Induction of apoptosis in human mitogen‐activated peripheral blood T‐lymphocytes by the ether phospholipid ET‐18‐OCH3: Involvement of the Fas receptor/ligand system

Activated T‐cells constitute a target for treatment of autoimmune diseases. We have found that the antitumour ether phospholipid 1‐O‐octadecyl‐2‐O‐methyl‐rac‐glycero‐3‐phosphocholine (ET‐18‐OCH3; edelfosine) induced dose‐ and time‐dependent apoptosis in human mitogen‐activated peripheral blood T‐lymphocytes, but not in resting T‐cells. T‐lymphocytes were stimulated with phytohemagglutinin and interleukin‐2 or with concanavalin A. Apoptosis was assessed by DNA fragmentation through cell cycle and TUNEL analyses, as well as through visualization of internucleosomal DNA fragmentation in agarose gels. The ET‐18‐OCH3‐mediated apoptotic response in activated T‐lymphocytes was less intense than in human leukaemic T cell lines, such as Jurkat cells and Peer cells; namely about 25% apoptosis in activated T‐cells versus about 46–61% apoptosis in T leukaemic cells after 24 h treatment with 10 μM ET‐18‐OCH3. The ET‐18‐OCH3 thioether analogue BM 41.440 (ilmofosine) showed a similar apoptotic capacity to that found with ET‐18‐OCH3 in activated T‐cells, whereas the phospholipid analogue hexadecylphosphocholine (miltefosine) failed to promote this response. The uptake of [3H]‐ET‐18‐OCH3 was much larger in activated T‐cells than in resting lymphocytes. Using a cytofluorimetric approach we have found that ET‐18‐OCH3 induced disruption of the mitochondrial transmembrane potential and production of reactive oxygen species in activated T‐cells, but not in resting lymphocytes. ET‐18‐OCH3 induced an increase in Fas (APO‐1/CD95) ligand mRNA expression in activated T‐cells, and incubation with a blocking anti‐Fas (APO‐1/CD95) antibody partially inhibited the ET‐18‐OCH3‐induced apoptosis of activated T‐lymphocytes. These results demonstrate that mitogen‐activated T‐cells, unlike resting lymphocytes, are able to take up significant amounts of ET‐18‐OCH3, and are susceptible to undergo apoptosis by the ether lipid via, in part, the Fas (APO‐1/CD95) receptor/ligand system. This ET‐18‐OCH3 apoptotic action can be of importance in the therapeutic action of this ether lipid in certain autoimmune diseases. British Journal of Pharmacology (1999) 127, 813–825; doi:10.1038/sj.bjp.0702606