Association of interleukin-6 and its -174G/C promoter polymorphism with clinical and laboratory characteristics of non hepatitis C virus rheumatoid arthritis patients

Abstract

Background: Interleukin-6 is a cytokine protein, which causes  inflammation, maintains immune homeostasis and shows a role in rheumatoid arthritis pathogenesis. IL-6-174G/C promoter polymorphism may have a role in susceptibility to RA.
Aim of the work: To evaluate the clinical significance of serum levels of IL-6 and its -174G/C promoter polymorphism in RA patients in comparison with the controls.
Patients and methods: This study enrolled 25 non hepatitis C virus RA  patients versus 25 age and gender matched controls. Demographic, clinical and laboratory data were prospectively evaluated. Serum IL-6 level and promoter (-174G/C) genotype were determined.
Results: Serum IL-6 levels was significantly higher in RA patients compared to control subjects (p = .001), especially those with CC promoter  polymorphism. There was a significant correlation between IL and 6 level and duration of morning stiffness, disease activity, hemoglobin  concentration and ESR level. 15/25 patients had (-174G/G) gene promoter polymorphism, 8/25 were GC and 2/25 were CC. All controls were GG. There was significant association between gene polymorphism and age at disease onset (p =.0172), which was older in those with GG genotype (38.5 ± 10.25 years) than those with CC (33.5 ± 0.7 1 years) and younger in GC genotypes (27.9 ± 7.9 years). None of the other clinical, laboratory or radiological parameters would predict the IL-6 promoter polymorphism.
Conclusion: Serum IL-6 levels and -174G/C promoter polymorphism were higher in RA patients than in healthy controls. The positive correlation of  IL-6 level with the DAS28 and duration of morning stiffness may confirm its’ increased involvement in the pathogenesis of RA and may point to the need for considering of anti-IL-6 agents in their management plan. The negative correlation of IL-6 level with the hemoglobin level may confirm IL-6 play a significant role in anemia of RA.

Keywords: IL-6 HCV (-174G/C) Promoter polymorphism Rheumatoid arthritis