Eubacterium rectale is a potential marker of altered gut microbiota in psoriasis and psoriatic arthritis

Previous studies have profiled the gut microbiota among psoriatic patients compared to that among healthy individuals. However, a comprehensive understanding of the magnitude, direction, and detailed compositional and functional profiles remains limited. Additionally, research exploring the gut microbiota in the context of both plaque psoriasis (PsO) and psoriatic arthritis (PsA) is lacking. To assess the taxonomic and functional characteristics of the gut microbiota in PsO and PsA patients and investigate potential links between the gut microbiota and disease pathogenesis. We collected fecal samples from 70 psoriatic patients (44 PsO and 26 PsA) and 25 age- and gender-matched healthy controls (HC) and employed deep metagenomic sequencing to characterize their gut microbiota. We noted significant alternations in the gut microbiota compositions of both PsO and PsA patients compared to those of HC. Despite limited effect sizes in alpha diversity (12.3% reduction of microbial richness but unchanged evenness in psoriatic patients) and beta diversity (disease accounts for 3.5% of total variations), we consistently observed substantial reductions of Eubacterium rectale in both PsO and PsA patients, with PsA patients exhibiting even lower levels of E. rectale than PsO patients. Additionally, two Alistipes species were also depleted in psoriatic patients. These microorganisms are known to play crucial roles in carbohydrate metabolism pathways, mainly producing short-chain fatty acids with anti-inflammatory effects. Overall, our observations supplemented the profiling of altered gut microbiota in patients with PsO and PsA at the species level and described a link between the dominant short-chain fatty acid-producing bacterial species and systemic immunity in psoriatic patients.

IMPORTANCE

In this observational clinical study with sufficient sample size and metagenomic sequencing to profile the gut microbiota, we identified consistent signals of the depleted abundance of Eubacterium rectale and related functional genes among psoriatic patients, including those with psoriatic arthritis. E. rectale may serve as an ecologically important functional unit in the gut microbiota, holding potential as a diagnostic marker and target for therapeutic interventions to achieve lasting effects. Our findings provide comprehensive gut microbiota profiling in psoriasis, resolving previous contradictions and generating new hypotheses for further investigation. These insights may significantly impact psoriasis management and related conditions.

Type 17-specific immune pathways are active in early spondyloarthritis

OBJECTIVE

Undifferentiated, early inflammatory arthritis (EIA) can differentiate into seropositive or seronegative rheumatoid arthritis (RA), peripheral spondyloarthritis (SpA) or remain as seronegative undifferentiated inflammatory arthritis (UIA). Little is known about immune pathways active in the early stages of SpA and seronegative UIA, in contrast to detailed knowledge of seropositive RA. The aim of this study was to examine if specific immune pathways were active in synovial CD4+ and CD8+ T cells in EIA.

METHODS

Synovial fluid (SF) samples from 30 patients with EIA were analysed for expression of IL-17A, IFNγ and TNFα in CD8+ or CD4+ T cells. Final clinical diagnoses were made at least 12 months after sample collection, by two independent clinicians blind to the study data.

RESULTS

Flow cytometry analysis of all EIA samples indicated considerable variation in synovial IL-17A+CD8+ T cells (Tc17) cell frequencies between patients. The group with a final diagnosis of SpA (psoriatic arthritis or peripheral SpA, n=14) showed a significant enrichment in the percentage of synovial Tc17 cells compared with the group later diagnosed with seronegative UIA (n=10). The small number of patients later diagnosed with seropositive RA (n=6) patients had few Tc17 cells, similar to our previous findings in established disease. In contrast, RA SF contained a significantly higher percentage of CD8+IFNγ+ T cells compared with SpA or seronegative UIA.

CONCLUSION

These results suggest that adaptive T cell cytokine pathways differ not only between RA and SpA but also seronegative UIA early in the disease process, with a particular activation of Tc17 pathways in early SpA.

Is the C-reactive protein-to-albumin ratio the most remarkable simple inflammatory marker showing active disease in patients with axial spondyloarthritis, psoriatic arthritis, and rheumatoid arthritis?

OBJECTIVE

To learn which of the simple inflammation markers obtained from routine laboratory tests showed active disease best.

METHODS

The study included 256 patients (102 patients with axial spondyloarthritis [axSpA], 54 with psoriatic arthritis [PsA], and 100 with rheumatoid arthritis [RA]). The results of the routine laboratory tests requested during the outpatient clinic visits of the patients were noted. Inflammation-related ratio/indices were then calculated from these laboratory tests. Active and inactive diseases were defined according to the disease activity scores for each disease. Logistic regression and receiver operating characteristic (ROC) analyses were performed to determine the best laboratory marker(s) showing active disease and its cutoff value for all three diseases.

RESULTS

C-reactive protein to albumin ratio (CAR) was significantly higher in patients with active axSpA, PsA, and RA diseases than those with inactive diseases (p < 0.001, p = 0.006, and p < 0.001, respectively). In the logistic regression analysis, the CAR was the most important predictor of active disease in patients with axSpA, PsA, and RA. CAR had also showed the active disease at an acceptable level in axSpA and PsA and very well in RA. The cutoff values for active disease in axSpA, PsA, and RA were 0.75, 0.92, and 0.89, respectively.

CONCLUSION

CAR may be a promising simple laboratory marker to distinguish active disease in patients with axSpA, PsA, and RA. Key Points • Acute phase reactants and circulating blood cells have become an important target because of the search for a disease activity marker that can be used cheaply and quickly in the daily outpatient routine. • One or more of these simple markers have been previously discussed in various studies with different hypotheses. • We aimed to determine which of the inflammation markers obtained from routine laboratory tests showed active disease and to determine a cutoff value for this/these marker(s). • CAR was the most important simple laboratory marker to distinguish active disease in patients with axSpA, PsA, and RA. In addition, CAR showed the active disease at an acceptable level in axSpA and PsA, and very well in RA.

Identifying Serum Metabolomic Markers Associated with Skin Disease Activity in Patients with Psoriatic Arthritis

Psoriatic arthritis (PsA) is a chronic, systemic, immune-mediated inflammatory disease causing cutaneous and musculoskeletal inflammation that affects 25% of patients with psoriasis. Current methods for evaluating PsA disease activity are not accurate enough for precision medicine. A metabolomics-based approach can elucidate psoriatic disease pathogenesis, providing potential objective biomarkers. With the hypothesis that serum metabolites are associated with skin disease activity, we aimed to identify serum metabolites associated with skin activity in PsA patients. We obtained serum samples from patients with PsA (n = 150) who were classified into mild, moderate and high disease activity groups based on the Psoriasis Area Severity Index. We used solid-phase microextraction (SPME) for sample preparation, followed by data acquisition via an untargeted liquid chromatography-mass spectrometry (LC-MS) approach. Disease activity levels were predicted using identified metabolites and machine learning algorithms. Some metabolites tentatively identified include eicosanoids with anti- or pro-inflammatory properties, like 12-Hydroxyeicosatetraenoic acid, which was previously implicated in joint disease activity in PsA. Other metabolites of interest were associated with dysregulation of fatty acid metabolism and belonged to classes such as bile acids, oxidized phospholipids, and long-chain fatty acids. We have identified potential metabolites associated with skin disease activity in PsA patients.

Clonally expanded CD38hi cytotoxic CD8 T cells define the T cell infiltrate in checkpoint inhibitor-associated arthritis

Immune checkpoint inhibitor (ICI) therapies used to treat cancer, such as anti-PD-1 antibodies, can induce autoimmune conditions in some individuals. The T cell mechanisms mediating such iatrogenic autoimmunity and their overlap with spontaneous autoimmune diseases remain unclear. Here, we compared T cells from the joints of 20 patients with an inflammatory arthritis induced by ICI therapy (ICI-arthritis) with two archetypal autoimmune arthritides, rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Single-cell transcriptomic and antigen receptor repertoire analyses highlighted clonal expansion of an activated effector CD8 T cell population in the joints and blood of patients with ICI-arthritis. These cells were identified as CD38hiCD127- CD8 T cells and were uniquely enriched in ICI-arthritis joints compared with RA and PsA and also displayed an elevated interferon signature. In vitro, type I interferon induced CD8 T cells to acquire the ICI-associated CD38hi phenotype and enhanced cytotoxic function. In a cohort of patients with advanced melanoma, ICI therapy markedly expanded circulating CD38hiCD127- T cells, which were frequently bound by the therapeutic anti-PD-1 drug. In patients with ICI-arthritis, drug-bound CD8 T cells in circulation showed marked clonal overlap with drug-bound CD8 T cells from synovial fluid. These results suggest that ICI therapy directly targets CD8 T cells in patients who develop ICI-arthritis and induces an autoimmune pathology that is distinct from prototypical spontaneous autoimmune arthritides.

More than skin-deep: visceral fat is strongly associated with disease activity, function and metabolic indices in psoriatic disease

OBJECTIVE

To compare body composition between patients with psoriatic disease (PsD), including cutaneous psoriasis (PsO) and psoriatic arthritis (PsA), and controls, and to explore associations between disease activity and measures of function and metabolic derangement.

METHODS

Body composition was assessed by air displacement plethysmography (ADP) and MRI-derived fat segmentation using an automated pipeline (FatSegNet). Function was assessed by Health Assessment Questionnaire (HAQ) and metabolic status by fasting lipid profile, insulin and adiponectin. Active and inactive PsO and PsA were defined by body surface area (BSA) and Psoriasis Area Severity Index (PASI) and minimal disease activity (MDA), respectively.

RESULTS

Thirty patients (median disease duration 15 years; median age 52 years) and 30 BMI-matched controls were enrolled. Compared with controls, all MRI-derived body composition parameters-whole-body volume, subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), abdominal adipose tissue (AAT), VAT/AAT and VAT/SAT-were higher in the PsD group, specifically, those with active disease. Body mass, body fat, whole-body volume and whole-body VAT were correlated with higher triglycerides, cholesterol:HDL (high-density lipoprotein), insulin resistance and lower adiponectin as well as higher HAQ and lower MDA.

CONCLUSIONS

In this pilot study, patients with PsD revealed excessive total adipose tissue and a greater volume of metabolically unfavourable ectopic fat, including VAT, compared with BMI-matched controls, which also correlated with HAQ, disease activity and overall dysmetabolism. We also provide the first evidence in patients with PsD for the clinical application of FatSegNet: a novel, automated and rapid deep learning pipeline for providing accurate MRI-based measurement of fat segmentation. Our findings suggest the need for a more integrated approach to the management of PsD, which considers both the metabolic and inflammatory burden of disease. More specifically, visceral fat is a surrogate marker of uncontrolled PsD and may be an important future target for both pharmacological and lifestyle interventions.

Psoriatic and rheumatoid arthritis joints differ in the composition of CD8+ tissue-resident memory T cell subsets

CD69+CD103+ tissue-resident memory T (TRM) cells are important drivers of inflammation. To decipher their role in inflammatory arthritis, we apply single-cell, high-dimensional profiling to T cells from the joints of patients with psoriatic arthritis (PsA) or rheumatoid arthritis (RA). We identify three groups of synovial CD8+CD69+CD103+ TRM cells: cytotoxic and regulatory T (Treg)-like TRM cells are present in both PsA and RA, while CD161+CCR6+ type 17-like TRM cells with a pro-inflammatory cytokine profile (IL-17A+TNFα+IFNγ+) are specifically enriched in PsA. In contrast, only one population of CD4+CD69+CD103+ TRM cells is detected and at similarly low frequencies in both diseases. Type 17-like CD8+ TRM cells have a distinct transcriptomic signature and a polyclonal, but distinct, TCR repertoire. Type 17-like cells are also enriched in CD8+CD103- T cells in PsA compared with RA. These findings illustrate differences in the immunopathology of PsA and RA, with a particular enrichment for type 17 CD8+ T cells in the PsA joint.

Role of Interleukin-36 in inflammatory joint diseases

Interleukin (IL)-36 is a family of cytokines that belongs to the larger IL-1 superfamily. IL-36 agonist/antagonist binds to the interleukin-36 receptor involving in physiological inflammation regulation and pathogenesis of many inflammatory diseases. In inflammatory joint diseases, the expression of IL-36 changes, and some studies have initially explored the role of IL-36 in these diseases. In psoriatic arthritis, IL-36 signal mediates plasma cell and fibroblast-like synoviocyte crosstalk presenting IL-36 agonist/antagonist imbalance. In rheumatoid arthritis, IL-36 agonists induce fibroblast-like synoviocyte to produce pro-inflammatory factors, while IL-36 antagonist deficiency leads to lesion progression. In osteoarthritis, IL-36 agonists induce chondrocytes to produce catabolic enzymes and pro-inflammatory factors. This article reviews the expression and function of IL-36 in different inflammatory joint diseases to provide a reference for revealing their pathogenic mechanisms and discovering therapeutic targets.

Characterization of the inflammatory proteome of synovial fluid from patients with psoriatic arthritis: Potential treatment targets

Objectives

1) To characterize the inflammatory proteome of synovial fluid (SF) from patients with Psoriatic Arthritis (PsA) using a high-quality throughput proteomic platform, and 2) to evaluate its potential to stratify patients according to clinical features.

Methods

Inflammatory proteome profile of SF from thirteen PsA patients with active knee arthritis were analyzed using proximity extension assay (PEA) technology (Olink Target 96 Inflammation panel). Four patients with OA were included as control group.

Results

Seventy-nine inflammation-related proteins were detected in SF from PsA patients (SF-PsA). Unsupervised analyzes of the molecular proteome profile in SF-PsA identified two specific phenotypes characterized by higher or lower levels of inflammation-related proteins. Clinically, SF-PsA with higher levels of inflammatory proteins also showed increased systemic inflammation and altered glucose and lipid metabolisms. Besides, SF from PsA patients showed 39 out of 79 proteins significantly altered compared to SF-OA specifically related to cell migration and inflammatory response. Among these, molecules such as TNFα, IL-17A, IL-6, IL-10, IL-8, ENRAGE, CCL20, TNFSF-14, OSM, IFNγ, MCP-3, CXCL-11, MCP4, CASP-8, CXCL-6, CD-6, ADA, CXCL-10, TNFβ and IL-7 showed the most significantly change.

Conclusion

This is the first study that characterizes the inflammatory landscape of synovial fluid of PsA patients by analyzing a panel of 92 inflammatory proteins using PEA technology. Novel SF proteins have been described as potential pathogenic molecules involved in the pathogenesis of PsA. Despite the flare, inflammatory proteome could distinguish two different phenotypes related to systemic inflammation and lipid and glucose alterations.

Leucocyte Abnormalities in Synovial Fluid of Degenerative and Inflammatory Arthropathies

Genome damage has been related to the induction of autoimmune processes, chronic inflammation, and apoptosis. Recent studies suggest that some rheumatological diseases are associated with overall genomic instability in the T cell compartment. However, no data regarding leucocyte abnormalities in synovial fluid (SF) and their relationship with inflammation are available. The aim of this study was to investigate cellular phenotypes in SF collected from patients with different inflammatory arthropathies, including rhematoid arthritis (RA), psoriatic arthritis (PsA), crystal-induced arthritis (CIA), and non-inflammatory arthropathies, such as osteoarthritis (OA). We found high percentage of micronuclei in SF from CIA compared to the other groups and a high frequency of pyknotic cell in RA and CIA patients. A correlation between pyknosis and immature polymorphonuclear cells with local inflammatory indices was observed. The study of the apoptosis process revealed an increased BAX expression in CIA and RA compared to OA and PsA, while Bcl-2 was higher in CIA. Caspase-3 activity was increased in SF from RA patients and correlates with inflammatory and anti-inflammatory cytokines. In conclusion, our results showed that inflammatory SF is associated with genomic instability and abnormal cell subsets.

IL-33 mediates Pseudomonas induced airway fibrogenesis and is associated with CLAD

BACKGROUND

Long term outcomes of lung transplantation are impacted by the occurrence of chronic lung allograft dysfunction (CLAD). Recent evidence suggests a role for the lung microbiome in the occurrence of CLAD, but the exact mechanisms are not well defined. We hypothesize that the lung microbiome inhibits epithelial autophagic clearance of pro-fibrotic proteins in an IL-33 dependent manner, thereby augmenting fibrogenesis and risk for CLAD.

METHODS

Autopsy derived CLAD and non-CLAD lungs were collected. IL-33, P62 and LC3 immunofluorescence was performed and assessed using confocal microscopy. Pseudomonas aeruginosa (PsA), Streptococcus Pneumoniae (SP), Prevotella Melaninogenica (PM), recombinant IL-33 or PsA-lipopolysaccharide was co-cultured with primary human bronchial epithelial cells (PBEC) and lung fibroblasts in the presence or absence of IL-33 blockade. Western blot analysis and quantitative reverse transcription (qRT) PCR was performed to evaluate IL-33 expression, autophagy, cytokines and fibroblast differentiation markers. These experiments were repeated after siRNA silencing and upregulation (plasmid vector) of Beclin-1.

RESULTS

Human CLAD lungs demonstrated markedly increased expression of IL-33 and reduced basal autophagy compared to non-CLAD lungs. Exposure of co-cultured PBECs to PsA, SP induced IL-33, and inhibited PBEC autophagy, while PM elicited no significant response. Further, PsA exposure increased myofibroblast differentiation and collagen formation. IL-33 blockade in these co-cultures recovered Beclin-1, cellular autophagy and attenuated myofibroblast activation in a Beclin-1 dependent manner.

CONCLUSION

CLAD is associated with increased airway IL-33 expression and reduced basal autophagy. PsA induces a fibrogenic response by inhibiting airway epithelial autophagy in an IL-33 dependent manner.

Could Targeted Pharmacotherapies Exert a “Disease Modification Effect” in Patients with Chronic Plaque Psoriasis?

Chronic plaque psoriasis is an immune-mediated skin disease with a chronic relapsing course, affecting up to ~2–3% of the general adult population worldwide. The interleukin (IL)-23/Th17 axis plays a key role in the pathogenesis of this skin disease and may represent a critical target for new targeted pharmacotherapies. Cutaneous lesions tend to recur in the same body areas, likely because of the reactivation of tissue-resident memory T cells. The spillover of different pro-inflammatory cytokines into systemic circulation can promote the onset of different comorbidities, including psoriatic arthritis. New targeted pharmacotherapies may lead to almost complete skin clearance and significant improvements in the patient’s quality of life. Accumulating evidence supports the notion that early intervention with targeted pharmacotherapies could beneficially affect the clinical course of psoriatic disease at three different levels: (1) influencing the immune cells infiltrating the skin and gene expression, (2) the prevention of psoriasis-related comorbidities, especially psoriatic arthritis, and (3) the improvement of the patient’s quality of life and reduction of cumulative life course impairment. The main aim of this narrative review is to summarize the effects that new targeted pharmacotherapies for psoriasis may have on the immune scar, both at the molecular and cellular level, on psoriatic arthritis and on the patient’s quality of life.

Peripheral γδ T Cells Regulate Neutrophil Expansion and Recruitment in Experimental Psoriatic Arthritis

OBJECTIVE

This study was undertaken to identify the mechanistic role of γδ T cells in the pathogenesis of experimental psoriatic arthritis (PsA).

METHODS

In this study, we performed interleukin-23 (IL-23) gene transfer in wild-type (WT) and T cell receptor δ-deficient (TCRδ-/- ) mice and conducted tissue phenotyping in the joint, skin, and nails to characterize the inflammatory infiltrate. We further performed detailed flow cytometry, immunofluorescence staining, RNA sequencing, T cell repertoire analysis, and in vitro T cell polarization assays to identify regulatory mechanisms of γδ T cells.

RESULTS

We demonstrated that γδ T cells support systemic granulopoiesis, which is critical for murine PsA-like pathology. Briefly, γδ T cell ablation inhibited the expression of neutrophil chemokines CXCL1 and CXCL2 and neutrophil CD11b+Ly6G+ accumulation in the aforementioned PsA-related tissues. Although significantly reduced expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-17A was detected systemically in TCRδ-/- mice, no GM-CSF+/IL-17A+ γδ T cells were detected locally in the inflamed skin or bone marrow in WT mice. Our data showed that nonresident γδ T cells regulate the expansion of an CD11b+Ly6G+ neutrophil population and their recruitment to joint and skin tissues, where they develop hallmark pathologic features of human PsA.

CONCLUSION

Our findings do not support the notion that tissue-resident γδ T cells initiate the disease but demonstrate a novel role of γδ T cells in neutrophil regulation that can be exploited therapeutically in PsA patients.

The Emerging Roles of Endocrine Hormones in Different Arthritic Disorders

The relationship between endocrine hormones and the spectrum of rheumatic conditions has long been discussed in the literature, focusing primarily on sexual hormones, such as estrogens, androgens, prolactin (PRL). Estrogens are indeed involved in the pathogenesis of the main inflammatory arthritis thanks to their effects on the immune system, both stimulatory and inhibitory. The PRL system has been discovered in synovial tissue of rheumatoid arthritis (RA) and psoriatic arthritis (PsA), patients and has been propose as a new potential therapeutic target. Besides sexual hormones, in the last years scientific interest about the crosstalk of immune system with other class of hormones has grown. Hormones acting on the bone tissue (i.e. parathyroid hormone, vitamin D) and modulators of the Wnt pathway (i.e. Dickkopf-1) have been demonstrated to play active role in inflammatory arthritis course, defining a new field of research named osteoimmunology. PTH, which is one of the main determinants of Dkkopf-1, plays a crucial role in bone erosions in RA and a correlation between PTH, Trabecular Bone Score (TBS) and disease activity has been found in ankylosing spondylitis (AS). In PSA is under studying the interaction among IL-17 and bone metabolism. The purpose of this review is to discuss and summarize the recent data about the interaction between endocrine hormone and immune system in the main rheumatic disorders, covering in particular the role of bone-related hormones and cytokines. We will describe this relationship from a biochemical, diagnostic and therapeutic perspective, with a particular focus on RA, PsA and AS.

An Overview of Bimekizumab for the Treatment of Psoriatic Arthritis: The Evidence so Far

Psoriatic arthritis is a complex and heterogeneous disease with potential significant disability and impaired quality of life. Although in the last decades new treatment options have led to a better management of this disease, there are still significant unmet therapeutic needs. Dual inhibitor antibodies target two different cytokines simultaneously, potentially offering a better disease control. In psoriatic arthritis, there is evidence for a pathogenic role not only of IL-17A but also the structurally homologous IL-17F. It is postulated that differential expression of both in several targets of PsA could account for disparities in clinical response to IL-17A inhibition alone (such as with secukinumab or ixekizumab). Here we review the evidence so far for the use in psoriatic arthritis of bimekizumab, the first humanized monoclonal IgG1 antibody that selectively neutralizes both IL-17A and IL-17F. A Phase 2b trial reports better outcomes over both placebo and IL-17A inhibition alone. Very recently encouraging results from open-label extensions with regards to both safety and maintenance of response were presented. Phase III trials are ongoing with the first results awaited in 2021.

Understanding the Pathogenesis of Spondyloarthritis

Spondyloarthritis comprises a group of inflammatory diseases of the joints and spine, with various clinical manifestations. The group includes ankylosing spondylitis, reactive arthritis, psoriatic arthritis, arthritis associated with inflammatory bowel disease, and undifferentiated spondyloarthritis. The exact etiology and pathogenesis of spondyloarthritis are still unknown, but five hypotheses explaining the pathogenesis exist. These hypotheses suggest that spondyloarthritis is caused by arthritogenic peptides, an unfolded protein response, HLA-B*27 homodimer formation, malfunctioning endoplasmic reticulum aminopeptidases, and, last but not least, gut inflammation and dysbiosis. Here we discuss the five hypotheses and the evidence supporting each. In all of these hypotheses, HLA-B*27 plays a central role. It is likely that a combination of these hypotheses, with HLA-B*27 taking center stage, will eventually explain the development of spondyloarthritis in predisposed individuals.

Upregulation of miR-941 in Circulating CD14+ Monocytes Enhances Osteoclast Activation via WNT16 Inhibition in Patients with Psoriatic Arthritis

Psoriatic arthritis (PsA) is a destructive joint disease mediated by osteoclasts. MicroRNAs (miRNAs) regulate several important pathways in osteoclastogenesis. We profiled the expression of miRNAs in CD14+ monocytes from PsA patients and investigated how candidate microRNAs regulate the pathophysiology in osteoclastogenesis. The RNA from circulatory CD14+ monocytes was isolated from PsA patients, psoriasis patients without arthritis (PsO), and healthy controls (HCs). The miRNAs were initially profiled by next-generation sequencing (NGS). The candidate miRNAs revealed by NGS were validated by PCR in 40 PsA patients, 40 PsO patients, and 40 HCs. The osteoclast differentiation and its functional resorption activity were measured with or without RNA interference against the candidate miRNA. The microRNA-941 was selectively upregulated in CD14+ monocytes from PsA patients. Osteoclast development and resorption ability were increased in CD14+ monocytes from PsA patients. Inhibition of miR-941 abrogated the osteoclast development and function while increased the expression of WNT16. After successful treatment, the increased miR-941 expression in CD14+ monocytes from PsA patients was revoked. The expression of miR-941 in CD14+ monocytes is associated with PsA disease activity. MiR-941 enhances osteoclastogenesis in PsA via WNT16 repression. The miR-941 could be a potential biomarker and treatment target for PsA.

RNAseq-Based Prioritization Revealed COL6A5, COL8A1, COL10A1 and MIR146A as Common and Differential Susceptibility Biomarkers for Psoriasis and Psoriatic Arthritis: Confirmation from Genotyping Analysis of 1417 Italian Subjects

Psoriasis (Ps) and Psoriatic Arthritis (PsA) are characterized by a multifactorial etiology, involving genetic and environmental factors. The present study aimed to investigate polymorphisms (SNPs) within genes involved in extracellular matrix and cell homeostasis and microRNA genes as susceptibility biomarkers for Ps and PsA. Bioinformatic analysis on public RNA-seq data allowed for selection of rs12488457 (A/C, COL6A5), rs13081855 (G/T, COL8A1), rs3812111 (A/T, COL10A1) and rs2910164 (C/G, MIR146A) as candidate biomarkers. These polymorphisms were analyzed by Real-Time PCR in a cohort of 1417 Italian patients (393 Ps, 424 PsA, 600 controls). Statistical and bioinformatic tools were utilized for assessing the genetic association and predicting the effects of the selected SNPs. rs12488457, rs13081855 and rs2910164 were significantly associated with both Ps (p = 1.39 × 10⁻⁸, p = 4.52 × 10⁻⁴, p = 0.04, respectively) and PsA (p = 5.12 × 10⁻⁵, p = 1.19 × 10⁻⁶, p = 0.01, respectively). rs3812111, instead, was associated only with PsA (p = 0.005). Bioinformatic analysis revealed common and differential biological pathways involved in Ps and PsA. COL6A5 and COL8A1 take part in the proliferation and angiogenic pathways which are altered in Ps/PsA and contribute to inflammation together with MIR146A. On the other hand, the exclusive association of COL10A1 with PsA highlighted the specific involvement of bone metabolism in PsA.

Interleukin-36 family dysregulation drives joint inflammation and therapy response in psoriatic arthritis

OBJECTIVES

IL-36 agonists are pro-inflammatory cytokines involved in the pathogenesis of psoriasis. However, their role in the pathogenesis of arthritis and treatment response to DMARDs in PsA remains uncertain. Therefore, we investigated the IL-36 axis in the synovium of early, treatment-naïve PsA, and for comparison RA patients, pre- and post-DMARDs therapy.

METHODS

Synovial tissues were collected by US-guided biopsy from patients with early, treatment-naïve PsA and RA at baseline and 6 months after DMARDs therapy. IL-36 family members were investigated in synovium by RNA sequencing and immunohistochemistry, and expression levels correlated with DMARDs treatment response ex vivo. Additionally, DMARDs effects on IL-36 were investigated in vitro in fibroblast-like synoviocytes.

RESULTS

PsA synovium displayed a reduced expression of IL-36 antagonists, while IL-36 agonists were comparable between PsA and RA. Additionally, neutrophil-related molecules, which drive a higher activation of the IL-36 pathway, were upregulated in PsA compared with RA. At baseline, the synovial expression of IL-36α was significantly higher in PsA non-responders to DMARDs treatment, with the differential expression being sustained at 6 months post-treatment. In vitro, primary PsA-derived fibroblasts were more responsive to IL-36 stimulation compared with RA and, importantly, DMARDs treatment increased IL-36 expression in PsA fibroblasts.

CONCLUSION

The impaired balance between IL-36 agonists-antagonists described herein for the first time in PsA synovium and the decreased sensitivity to DMARDs in vitro may explain the apparent lower efficacy of DMARDs in PsA compared with RA. Exogenous replacement of IL-36 antagonists may be a novel promising therapeutic target for PsA patients.

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients

OBJECTIVE

To examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA.

METHODS

Clinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex.

RESULTS

Tie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients.

CONCLUSION

Tie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases.

Gene Variant in the NF-κB Pathway Inhibitor NFKBIA Distinguishes Patients with Psoriatic Arthritis within the Spectrum of Psoriatic Disease

BACKGROUND AND AIMS

The NF-κB pathway has been implicated in the genetic aetiology of psoriatic disease. However, since most patients with arthritis have psoriasis, discerning the genetic contributions to both aspects of psoriatic disease is not easy. Our aim was to study the association of common polymorphisms in genes of the NF-κB pathway in patients with psoriatic disease in order to dissect the contribution of this pathway in the appearance of each component (skin and joint) of the disease.

PATIENTS AND METHODS

We investigated the association between three common variants in NFKB1 (rs230526), NFKBIA (rs7152376), and NFKBIZ (rs3217713 indel) and the risk of developing psoriatic disease. We genotyped a total of 690 psoriatic disease patients and 550 controls. Patients with cutaneous psoriasis of at least 10 years of evolution without associated arthritis were defined to have pure cutaneous psoriasis (PCP).

RESULTS

The rare NFKBIA rs7152376 C was significantly more frequent in the PsA group vs. controls (OR = 2.03 (1.3-3.1), p < 0.01). The difference was even higher between PsA and PCP patients (OR = 3.2 (2.1-5.1), p < 0.001). Neither NFKB1 rs230526 nor NFKBIZ rs3217713 indel was associated with the risk of developing psoriatic disease as a whole compared to controls.

CONCLUSIONS

Our study supports a significant effect of the NFKBIA gene on the risk of developing PsA, thus contributing to better discerning of the polymorphisms of this pathway that explain this risk within the spectrum of psoriatic disease. Additional studies with larger cohorts and from different populations are necessary to validate these results.

Differences in Osteoimmunological Biomarkers Predictive of Psoriatic Arthritis among a Large Italian Cohort of Psoriatic Patients

(1) Background: In literature it is reported that 20–30% of psoriatic patients evolve to psoriatic arthritis over time. Currently, no specific biochemical markers can either predict progression to psoriatic arthritis or response to therapies. This study aimed to identify osteoimmunological markers applicable to clinical practice, giving a quantitative tool for evaluating pathological status and, eventually, to provide prognostic support in diagnosis. (2) Methods: Soluble (serum) bone and cartilage markers were quantified in 50 patients with only psoriasis, 50 psoriatic patients with psoriatic arthritis, and 20 healthy controls by means of multiplex and enzyme-linked immunoassays. (3) Results: Differences in the concentrations of matrix metalloproteases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), receptor activator of nuclear factor kappa-B- ligand (RANK-L), procollagen type I N propeptide (PINP), C-terminal telopeptide of type I collagen (CTx-I), dickkopf-related protein 1 (DKK1), and sclerostin (SOST) distinguished healthy controls from psoriasis and psoriatic arthritis patients. We found that MMP2, MMP12, MMP13, TIMP2, and TIMP4 distinguished psoriasis from psoriatic arthritis patients undergoing a systemic treatment, with a good diagnostic accuracy (Area under the ROC Curve (AUC) > 0.7). Then, chitinase-3-like protein 1 (CHI3L1) and MMP10 distinguished psoriasis from psoriatic arthritis not undergoing systemic therapy and, in the presence of onychopathy, MMP8 levels were higher in psoriasis than in psoriatic arthritis. However, in these latter cases, the diagnostic accuracy of the identified biomarkers was low (0.5 < AUC < 0.7). (4) Conclusions. By highlighting never exploited differences, the wide osteoimmunological biomarkers panel provides a novel clue to the development of diagnostic paths in psoriasis and psoriasis-associated arthropathic disease.

Role of Microparticles in the Pathogenesis of Inflammatory Joint Diseases

Rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), ankylosing spondylitis (AS), and psoriatic arthritis (PsA) make up a group of chronic immune-mediated inflammatory diseases (IMIDs). The course of these diseases involves chronic inflammation of joints and enthesopathies, which can result in joint damage and disability. Microparticles (MPs) are a group of small spherical membranous vesicles. The structure and cellular origin of MPs, mechanisms that stimulate their secretion and the place of their production, determine their biological properties, which could become manifest in the pathogenesis of immune-mediated inflammatory diseases. Microparticles can stimulate synovitis with proinflammatory cytokines and chemokines. MPs may also contribute to the pathogenesis of rheumatic diseases by the formation of immune complexes and complement activation, pro-coagulation activity, activation of vascular endothelium cells, and stimulation of metalloproteinase production. It seems that in the future, microparticles can become a modern marker of disease activity, a response to treatment, and, possibly, they can be used in the prognosis of the course of arthritis. The knowledge of the complexity of MPs biology remains incomplete and it requires further comprehensive studies to explain how they affect the development of rheumatic diseases. This review focuses on the immunopathogenic and therapeutic role of MPs in chronic immune-mediated inflammatory joint diseases.

A Review of Cutaneous Microdialysis of Inflammatory Dermatoses

Microdialysis is a minimally invasive technique to study metabolic, biochemical, and pharmacological events in tissue. Factors that influence microdialysate collection include molecular weight cutoff of the membrane, perfusion rate, perfusate viscosity, duration of collection, depth of the catheter, length of the tubing and adsorption of hydrophobic molecules to the membrane. To standardize these factors, a robust sampling protocol needs to be established. Microdialysis is applied in healthy and inflamed skin. It enables the in vivo sampling of endogenous and exogenous substances in skin's extracellular fluid. In atopic dermatitis, levels of neuropeptides, eicosanoids and histamine pre- and post-treatment treatment have been conducted. Microdialysis in atopic skin has assessed the pharmodynamics of a number of topical drugs. In psoriatic skin, the 'cytokine fingerprint' has been evaluated through microdialysis and bioassays. This unique fingerprint has also been analyzed after certain pharmacological treatments for psoriasis.

Altered Lipid Metabolism in Blood Mononuclear Cells of Psoriatic Patients Indicates Differential Changes in Psoriasis Vulgaris and Psoriatic Arthritis

The aim of this study was to investigate possible stress-associated disturbances in lipid metabolism in mononuclear cells, mainly lymphocytes of patients with psoriasis vulgaris (Ps, n = 32) or with psoriatic arthritis (PsA, n = 16) in respect to the healthy volunteers (n = 16). The results showed disturbances in lipid metabolism of psoriatic patients reflected by different phospholipid profiles. The levels of non-enzymatic lipid metabolites associated with oxidative stress 8-isoprostaglandin F2α (8-isoPGF2α) and free 4-hydroxynonenal (4-HNE) were higher in PsA, although levels of 4-HNE-His adducts were higher in Ps. In the case of the enzymatic metabolism of lipids, enhanced levels of endocannabinoids were observed in both forms of psoriasis, while higher expression of their receptors and activities of phospholipases were detected only in Ps. Moreover, cyclooxygenase-1 (COX-1) activity was enhanced only in Ps, but cyclooxygenase-2 (COX-2) was enhanced both in Ps and PsA, generating higher levels of eicosanoids: prostaglandin E1 (PGE1), leukotriene B4 (LTB4), 13-hydroxyoctadecadienoic acid (13HODE), thromboxane B2 (TXB2). Surprisingly, some of major eicosanoids 15-d-PGJ₂ (15-deoxy-Δ12,14-prostaglandin J₂), 15-hydroxyeicosatetraenoic acid (15-HETE) were elevated in Ps and reduced in PsA. The results of our study revealed changes in lipid metabolism with enhancement of immune system-modulating mediators in psoriatic mononuclear cells. Evaluating further differential stress responses in Ps and PsA affecting lipid metabolism and immunity might be useful to improve the prevention and therapeutic treatments of psoriasis.

Adenoviral gene transfer of a single-chain IL-23 induces psoriatic arthritis-like symptoms in NOD mice

Previously, we demonstrated that intratumoral delivery of adenoviral vector encoding single-chain (sc)IL-23 (Ad.scIL-23) was able to induce systemic antitumor immunity. Here, we examined the role of IL-23 in diabetes in nonobese diabetic mice. Intravenous delivery of Ad.scIL-23 did not accelerate the onset of hyperglycemia but instead resulted in the development of psoriatic arthritis. Ad.scIL-23-treated mice developed erythema, scales, and thickening of the skin, as well as intervertebral disc degeneration and extensive synovial hypertrophy and loss of articular cartilage in the knees. Immunological analysis revealed activation of conventional T helper type 17 cells and IL-17-producing γδ T cells along with a significant depletion and suppression of T cells in the pancreatic lymph nodes. Furthermore, treatment with anti-IL-17 antibody reduced joint and skin psoriatic arthritis pathologies. Thus, these Ad.scIL-23-treated mice represent a physiologically relevant model of psoriatic arthritis for understanding disease progression and for testing therapeutic approaches.-Flores, R. R., Carbo, L., Kim, E., Van Meter, M., De Padilla, C. M. L., Zhao, J., Colangelo, D., Yousefzadeh, M. J., Angelini, L. A., Zhang, L., Pola, E., Vo, N., Evans, C. H., Gambotto, A., Niedernhofer, L. J., Robbins, P. D. Adenoviral gene transfer of a single-chain IL-23 induces psoriatic arthritis-like symptoms in NOD mice.

Pro- and anti-inflammatory eicosanoids in psoriatic arthritis

INTRODUCTION

Eicosanoids are biological lipids that serve as both activators and suppressors of inflammation. Eicosanoid pathways are implicated in synovitis and joint destruction in inflammatory arthritis, yet they might also have a protective function, underscoring the need for a comprehensive understanding of how eicosanoid pathways might be imbalanced. Until recently, sensitive and scalable methods for detecting and quantifying a high number of eicosanoids have not been available.

OBJECTIVE

Here, we intend to describe a detailed eicosanoid profiling in patients with psoriatic arthritis (PsA) and evaluate correlations with parameters of disease activity.

METHODS

Forty-one patients with PsA, all of whom satisfied the CASPAR classification criteria for PsA, were studied. Outcomes reflecting the activity of peripheral arthritis as well as skin psoriasis, Disease Activity Score (DAS)28, Clinical Disease Index (CDAI) and Body Surface Area (BSA) were assessed. Serum eicosanoids were determined by LC-MS, and the correlation between metabolite levels and disease scores was evaluated.

RESULTS

Sixty-six eicosanoids were identified by reverse-phase LC/MS. Certain eicosanoids species including several pro-inflammatory eicosanoids such as PGE2, HXB3 or 6,15-dk,dh,PGF1a correlated with joint disease score. Several eicosapentaenoic acid (EPA)-derived eicosanoids, which associate with anti-inflammatory properties, such as 11-HEPE, 12-HEPE and 15-HEPE, correlated with DAS28 (Disease Activity Score) and CDAI (Clinical Disease Activity Index) as well. Of interest, resolvin D1, a DHA-derived anti-inflammatory eicosanoid, was down-regulated in patients with high disease activity.

CONCLUSION

Both pro- and anti-inflammatory eicosanoids were associated with joint disease score, potentially representing pathways of harm as well as benefit. Further studies are needed to determine whether these eicosanoid species might also play a role in the pathogenesis of joint inflammation in PsA.

The Immunologic Role of IL-17 in Psoriasis and Psoriatic Arthritis Pathogenesis

Psoriasis is a chronic, immune-mediated, inflammatory disease that is pathogenically driven by proinflammatory cytokines. This article reviews the immunologic role of interleukin (IL)-17, the major effector cytokine in the pathogenesis of psoriatic disease, along with the rationale for targeting the IL-17 cytokine family (IL-17A, IL-17F, and IL-17 receptor A) in the treatment of psoriasis and psoriatic arthritis. Emerging evidence indicates that major sources of IL-17A in patients with psoriatic disease are mast cells, γδ T cells, αβ T cells, and innate lymphoid cells in lesional skin and synovial fluid. Within the skin and joints, IL-17A acts on cellular targets, including keratinocytes, neutrophils, endothelial cells, fibroblasts, osteoclasts, chondrocytes, and osteoblasts, to stimulate production of various antimicrobial peptides, chemokines, and proinflammatory and proliferative cytokines, which, in turn, promote tissue inflammation and bone remodeling. The critical importance of the IL-23/IL-17A axis to the pathogenesis of psoriatic disease has resulted in many new biologic treatments targeting these cytokines. These biologics dramatically improve skin and joint symptoms in patients with moderate-to-severe psoriasis and psoriatic arthritis.

Mannan-induced Nos2 in macrophages enhances IL-17-driven psoriatic arthritis by innate lymphocytes

Previous identification of the inducible nitric oxide synthase (NOS2) gene as a risk allele for psoriasis (Ps) and psoriatic arthritis (PsA) suggests a possible pathogenic role of nitric oxide (NO). Using a mouse model of mannan-induced Ps and PsA (MIP), where macrophages play a regulatory role by releasing reactive oxygen species (ROS), we found that NO was detectable before disease onset in mice, independent of a functional nicotinamide adenine dinucleotide phosphate oxidase 2 complex. MIP was suppressed by either deletion of Nos2 or inhibition of NO synthases with NG-nitro-l-arginine methyl ester, demonstrating that Nos2-derived NO is pathogenic. NOS2 expression was also up-regulated in lipopolysaccharide- and interferon-γ-stimulated monocyte subsets from patients with PsA compared to healthy controls. Nos2-dependent interleukin-1α (IL-1α) release from skin macrophages was essential for arthritis development by promoting IL-17 production of innate lymphoid cells. We conclude that Nos2-derived NO by tissue macrophages promotes MIP, in contrast to the protective effect by ROS.

Th17 gene expression in psoriatic arthritis synovial fluid and peripheral blood compared to osteoarthritis and cutaneous psoriasis

OBJECTIVES

The IL-23/IL-17 axis is central to the pathogenesis of psoriatic arthritis (PsA). We aimed to identify Th17 signalling genes that are dysregulated in synovial fluid of PsA compared to osteoarthritis (OA) patients and to determine if differences in peripheral blood can distinguish PsA from psoriasis patients and controls.

METHODS

Synovial fluid cells (SFCs) from 14 PsA and 9 OA patients were obtained and stored in TRIzol reagent. RNA was isolated by phenol-chloroform extraction and purified with RNeasy miniprep kits. Total RNA was extracted from PAXgene whole blood from 20 PsA, 20 psoriasis without arthritis (PsC) and 11 controls. Quantitative RT-PCR arrays were used to profile expression of 84 genes related to the Th17 regulatory network. Fold change differences were compared by Mann-Whitney U-test with false discovery rate (FDR) correction (FDR<0.05).

RESULTS

In PsA compared to OA SFCs, a total of 33 genes were up-regulated and 27 genes were down-regulated. Signalling molecules (such as STAT3, FOXP3) were highly expressed in PsA SFCs, while cytokines (such as IL17F, IL6) were more predominant in OA SFCs after non-supervised hierarchal clustering. Nine genes (MMP3, CCL1, IL17C, CCL20, IL17F, IL3, CXCL5, IL6 and CX3CL1) had concordant expression in SFCs and in peripheral blood cells (PBCs) of PsA compared to PsC and/or controls.

CONCLUSIONS

We identified expression differences in Th17 signalling genes in PsA compared to OA SFCs, with an elevation of signalling molecules and attenuation of cytokine expression in PsA. A subset of genes was concordant in PBCs; these may thus be potential biomarkers of PsA.

Role of the IL-23/IL-17 Axis in Psoriasis and Psoriatic Arthritis: The Clinical Importance of Its Divergence in Skin and Joints

Psoriasis is a chronic systemic inflammatory disease causing erythematosus and scaly skin plaques; up to 30% of patients with psoriasis develop Psoriatic Arthritis (PsA), which is characterised by inflammation and progressive damage of the peripheral joints and/or the spine and/or the entheses. The pathogenic mechanisms driving the skin disorder in psoriasis and the joint disease in PsA are sustained by the activation of inflammatory pathways that can be overlapping, but also, at least partially, distinct. Cytokines members of the IL-23/IL-17 family, critical in the development of autoimmunity, are abundantly expressed within the cutaneous lesions but also seem to be involved in chronic inflammation and damage of the synovium though, as it will be here discussed, not in all patients. In this review, we will focus on the state of the art of the molecular features of psoriatic skin and joints, focusing on the specific role of the IL-23/IL-17 pathway in each of these anatomical districts. We will then offer an overview of the approved and in-development biologics targeting this axis, emphasising how the availability of the “target” in the diseased tissues could provide a plausible explanation for the heterogeneous clinical efficacy of these drugs, thus opening future perspective of personalised therapies.

Differential expression of programmed death 1 (PD-1) on CD4+ and CD8+ T cells in rheumatoid arthritis and psoriatic arthritis

INTRODUCTION    Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are characterized by chronic inflammatory processes mediated by proinflammatory cytokines that affect the synovial lining. Programmed death 1 (PD‑1) is a critical regulator of T‑cell activation by downregulating immune responses.  OBJECTIVES    The aim of the study was to investigate whether the expression of PD‑1 on CD4+ and CD8+ T cells differs between patients with RA and those with PsA. PATIENTS AND METHODS    The study included 100 patients with RA, 31 patients with PsA, and 52 healthy controls. The percentages, absolute numbers, and mean fluorescence intensity (MFI) of CD4+PD‑1+ and CD8+PD‑1+T cells from peripheral blood were analyzed using flow cytometry. RESULTS    The percentages and absolute numbers of CD4+ and CD8+ T cells with PD‑1 expression were significantly higher in patients with RA than in controls. In patients with PsA, the percentages of CD4+PD‑1+ and CD8+PD‑1+ T cells were significantly lower than in controls. Because of the high frequency of PD-1‑positive T cells in RA and their low frequency in PsA, we analyzed the expression level by analyzing the MFI. The median MFI of PD‑1 on CD4+ and CD8+ T cells was significantly higher in patients with RA (median, 421 and 437, respectively) in comparison with patients with PsA (median, 222 and 198, respectively) and controls (median, 205 and 187, respectively). CONCLUSIONS    The differential expression of PD‑1 in RA and PsA suggests that PD‑1 might be involved in autoimmune mechanisms in RA and autoinflammatory mechanisms in PsA in a different manner.

Metabolic control of the scaffold protein TKS5 in tissue-invasive, proinflammatory T cells

Pathogenic T cells in individuals with rheumatoid arthritis (RA) infiltrate non-lymphoid tissue sites, maneuver through extracellular matrix and form lasting inflammatory microstructures. Here we found that RA T cells abundantly express the podosome scaffolding protein TKS5, which enables them to form tissue-invasive membrane structures. TKS5 overexpression was regulated by the intracellular metabolic environment of RA T cells-specifically, by reduced glycolytic flux that led to deficiencies in ATP and pyruvate. ATPlopyruvatelo conditions triggered fatty acid biosynthesis and the formation of cytoplasmic lipid droplets. Restoration of pyruvate production or inhibition of fatty acid synthesis corrected the tissue-invasiveness of RA T cells in vivo and reversed their proarthritogenic behavior. Thus, metabolic control of T cell locomotion provides new opportunities to interfere with T cell invasion into specific tissue sites.

Type I and III collagen turnover is increased in axial spondyloarthritis and psoriatic arthritis. Associations with disease activity and diagnostic capacity

OBJECTIVES

To investigate the turnover of type I and III collagen by neo-epitope markers in patients with axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA).

METHODS

Patients with PsA (n=101) or axSpA (n=110) and healthy subjects (n=120) were included. Demographic and clinical data were recorded. Markers of type I and III collagen were quantified by RIA (ICTP) or ELISA (C1M and C3M). Non-parametric statistics were applied for intergroup comparisons and correlation studies. The diagnostic potential of these marker molecules was assessed by ROC analysis.

RESULTS

C1M and C3M, which originate from soft connective tissues, were significantly higher in axSpA and PsA as compared with healthy control subjects. CIM and C3M correlated with ASDAS and DAS28. Overall, ICTP, which arises from bone degradation, did not differ between disease versus healthy. However, ICTP was lower in HLA-B27 positive than in HLA-B27 negative patients with axSpA. There was no association between bone and soft connective tissue collagen I markers (ICTP and C1M), while C1M and C3M were highly correlated (p<0.0001). C1M discriminated between healthy and diseased with AUCs of 0.83 for PsA and 0.79 for axSpA. C3M AUCs were 0.77 for PsA and 0.78 for axSpA.

CONCLUSIONS

Type I and III collagen remodelling in soft connective tissue is increased in axSpA and PsA and associates with disease activity. Bone collagen degradation is lower in HLA-B27 positive compared with HLA-B27 negative axSpA, which may represent an aspect of enhanced enthesopathic bone proliferation in HLA-B27 carriers. C1M and C3M distinguish well between healthy and diseased individuals.

[THE EFFECT OF BIOLOGIC THERAPY ON THE LIPID PROFILE OF RHEUMATOID ARTHRITIS (RA), PSORIATIC ARTHRITIS (PSA) AND ANKYLOSING SPONDYLITIS (AS) PATIENTS]

Cardiovascular (CV) morbidity and mortality is elevated in rheumatoid arthritis (RA), psoriatic arthritis (PSA) and ankylosing spondylitis (AS) patients. The inflammation not only accelerates atherosclerosis, but also influences CV risk factors such as lipid profile, blood pressure and insulin resistance. RA and PSA patients are initially treated with DMARDS (disease modifying anti-rheumatic drugs). However, if remission is not achieved in RA, a variety of biologics (anti- TNF rituximab, tocilizumab, abatacept) are added to the treatment regimen. In PSA, only anti-TNF drugs are approved. AS is treated solely by NSAIDS and anti-TNF drugs. DMARDS were found to reduce the CV morbidity in RA patients, in addition to their anti-inflammatory affect. However, it has not been proven that anti-inflammatory therapy reduces the cardiovascular risk in PSA and AS patients. Anti-TNF drugs have been shown to reduce CV morbidity and mortality in RA and AS patients, however their effect on these patient's lipid profile in not yet clear. Despite the scarce evidence available, it seems that rituximab may have a positive influence on the patient's lipid profile. Even though tocilizumab adversely affects the lipid profile, this drug's overall CV effect is still being examined in clinical trials. There is not enough evidence to determine the effect of abatacept on the lipid profile. These issues are currently in the focus of many clinical trials and no doubt these issues will be clarified in the future.

Role and Function of A2A and A₃ Adenosine Receptors in Patients with Ankylosing Spondylitis, Psoriatic Arthritis and Rheumatoid Arthritis

Rheumatoid arthritis (RA), ankylosing spondylitis (AS) and psoriatic arthritis (PsA) are chronic inflammatory rheumatic diseases that affect joints, causing debilitating pain and disability. Adenosine receptors (ARs) play a key role in the mechanism of inflammation, and the activation of A_2A and A₃AR subtypes is often associated with a reduction of the inflammatory status. The aim of this study was to investigate the involvement of ARs in patients suffering from early-RA (ERA), RA, AS and PsA. Messenger RNA (mRNA) analysis and saturation binding experiments indicated an upregulation of A_2A and A₃ARs in lymphocytes obtained from patients when compared with healthy subjects. A_2A and A₃AR agonists inhibited nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) activation and reduced inflammatory cytokines release, such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6. Moreover, A_2A and A₃AR activation mediated a reduction of metalloproteinases (MMP)-1 and MMP-3. The effect of the agonists was abrogated by selective antagonists demonstrating the direct involvement of these receptor subtypes. Taken together, these data confirmed the involvement of ARs in chronic autoimmune rheumatic diseases highlighting the possibility to exploit A_2A and A₃ARs as therapeutic targets, with the aim to limit the inflammatory responses usually associated with RA, AS and PsA.

Characterisation of peripheral blood mononuclear cell microRNA in early onset psoriatic arthritis

OBJECTIVES

To evaluate the micro-RNA (miRNA) expression profile in patients with early psoriatic arthritis (PsA) in order to assess the role of miRNAs as potential PsA biomarkers.

METHODS

The expression of 723 mature miRNAs in peripheral blood mononuclear cells of early PsA patients in comparison with early-rheumatoid arthritis (ERA) patients and healthy controls (HC) was evaluated using a miRNA microarray. All patients had active disease and were naïve from treatment. The results were validated for a specific miRNA (miR-21-5p) in the entire series of patients plus an additional group of early PsA, ERA and HC using droplet digital PCR.

RESULTS

In PsA, microarray analysis revealed a distinct pattern of 19 (vs. HC) and 48 (vs. ERA) deregulated miRNAs (p<0.05). The significant up-regulation of miR-21-5p both in early PsA and in ERA in comparison with HC was validated and confirmed. In PsA, miR-21-5p was found significantly down regulated after 12 weeks of therapy, which significantly correlated with the reduction of DAPSA score.

CONCLUSIONS

In early PsA, a 19- (vs. HC) and 48- (vs. ERA) miRNA signature was identified. A differential expression of miRNAs in patients with active disease makes them attractive biomarkers of psoriatic disease. MiR-21-5p was found up-regulated both in early PsA and ERA, a finding which highlights its role in the inflammatory process in general and its potential role as a therapeutic target in different inflammatory disorders. A potential role of miR-21-5p as a response to treatment biomarker in early PsA has been identified.

[Hepatobiliary System Diseases as the Predictors of Psoriasis Progression]

PURPOSE OF THE STUDY

To assess the state of the hepatobiliary system in psoriasis andpsoriatic arthritis in order to establish a causal relationship and to identify clinical and functional predictors of psoriatic disease progression.

METHODS

The study includedpatients with extensive psoriasis vulgaris (n = 175) aged 18 to 66 years old and healthy donors (n = 30), matched by sex and age: Group 1--patients with psoriasis (PS, n = 77), group 2--patients with psoriatic arthritis (PsA, n = 98), group 3--control. The evaluation of functional state of the hepatobiliary system was performed by the analysis of the clinical and anamnestic data and by the laboratory-instrumental methods.

RESULTS

We identified predictors of psoriasis: triggers (stress and nutritionalfactor), increased total bilirubin, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, eosinophilia, giardiasis, carriers of hepatitis C virus, ductal changes andfocal leisons in the liver, thickening of the walls of the gallbladder detected by ultrasound. Predictors ofpsoriatic arthritis: age over 50 years, dyspeptic complaints, the presence of hepatobiliary system diseases, the positive right hypochondrium syndrome, the clinical symptoms of chronic cholecystitis, excess body weight, high levels of bilirubin, cholesterol and low density lipoprotein, hepatomegaly, non-alcoholic fatty liver disease.

CONCLUSION

High activity of hepatocytes cytolysis, cholestasis, inflammation, metabolic disorders let us considerpsoriatic arthritis as a severe clinical stage psoriatic disease when the hepatobiliary system, in turn, is one of the main target organs in systemic psoriatic process. Non-alcoholic fatty liver disease and chronic cholecystitis are predictors of psoriatic disease progression.

Interactions of the Immune System with Skin and Bone Tissue in Psoriatic Arthritis: A Comprehensive Review

Cutaneous psoriasis (e.g., psoriasis vulgaris (PsV)) and psoriatic arthritis (PsA) are complex heterogeneous diseases thought to have similar pathophysiology. The soluble and cellular mediators of these closely related diseases are being elucidated through genetic approaches such as genome-wide association studies (GWAS), as well as animal and molecular models. Novel therapeutics targeting these mediators (IL-12, IL-23, IL-17, IL-17 receptor, TNF) are effective in treating both the skin and joint manifestations of psoriasis, reaffirming the shared pathophysiology of PsV and PsA. However, the molecular and cellular interactions between skin and joint disease have not been well characterized. Clearly, PsV and PsA are highly variable in terms of their clinical manifestations, and this heterogeneity can partially be explained by differences in HLA-associations (HLA-Cw*0602 versus HLA-B*27, for example). In addition, there are numerous other genetic susceptibility loci (LCE3, CARD14, NOS2, NFKBIA, PSMA6, ERAP1, TRAF3IP2, IL12RB2, IL23R, IL12B, TNIP1, TNFAIP3, TYK2) and geoepidemiologic factors that contribute to the wide variability seen in psoriasis. Herein, we review the complex interplay between the genetic, cellular, ethnic, and geographic mediators of psoriasis, focusing on the shared mechanisms of PsV and PsA.

Sustained Improvement of Arterial Stiffness and Blood Pressure after Long-Term Rosuvastatin Treatment in Patients with Inflammatory Joint Diseases: Results from the RORA-AS Study

OBJECTIVE

Patients with inflammatory joint diseases (IJD) have a high prevalence of hypertension and increased arterial stiffness. The aim of the present study was to evaluate the effect of long-term rosuvastatin treatment on arterial stiffness, measured by augmentation index (AIx) and aortic pulse wave velocity (aPWV), and blood pressure (BP) in IJD patients with established atherosclerosis.

METHODS

Eighty-nine statin naïve IJD patients with carotid atherosclerotic plaque(s) (rheumatoid arthritis n = 55, ankylosing spondylitis n = 23, psoriatic arthritis n = 11) received rosuvastatin for 18 months to achieve low-density lipoprotein cholesterol goal ≤1.8 mmol/L. Change in AIx (ΔAIx), aPWV (ΔaPWV), systolic BP (ΔsBP) and diastolic BP (ΔdBP) from baseline to study end was assessed by paired samples t-tests. Linear regression was applied to evaluate associations between cardiovascular disease (CVD) risk factors, rheumatic disease specific variables and medication, and ΔAIx, ΔaPWV, ΔsBP and ΔdBP.

RESULTS

AIx, aPWV, sBP and dBP were significantly reduced from baseline to study end. The mean (95%CI) changes were: ΔAIx: -0.34 (-0.03, -0.65)% (p = 0.03), ΔaPWV: -1.69 (-0.21, -3.17) m/s2 (p = 0.03), ΔsBP: -5.27 (-1.61, -8.93) mmHg (p = 0.004) and ΔdBP -2.93 (-0.86, -5.00) mmHg (p = 0.01). In linear regression models, ∆aPWV was significantly correlated with ΔsBP and ΔdBP (for all: p<0.001).

CONCLUSIONS

There is an unmet need of studies evaluating CVD prevention in IJD patients. We have shown for the first time that long-term intensive lipid lowering with rosuvastatin improved arterial stiffness and induced a clinically significant BP reduction in patients with IJD. These improvements were linearly correlated and may represent novel insight into the pleiotropic effects by statins.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01389388.

An Integrative Approach to Biomarker Development in Psoriatic Arthritis

The recent discovery that the interleukin 23/Th17 pathway is pivotal in the pathogenesis of psoriatic arthritis (PsA) creates new opportunities for the development of mechanistic biomarkers that will assist in the diagnosis and management of this disorder. While biomarkers are still in the discovery phase, new approaches including multiplex panels, fine sequencing of epigenetic and genetic data in non-coding regions of the human genome, and improved imaging modalities will likely foster the development of actionable biomarkers in PsA. In this report, I review the field of biomarkers, underscore the importance of an integrative approach that incorporates both descriptive and mechanistic biomarkers, and discuss the status of biomarker discovery in PsA.

Gene Expression Profiling in Peripheral Blood Cells and Synovial Membranes of Patients with Psoriatic Arthritis

Background

Psoriatic arthritis (PsA) is an inflammatory arthritis whose pathogenesis is poorly understood; it is characterized by bone erosions and new bone formation. The diagnosis of PsA is mainly clinical and diagnostic biomarkers are not yet available. The aim of this work was to clarify some aspects of the disease pathogenesis and to identify specific gene signatures in paired peripheral blood cells (PBC) and synovial biopsies of patients with PsA. Moreover, we tried to identify biomarkers that can be used in clinical practice.

Methods

PBC and synovial biopsies of 10 patients with PsA were used to study gene expression using Affymetrix arrays. The expression values were validated by Q-PCR, FACS analysis and by the detection of soluble mediators.

Results

Synovial biopsies of patients showed a modulation of approximately 200 genes when compared to the biopsies of healthy donors. Among the differentially expressed genes we observed the upregulation of Th17 related genes and of type I interferon (IFN) inducible genes. FACS analysis confirmed the Th17 polarization. Moreover, the synovial trascriptome shows gene clusters (bone remodeling, angiogenesis and inflammation) involved in the pathogenesis of PsA. Interestingly 90 genes are modulated in both compartments (PBC and synovium) suggesting that signature pathways in PBC mirror those of the inflamed synovium. Finally the osteoactivin gene was upregulared in both PBC and synovial biopsies and this finding was confirmed by the detection of high levels of osteoactivin in PsA sera but not in other inflammatory arthritides.

Conclusions

We describe the first analysis of the trancriptome in paired synovial tissue and PBC of patients with PsA. This study strengthens the hypothesis that PsA is of autoimmune origin since the coactivity of IFN and Th17 pathways is typical of autoimmunity. Finally these findings have allowed the identification of a possible disease biomarker, osteoactivin, easily detectable in PsA serum.

Dense genotyping of immune-related susceptibility loci reveals new insights into the genetics of psoriatic arthritis

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis and, despite the larger estimated heritability for PsA, the majority of genetic susceptibility loci identified to date are shared with psoriasis. Here, we present results from a case-control association study on 1,962 PsA patients and 8,923 controls using the Immunochip genotyping array. We identify eight loci passing genome-wide significance, secondary independent effects at three loci and a distinct PsA-specific variant at the IL23R locus. We report two novel loci and evidence of a novel PsA-specific association at chromosome 5q31. Imputation of classical HLA alleles, amino acids and SNPs across the MHC region highlights three independent associations to class I genes. Finally, we find an enrichment of associated variants to markers of open chromatin in CD8(+) memory primary T cells. This study identifies key insights into the genetics of PsA that could begin to explain fundamental differences between psoriasis and PsA.

Current concepts in psoriatic arthritis: pathogenesis and management

Psoriatic arthritis occurs in a subset of psoriasis patients and is therefore commonly encountered in dermatology practice. Although its exact pathogenesis is unknown, psoriatic arthritis is thought to share common mechanisms with psoriatic skin symptoms. Innate and adaptive immune responses are abnormally activated in psoriasis and may acquire the ability to attack peripheral joints and other sites following an environmental trigger (e.g. mechanical stress, trauma, infection) in genetically susceptible patients. The increased cardiovascular risk inherent in psoriasis appears further enhanced in psoriatic arthritis, likely reflecting the overall burden of systemic inflammation contributing to atherogenic processes. Basic research and clinical trials have suggested that tumour necrosis factor is important in psoriatic arthritis pathophysiology, and accumulating evidence suggests that Th17 cells and interleukin-17A may also be important. Basic research and clinical trials inform our understanding of psoriatic arthritis pathophysiology and, in turn, help dermatologists to make better treatment decisions.

Interleukin-17+CD8+ T cells are enriched in the joints of patients with psoriatic arthritis and correlate with disease activity and joint damage progression

OBJECTIVE

Psoriatic arthritis (PsA) is associated with HLA class I genes, in contrast to the association with HLA class II in rheumatoid arthritis (RA). Since IL-17+ cells are considered important mediators of synovial inflammation, we sought to determine whether IL-17-producing CD8+ T cells may be found in the joints of patients with PsA and whether these cells might contribute to the disease process.

METHODS

Mononuclear cells from paired samples of synovial fluid (SF) and peripheral blood (PB) from patients with PsA or patients with RA were stimulated ex vivo, and CD4- T cells were examined by flow cytometry for cytokine expression, cytotoxic markers, and frequencies of γ/δ or mucosal-associated invariant T cells. Clinical measures of arthritis activity (C-reactive protein [CRP] level, erythrocyte sedimentation rate [ESR], Disease Activity Score in 28 joints [DAS28]) and power Doppler ultrasound (PDUS) scores for the presence of active synovitis in the aspirated knee were recorded and assessed for correlations with immunologic markers.

RESULTS

Within the CD3+ T cell compartment, both IL-17+CD4- (predominantly CD8+) and IL-17+CD4+ T cells were significantly enhanced in the SF compared to the PB of patients with PsA (P = 0.0003 and P = 0.002, respectively; n = 21), whereas in patients with RA, only IL-17+CD4+ T cells were increased in the SF compared to the PB (P = 0.008; n = 14). The frequency of IL-17+CD4- T cells in PsA SF was positively correlated with the CRP level (r = 0.52, P = 0.01), ESR (r = 0.59, P = 0.004), and DAS28 (r = 0.52, P = 0.01), and was increased in patients with erosive disease (P < 0.05). In addition, the frequency of IL-17+CD4- T cells positively correlated with the PDUS score, a marker for active synovitis (r = 0.49, P = 0.04).

CONCLUSION

These results show, for the first time, that the PsA joint, but not the RA joint, is enriched for IL-17+CD8+ T cells. Moreover, the findings reveal that the levels of this T cell subset are correlated with disease activity measures and the radiographic erosion status after 2 years, suggesting a previously unrecognized contribution of these cells to the pathogenesis of PsA.

Treatment of psoriasis and psoriatic arthritis

Skin and joint manifestations associated with psoriasis and psoriatic arthritis (PsA) can significantly impact a patient's quality of life. Successful treatment is imperative in order to improve signs and symptoms of the disease, and to alleviate physical or psychological distress. For patients with mild psoriasis with or without PsA, topical agents and targeted phototherapy are appropriate treatments for psoriasis. Systemic therapies, such as methotrexate and phototherapy are recommended options for patients with more severe psoriasis, but their long-term use is hindered by safety concerns. Advancements in understanding the pathogenesis of psoriasis, including the role of T cells and cytokines, have been crucial to the development of biological therapies. These target the immune system and are suitable options for patients with extensive disease. Biological therapies for the treatment of psoriasis include targeted therapies (alefacept) and anti-cytokine therapies (anti-tumour necrosis factor [TNF] therapies [adalimumab, etanercept, infliximab] and a monoclonal antibody against interleukin [IL]-12 and IL-23 [ustekinumab]). Patients with PsA should be treated appropriately in order to improve symptoms and inhibit structural joint damage. Non-steroidal anti-inflammatory drugs or local intra-articular injections of corticosteroids can be used successfully in patients with mild PsA; however, neither treatment prevents the development of structural joint damage. For patients with moderate to severely active PsA, disease-modifying antirheumatic drugs (such as methotrexate), TNF inhibitor treatments (adalimumab, etanercept, infliximab and golimumab) or their combination are considered first-line treatment. This review provides a brief overview of treatment options for psoriasis and PsA, with an emphasis on the efficacy and safety of anti-TNF therapies.

The IL-23/IL-17 axis in psoriatic arthritis

Psoriatic arthritis (PsA) is an immune-mediated chronic inflammatory disease, affecting both the skin and joints. Disease progression is associated with aberrant cytokine expression, and TNF blockade is the most successful therapy to date. However, not all patients are responsive to anti-TNF treatment, highlighting the need to better understand the cellular and molecular mechanisms that govern the disease. PsA associations with single nucleotide polymorphisms in IL23R as well as TRAF3IP2 (Act1), a molecule downstream of the IL-17 receptor (IL-17R), have linked the IL-23/IL-17 axis to disease pathology. Although both cytokines are implicated in PsA, a full picture of their cellular targets and pathogenic mechanisms has not yet emerged. In this review, we focus on the IL-23/IL-17 axis-elicited responses mediated by osteoclasts, keratinocytes and neutrophils. Expanding our understanding of the cellular and molecular mechanisms that dictate pathogenicity in PsA will contribute to developing novel treatment strategies to combat disease.

Levels of chemerin and interleukin 8 in the synovial fluid of patients with inflammatory arthritides and osteoarthritis

OBJECTIVES

Chemerin and interleukin (IL)-8 are pro-inflammatory mediators whose role in joint inflammation and cartilage degradation has been demonstrated in in-vitro findings. Studies on their presence in synovial fluid (SF) samples may offer further information on their pathogenic role. The aim of this study was to investigate SF chemerin and IL-8 levels in patients with different joint diseases.

METHODS

37 patients were enrolled: 18 with rheumatoid arthritis (RA), 8 with psoriatic arthritis (PsA) and 11 with osteoarthritis (OA). 41 SF samples were obtained by arthrocentesis in case of knee synovitis. Serum samples were obtained from 13 patients (4 with RA, 6 with PsA and 3 with OA) at the time of arthrocentesis. Chemerin, IL-8, TNF-α and IL-6 levels were measured using commercially available ELISA kits. Immunohistochemical analysis of synovial RA specimens was also performed.

RESULTS

No difference in chemerin SF levels emerged between patients with immune-mediated inflammatory arthritides and those with OA (p=0.0656), while subjects with inflammatory arthritis displayed significantly higher levels of SF IL-8 compared to OA (p=0.0020). No significant difference emerged across the three conditions in the serum levels of both chemerin and IL-8. IL-8 strongly correlated with inflammatory markers as ESR, CRP, IL-6 and TNF-α.

CONCLUSIONS

We observed similar chemerin SF and serum levels in the three conditions. Although flawed by some limitations, our findings support the emerging concept of OA as an inflammatory disorder. However the increased IL-8 levels we described in patients with inflammatory arthritis suggest a selective involvement of this pro-inflammatory and angiogenic cytokine in these conditions.

Th17 and Th22 cells in psoriatic arthritis and psoriasis

INTRODUCTION

The aim of this study was to characterize interleukin 17 (IL-17) and interleukin 22 (IL-22) producing cells in peripheral blood (PB), skin, synovial fluid (SF) and synovial tissue (ST) in patients with psoriasis (Ps) and psoriatic arthritis (PsA).

METHODS

Flow cytometry was used to enumerate cells making IL-22 and IL-17, in skin and/or SF and PB from 11 patients with Ps and 12 patients with PsA; skin and PB of 15 healthy controls and SF from rheumatoid arthritis (RA) patients were used as controls. Expression of the interleukin 23 receptor (IL-23R) and chemokine receptors CCR4 and CCR6 was examined. Secretion of IL-17 and IL-22 was measured by ELISA. ST was analysed by immunohistochemical staining of IL-17 and IL-22.

RESULTS

Increased frequencies of IL-17+ and IL-22+ CD4+ T cells were seen in PB of patients with PsA and Ps. IL-17 secretion was significantly elevated in both PsA and Ps, whilst IL-22 secretion was higher in PsA compared to Ps and healthy controls. A higher proportion of the CD4+ cells making IL-17 or IL-22 expressed IL-23R and frequencies of IL-17+, CCR6+ and CCR4+ T cells were elevated in patients with Ps and those with PsA. In patients with PsA, CCR6+ and IL-23R + T cells numbers were elevated in SF compared to PB. Increased frequencies of IL-17+ and IL-22+ CD4+ T cells were demonstrated in Ps skin lesions. In contrast, whilst elevated frequencies of CD4+ IL-17+ cells were seen in PsA SF compared to PB, frequencies of CD4+ IL-22+ T cells were lower. Whereas IL-17 expression was equivalent in PsA, osteoarthritis (OA) and RA ST, IL-22 expression was higher in RA than either OA or PsA ST, in which IL-22 was strikingly absent.

CONCLUSIONS

Elevated frequencies of IL-17 and IL-22 producing CD4+ T cells were a feature of both Ps and PsA. However their differing distribution at disease sites, including lower frequencies of IL-22+ CD4+ T cells in SF compared to skin and PB, and lack of IL-22 expression in ST suggests that Th17 and Th22 cells have common, as well as divergent roles in the pathogenesis of Ps and PsA.

The role of p38 MAPK in the aetiopathogenesis of psoriasis and psoriatic arthritis

The pathogenetic mechanisms responsible for the induction of immune-mediated disorders, such as psoriasis, remain not well characterized. Molecular signaling pathways are not well described in psoriasis, as well as psoriatic arthritis, which is seen in up to 40% of patients with psoriasis. Signaling pathway defects have long been hypothesized to participate in the pathology of psoriasis, yet their implication in the altered psoriatic gene expression still remains unclear. Emerging data suggest a potential pathogenic role for mitogen activated protein kinases p38 (p38 MAPK) extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun N-terminal kinase (JNK) in the development of psoriasis. The data are still limited, though, for psoriatic arthritis. This review discusses the current data suggesting a crucial role for p38 MAPK in the pathogenesis of these disorders.