Thrombin induces the synthesis of stromelysin 1 (MMP-3): A novel effect of thrombin on extracellular matrix degradation

α-thrombin is a serine protease which not only plays a central role in hemostasis, but also possesses several cellular functions implicated in atherosclerosis and in extracellular matrix degradation. In the present study, we have investigated the effect of thrombin on some inflammatory responses at the level of cartilage destruction. When porcine articular chondrocytes were treated with α-thrombin (10 U/ml), proteoglycan release was increased in culture medium. This effect was due, in part, to the direct serine proteolytic activity of thrombin on matrix proteoglycans. Zymogram analysis on α-casein substrate gel electrophoresis revealed the presence of discrete bands of lysis that were inhibited by EDTA or 1,10-phenantroline, confirming that this activity could be ascribed to metalloproteinases. Thrombin induced the enhancement of a 55 kDa band of lyric activity, as assessed on casein substrate gel electrophoresis. The synthesis of thrombin- stimulated stromelysin was further assessed by Western blot using specific anti-stromelysin antibodies. This result was further confirmed by Northern blot analysis. These data demonstrate that thrombin is able to stimulate the stromelysin synthesis which is recognized to play a pivotal role in extracellular matrix remodelling and degradation.