Establishing a Method to Isolate Rat Brain Capillary Endothelial Cells by Magnetic Cell Sorting and Dominant mRNA Expression of Multidrug Resistance-associated Protein 1 and 4 in Highly Purified Rat Brain Capillary Endothelial Cells

PURPOSE

To establish a method for isolating highly purified brain capillary endothelial cells (BCECs) from rat brain by using magnetic cell sorting, and clarify the expression levels of multidrug resistance-associated protein (Mrp) subtypes in these highly purified BCECs.

METHODS

The cells were prepared from the capillary enriched-fraction by enzyme digestion, and reacted with anti-PECAM-1 antibody. The cell sorting was performed by autoMACS. The mRNA levels were measured by quantitative real-time PCR analysis.

RESULTS

From five rats, 2.3 x 10(6) cells were isolated in the PECAM-1(+) fraction and the percentage of labeled cells in this was 85.9%. PECAM-1, claudin-5 and Tie-2 mRNA were concentrated in the PECAM-1(+) fraction compared with rat brain. The contamination by neurons and astrocytes was markedly less than in the brain capillary fraction prepared by the glass bead column method. Mrp1 and 4 were predominantly expressed in the PECAM-1(+) fraction at similar levels to Mdr1a. The mRNA levels of Mrp5 and 3 were 10.6 and 7.60% of that of Mrp1, respectively.

CONCLUSIONS

This new purification method provides BCECs with less contamination by neural cells. In the isolated BCECs, Mrp1 and 4 are predominantly expressed, suggesting that they play an important role at the rat blood-brain barrier.

Activating of ATP-dependent K+ channels comprised of K(ir) 6.2 and SUR 2B by PGE2 through EP2 receptor in cultured interstitial cells of Cajal from murine small intestine

The interstitial cells of Cajal (ICC) are pacemaker cells in gastrointestinal tract and generate an electrical rhythm in gastrointestinal muscles. We investigated the possibility that PGE(2) might affect the electrical properties of cultured ICC by activating ATP-dependent K(+) channels and, the EP receptor subtypes and the subunits of ATP-dependent K(+) channels involved in these activities were identified. In addition, the regulation of intracellular Ca(2+) ([Ca(2+)](i)) mobilization may be involved the action of PGE(2) on ICC. Treatments of ICC with PGE(2) inhibited electrical pacemaker activities in the same manner as pinacidil, an ATP-dependent K(+) channel opener and PGE(2) had only a dose-dependent effect. Using RT-PCR technique, we found that ATP-dependent K(+) channels exist in ICC and that these are composed of K(ir) 6.2 and SUR 2B subunits. To characterize the specific membrane EP receptor subtypes in ICC, EP receptor agonists and RT-PCR were used: Butaprost (an EP(2) receptor agonist) showed the actions on pacemaker currents in the same manner as PGE(2). However sulprostone (a mixed EP(1) and EP(3) agonist) had no effects. In addition, RT-PCR results indicated the presence of the EP(2) receptor in ICC. To investigate cAMP involvement in the effects of PGE(2) on ICCs, SQ-22536 (an inhibitor of adenylate cyclase) and cAMP assays were used. SQ-22536 did not affect the effect of PGE(2) on pacemaker currents, and PGE(2) did not stimulate cAMP production. Also, we found PGE(2) inhibited the spontaneous [Ca(2+)](i) oscillations in cultured ICC. These observations indicate that PGE(2) alters pacemaker currents by activating the ATP-dependent K(+) channels comprised of K(ir) 6.2-SUR 2B in ICC and this action of PGE(2) are through EP(2) receptor subtype and also the activation of ATP-dependent K(+) channels involves intracellular Ca(2+) mobilization.

Existence of small slow-cycling Langerhans cells in the limbal basal epithelium that express ABCG2

Despite the obvious importance of limbal stem cells in corneal homeostasis and tumorigenesis, little is known about their specific biological characteristics. The purpose of this study was to characterize limbal slow-cycling cells based on the expression of ABCG2 and major histocompatibility complex (MHC) class II and the cell size. Wistar rats were daily injected with 5-bromo-2-deoxyuridine (BrdU) at a dose of 5 mg/100 g for 2 weeks. After 4-week BrdU-free period, corneal tissues were excised, and immunofluorescence staining for ABCG2, BrdU, and MHC class II was performed by confocal microscopy. In another series, corneal tissues of normal rat were double immunostained for ABCG2, keratin 14, keratin 3, CD11c, and MHC class II. In addition, limbal, peripheral and central corneal epithelial sheets were isolated by Dispase II digestion and dissociated into single cell by trypsin digestion and cytospin preparations were double immunostained for ABCG2 and MHC class II. The cell size and nucleus-to-cytoplasm (N/C) ratio of limbal ABCG2+ cells were analyzed and compared with those of cells from other zones. BrdU label-retaining cells (LRCs) with expression of ABCG2 were found in the limbal epithelial basal layer, but not in other parts of the cornea. Approximately 20% of these cells were MHC class II positive. All MHC class II+ cells in the corneal epithelium were positive for CD11c, a marker for dendritic cells (DCs). Double labeling with ABCG2 and keratin 14 showed that nearly four-fifth of limbal ABCG2+ cells were positive for keratin 14 but negative for keratin 3, exhibiting an undifferentiated epithelial cell lineage. Cytospin sample analysis revealed the presence of a distinct population of smaller ABCG2+ cells with expression of MHC class II with a larger N/C ratio in the limbal epithelium. A new population of small slow-cycling cells with large N/C ratio has been found to express ABCG2 in the limbal epithelial basal layer. Some of these cells normally express MHC class II antigen. These findings may have important implications for our understanding of the characteristics of limbal slow-cycling cells.

A Rapid Agglutination Assay for Canine Brucellosis Using Antigen Coated Beads

Brucella canis is the causative agent of canine brucellosis and facultative intracellular pathogen. The diagnosis of canine brucellosis is based on bacteriological examination and serological methods including agglutination and gel diffusion tests. In this study, crude antigens were extracted from B. canis using hot saline, coated on to latex beads and their usefulness in the serological diagnosis of canine brucellosis was examined. Mixing the antigen coated latex beads with the sera of dogs infected with B. canis produced clear agglutination, but this was not so for B. canis free dog sera. N-terminal amino acid sequence analysis of the crude hot saline extracts, showed that they contained copper-zinc superoxide dismutase, ribose ABC transporter and hypothetical protein of Brucella as antigens. A serological survey of canine serum samples conducted by means of an agglutination test using the antigen coated latex beads, showed that this method was more specific than the tube agglutination test using whole bacterial cell antigens. Although these results suggest that our method in which crude hot saline extracted antigens are coated on to latex beads would be useful in the serological diagnosis of canine brucellosis, we need further investigation using more serum samples to confirm the usefulness of our method.

Linkage between a new splicing site mutation in the MDR3 alias ABCB4 gene and intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy (ICP) is defined as pruritus and elevated bile acid serum concentrations in late pregnancy. Splicing mutations have been described in the multidrug resistance p-glycoprotein 3 (MDR3, ABCB4) gene in up to 20% of ICP women. Pedigrees studied were not large enough for linkage analysis. Ninety-seven family members of a woman with proven ICP were asked about pruritus in earlier pregnancies, birth complications and symptomatic gallstone disease. The familial cholestasis type 1 (FIC1, ATP8B1) gene, bile salt export pump (BSEP, ABCB11) and MDR3 gene were analyzed in 55 relatives. We identified a dominant mode of inheritance with female restricted expression and a new intronic MDR3 mutation c.3486+5G>A resulting in a 54 bp (3465-3518) inframe deletion via cryptic splicing site activation. Linkage analysis of the ICP trait versus this intragenic MDR3 variant yielded a LOD score of 2.48. A Bayesian analysis involving MDR3, BSEP, FIC1 and an unknown locus gave a posterior probability of >0.9966 in favor of MDR3 as causative ICP locus. During the episode of ICP the median gamma-glutamyl transpeptidase (gamma-GT) activity was 10 U/l (95% CI, 6.9 to 14.7 U/l) in the index woman. Four stillbirths were reported in seven heterozygous women (22 pregnancies) and none in five women (14 pregnancies) without MDR3 mutation. Symptomatic gallstone disease was more prevalent in heterozygous relatives (7/21) than in relatives without the mutation (1/34), (P = 0.00341).

CONCLUSION

This study demonstrates that splicing mutations in the MDR3 gene can cause ICP with normal gamma-GT and may be associated with stillbirths and gallstone disease.

Interactions among PIN-FORMED and P-glycoprotein auxin transporters in Arabidopsis

Directional transport of the phytohormone auxin is established primarily at the point of cellular efflux and is required for the establishment and maintenance of plant polarity. Studies in whole plants and heterologous systems indicate that PIN-FORMED (PIN) and P-glycoprotein (PGP) transport proteins mediate the cellular efflux of natural and synthetic auxins. However, aromatic anion transport resulting from PGP and PIN expression in nonplant systems was also found to lack the high level of substrate specificity seen in planta. Furthermore, previous reports that PGP19 stabilizes PIN1 on the plasma membrane suggested that PIN-PGP interactions might regulate polar auxin efflux. Here, we show that PGP1 and PGP19 colocalized with PIN1 in the shoot apex in Arabidopsis thaliana and with PIN1 and PIN2 in root tissues. Specific PGP-PIN interactions were seen in yeast two-hybrid and coimmunoprecipitation assays. PIN-PGP interactions appeared to enhance transport activity and, to a greater extent, substrate/inhibitor specificities when coexpressed in heterologous systems. By contrast, no interactions between PGPs and the AUXIN1 influx carrier were observed. Phenotypes of pin and pgp mutants suggest discrete functional roles in auxin transport, but pin pgp mutants exhibited phenotypes that are both additive and synergistic. These results suggest that PINs and PGPs characterize coordinated, independent auxin transport mechanisms but also function interactively in a tissue-specific manner.

Development of polyclonal antibodies specific to ATP-binding cassette transporters human ABCG4 and mouse Abcg4: site-specific expression of mouse Abcg4 in brain

In our recent study on seeking new mouse ATP-binding cassette (ABC) transporters of the G subfamily, we succeeded in cloning mouse Abcg4 from a cDNA library of mouse brain, and we characterized the tissue-specific expression and chromosomal localization of the mouse Abcg4 gene. To further characterize the physiological function of mouse Abcg4 protein and to compare its function with that of ABCG2, in the present study, we developed polyclonal antibodies against mouse Abcg4 and established the Abcg4-expression system. To raise antibodies, we selected three different epitope peptides that correspond to the amino acid residues of 46-60, 465-479, and 600-613 in mouse Abcg4 protein. The antibody raised against the epitope encoding the amino acids 46-60 was found to be specific to mouse Abcg4, exhibiting a band with molecular weight of 63,000 on immunoblotting, whereas this band was dose-dependently diminished by adding the corresponding epitope peptide into the immunoblot medium. Use of the antibody for immunoblot detection in mouse normal tissues revealed that the Abcg4 protein is expressed in brain, spleen, and testis. Immunohistochemical studies showed that mouse Abcg4 is site-specifically expressed in the cerebral cortex and medulla of mouse brain. These results suggest that mouse Abcg4 plays a certain physiological role in the brain. It is of importance to note that the sequence of amino acids 46-60 is completely identical between mouse Abcg4 and human ABCG4. Thus, this antibody is applicable to the detection of human ABCG4 as well as mouse Abcg4.

Biomarker discovery for inflammatory bowel disease, using proteomic serum profiling

Crohn's disease and ulcerative colitis known as inflammatory bowel diseases (IBD) are chronic immuno-inflammatory pathologies of the gastrointestinal tract. These diseases are multifactorial, polygenic and of unknown etiology. Clinical presentation is non-specific and diagnosis is based on clinical, endoscopic, radiological and histological criteria. Novel markers are needed to improve early diagnosis and classification of these pathologies. We performed a study with 120 serum samples collected from patients classified in 4 groups (30 Crohn, 30 ulcerative colitis, 30 inflammatory controls and 30 healthy controls) according to accredited criteria. We compared protein sera profiles obtained with a Surface Enhanced Laser Desorption Ionization-Time of Flight-Mass Spectrometer (SELDI-TOF-MS). Data analysis with univariate process and a multivariate statistical method based on multiple decision trees algorithms allowed us to select some potential biomarkers. Four of them were identified by mass spectrometry and antibody based methods. Multivariate analysis generated models that could classify samples with good sensitivity and specificity (minimum 80%) discriminating groups of patients. This analysis was used as a tool to classify peaks according to differences in level on spectra through the four categories of patients. Four biomarkers showing important diagnostic value were purified, identified (PF4, MRP8, FIBA and Hpalpha2) and two of these: PF4 and Hpalpha2 were detected in sera by classical methods. SELDI-TOF-MS technology and use of the multiple decision trees method led to protein biomarker patterns analysis and allowed the selection of potential individual biomarkers. Their downstream identification may reveal to be helpful for IBD classification and etiology understanding.

Analysis of the Soluble ATP-Binding Proteome of Plant Mitochondria Identifies New Proteins and Nucleotide Triphosphate Interactions within the Matrix

The interactions of ATP inside plant mitochondria were investigated by identifying the soluble nucleotide binding proteome captured using immobilized ATP. Selected proteins were separated by 1D SDS-PAGE and 2D IEF-SDS-PAGE and identified by ESI-Q-TOF MS/MS. A range of highly enriched proteins were identified from the mitochondrial proteome, including 14-3-3 proteins and RNA binding proteins, as well as proteins known to contain nucleotide binding domains and/or to be inhibited or stimulated by ATP.

Cultivation of human corneal limbal stem cells in Mebiol gel--A thermo-reversible gelation polymer

BACKGROUND & OBJECTIVES

Cultivated limbal stem cell transplantation is being used as a current treatment modality for limbal stem cell deficiency. However, use of allogenic biological material as substrate is associated with risks of transmission of certain diseases and allograft rejection. Therefore development of non-toxic biodegradable synthetic polymers is important. We undertook this study to evaluate the use of a synthetic polymer Mebiol gel as a substrate for the growth of limbal phenotype cells and cornea phenotype cells from limbal explants.

METHODS

Human cadaveric limbal explants cells were cultivated on Mebiol gel. The proliferative capacity of cultivated cells was analyzed with thymidine incorporation studies. Immunostaining for presumed limbal stem cell association markers and cornea differentiation markers was performed and confirmed with reverse transcription (RT-PCR).

RESULTS

The limbal explants underwent proliferation in vitro. The cultivated cells expressed the presumed limbal stem cell association markers (ABCG2 and p63), the transient amplifying cell markers (connexin 43, integrin alpha9) and the cornea differentiation marker (K3). RT PCR confirmed the immunohistochemical data.

INTERPRETATION & CONCLUSION

Our findings showed that the synthetic polymer Mebiol gel was able to support limbal explant proliferation. The cultured cells expressed presumed limbal stem cell association markers, transient amplifying cells and cornea phenotype markers. Mebiol Gel can be used as a scaffold for growing limbal explants.

ATP-binding and -hydrolysis activities of ALDP (ABCD1) and ALDRP (ABCD2), human peroxisomal ABC proteins, overexpressed in Sf21 cells

The peroxisomal ATP-binding cassette (ABC) proteins, adrenoleukodystrophy protein (ALDP, ABCD1) and ALD-related protein (ALDRP, ABCD2), were expressed in Spodoptera frugiperda 21 (Sf21) insect cells using a baculovirus-mediated expression system. Immunoelectron microscopy and subcellular fractionation revealed that the overexpressed ALDP was distributed in various subcellular organelles including mitochondria, nucleus and peroxisomes. The ALDP was not extractable with Na(2)CO(3) treatment, suggesting that it integrated into membranes. ATPase activity was detected in the membrane fraction expressing ALDP. The nucleotide-binding capacities of the expressed ALDP were estimated by the binding to ATP- or ADP-agarose. ALDP exhibited an affinity to both ADP and ATP. In contrast, ALDRP exhibited an affinity to ADP but scarcely to ATP. The ALDP in the Sf21 membrane fraction was extracted with n-dodecyl-beta-maltoside and successively purified with a chelate column. The nucleotide-binding and ATPase activities of the purified ALDP were, however, not detected. It may be that certain membranous components are required for the activity. We demonstrate for the first time that the peroxisomal ABC proteins can be expressed in Sf21 membranes maintaining their nucleotide-binding abilities and ATPase activities, and the expressed proteins will be of use for further characterization.

Actions of ZD0947, a novel ATP-sensitive K+ channel opener, on membrane currents in human detrusor myocytes

BACKGROUND AND PURPOSE

ATP-sensitive K+ channels (K(ATP) channels) play important roles in regulating the resting membrane potential of detrusor smooth muscle. Actions of ZD0947, a novel KATP channel opener, on both carbachol (CCh)-induced detrusor contractions and membrane currents in human urinary bladder myocytes were investigated.

EXPERIMENTAL APPROACH

Tension measurements and patch-clamp techniques were utilized to study the effects of ZD0947 in segments of human urinary bladder. Immunohistochemistry was also performed to detect the expression of the sulphonylurea receptor 1 (SUR1) and the SUR2B antigens in human detrusor muscle.

KEY RESULTS

ZD0947 (> or = 0.1 microM) caused a concentration-dependent relaxation of the CCh-induced contraction of human detrusor, which was reversed by glibenclamide. The rank order of the potency to relax the CCh-induced contraction was pinacidil > ZD0947 > diazoxide. In conventional whole-cell configuration, ZD0947 (> or = 1 microM) caused a concentration-dependent inward K+ current which was suppressed by glibenclamide at -60 mV. When 1 mM ATP was included in the pipette solution, application of pinacidil or ZD0947 caused no inward K+ current at -60 mV. Gliclazide (< or =1 microM), a selective SUR1 blocker, inhibited the ZD0947-induced currents (Ki = 4.0 microM) and the diazoxide-induced currents (high-affinity site, Ki1 = 42.4 nM; low-affinity site, Ki2 = 84.5 microM) at -60 mV. Immunohistochemical studies indicated the presence of SUR1 and SUR2B proteins, which are constituents of KATP channels, in the bundles of human detrusor smooth muscle.

CONCLUSIONS AND IMPLICATIONS

These results suggest that ZD0947 caused a glibenclamide-sensitive detrusor relaxation through activation of glibenclamide-sensitive KATP channels in human urinary bladder.

Functional activity of mitochondria in cultured neural precursor cells

We studied mitochondrial transmembrane potential of neural precursor cells forming neurospheres in culture. Uneven energization of mitochondria in neurosphere cells was detected. Heterogeneity of cells by the mitochondrial potential increased with neurosphere enlargement during culturing. Decrease in the mitochondrial potential in the central cells in large spheres, presumably caused by insufficient diffusion of oxygen and nutrients, can provoke their damage and death. Population of cells with high mitochondrial potential responded to addition of the nuclear dye by a decrease in mitochondrial potential, which can indicate functioning of ABCG2 complex in these cells, characteristic of undifferentiated stem cells. These data will help to create optimum conditions for culturing of neural stem cells for the maintenance of their maximum functional and proliferative activity.

Expression and Transport Activity of Breast Cancer Resistance Protein (Bcrp/Abcg2) in Dually Perfused Rat Placenta and HRP-1 Cell Line

Breast cancer resistance protein (BCRP/ABCG2) is a member of the ATP-binding cassette transporter family that recognizes a variety of chemically unrelated compounds. Its expression has been revealed in many mammal tissues, including placenta. The purpose of this study was to describe its role in transplacental pharmacokinetics using rat placental HRP-1 cell line and dually perfused rat placenta. In HRP-1 cells, expression of Bcrp, but not P-glycoprotein, was revealed at mRNA and protein levels. Cell accumulation studies confirmed Bcrp-dependent uptake of BODIPY FL prazosin. In the placental perfusion studies, a pharmacokinetic model was applied to distinguish between passive and Bcrp-mediated transplacental passage of cimetidine as a model substrate. Bcrp was shown to act in a concentration-dependent manner and to hinder maternal-to-fetal transport of the drug. Fetal-to-maternal clearance of cimetidine was found to be 25 times higher than that in the opposite direction; this asymmetry was partly eliminated by BCRP inhibitors fumitremorgin C (2 microM) or N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918; 2 microM) and abolished at high cimetidine concentrations (1000 microM). When fetal perfusate was recirculated, Bcrp was found to actively remove cimetidine from the fetal compartment to the maternal compartment even against a concentration gradient and to establish a 2-fold maternal-to-fetal concentration ratio. Based on our results, we propose a two-level defensive role of Bcrp in the rat placenta in which the transporter 1) reduces passage of its substrates from mother to fetus but also 2) removes the drug already present in the fetal circulation.

Microarray analysis of blood microvessels from PDGF-B and PDGF-Rbeta mutant mice identifies novel markers for brain pericytes

Normal blood microvessels are lined by pericytes, which contribute to microvessel development and stability through mechanisms that are poorly understood. Pericyte deficiency has been implicated in the pathogenesis of microvascular abnormalities associated with diabetes and tumors. However, the unambiguous identification of pericytes is still a problem because of cellular heterogeneity and few available molecular markers. Here we describe an approach to identify pericyte markers based on transcription profiling of pericyte-deficient brain microvessels isolated from platelet-derived growth factor (PDGF-B)-/- and PDGF beta receptor (PDGFRbeta)-/- mouse mutants. The approach was validated by the identification of known pericyte markers among the most down-regulated genes in PDGF-B-/- and PDGFRbeta-/- microvessels. Of candidates for novel pericyte markers, we selected ATP-sensitive potassium-channel Kir6.1 (also known as Kcnj8) and sulfonylurea receptor 2, (SUR2, also known as Abcc9), both part of the same channel complex, as well as delta homologue 1 (DLK1) for in situ hybridization, which demonstrated their specific expression in brain pericytes of mouse embryos. We also show that Kir6.1 is highly expressed in pericytes in brain but undetectable in pericytes in skin and heart. The three new brain pericyte markers are signaling molecules implicated in ion transport and intercellular signaling, potentially opening new windows on pericyte function in brain microvessels.

Oxidative stress and Mrp2 internalization

Oxidative stress in the liver is sometimes accompanied by cholestasis. We have described the internalization of multidrug resistance-associated protein 2/ATP-binding cassette transporter family 2 (Mrp2/Abcc2), a biliary transporter involved in bile-salt-independent bile flow, under ethacrynic acid (EA)-induced acute oxidative stress in rat liver. However, the signaling pathway and regulatory molecules have not been investigated. In the present study, we investigated the mechanism of EA-induced Mrp2 internalization using isolated rat hepatocyte couplets (IRCHs). The Mrp2 index, defined as the ratio of Mrp2-positive canalicular membrane staining in IRCHs per number of cell nuclei, was significantly reduced by treatment with EA. This reduction was abolished by a nonspecific protein kinase C (PKC) inhibitor Gö6850, a Ca(2+) chelator, EGTA, but not by a protein kinase A (PKA)-selective inhibitor, a Ca(2+)-dependent conventional PKC (cPKC) inhibitor Gö6976, or a protein kinase G (PKG) inhibitor (1 microM). Moreover, an increase in the intracellular Ca(2+) level and NO release into medium were observed shortly after the EA treatment. Both of these increases, as well as Mrp2 internalization, were completely blocked by EGTA. In conclusion, EA produced a reduction in GSH, Ca(2+) elevation, NO production, and nPKC activation in a sequential manner, finally leading to Mrp2 internalization.

[Progress of cancer stem cells of solid tumor]

Stem cells have some characteristics similar to tumor cells, and may be the origin of tumor cells. Stem cell-like subpopulation has been isolated and identified from hematopoietic system malignancies and solid tumors, and defined as cancer stem cells. Cancer stem cells play important roles in the initiation and progression of malignancies. Tumor might be a kind of diseases of stem cells, and this finding may help to understand the mechanisms of tumorigenesis and instruct clinical therapeutics.

ABC transporter expression profiling after ischemic reperfusion injury in mouse kidney

Renal ATP binding cassette (ABC) transporters have an important role in the elimination of metabolic waste products and compounds foreign to the body. The kidney has the ability to tightly control the expression of these efflux transporters to maintain homeostasis, and as a major mechanism of adaptation to environmental stress. In the present study, we investigated the expression of 45 ABC transporter genes in the mouse kidney under basal conditions, after induction of ischemia and after regeneration. Two days after clamping, mice showed a 76% decrease in renal creatinine clearance, which improved clearly within 7 days. This was confirmed by histological examinations. Seven days after ischemia, real-time quantitative Polymerase chain reaction data showed that transcript abundance of abcb1, abcb11, and abcc4 was increased, and that of abca3, abcc2, and abcg2 decreased. Expression of all transporters returned to baseline after 14 days, except for abcb11, which was reduced. Abcb11 is the major liver canalicular bile salt export pump. Here we show for the first time expression in the kidney and localization of the transporter to the apical membrane of proximal tubules. The presence of another novel renal transporter, abca3, was confirmed by Western blotting. Immunohistochemistry showed that abca3 is localized to the peritubular capillaries and apical membrane of proximal tubules. In conclusion, after inducing ischemic reperfusion injury in the kidney, ABC transporters appear to be differentially regulated, which might be associated with the renal regeneration process. Furthermore, we showed for the first time expression and subcellular localization of abcb11 and abca3 in mouse kidney.

Effect of a Novel Vacuolar-H+-ATPase Inhibitor on Cell and Tumor Response to Camptothecins

The vacuolar-H(+)-ATPase, functionally expressed in cell membranes, is known to play a relevant role in intracellular pH regulatory mechanisms, because it is implicated in pumping protons into the extracellular environment or in sequestrating excess protons into acidic vacuolar compartments. Because tumor cells exist in a hypoxic microenvironment and produce acidic metabolites, this regulatory mechanism is recognized as a protective function. This study was designed to investigate the effect of NiK-12192 [4-(5,6-dichloro-1H-indol-2-yl)-3-ethoxy-N-(2,2,6,6-tetramethyl-piperidin-4-yl)-benzamide], an indole derivative identified as an effective inhibitor of vacuolar-H(+)-ATPase, on the cytotoxic activity of two camptothecins, i.e., topotecan and SN-38 (7-ethyl-10-hydroxycamptothecin, the active metabolite of irinotecan). The cellular studies performed in two pairs of human colon carcinoma cell lines, i.e., LoVo and LoVo/DX (overexpressing P-glycoprotein) and HT29 and HT29/Mit (overexpressing breast cancer resistant protein), indicated an enhancement of the antiproliferative effect of camptothecins by concomitant exposure to subtoxic concentrations of NiK-12192. Studies of subcellular distribution indicated that whereas topotecan alone localized mainly in mitochondria and endoplasmic compartment, the simultaneous presence of NiK-12192 caused a cytoplasmic redistribution. In HT29/Mit cells, NiK-12192 reverted the pattern of acidification induced by topotecan. The potentiation of topotecan efficacy by NiK-12192 was documented by an increased efficacy of the combination in both the HT29 tumor xenografts, being more evident in the topotecan-resistant HT29/Mit tumor. In conclusion, the vacuolar-H(+)-ATPase inhibitor NiK-12192 was able to potentiate the cytotoxic/antitumor effects of camptothecins, either in in vitro or in in vivo systems. Such findings support a potential interest for the use of vacuolar-H(+)-ATPase inhibitors in combination therapy to improve camptothecin efficacy.

Early diet-induced non-alcoholic steatohepatitis in APOE2 knock-in mice and its prevention by fibrates

BACKGROUND/AIMS

The molecular mechanisms leading to Non-Alcoholic Steatohepatitis (NASH) are not fully understood. In mice, NASH can be inhibited by fenofibrate, a synthetic agonist for the nuclear receptor peroxisome proliferator activated receptor alpha, which regulates hepatic triglyceride metabolism. This study aimed to elucidate the relation between steatosis and inflammation in NASH in a human-like hyperlipidemic mouse model.

METHODS

Liver phenotype and gene expression were assessed in APOE2 knock-in mice that were fed a western-type high fat diet with or without co-administration of fenofibrate.

RESULTS

In response to a western diet, APOE2 knock-in mice developed NASH characterized by steatosis and inflammation. Strikingly, macrophage accumulation in the liver preceded the steatosis during progression of the disease. This phenotype was in line with gene expression patterns, which showed regulation of two major groups of genes, i.e. inflammatory and lipid genes. Fenofibrate treatment decreased hepatic macrophage accumulation and abolished steatosis. Moreover, a marked reduction in the expression of inflammatory genes occurred immediately after fenofibrate treatment.

CONCLUSIONS

These data indicate that inflammation might play an instrumental role during the development of NASH in this mouse model. Inhibition of NASH by fenofibrate may be due, at least in part, to its inhibitory effect on pro-inflammatory genes.

Stem cell markers: ABCG2 and MCM2 expression in retinoblastoma

BACKGROUND/AIM

The authors studied the expression of cancer stem cell surface marker, ABCG2, and neural stem cell marker, MCM2, in retinoblastoma and correlated clinicopathologically.

METHODS

Among 39 retinoblastomas, 18 tumours were not subjected to preoperative/postoperative chemotherapy, 15 tumours underwent postoperative chemotherapy, and six tumours had preoperative chemotherapy. There were 20 tumours with no invasion and 19 tumours with invasion of choroid/optic nerve. ABCG2 and MCM2 expression was studied by immunohistochemistry.

RESULTS

ABCG2 was positive in six of six and MCM2 was positive in five of six tumours that had recurred in the orbit or metastasised. ABCG2 was positive in 15/19 tumours with invasion. MCM2 was positive in 16/19 tumours with invasion. Invasive tumours showed higher expression of ABCG2 (p < 0.01) and MCM2 (p < 0.01) proteins. There was no correlation with differentiation and laterality of the tumours. Non-neoplastic retina was positive for ABCG2 and MCM2.

CONCLUSION

ABCG2 and MCM2 were expressed more in invasive tumours. Further studies are needed to understand the significance of ABCG2 and MCM2 expression in retinoblastoma.

A high-throughput cell-based assay for inhibitors of ABCG2 activity

ABCG2 is a member of the adenosine triphosphate (ATP)-binding cassette family of multidrug transporters associated with resistance of tumor cells to many cytotoxic agents. Evaluation of modulators of ABCG2 activity has relied on methods such as drug sensitization, biochemical characterization, and transport studies. To search for novel inhibitors of ABCG2, a fluorescent cell-based assay was developed for application in high-throughput screening. Accumulation of pheophorbide a (PhA), an ABCG2-specific substrate, forms the basis for the assay in NCI-H460/MX20 cells overexpressing wild-type ABCG2. Treatment of these cells with 10 microM fumitremorgin C (FTC), a specific ABCG2 inhibitor, increased cell accumulation of PhA to 5.6 times control (Z' 0.5). Validation included confirmation with known ABCG2 inhibitors: FTC, novobiocin, tariquidar, and quercetin. Verapamil, reported to inhibit P-glycoprotein but not ABCG2, had insignificant activity. Screening of a library of 3523 natural products identified 11 compounds with high activity (> or = 50% of FTC, confirmed by reassay), including 3 flavonoids, members of a family of compounds that include ABCG2 inhibitors. One of the inhibitors detected, eupatin, was moderately potent (IC50 of 2.2 microM) and, like FTC, restored sensitivity of resistant cells to mitoxantrone. Application of this assay to other libraries of synthetic compounds and natural products is expected to identify novel inhibitors of ABCG2 activity.

Spontaneous coronary vasospasm in KATP mutant mice arises from a smooth muscle-extrinsic process

In the vasculature, ATP-sensitive potassium channels (KATP) channels regulate vascular tone. Mice with targeted gene disruptions of KATP subunits expressed in vascular smooth muscle develop spontaneous coronary vascular spasm and sudden death. From these models, it was hypothesized that the loss of KATP channel activity in arterial vascular smooth muscle was responsible for coronary artery spasm. We now tested this hypothesis using a transgenic strategy where the full-length sulfonylurea receptor containing exon 40 was expressed under the control of a smooth muscle-specific SM22alpha promoter. Two transgenic founder lines were generated and independently bred to sulfonylurea receptor 2 (SUR2) null mice to generate mice that restored expression of KATP channels in vascular smooth muscle. Transgenic expression of the sulfonylurea receptor in vascular smooth muscle cells was confirmed by detecting mRNA and protein from the transgene. Functional restoration was determined by recording pinacidil-based KATP current by whole cell voltage clamping of isolated aortic vascular smooth muscle cells isolated from the transgenic restored mice. Despite successful restoration of KATP channels in vascular smooth muscle, transgene-restored SUR2 null mice continued to display frequent episodes of spontaneous ST segment elevation, identical to the phenotype seen in SUR2 null mice. As in SUR2 null mice, ST segment elevation was frequently followed by atrioventricular heart block. ST segment elevation and coronary perfusion pressure in the restored mice did not differ significantly between transgene-negative and transgene-positive SUR2 null mice. We conclude that spontaneous coronary vasospasm and sudden death in SUR2 null mice arises from a coronary artery vascular smooth muscle-extrinsic process.