Nitro-Triarylmethyl Radical as Dual Oxygen and Superoxide Probe

Superoxide radical is involved in numerous physiological and pathophysiological processes. Tetrathiatriarylmethyl (TAM) radicals are knows to react with superoxide allowing measurement of superoxide production in biological media. We report the synthesis of a Nitro conjugated TAM radical showing a rate constant of 7 × 105 M−1s−1 which is two order of magnitude higher than other TAMs allowing high sensitivity measurement of superoxid

Dioxygen Binding and Sensing Proteins

Oxygen binding proteins (O2BIP) have been actively investigated over the last five decades due to their rich redox chemistry and function as O2 carriers in blood cells, as well as their function as gasotransmitters and sensors that modulate cellular signaling. A series of meetings on the periodic advances in the knowledge gained in the field of globin structure and function are conducted typically on a biannual basis. In the fall of 2018, the XXth International Conference was conducted, and very important papers with breakthrough discoveries were presented and very enthusiastically discussed. This was yet another highly successful meeting in the series. Select papers from this meeting were recently reviewed, updated and published over several issues of Antioxidants and Redox Signaling (ARS), as forum papers communicating the latest advances in this important area of redox biology. This forum editorial introduces these articles, and highlights their scientific significance in advancing the field. Each of these articles grew out of lectures presented in the meeting, and appears either as an original contribution or a comprehensive review in the journal. Overall, the articles published in the forum provide in-depth details on the recent developments in the field as well as point the way to future directions. These forum papers thus serve as an important summary of progress and the ongoing direction of this field, and serve to highlight recent advances in our understanding of O2BIP

Role of Nrf2 signaling in regulation of antioxidants and phase 2 enzymes in cardiac fibroblasts: Protection against reactive oxygen and nitrogen species-induced cell injury

AbstractUnderstanding the molecular pathway(s) of antioxidant gene regulation is of crucial importance for developing antioxidant-inducing agents for the intervention of oxidative cardiac disorders. Accordingly, this study was undertaken to determine the role of Nrf2 signaling in the basal expression as well as the chemical inducibility of endogenous antioxidants and phase 2 enzymes in cardiac fibroblasts. The basal expression of a scope of key cellular antioxidants and phase 2 enzymes was significantly lower in cardiac fibroblasts derived from Nrf2−/− mice than those from wild type control. These include catalase, reduced glutathione (GSH), glutathione reductase (GR), GSH S-transferase (GST), and NAD(P)H:quinone oxidoreductase-1 (NQO1). Incubation of Nrf2+/+ cardiac fibroblasts with 3H-1,2-dithiole-3-thione (D3T) led to a significant induction of superoxide dismutase (SOD), catalase, GSH, GR, glutathione peroxidase (GPx), GST, and NQO1. The inducibility of SOD, catalase, GSH, GR, GST, and NQO1, but not GPx by D3T was completely abolished in Nrf2−/− cells. The Nrf2−/− cardiac fibroblasts were much more sensitive to reactive oxygen and nitrogen species-mediated cytotoxicity. Upregulation of antioxidants and phase 2 enzymes by D3T in Nrf2+/+ cardiac fibroblasts resulted in a dramatically increased resistance to the above species-induced cytotoxicity. In contrast, D3T-treatment of the Nrf2−/− cells only provided a slight cytoprotection. Taken together, this study demonstrates for the first time that Nrf2 is critically involved in the regulation of the basal expression and chemical induction of a number of antioxidants and phase 2 enzymes in cardiac fibroblasts, and is an important factor in controlling cardiac cellular susceptibility to reactive oxygen and nitrogen species-induced cytotoxicity

Electron paramagnetic resonance evidence that cellular oxygen toxicity is caused by the generation of superoxide and hydroxyl free radicals

AbstractCells require molecular oxygen for the generation of energy through mitochondrial oxidative phosphorylation; however, high concentrations of oxygen are toxic and can cause cell death. A number of different mechanisms have been proposed to cause cellular oxygen toxicity. One hypothesis is that reactive oxygen free radicals may be generated; however free radical generation in hyperoxic cells has never been directly measured and the mechanism of this radical generation is unknown. In order to determine if cellular oxygen toxicity is free radical mediated, we applied electron paramagnetic resonance, EPR, spectroscopy using the spin trap 5,5′-dimethyl-1-pyrroline-N-oxide, DMPO, to measure free radical generation in hyperoxic pulmonary endothelial cells. Cells in air did not give rise to any detectable signal. However, cells exposed to 100% O2 for 30 min exhibited a prominent signal of trapped hydroxyl radical, DMPO-OH, while cell free buffer did not give rise to any detectable radical generation. This cellular radical generation was demonstrated to be derived from the superoxide radical since the observed signal was totally quenched by superoxide dismutase, but not by equal concentrations of the denatured enzyme. It was confirmed that the hydroxyl radical was generated since in the presence of ethanol the CH3·CH(OH) radical was formed. Loss of cell viability as measured by uptake of trypan blue dye was observed paralleling the measured free radical generation. Thus, superoxide and hydroxyl radicals are generated in hyperoxic pulmonary endothelial cells and this appears to be an important mechanism of cellular oxygen toxicity