Lead Exposure Induced Copper Clearance Disorder of Blood-CSF Barrier

Abstract

Lead is a heavy metal commonly found in the environment with known neurotoxicity, hematological and other toxicities. It has been found that lead exposure can disturb partial metal regulatory function in the blood-CSF barrier (BCB). Copper, which play an important role in maintaining normal brain function, can accumulate in brain after lead exposure. The studies of Alzheimer's disease (AD) indicated that abnormal copper homeostasis in cerebrospinal fluid (CSF) may be involved in the pathogenesis. However, the mechanism of copper disturbance in the brain caused by lead is still unknown. This study was designed to investigate copper clearance by the BCB in central nervous system after lead exposure, with focus on copper transporter protein CTR1/ATP7A. Inductively coupled plasma mass spectrometry (ICP-MS) and principal component analysis (PCA) were used to identify the changes of heavy metal level in hippocampus and CSF after lead exposure. It was found that the change in copper level was most pronounced in the brain between 3 to 12 weeks post lead exposure. Ventriculo-cisternal (VC) perfusion in Sprague Dawley (SD) rat suggested that the ability of BCB to deliver copper from the CSF to blood was decreased after lead exposure. Confocal microscope showed evidence of the presence of excess copper in the choroid plexus cells leading to CTR1/ATP7A shifting toward the apical microvilli facing the CSF after lead exposure. Finally, transmission electron microscopy (TEM) was used for observation of the microstructure of choroid plexus showed altered mitochondrial morphology with decreased microvilli after lead exposure. Our data suggested that lead exposure may alter BCB cellular microscopic structure and its copper transport, clearance function that might further cause brain injury.