Interaction of 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate with mimetic membranes and cytotoxic effect on leukemic cells

Abstract

10-(Octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC) is an alkylphospholipid that can interact with cell membranes because of its amphiphilic character. We describe here the interaction of ODPC with liposomes and its toxicity to leukemic cells with an ED-50 of 5.4, 5.6 and 2.9 microM for 72 h of treatment for inhibition of proliferation of NB4, U937 and K562 cell lines, respectively, and lack of toxicity to normal hematopoietic progenitor cells at concentrations up to 25 microM. The ED-50 for the non-malignant HEK-293 and primary human umbilical vein endothelial cells (HUVEC) was 63.4 and 60.7 microM, respectively. The critical micellar concentration (CMC) of ODPC was 200 microM. Dynamic light scattering indicated that dipalmitoylphosphatidylcholine (DPPC) liposome size was affected only above the CMC of ODPC. Differential calorimetric scanning (DCS) of liposomes indicated a critical transition temperature (T(c)) of 41.5 degrees C and an enthalpy (H) variation of 7.3 kcal mol(-1). The presence of 25 microM ODPC decreased T(c) and H to 39.3 degrees C and 4.7 kcal mol(-1), respectively. ODPC at 250 microM destabilized the liposomes (36.3 degrees C, 0.46 kcal mol(-1)). Kinetics of 5(6)-carboxyfluorescein (CF) leakage from different liposome systems indicated that the rate and extent of CF release depended on liposome composition and ODPC concentration and that above the CMC it was instantaneous. Overall, the data indicate that ODPC acts on in vitro membrane systems and leukemia cell lines at concentrations below its CMC, suggesting that it does not act as a detergent and that this effect is dependent on membrane composition.

Linker for Activation of T-cell Family Member2 (LAT2) a Lipid Raft Adaptor Protein for AKT Signaling, Is an Early Mediator of Alkylphospholipid Anti-leukemic Activity

“…Cell viability was determined via trypan blue assay, and only cultures with Ն95% viability were used. ODPC was synthesized as described elsewhere (11,19) and tested at 25 M concentration for 3, 6, 12, and 24 h with phosphate buffered saline (PBS) as the vehicle control. Apoptotic events were detected via annexin-V and propidium iodide assays using flow cytometry (11).…”

“…There is strong experimental evidence that LAT2 is palmitoylated in vivo (36,44). We have demonstrated that ODPC disrupts model lipid bilayers (11). We tested whether other substances that target lipid rafts would have the same effects on LAT2 as observed for ODPC in NB4 cells.…”

“…We demonstrated that 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC) targets high cholesterol raft-like domains in model membranes and induces apoptosis in leukemia cells, with an effective dose of 25 M after 24 h in NB4 cells, but has no effect on normal hematopoietic and epithelial cells under the same conditions (11).…”

“…Therefore, the development of therapeutic strategies for disrupting raft-based cell signaling in cancer represents a potentially useful approach. We and others have presented evidence that alkylphospholipid (APL) 1 drugs target raft structure in leu- kemia (11) and lymphoma cells (12). One such APL, perifosine, is currently in clinical trials as an anti-cancer therapeutic agent (13).…”

Proteoliposomes in nanobiotechnology

“…These multilamellar systems can be sonicated or forced to go through (extrusion) pores of nanometric dimensions, to form unilamellar systems (with a single concentric bilayer), very similar to the natural membranes. The sonication as well as the extrusion process supplies the necessary energy to break the different lamellae and to re-organize the bilayers in uniform and control-sized vesicles (New 1990;Camolezi et al 1999Camolezi et al , 2002Ierardi et al 2002;Daghastanli et al 2004;Santos et al 2002Santos et al , 2005Rigos et al 2008;dos Santos et al 2010).…”