The effects of prolyl hydroxylase inhibition during and post, hypoxia, oxygen glucose deprivation and oxidative stress, in isolated rat hippocampal slices

The contributions of hypoxia and oxidative stress to the pathophysiology of acute ischemic stroke are well established and can lead to disruptions in synaptic signaling. Hypoxia and oxidative stress lead to the neurotoxic overproduction of Reactive Oxygen Species (ROS) and the stabilization of hypoxia inducible factors (HIF). Compounds such as prolyl-4-hydroxylase domain Enzyme inhibitors (PHDIs) have been shown to have a preconditioning and neuroprotective effect against ischemic insults such as hypoxia, anoxia, oxygen glucose deprivation (OGD) or H₂O₂. Therefore, this study explored the effects of two PHDIs, JNJ-42041935 (10µM) and roxadustat (100µM) on cell viability using organotypic hippocampal slice cultures. We also assessed the effects of these compounds on synaptic transmission during and post hypoxia, OGD and H₂O₂ application in isolated rat hippocampal slices using field recording electrophysiological techniques and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit trafficking using immunohistochemistry. Our organotypic data demonstrated a protective role for both inhibitors, where slices had significantly less cell death post anoxia and OGD compared to controls. We also report a distinct modulatory role for both JNJ-42041935 and roxadustat on fEPSP slope post hypoxia and OGD but not H₂O₂. In addition, we report that application of roxadustat impaired long-term potentiation, but only when applied post-hypoxia. This inhibitory effect was not reversed with co-application of the cyclin-dependent kinase 5 (CDK-5) inhibitor, roscovitine (10µM), suggesting a CDK-5 independent synaptic AMPAR trafficking mechanism. Both hypoxia and OGD induced a reduction in synaptic AMPA GluR2 subunits, the OGD effect being reversed by prior treatment with both JNJ-42041935 and roxadustat. These results suggest an important role for PHDs in synaptic signaling and plasticity during episodes of ischemic stress.

EPSP; Hippocampus; Hypoxia; Ischemia reperfusion injury; JNJ42041935; Oxidative stress; Oxygen glucose deprivation; Prolyl hydroxylase inhibition; Roxadustat; Synaptic transmission.