Enzymatic degradation of endothelin-1 by activated human polymorphonuclear neutrophils

Abstract

SummaryEndothelin-1 (ET-1) is a potent vasoconstrictor peptide secreted by endothelial cells. We investigated whether polymorphonuclear neutrophils (PMN) were able to destroy this peptide by enzymatic hydrolysis produced either by the membrane-bound endopeptidase 24.11 or by lysosomal proteinases released in the medium by activated cells. Resting and activated PMN were incubated with 125I-labelled ET-1 and the degradation fragments were analyzed by HPLC. A marked degradation of ET-1 was observed only in the presence of the stimulated cells, leading to the generation of seven radiolabelled peaks. Addition of phosphoramidon had no effect on the appearance of these metabolites, while soybean trypsin inhibitor abolished almost completely the degradation of the peptide, suggesting a role of cathepsin G in ET-1 hydrolysis.Among the purified leukocyte enzymes tested, cathepsin G hydrolyzed 125I-labelled ET-1 at the higher rate and gave rise to two radiolabelled peaks already observed in the presence of activated PMN. Incubation of unlabelled ET-1 with purified cathepsin G allowed to identify a major cleavage site corresponding to the Hisl6-Leu x7 bond, leading to the formation of inactive [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] fragments and the C-terminal pentapeptide.This mechanism of ET-1 inactivation could play a role in acute inflammatory reaction where PMN adhere to the vascular endothelial cells.

Endothelin‐1 does not modulate O2· release and [Ca2+]i variations in resting or differentiated HL‐60 cells

“…generation) responses to the chemotactic peptide fMLP. Endothelins have been shown to be rapidly degraded by multiple enzymes and particularly by NEP (Fagny et al, 1992). In the presence of phosphoramidon, we could not observe, in HL-60 cells, any [Ca2+Ii changes or 0,. generation linked to ET-1, or any modulation of these responses induced by fMLP on a short or long term, which rules out a possible rapid degradation of ET-1 by NEP in our cell system.…”

“…generation, which is higher in neutrophils from asthmatic patients than those from normal subjects (Meltzer et al 1989). Interestingly, human polymorphonuclear leukocytes are able to produce ET-1 (Sessa et al, 1991b) and to degrade it (Fagny et al, 1992) like airway epithelial cells do (Tschirhart et al, 1991). These facts led us to study the direct or priming effects of ET-I on 0 , .…”

Plasma Endothelin-1 Concentrations in Patients with Behçet' Disease

“…A possible deficit of the PMN-derived elastase and cathepsin G or blocking of these enzymes with eglin C, together with the endothelial damage, can represent a further mechanism leading to high levels of ET-1 (28)(29)(30)(31)(32). Lastly; endothelial damage is also a feature of many vasculitic conditions associated with BehGet's disease.…”

Airway endothelin levels in asthma: influence of endobronchial hypertonic saline challenge

“…Another possible explanation would be that hypertonic saline exposure results in increased metabolism of binding or ET. Degradation of ET in vivo is believed to involve the enzyme neutral endopeptidase [ 28], and in addition activated neutrophils have been shown to release an activity, identified as principally cathepsin G, that can degrade ET [ 29]. It is therefore possible that hypertonic saline exposure may release or modulate the activity of such enzymes.…”