Enhancement of Acetyl-CoA : 1-O-Alkyl-2-lyso-sn-glycero-3-phosphocholine Acetyltransferase Activity by Hydrogen Peroxide(Molecular and Cell Biology)

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The synthesis of platelet-activating factor (PAF) by human umbilical vein endothelial cell (HUVEC) in response to H_2O_2 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 5mM H_2O_2-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 H_2O_2-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 H_2O_2-treated cells. However, exogenous lyso-PAF addition had not effected to acetyltransferase activity. The acetyltransferase activity responded quickly to H_2O_2-treatment, but the activation was transitory. A tyrosine kinase inhibitor and a calmodulin antagonist blocked acetyltransferase activity in H_2O_2-stimulated cells, suggesting that tyrosine kinase and calcium/calmodulin-dependent protein kinase are involved in regulating acetyltransferase activity. These observations suggest that H_2O_2 is one of the modulators of lyso-PAF acetyltransferase activity via a phosphorylation system and platelet-activating factor (PAF) synthesis.
2007-02-01