kn-93 and diethyl-maleate

The synthesis of platelet-activating factor (PAF) by human umbilical vein endothelial cell (HUVEC) in response to H2O2 was significantly increased in a concentration-dependent manner. When HUVEC were pretreated with diethyl maleate, which depletes intracellular glutathione, PAF synthesis was enhanced 3-fold upon 5 mM H2O2-treatment. Intracellular redox was involved in regulating PAF synthesis, since the addition of antioxidants such as N-acetylcysteine, pyrrolidinecarbodithioic acid (PDTC), and Trolox reduced PAF production in H2O2-treated HUVEC. The activity of acetyl-CoA: 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyltransferase, which is involved in the last step of PAF synthesis, was also activated in H2O2-treated cells. However, exogenous lyso-PAF addition had not effected to acetyltransferase activity. The acetyltransferase activity responded quickly to H2O2-treatment, but the activation was transitory. A tyrosine kinase inhibitor and a calmodulin antagonist blocked acetyltransferase activity in H2O2-stimulated cells, suggesting that tyrosine kinase and calcium/calmodulin-dependent protein kinase are involved in regulating acetyltransferase activity. These observations suggest that H2O2 is one of the modulators of lyso-PAF acetyltransferase activity via a phosphorylation system and platelet-activating factor (PAF) synthesis.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Acetyltransferases; Antioxidants; Arachidonic Acid; Benzylamines; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Calmodulin; Cells, Cultured; Endothelial Cells; Genistein; Glutathione; Humans; Hydrogen Peroxide; Maleates; Oxidants; Platelet Activating Factor; Protein Kinase C; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Sulfonamides; Umbilical Veins