The Cholinergic Pathway and MitoKATP Induce UCP4 Expression Involved in neuroprotection of FN Stimulation in Rats

BACKGROUND: Electrical stimulation of the cerebellar fastigial nucleus (FN) reduces the infarct size induced by middle cerebral
artery occlusion in rats. FN stimulation confers long-lasting protection from brain injury; however, its underlying mechanism is
not yet understood. We aimed to elucidate the mechanism by which FN stimulation exerts neuroprotection. We hypothesized
that the neuroprotective effect of FN stimulation involves activation of cholinergic pathways, which increases reactive oxygen
species (ROS) production by opening mitochondrial K+
ATP channels, thus leading to an increase in UCP4 (uncoupling protein 4)
expression and subsequent neuroprotection.
METHODS: FN stimulation was performed for 1 hour in rats. The UCP4 protein and mRNA levels were measured by western
blot, dot blot, and in situ hybridization. Carbachol was applied following UCP4-promoter tdTomato reporter vector transfection
of the rat primary cortical cell culture (in vitro) and rat brain (in vivo). We observed cellular UCP4 expression using fluorescence
microscopy. UCP4 expression in the cell culture in response to diazoxide application was determined by a reverse transcriptionpolymerase
chain reaction and western blotting.
RESULTS: Whereas FN stimulation increased UCP4 protein and mRNA levels, carbachol administration induced UCP4 expression
in vitro and in vivo. The attenuation of this effect by atropine suggests that FN-induced UCP4 expression involves the cholinergic
pathway. The opening of mitochondrial K+
ATP channels with diazoxide increased the production of ROS and led to increased
UCP4 expression. In contrast, quenching ROS with superoxide dismutase reversed the effect of diazoxide on UCP4 expression.
Therefore, the opening of mitochondrial K+
ATP channels increased ROS production, which subsequently enhanced UCP4
expression and attenuated ROS generation.
CONCLUSION: Neuroprotective effect of FN stimulation involves activation of the cholinergic pathways, which increases ROS
production by opening mitochondrial K+
ATP channels, leading to increased expression of neuroprotective UCP4.