Suppression of hypoxia‐inducible factor‐1α and its downstream genes reduces acute hyperglycemia‐enhanced hemorrhagic transformation in a rat model of cerebral ischemia

We evaluated a role of hypoxia‐inducible factor‐1α (HIF‐1α) and its downstream genes in acute hyperglycemia‐induced hemorrhagic transformation in a rat model of focal cerebral ischemia. Male Sprague‐Dawley rats weighing 280–300 g (n = 105) were divided into sham, 90 min middle cerebral artery occlusion (MCAO), MCAO plus HIF‐1α inhibitors, 2‐methoxyestradiol (2ME2) or 3‐(5′‐hydroxymethyl‐2′‐furyl)‐1‐benzylindazole (YC‐1), groups. Rats received an injection of 50% dextrose (6 ml/kg intraperitoneally) at 15 min before MCAO. HIF‐1α inhibitors were administered at the onset of reperfusion. The animals were examined for neurological deficits and sacrificed at 6, 12, 24, and 72 hr following MCAO. The cerebral tissues were collected for histology, zymography, and Western blot analysis. The expression of HIF‐1α was increased in ischemic brain tissues after MCAO and reduced by HIF‐1α inhibitors. In addition, 2ME2 reduced the expression of vascular endothelial growth factor (VEGF) and the elevation of active matrix metalloproteinase‐2 and ?9 (MMP‐2/MMP‐9) in the ipsilateral hemisphere. Both 2ME2 and YC‐1 reduced infarct volume and ameliorated neurological deficits. However, only 2ME2 attenuated hemorrhagic transformation in the ischemic territory. In conclusion, the inhibition of HIF‐1α and its downstream genes attenuates hemorrhagic conversion of cerebral infarction and ameliorates neurological deficits after focal cerebral ischemia. © 2010 Wiley‐Liss, Inc.