Infarct size-limiting effect of epoxyeicosatrienoic acid analog EET-B is mediated by hypoxia-inducible factor-1 alpha via downregulation of prolyl hydroxylase 3
Abstract
Epoxyeicosatrienoic acids (EETs) decrease cardiac ischemia-reperfusion injury: however, the mechanism of their protective effect remains elusive. Here, we investigated the cardioprotective action of a novel EET analog, EET-B, in reperfusion and the role of hypoxia-inducible factor (HIF)-1 alpha in such action of EET-B.
Adult male rats were subjected to 30 min of left coronary artery occlusion followed by 2 h of reperfusion. Administration of 14,15-EET (2.5 mg/kg) or EET-B (2.5 mg/kg) 5 min before reperfusion reduced infarct size expressed as a percent-age of the area at risk from 64.3 +/- 1.3% in control to 42.6 +/- 1.9% and 46.0 +/- 11.6%, respectively, and their coadministration did not provide any stronger effect.
The 14,15-EET antagonist 14,15-epoxyeicosa-5(Z)-enoic acid (2.5 mg/kg) inhibited the infarct size-limiting effect of EET-B (62.5 +/- 1.1%). Similarly, the HIF-1 alpha inhibitors 2-methoxyestradiol (2.5 mg/kg) and acriflavine (2 mg/kg) completely abolished the cardioprotective effect of EET-B.
In a separate set of experiments, the immunoreactivity of HIE-1 alpha and its degrading enzyme prolyl hydroxylase domain protein 3 (PHD3) were analyzed in the ischemic areas and non ischemic septa. At the end of ischemia, the HIF-1 alpha immunogenic signal markedly increased in the ischemic area compared with the septum (10.31 +/- 0.78% vs. 0.34 +/- 0.08%).
After 20 min and 2 h of reperfusion, HIF-1 alpha immunoreactivity decreased to 2.40 +/- 0.48% and 1.85 +/- 0.43%, respectively, in the controls. EET-B blunted the decrease of HIF-1 alpha immunoreactivity (7.80 +/- 0.69% and 6.44 +/- 1.37%, respectively) and significantly reduced PHD3 inununogenic signal in ischemic tissue after reperfusion.
In conclusion, EET-B provides an infarct size-limiting effect at reperfusion that is mediated by HIF-1 alpha and downregulation of its degrading enzyme PHD3. NEW & NOTEWORTHY The present study shows that EET-B is an effective agonistic 14,15-epoxyeicosatrienoic acid analog, and its administration before reperfusion markedly reduced myocardial infarction in rats.
Most importantly, we demonstrate that increased hypoxia-inducible factor-1 alpha levels play a role in cardioprotection mediated by EET-B in reperfusion likely by mechanisms including downregulation of the hypoxia-inducible factor-1 alpha-degrading enzyme prolyl hydroxylase domain protein 3.