Inhibition of soluble epoxide hydrolase augments astrocyte release of vascular endothelial growth factor and neuronal recovery after oxygen-glucose deprivation.

Abstract

Epoxyeicosatrienoic acids (EETs) are synthesized in astrocytes, and inhibitors of soluble epoxide hydrolase (sEH), which hydrolyzes EETs, reduce infarct volume in ischemic stroke. Astrocytes can release protective neurotrophic factors, such as vascular endothelial growth factor (VEGF). We found that addition of sEH inhibitors to rat cultured astrocytes immediately after oxygen-glucose deprivation (OGD) markedly increased VEGF concentration in the medium 48h later and the effect was blocked by an EET antagonist. The sEH inhibitors increased EET concentrations to levels capable of increasing VEGF. When the sEH inhibitors were removed from the medium at 48h, the increase in VEGF persisted for an additional 48h. Neurons exposed to OGD and subsequently to astrocyte medium previously conditioned with OGD plus sEH inhibitors showed increased phosphorylation of their VEGF receptor-2, less TUNEL staining, and increased phosphorylation of Akt, which was blocked by a VEGF receptor-2 antagonist. Our findings indicate that sEH inhibitors, applied to cultured astrocytes after an ischemia-like insult, can increase VEGF secretion. The released VEGF then enhances Akt-enabled cell survival signaling in neurons through activation of VEGF receptor-2 leading to less neuronal cell death. These results suggest a new strategy by which astrocytes can be leveraged to support neuroprotection.