Peptides

Initially,peptides were derived from much larger molecules,which were enzymatically cleaved in order to isolate active fragments for use in skin care. Proteolytically cleaved peptides are still relatively large molecules.Advances in peptide chemistry were made with the advent of molecular biology. Molecular biology has enabled us to learn the exact amino acid sequences of molecules such as the matrix proteins type IV collagen and laminin. Knowing the amino acid sequence of these molecules enables the production of peptides that are five to ten amino acids in size.

The advantages of using tiny peptide fragments is in their specificity. In fact,much of the future of medicine including dermatology is in the use of peptides that will be able to stimulate or inhibit certain processes through receptor recognition. Currently, two of the most wellknown peptides being used in skin care are palmitoyl pentapeptides, also known as Matrixyl; and acetyl hexapeptide-3, also known as Argirelene.

Matrixyl is a pentapeptide that has been used as a procollagen analog to stimulate collagen production in skin. This procollagen pentapeptide sequence was first described in 1993 as being able to promote synthesis of types I and III collagen and fibronectin when added to fibroblast cell cultures [72]. The sequence Lys- Thr-Thr-Lys-Ser (KTTKS) has a fatty acid moiety called palmitoyl added to it in order to enhance its penetration in to the skin. Sederma (Le Perray en Yvelines, France), the company that holds the patents to pal-KTTKS (Matrixyl), sponsored a study that was presented as a poster at the 2002 World Congress of Dermatology in Paris, France. In this 4-month study, pal- KTTKS was able to decrease skin roughness by 27%, wrinkle volume by 36%, and wrinkle depth by 27%. Skin biopsies demonstrated increased density and thickness of elastin fibers in the dermis with improvement in type IV collagen. Studies performed by Sederma over 6 months using a cream containing 4% Matrixyl were impressive. Wrinkle depth decreased by 68% over 6 months, and wrinkle density decreased by 28%, 31%, and 47% over 2, 4, and 6 months, respectively. According to testing, in order to be effective at wrinkle reduction, Matrixyl must be used at a minimum concentration of 2% and ideally between 4 and 8%.

Argirelene has been marketed as having a relaxing effect on muscles and has therefore been touted as an alternative to Botox. Argirelene’s mechanism of action has been studied in vitro and appears to inhibit vesicle docking by inhibiting formation of the soluble N-ethylmaleimide-sensitive fusion attachment protein receptor complex (SNAP) [73, 74]. By inhibiting SNAP formation, Argirelene inhibits the release of catecholamines, including epinephrine and norepinephrine, in vitro. Clinical studies are rather limited at this time, and penetration in vivo has yet to be determined. One study using Argirelene around the eye area found a 17% improvement in periorbital rhytides after 15 days and a 27% improvement after 30 days. According to studies from the company, Argirelene should be used at a 10% concentration for optimal results.