Binding of Adriamycin to Liposomes as a Probe for Membrane Lateral Organization

Abstract

A stopped-flow spectrofluorometer equipped with a rapid scanning emission monochromator was utilized to monitor the binding of adriamycin to phospholipid liposomes. The latter process is evident as a decrease in fluorescence emission from a trace amount of a pyrene-labeled phospholipid analog (PPDPG, 1-palmitoyl-2-[(6-pyren-1-yl)]decanoyl-sn-glycero-3-phospho-rac-++ +glyce rol) used as a donor for resonance energy transfer to adriamycin. For zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes, fluorescence decay was slow, with a half-time t1/2 of approximately 2 s. When the mole fraction of the acidic phospholipid, 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol (POPG), was increased to XPG >/= 0.04, the decay of fluorescence became double exponential, and an additional, significantly faster process with t1/2 in the range between 2 and 4 ms was observed. Subsequently, as XPG was increased further, the amplitude of the fast process increased, whereas the slower process was attenuated, its t1/2 increasing to 20 s. Increasing [NaCl] above 50 mM or [CaCl2] above 150 microM abolished the fast component, thus confirming this interaction to be electrostatic. The critical dependence of the fast component on XPG allows the use of this process to probe the organization of acidic phospholipids in liposomes. This was demonstrated with 1, 2-palmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes incorporating PPDPG (XPPDPG = 0.03), i.e., conditions where XPG in fluid bilayers is below the required threshold yielding the fast component. In keeping with the presence of clusters of PPDPG, the fast component was observed for gel-state liposomes. At approximately 34 degreesC (i.e., 6 degrees below Tm), the slower fluorescence decay also appeared, and it was seen throughout the main phase transition region as well as in the liquid-crystalline state. The fluorescence decay behavior at temperatures below, above, and at the main phase transition temperature is interpreted in terms of thermal density fluctuations and an intermediate state between gel and liquid-crystalline states being involved in the phospholipid main phase transition. This is the first observation of a cluster constituted by acidic phospholipids controlling the membrane association of a drug.

Chronic clozapine reduces rat brain arachidonic acid metabolism by reducing plasma arachidonic acid availability

“…CLZ is an amphiphilic molecule that is positively charged at physiologic pH, and can interact with acidic and neutral phospholipid polar head groups via electrostatic and repulsion forces (Soderlund et al . ; Jutila et al . ; Parry et al .…”

Interactions of Cyclosporin A with Phospholipid Membranes: Effect of Cholesterol

“…There is no reason to believe that the modulation of specific properties of the lipid bilayer would be limited to the above cytotoxic peptides; it could contribute to both the therapeutic mechanism and side effects of membrane-partitioning compounds in general. To this end, a large variety of structurally dissimilar drugs are hydrophobic or amphiphilic and readily partition into lipid membranes; good examples are tacrine (Lehtonen et al, 1996), doxorubicin (Mustonen et al, 1993;Söderlund et al, 1999), andCsA (OЈLeary et al, 1986;Wiedmann et al, 1990). Drugs may also modulate peripheral lipid-protein interactions, as shown for chlorpromazine, doxorubicin, lidocaine, and gentamycin (Ito et al, 1983;Mustonen and Kinnunen, 1991;Jutila et al, 1998).…”

MPP1 interacts with DOPC/SM/cholesterol in an artificial membrane system using Langmuir-Blodgett monolayer

“…Therefore, it is relevant to understand the forces controlling the lateral ordering and diffusion of lipids and their basic physical chemistry. In brief, laterally-separated phases may be induced by enzymatic cleavage of lipids (Holopainen et al 1998), temperature (Mouritsen 1991), surface electrostatic associations (Rytömaa and Kinnunen 1996), and lipid-lipid (Lehtonen et al 1996;Söderlund et al 1999) or lipid-protein (Mouritsen and Bloom 1984) interactions. The ternary mixture consisting of dioleoylphosphatidylcholine (DOPC), sphingomyelin (SM) and cholesterol (Chol) has been used as a membrane-mimicking model (Yuan et al 2002;Kulma et al 2010;Nyholm et al 2011;Tsukamoto et al 2014).…”