In this review article, emphasis is placed on the critical survey of available data concerning modified nucleobase and 2-deoxyribose products that have been identified in cellular DNA following ...exposure to a wide variety of oxidizing species and agents including, hydroxyl radical, one-electron oxidants, singlet oxygen, hypochlorous acid and ten-eleven translocation enzymes. In addition, information is provided about the generation of secondary oxidation products of 8-oxo-7,8-dihydroguanine and nucleobase addition products with reactive aldehydes arising from the decomposition of lipid peroxides. It is worth noting that the different classes of oxidatively generated DNA damage that consist of single lesions, intra- and interstrand cross-links were unambiguously assigned and quantitatively detected on the basis of accurate measurements involving in most cases high performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The reported data clearly show that the frequency of DNA lesions generated upon severe oxidizing conditions, including exposure to ionizing radiation is low, at best a few modifications per 106 normal bases. Application of accurate analytical measurement methods has also allowed the determination of repair kinetics of several well-defined lesions in cellular DNA that however concerns so far only a restricted number of cases.
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•HPLC based methods are appropriate for monitoring oxidatively damage to DNA.•Single base lesions, intra- and interstrand cross-links were identified in cellular DNA.•Other modifications included halogenated bases and adducts with reactive aldehydes.•Paucity of reliable data on the base excision repair of oxidized bases in cells.
Singlet molecular oxygen (1O2) has been associated with a number of physiological processes. Despite the recognized importance of 1O2‐mediated protein modifications, little is known about the role of ...this oxidant in crosslink formation and protein aggregation. Thus, using lysozyme as a model, the present study sought to investigate the involvement of 1O2 in crosslink formation. Lysozyme was photochemically oxidized in the presence of rose bengal or chemically oxidized using 18O‐labeled 1O2 released from thermolabile endoperoxides. It was concluded that both 1O2 generating systems induce lysozyme crosslinking and aggregation. Using SDS‐PAGE and nano‐scale liquid chromatography coupled to electrospray ionization mass spectrometry, the results clearly demonstrated that 1O2 is directly involved in the formation of covalent crosslinks involving the amino acids histidine, lysine, and tryptophan.
Reactive oxygen species, as singlet oxygen (1O2) and hydrogen peroxide, are continuously generated by aerobic organisms, and react actively with biomolecules. At excessive amounts, 1O2 induces ...oxidative stress and shows carcinogenic and toxic effects due to oxidation of lipids, proteins and nucleic acids. Singlet oxygen is able to react with DNA molecule and may induce G to T transversions due to 8-oxodG generation. The nucleotide excision repair, base excision repair and mismatch repair have been implicated in the correction of DNA lesions induced by 1O2 both in prokaryotic and in eukaryotic cells. 1O2 is also able to induce the expression of genes involved with the cellular responses to oxidative stress, such as NF-κB, c-fos and c-jun, and genes involved with tissue damage and inflammation, as ICAM-1, interleukins 1 and 6. The studies outlined in this review reinforce the idea that 1O2 is one of the more dangerous reactive oxygen species to the cells, and deserves our attention.
Singlet molecular oxygen (1O2) is generated in biological systems and reacts with different biomolecules. Proteins are a major target for 1O2, and His, Tyr, Met, Cys, and Trp are oxidized at ...physiological pH. In the present study, the modification of lysozyme protein by 1O2 was investigated using mass spectrometry approaches. The experimental findings showed methionine, histidine, and tryptophan oxidation. The experiments were achieved using 18O‐labeled 1O2 released from thermolabile endoperoxides in association with nano‐scale liquid chromatography coupled to electrospray ionization mass spectrometry. The structural characterization by nLC‐MS/MS of the amino acids in the tryptic peptides of the proteins showed addition of 18O‐labeling atoms in different amino acids.
This survey focuses on recent aspects of the singlet oxygen oxidation of the guanine moiety of nucleosides, oligonucleotides, isolated and cellular DNA that has been shown to be the exclusive DNA ...target for this biologically relevant photogenerated oxidant. A large body of mechanistic data is now available from studies performed on nucleosides in both aprotic solvents and aqueous solutions. A common process to both reaction conditions is the formation of 8-oxo-7,8-dihydroguanine by reduction of 8-hydroperoxyguanine that arises from the rearrangement of initially formed endoperoxide across the 4,8-bond of the purine moiety. However, in organic solvent the hydroperoxide is converted as a major degradation pathway into a dioxirane that subsequently decomposes into a complex pattern of oxidation products. A different reaction that involved the formation of a highly reactive quinonoid intermediate consecutively to the loss of a water molecule from the 8-hydroperoxide has been shown to occur in aqueous solution. Subsequent addition of a water molecule at C5 leads to the generation of a spiroiminodihydantoin compound via a rearrangement that involves an acyl shift. However, in both isolated and cellular DNA the latter decomposition pathway is at the best a minor process, because only 8-oxo-7,8-dihydroguanine has been found to be generated. It is interesting to point out that singlet oxygen has been shown to contribute predominantly to the formation of 8-oxo-7,8-dihydroguanine in the DNA of bacterial and human cells upon exposure to UVA radiation. It may be added that the formation of secondary singlet-oxygen oxidation products of 8-oxo-7,8-dihydroguanine, including spiroiminodihydantoin and oxaluric acid that were characterized in nucleosides and oligonucleotide, respectively, have not yet been found in cellular DNA.
Singlet molecular oxygen is a reactive species involved in biological oxidative processes. The major cellular targets of singlet molecular oxygen are unsaturated fatty acids in the membrane, as well ...as nucleic acids and proteins. The aim of this study was to investigate whether lipids and commercial hydroperoxides generate singlet molecular oxygen, in presence of nitronium and activated nitronium ion. For this purpose, monomol light emitted in the near‐infrared region (λ = 1270 nm) was used to monitor singlet molecular oxygen decay in different solvents, with different hydroperoxides and in the presence of azide. Direct measurements of the singlet molecular oxygen spectrum at 1270 nm recorded during the reaction between lipids and commercial hydroperoxides and nitronium ions unequivocally demonstrated the formation of this excited species.
O2 (1Δg) is generated when lipid hydroperoxides (OAOOH, LAOOH and ChOOH) react with NO2+
The decomposition of organic hydroperoxides into peroxyl radicals is a potential source of singlet molecular oxygen O
2 (
1Δ
g) in biological systems. This study shows that ...5-(hydroperoxymethyl)uracil (5-HPMU), a thymine hydroperoxide within DNA, reacts with metal ions or HOCl, generating O
2 (
1Δ
g). Spectroscopic evidence for generation of O
2 (
1Δ
g) was obtained by measuring (i) the bimolecular decay, (ii) the monomolecular decay, and (iii) the observation of D
2O enhancement of O
2 (
1Δ
g) production and the quenching effect of NaN
3. Moreover, the presence of O
2 (
1Δ
g) was unequivocally demonstrated by the direct characterization of the near-infrared light emission. For the sake of comparison, O
2 (
1Δ
g) derived from the H
2O
2/HOCl system and from the thermolysis of the
N,N′-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide was also monitored. More evidence of O
2 (
1Δ
g) generation was obtained by chemical trapping of O
2 (
1Δ
g) with anthracene-9,10-divinylsulfonate (AVS) and detection of the specific AVS endoperoxide by HPLC/MS/MS. The detection by HPLC/MS of 5-(hydroxymethyl)uracil and 5-formyluracil, two thymine oxidation products generated from the reaction of 5-HPMU and Ce
4+ ions, supports the Russell mechanism. These photoemission properties and chemical trapping clearly demonstrate that the decomposition of 5-HPMU generates O
2 (
1Δ
g) by the Russell mechanism and point to the involvement of O
2 (
1Δ
g) in thymidine hydroperoxide cytotoxicity.
T. cruzi II strains accumulate more 8-oxoguanine in the kDNA after hydrogen peroxide-induced 18 oxidative stress than T. cruzi I strains. NT: untreated; T: treated. Display omitted
▶ Distinct levels ...of DNA mismatch repair activity are found among T. cruzi strains. ▶ In T. cruzi and T. brucei, MSH2 has a mitochondrial function involved in the response to oxidative stress.
Components of the DNA mismatch repair (MMR) pathway are major players in processes known to generate genetic diversity, such as mutagenesis and DNA recombination. Trypanosoma cruzi, the protozoan parasite that causes Chagas disease has a highly heterogeneous population, composed of a pool of strains with distinct characteristics. Studies with a number of molecular markers identified up to six groups in the T. cruzi population, which showed distinct levels of genetic variability. To investigate the molecular basis for such differences, we analyzed the T. cruzi MSH2 gene, which encodes a key component of MMR, and showed the existence of distinct isoforms of this protein. Here we compared cell survival rates after exposure to genotoxic agents and levels of oxidative stress-induced DNA in different parasite strains. Analyses of msh2 mutants in both T. cruzi and T. brucei were also used to investigate the role of Tcmsh2 in the response to various DNA damaging agents. The results suggest that the distinct MSH2 isoforms have differences in their activity. More importantly, they also indicate that, in addition to its role in MMR, TcMSH2 acts in the parasite response to oxidative stress through a novel mitochondrial function that may be conserved in T. brucei.
Acetaldehyde and crotonaldehyde are genotoxic aldehydes present in tobacco smoke and vehicle exhaust. The reaction of these aldehydes with 2'-deoxyguanosine in DNA produces alpha -methyl- gamma ...-hydroxy-1,N super(2)-prop ano-2'-deoxyguanosine (1,N super(2)-propanodGuo). Online HPLC-tandem mass spectrometry was utilized to accurately quantify 1,N super(2)-propanodGuo in human urinary samples from 47 residents of Sao Paulo City (SP) and 35 residents of the rural municipality of Sao Joao da Boa Vista (SJBV) in the state of Sao Paulo. Significantly higher 1,N super(2)-propanodGuo levels were found in the samples from SP donors than in samples from SJBV donors. Our results provide the first evidence that elevated levels of 1,N super(2)-propanodGuo in urinary samples may be correlated with urban air pollution.
We evaluated levels of serotonin (5HT) and dopamine (DOPA) in muscle and digestive glands of the mussel,
Perna perna, collected at different times of day; exposed to air for 24 h, followed by ...re-submersion; and after exposure to different metals. Mussels collected at different periods of day showed little oscillation in 5HT and DOPA levels. Mussels exposed to metals showed significant changes in 5HT and DOPA levels in digestive gland and muscle, as did mussels exposed to air. Our data suggest that analyses of 5HT and DOPA in tissues of mussels could serve as a tool to evaluate the presence and effects of heavy metal contamination in mussels. Care in data interpretation is required, however, since other environmental factors such as exposure of mussels to air (i.e. at low tides) can also cause changes in DOPA and 5HT levels. Additional research is necessary to separate such natural environmental effects from effects of contaminants.
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