INTRODUCTION:

Several studies have shown that skin aging takes place via different molecular mechanisms, including oxidative stress, DNA damage and mutations, telomere shortening, inflammation and build up of advanced end-product glycation (AGEs)¹. In addition reactive oxygen species (ROS) induce skin aging by stimulating expression by degrading different components of proteins such as collagen, fibronectin, elastin and proteoglycans in the form of a matrix of metalloproteinases (MMPs), which contribute to skin aging². Emil Fischer and Hofmeister identified the first peptides at the beginning of the 19th century. In 1901 Fischer and Fourneauin released the first peptide synthesis³.

Fischer described the first peptide as glycyl-glycine and explained more peptide structure, such as dipeptides, tripeptides and polypeptides in his lectures⁷. Years followed, and scientists synthesized new peptides, discovered more natural peptides, and learnt more about their functions⁴. Aside from through awareness of natural and synthetic peptides, numerous synthetic peptides have been produced. In 1973 Loren Pickard developed the copper glycine-histidine-lysine (Cu-GHK). The first copper peptide was used in skin care products during the late 80s. Still then, the development of peptides continued slowly until the beginning of 2000, when palmitoyl pentapeptide-4 was established⁵. Research and industry have since developed many short, stable, and synthetic peptides that play a role in the synthesis, pigmentation, innate immunity, and inflammation of extracellular matrixes⁶. These peptides are used for stimulation of collagen, wound healing, "botox-like" wrinkle smoothing, as well as for antioxidant, antimicrobial, and whitening. Topical cosmeceutical peptides may be categorized as signal peptides, messenger peptides, peptides regulators of neurotransmitters, and enzyme peptides⁷. The development of new cosmetics formulations based on the use of bioactive compounds has expanded rapidly due to demand by consumers for products with protective and therapeutic functions derived from natural sources⁸. Therefore, new cosmetic formulations have emerged which provide molecules with beneficial effects on human skin that influence the biological function of the skin such as cell protection, thermoregulation and immunity. Any of such compounds used are phytochemicals (e.g. plant extracts, polyphenols), microbial metabolites (e.g. microbial extracts, lactic acid, hyaluronic acid), and minerals/vitamins (e.g. selenium, vitamin E), either as isolated substances or as mixtures of extracts or suspensions. Some of these compounds, however, have demonstrated limitations such as high cost, lower availability and a few adverse side effects such as skin irritation, inflammatory response and allergicity. Similarly, scientists have proposed using bioactive peptides as functional ingredients because they generally have higher safety profiles, hypo-allergenicity, and are relatively cost-effective in production. Moreover, according to the FDA, protein hydrolysates containing bioactive peptides have the status of a food substance that is generally recognized as safe (GRAS). Peptides derived from protein hydrolysates were used extensively in food⁹. Topical cosmeceutical peptides can be categorized as signal peptides, carrier peptides, peptides that suppress neurotransmitters, and peptides that suppress enzymes. Cosmeceutical peptides should have some characteristics to get good effects¹⁰. Historically it has often been believed that the molecular weight of peptides should be less than 500 Da because of the skin barrier, otherwise the peptide will not pass the barrier. The moderate log of the octanol/water partition coefficient should be between 1 and 3, the melting point should be below 200^◦C, water solubility should be > 1 mg / mL and no or few polar centers should be present¹¹.

Bioactive peptides with anti-aging properties:

Alterations occur during intrinsic or chronological aging on the biosynthetic activity of skin-derived cells such as collagen, elastin, and hyaluronic acid, as well as the simultaneous overproduction of several skin enzymes, called aging-related enzymes (e.g. elastase, collagenase, tyrosinase, and hyaluronidase) that are involved in the degradation of the skin's protein matrix. In this context, intrinsic aging occurs in combination with extrinsic aging, which is a biochemical process driven by external factors (e.g. ultraviolet radiation, pollution), not directly associated with the body's biological processes which contribute to the visible signs of aging on the skin surface. Anti-skin aging properties are correlated with essential physiological enzymes such as elastase, collagenase, tyrosinase, and hyaluronidase inhibition. Current literature indicates that peptides from different sources (e.g., snake venom, yeast, skin frog, and toads) have anti-aging properties and are protected by patents. For example, snake venom-derived pentapeptide-3 (GPRPA) has shown a reduction in wrinkles and skin roughness, and hexapeptide11 (FVAPFP) isolated from yeast extract, increases skin firmness. This analysis focuses on bioactive peptides extracted from foods (e.g., rice, spirulina, and fish) as alternative sources that can directly target skin cells and prevent skin aging. An overview of the inhibition properties of these bioactive peptides towards the main enzymes associated with skin aging is provided below¹².

Multifunctional bioactive peptides with skin health improvement:

Multifunctional bioactive peptides may be favored over single activity peptides, as they can activate, modulate, or inhibit multiple physiological pathways simultaneously. Bioactive peptides exhibiting antioxidant, antimicrobial, anti-inflammatory and anti-aging activity have been reported which could provide partial or complete skinning protection. Taniguchi et al. found that rice bran protein-derived cationic peptides had multiple bioactivities, including antimicrobial, anti-inflammatory (e.g. LPS-neutralizing), and angiogenic activity. Aguilar-Toalá et al. reported that water Exhibited anti-inflammatory, antihemolytic, antioxidant, antimutagenic, and antimicrobial activity by water soluble extracts obtained from fermented milk by Lactobacillus strains. Furthermore, Mudgil et al. found that the peptide fractions derived from quinoa and amaranth proteins showed antioxidant, antimicrobial and antihemolytic activity, while Urbizo-Reyes et al. showed strong chemical and cellular antioxidant properties of chia seed peptides. Overall, bVG these studies indicate that peptides derived from fermentation and emerging protein sources (e.g., quinoa and chia seeds) possess strong bioactive properties (e.g. antioxidant) that could be used in skin-aging prevention items. Tanaka, Koyama, and Nomura recorded that, during a six-week period, oral administration of collagen peptides (0.2g/kg/day) to hairless HR-1 mice improved skin hydration and decreased epidermal hyperplasia in a UV-induced photo-damage mode¹³. A similar result was reported by Oba et al. who found that collagen peptide administration decreased skin barrier abnormalities and skin elasticity dysfunction in a skin damage model induced by UVB irradiation using mice. In vivo studies demonstrate the effect of bioactive peptides on skin enhancement. For example, Hakuta et al. have been investigating the impact of a collagen tripeptide product intake on patients with atopic dermatitis for 12 weeks under double-blind conditions. The findings showed that collagen tripeptide administration substantially decreased the region of the eruption, the intensity scoring values for atopic dermatitis, and the loss of transepiderminal water. Asserin et al. reported substantially improved skin hydration by consuming collagen peptide products, fish collagen peptides (Peptan ® F) and porcine peptides (Peptan ® P), and increased dermal collagen density in the dermis. Additionally a decrease in dermal collagen network fragmentation was observed. Duteil et al. [145] found that fish collagen peptide consumption, Naticol ® BPMG (2kDa), Naticol ® HPMG (4kDa), Naticol ® 1000MG (2kDa), significantly reduced wrinkles and improved skin strength and elasticity. Furthermore, the products showed good consumer satisfaction, and no related adverse side effects (e.g. gastrointestinal discomfort, diarrhea, headache, skin rash) were reported during the trial (8 weeks)¹⁴.

Peptides that Trigger the Signaling Cascade:

Several peptides can trigger a signaling cascade. They are released from the extracellular matrix, and they are also called matricins or stimulators of collagen. With these peptides there is increased production of collagen, elastin, proteoglycan, glycosaminoglycan, and fibronectin. As a result, the regeneration of the skin matrix cells decreases the pigmentation of photo-damaged skin and fine lines and wrinkles. The elasticity of the skin increases and the skin looks smoother and firmer. To rejuvenate the skin, synthetic peptides modeled on repair signaling sequences such as the following described in this section were developed¹⁵.

i. Carnosine and N-Acetylcarnosine:

Carnosineis adipeptide (Sequence: β-Ala-His) and a well-documented aqueous antioxidant with wound healing activity, and naturally occurs in high muscle and brain tissue concentrations. Carnosine is a scavenging reactive oxygen species, as well as an unsaturated α-β aldehyde formed during oxidative stress by the peroxidation of cell membrane fatty acids.

ii. Triﬂuoroacetyl-Tripeptide-2:

Trifluoroacetyl-tripeptide-2 (Sequence: TFA-Val-Try-Val-OH) was assessed in two studies of the in vivo split face. One study examined its anti-wrinkle and anti-sagging effects along 10 volunteers' jawline (56 days) through fringe projection profilometry; and the other study targeted skin firmness, elasticity, and viscoelasticity through cytometry 13 healthy volunteers (28 days). The trifluoroacetyl-tripeptide-2 has progressive effects on wrinkles, firmness, elasticity and sagging, according to the studies.

iii. Palmitoyl Tripeptide-3/5:

Palmitoyl tripeptide-3/5 mimics the effects of thrombospondin-1 (TSP-1), an extracellular matrix protein, a naturally occurring enzyme that increases TGFβ activity. TSP-1 works locally to enhance wound healing in animal models and human dermal fibroblast cell culture studies, and is suspected to be involved in the post-natal growth of skin structures. The TSP-1 protein's short sequence Lys-Arg-Phe-Lys is responsible for boosting TGFβ. TGFβ, in addition, causes the quantities of Type I and Type III collagen released by dermal fibroblasts to continue to increase. In in vitro and in vivo tests, Palmitoyl tripeptide-3/5 (Sequence: Pal-Lys-Val-Lys bistrifluoracetae salt) (SYN ® -COLL) induces collagen development through the growth factor TGFβ¹⁶.

Carrier Peptides:

Carrier peptides supply or stabilize trace elements such as copper and manganese, necessary for wound healing and enzymatic progression. These peptides involve ransport into skin cells by incopper or mangane. In addition, they are obtained by binding a tripeptide to copper.

i. Copper Tripeptide:

Copper tripeptide (Cu-GHK, lamin ®) complex (Sequence: Copper Gly-L-His-Lys) is one of the peptides that has been examined the most. It plays a role in the extracellular matrix, and is released to promote healing in wounds or inflammations. It acts as a signal and carrier peptide, promotes regular synthesis of collagen, elastin, proteoglycan, and glycosaminoglycan, and provides antioxidant and anti-inflammatory responses. Cu-GHK is used in cosmetic applications in products which stimulate anti-aging, anti-wrinkle, after-sun, skin renewal, skin moisturizer, hair growth.

ii. Manganese Tripeptide-1:

In addition to the well-researched copper tripeptide, there is also one clinical study based on tripeptide-1 manganese (Sequence: GHK-Mn2 +). This study assessed the effects of a complex of manganese peptides in treating various signs of cutaneous facial photo-damage. Throughout a 12-week period, subjects were instructed to twice daily apply a facial serum formulation containing the manganese peptide complex. That resulted in a shift from moderate to mild in the photo-damage ranking of their skin. Hyperpigmentation was associated with the most significantly improved parameters whereas no significant cutaneous inflammation was reported¹⁷.

Neurotransmitter Inhibitor Peptides:

Muscle contraction is another strategy that reduces common signs of ageing such as fine lines and wrinkles. Muscles are contracted by release of neurotransmitters from neurons. The neurotransmitter begins a cascade of protein-protein interactions that culminate in the fusion of vesicles filled with the neuron membrane by neurotransmitters. A local alteration of the membrane potential activates the entry of calcium ions through the terminal into the neuron. When these ions come into the pre-synaptic terminal, acetylcholine-containing vesicles join other parts of the neuron to release acetylcholine. A SNAP receptor protein, which includes the vesicle-associated membrane protein, the membrane-associated protein syntaxin, and synaptosomal-associated protein 25, is mediating this process. Through the formation of the SNARE complex these proteins directly manage vesicle docking and fusion. The SNARE complex captures and fuses vesicles to the membrane. Once these vesicles are fused, acetylcholine is released into the muscle/nerve synapse. Acetylcholine binds to receptors of acetylcholine located on the muscle cell surface and this leads to muscle contraction.

i. Acetylhexapeptide-3:

Acetylhexapeptide-3 (Argireline ®) has the Acetyl-Glu-Glu-Met-Gln-Arg-Arg-NH2 sequence, and is reported to inhibit the release of neurotransmitters accompanied by moisturizing, anti-rinkle effects. The firmness and texture of the skin tend to be improving. Acetylhexapeptide-3 is a copy of the synaptosomal-associated protein 25 competing for a SNARE complex position and destabilizing its formation without breaking any of its constituent parts. In addition it inhibits the secretion of catecholamine. An increase in peptide concentration and peptide permeation, and a decrease in coefficients of iontophoretic permeability, are influenced by a variety of parameters which can be optimized for successful transdermal peptide delivery.

ii. Pentapeptide-18:

In addition it inhibits the secretion of catecholamine. An increase in peptide concentration and peptide permeation, and a decrease in coefficients of iontophoretic permeability, are influenced by a variety of parameters which can be optimized for successful transdermal peptide delivery.

iii. Tripeptide-3:

Tripeptide-3 (Sequence: β-Ala-Pro-Dab-NHBn-2-Acetate), also known as dipeptide diaminobutyroyl benzylamide diacetate or SYN ® -AKE, imitates the effect of waglerin-1, a peptide found in the Tropidolaemus wagleri viper venom. Tripeptide-3 acts on the postsynaptic membrane, and is an acetylcholine receptor reversible antagonist¹⁸.

Enzyme Inhibitor Peptides:

The enzyme-inhibitor peptides inhibit enzymes directly or indirectly. Soy oligopeptides, peptides of silk fibroin, and peptides of rice act on the skin cells. These peptides inhibit enzymes such as tTAT-superoxide dismutase, activate hyaluronan synthase 2 or inhibit proteinases in the case of soy oligopeptides. This peptide category shows promising results but only very few or no in vivo studies have been conducted. The significance is therefore still uncertain.

i. Rice Peptides:

Low molecular weight peptides (< 3000 Da) were obtained after a specially processed protein for the rice bran. Black rice oligopeptides were approximately 1300 Da in measurement data. These oligopeptides were noted in dose-dependent manner for inhibiting MMP (matrix metalloproteinase) activity, and stimulated gene expression of hyaluronan synthase 2 in human keratinocytes. Three new rice bran protein peptides found had a residue of C-terminal tyrosine, and exhibited important inhibitory effects against monophenolase reactions mediated by tyrosinase. In addition, one peptide called CT-2 (Leu-Gln-Pro-Ser-His-Tyr) powerfully inhibited melanogenesis in mouse melanoma cells without causing cytotoxicity, which could be of interest to skin conditions related to melanin.

ii. Silk Fibroin Peptide:

Silk peptide fibroin is derived from Bombyx mori, a silkworm. Scientific results reveal inhibitory inflammation and enhance the anti-inflammatory activity of tTAT-superoxide dismutase, previously reported to effectively penetrate different cells and tissues, and exert anti-oxidant activity in an inflammatory mouse model. There are currently no details on the human effectiveness in vivo.

iii. Soybean Peptides:

Soybean peptides are obtained from soybean proteins, consisting of 3–6 amino acids, mostly 300–700 kDa in size range. Various biological activities have been identified for soybean oligopeptides, such as antioxidant, lowering blood pressure, and lowering effects of blood lipids. Topically applied soy oligopeptide data showed significantly increased protein expression of Bcl-2 and decreased cyclobutane pyrimidinedimer-positive cells, sunburn cells, apoptotic cells, protein expression of p53 and expression of Baxprotein in the UVB-irradiated foreskin epidermis. Topically used soy oligopeptides appear to protect the human skin (nine healthy male volunteers) against photo damage caused by UVB¹⁹.

Biological activities of peptides related to their potential cosmeceutical application: in silico, in vitro and in vivo evidence:

i. Peptides with antioxidant activity:

During long-term skin exposure to ultraviolet (UV) radiation or exposure to xenobiotic compounds with oxidative reactions (e.g. solvents, toxins), excessive production of reactive oxygen species (ROS), triggered by oxidative stress, is involved in dermatological disease pathogenesis, including skin cancer. In this sense, ROS may induce biomolecular oxidation and/or affect signaling pathways in the skin related to the tissue structure being properly cared for. ROS generated by UV radiation in the skin has been reported to have induced oxidation of collagen and oxidation of skin cells. Some studies have indicated that UV-induced ROS induces skin photo aging in human keratinocytes and dermal fibroblasts by encouraging MMP-1 activity. Bioactive peptides with antioxidant properties can, therefore, be used to avoid the deleterious effect of oxidative stress caused by excessive ROS production in the skin.

ii. Peptides with antimicrobial activity:

The skin, as our body's outermost barrier, is constantly exposed to microbial agents and therefore the antimicrobial function of the skin (i.e., the cutaneous production of antimicrobial peptides in response to microbial invasion) is lost with aging. Some microorganisms, such as Staphylococcus aureus in atopic dermatitis and Propionibacterium acnes in acne vulgaris, are related to skin diseases. Many micro-organisms responsible for skin and soft tissue infections include Enterococcus faecium, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter, which have been associated with the development of skin diseases such as psoriasis and rosacea. The use of bioactive peptides with antimicrobial activity against these micro-organisms is promising functional ingredients in cosmeceutical topical applications. Additionally, bioactive peptides in acne vulgaris are considered a potential alternative to antibiotic treatments because the development of a resistant strain of propionibacterium acnes has become problematic. Beaulieu et al. identified nine peptide sequences from macroalgae (Saccharina longicruris) peptide fractions (TITLDVEPSDTIDGVK, ISGLIYEETR, MALSSLPR, ILVLQSNQIR, ISAILPSR, IGNGGELPR, LPDAALNR, EAESSLTGNGCAK, and QVHPDTGISK) with antibacterial activity towards Staphylococcus aureus. Authors found that when the peptides were individually tested for their antimicrobial properties, they did not demonstrate bioactivity; however, when combined, the activity was significantly increased, suggesting a synergistic relationship between the peptides. Kobbi et al . synthesized six peptides (MDN, ELAAAC, LRDDF, GNAPGAVA, ALRMSG, and RDRFL) previously identified from the Alfalfa RuBisCo's most active peptide fraction. These peptides' antimicrobial mechanism against pathogen Listeria innocua has been observed through morphological changes and destruction of cell integrity via irreversible damage to the membrane. These changes could be related to certain peptide characteristics, in particular the presence of specific amino acids such as C, G, R, and D, as well as their short peptide chain (3–8 amino acids) and a random coil structure. In a related report, Lueangsakulthai et al. described a Siamese crocodile (Crocodylus siamensis) haemoglobin-derived antimicrobial peptide (QAIIHNEKVQAHGKKVL) that exhibited antimicrobial activity against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa. The peptide is characterized by its hydrophobic character (41 per cent), net charge of +2, and the probable underlying mechanism is connected to membrane permeabilization due to the loss of controlled iron transportAdditionally, it was observed that this peptide caused no damage to DNA. In general, the antimicrobial activity of bioactive peptides is attributed to the membrane-lytic mechanism which, through the formation of transmembrane channels in the membrane, directly affects the integrity of the cell membrane and cell wall by self-aggregation or polymerization which leads to cytoplasm leakage and/or cell death. They also exercise intracellular inhibitory activities towards the formation of protein folding, nucleic acid, cell wall and protein biosynthesis, cell division, and lipopolysaccharide²⁰.

CONCLUSION:

Naturally occurring human peptides are known for cellular communication, such as protein regulation, cell proliferation, cell migration, inflammation, angiogenesis, and melanogenesis, resulting in a wide range of physiological processes including defense, immunity, stress, development, homeostasis, and reproduction. Newer studies have shown that larger molecules, especially in the case of dry and aged skin, can traverse the skin barrier. Synthetic peptides consist of amino acid chains that can now be modified for various functions, such as increased skin penetration, and increased binding of special receptors, stability, and solubility. During the last decade, the development of active peptides has opened up a new field in cosmeceutical and pharmaceutical skin care.

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Received on 08.06.2020 Accepted on 18.08.2020

Research J. Topical and Cosmetic Sci. 2020; 11(2):77-82.

DOI: 10.5958/2321-5844.2020.00014.X