Tumor necrosis factor/cachectin stimulates peritoneal macrophages, polymorphonuclear neutrophils, and vascular endothelial cells to synthesize and release platelet-activating factor.

Abstract

Platelet-activating factor (PAF)' is a mediator of inflammation with a wide range of biological activities (see reference 1 for review) . PAF was initially recognized as a product of IgE-sensitized rabbit basophils (2) and was identified with 1-0-alkyl-2-sn-glyceryl-3-phosphorylcholine (3-5). It was subsequently shown that PAF is synthesized after appropriate stimulation by monocytes/macrophages (6-9), polymorphonuclear neutrophils (7, 10, 11), platelets (12) and endothelial cells (13-15) . PAF induces aggregation and degranulation of platelets (2, 16), stimulates contraction of smooth muscle (17), promotes chemotaxis and granule secretion of neutrophils (18-19) and monocytes (20), increases vascular permeability, and alters the vascular tone (21).It was recently suggested that PAF is a mediator of endotoxic shock (22-24) on the basis of the following observations : (a) PAF is produced during endotoxic shock and experimental sepsis by Gram-negative bacteria (23-25) ; (b) infusion of experimental animals with PAF results in hypotension, decrease in cardiac output, and hypovolemic shock (26-28) ; (c) three PAF receptor antagonists (CV3988, kadsurenone, and SRI 63072) inhibit or reverse endotoxin-induced hypotension and, in this way, prolong the survival of rats (22,23,29) .Tumor necrosis factor/cachectin (TNF) is a mediator of endotoxic shock (30). Because TNF administration to experimental animals reproduces several aspects of PAF infusion (30), it seems possible that PAF is synthesized in response to

The Long Pentraxin Ptx3 Is Synthesized in IgA Glomerulonephritis and Activates Mesangial Cells

“…The supernatants and cell pellets were extracted according to a modification of the Bligh and Dyer procedure (24), with formic acid added to lower the pH of the aqueous phase to 3.0. PAF was quantified after extraction and purification by TLC (silica gel plates 60 F254, Merck, Darmstadt, Germany) and HPLC ( Porasil column; Millipore Chromatographic Division, Waters Corp., Milford, MA) by aggregation of washed rabbit platelets as previously reported (23,25).…”

Platelet-activating Factor Receptor Agonists Mediate Xeroderma Pigmentosum A Photosensitivity

“…PAF is synthesized enzymatically in response to diverse stimuli, including cytokines, endotoxin, Ca 2ϩ ionophores, and PAF itself (22)(23)(24)(25). In addition, PAF and sn-2 short-chain acyl glycerophosphocholines (GPCs) with PAF receptor (PAF-R) agonistic activity can also be produced through free radical-mediated cleavage of membrane GPC (26 -29).…”

Application of Flow Cytometry in the Studies of Microparticles

“…It has been hypothesized that TMV shedding may be a way for the tumor cells to dispose of "unwanted", immunogenic molecules from their surface. Indeed, apoptosis-inducing proteins and terminal components of complement have been shown to be shed via TMV in some tumors [Abid Hussein et al 2007;van Doormaal, et al 2009;Camussi et al 1987;Sims et al 1988 [Whiteside, 2005, Abrahams et al, 2003, Bergmann C., et al 2009]. Suppressive activity of TMV was also described by Szajnik et al [Szajnik et al, 2010].…”