sdz-psc-833 and fluorexon

Sinonasal epithelial cells are recognized as drivers of inflammation in chronic sinusitis with nasal polyps (CRSwNP) through secretion of T helper 2 (Th2)-promoting cytokines. P-glycoprotein (P-gp) is overexpressed in nasal polyps and modulates epithelial cytokine secretion in healthy mucosa. The objective of this study is to determine whether P-gp overactivity promotes Th2-associated cytokine secretion in CRSwNP.. Polyp explants (n = 4) and primary epithelial cell cultures (n = 5) were cultivated from patients with CRSwNP. Explant P-gp activity was determined using a calcein assay. In culture, P-gp was quantified by enzyme-linked immunosorbent assay (ELISA) and sensitivity to PSC-833 inhibition was determined using a calcein assay. Lipopolysaccharide (LPS)-stimulated cytokine secretion of interleukin 6 (IL-6), IL-8, IL-25, and granulocyte macrophage colony stimulating factor (GM-CSF) were quantified by ELISA and compared to secretion following P-gp inhibition. Differences in P-gp expression and cytokine secretion were compared using a Mann-Whitney U test. Secretion was correlated with P-gp expression using a Pearson correlation coefficient.. Calcein retention is increased in P-gp inhibited vs uninhibited polyp explants (mean ± standard deviation [SD]; 5.17 ± 1.76 vs 2.55 ± 0.62; p < 0.05) but not in controls, indicating increased nasal polyp P-gp activity. P-gp is sensitive to dose-dependent P-gp inhibition with PSC-833 in vitro. LPS-stimulated secretion of normalized GM-CSF (45.21 ± 41.39) and IL-6 (63.16 ± 36.37) were significantly reduced following P-gp inhibition (8.47 ± 3.28; p < 0.01, and 39.94 ± 31.07; p < 0.05; respectively) and secretion was highly correlated with P-gp expression(r = 0.824, p < 0.05, and r = 0.833, p < 0.05; respectively).. P-gp overactivity promotes Th2-associated epithelial cytokine secretion in nasal polyps, suggesting a novel mechanism for maintaining chronic inflammation in CRSwNP.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Cells, Cultured; Chronic Disease; Cyclosporins; Cytokines; Epithelial Cells; Fluoresceins; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Lipopolysaccharides; Nasal Polyps; Primary Cell Culture; Sinusitis; Th2 Cells

P-glycoprotein (Pgp) is one of the active efflux pumps that are able to extrude a large variety of chemotherapeutic drugs from the cells, causing multidrug resistance. The conformation-sensitive UIC2 monoclonal antibody potentially inhibits Pgp-mediated substrate transport. However, this inhibition is usually partial, and its extent is variable because UIC2 binds only to 10 to 40% Pgp present in the cell membrane. The rest of the Pgp molecules become recognized by this antibody only in the presence of certain substrates or modulators, including vinblastine, cyclosporine A (CsA), and SDZ PSC 833 (valspodar). Simultaneous application of any of these modulators and UIC2, followed by the removal of the modulator, results in a completely restored steady-state accumulation of various Pgp substrates (calcein-AM, daunorubicin, and 99mTc-hexakis-2-methoxybutylisonitrile), indicating near 100% inhibition of pump activity. Remarkably, the inhibitory binding of the antibody is brought about by coincubation with concentrations of CsA or SDZ PSC 833 approximately 20 times lower than what is necessary for Pgp inhibition when the modulators are applied alone. The feasibility of such a combinative treatment for in vivo multidrug resistance reversal was substantiated by the dramatic increase of daunorubicin accumulation in xenotransplanted Pgp+ tumors in response to a combined treatment with UIC2 and CsA, both administered at doses ineffective when applied alone. These observations establish the combined application of a class of modulators used at low concentrations and of the UIC2 antibody as a novel, specific, and effective way of blocking Pgp function in vivo.

Topics: Animals; Antibodies, Monoclonal; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporine; Cyclosporins; Daunorubicin; Fluoresceins; Humans; Mice; NIH 3T3 Cells; Vinblastine

P-glycoprotein (Pgp) is one of the ABC transporters responsible for the multidrug resistance of cancer cells. The conformational changes of Pgp that occur in the presence of substrates/modulators or ATP depletion are accompanied by the up-shift of UIC2 monoclonal antibody (mAb) binding. In the case of cyclosporin A, vinblastine or valinomycin, this up-shift was found to be concomitant with the near-complete suppression of labeling with other mAbs specific for Pgp epitopes overlapping with UIC2, while pre-treatment with verapamil or Tween 80 brings about a modest suppression. Here we have extended these observations to 44 Pgp interacting agents, and found that only 8 fall into the cyclosporin-like category, inducing a conformational state characterized by the complete UIC2 dominance. The rest of the drugs either did not affect antibody competition or had a modest effect. Thus, Pgp substrates/modulators can be classified into distinct modalities based on the conformational change they elicit.

Topics: Adenosine Triphosphatases; Animals; Anti-Bacterial Agents; Antibodies, Monoclonal; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Binding, Competitive; Calcium Channel Blockers; Cyclosporine; Detergents; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Flow Cytometry; Fluoresceins; Humans; Ivermectin; Mice; NIH 3T3 Cells; Substrate Specificity

The pyrimidine analogue cytosine arabinoside (AraC) is one of the most effective drugs used in the treatment of acute leukaemia. Overexpression of the multidrug resistance (MDR-1) gene and its product, P-glycoprotein (P-gp), is associated with cellular resistance to drugs, such as anthracyclines and vinca alkaloids. This resistance can be reversed by cyclosporine analogues or verapamil (ver). We investigated the in vitro cross-resistance to AraC in a doxorubicin-resistant HL60 cell line, with an elevated expression of the MDR-1 gene. The resistant clone showed an eightfold increased resistance to AraC and a two- to fourfold resistance to the other analogues, as measured by cytotoxicity test. There was no significant increase in the activity of 5'-nucleotidase or in the amount of deoxyribonucleotide pools between cell lines. We could, however, detect a reduction in deoxycytidine kinase (dCK) activity (30%, P = 0.021, using deoxycytidine as substrate) and the level of AraC triphosphates was significantly reduced in the resistant cells (70%, P = 0.009). When the cells were exposed to cyclosporin A (CsA) or the cyclosporine analogue PSC 833 (PSC) in combination with AraC, there was more extensive apoptosis, as measured by formation of oligonucleosomal DNA fragmentation and caspase-3-like activity, than with exposure to AraC alone. We also found an increased retention of AraC in the resistant cells when incubated with AraC in combination with CsA. Ver in combination with AraC, failed to increase apoptosis for the resistant cell line. Our data suggests that the resistance to AraC for the P-gp-expressing cells is a result of a reduction of dCK activity and an increase in efflux, the latter possibly depending on P-gp. A combination of CsA or PSC with AraC may improve the effect of AraC in vivo.

Topics: Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cyclosporine; Cyclosporins; Cytarabine; Deoxycytidine Kinase; DNA Fragmentation; Doxorubicin; Drug Resistance, Multiple; Flow Cytometry; Fluoresceins; HL-60 Cells; Humans; Leukemia, Promyelocytic, Acute

Cadmium-mediated toxicity of cultured proximal tubule (PT) cells is associated with increased production of reactive oxygen species (ROS) and apoptosis. We found that cadmium-dependent apoptosis (Hoechst 33342 and annexin V assays) decreased with prolonged CdCl(2) (10 microM) application (controls: 2.4 +/- 1.6%; 5 h: +5.1 +/- 2.3%, 20 h: +5.7 +/- 2.5%, 48 h: +3.3 +/- 1.0% and 72 h: +2.1 +/- 0.4% above controls), while cell proliferation was not affected. Reduction of apoptosis correlated with a time-dependent up-regulation of the drug efflux pump multidrug resistance P-glycoprotein (mdr1) in cadmium-treated cells ( approximately 4-fold after 72 h), as determined by immunoblotting with the monoclonal antibody C219 and measurement of intracellular accumulation of the fluorescent probe calcein +/- the mdr1 inhibitor PSC833 (0.5 microM). When mdr1 inhibitors (PSC833, cyclosporine A, verapamil) were transiently added to cells with mdr1 up-regulation by pretreatment for 72 h with cadmium, cadmium-induced apoptosis increased significantly and to a percentage similar to that obtained in cells with no mdr1 up-regulation (72-h cadmium: 5.2 +/- 0.9% versus 72-h cadmium + 1-h PSC833: 7.2 +/- 1.4%; p < or = 0.001). Cadmium-induced apoptosis and mdr1 up-regulation depended on ROS, since co-incubation with the ROS scavengers N-acetylcysteine (15 mM) or pyrrolidine dithiocarbamate (0.1 mM) abolished both responses. Moreover, cadmium- and ROS-associated mdr1 up-regulation was linked to activation of the transcription factor NF-kappaB; N-acetylcysteine, pyrrolidine dithiocarbamate, and the IkappaB-alpha kinase inhibitor Bay 11-7082 (20 microM) prevented both, mdr1 overexpression and degradation of the inhibitory NF-kappaB subunit, IkappaB-alpha, induced by cadmium. The data show that 1) cadmium-mediated apoptosis in PT cells is associated with ROS production, 2) ROS increase mdr1 expression by a process involving NF-kappaB activation, and 3) mdr1 overexpression protects PT cells against cadmium-mediated apoptosis. These data suggest that mdr1 up-regulation, at least in part, provides anti-apoptotic protection for PT cells against cadmium-mediated stress.

Topics: Animals; Annexin A5; Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cadmium; Cadmium Chloride; Calcium Channel Blockers; Cell Line; Cyclosporine; Cyclosporins; Enzyme Inhibitors; Fluoresceins; Kidney Tubules, Proximal; Kinetics; Necrosis; NF-kappa B; Oxidative Stress; Rats; Rats, Inbred WKY; Reactive Oxygen Species; Time Factors; Up-Regulation; Verapamil