No abstract

Aerobic metabolism brings inexorably the production of reactive oxygen species (ROS), which are counterbalanced by intrinsic antioxidant defenses avoiding deleterious intracellular effects. Redox balance is the resultant of metabolic functioning under environmental inputs (i.e. diet, pollution) and the activity of intrinsic antioxidant machinery. Monitoring of intracellular hydrogen peroxide has been successfully achieved by redox biosensor advent; however, to track the intrinsic disulfide bond reduction capacity represents a fundamental piece to understand better how redox homeostasis is maintained in living cells.In the present work, we compared the informative value of steady-state measurements and the kinetics of HyPer, a H2O2-sensitive fluorescent biosensor, targeted at the cytosol, mitochondrion and endoplasmic reticulum. From this set of data, biosensor signal recovery from an oxidized state raised as a suitable parameter to discriminate reducing capacity of a close environment. Biosensor recovery was pH-independent, condition demonstrated by experiments on pH-clamped cells, and sensitive to pharmacological perturbations of enzymatic disulfide reduction. Also, ten human cell lines were characterized according their H2O2-pulse responses, including their capacity to reduce disulfide bonds evaluated in terms of their migratory capacity.Finally, cellular migration experiments were conducted to study whether migratory efficiency was associated with the disulfide reduction activity. The migration efficiency of each cell type correlates with the rate of signal recovery measured from the oxidized biosensor. In addition, HyPer-expressing cells treated with N-acetyl-cysteine had accelerated recovery rates and major migratory capacities, both reversible effects upon treatment removal. Our data demonstrate that the HyPer signal recovery offers a novel methodological tool to track the cellular impact of redox active biomolecules.

Most of the biological impacts of Vitamin E, including the redox effects, have been raised from studies with α-tocopherol only, despite the fact that tocopherol-containing foods carry mixed tocopherol isomers. Here, we investigated the cellular mechanisms involved in the immediate antioxidant responses evoked by α-, γand δ-tocopherol in Caco-2 cells. In order to track the cytosolic redox impact, we performed imaging on cells expressing HyPer, a fluorescent redox biosensor, while cytosolic calcium fluctuations were monitored by means of Fura-2 dye and imaging. With this approach, we could observe fast cellular responses evoked by the addition of α-, γand δ-tocopherol at concentrations as low as 2.5 µM. Each isomer induced rapid and consistent increases in cytosolic calcium with fast kinetics, which were affected by chelation of extracellular Ca 2+ , suggesting that tocopherols promoted a calcium entry upon the contact with the plasma membrane. In terms of redox effects, δ-tocopherol was the only isomer that evoked a significant change in the HyPer signal at 5 µM. By mimicking Ca 2+ entry with ionomycin and monensin, a decline in the HyPer signal was induced as well. Finally, by silencing calcium with 1,2-bis(o-aminophenoxy)ethane-N,N,N ,N -tetraacetic acid (BAPTA), an intracellular Ca 2+ chelator, none of the isomers were able to induce redox changes. Altogether, our data indicate that an elevation in cytoplasmic Ca 2+ is necessary for the development of a tocopherol-induced antioxidant impact on the cytoplasm of Caco-2 cells reported by HyPer biosensor.

Sucralose is a non-caloric artificial sweetener widely used in processed foods that reportedly affects energy homeostasis through partially understood mechanisms. Mitochondria are organelles fundamental for cellular bioenergetics that are closely related to the development of metabolic diseases. Here, we addressed whether sucralose alters mitochondrial bioenergetics in the enterocyte cell line Caco-2. Sucralose exposure (0.5–50 mM for 3–24 h) increased cellular reductive power assessed through MTT assay, suggesting enhanced bioenergetics. Low doses of sucralose (0.5 and 5 mM) for 3 h stimulated mitochondrial respiration, measured through oxygraphy, and elevated mitochondrial transmembrane potential and cytoplasmic Ca2+, evaluated by fluorescence microscopy. Contrary to other cell types, the increase in mitochondrial respiration was insensitive to inhibition of mitochondrial Ca2+ uptake. These findings suggest that sucralose alters enterocyte energy homeostasis, contributing to its effects on organismal metabolism.

Las legumbres han sido históricamente consideradas una apetecible fuente de proteínas y fibra. En estos tiempos caracterizados por una tendencia epidemiológica al sobrepeso y a la obesidad, corregir hábitos poco saludables es prioritario. La incorporación de legumbres al menú cotidiano como sustituto de carnes podría significar, a mediano y largo plazo, aminorar la prevalencia de enfermedades crónicas no-transmisibles. Este trabajo ofrece una mirada actualizada de algunos constituyentes claves presentes en las semillas de legumbres frecuentemente consumidas por la población chilena: porotos (Phaseolus vulgaris L.), lentejas (Lens culinaris L.); garbanzos (Cicer arietinum L.) y arvejas (Pisum sativum L.). Con una perspectiva realista, se expone el efecto del remojo y la cocción, ambos procesos simples utilizados frecuentemente en su preparación. Además, se ha considerado la digestión y fermentación como procesos claves en la liberación de compuestos bioactivos y su interacción con la microbiota residente en la porción distal del tracto gastrointestinal. Finalmente, estudios epidemiológicos en conjunto con datos experimentales permiten obtener una idea de los mecanismos que subyacen al impacto nutricional que tiene el consumo habitual de legumbres.