DNA damage and repair system in spinal cord ischemia.
OBJECTIVE
Spinal cord ischemia-reperfusion injury may be initiated by a number of mediators, including reactive oxygen species. Recent studies have shown that human MutY homologue (hMYH), human 8-oxo-7,8-dihydrodeoxyguanine (8-oxoG) glycosylase (hOGG1), and human MutS homologue 2 (hMSH2) are important DNA mismatch repair genes. We hypothesized that ischemia-reperfusion injury in spinal cord causes DNA damage manifested by 8-oxoG production and activates the DNA repair system involving hMYH, hOGG1, and hMSH2.


METHODS
Spinal cords of rabbits were removed at 1, 3, 6, 24, and 48 hours after 30 minutes of infrarenal aortic occlusion. DNA damage was determined with 8-oxoG staining. The expression and localization of DNA repair enzymes, such as hMYH, hOGG1, and hMSH2, were studied with Western blot analysis and immunohistochemical staining. The level of apoptosis was determined with TUNEL study. Activation of caspase-3, an enzyme induced by cellular injury that leads to apoptosis by degrading cellular structural proteins, was also studied.


RESULTS
DNA damage monitored with 8-oxoG level was significantly present from 1 hour to 6 hours after reperfusion in gray matter neurons of ischemic spinal cord. The levels of hMYH, hOGG1, and hMSH2 were markedly increased in gray matter neurons at 6 hours after reperfusion. Caspase-3 was also induced at 6 hours to 24 hours after reperfusion in ischemic spinal cord. However, the peak level of TUNEL reactivity was found at 48 hours after reperfusion in spinal cord neurons.


CONCLUSIONS
This study has shown, for the first time, the rapid expression of DNA damage-repair processes associated with spinal cord ischemia and subsequent reperfusion.
Lin
Ruxian
R
Cardiothoracic-Renal Research Program, Department of Surgery, University of Maryland School of Medicine, Baltimore, USA.
Roseborough
Glen
G
Dong
Yafeng
Y
Williams
G Melville
GM
Wei
Chiming
C
D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis; D004249:DNA Damage / Q000502:physiology*; D045647:DNA Glycosylases; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins; D043382:DNA-Formamidopyrimidine Glycosylase; D006151:Guanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D051718:MutS Homolog 2 Protein; D009699:N-Glycosyl Hydrolases / Q000096:biosynthesis; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D011817:Rabbits; D015427:Reperfusion Injury / Q000503:physiopathology*; D020760:Spinal Cord Ischemia / Q000503:physiopathology*; D013997:Time Factors
D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; D006151:Guanosine; C046215:8-hydroxyguanosine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase; D043382:DNA-Formamidopyrimidine Glycosylase; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D051718:MutS Homolog 2 Protein