Oxidative damage to the c-fos gene and reduction of its transcription after focal cerebral ischemia.
We investigated oxidative damage to the c-fos gene and to its transcription in the brain of Long-Evans rats using a transient focal cerebral ischemia and reperfusion (FCIR) model. We observed a significant (p < 0.001) increase in the immunoreactivity to 8-hydroxy-2'-guanine (oh8G) and its deoxy form (oh8dG) in the ischemic cortex at 0-30 min of reperfusion in all 27 animals treated with 15-90 min of ischemia. Treatment with a neuronal nitric oxide synthase (nNOS) inhibitor, 3-bromo-7-nitroindazole (60 mg/kg, i.p.), abolished the majority but not all of the oh8G/oh8dG immunoreactivity. Treatment with RNase A reduced the oh8G immunoreactivity, suggesting that RNA may be targeted. This observation was further supported by decreased levels of mRNA transcripts of the c-fos and actin genes in the ischemic core within 30 min of reperfusion using in situ hybridization. The reduction in mRNA transcription occurred at a time when nuclear gene damage, detected as sensitive sites to Escherichia coli Fpg protein in the transcribed strand of the c-fos gene, was increased 13-fold (p < 0.01). Our results suggest that inhibiting nNOS partially attenuates FCIR-induced oxidative damage and that nNOS or other mechanisms induce nuclear gene damage that interferes with gene transcription in the brain.
Cui
J
J
Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030, USA.
Holmes
E H
EH
Liu
P K
PK
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D004260:DNA Repair; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005786:Gene Expression Regulation; D016762:Genes, fos; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D002546:Ischemic Attack, Transient / Q000235:genetics* / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D020318:Rats, Long-Evans; D015427:Reperfusion Injury / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine