6 research outputs found
Characterization of the Interactions between Fluoroquinolone Antibiotics and Lipids: a Multitechnique Approach
Probing drug/lipid interactions at the molecular level represents an important challenge in pharmaceutical research and membrane biophysics. Previous studies showed differences in accumulation and intracellular activity between two fluoroquinolones, ciprofloxacin and moxifloxacin, that may actually result from their differential susceptibility to efflux by the ciprofloxacin transporter. In view of the critical role of lipids for the drug cellular uptake and differences observed for the two closely related fluoroquinolones, we investigated the interactions of these two antibiotics with lipids, using an array of complementary techniques. Moxifloxacin induced, to a greater extent than ciprofloxacin, an erosion of the DPPC domains in the DOPC fluid phase (atomic force microscopy) and a shift of the surface pressure-area isotherms of DOPC/DPPC/fluoroquinolone monolayer toward lower area per molecule (Langmuir studies). These effects are related to a lower propensity of moxifloxacin to be released from lipid to aqueous phase (determined by phase transfer studies and conformational analysis) and a marked decrease of all-trans conformation of acyl-lipid chains of DPPC (determined by ATR-FTIR) without increase of lipid disorder and change in the tilt between the normal and the germanium surface (also determined by ATR-FTIR). All together, differences of ciprofloxacin as compared to moxifloxacin in their interactions with lipids could explain differences in their cellular accumulation and susceptibility to efflux transporters
Kinetic analysis of the nucleic acid chaperone activity of the Hepatitis C virus core protein
The multifunctional HCV core protein consists of a hydrophilic RNA interacting D1 domain and a hydrophobic D2 domain interacting with membranes and lipid droplets. The core D1 domain was found to possess nucleic acid annealing and strand transfer properties. To further understand these chaperone properties, we investigated how the D1 domain and two peptides encompassing the D1 basic clusters chaperoned the annealing of complementary canonical nucleic acids that correspond to the DNA sequences of the HIV-1 transactivation response element TAR and its complementary cTAR. The core peptides were found to augment cTAR-dTAR annealing kinetics by at least three orders of magnitude. The annealing rate was not affected by modifications of the dTAR loop but was strongly reduced by stabilization of the cTAR stem ends, suggesting that the core-directed annealing reaction is initiated through the terminal bases of cTAR and dTAR. Two kinetic pathways were identified with a fast pre-equilibrium intermediate that then slowly converts into the final extended duplex. The fast and slow pathways differed by the number of base pairs, which should be melted to nucleate the intermediates. The three peptides operate similarly, confirming that the core chaperone properties are mostly supported by its basic clusters
Interactions between fluoroquinolones and lipids : biophysical studies
Probing fluoroquinolones/lipid interactions at the molecular level represents an important challenge in both membrane biophysics and pharmaceutical research.
As the pharmacological target of these antibiotics is intracellular, they must pass across the bacterial membranes. Likewise, fluoroquinolones enter eukaryotic cells, which imply their ability of interacting with lipids membranes. In this context, the aim of my Thesis has been to characterize the effect of two closely related fluoroquinolones, ciprofloxacin and moxifloxacin, on physicochemical properties of the major phospholipids DPPG and DOPC/DPPC that are mimicking the prokaryotic and eukaryotic lipid membranes, respectively, by means of biophysical methods.
First, I have studied the effect of these drugs on domains lipids erosion, lipids packing and their ability of modifying the conformation and orientation of the acyl chain(s) of phospholipids.
Second, I have determined the binding affinities of ciprofloxacin to different model lipid membranes (DPPG, DPPC) and its effects on head group mobility and on thermotropic profile of these two phospholipids.
The data reported in this Thesis point to different effects of ciprofloxacin and moxifloxacin on the phospholipids tested. Indeed, moxifloxacin induces more changes in the acyl chain conformation of phospholipids and has more lipid packing effects than ciprofloxacin. The latter interacts primarily with the head groups of lipids, and thereby modifies the orientation of the acyl chain. Thus, the first step in the interaction of ciprofloxacin with lipid membranes relates to its binding to these headgroups, which is stronger with negatively charged (DPPG) than with zwitterionic phospholipids (DPPC). Conversely, our results suggest that moxifloxacin is located in a more hydrophobic environment of the membranes, probably by creating a pocket in the interior of the lipid bilayer. These contrasting behaviors may be related to the fact that ciprofloxacin is, globally speaking, a more hydrophilic drug than moxifloxacin.
Our work may help in shedding more light on the role played by lipids in the transport of fluoroquinolones in both prokaryotic and eukaryotic cells.(FARM 3) -- UCL, 201
Kinetic analysis of the nucleic acid chaperone activity of the Hepatitis C virus core protein
10.1093/nar/gkq094NUCLEIC ACIDS RESEARCH38113632-364
Interactions Of Ciprofloxacin With Dppc And Dppg: Fluorescence Anisotropy, Atr-Ftir And P-31 Nmr Spectroscopies And Conformational Analysis
The interactions between a drug and lipids may be critical for the
pharmacological activity. We previously showed that the ability of a
fluoroquinolone antibiotic, ciprofloxacin, to induce disorder and modify the
orientation of the acyl chains is related to its propensity to be expelled from a
monolayer upon compression [1]. Here, we compared the binding of ciprofloxacin on
DPPC and DPPG liposomes (or mixtures of phospholipids [DOPC:DPPC], and
[DOPC:DPPG]) using quasi-elastic light scattering and steady-state fluorescence
anisotropy. We also investigated ciprofloxacin effects on the transition
temperature (T(m)) of lipids and on the mobility of phosphate head groups using
Attenuated Total Reflection Fourier Transform Infrared-Red Spectroscopy
(ATR-FTIR) and (31)P Nuclear Magnetic Resonance (NMR) respectively. In the
presence of ciprofloxacin we observed a dose-dependent increase of the size of
the DPPG liposomes whereas no effect was evidenced for DPPC liposomes. The
binding constants K(app) were in the order of 10(5) M(-1) and the affinity
appeared dependent on the negative charge of liposomes: DPPG>DOPC:DPPG (1:1;
M:M)>DPPC>DOPC:DPPC (1:1; M:M). As compared to the control samples, the chemical
shift anisotropy (Deltasigma) values determined by (31)P NMR showed an increase
of 5 and 9 ppm for DPPC:CIP (1:1; M:M) and DPPG:CIP (1:1; M:M) respectively.
ATR-FTIR experiments showed that ciprofloxacin had no effect on the T(m) of DPPC
but increased the order of the acyl chains both below and above this temperature.
In contrast, with DPPG, ciprofloxacin induced a marked broadening effect on the
transition with a decrease of the acyl chain order below its T(m) and an increase
above this temperature. Altogether with the results from the conformational
analysis, these data demonstrated that the interactions of ciprofloxacin with
lipids depend markedly on the nature of their phosphate head groups and that
ciprofloxacin interacts preferentially with anionic lipid compounds, like
phosphatidylglycerol, present at a high content in these membranes