Antimicrobial peptides (AMPs) represent a class of molecules synthesized by different organisms as an ancient innate defense mechanism against different pathogens like bacteria, fungi, viruses. Their characteristics make them good candidates to fight against bacteria together with or as an alternative to antibiotics. To decide on AMPs suitability for use in mammalian systems we redefined a 'therapeutic index' using the concentrations for which AMP is active against pathogens without inducing cytotoxic damage to the mammalian cells. Here we analyzed the toxic effects of eleven, highly active cationic AMPs towards human cells. The AMPs cytotoxicity was determined using common standardized assays measuring their effect on red blood cells (hemolytic index) and on lymphocytes (cell viability). The therapeutic index was calculated for all the AMPs tested. The highest therapeutic index was found for cecropins followed by magainins and the smallest for Melittin. For two peptides, Cecropin A which presents the highest therapeutic index and Melittin with the smallest therapeutic index we characterized in detail the cell death process distinguishing between apoptosis and necrosis. The toxic effects produced by Cecropin A and Melittin are induced mostly by means of apoptosis suggesting that the definition of therapeutic index has to consider the apoptotic effects of AMPs. Thus we provided here a unitary way to characterize the side effects of AMPs. The analysis of in vitro cytotoxic effects of AMPs using the global concept of therapeutic index can be a powerful way to decide which peptide can be taken for further testing in preclinical trials.
In this study, we have investigated the dependence of Na+ transport regulation on membrane cholesterol content in A6 renal epithelia. We continuously monitored short-circuit current (Isc), transepithelial conductance (GT), and transepithelial capacitance (CT) to evaluate the effects of cholesterol extraction from the apical and basolateral membranes in steady-state conditions and during activation with hyposmotic shock, oxytocin, and adenosine. Cholesterol extraction was achieved by perfusing the epithelia with methyl-beta-cyclodextrin (mbetaCD) for 1 h. In steady-state conditions, apical membrane cholesterol extraction did not significantly affect the electrophysiological parameters; in contrast, marked reductions were observed during basolateral mbetaCD treatment. However, apical mbetaCD application hampered the responses of Isc and GT to hypotonicity, oxytocin, and adenosine. Analysis of the blocker-induced fluctuation in Isc demonstrated that apical mbetaCD treatment decreased the epithelial Na+ channel (ENaC) open probability (Po) in the steady state as well as after activation of Na+ transport by adenosine, whereas the density of conducting channels was not significantly changed as confirmed by CT measurements. Na+ transport activation by hypotonicity was abolished during basolateral mbetaCD treatment as a result of reduced Na+/K+ pump activity. On the basis of the findings in this study, we conclude that basolateral membrane cholesterol extraction reduces Na+/K+ pump activity, whereas the reduced cholesterol content of the apical membranes affects the activation of Na+ transport by reducing ENaC Po.
Dielectrophoresis was employed to distinguish the electroporated from non-electroporated cells. It was found that the electric field frequency at which cells change the direction of their movement (the crossover frequency f(CO)) is higher when cells are electroporated. The contribution to the cell dielectrophoretic behavior of four electric and geometrical cell parameters was analyzed using a single shell model. f(CO) measurements were performed in media with conductivities of 0.001-0.09S/m, on B16F10 cells which were electroporated in a Mannitol solution (0.001S/m), using rectangular or exponential pulses. The control cells' f(CO) was found in a domain of 2 to 105 kHz, while the electroporated cells' f(CO) was in a domain of 5 to 350 kHz, depending on the external media conductivities. At exterior conductivities above ~0.02S/m, f(CO) of electroporated cells became significantly higher compared to controls. Even though the possible contribution of membrane permittivity to explain the observed f(CO) shift toward higher values cannot be excluded, the computations highlight the fact that the variation of cytosol conductivity might be the major contributor to the dielectrophoretic behavior change. Our experimental observations can be described by considering a linear dependence of electroporated cells' cytosol conductivity against external conductivity.
Nanotechnology has been successfully used for the fabrication of targeted anti-cancer drug carriers. This study aimed to obtain Fe3O4 nanoparticles functionalized with Gemcitabine to improve the cytotoxic effects of the chemotherapeutic substance on cancer cells. The (un) functionalized magnetite nanoparticles were synthesized using a modified co-precipitation method. The nanoconjugate characterization was performed by XRD, SEM, SAED and HRTEM; the functionalizing of magnetite with anti-tumor substances has been highlighted through TGA. The interaction with biologic media has been studied by means of stability and agglomeration tendency (using DLS and Zeta Potential); also, the release kinetics of the drug in culture media was evaluated. Cytotoxicity of free-Gemcitabine and the obtained nanoconjugate were evaluated on human BT 474 breast ductal carcinoma, HepG2 hepatocellular carcinoma and MG 63 osteosarcoma cells by MTS. In parallel, cellular morphology of these cells were examined through fluorescence microscopy and SEM. The localization of the nanoparticles related to the cells was studied using SEM, EDX and TEM. Hemolysis assay showed no damage of erythrocytes. Additionally, an in vivo biodistribution study was made for tracking where Fe3O4@Gemcitabine traveled in the body of mice. Our results showed that the transport of the drug improves the cytotoxic effects in comparison with the one produced by free Gemcitabine for the BT474 and HepG2 cells. The in vivo biodistribution test proved nanoparticle accumulation in the vital organs, with the exception of spleen, where black-brown deposits have been found. These results indicate that our Gemcitabine-functionalized nanoparticles are a promising targeted system for applications in cancer therapy.
Protein and peptide interactions are characterized in the liquid state by multidimensional NMR spectroscopy experiments, which can take hours to record. We show that starting from hyperpolarized HDO, two-dimensional (2D) proton correlation maps of a peptide, either free in solution or interacting with liposomes, can be acquired in less than 60 s. In standard 2D NMR spectroscopy without hyperpolarization, the acquisition time required for similar spectral correlations is on the order of hours. This hyperpolarized experiment enables the identification of amino acids featuring solvent-interacting hydrogens and provides fast spectroscopic analysis of peptide conformers. Sensitivityenhanced 2D proton correlation spectroscopy is a useful and straightforward tool for biochemistry and structural biology, as it does not recur to nitrogen-15 or carbon-13 isotope enrichment.
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