The inhibitory effect of A20 on the inflammatory reaction of epidermal keratinocytes

Associations of A20, CYLD, Cezanne and JAK2 Genes and Immunophenotype with Psoriasis Susceptibility

Background and Objectives: Psoriasis is an immune-mediated chronic inflammatory skin disorder and commonly associated with highly noticeable erythematous, thickened and scaly plaques. Deubiquitinase genes, such as tumor necrosis factor-alpha protein 3 (TNFAIP3, A20), the cylindromatosis (CYLD) and Cezanne, function as negative regulators of inflammatory response through the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathways. In this study, polymorphisms and expressions of A20, CYLD and Cezanne genes as well as immunophenotype in psoriatic patients were determined. Materials and Methods: In total, 82 patients with psoriasis and 147 healthy individuals with well-characterized clinical profiles were enrolled. Gene polymorphisms were determined by direct DNA sequencing, gene expression profile by quantitative real time-polymerase chain reaction (PCR), immunophenotype by flow cytometry, and the secretion of cytokines and cancer antigen (CA) 125 by enzyme-linked Immunosorbent assay (ELISA). Results: The inactivation of A20, CYLD and Cezanne and increased levels of TNF-α, IFN-γ and CA 125 was observed in psoriatic patients. Importantly, patients with low A20 expression had significant elevations of triglyceride and total cholesterol concentrations and higher numbers of CD13+CD117- and CD19+CD23+ (activated B) cells than those with high A20 expression. Genetic analysis indicated that all rs4495487 SNPs in the JAK2 gene, rs200878487 SNPs in the A20 gene and four SNPs (c.1584-375, c.1584-374, rs1230581026 and p.W433R) in the Cezanne gene were associated with significant risks, while the rs10974947 variant in the JAK2 gene was at reduced risk of psoriasis. Moreover, in the Cezanne gene, p.W433R was predicted to be probably damaging by the Polyphen-2 prediction tool and an AA/CC haplotype was associated with a high risk of psoriasis. In addition, patients with higher CA 125 levels than the clinical cutoff 35 U/mL showed increased levels of IFN-γ than those with normal CA 125 levels. Conclusions: A20 expression was associated with lipid metabolism and the recruitment of CD13+ CD117- and activated B cells into circulation in psoriatic patients. Besides this, the deleterious effect of the p.W433R variant in the Cezanne gene may contribute to the risk of psoriasis.

Immune Regulation of TNFAIP3 in Psoriasis through Its Association with Th1 and Th17 Cell Differentiation and p38 Activation

Background

Psoriasis is an immune-mediated chronic inflammatory skin disorder in which the dysregulation of immune cells plays an important role in its development. Tumor necrosis factor- (TNF-) α antagonists affect the immune repertoire, while TNF-α-induced protein 3 (TNFAIP3) has a protective role against the deleterious effects of inflammation and participates in immune regulation.

Objective

We investigated the immune regulation of TNFAIP3 in the pathogenesis of psoriasis and determined whether it is involved in the antipsoriatic effect of TNF-α antagonists.

Methods

mRNA levels were evaluated in blood from patients with moderate-to-severe psoriasis. The effects of TNF-α antagonists were examined in a mouse imiquimod- (IMQ-) induced psoriasis-like dermatitis model. In the mouse model, TNFAIP3 mRNA expression was determined using RT-PCR. Serum levels of IL-17A, IL-23, IFN-γ, TNF-α, phosphorylated ERK1/2, p38, and JNK were measured using ELISA. The proportion of Th1 and Th17 cells in mouse spleens was analyzed using flow cytometry.

Results

mRNA expression levels of TNFAIP3 in the blood were significantly lower in patients with moderate and severe psoriasis (mean ± SD = 0.44 ± 0.25) compared with normal subjects (mean ± SD = 1.00 ± 0.82) (P < 0.01). In the mouse model, IMQ downregulated TNFAIP3 expression levels, which were increased after TNF-α antagonist treatment (P < 0.05). Serum levels of Th17 cytokines (IL-17A and IL-23) and Th1 cytokines (IFN-γ and TNF-α) were significantly higher in the IMQ and IMQ/rat IgG1 groups compared with the control group, and the application of TNF-α antagonists significantly decreased the levels of inflammatory cytokines (P < 0.01). Notably, phosphorylated p38 levels were increased in the IMQ and IMQ/rat IgG1 groups compared with the control group but were downregulated by treatment with TNF-α antagonists (P < 0.05). Th1 and Th17 cells were significantly increased in the IMQ group compared with the control group (P < 0.01).

Conclusion

TNFAIP3 downregulation associated with Th1 and Th17 cell differentiation and p38 activation might contribute in part to the mechanism of immune dysfunction in psoriasis. TNF-α antagonists might partly exert their effects on psoriasis via this pathway.

Low TNFAIP3 expression in psoriatic skin promotes disease susceptibility and severity

Psoriasis vulgaris is a systemic disorder with an underlying immune dysregulation that predisposes to inflammatory skin lesions. Meanwhile, tumor necrosis factor alpha-induced protein 3 (TNFAIP3) has been described as a protective molecule against the deleterious effects of uncontrolled inflammation. In this study, we compared the expression levels of TNFAIP3 in blood and psoriatic skin biopsies from psoriatic patients versus those in normal individuals. Additionally, the levels of TNFAIP3 protein in psoriatic skin biopsies were compared to those in normal individuals. Thirty psoriatic patients and 30 healthy participants (control group) were enrolled. The expression levels of TNFAIP3 in blood and skin were measured by quantitative reverse transcription PCR, while the skin levels of TNFAIP3 protein were measured by western blot. Psoriatic patients showed significantly lower expression levels of TNFAIP3 in psoriatic skin and blood (P< 0.001) as well as of TNFAIP3 protein in psoriatic skin (P< 0.001) compared to controls. A significant lower expression of TNFAIP3 and TNFAIP3 protein in psoriatic skin was detected in moderate/severe cases compared to mild cases (P = 0.004 and 0.003 respectively). Moreover, a significant negative correlation was found between TNFAIP3 mRNA in psoriatic tissue and psoriasis area severity index values (rs = -0.382, P-value = 0.037). In conclusion, TNFAIP3 may serve as a predictive and prognostic biomarker in psoriatic patients. Enhancing the expression and/or function of TNFAIP3 in the affected cell type may be a promising therapeutic strategy.

Inhibition of Poly(I:C)-Induced Inflammation by Salvianolic Acid A in Skin Keratinocytes

Background

Skin keratinocytes participate actively in inducing immune responses when external pathogens are introduced, thereby contributing to elimination of pathogens. However, in condition where the excessive inflammation is occurred, chronic skin disease such as psoriasis can be provoked.

Objective

We tried to screen the putative therapeutics for inflammatory skin disease, and found that salvianolic acid A (SAA) has an inhibitory effect on keratinocyte inflammatory reaction. The aim of this study is to demonstrate the effects of SAA in poly(I:C)-induced inflammatory reaction in skin keratinocytes.

Methods

We pre-treated keratinocytes with SAA then stimulated with poly(I:C). Inflammatory reaction of keratinocytes was verified using real-time polymerase chain reaction, enzyme-linked immunosorbent assay and Western blot.

Results

When skin keratinocytes were pre-treated with SAA, it significantly inhibited poly (I:C)-induced expression of inflammatory cytokines including interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α, and CCL20. SAA inhibited poly(I:C)-induced activation of nuclear factor-κB signaling. And SAA also inhibited inflammasome activation, evidenced by decrease of IL-1β secretion. Finally, SAA markedly inhibited poly(I:C)-induced NLRP3 expression.

Conclusion

These results demonstrate that SAA has an inhibitory effect on poly(I:C)-induced inflammatory reaction of keratinocytes, suggesting that SAA can be developed for the treatment of inflammatory skin diseases such as psoriasis.

A20 and ABIN1 Suppression of a Keratinocyte Inflammatory Program with a Shared Single-Cell Expression Signature in Diverse Human Rashes

Genetic variation in the NF-κB inhibitors, ABIN1 and A20, increase risk for psoriasis. While critical for hematopoietic immune cell function, these genes are believed to additionally inhibit psoriasis by dampening inflammatory signaling in keratinocytes. We dissected ABIN1 and A20's regulatory role in human keratinocyte inflammation using an RNA sequencing-based comparative genomic approach. Here we show subsets of the IL-17 and tumor necrosis factor-α signaling pathways are robustly restricted by A20 overexpression. In contrast, ABIN1 overexpression inhibits these genes more modestly for IL-17, and weakly for tumor necrosis factor-α. Our genome-scale analysis also indicates that inflammatory program suppression appears to be the major transcriptional influence of A20/ABIN1 overexpression, without obvious influence on keratinocyte viability genes. Our findings thus enable dissection of the differing anti-inflammatory mechanisms of two distinct psoriasis modifiers, which may be directly exploited for therapeutic purposes. Importantly, we report that IL-17-induced targets of A20 show similar aberrant epidermal layer-specific transcriptional upregulation in keratinocytes from diseases as diverse as psoriasis, atopic dermatitis, and erythrokeratodermia variabilis, suggesting a contributory role for epidermal inflammation in a broad spectrum of rashes.

E3 Ligase Trim21 Ubiquitylates and Stabilizes Keratin 17 to Induce STAT3 Activation in Psoriasis

Keratin 17 (K17), a marker of keratinocyte hyperproliferation, is a type I intermediate filament that is overexpressed in psoriatic epidermis and plays a critical pathogenic role by stimulating T cells. However, the posttranslational modification of K17, which is reversible and targetable, has not been elucidated. Herein, we reported that K17 could be modified through ubiquitination that controlled its stability and led to the phosphorylation and nuclear translocation of its interactor signal transducers and activators of transcription 3 (STAT3), which is a key regulator of cell proliferation in psoriasis. First, we stimulated human keratinocyte cell line HaCaT cells with psoriasis (pso)-mix, which is a cytokine pool (IL-17, IL-22, tumor necrosis factor-α, and IFN-γ) mimicking the in vitro "psoriasis-like" status and found that the ubiquitination of K17 was essential to stabilize its protein expression in pso-mix-treated HaCaT cells. Subsequently, tripartite motif-containing protein 21 was identified as the E3 ligase of K17, which ubiquitylated K17 via K63 linkage to maintain K17 stabilization. More importantly, we uncovered that K17 was a direct interactor of STAT3, and K17 ubiquitination could promote STAT3 activation in pso-mix-treated HaCaT cells. Our study demonstrated that targeting K17 ubiquitination may be a potential therapeutic approach by attenuating STAT3 signaling in psoriasis.