Cytokine profile of the stratum corneum in atopic dermatitis lesions differs between the face and the trunk.

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disease with intense pruritus. Dupilumab, an anti-IL-4 receptor alpha antibody, has been revealed to be highly effective against the symptoms of AD; however, dupilumab takes longer to improve facial dermatitis in some patients. We thus examined whether the cytokine profiles in AD lesions differ between different anatomical locations. METHODS: Stratum corneum was collected by tape stripping from lesions of the forehead and abdomen of 24 patients with moderate to severe AD and at the same anatomical locations of 14 control subjects. These samples were then used to determine the expression profiles of Th1, Th2, and Th17 cytokines/chemokines by multiplex assay and immunocytochemistry. RESULTS: We found that cytokines/chemokines in the stratum corneum differed in their expression between different anatomical areas in AD patients and also in healthy control subjects. The expression of Th1 and Th17 cytokines/chemokines such as IP-10, MIG, and IL-17 tended to be higher in the forehead than in the abdomen in the AD group. Regarding Th2 cytokines/chemokines, some (e.g., IL-13 and IL-33) were highly expressed in the abdomen, others (e.g., IL-4 and IL-31) were highly expressed in the forehead, and a third group (e.g., TARC and TSLP) did not differ significantly in their expression between the forehead and abdomen. These patterns of Th2 cytokines were almost identical in the stratum corneum of healthy individuals. CONCLUSIONS: Differences in cytokine/chemokine profiles in the stratum corneum between different anatomical areas might affect the responsiveness to AD treatment.

Ninjurin1 Deletion in NG2-Positive Pericytes Prevents Microvessel Maturation and Delays Wound Healing.

The formation of mature vasculature through angiogenesis is essential for adequate wound healing, such that blood-borne cells, nutrients, and oxygen can be delivered to the remodeling skin area. Neovessel maturation is highly dependent on the coordinated functions of vascular endothelial cells and perivascular cells, namely pericytes (PCs). However, the underlying mechanism for vascular maturation has not been completely elucidated, and its role in wound healing remains unclear. In this study, we investigated the role of Ninjurin-1 (Ninj1), a new molecule mediating vascular maturation, in wound healing using an inducible PC-specific Ninj1 deletion mouse model. Ninj1 expression increased temporarily in NG2-positive PCs in response to skin injury. When tamoxifen treatment induced a decreased Ninj1 expression in PCs, the neovessels in the regenerating wound margins were structurally and functionally immature, but the total number of microvessels was unaltered. This phenotypic change is associated with a reduction in PC-associated microvessels. Wound healing was significantly delayed in the NG2-specific Ninj1 deletion mouse model. Finally, we showed that Ninj1 is a crucial molecule that mediates vascular maturation in injured skin tissue through the interaction of vascular endothelial cells and PCs, thereby inducing adequate and prompt wound healing.

Gender disparities in academic dermatology in Japan: Results from the first national survey.

BACKGROUND: A wide gender gap exists in many fields in Japan, including the academic society of dermatology. Women are substantially underrepresented in the highest academic ranks. OBJECTIVE: We aimed to clarify the possible factors contributing to the current gender gap in the field of academic dermatology and to recommend necessary measures to decrease the gender gap. METHODS: We performed a cross-sectional study of faculty members' academic productivity at the dermatology departments of all the educational institutions in Japan in 2019. RESULTS: Women had significantly lower academic productivity than men. A significant gender difference in academic productivity was found in lecturers and assistant professors but not in associate professor and professor positions. This gender difference was still significant after normalizing the productivity for career length. CONCLUSION: Our findings suggest the need to encourage women lecturers and assistant professors to improve their academic achievement to decrease the gender gap in academic dermatology.

Inclusion bodies are not uncommon in angioleiomyoma.

BACKGROUND: Leiomyomas with eosinophilic intracytoplasmic inclusion bodies have been described in the urinary bladder, brain, gastrointestinal tract, uterus, and oral cavity but not in the skin. Prompted by our recent experience with a case of cutaneous angioleiomyoma with many inclusion bodies, we hypothesized that similar cases might have been previously overlooked. METHODS: We retrospectively reviewed 30 cases of angioleiomyoma and 10 cases of piloleiomyoma focusing on inclusion bodies. RESULTS: More than 18 inclusion bodies per 250 µm squared were detected in five cases of angioleiomyoma, fewer than 11 bodies in 20 cases, and none in five cases. For the case with numerous inclusion bodies throughout the specimen, special staining was needed to make a diagnosis. No inclusion bodies were found in the piloleiomyomas. CONCLUSION: Inclusion bodies are relatively common in angioleiomyomas and can occasionally be numerous. They may serve as a point of distinction from piloleiomyomas. Because the presence of multiple eosinophilic intracytoplasmic inclusions can result in a rhabdoid appearance and make diagnosis challenging, we should be aware of this feature in angioleiomyomas.

Sphingosine 1-Phosphate Receptor 2 Is Central to Maintaining Epidermal Barrier Homeostasis.

The outer layer of the epidermis composes the skin barrier, a sophisticated filter constituted by layers of corneocytes in a lipid matrix. The matrix lipids, especially the ceramide-generated sphingosine 1-phosphate, are the messengers that the skin barrier uses to communicate with the basal layer of the epidermis where replicating keratinocytes are located. Sphingosine 1-phosphate is a bioactive sphingolipid mediator involved in various cellular functions through S1PR1‒5, expressed by keratinocytes. We discovered that the S1pr2 absence is linked to an impairment in the skin barrier function. Although S1pr2-/- mouse skin has no difference in its phenotype and barrier function compared with that of wild-type mouse, after tape stripping, S1pr2-/- mouse showed significantly higher transepidermal water loss and required another 24 hours to normalize their transepidermal water loss levels. Moreover, after epicutaneous Staphylococcus aureus application, impaired S1pr2-/- mouse epidermal barrier function allowed deeper bacterial penetration and denser neutrophil infiltration in the dermis. Microarray and RNA sequence of S1pr2-/- mouse epidermis linked the barrier dysfunction with a decrease in FLG2 and tight junction components. In conclusion, S1pr2-/- mice have compromised skin barrier function and increased bacteria permeability, making them a suitable model for diseases that present similar characteristics, such as atopic dermatitis.

Lipocalin 2: A New Antimicrobial in Mast Cells.

Mast cells (MCs) play a significant role in the innate immune defense against bacterial infection through the release of cytokines and antimicrobial peptides. However, their antimicrobial function is still only partially described. We therefore hypothesized that MCs express additional antimicrobial peptides. In this study, we used FANTOM 5 transcriptome data to identify for the first time that MCs express lipocalin 2 (LCN2), a known inhibitor of bacterial growth. Using MCs derived from mice which were deficient in LCN2, we showed that this antimicrobial peptide is an important component of the MCs' antimicrobial activity against Escherichia coli (E. coli). Since sphingosine-1-phosphate receptors (S1PRs) on MCs are known to regulate their function during infections, we hypothesized that S1P could activate LCN2 production in MCs. Using an in vitro assay, we demonstrated that S1P enhances MCs antimicrobial peptide production and increases the capacity of MCs to directly kill S. aureus and E. coli via an LCN2 release. In conclusion, we showed that LCN2 is expressed by MCs and plays a role in their capacity to inhibit bacterial growth.

Human Keratinocytes Use Sphingosine 1-Phosphate and its Receptors to Communicate Staphylococcus aureus Invasion and Activate Host Defense.

Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator generated when a cell membrane or its components are damaged by various factors. S1P regulates diverse cell activities via S1P receptors (S1PRs). Keratinocytes express S1PR1-5. Although it is known that S1PRs control keratinocyte differentiation, apoptosis, and wound healing, S1PR functions in keratinocyte infections have not been fully elucidated. We propose that the S1P-S1PR axis in keratinocytes works as a biosensor for bacterial invasion. Indeed, in human impetigo infection, we found high epidermal expression of S1PR1 and S1PR2 in the skin. Furthermore, in normal human epidermal keratinocytes in vitro, treatment with Staphylococcus aureus bacterial supernatant not only induced S1P production but also increased the transcription of S1PR2, confirming our in vivo observation, as well as increased the levels of TNFA, IL36G, IL6, and IL8 mRNAs. However, direct treatment of normal human epidermal keratinocytes with S1P increased the expressions of IL36G, TNFA, and IL8, but not IL6. In both S1P- and S. aureus bacterial supernatant-treated normal human epidermal keratinocytes, S1PR1 knockdown reduced IL36G, TNFA, and IL8 transcription, and the S1PR2 antagonist JTE013 blocked the secretion of these cytokines. Overall, we have proven that during infections, keratinocytes communicate damage by using S1P release and tight control of S1PR1 and 2.

Severe thiopurine-induced leukocytopenia and hair loss in Japanese patients with defective NUDT15 variant: Retrospective case-control study.

Azathioprine (AZA)-metabolizing enzyme gene polymorphism is strongly related to thiopurine-induced leukocytopenia, which has not been well recognized in dermatological practice. We tried to see whether NUDT15 gene polymorphism can be the most susceptible genetic factor for AZA toxicity and the gene screening is beneficial to avoid the adverse events of AZA for the treatment of skin diseases. A retrospective study was carried out on 15 adult Japanese patients who were treated with AZA. Gene polymorphism of thiopurine-metabolizing enzymes NUDT15 R139C, ITPA 94C>A, TPMT*2, TPMT*3B and TPMT*3C was analyzed. The single nucleotide polymorphisms were prospectively investigated in eight patients who were considered to have received AZA treatments. Two NUDT15 R139C homozygous patients developed agranulocytosis, severe thrombocytopenia and massive hair loss. The gene screening prior to AZA treatment identified one heterozygote of NUDT15 R139C and ITPA 94C>A, and three heterozygotes of ITPA 94C>A or TMPT*3C. Although this study was a retrospective single-center case-control observational study that enrolled a small number of patients, NUDT15 R139C homozygosity is a genetic risk of thiopurine-induced potentially fetal hematological abnormalities. To avoid serious adverse events, gene screening of thiopurine-metabolizing enzymes, at least NUDT15 R139C, should be considered prior to administration in genetically predisposed populations, such as Japanese. We highlight that massive hair loss in the early period of the initiation of AZA would be a sign of impending severe myelotoxicity.

Molecular basis of the skin barrier structures revealed by electron microscopy.

The barrier function of skin is indispensable for terrestrial animals. This function is mainly carried out by the epidermis, more specifically by its granular and cornified layers. The major structural components associated with this function are the intercellular lipid layer, desmosomes, corneodesmosomes, tight junctions, cornified cell envelope and keratin filaments. In this review, we discuss the current knowledge of their ultrastructure, their molecular basis and their relevance to skin disease.

RIPK1 downregulation in keratinocyte enhances TRAIL signaling in psoriasis.

BACKGROUND: Psoriasis, a common inflammatory skin disorder characterized by scaly erythema and plaques, is induced by dysregulation of dendritic cell- and T cell-mediated immune reaction. Receptor-interacting protein kinase 1 (RIPK1) regulates inflammatory signaling in response to stimuli such as TNF-α, TRAIL, and TLRs, resulting in apoptosis, necroptosis and NF-κB activation. However, the physiological relevance in human epidermis remains elusive. OBJECTIVE: In this study, we examined whether RIPK1 is involved in the pathogenesis of psoriasis vulgaris. METHODS: Skin samples of eight patients with psoriasis vulgaris were investigated by western blotting and immunohistochemistry. The functions of RIPK1 in keratinocytes were examined by RT-PCR and ELISA in vitro. TRAIL-neutralization-experiment was employed in an imiquimod-induced murine psoriasis model. RESULTS: In lesional psoriatic epidermis, RIPK1-expression was decreased compared with that in normal epidermis. Cytokines involved in the pathomechanism of psoriasis, such as IL-1ß, IL-17A, IL-22 and TRAIL, reduced RIPK1-expression in normal human epidermal keratinocytes (HEK) in vitro. In addition, RIPK1-knockdown enhanced TRAIL-mediated expression of psoriasis-relating cytokines, such as IL-1ß, IL-6, IL-8, TNF-α, in HEK. Numerous TRAIL-positive cells were detected in the dermis of lesional psoriatic skin, and TRAIL receptors were expressed in psoriatic epidermis and HEK in conventional cultures. Moreover, TRAIL-neutralization in an imiquimod-induced murine psoriasis model remarkably improved skin phenotypes, such as ear thickness, and TNF-α expression in lesional skin. CONCLUSIONS: These results lead us to conclude that RIPK1-downregulation in keratinocytes increases their susceptibility to TRAIL stimulation, and plays a role in the pathogenesis of psoriasis vulgaris.

Clinical and molecular implications of structural changes to desmosomes and corneodesmosomes.

Desmosomes provide the main intercellular adhesive properties between epidermal keratinocytes. Their distribution becomes uneven in severe dermatitis, multiple allergies and metabolic wasting syndrome due to desmoglein 1 deficiency and the loss of intercellular adhesion or acantholysis. When keratinocytes differentiate from granular cells into cornified cells, desmosomes are transformed into corneodesmosomes and can provide stronger intercellular adhesion. Degradation of corneodesmosomes is a tightly regulated process involving a number of proteases and their inhibitors. Peripheral corneodesmosomes are protected from proteolytic degradation by the tight junction-related structures around them, and this construction provides the basis for the normal basket weave-like structure of the stratum corneum. In Netherton syndrome, which is caused by an absence of the protease inhibitor lymphoepithelial Kazal-type-related inhibitor, premature degradation of corneodesmosomes occurs due to the overactivation of proteases involved in corneodesmosome degradation. Inflammatory peeling skin disease is caused by the absence of corneodesmosin, a unique component of corneodesmosomes. In this disease, corneodesmosomes are structurally abnormal, and their adhesiveness is compromised, which leads to intercellular splitting between the stratum corneum and stratum granulosum. The better we understand desmosome and corneodesmosome ultrastructure in normal and diseased skin, the clearer the physiological and pathological mechanisms of epidermal integrity become.

Skin microbiome and mast cells.

Microbiotas in the skin have high levels of diversity at the species level, but low phylum-level diversity. The human skin microbiota is composed predominantly of Gram-positive bacteria especially Actinobacteria, which are the dominant bacterial phylum on the skin. Lipoteichoic acid (LTA) is a major constituent of the cell wall of Gram-positive bacteria and is therefore abundant in the skin microbiome. Recent studies have shown that LTA, and other bacterial products, permeates the whole skin and comes into contact with epidermal and dermal cells, including mast cells (MCs), with the potential of stimulating MC toll-like receptors (TLRs). MCs express a variety of pattern recognition receptors, including TLRs, on their cell surface in order to detect bacteria. Recent publications suggest that the skin microbiome has influence on MC migration, localization and maturation in the skin. Germ free (no microbiome) animals possess an underdeveloped immune system and immature MCs. Despite much research done on skin microbiota and many papers describing skin interaction with "the good microbiota", there is still controversy regarding how mast cells, communicate with surface bacteria. The present review intends to quell the controversy by illuminating the communication mechanism between bacteria and MCs.

Incomplete KLK7 Secretion and Upregulated LEKTI Expression Underlie Hyperkeratotic Stratum Corneum in Atopic Dermatitis.

Atopic dermatitis (AD) is a common inflammatory skin disorder. Chronic AD lesions present hyperkeratosis, indicating a disturbed desquamation process. KLK7 is a serine protease involved in the proteolysis of extracellular corneodesmosome components, including desmocollin 1 and corneodesmosin, which leads to desquamation. KLK7 is secreted by lamellar granules and upregulated in AD lesional skin. However, despite increased KLK7 protein levels, immunostaining and electron microscopy indicated numerous corneodesmosomes remaining in the uppermost layer of the stratum corneum from AD lesions. We aimed to clarify the discrepancy between KLK7 overexpression and retention of corneodesmosomes on AD corneocytes. Western blot analysis indicated abnormal corneodesmosin degradation patterns in stratum corneum from AD lesions. The KLK activity of tape-stripped corneocytes from AD lesions was not significantly elevated in in situ zymography, which was our new attempt to detect the protease activity more precisely than conventional assays. This ineffective KLK activation was associated with impaired KLK7 secretion from lamellar granules and increased expression of LEKTI in AD. Such imbalances in protease-protease inhibitor interactions could lead to abnormal proteolysis of corneodesmosomes and compact hyperkeratosis. Upregulated expression of LEKTI might be a compensatory mechanism to prevent further barrier dysfunction in AD.