyzed by immunocytochemistry with QH-1. (3) Determine how arsenic exposure affects fecundity, placentation and vascular morphogenesis in vivo. Timed- pregnant mice will be exposed to arsenic and arsenic-metal mixtures in their drinking water. The rate of live births from treated mice will be compared to controls to assess fecundity. Embryos harvested at E4.5, E 7.5, E9.5, E10.5 and E15.5 from arsenic-treated tie2-LacZ transgenic (TgLacz) mice will be examined for vascular abnormalities. The key molecular regulatory elements for vascular development will be assayed in each group for comparison to the in vitro data collected in Specific Aim l.
