Volker Schreiner

The Acidic Milieu of the Horny Layer

The acidic pH of the horny layer, measurable on the skin surface, has long been regarded as a result of exocrine secretion of the skin glands. The ‘acid mantle’ was thought to regulate the bacterial skin flora and to be sensitive primarily to skin cleansing procedures.In recent years, an increasing number of investigations have been published on the changes in, and constituents and functions of, the pH of the deeper layers of the stratum corneum, as well as on the influence of physiological and pathological factors. A central role for the acidic milieu as a regulating factor in stratum corneum homeostasis is now emerging. This has relevance to the integrity of the barrier function, from normal maturation of the stratum corneum lipids through to desquamation. Changes in the pH and the organic factors influencing it appear to play a role, not only in the pathogenesis, prevention and treatment of irritant contact dermatitis, but also of atopic dermatitis and ichthyosis and in wound healing.On the basis of these findings, a broader concept, exceeding the superficial ‘acid mantle’ theory, has been formulated.

Stratum Corneum pH in Atopic Dermatitis

AbstractRecent studies have provided new insights into the occurrence, causes, and pathogenetic consequences of changes in the skin pH in atopic dermatitis, particularly with respect to skin barrier function and colonization with Staphylococcus aureus. Growing evidence suggests an impaired release of proton donors, such as amino acids, urocanic acid, and lactic acid, to the stratum corneum in atopic dermatitis, as a result of reductions in filaggrin proteolysis and sweat secretion. In addition, an impaired formation of free fatty acids from sebaceous lipids and epidermal phospholipids seems to be involved. Because both lipid organization and lipid metabolism in the stratum corneum requires an acidic pH, these alterations might contribute to the disturbance of skin barrier function observed in atopic dermatitis. Furthermore, bacterial growth and virulence of S. aureus, as well as defensive host mechanisms, have increasingly been delineated as pH dependent, giving rise to a new understanding of the pathophysiology underlying increased skin colonization seen in atopic dermatitis.

Corticosteroid-induced atrophy and barrier impairment measured by non-invasive methods in human skin.

Background/aims: Atrophy is a distressing side effect of potent corticosteroids. After open application of a high potency steroid, we monitored atrophogenicity by a variety of non‐invasive methods.

Comparative investigation of human stratum corneum ceramides

The stratum corneum (SC) requires ceramides, cholesterol, and fatty acids to provide the cutaneous permeability barrier. SC lipids can be analyzed by normal-phase high-performance thin-layer chromatography (HPTLC). However, without further analysis, some uncertainty remains about the molecular composition of lipids represented by every TLC band of an unknown sample. We therefore analyzed each ceramide band further by subjecting the isolated lipids to a direct coupling of reversed-phase high-performance liquid chromatography and electrospray ionization-mass spectrometry (HPLC/ESI-MS, or IC/MS). IC/MS analysis and ESI-MS/MS negative ion and collision-induced dissociation experiments revealed that ceramide band 4 contained not only N-(ω-OH-acyl)acyl-6-OH-sphingosine, Cer(EOH), but also N-(α-OH-acyl)-sphingosine. Band 5 exclusively contained N-acyl-6-OH-sphingosine. Our results demonstrate the benefit of LC/MS analysis for selective identification of human SC ceramides. Moreover, the combination of HPTLC for pre-separation and LC/MS for identification of lipids is an even more powerful tool for detailed ceramide analysis.

Non‐invasive monitoring of oxidative skin stress by ultraweak photon emission measurement. II: biological validation on ultraviolet A‐stressed skin

Background/purpose: Several physical or chemical environmental stressors generate reactive oxygen species, which trigger oxidation reactions of cells or tissues and thereby induce a correlated ultraweak photon emission (UPE) signal. The present study was designed to qualify and validate UPE measurement following ultraviolet (UV) excitation of porcine and human skin as an analytical method to assess the potency of topical antioxidants in vivo.

Non-invasive monitoring of oxidative skin stress by ultraweak photon emission (UPE)-measurement. I: mechanisms of UPE of biological materials

Background/purpose: Oxidation of proteins and amino acids is associated with generation of ultraweak photon emission (UPE), which may be used to assess oxidative processes in the skin in a non‐invasive way. This first part of a series of reports addresses the physicochemical basis of oxidation‐induced UPE in the skin, with a special focus on the contribution of amino acid oxidation.

Validation of the body scanner as a measuring tool for a rapid quantification of body shape

Background: Currently, the body scanner, using laser‐triangulation, is one of the most precise measuring tools for the rapid quantification of body shape. The VITUS body scanner is a laser‐based system based on a principle called triangulation and the scan produced describes the distance to a surface at each point in the picture. The body scanner has multiple applications such as determining body measurements for tailoring, anthropometric investigations and cosmetic surgery. There are also intensive investigations into the effect of weight gain and thus body shape on health risks. In order to be of value, the body scanner needs to generate precise, accurate and reproducible data.

The early phase of epidermal barrier regeneration is faster in patients with atopic eczema

BACKGROUND Altered epidermal barrier function as determined by transepidermal water loss (TEWL) is a typical feature in patients with atopic eczema (AE). OBJECTIVE The purpose of this study was to assess the kinetics of epidermal regeneration after barrier perturbation induced by two different stimuli, namely acetone treatment (removal of stratum corneum lipids) and tape stripping (removal of the nonviable stratum corneum). METHODS Fifteen patients with AE and 12 nonatopic healthy controls were investigated. An area of 9.0 cm2 of clinically normal skin of the forearm flexural side was treated by acetone or tape stripping in a way that an increase in TEWL of 3.5-4.0 times the pretreatment value was achieved. TEWL was recorded directly after perturbation (tO), after 15 min (tl), 3 h (t2), 6 h (t3), 24 h (t4), 48 h (t5), 72 h (t6) and 96 h (t7). RESULTS The speed of epidermal regeneration was faster after acetone treatment, both in the patient and the control groups, with no significant difference between the two. However, after tape stripping at points t2, t5 and t6, TEWL values relative to tO were significantly lower in atopic skin as compared to normal skin (p < 0.05). CONCLUSION The faster regeneration of barrier function after tape stripping in patients with AE may be the result of a persisting mild disturbance of barrier function. It may be speculated that repair mechanisms are permanently activated, and therefore barrier recovery is faster. However, a complete restoration of the epidermal barrier function is not achieved, perhaps because of the decreased content of ceramides in atopic skin.

MODULATION DES OXIDATIVEN STRESSES IN DER HUMANEN ALTERSHAUT

Zusammenfassung Oxidativer Streß (UV-Licht, freie Radikale) ist einer der wesentlichen Auslöser für vorzeitige Hautalterung. Als aktive Schutzmechanismen gegen diese oxidativen Schäden, die besonders im Alter zunehmen, können Koenzym Q10 (CoQ10), aber auch exogen applizierte Antioxidanzien wirken.Unsere vergleichenden In-vitro- und In-vivo-Untersuchungen an Haut alter Probanden zeigen anhand der Meßparameter (ultraschwache Photonenemission, Gesamtthiolstatus, Mitochondrienmembranpotential und Zellvitalität), daß die endogene Resistenz gegen UV-Licht in Keratinozyten alter Spender reduziert ist. Diese geringere Resistenz, d.h. der schlechtere Schutz der epidermalen Zellen gegen oxidative Stressoren, insbesondere gegen UV-Licht, kann durch topische Applikation von Verbindungen wie CoQ10 und Antioxidanzien wie alpha-Glucosylrutin (15) deutlich verbessert werden. Placebokontrollierte In-vivo-Studien zeigen außerdem, daß bereits vorhandene, vornehmlich durch Lichtalterung (Photoaging) bedingte Hautveränderungen, wie z.B. sichtbare Fältchen im Bereich der Augenwinkel, durch topische Langzeitbehandlung mit humanidentischem CoQ10 deutlich reduziert werden können.Summary Oxidative stress (UV irradiation, free radicals) plays a significant role in aging. Coenzyme Q10 (CoQ10) and exogenously applied antioxidants can significantly reduce the formation of oxidative stress with increasing age.In our in vitro and in vivo experiments concerning the parameters of ultraweak photon emission (UPE), intracellular thiol status, mitochondrial membrane potential and cell vitality, we demonstrated a diminished resistance in keratinocytes of old donors against UV irradiation. This reduced epidermal resistance against oxidative stressors, i.e. UV irradiation, can be improved by topical application of CoQ10 and antioxidants like alpha-glucosylrutin (15). Furthermore, our in vivo investigations show that wrinkles around the region of the eyes (“crow feet”) could be reduced by long-term application of CoQ10.

Nitric oxide regulates synthesis of gene products involved in keratinocyte differentiation and ceramide metabolism.

During terminal differentiation of keratinocytes the expression of various proteins, which are required for the formation of the epidermal water barrier in the skin of land dwelling animals, is upregulated. Using a cell culture model for the differentiation of human keratinocytes and real-time PCR, we quantified the mRNA levels of several proteins involved in differentiation and ceramide metabolism. A calcium shift (1.1 mM CaCl2, 10 microM linoleic acid) for 8 days triggered an increase in mRNA levels of keratin 10 (75-fold), profilaggrin (55-fold), glucosylceramide synthase (40-fold), beta-glucocerebrosidase (30-fold), prosaposin (15-fold), acid sphingomyelinase (5-fold), and serine palmitoyltransferase (SPTLC2, 4-fold). However, mRNA levels of keratin 14 and acid ceramidase did not change significantly. On the other hand nitric oxide added at concentrations lower than 0.25mM stimulates proliferation of keratinocytes (Krischel et al., J. Invest. Dermatol. 111, 286-291, 1998). Accordingly, the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 0.2 mM) had no effect on the morphology of cultured keratinocytes, whereas in cultured human fibroblasts apoptosis was induced. The expression patterns obtained suggest that keratinocytes remain in a basal proliferative state, with a 3-fold increase in keratin 14 expression, a marked decrease in mRNA levels of differentiation markers and of most ceramide-metabolizing enzymes to negligible levels. The inhibitor of the NO synthase, N(G)-nitro-L-arginine-methyl ester (L-NAME, 10 mM), induced a transient increase in ceramide formation, followed by apoptosis in keratinocytes but not in fibroblasts. Both, SNAP and L-NAME, decreased the mRNA levels of all proteins involved in ceramide metabolism.