Neurotoxicity induced by long-term exposure to copper chloride in C57BL/6J mice
CHEN JIE1, ZHANG CHEN1, YANG XIfei2
1. Department of Health Toxicology, School of Public Health, Xinjiang Medical University, Urumqi, Xinjiang 830011, China; 2. Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong 518055, China
Abstract：Objective To explore the effects of different doses of copper chloride exposure on motor function and development of neurons in substantia nigra in female C57BL/6J mice. Methods Thirty 12-week-old C57BL/6J mice were randomly divided into the control group, the 10 mg/Kg copper chloride treated group and the 20 mg/Kg copper chloride treated group (each n=10), and the mouse models were made by instillation for 8 weeks. At the end of the experiment, the mice were subjected to behavioral tests, including stick-turning, pole-climbing and open-field experiments, to detect their locomotor ability, and then the expression of neurons and inflammatory factors was probed by enzyme-linked immunosorbent assay and Western blot. Results The results of behavioral experiments displayed that the length of time on the rod was significantly higher in the copper-treated groups compared with the control group, and the length of time on the rod increased with the increase of toxicant concentration (F=27.03, P<0.05). The length of time on the rod in the copper-exposed mice decreased, and that in the 20 mg/Kg copper chloride treated group declined significantly (F=3.35, P=0.05). The results of open-field experiments revealed that the total distance traveled by mice in the open field decreased in the copper-treated groups compared with the control group (F=13.93, P<0.05). The results of Western blot showed that compared with the control group, the expression levels of tyrosine hydroxylase (F=8.74, P<0.05), dopamine transporter (F=13.09, P<0.05), Bcl-2 (F=9.23, P<0.05) and PGC-1α (F=5.04, P=0.03) protein in substantia nigra and the number of Nissl+ cells in substantia nigra (F=63.52, P<0.05) all decreased after copper treatment. Enzyme-linked immunosorbent assay presented that the copper levels in serum (F=5.93, P=0.02) and substantia nigra (F=7.48, P=0.01)in the copper-treated mice increased compared with the control group. The levels of pro-inflammatory factors IL-6 (F=28.89, P<0.05), TNF-α (F=22.73, P<0.05) and IL-1β (F=11.77, P=0.002) all increased in the copper-treated mice, and the levels of IL-6 and TNF-α also increased correspondingly with the increase of toxicant concentration. The copper-treated mice showed decreased levels of pro-inflammatory factors IL-4 (F=4.79, P=0.04), IL-10 (F=14.70, P=0.001) and TGF-β1 (F=6.19, P=0.02). Conclusion Long-term exposure to copper chloride increases the copper levels in serum and substantia nigra of the mice, induces neuron loss, activates neuroinflammation in the mice, and eventually leads to motor dysfunction.
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2023, Vol. 30 
