Interleukin-10 family cytokines pathway: genetic variants and psoriasis.

BACKGROUND: Interleukin (IL)-10 family cytokines IL-10, IL-19, IL-20 and IL-24 have been implicated in autoimmune diseases and we have previously reported that genetic variants in the IL10 gene cluster were associated with psoriasis. OBJECTIVES: To analyse the relationship between genetic polymorphisms in the IL10 gene cluster and psoriasis. This study also explores whether there are gene-gene interactions among these genetic polymorphisms. METHODS: A total of 377 patients with psoriasis and 403 matched healthy controls were enrolled to carry out a case-control study for 48 single-nucleotide polymorphisms (SNPs) of the IL10 gene cluster. Genotyping for the SNPs was conducted on the Applied Biosystems 3730 DNA Analyzer using SNPlex® technology. Generalized multifactor dimensionality reduction (GMDR) analysis was applied to discover a likely gene-gene interaction model among the SNPs. RESULTS: The results showed that the allele distributions of IL10 gene cluster SNPs are significantly different between the case and control groups. Carriers of the IL10 T allele (rs1554286) and the IL20 T allele (rs1400986) conferred protection from psoriasis [odds ratio (OR) = 0·63, corrected P-value (Pc) = 0·007; OR = 0·62, Pc = 0·038, respectively]. GMDR analysis displayed a significant gene-gene interaction between IL10 (rs1554286) and IL20 (rs1518108) variants. The strongest protective effect was found with the block 1 haplotype ACATA in the IL10 gene (Pc = 0·004). CONCLUSIONS: This study presents a novel finding that the combination of the two SNPs, IL10 (rs1554286) and IL20 (rs1518108), is associated with a reduced risk of psoriasis. Our results indicate that genetic variants of the immunomodulatory IL10 and IL20 genes may offer a protective effect in Europeans from Russia. Independent studies are required to verify the results and find a possible functional explanation.

Association analysis of IL20RA and IL20RB genes in psoriasis.

The interleukin-20-receptor I complex (IL-20-RI) is composed of two chains, IL20RA and IL20RB. Its ligands are the three members of the IL19 subfamily of cytokines, IL-19, IL-20 and IL-24. These cytokines are important in the manifestation of psoriatic lesions and, recently, an association of polymorphisms of IL20 with psoriasis has been described. In the present study we tested the hypotheses that genetic variations of the IL-20-RI influence susceptibility to psoriasis and investigated single nucleotide polymorphisms (SNPs) in the IL20RA and IL20RB genes in psoriasis patients (n=254) and healthy controls (n=224). We found no association of any of the investigated SNPs with the disease. Analysis of pairwise linkage disequilibrium (LD) across studied markers revealed a strong level of LD between SNPs within the IL20RA gene and SNPs within the IL20RB gene, and, for both genes six common haplotypes were identified with an estimated frequency >or=1%. Haplotype analyses suggested that the IL20RA haplotype CCG (rs1184860, rs1167846, rs1167849) is significantly associated with psoriasis (OR 3.14, 95% CI 1.61-6.14), whereas the TTG haplotype had a protective effect (OR 0.20, 95% CI 0.07-0.55). The risk haplotype defining SNPs 1167846 and 1184860 were found to modify paired box 5 and homeobox A9 sites, respectively, two transcription factors related to the differentiation of immune cells. Further studies are needed to confirm the genetic association and to investigate the functional relevance of IL20RA haplotypes in psoriasis.

Gene expression study of IL10 family genes in vitiligo skin biopsies, peripheral blood mononuclear cells and sera.

BACKGROUND: Vitiligo is a pigmentation disorder, the cause of which is complex and not yet fully understood. There is a significant change of epidermal cytokines in involved skin of patients with vitiligo compared with uninvolved skin and skin of healthy controls, thus suggesting a possible involvement of cytokines in the pathogenesis of vitiligo. OBJECTIVES: To evaluate potential roles of IL10 family cytokines (IL10, IL19, IL20, IL22 and IL24) in vitiligo. Along with the selected cytokines, we investigated subunits of the receptors (IL10RA, IL10RB, IL20RA and IL22RA1) which are involved in the signalling pathway of the cytokines. METHODS: Quantitative real-time polymerase chain reaction was used to detect mRNA expression levels in samples extracted from skin biopsies and peripheral blood mononuclear cells and an enzyme-linked immunosorbent assay was used to measure protein concentrations in serum from patients with vitiligo and healthy controls. RESULTS: IL22 is significantly associated with vitiligo, especially with the active stage of vitiligo, as shown by results of mRNA expression and supported by results of protein level in sera. IL22 may provoke inflammation which leads to destruction of melanocytes. CONCLUSIONS: The actual role of IL22 during pathogenesis of vitiligo remains to be better characterized. Signal transductions of other investigated cytokines seem to be regulated on the expression level of their receptor complex subunits.

Association analysis of IL19, IL20 and IL24 genes in palmoplantar pustulosis.

BACKGROUND: Interleukin (IL) 19, IL-20 and IL-24 belong to the IL-10 cytokine family and have been identified to play a role in the regulation of epidermal functions and in inflammation. The genes encoding IL-19, IL-20 and IL-24 are located within a gene cluster on chromosome 1q31-32 and carry frequent genetic variations. OBJECTIVES: This study investigated whether variations in the IL19, IL20 and IL24 genes that have previously been associated with plaque-type psoriasis may also play a role in palmoplantar pustulosis (PPP). PATIENTS: Fifteen polymorphisms were analysed in 43 patients with PPP and in 149 healthy control subjects. RESULTS: The rare allele of IL20 1380 A-->G (rs2981573) was less frequent in patients with PPP compared with healthy controls (OR 1 x 95, 95% CI 1 x 00-3 x 79). Haplotype analyses of IL19 and IL20 suggested an increased risk for PPP associated with IL20 haplotype GAA (OR 2 x 39, 95% CI 1 x 17-4 x 86) and a reduced risk for PPP associated both with IL19 haplotype GATGATA (OR 0 x 41, 95% CI 0 x 16-1 x 05) and IL20 haplotype GGG (OR 0 x 48, 95% CI 0 x 23-0 x 98). Extended haplotype analysis revealed an association of IL19/IL20 haplotype GACACCGGAA with a higher risk for PPP (OR 2 x 31, 95% CI 1 x 05-5 x 10) and of IL20/IL24 haplotype CAAAC with a reduced risk for PPP (OR 0 x 12, 95% CI 0 x 02-0 x 82). CONCLUSIONS: This exploratory study supports the hypothesis that variations of genes of the IL-19 subfamily of cytokines influence susceptibility to PPP. However, due to the limited size of the study samples, this current concept should be considered as preliminary and the results need to be confirmed in future independent studies.

Possible relations between the polymorphisms of the cytokines IL-19, IL-20 and IL-24 and plaque-type psoriasis.

The aim of present study was to elucidate the role of the interleukin (IL)-24 gene in predicting risk for plaque-type psoriasis and to describe the linkage disequilibrium (LD) pattern emerging from the genes of IL-19, IL-20 and IL-24. Genes encoding IL-19, IL-20 and IL-24 locate in the region q32 of chromosome 1. The association between the single-nucleotide polymorphisms (SNPs) or haplotypes of the IL-24 gene and the susceptibility of psoriasis was not found. However, a significant protective effect of the combined haplotype CAAAC of IL-20 and IL-24 genes against plaque-type psoriasis was established (OR 0.154). Protective effect against psoriasis was also observed with haplotype TGGGT (OR 0.591) and haplotype CGAGT (OR 0.457). Performing a comprehensive analysis using the data regarding SNPs of IL-24 gene together with the previously published data regarding IL-19 and IL-20 SNPs, we identified two haplotype blocks within the region q32 of chromosome 1. The main result of the present study is that while the IL-19/IL-20 extended haplotype CACCGGAA is a significant susceptibility factor for psoriasis (previous study), IL-20/IL-24 haplotypes CAAAC, TGGGT and CGAGT have a significant protective effect. Nevertheless, family-based studies are required to confirm the impact of IL-19, IL-20 and IL-24 genes in the genetic predisposition for psoriasis.

Combined haplotype analysis of the interleukin-19 and -20 genes: relationship to plaque-type psoriasis.

There is increasing evidence to suggest that the newly discovered cytokines interleukin (IL)-19 and -20 have a role in the function of epidermis and in psoriasis. The genes encoding these cytokines locate into the genomic IL-10 region on human chromosome 1. The aim of the present study was to analyze whether single-nucleotide polymorphisms (SNPs) in these genes have an impact on the susceptibility for psoriasis. From pairwise linkage disequilibrium (LD) matrix of the IL-19 and -20 gene polymorphisms, what reflects the nonrandom association of alleles at these markers, it was apparent that IL-19 and -20 genes form one block of LD. We found that the HT3 CACCGGAA haplotype of the IL-19 and -20 genes was associated with an increased risk of psoriasis, reflecting its role in determining susceptibility to plaque-type psoriasis. Although association analysis of the IL-19 gene indicated that minor alleles of the IL-19 gene SNPs (rs2243188, rs2243169 and rs2243158) revealed protective effect to psoriasis and haplotype analysis of the IL-19 gene proved significant protective effect of the TGATA haplotype in case of late-onset disease, combined haplotype analysis of the IL-19 and -20 genes demonstrated that protective effect of the IL-19 gene is secondary to the susceptibility effect of the IL-20 gene.