Molecular Mimics of Classic P-Glycoprotein Inhibitors as Multidrug Resistance Suppressors and Their Synergistic Effect on Paclitaxel

<div><p>P-glycoprotein (Pgp) is a membrane bound efflux pump spread in a variety of tumor cells and considered as a main component of multidrug resistance (MDR) to chemotherapies. In this work, three groups of compounds (imidazolone, oxazolone and vinyl dipeptide derivatives) were synthesized aiming to develop a molecular framework that effectively suppresses MDR. When tested for their influence on Pgp activity, four compounds coded Cur1-01, Cur1-12V, Curox-1 and Curox-3 significantly decreased remaining ATP concentration indicating Pgp substrate site blocking. On the other hand, Cur-3 and Cur-10 significantly increased remaining ATP concentration, which is indicative of Pgp ATPase inhibition. The cytotoxicity of synthesized compounds was examined against Pgp expressing/highly resistant colorectal cancer cell lines (LS-174T). Compounds Cur-1 and Cur-3 showed considerable cytotoxicity with IC₅₀ values of 7.6 and 8.9 μM, respectively. Equitoxic combination (at IC₅₀ concentrations) of PTX and Cur-3 greatly diminished resistant cell clone from 45.7% to 2.5%, albeit with some drop in potency from IC₅₀ of 7.9 nM to IC₅₀ of 23.8 nM. On the other hand, combination of PTX and the non-cytotoxic Cur1-12V (10 μM) significantly decreased the IC₅₀ of PTX to 3.8 nM as well as the resistant fraction to 16.2%. The combination test was confirmed using the same protocol but on another resistant CRC cell line (HCT-116) as we obtained similar results. Both Cur-3 and Cur1-12V (10 μM) significantly increased the cellular entrapment of Pgp probe (doxorubicin) elevating its intracellular concentration from 1.9 pmole/cell to 3.0 and 2.9 pmole/cell, respectively.</p></div

Cytotoxic Activity of synthesized compounds against LS174T CRC cell lines.

<p>Cytotoxic Activity of synthesized compounds against LS174T CRC cell lines.</p

Chemomedulatory effects of test compounds on the cytotoxicity parameters of PTX against LS-174T cell line.

<p>Chemomedulatory effects of test compounds on the cytotoxicity parameters of PTX against LS-174T cell line.</p

Structure and codes of the synthesized oxazolones and imidazolones.

<p>Structure and codes of the synthesized oxazolones and imidazolones.</p

(A) The effect of test compounds on the activity of P-glycoprotein efflux pump cell free isolated recombinant P-gp protein and (B) within LS-174T cells.

<p>The influence of test compounds on the cellular pharmacokinetics via inhibiting the activity of Pgp pump. Verapamil (VRP) is a standard direct Pgp blocker. Sod Vanadate is a standard ATPase inhibitor. Curcumin is the prototype compound in the design. The asterisk (*) denotes significant difference from control.</p

The effect of serial equitoxic concentrations (ratio 1:100) of Cur3 (A), and 10 μM (B), and serial concentration of Cur1-12V (ratio 1:100) (C) on the cytotoxicity of PTX in HCT-116 cells.

<p>Cells were exposed to serial dilution of PTX (●), Chemosensetizer (▼) or their combination (○) for 72 h. Cell viability was determined using SRB assay.</p

Examples of Pgp inhibitors.

<p>Examples of Pgp inhibitors.</p

Design of Pgp inhibitors by re-scaffolding of the linker region of curcumin and verapamil.

<p>Design of Pgp inhibitors by re-scaffolding of the linker region of curcumin and verapamil.</p

Chemical Synthesis Scheme.

<p>Reagents and Conditions: (a) Acetic anhydride, sodium acetate, heat. (b) Aniline, acetic acid, sodium acetate, 110°C, 24 hr. (c) Ammonium acetate, pyridine, 110°C, 18 hr. (d) <i>n</i>-PrNH₂, EtOH, r.t., 2h.</p

DataSheet1_Design, synthesis, molecular docking, and molecular dynamic studies of novel quinazoline derivatives as phosphodiesterase 7 inhibitors.PDF

Introduction: Phosphodiesterase 7 (PDE7) is a high-affinity cyclic AMP (cAMP)-specific PDE that is expressed in immune and proinflammatory cells. In this work, we explore the possibility that selective small molecule inhibitors of this enzyme family could provide a novel approach to alleviate the inflammation that is associated with many inflammatory diseases.Methods: A series of novel substituted 4-hydrazinoquinazoline derivatives and fused triazoloquinazolines were designed, synthesized, and evaluated in vitro for their PDE7A inhibition activities, in comparison with Theophylline, a non-selective PDE inhibitor, and BRL50481, a selective PDE7A inhibitor. This series of novel quinazoline derivatives were synthesized via multi-step reactions. The reaction sequence began with selective monohydrazinolysis of compounds 2a,b to give 3a,b. Schiff bases 4a-h were synthesized by the reaction of the quinazolylhydrazines 3a,b with various substituted aromatic aldehydes. The reaction of 4a-h with bromine in acetic acid, in turn, gave fused triazoloquinazolines 5a-h. These compounds were characterized by satisfied spectrum analyses mainly including 1HNMR, 13CNMR, and MS together with elemental analyses.Results and discussion: The results of in vitro PDE7A inhibition activity clearly indicated that compounds 4b, 4g, 5c, and 5f exhibited good potency. Molecular docking and molecular dynamic simulation studies further supported our findings and provided the basis of interaction in terms of conventional hydrogen bonds and π-π stacking patterns. The present results lay the groundwork for developing lead compounds with improved phosphodiesterase seven inhibitory activities.</p