Increased expression of cyclin G1 and p21WAF1/CIP1 in neurons following transient forebrain ischemia: comparison with early DNA damage.
Oxidative stress affecting DNA integrity may be an important mediator of cell death induced by cerebral ischemia followed by reperfusion. Genes involved in the DNA repair processes may play an important role in cell viability. We studied the spatial expression of the DNA damage inducible gene p53 and its transcriptional targets p21WAF1/CIP1, cyclin G1, and Bax and compared their expression with markers of early DNA damage following 10 min of transient forebrain ischemia in rats. Cyclin G1 and p21WAF1/CIP1 mRNA levels increased significantly between 2.5 and 4-fold in neurons of the hippocampus, cortex, and striatum during the first 24 hr after reperfusion and decreased at 48 hr of reperfusion. Significant increases in the protein levels of Cyclin G1 and p21 WAF1/CIP1 were only seen in the striatum at 48 hr of reperfusion. The mRNA levels of the p21 family members p27KIP1 or p57KIP2 demonstrated no significant changes. p53, baxalpha, and bcl-xl mRNA levels increased in all areas of the hippocampus by 12 to 24 hr and decreased over the next 2 days of reperfusion. baxalpha mRNA was specifically induced in neurons of the outer cortical layers at 12 and 24 hr after reperfusion, and protein levels increased in the striatum at 48 hr. No changes in protein levels of p53, Bcl-xl, or Bcl-2 were detected in the cerebral cortex, hippocampus, or striatum at any time point following reperfusion. Single-stranded DNA breaks detected with DNA polymerase I-mediated in situ nick translation partly overlapped with nuclear cyclin G1 protein in the striatum, cortex, and hippocampus at 24 hr, however at 48 hr cyclin G1 remained elevated only in neurons bordering areas exhibiting DNA damage. Nuclear p53 protein, p21 mRNA, and baxalpha mRNA were absent in cells stained with the in situ nick translation method but p21 mRNA and baxalpha mRNA were increased in neurons adjacent to those with detectable DNA nick ends at 24 and 48 hr following reperfusion. The enhanced expression of cyclin G1, p21WAF1/CIP1, and baxalpha in neurons surviving transient forebrain ischemia may indicate their participation in an adaptive response to cerebral ischemia and reperfusion.
Hoffmann-La Roche Ltd., Basel, Switzerland.
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M
van Lookeren Campagne
R
R
Gill
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D001794:Blood Pressure; D002540:Cerebral Cortex / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D003342:Corpus Striatum / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D056746:Cyclin G; D056766:Cyclin G1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis / Q000235:genetics*; D004249:DNA Damage / Q000502:physiology*; D018891:Dentate Gyrus / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000032:analysis / Q000378:metabolism*; D005609:Free Radicals / Q000378:metabolism; D005786:Gene Expression Regulation / Q000502:physiology; D002546:Ischemic Attack, Transient / Q000378:metabolism*; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D009474:Neurons / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D016548:Prosencephalon / Q000098:blood supply / Q000166:cytology / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000032:analysis / Q000235:genetics; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; C534704:Ccng1 protein, rat; C493958:Cdkn1a protein, rat; D056746:Cyclin G; D056766:Cyclin G1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D005609:Free Radicals; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein