title: Apoptosis-suppressor gene bcl-2 expression after traumatic brain injury in rats.
abstract: Neuronal death after experimental traumatic brain injury (TBI) has features of both apoptosis and necrosis. Neurons in the peritrauma cortex, hippocampus, and dentate gyrus are particularly vulnerable. The apoptosis-suppressor gene bcl-2 is induced in brain after ischemia and epilepsy-induced injury and may serve to regulate neuronal death. We studied expression of bcl-2 mRNA and protein after experimental TBI in rats. To determine whether bcl-2 protein expression occurred in cells with evidence of apoptosis, triple-labeling studies were performed using (1) antibody against bcl-2, (2) bis-benzimide dye to examine gross nuclear morphology, and (3) terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling (TUNEL) to assess for DNA fragmentation. At 6 and 24 hr, bcl-2 mRNA was induced in ipsilateral peritrauma cortex, hippocampus, and dentate gyrus. By 72 hr the increase in bcl-2 mRNA was detected only in cortex. bcl-2 protein was induced at 8, 24, 72, and 168 hr in ipsilateral cortex and hippocampus. Cells expressing bcl-2 protein included neurons in the peritrauma cortex, hippocampus, hilus, and dentate gyrus. The gross nuclear morphology of neurons expressing bcl-2 appeared normal. Furthermore, biochemical evidence of DNA fragmentation, in a pattern characteristic of either apoptosis or necrosis, was seldom seen in neurons expressing bcl-2 protein (bcl-2 colocalized with TUNEL in 0-2% of TUNEL-positive cells observed). These data suggest that bcl-2 may play an important role in the regulation of neuronal death after TBI, and they support a role for bcl-2 as an inducible neuroprotective gene.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, and the Safar Center for Resuscitation Research and the Brain Trauma Research Center, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Clark
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: S C
authors.initials: SC
authors.lastname: Watkins
authors.forename: P M
authors.initials: PM
authors.lastname: Kochanek
authors.forename: M
authors.initials: M
authors.lastname: Chen
authors.forename: R A
authors.initials: RA
authors.lastname: Stetler
authors.forename: J E
authors.initials: JE
authors.lastname: Loeffert
authors.forename: S H
authors.initials: SH
authors.lastname: Graham
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics*; D001930:Brain Injuries / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology; D053938:DNA Fragmentation; D018891:Dentate Gyrus / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D019254:Genes, bcl-2; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D008297:Male; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D015388:Organelles / Q000648:ultrastructure; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D009419:Nerve Tissue Proteins; D019253:Proto-Oncogene Proteins c-bcl-2