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Reversal of p-glycoprotein-mediated multidrug resistance by CJX1, an amlodipine derivative, in doxorubicin-resistant human myelogenous leukemia (K562/DOX) cells.

P-glycoprotein-mediated drug efflux can yield a multidrug resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy. Development of safe and effective MDR reversing agents is an important approach in the clinic. The aim of this study was to observe the effects of CJX1, an amlodipine derivative, on the inhibition of P-gp function and P-gp-mediated MDR in K562/DOX cells and parental K562 cells. Based on the flow cytometric technology, the uptake, accumulation and efflux of rhodamine123 (Rh123) were detected in these cells by measuring Rh123-associated mean fluorescence intensity (MFI). The effects of CJX1 on the doxorubicin cytotoxicity were evaluated by assaying for MTT (3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide) reduction and the reversal fold (RF) values. The DNA content, percentage of apoptosis and cell cycle analysis were monitored with flow cytometry. Intracellular accumulation of doxorubicin was also assessed by the determination of doxorubicin-associated MFI. Verapamil was employed as a comparative agent. Incubation of K562/DOX cells with CJX1 caused a marked increase in uptake and a notable decrease in efflux of Rh123, No such results were found in parental K562 cells. The inhibitory effect of the agent of P-gp function was reversible, but it persisted at least for 90 min after removal of 2.5 microM CJX1 from incubation medium. The doxorubicin-induced cytotoxicity, apoptosis and cell cycle perturbations were significantly potentiated by CJX1. The intracellular accumulation of doxorubicin was enhanced in the presence of various concentrations of CJX1. The CJX1 exhibited potent effects in vitro in the reversal of P-gp-mediated MDR, suggesting that the compound may become a candidate of effective MDR reversing agent in cancer chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Studies on the preparation, crystal structure and bioactivity of ginsenoside compound K.

Microbial transformation of Panaxnotoginseng saponins (PNS) using Aspergillus niger afforded, as the main metabolite, ginsenoside compound K (20-O-beta-glucopyranosyl-20(S)-protopanaxadiol). Its structure was determined spectroscopically and by X-ray analysis, and this is the first time the crystal structure of ginsenoside has been reported. In comparison with ginsenoside Rb1, the pro-drug for this metabolite, compound K exhibits potent cytotoxic activity against tumor cell lines. The mean concentrations of compound K needed to inhibit the proliferation of cells by 50% (IC50) were 12.7, 11.4, 8.5 and 9.7 microM for mouse high-metastatic melanoma (B16-BL6), human hepatoma (HepG2), human myeloid leukemia (K562) and human high-metastatic lung carcinoma (95-D) cell lines, respectively. The data show that ginsenoside compound K is a good antitumor drug candidate.

Animals↗

Synthesis and cytotoxic activity of indolyl thiazoles.

A number of indolyl thiazoles have been prepared and evaluated for their antitumor properties. The compounds were synthesized from the appropriate indole, building up the thiazole ring using the Hantzsch reaction. Cytotoxic activity was measured in the human breast cancer cell line SKBr3 using the MTT assay.

Antineoplastic Agents↗

Effects of drugs on 2',3'-dideoxy-2',3'-didehydrothymidine phosphorylation in vitro.

Drugs commonly administered to patients infected with the human immunodeficiency virus (HIV) have been studied for their propensity to alter the intracellular phosphorylation of the anti-HIV nucleoside analog stavudine (2',3'-dideoxy-2',3'-didehydrothymidine; d4T) in peripheral blood mononuclear cells (PBMCs) and U937 cells in vitro. PBMCs isolated from the blood of healthy volunteers were stimulated by the mitogen phytohemagglutinin (10 microg/ml) for 72 h. Stimulated PBMCs (3 x 10(6) cells/plate) were then incubated with [3H]d4T (0.65 microCi; 3 microM) and either acyclovir, dapsone, ddC, ddI, fluconazole, foscarnet, ganciclovir, itraconazole, lobucavir, ranitidine, ribavirin, rifampin, sorivudine, sulfamethoxazole, trimethoprim, lamivudine (3TC), zidovudine, or thymidine (30 and 300 microM) for 24 h. Doxorubicin and drugs showing some evidence of inhibition were also studied at 0.3 and 3 microM. Cells were extracted overnight with 60% methanol prior to analysis by radiometric high-performance liquid chromatography. Additional data for nine of the drugs were obtained by incubation with [3H]d4T in U937 cells for 24 h. The effect of d4T (0.2 to 20 microM) on zidovudine (0.65 microCi; 0.018 microCi) phosphorylation was also studied. Zidovudine significantly reduced d4T total phosphates in PBMCs and U937 cells (in PBMCs to 33% [P < 0.001] and 17% [P < 0.001] of that in control cells at 3 and 30 microM, respectively). A small reduction in zidovudine phosphorylation was seen with d4T but only at d4T:zidovudine ratios of 100 and 1,000. Of the other compounds screened, only thymidine, ribavirin, and doxorubicin produced inhibition of d4T phosphorylation in both PBMCs and U937 cells. However, doxorubicin was cytotoxic at 3 microM. The decrease in d4T phosphorylation in the presence of ribavirin is consistent with previous findings with zidovudine. Although ddC significantly inhibited the phosphorylation of d4T in PBMCs, this was not seen in U937 cells, and it is probable that the findings in PBMCs are related to mitochondrial toxicity [based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide cytotoxicity assay]. The only drugs screened which may interfere with d4T phosphorylation at clinically relevant concentrations were zidovudine, ribavirin, and doxorubicin.

Anti-HIV Agents↗

The influence of polycyclic hydrocarbons on the activity of NAD(P)H-dehydrogenating enzymes in rat thymus. A biochemical and histochemical study.

The action of benzo(a)pyrene, 3-methylcholanthrene and 7,12-dimethylbenzo(a)anthracene in the activity of the rat thymus D-T diaphorase (EC 1.6.99.2) and the NAD(P)H cytochrome C (EC 1.6.99.3) reductases of particulate fractions were studied in intact and adrenalectomized animals. These polycyclic hydrocarbons increased severalfold the activity of the D-T diaphorase in intact and adrenalectomized animals. The activities of the particulate enzymes were not affected by the carcinogens. Dicumarol suppresses the inducing effects of benzo(a)pyrene and adrenalectomy does not influence the inducing effects of benzo(a)pyrene and 3-methylcholanthrene. The histological distribution of the enzyme NAD(P)H-nitroblue tetrazolium reductase was studied and a marked increase in its activity in lymphocytes, macrophages and epithelial cells was found after the administration of the carcinogens.

9,10-Dimethyl-1,2-benzanthracene↗

Syntheses of 2, 5-dialkylfuran and tetrahydrofuran carbinols and their cytotoxic activity.

2, 5-Dialkylfuran and tetrahydrofuran compounds as structural elements of Annonaceae acetogenins like Asitrocinwere synthesized starting from furfural by Grignard reactions, lithiation of the furan ring and addition of aliphatic aldehydes. Hydrogenation of the furan rings over Pd-catalyst gave the corresponding tetrahydrofurans. All resulting compounds showed no or rather less antimicrobial activity against grampositive, gram-negative bacteria and fungi compared to tetracycline or clotrimazol but high cytotoxic activity against HL 60 cell line determined in the MTT assay.

Antineoplastic Agents↗

The use and effects of vital fluorescent dyes: observation of motor nerve terminals and satellite cells in living frog muscles.

Several different fluorescent mitochondrial dyes were tested as vital stains for motor nerve terminals and other cells in frog skeletal muscles. It was found that 3,3' diethyloxadicarbocyanine iodide and 4-(4-diethylaminostyryl)-N-methylpyridinium iodide were most useful. Both dyes labelled motor nerve terminals with high reliability. Electrophysiological and morphological control experiments showed that these dyes could be used to repeatedly observe neuromuscular junctions in living animals without affecting synaptic growth or remodelling. The importance of appropriate controls was emphasized by the finding that illumination, if excessively intense or prolonged, can cause physiological and structural damage to nerve terminals. Additional observations indicated that these dyes may be useful for determining the mitochondrial content, and therefore oxidative capacity, of living muscle fibres. It was also found that the fluorescent dyes labelled cells identified as muscle satellite cells, and that these myoblast precursors could be visualized in fixed whole mounts with a nitroblue tetrazolium stain. Both methods were used to study reactive cells that were closely associated with muscle fibres in lesioned muscles. Mitochondrial dyes also labelled the microvasculature, associated axons and other cells.

Animals↗

Complexes of ruthenium(III) with some 2-aminothiazole derivatives/synthesis, properties and pharmacological studies.

Four new complexes of Ru(III) with a general formula [Ru(L)2Cl2]Cl, where L = 2-amino-4-phenylthiazole (CAS 2010-06-2), 2-amino-4-methylthiazole (CAS 1603-91-4), ethyl 2-amino-4-methyl-5-thiazolecarboxylate (CAS 7210-76-6) and ethyl 2-amino-4-phenyl-5-thiazolecarboxylate (CAS 64399-23-1), were prepared. The syntheses were carried out in polar medium and inert atmosphere at a molar ratio Ru:L = 1:2 or 1:3. The compounds obtained were characterised by IR-, 1H-NMR- 13C-NMR-, UV-VIS-, EPR spectroscopy, magnetochemical and conductivity measurements. The ligands behaved as bidental, bounding Ru(III) through the nitrogen atoms from the amino group and the heterocycle. The complex of ethyl 2-amino-4-phenyl-5-thiazolecarboxylate showed significant antileukaemic activity on various human cells (IC50 values ranging from 20 to 92 micromol/l). Toxicological studies on mice indicated that such concentrations could be reached without mortality. This compound exhibited a promising antineoplastic potential and needs further pharmacological and toxicological evaluation.

Antineoplastic Agents↗

Fenugreek (Trigonella foenum graecum) seed extract prevents ethanol-induced toxicity and apoptosis in Chang liver cells.

The protective effect of a polyphenolic extract of fenugreek seeds (FPEt) against ethanol (EtOH)-induced toxicity was investigated in human Chang liver cells. Cells were incubated with either 30 mM EtOH alone or together in the presence of seed extract for 24 h. Assays were performed in treated cells to evaluate the ability of seeds to prevent the toxic effects of EtOH. EtOH treatment suppressed the growth of Chang liver cells and induced cytotoxicity, oxygen radical formation and mitochondrial dysfunction. Reduced glutathione (GSH) concentration was decreased significantly (P < 0.05) while oxidized glutathione (GSSG) concentration was significantly elevated in EtOH-treated cells as compared with normal cells. Incubation of FPEt along with EtOH significantly increased cell viability in a dose-dependent manner, caused a reduction in lactate dehydrogenase leakage and normalized GSH/GSSG ratio. The extract dose-dependently reduced thiobarbituric acid reactive substances formation. Apoptosis was observed in EtOH-treated cells while FPEt reduced apoptosis by decreasing the accumulation of sub-G1 phase cells. The cytoprotective effects of FPEt were comparable with those of a positive control silymarin, a known hepatoprotective agent. The findings suggest that the polyphenolic compounds of fenugreek seeds can be considered cytoprotective during EtOH-induced liver damage.

Antioxidants↗

Use of oxidizing dyes in combination with 2-cyanocinnamic acid to enhance hyperthermic cytotoxicity in L929 cells.

Two widely used oxidizing dyes, 2,3,5-triphenyltetrazolium chloride and methylene blue, can greatly potentiate hyperthermic cytotoxicity when administered simultaneously with 2-cyanocinnamic acid. The same compounds are virtually nontoxic to L929 cells if administered alone at 42 degrees C or in combination with 2-cyanocinnamic acid at 37 degrees C. Cytotoxicity was synergistically enhanced by the combined regimens after 3 h of heat exposure. Quercetin, a bioflavonoid known to enhance hyperthermic cytotoxicity, also acts synergistically when administered in combination with 2-cyanocinnamic acid and this effect is apparent after 1 h of heat exposure. Since these compounds do not greatly interfere with pyruvate metabolism at either normal or heat shock temperatures, a mechanism of action based on depletion of NAD(P)H is considered.

Animals↗

[Azoindoxyl methods for the investigation of hydrolases. III. Histochemical studies of beta-D-N-acetylglucosaminidase (author's transl)].

The suitability of various azoindoxyl procedures for the light microscopical demonstration of beta-N-acetylglucosaminidase is described. The incubation media tried consist of 0.5 mg N-Acetyl-(5-bromindol-3-yl)-beta-D-glucosaminide (5-Br-3-indolyl-beta-D-N-acetylglucosaminide; 1 mg dissolved in 0.05 ml N,N-dimethylformamide) in 1 ml 0.1 M citric acid phosphate buffer, pH 4.5 or 5. 0.02 ml hexazotized p-rosaniline or new fuchsine/ml or tetrazotized BAXD or 0.5 mg Fast Blue B or Garnet GBC/ml were employed as a coupling reagent. Hexazotized new fuchsine yields the best results independent on the pretreatment of the tissue and the organ investigated followed by hexazonium-p-rosaniline. Compared with the azo dye method using naphthol AS-BI beta-D-N-acetyl-glucosaminide as a substrate and hexazotized p-rosaniline or new fuchsine or tetrazotized BAXD for simultaneous coupling especially the azoindoxyl technique with the new fuchsine is equvialent or superior. When the indolyl glucosaminide is used in the indigogenic, tetrazolium or metal precipitation method the results are mostly inferior with the exception of the tetrazolium reaction using BSPT. However, the main advantage of the azoindoxyl procedure is that at least the azoindoxyl dye deriving from hexazotized p-rosaniline can be osmificated and withstands treatment with organic solvents and resins. Therefore, the reaction product seems to be suitable for the electron microscopic demonstration of glucosaminidase. Among the other reaction principles this can reliably be achieved only with BSPT as a tetrazolium salt followed by osmification of its formazan. After fixation of blocks of tissue in form- or glutaraldehyde beta-D-N-acetylglucosaminidase can be localized with 5-Br-3-indoxyl-beta-D-N-acetylglucosaminide as a substrate and hexazotized new fuchsine for simultaneous coupling in the lysosomes of many rat organs.

Acetylglucosaminidase↗

Identification, design, synthesis, and pharmacological activity of (4-ethyl-piperazin-1-yl)-phenylmethanone derivatives with neuroprotective properties against beta-amyloid-induced toxicity.

In search of novel therapeutic approaches for Alzheimer's disease (AD), we report herein the identification, design, synthesis, and pharmacological activity of (4-ethyl-piperaz-1-yl)-phenylmethanone derivatives with neuroprotective properties against beta-amyloid-induced toxicity. (4-ethyl-piperaz-1-yl)-phenylmethanone is a common substructure shared by molecules isolated from plants of the Asteraceae genus, traditionally used as restorative of lost or declining mental functions. (4-Ethyl-piperaz-1-yl)-phenylmethanone displayed strong neuroprotective properties against Abeta1-42 and reversed Abeta1-42-induced ATP depletion on neuronal cells, suggesting a mitochondrial site of action. Abeta1-42 has been described to induce a hyperactivity of the glutamate network in neuronal cells. (4-Ethyl-piperaz-1-yl)-phenylmethanone also inhibited the neurotoxic effect that glutamate displayed on PC12 cells, suggesting that the reduction of glutamate-induced neurotoxicity may be one of the mechanisms by which this compound exerts its neuroprotective properties against the deleterious effects of the Abeta1-42. These data suggest that the identified (4-ethyl-piperaz-1-yl)-phenylmethanone chemical entity exerts neuroprotective properties and may serve as a lead compound for the development of novel therapies for AD.

Adenosine Triphosphate↗

[[[(Thienylcarbonyl)alkyl]oxy]phenyl]- and [[[(pyrrylcarbonyl)alkyl]oxy]phenyl]oxazoline derivatives with potent and selective antihuman rhinovirus activity.

As an approach to more extensive structural modifications of [(oxazolylphenoxy)alkyl]isoxazoles, we synthesized new compounds characterized by the replacement of the isoxazole nucleus with furan, pyrrole, and thiophene rings and by the presence of a ketocarbonyl group in the aliphatic chain connecting these pentatomic heterocycles to the 4-(4,5-dihydro-2-oxazolyl)phenoxy, 4-(ethoxycarbonyl)phenoxy, and 4-carboxyphenoxy moieties. Some pentamethylene derivatives were also prepared, and their antirhinovirus activity was compared to that of the corresponding ketomethylene derivatives. Syntheses were carried out by Friedel-Crafts acylation of the above pentatomic heterocycles and subsequent reaction of chloroalkyl ketones with the proper 4-substituted phenol. Reduction of the ketone function afforded the related polymethylene derivatives. The new compounds were tested for antirhinovirus activity and cytotoxicity in comparison with WIN 51711, used as reference drug. Inspection of the structure-activity relationships revealed that the thiophene ring and the carbonyl group are the structural components which to a large extent contribute to the positive biological profile in terms of both wideness of spectrum and low cytotoxicity. Among the various derivatives, compounds 8e,d showed in vitro the same potency of WIN 51711 but a cytotoxicity at least 10 times lower.

Antiviral Agents↗

Cytotoxic effect of the diterpene lactone dehydrocrotonin from Croton cajucara on human promyelocytic leukemia cells.

Diterpenes exhibit potent antineoplastic properties against human and murine carcinoma cell lines. trans-Dehydrocrotonin from Croton cajucara, a Brazilian medicinal plant, is a nor-diterpene with antiulcerogenic activity. In this work, we examined the effect of trans-dehydrocrotonin (t-DCTN) on the vitality of HL60 cells by assessing the MTT reduction, protein content and phosphatase activity of these cells. Protein quantification indicated that t-DCTN reduced the number of cells with an IC50 of 500 microM; mitochondrial function (MTT reduction), was also inhibited (IC50 = 300 microM), when the cells were treated for 24 h. In contrast, when the cells were treated with this lactone in the initial plating and cultured for 96 h, t-DCTN was more toxic for all parameters analyzed: MTT and phosphatase activity (IC50 = 180 microM) and protein content (IC50 = 150 microM). The flavonoid utilized as positive control myricetin and the following IC50 values were obtained after 24 h of treatment: 300 and 192 microM for protein content and MTT reduction, respectively. According to the chemical characteristics of both compounds, the cytotoxic effect of t-DCTN could be explained through two mechanisms: adduct formation with DNA and proteins and/or oxidative stress induction.

Antineoplastic Agents, Phytogenic↗

Retinoic acid inhibits sodium butyrate-induced monocytic differentiation of HL60 cells while synergistically inducing granulocytoid differentiation.

The human myeloid leukemia cell line HL60 is an in vitro model to study myeloid differentiation. HL60 cells differentiate along different cell type lineages in response to a variety of compounds. The direction of differentiation is usually inducer-specific. However, the response of HL60 cells to sodium n-butyrate (NaB) is pleiotropic. NaB induces HL60 along the monocytic, neutrophilic, eosinophilic, and basophilic pathways. In this study we saw that physiologic concentrations of all-trans-retinoic acid (RA) switched the direction of NaB-induced differentiation from monocytic to granulocytic. We showed previously (Breitman & He, Cancer Res 1990: 50: 6268-6273) that combinations of RA and NaB synergistically induce HL60 to cells that reduce nitroblue tetrazolium. The present study shows that this synergy was even greater if the parameter measured was mature granulocytes. Our results raise the possibility that the endogenous RA in the serum used to grow cells in culture may affect the direction of differentiation of HL60 cells induced by NaB. Furthermore, our results may provide additional rationale for the use of combinations of RA and NaB in the treatment of some leukemias.

Butyrates↗

Active leflunomide metabolite inhibits interleukin 1beta, tumour necrosis factor alpha, nitric oxide, and metalloproteinase-3 production in activated human synovial tissue cultures.

BACKGROUND: Leflunomide is now an approved agent for the management of adult rheumatoid arthritis (RA). Its active metabolite A771726 inhibits de novo pyrimidine biosynthesis. Although considered to be an immunosuppressive agent, its mechanism of action remains obscure. OBJECTIVES: Evaluation of the leflunomide active metabolite A771726 (LEF) effect on interleukin 1beta (IL1beta), tumour necrosis factor (TNFalpha), nitric oxide (NO), and stromelysin (metalloproteinase-3 (MMP-3)) production by activated human synovial tissue in culture. METHODS: Synovial tissue was obtained during surgery from patients undergoing total knee replacement owing to RA or osteoarthritis (OA), cut into small pieces, and cultured in Petri dishes with test materials as previously described. IL1beta, TNFalpha, NO, and MMP-3 were measured in the culture media after 48 hours incubation with different doses of LEF by methods previously described. RESULTS: LEF (0.3, 3, and 9 micro g/ml) inhibited IL1beta production in the presence of lipopolysaccharide (LPS; 3 micro g/ml) in a dose dependent manner (p<0.01) at LEF 0.3 micro g/ml. TNFalpha production in the presence of IL1beta (1 ng/ml) was also inhibited in a dose dependent manner (p<0.05 at LEF 0.3 micro g/ml). NO and MMP-3 production in the presence of LPS (3 micro g/ml) was inhibited as well (p<0.01 at LEF 1 micro g/ml and at LEF 0.3 micro g/ml, respectively). Synovial cell viability evaluated by the tetrazolium salt XTT was unaffected by the LEF concentration used. There was no qualitative difference in the response of OA and RA synovial tissue. CONCLUSION: Leflunomide may modulate the rheumatoid articular process by inhibition of local production of IL1beta, TNFalpha, NO, and MMP-3.

Aged↗

The use of cultured hepatocytes to investigate the metabolism of drugs and mechanisms of drug hepatotoxicity.

Hepatotoxins can be classified as intrinsic when they exert their effects on all individuals in a dose-dependent manner, and as idiosyncratic when their effects are the consequence of an abnormal metabolism of the drug by susceptible individuals (metabolic idiosyncrasy) or of an immune-mediated injury to hepatocytes (allergic hepatitis). Some xenobiotics are electrophilic, and others are biotransformed by the liver into highly reactive metabolites that are usually more toxic than the parent compound. This activation process is the key to many hepatotoxic phenomena. Mitochondria are a frequent target of hepatotoxic drugs, and the alteration of their function has immediate effects on the energy balance of cells (depletion of ATP). Lipid peroxidation, oxidative stress, alteration of Ca(2+) homeostasis, and covalent binding to cell macromolecules are the molecular mechanisms that are frequently involved in the toxicity of xenobiotics. Against these potential hazards, cells have their own defence mechanisms (for example, glutathione, DNA repair, suicide inactivation). Ultimately, toxicity is the balance between bioactivation and detoxification, which determines whether a reactive metabolite elicits a toxic effect. The ultimate goal of in vitro experiments is to generate the type of scientific information needed to identify compounds that are potentially toxic to man. For this purpose, both the design of the experiments and the interpretation of the results are critical.]

Adenosine Triphosphate↗

Chemopreventive allylthiopyridazines inhibit invasion, migration and angiogenesis in hepatocarcinoma cells.

Numerous studies have revealed the chemopreventive and hepatoprotective activities of dietary and synthetic organosulfur compounds. We previously showed that synthetic allylthiopyridazine derivatives, designated as K compounds, induced apoptosis in SK-Hep-1 hepatocarcinoma cells. In order to extend our program to pursue the chemopreventive potential of these compounds, we investigated the effects of the K compounds on invasive and migrative properties of the SK-Hep-1 cells in this study. Here, we show that 3-methoxy-6-allylthiopyridazine (K6) and 3-propoxy-6-allylthiopyridazine (K17) efficiently inhibit SK-Hep-1 cell invasion and migration. A prominent downregulation of matrix metalloproteinase (MMP)-2, but not MMP-9, was observed, presenting MMP-2 as a potential target molecule for the anti-invasive and anti-migrative activities of the compounds. Since hepatocarcinoma is characterized as a hypervascular tumor, we examined the effect of the compounds on angiogenesis of human umbilical vein endothelial cells (HUVECs). The K compounds exerted anti-angiogenic activity, supporting that the development of these compounds would be a promising approach for treatment of hepatocarcinoma. Taken in conjunction with the fact that hepatocellular carcinoma is one of the most lethal malignancies, our findings may be critical to the chemopreventive potential of these synthetic organosulfur compounds for hepatocarcinoma.

Anticarcinogenic Agents↗