Ischemic reperfusion brain injury in fetal transgenic mice with elevated levels of copper-zinc superoxide dismutase

Aim: To examine the effect of overexpression of human intracellular copper-zinc superoxide dismutase (CuZnSOD I) gene on fetal mice brain exposed to in-utero ischemic reperfusion injury. Design: Transient in-utero ischemia (7 min) was induced in pregnant transgenic mice overexpressing human CuZnSOD1 and wild-type mice by occluding the blood supply to the uterine artery on day 17 of pregnancy, followed by 24 hours of reperfusion. The level of lipid peroxidation in fetal mice brains was compared between the transgenic and non-transgenic (control) fetal mice. Motor and coordination skills of transgenic and control adult mice (six to eight months old) which were exposed to ischemic reperfusion injury in-utero were compared by the rope grip test and visible platform task. Results: We first measured CuZnSOD1 activity in the brains of the transgenic fetal mice and confirmed that the enzyme activity is 4.2-fold higher than control. We also established that ischemia repcrfusion on day 17 of pregnancy led to increased level of TBARS (Thiobarbituric acid reactive substance) in brains of wild-type fetal mice when compared to sham operated mice (72.5 +/- 14 vs. 49.4 +/- 1.5 nmol/mg. p < 0.001), The increase was markedly accentuated in the CuZnSOD1 transgenic mice, and significantly higher compared to control mice exposed to ischemia-reperfusion (85.6 +/- 4.0 vs. 69.5 +/- 2.3 nmol/mg, p < 0.001). Moreover, we found that the transgenic mice that were subjected to in-utero ischemia reperfusion exhibited a significantly higher rate of failures in the rope grip test and poorer performance in the visible platform task, when compared to non-transgenic mice exposed to identical insult. Conclusions: Oxygen free radicals play an important role in the pathogenesis of perinatal hypoxia. Overexpression of the enzyme CuZnSOD I in transgenic mice exposes their brains to increased damage during ischemic-reperfusion insult.