The impact of external factors on psoriasis

Psoriasis is one of the most common chronic inflammatory skin diseases, constituting a significant health and socioeconomic problem. Despite numerous therapeutic options, the results of treatment very often remain insufficient. It is extremely important to remember that many external factors impact the effectiveness of therapy. This article discusses the importance of emollients in therapy and the influence of infectious agents and injuries on the course of psoriasis. Understanding the above-mentioned factors in the treatment of psoriasis is critical to achieve satisfactory therapeutic effects.

Malusides, novel glucosylceramides isolated from apple pomace (Malus domestica)

Three new glucosylceramides (GluCers) named malusides I-III (1-3) were isolated from apple (cultivars of Malus domestica) pomace (fruit material remaining after juice extraction). An unusual oxo/hydroxy group pattern within the sphingadienine (d18:2) type sphingoid base was observed. All compounds contained the same α-hydroxylated fatty acid (h16:0) and a β-D-glucose moiety. Their structures were assigned on the basis of one- and two-dimensional (1D and 2D) nuclear magnetic resonance (NMR) spectroscopic analyses and mass spectrometry (MS) measurements.

Potential Applications of Phyto-Derived Ceramides in Improving Epidermal Barrier Function

The outer most layer of the skin, the stratum corneum, consists of corneocytes which are coated by a cornified envelope and embedded in a lipid matrix of ordered lamellar structure. It is responsible for the skin barrier function. Ceramides (CERs) are the backbone of the intercellular lipid membranes. Skin diseases such as atopic dermatitis and psoriasis and aged skin are characterized by dysfunctional skin barrier and dryness which are associated with reduced levels of CERs. Previously, the effectiveness of supplementation of synthetic and animal-based CERs in replenishing the depleted natural skin CERs and restoring the skin barrier function have been investigated. Recently, however, the barrier function improving effect of plant-derived CERs has attracted much attention. Phyto-derived CERs (phytoCERs) are preferable due to their assumed higher safety as they are mostly isolated from dietary sources. The beneficial effects of phytoCER-based oral dietary supplements for skin hydration and skin barrier reinforcement have been indicated in several studies involving animal models as well as human subjects. Ingestible dietary supplements containing phytoCERs are also widely available on the market. Nonetheless, little effort has been made to investigate the potential cosmetic applications of topically administered phytoCERs. Therefore, summarizing the foregoing investigations and identifying the gap in the scientific data on plant-derived CERs intended for skin-health benefits are of paramount importance. In this review, an attempt is made to synthesize the information available in the literature regarding the effects of phytoCER-based oral dietary supplements on skin hydration and barrier function with the underlying mechanisms.

Effects of 6-Hydroxyceramides on the Thermotropic Phase Behavior and Permeability of Model Skin Lipid Membranes

Ceramides (Cer) based on 6-hydroxysphingosine are important components of the human skin barrier, the stratum corneum. Although diminished concentrations of 6-hydroxyCer have been detected in skin diseases such as atopic dermatitis, our knowledge on these unusual sphingolipids, which have only been found in the skin, is limited. In this work, we investigate the biophysical behavior of N-lignoceroyl-6-hydroxysphingosine (Cer NH) in multilamellar lipid membranes composed of Cer/free fatty acids (FFAs) (C16-C24)/cholesterol/cholesteryl sulfate. To probe the Cer structure-activity relationships, we compared Cer NH membranes with membranes containing Cer with sphingosine (Cer NS), dihydrosphingosine, and phytosphingosine (Cer NP), all with the same acyl chain length (C24). Compared with Cer NS, 6-hydroxylation of Cer not only increased membrane water loss and permeability in a lipophilic model compound but also dramatically increased the membrane opposition to electrical current, which is proportional to the flux of ions. Infrared spectroscopy revealed that Cer hydroxylation (in either Cer NH or Cer NP) increased the main transition temperature of the membrane but prevented good Cer mixing with FFAs. X-ray powder diffraction showed not only lamellar phases with shorter periodicity upon Cer hydroxylation but also the formation of an unusually long periodicity phase (d = 10.6 nm) in Cer NH-containing membranes. Thus, 6-hydroxyCer behaves differently from sphingosine- and phytosphingosine-based Cer. In particular, the ability to form a long-periodicity lamellar phase and highly limited permeability to ions indicate the manner in which 6-hydroxylated Cer contribute to the skin barrier function.

Lipid disturbances in psoriasis: an update

Psoriasis is a common disease with the population prevalence ranging from 2% to 3%. Its prevalence in the population is affected by genetic, environmental, viral, infectious, immunological, biochemical, endocrinological, and psychological factors, as well as alcohol and drug abuse. In the recent years, psoriasis has been recognised as a systemic disease associated with numerous multiorgan abnormalities and complications. Dyslipidemia is one of comorbidities in psoriatic patients. Lipid metabolism studies in psoriasis have been started at the beginning of the 20th century and are concentrated on skin surface lipids, stratum corneum lipids and epidermal phospholipids, serum lipids, dermal low-density lipoproteins in the psoriatic skin, lipid metabolism, oxidative stress and correlations between inflammatory parameters, lipid parameters and clinical symptoms of the disease. On the basis of the literature data, psoriasis can be described as an immunometabolic disease.

Genetics and molecular pathology of Stargardt-like macular degeneration

Stargardt-like macular degeneration (STGD3) is an early onset, autosomal dominant macular degeneration. STGD3 is characterized by a progressive pathology, the loss of central vision, atrophy of the retinal pigment epithelium, and accumulation of lipofuscin, clinical features that are also characteristic of age-related macular degeneration. The onset of clinical symptoms in STGD3, however, is typically observed within the second or third decade of life (i.e., starting in the teenage years). The clinical profile at any given age among STGD3 patients can be variable suggesting that, although STGD3 is a single gene defect, other genetic or environmental factors may play a role in moderating the final disease phenotype. Genetic studies localized the STGD3 disease locus to a small region on the short arm of human chromosome 6, and application of a positional candidate gene approach identified protein truncating mutations in the elongation of very long chain fatty acids-4 gene (ELOVL4) in patients with this disease. The ELOVL4 gene encodes a protein homologous to the ELO group of proteins that participate in fatty acid elongation in yeast. Pathogenic mutations found in the ELOVL4 gene result in altered trafficking of the protein and behave with a dominant negative effect. Mice carrying an Elovl4 mutation developed photoreceptor degeneration and depletion of very long chain fatty acids (VLCFA). ELOVL4 protein participates in the synthesis of fatty acids with chain length longer than 26 carbons. Studies on ELOVL4 indicate that VLCFA may be necessary for normal function of the retina, and the defective protein trafficking and/or altered VLCFA elongation underlies the pathology associated with STGD3. Determining the role of VLCFA in the retina and discerning the implications of abnormal trafficking of mutant ELOVL4 and depleted VLCFA content in the pathology of STGD3 will provide valuable insight in understanding the retinal structure, function, and pathology underlying STGD3 and may lead to a better understanding of the process of macular disease in general.

Analytical strategies in lipidomics and applications in disease biomarker discovery

Lipidomics is a lipid-targeted metabolomics approach aiming at comprehensive analysis of lipids in biological systems. Recently, lipid profiling, or so-called lipidomics research, has captured increased attention due to the well-recognized roles of lipids in numerous human diseases to which lipid-associated disorders contribute, such as diabetes, obesity, atherosclerosis and Alzheimer's disease. Investigating lipid biochemistry using a lipidomics approach will not only provide insights into the specific roles of lipid molecular species in health and disease, but will also assist in identifying potential biomarkers for establishing preventive or therapeutic approaches for human health. Recent technological advancements in mass spectrometry and rapid improvements in chromatographic techniques have led to the rapid expansion of the lipidomics research field. In this review, emphasis is given to the recent advances in lipidomics technologies and their applications in disease biomarker discovery.

On the effects of topical synthetic pseudoceramides: comparison of possible keratinocyte toxicities provoked by the pseudoceramides, PC104 and BIO391, and natural ceramides

BACKGROUND

Ceramides (Cer) in the stratum corneum are essential for epidermal permeability barrier function. Thus, topical Cer replacement therapy has been employed to improve barrier function in clinical situations associated with Cer deficiency, e.g., atopic dermatitis. Because of the disadvantages of both natural- and skin identical-Cer (central nervous system origins and cost, respectively), synthetic chemical mimics, or pseudoceramides (pseudo-Cer), have been utilized as Cer substitutes. Whereas increased levels of intracellular Cer trigger cell growth inhibition and apoptosis, Cer levels are maintained by metabolic/catabolic pathways protecting cells from Cer-induced apoptosis. However, since the metabolic fates of each pseudo-Cer remain unknown, their widespread deployment in topical agents has raised concern about potential toxicities.

OBJECTIVE

We compared the effects of two chemically unrelated commercially available pseudo-Cer to exogenous cell-permeant (C2)- or natural (C18)-Cer on cell growth and apoptosis thresholds in cultured human keratinocytes (CHK).

METHODS

Cell growth and cell toxicity of CHK exposed to either C2-Cer or pseudo-Cer were assessed by MTT and lactate dehydrogenase release assays. Mitochondrial membrane potential, an indicator of apoptosis, was measured using membrane permeabilized semi-intact keratinocytes exposed C2-Cer, natural-Cer or pseudo-Cer.

RESULTS

While the cell-permeant-Cer inhibits keratinocyte growth and increases cell toxicity, neither of the pseudo-Cer showed these effects. Decreased mitochondrial membrane potential occurred in CHK incubated with cell-permeant- and natural-Cer, but not pseudo-Cer.

CONCLUSIONS

Taken together with preclinical safety studies of these pseudo-Cer and their widespread use over the counter without evidence of toxicity, these studies provide further assurance about the safety of these pseudo-Cer for topical use.

The role of emollients in the management of diseases with chronic dry skin

Dry skin is a common skin condition as well as a key aspect of a number of diseases such as atopic dermatitis and psoriasis but also of other diseases and systemic conditions. Dry skin has an impact on the patient in terms of discomfort, pruritus and impaired quality of life. Within the overall treatment regimen for these diseases, the use of emollients to manage dry skin plays a considerable role in managing skin conditions. In atopic dermatitis and psoriasis, emollients help to improve skin condition and to reduce pruritus alongside more potent pharmacological agents. It is important to choose an emollient that not only soothes and rehydrates the skin but also offers numerous other dermatological supporting roles, especially induction of proper epidermal differentiation. This review will explain the role of emollients within the management of diseases with dry skin as a major symptom and the components of an ideal emollient.

Ceramide analogue 14S24 selectively recovers perturbed human skin barrier

BACKGROUND

Topical ceramide application is an effective therapeutic approach in skin disorders with disturbed barrier function, including atopic dermatitis and psoriasis.

OBJECTIVES

To evaluate ceramide analogue N-tetracosanoyl-(l)-serine tetradecyl ester (14S24) using a novel ex vivo model.

METHODS

Freshly excised human skin was disrupted by lipid extraction, tape stripping and sodium lauryl sulphate (SLS) treatment. Barrier perturbation was evaluated by the measurement of transepidermal water loss (TEWL), skin hydration and the penetration of model compound, theophylline (TH), assessed by microdialysis. The effect of topical 5% 14S24 was compared with a commercial formulation containing a skin lipid mixture (LR) and control formulation with no skin lipids (L).

RESULTS

Both LR and 14S24 produced significant recovery of TEWL and TH penetration in extracted and tape-stripped skin with 14S24 being significantly more effective. In SLS-treated skin, 14S24 decreased TEWL but not TH penetration; LR was inactive. L improved skin hydration but not barrier characteristics. Weak correlation between TEWL and TH penetration was observed in extracted and tape-stripped skin but not in SLS-treated skin.

CONCLUSIONS

Cutaneous microdialysis can serve as a useful tool for the evaluation of skin barrier recovery by topical formulations ex vivo whereas TEWL may not be an appropriate measure of skin barrier function in such studies. The excellent barrier repair activity of 14S24 could be beneficial in skin disorders with ceramide deficiency.

Tight junction components occludin, ZO-1, and claudin-1, -4 and -5 in active and healing psoriasis

BACKGROUND

Cells of the granular layer are interconnected by tight junctions (TJs) in normal epidermis. The structural proteins of epidermal TJs include occludin, ZO-1, and claudin-1 and -4.

OBJECTIVES

Our aim was to correlate the expression of TJ components with keratinocyte differentiation using psoriasis as a model of premature keratinization.

METHODS

The distribution of TJ proteins was evaluated in the skin of nine patients with psoriasis. Punch biopsies were taken from perilesional skin, from active psoriasis plaques, and from healed, previously lesional locations. The punch biopsies were analysed using indirect immunolabelling for ZO-1, occludin and claudin-1, -4 and -5. In addition, epidermal samples were analysed by reverse transcription-polymerase chain reaction for claudin-1, -4 and -5 mRNAs.

RESULTS

Claudin-5 was localized to the granular cell layers of normal control skin as well as perilesional and lesional psoriatic epidermis. This was unexpected, as previous studies have not detected claudin-5 in the epidermis. Occludin and ZO-1 were expressed in the granular cell layer in psoriatic perilesional epidermis. In the psoriasis plaques, ZO-1 and occludin were detected in a wider zone extending from the granular layer to the middle spinous cell layers. In healed psoriasis plaques, the expression of occludin and ZO-1 resumed a normal-looking profile, being restricted to the upper epidermis only. Claudin-1 and -4 did not show marked changes in psoriasis compared with normal skin.

CONCLUSIONS

The results demonstrate claudin-5 in normal epidermis and psoriatic skin, and abnormal distribution of occludin and ZO-1 in psoriasis plaques. Clinical healing of aberrant keratinization is associated with restoration of the normal distribution of occludin, ZO-1 and also involucrin.

Separation and mass spectrometric characterization of covalently bound skin ceramides using LC/APCI-MS and Nano-ESI-MS/MS

Ceramides covalently bound to keratinocytes are essential for the barrier function of the skin, which can be disturbed in diseases, such as psoriasis and atopic dermatitis. These ceramides of the classes omega-hydroxyacyl-sphingosine and omega-hydroxyacyl-6-hydroxysphingosine contain an omega-hydroxy fatty acid. For their separation and identification, a new analytical approach based on normal phase liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry and tandem nano-electrospray mass spectrometry, respectively, is presented here. Tandem mass spectrometry provided structural information about the sphingoid base as well as the fatty acid moieties. The chain lengths of the bases ranged from C12 to C22, the chain lengths of the fatty acids varied between C28 and C36. In total, 67 ceramide species have been identified in human skin. The analytical methods presented in this work can be helpful for investigating alterations in the ceramide composition of the skin as seen in psoriasis, atopic dermatitis, and diseases with impaired epidermal barrier function.

The clinical benefit of moisturizers

Moisturizing creams marketed to consumers often contain trendy ingredients and are accompanied by exciting names and attractive claims. Moisturizers are also an important part of the dermatologist's armamentarium to treat dry skin conditions and maintain healthy skin. The products can be regarded as cosmetics, but may also be regulated as medicinal products if they are marketed against dry skin diseases, such as atopic dermatitis and ichthyosis. When moisturizers are used on the so-called dry skin, many distinct disorders that manifest themselves with the generally recognized symptoms of dryness are treated. Dryness is not a single entity, but is characterized by differences in chemistry and morphology in the epidermis depending on the internal and external stressors of the skin. Patients and the society expect dermatologists and pharmacists to be able to recommend treatment for various dry skin conditions upon evidence-based medicine.

LEARNING OBJECTIVE

Upon completing this paper, the reader should be aware of different types of moisturizers and their major constituents. Furthermore, s/he will know more about the relief of dryness symptoms and the functional changes of the skin induced by moisturizers.

New advances on the functions of epidermal growth factor receptor and ceramides in skin cell differentiation, disorders and cancers

Recent advances in understanding of the biological functions of the epidermal growth factor and epidermal growth factor receptor (EGF-EGFR) system and ceramide production for the maintenance of skin integrity and barrier function are reported. In particular, the opposite roles of EGFR and ceramide cascades in epithelial keratinocyte proliferation, migration and terminal differentiation are described. Moreover, the functions of ceramides in the epidermal permeability barrier are reviewed. The alterations in EGFR signaling and ceramide metabolism, which might be involved in the etiopathogenesis of diverse skin disorders and cancers, are described. New progress in understanding of skin organization, which might provide the basis for the design of new transcutaneous drug delivery techniques as well as for the development of new therapies of skin disorders and cancers, are reported.

Analysis of epidermal lipids of the healthy human skin: factors affecting the design of a control population

The intervariability of studies on the lipids of human epidermis and stratum corneum is high because of the different origin of the skin samples and the variety of extraction methods used. In the present work, a high-performance thin-layer chromatographic technique has been used to study the parameters age, sex, and anatomical site for their effects on the lipid profiles recovered from healthy epidermal skin biopsy specimens. It was found that sex-related differences were seen at the level of the total ceramide concentration. Observed decreases in lipid concentration, due to ageing, depended on the anatomical site. Therefore, these variables should be controlled in a reproducible and standardized way in order to be able to study the direct relationship between skin condition and barrier lipid composition. Only when this relation is established, results of topical treatment can be scientifically evaluated.

Barrier repair in chronic plaque-type psoriasis

PURPOSE

To investigate barrier repair after mild trauma in lesional skin of psoriasis patients with chronic plaque-type disease and to compare this with non-involved psoriatic skin and normal controls.

METHODS

Transepidermal water loss (TEWL) readings were taken from involved psoriatic skin and non-involved skin of psoriasis patients as well as the skin of normal controls. Three readings were performed at each site: the basal state, immediately after 20 tape strippings and 1 week post stripping.

RESULTS

Higher baseline, post-stripping and 1-week recovery TEWL readings in psoriatic-involved skin compared to non-involved and normal control skin. No significant difference in barrier recovery rate in psoriatic-involved skin compared to non-involved and normal control.

CONCLUSION

Although there appears to be a derangement of barrier function in lesional skin of psoriasis patients compared to non-lesional skin and the skin of healthy controls, the barrier recovery function of lesional psoriatic skin is still fully operational.

The stratum corneum: structure and function in health and disease

Our understanding of the formation, structure, composition, and maturation of the stratum corneum (SC) has progressed enormously over the past 30 years. Today, there is a growing realization that this structure, while faithfully providing a truly magnificent barrier to water loss, is a unique, intricate biosensor that responds to environmental challenges and surface trauma by initiating a series of biologic processes which rapidly seek to repair the damage and restore barrier homeostasis. The detailed ultrastructural, biochemical, and molecular dissection of the classic "bricks and mortar" model of the SC has provided insights into the basis of dry, scaly skin disorders that range from the cosmetic problems of winter xerosis to severe conditions such as psoriasis. With this knowledge comes the promise of increasingly functional topical therapies.

Stratum corneum lipid profile and maturation pattern of corneocytes in the outermost layer of fresh scars: the presence of immature corneocytes plays a much more important role in the barrier dysfunction than do changes in intercellular lipids

BACKGROUND

The functional characteristics of the stratum corneum (SC) of fresh scars as well as keloids and hypertrophic scars are characterized by elevated transepidermal water loss (TEWL) and increased SC hydration.

OBJECTIVES

To study the composition of the intercellular lipids and maturation properties of the cornified envelope (CE) of the SC, as these are the most important components for the SC barrier function in fresh scars.

METHODS

SC lipids were extracted from the donor site for split-thickness skin grafting soon after re-epithelialization using a cup method, and were analysed with high-performance thin-layer chromatography. CEs, which were prepared from superficial layers of the SC, were double stained with Nile red and anti-involucrin.

RESULTS

We found a significant decrease in the proportion of ceramide (CER) in the SC lipids of fresh scars. We also observed changes in the SC CER profile that consisted of an increase in CER 4 and CER 7 and a decrease in CER 3, without any significant change in the proportion of CER 1. These changes were insufficient to explain the remarkably high TEWL recorded in the early stage of fresh scars. In contrast, with double staining of CE with Nile red and anti-involucrin, we detected the presence of numerous immature and less hydrophobic corneocytes in the outermost layer of the SC of fresh scars. Scanning electron microscopy of such corneocytes revealed numerous fine wrinkles on their enlarged surface area. Most of all, we found a closely similar, time-dependent, exponential decrease in the ratio of immature corneocytes with a poorly hydrophobic CE and in the recorded TEWL values in fresh scars. There was a highly significant positive correlation between the proportion of immature corneocytes in the outermost layer of the SC and TEWL values.

CONCLUSIONS

These results suggest that the SC barrier dysfunction of the fresh scars is attributable to the presence of immature corneocytes with a less hydrophobic CE, rather than to the changes in SC lipid composition.

Simultaneous quantitative determination method for ceramide species from crude cellular extracts by high-performance liquid chromatography-thermospray mass spectrometry

I have developed a simple method which enabled simultaneous analysis of ceramides in the subcellular fractions from cultured cells by HPLC-thermospray mass spectrometry. The HPLC-thermospray mass spectra from ceramide standards were characterized by the high intensity of the MNa(+) and MH(+)-H(2)O ions. As the other minor ions, MK(+), MH(+) and m/z 282 ions were detected. Although the preponderance of MNa(+) ions compared with the MH(+)-H(2)O ions was detected in non-hydroxy fatty acid-ceramides, the preponderance of MH(+)-H(2)O ions based on the elimination of the hydroxyl group introduced at the alpha-position of acyl-portion compared with the MNa(+) ions was detected in alpha-hydroxy fatty acid-ceramides. In calibrations for authentic ceramides using N-octanoylsphingosine as an internal standard, an approximately linear relationship existed between the ratios of peak-areas of each ceramide to that of the internal standard and the known amounts of each ceramide. The factor (f) of each ceramide was calculated as follows; N-oleoyl-D-sphingosine (f=0.45), N-palmitoyl-D-sphingosine (f=0.40), N-stearoyl-D-sphingosine (f=0.39), N-nervonoyl-D-sphingosine (f=0.39) and N-lignoceroyl-D-sphingosine (f=0.35). In subcellular fractions from A549 and HepG2 cells, although ceramide species content per mg protein was high in the nuclear envelope fractions, the 7000 g pellet fractions and the 100000 g pellet fractions, a large portion of the ceramide species was concentrated in the nuclear envelope fraction. In addition, this method was applied to a mild alkaline hydrolyzate of total ceramides from pig stratum corneum, and MNa(+)/MH(+)-H(2)O ions corresponding to several omega-hydroxyacyl-ceramides were detected.

Repair of acetone- and sodium lauryl sulphate-damaged human skin barrier function using topically applied emulsions containing barrier lipids

BACKGROUND

It is generally acknowledged that well-formulated moisturizing skin care products can restore disturbed barrier function that can be assessed by transepidermal water loss (TEWL) measurements. When ceramides and/or other barrier lipids are incorporated, it is, however, not always clearly demonstrated which ingredients of the formulation exert the beneficial effects.

OBJECTIVES

In this study the effects of topically applied ceramide-containing mixtures on the barrier repair of sodium lauryl sulphate (SLS)- and acetone-induced skin damage have been studied in human volunteers. TEWL and stratum corneum hydration measurements were carried out. The emulsions applied contained either a mixture of two types of ceramides, CerIII and CerIIIB (emulsion 1) or a complete mixture of ceramides III, IIIB and VI together with phytosphingosine, cholesterol and the free fatty acid linoleic acid (emulsion 2).

RESULTS

After SLS damage, it was observed that barrier recovery was significantly accelerated by topical application (14 days, 2 x/d) of emulsion 2 compared with the results obtained with emulsion 1. Corneometrical results were not relevant due to the occurrence of scaly fissured skin, failing to provide a good skin/probe contact. Although no effect on TEWL could be observed, the improvement of skin hydration after acetone treatment and a single application of the emulsions, was significantly more positive for emulsion 2 than for emulsion 1.

CONCLUSIONS

The investigative methods used in this study show that ceramides combined with other skin lipids can improve barrier repair after damage.

Topical corticosteroid therapy for acute radiation dermatitis: a prospective, randomized, double-blind study

BACKGROUND

Radiation dermatitis is a common side-effect of radiation therapy, but there is no current consensus about its appropriate therapy.

OBJECTIVES

To compare treatment with topical 0.1% methylprednisolone vs. 0.5% dexpanthenol in a cohort of patients undergoing fractionated radiation therapy for breast cancer.

METHODS

In a randomized, double-blind design, treatment was initiated at the beginning of radiation therapy and continued for 2 weeks after termination of radiation. Outcomes were compared by three different measures: clinical (symptom score), functional (transepidermal water loss, TEWL) and subjective (quality of life, QOL).

RESULTS

In a preliminary cohort of untreated patients undergoing radiation therapy, clinical signs and TEWL levels increased progressively during radiation therapy, reaching highest values at 5 and 4 weeks, respectively. Although neither topical treatment reduced the incidence of radiation dermatitis, both delayed the emergence of greatest clinical and TEWL scores until approximately 6 and 5 weeks, respectively. With topical corticosteroids, clinical symptoms and TEWL were less pronounced than with dexpanthenol. Whereas general QOL improved after completion of radiation therapy, skin-related QOL declined. However, the skin-related QOL decline could be at least in part reversed by use of topical corticosteroid vs. dexpanthenol-containing emollient.

CONCLUSIONS

We provide evidence that prophylactic and ongoing use of topical therapy with either topical corticosteroid or a dexpanthenol-containing emollient ameliorates, but does not prevent radiation dermatitis. Our data suggest, but do not prove, a benefit of a topical corticosteroid vs. a dexpanthenol-containing emollient. Further controlled studies with larger cohorts will be needed to determine optimal forms of topical therapy for radiation dermatitis.

Localization of sphingomyelin during the development of dorsal and tail epidermis of mice

BACKGROUND

The water permeability barrier of the stratum corneum seems to be regulated primarily by lamellar bodies situated between the corneocytes; the lamellar bodies originate largely from polar lipid precursors, mainly sphingomyelin (SM), provided by the cells of the stratum granulosum via exocytosis of their lamellar body content.

OBJECTIVES

The aim of our study was to evaluate the cellular distribution of SM during development of the epidermis. Methods In this study, we investigated the expression and localization of SM in both adult and fetal mouse skin by a cytochemical detection method, immunofluorescence microscopy and immunoelectron microscopy, using anti-SM antibody, a specific binding protein to SM (lysenin), and Nile red stain. In addition, we measured transepidermal water loss to estimate the barrier function of the fetal skin.

RESULTS

We observed that SM was widely distributed from the basal layer to the granular layer in the adult mouse epidermis. An intense cytochemical reaction for SM was observed on embryonic day E14.5 of gestation just before the differentiation of the granular and squamous cells from the intermediate cells. The immunofluorescence indicating SM was detected in two regions, i.e. the most superficial zone of the granular layer and the upper spinous layer after the cell differentiation at the late gestational age. This distribution was not detected by conventional lipid staining, such as with Nile red stain. Immunoelectron microscopy revealed that SM was mainly localized in the intercellular spaces of the adult mouse epidermis and in the intracellular vesicles without a complete lamellar structure in the cytoplasm of epidermal cells of E14.5 fetuses. It is well known that the formation of the structurally mature cornified cell envelope occurs at E15.5 of development. The skin of fetuses at E16.5 showed a definite barrier function.

CONCLUSIONS

These findings suggest that SM dynamics is related to the formation of the lipid envelope, cell differentiation, and epidermal barrier function during development.

Basis of occlusive therapy in psoriasis: correcting defects in permeability barrier and calcium gradient

BACKGROUND

Although occlusive dressings have great potential in the management of psoriasis vulgaris, the therapeutic mechanism is not completely understood. Occlusion artificially restores and corrects the defective barrier in psoriasis plaques. Additionally, occlusion is know to normalize the epidermal calcium gradients in hyperproliferative murine skin models.

METHODS

To investigate the basis of the therapeutic effect of occlusion on psoriatic plaques, we investigated the ultrastructural morphology of intercorneocyte lipid layers, lamellar bodies, and calcium gradient in chronic plaque-type psoriasis after occlusion with a water vapor-impermeable membrane. The specimens were processed for electron microscopy using: (i) ruthenium tetroxide postfixation; and (ii) ion-capture cytochemistry for calcium localization.

RESULTS

Occlusion for 7 days resulted in a nearly mature pattern of intercellular multilamellar structures, re-establishment of the near-normal epidermal calcium gradient, and disappearance of calcium precipitates from the stratum corneum interstices.

CONCLUSIONS

The normalization of the permeability barrier and epidermal calcium gradient may play important roles in the therapeutic effects of occlusive dressings in chronic plaque-type psoriasis.

The activity of fatty acid synthase of epidermal keratinocytes is regulated in the lower stratum spinousum and the stratum basale by local inflammation rather than by circulating hormones

The epidermal keratinocytes produce and secrete lipids to maintain the water barrier of the epidermis. To clarify the regulation of epidermal lipid synthesis, we investigated the hormonal effect on the activity of fatty acid synthase (FAS) of the keratinocytes, and the expression of FAS in the human skin. In cultured keratinocytes, the FAS activity, assayed by measuring the oxidation of NADPH, was slightly increased by hydrocortisone or testosterone, but not influenced by thyroid hormone, estrogen, progesterone or insulin. In immunohistochemical study of normal human epidermis, FAS was expressed strongly in the stratum granulosum and moderately in the uppermost layer of the stratum spinousum (SS), suggesting that fatty acid synthesis may increase during normal epidermal differentiation. In inflammatory disorders, such as psoriasis, lichen planus, and atopic dermatitis, FAS was also expressed in the lower SS and the stratum basale (SB), resulting in strong staining in the whole layers of the epidermis. Remarkable increase of FAS expression was only observed in the lower SS and the SB. Therefore, the activity of FAS in the epidermis may be regulated in the lower SS and the SB by local inflammation rather than by circulating hormones. In other components of the skin, FAS was strongly expressed not only in adipose tissue and sebaceous glands, which are known as active sites of lipid synthesis, but also in sweat glands, suggesting that the sweat glands can synthesize abundant fatty acids de novo.

Overexpression of CD1d by keratinocytes in psoriasis and CD1d-dependent IFN-gamma production by NK-T cells

The MHC class I-like protein CD1d is a nonpolymorphic molecule that plays a central role in development and activation of a subset of T cells that coexpress receptors used by NK cells (NK-T cells). Recently, T cells bearing NK receptors were identified in acute and chronic lesions of psoriasis. To determine whether NK-T cells could interact with epidermal cells, we examined the pattern of expression of CD1d in normal skin, psoriasis, and related skin disorders, using a panel of CD1d-specific mAbs. CD1d was expressed by keratinocytes in normal skin, although expression was at a relatively low level and was generally confined to upper level keratinocytes immediately beneath the lipid-rich stratum corneum. In contrast, there was overexpression of CD1d in chronic, active psoriatic plaques. CD1d could be rapidly induced on keratinocytes in normal skin by physical trauma that disrupted barrier function or by application of a potent contact-sensitizing agent. Keratinocytes displayed enhanced CD1d following exposure to IFN-gamma. Combining CD1d-positive keratinocytes with human NK-T cell clones resulted in clustering of NK-T cells, and while no significant proliferation ensued, NK-T cells became activated to produce large amounts of IFN-gamma. We conclude that CD1d can be expressed in a functionally active form by keratinocytes and is up-regulated in psoriasis and other inflammatory dermatoses. The ability of IFN-gamma to enhance keratinocyte CD1d expression and the subsequent ability of CD1d-positive keratinocytes to activate NK-T cells to produce IFN-gamma, could provide a mechanism that contributes to the pathogenesis of psoriasis and other skin disorders.

Alterations in stratum corneum lipid liposomes due to the action of triton X-100. Influence of the level of ceramides on this process

The role played by the ceramides (Cer) in the interaction of Triton X-100 (T(X-100)) with liposomes modeling the stratum corneum (SC) lipid composition was studied. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase partition coefficients (K) were determined at sublytic level by monitoring the changes in the fluorescence intensity of liposomes due to the 5(6)-carboxyfluorescein (CF) released from the interior of vesicles. Higher and lower Cer proportions than those existing in the SC (40%) led respectively to a fall and to a rise in the surfactant ability to alter these liposomes. However, the surfactant partitioning between bilayers and water (bilayer affinity with vesicles) exhibited a maximum for 40% Cer. Thus, at low Cer proportions the ability of T(X-100) molecules to alter these bilayers was maximum despite their reduced partitioning into bilayers, in line with the reported interaction of the anionic surfactant model sodium dodecyl sulfate with these vesicles. These findings underline the fragility of these bilayers as an effective barrier and could explain in part the reported dependencies of low level of Cer in skin lipids and function barrier abnormalities. The fact that the free surfactant concentration needed to achieve the two interaction levels investigated was lower than the surfactant CMC indicates that permeability alterations were mainly ruled by the action of surfactant monomers, regardless of Cer proportion in bilayers.

Galactocerebroside and not glucocerebroside or ceramide stimulate epidermal beta-glucocerebrosidase activity

Glycosphingolipids including glucocerebroside (GluCer) and galactocerebroside (GalCer) have been recognized as bioreguratory lipids by our group and others. In addition, our recent study demonstrated that GalCer corrects dry skin conditions in humans. The processing of stratum corneum lipids, which occurs when beta-glucocerebrosidase (beta-GluCer'ase) changes GluCer to ceramide (Cer), is required to form the epidermal permeability barrier. We herein investigated the effects of GluCer, GalCer and Cer on the processing of GluCer to Cer by assaying epidermal beta-GluCer'ase in mice (155%, P < 0.01) when compared to vehicle treated controls, while neither GluCer nor Cer had this effect. Studies using inhibitors of beta-GluCer'ase or beta-galactosidase and measuring the optimum pH of the enzyme verified that GalCer specifically activated beta-GluCer'ase. We confirmed that GalCer significantly increased beta-GluCer'ase activity in the outer epidermal fraction (172%, P < 0.01) and that the activation of beta-GluCer'ase is not due to a direct activating effect of GalCer on the enzyme. Furthermore, the induction of beta-GluCer'ase activity by GalCer was also observed in cultured normal human deratinocytes (123%, P < 0.01). Finally, acylceramide content in stratum corneum was increased in mice treated with GalCer (194%, P < 0.0005). These results indicate that GalCer appears to affect the Cer construct in the stratum corneum by the activation of beta-GluCer'ase, which ultimately contribute to an enhancement of barrier formation.

Effect of a chemically-synthesized acylglucosylceramide, epidermoside, on normal human keratinocyte differentiation

Epidemosides (N-(0-linoleoyl)-(1)-hydroxy fatty acyl sphingosyl glucose) are found exclusively in the epidermis not in dermis, and are thought to play important role in forming the mammalian epidermal permeability barrier. A species of epidermoside isolated from guinea pig epidermis and named lipokeratinogenoside has been shown to enhance fetal rat keratinocyte differentiation. In the present investigation, we studied the effects of a chemically synthesized equivalent of human epidermoside on the viability and differentiation of cultured human keratinocytes (HK Cells). The chemically-synthesized epidermoside was not toxic to cultured HK Cells at concentrations of 0.01 to 10 micrograms/ml. When 10 micrograms/ml of the chemically-synthesized epidermoside was added to keratinocyte growth medium containing 1.2 mM Ca2+, HK Cells showed a 5.6-fold increase of keratin content compared to the vehicle treated control at 144 h of cultivation, and they also displayed morphological changes suggestive of differentiation. A similar increase of cellular keratin content was observed in HK cells treated with tetradecanoyl phorbol-13 myristyl-12 acetate (TPA), an agent known to enhance the differentiation of keratinocytes. Lipokeratinogenoside also increased the keratin content of cultured HK cells. These results suggest that epidermosides have an ability to enhance keratinocyte differentiation. Epidermoside could thus be a key molecule, not only as a constituent of the epidermal permeability barrier, but also as a regulator of keratinocyte differentiation.