Human polymorphonuclear leukocytes have dual effects on endothelin-1: the induction of endothelin-1 mRNA expression in vascular endothelial cells and modification of the endothelin-1 molecule.

The effect of human polymorphonuclear leukocytes (PMNs) on the expression of the endothelin-1 (ET-1) gene and the production of ET-1 peptide was investigated. Human PMNs were separated from venous blood with Mono-Poly Resolving Medium and activated by incubation with formyl-methionyl-lencylphenylalanine (FMLP) (1 microM). Then PMN suspension was added to cultured porcine endothelial cell monolayers and coincubated for various periods. Following the coincubation, ET-1 mRNA in endothelial cells was examined by Northern blotting and immunoreactive ET-1 (irET-1) peptide levels in the conditioned media were measured by an enzyme-linked immunosorbent assay (ELISA). Similar experiments were also carried out with cell-free PMN supernatant. Untreated and activated PMNs led to a 1.4-fold and 6.3-fold increase in ET-1 mRNA levels in endothelial cells, respectively, at 6h, while irET-1 peptide levels did not significantly increase as compared with control. In contrast, when PMNs were coincubated in the presence of an Intercell chamber without direct contact to endothelial cells, PMNs did not induce ET-1 mRNA expression in endothelial cells, and significantly decreased irET-1 peptide levels in the conditioned media. Cell-free PMN supernatant did not have all these effects on ET-1. These findings suggest that direct PMN-endothelial cell contact was essential for PMN-induced expression of the ET-1 gene and that PMNs may decrease irET-1 through some modification of the ET-1 molecule.