diphenylhexatriene and cholesteryl-succinate

Infection of lymphocytes by the Epstein-Barr virus (EBV) is initiated by attachment of the major virus glycoprotein gp350/220 to a cell surface glycoprotein, known as CR2 (CD21). In a productive infection the virus envelope fuses with host cell membranes either at the cell surface or within endocytic vesicles. To investigate the relevance of host cell membrane properties in the fusion process, we used the lymphoblastoid cell lines Raji and Molt 4. Both cell lines express CR2 and bind EBV; however, only the Raji cell supports virus-cell fusion. Lipid analysis of the two cell lines indicated that Raji cells had a significantly lower cholesterol to phospholipid molar ratio due to a greater membrane content of phospholipid relative to protein. Determination of cell membrane fluid dynamics by fluorescence polarization indicated that the apparent membrane microviscosity of Molt 4 cells was significantly greater than that of Raji. Increasing Raji cell membrane apparent microviscosity to values similar to those of Molt 4 cells by incubation with cholesteryl-hemisuccinate caused a reduction in EBV fusion with Raji cells. However, experiments designed to allow EBV infection of Molt 4 cells whose plasma membranes had been fluidized were unsuccessful. These studies suggest that the lipid composition and other as yet unidentified factors are involved in entry of EBV into cells.

Topics: Cell Line; Cell Membrane; Cholesterol Esters; Diphenylhexatriene; Fluorescent Dyes; Herpesvirus 4, Human; Humans; Kinetics; Membrane Fluidity; Membrane Fusion; Membrane Lipids; Virus Replication; Viscosity

An experimental setup has been designed to allow fluorescence anisotropy measurements on labeled cell membranes under shear stress. An important change is observed when increasing the shear stress and varying the experimental parameters indicates that a decrease in membrane cohesion leads to a subsequent increase in the membrane alteration under shear stress. A model has been developed that shows, in agreement with experiment, that the effect observed is mainly the result of the alteration of the membrane, elongation, and orientation with respect to the fluid flow, which can be estimated.

Topics: Cholesterol; Cholesterol Esters; Diphenylhexatriene; Erythrocyte Membrane; Fluorescence Polarization; Fluorescent Dyes; Humans; Models, Biological; Stress, Mechanical; Temperature

The mitogenic effect of thyrotropin on functional rat thyroid cells of the line FRTL-5 is correlated with membrane lipid fluidity as evaluated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. Continued exposure of FRTL-5 cells to a medium lacking thyrotropin causes cessation of cell proliferation and a decrease in membrane lipid fluidity which reaches its minimum in approximately 8 days. The change in lipid fluidity is due to an absolute increase (greater than 2-fold) of membrane cholesterol, with an increased cholesterol/phospholipid ratio and an increased ratio of saturated to unsaturated fatty acids of the membrane phospholipids, contributed primarily by a nearly 4-fold increase in the ratio of saturated to unsaturated C16 fatty acids. It is also associated with a variation of the relative proportions of the major membrane phospholipids; thus, phosphatidylinositol and phosphatidylethanolamine decrease while phosphatidylcholine increases. Both membrane fluidity and lipid composition can be restored by thyrotropin to their original levels, i.e. levels measured under continuous exposure to the hormone. Complete reversal requires at least 48 h, i.e. approximately the same time required for resumption of growth when FRTL-5 cells, starved in thyrotropin, are re-exposed to the hormone. Changes in lipid composition and fluidity can be prevented or can be reversed if FRTL-5 cells are exposed to dibutyryl cAMP while being deprived of thyrotropin. Dibutyryl cAMP has only a modest direct effect on growth; however, this pretreatment eliminates the 48-h lag phase with respect to thyrotropin stimulation. It is proposed that the effects of thyrotropin on growth of FRTL-5 cells requires a modification of the molecular structure and the physical state of cell membranes, which can be mediated by cAMP, although cAMP is not sufficient by itself to promote growth.

Topics: Animals; Bucladesine; Cell Division; Cell Line; Cholesterol Esters; Cyclic AMP; Diphenylhexatriene; Fatty Acids; Fluorescence Polarization; Membrane Fluidity; Membrane Lipids; Rats; Thyroid Gland; Thyrotropin; Time Factors

Several chemical effectors were used to induce changes in spleen B cell membrane fluidity. Membrane fluidity was monitored by fluorescence polarization analysis of the hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene (DPH) and cell viability was checked not to be affected by the treatments. Membrane immunoglobulin (Ig) endocytosis by the living B cells with modified or unmodified membranes was quantitatively measured by flow cytometry, using a previously described method (Métézeau et al., 1982, 1984). The kinetics of endocytosis of membrane Ig was not affected by chemical effectors increasing membrane fluidity. On the contrary, increasing membrane microviscosity resulted in the slowing down and eventually the blocking of membrane Ig endocytosis. It is suggested that a step depending on membrane microviscosity is involved in the process of endocytosis; this step may become rate limiting when membranes are artificially rendered or naturally become (i.e. for pathological or particularly differentiated cells) more viscous.

Topics: Animals; B-Lymphocytes; Cell Membrane; Cell Survival; Cholesterol Esters; Diphenylhexatriene; Endocytosis; Flow Cytometry; Immunoglobulins; Liposomes; Male; Membrane Fluidity; Membrane Lipids; Mice; Mice, Inbred Strains; Phospholipids

Important cellular functions, such as rheological properties of cells are presumably related to the membrane lipid fluidity which may be approached by the use of fluorescence polarization method. However, biological membranes represent very heterogeneous media and the knowledge of the fluidity of membrane compartments requires the use of different probes. Two fluorescent probes, DPH and its cationic derivative, TMA-DPH, have been employed to probe the lipid fluidity of human platelets and red cell membranes. The results show that the informations given by DPH and TMA-DPH can present important differences, suggesting that DPH and TMA-DPH are localized in different regions of cell membranes. In an attempt to investigate relations between lipid fluidity and rheological properties of red cells, the behavior of probes was studied in a "Couette" viscometer with a device for studying the emissive properties of probes when red cell membranes are under shear conditions.

Topics: Blood Platelets; Cholesterol Esters; Diphenylhexatriene; Erythrocyte Membrane; Erythrocytes; Fluorescence Polarization; Fluorescent Dyes; Humans; Kinetics; Membrane Fluidity; Temperature

The effect of nitrogen mustard (2-chloro-N-2-chloroethyl-N-methylethanamine), Trenimon (2,3,5-trisethyleneiminobenzoquinone-1,4), chlorambucil (4-[p-(bis[2-chloroethyl]amino)-phenyl]butyric acid) and phosphamide mustard (N,N-bis(2-chloroethyl)-diamidophosphoric acid) on Na+/K+-ATPase, membrane fluidity and cell multiplication was studied. With the exception of chlorambucil which does not affect Na+/K+-ATPase all concentrations of the other alkylating agents which inhibit cell multiplication of Ehrlich ascites tumor cells depress the activity of the Na+/K+-ATPase. All alkylating agents--including chlorambucil--caused an increase in the apparent degree of fluorescence polarization after labelling of the plasma membrane with 1,6-diphenyl-1,3,5-hexatriene (DPH). This effect is interpreted as a decrease in membrane fluidity caused by the alkylating drugs. The decrease in membrane fluidity is due to a direct interaction of the alkylating agent with the plasma membrane and is expressed at all concentrations of the drug which inhibit cell proliferation. No effect on membrane fluidity is observed after treatment of cells resistant to nitrogen mustard. The biological consequence of a decrease in membrane fluidity was investigated by growing Friend erythroleukemia cells in the presence of 10 mM cholesterol hemisuccinate. This procedure raises the microviscosity of the plasma membrane and depresses cell proliferation.

Topics: Alkylating Agents; Animals; Antineoplastic Agents; Carcinoma, Ehrlich Tumor; Cell Division; Cell Survival; Chlorambucil; Cholesterol Esters; Diphenylhexatriene; Fluorescence Polarization; Membrane Fluidity; Mice; Nitrogen Mustard Compounds; Sodium-Potassium-Exchanging ATPase; Triaziquone; Viscosity