Intercellular adhesion molecule-1 and Na+, K+, ATPase in patients with rheumatoid arthritis

We measured the serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) and erythrocyte membrane Na+, K+, ATPase activity and the correlation of these parameters in patients with rheumatoid arthritis (RA) and investigated whether the levels of sICAM-1 were correlated with the disease activity. Serum sICAM-1 levels were determined with enzyme-linked immunosorbent sandwich assay (ELISA) and erythrocyte membrane Na+, K+, ATPase activity with spectrophotometric method in sera from 42 patients with RA and in 30 healthy controls. Erythrocyte sedimentation rate (ESR) was determined according to the Westergren method and C-reactive protein (CRP) by nephelometric method. Disease activity was assessed by disease activity criteria. Although erythrocyte membrane Na+, K+, ATPase activity decreased, serum levels of sICAM-1 were significantly higher in patients with RA than in healthy controls. Significant negative correlations between sICAM-1 levels and erythrocyte membrane Na+, K+, ATPase activity (r=-0.678, p<0.001) were observed. There was a statistically positive correlation between sICAM-1 levels with Ritchie articular index score and CRP (r=0.32, p<0.05; r=0.44, p<0.01, respectively), whereas no significant correlation was observed between sICAM-1 levels with ESR, age and disease duration. There was no correlation between values of CRP, RAI and ESR with erythrocyte membrane Na+, K+, ATPase activity. From these data, it is concluded that the decreases in erythrocyte membrane Na+, K+, ATPase activity and increases in sICAM-1, ESR and CRP levels are present in RA, and that the decrease in erythrocyte membrane Na+, K+, ATPase activity in RA might be due to increased sICAM-1, and increased levels of sICAM-1 and correlations with other parameters may be a significant and novel marker for evaluating the disease status and the activity of RA.