Cy. Huang et al., Overexpression of copper-zinc superoxide dismutase attenuates acute activation of activator protein-1 after transient focal cerebral ischemia in mice, STROKE, 32(3), 2001, pp. 741-747
Background and Purpose-Reactive oxygen species (ROS) have been implicated i
n reperfusion injury after focal cerebral ischemia (FCI). ROS are known to
regulate the activity of transcription factors such as activator protein-1
(AP-1), which is a dimer consisting of members of the Jun and Fos families.
We investigated the role of ROS in AP-1 activity after FCI using transgeni
c mice that overexpressed copper-zinc superoxide dismutase (SOD1) and that
had reduced infarction volume after FCI.
Methods-The SOD1 transgenic mice and their wild-type littermates were subje
cted to middle cerebral artery occlusion and reperfusion by intraluminal su
ture blockade. After 60 minutes of middle cerebral artery occlusion, mice w
ere allowed to recover for 1, 2, and 4 hours before euthanasia. Protein exp
ression of c-Jun and c-Fos was examined by immunohistochemistry and Western
blotting. AP-1 DNA-protein binding activity was assessed by electrophoreti
c mobility shirt assays.
Results-In wild-type mice, immunohistochemistry demonstrated acute c-Jun an
d c-Fos activation in ischemic cortex and its outer boundary. Expression of
both was reduced in SOD1 transgenic mice. Western blotting confirmed that
SOD1 overexpression was associated with reduced c-Jun and c-Fos protein lev
els in ischemic brain. Electrophoretic mobility shift assays revealed that
the ischemia-enhanced DNA binding activity observed in wild-type mice was r
educed in SOD1 transgenic mice. Supershift assays indicated that c-Jun part
icipated in the bound AP-1 complex.
Conclusions-SOD1 overexpression prevents early activation of AP-1 after tra
nsient FCI in mice. This may block the expression of downstream target gene
s that are injurious, thereby reducing the infarction volume after transien
t FCI in mice.