Tyrosinase deficiency increases protein carbonyl content in substantia nigra of mice administered retinol palmitate.

Tyrosinase is a key enzyme for the biosynthesis of melanin pigments in peripheral tissues such as skin and retina. Although tyrosinase activity is specifically detected in melanocytes, several studies have shown the expression and enzymatic activity of tyrosinase in the central nervous system, especially in the midbrain substantia nigra. In the present study, we investigated the antioxidative effects of tyrosinase on protein damage in the substantia nigra of mice. C57BL/10JMsHir (B10) and tyrosinase-deficient albino B10.C-Tyrc/Hir (B10-c) mice were intraperitoneally administered retinol palmitate to induce oxidative stress, and the protein carbonyl content, a hallmark of protein oxidative damage, was examined in the substantia nigra. Retinol palmitate administration was found to decrease catalase activity in the substantia nigra of both B10 and B10-c mice, suggesting the induction of oxidative stress due to imbalanced antioxidant systems. In this model, we found that tyrosinase deficiency markedly increases the protein carbonyl content in the substantia nigra. Thus, we concluded that tyrosinase activity prevents protein damage in the substantia nigra of mice that were challenged with oxidative stress. These findings provide novel insight into the physiological role of tyrosinase in the central nervous system.