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Psoriasis is a chronic inflammatory disease characterised by sharply demarcated erythematous and scaly skin lesions accompanied by systemic manifestations. Classified by WHO as one of the most serious non-infectious diseases, psoriasis affects 2–3% of the global population. Mechanistically, psoriatic lesions result from hyperproliferation and disturbed differentiation of epidermal keratinocytes that are provoked by immune mediators of the IL-23 and IL-17 pathway. Translational immunology has had impressive success in understanding and controlling psoriasis. Psoriasis is the first disease to have been successfully treated with therapeutics that directly block the action of the cytokines of this pathway; in fact, therapeutics that specifically target IL-23, IL-17, and IL-17RA are approved for clinical use and show excellent efficacy. Furthermore, inhibitors of IL-23 and IL-17 intracellular signalling, such as TYK2 or RORγt, are in clinical development. Although therapies that target the IL-23 and IL-17 pathway also improve psoriatic arthritis symptoms, their effects on long-term disease modification and psoriasis-associated comorbidities still need to be explored.

Psoriasis is a complex disease of skin with a prevalence of about 2%. We conducted the largest meta-analysis of genome-wide association studies (GWAS) for psoriasis to date, including data from eight different Caucasian cohorts, with a combined effective sample size >39,000 individuals. We identified 16 additional psoriasis susceptibility loci achieving genome-wide significance, increasing the number of identified loci to 63 for European-origin individuals. Functional analysis highlighted the roles of interferon signalling and the NFκB cascade, and we showed that the psoriasis signals are enriched in regulatory elements from different T cells (CD8 + T-cells and CD4 + T-cells including T H 0, T H 1 and T H 17). The identified loci explain ∼28% of the genetic heritability and generate a discriminatory genetic risk score (AUC=0.76 in our sample) that is significantly correlated with age at onset ( p= 2 × 10 −89 ). This study provides a comprehensive layout for the genetic architecture of common variants for psoriasis. Psoriasis is an immune-mediated skin disease with a complex genetic architecture. Here, Elder and colleagues identify 16 novel psoriasis susceptibility loci using GWAS meta-analysis with a combined effective sample size of over 39,000 individuals.

Psoriasis is an IL-23/Th17-mediated skin disorder with a strong genetic predisposition. The impact of its susceptibility gene nitric oxide synthase 2 (NOS2) remains unknown. Here, we demonstrate strong NOS2 mRNA expression in psoriatic epidermis, an effect that is IL-17 dependent. However, its complete translation to protein is prevented by the IL-17-induced miR-31 implying marginally upregulated NO levels in psoriatic skin. We demonstrate that lower levels of NO, as opposed to higher levels, increase keratinocyte proliferation and mediate IL-17 downstream effects. We hypothesized that the psoriatic phenotype may be alleviated by either eliminating or increasing cellular NO levels. In fact, using the imiquimod psoriasis mouse model, we found a profound impact on the psoriatic inflammation in both IMQ-treated NOS2 KO mice and wild-type mice treated with IMQ and the NO-releasing berdazimer gel. In conclusion, we demonstrate that IL-17 induces NOS2 and fine-tunes its translation towards a window of proinflammatory and hyperproliferative effects and identify NO donor therapy as a new treatment modality for psoriasis.

Psoriatic arthritis (PsA) is a complex chronic musculoskeletal condition that occurs in ~30% of psoriasis patients. Currently, no systematic strategy is available that utilizes the differences in genetic architecture between PsA and cutaneous-only psoriasis (PsC) to assess PsA risk before symptoms appear. Here, we introduce a computational pipeline for predicting PsA among psoriasis patients using data from six cohorts with >7000 genotyped PsA and PsC patients. We identify 9 new loci for psoriasis or its subtypes and achieve 0.82 area under the receiver operator curve in distinguishing PsA vs. PsC when using 200 genetic markers. Among the top 5% of our PsA prediction we achieve >90% precision with 100% specificity and 16% recall for predicting PsA among psoriatic patients, using conditional inference forest or shrinkage discriminant analysis. Combining statistical and machine-learning techniques, we show that the underlying genetic differences between psoriasis subtypes can be used for individualized subtype risk assessment. Approximately 30% of psoriasis patients develop psoriatic arthritis (PsA) and early diagnosis is crucial for the management of PsA. Here, Patrick et al. develop a computational pipeline involving statistical and machine-learning methods that can assess the risk of progression to PsA based on genetic markers.

Dermatofibromas (DFs) represent prevalent benign fibrohistiocytic tumors, typically manifesting as solitary lesions. In the majority of cases, the clinical presentation and dermoscopic and histopathological features of DFs adhere to a characteristic profile. However, DFs may exhibit atypical clinical presentations and, more commonly, histologic attributes, posing challenges in differential diagnosis. Both DFs and basal cell carcinomas (BCCs) are frequently encountered cutaneous lesions, each characterized by distinct clinical and dermoscopic features and microscopic morphology. The simultaneous occurrence of these two entities within the same lesion is rare. DFs have been documented to form collision tumors in conjunction with a spectrum of benign and malignant lesions, encompassing not only BCC but also balloon cell nevus, squamous cell carcinoma (SCC), and melanoma. Alterations in the epidermis overlaying a DF range from simple hyperplasia to the proliferation of basaloid cells. Accurate diagnosis, leading to the complete excision of the lesion, is contingent upon the recognition of dermoscopic criteria, precluding misinterpretation as a benign lesion. We present two cases of collision tumors comprising DF and BCC. This case report underscores the paramount importance of dermoscopy and adherence to dermoscopic criteria in the assessment of collision lesions and the diagnostic process related to cutaneous malignancies.

Psoriasin (S100A7), originally identified in psoriasis, is a calcium-binding protein belonging to the multigenic S100 family. In high-grade ductal carcinoma in situ, psoriasin was identified as one of the most abundant transcripts. We have previously shown that psoriasin was induced by reactive oxygen species (ROS). Moreover, the downregulation of psoriasin by short hairpin RNA (shRNA) led to the reduced expression of vascular endothelial growth factor (VEGF) and inhibited tumor growth in vivo. The aim of the present study was to investigate whether psoriasin could have direct effects on endothelial cells. In this study we demonstrated that psoriasin increased VEGF expression in mammary epithelial cells. The treatment of endothelial cells with recombinant psoriasin increased proliferation comparable to that of recombinant VEGF protein. No change in proliferation was seen when endothelial cells were infected with psoriasin-expressing adenoviruses, suggesting that the proliferative effect of psoriasin was mediated by a specific receptor. Treatment with sRAGE, targeting the receptor for advanced glycation end products (RAGE), thus inhibited endothelial cell proliferation and tube formation enhanced by recombinant psoriasin. We showed that VEGF expression was not induced by hydrogen peroxide, when psoriasin was silenced by shRNA, which led to the hypothesis that psoriasin induces ROS. Indeed, psoriasin was shown to induce ROS in both endothelial and epithelial cells. Moreover, sRAGE inhibited the psoriasin-dependent generation of ROS in endothelial cells. Finally, treatment with antioxidant Bcl-2 protein abolished the effect of psoriasin on endothelial cell proliferation. Our data suggest that psoriasin expression in mammary epithelial cells leads to increased endothelial cell proliferation in a paracrine manner through RAGE. Psoriasin may therefore play a role in breast cancer progression by promoting oxidative stress response and angiogenesis.

ObjectivesTo investigate the prevalence of psoriasis in SLE using a Swedish regional cohort and a nationwide cohort from the National Patient Register (NPR). Furthermore, we compared clinical features between patients with and without comorbid psoriasis.MethodsIn total, 351 patients diagnosed with SLE based on the 1982 American College of Rheumatology and/or the 2012 Systemic Lupus International Collaborating Clinics criteria from Linköping University Hospital were evaluated. We obtained patient-reported and relevant clinical data extracted in 2024. Individuals with coexisting psoriasis were identified via the International Classification of Diseases code L40 and subsequent confirmation through chart review in the regional cohort. In the NPR, 7490 subjects with SLE living in Sweden in 2022 were identified, as well as therapies obtained from the Prescribed Drug Register.ResultsWe identified 12 subjects with SLE and coexisting psoriasis (3.4%) in the regional cohort and 367 patients (4.9%) in the nationwide cohort. Men were proportionally more common in the group with comorbid psoriasis in both cohorts. Patients with psoriasis reported more pain on a visual analogue scale (median 45.5/100 mm, IQR 23.3–58.3) compared with those without coexisting psoriasis (median 27.0/100 mm, IQR 7.0–50.5, p<0.04). We observed no differences in damage accrual or clinical phenotypes between the two groups. Subjects with psoriasis were more frequently prescribed methotrexate in the nationwide cohort.ConclusionThe prevalence of coexisting psoriasis in patients with SLE in Sweden was estimated to be 3.4–4.9%. Individuals with comorbid psoriasis reported more pain and were more likely to be prescribed methotrexate than those without psoriasis.

Psoriasin (S100A7), a member of the S100 family of calcium-binding proteins, is highly expressed in high-grade ductal carcinoma in situ (DCIS) and in the benign hyperproliferative skin disorder psoriasis. The gene that encodes psoriasin and many other S100 genes are located within a gene cluster on chromosome region 1q21, known as the epidermal differentiation complex. This cluster contains genes for several differentiation markers that play important roles in the terminal differentiation of the epidermis. The purpose of the present study was to evaluate the role of psoriasin in the differentiation process of mammary epithelial cells. Normal mammary epithelial cells (MCF10A) cultured in confluence and suspension, conditions known to induce psoriasin expression, demonstrated a shift towards a more differentiated phenotype indicated by an increase in the expression of the luminal differentiation markers CD24 and MUC1 and the reduced expression of the breast stem cell marker CD44. The expression of psoriasin and MUC1 was most pronounced in the CD24(+)-enriched fraction of confluent MCF10A cells. The shift towards a more differentiated phenotype was abolished upon the downregulation of psoriasin using short hairpin RNA (shRNA) and small interfering RNA (siRNA). Using specific inhibitors, we showed that psoriasin and CD24 expression was regulated by reactive oxygen species (ROS) and the nuclear factor (NF)-κB signaling pathways. While immunohistochemical analyses of DCIS showed heterogeneity, the expression of psoriasin and CD24 showed a similar staining pattern. Our findings suggest that the expression of psoriasin is linked to the luminal differentiation marker CD24 in mammary epithelial cells. Psoriasin demonstrated an essential role in the shift towards a more differentiated CD24(+) phenotype, supporting the hypothesis that psoriasin plays a role in the differentiation of luminal mammary epithelial cells.

Psoriasis is a chronic autoimmune disease with complex genetic architecture. Previous genome-wide association studies (GWAS) and a recent meta-analysis using Immunochip data have uncovered 36 susceptibility loci. Here, we extend our previous meta-analysis of European ancestry by refined genotype calling and imputation and by the addition of 5,033 cases and 5,707 controls. The combined analysis, consisting of over 15,000 cases and 27,000 controls, identifies five new psoriasis susceptibility loci at genome-wide significance ( P <5 × 10 −8 ). The newly identified signals include two that reside in intergenic regions (1q31.1 and 5p13.1) and three residing near PLCL2 (3p24.3), NFKBIZ (3q12.3) and CAMK2G (10q22.2). We further demonstrate that NFKBIZ is a TRAF3IP2 -dependent target of IL-17 signalling in human skin keratinocytes, thereby functionally linking two strong candidate genes. These results further integrate the genetics and immunology of psoriasis, suggesting new avenues for functional analysis and improved therapies. About 2% of the population are affected by psoriasis, a chronic skin disease with complex genetics. Here Tsoi et al. conduct a meta-analysis of several genome-wide association studies and identify five novel loci, helping to further our understanding of the biology behind this condition.

Topically applied TH1579 alleviated the psoriatic phenotype in the imiquimod-induced psoriasis mouse model by decreasing CD45+, Ly6b+, and CD3+ cell infiltration and downregulating the expression of the proliferation marker PCNA. Moreover, TH1579 strongly suppressed IL-17 expression in mouse skin, accompanied by reduced infiltration of IL-17-producing γδ-T cells. Furthermore, TH1579 decreased keratinocyte viability and proliferation. Mass spectrometry data analysis revealed the enrichment of proteins associated with nucleotide excision repair and cell cycle regulation. The key cell cycle regulatory protein F-box protein S-phase kinase-associated protein 2 (SKP2) was significantly downregulated, along with the psoriasis-associated proliferation marker WNT5a, identified as a SKP2 downstream target. The downregulation of SKP2 and WNT5a was confirmed in MTH1i-treated mouse skin. Our findings support the topical administration of MTH1i TH1579 as a psoriasis treatment. The therapeutic effects depended on the SKP2/WNT5a pathway, which mediates psoriatic hyperproliferation. This study introduces a conceptually innovative topical treatment for psoriasis patients with mild-to-moderate disease who have limited therapeutic options.