Łukasz Pułaski

Montelukast treatment may alter the early efficacy of immunotherapy in children with asthma

BACKGROUND Allergen-specific immunotherapy (SIT) is the only available potentially curative approach in the management of allergic diseases. Therapies that boost regulatory T cell induction during SIT might further enhance its effectiveness. OBJECTIVE The purpose of this study was to assess the effect of montelukast treatment on early clinical and immunologic effects of allergen-specific immunotherapy in children with asthma. METHODS It was a randomized, double-blind, placebo-controlled trial conducted in 36 children with asthma and allergy to house dust mites who required from 400 to 800 microg of inhaled budesonide per day during the 7-month run-in period. Patients were randomly allocated to receive 5 mg montelukast daily (n = 18) or placebo (n = 18) as an addition to inhaled corticosteroid (ICS) treatment during the 3-month build-up phase of SIT, when modification of ICS doses was not allowed. During the 7 months of the maintenance phase of SIT, ICS doses were adjusted to control the asthma symptoms. RESULTS After 12 months of SIT, a reduction of the median daily ICS dose, necessary to control asthma symptoms, was 16.7% grater in patients from the placebo group than in patients from the montelukast group. Intervention with montelukast significantly impaired the induction of regulatory T lymphocytes. During the build-up phase of SIT, patients in the placebo group frequently experienced an increase in asthma symptoms leading to exclusions from the per protocol population. CONCLUSION Our study failed to show a beneficial effect of montelukast on SIT. In fact, quite the opposite occurred: compared with placebo, montelukast intervention led to less effectiveness of SIT.

Transport of bimane-S-glutathione in human erythrocytes.

Export of glutathione S-conjugate of bimane (BSG) was studied in human erythrocytes. Characteristics of the BSG transport is similar to that of dinitrophenyl-S-glutathione (DNP-SG). BSG transport has two kinetic components, one of high affinity and low capacity (Km = 7.4 +/- 0.2 mumol/ml cells, Vm = 2.7 +/- 0.1 nmol/min per ml RBC) and another of low affinity and high capacity (Km = 242 +/- 8 mumol/ml cells, Vm = 9.6 +/- 1.6 nmol/min per ml RBC). BSG export is inhibited by vanadate (Ki = 65 +/- 6 microM) and fluoride (Ki = 11.4 +/- 0.8 mM). Activation energy of the transport is 67 +/- 7 kJ/mol. BSG transport is independent of membrane potential; its rate increases with pH in the pH range of 6-8, in line with the assumption that the anionic conjugate is cotransported with proton. BSG import to erythrocyte membrane inside-out vesicles is stimulated by ATP. Fluorimetric measurements of BSG export require low amounts of cells and may also be useful for other cell types as an alternative to studies of glutatione S-conjugate transport using radioactive substrates.

Is the glutathione S-conjugate pump a flippase?

A hypothesis of the flippase nature of the glutathione S‐conjugate transport is presented. Experimental premises for this hypothesis include interaction of glutathione S‐conjugates with the membrane, as demonstrated by their effects on membrane fluidity, quenching of 1‐(4‐trimethylammoniumphenyl)‐6‐phenyl‐1,3,5‐hexatriene fluorescence and induction of echinocytosis by 2,4‐dinitrophenyl‐S‐glutathione (DNP‐SG). This hypothesis can rationalize, i. a., observations of the enhancement of DNP‐SG transport by butanol and stimulation of erythrocyte membrane Mg2+‐ATPase activity by albumin‐coupled DNP‐SG.

Mechanisms of Internalization of Maltose-Modified Poly(propyleneimine) Glycodendrimers into Leukemic Cell Lines

Poly(propyleneimine) dendrimers of fourth generation partially modified with maltose (open shell structure, PPI-m OS) have been proposed as carriers for nucleotide anticancer drugs. The aim of this work was to provide basic insight into interactions between fluorescently labeled PPI-m dendrimer and two distinct leukemia cell models: CCRF-1301 lymphoid cell line and HL-60 myeloid cell line. We applied qualitative confocal imaging and quantitative flow cytometry, as well as trypan blue quenching and pharmacological inhibition, to investigate the course, kinetics, and molecular mechanisms of internalization of nanoparticles. CCRF-1301 cells take up glycodendrimer macromolecules via a relatively slow, adsorptive endocytosis process, which is cholesterol-dependent, clathrin- and caveolin-independent, and not followed by recycling or exocytosis. Morphological features of this phenomenon point to the involvement of aggregation-induced cell polarity changes (capping). In HL-60 cells, internalization is very fast, independent of binding to the cell surface, and proceeds from the fluid phase via a classical clathrin-dependent mechanism, ending up in an endolysosomal compartment from which it is not further released. This substantial difference in internalization rate and mechanism between two cell types has important repercussions for potential application of this class of glycodendrimers as drug delivery agents.

ABCB1-overexpressing MDCK-II cells are hypersensitive to 3-bromopyruvic acid

AIMS Cancer cells, due to the Warburg effect, are more dependent on glycolysis than normal cells, so glycolytic inhibitor 3-bromopyruvic acid (3-BP) was proposed as a promising candidate for anticancer therapy. Overexpression of multidrug transporters is the main reason of resistance of cancer cells to chemotherapy. As the activity of multidrug transporters imposes an energetic burden on the cells, it can be expected that inhibition of ATP generation may exert a selective cytotoxicity to cells overexpressing multidrug transporters. The aim of this study was to compare the effect of 3-BP on the survival and ATP level in MDCK-II cells and MDCK-II cells overexpressing ABCB1 (Pgp) or ABCG2 (BCRP). MAIN METHODS Cell survival was measured with resazurin and with neutral red. ATP level was assayed with luciferin/luciferase kit. Luteolin transport was measured by an original method described in the paper. KEY FINDINGS 3-BP (10-200μM) induced a decrease of ATP level after 1-h incubation in all cell lines studied, more drastically in ABCB1-overexpressing cells. 50 and 200μM 3-BP significantly decreased cell viability; the effect was more pronounced for ABCB1-overexpressing cells. PSC833, inhibitor of ABCB1, ameliorated the toxic effect of 3-BP on MDCK-II ABCB1 cells and MDCK-II cells. 3-BP inhibited luteolin transport in MDCK-II ABCG2 cells. SIGNIFICANCE These results indicate that 3-BP shows selective toxicity against ABCB1- but not ABCG2-overexpressing cells, apparently due to enhanced ATP depletion but in a manner independent of the transport activity of Pgp, suggesting a novel mechanism of hypersensitivity of ABCB1-overexpressing cells to 3-BP.

Antioxidant action of SMe1EC2, the low-basicity derivative of the pyridoindole stobadine, in cell free chemical models and at cellular level.

Abstract The aim of the study was to evaluate the antioxidant action of SMe1EC2, the structural analogue of the hexahydropyridoindole antioxidant stobadine. The antiradical activity of SMe1EC2 was found to be higher when compared to stobadine, as determined both in cell-free model systems of AAPH-induced oxidation of dihydrorhodamine 123 and 2´,7´-dichloro-dihydrofluorescein diacetate, and in the cellular system of stimulated macrophages RAW264.7. Analysis of proliferation of HUVEC and HUVEC-ST cells revealed absence of cytotoxic effect of SMe1EC2 at concentrations below 100 μM. The antioxidant activity of SMe1EC2, superior to the parent drug stobadine, is accounted for by both the higher intrinsic free radical scavenging action and by the better bioavailability of the low-basicity SMe1EC2 relative to the high-basicity stobadine.

Poly(propylene imine) glycodendrimers non-covalently bind ATP in a pH- and salt-dependent manner - model studies for adenosine analogue drug delivery.

Graphical abstract Figure. No Caption available. Abstract Adenosine analogue drugs (such as fludarabine or cladribine) require transporter‐mediated uptake into cells and subsequent phosphorylation for anticancer activity. Therefore, application of nanocarrier systems for direct delivery of active triphosphate forms has been proposed. Here, we applied isothermal titration calorimetry and zeta potential titration to determine the stoichiometry and thermodynamic parameters of interactions between 4th generation poly(propyleneimine) dendrimers (unmodified or sugar‐modified for increased biocompatibility) and ATP as a model adenosine nucleotide. We showed that glycodendrimers have the ability to efficiently interact with nucleoside triphosphates and to form stable complexes via electrostatic interactions between the ionized phosphate and amino groups on the nucleotide and the dendrimer, respectively. The complexation process is spontaneous, enthalpy‐driven and depends on buffer composition (strongest interactions in organic buffer) and pH (more binding sites in acidic pH). These properties allow us to consider maltose‐modified dendrimers as especially promising carriers for adenosine analogues.

Terminal Sugar Moiety Determines Immunomodulatory Properties of Poly(propyleneimine) Glycodendrimers

Poly(propyleneimine) dendrimers fully surface-modified with disaccharide moieties (maltose, cellobiose, and lactose) designed to mimic natural lectin receptor ligands were tested for their bioactivity in two myeloid cell lines: THP-1 and HL-60. Depending on the sugar modification, we observed variable activation of NF-κB, AP-1, and NF-AT signaling pathways: lactose-coated dendrimers had the strongest impact on marker gene expression and most signaling events with the notable exception of NF-κB activation in THP-1 cells. The two cell lines showed an overall similar pattern of transcription factor and gene expression activation upon treatment with glycodendrimers, suggesting the involvement of galectin and C-type lectin receptor types. An important result of this action was the overexpression of CD40 and IL8 genes, potentially leading to an activated, proinflammatory phenotype in the monocyte/macrophage cell lineage. These pharmacodynamic characteristics of glycodendrimers need to be taken into account during their pharmaceutical applications both in drug delivery and direct immunomodulation.

Glycodendrimer Nanocarriers for Direct Delivery of Fludarabine Triphosphate to Leukemic Cells: Improved Pharmacokinetics and Pharmacodynamics of Fludarabine

Fludarabine, a nucleoside analogue antimetabolite, has complicated pharmacokinetics requiring facilitated transmembrane transport and intracellular conversion to triphosphate nucleotide form (Ara-FATP), causing it to be susceptible to emergence of drug resistance. We are testing a promising strategy to improve its clinical efficacy by direct delivery of Ara-FATP utilizing a biocompatible glycodendrimer nanocarrier system. Here, we present results of a proof-of-concept experiment in several in vitro-cultured leukemic cell lines (CCRF, THP-1, U937) using noncovalent complexes of maltose-modified poly(propyleneimine) dendrimer and fludarabine triphosphate. We show that Ara-FATP has limited cytotoxic activity toward investigated cells relative to free nucleoside (Ara-FA), but complexation with the glycodendrimer (which does not otherwise influence cellular metabolism) drastically increases its toxicity. Moreover, we show that transport via hENT1 is a limiting step in Ara-FA toxicity, while complexation with dendrimer allows Ara-FATP to kill cells even in the presence of a hENT1 inhibitor. Thus, the use of glycodendrimers for drug delivery would allow us to circumvent naturally occurring drug resistance due to decreased transporter activity. Finally, we demonstrate that complex formation does not change the advantageous multifactorial intracellular pharmacodynamics of Ara-FATP, preserving its high capability to inhibit DNA and RNA synthesis and induce apoptosis via the intrinsic pathway. In comparison to other nucleoside analogue drugs, fludarabine is hereby demonstrated to be an optimal candidate for maltose glycodendrimer-mediated drug delivery in antileukemic therapy.