Differentially expressed late constituents of the epidermal cornified envelope

Dynamics and Epigenetics of the Epidermal Differentiation Complex

Epidermis is the outer skin layer built of specialized cells called keratinocytes. Keratinocytes undergo a unique differentiation process, also known as cornification, during which their gene expression pattern, morphology and other properties change remarkably to the effect that the terminally differentiated, cornified cells can form a physical barrier, which separates the underlying tissues from the environment. Many genes encoding proteins that are important for epidermal barrier formation are located in a gene cluster called epidermal differentiation complex (EDC). Recent data provided valuable information on the dynamics of the EDC locus and the network of interactions between EDC gene promoters, enhancers and other regions, during keratinocytes differentiation. These data, together with results concerning changes in epigenetic modifications, provide a valuable insight into the mode of regulation of EDC gene expression.

Comparative genomics of monotremes provides insights into the early evolution of mammalian epidermal differentiation genes

The function of the skin as a barrier against the environment depends on the differentiation of epidermal keratinocytes into highly resilient corneocytes that form the outermost skin layer. Many genes encoding structural components of corneocytes are clustered in the epidermal differentiation complex (EDC), which has been described in placental and marsupial mammals as well as non-mammalian tetrapods. Here, we analyzed the genomes of the platypus (Ornithorhynchus anatinus) and the echidna (Tachyglossus aculeatus) to determine the gene composition of the EDC in the basal clade of mammals, the monotremes. We report that mammal-specific subfamilies of EDC genes encoding small proline-rich proteins (SPRRs) and late cornified envelope proteins as well as single-copy EDC genes such as involucrin are conserved in monotremes, suggesting that they have originated in stem mammals. Monotremes have at least one gene homologous to the group of filaggrin (FLG), FLG2 and hornerin (HRNR) in placental mammals, but no clear one-to-one pairwise ortholog of either FLG, FLG2 or HRNR. Caspase-14, a keratinocyte differentiation-associated protease implicated in the processing of filaggrin, is encoded by at least 3 gene copies in the echidna. Our results reveal evolutionarily conserved and clade-specific features of the genetic regulation of epidermal differentiation in monotremes.

Up-Regulated Expression of ICAM1, MT1A, PTGS2, LCE3D, PPARD, and GM-CSF2 Following Solar Skincare Protection and Repair Strategies in a 3-Dimensional Reconstructed Human Skin Model

Background

Clinical, optical and histological research confirms that solar skin damage continues to pose a threat to human skin health globally despite widespread sunscreen usage and sun awareness campaigns. Despite this, very few studies examine the critical changes in gene expression and DNA repair activity following recommended topical solar protection and repair strategies to ameliorate the harmful effects of ultraviolet, visible light and near-infrared radiation.

Purpose

To investigate alterations in gene expression following topical solar protection and solar repair strategies.

Methods

Using epidermal keratinocytes and dermal fibroblasts derived from a 3-dimensional reconstructed human skin model, gene expression was assessed via the Genemarkers Standard Skin Panel using 112 genes deploying two analytical techniques: DNA microarray and quantitative real-time PCR exploration. Tissues were inoculated with products then collected after 24 hours following application of solar protection formulations and 16 hours following solar repair formulations (The Essential Six, RATIONALE, Victoria, Australia).

Results

A DNA microarray revealed 67 genes that were significantly up-regulated or down-regulated following the treatment. The quantitative real-time PCR revealed that, in comparison to the control, the genes encoding Intercellular Adhesion Molecule 1 (ICAM1), Metallothionein 1A (MT1A), Prostaglandin-Endoperoxide Synthase 1 (PTGS2), Late Cornified Envelope 3D (LCE3D), Peroxisome Proliferator Activated Receptor (PPARD), and Granulocyte/Macrophage Colony Stimulating Factor 2 (GM-CSF2) have been up-regulated following usage of the solar protection regime, 1.87, 861.16, 4.34, 1.91, 1.06, and 3.6, respectively. ICAM1, MT1A, PTGS2, LCE3D, PPARD, and GM-CSF2 were up-regulated following use of the solar repair regime, 3.78, 2.98, 14.89, 5.09, 2.42, and 13.51, respectively.

Conclusion

This study demonstrates that a specific solar protection and repair regime upregulated genes involved in photoprotection and repair mechanisms in a 3-dimensional (3D) reconstructed human-like skin model.

0.5-5% Supramolecular Salicylic Acid Hydrogel is Safe for Long-Term Topical Application and Improves the Expression of Genes Related to Skin Barrier Homeostasis in Mice Models

Background

As a keratolytic, salicylic acid (SA) can be topically applied in various formulations and doses in dermatology. Supramolecular SA hydrogel, a new SA formulation with higher bioavailability, is developed and commercially available nowadays. However, there still remain concerns that the long-term and continual application of SA at low concentrations may jeopardize the cutaneous barrier properties.

Aim of the Study

To reveal the long-term effects of 0.5-5% supramolecular SA hydrogel on the skin barrier in normal mice models.

Materials and Methods

The 0.5%, 1%, 2%, and 5% supramolecular SA hydrogel or hydrogel vehicle without SA was applied to mice's shaved dorsal skin once per day respectively. Tissue samples of the dorsal skin were harvested on day 14 and 28 of the serial application of SA for histopathological observation and transcriptomic analysis.

Results

Following topical supramolecular SA hydrogel therapy with various concentrations of SA (0.5%, 1%, 2%, and 5%) for 14 days and 28 days, there were no obvious macroscopic signs of impaired cutaneous health and no inflammatory or degenerative abnormalities were observed in histological results. Additionally, the transcriptomic analysis revealed that on day 14, SA dramatically altered the expression of genes related to the extracellular matrix structural constituent. And on day 28, SA regulated gene expression profiles of keratinization, cornified envelope, and lipid metabolism remarkably. Furthermore, the expression of skin barrier related genes was significantly elevated after the application of SA based on RNA-seq results, and this is likely to be associated with the PPAR signaling pathway according to the enrichment analysis.

Conclusion

Our findings demonstrated that the sustained topical administration of the 0.5-5% supramolecular SA hydrogel for up to 28 days did no harm to normal murine skin and upregulated the expression of genes related to the epidermal barrier.

In silico analysis of the profilaggrin sequence indicates alterations in the stability, degradation route, and intracellular protein fate in filaggrin null mutation carriers

Background: Loss of function mutation in FLG is the major genetic risk factor for atopic dermatitis (AD) and other allergic manifestations. Presently, little is known about the cellular turnover and stability of profilaggrin, the protein encoded by FLG. Since ubiquitination directly regulates the cellular fate of numerous proteins, their degradation and trafficking, this process could influence the concentration of filaggrin in the skin. Objective: To determine the elements mediating the interaction of profilaggrin with the ubiquitin-proteasome system (i.e., degron motifs and ubiquitination sites), the features responsible for its stability, and the effect of nonsense and frameshift mutations on profilaggrin turnover. Methods: The effect of inhibition of proteasome and deubiquitinases on the level and modifications of profilaggrin and processed products was assessed by immunoblotting. Wild-type profilaggrin sequence and its mutated variants were analysed in silico using the DEGRONOPEDIA and Clustal Omega tool. Results: Inhibition of proteasome and deubiquitinases stabilizes profilaggrin and its high molecular weight of presumably ubiquitinated derivatives. In silico analysis of the sequence determined that profilaggrin contains 18 known degron motifs as well as multiple canonical and non-canonical ubiquitination-prone residues. FLG mutations generate products with increased stability scores, altered usage of the ubiquitination marks, and the frequent appearance of novel degrons, including those promoting C-terminus-mediated degradation routes. Conclusion: The proteasome is involved in the turnover of profilaggrin, which contains multiple degrons and ubiquitination-prone residues. FLG mutations alter those key elements, affecting the degradation routes and the mutated products' stability.

Presence of Uterine Leiomyomas Has No Significant Impact on Gene Expression Profile in the Scalp of Patients with Central Centrifugal Cicatricial Alopecia

Central centrifugal cicatricial alopecia (CCCA) is associated with increased expression of genes implicated in fibroproliferative disorders and a higher prevalence of uterine leiomyomas (ULs) among affected individuals. We sought to examine the effect of UL status on the gene expression profile of the lesional scalp in patients with CCCA. Scalp biopsy was obtained from 16 patients with a confirmed diagnosis of CCCA between 2017 and 2020. Microarray analysis was used to identify differential gene expression between patients with CCCA with a history of UL and those without the history. Of more than 20,000 genes analyzed, 23 of 25 genes with the highest expression in patients with CCCA with UL held no statistical significance. No genes previously implicated in fibroproliferative disorders were found among the upregulated transcripts. Of all genes analyzed, only eight upregulated genes and zero downregulated genes had a fold change in expression >2 in patients with CCCA with UL compared with those in patients with CCCA without UL. Our findings highlight similar gene expression patterns in the lesional scalp of patients with CCCA with and without a history of UL. This analysis is key in highlighting no evidence of causational or linked mechanobiology that accounts for the increased prevalence of UL seen in patients with CCCA that previous studies have not addressed.

Antimicrobial late cornified envelope (LCE) proteins: the psoriasis risk factor LCE3B/C-del affects microbiota composition

Late cornified envelope (LCE) proteins are predominantly expressed in the skin and other cornified epithelia. Based on sequence similarity, this eighteen-member homologous gene family has been subdivided into six groups. The LCE3 proteins have been the focus of dermatological research, as the combined deletion of LCE3B and LCE3C genes (LCE3B/C-del) is a risk factor for psoriasis. We previously reported that LCE3B/C-del increases expression of the LCE3A gene and that LCE3 proteins exert antibacterial activity. In the current study we analyzed the antimicrobial properties of other family members and the role of LCE3B/C-del in modulation of microbiota composition of the skin and oral cavity. Differences in killing efficiency and specificity between the LCE proteins and their target microbes were found, and the amino acid content, rather than the order, of the well-conserved central domain of the LCE3A protein was found responsible for its antibacterial activity. In vivo, LCE3B/C-del correlated with a higher beta-diversity in the skin and oral microbiota. From these results we conclude that all LCE proteins possess antimicrobial activity. Tissue-specific and genotype-dependent antimicrobial protein profiles impact skin and oral microbiota composition, which could direct towards LCE3B/C-del associated dysbiosis and a possible role for microbiota in the pathophysiology of psoriasis.

Effects of amniotic fluid on human keratinocyte gene expression - Implications for wound healing

Cutaneous wounds can lead to huge suffering for patients. Early fetal wounds have the capacity to regenerate without scar formation. Amniotic fluid (AF), containing hyaluronic acid (HA), may contribute to this regenerative environment. We aimed to analyse changes in gene expression when human keratinocytes are exposed to AF or HA. Human keratinocytes were cultured to subconfluence, starved for 12 h and then randomised to be maintained in (1) Dulbecco's modified Eagle's medium (DMEM), (2) DMEM with 50% AF, or (3) DMEM with 50% fetal calf serum (FCS). Transcriptional changes were analysed using microarray and enriched with WebGestalt and Enrichr. Additionally, eight diagnostic genes were analysed using semiquantitative real‐time PCR to investigate epidermal differentiation and cellular stress after HA exposure as an alternative for AF exposure. The AF and FCS treatments resulted in enrichment of genes relating to varied aspects of epidermal and keratinocyte biology. In particular, p63‐, AP1‐ and NFE2L2‐ (Nrf2) associated genes were found significantly regulated in both treatments. More genes regulated by FCS treatment were associated with inflammatory signalling, whilst AF treatment was dominantly associated with molecular establishment of epidermis and lipid metabolic activity. HA exposure mostly resulted in gene regulation that was congruent with the AF microarray group, with increased expression of ITGA6 and LOR. We conclude that AF exposure enhances keratinocyte differentiation in vitro, which suggests that AF constituents can be beneficial for wound‐healing applications.

High Glucose Causes Distinct Expression Patterns of Primary Human Skin Cells by RNA Sequencing

Diabetes-related skin problems represent the most common long-term complications in diabetes mellitus patients. These complications, which include diabetic dermopathy, diabetic blisters, necrobiosis lipoidica diabeticorum, and eruptive xanthomatosis, may dramatically impair patients' quality of life and cause long-lasting disability. However, the cellular and molecular mechanisms linking diabetes-related hyperglycemia and skin complications are still incompletely understood. To assess the role of the various skin-cell types in hyperglycemia-induced skin disorders, we performed RNA sequencing-based transcriptome analysis, measuring gene expression patterns in biological replicates in normal- and high glucose-stimulated skin cells. Three primary human skin-cell types were examined, i.e., epidermal keratinocytes, dermal fibroblasts, and dermal microvascular endothelial cells. For each separate cell type, we identified gene expression. Comparing gene abundances and expression levels revealed that transcription profiles exhibit distinct patterns in the three skin-cell types exposed to normal (i.e., physiological) glucose treatment and high (i.e., supraphysiological) glucose treatment. The obtained data indicate that high glucose induced differential gene expression and distinct activity patterns in signaling pathways in each skin-cell type. We are adding these data to the public database in the hope that they will facilitate future studies to develop novel targeted interventions for diabetic skin complications.

Effect of SUV39H1 Histone Methyltransferase Knockout on Expression of Differentiation-Associated Genes in HaCaT Keratinocytes

Keratinocytes undergo a complex differentiation process, coupled with extensive changes in gene expression through which they acquire distinctive features indispensable for cells that form the external body barrier—epidermis. Disturbed epidermal differentiation gives rise to multiple skin diseases. The involvement of epigenetic factors, such as DNA methylation or histone modifications, in the regulation of epidermal gene expression and differentiation has not been fully recognized yet. In this work we performed a CRISPR/Cas9-mediated knockout of SUV39H1, a gene-encoding H3K9 histone methyltransferase, in HaCaT cells that originate from spontaneously immortalized human keratinocytes and examined changes in the expression of selected differentiation-specific genes located in the epidermal differentiation complex (EDC) and other genomic locations by RT-qPCR. The studied genes revealed a diverse differentiation state-dependent or -independent response to a lower level of H3K9 methylation. We also show, by means of chromatin immunoprecipitation, that the expression of genes in the LCE1 subcluster of EDC was regulated by the extent of trimethylation of lysine 9 in histone H3 bound to their promoters. Changes in gene expression were accompanied by changes in HaCaT cell morphology and adhesion.

Cellular Imprinting Proteomics Assay: A Novel Method for Detection of Neural and Ocular Disorders Applied to Congenital Zika Virus Syndrome

Congenital Zika syndrome was first described due to increased incidence of congenital abnormalities associated with Zika virus (ZIKV) infection. Since the eye develops as part of the embryo central nervous system (CNS) structure, it becomes a specialized compartment able to display symptoms of neurodegenerative diseases and has been proposed as a noninvasive approach to the early diagnosis of neurological diseases. Ocular lesions result from defects that occurred during embryogenesis and can become apparent in newborns exposed to ZIKV. Furthermore, the absence of microcephaly cannot exclude the occurrence of ocular lesions and other CNS manifestations. Considering the need for surveillance of newborns and infants with possible congenital exposure, we developed a method termed cellular imprinting proteomic assay (CImPA) to evaluate the ocular surface proteome specific to infants exposed to ZIKV during gestation compared to nonexposure. CImPA combines surface cells and fluid capture using membrane disks and a large-scale quantitative proteomics approach, which allowed the first-time report of molecular alterations such as neutrophil degranulation, cell death signaling, ocular and neurological pathways, which are associated with ZIKV infection with and without the development of congenital Zika syndrome, CZS. Particularly, infants exposed to ZIKV during gestation and without early clinical symptoms could be detected using the CImPA method. Lastly, this methodology has broad applicability as it could be translated in the study of several neurological diseases to identify novel diagnostic biomarkers. Data are available via ProteomeXchange with identifier PXD014038.

Addressing Differentiation in Live Human Keratinocytes by Assessment of Membrane Packing Order

Differentiation of keratinocytes is critical for epidermal stratification and formation of a protective stratum corneum. It involves a series of complex processes leading through gradual changes in characteristics and functions of keratinocytes up to their programmed cell death via cornification. The stratum corneum is a relatively impermeable barrier, comprised of dead cell remnants (corneocytes) embedded in lipid matrix. Corneocyte membranes are comprised of specialized lipids linked to late differentiation proteins, contributing to the formation of a stiff and mechanically strengthened layer. To date, the assessment of the progression of keratinocyte differentiation is only possible through determination of specific differentiation markers, e.g., by using proteomics-based approaches. Unfortunately, this requires fixation or cell lysis, and currently there is no robust methodology available to study keratinocyte differentiation in living cells in real-time. Here, we explore new live-cell based approaches for screening differentiation advancement in keratinocytes, in a "calcium switch" model. We employ a polarity-sensitive dye, Laurdan, and Laurdan general polarization function (GP) as a reporter of the degree of membrane lateral packing order or condensation, as an adequate marker of differentiation. We show that the assay is straightforward and can be conducted either on a single cell level using confocal spectral imaging or on the ensemble level using a fluorescence plate reader. Such systematic quantification may become useful for understanding mechanisms of keratinocyte differentiation, such as the role of membrane in homogeneities in stiffness, and for future therapeutic development.

Human stratum corneum proteomics reveals cross-linking of a broad spectrum of proteins in cornified envelopes

Defects in keratinocyte transglutaminase (TGM1), resulting in an improper protein scaffold for deposition of the lipid barrier, comprise a major source of autosomal recessive congenital ichthyosis. For that reason, the composition and formation of the cornified (cross-linked) protein envelope of the epidermis have been of considerable interest. Since the isopeptide cross-linked protein components are not individually isolable once incorporated, purified envelopes were analysed by mass spectrometry after trypsin digestion. Quantitative estimates of the identified components revealed some 170 proteins, each comprising at least 0.001% of the total, of which keratins were major constituents accounting for ≈74% of the total. Some prevalent non-keratin constituents such as keratinocyte proline-rich protein, loricrin and late envelope protein-7 were preferentially incorporated into envelopes. The results suggest a model where, as previously observed in hair shaft and nail plate, a diversity of cellular proteins are incorporated. They also help rationalize the minimal effect on epidermis of ablating genes for specific single envelope structural components. The quantitative profile of constituent proteins provides a foundation for future exploration of envelope perturbations that may occur in pathological conditions.

SOX11 and SOX4 drive the reactivation of an embryonic gene program during murine wound repair

Tissue injury induces changes in cellular identity, but the underlying molecular mechanisms remain obscure. Here, we show that upon damage in a mouse model, epidermal cells at the wound edge convert to an embryonic-like state, altering particularly the cytoskeletal/extracellular matrix (ECM) components and differentiation program. We show that SOX11 and its closest relative SOX4 dictate embryonic epidermal state, regulating genes involved in epidermal development as well as cytoskeletal/ECM organization. Correspondingly, postnatal induction of SOX11 represses epidermal terminal differentiation while deficiency of Sox11 and Sox4 accelerates differentiation and dramatically impairs cell motility and re-epithelialization. Amongst the embryonic genes reactivated at the wound edge, we identify fascin actin-bundling protein 1 (FSCN1) as a critical direct target of SOX11 and SOX4 regulating cell migration. Our study identifies the reactivated embryonic gene program during wound repair and demonstrates that SOX11 and SOX4 play a central role in this process.

The skin transcriptome in hidradenitis suppurativa uncovers an antimicrobial and sweat gland gene signature which has distinct overlap with wounded skin

Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory skin disease resulting in non-healing wounds affecting body areas of high hair follicle and sweat gland density. The pathogenesis of HS is not well understood but appears to involve dysbiosis-driven aberrant activation of the innate immune system leading to excessive inflammation. Marked dysregulation of antimicrobial peptides and proteins (AMPs) in HS is observed, which may contribute to this sustained inflammation. Here, we analyzed HS skin transcriptomes from previously published studies and integrated these findings through a comparative analysis with a published wound healing data set and with immunofluorescence and qPCR analysis from new HS patient samples. Among the top differently expressed genes between lesional and non-lesional HS skin were members of the S100 family as well as dermcidin, the latter known as a sweat gland-associated AMP and one of the most downregulated genes in HS lesions. Interestingly, many genes associated with sweat gland function, such as secretoglobins and aquaporin 5, were decreased in HS lesional skin and we discovered that these genes demonstrated opposite expression profiles in healing skin. Conversely, HS lesional and wounded skin shared a common gene signature including genes encoding for S100 proteins, defensins, and genes encoding antiviral proteins. Overall, our results suggest that the pathogenesis of HS may be driven by changes in AMP expression and altered sweat gland function, and may share a similar pathology with chronic wounds.

All‑trans retinoic acid alters the expression of the tight junction proteins Claudin‑1 and ‑4 and epidermal barrier function‑associated genes in the epidermis

All‑trans retinoic acid (ATRA) regulates skin cell proliferation and differentiation. ATRA is widely used in the treatment of skin diseases, but results in irritation, dryness and peeling, possibly due to an impaired skin barrier, although the exact mechanisms are unclear. The present study established an ATRA‑associated dermatitis mouse model (n=32) in order to examine the molecular mechanisms of skin barrier impairment by ATRA. Changes in epidermal morphology and structure were observed using histological examination and transmission electron microscopy (TEM). Gene expression was analyzed by microarray chip assay. Histology and TEM demonstrated pronounced epidermal hyperproliferation and parakeratosis upon ATRA application. The stratum corneum layer displayed abnormal lipid droplets and cell‑cell junctions, suggesting alterations in lipid metabolism and dysfunctional cell junctions. Gene expression profiling revealed that factors associated with epidermal barrier function were differentially expressed by ATRA, including those associated with tight junctions (TJs), cornified envelopes, lipids, proteases, protease inhibitors and transcription factors. In the mouse epidermis, Claudin‑1 and ‑4 are proteins involved in TJs and have key roles in epidermal barrier function. ATRA reduced the expression and altered the localization of Claudin‑1 in HaCaT immortalized keratinocytes and the mouse epidermis, which likely leads to the disruption of the epidermal barrier. By contrast, Claudin‑4 was upregulated in HaCaT cells and the mouse epidermis following treatment with ATRA. In conclusion, ATRA exerts a dual effect on epidermal barrier genes: It downregulates the expression of Claudin‑1 and upregulates the expression of Claudin‑4. Claudin‑4 upregulation may be a compensatory response for the disrupted barrier function caused by Claudin‑1 downregulation.

Establishment of a complex skin structure via layered co-culture of keratinocytes and fibroblasts derived from induced pluripotent stem cells

Background

Skin is an organ that plays an important role as a physical barrier and has many other complex functions. Skin mimetics may be useful for studying the pathophysiology of diseases in vitro and for repairing lesions in vivo. Cord blood mononuclear cells (CBMCs) have emerged as a potential cell source for regenerative medicine. Human induced pluripotent stem cells (iPSCs) derived from CBMCs have great potential for allogenic regenerative medicine. Further study is needed on skin differentiation using CBMC-iPSCs.

Methods

Human iPSCs were generated from CBMCs by Sendai virus. CBMC-iPSCs were differentiated to fibroblasts and keratinocytes using embryonic body formation. To generate CBMC-iPSC-derived 3D skin organoid, CBMC-iPSC-derived fibroblasts were added into the insert of a Transwell plate and CBMC-iPSC-derived keratinocytes were seeded onto the fibroblast layer. Transplantation of 3D skin organoid was performed by the tie-over dressing method.

Results

Epidermal and dermal layers were developed using keratinocytes and fibroblasts differentiated from cord blood-derived human iPSCs, respectively. A complex 3D skin organoid was generated by overlaying the epidermal layer onto the dermal layer. A humanized skin model was generated by transplanting this human skin organoid into SCID mice and effectively healed skin lesions.

Conclusions

This study reveals that a human skin organoid generated using CBMC iPSCs is a novel tool for in-vitro and in-vivo dermatologic research.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0958-2) contains supplementary material, which is available to authorized users.

Recent evolution of the human skin barrier

The skin is the first line of defense against the environment, with the epidermis as the outermost tissue providing much of the barrier function. Given its direct exposure to and encounters with the environment, the epidermis must evolve to provide an optimal barrier for the survival of an organism. Recent advances in genomics have identified a number of genes for the human skin barrier that have undergone evolutionary changes since humans diverged from chimpanzees. Here, we highlight a selection of key and innovative genetic findings for skin barrier evolution in our divergence from our primate ancestors and among modern human populations.

Proteome-wide changes in primary skin keratinocytes exposed to diesel particulate extract-A role for antioxidants in skin health

BACKGROUND

Skin acts as a protective barrier against direct contact with pollutants but inhalation and systemic exposure have indirect effect on keratinocytes. Exposure to diesel exhaust has been linked to increased oxidative stress.

OBJECTIVE

To investigate global proteomic alterations in diesel particulate extract (DPE)/its vapor exposed skin keratinocytes.

METHODS

We employed Tandem Mass Tag (TMT)-based proteomics to study effect of DPE/DPE vapor on primary skin keratinocytes.

RESULTS

We observed an increased expression of oxidative stress response protein NRF2, upon chronic exposure of primary keratinocytes to DPE/its vapor which includes volatile components such as polycyclic aromatic hydrocarbons (PAHs). Mass spectrometry-based quantitative proteomics led to identification 4490 proteins of which 201 and 374 proteins were significantly dysregulated (≥1.5 fold, p≤0.05) in each condition, respectively. Proteins involved in cellular processes such as cornification (cornifin A), wound healing (antileukoproteinase) and differentiation (suprabasin) were significantly downregulated in primary keratinocytes exposed to DPE/DPE vapor. These results were corroborated in 3D skin models chronically exposed to DPE/DPE vapor. Bioinformatics analyses indicate that DPE and its vapor affect distinct molecular processes in skin keratinocytes. Components of mitochondrial oxidative phosphorylation machinery were seen to be exclusively overexpressed upon chronic DPE vapor exposure. In addition, treatment with an antioxidant like vitamin E partially restores expression of proteins altered upon exposure to DPE/DPE vapor.

CONCLUSIONS

Our study highlights distinct adverse effects of chronic exposure to DPE/DPE vapor on skin keratinocytes and the potential role of vitamin E in alleviating adverse effects of environmental pollution.

The epigenetic regulation of CXCL14 plays a role in the pathobiology of oral cancers

Background: Chemokines selectively attract and activate leukocytes and play roles in a variety of homeostatic and disease processes. Explore the biological properties of CXCL14 seems complicated due to unknown functional characteristics of CXCL14 in cancer. Methods: To study the multistep process of oral cancer development, we analyzed oral samples spanning normalcy, dysplasia and cancer from multiple perspectives, revealing a cascade of progressive changes. Results: CXCL14 protein was expressed in the cytoplasm adjacent to tumors. T classification (P<0.001), clinical stage (P=0.0013) and nodal metastasis (P=0.0035) were significantly associated with CXCL14 in relationships between CXCL14 expression levels and tumor and patient characteristics. Compared with non-tumor tissue, expression of the epidermal growth factor receptor (EGFR) gene was increased in dysplasia and was further sustained in cancer. Our data show an inverse relationship between CXCL14 and EGFR expression levels in tumor cells indicating that CXCL14 expression is beneficial for tumor suppression. To explore epigenetic regulation and the impact of CXCL14 on oral cancer, analysis of CpG islands methylation in the CXCL14 promoter region indicated that the abnormal hypermethylation of that promoter region in tumor cells and tissues is one of the mechanisms causing the reduced expression. Restoration of CXCL14 expression was induced by treatment with 5-aza-2'-deoxycytidine. Using in vivo mouse models, we demonstrate that the restoration of CXCL14 expression in irradiation-induced oral carcinoma cells induces the expression of Late Cornified Envelope (LCE) genes. Conclusions: Our data suggest that LCE genes are a novel target of CXCL14 and are likely to have a tumor suppressor function through the modulation of CXCL14 expression. In conclusion, CXCL14 might play a pivotal role in the pathobiology of oral cancer, probably by regulating DNA methylation and leukocyte migration. The level of CXCL14 expression may be a valuable adjuvant parameter to predict the prognosis of patients with oral carcinoma and may be a potential therapeutic target.

Systematic discovery of novel eukaryotic transcriptional regulators using sequence homology independent prediction

BACKGROUND

The molecular function of a gene is most commonly inferred by sequence similarity. Therefore, genes that lack sufficient sequence similarity to characterized genes (such as certain classes of transcriptional regulators) are difficult to classify using most function prediction algorithms and have remained uncharacterized.

RESULTS

To identify novel transcriptional regulators systematically, we used a feature-based pipeline to screen protein families of unknown function. This method predicted 43 transcriptional regulator families in Arabidopsis thaliana, 7 families in Drosophila melanogaster, and 9 families in Homo sapiens. Literature curation validated 12 of the predicted families to be involved in transcriptional regulation. We tested 33 out of the 195 Arabidopsis putative transcriptional regulators for their ability to activate transcription of a reporter gene in planta and found twelve coactivators, five of which had no prior literature support. To investigate mechanisms of action in which the predicted regulators might work, we looked for interactors of an Arabidopsis candidate that did not show transactivation activity in planta and found that it might work with other members of its own family and a subunit of the Polycomb Repressive Complex 2 to regulate transcription.

CONCLUSIONS

Our results demonstrate the feasibility of assigning molecular function to proteins of unknown function without depending on sequence similarity. In particular, we identified novel transcriptional regulators using biological features enriched in transcription factors. The predictions reported here should accelerate the characterization of novel regulators.

The Molecular Revolution in Cutaneous Biology: EDC and Locus Control

The epidermal differentiation complex (EDC) locus consists of a cluster of genes important for the terminal differentiation of the epidermis. While early studies identified the functional importance of individual EDC genes, the recognition of the EDC genes as a cluster with its shared biology, homology, and physical linkage was pivotal to later studies that investigated the transcriptional regulation of the locus. Evolutionary conservation of the EDC and the transcriptional activation during epidermal differentiation suggested a cis-regulatory mechanism via conserved noncoding elements or enhancers. This line of pursuit led to the identification of CNE 923, an epidermal-specific enhancer that was found to mediate chromatin remodeling of the EDC in an AP-1 dependent manner. These genomic studies, as well as the advent of high-throughput sequencing and genome engineering techniques, have paved the way for future investigation into enhancer-mediated regulatory networks in cutaneous biology.

Current and emerging concepts in atopic dermatitis pathogenesis

Atopic dermatitis is a common skin disorder with a complex, evolving pathogenesis. Research on the pathogenesis has shifted from focusing primarily on generalized immune system abnormalities in T helper 1/T helper 2 (T_h1/T_h2) activity to more targeted immune and skin barrier abnormalities contributing to the overall phenotype. Specific signaling pathways recently implicated in atopic dermatitis include production of interleukin (IL) 4 and IL-13, which promote immunoglobulin E production, T_h17 and T_h22 cells, and production of cytokines. Barrier defect abnormalities, such as a shared filaggrin mutation noted in ichthyosis vulgaris and atopic dermatitis, as well as reduced structural proteins and lipids (eg, ceramides), have been discovered as well. These alterations contribute to increased transepidermal water loss in addition to increased allergen exposure, resulting in debate over the "inside out" versus "outside in" theories-that is, the concept that immunity triggers barrier breakdown versus barrier abnormalities triggering immunologic alteration toward atopy. In fact, it is likely that all of these contribute to pathogenesis, with some individuals initially experiencing immunologic abnormalities more strongly than barrier defects and vice versa. Genetic analyses have continued to advance, leading to the discovery of potential candidate genes relating both to the impaired skin barrier and the altered immune system pathways. This review outlines the evolution of the field of current pathogenesis of atopic dermatitis, highlighting the most pertinent recent findings.

Neotenic phenomenon in gene expression in the skin of Foxn1- deficient (nude) mice - a projection for regenerative skin wound healing

Background

Mouse fetuses up to 16 day of embryonic development and nude (Foxn1- deficient) mice are examples of animals that undergo regenerative (scar-free) skin healing. The expression of transcription factor Foxn1 in the epidermis of mouse fetuses begins at embryonic day 16.5 which coincides with the transition point from scar-free to scar-forming skin wound healing. In the present study, we tested the hypothesis that Foxn1 expression in the skin is an essential condition to establish the adult skin phenotype and that Foxn1 inactivity in nude mice keeps skin in the immature stage resembling the phenomena of neoteny.

Results

Uninjured skin of adult C57BL/6J (B6) mice, mouse fetuses at days 14 (E14) and 18 (E18) of embryonic development and B6.Cg-Foxn1 nu (nude) mice were characterized for their gene expression profiles by RNA sequencing that was validated through qRT-PCR, Western Blot and immunohistochemistry. Differentially regulated genes indicated that nude mice were more similar to E14 (model of regenerative healing) and B6 were more similar to E18 (model of reparative healing). The up-regulated genes in nude and E14 mice were associated with tissue remodeling, cytoskeletal rearrangement, wound healing and immune response, whereas the down-regulated genes were associated with differentiation. E14 and nude mice exhibit prominent up-regulation of keratin (Krt23, -73, -82, -16, -17), involucrin (Ivl) and filaggrin (Flg2) genes. The transcription factors associated with the Hox genes known to specify cell fate during embryonic development and promote embryonic stem cells differentiation were down-regulated in both nude and E14. Among the genes enriched in the nude skin but not shared with E14 fetuses were members of the Wnt and matrix metalloproteinases (Mmps) families whereas Bmp and Notch related genes were down-regulated.

Conclusions

In summary, Foxn1 appears to be a pivotal control element of the developmental program and skin maturation. Nude mice may be considered as a model of neoteny among mammals. The resemblance of gene expression profiles in the skin of both nude and E14 mice are direct or indirect consequences of the Foxn1 deficiency. Foxn1 appears to regulate the balance between cell proliferation and differentiation and its inactivity creates a pro-regenerative environment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3401-z) contains supplementary material, which is available to authorized users.

How Does Chronic Cigarette Smoke Exposure Affect Human Skin? A Global Proteomics Study in Primary Human Keratinocytes

Cigarette smoking has been associated with multiple negative effects on human skin. Long-term physiological effects of cigarette smoke are through chronic and not acute exposure. Molecular alterations due to chronic exposure to cigarette smoke remain unclear. Primary human skin keratinocytes chronically exposed to cigarette smoke condensate (CSC) showed a decreased wound-healing capacity with an increased expression of NRF2 and MMP9. Using quantitative proteomics, we identified 4728 proteins, of which 105 proteins were overexpressed (≥2-fold) and 41 proteins were downregulated (≤2-fold) in primary skin keratinocytes chronically exposed to CSC. We observed an alteration in the expression of several proteins involved in maintenance of epithelial barrier integrity, including keratin 80 (5.3 fold, p value 2.5 × 10-7), cystatin A (3.6-fold, p value 3.2 × 10-3), and periplakin (2.4-fold, p value 1.2 × 10-8). Increased expression of proteins associated with skin hydration, including caspase 14 (2.2-fold, p value 4.7 × 10-2) and filaggrin (3.6-fold, p value 5.4 × 10-7), was also observed. In addition, we report differential expression of several proteins, including adipogenesis regulatory factor (2.5-fold, p value 1.3 × 10-3) and histone H1.0 (2.5-fold, p value 6.3 × 10-3) that have not been reported earlier. Bioinformatics analyses demonstrated that proteins differentially expressed in response to CSC are largely related to oxidative stress, maintenance of skin integrity, and anti-inflammatory responses. Importantly, treatment with vitamin E, a widely used antioxidant, could partially rescue adverse effects of CSC exposure in primary skin keratinocytes. The utility of antioxidant-based new dermatological formulations in delaying or preventing skin aging and oxidative damages caused by chronic cigarette smoke exposure warrants further clinical investigations and multi-omics research.

Induced Pluripotent Stem Cell Differentiation and Three-Dimensional Tissue Formation Attenuate Clonal Epigenetic Differences in Trichohyalin

The epigenetic background of pluripotent stem cells can influence transcriptional and functional behavior. Most of these data have been obtained in standard monolayer cell culture systems. In this study, we used exome sequencing, array comparative genomic hybridization (CGH), miRNA array, DNA methylation array, three-dimensional (3D) tissue engineering, and immunostaining to conduct a comparative analysis of two induced pluripotent stem cell (iPSC) lines used in engineering of 3D human epidermal equivalent (HEE), which more closely approximates epidermis. Exome sequencing and array CGH suggested that their genome was stable following 3 months of feeder-free culture. While the miRNAome was also not affected, ≈7% of CpG sites were differently methylated between the two lines. Analysis of the epidermal differentiation complex, a region on chromosome 1 that contains multiple genes involved in skin barrier maturation (including trichohyalin, TCHH), found that in one of the iPSC clones (iKCL004), TCHH retained a DNA methylation signature characteristic of the original somatic cells, whereas in other iPSC line (iKCL011), the TCHH methylation signature matched that of the human embryonic stem cell line KCL034. The difference between the two iPSC clones in TCHH methylation did not have an obvious effect on its expression in 3D HEE, suggesting that differentiation and tissue formation may mitigate variations in the iPSC methylome.

Lce1 Family Members Are Nrf2-Target Genes that Are Induced to Compensate for the Loss of Loricrin

Loricrin is a major component of the cornified cell envelope, a highly insoluble structure composed of covalently cross-linked proteins. Although loricrin knockout mice only exhibit a mild transient phenotype at birth, they show a marked delay in the formation of an epidermal barrier in utero. We recently discovered that induction of a compensatory response to repair the defective barrier is initiated by amniotic fluid via activation of NF-E2-related factor 2 and identified Sprr2d and Sprr2h as direct transcriptional targets. Proteomic analysis suggested that other proteins were also incorporated into the loricrin knockout cell envelope, in addition to the small proline rich proteins. Here we present evidence suggesting that the late cornified envelope 1 proteins are also compensatory components as determined by their localization within the loricrin knockout cell envelope via immunoelectron microscopy. We also demonstrate that late cornified envelope 1 genes are upregulated at the transcriptional level in loricrin knockout mouse skin and confirm that late cornified envelope 1 genes are transcriptional targets of NRF2. Our present study further highlights the complexity and importance of a compensatory mechanism that evolved in terrestrial animals to ensure the formation of a functional epidermal barrier.

Two Ancient Gene Families Are Critical for Maintenance of the Mammalian Skin Barrier in Postnatal Life

The skin barrier is critical for mammalian survival in the terrestrial environment, affording protection against fluid loss, microbes, toxins, and UV exposure. Many genes indispensable for barrier formation in the embryo have been identified, but loss of these genes in adult mice does not induce barrier regression. We describe a complex regulatory network centered on two ancient gene families, the grainyhead-like (Grhl) transcription factors and the protein cross-linking enzymes (tissue transglutaminases [Tgms]), which are essential for skin permeability barrier maintenance in adult mice. Embryonic deletion of Grhl3 induces loss of Tgm1 expression, which disrupts the cornified envelope, thus preventing permeability barrier formation leading to neonatal death. However, gene deletion of Grhl3 in adult mice does not disrupt the preformed barrier, with cornified envelope integrity maintained by Grhl1 and Tgm5, which are up-regulated in response to postnatal loss of Grhl3. Concomitant deletion of both Grhl factors in adult mice induced loss of Tgm1 and Tgm5 expression, perturbation of the cornified envelope, and complete permeability barrier regression that was incompatible with life. These findings define the molecular safeguards for barrier function that accompany the transition from intrauterine to terrestrial life.

Late Cornified Envelope Group I, a novel target of p53, regulates PRMT5 activity

p53 is one of the most important tumor suppressor genes involved in human carcinogenesis. Although downstream targets of p53 and their biologic functions in cancer cells have been extensively investigated, it is still far from the full understanding. Here, we demonstrate that Late Cornified Envelope Group I (LCE1) genes, which are located in the LCE gene clusters encoding multiple well-conserved stratum-corneum proteins, are novel downstream targets of p53. Exogenous p53 overexpression using an adenoviral vector system significantly enhanced the expression of LCE1 cluster genes. We also observed induction of LCE1 expressions by DNA damage, which was caused by treatment with adriamycin or UV irradiation in a wild-type p53-dependent manner. Concordantly, the induction of LCE1 by DNA damage was significantly attenuated by the knockdown of p53. Among predicted p53-binding sites within the LCE1 gene cluster, we confirmed one site to be a p53-enhancer sequence by reporter assays. Furthermore, we identified LCE1 to interact with protein arginine methyltransferase 5 (PRMT5). Knockdown of LCE1 by specific small interfering RNAs significantly increased the symmetric dimethylation of histone H3 arginine 8, a substrate of PRMT5, and overexpression of LCE1F remarkably decreased its methylation level. Our data suggest that LCE1 is a novel p53 downstream target that can be directly transactivated by p53 and is likely to have tumor suppressor functions through modulation of the PRMT5 activity.

Oxidative stress in aging human skin

Oxidative stress in skin plays a major role in the aging process. This is true for intrinsic aging and even more for extrinsic aging. Although the results are quite different in dermis and epidermis, extrinsic aging is driven to a large extent by oxidative stress caused by UV irradiation. In this review the overall effects of oxidative stress are discussed as well as the sources of ROS including the mitochondrial ETC, peroxisomal and ER localized proteins, the Fenton reaction, and such enzymes as cyclooxygenases, lipoxygenases, xanthine oxidases, and NADPH oxidases. Furthermore, the defense mechanisms against oxidative stress ranging from enzymes like superoxide dismutases, catalases, peroxiredoxins, and GSH peroxidases to organic compounds such as L-ascorbate, α-tocopherol, beta-carotene, uric acid, CoQ10, and glutathione are described in more detail. In addition the oxidative stress induced modifications caused to proteins, lipids and DNA are discussed. Finally age-related changes of the skin are also a topic of this review. They include a disruption of the epidermal calcium gradient in old skin with an accompanying change in the composition of the cornified envelope. This modified cornified envelope also leads to an altered anti-oxidative capacity and a reduced barrier function of the epidermis.

Genetic background of skin barrier dysfunction in the pathogenesis of psoriasis vulgaris

Psoriasis is a common inflammatory skin disease. It is known to be a complex condition with multifactorial mode of inheritance, however the associations between particular pathogenic pathways remain unclear. A novel report on the pathogenesis of psoriasis has recently included the genetic determination of the skin barrier dysfunction. In this paper, we focus on specific genetic variants associated with formation of the epidermal barrier and their role in the complex pathogenesis of the disease.

Gene regulatory mechanisms orchestrated by p63 in epithelial development and related disorders

The transcription factor p63 belongs to the p53 family and is a key regulator in epithelial commitment and development. Mutations in p63 give rise to several epithelial related disorders with defects in skin, limb and orofacial structures. Since the discovery of p63, efforts have been made to identify its target genes using individual gene approaches and to understand p63 function in normal epithelial development and related diseases. Recent genome-wide approaches have identified tens of thousands of potential p63-regulated target genes and regulatory elements, and reshaped the concept of gene regulation orchestrated by p63. These data also provide insights into p63-related disease mechanisms. In this review, we discuss the regulatory role of p63 in normal and diseased epithelial development in light of these novel findings. We also propose future perspectives for dissecting the molecular mechanism of p63-mediated epithelial development and related disorders as well as for potential therapeutic strategies.

Association of the late cornified envelope-3 genes with psoriasis and psoriatic arthritis: a systematic review

Psoriasis (Ps) and psoriatic arthritis (PsA) are genetically complex diseases with strong genetic evidence. Recently, susceptibility genes for Ps and PsA have been identified within the late cornified envelop (LCE) gene cluster, especially the cluster 3 (LCE3) genes. It is noteworthy that the deletion of LCE3B and LCE3C (LCE3C_LCE3B-del) is significantly associated with these two diseases. Gene-gene interactions between LCE3 genes and other genes are associated with Ps and PsA. LCE3 genes also have pleiotropic effect on some autoimmune diseases, such as rheumatoid arthritis, atopic dermatitis and systemic lupus erythematosus. Further studies need to focus on the potential function of LCE3 genes in the pathogenesis of Ps and PsA in the future.

Skin aging, gene expression and calcium

The human epidermis provides a very effective barrier function against chemical, physical and microbial insults from the environment. This is only possible as the epidermis renews itself constantly. Stem cells located at the basal lamina which forms the dermoepidermal junction provide an almost inexhaustible source of keratinocytes which differentiate and die during their journey to the surface where they are shed off as scales. Despite the continuous renewal of the epidermis it nevertheless succumbs to aging as the turnover rate of the keratinocytes is slowing down dramatically. Aging is associated with such hallmarks as thinning of the epidermis, elastosis, loss of melanocytes associated with an increased paleness and lucency of the skin and a decreased barrier function. As the differentiation of keratinocytes is strictly calcium dependent, calcium also plays an important role in the aging epidermis. Just recently it was shown that the epidermal calcium gradient in the skin that facilitates the proliferation of keratinocytes in the stratum basale and enables differentiation in the stratum granulosum is lost in the process of skin aging. In the course of this review we try to explain how this calcium gradient is built up on the one hand and is lost during aging on the other hand. How this disturbed calcium homeostasis is affecting the gene expression in aged skin and is leading to dramatic changes in the composition of the cornified envelope will also be discussed. This loss of the epidermal calcium gradient is not only specific for skin aging but can also be found in skin diseases such as Darier disease, Hailey-Hailey disease, psoriasis and atopic dermatitis, which might be very helpful to get a deeper insight in skin aging.

Fetal inhibition of inflammation improves disease phenotypes in harlequin ichthyosis

Harlequin ichthyosis (HI) is a severe skin disease which leads to neonatal death in ∼50% of cases. It is the result of mutations in ABCA12, a protein that transports lipids required to establish the protective skin barrier needed after birth. To better understand the life-threatening newborn HI phenotype, we analysed the developing epidermis for consequences of lipid dysregulation in mouse models. We observed a pro-inflammatory signature which was characterized by chemokine upregulation in embryonic skin which is distinct from that seen in other types of ichthyosis. Inflammation also persisted in grafted HI skin. To examine the contribution of inflammation to disease development, we overexpressed interleukin-37b to globally suppress fetal inflammation, observing considerable improvements in keratinocyte differentiation. These studies highlight inflammation as an unexpected contributor to HI disease development in utero, and suggest that inhibiting inflammation may reduce disease severity.

Regulation of the dynamic chromatin architecture of the epidermal differentiation complex is mediated by a c-Jun/AP-1-modulated enhancer

The epidermal differentiation complex (EDC) locus comprises a syntenic and linear cluster of genes whose concomitant expression is a hallmark feature of differentiation in the developing skin epidermis. Many of the EDC proteins are cross-linked together to form the cornified envelope, an essential and discrete unit of the mammalian skin barrier. The mechanism underlying coordinate transcriptional activation of the EDC is unknown. Within the human EDC, we identified an epidermal-specific regulatory enhancer, 923, which responded to the developmental and spatiotemporal cues at the onset of epidermal differentiation in the mouse embryo. Comparative chromosomal conformation capture assays in proliferating and differentiated primary mouse keratinocytes revealed multiple physiologically sensitive chromatin interactions between the 923 enhancer and EDC gene promoters, thus depicting the dynamic chromatin topology of the EDC. We elucidate a mechanistic link between c-Jun/AP-1 and 923, whereby AP-1- and 923-mediated EDC chromatin remodeling are required for functional EDC gene activation. Thus, we identify a critical enhancer/transcription factor axis governing the dynamic regulation of the EDC chromatin architecture and gene expression and provide a framework for future studies toward understanding gene regulation in cutaneous diseases.

Retinoic acid and hydroquinone induce inverse expression patterns on cornified envelope-associated proteins: implication in skin irritation

BACKGROUND

Hydroquinone (HQ) with or without retinoic acid (RA) is routinely used for the treatment of hyperpigmented conditions. Skin irritation is a major problem with popular depigmenting agents, resulting in postinflammatory hyperpigmentation.

OBJECTIVE

To examine the molecular mechanism associated with skin irritation by RA or HQ.

METHODS

A genome-wide transcriptional profiling analysis was performed using monolayer cultures of human keratinocytes treated with or without irritant doses of RA, HQ, or sodium lauryl sulfate (SLS), a representative irritant. Differentially expressed genes (DEGs) were mapped on human chromosomes using a Manhattan plot. For the validation of candidate DEGs, the chemicals with different concentrations of varying irritation intensities were applied in vitro and in vivo and analyzed using real time-PCR and Western blotting.

RESULTS

DEGs mapped to the 1q21 locus, which is composed of a cluster of genes encoding the cornified envelope precursors, showed an inverse expression pattern in response to HQ and RA. Concentrations of RA and HQ that induced a broad range of irritant responses in cultured cells or mice skin also induced inverse effects on the expression of cornified envelope-associated proteins.

CONCLUSIONS

Genetic modulation on cornified envelope-associated proteins by RA-induced irritation, which may be involved in physiological skin barrier disturbance, could be inverse to that by HQ- or SLS-induced irritation.

The sheep genome illuminates biology of the rumen and lipid metabolism

Sheep (Ovis aries) are a major source of meat, milk, and fiber in the form of wool and represent a distinct class of animals that have a specialized digestive organ, the rumen, that carries out the initial digestion of plant material. We have developed and analyzed a high-quality reference sheep genome and transcriptomes from 40 different tissues. We identified highly expressed genes encoding keratin cross-linking proteins associated with rumen evolution. We also identified genes involved in lipid metabolism that had been amplified and/or had altered tissue expression patterns. This may be in response to changes in the barrier lipids of the skin, an interaction between lipid metabolism and wool synthesis, and an increased role of volatile fatty acids in ruminants compared with nonruminant animals.

Pharmacogenetics of psoriasis: HLA-Cw6 but not LCE3B/3C deletion nor TNFAIP3 polymorphism predisposes to clinical response to interleukin 12/23 blocker ustekinumab

BACKGROUND

Our understanding of the genetic basis of predisposition to psoriasis is increasing exponentially due to the progress of genetic studies. However, so far little is known about genetic predisposition in relation to the response to psoriasis treatments. Recent data identified genetic predictors for the clinical outcome of conventional treatments such as methotrexate, acitretin and vitamin D derivatives, but few studies are available on genetic predictors of response to biologics. We hypothesized that genetic variations associated with increased risk of developing psoriasis may also act as predictors for the outcome of biologic therapy.

OBJECTIVES

The aim of our study was to analyse the presence of three different psoriasis susceptibility genetic variations (HLA-Cw6; TNFAIP3 rs610604 polymorphism; LCE3B/3C gene deletions) in a cohort of patients affected by moderate to severe psoriasis under ustekinumab treatment. Our primary endpoint was to evaluate the association between Psoriasis Area and Severity Index (PASI) 75 response at week 12 and HLA-Cw6 status.

METHODS

Fifty-one patients were genotyped by standard methods and psoriasis severity (PASI score) was evaluated at day 0 and after 4, 12, 24 and 40 weeks of treatment.

RESULTS

We observed increased response to ustekinumab in Cw6-positive (Cw6POS) patients [PASI 75 at week 12: 96·4% in Cw6POS vs. 65·2% in Cw6-negative (Cw6NEG) patients; P = 0·008]. In addition, we show that HLA-Cw6POS patients responded faster to ustekinumab, 89·3% of them reaching PASI 50 at week 4, after a single injection (vs. 60·9% of HLA-Cw6NEG patients). The superior response of HLA-Cw6POS patients was maintained throughout the study period, reaching the highest statistical significance for PASI 75 at week 28 (96·35% Cw6POS vs. 72·7% Cw6NEG; odds ratio 9·8). Analysis of TNFAIP3 rs610604 polymorphism and LCE3B/3C gene deletions did not show any significant association with response to ustekinumab.

CONCLUSIONS

Our observations underline the role of HLA-Cw6 not only as a psoriasis susceptibility gene, but also as a pharmacogenetic marker of response to ustekinumab in psoriasis.

Regulation of late cornified envelope genes relevant to psoriasis risk by plant-derived cyanidin

The PSORS4 genetic risk factor for psoriasis is a deletion of two late cornified envelope (LCE) genes (LCE3C_LCE3Bdel) in a cluster of five LCE3 genes with a proposed role in skin repair. We previously showed that 1,25-dihydroxyvitamin D3 (1,25D) modestly upregulates transcripts from all five LCE3 genes as monitored by real time PCR in primary human keratinocytes. Herein we report that cyanidin, a plant-derived compound with anti-inflammatory/anti-oxidant properties, upregulates expression of all five LCE3 genes in cultures of differentiating primary human keratinocytes to a greater extent that does 1,25D. This action of cyanidin is dependent on the differentiation state of the keratinocytes, with a stronger effect after the cells have been incubated with 1.2mM calcium for 24h. Competition displacement assays using radiolabeled 1,25D revealed that cyanidin directly competes as a ligand for vitamin D receptor (VDR) binding with an estimated IC50 of 500μM. However, 20μM cyanidin is sufficient to upregulate LCE3 genes. The 25-fold discrepancy between the cyanidin concentration required for upregulating LCE3 genes in intact keratinocytes vs. that required for direct binding to VDR in vitro suggests that cyanidin may be: (a) metabolized to a more active VDR ligand in keratinocytes and/or (b) functioning via a non-VDR mediated mechanism. The fact that cyanidin is the most potent upregulator of global LCE3 gene expression reported to date suggests that this or related compounds may have potential in psoriasis therapy.

Transcriptional profiling of epidermal barrier formation in vitro

BACKGROUND

Barrier function is integral to the health of epithelial tissues. Currently, there is a broad need to develop and improve our knowledge with regard to barrier function for reversal of mild skin irritation and dryness. However, there are few in vitro models that incorporate modulations of both lipids and epidermal differentiation programs for pre-clinical testing to aid in the understanding of barrier health.

OBJECTIVE

We have generated a reconstituted epidermis on a decellularized dermis (DED) and characterized its barrier properties relative to human epidermis in order to determine its utility for modeling barrier formation and repair.

METHODS

We followed the process of epidermal differentiation and barrier formation through immunocytochemistry and transcriptional profiling. We examined barrier functionality through measurements of surface pH, lipid composition, stratum corneum water content, and the ability to demonstrate topical dose-dependent exclusion of surfactant.

RESULTS

Transcriptional profiling of the epidermal model during its formation reveals temporal patterns of gene expression associated with processes regulating barrier function. The profiling is supported by gradual formation and maturation of a stratum corneum and expression of appropriate markers of epidermis development. The model displays a functional barrier and a water gradient between the stratum corneum and viable layers, as determined by confocal Raman spectroscopy. The stratum corneum layer displays a normal acidic pH and an appropriate composition of barrier lipids.

CONCLUSION

The epidermal model demonstrates its utility as an investigative tool for barrier health and provides a window into the transcriptional regulation of multiple aspects of barrier formation.

Amniotic fluid activates the nrf2/keap1 pathway to repair an epidermal barrier defect in utero

The loss of loricrin, a major component of the cornified envelope, results in a delay of epidermal barrier formation. Therefore, the living layers of the epidermis are aberrantly exposed to late-stage amniotic fluid, which may serve as the signal to upregulate genes that functionally compensate for the loss of loricrin. Consistent with this hypothesis, metabolomic studies revealed marked changes in amniotic fluid between E14.5 and E16.5 days postcoitum. In addition, we discovered that the Nrf2/Keap1 pathway detects these compositional changes and directly upregulates the expression of genes involved in the compensatory response, thus ensuring postnatal survival. In support of this finding, we demonstrate that genetically blocking the Nrf2 pathway abolishes the compensatory response and that preemptively activating Nrf2 pharmacologically rescues the delay in barrier formation in utero. Our findings reveal that the functions of Nrf2 and the composition of amniotic fluid have coevolved to ensure the formation of a functional barrier.