Franz Stäb

Aging and chronic sun exposure cause distinct epigenetic changes in human skin.

Epigenetic changes are widely considered to play an important role in aging, but experimental evidence to support this hypothesis has been scarce. We have used array-based analysis to determine genome-scale DNA methylation patterns from human skin samples and to investigate the effects of aging, chronic sun exposure, and tissue variation. Our results reveal a high degree of tissue specificity in the methylation patterns and also showed very little interindividual variation within tissues. Data stratification by age revealed that DNA from older individuals was characterized by a specific hypermethylation pattern affecting less than 1% of the markers analyzed. Interestingly, stratification by sun exposure produced a fundamentally different pattern with a significant trend towards hypomethylation. Our results thus identify defined age-related DNA methylation changes and suggest that these alterations might contribute to the phenotypic changes associated with skin aging.

Novel Aspects of Intrinsic and Extrinsic Aging of Human Skin: Beneficial Effects of Soy Extract¶

Abstract Biochemical and structural changes of the dermal connective tissue substantially contribute to the phenotype of aging skin. To study connective tissue metabolism with respect to ultraviolet (UV) exposure, we performed an in vitro (human dermal fibroblasts) and an in vivo complementary DNA array study in combination with protein analysis in young and old volunteers. Several genes of the collagen metabolism such as Collagen I, III and VI as well as heat shock protein 47 and matrix metalloproteinase-1 are expressed differentially, indicating UV-mediated effects on collagen expression, processing and degradation. In particular, Collagen I is time and age dependently reduced after a single UV exposure in human skin in vivo. Moreover, older subjects display a lower baseline level and a shorter UV-mediated increase in hyaluronan (HA) levels. To counteract these age-dependent changes, cultured fibroblasts were treated with a specific soy extract. This treatment resulted in increased collagen and HA synthesis. In a placebo-controlled in vivo study, topical application of an isoflavone-containing emulsion significantly enhanced the number of dermal papillae per area after 2 weeks. Because the flattening of the dermal–epidermal junction is the most reproducible structural change in aged skin, this soy extract appears to rejuvenate the structure of mature skin.

Vimentin Is the Specific Target in Skin Glycation STRUCTURAL PREREQUISITES, FUNCTIONAL CONSEQUENCES, AND ROLE IN SKIN AGING

Until now, the glycation reaction was considered to be a nonspecific reaction between reducing sugars and amino groups of random proteins. We were able to identify the intermediate filament vimentin as the major target for the AGE modification Nϵ-(carboxymethyl)lysine (CML) in primary human fibroblasts. This glycation of vimentin is neither based on a slow turnover of this protein nor on an extremely high intracellular expression level, but remarkably it is based on structural properties of this protein. Glycation of vimentin was predominantly detected at lysine residues located at the linker regions using nanoLC-ESI-MS/MS. This modification results in a rigorous redistribution of vimentin into a perinuclear aggregate, which is accompanied by the loss of contractile capacity of human skin fibroblasts. CML-induced rearrangement of vimentin was identified as an aggresome. This is the first evidence that CML-vimentin represents a damaged protein inside the aggresome, linking the glycation reaction directly to aggresome formation. Strikingly, we were able to prove that the accumulation of modified vimentin can be found in skin fibroblasts of elderly donors in vivo, bringing AGE modifications in human tissues such as skin into strong relationship with loss of organ contractile functions.

Anti-inflammatory efficacy of licochalcone a : correlation of clinical potency and in vitro effects

Licochalcone A (LicA), a major phenolic constituent of the licorice species Glycyrrhiza inflata, has recently been reported to have anti-inflammatory as well as anti-microbial effects. These anti-inflammatory properties might be exploited for topical applications of LicA. We conducted prospective randomized vehicle-controlled clinical trials to assess the anti-irritative efficacy of cosmetic formulations containing LicA in a post-shaving skin irritation model and on UV-induced erythema formation. The clinical trials were accompanied by a series of in vitro experiments to characterize anti-inflammatory properties of LicA on several dermatologically relevant cell types. Topical LicA causes a highly significant reduction in erythema relative to the vehicle control in both the shave- and UV-induced erythema tests, demonstrating the anti-irritative properties of LicA. Furthermore, LicA is a potent inhibitor of pro-inflammatory in vitro responses, including N-formyl-MET-LEU-PHE (fMLP)- or zymosan-induced oxidative burst of granulocytes, UVB-induced PGE2 release by keratinocytes, lipopolysaccharide (LPS)-induced PGE2 release by adult dermal fibroblasts, fMLP-induced LTB4 release by granulocytes, and LPS-induced IL-6/TNF-α secretion by monocyte-derived dendritic cells. The reported data suggest therapeutic skin care benefits from LicA when applied to sensitive or irritated skin.

Ultraweak photon emission of human skin in vivo: Influence of topically applied antioxidants on human skin

Publisher Summary This chapter discusses the method to detect ultraweak photon emission (UPE) of human skin in vivo. The monitoring of UPE directly on the skin has the advantages of being noninvasive and providing continuous and convenient monitoring. The effect of the topical application of a-tocopherol and B-carotene was also determined in this study. The UPE detection method provides a useful technique in vivo to determine peroxidative events and efficacy of topically applied antioxidants on human skin. To record the emissions from the skin of human volunteers in vivo, the instruments have to be adapted to special applications. It is necessary to replace small sample compartments and to keep the distance between photocathode and skin surface as short as possible. Avoidance of light from external sources is also necessary. The entire detector head has to be installed in rooms without phosphorescent walls, surfaces, and lamps, and it should be freely movable. Irrespective of theoretical considerations as to whether some kind of physical or biochemical phenomena may be occurring, skin as an organ designed for protection against noxious materials in the environment may be useful as an indicator of free-radical metabolism.

Epidermal Nerve Fibers Modulate Keratinocyte Growth via Neuropeptide Signaling in an Innervated Skin Model

Atopic eczema is a chronic inflammatory skin disease characterized by cutaneous nerve fiber sprouting and epidermal hyperplasia, pointing to an involvement of the peripheral nervous system in cutaneous homeostasis. However, the interaction of sensory neurons and skin cells is poorly understood. Using an innervated skin model, we investigated the influence of sensory neurons on epidermal morphogenesis. Neurons induced the proliferation of keratinocytes, resulting in an increase in the epidermal thickness. Inhibition of calcitonin gene-related peptide (CGRP), but not substance P (SP) signaling, reversed this effect. Human CGRP enhanced keratinocyte proliferation and epidermal thickness in skin models, demonstrating a key role of CGRP in modulating epidermal morphogenesis, whereas SP had only a moderate effect. Innervated skin models composed of atopic skin cells showed increased neurite outgrowth, accompanied by elevated CGRP release. As atopic keratinocytes were sensitized to CGRP owing to higher expression levels of the CGRP receptor components, receptor activity-modifying protein 1 (RAMP1) and receptor component protein (RCP), atopic innervated skin models displayed a thicker epidermis than did healthy controls. We conclude that neural CGRP controls local keratinocyte growth. Our results show that the crosstalk of the cutaneous peripheral nervous system and skin cells significantly influences epidermal morphogenesis and homeostasis in healthy and atopic skin.

White Tea extract induces lipolytic activity and inhibits adipogenesis in human subcutaneous (pre)-adipocytes

BackgroundThe dramatic increase in obesity-related diseases emphasizes the need to elucidate the cellular and molecular mechanisms underlying fat metabolism. To investigate how natural substances influence lipolysis and adipogenesis, we determined the effects of White Tea extract on cultured human subcutaneous preadipocytes and adipocytes.MethodsFor our in vitro studies we used a White Tea extract solution that contained polyphenols and methylxanthines. Utilizing cultured human preadipocytes we investigated White Tea extract solution-induced inhibition of triglyceride incorporation during adipogenesis and possible effects on cell viability. In vitro studies on human adipocytes were performed aiming to elucidate the efficacy of White Tea extract solution to stimulate lipolytic activity. To characterize White Tea extract solution-mediated effects on a molecular level, we analyzed gene expression of essential adipogenesis-related transcription factors by qRT-PCR and determined the expression of the transcription factor ADD1/SREBP-1c on the protein level utilizing immunofluorescence analysis.ResultsOur data show that incubation of preadipocytes with White Tea extract solution significantly decreased triglyceride incorporation during adipogenesis in a dose-dependent manner (n = 10) without affecting cell viability (n = 10). These effects were, at least in part, mediated by EGCG (n = 10, 50 μM). In addition, White Tea extract solution also stimulated lipolytic activity in adipocytes (n = 7). Differentiating preadipocytes cultivated in the presence of 0.5% White Tea extract solution showed a decrease in PPARγ, ADD1/SREBP-1c, C/EBPα and C/EBPδ mRNA levels. Moreover, the expression of the transcription factor ADD1/SREBP-1c was not only decreased on the mRNA but also on the protein level.ConclusionWhite Tea extract is a natural source that effectively inhibits adipogenesis and stimulates lipolysis-activity. Therefore, it can be utilized to modulate different levels of the adipocyte life cycle.

Effects of topically applied antioxidants in experimentally provoked polymorphous light eruption.

BACKGROUND Polymorphous light eruption (PLE) is the most common photodermatosis, with a prevalence of 10-20% in Western European countries and in the USA. Only few preventive measures for PLE exist, while its etiology and pathogenesis are still elusive. Recent theories on pathogenesis discuss the possible influence of oxidative stress. OBJECTIVE The presented randomized, placebo-controlled, double-blind study examines for the first time the protective effect of 3 different topically applied antioxidative preparations in experimentally photo-induced PLE. METHOD 30 patients with a history of PLE underwent photoprovocation after having had applied 3 different formulations with antioxidants and one formulation with the vehicle only to the extensor surface of their upper arms, representing the individual site of predilection, twice daily for 1 week prior to and during the consecutive week of photoprovocation. The antioxidants used were combinations of different concentrations of alpha-glycosylrutin, ferulic acid and tocopheryl acetate. RESULTS Evaluation after the 4th photoprovocation revealed that the development and severity of PLE and concomitant pruritus were significantly reduced by the application of distinct combinations of antioxidants. CONCLUSION The results offer a new insight into possible pathomechanisms of PLE and suggest a new approach for preventive and therapeutic measures.

4-n-butylresorcinol, a highly effective tyrosinase inhibitor for the topical treatment of hyperpigmentation

Background  Hyperpigmentary disorders like melasma, actinic and senile lentigines are a major cosmetic concern. Therefore, many topical products are available, containing various active ingredients aiming to reduce melanin production and distribution. The most prominent target for inhibitors of hyperpigmentation is tyrosinase, the key regulator of melanin production. Many inhibitors of tyrosinase are described in the literature; however, most of them lack clinical efficacy.

Contribution of UVB and UVA to UV-dependent stimulation of cyclooxygenase-2 expression in artificial epidermis

Both UVB (280-320 nm) and UVA (320-400 nm) radiation lead to an enhanced expression of cyclooxygenase-2 (COX-2) in epidermal cells in various in-vitro and in-vivo models. It is demonstrated here that the expression of COX-2 is induced in artificial human epidermis exposed to simulated solar light (>290 nm). Employing filters eliminating specified regions from the simulated solar spectrum, the UVB and UVA-2 (320-350 nm) regions are shown to fully account for induction of COX-2 mRNA and protein as well as the enhanced production of prostaglandin E(2) after irradiation. At the protein level, approximately 70% of the total induction by solar light is due to light in the UVA-2 region. UVA-1 (350-400 nm), visible light and IR radiation are practically ineffective. COX-2 induction by simulated solar light is attenuated in the presence of inhibitors of p38(MAPK) or of c-Jun-N-terminal kinases (JNK), whereas COX-2 induction by UVA is blocked only by inhibition of JNK. UV-induced COX-2 expression is not affected by inhibition of the MEK 1,2/ERK 1,2 pathways.