Relation of interleukin-6 in rheumatoid arthritis patients to systemic bone loss and structural bone damage

IL-6 plays a key role in local and systemic manifestation of RA. IL-6 is not only a pro-inflammatory cytokine, but also interacts in complex ways with the cells involved in bone remodeling. In RA, IL-6 may indirectly promote osteoclastogenesis by increasing the release of RANK-L by osteoblasts, and it diminishes the proliferation of osteoblasts at late differentiation stages. The aims of this work were to evaluate the level of serum IL-6 and to correlate it with the activity, severity, early development of osteoporosis, and early structural bone damage in RA patients. The following parameters were investigated in 40 RA patients and 20 healthy controls: IL-6 level, BMI, ESR, CRP, CBCs, serum ionized calcium, blood urea, serum creatinine, AST, ALT, anti-CCP, and RF. Bone mineral density was measured by dual-energy X-ray absorptiometry at lumbar spines and femoral neck. Drug history was taken stressing on steroid therapy. Data were processed and analyzed using computer-based program. IL-6 was significantly positively correlated with HAQ1, PTGA, grade of pain, ESR, platelet count, blood urea, AST level, and anti-CCP level; IL-6 showed an inverse significant correlation with T-score. IL-6 was positively correlated with TGC, DAS-28 score, and RF level. No correlation was found between T-score and morning stiffness duration, BMI, CRP, RBC, serum creatinine, and ALT. There was an inverse significant correlation between T-score and HAQ1, SJC, pain grade, DAS-28 score, PTGA, ESR, RF, anti-CCP, and IL-6. Patients with RA on steroid therapy had significantly higher TJC, SJC, and DAS-28 score, anti-CCP, and IL-6 than patients with RA not on steroid therapy. Patients with RA on steroid therapy had significantly lower T-score and lower serum ionized calcium than patients with RA not on steroid therapy. IL-6 has an important role in increasing osteoclastic activity and subsequent bone resorption in the patients with RA. Blocking IL-6 by using IL-6 inhibitors and anti-RANK-L therapy may be effective in inhibiting the inflammatory process and preventing the bone complications of RA disease.