ИСТИНА

Dietary supplementation of flavonoids is known to extend lifespan and enhance resistance to stress. Flavonoids are believed to exert their beneficial effects by triggering endogenous genetic adap-tive programs to hypoxic or oxidative stress via estrogen receptor engagement or upstream kinase activation. To test if there are specific structural requirements for direct activation of the antihypoxic genetic program, we studied flavones and isoflavones using a luciferase-based reporter specific for the first step in HIF1 protein stabilization (HIF1-luc reporter) and the enzyme in vitro assay. Flavonoids inhibit the enzyme activity in the in vitro homogeneous assay in high micromolar range (>10 µM), and no distinct structure-activity relationship is observed, supposedly being masked by non-specific reduc-tion of enzyme transient forms by flavonoids. The cell-based reporter assay is more sensitive and demonstrates that some but not all flavonoids stabilize HIF already at 2 µM via direct inhibition of HIF prolyl hydroxylase (HIF PHD). Rating of flavonoids in the reporter assay does not correlate with their iron binding affinity or antioxidant properties, on the contrary, there are distinct structural requirements for the reporter activation which correlate with in silico binding to HIF PHD. The most potent direct stabilizer is 3’-hydroxydaidzein, the immediate product of daidzein oxidation. Rating of flavonoids in reporter assay corresponds to their neuroprotective potency in a neuronal glutathione depletion model, and thus, confirm the key role played by HIF PHD inhibitors in neuronal survival. This work was supported by Russian Foundation for Basic Research, grant 14-04-32309-мол_а.