Edson Ferreira da Silva

Mechanisms of vanadate-induced cellular toxicity: role of cellular glutathione and NADPH

Besides its insulin-mimetic effects, vanadate is also known to have a variety of physiological and pharmacological properties, varying from induction of cell growth to cell death and is also a modulator of the multidrug resistance phenotype. However, the mechanisms underlying these effects are still not understood. The present report analyzes the mechanisms of vanadate toxicity in two cell lines previously found to have different susceptibilities to this compound. It was shown that catalase and GSH reversed the sensitivity of a vanadate-sensitive cell line and NADPH sensitized vanadate-resistant cells. NADPH also increased the residues of P-Tyr and the induction of Ras protein expression in vanadate-resistant cells, while GSH avoided these effects in vanadate-sensitive cells. Thus, it seems that the effects of vanadate in signal transduction are dependent on NADPH and are related to cell death. Based on the effects observed in the present study it was suggested that once inside the cell, vanadate is reduced to vanadyl in a process dependent on NADPH. Vanadyl then may react with H2O2 generating primarily peroxovanadium species (PV) rather than following the Fenton reaction. The PV compounds formed would be responsible for P-Tyr increase, Ras induction, and cell death. The results obtained also point to vanadate as a possible chemotherapic in the use of multidrug-resistant tumors.

Reduced glutathione protect cells from ouabain toxicity.

It is widely accepted that a prolonged ouabain blockade of the Na(+),K(+)-ATPase makes cells detach from each other and from the substrate, leading to their death and that cellular resistance to ouabain is due to the presence of isoforms of Na(+),K(+)-ATPase with low affinity to this glycoside. In the present work the effect of reduced glutathione in the response of two types of renal cells to ouabain: MDCK, a ouabain-sensitive cell line and Ma104, a ouabain-resistant one, was studied. Glutathione protected MDCK cells from ouabain toxicity and inhibition of glutathione synthesis by L-buthionine-S,R-sulfoximine sensitized Ma104 cells to ouabain. As glutathione is involved with multidrug resistance (MDR) in cells expressing the multidrug resistance-related protein MRP1 and as Ma104 cells have a MDR phenotype, it was investigated whether Ma104 cells express this protein. The expression of the MRP1-mRNA in Ma104 cells was detected by reverse transcriptase-polymerase chain reaction and ribonuclease protection assay, and the protein was detected by Western blotting and immunofluorescence. Treatment of Ma104 cells with ouabain increased MRP1-mRNA expression and altered the localization of MRP1 in these cells. Our results suggest that some cells may have mechanisms to protect themselves from ouabain toxicity and that MRP1 may have a role in controlling the toxic effects of ouabain.

5-Phenyl-2-(benzalhydrazonyl)-1,3,4-thiadiazoles, potential trypanocidal agents: consistent dimer formation via N–H · · · N intermolecular hydrogen bonds

Abstract The molecular and crystal structures of a series of 5-Ph-2-(arylCH=NNH)-1,3,4-thiadiazoles [2: aryl = 4-XC6H4 (X = H [2a], 4-Cl [2b], 4-Br [2c], 4-F3CO [2d], 2-HO [2e], 2-HO-3-MeO [2f] as well as [5-Ph-2-(4-HOC6H4CH=NNH)-1,3,4-thiadiazole]3(H2O)2] [(2g)3 · 2 (H2O)] are reported. The compounds were prepared as part of a study on typanocide reagents as possible treatments for Chagas‘ disease. The asymmetric unit of [(2g)3 · 2 (H2O)] consists of three independent molecules and two water molecules, in contrast to the single molecules comprising the asymmetric units of 2a–2f. In all cases, N–H · · · N intermolecular hydrogen bonding results in the formation of dimers linked by R22(8) rings. As well as the hydrogen-bonded dimers, the molecules of 2a–2f are also linked by other weak interactions including aromatic π–π stacking and C–H · · · X bonds.

Improvement of enantioselective syntheses and chiral high resolution gas chromatographic analyses of (+)-2-allyl-2-carboethoxy-cyclopentanol.

The improvement of the biocatalytic reduction of 2-allyl-carboethoxy-cyclopentanone (2) to the corresponding cyclopentanol derivative (+)-(1R,2R)-(1) was accomplished employing bakers yeast in organic media. This chiral cyclopentanol derivative (1), analyzed by high resolution gas chromatography performed over beta-cyclodextrin stationary phase, was obtained in 38% yield (> 99% e.e.).

Synthesis and antitubercular activity of new L-serinyl hydrazone derivatives.

A series of 32 L-serinyl hydrazone derivatives have been synthesized and evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H37Rv, being also evaluated their cell viabilities in non infected and infected macrophages with Mycobacterium bovis Bacillus Calmette-Guerin (BCG). The compounds 8c, 8e, 8h and 8i, were non-cytotoxic and exhibited an important minimum inhibitory concentration (MIC) activity between 25 and 100 μg/mL, which can be compared with that of the tuberculostatic drug D-cicloserine (5-20 μg/mL).

Crystal structures of 1-hydroxylimidazole and imidazole 1-oxide derivatives

Abstract The N-oxide or 1-hydroxy forms of four solid 1-hydroxy-5-(4-methyl-2-nitroimidazol-2-yl)-4-phenyl-2-(X-phenyl)-imidazole derivatives, 6, have been studied by X-ray crystallography. Compounds, (6: X=4-Br) and (6: X=2-O2N), both recrystallized from EtOH, and (6: X=4-F), recrystallized from EtOCH2CH2OH, were isolated in the 1-hydroxyimidazole form. In contrast, (6: X=H), recrystallized from EtOCH2CH2OH, was obtained in the imidazole N-oxide form. Two independent molecules, Mol A and Mol B, rotamers, are present in the asymmetric unit of the imidazole N-oxide compound, (6: X=H) and are linked into chains of alternating compounds, mainly by N–H···O hydrogen bonds, but also by N–H···N and C–H···O hydrogen bonds and π···π interactions. These chains are linked by other C–H···O and C–H···N hydrogen bonds and π···π interactions into a 3-D arrangement. In the 1-hydroxyimidazole compound, (6: X=2-O2N), classical hydrogen bonds, O1–H1···N3, are the major interactions linking molecules into C(5) chains: weak π···π stacking interactions also link the molecules within the chains. These chains are linked by C–H···O and hydrogen bonds and by N–O···π interactions into a three- dimensional array. The other 1-hydroxyimidazole compounds, (6: X=4-Br) and (6: X=4-F), have similar structures, which differ from that of (6: X=2-O2N). In (6: X=4-Br) and (6: X=4-F), pairs of classical O–H···N hydrogen bonds link molecules into symmetric dimers: these dimers are further stabilized by π···π interactions. Other intermolecular interactions found in both (6: X=4-Br) and (6: X=4-F) are C–H···O hydrogen bond and N–O···π interactions, which link the O–H···N hydrogen bonded dimers into a 3-dimensional array.

Novel Therapeutic Strategies for Chagas` Disease

Chagas’ disease, also called American trypanosomiasis, is one of the most neglected parasitic diseases in the world. An estimated 10 million people are infected worldwide, mostly in Latin America where Chagas disease is endemic. More than 25 million people are at risk of the disease. It is estimated that in 2008 Chagas disease killed more than 10,000 people. Its infectious agent is the protozoan parasite Trypanosoma cruzi with symptoms progressing from mild swelling to intestinal disease and ultimately heart failure. Currently, 2 antiparasitic drugs are recommended for the treatment of chagasic patients: nifurtimox and benznidazole. However, the effectiveness of both varies according to (i) the phase of the disease (acute and early latent infection), (ii) different parasite isolates, (iii) period of treatment and dosage and (iv) age of patient. Also, their well-known toxicity and limited effect make the search for new drugs imperative. Many trypanocidal compounds have been screened in the past few decades and some promising targets have been reported since the introduction of nifurtimox and benznidazole (1960-1970).