Retinoids modulate endothelial cell production of matrix-degrading proteases and tissue inhibitors of metalloproteinases (TIMP).

We have previously reported that vitamin A inhibits the growth of capillary endothelial cells (EC) (Braunhut, S.J., and Palomares, M. (1991) Microvasc. Res. 41, 47-62). In this study, we have analyzed the effect of retinoids on the production and activity of enzymes involved in the proteolytic degradation of extracellular matrix (ECM) by EC. Substrate gel electrophoresis (zymography) revealed several major matrix metalloproteinases (MMP), of approximately 98-96, 72-68, and 46-45 kDa, whose activities were altered in their amounts in the conditioned media (CM) of EC following retinol or retinoic acid treatment when compared to amounts detected in CM of control cells. All of these gelatinases were inactivated by 1,10-phenanthroline, indicating that they were MMPs. MMP inhibitors (MMPI) were also present in these CM and were separated by gel filtration. Four distinct peaks of MMPIs were detected in the CM of EC. Chromatographic profiles indicated that an approximately 27-kDa MMPI was specifically increased in the CM of retinol-treated cells, whereas a 22-18.5-kDa MMPI was increased in CM derived from retinoic acid-treated cells. The MMPI synthesized by retinol-treated EC was immunologically related to tissue inhibitor of metalloproteinases, type 1 (TIMP-1), and the MMPI produced by retinoic acid-treated cells was related to TIMP-2, as indicated by biosynthetic labeling and immunoprecipitation studies as well as Western blot analysis. Therefore, retinol and retinoic acid treatment of EC differentially affects the types and activity of MMPs and MMPIs produced by the cells, distinct changes which are both correlated with growth inhibition.