Are Reactive Oxygen Species Important Mediators of Vascular Dysfunction?

Reactive Oxygen Species (ROS) are reactive derivatives of oxygen metabolism. The ROS generation can be mediated by distinctive enzymatic systems including NADPH oxidases. The components of this enzyme are expressed in endothelial and vascular smooth muscle cells, adventitial fibroblasts, and infiltrating monocytes/macrophages. Oxidative stress is a molecular dysregulation in ROS generation/elimination, which plays a key role in the development of vascular dysfunction in distinctive conditions including hypertension. It is characterized by vascular inflammation, a loss of NO bioavailability and endothelial dysfunction. Considering that oxidative stress is a key mediator of vascular dysfunction, antioxidant therapy with classic antioxidants seemed to be a promising alternative for the treatment of vascular diseases. In this sense, some commonly used drugs for the treatment of cardiovascular diseases such as Angiotensin Converting Enzyme (ACE) inhibitors or angiotensin receptor AT1 antagonists showed antioxidant effects that might have contributed, at least in part, to the beneficial effects of these drugs on the treatment of cardiovascular diseases. The effectiveness of these drugs shows that ROS are in fact important mediators of vascular dysfunction and that angiotensin II plays a critical role in such response.

Gradiente de saturação de oxigênio e concentração de lactato entre átrio direito e artéria pulmonar no pós-operatório imediato de cirurgia cardíaca com circulação extracorpórea / Oxygen saturation and lactate concentration gradient from the right atrium to the pulmonary artery in the immediate postoperative following cardiac surgery with extracorporeal circulation

RESUMO Objetivo: Caracterizar as modificações na concentração sanguínea do lactato e da saturação de oxigênio em pacientes no pós-operatório imediato de cirurgia cardíaca com circulação extracorpórea. Métodos: Foram coletadas amostras de sangue de 35 pacientes, de forma rápida e aleatória, do acesso arterial e das portas proximal e distal de um cateter pulmonar. Resultados: Não foram verificadas diferenças estatisticamente significantes entre saturação de oxigênio no átrio direito (72% ± 0,11%) e na artéria pulmonar (71% ± 0,08%). A concentração sanguínea de lactato no átrio direito foi de 1,7mmol/L ± 0,5mmol/L, enquanto na artéria pulmonar esta concentração foi de 1,6mmol/L ± 0,5mmol/L (p < 0,0005). Conclusão: A diferença entre as concentrações sanguíneas de lactato no átrio direito e na artéria pulmonar pode ser consequência da baixa concentração de lactato no sangue do seio coronário, já que o lactato é um importante substrato para o miocárdio durante este período. A ausência de diferenças entre saturação sanguínea de oxigênio no átrio direito e na artéria pulmonar sugere extração de oxigênio mais baixa pelo miocárdio, em razão do menor consumo de oxigênio.

ABSTRACT Objective: This prospective study aimed to characterize the changes in blood lactate concentration and blood oxygen saturation in patients during the immediate postoperative period of cardiac surgery with extracorporeal circulation. Methods: Blood samples were collected from 35 patients in a rapid and random order from the arterial line and from the proximal and distal port of a pulmonary artery catheter. Results: The results showed no statistically significant differences between the blood oxygen saturation in the right atrium (72% ± 0.11%) and the blood oxygen saturation in the pulmonary artery (71% ± 0.08%). The blood lactate concentration in the right atrium was 1.7mmol/L ± 0.5mmol/L, and the blood lactate concentration in the pulmonary artery was 1.6mmol/L ± 0.5mmol/L (p < 0.0005). Conclusion: The difference between the blood lactate concentration in the right atrium and the blood lactate concentration in the pulmonary artery might be a consequence of the low blood lactate concentration in the blood from the coronary sinus, as it constitutes an important substrate for the myocardium during this period. The lack of differences between the blood oxygen saturation in the right atrium and the percentage of blood oxygen saturation in the pulmonary artery suggests a lower oxygen extraction by the myocardium given a lower oxygen consumption.

Cloning, Expression and Characterization of Recombinant, NADH Oxidase from Giardia lamblia.

The NADH oxidase family of enzymes catalyzes the oxidation of NADH by reducing molecular O2 to H2O2, H2O or both. In the protozoan parasite Giardia lamblia, the NADH oxidase enzyme (GlNOX) produces H2O as end product without production of H2O2. GlNOX has been implicated in the parasite metabolism, the intracellular redox regulation and the resistance to drugs currently used against giardiasis; therefore, it is an interesting protein from diverse perspectives. In this work, the GlNOX gene was amplified from genomic G. lamblia DNA and expressed in Escherichia coli as a His-Tagged protein; then, the enzyme was purified by immobilized metal affinity chromatography, characterized, and its properties compared with those of the endogenous enzyme previously isolated from trophozoites (Brown et al. in Eur J Biochem 241(1):155-161, 1996). In comparison with the trophozoite-extracted enzyme, which was scarce and unstable, the recombinant heterologous expression system and one-step purification method produce a stable protein preparation with high yield and purity. The recombinant enzyme mostly resembles the endogenous protein; where differences were found, these were attributable to methodological discrepancies or artifacts. This homogenous, pure and functional protein preparation can be used for detailed structural or functional studies of GlNOX, which will provide a deeper understanding of the biology and pathogeny of G. lamblia.

Copper-induced intra-specific oxidative damage and antioxidant responses in strains of the brown alga Ectocarpus siliculosus with different pollution histories.

Inter- and intra-specific variation in metal resistance has been observed in the ecologically and economically important marine brown macroalgae (Phaeophyceae), but the mechanisms of cellular tolerance are not well elucidated. To investigate inter-population responses of brown seaweeds to copper (Cu) pollution, the extent of oxidative damage and antioxidant responses were compared in three strains of the filamentous brown seaweed Ectocarpus siliculosus, the model organism for the algal class Phaeophyceae that diverged from other major eukaryotic groups over a billion year ago. Strains isolated from locations with different pollution histories (i.e. LIA, from a pristine site in Scotland; REP and Es524 from Cu-contaminated sites in England and Chile, respectively) were exposed to total dissolved Cu concentrations (CuT) of up to 2.4 µM (equivalent to 128 nM Cu(2+)) for 10 d. LIA exhibited oxidative stress, with increases in hydrogen peroxide (H2O2) and lipid peroxidation (measured as TBARS levels), and decreased concentrations of photosynthetic pigments. Es524 presented no apparent oxidative damage whereas in REP, TBARS increased, revealing some level of oxidative damage. Adjustments to activities of enzymes and antioxidant compounds concentrations in Es524 and REP were strain and treatment dependent. Mitigation of oxidative stress in Es524 was by increased activities of superoxide dismutases (SOD) at low CuT, and catalase (CAT) and ascorbate peroxidase (APX) at all CuT, accompanied by higher levels of antioxidants (ascorbate, glutathione, phenolics) at higher CuT. In REP, only APX activity increased, as did the antioxidants. For the first time evidence is presented for distinctive oxidative stress defences under excess Cu in two populations of a species of brown seaweed from environments contaminated by Cu.