Moisturizing at a molecular level - The basis of Corneocare

BACKGROUND

This review covers the last 20 years of research we and our collaborators have conducted on ethnic differences in facial skin moisturization placed in historical context with previous research.

METHODS

We have focussed particularly on the biochemical and cellular gradients of the stratum corneum (SC) with the aim of discovering new skin moisturization and SC maturation mechanisms, identifying new technologies and/or providing conceptual innovations for ingredients that will improve our understanding and treatment of dry skin. Specifically, we discuss gradients for corneodesmosomes and proteases, corneocyte phenotype-inducing enzymes, filaggrin and natural moisturizing factor (NMF), and barrier lipids. These gradients are interdependent and influence greatly corneocyte maturation.

RESULTS

The interrelationship between corneodesmolysis and the covalent attachment of ω-hydroxy ceramides and ω-hydroxy fatty acids to the corneocyte protein envelope forming the corneocyte lipid envelope is especially relevant in our new understanding of mechanisms leading to dry skin. This process is initiated by a linoleoyl-ω-acyl ceramide transforming enzyme cascade including 12R lipoxygenase (12R-LOX), epidermal lipoxygenase-3 (eLOX3), epoxide hydrolase 3 (EPHX3), short-chain dehydrogenase/reductase family 9C member 7 (SDR9C7), ceramidase and transglutaminase 1.

CONCLUSION

Our research has opened the opportunity of using novel treatment systems for dry skin based on lipids, humectants, niacinamide and inhibitors of the plasminogen system. It is clear that skin moisturization is a more complex mechanism than simple skin hydration.

Confocal Raman Spectroscopy as a tool to measure the prevention of skin penetration by a specifically designed topical medical device

BACKGROUND/AIM

The scope of this study was to utilize confocal Raman spectroscopy in the evaluation of the degree of non-penetration into the viable skin layers of a paraffin and petrolatum-based product for use in the intimate areas of the skin. The formulation was purposely designed with properties to prevent undesirable skin penetration.

METHODS

Product-The test product was a proprietary topical medical device comprising paraffinum liquidum, petrolatum, paraffin, and tocopheryl acetate. Volunteers-A total of 20 healthy volunteers were recruited onto the study-17 females and three males. Product Testing-Raman spectra were obtained at Baseline and 90 minutes after product application. Product Penetration-Skin penetration was calculated from Raman spectra taken at skin depths of -5, 0, 5, 10, 15, and 20 μm.

RESULTS

Raman spectra of the investigated product could be clearly differentiated from the skin spectrum. The minimum measurable concentration of the test product was determined at a detection level of 0.5%. In this study, the test product did not penetrate down to skin depths of 10 to 20 μm.

CONCLUSIONS

Within the precision range of the test method, the investigated product did not penetrate into the compact part of the stratum corneum. The study revealed Raman spectroscopy to be suitable to detect not only penetration but also non-penetration of substances into human skin.

The Precise Structures and Stereochemistry of Trihydroxy-linoleates Esterified in Human and Porcine Epidermis and Their Significance in Skin Barrier Function: IMPLICATION OF AN EPOXIDE HYDROLASE IN THE TRANSFORMATIONS OF LINOLEATE

Creation of an intact skin water barrier, a prerequisite for life on dry land, requires the lipoxygenase-catalyzed oxidation of the essential fatty acid linoleate, which is esterified to the ω-hydroxyl of an epidermis-specific ceramide. Oxidation of the linoleate moiety by lipoxygenases is proposed to facilitate enzymatic cleavage of the ester bond, releasing free ω-hydroxyceramide for covalent binding to protein, thus forming the corneocyte lipid envelope, a key component of the epidermal barrier. Herein, we report the transformations of esterified linoleate proceed beyond the initial steps of oxidation and epoxyalcohol synthesis catalyzed by the consecutive actions of 12R-LOX and epidermal LOX3. The major end product in human and porcine epidermis is a trihydroxy derivative, formed with a specificity that implicates participation of an epoxide hydrolase in converting epoxyalcohol to triol. Of the 16 possible triols arising from hydrolysis of 9,10-epoxy-13-hydroxy-octadecenoates, using LC-MS and chiral analyses, we identify and quantify specifically 9R,10S,13R-trihydroxy-11E-octadecenoate as the single major triol esterified in porcine epidermis and the same isomer with lesser amounts of its 10R diastereomer in human epidermis. The 9R,10S,13R-triol is formed by S_N2 hydrolysis of the 9R,10R-epoxy-13R-hydroxy-octadecenoate product of the LOX enzymes, a reaction specificity characteristic of epoxide hydrolase. The high polarity of triol over the primary linoleate products enhances the concept that the oxidations disrupt corneocyte membrane lipids, promoting release of free ω-hydroxyceramide for covalent binding to protein and sealing of the waterproof barrier.

The skin barrier in healthy and diseased state

The primary function of the skin is to protect the body for unwanted influences from the environment. The main barrier of the skin is located in the outermost layer of the skin, the stratum corneum. The stratum corneum consists of corneocytes surrounded by lipid regions. As most drugs applied onto the skin permeate along the lipid domains, the lipid organization is considered to be very important for the skin barrier function. It is for this reason that the lipid organization has been investigated quite extensively. Due to the exceptional stratum corneum lipid composition, with long chain ceramides, free fatty acids and cholesterol as main lipid classes, the lipid organization is different from that of other biological membranes. In stratum corneum, two lamellar phases are present with repeat distances of approximately 6 and 13 nm. Moreover the lipids in the lamellar phases form predominantly crystalline lateral phases, but most probably a subpopulation of lipids forms a liquid phase. Diseased skin is often characterized by a reduced barrier function and an altered lipid composition and organization. In order to understand the aberrant lipid organization in diseased skin, information on the relation between lipid composition and organization is crucial. However, due to its complexity and inter-individual variability, the use of native stratum corneum does not allow detailed systematic studies. To circumvent this problem, mixtures prepared with stratum corneum lipids can be used. In this paper first the lipid organization in stratum corneum of normal and diseased skin is described. Then the role the various lipid classes play in stratum corneum lipid organization and barrier function has been discussed. Finally, the information on the role various lipid classes play in lipid phase behavior has been used to interpret the changes in lipid organization and barrier properties of diseased skin.

Pharmacological activity of natural lipids on a skin barrier disruption model

The lipids of the stratum corneum are considered responsible for the most important functions of the skin, such as the transepidermal water loss, as well as the transdermal penetration of the chemical substances. Topical application of lipids similar to the physiological stratum corneum (SC) on barrier disrupted skin, could enhance the recovery rate of the skin barrier. A mixture of natural lipids or liposomes with the same lipid composition, were applied and their pharmacological action was investigated. The tests were done in vivo, on the back of hairless mice. Comparative results were obtained and showed that the liposomes had a higher turnover of the skin barrier in contrast to that of the mechanical mixture of lipids.

Dietary supplementation with very long-chain n-3 fatty acids in patients with atopic dermatitis. A double-blind, multicentre study

The purpose of this study was to investigate whether fish oil and/or corn oil had a beneficial effect on the clinical state of atopic dermatitis, and to evaluate the dietary intake of nutrients in this group of patients. In a double-blind, multicentre study lasting 4 months, during wintertime, 145 patients with moderate to severe atopic dermatitis were randomly assigned to receive either 6 g/day of concentrated n-3 fatty acids, or an isoenergetic amount of corn oil. As local treatment, only an emollient cream or hydrocortisone cream was allowed. The fatty acid pattern in serum phospholipids, and the dietary intake of nutrients were monitored in a subgroup of patients, and the results were compared with a group of patients with psoriasis. The overall clinical score, as evaluated by the physicians, improved during the trial by 30% in the fish oil (P < 0.001) and 24% in the corn oil group (P < 0.001). This was also consistent with the results from a selected skin area, and it was further confirmed by the total subjective clinical score reported by the patients. There were no significant differences in the clinical scores between the two groups at baseline, and at the end of the study. In the fish oil group, the amount of n-3 fatty acids in serum phospholipids was significantly increased at the end of the trial, compared with pretreatment values (P < 0.001), whereas the level of n-6 fatty acids was decreased (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)