– PEPTIDES FOR ANTI-AGING SKIN CARE

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ABSTRACT:

The first peptides for cosmetic use were developed in the early 1990s. Since that time, peptides have become an increasingly popular “cosmeceutical” ingredient in anti-aging products. These interesting and useful molecules are comprised of chains of at least two amino acids linked by a “peptide bond.” The peptide bond is a chemical bond characterized by a sharing of electrons between atoms that are formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule. This relationship constitutes the primary linkage of all protein structures. There is a specific association between the amino acid sequence in the peptide chain and its resulting bioactivity. Peptides are typically active at very low concentrations. The major challenge for the use of these molecules in the cosmetic and personal care area is to develop a peptide and formulate it into a vehicle that can be delivered to the target site in skin in order for the peptide to be effective.

TABLE OF CONTENTS

4.3.2.1 Peptides for Anti-Aging Skin Care

4.3.2.2 What is a peptide?

4.3.2.3 Skin Structure and Peptide Categories

4.3.2.4 Bioactive Peptides Marketed for Skin Care Products

Conclusion

References

4.3.2.1 PEPTIDES FOR ANTI-AGING SKIN CARE

Introduction

The term “cosmeceutical” was introduced over forty years ago by the famous dermatologist Albert Kligman, M.D. The word is ambiguous from a regulatory point of view since, in the United States, there is no such defined category for skin care products that is regulated by the Food and Drug Administration. However, recognizing the legal schism that exists between “drug” and “cosmetic,” the industry jumped at a chance to have a word that described the many new, effective ingredients it was developing that fell into the schism. Interestingly, at one point, Dr. Kligman told an audience he was sorry he had proposed the term, but, nevertheless, the industry needed a term to describe such materials.

It is generally accepted that cosmeceutical ingredients are safe, will not harm the individual and may actually be beneficial in skin care products. The market for “high performance” skin care products remains strong as an aging population seeks products to help restore its youthful appearance. The ingredients formulated in cosmeceuticals are important, as they provide the basis for efficacy and other marketing claims for the formulation. Peptides provide product differentiation and enhanced-performance claims, including “naturally derived” and other holistic “well-being” concepts. Such claims align with the popular concept of healthy aging (1). They are of high interest for use in cosmeceutical products, as they function to modulate cell proliferation, cell migration, inflammation, melanogenesis, protein synthesis, and cellular regulation. These materials are generally not considered immunogenic and they break down into natural amino acids conferring a high degree of safety for use in cosmetic products.

4.3.2.2 WHAT IS A PEPTIDE?

As stated above, a peptide is a chemical entity consisting of at least two amino acids that are joined together by a peptide bond. Alternatively, the peptide bond is called an amide bond, and is formed when the carboxyl group of one amino acid chemically links to the amino group of the next amino acid, releasing a molecule of water (Figure 1). Surprisingly, the International Union of Pure and Applied Chemists (IUPAC) provides no specific definition of a peptide. Short amino acid chains are considered peptides; long amino acid chains are termed proteins. Peptides consisting of two amino acids are termed a dipeptide, three amino acids are called a tripeptide, and so on. Peptides consisting of less than 20 amino acids are referred to as an oligopeptide. A polypeptide may consist of 50 to 100 amino acids. Amino acid chains above this range are usually considered proteins. Peptides may be found in a variety of configurations. For example, they occur as naturally occurring peptide sequences: peptides generated by the chemical or biochemical breakdown of proteins and peptides synthesized from naturally occurring or synthetically derived amino acids. In addition to length, the most important characteristic of a peptide is the amino acid sequence. The sequence order is crucial with respect to the biological properties of the peptide. These molecules perform a variety of biological functions; they may travel around the body until they interact with a target receptor either on the cell surface or within the nucleus of the cell. The interaction triggers additional activity resulting in a biological response.

Figure 1: Chemical structure of a peptide bond. The star indicates location of the peptide bond site.

4.3.2.3 SKIN STRUCTURE AND PEPTIDE CATEGORIES

As discussed in detail in other parts of this text, skin is composed of three differentiated layers. The epidermis, dermis and hypodermis. The epidermis and dermis are separated by a basement membrane rich in extracellular matrix (ECM) proteins. ECM proteins include collagens, laminin, fibronectin, elastins, and proteoglycans (2). The ECM anchors cells and organs together and also serves as a mediator of receptor-induced interactions between cells. The dermis provides a supporting matrix including collagen and elastin. The largest class of fibrous ECM molecules consists of the collagens, which include 16 different types of collagen. Collagen in the dermal matrix is composed of type I (80–85%) and type III (8–11%) collagen. Collagens are primarily responsible for the tensile strength of skin (3). Damage to the collagen network causes healing to take place. Cellular behavior in the ECM is related to signaling by matrix components to cells through cell membrane receptors. Common receptors are known as integrins, and are found on the cell surface. Some of the signaling molecules are produced by proteolytic degradation in the ECM that release soluble peptides termed matrikines (4).

Signal Peptides-Matrikines

Matrikines result from the degradation of extracellular matrix proteins. They function as cell messengers involved in wound-healing and tissue repair. Matrikines are peptide fragments released by the process of enzymatic protein breakdown during tissue renewal (5). Two classes of matrikines have been characterized: natural matrikines that signal directly from the extracellular matrix area, and cryptic matrikines that require separation of peptide bonds for cell signaling (6). Matrikines are found in collagen, elastin, decorin, laminins, fibronectin, and tenascins. Palmitoyl pentapeptide-3 introduced by Sederma is an example of a matrikine peptide. The trade name for this peptide is Matrixyl®. According to the patent filed in 1999 and subsequent publications, 50 parts per million (ppm) of this peptide have been shown to produce a significant benefit to lines and wrinkles around the eyes when compared to the vehicle alone in a randomized study (7, 8). Thus, this technology falls into the characterization of peptides as interesting and useful skin anti-aging ingredients.

Antioxidant Peptides

Reactive oxygen species (ROS) can damage cells by oxidizing membrane phospholipids, proteins, and nucleic acids.

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