3-[(E)-(acridin-9'-ylmethylidene)amino]-1-substituted thioureas and their biological activity

This paper describes the synthesis of a novel series of acridine thiosemicarbazones through a two-step reaction between various isothiocyanates and hydrazine followed by treatment with acridin-9-carbaldehyde. The properties of this series of seven new derivatives are studied using NMR and biochemical techniques, and the DNA-binding properties of the compounds are determined using spectrophotometric studies (UV-vis absorption, fluorescence, and circular/linear dichroism) and viscometry. The binding constants K are estimated as being in the range of 2.2 to 7.8×10⁴M^-1 and the percentage of hypochromism was found to be 22.11-49.75% (from UV-vis spectral titration). Electrophoretic experiments prove that the novel compounds demonstrate moderate inhibitory effects against Topo I activity at a concentration of 60×10^-6M.

C60-SIMS imaging of nanoparticles within mammalian cells

To achieve successful drug delivery via nanoparticles the interactions between the nanoparticle and the chemistry of the surrounding biological environment is of central importance. A thorough understanding of these interactions is necessary in order to better elucidate information regarding drug pathways and mechanisms of action in treatment protocols. As such, it is important to identify the location of the nanoparticle, the state of its functionalization, as well as any changes in the cellular environment. The use of cluster secondary ion mass spectrometry (SIMS) using C60 (+) primary ions makes simultaneous acquisition of this information possible. Here, SIMS has been successfully used to chemically image gold nanoparticles (AuNPs) within a model, single cell system involving macrophage-like RAW 264.7 cells. The macrophage-like properties of this cell line make it extremely well-suited for cell-uptake studies. Both AuNPs and two pharmaceutical compounds, amiodarone and elacridar, were successfully imaged within a cellular system using cluster SIMS. To verify that SIMS can also be used to detect functionalization and nanoparticles simultaneously, fluorophore-functionalized AuNPs were studied as a model system. The fluorescent characteristics of these functionalized nanoparticles enabled the visual confirmation of the presence and location of the particles within the cell.

Investigating the binding of acridine, acridine orange, and acridine yellow G to humic acid through fluorescence quenching

A fluorescence quenching method was used to determine the equilibrium binding constants for the association of acridine, acridine orange, and acridine yellow G to humic acid. The fluorescence of each polycyclic aromatic nitrogen heterocycle (PANH) was monitored as aliquots of humic acid were added, and a Stern-Volmer plot was produced in which the slope is the equilibrium constant of the binding reaction. The quenching experiments were performed at temperatures of 30, 35, 40, and 45 °C. A van't Hoff plot generated from the equilibrium binding constants as a function of temperature for a given PANH resulted in a linear plot. Calculation of the ΔHbinding, ΔGbinding, and ΔSbinding for each PANH leads to the conclusion that the equilibrium binding constant, and ΔGbinding, may be predictors of bioavailability. The other thermodynamic quantities, ΔHbinding and ΔSbinding, are helpful in understanding the relative binding of the compounds. For example, acridine yellow G appears to be the least bioavailable of the three PANHs studied because of its strong ΔHbinding = -29.8 kJ/mol, which leads to ΔGbinding = -0.71 kJ/mol. While acridine orange and acridine have similar ΔHbinding values, acridine orange is more likely to bind to humic acid because the ΔSbinding for the process is less negative. Thermodynamic values and equilibrium binding constants for all three compounds are reported.

Soft-modeling based spectrofluorimetric study of simultaneous equilibria

A two-way soft resolution method will fail when applied to a simultaneous equilibria system due to rank deficiency in its concentration profiles. Increasing the dimensionality of measurements from two-way to three-way data can be used to overcome this problem. Simultaneous dissociation of two weak acids is considered as a model for simultaneous equilibria. Three-way data obtained from excitation-emission spectrofluorimetric monitoring of a pH-metric titration is analyzed using a proper combination of well-known soft-modeling methods. Multivariate curve resolution-alternating least squares is used for calculating the excitation and emission spectral profiles of involved species and rank annihilation factor analysis for obtaining the contribution of each species in measured excitation-emission matrices at different pHs. The results of simulated and real simultaneous acids dissociation equilibria showed that the proposed combined method performs well even in situation when the equilibrium constants are close to each other. The applicability of method for study of an acidic dissociation is also shown.

Chronic exposure of the oligochaete Lumbriculus variegatus to polycyclic aromatic compounds (PACs): bioavailability and effects on reproduction

This study aimed to monitor PAC availability to the oligochaete Lumbriculus variegatus during 28 days of exposure to spiked sediments, in order to obtain reliable chronic effect concentrations for reproduction. Sediment toxicity tests were performed using three pairs of PAC isomers: two homocyclic compounds (anthracene and phenanthrene), two azaarenes (acridine and phenanthridine), and the two main transformation products of the azaarenes (acridone and phenanthridone). During the experiment, available PAC concentrations in pore water (estimated using solid phase microextraction) decreased more than total PAC concentrations in the sediment. Relating effect concentrations to PAC concentrations in pore water and in organisms showed that the two homocyclic compounds caused narcotic effects during chronic exposure, but only one of the four tested heterocyclic PACs caused narcotic effects. The transformation product phenanthridone was not toxic at the tested concentrations (up to 4000 micromol/kg dry sediment), whereas EC50 values for the parent compound phenanthridine and the isomer acridone were below the estimated limit for narcosis, suggesting a specific mode of action. These results demonstrated the unpredictable (isomer) specific toxicity of azaarenes and their transformation products, emphasizing the need of chronic toxicity testing to gain insight into the long-term effects of heterocyclic PACs, which have been overlooked in risk assessment.

Differentiation of heterocyclic regioisomers: a combined tandem mass spectrometry and computational study of N-acridin-4-ylbenzylamide and N-acridin-2-yl-benzylamide

Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) has been used to differentiate two positional isomers of acridine derivatives, N-acridin-4-ylbenzylamide and N-acridin-2-ylbenzylamide. The study revealed that the isomeric ion structures produced by these heterocycles could be distinguished upon collision-induced dissociations (CID). In particular, the loss of a water molecule was shown to be a regiospecific reaction of the protonated N-acridin-4-ylbenzylamide, in which the location of the benzylamide substituent with respect to the acridinic nitrogen greatly assists proton migration by allowing the creation of intramolecular hydrogen bonds. To a lesser extent, the two isomers could also be distinguished by the difference in the abundance of the benzoyl cation in the MS/MS spectra of the [M+H]+ ions, as this ion is produced with a much higher rate from N-acridin-4-ylbenzylamide. Calculations based on quantum-mechanical models have been performed to evaluate the stability of the ion structures and to support mechanisms proposed for these two dissociation reactions.

Resveratrol Improves Ischemia/Reperfusion-Induced Oxidative Renal Injury in Rats

BACKGROUND

The present study was designed to examine whether resveratrol, a potent antioxidant, protects against renal ischemia-reperfusion (I/R) injury.

METHODS

Wistar albino rats were unilaterally nephrectomized and subjected to 45 min of renal pedicle occlusion followed by 6 h of reperfusion. Resveratrol (RVT, 30 mg/kg, i.p.) or vehicle was administered twice, at 30 min prior to ischemia and immediately before the reperfusion period. At the end of the reperfusion period, rats were decapitated and kidney samples were taken for histological examination or determination of levels of renal malondialdehyde (MDA), an end product of lipid peroxidation; glutathione (GSH), a key antioxidant; and myeloperoxidase (MPO) activity, an index of tissue neutrophil infiltration. Formation of reactive oxygen species in hepatic tissue samples was monitored by using chemiluminescence (CL) technique with luminol and lucigenin probes. Renal tissue collagen content as a fibrosis marker was also determined, while serum creatinine and urea concentrations were measured for the evaluation of renal function. Tumor necrosis factor-alpha (TNF-alpha ) and lactate dehydrogenase (LDH) were also assayed in serum samples.

RESULTS

Ischemia/reperfusion caused a significant decrease in tissue GSH level, which was accompanied by significant increases in the renal luminol and lucigenin CL values, MDA level, MPO activity and collagen content. Similarly, serum creatinine and BUN levels, as well as LDH and TNF-alpha, were elevated in the I/R group as compared to control group. On the other hand, resveratrol treatment reversed all these biochemical indices, as well as histopathological alterations that were induced by I/R.

CONCLUSIONS

Findings of the present study suggest that resveratrol exerts renoprotective effects via its radical scavenging and antioxidant activities, which appear to involve the inhibition of tissue neutrophil infiltration.

Chemiluminescent acridinium-9-carboxamide boronic acid probes: Application to a homogeneous glycated hemoglobin assay

Chemiluminescent acridinium-9-carboxamide probes containing 1, 3, 9, and 27 phenylboronic acids were prepared and their chemiluminescent properties evaluated. The relative chemiluminescent signal from the probes varied from 4 to 0.83 x 10(19)counts/mol across the series, while the apparent affinity of the probes for the diabetes marker glycated hemoglobin increased from 211 to 0.43 microM. The dose-dependent modulation of the chemiluminescent intensity of the probes upon binding was used to demonstrate a homogeneous assay for glycated hemoglobin.

Quantitative analysis of the P-glycoprotein inhibitor Elacridar (GF120918) in human and dog plasma using liquid chromatography with tandem mass spectrometric detection

A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method for the determination of the P-glycoprotein and breast cancer resistance protein inhibitor Elacridar in human and dog plasma is described. The internal standard was stable isotopically labelled Elacridar. Sample pretreatment involved liquid-liquid extraction with tert-butyl methyl ether. Analysis of Elacridar and internal standard was performed by reversed-phase LC on a basic stable minibore analytical column with an eluent consisting of acetonitrile and aqueous ammonia. An API-2000 triple-quadrupole mass spectrometer with an electrospray ion source was used in the positive-ion multiple reaction monitoring mode. The run time per sample was only 6 min. The method is sensitive and specific, with a dynamic range from 1 to 500 ng ml(-1) from 100 microl of human or dog plasma. The accuracy of the method was within 15% bias and the precision was lower than 15% for all tested concentration levels and in both matrices. The method is simple and the liquid-liquid extraction produces clean samples. This method was successfully applied to support the pharmacokinetics of a clinical trial in which orally applied Elacridar was used as a bioavailability enhancer.

New acridone derivatives for the electrochemical DNA-hybridisation labelling

In the field of DNA sensing, DNA hybridisation detection is generally performed by fluorescence microscopy. However, fluorescence instrumentation is difficult to miniaturise in order to produce fully integrated DNA chips. In this context, electrochemical detection of DNA hybridisation may avoid this limitation. Therefore, the use of DNA intercalators is particularly attractive due to their selectivity toward DNA double strand enabling DNA labelling without target chemical modification and, for most of them, to their electroactivity. We have synthesized a pyridoacridone derivative dedicated to DNA hybridisation electrochemical-sensing which presents good electrochemical reversibility, electroactivity at mild potentials and specificity toward DNA double strand. The electrochemical behaviour of this molecule has been assessed using cyclic voltammetry (CV). DNA/intercalator interactions were studied by differential pulse voltammetry (DPV) before application to hybridisation detection onto DNA sensors based on polypyrrole modified electrodes.

Electrogenerated chemiluminescence reaction of lucigenin with isatin at a platinum electrode

The electrogenerated chemiluminescence (ECL) reaction of lucigenin with isatin was investigated at a platinum electrode in a neutral aqueous solution. The ECL intensity of lucigenin at -0.65 V was greatly enhanced by isatin, and the ECL intensity was about 50 times higher than that of lucigenin without isatin. The enhanced ECL was believed to be produced by the chemiluminescence reaction between reduced lucigenin and superoxide anion that was generated by the reaction of electrochemically reduced isatin with dissolved oxygen. The conditions for the determination of isatin were optimized. Under the optimized condition, the enhanced ECL intensity vs. isatin concentration was linear in the range 4.8 x 10(-7)-1.9 x 10(-5) g/mL; with a detection limit of 3.3 x 10(-8) g/mL, and the relative standard derivation 1.0 x 10(-6) g/mL isatin was 3.8%.

Density functional theory study of vibrational spectra of acridine and phenazine

Density functional theory (DFT) calculations using Becke's exchange in conjunction with Lee-Yang-Parr's correlation functionals (BLYP), Becke's three-parameter hybrid DFT/HF method using Lee-Yang-Parr's correlation functionals (B3LYP) and ab initio Hartree-Fock (HF) method have been carried out to investigate the structure and vibrational spectra of acridine and phenazine. Structural parameters obtained by B3LYP/6-31G* geometry optimization are in good agreement with available experimental data. The raw BLYP non-CH stretching frequencies approximate the experimental results much better than the HF results with the mean absolute deviation about 16 cm(-1). The scaled B3LYP frequencies are more reliable than that of the BLYP and HF methods with the mean absolute deviation about 17 cm(-1). On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined. Also the structure and vibrational frequencies are compared with those of anthracene, pyridine and benzene to study the similarities and differences.

Quantification and purity determination of newly synthesized thioacridines by capillary liquid chromatography

Capillary liquid chromatography (CLC) was applied for quantification and impurity profile determination of ten newly synthesized acridine thioderivatives. A reversed-phase CLC system employing two different stationary phases, Nucleosil C18 and LiChrosorb RP-select B, was used. The mobile phase composition was optimized to get a satisfactory separation of impurities from the main acridine component in a reasonable analysis time. Significant differences in the chromatographic behavior between acridine derivatives containing and lacking amino groups were observed. Optimized separation conditions were used in CLC to measure the calibration curves of the acridine derivatives in a concentration range from 1.0 x 10(-6) to 1.0 x 10(-3) M at two different detector wavelengths (214 and 230 nm). Limits of detection and quantification of all the substances were determined. The detection limits went down to units of microM for most of the derivatives. CLC was also demonstrated to be a suitable method for the purity determination of test batches of the acridine thioderivatives.

Effect of size of man-made and natural mineral fibers on chemiluminescent response in human monocyte-derived macrophages

Fiber size is an important factor in the tumorigenicity of various mineral fibers and asbestos fibers in animal experiments. We examined the time course of the ability to induce lucigenin-dependent chemiluminescence (CL) from human monocyte-derived macrophages exposed to Japan Fibrous Material standard reference samples (glass wool, rock wool, micro glass fiber, two types of refractory ceramic fiber, refractory mullite fiber, potassium titanium whisker, silicon carbide whisker, titanium oxide whisker, and wollastonite). We determined how fiber length or width might modify the response of cells. We found that the patterns of time-dependent increase of CL (sigmoid type) were similar for each sample except wollastonite. We observed a strong correlation between geometric-mean length and ability to induce CL in seven samples > 6 microm in length over the time course (largest r(2) = 0.9760). Although we also observed a close positive correlation between geometric-mean width and the ability to induce CL in eight samples < 1.8 microm in width at 15 min (r(2) = 0.8760), a sample of 2.4 microm in width had a low ability to induce CL. Moreover, the relationship between width and the rate of increase in ability to induce CL had a negative correlation at 30-60 min (largest r(2) = 0.7473). Our findings suggest that the release of superoxide from macrophages occurs nonspecifically for various types of mineral fibers depending on fiber length.

Effect of mixing modes on chemiluminescent detection of epinephrine with lucigenin by an FIA system fabricated on a microchip

The chemiluminescent (CL) detection of epinephrine (EP) with lucigenin (Luc) was performed using a micro flow cell fabricated on a silicon chip. A solution of EP was injected into the Luc carrier stream. The Luc solution containing EP and an alkaline solution were successively poured into the flow cell by a pressure-driven flow system. Two types of flow cells were fabricated for estimating the effect of the mixing modes in the flow cells on the intensity of light emission. In flow cell 1, two streams entered through separate inlet ports and merged to flow adjacently. In flow cell 2, a Luc solution containing EP was split up to 36 partial flows by passage through the nozzles, and was injected into the alkaline solution. The intensity of light emission in flow cell 2 increased markedly compared to that in flow cell 1. The detection limit of 8.0 x 10(-7) M for EP in flow cell 2 was a factor of six-times better than that in flow cell 1. The improvement in the sensitivity for EP could be explained in terms of the distortion of laminar flow in flow cell 2.

Electrochemiluminescence determination of 2',6'-difluorophenyl 10-methylacridan-9-carboxylate

Electrochemical oxidation of the acridan 2',6'-difluorophenyl 10-methylacridan-9-carboxylate produces the corresponding acridinium ester, which reacts with hydrogen peroxide forming a dioxetanone intermediate. Decomposition of the dioxetanone generates light at 430 nm when it relaxes to the ground state. The effect of pH and hydrogen peroxide concentration on this ECL reaction and on the stability of the acridan were investigated. At pH 8.0 and a hydrogen peroxide concentration of 10 mM, light emission from the ECL reaction was used to determine the acridan concentration with a detection limit of 54 pmol L(-1). Results suggest that acridan esters could be used as labels in ECL immunoassays and nucleotide assays.

Lucigenin chemiluminescence in human seminal plasma

Seminal plasma protects spermatozoa from the detrimental effects of reactive oxygen species such as hydrogen peroxide. We investigated the lucigenin-dependent chemiluminescence in cell-free seminal plasma from andrological patients. The seminal plasma was separated from cells by centrifugation. In all seminal plasmas studied lucigenin-dependent chemiluminescence (LCL) was detected. The LCL showed a strong pH-dependence. The signal was stable if samples were stored at +4 degrees C for up to 4 days or up to 8 days at -80 degrees C. Filtration of the samples (0.45 and 0.22 microm pore size) did not lower their luminescence. The addition of superoxide dismutase (SOD) and ascorbic acid oxidase (AAO) lowered LCL nearly to baseline values while trolox and desferal showed moderate effect, whereas allopurinol had no effect. Electron paramagnetic resonance spectroscopy demonstrated ascorbyl radicals in seminal plasma. Physiological concentrations of ascorbic acid yielded SOD-inhibitable lucigenin-chemiluminescence. The nitroblue-tetrazolium assay showed that ascorbic acid in buffer solution produced formazan. Superoxide-anion radicals were not detected in seminal plasma by the spin-trap DEPMPO due to their low steady state concentration. It is concluded that in seminal plasma ascorbate reacts with molecular oxygen yielding ascorbyl radicals and superoxide anion. If lucigenin is added to seminal plasma, reducing substances present, such as ascorbate, reduce lucigenin to the corresponding radical; this radical reacts with molecular oxygen and also forms O2-. So LCL in human seminal plasma results from the autoxidation of ascorbate and the oxidation of the reduced lucigenin. While the physiological relevance of the former mechanism is unknown, the latter is an artifact.

Quantitative determination of noncovalently bound acridinium in protein conjugates by liquid chromatography/electrospray ion trap mass spectrometry

A sensitive and robust liquid chromatography/electrospray ion trap mass spectrometry (LC/MS/MS) method has been developed for the quantitative determination of noncovalently bound acridinium free acid in protein-acridinium conjugates. The lower level of quantitation (LOQ) for acridinium free acid was determined to be 0.6 ng. The assay was validated with a linear concentration range of 0.6-60 ng. The method requires minimum sample handling and is specific, reproducible, and provides a new aspect for protein-acridinium conjugate characterization.

Increase in resting levels of superoxide anion in the whole blood of uremic patients on chronic hemodialysis

Recently, we developed a new method to measure the resting level of superoxide anion in whole blood using an ultrasensitive chemiluminescence analyzer and lucigenin amplification. The advantage of this method is that the assay system can be performed in the absence of leukocyte isolation and stimulant administration. In this study, we applied this method to measure the blood resting levels of superoxide anion in 104 uremic patients on chronic hemodialysis (CHD) and 98 sex- and age-matched healthy controls to clarify the influence of HD on blood levels of superoxide anion. Simultaneously, the plasma levels of copper, zinc superoxide dismutase (Cu,Zn-SOD), glutathion peroxidase (GPX), myeloperoxidase (MPO) and lactoferrin (Lacto-F) were measured. The results showed that the basal blood levels of superoxide anion, Cu,Zn-SOD, and MPO in CHD patients were significantly greater than those of healthy controls. However, there was no difference in the basal plasma levels of Lacto-F and GPX between CHD patients and healthy controls. One session of HD further increased the blood levels of superoxide anion, MPO, Lacto-F and Cu,Zn-SOD but not GPX. These results suggest that the blood levels of superoxide anion are higher in CHD patients and further increase after one session of HD. This mechanism should be studied further.

Increased NADH-oxidase-mediated superoxide production in the early stages of atherosclerosis: evidence for involvement of the renin-angiotensin system

BACKGROUND

Angiotensin II activates NAD(P)H-dependent oxidases via AT1-receptor stimulation, the most important vascular source of superoxide (O2*-). The AT1 receptor is upregulated in vitro by low-density lipoprotein. The present study was designed to test whether hypercholesterolemia is associated with increased NAD(P)H-dependent vascular O2*- production and whether AT1-receptor blockade may inhibit this oxidase and in parallel improve endothelial dysfunction.

METHODS AND RESULTS

Vascular responses were determined by isometric tension studies, and relative rates of vascular O2*- production were determined by use of chemiluminescence with lucigenin, a cypridina luciferin analogue, and electron spin resonance studies. AT1-receptor mRNA was quantified by Northern analysis, and AT1-receptor density was measured by radioligand binding assays. Hypercholesterolemia was associated with impaired endothelium-dependent vasodilation and increased O2*- production in intact vessels. In vessel homogenates, we found a significant activation of NADH-driven O2*- production in both models of hyperlipidemia. Treatment of cholesterol-fed animals with the AT1-receptor antagonist Bay 10-6734 improved endothelial dysfunction, normalized vascular O2*- and NADH-oxidase activity, decreased macrophage infiltration, and reduced early plaque formation. In the setting of hypercholesterolemia, the aortic AT1 receptor mRNA was upregulated to 166+/-11%, accompanied by a comparable increase in AT1-receptor density.

CONCLUSIONS

Hypercholesterolemia is associated with AT1-receptor upregulation, endothelial dysfunction, and increased NADH-dependent vascular O2*- production. The improvement of endothelial dysfunction, inhibition of the oxidase, and reduction of early plaque formation by an AT1-receptor antagonist suggests a crucial role of angiotensin II-mediated O2*- production in the early stage of atherosclerosis.

Analysis of lipophilic peptides and therapeutic drugs: on-line-nonaqueous capillary electrophoresis-mass spectrometry

This minireview addresses the usefulness of nonaqueous capillary electrophoresis-mass spectrometry (NACE-MS), mainly in the analysis of lipophilic peptides such as gramicidin S and bacitracin, and therapeutic drugs such as pyrazoloacridine, the H2-antagonist mifentidine, tamoxifen, and their metabolites. The beneficial effects of NACE-MS in typical bioanalytical applications are analyzed case by case. A suitable and widely applicable NACE-MS analysis is identified, which is an electrolyte buffer containing ammonium acetate (5-50 mM) and/or acetic acid (up to 100 mM) with varying composition of organic solvents. Either acetonitrile or methanol or a mixture of the two are mostly utilized in the nonaqueous media. Primary considerations in developing NACE-MS are also discussed.

Early detection of peritonitis in continuous ambulatory peritoneal dialysis patients by use of chemiluminescence: evaluation of diagnostic accuracy by receiver-operating characteristic curve analysis

Continuous ambulatory peritoneal dialysis (CAPD) is now a widely accepted treatment for end-stage renal disease. However, the high incidence of peritonitis is a major complication of CAPD. Polymorphonuclear leukocytes (PMNs) play a major role in antimicrobial response of the host. During phagocytosis, the PMNs undergo a striking increase in oxidative metabolism, known as the respiratory burst, and emit light as chemiluminescence (CL). CL is thus a sensitive measure of PMN oxidative potential and correlates well with antimicrobial activity. In view of the observation of increased susceptibility to infection in CAPD patients, we have studied lucigenin- and luminol-enhanced CL in peritoneal fluids of these patients and assessed the diagnostic accuracy of these tests by ROC curve analysis. ROC curves showed diagnostic accuracies for both tests that were superior to counts of PMNs in the dialysis fluid (P <0.001). At selected cutoff values of 150000 cpm/vial for lucigenin CL and 600000 cpm/vial for luminol CL, sensitivities were 100%. Specificities for lucigenin and luminol CL were 89% and 80%, respectively. Our results suggest that CL measurements can be used as an early marker for the presence of infection in CAPD patients.

High-performance liquid chromatographic determination of pyrazoloacridine, a nitro-9-methoxyacridine anticancer agent, in human plasma

Pyrazoloacridine (PZA) is a 9-methoxy substituted acridine with a reducible nitro group. PZA has shown selective solid tumor cytotoxicity with activity against hypoxic cells, non-cycling cells and cells expressing the multidrug resistant phenotype. A high-performance liquid chromatographic (HPLC) assay was developed and validated for the determination of PZA in human plasma to support phase II clinical trials. PZA and ethyl orange, the internal standard, were isolated from human plasma by precipitating plasma proteins with methanol, and centrifuging to pellet the proteins. The resulting supernatant was injected onto a cyanopropyl HPLC column eluted isocratically with a mobile phase consisting of 125 mM ammonium acetate buffer pH 4.75-acetonitrile (76:24, v/v). A single wavelength at 460 nm was used for detection. Relative standard deviations for the assay ranged from 5.0% to 12.2% for four different drug concentrations and the limit of quantitation was 100 ng/ml. During the validation short term stability of the drug in plasma and stability of PZA on repeated freezing and thawing of plasma was evaluated. Overall recovery of PZA was 88%. This simple assay was found suitable for studying the clinical pharmacokinetics of PZA.

Identification and antitumor activity of a reduction product in the murine metabolism of pyrazoloacridine (NSC-366140)

PURPOSE

Pyrazoloacridine (PZA) is a newly developed anticancer agent currently undergoing clinical trials. Its mode of action has not been elucidated but the presence in its chemical structure of a 5-nitro functional group and its activity against oxygen-deficient cancerous cells argue in favor of enzymatic nitro reduction as a possible pathway for its antitumor activity. In order to assess the involvement of the nitro functionality in PZA activity, as well as to determine other metabolic products, a pharmacological and chemical study of PZA was designed.

METHODS

Urine and stool samples were collected from mice before and after treatment with PZA. Samples were fractionated using chromatographic methods and then evaluated using mass spectrometry (MS). One of the characterized metabolites was synthesized and tested in vitro and in vivo for anticancer activity.

RESULTS

One major fraction from mouse stool was initially characterized by MS as the 5-aminopyrazoloacridine (5-APZ). This compound was chemically synthesized by catalytic hydrogenation of PZA was stabilized as the hydrochloride salt. 5-APZ was marginally cytotoxic in vitro and was inactive in vivo against a tumor cured by PZA (Panc 03).

CONCLUSIONS

Bioreduction of the nitro group to an amine compound from PZA represents a pathway in the metabolic sequence of PZA. The inactivity of the chemically generated amine product does not provide conclusive evidence that this pathway is not involved in the cytotoxicity of PZA because other intermediates in the nitro reduction pathway may have a role in the activity of PZA. In particular, the hydroxylamine derivative of PZA could give answers to the involvement of this pathway in PZA cytotoxicity.

Angiotensin II stimulates NADH and NADPH oxidase activity in cultured vascular smooth muscle cells

The signaling pathways involved in the long-term metabolic effects of angiotensin II (Ang II) in vascular smooth muscle cells are incompletely understood but include the generation of molecules likely to affect oxidase activity. We examined the ability of Ang II to stimulate superoxide anion formation and investigated the identity of the oxidases responsible for its production. Treatment of vascular smooth muscle cells with Ang II for 4 to 6 hours caused a 2.7 +/- 0.4-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. This superoxide appeared to result from activation of both the NADPH and NADH oxidases. NADPH oxidase activity increased from 3.23 +/- 0.61 to 11.80 +/- 1.72 nmol O2-/min per milligram protein after 4 hours of Ang II, whereas NADH oxidase activity increased from 16.76 +/- 2.13 to 45.00 +/- 4.57 nmol O2-/min per milligram protein. The NADPH oxidase activity was stimulated by exogenous phosphatidic and arachidonic acids and was partially inhibited by the specific inhibitor diphenylene iodinium. NADH oxidase activity was increased by arachidonic and linoleic acids, was insensitive to exogenous phosphatidic acid, and was inhibited by high concentrations of quinacrine. Both of these oxidases appear to reside in the plasma membrane, on the basis of migration of the activity after cellular fractionation and their apparent insensitivity to the mitochondrial poison KCN. These observations suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.

Modified screening procedure with fluorescence detection for flunitrazepam and its metabolites via acridine derivatives

A modified thin-layer chromatographic method with fluorescence detection is described for the screening of flunitrazepam and its major metabolites in urine. The method is based on the hydrolysis and subsequent formation of acridine derivatives by cyclization in dimethyl-formamide. This reliable screening procedure, which has proven its usefulness in many laboratories, provides valid results in the absence of diclofenac, carbamazepine, and tricyclic antidepressants. On the other hand these latter substances are frequently detectable in urine samples taken from addicts especially during therapy. So it was necessary to modify the procedure.

Methadone: a potent inhibitor of rat liver aldehyde oxidase

Several drugs with structural similarities to SKF-525A were tested for their ability to inhibit rat liver aldehyde oxidase using the experimental antitumour agent N-[(2'-dimethylamino)ethyl]acridine-4-carboxamide (AC; NSC 601316; acridine carboxamide) as substrate. The antihistamine D-chlorpheniramine, and the antiarrhythmics disopyramide, procainamide and lignocaine were ineffective in inhibiting this reaction. The antihistamines diphenhydramine, pheniramine, doxylamine, orphenadrine, methapyrilene and pyrilamine, gave IC50 values of 100-500 microM. The narcotic analgesics D-propoxyphene and, in particular, methadone were potent inhibitors of acridine formation with IC50 values of 15.5 and 0.31 microM, respectively. Further analysis indicates mixed non-competitive type inhibition by methadone with inhibition constants (Kis and Kii, respectively) of 0.03 +/- 0.01 (SE) and 0.57 +/- 0.12 microM.

Chromatographic techniques used to determine benz[c]acridines in environmental samples

Benz[c]acridine and many of its related compounds have been shown to exhibit carcinogenic activity. Unfortunately, these compounds are continually being found in many natural and environmental samples in widely divergent geographical locations. A review of chromatographic methods for mainly benz[c]acridine and its analogues is presented.

Comparative evaluation of several DNA binding dyes in the detection of apoptosis-associated chromatin degradation by flow cytometry

Mouse thymocytes readily undergo apoptosis-associated DNA degradation upon exposure to glucocorticoids or ionizing radiation. It has been previously shown that flow cytometric cell cycle analysis of propidium iodide-stained apoptotic thymocytes results in the appearance of a distinct cell cycle region (the A0 region) below the G0/G1 region. Cells in this region were shown to be undergoing apoptosis, and determination of apoptosis by flow cytometric analysis was proposed as a superior method for evaluating thymocyte apoptosis. In this study, a variety of DNA binding dyes with diverse primary binding mechanisms were evaluated for their ability to detect glucocorticoid and ionizing radiation-induced apoptosis in mouse thymocytes. Apoptotic thymocytes stained with DNA binding dyes from the phenanthridinium, acridine, actinomycin, chromomycinone, anthracycline, and bisbenzimidazole groups all demonstrated clearly defined A0 regions with percentages comparable to those obtained for propidium iodide. These results indicate that the appearance of the A0 region is not dependent on a particular dye binding characteristic and may be the consequence of extensive changes in chromatin structure resulting in a significant degree of dye exclusion.

Comparative evaluation of several DNA binding dyes in the detection of apoptosis-associated chromatin degradation by flow cytometry

Mouse thymocytes readily undergo apoptosis-associated DNA degradation upon exposure to glucocorticoids or ionizing radiation. It has been previously shown that flow cytometric cell cycle analysis of propidium iodide-stained apoptotic thymocytes results in the appearance of a distinct cell cycle region (the A0 region) below the G0/G1 region. Cells in this region were shown to be undergoing apoptosis, and determination of apoptosis by flow cytometric analysis was proposed as a superior method for evaluating thymocyte apoptosis. In this study, a variety of DNA binding dyes with diverse primary binding mechanisms were evaluated for their ability to detect glucocorticoid and ionizing radiation-induced apoptosis in mouse thymocytes. Apoptotic thymocytes stained with DNA binding dyes from the phenanthridinium, acridine, actinomycin, chromomycinone, anthracycline, and bisbenzimidazole groups all demonstrated clearly defined A0 regions with percentages comparable to those obtained for propidium iodide. These results indicate that the appearance of the A0 region is not dependent on a particular dye binding characteristic and may be the consequence of extensive changes in chromatin structure resulting in a significant degree of dye exclusion.

Intercalation complex of proflavine with DNA: structure and dynamics by solid-state NMR

The structure of the complex formed between the intercalating agent proflavine and fibrous native DNA was studied by one- and two-dimensional high-resolution solid-state nuclear magnetic resonance (NMR). Carbon-13-labeled proflavine was used to show that the drug is stacked with the aromatic ring plane perpendicular to the fiber axis and that it is essentially immobile. Natural abundance carbon-13 NMR of the DNA itself shows that proflavine binding does not change the puckering of the deoxyribose ring. However, phosphorus-31 NMR spectra show profound changes in the orientation of the phosphodiester grouping on proflavine binding, with some of the phosphodiesters tilting almost parallel to the helix axis, and a second set almost perpendicular. The first group to the phosphodiesters probably spans the intercalation sites, whereas the tilting of the second set likely compensates for the unwinding of the DNA by the intercalator.

Reversed-phase chromatography of novel biologically effective aminoacridine-N-glycosides by OPLC

The reversed-phase chromatographic behavior of novel biologically active aminoacridine-N-glycosides is studied. The chromatographic experiments are performed with overpressurized layer chromatography. Weak ion pairs are formed with methanesulfonic acid, but only at low concentrations of the ion-pairing reagent. The retention seems to involve a reversed-phase mechanism. The base compounds only slightly modify the retention, while the number and polarity of the substituents have larger effects. The pH dependence of the retention is very typical for the aminoacridine-N-glycosides, and it plays an important role in the separation. The monoglycosides are completely separated from the corresponding base compounds, as are the diglycosides from the monoglycosides, on RP-2, RP-8, and RP-18 layers with eluents containing 30 to 60% acetonitrile and at least 0.005 M ammonium carbonate at pH 4 to 6.

[Synergistic action of combinations of penicillin and perhydroacridine derivatives]

The effect of combinations of perhydroacridine derivatives such as 10-nitroso-trans-anti-cys-perhydroacridine (MT-2) and 10-isopropylamino-trans-anti-cys-perhydroacridine (MT-6) with benzylpenicillin on growth of two penicillinase-producing strains of Staphylococcus aureus was studied. The combination components were added to the culture simultaneously or at different periods i.e. the second component was added after preliminary exposure of the bacterial cells to the first component for 1-6 hours at 37 degrees C. It was shown that duration and efficacy of the combination synergistic action were directly proportional to the time of the component addition. The highest synergistic action of the combinations was observed when both the components were simultaneously added to the staphylococcal culture. The combinations were less efficient when the bacterial cells were preliminarily incubated with the perhydroacridines. Addition of the perhydroacridine derivatives after the strain contact with the penicillin resulted in elimination of the combination synergistic action. Thin-layer chromatography did not reveal complexing between the penicillin and perhydroacridines.

Analysis of benzodiazepines. II. High-performance liquid chromatography-fluorescence detection after molecular rearrangement to acridanones

A molecular rearrangement of benzophenones (hydrolysis products of 1,4-benzodiazepines) to 9-acridones has been studied. The compounds synthesized were analysed by high-performance liquid chromatography coupled with a fluorescence detector, because of their high luminescence. The method, which can detect sixteen benzodiazepines simultaneously, is highly sensitive and adequately specific. It is reliable for the analysis of these compounds in biological samples at therapeutic concentrations.

Tricyclic drugs: potent mutagenicity of traces of a nitroarene formed in the reaction of opipramol with nitrite

The tricyclic psychotropic drug opipramol (Insidon) reacts in vitro with sodium nitrite in acidic solution to form products including mutagens for Salmonella typhimurium TA98 and TA100. Two aspects are particularly noteworthy. The strong mutagenicity of the crude reaction mixture is almost exclusively due to a compound which is present only in trace quantities (less than 0.1%). This mutagen was identified as a nitroarene, 4-[3-(2-nitro-9-(10H)-acridinon-10-yl)propyl]-1-piperazine-ethanol . Hence, while the formation of carcinogenic N-nitroso compounds from the interaction of nitrogen-containing compounds with nitrite is well known, the present study demonstrates the formation of a highly mutagenic C-nitro compound in the presence of nitrite.

[Study of the interaction of proflavine and isomeric diribonucleoside monophosphates CpG and GpC by proton magnetic resonance]

A comparative study of the interaction of proflavine with isomeric diribonucleoside monophosphates CpG and GpC has been made by the method of 1H NMR (270 MHz). A method of calculation of the parameters of complex formation from the concentration dependences of proton chemical shifts of the dye has been proposed. The equilibrium constants of 1:1 and 1:2 complexes association of these molecules and the most probable structures of the complexes have been determined.

[Chemical-analytical characterization and determination of 10-carboxymethyl-9-acridanone]

The interferon inducer 10-carboxymethyl-9-acridanone, sodium salt (CMA) is chemically and physicochemically characterized. Furthermore, a fluorimetric method of specific determination of CMA is described. The use of this assay allows to determine the content of CMA both in aqueous solutions and also in serum with a sufficient accuracy.

The activation and DNA binding of 7-methylbenz[c]-acridine catalysed by mouse liver microsomes

The metabolism of the carcinogen, 7-methylbenz[c]acridine (7MBAC), in liver microsomes prepared from untreated, and phenobarbital sodium (PB) and 3-methylcholanthrene (MC) induced male C57BL/6 mice was examined by high pressure liquid chromatography (HPLC). The abilities of control and MC induced liver microsomes to catalyse covalent binding of the carcinogen to DNA were comparable (60 pmol 7MBAC bound/mg DNA), although this maximum binding level observed was achieved at different 7MBAC concentrations for control (100 microM) and MC induced (25 microM) preparations. In vivo binding of 7MBAC to liver DNA was greater than that observed for lung DNA of the same animals but over 21 h bound 7MBAC levels decreased to a greater extent in liver than in lung. One fraction of a digest of in vitro alkylated DNA gave a fluorescence emission spectrum very similar to that of 7-methyl-1,2,3,4-tetrahydrobenz[c]acridine. This result suggests that diol epoxides functionalised at the 1,2,3,4-positions may be ultimate carcinogens derived from 7MBAC.

[Mutagenicity of 3 organic fractions of atmospheric dust and gas chromatographic analysis of the basic fraction]

Suspended particulate matter (PM) with a Dae less than 0.4 micron was collected from July 1981 till January 1982. The ether/benzene soluble extract (EEOM) and the acidic, basic and neutral fractions were determined and investigated for their mutagenic activities in the Ames bioassay. In addition particles (Dae) less than 10.2 micron derived in January were investigated. Five compounds of the basic fraction were determined by gaschromatography. The following results were obtained: Suspended particulate matter (Dae less than 0.4 micron) and the ether/benzene extract increase from July to January. The lowest rates occur in July (PM: 16.9 micron/m3) and August (EEOM: 3.0 micrograms/m3), the highest in January (PM: 48.9 micrograms/m3, EEOM: 10.5 micrograms/m3). The ether/benzene soluble portion of the suspended particulate matter increases from the average rate of 16.3% (July-September) to 22.7% (November-January). The neutral fraction amounts to 44.9%, the acidic fraction to 27.3% and the basic fraction to 3.5% of the organic matter (on an average). In experiments with metabolic activation 99% of the total mutagenicity during the period of July till September can be demonstrated by summing up the mutagenicity of the three fractions on the other hand only 59.7% from November till January. The EEOMs derived from winter exhibit without metabolic activation (250 micrograms/plate) distinctively higher numbers of revertants than the single fractions. Dose-response curves of extracts derived from back-up filters (Dae less than 0.4 micron) in January show that the acidic fraction has a slightly higher mutagenic activity than the neutral fraction (mean values of tests with and without S9-mix). The basic fraction shows no mutagenicity without S9-mix, with activation the mutagenic activity is lower than that of the other fractions. Mutagenicity expressed as rev./m3 air shows, that the neutral fraction is most efficient. The number of revertants per plate reveals-in relation to the particle size-different results concerning the three fractions (January).

Identification of the principal biliary metabolite of 4'-(9-acridinylamino)methanesulfon-m-anisidide in rats

m-AMSA [4'-(9-acridinylamino)methanesulfon-m-anisidide] labeled in either the acridine or anilino portion was used to investigate the disposition of this antitumor agent in rats. The principal biliary metabolite, which accounts for approximately 80% of the total biliary radioactivity for 90 min after administration and greater than 50% of the administered dose by 180 min after administration, had both the acridine and the anilino portions intact. Isolation and purification of the principal metabolite was achieved by preparative thin-layer chromatography on silica gel and column chromatography on Amberlite XAD-2 resin. A nuclear magnetic resonance (NMR) spectrum of the CID salt in D2O showed that the metabolite is the m-AMSA-glutathione conjugate in which the thioether linkage occurs at the 5'-position of the anilino ring. Synthesis of the metabolite was achieved by oxidizing m-AMSA with active MnO2 to -methanesulfonyl - - (9-acridinyl)-3'-methoxy - 2',5' - cyclohexadiene-1',4'-diimine (m-AQDI) followed by reaction of m-AQDI with glutathione. The 1H-NMR spectrum of the synthetic product proved identical with that of the isolated metabolite. The demonstration that the principal biliary metabolite on m-AMSA involves glutathione bound to the 9-anilino ring suggests that m-AMSA may be bioactivated in vivo to the quinoidal diimine, m-AQDI.

Genetic effects of acridine compounds

Acridines and a very large number of acridine derivatives are used in enormous quantities both in medicine and industry. The mutagenic action of these compounds has been demonstrated in a wide variety of organisms and is known to occur both in the dark as well as in the presence of light (photodynamic action). At the molecular level, acridines have been shown to cause frameshift mutations of both the addition and deletion types, a characteristic which has been of tremendous help in elucidating the nature of the genetic code. These and various other biological effects of acridines, such as inhibition of DNA repair, curing of plasmids and cell-growth inhibition, are examined in this review.