Poster presentation, P10

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Characteristic roles for cochlear melanocytes in anti-oxidant responses related to and not related to theirmelanogenesis

BACKGROUND & OBJECTIVES: Mammalian melanocytes are derived from neural crest cells, migrate not only to the skin but also to other tissues, such as outer layers of eyes, heart valves, and the inner ears. The functions of those non-cutaneous melanocytes are not clearly understood. Among non-cutaneous melanocytes, the inner ear melanocytes localized in the cochlear stria vascularis are known to be essential for the maintenance of hearing acuity. However, melanin synthesis (pigmentation) in the cochlea is less associated with auditory function. Thus, the functions of non-cutaneous melanocytes seem not to be identical to those of cutaneous melanocytes. METHODS: We compared the expression patterns and enzymatic activities of melanocytes in the cochleae and on the skin of three types of mice, normally pigmented wild-type, albino and melanocyte-lacking mutants. RESULTS: Cochlear melanocytes have important roles in anti-oxidant responses in the normal (wild-type) cochleae that are correlated with the expression of glutathione S-transferase (GST) alpha (Gsta), which is lost in melanocyte-lacking cochleae. Concerning albino cochleae, which have melanocytes without melanogenesis, no differences were detected in anti-oxidant responses and Gsta expression compared with the wild-type. However, the expression patterns of another GST (Gstp) in albino cochleae were different from those of wild-type. GSTA was not detected in cutaneous melanocytes even in normally pigmented skin, but Gstp was expressed both in cochlear and in cutaneous melanocytes. CONCLUSION: Cochlear melanocytes have functions against oxidative stress. Both the existence and pigmentation of cochlear melanocytes are closely associated with the expression of different GST isoforms in the cochlea. Gsta expression has an essential function against oxidative stress in the cochlea, related to the existence of cochlear melanocytes, and is a specific function of cochlear melanocytes. Gstp expression is related to the pigmentation of cochlear melanocytes, and is a common function in cutaneous and cochlear melanocytes.

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