Effects of tetracyclines on the production of matrix metalloproteinases and plasminogen activators as well as of their natural inhibitors, tissue inhibitor of metalloproteinases-1 and plasminogen activator inhibitor-1

Abstract:

Objective: Evaluation of tetracycline effects on the expression of MMP-1, MMP-3, tissue inhibitor(s) of metalloproteinase-1 (TIMP-1), plasminogen activators (PA), and PA inhibitor-1, which are all involved in the ultimate regulation of MMP activity could provide new insight into how tetracyclines achieve their cartilage preserving effects.¶Materials and methods: We used bovine articular chondrocytes cultured in alginate gel beads for our studies which were initially treated with 10 μM tetracyclines in the presence of IL-1. Only significant effects were studied at additional concentrations. Expression of mRNA was analyzed by RT-PCR-ELISA. The activity of enzymes and TIMP was measured by functional assays; whereas, the level of PAI-1 was determined by ELISA.¶Results: Treating chondrocytes with IL-1 induced the expression of MMPs and downregulated TIMP-1 but stimulated both the expression of PAs and PAI-1. When tested at 10 μM only minocycline reduced collagenase activity and expression of MMP-1. Further pharmacokinetic analysis revealed IC₅₀ values of 26 μM and 16 μM for the inhibition of collagenase activity and mRNA expression, respectively. Production of MMP-3 was only decreased by tetracycline (IC₅₀ = 45.4 μM). No effects of tetracyclines could be observed on proteoglycan degradation, TIMP activity and the production of PAs, PAI-1, and TIMP-1.¶Conclusions: We conclude that the inhibition of MMPs by tetracyclines occurs mainly via down-regulation of the respective gene expression.¶