Chronic Obstructive Pulmonary Disease Adverse Event Signals Associated with Potential Inhibitors of Glutathione Peroxidase 1: A Sequence Symmetry Analysis

BACKGROUND AND OBJECTIVE

Prior molecular modelling analysis identified several medicines as potential inhibitors of glutathione peroxidase 1 (GPx1) which may contribute to development or progression of chronic obstructive pulmonary disease (COPD). This study investigates 40 medicines (index medicines) for signals of COPD development or progression in a real-world dataset.

METHODS

Sequence symmetry analysis (SSA) was conducted using a 10% extract of Australian Pharmaceutical Benefits Scheme (PBS) claims data between January 2013 and September 2019. Patients must have been initiated on an index medicine and a medicine for COPD development or progression within 12 months of each other. Sequence ratios were calculated as the number of patients who initiated an index medicine followed by a medicine for COPD development or progression divided by the number who initiated the index medicine second. An adjusted sequence ratio (aSR) was calculated which accounted for changes in prescribing trends. Adverse drug event signals (ADEs) were identified where the aSR lower 95% confidence interval (CI) was greater than 1.

RESULTS

Twenty-one of 40 (53%) index medicines had at least one ADE signal of COPD development or progression. Signals of COPD development, as identified using initiation of tiotropium, were observed for atenolol (aSR 1.32, 95% CI 1.23-1.42) and naproxen (aSR 1.14, 95% CI 1.06-1.23). Several signals of COPD progression were observed, including initiation of fluticasone propionate/salmeterol following initiation of atenolol (aSR 1.44, 95% CI 1.30-1.60) and initiation of aclidinium/formoterol following initiation of naproxen (aSR 2.21, 95% CI 1.34-3.65).

CONCLUSION

ADE signals were generated for several potential GPx1 inhibitors; however, further validation of signals is required in large well-controlled observational studies.

Combined Structure- and Ligand-Based Approach for the Identification of Inhibitors of AcrAB-TolC in Escherichia coli

The inhibition of efflux pumps is a promising approach to combating multidrug-resistant bacteria. We have developed a combined structure- and ligand-based model, using OpenEye software, for the identification of inhibitors of AcrB, the inner membrane protein component of the AcrAB-TolC efflux pump in Escherichia coli. From a database of 1391 FDA-approved drugs, 23 compounds were selected to test for efflux inhibition in E. coli. Seven compounds, including ivacaftor (25), butenafine (19), naftifine (27), pimozide (30), thioridazine (35), trifluoperazine (37), and meloxicam (26), enhanced the activity of at least one antimicrobial substrate and inhibited the efflux pump-mediated removal of the substrate Nile Red from cells. Ivacaftor (25) inhibited efflux dose dependently, had no effect on an E. coli strain with genomic deletion of the gene encoding AcrB, and did not damage the bacterial outer membrane. In the presence of a sub-minimum inhibitory concentration (MIC) of the outer membrane permeabilizer colistin, ivacaftor at 1 μg/mL reduced the MICs of erythromycin and minocycline by 4- to 8-fold. The identification of seven potential AcrB inhibitors shows the merits of a combined structure- and ligand-based approach to virtual screening.

Application of an Integrative Drug Safety Model for Detection of Adverse Drug Events Associated With Inhibition of Glutathione Peroxidase 1 in Chronic Obstructive Pulmonary Disease

BACKGROUND

Chronic Obstructive Pulmonary Disease is characterised by declining lung function and a greater oxidative stress burden due to reduced activity of antioxidant enzymes such as Glutathione Peroxidase 1.

OBJECTIVES

The extent to which drugs may contribute to this compromised activity is largely unknown. An integrative drug safety model explores inhibition of Glutathione Peroxidase 1 by drugs and their association with chronic obstructive pulmonary disease adverse drug events.

METHODS

In silico molecular modelling approaches were utilised to predict the interactions that drugs have within the active site of Glutathione Peroxidase 1 in both human and bovine models. Similarities of chemical features between approved drugs and the known inhibitor tiopronin were also investigated. Subsequently the Food and Drug Administration Adverse Event System was searched to uncover adverse drug event signals associated with chronic obstructive pulmonary disease.

RESULTS

Statistical and molecular modelling analyses confirmed that the use of several registered drugs, including acetylsalicylic acid and atenolol may be associated with inhibition of Glutathione Peroxidase 1 and chronic obstructive pulmonary disease.

CONCLUSION

The integration of molecular modelling and pharmacoepidemological data has the potential to advance drug safety science. Ongoing review of medication use and further pharmacoepidemiological and biological analyses are warranted to ensure appropriate use is recommended.

Discovery of N,4-Di(1H-pyrazol-4-yl)pyrimidin-2-amine-Derived CDK2 Inhibitors as Potential Anticancer Agents: Design, Synthesis, and Evaluation

Cyclin-dependent kinase 2 (CDK2) has been garnering considerable interest as a target to develop new cancer treatments and to ameliorate resistance to CDK4/6 inhibitors. However, a selective CDK2 inhibitor has yet to be clinically approved. With the desire to discover novel, potent, and selective CDK2 inhibitors, the phenylsulfonamide moiety of our previous lead compound 1 was bioisosterically replaced with pyrazole derivatives, affording a novel series of N,4-di(1H-pyrazol-4-yl)pyrimidin-2-amines that exhibited potent CDK2 inhibitory activity. Among them, 15 was the most potent CDK2 inhibitor (Ki = 0.005 µM) with a degree of selectivity over other CDKs tested. Meanwhile, this compound displayed sub-micromolar antiproliferative activity against a panel of 13 cancer cell lines (GI50 = 0.127–0.560 μM). Mechanistic studies in ovarian cancer cells revealed that 15 reduced the phosphorylation of retinoblastoma at Thr821, arrested cells at the S and G2/M phases, and induced apoptosis. These results accentuate the potential of the N,4-di(1H-pyrazol-4-yl)pyrimidin-2-amine scaffold to be developed into potent and selective CDK2 inhibitors for the treatment of cancer.

2-Anilino-4-(1-methyl-1H-pyrazol-4-yl)pyrimidine-derived CDK2 inhibitors as anticancer agents: Design, synthesis & evaluation

Deregulation of cyclin-dependent kinase 2 (CDK2) and its activating partners, cyclins A and E, is associated with the pathogenesis of a myriad of human cancers and with resistance to anticancer drugs including CDK4/6 inhibitors. Thus, CDK2 has become an attractive target for the development of new anticancer therapies and for the amelioration of the resistance to CDK4/6 inhibitors. Bioisosteric replacement of the thiazole moiety of CDKI-73, a clinically trialled CDK inhibitor, by a pyrazole group afforded 9 and 19 that displayed potent CDK2-cyclin E inhibition (K_i = 0.023 and 0.001 μM, respectively) with submicromolar antiproliferative activity against a panel of cancer cell lines (GI₅₀ = 0.025-0.780 μM). Mechanistic studies on 19 with HCT-116 colorectal cancer cells revealed that the compound reduced the phosphorylation of retinoblastoma at Ser807/811, arrested the cells at the G2/M phase, and induced apoptosis. These results highlight the potential of the 2-anilino-4-(1-methyl-1H-pyrazol-4-yl)pyrimidine series in developing potent and selective CDK2 inhibitors to combat cancer.

Cinnamaldehyde derivatives act as antimicrobial agents against Acinetobacter baumannii through the inhibition of cell division

Acinetobacter baumannii is a pathogen with high intrinsic antimicrobial resistance while multidrug resistant (MDR) and extensively drug resistant (XDR) strains of this pathogen are emerging. Treatment options for infections by these strains are very limited, hence new therapies are urgently needed. The bacterial cell division protein, FtsZ, is a promising drug target for the development of novel antimicrobial agents. We have previously reported limited activity of cinnamaldehyde analogs against Escherichia coli. In this study, we have determined the antimicrobial activity of six cinnamaldehyde analogs for antimicrobial activity against A. baumannii. Microscopic analysis was performed to determine if the compounds inhibit cell division. The on-target effect of the compounds was assessed by analyzing their effect on polymerization and on the GTPase activity of purified FtsZ from A. baumannii. In silico docking was used to assess the binding of cinnamaldehyde analogs. Finally, in vivo and in vitro safety assays were performed. All six compounds displayed antibacterial activity against the critical priority pathogen A. baumannii, with 4-bromophenyl-substituted 4 displaying the most potent antimicrobial activity (MIC 32 μg/mL). Bioactivity was significantly increased in the presence of an efflux pump inhibitor for A. baumannii ATCC 19606 (up to 32-fold) and significantly, for extensively drug resistant UW 5075 (greater than 4-fold), suggesting that efflux contributes to the intrinsic resistance of A. baumannii against these agents. The compounds inhibited cell division in A. baumannii as observed by the elongated phenotype and targeted the FtsZ protein as seen from the inhibition of polymerization and GTPase activity. In silico docking predicted that the compounds bind in the interdomain cleft adjacent to the H7 core helix. Di-chlorinated 6 was devoid of hemolytic activity and cytotoxicity against mammalian cells in vitro, as well as adverse activity in a Caenorhabditis elegans nematode model in vivo. Together, these findings present halogenated analogs 4 and 6 as promising candidates for further development as antimicrobial agents aimed at combating A. baumannii. This is also the first report of FtsZ-targeting compounds with activity against an XDR A. baumannii strain.

Therapeutic Potential of a Novel Vitamin D3 Oxime Analogue, VD1-6, with CYP24A1 Enzyme Inhibitory Activity and Negligible Vitamin D Receptor Binding

The regulation of vitamin D3 actions in humans occurs mainly through the Cytochrome P450 24-hydroxylase (CYP24A1) enzyme activity. CYP24A1 hydroxylates both 25-hydroxycholecalciferol (25(OH)D3) and 1,25-dihydroxycholecalciferol (1,25(OH)2D3), which is the first step of vitamin D catabolism. An abnormal status of the upregulation of CYP24A1 occurs in many diseases, including chronic kidney disease (CKD). CYP24A1 upregulation in CKD and diminished activation of vitamin D3 contribute to secondary hyperparathyroidism (SHPT), progressive bone deterioration, and soft tissue and cardiovascular calcification. Previous studies have indicated that CYP24A1 inhibition may be an effective strategy to increase endogenous vitamin D activity and decrease SHPT. This study has designed and synthesized a novel C-24 O-methyloxime analogue of vitamin D3 (VD1-6) to have specific CYP24A1 inhibitory properties. VD1-6 did not bind to the vitamin D receptor (VDR) in concentrations up to 10−7 M, assessed by a VDR binding assay. The absence of VDR binding by VD1-6 was confirmed in human embryonic kidney HEK293T cultures through the lack of CYP24A1 induction. However, in silico docking experiments demonstrated that VD1-6 was predicted to have superior binding to CYP24A1, when compared to that of 1,25(OH)2D3. The inhibition of CYP24A1 by VD1-6 was also evident by the synergistic potentiation of 1,25(OH)2D3-mediated transcription and reduced 1,25(OH)2D3 catabolism over 24 h. A further indication of CYP24A1 inhibition by VD1-6 was the reduced accumulation of the 24,25(OH)D3 , the first metabolite of 25(OH)D catabolism by CYP24A1. Our findings suggest the potent CYP24A1 inhibitory properties of VD1-6 and its potential for testing as an alternative therapeutic candidate for treating SHPT.

Neuron-specific responses to acetylcholine within the spinal dorsal horn circuits of rodent and primate

Excitatory and inhibitory neurotransmission within the spinal dorsal horn is tightly controlled to regulate transmission of nociceptive signals to the brain. One aspect of this control is modulation of neuronal activity through cholinergic signaling. Nociceptive neurons in the dorsal horn express both nicotinic and muscarinic cholinergic receptors and activation of these receptors reduces pain in humans, while inhibition leads to nociceptive hypersensitivity. At a cellular level, acetylcholine (ACh) has diverse effects on excitability which is dependent on the receptor and neuronal subtypes involved. In the present study we sought to characterize the electrophysiological responses of specific subsets of lamina II interneurons from rat and marmoset spinal cord. Neurons were grouped by morphology and by action potential firing properties. Whole-cell voltage-clamp recordings from lamina II dorsal horn neurons of adult rats showed that bath applied acetylcholine increased, decreased or had no effect on spontaneous synaptic current activity in a cell-type specific manner. ACh modulated inhibitory synaptic activity in 80% of neurons, whereas excitatory synaptic activity was affected in less than 50% of neurons. In whole-cell current clamp recordings, brief somatic application of ACh induced cell-type specific responses in 79% of rat lamina II neurons, which included: depolarization and action potential firing, subthreshold membrane depolarization, biphasic responses characterized by transient depolarization followed by hyperpolarization and membrane hyperpolarization alone. Similar responses were seen in marmoset lamina II neurons and the properties of each neuron group were consistent across species. ACh-induced hyperpolarization was blocked by the muscarinic antagonist atropine and all forms of acetylcholine-induced depolarization were blocked by the nicotinic antagonist mecamylamine. The cholinergic system plays an important role in regulating nociception and this study contributes to our understanding of how circuit activity is controlled by ACh at a cellular level in primate and rodent spinal cord.

Proton pump inhibitors may contribute to progression or development of chronic obstructive pulmonary disease-A sequence symmetry analysis approach

WHAT IS KNOWN AND OBJECTIVE

Proton pump inhibitors (PPIs), used to treat and prevent gastro-oesophageal conditions, are well-tolerated but have been associated with risk including pneumonia. The extent to which initiation of PPIs can contribute to other respiratory conditions such as chronic obstructive pulmonary disease (COPD) is largely unknown.

METHODS

A sequence symmetry analysis (SSA) approach was applied to the Australian Department of Human Services, Pharmaceutical Benefits Scheme 10% extract. Participants were aged 45 years and older and were dispensed PPIs (ATC Codes A02BC01, A02BC02, A02BC03, A02BC04 and A02BC05) and long-acting bronchodilators (LABDs) for COPD (ATC Codes R03BB04 (PBS Item Code 10509D and 08626B), R03BB05, R03BB06, R03BB07 and R03AC18 (PBS Item Code 05137J and 05134F)) between 2013 and 2019. The analysis included patients initiated on an LABD within 12 months before or after their first prescription of a PPI. The crude sequence ratio (cSR) was calculated as the number of patients prescribed their first LABD after starting a PPI divided by the number of patients prescribed their first LABD before starting a PPI. Calculation of the adjusted sequence ratio (aSR) accounted for prescribing trends over time in initiation of each of the medicines. A signal was identified where the aSR lower 95% confidence interval (CI) was greater than one.

RESULTS AND DISCUSSION

Initiation of omeprazole was associated with a 29% increased risk of initiating a LABD (ASR = 1.29 95% CI 1.22-1.36). Initiation of esomeprazole, rabeprazole, pantoprazole or lansoprazole was associated with 25%, 15%, 8% and 8% increased risk, respectively.

WHAT IS NEW AND CONCLUSION

There is an established association between gastro-oesophageal reflux disease and COPD which has been confirmed by implementation of a sequence symmetry-based approach which demonstrated that PPI initiation is potentially associated with progression or exacerbation of COPD. The impact PPI use has directly on this association requires further investigation.

A Systematic Review and Meta-Analysis Considering the Risk for Congenital Heart Defects of Antidepressant Classes and Individual Antidepressants

INTRODUCTION

Antidepressant use during the first trimester is reported in 4-8% of pregnancies. The use of some selective serotonin reuptake inhibitors during the first trimester has been identified as increasing the odds for congenital heart defects; however, little is known about the safety of non-selective serotonin reuptake inhibitor antidepressants.

OBJECTIVE

The objective of this study was to assess the odds of congenital heart defects associated with the use of antidepressants during the first trimester of pregnancy, and to update the literature as newer studies have been published since the latest systematic literature review and meta-analysis.

METHODS

PubMed and Embase were searched till 3 June, 2020. Study quality was assessed, and study details were extracted. Meta-analyses were performed using RevMan 5.4, which assessed: (1) any antidepressant usage; (2) classes of antidepressants; and (3) individual antidepressants.

RESULTS

Twenty studies were identified, encompassing 5,337,223 pregnancies. The odds ratio for maternal use of any antidepressant during the first trimester of pregnancy and the presence of congenital heart defects from the random effects meta-analysis was 1.28 (95% confidence interval [CI] 1.17-1.41). Significant odds ratios of 1.69 (95% CI 1.37-2.10) and 1.25 (95% CI 1.15-1.37) were reported for serotonin norepinephrine reuptake inhibitors and selective serotonin reuptake inhibitors, respectively. A non-statistically significant odds ratio of 1.02 (95% CI 0.82-1.25) was reported for the tricyclic antidepressants. Analyses of individual SSRIs produced significant odds ratios of 1.57 (95% CI 1.25-1.97), 1.36 (95% CI 1.08-1.72), and 1.29 (95% CI 1.14-1.45) for paroxetine, fluoxetine, and sertraline, respectively. The norepinephrine-dopamine-reuptake inhibitor bupropion also produced a significant odds ratio of 1.23 (95% CI 1.01-1.49).

CONCLUSIONS

The selective serotonin reuptake inhibitor and serotonin norepinephrine reuptake inhibitor classes of antidepressants pose a greater risk for causing congenital heart defects than the tricyclic antidepressants. However, this risk for individual antidepressants within each class varies, and information regarding some antidepressants is still lacking.

Design and structural optimization of novel 2H-benzo[h]chromene derivatives that target AcrB and reverse bacterial multidrug resistance

Drug efflux pumps have emerged as a new drug targets for the treatment of bacterial infections in view of its critical role in promoting multidrug resistance. Herein, novel chromanone and 2H-benzo[h]chromene derivatives were designed by means of integrated molecular design and structure-based pharmacophore modeling in an attempt to identify improved efflux pump inhibitors that target Escherichia coli AcrB. The compounds were tested for their efflux inhibitory activity, ability to inhibit efflux, and the effect on bacterial outer and inner membranes. Twenty-three novel structures were identified that synergized with antibacterials tested, inhibited Nile Red efflux, and acted specifically on the AcrB. Among them, WK2, WL7 and WL10 exhibiting broad-spectrum and high-efficiency efflux inhibitory activity were identified as potential ideal AcrB inhibitors. Molecular modeling further revealed that the strong π-π stacking interactions and hydrogen bond networks were the major contributors to tight binding of AcrB.

Discovery of CDK5 Inhibitors through Structure-Guided Approach

Specific abrogation of cyclin-dependent kinase 5 (CDK5) activity has been validated as a viable approach for the development of anticancer agents. However, no selective CDK5 inhibitor has been reported to date. Herein, a structure-based in silico screening was employed to identify novel scaffolds from a library of compounds to identify potential CDK5 inhibitors that would be relevant for drug discovery. Hits, representatives of three chemical classes, were identified as inhibitors of CDK5. Structural modification of hit-1 resulted in 29 and 30. Compound 29 is a dual inhibitor of CDK5 and CDK2, whereas 30 preferentially inhibits CDK5. Both leads exhibited anticancer activity against acute myeloid leukemia (AML) cells via a mechanism consistent with targeting cellular CDK5. This study provides an effective strategy for discovery of CDK5 inhibitors as potential antileukemic agents.

Molecular Modeling Approaches for the Prediction of Selected Pharmacokinetic Properties

Poor profiles of potential drug candidates, including pharmacokinetic properties, have been acknowledged as a significant hindrance to the development of modern therapeutics. Contemporary drug discovery and development would be incomplete without the aid of molecular modeling (in-silico) techniques, allowing the prediction of pharmacokinetic properties such as clearance, unbound fraction, volume of distribution and bioavailability. As with all models, in-silico approaches are subject to their interpretability, a trait that must be balanced with accuracy when considering the development of new methods. The best models will always require reliable data to inform them, presenting significant challenges, particularly when appropriate in-vitro or in-vivo data may be difficult or time-consuming to obtain. This article seeks to review some of the key in-silico techniques used to predict key pharmacokinetic properties and give commentary on the current and future directions of the field.

Antiproliferative Aporphine Alkaloids from Litsea glutinosa and Ethnopharmacological Relevance to Kuuku I’yu Traditional Medicine

Australian Aboriginal people have a long history of relying on plants for the treatment of various ailments and illnesses. Our ongoing collaborative research project initiated by Chuulangun Aboriginal Corporation (Cape York, Australia) has recently focussed on revealing whether Kuuku I’yu plant medicines possess anticancer-related activities and the chemistry responsible for this. Here, we present results from a study of the plant Litsea glutinosa, used traditionally for the treatment of gastrointestinal disorders. Four known aporphine alkaloids N-methylactinodaphnine (1), boldine (2), N-methyllaurotetanine (3), and isoboldine (4) were isolated by activity-guided fractionation and tested for cytotoxicity against HT29, SKMEL28, and primary human keratinocytes. Compound 1 was the most cytotoxic and this observation may be explained by the presence of a 1,2-methylenedioxy group. In silico docking revealed that a plausible mechanism for the observed cytotoxicity is the stabilization of a topoisomerase II (β) DNA–enzyme complex. The ethnopharmacological relevance of this study is discussed in the context of researching and using traditional knowledge in biomolecular discovery.

Insights into the Importance of DFD-Motif and Insertion I1 in Stabilizing the DFD-Out Conformation of Mnk2 Kinase

Human mitogen-activated protein kinases (MAPK)-interacting kinases 1 and 2 (Mnk1/2) are promising anticancer targets. Mnks possess special insertions and a DFD-motif that are distinct from other kinases. Crystallographic studies of Mnk1/2 have revealed that the DFD-motif adopts the DFG/D-out conformation in which residue F227 flips into the ATP binding pocket. This is rarely observed in other kinases. Although the DFG-out conformation has attracted great interest for designing selective inhibitors, structural requirements for binding and the mechanism governing the DFG-out conformation remain unclear. This work presents for the first time the applicability of 3D models of Mnk2 protein in studying conformational changes by utilizing homology modeling and molecular dynamics simulations. The study reveals that the interactions between residue K234 of insertion I1 and D226 of the DFD motif play a key role in inducing and stabilizing the DFD-out conformation. The structural features will aid in the rational design of Mnk2 inhibitors.

Synthesis and extended activity of triazole-containing macrocyclic protease inhibitors

Peptide-derived protease inhibitors are an important class of compounds with the potential to treat a wide range of diseases. Herein, we describe the synthesis of a series of triazole-containing macrocyclic protease inhibitors pre-organized into a β-strand conformation and an evaluation of their activity against a panel of proteases. Acyclic azido-alkyne-based aldehydes are also evaluated for comparison. The macrocyclic peptidomimetics showed considerable activity towards calpain II, cathepsin L and S, and the 20S proteasome chymotrypsin-like activity. Some of the first examples of highly potent macrocyclic inhibitors of cathepsin S were identified. These adopt a well-defined β-strand geometry as shown by NMR spectroscopy, X-ray analysis, and molecular docking studies.

Polymorphisms in the mitochondrial ribosome recycling factor EF-G2mt/MEF2 compromise cell respiratory function and increase atorvastatin toxicity

Mitochondrial translation, essential for synthesis of the electron transport chain complexes in the mitochondria, is governed by nuclear encoded genes. Polymorphisms within these genes are increasingly being implicated in disease and may also trigger adverse drug reactions. Statins, a class of HMG-CoA reductase inhibitors used to treat hypercholesterolemia, are among the most widely prescribed drugs in the world. However, a significant proportion of users suffer side effects of varying severity that commonly affect skeletal muscle. The mitochondria are one of the molecular targets of statins, and these drugs have been known to uncover otherwise silent mitochondrial mutations. Based on yeast genetic studies, we identify the mitochondrial translation factor MEF2 as a mediator of atorvastatin toxicity. The human ortholog of MEF2 is the Elongation Factor Gene (EF-G) 2, which has previously been shown to play a specific role in mitochondrial ribosome recycling. Using small interfering RNA (siRNA) silencing of expression in human cell lines, we demonstrate that the EF-G2mt gene is required for cell growth on galactose medium, signifying an essential role for this gene in aerobic respiration. Furthermore, EF-G2mt silenced cell lines have increased susceptibility to cell death in the presence of atorvastatin. Using yeast as a model, conserved amino acid variants, which arise from non-synonymous single nucleotide polymorphisms (SNPs) in the EF-G2mt gene, were generated in the yeast MEF2 gene. Although these mutations do not produce an obvious growth phenotype, three mutations reveal an atorvastatin-sensitive phenotype and further analysis uncovers a decreased respiratory capacity. These findings constitute the first reported phenotype associated with SNPs in the EF-G2mt gene and implicate the human EF-G2mt gene as a pharmacogenetic candidate gene for statin toxicity in humans.

The mitochondria are responsible for producing the cell's energy. Energy production is the result of carefully orchestrated interactions between proteins encoded by the mitochondrial DNA and by nuclear DNA. Sequence variations in genes encoding these proteins have been shown to cause disease and adverse drug reactions in patients. The cholesterol-lowering drugs statins are one class of drugs that interfere with mitochondrial function. Statins are one of the most prescribed drugs in the western world, but many users suffer side effects, commonly muscle pain. In severe cases this can lead to muscle breakdown and liver failure. In this study, we discover that disruption of a mitochondrial translation gene, EF-G2mt, impedes respiration and increases cell death when exposed to statin. Using the simple unicellular organism yeast as a model, the activity of naturally occurring human EF-G2mt variants is tested. Three of these variants render yeast cells more sensitive to statin. Patients who possess these EF-G2mt variations may be more susceptible to statin side effects. Importantly, the test for statin sensitivity also led to the discovery of mutants that have a reduced energy production capacity. The decreased ability to produce energy is linked to a number of diseases, including myopathies and liver failure.

Kinetics membrane disruption due to drug interactions of chlorpromazine hydrochloride

Drug-membrane interactions assume considerable importance in pharmacokinetics and drug metabolism. Here, we present the interaction of chlorpromazine hydrochloride (CPZ) with supported phospholipid bilayers. It was demonstrated that CPZ binds rapidly to phospholipid bilayers, disturbing the molecular ordering of the phospholipids. These interactions were observed to follow first order kinetics, with an activation energy of approximately 420 kJ mol(-1). Time-dependent membrane disruption was also observed for the interaction with CPZ, such that holes appeared in the phospholipid bilayer after the interaction of CPZ. For this process of membrane disruption, "lag-burst" kinetics was demonstrated.

Characterisation of the binding of cationic amphiphilic drugs to phospholipid bilayers using surface plasmon resonance

The interactions of three cationic amphiphilic drugs (CPZ, AMI, PROP) with phospholipid vesicles comprising DOPC, DMPC, or DSPC were investigated using surface plasmon resonance (SPR). Responses for CAD concentrations in the range 15.625 to 1500 microM were measured. The greatest uptake by each phospholipid bilayer occurred with CPZ. Inclusion of CAD concentrations between 750 and 1500 microM provided evidence for a second nonsaturable binding process, which may arise from intercalation of the drugs within the lipid bilayer. CAD binding was additionally shown to be dependent on membrane fluidity. Responses were initially fitted over a concentration range of 15.625 to 500 microM using a model which incorporated terms for a saturable binding site. This yielded very poor values of K(D) and nonsensible values of saturation responses. Subsequently, responses were fit to the expression for a model which incorporated terms for both a saturable binding site and second nonsaturable site. Measurable binding affinities (K(D) values ranged from 170 to 814 microM) were obtained for DOPC and DMPC bilayers which are similar to values reported previously. This work demonstrates that SPR studies with synthetic phospholipid bilayers provide a potentially useful approach for characterising drug-membrane binding interactions and for providing insight into the processes that contribute to drug-membrane binding.

Amino acid conjugation: contribution to the metabolism and toxicity of xenobiotic carboxylic acids

Despite being the first conjugation reaction demonstrated in humans, amino acid conjugation as a route of metabolism of xenobiotic carboxylic acids is not well characterised. This is principally due to the small number and limited structural diversity of xenobiotic substrates for amino acid conjugation. Unlike CYP and uridine 5'-diphosphate glucuronosyltransferase, which are localised in the endoplasmic reticulum, the enzymes of amino acid conjugation reside in mitochondria. Unique among drug metabolism pathways, amino acid conjugation involves initial formation of a xenobiotic acyl-CoA thioester that is then conjugated principally with glycine in humans. However, formation of the xenobiotic acyl-CoA thioester does not always infer subsequent amino acid conjugation. Evidence is presented that in the absence of glycine conjugation substrates that form acyl-CoA thioesters perturb mitochondrial function. This review discusses literature on the enzymes involved and the concept that xenobiotic substrate selectivity provides a barrier to protect the metabolic integrity of the mitochondria.

The Gaussian Generalized Born model: application to small molecules

This work presents a Generalized Born model for the computation of the electrostatic component of solvation energies which is based on volume integration. An analytic masking function is introduced to remove Coulombic singularities. This approach leads to analytic formulae for the computation of Born radii, which are differentiable to arbitrary order, and computationally straightforward to implement.

Molecular modeling approaches for the prediction of the nonspecific binding of drugs to hepatic microsomes

Molecular modeling approaches for the prediction of the nonspecific binding of drugs to hepatic microsomes were examined using a published database of 56 compounds. Models generated were evaluated using an independent test set of 13 compounds. A pharmacophore approach identified structural features of drugs associated with nonspecific binding. A side-chain amino group and complementary hydrophobic domain were the principal features noted. The use of shape overlays, based on the pharmacophore, in conjunction with a chemical force field in the program ROCS, yielded discrimination between molecules classified as strong binders (experimental fraction unbound in microsomes<0.50) and those with a lower degree of binding (experimental fraction unbound in microsomes>0.50). In the initial data set of 56 molecules, 18 were classified as strong binders (on the basis of the above criteria), and all of those were recovered in the top 22 molecular hits from ROCS. Additionally, computationally generated values of log P were shown to provide a reasonable estimate of the fraction unbound in microsomes, providing the compounds were in their basic form at physiological pH.

DNA binding of an organic dppz-based intercalator

An improved synthesis of a water-soluble derivative of dipyrido[3,2-a:2',3'-c]phenazine (dppz) is reported. The structures of both dppz and the cation ethylene-bipyridyldiylium-phenazine dinitrate [[1][(PF(6))(2)]] have been obtained via X-ray crystallography. Metal complex derivatives of dppz are very well studied. However, using the water soluble [1][(NO(3))(2)], the nature of the interaction of a simple dppz unit with duplex DNA has been investigated for the first time. In both organic solvents and water, 1 displays unstructured luminescence, assigned to an intramolecular charge transfer. The emission is quenched on binding to natural and synthetic duplex DNA, including poly(dA).poly(dT). A variety of techniques reveal that the cation binds to DNA with an affinity comparable to those of many metal dppz complexes, via an intercalative binding mode.

Quantum-mechanical QSAR/QSPR descriptors from momentum-space wave functions

It is shown that quantum-mechanical descriptors obtained as parameters from the one-dimensional radial distribution function of electron momentum can be used to predict molecular activities or properties to a precision that compares favorably with the more traditional QSAR/QSPR methods. The distribution function is derived from momentum space ab initio wave functions. The predictive value of the descriptors is illustrated by their application to the estimation of McGowan's volume, gas-chromatographic retention time, gas-hexadecane partition coefficient, second hyperpolarizability, and tadpole narcotic activity.

A Method for Calculating the Equilibrium Thermodynamic Properties of Gas Reaction Mixtures

A computational method has been developed for determining the equilibrium composition and thermodynamic properties of a multicomponent gas reaction mixture. The method uses the downhill simplex method and simulated annealing to minimize, subject to matter conservation, the total Gibbs energy of the mixture with respect to its composition. The method has been used to examine the properties of various high-temperature equilibrium mixtures of species containing carbon, hydrogen, nitrogen and oxygen.