The toxic effects of low lead upon the developing nervous system remain a major health issue in this country. Among the unsolved problems are mechanisms of cellular injury, as well as mechanisms of Pb uptake, storage, and tolerance in brain cells that accumulate Pb. The candidate's immediate career objective is to gain depth and experience in the field of neuroscience, specifically with astroglia and their interaction with the blood-brain barrier (BBB). We plans to thoroughly explore the multistep model of low-level lead (Pb) neurotoxicity presented in this application. The investigators propose to study the molecular changes that occur in astroglia and endothelial cells in culture, following exposure to low levels of Pb (0.01 to 1 microM). Parameters investigated will be Ca2+ homeostasis, mitochondrial membrane potential, and gap junction regulation. Reduction of glutamine synthetase activity in astroglia will also be measured as an indicator of Pb-induced toxicity. The investigators will also test the hypothesis that endothelial cells induce astroglial maturation and resistance to Pb2+ in co-culture. The candidate will exploit the powerful new technology of Interactive Laser Cytometry for probing the disruption of cell metabolism at discrete sites. the candidate's department is unique in that it has both state-of-the-art equipment and a highly trained support staff required for effective use of this technology. Interactive Laser Cytometry and biochemical assays will be combined to evaluate the molecular events transpiring in these cells after exposure to submicromolar Pb concentrations. In addition, an in vitro model of the blood-brain barrier (BBB), consisting of rat astroglial and brain capillary endothelial cells grown on opposite surfaces of a semi- permeable membrane, will be constructed and evaluated with respect to low-level Pb toxicity. Pb transport across the barrier formed by the cells will be measured, as well as Pb effects on barrier integrity. These experiments, which constitute Phase I of the research plan, will lead to her PhD degree. Finally, in Phase II, the candidate plans to specifically address the question of how lead enters cells (particularly astroglia and endothelial cells), and how it is stored. The candidate will be guided in this effort by a biochemist with extensive experience in protein-metal interactions, as well as transitional metal chemistry and metabolism. The PSA would relieve her of other responsibilities, particularly teaching, so she could commit 90% of her time to training and research. The candidate has two long-term career objectives, which she plans to attain as an academic scientist and teacher: first, to make significant strides in the development of a valid in vitro model of the BBB, and secondly to apply this model to study toxin-induced as well as infectious neuropathologies.
| Legare, M E; Hanneman, W H; Barhoumi, R et al. (2000) 2,3,7,8-Tetrachlorodibenzo-p-dioxin alters hippocampal astroglia-neuronal gap junctional communication. Neurotoxicology 21:1109-16 |
| Legare, M E; Barhoumi, R; Hebert, E et al. (1998) Analysis of Pb2+ entry into cultured astroglia. Toxicol Sci 46:90-100 |
| Legare, M E; Hanneman, W H; Barhoumi, R et al. (1997) The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure in primary rat astroglia: identification of biochemical and cellular targets. Neurotoxicology 18:515-24 |
| Hanneman, W H; Legare, M E; Barhoumi, R et al. (1996) Stimulation of calcium uptake in cultured rat hippocampal neurons by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicology 112:19-28 |
