HLA-C, CSTA and DS12346 susceptibility alleles confer over 100-fold increased risk of developing psoriasis: evidence of gene interaction

Gene interaction analysis of psoriasis in Chinese Han population

Background/aims

Psoriasis is a chronic immune‐mediated inflammatory skin disease characterized by excessive proliferation of keratinocytes. It has a strong genetic predisposition; gene‐gene interactions are important genetic models for common diseases. In this study, we explore pair‐wise interactions among SNPs contributing to psoriasis susceptibility.

Methods

We first performed gene interactions with exome‐sequencing, next, we analyzed gene interactions combining the exome sequencing data with the targeted sequencing data. After we sequenced HLA region, we analyzed gene interactions including HLA regions and non‐HLA regions.

Results

We found interactions between HLA regions were significant. We observed significant interactions between HLA‐C*06:02 and rs118179173 (snp31443520; p = 8.21 × 10⁻²⁰, OR = 0.22) and between HLA‐C*06:02 and HLA‐B:AA67 (p = 1.22 × 10⁻¹², OR = 0.45).

Conclusion

This study provides evidence that HLA is the most important susceptibility region on the risk of psoriasis and interactions that occur in this region are still significant.

Genomic alterations driving psoriasis pathogenesis

Psoriasis is an immune mediated inflammatory skin disease with complex etiology involving interplay between environmental and genetic risk factors as disease initiating event. Enhanced understanding on genetic risk factors, differentially expressed genes, deregulated proteins and pathway-targeted therapeutics have established multiple axis of psoriasis pathogenesis. So far, loci in 424 genes are reported to be associated with psoriasis alongside copy number variations and epigenetic alterations. From clinical perspective, presence of specific genetic trigger(s) in individual psoriasis patient could aid in devising a personalized therapeutic strategy. Therefore, the review presents an updates on reported genomic alterations and their subsequent course of cutaneous inflammations that potentially drive to psoriasis.

ERAP1 and HLA-C*06 are strongly associated with the risk of psoriasis in the population of northern Poland

INTRODUCTION

HLA-C*06 is a major psoriasis genetic risk marker. Recent reports have been focused on the role of different polymorphisms within genes involved in the functioning of the epidermal barrier and antigen processing in the pathogenesis of psoriasis. Data on the association between genetic variants of LCE3B_LCE3C, CSTA, ERAP1, ZAP70 and this dermatosis in the population from Eastern Europe are lacking.

AIM

To compare the association between known genetic risk markers and psoriasis in a cohort of northern Polish patients with psoriasis and healthy controls.

MATERIAL AND METHODS

Based on previous studies' results, five susceptibility loci: HLA-C, LCE3C_LCE3B, ERAP1, ZAP70 and CSTA were selected for genotyping in 148 patients with chronic plaque psoriasis and 146 healthy controls. Each patient with this disease was clinically assessed with the Psoriasis Area and Severity Index.

RESULTS

The study population showed a significant association of psoriasis and a single nucleotide polymorphism in the ERAP1 - rs26653 (p = 3.11 × 10-5) and HLA-C*06 allele (p = 1.02 × 10-11) when compared with the control group. The presence of HLA-C*06 or rs26653 G allele significantly increased the risk of psoriasis by 2.4 times or twice, respectively. Carrying rs26653 C allele considerably decreased the risk of psoriasis by 1.5 times.

CONCLUSIONS

In the context of pathogenesis of psoriasis, our findings might give the evidence on disturbances in the proteolytic processing of N-terminal fragments of antigens presented via major histocompatibility complex class I to T cells.

Evaluation of Psoriasis Genetic Risk Based on Five Susceptibility Markers in a Population from Northern Poland

Psoriasis genetic background depends on polygenic and multifactorial mode of inheritance. As in other complex disorders, the estimation of the disease risk based on individual genetic variants is impossible. For this reason, recent investigations have been focused on combinations of known psoriasis susceptibility markers in order to improve the disease risk evaluation. Our aim was to compare psoriasis genetic risk score (GRS) for five susceptibility loci involved in the immunological response (HLA-C, ERAP1, ZAP70) and in the skin barrier function (LCE3, CSTA) between patients with chronic plaque psoriasis (n = 148) and the control group (n = 146). A significantly higher number of predisposing alleles was observed in patients with psoriasis in comparison to healthy individuals (6.1 vs. 5.2, respectively; P = 8.8×10⁻⁷). The statistical significance was even more profound when GRS weighted by logarithm odds ratios was evaluated (P = 9.9×10⁻¹⁴). Our results demonstrate the developed panel of five susceptibility loci to be more efficient in predicting psoriasis risk in the Polish population and to possess higher sensitivity and specificity for the disease than any of the markers analyzed separately, including the most informative HLA-C*06 allele.

Proteomics of skin proteins in psoriasis: from discovery and verification in a mouse model to confirmation in humans

Herein, we demonstrate the efficacy of an unbiased proteomics screening approach for studying protein expression changes in the KC-Tie2 psoriasis mouse model, identifying multiple protein expression changes in the mouse and validating these changes in human psoriasis. KC-Tie2 mouse skin samples (n = 3) were compared with littermate controls (n = 3) using gel-based fractionation followed by label-free protein expression analysis. 5482 peptides mapping to 1281 proteins were identified and quantitated: 105 proteins exhibited fold-changes ≥2.0 including: stefin A1 (average fold change of 342.4 and an average p = 0.0082; cystatin A, human ortholog); slc25a5 (average fold change of 46.2 and an average p = 0.0318); serpinb3b (average fold change of 35.6 and an average p = 0.0345; serpinB1, human ortholog); and kallikrein related peptidase 6 (average fold change of 4.7 and an average p = 0.2474; KLK6). We independently confirmed mouse gene expression-based increases of selected genes including serpinb3b (17.4-fold, p < 0.0001), KLK6 (9-fold, p = 0.002), stefin A1 (7.3-fold; p < 0.001), and slc25A5 (1.5-fold; p = 0.05) using qRT-PCR on a second cohort of animals (n = 8). Parallel LC/MS/MS analyses on these same samples verified protein-level increases of 1.3-fold (slc25a5; p < 0.05), 29,000-fold (stefinA1; p < 0.01), 322-fold (KLK6; p < 0.0001) between KC-Tie2 and control mice. To underscore the utility and translatability of our combined approach, we analyzed gene and protein expression levels in psoriasis patient skin and primary keratinocytes versus healthy controls. Increases in gene expression for slc25a5 (1.8-fold), cystatin A (3-fold), KLK6 (5.8-fold), and serpinB1 (76-fold; all p < 0.05) were observed between healthy controls and involved lesional psoriasis skin and primary psoriasis keratinocytes. Moreover, slc25a5, cystatin A, KLK6, and serpinB1 protein were all increased in lesional psoriasis skin compared with normal skin. These results highlight the usefulness of preclinical disease models using readily-available mouse skin and demonstrate the utility of proteomic approaches for identifying novel peptides/proteins that are differentially regulated in psoriasis that could serve as sources of auto-antigens or provide novel therapeutic targets for the development of new anti-psoriatic treatments.

Secretion of interleukin-17 by CD8+ T cells expressing CD146 (MCAM)

Interleukin-17 (IL-17) has been associated with the pathogenesis of numerous autoimmune diseases. CD4+ T cells secreting IL-17 are termed Th17 cells. CD8+ T cells, designated Tc17 cells, are also capable of secreting IL-17. Here we describe a population of Tc17 cells characterized by the expression of surface CD146, an endothelial adhesion molecule. These cells display signatures of a human Tc17 genotype and phenotype. Circulating CD8+CD146+ T cells are present in low levels in healthy adults. Elevations in CD8+CD146+ T cells are found in Behcet's disease and birdshot retinochoroidopathy, which have been reported to have HLA class I associations. Sarcoidosis does not have a class I association and displays an increase in CD4+ CD146+ T cells but not in CD8+CD146+ T cells. CD146 on these cells may facilitate their ability to bind to, and migrate through, endothelium, as has been reported for CD4+CD146+ T cells.

Genetic Epidemiology of Psoriasis

Psoriasis is a chronic, inflammatory, immune-mediated skin condition with a prevalence of 0-11.8% across the world. It is associated with a number of cardiovascular, metabolic, and autoimmune disease co-morbidities. Psoriasis is a multifactorial disorder, influenced by both genetic and environmental factors. Its genetic basis has long been established through twin studies and familial clustering. The association of psoriasis with the HLA-Cw6 allele has been shown in many studies. Recent genome-wide association studies have identified a large number of other genes associated with psoriasis. Many of these genes regulate the innate and adaptive immune system. These findings indicate that a dysregulated immune system may play a major role in the pathogenesis of psoriasis. In this article, we review the clinical and genetic epidemiology of psoriasis with a brief description of the pathogenesis of disease.

Regulation of late cornified envelope genes relevant to psoriasis risk by plant-derived cyanidin

The PSORS4 genetic risk factor for psoriasis is a deletion of two late cornified envelope (LCE) genes (LCE3C_LCE3Bdel) in a cluster of five LCE3 genes with a proposed role in skin repair. We previously showed that 1,25-dihydroxyvitamin D3 (1,25D) modestly upregulates transcripts from all five LCE3 genes as monitored by real time PCR in primary human keratinocytes. Herein we report that cyanidin, a plant-derived compound with anti-inflammatory/anti-oxidant properties, upregulates expression of all five LCE3 genes in cultures of differentiating primary human keratinocytes to a greater extent that does 1,25D. This action of cyanidin is dependent on the differentiation state of the keratinocytes, with a stronger effect after the cells have been incubated with 1.2mM calcium for 24h. Competition displacement assays using radiolabeled 1,25D revealed that cyanidin directly competes as a ligand for vitamin D receptor (VDR) binding with an estimated IC50 of 500μM. However, 20μM cyanidin is sufficient to upregulate LCE3 genes. The 25-fold discrepancy between the cyanidin concentration required for upregulating LCE3 genes in intact keratinocytes vs. that required for direct binding to VDR in vitro suggests that cyanidin may be: (a) metabolized to a more active VDR ligand in keratinocytes and/or (b) functioning via a non-VDR mediated mechanism. The fact that cyanidin is the most potent upregulator of global LCE3 gene expression reported to date suggests that this or related compounds may have potential in psoriasis therapy.

TNIP1/ANXA6 and CSMD1 variants interacting with cigarette smoking, alcohol intake affect risk of psoriasis

BACKGROUND

Psoriasis is a common multi-factorial skin disease, in which gene-gene and gene-environment interactions may affect the onset, manifestation and clinical course.

OBJECTIVE

To investigate the underlying gene-environment interaction among several established susceptibility genes, cigarette smoking and alcohol intake.

METHODS

Using a two-stage case-control design, we searched for pairwise interactions between cigarette smoking and alcohol intake respectively with 9 single nucleotide polymorphisms (SNPs) at ERAP1, PTTG1, CSMD1, GJB2, SERPINB8, ZNF816A and TNIP1/ANXA6 that have been associated with risk for psoriasis in 7,223 subjects. Multiple logistic regression analysis was used for data analysis.

RESULTS

Significant interactions were found for alcohol intake with rs3762999 (p=0.0257) and rs999556 (p=0.0071) at TNIP/ANXA6; and for cigarette smoking with rs7007032 (p=0.0023) and rs10088247 (p=0.0023) at CSMD1.

CONCLUSION

This study provides empirical evidence for the gene-environment interactions between TNIP1/ANXA6 and alcohol use, CSMD1 and cigarette smoking, highlighting the importance of gene-environment interactions in the pathogenesis of psoriasis.

Cysteine proteases: mode of action and role in epidermal differentiation

Desquamation or cell shedding in mammalian skin is known to involve serine proteases, aspartic proteases and glycosidases. In addition, evidence continues to accumulate that papain-like cysteine proteases and an inhibitor cystatin M/E largely confined to the cutaneous epithelia also play key roles in the process. This involves the complete proteolysis of cell adhesive structures of the stratum corneum, the corneodesmosomes and notably of the desmogleins. Continual cell replacement in the epidermis is the result of the balance between the loss of the outer squames and mitosis of the cells in the basal cell layer. This article provides a brief account of the salient features of the characteristics and catalytic mechanism of cysteine proteases, followed by a discussion of the relevant epidermal biology. The proteases include the asparaginyl endopeptidase legumain, which exerts a strict specificity for the hydrolysis of asparaginyl bonds, cathepsin-V and cathepsin-L. The control of these enzymes by cystatin M/E regulates the processing of transglutaminases and is crucial in the biochemical pathway responsible for regulating the cross-linking and desquamation of the stratum corneum. In addition, caspase-14 has now been shown to play a major part in epidermal maturation. Uncontrolled proteolytic activity leads to abnormal hair follicle formation and deleterious effects on the skin barrier function.