Rhodamine-123 staining in hematopoietic stem cells of young mice indicates mitochondrial activation rather than dye efflux.
AuthorsKim M, Cooper DD, Hayes SF, Spangrude GJ
JournalBlood
PubMed ID9596656
'Low-intensity fluorescence of rhodamine-123 (Rh-123) discriminates a quiescent hematopoietic stem cell (HSC) population in mouse bone marrow, which provides stable, long-term hematopoiesis after transplantation. Rh-123 labels mitochondria with increasing intensity proportional to cellular activation, however the intensity of staining also correlates with the multidrug resistance (MDR) phenotype, as Rh-123 is ... More
Expression and function of P-glycoprotein and absence of multidrug resistance-related protein in rat and beige mouse peritoneal mast cells.
AuthorsCandussio L, Crivellato E, Rosati AM, Klugmann FB, Granzotto M, Giraldi T, Decorti G
JournalHistochem J
PubMed ID11563538
'To clarify the function of the multidrug transporter P-glycoprotein in mast cells we used the green fluorescent compound Bodipy-FL-verapamil, which is a substrate of P-glycoprotein. This compound is also transported by Multidrug Resistance-related Protein (MRP), another membrane transport protein expressed in many tumour resistant cells as well as in normal ... More
Influence of lipid lowering fibrates on P-glycoprotein activity in vitro.
AuthorsEhrhardt M, Lindenmaier H, Burhenne J, Haefeli WE, Weiss J
JournalBiochem Pharmacol
PubMed ID14698041
'Statin/fibrate combinations are frequently used to treat mixed dyslipidemia. However, these combinations may cause life-threatening drug interactions (e.g. rhabdomyolysis) possibly induced by modifications of cytochrome P450 isozyme activities. Some statins are also transported by P-glycoprotein (Pgp) and may act as inhibitors of this drug efflux pump. So far, nothing is ... More
A silent polymorphism in the MDR1 gene changes substrate specificity.
AuthorsKimchi-Sarfaty C, Oh JM, Kim IW, Sauna ZE, Calcagno AM, Ambudkar SV, Gottesman MM,
JournalScience
PubMed ID17185560
'Synonymous single-nucleotide polymorphisms (SNPs) do not produce altered coding sequences, and therefore they are not expected to change the function of the protein in which they occur. We report that a synonymous SNP in the Multidrug Resistance 1 (MDR1) gene, part of a haplotype previously linked to altered function of ... More
Interaction of antiepileptic drugs with human P-glycoprotein in vitro.
AuthorsWeiss J, Kerpen CJ, Lindenmaier H, Dormann SM, Haefeli WE
JournalJ Pharmacol Exp Ther
PubMed ID12954800
'About one-third of epilepsy patients are resistant to treatment with antiepileptic drugs (AEDs). This refractoriness is not fully understood, but is thought to be attributed to overexpression of multidrug transporters at the blood-brain barrier, particularly P-glycoprotein (Pgp). In certain cases pharmacoresistance can be overcome by add-on therapy, raising the question ... More
Major age-related changes of mouse hematopoietic stem/progenitor cells.
AuthorsKim M, Moon HB, Spangrude GJ
JournalAnn N Y Acad Sci
PubMed ID12799297
'To study age-related changes of mouse bone marrow (BM) cells and hematopoietic stem cells (HSCs), we isolated rhodamine-123(low) (Rh(low)) Thy1.1(low) Lin(-)Sca-1(+) (TLS) HSCs from the BM of old mice and compared their functional characteristics to cells of the same phenotype isolated from young mice. We observed impaired recovery of B ... More
Xenobiotic efflux pumps in isolated fish brain capillaries.
AuthorsMiller DS, Graeff C, Droulle L, Fricker S, Fricker G
JournalAm J Physiol Regul Integr Comp Physiol
PubMed ID11742838
'To identify specific transporters that drive xenobiotics from the central nervous system to blood, the accumulation of fluorescent drugs was studied in isolated capillaries from killifish and dogfish shark brain using confocal microscopy and quantitative image analysis. In killifish brain capillaries, luminal accumulation of fluorescent derivatives of cyclosporin A and ... More
Purification and characterization of recombinant, human acid ceramidase. Catalytic reactions and interactions with acid sphingomyelinase.
AuthorsHe X, Okino N, Dhami R, Dagan A, Gatt S, Schulze H, Sandhoff K, Schuchman EH
JournalJ Biol Chem
PubMed ID12815059
'Human acid ceramidase was overexpressed in Chinese hamster ovary cells by amplification of the transfected, full-length cDNA. The majority of the overexpressed enzyme was secreted into the culture media and purified to apparent homogeneity. The purified protein contained the same 13-(alpha) and 40 (beta)-kDa subunits as human acid ceramidase from ... More
Studies on ion channel antagonist-binding sites in sunflower protoplasts.
AuthorsVallée N, Brière C, Petitprez M, Barthou H, Souvré A, Alibert G
JournalFEBS Lett
PubMed ID9247154
The cytological location of ion channel antagonist-binding sites was studied in sunflower protoplasts using the fluorescent probes DM-Bodipy-PAA and DM-Bodipy-DHP. The binding specificity of the probes was established by competition experiments with Bepridil, phenylalkylamine (Verapamil) and dihydropyridine (Nifedipine) which are known as calcium and potassium channel antagonists. Quantitative image analysis ... More
Targeted delivery of a substrate for P-glycoprotein to renal cysts in vitro.
AuthorsSimmons NL, Hunter J, Jepson MA
JournalBiochim Biophys Acta
PubMed ID7619839
Bodipy-verapamil has been tested as a fluorescent substrate for P-glycoprotein-mediated transepithelial secretion in MDCK-C5A epithelia. Net transepithelial secretion (Jnet) of [3H]vinblastine from basal-to-apical surfaces of monolayer epithelia is inhibited by taxotere, verapamil and Bodipy-verapamil primarily by a reduction in basal to apical vinblastine (Jb-a) transport. Bodipy-verapamil is itself subject to ... More
Flow cytometry analysis of drug transport mechanisms in Haemonchus contortus susceptible or resistant to anthelmintics.
AuthorsKerboeuf D, Chambrier P, Le Vern Y, Aycardi J
JournalParasitol Res
PubMed ID9934960
The role of membrane drug-transport mechanisms in resistance to anthelmintics was examined using a flow cytometry method. This method was adapted from assays developed for the study of similar mechanisms in tumor cells. Rhodamine 123, a P-glycoprotein transport probe, associated with the reversal agent verapamil gave a significantly higher level ... More
Histological demonstration of voltage dependent calcium channels on calcitonin gene-related peptide-immunoreactive nerve fibres in the mouse knee joint.
AuthorsJust S, Leipold-Büttner C, Heppelmann B
JournalNeurosci Lett
PubMed ID11602328
The afferent (excitability) and efferent functions (release of neuropeptides) of primary afferent nerve fibres are based on Ca(2+)-influx. The aim of the present study was to examine the presence of L- and N-type Ca(2+)-channels at sensory nerve fibres in the mouse knee joint capsule. Specific fluorescent labelled channel blockers and ... More
Immune response against the murine mdri protein induced by vaccination with synthetic lipopeptides in liposomes.
AuthorsTosi PF, Radu D, Nicolau C
JournalBiochem Biophys Res Commun
PubMed ID7542878
Intrinsically, or after exposure to chemotherapeutic drugs, many cancer cells overexpress a class of high molecular weight membrane glycoproteins associated with the multidrug resistance (mdr) of these cells. This report describes an immunization protocol eliciting autoantibodies specific to extracellular epitopes of the murine mdr 1 P-glycoprotein (Pgp). Synthetic peptides with ... More
The fluorescent probe Bodipy-FL-verapamil is a substrate for both P-glycoprotein and multidrug resistance-related protein (MRP)-1.
AuthorsCrivellato E, Candussio L, Rosati AM, Bartoli-Klugmann F, Mallardi F, Decorti G
JournalJ Histochem Cytochem
PubMed ID11967284
Several fluorescent probes have been used in functional studies to analyze drug transport in multidrug-resistant cells by fluorescent microscopy. Because many of these molecules have some drawbacks, such as toxicity, nonspecific background, or accumulation in mitochondria, new fluorescent compounds have been proposed as more useful tools. Among these substances, Bodipy-FL-Verapamil, ... More
Fluorescent verapamil derivative for monitoring activity of the multidrug transporter.
AuthorsLelong IH, Guzikowski AP, Haugland RP, Pastan I, Gottesman MM, Willingham MC
JournalMol Pharmacol
PubMed ID1681415
Multidrug resistance to amphipathic natural product chemotherapeutic drugs is conferred on cancer cells by expression of the MDR1 gene, which encodes the 170-kDa multidrug transporter known as P glycoprotein. The P glycoprotein-mediated efflux of toxic chemotherapeutic drugs can be reversed by agents such as verapamil, which is a substrate for ... More
Permeability of porcine blood brain barrier to somatostatin analogues.
AuthorsFricker G, Nobmann S, Miller DS
JournalBr J Pharmacol
PubMed ID11877340
1. Transport of a fluorescent somatostatin analogue (NBD-octreotide) across freshly isolated functionally intact capillaries from porcine brain was visualized by confocal microscopy and quantitated by image analysis. 2. Luminal accumulation of NBD-octreotide showed all characteristics of specific and energy-dependent transport. Steady-state luminal fluorescence averaged 2 - 3 times cellular fluorescence ... More
Expression of L-type calcium channels associated with postnatal development of skeletal muscle function in mouse.
AuthorsMänttäri S, Pyörnilä A, Harjula R, Järvilehto M
JournalJ Muscle Res Cell Motil
PubMed ID11563550
Several factors have an influence on the improvement of muscle activity and motor co-ordination of mammals during post-natal development. One of them is voltage sensitive L-type calcium channel function. In striated muscles of adult mammals these channels are located in T-tubule membranes thus linking the on-coming action potential to the ... More
Kinetics of doxorubicin handling in the LLC-PK1 kidney epithelial cell line is mediated by both vesicle formation and P-glycoprotein drug transport.
AuthorsCrivellato E, Candussio L, Rosati AM, Decorti G, Klugmann FB, Mallardi F
JournalHistochem J
PubMed ID10576412
The subcellular distribution of doxorubicin was evaluated in living non-fixed LLC-PK1 cells, which maintain the structural and functional characteristics of the kidney proximal tubule epithelium and also express P-glycoprotein. After 10 min incubation, doxorubicin fluorescence was detectable in the nucleus. The intensity of nuclear fluorescence progressively increased, reaching the maximum ... More
Functional characterization of coding polymorphisms in the human MDR1 gene using a vaccinia virus expression system.
AuthorsKimchi-Sarfaty C, Gribar JJ, Gottesman MM
JournalMol Pharmacol
PubMed ID12065748
The human MDR1-encoded transporter is a 170-kDa plasma membrane glycoprotein [P-glycoprotein (P-gp)] capable of binding and energy-dependent extrusion of structurally diverse organic compounds and drugs. P-gp seems to play a significant role in uptake, distribution, and excretion of many different drugs. To determine whether common polymorphic forms of P-gp are ... More
A single amino acid residue contributes to distinct mechanisms of inhibition of the human multidrug transporter by stereoisomers of the dopamine receptor antagonist flupentixol.
AuthorsDey S, Hafkemeyer P, Pastan I, Gottesman MM
JournalBiochemistry
PubMed ID10350482
Both cis and trans isomers of the dopamine receptor antagonist flupentixol inhibit drug transport and reverse drug resistance mediated by the human multidrug transporter P-glycoprotein (Pgp) with a stereoselective potency. The rate of ATP hydrolysis by Pgp and photoaffinity labeling of Pgp with the substrate analogue [125I]iodoarylazidoprazosin ([125I]IAAP) are modulated ... More
Contribution to substrate specificity and transport of nonconserved residues in transmembrane domain 12 of human P-glycoprotein.
AuthorsHafkemeyer P, Dey S, Ambudkar SV, Hrycyna CA, Pastan I, Gottesman MM
JournalBiochemistry
PubMed ID9819232
P-glycoprotein (Pgp), the product of the MDR1 gene, confers multidrug resistance on cancer cells by ATP-dependent extrusion of anticancer drugs. Biochemical and genetic studies with Pgp have identified the putative transmembrane (TM) region 12 (residues 974-994) as a major region involved in drug interactions with amino acid residues conserved among ... More