A genome-wide meta-analysis of palmoplantar pustulosis implicates TH2 responses and cigarette smoking in disease pathogenesis.

BACKGROUND: Palmoplantar pustulosis (PPP) is an inflammatory skin disorder that mostly affects smokers and manifests with painful pustular eruptions on the palms and soles. Although the disease can present with concurrent plaque psoriasis, TNF and IL-17/IL-23 inhibitors show limited efficacy. There is therefore a pressing need to uncover PPP disease drivers and therapeutic targets. OBJECTIVES: We sought to identify genetic determinants of PPP and investigate whether cigarette smoking contributes to disease pathogenesis. METHODS: We performed a genome-wide association meta-analysis of 3 North-European cohorts (n = 1,456 PPP cases and 402,050 controls). We then used the scGWAS program to investigate the cell-type specificity of the association signals. We also undertook genetic correlation analyses to examine the similarities between PPP and other immune-mediated diseases. Finally, we applied Mendelian randomization to analyze the causal relationship between cigarette smoking and PPP. RESULTS: We found that PPP is not associated with the main genetic determinants of plaque psoriasis. Conversely, we identified genome-wide significant associations with the FCGR3A/FCGR3B and CCHCR1 loci. We also observed 13 suggestive (P < 5 × 10-6) susceptibility regions, including the IL4/IL13 interval. Accordingly, we demonstrated a significant genetic correlation between PPP and TH2-mediated diseases such as atopic dermatitis and ulcerative colitis. We also found that genes mapping to PPP-associated intervals were preferentially expressed in dendritic cells and often implicated in T-cell activation pathways. Finally, we undertook a Mendelian randomization analysis, which supported a causal role of cigarette smoking in PPP. CONCLUSIONS: The first genome-wide association study of PPP points to a pathogenic role for deregulated TH2 responses and cigarette smoking.

Cumulative methotrexate dose is not associated with liver fibrosis in patients with a history of moderate-to-severe psoriasis.

BACKGROUND: There are established risk factors for liver fibrosis (LF), but data on the impact of methotrexate on LF in patients with psoriasis are lacking. OBJECTIVES: This cross-sectional study aimed to determine the prevalence of LF in patients with psoriasis and to evaluate the relationship between LF, cumulative methotrexate dose and other LF risk factors. METHODS: Adults with a history of moderate-to-severe chronic plaque psoriasis were recruited between June 2020 and March 2021. Patients underwent transient elastography to evaluate LF. Three values for liver stiffness measurement (LSM) were assessed, indicating mild or worse LF (≥ 7 kPa), moderate or worse LF (≥ 7.9 kPa) and advanced LF (≥ 9.5kPa). Cumulative methotrexate dose and other potential risk factors for LF were assessed. RESULTS: Overall, 240 patients were recruited and 204 participants with valid LSM values were included in the analysis [median age 48 years [interquartile range (IQR) 37-57]; 51% female sex; 56% body mass index (BMI) ≥ 30 (kg m-2) and a median Alcohol Use Disorders Identification Test (AUDIT) score of 4 (IQR 1-7, 23% score ≥ 8)]. In total, 91% had received methotrexate [median duration 36 months (IQR 14-78)]. Prevalence of LF was 36%, 25% and 17% using LSM ≥ 7 kPa, ≥ 7.9 kPa and ≥ 9.5 kPa, respectively. There was no association between cumulative methotrexate dose [median 2.16 (IQR 0.93-5.2)] and continuous LSM values [unstandardized coefficient 0.16, 95% confidence interval (CI) -0.49 to 0.82, P = 0.626] or using the categorical LSM cutoff values: ≥ 7 kPa [unadjusted odds ratio 1.06 (95% CI 0.97-1.15), P = 0.192], ≥ 7.9 kPa [unadjusted odds ratio 1.03 (95% CI 0.94-1.12), P = 0.577] and ≥ 9.5 kPa (unadjusted odds ratio 1.01, 95% CI 0.91-1.12; P = 0.843). The following risk factors were associated with higher LSM values: BMI (P ≤ 0.001), waist circumference (P ≤ 0.001), metabolic syndrome (P ≤ 0.001), AUDIT score (P = 0.020) and FIB-4 score (P = 0.03). BMI ≥ 28, diabetes and metabolic syndrome were shown to be better predictors of LF compared with FIB-4 score. CONCLUSIONS: This study confirms a high prevalence of significant LF in patients with psoriasis. Cumulative methotrexate dose was not associated with LF. Patients with BMI ≥ 28, metabolic syndrome and diabetes are at higher risk for LF. These risk factors may help to identify when a more detailed liver health assessment is needed.

Psoriasis is a common inflammatory skin disease affecting 3% of the UK population. People with psoriasis appear to have higher rates of liver fibrosis (scarring in the liver from injury or inflammation) compared with people without psoriasis. There are several risk factors for increasing chances of developing liver fibrosis, including obesity, alcohol and diabetes; however, there have been some concerns that methotrexate (a medicine used to treat psoriasis) could also contribute to liver fibrosis. The majority of people needing systemic therapy (such as oral medicines) will try methotrexate first as per National Institute for Health and Care Excellence (NICE) guidance. In this study carried out in the UK, we aimed to look at the relationship between the cumulative dose (total over time) of methotrexate and liver fibrosis and the relationship between other risk factors and liver fibrosis (e.g. body mass index (BMI) (a measure that uses your height and weight to work out whether your weight is healthy), diabetes, alcohol intake and metabolic syndrome (a combination of diabetes, high blood pressure and obesity)). Liver fibrosis was measured using transient elastography, which is a non-invasive technique similar to an ultrasound. We also aimed to find out whether the clinical risk factors for liver fibrosis and a simple test called a 'FIB-4 score' (measured using blood test values and age) can predict a person's chance of developing liver fibrosis, in order to determine which people will benefit most from transient elastography. From our results, we were able to confirm that liver scarring is prevalent in our patients with psoriasis. We did not find an association between cumulative methotrexate and liver scarring. However, BMI, diabetes, metabolic syndrome and FIB-4 score were associated with liver scarring. We found that BMI ≥ 28, metabolic syndrome and diabetes can be used to identify patients who require a liver health assessment. Overall, the study findings suggest that cumulative methotrexate dose is not associated with liver fibrosis in people with a history of moderate-to-severe psoriasis.

Risk of Suicide and Suicidality in Patients with Moderate to Severe Psoriasis: results from the British Association of Dermatologists Biologic and Immunomodulators Register (BADBIR).

BACKGROUND: Psoriasis is associated with poor mental health and reduced quality of life. Although the high risk for depression in patients with psoriasis is well-established, their suicidality risk is uncertain. Previous studies provide contrasting results and have not included patients with clinically-confirmed severe disease. OBJECTIVES: Our aim was to determine risk of suicide among patients with moderate to severe psoriasis compared with the general population, and investigate if psychiatric comorbidity or history of suicidality increases future suicidality risk in psoriasis. We further estimated the incidence of suicidal and self-injurious behaviours in patients. METHODS: Analysis was performed using the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR). As controls, general population mortality and suicide data were used. RESULTS: There were 9 suicides in BADBIR. The incidence rate of suicide was 12.5 per 100,000 person-years (95% CI 6.53, 24.11) in BADBIR versus 11.0 per 100,000 person-years (95% CI 10.7, 11.3) in the general population in England and Wales. Among patients, psychiatric comorbidity or past suicidality was associated with higher risk for suicidal ideation, suicide attempts and self-injurious behaviours. CONCLUSIONS: Suicide rates among patients with moderate to severe psoriasis were not significantly higher compared with the general population. Suicide is a rare event and our results are limited by the uncertainty in the estimate reliability. However, considering the high depression prevalence in psoriasis, our findings support the need for prompt assessment of patients for psychiatric comorbidities and suicidality history. Further research is required on suicidal behaviours and the role of psoriasis severity.

Loss-of-Function Myeloperoxidase Mutations Are Associated with Increased Neutrophil Counts and Pustular Skin Disease.

The identification of disease alleles underlying human autoinflammatory diseases can provide important insights into the mechanisms that maintain neutrophil homeostasis. Here, we focused our attention on generalized pustular psoriasis (GPP), a potentially life-threatening disorder presenting with cutaneous and systemic neutrophilia. Following the whole-exome sequencing of 19 unrelated affected individuals, we identified a subject harboring a homozygous splice-site mutation (c.2031-2A>C) in MPO. This encodes myeloperoxidase, an essential component of neutrophil azurophil granules. MPO screening in conditions phenotypically related to GPP uncovered further disease alleles in one subject with acral pustular psoriasis (c.2031-2A>C;c.2031-2A>C) and in two individuals with acute generalized exanthematous pustulosis (c.1705C>T;c.2031-2A>C and c.1552_1565del;c.1552_1565del). A subsequent analysis of UK Biobank data demonstrated that the c.2031-2A>C and c.1705C>T (p.Arg569Trp) disease alleles were also associated with increased neutrophil abundance in the general population (p = 5.1 × 10-6 and p = 3.6 × 10-5, respectively). The same applied to three further deleterious variants that had been genotyped in the cohort, with two alleles (c.995C>T [p.Ala332Val] and c.752T>C [p.Met251Thr]) yielding p values < 10-10. Finally, treatment of healthy neutrophils with an MPO inhibitor (4-Aminobenzoic acid hydrazide) increased cell viability and delayed apoptosis, highlighting a mechanism whereby MPO mutations affect granulocyte numbers. These findings identify MPO as a genetic determinant of pustular skin disease and neutrophil abundance. Given the recent interest in the development of MPO antagonists for the treatment of neurodegenerative disease, our results also suggest that the pro-inflammatory effects of these agents should be closely monitored.

Effectiveness and persistence of acitretin, ciclosporin, fumaric acid esters and methotrexate for patients with moderate-to-severe psoriasis: a cohort study from BADBIR.

BACKGROUND: Real-world data evaluating effectiveness and persistence of systemic therapies for patients with psoriasis are limited. Objectives To determine the effectiveness and persistence of acitretin, ciclosporin, fumaric acid esters (FAEs) and methotrexate in patients with moderate-to-severe psoriasis. METHODS: Data from the British Association of Dermatologists Biologics and Immunomodulators Register (BADBIR), a prospective, multicentre pharmacovigilance register of patients with moderate-to-severe psoriasis receiving biologic and/or conventional systemic therapies, were analysed. Eligible patients were ≥ 16 years of age receiving a first course of acitretin, ciclosporin, FAEs or methotrexate between 2007 and 2021 with ≥ 6 months' follow-up. Effectiveness was defined as achieving absolute Psoriasis Area and Severity Index (aPASI) ≤ 2 reported ≥ 4 weeks after treatment start date until date of cessation. To identify baseline clinical variables associated with treatment effectiveness, we used multivariable logistic regression models estimating the adjusted odds ratio (aOR) of achieving aPASI ≤ 2. To describe drug persistence associated with ineffectiveness, occurrence of adverse events or other reasons for discontinuation, survival estimates with 95% confidence intervals (CIs) were obtained using a flexible parametric model. Results were obtained using multiple imputed data. RESULTS: In total, 5430 patients were included in the analysis. Overall, 1023 (19%) patients were receiving acitretin, 1401 (26%) patients were on ciclosporin, 347 (6%) patients were on FAEs, and 2659 (49%) patients were receiving methotrexate at registration. The proportion of patients who achieved aPASI ≤ 2 was lower for those treated with acitretin [n = 118 (21%)] compared with those receiving ciclosporin [n = 233 (34%)], FAEs [n = 43 (29%)] and methotrexate [n = 372 (32%)]. Factors associated with ineffectiveness included prior experience to previous nonbiologic systemic therapies (acitretin) (aOR 0.64, 95% CI 0.42-0.96), male sex (methotrexate) (aOR 0.58, 95% CI 0.46-0.74), comorbidities (aOR 0.70, 95% CI 0.51-0.97) and alcohol consumption (≤ 14 units per week) (ciclosporin) (aOR 0.70, 95% CI 0.50-0.98). Persistence associated with all reasons for discontinuation showed better survival for methotrexate compared with acitretin, ciclosporin and FAEs cohorts at 12 months [survival estimate 46.1 (95% CI 44.0-48.3), 31.9 (95% CI 29.4-34.7), 30.0 (95% CI 27.5-32.4) and 35.0 (95% CI 29.9-40.9), respectively]. CONCLUSIONS: The real-world effectiveness and persistence of acitretin, ciclosporin, FAEs and methotrexate were generally low. Previous nonbiologic systemic therapies, male sex, comorbidities and alcohol consumption were risk factors associated with treatment ineffectiveness.

Individualised computational modelling of immune mediated disease onset, flare and clearance in psoriasis.

Despite increased understanding about psoriasis pathophysiology, currently there is a lack of predictive computational models. We developed a personalisable ordinary differential equations model of human epidermis and psoriasis that incorporates immune cells and cytokine stimuli to regulate the transition between two stable steady states of clinically healthy (non-lesional) and disease (lesional psoriasis, plaque) skin. In line with experimental data, an immune stimulus initiated transition from healthy skin to psoriasis and apoptosis of immune and epidermal cells induced by UVB phototherapy returned the epidermis back to the healthy state. Notably, our model was able to distinguish disease flares. The flexibility of our model permitted the development of a patient-specific "UVB sensitivity" parameter that reflected subject-specific sensitivity to apoptosis and enabled simulation of individual patients' clinical response trajectory. In a prospective clinical study of 94 patients, serial individual UVB doses and clinical response (Psoriasis Area Severity Index) values collected over the first three weeks of UVB therapy informed estimation of the "UVB sensitivity" parameter and the prediction of individual patient outcome at the end of phototherapy. An important advance of our model is its potential for direct clinical application through early assessment of response to UVB therapy, and for individualised optimisation of phototherapy regimes to improve clinical outcome. Additionally by incorporating the complex interaction of immune cells and epidermal keratinocytes, our model provides a basis to study and predict outcomes to biologic therapies in psoriasis.

An open source pipeline for quantitative immunohistochemistry image analysis of inflammatory skin disease using artificial intelligence.

BACKGROUND: The application of artificial intelligence (AI) to whole slide images has the potential to improve research reliability and ultimately diagnostic efficiency and service capacity. Image annotation plays a key role in AI and digital pathology. However, the work-streams required for tissue-specific (skin) and immunostain-specific annotation has not been extensively studied compared with the development of AI algorithms. OBJECTIVES: The objective of this study is to develop a common workflow for annotating whole slide images of biopsies from inflammatory skin disease immunostained with a variety of epidermal and dermal markers prior to the development of the AI-assisted analysis pipeline. METHODS: A total of 45 slides containing 3-5 sections each were scanned using Aperio AT2 slide scanner (Leica Biosystems). These slides were annotated by hand using a commonly used image analysis tool which resulted in more than 4000 images blocks. We used deep learning (DL) methodology to first sequentially segment (epidermis and upper dermis), with the exclusion of common artefacts and second to quantify the immunostained signal in those two compartments of skin biopsies and the ratio of positive cells. RESULTS: We validated two DL models using 10-fold validation runs and by comparing to ground truth manually annotated data. The models achieved an average (global) accuracy of 95.0% for the segmentation of epidermis and dermis and 86.1% for the segmentation of positive/negative cells. CONCLUSIONS: The application of two DL models in sequence facilitates accurate segmentation of epidermal and dermal structures, exclusion of common artefacts and enables the quantitative analysis of the immunostained signal. However, inaccurate annotation of the slides for training the DL model can decrease the accuracy of the output. Our open source code will facilitate further external validation across different immunostaining platforms and slide scanners.

Mapping exercise and status update of eight established registries within the TREatment of ATopic eczema Registry Taskforce.

BACKGROUND: The TREatment of ATopic eczema (TREAT) Registry Taskforce is a collaborative international network of registries collecting data of atopic eczema (AE) patients receiving systemic and phototherapy with the common goal to provide long-term real-world data on the effectiveness, safety and cost-effectiveness of therapies. A core dataset, consisting of domains and domain items with corresponding measurement instruments, has been developed to harmonize data collection. OBJECTIVES: We aimed to give an overview of the status and characteristics of the eight established TREAT registries, and to perform a mapping exercise to examine the degree of overlap and pooling ability between the national registry datasets. This will allow us to determine which research questions can be answered in the future by pooling data. METHODS: All eight registries were asked to share their dataset and information on the current status and characteristics. The overlap between the core dataset and each registry dataset was identified (according to the domains, domain items and measurement instruments of the TREAT core dataset). RESULTS AND CONCLUSIONS: A total of 4702 participants have been recruited in the eight registries as of 1st of May 2022. Of the 69 core dataset domain items, data pooling was possible for 69 domain item outcomes in TREAT NL (the Netherlands), 61 items in A-STAR (UK and Ireland), 38 items in TREATgermany (Germany), 36 items in FIRST (France), 33 items in AtopyReg (Italy), 29 items in Biobadatop (Spain), 28 items in SCRATCH (Denmark) and 20 items in SwedAD (Sweden). Pooled analyses across all registries can be performed on multiple important domain items, covering the main aims of analysing data on the (cost-)effectiveness and safety of AE therapies. These results will facilitate future comparative or joint analyses.

Single-cell analysis implicates TH17-to-TH2 cell plasticity in the pathogenesis of palmoplantar pustulosis.

BACKGROUND: Palmoplantar pustulosis (PPP) is a severe inflammatory skin disorder characterized by eruptions of painful, neutrophil-filled pustules on the palms and soles. Although PPP has a profound effect on quality of life, it remains poorly understood and notoriously difficult to treat. OBJECTIVE: We sought to investigate the immune pathways that underlie the pathogenesis of PPP. METHODS: We applied bulk and single-cell RNA sequencing (RNA-Seq) methods to the analysis of skin biopsy samples and peripheral blood mononuclear cells. We validated our results by flow cytometry and immune fluorescence microscopy RESULTS: Bulk RNA-Seq of patient skin detected an unexpected signature of T-cell activation, with a significant overexpression of several TH2 genes typically upregulated in atopic dermatitis. To further explore these findings, we carried out single-cell RNA-Seq in peripheral blood mononuclear cells of healthy and affected individuals. Memory CD4+ T cells of PPP patients were skewed toward a TH17 phenotype, a phenomenon that was particularly significant among cutaneous lymphocyte-associated antigen-positive skin-homing cells. We also identified a subset of memory CD4+ T cells that expressed both TH17 (KLRB1/CD161) and TH2 (GATA3) markers, with pseudotime analysis suggesting that the population was the result of TH17 to TH2 plasticity. Interestingly, the GATA3+/CD161+ cells were overrepresented among the peripheral blood mononuclear cells of affected individuals, both in the single-cell RNA-Seq data set and in independent flow cytometry experiments. Dual-positive cells were also detected in patient skin by immune fluorescence microscopy. CONCLUSIONS: PPP is associated with complex T-cell activation patterns and may explain why biologic drugs that target individual T helper cell populations have shown limited therapeutic efficacy.

Dominant effect of gap junction communication in wound-induced calcium-wave, NFAT activation and wound closure in keratinocytes.

Wounding induces a calcium wave and disrupts the calcium gradient across the epidermis but mechanisms mediating calcium and downstream signalling, and longer-term wound healing responses are incompletely understood. As expected, live-cell confocal imaging of Fluo-4-loaded normal human keratinocytes showed an immediate increase in [Ca2+ ]i at the wound edge that spread as a calcium wave (8.3 µm/s) away from the wound edge with gradually diminishing rate of rise and amplitude. The amplitude and area under the curve of [Ca2+ ]i flux was increased in high (1.2 mM) [Ca2+ ]o media. 18α-glycyrrhetinic acid (18αGA), a gap-junction inhibitor or hexokinase, an ATP scavenger, blocked the wound-induced calcium wave, dependent in part on [Ca2+ ]o . Wounding in a high [Ca2+ ]o increased nuclear factor of activated T-cells (NFAT) but not NFkB activation, assessed by dual-luciferase receptor assays compared to unwounded cells. Treatment with 18αGA or the store-operated channel blocker GSK-7975A inhibited wound-induced NFAT activation, whereas treatment with hexokinase did not. Real-time cell migration analysis, measuring wound closure rates over 24 h, revealed that 18αGA essentially blocked wound closure whereas hexokinase and GSK-7975A showed relatively minimal effects. Together these data indicate that while both gap-junction communication and ATP release from damaged cells are important in regulating the wound-induced calcium wave, long-term transcriptional and functional responses are dominantly regulated by gap-junction communication.

microRNA-184 is induced by store-operated calcium entry and regulates early keratinocyte differentiation.

Extracellular calcium (Ca2+ ) and store-operated Ca2+ entry (SOCE) govern homoeostasis in the mammalian epidermis. Multiple microRNAs (miRNA) also regulate epidermal differentiation, and raised external Ca2+ modulates the expression of several such miRNAs in keratinocytes. However, little is known about the regulation of miR-184 in keratinocytes or the roles of miR-184 in keratinocyte differentiation. Here we report that exogenous Ca2+ stimulates miR-184 expression in primary epidermal keratinocytes and that this occurs in a SOCE-dependent manner. Levels of miR-184 were raised by about 30-fold after exposure to 1.5 mM Ca2+ for 5 days. In contrast, neither phorbol ester nor 1,25-dihydroxyvitamin D3 had any effect on miR-184 levels. Pharmacologic and genetic inhibitors of SOCE abrogated Ca2+ -dependent miR-184 induction by 70% or more. Ectopic miR-184 inhibited keratinocyte proliferation and led to a fourfold increase in the expression of involucrin, a marker of early keratinocyte differentiation. Exogenous miR-184 also triggered a threefold rise in levels of cyclin E and doubled the levels of γH2AX, a marker of DNA double-strand breaks. The p21 cyclin-dependent kinase inhibitor, which supports keratinocyte growth arrest, was also induced by miR-184. Together our findings point to an SOCE:miR-184 pathway that targets a cyclin E/DNA damage regulatory node to facilitate keratinocyte differentiation.

Human and computational models of atopic dermatitis: A review and perspectives by an expert panel of the International Eczema Council.

Atopic dermatitis (AD) is a prevalent disease worldwide and is associated with systemic comorbidities representing a significant burden on patients, their families, and society. Therapeutic options for AD remain limited, in part because of a lack of well-characterized animal models. There has been increasing interest in developing experimental approaches to study the pathogenesis of human AD in vivo, in vitro, and in silico to better define pathophysiologic mechanisms and identify novel therapeutic targets and biomarkers that predict therapeutic response. This review critically appraises a range of models, including genetic mutations relevant to AD, experimental challenge of human skin in vivo, tissue culture models, integration of "omics" data sets, and development of predictive computational models. Although no one individual model recapitulates the complex AD pathophysiology, our review highlights insights gained into key elements of cutaneous biology, molecular pathways, and therapeutic target identification through each approach. Recent developments in computational analysis, including application of machine learning and a systems approach to data integration and predictive modeling, highlight the applicability of these methods to AD subclassification (endotyping), therapy development, and precision medicine. Such predictive modeling will highlight knowledge gaps, further inform refinement of biological models, and support new experimental and systems approaches to AD.

HLA-C*06:02 genotype is a predictive biomarker of biologic treatment response in psoriasis.

BACKGROUND: Biologic therapies can be highly effective for the treatment of severe psoriasis, but response for individual patients can vary according to drug. Predictive biomarkers to guide treatment selection could improve patient outcomes and treatment cost-effectiveness. OBJECTIVE: We sought to test whether HLA-C*06:02, the primary genetic susceptibility allele for psoriasis, predisposes patients to respond differently to the 2 most commonly prescribed biologics for psoriasis: adalimumab (anti-TNF-α) and ustekinumab (anti-IL-12/23). METHODS: This study uses a national psoriasis registry that includes longitudinal treatment and response observations and detailed clinical data. HLA alleles were imputed from genome-wide genotype data for 1326 patients for whom 90% reduction in Psoriasis Area and Severity Index score (PASI90) response status was observed after 3, 6, or 12 months of treatment. We developed regression models of PASI90 response, examining the interaction between HLA-C*06:02 and drug type (adalimumab or ustekinumab) while accounting for potentially confounding clinical variables. RESULTS: HLA-C*06:02-negative patients were significantly more likely to respond to adalimumab than ustekinumab at all time points (most strongly at 6 months: odds ratio [OR], 2.95; P = 5.85 × 10-7), and the difference was greater in HLA-C*06:02-negative patients with psoriatic arthritis (OR, 5.98; P = 6.89 × 10-5). Biologic-naive patients who were HLA-C*06:02 positive and psoriatic arthritis negative demonstrated significantly poorer response to adalimumab at 12 months (OR, 0.31; P = 3.42 × 10-4). Results from HLA-wide analyses were consistent with HLA-C*06:02 itself being the primary effect allele. We found no evidence for genetic interaction between HLA-C*06:02 and ERAP1. CONCLUSION: This large observational study suggests that reference to HLA-C*06:02 status could offer substantial clinical benefit when selecting treatments for severe psoriasis.

Moving Toward Precision Medicine in Psoriasis and Psoriatic Arthritis.

Current management approaches for the treatment of psoriasis and psoriatic arthritis (PsA) are imprecise and depend largely on clinical assessment. A more precise approach, which takes into account an individual patient's variations in genes, proteins, environment, and lifestyle, is beginning to receive attention with the most advanced progress seen in the treatment of cancer. Herein, the methodological approaches required for this precision medicine approach to be adopted in psoriatic disease, as well as their advantages, are reviewed. In addition, advances that are being made to address areas of unmet need in PsA, notably the use of proteomic approaches, are presented with suggestions that combine genetic and protein data (proteogenomics). Finally, progress that is being made in 2 large-scale, multipartner studies focused on the development of a precision medicine approach to the treatment of skin psoriasis is presented and discussed.

Exome-wide association study reveals novel psoriasis susceptibility locus at TNFSF15 and rare protective alleles in genes contributing to type I IFN signalling.

Psoriasis is a common inflammatory skin disorder for which multiple genetic susceptibility loci have been identified, but few resolved to specific functional variants. In this study, we sought to identify common and rare psoriasis-associated gene-centric variation. Using exome arrays we genotyped four independent cohorts, totalling 11 861 psoriasis cases and 28 610 controls, aggregating the dataset through statistical meta-analysis. Single variant analysis detected a previously unreported risk locus at TNFSF15 (rs6478108; P = 1.50 × 10-8, OR = 1.10), and association of common protein-altering variants at 11 loci previously implicated in psoriasis susceptibility. We validate previous reports of protective low-frequency protein-altering variants within IFIH1 (encoding an innate antiviral receptor) and TYK2 (encoding a Janus kinase), in each case establishing a further series of protective rare variants (minor allele frequency < 0.01) via gene-wide aggregation testing (IFIH1: pburden = 2.53 × 10-7, OR = 0.707; TYK2: pburden = 6.17 × 10-4, OR = 0.744). Both genes play significant roles in type I interferon (IFN) production and signalling. Several of the protective rare and low-frequency variants in IFIH1 and TYK2 disrupt conserved protein domains, highlighting potential mechanisms through which their effect may be exerted.

Proteomic analysis of filaggrin deficiency identifies molecular signatures characteristic of atopic eczema.

BACKGROUND: Atopic eczema (AE) is characterized by skin barrier and immune dysfunction. Null mutations in filaggrin (FLG), a key epidermal barrier protein, strongly predispose to AE; however, the precise role of FLG deficiency in AE pathogenesis remains incompletely understood. OBJECTIVES: We sought to identify global proteomic changes downstream of FLG deficiency in human epidermal living skin-equivalent (LSE) models and validate findings in skin of patients with AE. METHODS: Differentially expressed proteins from paired control (nontargeting control short hairpin RNA [shNT]) and FLG knockdown (FLG knockdown short hairpin RNA [shFLG]) LSEs were identified by means of proteomic analysis (liquid chromatography-mass spectrometry) and Ingenuity Pathway Analysis. Expression of key targets was validated in independent LSE samples (quantitative RT-PCR and Western blotting) and in normal and AE skin biopsy specimens (immunofluorescence). RESULTS: Proteomic analysis identified 17 (P ≤ .05) differentially expressed proteins after FLG knockdown, including kallikrein-7 (KLK7; 2.2-fold), cyclophilin A (PPIA; 0.9-fold), and cofilin-1 (CFL1, 1.3-fold). Differential protein expression was confirmed in shNT/shFLG LSEs; however, only KLK7 was transcriptionally dysregulated. Molecular pathways overrepresented after FLG knockdown included inflammation, protease activity, cell structure, and stress. Furthermore, KLK7 (1.8-fold) and PPIA (0.65-fold) proteins were differentially expressed in lesional biopsy specimens from patients with AE relative to normal skin. CONCLUSIONS: For the first time, we show that loss of FLG in the absence of inflammation is sufficient to alter the expression level of proteins relevant to the pathogenesis of AE. These include proteins regulating inflammatory, proteolytic, and cytoskeletal functions. We identify PPIA as a novel protein with levels that are decreased in clinically active AE skin and show that the characteristic upregulation of KLK7 expression in patients with AE occurs downstream of FLG loss. Importantly, we highlight disconnect between the epidermal proteome and transcriptome, emphasizing the utility of global proteomic studies.