Doxorubicin interactions at the membrane: evidence for a biphasic modulation of inositol lipid metabolism.
Doxorubicin, when incubated for 30 minutes with [32P]-labelled human erythrocyte membrane vesicles, produced an elevation of [32P]inositol-1,4,5-trisphosphate levels. The maximum rise was obtained with 10(-8) mol/l doxorubicin [132 (S.E. 13%) of control, n = 6, P = 0.001]. However, when the inositol lipids were examined, there was no evidence that doxorubicin stimulated the breakdown of [32P]phosphatidylinositol-4,5-bisphosphate under resting conditions, suggesting that the elevated levels of [32P]inositol 1,4,5-trisphosphate were not the result of the stimulation of phospholipase C. Instead, it was found that the dephosphorylation of inositol 1,4,5-trisphosphate by a 5'-phosphomonoesterase was partially inhibited by 10(-8) mol/l doxorubicin so that the rise in [32P]inositol 1,4,5-trisphosphate resulted from the inhibition of the breakdown of constitutively released [32P] inositol 1,4,5-trisphosphate. Similar data was also obtained with another aminoglycoside antibiotic, neomycin. The release of [32P] inositol 1,4-bisphosphate and [32P] inositol 1,4,5-trisphosphate and the breakdown of the inositol lipids in response to calcium (2.5 x 10(-4) and 10(-3) mol/l) stimulation was enhanced by doxorubicin (10(-6) to 10(-12) mol/l). These effects on resting and stimulated inositol lipid metabolism are discussed with reference to the paradoxical effects of doxorubicin to both stimulate and inhibit proliferation, according to concentration.
Thompson
M G
MG
Pharmaceutical Sciences Institute, Aston University, Birmingham, U.K.
Hickman
J A
JA
D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007295:Inositol Phosphates / Q000378:metabolism*; D009355:Neomycin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism
D007295:Inositol Phosphates; C044259:inositol 1,4-bis(phosphate); D004317:Doxorubicin; D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D009355:Neomycin; D002118:Calcium