Currently there are more than 2 million citizens in this country who are disabled by stroke. Stroke caused by cerebral ischemia is the third leading cause of death and the leading cause of neurological disability. The annual direct and indirect loss from stroke is estimated to be $25 billion. Partial recovery of function is frequently noted in stroke patients. The molecular mechanism of functional recovery, however, is poorly understood. In a well developed stroke model of the rodents, cerebral ischemia causes an increase in superoxide and hydrogen peroxide, which are converted to hydroxyl radicals. Hydroxyl radical, a known mutagen, induces DNA repair synthesis and the expression of repair enzyme DNA polymerase-beta in cell culture. Therefore, hydroxyl radical could cause activation of a genetic program leading to delayed neuronal death (apoptosis). To reduce apoptosis in the brain is central to functional recovery after stroke. The hypothesis is that apoptosis is mediated via DNA damage by the elevated oxygen free radicals during and after cerebral ischemia. Preliminary studies from our laboratory using th stroke model of focal cerebral ischemia of 30 min demonstrated a disappearance of S1 nuclease sensitive sites and an increase in the expression of DNA polymerase-beta mRNA within 2 hr after ischemia, a 6-fold elevation in gene mutation frequency within 8 hr in the lacl gene of Big Blue transgenic mice, and an appearance of DNA fragmentation, a characteristics of apoptosis, 3 days after ischemia. It is known from studies by others and ours that gene mutations are results from errors introduced during DNA repair synthesis. Mutations could lead to apoptosis in the nervous system as a results of ischemia. The goal of this proposal is to determine the contribution of hydroxy radicals to cerebral gene mutation and apoptosis after cerebral ischemia. In this proposal, we will: (1) analyze the sequence change in the DNA of 150 lacl mutants from ischemia and 30 lacl mutants from normal brain samples; (2) determine DNA repair in the transcribed strand of neurotrophin, DNA polymerase-beta, p53 and actin genes; (3) measure the increase in 8-hydroxyldeoxyguanosine (oh8dG) in DNA from cortical cells after ischemia; (4) determine if there is a positive correlation between the formation of hydroxyl radicals and the increase in the physiological parameter of mutation frequency, DNA repair, oh8dG and apoptosis using intravenous infusion of superoxide dismutase plus catalase before ischemia. The mutation spectrum that is obtained from this project will be a direct indicator of DNA damage by hydroxyl radicals after cerebral ischemia. This model will be suitable for exploring pathobiological effect of oxygen stress, and for testing drugs that reduce or abolish the damaging effect of hydroxyl radical after stroke.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
3R01NS034810-04S1
Application #
6054350
Study Section
Special Emphasis Panel (ZRG1 (01))
Program Officer
Jacobs, Tom P
Project Start
1996-03-01
Project End
2001-02-28
Budget Start
1999-03-01
Budget End
2001-02-28
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Baylor College of Medicine
Department
Neurology
Type
Schools of Medicine
DUNS #
074615394
City
Houston
State
TX
Country
United States
Zip Code
77030
Mendez, Donna R; Cherian, Leela; Moore, Niki et al. (2004) Oxidative DNA lesions in a rodent model of traumatic brain injury. J Trauma 56:1235-40
Liu, Philip K (2003) Ischemia-reperfusion-related repair deficit after oxidative stress: implications of faulty transcripts in neuronal sensitivity after brain injury. J Biomed Sci 10:4-13
Liu, Philip K; Robertson, Claudia S; Valadka, Alex (2002) The association between neuronal nitric oxide synthase and neuronal sensitivity in the brain after brain injury. Ann N Y Acad Sci 962:226-41
Moore, N; Okocha, F; Cui, J K et al. (2002) Homogeneous repair of nuclear genes after experimental stroke. J Neurochem 80:111-8
Liu, Philip K; Arora, Tarun (2002) Transcripts of damaged genes in the brain during cerebral oxidative stress. J Neurosci Res 70:713-20
Liu, Philip K; Cui, Jiankun; Moore, Niki et al. (2002) The in situ detection of apurinic/apyrimidinic sites and DNA breaks bearing extension blocking termini. Methods Mol Biol 203:235-44
Liu, P K (2001) DNA damage and repair in the brain after cerebral ischemia. Curr Top Med Chem 1:483-95
Cui, J; Liu, P K (2001) Neuronal NOS inhibitor that reduces oxidative DNA lesions and neuronal sensitivity increases the expression of intact c-fos transcripts after brain injury. J Biomed Sci 8:336-41
Liu, P K; Grossman, R G; Hsu, C Y et al. (2001) Ischemic injury and faulty gene transcripts in the brain. Trends Neurosci 24:581-8
Lin, L H; Cao, S; Yu, L et al. (2000) Up-regulation of base excision repair activity for 8-hydroxy-2'-deoxyguanosine in the mouse brain after forebrain ischemia-reperfusion. J Neurochem 74:1098-105

Showing the most recent 10 out of 18 publications