Detailed genetic characterization of the interleukin-23 receptor in psoriasis

The attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies.

Extra-adrenal glucocorticoid synthesis at epithelial barriers

Epithelial barriers play an important role in the exchange of nutrients, gases, and other signals between our body and the outside world. However, they protect it also from invasion by potential pathogens. Defective epithelial barriers and associated overshooting immune responses are the basis of many different inflammatory disorders of the skin, the lung, and the intestinal mucosa. The anti-inflammatory activity of glucocorticoids has been efficiently used for the treatment of these diseases. Interestingly, epithelia in these tissues are also a rich source of endogenous glucocorticoids, suggesting that local glucocorticoid synthesis is part of a tissue-specific regulatory circuit. In this review, we summarize current knowledge about the extra-adrenal glucocorticoid synthesis at the epithelial barriers of the intestine, lung and the skin, and discuss their relevance in the pathogenesis of inflammatory diseases and as therapeutic targets.

The Decay of Disease Association with Declining Linkage Disequilibrium: A Fine Mapping Theorem

Several important and fundamental aspects of disease genetics models have yet to be described. One such property is the relationship of disease association statistics at a marker site closely linked to a disease causing site. A complete description of this two-locus system is of particular importance to experimental efforts to fine map association signals for complex diseases. Here, we present a simple relationship between disease association statistics and the decline of linkage disequilibrium from a causal site. Specifically, the ratio of Chi-square disease association statistics at a marker site and causal site is equivalent to the standard measure of pairwise linkage disequilibrium, r². A complete derivation of this relationship from a general disease model is shown. Quite interestingly, this relationship holds across all modes of inheritance. Extensive Monte Carlo simulations using a disease genetics model applied to chromosomes subjected to a standard model of recombination are employed to better understand the variation around this fine mapping theorem due to sampling effects. We also use this relationship to provide a framework for estimating properties of a non-interrogated causal site using data at closely linked markers. Lastly, we apply this way of examining association data from high-density genotyping in a large, publicly-available data set investigating extreme BMI. We anticipate that understanding the patterns of disease association decay with declining linkage disequilibrium from a causal site will enable more powerful fine mapping methods and provide new avenues for identifying causal sites/genes from fine-mapping studies.

Reflections on the Field of Human Genetics: A Call for Increased Disease Genetics Theory

Development of human genetics theoretical models and the integration of those models with experiment and statistical evaluation are critical for scientific progress. This perspective argues that increased effort in disease genetics theory, complementing experimental, and statistical efforts, will escalate the unraveling of molecular etiologies of complex diseases. In particular, the development of new, realistic disease genetics models will help elucidate complex disease pathogenesis, and the predicted patterns in genetic data made by these models will enable the concurrent, more comprehensive statistical testing of multiple aspects of disease genetics predictions, thereby better identifying disease loci. By theoretical human genetics, I intend to encompass all investigations devoted to modeling the heritable architecture underlying disease traits and studies of the resulting principles and dynamics of such models. Hence, the scope of theoretical disease genetics work includes construction and analysis of models describing how disease-predisposing alleles (1) arise, (2) are transmitted across families and populations, and (3) interact with other risk and protective alleles across both the genome and environmental factors to produce disease states. Theoretical work improves insight into viable genetic models of diseases consistent with empirical results from linkage, transmission, and association studies as well as population genetics. Furthermore, understanding the patterns of genetic data expected under realistic disease models will enable more powerful approaches to discover disease-predisposing alleles and additional heritable factors important in common diseases. In spite of the pivotal role of disease genetics theory, such investigation is not particularly vibrant.

Investigation of association of the IL-12B and IL-23R genetic variations with psoriatic risk in a South Indian Tamil cohort

BACKGROUND

Psoriasis is a T-cell mediated chronic systemic inflammatory skin disease. Emerging evidences suggest the interleukin (IL)-12B and IL-23R genes encoding the common p40 subunit of IL-12 and IL-23 are the key cytokines in T-helper (Th)1 and Th17 differentiation and function. Certain allelic variants of these genes significantly influence the risk of psoriasis. Hence we undertook to study the association of IL-12B and IL-23R gene polymorphisms with disease susceptibility in South Indian Tamil patients with psoriasis.

METHODS

360 psoriatics and 360 healthy controls were included in this case control study. IL-12B gene (rs3212227) and IL-23R gene (rs2201841, rs10889677 and rs11805303) polymorphisms were typed by using TaqMan 5'allele discrimination assay and cytokine levels were assayed by ELISA.

RESULTS

We observed that the patients carrying the risk genotypes of IL-12B (rs3212227) and IL-23R (rs2201841) conferred an increased susceptibility to psoriasis. We did not find any significant association between IL-23R (rs10889677 and rs11805303) gene polymorphisms and psoriasis risk in South Indian Tamil population. We did not observe any significant difference in haplotypes between the psoriasis cases and controls. We observed a significant increase in the mean IL-23 levels in psoriatics and the higher levels of IL-23 were found in the minor variant genotype CC when compared with that of heterozygous CT and major variant TT genotypes of rs2201841. Individual genotypes of rs10889677 and rs11805303 and IL-12 (rs3212227) were not significantly associated with their plasma levels.

CONCLUSION

Our results suggest that IL-12B (rs3212227) and IL-23R (rs2201841) polymorphisms confer increased risk of psoriasis in our ethnic South Indian Tamils.

[Psoriasis: physiopathology and immunogenetics]

Psoriasis is a multifactorial disease that involves genetic, immunological and environmental factors. During the last decade, several studies by genome scan on families or cases/controls helped to highlight more than ten loci "PSORS" located on different chromosomes and containing several candidate genes. Psoriasis appears as a genetic disease that follows the mixed model with the involvement of a major gene (PSORS1) and a set of minor genes with a variable penetrance depending on the locus. Genetic data have focused on the involvement of the immune system in the pathogenesis of psoriasis. It is now accepted that psoriasis is an immunological disease involving the response profiles TH1 and TH17. Much remains to be done to better elucidate the mechanisms involved in the genesis of psoriatic lesions to find new therapeutic targets.

Genetics of psoriasis and pharmacogenetics of biological drugs

Psoriasis is a chronic inflammatory disease of the skin. The causes of psoriasis are unknown, although family and twin studies have shown genetic factors to play a key role in its development. The many genes associated with psoriasis and the immune response include TNFα, IL23, and IL12. Advances in knowledge of the pathogenesis of psoriasis have enabled the development of new drugs that target cytokines (e.g., etanercept, adalimumab, and infliximab, which target TNFα, and ustekinumab, which targets the p40 subunit of IL23 and IL12). These drugs have improved the safety and efficacy of treatment in comparison with previous therapies. However, not all patients respond equally to treatment, possibly owing to interindividual genetic variability. In this review, we describe the genes associated with psoriasis and the immune response, the biological drugs used to treat chronic severe plaque psoriasis, new drugs in phase II and III trials, and current knowledge on the implications of pharmacogenomics in predicting response to these treatments.

Paradoxical inflammation induced by anti-TNF agents in patients with IBD

Anti-TNF antibodies have acquired a prominent place in the management of IBD (including Crohn's disease and ulcerative colitis), rheumatologic conditions (such as rheumatoid arthritis, ankylosing spondylitis and psoriatic arthritis) and psoriasis. They have a good safety profile, especially when contraindications such as demyelinating disease, active infections and/or abscesses are ruled out, and when necessary precautions to prevent reactivation of tuberculosis are taken. However, with increasing use of these agents, paradoxical adverse events have been reported. Some of these features are shared with the underlying disease for which these drugs are given, making management of these conditions challenging. For example, anti-TNF therapy is used for the treatment of psoriasis, but psoriasiform lesions are sometimes observed in patients receiving therapy. Similarly, anti-TNF therapy is used for the treatment of rheumatologic diseases, but arthralgias and arthritis are sometimes observed in patients receiving anti-TNF agents. We review the paradoxical inflammation induced by anti-TNF agents in patients with IBD, provide hypotheses for the occurrence of this paradoxical inflammation and give practical advice on how to manage these patients.

Association of IL23R polymorphisms with psoriasis and psoriatic arthritis: a meta-analysis

BACKGROUND

The association of variants in the IL23R gene with psoriasis and psoriatic arthritis (PsA) is a robust genetic finding

OBJECTIVES

To assess whether combined evidence shows the association between IL23R polymorphisms and susceptibility to psoriasis/PsA.

METHODS

We conducted a meta-analysis to examine the association between the IL23R rs11209026 (Q381R), rs7530511 (L310P), and rs2201841 polymorphisms and psoriasis/PsA.

RESULTS

Thirteen articles met the inclusion criteria and contributed data to the meta-analysis. For rs11209026, the odds ratios (ORs) of minor alleles for psoriasis and PsA were 0.616 [95 % confidence interval (CI) 0.563-0.674] and 0.630 (95 % CI 0.524-0.757), respectively. For rs7530511, the pooled ORs were 0.820 (95 % CI 0.764-0.879) for psoriasis and 0.875 (95 % CI 0.766-1.000) for PsA; for rs2201841 the OR was 1.121 (95 % CI 1.031-1.219) for psoriasis. In genotypic analysis, the association of rs11209026 (A) and rs7530511 (T) were compatible with the dominant model (P < 0.0001, P = 0.001 respectively). The overall ORs for GG vs. AA (OR 1.339; 95 % CI 1.151-1.558), GG vs. GA (OR 1.143; 95 % CI 1.004-1.300), dominant (OR 1.226; 95 % CI 1.143-1.316), and recessive (OR 1.254; 95 % CI 1.115-1.411) models of rs2201841 were all significantly increased in psoriasis. No publication bias was present.

CONCLUSIONS

Our results demonstrate a significant association between IL23R gene polymorphisms and psoriasis/PsA.

Interleukin-23-induced interleukin-23 receptor subunit expression is mediated by the Janus kinase/signal transducer and activation of transcription pathway in human CD4 T cells

Interleukin (IL)-23 plays a critical role in the development of the T helper (Th) cell response and is responsible for the maintenance of the IL-17 producing subset of Th cells, Th17. IL-23 is a heterodimeric cytokine composed of IL-23p19 and IL-12p40 subunits, and the signaling pathway for IL-23 involves 2 receptor chains: IL-12Rβ1 and IL-23Rα. The IL-23 receptor complex is expressed on a number of cells, including natural killer cells, monocytes, macrophages, dendritic cells, and CD4 T cells. Currently, the molecular mechanisms governing expression of the IL-23 receptor chains, IL-23Rα and IL-12Rβ1, are not well understood. Our results show that IL-23 induces upregulation of IL-23Rα and IL-12Rβ1 expression in human CD4 T cells. Further, we demonstrate that inhibition of the Janus kinase/signal transducer and activation of transcription (JAK/STAT) pathway by SD-1029, a JAK2 inhibitor, 5'-deoxy-5'-(methylthio) adenosine, a STAT1 inhibitor, and STAT3 VII, a STAT3 inhibitor, were able to block IL-23-induced expression of IL-23 receptor subunits in the human SUPT-1 T cell line and in primary CD4 human T cells. Taken together, our results suggest a positive feedback regulation of the IL-23 receptor via IL-23-mediated activation of the JAK/STAT pathway.

Replication of association between interleukin-23 receptor (IL-23R) and its ligand (IL-12B) polymorphisms and psoriasis in the Chinese Han population

Psoriasis is an inflammatory skin disease with a multifactorial genetic basis. A recent genome-wide association study identified several psoriasis-predisposing loci, including IL-12B, which encodes the common p40 subunit of interleukin (IL)-12 and IL-23 and the IL-23 receptor gene (IL-23R). To investigate the relationships of these predisposing polymorphisms with psoriasis in the Chinese Han population, we genotyped three representative variants (rs6887695, rs11465817, and rs1343152) in 217 unrelated patients and 288 control subjects using direct sequencing, We further replicated the positive polymorphism, rs6887695, in a larger combined sample that included 578 patients and 1422 controls. We found the single nucleotide polymorphism, rs6887695 (odds ratio = 1.33, 95% confidence interval 1.03-1.73, p = 0.028) of IL-2B to be significantly associated with psoriasis, and a novel halotype A-A of rs11465817-rs1343152 also showed a positive association. Our study confirms the effects of IL-12B and IL-23R variants on psoriasis in East Asian populations, and provides a reference point for further investigation of the role of the IL-12/IL-23 pathway in chronic epithelial inflammation in Asian and other ethnic populations.

Biology of interleukin-22

Interleukin (IL)-22 is a member of the IL-10 family of cytokines and represents an important effector molecule of activated Th22, Th1, and Th17 cells, as well as Tc-cell subsets, gammadelta T cells, natural killer (NK), and NKT cells. IL-22 mediates its effects via a heterodimeric transmembrane receptor complex consisting of IL-22R1 and IL-10R2 and subsequent Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling pathways including Jak1, Tyk2, and STAT3. Whereas in some aspects, IL-22 acts synergistically with tumor necrosis factor-alpha, IL-1beta, or IL-17, most functions of IL-22 are unique. Importantly, IL-22 does not serve the communication between immune cells. It mainly acts on epithelial cells and hepatocytes, where it favors the antimicrobial defense, regeneration, and protection against damage and induces acute phase reactants and some chemokines. This chapter illuminates in detail the properties of IL-22 with respect to its gene, protein structure, cellular sources, receptors, target cells, biological effects, and, finally, its role in chronic inflammatory diseases, tumors, and infection.

Molecular pathophysiology of psoriasis and molecular targets of antipsoriatic therapy

Psoriasis is a chronic inflammatory skin disease characterised by elevated red scaly plaques on specific body sites. Histologically, the plaques are defined by epidermal hyperplasia, epidermal and dermal infiltration by leukocytes, and changes in the dermal microvasculature. Differentiation and activation are disturbed in lesional psoriatic keratinocytes, and the pool of proliferating keratinocytes is increased, which is accompanied by enhanced production of proinflammatory cytokines, adhesion molecules and antimicrobial peptides. These changes in psoriatic keratinocytes are caused by altered expression of genes associated with epidermal differentiation, and by activation of signalling pathways involving signal transducer and activator of transcription 3 (STAT3), type I interferon (IFN) and mitogen-activated protein kinase (MAPK). The number of T cells, and myeloid and plasmacytoid dendritic cells (DCs) is markedly increased in psoriatic lesions. Myeloid DCs produce interleukin (IL)-23, tumour necrosis factor (TNF)-alpha and inducible nitric oxide synthase (iNOS), which are crucial cytokines in the pathogenesis of psoriasis. IL-23 stimulates the secretion of IL-22 by T helper 17 cells, and IL-22 induces epidermal hyperplasia. The crosstalk between keratinocytes and leukocytes via their proinflammatory cytokines creates the vicious circle of chronic skin inflammation seen in psoriasis. This suggests that optimal treatment of psoriasis needs to target pathogenic pathways in both leukocytes and keratinocytes.

Unraveling the genetics of complex diseases: susceptibility genes for rheumatoid arthritis and psoriasis

Talk of numerous genetic risk factors for rheumatoid arthritis (RA) and psoriasis has been percolating for years, but with the exception of the human leukocyte antigen (HLA) region, none have been definitively identified. Recently the results of multiple, well powered, genetic case-control studies have begun to appear providing convincing statistical evidence for at least ten non-HLA related risk genes or loci (C5/TRAF1, CD40, CTLA4, KIF5A/PIP4K2C, MMEL1/TNFRSF14, PADI4, PRKCQ, PTPN22, STAT4, and TNFAIP3/OLIG3) for RA and six (IL12B, IL13, IL23R, STAT2/IL23A, TNFAIP3, and TNIP1) for psoriasis. These initial, novel findings are beginning to shed light on the molecular pathways pertinent to the individual diseases and highlight the pleiotropic effects of several risk factors as well as the allelic heterogeneity underlying susceptibility to these and other autoimmune diseases.