Clinical significance of serum interleukin-6 and −174 G/C promoter polymorphism in Rheumatoid arthritis patients

Abstract

Aim of the workTo evaluate the clinical significance of serum levels of interleukin-6 (IL-6) and −174 G/C promoter polymorphism in Rheumatoid arthritis (RA) patients. Patients and methodsWe studied 37 RA patients and 10 age and gender matched healthy controls. Demographic, clinical and serological data were prospectively evaluated. Disease activity score (DAS28) and Health Assessment Questionnaire (HAQ) were assessed. Serum IL-6 level was measured and promoter (−174G/C) genotyped. ResultsSerum IL-6 levels were significantly higher in RA patients compared to control (p=0.04), especially those with CC promoter polymorphism. Twenty-four patients had GG IL-6 (−174 G/C) gene promoter polymorphism, 11 were GC and 2 CC. Nine controls were GG and 1 GC. In patients with more advanced polymorphism (−174 CC) there was a significantly increased functional impairment (HAQ score) (p=0.029) and platelet count (p=0.049). In those with GG genotype, there was a significant correlation between IL-6 and Morning stiffness duration (r=0.44,p=0.03), while those with GC genotype had a significant negative correlation of the IL-6 level with the parameters of disease activity and the DAS28 (r=−0.69,p=0.019). None of the studied parameters would predict the IL-6 promoter polymorphism. ConclusionSerum IL-6 levels and −174 G/C promoter polymorphism were higher in RA patients than in healthy controls. The inverse relation of IL-6 with the DAS28 in those with an increased IL-6 promoter polymorphism may confirm its increased involvement in the pathogenesis of RA and in the increased disease activity which may point to the need for considering of anti-IL-6 agents in their management plan.