Epidermal CCR6+ γδ T cells are major producers of IL-22 and IL-17 in a murine model of psoriasiform dermatitis

Long-term maintenance of responses to bimekizumab treatment in moderate-to-severe psoriasis: A real-world comparison of Q4W versus Q8W dosing or bio-naïve versus bio-switched patients

Bimekizumab, an interleukin (IL)-17A/IL-17F inhibitor, is effective for moderate-to-severe psoriasis. However, long-term maintenance of early treatment outcomes is not examined in real-world settings, with no analyses stratified by dosing intervals (every 4 weeks [Q4W] vs. 8 weeks [Q8W]) or histories of biologics (bio-naïve vs. bio-switched). We investigated whether the outcomes achieved at week 16 of bimekizumab treatment may be maintained until week 52, stratified by dosing intervals or histories of biologics. This prospective study included 63 Japanese patients (≥15 years) with moderate-to-severe psoriasis. All the patients received bimekizumab 320 mg Q4W until week 16, thereafter Q4W or Q8W. We evaluated the maintenance rates until week 52 for Psoriasis Area and Severity Index (PASI) 75, PASI 90, PASI 100, absolute PASI ≤2, absolute PASI ≤1, Static Physician's Global Assessment (sPGA) 0/1, or Dermatology Life Quality Index (DLQI) 0/1 achieved at week 16, stratified by dosing intervals or histories of biologics. In total patients, the maintenance rates for PASI 75, absolute PASI ≤2 or ≤1, or sPGA 0/1 were mostly 100% until week 52 while those for DLQI 0/1 decreased to around 80%, irrespective of dosing intervals or biologic histories. The maintenance rates for PASI 90 and 100 were mostly 100% in the Q4W group and bio-naïve patients in the Q8W group while both decreased to 71.4% at week 52 in bio-switched patients in the Q8W group. This study showed that the improvement of skin lesions at week 16 of bimekizumab treatment can be almost completely maintained until week 52.

Long-term real-world effectiveness of deucravacitinib in psoriasis: A 52-week prospective study stratified by prior apremilast or biologic therapy

Real-world evidence on the long-term effectiveness of deucravacitinib, a selective tyrosine kinase 2 inhibitor for psoriasis, remains limited, particularly in patients with different histories of systemic treatments. We evaluated the 52-week effectiveness of deucravacitinib in patients with psoriasis, stratified by a history of apremilast or biologic usage. This prospective, single-center study included 110 patients with moderate-to-severe psoriasis who received daily deucravacitinib (6 mg). Psoriasis Area and Severity Index (PASI) and Dermatology Life Quality Index (DLQI) scores during the treatment were analyzed in subgroups stratified by a history of apremilast or biologic usage. Deucravacitinib decreased PASI and DLQI scores for 52 weeks in psoriasis patients, both with and without prior apremilast or biologic usage. The percent reductions from baseline PASI or DLQI at week 52 were similar in apremilast-experienced patients (92% or 77.9%) and apremilast-naive patients (88.3% or 81.6%), respectively. The achievement rates of PASI 100 or absolute PASI ≤1 at week 52 in apremilast-experienced patients (30.8% or 61.5%) were slightly higher than those in apremilast-naive patients (20.5% or 46.2%). The percent reductions from baseline PASI or DLQI at week 52 in biologic-naive patients (91.6 or 82.8%) were slightly higher than those in biologic-experienced patients (57.6% or 63.6%), respectively. The achievement rates of PASI 75, 100 or absolute PASI ≤1 at week 52 in biologic-naive patients (84.4%, 24.4%, or 53.3%) were slightly higher than those in biologic-experienced patients (57.1%, 14.3%, or 28.6%), respectively. Deucravacitinib generated sustained 52-week effectiveness in diverse patient subgroups, supporting its role as a universal treatment for psoriasis.

The Association Between Life's Essential 8 and Psoriasis in American Adults: A Cross-Sectional NHANES Study

Purpose

Life's Essentials 8 (LE8) is a new indicator developed by the American Heart Association to assess cardiovascular health, including diet, physical activity, nicotine exposure, sleep health, body mass index, blood lipids, blood glucose and blood pressure. And more and more studies have shown that this index can evaluate other diseases, such as chronic kidney disease, abdominal aortic calcification and so on. However, there is no relevant study to evaluate the association between LE8 and psoriasis. The purpose of this study was to investigate the relationship between LE8 and the prevalence of psoriasis in American adults.

Patients and Methods

The data are from the National Health and Nutrition Examination Survey (NHANES) of the United States from 2003 to 2006, 2009 to 2014. Psoriasis was the dependent variable. LE8 is an independent variable and is divided into three levels: high, medium and low. Multivariate logistic regression model was used to explore the relationship between LE8 and psoriasis.

Results

A total of 13430 people were included in this study, including 391 patients with psoriasis and 13039 patients without psoriasis. The prevalence of psoriasis was 2.91%. In the fully adjusted logistic regression model, LE8 score was negatively correlated with psoriasis (OR=0.99; 95% CI, 0.98-0.99, P=0.0003). And this result still exists when LE8 is divided into high, medium and low groups. Compared with the low LE8 group, the high LE8 group had a 61% lower risk of psoriasis (OR=0.39; 95% CI, 0.26-0.57, p <0.0001).

Conclusion

This cross-sectional study suggested that LE8 score was negatively correlated with psoriasis risk.

Advancing Basic and Translational Science: Highlights From the Basic Science Workshop at the GRAPPA 2023 Annual Meeting

Contemporary translational and clinical research advances in psoriatic disease (PsD) were highlighted at the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) 2023 annual meeting basic science workshop. This year's workshop focused on key topics, including the significance of the annual GRAPPA meetings as a platform for collaboration and knowledge exchange. Discussions centered around expanding our understanding of tumor necrosis factor inhibitor (TNFi) treatment in PsD and enhancing early detection strategies for PsD comorbidities, specifically for the timely intervention and management of cardiovascular (CV) comorbidities. Insights on the role of the C-C chemokine receptor type 6 (CCR6) in PsD and psoriatic arthritis were provided, suggesting that blockade of CCR6 can reduce psoriasis-like dermatitis and joint inflammation in mouse models.

IL-17 in skin infections and homeostasis

Interleukin (IL) 17 is a proinflammatory cytokine belonging to a structurally related group of cytokines known as the IL-17 family. It has been profoundly studied for its contribution to the pathology of autoimmune diseases. However, it also plays an important role in homeostasis and the defense against extracellular bacteria and fungi. IL-17 is important for epithelial barriers, including the skin, where some of its cellular targets reside. Most of the research work on IL-17 has focused on its effects in the skin within the context of autoimmune diseases or sterile inflammation, despite also having impact on other skin conditions. In recent years, studies on the role of IL-17 in the defense against skin pathogens and in the maintenance of skin homeostasis mediated by the microbiota have grown in importance. Here we review and discuss the cumulative evidence regarding the main contribution of IL-17 in the maintenance of skin integrity as well as its protective or pathogenic effects during some skin infections.

Evidence of size-dependent toxicity of polystyrene nano- and microplastics in sea cucumber Apostichopus japonicus (Selenka, 1867) during the intestinal regeneration

Microplastics are ubiquitous pollutants in the global marine environment. However, few studies have adequately explored the different toxic mechanisms of microplastics (MPs) and nanoplastics (NPs) in aquatic organisms. The sea cucumber, Apostichopus japonicus, is a key organism in the marine benthic ecosystem due to its crucial roles in biogeochemical cycles and food web. This study investigated the bioaccumulation and adverse effects of polystyrene micro- and nanoplastics (PS-M/NPs) of different sizes (20 μm, 1 μm and 80 nm) in the regenerated intestine of A. japonicus using multi-omics analysis. The results showed that after 30-day exposure at the concentration of 0.1 mg L-1, PS-MPs and PS-NPs accumulated to 155.41-175.04 μg g-1 and 337.95 μg g-1, respectively. This excessive accumulation led to increased levels of antioxidases (SOD, CAT, GPx and T-AOC) and reduced activities of immune enzymes (AKP, ACP and T-NOS), indicating oxidative damage and compromised immunity in the regenerated intestine. PS-NPs had more profound negative impacts on cell proliferation and differentiation compared to PS-MPs. Transcriptomic analysis revealed that PS-NPs primarily affected pathways related to cellular components, e.g., ribosome, and oxidative phosphorylation. In comparison, PS-MPs had greater influences on actin-related organization and organic compound metabolism. In the PS-M/NPs-treated groups, differentially expressed metabolites were mainly amino acids, fatty acids, glycerol phospholipid, and purine nucleosides. Additionally, microbial community reconstruction in the regenerated intestine was severely disrupted by the presence of PS-M/NPs. In the PS-NPs group, Burkholderiaceae abundance significantly increased while Rhodobacteraceae abundance decreased. Correlation analyses demonstrated that intestinal regeneration of A. japonicus was closely linked to its enteric microorganisms. These microbiota-host interactions were notably affected by different PS-M/NPs, with PS-NPs exposure causing the most remarkable disruption of mutual symbiosis. The multi-omic approaches used here provide novel insights into the size-dependent toxicity of PS-M/NPs and highlight their detrimental effects on invertebrates in M/NPs-polluted marine benthic ecosystems.

Cytokines in psoriasis: From pathogenesis to targeted therapy

Psoriasis is a multifactorial disease that affects 0.84% of the global population and it can be associated with disabling comorbidities. As patients present with thick scaly lesions, psoriasis was long believed to be a disorder of keratinocytes. Psoriasis is now understood to be the outcome of the interaction between immunological and environmental factors in individuals with genetic predisposition. While it was initially thought to be solely mediated by cytokines of type-1 immunity, namely interferon-γ, interleukin-2, and interleukin-12 because it responds very well to cyclosporine, a reversible IL-2 inhibitor; the discovery of Th-17 cells advanced the understanding of the disease and helped the development of biological therapy. This article aims to provide a comprehensive review of the role of cytokines in psoriasis, highlighting areas of controversy and identifying the connection between cytokine imbalance and disease manifestations. It also presents the approved targeted treatments for psoriasis and those currently under investigation.

T cell-mediated skin-brain axis: Bridging the gap between psoriasis and psychiatric comorbidities

Psoriasis, a chronic inflammatory skin condition, is often accompanied by psychiatric comorbidities such as anxiety, depression, suicidal ideation, and other mental disorders. Psychological disorders may also play a role in the development and progression of psoriasis. The intricate interplay between the skin diseases and the psychiatric comorbidities is mediated by the 'skin-brain axis'. Understanding the mechanisms underlying psoriasis and psychiatric comorbidities can help improve the efficacy of treatment by breaking the vicious cycle of diseases. T cells and related cytokines play a key role in the pathogenesis of psoriasis and psychiatric diseases, and are crucial components of the 'skin-brain axis'. Apart from damaging the blood-brain barrier (BBB) directly, T cells and secreted cytokines could interact with the hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS) to exacerbate skin diseases or mental disorders. However, few reviews have systematically summarized the roles and mechanisms of T cells in the interaction between psoriasis and psychiatric comorbidities. In this review, we discussed several key T cells and their roles in the 'skin-brain axis', with a focus on the mechanisms underlying the interplay between psoriasis and mental commodities, to provide data that might help develop effective strategies for the treatment of both psoriasis and psychiatric comorbidities.

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Unconjugated bilirubin and its derivative ameliorate IMQ-induced psoriasis-like skin inflammation in mice by inhibiting MMP9 and MAPK pathway

Psoriasis is a chronic immune-mediated inflammatory skin disease that involves dysregulated proliferation of keratinocytes. Psoriatic skin lesions are characterized by redness, thickness, and scaling. The interleukin axis of IL-23/IL-17 is critically involved in the development of human psoriasis. Imiquimod (IMQ), an agonist of TLR7 is known to induce psoriatic-like skin inflammation in mice. The topical application of IMQ induces systemic inflammation with increased proinflammatory cytokines in serum and secondary lymphoid organs. Further, matrix metalloproteases (MMPs) have been implicated in the pathophysiology of psoriatic-like skin inflammation. The increased MMP9 activity and gene expression of proinflammatory cytokines in IMQ-induced psoriatic skin is mediated by the activation of the MAPK pathway. Moreover, the increased expression of neutrophil-specific chemokines confirmed the infiltration of neutrophils at the site of psoriatic skin inflammation. In contrast, expression of IL-10, an anti-inflammatory cytokine gene expression is reduced in IMQ-treated mice skin. Topical application of unconjugated bilirubin (UCB) and its derivative dimethyl ester of bilirubin (BD1) on IMQ-induced psoriatic mice skin significantly mitigated the symptoms of psoriasis by inhibiting the activity of MMP9. Further, UCB and BD1 reduced neutrophil infiltration as evidenced by decreased myeloperoxidase (MPO) activity and reduced gene expression of proinflammatory cytokines, and neutrophil-specific chemokines. Apart from these modulations UCB and BD1 reduced MAPK phosphorylation and upregulated anti-inflammatory cytokines. To conclude, UCB and BD1 immunomodulated the psoriatic skin inflammation induced by IMQ in mice by inhibiting neutrophil mediated MMP9, decreased proinflammatory cytokines gene expression and modulating the MAPK pathway.

Is Mir-205 a possible biomarker for evaluating treatment response in psoriasis?

Psoriasis is a chronic skin disease that affects a significant number of patients and can severely impair quality of life. Although the diagnosis is normally clinical, paraclinical determination can occasionally be useful either in differential diagnosis or in evaluating the inflammatory response to treatment. MicroRNAs (miRNAs) are small non-coding parts of the RNA family that regulate gene expression and may have an important role as biomarkers in evaluating treatment response. The dysregulation of miRNAs has been well studied in other diseases, especially in oncology, but their role in chronic skin conditions such as psoriasis is still not fully understood. This study aims to evaluate the levels of three miRNAs (miR-155, miR-210, and miR-205) in patients with psoriasis, treated either systemically or topically, compared to a control group, and to assess the possible relationship between miRNA levels and systemic therapy. Our findings show a constant dysregulation of miR-205 in patients with psoriasis, with significantly higher levels compared to the control group, which can be explained as conferring a protective effect to treated patients. Further studies are needed in order to fully understand the role of miRNAs in the physiopathology of psoriasis and even, potentially, to provide more targeted genetic therapies in the future.

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.

Keratinocyte proline-rich protein modulates immune and epidermal response in imiquimod-induced psoriatic skin inflammation

Psoriasis is a persistent inflammatory skin disease thought to arise as a result of the infiltration of inflammatory cells and activation of keratinocytes. Recent advances in basic research and clinical experience revealed that the interleukin (IL)-23/IL-17 axis has been identified as a major immune pathway in psoriasis. However, it remains unclear how keratinocyte factors contribute to the pathology of psoriasis. Keratinocyte proline-rich protein (KPRP) is a proline-rich insoluble protein, which is present in the epidermis and is likely to be involved in the skin barrier function. Here, to investigate the potential roles of KPRP in psoriatic skin inflammation, Kprp-modified mice were applied in the imiquimod (IMQ)-induced skin inflammation model, which develops psoriasis-like epidermal hyperplasia and cutaneous inflammation features. Then, heterozygous knockout (Kprp+/- ) but not homozygous knockout (Kprp-/- ) mice displayed attenuated skin erythema compared to control wild-type mice. In addition, RNA sequencing, quantitative PCR and/or histological analysis detected changes in the expression of several molecules related to psoriatic inflammation or keratinocyte differentiation in Kprp+/- mice, but not Kprp-/- mice. Further analysis exhibited reduced IL-17-producing γδlow T cells and amplified epidermal hyperplasia in Kprp+/- mice, which were implied to be related to decreased expression of β-defensins and increased expression of LPAR1 (Lysophosphatidic acid receptor 1), respectively. Thus, our results imply that KPRP has the potential as a therapeutic target in psoriatic skin inflammation.

γδ T cells: origin and fate, subsets, diseases and immunotherapy

The intricacy of diseases, shaped by intrinsic processes like immune system exhaustion and hyperactivation, highlights the potential of immune renormalization as a promising strategy in disease treatment. In recent years, our primary focus has centered on γδ T cell-based immunotherapy, particularly pioneering the use of allogeneic Vδ2+ γδ T cells for treating late-stage solid tumors and tuberculosis patients. However, we recognize untapped potential and optimization opportunities to fully harness γδ T cell effector functions in immunotherapy. This review aims to thoroughly examine γδ T cell immunology and its role in diseases. Initially, we elucidate functional differences between γδ T cells and their αβ T cell counterparts. We also provide an overview of major milestones in γδ T cell research since their discovery in 1984. Furthermore, we delve into the intricate biological processes governing their origin, development, fate decisions, and T cell receptor (TCR) rearrangement within the thymus. By examining the mechanisms underlying the anti-tumor functions of distinct γδ T cell subtypes based on γδTCR structure or cytokine release, we emphasize the importance of accurate subtyping in understanding γδ T cell function. We also explore the microenvironment-dependent functions of γδ T cell subsets, particularly in infectious diseases, autoimmune conditions, hematological malignancies, and solid tumors. Finally, we propose future strategies for utilizing allogeneic γδ T cells in tumor immunotherapy. Through this comprehensive review, we aim to provide readers with a holistic understanding of the molecular fundamentals and translational research frontiers of γδ T cells, ultimately contributing to further advancements in harnessing the therapeutic potential of γδ T cells.

Cellular Mechanisms of Psoriasis Pathogenesis: A Systemic Review

Psoriasis is a common inflammatory skin disease characterized by abnormal proliferation of epidermal keratinocytes and massive infiltration of inflammatory cells. Many kinds of cells, including keratinocytes, T lymphocytes, dendritic cells, neutrophils, and macrophages, are reported to play critical roles in the pathogenesis and progression of psoriasis. However, to date, the role of each kind of cell in the pathogenesis and development of psoriasis has not been systematically reviewed. In addition, although antibodies developed targeting cytokines (e.g. IL-23, IL-17A, and TNF-α) released by these cells have shown promising results in the treatment of psoriasis patients, these targeted antibodies still do not cure psoriasis and only provide short-term relief of symptoms. Furthermore, long-term use of these antibodies has been reported to have adverse physical and psychological effects on psoriasis patients. Therefore, gaining a deeper understanding of the cellular and molecular pathogenesis of psoriasis and providing new thoughts on the development of psoriasis therapeutic drugs is of great necessity. In this review, we summarize the roles of various cells involved in psoriasis, aiming to provide new insights into the pathogenesis and development of psoriasis at the cellular level and hoping to provide new ideas for exploring new and effective psoriasis treatments.

Lipoxin A4 Ameliorates Imiquimod-Induced Psoriasis-Like Dermatitis via Promoting the Regression of Inflammation

Introduction

As a mediator of inflammation resolution, lipoxin A4 (LXA4) mainly plays an anti-inflammatory role and promotes inflammation resolution. LXA4 plays an inhibiting inflammatory role in a variety of diseases, tissues and cells, including keratinocytes. Psoriasis is a chronic inflammatory skin disease mediated by dysregulation of inflammation of immune cells and keratinocytes. However, the expression and role of LXA4 in psoriasis-like mouse models are still unclear.

Methods

Imiquimod (IMQ) topical treatment of dorsal skin induces psoriasis-like dermatitis in BALB/c mice, pretreated intraperitoneally with or without LXA4 prior to IMQ application. Severity of dorsal lesions is assessed by using a modified human scoring system and histopathology. The concentration of LXA4 and the expression of ALOX15 (a key gene in LXA4 metabolic synthesis) in lesional skins were detected by ELISA and Western blot. Quantitative PCR and ELISA were conducted to detect the mRNA and secretion levels of inflammatory cytokines. The proportion of IL-17A-producing γδT cells in skin and skin draining cervical lymph nodes and helper (Th) 17 cells in spleens was evaluated by flow cytometry. Western blotting was used to analyze the expressions of p-STAT3 and TRAF6.

Results

The concentration of LXA4 and the expression of ALOX15 were decreased in IMQ-induced lesional skin. LXA4 significantly relieved psoriasis-like lesions in IMQ-induced mouse models. Furthermore, LXA4 decreased IMQ-induced systemic inflammation, including reduced the proportion of IL-17A-producing gdT cells in skin and skin draining cervical lymph nodes and Th17 cells in spleens, the secretion and expression of CCL20, IL-17A, IL-1β, and TNF-α in skin and serum. LXA4 markedly inhibited IMQ-induced expression of TRAF6 and p-STAT3.

Conclusion

LXA4 significantly ameliorates IMQ-induced psoriasis-like inflammation, and LXA4 can be used as a target for psoriasis treatment.

The Chemokine, CCL20, and Its Receptor, CCR6, in the Pathogenesis and Treatment of Psoriasis and Psoriatic Arthritis

Background

Chemokines represent a superfamily of immune-modulatory small protein molecules that regulate leukocyte migration to inflammatory sites through their chemoattractant and cell signaling properties. This review focuses on the immunological functions of the CCR6 chemokine receptor and is chemokine ligand, CCL20, that contribute to it role in inflammation in human psoriasis.

Methods

Peer-reviewed relevant articles are searched and selected from 2000 to 2022 using the search engines including PubMed and Google Scholar.

Results

After selectively reviewing and evaluating over seventy articles, a comprehensive overview on the immunology of CCL20-CCR6 axis in psoriasis and psoriatic arthritis, the X-ray crystal structures of CCL20 monomers, and the potential of developing clinical therapies targeting this axis is summarized.

Conclusions

Over the past decade, preclinical studies carried out in animal models of psoriasis involving agents targeting CCL20-CCR6 axis have yielded promising results. Other studies that this axis may play a role in a number of other autoimmune diseases, including rheumatoid arthritis, suggesting a rationale for further investigation into this key signaling/migratory pathway.

Immunoproteasome inhibition attenuates experimental psoriasis

Introduction

Psoriasis is an autoimmune skin disease associated with multiple comorbidities. The immunoproteasome is a special form of the proteasome expressed in cells of hematopoietic origin.

Methods

The therapeutic use of ONX 0914, a selective inhibitor of the immunoproteasome, was investigated in Card14ΔE138+/- mice, which spontaneously develop psoriasis-like symptoms, and in the imiquimod murine model.

Results

In both models, treatment with ONX 0914 significantly reduced skin thickness, inflammation scores, and pathological lesions in the analyzed skin tissue. Furthermore, immunoproteasome inhibition normalized the expression of several pro-inflammatory genes in the ear and significantly reduced the inflammatory infiltrate, accompanied by a significant alteration in the αβ+ and γδ+ T cell subsets.

Discussion

ONX 0914 ameliorated psoriasis-like symptoms in two different murine psoriasis models, which supports the use of immunoproteasome inhibitors as a therapeutic treatment in psoriasis.

The role of cells of the innate immune system in psoriasis

Psoriasis is an immune-mediated disease with a complex pathogenesis. The close relationship between the development of psoriasis and the adaptive immune response is already known. However, recent data have shown that innate immune cells also play an important role in the development of psoriasis. Congenital lymphoid cells, dendritic cells, T cells, NK cells, and NKT lymphocytes are activated in psoriasis, contributing to disease pathology through IL-17-dependent and independent mechanisms. During disease progression, T cells secrete proinflammatory cytokines that induce and exacerbate the course of psoriasis. T cells have memory cell properties that respond rapidly to secondary stimulation, which contributes to disease relapse. This article presents an overview of recent findings demonstrating the role of innate immunity in psoriasis.

Up-regulation of BTN3A1 on CD14+ cells promotes Vγ9Vδ2 T cell activation in psoriasis

Vγ9Vδ2 T cells play an important role in the development and progression of psoriasis vulgaris (PV), but how they promote skin inflammation and the molecular mechanisms underlying Vγ9Vδ2 T cell dysfunction are poorly understood. Here, we show that circulating Vγ9Vδ2 T cells are decreased and exhibit enhanced proliferation and increased production of IFN-γ and TNF-α in PV patients. Monocytes from PV patients express higher levels of the phosphoantigen sensor butyrophilin 3A1 (BTN3A1) than monocytes from healthy controls. Blockade of BTN3A1 suppresses Vγ9Vδ2 T cell activation and abolishes the difference in Vγ9Vδ2 T cell activation between PV patients and healthy controls. The CD14+ cells in PV skin lesions highly express BTN3A1 and juxtapose to Vδ2 T cells. In addition, IFN-γ induces the up-regulation of BTN3A1 on monocytes. Collectively, our results demonstrate a crucial role of BTN3A1 on monocytes in regulating Vγ9Vδ2 T cell activation and highlight BTN3A1 as a potential therapeutic target for psoriasis.

Gain-of-function of TRPM4 predisposes mice to psoriasiform dermatitis

Transient receptor potential melastatin 4 (TRPM4) is a Ca2+-activated, monovalent cation channel that is expressed in a wide range of cells. We previously reported two gain-of-function (GoF) mutations of TRPM4 as the cause of progressive symmetric erythrokeratodermia (PSEK), which shares similar clinical and histopathological features with psoriasis. Using CRISPR/Cas9 technology, we generated TRPM4I1029M mice that have the equivalent mutation to one of the two genetic mutations found in human PSEK (equivalent to human TRPM4I1033M). Using this mutant mice, we examined the effects of TRPM4 GoF at the cellular and phenotypic levels to elucidate the pathological mechanisms underlying PSEK. In the absence of experimental stimulation, TRPM4I1029M mice did not show a phenotype. When treated with imiquimod (IMQ), however, TRPM4I1029M mice were predisposed to more severe psoriasiform dermatitis (PsD) than wild-type (WT), which was characterized by greater accumulation of CCR6-expressing γδ T cells and higher mRNA levels of Il17a. In TRPM4I1029M mice, dendritic cells showed enhanced migration and keratinocytes exhibited increased proliferation. Moreover, a TRPM4 inhibitor, glibenclamide, ameliorated PsD in WT and TRPM4I1029M mice. Our results indicate elevated TRPM4 activities boosted susceptibility to cutaneous stimuli, likely through elevation of membrane potential and alteration of downstream cellular signaling, resulting in enhanced inflammation. Our results further suggest a possible therapeutic application of TRPM4 inhibitors in psoriasis.

Excessive intake of sugar: An accomplice of inflammation

High sugar intake has long been recognized as a potential environmental risk factor for increased incidence of many non-communicable diseases, including obesity, cardiovascular disease, metabolic syndrome, and type 2 diabetes (T2D). Dietary sugars are mainly hexoses, including glucose, fructose, sucrose and High Fructose Corn Syrup (HFCS). These sugars are primarily absorbed in the gut as fructose and glucose. The consumption of high sugar beverages and processed foods has increased significantly over the past 30 years. Here, we summarize the effects of consuming high levels of dietary hexose on rheumatoid arthritis (RA), multiple sclerosis (MS), psoriasis, inflammatory bowel disease (IBD) and low-grade chronic inflammation. Based on these reported findings, we emphasize that dietary sugars and mixed processed foods may be a key factor leading to the occurrence and aggravation of inflammation. We concluded that by revealing the roles that excessive intake of hexose has on the regulation of human inflammatory diseases are fundamental questions that need to be solved urgently. Moreover, close attention should also be paid to the combination of high glucose-mediated immune imbalance and tumor development, and strive to make substantial contributions to reverse tumor immune escape.

Single-cell transcriptomics reveals a senescence-associated IL-6/CCR6 axis driving radiodermatitis

Irradiation‐induced alopecia and dermatitis (IRIAD) are two of the most visually recognized complications of radiotherapy, of which the molecular and cellular basis remains largely unclear. By combining scRNA‐seq analysis of whole skin‐derived irradiated cells with genetic ablation and molecular inhibition studies, we show that senescence‐associated IL‐6 and IL‐1 signaling, together with IL‐17 upregulation and CCR6⁺‐mediated immune cell migration, are crucial drivers of IRIAD. Bioinformatics analysis colocalized irradiation‐induced IL‐6 signaling with senescence pathway upregulation largely within epidermal hair follicles, basal keratinocytes, and dermal fibroblasts. Loss of cytokine signaling by genetic ablation in IL‐6^−/− or IL‐1R^−/− mice, or by molecular blockade, strongly ameliorated IRIAD, as did deficiency of CCL20/CCR6‐mediated immune cell migration in CCR6^−/− mice. Moreover, IL‐6 deficiency strongly reduced IL‐17, IL‐22, CCL20, and CCR6 upregulation, whereas CCR6 deficiency reciprocally diminished IL‐6, IL‐17, CCL3, and MHC upregulation, suggesting that proximity‐dependent cellular cross talk promotes IRIAD. Therapeutically, topical application of Janus kinase blockers or inhibition of T‐cell activation by cyclosporine effectively reduced IRIAD, suggesting the potential of targeted approaches for the treatment of dermal side effects in radiotherapy patients.

Bile Acids Improve Psoriasiform Dermatitis through Inhibition of IL-17A Expression and CCL20-CCR6-Mediated Trafficking of T Cells

Bile acids (BAs), produced in the liver and further transformed in the gut, are cholesterol-derived molecules involved in essential physiological processes. Recent studies suggest that BAs regulate T helper 17 cell function, but the underlying mechanism of this action and their therapeutic value in disease models remains unclear. Using an IL-23 minicircle DNA-based murine model of psoriasiform dermatitis, we showed that oral administration of secondary BAs, including lithocholic acid (LCA), deoxycholic acid, and 3-oxoLCA, significantly improved psoriasiform dermatitis without inducing apparent hepatotoxicity. Of the BAs tested, LCA possessed the greatest potency in treating psoriasiform dermatitis. Intravenous administration of LCA at a much lower dosage (compared with oral treatment) showed a comparable antipsoriatic effect and markedly suppressed the IL-17A response. Ex vivo experiments revealed that LCA reduced IL-17A production in IL-23-stimulated murine T cells in the absence of BA receptors TGR5 or FXR. Strikingly, BAs inhibited CCL20 expression in keratinocytes, which led to reduced migration of CCR6-expressing Jurkat cells cultured in the conditioned medium of stimulated keratinocytes. Thus, BAs improve psoriasiform dermatitis with minimal toxicity via direct inhibition of IL-17A production and blockade of CCL20-mediated trafficking, supporting the potential use of BAs in psoriasis.

Topical astilbin ameliorates imiquimod-induced psoriasis-like skin lesions in SKH-1 mice via suppression dendritic cell-Th17 inflammation axis

Astilbin, an essential component of Rhizoma smilacis glabrae, exerts significant antioxidant and anti‐inflammatory effects against various autoimmune diseases. We have previously reported that astilbin decreases proliferation and improves differentiation of HaCaT keratinocytes in a psoriatic model. The present study was designed to evaluate the potential therapeutic effects of topical administration of astilbin on an imiquimod (IMQ)‐induced psoriasis‐like murine model and to reveal their underlying mechanisms. Topical administration of astilbin at a lower dose alleviated IMQ‐induced psoriasis‐like skin lesions by inducing the differentiation of epidermal keratinocytes in mice, and the therapeutic effect was even better than that of calcipotriol. Moreover, the inflammatory skin disorder was relieved by astilbin treatment characterized by a reduction in both IL‐17‐producing T cell accumulation and psoriasis‐specific cytokine expression in skin lesions. Furthermore, we found that astilbin inhibited R837‐induced maturation and activation of bone marrow‐derived dendritic cells and decreased the expression of pro‐inflammatory cytokines by downregulating myeloid differentiation factor 88. Our findings provide the convincing evidence that lower doses of astilbin might attenuate psoriasis by interfering with the abnormal activation and differentiation of keratinocytes and accumulation of IL‐17‐producing T cells in skin lesions. Our results strongly support the pre‐clinical application of astilbin for psoriasis treatment.

γδ T Cells in Skin Inflammation

Gamma delta (γδ) T cells are a subset of T lymphocytes that express T cell receptor γ and 5 chains and display structural and functional heterogeneity. γδ T cells are typically of low abundance in the body and account for 1-5% of the blood lymphocytes and peripheral lymphoid tissues. As a bridge between innate and adaptive immunity, γδ T cells are uniquely poised to rapidly respond to stimulation and can regulate immune responses in peripheral tissues. The dendritic epidermal T cells in the skin epidermis can secrete growth factors to regulate skin homeostasis and re-epithelization and release inflammatory factors to mediate wound healing during skin inflammatory responses. Dermal γδ T cells can regulate the inflammatory process by producing interleukin-17 and other cytokines or chemokines. Here, we offer a review of the immune functions of γδ T cells, intending to understand their role in regulating skin barrier integrity and skin wound healing, which may be crucial for the development of novel therapeutics in skin diseases like atopic dermatitis and psoriasis.

Psoriasiform skin reaction due to Brazilian keratin treatment: A clinical-dermatoscopic study of 43 patients

Introduction:

Hair straightening products like the Brazilian Keratin Treatment (BKT) contain high concentrations of formaldehyde, and its use is associated with adverse effects. In 2016, seven cases of eczema-like psoriasiform skin reaction secondary to BKT were described for the first time. We aim to investigate the clinical characteristics and dermatoscopic findings of patients with psoriasiform skin reactions due to BKT.

Materials and Methods:

A cross-sectional study was performed from October 2017 to June 2020. Patients who developed erythema and scales on the scalp following the use of BKT were included. Age, sex, number of BKTs, time elapsed between BKT and the skin reaction, pull test, and dermatoscopic findings were investigated. Descriptive and inferential statistics were used.

Results:

We found 43 patients with a mean age of 35 ± 10 years, predominantly females in 42 (98%) cases. The mean number of BKTs was 2 ± 2. The mean length of time elapsed to present the reaction was 12 ± 17 months and this was related to the number of BKTs (P = 0.01). The pull test was positive in 37 (86%) patients. The most frequent dermatoscopic findings were perifollicular scales in 42 (98%), red patches in 35 (81%), and peripilar desquamation resembling the outer skin of an onion bulb in 32 (74%).

Conclusion:

Hair straightening products are widely used and the psoriasiform skin reaction that develops afterward might be underdiagnosed. It is important to investigate the background of BKT in conjunction with the clinical and dermatoscopic findings suggestive of this cutaneous reaction.

Small molecule allosteric inhibitors of RORγt block Th17-dependent inflammation and associated gene expression in vivo

Retinoic acid receptor-related orphan nuclear receptor (ROR) γt is a member of the RORC nuclear hormone receptor family of transcription factors. RORγt functions as a critical regulator of thymopoiesis and immune responses. RORγt is expressed in multiple immune cell populations including Th17 cells, where its primary function is regulation of immune responses to bacteria and fungi through IL-17A production. However, excessive IL-17A production has been linked to numerous autoimmune diseases. Moreover, Th17 cells have been shown to elicit both pro- and anti-tumor effects. Thus, modulation of the RORγt/IL-17A axis may represent an attractive therapeutic target for the treatment of autoimmune disorders and some cancers. Herein we report the design, synthesis and characterization of three selective allosteric RORγt inhibitors in preclinical models of inflammation and tumor growth. We demonstrate that these compounds can inhibit Th17 differentiation and maintenance in vitro and Th17-dependent inflammation and associated gene expression in vivo, in a dose-dependent manner. Finally, RORγt inhibitors were assessed for efficacy against tumor formation. While, RORγt inhibitors were shown to inhibit tumor formation in pancreatic ductal adenocarcinoma (PDAC) organoids in vitro and modulate RORγt target genes in vivo, this activity was not sufficient to delay tumor volume in a KP/C human tumor mouse model of pancreatic cancer.

Psoriasis as an Immune-Mediated and Inflammatory Systemic Disease: From Pathophysiology to Novel Therapeutic Approaches

Psoriasis is an immune-mediated inflammatory disease, with a chronic relapsing-remitting course, which affects 2–3% of the worldwide population. The progressive acquisitions of the inflammatory pathways involved in the development of psoriasis have led to the identification of the key molecules of the psoriatic inflammatory cascade. At the same time, psoriasis therapy has radically evolved with the introduction of target molecules able to modify the natural history of the disease, acting specifically on these inflammatory pathways. For these reasons, biologics have been demonstrated to be drugs able to change the disease’s natural history, as they reduce the inflammatory background to avoid irreversible organ damage and prevent systemic complications. However, several issues related to the use of biologics in patients with systemic comorbidities, remain open. All these data reflect the extraordinary potentiality of biologics, but also the unmet medical need to improve our knowledge on the long-term risk related to continuous use of these drugs, and their administration in special populations. This narrative review aims to highlight both the efficacy and safety profile of biologics in psoriasis, starting from pathophysiology and moving towards their clinical application.

Targeting the CCR6/CCL20 axis in entheseal and cutaneous inflammation

OBJECTIVES

To assess the involvement of the CCR6/CCL20 axis in psoriatic arthritis (PsA) and psoriasis (PsO) and to evaluate its potential as a therapeutic target.

METHODS

First, we quantified CCL20 levels in peripheral blood and synovial fluid of PsA patients and the presence of CCR6⁺ cells in synovial and tendon tissue. Utilizing an IL-23 minicircle DNA (MC) mouse model exhibiting key features of both PsO and PsA, we investigated CCR6 and CCL20 expression and the preventive and therapeutical effect of CCL20 blockade. Healthy tendon stromal cells were stimulated in vitro with IL-1β to assess the production of CCL20 by qPCR and ELISA. The effect of conditioned media from stimulated tenocytes in inducing T cell migration was interrogated with a transwell system.

RESULTS

We observed an upregulation of both CCR6 and CCL20 in the enthesis of IL-23 MC-treated mice, which was confirmed in human biopsies. Specific targeting of the CCR6/CCL20 axis with a CCL20 locked dimer (CCL20LD) blocked entheseal inflammation, leading to profound reductions in clinical and proinflammatory markers in the joints and skin of IL-23 MC-treated mice. The stromal compartment in the tendon was the main source of CCL20 in this model and accordingly, in vitro activated human tendon cells were able to produce this chemokine and to induce CCR6+ T cell migration, the latter of which could be blocked by CCL20LD.

CONCLUSIONS

Our studies highlight the pathogenic role of CCR6-CCL20 axis in enthesitis and raise the prospect of a novel therapeutic approach for treating patients with PsO and PsA.

CCR6-CCL20 axis as a therapeutic target for autoimmune diseases

Chemokine receptor CCR6 is expressed on various cells such as B cells, immature dendritic cells, innate lymphoid cells (ILCs), regulatory CD4 T cells, and Th17 cells. CCL20 is the only known high-affinity ligand that binds to CCR6 and drives CCR6⁺ cells' migration in tissues. CCL20 is mainly produced by epithelial cells, and its expression is increased by several folds under inflammatory conditions. Genome-wide association studies (GWAS) in patients with inflammatory bowel disease (IBD), psoriasis (PS), rheumatoid arthritis (RA), and multiple sclerosis (MS) showed a very strong correlation between the expression of CCR6 and disease severity. It has been shown that disruption of CCR6-CCL20 interaction by using antibodies or antagonists prevents the migration of CCR6 expressing immune cells at the site of inflammation and reduces the severity of the disease. This review discussed the importance of the CCR6-CCL20 axis in IBD, PS, RA, and MS, and recent advances in targeting the CCR6-CCL20 in controlling these autoimmune diseases.

Fingolimod ameliorates imiquimod-induced psoriasiform dermatitis by sequestrating interleukin-17-producing ?d T cells in secondary lymph nodes

BACKGROUND

Psoriasis is a chronic inflammatory skin disease. Interleukin (IL)-17A plays a key role in the pathogenesis of psoriasis. Fingolimod, which is available for the treatment of multiple sclerosis, exerts anti-inflammatory effects by sequestrating inflammatory lymphocytes in secondary lymphoid tissues and the thymus. The effect of fingolimod on psoriasis has not been reported yet.

OBJECTIVE

Our objectives were to investigate the effect of fingolimod on psoriasis utilizing mice with imiquimod (IMQ)-induced psoriasiform dermatitis, and explore the possibility of fingolimod as a therapeutic agent for psoriasis.

METHODS

Psoriasiform dermatitis was induced by imiquimod application on murine shaved back skin for six days. Fingolimod prepared in phosphate-buffered saline (PBS), or PBS alone as a control, was administered intraperitoneally daily from days 0 to 5.

RESULTS

Fingolimod ameliorated IMQ-induced psoriasis dermatitis clinically and histologically. On day 6, the mRNA expression level of IL-17A was lower in the skin of fingolimod-treated mice than in that of PBS-treated mice, whereas it was higher in the inguinal lymph nodes of fingolimod-treated mice than in those of PBS-treated mice. Flow cytometric analyses revealed that fingolimod reduced IL-17A-producing ?d T cells infiltrating into the skin, whereas it increased these cells in the inguinal lymph nodes. Fingolimod inhibited egress of Langerhans cells from the skin to lymph nodes.

CONCLUSION

Our results demonstrated that fingolimod showed effectiveness for IMQ-induced psoriasiform dermatitis by hindering the emigration of IL-17A-producing ?d T cells from the lymph nodes to the skin, and suggest that fingolimod is a promising candidate for the treatment of psoriasis.

SZB120 Exhibits Immunomodulatory Effects by Targeting eIF2α to Suppress Th17 Cell Differentiation

IL-17-secreting Th17 cells play an important role in the pathogenesis of various inflammatory and autoimmune diseases. IL-17-targeted biologics and small molecules are becoming promising treatments for these diseases. In this study, we report that SZB120, a derivative of the natural compound 3-acetyl-β-boswellic acid, inhibits murine Th17 cell differentiation by interacting with the α-subunit of eukaryotic initiation factor 2 (eIF2α). We showed that SZB120 directly interacts with eIF2α and contributes to serine 51 phosphorylation of eIF2α. The suppressive effect of SZB120 on Th17 cell differentiation was reversed by GSK2606414, an inhibitor of eIF2α phosphokinase. Phosphorylation of eIF2α induced by SZB120 decreased the protein expression of IκBζ, which is important for Th17 cell differentiation. Notably, interaction with eIF2α by SZB120 also impaired glucose uptake and glycolysis in T cells. In vivo, SZB120 treatment of C57BL/6 mice significantly attenuated IL-17/Th17-mediated autoimmune disease. Our study indicates that SZB120 is a promising drug candidate for IL-17/Th17-mediated inflammatory diseases.

Gamma Delta T Cells and Their Pathogenic Role in Psoriasis

γδT cells are an unconventional population of T lymphocytes that play an indispensable role in host defense, immune surveillance, and homeostasis of the immune system. They display unique developmental, distributional, and functional patterns and rapidly respond to various insults and contribute to diverse diseases. Although γδT cells make up only a small portion of the total T cell pool, emerging evidence suggest that aberrantly activated γδT cells may play a role in the pathogenesis of psoriasis. Dermal γδT cells are the major IL-17-producing cells in the skin that respond to IL-23 stimulation. Furthermore, γδT cells exhibit memory-cell-like characteristics that mediate repeated episodes of psoriatic inflammation. This review discusses the differentiation, development, distribution, and biological function of γδT cells and the mechanisms by which they contribute to psoriasis. Potential therapeutic approaches targeting these cells in psoriasis have also been detailed.

Tissue Resident Memory γδT Cells in Murine Uterus Expressed High Levels of IL-17 Promoting the Invasion of Trophocytes

γδT cells are non-conventional T cells and serve as the bridge for connecting the innate and adaptive immune systems. γδT cells form a substantial population at barrier sites and play an important role in the development of physiology, inflammation, autoimmune diseases and tumors. γδT cells not only distribute in the maternal-fetal interface during pregnancy but also in non-pregnant uterus. However, the phenotypes and functions of γδT cells in uterus were not clear. In the current study, we found that the percentages of γδT cells were significantly higher in uterus than peripheral blood and most of γδT cells in uterus were distributed in endometrium. Further studies indicated that the majority of γδT cells in uterus were memory cells with higher expression of CD44 and CD27 but lower expression of CD62L and CCR7 compared to those in blood. In addition, we found that γδT cells in uterus were tissue resident memory γδT cells expressing CD69, expressed high levels of CCR6, GranzymeB and CD107a. Moreover, γδT cells in uterus were activated and fully expressed transcription factor RORγt. After short time of activation, γδT cells in uterus significantly expressed high levels of IL-17 but not IFN-γ, which promotes the invasion of murine trophocytes. Taken together, our study will lay the foundation for future research on uterine γδT cells in pregnancy and autoimmune disease.

Differential Requirement for CCR6 in IL-23-Mediated Skin and Joint Inflammation

CCR6 is important for the trafficking of IL-17A-producing γδ T cells and required for the development of psoriasiform dermatitis in an IL-23 intradermal injection model. The role of CCR6, however, in IL-23-mediated joint inflammation is unclear. We herein hydrodynamically delivered IL-23 minicircle DNA into wild-type and CCR6-deficient (CCR6-knockout) mice to induce overexpression of IL-23 systemically. After IL-23 gene transfer, wild-type mice exhibited concurrent skin and joint changes that recapitulate some features found in human psoriatic skin and joints. CCR6-knockout mice were resistant to IL-23-induced skin inflammation but exhibited no changes in joint inflammation compared with wild-type mice. Depletion of neutrophils protected wild-type mice from skin and joint disease without suppressing T helper type 17 cytokine expression. In contrast, mice lacking γδ T cells showed a partial reduction in neutrophilic recruitment and a significant decrease in IL-17A expression in skin and paw tissue. Thus, in an IL-23-mediated model that allows concurrent assessment of both skin and joint disease, we showed that CCR6 is critical for inflammation in the skin but not in the joint. Furthermore, our data suggest that neutrophils and γδ T cells are key effector cells in IL-23-mediated skin and joint inflammation in mice.

A gut dysbiotic microbiota-based hypothesis of human-to-human transmission of non-communicable diseases

Non-communicable diseases (NCDs) have replaced communicable diseases as the leading cause of premature death worldwide over the past century. Increasing numbers of studies have reported a link between NCDs and dysbiotic gut microbiota. Some gut microbiota, such as Helicobacter pylori, have been implicated in person-to-person transmission. Based on these reports, we develop a hypothesis regarding dysbiotic microbiota-associated NCDs, and explore how the presence of communicable NCDs could be confirmedexperimentally. We have also reviewed reports on environmental factors, including a high-fat diet, alcohol, smoking, exercise, radiation and air pollution, which have been associated with dysbiotic microbiota, and determined whether any of these parameters were also associated with NCDs. This review discusses the potential mechanism by which dysbiotic microbiota induced by environmental factors are directly or indirectly involved in person-to-person transmission. The hypothetical interplay between the environment, gut microbiota and host can be tested through high-throughput sequencing, animal models, and cell studies, although each of these modalities presents specific challenges. Confirmation of a causative association of dysbiotic microbiota with NCDs would represent a paradigm shift in efforts to prevent and control these diseases, and should stimulate additional studies on the associations among environmental factors, gut microbiota, and NCDs.

The double-edged role of IL-22 in organ fibrosis

Fibrosis is unregulated tissue repair in damaged or diseased organs, and the accumulation of excess extracellular matrix (ECM) impacts the structure and functions of organs, leading to death. Fibrosis is usually triggered by inflammation and tissue damage, and inflammatory mediators stimulate the proliferation of myofibroblasts and the excessive production of ECM. The IL-10 family cytokines play important roles in the development of fibrosis, and its member IL-22 has recently attracted specific attention. IL-22 plays great roles in preventing pathogens invasion and tissue damage, as well as making a contribution to pathogenic processes. Increasing evidence suggested that IL-22 is a key molecule in tissue repair, proliferation and mucosal barrier defense, and it has also been suggested to play both pro-fibrotic and anti-fibrotic roles in tissues. In this review, we summarized the pro-fibrotic and anti-fibrotic functions of IL-22 in various organs which may be of great significance for the development of potential therapeutic strategies for fibrosis-related diseases.

Role of Innate Immune Cells in Psoriasis

Psoriasis is a chronic inflammatory skin condition caused by a combination of hereditary and environmental factors. Its development is closely related to the adaptive immune response. T helper 17 cells are major IL-17-producing cells, a function that plays an important role in the pathogenesis of psoriasis. However, recent findings have demonstrated that innate immune cells also contribute to the development of psoriasis. Innate lymphoid cells, γδ T cells, natural killer T cells, and natural killer cells are activated in psoriasis, contributing to disease pathology through IL-17-dependent and -independent mechanisms. The present review provides an overview of recent findings, demonstrating a role for innate immunity in psoriasis.

Differential Roles of the mTOR-STAT3 Signaling in Dermal γδ T Cell Effector Function in Skin Inflammation

Dermal γδT cells play critical roles in skin homeostasis and inflammation. However, the underlying molecular mechanisms by which these cells are activated have not been fully understood. Here, we show that the mechanistic or mammalian target of rapamycin (mTOR) and STAT3 pathways are activated in dermal γδT cells in response to innate stimuli such as interleukin-1β (IL-1β) and IL-23. Although both mTOR complex 1 (mTORC1) and mTORC2 are essential for dermal γδT cell proliferation, mTORC2 deficiency leads to decreased dermal γδT17 cells. It appears that mitochondria-mediated oxidative phosphorylation is critical in this process. Notably, although the STAT3 pathway is critical for dermal Vγ4T17 effector function, it is not required for γδ6T17 cells. Transcription factor IRF-4 activation promotes dermal γδT cell IL-17 production by linking IL-1β and IL-23 signaling. The absence of mTORC2 in dermal γδT cells, but not STAT3, ameliorates skin inflammation. Taken together, our results demonstrate that the mTOR-STAT3 signaling differentially regulates dermal γδT cell effector function in skin inflammation.

Cai et al. demonstrate that the mTOR and STAT3 signaling pathways differentially regulate dermal Vγ4 and Vγ6 T cell effector function, leading to distinct outcomes in skin inflammation.

C5a/C5aR1 mediates IMQ-induced psoriasiform skin inflammation by promoting IL-17A production from γδ-T cells

Psoriasis is a chronic relapsing inflammatory skin disease, affecting up to 3% of the global population. Accumulating evidence suggests that the complement system is involved in its pathogenesis. Our previous study revealed that the C5a/C5aR1 pathway is crucial for disease development. However, the underlying mechanisms remain largely unknown. To explore potential mechanisms, psoriatic skin lesions and histological changes were assessed following imiquimod (IMQ) cream treatment. Inflammatory cytokine expression was tested by real-time RT-PCR. Immunohistochemistry and flow cytometry were used to identify inflammatory cell infiltration and interleukin (IL-17A) IL-17A expression. A C5aR1 antagonist (C5aR1a) and PI3K inhibitor (wortmannin) were used for blocking experiments (both in vivo and in vitro) to explore the mechanism. C5a/C5aR1-pathway inhibition significantly attenuated psoriasis-like skin lesions with decreased epidermal hyperplasia, downregulated type 17-related inflammatory gene expression, and reduced IL-17A-producing γδ-T cell responses. Mechanistically, C5a/C5aR1 promoted the latter phenotype via PI3K-Akt signaling. Consistently, C5aR1 deficiency clearly ameliorated IMQ-induced chronic psoriasiform dermatitis, with a significant decrease in IL-17A expression. Finally, blocking C5aR1 signaling further decreased psoriasiform skin inflammation in IL-17-deficient mice. Results suggest that C5a/C5aR1 mediates experimental psoriasis and skin inflammation by upregulating IL-17A expression from γδ-T cells. Blocking C5a/C5aR1/IL-17A axis is expected to be a promising strategy for psoriasis treatment.

Animal models of psoriasis-highlights and drawbacks

Research into the pathophysiology of psoriasis remains challenging, because this disease does not occur naturally in laboratory animals. However, specific aspects of its complex immune-pathology can be illuminated through transgenic, knockout, xenotransplantation, immunological reconstitution, drug-induced, or spontaneous mutation models in rodents. Although some of these approaches have already been pursued for more than 5 decades and even more models have been described in recent times, they have surprisingly not yet been systematically validated. As a consequence, researchers regularly examine specific aspects that only partially reflect the complex overall picture of the human disease. Nonetheless, animal models are of great utility to investigate inflammatory mediators, the communication between cells of the innate and the adaptive immune systems, the role of resident cells as well as new therapies. Of note, various manipulations in experimental animals resulted in rather similar phenotypes. These were called "psoriasiform", "psoriasis-like" or even "psoriasis" usually on the basis of some similarities with the human disorder. Xenotransplantation of human skin onto immunocompromised animals can overcome this limitation only in part. In this review, we elucidate approaches for the generation of animal models of psoriasis and assess their strengths and limitations with a certain focus on more recently developed models.

Development and Function of γδT Cells in the Oral Mucosa

To successfully withstand a wide variety of microbial and mechanical challenges, the immune system of the oral mucosa is composed of tissue-resident and specially recruited leukocytes. These leukocytes facilitate the establishment and maintenance of local homeostasis but are also capable to cause oral pathologies when are unrestrained. γδT cells represent an important tissue-resident innate T-cell population in various mucosal and nonmucosal barrier tissues, in which they are ideally located to assist in immunosurveillance, tissue repair, and homeostasis. Whereas most works studying γδT cells were focused on tissues such as the skin and intestine, these cells in the oral mucosa were only recently thoroughly studied. The findings obtained by those studies appear to be both complementary and contradicting, likely reflecting differences in the experimental settings and the type of transgenic mouse modalities employed by each study. Nevertheless, oral γδT cells were shown to consist of developmentally distinct tissue-resident Vγ6 cells and circulating Vγ1 and Vγ4 subsets that are independently maintained in the oral mucosa. In the gingiva, a particularly challenging barrier tissue due to its proximity to the dental plaque, γδT cells are strategically positioned close to the plaque and represent the major source of IL-17. While this suggests that γδT cells might be involved in controlling the dental biofilm, conflicting data were reported in this regard. In vivo studies have shown that γδT cells either play a protective role during age-associated bone loss or, alternatively, have no impact in this process. Also, recent reports suggested opposing data concerning the impact of γδT cells in experimental periodontitis based on the ligature model. This review summarizes and discusses the most up-to-date literature on oral γδT cells, providing a balanced perspective regarding our current understanding on the development of oral γδT cells and their role under physiologic conditions and certain oral pathologies.

Keratinocyte interleukin-36 receptor expression orchestrates psoriasiform inflammation in mice

IL-36 stimulation of keratinocytes orchestrates key pathogenic inflammatory responses in psoriatic skin.

The IL-36 family cytokines have emerged as important mediators of dermal inflammation in psoriasis and have been reported to provide a proinflammatory stimulus to a variety of immune and stromal cell subsets in the inflamed skin. However, it remains to be determined which cell type, if any, in the skin plays a predominant role in mediating IL-36 cytokines instructive role in disease. Here, we demonstrate that targeted deletion of Il36r in keratinocytes results in similar levels of protection from psoriasiform inflammation observed in “global” Il36r-deficient mice. Mice with deficiency in IL-36 receptor expression on keratinocytes had significantly decreased expression, comparable with Il36r-deficient mice, of established mediators of psoriatic inflammation, including, IL-17a, IL-23, IL-22, and a loss of chemokine-induced neutrophil and IL-17A–expressing γδ T-cell subset infiltration to the inflamed skin. These data demonstrate that keratinocytes are the primary orchestrating cell in mediating the effects of IL-36–driven dermal inflammation in the imiquimod model of psoriasiform inflammation and shed new light on the cell-specific roles of IL-36 cytokines during psoriatic disease.

Interleukin-17A and Keratinocytes in Psoriasis

The excellent clinical efficacy of anti-interleukin 17A (IL-17A) biologics on psoriasis indicates a crucial pathogenic role of IL-17A in this autoinflammatory skin disease. IL-17A accelerates the proliferation of epidermal keratinocytes. Keratinocytes produce a myriad of antimicrobial peptides and chemokines, such as CXCL1, CXCL2, CXCL8, and CCL20. Antimicrobial peptides enhance skin inflammation. IL-17A is capable of upregulating the production of these chemokines and antimicrobial peptides in keratinocytes. CXCL1, CXCL2, and CXCL8 recruit neutrophils and CCL20 chemoattracts IL-17A-producing CCR6⁺ immune cells, which further contributes to forming an IL-17A-rich milieu. This feed-forward pathogenic process results in characteristic histopathological features, such as epidermal hyperproliferation, intraepidermal neutrophilic microabscess, and dermal CCR6⁺ cell infiltration. In this review, we focus on IL-17A and keratinocyte interaction regarding psoriasis pathogenesis.

Short-Term Exposure to a Western Diet Induces Psoriasiform Dermatitis by Promoting Accumulation of IL-17A-Producing γδ T Cells

A Western diet (WD)-characterized by its high fat and simple sugar content-is thought to predispose individuals to inflammatory skin diseases such as psoriasis through the development of obesity. This scenario, however, is being challenged by emerging data suggesting that dietary components, rather than obesity itself, may exacerbate psoriasis. We herein show that short-term feeding with a diet analogous to the WD in mice leads to T helper type 1-/T helper type 17-biased skin inflammation before significant body weight gain. Feeding for as little as 4 weeks with a WD promoted mild dermatitis and accumulation of IL-17A-producing γδ T cells in the skin. Strikingly, γδ T cells from WD-fed mice exhibited enriched IL-23 receptor expression and increased the potential to produce IL-17A after IL-23 stimulation. In contrast to wild-type mice, WD-fed TCRδ-deficient and CCR6-deficient mice had reduced skin inflammation and IL-17A expression. Supplementation with a bile acid sequestrant, cholestyramine, prevented WD-induced skin inflammation along with a reduction in the infiltration of γδ T cells and the expression of proinflammatory mediators. In summary, our data revealed dietary influences in inflammatory signaling in the skin. The dysregulation of IL-23 pathways and bile acid pathways may be key to the development of WD-associated psoriasiform dermatitis.

Diet-induced obesity exacerbates imiquimod-mediated psoriasiform dermatitis in anti-PD-1 antibody-treated mice: Implications for patients being treated with checkpoint inhibitors for cancer

BACKGROUND

An ever-increasing number of cancer patients are being treated with checkpoint inhibitors such as anti-PD-1 antibodies, and a small percentage of these patients develop a psoriasis-like skin eruption or severe flares of prior psoriasis.

OBJECTIVE

We investigated the role of obesity in immune checkpoint inhibitors-exacerbated psoriasiform eruption.

METHODS

We fed female C57BL/6 mice a so-called Western diet (WD) or a control diet (CD). Imiquimod (IMQ) was applied topically on ears for 5 consecutive days to induce psoriasiform dermatitis (PsD). Psoriasis-related markers were examined by quantitative real-time PCR. Then we induced PsD in WD- and CD-fed mice in the presence or absence of systemic treatment of anti-PD-1 antibodies to examine if obese mice are more susceptible to anti-PD-1 related PsD than lean mice.

RESULTS

WD-fed mice showed higher baseline mRNA expression levels of psoriasis-associated cytokines such as IL-17, S100A8, and S100A9 compared to mice fed with CD. Furthermore, WD-fed mice had more γδ low (GDL) T cells in the whole skin and higher expression of PD-1 on GDL T cells than CD-fed mice. WD-fed mice receiving anti-PD-1 had more prominent ear swelling than lean mice receiving anti-PD-1 during the 5-day IMQ course (2-fold increase, P < 0.0001 on day 5).

CONCLUSION

WD-induced obesity enhances IMQ-induced psoriasiform inflammation. The finding that WD-fed mice have a more dramatic response to anti-PD-1 than lean mice in terms of IMQ-induced ear swelling suggests that obesity could be a risk factor in the development of psoriasiform eruption during anti-PD-1 therapy.

The EGFR-ERK/JNK-CCL20 Pathway in Scratched Keratinocytes May Underpin Koebnerization in Psoriasis Patients

Epidermal keratinocytes represent a rich source of C-C motif chemokine 20 (CCL20) and recruit CCR6⁺ interleukin (IL)-17A–producing T cells that are known to be pathogenic for psoriasis. A previous study revealed that scratch injury on keratinocytes upregulates CCL20 production, which is implicated in the Koebner phenomenon characteristically seen in psoriasis patients. However, the molecular mechanisms leading to scratch-induced CCL20 production remain elusive. In this study, we demonstrate that scratch injury upregulates the phosphorylation of epidermal growth factor receptor (EGFR) and that the specific EGFR inhibitor PD153035 attenuates scratch-induced CCL20 upregulation in an extracellular signal-related kinase (ERK)-dependent, and to a lesser extent, a c-Jun N-terminal kinase (JNK)-dependent but p38 mitogen-activated protein kinase (MAPK)–independent manner. Immunoreactive CCL20 was visualized in the keratinocytes that lined the scratched wound. IL-17A also induced the phosphorylation of EGFR and further augmented scratch-induced CCL20 upregulation. The EGFR-ERK/JNK-CCL20 pathway in scratched keratinocytes may explain why Koebnerization is frequently seen in psoriasis patients.