Prolyl Hydroxylase Domain Protein Inhibitor Not Harboring a 2-Oxoglutarate Scaffold Protects against Hypoxic Stress

Hypoxia-inducible factor-alpha (HIF-alpha) activation has shown promising results in the treatment of ischemia, such as stroke, myocardial infarction, and chronic kidney disease. A number of HIF-alpha activators have been developed to improve the symptoms of these diseases. Many feature 2-oxoglutarate (2-OG) scaffolds that interact with the active centers of prolyl hydroxylase domain-containing proteins (PHDs), displacing the coenzyme 2-OG. This stabilizes HIF-alpha. Therefore, the specificity of the 2-OG analogs is not high. Here, we identified 5-(1-acetyl-5-phenylpyrazolidin-3-ylidene)-1,3-dimethylbarbituric acid (PyrzA) among over 10 000 compounds as a novel HIF activator that does not contain a 2-OG scaffold. In cultured cells, PyrzA enhanced HIF-alpha stability and upregulated the expression of HIF target genes. Interestingly, PyrzA decreased HIF-1 alpha prolyl hydroxylation, suggesting that PyrzA may activate HIF to prevent the degradation of HIF-alpha. These results indicate that PyrzA stabilizes HIF via a novel mechanism and could be a potential HIF activator candidate.