Trace Amounts of Copper Exacerbate Beta Amyloid-induced Neurotoxicity in the Cholesterol-fed Mice Through TNF-mediated Inflammatory Pathway

Evidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Step-through task and Morris water maze task were used to evaluate cognitive function in the animals. Although a 16-week copper treatment alone in mice showed no significant change in learning and memory performances, cholesterol treatment significantly induced learning and memory impairments, which could be exacerbated by the co-treatment with copper. Immunohistochemical studies revealed that trace amounts of copper further stimulated the amyloid precursor protein (APP) upregulation and contributed to amyloid beta-peptide (Abeta) deposition in the brain of cholesterol-fed mice. Western blot analysis showed that copper also increased the protein expression levels of tumor necrosis factor-alpha (TNF-alpha) and the degradation of IkappaB proteins in the brain of cholesterol-fed mice. Furthermore, increased production of high inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expressions were detected in the hippocampus and cerebral cortex of copper and cholesterol co-treated mice by immunohistochemical analysis. These findings suggest that trace amounts of copper could induce APP upregulation, activate inflammatory pathway and exacerbate neurotoxicity in cholesterol-fed mice.