Regional distribution of manganese superoxide dismutase 2 (Mn SOD2) expression in rodent and primate spiral ganglion cells.
Manganese superoxide dismutase 2 (SOD2) is a key metabolic anti-oxidant enzyme for detoxifying free radicals inside mitochondria. This study documents a gradient in expression of SOD2 by spiral ganglion cells in basal versus apical turn of cochlea that is consistent with differential vulnerability of high frequency hearing to free radical damage. Immunohistochemical methods were used to identify distribution of SOD2 in temporal bone sections from mice, rats, macaques, and humans. In mice and rats, both the proportion of SOD2 immunopositive type 1 spiral ganglion cells and the intensity of immunoreactivity were elevated near cochlear apex. In macaques and humans, the proportion of SO2 immunopositive spiral ganglion cells was equal across cochlear turn, but the intensity of immunoreactivity remained highest for ganglion cells near cochlear apex. Strong SOD2 immunoreactivity was also observed in human type 1 spiral ganglion cells. The average area density of SOD2 immunoreactivity in ganglion cells for each species and cochlear turn showed an allometric relationship with body weight, which is consistent with a conserved basal metabolic characteristic. These findings suggest that spiral ganglion cell responses to ROS exposure may vary along cochlear spiral with lower response capacity at cochlear base contributing to cumulative susceptibility to high frequency hearing loss.
Ying
Yu-Lan Mary
YL
Department of Otolaryngology, University of Pittsburgh, 200 Lothrop Street, Suite # 500, Pittsburgh, PA 15213, USA. yingym@upmc.edu
Balaban
Carey D
CD
D000818:Animals; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008251:Macaca; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D051381:Rats; D020318:Rats, Long-Evans; D017208:Rats, Wistar; D013045:Species Specificity; D013136:Spiral Ganglion / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014018:Tissue Distribution; D000099156:Superoxide Dismutase 2
D013482:Superoxide Dismutase; D013481:Superoxides; D000099156:Superoxide Dismutase 2