Platelet-activating factor and kinin-dependent vascular leakage as a novel functional activity of the soluble terminal complement complex.
The infrequent occurrence of septic shock in patients with inherited deficiencies of the terminal complement components experiencing meningococcal disease led us to suspect that the terminal complement complex is involved in vascular leakage. To this end, the permeabilizing effect of the cytolytically inactive soluble terminal complement complex (SC5b-9) was tested in a Transwell system measuring the amount of fluorescein-labeled BSA (FITC-BSA) leaked through a monolayer of endothelial cells. The complex caused increased permeability to FITC-BSA after 15 min as opposed to the prompt response to bradykinin (BK). The effect of SC5b-9 was partially reduced by HOE-140 or CV-3988, two selective antagonists of BK B2 and platelet-activating factor receptors, respectively, and was completely neutralized by the mixture of the two antagonists. Also, DX-88, a specific inhibitor of kallikrein, partially inhibited the activity of SC5b-9. The permeabilizing factor(s) released after 30 min of incubation of endothelial cells with SC5b-9 caused a prompt leakage of albumin like BK. Intravital microscopy confirmed both the extravasation of circulating FITC-BSA across mesenteric microvessels 15 min after topical application of SC5b-9 and the complete neutralization by the mixture of HOE-140 and CV-3988. SC5b-9 induced opening of interendothelial junctions in mesenteric endothelium documented by transmission electron microscopy.
Bossi
Fleur
F
Department of Physiology and Pathology, University of Trieste, Trieste, Italy.
Fischetti
Fabio
F
Pellis
Valentina
V
Bulla
Roberta
R
Ferrero
Elisabetta
E
Mollnes
Tom Eirik
TE
Regoli
Domenico
D
Tedesco
Francesco
F
D000818:Animals; D001920:Bradykinin / Q000494:pharmacology / Q000502:physiology*; D002199:Capillary Permeability / Q000187:drug effects / Q000276:immunology*; D002460:Cell Line; D015938:Complement Membrane Attack Complex / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D004306:Dose-Response Relationship, Immunologic; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D016650:Fluorescein-5-isothiocyanate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D007082:Ileum / Q000098:blood supply / Q000276:immunology / Q000648:ultrastructure; D007365:Intercellular Junctions / Q000187:drug effects / Q000276:immunology; D008297:Male; D008643:Mesentery / Q000098:blood supply / Q000276:immunology / Q000648:ultrastructure; D010477:Perfusion; D010972:Platelet Activating Factor / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D012710:Serum Albumin, Bovine / Q000008:administration & dosage / Q000494:pharmacology; D012995:Solubility
D015938:Complement Membrane Attack Complex; D010972:Platelet Activating Factor; C039217:fluorescein isothiocyanate bovine serum albumin; D012710:Serum Albumin, Bovine; D016650:Fluorescein-5-isothiocyanate; D001920:Bradykinin