An integrated computational approach of molecular dynamics simulations, receptor binding studies and pharmacophore mapping analysis in search of potent inhibitors against tuberculosis

Tuberculosis is an infectious chronic disease caused by obligate pathogen Mycobacterium tuberculosis that affects millions of people worldwide. Although many first and second line drugs are available for its treatment, but their irrational use has adversely lead to the emerging cases of multiple drug resistant and extensively drug-resistant tuberculosis. Therefore, there is an intense need to develop novel potent analogues for its treatment. This has prompted us to develop potent analogues against TB. The Mycobacterium tuberculosis genome provides us with number of validated targets to combat against TB. Study of Mtb genome disclosed six epoxide hydrolases (A to F) which convert harmful epoxide into diols and act as a potential drug target for rational drug design. Our current strategy is to develop such analogues which inhibits epoxide hydrolase enzyme present in Mtb genome. To achieve this, we adopted an integrated computational approach involving QSAR, pharmacophore mapping, molecular docking and molecular dynamics simulation studies. The approach envisaged vital information about the role of molecular descriptors, essential pharmacophoric features and binding energy for compounds to bind into the active site of epoxide hydrolase. Molecular docking analysis revealed that analogues exhibited significant binding to Mtb epoxide hydrolase. Further, three docked complexes 2s, 37s and 15s with high, moderate and low docking scores respectively were selected for molecular dynamics simulation studies. RMSD analysis revealed that all complexes are stable with average RMSD below 2 Å throughout the 10 ns simulations. The B-factor analysis showed that the active site residues of epoxide hydrolase are flexible enough to interact with inhibitor. Moreover, to confirm the binding of these urea derivatives, MM-GBSA binding energy analysis were performed. The calculations showed that 37s has more binding affinity (ΔGtotal = −52.24 kcal/mol) towards epoxide hydrolase compared to 2s (ΔGtotal = −51.70 kcal/mol) and 15s (ΔGtotal = −49.97 kcal/mol). The structural features inferred in our study may provide the future directions to the scientists towards the discovery of new chemical entity exhibiting anti-TB property.AICTE and Department of Science and Technology, New Delhi.http://www.elsevier.com/locate/JMGM2019-08-01hj2018Plant Production and Soil Scienc

Interaction of Cu<SUP>2+</SUP> ion with milk xanthine oxidase

The interaction of Cu2+ ion with milk xanthine oxidase (XO) has been studied by optical spectroscopy, circular dichroism, ESR and transient kinetic techniques. It is observed that XO forms optically observable complexes with Cu2+ ion. The pH dependence studies of the formation of Cu2+-XO complex by optical spectroscopy and circular dichroism show that at least one ionizable group may be responsible for the formation of the complex. The EPR studies show that Cu2+ ion binds to XO with sulfur and nitrogenous ligands. The transient kinetic study of the interaction of Cu2+ with XO shows the existence of two Cu2+ bound XO complexes formed at two different time scales of the interaction, one at &#8804;5 ms and the other one at around 20 s. The complex formed at longer time scale may be responsible for the inhibition of the enzyme activity

Mechanism of the inhibition of milk xanthine oxidase activity by metal ions: a transient kinetic study

The nature and mechanism of the inhibition of the oxidoreductase activity of milk xanthine oxidase (XO) by Cu2+, Hg2+ and Ag+ ions has been studied by steady state and stopped flow transient kinetic measurements. The results show that the nature of the inhibition is noncompetitive. The inhibition constants for Cu2+ and Hg2+ are in the micromolar and that for Ag+ is in the nanomolar range. This suggests that the metal ions have strong affinity towards XO. pH dependence studies of the inhibition indicate that at least two ionisable groups of XO are involved in the binding of these metal ions. The effect of the interaction of the metal ions on the reductive and oxidative half reactions of XO has been investigated, and it is observed that the kinetic parameters of the reductive half reaction are not affected by these metal ions. However, the interaction of these metal ions with XO significantly affects the kinetic parameters of the oxidative half reaction. It is suggested that this may be the main cause for the inhibition of XO activity by the metal ions

siRNA Delivery Strategies: A Comprehensive Review of Recent Developments

siRNA is a promising therapeutic solution to address gene overexpression or mutations as a post-transcriptional gene regulation process for several pathological conditions such as viral infections, cancer, genetic disorders, and autoimmune disorders like arthritis. This therapeutic method is currently being actively pursued in cancer therapy because siRNA has been found to suppress the oncogenes and address mutations in tumor suppressor genes and elucidate the key molecules in cellular pathways in cancer. It is also effective in personalized gene therapy for several diseases due to its specificity, adaptability, and broad targeting capability. However, naked siRNA is unstable in the bloodstream and cannot efficiently cross cell membranes besides being immunogenic. Therefore, careful design of the delivery systems is essential to fully utilize the potential of this therapeutic solution. This review presents a comprehensive update on the challenges of siRNA delivery and the current strategies used to develop nanoparticulate delivery systems

Copper-Free ‘Click’ Chemistry-Based Synthesis and Characterization of Carbonic Anhydrase-IX Anchored Albumin-Paclitaxel Nanoparticles for Targeting Tumor Hypoxia

Triple negative breast cancer (TNBC) is a difficult to treat disease due to the absence of the three unique receptors estrogen, progesterone and herceptin-2 (HER-2). To improve the current therapy and overcome the resistance of TNBC, there is unmet need to develop an effective targeted therapy. In this regard, one of the logical and economical approaches is to develop a tumor hypoxia-targeting drug formulation platform for selective delivery of payload to the drug-resistant and invasive cell population of TNBC tumors. Toward this, we developed a Carbonic Anhydrase IX (CA IX) receptor targeting human serum albumin (HSA) carriers to deliver the potent anticancer drug, Paclitaxel (PTX). We used Acetazolamide (ATZ), a small molecule ligand of CA IX to selectively deliver HSA-PTX in TNBC cells. A novel method of synthesis involving copper free ‘click’ chemistry (Dibenzocyclooctyl, DBCO) moiety with an azide-labeled reaction partner, known as Strain-Promoted Alkyne Azide Cycloaddition (SPAAC) along with a desolvation method for PTX loading were used in the present study to arrive at the CA IX selective nano-carriers, HSA-PTX-ATZ. The anticancer effect of HSA-PTX-ATZ is higher compared to HSA, PTX and non-targeted HSA-PTX in MDA-MB-231 and MDA-MB-468 cells. The cell killing effect is associated with induction of early and late phases of apoptosis. Overall, our proof-of-concept study shows a promising avenue for hypoxia-targeted drug delivery that can be adapted to several types of cancers

Chemoselective Reduction of the Carbonyl Functionality through Hydrosilylation: Integrating Click Catalysis with Hydrosilylation in One Pot

Herein we report the chemoselective reduction of the carbonyl functionality via hydrosilylation using a copper­(I) catalyst bearing the abnormal N-heterocyclic carbene <b>1</b> with low (0.25 mol %) catalyst loading at ambient temperature in excellent yield within a very short reaction time. The hydrosilylation reaction of α,β-unsaturated carbonyl compounds takes place selectively toward 1,2-addition (CO) to yield the corresponding allyl alcohols in good yields. Moreover, when two reducible functional groups such as imine and ketone groups are present in the same molecule, this catalyst selectively reduces the ketone functionality. Further, <b>1</b> was used in a consecutive fashion by combining the Huisgen cycloaddition and hydrosilylation reactions in one pot, yielding a range of functionalized triazole substituted alcohols in excellent yields

CD44 Targeted Nanomaterials for Treatment of Triple-Negative Breast Cancer

Identified as the second leading cause of cancer-related deaths among American women after lung cancer, breast cancer of all types has been the focus of numerous research studies. Even though triple-negative breast cancer (TNBC) represents 15–20% of the number of breast cancer cases worldwide, its existing therapeutic options are fairly limited. Due to the pivotal role of the presence/absence of specific receptors to luminal A, luminal B, HER-2+, and TNBC in the molecular classification of breast cancer, the lack of these receptors has accounted for the aforementioned limitation. Thereupon, in an attempt to participate in the ongoing research endeavors to overcome such a limitation, the conducted study adopts a combination strategy as a therapeutic paradigm for TNBC, which has proven notable results with respect to both: improving patient outcomes and survivability rates. The study hinges upon an investigation of a promising NPs platform for CD44 mediated theranostic that can be combined with JAK/STAT inhibitors for the treatment of TNBC. The ability of momelotinib (MMB), which is a JAK/STAT inhibitor, to sensitize the TNBC to apoptosis inducer (CFM-4.16) has been evaluated in MDA-MB-231 and MDA-MB-468. MMB + CFM-4.16 combination with a combination index (CI) ≤0.5, has been selected for in vitro and in vivo studies. MMB has been combined with CD44 directed polymeric nanoparticles (PNPs) loaded with CFM-4.16, namely CD44-T-PNPs, which selectively delivered the payload to CD44 overexpressing TNBC with a significant decrease in cell viability associated with a high dose reduction index (DRI). The mechanism underlying their synergism is based on the simultaneous downregulation of P-STAT3 and the up-regulation of CARP-1, which has induced ROS-dependent apoptosis leading to caspase 3/7 elevation, cell shrinkage, DNA damage, and suppressed migration. CD44-T-PNPs showed a remarkable cellular internalization, demonstrated by uptake of a Rhodamine B dye in vitro and S0456 (NIR dye) in vivo. S0456 was conjugated to PNPs to form CD44-T-PNPs/S0456 that simultaneously delivered CFM-4.16 and S0456 parenterally with selective tumor targeting, prolonged circulation, minimized off-target distribution

Polyvalent Folate-Dendrimer-Coated Iron Oxide Theranostic Nanoparticles for Simultaneous Magnetic Resonance Imaging and Precise Cancer Cell Targeting

The low therapeutic index of conventional chemotherapy and poor prognosis of patients diagnosed with metastatic cancers are prompting clinicians to adopt newer strategies to simultaneously detect cancer lesions at an early stage and to precisely deliver anticancer drugs to tumor sites. In this study, we employed a novel strategy to engineer a polyvalent theranostic nanocarrier consisting of superparamagnetic iron oxide nanoparticle core (SPIONs) decorated with folic acid-polyamidoamine dendrimers surface (FA-PAMAM). In addition, a highly potent hydrophobic anticancer agent 3,4-difluorobenzylidene-curcumin (CDF) was coloaded in the FA-PAMAM dendrimer to increase its solubility and assess its therapeutic potentials. The resulting targeted nanoparticles (SPIONs@FA-PAMAM-CDF) exhibited high MR contrast. When tested on folate receptor overexpressing ovarian (SKOV3) and cervical (HeLa) cancer cells, the CDF loaded targeted nanoformulations showed higher accumulation with a better anticancer activity as compared to the nontargeted counterparts, possibly due to multivalent folate receptor binding interaction with cells overexpressing the target. The results were corroborated by observation of a larger population of cells undergoing apoptosis due to upregulation of tumor suppressor phosphatase and tensis homologue (PTEN), caspase 3, and inhibition of NF-κB in groups treated with the targeted formulations, which further confirmed the ability of the multivalent theranostic nanoparticles for simultaneous imaging and therapy of cancers

Folate Decorated Nanomicelles Loaded with a Potent Curcumin Analogue for Targeting Retinoblastoma

The aim of this study was to develop a novel folate receptor-targeted drug delivery system for retinoblastoma cells using a promising anticancer agent, curcumin-difluorinated (CDF), loaded in polymeric micelles. Folic acid was used as a targeting moiety to enhance the targeting and bioavailability of CDF. For this purpose, amphiphilic poly(styrene-co-maleic acid)-conjugated-folic acid (SMA-FA) was synthesized and utilized to improve the aqueous solubility of a highly hydrophobic, but very potent anticancer compound, CDF, and its targeted delivery to folate overexpressing cancers. The SMA-FA conjugate was first synthesized and characterized by 1H NMR, FTIR and DSC. Furthermore, the chromatographic condition (HPLC) for estimating CDF was determined and validated. The formulation was optimized to achieve maximum entrapment of CDF. The particle size of the micelles was measured and confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Cytotoxicity studies were conducted on (Y-79 and WERI-RB) retinoblastoma cells. Results showed that the solubility of CDF could be increased with the newly-synthesized polymer, and the entrapment efficiency was &gt;85%. The drug-loaded nanomicelles exhibited an appropriate size of &lt;200 nm and a narrow size distribution. The formulation did not show any adverse cytotoxicity on a human retinal pigment epithelial cell (ARPE-19), indicating its safety. However, it showed significant cell killing activity in both Y-79 and WERI-RB retinoblastoma cell lines, indicating its potency in killing cancer cells. In conclusion, the folic acid-conjugated SMA loaded with CDF showed promising potential with high safety and pronounced anticancer activity on the tested retinoblastoma cell lines. The newly-formulated targeted nanomicelles thus could be a viable option as an alternative approach to current retinoblastoma therapies