Complexation of daunomycin with a DNA oligomer in the presence of an aromatic vitamin (B2) determined by NMR spectroscopy

Spectroscopy studies of interaction hypericin with an anti-cancer therapy drug doxorubicin

The presented study was designed to estimate the ability of hypericin to interact with the anticancer drug doxorubicin. The hetero-association of hypericin and doxorubicin was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO in two-component mixtures: doxorubicin-hypericin and three component mixtures: DNA-doxorubicin-hypericin. The data indicate that hypericin forms complexes with doxorubicin and that the association constants are on the order of 300,000 M^-1 in a buffer with 30% DMSO content. The absorption spectra of the hypericin - doxorubicin complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule to detoxification of patients after chemotherapy.

The theory of interceptor-protector action of DNA binding drugs

The review discusses the theory of interceptor-protector action (the IPA theory) as the new self-consistent biophysical theory establishing a quantitative interrelation between parameters measured in independent physico-chemical experiment and in vitro biological experiment for the class of DNA binding drugs. The elements of the theory provide complete algorithm of analysis, which may potentially be applied to any system of DNA targeting aromatic drugs. Such analytical schemes, apart from extension of current scientific knowledge, are important in the context of rational drug design for managing drug's response by changing the physico-chemical parameters of molecular complexation.

Riboflavin-containing telodendrimer nanocarriers for efficient doxorubicin delivery: High loading capacity, increased stability, and improved anticancer efficacy

We have developed two linear-dendritic telodendrimers (TDs) with rational design using amphiphilic riboflavin (Rf) as building blocks for efficient doxorubicin (DOX) delivery. Micellar TD nanoparticles (NPs) are composed of a hydrophilic polyethylene glycol (PEG) shell and a Rf-containing affinitive core for DOX encapsulation. Strong DOX-Rf interactions and amphiphilic Rf structure render these nanocarriers with an ultra-high DOX loading capacity (>1/1, DOX/TD, w/w), ∼100% loading efficiency, the sustained drug release and the optimal particle sizes (20-40 nm) for efficient tumor-targeted drug delivery. These nanoformulations significantly prolonged DOX circulation time in the blood without the accelerated clearance observed after multiple injections. DOX-TDs target several types of tumors efficiently in vivo, e.g. Raji lymphoma, MDA-MB-231 breast cancer, and SKOV-3 ovarian cancer. In vivo maximum tolerated dose (MTD) of DOX was increased by 2-2.5 folds for the nanoformulations in mice relative to those of free DOX and Doxil^®. These nanoformulations significantly inhibited tumor growth and prolonged survival of mice bearing SKOV-3 ovarian cancer xenografts. In summary, Rf-containing nanoformulations with high DOX loading capacity, improved stability and efficient tumor targeting lead to superior antitumor efficacy, which merit the further development for clinical application.

NMR spectroscopy on flavins and flavoproteins

(1)H-, (11)B-, (13)C-, (15)N-, (17)O-, (19)F-, and (31)P-NMR chemical shifts of flavocoenzymes and derivatives of it, as well as of alloxazines and isoalloxazinium salts, from NMR experiments performed under various experimental conditions (e.g., dependence of the chemical shifts on temperature, concentration, solvent polarity, and pH) are reported. Also solid-state (13)C- and (15)N-NMR experiments are described revealing the anisotropic values of corresponding chemical shifts. These data, in combination with a number of coupling constants, led to a detailed description of the electronic structure of oxidized and reduced flavins. The data also demonstrate that the structure of oxidized flavin can assume a configuration deviating from coplanarity, depending on substitutions in the isoalloxazine ring, while that of reduced flavin exhibits several configurations, from almost planar to quite bended. The complexes formed between oxidized flavin and metal ions or organic molecules revealed three coordination sites with metal ions (depending on the chemical nature of the ion), and specific interactions between the pyrimidine moiety of flavin and organic molecules, mimicking specific interactions between apoflavoproteins and their coenzymes. Most NMR studies on flavoproteins were performed using (13)C- and (15)N-substituted coenzymes, either specifically enriched in the pterin moiety of flavin or uniformly labeled flavins. The chemical shifts of free flavins are used as a guide in the interpretation of the chemical shifts observed in flavoproteins. Although the hydrogen-bonding pattern in oxidized and reduced flavoproteins varies considerably, no correlation is obvious between these patterns and the corresponding redox potentials. In all reduced flavoproteins the N(1)H group of the flavocoenzyme is deprotonated, an exception is thioredoxin reductase. Three-dimensional structures of only a few flavoproteins, mostly belonging to the family of flavodoxins, have been solved. Also the kinetics of unfolding and refolding of flavodoxins has been investigated by NMR techniques. In addition, (31)P-NMR data of all so far studied flavoproteins and some (19)F-NMR spectra are discussed.

General analysis of competitive binding in drug-interceptor-DNA systems

A general model of competitive binding in drug-interceptor-DNA systems has been developed in order to quantify both the interceptor and protector mechanisms. The model involves full parameterization of the basic equations governing the mutual competition between drugs binding to DNA and incorporates as partial cases various similar models existing in the literature. The generality of the model results from strict accounting of the statistical effects of the binding of the drug and interceptor with DNA according to the McGhee-von Hippel formalism, and to the strict treatment of hetero-association between the drug and interceptor, which includes formation of all possible types of self- and hetero-complexes in solution. Indirect experimental evidence is provided for the importance of the protector mechanism in drug-caffeine-DNA systems, which is sometimes ignored in the literature because of the small magnitude of the CAF-DNA binding constant.

Quantification of the interceptor action of caffeine on the in vitro biological effect of the anti-tumour agent topotecan

Using published in vitro data on the dependence of the percentage of apoptosis induced by the anti-cancer drug topotecan in a leukaemia cell line on the concentration of added caffeine, and a general model of competitive binding in a system containing two aromatic drugs and DNA, it has been shown to be possible to quantify the relative change in the biological effect just using a set of component concentrations and equilibrium constants of the complexation of the drugs. It is also proposed that a general model of competitive binding and parameterization of that model may potentially be applied to any system of DNA-targeting aromatic drugs under in vitro conditions. The main reasons underpinning the proposal are the general feature of the complexation of aromatic drugs with DNA and their interaction in physiological media via hetero-association.

Attenuation of acridine mutagen ICR-191--DNA interactions and DNA damage by the mutagen interceptor chlorophyllin

We have investigated the ability of chlorophyllin (CHL) to interact with acridine mutagen ICR-191 (2-methoxy-6-chloro-9-(3-(2-chloroethyl)aminopropylamino)acridine) and also its ability to decrease binding of ICR-191 to DNA in a simple three-component competition system: CHL-ICR-DNA. Our data indicate a strong association of ICR-191 with CHL, stronger even than the association of ICR-191 with DNA. Calculations based on the measured affinity data show that a two- to three-fold excess of CHL reduces by about two-fold the concentration of the mutagen-DNA complex. We also exposed human leukemic HL-60 cells to ICR-191 in the absence and presence of CHL and measured the mutagen-induced DNA damage. The extent of DNA damage was assessed by analysis of histone H2AX phosphorylation. While ICR-191 induced significant increase in expression of phosphorylated H2AX (gammaH2AX), particularly in DNA replicating cells, this increase was totally abolished in the cells treated with ICR-191 in the presence of CHL.

Complexation of anthracycline drugs with DNA in the presence of caffeine

The competitive binding of anthracycline antitumour drugs, [daunomycin (DAU), doxorubicin (DOX) or nogalamycin (NOG)], with caffeine (CAF) to a model DNA oligomer has been investigated by 500 MHz 1H NMR spectroscopy under physiological solution conditions. The method depends on the stepwise analysis of one-component (self-association), two-component (hetero-association and DNA complexation) and three-component interactions, in order to de-convolute the overall binding of the anthracycline antibiotic and CAF to DNA into two competing processes, viz. hetero-association of the antibiotic-CAF ('interceptor' action of CAF) and CAF-DNA complexation ('protector' action of CAF). It is found that the complexation of DAU with DNA in the presence of CAF is mainly affected by the CAF-DNA complexation, whereas the binding of either DOX or NOG to DNA is affected approximately equally by both the CAF-DNA complexation and CAF-antibiotic hetero-association. Quantitative evaluation of the three-component mixture of drug-CAF-DNA has enabled the proportion of the antibiotic displaced from DNA on addition of CAF to be calculated over a large range of CAF concentration, which may provide a quantitative basis for the change in anthracycline-related toxicity on addition of CAF.

Complexation of norfloxacin with DNA in the presence of caffeine

(1)H NMR spectroscopy (500 MHz) has been used to quantify the complexation of the antibacterial antibiotic Norfloxacin (NOR) with DNA in the presence of Caffeine (CAF). Separate studies have been made for the self-association of NOR, its hetero-association with CAF and complexation with a model self-complementary DNA tetramer, 5'-d(TpGpCpA), in order to determine the equilibrium parameters (induced chemical shifts, association constants, enthalpy and entropy) of the two-component mixtures to aid the analysis of the three-component systems. Investigations of the self-association of NOR and its hetero-association with CAF show that the aggregation of NOR molecules and association with CAF in solution are driven by the stacking of aromatic chromophores. The complexation of NOR with d(TGCA) has been analysed in terms of intercalation with the double-stranded form and non-intercalative binding with the single-stranded form of DNA. Investigations of the competitive binding of NOR and CAF with DNA show that at physiological concentrations of NOR (muM) and CAF (mM) the dominant mechanism influencing the affinity of NOR with DNA is the displacement of bound NOR molecules from DNA due to CAF-DNA complexation (i.e. the protector action of Caffeine).