Normobaric hyperoxia attenuates early blood-brain barrier disruption by inhibiting MMP-9-mediated occludin degradation in focal cerebral ischemia.
Early blood-brain barrier (BBB) disruption resulting from excessive neurovascular proteolysis by matrix metalloproteinases (MMPs) is closely associated with hemorrhagic transformation events in ischemic stroke. We have shown that normobaric hyperoxia (NBO) treatment reduces MMP-9 increase in the ischemic brain. The aim of this study was to determine whether NBO could attenuate MMP-9-mediated early BBB disruption following ischemic stroke. Rats were exposed to NBO (95% O(2)) or normoxia (30% O(2)) during 90-min middle cerebral artery occlusion, followed by 3-hour reperfusion. NBO-treated rats showed a significant reduction in Evan's blue extravasation in the ischemic hemisphere compared with normoxic rats. Topographically, Evan's blue leakage was mainly seen in the subcortical regions including the striatum, which was accompanied by increased gelatinolytic activity and reduced immunostaining for tight-junction protein, occludin. Increased gelatinolytic activities and occludin protein loss were also observed in isolated ischemic microvessels. Gel gelatin zymography identified that MMP-9 was the main enzymatic source in the cerebral microvessels. Incubation of brain slices or isolated microvessels with purified MMP-9 revealed specific degradation of occludin. Inhibition of MMP-9 by NBO or MMP-inhibitor, BB1101, significantly reduced occludin protein loss in ischemic microvessels. These results suggest that NBO attenuates early BBB disruption, and inhibition of MMP-9-mediated occludin degradation is an important mechanism for this protection.
Liu
Wenlan
W
College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA.
Hendren
Jill
J
Qin
Xu-Jun
XJ
Shen
Jiangang
J
Liu
Ke Jian
KJ
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects*; D015153:Blotting, Western; D002196:Capillaries / Q000187:drug effects / Q000502:physiology; D004396:Coloring Agents; D005070:Evans Blue; D005780:Gelatin / Q000378:metabolism; D007150:Immunohistochemistry; D020244:Infarction, Middle Cerebral Artery / Q000378:metabolism / Q000473:pathology; D002546:Ischemic Attack, Transient / Q000378:metabolism* / Q000473:pathology; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D008565:Membrane Proteins / Q000378:metabolism*; D062793:Occludin; D010102:Oxygen Inhalation Therapy; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism / Q000473:pathology; D019108:Tight Junctions / Q000187:drug effects
D004396:Coloring Agents; D061965:Matrix Metalloproteinase Inhibitors; D008565:Membrane Proteins; D062793:Occludin; C568987:Ocln protein, rat; D005070:Evans Blue; D005780:Gelatin; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9