Pyruvate secreted by human lymphoid cell lines protects cells from hydrogen peroxide mediated cell death

Reactive oxygen species (ROS) released from polymorphonuclear leukocytes an d macrophages could cause DNA damage, but also induce cell death. Therefore inhibition of cell death must be an important issue for accumulation of ge netic changes in lymphoid cells in inflammatory foci. Scavengers in the pos t culture medium of four lymphoid cell lines, lymphoblastoid cell lines (LC L), Raji, BJAB and Jurkat cells, were examined, Over 80% of cultured cells showed cell death 24 h after xanthine (X)/xanthine oxidase (XOD) treatment, which was suppressed by addition of post culture medium from four cell lin es in a dose-dependent manner. H2O2 but not O-2(.-) produced by the X/XOD r eaction was responsible for the cytotoxity, thus we used H2O2 as ROS stress thereafter. The H2O2-scavenging activity of post culture media from four c ell lines increased rapidly at the first day and continued to increase in t he following 2-3 days for LCL, Raji and BJAB cells. The scavenging substanc e was shown to be pyruvate, with various concentrations in the cultured med ium among cell lines. Over 99% of total pyruvate was present in the extrace llular media and less than 1% in cells. alpha-Cyano-4-hydroxycinnamate, a s pecific inhibitor of the H+-monocarbohydrate transporter, increased the H2O 2-scavenging activity in the media from all four cell lines via inhibition of pyruvate re-uptake by cultured cells from the media. These findings sugg est that lymphoid cells in inflammatory foci could survive even under ROS b y producing pyruvate, so that accumulation of lymphoid cells with DNA damag e is possible.