RESUMO
The effect of various differentiation inducers on membrane cell dynamics was studied using HL-60 and K562 leukemic cell lines. Membrane lipid dynamics was measured by the steady-state fluorescence polarization (P) method utilizing either 1,6-diphenyl-1,3,5-hexatriene (DPH) or the trimethyl ammonium derivative of DPH (TMA-DPH), which ascertains anchorage of the label to the membrane-water-lipid interface. Decrease in membrane microfluidity was observed in HL-60 cells undergoing differentiation into macrophages by 1,25-dihydroxyvitamin D3 and by K562 cells induced to differentiate by DMSO. Sodium butyrate caused an increase in membrane fluidity in K562 cells undergoing differentiation into erythroid-like cells while in HL-60 cells a dual effect was observed. At 0.4 mM concentration, in which the cells were induced to differentiate along the monocyte pathway, a decrease in membrane fluidity was observed, while at 1 mM concentration an increase in membrane fluidity occurred. Interferon-gamma (IFN-gamma) induced an increase in membrane fluidity in both cell lines. Using HL-60 cells fluorescently labeled by TMA-DPH, similar results indicating fluidization of the membrane following IFN-gamma treatment were obtained. Advanced fluorescence lifetime measurements, evaluated either by phase modulation spectrofluorometry or by single photon correlation fluorometry confirmed that the decrease in fluorescence polarization by IFN-gamma resulted from membrane fluidization and not from elongation of the probe's excited state lifetime. It is suggested that the inducer mode of action, and not the differentiation route, determine the outcome of changes in membrane microviscosity.
Assuntos
Butiratos/farmacologia , Calcitriol/farmacologia , Células HL-60/efeitos dos fármacos , Interferon gama/farmacologia , Leucemia Eritroblástica Aguda/patologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Lipídeos de Membrana/metabolismo , Succímero/farmacologia , Ácido Butírico , Diferenciação Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Difenilexatrieno/análogos & derivados , Polarização de Fluorescência , Corantes Fluorescentes , Células HL-60/metabolismo , Humanos , Leucemia Eritroblástica Aguda/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Fluidez de Membrana/efeitos dos fármacos , Proteínas Recombinantes , Células Tumorais Cultivadas/efeitos dos fármacosRESUMO
Fluorescence polarization, P, of 1,6-diphenyl-1,3,5-hexatriene was studied in Escherichia coli B/r. Modification of nutritional conditions was not compensated by homeoviscous adaptation, demonstrated to exist for temperature variations. Cell diameter, which is known also to vary with nutrition but not with temperature, was found to be positively correlated with 1/P, and may therefore be regulated by membrane lipid order and fluidity.
