Post-insult minocycline treatment attenuates hypoxia-ischemia-induced neuroinflammation and white matter injury in the neonatal rat: a comparison of two different dose regimens

Int J Dev Neurosci. 2008 Aug;26(5):477-85. doi: 10.1016/j.ijdevneu.2008.02.005. Epub 2008 Mar 4.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / pharmacology
  • Anti-Bacterial Agents / therapeutic use
  • Brain Injuries / etiology
  • Brain Injuries / prevention & control*
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Encephalitis / etiology
  • Encephalitis / prevention & control*
  • Hypoxia-Ischemia, Brain / complications*
  • Injections, Intraperitoneal
  • Microglia / drug effects
  • Microglia / metabolism
  • Microglia / pathology
  • Minocycline / administration & dosage
  • Minocycline / pharmacology
  • Minocycline / therapeutic use*
  • Myelin Sheath / metabolism
  • Nerve Tissue / drug effects
  • Nerve Tissue / metabolism
  • Nerve Tissue / pathology
  • Neuroprotective Agents / administration & dosage
  • Neuroprotective Agents / pharmacology
  • Neuroprotective Agents / therapeutic use
  • Oligodendroglia / drug effects
  • Oligodendroglia / metabolism
  • Oligodendroglia / pathology
  • Rats
  • Rats, Sprague-Dawley
  • Stem Cells / drug effects
  • Stem Cells / metabolism
  • Stem Cells / pathology
  • Time Factors

Substances

  • Anti-Bacterial Agents
  • Neuroprotective Agents
  • Minocycline