Abstract
Purpose :
Hypoxiamimesis via stabilization of hepatic hypoxia inducible factor (HIF) protects against oxygen-induced retinopathy (OIR), brain hypomyelination, and bronchopulmonary dysplasia in mice. N-oxoglutarate (NOG) inhibits HIF prolyl hydroxylase (PHD), stimulating stabilization of the HIF-1a subunit, but is too polar to cross cell membranes. We hypothesized that PHD inhibition by small molecules containing NOG with modifications leading to enhanced drug levels in the liver would stabilize and activate hepatic HIF even in hyperoxic conditions.
Methods :
A library of 25 novel carbonyl glycine small molecules was synthesized by chemical modification of NOG with various R-groups to encourage accumulation of NOG in the liver. HIF stabilization and activity in vitro were assessed by immunoblot of Hep3B cells and luciferase activity in NIH3T3/HIF-luc cells treated with 1mM of each drug after 1, 3, 6, and 24 hrs. In vivo tissue distribution of PHD inhibition and HIF stabilization was determined by luciferase assay and immunoblot, respectively, of brain, liver, kidney, and retina from P8 luc-ODD mice 24 hrs after intraperitoneal (IP) drug injection (1 mmol/g). Protection against OIR at P17 was quantified by comparing vasoobliteration (VO) and neovascularization (NV) in retinas of C57BL/6J mice treated with 3 IP injections of either drug or vehicle at P6, 8, and 10.
Results :
Eleven compounds demonstrated >1.5-fold increase in luciferase activity after 24 hrs in vitro. Six induced >2-fold increase in HIF protein in cultured hepatocytes 3 hrs after treatment. Compound 209 sustained >2-fold increase in endogenous HIF over 24 hrs. When tested in the OIR model, 3 compounds decreased VO and NV in the retina, with Compound 209 demonstrating the greatest effect (65% VO reduction, p=0.004; 88% NV reduction, p=0.01). In luc-ODD reporter mice, Compound 209 showed a hepatotropic pattern of HIF PHD inhibition suggesting enhanced drug levels in the liver.
Conclusions :
A select group of small molecules formed by modification of NOG leads to PHD inhibition specifically in the liver when administered systemically. Stabilization of hepatic HIF during hyperoxia by brief treatment with these drugs confers protection against OIR, presenting a potential therapeutic strategy for the prevention of retinopathy of prematurity and other oxygen-induced organ toxicities.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.