Intracellular localization of drugs in cultured tumor cells by ion microscopy and image processing

Summary Several drugs, containing a halogen atom, F or Br, that are being used in antiviral or anticancer therapy, were studied for their localization in cultured cells by ion microanalysis. The association allows to reduce the exposure time to define the intracellular localization of the studied element. The topography of the cells is given by the image of the polyatomic ion ²⁶CN^–. The image of the distribution of ⁸¹Br^– or ¹⁹F^–, coded in another color scale, can be superimposed, giving a polychromic image of the cell, thus showing the intracellular localization of the compound. MCF-7 tumor cells were cultured in the presence of pyrimidine derivatives. 5-Bromo-2-deoxyuridine (BUdR) and 5-trifluorothymidine (F3TdR) were localized in the nucleus, 5-fluoro-2-deoxyuridine (FUdR) in the nucleus and only in some nucleoli. The method is simple and rapid, as compared with techniques using radiolabeled compounds, or with immunocytochemical techniques. It is possible to observe two different compounds in the same cell. It could be applied to other compounds containing a halogen atom.     

Mapping of intracellular halogenous molecules by low and high resolution SIMS microscopy.

The subcellular distribution of halogenous molecules has been studied by SIMS microscopy in cultured cells of a human breast carcinoma (MCF-7 cell line). Two instruments of microanalysis were used. A low lateral resolution ion microscope (SMI 300 CAMECA) and a prototype scanning ion microscope equipped with a cesium gun that gives high lateral resolution images. This apparatus has been developed by G Slodzian, in Onera Laboratories (Office National d'Etudes et de Recherches Aérospatiales). Molecules studied by low lateral resolution ion microscope were halogenous steroids: fluorometholone, triamcinolone, bromocriptine and bromoandrosterone. Analytical images show that the first two compounds are mainly localized in the nuclear structure of MCF-7 cells whereas the last two molecules are localized in cytoplasm of these cells. Images were obtained with a resolution of 1 micron. With the scanning ion microscope, it is now possible to obtain images at the ultrastructural level. Four analytical images can be simultaneously obtained by a single scan of the imaged area, corresponding to a depth of erosion of the section of ten nm. The intranuclear distributions of three pyrimidine analogs, 5-bromo-2'-deoxyuridine, 5-iodo-2'-deoxyuridine and 5-fluorouracil have been studied in phase S and M of MCF-7 cells and these images have been compared to the distribution of sulfur, nitrogen and phosphorus. All these images have been obtained with a lateral resolution better than 100 nm.     

Advantages of the scanning ion microscopy for mapping halogen corticoids in normal and transformed cells in culture

Summary— The intra-cellular distribution of eight halogen glucocorticoids was investigated by ion microscopy in two cellular varieties of cultured non-cancer cells (fibroblast 3T3) and cancer cells (human breast tumor cells MCF-7). Two types of ion microscopy helped to determine this distribution, a direct imaging ion microscope (SMI 300) with low spatial resolution, and a scanning ion microscope (IMS4F), featuring high resolution, serving to obtain maps representing the intra-cellular distribution of the fluorine elements and drugs present in these monolayer cultured cells. The fluorine images representative of the drugs containing fluorine showed that these drugs are essentially concentrated in the cell nuclei. In these nuclei, the distribution of these drugs is different from that of heterochromatin and of the nucleolus.     

Gas-liquid chromatographic analysis of fluoropyrimidine nucleosides and fluorouracil in plasma and urine

A gas-liquid chromatographic method employing on-column alkylation and a nitrogen-sensitive detector was developed for the analysis of 5-fluoro-2'-deoxyuridine, 5-fluorouridine, and 5-fluorouracil in plasma and urine. Samples (0.72 ml) containing the fluoropyrimidine and internal standard (5-chloro-2'-deoxyuridine for nucleoside analyses and 6-methyluracil for 5-fluorouracil analyses) were prepared for gas-liquid chromatography by sequential cation-exchange and anion-exchange column chromatography. Recoveries of fluoropyrimidines were 71-95% over the concentration ranges studied. The dried eluate from the anion-exchange column was dissolved in p-tolyltrimethylammonium hydroxide in methanol before gas-liquid chromatographic analysis. Columns packed with either 3% SP-2100 on Supelcoport or 3% OV-1 on Gas-Chrom Q were suitable for nucleoside analyses; a column packed with 0.75% Carbowax 20M-5% KOH on Chromsorb G was used for 5-fluorouracil analyses. The fluoropyrimidine nucleosides were well separated from each other and from the potentially interfering endogenous compounds 2'-deoxyuridine and uridine; 5-fluorouracil was well separated from uracil. Linear standard curves (peak area ratio method) were obtained for plasma containing 0.025 to 20 micrograms FdUrd (0.1 to 81 microM) or 0.05 to 1.0 microgram FUrd (0.2 to 3.8 microM), and for urine containing 0.2 to 1.0 microgram (0.8 to about 4 microM) of the nucleosides. Standard curves for 5-fluorouracil (1.5 to 7.9 microM) and 2'-deoxyuridine (0.9 to 4.4 microM) were also linear. A measurable amount of 5-fluorouracil, equivalent to 4 to 7% of the 5-fluoro-2'-deoxyuridine injected, was formed from the nucleoside on the gas-liquid chromatographic column, requiring correction of 5-fluorouracil concentrations measured in the presence of 5-fluoro-2'-deoxyuridine.     

Comparative molecular field analysis and comparative molecular similarity indices analysis of boron-containing human thymidine kinase 1 substrates

Three-dimensional quantitative structure-activity relationship (3D-QSAR) using CoMFA and CoMSIA techniques was applied to evaluate 56 pyrimidine nucleosides as substrates of human thymidine kinase 1 (hTK1), 27 of them containing a carborane substituent either at the 3-, 5-, or 3'-position of the 2'-deoxyuridine scaffold. This is the first report describing 3D-QSAR studies of compounds containing boron atoms. Both CoMFA and CoMSIA models were derived from a training set of 47 molecules and the predictive capacity of the CoMSIA model was successfully validated by accurately calculating known phosphorylation rates of both boronated and non-boron hTK1 substrates that were not included in the training set. The optimal CoMSIA model provided the following values: q(2) 0.622, r(2) 0.983, s 0.165, and F 187.5. Contour maps obtained from the CoMSIA model were in agreement with the experimentally determined biological data.     

Subcellular localization of two neurotropic drugs in three varieties of central nervous system cells by secondary ion mass spectroscopy (SIMS) microscopy.

The intracellular localization of two neurotropic drugs, flunitrazepam (benzodiazepine) and triflupromazine (phenothiazine), was studied by secondary ion mass spectrometry microscopy (SIMS) in three varieties of cells. The images of the intracellular distributions of the two drugs are easily obtained by selecting the fluorine atom of the molecules. These images show that the drug from the benzodiazepine group is mainly located in the nuclei, whereas the phenothiazine is exclusively located inside the cytoplasm.     

Intracellular changes of metal elements by fucoidan extracted from brown seaweed (Cladosiphon okamuranus)

This study was undertaken to elucidate the intracellular changes of metal elements after the administration of fucoidan extracted from Cladosiphon okamuranus. TRL1215 cells (normal rat liver cell line) were treated with 0, 0.1, or 1.0 mg/ml fucoidan and incubated in 5% CO2 at 37 degrees C. The cellular levels of Mg, Al, Fe, and Zn were significantly increased in the 1.0 mg/ml fucoidan-treated cells compared to those of the 0.1 mg/ml fucoidan-treated cells and the control. Next, TRL1215 cells were cultured on Mylar film overnight. At 24 h after 5-bromo-2'-deoxyuridine dosing, 0, 0.1, or 1.0 mg/ml fucoidan was treated for 9 h. The cellular distribution of elements was analyzed using in-air micro-micro-particle induced X-ray emission. The X-ray spectra showed that yields of Al, Mg, and Zn were high in order of the 1.0 mg/ml fucoidan-treated sample, the 0.1 mg/ml fucoidan-treated sample, and the control. Fe yield was mildly increased by fucoidan administration. In fucoidan-treated cells, the focal accumulation of Br was correlated spatially with phosphorous-rich region, suggesting that Br was localized within the nucleus. Al distribution provided a spatial association with Br map. These data suggest that fucoidan increases the accumulations of Al, Mg, Fe, and Zn in normal rat hepatocytes, and fucoidan-binding Al is postulated to be transferred into the nucleus.     

Expression and distribution of InsP(3) receptor subtypes in proliferating vascular smooth muscle cells

The expression and distribution of types 1, 2, and 3 inositol 1,4, 5-trisphosphate receptor (InsP(3)R) in proliferating, primary cultures of rat aortic smooth muscle were compared to fully developed and differentiated rat aortic smooth muscle. Subtype-specific InsP(3)R antibodies revealed that the expression of type 1 InsP(3)R was similar in cultured aortic cells and aorta homogenate but expression of type 2 and 3 InsP(3)R subtypes was increased 3-fold in cultured aortic cells. The distribution of the type 1 InsP(3)R was located throughout the cytoplasm; type 2 InsP(3)R was found closely associated with the nucleus and at the plasma membrane; type 3 InsP(3)R was distributed predominantly around the nucleus. Alterations in InsP(3)R subtype expression and localization may have important functions in regulating intracellular calcium release around the nucleus when vascular smooth muscle cells switch to a more proliferating phenotype.     

Enantioselective synthesis and biological evaluation of 5-o-carboranyl pyrimidine nucleosides

Base-modified carborane-containing nucleosides such as 5-o-carboranyl-2'-deoxyuridine (CDU) when combined with neutrons have potential for the treatment of certain malignancies. Lack of toxicity in various cells, high accumulation in cancer cells and intracellular phosphorylation are desirable characteristics for modified nucleosides used in boron neutron capture therapy (BNCT) for brain tumors and other malignancies. The aim of this work was to synthesize the two beta-enantiomers of several 5-o-carboranyl-containing nucleosides. These derivatives may possess favorable properties such as high lipophilicity, high transportability, the ability to be phosphorylated, and resistance to catabolism. Beta-isomers of 2',3'-dihydroxynucleosides and analogues containing a heteroatom in the sugar moiety were also synthesized. Carboranyl pyrimidine nucleosides were prepared either from the parent beta-D-nucleoside, beta-L-nucleoside, or by a coupling reaction. The dioxolane derivative 7 was prepared by a coupling reaction between protected 5-o-carboranyluracil (8, CU) and the corresponding protected heterocycle. Specific catalysts were used during the N-glycosylation process to favor the formation of the beta-isomer. Biological evaluation of these new chiral 5-o-carboranyl pyrimidine derivatives indicated that most of these compounds have low toxicity in a variety of normal and malignant cells and achieved high cellular levels in a lymphoblastoid cell line. Increasing the number of hydroxyl groups on the sugar moiety decreased the cellular accumulation and serum binding to different extents. Five compounds were identified for further biological evaluation as potential agents for BNCT.     

Subcellular localization of flavonol aglycone in hepatocytes visualized by confocal laser scanning fluorescence microscope

Flavonoids are widely distributed in the plant kingdom and show various biological activities. The bioavailability of flavonoids in biological samples has conventionally been quantified by high-performance liquid chromatography and mass spectrometry, but with these analytical techniques it is difficult to estimate the subcellular localization of flavonoids in intact cells. In this study, we attempted to examine the localization of flavonoids in cultured cells using a confocal laser scanning fluorescence microscope and mouse hepatoma Hepa-1c1c7 cells. Five flavonol aglycones showed autofluorescence in the cells under the conditions (Ex. 488 nm to Em. 515–535 nm), whereas three flavonol glycosides and eight compounds belonging to other flavonoid subclasses, i.e., flavones, flavanones, and catechins, did not. The autofluorescence of galangin and kaempferol appeared stronger in the nucleus than cytoplasm, suggesting that they are incorporated into the cells and accumulated in the nucleus. The proposed method provided evidence that flavonol aglycones are incorporated into, and accumulated in the nucleus of, hepatocytes.     

Assay of intracellular thymidylate synthetase activity and inhibition by 5-fluoro-2'-deoxyuridine in lymphocytes.

Thymidylate synthetase catalyses the formation of thymidine monophosphate from deoxyuridine monophosphate. Purified thymidylate synthetase can be assayed radiochemically using labelled deoxyuridine monophosphate as substrate, but cells are impervious to deoxyuridine monophosphate and so intracellular thymidylate synthetase activity cannot be assayed in this way. In this paper we describe the assay of intracellular thymidylate synthetase activity in intact cells using labelled 2'-deoxyuridine. The assay showed linear kinetics with respect to time, concentration of 2'-deoxyuridine, and cell concentration. 5-fluoro-2'-deoxyuridine inhibited intracellular thymidylate synthetase activity measured with this assay by 50% at 5 nM. Cell growth was inhibited by 50% at 6 nM 5-fluoro-2'-deoxyuridine. The assay was specific for thymidylate synthetase and enabled measurement of thymidylate synthetase activity in situ in intact cells.     

Nuclear localization of TRK-A in liver cells

The liver represents a site of expression of neurotrophins and their receptors. We have characterized the expression and intracellular localization of the nerve growth factor (NGF) receptor, Trk-A, in liver cells in vivo and in vitro. In both normal and fibrotic liver tissue, Trk-A immunostaining was present in different cell types, including parenchymal cells and cells of the inflammatory infiltrate. In hepatocytes and activated stellate cells (HSC), Trk-A showed a predominant nuclear localization, both in the presence and absence of injury. In cultured HSC, Trk-A was found to be functional, because exposure of the cells to recombinant NGF resulted in stimulation of cell migration and activation of intracellular signaling pathways, including Ras-ERK and PI3K/Akt. Remarkably, in cultured HSC, Trk-A staining was found constitutively in the nucleus. In these cells, Trk-A could be stained only by antibodies directed against the intracellular domain but not by those recognizing the extracellular portion of Trk-A suggesting that the intracellular portion of the receptor is the major determinant of nuclear Trk-A staining. In contrast to HSC, freshly isolated hepatocytes did not show any nuclear localization of the intracellular portion of Trk-A. In pheocromocytoma cells, nuclear staining for Trk-A was not present in conditions of serum deprivation, but could be induced by exposure to NGF or to a mixture of soluble mediators. We conclude that nuclear localization of the intracellular domain of Trk-A is observed constitutively in liver cells such as HSC, while in other cell types it could be induced in response to soluble factors.     

Localization of two neurotropic molecules in cultured glial cells by ion microscopy]

The intracellular localization of two families of neurotropic drugs: flunitrazepam and flurazepam (benzodiazepine), triflupromazine and trifluoperazine (phenothiazine) has been studied by ion microscopy. The molecules have been incubated with C6 glioblastoma cells from rat origin and with astroglial primary cultures. The images of the intracellular distributions of the two drugs are easily obtained by selecting the fluorine atom of the molecules. The images obtained show that flunitrazepam and flurazepam, two drugs of the benzodiazepine group are mainly located to the nuclei, whereas triflupromazine and trifluoperazine, two phenothiazines are exclusively located inside the cytoplasm.     

ABCG5 and ABCG8 are expressed in gallbladder epithelial cells

Gallbladder epithelial cells (GBEC) are exposed to high biliary cholesterol concentrations on their apical (AP) surface. The mechanisms of cholesterol absorption and efflux by these cells are not known. We hypothesized that ABCG5 and ABCG8 are expressed in GBEC and mediate AP cholesterol efflux. Human gallbladder cDNA expressed message for ABCG5 and ABCG8. Cultured murine GBEC also expressed abcg5 and abcg8 mRNA and protein, as did cultured canine GBEC. Interestingly, treatment with model bile containing supersaturating concentrations of cholesterol, or treatment with LXRalpha/RXR ligands, did not lead to differences in expression of ABCG5 or ABCG8 in the murine or the canine cells. The subcellular localization of ABCG5 and ABCG8 did show alterations, with predominantly intracellular localization at baseline and predominantly AP localization following treatment with model bile or LXRalpha ligand. GBEC therefore express ABCG5 and ABCG8; these sterol transporters may play a role in mediating AP cholesterol efflux in the gallbladder epithelium.     

Effect of analogues of phenylacetic acid (PA) on the PA transport system in Penicillium chrysogenum strains H1107 and M223

The phenylacetic acid (PA) transport system was studied in two industrial strains of Penicillium chrysogenum (M223 and H1107) and the effect of different PA analogues was established. In both strains the uptake capacity was enhanced when the cells were grown in medium containing palm oil (1.6% v/v). PA analogues containing hydroxy groups or halogen atom (chloro or fluoro) attached to the aromatic ring strongly inhibited the uptake, strain M223 being more sensitive to PA analogue inhibition. Correspondence to: I. K. P. Tan     

Oxidation of aliphatic olefins by toluene dioxygenase: enzyme rates and product identification.

Toluene dioxygenase from Pseudomonas putida F1 has been studied extensively with aromatic substrates. The present work examined the toluene dioxygenase-catalyzed oxidation of various halogenated ethenes, propenes, butenes and nonhalogenated cis-2-pentene, an isomeric mix of 2-hexenes, cis-2-heptene, and cis-2-octene as substrates for toluene dioxygenase. Enzyme specific activities were determined for the more water-soluble C2 to C5 compounds and ranged from <4 to 52 nmol per min per mg of protein. Trichloroethene was oxidized at a rate of 33 nmol per min per mg of protein. Products from enzyme reactions were identified by gas chromatography-mass spectrometry. Proton and carbon nuclear magnetic resonance spectroscopy of compounds from whole-cell incubation confirmed the identity of products. Substrates lacking a halogen substituent on sp2 carbon atoms were dioxygenated, while those with halogen and one or more unsubstituted allylic methyl groups were monooxygenated to yield allylic alcohols. 2,3-Dichloro-1-propene, containing both a halogenated double bond and a halogenated allylic methyl group, underwent monooxygenation with allylic rearrangement to yield an isomeric mixture of cis- and trans-2,3-dichloro-2-propene-1-ol.     

Nuclear translocation of intracellular domain of Protogenin by proteolytic cleavage

Protogenin (PRTG) is a transmembrane protein of immunoglobulin superfamily, which has multiple roles in embryogenesis as a receptor or an adhesion molecule. In this study, we present sequential proteolytic cleavage of PRTG. The cleavage first occurs at the extracellular domain, then at the interface of the transmembrane and the intracellular domain by γ-secretase, which results in the release of the intracellular domain of PRTG (PRTG-ICD). PRTG-ICD contains putative nuclear localization signal (NLS) at its N-terminal, and translocates to the nucleus in cultured cells and in the neuroepithelial cells of chick embryos. We propose that the PRTG-ICD is cleaved by γ-secretase and translocates to the nucleus, which is potentially implicated in signaling for neural differentiation and in cell adhesion mediated by PRTG.