Aβ₄₀ Improves Cerebrovascular Endothelial Function via NOX4-Dependent Hydrogen Peroxide Release

Alzheimer's disease (AD) is associated with an abnormal accumulation of amyloid β (Aβ) fibrils in the brain parenchyma and cerebrovasculature, which leads to cognitive impairment and cerebrovascular dysfunction. Cerebrovascular endothelial cells play a crucial role in regulating cerebral blood flow, vascular permeability, and neurovascular function. Reactive oxygen species (ROS), particularly those generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2), contribute to vascular dysfunction and amyloid deposition in the Alzheimer's disease (AD) brain. However, the role of the NOX4 isoform in AD pathogenesis remains to be examined. In the present study, we found that NOX4 among the NOX isoforms is predominantly expressed in bEnd.3 mouse brain endothelial cells. Treatment with Aβ₄₀ significantly enhanced the release of H₂O₂ and NO, and increased the endothelial cell viability. To test the involvement of NOX4 in Aβ₄₀-induced H₂O₂ production, we utilized pharmacological inhibitors of NOX isoforms. Aβ₄₀-induced H₂O₂ production was attenuated in the presence of the pan-NOX inhibitor, apocynin, or the NOX1/4-selective inhibitors, setanaxib and GKT136901. Since only the NOX4 isoform is expressed in bEnd.3 cells, these results indicate that NOX4 is responsible for the release of H₂O₂ stimulated by Aβ₄₀. Taken together, the present study demonstrated that Aβ₄₀ peptide exerts beneficial effects in bEnd.3 endothelial cells via the NOX4-dependent mechanism.