Endothelin-1 induces extracellular matrix degradation via matrix metalloproteinases induction in human osteosarcoma cells

Extracellular matrix (ECM) degradation plays an important part in many musculoskeletal pathologies including arthritis and bone tumour. Matrix metalloproteases (MMPs) degrade the ECM and are thus important in the development of these pathologies. Furthermore, recent evidence suggest the existence of interactions between endothelin-1 (ET-1) and MMPs.

This study aimed at determining the effect of ET-1, Big ET-1 (the immediate precursor of ET-1) and IL-1β (a proinflammatory cytokine that induces MMP synthesis) on MMPs in order to determine the mechanism of action of these factors in chondrosarcoma and osteosarcoma cells. We have also studied the effects of the NF-κB inhibitor and the inhibitor of furine convertase that is involved in Big ET-1 maturation. Here we characterized the MMPs, ET-1 and ET-1 receptors in SW1353 and MG63 cells by western blot, zymography, northern blot, immunohistochemistry, RT-PCR, and in situ hybridization.

First, we showed that ET-1 and its two receptors (ET_A and ET_B) areconstitutively expressed in osteosarcoma and chondrosarcoma cells. Then, we demonstrated that both ET-1 and Big ET-1 markedly induce synthesis and enzymatic activity of MMP-2 and that enzymatic activity is significantly increased when compared with MMP-9. Furthermore, inhibition of NF-κB activation (by pyrrolidinecarbodithioic acid) blocked MMP-2 production and activity, indicating the involvement of NF-κB. Similarly, inhibition of Big ET-1 maturation by the furin convertase inhibitor abrogated MMP-2 synthesis.

ET-1 and as its immediate precursor Big ET-1 can be considered as autocrine factors contributing to the activation of MMPs, thus favouring ECM degradation. MMPs, particularly MMP-9 and MMP-2, are hyperexpressed in chondrosarcoma and osteosarcoma cells. Their production is stimulated by ET-1, Big ET-1 and IL-1β while it is diminished when the NF-κB and furine convertase pathways are inhibited. Our study provides new insights on the catabolic role of ET-1 in ECM degradation. Thus ET-1 could be involved in diseases where ECM destruction is caused by an excess of MMP, including bone tumour, degenerative and inflammatory articular diseases. In an attempt to diminish this degradation, it would be beneficial to propose a double inhibition of both ET-1 receptors and MMPs.