β-Amyloid Fragment 25–35 Causes Mitochondrial Dysfunction in Primary Cortical Neurons

Abstract

β-Amyloid deposition and compromised energy metabolism both occur in vulnerable brain regions in Alzheimer's disease. It is not known whether β-amyloid is the cause of impairment of energy metabolism, nor whether impaired energy metabolism is specific to neurons. Our results, using primary neuronal cultures, show that 24-h incubation with Aβ 25–35 caused a generalized decrease in the specific activity of mitochondrial enzymes per milligram of cellular protein, induced mitochondrial swelling, and decreased total mitochondrial number. Incubation with Aβ 25–35 decreased ATP concentration to 58% of control in neurons and 71% of control in astrocytes. Levels of reduced glutathione were also lowered by Aβ 25–35 in both neurons (from 5.1 to 2.9 nmol/mg protein) and astrocytes (from 25.2 to 14.9 nmol/mg protein). We conclude that 24-h treatment with extracellular Aβ 25–35 causes mitochondrial dysfunction in both astrocytes and neurons, the latter being more seriously affected. In astrocytes mitochondrial impairment was confined to complex I inhibition, whereas in neurons a generalized loss of mitochondria was seen.