Identification of inhibitor concentrations to efficiently screen and measure inhibition Ki values against solute carrier transporters

Unveiling the anticancer potential and toxicity of Ganoderma applanatum wild mushroom derived bioactive compounds: An in vitro, in vivo and in silico evaluation

This study explores the anticancer potential of methanolic extract from Ganoderma applanatum, focusing on its cytotoxicity across various cancer cell lines and its safety and efficacy in an in vivo hepatocellular carcinoma (HCC) model, along with molecular docking analysis of its bioactive compounds targeting B-cell lymphoma 2 (Bcl-2) protein. The MTT assay revealed significant cytotoxicity of the extract against epidermoid carcinoma (A431), human alveolar carcinoma (A549), and hepatocellular carcinoma (HepG2) cell lines, with the extract exhibiting the highest potency (IC50 of 95.65 µg/ml) against HepG2 cells. Apoptosis induction and DNA degradation in HepG2 cells were confirmed through mitochondrial membrane potential analysis, ethidium bromide/acridine orange staining, and DNA fragmentation assays. In vivo studies on Wistar albino rats showed that administration of the extract up to 1000 mg/ml did not significantly affect body weight or hematological parameters, suggesting a favorable safety profile. Histopathological examination revealed normal liver architecture at most doses, with mild inflammation observed at the highest dose (1000 mg/ml). The G. applanatum extract were showed reducing liver weight and improving body weight in a Diethylnitrosamine (DEN)-induced HCC model was comparable to cyclophosphamide, indicating its potential as a less toxic alternative or adjunct to conventional chemotherapy. Additionally, the extract reduced elevated serum liver enzymes, demonstrating hepatoprotective effects. Molecular docking of nine bioactive compounds from G. applanatum identified 2h-3,11c-(epoxymethano)phenanthro[10,1-bc]pyran as a promising candidate for further investigation. These findings suggest G. applanatum as a novel anticancer agent with the potential for natural, effective cancer therapy.

Reduction of oxidative damage in prostate tissue caused by radiation and/or chloroquine by apocynin

Prostate damage can occur in men due to age and genetic factors, especially when exposed to external factors. Radiation (RAD) is a prominent factor leading to oxidative stress and potential prostate damage. Additionally, chloroquine (CQ), used in malaria treatment, can induce oxidative stress in a dose-dependent manner. Therefore, reducing and preventing oxidative damage in prostate tissue caused by external factors is crucial. Rats used in the study were divided into seven groups, CQ, apocynin (APO), RAD, CQ + APO, CQ + RAD, APO + RAD, CQ + APO + RAD. Subsequently, in vivo biochemical parameters of prostate tissues were examined, including reduced glutathione, lipid peroxidation, superoxide dismutase, glutathione reductase, glutathione peroxidase, glutathione-S-transferase activities, and total antioxidant status, total oxidant status, reactive oxygen species, oxidative stress index, advanced oxidation protein products and histologically. The in vivo results presented in our study showed that APO reduced oxidative stress and had a protective effect on prostate tissue in the CQ, RAD, and CQ + RAD groups as a results of biochemical and histological experiments. Additionally, in silico studies revealed a higher binding affinity of diapocynin to target proteins compared to APO. As a histological results, RAD and CQ alone or in combination did not induce damage in prostate tissues, whereas mild histopathological findings such as hyperemia and haemorrhage were observed in all APO-treated groups. The results suggest that the use of APO for the treatment of oxidative damage induced by CQ and RAD in rats.

Proteome-Based Investigation Identified Potential Drug Repurposable Small Molecules Against Monkeypox Disease

Monkeypox Virus (MPXV), the causative agent of Monkeypox (MPX) disease, is an emerging zoonotic pathogen spreading in different endemic and non-endemic nations and creating outbreaks. MPX treatment mainly includes Cidofovir and Tecovirimat but they have several side effects and solely depending on these drugs may promote the emergence of drug-resistant variants. Hence, new drugs are required to control the spread of the disease. In this study, we explored the MPXV proteome to suggest repurposable drugs. DrugBank screening revealed drugs such as Brinzolamide, Dorzolamide, Methazolamide, Zidovudine, Gemcitabine, Hydroxyurea, Fludarabine, and Tecovirimat as controls. Structural analogs of these compounds were extracted from ChEMBL Database. After Molecular docking and Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADMET)-based screening, we identified Zidovudine (binding affinity-5.9 kcal/mol) and a Harmala alkaloid (2S,4R)-4-(9H-Pyrido[3,4-b]indol-1-yl)-1,2,4-butanetriol (binding affinity - 6.6 kcal/mol) against L2R receptor (Thymidine Kinase). Moreover, Fludarabine (binding affinity - 6.4 kcal/mol) and 5'-Dehydroadenosine (binding affinity - 6.4 kcal/mol) can strongly interact with the I4L receptor (Ribonucleotide reductase large subunit R1). Molecular Dynamics (MD) simulations suggest all of these compounds can change the C-alpha backbone, residue mobility, compactness, and solvent accessible surface area of L2R and I4L. Our results strongly suggest that these drug repurposing small molecules are worth exploring in vivo and in vitro for clinical applications.

Novel pyrazole and imidazolone compounds: synthesis, X-ray crystal structure with theoretical investigation of new pyrazole and imidazolone compounds anticipated insecticide's activities against targeting Plodia interpunctella and nilaparvata lugens

In this study, we synthesized (2-propoxyphenyl)(3-(p-tolyl)oxiran-2-yl)methanone through oxidizing the double bond of the respective chalcone via the Weitz-Scheffer epoxidation reaction. Additionally, the chalcone with an oxirane ring served as a fundamental building block for the synthesis of various pyrazole and imidazole derivatives, employing diverse nitrogen nucleophiles. All synthesized compounds were confirmed via analytical and spectroscopic analysis, such as FT-IR, 1H NMR, 13C NMR, and mass spectroscopy. Furthermore, all these nitrogen heterocycles were optimized via the DFT/B3LYP/6-31G(d,p) basis set and their physical descriptors were identified. Compound 11 was further confirmed using single-crystal X-ray diffraction with Hirshfeld analysis, and the results were correlated with the optimized structure by comparing their bond length and bond angle, which provided excellent correlation. Additionally, the insecticidal activities of the newly synthesized compounds were tested against P. interpunctella and Nilaparvata lugens. The heterocyclic compounds exhibited remarkable activity compared to the standard reference thiamethoxam. These findings were further confirmed through docking simulation with different proteins, namely PDBID 3aqy and 3wyw. The compounds interacted effectively within the protein pockets, displaying a higher binding energy with amino acids.

Enhanced Antioxidant and Neuroprotective Properties of Pterostilbene (Resveratrol Derivative) in Amorphous Solid Dispersions

In this study, amorphous solid dispersions (ASDs) of pterostilbene (PTR) with polyvinylpyrrolidone polymers (PVP K30 and VA64) were prepared through milling, affirming the amorphous dispersion of PTR via X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC). Subsequent analysis of DSC thermograms, augmented using mathematical equations such as the Gordon-Taylor and Couchman-Karasz equations, facilitated the determination of predicted values for glass transition (Tg), PTR's miscibility with PVP, and the strength of PTR's interaction with the polymers. Fourier-transform infrared (FTIR) analysis validated interactions maintaining PTR's amorphous state and identified involved functional groups, namely, the 4'-OH and/or -CH groups of PTR and the C=O group of PVP. The study culminated in evaluating the impact of amorphization on water solubility, the release profile in pH 6.8, and in vitro permeability (PAMPA-GIT and BBB methods). In addition, it was determined how improving water solubility affects the increase in antioxidant (ABTS, DPPH, CUPRAC, and FRAP assays) and neuroprotective (inhibition of cholinesterases: AChE and BChE) properties. The apparent solubility of the pure PTR was ~4.0 µg·mL-1 and showed no activity in the considered assays. For obtained ASDs (PTR-PVP30/PTR-PVPVA64, respectively) improvements in apparent solubility (410.8 and 383.2 µg·mL-1), release profile, permeability, antioxidant properties (ABTS: IC50 = 52.37/52.99 μg·mL-1, DPPH: IC50 = 163.43/173.96 μg·mL-1, CUPRAC: IC0.5 = 122.27/129.59 μg·mL-1, FRAP: IC0.5 = 95.69/98.57 μg·mL-1), and neuroprotective effects (AChE: 39.1%/36.2%, BChE: 76.9%/73.2%) were confirmed.

Prediction of Phytochemicals for Their Potential to Inhibit New Delhi Metallo β-Lactamase (NDM-1)

The effectiveness of all antibiotics in the β-lactam group to cure bacterial infections has been impaired by the introduction of the New Delhi Metallo-β-lactamase (NDM-1) enzyme. Attempts have been made to discover a potent chemical as an inhibitor to this enzyme in order to restore the efficacy of antibiotics. However, it has been a challenging task to develop broad-spectrum inhibitors of metallo-β-lactamases. Lack of sequence homology across metallo-β-lactamases (MBLs), the rapidly evolving active site of the enzyme, and structural similarities between human enzymes and metallo-β-lactamases, are the primary causes for the difficulty in the development of these inhibitors. Therefore, it is imperative to concentrate on the discovery of an effective NDM-1 inhibitor. This study used various in silico approaches, including molecular docking and molecular dynamics simulations, to investigate the potential of phytochemicals to inhibit the NDM-1 enzyme. For this purpose, a library of about 59,000 phytochemicals was created from the literature and other databases, including FoodB, IMPPAT, and Phenol-Explorer. A physiochemical and pharmacokinetics analysis was performed to determine possible toxicity and mutagenicity of the ligands. Following the virtual screening, phytochemicals were assessed for their binding with NDM-1using docking scores, RMSD values, and other critical parameters. The docking score was determined by selecting the best conformation of the protein-ligand complex. Three phytochemicals, i.e., butein (polyphenol), monodemethylcurcumin (polyphenol), and rosmarinic acid (polyphenol) were identified as result of pharmacokinetics and molecular docking studies. Furthermore, molecular dynamics simulations were performed to determine structural stabilities of the protein-ligand complexes. Monodemethylcurcumin, butein, and rosmarinic acid were identified as potential inhibitors of NDM-1 based on their low RMSD, RMSF, hydrogen bond count, average Coulomb-Schrödinger interaction energy, and Lennard-Jones-Schrödinger interaction energy. The present investigation suggested that these phytochemicals might be promising candidates for future NDM-1 medication development to respond to antibiotic resistance.

Identification of Sesamin from Sesamum indicum as a Potent Antifungal Agent Using an Integrated in Silico and Biological Screening Platform

Due to the limited availability of antifungal drugs, their relevant side effects and considering the insurgence of drug-resistant strains, novel antifungal agents are urgently needed. To identify such agents, we have developed an integrated computational and biological screening platform. We have considered a promising drug target in antifungal drug discovery (exo-1,3-β-glucanase) and a phytochemical library composed of bioactive natural products was used. These products were computationally screened against the selected target using molecular docking and molecular dynamics techniques along with the evaluation of drug-like profile. We selected sesamin as the most promising phytochemical endowed with a potential antifungal profile and satisfactory drug-like properties. Sesamin was submitted to a preliminary biological evaluation to test its capability to inhibit the growth of several Candida species by calculating the MIC/MFC and conducting synergistic experiments with the marketed drug fluconazole. Following the screening protocol, we identified sesamin as a potential exo-1,3-β-glucanase inhibitor, with relevant potency in inhibiting the growth of Candida species in a dose-dependent manner (MIC and MFC of 16 and 32 µg/mL, respectively). Furthermore, the combination of sesamin with fluconazole highlighted relevant synergistic effects. The described screening protocol revealed the natural product sesamin as a potential novel antifungal agent, showing an interesting predicted pharmacological profile, paving the way to the development of innovative therapeutics against fungal infections. Notably, our screening protocol can be helpful in antifungal drug discovery.

Molecular Docking, Validation, Dynamics Simulations, and Pharmacokinetic Prediction of Phytochemicals Isolated From Croton dichogamus Against the HIV-1 Reverse Transcriptase

The human immunodeficiency virus (HIV) infection and the associated acquired immune deficiency syndrome (AIDS) remain global challenges even after decades of successful treatment, with eastern and southern Africa still bearing the highest burden of disease. Following a thorough computational study, we report top 10 phytochemicals isolated from Croton dichogamus as potent reverse transcriptase inhibitors. The pentacyclic triterpenoid, aleuritolic acid (L12) has displayed best docking pose with binding energy of -8.48 kcal/mol and Ki of 0.61 μM making it superior in binding efficiency when compared to all docked compounds including the FDA-approved drugs. Other phytochemicals such as crotoxide A, crothalimene A, crotodichogamoin B and crotonolide E have also displayed strong binding energies. These compounds could further be investigated as potential antiretroviral medication.

Kutkin, iridoid glycosides enriched fraction of Picrorrhiza kurroa promotes insulin sensitivity and enhances glucose uptake by activating PI3K/Akt signaling in 3T3-L1 adipocytes

BACKGROUND

Therapeutic failure and drug resistance are common sequelae to insulin resistance associated with type 2 diabetes mellitus (T2DM). Consequently, there is an unmet need of alternative strategies to overcome insulin resistance associated complications.

PURPOSE

To demonstrate whether Kutkin (KT), iridoid glycoside enriched fraction of Picrorhiza kurroa extract (PKE) has potential to increase the insulin sensitivity vis à vis glucose uptake in differentiated adipocytes.

METHODS

Molecular interaction of KT phytoconstituents, picroside-I (P-I) & picroside- II (P-II) with peroxisome proliferator-activated receptor gamma (PPARγ), phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) were analyzed in silico. Cellular viability and adipogenesis were determined by following 3-(4, 5-Dimethylthiazol-2-Yl)-2, 5-Diphenyltetrazolium bromide (MTT) assay and Oil Red-O staining. Further, ELISA kit based triglycerides and diacylglycerol-O-Acyltransferase-1 (DGAT1) were assessed in differentiated adipocytes. ELISA based determination were performed to check the levels of adiponectin and tumor necrosis factor alpha (TNF-α). However, Flow cytometry and immunofluorescence based assays were employed to measure the glucose uptake and glucose transporter 4 (glut4) expression in differentiated adipocytes, respectively. Further to explore the targeted signaling axis, mRNA expression levels of PPARγ, CCAAT/enhancer binding protein α (CEBPα), and glut4 were determined using qRT-PCR and insulin receptor substrate-1 (IRS-1), Insulin receptor substrate-2 (IRS-2), PI3K/Akt, AS160, glut4 followed by protein validation using immunoblotting in differentiated adipocytes.

RESULTS

In silico analysis revealed the binding affinities of major constituents of KT (P-I& P-II) with PPARγ/PI3K/Akt. The enhanced intracellular accumulation of triglycerides with concomitant activation of PPARγ and C/EBPα in KT treated differentiated adipocytes indicates augmentation of adipogenesis in a concentration-dependent manner. Additionally, at cellular level, KT upregulated the expression of DAGT1, and decreases fatty acid synthase (FAS), and lipoprotein lipase (LPL), further affirmed improvement in lipid milieu. It was also observed that KT upregulated the levels of adiponectin and reduced TNFα expression, thus improving the secretory functions of adipocytes along with enhanced insulin sensitivity. Furthermore, KT significantly promoted insulin mediated glucose uptake by increasing glut4 translocation to the membrane via PI3/Akt signaling cascade. The results were further validated using PI3K specific inhibitor, wortmannin and findings revealed that KT treatment significantly enhanced the expression and activation of p-PI3K/PI3K and p-Akt/Akt even in case of treatment with PI3K inhibitor wortmannin alone and co-treatment with KT in differentiated adipocytes and affirmed that KT as activator of PI3K/Akt axis in the presence of inhibitor as well.

CONCLUSION

Collectively, KT fraction of PKE showed anti-diabetic effects by enhancing glucose uptake in differentiated adipocytes via activation of PI3K/Akt signaling cascade. Therefore, KT may be used as a promising novel natural therapeutic agent for managing T2DMand to the best of our knowledge, this is the first report, showing the efficacy and potential molecular mechanism of KT in enhancing insulin sensitivity and glucose uptake in differentiated adipocytes.

Reimagining the Framework Supporting the Static Analysis of Transporter Drug Interaction Risk; Integrated Use of Biomarkers to Generate Pan‐Transporter Inhibition Signatures

Solute carrier (SLC) transporters present as the loci of important drug-drug interactions (DDIs). Therefore, sponsors generate in vitro half-maximal inhibitory concentration (IC₅₀ ) data and apply regulatory agency-guided "static" methods to assess DDI risk and the need for a formal clinical DDI study. Because such methods are conservative and high false-positive rates are likely (e.g., DDI study triggered when liver SLC R value ≥ 1.04 and renal SLC maximal unbound plasma (C_max,u )/IC₅₀ ratio ≥ 0.02), investigators have attempted to deploy plasma- and urine-based SLC biomarkers in phase I studies to de-risk DDI and obviate the need for drug probe-based studies. In this regard, it was possible to generate in-house in vitro SLC IC₅₀ data for various clinically (biomarker)-qualified perpetrator drugs, under standard assay conditions, and then estimate "% inhibition" for each SLC and relate it empirically to published clinical biomarker data (area under the plasma concentration vs. time curve (AUC) ratio (AUCR, AUC_inhibitor /AUC_reference ) and % decrease in renal clearance (ΔCL_renal )). After such a "calibration" exercise, it was determined that only compounds with high R values (> 1.5) and C_max,u /IC₅₀ ratios (> 0.5) are likely to significantly modulate liver (AUCR > 1.25) and renal (ΔCL_renal  > 25%) biomarkers and evoke DDI risk. The % inhibition approach supports integration of liver and renal SLC data and allows one to generate pan-SLC inhibition signatures for different test perpetrators (e.g., SLC % inhibition ranking). In turn, such signatures can guide the selection of the most appropriate individual (or combinations of) biomarkers for testing in phase I studies.

3β-Acetoxy-21α-H-hop-22(29)ene, a novel multitargeted phytocompound against SARS-CoV-2: in silico screening

The present pandemic disease COVID-19 demands an urgent need for more efficient antiviral drugs against SARS-CoV-2. Computational drug designing and discovery enable us to explore ethnomedicinal plants as a source of various lead molecules that can be used against present and future pathogens. Adiantum latifolium Lam., a common fern, is resistant to pathogens mainly due to the presence of various phytochemicals having antimicrobial properties. In our previous study, 3β-acetoxy-21α-H-hop-22(29)ene, a terpenoid has been characterized from the methanol extract of leaves of A. latifolium. The manuscript evaluates the antiviral potency of the compound against SARS-CoV-2 through molecular docking method. Proteins essential for SARS-CoV-2 multiplication in host cells are the target sites. The study revealed strong binding affinity of the compound for all the ten proteins selected, including seven nonstructural proteins, two structural proteins and one receptor protein, with a binding energy of -4.67 to -8.76 kcal/mol. MDS and MMPBSA analysis of the best ranked complex further confirmed the results. The multitargeted compound can be considered as a natural lead molecule in drug designing against COVID-19, but requires wet-lab experimentation and clinical trials.Communicated by Ramaswamy H. Sarma.

DK, Ragunathan V, Tiwari P, A. S, P BD. Molecular docking, validation, dynamics simulations, and pharmacokinetic prediction of natural compounds against the SARS-CoV-2 main-protease

The study aims to evaluate the potency of two hundred natural antiviral phytocompounds against the active site of the Severe Acquired Respiratory Syndrome - Coronavirus - 2 (SARS-CoV-2) Main-Protease (Mpro) using AutoDock 4.2.6. The three- dimensional crystal structure of the Mpro (PDB Id: 6LU7) was retrieved from the Protein Data Bank (PDB), the active site was predicted using MetaPocket 2.0. Food and Drug Administration (FDA) approved viral protease inhibitors were used as standards for comparison of results. The compounds theaflavin-3-3'-digallate, rutin, hypericin, robustaflavone, and (-)-solenolide A with respective binding energy of -12.41 (Ki = 794.96 pM); -11.33 (Ki = 4.98 nM); -11.17 (Ki = 6.54 nM); -10.92 (Ki = 9.85 nM); and -10.82 kcal/mol (Ki = 11.88 nM) were ranked top as Coronavirus Disease - 2019 (COVID-19) Mpro inhibitors. The interacting amino acid residues were visualized using Discovery Studio 3.5 to elucidate the 2-dimensional and 3-dimensional interactions. The study was validated by i) re-docking the N3-peptide inhibitor-Mpro and superimposing them onto co-crystallized complex and ii) docking decoy ligands to Mpro. The ligands that showed low binding energy were further predicted for and pharmacokinetic properties and Lipinski's rule of 5 and the results are tabulated and discussed. Molecular dynamics simulations were performed for 50 ns for those compounds using the Desmond package, Schrödinger to assess the conformational stability and fluctuations of protein-ligand complexes during the simulation. Thus, the natural compounds could act as a lead for the COVID-19 regimen after in-vitro and in- vivo clinical trials.Communicated by Ramaswamy H. Sarma.

Modelling and targeting mitochondrial protein tyrosine phosphatase 1: a computational approach

The present research scintillates on the homology modelling of rat mitochondrial protein tyrosine phosphatase 1 (PTPMT1) and targeting its activity using flavonoids through a computational docking approach. PTPMT1 is a dual-specificity phosphatase responsible for protein phosphorylation and plays a vital role in the metabolism of cardiolipin biosynthesis, insulin regulation, etc. The inhibition of PTPMT1 has also shown enhanced insulin levels. The three-dimensional structure of the protein is not yet known. The homology modelling was performed using SWISS-MODEL and Geno3D webservers to compare the efficiencies. The PROCHECK for protein modelled using SWISS-MODEL showed 91.6% of amino acids in the most favoured region, 0.7% residues in the disallowed region that was found to be significant compared to the model built using Geno3D. 210 common flavonoids were docked in the modelled protein using the AutoDock 4.2.6 along with a control drug alexidine dihydrochloride. Our results show promising candidates that bind protein tyrosine phosphatase 1, including, prunin (- 8.66 kcal/mol); oroxindin (- 8.56 kcal/mol); luteolin 7-rutinoside (- 8.47 kcal/mol); 3(2H)-isoflavenes (- 8.36 kcal/mol); nicotiflorin (- 8.29 kcal/mol), ranked top in the docking experiments. We predicted the pharmacokinetic and Lipinski properties of the top ten compounds with the lowest binding energies. To further validate the stability of the modelled protein and docked complexes molecular dynamics simulations were performed using Desmond, Schrodinger for 150 ns in conjunction with MM-GBSA. Thus, flavonoids could act as potential inhibitors of PTPMT1, and further, in-vitro and in-vivo studies are essential to complete the drug development process.

22-Hydroxyhopane, a novel multitargeted phytocompound against SARS-CoV-2 from Adiantum latifolium Lam

The present pandemic disease COVID-19 demands an urgent need for more efficient antiviral drugs against SARS-CoV-2. 22-Hydroxyhopane is a bioactive triterpenoid compound with antibacterial activity, present in the leaves of Adiantum latifolium. In this study, molecular docking method revealed strong binding affinity of the compound for ten proteins essential for SARS-CoV-2 multiplication in host cells, including seven nonstructural proteins, two structural proteins and one receptor protein, with a binding energy of -7.61 to -9.82 kcal/mol and inhibition constant <1 μM. MDS and MM-PBSA analysis of the best ranked complex further confirmed the results. The targets selected include six enzymes, RNA binding protein, spike protein, membrane protein and ACE2 receptor of SARS-CoV-2. It is the first report of a natural compound from A. latifolium having multitargeted activity against SARS-CoV-2. We conclude that 22-hydroxyhopane may be used as a best source for the development of novel therapeutic drugs for COVID-19, but requires further evaluations.

In vitro inhibition of human CYP2E1 and CYP3A by quercetin and myricetin in hepatic microsomes is not gender dependent

This is the first in vitro study to investigate gender-related differences in the regulation of human cytochrome P450 by the flavonoids. Activities of CYP2E1 and CYP3A were measured in the presence of quercetin, myricetin, or isorhamnetin in hepatic microsomal pools from male and female donors. Hydroxylation of p-nitrophenol (PNPH) was measured to determine CYP2E1 activity, and O-dealkylation of 7-benzyloxy-4-trifluoromethylcoumarin (BFC) was measured to determine CYP3A activity. Quercetin, but not myricetin or isorhamnetin, competitively inhibited PNPH activity in human recombinant cDNA-expressed CYP2E1 with the Ki=52.1±6.31μM. In the human microsomes, slight inhibition of PNPH activity by quercetin was not considered as physiologically relevant. Quercetin inhibited BFC activity in human recombinant cDNA-expressed CYP3A4 competitively with the Ki=15.4±1.52μM, and myricetin - noncompetitively with the Ki=74.6±7.99μM. The degree of inhibition by quercetin was similar between genders. Myricetin showed somewhat stronger inhibition in female pools, but the Ki values were higher than physiologically relevant concentrations. Isorhamnetin did not affect either PNPH or BFC activity. We concluded that observed inhibition of CYP2E1 and CYP3A by some flavonols were not gender-dependent.

Quantitative NTCP pharmacophore and lack of association between DILI and NTCP Inhibition

The human sodium taurocholate cotransporting polypeptide (NTCP) is a hepatic bile acid transporter. Inhibition of NTCP uptake may potentially also prevent hepatitis B virus (HBV) infection. The first objective was to develop a quantitative pharmacophore for NTCP inhibition. Recent studies showed that hepatotoxic drugs could inhibit bile acid uptake into hepatocytes, without inhibiting canalicular efflux, and cause bile acid elevation in plasma. Hence, a second objective was to examine whether NTCP inhibition is associated with drug induced liver injury (DILI). Twenty-seven drugs from our previous study were used as the training set to develop a quantitative pharmacophore. From secondary screening from a drug database, six retrieved drugs and three drugs not retrieved by the model were tested for NTCP inhibition. Tertiary screening involved drugs known to cause DILI and not cause DILI. Overall, ninety-four drugs were assessed for hepatotoxicity and were assessed relative to NTCP inhibition. The quantitative pharmacophore possessed one hydrogen bond acceptor, one hydrogen bond donor, a hydrophobic feature, and excluded volumes. From 94 drugs, NTCP inhibitors and non-inhibitors were approximately equally distributed across the drugs of most DILI concern, less DILI concern, and no DILI concern, indicating no relationship between NTCP inhibition and DILI risk. Hence, an approach to treat HBV via NTCP inhibition is not expected to be associated with DILI.

Synthesis and in vitro evaluation of bile acid prodrugs of floxuridine to target the liver

Floxuridine is often used to treat metastatic liver disease and is given as an infusion directly into the hepatic artery to increase the amount of intact drug that reaches the liver. The objective of this work was to design and synthesize prodrugs of floxuridine through conjugation to chenodeoxycholic acid (CDCA) to target the liver via the bile acid liver uptake transporter Na(+)/taurocholate cotransporting polypeptide (NTCP, SLC10A1). Two isomeric prodrugs of floxuridine were synthesized: floxuridine 3'glutamic acid-CDCA and floxuridine 5'-glutamic acid-CDCA. Both were potent inhibitors and substrates of NTCP. Floxuridine 3'glutamic acid-CDCA showed Ki=6.86±1.37 μM, Km=10.7±2.1 μM, and passive permeability=0.663(±0.121)×10(-7) cm/s while floxuridine 5'-glutamic acid-CDCA showed Ki=0.397±0.038 μM, Km=40.4±15.2 μM, and passive permeability=1.72(±0.18)×10(-7) cm/s. Floxuridine itself had a higher passively permeability of 7.54(±0.45)×10(-7) cm/s in the same cell line, indicating that both prodrugs have the potential for lower non-specific effects than the drug alone. Prodrugs were stable in rat plasma (t=3 h), but quickly released in rat liver s9 fraction, suggesting future in vivo evaluation.

Design and evaluation of a novel trifluorinated imaging agent for assessment of bile acid transport using fluorine magnetic resonance imaging

Previously, we developed a trifluorinated bile acid, CA-lys-TFA, with the objective of noninvasively assessing bile acid transport in vivo using (19) F magnetic resonance imaging (MRI). CA-lys-TFA was successfully imaged in the mouse gallbladder, but was susceptible to deconjugation in vitro by choloylglycine hydrolase (CGH), a bacterial bile acid deconjugating enzyme found in the terminal ileum and colon. The objective of the present study was to develop a novel trifluorinated bile acid resistant to deconjugation by CGH. CA-sar-TFMA was designed, synthesized, and tested for in vitro transport properties, stability, imaging properties, and its ability to differentially accumulate in the gallbladders of normal mice, compared with mice with known impaired bile acid transport (deficient in the apical sodium-dependent bile acid transporter, ASBT). CA-sar-TFMA was a potent inhibitor and substrate of ASBT and the Na(+) /taurocholate cotransporting polypeptide. Stability was favorable in all conditions tested, including the presence of CGH. CA-sar-TFMA was successfully imaged and accumulated at 16.1-fold higher concentrations in gallbladders from wild-type mice compared with those from Asbt-deficient mice. Our results support the potential of using MRI with CA-sar-TFMA as a noninvasive method to assess bile acid transport in vivo.

Mechanistic interpretation of conventional Michaelis-Menten parameters in a transporter system

The aim was to elucidate how steps in drug translocation by a solute carrier transporter impact Michaelis-Menten parameters Km, Ki, and Vmax. The first objective was to derive a model for carrier-mediated substrate translocation and perform sensitivity analysis with regard to the impact of individual microrate constants on Km, Ki, and Vmax. The second objective was to compare underpinning microrate constants between compounds translocated by the same transporter. Equations for Km, Ki, and Vmax were derived from a six-state model involving unidirectional transporter flipping and reconfiguration. This unidirectional model is applicable to co-transporter type solute carriers, like the apical sodium-dependent bile acid transporter (ASBT) and the proton-coupled peptide cotransporter (PEPT1). Sensitivity analysis identified the microrate constants that impacted Km, Ki, and Vmax. Compound comparison using the six-state model employed regression to identify microrate constant values that can explain observed Km and Vmax values. Results yielded some expected findings, as well as some unanticipated effects of microrate constants on Km, Ki, and Vmax. Km and Ki were found to be equal for inhibitors that are also substrates. Additionally, microrate constant values for certain steps in transporter functioning influenced Km and Vmax to be low or high.

Structure-activity relationship for FDA approved drugs as inhibitors of the human sodium taurocholate cotransporting polypeptide (NTCP)

The hepatic bile acid uptake transporter sodium taurocholate cotransporting polypeptide (NTCP) is less well characterized than its ileal paralog, the apical sodium dependent bile acid transporter (ASBT), in terms of drug inhibition requirements. The objectives of this study were (a) to identify FDA approved drugs that inhibit human NTCP, (b) to develop pharmacophore and Bayesian computational models for NTCP inhibition, and (c) to compare NTCP and ASBT transport inhibition requirements. A series of NTCP inhibition studies were performed using FDA approved drugs, in concert with iterative computational model development. Screening studies identified 27 drugs as novel NTCP inhibitors, including irbesartan (Ki = 11.9 μM) and ezetimibe (Ki = 25.0 μM). The common feature pharmacophore indicated that two hydrophobes and one hydrogen bond acceptor were important for inhibition of NTCP. From 72 drugs screened in vitro, a total of 31 drugs inhibited NTCP, while 51 drugs (i.e., more than half) inhibited ASBT. Hence, while there was inhibitor overlap, ASBT unexpectedly was more permissive to drug inhibition than was NTCP, and this may be related to NTCP possessing fewer pharmacophore features. Findings reflected that a combination of computational and in vitro approaches enriched the understanding of these poorly characterized transporters and yielded additional chemical probes for possible drug-transporter interaction determinations.