New insight into the structural changes of apoferritin pores in the process of doxorubicin loading at an acidic pH: Molecular dynamics simulations.

Apoferritin (APO-Fr) is one of the most investigated proteins proposed as an advanced structure for drug delivery systems. Herein, molecular dynamics simulation was employed to compare the opening of 3-fold and 4-fold pores in APO-Fr during the partial disassembly process at an acidic pH. We showed that more hydrophilic residues in the surface of 3-fold pores compared to 4-fold pores facilitate increased flexibility and a higher tendency to open. In particular, dissociation is induced by the presence of Doxorubicin (DOX) close to 3-fold pores. Our simulations showed loaded DOXs on the APO-Fr surface were mainly involved in the hydrogen bond interactions with the hydrophilic residues, suggesting the difficulty of hydrophobic drugs loading in APO-Fr with the partial disassembly process. However, π-π interactions as well as hydrogen bonds between protein and DOXs were mediated by the basic and acidic amino acids such as HIP128, GLU17, and LYS143 at the open pores, providing penetration of DOXs into the H-Apo-Fr. We conclude that increased drug encapsulations and loading capacity of hydrophobic drugs into the cavity of APO-Fr are feasible by further disassembly of openings to access the internal hydrophobic portions of the protein.

Theoretical studies on 1,4-dihydropyridine derivatives as P-glycoprotein allosteric inhibitors: insights on symmetry and stereochemistry.

P-glycoprotein (P-gp) is a key efflux pump involved in cellular multidrug resistance (MDR), lowering the concentration of many anticancer drugs in tumor cells by pumping them into the extracellular milieu. While previous studies identified 1,4-dihydropyridines (DHP) as putative P-gp allosteric inhibitors, none reported the effect of stereochemistry on the ability of DHPs to bind P-gp. In the present study both symmetric (1) and asymmetric (2 R,S) DHPs were designed as P-gp inhibitors and, after biological evaluation, molecular docking and molecular dynamics simulation (MD) studies were performed to gain insights on how both scaffolds interact with P-gp. The results were thoroughly analyzed i) to evaluate the role of the different substituents and ii) to assess how stereochemistry may affect binding of DHPs to P-gp. Our results suggest that both the substitution pattern and stereochemistry may have a significant impact not only in drug binding but also on membrane permeation/accumulation, thus compromising in which site the DHPs may exert their effect as P-gp efflux inhibitors. Therefore, it is our conclusion that the stereochemistry cannot be neglected during the development of novel 1,4-dihydropyridine derivatives.Communicated by Ramaswamy H. Sarma.

Recent advances in the redox-responsive drug delivery nanoplatforms: A chemical structure and physical property perspective.

Poor water solubility, off-target toxicity, and small therapeutic window are among major obstacles for the development of drug products. Redox-responsive drug delivery nanoplatforms not only overcome the delivery and pharmacokinetic pitfalls observed in conventional drug delivery, but also leverage the site-specific delivery properties. Cleavable diselenide and disulfide bonds in the presence of elevated reactive oxygen species (ROS) and glutathione concentration are among widely used stimuli-responsive bonds to design nanocarriers. This review covers a wide range of redox-responsive chemical structures and their properties for designing nanoparticles aiming controlled loading, delivery, and release of hydrophobic anticancer drugs at tumor site.

Synthesis, in silico and in vitro studies of new 1,4-dihydropiridine derivatives for antitumor and P-glycoprotein inhibitory activity.

P-glycoprotein (P-gp) is one of the cell membrane pumps which mediate the efflux of molecules such as anticancer drugs to the extracellular matrix of tumor cells. P_gp is a member of the ATP-binding cassette (ABC) transporter family that is implicated in cancer multidrug resistance (MDR). Since MDR is a contributor to cancer chemotherapy failure, modulation of efflux pumps is a viable therapeutic strategy. In this study, new synthetic 1,4 dihydropiridine (DHP) derivatives containing thiophenyl substitution were tested as inhibitors of P-gp. Efflux assay was conducted to evaluate the intracellular accumulation of Rhodamine123 (Rh123) as a pump substrate. MTT assay, cell cycle analysis and in silico methods were also examined. Flow cytometric analysis revealed that synthetic DHP derivatives (15 µM) increased intracellular concentration of the substrate by 2-3 folds compared with verapamil as a standard P-gp inhibitor. MTT assay on EPG85-257P and its drug-resistant EPG85-257RDB cell line revealed antitumor effects (30-45%) for new DHP derivatives at 15 µM following 72 h incubation. However, MTT test on normal cell line showed negligible toxic effects. Finally combination of synthetic derivatives with doxorubicin showed that these compounds decrease IC50 of doxorubicin in resistant cell lines from 9 to 1.5 µM. Sub-G1 peak-related apoptotic cells showed a stronger effect of synthetic compounds at 5 µM compared with verapamil. Molecular dynamic results showed a high binding affinity between DHP derivative and protein at drug binding site. Findings of these biological tests indicated the antitumor activity and P-gp inhibitory effects of new 1,4-DHP derivatives.

Structural and functional aspects of P-glycoprotein and its inhibitors.

P-glycoprotein (P-gp) is a member of ATP-binding cassette (ABC) superfamily which extrudes chemotherapeutic agents out of the cell. Suppression of this efflux activity has been the subject of numerous attempts to develop P-gp inhibitors. The aim of this review is to present up-to-date information on the structural and functional aspects of P-gp and its known inhibitors. The data presented also provide some information on drug discovery approaches for candidate P-gp inhibitors. Nucleotide-binding domains (NBDs) and drug-binding domains (DBDs) have been extensively studied to gain more information about P-gp inhibition and it looks that the ATPase activity of this pump has been the most attractive target for designing inhibitors. Hydrophobic and π-π (aromatic) interactions between P-gp binding domains and inhibitors are dominant intermolecular forces that have been reported in many studies using different methods. Many synthetic and natural products have been found to possess inhibitory or modulatory effects on drug transporter proteins. Log P value is an important factor in studying these inhibitors and has a crucial role on absorption, distribution, metabolism, and excretion (ADME) properties of candidate P-gp inhibitors.

Synthesis and DFT Study on Hantzsch Reaction to Produce Asymmetrical Compounds of 1,4-Dihydropyridine Derivatives for P-Glycoprotein Inhibition as Anticancer Agent.

BACKGROUND: P-glycoprotein (P-gp) causes the efflux of cancer chemotherapy drugs from tumor cells, so its inhibition can be one target for designing and synthesis of new anticancer drugs. OBJECTIVE: In this study, new compounds of 1,4-dihydropyridine (DHP) were recommended as inhibitors of P-gp. METHODS: We synthesized new symmetrical DHP with 36% - 43% yield by the reaction of new reactants. In biological studies, these compounds have high lipophilicity, and thus low water solubility. Four reactants I with different reactivity was computed and compared using DFT study. The LUMO-map was differently distributed on each reactant. Amine intermediate underwent tautomerism as a transition state and it seems to play important role in reaction progress. Calculations were performed to select suitable reactants. RESULTS: Two different reactants I, including one polar group and a non-polar group, were used to produce asymmetric compounds with 49% - 60% yield. These asymmetric DHPs were more soluble than symmetric DHPs. In the final step, another selected symmetric product (by the elimination of chlorine atom) was synthesized in high yield (74%) by using DFT study. CONCLUSION: In this study, selected reactants by DFT calculation have increased the yield of reaction from 36% to 74% without any catalyst. The diversity of products is a noticeable topic. Racemic asymmetric compounds with R and S enantiomers have the potential for enantiomeric separation. Each of these enantiomers could have a different physiological effect.

Docking and QSAR Studies of 1,4-Dihydropyridine Derivatives as Anti- Cancer Agent.

BACKGROUND: The multidrug resistance (MDR) of cancer cells has become a great barrier to the success of chemotherapy. OBJECTIVE: In this study, quantitative structure activity relationship (QSAR) modeling was applied to 46 1,4-dihydropyridine structures (DHPs), and some selected compounds were docked. METHODS: QSAR was used to generate models and predict the MDR inhibitory activity for a series of 1,4-dihydropyridines (DHP). The DHPs were built and optimized using the Sybyl program (x1.2 version). Descriptor generation was done by DRAGON package. Docking was carried out using Auto Dock 4.2 software. Multiple linear regression, and partial least square were performed as QSAR modelgeneration methods. External validation, cross-validation (leave one out) and y-randomization were used as validation methods. RESULTS: The constructed model using stepwise-MLR and GA-PLS revealed good statistical parameters. In the final step all compounds were divided into two parts: symmetric (PLS) and asymmetric (MLR) 1,4-dihydropyridines and two other models were built. The square correlation coefficient (R2) and root mean square error (RMSE) for train set for GA-PLS were (R2 = 0.734, RMSE train = 0.26). CONCLUSION: The predictive ability of the models was found to be satisfactory and could be employed for designing new 1,4-dihydropyridines as potent MDR inhibitors in cancer treatment. 1,4- Dihydropyridine ring containing protonable nitrogen as scaffold could be proposed. Sulfur, ester, amide, acyle, ether, fragments are connected to a 1,4-dihydropyridine ring. Phenyl groups (with an electronegative substituent) as a lipophilic part are essential for the inhibitory effect.