TRAF5 and TRAF3IP2 gene polymorphisms are associated with Behçet's disease and Vogt-Koyanagi-Harada syndrome: a case-control study

Abstract

Background: TRAF5 and TRAF3IP2 have been reported to be associated with several autoimmune diseases. Behçet's disease (BD) and Vogt-Koyanagi-Harada (VKH) syndrome are two autoimmune uveitis entities whereby both genetic and environmental factors are thought to be involved.

Objective: The role of TRAF5 and TRAF3IP2 in BD and VKH has not yet been reported and was therefore the subject of this study.

Methods: The study included 789 BD patients, 940 VKH patients and 1601 healthy unrelated individuals. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or TaqMan® SNP Genotyping Assay. Real-Time PCR was used to detect mRNA expression from PBMCs obtained from healthy controls with (n = 22) or without (n = 79) stimulation. Levels of TNF-α, IL-6 and IL-8 in culture supernatants were measured by ELISA (n = 22).

Results: Three SNPs (rs6540679, rs12569232, rs10863888) of TRAF5 and rs13210247 of TRAF3IP2 were significantly associated with Behçet's disease and VKH syndrome (corrected P values ranging from 9.45×10(-12) to 0.027). TRAF3IP2 rs33980500 and rs13190932 were not polymorphic in Han Chinese. Following stimulation by lipopolysaccharide (LPS), carriers of the GG genotype of rs6540679/TRAF5 had a higher TRAF5 mRNA expression (p = 0.004) and an increased TNF-α (p = 0.0052) and IL-6 (p = 0.0014) level compared with AA and AG genotype carriers.

Conclusion: This study provides evidence that TRAF5 and TRAF3IP2 genes are involved in the development of BD and VKH syndrome. Functional research suggested that TRAF5 gene polymorphisms may regulate TRAF5 expression and downstream inflammatory cytokines such as TNF-α and IL-6.

Figure 1. Schematic location of the chosen SNPs of TRAF5 and TRAF3IP2.

Figure 2. Effect of TRAF5 rs6540679 genotypes on mRNA expression by PBMCs stimulated with LPS (1 ng/ml).

The mean ± SD is given for each genotype.

Figure 3. The effect of different genotypes of SNP rs6540679/TRAF5 on LPS-stimulated cytokine secretion by PBMCs obtained from healthy individuals.

Supernatants of PBMCs co-cultured with 1 ng/mL LPS for 72 h were used to determine TRAF5 downstream cytokines (including TNF-α, IL-8, IL-6) levels by ELISA. Data are presented as means±SD.