Distribution of Pb and Se in mouse brain following subchronic Pb exposure by using synchrotron X-ray fluorescence.

Lead (Pb) is a well-known neurotoxicant and environmental hazard. Recent experimental evidence has linked Pb exposure with neurological deterioration leading to neurodegenerative diseases, such as Alzheimer's disease. To understand brain regional distribution of Pb and its interaction with other metal ions, we used synchrotron micro-x-ray fluorescence technique (µ-XRF) to map the metal distribution pattern and to quantify metal concentrations in mouse brains. Lead-exposed mice received oral gavage of Pb acetate once daily for 4 weeks; the control mice received sodium acetate. Brain tissues were cut into slices and subjected for analysis. Synchrotron µ-XRF scans were run on the PETRA III P06 beamline (DESY). Coarse scans of the entire brain were performed to locate the cortex and hippocampus, after which scans with higher resolution were run in these areas. The results showed that: a) the total Pb intensity in Pb-exposed brain slices was significantly higher than in control brain; b) Pb typically deposited in localized particles of <10 um2 in both the Pb-exposed and control brain slices, with more of these particles in Pb-exposed samples; c) selenium (Se) was significantly correlated with Pb in these particles in the cortex and hippocampus/corpus callosum regions in the Pb-exposed samples, and the molar ratio of the Se and Pb in these particles is close to 1:1. These results indicated that Se may play a crucial role in Pb-induced neurotoxicity. Our findings call for further studies to investigate the relationship between Pb exposure and possible Se detoxification responses, and the implication in the etiology of Alzheimer's disease.

Mitigation of lead neurotoxicity by the ethanolic extract of Laurus leaf in rats.

The present study was conducted in order to assess the chemical composition of Laurus, its antioxidant activities, and benefit from the Laurus extract effect on neurotoxicity caused by lead acetate (Pb). Chemical profile was assayed by using liquid chromatography coupled with high-resolution mass spectrometry (LC-HR-MS). In this study, 40 male rats were divided into four groups (10 rats per each group): (1) control group, (2) Laurus group: rats treated with 250 mg/kg b. wt. of Laurus leaves extract, (3) Pb group: rats treated with 100 mg/kg b. wt. of lead acetate, (4) Pb + Laurus group: rats treated with 250 mg/kg b. wt. of Laurus leaves extract in addition to lead acetate for 30 days. At the end of experiment, some estimates were calculated from blood samples, brain tissue, and histological examination. The results showed that the extract is highly affluent in total flavonoids, total phenolic, and also has antioxidant activity. The LC-MS appeared a wide range of compounds in the extract. The oxidative stress resulted from exposure to lead acetate has been reported to cause reduction in body and brain weights, levels of RBCs, acetylcholinesterase (AChE), GSH, SOD, and CAT in addition to increase in levels of WBCs and MAD. Moreover, Laurus leaves extract notably lessened the biochemical changes caused by lead acetate in the blood, homogenate, and brain tissue (P < 0.05). The current study indicates the antioxidant activity of Laurus leaves extract and assumes that it has a defensive role against the oxidative damage caused by lead in a rat's brain.

Attenuation of lead neurotoxicity by supplementation of polyunsaturated fatty acid in Wistar rats.

BACKGROUND: Among various types of polyunsaturated fatty acid (PUFA), omega-3 fatty acids play a crucial role in development and function of the brain. This study was undertaken to investigate the possible neuroprotective efficacy of omega-3 fatty acid on lead-induced neurotoxicity in rats. MATERIAL AND METHODS: The experiment was carried out on 32 male Wistar rats divided into four groups. The first group (control) was treated with distilled water and second group with lead acetate at the doses of 3 mg/kg b.wt. (body weight)/oral, whereas third and fourth groups were simultaneously treated with lead acetate (3 mg/kg b.wt.) plus omega-3 fatty acid (300 mg/kg b.wt./oral) and lead acetate (3 mg/kg b.wt.) plus vitamin E (100 mg/kg b.wt./oral), respectively, for a period of 90 days. Their biochemical and histopathological investigations have been carried out. RESULTS: The level of lead was markedly elevated in brain (4.71-fold) and blood (5.65-fold), also increased levels of ROS, GSH, LPO with concomitant reduction in the activities of delta-ALAD, CAT, SOD, and GPx. In addition, lead-induced brain damage was indicated by histopathological changes. Omega-3 fatty acid resulted in marked improvement in most of the biochemical parameters as well as histopathological changes in rats. The results obtained were compared with vitamin E as the standard antioxidant agents. DISCUSSION: Omega-3 fatty acid significantly (P < 0.05) decreased the effect of lead-induced brain damage as well as biochemical changes similar to that of standard drug, vitamin E. So, our result suggested that omega-3 fatty acid may play a protective role in lead-induced neurotoxicity and associated human health risk.

The protective effect of green tea extract on lead induced oxidative and DNA damage on rat brain.

The role of green tea in protection against neurotoxicity induced by lead acetate was investigated in rats. Five equal groups, each of ten rats were used. The first group was served as control, the second, third, and fourth groups were given lead acetate, lead acetate and green tea, and green tea only, respectively, for one month, the fifth group was administered lead acetate for one month followed by green tea for 15 days. Lead acetate was given orally at a dose of 100 mg/kg b. wt, while green tea was given in drinking water at a concentration of 5 g/L. Lead acetate administration induced loss of body weight and decreased concentration of reduced glutathione and SOD activity in brain tissues as well as significantly high DNA fragmentation and pathological changes. Co-administration of green tea with lead acetate significantly alleviated these adverse effects.

Locomotor damage and brain oxidative stress induced by lead exposure are attenuated by gallic acid treatment.

We investigated the antioxidant potential of gallic acid (GA), a natural compound found in vegetal sources, on the motor and oxidative damages induced by lead. Rats exposed to lead (50 mg/kg, i.p., once a day, 5 days) were treated with GA (13.5mg/kg, p.o.) or EDTA (110 mg/kg, i.p.) daily, for 3 days. Lead exposure decreased the locomotor and exploratory activities, reduced blood ALA-D activity, and increased brain catalase (CAT) activity without altering other antioxidant defenses. Brain oxidative stress (OS) estimated by lipid peroxidation (TBARS) and protein carbonyl were increased by lead. GA reversed the motor behavior parameters, the ALA-D activity, as well as the markers of OS changed by lead exposure. CAT activity remained high, possibly as a compensatory mechanism to eliminate hydroperoxides during lead poisoning. EDTA, a conventional chelating agent, was not beneficial on the lead-induced motor behavior and oxidative damages. Both GA (less) and EDTA (more) reduced the lead accumulation in brain tissue. Negative correlations were observed between the behavioral parameters and lipid peroxidation and the lead levels in brain tissue. In conclusion, GA may be an adjuvant in lead exposure, mainly by its antioxidant properties against the motor and oxidative damages resulting from such poisoning.

Combinational chelation therapy abrogates lead-induced neurodegeneration in rats.

Lead, a ubiquitous and potent neurotoxicant causes oxidative stress which leads to numerous neurobehavioral and physiological alterations. The ability of lead to bind sulfhydryl groups or compete with calcium could be one of the reasons for its debilitating effects. In the present study, we addressed: i) if chelation therapy could circumvent the altered oxidative stress and prevent neuronal apoptosis in chronic lead-intoxicated rats, ii) whether chelation therapy could reverse biochemical and behavioral changes, and iii) if mono or combinational therapy with captopril (an antioxidant) and thiol chelating agents (DMSA/MiADMSA) is more effective than individual thiol chelator in lead-exposed rats. Results indicated that lead caused a significant increase in reactive oxygen species, nitric oxide, and intracellular free calcium levels along with altered behavioral abnormalities in locomotor activity, exploratory behavior, learning, and memory that were supported by changes in neurotransmitter levels. A fall in membrane potential, release of cytochrome c, and DNA damage indicated mitochondrial-dependent apoptosis. Most of these alterations showed significant recovery following combined therapy with captopril with MiADMSA and to a smaller extend with captopril+DMSA over monotherapy with these chelators. It could be concluded from our present results that co-administration of a potent antioxidant (like captopril) might be a better treatment protocol than monotherapy to counter lead-induced oxidative stress. The major highlight of the work is an interesting experimental evidence of the efficacy of combinational therapy using an antioxidant with a thiol chelator in reversing neurological dystrophy caused due to chronic lead exposure in rats.

Protective effects of Hippophae rhamnoides L. juice on lead-induced neurotoxicity in mice.

We examined the effect of Hippophae rhamnoides L. (HRL) juice on lead-induced memory impairment and neuronal damage in the brains of adult mice. Kunming mice were exposed to lead acetate 10 mg/kg body weight for 20 d. Twenty percent and 40% HRL prevented the lead-induced decrease in step-through latency. In the water maze test, the swimming time was lengthened in mice treated with lead acetate, but this time was decreased in mice that received 20% and 40% HRL. The malondialdehyde (MDA) levels were increased in lead-treated mice, which were reduced by 20% and 40% HRL in dose-dependent manner. The activities of acetylcholinesterase (AchE) and monoamine oxidase-A and -B were significantly increased in the lead-treated group, which were decreased by 40% HRL but not by 20% HRL. The levels of norepinephrine, serotonin, and 5-hydroxyindole acetic acid were decreased significantly in the lead-treated mice, and the decreases were antagonized by 40% HRL, except for than in dopamine, but 20% HRL had no effect on this change. These data suggest that the different doses of the HRL juice protect against the lead acetate-induced deficits in learning and memory and changes in neurobiochemical parameters.

Zinc and calcium reduce lead induced perturbations in the aminergic system of developing brain.

Since alterations in monoamines and monoamine oxidase (MAO) have been postulated to play a role in toxic effects of lead (Pb) on the central nervous system, we have examined the protective effects of calcium (Ca2+) and zinc (Zn2+) supplementation on Pb-induced perturbations in the levels of monoamines and the activity of MAO. Swiss albino mice were lactationally exposed to low (0.2%) and high (1%) levels of Pb-acetate via drinking water of the mother. Pb-exposure commenced on postnatal day (PND) 1, continued up to PND 21 and stopped at weaning. Ca2+ or Zn2+ (0.02% in 0.2% Pb-water or 0.1% in 1% Pb-water) was supplemented separately to the mother up to PND 21. The levels of monoamines (epinephrine, norepinephrine, dopamine and serotonin) and the activity of MAO in the brain regions such as hippocampus, cortex, cerebellum and medulla of young (1 month old) and adult (3 month old) mice were determined in the synaptosomal fractions. The synaptosomal monoamines though increased with low level (0.2%) Pb-exposure, significantly decreased with high level (1%) Pb-exposure in all the brain regions in both the age groups. In general, the young mice seem to be more vulnerable to Pb-neurotoxicity. Ca2+ or Zn2+ supplementation significantly reversed the Pb-induced perturbations both in the levels of monoamines and in the activity of MAO. However, the recovery in monoamine levels and MAO activity was more pronounced with Ca2+ supplementation as compared to Zn2+. These results provide evidence that dietary Ca2+ and/or Zn2+ provide protection against Pb-induced neurotoxic effects.

Lead-induced developmental perturbations in hippocampal Sp1 DNA-binding are prevented by zinc supplementation: in vivo evidence for Pb and Zn competition.

Zinc finger protein (ZFP) transcription factors are essential for regulation of gene expression in the developing brain. We previously reported that Pb exposure perturbed the DNA-binding of ZFP such as Sp1 and Egr-1 in the cerebellum, which play critical role in CNS development. In this study, we focused on hippocampal Sp1 DNA-binding and mRNA expression in neonatal Pb-exposed animals. The expression pattern of an Sp1 target (NMDAR1) gene was also monitored. To study in vivo and in vitro competition between Pb and Zn, we supplemented animals with Zn, and examined the effects of both metals on hippocampal Sp1 DNA-binding and the DNA-binding of a recombinant Sp1 protein (rhSp1). Tissue metal analysis revealed that only the disposition of Pb in the brain but not its distribution in the blood was influenced by the presence of Zn. The developmental profile of Sp1 DNA-binding exhibited a peak on PND 15 which subsequently declined to adult levels. Consistent with earlier studies, Pb exposure produced premature peaks of Sp1 DNA-binding on PND 5 which later returned to adult levels. The basal and Pb-induced developmental patterns of Sp1 mRNA departed from its DNA-binding profiles. However, the expression patterns of the NMDAR1 gene were relative to Sp1 DNA-binding. Supplementation with zinc provided a protective effect on Pb-induced changes in Sp1 DNA-binding. Moreover, Pb and Zn directly interfered with the DNA-binding of rhSp1 in vitro. These data suggest that Pb and Zn can compete both in vivo and in vitro at the zinc finger domain of Sp1 with a consequential effect on Sp1 DNA-binding, subsequent gene expression and brain development.

Exposure to lead appears to selectively alter metabolism of cortical gray matter.

OBJECTIVE: The effects of lead poisoning on the development of children have been examined primarily in the context of behavioral and neuropsychological studies. The purpose of this study was to examine the in vivo use of magnetic resonance spectroscopy (MRS) for the evaluation of the neurotoxic effects of lead on the nervous system. MRS has the ability to monitor brain metabolism by detecting a number of neurochemicals among which is N-acetylaspartate, a metabolite shown to decrease in processes that involve neuronal loss. METHODS: In the present study we evaluated the metabolism of gray and white matter of frontal cortex using MRS in individuals with elevated blood lead levels and compared the results with those obtained on nonlead-exposed controls. RESULTS: Although all of the participants had normal MRI examinations of the brain, the lead-exposed individuals exhibited a significant reduction in the N-acetylaspartate/creatine and phosphocreatine ratios in frontal gray matter compared with the nonlead-exposed controls. CONCLUSIONS: The findings of this study suggest that lead has an effect on brain metabolites as detected by MRS in vivo. More specifically, we have found statistically significant reduced levels of brain metabolites in gray but not white matter in lead-exposed individuals. These results imply that MRS is able to detect metabolic abnormalities in individuals with lead poisoning.

Efficacy of succimer chelation for reducing brain lead in a primate model of human lead exposure.

The extent to which succimer (meso-2,3-dimercaptosuccinic acid [DMSA], Chemet) reduces brain lead (Pb) levels may be a primary consideration in evaluating its efficacy for reducing neurotoxicity. Clinical research in this area has been hampered by the need to use blood Pb levels as the index of treatment efficacy, despite the fact that brain Pb level is the exposure parameter of greater relevance to cognitive outcomes. Here, a nonhuman primate model of human Pb exposure was used to determine: (1) The efficacy of oral succimer for reducing brain Pb derived from chronic or recent exposures, and (2) The extent to which blood Pb levels reflect brain Pb prior to and following chelation. Adult rhesus monkeys were chronically exposed to Pb orally for 5 weeks to reach and maintain a target blood Pb level of 35-40 microg/dL. Chelation of Pb from recent exposures was assessed using a stable (204)Pb isotope tracer administered over 4 days prior to treatment. Immediately prior to chelation, a prefrontal cortex (PFC) biopsy was collected to determine pretreatment brain Pb levels. Subsequently, monkeys were assigned to vehicle (n = 5) or succimer (n = 6, 30 mg/kg/day x 5 days followed by 20 mg/kg/day x 14 days) groups. Blood and brain PFC, frontal lobe (FL), hippocampus (H), and striatum (S) were analyzed for total Pb and (204)Pb tracer concentrations by magnetic sector inductively coupled plasma-mass spectrometry. There were no measurable differences in brain Pb concentrations between the succimer and vehicle groups, indicating that succimer treatment was not efficacious in reducing brain Pb levels. In contrast, the cessation of Pb exposure significantly reduced brain (PFC) Pb ( approximately 34%) when compared to pretreatment levels (succimer and vehicle groups). Pb concentrations also varied among brain regions (PFC > FL approximately H > S). Finally, pretreatment PFC Pb concentrations were significantly correlated with the integrated blood Pb level (AUC) over the Pb exposure period, but not with the single pretreatment blood Pb collected concurrently with the PFC biopsy. Following treatment, blood Pb levels correlated only with Pb in the PFC, and not the other brain regions measured (FL, H, S). These data indicate that, under the conditions of this study, succimer treatment did not reduce brain Pb levels beyond the cessation of Pb exposure alone. Moreover, a single blood Pb measurement may be a poor predictor of brain Pb levels, reflecting limitations in the use of blood Pb level as an indicator of treatment efficacy.