A study on oxidative stress in lead-exposed workers

Biomonitoring of Oxidative-Stress-Related Genotoxic Damage in Patients with End-Stage Renal Disease

Chronic kidney disease (CKD), a common progressive renal failure characterized by the permanent loss of functional nephrons can rapidly progress to end-stage renal disease, which is known to be an irreversible renal failure. In the therapy of ESRD, there are controversial suggestions about the use of regular dialysis, since it is claimed to increase oxidative stress, which may increase mortality in patients. In ESRD, oxidative-stress-related DNA damage is expected to occur, along with increased inflammation. Many factors, including heavy metals, have been suggested to exacerbate the damage in kidneys; therefore, it is important to reveal the relationship between these factors in ESRD patients. There are very few studies showing the role of oxidative-stress-related genotoxic events in the progression of ESRD patients. Within the scope of this study, genotoxic damage was evaluated using the comet assay and 8-OHdG measurement in patients with ESRD who were undergoing hemodialysis. The biochemical changes, the levels of heavy metals (aluminum, arsenic, cadmium, lead, and mercury) in the blood, and the oxidative biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels were evaluated, and their relationship with genotoxic damages was revealed. Genotoxicity, oxidative stress, and heavy-metal levels, except mercury, increased significantly in all renal patients. DNA damage, 8OHdG, and MDA significantly increased, and GSH significantly decreased in patients undergoing dialysis, compared with those not having dialysis. The duration and the severity of disease was positively correlated with increased aluminum levels and moderate positively correlated with increased DNA damage and cadmium levels. In conclusion, this study revealed that the oxidative-stress-related DNA damage, and also the levels of Al and Cd, increased in ESRD patients. It is assumed that these changes may play an important role in the progression of renal damage. Approaches for reducing oxidative-stress-related DNA damage and heavy-metal load in ESRD patients are recommended.

Effects of vitamin E on lead-induced impairments in hippocampal synaptic plasticity

Lead (Pb) exposure during development is associated with impaired cognitive function and long-term potentiation (LTP). Vitamin E (VE) is an antioxidant that could have protective effects against Pb intoxication. In this study, we examined the protective effects of vitamin E against Pb-induced LTP impairments. Forty-six adult male Wistar rats were randomly divided into 6 treatment groups: (1) control; (2) Pb exposure; (3) VE; (4) Pb +VE; (5) Pb exposure followed by VE 2 months after exposure; (6) VE followed by Pb exposure 1 month after treatment. Rats were exposed to Pb through daily consumption of Pb-contaminated distilled water; VE was administered by daily gavage for 3 months. After this period, the population spike (PS) amplitudes and the slopes of excitatory postsynaptic potentials (EPSPs) were measured in the dentate gyrus (DG) area of the hippocampus in adult rats in response to electrical stimulation applied to the perforant pathway in vivo. Blood samples were also collected to evaluate malondialdehyde (MDA) levels, total antioxidant capacity (TAC), and total oxidant status (TOS). Biochemical analyses demonstrated significant increases in plasma MDA and TOS levels in the Pb-exposed group compared to the control group. VE-protected groups revealed significant increases in TAC levels. Our results demonstrate that Pb decreased EPSP slopes and PS amplitudes compared to the control group, whereas VE increased these parameters compared to the control group. Co-administration of VE with Pb exposure inhibited Pb-induced effects. These findings suggest that VE via its antioxidant activity reverses Pb-induced impairments of synaptic plasticity in the DG.

Effect of in vitro exposure to lead chloride on semen quality and sperm DNA fragmentation

Exposure to lead may cause changes in the male reproductive system. We evaluated the effect of lead chloride (PbCl2) in vitro on semen quality from 31 individuals. Samples were incubated at room temperature for two exposure times (4 h and 8 h) and with two concentrations of PbCl2 (15 μg/ml or 30 μg/ml). Results showed that PbCl2 significantly inhibited rapid progressive motility and caused an increase in the percentage of tail anomalies in both times and concentrations assessed, as well as a decrease in vitality in the group exposed to 30 μg/ml PbCl2. A significant increase in immotile sperm was also observed between the group control and the groups submitted to lead. Total motility and DNA fragmentation also showed a significant decrease and increase, respectively, after 4 h of incubation in the group exposed to 30 μg/ml and in both groups after 8 h of incubation. In conclusion, PbCl2 affected sperm parameters and DNA integrity, which are essential for male fertility.

Effect of vitamin E and C supplementation on oxidative damage and total antioxidant capacity in lead-exposed workers

The molecular response of the antioxidant system and the effects of antioxidant supplementation against oxidative insult in lead-exposed workers has not been sufficiently studied. In this work, antioxidants (vitamin E 400 IU+vitamin C 1g/daily) were supplemented for one year to 15 workers exposed to lead (73 μg of lead/dl of blood) and the results were compared with those on 19 non-lead exposed workers (6.7 μg of lead/dl). Lead intoxication was accompanied by a high oxidative damage and an increment in the erythrocyte antioxidant response due to increased activity of catalase and superoxide dismutase. Antioxidant supplementations decreased significantly the oxidative damage as well as the total antioxidant capacity induced by lead intoxication with reduction of the antioxidant enzyme activities. We conclude that antioxidant supplementation is effective in reducing oxidative damage and induces modifications in the physiopathological status of the antioxidant response in lead-exposed workers.

The impact of lead and cadmium on selected motility, prooxidant and antioxidant parameters of bovine seminal plasma and spermatozoa

The aim of this study was to investigate the effects of lead (Pb) and cadmium (Cd) content on basic motility characteristics (motility-MOT, progressive motility-PROG) as well as selected markers of the prooxidant-antioxidant balance (catalase-CAT, glutathione-GSH, malondialdehyde-MDA) in bovine seminal plasma and spermatozoa. Twenty five semen samples were collected from breeding bulls and used in the study. Motility analysis was carried out using the Computer Assisted Sperm Analysis (CASA) system. The samples were centrifuged, fractions of seminal plasma and spermatozoa were separated, lysates were prepared from the sperm cell fractions. Pb and Cd concentrations were determined by the voltametric method (ASV), antioxidants and MDA were analyzed by UV/Vis spectrophotometry. The analysis showed that the average concentration of Pb in the seminal plasma was 0.23 ± 0.02 μg/mL, while its amount in the sperm cells was significantly higher (0.41 ± 0.07 μg/mL; P < 0.05). The average Cd content in bovine seminal fractions was similar and non-significant: 0.09 ± 0.01 μg/mL in the seminal plasma and 0.11 ± 0.01 μg/mL in spermatozoa (P > 0.05). The correlation analysis revealed that both heavy metals were significantly negatively correlated with MOT and PROG (P < 0.05; P < 0.01; P < 0.001), CAT (P < 0.05; P < 0.01) as well as GSH (P < 0.05; P < 0.01) but significantly positively associated with MDA as the marker of lipid peroxidation (P < 0.05; P < 0.01). Moreover the samples were categorized in three quality groups (Excellent, Good, Moderate) according to their motility values. The lowest Pb, Cd and MDA concentrations but the best antioxidant characteristics were found in samples of the best quality, moderate quality samples exhibited the highest Pb, Cd and MDA content together with the worst antioxidant capacity. This study demonstrates that Pb and Cd are serious toxic elements, which are able to increase the risk of seminal oxidative stress development and a subsequent decrease of male fertility.

DNA damage and decreased DNA repair in peripheral blood mononuclear cells in individuals exposed to arsenic and lead in a mining site

The aim of this study was to evaluate DNA damage and the capacity for DNA repair in children exposed to arsenic and lead. During 2006, we studied a total of 85 healthy children (aged 4-11 years) who were residents of Villa de la Paz (community A), Matehuala (community B), and Soledad de Graciano Sanchez (community C) in San Luis Potosi, Mexico. The quantification of arsenic in urine (AsU) and lead in blood (PbB) was performed by atomic absorption spectrophotometry. The alkaline comet assay was used to evaluate DNA damage and DNA repair. The highest levels of AsU and PbB in children were found in community A (44.5 μg/g creatinine for arsenic and 11.4 μg/dL for lead), followed by community B (16.8 μg/g creatinine for arsenic and 7.3 μg/dL for lead) and finally by children living in community C (12.8 μg/g creatinine for arsenic and 5.3 μg/dL for lead). When DNA damage was assessed, children living in community A had the highest DNA damage. Analysis of these same cells 1 h after a challenge with H(2)O(2) 10 μM showed a dramatic increase in DNA damage in the cells of children living in community B and community C, but not in the cells of children living in community A. Moreover, significantly higher levels of DNA damage were observed 3 h after the challenge ended (repair period) in cells from individuals living in community A. Our results show that children exposed to metals might be more susceptible to DNA alterations.

Wolbachia infection decreased the resistance of Drosophila to lead

BACKGROUND

The heavy metal lead has been shown to be associated with a genotoxic risk. Drosophila melanogaster is a model organism commonly utilized in genetic toxicology testing. The endosymbionts--Wolbachia are now very common in both wild populations and laboratory stocks of Drosophila. Wolbachia may induce resistance to pathogenic viruses, filarial nematodes and Plasmodium in fruit fly and mosquito hosts. However the effect of Wolbachia infection on the resistance of their hosts to heavy metal is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Manipulating the lead content in the diet of Drosophila melanogaster, we found that lead consumption had no different effects on developmental time between Wolbachia-infected (Dmel wMel) and -uninfected (Dmel T) flies. While in Pb-contaminated medium, significantly reduced amount of pupae and adults of Dmel wMel were emerged, and Dmel wMel adults had significantly shorter longevity than that of Dmel T flies. Lead infusion in diet resulted in significantly decreased superoxide dismutase (SOD) activity in Dmel T flies (P<0.05), but not in Dmel wMel flies. Correspondingly, lead cultures induced a 10.8 fold increase in malonaldehyde (MDA) contents in Dmel T larvae (P<0.05). While in Dmel wMel larvae, it resulted in only a 1.3 fold increase. By quantitative RT-PCR, we showed that lead infused medium caused significantly increased expression level of relish and CecA2 genes in Dmel T flies (P<0.01). Lead cultures did not change dramatically the expression of these genes in Dmel wMel flies.

CONCLUSIONS/SIGNIFICANCE

These results suggest that Wolbachia infection decreased the resistance of Drosophila to lead likely by limiting the production of peroxides resulted from lead, thus being unable to activate the immunological pathway in the host to prevent them from lead damage. This represents a novel Wolbachia-host interaction and provides information that researchers working on Drosophila toxicology should take in consideration the presence of Wolbachia in the stocks they are analyzing.

Effects of flaxseed oil on lead acetate-induced neurotoxicity in rats

It is well known that chronic exposure to lead (Pb(+2)) alters a variety of behavioral tasks in rats and mice. Here, we investigated the effect of flaxseed oil (1,000 mg/kg) on lead acetate (20 mg/kg)-induced brain oxidative stress and neurotoxicity in rats. The levels of Pb(+2), lipid peroxidation, nitric oxide (NO), and reduced glutathione (GSH) and the activity of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione-S-transferase (GST), and glutathione peroxidase (GPx) were determined in adult male albino rats. The level of Pb(+2) was markedly elevated in brain and blood of rats. This leads to enhancement of lipid peroxidation and NO production in brain with concomitant reduction in GSH, CAT, SOD, GR, GST, and GPx activities. These findings were associated with DNA fragmentation. In addition, lead acetate induced brain injury as indicated by histopathological changes of the brain. Treatment of rats with flaxseed oil resulted in marked improvement in most of the studied parameters as well as histopathological features. These findings suggest to the conclusion that flaxseed oil significantly decreased the adverse harmful effects of lead acetate exposure on the brain as well as Pb(+2)-induced oxidative stress.

Genotoxic effects of lead: an updated review

Lead is a ubiquitous toxic heavy metal with unique physical and chemical properties that make it suitable for a great variety of applications. Because of its high persistence in the environment and its use since ancient times for many industrial activities, lead is a common environmental and occupational contaminant widely distributed around the world. Even though the toxic effects of lead and its compounds have been investigated for many years in a variety of systems, the data existing with regard to its mutagenic, clastogenic and carcinogenic properties are still contradictory. The International Agency for Research on Cancer has classified lead as possible human carcinogen (group 2B) and its inorganic compounds as probable human carcinogens (group 2A). Furthermore, although the biochemical and molecular mechanisms of action of lead remain still unclear, there are some studies that point out indirect mechanisms of genotoxicity such as inhibition of DNA repair or production of free radicals. This article reviews the works listed in the literature that use different parameters to evaluate the genotoxic effects of lead in vitro, in vivo and in epidemiological studies.

Elevated blood lead levels and cytogenetic markers in buccal epithelial cells of painters in India: genotoxicity in painters exposed to lead containing paints

BACKGROUND, AIM, AND SCOPE

Lead, a major contaminant, is highly used in paint manufacturing due to its anticorrosive properties. Recent reports indicated high lead content among Indian paints used for commercial purposes. Painters are continuously exposed to these lead containing paints during painting of both commercial as well as residential buildings. Lead is well-known for its genotoxicty in occupational workers; however, in Indian painters the genotoxic effects of lead have not been reported to date. Therefore we aimed to study the genotoxic end points in painters due to their long-term exposure to these high lead-containing Indian paints.

MATERIALS AND METHODS

Study group selection was made after a questionnaire administration, which included questions about lifestyle and medical history to exclude exposure to the other potential sources of genotoxics. Blood and buccal cell samples were obtained from 30 male painters and from a similar number of age-matched controls of same location with no occupational exposure to lead. Blood lead levels (Pb-B) were measured in painters and controls. Micronucleus (MN) frequencies and nuclear changes, i.e., karyorrhexis, karyolysis, broken egg, and binucleated, were investigated in buccal epithelial cells.

RESULTS

Painters had significantly (P < 0.01) greater lead levels in blood than the control group. MN frequencies and nuclear changes in buccal epithelial cells were also significantly (P < 0.01) elevated in painters as compared with control subjects. Regression analysis also revealed significant (P < 0.01) association of Pb-B with all the genotoxic endpoints in painters. Cytogenetic damage was significantly associated with Pb-B as no other co-founding factors (smoking, alcohols) showed significant difference between both groups.

DISCUSSION

Lead is widely used in paints which may serve as potential source of exposure among painters due to their long-term engagement with paints. Our results clearly demonstrated genotoxicity among the exposed population as evident from increase micronucleus frequencies, frequent nuclear changes, and apoptosis. Many studies had previously related nuclear change events in buccal epithelial cells with the progression of different carcinomas. Furthermore in-depth investigations with larger sample size are needed to provide evidence to this effect.

CONCLUSIONS

Here, we report cytogenetic toxicity to the exposed population by the high lead containing paints from India for the first time. Frequent, high and unregulated use of lead in paints may cause genetic mutation and may accelerate cytogenetic damage which may further lead to different carcinomas in painters. These findings need to be considered and necessary steps should be taken to protect the occupational workers engaged with these high lead-containing paints.

RECOMMENDATIONS

The use of lead in paints is completely unregulated in India and routine surveillance of paints for lead content is still lacking. These paints are readily available in markets and are also used in other products (jewelry, miniblinds) which could be exported to other countries including United States and Europe. Serious consideration should be given to the inclusion of regulations and bans on the use of lead in paints. Moreover, attention should also be paid towards the use of various protective measures (face-masks, hand gloves, and separate clothes) by the workers as safe work practices during working periods.

The role of the antioxidant enzymes in erythrocytes in the development of arterial hypertension among humans exposed to lead

The study population included employees of metal works, with significant exposure to lead (Pb) for about 20 years (mean blood lead level PbB = 43 microg/dl), divided into four groups: normotensive (Pb-normotensive), high-normotensive, first (HT-1), and second degree (HT-2) of hypertension. The control group comprised of 30 office workers with normal blood pressure and no history of occupational exposure to lead. In erythrocytes, the activity of antioxidant enzymes and lipid peroxidation (measured as concentration of malondialdehyde (MDA)) was estimated. MDA concentration, glutathione peroxide (GPx), and superoxide dimutase (SOD) activities were significantly higher in Pb-normotensive group when compared to the normotensive control. Body mass index, age, duration of exposure to lead, and PbB were higher in both hypertensive groups than in Pb-normotensive or high-normotensive groups. MDA increased in HT-1 group by 48% and in HT-2 by 72%, and the activity of GPx decreased significantly in HT-1 group, by 30% and in HT-2 by 43%. No significant differences were observed in their activity of SOD, catalase, and glutathione reductase in erythrocytes. Arterial blood pressure (both systolic and diastolic) positively correlated with body mass index (BMI), age, lead exposure duration, PbB, MDA, and negatively correlated with GPx. There was no significant correlation between BMI and MDA, BMI and GPx, age and MDA, AND age and GPx.

IN CONCLUSION

(1) lead increases erythrocyte MDA concentration and the activity of GPx as well as SOD in normotensive subjects. (2) Among individuals exposed to lead, with arterial hypertension diagnosed, higher body mass index, age, values of blood lead level, and prolonged exposure to lead have been noticed, accompanied by intensified oxidative stress and the decrease in the activity of glutathione peroxidase in erythrocytes. The reasons for increase of blood pressure in lead exposure remain unrecognized.

Role of wormwood (Artemisia absinthium) extract on oxidative stress in ameliorating lead induced haematotoxicity

Effects of ROS generation have been postulated to be major contributors to lead-exposure related disease. The aim of the study was to investigate the effect of aqueous extract of wormwood (Artemisia absinthium) on oxidative stress in rats protractedly exposed to lead. Aqueous extract of wormwood plant was administered orally (200 mg x kg(-1) body weight). Plasma vitamin C, E and non-protein thiol concentrations, red blood cells (RBC) thiobarbituric acid reactive substances, reduced glutathione levels and haemolysis test were evaluated. In addition, RBC antioxidant enzymes activities such as superoxide dismutases, catalase, glutathione peroxidase, glutathione reductase were also estimated. After 11-weeks, significant decreases of plasma vitamin C, E, non protein-thiol (NP-SH) and RBC-reduced glutathione levels were observed in Pb compared to control group (-32.9%, -57.1%, -53.1%, -33.9%, respectively); superoxide dismutase, glutathione peroxidase, uric aminolevulinic acid and haemolysis test significantly increased in Pb compared to control group (+64.3%, +40.3%, +145%, +44.3%, respectively). In our investigation, after 4-weeks of treatment all treated groups did not show any difference compared to the control group, except for glutathione peroxidase and RBC-superoxide dismutase activity (-15.7% and +16.4%, respectively). The findings of this study suggest that wormwood (Artemisia absinthium) extract restored the enzymes activities perturbed by exposure to lead, and had a protective role against lipid peroxidation.

Cumulative community-level lead exposure and pulse pressure: the normative aging study

BACKGROUND

Pulse pressure increases with age in industrialized societies as a manifestation of arterial stiffening. Lead accumulates in the vasculature and is associated with vascular oxidative stress, which can promote functional and structural vascular disease.

OBJECTIVES

We tested the hypothesis that cumulative community-level lead exposure, measured with K-X-ray fluorescence, is associated with pulse pressure in a cohort of adult men.

METHODS AND RESULTS

In a cross-sectional analysis of 593 men not treated with antihypertensive medication, tibia lead was positively associated with pulse pressure (p < 0.001). Adjusting for age, race, diabetes, family history of hypertension, education, waist circumference, alcohol intake, smoking history, height, heart rate, fasting glucose, and total cholesterol-to-HDL ratio, increasing quintiles of tibia lead remained associated with increased pulse pressure (ptrend = 0.02). Men with tibia lead above the median (19.0 microg/g) had, on average, a 4.2-mmHg (95% confidence interval, 1.9-6.5) higher pulse pressure than men with tibia lead level below the median. In contrast, blood lead level was not associated with pulse pressure.

CONCLUSIONS

These data indicate that lead exposure may contribute to the observed increase in pulse pressure that occurs with aging in industrialized societies. Lead accumulation may contribute to arterial aging, perhaps providing mechanistic insight into the observed association of low-level lead exposure with cardiovascular mortality.

Genotoxic Risks to Nurses from Contamination of the Work Environment with Antineoplastic Drugs in Japan

The aims of the present study were to clarify the work environment contamination by antineoplastic drugs in a hospital ward and to assess the genotoxic risks to nurses who routinely handle antineoplastic drugs in Japan. The exposed group consisted of 19 female nurses who routinely handled antineoplastic drugs. The control group consisted of 18 female nurses who did not handle antineoplastic drugs in the same hospital as the exposed group. The genotoxicity of the 19 antineoplastic drugs used in the hospital ward and 8 wipe samples of the workbench after handling of antineoplastic drugs were measured using the umu assay. Lymphocyte DNA damage (tail length) was measured with alkaline methods of the single cell gel electrophoresis assay (comet assay). Of the 19 antineoplastic drugs, dacarbazine, bleomycin, daunorubicin, doxorubicin, pirarubicin, carboplatin, cisplatin and etoposide induced genotoxicity. Of the 8 sampling d, the umu activity of the wipe sample was positive on 3 d. Contamination of the workbench was found when the nurses handled more drugs than on other days. The medians of the tail length in the comet assay were 8.5 and 5.1 microm, respectively, for the exposed and control groups, with a significant difference (p=0.004 by Mann-Whitney's U-test). In the present study, the nurses of the exposed group were considered to have been exposed to antineoplastic drugs and lymphocyte DNA damage of the exposed group was suggested to be induced by antineoplastic drugs.

Low-level lead exposure, metabolic syndrome, and heart rate variability: the VA Normative Aging Study

BACKGROUND

Altered heart rate variability (HRV), a marker of poor cardiac autonomic function, has been associated with sudden cardiac death and heart failure.

OBJECTIVE

We examined the association of low-level lead exposure measured in bone by K-X-ray fluorescence with alterations in HRV, and whether metabolic syndrome (MetS) or its individual components modify those associations.

METHODS

HRV measures [power in high-frequency (HFnorm) and low-frequency (LFnorm) in normalized units, and LF/HF] were taken among 413 elderly men from the Normative Aging Study. MetS was defined as subjects having three or more of the following criteria: abdominal obesity, hypertriglyceridemia, low high-density lipoprotein, high blood pressure, and high fasting glucose.

RESULTS

Of the subjects, 32% were identified as having MetS. Inverse but nonstatistically significant associations of both tibia and patella lead levels with HFnorm and nonstatistically significant positive relations with LFnorm and LF/HF were found in the entire cohort. There was a graded, statistically significant reduction in HFnorm and increases in LFnorm and LF/HF in association with an increase in patella lead as the number of metabolic abnormalities increased. We also observed that higher patella lead was consistently associated with lower HFnorm and higher LFnorm and LF/HF among subjects with MetS or its individual components. No statistically significant interaction between MetS and tibia lead was observed.

CONCLUSION

The results suggest that elderly men with MetS were more susceptible to autonomic dysfunction in association with chronic lead exposure as measured in patella. The modification by MetS is consistent with a role for oxidative stress in lead toxicity on the cardiovascular system.

Lipids, lipid peroxidation and 7-ketocholesterol in workers exposed to lead

The study population included healthy men and hypertensive employees of zinc and lead steelworks in the south of Poland. Workers exposed to lead (n=137) were divided into two groups: the first included employees with low exposure to lead (LL) with mean blood lead (PbB) 25-40 microg/dL and the second one with PbB over 40 microg/dL (HL group). The administration workers (n=35) were the control group. Evaluation of lipids and oxidative changes of cholesterol and lipids were estimated in blood samples. No significant changes in concentration of 7-ketocholesterol and blood lipids (cholesterol, HDL, LDL, triglycerides) were found. Lipid peroxidation (LP) was significantly higher in both exposed groups in plasma and in the HL group in erythrocytes when compared with control. There can be two independent sources of LP increase: the first is connected with the direct effect of lead's ions on erythrocytes, the second is the prooxidative effect of delta-aminolevulinic acid. Hypertension in the HL group when compared with people with PbB below 40 microg/dL (OR 4.4, 95%CI 1.4-14.5) was found more often. LP significantly increased by about 71% and concentration of 7-ketocholesterol by about 122% in hypertensives when compared with normotensives in the HL group.

2,3-Dimercaptopropanol, 2,3-dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase lead-induced inhibition of δ-aminolevulinate dehydratase in vitro and ex vivo

We investigated the effects of dimercaprol (BAL), meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercapto-1-propanesulphonic acid (DMPS) on human blood delta-aminolevulinate dehydratase (delta-ALA-D) activity, the most reliable indicator of lead intoxication in humans, in the presence of lead in vitro. Furthermore, we studied the effects of the chelating agents, administered subcutaneously, on delta-ALA-D activity in blood and tissues of mice submitted to sub-acute lead exposure (50 mg/kg for 15 consecutive days, subcutaneously). In vitro results demonstrated that human blood delta-ALA-D activity was significantly inhibited (62%) by lead acetate. Lead acetate (1-1000 microM) pre-incubated with human blood increased the inhibitory potency of this compound on delta-ALA-D when compared to the assay without pre-incubation (89%). Chelating agents caused a marked potentiation of delta-ALA-D inhibition induced by lead, in vitro. One of the most notable observations in the present study was the correspondence between in vitro and ex vivo effects. In fact, BAL and DMPS increase the inhibitory effect of lead on delta-ALA-D activity from mice blood. The complexes formed (lead and chelators) were more inhibitory than lead alone in kidney and liver enzyme activity, ex vivo.

The effect of smoking on DNA effects in the comet assay: a meta-analysis

The comet assay (alkaline single-cell gel electrophoresis, SCG or SCGE) is frequently used in biomonitoring to detect genotoxic effects in humans exposed at the workplace or in their environment. Because of its ready accessibility, blood is most frequently used in such studies. Many studies investigated cigarette smoking either as a genotoxic exposure itself or as a potential confounding factor in occupational studies. However, although smoking is considered to be a relevant exposure towards various genotoxins, conflicting results have been reported in the comet assay studies. The actual reasons for this discrepancy are not known. To further evaluate evidence for smoking-related DNA effects in the comet assay, we now used a meta-analysis approach based on a literature search. We identified 38 studies from 37 publications which were suited for a formal meta-analysis based on the standardized mean difference (SMD) between the study groups. The evaluation of these 38 studies indicated higher levels of DNA damage in smokers than in non-smokers [under a random effects model, SMD = 0.55, 95% confidence interval = (0.16-0.93)]. Subdividing these studies into studies investigating the effect of smoking as a genotoxic exposure (Type A studies, n = 12) and studies investigating smoking as a potential confounder in occupational studies (Type B, n = 26) indicated a significant difference only in Type A studies but not in Type B studies. Furthermore, studies using image analysis or image length measurements (n = 23) only indicated a tendency for a genotoxic effect of smoking, whereas studies using an arbitrary score (n = 15) found a significantly higher level of DNA damage in smokers.

Detection of lead-induced oxidative stress in the rat epididymis by chemiluminescence

It has been shown that lead (Pb) is able to induce lipid peroxidation, one of the main manifestations of oxidative stress. In this study we examined the relationship between chronic Pb exposure and level of reactive oxygen species (ROS) in reproductive system tissues of sexually mature male Wistar rats. One group of animals (control, K) was allowed to drink distilled water, the second group (Pb) was allowed to drink freely 1% aqueous solution of lead acetate. Another groups had a following supplements: rats were allowed to drink distilled water containing vitamin C (vit C) at concentration of 500 mg/l or Trolox (a vitamin E analog) at concentration of 48 mg/l or vit C (500 mg/l) + Trolox (48 mg/l). The similar groups among Pb-treated animals were examined after treatment with the same vitamins and using the same vitamin doses, dissolved in 1% aqueous solution of lead acetate. In all cases the time of drinking was 6 months. It was found that lead content in samples of tissues from testis, epididymis and in a whole blood in Pb- and Pb with antioxidants treated rats was significantly elevated. Chemiluminescence (CL) emitted by the Pb-treated tissues was significantly higher when compared to the light emission by tissues isolated from the animals of control group. The increase in the CL caused by lead occurs in the following increasing order within the studied tissues: cauda of epididymis < testis < caput of epididymis (19%, 39% and 51%, respectively). Dietary vit C supplementation to the Pb-treated rats for 6 months period decreased the CL from caput of epididymis, cauda of epididymis and testis (by 43%, 24%, 39%, respectively) more effectively in comparison to the control group (35%, 17%, 33%, respectively). Also stronger quenching effect on the light emission from the above mentioned tissues after Trolox supplementation was observed in the Pb-treated group (42%, 21%, 35%, respectively) than in the control group (23%, 13%, 13% respectively). The combination of both antioxidants treatments (vit C and Trolox) did not give a higher significant quenching effect compared to the treatment with the vitamins separately. No ultrastructural changes were found in the seminiferous epithelium of Pb-treated animals. However, we found abnormalities in ultrastructure of epididymal epithelial cells and epididymal spermatozoa in rats of Pb-treated groups. These findings provide ex vivo evidence that Pb causes oxidative cellular damage in reproductive system tissues of adult male rats, which may be closely associated with the ROS production.

Toxicological characteristics of endocrine-disrupting chemicals: developmental toxicity, carcinogenicity, and mutagenicity

It is generally accepted that endocrine-disrupting chemicals (EDCs) play a role in a variety of adverse health effects in an intact organism or its progeny as a consequence of changes in the endocrine system. Primary toxic effects of EDCs were reported to be related to infertility, reduction in sperm count, and teratogenicity, but other important toxic effects of EDCs such as carcinogenicity and mutagenicity have also been demonstrated. The aim of the present study was to systematically analyze the toxicological characteristics of EDCs in pesticides, industrial chemicals, and metals. A comprehensive literature survey on the 48 EDCs classified by the Centers for Disease Control and Prevention (CDC) was conducted using a number of databases which included Medline, Toxline, and Toxnet. The survey results revealed that toxicological characteristics of EDCs were shown to produce developmental toxicity (81%), carcinogenicity (79%, when positive in at least one animal species; 48%, when classified based on IARC evaluation), mutagenicity (79%), immunotoxicity (52%), and neurotoxicity (50%). Regarding the hormone-modulating effects of the 48 EDCs, estrogenic effects were the most predominant in pesticides, while effects on thyroid hormone were found for heavy metals. EDCs showing estrogen-modulating effects were closely related to carcinogenicity or mutagenicity with a high degree of sensitivity. Systematic information on the toxicological characteristics of the EDCs will be useful for future research directions on EDCs, the development of new screening methods, legal regulation, and for investigations of their mechanism of action.

DNA damage in blood cells from children exposed to arsenic and lead in a mining area

In this work, we studied the frequency of DNA damage in children living in Villa de la Paz, Mexico, a mining site contaminated with arsenic and lead. DNA damage in blood cells was assessed using the Comet assay, and the results were compared to those found in children living in a less exposed town (Matehuala). In Villa de la Paz, high concentrations of arsenic and lead in surface soil and household dust were found. All of the soil samples had concentrations above 100 mg/kg of arsenic, and 58% of the samples were higher than 400 mg/kg of lead (these concentrations are used as intervention guidelines by the United States Environmental Protection Agency). In agreement with the environmental results, urinary arsenic in children living in Villa de la Paz (geometric mean 136 microg/g creatinine) was significantly higher than that found in children living in Matehuala (34 microg/g creatinine). Blood lead levels were also significantly higher in children from Villa de la Paz (11.6 microg/dL) than in children from Matehuala (8.3 microg/dL). The results of the Comet assay showed that the tail length and the tail moment in children living in Villa de la Paz were higher than those observed for children in Matehuala (P<0.05). Taking all the data into account, our study has shown increased DNA damage in children exposed to arsenic and lead in the mining site of Villa de la Paz.

Relationship between oxidative stress, pathology, and behavioral signs of lead poisoning in mallards

Some of the adverse effects of lead (Pb) may be associated with oxidative damage of lipids, proteins, or DNA. In a previous study a linkage was observed between the susceptibilities of waterfowl species to Pb poisoning with oxidative stress. To investigate this relationship among the individuals of a single species, for 3 wk 4 groups of 12 mallards were fed diets containing high or low levels of vitamin E (20 or 220 UI/kg) and high or low levels of Pb (0 or 2 g/kg). During the first week of Pb exposure, mallards developed hemolytic anemia, and during the second week, signs of neurological impairment. Histological findings in the Pb-exposed mallards were hemosiderosis, demyelinization of sciatic and brachial nerves, and tumefaction of renal tubular epithelium with the presence of intranuclear inclusion bodies. Lipid peroxidation increased with Pb exposure in blood, liver, bile, and brain, but decreased in nerves. Glutathione (GSH) increased with Pb exposure in liver and bile, and its oxidized/reduced ratio only increased in bile. Pb exposure inhibited GSH peroxidase activity (GPX) in plasma, liver, and brain, and decreased protein thiols (PSH) in blood and liver. Vitamin E resulted in significantly lower lipid peroxidation in nerves of control birds relative to unsupplemented controls, but did not alleviate any sign of lead posioning. Pb-induced pathological changes associated with hepatic and nervous functions were significantly correlated with lower GPX activity and PSH concentrations in these tissues rather than lipid peroxidation. Data suggest that inhibition of antioxidant enzymes and interaction with sulfhydryl groups of proteins may play a more important role in Pb poisoning of waterfowl than lipid peroxidation.

Effects of ascorbic acid on lead induced alterations of synaptic transmission and contractile features in murine dorsiflexor muscle

Lead is a common environmental toxin that affects neuromuscular junction and potentially might cause muscle weakness. Antioxidants like ascorbic acid may protect against lead induced myopathy. The present study measured isometric twitch tensions (evoked either directly by muscle stimulation or indirectly by nerve stimulation) to study effects of ascorbic acid on lead induced alterations at murine dorsiflexor skeletal muscle. Resting membrane potentials (RMPs), endplate potentials (EPPs) and miniature endplate potentials (MEPPs) were also recorded. Forty animals were divided into four groups of n = 10 each. (10 control, 10 lead alone, 10 ascorbic acid alone, 10 lead treated plus ascorbic acid). Lead (1 mg/kg) i.p, was administered daily for 2 weeks before the recording day and ascorbic acid (200 mg/kg, i.p) was given daily for 3 weeks prior to the experiment day. Lead treatment reduced twitch tension significantly (from 4.3 +/- 0.5 g to 2.7 +/- 0.2 g) and delayed half time of decay compared to the control. Similarly MEPPs frequencies were reduced following lead treatment. Application of ascorbic acid prevented twitch tension reduction in lead treated mice (3.3 +/- 0.3 g) and reversed lead induced delay in half time of decay. The negative actions of lead treatment on MEPPs frequencies were also modified with ascorbic acid. It appears that ascorbic acid exerts a protective role against lead induced peripheral nerve and muscle dysfunction. This effect of ascorbic acid on lead induced neuromyopathy is probably mediated via a free radical scavenging mechanism or modification of Ca(2+) homeostasis.

hOGG1 Ser326Cys polymorphism modifies the significance of the environmental risk factor for colon cancer

AIM: To determine the association of hOGG1 (8-oxoguanine glycosylase I, OGG1) polymorphism of Ser326Cys substitution with colon cancer risk and possible interaction with known environmental risk factors.

METHODS: A case-control study with 125 colon cancer cases and 247 controls was conducted.

RESULTS: There was no major difference in Ser326Cys genotype distribution between cases and controls. The meat intake tended to increase the odds ratio for colon cancer with an OR of 1.72 (95% confidence interval; CI = 1.12-2.76). Such tendency was more prominent in Cys/Cys carriers (OR = 4.31, 95%CI = 1.64-11.48), but meat intake was not a significant risk factor for colon cancer in Ser/Ser or Ser/Cys carriers. The OR for colon cancer was elevated with marginal significance in smokers who were Cys/Cys carriers (OR = 2.75, 95%CI = 1.07-7.53) but not in Ser/Ser or Ser/Cys carriers.

CONCLUSION: These results suggest that the hOGG1 Ser326Cys polymorphism is probably not a major contributor to individual colon cancer susceptibility overall, but the Cys/Cys genotype may alter the impact of some environmental factors on colon cancer development.

In vitro genotoxicity of lead acetate: induction of single and double DNA strand breaks and DNA-protein cross-links

Lead is present in the natural and occupational environment and is reported to interact with DNA, but the mechanism of this interaction is not fully understood. Using the alkaline comet assay we showed that lead acetate at 1-100 microM induced DNA damage in isolated human lymphocytes measured the change in the comet tail length. At 1 and 10 microM we observed an increase in the tail length, whereas at 100 microM a decrease was seen. The former effect could follow from the induction of DNA strand breaks and/or alkali-labile sites (ALS), the latter from the formation of DNA-DNA and/or DNA-protein cross-links. No difference was observed between tail length for the alkaline and pH 12.1 versions of the assay, which indicates that strand breaks and not ALS are responsible for the tail length increase induced by lead. The neutral version of the test revealed that lead acetate induced DNA double-strand breaks at all concentrations tested. The presence of spin traps, 5,5-dimethyl-pyrroline N-oxide (DMPO) and N-tert-butyl-alpha-phenylnitrone (PBN) did not influence the level of DNA damage induced by lead. Post-treatment of the lead-damaged DNA (at 100 microM treatment concentration) by endonuclease III (Endo III) and formamidopyrimidine-DNA glycosylase (Fpg), enzymes recognizing oxidized DNA bases, as well as 3-methyladenine-DNA glycosylase II, an enzyme recognizing alkylated bases, gave rise to a significant increase in the extent of DNA damage. Proteinase K caused an increase in comet tail length, suggesting that lead acetate might cross-link DNA with nuclear proteins. Vitamin A, E, C, calcium chloride and zinc chloride acted synergistically on DNA damage evoked by lead. The results obtained suggest that lead acetate may induce single-strand breaks (SSB) and double-strand breaks (DSB) in DNA as well as DNA-protein cross-links. The participation of free radicals in DNA-damaging potential of lead is not important and it concerns other reactive species than could be trapped by DMPO or PBN.

Genetic polymorphism of drug-metabolizing enzymes and styrene-induced DNA damage

A cross-sectional study was carried out on 48 workers exposed to styrene and 14 unexposed healthy controls in order to investigate the genotoxic potential of styrene exposure. DNA damage was assessed in peripheral blood leukocytes (WBCs) by the comet assay. Polymorphisms in glutathione S-transferase genes (GSTM1, GSTT1, GSTP1) and the gene encoding microsomal epoxide hydrolase (EPHX) were characterized to assess their possible modifying role in styrene metabolism and subsequent DNA damage. Exposed workers showed significantly higher levels of DNA damage compared to controls. Among workers, the GSTM1 and GSTT1 polymorphisms significantly affected comet parameters. Subjects bearing a GSTM1pos genotype showed a significantly higher proportion of damaged nuclei compared to people lacking GSTM1-1 expression (GSTM1null), whereas GSTT1pos workers showed significantly lower DNA damage than GSTT1null individuals. Styrene-7,8-oxide (SO)-induced DNA damage was assessed in vitro in WBCs isolated from the healthy controls. A clear dose-response relationship at micromolar doses of SO was found for the whole group. WBCs collected from subjects bearing the homozygous wildtype GSTP1 genotype showed a significant protection compared to cells from subjects bearing at least one GSTP1 variant allele. The field survey confirms that styrene exposure is associated with increased DNA damage and indicates a modulating role for GSTM1 and GSTT1 genotypes. In vitro experiments suggest that the extent of SO-induced DNA strand breaks depends, at least in part, on interindividual differences in GSH-conjugation capabilities.

Reversal of lead-induced oxidative stress by chelating agent, antioxidant, or their combination in the rat

The influence of N-acetyl cysteine (NAC), an antioxidant, on the therapeutic efficacy of meso-2,3-dimercaptosuccinic acid (DMSA), a hydrophilic, and its ester, monoisoamyl 2,3-dimercaptosuccinate (MiADMS), a lipophilic, both soft tissue lead mobilizers, was investigated in lead-preexposed rats. The subsequent treatment of lead-exposed animals with DMSA, MiADMS, or NAC reversed the lead-induced alterations in blood delta-aminolevulinic acid dehydratase, catalase, malondialdehyde (MDA), reduced glutathione, oxidized glutathione, and brain MDA levels. The combined treatment with DMSA and NAC was more effective than that with MiADMS and NAC in enhancing the restoration of all these parameters indicative of lead-induced oxidative stress. These reversals were consistent with the lead-removing ability of DMSA and MiADMS but not that of NAC. As the reversal of these parameters by NAC was independent of its lead-mobilizing capability, this ought to be mainly due to its strong antioxidant property. The increase in blood and brain zinc levels upon lead exposure appears to be the result of the redistribution of endogenous zinc due to lead. Subsequent treatment with DMSA, MiADMS, NAC, or their combination decreased the brain zinc as its excretable complexes with a transient increase in blood zinc level. The ideal treatment of lead poisoning seems to be a combination of a lead chelator and an antioxidant.

Differences in oxidative stress between young Canada geese and mallards exposed to lead-contaminated sediment

Lead (Pb) exposure results in an increase in tissue lipid peroxides and variation in glutathione (GSH) concentrations, which can be related to peroxidative damage of cell membranes in Pb-poisoned animals. Species and individual variation in sensitivity to Pb poisoning among animals may be due to differential resistance to oxidative stress. The effects of oxidative stress caused by Pb exposure (1.7, 414, and 828 microg/g of diet) were compared for the first 6 wk in growing young of two species of waterfowl, Canada geese (Branta canadensis) and mallards (Anas platyrhynchos), with the first species being possibly more sensitive to Pb poisoning based on previous field and laboratory observations. Blood and liver Pb concentrations increased more in mallards than in geese. This may be explained on the basis of body weight, being 3.2 times higher in geese, and by hepatic metabolism, where GSH S-transferase (GST) activity is 2.9-fold higher in geese and presumably has a role in the binding of Pb to GSH and subsequent biliary excretion. In contrast, mallards showed higher hepatic levels of GSH and activities of CSH peroxidase (GPX) and GSH reductase (GR). Although both species showed a rise in hepatic GSH concentration with Pb exposure, the relationship between increased lipid peroxidation and Pb exposure was only significant in geese. Within treatment groups, hepatic GSH concentrations were inversely related to liver Pb concentrations in both species, which may correspond to the role of GSH in Pb excretion. Hepatic GSH was also inversely related to hepatic lipid peroxidation, but only in mallards and in agreement with the species differences observed in GPX and GR activities. The lower resistance to lipid peroxidation of Canada geese may explain why geese can die in the field from Pb poisoning after ingesting fewer shot than found in the gizzards of mallards and with lower liver Pb concentrations than in mallards.