Lead affects apoptosis and related gene XIAP and Smac expression in the hippocampus of developing rats. Neurochem Res. 2010;35:473-479. [PMID: 19911273 DOI: 10.1007/s11064-009-0083-9]

Lead exposure disturbs ATP7B-mediated copper export from brain barrier cells by inhibiting XIAP-regulated COMMD1 protein degradation

The brain barrier is an important structure for metal ion homeostasis. According to studies, lead (Pb) exposure disrupts the transportation of copper (Cu) through the brain barrier, which may cause impairment of the nervous system; however, the specific mechanism is unknown. The previous studies suggested the X-linked inhibitor of apoptosis (XIAP) is a sensor for cellular Cu level which mediate the degradation of the MURR1 domain-containing 1 (COMMD1) protein. XIAP/COMMD1 axis was thought to be an important regulator in Cu metabolism maintenance. In this study, the role of XIAP-regulated COMMD1 protein degradation in Pb-induced Cu disorders in brain barrier cells was investigated. Pb exposure significantly increased Cu levels in both cell types, according to atomic absorption technology testing. Western blotting and reverse transcription PCR (RT-PCR) showed that COMMD1 protein levels were significantly increased, whereas XIAP, ATP7A, and ATP7B protein levels were significantly decreased. However, there were no significant effects at the messenger RNA (mRNA) level (XIAP, ATP7A, and ATP7B). Pb-induced Cu accumulation and ATP7B expression were reduced when COMMD1 was knocked down by transient small interfering RNA (siRNA) transfection. In addition, transient plasmid transfection of XIAP before Pb exposure reduced Pb-induced Cu accumulation, increased COMMD1 protein levels, and decreased ATP7B levels. In conclusion, Pb exposure can reduce XIAP protein expression, increase COMMD1 protein levels, and specifically decrease ATP7B protein levels, resulting in Cu accumulation in brain barrier cells.

Apigenin protects from hepatorenal damage caused by lead acetate in rats

Exposure to lead (Pb) is associated with serious health problems including hepatorenal toxicity. Apigenin is a natural-sourced flavonoid with promising antioxidant and anti-inflammatory effects. In this research, we investigated the potential protective role of apigenin against lead acetate (PbAc)-induced hepatorenal damage. Thus, this experiment studied the exposure of male Wistar Albino rats to apigenin and/or PbAc and their effects in comparison to the control rats. Apigenin administration decreased the levels of Pb and prevented the histopathological deformations in liver and kidney tissues following PbAc exposure. This was confirmed by the normalized levels of liver and kidney function markers. Additionally, apigenin inhibited significantly oxidative reactions through upregulating Nrf2 and HO-1, and activating their downstreamed antioxidants accompanied by a marked depletion of pro-oxidants. Moreover, apigenin decreased the elevated pro-inflammatory cytokines and inhibited cell loss in liver and kidney tissues in response to PbAc intoxication in both tissues. The obtained results demonstrated that apigenin could be used to attenuate the molecular, biochemical, and histological alterations associated with Pb exposure due to its potent antioxidant, anti-inflammatory, and antiapoptotic effects.

Possible mechanisms involved in the protective effects of chrysin against lead-induced cognitive decline: An in vivo study in a rat model

Lead (Pb) is a highly poisonous environmental pollutant that can induce cognitive decline. Chrysin, a natural flavonoid compound, has anti-oxidative, anti-inflammatory, and neuroprotective properties in different neurodegenerative disorders. The present study was designed to examine the putative effects of chrysin against Pb-induced cognitive impairment and the possible involved mechanisms. Adult male Wistar rats were exposed to Pb acetate (500 ppm in standard drinking water) either alone or in combination with daily oral administration of chrysin (30 mg/kg) for eight consecutive weeks. During the eight-week period of the study, the cognitive capacity of the rats was evaluated by employing both novel object recognition and passive avoidance tests. On day 56, hippocampal synaptic plasticity (long-term potentiation; LTP) was recorded in perforant path-dentate gyrus (PP-DG) synapses to assess field excitatory postsynaptic potentials (fEPSPs) slope and population spike (PS) amplitude. Subsequently, pro- and anti-inflammatory cytokines and histological changes were evaluated in the cerebral cortex and hippocampus of the rats. Moreover, Pb levels in blood and brain tissues were assessed. The results showed that Pb exposure causes cognitive decline, inhibition of hippocampal LTP induction, imbalance of pro- and anti-inflammatory cytokines, enhancement of Pb levels in blood and brain tissues, and neuronal loss. However, chrysin treatment improved cognitive dysfunction, ameliorated hippocampal LTP impairment, modulated inflammatory status, reduced Pb concentration, and prevented neuronal loss in the Pb-exposed rats. The results suggest that chrysin alleviates Pb-induced cognitive deficit, possibly through mitigation of hippocampal synaptic dysfunction, modulation of inflammatory status, reduction of Pb concentration, and prevention of neuronal loss.

Cognitive decline prevention in offspring of Pb+2 exposed mice by maternal aerobic training and Cur/CaCO3@Cur supplementations: In vitro and in vivo studies

Heavy metals are considered contaminants that hazardously influence the healthy life of humans and animals as they are widely used in industry. Contact of youngsters and women at ages of parturition with lead (Pb⁺²) is a main related concern, which passes through the placental barricade and its better absorption in the intestine leads to flaws in the fetal developfment. However, the metals threaten animal and human life, in particular throughout developmental stages. Products existing in the nature have a major contribution to innovating chemo-preventives. As a naturally available polyphenol and necessary curcuminoid, curcumin (Cur) is a derivative of the herb Curcuma longa (L.) rhizome, which globally recognized as "wonder drug of life"; however, Cur has a limited clinical use as it is poorly dissolved in water. Therefore, to enhance its clinically relevant parameters, curcumin-loaded calcium carbonate (CaCO₃@Cur) was synthesized by one step coprecipitation method as a newly introduced in this research. Initially, its structure was physio chemically characterized using FT-IR, FESEM and DLS equipment and then the cytotoxicity of lead when it was pretreated with Cur/CaCO₃@Cur were assessed by MTT assay. Both Cur and CaCO₃@Cur diminished the toxic effects of Pb⁺² while the most protective effect on the Pb⁺² cytotoxicity was achieved by pre-incubation of cells with CaCO₃@Cur. Besides, the morphological changes of Pb⁺²-treated cells that were pre-incubated with or without Cur/CaCO₃@Cur were observed by normal and florescent microscopes. A non-pharmacologic method that lowers the hazard of brain damage is exercise training that is capable of both improving and alleviating memory. In the current study, the role of regular aerobic training and CaCO₃@Cur was assessed in reducing the risk of brain damage induced by lead nitrate contact. To achieve the mentioned goal, pregnant Balb/C mice were assigned to five groups (six mice/group) at random: negative and positive controls, aerobic training group and Cur and CaCO₃@Cur treated (50 mg/kg/b.wt) trained groups that exposed to Pb⁺² (2 mg/kg) by drinking water during breeding and pregnancy. With the completion of study, offspring were subjected to the behavioral tasks that was tested by step-through ORT, DLB, MWM and YM tests. As a result, having regular aerobic training and CaCO₃@Cur co-administration with lead nitrate could reverse the most defected behavioral indicators; yet, this was not visible for both sexes and it seems that gender can also be a source of different effects in the animal's body. In fact, having regular aerobic training along with CaCO₃@Cur supplementation during pregnancy may be encouraging protecting potential agents towards the toxicity of Pb⁺² that could be recommended in the areas with high pollution of heavy metals.

Evaluation of long-term dermal exposure to soil contaminated with spent engine oil in male Wistar rats: An experimental approach

Continuous occupational exposure to spent engine oil (SEO) poses physiological risks to humans, especially to automobile mechanics. This study investigated the physiological effects of SEO-contaminated soil in a male Wistar rat model. Animals were dermally exposed to soil contaminated with SEO for 120 consecutive days and compared with rats exposed to uncontaminated soil (negative control). Heavy metal (lead (Pb), nickel (Ni), zinc, and cadmium (Cd)) accumulations, hematology, biochemical (aspartate aminotransferase (AST), alanine aminotransferase, alkaline phosphatase (ALP), urea, and creatinine) parameters, sperm morphology, and histopathology (liver, kidney, lungs, brain, skin, and testis) were evaluated as end points. Results revealed that the heavy metals in SEO-contaminated soil are far greater than the World Health Organisation permissible limits, with significant (p < 0.05) increases of Pb and Ni present in the brain, and Pb and Cd in the serum compared with the uncontaminated soil for the negative control. Only significant (p < 0.05) values were observed in the lymphocytes, activities of AST and ALP, and sperm abnormalities of the exposed rats compared with those used for the negative control. Histopathological changes were not evident in the brain but lesions were observed in the liver, kidney, lungs, skin, and testis of the exposed rats. Results herein suggest that the constituents of SEO may elicit harmful physiological changes to humans who are directly exposed to them.

E-waste lead exposure and children's health in China

China is one of the countries worldwide confronted with serious e-waste pollution and associated detrimental health effects, which has aroused public, academic and governmental concerns. Most local residents are exposed to hazardous substances such as lead (Pb) and other persistent organic pollutants because of informal e-waste recycling activities. This study reviews recent studies on children exposed to e-waste Pb in China focusing on health-related effects in children (e.g. growth and development, cardiovascular, immune, nervous, respiratory, reproductive, skeletal, and urinary systems) and evaluating the evidence for the association between e-waste Pb exposure and the children health outcomes in China. Children are one of most sensitive and vulnerable groups when facing e-waste Pb exposure. Previous data indicate that exposure to e-waste Pb has adverse effect on human health such as delayed and damaged physical and nervous development. It is the time to take effective measures, such as upgrading e-waste recycling technology, enhancing government policy guidance and support, and strengthening environmental protection and health awareness of the local inhabitants, to prevent the adverse effects of e-waste.

MicroRNA-106b-5p participates in lead (Pb2+)-induced cell viability inhibition by targeting XIAP in HT-22 and PC12 cells

Previous studies reported perturbed expressing of X-linked inhibitor of apoptosis protein (XIAP) under lead (Pb) exposure. However, researches on XIAP expression mainly focused on its transcriptional and post-translational regulation, rarely involving post-transcriptional mechanism manipulated by certain indispensable microRNAs (miRNAs). Interestingly, we unveiled that miR-106b-5p, a widely expressed miRNA in various tissues, is up-regulated by Pb²⁺-induced stress. Moreover, we found a binding site for miR-106b-5p in the 3'-UTR of xiap mRNA using bioinformatics analysis, and provided the evidences that miR-106b-5p can interact and function with this regulatory region via luciferase reporter assay. Our results further showed that miR-106b-5p down-regulates XIAP protein level, and suppression of miR-106b-5p reverses the decrease in both XIAP level and cell viability in Pb²⁺-treated HT-22 and PC12 cells. In brief, we identified a novel function of miR-106b-5p in the post-transcriptional regulation of XIAP expression associated with Pb neurotoxicity.

Thymoquinone ameliorates oxidative damage and histopathological changes of developing brain neurotoxicity

Lead (Pb) toxicity is known to be a chief environmental health issue, especially for pregnant women and young children. Today, the use of medicinal herbs in the treatment of many diseases and different toxic agents has become highly accepted due to their effectiveness and lower costs. Thymoquinone (TQ), which is extracted from Nigella sativa seeds, is a potent antioxidant and anti-inflammatory agent. This study was designed to explore the optional protectivity of TQ against maternal and fetal oxidative stress and brain damage induced by Pb administration. Pregnant rats were distributed into seven groups: control group, TQ group, DMSO group, two groups Pb-treated (160 and 320 ppm), and two groups Pb-treated (160 and 320 ppm) co-treated with TQ. Administration started from gestation day 1 (GD1) to day 20 (GD20) through oral gavage once daily. Lead administration caused a dose-dependent toxicity for both mothers and fetuses. Also, the histopathological assessment of the brains from Pb-treated groups showed marked alterations. Co-treatment of with TQ and Pb caused a significant decrease in Pb levels as compared with those treated with Pb alone and amelioration of histopathological changes in the brains. It was concluded that co-treatment of TQ along with gestational Pb exposure could mitigate the effects against Pb-induced maternal and fetal neurotoxicity.

Neurotoxicity of low-level lead exposure: History, mechanisms of action, and behavioral effects in humans and preclinical models

Lead is a neurotoxin that produces long-term, perhaps irreversible, effects on health and well-being. This article summarizes clinical and preclinical studies that have employed a variety of research techniques to examine the neurotoxic effects of low levels of lead exposure. A historical perspective is presented, followed by an overview of studies that examined behavioral and cognitive outcomes. In addition, a short summary of potential mechanisms of action is provided with a focus on calcium-dependent processes. The current level of concern, or reference level, set by the CDC is 5 μg/dL of lead in blood and a revision to 3.5 μg/dL has been suggested. However, levels of lead below 3 μg/dL have been shown to produce diminished cognitive function and maladaptive behavior in humans and animal models. Because much of the research has focused on higher concentrations of lead, work on low concentrations is needed to better understand the neurobehavioral effects and mechanisms of action of this neurotoxic metal.

The antagonistic effect of Se on the Pb-weakening formation of neutrophil extracellular traps in chicken neutrophils

Neutrophils represent an important part of the body's innate immunity and can resist the invasion of pathogenic microorganisms by releasing neutrophil extracellular traps (NETs). In this study, we investigated the toxic effects of lead (Pb) on the release of NETs, the antagonism of selenium (Se) on Pb toxicity and the potential molecular mechanisms. Our model was an in vitro exposure model for the addition of Se, Pb or both in the culture medium and was based on the separation of neutrophils from the peripheral blood of healthy chickens. Phorbol-myristate-acetate (PMA) was used as a stimulant. The scanning electron microscopy and fluorescence microscopy results showed that Pb weakened the PMA-induced formation of NETs. Exposure to Pb reduced the expression of the extracellular regulated protein kinase (ERK) pathway and the respiratory burst. Exposure to Pb also attenuated the release of Ca²⁺ in the endoplasmic reticulum mediated by the inositol 1,4,5-trisphosphate receptor (IP3R). These are two ways by which Pb decreases the formation of NETs. Pb also attenuates the expression levels of myeloperoxidase (MPO) and neutrophil elastase (NE), and attenuates histone removal by affecting the expression of different protein kinase C (PKC) isoforms. In contrast, Se can reduce the toxic damage caused by Pb. These results indicate that exposure to Pb decreases the formation of NETs, while Se can antagonize the toxicity of Pb to allow the formation of NETs.

Selenium and zinc protections against metal-(loids)-induced toxicity and disease manifestations: A review

Metals are ubiquitous in the environment due to huge industrial applications in the form of different chemicals and from extensive mining activities. The frequent exposures to metals and metalloids are crucial for the human health. Trace metals are beneficial for health whereas non-essential metals are dangerous for the health and some are proven etiological factors for diseases including cancers and neurological disorders. The interactions of essential trace metals such as selenium (Se) and zinc (Zn) with non-essential metals viz. lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) in biological system are very critical and complex. A huge number of studies report the protective role of Se and Zn against metal toxicity, both in animal and cellular levels, and also explain the numerous mechanisms involved. However, it has been considered that a tiny dyshomeostasis in the metals/trace metals status in biological system could induce severe deleterious effects that can manifest to numerous diseases. Thus, in this particular review, we have demonstrated the critical protection mechanism/s of Se and Zn against Cd, Pb, As and Hg toxicity in a one by one manner to clarify the up-to-date findings and perspectives. Furthermore, biomolecular consequences are comprehensively presented in light of particular cellular/biomolecular events which are somehow linked to a subsequent disease. The analyzed reports support significant protection potential of Se and Zn, either alone or in combination with other agents, against each of the abovementioned non-essential metals. However, Se and Zn are still not being used as detoxifying agents due to some unexplained reasons. We hypothesized that Se could be a potential candidate for detoxifying As and Hg regardless of their chemical speciations, but requires intensive clinical trials. However, particularly Zn-Hg interaction warrants more investigations both in animal and cellular level.

Development of the Adverse Outcome Pathway (AOP): Chronic binding of antagonist to N-methyl-d-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities of children

The Adverse Outcome Pathways (AOPs) are designed to provide mechanistic understanding of complex biological systems and pathways of toxicity that result in adverse outcomes (AOs) relevant to regulatory endpoints. AOP concept captures in a structured way the causal relationships resulting from initial chemical interaction with biological target(s) (molecular initiating event) to an AO manifested in individual organisms and/or populations through a sequential series of key events (KEs), which are cellular, anatomical and/or functional changes in biological processes. An AOP provides the mechanistic detail required to support chemical safety assessment, the development of alternative methods and the implementation of an integrated testing strategy. An example of the AOP relevant to developmental neurotoxicity (DNT) is described here following the requirements of information defined by the OECD Users' Handbook Supplement to the Guidance Document for developing and assessing AOPs. In this AOP, the binding of an antagonist to glutamate receptor N-methyl-d-aspartate (NMDAR) receptor is defined as MIE. This MIE triggers a cascade of cellular KEs including reduction of intracellular calcium levels, reduction of brain derived neurotrophic factor release, neuronal cell death, decreased glutamate presynaptic release and aberrant dendritic morphology. At organ level, the above mentioned KEs lead to decreased synaptogenesis and decreased neuronal network formation and function causing learning and memory deficit at organism level, which is defined as the AO. There are in vitro, in vivo and epidemiological data that support the described KEs and their causative relationships rendering this AOP relevant to DNT evaluation in the context of regulatory purposes.

Abd El-Aziz G, N. Mustafa H, El-Fark M, Mansour Tashkandi J, Hassan Alzahrani A, Mal A, AboRass M, Halim Deifalla A. Beneficial Effects of Curcumin in Maternal and Fetal Oxidative Stress and Brain Damage Induced by Gestational Lead Administration

This study was planned to explore the protective role of curcumin (Cur) against maternal and fetal oxidative stress and cerebral damage induced by lead (Pb) during pregnancy. Positively pregnant female rats were divided into seven groups: control group, Cur group (300 mg/kg of Cur/b.wt.), DMSO group (50% DMSO), two Pb-treated groups (exposed to 160 and 320 mg/kg b.wt./day of Pb acetate, respectively), and two groups treated with both Pb and Cur (exposed to Pb as previous groups together with 300 mg/kg b.wt./day of Cur). Treatments through oral gavage once a day started from gestation day 1 (GD1) till day 20 (GD20), where the mother rats of different experimental groups were sacrificed to obtain the fetuses. Different chemical parameters were assessed. Brain specimens of mother and fetal groups were processed with examination. The results displayed that Pb administration to pregnant rats resulted in a dose-dependent toxicity for both mothers and fetuses. Also, there was a significant rise in lipid peroxidation and decreased antioxidant enzyme activities in the brains of the different Pb-treated groups. The histological examination of the brain of treated dams and fetuses showed marked alterations. Co-treatment of Cur along with Pb caused a significant decrease in Pb levels as compared with those treated with Pb alone, improving the oxidative condition with amelioration of the brain’s histopathological changes. Co-administration of Cur could have ameliorative effect against Pb-induced neurotoxicity through the reduction of oxidative stress and reversal of histopathological changes.

Effects of selenium-lead interaction on the gene expression of inflammatory factors and selenoproteins in chicken neutrophils

Lead (Pb) is one of the most highly toxic metal pollutant that can cause damage to the immune system. It is known that selenium (Se) can antagonize heavy metals. To explore the toxic effects of Pb poisoning on bird immune cells, as well as the alleviating effects of Se on Pb, Se supplement and/or Pb poisoning chicken models were established. One hundred and eighty Hyline 7-day-old male chickens received either Se (1mg Se per kg of diet), Pb (350mg Pb per liter water) or Se+Pb in their diet and water for 90 days. Then, whole blood was collected from the four groups of chickens, and serum and neutrophils were isolated. The levels of Se and Pb in chicken serum, mRNA levels of 24 selenoproteins (GPX1, GPX2, GPX3, GPX4, Dio1, Dio2, Dio3, Txnrd1, Txnrd2, Txnrd3, SELS, SPS2, SELK, SELW1, SEP15, SEPX1, SELT, SELI, SELO, SELM, SEPN1, SEPP1, SELU, SELH) and inflammatory factors (TNF-α, COX-2, iNOS, NF-κB), and iNOS protein level in chicken neutrophils were determined, and protein-protein interaction prediction and principal component analysis were performed. The data showed that Pb exposure increased Pb content in serum, activated the NF-κB pathway, and increased the expression of selenoproteins in chicken neutrophils. Se supplements could reduce Pb concentration in serum, had a mitigative effect on the activation of the NF-κB pathway and further enhanced the upward trend of selenoprotein expression induced by Pb exposure. These results suggest that Se supplement could eliminate Pb in serum and alleviate the activation of the NF-κB pathway under Pb exposure by increasing the expression of selenoproteins.

Causes of genome instability: the effect of low dose chemical exposures in modern society

Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis.

Gestational lead exposure induces developmental abnormalities and up-regulates apoptosis of fetal cerebellar cells in rats

Lead (Pb), a known environmental toxicant, adversely affects almost all organ systems. In this study, we investigated the effects of maternal lead exposure on fetal rat cerebellum. Female Sprague-Dawley rats were given lead nitrate in drinking water (0, 0.5, and 1%) for two weeks before conception, and during pregnancy. Fetuses were collected by caesarian section on gestational day 21 and observed for developmental abnormalities. The fetal cerebellar sections from control and 1% lead group were stained with cresyl violet. Immunohistochemical expressions of p53, Bax, Bcl-2, and caspase 3 were quantified by AnalySIS image analyzer (Life Science, Germany). Lead exposure induced developmental abnormalities of eyes, ear, limbs, neck and ventral abdominal wall; however, these abnormalities were commonly seen in the 1% lead-treated group. In addition, lead also caused fetal mortality and reduced body growth in both dose groups and reduced brain weight in the 1% lead-treated group. The fetal cerebella from the 1% lead-treated group showed unorganized cerebellar cortical layers, and degenerative changes in granule and Purkinje cells such as the formation of clumps of Nissl granules. An increase in Bax and caspase 3, and a decrease in Bcl-2 (p < 0.05), but not in p53, showed apoptosis of the neurons. In conclusion, gestational lead exposure in rats induces fetal toxicity and developmental abnormalities. The lead exposure also impairs development of cerebellar layers, induces structural changes, and apoptosis in the fetal cerebellar cortex. These results suggest that lead exposure during gestation is extremely toxic to developing cerebellum in rats.

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.

Perinatal exposure to lead induces morphological, ultrastructural and molecular alterations in the hippocampus

The aim of this paper is to examine if pre- and neonatal exposure to lead (Pb) may intensify or inhibit apoptosis or necroptosis in the developing rat brain. Pregnant experimental females received 0.1% lead acetate (PbAc) in drinking water from the first day of gestation until weaning of the offspring; the control group received distilled water. During the feeding of pups, mothers from the experimental group were still receiving PbAc. Pups were weaned at postnatal day 21 and the young rats of both groups then received only distilled water until postnatal day 28. This treatment protocol resulted in a concentration of Pb in rat offspring whole blood (Pb-B) below the threshold of 10 μg/dL, considered safe for humans.We studied Casp-3 activity and expression, AIF nuclear translocation, DNA fragmentation, as well as Bax, Bcl-2 mRNA and protein expression as well as BDNF concentration in selected structures of the rat brain: forebrain cortex (FC), cerebellum (C) and hippocampus (H). The microscopic examinations showed alterations in hippocampal neurons.Our data shows that pre- and neonatal exposure of rats to Pb, leading to Pb-B below 10 μg/dL, can decrease the number of hippocampus neurons, occurring concomitantly with ultrastructural alterations in this region. We observed no morphological or molecular features of severe apoptosis or necrosis (no active Casp-3 and AIF translocation to nucleus) in young brains, despite the reduced levels of BDNF. The potential protective factor against apoptosis was probably the decreased Bax/Bcl-2 ratio, which requires further investigation. Our findings contribute to further understanding of the mechanisms underlying Pb neurotoxicity and cognition impairment in a Pb-exposed developing brain.

Lead acetate induces cell apoptosis and promotes caspase-3 expression in human liver cell line L-02

AIM: To investigate the impact of lead acetate on cell apoptosis and caspase-3 expression in human liver cell line L-02.

METHODS: After L-02 cells were treated with different concentrations (0, 2.5, 40, 100, 200, 400 μmol/L) of lead acetate for 24 or 48 h, the proliferation of L-02 cells was assayed by MTT assay; cell morphological changes were observed after Hoechest33258 staining; and the expression of caspase-3 mRNA and protein was determined by RT-PCR and Western blot.

RESULTS: Compared to the normal control group, the proliferation of L-02 cells was significantly inhibited after treatment with different concentrations of lead acetate for 24 or 48 h (24 h: 0.4678 ± 0.0438, 0.4686 ± 0.0733, 0.4500 ± 0.0712, 0.4244 ± 0.0407, 0.3998 ± 0.0499 vs 0.5234 ± 0.0589; 48 h: 0.4290 ± 0.0607, 0.4184 ± 0.0296, 0.4032 ± 0.0499, 0.3856 ± 0.0386, 0.3750 ± 0.0149 vs 0.5300 ± 0.0397, all P < 0.05 or 0.01). Significant morphological changes were noted in cells treated with lead acetate for 48 h. Compared to the normal control group, the levels of caspase-3 mRNA increased significantly in a dose-dependent manner in L-02 cells treated with lead acetate (1.0912 ± 0.0769, 1.2874 ± 0.144, 1.4536 ± 0.1046, 1.6986 ± 0.1371, 1.9882 ± 0.0925 vs 0.8438 ± 0.0933, all P < 0.01). Additionally, the expression levels of caspase-3 protein also significantly increased after treatment with lead acetate.

CONCLUSION: Lead acetate inhibits proliferation and induces apoptosis of L-02 cells possibly via a mechanism associated with the activation of caspase-3.

Low-level lead exposure triggers neuronal apoptosis in the developing mouse brain

While the toxic effects of lead have been recognized for millennia, it has remained a significant public health concern due to its continued use and toxicological potential. Of particular interest is the increased susceptibility of young children to the toxic effects of lead. Although the exact mechanism(s) for lead toxicity is currently not well understood, research has established that it can be a potent NMDA antagonist. Previous research has established that exposure to NMDA antagonists during the brain growth spurt period (first 2 weeks of life in mice) can produce apoptotic neurodegeneration throughout the brain. Based on this information, the ability of lead exposure (two injections of 350 mg/kg lead 4h apart) to produce apoptosis in the neonatal mouse brain was assessed histologically 8-24h after treatment using activated caspase-3 immunohistochemistry, De Olmos silver technique, Nissl staining, and electron microscopy. Lead exposure produced significant neurodegeneration in the caudate/putamen, hippocampus, subiculum, and superficial and deep cortical layers of the frontal cortical regions. Further ultrastructural examination revealed cellular profiles consistent with apoptotic cell death. Statistical results showed that lead exposure significantly increased apoptotic neurodegeneration above that seen in normal controls in animals treated at postnatal day 7, but not on day 14. The results of this study may provide a basis for further elucidation of mechanisms through which the immature nervous system may be particularly susceptible to lead exposure.