Free Radical Research | 2021
Special issue on “recent topics of redox chemistry and biology”
Abstract
Redox reactions mediated by various reactive species play an important role in the birth, health, disease, and death of humans. Some redox reactions proceed by regulated manner, while others randomly. The underlying mechanisms and physiological and pathophysiological effects have been the subjects of extensive studies and arguments. A large number of excellent reviews have been published over the years to summarize the progress owing to the contributions of many researchers in this field but many issues still remain to be addressed. In this special issue of Free Radical Research, we aimed at providing recent topics of several issues in redox chemistry and biology, special attention being paid to include topics which have not been covered before and to avoid overlap from existing popular topics. Coronavirus disease 2019, COVID-19, is a pandemic affecting billions of people worldwide now. Chiu and his colleagues reviewed the role of glucose-6-phosphate dehydrogenase (G6PD) against SARS-CoV-2, the pathogenic agent which caused hyperinflammation and a cytokine storm, leading to cell death by imbalanced redox status [1]. They showed that G6PD deficiency was a predisposing factor of COVID-19 and that individuals with G6PD deficiency were more susceptible to coronavirus infection than individuals with normally functioning G6PD. Hyodo introduced their work on noninvasive visualization of free radicals derived from biological molecules using an in vivo dynamic nuclear polarization (DNP) magnetic resonance imaging (MRI) system [2]. They discussed on the free radicals of flavins, ubiquinone, vitamin E, vitamin C, and melanin. The DNP-MRI method may help to shed more light on the action and role of these radicals in vivo. Yamada and his colleagues summarized recent advances in the detection of lipid-derived radicals in vitro and in cultured cells [3]. They also discussed the possibility of visualization and structural analysis of lipid-derived radicals generated not only in cells but also in animal tissue samples using fluorescence probe that combines with piperidine-based nitroxide. Oxidative modification of DNA bases induced by multiple oxidizing species is one of the most important reactions in redox chemistry. Chatgilialoglu focused on the mechanistic aspects for the various lesion formation and their interconnections in purine DNA damage by hydroxyl radical [4]. It was shown that, although majority of the purine DNA lesions are generated by various ROS, the formation of 50,8-cyclopurine (cPu) lesions in vitro and in vivo relies exclusively on the hydroxyl radical attack. Methodologies generally utilized for the purine lesions quantification in biological samples are critically discussed. Carbon ion radiotherapy is more effective than conventional photon beam radiotherapy in treating cancer because of its excellent dose localization and high biological effect on tumors. Matsumoto reviewed the generation of reactive oxygen species by local ionization in water and subsequent estimation by simulations and pulse radiolysis experiments using EPR pain trap and spin probe [5]. Akagawa reviewed protein carbonylation at the amino acid side chains, a major hallmark of oxidative modification of proteins mediated by reactive oxygen species and lipid oxidation-derived aldehydes [6]. Analytical approaches for the measurements of carbonylated proteins were also reviewed. Cholesterol is oxidized by enzymes and non-enzymatic oxidants to give diverse products termed oxysterols including hydroxides, hydroperoxides, epoxides, and carbonyl compounds. Miyamoto et al. [7] reviewed the generation and measurement of reactive sterol oxidation products with emphasis on electrophilic oxysterols which modify a variety of proteins, changing their structures and eliciting a broad range of cellular effects. They also showed that secosterol aldehydes were formed as secondary products derived from cholesterol hydroperoxide decomposition. Iron is an essential element for humans but iron promotes free radical generation and lipid peroxidation, causing oxidative damage and cell death. Shi and his colleagues reviewed rapid progress in recent years in understanding molecular mechanisms of iron homeostasis with a focus on epigenetic regulation of hepcidin, ferritin, and ferroptosis [8]. Recent topics including the interactions between methionine and iron and iron regulation in stroke were discussed. Ferroptosis is a form of regulated cell death characterized by the iron-dependent decomposition of lipid hydroperoxides, which exhibits distinct features from apoptosis and necrosis. Yin and colleagues summarized the recent progress on ferroptosis in connection with cardiovascular disease and atherosclerosis, highlighting the role of free radical mediated lipid peroxidation [9]. The evidence underlying the ferroptosis and challenges in the field was also critically discussed. Nanomaterials defined as materials possessing, at minimum, one external dimension measuring 1-100nm have received much attention for unique properties and