Localization of sirtuins (SIRT1-7) in the aged mouse inner ear.

CONCLUSION

The expression of sirtuin in vestibular end organs and cochlea responds differently to age-related changes. Down-regulation of SIRT1, 3, and 5 in the cochlea may weaken the protective activity regarding degeneration of the organ of Corti as well as of spiral ganglion cells, resulting in the development of age-related hearing loss. An increase in SIRT 1, 4, or 5 in vestibular tissue could indicate an increased need of detoxification of reactive oxygen species and an increased anti-ageing potential.

OBJECTIVE

To analyse the expression of sirtuins (SIRT1-7) in the normal young and old mouse inner ears.

METHODS

Young (8 weeks) and old (22 months) CBA/J mice were used in this study. Localization of SIRT1-7 in the inner ear, i.e. cochlea, vestibular end organs, and vestibular ganglion, was investigated using real-time PCR and immunohistochemistry.

RESULTS

In the vestibular end organs, the expression of SIRT1, 2, 4, 5 (both mRNA and protein), SIRT6, and 7 (only mRNA) was found to be increased, while a slightly decreased immunoreactivity was observed in SIRT3. In the cochlea, the expression of SIRT1, 3, and 5 (both mRNA and protein) was decreased in the old mice, whereas no noticeable difference was observed regarding SIRT2, 4, 6, or 7.