Selenium methylselenocysteine (Se-MeSeCys) is a common selenocompound in the diet with a tested chemopreventive effect. This study investigated the potential protective effect of Se-MeSeCys against a chemical oxidative stress induced by tert-butyl hydroperoxide (t-BOOH) on human hepatoma HepG2 cells. Speciation of selenium derivatives by liquid chromatography-inductively coupled plasma mass spectrometry depicts Se-MeSeCys as the only selenocompound in the cell culture. Cell viability (lactate dehydrogenase) and markers of oxidative status--concentration of reduced glutathione (GSH) and malondialdehyde (MDA), generation of reactive oxygen species (ROS) and activity of the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GR)--were evaluated. Pretreatment of cells with Se-MeSeCys for 20 h completely prevented the enhanced cell damage, MDA concentration and GR and GPx activity and the decreased GSH induced by t-BOOH but did not prevent increased ROS generation. The results show that treatment of HepG2 cells with concentrations of Se-MeSeCys in the nanomolar to micromolar range confers a significant protection against an oxidative insult.

No abstract

Mercury toxicity and its implications in development are a major concern, due to the major threat to ecosystems and human health that this compound represents. Although some of the effects of methylmercury (MeHg) exposure have been extensively studied, the molecular mechanisms of interaction between this compound and developing organisms are still not completely understood. To provide further insights into these mechanisms, we carried out a quantitative proteomic study (iTRAQ) using zebrafish larvae exposed to 5 μg L(-1) and 25 μg L(-1) MeHg as a model. In this study, a multidimensional approach combining isoelectric focusing (IEF) and strong cation exchange (SCX) followed by reversed phase liquid chromatography prior to MALDI TOF/TOF analysis was employed, which resulted in a substantial increase in proteome coverage. Among the proteins identified, 71 were found de-regulated by more than 1.5-fold, and implicated in embryonic development, protein synthesis, calcium homeostasis and energy production. Furthermore, morphological and histological analysis of exposed larvae was carried out, reflecting changes such as smaller swim bladder, remaining yolk, bent body axis and accumulation of blood in the heart, among others.

No abstract

This paper provides first quantitative speciation data for chromium in tobacco and tobacco smoke by using complementary HLPC-ICP-MS and XANES.