Potent low toxicity inhibition of human melanogenesis by novel indole-containing octapeptides

• Published in: Biochimica et biophysica acta 2012-10, Vol.1820 (10), p.1481-1489
• Main Authors: Ubeid, Anan Abu, Do, Sylvia, Nye, Chris, Hantash, Basil M.
• Format: Article
• Language: English
• Subjects: Agaricales - enzymology; Agaricales - metabolism; cell death; cell viability; Cells, Cultured; Copper chelation; crystal structure; cytotoxicity; Drug Evaluation, Preclinical; fibroblasts; Humans; Hydroquinone; Hyperpigmentation - drug therapy; Hyperpigmentation - pathology; Hyperpigmentation - prevention & control; Indoles - pharmacology; Indoles - therapeutic use; Infant; keratinocytes; melanin; Melanins - metabolism; Melanins - toxicity; melanocytes; Melanocytes - drug effects; Melanocytes - metabolism; Melanocytes - pathology; Melanogenesis; Models, Molecular; Molecular docking; Molecular Docking Simulation; Monophenol Monooxygenase - antagonists & inhibitors; Monophenol Monooxygenase - chemistry; Monophenol Monooxygenase - metabolism; mushrooms; Octapeptide; oligopeptides; Oligopeptides - pharmacology; Oligopeptides - therapeutic use; Protein Interaction Mapping; skin diseases; Skin Pigmentation - drug effects; Tyrosinase inhibition
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2012.05.003

Abnormal production and accumulation of melanin are characteristics of a number of skin disorders, including postinflammatory hyperpigmentation and melasma. Our objective was to develop and validate novel oligopeptides with potent inhibitory activity against mushroom and human tyrosinase with minimal toxicity toward melanocytes, keratinocytes, and fibroblasts. A library of short sequence oligopeptides was docked against the crystal structure of mushroom tyrosinase to screen for favorable binding free energies and direct interaction with the catalytic pocket. The inhibitory activity of the octapeptides and hydroquinone (HQ) was assessed using mushroom and human tyrosinase and melanin content via human primary melanocytes. Effects on cell viability and proliferation were determined using the MTT assay and cytotoxicity via trypan blue exclusion. Octapeptides P16–18 outperformed HQ, the benchmark of hypopigmenting agents, in all tested categories. Prolonged incubation of human keratinocytes, fibroblasts, or melanocytes with 30–3000μM HQ led to 8- to 65-fold greater cell death than with octapeptides. After 6d of incubation with 30μM HQ, we observed 70±3% and 60±2% cell death in melanocytes and fibroblasts, respectively, versus minimal toxicity up to an octapeptide concentration of 3mM. Octapeptides P16–18 are potent competitive tyrosinase inhibitors with minimal toxicity toward the major cell types of human skin. The findings in our study suggest that all three novel octapeptides may serve as safe and efficacious replacements of HQ for the treatment of pigmentary disorders. ► P16–18 octapeptides are potent competitive inhibitors of mushroom/human tyrosinase. ► P16–18 are 29% to 58% more potent tyrosinase inhibitors than hydroquinone. ► P16–18 octapeptides were 8- to 65-fold less toxic than hydroquinone. ► P16–18 reduced melanin content by 29–58%. ► Octapeptide inhibition may involve indole moiety binding catalytic site copper ions.