Altered brain copper (Cu) homeostasis has been associated with idiopathic Parkinson's disease (IPD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Prion disease. We have recently discovered that Cu levels in blood and saliva of Mn-exposed workers from human cohorts are significantly increased, and so are the Cu levels in the CSF and brain tissues of Mn- exposed animals. While the presence of transporters possibly responsible for Cu transport in brain barriers such as Cu transport protein-1 (Ctr1), divalent metal transporter-1 (DMT1) and ATP7A has been demonstrated, how Cu is transported by these transporters in brain barriers and by what mechanism exposure to manganese (Mn) alters the expression and function of these transporters are unknown. This research project is designed to test the hypothesis that the choroid plexus, a brain tissue forming a barrier between the blood and cerebrospinal fluid (CSF), regulates Cu transport between the blood and CSF through the critical transporters;exposure to Mn alters the functions of these transporters, leading to a distorted Cu homeostasis in the CSF. To test this hypothesis, we have designed 4 specific aims.
In Aim 1, we will determine if subchronic exposure to Mn in a rat model alters the expression of Ctr1, DMT1 and ATP7A in blood-brain barrier (BBB) and blood-CSF barrier (BCB), leading to an increased influx of Cu from the blood to brain parenchyma and a decreased Cu efflux from the CSF to blood.
In Aim 2, we will reveal if Ctr1 and DMT1 coordinate the Cu uptake on the surface of the BBB and BCB and if Mn exposure disrupts these processes, leading to cellular overload of Cu by the brain barrier cells.
Aim 3 is designed to investigate if the intracellular trafficking of ATP7A determines the direction of Cu transport by the BCB and if Mn exposure, by acting on ATP7A, may alter the direction of Cu transport between the blood and the CSF. Finally, in Aim 4, we will use the synchrotron rapid scanning X-ray fluorescence (RS-XRF) technique, by collaboration with the professor in Purdue's Physics department, to establish 3D model to simultaneously localize and quantify Cu, Fe, Mn and Zn in brains of Mn-exposed rats. The studies proposed in this application will define the inter-relationship between Ctr1, DMT1 and ATP7A in brain barriers with regard to their subcellular locations, roles in transport of Cu, and their regulation as affected by Mn exposure;will provide the insight into the molecular mechanism by which Mn affects Cu transport by brain barriers;and will ultimately provide a better understanding of Cu dysregulation-related neurodegenerative diseases.
Altered brain copper (Cu) homeostasis has been associated with idiopathic Parkinson's disease (IPD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS) and Prion disease. This project will uncover how Cu is transferred in and out of the brain and how exposure to environmental toxicant manganese (Mn) interferes with the Cu balance in brain, which in turn causes the degenerative manganese parkinsonism.
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