Endothelial cells inhibit receptor-mediated superoxide anion production by human polymorphonuclear leukocytes via a soluble inhibitor.
Confluent monolayers of bovine pulmonary artery endothelial cells (BPAE) or human umbilical vein endothelial cells (HUVE) inhibited by 80 to 90% the production of O2- by added human neutrophils (PMNs) stimulated by plasma membrane receptor-mediated activators (formylmethionylleucylphenylalanine [fMLP], opsonized zymosan, heat-killed Staphylococci), but not by non-plasma membrane receptor-mediated activators (phorbol myristate acetate and delta-hexachlorocyclohexane). Degranulation induced by fMLP was also inhibited by BPAE. Inhibition was not affected by eicosatetraynoic acid (ETYA) or indomethacin. To assess the role of cell-cell contact, 0.45-microns-pore culture plate inserts were employed to prevent PMN-endothelial cell contact during incubation. A similar amount of inhibition of stimulated PMNs superoxide production was seen as compared to PMN-endothelial incubations where contact occurred. A soluble component released by BPAE monolayers, when added to PMNs, duplicated the inhibition seen by BPAE-PMN co-incubation. Incubation of BPAE with adenosine deaminase did not reduce inhibition of O2- production compared to controls without adenosine deaminase. There was no evidence of endothelial scavenging of O2- generated by hypoxanthine-xanthine oxidase, and inhibition of endothelial superoxide dismutase did not diminish the inhibitory effort. We conclude that cell contact is not required for BPAE inhibition of fMLP-stimulated O2- production by PMN, and that scavenging of superoxide anion is not the mechanism. The inhibitor appears to be a polypeptide with an apparent molecular weight between 1,000 and 10,000 D and does not appear to be adenosine, an arachidonate metabolite, or superoxide dismutase. The mechanism may involve down-regulation of plasma membrane receptor-mediated activation of PMNs.
Basford
R E
RE
Department of Microbiology, University of Pittsburgh School of Medicine, Pennsylvania.
Clark
R L
RL
Stiller
R A
RA
Kaplan
S S
SS
Kuhns
D B
DB
Rinaldo
J E
JE
D000241:Adenosine / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D002417:Cattle; D002448:Cell Adhesion; D002478:Cells, Cultured; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006801:Humans; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000378:metabolism*; D011651:Pulmonary Artery; D012995:Solubility; D013211:Staphylococcus aureus / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014471:Umbilical Veins; D015054:Zymosan / Q000494:pharmacology
D001095:Arachidonic Acids; D013481:Superoxides; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015054:Zymosan; D000241:Adenosine; D013755:Tetradecanoylphorbol Acetate