Objective: To investigate the effects of lead exposure on the copper concentration in the brain and serum and the expression of copper transporters in the choroid plexus among rats.
Methods: Sixty specific pathogen-free Sprague-Dawley rats were randomly divided into a control group and three lead-exposed groups, with 8 mice in each group. The lead-exposed groups were orally administrated with 500 (low-dose group)), 1 000 (middle-dose group), and 2 000 mg/L (high-dose group) lead acetate in drinking water for eight weeks. And the rats in control group were given 2 000 mg/L sodium acetate in drinking water. The content of lead and copper in the serum, hippocampus, cortex, choroid plexus, bones, and cerebrospinal fluid (CSF) was determined by inductively coupled plasma-mass spectrometry (ICP-MS). Confocal and real-time PCR methods were applied to measure the expression of copper transporters including copper transporter 1 (Ctr1), antioxidant protein 1 (ATX1), and Cu ATPase (ATP7A).
Results: Compared with the control group, the lead-exposed groups showed significantly higher lead concentrations in the serum, cortex, hippocampus, choroid plexus, CSF, and bones (P < 0.05) and significantly higher copper concentrations in the CSF, choroid plexus, serum, and hippocampus (P < 0.05). Confocal images showed that Ctr1 protein was expressed in the cytoplasm and cell membrane of choroid plexus in control group. However, Ctr1 migrated to CSF surface microvilli after lead exposure. Ctr1 fluorescence intensity gradually increased with increasing dose of lead, except that the middle-dose group had a higher Ctr1 fluorescence intensity than the high-dose group. In addition, the middle- and high-dose groups showed a lower ATX1 fluorescence intensity compared with the control group. Real-time PCR data indicated that the three lead-exposed groups showed significantly higher mRNA levels of Ctr1 and ATP7A compared with the control group (P < 0.05).
Conclusion: Copper homeostasis in the choroid plexus is affected by lead exposure to induce copper homeostasis disorders in brain tissue, which may be one of the mechanisms of lead neurotoxicity.