Redox Biochemistry and Chemistry最新文献

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.

This review focuses on HNO, a molecule of immense chemical and biological importance that has intrigued scientists for decades. Despite its elusive and transient nature, HNO may play an important role in various physiological processes, particularly in cardiovascular regulation. This review thoroughly examines the formation, chemical properties, and biological significance of HNO and highlights ongoing research efforts to unravel its mysteries. Challenges in studying HNO arise from its high reactivity, short half-life, and complex interactions with other nitrogen oxides, particularly nitric oxide. Detection and quantification of HNO in biological systems pose difficulties, prompting the development of advanced techniques. Active research into endogenous HNO formation is revealing intricate pathways within biological systems, the elucidation of which is crucial for exploiting its therapeutic potential. The multifaceted role of HNO in cardiovascular regulation, influencing vasorelaxation, blood pressure reduction, and enhanced cardiac contractility, underscores its profound impact on the circulatory system. Ongoing research holds promise for treating conditions such as hypertension and heart failure. As clinical applications expand, HNO research may unlock treatments for cardiovascular disease, inflammatory disorders, and cancer. The recent discovery of endogenous HNO production in plants adds a new dimension. While numerous clues have emerged, the scientific saga underscores that mysteries persist, evolve, and beckon to perpetual exploration in the realm of science.

The production of reactive oxygen species and oxidative stress promote β-cell dysfunction and impair insulin secretion, thereby contributing to the pathogenesis of type 2 diabetes mellitus (T2DM). The nucleobase guanine is highly sensitive to oxidation, which results in the formation of 8-oxoguanosine (8oxoG) and 8-oxodeoxyguanosine (8oxodG). The urinary excretion of 8oxoG is associated with the risk of mortality in people with T2DM, including from diabetic complications such as cardiovascular disease. However, the cellular mechanisms responsible for this association are poorly defined. Therefore, in this study, we examined the effect of 8oxoG, 8oxodG and other oxidized guanosine derivatives, on the INS-1E β-cell line. Exposure of INS-1E cells to 8oxoG and 8oxodG decreased metabolic activity and promoted cell death by apoptosis. The change in cell viability was similar to that induced by treatment of INS-1E cells with the inflammatory cytokines interleukin 1β (Il-1β) and tumour necrosis factor α (TNFα). Changes in mitochondrial membrane permeability and superoxide radical formation were also observed with 8oxoG, but there was no significant change in the oxidation state of mitochondrial cytochromes or hydrogen peroxide levels in the INS-1E cells. Interestingly, exposure to 8oxoG and 8-oxodG also increased the mRNA expression of stress response genes, including NADPH dehydrogenase quinone 1 (NQO1), and thioredoxin-interacting protein (TXNIP). Together, these results support a potential role of oxidized guanosine derivatives in the induction of β-cell dysfunction, which could be relevant to the pathogenesis of T2DM.

The biological chemistry of hydrogen sulfide (H₂S) with physiologically important heme proteins is in the focus of redox biology research. In this study, we investigated the interactions of lactoperoxidase (LPO) with H₂S in the presence and absence of molecular dioxygen (O₂) or hydrogen peroxide (H₂O₂). Under anaerobic conditions, native LPO forms no heme-H₂S complex upon sulfide exposure. However, under aerobic conditions or in the presence of H₂O₂ the formation of both ferrous and ferric sulfheme (sulfLPO) derivatives was observed based on the appearances of their characteristic optical absorptions at 638 nm and 727 nm, respectively. Interestingly, we demonstrate that LPO can catalytically oxidize H₂S by H₂O₂ via intermediate formation of relatively short-lived ferrous and ferric sulfLPO derivatives. Pilot product analyses suggested that the turnover process generates oxidized sulfide species, which include sulfate (SO₄²⁻) and inorganic polysulfides (HS_x⁻; x = 2–5). These results indicated that H₂S can serve as a non-classical LPO substrate by inducing a reversible sulfheme-like modification of the heme porphyrin ring during turnover. Furthermore, electron paramagnetic resonance data suggest that H₂S can act as a scavenger of H₂O₂ in the presence of LPO without detectable formation of any carbon-centered protein radical species, suggesting that H₂S might be capable of protecting the enzyme from radical-mediated damage. We propose possible mechanisms, which explain our results as well as contrasting observations with other heme proteins, where either no sulfheme formation was observed or the generation of sulfheme derivatives provided a dead end for enzyme functions.