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

The Association between Genetics and Response to Treatment with Biologics in Patients with Psoriasis, Psoriatic Arthritis, Rheumatoid Arthritis, and Inflammatory Bowel Diseases: A Systematic Review and Meta-Analysis

Genetic biomarkers could potentially lower the risk of treatment failure in chronic inflammatory diseases (CID) like psoriasis, psoriatic arthritis (PsA), rheumatoid arthritis (RA), and inflammatory bowel disease (IBD). We performed a systematic review and meta-analysis assessing the association between single nucleotide polymorphisms (SNPs) and response to biologics. Odds ratio (OR) with 95% confidence interval (CI) meta-analyses were performed. In total, 185 studies examining 62,774 individuals were included. For the diseases combined, the minor allele of MYD88 (rs7744) was associated with good response to TNFi (OR: 1.24 [1.02-1.51], 6 studies, 3158 patients with psoriasis or RA) and the minor alleles of NLRP3 (rs4612666) (OR: 0.71 [0.58-0.87], 5 studies, 3819 patients with RA or IBD), TNF-308 (rs1800629) (OR: 0.71 [0.55-0.92], 25 studies, 4341 patients with psoriasis, RA, or IBD), FCGR3A (rs396991) (OR: 0.77 [0.65-0.93], 18 studies, 2562 patients with psoriasis, PsA, RA, or IBD), and TNF-238 (rs361525) (OR: 0.57 [0.34-0.96]), 7 studies, 818 patients with psoriasis, RA, or IBD) were associated with poor response to TNFi together or infliximab alone. Genetic variants in TNFα, NLRP3, MYD88, and FcRγ genes are associated with response to TNFi across several inflammatory diseases. Most other genetic variants associated with response were observed in a few studies, and further validation is needed.

Identifying the association between polymorphisms in the GZMB and IFIH1 genes and psoriasis in Egyptians

OBJECTIVES

This study aims to examine whether the genetic variants in the genes for Granzyme B (GZMB) and Interferon Induced with Helicase C domain 1 (IFIH1) were associated with psoriasis.

BACKGROUND

Psoriasis, a papulosquamous skin disease, was initially thought of as a disorder primarily of epidermal keratinocytes but is now recognized as one of the most common immune-mediated disorders. It is caused by the interplay between multiple genetic and environmental risk factors.

SUBJECTS AND METHODS

This case-control study has 65 participants with psoriasis and 65 healthy controls. Real-time PCR was used to genotype GZMB (rs8192917) and IFIH1 (rs35667974).

RESULTS

Genotype occurrence and allelic spreading for both SNPs are in Hardy - Weinberg equilibrium. The genotype and allele distributions of rs35667974 showed no differences between the studied groups. Regarding rs8192917, compared to Group II, there is a statistically significant rise in the CC genotype and C allele in Group I. Higher PASI scores are detected in the C/C and C/T genotypes more than the T/T genotype. Univariate and multivariate analyses revealed that BMI, catalase, MDA, and rs8192917 (C/C) are associated with psoriasis.

CONCLUSION

GZMB rs8192917 was significantly related to psoriasis risk; its C allele is likewise associated with psoriasis vulnerability. However, our investigation found no link between rs35667974 and psoriasis.

Finding Gene Regulatory Networks in Psoriasis: Application of a Tree-Based Machine Learning Approach

Psoriasis is a chronic inflammatory skin disorder. Although it has been studied extensively, the molecular mechanisms driving the disease remain unclear. In this study, we utilized a tree-based machine learning approach to explore the gene regulatory networks underlying psoriasis. We then validated the regulators and their networks in an independent cohort. We identified some key regulators of psoriasis, which are candidates to serve as potential drug targets and disease severity biomarkers. According to the gene regulatory network that we identified, we suggest that interferon signaling represents a key pathway of psoriatic inflammation.

Cognitive Process of Psoriasis and Its Comorbidities: From Epidemiology to Genetics

Psoriasis (PsO) is a chronic inflammatory skin disease that affects approximately 2% of the population all over the world. Comorbidities of PsO have increasingly garnered more interest in the past decades. Compared with the normal population, the incidences of comorbidities are higher among patients with PsO. In the last 20 years, researchers have focused on studying the genetic components of PsO, and genetic associations between PsO and its comorbidities were elucidated. This review provides an in-depth understanding and summarization of the connection between PsO and its comorbidities from the perspectives of epidemiology and genetics. Further understanding of PsO and its comorbidities will promote research on the pathogenesis, drug development, novel therapy methods, and personalized and precision treatment of PsO and its comorbidities.

A retrospective cohort study to evaluate the development of comorbidities, including psychiatric comorbidities, among a pediatric psoriasis population

BACKGROUND/OBJECTIVE

Compared with the adult psoriasis population, knowledge about the incidence of comorbidities in the pediatric psoriasis population is limited. The objective of this study was to assess the prevalence and incidence of comorbidities, including psychiatric comorbidities, in patients with pediatric psoriasis.

METHODS

In this claims-based, retrospective cohort study, patients with pediatric psoriasis were matched 1:3 with a nonpsoriasis cohort based on age, sex, and index date (the earliest of inpatient claims or the latter of two outpatient claims).

RESULTS

Obesity, serious infection, and juvenile idiopathic arthropathy had higher prevalence and incidence rates in the psoriasis cohort than the nonpsoriasis cohort. Psychiatric comorbidities were also more common in the psoriasis cohort than the nonpsoriasis cohort, as were ulcerative colitis and Crohn disease. Stratifying the psoriasis cohort by disease severity-mild and moderate-to-severe-found no differences in incidence rates of comorbidities between the two subsets.

CONCLUSION

The incidence rates of many comorbid conditions were higher for patients with pediatric psoriasis compared with patients without pediatric psoriasis, and similar between patients with moderate-to-severe and mild pediatric psoriasis.

The genetic pathogenesis, diagnosis and therapeutic insight of rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that causes chronic inflammation of the joints. RA is a heterogeneous disorder caused by an abnormal autoimmune response triggered by the complex interactions of genetic and environmental factors that contribute to RA etiology. However, its underlying pathogenic mechanisms are yet to be fully understood. In this review, I provide an overview of the pathogenesis, diagnosis and therapeutic insight in the clinical management of RA in light of the recent updates to classification criteria and recent discoveries of genetic loci associated with susceptibility for RA.

Genetic polymorphism in psoriasis and its meaning for the treatment efficacy in the future

The concept of personalized medicine is a new individualized approach which helps application of the targeted therapy. In fact, tailored medicine is mostly present in the field of life-threatening diseases such as oncology. However, skin diseases as such might be regarded as a potential area of implementation of this approach in the future. Stratified medicine in polygenetic and heterogeneous diseases, such as psoriasis, is more complex. Rapid development of science and novel molecular techniques led to better understanding of molecular pathogenetic pathways of many diseases including psoriasis. Identification of the particular immunopathogenetic pathways led to further development of targeted therapies such as biologic drugs. Actually the goal of individualized therapy is to determine the identical homogenous subgroups of patients, according to a biomarker, in which the response to that therapy will be the best and will carry the lowest risk of side effects. This review attempts to analyze the associations between polymorphisms of certain genes and the increased risk of developing psoriasis or psoriatic arthritis. The review of literature has also included the studies investigating the associations between gene polymorphisms and response to biologic therapy in psoriasis and psoriatic arthritis patients.

Pediatric Psoriasis

Psoriasis is a chronic inflammatory systemic disease associated with an important physical and physiological burden. It primarily affects the skin, but it is associated with several serious medical co-morbidities. One third of total psoriatic cases have their onset during the pediatric age, although some of them may not be diagnosed until the patient reaches adulthood. Additionally, in the pediatric age, there is an association with several medical co-morbidities; thus, an early recognition of the disease and a subsequent appropriate approach may delay or even prevent considerable co-morbidities. Because children are not just 'small adults', specific guidelines for the diagnosis, management, and treatment of psoriasis are of extreme importance. However, these guidelines are still lacking in this age group. Most of the psoriasis treatments used in adults are not officially approved for the pediatric age and require off-label prescription. Moreover, efficacy and safety studies are lacking in this population, especially with long-term follow-up and outcomes. Many biologic agents have been recently approved for the treatment of psoriasis in children, while others are currently being studied. This bibliographic review aims to summarize the most relevant aspects, as well as updated information about the epidemiology, pathogenesis, clinical features, diagnosis, co-morbidities and treatment of pediatric psoriasis.

Induction of Interleukin-22 (IL-22) production in CD4+ T Cells by IL-17A Secreted from CpG-Stimulated Keratinocytes

Background

Interleukin-17A (IL-17A) is mainly secreted from Th17 cells that are activated by various stimuli including CpG oligodeoxynucleotide, a Toll-like receptor 9 (TLR9) ligand. Recently, it has been demonstrated that keratinocytes play an important role in the pathogenesis of psoriasis.

Objective

To investigate the potential role of keratinocytes, we examined whether TLR9 ligand CpG induces IL-17A expression in keratinocytes.

Methods

We used HaCaT keratinocytes as a model system, and determined CpG-induced IL-17A using enzyme-linked immunosorbent assay and Western blot.

Results

When HaCaT keratinocytes were treated with CpG, the expression of several cytokines including IL-17A, tumor necrosis factor-α and CCL20 was markedly increased. Treatment with nuclear factor (NF)-κB inhibitor significantly blocked the CpG-induced IL-17A production, indicating that CpG induced IL-17A expression through the NF-κB signaling pathway. In addition, IL-17A secreted from keratinocytes stimulated the CD4⁺ T cells, resulting in strong induction of IL-22 production.

Conclusion

Since IL-22 is an important mediator for psoriatic inflammation, our data suggest that keratinocytes can participate in the pathogenesis of psoriasis via the TLR9-dependent IL-17A production.

Urine metabolome profiling of immune-mediated inflammatory diseases

BACKGROUND

Immune-mediated inflammatory diseases (IMIDs) are a group of complex and prevalent diseases where disease diagnostic and activity monitoring is highly challenging. The determination of the metabolite profiles of biological samples is becoming a powerful approach to identify new biomarkers of clinical utility. In order to identify new metabolite biomarkers of diagnosis and disease activity, we have performed the first large-scale profiling of the urine metabolome of the six most prevalent IMIDs: rheumatoid arthritis, psoriatic arthritis, psoriasis, systemic lupus erythematosus, Crohn's disease, and ulcerative colitis.

METHODS

Using nuclear magnetic resonance, we analyzed the urine metabolome in a discovery cohort of 1210 patients and 100 controls. Within each IMID, two patient subgroups were recruited representing extreme disease activity (very high vs. very low). Metabolite association analysis with disease diagnosis and disease activity was performed using multivariate linear regression in order to control for the effects of clinical, epidemiological, or technical variability. After multiple test correction, the most significant metabolite biomarkers were validated in an independent cohort of 1200 patients and 200 controls.

RESULTS

In the discovery cohort, we identified 28 significant associations between urine metabolite levels and disease diagnosis and three significant metabolite associations with disease activity (P FDR < 0.05). Using the validation cohort, we validated 26 of the diagnostic associations and all three metabolite associations with disease activity (P FDR < 0.05). Combining all diagnostic biomarkers using multivariate classifiers we obtained a good disease prediction accuracy in all IMIDs and particularly high in inflammatory bowel diseases. Several of the associated metabolites were found to be commonly altered in multiple IMIDs, some of which can be considered as hub biomarkers. The analysis of the metabolic reactions connecting the IMID-associated metabolites showed an over-representation of citric acid cycle, phenylalanine, and glycine-serine metabolism pathways.

CONCLUSIONS

This study shows that urine is a source of biomarkers of clinical utility in IMIDs. We have found that IMIDs show similar metabolic changes, particularly between clinically similar diseases and we have found, for the first time, the presence of hub metabolites. These findings represent an important step in the development of more efficient and less invasive diagnostic and disease monitoring methods in IMIDs.

Treating pediatric plaque psoriasis: challenges and solutions

Psoriasis is a T-lymphocyte-mediated chronic inflammatory disorder involving the skin and joints. Nearly 3.5% of the population has been diagnosed to have psoriasis. In a dermatology department, almost one-third of psoriasis patients are in the pediatric age group. With an annual prevalence of up to 0.71%, childhood psoriasis can now be regarded as a frequently seen chronic inflammatory skin disorder having a significant impact on the quality of life. Based on the age of onset, psoriasis in children can be broadly classified as infantile psoriasis that can be mostly self-limited, psoriasis having an early onset, which needs specific treatment, and psoriasis that is associated with arthritis. Treating a child with psoriasis is a challenge, considering the physical development, body metabolism, rate of cutaneous absorption, and metabolism of drugs, which are quite different from those of the adults. The long duration of sun exposure for the rest of their life makes it more demanding while considering phototherapy in children. Long-term treatment of psoriasis, with phototherapy or drugs, needs critical evaluation in children. Hence, a thorough understanding of the disease in all its aspects will certainly help manage childhood psoriasis better. Timely diagnosis and adequate management not only arrest progression but also minimize the psychological burden caused by the disease, averting disfiguring states and evolution into a metabolic syndrome.

Meta-analysis reveals PTPN22 1858C/T polymorphism confers susceptibility to rheumatoid arthritis in Caucasian but not in Asian population

The PTPN22 1858C/T polymorphism is associated with rheumatoid arthritis (RA). However, reports from the Asian populations are conflicting in nature and lacks consensus. The aim of our study was to evaluate the association between the PTPN22 1858C/T polymorphism and RA in Asian and Caucasian subjects by carrying out a meta-analysis of Asian and Caucasian data. A total of 27 205 RA cases and 27 677 controls were considered in the present meta-analysis involving eight Asian and 35 Caucasian studies. The pooled odds ratios (ORs) were performed for the allele, dominant, and recessive genetic model. No statistically significant association was found between the PTPN22 1858C/T polymorphism and risk of RA in Asian population (allele genetic model: OR = 1.217, 95% confidence interval (CI) = 0.99-1.496, p value 0.061; dominant genetic model: OR = 1.238, 95% CI = 0.982-1.562, p value 0.071; recessive genetic model: OR = 1.964, 95% CI = 0.678-5.693, p value 0.213). A significant association with risk of RA in Caucasian population suggesting that T-- allele does confer susceptibility to RA in this subgroup was observed (allele genetic model: OR = 1.638, 95% CI = 1.574-1.705, p value < 0.0001; dominant genetic model: OR = 1.67, 95% CI = 1.598-1.745, p value < 0.0001; recessive genetic model: OR = 2.65, 95% CI = 2.273-3.089, p value < 0.0001). The PTPN22 1858C/T polymorphism is not associated with RA risk in Asian populations. However, our meta-analysis confirms that the PTPN22 1858C/T polymorphism is associated with RA susceptibility in Caucasians.

Inhibitory effect of cucurbitacin B on imiquimod-induced skin inflammation

Psoriasis is a common skin disease, of which pathogenesis involves the increase of inflammatory reaction in epidermal cells. In an attempt to find therapeutics for psoriasis, we found that cucurbitacin B has an inhibitory potential on imiquimod-induced inflammation of keratinocytes. Cucurbitacin B significantly inhibited imiquimod-induced expression of crucial psoriatic cytokines, such as IL-8 and CCL20, via down-regulation of NF-κB and STAT3 signaling pathway in human keratinocytes. In addition, keratinocyte proliferation was markedly inhibited by cucurbitacin B. The potential beneficial effect of cucurbitacin B on psoriasis was further validated in imiquimod-induced psoriasiform dermatitis of experimental animal. Topical application of cucurbitacin B resulted in significant reduction of epidermal hyperplasia and inflammatory cytokines production, and ameliorated the psoriatic symptom. Taken together, these results suggest that cucurbitacin B may be a potential candidate for the treatment of psoriasis.

Identification of rheumatoid arthritis biomarkers based on single nucleotide polymorphisms and haplotype blocks: A systematic review and meta-analysis

Genetics of autoimmune diseases represent a growing domain with surpassing biomarker results with rapid progress. The exact cause of Rheumatoid Arthritis (RA) is unknown, but it is thought to have both a genetic and an environmental bases. Genetic biomarkers are capable of changing the supervision of RA by allowing not only the detection of susceptible individuals, but also early diagnosis, evaluation of disease severity, selection of therapy, and monitoring of response to therapy. This review is concerned with not only the genetic biomarkers of RA but also the methods of identifying them. Many of the identified genetic biomarkers of RA were identified in populations of European and Asian ancestries. The study of additional human populations may yield novel results. Most of the researchers in the field of identifying RA biomarkers use single nucleotide polymorphism (SNP) approaches to express the significance of their results. Although, haplotype block methods are expected to play a complementary role in the future of that field.

Elevated odds of metabolic syndrome in psoriasis: a population-based study of age and sex differences

BACKGROUND

Questions remain concerning to what extent age and sex may modify the suggested association between psoriasis and the metabolic syndrome in the general population.

OBJECTIVES

To investigate the association between psoriasis and the metabolic syndrome within a large population-based cohort by age and sex.

METHODS

A cross-sectional study including 10 521 participants aged 30-79 years from the Tromsø Study cohort was performed; 1137 participants reported lifetime psoriasis of a mainly mild character. The new harmonized definition of metabolic syndrome was used in the multivariable logistic regression analysis.

RESULTS

There was a uniformly higher prevalence of metabolic syndrome in men and women with psoriasis compared with those without across all age groups. In women, psoriasis was associated with a 3·8-times higher odds of metabolic syndrome at age 30 years (95% confidence interval 1·5-9·7), with a decreasing odds ratio with increasing age. In men, psoriasis was associated with a stable 1·35-times higher odds of metabolic syndrome (95% confidence interval 1·1-1·6) at all ages. Abdominal obesity was the most frequent metabolic syndrome component in women in this study, and there was indication of a dose-response relationship between psoriasis severity, indicated through treatment, and having a high waistline in women.

CONCLUSIONS

This study suggests age and sex variations in the risk of metabolic syndrome among individuals with psoriasis. Given the high prevalence of psoriasis and the significantly elevated burden of metabolic syndrome in this patient group, there may be a benefit from targeted screening of metabolic syndrome among individuals with psoriasis regardless of age and disease severity.

Management of psoriasis in adolescence

Psoriasis is a chronic inflammatory cutaneous disorder affecting 2%–4% of the world’s population. The prevalence of the disease in childhood and adolescence ranges between 0.5% and 2%. The management of psoriasis in adolescence is an intriguing and complicated task. Given the paucity of officially approved therapies, the very limited evidence-based data from randomized controlled trials, and the absence of standardized guidelines, physicians must rely on published experience from case reports both from the field of dermatology as well as from the application of these drugs for other pediatric conditions coming from the disciplines of rheumatology, gastroenterology, and oncology. Psoriatic adolescents deal with a potentially disfiguring and lifelong disease that could permanently impair their psychological development. It must be clarified to them that psoriasis does not have a permanent cure, and therefore the main goal of treatments is to establish disease control and prolonged periods between flares. The majority of adolescents suffer from mild psoriasis, and thus they are treated basically with topical treatment modalities. Phototherapy is reserved for adolescents with mild-to-moderate plaque disease and/or guttate psoriasis when routine visits to specialized centers do not create practical problems. Systemic agents and biologics are administered to patients with moderate-to-severe plaque psoriasis, pustular psoriasis, or erythrodermic psoriasis.

Treatment of psoriasis: focus on clinic-based management with infliximab

Psoriasis is a disabling chronic inflammatory condition of the skin and joints that typically requires long-term treatment. Recommended treatments for psoriasis include a wide range of topical and systemic options, from topical agents and targeted phototherapy for mild psoriasis to traditional systemic agents such as methotrexate, cyclosporine and acitretin for more serious disease. The introduction of targeted biological agents such as T-cell-modulating agents, tumor necrosis factor α (TNFα) antagonists and interleukin (IL)-12 and IL-23 inhibitors has provided new choices for the management of psoriasis and psoriatic arthritis that may offer better long-term efficacy and tolerability than traditional approaches. Most biological agents are administered by subcutaneous injection. Infliximab, a TNFα antagonist, is the only biological agent approved for psoriasis that is administered by intravenous infusion, in the setting of hospital-based or specialized infusion center-based clinics. Infliximab allows weight-based dosing and may offer more rapid disease control than other biological agents, with significant improvements seen as early as 1 week after treatment initiation. This article gives an overview of psoriasis management, focusing on clinic-based infusion therapy with infliximab.

Association of STAT4 gene polymorphism with increased susceptibility of rheumatoid arthritis in a northern Chinese Han subpopulation

OBJECTIVE

Several studies have reported STAT4 polymorphism is strongly associated with increased susceptibility to rheumatoid arthritis (RA). However, a study from China showed no association between STAT4 and RA susceptibility in a Chinese Han subpopulation. Since the northern Hans are known to be genetically different from the southern Hans, the aim of this study was to investigate the association of STAT4 polymorphism with RA in a large cohort of a northern Chinese Han subpopulation.

METHODS

640 RA patients and 662 healthy controls were enrolled. DNA samples were genotyped for STAT4 rs7574865 by direct sequencing. The association of single nucleotide polymorphism (SNP) rs7574865 with RA susceptibility was calculated and the relationship between rs7574865 polymorphism and RA subgroups stratified by clinical features was estimated.

RESULTS

We confirmed a significant association of STAT4 rs7574865 polymorphism with RA susceptibility in northern Chinese Han population. The frequency of the minor T allele in RA was significantly higher than in healthy controls (35.2% vs. 31.1%; P = 0.029, OR 1.2 [95% CI 1.02-1.41]). There was also a significant difference in the distribution of the genotypes of SNP rs7574865 between RA patients and healthy controls (P = 0.02). Stratification analyses showed no associations between the genetic risk and clinical/serologic features, but a potential high frequency of TT genotype in a rheumatoid factor-negative subgroup, although it did not reach statistical significance (P = 0.084, OR 2.01 [95% CI 0.91-4.45]).

CONCLUSION

STAT4 rs7574865 is significantly associated with RA susceptibility in northern Chinese Han subpopulations. The genetic differences of Han subpopulations should be considered when genetic susceptibility for diseases is studied.

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.

Meta-analysis of 125 rheumatoid arthritis-related single nucleotide polymorphisms studied in the past two decades

Objective

Candidate gene association studies and genome-wide association studies (GWAs) have identified a large number of single nucleotide polymorphisms (SNPs) loci affecting susceptibility to rheumatoid arthritis (RA). However, for the same locus, some studies have yielded inconsistent results. To assess all the available evidence for association, we performed a meta-analysis on previously published case-control studies investigating the association between SNPs and RA.

Methods

Two hundred and sixteen studies, involving 125 SNPs, were reviewed. For each SNP, three genetic models were considered: the allele, dominant and recessive effects models. For each model, the effect summary odds ratio (OR) and 95% CIs were calculated. Cochran’s Q-statistics were used to assess heterogeneity. If the heterogeneity was high, a random effects model was used for meta-analysis, otherwise a fixed effects model was used.

Results

The meta-analysis results showed that: (1) 30, 28 and 26 SNPs were significantly associated with RA (P<0.01) for the allele, dominant, and recessive models, respectively. (2) rs2476601 (PTPN22) showed the strongest association for all the three models: OR = 1.605, 95% CI: 1.540–1.672, P<1.00E−15 for the T-allele; OR = 1.638, 95% CI: 1.565–1.714, P<1.00E−15 for the T/T+T/C genotype and OR = 2.544, 95% CI: 2.173–2.978, P<1.00E−15 for the T/T genotype. (3) Only 23 (18.4%), 13 (10.4%) and 15 (12.0%) SNPs had high heterogeneity (P<0.01) for the three models, respectively. (4) For some of the SNPs, there was no publication bias according to Funnel plots and Egger’s regression tests (P<0.01). For the other SNPs, the associations were tested in only a few studies, and may have been subject to publication bias. More studies on these loci are required.

Conclusion

Our meta-analysis provides a comprehensive evaluation of the RA association studies from the past two decades. The detailed meta-analysis results are available at: http://210.46.85.180/DRAP/index.php/Metaanalysis/index.

A haplotype at STAT2 Introgressed from neanderthals and serves as a candidate of positive selection in Papua New Guinea

Signals of archaic admixture have been identified through comparisons of the draft Neanderthal and Denisova genomes with those of living humans. Studies of individual loci contributing to these genome-wide average signals are required for characterization of the introgression process and investigation of whether archaic variants conferred an adaptive advantage to the ancestors of contemporary human populations. However, no definitive case of adaptive introgression has yet been described. Here we provide a DNA sequence analysis of the innate immune gene STAT2 and show that a haplotype carried by many Eurasians (but not sub-Saharan Africans) has a sequence that closely matches that of the Neanderthal STAT2. This haplotype, referred to as N, was discovered through a resequencing survey of the entire coding region of STAT2 in a global sample of 90 individuals. Analyses of publicly available complete genome sequence data show that haplotype N shares a recent common ancestor with the Neanderthal sequence (~80 thousand years ago) and is found throughout Eurasia at an average frequency of ~5%. Interestingly, N is found in Melanesian populations at ~10-fold higher frequency (~54%) than in Eurasian populations. A neutrality test that controls for demography rejects the hypothesis that a variant of N rose to high frequency in Melanesia by genetic drift alone. Although we are not able to pinpoint the precise target of positive selection, we identify nonsynonymous mutations in ERBB3, ESYT1, and STAT2-all of which are part of the same 250 kb introgressive haplotype-as good candidates.

Identification of TNIP1 Polymorphisms by High Resolution Melting Analysis with Unlabelled Probe: Association with Systemic Lupus Erythematosus

Background. TNFα-induced protein 3 (TNFAIP3) interacting with protein 1 (TNIP1) acts as a negative regulator of NF-κB and plays an important role in maintaining the homeostasis of immune system. A recent genome-wide association study (GWAS) showed that the polymorphism of TNIP1 was associated with the disease risk of SLE in Caucasian. In this study, we investigated whether the association of TNIP1 with SLE was replicated in Chinese population. Methods. The association of TNIP1 SNP rs7708392 (G/C) was determined by high resolution melting (HRM) analysis with unlabeled probe in 285 SLE patients and 336 healthy controls. Results. A new SNP rs79937737 located on 5 bp upstream of rs7708392 was discovered during the HRM analysis. No association of rs7708392 or rs79937737 with the disease risk of SLE was found. Furthermore, rs7708392 and rs79937737 were in weak linkage disequilibrium (LD). Hypotypes analysis of the two SNPs also showed no association with SLE in Chinese population. Conclusions. High resolution melting analysis with unlabeled probes proves to be a powerful and efficient genotyping method for identifying and screening SNPs. No association of rs7708392 or rs79937737 with the disease risk of SLE was observed in Chinese population.

The concept of psoriasis as a systemic inflammation: implications for disease management

Psoriasis is a systemic, immune-mediated disorder, characterized by inflammatory skin and joint manifestations. A range of co-morbidities is associated with psoriasis, including metabolic diseases, such as diabetes, and psychological disorders. Although the systemic nature of psoriasis often remains unrecognized, the inflammatory processes involved may be associated with the development of co-morbidities, which, themselves, have a significant impact on the patient's health and quality of life. The relative risks of myocardial infarction (MI) and stroke are increased in patients with psoriasis compared with the general population. These are especially seen in younger patients with more severe disease, and are believed to contribute to the 3- to 4-year reduction in life expectancy among patients with severe psoriasis. The recent results of large studies indicate that the increased cardiovascular (CV) risk is at least partially attributable to psoriasis and independent of the presence of metabolic co-morbidities. The possible interplay between psoriasis and CV disease is complex. Metabolic diseases such as obesity and diabetes have overlapping genetic predispositions with psoriasis. Both conditions are likely to also interact at a functional level because obesity and the up-regulation of pro-inflammatory mediators in psoriasis appear to influence adipocyte homoeostasis, inducing non-professional immune functions. This may perpetuate psoriatic inflammation, displaying similarities to the immunopathogenesis of atherosclerosis. Finally, the disturbed adipokine profile and inflammation associated with psoriasis enhances insulin resistance, causing subsequent endothelial dysfunction, atherosclerosis and eventual coronary events. The differential contribution of psoriasis and uncontrolled classical CV risk factors to the increased CV risk seen in psoriasis patients is not clear. Successful treatment with methotrexate appears to lower the rates of MI in patients with psoriasis. Tumour necrosis factor-α (TNF-α) inhibitors are known to counteract insulin resistance and emerging studies demonstrate an even higher protective effect of TNF-α antagonist therapy against the development of diabetes or CV co-morbidities in patients. The recent data reviewed here indicate a role for earlier and more appropriate treatment of psoriasis with drugs such as TNF-α antagonists. Such an approach has the potential to significantly improve patient outcomes through the treatment of psoriasis itself and possibly also in protection against co-morbidities.

The association of psoriasis with autoimmune diseases

BACKGROUND

Previous studies provide evidence that there is a greater frequency of autoimmune diseases among patients with psoriasis than in the general population.

OBJECTIVE

This study examined the association between psoriasis and 21 common autoimmune diseases, specified a priori.

METHODS

A retrospective cohort study was conducted among persons who were members of Kaiser Permanente Southern California from 2004 to 2011. A total of 25,341 patients with 2 or more diagnosis codes for any psoriatic disease were evaluated. Five persons not meeting this case definition were matched to each psoriatic patient based on age, sex, and length of enrollment.

RESULTS

Patients with psoriasis were more likely to have at least 1 other autoimmune disease (odds ratio [OR] 1.6; 95% confidence interval [CI] 1.5-1.7) and to have at least 2 other autoimmune diseases (1.9; 95% CI 1.6-2.4). Of the 17 conditions evaluated, associations with 14 were found to be statistically significant. The strongest association was with rheumatoid arthritis (3.6; 95% CI 3.4-3.9).

LIMITATIONS

Patients with autoimmune conditions are likely to have a greater number of health care encounters, which may result in overascertainment and misascertainment of immune-mediated conditions, although the patients included in the study averaged 5.2 years of observation and the comparison subjects were matched on length of enrollment.

CONCLUSIONS

The study suggests a genetic or environmental cause common across autoimmune diseases. Further investigation of individuals with multiple autoimmune diseases may yield important clues about the origin and pathogenesis of the disease.

Association of NCF2, IKZF1, IRF8, IFIH1, and TYK2 with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex trait characterised by the production of a range of auto-antibodies and a diverse set of clinical phenotypes. Currently, ~8% of the genetic contribution to SLE in Europeans is known, following publication of several moderate-sized genome-wide (GW) association studies, which identified loci with a strong effect (OR>1.3). In order to identify additional genes contributing to SLE susceptibility, we conducted a replication study in a UK dataset (870 cases, 5,551 controls) of 23 variants that showed moderate-risk for lupus in previous studies. Association analysis in the UK dataset and subsequent meta-analysis with the published data identified five SLE susceptibility genes reaching genome-wide levels of significance (P(comb)<5×10(-8)): NCF2 (P(comb) = 2.87×10(-11)), IKZF1 (P(comb) = 2.33×10(-9)), IRF8 (P(comb) = 1.24×10(-8)), IFIH1 (P(comb) = 1.63×10(-8)), and TYK2 (P(comb) = 3.88×10(-8)). Each of the five new loci identified here can be mapped into interferon signalling pathways, which are known to play a key role in the pathogenesis of SLE. These results increase the number of established susceptibility genes for lupus to ~30 and validate the importance of using large datasets to confirm associations of loci which moderately increase the risk for disease.

Proteomic detection of cancer in asbestosis patients using SELDI-TOF discovered serum protein biomarkers

OBJECTIVES

To identify biomarkers for cancer in asbestosis patients.

METHODS

SELDI-TOF and CART were used to identify serum biomarker profiles in 35 asbestosis patients who subsequently developed cancer and 35 did not develop cancer.

RESULTS

Three polypeptide peaks (5707.01, 6598.10, and 20,780.70 Da) could predict the development of cancer with 87% sensitivity and 70% specificity. The first two peaks were identified as KIF18A and KIF5A, respectively, and are part of the Kinesin Superfamily of proteins.

CONCLUSIONS

We identified two Kinesin proteins that can be potentially used as blood biomarkers to identify asbestosis patients at risk of developing lung cancer.

Genetic predisposition to autoimmunity--what have we learned?

Rapid advances in genetic technologies have led to the identification of more than 85 loci that contribute to susceptibility to autoimmune diseases. These susceptibility genes are distributed throughout the innate and adaptive immune systems, indicating that dysregulations in both immune systems participate in the development of autoimmunity. A significant subset of these susceptibility genes are shared between multiple autoimmune diseases. However, the dysregulation of specific pathways, such as the pathogen recognition receptors of the innate immune system and the TNF supergene family, are significantly involved in some autoimmune diseases. Although these findings dramatically increase the details available concerning the nature of genetic predisposition to autoimmunity, a mechanistic understanding of the processes involved has not been achieved. Future studies must focus on correlating phenotypes with specific genotypes to improve our understanding of the immune processes that are dysregulated during the development of autoimmunity.

Analysis of single nucleotide polymorphisms in case-control studies

Single nucleotide polymorphisms (SNPs) are the most common type of genetic variants in the human genome. SNPs are known to modify susceptibility to complex diseases. We describe and discuss methods used to identify SNPs associated with disease in case-control studies. An outline on study population selection, sample collection and genotyping platforms is presented, complemented by SNP selection, data preprocessing and analysis.

Kawasaki disease: update on pathogenesis

PURPOSE OF REVIEW

This review will highlight recent advances in our understanding of the pathogenesis of Kawasaki disease, highlighting the molecular players involved in regulation of T-cell activation and their affect on disease incidence and outcome in both humans and mouse.

RECENT FINDINGS

Kawasaki disease is the most common cause of multisystem vasculitis in childhood. The vessels most commonly damaged are the coronary arteries, making Kawasaki disease the number one cause of acquired heart disease in children from the developed world. The contribution of genetics to disease predisposition is clearly implicated, but the mechanisms involved in regulating predisposition to disease susceptibility and outcome are not clearly understood. Two independent approaches have recently identified regulation of T-cell activation as the critical factor in determining susceptibility and severity of Kawasaki disease. Firstly, genetic analysis of affected Japanese children identified ITPKC, 1,4,5-triphosphate 3-kinase C, a kinase involved in regulation of T-cell activation, to be significantly associated with susceptibility to and increased severity of Kawasaki disease. A second independent approach using an animal model of Kawasaki disease has also identified regulation of T-cell activation, specifically costimulation, the second signal regulating optimal T-cell activation as the critical regulator of susceptibility to and severity of disease.

SUMMARY

Understanding the molecular players responsible for dysregulation of the immune response in Kawasaki disease will foster development of improved diagnostic/predictive tools and more rational use of therapeutic agents to improve outcome in affected children.

Carriers of rare missense variants in IFIH1 are protected from psoriasis

Testing of ∼25,000 putative functional single-nucleotide polymorphisms (SNPs) across the human genome in a genetic association study has identified three psoriasis genes, IL12B, IL23R, and IL13. We now report evidence for the association of psoriasis risk with missense SNPs in the interferon induced with helicase C domain 1 gene (IFIH1). The rare alleles of two independent SNPs were associated with decreased risk of psoriasis--rs35667974 (Ile923Val): odds ratio (OR) for minor allele carriers is 0.43, P=2.36 × 10(-5) (2,098 cases vs. 1,748 controls); and rs10930046 (His460Arg): OR for minor allele carriers is 0.51, P=6.47 × 10(-4) (2,098 cases vs. 1,744 controls). Compared to noncarriers, carriers of the 923Val and/or 460Arg variants were protected from psoriasis (OR=0.46, P=5.56 × 10(-8)). To our knowledge, these results suggest that IFIH1 is a previously unreported psoriasis gene.

Expression, biological activities and mechanisms of action of A20 (TNFAIP3)

A20 (also known as TNFAIP3) is a cytoplasmic protein that plays a key role in the negative regulation of inflammation and immunity. Polymorphisms in the A20 gene locus have been identified as risk alleles for multiple human autoimmune diseases, and A20 has also been proposed to function as a tumor suppressor in several human B-cell lymphomas. A20 expression is strongly induced by multiple stimuli, including the proinflammatory cytokines TNF and IL-1, and microbial products that trigger pathogen recognition receptors, such as Toll-like receptors. A20 functions in a negative feedback loop, which mediates its inhibitory functions by downregulating key proinflammatory signaling pathways, including those controlling NF-κB- and IRF3-dependent gene expression. Activation of these transcription factors is controlled by both K48- and K63- polyubiquitination of upstream signaling proteins, respectively triggering proteasome-mediated degradation or interaction with other signaling proteins. A20 turns off NF-κB and IRF3 activation by modulating both types of ubiquitination. Induction of K48-polyubiquitination by A20 involves its C-terminal zinc-finger ubiquitin-binding domain, which may promote interaction with E3 ligases, such as Itch and RNF11 that are involved in mediating A20 inhibitory functions. A20 is thought to promote de-ubiquitination of K63-polyubiquitin chains either directly, due to its N-terminal deubiquitinase domain, or by disrupting the interaction between E3 and E2 enzymes that catalyze K63-polyubiquitination. A20 is subject to different mechanisms of regulation, including phosphorylation, proteolytic processing, and association with ubiquitin binding proteins. Here we review the expression and biological activities of A20, as well as the underlying molecular mechanisms.

Deletion of the late cornified envelope genes, LCE3C and LCE3B, is associated with rheumatoid arthritis

OBJECTIVE

The risk of rheumatoid arthritis (RA) is increased in the offspring of individuals affected with various autoimmune disorders, including psoriasis. Recently, the deletion of 2 genes from the late cornified envelope (LCE) gene cluster, LCE3C and LCE3B, has been associated with psoriasis in several populations. The purpose of this study was to assess whether this polymorphic gene deletion could also be involved in susceptibility to RA.

METHODS

We tested for association between the LCE3C_LCE3B copy number variant and a single-nucleotide polymorphism in strong linkage disequilibrium with this variant (rs4112788) and RA in 2 independent case-control data sets (197 and 400 samples from patients with RA, respectively, and 411 and 567 samples from control subjects, respectively), collected at 4 Spanish hospitals. All samples were directly typed for presence of the LCE3C_LCE3B deletion (LCE3C_LCE3B-del) by polymerase chain reaction, and association analysis was performed using the SNPassoc R package.

RESULTS

An association of homozygosity for the LCE3C_LCE3B-del and rs4112788 C allele with the risk of RA was observed in the first data set and was replicated in an independent case-control set. A combined analysis showed an overall P value of 0.0012 (odds ratio [OR] 1.45, 95% confidence interval [95% CI] 1.16-1.81) for association of the LCE3C_LCE3B-del. When the analysis was stratified for serologic data, we observed association in anti-cyclic citrullinated peptide (anti-CCP)-positive patients (P = 0.012, OR 1.51 [95% CI 1.09-2.13]) but not in anti-CCP-negative patients.

CONCLUSION

We have identified an association between the LCE3C_LCE3B-del and RA, and we have verified a pleiotropic effect of a common genetic risk factor (LCE3C_LCE3B-del) for autoimmune diseases that is involved in both psoriasis and RA.

Peripheral blood gene expression patterns discriminate among chronic inflammatory diseases and healthy controls and identify novel targets

Background

Chronic inflammatory diseases including inflammatory bowel disease (IBD; Crohn's disease and ulcerative colitis), psoriasis and rheumatoid arthritis (RA) afflict millions of people worldwide, but their pathogenesis is still not well understood.

It is also not well known if distinct changes in gene expression characterize these diseases and if these patterns can discriminate between diseased and control patients and/or stratify the disease. The main focus of our work was the identification of novel markers that overlap among the 3 diseases or discriminate them from each other.

Methods

Diseased (n = 13, n = 15 and n = 12 in IBD, psoriasis and RA respectively) and healthy patients (n = 18) were recruited based on strict inclusion and exclusion criteria; peripheral blood samples were collected by clinicians (30 ml) in Venous Blood Vacuum Collection Tubes containing EDTA and peripheral blood mononuclear cells were separated by Ficoll gradient centrifugation. RNA was extracted using Trizol reagent. Gene expression data was obtained using TaqMan Low Density Array (TLDA) containing 96 genes that were selected by an algorithm and the statistical analyses were performed in Prism by using non-parametric Mann-Whitney U test (P-values < 0.05).

Results

Here we show that using a panel of 96 disease associated genes and measuring mRNA expression levels in peripheral blood derived mononuclear cells; we could identify disease-specific gene panels that separate each disease from healthy controls. In addition, a panel of five genes such as ADM, AQP9, CXCL2, IL10 and NAMPT discriminates between all samples from patients with chronic inflammation and healthy controls. We also found genes that stratify the diseases and separate different subtypes or different states of prognosis in each condition.

Conclusions

These findings and the identification of five universal markers of chronic inflammation suggest that these diseases have a common background in pathomechanism, but still can be separated by peripheral blood gene expression. Importantly, the identified genes can be associated with overlapping biological processes including changed inflammatory response. Gene panels based on such markers can play a major role in the development of personalized medicine, in monitoring disease progression and can lead to the identification of new potential drug targets in chronic inflammation.

Dendritic cells as targets for therapy in rheumatoid arthritis

Dendritic cells (DCs) are central in inducing immunity and in mediating immune tolerance in their role as professional antigen-presenting cells. In the absence of DCs, a fatal autoimmunity develops in animal models. Although the role of DCs has been investigated extensively in the pathogenesis of rheumatoid arthritis (RA), it remains unclear whether DCs initiate autoimmunity in this disease. Nevertheless, evidence points towards a significant role for DCs in disease maintenance and progression. Current biologic therapies target cytokine products of antigen-presenting cells, such as tumor necrosis factor, interleukin-1 and interleukin-6. Emerging therapies for RA exploit the tolerogenic capacity of DCs. 'Tolerogenic' DCs can be generated from myeloid precursors ex vivo, loaded with antigen, and manipulated to suppress autoimmune responses in vivo, through the induction of activation-induced cell death, anergy, and/or regulatory T cells. Cells that are primed by DCs, such as B cells, type 1 and type 17 T helper cells, and that have been implicated in certain models of autoimmunity, are also being considered as additional targets for immune-based therapy. Studies to validate these approaches to ameliorate autoimmunity will be necessary before their application in the clinic.

Rheumatoid arthritis: Disease or syndrome?

Rheumatoid arthritis (RA) has been described in the medical literature for over two hundred years, but its etiology remains unknown. RA displays phenotypic heterogeneity, and it is a relatively prevalent clinical entity: it affects approximately 1% of the population, resulting in enormous pathologic sequelae. Earlier studies targeting the cause(s) of RA suggested potential infectious involvement, whereas more recent reports have focused on a genetic origin of the disease. However, neither infection nor genetics, nor any other single factor is currently accepted as causative of RA. In this article we review studies relating to the etiology of RA, and those of several related matters, and we conclude that the literature indeed does provide insight into the causes underlying the initiation of RA pathogenesis. Briefly, given the remarkable phenotypic variation of RA, especially in its early stages, as well as a number of other characteristics of the condition, we contend that RA is not a discrete clinical entity with a single etiological source. Rather, we argue that it represents a common clinical endpoint for various starting points, each of which is largely guided by as yet poorly understood aspects of the genetic background of the affected individual. Adoption of this alternative view of the origin of RA will have significant consequences for future research and for development of new therapeutic interventions for this burdensome condition.

Pediatric psoriasis: an update

Pediatric psoriasis consists broadly of 3 age groups of psoriatic patients: infantile psoriasis, a self-limited disease of infancy, psoriasis with early onset, and pediatric psoriasis with psoriatic arthritis. About one-quarter of psoriasis cases begin before the age of 18 years. A variety of clinical psoriasis types are seen in childhood, including plaque-type, guttate, erythrodermic, napkin, and nail-based disease. Like all forms of auto-immunity, susceptibility is likely genetic, but environmental triggers are required to initiate disease activity. The most common trigger of childhood is an upper respiratory tract infection. Once disease has occurred, treatment is determined based on severity and presence of joint involvement. Topical therapies, including corticosteroids and calcipotriene, are the therapies of choice in the initial care of pediatric patients. Ultraviolet light, acitretin and cyclosporine can clear skin symptoms, while methotrexate and etanercept can clear both cutaneous and joint disease. Concern for psychological development is required when choosing psoriatic therapies. This article reviews current concepts in pediatric psoriasis and a rational approach to therapeutics.