Synthesis of 4-Amino-1-Hydroxy-Butane-1,1-Diphosphonate (AHBDP) - Stannous Complexes for the Preparation of Ahbdp-Sn(II)-Tc and its Biodistribution in Rats

The new potential tracer of bone imaging, AHBDP-Sn(II)-TcO.3H2O was synthesized by reducing the TcO4− to TcO2+ in the presence of AHBDP and Sn(ll)’s reducing agent. We found that tin rapidly forms a stable complex with AHBDP, giving AHBDP-Sn(II).3H2O. In the excess of AHBDP-Sn(ll).3H2O, the AHBDP-Sn(II).3H2O coordinates with TcO2+ to give AHBDP-Sn(II)-TcO.3H2O which could polymerise or oligomerise to give hydrophobic species. The overall process appears as a first-order reaction (K= 0.67 ± 0.005s−1). In rats, the fixation of AHBDP-Sn(II)-99mTcO. 3H2O on bone is homogeneous and the scintigraphic images have the same quality as those of 1-hydroxymethane-1,1-diphosphonate-Technetium (HMDP-99mTc). The activity in non-target organs was neglible

Differential chemosensitization of P-glycoprotein overexpressing K562/Adr cells by withaferin A and Siamois polyphenols

Background: Multidrug resistance (MDR) is a major obstacle in cancer treatment and is often the result of overexpression of the drug efflux protein, P-glycoprotein (P-gp), as a consequence of hyperactivation of NF-kappa B, AP1 and Nrf2 transcription factors. In addition to effluxing chemotherapeutic drugs, P-gp also plays a specific role in blocking caspase-dependent apoptotic pathways. One feature that cytotoxic treatments of cancer have in common is activation of the transcription factor NF-kappa B, which regulates inflammation, cell survival and P-gp expression and suppresses the apoptotic potential of chemotherapeutic agents. As such, NF-kappa B inhibitors may promote apoptosis in cancer cells and could be used to overcome resistance to chemotherapeutic agents. Results: Although the natural withanolide withaferin A and polyphenol quercetin, show comparable inhibition of NF-kappa B target genes (involved in inflammation, angiogenesis, cell cycle, metastasis, anti-apoptosis and multidrug resistance) in doxorubicin-sensitive K562 and -resistant K562/Adr cells, only withaferin A can overcome attenuated caspase activation and apoptosis in K562/Adr cells, whereas quercetin-dependent caspase activation and apoptosis is delayed only. Interestingly, although withaferin A and quercetin treatments both decrease intracellular protein levels of Bcl2, Bim and P-Bad, only withaferin A decreases protein levels of cytoskeletal tubulin, concomitantly with potent PARP cleavage, caspase 3 activation and apoptosis, at least in part via a direct thiol oxidation mechanism. Conclusions: This demonstrates that different classes of natural NF kappa B inhibitors can show different chemosensitizing effects in P-gp overexpressing cancer cells with impaired caspase activation and attenuated apoptosis

The role of bioreductive activation of doxorubicin in cytotoxic activity against leukaemia HL60-sensitive cell line and its multidrug-resistant sublines

Clinical usefulness of doxorubicin (DOX) is limited by the occurrence of multidrug resistance (MDR) associated with the presence of membrane transporters (e.g. P-glycoprotein, MRP1) responsible for the active efflux of drugs out of resistant cells. Doxorubicin is a well-known bioreductive antitumour drug. Its ability to undergo a one-electron reduction by cellular oxidoreductases is related to the formation of an unstable semiquionone radical and followed by the production of reactive oxygen species. There is an increasing body of evidence that the activation of bioreductive drugs could result in the alkylation or crosslinking binding of DNA and lead to the significant increase in the cytotoxic activity against tumour cells. The aim of this study was to examine the role of reductive activation of DOX by the human liver NADPH cytochrome P450 reductase (CPR) in increasing its cytotoxic activity especially in regard to MDR tumour cells. It has been evidenced that, upon CPR catalysis, DOX underwent only the redox cycling (at low NADPH concentration) or a multistage chemical transformation (at high NADPH concentration). It was also found, using superoxide dismutase (SOD), that the first stage undergoing reductive activation according to the mechanism of the redox cycling had the key importance for the metabolic conversion of DOX. In the second part of this work, the ability of DOX to inhibit the growth of human promyelocytic-sensitive leukaemia HL60 cell line as well as its MDR sublines exhibiting two different phenotypes of MDR related to the overexpression of P-glycoprotein (HL60/VINC) or MRP1 (HL60/DOX) was studied in the presence of exogenously added CPR. Our assays showed that the presence of CPR catalysing only the redox cycling of DOX had no effect in increasing its cytotoxicity against sensitive and MDR tumour cells. In contrast, an important increase in cytotoxic activity of DOX after its reductive conversion by CPR was observed against HL60 as well as HL60/VINC and HL60/DOX cells

Induction de l'apoptose et de la réversion de la résistance multiple aux drogues engendrées par les flavonoïdes et mise en évidence de la cible intracellulaire de ces molécules dans les cellules cancéreuse

PARIS13-BU Sciences (930792102) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Modeling of C-SNARF-1 pH fluorescence properties: towards calibration free optical fiber pH sensing for in vivo applications

International audienceOrganic functions of the human body are related to biological constants. Variations of these constants, among them pH, induce pathological troubles. The general goal of our work is to fabricate a fluorescent pH sensor at the end of an optical fiber for in vivo pH measurements. One difficulty using fluorescence indicators is the need to perform an accurate calibration. In this communication, we present methods used to simplify and potentially avoid calibration procedures of fluorescence indicators. The first method concerns the simplification of calibration procedures making them independent of the indicator’s concentration, path length and equipment used. The second method concerns modelling the fluorescence emission of the molecules as a function of pH only. This model is used to fit the exact shape of C-SNARF-1 fluorescence spectra obtained at any pH. Subsequently, the pH of a solution can be computed with an accuracy of 0.1 pH unit without the calibration procedure employed up to now. These methods constitute the first steps toward calibration free pH measurements. They can be applied to any fluorescent indicator exhibiting a dual emission peak. As a conclusion, this is the first time that fluorescence properties of C-SNARF-1 are fully mathematically described

Improving the sensitivity of amino-silanized sensors using self-structured silane layers: application to fluorescence pH measurement

International audienceWe investigated the possibility to grow molecularly porous amino-silane layers on glass-like substrates.The goal of this work is to show that it is possible to substantially increase the sensitivity of a fluorescencesensor by adjusting the functionalization strategy. Two methods are studied, one using APTMS only andanother one using both APTMS and APDMS. We show that, using the second method, sensor sensitivityis improved by a factor of about 5. In order to demonstrate this, we applied the technique to the graftingof fluorescein in order to build a fluorescence pH senso

Simplifying ratiometric C-SNARF-1 pH calibration procedures with a simple post-processing

International audienceA simple and easy to implement numerical method is proposed in order to considerably simplify the experimental calibration procedure of C-SNARF-1 indicator used for ratiometric pH sensing. Usually, calibration is based on the measurement of fluorescence spectra using perfectly calibrated equipment at extreme pH values. The calibration solutions must be extremely well controlled in terms of indicator concentration and path length. Also, the optical equipment used must be well controlled and excitation energy as well as fluorescence collection efficiency must be perfectly constant over the whole calibration procedure. The method we propose is based on the fact that the emission fluorescence energy does not only depend on pH but also on the excitation wavelength. In this paper, we propose a model describing the evolution of the emitted energy as a function of pH and excitation wavelength. We show that the emitted energy evolves linearly with pH and we express this linear evolution as a function of the excitation wavelength. We also show the evolution of the isosbestic (or isoemitting) point as a function of the excitation wavelength. Knowing the linear dependence of the emitted energy as a function of excitation wavelength allows post-processing calibration spectra obtained with basic optical equipment where the excitation energy, fluorescence collection efficiency, indicator concentration and path length can vary over the calibration session. Because the calibration procedure becomes independent of the above mentioned parameters, the post-processing we propose considerably simplify indicators calibration. This method can easily be transposed, not only to other ratiometric pH indicators, but also to ion sensing fluorescent indicators exhibiting dual emission peaks

Sensitivity enhancement of a fluorescent pH sensor by double silanization of the sensing surface

International audienceThe goal of this work concerns a new method to substantially increase the sensitivity of a fluorescence pH sensor. The method is based on a double silanization method. Two methods are compared: one using APTMS (3-Aminopropyl)trimethoxysilane) only and another one using both APTMS and APDMS (3-Aminopropyl)dimethoxymethylsilane). Using the second method, sensor’s sensitivity is improved by more than 500 %