Beneficial role of monoesters of meso-2,3-dimercaptosuccinic acid in the mobilization of lead and recovery of tissue oxidative injury in rats

Molecular Mechanisms of Selenium Mitigating Lead Toxicity in Chickens via Mitochondrial Pathway: Selenoproteins, Oxidative Stress, HSPs, and Apoptosis

Lead (Pb), a hazardous heavy metal, can damage the health of organisms. However, it is not clear whether Pb can damage chicken cerebellums and thalami. Selenium (Se), an essential nutrient for organisms, has a palliative effect on Pb poisoning in chickens. In our experiment, a model of chickens treated with Pb and Se alone and in combination was established to investigate the molecular mechanism of Se alleviating Pb-caused damage in both chicken cerebellums and thalami. Our morphological results indicated that Pb caused apoptotic lesions, such as mitochondrial and nuclear damage. Further, the anti-apoptotic gene Bcl-2 decreased; on the contrary, four pro-apoptotic genes (p53, Bax, Cyt c, and Caspase-3) increased under Pb treatment, meaning that Pb caused apoptosis via the p53-Cyt c-Caspase-3 pathway. Furthermore, we further demonstrated that Pb elevated four HSPs (HSP27, HSP40, HSP70, and HSP90), as well as HSP70 took part in the molecular mechanism of Pb-caused apoptosis. In addition, we found that Pb exposure led to oxidative stress via up-regulating the oxidant H2O2 and down-regulating four antioxidants (CAT, SOD, GST, and GPx). Moreover, Pb decreased three Se-containing factors (Txnrd1, Txnrd2, and Txnrd3), further confirming that Pb caused oxidative stress. Interestingly, Se supplementation reversed the above changes caused by Pb and alleviated Pb-induced oxidative stress and apoptosis. A time dependency was demonstrated for Bcl-2, Bax, and Cyt c in the cerebellums, as well as CAT, GPx, and p53 in the thalami of Pb-exposed chickens. HSP70 in cerebellums and HSP27 in thalami were more sensitive than those in thalami and cerebellums, respectively, under Pb exposure. Pb-induced apoptosis of thalami was more severe than cerebellums. In conclusion, after Pb treatment, Txnrds mediated oxidative stress, oxidative stress up-regulated HSPs, and finally, HSP70 triggered apoptosis. Se supplementation antagonized Pb-induced oxidative stress and apoptosis via the mitochondrial pathway and selenoproteins in chicken cerebellums and thalami. This study provides new information for the mechanism of environmental pollutant poisoning and the detoxification of Se on abiotic stress.

Intermittent Lead Exposure Induces Behavioral and Cardiovascular Alterations Associated with Neuroinflammation

The nervous system is the primary target for lead exposure and the developing brain appears to be especially susceptible, namely the hippocampus. The mechanisms of lead neurotoxicity remain unclear, but microgliosis and astrogliosis are potential candidates, leading to an inflammatory cascade and interrupting the pathways involved in hippocampal functions. Moreover, these molecular changes can be impactful as they may contribute to the pathophysiology of behavioral deficits and cardiovascular complications observed in chronic lead exposure. Nevertheless, the health effects and the underlying influence mechanism of intermittent lead exposure in the nervous and cardiovascular systems are still vague. Thus, we used a rat model of intermittent lead exposure to determine the systemic effects of lead and on microglial and astroglial activation in the hippocampal dentate gyrus throughout time. In this study, the intermittent group was exposed to lead from the fetal period until 12 weeks of age, no exposure (tap water) until 20 weeks, and a second exposure from 20 to 28 weeks of age. A control group (without lead exposure) matched in age and sex was used. At 12, 20 and 28 weeks of age, both groups were submitted to a physiological and behavioral evaluation. Behavioral tests were performed for the assessment of anxiety-like behavior and locomotor activity (open-field test), and memory (novel object recognition test). In the physiological evaluation, in an acute experiment, blood pressure, electrocardiogram, and heart and respiratory rates were recorded, and autonomic reflexes were evaluated. The expression of GFAP, Iba-1, NeuN and Synaptophysin in the hippocampal dentate gyrus was assessed. Intermittent lead exposure induced microgliosis and astrogliosis in the hippocampus of rats and changes in behavioral and cardiovascular function. We identified increases in GFAP and Iba1 markers together with presynaptic dysfunction in the hippocampus, concomitant with behavioral changes. This type of exposure produced significant long-term memory dysfunction. Regarding physiological changes, hypertension, tachypnea, baroreceptor reflex impairment and increased chemoreceptor reflex sensitivity were observed. In conclusion, the present study demonstrated the potential of lead intermittent exposure inducing reactive astrogliosis and microgliosis, along with a presynaptic loss that was accompanied by alterations of homeostatic mechanisms. This suggests that chronic neuroinflammation promoted by intermittent lead exposure since fetal period may increase the susceptibility to adverse events in individuals with pre-existing cardiovascular disease and/or in the elderly.

Association between Pb, Cd, and Hg Exposure and Liver Injury among Korean Adults

BACKGROUND

Exposure to lead (Pb), cadmium (Cd), and mercury (Hg) has been reported to be associated with liver-related diseases. However, studies examining the association between heavy metal exposure and liver injury in a large population are scant and characterized by inconsistent results. This study aimed to evaluate the association between levels of heavy metal exposure and liver injury in the general population.

METHODS

Data for 2953 participants aged 19 years or more obtained from the Korean National Environmental Health Survey (KoNEHS) Cycle 3 (2015-2017) were used. The associations between levels of blood or urine heavy metals (Pb, Cd, and Hg) and liver function biomarkers [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT)] were evaluated using multiple linear regression analysis.

RESULTS

Regarding the blood Pb (BPb), AST was higher in those of the 4th quartile, ALT was higher in those of the 2nd and 4th quartiles, and GGT was higher in those of the 3rd and 4th quartiles than in the 1st quartile. For urinary Cd (UCd), AST was higher in those of the 4th quartile; ALT was higher in those of the 2nd, 3rd, and 4th quartiles; and GGT was higher in the 4th quartile than in the 1st quartile. For the blood Hg (BHg), AST was higher in those of the 2nd and 4th quartile, ALT was higher in those of the 2nd, 3rd, and 4th quartiles; and GGT was higher in those of the 3rd and 4th quartiles than in the 1st quartile. There was no significant difference between urinary Hg (UHg) and liver function markers.

CONCLUSION

Heavy metal exposure showed an association with liver injury among the general adult population in Korea. Further studies are required to clarify the relationship between heavy metals and liver injury.

A potential mechanism associated with lead-induced spermatogonia and Leydig cell toxicity and mitigative effect of selenium in chicken

Lead (Pb) is a toxic heavy metal pollutants and can damage male reproductive function. Selenium (Se) possesses an ability of antagonizing Pb toxicity. However, biological events in the process of Pb toxicity and mitigative effect of Se are not well understood. The aim of present research was to investigate potential mechanism of Se against Pb toxicity from the perspective of oxidative stress, heat shock response and autophagy in the spermatogonia and Leydig cell of chicken. The cells from one-day-old male Hyline chickens were treated with Se (0.5 μmol/L) and/or Pb (20 μmol/L) for 24 h, respectively. Cell viability, cell ultrastucture, Pb and Se concentrations, testosterone level, oxidative stress indicators and relative expression of heat shock proteins (HSPs) and autophagy-related genes were measured. The results showed that spermatogonia was more tolerant to Pb than Leydig cell; cell injury was confirmed via histological assessment, cell viability and testosterone level; oxidative stress was further indicated by the decrease of catalase, glutathione peroxidase, glutathione-s-transferase and superoxide dismutase activities and the increase of malondialdehyde and reactive oxygen species contents. Pb increased expression of HSPs (27, 40, 60, 70 and 90). Meanwhile Pb induced autophagy through up-regulation of autophagy-related proteins 5, Beclin 1, Dynein, light chain 3 (LC3)-I and LC3-II and down-regulation of mammalian target of rapamycin in two type cells of chicken. However, Se intervention mitigated the aforementioned alterations caused by Pb. In conclusion, Pb led to oxidative stress, which triggered heat shock response and autophagy; Se administration mitigated reproductive toxicity of Pb through strengthening antioxidant defense in the spermatogonia and Leydig cell of chicken.

Changes in tissue gadolinium biodistribution measured in an animal model exposed to four chelating agents

PURPOSE

This study investigated the potential to reduce gadolinium levels in rodents after repetitive IV Gadodiamide administration using several chelating agents.

MATERIALS AND METHODS

The following six groups of rats were studied. Group 1: Control; Group 2: Gadodiamide only; Group 3: Meso-2,3-Dimercaptosuccinic acid (DMSA) + Gadodiamide; Group 4: N-Acetyl-L-cysteine (NAC) + Gadodiamide; Group 5: Coriandrum sativum extract + Gadodiamide; and Group 6: Deferoxamine + Gadodiamide. Brain, kidney, and blood samples were evaluated via inductively coupled plasma mass spectrometry. The brain was also evaluated histologically.

RESULTS

Kidney gadolinium levels in Groups 4 and 5 were approximately double that of Group 2 (p = 0.033 for each). There was almost no calcification in rat hippocampus for Group 4 rodents when compared with Groups 2, 3, 5 and 6.

CONCLUSION

Our preliminary study shows that excretion to the kidney has a higher propensity in NAC and Coriandrum sativum groups. It may be possible to change the distribution of gadolinium by administrating several agents. NAC may lower Gadodiamide-induced mineralization in rat hippocampus.

Lead induces DNA damage and alteration of ALAD and antioxidant genes mRNA expression in construction site workers

Oxidative stress and DNA damage are considered as possible mechanisms involved in lead toxicity. To test this hypothesis, DNA damage and expression variations of aminolevulinic acid dehydratase (ALAD), superoxide dismutase 2 (SOD2), and 8-oxoguanine DNA glycosylase 2a (OGG1-2a) genes was studied in a cohort of 100 exposed workers and 100 controls with comet assay and real-time polymerse chain reaction (PCR). Results indicated that increased number of comets was observed in exposed workers versus controls (p < 0.001). After qPCR analysis, significant down-regulation in ALAD (p < 0.0001), SOD2 (p < 0.0001), and OGG1-2a (p < 0.0001) level was observed in exposed workers versus controls. Additionally, a positive spearmen correlation was observed between ALAD versus SOD2 (r = 0.402**, p < 0.001), ALAD versus OGG1-2a (r = 0.235*, p < 0.05), and SOD2 versus OGG1-2a (r = 0.292*, p < 0.05). This study showed that lead exposure induces DNA damage, which is accompanied by an elevated intensity of oxidative stress and expression variation of lead-related gene.

Role of geraniol against lead acetate-mediated hepatic damage and their interaction with liver carboxylesterase activity in rats

In this study, the effect of geraniol (50 mg/kg for 30 d), a natural antioxidant and repellent/antifeedant monoterpene, in a rat model of lead acetate-induced (500 ppm for 30 d) liver damage was evaluated. Hepatic malondialdehyde increased in the lead acetate group. Reduced glutathione unchanged, but glutathione S-transferase, glutathione reductase, as well as carboxylesterase activities decreased in geraniol, lead acetate and geraniol + lead acetate groups. 8-OhDG immunoreactivity, mononuclear cell infiltrations and hepatic lead concentration were lower in the geraniol + lead acetate group than the lead acetate group. Serum aspartate aminotransferase and alanine aminotransferase activities increased in the Pb acetate group. In conclusion, lead acetate causes oxidative and toxic damage in the liver and this effect can reduce with geraniol treatment. However, we first observed that lead acetate, as well as geraniol, can affect liver carboxylesterase activity.

Antioxidant protection of gallic acid against toxicity induced by Pb in blood, liver and kidney of rats

The effect of the antioxidant gallic acid (GA) on Pb toxicity in blood, liver and kidney was investigated in the present study. Rats Wistar received Pb nitrate (50 mg/Kg/day, i.p., 5 days) followed by GA (13.5 mg/Kg, p.o., 3 days) or a chelating agent (EDTA, 55 mg/Kg, i.p.). As result, Pb decreased body weight, hematocrit and blood δ-aminolevulinic acid dehydratase (ALA-D) activity. In addition, high Pb levels were observed in blood and tissues, together with increased (1) lipid peroxidation in erythrocytes, plasma and tissues, (2) protein oxidation in tissues and (3) plasma aspartate transaminase (AST) levels. These changes were accompanied by decreasing in antioxidant defenses, like superoxide dismutase (SOD) activity in tissues and catalase (CAT) activity and reduced glutathione (GSH) in liver. GA was able to reverse Pb-induced decrease in body weight and ALA-D activity, as well as Pb-induced oxidative damages and most antioxidant alterations, however it did not decrease Pb bioaccumulation herein as EDTA did. Furthermore, EDTA did not show antioxidant protection in Pb-treated animals as GA did. In conclusion, GA decreased Pb-induced oxidative damages not by decreasing Pb bioaccumulation, but by improving antioxidant defenses, thus GA may be promising in the treatment of Pb intoxications.

Morphological Analysis of Reticuloendothelial System in Capuchin Monkeys (Sapajus spp.) after Meso-2,3-Dimercaptosuccinic Acid (DMSA) Coated Magnetic Nanoparticles Administration

Magnetic nanoparticles can be used for numerous in vitro and in vivo applications. However, since uptake by the reticuloendothelial system represents an obstacle for the achievement of nanoparticle diagnostic and therapeutic goals, the aim of the present study was to evaluate the uptake of dimercaptosuccinic acid coated magnetic nanoparticles by reticuloendothelial system phagocytic cells present in lymph nodes, spleen, and liver tissue and how the presence of these particles could have an impact on the morphology of these organs in capuchin monkeys (Sapajus spp.). Animals were intravenously injected with dimercaptosuccinic acid coated magnetic nanoparticles and euthanized 12 hours and 90 days post-injection. Organs were processed by transmission electron microscopy and histological techniques. Samples of spleen and lymph nodes showed no morphological changes. Nevertheless, liver samples collected 90 days post-administration showed slight morphological alteration in space of Disse. Moreover, morphometrical analysis of hepatic mitochondria was performed, suggesting a clear positive correlation between mitochondrial area and dimercaptosuccinic acid coated magnetic nanoparticles administration time. The present results are directly relevant to current safety considerations in clinical diagnostic and therapeutic uses of magnetic nanoparticles.

The role of Nrf2 in protection against Pb-induced oxidative stress and apoptosis in SH-SY5Y cells

Lead exerts severe adverse effects on the nervous system in which oxidative stress might mediate impairments. In this study, we focused on Nrf2, which has been identified to significantly influence the protection of a cellular system against many xenobiotic compounds. We found that PbAc exhibited neurotoxicity mainly through oxidant-based processes and could be inhibited by NAC and DPI in SH-SY5Y cells. As a defense response, Nrf2 was activated when exposed to PbAc, thereby inducing a rapid increase in Nrf2 nuclear accumulation, as well as Nrf2-ARE binding activities in a ROS-dependent manner. Analysis of Nrf2-regulated gene expression and protein showed that PbAc could induce the mRNA transcription of HO-1, GSTα1, GCLM, GCLC, and NQO1, as well as the protein expression of HO-1 and γ-GCS. The responses of these genes to PbAc were regulated by Nrf2. Silencing Nrf2 expression in SH-SY5Y cells inhibited PbAc-induced gene transcription and protein expression. Overexpression of Nrf2 led to decreased ROS production and cell apoptosis, as well as increased cell viability under PbAc exposure. These results indicated that the Nrf2-ARE system exhibited a protective role in Pb-induced neurotoxicity, providing potential therapeutic strategies for the prevention and treatment of Pb-related diseases.

Failure of recovery from lead induced hepatoxicity and disruption of erythrocyte antioxidant defence system in Wistar rats

Lead acetate (PbA) is one of the major environmental contaminants with grave toxicological consequences both in the developing and developed countries. The liver and erythrocyte antioxidant status and markers of oxidative were assessed. Exposure of rats to PbA led to significant decline (p < 0.05) in hepatic and erythrocyte glutathione peroxidase (GPx), glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), and reduced glutathione (GSH) content. Similarly, malondialdehyde (MDA) and H(2)O(2) concentrations were significantly (p < 0.05) elevated. Histopathology and immunohistology of liver of rats exposed to PbA showed focal areas of necrosis and COX-2 expression after 6 weeks of PbA withdrawal. Taken together, hepatic and erythrocytes antioxidant defence system failed to recover after withdrawal of the exposed PbA for the period of the study. In conclusion, experimental animals exposed to PbA did not recover from hepatotoxicity and disruption of erythrocyte antioxidant defence system via free radical generation and oxidative stress.

Environmental factors and unhealthy lifestyle influence oxidative stress in humans--an overview

Oxygen is the most essential molecule for life; since it is a strong oxidizing agent, it can aggravate the damage within the cell by a series of oxidative events including the generation of free radicals. Antioxidative agents are the only defense mechanism to neutralize these free radicals. Free radicals are not only generated internally in our body system but also trough external sources like environmental pollution, toxic metals, cigarette smoke, pesticides, etc., which add damage to our body system. Inhaling these toxic chemicals in the environment has become unavoidable in modern civilization. Antioxidants of plant origin with free radical scavenging properties could have great importance as therapeutic agents in several diseases caused by environmental pollution. This review summarizes the generation of reactive oxygen species and damage to cells by exposure to external factors, unhealthy lifestyle, and role of herbal plants in scavenging these reactive oxygen species.

The effect of sodium selenite on lead induced cognitive dysfunction

The effect of lead (Pb) on spatial memory and hippocampal long-term potentiation (LTP) as a key risk factor has been widely recognized and the oxidative damage has been proposed as a possible mechanism of lead neurotoxicity. Selenium (Se) is a nutritionally essential trace element with known antioxidant potential. In this study we investigated the effect and the underlying mechanisms of Se supplementary on Pb induced cognition and synaptic plasticity impairment. Lactating Sprague-Dawley rats (SD rats) were randomly divided to four groups: 0ppm lead acetate (Pb); 0ppm Pb and 0.2ppm sodium selenite (Se); 100ppm Pb; 100ppm Pb and 0.2ppm Se. Lactating rats were treated with or without Pb and/or Se throughout lactation until weaning. The levels of hippocampal LTP, the spatial memory, the apoptosis of hippocampal neurons, the levels of lactate dehydrogenase (LDH) release, and the serum level of superoxide dismutase (SOD) and malondialdehyde (MDA) were assayed. It had been observed that in Pb group the spatial memory, the induce level of LTP, the serum SOD level decreased, the LDH release level, the neurons apoptosis level, the serum MDA level increased, while in the Se supplements groups, the spatial memory, the induce level of LTP increased significantly. Compared with the Pb group, Se supplements shown down regulated the level of LDH, the neurons apoptosis and the serum MDA, and up regulated the level of serum SOD. We could draw the conclusion that Se supplements could alleviate toxic effect of lead on hippocampal LTP and spatial memory. The treated with selenium around 0.2ppm may protect against spatial memory dysfunction induced by lead exposure.

Flaxseed oil as a neuroprotective agent on lead acetate-induced monoamineric alterations and neurotoxicity in rats

Lead remains a considerable occupational and public health problem, which is known to cause a number of adverse effects in both man and animals. Here, the neuroprotective effect of flaxseed oil (1,000 mg/kg) on lead acetate (20 mg/kg) induced alternation in monoamines and brain oxidative stress was examined in rats. The levels of lead, dopamine (DA), norepinephrine (NE), serotonin (5-HT), lipid peroxidation, nitrite/nitrate (NO), and glutathione (GSH) were determined; also, the activity of acetylcholinesterase (AChE) and Na(+)-K(+)-ATPase were estimated on different brain regions of adult male albino rats. The level of lead was markedly elevated in different brain regions of rats. This leads to enhancement of lipid peroxidation and NO production in brain with concomitant reduction in AChE activity and GSH level. In addition, the levels of DA, NE, and 5-HT were decreased in the brain. These findings were associated with BAX over expression. Treatment of rats with flaxseed oil induced a marked improvement in most of the studied parameters as well as the immunohistochemistry features. These data indicated that dietary flaxseed oil provide protection against lead-induced oxidative stress and neurotoxic effects.

Protective role of puerarin on lead-induced alterations of the hepatic glutathione antioxidant system and hyperlipidemia in rats

Puerarin (PU), a natural flavonoid, has been reported to have many benefits and medicinal properties. The aim of the present study was to investigate the effects of puerarin on hepatic oxidative stress and hyperlipidemia in rats exposed to lead. Our data showed that puerarin significantly prevented lead-induced hepatotoxicity, indicated by both diagnostic indicators of liver damage (serum aminotransferase levels) and histopathological analysis. Moreover, lead-induced profound elevation of ROS production and oxidative stress, as evidenced by increasing of lipid peroxidation level, reducing of GPx, GST, GR and GCL activities and depleting of intracellular reduced GSH level in liver, were suppressed by treatment with puerarin. Furthermore, the increase of serum cholesterol, triglycerides and LDL induced by lead was effectively suppressed by puerarin. The HDL level in the lead treatment rats was also increased by puerarin. Western blot analysis showed that puerarin remarkably inhibited hyperlipidemia by regulating the expression of cholesterol 7a-hydroxylase (CYP7A1), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) and low-density lipoprotein receptor (LDL-R) in liver of lead treated rats. Altogether, these results suggest that puerarin could protect the lead-induced liver injury and hyperlipidemia by reducing ROS production, renewing the activities of antioxidant enzymes and influencing expression of hepatic lipid biosynthesis and metabolism genes.

Inhibition effect of poly(γ-glutamic acid) on lead-induced toxicity in mice

The objectives of this study were to evaluate the efficiency in treatment of lead-induced intoxication in mice with γ-PGA as chelating agent and compare with the drug (meso-2,3-dimercaptosuccinic acid). The results showed the incorporation of γ-PGA at 200 and 400 mg/kg could reduce the accumulation of lead in the liver, heart, and testis; however, the latter was more effective in decreasing the lead content in the kidney and spleen. Nevertheless, both doses failed to inhibit the lead accumulation in the lung and brain. Additionally, both doses of γ-PGA could reduce TBARs in the kidney and brain, as well as elevate δ-aminolevulinic acid dehydrase (δ-ALAD) activity in blood and decrease glutamic pyruvic transaminase (GPT) and lactic dehydrogenase (LDH) activities in the serum. For hematological parameters, both white blood cells (WBCs) and hematocrite (HCT) were raised by 400 mg/kg of γ-PGA, while for both doses of γ-PGA, a slight decline in hemoglobin (HGB), mean cell volume (MCV), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC) was observed, with the red blood cells (RBCs) being unaffected.

Thiamine reduces tissue lead levels in rats: mechanism of interaction

Lead (Pb) toxicity has been a serious concern in industrialized societies because of its association with functional deficits in nervous, haematopoietic and renal systems. Several studies have shown beneficial effects of thiamine on Pb toxicity. It is speculated that Pb chelation by thiamine may be a possible mechanism. However, the exact nature of these interactions remained elusive. In the present study we have characterized the interaction of Pb with thiamine using UV-Vis as well as fluorescence spectroscopic methods and studied the effect of thiamine treatment on blood and tissue Pb levels during simultaneous or post-exposure to Pb in rat model. The spectroscopic studies revealed that Pb interacts with the pyrimidine ring of thiamine, leading to its solubilization at physiological pH. Further, thiamine reduced the Pb levels in blood, kidney and bone during both simultaneous and post-exposure Pb treatment. Interestingly, thiamine appears to prevent the accumulation of Pb in bone during simultaneous treatment. Together these results suggest that pyrimidine ring of thiamine mediates its interaction with Pb, leading to the prevention of its accumulation and/or increased clearance from tissues.

Co-administration of monoisoamyl dimercaptosuccinic acid and Moringa oleifera seed powder protects arsenic-induced oxidative stress and metal distribution in mice

Arsenic contamination of groundwater in the West Bengal basin in India is unfolding as one of the worst natural geo-environmental disasters to date. Chelation therapy with chelating agents is considered to be the best known treatment against arsenic poisoning; however, they are compromised with certain serious drawbacks/side-effects. Efficacy of combined administration of Moringa oleifera (M. oleifera) (English: Drumstick tree) seed powder, a herbal extract, with a thiol chelator monoisoamyl DMSA (MiADMSA) post-arsenic exposure in mice was studied. Mice were exposed to 100 ppm arsenic in drinking water for 6 months, followed by 10-days treatment with M. oleifera seed powder (500 mg/kg, orally through gastric gavage, once daily), MiADMSA (50 mg/kg, intraperitoneally, once daily) either individually or in combination. Arsenic exposure caused significant decrease in blood glutathione, delta-aminolevulinic acid dehydratase (ALAD), accompanied by increased production of reactive oxygen species in blood and soft tissues. Significant inhibition of superoxide dismutase, catalase, and glutathione peroxidase activities in tissues (liver in particular) along with significant increase in thiobarbituric acid reactive substances and metallothionein levels in arsenic intoxicated mice was also noted. Combined administration of MiADMSA with M. oleifera proved better than all other treatments in the recovery of most of the above parameters accompanied by more pronounced depletion of arsenic. The results suggest that concomitant administration of M. oleifera during chelation treatment with MiADMSA might be a better treatment option than monotherapy with the thiol chelator in chronic arsenic toxicity.

Monoisoamyl dimercaptosuccinic acid abrogates arsenic-induced developmental toxicity in human embryonic stem cell-derived embryoid bodies: comparison with in vivo studies

The ability of human embryonic stem (ES) cells to differentiate into the three germ layers has proposed its application in studying human developmental toxicity in vitro. In the current study we investigated if the prompted application could be utilized to evaluate the efficacy of a newly developed arsenic antidote, monoisoamyl dimercaptosuccinic acid (MiADMSA) against arsenic (III) and if the results obtained in vitro were in concordance with the animal model for studying developmental toxicity. On the basis of real time PCR (qRT-PCR) and cytotoxicity analysis of human embryoid bodies (EBs), we observed that arsenic (III) caused a significant down regulation of gene expression in all the three germ layers, which could be correlated with high mortality, visceral and skeletal defects in pups. Reversal of arsenic-induced dysfunctioning could be observed with concomitant treatment of MiADMSA in vitro and in vivo, indicating ES-EB model could provide toxicity information similar to in vivo model. IR spectroscopy further suggested that MiADMSA bind to arsenic to form adduct, which prevents arsenic from exerting its toxic effect in both models. To our knowledge this study provides first experimental evidence suggesting human ES cells could be utilized in studying the efficacy of drugs in a comparable manner with animal models. We conclude that the ES-EB model seems to be an effective, faster, cost effective method for predicting efficacy of a drug.

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.

The effect of adrenomedullin on rats exposed to lead

Adrenomedullin (AdM) was originally discovered as a vasorelaxant peptide. The antioxidative properties of AdM have been reported recently. Through its antioxidative effect, adrenomedullin can protect organs from damage induced by stressors. Lead, commonly detected in air, soil, water and food, is a major source of oxidative stress. The effect of AdM in the liver of rats exposed to lead was investigated. Twenty-four female Wistar rats were divided into four groups: a control group (C), adrenomedullin group (AdM), lead (Pb) group and lead + adrenomedullin (Pb + AdM) group. In the Pb-treated groups, the animals were exposed to lead in drinking water containing 250 ppm PbCl2 for 4 weeks. In the AdM-treated group, the animals received an i.p. injection of AdM (3000 ng kg(-1) body weight) in the third week of lead treatment for 1 week. The activities of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and the level of malondialdehyde (MDA) were determined in the liver of rats. Histological changes in the liver were examined by light and electron microscopy as well. The MDA levels were increased significantly in the Pb-treated groups, but in the Pb + AdM group the MDA levels were decreased significantly when compared with the Pb group. AdM reduced hepatic damage in the Pb + AdM group, but the difference in the total histopathological scores between the Pb and Pb + AdM groups was not significant. When the results are taken together, it can be concluded that AdM may have protective or compensating effects in lead toxicity.

Response of lead-induced oxidative stress and alterations in biogenic amines in different rat brain regions to combined administration of DMSA and MiADMSA

The present study was planned to investigate if combined administration of meso-2,3-dimercaptosuccinic acid (DMSA) and monoisoamyl DMSA (MiADMSA) could achieve better recovery in the altered biochemical parameters suggestive of brain oxidative stress and depletion of lead from blood and brain following acute lead exposure. Male Wistar rats were exposed to lead nitrate (50 mg/kg, i.p., once daily for 5 days) followed by treatment with the above chelating agents using two different doses of 25 or 50 mg/kg (orally) either alone and in combination once daily for five consecutive days. Lead exposure resulted in the significant inhibition of delta-aminolevulinic acid dehydratase activity and depletion of glutathione (GSH) in blood. These changes were accompanied by significant reduction in blood hemoglobin, RBC levels and superoxide dismutase and catalase activities. Significant increase in blood reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) levels were noted. We observed marked increase in brain ROS level while GSH/oxidized glutathione ratio showed significant decrease accompanied by a significant increase in blood and brain lead concentration. The levels of norepinephrine, dopamine and serotonin in different brain regions were also altered on lead exposure. Co-administration of DMSA and MiADMSA particularly at the lower dose was most effective in the recovery of lead-induced changes in the hematological variables and oxidative stress and resulted in more pronounced depletion of lead from blood and brain compared to monotherapy with these chelators. On the other hand, combined administration of MiADMSA (50 mg/kg) in combination with DMSA (25 mg/kg each) had additional beneficial effect over the individual effect of chelating agent in the recovery of altered levels of brain biogenic amines. The study suggests that administration of MiADMSA is generally a better lead chelator than DMSA while combined administration of DMSA and MiADMSA might be a better treatment option compared to monotherapy at least in the removal of lead from the target tissues.

Efficacy of diphenyl diselenide against cerebral and pulmonary damage induced by cadmium in mice

This study was designed to examine if diphenyl diselenide (PhSe)(2), an organoselenium compound, attenuates pulmonar and cerebral oxidative stress caused by sub-chronic exposure to CdCl(2). Male adult Swiss albino mice received CdCl(2) (10 micromol/kg, subcutaneously), 5 times/week, for 4 weeks. (PhSe)(2) (10 micromol/kg or 20 micromol/kg, orally) was given concomitantly with CdCl(2) to mice. A number of toxicological parameters in lung and brain of mice were examined including delta-aminolevulinic acid dehydratase (delta-ALA-D), superoxide dismutase (SOD) and catalase activities, lipid peroxidation, non-protein thiols (NPSH) and ascorbic acid content. Na(+),K(+)-ATPase activity, acetylcholinesterase (AChE) activity, [(3)H]glutamate uptake and [(3)H]glutamate release were also carried out in brain. Cadmium concentration and histopathological analysis were carried out in lung tissue. (PhSe)(2) at the dose of 20 micromol/kg protected the inhibition of delta-ALA-D, SOD and CAT activities, the reduction of vitamin C content and the increase of lipid peroxidation levels caused by CdCl(2) in lungs. At 10 micromol/kg, (PhSe)(2) protected cerebral AChE and CAT activities inhibited by CdCl(2). There were no histopathological alterations in the lung of mice after CdCl(2) exposure. The pulmonary cadmium concentration was higher (2.8-fold) in the group exposed to CdCl(2) than in control mice. (PhSe)(2) at dose of 20 micromol/kg reduced cadmium concentration towards the control level. The results suggest that oral administration of (PhSe)(2) attenuated the oxidative damage induced by CdCl(2) in lung and brain of mice.

Reversal of lead-induced neuronal apoptosis by chelation treatment in rats: role of reactive oxygen species and intracellular Ca(2+)

Lead, a ubiquitous and potent neurotoxicant causes several neurophysiological and behavioral alterations. Toxic properties of lead have been attributed to its capability to mimic calcium and alter calcium homeostasis. In this study, we have addressed the following issues: 1) whether chelation therapy could circumvent the altered Ca(2+) homeostasis and prevent neuronal death in chronic lead-intoxicated rats, 2) whether chelation therapy could revert altered biochemical and behavioral changes, 3) whether combinational therapy using two different chelating agents was more advantageous over monotherapy in lead-treated rats, and 4) what could be the mechanism of neuronal apoptosis. Results indicated that lead caused a significant increase in reactive oxygen species, neuronal nitric-oxide synthetase, 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 altered bcl(2)/bax ratio indicated mitochondrial-dependent apoptosis. Most of these alterations reverted toward normal level following combination therapy over monotherapy with calcium disodium EDTA (CaNa(2)EDTA) or monoisoamyl meso-2,3-dimercaptosuccinic acid (MiADMSA). It could be concluded from our present results that combined therapy with CaNa(2)EDTA and MiADMSA might be a better treatment protocol than monotherapy with these chelators in lead-induced neurological disorders. We for the first time report the role of Ca(2+) in regulating neurological dystrophy caused by chronic lead exposure in rats and its recovery with a two-course treatment regime of mono or combination therapy.

Response of arsenic-induced oxidative stress, DNA damage, and metal imbalance to combined administration of DMSA and monoisoamyl-DMSA during chronic arsenic poisoning in rats

Arsenic and its compounds cause adverse health effects in humans. Current treatment employs administration of thiol chelators, such as meso-2,3-dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercaptopropane 1-sulfonate (DMPS), which facilitate its excretion from the body. However, these chelating agents are compromised by number of limitations due to their lipophobic nature, particularly in case of chronic poisoning. Combination therapy is a new approach to ensure enhanced removal of metal from the body, reduced doses of potentially toxic chelators, and no redistribution of metal from one organ to another, following chronic metal exposure. The present study attempts to investigate dose-related effects of two thiol chelators, DMSA and one of its new analogues, monoisoamyl dimercaptosuccinic acid (MiADMSA), when administered in combination with the aim of achieving normalization of altered biochemical parameters suggestive of oxidative stress and depletion of inorganic arsenic following chronic arsenic exposure. Twenty-five adult male Wistar rats were given 25 ppm arsenic for 10 weeks followed by chelation therapy with the above chelating agents at a dose of 0.3 mmol/kg (orally) when administered individually or 0.15 mmol/kg and 0.3 mmol/kg (once daily for 5 consecutive days), respectively, when administered in combination. Arsenic exposure led to the inhibition of blood delta-aminolevulinic acid dehydratase (ALAD) activity and depletion of glutathione (GSH) level. These changes were accompanied by significant depletion of hemoglobin, RBC and Hct as well as blood superoxide dismutase (SOD) acitivity. There was an increase in hepatic and renal levels of thiobarbituric acid-reactive substances, while GSH:GSSG ratio decreased significantly, accompanied by a significant increase in metallothionein (MT) in hepatocytes. DNA damage based on denaturing polyacrylamide gel electrophoresis revealed significant loss in the integrity of DNA extracted from the liver of arsenic-exposed rats compared to that of normal animals. These changes were accompanied by a significant elevation in blood and soft-tissue arsenic concentration. Co-administration of DMSA and MiADMSA at lower dose (0.15 mmol/kg) was most effective not only in reducing arsenic-induced oxidative stress but also in depleting arsenic from blood and soft tissues compared to other treatments. This combination was also able to repair DNA damage caused following arsenic exposure. We thus recommend combined administration of DMSA and MiADMSA for achieving optimum effects of chelation therapy.

Changes in brain biogenic amines and haem biosynthesis and their response to combined administration of succimers and Centella asiatica in lead poisoned rats

This study was designed to investigate the therapeutic potential of meso 2,3-dimercaptosuccinic acid (DMSA) and one of its monoesters, monoisoamyl DMSA (MiADMSA), individually or when administered in combination with an extract of Centella asiatica against experimental lead intoxication in rats. Biochemical variables indicative of alterations in the central nervous system and haem biosynthesis were investigated to determine the toxicity in male Wistar rats. Thirty five rats were exposed to 0.2% lead acetate for 10 weeks, followed by 10 days of treatment with DMSA and MiADMSA (50 mg kg(-1), i.p., once daily) alone and in combination with C. asiatica (200 mg kg(-1), p.o., once daily). Biochemical variables indicative of oxidative stress and brain biogenic amines, along with lead concentration in blood and brain, were measured. Lead exposure caused a significant depletion of blood and brain delta-aminolevulinic acid dehydratase (ALAD) activity, an important enzyme of the haem biosynthesis pathway, and glutathione (GSH) level. These changes were accompanied by a marked increase in reactive oxygen species (ROS) level, thiobarbituric acid reactive substances (TBARS), delta-aminolevulinic acid synthase (ALAS) and oxidized glutathione (GSSG) activity in blood and brain. Significant depletion of brain noradrenaline (norepinephrine, NE), 5-hydroxytryptamine (5-HT), dopamine (DA) and acetylcholinesterase (AChE) also were observed following lead exposure. Also seen was a significant depletion in brain glutathione peroxidase (GPx), glutathione S-transferase (GST) and monoamine oxidase activity, as well as blood and brain superoxide dismutase (SOD) activity. These biochemical changes were correlated with an increased uptake of lead in blood and brain. Combined administration of MiADMSA and C. asiatica was most effective in reducing these alterations, including biogenic amines, besides reducing body lead burden, compared with individual treatment with MiADMSA. Certain other biochemical variables responded favourably to combination therapy and monotherapy with MiADMSA. Thus, supplementation of C. asiatica during chelation could be recommended for achieving optimum effects of chelation therapy.