Vulnerability to oxygen-glucose deprivation of primary neurons derived from Tg2576 Alzheimer mice: role of intraneuronal Abeta accumulation and astrocytes

Microvascular dysfunction is considered an integral part of Alzheimer disease (AD) pathogenesis, but the possible relationship between amyloid pathology, microvascular dysfunction and cell death is still unclear. In order to investigate the influence of intraneuronal Abeta (Aβ) accumulation on vulnerability to hypoxia, we isolated primary cortical neurons from Tg2576 (carrying the APPSwe mutation) and Wt fetal mice. We first demonstrated that neurons isolated from Tg2576 new-born mice show an increase in VEGFa mRNA expression and a decrease in the expression of the two VEGF receptors, i.e. Flt1 and Kdr, compared to Wt cells. Moreover, APPSwe primary neurons displayed higher spontaneous and glutamate-induced cell death. We then exposed the cultures to Oxygen Glucose Deprivation (OGD) as an in vitro model of hypoxia. When exposed to OGD, APPSwe neurons also display higher cell death in terms of percentage of pyknotic/fragmented nuclei and mitochondrial depolarization, accompanied by an increase in the Amyloid beta intraneuronal content. To explore the influence of intraneuroal amyloid peptide accumulation, we used the gamma-secretase inhibitor LY450139, which showed that the reduction of the intracellular amyloid fully protects APPSwe neurons from OGD-induced degeneration. To explore the possible role of astrocytes in OGD, conditioned media from OGD-exposed astrocyte obtained from either Tg2576 and Wt animals were used during neuron exposure to OGD, showing that they protect both Wt and APPSwe neurons during OGD. In conclusion, we showed that the presence of the mutated human APP gene, leading to the intracellular accumulation of APP and Abeta fragments worsens OGD toxicity. Neuroprotection of APPSwe neurons can be obtained either using a γ-secretase inhibitor or astrocyte conditioned medium.