Knockdown of Nrf2 inhibits angiogenesis by downregulating VEGF expression through PI3K/Akt signaling pathway in cerebral microvascular endothelial cells under hypoxic conditions

Ischemic stroke is a major cerebrovascular disease resulting from a transient or permanent local reduction of cerebral blood flow. Angiogenesis plays an important role in cerebral microvascular repair after ischemic stroke. This study aimed at investigating the effect of NF-E2-related factor 2 (Nrf2) on the angiogenesis of mouse cerebral microvascular endothelial bEnd.3 cells in a hypoxic environment. We found that Nrf2 expression was temporarily increased in hypoxia-induced bEnd.3 cells. Knockdown of Nrf2 inhibited the proliferation, migration, as well as tube formation in hypoxia-induced bEnd.3 cells. Meanwhile, vascular endothelial growth factor and PI3K/Akt signaling pathways were identified to be regulated by Nrf2 in hypoxia-induced bEnd.3 cells. It was found that silencing of Nrf2 downregulated the expression levels of NAD(P)H:quinine oxidoreductase-1, vascular endothelial growth factor, p-Akt, and heme oxygenise-1 in hypoxia-induced bEnd.3 cells. Data suggested that hypoxia induced the transient increase of Nrf2, which plays a key role in the angiogenesis of cerebral microan-giogenesis, and that Nrf2 regulates the proliferation, migration, as well as tube formation likely through PI3K/Akt signaling pathway in hypoxia-induced bEnd.3 cells. Our study provides proof of concept for the modulation of Nrf2, so as to tilt the balance toward angiogenesis, representing a therapeutic strategy for hypoxia or ischemia disorders such as stroke.