The present study was designed to investigate the role of
matrix metalloproteinases (
MMPs) in the immature brain and the long term effects of early
MMPs inhibition after hypoxic-ischemic (HI) injury. HI was induced by unilateral
ligation of the right carotid artery followed by
hypoxia (8% O(2) for 2 h) in P7 rat pups.
GM6001, a broad spectrum
MMPs inhibitor, was injected (50 mg/kg or 100 mg/kg) intraperitoneally at 2 h and 24 h after HI injury. Blood-brain barrier (BBB) integrity,
brain edema,
MMP-2/-9 activity, TIMP-1/-2 and
tight junction protein (TJP) level were evaluated using
IgG staining,
Evan's blue extravasation, brain water content, zymography and western blot.
Doxycycline, another
MMPs inhibitor, was injected (10 mg/kg or 30 mg/kg) intraperitoneally at 2 h after HI, then BBB integrity and
brain edema were measured at 48 h post-HI using brain water content measurement and
IgG staining. The long-term effects of early
MMPs inhibition (
GM6001, 100 mg/kg) were evaluated by neurobehavioral tests,
body weight, and brain
atrophy measurement.
GM6001 attenuated
brain edema and BBB disruption at the dosage of 100 mg/kg. MMP-2 activity increased at 24 h and peaked at 48 h after HI, whereas MMP-9 activity peaked at 24 h and tapered by 48 h after HI.
MMP-9/-2 activities were significantly attenuated by
GM6001 at 24 h and 48 h after HI. The degradation of TJPs (ZO-1 and
occludin) at 48 h after HI was reversed by
GM6001 treatment. Early
MMPs inhibition had long-term effects that attenuated ipsilateral brain tissue loss, and improved neurobehavioral outcomes after HI. These results suggest that early
MMPs inhibition with a broad-spectrum inhibitor provides both acute and long-term neuroprotection in the developing brain by reducing TJPs degradation, preserving BBB integrity, and ameliorating
brain edema after neonatal HI injury.