title: Post-insult minocycline treatment attenuates hypoxia-ischemia-induced neuroinflammation and white matter injury in the neonatal rat: a comparison of two different dose regimens.
abstract: An increase in the number of activated microglia in the brain is a key feature of neuroinflammation after a hypoxic-ischemic insult to the preterm neonate and can contribute to white matter injury in the brain. Minocycline is a potent inhibitor of microglia and may have a role as a neuroprotective agent that ameliorates brain injury after hypoxia-ischemia in neonatal animal models. However to date large doses, pre-insult administration and short periods of treatment after hypoxia-ischemia have mostly been investigated in animal models making it difficult to translate minocycline's potential applicability to protect the human preterm neonatal brain exposed to hypoxia-ischemia. We investigated whether repeated doses of minocycline can minimize white matter injury and neuroinflammation one week after hypoxia-ischemia (right carotid artery ligation and 30 min 6% O(2)) in the post-natal day 3 rat pup. Two dosage regimens of minocycline were administered for one week; a high dose of 45 mg/kg 2h after hypoxia-ischemia then 22.5 mg/kg daily or a low dose 22.5 mg/kg 2h after hypoxia-ischemia then 10 mg/kg. Post-natal day 3 hypoxia-ischemia significantly reduced myelin content, numbers of O1- and O4-positive oligodendrocyte progenitor cells and increased activated microglia one week later on post-natal day 10. The low dose minocycline regimen was as effective as the high dose in ameliorating neuroinflammation after post-natal day 3 hypoxia-ischemia. However only the high dose regimen significantly attenuated reductions in O1- and O4-positive oligodendrocyte progenitor cells and myelin content. The low dose only significantly attenuated the reduction in O1-positive oligodendrocyte cell counts. Repeated, daily, post-insult treatment with minocycline abolished neuroinflammation and may provide neuroprotection to white matter for up to one week after hypoxia-ischemia in a rodent preterm model. The present findings suggest the potential clinical relevance of a repeated, daily minocycline treatment strategy, administered after a hypoxia-ischemia insult, as a therapeutic intervention for hypoxia-ischemia-affected preterm neonates.
authors.affiliation: Perinatal Research Centre, School of Medicine, University of Queensland, Herston, Queensland 4029, Australia.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Carty
authors.forename: Julie A
authors.initials: JA
authors.lastname: Wixey
authors.forename: Paul B
authors.initials: PB
authors.lastname: Colditz
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Buller
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D001930:Brain Injuries / Q000209:etiology / Q000517:prevention & control*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004660:Encephalitis / Q000209:etiology / Q000517:prevention & control*; D020925:Hypoxia-Ischemia, Brain / Q000150:complications*; D007274:Injections, Intraperitoneal; D017628:Microglia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008911:Minocycline / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D009186:Myelin Sheath / Q000378:metabolism; D009417:Nerve Tissue / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D018696:Neuroprotective Agents; D008911:Minocycline