Five Types of Skin-Repairing Peptides

Peptides are multifunctional skin-care actives that can reduce wrinkles, treat acne, improve skin tone and elasticity and lighten or tan skin. They currently are among the most popular actives used in skin-care products today because they are potent, easy to formulate and very cost effective on a use basis (typically <20ppm).

Peptides are short chains of amino acids linked by amide bonds formed when the carboxyl group of one amino acid reacts with the amino group of another. Peptides are differentiated from proteins based on size, with peptides normally containing less than 50 amino acids. Bioactive peptides typically contain only two to ten  amino acids, which is important from a cost perspective because their cost increases dramatically as the number of amino acids increases.

There are five different types of peptides used as skin-care actives: signaling peptides, carrier peptides, enzyme-inhibiting peptides, neurotransmitter-inhibiting peptides and antimicrobial peptides.

When skin is injured, proteases break down damaged tissue into different peptide fragments. These peptides act as messengers to signal skin to produce different types of tissue to promote healing. Applying peptides tricks skin into thinking that it is injured and needs to make additional types of proteins. Signaling peptides typically contain an active amino acid sequence that can induce or inhibit the formation of a specific type of protein.

Signaling peptides have been developed that claim to stimulate collagen, elastin, laminin, hyaluronic acid, elafin, epidermal growth factor (EGF), thrombospondin I (THBS1), decorin, melanocyte-stimulating hormones (MSH), granulocyte- macrophage colony-stimulating factor (GM-CSF) and fibronectin.

Enzyme-inhibitor peptides act directly or indirectly to inhibit an enzyme. These enzymes include tyrosinase, which stimulates skin darkening and matrix metalloproteases (MMPs 1, 2 and 9) that can degrade tissue.

Carrier peptides act as facilitators to transport important trace elements (such as  copper and manganese) necessary for wound healing and enzymatic processes1. Dr. Loren Pickart is credited as discovering the wound-healing and skin-repair properties of carrier peptides when he first isolated the copper peptide GHK-Cu from human plasma albumin in 1973. Pickart noticed that when liver cells from old patients were incubated in the blood from younger patients, the older cells started behaving like younger cells. Follow-up experiments determined that this effect was due to a small peptide that behaved similarly to the synthetic peptide Glycyl-L-Histidyl-L-Lysine (GHK). In 1977, Dr. David Schlesinger of Harvard University confirmed that the peptide isolated by Pickart was a GHK peptide2.

In 1985 Pickart started a company called Procyte to patent and commercialize personal-care products containing GHK-Cu.3 In a key skin-repair study, after one month, GHK-Cu had the most significant effect on collagen production compared with vitamin C and retinoic acid. Significant increases in collagen production were found in 70 percent of the persons treated with copper-peptide creams, 50 person of the persons treated with the vitamin C cream and 40 percent of the persons treated with retinoic acid.4 To date, GHK-Cu is the most researched and documented peptide used in wound-healing and skin-repair products5.

Optimum stability and bioavailability of bioactive peptides is critical to achieve highly efficacious formulations. Acylation of the peptide using long chain fatty groups has been shown to significantly increase penetration into the stratum corneum, the top layer of the epidermis. For example, Lintner and Peschard have shown that palmitoylation of short peptides can improve skin penetration by a factor of 100 to 10006. Another important factor is the pH of the formulation. Because peptides are normally amphoteric molecules, they can either be positively charged below their isoelectric point or negatively charged above. (Note: Antimicrobial peptides are cationic.) Formulating at the isoelectric point, or where the molecule has the least charge, should help skin penetration. If formulating below the isoelectric point, the peptide would be cationic and may have compatibility issues with anionic polymers, typically used to thicken formulations. Phospholipids have also been shown to enhance the penetration of acylated peptides by up to three times.

Product formulation can greatly influence the stability of the bioactive peptide. Palmitoyl-KTTKS (Lysine-Threonine-Threonine-Lysine-Serine) was shown to vary in six different anti-wrinkle creams from 99.9 percent to only 23.5 percent of the initial value.7 The current formulation trend is to use synergistic combinations of peptides that work by different mechanisms along with a suitable delivery technology, such as a phospholipid or lamellar liquid-crystal-based formulation.

References

1. Gorouhi F, Maibach HI. Role of topical peptides in preventing or treating aged skin. International Journal of Cosmetic Science. 2009; 31: 327–345.
2. Copper peptide GHK-Cu. San Francisco (CA): Wikipedia; c.2016 [accessed 2016 Jun 1]. https://en.wikipedia.org/wiki/Copper_peptide_GHK-Cu.
3. Pickart LR, inventor; Procyte Corporation, assignee.Cosmetic and skin treatment compositions. United States patent US 5,135,913. 1992 Aug 4.  Pickart LR, inventor; Procyte Corporation, assignee. Cosmetic and skin treatment compositions. United States patent US 5,348,943. 1994 Sep 20.
4. Abdulghani AA, Sherr A, Shirin S, Solodkina G, Tapia EM, Wolf, Gottlieb AB. Effects of topical creams containing vitamin C, a copper-binding peptide cream and melatonin compared with tretinoin on the ultrastructure of normal skin: A pilot clinical, histologic, and ultrastructural study. Disease Management and Clinical Outcomes. 1998. 1:136-141.
5. Peptides and Skin Health. Corvallis (OR): Oregon State University; c.2016 [accessed 2016 Jun 1]. http://lpi.oregonstate.edu/mic/micronutrients-health/skin-health/nutrient-index/peptides
6. Lintner K, Peschard O. Biologically active peptides: from a lab bench curiosity to a functional skin care product. International Journal of Cosmetic Science. 2000. 22: 207-218.
7. Published Studies on GHK. Bellevue (WA): Skin Biology; c.2016 [accessed 2016 Jun 1].
8. http://skinbiology.com/copperpeptideregeneration.html

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