Changes in mitochondrial uncoupling protein expression in the rat vestibular nerve after labyrinthectomy

In the present study, to elucidate the role of mitochondrial uncoupling proteins (UCPs) in inner ear, we examined quantitative changes in the mRNA expression in vestibular ganglion (VG) after unilateral labyrinthectomy (UL) in rats. Using real-time PCR methods, UCP2, 3 and 4 mRNA expressions in the ipsilateral VG were significantly up-regulated with the maximum increase at the post-operative 1 day and all but UCP2 returned to the control level 1 week after UL. UCP2 mRNA expression was significantly up-regulated even 4 weeks after UL. Only UCP2 mRNA expression in the contralateral VG was gradually up-regulated between 1 and 4 weeks after UL. According to previous reports, UCP2 and 3 as well as UCP1 were thermogenic in yeast and brain UCP2 was suggested to modulate pre- and post-synaptic events by axonal thermogenesis. It was also reported that UCP1, 2 and 3 responses to superoxide application were an antioxidant protective mechanism. These findings suggest that mitochondrial UCPs could play both a neuro-protective role against oxidative damage and a thermal signaling role for neuro-modulation in vestibular nerve.