Every day, in our bodies, molecules (cytokines, molecular mediators such as nucleotides, lipids and proteins) are secreted and transfer messages and signals between cells. Cells are “armed” with receptors that will bind these molecules, initiating further processes within cells. How do cosmetic ingredients – cell communicators induce normal communication between cells is explained by our dear associate Lucija Božičević.
The process of intercellular communication is regulated by various mechanisms that prompt or stop the secretion of signalling molecules. Regulation depends on factors such as the body’s health condition or environmental factors which can have different effects on bodily functions. Except with the help of intermediaries, cells can also communicate through mutual connections such as gap junction, but also through mutual adhesion.
In numerous pathophysiological conditions certain components of the system responsible for transferring information between cells are disrupted. It may happen that the molecule that is carrying the signal relevant for the cell is not produced in sufficient amounts or that the cells do not possess a sufficient number of receptors. It is also possible that a new molecule appears in the body and binds to a cell receptor, but at the same time prompts unfavourable processes in the body. Intercellular communication is the basis for physiological and regular functioning of cells in the body, so it’s no wonder that in all segments of the biomedical sector including dermatology, or more precisely dermocosmetics, more and more research is beginning to be carried out on so-called cell-communicating ingredients.
Cell-communicating ingredients prompt the synthesis of numerous molecules responsible for the normal communication of skin cells and in that way, simply put, they prompt cells to act in the way normal cells do. The most commonly mentioned and used cell-communicating ingredients of today are retinoids, peptides, niacinamide and ceramides.
Retinoids are an extremely wide group of compounds, of which all are vitamin A derivatives, but vary in potency depending on how much activation they need to be transformed into the active form of the same vitamin – all-trans retinoic acid. The form that we’ll most often find in skincare products is retinol, one of the somewhat milder forms of retinol. Another form appearing more and more often in products today is bakuchiol, an analogue of retinol with somewhat milder effects but with benefits extremely comparable to those of retinol. Due to its milder effects, certain sources state that bakuchiol can also be used by pregnant women to whom retinoids are strictly forbidden due to their teratogenic properties. Retinoids owe their extreme popularity primarily to their anti-aging effects since one of their ways of operating is to weaken the intercellular connections between keratinocytes in the horny skin layer, thereby increasing cell turnover and speeding up repair of the skin’s surface layers. Retinoic acid also has an effect on the gene transcription level by activating retinoic acid receptors. At the skin level, modulation of cell differentiation and proliferation is noticeable due to activation of gene transcription for specific growth factors. It also has anti-inflammatory effects due to its effects on certain cytokines secreted by skin cells. Application of retinoids leads to stimulation of collagen production, making the skin appear fresher and healthier.
Peptides are another group of compounds that owe their popularity in the anti-aging realm mostly to interference with intercellular communication. Peptides which are used in cosmetics are divided into signalling peptides, peptide carriers, neurotransmitter inhibitors and enzyme inhibitors. Signalling peptides in products used for topical application prompt cascades for synthesis of collagen, fibronectin, elastin, proteoglycan and glycosaminoglycan. All of this helps keep skin plump and youthful. Protein carriers introduce copper and manganese into the cells which elements are necessary for the operation of numerous enzymes producing different signalling molecules enabling cells to communicate between themselves. Copper and manganese are also important for healing wounds. Neurotransmitter inhibitors reduce signs of aging by relaxing the muscles due to the very inhibition of signals transferred by the neurotransmitters to the muscles. Such peptides mimic the amino acid sequence of the SNAP-25 peptides which are proven inhibitors of neurotransmitter release. In this context, protein inhibitors of enzymes play the most significant role when they inhibit proteases, thus preventing the breakdown of numerous proteins responsible for transmitting different signals between cells.
Niacinamide has a wide range of functions. It has an effect on hyperpigmentation by interfering in the transfer of melanosomes from melanocytes to keratinocytes which is why it is used in synergy with vitamin C, arbutin and other products for lightening hyperpigmentation marks. It also takes part in the regulation of sebum secretion which is directly linked to the appearance and width of pores – less sebum means less visible pores. In the human body niacinamide is a very common molecule since it is a component part of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), coenzymes of numerous, physiologically extremely important reactions that could not take place without them. Niacinamide owes its anti-inflammatory effect to the inhibition of the poly (ADP-ribose) polymerase-1 enzymes, thereby modulating the action of the NFκB transcription factor which has great anti-inflammatory properties. Another useful role of this ingredient is repair of the hydrolipidic barrier by activation of the mRNA expression of the serine palmitoyltransferase enzyme responsible for sphingolipid synthesis.
Ceramides in the skin may be regarded as the mortar between bricks. They hold the cells together, ensure a proper distribution of cells (strengthening and enabling intercellular connections used by the cells to communicate) and prevent transepidermal water loss. Ceramides are molecules made up of sphingosine attached to a fatty acid through amide linkage and, as already mentioned, they are naturally present in our body. However, in our 30s their level in skin decreases, the skin loses elasticity, the hydrolipidic barrier becomes compromised and the skin more susceptible to external influences. Repairing keratinocyte functions is somewhat slower since communication between cells is slowed down due to disruption of the structure of the skin’s surface layers. That is why it is important to start “feeding” your skin with ceramides on time, in order to avoid the consequences of their deficiency caused by, among other things, poorer communication between cells.
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