Design of Drugs by Filtering Through ADMET, Physicochemical and Ligand-Target Flexibility Properties

There is a synergistic interaction between medicinal chemistry, chemoinformatics, and bioinformatics. The last one includes analyses of sequences as well as structural analysis which employ computational techniques such as docking studies and molecular dynamics (MD) simulations. Over the last years these techniques have allowed the development of new accurate computational tools for drug design. As a result, there have been an increased number of publications where computational methods such as pharmacophore modeling, de novo drug design, evaluation of physicochemical properties, and analysis of ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties have been quite useful for eliminating the compounds with poor physicochemical or toxicological properties. Furthermore, using MD simulations and docking analysis, it is possible to estimate the binding energy of the protein-ligand complexes by using scoring functions, as well as to structurally depict the binding pose of the compounds on proteins, in order to select the best evaluated compounds for subsequent synthetizing and evaluation through biological assays. In this work, we describe some computational tools that have been used for structure-based drug design of new compounds that target histone deacetylases (HDACs), which are known to be potential targets in cancer and parasitic diseases.

Parasite Cathepsin D-Like Peptidases and Their Relevance as Therapeutic Targets

Inhibition of aspartic cathepsin D-like peptidases (APDs) has been often discussed as an antiparasite intervention strategy. APDs have been considered as virulence factors of Trypanosoma cruzi and Leishmania spp., and have been demonstrated to have important roles in protein trafficking mechanisms of apicomplexan parasites. APDs also initiate blood digestion as components of multienzyme proteolytic complexes in malaria, platyhelminths, nematodes, and ticks. Increasing DNA and RNA sequencing data indicate that parasites express multiple APD isoenzymes of various functions that can now be specifically evaluated using new functional-genomic and biochemical tools, from which we can further assess the potential of APDs as targets for novel effective intervention strategies against parasitic diseases that still pose an alarming threat to mankind.

[Pyrophosphate in medicine]

In all organisms from bacteria to humans, specific hydrolases--pyrophosphatases--hydrolyse inorganic pyrophosphate to phosphate. Without this, DNA, RNA and protein synthesis stops. Pyrophosphatases are thus essential for all life. In humans, disorders in pyrophosphate metabolism cause chondrocalcinosis and hypophosphatasia. Currently, pyrophosphate analogues, e.g. alendronate, are in clinical use in osteoporosis and Paget's disease but also for e.g. complications of prostate cancer. In bacteria and protozoan parasites, membrane-bound pyrophosphatases (mPPases), which do not occur in humans, convert pyrophosphate to a proton or sodium gradient. mPPases, which are crucial for protozoan parasites, are thus promising drug targets e.g. for malaria and leishmaniasis.

[Enolase and parasitic infection]

Enolase is one kind of important glycolytic enzymes which widely exists in most organisms. A number of recent studies confirm that this enzyme has the functions of activating the plasminogen, involving in the processes of infection and migration of parasites, reducing the immune function of the host as well as preventing parasites from the immune attack of the host. This paper reviews the current research advances in the parasite enolase, and explores its potential for diagnosis, drug development and vaccine target of parasitic diseases.

Apicomplexa, trypanosoma and parasitic nematode protein kinases as antiparasitic therapeutic targets

Parasitic infections caused by Plasmodium, Trypanosoma, Leishmania, Toxoplasma and parasitic nematodes affect hundreds of millions of individuals worldwide and are the cause of significant mortality and morbidity, particularly in developing countries. These diseases also have an impact on individuals from developed countries; for example, some US troops in Iraq and Afghanistan have been infected with Leishmania. The annual mortality associated with parasitic infections is estimated to be 1.5 million deaths. The socioeconomic impact of the morbidity associated with parasitic infections is significant, and the development of new drugs, aimed at novel targets, is urgently needed to develop effective treatments for these diseases. The small-molecule inhibitors discussed in this review constitute useful tools with which to explore the relevance of kinase inhibition in inducing antiparasitic activity. The aim of recent target-based approaches used in the development of parasite kinase inhibitors is to identify novel antiparasitic agents with therapeutic potential.

Protein phosphatase 2A: the Trojan Horse of cellular signaling

Dynamic phosphorylation and dephosphorylation of proteins are fundamental mechanisms utilized by cells to transduce signals. Whereas transduction by protein kinases has been a major focus of studies in the last decade, protein phosphatase 2A (PP2A) enzymes emerge in this millenium as the most fashionable players in cellular signaling. Viral proteins target specific PP2A enzymes in order to deregulate chosen cellular pathways in the host and promote viral progeny. The observation that a variety of viruses utilize PP2A to alienate cellular behavior emphasizes the fundamental importance of PP2A in signal transduction. This review will primarily focus on discussing the uniqueness of PP2A regulation and uncovering the critical role played by protein-protein interactions in the modulation of PP2A signaling. Moreover, the place of PP2A in signaling pathways and its functional significance for human diseases will be discussed.

Nongenetic variation, genetic-environmental interactions and altered gene expression. II. Disease, parasite and pollution effects

The use of protein electrophoretic data for determining the relationships among species or populations is widespread and generally accepted. However, there are many confounding factors that may alter the results of an electrophoretic study and may possibly allow erroneous conclusions to be drawn in taxonomic, systematic or population studies. Measured enzyme activities can also be affected significantly. Parasites, disease and pollution can affect levels of enzyme activity, and electrophoretic results can be affected both quantitatively and qualitatively. Blood serum is particularly vulnerable to variation to variation due to disease, pollution or parasites because damaged tissues may release tissue-specific enzymes into the bloodstream. Capture, handling, chemical treatments, bacteria, natural toxins and consumed food may also contribute to variation. Potential pollution impacts at specimen collection sites should be investigated, and study organisms should be inspected and/or treated for detection and elimination of parasites and disease.

[Hypereosinophilias of the blood. I. Eosinophilic granulocytes]

A knowledge of eosinophil granulocytes is indispensable for the study of hypereosinophilia. For this reason, the most recent findings relating to eosinophil morphology, production/regulation mechanism, and function are reported. Particular attention is given to enzyme populations, local control mechanisms and eosinophil cell surface receptors. Among the various enzymes present in the eosinophil, major basic protein (MBP), with its capacity to damage the cells of many organs, plays an important part; other enzymes include eosinophil peroxidase (EPO), arylsulphatase B, phospholipase D, histaminase and cationic proteins (ECP). Factors influencing eosinophil tissue concentrations and mode of action are considered. Recent findings agree on the role of eosinophils in immunological reactions and parasitic infestations: eosinophil plays a part in an immunological physiopathological sequence: it may, act as a killer cell with selective action against invading parasites, or it may be an immune modulator, anti-inflammatory cell able to surround inflammatory reactions and prevent them from spreading.

LDH isoenzyme distribution in human eosinophils

The lactate dehydrogenase (LDH) isoenzyme pattern has been determined in human eosinophils isolated from the peripheral blood of healthy donors and patients with parasitic diseases. Almost equal LDH1 and LDH5 values appear to be a characteristic of the eosinophils obtained from healthy subjects. Eosinophilic granulocytes which have been isolated from the peripheral blood of patients with eosinophilia due to parasitic infestations have reduced values of LDH5 accompanied by higher LDH1 as compared with eosinophils from healthy donors. Centrifugation of cells through multiple discontinuous gradients of polyvinylpyrrolidone-coated silica particles made it possible to isolate distinct eosinophil subpopulations of differing densities which showed differences in cell surface markers, K-cell activity and also LDH patterns. Analysis of the lactate dehydrogenase isoenzyme patterns showed that EAG+ and EAC+ eosinophilic leukocytes are characterized by very low values of LDH5.

[Clinical examination of the blood of red deer (Cervus elaphus L.) naturally infested with parasites]

In six animals hunted and four immobilized animals of red deer (Cervus elaphus L.) of both sexes and of different age, kept at three game preserves in Bohemia, the psychological values were ascertained: the number of erythrocytes and leucocytes, the hemoglobin content, the hematocrit, MCV, MCH, MCHC, the white blood count, the total serum protein, the fractions: albumin, alpha-, beta- and gamma-globulin, the activity of SGOT, and SGPT, the alkaline phosphatase and the metabolism of calcium, phosphorus, and magnesium in the blood serum. The blood from the heart shortly after killing of the animal was examined, and in immobilized animals the blood was taken from the vena jugularis. In the red deer, a variable intensity of the polyvalent infection of parasites of the species Dictyocaulus viviparus, Bicalulus sagittatus, Fascioloides magna, Paramphistomum spec., Haemonchus contortus, Ostertagia ostertagi, O. circumcincta, Trichostrongylus axei, Nematodirus filicollis, Chabertia ovina, and Trichocephalus globulosa was found. In the immobilized deer no marked deviations were found in the examined values of blood that had been taken within 10 minutes after the calming of the animals.

[Clinical examination of the blood of wild boars (Sus scrofa L.) naturally infested with parasites following administration of anthelminthics]

With 24 head of wild boars (Sus scrofa L.) of both sexes of the age of one to two years, kept in a game preserve and naturally infected with parasites of the species Mestastrongylus pudendotectus, M. elongatus, Ascarops strongylina, Physocephalus sexalatus, Ascaris suum, Globocephalus urosubulatus, Oesophagostomum dentatum, Trichocephalus suis, Eimeria debliecki, and E. perminuta, three experiments were performed with feeds premedicated with anthelmintics: pyrantel tartrate + diethylcarbamazine tartrate (a dose of 25 + 50 mg kg-1 of live weight), Mebendazole 5 p. c. premix and Mebendazole 50 p. c. premix (doses of 10 mg kg-1 and 40 mg kg-1 of live weight) administered for three consecutive days. According to the results of the helminthological dissections the effectiveness of pyrantel tartrate + diethylcarbamazine tartrate reached from 58.1 to 100 p. c. compared with the different species of nematodes, Mebendazole 5 p.c. premix from 47.8 to 100 p. c., and Mebendazole 50 p. c. premix reached the effectiveness of 85.4 to 100 p.c with the mentioned therapeutic doses. The results obtained from a coprological investigation showed the effectiveness, in the case of pyrantel tartrate + diethylcarbamazine tartrate, of 99.2 and 70.65 p. c. on the sixth and fifteeenth day after application, in the case of Mebendazole 5 p. c. premix 94.4 and 79.41 p. c. on the tenth and twentieth day after application, and in the case of of Mebendazole 50 p. c. premix it amounted to 96.0 and 100 p. c. on the tenth and twentieth day after application. In 22 head of wild boars of the total number of examined animals the minimum, maximum, and average values of the number of erythrocytes, leucocytes, of the hemoglobin content, of the hematocrit, MCV, MCH, MCHC, of the white blood count, of the protein total, of the fractions of albumin, alpha-, beta-, and gamma-globulin, of the activity of SGOT and SGPT, and of the metabolism of calcium, phosphorus, and magnesium were determined. The investigation was performed in the shortest possible time after the killing of the animals. In the examined values no marked deviations in 48 hours were found after the application had finished compared with the values determined in non-treated animals.

[Clinical examination of the blood of roe deer (Capreolus capreolus L.) and fallow deer (Dama dama L.) naturally invaded by parasites]

Roe-deer (Capreolus capreolus L. -- five animals) and fallow deer (Dama dama L. -- eleven animals) of both sexes and at different age were subject to blood examination. The deer were killed in several preserves in Bohemia during autumn and winter shootings in two years. The following blood values were determined: erythrocyte count, leucocyte count, hemoglobin content, hematocrit values, MCV, MCH, MCHC, white blood picture, total protein, its fractions (albumin, alpha-, beta-, and gamma-globulin) SGOT, SGPT, and alkaline phosphatase activities, and calcium, phoshporus, and magnesium levels. Examinations were performed in the blood collected from heart soon after the killing of the animals and the results were evaluated in relation to natural polyvalent invasions by parasites of the following species: Bicaulus sagittatus, Dictyocaulus viviparus, Paramphistomum sp., Haemonchus contortus, Ostertagia circumcincta, O. ostertagi, Trichostrongylus colubriformis, Bunostomum trigonocephalum, Nematodirus filicollis, Chabertia ovina, Oesophagostomum columbianum, Trichocephalus ovis, Eimeria auburnensis, E. faurei, and E. ninaekohlyakimovae, occurring in different intensities and species composition in individual animals of the deer tested.