Figure 3
From: D-tyrosine adds an anti-melanogenic effect to cosmetic peptides
Pentapeptide-18 with terminal D-tyrosine inhibits melanin synthesis in human melanocytes. (A) Human melanocytes were incubated with 500 μM of the indicated peptides for 24 h. The melanin content was measured by absorbance at 405 nm and is given as the mean of three independent experiments ± SD; *P < 0.05 (top panel). Cell lysates (80 μg) were reacted with L-DOPA at 37 °C for 30 min, and tyrosinase activity was determined at 470 nm. The mean percentages (n = 3) ± SD are shown; *P < 0.05 (bottom panel). (B) Human melanocytes plated to 12-well plates were treated with 500 μM of the indicated peptides for 24 h and reacted with L-DOPA at 37 °C for 30 min. Bright-field microscopic images are shown (top panel). Scale bars = 20 μm. Relative amounts of stained regions were measured using the ImageJ program (bottom panel). *P < 0.05. (C) Human melanocytes were either treated with α-MSH (1 μM) plus 500 μM of the indicated peptide for 24 h (top panel), or irradiated with 100 mJ/cm2 UVB and treated with 500 μM of peptide for 24 h (bottom panel). Melanin contents were measured by absorbance at 405 nm. The mean percentages (n = 3) ± SD are shown; *P < 0.05 and **P < 0.01. (D) Human melanocytes distributed to 12-well plates were irradiated with 100 mJ/cm2 UVB, treated with 500 μM of peptide for 24 h, and reacted with L-DOPA at 37 °C for 30 min. Bright-field microscopic images are shown (top panel). Scale bars = 20 μm. Relative amounts of stained regions were measured using the ImageJ program (bottom panel). *P < 0.05.
