Increased basal transepidermal water loss leads to elevation of some but not all stratum corneum serine proteases

There are indications of elevation of some inflammatory serine proteases in barrier damaged skin (e.g. plasmin and urokinase). Moreover, many other serine protease activities are present such as desquamatory enzymes as well as a newly detected tryptase‐like serine protease. However, the activities of these proteases have never been correlated with stratum corneum (SC) barrier function. The activity of extractable key serine proteases (SC trypsin‐like kallikreins, SC chymotrypsin‐like kallikreins, SC tryptase‐like serine protease, urokinase and plasmin) was measured from the outermost layers of SC obtained from facial tape strippings in clinically normal subjects. The protein content of the tape strippings was quantified by absorption measurements with the novel infrared densitometer SquameScan^TM 850A and the protease activities by the use of fluorogenic peptide substrates. SC barrier function, SC hydration and skin surface pH were measured using AquaFlux^TM, NOVA dermal phase meter and Skin‐pH‐Meter^®, respectively. As expected, SC hydration was reduced with increased transepidermal water loss (TEWL) values indicative of barrier impairment. Surprisingly, SC chymotrypsin‐like activity showed no correlation with hydration or TEWL, whereas all other enzymes positively correlated with impaired barrier function and some were statistically significant: SC trypsin‐like kallikreins (R² = 0.66, P < 0.01), SC tryptase‐like enzyme (R² = 0.95, P < 0.001), plasmin (R² = 0.86, P < 0.001) and urokinase (R² = 0.50, P < 0.05). All enzymes except urokinase also negatively correlated with SC hydration. Elevated levels of SC serine proteases have been associated with some dermatological disorders, such as atopic dermatitis, psoriasis and rosacea but these results indicate that these enzymes are also elevated with milder forms of barrier disruption, which is not clinically evident as irritated skin. As these proteases are elevated in the SC, they will also be elevated in the epidermis where they can be involved in neurogenic inflammation and epidermal barrier impairment via activation of the protease‐activated receptors. These results highlight the need for using serine protease inhibitors especially for urokinase and plasmin, SC tryptase‐like serine protease and possibly SC trypsin‐like kallikreins even in milder forms of barrier damage.     

The influence of a cream containing 20% glycerin and its vehicle on skin barrier properties

Glycerin is widely used in cosmetics and well as in pharmaceutical formulations, mainly as humectant. In vitro studies have shown glycerin to prevent crystallization of stratum corneum model lipid mixture at low room humidity. Whether this may affect the skin barrier function during repeated application of glycerin in a cream base to normal skin is not known. Therefore, the influence of a cream containing 20% glycerin was compared with its placebo cream in a bilateral, double-blind study on 17 healthy volunteers. The effect was evaluated as influence on hydration with a corneometer and on skin barrier function. Skin barrier function was assessed as permeability to water with an evaporimeter (transepidermal water loss; TEWL) and as sensitivity to an irritating surfactant by measuring the biological response (measured as TEWL and skin blood flow). Ten days treatment of normal skin with 20% glycerin significantly increased skin corneometer values, indicating an increased hydration. However, our study failed to show an influence of glycerin on human skin, in terms of TEWL and skin sensitivity to SLS-induced irritation.     

TEWL在评价皮肤屏障功能研究中的应用

文章介绍了经表皮失水(TEWL)屏障的基本原理并且用菲克第一定律表示,对近几年运用经表皮失水(TEWL)评价皮肤屏障功能在化妆品保湿以及相关临床研究中的应用研究作了简要的综述。经表皮失水(TEWL)作为评价皮肤屏障功能的重要指标之一,目前和未来一段时间内在化妆品功效评价和皮肤临床应用研究上的具有非常广阔的应用前景。     

Topical emulsions containing ceramides: Effects on the skin barrier function and anti‐inflammatory properties

The barrier properties of the stratum corneum (SC) are largely dependent on the intactness of the lipid lamellae that surround the corneocytes. Ceramides, fatty acids, and cholesterol together with hydrocortisone (HC) have thus been proposed as protective or therapeutic agents against xerosis and atopic dermatitis (AD). However, topical delivery of these substances is still a challenge because of the excellent barrier function of the skin. The aim of the present study was to develop a formulation with combined anti‐inflammatory/barrier repair properties. In order to achieve this goal, a new non‐ionic O/W emulsion (CerEmulsion) containing skin barrier lipids and HC was prepared. Its physicochemical and microbiological stability and skin permeation performance were compared to a blank emulsion (NoCerEmulsion). Placebos described as PlaceboCerEmulsion and PlaceboNoCerEmulsion of CerEmulsion and NoCerEmulsion, respectively, were also prepared in order to study the transepidermal water loss (TEWL) profiles. The emulsions presented white glossy and pourable characteristics with an acidic pH. CerEmulsion showed smaller droplet sizes and higher viscosity values (5000 mPas) while NoCerEmulsion presented viscosity values of 2000 mPas. Crystalline structures were prominent in both emulsions. The microbiological analysis showed that the results were within the established specification limits. CerEmulsion and NoCerEmulsion have shown similar release profiles and CerEmulsion presented a similar anti‐inflammatory activity in vivo when compared with a commercially available 1% HC emulsion. Both emulsions were chemically, physically, and microbiologically stable. TEWL was significantly lower for the group treated with PlaceboCerEmulsion, suggesting that skin hydration was higher with this ceramide‐containing formulation. Practical applications: In this work, the authors develop and characterize a new non‐ionic HC/ceramide‐dominant O/W emulsion as a topical therapy for the improvement of skin barrier abnormalities in atopic dermatitis (AD). This unique formulation includes high concentrations of three lipids (ceramides, cholesterol, and free fatty acids) and paraffin. Its use is recommended for AD patients ≥6 months of age. It is also indicated for the management and relief of burning and itching associated with various dermatoses, including AD, irritant contact dermatitis, and radiation dermatitis.     

Natural skin surface pH is on average below 5, which is beneficial for its resident flora

Variable skin pH values are being reported in literature, all in the acidic range but with a broad range from pH 4.0 to 7.0. In a multicentre study (N = 330), we have assessed the skin surface pH of the volar forearm before and after refraining from showering and cosmetic product application for 24 h. The average pH dropped from 5.12 +/- 0.56 to 4.93 +/- 0.45. On the basis of this pH drop, it is estimated that the 'natural' skin surface pH is on average 4.7, i.e. below 5. This is in line with existing literature, where a relatively large number of reports (c. 50%) actually describes pH values below 5.0; this is in contrast to the general assumption, that skin surface pH is on average between 5.0 and 6.0. Not only prior use of cosmetic products, especially soaps, have profound influence on skin surface pH, but the use of plain tap water, in Europe with a pH value generally around 8.0, will increase skin pH up to 6 h after application before returning to its 'natural' value of on average below 5.0. It is demonstrated that skin with pH values below 5.0 is in a better condition than skin with pH values above 5.0, as shown by measuring the biophysical parameters of barrier function, moisturization and scaling. The effect of pH on adhesion of resident skin microflora was also assessed; an acid skin pH (4-4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8-9) promotes the dispersal from the skin.     

Mascaras may cause irritant contact dermatitis

The majority of adverse effects of cosmetics have been attributed to soaps in Dutch and English studies, but to eye makeup in a recent Swedish study. The reactions may be caused by irritants or by sensitizing substances. The aim of the present study was to evaluate the irritation potential of commercially available mascaras. The mascaras were exposed to the skin in aluminium chambers. The skin reaction was evaluated using both visual assessments of erythema and non-invasive measurements of the skin reaction. Seven mascaras were tested on 15 healthy individuals in a randomized and blinded fashion. Two of the seven tested mascaras induced pronounced skin inflammation, when applied to normal skin under occlusion. These two mascaras were based on volatile petroleum distillate, in contrast to the other five mascaras that were conventional emulsions with stearate as the main emulsifier. The findings suggest that solvent-based mascaras might induce contact dermatitis due to its content of irritating substances.     

A new technique associated with the evaporimetry method for evaluating occlusion

The stratum corneum is the outermost layer of the skin. It constitutes a permeability barrier that keeps micro-organisms and toxic agents from entering the skin, while retaining water and electrolytes. In order to preserve its colour and elasticity, the skin needs lipids and water. Certain occlusive products in contact with the skin diminish its natural transepidermal water loss (TEWL), and the occlusion potential of such products can be evaluated with the aid of evaporimetry. The purpose of this work was to increase the sensitivity of the method by associating the well-established methodology for measuring TEWL with a technique for removing occlusive products from the skin. The present study was designed to evaluate the procedure of measuring TEWL evaporimetrically (the traditional method) in comparison with our new method, which employs the same evaporimetric measurement combined with a removal technique that uses cotton to remove the physical barrier that occlusive products form on the skin. The product used in this study was solid petrolatum (petroleum jelly), which possesses well-known occlusive properties. The TEWL measurements were made over a pre-defined period of time, on different skin sites, and were systematically compared with the results generated by an untreated control site. The TEWL was first determined by the classic method (without product removal), then the product was removed and new readings were taken. Our results show that the classic technique was unable to show a statistical distinction between the occlusion capability of solid petrolatum and the untreated control site, whereas this same method used in association with product removal provided a statistically significant difference between the TEWL measured on the occluded and control sites. Therefore, our removal technique associated with the traditional method for measuring TEWL proved capable of increasing the response sensitivity of evaporimetry with occlusive products.     

Role of ERK Pathway in the Pathogenesis of Atopic Dermatitis and Its Potential as a Therapeutic Target

Atopic dermatitis (AD) is an eczematous skin disorder characterized by type 2 inflammation, barrier disruption, and intense itch. In addition to type 2 cytokines, many other cytokines, such as interferon gamma (IFN-γ), interleukin 17 (IL-17), and interleukin 22 (IL-22), play roles in the pathogenesis of AD. It has been reported that the extracellular signal-regulated kinase (ERK) is downstream of such cytokines. However, the involvement of the ERK pathway in the pathogenesis of AD has not yet been investigated. We examined the expression of p-ERK in mouse and human AD skin. We also investigated the effects of the topical application of an ERK inhibitor on the dermatitis score, transepidermal water loss (TEWL), histological change, and expression of filaggrin, using an AD-like NC/Nga murine model. The effects of an ERK inhibitor on filaggrin expression in normal human epidermal keratinocytes (NHEKs) and on chemokine production from bone marrow-derived dendritic cells (BMDCs) were also evaluated. p-ERK was highly expressed in mouse and human AD skin. Topical application of an ERK inhibitor alleviated the clinical symptoms, histological changes, TEWL, and decrease in expression of filaggrin in the AD-like NC/Nga murine model. The ERK inhibitor also restored the IL-4 induced reduction in the expression of filaggrin in NHEK, and inhibited chemokine production from BMDC induced by IL-4. These results indicate that the ERK pathway is involved in the pathogenesis of AD, and suggest that the ERK pathway has potential as a therapeutic target for AD in the future.     

化妆品保湿功效评价研究

通过测定不同质量分数保湿剂的皮肤水分含量（MMV）值和经表皮水分散失（TEWL）值,研究了保湿功效评价方法。研究得到了不同质量分数的保湿剂在化妆品配方中的保湿效果存在显著性差异,啫哩配方中的基质成分主要是水,能够准确地测定出添加保湿剂的保湿功效;而乳液配方中的基质含有保湿成分,测定保湿剂与基质复合的保湿功效。结果表明,通过测定MMV和TEWL评定化妆品保湿性具有准确度高和灵敏度好且易操作等特点,能够全面综合地评价化妆品保湿功效,是保湿化妆品功效评价的有效方法。     

辛基十二醇月桂酰谷氨酸双酯的结构表征及保湿性能评价北大核心CSCD

为了开发具有保湿、修复功效的类神经酰胺产品,以月桂酰谷氨酸、辛基十二醇为原料,通过无溶剂法制备了辛基十二醇月桂酰谷氨酸双酯(PS-203),并对PS-203结构进行了表征。借助皮肤探头测试系统研究了PS-203在两种挥发性溶液体系中的保湿效果,并与神经酰胺2等保湿成分进行了对比。另外,构建离体猪皮模型,采用皮肤超声诊断法评价了PS-203对受损皮肤的修复效果。结果表明:通过结构表征,证明了PS-203被成功合成;质量分数为3%、4%、5%的PS-203溶液保湿效果最好,使用后3 h内皮肤水分含量(MMV)变化率可提高至8.9%,经皮水分散失(TEWL)降低率可达24.4%;PS-203能达到与神经酰胺2相近的保湿效果,且保湿效果明显优于角鲨烷、霍霍巴油、棕榈酸乙基己酯和辛酸/癸酸甘油三酯;PS-203可使离体受损猪皮角质层密度提高3百分点,皮肤厚度增加7μm,效果与神经酰胺2相近。综上,PS-203在皮肤保湿及修复方面均具有优异的表现。