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Crystallographic analysis reveals common modes of binding of medium and long-chain fatty acids to human serum albumin.

Human serum albumin (HSA) is an abundant plasma protein that is responsible for the transport of fatty acids. HSA also binds and perturbs the pharmacokinetics of a wide range of drug compounds. Binding studies have revealed significant interactions between fatty acid and drug-binding sites on albumin but high-resolution structural information on ligand binding to the protein has been lacking. We report here a crystallographic study of five HSA-fatty acid complexes formed using saturated medium-chain and long-chain fatty acids (C10:0, C12:0, C14:0, C16:0 and C18:0). A total of seven binding sites that are occupied by all medium-chain and long-chain fatty acids have been identified, although medium-chain fatty acids are found to bind at additional sites on the protein, yielding a total of 11 distinct binding locations. Comparison of the different complexes reveals key similarities and significant differences in the modes of binding, and serves to rationalise much of the biochemical data on fatty acid interactions with albumin. The two principal drug-binding sites, in sub-domains IIA and IIIA, are observed to be occupied by fatty acids and one of them (in IIIA) appears to coincide with a high-affinity long-chain fatty acid binding site.

Binding Sites↗

Molecular flexibility in ab initio drug docking to DNA: binding-site and binding-mode transitions in all-atom Monte Carlo simulations.

The dynamics of biological processes depend on the structure and flexibility of the interacting molecules. In particular, the conformational diversity of DNA allows for large deformations upon binding. Drug-DNA interactions are of high pharmaceutical interest since the mode of action of anticancer, antiviral, antibacterial and other drugs is directly associated with their binding to DNA. A reliable prediction of drug-DNA binding at the atomic level by molecular docking methods provides the basis for the design of new drug compounds. Here, we propose a novel Monte Carlo (MC) algorithm for drug-DNA docking that accounts for the molecular flexibility of both constituents and samples the docking geometry without any prior binding-site selection. The binding of the antimalarial drug methylene blue at the DNA minor groove with a preference of binding to AT-rich over GC-rich base sequences is obtained in MC simulations in accordance with experimental data. In addition, the transition between two drug-DNA-binding modes, intercalation and minor-groove binding, has been achieved in dependence on the DNA base sequence. The reliable ab initio prediction of drug-DNA binding achieved by our new MC docking algorithm is an important step towards a realistic description of the structure and dynamics of molecular recognition in biological systems.

Algorithms↗

Hypertension, renal disease, and drug considerations.

The incidence of chronic kidney disease is steadily increasing in the United States. The magnitude of this problem is such that virtually all health care providers are being called upon to manage these patients. The interplay between chronic kidney disease and drug therapy is complex in that the kidney is both a target for drug effect as well as a moderator of drug elimination. Renal drug elimination occurs by filtration, secretion, and/or metabolism. For renally-cleared compounds, drug clearance typically falls in tandem with the loss of renal function. This process is noteworthy for drug accumulation when the glomerular filtration rate approaches the 30-cc/min range. The kidney is a target for drug effect in relationship to blood pressure and protein excretion. Angiotensin-converting enzyme inhibitor and angiotensin receptor blocker therapy (usually given along with a diuretic) are the drug classes that have been shown to be effective for reduction in both blood pressure and protein excretion in the chronic kidney disease patient. A number of questions still remain unanswered in the pharmacotherapy of chronic kidney disease, including the optimal dose for these drugs as well as what represents the most favorable achieved blood pressure.

Adrenergic alpha-Agonists↗

[Ototoxic factors requiring consideration in the diagnosis of occupational hearing loss].

In the practice of diagnosing occupational deafness resulting from noise effects of factors determining workers' hearing, such as living conditions, working conditions, nutritional and other habits, diseases and their therapy, are often neglected. Discussed in the paper are the significance and ototoxic effects of such factors as: aminoglycoside antibiotics, diuretics, salicylic acid derivatives, fenacetin, quinine, fluorine compounds, cytotoxic drugs, chemical compounds other than drugs (carbon monoxide, carbon disulphide, lead, organic solvents), ethyl alcohol, diseases (abdominal typhus, bacillary dysentery, diphtheria, brucellosis, epidemic parotiditis, poliomyelitis, rubella, aural shingles, syphilis, diabetes mellitus, chronic renopathies, hypothyroidism, serologic conflict, pigmentary retinitis). Exposure to intense noise is more and more frequently juxtaposed with the impact of the mentioned factors. If industrial physicians get aware of this association the prevention of deafness and reliability of treatment may be largely promoted.

Anti-Bacterial Agents↗

Design, synthesis and diuretic activity of some novel 2,4-diamino-6-aryl-7-arylaminopyrimido [4,5-d]pyrimidin-5(6H)-ones.

Synthesis and diuretic activity of some novel 2,4-diamino-6-aryl-7-arylaminopyrimidol4,5-d]pyrimidin-5(6H) -ones were described. The series was designed on the basis of structural similarity between pteridines and pyridopyrimidines. Designed molecules were synthesized by cyclo-condensation of 5-cyano-6-methylmercapto-3-aryl-2-arylaminopyrimidin-4(3H)-one with guanidine. All the compounds were screened for their diuretic activity using triamterene and furosemide as standard drugs. Compounds 2a, 2b, 2d, 2e and 2f were found more potent than triamterene. Compound 2e exhibited diuretic activity comparable to furosemide with greater natriuretic effect. It also exhibited significant antihypertensive activity.

Animals↗

Inverse drug screens: a rapid and inexpensive method for implicating molecular targets.

Identification of gene products that function in some specific process of interest is a common goal in developmental biology. Although use of drug compounds to probe biological systems has a very long history in teratology and toxicology, systematic hierarchical drug screening has not been capitalized upon by the developmental biology community. This "chemical genetics" approach can greatly benefit the study of embryonic and regenerative systems, and we have formalized a strategy for using known pharmacological compounds to implicate specific molecular candidates in any chosen biological phenomenon. Taking advantage of a hierarchical structure that can be imposed on drug reagents in a number of fields such as ion transport, neurotransmitter function, metabolism, and cytoskeleton, any assay can be carried out as a binary search algorithm. This inverse drug screen methodology is much more efficient than exhaustive testing of large numbers of drugs, and reveals the identity of a manageable number of specific molecular candidates that can then be validated and targeted using more expensive and specific molecular reagents. Here, we describe the process of this loss-of-function screen and illustrate its use in uncovering novel bioelectrical and serotonergic mechanisms in embryonic patterning. This technique is an inexpensive and rapid complement to existing molecular screening strategies. Moreover, it is applicable to maternal proteins, and model species in which traditional genetic screens are not feasible, significantly extending the opportunities to identify key endogenous players in biological processes.

Biological Assay↗

Placental transfer of sulindac, sulindac sulfide, and indomethacin in a human placental perfusion model.

OBJECTIVE: Evaluation of the transplacental transfer and placental metabolism of sulindac, its active sulfide metabolite, and indomethacin, drugs used as tocolytic agents, in dual recirculating human placental perfusion. STUDY DESIGN: Term placentas were obtained with maternal consent immediately after delivery. Drugs were added to the maternal reservoir, together with antipyrine as a reference compound, and disappearance from the maternal circulation and appearance in the fetal circulation were followed up for 2 hours in 4 experiments for each compound. Drug concentrations were analyzed by high-performance liquid chromatography. RESULTS: The fetal/maternal concentration ratios after 2-hour perfusions were 0. 34 +/- 0.19 (mean +/- SD, sulindac), 0.54 +/- 0.17 (sulfide), and 0. 45 +/- 0.16 (indomethacin), and the fetal-maternal transfer percentages at 2 hours were 11.6 +/- 5.9 (sulindac), 18.2 +/- 5.2 (sulfide), and 15.3 +/- 4.5 (indomethacin). No metabolism of sulindac or indomethacin was detected. CONCLUSION: Sulindac sulfide, formed through hepatic metabolism, reaches the fetus in higher concentrations than does sulindac or indomethacin. Neither sulindac nor indomethacin is metabolized by the human placenta.

Chromatography, High Pressure Liquid↗

Role of plasma lipoproteins in modifying the biological activity of hydrophobic drugs.

The plasma lipoprotein distribution of potential drug candidates is not commonly studied. For some hydrophobic drug candidates, attainment of similar plasma free drug levels has not been associated with uniform production of pharmacological activity in different animal species. It is well-known that plasma lipoprotein lipid profiles vary considerably between different animal species. In addition, human disease states can significantly influence plasma lipoprotein profiles, resulting in altered therapeutic outcomes. Current research has shown that lipoprotein binding of drug compounds can significantly influence not only the pharmacological and pharmacokinetic properties of the drug, but the relative toxicity as well. Elucidation of drug distribution among plasma lipoproteins is expected to yield valuable insight into factors governing the pharmacological activity and potential toxicity of the drug. This paper will present an historical perspective and summarize the latest research in the area of lipoprotein-drug interactions.

Animals↗

Uptake, cytofluorescence, and cytotoxicity of oxazolopyridocarbazoles (amino acid-ellipticine conjugates) in murine sarcoma cells.

The uptake, cytofluorescence, and cytotoxicity of elliptinium (NMHE) and a series of fluorescent oxazolopyridocarbazoles [amino acid-ellipticine conjugates (AA-NMHE)] were studied in murine sarcoma cells. For all these drugs, the uptake was rapid, directly proportional to the drug concentration, and unaffected by metabolic inhibitors which is consistent with a diffusion mechanism. By 4 h, the intracellular concentration of NMHE exceeded the external drug concentration by about 100 times; this suggests that the toxicity of NMHE is not, as previously assumed, limited by its transport across tumor cell membranes. Conjugation of NMHE with aliphatic amino acids increased the cellular uptake 5- to 7-fold. Cellular exposure to AA-NMHE conjugates resulted in the appearance of granular cytoplasmic fluorescence which was readily translocated to the nucleus upon continued exposure to fluorescent light. The cytotoxicity of the AA-NMHE conjugates (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 3-14 microM) was less than of NMHE (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 0.7 microM) as shown by colony formation following 4 h drug exposure. In contrast, the isoleucine-NMHE conjugate was the most cytotoxic compound (drug concentration required to reduce colony formation by 63% on the exponential part of the survival curve = 0.045 microM) when the drug exposure period was extended to 8 days. The general lower toxicity of the AA-NMHE conjugates is likely due to loss of the phenolic character of the NMHE moiety; therefore, attempts to link NMHE to amino acids remain attractive but will have to be done without affecting the 9-hydroxy group of NMHE.

Alkaloids↗

Collaborative translational research leading to multicenter clinical trials in Duchenne muscular dystrophy: the Cooperative International Neuromuscular Research Group (CINRG).

Progress in the development of rationally based therapies for Duchenne muscular dystrophy has been accelerated by encouraging multidisciplinary, multi-institutional collaboration between basic science and clinical investigators in the Cooperative International Research Group. We combined existing research efforts in pathophysiology by a gene expression profiling laboratory with the efforts of animal facilities capable of conducting high-throughput drug screening and toxicity testing to identify safe and effective drug compounds that target different parts of the pathophysiologic cascade in a genome-wide drug discovery approach. Simultaneously, we developed a clinical trial coordinating center and an international network of collaborating physicians and clinics where those drugs could be tested in large-scale clinical trials. We hope that by bringing together investigators at these facilities and providing the infrastructure to support their research, we can rapidly move new bench discoveries through animal model screening and into therapeutic testing in humans in a safe, timely and cost-effective setting.

Animals↗

Development of predictive pharmacokinetic simulation models for drug discovery.

As discovery chemistry produces increased numbers of potential drug compounds, the use of ADME (absorption, distribution, metabolism, and excretion) properties is becoming increasingly important in the drug selection and promotion process. A computer simulation model has been developed and validated to predict ADME outcomes, such as rate of absorption, extent of absorption, etc. using a limited number of in vitro data inputs. The oral bioavailability of ganciclovir in dogs and humans was simulated using a physiologically based model that utilized many biopharmaceutically relevant parameters, such as the concentration of ganciclovir in the duodenum, jejunum, ileum, and colon at various dose levels and solubility values. The simulations were run and compared to dog and human in vivo data. The simulation results demonstrated that the low bioavailability of ganciclovir is limited by compound solubility rather than permeability due to partitioning as previously speculated. This technology provides a breakthrough in in silico prediction of absorption and with its continued development and improvement, will aid drug discovery and development scientists to produce better pharmaceutical products.

Animals↗

Optimisation and use of water-in-oil MEEKC in pharmaceutical analysis.

Water-in-oil microemulsion electrokinetic chromatography has been applied to the separation of a range of acids, bases and neutrals and is especially suitable for very water-insoluble drug compounds. A number of operating parameters were evaluated. An optimised set of operating conditions allowed separation of a range of pharmaceutical formulations containing water-insoluble compounds. A number of novel applications for W/O microemulsions were developed and ability to quantify drug contents in tablets and a cream was shown with good precision, detector linearity and accuracy. Comparison of obtained data with those determined from a HPLC method showed acceptable agreement.

Chemistry, Pharmaceutical↗

[Effects of nonsteroidal anti-inflammatory agents on the gastrointestinal tract].

Non-steroidal anti-inflammatory drugs (NSAID) belong to the most commonly used drugs worldwide. NSAIDs can cause serious side effects to the gastrointestinal tract. During NSAIDs treatment 10-12% patients suffer from dyspepsia. Up to 1% patients develop severe gastrointestinal complications (ulcer, bleeding, perforation). Any part of gastrointestinal tract could be affected. In oesophagus, NSAIDs can cause oesophagitis of fibrous stricture. NSAID gastropathy can be detected in 40% patients chronically treated with NSAIDs. NSAIDs toxic injury to small and large bowel is frequent but only seldom properly recognised. Serious hepatic lesions are rare. There is no fully reliable and sure prophylaxis or treatment of NSAIDs impairment of to the gastrointestinal tract. Rate of side effects can be reduced by reasonable prescriptions and by primary and secondary prophylaxis. Low rate of side effects is associated with the use of pro-drugs (compound is metabolised to an active substance after absorption from the gastrointestinal tract). New promising drugs were developed with dual action (5-lipoxygenase- and COX-inhibition) and NSAID releasing NO (nitronaproxen, nitrophenac). Specific COX-2 inhibitors (coxibes) provide comparable anti-inflammatory and analgesic effect but the risk of serious side effects to the gastrointestinal tract is significantly lower (when compared with non-specific NSAIDs). Beside harmful effects, NSAIDs are powerful tool in chemoprevention of colorectal cancer.

Anti-Inflammatory Agents, Non-Steroidal↗

Understanding the mechanism of action of atypical antipsychotic drugs. A review of compounds in use and development.

The thrust of development of new antipsychotic drugs has been to identify new compounds that have enhanced antipsychotic efficacy and have lesser side-effects than standard neuroleptic compounds. Drug development strategies no longer concentrate on D2 receptor antagonism but aim to produce novel compounds. The following have been pursued: (a) selective dopamine receptor antagonists; (b) serotonin receptor agonists and antagonists (5-HT1a,e'5-HT2,5-HT3) or mixed 5-HT2-D2 receptor antagonist; (c) selective dopamine agonists or partial agonists; and (d) sigma-site and excitatory amino-acid antagonists. Such compounds are at various stages of development. The only drug which has truly distinguished itself as 'atypical' is clozapine. Its mechanism of action is unknown and the search for it, in large part, has been the impetus for development of the compounds listed above.

Antipsychotic Agents↗

Determining drug-drug interactions and related effects on microcomputers.

Algorithms for determining drug-drug interactions are described. They handle all the generic drugs in the British National Formulary (BNF) (Number 5, British Medical Association and Pharmaceutical Society of Great Britain, 1984) and allow these drugs to be identified by generic or trade name. They also accept and identify interactions for compound drugs prescribed by a single trade name. The algorithms can be implemented on any microcomputer and in a number of languages. The choice of algorithm and number of drugs handled depend on size and disk storage of the microcomputer. It was tested in collaboration with the Department of Geriatric Medicine, Liverpool University, and is used in a prescribing monitoring system operational in some wards of the Royal Liverpool Hospital. The drug data are stored in the form given in the BNF and can be easily updated from this publication. The algorithms can also handle drug allergies and cross-sensitivities.

Algorithms↗

The characterisation of selected drugs with amine-containing side chains using electrospray ionisation and ion trap mass spectrometry and their determination by HPLC-ESI-MS.

The electrospray ionisation-ion-trap mass spectrometry (ESI-MS(n)) of selected drug compounds with amine-containing side chains has been investigated. Certain characteristic in-source fragmentations have been observed for these molecules. Sequential product ion fragmentation experiments (MS(n)) have been performed in order to elucidate the degradation pathways for the [M + H](+) ions and their predominant fragment ions. These MS(n) experiments also show certain characteristic fragmentations with respect to the amine-containing side chains. QTOF-MS/MS has been used to support the identity of the proposed fragments. The data presented in this paper therefore provides useful information on the structure of these compounds with amine-containing side chains and can be used in the characterisation of such drugs, their structurally related metabolites and unknown molecules of pharmaceutical significance extracted from animal and plant sources, for example. Amphetamine, clenbuterol, flurazepam and methadone can be identified and determined in mixtures at low ng/ml concentrations by the application of HPLC-ESI-MS which can also be used for their analysis in saliva samples.

Amines↗

Estimation of blood-brain barrier crossing of drugs using molecular size and shape, and H-bonding descriptors.

The influence of physicochemical properties, including lipophilicity, H-bonding capacity and molecular size and shape descriptors on brain uptake has been investigated using a selection of marketed CNS and CNS-inactive drugs. It is demonstrated that the polar surface area of a drug can be used as a suitable descriptor for the drugs' H-bonding potential. A combination of a H-bonding and a molecular size descriptor, i.e., the major components of lipophilicity and permeability, avoiding knowledge of distribution coefficients, is proposed to estimate brain penetration potential of new drug candidates. Previously reported experimental surface activity data appear to be strongly correlated to molecular size of the drug compounds. Present analysis offers a modern basis for property-based design and targeting of CNS drugs.

Blood-Brain Barrier↗