Receptor antagonist of platelet activating factor inhibits inflammatory injury induced by in situ formation of immune complexes in renal glomeruli and in the skin.

Experiments were designed to test the effect of a receptor antagonist of platelet activating factor (PAF), SRI63072, on inflammatory injury induced by in situ formation of immune complexes in two vascular districts of the rat that have different structural and hemodynamic characteristics: unilateral glomerulonephritis induced by perfusion of the left kidney of preimmunized animals with cationic human IgG, and passive reversed Arthus reaction in the skin. Three days after perfusion the left kidneys of rats not treated with SRI63072 (group I) were greatly enlarged, and pale and severe exudative and proliferative lesions were present in glomeruli. Granular deposits of human IgG, rat IgG, and rat C3 were seen by immunofluorescence microscopy, and subepithelial electron-dense deposits were visualized by electron microscopy.

Release of platelet-activating factor from rabbit heart perfused in vitro by sera with transplantation alloantibodies.

During "hyperacute rejection" of rabbit heart perfused with transplantation alloantibodies, platelet activating factor (PAF) was released into the coronary effluent, which appeared to have physicochemical and functional properties similar to the 1-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (synthetic PAF) and to PAF obtained from IgE-sensitized rabbit basophils. The release of PAF was associated with an early tachycardia, followed by increasing bradycardia and conduction arrhythmias, as well as decrease of coronary flow and of amplitude of electrogram. The heart stopped beating within 30 min.

The pattern of cardiovascular alterations induced by infusion of platelet-activating factor in rabbit is modified by pretreatment with H1-H2 receptor antagonists but not by cyclooxygenase inhibition.

The intravenous infusion of platelet activating factor (PAF) (0.8 micrograms/kg b.w.

Lung injury mediated by antibodies to endothelium. II. Study of the effect of repeated antigen-antibody interactions in rabbits tolerant to heterologous antibody.

The effect of repeated interactions of antibodies with cell surface antigens have been examined in in vitro, but not in in vivo systems. In this study are described the results of multiple antibody-cell surface antigen interactions in vivo. Rabbits were given repeated intravenous injections of goat antibodies to angiotensin converting enzyme (ACE), an antigen expressed on the surface of lung endothelial cells.

In vitro complement-independent activation of human neutrophils by hemodialysis membranes: role of the net electric charge.

Polymethylmethacrylate (PMMA) membranes with different net electric charges and percentage water contents (anionic 71%, neutral 70%, cationic 75%) were evaluated for their ability to stimulate plasma-free human polymorphonuclear neutrophils (PMN), and compared for potency to cuprophan (Cu), already described as being a potent trigger of PMN. The release of lysozyme, beta-glucuronidase, lactic dehydrogenase (LDH), and the generation of a platelet aggregating activity were studied in the supernatants from plasma-free human PMN incubated with different membranes. The PMN intracellular content of neutrophil cationic proteins (NCP), elastase, and cathepsin G were also studied by immunofluorescence using specific antisera on smears of PMN before and after incubation with each membrane.

Protective effect of verapamil on the cardiac and circulatory alterations induced by platelet-activating factor.

The role of calcium channels in the mediation of the cardiovascular effects of synthetic (1-O-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) platelet-activating factor (PAF) was studied in vivo in the rabbit and in vitro in the coronary-perfused isolated heart and papillary muscle of the guinea pig following pretreatment with verapamil, a calcium antagonist. In the rabbit, verapamil (0.3 mg/kg) abrogated the ECG changes, and reduced all the hemodynamic alterations caused by PAF (0.

Production of platelet-activating factor by chick retina.

In the present study it is demonstrated that platelet-activating factor (PAF) was produced by chick retinas, upon stimulation with neurotransmitters such as acetylcholine (ACh), dopamine, or with calcium ionophore A23187, but not upon stimulation with gamma-amino-n-butyric acid, L-glycine, L-glutamate, epinephrine, or histamine. PAF produced in response to ACh, dopamine, or A23187 was not released into supernatants but was extractable from retinas. The amounts of extractable PAF increased after sonication of stimulated retinas.

Platelet-activating factor contracts human myometrium in vitro.

The myometrial contractile responses to synthetic 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (platelet-activating factor, PAF) and to oxytocin were evaluated in vitro on uterine (lower segment) strips obtained from pregnant women at term (39th week), undergoing elective cesarean section. Contractility was measured isometrically in an isolated organ bath using a superfusion technique. PAF in a concentration range between 5 and 100 nM as well as oxytocin (0.

In vitro contractile effect of platelet-activating factor on guinea-pig myometrium.

Platelet-activating factor (PAF) evoked myometrial contractions in two different patterns, depending on whether spontaneous activity was present. In spontaneously active myometrial strips (58%), both PAF and oxytocin enhanced the amplitude of myometrial contractions. In quiescent myometrial strips, PAF induced contractions characterized by a prompt development of tension, a plateau, and a final, rapid relaxation.

Platelet cationic proteins are present in glomeruli of lupus nephritis patients.

Synthetic polycations have been shown to bind and neutralize glomerular polyanions (GPA), thereby increasing the permeability of the glomerular capillary wall (GCW). In the present study it is demonstrated that human platelet-derived cationic proteins (HuPlt CP), which are able to increase cutaneous vascular permeability, bind in vitro to the GCW following incubation of normal human kidney sections with purified HuPlt CP or with washed human platelets stimulated with thrombin, immune complexes (IC) and platelet-activating factor (PAF), or stimulated with a suspension of washed human platelets and polymorphonuclear leukocytes in the presence of phagocytable substrate. The antiserum used in immunofluorescence test to detect the binding of HuPlt CP was specific for two different molecular types of HuPlt CP, both with an isoelectric point (pI) of 10.

Localization of cationic proteins derived from platelets and polymorphonuclear neutrophils and local loss of anionic sites in glomeruli of rabbits with experimentally-induced acute serum sickness.

The localization of cationic proteins (CP) derived from platelets and from polymorphonuclear neutrophils (PMN) in glomeruli of 42 rabbits injected i.v. with a large amount of bovine serum albumin, was investigated in sequential biopsies by immunofluorescence, using goat-anti-platelet CP and anti-PMN CP sera.

Fc receptor triggering induces expression of surface activation antigens and release of platelet-activating factor in large granular lymphocytes.

Triggering of large granular lymphocyte (LGL) Fc receptor with a specific monoclonal antibody (AB8.28) linked to an insoluble matrix induces cell activation, as witnessed by expression of HLA class II (DR and DQ) molecules and interleukin 2 receptor. Moreover, this event is accompanied by a concomitant release of platelet-activating factor by LGL.

Pathogenesis of passive Heymann glomerulonephritis: chlorpromazine inhibits antibody-mediated redistribution of cell surface antigens and prevents development of the disease.

Two hypotheses were tested: first, that in LEW rats the interaction of sheep (or rabbit) anti-brush border antibodies with antigens (Heymann antigens) expressed on the plasma membrane of glomerular visceral epithelial cells is characterized by initial redistribution of immune complexes on the cell surface and by subsequent shedding of immune complexes in the subepithelial part of the capillary wall; and secondly, that this interaction is inhibited by chlorpromazine, a drug that displaces calcium ions from binding sites linking the plasma membrane to the cytoskeleton, and which blocks the redistribution of IgG on the surface of B lymphocytes exposed to anti-IgG antibodies. The studies were performed in vitro on cultured LEW glomerular epithelial cells and in vivo in LEW rats. In cultured glomerular epithelial cells exposed at 37 degrees C to anti-brush border IgG, chlorpromazine prevented, in a dose-dependent manner, the redistribution ("capping") of Heymann antigens and the fixation of complement.

Effect of platelet-activating factor (PAF) on human cardiac muscle.

The effect of platelet activating factor (PAF) on three mechanical [maximal mechanical tension (Pmax); time to peak tension; maximal rate of rise of tension (+dP/dt)] and four electrical [action potential duration (APD); resting membrane potential; overshoot; maximum rate of depolarization] parameters of cardiac function was studied on fragments of isolated human cardiac papillary muscle. 20 specimens of small tissue fragments excised from the left ventricle by open heart surgery were challenged with various doses of synthetic PAF (10(-10)-10(-6) M). PAF, but not its biologically inactive 2-lyso-derivative (lyso-PAF), induced a biphasic dose-dependent effect, characterized by a transient positive effect on inotropism (increased Pmax, +dP/dt) and of APD, followed by a marked, prolonged negative effect on both inotropism (decreased Pmax, time to peak tension, +dP/dt) and APD.

In vivo interaction of antibodies with cell surface proteins used as antigens.

Antibody interactions with cell membrane glycoproteins in vivo exhibit features of aggregation and capping with resultant shedding similar to those events described in several in vitro isolated cell systems. Requirements for divalent ligand binding and participation of cytoskeletal elements are demonstrated in vivo as well. Persistence of antigen in immune complexes with complement interaction in situ appear to be necessary to induce an inflammatory response in vivo.

Cardiovascular alterations in the rabbit infused with platelet activating factor (PAF): effect of kadsurenone, a PAF-receptor antagonist.

The ECG and haemodynamic alterations caused by the i.v. infusion of platelet-activating factor (PAF) in the rabbit were studied after pretreatment with Kadsurenone, a specific PAF-receptor antagonist.

Antibody-induced redistribution of Heymann antigen on the surface of cultured glomerular visceral epithelial cells: possible role in the pathogenesis of Heymann glomerulonephritis.

In this study we analyze the ability of antibodies that produce passive Heymann glomerulonephritis to induce antigen redistribution on the surface of cultured glomerular visceral epithelial cells (GEC). Polyclonal antibodies produced by immunization with membrane vesicles prepared from proximal tubule brush borders (BB) and polyclonal (rabbit) and monoclonal (mouse) antibodies to a membrane glycoprotein (gp 330) purified from epithelial cells of rat proximal tubule were used. The study by immunofluorescence of GEC kept at 4 degrees C or fixed with paraformaldehyde showed that the three antibody preparations reacted with the plasma membrane in a punctate pattern known to be due to staining of coated pits or coated vesicles on the cell surface.

Murine monoclonal antibodies as probes for the phenotypical, functional, and molecular analysis of a discrete peripheral blood lymphocyte population exerting natural killer activity in vitro.

Two monoclonal antibodies (AB8.28 and A10) reacting with large granular lymphocytes were extensively studied and characterized. The two peripheral blood lymphocyte subsets positive for the expression of AB8.

Alkyl-ether phosphoglycerides influence calcium fluxes into human endothelial cells.

Suspended or adherent human endothelial cells (HEC) treated with 5 to 100 nM 1-O-octadecyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC, platelet-activating factor) showed a marked concentration and temperature-dependent increase in calcium uptake. This effect was also elicited by some AGEPC analogs. At 10 nM, the relative potencies were AGEPC = 100; 1-O-octadecyl-2-acetyl-sn-glycero-3-phosphoric acid (AGEPA) = 52.