Effects of sub-chronic low-level lead exposure on the homeostasis of copper and zinc in rat tissues

Neurotoxic effects of low dose ranges of environmental metal mixture in a rat model: The benchmark approach

Metals exert detrimental effects on various systems within the body, including the nervous system. Nevertheless, the dose-response relationship concerning the administration of low doses of metal mixtures remains inadequately explored. The assessment of neurotoxic effects of lead, cadmium, mercury, and arsenic mixture (MIX) administered at low dose ranges, was conducted using an in vivo approach. A subacute study was conducted on a rat model consisting of a control and five treatment groups subjected to oral exposure with gradually increasing doses (from MIX 1 to MIX 5). The results indicated that behavioural patterns in an already developed nervous system displayed a reduced susceptibility to the metal mixture exposure with tendency of higher doses to alter short term memory. However, the vulnerability of the mature brain to even minimal amounts of the investigated metal mixture was evident, particularly in the context of oxidative stress. Moreover, the study highlights superoxide dismutase's sensitivity as an early-stage neurotoxicity marker, as indicated by dose-dependent induction of oxidative stress in the brain revealed through Benchmark analysis. The narrowest Benchmark Dose Interval (BMDI) for superoxide dismutase (SOD) activity (1e-06 - 3.18e-05 mg As/kg b.w./day) indicates that arsenic may dictate the alterations in SOD activity when co-exposed with the other examined metals. The predicted Benchmark doses for oxidative stress parameters were very low, supporting "no-threshold" concept. Histopathological alterations were most severe in the groups treated with higher doses of metal mixture. Similarly, the brain acetylcholinesterase (AChE) activity demonstrated a dose-dependent decrease significant in higher doses, while BMDI suggested Cd as the main contributor in the examined metal mixture. These findings imply varying susceptibility of neurotoxic endpoints to different doses of environmentally relevant metal mixtures, advocating for risk assessment and regulatory measures to address metal pollution and enhance remediation strategies.

Integrative investigation of hematotoxic effects induced by low doses of lead, cadmium, mercury and arsenic mixture: In vivo and in silico approach

The effect of the lead (Pb), cadmium (Cd), mercury (Hg) and arsenic (As) mixture (MIX) on hematotoxicity development was investigated trough combined approach. In vivo subacute study (28 days) was performed on rats (5 per group): a control group and five groups orally exposed to increasing metal(loid) mixture doses, MIX 1- MIX 5 (mg/kg bw./day) (Pb: 0.003, 0.01, 0.1, 0.3, 1; Cd: 0.01, 0.03, 0.3, 0.9, 3; Hg: 0.0002, 0.0006, 0.006, 0.018, 0.06; As: 0.002, 0.006, 0.06, 0.18, 0.6). Blood was taken for analysis of hematological parameters and serum iron (Fe) analysis. MIX treatment increased thrombocyte/platelet count and MCHC and decreased Hb, HCT, MCV and MCH values compared to control, indicating the development of anemia and thrombocytosis. BMDIs with the narrowest width were identified for MCH [pg] (6.030E-03 - 1.287E-01 mg Pb/kg bw./day; 2.010E-02 - 4.290E-01 mg Cd/kg bw./day; 4.020E-04 - 8.580E-03 mg Hg/kg bw./day; 4.020E-03 - 8.580E-02 mg As/kg bw./day). In silico analysis showed target genes connected with MIX and the development of: anemia - ACHE, GSR, PARP1, TNF; thrombocytosis - JAK2, CALR, MPL, THPO; hematological diseases - FAS and ALAD. The main extracted pathways for anemia were related to apoptosis and oxidative stress; for thrombocytosis were signaling pathways of Jak-STAT and TPO. Changes in miRNAs and transcription factors enabled the mode of action (MoA) development based on the obtained results, contributing to mechanistic understanding and hematological risk related to MIX exposure.

Assessment of the effect of sodium tetraborate on oxidative stress, inflammation, and apoptosis in lead-induced nephrotoxicity

Exposure to Pb, a toxic heavy metal, is a risk factor for renal damage. Borax, an essential trace element in cellular metabolism, is a naturally occurring compound found in many foods. This study investigated the effects of sodium tetraborate (ST), a source of borax, on renal oxidative stress and inflammation in rats exposed to Pb. Wistar Albino rats (n = 24) were divided into four groups: Control (0.5 mL, i.p. isotonic), Pb (50 mg/kg/day/i.p.), ST (4.0 mg/kg/day/oral), and Pb + ST groups. At the end of the five-day experimental period, kidney tissue samples were obtained and analyzed. Histopathologically, the Pb-induced damage observed in the Pb group improved in the Pb + ST group. Immunohistochemically, Pb administration increased the expression of inducible nitric oxide synthase, cyclooxygenase-2, and caspase-3. When evaluated biochemically, Pb application inhibited catalase and glutathione peroxidase (GSH-Px) enzyme activities and activated superoxide dismutase enzyme activity. An increase in malondialdehyde levels was considered an indicator of damage. ST application increases glutathione peroxidase enzyme activity and decreased malondialdehyde levels. These results indicate that ST might play a protective role against Pb-induced renal damage via the upregulation of renal tissue antioxidants and cyclooxygenase-2, inducible nitric oxide synthase, and caspase-3 immunoexpression.

Subacute Exposure to Low Pb Doses Promotes Oxidative Stress in the Kidneys and Copper Disturbances in the Liver of Male Rats

Recent data indicate that lead (Pb) can induce adverse effects even at low exposure levels. Moreover, the corresponding mechanisms of low Pb toxicity have not been well identified. In the liver and the kidneys, Pb was found to induce various toxic mechanisms leading to organ physiological disruption. Therefore, the purpose of the study was to simulate low-dose Pb exposure in an animal model with the aim of assessing oxidative status and essential element levels as the main mechanism of Pb toxicity in the liver and kidneys. Furthermore, dose-response modelling was performed in order to determine the benchmark dose (BMD). Forty-two male Wistar rats were divided into seven groups: one control group, and six groups treated for 28 days with 0.1, 0.5, 1, 3, 7, and 15 mg Pb/kg b.w./day, respectively. Oxidative status parameters (superoxide dismutase activity (SOD), superoxide anion radical (O₂^-), malondialdehyde (MDA), total sulfhydryl groups (SHG), and advanced oxidation protein products (AOPP)) and Pb, copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) levels were measured. Lowering Cu levels (BMD: 2.7 ng/kg b.w./day), raising AOPP levels (BMD: 0.25 µg/kg b.w./day) in the liver, and inhibiting SOD (BMD: 1.3 ng/kg b.w./day) in the kidneys appear to be the main mechanisms of Pb toxicity. The lowest BMD was derived for a decrease in Cu levels in liver, indicating that this effect is the most sensitive.

Oxidative stress, metallomics and blood toxicity after subacute low-level lead exposure in Wistar rats: Benchmark dose analyses

Exposure to lead (Pb) is still rising concern worldwide, having in mind that even low-dose exposure can induce various harmful effects. Thus, in-depth knowledge of the targets of Pb toxicity and corresponding mechanisms is essential. In the presented study, the six groups (male Wistar rats, n = 6) received 0.1; 0.5; 1; 3; 7; 15 mg Pb/kg body weight/day for 28 days, each day by oral gavage, while the control group received distilled water only. All animals were sacrificed 24 h after the treatment, and blood was collected for the analysis of hematological, biochemical, oxidative status and essential elements levels. An external and internal dose-response relationship was performed using PROASTweb 70.1 software. The results showed that low doses of Pb affect hematological parameters and lipid profile after 28 days. The possible mechanisms at examined Pb dose levels were a decrease in SOD, O₂^•- and Cu and an increase in Zn levels. The dose-dependent nature of changes in cholesterol, HDL cholesterol, O₂^.-, SOD, AOPP in serum and hemoglobin, Fe, Zn, Cu in blood were obtained in this study. The most sensitive parameters that were alerted are Cu blood levels (BMDL₅: 1.4 ng/kg b.w./day) and SOD activity (BMDL₅: 0.5 μg/kg b.w./day). The presented results provide information that may be useful in further assessing the health risks of low-level Pb exposure.

Redox and essential metal status in the brain of Wistar rats acutely exposed to a cadmium and lead mixture

Most Pb and Cd neurotoxicity studies investigate exposure to either of the toxic metals alone, while data on co-exposure are scarce. The aim of our study was to fill that gap by investigating acute combined effects of Pb and Cd on redox and essential metal status in the brain of Wistar rats. Animals were randomised in four groups of six to eight rats, which received 15 or 30 mg/kg of Cd, 150 mg/kg of Pb, or 150 mg/kg of Pb + 15 mg/kg of Cd by gavage. The fifth, control, group received distilled water only. Co-treatment with Pb and Cd induced significant increase in malondialdehyde (MDA) and thiobarbituric acid-reactive substances (TBARS) compared to control and groups receiving either metal alone. This is of special importance, as MDA presence in the brain has been implicated in many neurodegenerative disorders. The groups did not significantly differ in Zn, Cu, Mn, and Fe brain levels. Our findings highlight the importance of metal mixture studies. Neurotoxicity assessments of single chemicals do not provide a real insight into exposure to mixtures in real life. Further research should look into interactions between these metals to reveal complex molecular mechanisms of their neurotoxicity.

Bioaccumulation of heavy metals, lipid profiles, and antioxidant status of snails (Achatina achatina) around cement factory vicinities

Some snails (Achatina spp) can be used as a biosensor of heavy metal poisoning. This study thus estimated some heavy metal levels, antioxidant markers, and lipid profiles of snails handpicked around cement factory vicinities in Ogun State, Nigeria. Snails and soil samples were collected from Oke, Ewekoro, Papalanto, and Mowodani Imeko-Afon (control site). Lead (Pb), cadmium (Cd), and arsenic (As) levels were estimated in the soil, snail foot, hemolymph, and shell using Atomic Absorption Spectrophotometry. Triacylglycerol (TAG), phospholipids (PHOL), cholesterol (CHOL), malondialdehyde (MDA), and reduced glutathione (GSH) levels, as well as glutathione-S-transferase (GST), lactate dehydrogenase (LDH), and arylesterase (AR) activities in the hemolymph, were estimated spectrophotometrically. The snails collected from the Oke site had the highest foot Pb (274.66 ± 13.50 mg/g tissue), CHOL, TAG, PHOL levels, and GST activity when compared with other sites. Snails collected from Papa had the highest Cd levels (1.79 ± 0.74 mg/kg), As (1206 ± 18.87 mg/g tissue) in the foot, and LDH activity, while Ewekoro snails had highest MDA levels and AR activities but the lowest GSH levels. Additionally, there were negative correlations between the heavy metal levels and the activities of GST and AR as well as GSH levels, while positively correlating with LDH activity and MDA level. Workers and the general public around cement factories are at a greater risk of heavy metal-induced pathologies. More so, consumption of snails around these sites may be deleterious to health.

Assessment of Thyroid Function and Oxidative Stress State in Foundry Workers Exposed to Lead

BACKGROUND

Exposure to lead (Pb) has been associated with endocrine, hematological, gastrointestinal, renal and neurological problems in humans. However, effects on the thyroid gland are controversial.

OBJECTIVES

The aim of the present study was to assess thyroid function in foundry workers occupationally exposed to Pb and the mechanism of oxidative-antioxidant imbalance.

METHODS

Thyroid function parameters and markers of oxidative stress were examined in 59 adult males who had been occupationally exposed to Pb. The results were then compared to those of 28 male subjects who had no history of Pb exposure or thyroid abnormalities and served as a control group.

RESULTS

Mean blood lead levels (16.5±1.74 μg/dl) were significantly higher among the exposed workers compared to those of the control group (12.8±1.16 μg/dl, (p <0.001)). The exposed group had significantly increased free triiodothyronine (FT3), free thyroxine (FT4) and significantly decreased thyroid stimulating hormone (TSH) (1.77±0.44 μIU/ml), whereas the control group had a TSH level of 2.61±0.94 μIU/ml (p< 0.0001). A state of oxidative stress was indicated by the significant increase in mean levels of malondialdehyde (MDA) and significant decrease in glutathione (GSH) (p < 0.0001). There was a significant positive correlation (r=0.358, p <0.05) between blood lead levels (BLL) and duration of employment, while BLL showed a significant negative correlation with TSH (r =-0.486, p <0.001), and GSH (r =-0.336, p <0.05). Of the occupationally exposed workers, 32.76% had elevated thyroid hormones. The results showed a significant positive relationship between GSH and TSH (β coefficient=0.274, p < 0.05), MDA with FT3 (β coefficient=0.355, p < 0.05) and FT4 (β coefficient = 0.491, p < 0.0001) among exposed workers.

CONCLUSIONS

Workers exposed to Pb dust proved to be at risk for hyperthyroidism, which was found to have a significant role in oxidative-antioxidant imbalance present among workers with increasing duration of exposure.

PARTICIPANT CONSENT

Obtained.

ETHICS APPROVAL

This study was approved by the Ethical Committee of the National Research Centre in Egypt (NRC) under the registration number 15225.

COMPETING INTERESTS

The authors declare no competing financial interests.

Comparative study on the effects of salinomycin, monensin and meso-2,3-dimercaptosuccinic acid on the concentrations of lead, calcium, copper, iron and zinc in lungs and heart in lead-exposed mice

BACKGROUND AND AIM

Environmental lead (Pb) exposure damages the lungs and is a risk factor for death from cardiovascular disease. Pb induces toxicity by a mechanism, which involves alteration of the essential elements homeostasis. In this study we compare the effects of salinomycin (Sal), monensin (Mon) and meso-2,3-dimercaptosuccinic acid (DMSA) on the concentrations of lead (Pb), calcium (Ca), copper (Cu), iron (Fe) and zinc (Zn) in the lungs and heart of lead-exposed mice.

METHODS

Sixty days old male ICR mice were divided into five groups: control (Ctrl) - untreated mice obtained distilled water for 28 days; Pb-intoxicated group (Pb) - exposed to 80 mg/kg body weight (BW) Pb(NO₃)₂ during the first 14 days of the experimental protocol; DMSA-treated (Pb + DMSA) - Pb-exposed mice, subjected to treatment with an average daily dose of 20 mg/kg BW DMSA for two weeks; Monensin-treated (Pb + Mon) - Pb-exposed mice, obtained an average daily dose of 20 mg/kg BW tetraethylammonium salt of monensic acid for 14 days; Pb + Sal - Pb-exposed mice, treated with an average daily dose of 20 mg/kg BW tetraethylammonium salt of salinomycinic acid for two weeks. On the 29^th day of the experiment the samples (lungs and heart) were taken for atomic absorption analysis.

RESULTS

The results revealed that exposure of mice to Pb for 14 days significantly increased the concentration of the toxic metal in both organs and elevated the cardiac concentrations of Ca, Cu and Fe compared to untreated mice. Pb exposure diminished the lung concentrations of Ca and Zn compared to that of untreated controls. DMSA, monensin and salinomycin decreased the concentration of Pb in the lungs and heart. Among the tested chelating agents, only salinomycin restored the cardiac Fe concentration to normal control values.

CONCLUSION

The results demonstrated the potential application of polyether ionophorous antibiotic salinomycin as antidote for treatment of Pb-induced toxicity in the lungs and heart. The possible complexation of the polyether ionophorous antibiotics with Ca(II) and Zn(II), which can diminish the endogenous concentrations of both ions in the lungs should be taken into account.

Role of lead in dental diseases

Lead (Pb) is ubiquitous in our environment and causes many pathophysiological health effects, including dental diseases. Dental Pb levels are considered good biological indicators of environmental and occupational Pb exposure. Pb in blood and saliva causes imbalances in the growth of oral microflora. The pH of saliva decreases, interferes with and interacts with bone-seeking elements, changes oral inflammatory parameters, generates reactive oxygen species, causes oxidative damage, and delays the mineralization process, leading to dental diseases. Pb's dental diseases include periodontitis, enamel lesions and defects, fluorosis, Burton's line, and tooth loss. Environmental and physiological factors, including age, gender, tooth type and position, pregnancy and lactation, eating and drinking habits, smoking habits, and exposures from Pb-contaminated residential and occupational areas, affect the distribution of Pb in blood, bone, and saliva, which contributes to dental diseases. However, living and working in Pb free areas can prevent environmental and occupational Pb exposure. Healthy lifestyles and eating habits, prohibiting smoking and alcohol drinking, further help prevent Pb exposure. Also, the fluoridation of water, salt, and milk provide nutritional supplements of trace elements, which can help prevent teeth from absorbing Pb from the environment, thereby reducing the risk of dental diseases.

Enhancement of bone mineral density and body mass in newborn chickens by in ovo injection of ionic-hydroxyapatite nanoparticles of bacterial origin

Using non-drug, non-surgical treatments for improving bone mineral diseases in newborn babies is an important topic for neonatologists. The present study introduces bacterial synthesized ionic nano-hydroxyapatite (Bio-HA) for the development of bone mineral density in the chicken embryo model. In vitro cytotoxicity analyses were demonstrated the optimal concentrations of Bio-HA compared to a chemically-synthesized hydroxyapatite (Ch-HA). Toxicity of Bio-HA on MCF-7 human cell lines was negligible at the concentrations less than 500 μg/mL whereas Ch-HA showed similar results at the concentrations less than 100 μg/mL. Therefore, concentrations at 50 μg/mL and 100 μg/mL were selected for in ovo injection of both materials into the fertilized eggs. The newly hatched chickens were sacrificed in order to monitor their serological factors, total body mass, bone mineral contents and bone mineral density. The results confirmed that Bio-HA increased the average body weight and bone mineral indices of chickens in comparison to the Ch-HA and negative controls (normal saline and intact groups). In view of the intact group, no liver or kidney damage occurred in the groups receiving Bio-HA which promises the effectiveness of these nanoparticles for the treatment of afterbirth bone mineral deficiency.

Cadmium-Induced Oxidative Stress Impairs Glycemic Control in Adolescents

Experimental evidence suggests that cadmium (Cd) boosts oxidative stress that may result in toxicity on the endocrine system also in humans. The aim of this study was to investigate the glycemic control and oxidative stress markers in male adolescents with increased urinary levels of cadmium. We investigated 111 males, aged 12–14 years, living in a polluted area of Sicily and a control age-matched population (n = 60) living 28–45 km far from the polluted site. Malondialdehyde (MDA), total antioxidant activity (TAC), metallothionein-1A (MT-1A) gene expression, insulin resistance by the homeostatic model assessment (HOMA-IR), and urinary cadmium were investigated. Cd levels were significantly higher in adolescents living in the polluted area than in control age-matched subjects. Adolescents with elevated Cd levels had a significant increase in MDA, MT-1A, and HOMA-IR and reduced TAC compared to the control group. A robust correlation was found between urinary cadmium and MT-1A, HOMA-IR, and MDA whereas an inverse correlation was identified between urinary cadmium and TAC. This study indicates that cadmium burden alters glycemic control in adolescents and suggests that oxidative stress plays a key role in cadmium-induced insulin resistance, increasing the risk of developing metabolic disorders.

Health risks in rural populations due to heavy metals found in agricultural soils irrigated with wastewater in the Alto Balsas sub-basin in Tlaxcala and Puebla, Mexico

The aim of this study was to determine the hazard ratio (HQ), the risk index (HI), and the cancer risk index (CRI) for populations of adults and children exposed to ingestion, dermal contact and inhalation of heavy metals in agricultural soil. For these, the contents of Cd, Pb, Ni, Cu, Co, Cr, Zn, and the metalloid As were determined in soils of four zones of the sub-basin of Alto Balsas, during two different periods of the year. The average content of metals in the soil was 1.24, 14.77, 14.80, 13.06, 5.50, 17.65, 22.89, and 5.32 mg kg^-1 for Cd, Pb, Ni, Cu, Co, Cr, Zn, and As, respectively. The highest risk in terms of HQ and HI was for adults, especially for men who are affected through the skin, with Cd and Cr being the most dangerous. CRI values were within the allowable range, without posing problems for adult and child populations.

Heavy metal burdens of public primary school children related to playground soils and classroom dusts in Ibadan North-West local government area, Nigeria

Information about heavy metal burden of children in Nigeria related to playground soils and classroom dusts is lacking. Playground soil, classroom dust, blood and spot urine samples (n=253) were collected from 6 urban and 2 semi-rural public schools in Ibadan North-West, Nigeria. Samples were analysed for Pb, Cu, Zn, Fe and Mn. Mean blood Pb levels in urban area (male, 41.66±8.78μg/dl vs. female, 40.64±5.46μg/dl) were twice as high as those in semi-rural area (male, 19.71±3.73μg/dl vs. female, 20.65±2.26μg/dl). Concentrations of Pb, Cu, Zn, and Fe in soil and dust samples in the urban schools were between 2- to 4-fold greater than that of semi-rural schools. No correlation was observed between blood and dust metals. A positive correlation (r=0.168, p=0.008) was observed between blood Pb and playground soil Pb. Pb burden in the children might be from their schools' playgrounds and other yet unidentified sources.

Effect of Selenium Against Lead-Induced Damage on the Gene Expression of Heat Shock Proteins and Inflammatory Cytokines in Peripheral Blood Lymphocytes of Chickens

The possible beneficial role of selenium (Se) in heat shock proteins (HSPs) and inflammation damage induced by lead (Pb) in chickens is unclear. Therefore, the aim of this study was to investigate the effect of Se against Pb on the messenger RNA (mRNA) expression levels of HSPs (HSP 27, 40, 60, 70, and 90); heme oxygenase-1 (HO-1); and the inflammatory cytokines nuclear factor kappa B (NF-κB), tumor necrosis factor alpha (TNF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) in the peripheral blood lymphocytes of chickens. A total of 360 1-day-old broiler chickens were randomly allocated into four groups (n = 90/group). The control group was fed a basic diet containing 0.2 mg/kg Se and 0.5 mg/kg Pb; the Se supplementation group (+Se group) was fed a Se-adequate (sodium selenite) diet containing 1 mg/kg Se and 0.5 mg/kg Pb; the Pb-supplemented group (+Pb group) was fed a Pb acetate diet containing 0.2 mg/kg Se and 350 mg/kg Pb; and the Se and Pb compound group (Se + Pb group) was fed a diet containing 1 mg/kg Se and 350 mg/kg Pb. The blood was collected and examined for the mRNA levels of HSP and inflammatory cytokine genes at 30 and 60 days old. The results showed that Pb poisoning induced the mRNA expression of HSPs and inflammatory cytokines in the peripheral blood lymphocytes of chickens. In addition, Se alleviated the Pb-induced increase in HSP and inflammatory cytokine mRNA levels in chicken peripheral blood lymphocytes. In conclusion, Se can antagonize the toxic effects of Pb on chickens and protect the chickens' peripheral blood lymphocytes in normal physiological function.

Comparative assessment of the effects of salinomycin and monensin on the biodistribution of lead and some essential metal ions in mice, subjected to subacute lead intoxication

In this study, we present a comparative assessment of the effects of two polyether ionophorous antibiotics (monensin and salinomycin) on the concentrations of lead (Pb), cooper (Cu), zinc (Zn) and iron (Fe) in the kidneys, spleen, liver and brain of Pb-intoxicated animals. Our data demonstrated that the intoxication of ICR male mice with Pb salt resulted in a significant accumulation of Pb in all studied organs of the mice compared to the untreated control animals. The biodistribution of the toxic metal was in the order kidneys>spleen>liver>brain. The treatment of the Pb-intoxicated animals with tetraethylammonium salts of monensic and salinomycinic acids significantly decreased the concentration of the toxic metal ion compared to the toxic control. The effect varied in the interval 38% (for kidneys) to 52% (for brain) compared to the toxic control group (Pb). The tetraethylammonium salt of salinomycinic acid was more effective in reducing the Pb concentration in the brain of the Pb-treated mice compared to monensin. Pb-intoxication did not affect significantly the Zn endogenous concentration compared to the normal values. The treatment of ICR male mice with Pb-salt decreased the Cu concentration in the spleen and increased the Cu concentration in the liver compared to the untreated control animals. The detoxification of the Pb-intoxicated mice with tetraethylammonium salts of salinomycinic and monensic acids restored the Cu concentration in the spleen, but did not affect the Cu levels in the liver. The Pb-intoxication of the ICR mice resulted in a significant decrease of the Fe-concentration in the spleen and liver compared to the untreated control animals. The administration of the tetraethylammonium salts of salinomycinic and monensic acids to the Pb-treated animals restored the levels of Fe in both organs.

Cadmium delays puberty onset and testis growth in adolescents

OBJECTIVE

Cadmium (Cd) has been shown to impair pubertal development in experimental animals. However, no data are available for male adolescents with increased urinary cadmium levels.

DESIGN

The aim of this cross-sectional study was to evaluate pubertal onset and pituitary-gonadal axis hormones in male adolescents with increased urinary levels of Cd.

SUBJECTS

We studied 111 males, aged 12-14 years living in the Milazzo-Valle del Mela area. A control age-matched population (n = 60) living 28-45 km far from the industrial site was also enrolled.

MEASUREMENTS

Pubertal stages were assessed by clinical examination according to Tanner's score. Mean testicular volume was also investigated by ultrasound examination. Urinary Cd concentration and blood levels of FSH, LH, testosterone and inhibin B were also investigated.

RESULTS

Cd levels were significantly higher in adolescents living in the Milazzo-Valle del Mela area, compared to both age-matched subjects living far from the industrial plants and the reference values. Our population showed also a delayed onset of puberty, a smaller testicular volume and lower testosterone levels. An inverse correlation was found between urinary Cd and testicular volume (r = -0·25; P = 0·0008), testosterone levels (Spearman's r = -0·0·37; two-tailed P < 0·0001) and LH levels (Spearman's r = 0·048; P < 0·05). Testosterone levels were positively correlated with testicular volume (Spearman's r = 0·48; P < 0·0001).

CONCLUSIONS

This study, for the first time, suggests that increased Cd burden is associated with delayed onset of puberty in male adolescents and impaired testicular growth.

Blood lead level and its relationship to essential elements in preschool children from Nanning, China

OBJECTIVE

Our study aimed to assess the distribution of blood lead level and its relationship to essential elements in preschool children in an urban area of China.

DESIGN AND METHODS

A total of 6741 children aged 0- to 6-year-old were recruited. Levels of lead, zinc, copper, iron, calcium, and magnesium in whole blood samples were determined using atomic absorption spectrometry.

RESULTS

The mean blood lead level (BLL) and the prevalence of BLL≥10μg/dl (5.26±4.08μg/dl and 6.84%, respectively) increased with age gradually, and there was a gender-difference for blood lead, copper, zinc and iron levels. Compared with the group of children who had BLLs<5μg/dl, the groups of 5≤BLLs<10μg/dl and 10≤BLLs<15μg/dl showed higher blood zinc, iron and magnesium levels, and a lower blood calcium level. A positive correlation of lead with zinc, iron and magnesium, and a negative correlation of lead with calcium were found in the group of children with BLL<5μg/dl.

CONCLUSION

Age- and gender-differences were found when assessing the BLL and intoxication prevalence in preschool children. Metabolic disorder of essential elements was found even with a low level of lead exposure.

Oxidative stress and DNA repair and detoxification gene expression in adolescents exposed to heavy metals living in the Milazzo-Valle del Mela area (Sicily, Italy)

BACKGROUND

The area of Milazzo-Valle del Mela (Sicily, Italy) is considered at high risk of environmental crisis by regional authorities.

OBJECTIVE

To measure oxidative-stress, DNA repair and detoxification genes in school children living near the industrial area and in age-matched controls.

METHODS

The parent study was a biomonitoring investigation evaluating heavy metal urine levels in 226 children aged 12-14 years, living in the high risk area, and in 29 age-matched controls living 45 km far from the industrial site. In the present study 67 exposed adolescents and 29 controls were included. Samples were analyzed for urinary 8-hydroxydeoxyguanosine (8OHdG) levels, and gene expression of OGG1 (DNA repair gene), NQO1, ST13, and MT1A (detoxifying genes).

RESULTS

Urinary cadmium was higher (p = 0.0004) in exposed [geometric mean, 0.46 µg/L; 25th-75th percentile: 0.3-0.56] than in control adolescents [geometric mean, 0.26 µg/L; 25th-75th percentile: 0.2-0.3]. Chromium was also significantly elevated in exposed [geometric mean, 1.52 µg/L; 25th-75th percentile: 1.19-1.93] compared with controls [geometric mean, 1.25 µg/L; 25th-75th percentile: 1.05-1.48; p = 0.02]. Urinary 8-OHdG concentration was greater in exposed than in controls (71.49 vs 61.87 µg/L, p = 0.02), and it was correlated with cadmium levels (r = 0.46, p < 0.0001), and with the combined exposure index (r = 0.43, p < 0.0001). Moreover, cadmium levels showed a robust correlation with OGG1 and MT1A gene expression levels (r = 0.44, p < 0.0001; r = 0.39, p < 0.0001, respectively). Finally, OGG1 and MT1A were over-expressed in adolescents from Milazzo-Valle del Mela area compared with controls (p = 0.0004; p < 0.0001, respectively).

CONCLUSIONS

Continuous exposure at relatively low concentrations of heavy metals is associated with increased oxidative DNA damage and impaired expression of DNA repair and detoxification genes in adolescents.

Effect of long-term human exposure to environmental heavy metals on the expression of detoxification and DNA repair genes

The present study was designed to evaluate the influence of long-term environmental human exposure to three heavy metals, lead (Pb), cadmium (Cd), and mercury (Hg), on the expression of detoxifying, xenobiotic metabolizing, and DNA repair genes in Mahd Ad-Dahab city. The study groups consisted of 40 healthy male residents (heavy metal-exposed) and 20 healthy male from Riyadh city, 700 km away, and served as control group. The heavy metal-exposed group with high exposure to Pb, Cd, or Hg was divided into three subgroups Pb-, Cd-, and Hg-exposed groups, respectively. The mRNA expression levels of detoxifying, NQO1, HO-1, GSTA1, MT-1, and HSP70, were significantly decreased in all heavy metal-exposed group as compared to control group. This was accompanied with a proportional decrease in the expression of xenobiotic metabolizing gene, cytochrome P4501A1. On the other hand, the DNA repair gene OGG1 and the 8-OHdG level were dramatically inhibited in Cd-exposed group only.