Assessment of changes in membrane properties of platelets from patients with chronic myeloid leukaemia in different stages of the disease.

Patients with chronic myeloproliferative leukemia (CML) have frequent haemorrhage and/or thrombosis in their medical history. The mechanisms of these major and life-threatening complications remain unclear. Membrane organization influences many of the unique cellular functions and is strongly correlated, among other factors, to the membrane lipid composition; it may be evaluated by following up the membrane fluidity and aggregation properties of the platelet. In this study, we evaluated the platelet aggregation, the expression of platelet surface receptors, the membrane fluidity (as evaluated by fluorescence anisotropy) and its correlation to reactive oxygen species (ROS) production, in patients with chronic myeloid leukaemia (CML). It was found that the patients in accelerated and blastic phase of CML present an altered platelet aggregation response to all reagents except for ristocetin as compared with chronic phase group, which shows only epinephrine-altered response. We also found that BCR/ABL transcript leads to higher levels of ROS in accelerated and blastic CML phases. Patients without molecular remission have lower platelet membrane fluidity. We obtained a positive correlation between ROS level and membrane fluorescence anisotropy changes. The CD41 expression was decreased in CML patients and P selectin expression was found to be higher in these patients than in healthy volunteers. Platelets of CML patients have altered aggregation parameters in accelerated and blastic phases, in which BCR/ABL transcript level is increased. The increased level of ROS in CML patients without molecular remission is associated with a decrease in fluidity of platelet membrane and expression of CD41/CD61 receptors. These findings may contribute to understanding the mechanism of the altered platelet response reported in CML patients.

Interaction of gentamicin polycation with model and cell membranes.

The interaction of positively-charged antibiotic gentamicin with cell membranes was studied to determine if any changes in membrane organization were induced by the drug. Opossum kidney epithelia (OK) cells were used as models of eukaryotic cells. Two methods were used: laurdan fluorescence spectroscopy and fluorescence anisotropy recordings on 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH) labeled cell suspensions. Both methods showed an altered membrane hydration and fluidity of gentamicin treated cells. Liposomes prepared from dimyristoyl-phosphatidylcholine (DMPC) mixed with cardiolipin, which mimics the heterogeneous charge composition of the natural cell membrane, were used to determine the effect of gentamicin on artificial bilayers. The membrane lipid packing as revealed by generalized polarization (GP) and fluorescence anizotropy variation with increasing temperature was studied. It was found that the generalized polarization of liposomal membranes containing a negatively charged lipid (cardiolipin) is higher in the presence of gentamicin; in the membrane of living cell (OK), gentamicin induces, on the contrary, a decrease of general polarization. Considering the role of membrane organization in the function of transmembrane channels and receptors, our findings suggest hypotheses that may explain the permeation of gentamicin through the living cell membrane by using these channels.