Adenosine triphosphatase activities in Trypanosoma cruzi.

1. Subcellular fractions obtained from epimastigotes of Trypanosoma cruzi, disrupted by three different procedures, contained in addition to the already known Mg2+-activated adenosine triphosphatase (ATPase; E.C.3.6.1.4), a Ca2+-ATPase activity. 2. The Ca2+-ATPase (a) was activated by low concentrations of CaCl2 (apparent Ka, 80 microM); (b) had a Km for ATP of 0.6 mM (at 1 mM CaCl2, pH 8.0); (c) presented a broad pH curve (optimum 7.1-8.6); and (d) was insensitive to oligomycin concentrations which inhibited the Mg2+-ATPase present in the same preparations. 3. All attempts to find a (Na+-K+)-activated, ouabain-inhibited, ATPase have been unsuccessful, in spite of the fact that living epimastigoes of T. cruzi are able to concentrate K+ and exclude Na+ from the medium.     

3D QSAR studies on GSK-3 inhibition by aloisines

GSK-3 is involved in various physiological processes and its inhibitors have been evaluated as promising drug candidates for a lot of unmet pathologies. In this paper, inhibition of GSK-3 by aloisines is investigated by 3D QSAR studies. Two alignment rules were applied to check the influence of spatial alignment of the compounds. Both the CoMFA and CoMSIA techniques were carried out and ASS procedure was applied for CoMFA to find a satisfactory model. The best QSAR model obtained is a CoMSIA model characterized with r(2) of 0.938 and q(2) of 0.673 including steric, electrostatic and hydrophobic fields, possessing good predicting ability. To get a better understanding of the relationship between chemical structure and biological activity, a complex structure of aloisine with GSK-3 was obtained by superimposing GSK-3 into the known cocrystal structure of aloisine-CDK2, and then factors that affect the inhibition activity were investigated further, combining the QSAR study with the complex structure, the results of which are in good accordance and complementary to each other.     

3-D QSAR studies of triazolinone based balanced AT1/AT2 receptor antagonists

Essential structural and physicochemical requirements in terms of common biophoric sites (pharmacophore) and secondary sites for binding and interacting with AT1 and AT2 receptors have been identified using APEX-3-D expert system on 16 N2- aryl triazolinone biphenyl sulphonamides. Among several biophoric 3-D QSAR models two models (Nos. 1 and 2) having R2 > 0.7, chance <0.05 and match >0.5 and two models (Nos. 3 and 4) having R2 > 0.89, chance <0.03 and match >0.5 with three biophoric sites and two secondary sites (except model No. 4 with three secondary sites) describe the variation in AT1 and AT2 antagonistic activities, respectively.     

2D QSAR studies on thyroid hormone receptor ligands

2D QSAR studies were carried out for a series of 55 ligands for the Thyroid receptors, TRalpha and TRbeta. Significant cross-validated correlation coefficients (q(2)=0.781 (TRalpha) and 0.693 (TRbeta)) were obtained. The models' predictive abilities were proved more valuable than the classical 2D-QSAR, and were further investigated by means of an external test set of 13 compounds. The predicted values are in good agreement with experimental values, suggesting that the models could be useful in the design of novel, more potent TR ligands. Contribution map analysis identified a number of positions that are promising for the development of receptor isoform specific ligands.     

Trypanosoma cruzi: experimental Chagas' disease in rhesus monkeys. II. Ultrastructural and cytochemical studies of peroxidase and acid phosphatase activities

Ultrastructural and cytochemical studies of peroxidase and acid phosphatase were performed in skin, lymph node and heart muscle tissue of rhesus monkeys with experimental Chagas' disease. At the site of inoculation there was a proliferative reaction with the presence of immature macrophages revealed by peroxidase technique. At the lymph node a diffuse inflammatory exudate with mononuclear cells, fibroblasts and immature activated macrophages reproduces the human pattern of acute Chagas' disease inflammatory lesions. The heart muscle cells present different degrees of degenerative alterations and a striking increase in the number of lysosomal profiles that exhibit acid hydrolase reaction product. A strong inflammatory reaction was present due to lymphocytic infiltrate or due to eosinophil granulocytes associated to ruptured cells. The present study provides some experimental evidences that the monkey model could be used as a reliable model to characterize histopathological alterations of the human disease.     

Synthesis, antimicrobial activity, and QSAR studies of furan-3-carboxamides

The synthesis and characterization of a new series of furan-3-carboxamides, from the aromatization of 4-trichloroacetyl-2,3-dihydrofuran to 3-trichloroacetyl furan followed by nucleophilic displacement of the trichloromethyl group or the corresponding carboxylic acid chloride by nitrogen-containing compounds, is presented. Preliminary in vitro antimicrobial activity of the title compounds was assessed against a panel of microorganisms including yeast, filamentous fungi, bacteria, and alga. Some of the furan-3-carboxamides exhibited significant in vitro antimicrobial activity. QSAR investigation was applied to find a correlation between the different physicochemical parameters of the compounds studied and their biological activity.     

3D QSAR studies on new oxazolidinone antibacterial agents by comparative molecular field analysis.

Three-dimensional QSAR studies for two series of new oxazolidinone antibacterial agents were conducted using the comparative molecular field analysis (CoMFA). In vitro activities (MICs) of the compounds against methicillin-resistant Staphylococcus aureus 88 (MRSA 88) exhibited a strong correlation with their steric, electrostatic factors and lipophilicities.     

Pharmacophore generation and atom-based 3D-QSAR of novel quinoline-3-carbonitrile derivatives as Tpl2 kinase inhibitors

Tumour progression locus-2 (Tpl2) is a serine/threonine kinase, which regulates the expression of tumour necrosis factor α. The article describes the development of a robust pharmacophore model and the investigation of structure-activity relationship analysis of quinoline-3-carbonitrile derivatives reported for Tpl2 kinase inhibition. A five point pharmacophore model (ADRRR) was developed and used to derive a predictive atom-based 3-dimensional quantitative structure activity relationship (3D-QSAR) model. The obtained 3D-QSAR model has an excellent correlation coefficient value (r(2)= 0.96), Fisher ratio (F = 131.9) and exhibited good predictive power (q(2) = 0.79). The QSAR model suggests that the inclusion of hydrophobic substituents will enhance the Tpl2 kinase inhibition. In addition, H-bond donating groups, negative ionic groups and electron withdrawing groups positively contribute to the Tpl2 kinase inhibition. Further, pharmacophoric model was validated by the receiver operating characteristic curve analysis and was employed for virtual screening to identify six potential Tpl2 kinase inhibitors. The findings of this study provide a set of guidelines for designing compounds with better Tpl2 kinase inhibitory potency.     

3D QSAR studies on T-type calcium channel blockers using CoMFA and CoMSIA

Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on a series of isoxazolyl compounds as a potent T-type calcium channel blockers. A set of 24 structurally similar compounds served to establish the model. Four different conformations of the most active compound were used as template structures for the alignment, three of which were obtained from Catalyst pharmacophore modeling and one by using SYBYL random search option. All CoMFA and CoMSIA models gave cross-validated r(2) (q(2)) value of more than 0.5 and conventional r(2) value of more than 0.85. The predictive ability of the models was validated by an external test set of 10 compounds, which gave satisfactory pred r(2) values ranging from 0.577 to 0.866 for all models. Best predictions were obtained with CoMFA std model of Conformer no: 3 alignment (q(2)=0.756, r(2)=0.963), giving predictive r(2) value of 0.866 for the test set. CoMFA and CoMSIA contour maps were used to analyze the structural features of the ligands accounting for the activity in terms of positively contributing physicochemical properties: steric, electrostatic, hydrophobic and hydrogen bonding fields.     

Pharmacophore generation and atom-based 3D-QSAR of novel quinoline-3-carbonitrile derivatives as Tpl2 kinase inhibitors

Tumour progression locus-2 (Tpl2) is a serine/threonine kinase, which regulates the expression of tumour necrosis factor α. The article describes the development of a robust pharmacophore model and the investigation of structure-activity relationship analysis of quinoline-3-carbonitrile derivatives reported for Tpl2 kinase inhibition. A five point pharmacophore model (ADRRR) was developed and used to derive a predictive atom-based 3-dimensional quantitative structure activity relationship (3D-QSAR) model. The obtained 3D-QSAR model has an excellent correlation coefficient value (r²?=?0.96), Fisher ratio (F?=?131.9) and exhibited good predictive power (q²?=?0.79). The QSAR model suggests that the inclusion of hydrophobic substituents will enhance the Tpl2 kinase inhibition. In addition, H-bond donating groups, negative ionic groups and electron withdrawing groups positively contribute to the Tpl2 kinase inhibition. Further, pharmacophoric model was validated by the receiver operating characteristic curve analysis and was employed for virtual screening to identify six potential Tpl2 kinase inhibitors. The findings of this study provide a set of guidelines for designing compounds with better Tpl2 kinase inhibitory potency.     

QSAR studies on CCR2 antagonists with chiral sensitive hologram descriptors

Chemokines are small molecular weight water-soluble proteins playing a key role in immunomodulation and host-defense mechanisms. CCR2 receptor is targeted for diseases like arthritis, multiple sclerosis, vascular disease, obesity, and type 2 diabetes. Reported, herein are the QSAR studies performed on a diverse set of enantiopure analogues reported as CCR2 antagonists by hologram analysis. The best model highlights the importance of chirality feature in comparison with the other models developed without the chirality. The validated model showed high internal and external predictive power. The robustness of the model was achieved with good statistical r(2) of 0.945 and cross-validated r(cv)(2) of 0.837. The challenging test predictivity of the model was confirmed with r(pred)(2) of 0.807. The fragment fingerprints help in understanding essential pharmacophoric features for CCR2 antagonism and provide basis for SAR of the molecules. The 2D contribution maps with fragment information will be useful for the design of novel CCR2 antagonists having improved efficacy.     

Anti-Trypanosoma cruzi and cytotoxic activities of Eugenia uniflora L

Chagas disease is caused by Trypanosoma cruzi, being considered a public health problem. An alternative to combat this pathogen is the use of natural products isolated from fruits such as Eugenia uniflora, a plant used by traditional communities as food and medicine due to its antimicrobial and biological activities. Ethanolic extract from E. uniflora was used to evaluate in vitro anti-epimastigote and cytotoxic activity. This is the first record of anti-Trypanosoma activity of E. uniflora, demonstrating that a concentration presenting 50% of activity (EC(50)) was 62.76 μg/mL. Minimum inhibitory concentration (MIC) was ≤ 1024 μg/mL. Our results indicate that E. uniflora could be a source of plant-derived natural products with anti-epimastigote activity with low toxicity.     

3D QSAR models for alpha2a-adrenoceptor agonists

Three-dimensional structure-activity relationship studies of alpha2a-adrenoceptor agonists were carried out by Distance Comparison (DISCOthech) and Comparative Molecular Field Analysis (CoMFA) methods to define the pharmacophore and a quantitative model, respectively, of this class of compounds. The statistical validation of the CoMFA model indicates its high predictive performance for binding affinities of new alpha2a-adrenoceptor agonists.     

Biochemical and immunological studies of protein kinase C from Trypanosoma cruzi.

Phorbol ester binding was studied in protein kinase C-containing extracts obtained from Trypanosoma cruzi epimastigote forms. Specific 12-O-tetradecanoyl phorbol 13-acetate, [3H]PMA, or 12,13-O-dibutyryl phorbol, [3H]PDBu, binding activities, determined in T. cruzi epimastigote membranes, were dependent on ester concentration with a Kd of 9x10(-8) M and 11.3x10(-8) M, respectively. The soluble form of T. cruzi protein kinase C was purified through DEAE-cellulose chromatography. Both protein kinase C and phorbol ester binding activities co-eluted in a single peak. The DEAE-cellulose fraction was further purified into three subtypes by hydroxylapatite chromatography. These kinase activity peaks were dependent on Ca2+ and phospholipids and eluted at 40 mM (PKC I), 90 mM (PKC II) and 150 mM (PKC III) phosphate buffer, respectively. Western blot analysis of the DEAE-cellulose fractions, using antibodies against different isoforms of mammalian protein kinase C enzymes, revealed that the parasite expresses high levels of the alpha-PKC isoform. Immunoaffinity purified T. cruzi protein kinase C, isolated with an anti-protein kinase C antibody-sepharose column, were subjected to phosphorylation in the absence of exogenous phosphate acceptor. A phosphorylated 80 kDa band was observed in the presence of Ca2+, phosphatidylserine and diacylglycerol.