Abstract
IntroductionExpression of TXNDC5, which is induced by hypoxia, stimulates cell proliferation and angiogenesis. Our previous study detected increased TXNDC5 expression in the synovial tissues of rheumatoid arthritis (RA) patients using proteomic methods. The current study investigated a pathogenic role for TXNDC5 in RA.MethodExpression of TXNDC5 in synovial membranes was quantitatively analyzed by immunohistochemistry, Western blotting and real-time polymerase chain reaction (PCR). Serum TXNDC5 levels and serum anti-TXNDC5 antibody levels were determined using sandwich enzyme-linked immunosorbent assay (ELISA). A total of 96 single nucleotide polymorphisms (SNPs) in or near the TXNDC5 gene were genotyped using custom-designed Illumina 96-SNP VeraCode microassay. Allele frequencies and genotype frequencies of SNPs were assessed using a case-control design in a cohort of 267 Chinese patients with RA, 51 patients with ankylosing spondylitis (AS) and 160 healthy controls. Additional genotyping of 951 patients with RA and 898 healthy controls was performed for four SNPs (rs2277105, rs369086, rs443861 and rs11962800) using the TaqMan method.ResultsReal-time PCR, Western blotting and immunohistochemistry detected significantly higher TXNDC5 expression in the synovial tissues of RA patients compared to samples from patients with osteoarthritis (OA) or AS. ELISA detected significantly higher levels of TXNDC5 in the blood of RA patients compared to OA, AS and systemic lupus erythematosus patients, and healthy controls. ELISA did not detect significantly different levels of anti-TXNDC5 antibody in the blood of RA, OA and AS patients and healthy controls. A total of 9 SNPs (rs9505298, rs41302895, rs1225936, rs1225938, rs372578, rs443861, rs408014, rs9392189 and rs2743992) showed significant association with RA, while 16 SNPs (rs1044104, rs1225937, rs1225938, rs372578, rs89715, rs378963, rs1225944, rs1225947, rs1238994, rs369086, rs408014, rs368074, rs1225954, rs1225955, rs13209404 and rs3812162) showed significant association with AS. Taqman SNP assay demonstrated that rs443861 has an association with RA, which correlates with the microassay results.ConclusionsTXNDC5 is up-regulated in synovial tissues of RA patients. TXNDC5 has a genetic effect on the risk of RA and AS.
Highlights
Expression of Thioredoxin domain containing 5 (TXNDC5), which is induced by hypoxia, stimulates cell proliferation and angiogenesis
Real-time polymerase chain reaction (PCR), Western blotting and immunohistochemistry detected significantly higher TXNDC5 expression in the synovial tissues of rheumatoid arthritis (RA) patients compared to samples from patients with osteoarthritis (OA) or ankylosing spondylitis (AS)
enzyme-linked immunosorbent assay (ELISA) detected significantly higher levels of TXNDC5 in the blood of RA patients compared to OA, AS and systemic lupus erythematosus patients, and healthy controls
Summary
Expression of TXNDC5, which is induced by hypoxia, stimulates cell proliferation and angiogenesis. Our previous study detected increased TXNDC5 expression in the synovial tissues of rheumatoid arthritis (RA) patients using proteomic methods. The current study investigated a pathogenic role for TXNDC5 in RA. Abnormal proliferation of synovial fibroblasts and increased angiogenesis are pathological characteristics of rheumatoid arthritis (RA), an autoimmune disease that results in inflammation of the joints [5]. We detected increased TXNDC5 expression in synovial tissues from RA patients [6]. We detected significantly elevated levels of TXNDC5 in the synovial fluid of patients with RA [6]. We believe that up-regulation of TXNDC5 may play an important role in the pathogenesis of RA in the hypoxic environment
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