Hyperoxia causes maturation-dependent cell death in the developing white matter.
Periventricular leukomalacia is the predominant injury in the preterm infant leading to cerebral palsy. Oxygen exposure may be an additional cause of brain injury in these infants. In this study, we investigated pathways of maturation-dependent oligodendrocyte (OL) death induced by hyperoxia in vitro and in vivo. Developing and mature OLs were subjected to 80% oxygen (0-24 h). Lactate dehydrogenase (LDH) assay was used to assess cell viability. Furthermore, 3-, 6-, and 10-d-old rat pups were subjected to 80% oxygen (24 h), and their brains were processed for myelin basic protein staining. Significant cell death was detected after 6-24 h incubation in 80% oxygen in pre-OLs (O4+,O1-), but not in mature OLs (MBP+). Cell death was executed by a caspase-dependent apoptotic pathway and could be blocked by the pan-caspase inhibitor zVAD-fmk. Overexpression of BCL2 (Homo sapiens B-cell chronic lymphocytic leukemia/lymphoma 2) significantly reduced apoptosis. Accumulation of superoxide and generation of reactive oxygen species (ROS) were detected after 2 h of oxygen exposure. Lipoxygenase inhibitors 2,3,5-trimethyl-6-(12-hydroxy-5-10-dodecadiynyl-1,4-benzoquinone and N-benzyl-N-hydroxy-5-phenylpentamide fully protected the cells from oxidative injury. Overexpression of superoxide dismutase (SOD1) dramatically increased injury to pre-OLs but not to mature OLs. We extended these studies by testing the effects of hyperoxia on neonatal white matter. Postnatal day 3 (P3) and P6 rats, but not P10 pups, showed bilateral reduction in MBP (myelin basic protein) expression with 24 h exposure to 80% oxygen. Hyperoxia causes oxidative stress and triggers maturation-dependent apoptosis in pre-OLs, which involves the generation of ROS and caspase activation, and leads to white matter injury in the neonatal rat brain. These observations may be relevant to white matter injury observed in premature infants.
Gerstner
Bettina
B
Department of Neurology and the F. M. Kirby Neurobiology Center, Children's Hospital Boston, Boston, Massachusetts 02115, USA.
DeSilva
Tara M
TM
Genz
Kerstin
K
Armstrong
Amy
A
Brehmer
Felix
F
Neve
Rachael L
RL
Felderhoff-Mueser
Ursula
U
Volpe
Joseph J
JJ
Rosenberg
Paul A
PA
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018496:Hyperoxia / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000502:physiology; D009836:Oligodendroglia / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar
D010100:Oxygen