Transgenic CuZn-Superoxide Dismutase Inhibits NO Synthase Induction in Experimental Subarachnoid Hemorrhage

Abstract

Background and Purpose —The expression of inducible NO synthase (iNOS) after experimental subarachnoid hemorrhage (SAH) has been postulated to play a critical role in the pathogenesis of SAH and subsequent cerebral vasospasm. The inhibitory effect of CuZn-superoxide dismutase (CuZn-SOD) on the induction of iNOS after SAH was examined by using transgenic mice overexpressing CuZn-SOD. Methods —SOD-transgenic mice and nontransgenic littermates were subjected to SAH by endovascular perforation of the left anterior cerebral artery. The iNOS mRNA expression after SAH was determined by reverse transcription–polymerase chain reaction, and the distribution of iNOS-positive cells was immunohistochemically examined. The nuclear expression of activated nuclear factor-κB, a major transcription factor of iNOS gene, was also immunohistochemically examined. Results —In nontransgenic mice, SAH-induced iNOS protein and mRNA expressions in the arteries of basal cistern as well as in the cerebral cortex were demonstrated by immunohistochemistry and reverse transcription–polymerase chain reaction. SAH-induced iNOS protein and mRNA expressions in those tissues were much reduced in SOD-transgenic mice compared with nontransgenic mice. Moreover, the nuclear expression of the activated form of nuclear factor-κB was immunohistochemically detected in the cerebral cortices of nontransgenic mice but not in those of SOD-transgenic mice. Conclusions —These results indicate that oxygen-derived free radicals, particularly superoxide, play an important role in the iNOS gene expression after SAH and provide a molecular basis for the protective role of SOD against vasospasm after SAH.