Mitochondrial Calcium Uniporter Opener Spermine Attenuates the Cerebral Protection of Diazoxide through Apoptosis in Rats

Abstract

It is reported that ischemic penumbra is a dynamic process, in which irreversible necrosis in the center of ischemia propagates to the neighboring tissue over time. Recent research has indicated that mitochondrial adenosine triphosphate (ATP)-sensitive potassium channels (mitoKATP) opener diazoxide plays an important role in cerebral protection; however, the role of mitochondrial calcium uniporter (MCU) in the effect of diazoxide on penumbra and infarct core remains unclear. Adult male Wistar rats were randomly divided into 5 groups: the Sham group, the ischemia-reperfusion (I/R) group, the diazoxide and ischemia-reperfusion (Dzx + I/R) group, the diazoxide and spermine and ischemia-reperfusion (Dzx + Sper + I/R) group, and the spermine and ischemia-reperfusion (Sper + I/R) group. The animals were exposed to 24-hour reperfusion after 2-hour ischemia. Diazoxide and spermine were administrated at 30 minutes or 10 minutes before the beginning of ischemia or reperfusion, respectively. After 24-hour reperfusion, animals were given neurologic performance tests and when overdosed with general anesthesia their brains were excised for infarct volume, apoptosis, and immunohistochemical. Rats in the Dzx + I/R group displayed improved neurologic deficits, decreased infarct volume in cortex but not in subcortex, and apoptosis (evidenced by decreased terminal deoxynucleotidyl transferase-mediated dUTP nick end lebeling-positive percentage and the immunohistochemistry of cytochrome c) in cortex caused by ischemia/reperfusion. Rats in the Dzx + Sper + I/R group displayed worse neurologic deficits, larger infarct volume in cortex but not in subcortex, and more apoptosis both in penumbra and infarct core of cortex than those in the Dzx + I/R group. Results in our study suggested that diazoxide improved neurologic deficits, decreased infarct volume in cortex but not in subcortex, and apoptosis in cortex against ischemia/reperfusion injury is mediated by spermine.