Loss or Silencing of the PHD1 Prolyl Hydroxylase Protects Livers of Mice Against Ischemia/Reperfusion Injury

Background & Aims

Liver ischemia/reperfusion (I/R) injury is a frequent cause of organ dysfunction. Loss of the oxygen sensor prolyl hydroxylase domain enzyme 1 (PHD1) causes tolerance of skeletal muscle to hypoxia. We assessed whether loss or short-term silencing of PHD1 could likewise induce hypoxia tolerance in hepatocytes and protect them against hepatic I/R damage.

Methods

Hepatic ischemia was induced in mice by clamping of the portal vessels of the left lateral liver lobe; 90 minutes later livers were reperfused for 8 hours for I/R experiments. Hepatocyte damage following ischemia or I/R was investigated in PHD1-deficient (PHD1^−/−) and wild-type mice or following short hairpin RNA-mediated short-term inhibition of PHD1 in vivo.

Results

PHD1^−/− livers were largely protected against acute ischemia or I/R injury. Among mice subjected to hepatic I/R followed by surgical resection of all nonischemic liver lobes, more than half of wild-type mice succumbed, whereas all PHD1^−/− mice survived. Also, short-term inhibition of PHD1 through RNA interference−mediated silencing provided protection against I/R. Knockdown of PHD1 also induced hypoxia tolerance of hepatocytes in vitro. Mechanistically, loss of PHD1 decreased production of oxidative stress, which likely relates to a decrease in oxygen consumption as a result of a reprogramming of hepatocellular metabolism.

Conclusions

Loss of PHD1 provided tolerance of hepatocytes to acute hypoxia and protected them against I/R-damage. Short-term inhibition of PHD1 is a novel therapeutic approach to reducing or preventing I/R-induced liver injury.

Keywords: PHD1, Prolyl Hydroxylase, Ischemia/Reperfusion

Abbreviations used in this paper: ALT, alanine aminotransferase, HIF, hypoxia inducible factor, I/R, ischemia/reperfusion, 8-OHdG, 8-hydroxy-2′-deoxyguanosine, PDC, pyruvate dehydrogenase enzyme complex, PDK, pyruvate dehydrogenase kinase, PHD, prolyl hydroxylase domain, ROS, reactive oxygen species, WT, wild-type