Differential activation of c-fos and caspase-3 in hippocampal neuron subpopulations following neonatal hypoxia-ischemia.
Neonatal hypoxia-ischemia (HI) induces immediate early gene (IEG) c-fos expression as well as neuron death. The precise role of IEGs in neonatal HI is unclear. We investigated the temporal and spatial patterns of c-Fos expression in postnatal day 7 mice after unilateral carotid ligation and exposure to 8% oxygen. mRNA levels of c-fos quantitated by real-time polymerase chain reaction (PCR) increased nearly 40-fold (log 1.2 +/- 0.4) in the ipsilateral hippocampus 3 hr following neonatal HI, then returned to basal levels within 12 hr, although no change was observed in c-jun mRNA. Frozen coronal brain sections were stained with cresyl violet or used for immunohistochemical detection of c-Fos, cleaved caspase-3, glial fibrillary acidic protein (GFAP), and the mature neuron marker NeuN. c-Fos immunoreactivity increased throughout the injured hippocampus 3 hr after HI but became restricted to the CA2-3 subregion and the dentate gyrus (DG) at 6-12 hr and declined by 24 hr. In contrast, cleaved (activated) caspase-3 immunoreactivity was most abundant in the ipsilateral CA1 region at 3-6 hr after neonatal HI, then became more prominent in CA2-3 and DG. Double-labeling experiments showed c-Fos and cleaved caspase-3 immunoreactivity localized in spatially distinct neuron subpopulations. Prominent c-Fos immunoreactivity was observed in surviving CA2-3 and external granular DG neurons, and robust cleaved caspase-3 immunoreactivity was observed in pyknotic CA1, CA2-3, and subgranular DG neurons. The differential expression of c-Fos in HI-resistant hippocampal subpopulations vs. cleaved caspase-3 in dying neurons suggests a neuroprotective role for c-Fos expression in neonatal HI.
Ness
Jayne M
JM
Department of Pediatrics, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA. jness@peds.uab.edu
Harvey
Cary R
CR
Washington
Jason D
JD
Roth
Kevin A
KA
Carroll
Steven L
SL
Zhang
Jianhua
J
D000818:Animals; D000831:Animals, Newborn; D053148:Caspase 3 / Q000378:metabolism*; D016923:Cell Death; D019610:Cytoprotection / Q000502:physiology; D004268:DNA-Binding Proteins; D018891:Dentate Gyrus / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D051379:Mice; D009410:Nerve Degeneration / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D015854:Up-Regulation
D004268:DNA-Binding Proteins; D005904:Glial Fibrillary Acidic Protein; D009419:Nerve Tissue Proteins; C492380:NeuN protein, mouse; D009687:Nuclear Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D053148:Caspase 3