Cationic antimicrobial peptides are ancient natural broad-spectrum antibiotics, and several compounds also exhibit anticancer activity. However, most applications pertain to bacterial infections, and treatment for skin cancer is less frequently considered. The cytotoxicity of melittin, cecropin A, protegrin-1 and histatin 5 against squamous skin cancer cell lines and normal human keratinocytes was evaluated and compared to established drugs. The results show that melittin clearly outperforms 5-fluorouracil regarding antitumor activity. Importantly, combined melittin and 5-fluorouracil enhanced cytotoxic effects on cancer cells and reduced toxicity on normal keratinocytes. Additionally, minimum inhibitory concentrations indicate that melittin also shows superior activity against clinical and laboratory strains of Candida albicans compared to amphotericin B. To evaluate its potential for topical applications, human skin penetration of melittin was investigated ex vivo and compared to two non-toxic cell-penetrating peptides (CPPs), low molecular weight protamine (LMWP) and penetratin. The stratum corneum prevents penetration into viable epidermis over 6 h; however, the peptides gain access to the viable skin after 24 h. Inhibition of digestive enzymes during skin penetration significantly enhances the availability of intact peptide. In conclusion, melittin may represent an innovative agent for non-melanoma skin cancer and infectious skin diseases. In order to develop a drug candidate, skin absorption and proteolytic digestion by skin enzymes need to be addressed.
Loss-of-function mutations in the filaggrin gene (FLG) are a strong predisposing factor for atopic dermatitis, although their relevance to the disease pathomechanism needs further elucidation. The generation of an in vitro model of atopic skin would not only permit further evaluation of the underlying pathogenetic mechanisms and the testing of new treatment options, but would also allow toxicological studies to be performed in a simple, rapid and inexpensive manner. In this study, we have knocked down FLG expression in human keratinocytes and created three-dimensional skin models, which we used to investigate the impact of FLG on epidermal maturation and on skin absorption and its response to irritation. Histopathological evaluation of the skin models showed impaired epidermal differentiation in the FLG knock-down model. In addition, skin irritation induced by an application of sodium dodecyl sulphate resulted in significantly higher lactate dehydrogenase leakage, and interleukin (IL)-6 and IL-8 levels, than in the control model. To assess the effect of filaggrin deficiency on skin absorption of topically applied agents, we quantified the percutaneous absorption of lipophilic and hydrophilic model drugs, finding clinical relevance only for lipophilic drugs. This study clearly demonstrates that important clinical characteristics of atopic skin can be mimicked by using in vitro skin models. The FLG knock-down construct is the first step toward an in vitro model that allows clinical and toxicological studies of atopic-like skin.
Due to its strong water-binding potential, hyaluronic acid (HA) is a well-known active ingredient for cosmetic applications. Native HA is proposed to help the skin to retain and maintain elasticity, turgor and moisture.
In recent years, topically applied semi-solid formulations certified as medicals devices and not as topical drugs are increasingly used for the treatment of skin diseases. Medical devices primarily unfold their therapeutic effect by physical means, not by pharmacological, immunological or metabolic means. Intensified placing of medical devices on the dermatological market may at least partly be explained by a less complex marketing authorization process compared to topical drugs. If the requirements are fulfilled to certify a product as a medical device the opportunity will be offered to quickly introduce innovations onto the market and propagate them. A variety of evidence-based medical devices for several dermatological indications are presented here.
Chitin, after cellulose the second most abundant polysaccharide in nature, is an essential component of exoskeletons of crabs, shrimps and insects and protects these organisms from harsh conditions in their environment. Unexpectedly, chitin has been found to activate innate immune cells and to elicit murine airway inflammation. The skin represents the outer barrier of the human host defense and is in frequent contact with chitin-bearing organisms, such as house-dust mites or flies. The effects of chitin on keratinocytes, however, are poorly understood.
Excessive scars form as a result of aberrations of physiologic wound healing and may arise following any insult to the deep dermis. By causing pain, pruritus and contractures, excessive scarring significantly affects the patients quality of life, both physically and psychologically. Multiple studies on hypertrophic scar and keloid formation have been conducted for decades and have led to a plethora of therapeutic strategies to prevent or attenuate excessive scar formation. However, most therapeutic approaches remain clinically unsatisfactory, most likely owing to poor understanding of the complex mechanisms underlying the processes of scarring and wound contraction. In this review we summarize the current understanding of the pathophysiology underlying keloid and hypertrophic scar formation and discuss established treatments and novel therapeutic strategies.
This paper continues our review of scientifically evaluated plant extracts in dermatology. After plants effective against dermatophytes, botanicals with anti-edema effects in chronic venous insufficiency are discussed. There is good evidence from randomized clinical studies that plant extracts from grape vine leaves (Vitis vinifera), horse chestnut (Aesculus hippocastanum), sea pine (Pinus maritima) and butchers broom (Ruscus aculeatus) can reduce edema in chronic venous insufficiency. Plant extracts from witch hazel (Hamamelis virginiana), green tea (Camellia sinensis), the fern Polypodium leucotomos and others contain antioxidant polyphenolic compounds that may protect the skin from sunburn and photoaging when administered topically or systemically. Extracts from the garden spurge (Euphorbia peplus) and from birch bark (Betula alba) have been shown to be effective in the treatment of actinic keratoses in phase II studies. Some plant extracts have also been investigated in the treatment of vitiligo, various forms of hair loss and pigmentation disorders, and in aesthetic dermatology.
Modern tissue culture technology has made it possible to generate human skin equivalents that represent either epidermis or epidermis plus dermis (full-thickness skin) in vitro. Commercially available skin equivalents and in-house models are used for safety analysis of cosmetics and toxicity screening of various pharmaceutical compounds. Recently, tissue culture technology has also been used to develop in vitro models of skin disease, in particular to promote cutaneous drug research while sparing experimental animals. The spectrum of model diseases available covers a range from inflammatory disease to cancer. It has, thus, been possible to gain more insight into the role of active pharmaceutical ingredients of various dermatologically relevant drug classes as well as conventional and innovative formulations.
Human immunodeficiency virus (HIV)-associated facial lipoatrophy (FLA) represents a common and highly stigmatizing side effect of retroviral therapy. By causing loss of subcutaneous adipose tissue mainly in the cheek, temple and periocular area, FLA can significantly affect the patients quality of life, both physically and psychologically. A limited quantity of data has been published on various filling substances for the management of FLA. Here, the authors present two patients with HIV-associated FLA successfully treated with a novel HA filler over a period of 24 months.
Sertaconazole nitrate is a broad-spectrum antifungal agent indicated in the United States for the treatment of tinea pedis interdigitalis. The objective of this subgroup analysis was to evaluate the safety and efficacy of sertaconazole nitrate cream 2%, specifically in participants with tinea pedis interdigitalis (ie, fungal skin disease of the toe web) of dermatophyte origin. A total of 92 participants were included in this analysis. The primary end points were eradication of the pathogen (confirmed by fungal culture results) and reduction in total clinical score (TCS) of at least 2 points. Secondary end points included reducing signs and symptoms and reporting adverse events (AEs). After 4 weeks of treatment, 88.8% (79/89) of evaluable participants achieved success on the primary end points. Most participants also demonstrated substantial improvement in signs and symptoms after 4 weeks of treatment: 63.7% (58/91) were free of erythema, 33.0% (30/91) were free of desquamation, and 91.2% (83/91) were free of itch. The rate of reported AEs was low (8.7% [8/92]), and none were considered serious. These findings indicate that sertaconazole nitrate cream 2% is highly safe and effective in the treatment of tinea pedis interdigitalis.
Aiming to address new drug targets, molecular modelling is gaining increasing importance although the prediction capability of the in silico method is still under debate. For an improved treatment of actinic keratosis and squamous cell carcinoma, inhibitors of human DNA polymerase alpha (pol alpha) are developed by docking nucleoside phosphonate diphosphates into the active site of pol alpha. The most promising prodrugs OxBu and OxHex were then prepared by total synthesis and tested in the squamous cancer cell line SCC25. OxBu and OxHex proved cytotoxic and antiproliferative in the nanomolar concentration range and thus exceeded activity of aphidicolin, the relevant model compound, and 5-fluorouracil, the current standard for the therapy of actinic keratosis. Interestingly, the cytotoxicity in normal human keratinocytes with OxHex was clearly less pronounced and even not detectable with OxBu. Moreover, cytotoxicity of OxBu in particular with the colorectal carcinoma cell line HT29 even surmounted cytotoxicity in SCC25, and other tumor cell lines were influenced, too, by both agents. Taken together, OxBu and OxHex may offer a new approach to cancer therapy, given the agents are sufficiently well tolerated in vivo which is to be suspected beside their chemical structure.
Recently, the three-dimensional structure of the active site of human DNA polymerase alpha (pol alpha) was proposed based on the application of molecular modeling methods and molecular dynamic simulations. The modeled structure of the enzyme was used for docking selective inhibitors (nucleotide analogs and the non-nucleoside inhibitor aphidicolin) in its active site in order to design new drugs for actinic keratosis and squamous cell carcinoma (SCC). The resulting complexes explained the geometrical and physicochemical interactions of the inhibitors with the amino acid residues involved in binding to the catalytic site, and offered insight into the experimentally derived binding data. The proposed structures were synthesized and tested in vitro for their influence on human keratinocytes and relevant tumor cell lines. Effects were compared to aphidicolin which inhibits pol alpha in a non-competitive manner, as well as to diclofenac and 5-fluorouracil, both approved for therapy of actinic keratosis. Here we describe three new nucleoside analogs inhibiting keratinocyte proliferation by inhibiting DNA synthesis and inducing apoptosis and necrosis. Thus, the combination of modeling studies and in vitro tests should allow the derivation of new drug candidates for the therapy of skin tumors, given that the agents are not relevant substrates of nucleotide transporters expressed by skin cancer cells. Kinases for nucleoside activation were detected, too, corresponding with the observed effects of nucleoside analogs.
Topical drug application is less prone to severe systemic side-effects than systemic application. Starting with the liposomes, various types of nanosized and microsized drug carriers have been developed to increase the notoriously low penetration of active agents into the skin, which limits not only the topical therapy of skin disease but also transdermal therapy. Today, liposome- and microsponge-based preparations are approved for dermatomycosis, acne and actinic keratosis. Under investigation are drug carriers such as lipid nanoparticles, polymeric particles, dendrimers, and dendritic-core multi-shell nanotransporters. According to the rapidly increasing research in this field, both in academia and industry, a breakthrough appears likely, once stability problems (nanoparticles) and safety concerns (dendrimers) are overcome. Technical approaches and results of in vitro, ex vivo and in vivo testing are described, taking into account pharmacokinetic, efficacy and safety aspects.
An adolescent boy presented with isolated, symmetrical, bilateral areolar and periareolar pityriasis versicolor. This extremely rare condition should be considered in the differential diagnosis of light brown patches on the areolae.
As well as for topically used dermatological agents, studies performed according to the rules of evidence-based medicine (EBM) are also needed for cosmetics. Although the concept of evidence-based cosmetics has been only partly developed so far, there are some agents and preparations available that can be considered as evidence-based. In this paper we present data from several studies that claim to have examined and demonstrated the efficacy of cosmetic preparations for the management of solar damage and aging skin as well as lentigo and melanosis according to EBM criteria. Certainly, further controlled studies are needed to cover the main application areas of dermocosmetics. Retinol and antioxidant agents such as vitamin C and coenzymes that positively act via several mechanisms on collagen biosynthesis can be considered evidence-based substances for the management of aging skin. According to the same criteria, the preventive effect of regularly applied dermocosmetic sun screens on the development of actinic keratosis could also be shown. Dermocosmetic sun screens should offer adequate protection against UV-B and UV-A light by combining compatible organic and/or non-organic UV-filters and at the same time be well tolerated. Furthermore, they may contain some additional agents such as antioxidants, DNA repair enzymes, dexpanthenol, glycerin or hamamelis distillate. In the treatment of melanosis, a substantial bleaching effect corresponding to that of 0.1% topical tretinoin can be achieved with 10% all-trans-retinol gel. Preparations containing urea, ammonium lactate or glycerol in different concentrations are considered the best characterized and most effective substances for the care of dry skin. However, the lack of controlled studies confirming the efficacy of dermocosmetic products as well as the superiority of the preparation incorporating the active agent over the corresponding base is a problem yet to be solved. Undoubtedly, the efficacy and the sustainability of the achieved effects have to be examined and proven accordingly to EBM criteria in further active cosmetic agents. Moreover, generally accepted guidelines for the examination of efficacy and tolerability of dermocosmetics have to be developed.
Itraconazole is an antifungal drug from the triazole group with distinct in vitro activity against dermatophytes, yeasts and some molds. Itraconazole has a primarily fungistatic activity. Itraconazole accumulates in the stratum corneum and in nail material due to its high affinity to keratin, as well as in sebum and vaginal mucosa. Together with terbinafine and fluconazole, itraconazole belongs to the modern highly effective systemic antifungal drugs with a favorable risk-benefit ratio and for this reason is a preferred therapy option for fungal infections of skin, nails and mucous membranes. Compared to terbinafine in the treatment of fingernail and toenail fungal infections, itraconazole offers the advantage of a broad antifungal spectrum and better effectiveness against onychomycosis caused by yeasts yet appears inferior with regard to the more common dermatophyte infections. Itraconazole constitutes an important therapy option, along with fluconazole, terbinafine, ketoconazole and griseofulvin, for the treatment of dermatophyte infections of glabrous skin (tinea pedis, tinea manuum, tinea corporis and tinea cruris) in adults following unsuccessful topical therapy. In the oral therapy of tinea capitis, itraconazole plays an especially important role, in particular for disease caused by Microsporum canis (for children, however, only off-label use is feasible currently). In the treatment of oropharyngeal candidiasis, candidiasis of the skin and vulvovaginal candidiasis, itraconazole and fluconazole are the preferred treatment options in cases in which topical therapy has proven unsuccessful.
The synthetic route to pepstatin derivatives by a solid phase peptide synthesis using either O-protected or O-unprotected statine as a building block has been investigated. Statine was prepared according to a modified literature procedure, whereas protection of its 3-hydroxyl moiety using tert-butyldimethylsilylchloride (TBSCl) provided the novel O-TBS-protected statine building block. The O-tert-butyldimethylsilyl (TBS)-protected statine approach provides an improved synthetic strategy for the preparation of statine-containing peptides as demonstrated by the synthesis of the pepstatin analogue iva-Val-Leu-Sta-Ala-Sta.
In the recent past, we have found ourselves in need of truly novel antifungal drugs as drug resistance in fungi has been evolving. Moreover, effective therapy has become particularly important as the number of immuno-compromised patients with life-threatening fungal infections increases. Fortunately, during the last few years, virulence factors of fungi and their inhibitors have, at least to some extent, been discovered and characterized. This should provide new options for the development of potential antifungal therapeutics. Inhibitors of the secreted aspartic proteinase of Candida albicans might turn out to be particularly rewarding.
The family of secreted aspartic proteinases is known as an important virulence factor of yeast infections by Candida albicans in particular, which is the most common fungal pathogen for humans with respect to systemic disease. Due to the continuing increase of drug resistant strains, these proteinases are currently considered as promising drug target candidates. Based on the known Sap2-substrate specificity data and X-ray analyses of Sap/inhibitor complexes, three libraries of inhibitors were designed and synthesized by modifying the structure of pepstatin A, a common non-selective aspartic proteinase inhibitor, at the P3, P2, or P2 position. These novel inhibitors showed high inhibitory potencies for the isoenzymes Sap1, Sap3, Sap5 and Sap6. Then, the affinity and selectivity of the peptide ligands were investigated by molecular modeling, highlighting new key structural information for the design of potent and selective anti-virulence agents targeting Candida albicans.
C. albicans is one of the most common fungal pathogen of humans, causing local and superficial mucosal infections in immunocompromised individuals. Given that the key structure mediating host-C. albicans interactions is the fungal cell wall, we aimed to identify features of the cell wall inducing epithelial responses and be associated with fungal pathogenesis. We demonstrate here the importance of cell wall protein glycosylation in epithelial immune activation with a predominant role for the highly branched N-glycosylation residues. Moreover, these glycan moieties induce growth arrest and apoptosis of epithelial cells. Using an in vitro model of oral candidosis we demonstrate, that apoptosis induction by C. albicans wild-type occurs in early stage of infection and strongly depends on intact cell wall protein glycosylation. These novel findings demonstrate that glycosylation of the C. albicans cell wall proteins appears essential for modulation of epithelial immunity and apoptosis induction, both of which may promote fungal pathogenesis in vivo.
Reconstructed human epidermis (RHE) is used in non-animal testing for hazard analysis and reconstructed human skin (RHS) gains growing interest in preclinical drug development. RHE and RHS have been characterised regarding their barrier function, but knowledge about biotransformation capacity in these constructs and in human skin remains rather poor. However, metabolising enzymes can be highly relevant for the efficacy of topical dermatics as well as genotoxicity and sensitisation. We have compared the esteratic cleavage of the prednisolone diester prednicarbate and the enzyme kinetic parameters (Vmax and S0.5) of the model substrate fluorescein diacetate (FDA) in commercially available RHS and RHE with excised human skin and monolayer cultures of normal and immortalised human keratinocytes and of fibroblasts. Formation of the main metabolite prednisolone and of fluorescein ranked as: RHS~RHE>excised human skin and keratinocytes>fibroblasts, respectively. Because of the aromatic probe, however, Vmax of FDA cleavage did not show a linear relationship with prednicarbate metabolism. In conclusion, RHE and RHS may be useful to quantitatively address esterase activity of human skin in drug development and hazard analysis, although an increased activity compared to native human skin has to be taken into account.
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has an important role not only in glycolysis but also in nonmetabolic processes, including transcription activation and apoptosis. We report the isolation of a human GAPDH (hGAPDH) (2-32) fragment peptide from human placental tissue exhibiting antimicrobial activity. The peptide was internalized by cells of the pathogenic yeast Candida albicans and initiated a rapid apoptotic mechanism, leading to killing of the fungus. Killing was dose-dependent, with 10??g?ml (3.1??M) and 100??g?ml hGAPDH (2-32) depolarizing 45% and 90% of the fungal cells in a population, respectively. Experimental C. albicans infection induced epithelial hGAPDH (2-32) expression. Addition of the peptide significantly reduced the tissue damage as compared with untreated experimental infection. Secreted aspartic proteinase (Sap) activity of C. albicans was inhibited by the fragment at higher concentrations, with a median effective dose of 160?mg?l(-1) (50??M) for Sap1p and 200?mg?l(-1) (63??M) for Sap2p, whereas Sap3 was not inhibited at all. Interestingly, hGAPDH (2-32) induced significant epithelial IL-8 and GM-CSF secretion and stimulated Toll-like receptor 4 expression at low concentrations independently of the presence of C. albicans, without any toxic mucosal effects. In the future, the combination of different antifungal strategies, e.g., a conventional fungicidal with immunomodulatory effects and the inhibition of fungal virulence factors, might be a promising treatment option.
pH is known as an important parameter in epidermal barrier function and homeostasis.
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