Influence of lead acetate on glutathione and its related enzymes in different regions of rat brain

Developmental effects of zebrafish (Danio rerio) embryos after exposure to glyphosate and lead mixtures

Natural aquatic environments have a heterogeneous composition; therefore, simultaneous exposure to multiple contaminants is relevant and more realistic when assessing exposure and toxicity. This study examines the combinatorial effects of two compounds found ubiquitously in drinking water across the United States: glyphosate and lead acetate. Zebrafish (Danio rerio) embryos were used as a model for investigating developmental delays following controlled exposures. Six different environmentally relevant exposure concentrations of glyphosate, ranging from 0.001 to 10 ppm, and lead acetate, ranging from 0.5 to 4 ppm, were applied first as single exposures and then as co-exposures. The sublethal endpoints of hatching and coagulation were quantified to determine potencies. Results indicate that higher concentrations of the individual chemicals correlate with later hatching with correlation coefficients of 0.71 and 0.40 for glyphosate and lead acetate respectively, while the co-exposure at lower concentrations induced earlier hatching with a correlation coefficient 0.74. In addition, increased levels of coagulation and glutathione reductase activity were observed following co-exposure, as compared to the individual exposures, suggesting potential toxicological interactions. These results support the need for further work assessing the combined potencies of aquatic contaminants rather than individual exposures.

MOLECULAR MECHANISMS OF LEAD NEUROTOXICITY

Lead (Pb2+) is a non-essential metal with numerous industrial applications that have led to ts ubiquity in the environment. Thus, not only occupational-exposed individuals' health is compromised, but also that of the general population and in particular children. Notably, although the central nervous system is particularly susceptible to Pb2+, other systems are affected as well. The present study focuses on molecular mechanisms that underlie the effects that arise from the presence of Pb2+ in situ in the brain, and the possible toxic effects that follows. As the brain barriers represent the first target of systemic Pb2+, mechanisms of Pb2+ entry into the brain are discussed, followed by a detailed discussion on neurotoxic mechanisms, with special emphasis on theories of ion mimicry, mitochondrial dysfunction, redox imbalance, and neuroinflammation. Most importantly, the confluence and crosstalk between these events is combined into a cogent mechanism of toxicity, by intertwining recent and old evidences from humans, in vitro cell culture and experimental animals. Finally, pharmacological interventions, including chelators, antioxidants substances, anti-inflammatory drugs, or their combination are reviewed as integrated approaches to ameliorate Pb2+ harmful effects in both developing or adult organisms.

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.

Vitamin C and Turmeric Attenuate Bax and Bcl-2 Proteins' Expressions and DNA Damage in Lead Acetate-Induced Liver Injury

Background:

Lead is a common environmental and occupational pollutant which induced multiorgans dysfunction. The present study was designed to investigate the hepatoprotective effects of turmeric (TUR) and/or vitamin C (Vit-C) alone or together against lead acetate toxicity and to explore novel molecular pathways.

Method:

Acute hepatotoxicity was induced by lead acetate (100 mg/kg/day, i.p.) in male rats, and the effect of TUR (200 mg/kg/day, orally) and/or Vit-C (250 mg/kg/day, orally) along with lead acetate for 7 days was studied.

Results:

Lead acetate increased serum alanine transaminase, aspartate transaminase, lactate dehydrogenase, hepatic lipid peroxidation and nitric oxide; while, hepatic superoxide dismutase and glutathione activities were downregulated. Hepatic Bcl-2-associated X (Bax) and B-cell lymphoma-2 (Bcl-2) proteins expressions were altered and hepatic DNA damaged was increased as well. Liver/body weight ratio was decreased. Hematoxylin and eosin demonstrated that lead acetate induced focal areas of massive hepatic degeneration of the hepatocytes. Treatment with both antioxidants ameliorated all the altered parameters and induced marked improvement of liver architecture.

Conclusion:

The combination of TUR and Vit-C has shown the most protective effects against lead acetate-induced hepatotoxicity.

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.

Diabetes and Exposure to Environmental Lead (Pb)

Although the increased incidence of type 2 diabetes since the 1950s is thought to be primarily due to coincident alterations in lifestyle factors, another potential contributing factor in industrialized countries is exposure of the population to environmental pollutants and industrial chemicals. Exposure levels of many environmental toxicants have risen in the same time-frame as the disease incidence. Of particular interest in this regard is the metal lead. Although overall lead exposure levels have diminished in recent decades, there is an under-recognized but persistent occurrence of lead exposure in poor underserved urban populations. Although the neural developmental pathologies induced by lead exposures have been well documented, very little is known about the effect of lead exposure on the incidence of chronic metabolic diseases such as type 2 diabetes. Although our understanding of the metabolic health effects of lead exposure is incomplete, there are studies in model systems and a small amount of epidemiological data that together suggest a deleterious effect of environmental lead exposure on metabolic health. This article reviews the human, animal and in vitro studies that have examined the effects of lead exposure on the development of diabetes and related metabolic conditions.

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.

Protective effect of Allium sativum (garlic) aqueous extract against lead-induced oxidative stress in the rat brain, liver, and kidney

The present investigation was undertaken to evaluate the ameliorative activity of Allium sativum against lead-induced oxidative stress in the brain, liver, and kidney of male rats. Four groups of male Wistar strain rats (100-120 g) were taken: group 1 received 1000 mg/L sodium acetate and group 2 was given 1000 mg/L lead acetate through drinking water for 2 weeks. Group 3 and 4 were treated with 250 mg/kg body weight/day of A. sativum and 500 mg/kg body weight/day of A. sativum, respectively, by oral intubation for a period of 2 weeks along with lead acetate. The rats were sacrificed after treatment and the brain, liver, and kidney were isolated on ice. In the brain, four important regions namely the hippocampus, cerebellum, cerebral cortex, and brain stem were separated and used for the present investigation. Blood was also drawn by cardiac puncture and preserved in heparinized vials at 4 °C for estimation of delta-aminolevulinic acid dehydratase (ALAD) activity. The results showed a significant (p < 0.05) increase in reactive oxygen species (ROS), lipid peroxidation products (LPP), total protein carbonyl content (TPCC), and lead in the selected brain regions, liver, and kidney of lead-exposed group compared with their respective controls. Blood delta-ALAD activity showed a significant (p < 0.05) decrease in the lead-exposed rats. However, the concomitant administration of A. sativum resulted in tissue-specific recovery of oxidative stress parameters namely ROS, LPP, and TPCC. A. sativum treatment also restored the blood delta-ALAD activity back to control. Overall, our results indicate that A. sativum administration could be an effective antioxidant treatment strategy for lead-induced oxidative insult.

Neuroprotective potential of Indigofera oblongifolia leaf methanolic extract against lead acetate-induced neurotoxicity

Lead (Pb) is one of the most common environmental toxicants, exposure to which can cause significant neurotoxicity and an associated decline in brain function. This study investigated the possible neuroprotective role of Indigofera oblongifolia leaf methanolic extract (IOLME) against lead-induced neurotoxicity. Rats were intraperitoneally injected with lead acetate, with or without IOLME (intragastric administration for 5 days), and the neuroprotective effect of IOLME was assessed by measuring the lead concentration, redox status (lipid peroxidation, nitric oxide and glutathione), enzymatic antioxidant activities (superoxide dismutase, catalase, glutathione peroxidase and reductase), PCR assays of apoptosis markers (Bax and Bcl-2) and histopathology of the brain. The increases in the lipid peroxidation, nitric oxide, and apoptosis, the decreases in the glutathione level and the activity of antioxidant enzymes, and the altered histology of the brain induced by lead acetate were mitigated in the brain of rats pre-treated with IOLME. These findings indicate that IOLME has beneficial effects and it mitigates lead acetate-induced neurotoxicity via its antioxidant and anti-apoptotic activities.

Hydroalcoholic seed extract of Coriandrum sativum (Coriander) alleviates lead-induced oxidative stress in different regions of rat brain

Lead exposure is known to cause apoptotic neurodegeneration and neurobehavioral abnormalities in developing and adult brain by impairing cognition and memory. Coriandrum sativum is an herb belonging to Umbelliferae and is reported to have a protective effect against lead toxicity. In the present investigation, an attempt has been made to evaluate the protective activity of the hydroalcoholic extract of C. sativum seed against lead-induced oxidative stress. Male Wistar strain rats (100-120 g) were divided into four groups: control group: 1,000 mg/L of sodium acetate; exposed group: 1,000 mg/L lead acetate for 4 weeks; C. sativum treated 1 (CST1) group: 250 mg/kg body weight/day for seven consecutive days after 4 weeks of lead exposure; C. sativum treated 2 (CST2) group: 500 mg/kg body weight/day for seven consecutive days after 4 weeks of lead exposure. After the exposure and treatment periods, rats were sacrificed by cervical dislocation, and the whole brain was immediately isolated and separated into four regions: cerebellum, hippocampus, frontal cortex, and brain stem along with the control group. After sacrifice, blood was immediately collected into heparinized vials and stored at 4 °C. In all the tissues, reactive oxygen species (ROS), lipid peroxidation products (LPP), and total protein carbonyl content (TPCC) were estimated following standard protocols. An indicator enzyme for lead toxicity namely delta-amino levulinic acid dehydratase (δ-ALAD) activity was determined in the blood. A significant (p<0.05) increase in ROS, LPP, and TPCC levels was observed in exposed rat brain regions, while δ-ALAD showed a decrease indicating lead-induced oxidative stress. Treatment with the hydroalcoholic seed extract of C. sativum resulted in a tissue-specific amelioration of oxidative stress produced by lead.

Ascorbic acid ameliorates oxidative damage induced by maternal low-level lead exposure in the hippocampus of rat pups during gestation and lactation

This study was to investigate the effects of ascorbic acid on the hippocampus of suckling rats in the presence of lead (Pb)-induced oxidative stress. Pregnant Sprague-Dawley rats received treatment with drinking water, divided into three groups, as follows: (1) distilled water; (2) 0.2% Pb; (3) 0.2% Pb+ascorbic acid (100mg/kg/day). Rat pups were euthanized at the age of 21days and their brain tissue was examined using light microscopy. Protein levels of Cu/Zn superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD), and catalase (CAT) in the hippocampus were determined by Western blotting. We found a significant decrease in levels of Cu/Zn SOD and Mn SOD among Pb-exposed pups. Ascorbic acid supplementation appeared to negate the decrease in protein levels for Cu/Zn SOD and Mn SOD. In the case of CAT, there was no effect from Pb administration alone and Pb plus ascorbic acid appeared to increase the levels. In histopathology, ascorbic acid decreased the number of damaged cells in cornu ammonis areas CA1, CA3, and the dentate gyrus (DG) in hippocampus. Our results showed that administration of ascorbic acid during pregnancy and lactation could ameliorate some of the oxidative damage induced by Pb exposure in the developing rat hippocampus.

Antioxidant effects of Etlingera elatior flower extract against lead acetate - induced perturbations in free radical scavenging enzymes and lipid peroxidation in rats

Background

Etlingera elatior or 'pink torch ginger' (Zingiberaceae) are widely cultivated in tropical countries and used as spices and food flavoring. The purpose of this study was to evaluate the antioxidant effects of Etlingera elatior against lead - induced changes in serum free radical scavenging enzymes and lipid hydroperoxides in rats.

Findings

Rats were exposed to lead acetate in drinking water (500 ppm) for 14 days alone or plus the ethanol extract of E. elatior (50, 100 and 200 mg/kg). Blood lead levels, lipid hydroperoxides, protein carbonyl contents and oxidative marker enzymes were estimated. Lead acetate in drinking water elicited a significant increase in lipid hydroperoxides (LPO) and protein-carbonyl-contents (PCC). There was a significant decrease in total antioxidants, superoxide dismutase, glutathione peroxidase and glutathione S-transferase levels with lead acetate treatment. Supplementation of E. elatior was associated with reduced serum LPO and PCC and a significant increase in total antioxidants and antioxidant enzyme levels.

Conclusions

The results suggest that flower extract of Etlingera elatior has powerful antioxidant effect against lead - induced oxidative stress and the extract may be useful therapeutic agent against lead toxicity. However, detailed evaluations are required to identify the active antioxidant compounds from this plant extract.

Expression profiling of Ca(2+)/calmodulin-dependent signaling molecules in the rat dorsal and ventral hippocampus after acute lead exposure

The septal and temporal poles of the hippocampus differ markedly in their anatomical organization, but whether these distinct regions exhibit differential neurochemical profiles underlying lead (Pb(2+)) neurotoxicity remains to be determined. In the present study, we examined changes in the expression of Ca(2+)/calmodulin-dependent enzymes, including calpain, calcineurin, phospho-CaMKII (Thr286) and neuronal nitric oxide synthase (nNOS), in the rat dorsal and ventral hippocampus (DH and VH) after acute Pb(2+) exposure. Five days after Pb(2+) exposure, we observed constitutively active forms of calcineurin (45 kDa and 48 kDa) in ventral portions of the hippocampus, a result consistent with the observed calpain activation that is indicated by the breakdown of spectrin in this region. Our data demonstrate that nNOS expression is significantly higher in the ventral region of the hippocampus when compared to the dorsal region, whereas phosphorylation of CaMKII (Thr286) is less pronounced in the ventral portion of the hippocampus and more pronounced in dorsal regions after acute Pb(2+) exposure. Thus, it appears likely that the ventral region of hippocampus is more vulnerable to the neurotoxic effects of Pb(2+) than the dorsal region. Taken together, the present data suggest that acute lead exposure leads to differential expression patterns of Ca(2+)/calmodulin-dependent enzymes along the dorsoventral axis of the hippocampus.

Protective effect of Etlingera elatior (torch ginger) extract on lead acetate--induced hepatotoxicity in rats

Lead is known to disrupt the biological systems by altering the molecular interactions, cell signaling, and cellular function. Exposure to even low levels of lead may have potential hazardous effects on brain, liver, kidneys and testes. The efficacy of Etlingera elatior (torch ginger) to protect hepatotoxicity induced by lead acetate was evaluated experimentally in male Sprague - Dawley rats. Rats were exposed to lead acetate in drinking water (500 ppm) for 21 days and the effects of concurrent treatment with extract of E. elatior on hepatic lipid hydroperoxides (LPO), protein carbonyl content (PCC), total antioxidants (TA), superoxide dismutase (SOD), glutathione peroxidase (GPX) and glutathione S- Transferase (GST) levels and histopathological changes in liver were evaluated. There was a significant decrease in TA and other antioxidant enzymes (p < 0.05) and increase in LPO and PCC (p < 0.05) with lead acetate ingestion. Concurrent treatment with E. elatior extract significantly reduced the LPO and PCC (p < 0.05) in serum and increased the antioxidant enzyme levels (p < 0.05) in the liver. Significant histopathological changes were seen in hepatic tissue with chronic lead ingestion. Treatment with E. elatior significantly reduced these lead-induced changes in hepatic architecture. E. elatior has also reduced the blood lead levels (BLL). Thus, there has been extensive biochemical and structural alterations indicative of liver toxicity with exposure to lead and E. elatior treatment significantly reduced these oxidative damage. Our results suggest that E. elatior has a powerful antioxidant effect against lead-induced hepatotoxicity.

The relevance of the individual genetic background for the toxicokinetics of two significant neurodevelopmental toxicants: mercury and lead

The heavy metals mercury and lead are well-known and significant developmental neurotoxicants. This review summarizes the genetic factors that modify their toxicokinetics. Understanding toxicokinetics (uptake, biotransformation, distribution, and elimination processes) is a key precondition to understanding the individual health risks associated with exposure. We selected candidate susceptibility genes when evidence was available for (1) genes/proteins playing a significant role in mercury and lead toxicokinetics, (2) gene expression/protein activity being induced by these metals, and (3) mercury and lead toxicokinetics being affected by gene knockout/knockdown or (4) by functional gene polymorphisms. The genetic background is far better known for mercury than for lead toxicokinetics. Involved are genes encoding L-type amino acid transporters, organic anion transporters, glutathione (GSH)-related enzymes, metallothioneins, and transporters of the ABC family. Certain gene variants can influence mercury toxicokinetics, potentially explaining part of the variable susceptibility to mercury toxicity. Delta-aminolevulinic acid dehydratase (ALAD), vitamin D receptor (VDR) and hemochromatosis (HFE) gene variants are the only well-established susceptibility markers of lead toxicity in humans. Many gaps remain in our knowledge about the functional genomics of this issue. This calls for studies to detect functional gene polymorphisms related to mercury- and lead-associated disease phenotypes, to demonstrate the impact of functional polymorphisms and gene knockout/knockdown in relation to toxicity, to confirm the in vivo relevance of genetic variation, and to examine gene-gene interactions on the respective toxicokinetics. Another crucial aspect is knowledge on the maternal-fetal genetic background, which modulates fetal exposure to these neurotoxicants. To completely define the genetically susceptible risk groups, research is also needed on the genes/proteins involved in the toxicodynamics, i.e., in the mechanisms causing adverse effects in the brain. Studies relating the toxicogenetics to neurodevelopmental disorders are lacking (mercury) or very scarce (lead). Thus, the extent of variability in susceptibility to heavy metal-associated neurological outcomes is poorly characterized.