Bedside to bench: defining the immunopathogenesis of psoriatic arthritis

Changes in Inflammatory Cytokines in Responders and Non-Responders to TNFα Inhibitor and IL-17A Inhibitor: A Study Examining Psoriatic Arthritis Patients

This study aimed to examine the changes in biomarker levels in responders and non-responders to tumor necrosis factor alpha inhibitor (TNFi) and interleukin-17A inhibitor (IL-17Ai) in psoriatic arthritis (PsA) patients over a 4-month period after treatment initiation. A total of 68 PsA patients initiating either TNFi, IL-17Ai, or methotrexate treatment were included. Blood plasma and clinical outcome measures were collected adjacent to treatment initiation and after four months. A commercially available multiplex immunoassay was included to evaluate 54 biomarkers. Mean changes were used to evaluate change over time. A statistically significant decrease in pro-inflammatory cytokines IL-6 (log-transformed mean change -0.97, 95%CI -4.30; 2.37, [p = 0.032]) and an increase in anti-inflammatory IL-10 (0.38, 95%CI 1.74; 2.50 [p = 0.010]) were seen in TNFi responders. Meanwhile, a statistically significant increase in the target cytokine IL-17A was seen in both IL-17Ai responders (2.49, 95%CI -1.84; 6.85 [p = 0.031]) and non-responders (2.48, 95%CI -1.46; 6.41 [p = 0.001]). This study demonstrated differing changes in cytokine levels when comparing treatment responders and non-responders, highlighting the need to improve the understanding of the different immune response mechanisms explaining different responses to medical treatment in PsA patients.

The Involvement of Cysteine-X-Cysteine Motif Chemokine Receptors in Skin Homeostasis and the Pathogenesis of Allergic Contact Dermatitis and Psoriasis

Members of the C-X-C motif chemokine receptor (CXCR) superfamily play central roles in initiating the innate immune response in mammalian cells by orchestrating selective cell migration and immune cell activation. With its multilayered structure, the skin, which is the largest organ in the body, performs a crucial defense function, protecting the human body from harmful environmental threats and pathogens. CXCRs contribute to primary immunological defense; these receptors are differentially expressed by different types of skin cells and act as key players in initiating downstream innate immune responses. While the initiation of inflammatory responses by CXCRs is essential for pathogen elimination and tissue healing, overactivation of these receptors can enhance T-cell-mediated autoimmune responses, resulting in excessive inflammation and the development of several skin disorders, including psoriasis, atopic dermatitis, allergic contact dermatitis, vitiligo, autoimmune diseases, and skin cancers. In summary, CXCRs serve as critical links that connect innate immunity and adaptive immunity. In this article, we present the current knowledge about the functions of CXCRs in the homeostasis function of the skin and their contributions to the pathogenesis of allergic contact dermatitis and psoriasis. Furthermore, we will examine the research progress and efficacy of therapeutic approaches that target CXCRs.

Intestinal dysbiosis exacerbates the pathogenesis of psoriasis-like phenotype through changes in fatty acid metabolism

The intestinal microbiota has been associated with host immunity as well as psoriasis; however, the mechanism of intestinal microbiota regulating psoriasis needs to be demonstrated systematically. Here, we sought to examine its role and mechanism of action in the pathogenesis of psoriasis. We found that the severity of psoriasis-like skin phenotype was accompanied by changes in the composition of the intestinal microbiota. We performed co-housing and fecal microbial transplantation (FMT) experiments using the K14-VEGF transgenic mouse model of psoriasis and demonstrated that the transfer of intestinal microbiota from mice with severe psoriasis-like skin phenotype exacerbated psoriasiform skin inflammation in mice with mild symptoms, including increasing the infiltration and differentiation of Th17, and increased the abundance of Prevotella, while decreasing that of Parabacteroides distasonis, in the colon. These alterations affected fatty acid metabolism, increasing the abundance of oleic and stearic acids. Meanwhile, gentamicin treatment significantly reduced the abundance of Prevotella and alleviated the psoriasis-like symptoms in both K14-VEGF mice and imiquimod (IMQ)-induced psoriasis-like mice. Indeed, administration of oleic and stearic acids exacerbated psoriasis-like symptoms and increased Th17 and monocyte-derived dendritic cell infiltration in the skin lesion areas in vivo, as well as increased the secretion of IL-23 by stimulating DCs in vitro. At last, we found that, treatment of PDE-4 inhibitor alleviated psoriasis-like phenotype of K14-VEGF mice accompanied by the recovery of intestinal microbiota, including the decrease of Prevotella and increase of Parabacteroides distasonis. Overall, our findings reveal that the intestinal microbiota modulates host metabolism and psoriasis-like skin inflammation in mice, suggesting a new target for the clinical diagnosis and treatment of psoriasis.

Horizon scan: State-of-the-art therapeutics for psoriatic arthritis

Psoriatic arthritis (PsA) is a common immune-mediated inflammatory disease (IMID) that can present with a heterogenous clinical phenotype. The advent of advanced therapies has substantially improved patient outcomes, but many patients still have suboptimal or unsustained response, resulting in morbidity, structural damage and functional impairment. There remains a need for better therapeutic options and precision medicine approaches to improve outcomes for patients with PsA. This review synthesises recently approved the state-of-the-art therapeutics for PsA, including inhibitors of IL-23, Janus kinase (JAK), tyrosine kinase 2 (TYK2) and dual-target IL-17A/F. The evidence base for emerging therapeutics, including MK-2 inhibitors, nano-IL-17 inhibitors, nanobodies and other dual-target therapies for PsA is also reviewed. Potential future therapeutic strategies and unmet research needs are discussed.

Peripheral Helper T Cell Responses in Human Diseases

A series of rheumatoid arthritis (RA) studies established a PD-1^hiCXCR5^-CD4⁺ T-cell subset that was coined peripheral helper T (Tph) cells. CXCL13 production is a key feature of Tph cells and may contribute to the formation of tertiary lymphoid structures (TLS) in inflamed tissues. In addition, Tph cells provide help to B cells in situ as efficiently as follicular helper T (Tfh) cells, and these features would implicate Tph cells in the pathogenesis of RA. Subsequent studies have revealed that Tph cells are involved in various human diseases such as autoimmune diseases, infectious diseases, and cancers. Although the analysis of human immunity has various limitations, accumulating evidence demonstrated the expansion of B cells with low somatic hypermutation and a link between TLS and immune functions in these diseases. We discuss about the emerging roles of the Tph cell and its relevant immune responses in peripheral tissues including B-cell expansion with atypical features.

High Dimensional Analyses of Circulating Immune Cells in Psoriatic Arthritis Detects Elevated Phosphorylated STAT3

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis, affecting up to 40% of patients with psoriasis. Constitutive expression by CD4+ T cells of an active form of STAT3, a signal transducer and transcription factor, has been shown to induce many of the major features of PsA in an animal model. We used high dimensional mass cytometry (CyTOF) to probe ex-vivo levels of phosphorylated STAT3 (pSTAT3) in circulating immune cell subpopulations from PsA patients during active and inactive states. We evaluated the frequency of 16 immune cell populations and the levels of the activated forms of STAT3 (pSTAT3) and, for comparison, STAT1 (pSTAT1) and Src (pSrc) in whole blood fixed shortly after collection. In addition to PsA patients, we studied active rheumatoid arthritis (RA) patients. Increased levels of pSTAT3 were found in all the CD4+ T cell subsets analyzed, specifically, Th1, Th2, Th17, T follicular helper (Tfh) and T regulatory (Treg) as well as in CD14+CD16- (classical) monocytes from active PsA patients compared to inactive patients. After correcting for body mass index (BMI), smoking and conventional disease modifying antirheumatic drugs (c-DMARDs), levels of pSTAT3 levels remained increased in Th1 and Tfh CD4+ T cells, and in CD14+CD16- monocytes from active patients compared to inactive patients. No differences between the patient groups were observed for pSTAT1 or pSrc. No differences were found between the active PsA and active RA groups after correction for multiple testing. During active PsA, circulating Th1 and Tfh CD4+ T cells, and CD14+CD16- monocytes expressing high levels of pSTAT3 may play a role in PsA pathophysiology, perhaps by migration to inflamed sites.

Janus kinase-targeting therapies in rheumatology: a mechanisms-based approach

The four Janus kinase (JAK) proteins and seven signal transducer and activator of transcription (STAT) transcription factors mediate intracellular signal transduction downstream of cytokine receptors, which are implicated in the pathology of autoimmune, allergic and inflammatory diseases. Development of targeted small-molecule therapies such as JAK inhibitors, which have varied selective inhibitory profiles, has enabled a paradigm shift in the treatment of diverse disorders. JAK inhibitors suppress intracellular signalling mediated by multiple cytokines involved in the pathological processes of rheumatoid arthritis and many other immune and inflammatory diseases, and therefore have the capacity to target multiple aspects of those diseases. In addition to rheumatoid arthritis, JAK inhibition has potential for treatment of autoimmune diseases including systemic lupus erythematosus, spondyloarthritis, inflammatory bowel disease and alopecia areata, in which stimulation of innate immunity activates adaptive immunity, leading to generation of autoreactive T cells and activation and differentiation of B cells. JAK inhibitors are also effective in the treatment of allergic disorders, such as atopic dermatitis, and can even be used for the COVID-19-related cytokine storm. Mechanism-based treatments targeting JAK-STAT pathways have the potential to provide positive outcomes by minimizing the use of glucocorticoids and/or non-specific immunosuppressants in the treatment of systemic immune-mediated inflammatory diseases.

Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA): updated treatment recommendations for psoriatic arthritis 2021

Since the second version of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) treatment recommendations were published in 2015, therapeutic options for psoriatic arthritis (PsA) have advanced considerably. This work reviews the literature since the previous recommendations (data published 2013-2020, including conference presentations between 2017 and 2020) and reports high-quality, evidence-based, domain-focused recommendations for medication selection in PsA developed by GRAPPA clinicians and patient research partners. The overarching principles for the management of adults with PsA were updated by consensus. Principles considering biosimilars and tapering of therapy were added, and the research agenda was revised. Literature searches covered treatments for the key domains of PsA: peripheral arthritis, axial disease, enthesitis, dactylitis, and skin and nail psoriasis; additional searches were performed for PsA-related conditions (uveitis and inflammatory bowel disease) and comorbidities. Individual subcommittees used a GRADE-informed approach, taking into account the quality of evidence for therapies, to generate recommendations for each of these domains, which were incorporated into an overall schema. Choice of therapy for an individual should ideally address all disease domains active in that patient, supporting shared decision-making. As safety issues often affect potential therapeutic choices, additional consideration was given to relevant comorbidities. These GRAPPA treatment recommendations provide up-to-date, evidence-based guidance on PsA management for clinicians and people with PsA.

The Role of Interleukin-23 Inhibition in the Treatment of Psoriatic Arthritis

Psoriatic arthritis is a chronic inflammatory autoimmune disease with varied manifestations, including functional limitation and reduced quality of life. Improved understanding of the immunopathogenesis of psoriatic arthritis, particularly the role of the interleukin-23 and interleukin-17 axis, has led to the development of therapeutic targets to alter the natural history of the condition. In this article, we review the role of monoclonal antibodies targeting the p19 subunit of interleukin-23 in the treatment of psoriatic arthritis.

Interleukin-2 and regulatory T cells in rheumatic diseases

Failure of regulatory T (T_reg) cells to properly control immune responses leads invariably to autoimmunity and organ damage. Decreased numbers or impaired function of T_reg cells, especially in the context of inflammation, has been documented in many human autoimmune diseases. Restoration of T_reg cell fitness and/or expansion of their numbers using low-dose natural IL-2, the main cytokine driving T_reg cell survival and function, has demonstrated clinical efficacy in early clinical trials. Genetically modified IL-2 with an extended half-life and increased selectivity for T_reg cells is now in clinical development. Administration of IL-2 combined with therapies targeting other pathways involved in the expression of autoimmune diseases should further enhance its therapeutic potential. Ongoing clinical efforts that capitalize on the early clinical success of IL-2 treatment should bring the use of this cytokine to the forefront of biological treatments for autoimmune diseases.

Mitochondrial Reactive Oxygen Species Are Essential for the Development of Psoriatic Inflammation

Psoriasis is a common immune-mediated, chronic, inflammatory skin disease that affects approximately 2-3% of the population worldwide. Although there is increasing evidence regarding the essential roles of the interleukin (IL)-23/IL-17 axis and dendritic cell (DC)-T cell crosstalk in the development of skin inflammation, the contributions of mitochondrial function to psoriasis are unclear. In a mouse model of imiquimod (IMQ)-induced psoriasiform skin inflammation, we found that hematopoietic cell-specific genetic deletion of p32/C1qbp, a regulator of mitochondrial protein synthesis and metabolism, protects mice from IMQ-induced psoriatic inflammation. Additionally, we demonstrate that p32/C1qbp is an important regulator of IMQ-induced DC activation, both in vivo and in vitro. We also found that p32/C1qbp-deficient DCs exhibited impaired production of IL-1β, IL-23, and mitochondrial reactive oxygen species (mtROS) after IMQ stimulation. Because the inhibition of mtROS suppressed IMQ-induced DC activation and psoriatic inflammation, we presume that p32/C1qbp and mtROS can serve as therapeutic targets in psoriasis.

Incidence of Psoriatic Arthritis Among Patients Receiving Biologic Treatments for Psoriasis: A Nested Case-Control Study

OBJECTIVE

To investigate the effect of biologic treatments for psoriasis on the incidence of psoriatic arthritis (PsA).

METHODS

This retrospective cohort study was conducted using electronic medical records from a large health maintenance organization. Patients who received biologic treatment for psoriasis and were not diagnosed as having PsA before or at the time of biologic treatment initiation were included. Control psoriasis patients who did not receive biologic treatment were matched by age at time of diagnosis, sex, time from psoriasis diagnosis until treatment initiation, maximum body mass index, and smoking status. The groups were different in most characteristics. Therefore, propensity score matching was implemented. Log rank test and multivariable Cox proportional hazards regression were used to compare the groups.

RESULTS

Overall, 1,326 patients were included, of whom 663 had received biologic treatment and 663 had not. The Kaplan-Meier curve for the propensity score-matched groups reflected a statistically significant increased risk for PsA among the control group compared to the biologic treatment group. The results of the multivariable Cox regression showed that the control group had a significantly higher risk for PsA compared to the biologic treatment group within 10 years of follow-up (adjusted hazard ratio 1.39 [95% confidence interval 1.03-1.87]).

CONCLUSION

Our findings show a statistically and clinically significant decreased risk for developing PsA among patients with psoriasis who receive biologic treatments. The results suggest that biologic medications should be considered for patients who present with significant risk factors for PsA at an earlier stage of treatment.

Pooled Safety Results Through 1 Year of 2 Phase III Trials of Guselkumab in Patients With Psoriatic Arthritis

OBJECTIVE

Evaluate the safety of guselkumab (monoclonal antibody targeting interleukin [IL]-23p19) in patients with psoriatic arthritis (PsA) through 1 year (1Y) of the phase III DISCOVER-1 and DISCOVER-2 trials.

METHODS

Patients with active PsA (n = 1120; biologic-naïve except 118 patients treated with tumor necrosis factor inhibitors in DISCOVER-1) were randomized to subcutaneous guselkumab 100 mg every 4 weeks (Q4W) or at Week 0, Week 4, then every 8 weeks (Q8W); or placebo. At Week 24, patients in the placebo group switched to guselkumab 100 mg Q4W. Treatment continued through 1Y and 2 years for DISCOVER-1 and DISCOVER-2, respectively. In this pooled analysis, patients with ≥ 1 adverse event (AE) through 1Y were standardized for 100 patient-years [100 PYs] of follow-up.

RESULTS

Through Week 24, adverse events (AEs) were consistent between patients treated with placebo and guselkumab (Q4W + Q8W). AEs were 142.8/100 PYs and 150.6/100 PYs, serious AEs were 7.1/100 PYs and 4.4/100 PYs, and AEs leading to study agent discontinuation were 4.1/100 PYs and 3.8/100 PYs, respectively. Through 1Y in patients treated with guselkumab, no uveitis, active tuberculosis, opportunistic infections, or inflammatory bowel disease were observed, and low rates of malignancy and major adverse cardiovascular (CV) events were observed. Injection-site reactions occurred in 1.7%, and antibodies to guselkumab in 4.5% of patients treated with guselkumab through 1Y; the vast majority of antibodies to guselkumab were nonneutralizing. Serum hepatic transaminase elevations (more common with Q4W than Q8W dosing) and decreased neutrophil counts were generally mild, transient, and did not require treatment discontinuation, with minimal change from Week 24 to 1Y.

CONCLUSION

Guselkumab 100 mg Q4W and Q8W were well tolerated in patients with PsA, with no new safety concerns through 1Y of the phase III DISCOVER trials. Guselkumab safety through 1Y in patients with PsA is consistent with that established in patients with psoriasis who were treated with guselkumab.

Interleukin-17 and Interleukin-23: A Narrative Review of Mechanisms of Action in Psoriasis and Associated Comorbidities

Psoriasis is an immune-mediated inflammatory skin disease associated with numerous inflammatory comorbidities, including increased cardiovascular risk. The interleukin (IL)-23/IL-17 axis plays a central role in the immunopathogenesis of psoriasis and related comorbidities by acting to stimulate keratinocyte hyperproliferation and feed-forwarding circuits of perpetual T cell-mediated inflammation. IL-17 plays an important role in the downstream portion of the psoriatic inflammatory cascade. This review discusses the distinct mechanisms of action of IL-17 and IL-23 in the immunopathogenesis of psoriasis and related comorbidities plus the significant therapeutic benefits of selectively inhibiting these cytokines in patients with moderate to severe plaque psoriasis.

Anti- and non-tumor necrosis factor-α-targeted therapies effects on insulin resistance in rheumatoid arthritis, psoriatic arthritis and ankylosing spondylitis

In addition to β-cell failure with inadequate insulin secretion, the crucial mechanism leading to establishment of diabetes mellitus (DM) is the resistance of target cells to insulin, i.e. insulin resistance (IR), indicating a requirement of beyond-normal insulin concentrations to maintain euglycemic status and an ineffective strength of transduction signaling from the receptor, downstream to the substrates of insulin action. IR is a common feature of most metabolic disorders, particularly type II DM as well as some cases of type I DM. A variety of human inflammatory disorders with increased levels of proinflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β, have been reported to be associated with an increased risk of IR. Autoimmune-mediated arthritis conditions, including rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS), with the involvement of proinflammatory cytokines as their central pathogenesis, have been demonstrated to be associated with IR, especially during the active disease state. There is an increasing trend towards using biologic agents and small molecule-targeted drugs to treat such disorders. In this review, we focus on the effects of anti-TNF-α- and non-TNF-α-targeted therapies on IR in patients with RA, PsA and AS. Anti-TNF-α therapy, IL-1 blockade, IL-6 antagonist, Janus kinase inhibitor and phospho-diesterase type 4 blocker can reduce IR and improve diabetic hyper-glycemia in autoimmune-mediated arthritis.

Recent advances on the role of cytotoxic T lymphocytes in the pathogenesis of spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disorder with complex etiology and pathogenesis. Its pathogenesis likely involves a combination of different factors. These factors include host genetics, environmental triggers, and immune and microbiota dysregulation. One of the strongest genetic associations with SpA is HLA-B27, implicating the involvement of cytotoxic T lymphocytes (CTLs) in SpA pathogenesis. Despite this discovery dating back decades ago, the CTL compartment that underlies SpA inflammation has yet to be fully defined until recently. Indeed, recent published studies support a significant role that CTLs play in contributing to chronic joint inflammation, which is a hallmark of SpA pathology. In this review chapter, we discuss emerging evidence that supports a newfound role of CTLs in SpA pathogenesis. This emerging evidence includes enrichment of CTL-related genes from genome-wide association studies, overrepresentation of pathogenic synovial CTL phenotype, clonal expansion, and immune dysregulation of CTLs. The discoveries of this mounting evidence suggest that CTL homeostasis is altered, and a disrupted adaptive immunity underlies the chronic inflammatory features seen in SpA pathology.

Candida infections in patients with psoriasis and psoriatic arthritis treated with interleukin-17 inhibitors and their practical management

INTRODUCTION

Interleukin 17A (IL-17A) is a pro-inflammatory cytokine produced by helper T cells (Th17) and other cells of the immune system and exerts pleiotropic effects on multiple cell lines. The role of IL-17 in the pathogenesis of numerous inflammatory disorders is well-documented. IL-17 activates signaling through the IL-17 receptor, which induces other proinflammatory cytokines, antimicrobial peptides, and neutrophil chemokines that are important for antifungal activity.

EVIDENCE ACQUISITION

Healthy levels of IL-17 can protect the host against extracellular bacterial and fungal infections in mucous membranes and epithelia. IL-17 deficiency reduces control of certain infections, while excessive IL-17 can produce unwanted inflammatory effects.

EVIDENCE SYNTHESIS

Although the efficacy of the therapeutic blockade of this cytokine has been proven in several autoimmune diseases such as psoriasis and psoriatic arthritis, this strategy could also exacerbate fungal infections in such patients. Therefore, a better understanding of IL-17-mediated immunity to Candida is necessary for the development of autoimmune therapeutics that maintain antifungal immunity.

CONCLUSIONS

In this review, we include a study of the new anti-IL-17 biological agents (secukinumab, ixekizumab, and bromalizumab) used for moderate-to-severe psoriasis and psoriatic arthritis treatment in clinical practice, as well as pivotal trials with bimekizumab. We study the relationship of these biological agents and the appearance of candidiasis in its various clinical forms.

A novel treatment for psoriatic arthritis: Janus kinase inhibitors

Psoriatic arthritis (PsA) is a type of chronic inflammatory arthritis which is associated with psoriasis. The early recognition and treatment for PsA are of critical importance. Janus kinase (JAK) inhibitors, as a kind of orally small molecules, have emerged as an encouraging class of drug in PsA treatment. This review provides a discussion of the role and current status of JAK inhibitors in the control of PsA. There are three JAK inhibitors approved for use in autoimmune diseases, for example, tofacitinib, baricitinib, and upadacitinib, and only tofacitinib has been approved in PsA treatment. The clinical trials of upadacitinib and filgotinib in PsA patients are undergoing. The efficacy and safety of these agents were briefly discussed. Although there are still issues in terms of their efficacy and safety currently, JAK inhibitors are expected to benefit more PsA patients in future.