Oxidative stress caused by lead (Pb) induces iron deficiency in Drosophila melanogaster

Intestinal toxicity of Pb: Structural and functional damages, effects on distal organs and preventive strategies

Lead (Pb) is one of the most common heavy metal pollutants that possesses multi-organ toxicity. For decades, great efforts have been devoted to investigate the damage of Pb to kidney, liver, bone, blood cells and the central nervous system (CNS). For the common, dietary exposure is the main avenue of Pb, but our knowledge of Pb toxicity in gastrointestinal tract (GIT) remains quite insufficient. Importantly, emerging evidence has documented that gastrointestinal disorders affect other distal organs like brain and liver though gut-brain axis or gut-liver axis, respectively. This review focuses on the recent understanding of intestinal toxicity of Pb exposure, including structural and functional damages. We also review the influence and mechanism of intestinal toxicity on other distal organs, mainly concentrated on brain and liver. At last, we summarize the bioactive substances that reported to alleviate Pb toxicity, providing potential dietary intervention strategies to prevent or attenuate Pb toxicity.

Co-administration of resveratrol rescued lead-induced toxicity in Drosophila melanogaster

Lead toxicity poses a significant environmental concern linked to diverse health issues. This study explores the potential mitigating effects of resveratrol on lead-induced toxicity in Drosophila melanogaster. Adult fruit flies, aged three days, were orally exposed to lead (60 mg/L), Succimer (10 mg), and varying concentrations of resveratrol (50, 100, and 150 mg). The investigation encompassed the assessment of selected biological parameters, biochemical markers, oxidative stress indicators, and antioxidant enzymes. Resveratrol exhibited a dose-dependent enhancement of egg-laying, eclosion rate, filial generation output, locomotor activity, and life span in D. melanogaster, significantly to 150 mg of diet. Most of the investigated biochemical parameters were significantly rescued in lead-exposed fruit flies when co-treated with resveratrol (p < 0.05). However, oxidative stress remained unaffected by resveratrol. The findings suggest that resveratrol effectively protects against lead toxicity in Drosophila melanogaster and may hold therapeutic potential as an agent for managing lead poisoning in humans.

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.

Interaction of heavy metals in Drosophila melanogaster larvae: Fourier transform infrared spectroscopy and single-cell electrophoresis study

The present study evaluates the Murraya Koenigii (CuLE) and Tinospora Crispa (TiSE) antimutagenic effect and the impact of industrial soil and solid waste leachate on Drosophila larvae. Larvae were exposed to leachate prepared at different pH (7, 4.93, 2.88) and treated with TiSE and CuLE at different concentration (4 g/L and 6 g/L) mixed with standard Drosophila medium. Emphasis was given to the binding interaction of heavy metals with proteins in Drosophila. The change in structure and molecular composition in Drosophila by leachate containing heavy metals induced toxicity has been studied by using Fourier transform infrared (FTIR) spectroscopy. Results from the study demonstrated that CuLE/TiSE administration restored the level of oxidative stress as evidenced by an enhanced antioxidant system and a decrease in lipid peroxidation and protein oxidation. The amide I and amide II bands spectral shifting revealed the binding interaction. The shift in the peak of PO2- asymmetric stretching might be due to compositional changes in nucleic acids. Single-cell electrophoresis was performed to detect the DNA damage which also proved to be ameliorated by administration of CuLE/TiSE. The result concludes that CuLE/TiSE may have great potential in the protection of Drosophila larvae from leachate induced oxidative stress through antioxidant and antimutagenic mechanisms this might help to cope with environmental toxicants.Communicated by Ramaswamy H. Sarma.

Developmental neurotoxic effects of bisphenol A and its derivatives in Drosophila melanogaster

As a result of the ban on bisphenol A (BPA), a hormone disruptor with developmental neurotoxicity, several BPA derivatives (BPs) have been widely used in industrial production. However, there are no effective methods for assessing the neurodevelopmental toxic effects of BPs. To address this, a Drosophila exposure model was established, and W¹¹¹⁸ was reared in food containing these BPs. Results showed that each BPs displayed different semi-lethal doses ranging from 1.76 to 19.43 mM. Exposure to BPs delayed larval development and affected axonal growth, resulting in the abnormal crossing of the midline of axons in the β lobules of mushroom bodies, but the damage caused by BPE and BPF was relatively minor. BPC, BPAF, and BPAP have the most significant effects on locomotor behavior, whereas BPC exhibited the most affected social interactions. Furthermore, exposure to high-dose BPA, BPC, BPS, BPAF, and BPAP also significantly increased the expression of Drosophila estrogen-related receptors. These demonstrated that different kinds of BPs had different levels of neurodevelopmental toxicity, and the severity was BPZ > BPC and BPAF > BPB > BPS > BPAP ≈ BPAl ≈ BPF > BPE. Therefore, BPZ, BPC, BPS, BPAF, and BPAP should be evaluated as potential alternatives to BPA.

Newly discovered developmental and ovarian toxicity of 3-monochloro-1,2-propanediol in Drosophila melanogaster and cyanidin-3-O-glucoside's protective effect

3-Monochloro-1,2-propanediol (3-MCPD) is a pervasive environmental pollutant that is unintentionally produced during industrial production and food processing. Although some studies reported the carcinogenicity and male reproduction toxicity of 3-MCPD thus far, it remains unexplored whether 3-MCPD hazards to female fertility and long-term development. In this study, the model Drosophila melanogaster was employed to evaluate risk assessment of emerging environmental contaminants 3-MCPD at various levels. We found that flies on dietary exposure to 3-MCPD incurred lethality in a concentration- and time-dependent way and interfered with metamorphosis and ovarian development, resulting in developmental retardance, ovarian deformity and female fecundity disorders. Mechanistically, 3-MCPD caused redox imbalance observed as a drastically increased oxidative status in ovaries, confirmed by increased reactive oxygen species (ROS) and decreased antioxidant activities, which is probably responsible for female reproductive impairments and developmental retardance. Intriguingly, these defects can be substantially prevented by a natural antioxidant, cyanidin-3-O-glucoside (C3G), further confirming a critical role of ovarian oxidative damage in the developmental and reproductive toxicity of 3-MCPD. The present study expanded the findings that 3-MCPD acts as a developmental and female reproductive toxicant, and our work provides a theoretical basis for the exploitation of a natural antioxidant resource as a dietary antidote for the reproductive and developmental hazards of environmental toxicants that act via increasing ROS in the target organ.

The association of trace elements with arthritis in US adults: NHANES 2013-2016

BACKGROUND

Arthritis is a common chronic disease, and is a major cause of disability and chronic pain in adults. Considering inflammatory responses is closely related with trace elements (TEs), the role of TEs in arthritis has attracted much attention. This study aimed to assess the association between TEs and arthritis.

METHODS

Concentrations of TEs in whole blood [cadmium (Cd), lead (Pb), mercury (Hg), selenium (Se), and manganese (Mn)] and serum [copper (Cu) and zinc (Zn)] were measured in adults who participated in the US National Health and Nutrition Examination Survey. Logistic regression model and Bayesian kernel machine regression model were used to explore the association between TEs and arthritis.

RESULTS

The levels of five TEs (Pb, Hg, Cd, Se, and Cu) in the arthritis group changed significantly. Three TEs were found to be associated with an increased risk of arthritis: Pb [OR (95% CI): 2.96 (2.18, 4.03), p-value for trend (P-t) < 0.001], Cd [OR (95% CI): 2.28 (1.68, 3.11), P-t < 0.001], Cu [OR (95% CI): 2.05 (1.53, 2.76), P-t < 0.001]. The Relative Excess Risk of Interaction was 0.35 (95% CI: 0.06-0.65) and 0.38 (95% CI: 0.11-0.64), respectively, suggesting that Hg ions and Se ions have positive additional interactions with alcohol consumption, which reduced the risk of arthritis. Subgroup analysis showed that Pb ions and Cd ions were significantly correlated with osteoarthritis and rheumatoid arthritis.

CONCLUSION

Elevated concentrations of Pb, Cd, and Cu were associated with increased risk of arthritis. Drinking with high levels of Hg or Se may be a protective factor for arthritis. Future studies are warranted to validate these findings in prospective studies.

Effects of wildfire ashes on aquatic invertebrates: First molecular approach on Chironomus riparius larvae

The wildfire magnification in recent years has raised increasing concern about their adverse impacts on the environment. Wildfires are recognized as an important source of diffuse pollution for the nearby aquatic systems being potentially toxic to aquatic life. Albeit previous studies with wildfire runoff/ashes observed effects in aquatic organisms, to date, different severity origins of ashes and their impact at the sub-organismal level on aquatic biota have not been assessed. In this work, the molecular response of Chironomus riparius exposed to wildfire with low (LS) and high (HS) severity ashes from burnt Pine plantations was evaluated by employing an array of 42 genes related to crucial metabolic pathways by Real time-PCR. IV instar larvae were exposed for 72 h to aqueous extract of ashes (12.5 %, 25 %, 50 %, 75 % and 100 %) prepared from LS and HS ashes. Mn, Zn, and Pb were the metals found at highest concentration in both ash extracts, for HS notable Cd, Mn and Cr presence. From the 42 genes studied only 4 were not altered (22 genes modulated their response by LS and 38 genes in the case of HS) showing the opposite response at 100% with downregulated by LS and upregulated by HS. The 12.5 %, 25 %, 100 % HS and 25 % LS were the main modulators, confirmed by the integrative biomarkers response (IBR). Remarkable genotoxicity was generated by ashes even activating the apoptosis response, and endocrine disruption observed could modify the development. Moreover, detoxification and stress response were strongly activated, limiting the organism's future response to external aggressions. The employment of this novelty approach with molecular tools act as early alarm signal preventing greater damages. Overall, wildfire ashes showed to be a significant environmental disruptor to C. riparius even at lower concentration and the short exposure time employed, emphasizing the strong impact of wildfires on aquatic systems.

Cyto-Genotoxic and Behavioral Effects of Flubendiamide in Allium cepa Root Cells, Drosophila melanogaster and Molecular Docking Studies

Flubendiamide (FLB) is an insecticide that is commonly employed to control pests on a variety of vegetables and fruits, with low toxicity for non-target organisms. However, due to its widespread use, the environmental risks and food safety have become major concerns. In this study, the toxicity potential of FLB was studied in the model organisms, Allium cepa and Drosophila melanogaster. The cyto-genotoxic effects of FLB on the root growth, mitotic index (MI), chromosomal aberrations (CAs) and deoxyribonucleic acid (DNA) damage in A. cepa root meristematic cells were investigated using the root growth inhibition Allium test and Comet assays. FLB caused CAs in the form of disturbed ana-telophase, chromosome laggards, stickiness, anaphase-bridge and polyploidy depending on the concentration and the exposure time. The toxicity and genotoxicity of FLB at various doses (0.001, 0.01, 0.1 and 1 mM) on D. melanogaster were investigated from the point of view of larval weight and movement, pupal formation success, pupal position, emergence success and DNA damage, respectively. FLB exposure led to a significant reduction of the locomotor activity at the highest concentration. While DNA damage increased significantly in the FLB-treated onions depending on the concentration and time, DNA damage in the FLB-treated D. melanogaster significantly increased only at the highest dose compared to that which occurred in the control group. Moreover, to provide a mechanistic insight into the genotoxic and locomotion-disrupting effects of FLB, molecular docking simulations of this pesticide were performed against the DNA and diamondback moth (DBM) ryanodine receptor (RyR) Repeat34 domain. The docking studies revealed that FLB binds strongly to a DNA region that is rich in cytosine-guanine-adenine bases (C-G-A) in the minor groove, and it displayed a remarkable binding affinity against the DBM RyR Repeat34 domain.

Effects of Sub-chronic Lead Exposure on Essential Element Levels in Mice

Lead (Pb), a corrosion-resistant heavy non-ferrous metal, is one of the most common environmental neurotoxic metals. The effects of Pb on other essential metal elements are contradictory. Therefore, this in vivo study addressed the effects of sub-chronic Pb exposure on the distribution of other divalent metals, exploring the relationships between Pb levels in blood, teeth, bones, hair, and brain tissues. Thirty-two healthy male C57BL/6 mice received intragastric administration (i.g.) with 0, 12.5, 25, and 50 mg/kg Pb acetate, once a day for 8 weeks. Levels of Pb and other metal elements [including iron(Fe), zinc (Zn), magnesium (Mg), copper (Cu), and calcium(Ca)] in the whole blood, teeth, the right thighbone, hair, and brain tissues (including cortex, hippocampus, striatum, and hypothalamus) were detected with inductively coupled plasma-mass spectrometry (ICP-MS). Pb levels in all detected organs were increased after Pb-exposed for 8 weeks. The results of relationship analysis between Pb levels in the tissues and lifetime cumulative Pb exposure (LCPE) showed that Pb levels in the blood, bone, and hair could indirectly reflect the Pb accumulation in the murine brain. These measures might serve as valuable biomarkers for chronic Pb exposure reflective of the accumulation of Pb in the central nervous system (CNS). Sub-chronic Pb exposure for 8 weeks altered Ca, Cu, Fe, and Zn levels, but no effects were noted on Mg levels in any of the analyzed tissues. Pb decreased Ca in teeth, Cu in thighbone and teeth, Zn in whole blood and hair, and Fe in hair. In contrast, Pb increased Ca levels in corpus striatum and hypothalamus, Cu levels in striatum, Zn levels in teeth, and Fe levels in hippocampus, thighbone, and teeth. The Pb-induced changes in metal ratios in various tissues may serve as valuable biomarkers for chronic Pb exposure as they are closely related to the accumulations of Pb in the murine CNS. The results suggest that altered distribution of several essential metal elements may be involved in Pb-induced neurotoxicity. Additional studies should address the interaction between Pb and essential metal elements in the CNS and other organs.

Toxic metals that interact with thiol groups and alteration in insect behavior

Toxic metals, such as mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu), are widespread in the biosphere, and human activities have contributed to their continuous release into the ecosystems. Metal-induced toxicity has been extensively studied in mammals; however, the effects of these metals on insects' behavior have been explored to far lesser degree. As the main mechanism of toxicity, the cationic metals, explored in this review, have high affinity for thiol-containing molecules, disrupting the function of several proteins and low-molecular-weight thiol-containing molecules. Existing literature has corroborated that Hg, Pb, Cd, and Cu can disrupt locomotor and mating behaviors, but their effects on insects' memory and learning have yet to be fully characterized. Though field studies on metal-induced toxicity in insects are limited, results from Drosophila melanogaster as an experimental model suggest that insects living in contaminated environments can have behavioral foraging and reproductive deficits, which may cause population decline. In this review, we address the interaction between metals and endogenous thiol groups, with emphasis on alterations in insect behavior.

Ferroptosis as a mechanism of non-ferrous metal toxicity

Ferroptosis is a recently discovered form of regulated cell death, implicated in multiple pathologies. Given that the toxicity elicited by some metals is linked to alterations in iron metabolism and induction of oxidative stress and lipid peroxidation, ferroptosis might be involved in such toxicity. Although direct evidence is insufficient, certain pioneering studies have demonstrated a crosstalk between metal toxicity and ferroptosis. Specifically, the mechanisms underlying metal-induced ferroptosis include induction of ferritinophagy, increased DMT-1 and TfR cellular iron uptake, mitochondrial dysfunction and mitochondrial reactive oxygen species (mitoROS) generation, inhibition of Xc-system and glutathione peroxidase 4 (GPX4) activity, altogether resulting in oxidative stress and lipid peroxidation. In addition, there is direct evidence of the role of ferroptosis in the toxicity of arsenic, cadmium, zinc, manganese, copper, and aluminum exposure. In contrast, findings on the impact of cobalt and nickel on ferroptosis are scant and nearly lacking altogether for mercury and especially lead. Other gaps in the field include limited studies on the role of metal speciation in ferroptosis and the critical cellular targets. Although further detailed studies are required, it seems reasonable to propose even at this early stage that ferroptosis may play a significant role in metal toxicity, and its modulation may be considered as a potential therapeutic tool for the amelioration of metal toxicity.

Study of the neurochemical alterations produced by acute and subchronic Pb-exposure in Meriones shawi: Immunohistochemical study of Reissner's fiber secretion by the subcommissural organ after curcumin-III treatment

BACKGROUND

Lead neurotoxicity is associated with numerous alterations including behavioral and neurochemical disruptions. This study evaluates the possible neurochemical disruption in the subcommissural organ (SCO) after acute (three days) and subchronic (six weeks) Pb-exposure inMeriones shawi, and the possible effect of the third active compound, curcumin-III, in mitigating the neurological alterations caused by lead exposure.

METHODS

Using immunohistochemical stainings, we evaluated the Reissner's fiber (RF) secretion utilizing RF-antibody in the SCO. We compared both acute (25 mg/kg bw of Pb i.p. for 3 days) and subchronic (3 g/l of Pb in drinking water for six weeks) Pb-treatedMeriones shawi.

RESULTS

The two models of lead exposure showed a significant increase in RF level in the SCO. Conversely, co-treatment with Curcumin-III at a dose of 30 mg/kg bw significantly ameliorate SCO secretory activity, as revealed by decreased RF-immunoreactivity.

CONCLUSION

Together, our findings suggest the protective effects of Curcumin-III in regulating the secretory activity of the SCO after Pb-induced neuroanatomical disruptions of the SCO in Meriones.

Dietary cadmium induced declined locomotory and reproductive fitness with altered homeostasis of essential elements in Drosophila melanogaster

Cadmium (Cd) exerts detrimental effects on multiple biological processes of the living organisms along with epigenetic transgenerational effect. Drosophila melanogaster offers unique opportunity to evaluate Cd toxicity when studying important life traits in short duration of time by designing distinct behavioural assays. Present study utilized this model organism to assess Cd induced lethality, retarded growth, decreased life span and altered behaviour of the animals either at larval or adult stage. Our investigations revealed reduced locomotion and reproductive fitness of the animals upon Cd exposure. Transgenerational effect on locomotion was found to be behaviour specific as larval crawling was affected, but adult fly negative geotaxis was comparable to the control. Mechanistically, decreased antioxidant enzymes activity, superoxide dismutase (SOD) and catalase (CAT) together with altered homeostasis of essential elements (Fe, Zn and Mg) may be responsible for the observed effects. Altogether our work showed extensive range of Cd altered Drosophila behaviour which warrants need to control environmental Cd toxicity.

Persistent activation of Nrf2 in a p62-dependent non-canonical manner aggravates lead-induced kidney injury by promoting apoptosis and inhibiting autophagy

INTRODUCTION

Lead (Pb) is an environmental toxicant that poses severe health risks to humans and animals, especially renal disorders. Pb-induced nephrotoxicity has been attributed to oxidative stress, in which apoptosis and autophagy are core events.

OBJECTIVES

Nuclear factor erythroid 2-related factor 2 (Nrf2) acts as a major contributor to counteract oxidative damage, while hyperactivation or depletion of Nrf2 pathway can cause the redox imbalance to induce tissue injury. This study was performed to clarify the function and mechanism of Nrf2 in Pb-triggered kidney injury.

METHODS AND RESULTS

First, data showed that Pb exposure activates Nrf2 pathway in primary rat proximal tubular cells. Next, Pb-induced Nrf2 activation was effectively regulated by pharmacological modulation or siRNA-mediated knockdown in vitro and in vivo assays. Notably, Pb-triggered cytotoxicity, renal injury and concomitant apoptosis were improved by Nrf2 downregulation, confirming that Pb-induced persistent Nrf2 activation contributes to nephrotoxicity. Additionally, Pb-triggered autophagy blockage was relieved by Nrf2 downregulation. Mechanistically, we found that Pb-induced persistent Nrf2 activation is attributed to reduced Nrf2 ubiquitination and nuclear-cytoplasmic loss of Keap1 in a p62-dependent manner.

CONCLUSIONS

In conclusion, these findings highlight the dark side of persistent Nrf2 activation and potential crosstalk among Pb-induced persistent Nrf2 activation, apoptosis and autophagy blockage in Pb-triggered nephrotoxicity.

Effects of cadmium on oxidative stress and cell apoptosis in Drosophila melanogaster larvae

With the increase of human activities, cadmium (Cd) pollution has become a global environmental problem affecting biological metabolism in ecosystem. Cd has a very long half-life in humans and is excreted slowly in organs, which poses a serious threat to human health. In order to better understand the toxicity effects of cadmium, third instar larvae of Drosophila melanogaster (Canton-S strain) were exposed to different concentrations (1.125 mg/kg, 2.25 mg/kg, 4.5 mg/kg, and 9 mg/kg) of cadmium. Trypan blue staining showed that intestinal cell damage of Drosophila larvae increased and the comet assay indicated significantly more DNA damage in larvae exposed to high Cd concentrations. The nitroblue tetrazolium (NBT) experiments proved that content of reactive oxygen species (ROS) increased, which indicated Cd exposure could induce oxidative stress. In addition, the expression of mitochondrial adenine nucleotide transferase coding gene (sesB and Ant2) and apoptosis related genes (Debcl, hid, rpr, p53, Sce and Diap1) changed, which may lead to increased apoptosis. These findings confirmed the toxicity effects on oxidative stress and cell apoptosis in Drosophila larvae after early cadmium exposure, providing insights into understanding the effects of heavy metal stress in animal development.

Heterogeneity effects of nanoplastics and lead on zebrafish intestinal cells identified by single-cell sequencing

Plastic particles in water environment can adsorb heavy metals, leading to combined toxicity on aquatic organisms. However, current conclusions are mostly obtained based on cell population-average responses. Heterogeneity effects among cell populations in aquatic organisms remain unclear. This study firstly analyzed the basic toxic effects of 20 μg L^-1, 200 μg L^-1 100 nm polystyrene nanoplastics (PS-NPs), 50 μg L^-1 lead (Pb), and their combined exposures on zebrafish intestine. Results found that combined exposure of 200 μg L^-1 PS-NPs and 50 μg L^-1 Pb induced highest MDA, 8-OHdG, and TNF-α levels. Thus 200 μg L^-1 PS-NPs, 50 μg L^-1 Pb and their combined exposures were chosen to analyze the heterogeneity effects on zebrafish intestine cells by single-cell RNA sequencing. A total of 38,640 zebrafish intestinal cells were obtained and identified as seven cell populations, including enterocytes, macrophages, neutrophils, B cells, T cells, enteroendocrine cells, and goblet cells. 200 μg L^-1 PS-NPs exposure had the greatest influence on macrophages, while Pb exposure mostly influenced enterocytes. Results of MDA, 8-OHdG, and TNF-α analyses indicated that 20 μg L^-1 and 200 μg L^-1 PS-NPs increased the Pb toxicity. However, the scRNA-seq showed that the synergistic effects did not exist in most cell populations, except for goblet cells. Co-exposure of 200 μg L^-1 PS-NPs and Pb caused similar transcriptome profiles with 200 μg L^-1 PS-NPs exposure in macrophages, which changed immunological recognition and apoptosis processes. The Pb exposure influenced the macrophages by direct cytotoxicity. However, the Pb alone and combined exposures induced similar toxicities in the enterocytes, including the generation of oxidative stress and abnormality of lipid metabolism. This study shows the scRNA-seq is a powerful method to identify the target cell populations and corresponding toxic effects during combined exposure of pollutants.

Genes from Carboxypeptidase A, glutathione S-transferase, and cytochrome b families were found involved in lead transport in insect Musca domestica

Lead (Pb) is a typical toxic contamination source all over the world. In this research, larvae of the housefly (Musca domestica) were fed a Pb-contaminated diet at different Pb doses of 0, 20 and 5000 mg/kg. RNA sequencing was used to identify genes that were differentially expressed in relation to lead transport or detoxification. RNA interference (RNAi) was carried on 12 candidate genes. The results showed that three luminal pH regions of mid-gut were at pH values of 6.33, 3.10, and 7.80. With increasing Pb concentration, the pH of the middle mid-gut decreased by one unit. The expression levels of carboxypeptidase A (CPA1), glutathione S-transferase (GST), and cytochrome b (Cyt b) were linked to Pb treatments, particularly high Pb concentration of 5000 mg/kg. RNAi-mediated down expression of CPA1, GST2, and CYTb-c1 resulted in low Pb accumulation in the larvae of 5000 mg/kg Pb group. These proteins played key roles in Pb transport and detoxification in M. domestica larvae.

Life History Traits in Two Drosophila Species Differently Affected by Microbiota Diversity under Lead Exposure

Simple Summary

Microbiota have a significant functional role in the life of the host, including immunity, lifespan and reproduction. Drosophila species are attractive model organisms for investigating microbiota diversity from different aspects due to their simple gut microbiota, short generation time and high fertility. Considering such an important role of the microbiota in the life of Drosophila, we investigated the extent to which lead (Pb), as one of the most abundant heavy metals in the environment, affects the microbiota and the fitness of this insect host. The results indicate that different factors, such as population origin and sex, may affect individual traits differently and this could be species-specific. In addition, there are members of microbiota that help the host to overcome environmental stress and they could play a key role in reducing the fitness cost in such situations. Studying the influence of microbiota on the adaptive response to heavy metals and the potential implications on overall host fitness is of great pertinence.

Abstract

Life history traits determine the persistence and reproduction of each species. Factors that can affect life history traits are numerous and can be of different origin. We investigated the influence of population origin and heavy metal exposure on microbiota diversity and two life history traits, egg-to-adult viability and developmental time, in Drosophila melanogaster and Drosophila subobscura, grown in the laboratory on a lead (II) acetate-saturated substrate. We used 24 samples, 8 larval and 16 adult samples (two species × two substrates × two populations × two sexes). The composition of microbiota was determined by sequencing (NGS) of the V3–V4 variable regions of the 16S rRNA gene. The population origin showed a significant influence on life history traits, though each trait in the two species was affected differentially. Reduced viability in D. melanogaster could be a cost of fast development, decrease in Lactobacillus abundance and the presence of Wolbachia. The heavy metal exposure in D. subobscura caused shifts in developmental time but maintained the egg-to-adult viability at a similar level. Microbiota diversity indicated that the Komagataeibacter could be a valuable member of D. subobscura microbiota in overcoming the environmental stress. Research on the impact of microbiota on the adaptive response to heavy metals and consequently the potential tradeoffs among different life history traits is of great importance in evolutionary research.

Relationship between lead absorption and iron status and its association with oxidative stress markers in lead-exposed workers

BACKGROUND

The emission of lead (Pb) occurring during the extraction, processing and industrial applications of this element remains a significant environmental risk factor. The absorbability of lead in humans is strongly associated with the general health status of exposed individuals. Existing mineral deficiencies are considered being a predisposition to an increased Pb uptake. Both, iron deficiency and lead poisoning are the major causative factors responsible for the prevalence of anemia within the vulnerable population, especially in children. Although some of the intervention programs of counteracting lead poisoning by iron supplementation proved to be effective in the Pb-exposed population, the exact mechanisms of this interaction still require further studies. The objective of the presented study was to examine the association of iron level on oxidative stress measures and its effects on the severity of lead toxicity in the exposed population.

METHODS

The analyzed population consisted of 270 male workers from the lead-zinc smelter. The studied population was divided into two sub-groups based on the serum iron concentration: low iron level group (L-Fe; Fe < median value) and high iron level group (H-Fe; Fe > median value). Measured traits comprised of blood lead (PbB), serum Fe and zinc protoporphyrin (ZPP) levels as well as a blood count and oxidative stress markers.

RESULTS

No significant correlation between serum iron concentration and PbB in the tested cohort was found. On the contrary, the analysis of ZPP levels (long-term marker related to a hematologic toxic effect of Pb) within the subgroups differing in serum Fe level shown that ZPP was 12.3 % lower (p = 0.043) in subjects classified within the H-Fe group. A positive correlation of serum Fe and total antioxidant capacity (TAC) was found (R = 0.1999). The conducted 3-D PCA analysis showed that individuals classified within the H-Fe group were characterized by the co-occurrence of higher Fe levels, lower ZPP, and higher TAC value.

CONCLUSION

These results support the existing evidence providing that maintaining the optimal status of Fe may play a significant role in preventing the lead poisoning and alleviating harmful effects of Pb on the oxidative balance in humans.

Effects of environmental and occupational lead toxicity and its association with iron metabolism

BACKGROUND

Discrepancies are present in the findings from clinical trials evaluating a physiological role of iron status in the lead-exposed population.

OBJECTIVE

The purpose of this article was to summarize the current understanding of cellular mechanisms of lead toxicity and present a comprehensive review of existing clinical trials related to associations of lead poisoning and iron status. Although an association of iron metabolism pathways that are affected by lead intoxication has been studied, there are still aspects that remain to be elucidated. The existence of additional Pb uptake pathways besides DMT1 transporter-mediated is postulated to non-specifically regulate lead absorption.

METHODS

Authors performed a systematic search of PubMed, EMBASE® and Web of Science databases to identify studies that reported an association between health risks of non-organic lead that are associated with iron status markers as possible effect modifier.

RESULTS

There were 58 studies that met the pre-defined inclusion criteria for the systematic review. There is a strong body of evidence supporting the hypothesis that alleviated blood lead level can be correlated with a reduced body iron store and increasing the risk of anemia. This association is of a high significance in cases of a young adolescent, weaker in groups of older children and often without a statistical significance in adults.

DISCUSSION

Discrepancies in the observations may result from different specificities of lead absorption pathways in children and adults, as well as the power of the statistical tests in varying population sizes. It may be assumed that the extent of iron deficits coupled together with source, timing, and severity of lead exposure, significantly influence the correlation between these factors. Some of the intervention programs of counteracting lead poisoning by iron supplementation proved to be effective and may be a promising prevention strategy for the exposed population.

The Effects of Essential and Non-Essential Metal Toxicity in the Drosophila melanogaster Insect Model: A Review

The biological effects of environmental metal contamination are important issues in an industrialized, resource-dependent world. Different metals have different roles in biology and can be classified as essential if they are required by a living organism (e.g., as cofactors), or as non-essential metals if they are not. While essential metal ions have been well studied in many eukaryotic species, less is known about the effects of non-essential metals, even though essential and non-essential metals are often chemically similar and can bind to the same biological ligands. Insects are often exposed to a variety of contaminated environments and associated essential and non-essential metal toxicity, but many questions regarding their response to toxicity remain unanswered. Drosophila melanogaster is an excellent insect model species in which to study the effects of toxic metal due to the extensive experimental and genetic resources available for this species. Here, we review the current understanding of the impact of a suite of essential and non-essential metals (Cu, Fe, Zn, Hg, Pb, Cd, and Ni) on the D. melanogaster metal response system, highlighting the knowledge gaps between essential and non-essential metals in D. melanogaster. This review emphasizes the need to use multiple metals, multiple genetic backgrounds, and both sexes in future studies to help guide future research towards better understanding the effects of metal contamination in general.

Regulation and biological function of metal ions in Drosophila

A conceptual framework is offered for critically approaching the formidable ability of insects to segregate metal ions to their multiple destinations in proteins and subcellular compartments. New research in Drosophila melanogaster suggests that nuclear iron regulatory proteins and oxidative stress transcription factors mediate metal-responsive gene expression. Identification of a zinc-regulated chaperone in the endoplasmic reticulum potentially explains membrane protein trafficking defects observed in zinc transporter mutants. Compartmentalized zinc is utilized in fertilization, embryogenesis and for the activation of zinc-finger transcription factors - the latter function demonstrated during muscle development, while dietary zinc is sensed through gating of a chloride channel. Another emerging theme in cellular metal homeostasis is that transporters and related proteins meet at endoplasmic reticulum-mitochondria associated membranes with physiologically relevant consequences during aging.

Metallobiology and therapeutic chelation of biometals (copper, zinc and iron) in Alzheimer's disease: Limitations, and current and future perspectives

BACKGROUND

Alzheimer's disease (AD) is the most prevalent cause of cognitive impairment and dementia worldwide. The pathobiology of the disease has been studied in the form of several hypotheses, ranging from oxidative stress, amyloid-beta (Aβ) aggregation, accumulation of tau forming neurofibrillary tangles (NFT) through metal dysregulation and homeostasis, dysfunction of the cholinergic system, and to inflammatory and autophagic mechanism. However, none of these hypotheses has led to confirmed diagnostics or approved cure for the disease.

OBJECTIVE

This review is aimed as a basic and an encyclopedic short course into metals in AD and discusses the advances in chelation strategies and developments adopted in the treatment of the disease. Since there is accumulating evidence of the role of both biometal dyshomeostasis (iron (Fe), copper (Cu), and zinc (Zn)) and metal-amyloid interactions that lead to the pathogenesis of AD, this review focuses on unraveling therapeutic chelation strategies that have been considered in the treatment of the disease, aiming to sequester free and protein-bound metal ions and reducing cerebral metal burden. Promising compounds possessing chemically modified moieties evolving as multi-target ligands used as anti-AD drug candidates are also covered.

RESULTS AND CONCLUSION

Several multidirectional and multifaceted studies on metal chelation therapeutics show the need for improved synthesis, screening, and analysis of compounds to be able to effectively present chelating anti-AD drugs. Most drug candidates studied have limitations in their physicochemical properties; some enhance redistribution of metal ions, while others indirectly activate signaling pathways in AD. The metal chelation process in vivo still needs to be established and the design of potential anti-AD compounds that bi-functionally sequester metal ions as well as inhibit the Aβ aggregation by competing with the metal ions and reducing metal-induced oxidative damage and neurotoxicity may signal a bright end in chelation-based therapeutics of AD.

Methods to Assay the Behavior of Drosophila melanogaster for Toxicity Study

Drosophila melanogaster, the fruit fly, has been widely used in biological investigation as an invertebrate alternative to mammals for its various advantages compared to other model organisms, which include short life cycle, easy handling, high prolificacy, and great availability of substantial genetic information. The behavior of Drosophila melanogaster is closely related to its growth, which can reflect the physiological conditions of Drosophila. We have optimized simple and robust behavioral assays for determining the larvae survival, adult climbing ability (mobility assay), reproductive behavior, and lifespan of Drosophila. In this chapter, we present the step-by-step detailed method for studying Drosophila behavior.

Determination of Metal Content in Drosophila melanogaster During Metal Exposure

Trace metal elements, such as zinc, iron, copper, and manganese, play catalytic or structural roles in many enzymes and numerous proteins, and accordingly, contribute to a variety of fundamental biological processes. During the past decade, the fruit fly (Drosophila melanogaster) has become an important model organism for elucidating metal homeostasis in metazoan. We have been using Drosophila as a model to study metal metabolism for many years and have optimized simple and robust assays for determining the metal content in Drosophila, such as inductively coupled plasma mass spectrometry (ICP-MS), the activity assay of enzymes dependent on metals, and staining metal ions in tissues of Drosophila. In this chapter, we present the step-by-step detailed methods for detecting the metal content in Drosophila melanogaster during metal toxicity study.

Metal-metal interaction and metal toxicity: a comparison between mammalian and D. melanogaster

1. Non-essential heavy metals such as mercury (Hg), arsenic (As), cadmium (Cd), and aluminium (Al) are useless to organisms and have shown extensive toxic effects. Previous studies show that two main molecular mechanisms of metal toxicity are oxidative stress and metal-metal interaction which can disrupt metal homeostasis.2. In this paper, we mainly illustrate metal toxicity and metal-metal interaction through examples in mammalians and D. melanogaster (fruit fly).3. We describe the interference of metal homeostasis by metal-metal interactions in three aspects including replacement, cellular transporter competition, and disruption of the regulation mechanism, and elaborate the mechanisms of metal toxicity to better deal with the challenges of heavy metal pollution and related health problems.

Detrimental effects induced by diisononyl phthalate on development and behavior of Drosophila larva and potential mechanisms

Diisononyl phthalate (DINP) as one of the most commonly used phthalates, has been found in various environmental samples and is considered to have potential risks to ecosystem. Till now, DINP has no clear effect consensus on insects from development to behavior and even mechanisms. Here, Drosophila melanogaster was selected as model organisms and the toxic effects of DINP (0.1%, 0.2%, 0.5% and 1.0%) (v/v) on its metamorphosis, crawling behavior, intestinal cells and cellular redox balance were investigated. During metamorphosis process, lower hatching rate, longer development time, lighter body weight and malformation were observed at high concentration groups. The crawling ability of larvae was severely inhibited by DINP and the movement distance was drastically reduced. DINP could cause severe damage to the larval intestinal cells in the dose-dependent and time-dependent manners. DINP was found to induce redox imbalance with activities of two important antioxidant enzymes (catalase (CAT) and superoxide dismutase (SOD)) increasing, and reactive oxygen species (ROS) level fluctuation in larvae. Our findings provide theoretical basis and data support for scientific management of DINP to reduce ecological risk.

Iron Status in Relation to Low-Level Lead Exposure in a Large Population of Children Aged 0-5 Years

There are limited data regarding low lead exposure and iron status in Chinese children. This study aimed to examine the association between low-level lead exposure and iron status in a large population of children aged 0-5 years. We reviewed the records of children aged 0-5 years who had blood lead, iron, ferritin, and hemoglobin measurements during 2014-2017 at the Guangdong Women and Children Hospital. We identified 17,486 children with a blood lead level < 100 μg/L. Multiple linear and logistic regression analyses were performed to estimate the associations between blood lead levels and blood iron, serum ferritin, and hemoglobin. The mean concentrations of blood lead, iron, ferritin, and hemoglobin were 31.50 μg/L, 7.50 mmol/L, 46.98 ng/mL, and 120.41 g/L, respectively. Adjusting for age and sex, blood lead was negatively correlated with iron (r = - 0.073, p < 0.05), ferritin (r = - 0.043, p < 0.05), and hemoglobin (r = - 0.047, p < 0.05). Compared with the 1st quintile of lead exposure, the 5th quintile of lead exposure was associated with a 0.146 mmol/L decrease in blood iron, a 4.678 ng/mL decrease in serum ferritin, and a 1.245 g/L decrease in hemoglobin. Adjusted odds ratios (95% confidence interval) for the 5th quintile of blood lead were 1.39 (1.25-1.55) for iron deficiency and 1.45 (1.26-1.67) for anemia, relative to the 1st quintile. Our study findings confirmed the previously established association of blood lead levels with decreasing iron status and extended previous findings to even low-level lead exposure in Chinese children.

Cognitive Impairment Induced by Lead Exposure during Lifespan: Mechanisms of Lead Neurotoxicity

Lead (Pb) is considered a strong environmental toxin with human health repercussions. Due to its widespread use and the number of people potentially exposed to different sources of this heavy metal, Pb intoxication is recognized as a public health problem in many countries. Exposure to Pb can occur through ingestion, inhalation, dermal, and transplacental routes. The magnitude of its effects depends on several toxicity conditions: lead speciation, doses, time, and age of exposure, among others. It has been demonstrated that Pb exposure induces stronger effects during early life. The central nervous system is especially vulnerable to Pb toxicity; Pb exposure is linked to cognitive impairment, executive function alterations, abnormal social behavior, and fine motor control perturbations. This review aims to provide a general view of the cognitive consequences associated with Pb exposure during early life as well as during adulthood. Additionally, it describes the neurotoxic mechanisms associated with cognitive impairment induced by Pb, which include neurochemical, molecular, and morphological changes that jointly could have a synergic effect on the cognitive performance.

Hesperidin modulates the rhythmic proteomic profiling in Drosophila melanogaster under oxidative stress

The circadian clock regulates vital aspects of physiology including protein synthesis and oxidative stress response. In this investigation, we performed a proteome-wide scrutiny of rhythmic protein accrual in Drosophila melanogaster on exposure to rotenone, rotenone + hesperidin and hesperidin in D. melanogaster. Total protein from fly samples collected at 6 h intervals over the 24 h period was subjected to two-dimensional gel electrophoresis and mass spectrometry. Bioinformatics tool, Protein ANalysis THrough Evolutionary Relationships classification system was used to the determine the biological processes of the proteins of altered abundance. Conspicuous variations in the proteome (151 proteins) of the flies exposed to oxidative stress (by rotenone treatment) and after alleviating oxidative stress (by hesperidin treatment) were observed during the 24 h cycle. Significantly altered levels of abundance of a wide variety of proteins under oxidative stress (rotenone treatment) and under alleviation of oxidative stress (rotenone + hesperidin treatment) and hesperidin (alone) treatment were observed. These proteins are involved in metabolism, muscle activity, heat shock response, redox homeostasis, protein synthesis/folding/degradation, development, ion-channel/cellular transport, and gustatory and olfactory function of the flies. Our data indicates that numerous cellular processes are involved in the temporal regulation of proteins and widespread modulations happen under rotenone treatment and, action of hesperidin could also be seen on these categories of proteins.