ABSTRACT
The aggregation of amyloid-ß in Alzheimer's disease can be affected by free transition metals such as copper and zinc in the brain. Addition of copper and zinc with amyloid acts to increase aggregation and copper additionally promotes the formation of reactive oxygen species. We propose that reduction of brain copper by blocking uptake of copper from the diet is a viable strategy to regulate the formation of insoluble amyloid-ß in the brain of Tg2576 mice. Mice were treated with regimens of zinc acetate, which acts with metallothionein to block copper uptake in the gut, at various times along their lifespan to model prevention and treatment paradigms. We found that the mice tolerated zinc acetate well over the six month course of study. While we did not observe significant changes in cognition and behavior, there was a reduction in insoluble amyloid-ß in the brain. This observation coincided with a reduction in brain copper and interestingly no change in brain zinc. Our findings show that blocking copper uptake from the diet can redistribute copper from the brain and reduce amyloid-ß aggregation.
Subject(s)
Amyloidosis/drug therapy , Amyloidosis/physiopathology , Brain/drug effects , Brain/physiopathology , Neuroprotective Agents/administration & dosage , Zinc Acetate/administration & dosage , Administration, Oral , Alzheimer Disease , Amyloid beta-Protein Precursor/genetics , Amyloidosis/pathology , Animals , Body Weight/drug effects , Body Weight/physiology , Brain/pathology , Ceruloplasmin/metabolism , Copper/metabolism , Disease Models, Animal , Female , Humans , Maze Learning/drug effects , Maze Learning/physiology , Mice, Inbred C57BL , Mice, Transgenic , Motor Activity/drug effects , Motor Activity/physiology , Random Allocation , Spatial Memory/drug effects , Spatial Memory/physiology , Zinc/metabolismABSTRACT
Alzheimer's disease (AD) causes progressive, age-dependent cortical and hippocampal dysfunction leading to abnormal intellectual capacity and memory. We propose a novel protective treatment for AD pathology with phytic acid (inositol hexakisphosphate), a phytochemical found in food grains and a key signaling molecule in mammalian cells. We evaluated the protective and beneficial effects of phytic acid against amyloid-ß (Aß) pathology in MC65 cells and the Tg2576 mouse model. In MC65 cells, 48-72-hour treatment with phytic acid provided complete protection against amyloid precursor protein-C-terminal fragment-induced cytotoxicity by attenuating levels of increased intracellular calcium, hydrogen peroxide, superoxide, Aß oligomers, and moderately upregulated the expression of autophagy (beclin-1) protein. In a tolerance paradigm, wild type mice were treated with 2% phytic acid in drinking water for 70 days. Phytic acid was well tolerated. Ceruloplasmin activity, brain copper and iron levels, and brain superoxide dismutase and ATP levels were unaffected by the treatment. There was a significant increase in brain levels of cytochrome oxidase and a decrease in lipid peroxidation with phytic acid administration. In a treatment paradigm, 12-month old Tg2576 and wild type mice were treated with 2% phytic acid or vehicle for 6 months. Brain levels of copper, iron, and zinc were unaffected. The effects of phytic acid were modest on the expression of AßPP trafficking-associated protein AP180, autophagy-associated proteins (beclin-1, LC3B), sirtuin 1, the ratio of phosphorylated AMP-activated protein kinase (PAMPK) to AMPK, soluble Aß1-40, and insoluble Aß1-42. These results suggest that phytic acid may provide a viable treatment option for AD.
Subject(s)
Alzheimer Disease/drug therapy , Alzheimer Disease/pathology , Antipsychotic Agents/therapeutic use , Phytic Acid/therapeutic use , Adenosine Triphosphate/metabolism , Amyloid beta-Peptides/metabolism , Analysis of Variance , Animals , Apoptosis Regulatory Proteins/metabolism , Autophagy/drug effects , Beclin-1 , Body Weight/drug effects , Cell Line, Tumor , Ceruloplasmin/metabolism , Cyclooxygenase 1/metabolism , Disease Models, Animal , Dose-Response Relationship, Drug , Electron Transport Complex IV/metabolism , Enzyme-Linked Immunosorbent Assay/methods , Female , Gene Expression Regulation/drug effects , Humans , Hydrogen Peroxide/pharmacology , Malondialdehyde/metabolism , Mice , Mice, Inbred C57BL , Mice, Transgenic , Neuroblastoma , Sirtuins/metabolism , Time FactorsABSTRACT
There is strong evidence that intracellular calcium dysregulation plays an important pathological role in Alzheimer's disease, and specifically that beta amyloid may induce increases in intracellular calcium and lead to neuronal cell dysfunction and death. Here we investigated the feasibility of modifying Alzheimer's pathology with the L-type voltage-gated calcium channel blockers verapamil, diltiazem, isradipine and nimodipine. All four compounds protected MC65 neuroblastoma cells from amyloid beta protein precursor C-terminal fragment (APP CTF)-induced neurotoxicity. Isradipine was the most potent blocker, preventing APP CTF neurotoxicity at nanomolar concentrations. Intracellular beta amyloid expression was associated with increased expression of Cav 1.2 calcium channels and increased intracellular calcium influx from the extracellular space. Despite the cytoprotection afforded by calcium channel blockers, amyloid beta oligomer formation was not suppressed. The mechanism of cell death in MC65 cells is appeared to be caspase-3 independent. With the goal of determining if there is sufficient experimental support to move forward with animal trials of isradipine, we determined its bioavailability in the triple transgenic mouse model of AD. Subcutaneous implantation of carrier-bound isradipine (3 µg/g/day) for 60 days resulted in nanomolar concentrations in both the plasma and brain. Taken together, our in vitro results support the theory that calcium blockers exert protective effects downstream of the effects of beta amyloid. Isradipine's neuroprotective effect at concentrations that are clinically relevant and achievable in vitro and in vivo suggests that this particular calcium blocking agent may have therapeutic value in the treatment of Alzheimer's disease.
