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

The immunologic role of IL-23 in psoriatic arthritis: a potential therapeutic target

INTRODUCTION

Psoriatic arthritis (PsA) is a debilitating chronic condition characterized by inflammation of the joints, bones, enthesis, and skin. The pivotal role of interleukin-23 (IL-23) in the pathogenesis of PsA has become increasingly evident. This proinflammatory cytokine is markedly elevated in patients with PsA, suggesting its potential as a therapeutic target. Consequently, IL-23 inhibitors have emerged as promising first-line biologic treatments for PsA.

AREAS COVERED

This review delves into the immunopathogenic mechanisms of IL-23 at the cellular and molecular levels in PsA. Furthermore, it provides the recent efficacy and safety profiles of IL-23 inhibitors. We conducted a literature search in PubMed for the following terms: 'IL-23 and psoriatic arthritis,' 'Ustekinumab,' 'Guselkumab,' 'Risankizumab,' and 'Tildrakizumab.' In addition, we retrieved clinical trials involving IL-23 inhibitors registered in ClinicalTrials.gov, EudraCT, and ICTRP.

EXPERT OPINION

Despite the promising outcomes observed with IL-23 inhibitors, several challenges persist. The long-term effects of these agents require further investigation through prospective studies, and their limited accessibility worldwide necessitates urgent attention. Additionally, ongoing research is warranted to explore other potential drug targets within the IL-23/IL-23 R axis. The development of reliable biomarkers could greatly enhance early detection, tailored management strategies, and personalized treatment approaches for patients with PsA.

Targeting cytokines in psoriatic arthritis

Psoriatic arthritis (PsA) is part of the psoriatic disease spectrum and is characterized by a chronic inflammatory process that affects entheses, tendons and joints. Cytokines produced by immune and non-immune cells play a central role in the pathogenesis of PsA by orchestrating key aspects of the inflammatory response. Pro-inflammatory cytokines such as TNF, IL-23 and IL-17 have been shown to regulate the initiation and progression of PsA, ultimately leading to the destruction of the architecture of the local tissues such as soft tissue, cartilage and bone. The important role of cytokines in PsA has been underscored by the clinical success of antibodies that neutralize their function. In addition to biologic agents targeting individual pro-inflammatory cytokines, signaling inhibitors that block multiple cytokines simultaneously such as JAK inhibitors have been approved for PsA therapy. In this review, we will focus on our current understanding of the role of cytokines in the disease process of PsA and discuss potential new treatment options based on modulation of cytokine function.

The role of adipokines in the pathogenesis of psoriasis - a focus on resistin, omentin-1 and vaspin

BACKGROUND

Psoriasis is a chronic immune-mediated skin condition with several types of manifestation, including psoriatic arthritis. In recent years, studies have demonstrated multiple molecules and mechanisms that play important roles in the pathophysiology of psoriasis. Studies have been conducted to determine the role of adipokines, bioactive peptides secreted by the adipose tissue, in the pathogenesis of inflammatory diseases. These studies have shown that adipokines are dysregulated in psoriasis and their abnormal expression profile could contribute to the inflammatory mechanisms observed in psoriasis.

AREAS COVERED

In this review, we discuss the immunomodulatory features of resistin, omentin-1, and vaspin, and discuss their potential involvement in the pathogenesis of psoriasis.

EXPERT OPINION

The adipokines resistin, omentin, and vaspin appear to be promising therapeutic targets in psoriasis. It is important to seek to block the action of resistin, either by blocking its receptors or by blocking its systemic effects with antibodies. In the case of omentin and vaspin, substances that are receptor mimetics of these adipokines should be sought and studies conducted of their analogues for the treatment of psoriasis. To introduce these therapies into clinical practice, multicentre clinical trials are required to confirm their efficacy and safety after initial studies in animal models.

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.

From psoriasis to psoriatic arthritis: epidemiological insights from a retrospective cohort study of 74,046 patients

Introduction

To verify our hypothesis that psoriatic arthritis (PsA) is mainly genetically predetermined and distinct from psoriasis (PsO), we use the TriNetX database to investigate whether intrinsic factors outweigh externals in PsA emergence in PsO patients.

Methods

We conducted three retrospective cohort studies utilizing information from the TriNetX network, whether (a) PsO patients with type 2 diabetes mellitus (DM) face an elevated risk of developing PsA compared to those without type 2 DM; (b) PsO patients who smoke face a higher risk of PsA; and (c) PsO patients with type 2 DM who smoke are more likely to develop PsA than those who do not smoke.

Results

PsO patients with type 2 DM exhibited an elevated risk of developing PsA [hazard ratio (HR), 1.11; 95% CI 1.03-1.20], with the combined outcome demonstrating a heightened HR of 1.31 (95% CI 1.25-1.37). PsO patients with a smoking history exhibited an elevated risk of developing PsA (HR, 1.11; 95% CI 1.06-1.17), with the combined outcome demonstrating a heightened HR of 1.28 (95% CI 1.24-1.33). PsO patients with type 2 DM and a history of smoking were not found to be associated with an increased risk of developing PsA (HR, 1.05; 95% CI 0.92-1.20). However, the combined result revealed a higher risk of 1.15 (95% CI 1.06).

Discussion

These findings suggested that intrinsic factors outweigh external factors in PsA emergence in PsO patients. Further studies may focus on genetic disparities between PsO and PsA as potential risk indicators rather than solely on phenotypic distinctions.

Efficacy and safety of guselkumab in patients with active psoriatic arthritis who had inadequate efficacy and/or intolerance to one prior tumor necrosis factor inhibitor: study protocol for SOLSTICE, a phase 3B, multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

Tumor necrosis factor inhibitors (TNFi) are frequently chosen as the first biologic for patients with psoriatic arthritis (PsA). Given that many patients with PsA are TNFi inadequate responders (TNF-IR; either inadequate efficacy or intolerance), treatments utilizing alternative mechanisms of action are needed. In phase 3 studies, the fully human interleukin (IL)-23p19 subunit-inhibitor, guselkumab, was efficacious in patients with active PsA, including TNFi-IR. Efficacy was generally consistent between TNFi-naïve and TNFi-experienced cohorts; however, in the latter, higher response rates have been observed with the Q4W dosing regimen relative to the Q8W dosing regimen for some endpoints, suggesting the need to evaluate whether more frequent dosing may provide an incremental clinical benefit for TNFi-IR patients.

METHODS

The phase 3b SOLSTICE study will assess guselkumab efficacy and safety in TNFi-IR PsA patients. Eligibility criteria include a PsA diagnosis for ≥ 6 months; active disease (≥ 3 swollen, ≥ 3 tender joints, C-reactive protein ≥ 0.3 mg/dL); and inadequate efficacy with, and/or intolerance to, one prior TNFi. Participants will be randomized 1:1:1 to guselkumab Q4W or Q8W or placebo→guselkumab Q4W (at Week 24). The primary endpoint is the proportion of patients achieving ≥ 20% improvement in the American College of Rheumatology criteria (ACR20) at Week 24. Major secondary endpoints include ACR50, ACR70; an Investigator's Global Assessment (IGA) of psoriasis score of 0/1 plus ≥ 2-grade reduction and ≥ 90% improvement in Psoriasis Area and Severity Index (both among patients with ≥ 3% body surface area affected by psoriasis and baseline IGA ≥ 2); minimal/very low disease activity; and changes from baseline in Health Assessment Questionnaire-Disability Index, the 36-item Short-Form Health Survey Physical Component Summary, and Functional Assessment of Chronic Illness Therapy-Fatigue scores. The target sample size (N = 450) is estimated to provide > 90% power in detecting differences between each guselkumab group and the placebo group for the primary endpoint assuming a 2-sided α = 0.05. Cochran-Mantel-Haenszel testing and analyses of covariance will be used to compare efficacy for binary and continuous endpoints, respectively.

DISCUSSION

Findings from the phase 3b SOLSTICE study, the design of which was informed by results from previously conducted phase 3 studies, is expected to provide important efficacy and safety information on guselkumab therapy in TNFi-IR patients with PsA.

TRIAL REGISTRATION

This trial was registered at ClinicalTrials.gov, NCT04936308, on 23 June 2021.

Osteoarthritis versus psoriasis arthritis: Physiopathology, cellular signaling, and therapeutic strategies

Osteoarthritis and psoriasis arthritis are two degenerative forms of arthritis that share similar yet also different manifestations at the histological, cellular, and clinical levels. Rheumatologists have marked them as two entirely distinct arthropathies. Given recent discoveries in disease initiation and progression, potential mechanisms, cellular signaling pathways, and ongoing clinical therapeutics, there are now more opportunities for discovering osteoarthritis drugs. This review summarized the osteoarthritis and psoriasis arthritis signaling pathways, crosstalk between BMP, WNT, TGF-β, VEGF, TLR, and FGF signaling pathways, biomarkers, and anatomical pathologies. Through bench research, we demonstrated that regenerative medicine is a promising alternative for treating osteoarthritis by highlighting significant scientific discoveries on entheses, multiple signaling blockers, and novel molecules such as immunoglobulin new antigen receptors targeted for potential drug evaluation. Furthermore, we offered valuable therapeutic approaches with a multidisciplinary strategy to treat patients with osteoarthritis or psoriasis arthritis in the coming future in the clinic.

Skin Barrier Function: The Interplay of Physical, Chemical, and Immunologic Properties

An intact barrier function of the skin is important in maintaining skin health. The regulation of the skin barrier depends on a multitude of molecular and immunological signaling pathways. By examining the regulation of a healthy skin barrier, including maintenance of the acid mantle and appropriate levels of ceramides, dermatologists can better formulate solutions to address issues that are related to a disrupted skin barrier. Conversely, by understanding specific skin barrier disruptions that are associated with specific conditions, such as atopic dermatitis or psoriasis, the development of new compounds could target signaling pathways to provide more effective relief for patients. We aim to review key factors mediating skin barrier regulation and inflammation, including skin acidity, interleukins, nuclear factor kappa B, and sirtuin 3. Furthermore, we will discuss current and emerging treatment options for skin barrier conditions.

Inflammatory Cytokines in Psoriatic Arthritis: Understanding Pathogenesis and Implications for Treatment

Psoriatic arthritis (PsA) is a persistent, inflammatory disease that affects individuals with psoriasis, arthritis, and enthesitis. Research has demonstrated that inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin-23 (IL-23), and interleukin-17 (IL-17) play a pivotal role in both the onset and progression of PsA. These cytokines are generated by activated immune cells and stimulate the attraction of inflammatory cells to the synovium and joint tissues, resulting in the deterioration of cartilage and bone. The blocking of these cytokines has become a successful treatment strategy for PsA, as biological drugs that inhibit TNF-α, IL-23, and IL-17 have demonstrated notable clinical benefits. The association between PsA and other types of inflammatory cytokines or chemokines, excluding TNF-α, IL-23, and IL-17, has been extensively investigated in numerous studies. These findings may provide a chance for the discovery of novel therapeutic agents targeting other molecules, distinct from the currently approved biologics and targeted synthetic disease-modifying anti-rheumatic drugs. In this review, we discuss the current understanding of the role of inflammatory cytokines in PsA pathogenesis and clinical implications of targeting these cytokines for PsA treatment.

Proteomic and Metabolomic Changes in Psoriasis Preclinical and Clinical Aspects

Skin diseases such as psoriasis (Ps) and psoriatic arthritis (PsA) are immune-mediated inflammatory diseases. Overlap of autoinflammatory and autoimmune conditions hinders diagnoses and identifying personalized patient treatments due to different psoriasis subtypes and the lack of verified biomarkers. Recently, proteomics and metabolomics have been intensively investigated in a broad range of skin diseases with the main purpose of identifying proteins and small molecules involved in the pathogenesis and development of the disease. This review discusses proteomics and metabolomics strategies and their utility in research and clinical practice in psoriasis and psoriasis arthritis. We summarize the studies, from in vivo models conducted on animals through academic research to clinical trials, and highlight their contribution to the discovery of biomarkers and targets for biological drugs.

Guselkumab, a Selective Interleukin-23 p19 Subunit Inhibitor, Resolves Dactylitis in Patients With Active Psoriatic Arthritis: Pooled Results Through Week 52 From Two Phase 3 Studies

OBJECTIVE

Previous analyses of pooled DISCOVER-1 and DISCOVER-2 data through Week 24 showed significantly higher rates of dactylitis resolution in patients treated with guselkumab compared with placebo. Here, we investigate associations between dactylitis resolution and other outcomes through 1 year.

METHODS

Patients were randomized 1:1:1 to receive subcutaneous injections of guselkumab 100 mg at Week 0, Week 4, and then every 4 or 8 weeks, or placebo with crossover to guselkumab at Week 24. Independent assessors determined dactylitis severity score (DSS; 0-3/digit; total = 0-60). Dactylitis resolution (DSS = 0) (prespecified) and at least 20%, at least 50%, and at least 70% DSS improvement from baseline (post hoc) were determined through Week 52 (nonresponder imputation for treatment failure through Week 24 and for missing data through Week 52). ACR50, tender/swollen joints, low disease activity (LDA) as assessed by composite indices, and radiographic progression (DISCOVER-2 only) were assessed in patients with dactylitis versus without dactylitis resolution at Week 24 and Week 52.

RESULTS

Patients with dactylitis at baseline (473 of 1118) had more severe joint and skin disease than those without dactylitis (645 of 1118). At Week 52, approximately 75% of guselkumab-randomized patients with dactylitis at baseline had complete resolution; approximately 80% had at least 70% DSS improvement. Through Week 52, new-onset dactylitis (DSS ≥1) was uncommon among patients with a DSS of 0 at baseline. Guselkumab-randomized patients with dactylitis resolution were more likely to achieve ACR50, at least 50% reduction in tender and swollen joints, and LDA at Week 24 and Week 52 than those without resolution. At Week 52, patients with dactylitis resolution had numerically less radiographic progression from baseline (DISCOVER-2).

CONCLUSION

Through 1 year, approximately 75% of guselkumab-randomized patients had complete resolution of dactylitis; patients exhibiting resolution were more likely to achieve other important clinical outcomes. Given the high burden of dactylitis, resolution may be associated with better long-term patient outcomes.

Low rates of radiographic progression associated with clinical efficacy following up to 2 years of treatment with guselkumab: results from a phase 3, randomised, double-blind, placebo-controlled study of biologic-naïve patients with active psoriatic arthritis

OBJECTIVE

Evaluate relationship between radiographic progression and clinical outcomes in post hoc analyses of patients with psoriatic arthritis (PsA) receiving up to 2 years of guselkumab therapy in the phase 3, placebo-controlled, randomised trial, DISCOVER-2.

METHODS

Biologic-naïve adults with active PsA (≥5 swollen joints /≥5 tender joints ; C reactive protein ≥0.6 mg/dL) were randomised to guselkumab 100 mg every 4 weeks (Q4W); guselkumab 100 mg at week 0, week 4, then every 8 weeks (Q8W); or placebo→guselkumab 100 mg Q4W (week 24). Radiographs (hands/feet) at week 0, week 24, week 52 and week 100 were scored via PsA-modified van der Heijde-Sharp (vdH-S) methodology. In these post hoc analyses, mean changes in vdH-S scores were summarised according to achievement of American College of Rheumatology 20/50/70 response; low disease activity (LDA) defined by Disease Activity in Psoriatic Arthritis (DAPSA) ≤14 or Psoriatic ArthritiS Disease Activity Score (PASDAS) ≤3.2, or minimal/very low disease activity (MDA/VLDA); and normalised physical function (Health Assessment Questionnaire-Disability Index (HAQ-DI) ≤0.5). Response rates for achieving MDA/VLDA and each component were determined among patients with and without radiographic progression (change in total vdH-S score >0.5). No formal hypothesis testing was performed.

RESULTS

664 of 739 treated patients in DISCOVER-2 continued study treatment at week 52 and were included in these analyses. Mean changes in vdH-S scores from weeks 0 to 100 among all patients in the Q4W and Q8W groups were 1.7 and 1.5, respectively. Among all guselkumab-randomised patients, those who achieved ACR20/50/70, DAPSA LDA, PASDAS LDA, MDA, VLDA and HAQ-DI ≤0.5 (normalised physical function) had smaller mean changes in vdH-S scores than did non-responders at week 52 (0.2-1.2 vs 1.7-4.1) and week 100 (0.3-1.2 vs 2.0-4.6). Relative to patients with radiographic progression, those without progression were more likely to achieve the MDA criteria related to swollen and tender joint counts, patient-reported pain and global assessment, and normalised physical function through week 100.

CONCLUSION

In these post hoc analyses, the achievement of low levels of disease activity, including MDA, was associated with diminished rates of radiographic progression observed in patients receiving up to 2 years of guselkumab. Radiographic non-progressors were more likely to achieve patient-reported MDA criteria of minimal pain and normalised physical function compared with radiographic non-responders.

TRIAL REGISTRATION NUMBER

NCT03158285.

How does age determine the development of human immune-mediated arthritis?

Does age substantially affect the emergence of human immune-mediated arthritis? Children do not usually develop immune-mediated articular inflammation during their first year of life. In patients with juvenile idiopathic arthritis, this apparent ‘immune privilege’ disintegrates, and chronic inflammation is associated with variable autoantibody signatures and patterns of disease that resemble adult arthritis phenotypes. Numerous mechanisms might be involved in this shift, including genetic and epigenetic predisposing factors, maturation of the immune system with a progressive modulation of putative tolerogenic controls, parallel development of microbial dysbiosis, accumulation of a pro-inflammatory burden driven by environmental exposures (the exposome) and comorbidity-related drivers. By exploring these mechanisms, we expand the discussion of three (not mutually exclusive) hypotheses on how these factors can contribute to the differences and similarities between the loss of immune tolerance in children and the development of established immune-mediated arthritis in adults. These three hypotheses relate to a critical window in genetics and epigenetics, immune maturation, and the accumulation of burden. The varied manifestation of the underlying mechanisms among individuals is only beginning to be clarified, but the establishment of a framework can facilitate the development of an integrated understanding of the pathogenesis of arthritis across all ages.

In this Review, the authors discuss age-related arthropathy and the similarities and differences between childhood loss of immune tolerance and adult development of immune-mediated arthritis, and develop three hypotheses describing age-related mechanisms that contribute to the onset of arthritis.

The arthritis-free ‘immune privilege’ of early childhood is overridden by multiple mechanisms, progressively and age-dependently, generating recognizable patterns of chronic inflammatory arthritis.

The emergence of arthritis involves interconnected mechanisms related to immune priming, to a situational susceptibility and to the accumulation of an inflammatory burden.

The accumulation of epigenetic drift may contribute to differences across ages.

The exposome is expected to contribute to arthritis emergence in adults as well as in children.

The Role of T Helper 22 Cells in Dermatological Disorders

T helper 22 (Th22) cells are a newly identified subset of CD4+ T cells that secrete the effector cytokine interleukin 22 (IL-22) upon specific antigen stimulation, barely with IFN-γ or IL-17. Increasing studies have demonstrated that Th22 cells and IL-22 play essential roles in skin barrier defense and skin disease pathogenesis since the IL-22 receptor is widely expressed in the skin, especially in keratinocytes. Herein, we reviewed the characterization, differentiation, and biological activities of Th22 cells and elucidated their roles in skin health and disease. We mainly focused on the intricate crosstalk between Th22 cells and keratinocytes and provided potential therapeutic strategies targeting the Th22/IL-22 signaling pathway.

Keratinocyte-derived S100A9 modulates neutrophil infiltration and affects psoriasis-like skin and joint disease

OBJECTIVES

S100A9, an alarmin that can form calprotectin (CP) heterodimers with S100A8, is mainly produced by keratinocytes and innate immune cells. The contribution of keratinocyte-derived S100A9 to psoriasis (Ps) and psoriatic arthritis (PsA) was evaluated using mouse models, and the potential usefulness of S100A9 as a Ps/PsA biomarker was assessed in patient samples.

METHODS

Conditional S100A9 mice were crossed with DKO* mice, an established psoriasis-like mouse model based on inducible epidermal deletion of c-Jun and JunB to achieve additional epidermal deletion of S100A9 (TKO* mice). Psoriatic skin and joint disease were evaluated in DKO* and TKO* by histology, microCT, RNA and proteomic analyses. Furthermore, S100A9 expression was analysed in skin, serum and synovial fluid samples of patients with Ps and PsA.

RESULTS

Compared with DKO* littermates, TKO* mice displayed enhanced skin disease severity, PsA incidence and neutrophil infiltration. Altered epidermal expression of selective pro-inflammatory genes and pathways, increased epidermal phosphorylation of STAT3 and higher circulating TNFα were observed in TKO* mice. In humans, synovial S100A9 levels were higher than the respective serum levels. Importantly, patients with PsA had significantly higher serum concentrations of S100A9, CP, VEGF, IL-6 and TNFα compared with patients with only Ps, but only S100A9 and CP could efficiently discriminate healthy individuals, patients with Ps and patients with PsA.

CONCLUSIONS

Keratinocyte-derived S100A9 plays a regulatory role in psoriatic skin and joint disease. In humans, S100A9/CP is a promising marker that could help in identifying patients with Ps at risk of developing PsA.

IFN-γ+ cytotoxic CD4+ T lymphocytes are involved in the pathogenesis of colitis induced by IL-23 and the food colorant Red 40

The food colorant Red 40 is an environmental risk factor for colitis development in mice with increased expression of interleukin (IL)-23. This immune response is mediated by CD4⁺ T cells, but mechanistic insights into how these CD4⁺ T cells trigger and perpetuate colitis have remained elusive. Here, using single-cell transcriptomic analysis, we found that several CD4⁺ T-cell subsets are present in the intestines of colitic mice, including an interferon (IFN)-γ-producing subset. In vivo challenge of primed mice with Red 40 promoted rapid activation of CD4⁺ T cells and caused marked intestinal epithelial cell (IEC) apoptosis that was attenuated by depletion of CD4⁺ cells and blockade of IFN-γ. Ex vivo experiments showed that intestinal CD4⁺ T cells from colitic mice directly promoted apoptosis of IECs and intestinal enteroids. CD4⁺ T cell-mediated cytotoxicity was contact-dependent and required FasL, which promoted caspase-dependent cell death in target IECs. Genetic ablation of IFN-γ constrained IL-23- and Red 40-induced colitis development, and blockade of IFN-γ inhibited epithelial cell death in vivo. These results advance the understanding of the mechanisms regulating colitis development caused by IL-23 and food colorants and identify IFN-γ⁺ cytotoxic CD4⁺ T cells as a new potential therapeutic target for colitis.

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.

Pathogenesis of Paradoxical Reactions Associated with Targeted Biologic Agents for Inflammatory Skin Diseases

Targeted biologic agents have dramatically changed the therapeutic landscape for immune-mediated inflammatory diseases, particularly in rheumatology and dermatology. Their introduction has resulted in a paradigm shift, i.e., they produce significant clinical improvements in most patients with such diseases. Nevertheless, a variety of adverse reactions associated with these agents have been observed, including so-called paradoxical reactions (PRs), which are a new class of adverse events. PRs involve the de novo development or worsening of immune-mediated inflammatory disease during treatment with a targeted biologic agent that is commonly used to treat the idiopathic counterpart of the drug-induced reaction. In addition, the efficacy of biologic agents targeting individual cytokines and the existence of PRs to them have provided proof that cytokines are key drivers of various immune-mediated inflammatory diseases and helped researchers elucidate the molecular pathways underlying the pathophysiology of these diseases. Here, a comprehensive review of the targeted biologic agents used to treat immune-mediated inflammatory diseases, particularly psoriasis and atopic dermatitis, is provided, with a specific focus on biologic agents that inhibit cytokine signaling involving tumor necrosis factor-α, interleukin (IL)-12/23 (p40), IL-17A (and the IL-17 receptor [R]), IL-23 (p19), and the IL-4Rα, and their associated PRs. The characteristic clinical manifestations and potential immunological mechanisms of the PRs induced by these biologic agents are also reviewed.

Comparative Analysis of Single-Cell Transcriptome Data Reveals a Novel Role of Keratinocyte-Derived IL-23 in Psoriasis

Psoriasis, a common inflammatory skin disease, is critically dependent on the IL-23/IL-17 cytokine axis. Although immune cell-derived IL-23 is generally associated with the disease pathogenesis, there have been reports of IL-23 production in keratinocytes. To determine the presence and potential role of keratinocyte-derived IL-23 in psoriasis, we investigated its expression levels using publicly available single-cell RNA sequencing data from human samples. We discovered that the expression of IL23A was detectable in keratinocytes as well as dendritic cells. Furthermore, we examined the IL-23p19 expression in an imiquimod-induced mouse model of psoriasis and found a close relationship between keratinocyte-produced IL-23 and IL-36, another key cytokine in psoriasis pathogenesis. The blockade of IL-23 signaling resulted in the reduced expression of IL-36 in the keratinocytes. Our findings reveal the novel association between keratinocyte-derived IL-23 and IL-36 in psoriasis progression.

Chloroform Extract of Plumbago zeylanica Linn. Roots Ameliorates the Epidermal Thickness of Imiquimod-induced Psoriatic Mice through Cell Cycle and Apoptosis

Introduction: Psoriasis vulgaris is a chronic skin disease which is characterized by recurrent scales on skin. The global prevalence of this disease has increased in ten years. Plumbagin is an active compound in the P. zeylanica Linn. Some recent studies revealed that P. zeylanica Linn extracts have the antiproliferative activity, which is used for treatment of some human diseases. The aim of this study was to investigated the effect of Chloroform extract of P. zeylanica Linn roots (CEP) on epidermal thickness of Imiquimod-induced psoriatic mice. Methods: This was a post-test only control group design. A total of 42 male BALB/c mice was divided into six groups. Mice in treatment groups orally received 25, 50, and 100 mg/kg body weight CEP, respectively while positive control orally received 1 mg/kg body weight Methotrexate for seven days. Evaluation of epidermal thickness based on histological changes, serum IL-23 level by ELISA, and Cyclin-dependent kinase 2, Cyclin A, and Caspase-3 expressions by immunohistochemistry. Results: Administrations of CEP decreased the epidermal thickness of psoriatic plaques in all treatment groups (p = 0.002, 0.003, and 0.016 respectively) compared to negative control but it did not reduce the serum IL-23 level.  The expressions of CDK2 and Cyclin A reduced in T2 and T3 groups and the expression of Caspase-3 increased was only in T3 group. Conclusion: Chloroform extract of P. zeylanica Linn roots administrations reduce the epidermal thickness of Imiquimod-induced psoriatic mice by inhibition of keratinocyte cell cycle and induction of Caspase-3 expression.

Orchestrated Cytokines Mediated by Biologics in Psoriasis and Its Mechanisms of Action

Psoriasis is an autoimmune disease mediated by disturbed T cells and other immune cells, and is defined by deep-red, well-demarcated skin lesions. Due to its varied etiologies and indefinite standard pathogenesis, it is challenging to consider the right treatment exclusively for each psoriasis patient; thus, researchers yearn to seek even more precise treatments other than topical treatment and systemic therapy. Using biologics to target specific immune components, such as upregulated cytokines secreted by activated immune cells, is the most advanced therapy for psoriasis to date. By inhibiting the appropriate pro-inflammatory cytokines, cellular signaling can be altered and, thus, can inhibit further downstream inflammatory pathways. Herein, the roles of cytokines with their mechanisms of action in progressing psoriasis and how the usage of biologics alleviates cellular inflammation are discussed. In addition, other potential pro-inflammatory cytokines, with their mechanism of action, are presented herein. The authors hope that this gathered information may benefit future research in expanding the discovery of targeted psoriasis therapy.

The Antidiabetic Agent Metformin Inhibits IL-23 Production in Murine Bone-Marrow-Derived Dendritic Cells

Psoriasis is a chronic inflammatory skin disease, and its immune mechanism has been profoundly elucidated. Biologics targeting interleukin (IL)-23 have prevented the development of psoriasis. As major sources of IL-23, dendritic cells (DCs) play a pivotal role in psoriasis; however, the regulatory mechanism of IL-23 in DCs remains unclear. IL-36γ was reported to reflect the disease activity of psoriasis. Therefore, we hypothesized that IL-36γ may affect IL-23 production in DCs. To reveal the mechanism by which IL-36γ controls IL-23 production in DCs, we analyzed murine bone marrow-derived DCs (BMDCs) stimulated with IL-36γ. IL-36γ stimulation upregulated the mRNA and protein expression of Nfkbiz in BMDCs. Nfkbiz knockdown using siRNA transfection partially inhibited the upregulation of IL-23 mRNA expression induced by IL-36γ stimulation. Since NF-κB signaling regulates Nfkbiz expression and the anti-diabetic agent metformin reportedly modulates NF-κB signaling, we examined the effect of metformin treatment on IL-36γ-induced IL-23 production. Metformin treatment impaired the phosphorylation of NF-κB induced by IL-36γ stimulation with the subsequent downregulation of Nfkbiz, resulting in the inhibition of IL-23 production in BMDCs. These data provided evidence that metformin treatment can inhibit IL-36γ-mediated IL-23 production in BMDCs, which might contribute to the prevention of psoriasis.

Ginsenoside Rg3 attenuates skin disorders via down-regulation of MDM2/HIF1α signaling pathway

Background

Thymic stromal lymphopoietin (TSLP) acts as a master switch for inflammatory responses. Ginsenoside Rg3 (Rg3) which is an active ingredient of Panax ginseng Meyer (Araliaceae) is known to possess various therapeutic effects. However, a modulatory effect of Rg3 on TSLP expression in the inflammatory responses remains poorly understood.

Methods

We investigated antiinflammatory effects of Rg3 on an in vitro model using HMC-1 cells stimulated by PMA plus calcium ionophore (PMACI), as well as an in vivo model using PMA-induced mouse ear edema. TSLP and vascular endothelial growth factor (VEGF) levels were detected using enzyme-linked immunosorbent assay or real-time PCR analysis. Murine double minute 2 (MDM2) and hypoxia-inducible factor 1α (HIF1α) expression levels were detected using Western blot analysis.

Results

Rg3 treatment restrained the production and mRNA expression levels of TSLP and VEGF in activated HMC-1 cells. Rg3 down-regulated the MDM2 expression level increased by PMACI stimulation. The HIF1α expression level was also reduced by Rg3 in activated HMC-1 cells. In addition, Rg3-administered mice showed the decreased redness and ear thickness in PMA-irritated ear edema. Rg3 inhibited the TSLP and VEGF levels in the serum and ear tissue homogenate. Moreover, the MDM2 and HIF1α expression levels in the ear tissue homogenate were suppressed by Rg3.

Conclusion

Taken together, the current study identifies new mechanistic evidence about MDM2/HIF1α pathway in the antiinflammatory effect of Rg3, providing a new effective therapeutic strategy for the treatment of skin inflammatory diseases.

Translational Research Studies Unraveling the Origins of Psoriatic Arthritis: Moving Beyond Skin and Joints

Patients with psoriatic arthritis (PsA) are suffering from a decreased quality of life despite currently available treatments. In the latest years, novel therapies targeting the IL-17/IL-23 and TNF pathways improved clinical outcome. Despite this, remission of disease is not achieved in a considerable group of patients, continuous treatment is very often required to reach clinical remission, and prevention of PsA in patients with psoriasis (PsO) is currently impossible. A better understanding of PsA pathogenesis is required to develop novel treatment strategies that target inflammation and destruction more effectively and at an early stage of the disease, or even before clinically manifest disease. The skin is considered as one of the sites of onset of immune activation, triggering the inflammatory cascade in PsA. PsO develops into PsA in 30% of the PsO patients. Influenced by environmental and genetic factors, the inflammatory process in the skin, entheses, and/or gut may evolve into synovial tissue inflammation, characterized by influx of immune cells. The exact role of the innate and adaptive immune cells in disease pathogenesis is not completely known. The involvement of activated IL-17A+ T cells could implicate early immunomodulatory events generated in lymphoid organs thereby shaping the pathogenic inflammatory response leading to disease. In this perspective article, we provide the reader with an overview of the current literature regarding the immunological changes observed during the earliest stages of PsA. Moreover, we will postulate future areas of translational research aimed at increasing our knowledge on the molecular mechanisms driving disease development, which will aid the identification of novel potential therapeutic targets to limit the progression of PsA.

IL-23 receptor deficiency results in lower bone mass via indirect regulation of bone formation

The IL-23 receptor (IL-23R) signaling pathway has pleiotropic effects on the differentiation of osteoclasts and osteoblasts, since it can inhibit or stimulate these processes via different pathways. However, the potential role of this pathway in the regulation of bone homeostasis remains elusive. Therefore, we studied the role of IL-23R signaling in physiological bone remodeling using IL-23R deficient mice. Using µCT, we demonstrate that 7-week-old IL-23R^−/− mice have similar bone mass as age matched littermate control mice. In contrast, 12-week-old IL-23R^−/− mice have significantly lower trabecular and cortical bone mass, shorter femurs and more fragile bones. At the age of 26 weeks, there were no differences in trabecular bone mass and femur length, but most of cortical bone mass parameters remain significantly lower in IL-23R^−/− mice. In vitro osteoclast differentiation and resorption capacity of 7- and 12-week-old IL-23R^−/− mice are similar to WT. However, serum levels of the bone formation marker, PINP, are significantly lower in 12-week-old IL-23R^−/− mice, but similar to WT at 7 and 26 weeks. Interestingly, Il23r gene expression was not detected in in vitro cultured osteoblasts, suggesting an indirect effect of IL-23R. In conclusion, IL-23R deficiency results in temporal and long-term changes in bone growth via regulation of bone formation.

Crossing the boundaries: IL-23 and its role in linking inflammation of the skin, gut and joints

Several lines of evidence point towards the central role of IL-23 as a crucial inflammatory mediator in the pathogenesis of SpA—a group of inflammatory arthritic diseases whose symptoms span the skin, gastrointestinal tract and joints. While therapeutic blockade of IL-23 proved successful in the treatment of IBD, psoriatic skin disease and peripheral SpA, it failed in patients suffering from SpA with predominantly axial involvement. Here we review state-of-the-art discoveries on IL-23 signalling pathways across target tissues involved in SpA. We discuss the discrepancies in resident IL-23–responding cells and their downstream activities across skin, gut and joint that shape the unique immunological landscape of SpA.

Immune responses and therapeutic options in psoriasis

Psoriasis is a chronic inflammatory disease of the skin that affects about 2-3% of the population and greatly impairs the quality of life of affected individuals. Psoriatic skin is characterized by excessive proliferation and aberrant differentiation of keratinocytes, as well as redness caused by increased dilation of the dermal blood vessels and infiltration of immune cells. Although the pathogenesis of psoriasis has not yet been completely elucidated, it is generally believed to arise from a complex interplay between hyperproliferating keratinocytes and infiltrating, activated immune cells. So far, the exact triggers that elicit this disease are still enigmatic, yet, it is clear that genetic predisposition significantly contributes to the development of psoriasis. In this review, we summarize current knowledge of important cellular and molecular mechanisms driving the initiation and amplification stages of psoriasis development, with a particular focus on cytokines and emerging evidence illustrating keratinocyte-intrinsic defects as key drivers of inflammation. We also discuss mouse models that have contributed to a better understanding of psoriasis pathogenesis and the preclinical development of novel therapeutics, including monoclonal antibodies against specific cytokines or cytokine receptors that have revolutionized the treatment of psoriasis. Future perspectives that may have the potential to push basic research and open up new avenues for therapeutic intervention are provided.

Use of IL-23 Inhibitors for the Treatment of Plaque Psoriasis and Psoriatic Arthritis: A Comprehensive Review

Psoriasis is a common inflammatory skin disease with multiple comorbidities, including psoriatic arthritis and coronary artery disease, that can severely impact an individual’s quality of life and daily functioning. In recent years, enhanced understanding of the pathogenesis of psoriasis, especially the role of T helper 17 cells, has resulted in the development of new classes of biologic drugs targeting modulators along its disease pathway. Among these, inhibitors of interleukin-23 (e.g., ustekinumab, guselkumab, tildrakizumab, and risankizumab) have emerged as safe and effective options for the treatment of moderate-to-severe plaque psoriasis; ustekinumab and guselkumab have additionally been approved to treat psoriatic arthritis. Selective interleukin-23 inhibitors require less frequent dosing than interleukin-17 inhibitors and may possess a more favorable risk profile without an increased risk of candidiasis or inflammatory bowel disease. Overall, these highly effective medications are contributing to a rising standard for psoriasis outcomes through resolution of skin lesions and joint manifestations and improvement of patient quality of life.

Efficacy and safety of guselkumab in psoriasis patients who failed ustekinumab and/or anti-interleukin-17 treatment: A real-life 52-week retrospective study

Recent major research advancements have significantly expanded our understanding of psoriasis pathophysiology, resulting in the development of highly effective, targeted therapies. Guselkumab is the first interleukin (IL)-23 inhibitor approved for the treatment of moderate-to-severe-psoriasis, providing a new therapeutical option for psoriasis. The aim of our study was to evaluate the efficacy of guselkumab in psoriatic patients who previously failed anti-IL-12/23 and/or anti-IL-17 treatment. A 52-week single-center retrospective study was performed enrolling moderate-to-severe patients attending our Psoriasis Care Center from October 2018 to May 2020. Study population included 13 patients; 46.1% have been previously treated with ustekinumab, while 69.2% have previously failed an anti-IL-17 treatment (38.5% secukinumab, 30.8% ixekizumab, and 38.5% both). At baseline, mean Psoriasis Area and Severity Index was 13.2 ± 6.8, reducing up to 0.5 ± 0.7 at week 52 (P < .001). Body surface area reduced from 22.3 ± 10.5 (baseline) to 0.8 ± 1.1 at week 52 (P < .001). No statistically significant differences have been found between patients previously treated with anti-IL-12/23 compared to anti-IL-17 or both. Only one patient discontinued guselkumab at week 36 due to secondary inefficacy. This is a single institution study with a relatively small sample size. Our real-life data confirm trial results, showing guselkumab as a safe and effective option in patients with moderate-to-severe psoriasis even in those who previously failed ustekinumab and/or anti-IL-17 treatment.

The attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies.

IL-23/IL-17 Axis in Inflammatory Rheumatic Diseases

In inflammatory rheumatic disorders, the immune system attacks and damages the connective tissues and invariably internal organs. During the past decade, remarkable advances having been made towards our understanding on the cellular and molecular mechanisms involved in rheumatic diseases. The discovery of IL-23/IL-17 axis and the delineation of its important role in the inflammation led to the introduction of many needed new therapeutic tools. We will present an overview of the rationale for targeting therapeutically the IL-23/IL-17 axis in rheumatic diseases and the clinical benefit which has been realized so far. Finally, we will discuss the complex interrelationship between IL-23 and IL-17 and the possible uncoupling in certain disease settings.