Oxidative DNA damage from potassium bromate exposure in Long-Evans rats is not enhanced by a mixture of drinking water disinfection by-products

Association of Ozone Exposures with the risk of thyroid nodules in Hunan Province: a population-based cohort study

BACKGROUND

Increasing evidence associates air pollution with thyroid dysfunction, whereas the potential relationship between exposure to ozone (O₃) and Thyroid Nodules (TNs) is unclear.

METHODS

This retrospective cohort study investigated the association between O₃ exposure and TNs in Hunan province, enrolling 191,357 Chinese adults who lived in Hunan province from January 2009 to December 2019 and received voluntary medical examinations. Individual exposure levels to O₃ from 2010 to 2019 were measured on account of participants' residential addresses at the district level. Associations of O₃ exposure with the risk of incidental TNs were assessed by restricted cubic splines and surveyed as odds ratios after adjusting for demographic factors.

RESULTS

In total, 81,900 adults were newly diagnosed with TNs during the study period. Age-standardized TNs detection rate in Hunan province increased from 25.9 to 46.3% between 2010 and 2019, with the greatest annual percent change being 8.1 [95% CI, 7.3-8.8]. A similar trend has been found in all tumor sizes, ages, and both sexes. O₃ exposure presented a statistically significant dose-dependent positive correlation (greater than 0.036 ppm) with TNs. Similarly, long-term exposure to high levels of O₃ (1-year average O₃ concentrations exceeding 0.0417 ppm) was found positively associated with increased TSH levels.

CONCLUSIONS

High-level O₃ exposure in the long term was associated with an increase in TSH. Consequently, increased TSH was related to the increased risk of TNs. Being exposed to high-level O₃ in the long term was related to the increased detection rates of TNs in Hunan province, which could be mediated by TSH.

8-oxoguanine and 8-oxodeoxyguanosine Biomarkers of Oxidative DNA Damage: A Review on HPLC-ECD Determination

Reactive oxygen species (ROS) are continuously produced in living cells due to metabolic and biochemical reactions and due to exposure to physical, chemical and biological agents. Excessive ROS cause oxidative stress and lead to oxidative DNA damage. Within ROS-mediated DNA lesions, 8-oxoguanine (8-oxoG) and its nucleotide 8-oxo-2'-deoxyguanosine (8-oxodG)-the guanine and deoxyguanosine oxidation products, respectively, are regarded as the most significant biomarkers for oxidative DNA damage. The quantification of 8-oxoG and 8-oxodG in urine, blood, tissue and saliva is essential, being employed to determine the overall effects of oxidative stress and to assess the risk, diagnose, and evaluate the treatment of autoimmune, inflammatory, neurodegenerative and cardiovascular diseases, diabetes, cancer and other age-related diseases. High-performance liquid chromatography with electrochemical detection (HPLC-ECD) is largely employed for 8-oxoG and 8-oxodG determination in biological samples due to its high selectivity and sensitivity, down to the femtomolar range. This review seeks to provide an exhaustive analysis of the most recent reports on the HPLC-ECD determination of 8-oxoG and 8-oxodG in cellular DNA and body fluids, which is relevant for health research.

Estimation of the Level of Abasic Sites in Plant mRNA Using Aldehyde Reactive Probe

Oxidation of RNA is associated with the development of numerous disorders including Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), cancer, and diabetes. Additionally, a correlation has been found between increase in RNA oxidation and the process of aging. In plants, elevated level of oxidatively modified transcripts has been detected during alleviation of seeds dormancy and stress response. Increasing interest on the topic of RNA oxidative modifications requires elaboration of new laboratory techniques. So far, the most common method used for the assessment of RNA oxidation is quantification of 8-hydroxyguanine (8-OHG). However, reactive oxygen species (ROS) induce also numerous other changes in nucleic acids, including formation of abasic sites (AP-sites). Recently, the level of AP-sites in RNA has been measured with the use Aldehyde Reactive Probe (ARP). In the present chapter, we describe application of this technique for the evaluation of the level of AP-sites in plant transcripts.

The relationship among noise, total oxidative status and DNA damage

PURPOSE

Noise is one of the major environmental health problems and is defined as any unpleasant sound. It was shown that prolonged exposure to noise was associated with progress of diseases. There is no study evaluating the effect of noise on the oxidative parameters of Total Antioxidant Capacity (TAC), Total Oxidant Status (TOS) and DNA damage.

AIM

This study aimed to evaluate the effect of noise on TOS, TAC and DNA damage.

METHODS

In this study, we included 100 textile factory workers affected by noise as a noise group, and 56 healthy volunteers employed as office workers in our hospital who were not exposed to noise as the control group. Blood samples were obtained from both the groups. Oxidative Stress (OS) was measured by Oxidative stress index (OSI), TOS and TAC. The DNA damage level was measured by 8-Hydroxydeoxyguanosine (8-OHdG).

RESULTS

8-OHdG (21.8 ± 12.0 vs. 14.7 ± 5.6 pg/ml, p = 0.001),TOS (14.1 ± 2.5 vs. 10.9 ± 1.5 mol H2O2 equivalent/l, p < 0.001), TAC (0.96 ± 0.19 vs. 1.54 ± 0.28 Trolox equivalent/l, p < 0.001) and OSI (1.52 ± 0.37, etc. 0.76 ± 0.35 arbitrary units, p < 0.001) were significantly higher in noise group compared to control group. Linear regression analysis showed that noise was the independent predictor of DNA damage (β = 0.310, p < 0.001).

CONCLUSION

In this study, we showed that TOS and DNA damage were significantly higher in subjects exposed to noise when compared with subjects of the control group. Noise was the only independent predictor of the DNA damage. Therefore, early detection of DNA damage and increased OS, early corrective measures may delay the development and progression of diseases such as hypertension, arrhythmias.

The Effect of Iron Deficiency Anemia and Different Treatment Methods on DNA Damage: 8-hydroxy-2-deoxyguanosine Level

Ionic iron causes damages at the cellular level by forming free radicals. Reactive oxygen species lead to the formation of oxidative base damages in DNA. Among these forms the most common one and the one which has the best known mutagenity is 8-hydroxy-2′-deoxyguanosine (8-OHdG). We aimed to determine iron deficiency anemia (IDA) and its different forms of treatments; probable oxidative damage on DNA by looking at the level of 8-OHdG. The patients were divided into 4 subgroups: Oral treatment (p.o.) group; Intramuscular treatment (i.m.) group; Intravenous treatment (i.v.) group; Healthy control group. Blood and urine samples were taken from all patients totally 4 times. 8-OHdG levels detected in blood and urine samples were compared with the control group. IDA and the treatment of it affect the level of 8-OHdG. p.o. therapy should be the top priority on children.

DNA damage and DNA protection from digested raw and griddled green pepper (poly)phenols in human colorectal adenocarcinoma cells (HT-29)

PURPOSE

To determine whether (poly)phenols from gastrointestinal-digested green pepper possess genoprotective properties in human colon cells and whether the application of a culinary treatment (griddling) on the vegetable influences the potential genoprotective activity.

METHODS

(Poly)phenols of raw and griddled green pepper (Capsicum annuum L.) submitted to in vitro-simulated gastrointestinal digestion were characterized by LC-MS/MS. Cytotoxicity (MTT, trypan blue and cell proliferation assays), DNA damage and DNA protection (standard alkaline and formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay) of different concentrations of (poly)phenolic extracts were assessed in colon HT-29 cells.

RESULTS

A total of 32 (poly)phenolic compounds were identified and quantified in digested raw and griddled green pepper. Twenty of them were flavonoids and 12 were phenolic acids. Griddled pepper doubled the (poly)phenol concentration compared to raw; luteolin 7-O-(2-apiosyl)-glucoside and quercitrin constituted the major (poly)phenols in both extracts. Raw and griddled pepper (poly)phenolic extracts impaired cell proliferation and induced low levels of Fpg-sensitive sites, in a dose-dependent manner, even at a non-cytotoxic concentration. None of the concentrations tested induced DNA strand breaks or alkaline labile sites. Nor did they show significant genoprotection against the DNA damage induced by H₂O₂ or KBrO₃.

CONCLUSIONS

Green pepper (poly)phenols did not show genoprotection against oxidatively generated damage in HT-29 cells at simulated physiological concentrations, regardless of the application, or not, of a culinary treatment (griddling). Furthermore, high concentrations of (poly)phenolic extracts induced a slight pro-oxidant effect, even at a non-cytotoxic concentration.

Apocynin alleviates cisplatin-induced testicular cytotoxicity by regulating oxidative stress and apoptosis in rats

The aim of this study was to investigate possible protective effects of apocynin (APO), an NADPH oxidase (NOX2) inhibitor, on cisplatin (CIS)-induced testicular damage. Four groups of Sprague Dawley rats were used: control, APO, CIS and CIS+APO. Following a single intraperitoneal dose of CIS (7 mg/kg), either dimethyl sulfoxide or APO (25 mg/kg) was administered orally for 5 days. Testis samples were evaluated microscopically for general histopathology and ultrastructure, proliferating and apoptotic cells, and NOX2 localization. Sperm parameters were evaluated. Malondialdehyde (MDA) and glutathione (GSH) levels and superoxide dismutase (SOD), myeloperoxidase (MPO) and 8-hydroxy-2-deoxyguanosine (8-OHdG) activities were analysed biochemically. The CIS group had a greater number of abnormal spermatozoa, atrophic seminiferous tubules, apoptotic and NOX2-immunoreactive cells; numerous large vacuole formations in the cytoplasm of germinal epithelial cells; degenerated intercellular tight junctions; higher MDA, 8-OHdG and MPO levels; decreased numbers of spermatozoa; and lower proliferative index and GSH and SOD levels. All these histologic and biochemical results were better in the CIS+APO group. CIS causes testicular damage by decreasing spermatogenic cell lines and increasing NOX2 activity and apoptosis through oxidative stress. APO prevents testicular damage, possibly by its antioxidant effects.

Potassium bromate – inhalable fraction. Documentation of proposed values of occupational exposure limits (OELs)

Potassium bromate (V), (KBrO3) exists as white crystals, crystalline powder or granules. It is highly soluble in water, tasteless and odourless. Potassium bromate is a strong oxidizing agent. In the past it has been used as food additive in flour milling, as an ingredient in fish-paste in Japan, in cheese making, in beer malting, as a component of cold hair wave liquid and an oxidizing compound. Moreover, bromate is formed as a by-product of water disinfection by ozonation and is frequently detected in tap and bottled water. In fact bromate is one of the most prevalent disinfection by-product of surface water. Occupational exposure to potassium bromate occurs mainly in production plants during packaging processes. In Poland, about 1 160 persons were exposed to this compound in 2016. Bromate caused many acute poisonings by accidental ingestion, mainly among children, and more often ingested for tentative suicide by young women, especially hairdressers. In the acute phase of poisoning, gastrointestinal disturbances, irreversible hearing loss, and acute renal failure were observed. Acute renal failure was associated with hemolytic uremic syndrome. There are no data on chronic intoxication of humans by potassium bromate and epidemiological studies on this subject. On the basis of the value of median lethal dose (LD50) per os in rat, potassium bromate has been classified as a compound belonging to the category „Toxic”. Major toxic signs and symptoms in animals after a single intragastric administration of potassium bromate were tachypnea, hypothermia, diarrhea, lacrimation, suppression of locomotor movement, ataxic gait, and animals lying in a prone position. At autopsy the major findings were strong hyperemia of glandular stomach mucosa and congestion of lungs. Microscopically, necrosis and degenerative changes of the proximal tubular epithelium and hearing cells of internal ear were found. It was stated that the compound is not irritating, corrosive or sensitizing. In subchronic and chronic exposure of rodents, potassium bromate led to liver and kidney dysfunction and tubular epithelial damage. Potassium bromate had mutagenic and clastogenic effects. It induced point mutations, structural chromosome aberrations, micronuclei in polychromatic erythrocytes in male mice, DNA oxidative damage by modification of deoxyguanosine to 8-hydroxydeoxyguanosine, and DNA double-strand breakage. Potassium bromate induced neoplasms in rodents and exerted promotion effect in comparison with well-known carcinogens. Besides from preneoplastic changes, expressed by high incidences of renal cell tumors and dysplastic foci, bromate induced solid neoplasms, such as adenomas and adenocarcinomas in a rat kidney and thyroid, and mesotheliomas of peritoneum and tunica vaginalis testis. The European Union classified potassium bromate as a substance that can cause cancer (Group 1.B), whereas IARC classified it as a presumably carcinogenic agent for human (Group 2.B). In principle, effects of bromate on reproduction and ontogenetic development of offspring were not observed. Animal studies suggest that a kidney is a critical organ in the exposure to potassium bromate. The results of subchronic exposure of male rats to potassium bromate administered with drinking water were used to calculate the value of MAC-NDS. The critical effects in kidney were: an increase of organ weight and dose-dependent histopathological alterations defined as epithelium urinary tract hypertrophy. The NOAEL value is 1.5 mg/kg b.w./day. For the calculation of the maximum allowable concentration (MAC) value, 5 uncertainty factors with total value of 24 were used. Based on this estimation it is proposed to accept the MAC-TWA value for potassium bromate at 0.44 mg/m3. The risks of kidney and thyroid cancer in condition of occupational exposure are 2.2 · 10-3 and 0.6 · 10-3, respectively. There is no reason to determine the value of short-term exposure limit (STEL) and the biological exposure index (BEI). „Carc.1.B” notation (carcinogenic substance) was proposed

Effects of Zinc Supplementation on DNA Damage in Rats with Experimental Kidney Deficiency

This study was carried out to determine the effect of zinc on oxidative DNA damage in rats with experimental acute and chronic kidney deficiency. Six groups of five Wistar-Albino rats each were assigned as controls (C), acute kidney deficiency (AKD), zinc-supplemented (+Zn), acute kidney deficiency, zinc-supplemented (AKD + Zn), chronic kidney deficiency (CKD) and zinc-supplemented chronic kidney deficiency (CKD + Zn). The levels of 8-Oxo-2'-deoxyguanosine (8-OHdG) were determined, being the lowest in the CKD group (p < 0.05), higher in the C group than those of rats with CKD but lower than that of all the other groups (p < 0.05). There were no significant differences between the controls and the CKD + Zn group, or between the AKD and the +Zn groups. Among all groups, the highest 8-OHdG level was found in the AKD + Zn group (p < 0.05). DNA damage was greater in acute renal failure than in rats with chronic renal failure. The DNA damage in the zinc group was significantly higher than in the controls.

Biological properties of Alsidium corallinum and its potential protective effects against damage caused by potassium bromate in the mouse liver

In the course of searching for hepatoprotective agents from natural sources, the protective effect of chemical constituents of the marine red alga Alsidium corallinum (A. corallinum) against potassium bromate (KBrO3)-induced liver damage in adult mice was investigated. The in vitro antioxidant and antibacterial properties of A. corallinum were firstly investigated. Then, A. corallinum was tested in vivo for its potential protective effects against damage caused by KBrO3 in mice models divided into four groups: controls, KBrO3, KBrO3 + A. corallinum, and A. corallinum. Our results demonstrated the rich composition of A. corallinum in antioxidant compounds like phenolics, flavonoids, anthocyanins, polysaccharides, chlorophyll and carotenoids. Its antioxidant activity was also confirmed using β-carotene bleaching by linoleic acid assay, reducing sugar test and trolox equivalent antioxidant capacity. The ethanolic extract of A. corallinum also showed good inhibition of the tested bacteria. The coadministration of the red alga associated to the KBrO3 alleviated hepatotoxicity as monitored by the improvement of hepatic oxidative stress biomarkers and plasma biochemical parameters, when compared to the KBrO3-treated mice. These results were confirmed by the improvement of histological and molecular changes. Treatment with A. corallinum prevented liver damage induced by KBrO3, thus protecting the body against free radicals and reducing inflammation and hypercholesterolemia risks.

Protective effects of extracts from Fructus rhodomyrti against oxidative DNA damage in vitro and in vivo

OBJECTIVE

To evaluate the potential protective effects of extracts from Fructus rhodomyrti (FR) against oxidative DNA damage using a cellular system and the antioxidant ability on potassium bromate- (KBrO3-) mediated oxidative stress in rats.

METHODS

The effects of FR on DNA damage induced by hydrogen peroxide (H2O2) were evaluated by comet assay in primary spleen lymphocytes cultures. The effects of FR on the activities of SOD, CAT, and GPx and the levels of GSH, hydroperoxides, and 8-OHdG were determined in the plasma and tissues of rats treated with KBrO3.

RESULTS

FR was shown to effectively protect against DNA damage induced by H2O2  in vitro, and the maximum protective effect was observed when FR was diluted 20 times. Endogenous antioxidant status, namely, the activities of SOD, CAT, and GPx and the levels of GSH were significantly decreased in the plasma, the liver, and the kidney of the KBrO3-treated rats, while the pretreatment of FR prevented the decreases of these parameters. In addition, the pretreatment of FR was also able to prevent KBrO3-induced increases in the levels of hydroperoxides and 8-OHdG in the plasma, the liver, and the kidney in rats.

CONCLUSIONS

Our findings suggested that FR might act as a chemopreventive agent with antioxidant properties offering effective protection against oxidative DNA damage in a concentration-dependent manner in vitro and in vivo.

Dose-response analysis of bromate-induced DNA damage and mutagenicity is consistent with low-dose linear, nonthreshold processes

Mutagenic agents have long been inferred to act through low-dose linear, nonthreshold processes. However, there is debate about this assumption, with various studies interpreting datasets as showing thresholds for DNA damage and mutation. We have applied rigorous statistical analyses to investigate the shape of dose-response relationships for a series of in vitro and in vivo genotoxicity studies using potassium bromate (KBrO(3) ), a water ozonation byproduct that is bioactivated to a reactive species causing oxidative damage to DNA. We analyzed studies of KBrO(3) genotoxicity where no-effect/threshold levels were reported as well as other representative datasets. In all cases, the data were consistent with low-dose linear models. In the majority of cases, the data were fit either by a linear (straight line) model or a model which was linear at low doses and showed a saturation-like downward curvature at high doses. Other datasets with apparent upward curvature were still adequately represented by models that were linear at low dose. Sensitivity analysis of datasets showing upward curvature revealed that both low-dose linear and nonlinear models provide adequate fits. Additionally, a simple biochemical model of selected key processes in bromate-induced DNA damage was developed and illustrated a situation where response for early primary events suggested an apparent threshold while downstream events were linear. Overall, the statistical analyses of DNA damage and mutations induced by KBrO(3) are consistent with a low-dose linear response and do not provide convincing evidence for the presence of a threshold.

Comparison of 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels using mass spectrometer and urine albumin creatinine ratio as a predictor of development of diabetic nephropathy

BACKGROUND

Measurement of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) has recently become more popular as a means of assessing oxidative stress in the human body. The aim of this study is to compare the levels of urine 8-OHdG in patients with type 2 diabetes with and without nephropathy and to evaluate its role as a biochemical marker for distinguishing these patients from healthy and patients without complications.

METHODS

For this purpose, 52 patients with type 2 diabetes mellitus (32 with nephropathy (DMN), 20 without nephropathy (DM)) and 20 healthy control subjects (C) were included in this study. The urine concentrations of 8-OHdG were measured by modified LC-MS/MS method and compared with the first morning voiding urine albumin/creatinine ratio (UACR) and HbA1c values of the same patients.

RESULTS

The concentrations of urine 8-OHdG in DMN and DM patients were higher than those of the control subjects (3.47 ± 0.94, 2.92 ± 1.73, 2.1 ± 0.93 nmol/mol creatinine, respectively). But there was no statistical difference between DMN and DM (p = 0.115). There is significant correlation between urinary 8-OHdG and UACR (r = 0.501, p < 0.001). According to ROC analysis, the AUC value of HbA1c was higher than the value of the AUC of 8-OHdG (0.882 and 0.771, respectively).

CONCLUSIONS

This study shows that the urine 8-OHdG levels increase in diabetic patients. However, urinary 8-OHdG is not a useful clinical marker, compared with UACR, to predict the development of diabetic nephropathy in diabetic patients.

Assessment of multiple types of DNA damage in human placentas from smoking and nonsmoking women in the Czech Republic

Three classes of DNA damage were assessed in human placentas collected (2000-2004) from 51 women living in the Teplice region of the Czech Republic, a mining area considered to have some of the worst environmental pollution in Europe in the 1980s. Polycyclic aromatic hydrocarbon (PAH)-DNA adducts were localized and semiquantified using immunohistochemistry (IHC) and the Automated Cellular Imaging System (ACIS). More generalized DNA damage was measured both by (32)P-postlabeling and by abasic (AB) site analysis. Placenta stained with antiserum elicited against DNA modified with 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydro-benzo[a]pyrene (BPDE) revealed PAH-DNA adduct localization in nuclei of the cytotrophoblast (CT) cells and syncytiotrophoblast (ST) knots lining the chorionic villi. The highest levels of DNA damage, 49-312 PAH-DNA adducts/10(8) nucleotides, were found by IHC/ACIS in 14 immediately fixed placenta samples. An additional 37 placenta samples were stored frozen before fixation and embedding, and because PAH-DNA adducts were largely undetectable in these samples, freezing was implicated in the loss of IHC signal. The same placentas (n = 37) contained 1.7-8.6 stable/bulky DNA adducts/10(8) nucleotides and 0.6-47.2 AB sites/10(5) nucleotides. For all methods, there was no correlation among types of DNA damage and no difference in extent of DNA damage between smokers and nonsmokers. Therefore, the data show that DNA from placentas obtained in Teplice contained multiple types of DNA damage, which likely arose from various environmental exposures. In addition, PAH-DNA adducts were present at high concentrations in the CT cells and ST knots of the chorionic villi.

Induction of abasic sites by the drinking-water mutagen MX in Salmonella TA100

Mutagen X (MX) is a chlorinated furanone that accounts for more of the mutagenic activity of drinking water than any other disinfection by-product. It is one of the most potent base-substitution mutagens in the Salmonella (Ames) mutagenicity assay, producing primarily GC to TA mutations in TA100. MX does not produce stable DNA adducts in cellular or acellular DNA. However, theoretical calculations predict that it might induce abasic sites, which it does in supercoiled plasmid DNA but not in rodents. To investigate the ability of MX to induce abasic sites in cellular DNA, we used an aldehydic site assay to detect abasic sites in DNA from Salmonella TA100 cells treated for 1.5 h with MX. At 0, 2.3, and 4.6 microM, MX induced mutant frequencies (revertants/10(6) survivors) and percent survivals of 2 (100%), 14.9 (111%), and 59.3 (45%), respectively. The frequencies of abasic sites (sites/10(5) nucleotides) for the control and two concentrations were 5.9, 6.2, and 9.7, respectively, with the frequency at the highest concentration being significant (P<0.001). These results provide some evidence for the ability of MX to induce abasic sites in cellular DNA. However, the lack of a dose response makes it unclear whether this DNA damage underlies the mutagenic activity of MX.

Mutagenicity, stable DNA adducts, and abasic sites induced in Salmonella by phenanthro[3,4-b]- and phenanthro[4,3-b]thiophenes, sulfur analogs of benzo[c]phenanthrene

Sulfur-containing polycyclic aromatic hydrocarbons (thia-PAHs or thiaarenes) are common constituents of air pollution and cigarette smoke, but only a few have been studied for health effects. We evaluated the mutagenicity in Salmonella TA98, TA100, and TA104 of two sulfur-containing derivatives of benzo[c]phenanthrene, phenanthro[3,4-b]thiophene (P[3,4-b]T), and phenanthro[4,3-b]thiophene (P[4,3-b]T) as well as their dihydrodiol and sulfone derivatives. In addition, we assessed levels of stable DNA adducts (by (32)P-postlabeling) as well as abasic sites (by an aldehydic-site assay) produced by six of these compounds in TA100. P[3,4-b]T and its 6,7- and 8,9-diols, P[3,4-b]T sulfone, P[4,3-b]T, and its 8,9-diol were mutagenic in TA100. P[3,4-b]T sulfone, the most potent mutagen, was approximately twice as potent as benzo[a]pyrene in both TA98 and TA100. Benzo-ring dihydrodiols were much more potent than K-region dihydrodiols, which had little or no mutagenic activity in any strain. P[3,4-b]T sulfone produced abasic sites and not stable DNA adducts; the other five compounds examined, B[c]P, B[c]P 3,4-diol, P[3,4-b]T, P[3,4-b]T 8,9-diol, and P[4,3-b]T 8,9-diol, produced only stable DNA adducts. P[3,4-b]T sulfone was the only compound that produced significant levels of frameshift mutagenicity and induced mutations primarily at GC sites. In contrast, B[c]P, its 3,4-diol, and the 8,9 diols of the phenanthrothiophenes induced mutations primarily at AT sites. P[3,4-b]T was not mutagenic in TA104, whereas P[3,4-b]T sulfone was. The two isomeric forms (P[3,4-b]T and P[4,3-b]T) are apparently activated differently, with the latter, but not the former, involving a diol pathway. This study is the first illustrating the potential importance of abasic sites in the mutagenicity of thia-PAHs.

In vivo Comet assay on isolated kidney cells to distinguish genotoxic carcinogens from epigenetic carcinogens or cytotoxic compounds

The objective of this study was to determine the ability of the alkaline in vivo Comet assay (pH>13) to distinguish genotoxic carcinogens from epigenetic carcinogens when performed on freshly isolated kidney cells and to determine the possible interference of cytotoxicity by assessing DNA damage induced by renal genotoxic, epigenetic or toxic compounds after enzymatic isolation of kidney cells from OFA Sprague-Dawley male rats. The ability of the Comet assay to distinguish (1) genotoxicity versus cytotoxicity and (2) genotoxic versus non-genotoxic (epigenetic) carcinogens, was thus investigated by studying five known genotoxic renal carcinogens acting through diverse mechanisms of action, i.e. streptozotocin, aristolochic acids, 2-nitroanisole, potassium bromate and cisplatin, two rodent renal epigenetic carcinogens: d-limonene and ciclosporine and two nephrotoxic compounds: streptomycin and indomethacin. Animals were treated once with the test compound by the appropriate route of administration and genotoxic effects were measured at the two sampling times of 3-6 and 22-26h after treatment. Regarding the tissue processing, the limited background level of DNA migration observed in the negative control groups throughout all experiments demonstrated that the enzymatic isolation method implemented in the current study is appropriate. On the other hand, streptozotocin, 20mg/kg, used as positive reference control concurrently to each assay, caused a clear increase in the mean Olive Tail Moment median value, which allows validating the current methodology. Under these experimental conditions, the in vivo rodent Comet assay demonstrated good sensitivity and good specificity: all the five renal genotoxic carcinogens were clearly detected in at least one expression period either directly or indirectly, as in the case of cisplatin: for this cross-linking agent, the significant decrease in DNA migration observed under standard electrophoresis conditions was clearly amplified when the duration of electrophoresis was increased up to 40min. In contrast, epigenetic and nephrotoxic compounds failed to induce any signifcant increase in DNA migration. In conclusion, the in vivo rodent Comet assay performed on isolated kidney cells could be used as a tool to investigate the genotoxic potential of a test compound if neoplasic/preneoplasic changes occur after subchronic or chronic treatments, in order to determine the role of genotoxicity in tumor induction. Moreover, the epigenetic carcinogens and cytotoxic compounds displayed clearly negative responses in this study. These results allow excluding a DNA direct-acting mechanism of action and can thus suggest that a threshold exists. Therefore, the current in vivo rodent Comet assay could contribute to elucidate an epigenetic mechanism and thus, to undertake a risk assessment associated with human use, depending on the exposure level.

Comparative efficacy of oligonol, catechin and (−)-epigallocatechin 3-O-gallate in modulating the potassium bromate-induced renal toxicity in rats

Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen. Oligonol is a product emanating from the oligomerization of polyphenols, typically proanthocyanidin from a variety of fruits (grapes, apples, persimmons, etc.) and contains catechin-type monomers and proanthocyanidin oligomers. In this study, the ability of oligonol derived from grape seeds, grape seeds extracts (Product A, containing biologically active flavonoids and the oligomeric proanthocyanidin) and pine bark extracts (Product B, composed of flavan-3-ol derivatives) to modulate the KBrO(3)-induced renal toxicity was compared with (+) catechin and (-)-epigallocatechin 3-O-gallate (EGCG). In the Trolox equivalent antioxidant capacity (TEAC) assay, the order of the antioxidant activity was EGCG>catechin>oligonol>Product A>Product B. However, oligonol elicits the strongest antioxidant capacity following in vivo supplementation to rats, with the order of efficacy of oligonol>Product A> or =Product B>EGCG>catechin. Blood levels of lipid peroxidation products (LPO), urea nitrogen (BUN) and creatinine were elevated by KBrO(3) treatment. Oligonol significantly restored LPO to the level in the untreated rats and had the strongest potency when compared with the effects of Products A and B. The five materials lowered KBrO(3)-induced BUN level, but this was not statistically significant. Oligonol significantly reduced the increased level of the creatinine, seconded by Product A, Product B and EGCG. Catechin had the lowest effect in both the BUN and creatinine levels. That oligonol was able to modulate KBrO(3)-induced lipid peroxidation and the levels of blood urea nitrogen and creatinine suggests potential chemopreventive function and application in mitigating toxicity due to long-term exposure to KBrO(3) in public drinking water.