Acute iron overload aggravates blood-brain barrier disruption and hemorrhagic transformation after transient focal ischemia in rats with hyperglycemia

Abstract

Hemorrhagic transformation (HT) has been reported to be associated with a poor prognosis after acute ischemic stroke. Blood-brain barrier (BBB) damage is considered as the major pathophysiologic mechanism of HT. Our aim was to investigate the role of acute iron overload in BBB damage and HT after transient focal ischemia in rats with hyperglycemia. Transient middle cerebral artery occlusion (MCAO) was induced in rats with hyperglycemia. Animals were assigned to four groups: Sham, Vehicle, Iron overload and Iron chelator treatment groups. Brain samples were collected at 24 h after surgery to quantify the amount of hemorrhage, determine extravasation of Evans blue and detect the levels of following proteins: ferritin, matrix metalloproteinase-9 (MMP-9), zonula occludens-1 (ZO-1), Occludin and Claudin-5 by western blot analysis and immunohistochemistry. Compared to the Vehicle group, the Iron overload group had a significantly higher amount of hemorrhage and more extravasation of Evans blue. The Iron overload group had lower levels of ZO-1, Occludin and Claudin-5 and higher levels of ferritin and MMP-9 than the Vehicle group. Administering iron chelator reduced the extension of hemorrhage and extravasation of Evans blue, reversed the MCAO-induced reduction of ZO-1, Occludin and Claudin-5 and decreased the levels of ferritin and MMP-9. Our results suggest that acute iron overload aggravates BBB damage and HT after transient ischemia in rats with hyperglycemia, which provides basic evidence for iron overload as a potential factor associated with BBB damage and HT in ischemic stroke patients when accompanied with hyperglycemia.

Keywords

• Iron overload
• Blood-brain barrier
• Hemorrhagic transformation
• Iron chelator
• Ferritin
• Metalloproteinase-9