Increased Levels of Matrix Metalloproteinase-3 in Sera from Patients with Active Lupus Nephritis

Objective: To determine the matrix metalloproteinase-3 (MMP-3) levels in sera from patients with systemic lupus erythematosus (SLE) and to analyse the relationships between MMP-3 and clinical and laboratory features.

Methods: Serum MMP-3 levels were measured by an enzyme immunoassay in 124 patients with SLE and 237 patients with other systemic rheumatic diseases.

Results: The frequencies of patients with high MMP-3 levels were 76% in SLE and 82% in rheumatoid arthritis (RA). The level of MMP-3 in the SLE patients was 193.0 +/- 171.5 ng/ml (mean +/- SD) and was almost equal to the level in the RA patients (259.5 +/- 255.6 ng/ml). The MMP-3 levels were significantly higher in SLE patients who had a history of the following abnormalities: persistent proteinuria, cellular casts, anti-double stranded DNA antibodies, decreased C3, decreased creatinine clearance (p < 0.001), circulating immune complex (p < 0.01), malar rash, hypoalbuminemia, or decreased C4 (p < 0.05). The serum MMP-3 level in patients with SLE at admission showed direct correlations with serum uric acid, total cholesterol (p < 0.001), triglyceride, the white blood cell count, and the neutrophil count (p < 0.05), as well as inverse correlations with the total protein (p < 0.01), and IgG (p < 0.05). In SLE patients with active renal disease, the median MMP-3 level at admission and that at 6 months after admission were significantly higher than that at 6 months before admission.

Conclusions: The increased level of serum MMP-3 in SLE is closely associated with clinical features relevant to lupus nephritis, suggesting that it plays a role in the pathogenesis of this condition.