Basic apoptotic mechanisms of lead toxicity in human leukemia (HL-60) cells

Acute lead (Pb2+) exposure increases calcium oxalate crystallization in the inner medullary collecting duct, and is ameliorated by Ca2+/Mg2+-ATPase inhibition, as well as Capa receptor and SPoCk C knockdown in a Drosophila melanogaster model of nephrolithiasis

Calcium oxalate (CaOx) kidney stones accumulate within the renal tubule due to high concentrations of insoluble deposits in the urine. Pb2+-induced Ca2+ mobilization along with Pb2+-induced nephrotoxic effects within the proximal tubule have been well established; however, Pb2+ mediated effects within the collecting duct remains insufficiently studied. Thus in vitro and ex vivo model systems were treated with increasing concentrations of lead (II) acetate (PbAc) ± sodium oxalate (Na2C2O4) for 1 h, both individually and in combination. Pb2+-mediated solution turbidity increased 2 to 5 times greater post-exposure to 75, 100 and 200 μM Pb2+ with the additional co-treatment of 10 mM oxalate in mouse inner medullary collecting duct (mIMCD-3) cells. Additionally, 100 μM and 200 μM Pb2+ alone induced significant levels of intracellular Ca2+ release. To validate Pb2+-mediated effects on the formation of CaOx crystals, alizarin red staining confirmed the presence of CaOx crystallization. Pb2+-induced intracellular Ca2+ was also observed ex vivo in fly Malpighian tubules with significant increases in CaOx crystal formation via Pb2+-induced intracellular Ca2+ release significantly increasing the average crystal number, size, and total area of crystal formation, which was ameliorated by tissue-specific SPoCk C transporter and Capa receptor knockdown. These studies demonstrate Pb2+-induced Ca2+ release likely increases the formation of CaOx crystals, which is modulated by a Gq-linked mechanism with concurrent Ca2+ extracellular mobilization.

Comparison of sensitivity between blood parameters and a genotoxic biomarker at low blood Pb levels: A population-based study

BACKGROUND

Previous studies reported that lead (Pb) exposure induced adverse health effects at high exposure concentrations, however, there have been limited data on sensitivity comparisons among different health outcomes at low blood Pb levels.

OBJECTIVES

To compare sensitivity between blood parameters and a genotoxic biomarker among workers exposed to low blood Pb levels (< 20 µg/dl), and to estimate a benchmark dose (BMD).

METHODS

Pb-exposed workers were recruited from a lead-acid storage battery plant. Their blood lead levels (BLLs) were measured. Blood parameters and micronuclei (MN) frequencies were determined. Multivariate linear or Poisson regression was used to analyze relationships between blood parameters or MN frequencies with BLLs. Two BMD software were used to calculate BMD and its 95 % lower confidence limit (BMDL) for BLLs.

RESULTS

The median BLL for 611 workers was 10.44 µg/dl with the 25th and 75th percentile being 7.37 and 14.62 µg/dl among all participants. There were significantly negative correlations between blood parameters and BLLs. However, MN frequencies correlated positively with BLLs (all P<0.05). Results from the two BMD software revealed that the dichotomous model was superior to the continuous model, and the BMDL for BLL derived from red blood cell (RBC) was 15.11 µg/dl, from hemoglobin (HGB) was 8.50 µg/dl, from mean corpuscular hemoglobin (MCH) was 7.87 µg/dl, from mean corpuscular hemoglobin concentration (MCHC) was 3.98 µg/dl, from mean corpuscular volume (MCV) was 11.44 µg/dl, and from hematocrit (HCT) was 6.65 µg/dl. The conservative BMDL obtained from the MN data was 7.52 µg/dl.

CONCLUSION

Our study shows that low dose Pb exposure caused decrease of blood parameters and increase of MN frequencies. The genotoxic biomarker was more sensitive than most blood parameters. BMDLs for BLL derived from MN frequencies and the red blood cell indicators should be considered as new occupational exposure limits. Our results suggest that MN assay can be considered as a part of occupational health examination items.

Pb(NO3 )2 induces cell apoptosis through triggering of reactive oxygen species accumulation and disruption of mitochondrial function via SIRT3/SOD2 pathways

Lead (Pb) is nonbiodegradable and toxic to the lungs. To investigate the potential mechanisms of Pb-induced reactive oxygen species (ROS) accumulation and cell death in the lungs, human non-small lung carcinoma H460 cells were stimulated with Pb(NO3 )2 in this study. The results showed that Pb(NO3 )2 stimulation increased cell death by inducing cell apoptosis which showed a reduced Bcl-2 expression and an enhanced caspase 3 activation. Pb(NO3 )2 also caused the production of H2 O2 in H460 cells that triggering the buildup of ROS and mitochondrial membrane potential loss. We found that Pb(NO3 )2 modulates oxidoreductive activity through reduced the glutathione-disulfide reductase and glutathione levels in Pb(NO3 )2 -exposed H460 cells. Furthermore, the superoxide dismutase (SOD) upstream molecule sirtuin 3 (SIRT3) was increased with Pb(NO3 )2 dose. Collectively, these results demonstrate that Pb(NO3 )2 promotes lung cell death through SIRT3/SOD-mediated ROS accumulation and mitochondrial dysfunction.

Anticancer effects of phytol against Sarcoma (S-180) and Human Leukemic (HL-60) cancer cells

Phytol (Pyt), a diterpenoid, possesses many important bioactivities. This study evaluates the anticancer effects of Pyt on sarcoma 180 (S-180) and human leukemia (HL-60) cell lines. For this purpose, cells were treated with Pyt (4.72, 7.08, or 14.16 μM) and a cell viability assay was performed. Additionally, the alkaline comet assay and micronucleus test with cytokinesis were also performed using doxorubicin (6 μM) and hydrogen peroxide (10 mM) as positive controls and stressors, respectively. Results revealed that Pyt significantly reduced the viability and rate of division in S-180 and HL-60 cells with IC50 values of 18.98 ± 3.79 and 1.17 ± 0.34 μM, respectively. Pyt at 14.16 μM exerted aneugenic and/or clastogenic effects in S-180 and HL-60 cells, where the number of micronuclei and other nuclear abnormalities (e.g., nucleoplasmic bridges and nuclear buds) were frequently observed. Moreover, Pyt at all concentrations induced apoptosis and showed necrosis at 14.16 μM, suggesting its anticancer effects on the tested cancer cell lines. Taken together, Pyt showed promising anticancer effects, possibly through inducing apoptosis and necrosis mechanisms, and it exerted aneugenic and/or clastogenic effects on the S-180 and HL-60 cell lines.

“Gamma Irradiation Synthesis of Carboxymethyl Chitosan-Nanoclay Hydrogel for the Removal of Cr(VI) and Pb(II) from Aqueous Media”

Hydrogel composites comprised of N,O carboxymethyl chitosan crosslinked with different weight ratios of acrylic acid and fabricated with nanoclay particle were prepared via gamma irradiation at 25 kGy irradiation dose. The prepared composites were coded as CsAA1Cl, CsAA2Cl and CsAA3Cl based on the weight ratio of acrylic acid to the chitosan derivative. The claimed hydrogels were characterized by FTIR, TGA and XRD. The TGA data implied that the incorporation of clay nanoparticles enhanced the thermal stability of the composites; the decomposition temperature increased up to 500 °C for CsAA3Cl. Three AFM outcomes were used to compare the surface features of the samples; topography, height and surface roughness. The topography data reveals that the nanoclay particles incorporated in CsAA3Cl are intercalated and exfoliated. Then, the optimized sorbent (CsAA3Cl) was investigated as green sorbents for chromium (VI) and lead (II). The data revealed that CsAA3Cl displayed maximum removal performance towards both lead and chromium with removal efficiencies 125 mg/g and 205 mg/g respectively at the optimum application conditions within 90 min only. Also, it was found that the optimum pH value was 9 for chromium and 8 for lead. The data proved that the adsorption of both cations followed pseudo-first order kinetic model. The prepared composites showed acceptable metal uptake capacity at three successive cycles.

Graphical Abstract

Impact of petroleum industry on goats in Saudi Arabia: heavy metal accumulation, oxidative stress, and tissue injury

Heavy metals (HMs) constitute a group of persistent toxic pollutants, and the petroleum industry is one of the sources of these metals. This study aimed to evaluate the levels of lead (Pb), cadmium (Cd), nickel (Ni), and vanadium (V) in Plantago ovata and milk and tissues of domestic goats in the eastern region of Saudi Arabia. Plant samples and blood, milk, muscle, liver, and kidney samples were collected from domestic goats and the levels of Pb, Cd, V, and Ni were determined. Liver and kidney tissue injury, oxidative stress, and expression of pro-inflammatory and apoptosis markers were evaluated. Pb, Cd, V, and Ni were increased in Plantago ovata as well as in milk, blood, muscle, liver, and kidney of goats collected from the polluted site. Aminotransferases, creatinine, and urea were increased in serum, and histopathological changes were observed in the liver and kidney of goats at the oil extraction site. Malondialdehyde and the expression levels of pro-inflammatory cytokines, Bax, and caspase-3 were increased, whereas cellular antioxidants and Bcl-2 were decreased in liver and kidney of goats at the polluted site. In conclusion, petroleum industry caused liver and kidney injury, oxidative stress, and upregulated pro-inflammatory and apoptosis markers in goats. These findings highlight the negative impact of petroleum industry on the environment and call attention to the assessment of its effect on the health of nearby communities.

Evaluation of Shallow Groundwater Quality at Regional Scales Using Adaptive Water Quality Indices

Groundwater, which is the main source of water for human consumption in many rural areas, has its quality determined by the complex interaction of environmental factors and anthropogenic activities. The present study evaluated the quality of shallow groundwater (1 to 25 m depth) in the rural area of the Târgovişte Plain, a densely populated area (200 inhabitants/km²) using 80 water samples collected from public wells. In order to explain the spatial distribution of the concentrations of the 19 physicochemical parameters considered (including heavy metals), the evaluation of groundwater quality for human consumption and potential impact on human health was conducted using the Water Quality Index (WQI), Integrated Weight Water Quality Index (IwWQI), Total Hazard Index (THI), and cumulative carcinogenic risk (CCR). For the WQI/IwWQI the comparative analysis of the two indices showed that for the WQI, it is important to select an optimal set of parameters, because use of a large number of physicochemical parameters can eclipse the values that exceed WHO guideline limits. In contrast, the use of entropy in the calculation of the IwWQI did not lead to eclipsing of exceedance, no matter the number of parameters used. Areas with poor and very poor groundwater quality according to the WQI/IwWQI overlapped, with a moderate risk to human health (THI > 1) for noncarcinogenic contaminants and also a risk of developing cancer according to the CCR average value (1.15 × 10^-2). The health of 43% of the rural population in the Târgovişte Plain can be affected if they drink contaminated groundwater, and it is estimated that about 600 people can develop cancer during their lifetime. If the risk of developing cancer is reduced only in the rural population that does not have access to a water source from a centralized and verified network, the results suggest that 385 people (1.15%) can develop cancer as a result of consuming groundwater contaminated with heavy metals based on the average value of CCR. This value is lower than the general mortality rate in areas with high CCR and below the average number of cancer patients in Romania (2.65%). The quality of groundwater and the risk of developing diseases and cancer due to water consumption is directly proportional to the intensity of agricultural land use and inversely proportional to the depth of the groundwater layer, the distance from the main hydrographic network and the reservoirs, and the distance from the main city, Târgovişte. The complex and integrated analysis of groundwater quality using quality indices and indicators of health risk for the population, validated by hot-spot analysis and compared to the mortality rate, is an approach with practical applicability. This integrated approach allows public authorities, policymakers, and health services to implement an efficient monitoring program and optimize anthropogenic activities in order to prevent groundwater contamination and finally improve the quality of life for the residents in the area of this study.

Heavy Metal Accumulation, Tissue Injury, Oxidative Stress, and Inflammation in Dromedary Camels Living near Petroleum Industry Sites in Saudi Arabia

The petroleum industry can impact the environment and human health. Heavy metals (HMs), including lead (Pb), cadmium (Cd), nickel (Ni), and vanadium (V), are toxic pollutants found in petroleum that can cause several severe diseases. This study investigated the impact of the oil industry on the Arabian camel (Camelus dromedarius) in the eastern region of Saudi Arabia, pointing to HMs accumulation, tissue injury, redox imbalance, inflammation, and apoptosis. Soil and camel samples (milk, blood, muscle, liver, and kidney) were collected from a site near an oil industry field and another two sites to analyze HMs. Pb, Cd, Ni, and V were increased in the soil and in the camel’s milk, blood, muscle, liver, and kidney at the polluted site. Serum aminotransferases, urea, and creatinine were elevated, and histopathological alterations were observed in the liver and kidney of camels at the oil industry site. Hepatic and renal lipid peroxidation, pro-inflammatory cytokines, Bax, and caspase-3 were increased, whereas cellular antioxidants and Bcl-2 declined in camels at the oil extraction site. In conclusion, the oil industry caused soil and tissue accumulation of HMs, liver and kidney injury, oxidative stress, and apoptosis in camels living close to the oil extraction site. These findings pinpoint the negative impact of the oil industry on the environment, animal, and human health.

Protective Effect of Chlorogenic Acid and Its Analogues on Lead-Induced Developmental Neurotoxicity Through Modulating Oxidative Stress and Autophagy

Lead (Pb) is among the deleterious heavy metal and has caused global health concerns due to its tendency to cause a detrimental effect on the development of the central nervous system (CNS). Despite being a serious health concern, treatment of Pb poisoning is not yet available, reflecting the pressing need for compounds that can relieve Pb-induced toxicity, especially neurotoxicity. In the quest of exploring protective strategies against Pb-induced developmental neurotoxicity, compounds from natural resources have gained increased attention. Chlorogenic acid (CGA) and its analogues neochlorogenic acid (NCGA) and cryptochlorogenic acid (CCGA) are the important phenolic compounds widely distributed in plants. Herein, utilizing zebrafish as a model organism, we modeled Pb-induced developmental neurotoxicity and investigated the protective effect of CGA, NCGA, and CCGA co-treatment. In zebrafish, Pb exposure (1,000 μg/L) for 5 days causes developmental malformation, loss of dopaminergic (DA) neurons, and brain vasculature, as well as disrupted neuron differentiation in the CNS. Additionally, Pb-treated zebrafish exhibited abnormal locomotion. Notably, co-treatment with CGA (100 µM), NCGA (100 µM), and CCGA (50 µM) alleviated these developmental malformation and neurotoxicity induced by Pb. Further underlying mechanism investigation revealed that these dietary phenolic acid compounds may ameliorate Pb-induced oxidative stress and autophagy in zebrafish, therefore protecting against Pb-induced developmental neurotoxicity. In general, our study indicates that CGA, NCGA, and CCGA could be promising agents for treating neurotoxicity induced by Pb, and CCGA shows the strongest detoxifying activity.

A novel calibration for L-shell x-ray fluorescence measurements of bone lead concentration using the strontium Kβ/Kαratio

Objective. Lead (Pb) is a well-known toxic element.In vivobone Pb concentration measurement is a long-term exposure metric complementary to blood Pb concentration measurement which is a metric of recent exposure.In vivohuman tibia bone Pb measurements using Pb K-shell or L-shell x-ray fluorescence (KXRF or LXRF) emissions were developed in the 1980s. KXRF bone Pb measurements using Cd-109 gamma rays and coherent-to-fluorescence ratio to account for differences between phantom andin vivomeasurements, was employed in human studies. Bone Pb LXRF method employed x-ray tubes. However, calibration procedures using ultrasound measurements of the soft tissue thickness (STT) proved inaccurate.Approach. In this study, bone and soft tissue (ST) phantoms simulatedin vivobone Pb measurements. Seven plaster-of-Paris cylindrical bone phantoms containing 1.01 mg g-1of strontium (Sr) were doped with Pb in 0, 8, 16, 29, 44, 59, and 74 μg g-1concentrations. Polyoxymethylene (POM), resin, and wax were each used to fabricate four ST phantoms in the approximate 1-4 mm thickness range. Pb LXRF measurements were performed using a previously developed optimal grazing incidence position method.Main results. Linear attenuation coefficients measurements of ST materials indicated that POM and resin mimicked well attenuation of Pb x-rays in skin and adipose tissue, respectively. POM and resin data indicated a bone Pb detection limit of 20 μg g-1for a 2 mm STT. Derived relationships between the Pb concentration, Pb LXRF and Sr Kβ/Kαratio data did not require STT knowledge. Applied to POM and resin data, the new calibration method yielded unbiased results.Significance.In vivobone Pb measurements in children were suggested following considerations of radiation dose, STT, detectability and distribution of Pb and Sr in bone. This research meets with the concerns regarding the negative effects of low levels of Pb exposure on neurodevelopment of children.

Photochemistry of biochar during ageing process: Reactive oxygen species generation and benzoic acid degradation

In this study, the photogeneration of OH and ¹O₂ and the degradation mechanism of organic pollutants in biochar suspension under the simulated solar light irradiations were investigated. Biochar derived from rice husk with 550 °C of charring temperature (R550) was selected to degrade benzoic acid. It was found that 10 g/L of R550 could degrade 78.7% of benzoic acid within 360 min at pH 3, and the degradation efficiency was promoted to 95.2% as ultraviolet (UV) presented. By checking the production of p-hydroxybenzoic acid, UV accelerated the production of OH, which was confirmed by the enhanced degradation efficiency of 59.2% caused by the evaluated OH as UV appeared. The furfuryl alcohol loss in the R550 suspension under light irradiations testified to the production of ¹O₂, which contributed to 9.3% of benzoic acid degradation. Oxidization treatment using gradient concentrations of H₂O₂ was employed to enhance the ageing process of biochar. As the ageing processed, the biochar possessed a declined performance towards OH production from O₂ activation and the radical degradation of organic pollutants. As a contrast, the evaluated content of ¹O₂ and enhanced non-radical degradation of organic pollutants was reached as UV presented. The further study indicated that phenolic hydroxyl groups on biochar facilitated the production of OH via the electron transfer, and quinone like structures (C=O) on biochar boosted the generation of ¹O₂ via the energy transfer. Moreover, upon eliminating the BA degradation, persistent free radicals were formed on biochar, which was enhanced owing to the presence of UV.

Lead (Pb) Accumulation in Human THP-1 Monocytes/Macrophages In Vitro and the Influence on Cell Apoptosis

In this study, we investigated the ability of THP-1 monocytes and macrophages to accumulate lead (Pb) in vitro, relative to Pb concentration and length of exposure. Moreover, we also evaluated the effect of Pb accumulation on cell viability and apoptosis. THP-1 monocytes and macrophages were cultured in the presence of Pb at 1.25 μg/dL, 2.5 μg/dL, 5 μg/dL, and 10 μg/dL. Pb accumulation was examined by inductively coupled plasma and confocal microscopy. The influence of Pb on cell viability, apoptosis, and necrosis was assessed using flow cytometry. The results showed that Pb was toxic to THP-1 monocytes/macrophages even at very low environmental concentrations. Despite the use of low concentrations, both monocytes and macrophages showed dose-dependent and time-dependent decreases in viability, with a simultaneous increase in the percentage of early and late apoptotic cells. Macrophages reacted more strongly to Pb than monocytes. When exposed to the same Pb concentrations, they showed lower viability and a higher percentage of necrotic cells. The incubation time positively correlated with Pb accumulation in a dose-dependent manner. The obtained results indicate that environmental exposure to low Pb concentrations may significantly impair the function of macrophages, with the increased number of apoptotic cells potentially contributing to the development of many pathologies in the brain and whole body.

Ecogenetics of lead toxicity and its influence on risk assessment

Lead (Pb) toxicity is a public health problem affecting millions worldwide. Advances in 'omic' technology have paved the way to toxico-genomics which is currently revolutionizing the understanding of interindividual variations in susceptibility to Pb toxicity and its functional consequences to exposure. Our objective was to identify, comprehensively analyze, and curate all the potential genetic and epigenetic biomarkers studied to date in relation to Pb toxicity and its association with diseases. We screened a volume of research articles that focused on Pb toxicity and its association with genetic and epigenetic signatures in the perspective of occupational and environmental Pb exposure. Due to wide variations in population size, ethnicity, age-groups, and source of exposure in different studies, researchers continue to be skeptical on the topic of the influence of genetic variations in Pb toxicity. However, surface knowledge of the underlying genetic factors will aid in elucidating the mechanism of action of Pb. Moreover, in recent years, the application of epigenetics in Pb toxicity has become a promising area in toxicology to understand the influence of epigenetic mechanisms such as DNA methylation, chromatin remodeling, and small RNAs for the regulation of genes in response to Pb exposure during early life. Growing evidences of ecogenetic understanding (both genetic and epigenetic processes) in a dose-dependent manner may help uncover the mechanism of action of Pb and in the identification of susceptible groups. Such studies will further help in refining uncertainty factors and in addressing risk assessment of Pb poisoning.

Amelioration of Prenatal Lead-Induced Learning and Memory Impairments by Methanolic Extract of Zataria Multiflora in Male Rats

Introduction

The current study aimed at evaluating the effects of Zataria Multiflora (ZM) on learning and memory of adult male offspring rats with prenatal lead-exposure.

Methods

Pregnant rats in the case group received tap water containing 0.2% lead acetate throughout the gestation period. Control rats had free access to lead-free tap water. Two male offspring (two-month-old, weighing 180-200 g) from each mother were randomly selected and treated with either Z. Multiflora (50, 200, 400, and 800 mg/kg/Intraperitoneally (I.P)/20 day) or saline. Spatial memory of the control, saline, and ZM-treated rats was evaluated by a training trial and probe test using Morris water maze (6-8 rat/group).

Results

The obtained results showed memory deficits including increased escape latency, and a greater traveled distance, as well as decrements in the frequency of crossings into target quadrants in prenatally lead-exposed male offspring compared with the controls. ZM treatment (200 mg/kg/i.p) ameliorated the memory deficits in male offspring by increasing the time spent and traveled distance in the trigger zone (P<0.01 vs. saline).There was no significant difference in swimming speed between the groups.

Conclusion

The results showed memory deficits in prenatally lead-exposed male offspring. ZM treatment (especially 200 mg/kg) had beneficial effects on cognitive behavior and was indicated as the improvement of lead-induced memory deficits in prenatally lead-exposed male rats. The exact mechanism(s) is not determined yet, but it could be mediated through the anticholinesterase and antioxidant effects and also alterations in Central Nervous System (CNS) and neurotransmission in the central nervous system.

Amelioration of Prenatal Lead-Induced Learning and Memory Impairments by Methanolic Extract of Zataria Multiflora in Male Rats

Introduction:

The current study aimed at evaluating the effects of Zataria Multiflora (ZM) on learning and memory of adult male offspring rats with prenatal lead-exposure.

Methods:

Pregnant rats in the case group received tap water containing 0.2% lead acetate throughout the gestation period. Control rats had free access to lead-free tap water. Two male offspring (two-month-old, weighing 180–200 g) from each mother were randomly selected and treated with either Z. Multiflora (50, 200, 400, and 800 mg/kg/Intraperitoneally (I.P)/20 day) or saline. Spatial memory of the control, saline, and ZM-treated rats was evaluated by a training trial and probe test using Morris water maze (6–8 rat/group).

Results:

The obtained results showed memory deficits including increased escape latency, and a greater traveled distance, as well as decrements in the frequency of crossings into target quadrants in prenatally lead-exposed male offspring compared with the controls. ZM treatment (200 mg/kg/i.p) ameliorated the memory deficits in male offspring by increasing the time spent and traveled distance in the trigger zone (P<0.01 vs. saline).There was no significant difference in swimming speed between the groups.

Conclusion:

The results showed memory deficits in prenatally lead-exposed male offspring. ZM treatment (especially 200 mg/kg) had beneficial effects on cognitive behavior and was indicated as the improvement of lead-induced memory deficits in prenatally lead-exposed male rats. The exact mechanism(s) is not determined yet, but it could be mediated through the anticholinesterase and antioxidant effects and also alterations in Central Nervous System (CNS) and neurotransmission in the central nervous system.

Heme bioavailability and signaling in response to stress in yeast cells

Protoheme (hereafter referred to as heme) is an essential cellular cofactor and signaling molecule that is also potentially cytotoxic. To mitigate heme toxicity, heme synthesis and degradation are tightly coupled to heme utilization in order to limit the intracellular concentration of "free" heme. Such a model, however, would suggest that a readily accessible steady-state, bioavailable labile heme (LH) pool is not required for supporting heme-dependent processes. Using the yeast Saccharomyces cerevisiae as a model and fluorescent heme sensors, site-specific heme chelators, and molecular genetic approaches, we found here that 1) yeast cells preferentially use LH in heme-depleted conditions; 2) sequestration of cytosolic LH suppresses heme signaling; and 3) lead (Pb²⁺) stress contributes to a decrease in total heme, but an increase in LH, which correlates with increased heme signaling. We also observed that the proteasome is involved in the regulation of the LH pool and that loss of proteasomal activity sensitizes cells to Pb²⁺ effects on heme homeostasis. Overall, these findings suggest an important role for LH in supporting heme-dependent functions in yeast physiology.

Effect of Lead on Human Middle Ear Epithelial Cells

Lead is a ubiquitous metal in the environment, but no studies have examined lead toxicity on the middle ear. Here, we investigated lead toxicity and its mechanism in human middle ear epithelial cells (HMEECs). Moreover, we investigated the protective effects of amniotic membrane extract (AME) and chorionic membrane extract (CME) against lead toxicity in HMEECs. Cell viability was analyzed using the cell counting kit, and reactive oxygen species (ROS) activity was measured using a cellular ROS detection kit. After lead(II) acetate trihydrate treatment, mRNA levels of various genes were assessed by semiquantitative real-time polymerase chain reaction. Following treatment with AME or CME after lead exposure, the changes in cell viability, ROS activity, and gene expression were analyzed. Exposure to >100 μg/mL of lead(II) acetate trihydrate caused a significant decrease in cell viability and increased ROS production in HMEECs. Lead exposure significantly increased the mRNA expression of genes encoding inflammatory cytokines and mucins. Administration of AME or CME restored cell viability, reduced ROS activity, and ameliorated mRNA levels. Our findings suggest that environmental lead exposure is related to the development of otitis media, and AME and CME may have antioxidative and anti-inflammatory effects against lead toxicity.

Fluorescent Lead(IV) Sulfide Nanoparticles Synthesized by Idiomarina sp. Strain PR58-8 for Bioimaging Applications

The fabrication of nanoparticles by microorganisms presents a "green" method for generating biocompatible nanomaterials. We discovered the intracellular biosynthesis of fluorescent lead(IV) sulfide nanoparticles by the moderate halophile, Idiomarina sp. strain PR58-8. The bacterium tolerated up to 8 mM Pb(NO3)2 during growth. Non-protein thiols dose-dependently increased in response to metal exposure, which suggests they are involved in the growth of PbS2 crystals and lead detoxification. Using X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and energy dispersive analysis of X-rays, the nanoparticles were characterized as spherical β-PbS2 nanoparticles (PbS2NPs) with a tetragonal crystal lattice, a crystallite domain size of 2.38 nm, and an interplanar distance of 0.318 nm. A narrow symmetric emission spectrum with a Gaussian distribution and an emission maximum at 386 nm was obtained when the particles were excited at 570 nm. The PbS2NPs exhibited a large Stokes' shift (8,362 cm-1) and a relatively high quantum yield (67%). These properties, along with fluorescence that was maintained in various microenvironments and their biocompatibility, make these nanoparticles excellent candidates for bioimaging. The particles were internalized by HeLa cells and evenly distributed within the cytoplasm, exhibiting their potential for in situ bioimaging applications. The "as-synthesized" lead(IV) sulfide nanoparticles may provide expanded opportunities for targeted bioimaging via modifying the surface of the particles.IMPORTANCE This article reports the intracellular synthesis of fluorescent lead(IV) sulfide nanoparticles (PbS2NPs) by a microorganism. All previous reports on the microbial synthesis of lead-based nanoparticles are on lead(II) sulfide that exhibits near-infrared fluorescence, requiring expensive instrumentation for bioimaging. Bioimaging using PbS2NPs can be achieved using routine epifluorescence microscopes, as it fluoresces in the visible range. The research on PbS2 nanoparticles to date is on their chemical synthesis employing toxic precursors, extreme pH, pressure, and temperature, resulting in cytotoxic products. In this context, the synthesis of PbS2 nanoparticles by Idiomarina sp. strain PR58-8, described in this work, occurs at ambient temperature and pressure and results in the generation of biocompatible nanoparticles with no hazardous by-products. The excellent fluorescence properties that these particles exhibit, as well as their abilities to easily penetrate the cells and evenly distribute within the cytoplasm, make them exceptional candidates for bioimaging applications. This study demonstrated the synthesis and fluorescence bioimaging application of microbially synthesized PbS2 nanoparticles.

Indigofera oblongifolia mitigates lead-acetate-induced kidney damage and apoptosis in a rat model

This study was conducted to appraise the protective effect of Indigofera oblongifolia leaf extract on lead acetate (PbAc)-induced nephrotoxicity in rats. PbAc was intraperitoneally injected at a dose of 20 mg/kg body weight for 5 days, either alone or together with the methanol extract of I. oblongifolia (100 mg/kg). Kidney lead (Pb) concentration; oxidative stress markers including lipid peroxidation, nitrite/nitrate, and glutathione (GSH); and antioxidant enzyme activities, namely superoxide dismutase, catalase, GSH peroxidase, and GSH reductase were all determined. The PbAc injection elicited a marked elevation in Pb concentration, lipid peroxidation, and nitrite/nitrate, with a concomitant depletion in GSH content compared with the control and a remarkable decrease in antioxidant enzymes. Oxidant/antioxidant imbalance, Pb accumulation, and histological changes in the kidneys were successfully prevented by the pre-administration of I. oblongifolia extract. In addition, the elevated expression of proapoptotic protein, Bax, in the kidneys of the PbAc-injected rats was reduced as a result of I. oblongifolia pre-administration, while the hitherto reduced expression of the anti-apoptotic protein Bcl-2 was elevated. Based on the current findings, it can be concluded that I. oblongifolia successfully minimizes the deleterious effects in kidney function and histological coherence associated with nephrotoxicity by strengthening the antioxidant defense system, suppressing oxidative stress, and mitigating apoptosis.

DNA Damage, Cell Cycle Arrest, and Apoptosis Induction Caused by Lead in Human Leukemia Cells

In recent years, the industrial use of lead has been significantly reduced from paints and ceramic products, caulking, and pipe solder. Despite this progress, lead exposure continues to be a significant public health concern. The main goal of this research was to determine the in vitro mechanisms of lead nitrate [Pb(NO₃)₂] to induce DNA damage, apoptosis, and cell cycle arrest in human leukemia (HL-60) cells. To reach our goal, HL-60 cells were treated with different concentrations of Pb(NO₃)₂ for 24 h. Live cells and necrotic death cells were measured by the propidium idiode (PI) assay using the cellometer vision. Cell apoptosis was measured by the flow cytometry and DNA laddering. Cell cycle analysis was evaluated by the flow cytometry. The result of the PI demonstrated a significant (p < 0.05) increase of necrotic cell death in Pb(NO₃)₂-treated cells, indicative of membrane rupture by Pb(NO₃)₂ compared to the control. Data generated from the comet assay indicated a concentration-dependent increase in DNA damage, showing a significant increase (p < 0.05) in comet tail-length and percentages of DNA cleavage. Data generated from the flow cytometry assessment indicated that Pb(NO₃)₂ exposure significantly (p < 0.05) increased the proportion of caspase-3 positive cells (apoptotic cells) compared to the control. The flow cytometry assessment also indicated Pb(NO₃)₂ exposure caused cell cycle arrest at the G₀/G₁ checkpoint. The result of DNA laddering assay showed presence of DNA smear in the agarose gel with little presence of DNA fragments in the treated cells compared to the control. In summary, Pb(NO₃)₂ inhibits HL-60 cells proliferation by not only inducing DNA damage and cell cycle arrest at the G₀/G₁ checkpoint but also triggering the apoptosis through caspase-3 activation and nucleosomal DNA fragmentation accompanied by secondary necrosis. We believe that our study provides a new insight into the mechanisms of Pb(NO₃)₂ exposure and its associated adverse health effects.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Neurotoxic effect of lead on rats: Relationship to Apoptosis

BACKGROUND

Lead toxicity has been subjected to intensive research work, but some aspects of its mechanism needs to be elucidated.

OBJECTIVES

In the current study we aim to investigate the impact of lead toxicity on some different intermediates of apoptotic signaling pathway in experimental rats.

DESIGN AND METHODS

We measured caspase-8 and caspase-9 [by chemilumenescence], Bax and Bcl-2 [by ELISA] in Experimental rats, injected intraperitoneally with lead acetate for 7days at the dosage of 25, 50 and l00 mg/kg body weight and compared to control rats injected with deionized distilled water instead. instead.

RESULTS

Lead acetate significantly increased the levels of caspase 8, caspase 9 and Bax in liver, kidney and brain of experimental animals especially those with high doses. Meanwhile, caspase 8 and Bax significantly increased in brain tissue at low dose of lead, while Bcl-2 significantly increased only with advanced toxicity. Furthermore, Bax/bcl2 ratio was significantly high in kidney (p<0.05), liver (p<0.01) and brain (p<0.01) at higher doses of lead toxicity. However, brain tissues showed significant Bax/Bcl2 ratio (p<0.05) at low lead dose. A significant positive correlation was noticed between the blood level of lead and enzymatic level of caspase 8, caspase 9 and Bax in different tissues.

CONCLUSION

: we concluded that lead might have toxic effect through intrinsic and extrinsic induction of apoptotic pathway with prominent effect on brain tissue even at low dose.

Cellular apoptosis of hemocytes from Dendrolimus tabulaeformis Tsai et Liu larvae induced with the secondary metabolites of Beauveria brongniartii (Sacc.) Petch

To investigate the effect of the secondary metabolites of entomopathogenic fungus on the hemocyte immunity of host insect, the secondary metabolite complex (SMC) of Beauveriabrongniartii was used in three concentrations (5.5, 55, and 550 µg/mL), and the 4^th instar larvae of the pine caterpillar Dendrolimustabulaeformis were employed as host insects. The larvae were inoculated with the SMC solutions by injection in bioassays. Apoptosis of the larval hemocytes was observed using fluorescence microscopy (FM), transmission electron microscopy (TEM), and flow cytometry (FCM). The FM results showed that in the treated groups, larval hemocytes exhibited symptoms of early apoptosis at 6 h post-treatment by radiating a non-uniform kelly fluorescence and exhibited symptoms of late apoptosis at 12 h post-treatment by radiating a non-uniform orange fluorescence. Under TEM, the following ultra-structural changes associated with apoptosis of the larval hemocytes were observed in the treated groups: the nuclei were hypertrophied, slight folds were on the nuclear envelope, the chromatin became concentrated, the mitochondrial cristae disappeared or were disorderly, most cells developed blebs, and fibrillar aggregation appeared and accumulated in the cytoplasm. Apoptosis of the larval hemocytes was detected by FCM at 6 h post-treatment; the percentage of early apoptotic cells in the SMC 5.5, 55, and 550 µg/mL treatment groups were 11.93%, 13.10%, and 18.42%, respectively. Late apoptosis first occurred at 12 h post-treatment; the highest rate of apoptosis was 36.54 ± 4.37% at 24 h post-treatment in the SMC 55 µg/mL treatment group. In general, the cellular apoptosis rate was positively correlated with the SMC concentration and the time post-treatment. These results indicate that secondary metabolites of B. brongniartii are able to attack the hemocytes of D. tabulaeformis larvae and induce cellular apoptosis, thereby providing new evidence that secondary metabolites of mycopathogens can act on host immune systems.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Effects of delta-aminolevulinic acid dehydratase polymorphisms on susceptibility to lead in Han subjects from southwestern China

This study is to determine the distribution of the delta-aminolevulinic acid dehydratase (ALAD) polymorphism among Han subjects of the Chinese population and to study whether the polymorphism in the ALAD gene modifies the toxicity of lead in lead-exposed workers. For this purpose we conducted a cross-sectional study on 156 Chinese workers who were exposed to lead in lead-acid battery and electric-flex manufacturing plants. The authors found that the allele frequencies of ALAD1 and ALAD2 were 0.9679 and 0.0321, respectively. Workers with the ALAD 1-1 genotype were associated with higher blood lead levels than those with the ALAD 1-2 genotype. Blood and urine lead levels were much higher in storage battery workers than in cable workers. The self-conscious symptom survey showed that the incidences of debilitation, amnesia and dreaminess were much higher in those had more than five years of tenure or contact with lead on the job within the ALAD 1-1 genotype subgroup. Laboratory examinations showed that serum iron and zinc levels in workers' with the ALAD 1-2 genotype were higher than those with the ALAD 1-1 genotype, especially in storage-battery workers. Correlation analysis indicated that the blood lead level negatively correlated with serum calcium, iron and zinc level. The data of this study suggest that the ALAD gene polymorphism and serum ion levels may modify the kinetics of lead in blood. Therefore, the authors recommend that an adequate intake of dietary calcium, iron, and zinc or the calcium, iron, and zinc supplementation should be prescribed to Chinese lead exposed workers.

Heavy metal toxicity and the environment

Heavy metals are naturally occurring elements that have a high atomic weight and a density at least five times greater than that of water. Their multiple industrial, domestic, agricultural, medical, and technological applications have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. Their toxicity depends on several factors including the dose, route of exposure, and chemical species, as well as the age, gender, genetics, and nutritional status of exposed individuals. Because of their high degree of toxicity, arsenic, cadmium, chromium, lead, and mercury rank among the priority metals that are of public health significance. These metallic elements are considered systemic toxicants that are known to induce multiple organ damage, even at lower levels of exposure. They are also classified as human carcinogens (known or probable) according to the US Environmental Protection Agency and the International Agency for Research on Cancer. This review provides an analysis of their environmental occurrence, production and use, potential for human exposure, and molecular mechanisms of toxicity, genotoxicity, and carcinogenicity.

Effects of lead on neurogenesis during zebrafish embryonic brain development

Lead neurotoxicity has caused wide public concern in recent decades, yet little is known about its effects on cellular and molecular mechanisms during the sensitive early life stages of animals. This study examines neurological deficits caused by lead acetate (Pb) during early embryonic stages in the zebrafish (Danio rerio) and further explores its potential molecular mechanism. Zebrafish embryos showed varying levels of toxicity, which was proportional to the concentration of Pb to which the embryos were exposed. Following Pb exposure (0.2mM), embryos showed obvious neurotoxic symptoms with "sluggish" action, slow swimming movements and slow escape action. Whole mount in situ hybridization showed that gfap and huC gene expression patterns decreased significantly throughout the brains of the Pb-treated embryos, particularly in the diencephalon region. RT-PCR further proved the downregulation of the two genes. However, ngn1 and crestin gene expression patterns were similar in both the Pb-treated embryos and the control embryos. The TUNEL assay demonstrated that the reduction of nerve cells was due to increased apoptosis of neuron and glia cells. In conclusion, these findings identify that Pb-induced neurotoxicity can be caused by impaired neurogenesis, resulting in markedly increased apoptosis of special types of neural cells, neuron and glia cells.

Lead-Induced Cell Cycle Arrest in Human Liver Carcinoma (HepG2) Cells: Involvement of oxidative stress, p53 and Cyclin A

BACKGROUND

Recent studies in our laboratory have demonstrated that lead is cytotoxic to human liver carcinoma (HepG2) cells, showing a 48 h-LD50 of 35.5 ± 9.2ug/mL. However, its molecular mechanisms of toxicity are still largely unknown. Hence, the aim of the present study was to use HepG2 cells as a test model to investigate the molecular mechanisms of lead-induced oxidative stress and modulation of cellular response proteins.

METHODS

To achieve this goal, we performed lipid peroxidation assay for malondialdehyde (MDA) determination, western blot and densitometric analyses for genes and related proteins expression in human liver carcinoma cells.

RESULTS

Data obtained from the lipid peroxidation assay demonstrated a significant increase (p ≤ 0.05) of MDA levels in lead-treated HepG2 cells compared to control cells. Western Blot analysis showed a strong dose-response relationship with regard to p53 expression, and a significant repression in cyclin A in lead-treated cells.

CONCLUSIONS

Findings from this research indicate that lead is able to cause oxidative stress, cell cycle arrest through activation of the 53-kDa tumor suppressor protein and down regulation of the cyclin A protein in human liver carcinoma (HepG2) cells.

Lead induces oxidative stress and phenotypic markers of apoptosis in Saccharomyces cerevisiae

In the present work, the mode of cell death induced by Pb in Saccharomyces cerevisiae was studied. Yeast cells Pb-exposed, up to 6 h, loss progressively the capacity to proliferate and maintained the membrane integrity evaluated by the fluorescent probes bis(1,3-dibutylbarbituric acid trimethine oxonol) and propidium iodide. Pb-induced death is an active process, requiring the participation of cellular metabolism, since the simultaneous addition of cycloheximide attenuated the loss of cell proliferation capacity. Cells exposed to Pb accumulated intracellularly reactive oxygen species (ROS), evaluated by 2',7'-dichlorodihydrofluorescein diacetate. The addition of ascorbic acid (a ROS scavenger) strongly reduced the oxidative stress and impaired the loss of proliferation capacity in Pb-treated cells. Pb-exposed cells displayed nuclear morphological alterations, like chromatin fragmentation, as revealed by diaminophenylindole staining. Together, the data obtained indicate that yeast cells exposition to 1 mmol/l Pb results in severe oxidative stress which can be the trigger of programmed cell death by apoptosis.