Matrix metalloproteinases regulate neutrophil-endothelial cell adhesion through generation of endothelin-1[1-32]

We recently reported that matrix metalloproteinase 2 (MMP-2, gelatinase A) cleaves big endothelin 1 (ET-1), yielding the vasoactive peptide ET-1[1-32]. We tested whether ET-1[1-32] could affect the adhesion of human neutrophils to coronary artery endothelial cells (HCAEC). ET-1[1-32] rapidly downregulated the expression of L-selectin and up-regulated expression of CD11b/CD18 on the neutrophil surface, with EC50 values of 1-3 nM. These actions of ET-1[1-32] were mediated via ETA receptors and did not require conversion of ET-1[1-32] into ET-1 by neutrophil proteases, as revealed by liquid chromatography and mass spectroscopy. Moreover, ET-1[1-32] evoked release of neutrophil gelatinase B, which cleaved big ET-1 to yield ET-1[1-32], thus revealing a positive feedback loop for ET-1[1-32] generation. Up-regulation of CD11b/CD18 expression and gelatinase release was tightly associated with activation of extracellular signal-regulated kinase (Erk). Stimulation of Erk activity was due to activation of Ras, Raf-1, and MEK (MAPK kinase). ET-1[1-32] also produced slight increases in the expression of ICAM-1 and E-selectin on HCAEC, and markedly enhanced beta (2) integrin-dependent adhesion of neutrophils to activated HCAEC. These results are the first indication that gelatinolytic MMPs via cleavage of big ET-1 to yield ET-1[1-32] activate neutrophils and promote leukocyte-endothelial cell adhesion and, consequently, neutrophil trafficking into inflamed tissues.