Impaired Langerhans cell migration in psoriasis

Prevalence and trends of contact sensitization in patients with psoriasis in Lithuania

Background

Psoriasis and allergic contact dermatitis are 2 very common dermatoses. The relationship between them has not yet been fully understood. Contact dermatitis can be an additional cause of epidermal disruption in psoriasis patients, resulting in poor management of the disease.

Objective

To analyze the tendencies of contact sensitization in a cohort of psoriasis patients with suspected allergic contact dermatitis.

Methods

Psoriasis patients (n = 85) with suspected contact dermatitis underwent patch testing with European Baseline allergen series S-1000 in Vilnius University Hospital Santaros Klinikos Centre of Dermatovenereology from August 2020 to August 2021. Their results are presented in this study.

Results

The patch test was positive in 43.5% (n = 37) of patients. Contact sensitization was more prevalent in patients with mild psoriasis, as characterized by Psoriasis Area Surface Index scores ≤10, compared to those with moderate-to-severe psoriasis (P < .05). Generalized psoriasis and nail involvement were more common among nonsensitized patients (P < .05). Most common contact allergens among sensitized patients were nickel (II) sulfate, formaldehyde, and potassium dichromate.

Conclusion

An inverse trend was observed between psoriasis severity and contact sensitization. Extended psoriatic involvement was uncommon in sensitized patients.

Systemic cellular migration: The forces driving the directed locomotion movement of cells

Directional motility is an essential property of cells. Despite its enormous relevance in many fundamental physiological and pathological processes, how cells control their locomotion movements remains an unresolved question. Here, we have addressed the systemic processes driving the directed locomotion of cells. Specifically, we have performed an exhaustive study analyzing the trajectories of 700 individual cells belonging to three different species (Amoeba proteus, Metamoeba leningradensis, and Amoeba borokensis) in four different scenarios: in absence of stimuli, under an electric field (galvanotaxis), in a chemotactic gradient (chemotaxis), and under simultaneous galvanotactic and chemotactic stimuli. All movements were analyzed using advanced quantitative tools. The results show that the trajectories are mainly characterized by coherent integrative responses that operate at the global cellular scale. These systemic migratory movements depend on the cooperative nonlinear interaction of most, if not all, molecular components of cells.

Integrin α5 regulates motility of human monocyte-derived Langerhans cells during immune response

Langerhans cells (LCs) are mainly present in the epidermis and mucosa, and have important roles during skin infection. Migration of LCs to lymph nodes is essential for antigen presentation. However, due to the difficulties in isolating and culturing human LCs, it is not fully understood how LCs move and interact with the extracellular matrix (ECM) through their adhesion molecules such as integrin, during the immune responses. In this study, we aimed to investigate LC motility, cell shape and the role of integrin under inflammatory conditions using monocyte-derived Langerhans cells (moLCs) as a model. As a result, lipopolysaccharide (LPS) stimulation increased adhesion on fibronectin coated substrate and integrin α5 expression in moLCs. Time-lapse imaging of moLCs revealed that stimulation with LPS elongated cell shape, whilst decreasing their motility. Additionally, this decrease in motility was not observed when pre-treated with a neutralising antibody targeting integrin α5. Together, our data suggested that activation of LCs decreases their motility by promoting integrin α5 expression to enhance their affinity to the fibronectin, which may contribute to their migration during inflammation.

Yinxieling decoction ameliorates psoriasis by regulating the differentiation and functions of Langerhans cells via the TGF-β1/PU.1/IL-23 signal axis

Langerhans cells (LCs) play a critical role in skin immune responses and the development of psoriasis. Yinxieling (YXL) is a representative Chinese herbal medicine for the treatment of psoriasis in South China. It was found to improve psoriasis without obvious side effects in the clinic. Here we attempted to clarify whether and how YXL regulates the differentiation and functions of LCs in Imiquimod (IMQ)-induced psoriasis in vivo and induced LCs in vitro. The Psoriasis Area Severity Index (PASI) score was used to evaluate the efficacy of YXL for IMQ-induced psoriasis-like mice. Flow cytometry was utilized to analyze the effects of YXL, to regulate the differentiation, migration, maturation, and antigen presentation of LCs. The results show that YXL significantly alleviated skin inflammation, as reduced in PASI score and classic psoriasis characteristics in pathological sections. Although there was no effect on the proportion of total DCs in the skin-draining lymph nodes, the expression of epidermal LCs and its transcription factor PU.1 were both markedly inhibited. LCs were also prevented from migrating from epidermal to skin-draining lymph nodes and mature. In addition, the number of LCs carrying antigens in the epidermis increased, which suggested that YXL could effectively prevent LCs from presenting antigens. In vitro, YXL had a significant impact on inhibiting the differentiation of LCs. Further data showed that YXL decreased the relative expression of transforming growth factor-β (TGFβ) messenger RNA (mRNA) and interleukin-23 (IL-23) mRNAs. Thus, YXL alleviates psoriasis by regulating differentiation, migration, maturation, and antigen presentation via the TGFβ/PU.1/IL-23 signal axis.

SPRR1B is Related to the Immune Microenvironment and Can Be Used as a Biomarker for the Diagnosis of Psoriasis

Background

Psoriasis, a chronic inflammatory disorder with an unknown cause, significantly impacts the physical and psychological well-being of patients. However, current biomarkers related to psoriasis lack clinical specificity, sensitivity, and predictive ability.

Methods

In this study, we collected skin lesion tissues from 20 psoriasis patients and 20 normal skin samples. Additionally, we obtained four datasets from the GEO database, which included human psoriasis and healthy specimens. We utilized SVM-RFE analysis and the LASSO regression model to identify potential biomarkers. Furthermore, we examined the composition of immune cell types in psoriasis and their correlation with specific genes.

Results

Our investigation revealed 57 differentially expressed genes (DEGs), and we identified significantly enriched pathways through KEGG pathway analysis. The results of machine learning and WGCNA suggested that LCE3D and SPRR1B could potentially be used as marker genes for diagnosing psoriasis. RT-PCR and immunohistochemical detection confirmed the abnormally high expression of the SPRR1B gene in psoriasis. Analysis of immune cell infiltration revealed a strong positive correlation between SPRR1B and Macrophages M0 and T cells follicular helper, while showing the strongest negative correlation with resting Mast cells. In addition, we found that silencing SPRR1B in IFN-γ-treated HaCat cells could significantly reduce the increase in IL-17, IL-22, KRT6, and KRT16 caused by IFN-γ.

Conclusion

These findings suggest that SPRR1B may have a significant role in the pathogenesis of psoriasis and could be employed as a novel immunomarker for its development.

Single cell and spatial sequencing define processes by which keratinocytes and fibroblasts amplify inflammatory responses in psoriasis

The immunopathogenesis of psoriasis, a common chronic inflammatory disease of the skin, is incompletely understood. Here we demonstrate, using a combination of single cell and spatial RNA sequencing, IL-36 dependent amplification of IL-17A and TNF inflammatory responses in the absence of neutrophil proteases, which primarily occur within the supraspinous layer of the psoriatic epidermis. We further show that a subset of SFRP2+ fibroblasts in psoriasis contribute to amplification of the immune network through transition to a pro-inflammatory state. The SFRP2+ fibroblast communication network involves production of CCL13, CCL19 and CXCL12, connected by ligand-receptor interactions to other spatially proximate cell types: CCR2+ myeloid cells, CCR7+ LAMP3+ dendritic cells, and CXCR4 expressed on both CD8+ Tc17 cells and keratinocytes, respectively. The SFRP2+ fibroblasts also express cathepsin S, further amplifying inflammatory responses by activating IL-36G in keratinocytes. These data provide an in-depth view of psoriasis pathogenesis, which expands our understanding of the critical cellular participants to include inflammatory fibroblasts and their cellular interactions.

Molecular treatment trajectories within psoriatic T lymphocytes: a mini review

Multiple biological processes in mammalian cells are implicated in psoriasis (Ps) development and progression, as well as in the pathogenic mechanisms associated with this chronic immune-mediated inflammatory disease (IMID). These refer to molecular cascades contributing to the pathological topical and systemic reactions in Ps, where local skin-resident cells derived from peripheral blood and skin-infiltrating cells originating from the circulatory system, in particular T lymphocytes (T cells), are key actors. The interplay between molecular components of T cell signalling transduction and their involvement in cellular cascades (i.e. throughout Ca²⁺/CaN/NFAT, MAPK/JNK, PI3K/Akt/mTOR, JAK/STAT pathways) has been of concern in the last few years; this is still less characterised than expected, even though some evidence has accumulated to date identifying them as potential objects in the management of Ps. Innovative therapeutic strategies for the use of compounds such as synthetic Small Molecule Drugs (SMDs) and their various combinations proved to be promising tools for the treatment of Ps via incomplete blocking, also known as modulation of disease-associated molecular tracks. Despite recent drug development having mainly centred on biological therapies for Ps, yet displaying serious limitations, SMDs acting on specific pathway factor isoforms or single effectors within T cell, could represent a valid innovation in real-world treatment patterns in patients with Ps. Of note, due to the intricate crosstalk between intracellular pathways, the use of selective agents targeting proper tracks is, in our opinion, a challenge for modern science regarding the prevention of disease at its onset and also in the prediction of patient response to Ps treatment.

The emerging role of exosomes in innate immunity, diagnosis and therapy

Exosomes, which are nano-sized transport bio-vehicles, play a pivotal role in maintaining homeostasis by exchanging genetic or metabolic information between different cells. Exosomes can also play a vital role in transferring virulent factors between the host and parasite, thereby regulating host gene expression and the immune interphase. The association of inflammation with disease development and the potential of exosomes to enhance or mitigate inflammatory pathways support the notion that exosomes have the potential to alter the course of a disease. Clinical trials exploring the role of exosomes in cancer, osteoporosis, and renal, neurological, and pulmonary disorders are currently underway. Notably, the information available on the signatory efficacy of exosomes in immune-related disorders remains elusive and sporadic. In this review, we discuss immune cell-derived exosomes and their application in immunotherapy, including those against autoimmune connective tissue diseases. Further, we have elucidated our views on the major issues in immune-related pathophysiological processes. Therefore, the information presented in this review highlights the role of exosomes as promising strategies and clinical tools for immune regulation.

Effects of Neuropeptides on Dendritic Cells in the Pathogenesis of Psoriasis

Psoriasis is an autoimmune disease that is characterized by discolored, scaled patches of skin. Clinically, it is found that psychological factors often induce or aggravate the disease. Current research suggests that the pathogenesis of psoriasis involves the nervous and immune systems. This article reviews how neuropeptides secreted by nerve fibers affect dendritic cells in psoriasis. In this review, we describe that the neuropeptides calcitonin gene-related peptide, substance P, and vasoactive intestinal peptide can act on dendritic cells and participate in the pathogenesis of psoriasis. These neuropeptides can affect the secretion of interleukin (IL)-12 and IL-23 by dendritic cells, which stimulate T helper (Th)1, Th17, and Th22 cells to produce immune responses and cause the manifestation of psoriasis. The application of neuropeptide inhibitors can improve the skin lesions of psoriasis, which has been confirmed in clinical trials. Therefore, neuroimmune response may be a new direction to develop new drug treatments and perspectives in the development of psoriasis.

Abnormal lipid metabolism in epidermal Langerhans cells mediates psoriasis-like dermatitis

Psoriasis is a chronic, inflammatory skin disease, frequently associated with dyslipidemia. Lipid disturbance in psoriasis affects both circulatory system and cutaneous tissue. Epidermal Langerhans cells (LCs) are tissue-resident DCs that maintain skin immune surveillance and mediate various cutaneous disorders, including psoriasis. However, the role of LCs in psoriasis development and their lipid metabolic alternation remains unclear. Here, we demonstrate that epidermal LCs of psoriasis patients enlarge with longer dendrites and possess elevated IL-23p19 mRNA and a higher level of neutral lipids when compared with normal LCs of healthy individuals. Accordantly, epidermal LCs from imiquimod-induced psoriasis-like dermatitis in mice display overmaturation, enhanced phagocytosis, and excessive secretion of IL-23. Remarkably, these altered immune properties in lesional LCs are tightly correlated with elevated neutral lipid levels. Moreover, the increased lipid content of psoriatic LCs might result from impaired autophagy of lipids. Bulk RNA-Seq analysis identifies dysregulated genes involved in lipid metabolism, autophagy, and immunofunctions in murine LCs. Overall, our data suggest that dysregulated lipid metabolism influences LC immunofunction, which contributes to the development of psoriasis, and therapeutic manipulation of this metabolic process might provide an effective measurement for psoriasis.

Molecular and cellular regulation of psoriatic inflammation

This review highlights the molecular and cellular mechanisms underlying psoriatic inflammation with an emphasis on recent developments which may impact on treatment approaches for this chronic disease. We consider both the skin and the musculoskeletal compartment and how different manifestations of psoriatic inflammation are linked. This review brings a focus to the importance of inflammatory feedback loops that exist in the initiation and chronic stages of the condition, and how close interaction between the epidermis and both innate and adaptive immune compartments drives psoriatic inflammation. Furthermore, we highlight work done on biomarkers to predict the outcome of therapy as well as the transition from psoriasis to psoriatic arthritis.

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.

Break on through: The role of innate immunity and barrier defence in atopic dermatitis and psoriasis

The human skin can be affected by a multitude of diseases including inflammatory conditions such as atopic dermatitis and psoriasis. Here, we describe how skin barrier integrity and immunity become dysregulated during these two most common inflammatory skin conditions. We summarise recent advances made in the field of the skin innate immune system and its interaction with adaptive immunity. We review gene variants associated with atopic dermatitis and psoriasis that affect innate immune mechanisms and skin barrier integrity. Finally, we discuss how current and future therapies may affect innate immune responses and skin barrier integrity in a generalized or more targeted approach in order to ameliorate disease in patients.

Relationship between Immune Cells, Depression, Stress, and Psoriasis: Could the Use of Natural Products Be Helpful?

Psoriasis is one of the most widespread chronic inflammatory skin diseases, affecting about 2%-3% of the worldwide adult population. The pathogenesis of this disease is quite complex, but an interaction between genetic and environmental factors has been recognized with an essential modulation of inflammatory and immune responses in affected patients. Psoriatic plaques generally represent the clinical psoriatic feature resulting from an abnormal proliferation and differentiation of keratinocytes, which cause dermal hyperplasia, skin infiltration of immune cells, and increased capillarity. Some scientific pieces of evidence have reported that psychological stress may play a key role in psoriasis, and the disease itself may cause stress conditions in patients, thus reproducing a vicious cycle. The present review aims at examining immune cell involvement in psoriasis and the relationship of depression and stress in its pathogenesis and development. In addition, this review contains a focus on the possible use of natural products, thus pointing out their mechanism of action in order to counteract clinical and psychological symptoms.

Phospholipase activity of acyloxyacyl hydrolase induces IL-22-producing CD1a-autoreactive T cells in individuals with psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by Th17 responses. Recent evidence has identified Langerhans cells to have a key role in disease pathogenesis, with constitutive high expression of CD1a and capacity to present lipid antigens to T cells. Phospholipase A2 enzymes generate neolipid antigens for recognition by CD1a-reactive T cells; however, the broader enzymatic pathways of CD1a lipid ligand generation have not been thoroughly investigated. In this study, we used immunofluorescence of skin and ELISpot analyses of CD1a-reactive T cells to investigate the role of the lipase acyloxyacyl hydrolase (AOAH) in CD1a ligand generation with relevance to the pathogenesis of psoriasis. We found that the PLA2 activity of rAOAH leads to the activation of circulating CD1a auto-reactive T cells, leading to the production of IFN-γ and IL-22. Circulating AOAH-responsive CD1a-reactive T cells from patients with psoriasis showed elevated IL-22 production. We observed that AOAH is highly expressed in psoriatic lesions compared to healthy skin. Overall, these data present a role for AOAH in generating antigens that activate circulating lipid-specific CD1a-restricted T cells and, thus, contribute to psoriatic inflammation. These findings suggest that inhibition of PLA2 activity of AOAH may have therapeutic potential for individuals with psoriasis.

CD1a function in human skin disease

The high expression of CD1a on Langerhans cells in normal human skin suggests a central role for this lipid antigen presenting molecule in skin homeostasis and immunity. Although the lipid antigen presenting function of CD1a has been known for years, the physiological and pathological functions of the CD1a system in human skin remain incompletely understood. This review provides an overview of this active area of investigation, and discusses recent insights into the functions of CD1a, CD1a-restricted T cells, and lipid antigens in inflammatory and allergic skin disease. We include recent publications and work presented at the biennial CD1-MR1 EMBO workshop held in 2019 in Oxford, regarding lipids that increase and those that decrease T cell responses to CD1a.

Novel Concepts: Langerhans Cells in the Tumour Microenvironment

Langerhans cells (LCs) are immune cells that reside in the stratified epithelium of the skin and mucosal membranes. They play a range of roles in the skin, including antigen presentation and maintenance of peripheral tolerance. Reports of LC numbers have been variable in different cancer types, with the majority of studies indicating a reduction in their number. Changes in the cytokine profile and other secreted molecules, downregulation of surface molecules on cells and hypoxia all contribute to the regulation of LCs in the tumour microenvironment. Functionally, LCs have been reported to regulate immunity and carcinogenesis in different cancer types. An improved understanding of the function and biology of LCs in tumours is essential knowledge that underpins the development of new cancer immunotherapies.

Cellular scars and local crosstalk in relapsing psoriasis: an example of a skin sticking disease

Psoriasis is an inflammatory disease that arises in genetically predisposed individuals. Chronic skin lesions that contain activated immune cells can persist for years. Systemic inhibition of TNF, IL‐17 and IL‐23 cytokines has revolutionized psoriasis care during the recent decades. Unfortunately, local relapse of disease is common at previously inflamed sites after cessation of treatment. This highlights that fundamental pathologic alterations of the affected tissues are not completely resolved during clinical remission. Here, we present arguments for a local disease memory located in both dermis and epidermis in psoriasis skin. We decipher different cellular components and intercellular crosstalk that sustain local disease memory and amplify disease relapse in human psoriasis. Decrypting the mechanisms underlying the establishment and persistence of pathogenic memory cells in resolved psoriasis may provide new therapeutic perspectives aimed at long‐term remission of psoriasis.

The role of Langerhans cells in epidermal homeostasis and pathogenesis of psoriasis

The skin is the main barrier between the human body and the outside world, which not only plays the role of a physical barrier but also functions as the first line of defence of immunology. Langerhans cells (LCs), as dendritic cells (DC) that play an important role in the immune system, are mainly distributed in the epidermis. This review focuses on the role of these epidermal LCs in regulating skin threats (such as microorganisms, ultraviolet radiation and allergens), especially psoriasis. Since human and mouse skin DC subsets share common ontogenetic characteristics, we can further explore the role of LCs in psoriatic inflammation.

Immunological Memory of Psoriatic Lesions

The natural course of psoriasis is the appearance of new lesions in the place of previous ones, which disappeared after a successful therapy. Recent studies of psoriasis etiopathogenesis showed that after psoriatic plaques have disappeared, in healthy skin we can still find a trace of inflammation in the form of tissue resident memory cells (TRM). They are originally responsible for protection against viral and bacterial infections in non-lymphatic tissues. In psoriatic inflammation, they are characterized by heterogeneity depending on their origin. CD8+ T cells TRM are abundantly present in psoriatic epidermis, while CD4+ TRM preferentially populate the dermis. In psoriasis, epidermal CD8+ TRM cells express CLA, CCR6, CD103 and IL-23R antigen and produce IL-17A during ex vivo stimulation. However, CD4+ CD103+ TRM can also colonize the epidermis and produce IL-22 during stimulation. Besides T cells, Th22 and epidermal DCs proved that epidermal cells in healed skin were still present and functioning after several years of disease remission. It explains the clinical phenomenon of the tendency of psoriatic lesions to relapse in the same location and it allows to develop new therapeutic strategies in the future.

Dendritic cells: The driver of psoriasis

Psoriasis is a chronic skin inflammatory disorder, the immune mechanism of which has been profoundly elucidated in the past few years. The dominance of the interleukin (IL)-23/IL-17 axis is a significant breakthrough in the understanding of the pathogenesis of psoriasis, and treatment targeting IL-23 and IL-17 has successfully benefited patients with the disease. The skin contains a complex network of dendritic cells (DC) mainly composed of epidermal Langerhans cells, bone marrow-derived dermal conventional DC, plasmacytoid DC and inflammatory DC. As the prominent cellular source of α-interferon, tumor necrosis factor-α, IL-12 and IL-23, DC play a pivotal role in psoriasis. Thus, targeting pathogenic DC subsets is a valid strategy for alleviating and preventing psoriasis and other DC-derived diseases. In this review, we survey the known role of DC in this disease.

The efficacy of UVA1 phototherapy in psoriasis: Clinical and histological aspects

BACKGROUND

Although ultraviolet A1 (UVA1) phototherapy is available for nearly 30 years, only few studies have been conducted for plaque-type psoriasis.

OBJECTIVES

To determine the efficacy and safety of UVA1 phototherapy in psoriasis by assessing the clinical and histological outcomes.

METHODS

This open study enrolled 15 patients with moderate to severe plaque-type psoriasis. All of the patients had skin type IV. A whole-body UVA1 device consisting of 24 lamps, was irradiated at a medium dose of 50 J/cm² three-times weekly for 30 sessions. Topical and systemic psoriasis treatments were discontinued before and during treatment; patients could only use emollients and antihistamines until 1-month post-completion. Psoriasis Area and Severity Index (PASI) scores were determined at baseline; at sessions 10th, 20th and 30th; and 1 month after treatment. Four-millimetre punch biopsies were obtained from the same psoriasis lesion at baseline and session 30th. Changes in histopathological gradings and polymorphonuclear, lymphocyte and Langerhans cell numbers were monitored.

RESULTS

Twelve patients completed the study. The mean age was 41.3 years (range: 25-71). The median PASI scores at baseline, session 30th and 1-month post-treatment were 16 (8.2, 43.3), 11 (4.4, 43.3) and 9.2 (2.7, 36.4), respectively. Although the PASI scores had improved significantly by 1-month post-treatment (P = .006), the histological parameters demonstrated minimal changes. All patients tolerated the phototherapy well and the most common side effect was skin tanning.

CONCLUSIONS

While medium-dose UVA1 phototherapy demonstrated some efficacy in moderate to severe plaque-type psoriasis. However, it might not be an excellent choice.

The role of Langerhans cells in pathologies of the skin

Langerhans cells (LCs) are epidermal immune cells of myeloid origin. Although these cells were primarily thought to play a defensive role in the skin, evidence now indicates a diverse range of LC-mediated effects including the relay of viral antigens in herpes simplex infection, recruitment of eosinophils in atopic dermatitis and promotion of a Th17 response in Candida infection. LCs may have a protective or suppressive function in pathologies of the skin, with differing functions being driven by the skin milieu. Understanding LC function will help guide the development of interventions that modulate these cells for therapeutic benefit.

Ezh2 Controls Skin Tolerance through Distinct Mechanisms in Different Subsets of Skin Dendritic Cells

Ezh2, a well-established epigenetic repressor, can down-regulate leukocyte inflammatory responses, but its role in cutaneous health remains elusive. Here we demonstrate that Ezh2 controls cutaneous tolerance by regulating Langerhans cell (LC) transmigration across the epidermal basement membrane directly via Talin1 methylation. Ezh2 deficiency impaired disassembly of adhesion structures in LCs, leading to their defective integrin-dependent emigration from the epidermis and failure in tolerance induction. Moreover, mobilization of Ezh2-deficient Langerin^– dermal dendritic cells (dDCs) via high-dose treatment with a weak allergen restored tolerance, which is associated with an increased tolerogenic potential of Langerin^– dDCs likely due to epigenetic de-repression of Aldh in the absence of Ezh2. Our data reveal novel roles for Ezh2 in governing LC- and dDC-mediated host protection against cutaneous allergen via distinct mechanisms.

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Ezh2 regulates LC transmigration across basement membrane via Talin1 methylation

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Ezh2-mediated LC migration is required for cutaneous tolerance induction

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Ezh2 represses Aldh epigenetically in dermal DCs

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Ezh2-deficient dermal DCs exhibit increased tolerogenicity

Human Langerhans Cells with Pro-inflammatory Features Relocate within Psoriasis Lesions

Psoriasis is a common skin disease that presents with well-demarcated patches of inflammation. Recurrent disease in fixed areas of the skin indicates a localized disease memory that is preserved in resolved lesions. In line with such concept, the involvement of tissue-resident immune cells in psoriasis pathology is increasingly appreciated. Langerhans cells (LCs) are perfectly placed to steer resident T cells and local tissue responses in psoriasis. Here, we present an overview of the current knowledge of LCs in human psoriasis, including findings that highlight pro-inflammatory features of LCs in psoriasis lesions. We also review the literature on conflicting data regarding LC localization and functionality in psoriasis. Our review highlights that further studies are needed to elucidate the molecular mechanisms that drive LCs functionality in inflammatory diseases.

TIM-4 is differentially expressed in the distinct subsets of dendritic cells in skin and skin-draining lymph nodes and controls skin Langerhans cell homeostasis

T cell immunoglobulin and mucin-4 (TIM-4), mainly expressed on dendritic cells (DC) and macrophages, plays an essential role in regulating immune responses. Langerhans cells (LC), which are the sole DC subpopulation residing at the epidermis, are potent mediators of immune surveillance and tolerance. However, the significance of TIM-4 on epidermal LCs, along with other cutaneous DCs, remains totally unexplored. For the first time, we discovered that epidermal LCs expressed TIM-4 and displayed an increased level of TIM-4 expression upon migration. We also found that dermal CD207⁺ DCs and lymph node (LN) resident CD207⁻CD4⁺ DCs highly expressed TIM-4, while dermal CD207⁻ DCs and LN CD207⁻CD4⁻ DCs had limited TIM-4 expressions. Using TIM-4-deficient mice, we further demonstrated that loss of TIM-4 significantly upregulated the frequencies of epidermal LCs and LN resident CD207⁻CD4⁺ DCs. In spite of this, the epidermal LCs of TIM-4-deficient mice displayed normal phagocytic and migratory abilities, comparable maturation status upon the stimulation as well as normal repopulation under the inflamed state. Moreover, lack of TIM-4 did not affect dinitrofluorobenzene-induced contact hypersensitivity response. In conclusion, our results indicated that TIM-4 was differentially expressed in the distinct subsets of DCs in skin and skin-draining LNs, and specifically regulated epidermal LC and LN CD207⁻CD4⁺ DC homeostasis.

Study of serum levels and skin expression of S100B protein in psoriasis

Background

S100B protein was reported to be elevated in psoriatic patients' serum, with no previous evaluation of its skin expression, in contrast to the extensively studied S100 protein.

Objective

To evaluate the serum level and skin expression of S100B in psoriasis to assess its possible involvement in its pathogenesis.

Methods

Serum level of S100B protein was estimated in 40 psoriatic patients of different clinical varieties and 10 healthy controls. S100B protein expression was assessed immunohistochemically in lesional and non-lesional skin of patients and in normal skin of controls. Relation to disease severity was also evaluated.

Results

Serum level of S100B protein was significantly higher in psoriatic patients (0.15±0.03 µg/l) than in controls (0.03±0.007 µg/l) (P-value <0.001) with no significant correlation with PASI score. On comparing grades of S100B protein skin expression in lesional and non-lesional skin biopsies, a statistically significant difference was found (P=0.046) with higher percentage of strong S100B skin expression (60%) in non-lesional than in lesional (42%) skin. All the control biopsies showed negative expression.

Study limitations

Relatively small sample size with a limited range of low PASI scores.

Conclusion

This study points to a potential link between psoriasis and S100B protein with higher serum and skin expression in patients than in controls.

Lower levels of interleukin-1β gene expression are associated with impaired Langerhans' cell migration in aged human skin

Langerhans' cells (LC) play pivotal roles in skin immune responses, linking innate and adaptive immunity. In aged skin there are fewer LC and migration is impaired compared with young skin. These changes may contribute to declining skin immunity in the elderly, including increased skin infections and skin cancer. Interleukin-1β (IL-1β) and tumour necrosis factor-α (TNF-α) are mandatory signals for LC migration and previous studies suggest that IL-1β signalling may be dysregulated in aged skin. Therefore, we sought to explore the mechanisms underlying these phenomena. In skin biopsies of photoprotected young (< 30 years) and aged (> 70 years) human skin ex vivo, we assessed the impact of trauma, and mandatory LC mobilizing signals on LC migration and gene expression. Biopsy-related trauma induced LC migration from young epidermis, whereas in aged skin, migration was greatly reduced. Interleukin-1β treatment restored LC migration in aged epidermis whereas TNF-α was without effect. In uncultured, aged skin IL-1β gene expression was lower compared with young skin; following culture, IL-1βmRNA remained lower in aged skin under control and TNF-α conditions but was elevated after culture with IL-1β. Interleukin-1 receptor type 2 (IL1R2) gene expression was significantly increased in aged, but not young skin, after cytokine treatment. Keratinocyte-derived factors secreted from young and aged primary cells did not restore or inhibit LC migration from aged and young epidermis, respectively. These data suggest that in aged skin, IL-1β signalling is diminished due to altered expression of IL1B and decoy receptor gene IL1R2.

Langerhans cell markers CD1a and CD207 are the most rapidly responding genes in lesional psoriatic skin following adalimumab treatment

TNFα-, IL-23- and IL-17-targeting drugs are highly effective in the treatment of psoriasis. However, the precise molecular mechanism remains unknown. In psoriatic skin, the presence of Langerhans cells (LCs) is reduced, but the role of LC is poorly understood. The purpose of this study was to investigate the impact of TNFα and IL-23/IL-17 on the presence of LC in the skin during treatment. Therefore, psoriatic skin was investigated before and after 4 days of adalimumab or ustekinumab treatment. Furthermore, TNFα and IL-17A stimulation was investigated in an ex vivo model of epidermis and dermis from healthy normal skin kept in cultures at an air-liquid interphase for 4 days. In a gene array analysis, we found that the two LC markers, CD1a and CD207, were among the most up- or downregulated genes in psoriatic skin after anti-TNFα therapy. Validation showed that both mRNA expression and protein level followed the same pattern and became significantly upregulated after 4 days of treatment. No changes were seen after ustekinumab treatment. In the ex vivo skin model, a decrease in the CD1a level was seen after TNFα stimulation and it was caused by LC migration from epidermis. No response in LC migration was seen after IL-17A stimulation. Taken together, we demonstrated that changes in the LC level in epidermis precede the histological and clinical changes during adalimumab treatment in psoriatic skin. Furthermore, TNFα plays a prominent role in orchestrating LC migration in the skin. This seems not to be the true for the IL-23/IL-17A pathway.

Dynamic Changes in Resident and Infiltrating Epidermal Dendritic Cells in Active and Resolved Psoriasis

Epidermal Langerhans cells (LCs) are spatially separated from dermal dendritic cells (DCs) in healthy human skin. In active psoriasis, maintained by local production of IL-23 and IL-17, inflammatory DCs infiltrate both skin compartments. Here we show that CCR2⁺ epidermal DCs (eDCs) were confined to lesional psoriasis and phenotypically distinct from dermal DCs. The eDCs exceeded the number of LCs and displayed high expression of genes involved in neutrophil recruitment and the activation of keratinocytes and T cells. Resident LCs responded to toll-like receptor 4 and toll-like receptor 7/8 activation with increased IL-23 production, whereas eDCs additionally produced IL-1β together with IL-23 and tumor necrosis factor. Psoriasis typically recur in fixed skin lesions. eDCs were absent from resolved psoriasis. Instead, LCs from anti-tumor necrosis factor-treated lesions retained high IL23A expression and responded to toll-like receptor stimulation by producing IL-23. Our results reveal phenotypic and functional properties of eDCs and resident LCs in different clinical phases of psoriasis, and the capacity of these cells to amplify the epidermal microenvironment through the secretion of IL-17 polarizing cytokines.

Psoriatic T cells recognize neolipid antigens generated by mast cell phospholipase delivered by exosomes and presented by CD1a

Psoriasis is a chronic inflammatory skin disease associated with a T helper 17 response. Yet, it has proved challenging to identify relevant peptide-based T cell antigens. Antigen-presenting Langerhans cells show a differential migration phenotype in psoriatic lesions and express constitutively high levels of CD1a, which presents lipid antigens to T cells. In addition, phospholipase A2 (PLA2) is highly expressed in psoriatic lesions and is known to generate neolipid skin antigens for recognition by CD1a-reactive T cells. In this study, we observed expression of a cytoplasmic PLA2 (PLA2G4D) in psoriatic mast cells but, unexpectedly, also found PLA2G4D activity to be extracellular. This was explained by IFN-α-induced mast cell release of exosomes, which transferred cytoplasmic PLA2 activity to neighboring CD1a-expressing cells. This led to the generation of neolipid antigens and subsequent recognition by lipid-specific CD1a-reactive T cells inducing production of IL-22 and IL-17A. Circulating and skin-derived T cells from patients with psoriasis showed elevated PLA2G4D responsiveness compared with healthy controls. Overall, these data present an alternative model of psoriasis pathogenesis in which lipid-specific CD1a-reactive T cells contribute to psoriatic inflammation. The findings suggest that PLA2 inhibition or CD1a blockade may have therapeutic potential for psoriasis.

Analysis of selected allergic reactions among psoriatic patients

Introduction

Psoriasis is a chronic and recurrent inflammatory skin disease. The aetiology is still unknown in spite of numerous scientific researches. There is very little evidence which does not provide enough knowledge about allergic reactions in psoriatic patients. Based on the fact that the epidermal barrier damage allows different allergen types to penetrate into deep layers of epidermis and skin, we can assume that it may lead to immunological reactions.

Aim

To investigate the allergic reaction indicators and hypersensitivity assessment about contact, inhalant and food allergens. The results were analysed with regard to clinical disease indicators and progression stage of dermal lesions.

Material and methods

Eighty patients with psoriasis were examined. The concentration of total IgE antibodies and allergen specific IgE antibodies (asIgE) were analysed. Standard epidermal tests and atopy patch tests were performed. All the patients were estimated for their dermatological condition based on the PASI scale. The control group consisted of 50 patients without psoriasis and allergic history.

Results

Significantly higher concentration of total E immunoglobulin has been stated in the patients with psoriasis. Higher concentrations of specific allergic IgE antibodies were more often observed in the examined group but the most frequently observed values were present in 1–3 class. The most common airborne allergens were birch, artemisia, timothy and rye pollens. There have not been any significant statistical differences in the case of positive epidermal test results.

Conclusions

There is slightly expressed hypersensitivity in psoriatic patients. This hypersensitivity degree correlates with the intensification of symptoms.

Interleukin 20 regulates dendritic cell migration and expression of co-stimulatory molecules

Background

Psoriasis is an inflammatory disease characterized by leukocyte skin infiltration. Interestingly, recent works suggest that the migration of dendritic cells (DCs) is abnormal in psoriatic skin. DCs have significant role in regulating the function of T lymphocytes, at least in part influenced by the local environment of cytokines. In psoriatic skin lesions the expression of IL-20 is highly up-regulated. It is unclear if this cytokine has any influence on DCs.

Methods

Here, we investigated the influence of IL-20 in monocyte-derived dendritic cell (MDDCs) in vitro. This work addressed IL-20 effects on DC maturation, receptor expression and signaling. By use of extra cellular matrix components mimicking the skin environment, we also studied the functional effects of IL-20 on the chemotactic migration of DCs. Based on the recent finding that CD18 integrin are shed during migration of myeloid leukocytes, the concentration of these adhesion molecules was measured in MDDCs culture supernatants post migration.

Results

Following stimulation with IL-20, immature human MDDCs enhanced the expression of the co-stimulatory molecule CD86, further enabling activation of the p38 MAPK, but not the STAT3, pathway. IL-20 increased the migration of MDDCs in a biphasic response narrowly controlled by the interleukin concentration. A concomitant change in the shedding of CD18 integrins suggested that these adhesion molecules play a role in the migration of the MDDCs through the extracellular matrix layer.

Conclusion

Taken together, our findings points to a possible, yet subtle, role of IL-20 in DCs migration. The biphasic response suggests that the aberrant IL-20 expression in psoriasis impedes DC migration, which could be a part of the processes that precipitates the dysregulated inflammatory response associated with this disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s40591-016-0046-x) contains supplementary material, which is available to authorized users.

Interleukin 20 regulates dendritic cell migration and expression of co-stimulatory molecules

BACKGROUND

Psoriasis is an inflammatory disease characterized by leukocyte skin infiltration. Interestingly, recent works suggest that the migration of dendritic cells (DCs) is abnormal in psoriatic skin. DCs have significant role in regulating the function of T lymphocytes, at least in part influenced by the local environment of cytokines. In psoriatic skin lesions the expression of IL-20 is highly up-regulated. It is unclear if this cytokine has any influence on DCs.

METHODS

Here, we investigated the influence of IL-20 in monocyte-derived dendritic cell (MDDCs) in vitro. This work addressed IL-20 effects on DC maturation, receptor expression and signaling. By use of extra cellular matrix components mimicking the skin environment, we also studied the functional effects of IL-20 on the chemotactic migration of DCs. Based on the recent finding that CD18 integrin are shed during migration of myeloid leukocytes, the concentration of these adhesion molecules was measured in MDDCs culture supernatants post migration.

RESULTS

Following stimulation with IL-20, immature human MDDCs enhanced the expression of the co-stimulatory molecule CD86, further enabling activation of the p38 MAPK, but not the STAT3, pathway. IL-20 increased the migration of MDDCs in a biphasic response narrowly controlled by the interleukin concentration. A concomitant change in the shedding of CD18 integrins suggested that these adhesion molecules play a role in the migration of the MDDCs through the extracellular matrix layer.

CONCLUSION

Taken together, our findings points to a possible, yet subtle, role of IL-20 in DCs migration. The biphasic response suggests that the aberrant IL-20 expression in psoriasis impedes DC migration, which could be a part of the processes that precipitates the dysregulated inflammatory response associated with this disease.

Update on psoriasis immunopathogenesis and targeted immunotherapy

Over recent years, significant progress has been made in characterisation of the underlying pathogenic mechanisms in psoriasis, a common cutaneous disease that is associated with major systemic co-morbidity and reduced life expectancy. Basic science discoveries have informed the design of novel therapeutic approaches, many of which are now under evaluation in late-stage clinical trials. Here we describe the complex interplay between immune cell types and cytokine networks that acts within self-perpetuating feedback loops to drive cutaneous inflammation in psoriasis. Genetic studies have been pivotal in the construction of the disease model and more recently have uncovered a distinct aetiology for rare, pustular variants of psoriasis. The translation of mechanistic insights into potential advancements in clinical care will also be described, including several treatments that target the interleukin-23 (IL-23)/T17 immune axis.

The immunopathogenesis of psoriasis

Psoriasis vulgaris is a chronic inflammatory skin disease that results from the complex interplay between keratinocytes, dendritic cells, and T cells. Keratinocytes trigger innate and adaptive immune responses. Dermal myeloid dendritic cells regulate T cell activation and production of cytokines and chemokines that amplify inflammation. Most of the psoriatic T cells discretely produce interferon-γ, interleukin (IL)-17, and IL-22. The initiation phase of psoriasis involves Toll-like receptors, antimicrobial peptide LL37, and plasmacytoid dendritic cells. Keratinocytes are the main cutaneous cell type expressing IL-17 receptors and hence the immune circuit is amplified by keratinocytes upregulating mRNAs for a range of inflammatory products.

Regulation of Dendritic Cell Function in Inflammation

Dendritic cells (DC) are professional antigen presenting cells and link the innate and adaptive immune system. During steady state immune surveillance in skin, DC act as sentinels against commensals and invading pathogens. Under pathological skin conditions, inflammatory cytokines, secreted by surrounding keratinocytes, dermal fibroblasts, and immune cells, influence the activation and maturation of different DC populations including Langerhans cells (LC) and dermal DC. In this review we address critical differences in human DC subtypes during inflammatory settings compared to steady state. We also highlight the functional characteristics of human DC subsets in inflammatory skin environments and skin diseases including psoriasis and atopic dermatitis. Understanding the complex immunoregulatory role of distinct DC subsets in inflamed human skin will be a key element in developing novel strategies in anti-inflammatory therapy.

Angiogenic Potential of Human Neonatal Foreskin Stromal Cells in the Chick Embryo Chorioallantoic Membrane Model

Several studies have demonstrated the multipotentiality of human neonatal foreskin stromal cells (hNSSCs) as being able to differentiate into adipocytes and osteoblasts and potentially other cell types. Recently, we demonstrated that hNSSCs play a role during in vitro angiogenesis and appear to possess a capacity to differentiate into endothelial-like cells; however, their angiogenic potential within an ex vivo environment remains unclear. Current study shows hNSSCs to display significant migration potential in the undifferentiated state and high responsiveness in the in vitro wound healing scratch assay. When hNSSCs were seeded onto the top of the CAM, human von Willebrand factor (hVWF), CD31, smooth muscle actin (SMA), and factor XIIIa positive cells were observed in the chick endothelium. CAMs transplanted with endothelial-differentiated hNSSCs displayed a higher number of blood vessels containing hNSSCs compared to CAMs transplanted with undifferentiated hNSSCs. Interestingly, undifferentiated hNSSCs showed a propensity to differentiate towards ectoderm with indication of epidermal formation with cells positive for CD1a, CK5/6, CK19, FXIIIa, and S-100 cells, which warrant further investigation. Our findings imply a potential angiogenic role for hNSSCs ex vivo in the differentiated and undifferentiated state, with potential contribution to blood vessel formation and potential application in tissue regeneration and vascularization.

Specific roles for dendritic cell subsets during initiation and progression of psoriasis

Several subtypes of APCs are found in psoriasis patients, but their involvement in disease pathogenesis is poorly understood. Here, we investigated the contribution of Langerhans cells (LCs) and plasmacytoid DCs (pDCs) in psoriasis. In human psoriatic lesions and in a psoriasis mouse model (DKO* mice), LCs are severely reduced, whereas pDCs are increased. Depletion of pDCs in DKO* mice prior to psoriasis induction resulted in a milder phenotype, whereas depletion during active disease had no effect. In contrast, while depletion of Langerin-expressing APCs before disease onset had no effect, depletion from diseased mice aggravated psoriasis symptoms. Disease aggravation was due to the absence of LCs, but not other Langerin-expressing APCs. LCs derived from DKO* mice produced increased IL-10 levels, suggesting an immunosuppressive function. Moreover, IL-23 production was high in psoriatic mice and further increased in the absence of LCs. Conversely, pDC depletion resulted in reduced IL-23 production, and therapeutic inhibition of IL-23R signaling ameliorated disease symptoms. Therefore, LCs have an anti-inflammatory role during active psoriatic disease, while pDCs exert an instigatory function during disease initiation.