Plasma concentration of osteopontin [OPN] in children with systemic lupus erythematosus: relationship with disease activity

ABSTRACT

Osteopontin [OPN] is an important bone matrix mediator found to have key roles in inflammation and immunity. OPN is a cytokine which can play a number of roles in promoting activation of T lymphocyte, regulating balance between T-helper 1 and T-helper 2, participating in cell-induced immunologic response and stimulating B lymphocyte to express multi-clone antibodies. Overexpression of OPN has been associated with the development of the autoimmune/lymphoproliferative syndrome. The aim of our present study was to analyze the possible correlation between the plasma concentration of OPN and disease activity in children with Systemic Lupus Erythematosus [SLE]. We also investigated the correlation between plasma IL-18 and OPN concentrations to further confirm the association of OPN with disease activity. We measured the plasma concentration of OPN, and the plasma proinflammatory IL-18 concentration in 40 SLE patients with or without renal disease [RSLE group and SLE group, respectively] and in 30 sex-and age-matched controls using enzyme immunoassay. Plasma OPN concentrations were significantly higher in RSLE and SLE patients than in the controls [p=0.000 and p=0.002]. Increase in OPN concentration correlated positively and significantly with SLE disease activity index in all SLE patients [r=0.34; p=0.04]. In RSLE patients, plasma OPN concentration showed a significant positive correlation with proinflammatory cytokine IL-18 concentration [r=0.48; p=0.004]. In conclusion, The above results suggest that the production of OPN is associated with the inflammatory process and SLE development, and may serve as a potential disease marker of SLE