Qualitative and quantitative analysis of therapeutic solutions using Raman and infrared spectroscopy

Anticancer drugs are prescribed and administrated to an increasing number of patients on a daily basis. As a consequence, a number of concerns have been raised about the patient health and safety in the case that the drugs administered are not at the required concentration or even worse not the correct ones. Quality control of therapeutic solutions has therefore been extensively implemented in hospital environments, in order to avoid any failure in the intense workflow faced by administering pharmacists. In the present study, infrared (IR) and Raman spectroscopy have been employed for the analysis of 3 commercially available therapeutic solutions TEVA®, MYLAN®, CERUBIDINE®, respectively containing doxorubicin, epirubicin and daunorubicin. They perfectly illustrate the analytical difficulties encountered, as these 3 chemotherapeutic drugs are isomers, hardly distinguishable with conventional approaches such as UV/VIS spectrometry. Any analytical failure to identify these molecules can lead to delays in patient treatment. While Partial Least Squares Regression analysis demonstrates that both Raman and IR can deliver satisfactory quantitative analysis in the clinical range, with respective Root Mean Square Error of Cross Validation (RMSECV) between 0.0127 - 0.0220 g·L^-1 and 0.0573 - 0.0759 g·L^-1, the identification rate between the 2 techniques differs substantially. Indeed, Principal Component Analysis - Factorial Discriminant Analysis (PCA-FDA) highlights that, depending on the data preprocessing applied to Raman spectra, the discrimination between the 3 drugs is decreased, with in some cases specificity and sensitivity below 50%. However, IR analysis displays encouraging results with an overall specificity and sensitivity between 99 and 100%, suggesting that reliable validation of the therapeutic solution for administration to patients can be achieved. IR and Raman spectroscopy could assist and support quality control of chemotherapeutic solutions prepared in personalised concentrations for each patient. The effective and reliable characterisation of therapeutic solutions could have a lot to offer to improve current practices in a near future.

An electrochemical daunorubicin sensor based on the use of platinum nanoparticles loaded onto a nanocomposite prepared from nitrogen decorated reduced graphene oxide and single-walled carbon nanotubes

A glassy carbon electrode (GCE) was modified with a nanocomposite prepared from nitrogen-doped reduced graphene oxide (N-rGO) and single walled carbon nanotubes (SWCNTs), and then loaded with platinum nanoparticles (Pt NPs) to obtain a voltammetric sensor for daunorubicin (DNR). Reductive doping of GO and the crystallization of the Pt NPs were carried out in a one-step hydrothermal process. The modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry. It exhibited high sensitivity compared with unmodified electrode. Some experimental parameters which affected sensor response were optimized. Under optimum conditions and at a working voltage of typically -0.56 V (vs. Ag/AgCl), the sensor has a low detection limit (3 ng mL^-1), a wide linear range (0.01-6 μg mL^-1) and good long-term stability. The method was successfully applied to the sensitive and rapid determination of DNR in spiked human serum samples. Graphical abstract Platinum nanoparticles were loaded onto a nanocomposite prepared from nitrogen decorated reduced graphene oxide and single-walled carbon nanotubes (N-rGO-SWCNTs-Pt) and then used for electrochemical determination of daunorubicin (DNR).

Immunocytochemistry for Drugs Containing an Aliphatic Primary Amino Group in the Molecule, Anticancer Antibiotic Daunomycin as a Model

An immunocytochemistry (ICC) for the anticancer antibiotic daunomycin (DM) was developed using a combination of anti-DM serum produced against N-(gamma-male-imidobutyryloxy)succinimide (GMBS)-conjugated DM, and DM-uptake human melanoma BD cells. The antiserum was demonstrated to be specific for DM and the structurally related analogs adriamicin and epirubicin by an ICC model system of the enzyme immunoassay (EIA) using glutaraldehyde (GA)-conjugated DM as a solid phase antigen. No cross-reaction occurred with any of the other antibiotics tested such as bleomycin, pepleomycin, and mitomycin C. Successful DM ICC required a series of processes prior to the immunocytochemical reaction: the cells were first fixed with GA, then reduced with NaBH4, treated with hydrochloric acid, and finally digested with protease. The cell specimens were then subjected to immunoreaction with anti-DM serum followed by peroxidase-labeled goat anti-rabbit IgG/Fab', and in both immune reagents the detergent Triton X-100 was contained as well. The present ICC covering all these processes successfully stained for DM in the nucleus and in the perinuclear Golgi region of the cytoplasm of the BD cells, consistent with the results obtained by the DM autofluorescence method. This ICC was found to be three times as sensitive as the cytofluorometric method and applicable to the paraffin sections of the liver of rats 24 hr after an IV injection of DM. The principle used in the present study for developing DM ICC might be applied to other drugs containing the primary amino group(s) in the molecule. Thus, these ICCs for drugs are direct, precise and easy new methods that should have potential for pharmacology and toxicology studies of drugs, revealing the localization of a drug in cells and tissues.

Fluorescence quenching and spectrophotometric methods for the determination of daunorubicin with meso-tera (4-sulphophenyl) porphyrin as probe

In this work, a synthetic meso-tera (4-sulfophenyl) porphyrin (TPPS4) was used as a probe to determine daunorubicin (DNR) by fluorescence quenching and spectrophotometric methods. At pH 4.6 potassium acid phthalate-NaOH buffer solution, a 1:1 complex of DNR interacted with TPPS4 formed via the electrostatic attractions and hydrophobic interactions, thus resulted in TPPS4 fluorescence quenching and absorption spectra change. The maximum excitation wavelength (λex) and the maximum emission wavelength (λem) are 435 nm and 672 nm, respectively. The fluorescence quenching values (ΔF) are the good linear relationship to the concentration of DNR in the range of 0.8-6.0 mgL(-1). The method exhibits high sensitivity with the detection limit (3σ) being 27.0 ng mL(-1). Meanwhile, a decrease of absorbance is detected at 433 nm with the appearance of a new absorption peak at 420 nm. The optimum reaction conditions, influencing factors and the effect of coexisting substances have been investigated in our experiment. The results showed that the method had a good selectivity and could be applied to determine DNR in serum and urine samples. In addition, the combine ratio between DNR and TPPS4 was measured and the charge distribution before and after reaction was calculated by quantum chemistry calculation AM1 method. The type of fluorescence quenching was discussed by the absorption spectra change, Stern-Volmer plots and fluorescence lifetime determination.

Stability of [(N-morpholine)metylene]daunorubicin hydrochloride in solid state

The influence of temperature and relative air humidity on the stability of the novel derivative of daunorubicin: [(N-morpholine)metylene]daunorubicin hydrochloride was investigated. The process of degradation was studied by using high-performance liquid chromatography with ultraviolet (UV) detection. In dry air, the degradation of [(N-morpholine)metylene]daunorubicin hydrochloride was a first-order reaction depending on the substrate concentration, while at relative air humidity from 60.5 to 90.0% it was an autocatalytic reaction of the first order with respect to MMD concentration. The kinetic and thermodynamic parameters of degradation were calculated.

Sensitive absorption-based wave-mixing detector for anthracycline drugs separated by capillary electrophoresis

Sensitive absorption-based detection of anthracycline antibiotics, daunorubicin and doxorubicin is demonstrated using a capillary electrophoresis system interfaced to a nonlinear wave-mixing detection system. Unlike conventional absorption methods, this nonlinear absorption method can detect very thin analytes (50 microm) efficiently. At the same peak height, the wave-mixing CE peak is narrower than a conventional CE peak, and hence, compared to other laser-based or non-laser-based CE on-column detection methods, our wave-mixing detection method offers intrinsically enhanced separation resolution even when using identical CE separation conditions. In this unusually sensitive "absorbance" detection method, two input laser beams interact to produce a thermally induced grating from which coherent laser-like wave-mixing signal beams are created. Using our sensitive "absorbance" on-column CE detector, we report a preliminary concentration detection limit of 9.9x10(-10)M using a 50-mum i.d. capillary column. The corresponding "injected" mass detection limit is 9.1x10(-18)mol using an injection volume of 9.2nL. The corresponding preliminary "detected" mass detection limit inside the 12-pL detector probe volume is 1.2x10(-20)M.

Immunocytochemical studies on the distribution pattern of daunomycin in rat gastrointestinal tract

The cancer drug daunomycin is used in treatment of leukemia but possesses severe side effects that involve the gastrointestinal tract. We therefore used a newly developed immunocytochemical procedure to determine the distribution of DM in the gastrointestinal tracts of rats after i.v. injection. Two hours after injection, DM was diffusely distributed in nuclei and most parts of the cytoplasm of intestinal epithelial cells. The cytoplasmic immunoreactivity for DM was most pronounced in small granules of the apical cytoplasm. Sixteen hours after injection, DM immunostaining was by and large absent in the villous epithelium but persisted in the intestinal crypts. In addition, staining was also detected in endothelial cells, scattered cells of the lamina propria and in smooth muscle cells. After 5 days, only little staining for DM remained. Similar findings were made in the colon. In the gastric mucosa, DM accumulation persisted at 16 h in some glandular cells but was lost from the surface epithelium. No staining was detected in saline-injected control rats. The distribution of DM accumulation correlated partially with the distribution of apoptotic cells as detected by the TUNEL procedure. Our results pinpoint that DM may exert prolonged effects on glandular and regenerative cells of the gastrointestinal tract-an observation that may explain the gastrointestinal toxicity of the drug. It seems possible that DM accumulation in surface epithelial cells is rapidly cleared through drug transporters.

Analytical Method for β-Amyloid Fibrils Using CE-Laser Induced Fluorescence and Its Application to Screening for Inhibitors of β-Amyloid Protein Aggregation

More than 20 million people are suffering from Alzheimer's disease, and the number of patients will dramatically increase with the arrival of an aging society unless preventive or curative medications are discovered. A fast and sensitive analytical method for beta-amyloid (Abeta) aggregates was developed by the combination of CE-laser induced fluorescence and the fluorescence reagent, thioflavine T. The developed method separates two different fibrils within 5 min. The first peak, which migrated at approximately 4 min, was supposed to be derived from a precursor of a fibril that migrated at approximately 3.5 min. The developed method was also applicable to the high-throughput screening of the Abeta aggregation inhibitors, which was expected to be an effective therapeutic agent candidate of Alzheimer's disease. Three compounds (daunomycin, 3-indolepropionic acid (3-IPA), melatonin) were used for the assay. The order of the antiaggregation activity of these compounds was daunomycin > 3-IPA > melatonin, which was the same as that of the reported one. These results suggest that this analytical method may be used to analyze the Abeta fibrils and identify potential therapeutic agents for the treatment of Alzheimer's disease.

Improved immunocytochemical detection of daunomycin

Improved immunocytochemical (ICC) detection of the anthracycline anticancer antibiotic daunomycin (DM) has been achieved by use of hydrogen peroxide oxidation prior to ICC staining for DM. The new method greatly enhanced the localization of DM accumulation in cardiac, smooth and skeletal muscle of rats after a single i.v. dose of the drug. DM accumulated in the nuclei as well as in the sarcoplasm, where it occurred in the form of small granules, which were particularly evident in cardiac muscle cells. The distribution of the granules coincided with that of mitochondria. Uptake of DM in nuclei and mitochondria of heart muscle cells may help to improve our understanding of the cardiac toxicity of DM and related anthracycline antibiotics. A number of ELISA tests were carried out in order to elucidate the mechanisms of H2O2-assisted antigen retrieval. A possible mechanism is that DM is reduced and converted to its semiquinone and/or hydroquinone derivative in vivo. Oxidation by hydrogen peroxide acts to convert these derivatives back to the native antigen. The improved ICC methodology using oxidation to recreate native antigens from reduced metabolites may be helpful also with respect to the localization of other drugs.

Determination of daunomycin at a novel COOH/indium tin oxide ion implantation-modified electrode

A novel COOH+ ion implantation-modified indium tin oxide (COOH/ITO) electrode was prepared for the first time and applied for determination of daunomycin (or daunorubicin [DNR]). The electrode showed higher catalytic activity than bare ITO electrode with good reproducibility and stability. The determination condition of linear voltammetry was optimized. A calibration curve was obtained over the range 2.0 x 10(-7) to 5.0 x 10(-6)mol/L, with a correlation coefficient of 0.9909 and a limit of detection of 1.0 x 10(-7)mol/L. The selectivity of the electrode was illustrated by determination of DNR in samples prepared of urine. X-ray photoelectron spectroscopy (XPS) analysis results showed that the implanted COOH+ maintained characteristics of organic group -COOH. A field emission-scanning electron microscope (FSEM) result showed that the implanted surface caused defects and partial dislocations and formed many active centers.

Electrochemical detection and control of interactions between DNA and electroactive intercalator using a DNA-alginate complex film modified electrode

The surface of a glassy carbon electrode was modified with a DNA-alginate complex film in which water-soluble DNA was encapsulated into a calcium-alginate gel. The resulting modified electrode (DAFE) was used to detect ethidium bromide (EtBr), after its accumulation on the electrode. The intercalative behavior of EtBr for dsDNA in the film was investigated by measuring the electrode response based on the intercalation of EtBr separated from nonspecific interactions (electrostatic interaction). The accumulation of EtBr in the dsDAF was enhanced by applying a negative potential below -200 mV at the dsDAFE. When a positive potential above +700 mV was applied to the dsDAFE for a constant time with stirring in a Tris buffer solution, the amount accumulated decreased. These results indicate that it is possible to electrochemically control the accumulation and release of EtBr when a dsDAFE is used. In addition, the accumulation and detection of EtBr in spiked river water samples and daunomycin, an antitumor agent, is described.

Determination of Daunomycin in Human Plasma and Urine by Using an Interference-free Analysis of Excitation-Emission Matrix Fluorescence Data with Second-Order Calibration

Daunorubicin (DNR) is a significant antineoplastic antibiotic, which is usually applied to a chemotherapy of acute lymphatic and myelogenous leukaemia. Unfortunately, cardiotoxicity research in animals has indicated that DNR is cardiotoxic. Therefore, it is important to quantify DNR in biological fluids. A new algorithm, the alternating fitting residue (AFR) method, and the traditional parallel factor analysis (PARAFAC) have been utilized to directly determine DNR in human plasma and urine. These methodologies fully exploit the second-order advantage of the employed three-way fluorescence data, allowing the analyte concentrations to be quantified even in the presence of unknown fluorescent interferents. Furthermore, in contrast to PARAFAC, more satisfactory results were gained with AFR.

Modulation of MDR1 gene expression in multidrug resistant MCF7 cells by low concentrations of small interfering RNAs

MDR1 overexpression is one form of the multidrug resistance (MDR) phenotype, which can be acquired by patients initially responsive to chemotherapy. Because of the high toxicity of the inhibitors of P-glycoprotein (P-gp), the protein encoded by MDR1, attention has been focused on selective modulation of the MDR1 gene. Small interfering RNAs (siRNAs) were shown to be powerful tools for such a purpose, even when used at low concentrations (< or =20 nM) in order to avoid sequence nonspecific effects. Two siRNAs used at 20 nM were shown to lead to efficient down-regulation of MDR1 at the protein level (only ca. 20% total P-gp expression remaining) in the doxorubicin selected MCF7-R human cell line. Cell surface expression of P-gp was inhibited, leading to reversal of the drug efflux phenotype (about 40% reversal with the most efficient siRNA) and enhancement of chemosensitivity (about 35%). At the mRNA level, the down-regulation of MDR1 obtained with the most efficient siRNA increased from about 50% (5 nM siRNA) to 60% (10 or 20 nM). The advantage of using a combination of siRNAs instead of a single one has been suggested.

[Electrochemical behavior of daunorubicin at Co/GC ion implantation modified electrode and the application of the electrode]

AIM

To study the electrochemical behavior of daunorubicin at Co/GC ion implantation modified electrode.

METHODS

With Co/GC ion implantation modified electrode as working electrode, daunorubicin was determined by voltammetry in 0.05 mol x L(-1) Na2HPO4-KH2PO4 (pH 6.82) solution.

RESULTS

A sensitive reductive peak of daunorubicin was obtained by linear sweep voltammetry. The peak potential was -0.60 V (vs SCE). The peak current was proportional to the concentration of daunorubicin over the range of 2.84 x 10(-8) - 1.42 x 10(-6) mol x L(-1) and 1.42 x 10(-6) - 1.28 x 10(-5) mol x L(-1) with the detection limit of 1.42 x 10(-8) mol x L(-1). The reduction wave was applied to the determination of daunorubicin. The electrochemical behavior and reaction mechanism were studied by linear sweep and cyclic voltammetry.

CONCLUSION

The reduction process was quasi-reversible with adsorption characteristics.

Fluorescence-based assessment of LRP activity: a comparative study

BACKGROUND

Broad resistance to anticancer drugs is a major cause of failure in cancer treatment. The Lung Resistance-related Protein (LRP) is a protein associated with drug resistance, which is involved in nucleo-cytoplasmic transport and is known to predict a poor response to chemotherapy in acute myeloid leukaemia. The only method allowing the detection of LRP activity is based on radio-labelled daunorubicin incorporation. Our goal was to develop a fluorescence-based assay to analyse LRP function.

MATERIALS AND METHODS

We used human colon carcinoma cell lines treated with sodium butyrate (NaB) in order to induce LRP expression. Daunorubicin efflux in isolated nuclei was measured by flow cytometry, the localization and quantification of Daunorubicin analysed by confocal laser scanning microscopy (CLSM) and the diffusion coefficient of this drug estimated by Fluorescence Correlation Spectrometry (FCS).

RESULTS

According to the method using [14C] Doxorubicin cells incubated with NaB displayed an efflux of Daunorubicin out of isolated nuclei demonstrated by flow cytometry or CLSM. The FCS method was able to evaluate kinetics of Daunorubicin molecules in nucleus and cytoplasm and showed a higher dispersion of Daunorubicin kinetics with cells previously NaB-treated. This argument is in favour of an increase of nucleo-cytoplasmic exchange.

CONCLUSION

Using CLSM we showed that LRP was able to modify anticancer drug repartition in the cells. LRP activity assessment needs either isolated nuclei if flow cytometry is employed, or FCS, and only a few cells may be analysed.

Anthracyclines: recent developments in their separation and quantitation

Anthracyclines are among the most widely used anticancer agents. Notwithstanding the large efforts to develop new drugs with a better pharmaceutical profile, daunorubicin, doxorubicin, epirubicin and idarubicin are still the most used in clinical practice. Many efforts are now ongoing to reduce the side effects by using pharmaceutical formulations able to release the drug in the most appropriate way and monitoring the quantity of anthracyclines and their metabolites in the body fluids or tissues frequently and in every patient to maintain the drug concentration within the expected range. This review describes the most recent developments in the separation and quantitation of the above clinically useful drugs, together with their principal metabolites. Some less widely used derivatives will also be considered.

Development of obesity and neurochemical backing in aurothioglucose-treated mice

To clarify the neurochemical backing of aurothioglucose (ATG)-induced obesity in mice, we investigated lesion sites, hypothalamic neurotransmitters and c-Fos-like immunoreactivity (Fos-IR). At day 2 after ATG, tissue loss or cells death was observed in several parts of the ventral area of the ventromedial hypothalamic nucleus (VMH), and the dorsal area of arcuate nucleus and in the nucleus of the solitary tract (NTS). However, the greater part of the VMH was retained. Body weight began to increase in week 1. Hypothalamic serotonin (5-HT) and the metabolites were increased at day 2. The contents of acetylcholine, norepinephrine and dopamine in the hypothalamus showed no significant change. In week 1, the area shown tissue loss was compacted and plugged up. In the control group, most obvious c-Fos-like immunoreactive region was paraventricular nucleus (PVN). At day 2, Fos-IR was observed around destroyed regions in the hypothalamus and NTS, but few Fos-IR was found in the other regions including PVN. The Fos-IR around destroyed regions diminished after week 1. In week 3, Fos-IR in the PVN increased. These results suggest that the development of ATG-induced obesity cannot be attributed to solely VMH destruction. The restoration processes of the neuronal dysfunction involving PVN seem to play an important role in the development of obesity. NTS lesion and 5-HT system might contribute to decrease in food intake for several days after ATG.

Determination of anthracycline antibiotics doxorubicin and daunorubicin by capillary electrophoresis with UV absorption detection

Sweeping preconcentration and electrokinetic injection was used for the capillary electrophoretic analysis of trace amounts of biologically active anthracyclines with UV absorption detection. Phosphate buffer (100 mM), pH 2.5, with addition of 40% v/v methanol was used as background electrolyte (BGE). Sodium dodecyl sulfate (150 mM) was added to BGE in the inlet vial as the sweeping agent. The system enables effective separation of anthracyclines as well as cleanup from matrix impurities. Sweeping preconcentration of sample provides an excellent detection limit (1 x 10(-9) mol L(-1)). The method was applied for the determination of therapeutic levels of doxorubicin in real plasma samples.

Positive ion electrospray ionization mass spectrometry of double-stranded DNA/drug complexes

Positive ion electrospray ionization mass spectra of 16 base-pair double-stranded (ds)DNA have been obtained with essentially no ions from single-stranded DNA present. Single-stranded DNA was minimized by: (1) careful choice of DNA sequences; (2) the use of a relatively high salt concentration (0.1 M ammonium acetate, pH 8.5), and, (3) a low desolvation temperature (40 degrees C). Similarly, ESI-MS complexes of dsDNA with cisplatin, daunomycin and distamycin were obtained that contained only negligible amounts of single-stranded DNA. The complexes with daunomycin and distamycin were more stable to strand separation in the gas phase than dsDNA alone. This is in agreement with solution studies and with other recent gas phase results. These data contrast with many earlier ESI-MS studies of dsDNA and DNA/drug complexes in which ions from ssDNA are also normally observed.

The effect of liposome encapsulated daunorubicin on rabbit eyes after extracapsular lens extraction

PURPOSE

To investigate the effect of liposome encapsulated daunorubicin (DNR) on rabbit eyes when it was used in prevention of posterior capsule opacification (PCO).

METHODS

The liposome encapsulated DNR was prepared by modified freeze-thawing method. Each eye was injected with 0.1 ml liposomes (0.2 mg/ml and 20 micrograms/ml DNR) into the capsular bag during the extracapsular lens extraction (ECLE) in 10 rabbit eyes respectively. The phosphate buffer solution (PBS) was injected as control. Besides biomicroscope observation and histology examination of all eyes, the concentration of DNA in aqueous humor was also determined by high performance liquid chromatography (HPLC).

RESULTS

The morphology of liposome encapsulated DNR were similar to the blank liposome with round or ellipse shape. The encapsulated effeciency of liposome encapsulated DNR was 45.1%. The inflammatory response was much more severe both in 0.2 mg/ml and 20 micrograms/ml DNR group than the control after liposome injection. All eyes in DNR group were showed severe corneal edema and opacity and lasted for 4 to 8 weeks. Histopathological study revealed that lens epithelial proliferation occured by 4 weeks and Soemmering's ring developed by 8 weeks in control; However, in DNR group eye only a few LECs remained in the bag and there were obvious corneal edema and eosinophiles infiltration. Corneal endothelial cells were severely lost.

CONCLUSION

The results suggest that liposome encapsulated DNR could inhibit metaplasia and proliferation of remnant lens epithelial cells after ECLE in rabbit eyes, but the severe toxicity must be avoided by further study.

Regulation of cellular glutathione modulates nuclear accumulation of daunorubicin in human MCF7 cells overexpressing multidrug resistance associated protein

Multidrug resistance (MDR) is frequently associated with the overexpression of P-glycoprotein (Pgp) and/or multidrug resistance associated protein (MRP1), both members of the ABC superfamily of transporters. Pgp and MRP1 function as ATP-dependent efflux pumps that extrude cytotoxic drugs from tumour cells. Glutathione (GSH) has been considered to play an important role in the MRP1-mediated MDR. In our study, we examined the effects of buthionine sulphoximine (BSO), an inhibitor of GSH biosynthesis, on the nuclear accumulation of daunorubicin (DNR), in etoposide (VP16) and doxorubicin (ADR) resistant MCF7 cell lines, overexpressing respectively MRP1 (MCF7/VP) and Pgp (MCF7/ADR). The study of DNR transport was carried out using scanning confocal microspectrofluorometry. This technique allows the determination of the nuclear accumulation of anthracyclines in single living tumour cells. Treatment of MCF7/VP cells with BSO increased the sensitivity of these cells to DNR whilst the cytotoxicity of the drug in MCF7/ADR cells remained unchanged. In MCF7 resistant cells treated with BSO, their GSH level decreased as observed by confocal microscopy. DNR nuclear accumulation in MCF7/VP cells was increased by BSO whereas in MCF7/ADR cells BSO was unable to significantly increase the DNR nuclear accumulation. These data suggest a requirement for GSH in MRP1-mediated resistance whilst the nuclear efflux of GSH conjugates is probably not the primary mechanism of Pgp-mediated MDR. Finally, BSO might be a useful agent in clinical assays for facilitating detection of MRP1 expression.

A simple HPLC method using a microbore column for the analysis of doxorubicin

Doxorubicin is one of the most potent anti-tumor agents generally used in the treatment of bone cancer. A simple and sensitive HPLC method was developed and validated for the assay of doxorubicin. The method used a C18 Luna microbore column (50 x 1 mm) with a fluorescent detector (505 nm Ex. and 550 nm Em.). The mobile phase consisted of water-acetonitrile-acetic acid (80:19:1, v/v/v, pH 3.0) and the flow rate was 0.1 ml min(-1). Daunomycin was used as the internal standard. This isocratic system required a 10-min run-time, giving a detection limit of 0.02 ng (0.035 pmol per injection). Standard curves were linear over the concentration range of 0.01-0.1 microg ml(-1). Relative standard deviations (R.S.D.) for the within-day, day-to-day precision, and the accuracy measurement for the assay were less than 4.0, 3.2, and 4.1%, respectively. This HPLC method was used to study the in vitro release characteristics of doxorubicin from implantable drug delivery system.

[Preparation of liposome encapsulated daunorbicine and determination of daunorubicine of aqueous humor in rabbit eyes]

PURPOSE

To investigate the method of determination the concentration of daunorubicine(DNR) and liposome encapsulated daunorubicine(LDNR) of aqueous humor in rabbit eyes.

METHODS

After extracapsular lens extraction, 0.1 ml of 1 mg/ml DNA and LDNR were injected into the anterior chamber. At the 12, 24, 48 hours and 1 week after operation, the aqueous humor were aspirated to determine the concentration of DNR by high performance liquid chromatography(HPLC).

RESULTS

At the 12, 24, 48 hours after operation, DNR were determined in all eyes, but at one week after operation, the DNR could only be detected in LDNR group. The concentration of DNR in LDNR group were higher than DNR group.

Idarubicin and idarubicinol are less affected by topoisomerase II-related multidrug resistance than is daunorubicin

We investigated the cytotoxicity and cellular pharmacology of idarubicin (IDA), idarubicinol (IDAol) and daunorubicin (DNR) in K562/VP-H2 cells, which show topoisomerase II-related multidrug resistance but do not overexpress P-glycoprotein. K562/VP-H2 cells were less resistant to IDA and IDAol than to DNR. There was no significant difference in the accumulation of each drug between K562 and K562/VP-H2 cells. The cleavage of DNA induced by each drug was decreased in K562/VP-H2 cells, however, the decrease in cleavage in K562/VP-H2 cells was less with IDA and IDAol than with DNR. These results suggest that IDA and IDAol have more cytotoxic potency than DNR in topoisomerase II-related multidrug-resistant leukemia cells.

Rapid DNA quantification method in microplates using daunorubicine fluorescence quenching

We have developed a rapid, sensitive and inexpensive method to quantify DNA in crude extracts or PCR reaction products using daunorubicine fluorescence quenching. We obtained a linear standard curve from 4.7 ng to 600 ng DNA and no interaction was observed in the presence of proteins.

P-glycoprotein (PGP), and not lung resistance-related protein (LRP), is a negative prognostic factor in secondary leukemias

BACKGROUND AND OBJECTIVE

In cell lines, there is an ongoing debate about the role of the lung resistance-related protein (LRP) whereas the role played by P-glycoprotein (PGP) in determining a multidrug resistance is well known. The aim of this study was to evaluate the frequency and the role of a PGP and an LRP overexpression in affecting the intracellular daunorubicin accumulation (IDA) and in predicting the therapy outcome on a subset of overt secondary acute non lymphocytic leukemias (ANLL). An adjunctive point was to evaluate the efficacy of the reversal agent SDZ PSC 833 (PSC) in counteracting impaired IDA.

DESIGN AND METHODS

By flow cytometry, PGP and LRP expression and the IDA were evaluated on 54 overt secondary ANLL PGP and LRP overexpressions were respectively defined by an MRK-16 mean fluorescence index (MFI) > or = 6 (PGP+) and by an LRP-56 MFI > or = 5 i.e. by MRK-16 and LRP-56 MFIs higher than the one observed in normal leukocytes. The blasts' IDA was studied after a two-hour incubation in 1000 ng/mL daunorubicin in the presence or in the absence of the MDR reversal agent SDZ PSC 833 (PSC) 1.6 mumol.

RESULTS

A PGP overexpression was detected in 40/54 (74%) cases while an LRP overexpression was observed on 33/54 (61%) cases. No differences were found in terms of PGP and LRP expressions between ANLL developing after chemo/radiotherapy (therapy-related ANLL) or evolving from a myelodysplastic syndrome (MDS-related ANLL). Compared to the PGP-, the PGP+ cases showed a significantly lower mean IDA (DNR NMFI 196 +/- 46 vs. 267 +/- 53, p < 0.001). The co-incubation of DNR with the PSC significantly increased only the mean IDA of the PGP+ cases, that grew from a DNR NMFI of 196 +/- 46 to a DNR NMFI of 284 +/- 67 (p < 0.0001). With respect to normal leukocytes, even the PGP- cases had an impaired IDA suggesting that other mechanisms, including an LRP overexpression, could affect the IDA. A strongly negative correlation was observed between PGP overexpression and therapy outcome, in fact, 8/10 (80%) PGP- but only 2/27 (7%) PGP+ patients obtained complete remission (p = 0.0002). Moreover, 7/33 (21%) cases showing an impaired IDA (NMFI < 280) but 4/4 (100%) with NMFI > 280 had complete remission (p = 0.006). No correlation was found between therapy response and LRP or CD34 expression.

INTERPRETATION AND CONCLUSIONS

This data suggests that an important role in determining therapy outcome is played by PGP in secondary leukemias. Even if the LRP is frequently overexpressed in secondary leukemias and is likely to contribute to the reduction of the intracellular drug accumulation, the role played by LRP in determining the therapy-outcome has still to be cleared.

Flow cytometric analysis of P-glycoprotein expression and drug efflux in human soft tissue and bone sarcomas

Twenty-two fresh surgical specimens of human sarcomas (soft tissue and bone) from 20 patients were analyzed by flow cytometry for the expression of drug resistance-related P-glycoprotein (P-gp) and cellular daunorubicin (DNR) accumulation with or without the presence of DNR efflux blockers. Single-cell suspensions prepared from the tumor specimens were analyzed by dual-color flow cytometry after reaction with MRK-16 (anti-P-gp) and anti-CD45 (pan-leukocyte) antibodies. MRK-16 reactivity of tumor cells was evaluated after exclusion of CD45-positive cells by electronic gates. Parallel samples were incubated with DNR alone or in combination with DNR efflux blockers, verapamil (VPL), or dipyridamole (DPD) for determination of cellular DNR accumulation and the effect of the efflux blockers. Extensive heterogeneity was observed in both P-gp expression and DNR accumulation of the tumor specimens examined. Eight of the 22 tumor specimens had significant numbers of P-gp-positive cells. In three of the eight P-gp-positive tumors, cellular DNR accumulation was significantly increased by co-incubation with the efflux blockers VPL or DPD. These results indicate that both quantitative and functional analysis of P-gp expression may be essential in determining the cellular drug resistance phenotype of tumor cells and its correlation with therapeutic outcome.

Probenecid reverses multidrug resistance in multidrug resistance-associated protein-overexpressing HL60/AR and H69/AR cells but not in P-glycoprotein-overexpressing HL60/Tax and P388/ADR cells

PURPOSE

To determine whether probenecid, an inhibitor of organic anion transport, is able to reverse multidrug resistance (MDR) through modulation of the drug transport function of MDR-associated protein (MRP) and P-glycoprotein (P-gP).

METHODS

Two MRP-overexpressing cell lines (HL60/AR and H69/AR) and two P-gP-overexpressing cell lines (HL60/Tax and P388/ADR) were cultured with different concentrations of daunorubicin (DNR) or vincristine (VCR) in the presence or absence of various concentrations of probenecid (0.01-10 mM). Drug sensitivity was determined using an MTT assay. DNR accumulation and subcellular distribution were determined by flow cytometry and confocal microscopy respectively. VCR accumulation was determined by scintillation spectrometry.

RESULTS

Probenecid, in a concentration-dependent manner, reversed resistance to DNR and VCR in HL60/AR and H69/AR tumor cell lines. This effect of probenecid on MDR was associated with an increased accumulation of DNR and VCR and correction of the altered subcellular distribution of DNR. The concentrations of probenecid that reversed MDR are clinically achievable in vivo. In contrast, probenecid did not reverse MDR in either HL60/Tax or P388/ADR tumor cell lines that overexpress P-gP.

CONCLUSION

These results suggest that probenecid is an effective chemosensitizer of MRP-associated MDR tumor cells and is a potential candidate for clinical use to reverse MDR.

[Rubomycin Q1--an anthracycline metabolite from Streptomyces coeruleorubidus 2679, a strain producing rubomycin C]

In the programme of screening of biologically active secondary metabolites produced by Streptomyces coeruleorubidus 2679 a new reddish-violet component (rubomycin Q1) with antibacterial and cytotoxic activity was isolated from the culture fluid of the organism. Some physico-chemical and biological properties of a chromatographically pure rubomycin Q1 were investigated. It was shown with the use of 1H NMR, UV, IR and mass spectrometry that rubomycin Q1 was an anthracycline antibiotic (9,10-anhydro-13-desoxycarminomycin).

Intracellular localization, vesicular accumulation and kinetics of daunorubicin in sensitive and multidrug-resistant gastric carcinoma EPG85-257 cells

In the human gastric carcinoma cell line EPG85-257P (parent) induction of resistance to daunorubicin (DAU) was achieved by selection with stepwise increased concentrations of the drug. The new variant was named EPG85-257DAU and was shown to overexpress the mdr1 gene product 170 kDa P-glycoprotein (P-Gp) as demonstrated by immunocytochemistry and mdr1-specific RT-PCR. To investigate the intracellular pathway of DAU the subcellular distribution of this autofluorescent drug was studied in the resistant cells and compared to its chemosensitive counterpart EPG85-257P. When sensitive cells were exposed to DAU the drug rapidly accumulated in the nucleus until cell death. No redistribution of DAU to the cytoplasm was observed. In resistant cells exposed to the drug DAU also accumulated in the nucleus but to a lesser extent than in parent cells. Following exposure, nuclear fluorescence was observed to decrease over a time period of up to 48 h. Six hours after DAU exposure formation of fluorescent vesicle formation started in the perinuclear region and increased continuously. After 48 h nuclear fluorescence was no longer detectable and DAU was located exclusively in vesicles. During this period the vesicles moved from the region of origin to the cell periphery. A pulse chase experiment showed, that vesicles may contain DAU derived from the nucleus. Treatment of EPG85-257DAU cells with DAU in conjunction with the chemosensitizer cyclosporin A (CsA) increased nuclear fluorescence without impairing vesicle formation. Disruption of microtubules by nocodazole led to an accumulation of vesicles in the perinuclear region indicating that microtubules are involved in vesicular transport. Treatment of EPG85-257DAU cells with the actin disruptor cytochalasin B led to accumulation of vesicles in the cell periphery indicating that actin may be involved in exocytosis. Uptake and efflux of DAU and rhodamin (RH) were determined in sensitive and resistant cells using a fluorescence activated cell sorter. Uptake of both compounds was distinctly lower in resistant than in sensitive cells. When resistant cells preloaded for 2 h with RH subsequently were incubated in drug free medium the substance was rapidly released indicating transmembrane transport by P-Gp. In contrast, despite expression of P-Gp in resistant cells no considerable release of DAU was observed for up to 2 h under the same experimental protocol. This indicates that in resistant cells intracellular DAU at least in part may be inaccessible for P-Gp and that vesicular drug transport appears to contribute to DAU resistance by removing intracellular DAU via exocytosis.

Multidrug resistance phenotype evaluation by immunofluorescence and functional tests: comparison of two monoclonal antibodies and three fluorescent dyes in three cells lines

Various agents have been shown to enhance drug sensitivity of multidrug resistant (MDR) cells and are thus of interest when the MDR phenotype is identified. Detection of MDR cells is of importance and can be carried out either by immunofluorescence with monoclonal antibodies or by functional tests using fluorescent dyes uptake. MDR has been analysed by flow cytometry on three sensitive and resistant cell lines, with MRK16 and C219 monoclonal antibodies directed against P-glycoprotein (P-gp) and with rhodamine 123, Hoechst 33342 and daunorubicin. Resistant cells were revealed by MRK16 and C219 but the results obtained with MRK16 gave higher both percentages of fluorescent cells and mean fluorescence. Fluorescence intensity observed with daunorubicin was lower than with rhodamine 123. With Hoechst 33342, mean fluorescence was quite identical on sensitive and on resistant cells. It was concluded that MRK16 and rhodamine 123 were well adapted to detect P-gp and evaluate its functional ability.

Validation of a single point flow cytometric assay for determining P-glycoprotein activity in multidrug resistant cell lines

P-glycoprotein, a transmembrane protein which acts as an energy dependent efflux pump, has been implicated as one mechanism of multidrug resistance (MDR) in human tumours. Commonly employed assays measure P-glycoprotein immunohistochemically or mdr1 messenger RNA. In this study we compared a single point flow cytometric assay for determining activity of P-glycoprotein with cellular expression of P-glycoprotein determined by Western blot. Five cell lines, with varying levels of multiple drug resistance, were incubated with daunorubicin (DNR) in the presence (treated) and absence (control) of cyclosporine or verapamil, agents known to inhibit the activity of P-glycoprotein. The treated cell lines, along with non-treated controls were examined for intracellular concentrations of DNR measured by fluorescence intensity using a flow cytometer. The ratio of fluorescence intensity expressed in the treated/control was used as an index of functional activity of P-glycoprotein. Functional activity of the P-glycoprotein as determined by flow cytometry correlates highly with cellular content of P-glycoprotein measured by western blot (correlation coefficients of r = 0.90-0.98 for the various cell line combinations). This method represents a rapid single point flow cytometric assay which may be suitable for screening clinical samples for P-glycoprotein activity.

Ultrastructural localization of daunomycin in multidrug-resistant cultured cells with modulation of the multidrug transporter

We localized the chemotherapeutic drug daunomycin inside cultured cells by taking advantage of its inherent fluorescence. Multidrug-resistant cultured cells, in which the accumulation of daunomycin can be reversibly controlled with verapamil to block the multidrug transporter, were incubated in daunomycin and verapamil and the accumulated daunomycin was visualized with epifluorescence optics. After fixation under a variety of different conditions to make cells permeable to diaminobenzidine (DAB), the internal daunomycin was illuminated under the fluorescence microscope in the presence of DAB. Photooxidation of DAB in sites of fluorescing daunomycin (photoconversion) resulted in intracellular deposition of oxidized DAB product. These sites were then visualized by transmission electron microscopy. In cells in which the multidrug transporter was inhibited by verapamil, daunomycin was localized in the nucleus of cells by mild fixation conditions such as formaldehyde. Increasing amounts of glutaraldehyde in the fixative caused apparent quenching of the nuclear fluorescence but still allowed fluorescence to occur in other cell organelles, which were then well preserved. Daunomycin was found in the nuclear envelope, the endoplasmic reticulum, and in lysosomes in cells in which the multidrug transporter was inhibited. Lysosomal accumulation has been previously described and was expected because of the known accumulation of positively charged molecules in organelles with low pH. However, the accumulation of daunomycin in the nuclear envelope and endoplasmic reticulum has not been previously observed. These results clearly demonstrate the utility of fluorescence photoconversion methodology for the high-resolution ultrastructural localization of fluorescent materials.

Effect of differentiating agents on modulation of MDR1 gene expression in multidrug-resistant hematopoietic HL60/DNR cell line

The phenomenon of multidrug resistance (MDR) is frequently encountered in clinical situations, and could contribute to the failure of chemotherapy in acute leukemia. Preliminary studies have suggested that MDR1 gene expression in normal hematopoietic stem cells might be downregulated during differentiation. In the present study, we induced a multidrug-resistant promyelocytic leukemia cell line, HL60/DNR, to myeloid differentiation by exposure to all-trans retinoid acid and dimethyl sulfoxide (DMSO). We found that HL60/DNR cells retained the ability to respond to the differentiation stimulus. However, although MTT assays revealed a slight decrease of IC50 in differentiated cells, neither efflux of daunorubicin (DNR), nor expression of P-glycoprotein (P-gp), nor quantity of MDR1 mRNA has been downregulated in differentiated cells. We can conclude, therefore, that MDR1 gene expression in this multidrug-resistant myeloid cell line is not modified by induction of its differentiation.

Solid-phase extraction and optimized separation of doxorubicin, epirubicin and their metabolites using reversed-phase high-performance liquid chromatography

A reversed-phase isocratic high-performance liquid chromatographic method is described in which a formal structured procedure was applied to predict the mobile phase composition giving optimal baseline resolution of the clinically important anticancer agents doxorubicin and 4'-epidoxorubicin (epirubicin), their principal metabolites, and daunorubicin (internal standard). These formal statistical procedures included the simultaneous techniques of solvent selectivity triangle and factorial design for range-finding preliminary studies, followed by use of the modified simplex, a sequential procedure. These were used to select the parameters of organic modifier, buffer strength and pH necessary for use with a Spherisorb ODS 1 column, to achieve optimal separation of eight anthracycline solutes. Ultraviolet and fluorescence detection was used (lambda ex = 254 nm, lambda em = 560 nm), and the latter gave a low detection limit for doxorubicin in serum of 1 ng ml-1. The optimal mobile phase composition was determined to be acetonitrile-0.06 M Na2 HPO4 containing 0.05% (v/v) triethylamine adjusted to pH 4.6 with 0.03 M citric acid (35:65, v/v). A solid-phase extraction method was developed to enable the selective isolation of anthracyclines by adsorption onto C8 Bond-Elut cartridges, and is based on extraction of serum spiked with a mixture of the anthracycline solutes. The anthracyclines were eluted using acetonitrile-0.2 M Na2 HPO4 containing 0.05% (v/v) triethylamine adjusted to pH 3.6 with 0.1 M citric acid (67.5:32.5, v/v). Reproducible recoveries for doxorubicin (94 +/- 8%) and for epirubicin (96 +/- 8%) were obtained (n = 5). In particular, recoveries for the 7-deoxyaglycone metabolite (99%) were higher than other extraction methods cited.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of secondary metabolism in Streptomyces spp. and overproduction of daunorubicin in Streptomyces peucetius

Two DNA segments, dnrR1 and dnrR2, from the Streptomyces peucetius ATCC 29050 genome were identified by their ability to stimulate secondary metabolite production and resistance. When introduced into the wild-type ATCC 29050 strain, the 2.0-kb dnrR1 segment caused a 10-fold overproduction of epsilon-rhodomycinone, a key intermediate of daunorubicin biosynthesis, whereas the 1.9-kb dnrR2 segment increased production of both epsilon-rhodomycinone and daunorubicin 10- and 2-fold, respectively. In addition, the dnrR2 segment restored high-level daunorubicin resistance to strain H6101, a daunorubicin-sensitive mutant of S. peucetius subsp. caesius ATCC 27952. Analysis of the sequence of the dnrR1 fragment revealed the presence of two closely situated open reading frames, dnrI and dnrJ, whose deduced products exhibit high similarity to the products of several other Streptomyces genes that have been implicated in the regulation of secondary metabolism. Insertional inactivation of dnrI in the ATCC 29050 strain with the Tn5 kanamycin resistance gene abolished epsilon-rhodomycinone and daunorubicin production and markedly decreased resistance to daunorubicin. Sequence comparison between the products of dnrIJ and the products of the Streptomyces coelicolor actII-orf4, afsR, and redD-orf1 genes and of the Streptomyces griseus strS, the Saccharopolyspora erythraea eryC1, and the Bacillus stearothermophilus degT genes reveals two families of putative regulatory genes. The members of the DegT, DnrJ, EryC1, and StrS family exhibit some of the features characteristic of the protein kinase (sensor) component of two-component regulatory systems from other bacteria (even though none of the sequences of these four proteins show a significant overall or regional similarity to such protein kinases) and have a consensus helix-turn-helix motif typical of DNA binding proteins. A helix-turn-helix motif is also present in two of the proteins of the other family, AfsR and RedD-Orf1. Both sets of Streptomyces proteins are likely to be trans-acting factors involved in regulating secondary metabolism.

Relations between the penetration, binding and average concentration of cytostatic drugs in human tumour spheroids

A penetration assay based on freeze-drying and vapour fixation was applied to show the spatial distribution of non-bound and bound cytostatic drugs in cellular spheroids. Several studies have proposed that peripheral binding of drugs correlates with limited penetration. We showed that granular accumulation, mainly at the peripheral part of spheroids, might occur in parallel with good penetration. For example, this was the case in human glioma spheroids after incubation with Adriamycin for 15-30 min. Following treatment with actinomycin D, colon carcinoma spheroids exhibited rather good penetration but also showed granular accumulation mainly in their peripheral regions. Ara-C accumulated largely and homogeneously in the peripheral regions of colon carcinoma spheroids and this severely delayed penetration. It took about 1 h for ara-C in the central regions of the spheroids to reach the same concentration as in the culture medium. In contrast, ara-C easily penetrated glioma spheroids without accumulating noticeably at the periphery. Retention tests involving washing and further incubation in drug-free culture medium revealed that the areas demonstrating extensive accumulation most often retained the drug, indicating binding, whereas the concentration of drug in other areas decreased. The oil-centrifugation method, which was used for rapid separation of the spheroids from the drug-containing medium, showed that the average concentration of daunomycin in the spheroids exceeded that in the culture medium as early as after 15 min, by which time only limited penetration had occurred. We found that good penetration of ara-C correlated with a low average concentration in glioma spheroids, whereas limited penetration correlated with a high average concentration in colon carcinoma spheroids. The latter finding was attributable to the high accumulation of drug at the spheroid periphery. Thus, there was an inverse relationship between penetration and binding and between penetration and average drug concentration. It seemed that binding delayed or prevented penetration, whereas little, if any binding resulted in better penetration. Granular binding such as that observed Adriamycin and actinomycin D gave intermediately good penetration.

High-performance liquid chromatographic analysis of idarubicin and fluorescent metabolites in biological fluids

A specific, sensitive, and reliable high-performance liquid chromatographic (HPLC) method for the determination of idarubicin (IDA) and its known fluorescent metabolites idarubicinol (IDAol) and 4-demethoxy-daunomycinone (AG1) in biological fluids (human plasma and urine) was developed and tested. Plasma samples were solid-phase-extracted (C18 bonded silica cartridges). Complete separation of unchanged drugs and metabolites was achieved on a Cyanopropyl chromatographic column (25 cm x 4.6 mm inside diameter; particle size, 5 microns) using fluorescence detection (excitation wavelength, 470 nm; emission wavelength, 580 nm). Sensitivity was better than 0.2 ng/ml for all analytes; rates of recovery of unchanged drug and metabolites were better than 84.5% (IDA), 80.3% (IDAol), and 83.9% (AG1). The interassay coefficient of variation was 6.5% for IDA, 5.8% for IDAol, and 9.8% for AG1. Mean intra-assay precision was 4.6% for IDA, 5.9% for IDAol, and 5.0% for AG1 at sample concentrations of above 1 ng/ml and 12.1% for IDA, 10.8% for IDAol, and 14.1% for AG1 at sample concentrations of below 1 ng/ml.

Laser scanning and confocal microscopy of daunorubicin, doxorubicin, and rhodamine 123 in multidrug-resistant cells

The multidrug-resistant gene (MDR1) encodes an energy-dependent drug efflux pump (P-glycoprotein) for many anti-cancer drugs. We have studied the intracellular distribution of rhodamine 123 (R123), daunorubicin (DN), and doxorubicin (DOX) in cells expressing a human MDR1 gene. The distribution of these fluorescent drugs was measured by laser scanning microscopy and confocal microscopy. We devised a new method for analysis of fluorescence line scan data to determine the intracellular distribution of fluorescent probes. This method and confocal microscopy showed that R123, DN, and DOX are localized to both plasma membrane and intracellular compartments in multidrug-resistant cells. When the cells are treated with verapamil, an inhibitor of the multidrug transporter, the amount of DOX, DN, and R123 associated with the cell rises. After inhibition, the relative distribution of DOX and DN between the cell surface and intracellular structures does not change dramatically. However, R123 tends to relocalize to intracellular sites from predominantly plasma membrane sites, indicating that this dye behaves differently than the anti-cancer drugs. These results show the subcellular distributions of R123, DN, and DOX in plasma membrane, cytoplasm, and intracellular membrane systems, but do not allow definitive distinctions among existing models of how P-glycoprotein affects the distribution of drugs.

The SOS-Chromo-spottest: evaluation of a short-term test for the determination of genotoxic compounds in contaminated environmental samples

To evaluate the sensitivity of the SOS-Chromo-spottest towards genotoxic compounds 5 reference chemicals (4-nitroquinoline-1-oxide (4-NQO), methylmethansulfonate (MMS), 2,4,7-trinitro-9-fluorenone (TNF), sodium azide (SA) and daunomycin (DM) were tested by 3 different agar plate media (STA-plates: synthetic media containing Xgal, B-plates: synthetic media containing 1% lactose and bromocresolpurple, C-plates: 1% lactose bromocresolpurple media containing complex nutrients). Even 1 ng of 4-NQO showed genotoxic effects by using STA-plates. The threshold value for MMS was 80 nl, for TNF 160 ng and for DM 80 ng. Similarly the spottest with B-plates are positive results, but the sensitivity of this test procedure was 80 to 250 times lower than the STA-plate test. The C-plate test only reacted with high amounts of 4-NQO (1000 ng). Therefore, the SOS-chromo-spottest with STA-media described by Quillardet and Hofnung seems to be a sufficient procedure to detect genotoxic compounds in contaminated environmental samples directly without previous extraction procedures. The simpler B-plates can be used to examine the genotoxicity of certain compounds like industrial or household chemicals where the genotoxicants can be expected to be present in high doses.

Sensitive method for the determination of daunorubicin and all its known metabolites in plasma and heart by high-performance liquid chromatography with fluorescence detection

The cytostatic agent daunorubicin is effective against leukaemia. An important side-effect is cardiomyopathy, common to all anthracyclines. Since anthracycline metabolites are thought to contribute to the observed cardiotoxicity, a method for the quantitative determination of all metabolites in plasma as well as in tissues is needed as a basis for the further investigation of the correlation between toxicity and the amount of each metabolite formed. Using Sep-Pak C18 cartridges we were able to extract daunorubicin and its five metabolites, including the aglycones, with recoveries in the range 50-90%. Depending on the chemical properties of each metabolite, fluorescence detection following high-performance liquid chromatographic separation permitted detection limits as low as 0.2-0.9 nM in plasma and 0.8-3.10(-11) mol/g in tissue, at a signal-to-noise ratio of 2, which compare favourably with literature data. The method showed linearity in the ranges 1-250 nM in plasma and 0.04-4.0 nmol/g in tissue (r greater than or equal to 0.998). The accuracy determined at 10 and 100 nM for plasma and at 0.1 and 1.0 nmol/g for tissue, was in the range 86-103 and 85-110% for plasma and tissue, respectively. The within-day and between-day repeatability values were acceptable (between 2 and 12%). Because of large inter-compound differences, separate calibration curves were used for each anthracycline. Application of the assay to the analysis of plasma and tissue samples of mice after intravenous injection of daunorubicin proved successful.

Effect of cyclosporin A on daunorubicin accumulation in multidrug-resistant P388 leukemia cells measured by real-time flow cytometry

We investigated the mode of action of cyclosporin A (Cy-A) as a modifier of multidrug resistance in P388 mouse leukemia cells. A fluorescence-activated flow cytometer (FCM) was modified with a flow-through cuvette to allow continuous on-line monitoring of daunorubicin uptake in vitro. The addition of Cy-A to multidrug-resistant P388/R cells at steady-state daunorubicin uptake, led to a dose-dependent increase in cellular daunorubicin accumulation, as measured by FCM and high-performance liquid chromatography (HPLC). A linear relationship was found between the daunorubicin concentration in the incubation medium and the Cy-A concentration required for optimal stimulation of cellular anthracycline accumulation. The results of a cytotoxicity assay indicated that Cy-A completely restored the chemosensitivity of the P388/R cells. Intracellular Cy-A measurements in P388/S and P388/R cells showed that P388/R cells accumulated significantly less Cy-A than P388/S cells. Relatively high daunorubicin concentrations could not restore that accumulation defect. These results suggest that Cy-A promotes cellular anthracycline accumulation by competing for an outward drug-transport system that operates in multidrug-resistant cells.

Improvement of flow-cytometric detection of multidrug-resistant cells by cell-volume normalization of intracellular daunorubicin content

To improve the ability of flow cytometry to detect multidrug-resistant cells, we studied the extent to which cell volume heterogeneity accounts for the variance of intracellular daunorubicin (DNR) content. For P388 murine or HL-60 human leukemia cells exposed to DNR (1 micrograms/ml, 60 min), log intracellular DNR content varied in direct proportion to log cell volume measured by flow cytometry, with a correlation coefficient of .9. This relationship was confirmed by cell sorting based on intracellular DNR content with subsequent volume determination of the sorted cells. Normalization of intracellular DNR content for cell volume (thus obtaining intracellular DNR concentration) was accomplished by subtracting log cell volume from log intracellular DNR content for each cell. This resulted in a 34% decrease (range 23-58%) in standard deviation compared to DNR content measurements without volume normalization for all cell types tested. Following exposure to DNR (as above), intracellular DNR content of drug-sensitive P388 or HL-60 cells measured by flow cytometry was 12- and 8-fold greater than that of the multidrug-resistant sublines P388/ADR and HL-60/AR, respectively. However, because of the variance of intracellular DNR content, the predictive value of flow-cytometric determination of intracellular DNR content as a discriminant assay for detecting the frequency of drug-resistant cells in a mixed population was acceptable only when the frequency of resistant cells in the population exceeded 10%. In contrast, volume normalization of intracellular DNR content enhanced the ability of the flow-cytometric assay to discriminate resistant cells by 10-fold for P388 cells and 100-fold for HL-60 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of doxorubicin photodegradation in plasma, urine and cell culture medium by HPLC

An HPLC method was used to monitor the chemical stability of doxorubicin-HCl (DXR) to light in plasma, urine and cell culture medium at room temperature. The results indicated that DXR was very unstable in cell culture medium and urine when exposed to light. It was more stable in plasma under the same conditions. In all the cases, the decrease in the amount of DXR is greatly dependent on light intensity (no noticeable degradation was observed after 8 h in the dark). These observations may be important for the correct interpretation of the effects and the toxicity of doxorubicin on cells incubated in cell medium, and for determination of urinary or plasma pharmacokinetic parameters.

Fast atom bombardment mass spectrometric analysis of anthracyclines and anthracyclinones

A mass spectral characterization of a set of anthracyclines and anthracyclinones comprised of daunorubicin, adriamycin and their modified analogs was carried out by using negative and positive fast atom bombardment (FAB) ionization techniques. Addition of more than one hydrogen to the molecular ions of the anthracyclines was observed. The choice of the FAB matrix played an important role in the characterization of these compounds. The dominant ions in the molecular ion region were M-. (or M+.) and MH- (or MH+.2) when sulfolane and glycerol, respectively, were employed as the FAB solvents. The major fragmentation was cleavage of the glycosidic bond with the charge retention mainly on the aglycone moiety. Aromatization of the tetracyclic ring promoted further fragmentation of the aglycone moiety. The anthracyclinones could be characterized only by negative FAB ionization using sulfolane as the FAB matrix. The assigned fragmentation pathways were confirmed by acquiring metastable ion spectra using B/E linked-field scans.

Isolation of highly multidrug-resistant P388 cells from drug-sensitive P388/S cells by flow cytometric cell sorting

To investigate the spontaneous frequency of occurrence of stable multidrug-resistant cells in a population of drug-sensitive cells, we exposed drug sensitive P388/S cells to daunorubicin (dnr) for 1 h, then used fluorescence-activated cell sorting based on intracellular dnr fluorescence to isolate cells within P388/S having different intracellular content of drug. One of the sort windows chosen (low dnr content sort window) isolated only P388/S cells with intracellular drug content equal to or less than that of the known multidrug-resistant subline P388/adr. This sort window constituted approximately 3% of P388/S cells with lowest dnr content. By such a procedure we were able, on one of seven attempts, to isolate and cultivate stable, highly multidrug-resistant cells (comparable to that of P388/adr) from the P388/S cells obtained from the low dnr-content sort window. Net growth of cells in culture was observed 15-20 days after sorting, indicating that of the P388/S cells collected from the low dnr-content sort window, very few were actually highly drug-resistant. On no occasion could resistant cells be cultivated from cells sorted from P388/S with higher dnr content, as would be expected if mutation to a multidrug-resistant phenotype had occurred as a result of exposure to drug. The resistant cells isolated from P388/S by sorting (called P388/LoSort) displayed low intracellular accumulation of dnr that was enhanced by verapamil, were cross-resistant to vincristine and actinomycin-D, and distinct from P388/S, possessed a 150- to 160-kD membrane species identified by Vinca alkaloid photoaffinity labeling.(ABSTRACT TRUNCATED AT 250 WORDS)

Fast atom bombardment mass spectrometry of some anthracycline and bisanthracycline derivatives

Fast atom bombardment (FAB) mass spectra of daunomycin, four of its derivatives, seven bisanthracyclines and three mixed-functional daunomycin-acridine derivatives are reported. These anthracyclines all exhibited their expected [MH]+ ions and peaks corresponding to the fragmentations which are characteristic of the anthracycline moiety, and in addition the spectra showed enhanced [MH + n]+ (n = 1-4) ions which were attributed to reductive processes occurring in the liquid matrix under FAB conditions. Daunomycin was also observed to form a dimeric cluster ion [M2H]+ together with associated reduced ions under FAB conditions. We have found that FAB mass spectrometry is an ideal method for the qualitative analysis of large, non-volatile derivatives of anthracyclines.