SYNERGISTIC ENHANCEMENT OF NITRITE ON LYSOPHOSPHOLIPID-MEDIATED CYTOLYSIS

Nitrogen oxide, which is produced by activated macrophages, has been d emonstrated to possess anti-tumor activity. We report herein the syner gistic effect of sodium nitrite (NO2-) and/or sodium nitroprusside (SN P) on lysophospholipid (LysoPL)-mediated cytolysis. The incubation of Cr-51-labeled mouse melanoma (B16) cells with NO2- alone for 3h at 37 degrees C did not induce cytolysis. On the other hand, NO2- significan tly enhanced the cytolysis of B16 cells in the presence of lysophospha tidylcholine (LysoPC; 2.0 mu M). A similar effect of NO2- on B16-cytol ysis was also observed in the presence of 1-O-alkyl-sn-glycero-3-phosp hocholine (LysoPAF). In addition, SNP (0.05-0.5 mM) synergistically en hanced B16-cytolysis in the presence of LysoPC. However, nitrate had n o effect on the cytolysis of B16 cells treated with LysoPC. Furthermor e, NO2- synergistically enhanced the hemolysis of sheep erythrocytes i n the presence of LysoPC, but not in the presence of an anti-sheep ery throcyte antibody and complement. These findings suggest that NO2- dir ectly affects membrane damage in the presence of LysoPL.