Alpha-Deoxyguanosine to Reshape the Alpha-Thrombin Binding Aptamer.

Modification of DNA aptamers is aimed at increasing their thermodynamic stability, and improving affinity and resistance to biodegradation. G-quadruplex DNA aptamers are a family of affinity ligands that form non-canonical DNA assemblies based on a G-tetrads stack. Modification of the quadruplex core is challenging since it can cause complete loss of affinity of the aptamer. On the other hand, increased thermodynamic stability could be a worthy reward. In the current paper, we developed new three- and four-layer modified analogues of the thrombin binding aptamer with high thermal stability, which retain anticoagulant activity against alpha-thrombin. In the modified aptamers, one or two G-tetrads contained non-natural anti-preferred alpha-deoxyguanosines at specific positions. The use of this nucleotide analogue made it possible to control the topology of the modified structures. Due to the presence of non-natural tetrads, we observed some decrease in the anticoagulant activity of the modified aptamers compared to the natural prototype. This negative effect was completely compensated by conjugation of the aptamers with optimized tripeptide sequences.

Nightshift work can induce oxidative DNA damage: a pilot study.

BACKGROUND: Regular sleep is very important for human health; however, the short-term and long-term effects of nightshift with sleep deprivation and disturbance on human metabolism, such as oxidative stress, have not been effectively evaluated based on a realistic cohort. We conducted the first long-term follow-up cohort study to evaluate the effect of nightshift work on DNA damage. METHODS: We recruited 16 healthy volunteers (aged 33 ± 5 years) working night shifts at the Department of Laboratory Medicine at a local hospital. Their matched serum and urine samples were collected at four time points: before, during (twice), and after the nightshift period. The levels of 8-oxo-7,8-dihydroguanosine (8-oxoG) and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), two important nucleic-acid damage markers, were accurately determined based on a robust self-established LC‒MS/MS method. The Mann-Whitney U or Kruskal-Wallis test was used for comparisons, and Pearson's or Spearman's correlation analysis was used to calculate the correlation coefficients. RESULTS: The levels of serum 8-oxodG, estimated glomerular filtration rate-corrected serum 8-oxodG, and the serum-to-urine 8-oxodG ratio significantly increased during the nightshift period. These levels were significantly higher than pre-nightshift work level even after 1 month of discontinuation, but no such significant change was found for 8-oxoG. Moreover, 8-oxoG and 8-oxodG levels were significantly positively associated with many routine biomarkers, such as total bilirubin and urea levels, and significantly negatively associated with serum lipids, such as total cholesterol levels. CONCLUSION: The results of our cohort study suggested that working night shifts may increase oxidative DNA damage even after a month of discontinuing nightshift work. Further studies with large-scale cohorts, different nightshift modes, and longer follow-up times are needed to clarify the short- and long-term effects of night shifts on DNA damage and find effective solutions to combat the negative effects.

The Influence of Spirodi(Iminohydantoin) on Charge Transfer through ds-DNA Containing 8-OXO-dG: A Theoretical Approach.

Genetic information stored in a DNA base sequence is continuously exposed to harmful factors. It has been determined that 9 × 104 different DNA damage events occur in a single human cell every 24 h. Of these, 7,8-dihydro-8-oxo-guanosine (OXOG) is one of the most abundant and can undergo further transformations towards spirodi(iminohydantoin) (Sp). Sp is highly mutagenic in comparison to its precursor if not repaired. In this paper, the influence of both Sp diastereomers 4R and 4S as well as their anti and syn conformers on charge transfer through the double helix was taken into theoretical consideration. In addition, the electronic properties of four modelled double-stranded oligonucleotides (ds-oligos) were also discussed, i.e., d[A1Sp2A3oxoG4A5] * [T5C4T3C2T1]. Throughout the study, the M06-2X/6-31++G** level theory was used. Solvent-solute non-equilibrated and equilibrated interactions were also considered. The subsequent results elucidated that the 7,8-dihydro-8-oxo-guanosine:cytidine (OXOGC) base pair is the settled point of a migrated radical cation in each of the discussed cases, due to its low adiabatic ionization potential, i.e., ~5.55 [eV]. The opposite was noted for excess electron transfer through ds-oligos containing anti (R)-Sp or anti (S)-Sp. The radical anion was found on the OXOGC moiety, whereas in the presence of syn (S)-Sp or syn (R)-Sp, an excess electron was found on the distal A1T5 or A5T1 base pair, respectively. Furthermore, a spatial geometry analysis of the discussed ds-oligos revealed that the presence of syn (R)-Sp in the ds-oligo caused only a slight deformation to the double helix, while syn (S)-Sp formed an almost ideal base pair with a complementary dC. The above results are in strong agreement with the final charge transfer rate constant, as calculated according to Marcus' theory. In conclusion, DNA damage such as spirodi(iminohydantoin), especially when becoming part of clustered DNA damage, can affect the effectiveness of other lesion recognition and repair processes. This can lead to the acceleration of undesired and deleterious processes such as carcinogenesis or aging. However, in terms of anticancer radio-/chemo- or combined therapy, the slowing down of the repair machinery can result in increased effectiveness. With this in mind, the influence of clustered damage on charge transfer and its subsequent effect on single-damage recognition by glycosylases justifies future investigation.

Rapid extraction and analysis of oxidative stress and DNA damage biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine: Application to a study with pregnant women.

Oxidative stress is an important toxicity and genotoxicity mechanism of many chronic adverse health outcomes. This study developed a sensitive extraction method for urine matrix (based on lyophilization, without the need for pre-cleaning by solid phase extraction), coupled to LC-MS/MS analysis of the biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG). The methodology was validated in urine samples from a cohort of Spanish pregnant women collected during the first, second and third trimester of pregnancy, and urine samples collected within 24 h after delivery (n = 85). A detection and quantification limit of 0.01 and 0.05 µg/L, respectively, were established. The median 8-OHdG concentration was 2.18 µg/L (range 0.33-7.79); and the corresponding creatinine-adjusted concentrations ranged from 1.04 to 13.12 with median of 4.48 µg 8-OHdG/g creatinine. The concentrations of non-adjusted 8-OHdG significantly decreased (p < 0.05) in the 3rd trimester and post-delivery urine samples when compared to the 1st trimester levels. 8-OHdG concentrations were further studied in placenta samples matching the same urine samples (n = 26), with a median value of 1.3 ng 8-OHdG/g of tissue. Placental 8-OHdG concentrations were correlated with urinary levels of non-adjusted 8-OHdG in the 3rd trimester. Considering the small cohort size, results must be interpreted with caution, however statistical analyses revealed elevated urinary non-adjusted 8-OHdG levels in the 1st trimester of mothers that delivered boys compared to those who delivered girls (p < 0.01). Increased urinary non-adjusted 8-OHdG concentrations at the time of delivery were significantly associated with clinical records (any type of clinical record during pregnancy; p < 0.05). The novel extraction and analytical method for the assessment of 8-OHdG is applicable for sensitive analysis of multiple analytes or biomarkers in urine matrix. This method could also be applied for other matrices such as blood or tissues. Our findings show that 8-OHdG in urine of pregnant women could predict oxidative stress in placenta and can be related to characteristics such as maternal obesity, mode of delivery and newborn sex.

8-Oxo-2'-deoxyguanosine Replication in Mutational Hot Spot Sequences of the p53 Gene in Human Cells Is Less Mutagenic than That of the Corresponding Formamidopyrimidine.

7,8-Dihydro-8-oxo-2'-deoxyguanosine (8-OxodGuo) is a ubiquitous DNA damage formed by oxidation of 2'-deoxyguanosine. In this study, plasmid DNA containing 8-OxodGuo located in three mutational hot spots of human cancers, codons 248, 249, and 273 of the Tp53 tumor suppressor gene, was replicated in HEK 293T cells. 8-OxodGuo was only a weak block of replication, and the bypass was largely error-free. The mutations (1-5%) were primarily G → T transversions, and the mutation frequency was generally lower than that of the chemically related Fapy·dG. A unique 8-OxodGuo mutation spectrum was observed at each site, as reflected by replication in translesion synthesis (TLS) polymerase- or hPol λ-deficient cells. In codon 248 (CG*G) and 249 (AG*G), where G* denotes 8-OxodGuo, hPol η and hPol ζ carried out largely error-free bypass of the lesion, whereas hPol κ and hPol ι were involved mostly in error-prone TLS, resulting in G → T mutations. 8-OxodGuo bypass in codon 273 (CG*T) was unlike the other two sites, as hPol κ participated in the mostly error-free bypass of the lesion. Yet, in all three sites, including codon 273, simultaneous deficiency of hpol κ and hPol ι resulted in reduction of G → T transversions. This indicates a convincing role of these two TLS polymerases in error-prone bypass of 8-OxodGuo. Although the dominant mutation was G → T in each site, in codon 249, and to a lesser extent in codon 248, significant semi-targeted single-base deletions also occurred, which suggests that 8-OxodGuo can initiate slippage of a base near the lesion site. This study underscores the importance of sequence context in 8-OxodGuo mutagenesis in human cells. It also provides a more comprehensive comparison between 8-OxodGuo and the sister lesion, Fapy·dG. The greater mutagenicity of the latter in the same sequence contexts indicates that Fapy·dG is a biologically significant lesion and biomarker on par with 8-OxodGuo.

Exploring Glycosylated Soy Isoflavones Affinities toward G-tetrads as Studied by Survival Yield Method.

Taking soy-based food supplements for menopausal symptoms by women may reduce the risk of cancer. Therefore, the interaction between nucleic acids (or their constituents) and ingredients of the supplements, e. g., isoflavone glucosides, on the molecular level, has been of interest with respect to cancer therapy. In this work, the interaction between isoflavone glucosides and G-tetrads, namely [4G+Na]+ ions (G stands for guanosine or deoxyguanosine), were analyzed by using electrospray ionization-collision induced dissociation-mass spectrometry (ESI-CID-MS) and survival yields method. The strength of isoflavone glucosides-[4G+Na]+ interaction in the gas phase was determined from Ecom50 - the energy required to fragment 50 % of selected precursor ions. Glycitin-[4G+Na]+ interaction was found to be the strongest, and the interaction between isoflavone glucosides and guanosine tetrad was established to be stronger than that between isoflavone glucosides and deoxyguanosine tetrad.

Oligonucleotide Containing 8-Trifluoromethyl-2'-Deoxyguanosine as a Z-DNA Probe.

Z-DNA structure is a noncanonical left-handed alternative form of DNA, which has been suggested to be biologically important and is related to several genetic diseases and cancer. Therefore, investigation of Z-DNA structure associated with biological events is of great importance to understanding the functions of these molecules. Here, we described the development of a trifluoromethyl labeled deoxyguanosine derivative and employed it as a 19F NMR probe to study Z-form DNA structure in vitro and in living cells.

The role of oxidative stress, tumor and inflammatory markers in colorectal cancer patients: A one-year follow-up study.

Oxidative stress (OS) and inflammation are known to play an important role in colorectal cancer (CRC). This study analyzed tumor, inflammatory and OS markers in CRC patients and in a control group. In addition, the evolution of these markers was evaluated after one-year of follow-up treatment. This was a longitudinal and prospective, observational study in 80 CRC patients who were candidates for tumor resection surgery and/or chemo-radiotherapy treatment and a healthy control group (n = 60). Subsequently, catalase (CAT), reduced glutathione (GSH), oxidized glutathione (GSSG) and GSSG/GSH ratio in serum and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and F2-IsoProstanes (F2-IsoPs) in urine at 1, 6 and 12 months after treatment was analyzed. Tumor markers (CEA and CA 19.9), as well as inflammatory markers-leukocytes, neutrophils, neutrophil/lymphocyte (N/L) index, platelets, fibrinogen, C-reactive protein (CRP), and interleukin 6 (IL6)- were also analyzed. As expected, levels of CEA and CA 19.9 and markers of inflammation, except CRP, were significantly higher in CRC compared to the control group. Regarding OS markers, a decrease in CAT and GSH and an increase in GSSG, GSSG/GSH ratio, 8-oxodG and F2-IsoPs were found in CRC patients compared to healthy controls at baseline. After treatment, an improvement of their inflammation profile was accompanied by a progressive recovery of antioxidant enzyme activities and the decline of oxidative byproducts both in serum and urine. Based on the results obtained, we propose the assay of urinary 8-oxodG and F2-IsoPs, as well as serum CAT, GSH, GSSG as a marker for the evaluation of OS and the clinical follow-up of CRC patients.

Preparation of DNA and RNA Fragments Containing Guanine N2 -Thioalkyl Tethers.

This article describes procedures for preparation of deoxyguanosine and guanosine derivatives in which the guanine N2 contains a thiopropyl tether, protected as a tert-butyl disulfide. After incorporation into a DNA or RNA fragment, this tether allows site-specific cross-linking to a thiol of a protein or another nucleic acid. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Preparation of diisopropyl-1-(tert-butylthio)-1,2-hydrazinedicarboxylate (4) Basic Protocol 2: Preparation of the 2'-deoxyguanosine N2 -propyl-tert-butyl disulfide phosphoramidite (12) Basic Protocol 3: Preparation of the guanosine N2 -propyl-tert-butyl disulfide phosphoramidite (20) Basic Protocol 4: Preparation of DNA fragments containing N2 -propyl-tert-butyl disulfide guanine Alternate Protocol: Preparation of RNA fragments containing N2 -propyl-tert-butyl disulfide guanine Basic Protocol 5: Conversion of N2 -propyl-tert-butyl disulfide to the free thiol, disulfide 5-thio-2-nitrobenzoic acid disulfide, or ethylamine disulfide.

A comparative meta-analysis of peripheral 8-hydroxy-2'-deoxyguanosine (8-OHdG) or 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) levels across mood episodes in bipolar disorder.

OBJECTIVE: Oxidative DNA damage has been associated with the pathophysiology of bipolar disorder (BD) as one of the common pathways between increased medical comorbidity and premature aging in BD. Previous evidence shows increased levels of oxidatively induced DNA damage markers, 8-hydroxy-2'-deoxyguanosine (8-OHdG) or its tautomer 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), in patients with BD in comparison to healthy individuals. With the current research, we aim to analyze data on peripheral (blood or urine) 8-OHdG/8-oxo-dG levels across mood states of BD using a meta-analytical approach. METHOD: A literature search was conducted using the databases PubMed, Scopus, and Web of Science to identify eligible studies (January 1989 to July 2022). Relevant studies were systematically reviewed; a random-effects meta-analysis and a meta-regression analysis were conducted. RESULTS: The current meta-analysis included 12 studies consisting of 808 BD patients (390 in euthymia, 156 in mania, 137 in depression, 16 in mixed episode, 109 not specified) and 563 healthy controls. BD patients that were currently depressed had significantly higher levels of 8-OHdG/8-oxo-dG than healthy controls, while euthymic or manic patients did not differ from healthy controls. A meta-regression analysis showed sex distribution (being female) and older age to be significantly related to increased 8-OHdG/8-oxo-dG levels. CONCLUSION: Our findings suggest that 8-OHdG/8-oxo-dG may be a state-related marker of depression in BD and may be affected by older age and female gender.

The 2Ih and OXOG Proximity Consequences on Charge Transfer through ds-DNA: Theoretical Studies of Clustered DNA Damage.

Genetic information is continuously exposed to harmful factors, both intra- and extracellular. Their activity can lead to the formation of different types of DNA damage. Clustered lesions (CDL) are problematic for DNA repair systems. In this study, the short ds-oligos with a CDL containing (R) or (S) 2Ih and OXOG in their structure were chosen as the most frequent in vitro lesions. In the condensed phase, the spatial structure was optimized at the M062x/D95**:M026x/sto-3G level of theory, while the electronic properties were optimized at the M062x/6-31++G** level. The influence of equilibrated and non-equilibrated solvent-solute interactions was then discussed. It was found that the presence of (R)2Ih in the ds-oligo structure causes a greater increase in structure sensitivity towards charge adoption than (S)2Ih, while OXOG shows high stability. Moreover, the analysis of charge and spin distribution reveals the different effects of 2Ih diastereomers. Additionally, the adiabatic ionization potential was found as follows for (R)-2Ih and (S)-2Ih in eV: 7.02 and 6.94. This was in good agreement with the AIP of the investigated ds-oligos. It was found that the presence of (R)-2Ih has a negative influence on excess electron migration through ds-DNA. Finally, according to the Marcus theory, the charge transfer constant was calculated. The results presented in the article show that both diastereomers of 5-carboxamido-5-formamido-2-iminohydantoin should play a significant role in the CDL recognition process via electron transfer. Moreover, it should be pointed out that even though the cellular level of (R and S)-2Ih has been obscured, their mutagenic potential should be at the same level as other similar guanine lesions found in different cancer cells.

How Clustered DNA Damage Can Change the Electronic Properties of ds-DNA-Differences between GAG, GAOXOG, and OXOGAOXOG.

Every 24 h, roughly 3 × 1017 incidences of DNA damage are generated in the human body as a result of intra- or extra-cellular factors. The structure of the formed lesions is identical to that formed during radio- or chemotherapy. Increases in the clustered DNA damage (CDL) level during anticancer treatment have been observed compared to those found in untreated normal tissues. 7,8-dihydro-8-oxo-2'-deoxyguanosine (OXOG) has been recognized as the most common lesion. In these studies, the influence of OXOG, as an isolated (oligo-OG) or clustered DNA lesion (oligo-OGOG), on charge transfer has been analyzed in comparison to native oligo-G. DNA lesion repair depends on the damage recognition step, probably via charge transfer. Here the electronic properties of short ds-oligonucleotides were calculated and analyzed at the M062x/6-31++G** level of theory in a non-equilibrated and equilibrated solvent state. The rate constant of hole and electron transfer according to Marcus' theory was also discussed. These studies elucidated that OXOG constitutes the sink for migrated radical cations. However, in the case of oligo-OGOG containing a 5'-OXOGAXOXG-3' sequence, the 3'-End OXOG becomes predisposed to electron-hole accumulation contrary to the undamaged GAG fragment. Moreover, it was found that the 5'-End OXOG present in an OXOGAOXOG fragment adopts a higher adiabatic ionization potential than the 2'-deoxyguanosine of an undamaged analog if both ds-oligos are present in a cationic form. Because increases in CDL formation have been observed during radio- or chemotherapy, understanding their role in the above processes can be crucial for the efficiency and safety of medical cancer treatment.

FapydG in the Shadow of OXOdG-A Theoretical Study of Clustered DNA Lesions.

Genetic information, irrespective of cell type (normal or cancerous), is exposed to a range of harmful factors, which can lead to more than 80 different types of DNA damage. Of these, oxoG and FapyG have been identified as the most abundant in normoxic and hypoxic conditions, respectively. This article considers d[AFapyGAOXOGA]*[TCTCT] (oligo-FapyG) with clustered DNA lesions (CDLs) containing both the above types of damage at the M06-2x/6-31++G** level of theory in the condensed phase. Furthermore, the electronic properties of oligo-FapyG were analysed in both equilibrated and non-equilibrated solvation-solute interaction modes. The vertical/adiabatic ionization potential (VIP, AIP) and electron affinity (VEA, AEA) of the investigated ds-oligo were found as follows in [eV]: 5.87/5.39 and -1.41/-2.09, respectively. The optimization of the four ds-DNA spatial geometries revealed that the transFapydG was energetically privileged. Additionally, CDLs were found to have little influence on the ds-oligo structure. Furthermore, for the FapyGC base-pair isolated from the discussed ds-oligo, the ionization potential and electron affinity values were higher than those assigned to OXOGC. Finally, a comparison of the influence of FapyGC and OXOGC on charge transfer revealed that, in contrast to the OXOGC base-pair, which, as expected, acted as a radical cation/anion sink in the oligo-FapyG structure, FapyGC did not significantly affect charge transfer (electron-hole and excess-electron). The results presented below indicate that 7,8-dihydro-8-oxo-2'-deoxyguanosine plays a significant role in charge transfer through ds-DNA containing CDL and indirectly has an influence on the DNA lesion recognition and repair process. In contrast, the electronic properties obtained for 2,6-diamino-4-hydroxy-5-foramido-2'deoxypyrimidine were found to be too weak to compete with OXOG to influence charge transfer through the discussed ds-DNA containing CDL. Because increases in multi-damage site formation are observed during radio- or chemotherapy, understanding their role in the above processes can be crucial for the efficiency and safety of medical cancer treatment.

The Intertwined Role of 8-oxodG and G4 in Transcription Regulation.

The guanine base in nucleic acids is, among the other bases, the most susceptible to being converted into 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) when exposed to reactive oxygen species. In double-helix DNA, 8-oxodG can pair with adenine; hence, it may cause a G > T (C > A) mutation; it is frequently referred to as a form of DNA damage and promptly corrected by DNA repair mechanisms. Moreover, 8-oxodG has recently been redefined as an epigenetic factor that impacts transcriptional regulatory elements and other epigenetic modifications. It has been proposed that 8-oxodG exerts epigenetic control through interplay with the G-quadruplex (G4), a non-canonical DNA structure, in transcription regulatory regions. In this review, we focused on the epigenetic roles of 8-oxodG and the G4 and explored their interplay at the genomic level.

Selenium exposure and urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine: Major effects of chemical species and sex.

Selenium is an element present in trace amounts and different chemical forms. It may exert both beneficial and adverse effects on cellular redox status and on the generation of reactive oxygen species. 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) is an oxidized derivative of deoxyguanosine, and a sensitive biomarker of oxidative stress and genotoxicity. The present study assessed the extent to which selenium status was associated with urinary 8-oxodG concentrations in a Northern Italian population. We recruited healthy, non-smoking blood donors living in the Reggio Emilia province during 2017-2019. We measured urinary 8-oxodG concentrations and used restricted cubic spline regression analyses to investigate the association between selenium status (estimated using food frequency questionnaires, urinary concentrations, and serum concentrations of selenium and selenium species) and 8-oxodG/g creatinine. Among 137 participants aged 30-60 years, median urinary selenium and 8-oxodG concentrations were 22.02 µg/L and 3.21 µg/g creatinine, respectively. Serum samples and selenium speciation analyses were available for 104 participants. Median total serum selenium levels and dietary intake were 116.5 µg/L and 78.7 µg/day, respectively. In spline regression analysis, there was little association between dietary, serum, or urinary selenium with 8-oxodG concentrations. In sex-specific analyses, urinary selenium showed a positive association with the endpoint among males. For single selenium species, we observed positive associations with urinary 8-oxodG for serum organic selenium species, and negative associations for inorganic selenium forms. In the most adjusted analysis, urinary 8-oxodG concentrations showed a strong positive association with selenomethione-bound selenium (Se-Met) and a negative association with inorganic tetravalent selenium, selenite. In sex-specific analyses, these associations were considerably stronger in males than in females. Overall, study findings indicate that selenium species exhibited very different patterns of associations with the biomarker of oxidative stress, and that these associations also depended on sex. Background exposure to Se-Met appears to be strongly and positively associated with oxidative stress.

A new toxicity mechanism of N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone: Formation of DNA adducts in mammalian cells and aqueous organisms.

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPDQ), one of the oxidation products of rubber antioxidant 6PPD, has been identified as a novel toxicant to many organisms. However, an understanding of its underlying toxicity mechanisms remained elusive. In this study, we reported that 6PPDQ could react with deoxyguanosine to form one isomer of 3-hydroxy-1, N2-6PPD-etheno-2'-deoxyguanosine (6PPDQ-dG). Next, by employing an ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) method, we found that 6PPDQ-dG could be detected in genomic DNA from 6PPDQ-treated mammalian cells and Chlamydomonas reinhardtii. We observed positive correlations between concentrations of exogenous 6PPDQ and the amounts of 6PPDQ-dG, and a recovery period after removal of 6PPDQ also led to decreased levels of the adduct in both organisms, which suggested potential repair pathways for this adduct in mammalian cells and unicellular algae. Additionally, we extracted the genomic DNA from tissues of frozen capelin and observed substantial amounts of the adduct in roe and gills, as well as livers at a relatively lower level. These results provided insights into the target organs and tissues that 6PPDQ might accumulate or harm fish. Overall, our study provides a new understanding of the mechanisms of toxicity of 6PPDQ in mammalian cells and aqueous organisms.

Hydrogen exerts neuroprotective effects by inhibiting oxidative stress in experimental diabetic peripheral neuropathy rats.

Diabetic peripheral neuropathy (DPN) is a complex disorder caused by long-standing diabetes. Oxidative stress was considered the critical creed in this DPN pathophysiology. Hydrogen has antioxidative effects on diabetes mellitus and related complications. However, there is still no concern on the beneficial effects of hydrogen in DPN. This paper aimed to evaluate the effects of exogenous hydrogen to reduce the severity of DPN in streptozotocin-induced diabetic rats. Compared with hydrogen-rich saline treatment, hydrogen inhalation significantly reduced blood glucose levels in diabetic rats in the 4th and 8th weeks. With regard to nerve function, hydrogen administration significantly attenuated the decrease in the velocity of motor nerve conduction in diabetic animals. In addition, hydrogen significantly attenuated oxidative stress by reducing the level of malondialdehyde, reactive oxygen species, and 8-hydroxy-2-deoxyguanosine and meaningfully enhanced the antioxidant capability by partially restoring the activities of superoxide dismutase. Further studies showed that hydrogen significantly upregulated the expression of nuclear factor erythroid-2-related factor 2 and downstream proteins such as catalase and hemeoxygenase-1 in the nerves of diabetic animals. Our paper showed that hydrogen exerts significant protective effects in DPN by downregulating oxidative stress via the pathway of nuclear factor erythroid-2-related factor 2, which suggests its potential value in clinical applications.

Translesion Synthesis across the N2-Ethyl-deoxyguanosine Adduct by Human PrimPol.

Primase-DNA polymerase (PrimPol) is involved in reinitiating DNA synthesis at stalled replication forks. PrimPol also possesses DNA translesion (TLS) activity and bypasses several endogenous nonbulky DNA lesions in vitro. Little is known about the TLS activity of PrimPol across bulky carcinogenic adducts. We analyzed the DNA polymerase activity of human PrimPol on DNA templates with seven N2-dG lesions of different steric bulkiness. In the presence of Mg2+ ions, bulky N2-isobutyl-dG, N2-benzyl-dG, N2-methyl(1-naphthyl)-dG, N2-methyl(9-anthracenyl)-dG, N2-methyl(1-pyrenyl)-dG, and N2-methyl(1,3-dimethoxyanthraquinone)-dG adducts fully blocked PrimPol activity. At the same time, PrimPol incorporated complementary deoxycytidine monophosphate (dCMP) opposite N2-ethyl-dG with moderate efficiency but did not extend DNA beyond the lesion. We also demonstrated that mutation of the Arg288 residue abrogated dCMP incorporation opposite the lesion in the presence of Mn2+ ions. When Mn2+ replaced Mg2+, PrimPol carried out DNA synthesis on all DNA templates with N2-dG adducts in standing start reactions with low efficiency and accuracy, possibly utilizing a lesion "skipping" mechanism. The TLS activity of PrimPol opposite N2-ethyl-dG but not bulkier adducts was stimulated by accessory proteins, polymerase delta-interacting protein 2 (PolDIP2), and replication protein A (RPA). Molecular dynamics studies demonstrated the absence of stable interactions with deoxycytidine triphosphate (dCTP), large reactions, and C1'-C1' distances for the N2-isobutyl-dG and N2-benzyl-dG PrimPol complexes, suggesting that the size of the adduct is a limiting factor for efficient TLS across minor groove adducts by PrimPol.

The effectiveness of berberine on noise-induced hearing loss: a rat model.

OBJECTIVE: Noise-induced hearing loss is a preventable form of hearing loss that has serious social and economic impacts. This study aimed to investigate the protective effect of berberine, a potent antioxidant and anti-inflammatory agent, against Noise-induced hearing loss. METHODS: After applying distortion product otoacoustic emission, 28 female Sprague-Dawley rats were randomly divided into four groups. Group 1 was designated as acoustic trauma group, and rats in this group were exposed to white noise for 12 h at an intensity of 4 kHz 110 dB sound pressure level. Group 2 was the control group. Group 3 was designated as the berberine group, and 100 mg/kg of berberine was administered to rats in this group by intragastric lavage for five consecutive days. Group 4 was designated as the acoustic trauma+berberine group. distortion product otoacoustic emission was repeated on the 6th day of the study and cochlear tissues of rats were dissected for histopathological and immunohistochemical analyses after sacrificing rats. RESULTS: The distortion product otoacoustic emission results showed a significant decrease in signal-noise ratio values at higher frequencies in rats of the trauma group compared to those in other groups. Acoustic trauma caused severe histopathological impairment at cochlear structures together with severe 8-hydroxy-2-deoxyguanosine expression. Rats in the acoustic trauma+berberine group showed mild histopathological changes with mild 8-hydroxy-2-deoxyguanosine expression and better signal-noise ratio values. CONCLUSION: The histopathological and audiological findings of this experimental study showed that berberine provides protection in Noise-induced hearing loss and may have the potential for use in acoustic trauma-related hearing losses.