Bis(thiosemicarbazone) copper complexes: mechanism of intracellular accumulation.

The molecular basis of Alzheimer's disease has not been clearly established, but disruption of brain metal ion homeostasis, particularly copper and zinc, might be closely involved in the pathogenesis of this disease and its characteristic β-amyloid neuropathological features. The use of complexes of copper with bis(thiosemicarbazones) ([Cu(btsc)]) has been proposed for the treatment of Alzheimer's disease. Their mode of action could involve modulation of the concentration of copper or zinc, and it has been suggested that the compounds can modulate the production of β-amyloid peptide at the neuron level.

Accumulation of Eu3+ chelates in cells expressing or not P-glycoprotein: implications for blood-brain barrier crossing.

Alzheimer's disease (AD) is the most commonly form of dementia in the elderly. The development of molecules able to detect biomarkers characteristic of AD is critical to its understanding and treatment. However, such molecules must be able to pass blood-brain barrier (BBB) which is a major impediment to the entry of many therapeutic drugs into the brain.

Impact of intracellular chloride concentration on cisplatin accumulation in sensitive and resistant GLC4 cells.

Resistance to cisplatin [cis-diamminedichloroplatinum(II), CDDP] chemotherapy is a major problem in the clinic. Understanding the molecular basis of the intracellular accumulation of CDDP and other platinum-based anticancer drugs is of importance in delineating the mechanism of resistance to these clinically important therapies. Different molecular mechanisms may coexist, but defective uptake of CDDP is one of the most consistently identified characteristics of cells selected for CDDP resistance.

Resistance to arsenic- and antimony-based drugs.

Organic arsenicals were the first antimicrobial agents specifically synthesized for the treatment of infectious diseases such as syphilis and sleeping sickness. For the treatment of diseases caused by trypanosomatid parasites, organic derivatives of arsenic and the related metalloid antimony are still the drugs of choice. Arsenic trioxide, As203, has been used for a long time in traditional Chinese medicines for treatment of various diseases, and it has recently been shown to be clinically active in acute promyelocytic leukemias.

Impact of the carbon chain length of novel platinum complexes derived from N-alkyl-propanediamines on their cytotoxic activity and cellular uptake.

This work describes the synthesis and characterization of four new ligands derived from 1,3-propanediamine in addition to the preparation and characterization of their respective platinum(II) complexes by reaction with K(2)PtCl(4). These ligands were obtained by the reaction of the corresponding alkyl mesylate with 1,3-propanediamine. We have prepared compounds having different carbon chains lengths in an attempt to correlate this factor, which influences the lipophilicity of the compounds, with cytotoxic activity.

Perturbation of membrane microdomains in GLC4 multidrug-resistant lung cancer cells--modification of ABCC1 (MRP1) localization and functionality.

The multidrug resistance-associated protein transporter ABCC1 (MRP1) is an integral plasma membrane protein involved in the multidrug resistance phenotype. It actively expels a number of cytotoxic molecules from cells. To gain insight into the modulation of the functional properties of this integral membrane protein by cholesterol, a main component of the lipid bilayer, we used multidrug-resistant GLC4/ADR cells, which overexpress MRP1.

Ability of carbazole salts, inhibitors of Alzheimer beta-amyloid fibril formation, to cross cellular membranes.

Alzheimer's disease is characterized by the presence of beta-amyloid fibril formation. The inhibition of this peptide accumulation may be a prevention method for Alzheimer's disease. Several classes of molecules have been reported to inhibit beta-amyloid fibril formation and among them carbazoles.

Isomeric N,N-bis(cyclohexanol)amine aryl esters: the discovery of a new class of highly potent P-glycoprotein (Pgp)-dependent multidrug resistance (MDR) inhibitors.

A new series of P-glycoprotein (Pgp)-dependent multidrug resistance (MDR) inhibitors having a N,N-bis(cyclohexanol)amine scaffold have been designed, following the frozen analog approach. With respect to the parent flexible molecules, the new compounds show improved potency and efficacy. Among them, compound 1d, on anthracycline-resistant erythroleukemia K562 cells, is able to completely reverse Pgp-dependent MDR at low nanomolar concentration.

Preferential energy- and potential-dependent accumulation of cisplatin-gutathione complexes in human cancer cell lines (GLC4 and K562): A likely role of mitochondria.

cis-Diamminedichloroplatinum(II) (CDDP) is an important chemotherapeutic agent used in the treatment of a wide variety of solid tumors. We have recently shown that aquated forms of cisplatin (aqua-Pt) rapidly accumulate in K562 and GLC4 cultured cells, in comparison to CDDP. Thus, when cells are incubated with aquated forms of cisplatin a gradient of concentration is observed after a short time, approximately 40 min, with an intracellular concentration of aqua-Pt of 20-30 times higher than that of extracellular aqua-Pt.

Mechanism of thioflavin T accumulation inside cells overexpressing P-glycoprotein or multidrug resistance-associated protein: role of lipophilicity and positive charge.

Alzheimer's disease is characterized by the presence of amyloid deposition. Thioflavin T (ThT) has been one of the molecules of choice to attempt the detection of these amyloid deposits. However, it has been reported that ThT was unable to cross blood-brain barrier (BBB).

Role of residual Sb(III) in meglumine antimoniate cytotoxicity and MRP1-mediated resistance.

Despite the clinical use of pentavalent antimonials for more than half a century, their metabolism in mammals and mechanisms of action and toxicity remain poorly understood. It has been proposed that the more active and toxic trivalent antimony form Sb(III) plays a critical role in their antileishmanial activity and toxicity. The aim of this work was to investigate the role of residual Sb(III) both in the antileishmanial/antitumoral activities of the pentavalent meglumine antimoniate and in the MRP1 (multidrug resistance-associated protein 1)-mediated resistance to this drug.

Exploratory chemistry toward the identification of a new class of multidrug resistance reverters inspired by pervilleine and verapamil models.

On the basis of the present knowledge of the substrate recognition site of ABC transporter proteins and inspired by the structures of verapamil and pervilleine A, a new class of Pgp-mediated multidrug resistance (MDR) reverters has been designed and synthesized. The new compounds are flexible molecules carrying one or two basic nitrogen atoms flanked, at properly modulated distance, by two aromatic moieties. Most of the molecules studied possess MDR inhibitory activity on anthracycline-resistant erythroleukemia K 562 cells, showing a potency that is higher than that of the reference compound verapamil and, in a few cases (7, 12, 13,17, 20, 22, 28), is in the high nanomolar range.

Decrease of P-glycoprotein activity in K562/ADR cells by MbetaCD and filipin and lack of effect induced by cholesterol oxidase indicate that this transporter is not located in rafts.

The effect of low-density membrane domains on function of the plasma membrane transporter P-glycoprotéine (P-gp), involved in multidrug resistance (MDR) phenotype, has been investigated in K562/ADR cells. To this end we reversibly altered the cholesterol content of K562/ADR cells by using methyl-beta-cyclodextrin as a cholesterol chelator and conversely we repleted them through incubation with cholesterol in culture medium. We also used the cholesterol-binding fluorochrome filipin and cholesterol oxidase.

Diphenylcyclohexylamine derivatives as new potent multidrug resistance (MDR) modulators.

A series of compounds with a diphenylmethyl cyclohexyl skeleton, loosely related to verapamil, has been synthesized and tested as MDR modulators on anthracycline-resistant erythroleukemia K 562 cells. Their residual cardiovascular action (negative inotropic and chronotropic activity as well as vasorelaxant activity) was evaluated on guinea-pig isolated atria preparations and on guinea-pig aortic strip preparations. Most compounds of the series possess a good MDR-reverting activity together with a low cardiovascular action.

The role of structural factors in the kinetics of cellular uptake of pyrazoloacridines and pyrazolopyrimidoacridines: implications for overcoming multidrug resistance towards leukaemia K562/DOX cells.

The appearance of multidrug resistance (MDR) of tumour cells to a wide array of antitumour drugs, structurally diverse and having different mechanisms of action, constitutes the major obstacle to the successful treatment of cancer. Our approach to search for non-cross resistant antitumour agents is based on the rational design of derivatives, which have a high kinetics of passive cellular uptake rendering their active efflux by MDR exporting pumps inefficient. Recently, two families of acridine cytotoxic agents were obtained, pyrazoloacridines (PACs) and pyrazolopyrimidoacridines (PPACs).

Kinetic analysis of rhodamines efflux mediated by the multidrug resistance protein (MRP1).

Characterization of rhodamine 123 as functional assay for MDR has been primarily focused on P-glycoprotein-mediated MDR. Several studies have suggested that Rh123 is also a substrate for MRP1. However, no quantitative studies of the MRP1-mediated efflux of rhodamines have, up to now, been performed.

Synthesis, characterization, cytotoxic activity, and cellular accumulation of dinuclear platinum complexes derived from N,N'-di-(2-aminoethyl)-1,3-diamino-2-propanol, aryl substituted N-benzyl-1,4-butanediamines, and N-benzyl-1,6-hexanediamines.

This work describes the synthesis and characterization of six new dinuclear platinum complexes having N,N'-di-(2-aminoethyl)-1,3-diamino-2-propanol, aryl substituted N-benzyl-1,4-butanediamines and N-benzyl-1,6-hexanediamines as ligands. They were prepared by the reaction of cis-[PtCl(2)(DMSO)(2)] (DMSO=dimethyl sulfoxide) with the appropriate ligand in water, except for one of them, which was prepared from K(2)PtCl(4). We also report the cytotoxic activity and cellular accumulation of three of these complexes in a human small-cell lung carcinoma cell line and its resistant subline.

A structural model for the open conformation of the mdr1 P-glycoprotein based on the MsbA crystal structure.

The validity of the structure of the Escherichia coli MsbA lipid transporter as a model from the mdr1 P-glycoprotein has been evaluated. Comparative sequence analyses, motif search and secondary structure prediction indicated that each of the two P-glycoprotein halves is structurally similar to the MsbA monomer and also suggested that the open dimer structure is valid for P-glycoprotein. Homology modeling was used to predict the structure of P-glycoprotein using MsbA as a template.

Impaired hydrolysis of cisplatin derivatives to aquated species prevents energy-dependent uptake in GLC4 cells resistant to cisplatin.

It has been widely stated that cisplatin enters cells by passive diffusion, despite some reports supporting a carrier-mediated mechanism. We have determined the rate of uptake of carboplatin (CBDCA), of cisplatin (CDDP) and of aquated forms, at different values of the extracellular pH, in the small lung-cancer cells GLC4 and GLC4/CDDP, cells resistant to CDDP. The rate of CDDP uptake is about 2-fold lower in resistant cells than in sensitive ones; in ATP-depleted cells this rate is about the same for both cell lines.

New findings in the study on the intercalation of bisdaunorubicin and its monomeric analogues with naked and nucleus DNA.

DNA is a target molecule for anthracycline anticancer drugs. We have used new anthracycline derivatives, bisdaunorubicin (WP631) and its monomeric analogues (WP700 serie), and look if there was a relation between the drug binding affinity to naked DNA and to cell nucleus in the cell with its cytotoxicity. Circular dichroism (CD) and fluorescence were used to follow the interaction of anthracycline derivatives with naked DNA and cell nuclei.

Mitomycin antitumor compounds. 2. Interaction of transition metal ions with mitomycin C. Solution structure and biological activity of a Pd(2+)-MMC complex.

Interactions of Cu(2+), Zn(2+), and Pd(2+) ions with the antitumor compound mitomycin C (MMC) have been investigated by UV-vis, circular dichroism, and (13)C NMR spectroscopy. While Zn(2+) and Cu(2+) neither interacted with MMC nor catalyzed the formation of mitosenes, Pd(2+) induced strong MMC spectral modifications, suggesting the formation of a major complex, in which MMC acted as a bidentate ligand through N(1) and N(4) atoms. The coordination mode in this complex was solvent dependent: in MeOH, the NH(2) of the carbamate function was also involved as a third coordination site whereas, in H(2)O, Pd(2+) hydrolysis was more effective, leading to the replacement of the carbamoyl NH(2) function with either H(2)O or OH(-) ligands.

Kinetic analysis of fluorescein and dihydrofluorescein effluxes in tumour cells expressing the multidrug resistance protein, MRP1.

Multidrug resistance (MDR) in tumour cells is often caused by the overexpression of two transporters the P-glycoprotein (P-gp) and the multidrug resistance-associated protein (MRP1) which actively pump out multiple chemically unrelated substrates across the plasma membrane. A clear distinction in the mechanism of translocation of substrates by MRP1 or P-gp is indicated by the finding that, in most of cases, the MRP1-mediated transport of substrates is inhibited by depletion of intracellular glutathione (GSH), which has no effect on their P-gp-mediated transport. The aim of the present study was to quantitatively characterise the transport of anionic compounds dihydrofluorescein and fluorescein (FLU).

New insights into the P-glycoprotein-mediated effluxes of rhodamines.

Multidrug resistance (MDR) in tumour cells is often caused by the overexpression of the plasma drug transporter P-glycoprotein (P-gp). This protein is an active efflux pump for chemotherapeutic drugs, natural products and hydrophobic peptides. Despite the advances of recent years, we still have an unclear view of the molecular mechanism by which P-gp transports such a wide diversity of compounds across the membrane.

The MRP1-mediated effluxes of arsenic and antimony do not require arsenic-glutathione and antimony-glutathione complex formation.

Arsenic trioxide is an effective treatment for acute promyelocytic leukemia, but resistance to metalloid salts is found in humans. Using atomic absorption spectroscopy, we have measured the rate of uptake of arsenic trioxide and of antimony tartrate in GLC4 and GLC4/ADR cells overexpressing MRP1 and the rate of their MRP1-mediated effluxes as a function of the intracellular GSH concentration. In sensitive cells, after 1 h, a pseudosteady state is reached where intra- and extracellular concentrations of metalloid are the same.

MRP1 modulation by PAK-104P: detection with technetium-99m-MIBI in cultured lung tumor cells.

Background: Resistance mediated by the MultiDrug Resistance protein (P-glycoprotein and MRP1), results in energy-dependent efflux of drugs and 99mTc-MIBI from the cells. The goal of our investigation was to evaluate the capacity of PAK-104P to lower multidrug resistance by decreasing substrate efflux.

Materials And Methods: 99mTc-MIBI accumulation was quantified in the leukaemia cell line which expresses the P-glycoprotein (K562/R) or not (K562/S) and the small lung cancer cell line which expresses MRP1 (GLC4/R) or not (GLC4/S).