Redox Biochemistry and Chemistry最新文献

Peroxynitrite (ONOO⁻/ONOOH) is a short-lived but highly reactive species that is formed in the diffusion-controlled reaction between nitric oxide and the superoxide radical anion. It can oxidize certain biomolecules and has been considered as a key cellular oxidant formed under various pathophysiological conditions. It is crucial to selectively detect and quantify ONOO⁻ to determine its role in biological processes. In this review, we discuss various approaches used to detect ONOO⁻ in cell-free and cellular systems with the major emphasis on small-molecule chemical probes. We review the chemical principles and mechanisms responsible for the formation of the detectable products, and plausible limitations of the probes. We recommend the use of boronate-based chemical probes for ONOO⁻, as they react directly and rapidly with ONOO⁻, they produce minor but ONOO⁻‒specific products, and the reaction kinetics and mechanism have been rigorously characterized. Specific experimental approaches and protocols for the detection of ONOO⁻ in cell-free, cellular, and in vivo systems using boronate-based molecular probes are provided (as shown in Boxes 1-6).

Peroxynitrite is a powerful oxidant formed in vivo in sites where superoxide and nitric oxide coincide. Peroxynitrite is cytotoxic through oxidative modification of target biomolecules that can occur by direct or indirect reactions. Indirect reactions usually involve the generation of peroxynitrite-derived radicals that include nitrogen dioxide, hydroxyl radical, and carbonate radical. All these species have different behaviors in vivo, because of their intrinsic reactivity and how effectively they can be compartmentalized by cellular membranes. In this review, we analyze quantitative information on the estimated half-lives and the corresponding estimated diffusion distances of peroxynitrite, its precursors, and its derived reactive species in vivo. Furthermore, we discuss the permeability of cellular and synthetic lipid membranes to the different species and how effective compartmentalization is achieved for some of them, limiting the biological site of reactions.

HNO (azanone or nitroxyl), formally a product of the one-electron reduction of a nitric oxide, exhibits diverse and unique biological activity. The chemistry, biochemistry, and biological/pharmacological effects of HNO have been studied extensively. Due to rapid dimerization and hence short lifetime in solutions, in chemical and biological studies HNO is typically produced in situ from its thermal donors. To date, a great variety of chemical HNO donors have been synthesized, characterized, and utilized in biological studies. Here, we discuss the chemistry of HNO-releasing compounds, with the emphasis on the complexity of the proposed reaction mechanisms.

Protein tyrosine nitration is a post-translational modification originating from the biological chemistry of nitric oxide. This article highlights key milestones, discusses apparent controversies and perspectives that have emerged in the last 35 years of research on protein tyrosine nitration. Since the execution of nitric oxide signaling is accomplished entirely by protein post translational modifications (PTMs), the prospect that protein tyrosine nitration augments nitric oxide signaling remains an intriguing but incomplete concept deserving further consideration.

Tellurium (Te) is an industrially useful element but its oxyanions, such as tellurite and tellurate, are naturally occurring chemical forms that can become a potential source of toxicity to humans and animals. As a means of mitigating the toxicity of Te oxyanions, the formation of less toxic zero-valent elemental Te (Te⁰) nanostructures has been observed in various species including bacteria, fungi, green algae, and higher plants. In this study, we investigated the formation of Te⁰ nanorods in human hepatoma HepG2 cells. We detected electron-dense Te nanorods in lysosomes after exposure to potassium tellurite. The amount of Te nanorods in the cells gradually increased with the exposure period. Interestingly, the amount of Te in the insoluble fraction of the culture supernatant was approximately 10 times higher than that in HepG2 cells, suggesting that extracellular reducing agents originating from HepG2 cells transformed tetravalent Te (TeO₃²⁻) into Te⁰ in the culture medium. As an extracellular reducing agent, sulfane sulfur species were considered responsible for the reduction of Te(IV). Then, by inhibiting cystathionine γ-lyase with propargylglycine (PPG), we were able to reduce the amount of sulfane sulfur species generated in the cells. In the presence of PPG, the amount of insoluble Te in the culture supernatant, which was possibly composed of Te⁰ nanorods, was significantly decreased. The results suggest that sulfane sulfur species are involved in the formation of Te⁰ nanorods from tellurite in mammalian cells and play a critical role in the amelioration of Te oxyanion toxicity.

Nitration is a well-established post-translational modification of selected free amino acids, as well as proteins, lipids and nucleic acids. Considerable evidence is now available for the formation of long-lived species containing an added –NO₂ function on the aromatic rings of tyrosine (Tyr) and tryptophan (Trp) residues (both free and on proteins), to purine nucleobases (and particularly guanine), and to unsaturated lipids within biological systems. Multiple potential mechanisms that give rise to these nitrated species have been identified including reactions of the potent oxidant and nitrating species peroxynitrous acid/peroxynitrite (ONOOH/ONOO⁻) and via oxidative reactions of heme proteins/enzymes (e.g. peroxidases) with the biologically-relevant anion nitrite (NO₂⁻). ^•NO₂ is likely to be a key intermediate, though involvement of HNO₂, NO₂⁺ and NO₂Cl has also been proposed. The resulting nitrated products have been widely employed as qualitative or quantitative biomarkers of nitration events in vitro and in vivo. Increasing evidence suggests that at least some of these products are not benign species, with evidence for pro-inflammatory actions. In this article the mechanisms and role of nitration, and particularly that on proteins within the artery wall, in cardiovascular disease is discussed, together with emerging data suggesting that low levels of nitration occur within biological systems in the absence of added oxidants. Both stimulated and endogenous nitration may play a role in modulating cell signaling, alter the structure and function of both cellular- and extracellular proteins, and contribute to various inflammatory pathologies, including atherosclerosis.

Nitro-oxidative stress affects DNA, leading to special chemical modifications of nucleobases and deoxyribose, impacting DNA integrity and stability. Because of the importance of the topic, the state of the knowledge on purine, nucleoside, and DNA nitration by the reactive nitrogen species peroxynitrite was reviewed. Following a description of the chemical and physicochemical characteristics of purines and peroxynitrite, purine nitro-oxidation and its products, the reaction mechanisms, and the recently reported kinetic behavior of 8-NitroGua formation are discussed. Moreover, novel computational studies report structural and conformational DNA changes resulting from the formation of guanine nitration products. Given the relevance of the subject, surprisingly few publications deal with this topic, even considering the past five years.

This review explores the interaction between nitric oxide-derived reactive species and unsaturated fatty acids, leading to the formation of electrophilic nitroalkenes, named nitro-fatty acids (NO₂-FA). These species serve as endogenously produced anti-inflammatory signaling mediators, demonstrating protective effects in pre-clinical animal disease models. The discussion herein focuses on the cell signaling actions of NO₂-FA, drawing insights from both existing knowledge and recent in vivo data. Additionally, this review addresses the potential pharmacological utility of NO₂-FA and ongoing trials, highlighting their promising prospects based on the gathered information.

Dinitrogen trioxide (N₂O₃) mediates low-molecular weight and protein S- and N-nitrosation, with recent reports suggesting a role in the formation of nitrating intermediates as well as in nitrite-dependent hypoxic vasodilatation. However, the reactivity of N₂O₃ in biological systems results in an extremely short half-life that renders this molecule essentially undetectable by currently available technologies. As a result, evidence for in vivo N₂O₃ formation derives from the detection of nitrosated products as well as from in vitro kinetic determinations, isotopic labeling studies, and spectroscopic analyses. This review will discuss mechanisms of N₂O₃ formation, reactivity and decomposition, as well as address the role of sub-cellular localization as a key determinant of its actions. Finally, evidence will be discussed supporting different roles for N₂O₃ as a biologically relevant signaling molecule.

The peroxiredoxins are an important antioxidant protein family and their ability to neutralise oxidants is regularly investigated using horse radish peroxidase in a competition assay system. In this method, the rate constant of a peroxiredoxin is calculated from the fractional inhibition of horse radish peroxidase activity caused by competition with the peroxiredoxin for an oxidant substrate. We developed a model capable of simulating this assay and, using this model, demonstrate that the fractional inhibition calculation significantly and systematically mis-estimates the rate constant under fairly common conditions. We go on to develop a method for fitting simulated assay time-courses to experimental data directly, which significantly outperforms the fractional inhibition method yielding more accurate results. Based on our findings, we recommend using the direct fitting approach to determine peroxidase rate constants from horseradish peroxidase experiments.