Formation Of 8-hydroxyguanine Research Articles

STUDY THE EFFECTS OF (8-OXO-GUANINE DNA GLYCOSYLASE 1 RS1052133) POLYMORPHISM ON GENE EXPRESSION AS A PREDISPOSING FACTOR FOR DNA MUTATION IN MIDLAND REFINERIES COMPANY-DURA REFINERY WORKERS

Background: Refineries are exposed to different types of air pollutants, among them, polycyclic aromatic hydrocarbons (PAHs), they are a group of over hundred different kinds of hazardous organic chemicals (pollutants), which are formed primarily during the incomplete burning of oil, gas and coal. PAHs are metabolized in different organs of human body especially in the liver leading to generation of mutagenic metabolites, of them, the reactive oxygen species, which damage DNA by binding with guanine base leading to formation of 8-hydroxyguanine. The 8-oxo-guanine DNA glycosylase (hOGG1 rs1052133) gene, is a regulatory gene binds with 8-oxo-DG in the DNA to initiate base excision repair (BER) pathway. Objective: To investigate the role of (hOGG1 rs1052133) gene polymorphism in single nucleotide polymorphism repair. Methods: One hundred sixty-eight (168) subjects were participated in this study. They were they divided into three groups (country side, office workers and field workers). PAHs were analyzed in all participant by Gas Chromatography Coupled with a Mass Spectrophotometry GC/MS. SNP for hOGG1 and gene expression were detecting by real time polymerase chain reaction and quantitative polymerase chain reaction for each subject respectively. Results: PAH were detected in blood serum of refineries workers and not detected in country side participants. The level of hOGG1 gene expression was higher in GG genotype than GC and CC genotype. Conclusion: Refineries worker are at high risk of developing malignant transformation and serious disease due to high level of PAH compared to other population. hOGG1 plays an important role in DNA repair following DNA mutation. Keywords: Poly cyclic aromatic hydrocarbons, HOGGI, gene expression Citation: Al-Ani RH, Al-Wasiti EA, Shukur AS. Study the Effects of (8-oxo-Guanine DNA Glycosylase 1 rs1052133) Polymorphism on Gene Expression as a Predisposing Factor for DNA Mutation in Midland Refineries Company-Dura Refinery Workers. Iraqi JMS. 2022; 20(1): 90-97. doi: 10.22578/IJMS.20.1.12

Effect of sodium and acetate ions on 8-hydroxyguanine formation in irradiated aqueous solutions of DNA and 2′-deoxyguanosine 5′-monophosphate

Purpose: The aim of this work was to study the combined effect of sodium and acetate ions on the radiation yield of 8-hydroxyguanine (8-OHG), one of the major DNA base lesions induced by free radicals.Materials and methods: Aqueous solutions of DNA and 2′-deoxyguanosine 5′-monophosphate (dGMP) with various concentrations of sodium acetate and sodium perchlorate were γ-irradiated, enzymatically digested and analyzed by high-performance liquid chromatography (HPLC) methods.Results: It was found that both salts decrease the 8-OHG radiation yield in the concentration range studied for both DNA and dGMP, except in the case of dGMP wherein an increase in yield occurs in the concentration range from 0.1–1 mM. The dependence of the 8-hydroxy-2′-deoxyguanosine radiation yield on the concentration of both sodium acetate and sodium perchlorate have different shapes and have steeper slopes for the DNA compared with the dGMP solutions.Conclusions: The observed decrease in the radiation yield of 8-OHG with increasing concentrations of sodium acetate is consistent with the hypothesis that sodium acetate produces two concentration-dependent effects in the DNA solutions: (1) A conformational change in the DNA caused by Na+ counterions; and (2) free radical reactions related to the radiolysis of acetate ion.

Roles of specialized DNA polymerases in mutagenesis by 8-hydroxyguanine in human cells

The formation of 8-hydroxyguanine (8-OH-Gua, 7,8-dihydro-8-oxoguanine) in DNA and in the nucleotide pool results in G:C-->T:A and A:T-->C:G substitution mutations, respectively, due to the ability of 8-OH-Gua to pair with both C and A. In this study, shuttle plasmid DNAs containing 8-OH-Gua paired with C and A in the supF gene were transfected into human 293T cells, in which specialized DNA polymerases were knocked-down. The DNAs replicated in the cells were recovered and then introduced into an indicator strain of Escherichia coli. Mutation analysis indicated that the knock-downs of DNA polymerases eta and zeta by siRNAs enhanced the G:C-->T:A mutations caused by 8-OH-Gua:C. The 8-OH-Gua:C-induced mutation frequency was not further increased by double knock-downs of DNA polymerases eta and zeta, suggesting that the two DNA polymerases work in the same pathway. In addition, the reduction of DNA polymerase eta slightly decreased the A:T-->C:G substitutions caused by 8-OH-Gua:A. These results suggest that DNA polymerases eta and zeta are involved in the bypass of 8-OH-Gua in human cells.

Effect of Quadruplex Conformation on Radiation-Induced Formation of 8-Hydroxyguanine and Unaltered Base Release in Polyguanylic Acid

The ability of guanine-rich sequences to form quadruplex structures in telomeres for example is important in a number of biological processes such as aging, carcinogenesis and gene regulation. Ionizing radiation can cause damage to guanine moieties that can affect the stability or formation of the guanine quadruplex structures. In addition, the mechanisms of formation of these radiation damages in quadruplex structures may be different from those that occur in single- or double-stranded conformations. We have studied the quantitative aspects of the radiation induced formation of 8-hydroxy-2'-guanine base modifications and unaltered guanine base release in single-, double- and four-stranded conformations of polyriboguanylic acid as a model of guanine-rich sequences in telomere-like structures. The results show that the strandedness of guanine-rich sequences is an important variable in the observed yields of these base damages and suggests that telomere-like structures with G-quadruplexes will be relatively more radiosensitive than the other regions of duplex DNA. Hydroxyl radicals are the major reactive species that produce the DNA damage, although the presence of oxygen significantly reduces their radiation yields for all conformations of polyriboguanylic acid and changes the proportions of the yields of the various damages among the polymer conformations.

Glutathione Depletion by Buthionine Sulfoximine Induces Oxidative Damage to DNA in Organs of Rabbits in Vivo

Glutathione (GSH) exists in mammalian tissues in vivo at high concentrations and plays an important protective role against oxidatively induced damage to biological molecules, including DNA. We investigated oxidatively induced damage to DNA by GSH depletion in different organs of rabbits in vivo. Rabbits were treated subcutaneously with buthionine sulfoximine (BSO), an effective GSH-depleting compound. GSH levels were measured in heart, brain, liver, and kidney of animals. BSO treatment significantly reduced GSH levels in heart, brain, and liver, but not in kidney. DNA was isolated from these tissues to test whether GSH depletion causes oxidatively induced DNA damage in vivo. Gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry with isotope dilution methods were applied to measure typical products of oxidatively induced damage in isolated DNA samples. Several such products were identified and quantified in all organs. BSO treatment caused significant formation of 8-hydroxyguanine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyadenine, and (5'S)-8,5'-cyclo-2'-deoxyadenosine in DNA of organs of rabbits. Animals were fed with the semiessential amino acid 2-aminoethanesulfonic acid (taurine) during BSO treatment. Taurine significantly inhibited GSH depletion and also formation of DNA products. Depletion of GSH correlated well with formation of DNA products, indicating the role of GSH in preventing oxidatively induced DNA damage. Our findings might contribute to the understanding of pathologies associated with DNA damage, oxidative stress, and/or defective antioxidant responses and improve our understanding of the effect of BSO in increasing the efficacy of anticancer therapeutics.

Non-linear effects in the formation of DNA damage in medaka fish fibroblast cells caused by combined action of cadmium and ionizing radiation.

Ionizing radiation-induced formation of genomic DNA damage can be modulated by nearby chemical species such as heavy metal ions, which can lead to non-linear dose response. To investigate this phenomenon, we studied cell survival and formation of 8-hydroxyguanine (8-OHG) base modifications and double strand breaks (DSB) caused by combined action of cadmium (Cd) and gamma radiation in cultured medaka fish (Oryzias latipes) fibroblast cells. Our data show that the introduction of Cd leads to a significant decrease in the fraction of surviving cells and to increased sensitivity of cells to ionizing radiation (IR). Cd also appears to cause non-linear increases in radiation-induced yields of 8-OHG and DSB as dose-yield plots of these lesions exhibit non-linear S-shaped curves with a sharp increase in the yields of lesions in the 10-20 microM range of Cd concentrations. The combined action of ionizing radiation and Cd leads to increased DNA damage formation compared to the effects of the individual stressors. These results are consistent with a hypothesis that the presence of Cd modulates the efficiency of DNA repair systems thus causing increases in radiation-induced DNA damage formation and decreases in cell survival.

Dysfunction of Nrf2 decreases KBrO 3-induced oxidative DNA damage in Ogg1-null mice

Transcription factor Nrf2 regulates production of antioxidants and protects cells from oxidative/electrophilic stresses. Paradoxically, glutathione, one of the Nrf2-regulated antioxidants, has been assumed to promote genotoxicity of KBrO 3. To address this glutathione hypothesis, we examined roles Nrf2 plays in the cellular defense against KBrO 3-induced oxidative damage using Nrf2 −/− , Ogg1 −/− and Nrf2::Ogg1 double knockout mice. We found that upon KBrO 3 treatment Nrf2::Ogg1 double knockout animals suffered from severe kidney damage, but unexpectedly the double knockout mice accumulated lower level of 8-hydroxyguanine than Ogg1 −/− mice. Thus, KBrO 3-induced nephrotoxicity appears not to depend on the formation of 8-hydroxyguanine. Our data also indicate that both the KBrO 3-induced nephrotoxicity and formation of 8-hydroxyguanine are Nrf2-controlled processes, but the changes of the glutathione level are Nrf2-independent. Based on these results we conclude that glutathione is a minor part of the mechanism promoting genotoxicity of KBrO 3 in Ogg1 knockout mice.

Contrasting Genome-Wide Distribution of 8-Hydroxyguanine and Acrolein-Modified Adenine during Oxidative Stress-Induced Renal Carcinogenesis

Oxidative stress is a persistent threat to the genome and is associated with major causes of human mortality, including cancer, atherosclerosis, and aging. Here we established a method to generate libraries of genomic DNA fragments containing oxidatively modified bases by using specific monoclonal antibodies to immunoprecipitate enzyme-digested genome DNA. We applied this technique to two different base modifications, 8-hydroxyguanine and 1,N6-propanoadenine (acrotein-Ade), in a ferric nitrilotriacetate-induced murine renal carcinogenesis model. Renal cortical genomic DNA derived from 10- to 12-week-old male C57BL/6 mice, of untreated control or 6 hours after intraperitoneal injection of 3 mg iron/kg ferric nitrilotriacetate, was enzyme digested, immunoprecipitated, cloned, and mapped to each chromosome. The results revealed that distribution of the two modified bases was not random but differed in terms of chromosomes, gene size, and expression, which could be partially explained by chromosomal territory. In the wild-type mice, low GC content areas were more likely to harbor the two modified bases. Knockout of OGG1, a repair enzyme for genomic 8-hydroxyguanine, increased the amounts of acrolein-Ade as determined by quantitative polymerase chain reaction analyses. This versatile technique would introduce a novel research area as a high-throughput screening method for critical genomic loci under oxidative stress.

Inherited Polyposis Syndromes: Molecular Mechanisms, Clinicopathology, and Genetic Testing

The inherited polyposis syndromes are a group of conditions in which multiple gastrointestinal polyps occur in the lumen of the gastrointestinal tract, most exhibit an increased risk of colon cancer. Benign and malignant extraintestinal tumors might also be observed. Recent elucidation of the underlying gene mutations has contributed to our understanding of the cell biology and molecular mechanisms associated with gastrointestinal tumorigenesis. Developments have also allowed genetic testing to become an integral component in accurate diagnosis, categorization, and management of inherited polyposis syndromes. In this review, we will focus on familial adenomatous polyposis, mutY human homologue-associated polyposis, Peutz-Jeghers syndrome, juvenile polyposis, and Cowden syndrome. It is essential that both physician and patient understand the benefits and limitations of genetic testing before submission of samples to the laboratory. There are many issues accompanying molecular diagnosis of cancer syndromes, and genetic counseling is an essential prelude to genetic testing.

NTA and Fe(III)NTA: differential patterns of renal toxicity in subchronic studies.

Differential patterns in terms of nephropathology and 8-hydroxyguanine formation in the course of oral 28-day studies were observed with nitrilotriacetic acid (NTA) and FeNTA. FeNTA, but not NTA, caused enhanced 8-hydroxyguanine formation in kidney DNA after oral and intraperitoneal administration. Enhanced lipid peroxidation in the kidney homogenate was observed with FeNTA as well as with NTA. For NTA, the low dose (9 mg/kg per day) was without adverse effect. The kidney toxicity of oral FeNTA (50, 200, and 1000 mg/kg per day) was only mild, 50 mg/kg per day; however, it still led to an increased 8-hydroxyguanine content. The relevance of Iron(III) (Fe(III)) or Fe(III)NTA formation as a relevant mediator of NTA-related toxicity was excluded on the basis of these data. Also, a thermodynamic consideration presented here, supports the view that zinc (Zn), and not Fe, is likely to mediate the tubular cell cytotoxicity of NTA.

DNA strand break and 8-hydroxyguanine formation induced by 2-hydroxyestradiol dispersed in liposomes

DNA damage induced by estrogens dispersed in liposomes was investigated. 2-Hydroxyestradiol (2HOE 2) and 4-hydroxyestradiol (4HOE 2), but not estrone, estradiol-17β or estriol, caused strand break of plasmid DNA damage in the presence of ADP-Fe 3+. The catechol structure may be necessary for DNA damage. When DNA was incubated with 2HOE 2 for a long time (24 h), DNA damage was induced even at very low concentrations. Adding hydrogen peroxide markedly enhanced the sensitivity of DNA to the attack by 2HOE 2. Hydroxyl radical (HO ) scavengers strongly inhibited the 2HOE 2-induced DNA damage, and EDTA partially inhibited DNA damage. However, 2HOE 2 caused 8-hydroxyguanine formation from calf thymus DNA only in the presence of EDTA-Fe 3+, but not ADP-Fe 3+. In addition, deoxyribose, which is a detective molecule of HO , was not degraded by 2HOE 2 in the presence of ADP-Fe 3+. Upon adding EDTA 2HOE 2 rapidly degraded deoxyribose. These results suggest that DNA strand break caused by 2HOE 2 in the presence of ADP-Fe 3+ was due to ferryl ion rather than HO , whereas 8-hydroxyguanine (8HOG) induced by 2HOE 2 in the presence of EDTA-Fe 3+ was due to HO .

Viral inactivation of fresh frozen plasma.

Viral inactivation of fresh frozen plasma.

Increased 8-Hydroxyguanine Formation and Endonuclease Activity for Its Repair in Ischemic-Reperfused Hearts of Rats

H.-j. You, G.-t. Kim, Y.-h. Kim, Y.-s. Chun, J.-w. Park, M.-H. Chung and M.-s. Kim. Increased 8-Hydroxyguanine Formation and Endonuclease Activity for Its Repair in Ischemic-Reperfused Hearts of Rats. Journal of Molecular and Cellular Cardiology (2000) 32, 1053–1059. A type of oxidative DNA damage, 8-hydroxyguanine (8-OH-Gua) formation, and the activity for its subsequent repair, 8-OH-Gua endonuclease activity, were examined in an ischemia-reperfusion model of isolated rat hearts. The level of 8-OH-Gua in myocardial DNA was measured by a high performance liquid chromatography (HPLC) equipped with an electrochemical detector, and the 8-OH-Gua endonuclease activity was analysed by the endonuclease nicking assay using a synthetic double-stranded oligonucleotide containing an 8-OH-Gua residue as a substrate. The Langendorff-perfused rat hearts were subjected to 30 or 60 min of global ischemia, followed by reperfusion with an oxygenated or a nitrogenated Krebs-Henseleit solution. The 8-OH-Gua content in the DNA of the ischemic hearts reperfused with an oxygenated solution was three to four times higher than that of the control hearts. The levels of 8-OH-Gua did not increase either in the ischemic hearts reperfused with a nitrogenated solution or in the ischemic-reperfused hearts treated with SOD, mannitol or allopurinol. When the myocardial extract was incubated with the 8-OH-Gua-containing oligonucleotide substrate, a specific cleavage at the site of an 8-OH-Gua residue was detected. The endonuclease activity responsible for this cleavage increased two-fold in the ischemic-reperfused hearts, compared to the control. This study demonstrates that the formation of 8-OH-Gua in DNA as well as the level of its repair process, 8-OH-Gua endonuclease activity, increase in the ischemic-reperfused rat hearts in response to oxidative stress due to higher levels of oxygen free radicals.

DNA damage induced by catechol derivatives

We investigated the effect of catechol derivatives, including dopa, dopamine, adrenaline and noradrenaline, on DNA damage and the mechanisms of DNA strand breakage and formation of 8-hydroxyguanine (8HOG). The catechol derivatives caused strand breakage of plasmid DNA in the presence of ADP-Fe 3+. The DNA damage was prevented by catalase, mannitol and dimethylsulfoxide, suggesting hydroxyl radical (HO )-like species are involved in the strand breakage of DNA. Iron chelators, such as desferrioxamine and bathophenanthroline, and reduced glutathione also inhibited the DNA damage. Deoxyribose, a molecule that is used to detect HO , was not degraded by dopa in the presence of ADP-Fe 3+. By adding EDTA, however, dopa induced the marked deoxyribose degradation in the presence of ADP-Fe 3+, indicating that EDTA may extract iron from ADP-Fe 3+ to catalyze HO formation by dopa. Thus, EDTA was a good catalyst for HO -generation, whereas it did not promote the strand breakage of DNA. However, calf thymus DNA base damage, which was detected as 8-HOG formation, was caused by dopa in the presence of EDTA-Fe 3+, but not in the presence of ADP-Fe 3+. The 8HOG formation was also inhibited by catalase and HO scavengers, indicating that HO was involved in the base damage. These results suggest that DNA strand breakage is due to ferryl species rather than HO , and that 8HOG formation is due to HO rather than ferryl species.

Activated leukocytes oxidatively damage DNA, RNA, and the nucleotide pool through halide-dependent formation of hydroxyl radical.

A variety of chronic inflammatory conditions are associated with an increased risk for the development of cancer. Because of the numerous links between DNA oxidative damage and carcinogenesis, a potential role for leukocyte-generated oxidants in these processes has been suggested. In the present study, we demonstrate a novel free transition metal ion-independent mechanism for hydroxyl radical ((*)OH)-mediated damage of cellular DNA, RNA, and cytosolic nucleotides by activated neutrophils and eosinophils. The mechanism involves reaction of peroxidase-generated hypohalous acid (HOCl or HOBr) with intracellular superoxide (O(2)(*)(-)) forming (*)OH, a reactive oxidant species implicated in carcinogenesis. Incubation of DNA with either isolated myeloperoxidase (MPO) or eosinophil peroxidase (EPO), plasma levels of halides (Cl(-) and Br(-)), and a cell-free O(2)(*)(-) -generating system resulted in DNA oxidative damage. Formation of 8-hydroxyguanine (8-OHG), a mutagenic base which is a marker for (*)OH-mediated DNA damage, required peroxidase and halides and occurred in the presence of transition metal chelators (DTPA +/- desferrioxamine), and was inhibited by catalase, superoxide dismutase (SOD), and scavengers of hypohalous acids. Similarly, exposure of DNA to either neutrophils or eosinophils activated in media containing metal ion chelators resulted in 8-OHG formation through a pathway that was blocked by peroxidase inhibitors, hypohalous acid scavengers, and catalytically active (but not heat-inactivated) catalase and SOD. Formation of 8-OHG in target cells (HA1 fibroblasts) occurred in all guanyl nucleotide-containing pools examined following exposure to both a low continuous flux of HOCl (at sublethal doses, as assessed by [(14)C]adenine release and clonogenic survival), and hyperoxia (to enhance intracellular O(2)(*)(-) levels). Mitochondrial DNA, poly A RNA, and the cytosolic nucleotide pool were the primary targets for oxidation. Moreover, modest but statistically significant increases in the 8-OHG content of nuclear DNA were also noted. These results suggest that the peroxidase-H(2)O(2)-halide system of leukocytes is a potential mechanism contributing to the well-established link between chronic inflammation, DNA damage, and cancer development.

Formation of 8-Hydroxyguanine and 2,6-Diamino- 4-hydroxy-5-formamidopyrimidine in DNA by Riboflavin Mediated Photosensitization

Calf thymus DNA was photoirradiated in the presence of riboflavin. Altered bases were detected and quantified by the GC/MS-SIM method after hydrolysis and derivatization of DNA. Seven types of modified purine bases were detected in control DNA. Among them, the yields of 8-OH-Gua and FapyGua increased significantly in DNA photoirradiated with riboflavin, whereas the yields of xanthine, 8-OH-Ade, 2-OH-Ade, FapyAde and hypoxanthine were not affected. A dose dependent increase in the formation of 8-OH-Gua was observed with increasing riboflavin concentration for 30 min irradiation. On the other hand, FapyGua reached plateau at 10 μg/ml of riboflavin for 30 min irradiation. Our results indicate that guanine moiety in DNA is the most susceptible to riboflavin mediated photosensitization.

Ultraviolet-B-light-induced mutagenesis of C-H-ras codons 11 and 12 in human skin fibroblasts.

Mutations in the ras oncogene are detected with a high frequency in non-melanoma skin cancer. Approximately half of the squamous-cell carcinomas (SCC) and one third of the basal-cell carcinomas (BCC) carry mutations at the second position of Ha-ras codon 12 (GGC to GTC), whereas mutations in Ki-ras codon 12 occur less frequently. Since the mutations in the Ha-ras and Ki-ras oncogenes are located opposite potential pyrimidine dimer sites (C-C), it is likely that the mutations are induced by ultraviolet radiation present in sunlight. We studied the capacity of ultraviolet B (UVB) light to induce base-pair changes in Ha-ras codons 11 and 12 in human skin fibroblasts. UVB induced mostly C to T and G to A transitions and C to A and G to T transversions. The base-pair change with the highest relative abundance was C to T in the middle position of codon 11 followed by (in diminishing relative abundance) C to A in the middle position of codon 11, G to A and G to T in the middle position of codon 12. The C to T and G to A transitions are compatible with pyrimidine photodimers as pre-mutagenic lesions, whereas the C to A and G to T transversions could be generated due to the formation of 8-hydroxyguanine, which is the major oxidation product of guanine. The relative abundance of mutations induced by UVB in Ha-ras codons 11 and 12 does not correlate with mutations observed in the DNA from non-melanoma skin cancer, where the G to T transversion in the middle position of codon 12 is selected.

Formation of 8-Hydroxyguanine by Oxygen Radicals and Its Biological Effects: Mutagenesis, Carcinogenesis, and Repair.

Reactive oxygen species (ROS) are produced by the normal oxygen metabolism in cells as a consequence of respiration in an oxygen atmosphere and by some kinds of environmental mutagens. ROS attack and modify cellular macromolecules including DNA. 8-Hydroxyguanine (8-OH-Gua) is one of the DNA lesions which are produced by ROS. 8-OH-Gua mainly induces G→T mutations in vitro, in E. coli and mammalian cells. Repair enzymes for 8-OH-Gua are present in cells and prevent the mutations induced by the DNA lesion. Formation of oxidative DNA lesions which are produced by ROS appears to be involved in many biological processes including carcinogenesis and ageing. Therefore, 8-OH-Gua may be a good marker of cellular production of ROS to estimate mutagenicities and carcinogenicities of chemical compounds.

Mutagenesis resulting from DNA damage by lipid peroxidation in the supF gene of Escherichia coli

In vitro incubation of rat microsomal lipids with NADPH and Fe3+ in the presence of cytochrome P450 reductase produces lesions in double-stranded pZ189 plasmid DNA, the mutagenic potential of which was analyzed after transfection into Escherichia coli host cells that had been induced for SOS functions by ultraviolet irradiation. The extent of lipid peroxidation, when monitored by the formation of thiobarbituric acid reaction substances, was increased with increased addition of lipids in the reaction mixture. Mutagenesis was determined with the forward mutation assay using the supF gene of pZ189 as a target. When treated pZ189 DNA was used to transfect host cells, a seven-fold increase in mutation frequency for SOS uninduced hosts and a 12-fold increase in mutation frequency for SOS induced hosts was observed at 50% survival compared to that observed with untreated DNA. Sequence analysis shows that incubation of pZ189 DNA in the lipid peroxidation reaction mixture results mostly in single base substitutions, the most frequent base changes being G:C → C:G treansversion, followed by G:C → T:A transversion. The fact that, in the SOS induced hosts, the spectrum obtained by lipid peroxidation is similar to that of hydrogen peroxide suggests the possible involvement for mutagenesis of superoxide produced during lipid peroxidation, but not lipid peroxiation end products such as aldehyde or alkane. Treatment of pZ189 DNA with increasing extents of lipid peroxidation did not yield increasing formation of 8-hydroxyguanine. The results suggest that the origins of G:c → C:g and G:C → T:A transversions may be (an) as yet unidentified lesion9s) generated by lipid peroxidation.

Selective 8-hydroxyguanine formation in pancreatic DNA due to a single intravenous administration of 4-hydroxyaminoquinoline l-oxide in rats

8-Hydroxyguanine (8-OHG) formation, a possible initiating event, was determined in pancreatic and liver DNA and compared with the genesis of acinar cell and hepatocyte necrosis in male Wistar rats given a single intravenous administration of 4-hydroxyaminoquinoline 1-oxide (4-HAQO). At the non-necrotic but tumorigenic dose of 7.0 mg/kg body weight, 8-OHG was selectively generated in pancreatic DNA, in the absence of acinar cell necrosis, at the 6 and 24 h time points and repaired by the 48 h time point. When rats were exposed to 4-HAQO at a necrotic dose of 14.0 mg/kg body weight, 8-OHG was also selectively formed in pancreatic DNA with the same time-dependence of generation and repair, while acinar cell necrosis became evident at the 24 h time point and progressed thereafter. Whereas no hepatocyte necrosis was detected in any rats, 8-OHG values for liver DNA merely expressed slight increases only at the 24 and 48 h time points in rats given 14.0 mg/kg body weight of 4-HAQO. The present data suggest that formation of oxidative DNA damage, assayed by 8-OHG, in pancreatic DNA is independent from toxicity and may be involved, along with quinoline adducts, in mutational events underlying 4-HAQO-induced rat acinar cell carcinogenesis.