Background: In periodontitis, matrix metalloproteinase-3 (MMP-3, stromelysin 1) is present at increased levels in active disease sites compared to inactive or healthy sites, and the levels are correlated with clinical parameters and associated with progression of the disease. Interleukin (IL)-4 has been shown in human skin and synovial fibroblasts and articular chondrocytes to suppress IL-1-induced expression of MMP-3, but this has not been shown in human gingival fibroblasts. The objective of this study is to determine the effects of IL-4 on the IL-1-induced expression of MMP-3 in human gingival fibroblasts isolated from patients with periodontitis.
Methods: Northern blot analysis was performed to determine the effects of IL-4 on the IL-1 induction of MMP-3 mRNA. MMP-3 protein levels were determined by enzyme-linked immunosorbent assay (ELISA), and prostaglandin E2 (PGE2) levels were measured by enzyme immunoassay (EIA). DNA binding of activator protein (AP)-1 and nuclear factor (NF)-kappaB was assessed by electrophoretic mobility shift assay (EMSA).
Results: Northern blot analysis revealed that co-incubation of gingival fibroblasts with IL-1 and IL-4 resulted in a significant decrease in MMP-3 mRNA levels compared to IL-1 alone, with a concomitant decrease in protein levels. This inhibition is dose-dependent, and is apparent as early as 3 hours after stimulation. IL-1-induced production of PGE2 was not affected in four of six cultures isolated from different individuals. Addition of exogenous PGE2 had no effect on the suppressive effects of IL-4. DNA binding of transcription factors AP-1 and NF-kappaB was not affected by IL-4.
Conclusions: IL-4 inhibits the IL-1 induction of MMP-3 in human gingival fibroblasts isolated from patients with periodontitis. This effect is independent of PGE2 and is not due to inhibition of the DNA binding activity of known transcription factors binding to the MMP-3 promoter.