today’s study we examined whether motility of Kaposi’s sarcoma (KS) spindle cells induced by HIV-1 Tat protein would depend on the formation of platelet-activating factor (PAF). affecting sufferers with individual immunodeficiency pathogen-1 (HIV-1) infections. KS is really a hemoangiosarcoma containing spindle-shaped cells vascular smooth cells endothelial cells and fibroblasts. 1-3 The growth and diffusion of KS have been ascribed to an imbalance in the network of soluble mediators caused by HIV-1 infection. 4 We have recently observed that platelet-activating Chelerythrine Chloride factor (PAF) produced by KS-derived spindle cells induces and sustains angiogenesis in a murine model. 5 Indeed PAF is a phospholipid mediator of cell-to-cell communication that belongs to the structurally related family of acetylated phosphoglycerides. 6 Recently it has been found that a mutation of a PAF-specific acetyl-hydrolase is the underlying defect of a congenital neurological disorder named Miller-Dieker lissencephaly Chelerythrine Chloride characterized by impaired migration Chelerythrine Chloride of central neurons. 7 Indeed several lines of evidence provide support for a role of this agent in regulating cell contraction migration and adhesion. 8 9 A number of factors such as tumor necrosis factor-α (TNFα) hepatocyte growth factor (HGF) and interleukin-12 able to induce these events were shown to act at least in part through the rapid synthesis of PAF. 10-12 A number of cell surface structures were shown to interact with Tat. First α5β1 and αvβ3 integrins may bind to Tat through its arginine-glycine-aspartic acid (RGD) sequence. 13 Moreover we found that HIV-1 Tat protein may interact with endothelial cells through binding to the mitogenic vascular endothelial growth factor-A (VEGF-A) receptor Flk-1. 14 Furthermore the chemokine receptors CCR2 and CCR3 may act as additional Tat receptors on monocytes. 15 Finally it has been shown that HIV-1 Tat may interact with Flk-1 on KS 38 cells activating a number of signal transduction pathways. 16 The aim of the present study was to evaluate whether HIV-1 Tat can stimulate the synthesis of PAF by KS cells and whether the newly synthesized PAF mediates the motogenic activity of Tat on these cells. Materials and Methods Reagents Synthetic C16 PAF (1-hexadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) was obtained from Bachem Feinchemikalien (Bubendorf Switzerland). CV 3988 was from Takeda Chemical Industries (Kyoto Japan). 15 CV 6209 and BN 52021 were purchased from Biomol (Plymouth Meeting PA). WEB 2170 was obtained from Boehringer Ingelheim KG Germany. 16 Silica gel 60F254 thin-layer chromatography (TLC) plates were obtained from Merck (Darmstadt Germany). mPorasil high-performance liquid chromatography (HPLC) columns were provided by Millipore Chromatographic Division (Waters Milford MA). RPMI 1640 medium was from GIBCO (Grand Island NY) and bovine calf serum (BCS) was from Hyclone Lab (Logan UT). Recombinant Tat was obtained from Intracell (London Chelerythrine Chloride UK). Polymyxin B phospholipase A2 phospholipase A1 bovine serum albumin (BSA) fraction V (tested for not more than 1 ng endotoxin per mg) FMLP phosphatidylcholine phosphatidylserine phosphatidylethanolamine were purchased from Sigma Chemical Company (St. Louis MO). Rabbit polyclonal IgG anti-human flk-1 Chelerythrine Chloride was obtained from Santa Cruz Biotechnology (Santa Cruz CA). RNF75 [3H]acetate ([3H]CH3CO2Na; 2.5 Ci/mmol) was obtained from NEN Life Science Products (Boston MA). In VitroPAF Synthesis by KS Cells KS Cell Migration Migration of KS Cells migration of endothelial cells and promote angiogenesis. 9 Recently we found that KS cells synthesize PAF after stimulation with cytokines and that PAF released in the supernatant of KS cells accounts at least in part for its angiogenic activity KS cell migration induced by Tat was inhibited by a panel of chemically different PAF receptor antagonists. Therefore one can envisage that PAF..