Amyloid beta aggregation promoted by iron leads to neuronal loss in an ex vivo model of Alzheimer's disease

Alzheimers disease (AD) is a progressive neurodegenerative disorder characterized by amyloid beta (A{beta}) plaques and neurofibrillary tangles. Despite well-established iron accumulation in the AD brain, its role in exacerbating A{beta} toxicity is often overlooked in therapeutic research. We developed a 3D ex vivo organotypic brain slice cultures (OBSC) with A{beta} monomers and ferric citrate to mimic A{beta} deposits and iron overload to investigate the impact of excess iron on A{beta} toxicity in pig and human brains. Light and electron microscopy, biochemical assays, and multiple regression modeling were employed to assess iron-mediated A{beta} toxicity in neurons and glial cells. We show that OBSC offer a close approximation of in vivo morphological and physiological properties and can retain both neurons and glial cells for extended periods, and respond to experimental manipulations. We show that iron promotes A{beta} fibrillization into long fibrils, with this process further influenced by temperature. A{beta} selectively accumulated in neurons, leading to their death, sparing glial cells. In contrast, Iron, though generally toxic to neurons, exhibited unspecific cytotoxicity. Notably, the combined presence of A{beta} and iron synergistically increased neuronal death while reducing glial cell loss. Correlation analysis revealed that this synergic interaction enhances the toxicity of each other in a mutual fashion - A{beta} directs the neuronal toxicity while iron promotes A{beta} fibrillization, leading to targeted neuronal loss. In conclusion, our findings emphasize the critical role of excess iron and A{beta} in driving neuronal death in AD, underlining the importance of targeting iron accumulation along with A{beta} clearance but also addressing in future AD therapies, while also supporting our OBSC model as a valuable platform for studying the same.