Glutathione Directly Intercepts DNA Radicals To Inhibit Oxidative DNA–Protein Cross-Linking Induced by the One-Electron Oxidation of Guanine

Abstract

Oxidative DNA damage can lead to cancer, and as enzymatic DNA repair systems become compromised during the aging process, the role of exogenous antioxidants becomes more critical. Here, we examined whether such non-enzymatic DNA repair can be effected by the common cellular antioxidant glutathione, investigating both permanent DNA damage products and the guanine radical intermediates that form them, using the flash-quench technique to carry out the one-electron oxidation of guanine. In gel-shift assays, the presence of reduced glutathione at physiological (millimolar) concentrations strongly inhibits oxidative DNA–protein cross-linking. In contrast, the oxidized glutathione dimer affords only a minimal amount of protection, even at elevated pH where there is more of the strongly reducing thiolate form. In flash photolysis experiments, the formation and decay of the guanine neutral radical were monitored at 510 nm. Transient absorption measurements with a guanine-rich 22-mer DNA duplex on the millisecond time scale show that the yield of this long-lived signal is significantly diminished in the presence of reduced glutathione, suggesting a reduction process that is fast relative to the measurement. Indeed, transient absorption experiments carried out on faster time scales show that the microsecond decay of the guanine radical signal is visibly faster with glutathione present. Glutathione is perhaps best known as an electron source in enzymatic reactions, to maintain cysteines in reduced states in proteins and to deactivate reactive oxygen species. However, these results show that another important task for glutathione may be to directly intercept DNA radicals before permanent DNA damage can occur.

Interstrand Crosslinking Involving Guanine: A New Major UVC Laser‐Induced Biphotonic Oxidatively Generated DNA Damage†

“…This is confirmed in this study by the predominant formation of piperidine‐labile sites and Fpg‐sensitive sites at guanine bases. Furthermore, abundant information is available on the reactivity of Gua • toward several nucleophiles including hydroxide anion (33,34), N3 atom of thymine (46,25), free amino group of polylysine (47–49) and polyamines (50,51). The formation of ICL could be explained by the covalent bond formation between Gua •+ and cytosine or guanine through 4‐ and 2‐amino group, respectively, on the opposite strand.…”

Omega-Class Glutathione Transferases Protect DNA from Oxidative Stress in Pathogenic Helminth Reproductive Cells

“…When C. sinensis , having a normal GSTO function, is subjected to oxidative stress, CsGSTOs intervene and perform an appropriate role in DNA protection ( Figure 5 C). ROS can directly cause DNA damage, but this can be prevented by GSH [ 40 ]. Here, we describe the as-yet unknown and unique role of GSTO and provide prospects for new ways in which CsGSTOs utilize GSH to protect DNA from oxidative damage.…”

Dual-Fluorophore and Dual-Site Multifunctional Fluorescence Sensor for Visualizing the Metabolic Process of GHS to SO2 and the SO2 Toxicological Mechanism by Two-Photon Imaging

“…It is well known that glutathione (GSH) (0.5–10 mM), the most abundant nonprotein thiol, major antioxidant, and antidote in mammalian cells, − plays a vital role in diverse physiological processes involving biocatalysis, protein synthesis, cell metabolism, signal transduction, and maintenance of redox homeostasis, − and its abnormal fluctuation may lead to a series of disorders, (e.g., neurological disease, liver damage, and rheumatoid arthritis). − Studies have shown that endogenous sulfur dioxide (SO 2 , 0–5 μM) can be produced by GSH and thiosulfate (S 2 O 3 2– ) via thiosulfate sulphurtransferase (TST) in mitochondria, equilibrating with its derivatives sulfite (SO 3 2– )/bisulfite (HSO 3 – ). , By reacting with disulfide bonds of proteins and small molecules, SO 2 takes part in diverse physiological activities, such as regulating cardiac channels, inhibiting myocardial damage, and resisting hypertension. − Nevertheless, excess SO 2 may cause damage to respiratory, neurological, cardiovascular, and nervous systems. − That is to say, high-dose SO 2 has toxic effects on living organisms, which can be relieved by redox reactions. On the one hand, through the sulfur assimilation pathway, SO 3 2 /HSO 3 – is reduced to S 2– , and Cys is catalyzed by sulfite reductase (SiR) and O-acetylserine lyase (OASTL), respectively.…”