Pb-exposed Rats Research Articles

Gonadal health benefits of black cumin (Nigella sativa) seed oil on chronic lead-exposed male Wistar rats

Lead (Pb) is a highly toxic heavy metal that can cause harm even at extremely low concentrations and damage various organs, including those of reproduction. Medical herbs like Nigella sativa include antioxidants that have been shown to enhance spermatogenesis and male fertility. This research aimed to investigate the gonadal health benefits of Nigella sativa seed oil (NSO) as an antidote in male rats exposed to chronic Pb toxicity. Forty rats were divided into four groups: a control group, a group exposed to Pb acetate (75 mg/kg body weight), a group given NSO (1ml/kg feed), and a group exposed to Pb acetate (75 mg/kg body weight) along with NSO (1ml/kg feed). Pb was administered through water, while NSO with fed for 16 weeks. Rats were euthanized, blood was obtained, and serum was prepared to perform hormonal study. Sperm concentration and motility along with testis weight and diameter were measured. The testes were collected for histology. The findings indicated a significant drop in serum concentrations of testosterone and thyroxin (T4) in Pb-exposed rats, whereas NSO demonstrated a remarkable ability to restore these hormone levels. Moreover, Pb exposure led to a notable reduction in sperm motility, sperm concentration, testis weight, and testis diameter, accompanied by seminiferous tubule degeneration. However, the administration of NSO effectively counteracted the adverse effects induced by chronic Pb exposure in rats. Together, these findings revealed the gonadoprotective effects of NSO against lead toxicity, suggesting its preventive as well as therapeutic potential in preserving the testicular function of rats exposed to chronic Pb toxicity.

Comparative protective activity of aqueous Zingiber officinale root and Theobroma cacao seed extracts on lead acetate-induced cerebellar toxicity in rats

BackgroundLead has been associated with human activities since time immemorial and is reported to induce antioxidant and neurobehavioral impairments in animals and humans. The present study examined and compared the protective activity of aqueous Zingiber officinale root (ZO) and Theobroma cacao seed (TC) extracts against Pb-induced cerebellar toxicity. MethodologyTwenty-four rats, divided into four equal groups, received as follows: 1 ml H2O/day; 100 mg.kg-1 body weight (BW)/day of lead acetate (Pb) only; 500 mg.kg-1 BW/day of ZO and 100 mg.kg-1 BW/day of Pb; and 500 mg.kg-1 BW/day of TC and 100 mg.kg-1 BW/day of Pb, orally for twenty-eight days. Afterwards, neurobehavioural tests were conducted and the harvested cerebellums were used for antioxidant enzymes activity, Pb and lipid peroxidation concentrations as well as histological evaluations, following the sacrifice of experimental rats. ResultsFindings revealed significant neurobehavioural and antioxidant enzymes impairment, elevated levels of cerebellar Pb and lipid peroxidation, and microstructure alterations in the cerebellum of Pb-exposed rats. Although pretreatment with ZO and TC significantly attenuated these Pb-induced effects, ZO was more potent in its neuroprotective activity than TC. ConclusionTaken together, ZO and TC can be further developed as novel neuroprotective agents against Pb toxicity.

Cognitive- and memory-enhancing activity of Cinnamon (Cinnamomum zeylanicum) aqueous extract in lead acetate-exposed rats

BackgroundLead (Pb) exposure has been linked to reduced academic performance, lower IQ, cognitive and memory impairments, and other psychiatric conditions such as depression and anxiety. Natural antioxidants and dietary sources of phytochemicals, including Cinnamomum zeylanicum (CZ), have been investigated to possibly replace the current adverse reacting drugs used to treat Pb poisoning. Consequently, this study evaluated the activity of CZ against Pb-mediated neurotoxicity. MethodsWistar rats were assigned into six groups (n = 8) namely: Control; Lead acetate (Pb; 100 mg kg−1 body weight [BW]); CZ-pre-treated groups (CZ1 [200 mg.kg−1 BW] + Pb and CZ2 [400 mg kg−1 BW] + Pb); and CZ-only groups (CZ1 and CZ2). After 28 days, neurobehavioral, antioxidant, lipid peroxidation, nitric oxide, and Pb concentration levels, as well as hippocampal and cerebral histology, were evaluated. ResultsFindings showed a significant reduction (p < 0.05) in final body and whole brain weights, cognition, and memory impairments, dysregulation of antioxidant enzymes, lipid peroxidation, and elevated nitric oxide as well as high Pb concentrations in the hippocampus and cerebrum of Pb-exposed rats following comparison to the control and CZ pretreated rats. Histological findings revealed morphological alterations with vacuolated tissue architecture in the hippocampus and cerebrum of Pb-exposed rats while the rats pre-treated with CZ showed similar morphology to the control rats. ConclusionAltogether, the findings showed that CZ was not toxic to the rats but protected against Pb toxicity, mediated possibly through its potent antioxidant, nitric oxide scavenging, and metal chelation activity.

Effect of Ginkgo biloba administration to apoptosis in rat (Rattus novergicus) brain cells exposed to Plumbum.

Lead (Plumbum/Pb) has been identified as a potential cause of Parkinson's disease as well as possibly contributing to disease progression. Ginkgo biloba extract has been widely used to prevent and treat stroke which prevents brain cell apoptosis and neuroinflammation. This has been shown to be beneficial in cognitive recovery in stroke incidents. This study aimed to determine the effect of G. biloba on the expression of superoxide dismutase (SOD), malondialdehyde (MDA), and apoptosis-inducing factor (AIF) in the brain cells of rats (Rattus novergicus) exposed to Plumbum. The experimental animals used were 36 male white rats divided into 4 groups with different treatments of Plumbum and G. biloba at varying doses for 42 days, after which the brains were collected for examination of SOD, MDA, and AIF expressions using immunohistochemical methods and analyzed using analysis of variance and Duncan's test. Plumbum administration caused a significant decrease in SOD expression and an increase in MDA and AIF expressions (p < 0.05). Ginkgo biloba administration significantly increased SOD expression and decreased MDA and AIF expressions (p < 0.05), with optimal increases in SOD, decreases in MDA, and modulation of AIF observed in the group exposed to 50 mg/kg BW Pb and 300 mg/kg BW G. biloba. Preventive administration of G biloba increased SOD expression, and reduced MDA and AIF expressions in Pb-exposed rats, with an optimal dose of 300 mg/kg BW, suggesting its potential as an affordable drug to prevent brain cell death-related diseases.

Kaempferol improves Pb-induced cognitive impairments via inhibiting autophagy

Kaempferol (Kam) is a flavonoid antioxidant found in fruits and vegetables, which was discovered as neuroprotective antioxidants. Lead (Pb), an environmental pollution, could induce learning and memory deficits. Nevertheless, little is known about the mechanisms underlying Kam actions in Pb-induced learning and memory deficits. In this study, we investigated the effects of Kam on Pb-induced cognitive deficits. Pb-exposed rats were treated with 50 mg/kg Kam from postnatal day (PND) 30 to PND 60. Then, Y-maze and Morris water maze have been used to detect the spatial memory in all groups of rats. Hematoxylin and eosin (HE) staining and Nissl staining were used to analyze the neuronal structure damages. The results found Kam treatment improved the learning and memory ability and alleviated hippocampal neuronal pathological damages. Besides, Kam could significantly reverse the synaptic transmission related protein expression including PSD95 and NMDAR2B. Further research found that Kam downregulated autophagy markers, P62, ATG5, Beclin1, and LC3-II. Furthermore, 3-MA, autophagy inhibitor, increased the levels of NMDAR2B and PSD95 in Pb-induced PC12 cells, indicating Kam alleviated Pb-induced neurotoxicity through inhibiting autophagy activation. Our results showed that Kam could ameliorate Pb-induced cognitive impairments and neuronal damages by decreasing Pb-induced excess autophagy accumulation.

Sesamin mitigates lead-induced behavioral deficits in male rats: The role of oxidative stress

Lead (Pb) is a well-known toxic pollutant that has negative effects on behavioral functions. Sesamin, a phytonutrient of the lignan class, has shown neuroprotective effects in various neurological disorder models. The present study was undertaken to evaluate the putative protective effects of sesamin against Pb-induced behavioral deficits and to identify the role of oxidative stress in male rats. The rats were exposed to 500 ppm of Pb acetate in their drinking water and simultaneously treated orally with sesamin at a dose of 30 mg/kg/day for eight consecutive weeks. Standard behavioral paradigms were used to assess the behavioral functions of the animals during the eighth week of the study. Subsequently, oxidative stress factors were evaluated in both the cerebral cortex and hippocampal regions of the rats. The results of this study showed that Pb exposure triggered anxiety-/depression-like behaviors and impaired object recognition memory, but locomotor activity was indistinguishable from the normal control rats. These behavioral deficiencies were associated with suppressed enzymatic and non-enzymatic antioxidant levels, and enhanced lipid peroxidation in the investigated brain regions. Notably, correlations were detected between behavioral deficits and oxidative stress generation in the Pb-exposed rats. Interestingly, sesamin treatment mitigated anxio-depressive-like behaviors, ameliorated object recognition memory impairment, and modulated oxidative-antioxidative status in the rats exposed to Pb. The results suggest that the anti-oxidative properties of sesamin may be one of the underlying mechanisms behind its beneficial effect in ameliorating behavioral deficits associated with Pb exposure.

Role of Nitric Oxide, TNF-α and Caspase-3 in Lead Acetate-Exposed Rats Pretreated with Aqueous Rosmarinus officinalis Leaf Extract.

Lead (Pb) toxicity is a worldwide significant public health challenge causing several neurological disorders. Reports indicate that plants rich in antioxidants, such as Rosmarinus officinalis (RO), can counteract Pb accumulation and its toxicity in the brain. Due to a dearth of literature evidence demonstrating the protective activity of RO against Pb toxicity, this study investigated such activity in Wistar rats. Thirty-six Wistar rats were allocated into six groups (n=6), namely I (control), II (lead acetate [Pb]; 100 mg/kg b.w.), III (100 mg/kg of RO and 100 mg/kg of Pb), IV (200 mg/kg of RO and 100 mg/kg of Pb), V (100 mg/kg b.w. of RO) and VI (200 mg/kg b.w. of RO). After 28 days, neurobehavioural, antioxidant, lipid peroxidation, apoptotic and inflammatory activities as well as the histology of the cerebellum were evaluated. Body weight, locomotion and exploration as well as antioxidant enzymes were significantly (p < 0.05) decreased in Pb-exposed rats when compared to control. Conversely, lipid peroxidation, nitric oxide, tumour necrosis factor-alpha and caspase-3 activities were significantly (p < 0.05) upregulated in the Pb-exposed rats when compared to control. These parameters were, however, significantly (p<0.05) attenuated in the RO-pretreated rats when compared to Pb-exposed rats. Cerebellar histology of the Pb-exposed rats showed severe degeneration of the Purkinje cells whereas the RO-pretreated rats showed better cerebellar architecture. These findings demonstrate that the neuroprotective activity of RO is facilitated via its effective antioxidant, anti-inflammatory and anti-apoptotic effects.

Metabolomics insights into the effects of pre-pregnancy lead exposure on bone metabolism in pregnant rats

Today's women of childbearing age with a history of high lead (Pb) exposure in childhood have large Pb body burdens, which increases Pb release during pregnancy by promoting bone Pb mobilisation. The purpose of this study was to investigate the metabolic mechanisms underlying bone Pb mobilisation and explore the bone metabolism-related pathways during pregnancy. Drinking water containing 0.05% sodium acetate or Pb acetate was provided to weaned female rats for 4 weeks followed by a 4-week washout period, and then rats were co-caged with healthy males of the same age until pregnancy. Blood and bone tissues of the female rats were collected at gestational day (GD) 3 (early pregnancy), GD 10 (middle pregnancy), and GD 17 (late pregnancy), respectively. Pb and calcium concentrations, biomarkers for bone turnover, bone microstructure, serum metabolomics, and metabolic indicators were intensively analyzed. The results demonstrated that pre-pregnancy Pb exposure elevated blood lead levels (BLLs) at GD17, accompanied by a negative correlation between BLLs and trabecular bone Pb levels. Meanwhile, Pb-exposed rats had low bone mass and aberrant bone architecture with a larger number of mature osteoclasts (OCs) compared to the control group. Moreover, the metabolomics uncovered that Pb exposure caused mitochondrial dysfunction, such as enhanced oxidative stress and inflammatory response, and suppressed energy metabolism. Additionally, the levels of ROS, MDA, IL-1β, and IL-18 involved in redox and inflammatory pathways of bone tissues were significantly increased in the Pb-exposed group, while antioxidant SOD and energy metabolism-related indicators including ATP levels, Na+-K+-ATPase, and Ca2+-Mg2+-ATPase activities were significantly decreased. In conclusion, pre-pregnancy Pb exposure promotes bone Pb mobilisation and affects bone microstructure in the third trimester of pregnancy, which may be attributed to OC activation and mitochondrial dysfunction.

Lipoic acid abates testis lead accumulation, sperm-endocrine deficits, testicular oxidative inflammation and apoptosis and modulates gene expression of Bax and Bcl-2 in rats

The current study explored whether ALA could prevent testis Pb accumulation and Pb-induced oxidative testicular toxicity in rats. Adult male rats were randomly divided and administered ALA (25 mg/kg/day) and/or Pb (Pb acetate, 20 mg/kg/day) in Control group, ALA group, Pb group, and ALA + Pb group for 4 weeks consecutively. Pb exposure significantly increased Pb accumulation in the testes and blood of Pb-exposed rats compared to the control. Pb caused marked deficits in sperm count, motility along with elevated abnormal sperm cells, while serum testosterone, follicle stimulating hormone (FSH) and leutenizing hormone (LH) levels reduced prominently in comparison to the control. It remarkably depressed the testicular activities of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), as well as levels of interleukin-4 (IL-4) and interleukin-10 (IL-10), whereas malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) increased significantly compared to the control. The levels of caspase-3, capsase-9, and the PCR gene expression of Bax and Bcl2 were adversely altered with alterations in testis histology. Interestingly, the co-treatment with ALA blocks Pb accumulation in the testis and blood. It inhibited the Pb-induced alterations in reproductive indices and reversed the oxidative stress-mediated inflammatory stress, apoptotic signaling and histopathological abrasions. The findings reveal that ALA could abrogate Pb-induced testicular toxicity through blocking testicular oxidative inflammation and apoptosis in rats.

Pharmacological effect of Argyrolobium roseum (Camb.) Jaub & Spach extracts against lead-induced toxicity in rats.

Argyrolobium roseum (Camb.) Jaub & Spach (Papilionaceae) is a medicinal plant, cultivated in northern areas of Pakistan. The consumption of trace minerals (lead) is very toxic to the vital organs of the body, therefore the overcome of these minerals is very necessary. In this regard, this study aimed to assess the potential pharmacological effect of aqueous and ethanolic extract of Argyrolobium roseum (Camb.) Jaub & Spach against pb-induced oxidative stress, histological changes in Pb-induced rats' liver and kidney, and anti-inflammatory effect. The metal concentrations in liver and kidney homogenates were measured through atomic absorption spectrophotometer. The antioxidant activity was measured through DPPH and FRAP assay. Pb concentrations were significantly higher in liver and kidney homogenates after injection of Pb acetate was given intraperitoneally (45.2 ± 6.8 and 58.8 ± 7.9, respectively; p < .0001). The level of Pb in liver and kidney homogenates was significantly reduced by aqueous and ethanolic extracts of Argyrolobium roseum (Camb.) Jaub & Spach. The Pb + Aq-600 mg/kg-treated rats exhibited a protective effect on hepatocytes cells against Pb-induced liver injury and restored the cells of the kidney. Pb + Aq-600 mg/kg showed higher antioxidant activity as compared to other treated groups. The highest decreased MDA level was found in liver and kidney homogenate of Pb + Aq-600 mg/kg rats (11.2 ± 1.51 nmol/mg; p < .001) and GSH and CAT levels tended to normal after treatment of Pb + Aq-600 mg/kg in rats. The ALAD, ALT, AST, and ALP level were enhanced and tended to be normal after the Aq-400 and Aq-600 mg/kg treatment in Pb-exposed rats. The result showed that 600 mg/kg Aq + Pb exhibited significant (p < .001) anti-inflammatory activity. The findings of this study concluded that treatment of the aqueous extract of Argyrolobium roseum (Camb.) Jaub & Spach reduces the renal and hepatic damage in Pb-induced rats and it also decreases oxidative stress via improving antioxidant components.

Sodium para-aminosalicylic acid ameliorates brain neuroinflammation and behavioral deficits in juvenile lead-exposed rats by modulating MAPK signaling pathway and alpha-synuclein

Lead (Pb) is a developmental neurotoxin that can disrupt brain development and damage the brain regions responsible for executive function, behavioral regulation and fine motor control. Sodium para-aminosalicylic acid (PAS-Na) is a non-steroidal anti-inflammatory drug that can cross the blood-brain barrier. The purpose of this study was to examine the effects of juvenile rat Pb exposure on behavioral changes and brain inflammation, and the efficacy of PAS-Na in ameliorating these effects. The results showed that Pb exposure during the juvenile period (from weaning to adult period) delayed rats’ growth development and impaired their motor learning. Pb exposure not only increased Pb concentrations in several brain regions (including hippocampus, striatum and substantia nigra), but also disrupted metal-homeostasis in the brain, as higher levels of iron (Fe) and calcium (Ca) were observed in the substantia nigra. Moreover, Pb activated the MAPK pathway and increased levels of inflammatory factors such as IL-1β, TNF-α and IL-6 in the hippocampus, striatum and substantia nigra. Furthermore, Pb increased the levels of alpha-synuclein (α-syn) in these brain sites. PAS-Na improved the motor deficits and brain inflammation in the Pb-exposed rats. Moreover, the elevated Pb, Fe and Ca concentrations in the brain were significantly reduced by PAS-Na, which contains amino, carboxyl and hydroxyl functional groups, suggesting that it may act as a chelator of brain metals. In addition, PAS-Na inhibited the Pb-induced MAPK pathway activation and α-syn accumulation in the same brain regions. Taken together, our novel study suggest that PAS-Na shows efficacy in improving the Pb-induced behavioral changes in rats by inhibiting MAPK-dependent inflammatory pathways and reducing α-syn accumulation.

RETRACTED: 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.

Probiotic Lactobacillus rhamnosus GR-1 supplementation attenuates Pb-induced learning and memory deficits by reshaping the gut microbiota.

Lead (Pb) exposure during early life has been associated with an increased risk of neurodevelopmental disorders, including learning and memory deficits. The intestinal flora, via the microbiome–gut–brain axis, could play a significant role in the nervous system. However, the effects of probiotics on ameliorating Pb-induced learning and memory deficits are still unclear. In this study, we showed that adolescent Pb exposure (150 ppm) for 2 months impaired spatial learning and memory ability, accompanied by the decreasing diversity of gut microbiota, and the decreasing abundance of Lactobacillus at the genus level. Surprisingly, administration of the Lactobacillus rhamnosus GR-1 (1010 organisms/rat/day), not L. rhamnosus LGG or Lactobacillus reuteri RC-14, reversed learning and memory deficits induced by Pb exposure. Meanwhile, administration of the L. rhamnosus GR-1 increased the diversity of the gut microbiota composition and partially normalized the genus level of Lactobacillus, Parabacteroides, Enterococcus, and Akkermansia in Pb-exposed rats. Notably, supplementation of L. rhamnosus GR-1 decreased the gut permeability of Pb-exposed rats, reduced proinflammatory cytokines [interleukin-1β (IL-1β) and IL-6] expression, and promoted anti-inflammatory cytokines [granulocyte colony-stimulating factor (G-CSF)] expression. Interestingly, neural cell treatment with G-CSF rescued Pb-induced neurotoxicity. In general, L. rhamnosus GR-1 supplementation recovered the Pb-induced loss of intestinal bacteria (Lactobacillus), which may have reversed the damage to learning and memory ability. Collectively, our findings demonstrate an unexpectedly pivotal role of L. rhamnosus GR-1 in Pb-induced cognitive deficits and identify a potential probiotic therapy for cognitive dysfunction during early life.

Hydrogen sulfide protects hippocampal CA1 neurons against lead mediated neuronal damage via reduction oxidative stress in male rats

H2S plays vital roles in modulation brain function. It is associated with antioxidant and anti-inflammatory properties. We assessed the H2S impact on spatial learning and memory deficit and cell death due to lead exposure, and probable mechanisms of action.The 36 male Wistar rats that (200−220 g), were in random assigned to 3 groups, control group (12 rats), lead acetate group (12 rats), and lead acetate +H2S groups (NaHS as a H2S donor; 5/6 mg/kg; 12 rats). Administration of lead to rats was performed through acute lead poisoning (25 mg/kg of lead acetate, IP through 3 days). Using male Morris water maze, their spatial learning and memory function were measured. We carried out ELISA method to calculate TNF-α and antioxidant enzymes level. Immunohistochemical staining was applied for evaluating the caspase-3 expression levels. Treatment with H2S improved learning and memory impairment in Pb-exposed rats (P<0.05). H2S treatment suppressed Pb-related apoptosis in the hippocampal CA1 subfield (P<0.01). Also, the TNF-α over-expression in the CA1 region of hippocampus due to lead exposure showed a significant reduction (P<0.05) after administrating H2S. Simultaneously, H2S treatment reduced the MDA levels, enhanced SOD, GSH level than the Pb-exposed group in hippocampus (P<0.05). H2S was able to significantly improve Pb-related spatial learning and memory deficit, and neuronal cell death in the CA1 region of hippocampus in the male rats at least partly by reducing oxidative stress and TNF

Lactobacillus plantarum LP33 attenuates Pb-induced hepatic injury in rats by reducing oxidative stress and inflammation and promoting Pb excretion

Lead (Pb) is one of the most common heavy metals and is harmful to human health. The liver is considered as a major target organ for Pb poisoning. Although probiotics have been shown to alleviate liver injury, the protective effect of Lactobacillus plantarum LP33 (LP33) against Pb-induced hepatotoxicity remains unclear. In order to explore the hepatoprotective effect of LP33, LP33 was administered to Pb-intoxicated Sprague-Dawley rats once daily by oral gavage for 8 weeks. The present results showed that LP33 supplementation alleviated liver injury, and inhibited oxidative stress and inflammation in Pb-exposed rats. Treatment with LP33 also promoted the phosphorylation of adenosine monophosphate-activated protein kinase and protein kinase B, activated nuclear factor erythroid 2-related factor 2 signaling and inhibited the activation of nuclear factor-κB signaling in liver tissues of rats exposed to Pb. Additionally, LP33 exhibited adequate Pb-binding capacity and satisfactory survival under simulated gastrointestinal conditions in vitro, and promoted Pb excretion via enterohepatic circulation of bile acids. This study demonstrated that LP33 reduced Pb-induced oxidative stress and inflammation and promoted Pb excretion, thereby attenuating the Pb-induced hepatic injury. Our findings suggest that LP33 supplementation may be a potential strategy for the treatment of Pb-induced hepatic toxicity.

Effect of lead exposure and nutritional iron-deficiency on immune response: A vaccine challenge study in rats

The prevalence of iron (Fe) deficiency and subclinical lead (Pb) toxicity is high in developing countries like India, and information on their potential additive effects on immune responses is scant. The current study assessed immune parameters in dual Pb-exposed\\Fe-deficient weanling SD rats. Rats were fed a control (CD) or Fe-deficient (ID) diet for 4 weeks and then evaluated for hemoglobin (Hb) and serum Fe status. Then, half the rats in each group began to receive daily oral Pb exposure (25 mg/4 ml/kg BW; gavage) or vehicle for a further 4 weeks (while maintained on original respective diets). After the 4-weeks of dosing, rats were assessed for Hb and serum Fe, and for blood lead level (BLL) and δ-aminolevulinic acid dehydratase (ALAD) activity. At this point, half the rats in each group (now n = 8) were then vaccinated with tetanus toxoid (TT), and then two boosters at 2-week intervals. All the time, rats stayed on their original respective diets along with exposure to Pb on alternate days. At 2 weeks after the final booster, rats were euthanized and blood collected to assess total/specific IgG and IgM levels; mucosal (intestinal) IgA levels were also determined. Spleens were taken to assess CD4+ and CD8+ cell levels and for ex vivo measures of splenocyte proliferation/TH1 and TH2 cytokine formation. The results indicated significant lowering of Hb and serum Fe levels in ID rats and increased blood Pb and decreased ALAD activity in all Pb-exposed rats. Fe-deficiency alone induced significant increases in ALAD activity, but only in an absence of Pb. While there was no impact of any regimen on total or TT-specific IgG, significant decreases in mucosal IgA and TT-specific IgM were seen in ID-fed Pb-exposed rats. CD4+ cell levels were not impacted by treatment; CD8+ levels were increased in all ID/Pb-exposed rats. Ex-vivo splenocyte proliferation was significantly higher among vaccinated rats, as well as ID-fed Pb-exposed unvaccinated rats. Cytokine formation in all cases was highly variable. The results suggest that Fe deficiency compromised cell-mediated, mucosal, and/or humoral immune response-related endpoints and that Pb exposure during the deficiency further impacted these outcomes.

Epigenetics of Neurotoxicity Caused by Lead: Interplay of miR-137 and EZH2 Contributes to the Genome-Wide Redistribution of H3K27me3 Underlying the Pb-Dependent Memory Deficits

Background: Lead (Pb) is an environmental neurotoxicant which threatens human health, especially the cognitive memory in children. While its molecular basis is multifactorial, growing evidence implicates epigenetic modifications in the Pb-mediated memory deficits. Methods: We utilized molecular biology techniques, luciferase assay, miRNA profiling and quantification, immunoblots, co-immunoprecipitation, Chromatin immunoprecipitation (CHIP), lentivirus (LV)-based overexpression, Golgi-staining, and behavioral tests to access the roles of H3K27me3 and EZH2 (enhancer of zeste homolog 2) in lead-induced cognitive declines. Findings: Here we found that Pb exposure diminished H3K27me3 levels in vivo through suppressing EZH2 expression at early developmental stages. Notably, intervention of EZH2 in Pb-exposed rats efficiently rescued the H3K27me3 profile and repaired the spatial memory deficits. Furthermore, miR-137 and EZH2 constitute mutually inhibitory loop to regulate the H3K27me3 level, and this feedback regulation could be specifically activated by Pb exposure. Considering molecular events relayed by H3K27me3, ChIP-chip studies revealed that Pb could reshape the genomewide distribution of H3K27me3, including in the Wnt9b and 6 loci. Interestingly, Wnt9b and Wnt6 were regulated by the opposite modifications of H3K4me3 and H3K27me3 in Pb-exposed neurons. Rescue trials further validated the contribution of Wnt9b to Pb-induced neuronal impairments. Interpretation: Our results provided that a new epigenetic pathway, namely miR-137-EZH2-H3K27me3-targets, was suggested to mediate Pbdependent memory impairment, suggesting that a further step towards understanding the molecular basis of lead neurotoxicity. Funding Statement: This work was supported by the National Key Basic Research Program of China (No. 2018YFC1602201, 2018YFC1602204, 2012CB525003)，the National Science Foundation of China (No. 81773475, 21477031, 31401671) , the Key Laboratory of Xin'an Medicine Ministry of Education, Anhui University of Chinese Medicine (No. 2018xayx01) and the Fundamental Research Funds for the Central Universities (PA2017GDQT0018). Declaration of Interests: The authors declare that they have no conflict of interest. Ethics Approval Statement: All animal procedures were carried out in accordance with National Institute of Health Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committee of Hefei University of Technology, China.

The attention set-shifting test is sensitive for revealing sex-based impairments in executive functions following developmental lead exposure in rats

The literature on lead (Pb) exposure has focused in large part on hippocampal-based learning and memory deficits, although frontoexecutive dysfunctions are known to exist in Pb-exposed humans. This study examined the effects of perinatal (PERI) and early postnatal (EPN) developmental low-level Pb-exposures in rats on frontoexecutive functions, using the Attention Set-Shift Test (ASST). Control males and females performed the ASST similarly. Male EPN rats had difficulty with simple discrimination (SD) of odors and failed to complete the compound discrimination (CD) stage of the ASST. All other Pb-exposed rats completed the training and testing. Male PERI rats performed worse on the SD, intradimensional (ID), and intradimensional-reversal (ID-Rev) ASST stages when compared to male Control rats. Female EPN rats performed similar to Controls on the ID-Rev rats, whereas PERI rats performed better the trials-to-criterion on the ID-Rev than EPN and Control rats. Pb-exposed female rats had significant difficulty performing the ED/ED-Rev stages, with the number of trials-to-criterion double that required by Pb-exposed and Control male rats and Control female rats. Together, the ASST results showed that developmental Pb-exposure induces frontoexecutive dysfunction that persists into adulthood, with different sex-based vulnerabilities dependent upon the time-period of neurotoxicant exposure.

Oxidative stress in the neurodegenerative brain following lifetime exposure to lead in rats: Changes in lifespan profiles

A large number of studies have evidenced that developmental neurotoxicity induced by lead (Pb) is related to oxidative injury. Furthermore, recent studies have found that developmental Pb exposure can induce neurodegeneration in old age. Because of the common presence of Pb in the environment, humans are exposed to this metal throughout their lifetime. However, few studies have explored the changes in lifespan profiles of neurotoxicity, as well as oxidative stress following lifetime Pb exposure. In the present study, rats were exposed to lead acetate from their embryonic stage to old age. Dynamic changes in neurodegeneration, oxidative stress, and endoplasmic reticulum (ER) stress in the brains at postnatal week 3 (PNW3, weaning), 41 weeks (PNW41, adulthood) and 70 weeks (PNW70, old age) were investigated. Pb exposure resulted in neurodegeneration with decreased neuronal densities and brain volumes in PNW3 and PNW70 rats; however, no significant changes occurred in PNW41 rats based on thionine stain analysis and magnetic resonance imaging (MRI) scans. Expression of the ER stress protein glucose-regulated protein 78 (GRP78) increased in Pb-exposed rats, which was associated with high levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) in rat brains after Pb exposure in PNW3 and PNW70 rats. Our findings suggested that lifetime Pb exposure induced neurodegenerative injuries that began to occur in infancy, were relieved in adulthood, but intensified in old age. The critical periods for prevention or intervention in neurodegenerative diseases induced by Pb exposure occurred in early life.

Silencing brain catalase expression reduces ethanol intake in developmentally-lead-exposed rats

Lead (Pb) is a developmental neurotoxicant. We have demonstrated that perinatally Pb-exposed rats consume more ethanol than their control counterparts, a response that seems to be mediated by catalase (CAT) and centrally-formed acetaldehyde, ethanol’s first metabolite with attributed reinforcing effects in the brain. The present study sought to disrupt ethanol intake (2–10% ethanol v/v) in rats exposed to 220 ppm Pb or filtered water during gestation and lactation. Thus, to block brain CAT expression, a lentiviral vector coding for a shRNA against CAT (LV-antiCAT vector) was microinfused in the posterior ventral tegmental area (pVTA) either at the onset or towards the end of a chronic voluntary ethanol consumption test. At the end of the study, rats were euthanized and pVTA dissected to measure CAT expression by Western blot. The LV-antiCAT vector administration not only reversed, but also prevented the emergence of the elevated ethanol intake reported in the perinatally Pb-exposed animals, changes that were supported by a significant reduction in CAT expression in the pVTA. These results provide further evidence of the crucial role of this enzyme in the reinforcing properties of ethanol and in the impact of the perinatal Pb programming to challenging events later in life.