Low expression of the IL-23/Th17 pathway in atopic dermatitis compared to psoriasis

Characterization of Different Inflammatory Skin Conditions in a Mouse Model of DNCB-Induced Atopic Dermatitis

The mouse model of 2,4-dinitrochlorbenzene (DNCB)-induced human-like atopic dermatitis (hlAD) has been widely used to test novel treatment strategies and compounds. However, the study designs and methods are highly diverse, presenting different hlAD disease patterns that occur after sensitization and repeated challenge with DNCB on dorsal skin. In addition, there is a lack of information about the progression of the disease during the experiment and the achieved pheno- and endotypes, especially at the timepoint when therapeutic treatment is initiated. We here examine hlAD in a DNCB-induced BALB/cJRj model at different timepoints: (i) before starting treatment with dexamethasone, representing a standard drug control (day 12) and (ii) at the end of the experiment (day 22). Both timepoints display typical AD-associated characteristics: skin thickening, spongiosis, hyper- and parakeratosis, altered cytokine and gene expression, increased lipid mediator formation, barrier protein and antimicrobial peptide abnormalities, as well as lymphoid organ hypertrophy. Increased mast cell infiltration into the skin and elevated immunoglobulin E plasma concentrations indicate a type I allergy response. The DNCB-treated skin showed an extrinsic moderate sub-acute hlAD lesion at day 12 and an extrinsic mild sub-acute to chronic pheno- and endotype at day 22 with a dominating Th2 response. A dependency of the filaggrin formation and expression in correlation to the disease severity in the DNCB-treated skin was found. In conclusion, our study reveals a detailed classification of a hlAD at two timepoints with different inflammatory skin conditions and pheno- and endotypes, thereby providing a better understanding of the DNCB-induced hlAD model in BALB/cJRj mice.

High-throughput proteomic analysis of chronic inflammatory skin diseases: Psoriasis and atopic dermatitis

Common characteristics in the pathogenesis of psoriasis (PS) and atopic dermatitis (AD) have been presumed, but only a few studies have clearly supported this. The current aim was to find possible similarities and differences in protein expression patterns between these two major chronic inflammatory skin diseases. High-throughput tandem mass spectrometry proteomic analysis was performed using full thickness skin samples from adult PS patients, AD patients and healthy subjects. We detected a combined total of 3045 proteins in the three study groups. According to principal component analysis, there was significant overlap between the proteomic profiles of PS and AD, and both clearly differed from that of healthy skin. The following validation of selected proteins with western blot analysis showed similar tendencies in expression levels and produced statistically significant results. The expression of periostin (POSTN) was consistently high in AD and very low or undetectable in PS (5% FDR corrected p < 0.001), suggesting POSTN as a potential biomarker to distinguish these diseases. Immunohistochemistry further confirmed higher POSTN expression in AD compared to PS skin. Overall, our findings support the concept that these two chronic skin diseases might share considerably more common mechanisms in pathogenesis than has been suspected thus far.

Interplay of cytokines in the pathophysiology of atopic dermatitis: insights from Murin models and human

The pathogenesis of atopic dermatitis (AD) is understood to be crucially influenced by three main factors: dysregulation of the immune response, barrier dysfunction, and pruritus. In the lesional skin of AD, various innate immune cells, including Th2 cells, type 2 innate lymphoid cells (ILC2s), and basophils, produce Th2 cytokines [interleukin (IL)-4, IL-5, IL-13, IL-31]. Alarmins such as TSLP, IL-25, and IL-33 are also produced by epidermal keratinocytes, amplifying type 2 inflammation. In the chronic phase, not only Th2 cells but also Th22 and Th17 cells increase in number, leading to suppression of filaggrin expression by IL-4, IL-13, and IL-22, which further deteriorates the epidermal barrier function. Dupilumab, which targets IL-4 and IL-13, has shown efficacy in treating moderate to severe AD. Nemolizumab, targeting IL-31RA, effectively reduces pruritus in AD patients. In addition, clinical trials with fezakinumab, targeting IL-22, have demonstrated promising results, particularly in severe AD cases. Conversely, in murine models of AD, several cytokines, initially regarded as promising therapeutic targets, have not demonstrated sufficient efficacy in clinical trials. IL-33 has been identified as a potent activator of immune cells, exacerbating AD in murine models and correlating with disease severity in human patients. However, treatments targeting IL-33 have not shown sufficient efficacy in clinical trials. Similarly, thymic stromal lymphopoietin (TSLP), integral to type 2 immune responses, induces dermatitis in animal models and is elevated in human AD, yet clinical treatments like tezepelumab exhibit limited efficacy. Therapies targeting IL-1α, IL-5, and IL-17 also failed to achieve sufficient efficacy in clinical trials. It has become clear that for treating AD, IL-4, IL-13, and IL-31 are relevant therapeutic targets during the acute phase, while IL-22 emerges as a target in more severe cases. This delineation underscores the necessity of considering distinct pathophysiological aspects and therapeutic targets in AD between mouse models and humans. Consequently, this review delineates the distinct roles of cytokines in the pathogenesis of AD, juxtaposing their significance in human AD from clinical trials against insights gleaned from AD mouse models. This approach will improve our understanding of interspecies variation and facilitate a deeper insight into the pathogenesis of AD in humans.

Genomic Profiling of the Overlap Phenotype between Psoriasis and Atopic Dermatitis

Clinical overlaps between psoriasis and atopic dermatitis (AD) are sometimes undiscernible, and there is no consensus on whether to treat the overlap phenotype as psoriasis or AD. We enrolled 41 patients diagnosed with either psoriasis or AD and clinically re-stratified them into classic psoriasis (n = 11), classic AD (n = 13), and the overlap phenotype between psoriasis and AD (n = 17). We compared the gene expression profiles of lesional and nonlesional skin biopsy tissues and the proteomic profiles of blood samples among the three comparison groups. Global mRNA expression and T-cell subset cytokine expression in the skin and protein biomarker elevation in the blood of the overlap phenotype were consistent with the profiles of psoriasis and different from the profiles of AD. Unsupervised k-means clustering indicated that the best number of distinct clusters for the total population of the three comparison groups was two, and the two clusters of psoriasis and AD were differentiated by gene expression. Our study suggests that the clinical overlap phenotype between psoriasis and AD has dominant molecular features of psoriasis, and genomic biomarkers can differentiate psoriasis and AD at molecular levels in patients with a spectrum of psoriasis and AD.

Tripterygium wilfordii Hook. F. and Its Extracts for Psoriasis: Efficacy and Mechanism

Psoriasis is an inflammatory autoimmune skin condition that is clinically marked by chronic erythema and scaling. The traditional Chinese herb Tripterygium wilfordii Hook. F. (TwHF) is commonly used in the treatment of immune-related skin illnesses, such as psoriasis. In clinical studies, PASI (Psoriasis Area and Severity Index) were dramatically decreased by TwHF and its extracts. Their benefits for psoriasis also include relief from psoriasis symptoms such as itching, dryness, overall lesion scores and quality of life. And the pathological mechanisms include anti-inflammation, immunomodulation and potentially signaling pathway modulations, which are achieved by modulating type-3 inflammatory cytokines including IL-22, IL-23, and IL-17 as well as immune cells like Th17 lymphocytes, γδT cells, and interfering with IFN-SOCS1, NF-κB and IL- 36α signaling pathways. TwHF and its extracts may cause various adverse drug reactions, such as gastrointestinal responses, aberrant hepatocytes, reproductive issues, and liver function impairment, but at adequate doses, they are regarded as an alternative therapy for the treatment of psoriasis. In this review, the effectiveness and mechanisms of TwHF and its extracts in psoriasis treatment are elucidated.

The role of Janus kinase signaling in the pathology of atopic dermatitis

Atopic dermatitis (AD) is a heterogeneous, chronic, relapsing, inflammatory skin disease associated with considerable physical, psychological, and economic burden. The pathology of AD includes complex interactions involving abnormalities in immune and skin barrier genes, skin barrier disruption, immune dysregulation, microbiome disturbance, and other environmental factors. Many of the cytokines involved in AD pathology, including IL-4, IL-13, IL-22, IL-31, thymic stromal lymphopoietin, and IFN-γ, signal through the Janus kinase (JAK)-signal transducer and activation of transcription (STAT) pathway. The JAK family includes JAK1, JAK2, JAK3, and tyrosine kinase 2; the STAT family includes STAT1, STAT2, STAT3, STAT4, STAT5A/B, and STAT6. Activation of the JAK-STAT pathway has been implicated in the pathology of several immune-mediated inflammatory diseases, including AD. However, the exact mechanisms of JAK-STAT involvement in AD have not been fully characterized. This review aims to discuss current knowledge about the role of the JAK-STAT signaling pathway and, specifically, the role of JAK1 in the pathology and symptomology of AD.

"De Novo" Psoriasis and Relapse of Psoriasis Induced by Dupilumab: Three New Cases and Review of the Literature

Atopic dermatitis and psoriasis are traditionally considered diseases that cannot coexist, since they are described as the result of the activation of opposing inflammatory pathways. However, this belief has been debunked, and numerous cases of psoriasis induced by dupilumab, a biologic treatment for atopic dermatitis, have been reported. We report three cases of dupilumab-induced psoriasis and we present a literature review including cases of "de novo" psoriasis and of the relapse of psoriasis that occurred during treatment with dupilumab. In total, 39 publications met the inclusion criteria, including 112 AD patients, 101 of whom developed "de novo" psoriasis, and 11 with a flare of pre-existent psoriasis. In the first group, patients more frequently developed plaque psoriasis on the scalp and extremities, after an average latency period from the initiation of dupilumab of 5 months. In the second group, the incidence of dupilumab-induced relapses of psoriasis was 43%, after an average of 4 months since the first administration. The most common psoriasis type was plaque psoriasis, with the involvement of the scalp and upper extremities. Dupilumab was interrupted in 38% of patients with "de novo" psoriasis and in 50% of relapsed patients, leading, in most cases, to an improvement of psoriasis. In conclusion, atopic dermatitis and psoriasis can definitely co-exist, and biologic drugs used to treat the former can promote the latter. It is thus crucial to perform a careful personal and familiar anamnesis before prescribing any biologic treatment. Moreover, a study of cytokine expression and blood proteomic markers could be considered in these patients.

Pathogenic role of S100 proteins in psoriasis

Psoriasis is a chronic inflammatory skin disease. The histopathological features of psoriasis include excessive proliferation of keratinocytes and infiltration of immune cells. The S100 proteins are a group of EF-hand Ca2+-binding proteins, including S100A2, -A7, -A8/A9, -A12, -A15, which expression levels are markedly upregulated in psoriatic skin. These proteins exert numerous functions such as serving as intracellular Ca2+ sensors, transduction of Ca2+ signaling, response to extracellular stimuli, energy metabolism, and regulating cell proliferation and apoptosis. Evidence shows a crucial role of S100 proteins in the development and progress of inflammatory diseases, including psoriasis. S100 proteins can possibly be used as potential therapeutic target and diagnostic biomarkers. This review focuses on the pathogenic role of S100 proteins in psoriasis.

The translational revolution in atopic dermatitis: the paradigm shift from pathogenesis to treatment

Atopic dermatitis (AD) is the most common inflammatory skin disease, and it is considered a complex and heterogeneous condition. Different phenotypes of AD, defined according to the patient age at onset, race, and ethnic background; disease duration; and other disease characteristics, have been recently described, underlying the need for a personalized treatment approach. Recent advancements in understanding AD pathogenesis resulted in a real translational revolution and led to the exponential expansion of the therapeutic pipeline. The study of biomarkers in clinical studies of emerging treatments is helping clarify the role of each cytokine and immune pathway in AD and will allow addressing the unique immune fingerprints of each AD subset. Personalized medicine will be the ultimate goal of this targeted translational research. In this review, we discuss the changes in the concepts of both the pathogenesis of and treatment approach to AD, highlight the scientific rationale behind each targeted treatment and report the most recent clinical efficacy data.

Causal association between atopic eczema and inflammatory bowel disease: A two-sample bidirectional Mendelian randomization study of the East Asian population

Observation studies have postulated that atopic eczema is associated with a risk of inflammatory bowel disease in the East Asian population; however, this association does not obviate the biases resulting from confounding effects and reverse causation. This study aimed to determine whether this association is causal in the East Asian population using a bidirectional two-sample Mendelian randomization design. Independent genetic variants obtained from public genome-wide association studies for atopic eczema (4296 cases, 163 807 controls) were extracted to estimate the causal effects on inflammatory bowel disease (2824 cases, 3719 controls) and its two main conditions: Crohn's disease (1690 cases, 3719 controls) and ulcerative colitis (1134 cases, 3719 controls). Atopic eczema was found to be strongly associated with inflammatory bowel disease (odds ratio [95% confidence interval]: 1.520 [1.179, 1.959]; p = 0.001), but not vice versa. Subtype analyses revealed that atopic eczema is significantly associated with Crohn's disease (1.650 [1.293, 2.106]; p = 0.000) but not with ulcerative colitis. Both Crohn's disease and ulcerative colitis were found to be causally related to atopic eczema; Crohn's disease could reduce the risk of atopic eczema (0.866 [0.807, 0.930]; p = 0.000) while ulcerative colitis could increase the risk of atopic eczema (1.112 [1.021, 1.212]; p = 0.015). In conclusion, this study revealed that statistically causal relationships are present between atopic eczema and inflammatory bowel disease in the East Asian population. These findings are significant for guiding the treatment of atopic eczema and inflammatory bowel disease in clinical practice.

Induction of psoriasis- and atopic dermatitis-like phenotypes in 3D skin equivalents with a fibroblast-derived matrix

Skin homeostasis is a complex regulated process relying on the crosstalk of keratinocytes, fibroblasts and immune cells. Imbalances of T-cell subsets and the cytokine environment can lead to inflammatory skin diseases such as psoriasis (Ps) and atopic dermatitis (AD). Modern tissue engineering provides several in vitro models mimicking Ps and AD phenotypes. However, these models are either limited in their pathological features, life span, sample availability, reproducibility, controlled handling or simplicity. Some models further lack intensive characterization as they solely focus on differentiation and proliferation aspects. This study introduces a self-assembly model in which the pathological T-cell-signalling of Ps and AD was simulated by subcutaneous Th1 and Th2 cytokine stimulation. The self-established dermal fibroblast-derived matrices of these models were hypothesized to be beneficial for proximal cytokine signalling on epidermal keratinocytes. Comprehensive histological and mRNA analyses of the diseased skin models showed a weakened barrier, distinct differentiation defects, reduced cellular adhesion, inflammation and parakeratosis formation. A keratin shift of declining physiological cytokeratin-10 (CK10) towards increasing inflammatory CK16 was observed upon Th1 or Th2 stimulation. Antimicrobial peptides (AMPs) were upregulated in Ps and downregulated in AD models. The AD biomarker genes CA2, NELL2 and CCL26 were further induced in AD. While Ps samples featured basal hyperproliferation, cells in AD models displayed apoptotic signs. In accordance, these well-controllable three-dimensional in vitro models exhibited Ps and AD-like phenotypes with a high potential for disease research and therapeutic drug testing.

Psoriatic Dermal-Derived Mesenchymal Stem Cells Induced C3 Expression in Keratinocytes

Purpose

Patients and Methods

Results

Conclusion

Dendritic Cells and Macrophages in the Pathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by scaly indurated erythema. This disease impairs patients’ quality of life enormously. Pathological findings demonstrate proliferation and abnormal differentiation of keratinocytes and massive infiltration of inflammatory immune cells. The pathogenesis of psoriasis is complicated. Among immune cells, dendritic cells play a pivotal role in the development of psoriasis in both the initiation and the maintenance phases. In addition, it has been indicated that macrophages contribute to the pathogenesis of psoriasis especially in the initiation phase, although studies on macrophages are limited. In this article, we review the roles of dendritic cells and macrophages in the pathogenesis of psoriasis.

Analysis of the Serum Profile of Cytokines Involved in the T-Helper Cell Type 17 Immune Response Pathway in Atopic Children with Food Allergy

The main risk factor for the development of food allergies (FAs) in children is atopic dermatitis (AD). AD is usually recognized as the Th1/Th2 paradigm of allergic disease. Recently, the Th1/Th2 paradigm in allergy and autoimmunity has been revised, including the role of the Th17 cell population and related cytokines. However, there are only a few studies that have found Th17 cytokine involvement in the allergic inflammatory response, especially with food allergens. This research aimed to analyze the serum profile of cytokines involved in the T-helper cell type 17 immune response pathway in young, atopic children with an IgE-mediated and delayed-type FA. The study involved 76 children (0−5 years old) with chronic AD. We used the Bio-Plex system to simultaneously determine the concentrations of 15 different cytokines in one experiment. In accordance with complete dermatological and allergological examination, including OFC testing and ALEX2 assays, participants were divided into 3 groups: IgE-mediated FA, delayed-type FA, and the control group. Data were analyzed using univariate statistical tests. In the IgE-mediated FA group, the circulating levels of tested cytokines had increased compared with those of other patients; however, a statistically significant difference was only obtained for IL-1beta (p < 0.05). According to the ROC curves, IL-1beta may be considered an effective predictor of IgE-mediated FA in AD children (p < 0.05; AUC = 0.67). In the delayed-type FA group, the concentration of most cytokines had slightly decreased compared to the control group. The obtained results suggest that FA influences the Th17-related cytokine profile in the serum of AD children. More advanced studies are needed to confirm the involvement of Th17 cytokines in the allergic inflammatory response and to prove their usefulness in clinical practice.

Integrating complex host-pathogen immune environments into S. aureus vaccine studies

Staphylococcus aureus (SA) is a leading cause of bacterial infection and antibiotic resistance globally. Therefore, development of an effective vaccine has been a major goal of the SA field for the past decades. With the wealth of understanding of pathogenesis, the failure of all SA vaccine trials has been a surprise. We argue that experimental SA vaccines have not worked because vaccines have been studied in naive laboratory animals, whereas clinical vaccine efficacy is tested in immune environments reprogrammed by SA. Here, we review the failed SA vaccines that have seemingly defied all principles of vaccinology. We describe major SA evasion strategies and suggest that they reshape the immune environment in a way that makes vaccines prone to failures. We propose that appropriate integration of concepts of host-pathogen interaction into vaccine study designs could lead to insight critical for the development of an effective SA vaccine.

Transcriptome-based identification of novel endotypes in adult atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a frequent and heterogeneous inflammatory skin disease, for which personalized medicine remains a challenge. High-throughput approaches have improved understanding of the complex pathophysiology of AD. However, a purely data-driven AD classification is still lacking.

METHODS

To address this question, we applied an original unsupervised approach on the largest available transcriptome dataset of AD lesional (n = 82) and healthy (n = 213) skin biopsies.

RESULTS

Taking into account pathological and physiological state, a variance-based filtering revealed 222 AD-specific hyper-variable genes that efficiently classified the AD samples into 4 clusters that turned out to be clinically and biologically distinct. Comparison of gene expressions between clusters identified 3 sets of upregulated genes used to derive metagenes (MGs): MG-I (19 genes) was associated with IL-1 family signaling (including IL-36A and 36G) and skin remodeling, MG-II (23 genes) with negative immune regulation (including IL-34 and 37) and skin architecture, and MG-III (17 genes) with B lymphocyte immunity. Sample clusters differed in terms of disease severity (p = .02) and S. aureus (SA) colonization (p = .02). Cluster 1 contained the most severe AD, highest SA colonization, and overexpressed MG-I. Cluster 2 was characterized by less severe AD, low SA colonization, and high MG-II expression. Cluster 3 included mild AD, mild SA colonization, and mild expression of all MGs. Cluster 4 had the same clinical features as cluster 3 but had hyper-expression of MG-III. Last, we successfully validated our method and results in an independent cohort.

CONCLUSION

Our study revealed unrecognized AD endotypes with specific underlying biological pathways, highlighting novel pathophysiological mechanisms. These data could provide new insights into personalized treatment strategies.

Cytokine-Mediated Crosstalk Between Keratinocytes and T Cells in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by barrier dysfunction, dysregulated immune response, and dysbiosis with increased Staphylococcus aureus colonization. Infiltration of various T helper cell subsets into lesional skin and subsequent cytokine release are a hallmark of AD. Release of cytokines by both T cells and keratinocytes plays a key role in skin inflammation and drives many AD features. This review aims to discuss cytokine-mediated crosstalk between T cells and keratinocytes in AD pathogenesis and the potential impact of virulence factors produced by Staphylococcus aureus on these interactions.

Novel role for caspase recruitment domain family member 14 and its genetic variant rs11652075 in skin filaggrin homeostasis

BACKGROUND

Low epidermal filaggrin (FLG) is a risk factor for atopic dermatitis (AD) and allergic comorbidity. FLG mutations do not fully explain the variation in epidermal FLG levels, highlighting that other genetic loci may also regulate FLG expression.

OBJECTIVE

We sought to identify genetic loci that regulate FLG expression and elucidate their functional and mechanistic consequences.

METHODS

A genome-wide association study of quantified skin FLG expression in lesional and baseline non(never)-lesional skin of children with AD in the Mechanisms of Progression of Atopic Dermatitis to Asthma in Children cohort was conducted. Clustered regularly interspaced short palindromic repeat approaches were used to create isogenic human keratinocytes differing only at the identified variant rs11652075, and caspase recruitment domain family member 14 (CARD14)-deficient keratinocytes for subsequent mechanistic studies.

RESULTS

The genome-wide association study identified the CARD14 rs11652075 variant to be associated with FLG expression in non(never)-lesional skin of children with AD. Rs11652075 is a CARD14 expression quantitative trait locus in human skin and primary human keratinocytes. The T variant destroys a functional cytosine-phosphate-guanine site, resulting in reduced cytosine-phosphate-guanine methylation at this site (but not neighboring sites) in TT and CT compared with CC primary human keratinocytes and Mechanisms of Progression of Atopic Dermatitis to Asthma in Children children's skin samples, and rs11652075 increases CARD14 expression in an allele-specific fashion. Furthermore, studies in clustered regularly interspaced short palindromic repeat-generated CC and TT isogenic keratinocytes, as well as CARD14-haplosufficient and deficient keratinocytes, reveal that IL-17A regulates FLG expression via CARD14, and that the underlying mechanisms are dependent on the rs11652075 genotype.

CONCLUSIONS

Our study identifies CARD14 as a novel regulator of FLG expression in the skin of children with AD. Furthermore, CARD14 regulates skin FLG homeostasis in an rs11652075-dependent fashion.

IL-17 Pathway Members as Potential Biomarkers of Effective Systemic Treatment and Cardiovascular Disease in Patients with Moderate-to-Severe Psoriasis

Psoriasis is a chronic inflammatory condition associated with atherosclerotic cardiovascular disease (CVD). Systemic anti-psoriatic treatments mainly include methotrexate and biological therapies targeting TNF, IL-12/23 and IL-17A. We profiled plasma proteins from patients with moderate-to-severe psoriasis to explore potential biomarkers of effective systemic treatment and their relationship to CVD. We found that systemically well-treated patients (PASI < 3.0, n = 36) had lower circulating levels of IL-17 pathway proteins compared to untreated patients (PASI > 10, n = 23). Notably, IL-17C and PI3 were decreased with all four examined systemic treatment types. Furthermore, in patients without CVD, we observed strong correlations among IL-17C/PI3/PASI (r ≥ 0.82, p ≤ 1.5 × 10⁻¹²) pairs or between IL-17A/PASI (r = 0.72, p = 9.3 × 10⁻⁸). In patients with CVD, the IL-17A/PASI correlation was abolished (r = 0.2, p = 0.24) and the other correlations were decreased, e.g., IL-17C/PI3 (r = 0.61, p = 4.5 × 10⁻⁵). Patients with moderate-to-severe psoriasis and CVD had lower levels of IL-17A compared to those without CVD (normalized protein expression [NPX] 2.02 vs. 2.55, p = 0.013), and lower IL-17A levels (NPX < 2.3) were associated with higher incidence of CVD (OR = 24.5, p = 0.0028, 95% CI 2.1–1425.1). As a result, in patients with moderate-to-severe psoriasis, we propose circulating IL-17C and PI3 as potential biomarkers of effective systemic anti-psoriatic treatment, and IL-17A as potential marker of CVD.

Multifaceted Analysis of IL-23A- and/or EBI3-Including Cytokines Produced by Psoriatic Keratinocytes

Interleukin (IL) 23 (p19/p40) plays a critical role in the pathogenesis of psoriasis and is upregulated in psoriasis skin lesions. In clinical practice, anti-IL-23Ap19 antibodies are highly effective against psoriasis. IL-39 (p19/ Epstein-Barr virus-induced (EBI) 3), a newly discovered cytokine in 2015, shares the p19 subunit with IL-23. Anti-IL-23Ap19 antibodies may bind to IL-39; also, the cytokine may contribute to the pathogenesis of psoriasis. To investigate IL23Ap19- and/or EBI3-including cytokines in psoriatic keratinocytes, we analyzed IL-23Ap19 and EBI3 expressions in psoriasis skin lesions, using immunohistochemistry and normal human epidermal keratinocytes (NHEKs) stimulated with inflammatory cytokines, using quantitative real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and liquid chromatography-electrospray tandem mass spectrometry (LC-Ms/Ms). Immunohistochemical analysis showed that IL-23Ap19 and EBI3 expressions were upregulated in the psoriasis skin lesions. In vitro, these expressions were synergistically induced by the triple combination of tumor necrosis factor (TNF)-α, IL-17A, and interferon (IFN)-γ, and suppressed by dexamethasone, vitamin D3, and acitretin. In ELISA and LC-Ms/Ms analyses, keratinocyte-derived IL-23Ap19 and EBI3, but not heterodimeric forms, were detected with humanized anti-IL-23Ap19 monoclonal antibodies, tildrakizumab, and anti-EBI3 antibodies, respectively. Psoriatic keratinocytes may express IL-23Ap19 and EBI3 proteins in a monomer or homopolymer, such as homodimer or homotrimer.

Treatment of Connective Tissue Disease-Related Intractable Disease with Biological Therapeutics

The treatment of connective tissue disease (CTD) and CTD-related intractable diseases (CTD-IDs) currently depends on the use of steroid therapy. Approximately 20 years have passed since the approval of infliximab for rheumatoid arthritis in 2003. Since then, several biological therapeutics have been marketed and adapted for many CTDs and CTD-IDs other than rheumatoid arthritis. Although conventional treatment for patients with these diseases is rarely used because of their poor prognosis, these cases may benefit from biological therapeutics. However, choosing biological therapeutics is difficult because they have different target molecules compared with conventional therapeutics. In this review, we address the current situation of biological therapeutics for CTD-IDs including Behcet's disease, psoriatic arthritis, ankylosing spondylitis, anti-neutrophil cytoplasmic antibody-related arthritis, and adult Still's disease, as well as the choice of biological therapeutics in clinical practice.

The role of IL-17, IL-23 and IL-31, IL-33 in allergic skin diseases

PURPOSE OF REVIEW

Allergic skin diseases such as urticaria, atopic dermatitis and allergic contact dermatitis are among the most common skin diseases with severe socioeconomic consequences. The pathogenesis of allergic skin diseases is complex. This review provides an overview of cytocines IL-17, IL-23, IL-31 and IL-33.

RECENT FINDINGS

Current research results show a variety of immunological processes in the pathogenesis of the allergic skin diseases, including the role of cytokines. In addition to the Th1 and Th2 immune response, the immune response via Th17 is becoming increasingly important in allergic skin diseases but also the cytokines IL-23, IL-31 and IL-33 have been discussed in the literature recently. Different cytokines promote in a kind of orchestra the different symptoms seen in the different allergic skin diseases, including pruritus, dermatitis, mast cell mediator release and inflammation.

SUMMARY

We are still in the early stages of understanding pathophysiology of allergic skin diseases and the role of various cytokines in the immune system. With the development of targeted antibodies against the proinflammatory cytokines, the variety of normal therapeutic options can be expected to evolve.

Current Insights into Immunology and Novel Therapeutics of Atopic Dermatitis

Atopic dermatitis (AD) is one of the most prevalent inflammatory disease among non-fatal skin diseases, affecting up to one fifth of the population in developed countries. AD is characterized by recurrent pruritic and localized eczema with seasonal fluctuations. AD initializes the phenomenon of atopic march, during which infant AD patients are predisposed to progressive secondary allergies such as allergic rhinitis, asthma, and food allergies. The pathophysiology of AD is complex; onset of the disease is caused by several factors, including strong genetic predisposition, disrupted epidermal barrier, and immune dysregulation. AD was initially characterized by defects in the innate immune system and a vigorous skewed adaptive Th2 response to environmental agents; there are compelling evidences that the disorder involves multiple immune pathways. Symptomatic palliative treatment is the only strategy to manage the disease and restore skin integrity. Researchers are trying to more precisely define the contribution of different AD genotypes and elucidate the role of various immune axes. In this review, we have summarized the current knowledge about the roles of innate and adaptive immune responsive cells in AD. In addition, current and novel treatment strategies for the management of AD are comprehensively described, including some ongoing clinical trials and promising therapeutic agents. This information will provide an asset towards identifying personalized targets for better therapeutic outcomes.

IL-25 (IL-17E) in epithelial immunology and pathophysiology

IL-25, also known as IL-17E, is a unique cytokine of the IL-17 family. Indeed, IL-25 exclusively was shown to strongly induce expression of the cytokines associated with type 2 immunity. Although produced by several types of immune cells, such as T cells, dendritic cells, or group 2 innate lymphoid cells, a vast amount of IL-25 derives from epithelial cells. The functions of IL-25 have been actively studied in the context of physiology and pathology of various organs including skin, airways and lungs, gastrointestinal tract, and thymus. Accumulating evidence suggests that IL-25 is a "barrier surface" cytokine whose expression depends on extrinsic environmental factors and when upregulated may lead to inflammatory disorders such as atopic dermatitis, psoriasis, or asthma. This review summarizes the progress of the recent years regarding the effects of IL-25 on the regulation of immune response and the balance between its homeostatic and pathogenic role in various epithelia. We revisit IL-25's general and tissue-specific mechanisms of action, mediated signaling pathways, and transcription factors activated in immune and resident cells. Finally, we discuss perspectives of the IL-25-based therapies for inflammatory disorders and compare them with the mainstream ones that target IL-17A.

Suppression of IL-17A-induced CCL20 production by cytokine inducible SH2-containing protein 1 in epidermal keratinocytes

BACKGROUND

Lesions of atopic dermatitis have fewer Th17 cells than those of psoriasis, resulting in frequent skin infections. Expression of CCL20, a chemokine that is important for recruiting Th17 cells, is suppressed in the lesions of atopic dermatitis. We previously reported that IL-4 induces the expression of cytokine-inducible SH2-containing protein 1 (CIS1), a member of the CIS/SOCS family, in epidermal keratinocytes.

OBJECTIVE

To investigate whether CIS1 influences CCL20 production in epidermal keratinocytes.

METHODS

Expression of CIS1 was examined in atopic dermatitis skin and in cultured keratinocytes. The effects of overexpression of CIS1 on CCL20 production by IL-17A, and on signaling pathways inhibited by CIS1, were assessed in vitro.

RESULTS

Expression of CIS1 was enhanced in the basal layer of the lesional epidermis of skin with atopic dermatitis. When CIS1 was expressed in keratinocytes using adenoviral vectors, IL-17A-induced CCL20 expression, but not HBD2 or S100A7 expression, was significantly suppressed. TNF-α/IL-1-induced CCL20 production was not altered by CIS1. Overexpression of CIS1 attenuated IL-17A-induced ERK phosphorylation. ERK phosphorylation was mediated by the Act1 and Src family kinase pathways. CIS1 overexpression suppressed Src phosphorylation. Among the Src family kinases, the Yes kinase may have an important role because knockdown of Yes in epidermal keratinocytes resulted in suppression of ERK phosphorylation and CCL20 mRNA expression by IL-17A.

CONCLUSION

CIS1 induced by Th2 cytokines has the ability to change the response of epidermal keratinocytes to IL-17A by suppression of Src family kinases.

Bioinformatic analysis of key pathways and genes involved in pediatric atopic dermatitis

The initiation of atopic dermatitis (AD) typically happens very early in life, but most of our understanding of AD is derived from studies on AD patients in adult. The aim of the present study was to identify gene signature speficic to pediatric AD comapred with adult AD. The gene expression profiles of four datasets (GSE32924, GSE36842, GSE58558, and GSE107361) were downloaded from the GEO database. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses were performed, and protein–protein interaction (PPI) network was constructed by Cytoscape software. Total 654 differentially expressed genes (DEGs) (394 up-regulated and 260 down-regulated) were identified in pediatric AD samples with adult AD samples as control. The up-regulated DEGs were significantly enriched in the migration and chemotaxis of granulocyte and neutrophil, while down-regulated DEGs were significantly enriched in biological adhesion. KEGG pathway analysis showed that up-regulated DEGs participated in chemokine signaling pathway while down-regulated DEGs participated in adherens junction, focal adhesion, and regulation of actin cytoskeleton. The top 10 hub genes GAPDH, EGFR, ACTB, ESR1, CDK1, CXCL8, CD44, KRAS, PTGS2, and SMC3 were involved in chemokine signaling pathway, cytokine–cytokine receptor interaction, interleukin-17 signaling pathway, and regulation of actin cytoskeleton. In conclusion, we identified DEGs and hub genes involved in pediatric AD, which might be used as therapeutic targets and diagnostic biomarkers for pediatric AD.

Galectin-7 downregulation in lesional keratinocytes contributes to enhanced IL-17A signaling and skin pathology in psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by inflammatory cell infiltration, as well as hyperproliferation of keratinocytes in skin lesions, and is considered a metabolic syndrome. We found that the expression of galectin-7 is reduced in skin lesions of patients with psoriasis. IL-17A and TNF-α, 2 cytokines intimately involved in the development of psoriatic lesions, suppressed galectin-7 expression in human primary keratinocytes (HEKn cells) and the immortalized human keratinocyte cell line HaCaT. A galectin-7 knockdown in these cells elevated the production of IL-6 and IL-8 and enhanced ERK signaling when the cells were stimulated with IL-17A. Galectin-7 attenuated IL-17A-induced production of inflammatory mediators by keratinocytes via the microRNA-146a/ERK pathway. Moreover, galectin-7-deficient mice showed enhanced epidermal hyperplasia and skin inflammation in response to intradermal IL-23 injection. We identified fluvastatin as an inducer of galectin-7 expression by connectivity map analysis, confirmed this effect in keratinocytes, and demonstrated that fluvastatin attenuated IL-6 and IL-8 production induced by IL-17A. Thus, we validate a role of galectin-7 in the pathogenesis of psoriasis, in both epidermal hyperplasia and keratinocyte-mediated inflammatory responses, and formulate a rationale for the use of statins in the treatment of psoriasis.

A deep dive into UV-based phototherapy: Mechanisms of action and emerging molecular targets in inflammation and cancer

UV-based phototherapy (including psoralen plus UVA (PUVA), UVB and UVA1) has a long, successful history in the management of numerous cutaneous disorders. Photoresponsive diseases are etiologically diverse, but most involve disturbances in local (and occasionally systemic) inflammatory cells and/or abnormalities in keratinocytes that trigger inflammation. UV-based phototherapy works by regulating the inflammatory component and inducing apoptosis of pathogenic cells. This results in a fascinating and complex network of simultaneous events-immediate transcriptional changes in keratinocytes, immune cells, and pigment cells; the emergence of apoptotic bodies; and the trafficking of antigen-presenting cells in skin-that quickly transform the microenvironment of UV-exposed skin. Molecular elements in this system of UV recognition and response include chromophores, metabolic byproducts, innate immune receptors, neurotransmitters and mediators such as chemokines and cytokines, antimicrobial peptides, and platelet activating factor (PAF) and PAF-like molecules that simultaneously shape the immunomodulatory effects of UV and their interplay with the microbiota of the skin and beyond. Phototherapy's key effects-proapoptotic, immunomodulatory, antipruritic, antifibrotic, propigmentary, and pro-prebiotic-promote clinical improvement in various skin diseases such as psoriasis, atopic dermatitis (AD), graft-versus-host disease (GvHD), vitiligo, scleroderma, and cutaneous T-cell lymphoma (CTCL) as well as prevention of polymorphic light eruption (PLE). As understanding of phototherapy improves, new therapies (UV- and non-UV-based) are being developed that will modify regulatory T-cells (Treg), interact with (resident) memory T-cells and /or utilize agonists and antagonists as well as antibodies targeting soluble molecules such as cytokines and chemokines, transcription factors, and a variety of membrane-associated receptors.

CCL20 in psoriasis: A potential biomarker of disease severity, inflammation, and impaired vascular health

BACKGROUND

Psoriasis is associated with increased cardiovascular risk that is not captured by traditional proinflammatory biomarkers.

OBJECTIVE

To investigate the relationship between Psoriasis Area and Severity Index, circulating proinflammatory biomarkers, and vascular health in psoriasis.

METHODS

In patients with psoriasis and in age and sex-matched controls, 273 proteins were analyzed with the Proseek Multiplex Cardiovascular disease reagents kit and Inflammatory reagents kit (Olink Bioscience), whereas vascular endothelial inflammation and health were measured via direct transcriptomic analysis of brachial vein endothelial cells.

RESULTS

In psoriasis, chemokine ligand 20 (CCL20), interleukin (IL) 6, and IL-17A were the top 3 circulating proinflammatory cytokines. Vascular endothelial inflammation correlated with CCL20 (r = 0.55; P < .001) and less so with IL-6 (r = 0.36; P = .04) and IL-17A (r = 0.29; P = .12). After adjustment for potential confounders, the association between CCL20 and vascular endothelial inflammation remained significant (β = 1.71; P = .02). In nested models, CCL20 added value (χ² = 79.22; P < .001) to a model already incorporating the Psoriasis Area and Severity Index, Framingham risk, high-sensitivity C-reactive protein, Il-17A, and IL-6 (χ² = 48.18; P < .001) in predicting vascular endothelial inflammation.

LIMITATIONS

Our study was observational and did not allow for causal inference in the relationship between CCL20 and cardiovascular risk.

CONCLUSION

We demonstrate that CCL20 expression has a strong association with vascular endothelial inflammation, reflects systemic inflammation, and may serve as a potential biomarker of impaired vascular health in psoriasis.

Current and emerging biologics for the treatment of pediatric atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) is a chronic inflammatory skin condition characterized by erythematous lesions, pruritus, and a skin barrier defect. Long-term treatment in children is challenging, as there is only one Food and Drug Administration-approved systemic medication. Current treatments may have limited efficacy or serious side effects in children. With a deeper understanding of AD pathogenesis and the advent of target-specific medications, several biologics are undergoing clinical trials for future use in pediatric AD.

AREAS COVERED

This article reviews the current and emerging biologic therapies for treatment of pediatric AD. It allows for comprehensive comparison of medications and their clinical trials to help providers optimize patient treatment plans while providing expert insight into upcoming advancements in the treatment of pediatric AD.

EXPERT OPINION

Treating pediatric AD is complicated given the variety of disease severity, psychosocial impact, and relative lack of approved medications for severe disease. Given the safety data on dupilumab, newer biologics will likely be second-line. We do not yet understand the long-term impact of newer biologics on an immature immune system, nor do we fully understand their risks and toxicities. We should proceed optimistically, yet cautiously, with the study of biologics in children.

Synergistic induction of IL-23 by TNFα, IL-17A, and EGF in keratinocytes

IL-23 is an inflammatory cytokine that plays an essential role in Th17 immunity by enhancing Th17 cell proliferation and survival, and Th17 cytokine production. IL-23 has pathogenic roles in the development of Th17-mediated inflammatory diseases including psoriasis. Despite successful treatment of psoriasis by blocking IL-23, the regulation of IL-23 expression in psoriasis patients is largely unknown. Dendritic cells are generally considered to be the primary source of IL-23 in psoriasis. While high levels of IL-23 are found in psoriatic epidermis, IL-23 expression in psoriatic keratinoctyes remains a controversial issue. In this study, we demonstrated that IL-23 production is induced by a combination of TNFα and IL-17A in human keratinocytes. Additionally, this IL-23 induction by TNFα and IL-17A is further increased in psoriatic keratinocytes and is enhanced by EGFR signaling. Although IL-23 is also robustly induced by toll-like receptor agonists in dendritic cells and macrophages, IL-23 expression in these cell types is not regulated by TNFα, IL-17A, and EGFR signaling. Given that IL-23 is essential for maintaining Th17 activation, IL-23 induction by TNFα, IL-17A, and EGF in keratinocytes could play an important pathological role in psoriasis pathogenesis as well as the cutaneous rash associated with EGFR inhibition therapy.

Single-cell transcriptomics combined with interstitial fluid proteomics defines cell type-specific immune regulation in atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease, but its complex pathogenesis is only insufficiently understood, resulting in still limited treatment options.

OBJECTIVE

We sought to characterize AD on both transcriptomic and proteomic levels in humans.

METHODS

We used skin suction blistering, a painless and nonscarring procedure that can simultaneously sample skin cells and interstitial fluid. We then compared results with conventional biopsies.

RESULTS

Suction blistering captured epidermal and most immune cells equally well as biopsies, except for mast cells and nonmigratory CD163+ macrophages that were only present in biopsy isolates. Using single-cell RNA sequencing, we found comparable transcriptional profiles of key inflammatory pathways between blister and biopsy AD, but suction blistering was superior in cell-specific resolution for high-abundance transcripts (KRT1/KRT10, KRT16/KRT6A, S100A8/S100A9), which showed some background signals in biopsy isolates. Compared with healthy controls, we found characteristic upregulation of AD-typical cytokines such as IL13 and IL22 in Th2 and Th22 cells, respectively, but we also discovered these mediators in proliferating T cells and natural killer T cells, that also expressed the antimicrobial cytokine IL26. Overall, not T cells, but myeloid cells were most strongly enriched in AD, and we found dendritic cell (CLEC7A, amphiregulin/AREG, EREG) and macrophage products (CCL13) among the top upregulated proteins in AD blister fluid proteomic analyses.

CONCLUSION

These data show that by using cutting-edge technology, suction blistering offers several advantages over conventional biopsies, including better transcriptomic resolution of skin cells, combined with proteomic information from interstitial fluid, unraveling novel inflammatory players that shape the cellular and proteomic microenvironment of AD.

The Emerging Role of IL-17 in the Immune-Pathogenesis of Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is considered to be an autoimmune disorder (type I and type II) in 50% of all cases. However, autoreactive T cells and their proximity with activated mast cells in the skin of CSU patients are believed to be the primary event in mast cell degranulation. The finding of anti-FcɛRIα on mast cells or IgE autoantibodies against thyroid antigens should be considered to be a consequence of the auto-reactive T cells’ recognition of the above-mentioned antigens. Our recent finding of increased Th17 and IL-17 expression in both CD4+ T cells and mast cells in the skin of severe CSU patients is supportive for the major role that T cells perform in the pathogenesis of CSU. Supporting this are numerous previous reports in which increased serum IL-17 was found to be in association with CSU disease severity. The beneficial effect of anti-IL-17A (secukinumab) in CSU patients in whom high dose anti-histamines, recurrent course of steroids and omalizumab fail to achieve a reasonable response should be investigated as a new therapeutic strategy in future studies with a large cohort of patients.

Cutaneous Immune Cell-Microbiota Interactions Are Controlled by Epidermal JunB/AP-1

Atopic dermatitis (AD) is a multi-factorial skin disease with a complex inflammatory signature including type 2 and type 17 activation. Although colonization by S. aureus is common in AD, the mechanisms rendering an organism prone to dysbiosis, and the role of IL-17A in the control of S. aureus-induced skin inflammation, are not well understood. Here, we show several pathological aspects of AD, including type 2/type 17 immune responses, elevated IgE, barrier dysfunction, pruritus, and importantly, spontaneous S. aureus colonization in JunB^Δep mice, with a large transcriptomic overlap with AD. Additionally, using Rag1^−/− mice, we demonstrate that adaptive immune cells are necessary for protection against S. aureus colonization. Prophylactic antibiotics, but not antibiotics after established dysbiosis, reduce IL-17A expression and skin inflammation, examined using Il17a-eGFP reporter mice. Mechanistically, keratinocytes lacking JunB exhibit higher MyD88 levels in vitro and in vivo, previously shown to regulate S. aureus colonization. In conclusion, our data identify JunB as an upstream regulator of microbiota-immune cell interactions and characterize the IL-17A response upon spontaneous dysbiosis.

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JunB^Δep mice display several defining features of atopic dermatitis

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Skin of JunB^Δep mice are colonized by human-derived S. aureus

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Adaptive immune system is necessary for protection against S. aureus

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JunB is an upstream regulator of the microbiota-immune cell interactions

Decoding IL-23 Signaling Cascade for New Therapeutic Opportunities

The interleukin 23 (IL-23) is a key pro-inflammatory cytokine in the development of chronic inflammatory diseases, such as psoriasis, inflammatory bowel diseases, multiple sclerosis, or rheumatoid arthritis. The pathological consequences of excessive IL-23 signaling have been linked to its ability to promote the production of inflammatory mediators, such as IL-17, IL-22, granulocyte-macrophage colony-stimulating (GM-CSF), or the tumor necrosis factor (TNFα) by target populations, mainly Th17 and IL-17-secreting TCRγδ cells (Tγδ17). Due to their pivotal role in inflammatory diseases, IL-23 and its downstream effector molecules have emerged as attractive therapeutic targets, leading to the development of neutralizing antibodies against IL-23 and IL-17 that have shown efficacy in different inflammatory diseases. Despite the success of monoclonal antibodies, there are patients that show no response or partial response to these treatments. Thus, effective therapies for inflammatory diseases may require the combination of multiple immune-modulatory drugs to prevent disease progression and to improve quality of life. Alternative strategies aimed at inhibiting intracellular signaling cascades using small molecule inhibitors or interfering peptides have not been fully exploited in the context of IL-23-mediated diseases. In this review, we discuss the current knowledge about proximal signaling events triggered by IL-23 upon binding to its membrane receptor to bring to the spotlight new opportunities for therapeutic intervention in IL-23-mediated pathologies.

Precision medicine in atopic diseases

PURPOSE OF REVIEW

To analyze the status of precision medicine in atopic diseases.

RECENT FINDINGS

Atopic diseases are increasingly recognized as heterogeneous in nature and they can be quite different in severity, response to therapy, triggers, genetic back ground, ancestral risk and type of inflammation. This significant variability in the landscape of atopic diseases is not reflected in the common treatment guidelines that follow 'one fits all' approach for their management. Such an approach is largely based on minimal 'phenotype' elements, such as severity of disease and response to therapy and does not reflect the information accumulate in the last 20 years about particular pathogenic pathways (endotypes) leading to disease (phenotypes) based on biomolecular analysis of the single individuals. Accumulating data have defined asthma allergic rhinitis, food allergy based on their endotypes and clinically relevant phenotypes. In general, atopic diseases can be largely classified as high or low Th2 inflammatory status, which may explain the severity and response to therapy.

SUMMARY

Precision medicine is aiming to use known endotype phenotype to guide specific individualized treatment. The work aimed in deep characterization of diseases to guide the disease management is crucial in light of the availability of ever more precise treatment able to target specific pathways.

Skin expression of IL-23 drives the development of psoriasis and psoriatic arthritis in mice

Psoriasis (PS) is a chronic skin inflammation. Up to 30% of the patients with PS develop psoriatic arthritis (PsA), a condition characterized by inflammatory arthritis that affects joints or entheses. Although there is mounting evidence for a critical role of interleukin-23 (IL-23) signaling in the pathogenesis of both PS and PsA, it remains unclear whether IL-23-induced skin inflammation drives joint disease. Here, we show that mice expressing increased levels of IL-23 in the skin (K23 mice) develop a PS-like disease that is characterized by acanthosis, parakeratosis, hyperkeratosis, and inflammatory infiltrates in the dermis. Skin disease preceded development of PsA, including enthesitis, dactylitis, and bone destruction. The development of enthesitis and dactylitis was not due to high circulating levels of IL-23, as transgenic animals and controls had similar levels of this cytokine in circulation. IL-22, a downstream cytokine of IL-23, was highly increased in the serum of K23 mice. Although IL-22 deficiency did not affect skin disease development, IL-22 deficiency aggravated the PsA-like disease in K23 mice. Our results demonstrate a central role for skin expressed IL-23 in the initiation of PS and on pathogenic processes leading to PsA.

Interleukin-17 receptor D constitutes an alternative receptor for interleukin-17A important in psoriasis-like skin inflammation

T helper 17 (T_H17) cells and interleukin-17A (IL-17A) produced by them are critical in autoinflammatory diseases, such as psoriasis. IL-17A has been shown to signal through IL-17 receptor A/IL-17 receptor C (IL-17RA/IL-17RC) complex to drive inflammatory responses. However, in a psoriasis model, we found that Il17rc deficiency did not completely ameliorate the disease, suggesting another receptor. In search for another IL-17A-interacting receptor, we found that IL-17RD directly bound IL-17A but not IL-17F or IL-17A/F heterodimer and formed a heterodimer with IL-17RA. IL-17A-, but not IL-17F- or IL-17A/F-, mediated gene expression was defective in Il17rd-deficient keratinocytes. Il17rd deficiency in nonhemopoietic cells attenuated imiquimod-induced psoriasis-like skin inflammation. Although IL-17RC and IL-17RD differentially activated IL-17A-dependent signaling and gene expression, their compound mutation led to complete deficits in keratinocytes. IL-23 was found induced by IL-17A in keratinocytes, dependent on both IL-17RC and IL-17RD, suggesting feed-forward regulation of IL-23/IL-17 axis in psoriasis. Together, IL-17RD constitutes a second functional receptor for IL-17A and, together with IL-17RC, mediates the proinflammatory gene expression downstream of IL-17A.

Activated Platelets Induce Endothelial Cell Inflammatory Response in Psoriasis via COX-1

OBJECTIVE

Patients with psoriasis have impaired vascular health and increased cardiovascular disease (CVD). Platelets are key players in the pathogenesis of vascular dysfunction in cardiovascular disease and represent therapeutic targets in cardiovascular prevention. The object of this study was to define the platelet phenotype and effector cell properties on vascular health in psoriasis and evaluate whether aspirin modulates the platelet-induced phenotype. Approach and Results: Platelets from psoriasis patients (n=45) exhibited increased platelet activation (relative to age- and gender-matched controls, n=18), which correlated with psoriasis skin severity. Isolated platelets from psoriasis patients demonstrated a 2- to 3-fold (P<0.01) increased adhesion to human aortic endothelial cells and induced proinflammatory transcriptional changes, including upregulation of IL 8 (interleukin 8), IL1β, and Cox (cyclooxygenase)-2 Platelet RNA sequencing revealed an interferon signature and elevated expression of COX-1, which correlated with psoriasis disease severity (r=0.83, P=0.01). In a randomized trial of patients with psoriasis, 2 weeks of 81 mg low-dose aspirin, a COX-1 inhibitor, reduced serum thromboxane (Tx) B2 and reduced brachial vein endothelial proinflammatory transcript expression >70% compared with the no-treatment group (P<0.01). Improvement in brachial vein endothelial cell inflammation significantly correlated with change in serum TxB2 (r=0.48, P=0.02).

CONCLUSIONS

In patients with psoriasis, platelets are activated and induce endothelial cell inflammation. Low-dose aspirin improved endothelial cell health in psoriasis via platelet COX-1 inhibition. These data demonstrate a previously unappreciated role of platelets in psoriasis and endothelial cell inflammation and suggests that aspirin may be effective in improving vascular health in patients with psoriasis. Registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT03228017.

[Role of IL-17A and neutrophilic granulocytes in the pathogenesis of psoriasis]

OBJECTIVE

To study the expression of IL-17A in the inflammatory infiltrating cells in the plaques as one of the key points in the pathological process in moderate to severe psoriasis.

MATERIAL AND METHODS

The material obtained from 50 patients with moderate and severe psoriasis was examined by an indirect immunofluorescence assay to determine the composition of cell infiltrate and the type of IL-17A-producing cells in the foci of lesion. The markers of lymphocytes (CD3), dendritic cells (CD11c), neutrophilic granulocytes (Mpo), and mast cells (Trp) were used. The proliferative activity of basal keratinocytes (Ki-67), the expression of IL-17A, and the co-expression of IL-17A, Mpo, and Trp were also studied.

RESULTS

A positive correlation was established between the count of neutrophilic granulocytes in the infiltrate, the expression of IL-17A, and the number of neutrophils expressing IL-17A with the duration of the disease and the severity of the patient's condition.

CONCLUSION

Neutrophilic granulocytes and their expression of IL-17A play one of the key roles in the pathogenesis of psoriasis.

Review-Current Concepts in Inflammatory Skin Diseases Evolved by Transcriptome Analysis: In-Depth Analysis of Atopic Dermatitis and Psoriasis

During the last decades, high-throughput assessment of gene expression in patient tissues using microarray technology or RNA-Seq took center stage in clinical research. Insights into the diversity and frequency of transcripts in healthy and diseased conditions provide valuable information on the cellular status in the respective tissues. Growing with the technique, the bioinformatic analysis toolkit reveals biologically relevant pathways which assist in understanding basic pathophysiological mechanisms. Conventional classification systems of inflammatory skin diseases rely on descriptive assessments by pathologists. In contrast to this, molecular profiling may uncover previously unknown disease classifying features. Thereby, treatments and prognostics of patients may be improved. Furthermore, disease models in basic research in comparison to the human disease can be directly validated. The aim of this article is not only to provide the reader with information on the opportunities of these techniques, but to outline potential pitfalls and technical limitations as well. Major published findings are briefly discussed to provide a broad overview on the current findings in transcriptomics in inflammatory skin diseases.

Skin immunity and its dysregulation in atopic dermatitis, hidradenitis suppurativa and vitiligo

While the epidermis is the frontline defense against infections and indeed, it is a peripheral lymphoid organ, the same immunological mechanisms may initiate and sustain pathological conditions. Indeed, a deregulated action against exogenous pathogens could activate a T cell response in atopic dermatitis, hidradenitis suppurativa and vitiligo. Atopic dermatitis (AD) is a chronic inflammatory skin condition with a complex pathophysiology. Although T helper 2 immunity dysregulation is thought to be the main cause of AD etiopathogenesis, the triggering mechanism is not well understood, and the treatment is often difficult. As the AD, hidradenitis suppurativa (HS) is a chronic inflammatory skin disease with a dramatic impact on the quality of life of the affected patients. The exact pathophysiology of HS is still unclear, but many evidences report a follicular obstruction and subsequent inflammation with TNF-α, interleukin (IL)-1β, IL-10, and IL-17 involvement. Vitiligo is an autoimmune epidermal disorder which consists of melanocytes destruction and skin depigmentation. Melanocytes destruction is mainly due to their increased oxidative-stress sensitivity with a consequent activation of innate first and adaptative immunity (CD8⁺ T cells) later. The understanding of the triggering mechanisms of AD, HS and Vitiligo is pivotal to outline novel therapies aimed at regaining the physiological immune homeostasis of healthy skin. The aim of this review is to provide new insight on the pathogenesis of these skin diseases and to highlight on the new therapeutic approaches adopted in the treatment of AD, HS and Vitiligo.

A potential association between psoriasin to rs4819554 of IL-17RA gene polymorphism in psoriasis Egyptian patients

Interleukin 17 (IL-17) is one of the pro-inflammatory cytokine. Psoriasin is a noticeably over-expressed protein found in the skin lesions of psoriatic patients. Our current study was planned to examine the association of (- 947 A/G) single nucleotide polymorphism (SNP) in IL-17RA promoter region (rs4819554) with psoriasis susceptibility in Egyptian psoriatic patients. Our study included 100 patients and 100, age as well as sex matched, control groups. IL-17RA SNP association was studied using allelic discrimination. RT-qPCR and ELISA were done to assess IL-17 expression. ELISA was performed to assess psoriasin expression. Our study showed a significant association between IL-17 rs4819554 SNP and psoriasis risk, evidenced by higher G allele and AG genotype frequencies in psoriatic patients when compared to controls (allelic: OR 2.283, 95% CI 1.321-3.946, p = 0.003, and genotype: OR 3.026, 95% CI 1.356-6.752, p = 0.007). Additionally, serum psoriasin level was significantly increased when comparing psoriatic patients to controls (p = 0.0003). Moreover, significant increase in IL 17 gene and protein level in AA, AG psoriatic genotypes compared to the corresponding genotypes in normal control (p = 0.0004). IL-17 rs4819554 is significantly associated with psoriasis, and with psoriasin level, in the Egyptian population.