Dissolution behavior and gastrointestinal absorption of dicumarol from solid dispersion systems of dicumarol-polyvinylpyrrolidone and dicumarol-beta-cyclodextrin.
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Pronounced intersubject differences in the apparent first-order elimination rate constant (kapp) for dicumarol in rats have been found to be due to corresponding differences in the distribution of dicumarol between the liver (the site of dicumarol biotransformation) and the rest of the body. From theoretical considerations and experimental results in animals given only dicumarol, it has been shown that kapp is linearly related to the fraction of drug in the liver (FL). The proportionality constant (k) for these variables was defined as the intrinsic elimination rate constant for dicumarol which should reflect the activity of the enzyme system(s) involved in the elimination of this drug. The purpose of this investigation was to determine the effect of enzyme induction on dicumarol distribution and on the relationship between kapp and FL in rats. It was found that pretreatment with phenobarbital caused a substantial increase in kapp, but that it had no apparent effect on the serum/liver and serum/kidney concentration ratios of dicumarol. The relative weight of the liver was significantly increased by phenobarbital treatment but the weight of the kidneys was not affected. Linear relationships between kapp and FL were found for both the control and the phenobarbital treated groups, but with a significant difference in the slopes of the regression lines. This study illustrates the application of a pharmacokinetic technique which permits a clear and quantitative distinction between the relative contributions of enzyme activity and body distribution to the in vivo elimination kinetics of a drug.
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The water-soluble derivative of vitamin K, menadiol sodium bisulfite (K3), and the related anticoagulant dicumarol, inhibited growth of murine leukemia L1210 in liquid suspension culture. K3, but not dicumarol, cytotoxicity was abrogated by 1 mM cysteine. Isobolographic analysis of the effect of K3-dicumarol combinations, in the concentration ranges between 5 and 75 microM, on L1210 growth, indicated synergy between the two drugs. K3 (10 microM) caused a 3-fold stimulation of KCN-resistant O2 consumption by L1210 cells; addition of 50 microM dicumarol did not enhance KCN-resistant O2 consumption further, suggesting that K3-dicumarol synergy in L1210 was not due to dicumarol-mediated augmentation of K3-semiquinone-free radical formation. We examined the effect of dicumarol addition on L1210 cellular metabolites known to be affected by K3, i.e., glutathione, NADPH and ATP. Dicumarol prevented the elevation of the glutathione pool caused by less than or equal to 18 microM K3. K3-dicumarol combinations depleted the NADPH pool significantly, at concentrations of each which did not affect the NADPH pool. No synergistic effect on the ATP pool was observed. Thus, although the mechanism of K3-dicumarol synergy vs. leukemia remained unclear, it was possible that effects on the glutathione and/or NADPH pools contributed. We also investigated the effect of K3 and dicumarol on 45Ca++ transport by L1210 cells because of their effects on glutathione. Neither drug affected 45Ca++ influx or efflux rate constants. However, equilibrium 45Ca++ uptake was suppressed by K3 at concentrations lower than those which depleted glutathione.
Dicumarol is a naturally occurring anticoagulant derived from coumarin that induces cytotoxicity and oxidative stress in human pancreatic cancer cells (Cullen, J. J., Hinkhouse, M. M., Grady, M., Gaut, A. W., Liu, J., Zhang, Y., Weydert, C. J. D., Domann, F. E., and Oberley, L. W. (2003) Cancer Res. 63, 5513-5520). Although dicumarol has been used as an inhibitor of the two-electron reductase NAD(P)H:quinone oxidoreductase (NQO1), dicumarol is also thought to affect quinone-mediated electron transfer reactions in the mitochondria, leading to the production of superoxide (O2*-) and hydrogen peroxide (H(2)O(2)). We hypothesized that mitochondrial production of reactive oxygen species mediates the increased susceptibility of pancreatic cancer cells to dicumarol-induced metabolic oxidative stress. Dicumarol decreased clonogenic survival equally in both MDA-MB-468 NQO1(-) and MDA-MB-468 NQO1+ breast cancer cells. Dicumarol decreased clonogenic survival in the transformed fibroblast cell line IMRSV-90 compared with the IMR-90 cell line. Dicumarol, with the addition of mitochondrial electron transport chain blockers, decreased clonogenic cell survival in human pancreatic cancer cells and increased superoxide levels. Dicumarol with the mitochondrial electron transport chain blocker antimycin A decreased clonogenic survival and increased superoxide levels in cells with functional mitochondria but had little effect on cancer cells without functional mitochondria. Overexpression of manganese superoxide dismutase and mitochondrial-targeted catalase with adenoviral vectors reversed the dicumarol-induced cytotoxicity and reversed fluorescence of the oxidation-sensitive probe. We conclude mitochondrial production of reactive oxygen species mediates the increased susceptibility of cancer cells to dicumarol-induced cytotoxicity.
The effect of serum protein binding on the elimination kinetics of dicumarol was studied. The serum free fraction of dicumarol was essentially independent of concentration over a wide concentration range and ranged from 0.00015 to 0.00079 in 10 adult rats. The total clearance of dicumarol in these animals ranged from 3.93 to 14.5 ml/kg/hr. As in previous studies, there was an excellent linear correlation between the elimination rate constant for dicumarol and the fraction of dicumarol in the liver (i.e., the amount of drug in the liver divided by the amount of drug in the body). Consistent with theoretical considerations, there was a positive and apparently linear relationship between the total clearance and the serum free fraction of dicumarol. The individual serum free fraction and the fraction in liver values for dicumarol were strongly correlated. The pharmacokinetic model based on a proportional relationship between the apparent elimination rate constant and the fraction in the liver applies to dicumarol but not to warfarin and has limited utility. On the other hand, the model relating total clearance to the serum free fraction has been found to apply to dicumarol, warfarin, and other extensively plasma protein-bound drugs and can be utilized under clinical conditions.
Dicumarol is routinely added to the 3-[4,4-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay to study the role of NAD(P)H:quinone oxido-reductase in drug activation and detoxification. We assessed the direct impact of dicumarol (a mitochondrial uncoupler) on the MTT assay. Mouse mammary tumor (EMT6) and Chinese hamster ovary (CHO) cells were treated with media containing either 10 or 1% fetal bovine serum and dicumarol (0-1000 microM) mimicking standard assay conditions. MTT, clonogenic, total reactive oxygen species (ROS), and oxygen consumption assays were performed. Significant increases in the apparent viability of EMT6 and CHO cells were observed with MTT assays after short time periods with maximum effects at 2 hr. Reduced serum concentrations intensified this effect. Conversely, significant decreases in viability for both cell lines occurred after longer incubations and serum withdrawal enhanced this effect in both cell lines. Clonogenic assays provided contrasting results where viability increased significantly only in EMT6 cells (not CHO) and was smaller than that reported by MTT. Furthermore, greater dicumarol toxicity was observed in clonogenic assays. Significant toxicity compared to control occurred after 4-hr treatment (vs. 12 hr MTT) and serum withdrawal also increased the toxicity of dicumarol with extended culture. ROS production in EMT6 and CHO cells increased in a concentration-dependent manner with 20-min dicumarol administration and thereafter declined. The EC(50) for dicumarol-induced oxygen consumption was 0.84 microM in CHO compared to 1.18 microM in EMT6 cells. Cell lines are differentially sensitive to the toxicity of dicumarol and cell survival data may be skewed by its inclusion, probably due to ROS production and mitochondrial uncoupling. Dicumarol is not recommended for inclusion in the MTT assay.
Dicumarol (3,3'-methylenebis[4-hydroxycoumarin]) is an inhibitor of brefeldin-A-dependent ADP-ribosylation that antagonises brefeldin-A-dependent Golgi tubulation and redistribution to the endoplasmic reticulum. We have investigated whether dicumarol can directly affect the morphology of the Golgi apparatus. Here we show that dicumarol induces the breakdown of the tubular reticular networks that interconnect adjacent Golgi stacks and that contain either soluble or membrane-associated cargo proteins. This results in the formation of 65-120-nm vesicles that are sometimes invaginated. In contrast, smaller vesicles (45-65 nm in diameter, a size consistent with that of coat-protein-I-dependent vesicles) that excluded cargo proteins from their lumen are not affected by dicumarol. All other endomembranes are largely unaffected by dicumarol, including Golgi stacks, the ER, multivesicular bodies and the trans-Golgi network. In permeabilized cells, dicumarol activity depends on the function of CtBP3/BARS protein and pre-ADP-ribosylation of cytosol inhibits the breakdown of Golgi tubules by dicumarol. In functional experiments, dicumarol markedly slows down intra-Golgi traffic of VSV-G transport from the endoplasmic reticulum to the medial Golgi, and inhibits the diffusional mobility of both galactosyl transferase and VSV-G tagged with green fluorescent protein. However, it does not affect: transport from the trans-Golgi network to the cell surface; Golgi-to-endoplasmic reticulum traffic of ERGIC58; coat-protein-I-dependent Golgi vesiculation by AlF4 or ADP-ribosylation factor; or ADP-ribosylation factor and beta-coat protein binding to Golgi membranes. Thus the ADP-ribosylation inhibitor dicumarol induces the selective breakdown of the tubular components of the Golgi complex and inhibition of intra-Golgi transport. This suggests that lateral diffusion between adjacent stacks has a role in protein transport through the Golgi complex.
The mean half-life of dicumarol in the plasma of seven sets of identical and seven sets of fraternal twins after a single oral dose of 4 mg/kg was 43.6+/-SD 17.9 hr. Half-lives ranged from 7 to 74 hr in these 28 normal adults not receiving other drugs for 2 wk preceding dicumarol administration. Large differences among unrelated individuals in dicumarol half-life disappeared almost completely in identical twins, but persisted to some extent in most sets of fraternal twins. These results indicate that marked differences among subjects in dicumarol half-life are under genetic rather than environmental control. Reproducibility of values for dicumarol half-life was demonstrated. A direct relationship between the dose and the half-life of dicumarol occurred in unrelated volunteers administered progressively larger doses at 10-day intervals. Dose dependence of the half-life of a drug results in increased variability of half-life and hence in greater risks of toxicity on long-term therapy. Risks of toxicity on the one hand and of failure to anticoagulate adequately on the other can be reduced by determining dicumarol half-life before starting long-term therapy. Half-lives for dicumarol and phenylbutzone tended to be correlated in the 28 twins, but no correlation occurred between dicumarol and antipyrine half-lives.
Several quinoneimines have been shown to be substrates for partly purified rat liver cytosolic quinone reductase with either NADH or NADPH as cofactor. Km and Vmax values with NADH as cofactor for N-acetyl-p-benzoquinoneimine were 54.9 microM and 278 mumol/min/mg; for 2-amino-1,4-naphthoquinoneimine, 2.8 microM and 38 mumol/min/mg; for N,N-dimethylindoaniline, 1.7 microM and 22 mumol/min/mg; and 2-acetamido-N,N-dimethylindoaniline, 0.4 microM and 9 mumol/min/mg. All the quinoneimines showed substrate inhibition at high concentrations. At 30 microM dicumarol, an inhibitor of quinone reductase, potentiated the acute toxicity of quinoneimines to cultured phenobarbital-induced rat hepatocytes by 0.7- to 2.9-fold. Dicumarol was toxic to cultured non-induced rat hepatocytes and produced little or no increase in quinoneimine toxicity. Dicumarol potentiated the toxicity of 2-methyl-1,4-naphthoquinone (menadione) to cultured non-induced, as well as phenobarbital-induced, hepatocytes. Levels of quinone reductase in both types of hepatocytes were similar. Quinoneimines exhibited strong growth inhibitory properties with Chinese hamster ovary (CHO) cells and A204 human rhabdomyosarcoma cells. Dicumarol, 0.1 mM, potentiated growth inhibition by N,N-dimethylindoaniline and 2-acetamido-N,N-dimethylindoaniline in A204 but not in CHO cells. Growth inhibition by 2-amino-1,4-naphthoquinoneimine was inhibited by dicumarol in both cell lines. Dicumarol potentiated growth inhibition by 2-methyl-1,4-naphthoquinone in A204 and CHO cells. Quinone reductase activity in A204 cells was 48% and in CHO cells 1% of the activity in cultured hepatocytes. The lack of a correlation between the effects of dicumarol on quinoneimine and quinone growth inhibition and levels of cellular quinone reductase suggests that dicumarol has effects in cells in addition to, or other than, inhibition of quinone reductase. It is concluded that quinone reductase may protect cells against quinoneimine toxicity under certain conditions, as with phenobarbital-induced hepatocytes, but does not appear to play a major role in modifying quinoneimine toxicity in non-induced hepatocytes, or growth inhibition in CHO cells or A204 cells.
Dicumarol, often used as a specific inhibitor of DT diaphorase (NAD(P)H:(quinone-acceptor) oxidoreductase; EC 1.6.99.2), was found to potently inhibit GSH transferases (EC 2.5.1.18). Dicumarol exhibited an IC50 of 11 microM in inhibiting the conjugation of 1-chloro-2,4-dinitrobenzene (50 microM) by GSH transferase GT-8.7, the major hepatic class mu isoenzyme of CD-1 mice. The activities of GT-8.7 and of the class pi isoenzyme, GT-9.0, toward a carcinogenic substrate, 4-nitroquinoline 1-oxide (100 microM), were inhibited by dicumarol with IC50 values of 14 and 9 microM, respectively. Dicumarol also affected GSH peroxidase II activity, inhibiting the reduction of cumene hydroperoxide by GT-10.6, the predominant class alpha GSH transferase of mouse liver, with an IC50 of 14 microM. GSH peroxidase I (EC 1.11.1.9) and GSH peroxidase II activities were resolved by chromatography of liver and testis cytosols. While inhibiting GSH peroxidase II with IC50 of 9-10 microM, dicumarol did not affect the activity of the selenoenzyme, GSH peroxidase I. Whereas several other non-substrate ligands were more potent inhibitors of 1-chloro-2,4-dinitrobenzene conjugation, dicumarol effectively inhibited GSH transferase and GSH peroxidase II activities in the range of dicumarol concentrations frequently used for detection of DT diaphorase action. These results indicate that physiological consequences resulting from the use of supramicromolar concentrations of dicumarol should not be interpreted in terms of DT diaphorase inhibition alone.
The interaction of dicumarol derivatives and protriptyline with respect to the binding to alpha 1-acid glycoprotein (AGP) has been investigated by circular dichroism (CD), equilibrium dialysis and ultrafiltration. Investigation of the induced CD spectra of dicumarol derivatives bound to AGP indicated that the conformations of these compounds were different when bound to AGP. Though all the dicumarol derivatives, protriptyline and AGP formed a ternary complex, interaction modes were different, depending upon the substituent groups at position 3 of the dicumarol molecule. On the basis of the protriptyline effect on the CD spectra of all dicumarol derivatives bound to AGP, the compounds were classified in the following way: (1) Dicumarol, ethylidenebis 4-hydroxycoumarin and propylidenebis 4-hydroxycoumarin caused reversal of the sign of ellipticity. This interaction was explained by cooperative binding. (2) Butylidenebis 4-hydroxycoumarin and pentylidenebis 4-hydroxycoumarin generated new band and disappeared ellipticity of the original Cotton effect. This interaction was also explained by the cooperative binding mode. (3) Ethylbiscoumacetate which generated the CD band similar to that of dicumarol in the absence of protriptyline, reversed the sign of the CD spectrum only at 325 nm. The interaction was anticooperative in nature. (4) Benzylidenebis 4-hydroxycoumarin represented type four which had no change in the CD spectrum by the addition of protriptyline. This interaction was explained by the two-state model accompanying the conformational change of AGP. These results suggested that all compounds, except for benzylidenebis 4-hydroxycoumarin, induced negative Cotton effects at 325 nm by taking the same asymmetrical perturbation by the addition of protriptyline and the interaction was carried out according to model 2. An attempt to study the interaction mechanism of two or more drugs with regard to the binding to protein using these models is thought to help in understanding drug-protein interactions.
Dicumarol [3,3'-methylene-bis(4-hydroxycoumarin)] is a potent inhibitor of NAD(P)H:quinone oxidoreductase-1. Exposure of rat liver epithelial cells or of human skin fibroblasts to dicumarol resulted in a rapid and complete inhibition of connexin-43-dependent gap junctional intercellular communication (GJC). GJC was restored within 60min following removal of dicumarol. The concentration of dicumarol required for half maximal inhibition of GJC was 3muM, making dicumarol about 10-fold more effective in blocking GJC than 1-octanol and flufenamic acid, known inhibitors of GJC. Warfarin, a related coumarin derivative, also attenuated GJC, yet very high concentrations of 5-10mM were required. Dicumarol-induced downregulation of GJC was found not to be due to an interference with pathways enhancing the phosphorylation of connexin-43, such as epidermal growth factor receptor and extracellular signal-regulated kinase pathways. Rather, inhibition of GJC by dicumarol was paralleled by a reversible loss of a phosphorylated form ("P2") of connexin-43.
The interaction of dicumarol and phenothiazine neuroleptics binding to alpha 1-acid glycoprotein (AGP) was investigated by circular dichroism (CD) and equilibrium dialysis. The induced CD spectra of the dicumarol-AGP complex were affected differently by the different substituents of the phenothiazine molecule. The sign of the induced Cotton effect of dicumarol bound to AGP was reversibly changed with the introduction of the propyldimethylamine substituent at position 10 or chloride group at position 2 of the phenothiazine molecule. Chlorpromazine, which contains both of these substituents reversed the sign of the induced Cotton effect with the highest intensity. The addition of trifluoperazine, fluphenazine, and promethazine containing neither of the two substituents generated a new negative CD band. However, the addition of opromazine, which contains sulfoxide at position 5, decreased the CD intensity of the dicumarol-AGP complex without changing the shape of the CD spectra. Equilibrium dialysis studies revealed that the interaction of dicumarol-AGP with phenothiazine derivatives occurred simultaneously, and the interaction followed a cooperative and anticooperative binding model. Further, among the six phenothiazine derivatives that reversed the signs of the induced Cotton effects of the dicumarol-AGP complex, a linear relationship was observed between coupling constants and the difference in the induced optical ellipticity. The opromazine and dicumarol interaction was competitive for a common binding site on the AGP molecule. Removal of sialic acid did not have any effect on this interaction. These data support the hypothesis that the acidic and the basic drug binding sites overlap each other.
PURPOSE NAD(P)H: quinone oxidoreductase (NQO(1)) catalyzes the two-electron reduction of quinones to hydroquinones. This reaction is believed to prevent the one-electron reduction of quinones that would result in redox cycling with generation of superoxide (O(2)(.-)). We have recently demonstrated that inhibition of NQO(1) with dicumarol increases intracellular O(2)(.-) production and inhibits the in vitro malignant phenotype of pancreatic cancer cells (J. Cullen et al., Cancer Res., 63: 5513-5520, 2003). We hypothesized that inhibition of NQO(1) would increase cell killing, induce oxidative stress, and inhibit in vivo tumor growth. EXPERIMENTAL DESIGN AND RESULTS: In the human pancreatic cancer cell line MIA PaCa-2, dicumarol decreased cell viability, as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and decreased clonogenic survival. Dicumarol increased the percentage of apoptotic cells in a time-dependent and dose-dependent manner as measured by 3,3'-diaminobenzidine staining and flow cytometry, which was associated with cytochrome c release and poly(ADP-ribose) polymerase cleavage. Dicumarol also induced oxidative stress as evidenced by increased total glutathione and oxidized glutathione, as well as sensitizing to cell killing mediated by menadione. In established orthotopic pancreatic tumors in nude mice, intratumoral injections of dicumarol slowed tumor growth and extended survival. CONCLUSIONS: Inhibition of NQO(1) with dicumarol induces cell killing and oxidative stress in pancreatic cancer cells and speculate that dicumarol may prove to be useful in pancreatic cancer therapeutics.
The distribution, elimination, and anticoagulant effect of dicumarol and warfarin were determined in adult males rats following intravenous injection of single doses of these drugs in crossover experiments. The biological half-life of dicumarol ranged from 5 to 28 hr; that of warfarin ranged from 9 to 30 hr. There was a statistically significant correlation between the following pharmacokinetic characteristics of dicumarol and warfarin in individual animals: biological half-life, apparent volume of distribution, total plasma clearance, and concentration in plasma eliciting one-half the maximum anticoagulant effect (effective concentration). The mean ratio of the respective biological half-lives (warfarin/dicumarol) was 1.42, and that of the apparent volumes of distribution was 1.50. The ratio of the effective plasma concentrations (dicumarol/warfarin) was correlated negatively with the half-life of dicumarol and positively with the ratio of the half-life values (warfarin/dicumarol) in individual animals. Additional studies with serum samples from other rats showed pronounced interindividual differences in the serum protein binding of both dicumarol and warfarin and a strong correlation between the protein binding of these two drugs in serum of individual animals. The results of this study, together with the results of previous studies in this series, indicate that serum protein binding is the major determinant of interindividual differences in the pharmacokinetics of dicumarol and warfarin in rats under these experimental conditions.
The total clearance of dicumarol was determined in 172 adult male Sprague-Dawley rats. Clearance values ranged from 1.46 to 27.0 ml/hr/kg. Statistical analysis of a histogram of the total clearance values indicated a trimodal distribution, with modes at 6.28, 14.8, and 23.7 ml/hr/kg. The percentage of animals in each of these components was 60.5, 33.7, and 5.8. A previous study had shown that the total clearance of dicumarol was proportional to the fraction of nonprotein-bound drug in serum (serum free fraction) and that interindividual differences in total clearance of dicumarol in rats were due almost entirely to corresponding differences in the serum free fraction. Therefore, it is likely that the observed trimodal frequency distribution of total clearance values reflects a similar distribution of serum free fraction values of dicumarol. The frequency distribution curve for dicumarol total clearance is very similar to the trimodal frequency distribution curve for warfarin serum free fraction values in rats. This observation is consistent with the previously demonstrated strong correlation of serum free fraction values of dicumarol and warfarin in individual animals.