Karen Lilian Schott

Synthesis and biological evaluation of new nitrogen-containing diselenides

The antioxidant properties of organoselenium compounds have been extensively investigated with the aim of developing new drugs, since oxidative stress is responsible for a variety of chronic human diseases. Herein, we reported the synthesis of new nitrogen-containing diselenides by a simple and efficient synthetic route. The products were obtained in good to excellent yields and their identification and characterization were achieved by NMR and HRMS techniques. The new derivatives may represent promising structures with different biological activities, which can act against oxidative stress through diverse mechanisms of action. The glutathione peroxidase-like assay (GPx-like activity) of the new synthesized compounds indicated that they reduced H2O2 to water at the expense of PhSH. The best results were obtained with diselenide 2b, which was 9 times more active than the standard organoselenium drug ebselen and, in contrast, this compound was not reduced by hepatic TrxR. All of the new compounds inhibited Fe(II)-induced TBARS.

Methotrexate-Related Response on Human Peripheral Blood Mononuclear Cells May Be Modulated by the Ala16Val-SOD2 Gene Polymorphism

Methotrexate (MTX) is a folic acid antagonist used in high doses as an anti-cancer treatment and in low doses for the treatment of some autoimmune diseases. MTX use has been linked to oxidative imbalance, which may cause multi-organ toxicities that can be attenuated by antioxidant supplementation. Despite the oxidative effect of MTX, the influence of antioxidant gene polymorphisms on MTX toxicity is not well studied. Therefore, we analyzed here whether a genetic imbalance of the manganese-dependent superoxide dismutase (SOD2) gene could have some impact on the MTX cytotoxic response. An in vitro study using human peripheral blood mononuclear cells (PBMCs) obtained from carriers with different Ala16Val-SOD2 genotypes (AA, VV and AV) was carried out, and the effect on cell viability and proliferation was analyzed, as well as the effect on oxidative, inflammatory and apoptotic markers. AA-PBMCs that present higher SOD2 efficiencies were more resistance to high MTX doses (10 and 100 µM) than were the VV and AV genotypes. Both lipoperoxidation and ROS levels increased significantly in PBMCs exposed to MTX independent of Ala16Val-SOD2 genotypes, whereas increased protein carbonylation was observed only in PBMCs from V allele carriers. The AA-PBMCs exposed to MTX showed decreasing SOD2 activity, but a concomitant up regulation of the SOD2 gene was observed. A significant increase in glutathione peroxidase (GPX) levels was observed in all PBMCs exposed to MTX. However, this effect was more intense in AA-PBMCs. Caspase-8 and -3 levels were increased in cells exposed to MTX, but the modulation of these genes, as well as that of the Bax and Bcl-2 genes involved in the apoptosis pathway, presented a modulation that was dependent on the SOD2 genotype. MTX at a concentration of 10 µM also increased inflammatory cytokines (IL-1β, IL-6, TNFα and Igγ) and decreased the level of IL-10 anti-inflammatory cytokine, independent of SOD2 genetic background. The results suggest that potential pharmacogenetic effect on the cytotoxic response to MTX due differential redox status of cells carriers different SOD2 genotypes.

Quantification of reduced glutathione by HPLC‐UV in erythrocytes of hemodialysis patients

Reduced glutathione (GSH) is a well-known multifunctional antioxidant. Its depletion is linked to a number of pathologies, such as renal insufficiency. Feasible methodologies in clinical chemistry are vital. Therefore a methodology for GSH quantification was optimized and validated by HPLC-UV. Important aspects such as acid deproteinization and GSH stability were established. The erythrocytes were hemolyzed, deproteinized, derivatized with 5,5-dithio-bis (2-nitrobenzoic) acid and analyzed using HPLC, on an RP18 gradient elution, lambda=330 nm. The method was applied to hemodialysis patients (n=75) compared with healthy subjects (n=40). The assay was linear from 0.5 to 3.0 mm (r2>0.99). The intra- and inter-run reproducibilities were obtained with CV%<10%. The accuracy (bias %) ranged from 1.32 to -6.38%, and the recovery was >94%. The derivatized sample was stable for 60 days at -20 degrees C. The GSH levels in hemodialysis patients showed a significant increase compared with healthy subjects (p<0.05) and an inverse correlation with age (r=-0.286; p=0.013) was found. This method used UV detection, reduction of the phosphate concentration in the mobile phase and effective protein removal with trichloroacetic acid. The method proved to be reproducible, precise, accurate and stable. Thus, it can be suggested for routine laboratory tests for the verification of physiopathological conditions.

Aspectos gerais e diagnóstico clinicolaboratorial da intoxicação por paraquat

INTRODUCTION: Paraquat is a herbicide widely used in agriculture. It is a very toxic product, fatally poisoning mainly by the lack of an efficient antidote to revert the clinical state. FISIOPATHOLOGY: Toxicological effects are decurrent of oxidative stress. The most important target organ is the lung, which can display edema, hemorrhage, interstitial inflammation and fibroses, culminating in serious respiratory failure and death. Moreover, it is nephrotoxic, hepatotoxic, miotoxic and neurotoxic. TREATMENT: Besides aiming the decrease of absorption and stimulating the excretion of absorbed paraquat, the poisoning treatment nowadays is based on measures that decrease oxidative stress using antioxidants, consequently reverting clinical state, mainly the pulmonary. Diagnostic methods: Among the available quantitative methods, the chromatographic are the most reported ones for biological samples. However, capillary electrophoresis and immunoassay methods can be used. Immunoassays stand out for being typically found in hospital laboratories, while chromatographic and electrophoretic methods are not. On the other hand, a simple and fast urinary reaction with sodium dithionite is very utilized because it is predictive in acute poisoning suspect. CONCLUSION: In the presence of high morbimortality potential in paraquat intoxications, the reversion of pulmonary toxicity with antioxidants is extensively studied, but a specific antidote is not established. In laboratorial diagnostic, chromatographic, electrophoretic and immunologic techniques are applied to paraquat quantification, although in clinical toxicology the sodium dithionite reaction is still significant.

Ciclosporina A e tacrolimus: uma revisão

INTRODUCTION: Therapeutic monitoring of immunosuppressants cyclosporine A (CsA) and tacrolimus (FK506) is indispensable to maintain stable levels of these drugs, avoiding graft rejection in the transplanted patient in the case of low dosage, or toxicity in high dosage, and allowing monitoring of individual treatment. BACKGROUND: In the 80s, the introduction of the potent immunosuppressive drugs CsA and FK506 reduced the incidence of rejection episodes after solid organ transplantation. MECHANISM OF ACTION: CsA and FK506 have distinct chemical structures but similar mechanisms of action, inhibiting the transcription of the first signal for T-lymphocyte activation. TOXICITY: The major side effects associated with CsA and FK506 therapies are nephrotoxicity and neurological disturbances. However, clinical studies demonstrate that FK506 is a potent alternative to CsA due to its lower nephrotoxicity and reversible neurotoxicity when the dosage is decreased. ANALYTICAL METHODOLOGY: For routine monitoring of CsA, the high-performance liquid chromatography with ultraviolet detection (HPLC-UV) was replaced by the radioimmunoassay (RIA) and monoclonal antibody-based fluorescence polarization immunoassay (mFPIA). For the assessment of FK506, it is consensus that highly specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) is the reference method, although the microparticle enzyme immunoassay (MEIA) and the enzyme-linked immunosorbent assay (ELISA) are currently used for routine monitoring. CONCLUSION: There is a tendency to substitute CsA by FK506 at immunosuppressive regimens, but this is not a consensus yet. The analytical methodology for CsA analysis is well established in the clinical laboratory, but further studies are needed to define the best methodologies for routine FK506 analysis.

Influência de desproteinizantes ácidos na quantificação da glutationa reduzida eritrocitária por CLAE-UV

Large differences in reduced glutathione (GSH) levels have been found in different investigations, also in healthy people. GSH oxidation in vitro has been associated with sample acidification in the presence of oxihemoglobin. In this work, the influence of different acids on GSH determination utilizing HPLC with UV detection was evaluated. The results showed that metaphosphoric acid and sulfosalicylic acid were inadequate for analysis, because metaphosphoric acid showed to be inefficient for deproteinization and with sulfosalicylic acid loss of GSH was observed. Trichloroacetic acid did not effect GSH quantification, since the deproteinized form was immediately derivatized with 5, 5´-dithio-bis (2-nitrobenzoic) acid. Methods with TCA deproteinization presented linear results from 0.5 to 3.0 mM. The correlation coefficient between aqueous curves and GSH spiked RBC exceeded 0.99. Precision calculations showed CV lower than 10% and bias within ± 10% for concentrations of 0.5; 1.5 and 3.0 mM GSH. The recovery was higher than 94%. Moreover, GSH blood concentrations were independent of hemoglobin concentrations.

Brazil nut improves the oxidative metabolism of superoxide-hydrogen peroxide chemically-imbalanced human fibroblasts in a nutrigenomic manner

There are some genes associated to the risk of chronic diseases that present potential nutrigenetic response, such as the human manganese-dependent superoxide dismutase gene (Val16Ala-SOD2, rs4880) for which homozygous genotypes (VV and AA) are associated with higher basal superoxide (S) and hydrogen peroxide (HP) levels, respectively. It is possible that the VV- and AA-imbalance could be attenuated by selenium(Se)-rich foods such as Brazil nut (BN). To test this hypothesis, we conducted an in vitro protocol triggering a chemical S-HP imbalance by exposure of dermal fibroblast cells (HFF-1) to paraquat, which generates high S levels (VV-like treatment) and porphyrin (MnTBAP), which generates high HP levels (AA-like treatment). Modulation of cell growth and pro-oxidative and antioxidant markers were evaluated. BN aqueous extract (BNAE) most effective concentration which increased cell growth and decreased oxidative metabolism indicators of imbalanced cells was 75 ng Se/mL. However, this effect was not directly affected by the S-HP imbalance: in AA-SOD2-like cells, thioredoxin reductase (TrxR-1) gene was upregulated and in VV-SOD2-like cells an upregulation of glutathione peroxidase (GPx-1) gene expression was observed, however, this regulation occured in a homeostatic manner. These results suggest that BNAE was able to minimize negative effects in both directions of the S-HP imbalance, by modulation of different oxidative-metabolic pathways.