IL-6 Signaling in Myelomonocytic Cells Is Not Crucial for the Development of IMQ-Induced Psoriasis

Cytokines in psoriasis: From pathogenesis to targeted therapy

Psoriasis is a multifactorial disease that affects 0.84% of the global population and it can be associated with disabling comorbidities. As patients present with thick scaly lesions, psoriasis was long believed to be a disorder of keratinocytes. Psoriasis is now understood to be the outcome of the interaction between immunological and environmental factors in individuals with genetic predisposition. While it was initially thought to be solely mediated by cytokines of type-1 immunity, namely interferon-γ, interleukin-2, and interleukin-12 because it responds very well to cyclosporine, a reversible IL-2 inhibitor; the discovery of Th-17 cells advanced the understanding of the disease and helped the development of biological therapy. This article aims to provide a comprehensive review of the role of cytokines in psoriasis, highlighting areas of controversy and identifying the connection between cytokine imbalance and disease manifestations. It also presents the approved targeted treatments for psoriasis and those currently under investigation.

Elevated serum IL-6 levels predict treatment interruption in patients with moderate to severe psoriasis: a 6-year real-world cohort study

BACKGROUND

Real-world, primary data on the treatment of psoriasis are scarce, especially concerning the role of soluble biomarkers as outcome predictors.

OBJECTIVE

The authors evaluated the utility of Th1/Th17 serum cytokines along with clinical characteristics as predictors of drug survival in the treatment of psoriasis.

METHODS

The authors consecutively included participants with moderate to severe psoriasis who were followed up for 6 years. Baseline interferon-α, tumor necrosis factor-α, and interleukin (IL)-2, IL-4, IL-6, IL-10, and IL-17A were measured using a cytometric bead array; clinical data were assessed. The authors calculated hazard ratios (HRs) for drug survival using a Cox proportional hazards model.

RESULTS

The authors included 262 patients, most of whom used systemic immunosuppressants or biologics. In the multivariate model, poor quality of life measured by the Dermatology Life Quality Index (HR = 1.04; 95% CI 1.01‒1.07; p = 0.012) and elevated baseline IL-6 (HR = 1.99; 95% CI 1.29‒3.08; p = 0.002) were associated with treatment interruption.

STUDY LIMITATIONS

The main limitation of any cohort study is the presence of confounders that could not be detected in clinical evaluation.

CONCLUSIONS

Poor quality of life and elevated baseline serum IL-6 level predicted treatment interruption in patients with moderate to severe psoriasis. Although IL-6 is not the most important mediator of the inflammatory pathway in the skin environment, it is an interesting biomarker candidate for predicting psoriasis treatment response.

Dupuytren's contracture-associated SNPs increase SFRP4 expression in non-immune cells including fibroblasts to enhance inflammation development

Dupuytren's contracture (DC) is an inflammatory fibrosis characterized by fibroproliferative disorders of the palmar aponeurosis, for which there is no effective treatment. Although several genome-wide association studies have identified risk alleles associated with DC, the functional linkage between these alleles and the pathogenesis remains elusive. We here focused on two single nucleotide polymorphisms (SNPs) associated with DC, rs16879765 and rs17171229, in secreted frizzled related protein 4 (SFRP4). We investigated the association of SRFP4 with the IL-6 amplifier, which amplifies the production of IL-6, growth factors and chemokines in non-immune cells and aggravates inflammatory diseases via NF-κB enhancement. Knockdown of SFRP4 suppressed activation of the IL-6 amplifier in vitro and in vivo, whereas the overexpression of SFRP4 induced the activation of NF-κB-mediated transcription activity. Mechanistically, SFRP4 induced NF-κB activation by directly binding to molecules of the ubiquitination SFC complex, such as IkBα and βTrCP, followed by IkBα degradation. Furthermore, SFRP4 expression was significantly increased in fibroblasts derived from DC patients bearing the risk alleles. Consistently, fibroblasts with the risk alleles enhanced activation of the IL-6 amplifier. These findings indicate that the IL-6 amplifier is involved in the pathogenesis of DC, particularly in patients harboring the SFRP4 risk alleles. Therefore, SFRP4 is a potential therapeutic target for various inflammatory diseases and disorders, including DC.

Genetic variants affecting chemical mediated skin immunotoxicity

The skin is an immune-competent organ and this function may be impaired by exposure to chemicals, which may ultimately result in immune-mediated dermal disorders. Interindividual variability to chemical-induced skin immune reactions is associated with intrinsic individual characteristics and their genomes. In the last 30-40 years, several genes influencing susceptibility to skin immune reactions were identified. The aim of this review is to provide information regarding common genetic variations affecting skin immunotoxicity. The polymorphisms selected for this review are related to xenobiotic-metabolizing enzymes (CYPA1 and CYPB1 genes), antioxidant defense (GSTM1, GSTT1, and GSTP1 genes), aryl hydrocarbon receptor signaling pathway (AHR and ARNT genes), skin barrier function transepidermal water loss (FLG, CASP14, and SPINK5 genes), inflammation (TNF, IL10, IL6, IL18, IL31, and TSLP genes), major histocompatibility complex (MHC) and neuroendocrine system peptides (CALCA, TRPV1, ACE genes). These genes present variants associated with skin immune responses and diseases, as well as variants associated with protecting skin immune homeostasis following chemical exposure. The molecular and association studies focusing on these genetic variants may elucidate their functional consequences and contribution in the susceptibility to skin immunotoxicity. Providing information on how genetic variations affect the skin immune system may reduce uncertainties in estimating chemical hazards/risks for human health in the future.

Association of HOTAIR Polymorphisms with Susceptibility to Psoriasis in a Chinese Han Population

Psoriasis is a common disease in dermatology, but its etiology and pathogenesis have not been fully elucidated. In recent years, researchers have found that HOX transcript antisense RNA (HOTAIR) plays an important role in biological processes as an important long-chain noncoding RNA (lncRNA). The goal of this study was to investigate the association between HOTAIR polymorphisms and psoriasis in a Chinese Han population by screening key candidate single-nucleotide polymorphism (SNPs) sites in HOTAIR. A total of 269 patients diagnosed with psoriasis and 273 healthy control subjects were enrolled in this case-control study. Three SNPs of HOTAIR were genotyped: SNP1 (rs12826786), SNP2 (rs1899663), and SNP3 (rs4759314). All polymorphisms were in Hardy-Weinberg equilibrium in both the control and patient groups, and the SNPs were in linkage disequilibrium. The distribution of the rs4759314 genotype in the control group and case group was statistically significant according to all the models except the recessive model (adjusted p value < 0.05), and the CCG haplotype group had a significant difference (OR (95%CI) = 2.907 (1.344 - 6.289), adjusted p value = 0.0263). rs12826786 was associated with a risk of psoriasis according to the dominant model (C/T-T/T vs. C/C: OR (95%CI) = 0.70 (0.48 - 1.01), adjusted p value = 0.049) and overdominant model (C/T vs. C/C-T/T: OR (95%CI) = 0.69 (0.47 - 1.01), adjusted p value = 0.048). The current work showed that a genomic variant within HOTAIR was associated with a risk of psoriasis, and the clinical value of this study should be further evaluated in the future.

IL6Rα function in myeloid cells modulates the inflammatory response during irritant contact dermatitis

Irritant contact dermatitis (ICD) is characterized by epidermal hyperplasia, infiltration of leucocytes into lesional skin and inflammatory cytokine release. The cellular infiltrate during ICD comprises primarily cells of the myeloid lineage. Our group has previously shown that the cytokine IL-6 confers a protective effect to lesional skin during ICD. How IL-6Rα function in myeloid cells is involved in the inflammatory response during ICD is, however, unknown. In the present study, utilizing a chemical model of ICD, it is shown that mice with a myeloid-specific knockout of the IL-6Rα (IL-6Rα^Δmyeloid ) display an exaggerated inflammatory response to benzalkonium chloride (BKC) and Jet propellant-8 (JP8) fuel, two well-characterized irritants relative to littermate control. Results from immunohistochemical and flow cytometric analyses revealed that IL-6Rα^Δmyeloid mouse skin displayed increased epidermal hyperplasia and inflammatory monocyte influx into lesional skin but lower numbers of resident macrophages relative to littermate controls after irritant exposure. Multiplex immunoassay revealed significantly higher levels of pro-inflammatory cytokines IL-1α and TNF-α, but reduced expression of chemokine proteins including CCL2-5, CCL7, CCL11, CXCL1 and CXCL10 in IL-6Rα^Δmyeloid mouse skin relative to littermate control following irritant exposure. These results highlight a previously unknown role of IL-6Rα function in myeloid cells in modulating the inflammatory response and myeloid population dynamics during ICD.

Cytokine Imbalance as a Common Mechanism in Both Psoriasis and Rheumatoid Arthritis

Psoriasis (PS) and rheumatoid arthritis (RA) are immune-mediated inflammatory diseases. Previous studies showed that these two diseases had a common pathogenesis, but the precise molecular mechanism remains unclear. In this study, RNA sequencing of peripheral blood mononuclear cells was employed to explore both the differentially expressed genes (DEGs) of 10 PS and 10 RA patients compared with those of 10 healthy volunteers and the shared DEGs between these two diseases. Bioinformatics network analysis was used to reveal the connections among the shared DEGs and the corresponding molecular mechanism. In total, 120 and 212 DEGs were identified in PS and RA, respectively, and 31 shared DEGs were identified. Bioinformatics analysis indicated that the cytokine imbalance relevant to key molecules (such as extracellular signal-regulated kinase 1/2 (ERK1/2), p38 mitogen-activated protein kinase (MAPK), tumor necrosis factor (TNF), colony-stimulating factor 3 (CSF3), interleukin- (IL-) 6, and interferon gene (IFNG)) and canonical signaling pathways (such as the complement system, antigen presentation, macropinocytosis signaling, nuclear factor-kappa B (NF-κB) signaling, and IL-17 signaling) was responsible for the common comprehensive mechanism of PS and RA. Our findings provide a better understanding of the pathogenesis of PS and RA, suggesting potential strategies for treating and preventing both diseases. This study may also provide a new paradigm for illuminating the common pathogenesis of different diseases.