Delayed administration of a matrix metalloproteinase inhibitor limits progressive brain injury after hypoxia-ischemia in the neonatal rat.
BACKGROUND
Hypoxia-ischemia (H-I) can produce widespread neurodegeneration and deep cerebral white matter injury in the neonate. Resident microglia and invading leukocytes promote lesion progression by releasing reactive oxygen species, proteases and other pro-inflammatory mediators. After injury, expression of the gelatin-degrading matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are thought to result in the proteolysis of extracellular matrix (ECM), activation of cytokines/chemokines, and the loss of vascular integrity. Thus, therapies targeting ECM degradation and progressive neuroinflammation may be beneficial in reducing H-I - induced neuropathy. Minocycline has MMP-inhibitory properties and is both anti-inflammatory and neuroprotective. AG3340 (prinomastat) is an MMP inhibitor with high selectivity for the gelatinases. The purpose of this study was to determine whether these compounds could limit H-I--induced injury when administered at a delayed time point.


METHODS
Sprague-Dawley rats were exposed to H-I at postnatal day 7 (P7), consisting of unilateral carotid artery ligation followed by 90 min exposure to 8% O2. Minocycline, AG3340, or vehicle were administered once daily for 6 days, beginning 24 hours after insult. Animals were sacrificed at P14 for neurohistological assessments. Immunohistochemistry was performed to determine the degree of reactive astrogliosis and immune cell activation/recruitment. Neural injury was detected using the Fluoro-Jade stain, a marker that identifies degenerating cells.


RESULTS
CD11b and glial fibrillary acidic protein (GFAP) immunopositive cells increased in ipsilateral cortex after treatment with vehicle alone, demonstrating microglia/macrophage recruitment and reactive astrogliosis, respectively. Fluoro-Jade staining was markedly increased throughout the fronto-parietal cortex, striatum and hippocampus. Treatment with minocycline or AG3340 inhibited microglia/macrophage recruitment, attenuated astrogliosis and reduced Fluoro-Jade staining when compared to vehicle alone.


CONCLUSIONS
The selective gelatinase inhibitor AG3340 showed equal efficacy in reducing neural injury and dampening neuroinflammation when compared to the anti-inflammatory compound minocycline. Thus, MMP-2 and MMP-9 may be viable therapeutic targets to treat neonatal brain injury.
Leonardo
Christopher C
CC
Department of Molecular Pharmacology and Physiology, School of Basic Biomedical Sciences, College of Medicine, University of South Florida, Tampa, FL 33612, USA. cleonard@health.usf.edu
Eakin
Autumn K
AK
Ajmo
Joanne M
JM
Collier
Lisa A
LA
Pennypacker
Keith R
KR
Strongin
Alex Y
AY
Gottschall
Paul E
PE
D000818:Animals; D000831:Animals, Newborn; D001930:Brain Injuries / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D020925:Hypoxia-Ischemia, Brain / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D061965:Matrix Metalloproteinase Inhibitors; D017628:Microglia / Q000166:cytology / Q000378:metabolism; D008911:Minocycline / Q000627:therapeutic use*; D018696:Neuroprotective Agents / Q000627:therapeutic use; D009930:Organic Chemicals / Q000627:therapeutic use*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D061965:Matrix Metalloproteinase Inhibitors; D018696:Neuroprotective Agents; D009930:Organic Chemicals; C113282:prinomastat; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D008911:Minocycline