Dissociation of the effects of the antitumour ether lipid ET-18-OCH3 on cytosolic calcium and on apoptosis.
1. We have compared the effects of 1-O-octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-OCH3) on the cytosolic free calcium concentration ([Ca2+]i) and on apoptosis in several normal and leukaemia cells, including human polymorphonuclear neutrophils (PMNs), U937 cells, and undifferentiated as well as dimethylsulphoxide-differentiated HL60 cells (uHL60 and dHL60, respectively). 2. ET-18-OCH3 produced apoptosis, as evidenced by DNA degradation into oligonucleosome-size fragments, in U937 and uHL60 cells, but not in dHL60 cells or PMNs. 3. ET-18-OCH3 induced an increase in [Ca2+]i mediated through the platelet-activating factor (PAF) receptor in U937, dHL60 cells and PMNs, as shown by cross-desensitization experiments and by prevention of the [Ca2+]i changes by the PAF antagonist WEB-2170. The EC50 values for the increase in [Ca2+]i induced by PAF and ET-18-OCH3 were 5 x 10(-11) and 2.5 x 10(-7) M, respectively. In uHL60 cells the effect of ET-18-OCH3 on [Ca2+]i was very small and was not affected by WEB-2170. 4. PAF did not produce apoptosis in any of the cell types tested. WEB-2170 did not prevent the apoptosis induced by ET-18-OCH3. 5. The uptake of [3H]-ET-18-OCH3 was much larger in U937 and uHL60 cells than in dHL60 cells and PMNs. 6. Our results indicate that the apoptotic effect of ET-18-OCH3 is not related to the changes in [Ca2+]i, effected by interaction with plasma membrane PAF receptors, but to other actions which are associated with the uptake of this drug into the cells.
Alonso
M T
MT
Departamento de Bioquímica y Biología Molecular y Fisiología, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid-Consejo Superior de Investigaciones Científicas, Facultad de Medicina, Spain.
Gajate
C
C
Mollinedo
F
F
Modolell
M
M
Alvarez
J
J
García-Sancho
J
J
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D010742:Phospholipid Ethers / Q000494:pharmacology*; D010972:Platelet Activating Factor / Q000494:pharmacology
D000970:Antineoplastic Agents; D010742:Phospholipid Ethers; D010972:Platelet Activating Factor; C026659:edelfosine; D002118:Calcium