Alterations in the desquamation-related proteolytic cleavage of corneodesmosin and other corneodesmosomal proteins in psoriatic lesional epidermis

The Efficacy and Safety of Pimecrolimus in Patients With Facial Seborrheic Dermatitis: A Systematic Review of Randomized Controlled Trials

Facial seborrheic dermatitis (SD) is a chronic inflammatory skin condition that can affect the quality of life with frequent recurrences. There is no medication as yet to cure this disease completely. There are four general categories of agents that are used to treat SD: antifungal agents, keratolytics, corticosteroids, and lastly calcineurin inhibitors. Topical therapies are the mainstream line of treatment to be used for this skin condition.

The objective of this article is to critically review the published data in the literature on the use of topical pimecrolimus 1% topical cream as an option for treating facial SD. The final purpose of this review is to answer two questions: whether pimecrolimus topical cream is effective for the treatment of SD compared to the conventional current treatments and how safe is this treatment. 

The PubMed, Clinicaltrials.gov, MEDLINE + Embase, and Cochrane library databases were searched for original randomized clinical trials (RCTs) evaluating pimecrolimus 1% topical cream and comparing it with other topical treatments for SD. A systematic review and meta-analysis were then conducted on the selected studies by grading the evidence and qualitative comparison of results among and within studies. A total of five studies were included in the review; however, only four were eligible for inclusion in the meta-analysis, in which pimecrolimus was compared with other treatments for the management of facial SD.

Pimecrolimus was found to be an effective topical treatment for facial SD, as it showed considerable desirable control of the symptoms in patients with facial SD clinically, in addition to a lower recurrence or relapsing rates; however, it had more side effects compared to other topical treatments, but the side effects were mild and tolerable.

Loricrin and NRF2 Coordinate Cornification

Cornification involves cytoskeletal cross-linkages in corneocytes (the brick) and the secretion of lipids/adhesion structures to the interstitial space (the mortar). Because the assembly of lipid envelopes precedes corneocyte maturation, loricrin is supposed to be dispensable for the protection against desiccation. Although the phenotypes of Lor knockout (LKO) mice are obscure, the antioxidative response on the KEAP1/NRF2 signaling pathway compensates for the structural defect in utero. In this study, we asked how the compensatory response is evoked after the defects are repaired. To this end, the postnatal phenotypes of LKO mice were analyzed with particular attention to the permeability barrier function primarily maintained by the mortar. Ultrastructural analysis revealed substantially thinner cornified cell envelopes and increased numbers of lamellar granules in LKO mice. Superficial epidermal damages triggered the adaptive repairing responses that evoke the NRF2-dependent upregulation of genes associated with lamellar granule secretion in LKO mice. We also found that corneodesmosomes are less degraded in LKO mice. The observation suggests that loricrin and NRF2 are important effectors of cornification, in which proteins need to be secreted, cross-linked, and degraded in a coordinated manner.

The Epidermis: Redox Governor of Health and Diseases

A functional epithelial barrier necessitates protection against dehydration, and ichthyoses are caused by defects in maintaining the permeability barrier in the stratum corneum (SC), the uppermost protective layer composed of dead cells and secretory materials from the living layer stratum granulosum (SG). We have found that loricrin (LOR) is an essential effector of cornification that occurs in the uppermost layer of SG (SG1). LOR promotes the maturation of corneocytes and extracellular adhesion structure through organizing disulfide cross-linkages, albeit being dispensable for the SC permeability barrier. This review takes psoriasis and AD as the prototype of impaired cornification. Despite exhibiting immunological traits that oppose each other, both conditions share the epidermal differentiation complex as a susceptible locus. We also review recent mechanistic insights on skin diseases, focusing on the Kelch-like erythroid cell-derived protein with the cap "n" collar homology-associated protein 1/NFE2-related factor 2 signaling pathway, as they coordinate the epidermis-intrinsic xenobiotic metabolism. Finally, we refine the theoretical framework of thiol-mediated crosstalk between keratinocytes and leukocytes in the epidermis that was put forward earlier.

Skin Barrier Dysregulation in Psoriasis

The skin barrier is broadly composed of two elements-a physical barrier mostly localised in the epidermis, and an immune barrier localised in both the dermis and epidermis. These two systems interact cooperatively to maintain skin homeostasis and overall human health. However, if dysregulated, several skin diseases may arise. Psoriasis is one of the most prevalent skin diseases associated with disrupted barrier function. It is characterised by the formation of psoriatic lesions, the aberrant differentiation and proliferation of keratinocytes, and excessive inflammation. In this review, we summarize recent discoveries in disease pathogenesis, including the contribution of keratinocytes, immune cells, genetic and environmental factors, and how they advance current and future treatments.

Tape strips in dermatology research

Tape strips have been used widely in dermatology research as a minimally invasive method to sample the epidermis, avoiding the need for skin biopsies. Most research has focused on epidermal pathology, such as atopic eczema, but there is increasing research into the use of tape strips in other dermatoses, such as skin cancer, and the microbiome. This review summarizes the technique of tape stripping, and discusses which dermatoses have been studied by tape stripping and alternative minimally invasive sampling methods. We review the number of tape strips needed from each patient and the components of the epidermis that can be obtained by tape stripping. With a focus on protein and RNA extraction, we address the techniques used to process tape strips. There is no optimal protocol to extract protein, as this depends on the abundance of the protein studied, its level of expression in the epidermis and its solubility. Many variables can alter the amount of protein obtained from tape strips, which must be standardized to ensure consistency between samples. No study has compared different RNA extraction techniques, but our own experience is that RNA yield is optimized by using 20 tape strips and the use of a cell scraper.

A Timosaponin B-II containing scalp care solution for improvement of scalp hydration, dandruff reduction, and hair loss prevention: A comparative study on healthy volunteers before and after application

BACKGROUND

The plant species Anemarrhena asphodeloides has commonly been used for health and therapeutic purposes. Timosaponin B-II, which is present at a high concentration in A asphodeloides, was found to enhance the immune and anti-inflammatory responses of human bodies.

AIMS

To evaluate benefits of a timosaponin B-II containing scalp care solution on hair loss prevention and scalp healthiness in multiple physiological and biological profiles.

METHODS

Prior the study, 90 subjects applied scalp care solution base without timosaponin B-II for two weeks followed by application of the scalp care solution containing 0.5% timosaponin B-II for 28 days. The subject's hair follicle hydrocortisone level, hair fall number, hair luster level, dandruff level, sensation score, hydration level, lipid level, redness as well as the pH level of scalps were quantitatively assessed every 7 days.

RESULTS

Multiple parameters on hair and scalp conditions were promoted by application of the timosaponin B-II containing scalp care solution. Compared to baseline values, significant improvements in hair luster, scalp hydration, hair fall number, and scalp redness level could be observed.

CONCLUSION

Timosaponin B-II promotes multiple physiological factors on hair and scalps. The scalp care solution containing A asphodeloides extracts may benefit the scalp healthiness and hair loss prevention.

Skin characteristics associated with foot callus in people with diabetes: A cross-sectional study focused on desmocollin1 in corneocytes

AIM

The purpose of this study was to investigate the degradation of desmocollin-1 (DSC1), a member of the desmosomal cadherin family in patients with diabetes, as well as the factors associated with the suppression of DSC1 degradation.

METHODS

This cross-sectional study included 60 cases of foot callus involving 30 patients with diabetes (DM) and 30 matched volunteers without diabetes (non-DM). DSC1 degradation in samples from debrided calluses was analysed using western blotting. Skin hydration, a factor reported to suppress DSC1 degradation, was measured using a mobile moisture device.

RESULTS

Full-length DSC1 (approximately 100 kDa) was detected in six participants only in the DM group, and no relationship was found between the suppression of DSC1 degradation and decreased skin hydration in the DM group. There was no significant difference in skin hydration values between the DM and non-DM groups.

CONCLUSION

DSC1 degradation was suppressed in the DM group. There was no relationship between the suppression of DSC1 degradation and decreased skin hydration in the DM group. Current external force callus care would not be sufficient. This study highlights the need to develop novel callus care to enhance the degradation of DSC1.

Quantitation of peptides from non-invasive skin tapings using isotope dilution and tandem mass spectrometry

Previous work from our laboratories utilized a novel skin taping method and mass spectrometry-based proteomics to discover clinical biomarkers of skin conditions; these included atopic dermatitis, Staphylococcus aureus colonization, and eczema herpeticum. While suitable for discovery purposes, semi-quantitative proteomics is generally time-consuming and expensive. Furthermore, depending on the method used, discovery-based proteomics can result in high variation and inadequate sensitivity to detect low abundant peptides. Therefore, we strove to develop a rapid, sensitive, and reproducible method to quantitate disease-related proteins from skin tapings. We utilized isotopically-labeled peptides and tandem mass spectrometry to obtain absolute quantitation values on 14 peptides from 7 proteins; these proteins had shown previous importance in skin disease. The method demonstrated good reproducibility, dynamic range, and linearity (R² > 0.993) when n = 3 standards were analyzed across 0.05-2.5 pmol. The method was used to determine if differences exist between skin proteins in a small group of atopic versus non-atopic individuals (n = 12). While only minimal differences were found, peptides were detected in all samples and exhibited good correlation between peptides for 5 of the 7 proteins (R² = 0.71-0.98). This method can be applied to larger cohorts to further establish the relationships of these proteins to skin disease.

Seborrheic Dermatitis and Dandruff: A Comprehensive Review

Seborrheic Dermatitis (SD) and dandruff are of a continuous spectrum of the same disease that affects the seborrheic areas of the body. Dandruff is restricted to the scalp, and involves itchy, flaking skin without visible inflammation. SD can affect the scalp as well as other seborrheic areas, and involves itchy and flaking or scaling skin, inflammation and pruritus. Various intrinsic and environmental factors, such as sebaceous secretions, skin surface fungal colonization, individual susceptibility, and interactions between these factors, all contribute to the pathogenesis of SD and dandruff. In this review, we summarize the current knowledge on SD and dandruff, including epidemiology, burden of disease, clinical presentations and diagnosis, treatment, genetic studies in humans and animal models, and predisposing factors. Genetic and biochemical studies and investigations in animal models provide further insight on the pathophysiology and strategies for better treatment.

Epidermal barrier disorders and corneodesmosome defects

Corneodesmosomes are modified desmosomes present in the stratum corneum (SC). They are crucial for SC cohesion and, thus, constitute one of the pivotal elements of the functional protective barrier of human skin. Expression of corneodesmosomes and, notably, the process of their degradation are probably altered during several dermatoses leading to the disruption of the permeability barrier or to abnormal, often compensative, SC accumulation. These different situations are reviewed in the present paper.

Kallikrein-related peptidase-7 regulates caspase-14 maturation during keratinocyte terminal differentiation by generating an intermediate form

The maturation and activation mechanisms of caspases are generally well understood, except for those of caspase-14, which is activated at the onset of keratinocyte terminal differentiation. We investigated the possible involvement of epidermal proteases expressed in the late stage of differentiation, and found that the chymotrypsin-like serine protease kallikrein-related peptidase-7 (KLK7) cleaved procaspase-14 at Tyr(178), generating an intermediate form that consists of a large (20 kDa) and a small subunit (8 kDa). We prepared an antibody directed to this cleavage site (h14Y178 Ab), and confirmed that it recognized a 20-kDa band formed when procaspase-14 was incubated with chymotrypsin or KLK7. We then constructed a constitutively active form of the intermediate, revC14-Y178. The substrate specificity of revC14-Y178 was completely different from that of caspase-14, showing broad specificity for various caspase substrates except WEHD-7-amino-4-trifluoromethylcoumarin (AFC), the preferred substrate of active, mature caspase-14. K(m) values for VEID-AFC, DEVD-AFC, LEVD-AFC, and LEHD-AFC were 0.172, 0.261, 0.504, and 0.847 μM, respectively. We confirmed that the mature form of caspase-14 was generated when procaspase-14 was incubated with KLK7 or revC14-Y178. Expression of constitutively active KLK7 in cultured keratinocytes resulted in generation of both the intermediate form and the mature form of caspase-14. Immunohistochemical analysis demonstrated that the intermediate form was localized at the granular layer. Our results indicate that regulation of procaspase-14 maturation during terminal differentiation is a unique two-step process involving KLK7 and an activation intermediate of caspase-14.

Stratum corneum dysfunction in dandruff

Synopsis

Dandruff is characterized by a flaky, pruritic scalp and affects up to half the world’s population post-puberty. The aetiology of dandruff is multifactorial, influenced by Malassezia, sebum production and individual susceptibility. The commensal yeast Malassezia is a strong contributory factor to dandruff formation, but the presence of Malassezia on healthy scalps indicates that Malassezia alone is not a sufficient cause. A healthy stratum corneum (SC) forms a protective barrier to prevent water loss and maintain hydration of the scalp. It also protects against external insults such as microorganisms, including Malassezia, and toxic materials. Severe or chronic barrier damage can impair proper hydration, leading to atypical epidermal proliferation, keratinocyte differentiation and SC maturation, which may underlie some dandruff symptoms. The depleted and disorganized structural lipids of the dandruff SC are consistent with the weakened barrier indicated by elevated transepidermal water loss. Further evidence of a weakened barrier in dandruff includes subclinical inflammation and higher susceptibility to topical irritants. We are proposing that disruption of the SC of the scalp may facilitate dandruff generation, in part by affecting susceptibility to metabolites from Malassezia. Treatment of dandruff with cosmetic products to directly improve SC integrity while providing effective antifungal activity may thus be beneficial.

Résumé

Les pellicules se caractérisent par un cuir chevelu prurigineux, squameux, et affectent jusqu’à la moitié de la population post-pubertaire du monde. L’étiologie des pellicules est multifactorielle, influencée par Malassezia, par la production de sébum, et par la susceptibilité individuelle. La levure commensale Malassezia est un facteur fortement contributif à la formation de pellicules, mais la présence de Malassezia aussi sur les cuirs chevelus sains indique que Malassezia seule n’est pas une cause suffisante. Un stratum corneum (SC) sain forme une barrière protectrice pour empêcher la perte d’eau et maintenir l’hydratation du cuir chevelu. Il protège également contre les agressions externes tels les micro-organismes, y compris Malassezia, ou des substances toxiques. Des dommages aigus ou chroniques au niveau de la barrière peuvent nuire à une bonne hydratation, conduisant à des effets atypiques de la prolifération épidermique, de la différenciation des kératinocytes, et de la maturation du SC, ce qui peut expliquer une partie des symptômes des pellicules. L’appauvrissement et la désorganisation des lipides structurels d’un stratum corneum sujet aux pellicules sont compatibles avec la notion d’une barrière affaiblie telle qu’indiquée par une perte d’eau transépidermique élevée. Une preuve supplémentaire d’une barrière affaiblie dans les cas des pellicules est fournie par un niveau d’inflammation infraclinique et une plus grande susceptibilité aux irritants topiques. Nous proposons que la perturbation du SC du cuir chevelu facilite la production de pellicules, en partie en augmentant la sensibilité aux métabolites de Malassezia. Le traitement des pellicules avec des produits cosmétiques pour améliorer directement l’intégrité du SC, tout en offrant une activité antifongique efficace peut donc être bénéfique.

Epidermal ablation of Dlx3 is linked to IL-17-associated skin inflammation

In an effort to understand the role of Distal-less 3 (Dlx3) in cutaneous biology and pathophysiology, we generated and characterized a mouse model with epidermal ablation of Dlx3. K14cre;Dlx3(Kin/f) mice exhibited epidermal hyperproliferation and abnormal differentiation of keratinocytes. Results from subsequent analyses revealed cutaneous inflammation that featured accumulation of IL-17-producing CD4(+) T, CD8(+) T, and γδ T cells in the skin and lymph nodes of K14cre;Dlx3(Kin/f) mice. The gene expression signature of K14cre;Dlx3(Kin/f) skin shared features with lesional psoriatic skin, and Dlx3 expression was markedly and selectively decreased in psoriatic skin. Interestingly, cultured Dlx3 null keratinocytes triggered cytokine production that is potentially linked to inflammatory responses in K14cre;Dlx3(Kin/f) mice. Thus, Dlx3 ablation in epidermis is linked to altered epidermal differentiation, barrier development, and IL-17-associated skin inflammation. This model provides a platform that will allow the systematic exploration of the contributions of keratinocytes to cutaneous inflammation.