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Updated: Jul 1, 2026
Quantification of Neurovascular Protection Following Repetitive Hypoxic Preconditioning and Transient Middle Cerebral Artery Occlusion in Mice
Published on: May 4, 2015
Normobaric hyperoxia inhibits NADPH oxidase-mediated matrix metalloproteinase-9 induction in cerebral microvessels in
Wenlan Liu1, Rohit Sood, Qingchuan Chen
1College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, USA.
Abstract:
Matrix metalloproteinase-9 (MMP-9) and NADPH oxidase contribute to blood-brain barrier (BBB) disruption after ischemic stroke. We have previously shown that normobaric hyperoxia (NBO) treatment reduces MMP-9 and oxygen free radical generation in ischemic brain. In this study, we tested the hypothesis that NBO protects the BBB through inhibiting NADPH oxidase-mediated MMP-9 induction in transient focal cerebral ischemia. Male Sprague-Dawley rats (n = 69) were given NBO (95% O2) or normoxia (21% O2) during 90-min filament occlusion of the middle cerebral artery. Cerebral microvessels were isolated for analyzing MMP-9 and NADPH oxidase. BBB damage was non-invasively quantified with magnetic resonance imaging. In normoxic rats, both NADPH oxidase catalytic subunit gp91(phox) and MMP-9 expression were up-regulated in ischemic hemispheric microvessels after 90-min middle cerebral artery occlusion with 22.5 h reperfusion. Inhibition of NADPH oxidase with apocynin reduced the MMP-9 increase, indicating a causal link between NADPH oxidase-derived superoxide and MMP-9 induction. NBO treatment inhibited gp91(phox) expression, NADPH oxidase activity, and MMP-9 induction, which led to significantly less BBB damage and brain edema in the ischemic brain. These results suggest that gp91(phox) containing NADPH oxidase plays an important role in MMP-9 induction in ischemic BBB microvasculature, and that NBO treatment may attenuate MMP-9 induction and brain edema through inhibiting NADPH oxidase after transient cerebral ischemia.
Insights
Normobaric hyperoxia (NBO) reduces blood-brain barrier (BBB) damage after stroke by inhibiting NADPH oxidase and matrix metalloproteinase-9 (MMP-9) induction. This treatment lessens brain edema and protects the BBB in ischemic stroke models.
Area of Science:
- Neuroscience
- Biochemistry
- Cardiovascular Science
Background:
- Matrix metalloproteinase-9 (MMP-9) and NADPH oxidase are implicated in blood-brain barrier (BBB) disruption following ischemic stroke.
- Previous research indicates normobaric hyperoxia (NBO) can decrease MMP-9 and free radical generation in the ischemic brain.
Purpose of the Study:
- To investigate if NBO protects the BBB by inhibiting NADPH oxidase-mediated MMP-9 induction during transient focal cerebral ischemia.
- To establish a causal link between NADPH oxidase activity and MMP-9 upregulation in ischemic conditions.
Main Methods:
- Male Sprague-Dawley rats underwent 90-minute middle cerebral artery occlusion followed by reperfusion, receiving either NBO (95% O2) or normoxia (21% O2).
- Cerebral microvessels were isolated to measure MMP-9 and NADPH oxidase (gp91(phox)) expression and activity.
- Blood-brain barrier damage and brain edema were quantified using magnetic resonance imaging.
Main Results:
- In normoxic conditions, both NADPH oxidase (gp91(phox)) and MMP-9 were upregulated in ischemic microvessels post-stroke.
- Inhibition of NADPH oxidase with apocynin reduced MMP-9 levels, confirming a causal relationship.
- NBO treatment significantly inhibited gp91(phox) expression, NADPH oxidase activity, and MMP-9 induction, leading to reduced BBB damage and brain edema.
Conclusions:
- NADPH oxidase, specifically the gp91(phox) subunit, plays a critical role in inducing MMP-9 within the ischemic BBB microvasculature.
- Normobaric hyperoxia offers neuroprotection by inhibiting NADPH oxidase, thereby attenuating MMP-9 induction and subsequent BBB damage and brain edema in ischemic stroke.
