Human mast cell chymase and leukocyte elastase release latent transforming growth factor-β1 from the extracellular matrix of cultured human epithelial and endothelial cells

Abstract

Monolayer cultures of human epithelial and endothelial cells were used to study the association of latent transforming growth factor-β1 (TGF-β1) to extracellular matrices and its release and activation during matrix degradation. Human umbilical vein endothelial cells and embryonic lung flbroblasts produced relatively high levels of TGF-β1, its propeptide (β1- latency-associated protein), and latent TGF-β-binding protein and incorporated latent TGF-β1 into their matrices as shown by immunoblotting. Amnion epithelial cells produced lower levels of these proteins. Confluent cultures of epithelial cells were exposed to matrix-degrading proteases and glycosidases. Mast cell chymase, leukocyte elastase, and plasmin efficiently released matrix-bound latent TGF-β1 complexes, while chondroitinase ABC and heparitinases were ineffective. The ability of the proteases to activate recombinant latent TGF-β1 was tested using growth inhibition assays and a novel sodium deoxycholate-polyacrylamide gel electrophoresis followed by immunoblotting. Sodium deoxycholate solubilized M(r) 25,000 TGF-β1 but did not dissociate high M(r) latent TGF-β1 complexes, allowing separation of these forms by polyacrylamide gel electrophoresis. Mast cell chymase and leukocyte elastase did not activate latent TGF-β1, suggesting that its release from matrix and activation are controlled by different mechanisms. The release of TGF-β from the matrix by leukocyte and mast cell enzymes may contribute to the accumulation of connective tissue in inflammation.