Calibration of the comet assay using ionising radiation.

Several trials have attempted to identify sources of inter-laboratory variability in comet assay results, aiming at achieving more equal responses. Ionising radiation induces a defined level of DNA single-strand breaks (per dose/base pairs) and is used as a reference when comparing comet results but relies on accurately determined radiation doses. In this ring test we studied the significance of dose calibrations and comet assay protocol differences, with the object of identifying causes of variability and how to deal with them. Eight participating laboratories, using either x-ray or gamma radiation units, measured dose rates using alanine pellet dosimeters that were subsequently sent to a specialised laboratory for analysis. We found substantial deviations between calibrated and nominal (uncalibrated) dose rates, with up to 46% difference comparing highest and lowest values. Three additional dosimetry systems were employed in some laboratories: thermoluminescence detectors and two aqueous chemical dosimeters. Fricke's and Benzoic Acid dosimetry solutions gave reliable quantitative dose estimations using local equipment. Mononuclear cells from fresh human blood or mammalian cell lines were irradiated locally with calibrated (alanine) radiation doses and analysed for DNA damage using a standardised comet assay protocol and a lab-specific protocol. The dose response of eight laboratories, calculated against calibrated radiation doses, was linear with slope variance CV= 29% with the lab-specific protocol, reduced to CV= 16% with the standard protocol. Variation between laboratories indicate post-irradiation repair differences. Intra-laboratory variation was very low judging from the dose response of 8 donors (CV=4%). Electrophoresis conditions were different in the lab-specific protocols explaining some dose response variations which were reduced by systematic corrections for electrophoresis conditions. The study shows that comet assay data obtained in different laboratories can be compared quantitatively using calibrated radiation doses and that systematic corrections for electrophoresis conditions are useful.

An investigation of DNA damage and DNA repair in chemical carcinogenesis triggered by small-molecule xenobiotics and in cancer: Thirty years with the comet assay.

In the present review we addressed the determination of DNA damage induced by small-molecule carcinogens, considered their persistence in DNA and mutagenicity in in vitro and in vivo systems over a period of 30 years. The review spans from the investigation of the role of DNA damage in the cascade of chemical carcinogenesis. In the nineties, this concept evolved into the biomonitoring studies comprising multiple biomarkers that not only reflected DNA/chromosomal damage, but also the potential of the organism for biotransformation/elimination of various xenobiotics. Since first years of the new millennium, dynamic system of DNA repair and host susceptibility factors started to appear in studies and a considerable knowledge has been accumulated on carcinogens and their role in carcinogenesis. It was understood that the final biological links bridging the arising DNA damage and cancer onset remain to be elucidated. In further years the community of scientists learnt that cancer is a multifactorial disease evolving over several decades of individual´s life. Moreover, DNA damage and DNA repair are inseparable players also in treatment of malignant diseases, but affect substantially other processes, such as degeneration. Functional monitoring of DNA repair pathways and DNA damage response may cast some light on above aspects. Very little is currently known about the relationship between telomere homeostasis and DNA damage formation and repair. DNA damage/repair in genomic and mitochondrial DNA and crosstalk between these two entities emerge as a new interesting topic.

Oxidative Damage in Sporadic Colorectal Cancer: Molecular Mapping of Base Excision Repair Glycosylases in Colorectal Cancer Patients.

Oxidative stress with subsequent premutagenic oxidative DNA damage has been implicated in colorectal carcinogenesis. The repair of oxidative DNA damage is initiated by lesion-specific DNA glycosylases (hOGG1, NTH1, MUTYH). The direct evidence of the role of oxidative DNA damage and its repair is proven by hereditary syndromes (MUTYH-associated polyposis, NTHL1-associated tumor syndrome), where germline mutations cause loss-of-function in glycosylases of base excision repair, thus enabling the accumulation of oxidative DNA damage and leading to the adenoma-colorectal cancer transition. Unrepaired oxidative DNA damage often results in G:C>T:A mutations in tumor suppressor genes and proto-oncogenes and widespread occurrence of chromosomal copy-neutral loss of heterozygosity. However, the situation is more complicated in complex and heterogeneous disease, such as sporadic colorectal cancer. Here we summarized our current knowledge of the role of oxidative DNA damage and its repair on the onset, prognosis and treatment of sporadic colorectal cancer. Molecular and histological tumor heterogeneity was considered. Our study has also suggested an additional important source of oxidative DNA damage due to intestinal dysbiosis. The roles of base excision repair glycosylases (hOGG1, MUTYH) in tumor and adjacent mucosa tissues of colorectal cancer patients, particularly in the interplay with other factors (especially microenvironment), deserve further attention. Base excision repair characteristics determined in colorectal cancer tissues reflect, rather, a disease prognosis. Finally, we discuss the role of DNA repair in the treatment of colon cancer, since acquired or inherited defects in DNA repair pathways can be effectively used in therapy.

Does Neuraxial Anesthesia as General Anesthesia Damage DNA? A Pilot Study in Patients Undergoing Orthopedic Traumatological Surgery.

The human organism is exposed daily to many endogenous and exogenous substances that are the source of oxidative damage. Oxidative damage is one of the most frequent types of cell component damage, leading to oxidation of lipids, proteins, and the DNA molecule. The predominance of these damaging processes may later be responsible for human diseases such as cancer, neurodegenerative disease, or heart failure. Anesthetics undoubtedly belong to the group of substances harming DNA integrity. The goal of this pilot study is to evaluate the range of DNA damage by general and neuraxial spinal anesthesia in two groups of patients undergoing orthopedic traumatological surgery. Each group contained 20 patients, and blood samples were collected before and after anesthesia; the degree of DNA damage was evaluated by the comet assay method. Our results suggest that general anesthesia can cause statistically significant damage to the DNA of patients, whereas neuraxial anesthesia has no negative influence.

The evaluation of oxidative damage of DNA after poisoning with nerve agents.

The potency of three nerve agents (sarin, soman, tabun) to induce oxidative damage of DNA in lymphocytes, liver and brain during lethal or sublethal poisoning was investigated. The single strand breaks or oxidative base DNA damage was evaluated with the help of Comet assay and a specific enzyme able to detect oxidative bases of DNA (endonuclease III). While sarin and soman administered at sublethal doses corresponding to 50% of their LD50 values were not able to induce oxidative damage of DNA, their lethal dose (LD50) induced the significant increase of the number of oxidative bases in DNA of hepatocytes. In addition, tabun administered at lethal dose (LD50) induced significant increase of the number of single strand breaks and oxidative bases of DNA in glial cells isolated from pontomedullar brain region. Thus, some nerve agents were able to induce oxidative damage in the peripheral as well as central compartment but only in the case of severe poisoning caused by lethal doses of nerve agents. This non-cholinergic effect of nerve agents has probably consequences with nerve agents-induced hypoxic status during acute cholinergic crisis and it can contribute to their long-term toxic effects.

Screening of the chemoprotective effect of 13 compounds and their mixtures with sodium 2-mercaptoethanesulfonate against 2-chloroethyl ethyl sulfide.

2-chloroethyl ethyl sulfide (CEES) is a vesicant agent, commonly referred to half mustard due to its ability to form monofunctional adducts with DNA. In this study, we evaluated the chemoprotective potential of 13 compounds and their mixtures with sodium 2-mercaptoethanesulfonate (MESNA) against CEES-induced geno- and cytotoxicity in human lung cell line A-549. MESNA, L-glutathione (GSH), thiourea, sodium thiosulfate, hexamethylenetetramine, 4-acetamidophenol, asoxime dichloride (HI-6), N-acetyl-L-cysteine (NAC), sodium pyruvate, myo-inositol, 3-aminobenzamide (3-AB), nicotinamide, and Nω-nitro-L-arginine methyl ester hydrochloride and combinations of these compounds with MESNA were applied 30 min before CEES. DNA alkylation was measured using modified comet assay 1 and 24 h after the exposure. Cell viability was determined using MTT assay at 24 and 72 h. The mono-therapeutical approach identified MESNA and GSH to provide significant chemoprotection. NAC and 3-AB supported DNA damage repair, while cell viability remained unaffected. Mixtures of GSH or NAC with MESNA showed protective synergism against DNA damage. Other compounds or their combinations with MESNA failed due to the potentiation of CEES-induced cytotoxicity. The chemoprotection against CEES remains limited; however, the combination of substances can provide protective synergy and may represent a promising strategy in the treatment of accidental exposure to monoalkylating agents.

Inter strand crosslinks in DNA induced in vivo by percutaneous application of sulphur mustard to rats and mice.

Inter-strand crosslinks (ICL) in the DNA are regarded to be the main toxic lesions induced by sulphur mustard (SM). We have followed the induction of ICL in the DNA of different organs of Wistar rats and Balb/c or NMRI mice by the percutaneous application of SM using the modified (reverse) comet assay. Significant amounts of ICL were found in Balb/C lymphocytes, in bone marrow and liver cells after the dose of 80 mg/kg. A dose-dependent amount of ICL was induced in rats, with efficient induction in lymphocytes and spleen cells already after 5 mg SM/kg, indicating a higher susceptibility of rats to the DNA-damaging effect of SM compared with mice. A significant induction of ICL in other tested tissues (liver, bone marrow, colon epithelium) was seen at the dose of 20 mg/kg. The induced ICL were removed from the DNA during 48 h except for rats at the dose of 80 mg/kg. In fact, we observed that ICL are almost completely repaired in tissues of rats receiving high lethal doses. Results suggest that the unhooking of ICL, which we followed with the comet assay, may lead to the formation of another toxic DNA lesion during the repair process.

Protective potential of different compounds and their combinations with MESNA against sulfur mustard-induced cytotoxicity and genotoxicity.

The purpose of this study was to evaluate the efficacy of potential candidate molecules or their combinations against strong alkylation agent sulfur mustard (SM) on the human lung alveolar epithelial cell line A-549. Candidate molecules were chosen on the basis of their previously observed protective effects in vitro. The tested compounds, including antioxidants, sulfhydryl or other sulfur-containing molecules, nitrogen-containing molecules, PARP inhibitors and a NO synthase inhibitor, were applicated 30min before SM treatment. The efficiency of candidate molecules to protect cells against DNA damage and cell death induced by SM was determined using single-cell gel electrophoresis (comet assay) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction by viable cells. The damage of DNA was assessed 1 and 24h after dose 50µM SM. Cell survival was assessed 24 and 72h after the exposure. To achieve maximal cytoprotection, combinations of selected compounds with sodium 2-mercaptoethane sulphonate (MESNA) were tested. We found significant protective effects by several drugs used individually and also in combination with MESNA. High protection was achieved by sodium thiosulphate, which was further potentiated when combined with MESNA. Most of the selected compounds or mixture provided only moderate genoptotection without having any effect towards cell viability.

Induction and repair of DNA cross-links induced by sulfur mustard in the A-549 cell line followed by a comet assay.

Sulfur mustard is a highly toxic chemical warfare agent with devastating impact on intoxicated tissues. DNA cross-links are probably the most toxic DNA lesions induced in the cell by sulfur mustard. The comet assay is a very sensitive method for measuring DNA damage. In the present study using the A-549 lung cell line, the comet assay protocol was optimized for indirect detection of DNA cross-links induced by sulfur mustard. The method is based on the additional treatment of the assayed cells containing cross-links with the chemical mutagen, styrene oxide. Alkali-labile adducts of styrene oxide cause DNA breaks leading to the formation of comets. A significant dose-dependent reduction of DNA migration of the comet's tail was found after exposing cells to sulfur mustard, indicative of the amount of sulfur mustard induced cross-links. The remarkable decrease of % tail DNA could be observed as early as 5min following exposure to sulfur mustard and the maximal effect was found after 30min, when DNA migration was reduced to the minimum. Sulfur mustard preincubated in culture medium without cells lost its ability to induce cross-links and had a half-life of about 15min. Pre-incubation longer than 30min does not lead to a significant increase in cross-links when applied to cells. However, the amount of cross-links is decreased during further incubation due to repair. The current modification of the comet assay provides a useful tool for detecting DNA cross-links induced by sulfur mustard and could be used for detection of other DNA cross-linking agents such as chemotherapeutic drugs.

DNA crosslinks, DNA damage and repair in peripheral blood lymphocytes of non-small cell lung cancer patients treated with platinum derivatives.

Lung cancer is the leading cause of cancer-related mortality in the world. Chemotherapy has been the mainstay of treatment for advanced non-small cell lung cancer (NSCLC) and platinum-based derivatives have been shown to improve overall survival. The aim of the present study was to investigate the DNA damage [single strand breaks (SSBs) and DNA crosslinks] and DNA repair in peripheral blood lymphocytes in patients with NSCLC treated with platinum derivatives using modified comet assay. Twenty patients in the final (4th) stage of NSCLC and 10 age-corresponding healthy controls participated in the study. Alkaline comet assay was performed according to the appropriate protocol. The DNA base excision repair (BER) activity of the controls was significantly higher compared to that of cancer patients, and the activity of DNA nucleotide excision repair (NER) was almost at the same level both in controls and patients. We observed changes in the amount of SSBs and DNA crosslinks during the course of chemotherapy. We found a significantly higher level of SSBs immediately after administration of chemotherapy. Similarly, we found the highest incidence of DNA crosslinks immediately or 1 day after chemotherapy (compared to measurement before chemotherapy). Moreover, we compared the levels of DNA repair in patients who survived chemotherapy with those in patients who died in the course of chemotherapy: the activity of BER was higher in the case of surviving patients, while the levels of NER were essentially the same. The data arising from the present study confirm the findings of other studies dealing with DNA damage and repair in cancer patients treated with chemotherapy. Moreover, our results indicated that despite the fact that cisplatin-DNA adducts are removed by the NER pathway, BER may also play a role in the clinical status of patients and their survival.

Sulfur mustard causes oxidative stress and depletion of antioxidants in muscles, livers, and kidneys of Wistar rats.

Sulfur mustard (SM) is a chemical warfare agent with cytotoxic effect and a tight link to oxidative stress (OS). Depletion of antioxidants is considered as a cause of detrimental consequence and belongs to the important steps leading to cell death. The oxidative injury appearing after SM exposure is not well understood. Nevertheless, identification of the pathological processes would be a good opportunity to establish an efficient therapy. Here, we focused our effort on an estimation of reactive oxygen species homeostasis and apoptotic processes in Wistar rats exposed to 0-160 mg/kg of SM. We assayed antioxidant activity, thiobarbituric acid reactive substances, reduced glutathione/oxidized glutathione, metallothionein, glutathione reductase, glutathione peroxidase, glutathione S-transferase, caspase 3, and glucose in the livers, kidneys, and muscles of the animals. Significant OS, depletion of low-molecular-mass antioxidants, increase in caspase activity, and some other processes related to SM action were determined. Moreover, we infer a principal role of OS in the tested organs.

Sulfur mustard induced oxidative stress and its alteration using asoxime (HI-6).

Sulfur mustard (SM) is a blister agent with cytotoxic mechanism of action. There is no suitable treatment based on administration of an antidote. In this study, Wistar rats were exposed to SM in doses of 0-40 mg/kg body weight and treated with the compound HI-6. The treatment provided no significant effect on ferric reducing antioxidant power of blood and plasma. However, HI-6 caused an increase in the level of thiobarbituric acid reactive substances. This stressogenic response was presumably the cause of the significant elevation of the blood level of both glutathione reductase and reduced glutathione. HI-6 appears to be suitable for enhancing prophylactically oxidative stress protection from small oxidative insult.

Cytotoxicity and genotoxicity evaluation of antidote oxime HI-6 tested on eight cell lines of human and rodent origin.

Oxime HI-6 is an efficient reactivator of the acetylcholinesterase inhibited by organophosphorous nerve agents. In this study we have estimated cytotoxicity of HI-6 by the colony forming assay and genotoxicity by the comet assay on human and rodent cell lines. IC50 of HI-6 assessed by the colony forming capacity was 3.59 mM for HeLa cells and 5.18 mM for a mouse cell line L929. Small difference in cytotoxicity was found among other cell lines tested: IC50 was 1.61 mM for human A549 cells, 1.14 mM for UROtse line, 1.96 mM and 1.71 mM for Chinese hamster cells AA8 and UV-20, respectively. The A549 cell viability measured with the MTT test was 5 times decreased comparing 2 and 24 hours of HI-6 oxime treatment. The 5 mM HI-6 concentration reduced the viability within 2 hours to 95% only, however, it induced a significant number of DNA breaks in mouse cells L929, and also in human UROtse and HepG2 cells. 1-ß-D-arabinofuranosylcytosine (10(-4) M) and hydroxyurea (10(-2) M), supplemented to the cultivation medium, did not cause any significant accumulation of DNA breaks during treatment, which indicated that the nucleotide excision repair was not acting on the induced DNA damage.

Application of the comet assay method in clinical studies.

The comet assay or single-cell gel electrophoresis (SCGE) assay is now widely accepted as a standard method for assessing DNA damage in individual cells. It finds use in a broad variety of applications including human biomonitoring, genotoxicology, ecological monitoring and as a tool for investigation of DNA damage and repair in different cell types in response to a range of DNA-damaging agents. The comet assay should be eminently suitable for use in clinical practice since it is a relatively simple and inexpensive technique which requires only a few cells, and results can be obtained within a matter of hours. This method can be used in the study of cancer as well as in lifestyle and dietary studies. In cancer it is useful for measuring DNA damage before, throughout and after therapy (either radiotherapy or chemotherapy). Another use of this method is in lifestyle study, such as investigation of the effect on DNA of common human activities (e.g. smoking, or working with a potentially genotoxic agent). The final use of comet assay in this paper is dietary study. In this type of study we observe the effects of consumption of specific foods or supplements which may be protective for DNA against damage.

Investigation of oxidative stress in blood, brain, kidney, and liver after oxime antidote HI-6 application in a mouse experimental model.

Oxime reactivator HI-6 (asoxime, in some sources) is a potent antidote suitable for treatment of intoxication by nerve agents. Despite the fact that HI-6 is considered for practical application in emergency situations, the impact of HI-6 on patients' bodies has not been established yet. The present experiment was carried out in order to estimate whether HI-6 would be able to trigger or protect from oxidative stress in a BALB/c mice model. HI-6 was applied in doses ranging from 0.2 to 20% of LD50. Ferric-reducing antioxidant power (FRAP), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), and glutathione reductase (GR) were assayed in the blood, liver, kidney, and brain of treated animals. It was found that HI-6 does not increase GR or TBARS. On the contrary, TBARS levels in the brain and liver were found to be significantly decreased in HI-6-treated animals. Pertinent antioxidant properties of HI-6 were excluded by the FRAP method. Endogenous antioxidants were unchanged, with the exception of the kidney. Low-molecular-weight antioxidants assayed by the FRAP method were significantly decreased in kidneys of animals treated with HI-6. However, GSH partially recovered the loss of the other low-molecular-weight antioxidants and was significantly increased in the kidney of HI-6-exposed mice. HI-6 potential to produce nephropathy is hypothesized. The achieved conclusions were quite surprising and showed a complex impact of HI-6 on the body.

DNA damage and nucleotide excision repair capacity in healthy individuals.

Interindividual differences in DNA repair capacity (DRC) represent an important source of variability in genome integrity and thus influence health risk. In the last decade, DRC measurement has attracted attention as a potential biomarker in cancer prediction. Aim of the present exploratory study was to characterize the variability in DNA damage and DRC on 100 healthy individuals and to identify biological, lifestyle, or genetic factors modulating these parameters. The ultimate goal was to obtain reference data from cancer-free population, which may constitute background for further investigations on cancer patients. The endogenous DNA damage was measured as a level of DNA single-strand breaks and DRC, specific for nucleotide excision repair (NER), was evaluated using modified comet assay, following the challenge of peripheral blood mononuclear cells with benzo[a]pyrene diolepoxide. Additionally, genetic polymorphisms in NER genes (XPA, XPC, XPD, and XPG) were assessed. We have observed a substantial interindividual variability for both examined parameters. DNA damage was significantly affected by gender and alcohol consumption (P = 0.003 and P = 0.012, respectively), whereas DRC was associated with family history of cancer (P = 0.012). The stratification according to common variants in NER genes showed that DNA damage was significantly modulated by the presence of the variant T allele of XPC Ala499Val polymorphism (P = 0.01), while DRC was modulated by the presence of the A allele of XPA G23A polymorphism (P = 0.048). Our results indicate the range of endogenous DNA single-strand breaks and capacity of NER in healthy volunteers as well as the role of potentially relevant confounders. Environ. Mol. Mutagen. 2011. © 2011 Wiley-Liss, Inc.

Parameters of oxidative stress, DNA damage and DNA repair in type 1 and type 2 diabetes mellitus.

OBJECTIVES: (i) to determine the extent of oxidative stress and DNA damage and repair using a panel of selected markers in patients with type 1 and type 2 diabetes mellitus (T1DM, T2DM), (ii) to find their possible relationships with diabetes compensation and duration, and finally (iii) to test for the effect of functional polymorphisms in the 8-oxoguanin DNA glycosylase (rs1052133), catalase (rs1001179) and superoxide dismutase (rs4880) genes on respective intermediate phenotypes. METHODS: A total of 207 subjects (23 children and 44 adults with T1DM, 52 adult patients with T2DM and 88 healthy adult control subjects) were enrolled in the study. The following markers of redox state were determined in participants: erythrocyte superoxide dismutase (Ery-SOD), whole blood glutathione peroxidase (WB-GPx), erythrocyte glutathione (Ery-GSH), plasma total antioxidant capacity (P-tAOC) and plasma malondialdehyde (P-MDA). Furthermore, the extent of DNA damage and repair was ascertained using the following parameters: DNA single strand breaks (DNAssb), DNA repair capacity (DNArc) and DNA repair index (DNRI). RESULTS: Comparison of T1DM vs. T2DM patients revealed significantly higher Ery-GSH content (P < 0.0001) and significantly lower Ery-SOD activity (P = 0.0006) and P-tAOC level (P < 0.0001) in T1DM subjects. T2DM diabetics exhibited a significant increase in DNAssb (P < 0.0001) and significant decrease in both DNArc (P < 0.0001) and DNRI (P < .0001) compared with T1DM patients. Patient's age (irrespective of DM type) significantly correlated with DNAssb (r = 0.48, P < 0.0001), DNArc (r = -0.67, P < 0.0001) and DNRI (r = -0.7, P < 0.0001). Allele frequencies of all studied polymorphisms did not exhibit any significant association with the investigated parameters. CONCLUSION: We demonstrated significant age- and DM type-related changes of oxidative DNA modification and capacity for its repair in subjects with T1DM and T2DM.

DNA damage, DNA repair rates and mRNA expression levels of cell cycle genes (TP53, p21(CDKN1A), BCL2 and BAX) with respect to occupational exposure to styrene.

We studied the relationship between DNA damage, DNA repair rates and messenger RNA (mRNA) expression levels of cell cycle genes TP53, p21(CDKN1A), BCL2 and BAX in a group of 71 styrene-exposed workers and 51 control individuals. The exposure was assessed by measuring the concentration of styrene at workplace and in blood. Parameters of DNA damage [measured as single-strand breaks (SSBs) and endonuclease III-sensitive sites], γ-irradiation-specific DNA repair rates and mRNA levels of studied genes were analyzed in peripheral blood lymphocytes. The workers were divided into low (<50 mg/m³) and high (>50 mg/m³) styrene exposure groups. We found negative correlations between mRNA expression of TP53, BCL2, BAX and styrene exposure (P < 0.001 for all parameters). In contrast, p21(CDKN1A) mRNA expression significantly increased with increasing styrene exposure (P = 0.001). SSBs and endonuclease III-sensitive sites increased with increasing mRNA levels of TP53 (P < 0.001 for both) and BCL2 (P = 0.038, P = 0.002, respectively), whereas the same parameters decreased with increasing mRNA levels of p21(CDKN1A) (P < 0.001, P = 0.007, respectively). γ-Irradiation-specific DNA repair rates increased with p21(CDKN1A) mRNA levels up to the low exposure level (P = 0.044). Our study suggests a possible relationship between styrene exposure, DNA damage and transcript levels of key cell cycle genes.

Oxidative stress after sulfur mustard intoxication and its reduction by melatonin: efficacy of antioxidant therapy during serious intoxication.

Sulfur mustard (SM) is an important chemical warfare agent. The mechanism of SM toxicity still has not been fully recognized. However, oxidative stress and following the damaging of macromolecules in the human body is considered one of the crucial steps in SM toxicity. Rats intoxicated with pure (i.e., distilled) SM were used as a model organism. The doses, 0 (control), 5, 20, and 80 mg/kg of body weight, were applied intradermally. A hormone with strong antioxidant potency, melatonin, was applied (25 and 50 mg/kg, subcutaneously) into the other group of rats exposed with the same doses of SM. Total plasma protein, ferric-reducing antioxidant power (FRAP), thiobarbituric-acid-reactive substances (TBARS), and plasma protein carbonyls were assayed in blood plasma. A significant decrease of total plasma proteins was found for control, and the lowest dose of SM was treated with melatonin. Melatonin was also able to enhance the production of low-molecular-weight antioxidants, as the SM-intoxicated rats had significantly (P ≤ 0.01) increasing FRAP levels after intoxication with SM in doses of 20 and 80 mg/kg, when compared to the control treated with melatonin. Melatonin also decreased TBARS level, representing reduced lipid peroxidation (LPO). However, LPO seems to be of less importance for SM toxic impact. The more reliable parameter was the level of total plasma protein carbonyls. The carbonyl levels were significantly increased due to SM, and the carbonylation was slowed due to melatonin intake. In conclusion, melatonin seems to be a prospective compound in reducing SM toxicity impact in the rat.

Sulfur mustard induced oxidative stress and its alteration by epigallocatechin gallate.

Sulfur mustard (bis(2-chloroethyl)sulfide; CAS: 505-60-2; abbreviated as HD) is a chemical warfare agent with not well understood mechanism of toxic effect. Deprivation of energy in cells and arising of oxidative stress appears during the exposure. Our experiment is based on investigation of 10mg or 20mg epigallocatechin gallate (EGCG) dose prophylactic effect (1h before HD) in rats exposed to either 20mg or 80 mg of HD. Blood mass, plasma and liver were sampled. Ferric reducing antioxidant power (FRAP), reduced glutathione, thiobarbuturic acid reactive substances (TBARSs), glutathione reductase, glutathione S-transferase and caspase 3 were assessed. Animals were sacrificed one day after exposure. We found significant deprivation of low molecular weight antioxidants due to EGCG but not due to HD. However, HD depleted reduced glutathione. EGCG has no effect to influence TBARS level. EGCG and HD up-regulated glutathione reductase and EGCG down regulated glutathione S-transferase in liver tissue. Regarding caspase, EGCG had anti apoptotic potency. We discuss potency to use EGCG to ameliorate redox balance after HD exposure. The data also appoints at difficulty in antioxidant therapy as prophylaxis to the oxidative stress related toxins exposure and ambivalent modulation of oxidative stress.