Question: 

Prolyl-4-hydroxylase domain proteins (PHDs) regulate endogenous adaptive reactions towards hypoxia and ischemia. We aimed to analyze the effect of neuron-restricted PHD2 deletion on the outcome from acute ischemic stroke.

Methods: 

Mice with neuron-specific PHD2 deletion (nPhd2^D/D) were generated by crossing Phd2 ^flox/flox with CaMKIIa-Cre mice. Animals were exposed to normobaric hypoxia or were subjected to transient middle cerebral artery occlusion. Infarct size and cell death was determined through Nissl staining and TUNEL-Assay, respectively. Gene expression in brain tissue was analyzed by real-time PCR and Western Blotting.

Results: 

We confirmed that Cre/loxP recombination is restricted to forebrain structures including hippocampus, striatum and cortex. In comparison to Phd2 ^flox/flox mice, PHD2 mRNA and protein was decreased by 75% and 90%, respectively in the forebrain of homozygous nPhd2^D/D mice. Hypoxia-inducible transcription factor-1a (HIF-1a) protein abundance and expression of HIF-1 target genes such as vascular endothelial growth factor (VEGF) and erythropoietin (Epo) was significantly increased in the forebrain of nPhd2^D/D mice under both hypoxic and ischemic conditions. Moreover, the infarct size of nPhd2^D/D mice was significantly reduced by more than 50% compared to Phd2 ^flox/flox mice. Accordingly, neuronal apoptosis was reduced in peri-infarct regions such as the hippocampal CA1 region.

Conclusion: 

Neuron-specific PHD2 inactivation improves the outcome from transient cerebral ischemia, and thus may represent a promising molecular target for new therapeutic approaches against cerebral ischemia.