Hyperglycemia enhances excessive superoxide anion radical generation, oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion rats.

The aim of this study was to confirm the effect of acute hyperglycemia on the superoxide anion radical (O(2)(-)) generation, using a novel electrochemical O(2)(-) sensor in forebrain ischemia/reperfusion rats. Fourteen male Wistar rats were allocated to a normoglycemia group (n= 7) and a hyperglycemia group (n=7). Hyperglycemia was induced by intravenous infusion of glucose solution. Forebrain ischemia was induced by bilateral common carotid arteries occlusion with hemorrhagic hypotension for 10 min and then was reperfused. The generated O(2)(-) was measured as the current produced, which was integrated as a quantified partial value of electricity (Q), in the jugular vein using the O(2)(-) sensor. The reacted O(2)(-) current and the Q began to increase gradually during the forebrain ischemia in both groups. These values increased remarkably just after reperfusion in the normoglycemia group and were further increased significantly in the hyperglycemia group after the reperfusion. Concentrations of malondialdehyde (MDA) and high-mobility group box 1 (HMGB1) in the brain and plasma, and soluble intercellular adhesion molecule-1 (ICAM-1) in the plasma in the hyperglycemia group were significantly higher than those in the normoglycemia group. Brain and plasma MDA, HMGB1, and ICAM-1 were correlated with a sum of Q during ischemia and after reperfusion. In conclusion, acute transient hyperglycemia enhanced the O(2)(-) generation in blood and exacerbated oxidative stress, early inflammation, and endothelial injury after the forebrain ischemia/reperfusion in the rats.

In vivo real-time measurement of superoxide anion radical with a novel electrochemical sensor.

The dynamics of superoxide anion (O(2)(-)) in vivo remain to be clarified because no appropriate method exists to directly and continuously monitor and evaluate O(2)(-) in vivo. Here, we establish an in vivo method using a novel electrochemical O(2)(-) sensor. O(2)(-) generated is measured as a current and evaluated as a quantified partial value of electricity (Q(part)), which is calculated by integration of the difference between the baseline and the actual reacted current. The accuracy and efficacy of this method were confirmed by dose-dependent O(2)(-) generation in xanthine-xanthine oxidase in vitro in phosphate-buffered saline and human blood. It was then applied to endotoxemic rats in vivo. O(2)(-) current began to increase 1 h after lipopolysaccharide, and Q(part) increased significantly for 6 h in endotoxemic rats, in comparison to sham-treated rats. These values were attenuated by superoxide dismutase. The generation and attenuation of O(2)(-) were indirectly confirmed by plasma lipid peroxidation with malondialdehyde, endothelial injury with soluble intercellular adhesion molecule-1, and microcirculatory dysfunction. This is a novel method for measuring O(2)(-) in vivo and could be used to monitor and treat the pathophysiology caused by excessive O(2)(-) generation in animals and humans.

Elevation of jugular venous superoxide anion radical is associated with early inflammation, oxidative stress, and endothelial injury in forebrain ischemia-reperfusion rats.

A novel electrochemical sensor was used in this study to determine the correlations between jugular venous O(2)(-) and HMGB1, malondialdehyde (MDA), and intercellular adhesion molecule-1 (ICAM-1) in rats with forebrain ischemia/reperfusion (FBI/R). Twenty-one male rats were divided into a Sham group, a hemorrhagic shock/reperfusion (HS/R) group, and a forebrain ischemia/reperfusion (FBI/R) group. The O(2)(-) sensor in the jugular vein detected the current derived from O(2)(-) generation (abbreviated as "O(2)(-) current"), which was integrated as the partial value of quantified electricity during ischemia (Q(I)) and after reperfusion (Q(R)). The plasma O(2)(-) current showed a gradual increase during forebrain ischemia in the HS/R and the FBI/R groups. The current showed a marked increase immediately after reperfusion and continued for more than 60 min in the FBI/R group. In the HS/R group, the current was gradually attenuated to the baseline level. Brain and plasma HMGB1 increased significantly in the FBI/R group compared with those in the Sham and the HS/R groups, and both brain and plasma HMGB1 correlated significantly with the sum of Q(I) and Q(R) (total Q). Brain and plasma MDA and plasma soluble ICAM-1 also correlated significantly with total Q. Here, we report the correlation between O(2)(-) and HMGB1, MDA, and sICAM-1 in rats with cerebral ischemia-reperfusion, using a novel electrochemical sensor. These data indicated that excessive production of O(2)(-) after ischemia-reperfusion was associated with early inflammation, oxidative stress, and endothelial activation in the brain and plasma, which might enhance the ischemia-reperfusion injury.