Low level lead exposure and oxidative stress: Current opinions

Current situation of lead (Pb) exposure in raptors and waterfowl in Japan and difference in sensitivity to in vitro lead exposure among avian species

Although lead (Pb) poisoning in wild birds has been considered a serious problem in Japan for over 30 years, there is little information about Pb exposure and its sources throughout Japan except for Hokkaido. Furthermore, to identify and effectively prioritize the conservation needs of highly vulnerable species, differences in sensitivity to Pb exposure among avian species need to be determined. Therefore, we investigated the current situation of Pb exposure in raptors (13 species, N = 82), waterfowl (eight species, N = 44) and crows (one species, N = 6) using concentration and isotope analysis. We employed blood or tissue samples collected in various Japanese facilities mainly in 2022 or 2023. We also carried out a comparative study of blood δ-ALAD sensitivity to in vitro Pb exposure using blood of nine avian species. Pb concentrations in the blood or tissues displayed increased levels (>0.1 μg/g blood) in two raptors (2.4%), ten waterfowl (23%) and one crow (17%). Among them, poisoning levels (>0.6 μg/g blood) were found in one black kite and one common teal. The sources of Pb isotope ratios in ten blood samples with high Pb levels were determined as deriving from shot pellets (N = 9) or rifle bullets (N = 1). In the δ-ALAD study, red-crowned crane showed the highest sensitivity among the nine tested avian species and was followed in order by five Accipitriformes species (including white-tailed and Steller's sea eagle), Blakiston's fish owl, Muscovy duck and chicken, suggesting a genetically driven variance in susceptibility. Further studies on contamination conditions and exposure sources are urgently needed to inform strict regulations on the usage of Pb ammunition. Furthermore, detailed examinations of δ-ALAD sensitivity, interspecific differences, and other factors involved in the variability in sensitivity to Pb are required to identify and prioritize highly sensitive species.

Computational models as catalysts for investigating redoxin systems

Thioredoxin, glutaredoxin and peroxiredoxin systems play central roles in redox regulation, signaling and metabolism in cells. In these systems, reducing equivalents from NAD(P)H are transferred by coupled thiol-disulfide exchange reactions to redoxins which then reduce a wide array of targets. However, the characterization of redoxin activity has been unclear, with redoxins regarded as enzymes in some studies and redox metabolites in others. Consequently, redoxin activities have been quantified by enzyme kinetic parameters in vitro, and redox potentials or redox ratios within cells. By analyzing all the reactions within these systems, computational models showed that many kinetic properties attributed to redoxins were due to system-level effects. Models of cellular redoxin networks have also been used to estimate intracellular hydrogen peroxide levels, analyze redox signaling and couple omic and kinetic data to understand the regulation of these networks in disease. Computational modeling has emerged as a powerful complementary tool to traditional redoxin enzyme kinetic and cellular assays that integrates data from a number of sources into a single quantitative framework to accelerate the analysis of redoxin systems.

Influence of lead-induced toxicity on the inflammatory cytokines

Lead (Pb2+) is a hazardous heavy metal that is pervasive in the human environment as a result of anthropogenic activity, and poses serious health risks, particularly in children. Due to its innumerable unique physical and chemical properties, it has various applications; therefore, it has become a common environmental pollutant. Lead may cause oxidative stress, and accumulating evidence indicates that oxidative stress influences the pathophysiology of lead poisoning, also called plumbism. The immune system is continually exposed to various environmental pathogens and xenobiotics, including heavy metals such as lead, and appears to be one of the most vulnerable targets. After being exposed to lead, cells are subjected to oxidative stress as a result of reactive oxygen species (ROS) production. When the generation and consumption of ROS are out of equilibrium, various cell structures, particularly phospholipids are disrupted leading to lipid peroxidation. Various inflammatory signalling pathways are activated as a consequence, along with reduced disease resistance, inflammation, autoimmunity, sensitization and disruption of the cell-mediated and humoral immune systems. Lead negatively affects the metabolism of cytokines, including the interleukins IL-2, IL-1b, IL-6, IL-4, IL-8, tumor necrosis factor-alpha (TNF-α), and interferon-gamma (IFN), as well as the expression and functioning of inflammatory enzymes such as cyclooxygenases. However, the cause of toxicity depends on the kind of lead, dosage, route of entry, exposure period, age, host and genetic predisposition.

Maternal prenatal lead levels and neonatal brain volumes: Testing moderations by maternal depressive symptoms and family income

There is considerable evidence that prenatal lead exposure is detrimental to child cognitive and socio-emotional development. Further evidence suggests that the effects of prenatal lead on developmental outcomes may be conditional upon exposure to social stressors, such as maternal depression and low socioeconomic status. However, no studies have examined associations between these co-occurring stressors during pregnancy and neonatal brain volumes. Leveraging a sample of 101 mother-infant dyads followed beginning in mid-pregnancy, we examined the main effects of prenatal urinary lead levels on neonatal lateralized brain volumes (left and right hippocampus, amygdala, cerebellum, frontal lobes) and total gray matter. We additionally tested for moderations between lead and depressive symptoms and between lead and family income relative to the federal poverty level (FPL) on the same neurodevelopmental outcomes. Analyses of main effects indicated that prenatal lead was significantly (ps < 0.05) associated with reduced right and left amygdala volumes (βs = -0.23- -0.20). The testing and probing of cross-product interaction terms using simple slopes indicated that the negative effect of lead on the left amygdala was conditional upon mothers having low depressive symptoms or high income relative to the FPL. We interpret the results in the context of trajectories of prenatal and postnatal brain development and susceptibility to low levels of prenatal lead in the context of other social stressors.

Elevated lead (Pb) in urban European starling (Sturnus vulgaris) feathers is not correlated to physiology or behavior

Urbanization is rapidly changing the environment and creating new challenges in the lives of animals across the globe. Anthropogenic contaminants-like heavy metals-can persist within the environment for prolonged periods of time and present a widespread problem for those living near contaminated areas. Lead (Pb) was a commonly used heavy metal that continues to threaten the health of all organisms despite being phased out, especially in urban areas where historical use was more common. In this study, a common urban-adapter, the European starling (Sturnus vulgaris), was trapped to explore whether feather Pb burden is greater in birds from urban habitats than rural habitats, as well as whether Pb burdens were correlated with behavior, physiology, and feather development. Across four sites (two rural and two urban), soil Pb concentrations were measured and 197 free-living starlings were captured to measure feather Pb concentrations. Using linear mixed models, this study found that urban starling nestlings had elevated feather Pb burdens compared to rural nestlings. In contrast, there was no correlation between Pb and urbanization in adult birds whose exposure to Pb may reflect a larger spatial range compared to nestlings. For both nestlings and adults, feather Pb was uncorrelated to corticosterone, testosterone, aggressive behavior, or feather growth rates. These findings suggest that starlings may be a useful biomonitoring tool to detect Pb in the local environment, however, the age and spatial range of birds is a critical consideration in applying this tool. Further work is needed to understand the intricate relationship between heavy metals, behavior, morphological development, and physiology in free-living organisms.

Protective Effect of Protocatechuic Acid on Oxidative Damage and Cognitive Impairment in Pb-Induced Rats

Protocatechuic acid (PCA), a class of water-soluble phenolic acid abundant in the human diet, has been shown to be of great nutritional interest and to have medicinal value. However, the protective effects against lead (Pb)-induced body injury have not been elucidated. In this study, we explored the protective effect of PCA on Pb-induced oxidative damage and cognitive impairment in rats. The results showed that PCA could reduce the Pb content in rat bodies (blood, bone, brain, liver, and kidney) after Pb exposure. Moreover, PCA may inhibit Pb-induced oxidative damage by increasing the activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and decreasing the level of malondialdehyde (MDA) in the brain, liver, and kidney. In addition, PCA may alleviate Pb-induced learning and memory impairment by upregulating neurotransmitter levels; maintaining the normal function of N-methyl-D-aspartate receptors (NMDARs); and promoting Ca2+ influx, thus activating signaling molecules, related protein kinases, and transcription factors in the cAMP-PKA-CREB pathway. In general, PCA could reduce oxidative stress and ameliorate the learning and memory deficits in Pb-treated rats, indicating that PCA may be an effective preventive agent and treatment or plumbism.

An Industry-Relevant Metal Mixture, Iron Status, and Reported Attention-Related Behaviors in Italian Adolescents

BACKGROUND

Exposure to environmental metals has been consistently associated with attention and behavioral deficits in children, and these associations may be modified by coexposure to other metals or iron (Fe) status. However, few studies have investigated Fe status as a modifier of a metal mixture, particularly with respect to attention-related behaviors.

METHODS

We used cross-sectional data from the Public Health Impact of Metals Exposure study, which included 707 adolescents (10-14 years of age) from Brescia, Italy. Manganese, chromium, and copper were quantified in hair samples, and lead was quantified in whole blood, using inductively coupled plasma mass spectrometry. Concentrations of Fe status markers (ferritin, hemoglobin, transferrin) were measured using immunoassays or luminescence assays. Attention-related behaviors were assessed using the Conners Rating Scales Self-Report Scale-Long Form, Parent Rating Scales Revised-Short Form, and Teacher Rating Scales Revised-Short Form. We employed Bayesian kernel machine regression to examine associations of the metal mixture with these outcomes and evaluate Fe status as a modifier.

RESULTS

Higher concentrations of the metals and ferritin were jointly associated with worse self-reported attention-related behaviors: metals and ferritin set to their 90th percentiles were associated with 3.0% [β = 0.03 ; 95% credible interval (CrI): - 0.01 , 0.06], 4.1% (β = 0.04 ; 95% CrI: 0.00, 0.08), and 4.1% (β = 0.04 ; 95% CrI: 0.00, 0.08) higher T -scores for self-reported attention deficit/hyperactivity disorder (ADHD) index, inattention, and hyperactivity, respectively, compared with when metals and ferritin were set to their 50th percentiles. These associations were driven by hair manganese, which exhibited nonlinear associations with all self-reported scales. There was no evidence that Fe status modified the neurotoxicity of the metal mixture. The metal mixture was not materially associated with any parent-reported or teacher-reported scale.

CONCLUSIONS

The overall metal mixture, driven by manganese, was adversely associated with self-reported attention-related behavior. These findings suggest that exposure to multiple environmental metals impacts adolescent neurodevelopment, which has significant public health implications. https://doi.org/10.1289/EHP12988.

Assessing the mediating role of iron status on associations between an industry-relevant metal mixture and verbal learning and memory in Italian adolescents

BACKGROUND

Metals, including lead (Pb), manganese (Mn), chromium (Cr) and copper (Cu), have been associated with neurodevelopment; iron (Fe) plays a role in the metabolism and neurotoxicity of metals, suggesting Fe may mediate metal-neurodevelopment associations. However, no study to date has examined Fe as a mediator of the association between metal mixtures and neurodevelopment.

OBJECTIVE

We assessed Fe status as a mediator of a mixture of Pb, Mn, Cr and Cu in relation to verbal learning and memory in a cohort of Italian adolescents.

METHODS

We used cross-sectional data from 383 adolescents (10-14 years) in the Public Health Impact of Metals Exposure Study. Metals were quantified in blood (Pb) or hair (Mn, Cr, Cu) using ICP-MS, and three markers of Fe status (blood hemoglobin, serum ferritin and transferrin) were quantified using luminescence assays or immunoassays. Verbal learning and memory were assessed using the California Verbal Learning Test for Children (CVLT-C). We used Bayesian Kernel Machine Regression Causal Mediation Analysis to estimate four mediation effects: the natural direct effect (NDE), natural indirect effect (NIE), controlled direct effect (CDE) and total effect (TE). Beta (β) coefficients and 95 % credible intervals (CIs) were estimated for all effects.

RESULTS

The metal mixture was jointly associated with a greater number of words recalled on the CVLT-C, but these associations were not mediated by Fe status. For example, when ferritin was considered as the mediator, the NIE for long delay free recall was null (β = 0.00; 95 % CI = -0.22, 0.23). Conversely, the NDE (β = 0.23; 95 % CI = 0.01, 0.44) indicated a beneficial association of the mixture with recall that operated independently of Fe status.

CONCLUSION

An industry-relevant metal mixture was associated with learning and memory, but there was no evidence of mediation by Fe status. Further studies in populations with Fe deficiency and greater variation in metal exposure are warranted.

Oyster (Crassostrea gigas) ferritin relieves lead-induced liver oxidative damage via regulating the mitophagy

Lead can induce oxidative stress and increase lipid peroxidation in biofilms, leading to liver damage and physiological dysfunction. This study aimed to investigate how oyster ferritin (GF1) attenuates lead-induced oxidative damage to the liver in vitro and in vivo. Animal experiments have confirmed that lead exposure can lead to oxidative damage and lipid peroxidation of the liver, and ferritin can regulate the activity of antioxidant enzymes and alleviate pathological changes in the liver. At the same time, oyster ferritin can regulate the expression of oxidative stress-related genes and reduce the expression of inflammasome-related genes. In addition, lead can induce apoptosis and mitophagy, leading to overproduction of reactive oxygen species and cell death, which can be effectively alleviated by oyster ferritin. Overall, this study provides a theoretical foundation for the use of oyster ferritin as a means of mitigating and preventing lead-induced damage.

Environmental relevant concentrations of polystyrene nanoplastics and lead co-exposure triggered cellular cytotoxicity responses and underlying mechanisms in Eisenia fetida

Heavy metal pollution of soils and the widespread use of plastics have caused environmental problems worldwide. Nanoplastics (NPs) contaminants in water and soil environments can adsorb heavy metals, thereby affecting the bioavailability and toxicity of heavy metals. In this paper, the effect of co-exposure of polystyrene microspheres with 100 nm particle size and lead acetate (Pb) on the Eisenia fetida coelomocytes was investigated. The environmental concentration of NPs used was 0.01 mg/L and the concentration of Pb ranged from 0.01 to 1 mg/L, and the exposed cells were incubated at 298 k for 24 h. Our study demonstrated that exposure of cells to environmental relevant concentrations of NPs did not significantly affect the cytotoxicity of Pb exposure. It was shown that co-exposure induced cellular production of reactive oxygen species (ROS, increased to 134.4 %) disrupted the antioxidant system of earthworm body cavity cells, activated superoxide dismutase and catalase (CAT), produced reduced glutathione, and inhibited glutathione-dependent enzyme (GST) activity (Reduced to 64 %). Total antioxidant capacity (T-AOC) is first enhanced against ROS due to the stress of NPs and Pb. When the antioxidant reserves of cells are exhausted, the antioxidant capacity will decrease. The level of malondialdehyde, a biomarker of eventual lipid peroxidation, increased to 231.7 %. At the molecular level, due to co-exposure to NPs and Pb, CAT was loosely structured and the secondary structure is misfolded, which was responsible for exacerbating oxidative damage in E. fetida coelomocytes. The findings of this study have significant implications for the toxicological interaction and future risk assessment of co-contamination of NPs and Pb in the environment.

Oxidative Stress in Pregnancy

Recent years have seen an increased interest in the role of oxidative stress (OS) in pregnancy. Pregnancy inherently heightens susceptibility to OS, a condition fueled by a systemic inflammatory response that culminates in an elevated presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the circulatory system. The amplified OS in pregnancy can trigger a series of detrimental outcomes such as underdevelopment, abnormal placental function, and a host of pregnancy complications, including pre-eclampsia, embryonic resorption, recurrent pregnancy loss, fetal developmental anomalies, intrauterine growth restriction, and, in extreme instances, fetal death. The body's response to mitigate the uncontrolled increase in RNS/ROS levels requires trace elements that take part in non-enzymatic and enzymatic defense processes, namely, copper (Cu), zinc (Zn), manganese (Mn), and selenium (Se). Determination of ROS concentrations poses a challenge due to their short half-lives, prompting the use of marker proteins, including malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), and glutathione (GSH). These markers, indicative of oxidative stress intensity, can offer indirect assessments of pregnancy complications. Given the limitations of conducting experimental studies on pregnant women, animal models serve as valuable substitutes for in-depth research. This review of such models delves into the mechanism of OS in pregnancy and underscores the pivotal role of OS markers in their evaluation.

Pb exposure causes non-linear accumulation of Pb in D. melanogaster controlled by metallothionein B and exerts ecological effects

Pb pollution can harm human health and the ecosystem. Therefore, it is worthwhile to study the metabolic processes of heavy metals in individual bodies and their influence on ecological systems. In this work, we analyzed the genetic responses and physiological changes of D. melanogaster which took diets exposed to different doses of Pb using transcriptomic analysis, ICP-MS, and various other physiological methods. We found that the Pb accumulated in D. melanogaster in a nonlinear pattern with the increase of Pb content in food. Metallothioneins (Mtns), especially the MtnB directly affects the accumulation and excretion of metal Pb in D. melanogaster, and causes the nonlinear accumulation. Metal regulatory transcription factor-1 (MTF-1) is involved in the regulation of Pb-induced high expressions of Mtns. Furthermore, an interaction between the metal metabolism pathway and xenobiotic response pathway leads to the cross-tolerances of Pb-exposed D. melanogaster to insecticides and other toxins. The oxidative stress induced by Pb toxicity may be the bridge between them. Our findings provide a physiological and molecular genetic basis for further study of the accumulation and metabolism of Pb in D. melanogaster.

In vivo and in silico approach in revealing the influence of lead (Pb) on thyroid gland function

The purpose of this study was to examine the impact of low doses of lead (Pb) on levels of thyroid hormones (T3, T4, FT3, and FT4) and thyroid-related antibodies (anti-Tg and anti-TPO) in the rat model, as well as genes that are related to Pb and thyroid function, relationships between genes, biological processes, molecular processes, and pathways using an in silico approach. Male rats were randomized into seven groups (n = 42), one control group and six groups that received a range of Pb doses: 0.1, 0.5, 1, 3, 7, and 15 mg Pb/kg body weight (b.w.). Dose-response modelling was performed by PROAST software using model averaging method. The Comparative Toxicogenomics Database, GeneMANIA server, and ToppGene Suite portal were used as the main bioinformatic tools in this analysis. The results of our study have shown that low Pb doses induced elevation of thyroid hormones (T4, FT4, and TSH) in rats after subacute exposure, while had no impact on T3, FT3, anti-TPO, and anti-Tg, indicating hyperthyroidism. Dose-dependent effects were increases in T4 and FT4, with the lowest benchmark dose derived for FT4 levels. In silico toxicogenomic data analysis showed that the main molecular pathways/process related to Pb-induced hyperthyroidism are connected with 14 genes involved in antioxidant defense and Se-dependent processes. The results presented here may be useful in further investigation of the health impacts of low-level Pb exposure on thyroid function and endocrine disruption effects.

Association of urinary heavy metal combined exposure with periodontitis among US adults from NHANES 2011-2014

Some heavy metals are associated with periodontitis; whereas most of these associations have focused on individual metal, there are no specific studies on the effects of combined heavy metal exposure on periodontitis. We conducted an analysis on the association between urinary heavy metal exposure and periodontitis in participants aged 30 years and older using multiple logistic regression and Bayesian kernel machine regression (BKMR). This analysis was performed on data from the National Health and Nutrition Examination Survey from 2011 to 2014. The study found that using logistic regression, the 4th quartile of urinary lead and molybdenum and the 3rd quartile of urinary strontium were positively associated with periodontitis compared to the reference quartile after adjusting for covariates. Odds ratio (OR) with 95% confidence interval (CI) was 1.738 (1.069-2.826), 1.515 (1.025-2.239), and 1.498 (1.010-2.222), respectively. The 3rd and 4th quartiles of urinary cobalt were negatively associated with periodontitis, and their ORs and 95% CIs were 0.639 (0.438-0.934) and 0.571 (0.377-0.964), respectively. The BKMR model showed that urinary barium, lead, and molybdenum were positively associated with periodontitis in a range of concentrations and urinary cobalt, manganese, tin, and strontium were negatively correlated with periodontitis. Furthermore, the overall association between urinary heavy metals and periodontitis was positive. Our study provides evidence for an association between exposure to multiple urinary heavy metals and periodontitis. However, further longitudinal studies are needed to explore the specific mechanisms involved.

Association Between Blood Lead Levels and Thyroid Function: An Updated Systematic Review and Meta-Analysis

Chronic Lead (Pb) exposure is associated with disrupting certain endocrine levels and is referred to as an endocrine disruptor. Thyroid hormones, involved in regulating numerous physiological functions, are reported with conflicting associations with chronic Pb exposure. This study broadly evaluated the association between long-term lead exposure and thyroid function parameters. In this systematic review, the observational studies documenting the changes in thyroid function parameters between the chronically Pb-exposed and controls were systematically identified from PubMed-Medline, Scopus, and Embase digital databases from the beginning to March 31, 2022. The protocol was previously registered with PROSPERO (ID: CRD42022315520) and executed following PRISMA 2020 guidelines. The random-effects model was used to analyze the mean differences in thyroid function parameters between groups. The classical I2 statistic was applied to assess heterogeneity, while the Newcastle Ottawa Scale was used to assess the risk of various biases. Where data allowed, sub-group, sensitivity, and meta-regression analyses were carried out. The current systematic review included fifteen observational studies. The Pb-exposed have a higher mean blood Pb level [i.e. 28.07 (95% CI 21.43-34.72) µg/dl], significantly higher free T3 [(i.e. 0.48 pg/dl (95% CI 0.05-0.95)] and trend of higher T3. T4, FT4, and TSH levels than controls with high heterogeneity (I2 > 85%). Considering the important role of thyroid hormone in multiple biological functions, the present findings emphasize the requisite for high-quality studies to investigate the association between levels of thyroid function parameters among individuals known for cumulative exposure to Pb.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-023-01113-8.

Design, synthesis, and density functional theory studies of a new selective chemosensor for Pb2

Herein, we have focused on a new colorimetric ligand synthesized from the reaction of 2-hydroxy-5-methylbenzene-1,3-dialdehyde with 2-amino-thiophenol, and investigated its activity as a sensor. In this regard, the sensory activity of the ligand towards different ions (Mn2+, Cu2+, Co2+, Fe2+, Fe3+, Zn2+, Ni2+, Cd2+, Ag+, Na+, Cs+, Mg2+, Al3+, Ba2+, K+, and Pb2+) was studied. The specificity of ion bindings is discussed through UV-Vis analysis. The ligand that was synthesized showed remarkable sensitivity, with a detection limit of 0.001 ppb. Additionally, the presence of Pb2+ ions can be visually detected through a color change from colorless to yellow. In the last part of this work, we seek to predict the available experimental measurements. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) are employed to examine the bonding between the ligand and the Pb2+ ion. The effect of water solvent was thoroughly examined for all the steps via the conductor-like Polarizable Continuum Model (CPCM). The theoretical findings revealed that electronic properties, including energy gap, adsorption energy, charge/energy transfer, and optical characteristics, undergo significant changes when Pb2+ cations are present. Hence, it can be inferred that the newly synthesized chemosensor (NC) is highly efficient in detecting Pb2+.

The "parasite detoxification hypothesis": lead exposure potentially changes the ecological interaction from parasitism to mutualism

In urban areas, organisms are exposed to high pollutant levels, especially element trace metals that may impact host-parasite interactions. Indeed, parasites have been reported to reduce the negative effects of pollutants on their hosts. The fitness of parasitized organisms in polluted environments may therefore be greater than that of unparasitized organisms. In our study, we used an experimental approach to test this hypothesis on feral pigeons (Columba livia), which are endemically parasitized by nematodes and exposed to high levels of lead in urban areas. We tested the combined effects of lead exposure and helminth parasitism on different pigeon fitness components: preening, immunocompetence, abundance of lice (Columbicola columbae) and haemosporidian parasites (Heamoproteus spp., Plasmodium spp.), reproduction investment, and oxidative stress. Our results show that among pigeons exposed to lead treatment, individuals harboring nematode parasites exhibit more preening activity and have fewer ectoparasites lice than nematode-free individuals. Benefits for nematode-parasitized individuals exposed to lead were not detected for other fitness parameters. Further studies are required to confirm the "parasite detoxification hypothesis" in pigeons and to identify the mechanisms by which this detoxification occurs.

Impact of DNA repair polymorphisms on DNA instability biomarkers induced by lead (Pb) in workers exposed to the metal

Although the mechanisms of Pb-induced genotoxicity are well established, a wide individual's variation response is seen in biomarkers related to Pb toxicity, despite similar levels of metal exposure. This may be related to intrinsic variations, such as genetic polymorphisms; moreover, very little is known about the impact of genetic variations related to DNA repair system on DNA instability induced by Pb. In this context, the present study aimed to assess the impact of SNPs in enzymes related to DNA repair system on biomarkers related to acute toxicity and DNA damage induced by Pb exposure, in individuals occupationally exposed to the metal. A cross-sectional study was run with 154 adults (males, >18 years) from an automotive batteries' factory, in Brazil. Blood lead levels (BLL) were determined by ICP-MS; biomarkers related to acute toxicity and DNA instability were monitored by the buccal micronucleus cytome (BMNCyt) assay and genotyping of polymorphisms of MLH1 (rs1799977), OGG1 (rs1052133), PARP1 (rs1136410), XPA (rs1800975), XPC (rs2228000) and XRCC1 (rs25487) were performed by TaqMan assays. BLL ranged from 2.0 to 51 μg dL^-1 (mean 20 ± 12 μg dL^-1) and significant associations between BLL and BMNCyt biomarkers related to cellular proliferation and cytokinetic, cell death and DNA damage were observed. Furthermore, SNPs from the OGG1, XPA and XPC genes were able to modulate interactions in nuclear bud formation (NBUDs) and micronucleus (MNi) events. Taken together, our data provide further evidence that polymorphisms related to DNA repair pathways may modulate Pb-induced DNA damage; studies that investigate the association between injuries to genetic material and susceptibilities in the workplace can provide additional information on the etiology of diseases and the determination of environmentally responsive genes.

Associations of an industry-relevant metal mixture with verbal learning and memory in Italian adolescents: The modifying role of iron status

BACKGROUND

Biomarker concentrations of metals are associated with neurodevelopment, and these associations may be modified by nutritional status (e.g., iron deficiency). No prior study on associations of metal mixtures with neurodevelopment has assessed effect modification by iron status.

OBJECTIVES

We aimed to quantify associations of an industry-relevant metal mixture with verbal learning and memory among adolescents, and to investigate the modifying role of iron status on those associations.

METHODS

We used cross-sectional data from 383 Italian adolescents (10-14 years) living in proximity to ferroalloy industry. Verbal learning and memory was assessed using the California Verbal Learning Test for Children (CVLT-C), and metals were quantified in hair (manganese, copper, chromium) or blood (lead) using inductively coupled plasma mass spectrometry. Serum ferritin, a proxy for iron status, was measured using immunoassays. Covariate-adjusted associations of the metal mixture with CVLT subtests were estimated using Bayesian Kernel Machine Regression, and modification of the mixture associations by ferritin was examined.

RESULTS

Compared to the 50th percentile of the metal mixture, the 90th percentile was associated with a 0.12 standard deviation [SD] (95% CI = -0.27, 0.50), 0.16 SD (95% CI = -0.11, 0.44), and 0.11 SD (95% CI = -0.20, 0.43) increase in the number of words recalled for trial 5, long delay free, and long delay cued recall, respectively. For an increase from its 25th to 75th percentiles, copper was beneficially associated the recall trials when other metals were fixed at their 50th percentiles (for example, trial 5 recall: β = 0.31, 95% CI = 0.14, 0.48). The association between copper and trial 5 recall was stronger at the 75th percentile of ferritin, compared to the 25th or 50th percentiles.

CONCLUSIONS

In this metal mixture, copper was beneficially associated with neurodevelopment, which was more apparent at higher ferritin concentrations. These findings suggest that metal associations with neurodevelopment may depend on iron status, which has important public health implications.

Potential diagnostic biomarkers for lead-induced hepatotoxicity and the role of synthetic chelators and bioactive compounds

Lead (Pb2+) poisoning is a public health concern of global dimensions. Although several public health guidelines and workplace safety policies are existing and enforced, lead toxicity cases are drastically increasing. Lead exposure leads to numerous harmful consequences and causes adverse effects on different body organs and systems, mainly via the generation of reactive oxygen species, leading to augmented oxidative stress, competing with metal ions, and binding with the sulfhydryl groups. In several instances, lead poisoning cases remain undiagnosed and untreated or receive only symptomatic treatment. Estimation of blood lead levels reflects only a recent exposure, however, which does not reveal the total body burden. This review summarizes the effects of lead with special reference to hepatotoxicity and some of the potential diagnostic biomarkers. Furthermore, it also focuses on synthetic chelators used in the treatment of lead poisoning and the advantage of using bioactive compounds with an emphasis on the ameliorative effect of garlic.

Sequential exposures of single walled carbon nanotubes and heavy metal ions to macrophages induce different cytotoxicity

The probability of occupational exposure rises with the increasing production and biomedical application of carbon nanotubes (CNTs). Thus, the risk of co-exposure of nanomaterials with environmental pollutants is also increasing. Although many studies have focused on the combined toxicity of nanomaterials and pollutants, more attention has been paid to the toxicity of nanomaterials after adsorbing pollutants or the toxicity of nanomaterials and pollutants exposed simultaneously. Few studies have been conducted on the toxicity and toxicity mechanisms of nanomaterials and environmental pollutants following sequential exposure. In this study, we employed THP-1 cells to investigate how pristine single walled CNTs (p-SWCNTs) and oxidized single walled CNTs (SWCNT-COOHs) pretreatments at a non-lethal dose of 10 μg/mL affect cell responses to metal ions (i. e., Pb²⁺, Cu²⁺, and Cr(VI)). We found that p-SWCNTs caused more significant damage to cell membrane integrity than SWCNT-COOHs, which led to higher metallothionein (MT) levels and increased transport of metal ions into cells. Pretreatment of p-SWCNTs in cells significantly increased the cytotoxicity of Pb²⁺, Cu²⁺, and Cr(VI) by 2-4-fold, whereas SWCNT-COOHs pretreated cells showed no noteworthy changes in response to heavy metals, which were further confirmed by the cellular reactive oxygen species (ROS) assays. These findings indicate that understanding the effects of the exposure sequence of engineered nanomaterials and environmental pollutants on their toxicity provides an excellent complement to combined toxicity evaluation.

Lead exposure exacerbates adverse effects of HFD on metabolic function via disruption of gut microbiome, leading to compromised barrier function and inflammation

PURPOSE

The toxicity of lead (Pb) has been intensively studied, while the adverse effects in the population on a high-fat diet (HFD) remain unclear. This study compared the different biologic effects of Pb in CHOW and HFD-fed mice and investigated the important role that gut microbiota may play.

METHODS

C57BL/6 mice were fed a CHOW diet and HFD with or without 1 g/L Pb exposure through drinking water for 8 weeks. Using oral glucose tolerance test, histopathological observation, real-time fluorescence quantitative PCR, enzyme-linked immunosorbent assay, and 16S high-throughput sequencing to compare the Pb toxicity, fecal microbiota transplantation was conducted to investigate the key role of gut microbiota.

RESULTS

The metabolic disorders induced by HFD were aggravated by chronic Pb intake, and HFD exacerbated the Pb accumulation in the colon by 96%, 32% in blood, 27% in the liver, and 142% in tibiae. Concomitantly, Pb induced more serious colonic injury, further disturbing the composition of gut microbiota in the HFD-fed mice. Moreover, altered fecal microbiota by HFD and Pb directly mediated metabolic disorders and colonic damage in recipient mice, which emphasized the importance of gut microbiota.

CONCLUSION

These findings indicated that the population with HFD has lower resistance and would face more security risks under Pb pollution, and pointed out the importance of assessing the health impacts of food contaminants in people with different dietary patterns.

GDNF-Loaded Polydopamine Nanoparticles-Based Anisotropic Scaffolds Promote Spinal Cord Repair by Modulating Inhibitory Microenvironment

Spinal cord injury (SCI) is a devastating injury that causes permanent loss of sensation and motor function. SCI repair is a significant challenge due to the limited regenerating ability of adult neurons and the complex inflammatory microenvironment. After SCI, the oxidative stress induced by excessive reactive oxygen species (ROS) often leads to prolonged neuroinflammation that results in sustained damage to the spinal cord tissue. Polydopamine (PDA) shows remarkable capability in scavenging ROS to treat numerous inflammatory diseases. In this study, glial cell-derived neurotrophic factor (GDNF)-loaded PDA nanoparticle-based anisotropic scaffolds for spinal cord repair are developed. It is found that mesoporous PDA nanoparticles (mPDA NPs) in the scaffolds efficiently scavenge ROS and promote microglia M2 polarization, thereby inhibiting inflammatory response at the injury site and providing a favorable microenvironment for nerve cell survival. Furthermore, the GDNF encapsulated in mPDA NPs promotes corticospinal tract motor axon regeneration and its locomotor functional recovery. Together, findings from this study reveal that the GDNF-loaded PDA/Gelatin scaffolds hold potential as an effective artificial transplantation material for SCI treatment.

Trends in elemental Pb concentrations within atmospheric PM2.5 and associated risk to human health in major cities of China

High concentrations of elemental lead (Pb) in the atmosphere pose a serious threat to human health. This study presents and summarizes data obtained from relevant literature on Pb concentrations within fine particulate matter (PM_2.5) recorded in major cities in China from 2008 to 2019. An environmental health risk assessment model was then used to evaluate the health hazards of inhaling Pb among adults and children in China. Owing to the promulgation and implementation of a series of air pollution control measures, the Pb concentrations within PM_2.5 measured in major cities in China showed a downward trend after peaking in 2013. The concentrations were higher in winter than in summer, and higher in northern cities than in southern cities. Although the Pb concentrations in most cities did not exceed the limit (500 ng/m³) set by China, they remained much higher than concentrations recorded in developed countries. The results of the environmental health risk analysis showed that the non-carcinogenic risk from atmospheric Pb exposure was higher in children than in adults (adult females > adult males), while the carcinogenic risk was higher in adults than in children. This study shows that even if the health risk of Pb in PM_2.5 does not exceed the acceptable limit, stricter Pb pollution control measures are required to safeguard population health due to the dangers of Pb.

Exposure of combination of environmental pollutant, lead (Pb) and β-amyloid peptides causes mitochondrial dysfunction and oxidative stress in human neuronal cells

Exposure to the environmental pollutant lead (Pb) has been linked to Alzheimer's disease (AD), in which mitochondrial dysfunction is a pathological consequence of neuronal degeneration. The toxicity of Pb in combination with β-amyloid peptides (1-40) and (25-35) causes selective death in neuronal cells. However, the precise mechanism through which Pb induces Alzheimer's disease, particularly mitochondrial damage, is unknown. Changes in mitochondrial mass, membrane potential, mitochondrial complex activities, mitochondrial DNA and oxidative stress were examined in neuronal cells of human origin exposed to Pb and β-amyloid peptides (1-40) and (25-35) individually and in different combinations. The results showed depolarization of mitochondrial membrane potential, decrease in mitochondrial mass, ATP levels and mtDNA copy number in Pb and β-amyloid peptides (1-40) and (25-35) exposed cells. Also, significant reductions in the expression of mitochondrial electron transport chain (ETC) complex proteins (ATP5A, COXIV, UQCRC2, SDHB, NDUFS3), as well as down regulation of ETC complex gene expressions such as COXIV, ATP5F1 and NDUFS3 and antioxidant gene expressions like MnSOD and Gpx4 were observed in exposed cells. Furthermore, Pb and β-amyloid peptides exposure resulted in elevated mitochondrial malondialdehyde levels and a decrease in mitochondrial GSH levels. Our findings suggest that Pb toxicity could be one of the causative factors for the mitochondrial dysfunction and oxidative stress in Alzheimer's disease progression.

Lactobacillus fermentum HNU312 alleviated oxidative damage and behavioural abnormalities during brain development in early life induced by chronic lead exposure

Lead exposure is a global public health safety issue that severely disrupts brain development and causes damage to the nervous system in early life. Probiotics and gut microbes have been highlighted for their critical roles in mitigating lead toxicity. However, the underlying mechanisms by which they work yet to be fully explored. Here, we designed a two-stage experiment using the probiotic Lactobacillus fermentum HNU312 (Lf312) to uncover how probiotics alleviate lead toxicity to the brain during early life. First, we explored the tolerance and adsorption of Lf312 to lead in vitro. Second, the adsorption capacity of the strain was determined and confirmed in vivo. The shotgun metagenome sequencing showed lead exposure-induced imbalance and dysfunction of the gut microbiome. In contrast, Lf312 intake significantly modulated the structure of the microbiome, increased the abundance of beneficial bacteria and short-chain fatty acids (SCFAs)-producing bacteria, and upregulated function-related metabolic pathways such as antioxidants. Notably, Lf312 enhanced the integrity of the blood-brain barrier by increasing the levels of SCFAs in the gut, alleviated inflammation in the brain, and ultimately improved anxiety-like and depression-like behaviours induced by lead exposure in mice. Subsequently, the effective mechanism was confirmed, highlighting that Lf312 worked through integrated strategies, including ionic adsorption and microbiota-gut-brain axis regulation. Collectively, this work elucidated the mechanism by which the gut microbiota mitigates the toxic effects of lead in the brain and provides preventive measures and intervention measures for brain damage due to mass lead poisoning in children.

Evaluation of some trace elements and antioxidants in sera of patients with rheumatoid arthritis: a case-control study

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease that destroys joints. The concentrations of elements (Zn, Cu, Mg, Mn, Fe, Ni, Cr, K, Na, Ca, Pb, and Cd), as well as antioxidant glutathione GSH and lipid peroxidation marker malondialdehyde MDA, will be determined in this study.

METHOD

The study involves 120 female RA patients and 60 healthy females in the control group, all of whom are between the ages of 20 and 60. Patients having diabetes, hypertension, hyperthyroidism, or psoriasis, in addition to RA, were excluded.

RESULTS

When RA patients were compared to healthy individuals, the levels of Cu, Ni, Na, Pb, and Cd were significantly higher (p < 0.01), whereas the levels of Zn, Mg, Mn, Cr, Ca, K, and Fe were significantly lower (p < 0.01). The Cu/Zn (2.21 and 1.16) and Na/k (38.67 and 34.87) ratios were also found to be significantly higher in RA patients compared to controls. Furthermore, the data indicated that GSH concentrations in RA patients were significantly lower (p < 0.01) than those in controls (655.90 and 1345.17 mol/l, respectively). MDA levels in RA patients were significantly higher (p < 0.01) than those in controls (2.739 and 1.673 mol/l, respectively).

CONCLUSIONS

The data indicate that Cu/Zn and Na/k ratios can be of great value in the diagnosis and evaluation of RA patients. On this basis, we conclude that these elements can be relied upon to provide indications of RA risk and the measurement of oxidative stress can serve as a biomarker to monitor disease activity and severity in RA patients. Key Points • Trace elements may be of value and may have an expected significance in the early diagnosis, prognosis, and treatment evaluation of rheumatoid arthritis. • The distortion in the levels of trace elements may reflect their possible role in the pathogenesis of rheumatoid arthritis. • Oxidative stress can act as a biomarker to monitor disease activity and severity in patients with rheumatoid arthritis. • The trace elements can contribute to the manifestation of inflammatory diseases due to their role in the synthesis of some antioxidants or due to their effect on the immune system.

Oxidative stress in the ovaries of mice chronically exposed to a low lead concentration: A generational approach

Lead (Pb) is a heavy metal that alters the oxidation-reduction balance, affecting reproductive health and transfer during pregnancy and lactation. However, the multigenerational impact of exposure to low concentrations of Pb on mammalian ovaries has not been assessed. This study evaluated general parameters, histology, redox state (RS), protein carbonylation (PC), lipid peroxidation (LP), and hormone concentrations in the ovaries of mice (CD1® ICR) of three successive generations with both unigenerational (E1) and multigenerational (E2) exposure to 0.2 ppm lead acetate through the drinking water and a control group. Body weight, food consumption, the number of born pups, and their weight after weaning were not significantly affected by Pb exposure in E1 and E2. However, the ovaries of three successive generations of the E1 group, in which only the F0 was exposed, showed alterations in the ovarian histoarchitecture, increase in follicular atresia, decrease in the number of available follicles, and a significant RS and PC elevation that were surprisingly similar to those observed in the E2 group. LP increased in the second generation of E1 and E2, while hormone concentration was not altered. This is the first demonstration that exposure to low concentration of Pb induces multigenerational histological alterations and oxidative stress in mouse ovaries, that the termination of this exposure does not ensure the safety of later generations and that the lack of modifications in general parameters may facilitate the silent development of pathologies that affect ovarian health.

Maternal exposure to metal mixtures during early pregnancy and fetal growth in the Jiangsu Birth Cohort, China

Previous epidemiological studies have reported that prenatal exposure to metals might have influence on fetal growth. Most studies assessed the effect of individual metals, while the investigation on the relationship between multiple metal exposure and fetal growth is sparse. The objective of the present study is to assess the joint impact of metal mixtures on fetal growth during pregnancy. A total of 1275 maternal-infant pairs from the Jiangsu Birth Cohort (JBC) Study were included to investigate the effect of maternal metal exposure on fetal biometry measures at 22-24, 30-32, and 34-36 weeks of gestation. Lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg), chromium (Cr), vanadium(V), thallium (Tl) and barium (Ba) were measured by inductively coupled plasma mass spectrometry (ICP-MS) in maternal urine samples collected in the first trimester. We used general linear models and restricted cubic splines to test dose-response relationships between single metals and fetal growth. The weighted quantile sum (WQS) models were then applied to evaluate the overall effect of all these metals. We observed inverse associations of exposure to Pb, V and Cr with estimated fetal weight (EFW) at 34-36 weeks of gestation. Notably, maternal exposure to metal mixtures was significantly associated with reduced EFW at 34-36 weeks of gestation after adjusting for some covariates and confounders (aβ -0.05 [95% CI: 0.09, -0.01], P = 0.023), and this association was mainly driven by Cr (30.41%), Pb (23.92%), and Tl (15.60%). These findings indicated that prenatal exposure to metal mixtures might impose adverse effects on fetal growth.

Biochemical profiling of lead-intoxicated impaired lipid metabolism and its amelioration using plant-based bioactive compound

The aim of this study was to investigate the lead (Pb)-induced lipid metabolism impairment and its amelioration using plant-based therapeutic interventions. Pb-induced hepatotoxicity can disturb the normal levels of natural antioxidant enzymes including glutathione (GSH) and superoxide dismutase (SOD) exerting a crucial impact on membrane unsaturated fatty acids (FA), hence leading to lipid peroxidation. Furthermore, Pb toxicity can also alter the regulation of various hormones involved in the synthesis of 3-hydroxy-methyl glutaryl CoA (HMG-CoA reductase), leading to an impairment in normal levels of serum cholesterol and other associated conjugated lipid molecules such HDL-cholesterol, LDL-cholesterol and VLDL-cholesterol. In this study, the lipoprotein fractions, cholesterol, triglyceride (TGs) and biomarkers of liver functions were estimated by employing respective assay kits. The levels of antioxidant enzymes, FFAs and HMG-CoA reductase were determined by employing sandwich ELISA method. The administration of PbAc in experimental rats induced a significant disturbance in lipid profile (P < 0.05) accompanying a significant reduction in natural antioxidant defence system (P < 0.05). The significant alteration in the levels of serum antioxidant enzymes can lead to membrane lipid peroxidation that is reflected by a significantly (P < 0.05) high level of serum MDA in PbAc-induced experimental rats. However, the administration of resveratrol proved therapeutically effective in the treatment of Pb toxicity. Overall, the results of this study accompanying histopathological examination had proved the ameliorating effect of resveratrol in Pb-induced lipid metabolism impairment by adopting vitamin C as a standard therapeutic intervention.

Examination of Trace Metals and Their Potential Transplacental Transfer in Pregnancy

With the ever-growing concern for human health and wellbeing, the prenatal period of development requires special attention since fetuses can be exposed to various metals through the mother. Therefore, this study explored the status of selected toxic (Pb, Cd, Ni, As, Pt, Ce, Rb, Sr, U) and essential trace metals (Mn, Co, Cu, Zn, Se) in the umbilical cord (UC) sera, maternal sera, and placental tissue samples of 92 healthy women with normal pregnancies. A further aim focuses on the potential transplacental transfer of these trace metals. Based on the obtained levels of investigated elements in clinical samples, it was observed that all of the trace metals cross the placental barrier and reach the fetus. Furthermore, statistical analysis revealed significant differences in levels of toxic Ni, As, Cd, U, Sr, Rb, and essential Mn, Cu, and Zn between all three types of analyzed clinical samples. Correlation analysis highlighted As to be an element with levels that differed significantly between all tested samples. Principal component analysis (PCA) was used to enhance these findings. PCA demonstrated that Cd, Mn, Zn, Rb, Ce, U, and Sr were the most influential trace metals in distinguishing placenta from maternal and UC serum samples. As, Co, and Cu were responsible for the clustering of maternal serum samples, and PCA demonstrated that the Pt level in UC sera was responsible for the clustering of these samples. Overall, the findings of this study could contribute to a better understanding of transplacental transfer of these trace metals, and shed a light on overall levels of metal exposure in the population of healthy pregnant women and their fetuses.

Glycine Betaine Relieves Lead-Induced Hepatic and Renal Toxicity in Albino Rats

Lead (Pb) is a widespread and nondegradable environmental pollutant and affects several organs through oxidative mechanisms. This study was conducted to investigate the antioxidant protective effect of glycine betaine (GB) against Pb-induced renal and hepatic injury. Male albino rats (n = 45) were divided into three groups: G1 untreated control, G2 Pb-acetate (50 mg/kg/day), and G3 Pb-acetate (50 mg/kg/day) plus GB (250 mg/kg/day) administered for 6 weeks. For G3, Pb-acetate was administered first and followed by GB at least 4 h after. Pb-acetate treatment (G2) resulted in a significant decrease in renal function, including elevated creatinine and urea levels by 17.4% and 23.7%, respectively, and nonsignificant changes in serum uric acid levels. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphates (ALP) activities were significantly increased with Pb treatment by 37.6%, 59.3%, and 55.1%, respectively. Lipid peroxidation level was significantly increased by 7.8 times after 6 weeks of Pb-acetate treatment. The level of reduced glutathione (GSH-R) significantly declined after Pb-acetate treatment. Pb-acetate treatment also reduced the activities of superoxide dismutase (SOD), glutathione-S-transferase (GST), and glutathione peroxidase (GSH-PX) by 74.1%, 85.0%, and 40.8%, respectively. Treatment of Pb-intoxicated rats with GB resulted in a significant reduction in creatinine, urea, ALT, AST, and lipid peroxidation, as well as a significant increase in the level of GSH-R and in the activities of ALP, SOD, GST, and GSH-PX. The molecular interaction between GB and GSH-PX indicated that the activation of GSH-PX in Pb-intoxicated rats was not the result of GB binding to the catalytic site of GSH-PX. The affinity of GB to bind to the catalytic site of GSH-PX is lower than that of H₂O₂. Thus, GB significantly mitigates Pb-induced renal and liver injury through the activation of antioxidant enzymes and the prevention of Pb-induced oxidative damage in the kidney and liver.

Joint associations among prenatal metal mixtures and nutritional factors on birth weight z-score: Evidence from an urban U.S. population

The benefits of nutritional factors on birth outcomes have been recognized, however, limited studies have examined the role of nutritional factors in mitigating the detrimental effects of metals exposure during gestation. We used data collected from 526 mother-infant dyads enrolled in the Programming of Intergenerational Stress Mechanisms longitudinal pregnancy cohort to examine the joint effects of prenatal exposure to metals and maternal nutrition on birth weight for gestational age (BWGA) z-scores. We measured concentrations of twelve metals and trace elements in urine samples collected during pregnancy. Maternal nutritional intake was measured using the Block98 Food Frequency Questionnaire and converted into energy-adjusted consumption of individual nutrients. Using multivariable linear regression and Bayesian Kernel Machine Regression, we found that three metals [cobalt (Co), nickel (Ni), and lead (Pb)] and five metals [barium (Ba), caesium (Cs), copper (Cu), Ni, and zinc (Zn)] were associated with BWGA z-score in male and female infants, respectively. When examining the sex-specific interactions between these metals and nutrient groups [macro nutrients, minerals, A vitamins, B vitamins, anti-oxidant, methyl-donor nutrients, and inflammatory (pro- and anti-)] using a Cross-validated Kernel Ensemble model, we identified significant interactions between the macro nutrients and Co (p = 0.05), minerals and Pb (p = 0.04), and A vitamins and Ni (p = 0.001) in males. No significant interactions were found in females. Furthermore, three minerals (phosphorus, iron, potassium) and vitamin A were found to be more crucial than other nutrients in modifying the association between each respective metal and BWGA z-score in males. A better understanding of the sex-specific interactions between nutrients and metals on birth weight can guide pregnant women to protect their neonates from the adverse health impacts of metal exposures by optimizing nutrient intakes accordingly.

Associations of a metal mixture with iron status in U.S. adolescents: Evidence from the National Health and Nutrition Examination Survey

Iron is needed for normal development in adolescence. Exposure to individual environmental metals (e.g., lead) has been associated with altered iron status in adolescence, but little is known about the cumulative associations of multiple metals with Fe status. We used data from the 2017-2018 National Health and Nutrition Examination Survey (NHANES) to examine associations between a metal mixture (lead, manganese, cadmium, selenium) and iron status in 588 U.S. adolescents (12-17 years). We estimated cumulative and interactive associations of the metal mixture with five iron status metrics using Bayesian Kernel Machine Regression (BKMR). Higher concentrations of manganese and cadmium were associated with lower log-transformed ferritin concentrations. Interactions were observed between manganese, cadmium, and lead for ferritin and the transferrin receptor, where iron status tended to be worse at higher concentrations of all metals. These results may reflect competition between environmental metals and iron for cellular uptake. Mixed metal exposures may alter normal iron function, which has implications for adolescent development.

Estimation of Serum Levels of Heavy Metals in Patients with Chronic Invasive Fungal Rhinosinusitis Before the COVID-19 Era: A Pilot Study

Objective:

Various metals play role in the survival and pathogenesis of the invasive fungal disease. The objectives of this study were to compare the levels of heavy metals in patients with chronic invasive fungal rhinosinusitis (CIFR) and healthy controls, and to analyze their role in disease outcome.

Methods:

Twenty-three patients (15 with invasive mucormycosis and 8 with invasive aspergillosis, Group 1), and 14 healthy controls (Group 2) were recruited. Blood samples were collected from each group into ion-free tubes and analyzed for serum levels of Nickel (Ni), Copper (Cu), Zinc (Zn), Gallium (Ga), Arsenic (As), Selenium (Se), Rubidium (Rb), Strontium (Sr), Cadmium (Cd), and Lead (Pb). The final outcome of the patients during their hospital stay was categorized clinico-radiologically as improved or worsened, or death.

Results:

The levels of all metals were higher in Group 1 except for As and Pb. However, the differences in Cu (p=0.0026), Ga (p=0.002), Cd (p=0.0027), and Pb (p=0.0075) levels were significant. Higher levels of Zn (p=0.009), Se (p=0.020), and Rb (p=0.016) were seen in the invasive aspergillosis subgroup. Although Zn (p=0.035), As (p=0.022), and Sr (p=0.002) levels were higher in patients with improved outcome, subgroup analysis showed no differences.

Conclusion:

The levels of some heavy metals in CIFR significantly differ from those of the general population and also vary with the type of the disease and its outcome. These levels may not have a direct effect on the outcome of the patient, but they do play a role in the pathogenesis of the invading fungus.

Characterization of plant growth-promoting bacteria isolated from the rhizosphere of Robinia pseudoacacia growing in metal-contaminated mine tailings in eastern Morocco

BACKGROUND

Mining activity in the Touissit district of Eastern Morocco has led to an unprecedented accumulation of heavy metals, mainly lead and zinc, in the tailing ponds of the open-air mines. This poses a real danger to both the environment and local population.

OBJECTIVES

The goal of this work was to characterize the Plant Growth Promoting Rhizobacteria (PGPR) isolated from the rhizosphere soil of R. pseudoacacia plants grown wild in the abandoned Pb- and Zn-contaminated tailing ponds in the mining district of Touissit, in Eastern Morocco.

MAIN RESULTS

One hundred bacterial strains were isolated from the rhizosphere of black locust (Robinia pseudoacacia L.) plants growing naturally in the Touissit mine tailings. Quantitative determination of indole-acetic and siderophores production, inorganic phosphate solubilization, hydrolysis of 1-aminocyclopropane-1-carboxylic acid (ACC deaminase activity), and ability to act as a biocontrol agent allowed selection of the 3 strains, 7MBT, 17MBT and 84MBT with improved PGP properties. The three strains grew well in the presence of high concentration of Pb-acetate and ZnCl_2; and the addition of Pb or Zn to the culture medium differently affected the PGP properties analyzed.

NOVELTY STATEMENT

Inoculation of black locust grown with the 3 selected strains, in the presence 1000 μg ml^-1 of Pb-acetate, produced varying effects on the plant dry weight. The strain 84MBT alone or in combination with strains 7MBT and 17MBT increased significantly the dry weight of the plants by 91, 62, and 85% respectively. The 16S rRNA gene sequence analysis of each strain showed that the strains 7MBT 17MBT and 84MBT had 99.34, 100, and had 99.72% similarity with Priestia endophytica (formerly B. endophyticus), B. pumilus NBRC 12092^T, and B. halotolerans NBRC 15718^T, respectively.

Low-lead doses induce oxidative damage in cardiac tissue: Subacute toxicity study in Wistar rats and Benchmark dose modelling

Exposure to toxic metals, including lead (Pb), were found as important risk factor for cardiovascular diseases. The aim of the study was to simulate low-level subacute Pb exposure scenario and to determine redox status, redox scores (OXY-score, damage score and protective score) and copper (Cu), zinc (Zn), iron (Fe) and manganese (Mn) levels in cardiac tissue of Wistar rats. Based on the obtained results we have established dose-toxic response relationship and derived Benchmark dose. The male Wistar rats were divided in seven groups (n = 6), six threated groups that received 0.1; 0.5; 1; 3; 7; 15 mg Pb/kg body weight/day for 28 days, by oral gavage and control group. The results of the presented study demonstrated that Pb affect cardiac tissue by inducing production of superoxide anion radical (O₂^.-) and consequently raising malondialdehyde (MDA) levels. The positive trend in OXY-score and damage score were determined. Effect size analysis showed that the main toxic effects were oxidative damage and elevation of MDA. The lowest BMD was calculated for MDA (2.2e-0.6 mg Pb/kg b.w./day). Obtained BMD may be useful in further assessing point of departure in the human health risks assessment of low-level Pb exposure scenario.

Exposure to heavy metals and red blood cell parameters in children: A systematic review of observational studies

BACKGROUND

Mechanistic studies show that heavy metals interfere with the hematopoietic system by inhibiting key enzymes, which could lead to anemia. However, the link between children's exposure and red blood cell (RBC) parameters has been inconsistent. We aimed to summarize evidence on human studies exploring the association between exposure to lead, mercury, cadmium, arsenic, and chromium VI and RBC parameters in children.

METHODS

Following the PRISMA guidelines, we searched PubMed, Scopus, and Web of Science databases for studies published between January 2010 and April 2022. Eligible papers included human observational studies that directly assessed exposure (internal dose) to the heavy metals under study and RBC parameters in participants aged ≤ 18 years. We excluded studies using hospital-based samples. Study quality was assessed using the National Institutes of Health's Quality Assessment Tools for Cohort and Cross-Sectional Studies. We synthesized the evidence using vote counting based on the direction of the relationship.

RESULTS

Out of 6,652 retrieved papers, we included a total of 38 (33 assessing lead, four mercury, two cadmium, and two arsenic; chromium VI was not assessed in any included paper). More than half of the studies were conducted in Asia. We found evidence of a positive relationship between lead concentration and hemoglobin (proportion of studies reporting negative relationships = 0.750; 95% Confidence Interval (CI) 0.583, 0.874) and mean corpuscular hemoglobin (0.875; 95% CI 0.546, 0.986), and a positive relationship with red cell distribution width (0.000; 95%CI 0.000, 0.379). When considering only good-quality studies (24% of the Pb studies), only the relationship with hemoglobin levels remained (0.875; 95% CI: 0.546, 0.986).

CONCLUSION

We found evidence of a negative relationship between lead concentration and hemoglobin and mean corpuscular hemoglobin and of a positive relationship with red cell distribution width in children. We also identified a need to conduct more studies in European countries. Future studies should use standardized practices and make efforts to increase study quality, namely by conducting comprehensive longitudinal studies. Our findings support the need to take further actions to limit heavy metal exposure during childhood.

Tannic Acid-Capped Gold Nanoparticles as a Novel Nanozyme for Colorimetric Determination of Pb2+ Ions

In this study, tannic acid-modified gold nanoparticles were found to have superior nanozyme activity and catalyze the oxidation reaction of 3,3′,5,5′-tetramethylbenzidine in the presence of hydrogen peroxide. Enhancing the catalytic activity of the nanozyme by Pb2+ ions caused by selectively binding metal ions by the tannic acid-capped surface of gold nanoparticles makes them an ideal colorimetric probe for Pb2+. The parameters of the reaction, including pH, incubation time, and concentration of components, were optimized to reach maximal sensitivity of Pb2+ detection. The absorption change is directly proportional to the Pb2+ concentration and allows the determination of Pb2+ ions within 10 min. The colorimetric sensor is characterized by a wide linear range from 25 to 500 ng×mL−1 with a low limit of detection of 11.3 ng×mL−1. The highly sensitive and selective Pb2+ detection in tap, drinking, and spring water revealed the feasibility and applicability of the developed colorimetric sensor.

Higher Blood Lead Level Is Associated With Increased Likelihood of Abdominal Aortic Calcification

Aims: This study aimed to evaluate the association between blood lead level (BLL) and abdominal aortic calcification (AAC) in US adults aged ≥40 years.

Methods: We obtained data from 2013 to 2014 National Health and Nutrition Examination Survey (NHANES). Participants missing the data of BLL and AAC scores were excluded. BLL was measured using inductively coupled plasma mass spectrometry directly. AAC scores were quantified by Kauppila score system, and severe AAC was defined as AAC score >6. Weighted multivariable regression analysis and subgroup analysis were conducted to explore the independent relationship between BLL with AAC score and severe AAC.

Results: A total of 1,530 participants were included with the mean BLL of 1.45 ± 1.31 ng/dl and mean AAC score of 1.40 ± 3.13. The prevalence of severe AAC was 7.98% overall, and participants in higher BLL quartile showed higher prevalence of severe AAC (Quartile 1: 3.55%, Quartile 2: 7.28%, Quartile 3: 9.88%, Quartile 4: 12.58%, P < 0.0001). BLL was positively associated with higher AAC score (β = 0.15, 95% CI: 0.02, 0.27, P = 0.021) and increased risk of severe AAC (OR = 1.11; 95% CI: 1.00–1.22; P = 0.047). Subgroup analysis and interaction test indicated that the association between BLL and AAC was similar in different population settings.

Conclusions: Higher BLL was associated with higher AAC score and increased risk of severe AAC. Lead burden should be considered for people with AAC in clinical settings.

Multibiomarker approach to assess the magnitude of occupational exposure and effects induced by a mixture of metals

Metals and metalloids including lead (Pb), arsenic (As) and manganese (Mn) can occur as mixtures in occupational contexts, such as mines. These chemicals are all known to be neurotoxic and provoke changes in heme metabolism also known to induce neurotoxicity. The objective of this work was to propose a multi-biomarker (BM) methodology to screen subjects exposed to the mixture of Pb, As and Mn and assess the severity of their exposure/effects, in an individual basis. The urinary levels of the metals, dela-aminolevulinic acid (ALA) and porphyrins were determined in Portuguese miners and in a control group. The combination of Pb and As urinary levels had the highest capability to identify subjects occupationally exposed to this mixture in mines, as evaluated through Receiver Operating Characteristic (ROC) (A = 98.2%; p < 0.05), allowing that 94.2% of 86 studied subjects were properly identified and the generation of an equation indicating the odd of a subject be considered as exposed to the metal mixture. The combination of urinary ALA and porphyrins revealed to be best one to be applied in the assessment of subjects with high, intermediate, and low magnitudes of exposure/effects, with 95.7% of 46 miners classified correctly according to their severity sub-group and allowing to generate equations, which can be applied in new subjects. The proposed methodology showed a satisfactory performance, evaluating in an integrated manner the magnitude of exposure/effects of the exposed workers, may contributing to improve the control of their health.

Blood lead levels in Peruvian adults are associated with proximity to mining and DNA methylation

BACKGROUND

Inorganic lead (Pb) is common in the environment, and is toxic to neurological, renal, and cardiovascular systems. Pb exposure influences the epigenome with documented effects on DNA methylation (DNAm). We assessed the impact of low levels of Pb exposure on DNAm among non-miner individuals from two locations in Peru: Lima, the capital, and Cerro de Pasco, a highland mining town, to study the effects of Pb exposure on physiological outcomes and DNAm.

METHODS

Pb levels were measured in whole blood (n = 305). Blood leukocyte DNAm was determined for 90 DNA samples using the Illumina MethylationEPIC chip. An epigenome-wide association study was performed to assess the relationship between Pb and DNAm.

RESULTS

Individuals from Cerro de Pasco had higher Pb than individuals from Lima (p-value = 2.00E-16). Males had higher Pb than females (p-value = 2.36E-04). Pb was positively associated with hemoglobin (p-value = 8.60E-04). In Cerro de Pasco, blood Pb decreased with the distance from the mine (p-value = 0.04), and association with soil Pb was approaching significance (p-value = 0.08). We identified differentially methylated positions (DMPs) associated with genes SOX18, ZMIZ1, and KDM1A linked to neurological function. We also found 45 differentially methylated regions (DMRs), seven of which were associated with genes involved in metal ion binding and nine to neurological function and development.

CONCLUSIONS

Our results demonstrate that even low levels of Pb can have a significant impact on the body including changes to DNAm. We report associations between Pb and hemoglobin, Pb and distance from mining, and between blood and soil Pb. We also report associations between loci- and region-specific DNAm and Pb.

Impact of modernization on urinary concentrations of arsenic, cadmium, lead, and selenium in rural residents of Northern Laos

OBJECTIVES

The impacts of modernization on toxic heavy metal exposure and essential trace element intake in indigenous populations of subsistence societies are unknown. We assessed urinary trace element concentrations in rural residents of Northern Laos and examined associations with levels of modernization.

METHODS

A cross-sectional study was conducted comprising 380 residents of three villages in Northern Laos with different levels of modernization. We surveyed general characteristics and measured the weight and height of 341 participants. Arsenic, cadmium, lead, and selenium concentrations were measured in spot urine samples by inductively coupled plasma mass spectrometry. We examined associations between urinary trace element concentrations and variables related to modernization (village, roofing material, possessions index [total number of possessions], and body mass index [BMI]) using multilevel analyses with household as a random effect, after adjusting for sex, age, and smoking status.

RESULTS

Urinary concentrations of arsenic and cadmium were high, while those of lead and selenium were low in comparison to previous reports of populations in non-contaminated regions or without excess/deficiency. We observed associations between urinary trace element concentrations and village-level modernization: lead and selenium concentrations were higher in more modernized villages and cadmium concentration was highest in the least modernized village. Urinary arsenic concentration was not predicted by the modernization level of a village, although we observed significant differences among villages. In addition, urinary selenium concentration was higher in participants inhabiting more modernized houses.

CONCLUSION

Modernization of villages may impact toxic heavy metal exposure and selenium intake in rural residents of Northern Laos.

Repeated exposure to fine particulate matter constituents lead to liver inflammation and proliferative response in mice

BACKGROUND

Fine particulate matter (particulate matter with aerodynamic diameter of ≦2.5 µm, PM2.5) exposure cause adverse health effects, including lung inflammation. Through intra-tracheal instillation of PM2.5 components, the study aimed to evaluate the inflammatory and proliferative effects on mice liver. PM2.5 samples were collected near an industrial complex at southern Taiwan. Mice were exposed to water extracts or insoluble particles by intra-tracheal instillation. Male C57BL/6 mice were divided into five groups: control, low dose insoluble particle exposure (LP), high dose insoluble particle exposure (HP), low dose water extract exposure (LW), and high dose water extract exposure (HW). Biochemical analysis, western blotting, histological examination, and immunohistochemistry were employed to evaluate the results.

RESULT

Enrichment factor (EF) of metallic elements showed that the EFs of trace elements (Ti, V, Ni, Zn, Pb, Cr, and Cu) in PM2.5 were above 10. Hematoxylin and Eosin (H&E) staining of the liver tissue showed inflammatory infiltration in particle exposure group; hepatocyte ballooning degeneration and karyomegaly were seen in the water extract exposure group. Upregulation of inflammatory signaling, p65 and p50, and caspase-3 (an important effector involved in apoptosis) positive hepatocytes was significantly increased in the HP group, followed by an elevation in protein levels of growth arrest and DNA damage-inducible protein 153 (GADD153). Increased protein expression of proliferating cell nuclear antigen (PCNA) was noted in the LW and HW groups. An increase in phosphorylation of regulators of cell proliferation, Akt and extracellular signal-regulated kinase (ERK) 1/2, were detected in the LW and HW groups.

CONCLUSION

The present study shows that the insoluble particle composition of PM2.5 induced inflammatory signaling and cytokines upregulation in the liver, accompanied with inflammatory cell and macrophage infiltration and an abnormal liver function. Exposure of water extract to PM2.5 induced signals of upregulated cellular proliferation, elevated markers of cell proliferation in liver, hepatocyte ballooning degeneration and karyomegaly.

Impact of environmental mercury exposure on the blood cells oxidative status of fishermen living around Mundaú lagoon in Maceió - Alagoas (AL), Brazil

Mercury in the aquatic environment can lead to exposure of the human population and is a known toxic metal due to its capacity for accumulation in organs. We aimed to evaluate the mercury level in the blood and urine of fishermen and correlate it with the level of oxidative stress in blood cells. We show in this case-control study that the fishermen of the exposed group (case) of Mundaú Lagoon (Maceió - Alagoas, Brazil) have higher concentrations of total mercury in the blood (0.73-48.38 μg L^-1) and urine (0.430-10.2 μg L^-1) than the total mercury concentrations in blood (0.29-17.30 μg L^-1) and urine (0.210-2.65 μg L^-1) of the control group. In the blood cells of fishermen, we observed that the lymphomononuclear cells produced high levels of reactive oxygen species (61.7%), and the erythrocytes presented increased lipid peroxidation (151%) and protein oxidation (41.0%) and a decrease in total thiol (36.5%), GSH and the REDOX state (16.5%). The activity of antioxidant system enzymes (SOD, GPx, and GST) was also reduced in the exposed group by 26.9%, 28.3%, and 19.0%, respectively. Furthermore, hemoglobin oxygen uptake was decreased in the exposed group (40.0%), and the membrane of cells presented increased osmotic fragility (154%) compared to those in the control group. These results suggest that mercury in the blood of fishermen can be responsible for causing impairments in the oxidative status of blood cells and is probably the cause of the reduction in oxygen uptake capacity and damage to the membranes of erythrocytes.

Case-control study in ALS using the National ALS Registry: lead and agricultural chemicals are potential risk factors

Objective: To identify occupational risk factors for ALS using well-characterized participants with ALS (P-ALS), sibling controls (S-controls), and matched population controls (P-controls) within the National ALS Registry. We also compared oxidative stress (OS) biomarkers between groups. Methods: P-ALS were recruited over 4 years. Demographic, socioeconomic, and medical data were ascertained from medical records and structured interviews. P-ALS were followed prospectively for 2 years or until death, whichever came sooner. S-controls and age-, sex-, race/ethnicity-, and residential location-matched P-controls were recruited over 3 years. Occupational exposure to lead and agricultural chemicals (ACs) were assigned by an occupational hygienist, blinded to case status. OS biomarkers in urine were measured. Results: P-ALS (mean age 62.8 years; 63% males) resided across the United States. Demographic and socioeconomic variables did not differ among P-ALS, S-controls, and P-controls. P-ALS were more likely to report occupations with exposure to lead (adjusted OR (aOR)=2.3, 95% CI 1.1, 4.6) and ACs (aOR = 2.4, 95% CI 1.2, 4.6) compared to pooled controls. Among those with occupations with exposure to both lead and ACs, aOR was 7.2 (95% CI 2.0, 26.1). Urinary 8-oxo-dG was significantly elevated among P-ALS (11.07 ± 5.42 ng/mL) compared to S-controls, P-controls, or pooled controls (pooled 7.43 ± 5.42 ng/mL; p < 0.0001) but was not associated with occupational exposure to either lead or ACs. Conclusions: Findings reveal increased risk of ALS diagnosis among those with occupational exposure to lead and ACs and increased OS biomarkers among cases compared to controls. OS may be an important pathogenic mechanism in ALS.

Reversible and irreversible transgenerational effects of metal exposure on nine generations of a tropical micro-crustacean

Micro-crustaceans are important grazers that control the algal blooms in eutrophic lakes. However, we know little about how these key species may be affected by long-term exposure to contaminants and when the transgenerational effects are reversible and irreversible. To address this, we investigated the effects of lead (Pb, 100 μg L^-1) exposure on morphology and reproduction of Moina dubia for nine consecutive generations (F1-F9) in three treatments: control, Pb, and pPb (M. dubia from Pb-exposed parents returned to the control condition). In F1-F2, Pb did not affect morphology, and reproduction of M. dubia. In all later generations, Pb-exposed M. dubia had a smaller body and shorter antennae than those in control. In F3-F6, pPb-exposed animals showed no differences in body size and antennae compared to the control, suggesting recoverable effects. In F7-F9, the body size and antennae of pPb-exposed animals did not differ compared to Pb-exposed ones, and both were smaller than the control animals, suggesting irreversible effects. Pb exposure reduced the brood size, number of broods and total neonates per female in F3-F9, yet the reproduction could recover in pPb treatment until F7. No recovery of the brood size and number of broods per female was observed in pPb-exposed animals in the F8-F9. Our study suggests that long-term exposure to metals, here Pb, may cause irreversible impairments in morphology and reproduction of tropical urban micro-crustaceans that may lower the top-down control on algal blooms and functioning of eutrophic urban lakes.