Inhibition of phosphatidylserine synthesis in Jurkat T cells by hydrogen peroxide

Incubation of Jurkat cells in the presence of H2O2 either directly added to the culture medium or generated with glucose oxidase. menadione or the couple xanthinr/xanthine oxidase induced a marked decrease of phosphatidylserine synthesis in the absence of changes in the synthesis of phosphatidylcholine and phosphatidylethanolamine. Concentration dependent response curves indicated that H2O2 induced inhibition of phosphatidylserine synthesis with an IC50 = 5 muM while both induction of tyrosine phosphorylation of proteins and Ca2+ signals were obtained with an EC50 = 300 muM. The tyrosine kinase and Ca2+ independent mechanism was confirmed by comparing the H2O-induced and the CD3-induced inhibition of phosphatidylserine synthesis using several Jurkat clones differing in the expression of cell surface receptors such as CD3/TCR and CD45 and protein tyrosine kinase such as p72(syk) ZAP-70 and p56(ick). While CD3-induced inhibition of phosphatidylserine synthesis necessitates protein tyrosine phosphorylation and Ca2+ signals, H2O2 provoked its effect in all the clones studied independently of the presence or absence of the proteins previously shown to be key elements in T cell signal transduction. Conversely. the antioxidant molecule, butylated hydroxanisole, generates an increased PtdSer synthesis, suggesting that the synthesis of this phospholipid is regulated by the redox status of the cells. (C) 2001 Elsevier Science B.V. All rights reserved.