Effect of cytotoxic T lymphocyte‐associated molecule 4 1661 gene polymorphism on its expression and transcription in ulcerative colitis

Abstract

Our aim was to investigate the expression of cytotoxic T lymphocyte-associated molecule 4 (CTLA-4) in ulcerative colitis (UC) and to evaluate the effect of CTLA-4 gene -1661A/G polymorphism on CTLA-4 expression and transcription. A total of 20 UC patients and 22 healthy controls matched by age and sex were enrolled at Zhongnan Hospital of Wuhan University in central China. The CTLA-4 -1661A/G polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism method. A Western blot analysis was performed to determine the full length CTLA-4 (flCTLA-4) protein expression in the peripheral blood of the UC patients. Serum-soluble CTLA-4 (sCTLA-4) levels were measured by enzyme-linked immunosorbent assay. CTLA-4-1661G mutant promoter transcription function was analyzed by site-directed PCR-based mutagenesis. CTLA-4 protein expression on CD4(+) T cells in UC patients was lower than that in the healthy controls (P < 0.001) while serum sCTLA-4 in the UC patients was significantly higher than that in the healthy controls (P < 0.001). No correlation was found between flCTLA-4 and sCTLA-4 expression levels and the -1661 A/G polymorphism of the CTLA-4 gene. Meanwhile, CTLA-4 -1661 allele A had no significant impact on the promoter activity compared with allele G (P > 0.05). CTLA-4 expressions were aberrant in UC patients compared with the healthy controls. CTLA-4 -1661A/G polymorphism had no significant impact on CTLA-4 expression and transcription in the peripheral CD4 T cells of UC patients.