Application of the comet assay for investigation of oxidative DNA damage in equine peripheral blood mononuclear cells

Biocompatibility of nano/micro-sized pyrophyllite particles by pulmo, liver, kidney and gastric mucosis cells

Pyrophyllite is the least studied natural clay in terms of its potential in biomedical applications, although there are many deposits of this aluminosilicate around the world. Genotoxicity study was performed in vitro for this mineral. Subsequently, Wister rats were exposed to the pyrophyllite micronized to below 100 µm. After the exposure period, histology of the lung, liver, kidney and gastric tissues were performed, followed by the stereological and hematological analysis. The physicochemical analyses revealed typical XRD characteristics of pyrophyllite clay with particle-size distribution ranging 50 nm-100 μm with stable mineral composition and unique buffering property to pH around 8. The results showed that there were no cytotoxic effects on to THP-1 cells, or genotoxicity of pyrophyllite measured by the Comet assay. In vivo studies are accompanied by the thorough physicochemical characterization of the micronized pyrophyllite. Histology of the lung tissue proved presence of an inflammatory reaction. On the other hand, gastric tissue has shown the selective accumulation of nanoparticles in enterocytes of the stomach only, as supported by ultrastructural analysis. Liver and kidney tissues have shown tolerability for pyrophyllite particles. The results give directions for further comprehensive studies of potential biomedical applications of the pyrophyllite.

Analyses of oxidative DNA damage among coal vendors via single cell gel electrophoresis and quantification of 8-hydroxy-2'-deoxyguanosine

Looking at the development status of Nigeria and other developing nations, most low-income and rural households often use coal as a source of energy which necessitates its trade very close to the communities. Moreover, the effects of exposure to coal mining activities are rarely explored or yet to be studied, not to mention the numerous street coal vendors in Nigeria. This study investigated the oxidative stress levels in serum and urine through the biomarker 8-OHdG and DNA damage via single cell gel electrophoresis (alkaline comet assay). Blood and urine levels of 8-OHdG from 130 coal vendors and 130 population-based controls were determined by ELISA. Alkaline comet assay was also performed on white blood cells for DNA damage. The average values of 8-OHdG in serum and urine of coal vendors were 22.82 and 16.03 ng/ml respectively, which were significantly greater than those detected in controls (p < 0.001; 15.46 and 10.40 ng/ml of 8-OHdG in serum and urine respectively). The average tail length, % DNA in tail and olive tail moment were 25.06 μm, 18.71% and 4.42 respectively for coal vendors. However, for controls, the average values were 4.72 μm, 3.63% and 1.50 for tail length, % DNA in tail and olive tail moment respectively which were much lower than coal vendors (p < 0.001). Therefore, prolonged exposure to coal dusts could lead to higher serum and urinary 8-OHdG and significant DNA damage in coal vendors observed in tail length, % DNA in tail, and olive tail moment by single cell gel electrophoresis. It is therefore established that coal vendors exhibit a huge risk from oxidative stress and assessment of 8-OHdG with single cell gel electrophoresis has proven to be a feasible tool as biomarkers of DNA damage.

The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma

Aging is associated with a dysregulation of the immune system, leading to a general pro-inflammatory state of the organism, a process that has been named inflamm-aging. Oxidative stress has an important role in aging and in the regulation of immune responses, probably playing a role in the development of age-related diseases. The respiratory system function physiologically declines with the advancement of age. In elderly asthmatic patients, this may contribute to disease expression. In this review, we will focus on age-related changes affecting the immune system and in respiratory structure and function that could contribute to asthma occurrence, and/or clinical presentation in the elderly. Also, naturally occurring equine asthma will be discussed as a possible model for studying the importance of oxidative stress and immun-aging/inflamm-aging in humans.

Single-cell gel electrophoresis assay in the ten spotted live-bearer fish, Cnesterodon decemmaculatus (Jenyns, 1842), as bioassay for agrochemical-induced genotoxicity

The ability of two 48 percent chlorpyrifos-based insecticides (Lorsban* 48E® and CPF Zamba®), two 50 percent pirimicarb-based insecticides (Aficida® and Patton Flow®), and two 48 percent glyphosate-based herbicides (Panzer® and Credit®) to induce DNA single-strand breaks in peripheral blood erythrocytes of Cnesterodon decemmaculatus (Jenyns, 1842) (Pisces, Poeciliidae) exposed under laboratory conditions was evaluated by the single-cell gel electrophoresis (SCGE) assay. In those fish exposed to Lorsban* 48E®, CPF Zamba®, Aficida®, Patton Flow®, Credit®, and Panzer®, a significant increase of the genetic damage was observed for all formulations regardless of the harvesting time. This genotoxic effect was achieved by an enhancement of Type II-IV comets and a concomitant decrease of Type 0-I comets over control values. A regression analysis revealed that the damage varied as a negative function of the exposure time in those Lorsban* 48E®- and Aficida®-treated fish. On the other hand, a positive correlation between damage increase and exposure time was achieved after Patton Flow® and Credit® treatment. Finally, no correlation was observed between increase in the genetic damage and exposure time after treatment with CPF Zamba® or Panzer®. These results highlight that all agrochemicals inflict primary genotoxic damage at the DNA level at sublethal concentrations, regardless of the exposure time of the aquatic organisms under study, at least within a period of 96 h of treatment.

Polycyclic aromatic hydrocarbons (PAHs) as determinants of various anthropometric measures of birth outcome

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants that are known to induce oxidative stress. There have been several reports about the link between PAH exposure and complications in pregnancy. This cross-sectional study was conducted to: (1) measure the levels of benzo(a)anthracene (BaA), chrysene (Ch), benzo(b)fluoranthene (BbF), benzo(a)pyrene (BaP), and dibenzo(a,h)anthracene (DBahA) in placentas and maternal and -umbilical cord blood obtained at delivery from 1578 women between June 2005 and 2006 in the area of Al-Kharj, Saudi Arabia; (2) assess their influence on various anthropometric measures of birth outcome taking into consideration the carcinogenic properties of these PAHs; and (3) determine the degree of PAH-related oxidative DNA damage and birth outcome. Among the five tested PAHs, only BaP was carcinogenic; therefore, the levels of the other four probable or possible carcinogenic PAHs (BaA, Ch, BaF, and DBahA) were summed as ∑4-PAHs. Levels of 1-hydroxypyrene (1-HP) were determined in maternal urine samples as a biomarker of PAH internal dose. Urinary cotinine (COT) was measured as an index of smoking. The following markers of oxidative stress were selected: malondialdehyde (MDA) in cord (C-MDA) and maternal (M-MDA) serum and 8-hydroxy-2-deoxyguanosine (8-OHdG) in maternal urine. None of the tested PAHs was found in maternal or cord blood. However, all five PAH compounds were detected in placentas; Ch was the highest (6.582 μg/kg dry wt.), and BaA was the lowest (0.236 μg/kg dry wt.). The mean concentration of urinary 1-HP found in this study was 0.216 ± 0.856 μg/g Cr. After adjusting for gestational age and other confounding variables, regression models revealed an inverse relationship between placental weight, cord length and placental BaP. A similar trend was observed between cord length and ∑4-PAHs in placental tissues. Urinary 1-HP, though, cannot be used as an unequivocal biomarker of PAH exposure, but it can be an appropriate indicator of exposure to environmental tobacco smoke (ETS). The data demonstrate that ETS exposure (as measured by urinary COT) may adversely affect birth outcome as shown by reduced head circumference, birth weight, and birth length, as well as increased cephalization index. The positive relationship between 8-OHdG levels and 1-HP in urine provides evidence of an oxidative stress mechanism. Although this study provides no direct evidence of an association between PAH exposure and DNA damage, increased oxidative stress in the form of lipid peroxidation significantly affected various birth measures. Therefore, there is a need for studies regarding PAH exposure and its associated biological effects to determine the extent of potential fetal damage as well as possible long-term effects, such as cancer.

Alterations of GSH and MDA levels and their association with bee venom-induced DNA damage in human peripheral blood leukocytes

Bee venom (BV) has toxic effects in a variety of cell systems and oxidative stress has been proposed as a possible mechanism of its toxicity. This study investigated the in vitro effect of BV on glutathione (GSH) and malondialdehyde (MDA) levels, and their association with BV-induced DNA strand breaks and oxidative DNA damage in human peripheral blood leukocytes (HPBLs). Blood samples were treated with BV at concentrations ranging from 0.1 to 10 μg/ml over different lengths of time, and DNA damage in HPBLs was monitored with the alkaline and formamidopyrimidine glycoslyase (FPG)-modified comet assays, while GSH and MDA levels were determined in whole blood. Results showed a significant increase in overall DNA damage and FPG-sensitive sites in DNA of HPBLs exposed to BV compared with HPBLs from controls. An increase in DNA damage (assessed with both comet assays) was significantly associated with changes in MDA and GSH levels. When pretreated with N-acetyl-L-cysteine, a source of cysteine for the synthesis of the endogenous antioxidant GSH, a significant reduction of the DNA damaging effects of BV in HPBLs was noted. This suggests that oxidative stress is at least partly responsible for the DNA damaging effects of BV.

Oxidative stress status of highly prolific sows during gestation and lactation

Elevated oxidative stress is reported to be associated with pregnancy complications in highly prolific sows. Oxidative DNA damage and the antioxidant status were determined in blood samples collected during the course of gestation and lactation in multiparous sows. Blood samples were drawn from sows (n = 5) on days 30, 60, 90 and 110 of gestation (G30, G60, G90 and G110, respectively), on day 3, 10 and 18 of lactation (L3, L10 and L18, respectively) and on day 5 of postweaning (W5). Lymphocytes were isolated from the fresh blood and cryopreserved in each time point. Lymphocyte DNA damage was analyzed by alkaline single-cell gel electrophoresis (comet assay) to determine the single- and double-strand brakes and endogenous antioxidant concentrations using an HPLC system with UV detection. The comet assay showed elevated (P < 0.05) DNA damage (between 38% and 47%) throughout the gestational and lactational periods than during early gestation (G30; 21%). Plasma retinol concentration was reduced (P < 0.05) at the end of gestation (G110) compared with G30. Plasma α-tocopherol concentrations also showed a similar trend as to retinol. This study indicates that there is an increased systemic oxidative stress during late gestation and lactation, which are not fully recovered until the weaning compared with the G30, and that antioxidant nutrients in circulation substantially reduced in the mother pig at G110.

Protective effects of green and white tea against benzo(a)pyrene induced oxidative stress and DNA damage in murine model

In the current investigation, the ameliorative effect of green tea (GT) and white tea (WT) against benzo(a)pyrene (BaP) induced oxidative stress and DNA damage has been studied in the livers and lungs of Balb/c mice. A single dose of BaP (125 mg/kg, b.w. orally) increased the levels of lipid peroxidation (LPO) and decreased endogenous antioxidants such as superoxide dismutase (SOD), glutahione reductase (GR), catalase (CAT), and glutathione (GSH) significantly. Pretreatment with GT and WT for 35 days before a single dose of BaP elevated the decreased activity of GR, SOD, and CAT in liver tissue and also tended to normalize the levels of GSH and LPO in both hepatic and pulmonary tissues. The percentage of DNA in comet tail and 8-hydroxy-2'-deoxyguanosine levels reflected the decreasing pattern of DNA damage from the BaP-treated group to the groups that received pretreatment with GT and WT. Our study concludes that both GT and WT are effective in combating BaP induced oxidative insult and DNA damage. However, WT was found to be more protective than GT with respect to CAT (only in the liver), percentage of DNA in comet tail (only in the lungs), GST activity, and GSH content in both the tissues.

Immunomodulation during and after castration under inhalation anaesthetic without genotoxic effects on equine lymphocytes

Genotoxic DNA damage due to inhalation anaesthesia has been demonstrated in human lymphocytes. In order to evaluate anaesthesia-associated changes in cell-mediated immunity on the basis of a potential DNA damage as a health risk in horses, single cell gel electrophoresis and lymphocyte proliferation assay were performed on equine lymphocytes which were obtained before, during and after regular castration under inhalation anaesthetic. No significant lymphocytic DNA damage due to isoflurane anaesthesia was observed, whereas lymphocyte proliferative reactivity and lymphocyte counts decreased significantly (p≤0.05) during and after anaesthesia. The present study thus indicates that the combined anaesthesia does not result in significant DNA damage, which hence cannot be held responsible for the observed changes in the immune response of equine lymphocytes. However, the recognized compromises of immune function ought to be considered especially in immunologically challenged animals.

Evaluation of DNA damage after tourniquet-induced ischaemia/reperfusion injury during lower extremity surgery

Ischemia/reperfusion (I/R) injury represents a source of substantial morbidity and mortality in various statuses that is, coronary bypass, myocardial infarction, and so on. Oxygen free radicals, formed during I/R, have been proposed as one of the main causes of tissue injury and play important role in I/R injury. Leucocytes have been shown to play an important role in the development of tissue injury after I/R. Accordingly, numerous studies have shown that even short-time I/R-induced DNA damage can be investigated in human peripheral leucocytes using the alkaline single-cell gel-electrophoresis assay (comet assay). After ischaemia, the genotoxic damage detected in human peripheral leucocytes locally in the reperfused tissue results in numerical, morphologic and biochemical alterations of all circulating white blood cells in the human organism. It leads particularly to the release of substantial amounts of oxygen radicals and other reactive agents. Simultaneously, local ischaemia in the reperfused tissue is extended to the whole body systemically through these activated inflammatory cells and, possibly, results in secondary detectable tissue damage in endothelial cells of the systemic circulation inducing prolonged DNA damage even in the early reperfusion period. Thus, we aimed to investigate whether the I/R during the routinely practised operation causes DNA damage, since other published studies were on animal and in vitro models and did not exactly reflect the operation procedure in the clinic. We measured DNA damage (single-strand breaks, oxidised purines and pyrimidines) by modified alkaline comet assay using two bacterial enzymes (formamidopyrimidine glycosylase (Fpg), endonuclease III (EndoIII)), which recognise oxidised purines and pyrimidine bases, in patients who had lower extremity surgery. There was no statistically significant difference in DNA damage between time periods (before surgery, after I/R; T1, T2 and T3). According to our findings, we indicate that at the molecular level DNA is damaged due to the I/R during the routinely practised operation; however, this effect could not be determined phenotypically. Thus, we may suggest that the surgeons and anaesthetist/operation room personnel could be informed about that fact and encouraged to use antioxidants and/or apply prophylaxis. Our findings showed that I/R injury did not induce DNA damage. Further studies of this approach are needed.

Patterns of persistent DNA damage associated with sun exposure and the glutathione S-transferase M1 genotype in melanoma patients

Solar radiation can lead to changes affecting DNA metabolism resulting in loss of DNA integrity. Skin specimens obtained from melanoma patients treated at the Memorial Sloan-Kettering Cancer Center were used to study patterns of DNA fragmentation using the comet assay and levels of deletions in mitochondrial DNA (mtDNA) using real-time PCR. Skin specimens were classified according to the glutathione S-transferase M1 (GSTM1) genotype (either wild type [WT] or null) and patient sunburn history. GSTM1 null individuals with a sunburn history showed increased levels of both DNA fragmentation by comet assays and mtDNA deletions relative to GSTM1 WT patients with little or no sunburn history. Microarray analyses identified a number of genes whose expression was upregulated >or=5-fold in cells from GSTM1-null patients or from those reporting histories of sunburn. These genes encoded small molecule transporters, various growth factor/chemokine receptors, transcription factors and tumor suppressors. Of 17 genes directly involved in DNA repair, three DNA ligases were highly upregulated while the RAD23 UV excision repair gene and the Growth Arrest and DNA Damage gene (GADD45) were downregulated. These findings support the idea that exposure to solar radiation early in life may induce long-term cellular changes that lead to persistent DNA damage and altered patterns of gene expression.

Geostatistical analysis of biomarkers of genotoxicity in cattle, Bos taurus and Bos taurus x Bos indicus, sentinels near industrial facilities

This study, performed at the behest of ranchers living and working down-prevailing wind from industrial facilities located in Calhoun County, Texas investigated locational risks to ecosystem health associated with proximity to specific industrial complexes. Concerns expressed were for potential genotoxicity in cattle resulting from the release of complex chemical mixtures. The Comet Assay and flow cytometric evaluation of variations in DNA content were utilized to evaluate DNA damage. Bayesian geo-statistical analysis revealed the presence of important spatial processes. The Comet assay's optical density provided a strong indication of increased damage down-prevailing wind from the industrial complexes. Results indicated that proximity to and location down-prevailing winds from industrial facilities increased the locational risk of genotoxicity in this sentinel species.

Geostatistical analysis of DNA damage in oysters, Crassostrea virginica, in Lavaca Bay, Texas

This study evaluated the health of the marine ecosystem in Lavaca Bay, Texas using the Eastern oyster (Crassostrea virginica) as the sentinel species. Lavaca Bay has a history of having gradients of concentrations of pollutants present with some areas containing concentrations high enough to pose a threat to marine ecosystem health. The Comet assay was used to evaluate for the presence of genotoxic response in oyster hematocytes. Bayesian geostatistical analysis was then used to determine if the DNA damage in oyster hematocytes was spatially oriented and to develop continuous surface maps of the risk of DNA damage in this sentinel species. Results indicated that proximity to industrial facilities increased the locational risk of genotoxicity in this species.

Chicken nucleated blood cells as a cellular model for genotoxicity testing using the comet assay

Mycotoxins can frequently occur in animal feed and human food. T-2 toxin, as the most toxic trichothecene, has been implicated as the causative agent in a variety of animal diseases and is associated with some human diseases. The comet assay was performed as a test for detection of DNA damage caused by T-2 toxin in peripheral blood cells of chicken. The suitability of the comet assay as a biomarker for genotoxic analysis has been applied in studies using human white blood cells. It can be applied to any tissue from which a single cell suspension can be obtained. The method has already been applied to chicken as a foodstuff for detection of irradiation of food containing DNA. However, application of the method on chicken blood cells has not been set up yet. The aim of this research was to develop a protocol for detection of DNA damage induced by T-2 toxin in chicken blood cells. Chickens were administered orally with T-2 toxin and the samples of whole blood were collected at 24 h post treatment. The DNA damage was determined by an increase in the comet parameters in tested animals. Our results show that T-2 toxin had induced significant DNA damage in treated chicken as compared with control animals, indicating that the assay can be used for the assessment of primary DNA damage caused by mycotoxins.