Background and Purpose
Oxidative stress contributes to post-ischemic brain damage. There is a time lag between the oxidative brain damage and the neuronal cell death and the part of the oxidative damaged cells have been considered to be salvageable. If we can predict the oxidative brain damage using plasma biomarkers, it would be useful to detect patients with the salvageable cells. Previously, we first demonstrated that plasma oxidized low-density lipoprotein (OxLDL) increased in the patients with acute cerebral infarction. However, whether plasma biomarker reflects the cerebral oxidative damage remains unclear. In this study, we assessed the correlation between plasma 8-hydroxy-2′-deoxyguanosine (8-OHdG), as a marker of oxidative DNA damage and progressive brain damage in rats subjected to transient and permanent ischemia. Furthermore, we monitored the change of the plasma 8-OHdG and OxLDL in patients with hypothermia.
Methods
Male wistar rats were subjected to permanent-, 0. 5-, 1-, 2-h MCAO. At various times thereafter, the infarct volume, 8-OHdG levels in plasma and brain tissue, DNA fragmentation, and immunohistochemical observations on their brains were recorded and compared. Plasma OxLDL levels were determined by ELISA using DLH3, anti-oxidized phosphatidylcholine antibody.
Results
At 12 h after 2-h MCAO-reperfusion, the infarct volume was increased; it peaked at 24–72 h. 8-OHdG-containing cells in the cortical infarct border zone and penumbra were observed at 12 h, the number of 8-OHdG-positive cells was highest at 24 h and they co-localized with DNA single-strand breaks (SSB) indicating apoptosis cells only within infarct border. SSB positive cells were expansively observed from the caudate putamen into the cortical region at 6–12 h and highest in the cortical region at 72 h; it was consistent with DNA degradation. Plasma 8-OHdG significantly increased at 12 h, and peaked at 24 h after reperfusion (1.1 ± 0.7 ng/mL (mean ± SD); controls 0.3 ± 0.1; p<0.01); this increase was in step with increased cortical infarct volume, and reflected immunohistochemical findings in the cortical region but not the caudate putamen. These findings indicate that the increased plasma 8-OHdG in acute phase after MCAO-reperfusion reflects the cortical oxidative damage and precedes the cortical neuronal cell death. In the permanent MCAO model, plasma 8-OHdG levels were associated with the brain contents of 8-OHdG. Plasma 8-OHdG was lower in the 0.5- and 1-h than 2-h MCAO model in consistent with the cortical infarct volume size, suggesting that it corresponds to the severity of the oxidative cortical damage. During hypothermia, patients with cortical infarction had the decreased OxLDL and 8-OHdG levels in their plasma. However, in step with rewarming both markers transiently increased. This finding suggests that the oxidative markers could be served the monitoring of the treatment of acute cerebral infarction.
Conclusions
Our findings indicate that oxidative markers in plasma may be an indicator of oxidative brain damage in acute cerebral infarction and increased plasma marker predict the presence of the penumbra as well as the cortical infarct.