Predicting potential antitumor targets of Aconitum alkaloids by molecular docking and protein–ligand interaction fingerprint

Aconitine compounds are found in Aconitum Ouwu head, Chuan Wu, Aconitum, and other Ranunculaceae aconitum plants, which are not only active ingredient but also toxic component. In present study, 20 antitumor target proteins of different types were selected from Protein Data Bank (http://www.rcsb.org), for the purpose of finding potential antitumor targets of aconitum alkaloids, top ranked proteins were screened by molecular docking method, using the docking module in Sybyl-X 1.1 and Molecular Operating Environment (MOE) 2008, and screening result was verified by protein–ligand interaction fingerprint (PLIF) in MOE. Mesaconitine showed a C-shaped conformation when docking into heat-shock protein 90 (HSP90), which was similar with ANSA ring of geldanamycin. And the PLIF indicated that they shared many common amino acid residues interacted with HSP90; equally, Yunaconitine was found having similar conformation with the inhibitor of poly ADP-ribose polymerase-1 (PARP-1).     

The impact of molecular dynamics on drug design: applications for the characterization of ligand–macromolecule complexes

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Understanding molecular recognition by G protein βγ subunits on the path to pharmacological targeting

Heterotrimeric G proteins, composed of Gα and Gβγ subunits, transduce extracellular signals via G-protein-coupled receptors to modulate many important intracellular responses. The Gβγ subunits hold a central position in this signaling system and have been implicated in multiple aspects of physiology and the pathophysiology of disease. The Gβ subunit belongs to a large family of WD40 repeat proteins with a circular β-bladed propeller structure. This structure allows Gβγ to interact with a broad range of proteins to play diverse roles. How Gβγ interacts with and regulates such a wide variety of partners yet maintains specificity is an interesting problem in protein-protein molecular recognition in signal transduction, where signal transfer by proteins is often driven by modular conserved recognition motifs. Evidence has accumulated that one mechanism for Gβγ multitarget recognition is through an intrinsically flexible protein surface or "hot spot" that accommodates multiple modes of binding. Because each target has a unique recognition mode for Gβγ subunits, it suggests that these interactions could be selectively manipulated with small molecules, which could have significant therapeutic potential.     

Validation of membrane vesicle-based breast cancer resistance protein and multidrug resistance protein 2 assays to assess drug transport and the potential for drug–drug interaction to support regulatory submissions

1. Breast cancer resistance protein (BCRP) and multidrug resistance protein 2 (MRP2) can play a role in the absorption, distribution, metabolism, and excretion of drugs, impacting on the potential for drug–drug interactions. This study has characterized insect cell– and mammalian cell–derived ABC-transporter–expressing membrane vesicle test systems and validated methodologies for evaluation of candidate drugs as substrates or inhibitors of BCRP or MRP2.

2. Concentration-dependent uptake of BCRP ([³H]oestrone 3-sulfate, [³H]methotrexate, [³H]rosuvastatin) and MRP2 ([³H]oestradiol 17β-glucuronide, [³H]pravastatin, carboxydichlorofluorescein) substrates, and inhibitory potencies (IC₅₀) of BCRP (sulfasalazine, novobiocin, fumitremorgin C) and MRP2 (benzbromarone, MK-571, terfenadine) inhibitors were determined.

3. The apparent K_m for probes [³H]oestrone 3-sulfate and [³H]oestradiol 17β-glucuronide was determined in insect cell vesicles to be 7.4?±?1.7 and 105?±?8.3?µM, respectively. All other substrates exhibited significant uptake ratios. Positive control inhibitors sulfasalazine and benzbromarone gave IC₅₀ values of 0.74?±?0.18 and 36?±?6.1 µM, respectively. All other inhibitors exhibited concentration-dependent inhibition. There was no significant difference in parameters generated between test systems.

4. On the basis of the validation results, acceptance criteria to identify substrates/inhibitors of BCRP and MRP2 were determined for insect cell vesicles. The approach builds on earlier validations to support drug registration and extends from those cell-based systems to encompass assay formats using membrane vesicles.

     

A systematic review of the drug–drug interaction between statins and colchicine: Patient characteristics,etiologies, and clinical management strategies

Colchicine and statins are frequently co-prescribed for prevention and treatment of cardiovascular diseases, auto-inflammatory diseases, and gout. Both are substrates and inhibitors of the cytochrome P-450 (CYP) 3A4 isozyme and P-glycoprotein so that taken together, they represent a clinically significant interaction. Data suggest the interaction may be associated with potentially life-threatening myopathies and rhabdomyolysis. The purposes of this systematic review (SR) were to gather and appraise evidence surrounding the statin-colchicine drug interaction and discuss related risk-mitigation strategies. An electronic literature search was performed. Twenty-one articles met the protocol to be included in the qualitative analysis: 18 case reports/series, 2 retrospective observational cohort studies, and 1 retrospective case-control study. Thirty-eight patients developed an adverse drug event (ADE) receiving statin-colchicine combination therapy; 25 (66%) patients developed myopathy; 10 (26%) patients developed rhabdomyolysis, and three (8%) patients developed neuromyopathy. Over 70% of patients developed ADEs on simvastatin or atorvastatin, and 80% of studies reported moderate-to-high intensity statins. Colchicine dosing varied but ranged between 0.5 to 1.5 mg daily. Sixty-two percent of patients in the case reports/series had comorbid renal disease. Seven studies (33% of all included studies) reported patients taking concomitant interacting medications at the CYP3A4 and/or P-glycoprotein efflux pump. Seventeen studies (81% of all included studies) reported ADEs leading to hospitalization. A multivariate analysis from one case-control study identified risk factors prognosticating myopathy ADEs in patients taking statin-colchicine therapy: comorbid renal disease and/or cirrhosis, colchicine doses 1.2 mg daily or greater, and concomitant interacting medications. Clinicians must be cognizant that the statin-colchicine drug interaction may lead to patient harm and thus should employ risk-mitigation strategies for statin-associated muscle symptoms. Future studies are warranted to validate clinically relevant risk factors that are strongly associated with the complications owing to the statin-colchicine drug interaction.     

Validation of cell-based OATP1B1 assays to assess drug transport and the potential for drug–drug interaction to support regulatory submissions

1. Transporters are carrier proteins that may influence pharmacokinetic, pharmacodynamic, and toxicological characteristics of drugs. The development of validated in vitro transporter models is imperative to support regulatory submissions of drug candidates. This study is focused on utilizing human embryonic kidney (HEK) 293 cell cultures genetically transfected with the human organic anion transporting polypeptides (OATP) 1B1 transporter to identify substrates and inhibitors in drug development.

2. The kinetics of OATP1B1-mediated uptake of [³H]-oestradiol 17β-glucuronide and inhibition of uptake by rifamycin SV were used to determine K_m, V_max, and IC₅₀ values over a range of passage numbers to investigate accuracy and precision. The mean K_m and V_max values were found to be 6.3?±?1.2 μM and 460?±?96 pmol min^?1 mg^?1, respectively. The mean IC₅₀ value for rifamycin SV was 0.23?±?0.07 μM on uptake of 1 μM [³H]-oestradiol 17β-glucuronide. These data were similar to previously reported values (accuracy greater than 82%), reproducible (precision less than 29%) and exhibited low standard deviations (SDs) obviating the need to study test compounds on more than one occasion.

3. [³H]-oestrone 3-sulfate and [³H]-pravastatin exhibited concentration-dependent OATP1B1 uptake, and statistically significant differences were observed at each concentration between uptake rates of HEK293-OATP1B1 and HEK293-MOCK cells (uptake ratios greater than or equal to 3). Propranolol showed no positive uptake ratio. Bezafibrate and gemfibrozil exhibited concentration-dependent inhibition of OATP1B1-mediated uptake of [³H]-oestradiol 17β-glucuronide with mean IC₅₀ values of 16 and 27 μM, respectively.

4. Based on the validation results, acceptance criteria to identify a test compound as a substrate and/or inhibitor using these specific cell lines were determined. These validated OATP1B1 assays were robust, reproducible, and suitable for routine in vitro evaluation of candidate drugs.

     

Characterization of the mangiferin–human serum albumin complex by spectroscopic and molecular modeling approaches

The interactions between mangiferin and human serum albumin (HSA) were investigated by spectroscopy and molecular modeling. The results proved the formation of complex between mangiferin and HSA. Hydrophobic interaction dominated in the association reaction. Mangiferin statically quenched the fluorescence of HSA in a concentration dependent manner positively deviating from the linear Scatchard equation. The binding of mangiferin to HSA lead to changes in the conformation of HSA according to synchronous fluorescence spectra, FT-IR, UV–vis and CD data. The presence of amino acids and metal ion affected the binding constant of mangiferin–HSA complex. Computational mapping of the possible binding sites of mangiferin revealed the molecule to be bound in the large hydrophobic cavity of subdomain IIA.     

Elucidation of the molecular mechanism and exploration of novel therapeutics for spinocerebellar ataxia caused by mutant protein kinase Cγ

Spinocerebellar ataxia (SCA) is an inherited neurodegenerative disorder that is characterized by cerebellar atrophy and progressive ataxia and is classified into 31 types by the genetic locus. Recently, missense mutations of PRKCG genes that code protein kinase Cγ (γPKC) have been identified as a causal gene of SCA14. To explore the molecular mechanism of SCA14 pathogenesis, we investigated how mutant γPKC causes the neurodegeneration of cerebellar Purkinje cells (PCs) by expressing mutant γPKC-GFP in cell lines and primary cultured PCs. Mutant γPKC was susceptible to aggregation in the cytoplasm, which led to an impairment of the ubiquitin-proteasome system and apoptosis. Furthermore, mutant γPKC induced improper dendritic development of cultured PCs in an aggregation-independent manner. Stimulation-induced translocation of mutant γPKC in PC dendrites was prominently attenuated by the reduced mobility of oligomerized mutant γPKC, which resulted in attenuated signal transduction and the improper morphology of PC dendrites. These findings suggested that the oligomerization and aggregation of mutant γPKC caused improper dendritic development and apoptosis of PCs, which led to cerebellar dysfunction and SCA14 pathogenesis. We screened the chemicals that improved these cellular dysfunctions and identified several compounds, including trehalose and Congo red, which could be novel therapeutics for SCA14.     

Physiologically based mechanistic modelling to predict complex drug–drug interactions involving simultaneous competitive and time-dependent enzyme inhibition by parent compound and its metabolite in both liver and gut—The effect of diltiazem on the time-course of exposure to triazolam

AimTo predict the magnitude of metabolic drug–drug interaction (mDDI) between triazolam and diltiazem and its primary metabolite N-desmethyldiltiazem (MA).MethodsRelevant in vitro metabolic and inhibitory data were incorporated into a mechanistic physiologically based pharmacokinetic model within Simcyp (Version 9.1) to simulate the time-course of changes in active CYP3A4 content in gut and liver and plasma concentrations of diltiazem, MA and triazolam in a virtual population with characteristics related to in vivo studies.ResultsThe predicted median increases in AUC(0,∞) of triazolam, which ranged from 3.9 to 9.5 for 20 simulated trials (median 5.9), were within 1.5-fold of the observed median value (4.4) in 14 of the trials. Considering the effects of diltiazem only and not those of MA, and ignoring auto-inhibition of MA metabolism and inhibition of its metabolism by diltiazem, resulted in lower increases in triazolam exposure (AUC ratios of 1.5–2.0 (median 1.7) and 2.7–5.3 (median 3.4), respectively).ConclusionPrediction of mDDIs involving diltiazem requires consideration of both competitive and time-dependent inhibition in gut and liver by both diltiazem and MA, as well as the complex interplay between the two moieties with respect to mutual inhibition of parent compound and its metabolite.     

Efflux transporter breast cancer resistance protein dominantly expresses on the membrane of red blood cells,hinders partitioning of its substrates into the cells,and alters drug–drug interaction profiles

1. Red blood cell (RBC) partitioning is important in determining pharmacokinetic and pharmacodynamic properties of a compound; however, active transport across RBC membranes is not well understood, particularly without transporter-related cell membrane proteomics data.

2. In this study, we quantified breast cancer resistance protein (BCRP/Bcrp) and MDR1/P-glycoprotein (P-gp) protein expression in RBCs from humans, monkeys, dogs, rats and mice using nanoLC/MS/MS, and evaluated their effect on RBC partitioning and plasma exposure of their substrates. BCRP-specific substrate Cpd-1 and MDR1-specific substrate Cpd-2 were characterized using Caco-2 Transwell® system and then administered to Bcrp or P-gp knockout mice.

3. The quantification revealed BCRP/Bcrp but not MDR1/P-gp to be highly expressed on RBC membranes. The knockout mouse study indicated BCRP/Bcrp pumps the substrate out of RBCs, lowering its partitioning and thus preventing binding to intracellular targets. This result was supported by a Cpd-1 and Bcrp inhibitor ML753286 drug–drug interaction (DDI) study in mice. Because of enhanced partitioning of Cpd-1 into RBCs after BCRP/Bcrp inhibition, Cpd-1 plasma concentration changed much less extent with genetic or chemical knockout of Bcrp albeit marked blood concentration increase, suggesting less DDI effect.

4. This finding is fundamentally meaningful to RBC partitioning, pharmacokinetics and DDI studies of BCRP-specific substrates.     

The impact of lipids on the cancer–immunity cycle and strategies for modulating lipid metabolism to improve cancer immunotherapy

Lipids have been found to modulate tumor biology, including proliferation, survival, and metastasis. With the new understanding of tumor immune escape that has developed in recent years, the influence of lipids on the cancer–immunity cycle has also been gradually discovered. First, regarding antigen presentation, cholesterol prevents tumor antigens from being identified by antigen presenting cells. Fatty acids reduce the expression of major histocompatibility complex class I and costimulatory factors in dendritic cells, impairing antigen presentation to T cells. Prostaglandin E2 (PGE2) reduce the accumulation of tumor-infiltrating dendritic cells. Regarding T-cell priming and activation, cholesterol destroys the structure of the T-cell receptor and reduces immunodetection. In contrast, cholesterol also promotes T-cell receptor clustering and relative signal transduction. PGE2 represses T-cell proliferation. Finally, regarding T-cell killing of cancer cells, PGE2 and cholesterol weaken granule-dependent cytotoxicity. Moreover, fatty acids, cholesterol, and PGE2 can improve the activity of immunosuppressive cells, increase the expression of immune checkpoints and promote the secretion of immunosuppressive cytokines. Given the regulatory role of lipids in the cancer–immunity cycle, drugs that modulate fatty acids, cholesterol and PGE2 have been envisioned as effective way in restoring antitumor immunity and synergizing with immunotherapy. These strategies have been studied in both preclinical and clinical studies.     

Thermodynamics and docking of agonists to the β(2)-adrenoceptor determined using [(3)H](R,R')-4-methoxyfenoterol as the marker ligand

G protein-coupled receptors (GPCRs) are integral membrane proteins that change conformation after ligand binding so that they can transduce signals from an extracellular ligand to a variety of intracellular components. The detailed interaction of a molecule with a G protein-coupled receptor is a complicated process that is influenced by the receptor conformation, thermodynamics, and ligand conformation and stereoisomeric configuration. To better understand the molecular interactions of fenoterol analogs with the β(2)-adrenergic receptor, we developed a new agonist radioligand for binding assays. [(3)H](R,R')-methoxyfenoterol was used to probe the binding affinity for a series of fenoterol stereoisomers and derivatives. The results suggest that the radioligand binds with high affinity to an agonist conformation of the receptor, which represents approximately 25% of the total β(2)-adrenoceptor (AR) population as determined with the antagonist [(3)H]CGP-12177. The β(2)-AR agonists tested in this study have considerably higher affinity for the agonist conformation of the receptor, and K(i) values determined for fenoterol analogs model much better the cAMP activity of the β(2)-AR elicited by these ligands. The thermodynamics of binding are also different when interacting with an agonist conformation, being purely entropy-driven for each fenoterol isomer, rather than a mixture of entropy and enthalpy when the fenoterol isomers binding was determined using [(3)H]CGP-12177. Finally, computational modeling identified the molecular interactions involved in agonist binding and allow for the prediction of additional novel β(2)-AR agonists. The study underlines the possibility of using defined radioligand structure to probe a specific conformation of such shape-shifting system as the β(2)-adrenoceptor.     

A novel strategy to rapidly explore potential chemical markers for the discrimination between raw and processed Radix Rehmanniae by UHPLC–TOFMS with multivariate statistical analysis

In traditional Chinese medicine, raw and processed herbs are used to treat different diseases. Suitable chemical markers are crucial for the discrimination between raw and processed herbs. In this study, a novel strategy using UHPLC–TOFMS coupled with multivariate statistical analysis to rapidly explore potential chemical markers was proposed and validated. Using Radix Rehmanniae as a model herb, batches of raw and processed samples were determined by UHPLC–TOFMS. The datasets of t_R–m/z pair, ion intensity and sample code were subjected to principal component analysis (PCA) and orthogonal partial least squared discriminant analysis (OPLS-DA) to holistically compare the difference between raw and processed samples. Once a clear cluster was found, extended statistics was performed to generate S-plot, in which the variables (t_R–m/z pair) contributing most to the difference were clearly indicated as points at the two ends of “S”, and the components that correlate to these ions should be the processing-induced transformed components. These transformed components could be regarded as the potential chemical markers that can be used to distinguish between raw and processed herbs. The identity of the potential markers can be identified by comparing the mass/UV spectra and retention time with that of reference compounds and/or tentatively assigned by matching empirical molecular formula with that of the known compounds published. Using this proposed strategy, leonuride or its isomer and 5-(α-d-glucopyranosyl-(1-6)-α-d-glucopyranosyloxymethyl)-2-furancarboxaldehyde were rapidly explored as the most characteristic markers of raw and processed Radix Rehmanniae, respectively. This newly proposed strategy can not only be used to explore chemical markers but also to investigate the chemical transforming mechanisms underlying traditional herb processing.     

Parent–child connectedness and communication in relation to alcohol,tobacco and drug use in adolescence: An integrative review of the literature

Previous reviews have highlighted parent–child connectedness and communication as important protective factors against adolescent substance use. However, these reviews focus on single substances such as alcohol. An integrative review of the literature was conducted to examine which elements of parent–child connectedness and substance-use specific communication are effective across adolescent alcohol, tobacco and drug use. Forty-two English language, peer reviewed articles were reviewed. Open communication occurs within the context of high connectedness between parents and their children. Conversations about health risks are associated with lower levels of substance use while more frequent conversations, those about parents’ own use, permissive messages and consequences of use are associated with higher levels of use. There are disparities regarding conversations about use of each substance: alcohol and tobacco are easier topics of conversation while drug use is rarely discussed. Parental alcohol and tobacco use can influence the credibility of their communication with their child. Parents should be encouraged to have open, constructive, credible, two-sided conversations with their adolescents about substance use. Interventions to improve parents’ communication skills around substance use, particularly drug use, should include the types of approaches and messages highlighted in this review, and, where possible, these interventions should include all family members.     

Role for protein kinase C delta in the functional activity of human UGT1A6: implications for drug–drug interactions between PKC inhibitors and UGT1A6

1. Many UDP-glucuronosyltransferases (UGTs) require phosphorylation by protein kinase C (PKC) for glucuronidation activity. Inhibition of UGT phosphorylation by PKC inhibitor drugs may represent a novel mechanism for drug–drug interactions.

2. The potential for PKC-mediated inhibition of human UGT1A6, an isoform involved in the glucuronidation of drugs such as acetaminophen (paracetamol) and endogenous substrates including serotonin, was evaluated using various cell model systems.

3. Of ten different PKC inhibitors screened for their effects on acetaminophen glucuronidation by human LS180 colon cells, only rottlerin (PKC δ selective inhibitor; IC₅₀?=?9.0?±?1.2 μM) and the non-selective PKC inhibitors (calphostin-C, curcumin and hypericin) decreased glucuronidation by more than 50%.

4. Using UGT1A6-infected Sf9 insect cells, calphostin-C and hypericin showed three times more potent inhibition of serotonin glucuronidation in treated whole cells versus cell lysates. However, both curcumin and rottlerin showed significant direct inhibition and so (indirect) PKC effects could not be differentiated in this model system.

5. Of nine PKC isoforms co-expressed with UGT1A6 in human embryonic kidney 293T cells only PKC δ increased protein-normalized UGT1A6-mediated serotonin glucuronidation significantly (by 63% ± 4%).

6. These results identify an important role for PKC δ in UGT1A6-mediated glucuronidation and suggest that PKC δ inhibitors could interfere with glucuronidation of UGT1A6 substrates.

     

Effects of chronic cirrhosis induced by intraperitoneal thioacetamide injection on the protein content and Michaelis–Menten kinetics of cytochrome P450 enzymes in the rat liver microsomes

Chronic intraperitoneal injection of thioacetamide (TAA) in rats has been used as an animal model of human cirrhosis to study the effects of the disease on drug metabolism. However, TAA inhibits P450 enzymes directly and independently of cirrhosis. We investigated the effects of chronic cirrhosis in rats, induced by 10 weeks of intraperitoneal TAA, on the P450 enzymes after a 10-day washout period to eliminate TAA. Liver histology and serum biomarkers of hepatic function confirmed cirrhosis in all animals. Microsomal total P450 content, P450 reductase activity and ethoxycoumarin O-deethylase activity, a general marker of P450 activity, were significantly reduced by 30%–50% in cirrhotic animals. Additionally, the protein content and Michaelis–Menten kinetics of the activities of CYP2D, CYP2E1 and CYP3A were investigated. Whereas cirrhosis reduced the microsomal protein contents of CYP2D and CYP3A by 70% and 30%, respectively, the protein contents of CYP2E1 were not affected. However, the activities of all the tested isoenzymes were substantially lower in the cirrhotic livers. It is concluded that the TAA model of cirrhosis that incorporates a 10-day washout period after intraperitoneal injection of the chemical to rats produces isoenzyme-selective reductions in the P450 proteins or activities, which are independent of the direct inhibitory effects of TAA.     

Drug–drug interactions in the metabolism of imidafenacin: Role of the human cytochrome P450 enzymes and UDP-glucuronic acid transferases,and potential of imidafenacin to inhibit human cytochrome P450 enzymes

Imidafenacin (IM), 4-(2-methyl-1H-imidazol-1-yl)-2,2-diphenylbutanamide, is a newly synthesized antimuscarinic drug developed for the treatment of overactive bladder. To predict clinically relevant drug interactions in the metabolism of IM, the paper investigated: (1) the major enzymes responsible for the metabolism of IM, (2) the effects of concomitant drugs on the inhibition of metabolism of IM, and (3) the effects of IM and its metabolites on the inhibition of human cytochrome P450 (CYP). The elimination of IM and production of oxidative metabolites were mainly catalysed by recombinant CYP3A4, and the elimination of IM by human liver microsomes (HLM) was markedly inhibited by co-incubation with ketoconazole. The production of the N-glucuronide metabolite was only catalysed by recombinant UGT1A4. Clinically established CYP3A4 inhibitors including itraconazole, ketoconazole, erythromycin and clarithromycin inhibited the elimination of IM in HLM. IM and its major metabolites did not affect the activities of CYP enzymes in vitro. The results suggest that the major enzymes responsible for the metabolism of IM are CYP3A4 and UGT1A4, and oxidative metabolism of IM is reduced by concomitant administration of CYP3A4 inhibitors. In contrast, IM and its metabolites have no inhibitory effect on the CYP-mediated metabolism of concomitant drugs.     

Development and validation of a highly sensitive LC–MS/MS method for the determination of acacetin in human plasma and its application to a protein binding study

A highly sensitive bioanalytical method for the quantification of acacetin in human plasma was developed and comprehensively validated using liquid chromatography-tandem mass spectrometry (LC–MS/MS). A minimal volume of human plasma sample (20 μL) was prepared by simple deproteinization with 80 μL of acetonitrile. Chromatographic separation was performed using Kinetex C₁₈ column with an isocratic mobile phase consisting of water and acetonitrile (20:80, v/v) containing 0.1 % formic acid at a flow rate of 0.3 mL/min over a total run time of 2.0 min. Mass spectrometric detection was performed using multiple reaction-monitoring modes at the mass/charge transitions m/z 285.22 → 242.17 for acacetin and m/z 277.59 → 175.04 for chlorpropamide (internal standard). The calibration curve was linear over the range of 0.1–500 ng/mL with a lower limit of quantitation of 0.1 ng/mL. The coefficients of variation for both intra- and inter-day validation were less than 11.9 %, and the intra- and inter-day accuracy ranged from 96.8 to 108 %. Mean recovery of acacetin in human plasma was within the range of 91.5–95.6 %. This validated LC–MS/MS method was successfully applied to a human plasma protein binding study that indicated extensive and concentration-independent protein binding of acacetin in human plasma.