Abstract 17944: Increased Susceptibility to β-amyloid Toxicity In Rat Brain Microvascular Endothelial Cells Under Hyperglycemic Conditions
β-amyloid peptide (Aβ) accumulation is the hallmark of Alzheimer's Disease (AD), but the mechanisms underlying its cellular toxicity are unclear. Evidence shows a close association between Type 2 diabetes (DM) and AD. DM also promotes impaired function of cerebrovascular endothelium that constitutes the blood-brain barrier. We hypothesized that hyperglycemia-induced mitochondrial dysfunction and oxidative stress promote Aβ toxicity in endothelial cells.
Methods. Rat brain microvascular endothelial cells (RBMEC) were isolated from adult Sprague-Dawley rats and cultured in normoglycemic and hyperglycemic media followed by exposure to Aβ peptide or Aβ 40-1. Cell viability was measured by the Alamar blue assay and mitochondrial membrane potential (Ψmito) was measured by confocal microscopy and microplate reader (rhodamine 123). Also, mitochondrial superoxide (mitoSO) was measured by fluorescence microscopy (MitoSOX) and Hydrogen peroxide (H2O2) levels by microplate reader (Amplex Red). RBMECs were treated with antioxidants (MitoTempo and PEG-SOD) to study the role of oxidative stress in Aβ-toxicity.
Results. Hyperglycemia, mannitol, Aβ or Aβ 40-1 alone did not affect cell viability. However, during hyperglycemia, Aβ reduced the cell viability compared to normoglycemic conditions. Baseline Ψmito and depolarization in response to ionophore were not different among all treatment groups. Aβ and hyperglycemia together induced a reduction in Ψmito, promoted mitochondrial fission and enhanced mitoSO production and H2O2 levels. Only MitoTempo and PEG-SOD treatments were able to counteract Aβ toxicity by increasing cell viability and recovering Ψmitoresponse.
Conclusion. Hyperglycemia increases RBMEC susceptibility to Aβ toxicity leading to cell death by promoting the alterations of mitochondrial morphology, electromotive force and enhanced oxidative stress. The effect of hyperglycemia to promote Aβ toxicity appears to be mediated by mitoSO.
- © 2012 by American Heart Association, Inc.