Vascular endothelial growth factor (VEGF) affects processing of amyloid precursor protein and β-amyloidogenesis in brain slice cultures derived from transgenic Tg2576 mouse brain

The up-regulation of the angiogenic vascular endothelial growth factor (VEGF) in brains of Alzheimer patients in close relationship to β-amyloid (Aβ) plaques, suggests a link of VEGF action and processing of the amyloid precursor protein (APP). To reveal whether VEGF may affect APP processing, brain slices derived from 17-month-old transgenic Tg2576 mice were exposed with 1 ng/ml VEGF for 6, 24, and 72 h, followed by assessing cytosolic and membrane-bound APP expression, level of both soluble and fibrillar Aβ-peptides, as well as activities of α- and β-secretases in brain slice tissue preparations.Treatment of brain slices with VEGF did not significantly affect the expression level of APP, regardless of the exposure time studied. In contrast, VEGF exposure of brain slices for 6 h reduced the formation of soluble, SDS extractable Aβ(1–40) and Aβ(1–42) as compared to brain slice cultures incubated in the absence of any drug, while the fibrillar Aβ peptides did not change significantly. This effect was less pronounced 24 h after VEGF exposure, but was no longer detectable when brain slices were exposed by VEGF for 72 h, which indicates an adaptive response to chronic VEGF exposure. The VEGF-mediated reduction in Aβ formation was accompanied by a transient decrease in β-secretase activity peaking 6 h after VEGF exposure. To reveal whether the VEGF-induced changes in soluble Aβ-level may be due to actions of VEGF on Aβ fibrillogenesis, the fibrillar status of Aβ was examined using the thioflavin-T binding assay. Incubation of Aβ preparations obtained from Tg2576 mouse brain cortex, in the presence of VEGF slightly decreased the fibrillar content with increasing incubation time up to 72 h. The data demonstrate that VEGF may affect APP processing, at least in vitro, suggesting a role of VEGF in the pathogenesis of Alzheimer's disease.