Abstract: Objective To determine the serum levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in patients with systemic lupus erythematosus (SLE) and their clinical significances. Methods The serum concentrations of MMP-9 and TIMP-1 were measured by ELISA in 46 patients with SLE and age-and sex-matched normal controls. Results ①Serum levels of MMP-9 was significantly decreased in patients with SLE compared with those in normal controls (P<0.001). ②In SLE patients, serum levels of MMP-9 were significantly decreased in patients with active diseases and renal involvement compared with those in patients with inactive diseases and no renal involvement (P<0.05 and P<0.01, respectively). Serum levels of MMP-9 were also significantly decreased in SLE patients with the following abnormalities:decreased C3 (P<0.05), hypoalbuminemia (P<0.05) and leucocytopenia (P<0.01). ③Serum levels of MMP-9 were markedly increased in 11 patients after treatment with steroids (P<0.05). ④Serum levels of MMP-9 had negative correlation with SLEDAI scores (P<0.01), and positive correlation with serum C3 levels (P<0.05), white blood cell counts (P<0.01), and serum albumin-globulin ratio (P<0.05). ⑤No significant differences of serum TIMP-1 levels were found between patients with SLE and healthy controls, and between different groups of SLE. Conclusions The results suggest that MMP-9 may play certain roles in the pathogenesis of SLE. Serum MMP-9 level could be used as an indicator for measuring disease activity of SLE, observing renal involvement and evaluation of therapeutic efficacy of steroids.

Key words: Lupus erythematosus, systemic, Gelatinase B, Tissue inhibitor of metalloproteinase-1