Frank Dreher

Physical and physiological effects of stratum corneum tape stripping

Background/aims: Tape stripping of human stratum corneum has been performed to measure stratum corneum mass, barrier function, drug reservoir and percutaneous penetration. However, the technique itself requires further development to facilitate interpretation.

Colorimetric method for quantifying human Stratum corneum removed by adhesive-tape stripping.

Tape-stripping of the skin is a useful method for removing the stratum corneum and obtaining more information about the function of this skill layer as the main barrier for skin penetration. The amount of stratum corneum removed is of relevance in establishing the concentration profile of chemicals within the stratum corneum after topical application. Weighing is the preferred method for measuring the amount stripped, but because it is often subject to artifacts, alternative methods are sought. We present a simple, colorimetric method for determining the amount stratum corneum removed by sequential adhesive-tape-stripping of human skin in vivo. The method is based on quantification of the sodium hydroxide soluble protein fraction using a commercially available protein assay similar to the Lowry assay. The method is shown to be an accurate and reproducible alternative to weighing, also demonstrating uniform removal of stratum corneum layers following the very initial strips.

Stratum corneum adhesive tape stripping: influence of anatomical site, application pressure, duration and removal

Background  Tape stripping is a common method for investigating stratum corneum (SC) physiology as well as bioavailability and bioequivalence of topical drugs.

Effect of Topical Antioxidants on UV-Induced Erythema Formation when Administered after Exposure

Background: Photoprotective effects of topically applied antioxidants when applied before ultraviolet radiation (UVR) exposure are well known. Their protective effect when applied after UVR exposure is, however, less established. Objective: In a randomized, double-blinded, placebo-controlled human study the short-term photoprotective effects of different antioxidants and of their combinations were evaluated when applied after UVR exposure. Methods: Melatonin (N-acetyl-5-methoxytryptamine), vitamin E (α-tocopherol) and vitamin C (ascorbic acid) were topically administered alone or in combination following UVR exposure as single applications (immediately or 30 min after irradiation, respectively) or as multiple applications (three times: 30 min, 1 h and 2 h after irradiation). The erythemal reaction was evaluated visually and noninvasively with bioengineering methods (skin color and skin blood flow). Results: No significant protective effect of melatonin or the vitamins when applied alone or in combination were obtained when antioxidants were applied after UVR exposure. No improved photoprotective effect was obtained when multiple applications were done. Conclusion: UVR-induced skin damage is a rapid event, and antioxidants possibly prevent such damage only when present in relevant concentration at the site of action beginning and during oxidative stress.

Quantification of stratum corneum removal by adhesive tape stripping by total protein assay in 96-well microplates.

Background/aims: Examination of stratum corneum (SC) content with tape stripping and a colorimetric method is increasingly used. We examined the possible use of microplates in tandem with a colorimetric method to examine SC removed with tape stripping. As a corollary to this examination, the homogeneity of tape strips was examined.

‘Keratolytic’ Properties of Benzoyl Peroxide and Retinoic Acid Resemble Salicylic Acid in Man

Objectives: Retinoic acid (RA) and benzoyl peroxide (BP) were studied, comparing their keratolytic efficacy and water barrier disruption to that of salicylic acid (SA), a well-established keratolytic, under similar conditions. Patients/Methods:Six volunteers were included in this blinded study. Eleven randomized test sites were marked on the volar forearms, containing sites for untreated skin at time zero, unoccluded, occlusion, and vehicle controls for 3 and 6 h, and each of BP, RA, and SA solutions for 3 and 6 h. At each time point, occlusion at 5 of the test sites was removed, and chromameter measurements were performed over 30 min. Each site then underwent 25 stratum corneum (SC) tape strippings. At 1, 5, and 30 min after the last stripping at each site, TEWL measurements were performed. Quantitative protein analysis of the SC from the tapes was then performed. Results and Conclusion: After 3 h, BP was significantly more effective in disrupting SC cohesion than SA and RA, indicating BP is a moderate keratolytic agent in addition to its antimicrobial properties. After 6 h, all three agents were similarly effective in keratolysis. Barrier disruption, as measured by TEWL, paralleled depth of SC removal. SA tended to exhibit the greatest keratolytic efficacy superficially, hence its clinical effectiveness in superficial conditions such as comedonal acne, whereas BP was more effective at deeper levels, complimenting its antimicrobial effects and enabling it to treat deeper, more inflammatory lesions. None of the agents significantly affected skin erythema. These techniques provide a robust and rapid assay for in vivo keratolytic demonstration.

Antioxidant defense systems in skin

Currently available kwowledge on 1)the presence and physiological distribution of natural antioxidants in skin 2)their response to oxidative environmental stressors 3)the photoprotective potential of topically applied antioxidants.

Impact of Ultraviolet Radiation and Ozone on the Transepidermal Water Loss as a Function of Skin Temperature in Hairless Mice

Exposure to ultraviolet radiation or ozone leads to skin damage including oxidation of skin biomolecules, as well as to depletion of constitutive antioxidants. The highly organized stratum corneum forming the main barrier against most xenobiotics is particularly susceptible to such damage and possible barrier perturbation may be the consequence. Whereas ample evidence exists for an increased permeability for different solutes including water after exposure to ultraviolet radiation, such an effect has not yet been reported for ozone. This study reports on the effect of such oxidative stressors using the hairless mouse as the skin model and measuring temperature-controlled transepidermal water loss (TEWL) as an indicator for skin barrier integrity. First, a strong dependency of the TEWL on skin temperature was observed, an effect that was clearly more pronounced than that found in man. Given this temperature dependency in untreated animals, we proceeded to determine the effects of both ultraviolet radiation and ozone on TEWL over a relevant physiological skin temperature range. Solar-simulated ultraviolet radiation (0.75–3 minimal erythemal dose) resulted in a delayed and dose-dependent skin barrier disruption over the entire temperature range investigated. Conversely, daily ozone exposure at 2 ppm for 1 week, however, did not significantly alter TEWL up to 72 h after the last exposure. The results demonstrate a differential response of the epidermis to two environmental stressors associated with oxidative damage; they suggest that chronic ozone exposure at relevant environmental levels does not lead to a detectable skin barrier defect, while solar UV exposure was demonstrated to increase epidermal water loss. Furthermore, experimental evidence clearly suggests that future studies applying TEWL measurements in animal models should be performed under carefully controlled skin temperature conditions.

Effect of Tape Stripping on Percutaneous Penetration and Topical Vaccination

The stratum corneum provides the first barrier to the percutaneous absorption of drugs as well as regulating water loss. This barrier limits the topical/transdermal delivery of drugs and biological macromolecules. Chemical and physical approaches have been examined to decrease these properties. Tape stripping is commonly used to disrupt the epidermal barrier, to enhance the delivery of drugs and to obtain information about stratum corneum function. Tape stripping results in the production and release of cytokines and co-stimulatory molecules and increases the humoral and cellular immune responses against peptide, protein and DNA antigens by a topical vaccination in vivo. This paper reviews the stripping method, experimental factors and its applications for penetration and topical vaccination.

Current and Emerging Treatment Options for Vulvovaginal Atrophy

Vulvovaginal atrophy in postmenopausal women is common and manifests in vaginal dryness, irritation, itching, dysuria, and dyspareunia. Treatment used to be limited to estrogen-containing regimens which pose safety concerns. Today, however, practitioners are becoming better equipped to offer a wider range of treatment options due to increased reassurance of safety for existing therapies and advances in novel treatment options. Novel options include selective estrogen receptor modulators (SERMs), tissue-selective estrogen complexes (TSECs), local androgens such as testosterone and dehydroepiandrosterone (DHEA), the peptide hormone oxytocin, as well as phytoestrogens such as genistein and daidzein found in soybeans. Nonhormonal, over-the-counter vaginal lubricants and moisturizers are additional treatment options, in particular, for women contraindicated to estrogen use.