The effects of early life Pb exposure on the expression of IL1-β, TNF-α and Aβ in cerebral cortex of mouse pups

Differential expression of SLC30A10 and RAGE in mouse pups by early life lead exposure

BACKGROUND

SLC30A10 and RAGE are widely recognized as pivotal regulators of Aβ plaque transport and accumulation. Prior investigations have established a link between early lead exposure and cerebral harm in offspring, attributable to Aβ buildup and amyloid plaque deposition. However, the impact of lead on the protein expression of SLC30A10 and RAGE has yet to be elucidated. This study seeks to confirm the influence of maternal lead exposure during pregnancy, specifically through lead-containing drinking water, on the protein expression of SLC30A10 and RAGE in mice offspring. Furthermore, this research aims to provide further evidence of lead-induced neurotoxicity.

METHODS

Four cohorts of mice were subjected to lead exposure at concentrations of 0 mM, 0.25 mM, 0.5 mM, and 1 mM over a period of 42 uninterrupted days, spanning from pregnancy to the weaning phase. On postnatal day 21, the offspring mice underwent assessments. The levels of lead in the blood, hippocampus, and cerebral cortex were scrutinized, while the mice's cognitive abilities pertaining to learning and memory were probed through the utilization of the Morris water maze. Furthermore, Western blotting and immunofluorescence techniques were employed to analyze the expression levels of SLC30A10 and RAGE in the hippocampus and cerebral cortex.

RESULTS

The findings revealed a significant elevation in lead concentration within the brains and bloodstreams of mice, mirroring the increased lead exposure experienced by their mothers during the designated period (P < 0.05). Notably, in the Morris water maze assessment, the lead-exposed group exhibited noticeably diminished spatial memory compared to the control group (P < 0.05). Both immunofluorescence and Western blot analyses effectively demonstrated the concomitant impact of varying lead exposure levels on the hippocampal and cerebral cortex regions of the offspring. The expression levels of SLC30A10 displayed a negative correlation with lead doses (P < 0.05). Surprisingly, under identical circumstances, the expression of RAGE in the hippocampus and cortex of the offspring exhibited a positive correlation with lead doses (P < 0.05).

CONCLUSION

SLC30A10 potentially exerts distinct influence on exacerbated Aβ accumulation and transportation in contrast to RAGE. Disparities in brain expression of RAGE and SLC30A10 may contribute to the neurotoxic effects induced by lead.

Microglia and Astroglia-The Potential Role in Neuroinflammation Induced by Pre- and Neonatal Exposure to Lead (Pb)

Neuroinflammation is one of the postulated mechanisms for Pb neurotoxicity. However, the exact molecular mechanisms responsible for its pro-inflammatory effect are not fully elucidated. In this study, we examined the role of glial cells in neuroinflammation induced by Pb exposure. We investigated how microglia, a type of glial cell, responded to the changes caused by perinatal exposure to Pb by measuring the expression of Iba1 at the mRNA and protein levels. To assess the state of microglia, we analyzed the mRNA levels of specific markers associated with the cytotoxic M1 phenotype (Il1b, Il6, and Tnfa) and the cytoprotective M2 phenotype (Arg1, Chi3l1, Mrc1, Fcgr1a, Sphk1, and Tgfb1). Additionally, we measured the concentration of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α). To assess the reactivity and functionality status of astrocytes, we analyzed the GFAP (mRNA expression and protein concentration) as well as glutamine synthase (GS) protein level and activity. Using an electron microscope, we assessed ultrastructural abnormalities in the examined brain structures (forebrain cortex, cerebellum, and hippocampus). In addition, we measured the mRNA levels of Cxcl1 and Cxcl2, and their receptor, Cxcr2. Our data showed that perinatal exposure to Pb at low doses affected both microglia and astrocyte cells' status (their mobilization, activation, function, and changes in gene expression profile) in a brain-structure-specific manner. The results suggest that both microglia and astrocytes represent a potential target for Pb neurotoxicity, thus being key mediators of neuroinflammation and further neuropathology evoked by Pb poisoning during perinatal brain development.

Among Gerontogens, Heavy Metals Are a Class of Their Own: A Review of the Evidence for Cellular Senescence

Advancements in modern medicine have improved the quality of life across the globe and increased the average lifespan of our population by multiple decades. Current estimates predict by 2030, 12% of the global population will reach a geriatric age and live another 3-4 decades. This swelling geriatric population will place critical stress on healthcare infrastructures due to accompanying increases in age-related diseases and comorbidities. While much research focused on long-lived individuals seeks to answer questions regarding how to age healthier, there is a deficit in research investigating what aspects of our lives accelerate or exacerbate aging. In particular, heavy metals are recognized as a significant threat to human health with links to a plethora of age-related diseases, and have widespread human exposures from occupational, medical, or environmental settings. We believe heavy metals ought to be classified as a class of gerontogens (i.e., chemicals that accelerate biological aging in cells and tissues). Gerontogens may be best studied through their effects on the "Hallmarks of Aging", nine physiological hallmarks demonstrated to occur in aged cells, tissues, and bodies. Evidence suggests that cellular senescence-a permanent growth arrest in cells-is one of the most pertinent hallmarks of aging and is a useful indicator of aging in tissues. Here, we discuss the roles of heavy metals in brain aging. We briefly discuss brain aging in general, then expand upon observations for heavy metals contributing to age-related neurodegenerative disorders. We particularly emphasize the roles and observations of cellular senescence in neurodegenerative diseases. Finally, we discuss the observations for heavy metals inducing cellular senescence. The glaring lack of knowledge about gerontogens and gerontogenic mechanisms necessitates greater research in the field, especially in the context of the global aging crisis.

Sodium Para-aminosalicylic Acid Inhibits Lead-Induced Neuroinflammation in Brain Cortex of Rats by Modulating SIRT1/HMGB1/NF-κB Pathway

Lead (Pb) is considered to be a major environmental pollutant and occupational health hazard worldwide which may lead to neuroinflammation. However, an effective treatment for Pb-induced neuroinflammation remains elusive. The aim of this study was to investigate the mechanisms of Pb-induced neuroinflammation, and the therapeutic effect of sodium para-aminosalicylic acid (PAS-Na, a non-steroidal anti-inflammatory drug) in rat cerebral cortex. The results indicated that Pb exposure induced pathological damage in cerebral cortex, accompanied by increased levels of inflammatory factors tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β). Moreover, Pb decreased the expression of silencing information regulator 2 related enzyme 1 (SIRT1) and brain-derived neurotrophic factor (BDNF), and increased the levels of high mobile group box 1 (HMGB1) expression and p65 nuclear factor-κB (NF-κB) phosphorylation. PAS-Na treatment ameliorated Pb-induced histopathological changes in rat cerebral cortex. Moreover, PAS-Na reduced the Pb-induced increase of TNF-α and IL-1β levels concomitant with a significant increase in SIRT1 and BDNF levels, and a decrease in HMGB1 and the phosphorylation of p65 NF-κB expression. Thus, PAS-Na may exert anti-inflammatory effects by mediating the SIRT1/HMGB1/NF-κB pathway and BDNF expression. In conclusion, in this novel study PAS-Na was shown to possess an anti-inflammatory effect on cortical neuroinflammation, establishing its efficacy as a potential treatment for Pb exposures.

The effects of lead exposure on the expression of IGF1R, IGFBP3, Aβ40, and Aβ42 in PC12 cells

BACKGROUND

To investigate the effects of lead exposure and IGF1R inhibitor AG1024 on the expression of IGF1R and IGFBP3 in PC12 cells. It is clear that the mechanism of the related proteins inducing AD is regulated by them, thus providing theoretical guidance for the prevention and treatment of lead poisoning.

METHODS

This study is mainly used PC12 neuron cell to cultivate and establish a corresponding lead exposure model, deal with cells with different concentrations of lead acetate respectively, divide the experiment into control group, 1 μmoL/L PbAc, 10 μmoL/L PbAc group, IGF1R inhibitor (AG1024) group, IGF1R inhibitor group (AG1024) + 1 μmoL/L PbAc group, IGF1R inhibitor group (AG1024) + 10 μmoL/L PbAc group, respective contamination's three periods of time 24 h, 48 h, and 72 h. Lead exposure dose on cell proliferation was examined by MTT. The protein expression of IGF1R and IGFBP3 in PC12 cells were tested by western blotting and immunohistochemistry, The expression of Aβ40 and Aβ42 in cell supernatant was determined by ELISA.

RESULTS

Compared with the control group, the proliferation of the cells in the high-dose lead-exposed group was significantly inhibited (P < 0.05), and the expression of IGF1R and IGFBP3 was significantly decreased (P < 0.05); the contents of Aβ40 and Aβ42 were not statistically significant among the groups (P > 0.05).

CONCLUSION

This study shows that lead can obviously down-regulate the expression of IGF1R and IGFBP3, lead and inhibitor can inhibit the proliferation of cells, promote the tendency of apoptosis, and damage the nervous system.

A mechanistic view on the neurotoxic effects of air pollution on central nervous system: risk for autism and neurodegenerative diseases

Many reports have shown a strong association between exposure to neurotoxic air pollutants like heavy metal and particulate matter (PM) as an active participant and neurological disorders. While the effects of these toxic pollutants on cardiopulmonary morbidity have principally been studied, growing evidence has shown that exposure to polluted air is associated with memory impairment, communication deficits, and anxiety/depression among all ages. So, these toxic pollutants in the environment increase the risk of neurodegenerative disease, ischemia, and autism spectrum disorders (ASD). The precise mechanisms in which air pollutants lead to communicative inability, social inability, and declined cognition have remained unknown. Various animal model studies show that amyloid precursor protein (APP), processing, oxidant/antioxidant balance, and inflammation pathways change following the exposure to constituents of polluted air. In the present review study, we collect the probable molecular mechanisms of deleterious CNS effects in response to various air pollutants.

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.

Astrocytes in heavy metal neurotoxicity and neurodegeneration

With the industrial development and progressive increase in environmental pollution, the mankind overexposure to heavy metals emerges as a pressing public health issue. Excessive intake of heavy metals, such as arsenic (As), manganese (Mn), mercury (Hg), aluminium (Al), lead (Pb), nickel (Ni), bismuth (Bi), cadmium (Cd), copper (Cu), zinc (Zn), and iron (Fe), is neurotoxic and it promotes neurodegeneration. Astrocytes are primary homeostatic cells in the central nervous system. They protect neurons against all types of insults, in particular by accumulating heavy metals. However, this makes astrocytes the main target for heavy metals neurotoxicity. Intake of heavy metals affects astroglial homeostatic and neuroprotective cascades including glutamate/GABA-glutamine shuttle, antioxidative machinery and energy metabolism. Deficits in these astroglial pathways facilitate or even instigate neurodegeneration. In this review, we provide a concise outlook on heavy metal-induced astrogliopathies and their association with major neurodegenerative disorders. In particular, we focus on astroglial mechanisms of iron-induced neurotoxicity. Iron deposits in the brain are detected in main neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Accumulation of iron in the brain is associated with motor and cognitive impairments and iron-induced histopathological manifestations may be considered as the potential diagnostic biomarker of neurodegenerative diseases. Effective management of heavy metal neurotoxicity can be regarded as a potential strategy to prevent or retard neurodegenerative pathologies.

Mitochondrion: a sensitive target for Pb exposure

Pb exposure is a worldwide environmental contamination issue which has been of concern to more and more people. Exposure to environmental Pb and its compounds through food and respiratory routes causes toxic damage to the digestive, respiratory, cardiovascular and nervous systems, etc. Children and pregnant women are particularly vulnerable to Pb. Pb exposure significantly destroys children's learning ability, intelligence and perception ability. Mitochondria are involved in various life processes of eukaryotes and are one of the most sensitive organelles to various injuries. There is no doubt that Pb-induced mitochondrial damage can widely affect various physiological processes and cause great harm. In this review, we summarized the toxic effects of Pb on mitochondria which led to various pathological processes. Pb induces mitochondrial dysfunction leading to the increased level of oxidative stress. In addition, Pb leads to cell apoptosis via mitochondrial permeability transition pore (MPTP) opening. Also, Pb can stimulate the development of mitochondria-mediated inflammatory responses. Furthermore, Pb triggers the germination of autophagy via the mitochondrial pathway and induces mitochondrial dysfunction, disturbing intracellular calcium homeostasis. In a word, we discussed the effects of Pb exposure on mitochondria, hoping to provide some references for further research and better therapeutic options for Pb exposure.

Broader Insights into Understanding Tumor Necrosis Factor and Neurodegenerative Disease Pathogenesis Infer New Therapeutic Approaches

Proinflammatory cytokines such as tumor necrosis factor (TNF), with its now appreciated key roles in neurophysiology as well as neuropathophysiology, are sufficiently well-documented to be useful tools for enquiry into the natural history of neurodegenerative diseases. We review the broader literature on TNF to rationalize why abruptly-acquired neurodegenerative states do not exhibit the remorseless clinical progression seen in those states with gradual onsets. We propose that the three typically non-worsening neurodegenerative syndromes, post-stroke, post-traumatic brain injury (TBI), and post cardiac arrest, usually become and remain static because of excess cerebral TNF induced by the initial dramatic peak keeping microglia chronically activated through an autocrine loop of microglial activation through excess cerebral TNF. The existence of this autocrine loop rationalizes post-damage repair with perispinal etanercept and proposes a treatment for cerebral aspects of COVID-19 chronicity. Another insufficiently considered aspect of cerebral proinflammatory cytokines is the fitness of the endogenous cerebral anti-TNF system provided by norepinephrine (NE), generated and distributed throughout the brain from the locus coeruleus (LC). We propose that an intact LC, and therefore an intact NE-mediated endogenous anti-cerebral TNF system, plus the DAMP (damage or danger-associated molecular pattern) input having diminished, is what allows post-stroke, post-TBI, and post cardiac arrest patients a strong long-term survival advantage over Alzheimer's disease and Parkinson's disease sufferers. In contrast, Alzheimer's disease and Parkinson's disease patients remorselessly worsen, being handicapped by sustained, accumulating, DAMP and PAMP (pathogen-associated molecular patterns) input, as well as loss of the LC-origin, NE-mediated, endogenous anti-cerebral TNF system. Adrenergic receptor agonists may counter this.

Amyotrophic lateral sclerosis and lead: A systematic update

Heavy metals are considered to be among the leading environmental factors that trigger amyotrophic lateral sclerosis (ALS). However, no convincing biopathological mechanism and therapeutic clinical implication of such metals in ALS pathogenesis have been established. This is partly attributable to the technical and scientific difficulties in demonstrating a direct and causative role of heavy metals in the onset of ALS in patients. However, a body of epidemiological, clinical and experimental evidences suggest that lead (Pb), more than other metals, could actually play a major role in the onset and progression of ALS. Here, to clarify the nature of the association and the causative role of Pb in ALS, we comprehensively reviewed the scientific literature of the last decade with objective database searches and the methods typically adopted in systematic reviews, critically analysing and summarising the various scientifically sound evidence on the relationship between ALS and Pb. From these tasks, we noted a number of multidisciplinary associations between ALS and Pb, and specifically the importance of occupational exposure to Pb in ALS development and/or progression. We also report the possible involvement of TAR DNA binding protein (TDP-43)-based molecular mechanism in Pb-mediated ALS, although these data rely on a single study, which included both in vitro experiments and an animal model, and are therefore still preliminary. Finally, we briefly examined whether this knowledge could inspire new targeted therapies and policies in the fight against ALS.

Carvacrol reduces hippocampal cell death and improves learning and memory deficits following lead-induced neurotoxicity via antioxidant activity

Carvacrol is a monoterpene with neuroprotective effects in several animal models of neurodegeneration, including epilepsy, ischemia, and traumatic neuronal events. In this study, we aimed to examine the effects of carvacrol on neurodegeneration induced by lead acetate in rats. A total of 50 male Wistar rats were divided into five equal groups. The control group received drinking water, while the neurotoxic group was exposed to 500 ppm of lead acetate in drinking water for 40 days. The three remaining groups, which were also exposed to 500 ppm of lead acetate, received carvacrol at doses of 25, 50, and 100 mg/kg orally for 40 days. The Morris water maze test was employed to examine spatial learning and memory. Pathological damage to the hippocampus was determined by Nissl staining. The level of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were detected using biochemical analysis and the free radical scavenging activity as evaluated by the DPPH test. Administration of carvacrol significantly restored learning and memory impairment induced by lead acetate. Moreover, carvacrol ameliorated neurodegeneration, antioxidative capacity, and lipid peroxidation in the hippocampus of rats exposed to lead. The present results provide a rationale for the inhibitory role of carvacrol in the attenuation of lead-induced neurotoxicity.

Pre- and Neonatal Exposure to Lead (Pb) Induces Neuroinflammation in the Forebrain Cortex, Hippocampus and Cerebellum of Rat Pups

Lead (Pb) is a heavy metal with a proven neurotoxic effect. Exposure is particularly dangerous to the developing brain in the pre- and neonatal periods. One postulated mechanism of its neurotoxicity is induction of inflammation. This study analyzed the effect of exposure of rat pups to Pb during periods of brain development on the concentrations of selected cytokines and prostanoids in the forebrain cortex, hippocampus and cerebellum. Methods: Administration of 0.1% lead acetate (PbAc) in drinking water ad libitum, from the first day of gestation to postnatal day 21, resulted in blood Pb in rat pups reaching levels below the threshold considered safe for humans by the Centers for Disease Control and Prevention (10 µg/dL). Enzyme-linked immunosorbent assay (ELISA) method was used to determine the levels of interleukins IL-1β, IL-6, transforming growth factor-β (TGF-β), prostaglandin E2 (PGE2) and thromboxane B2 (TXB2). Western blot and quantitative real-time PCR were used to determine the expression levels of cyclooxygenases COX-1 and COX-2. Finally, Western blot was used to determine the level of nuclear factor kappa B (NF-κB). Results: In all studied brain structures (forebrain cortex, hippocampus and cerebellum), the administration of Pb caused a significant increase in all studied cytokines and prostanoids (IL-1β, IL-6, TGF-β, PGE2 and TXB2). The protein and mRNA expression of COX-1 and COX-2 increased in all studied brain structures, as did NF-κB expression. Conclusions: Chronic pre- and neonatal exposure to Pb induces neuroinflammation in the forebrain cortex, hippocampus and cerebellum of rat pups.

Heavy Metals Exposure and Alzheimer's Disease and Related Dementias

Alzheimer's disease and related dementias lack effective treatment or cures and are major public health challenges. Risk for Alzheimer's disease and related dementias is partially attributable to environmental factors. The heavy metals lead, cadmium, and manganese are widespread and persistent in our environments. Once persons are exposed to these metals, they are adept at entering cells and reaching the brain. Lead and cadmium are associated with numerous health outcomes even at low levels of exposure. Although manganese is an essential metal, deficiency or environmental exposure or high levels of the metal can be toxic. In cell and animal model systems, lead, cadmium, and manganese are well documented neurotoxicants that contribute to canonical Alzheimer's disease pathologies. Adult human epidemiologic studies have consistently shown lead, cadmium, and manganese are associated with impaired cognitive function and cognitive decline. No longitudinal human epidemiology study has assessed lead or manganese exposure on Alzheimer's disease specifically though two studies have reported a link between cadmium and Alzheimer's disease mortality. More longitudinal epidemiologic studies with high-quality time course exposure data and incident cases of Alzheimer's disease and related dementias are warranted to confirm and estimate the proportion of risk attributable to these exposures. Given the widespread and global exposure to lead, cadmium, and manganese, even small increases in the risks of Alzheimer's disease and related dementias would have a major population impact on the burden on disease. This article reviews the experimental and epidemiologic literature of the associations between lead, cadmium, and manganese on Alzheimer's disease and related dementias and makes recommendations of critical areas of future investment.

Progress in Research on Brain Development and Function of Mice During Weaning

Lactation is a critical phase for brain function development. New dietary experiences of mouse caused by weaning can regulate brain development and function, increase their response to food and environment, and eventually give rise to corresponding behavioral changes. Changes in weaning time induce the alteration of brain tissues morphology and molecular characteristics, glial cell activity and behaviors in the offspring. In addition, it is also sensitive to the intervention of environment and drugs during this period. That is to say, the study focused on brain development and function based on mouse weaning is critical to demonstrate the underlying pathogenesis of neuropsychiatric diseases and find new drug targets. This article mainly focuses on the developmental differentiation of the brain during lactation, especially during weaning in mice.

Epigenetic and Neurological Impairments Associated with Early Life Exposure to Persistent Organic Pollutants

The incidence of neurodevelopmental and neurodegenerative diseases worldwide has dramatically increased over the last decades. Although the aetiology remains uncertain, evidence is now growing that exposure to persistent organic pollutants during sensitive neurodevelopmental periods such as early life may be a strong risk factor, predisposing the individual to disease development later in life. Epidemiological studies have associated environmentally persistent organic pollutant exposure to brain disorders including neuropathies, cognitive, motor, and sensory impairments; neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD); and neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS). In many ways, this expands the classical “Developmental Origins of Health and Disease” paradigm to include exposure to pollutants. This model has been refined over the years to give the current “three-hit” model that considers the individual's genetic factors as a first “hit.” It has an immediate interaction with the early-life exposome (including persistent organic pollutants) that can be considered to be a second “hit.” Together, these first two “hits” produce a quiescent or latent phenotype, most probably encoded in the epigenome, which has become susceptible to a third environmental “hit” in later life. It is only after the third “hit” that the increased risk of disease symptoms is crystallised. However, if the individual is exposed to a different environment in later life, they would be expected to remain healthy. In this review, we examine the effect of exposure to persistent organic pollutants and particulate matters in early life and the relationship to subsequent neurodevelopmental and neurodegenerative disorders. The roles of those environmental factors which may affect epigenetic DNA methylation and therefore influence normal neurodevelopment are then evaluated.

Effect of Lead on Antioxidant Ability and Immune Responses of Crucian Carp

The aim of this study was to explore the effects of lead exposure on the antioxidant and immune responses of Crucian carp. Three hundred sixty healthy Crucian carp were randomly grouped into four groups and exposed to different doses of lead (0, 0.05, 0.5, and 1 mg/L). Fish were sampled at 30 and 60 days, respectively, and antioxidant capability, immune parameters, ALAD activity, and immune-related genes were assessed. The results showed that T-AOC and GSH activities of the liver were significantly increased in 60 days (P < 0.05); the activities of SOD, CAT, T-AOC, and GSH were significantly increased (P < 0.05) compared to the control in the kidney in 60 days. With an increase in Pb dose, the activity and expression of lysozyme and the content of immunoglobulin M were significantly decreased compared to the control. Compared with the control group, the activity of ALAD in the lead-exposed group decreased significantly (P < 0.05). The expression of the HSP70, tumor necrosis factor-α (TNF-α), interleukins (IL-10), and immunoglobulin M genes was all enhanced in lead-exposed group, whereas lysozyme gene expression was decreased. The results indicated that lead induced oxidative stress and had immunotoxic effects on Crucian carp.

Toxic metal(loid)-based pollutants and their possible role in autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in social interaction, verbal and non-verbal communication, and stereotypic behaviors. Many studies support a significant relationship between many different environmental factors in ASD etiology. These factors include increased daily exposure to various toxic metal-based environmental pollutants, which represent a cause for concern in public health. This article reviews the most relevant toxic metals, commonly found, environmental pollutants, i.e., lead (Pb), mercury (Hg), aluminum (Al), and the metalloid arsenic (As). Additionally, it discusses how pollutants can be a possible pathogenetic cause of ASD through various mechanisms including neuroinflammation in different regions of the brain, fundamentally occurring through elevation of the proinflammatory profile of cytokines and aberrant expression of nuclear factor kappa B (NF-κB). Due to the worldwide increase in toxic environmental pollution, studies on the role of pollutants in neurodevelopmental disorders, including direct effects on the developing brain and the subjects' genetic susceptibility and polymorphism, are of utmost importance to achieve the best therapeutic approach and preventive strategies.

Therapeutic implications of how TNF links apolipoprotein E, phosphorylated tau, α-synuclein, amyloid-β and insulin resistance in neurodegenerative diseases

While cytokines such as TNF have long been recognized as essential to normal cerebral physiology, the implications of their chronic excessive production within the brain are now also increasingly appreciated. Syndromes as diverse as malaria and lead poisoning, as well as non‐infectious neurodegenerative diseases, illustrate this. These cytokines also orchestrate changes in tau, α‐synuclein, amyloid‐β levels and degree of insulin resistance in most neurodegenerative states. New data on the effects of salbutamol, an indirect anti‐TNF agent, on α‐synuclein and Parkinson's disease, APOE4 and tau add considerably to the rationale of the anti‐TNF approach to understanding, and treating, these diseases. Therapeutic advances being tested, and arguably useful for a number of the neurodegenerative diseases, include a reduction of excess cerebral TNF, whether directly, with a specific anti‐TNF biological agent such as etanercept via Batson's plexus, or indirectly via surgically implanting stem cells. Inhaled salbutamol also warrants investigating further across the neurodegenerative disease spectrum. It is now timely to integrate this range of new information across the neurodegenerative disease spectrum, rather than keep seeing it through the lens of individual disease states.

Effects of sulforaphane and vitamin E on cognitive disorder and oxidative damage in lead-exposed mice hippocampus at lactation

OBJECT

To investigate the effects of sulforaphane (SFN) and vitamin E (VE) on spatial learning and memory ability and oxidative damage of hippocampus in lead-exposed mice at lactation.

METHODS

A total of 18 adult Kunming mice, all 12 female mice were divided into two groups by body weight randomly, 10 mice drank water containing 0.2% lead acetate at lactation, the other 2 mice drank lead free deionized water named as the normal group. Then, they were mated at a 1:2 ratio of male to female. After weaning, the pups were divided into 5 groups by weight randomly (10 each group): normal saline (NS) group, corn oil (CO) group, SFN group, VE group and SFN+VE group. They were subject to gavage daily for four weeks. Gavage doses of SFN and VE were 25mg/kg and 30 IU/kg respectively. Meanwhile, 10 pups of the normal group were selected randomly as the control (C) group. The C group was normally raised for 4 weeks. The spatial learning and memory ability of them were evaluated by the Morris water maze test, and the lead level in the blood was determined by polarography. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in hippocampus were measured by the kits.

RESULTS

Compared with the NS and CO groups, the lead level in the blood of SFN and SFN+VE group had a significant decrease. In water maze test, the mice treated with SFN or/and VE performed better than mice of the NS and CO groups. In addition, a remarkable decrease in MDA level was found in mice treated with SFN or/and VE than those in NS and CO groups. What's more, there was no statistical distinction of SOD activity in SFN group than that of NS group. SOD activity significantly increased was observed in VE and SFN+VE groups than that of CO group.

CONCLUSION

Sulforaphane and vitamin E could ameliorate cognitive decline and oxidative damage in pups with lead exposure at lactation from maternal milk.

Early-Life Exposure to Lead Induces Cognitive Impairment in Elder Mice Targeting SIRT1 Phosphorylation and Oxidative Alterations

Pb is a potential risk factor for cognition, mainly mediated by enhanced oxidative stress. Resveratrol, a natural polyphenol with crucial anti-oxidative property, is recently implicated in preventing cognitive deficits in normal aging and neurodegenerative disorders. Its beneficial effects have been linked to sirtuin 1(SIRT1) activation. The aim of this work is to investigate the possible linkage between alterations in Pb-induced oxidative damage and cognitive impairment by prolonged treatment of resveratrol. Male C57BL/6 mice were given Pb(Ac)₂ treatment or deionized H₂O for 12 weeks, and subjected to resveratrol gavage at the dose of 50 mg/kgBw•d or vehicle after Pb exposure. Results from biochemical analysis and immunohistofluorescence showed that Pb induced oxidative DNA damage and decreased cortical antioxidant biomarker. As expected, these abnormalities were improved by resveratrol treatment. Morris water maze test, Western blotting, immunohistofluorescence staining and RT-qPCR indicated that resveratrol ameliorated spatial learning and memory deficits with alterations in hippocampal BDNF-TrkB signaling, promoted nuclear localization and phosphorylation of hippocampal SIRT1, partly increased protein levels of AMPK and PGC-1α involving in modulation of antioxidant response in Pb-exposed mice. Our results support the hypothesis that resveratrol could attenuate Pb-induced cognitive impairment which was associated with activating SIRT1 via modulation of oxidative stress. Additionally, resveratrol also repressed the Pb-induce amyloidogenic processing with resultant decline in cortical Aβ₁₋₋₄₀. Noteworthy, such effects were not mediated by resveratrol treatment alone. These findings emphasize the potential of SIRT1 activator as an efficacious dietary intervention to downgrade the Pb-induced neurotoxic lesion.

The influence of occupational chronic lead exposure on the levels of selected pro-inflammatory cytokines and angiogenic factors

The aim of the study was to determine the effect of occupational exposure to lead on the blood levels of pro-inflammatory cytokines and selected factors that influence angiogenesis. The study population was divided into two groups. The first group consisted of 56 male workers chronically exposed to lead. The second group (control) was comprised of 24 male administrative workers. The serum levels of interleukin 1β (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α) were significantly higher in the group of workers chronically exposed to lead compared to control values by 38%, 68%, and 57%, respectively. Similarly, the values of soluble vascular endothelial growth factor receptor-1 (sVEGFR-1) and fibroblast growth factor-basic (FGF-basic) were higher by 19% and 63%, respectively. In the group of workers chronically exposed to lead, there were positive correlations between the levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) and angiogenic factors (VEGF, FGF-basic, sVEGFR-1, and soluble angiopoietin receptor). In the control group, there were no correlations between the levels of the abovementioned parameters. Results of the present study indicate that chronic occupational lead exposure promotes inflammatory processes via induction of pro-inflammatory cytokines, modulates angiogenesis, and elicits interdependencies between the immune response and angiogenic factors.

Elevated lead levels and adverse effects on natural killer cells in children from an electronic waste recycling area

Lead (Pb) has been proved to exert immunotoxicity to influence immune homeostasis in humans. To monitor the internal Pb level and evaluate its effect on natural killer (NK) cells and cytokine/chemokine concentrations, we recruited 285 preschool children from Guiyu, one of the largest electronic waste (e-waste) destinations and recycling areas in the world, and known to have high concentrations of Pb in the air, soil, water, sediment and plants. A total of 126 preschool children were selected from Haojiang as a reference group. Results showed that children in Guiyu, the exposed area, had higher blood Pb levels and lower percentages of NK cells than children from the reference area. A significantly negative association was found between the percentage of NK cells and increasing Pb levels. Moreover, children in Guiyu area had higher platelet counts and IL-1β concentrations, and lower levels of IL-2, IL-27, MIP-1α and MIP-1β were observed in the exposed children. These changes might not be conducive to the development and differentiation of NK cells. Taken together, the elevated Pb levels result in the lower percentages of NK cells, but also alter the levels of platelets, IL-1β and IL-27, which might be unconducive to the activity and function of NK cells.

The Effects of Early Life Lead Exposure on the Expression of Glycogen Synthase Kinase-3β and Insulin-like Growth Factor 1 Receptor in the Hippocampus of Mouse Pups

The present study was undertaken to investigate the effects of maternal lead exposure on expression of GSK-3β and IGF1R in the hippocampus of mice offspring. Lead exposure initiated from beginning of gestation to weaning. Lead acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1, 0.5, and 1%, respectively. On the 21st postnatal day, the Pb levels were determined by graphite furnace atomic absorption spectrometry. The expression of GSK-3β and IGF1R in hippocampus was examined by immunohistochemistry and Western blotting. The lead levels in blood and hippocampus of all lead exposure groups were significantly higher than those of the control group (P < 0.05). Compared with the control group, the expression of GSK-3β was increased in lead-exposed groups (P < 0.05), but the expression of IGF1R was decreased (P < 0.05). The high expression of GSK-3β and low expression of IGF1R in the hippocampus of pups may contribute to the neurotoxicity associated with maternal Pb exposure.

Environmental pollutants as risk factors for neurodegenerative disorders: Alzheimer and Parkinson diseases

Neurodegenerative diseases including Alzheimer (AD) and Parkinson (PD) have attracted attention in last decades due to their high incidence worldwide. The etiology of these diseases is still unclear; however the role of the environment as a putative risk factor has gained importance. More worryingly is the evidence that pre- and post-natal exposures to environmental factors predispose to the onset of neurodegenerative diseases in later life. Neurotoxic metals such as lead, mercury, aluminum, cadmium and arsenic, as well as some pesticides and metal-based nanoparticles have been involved in AD due to their ability to increase beta-amyloid (Aβ) peptide and the phosphorylation of Tau protein (P-Tau), causing senile/amyloid plaques and neurofibrillary tangles (NFTs) characteristic of AD. The exposure to lead, manganese, solvents and some pesticides has been related to hallmarks of PD such as mitochondrial dysfunction, alterations in metal homeostasis and aggregation of proteins such as α-synuclein (α-syn), which is a key constituent of Lewy bodies (LB), a crucial factor in PD pathogenesis. Common mechanisms of environmental pollutants to increase Aβ, P-Tau, α-syn and neuronal death have been reported, including the oxidative stress mainly involved in the increase of Aβ and α-syn, and the reduced activity/protein levels of Aβ degrading enzyme (IDE)s such as neprilysin or insulin IDE. In addition, epigenetic mechanisms by maternal nutrient supplementation and exposure to heavy metals and pesticides have been proposed to lead phenotypic diversity and susceptibility to neurodegenerative diseases. This review discusses data from epidemiological and experimental studies about the role of environmental factors in the development of idiopathic AD and PD, and their mechanisms of action.

Proanthocyanidins improves lead-induced cognitive impairments by blocking endoplasmic reticulum stress and nuclear factor-κB-mediated inflammatory pathways in rats

Proanthocyanidins (PCs), a class of naturally occurring flavonoids, had been reported to possess a variety of biological activities, including anti-oxidant, anti-tumor and anti-inflammatory. In this study, we examined the protective effect of PCs against lead-induced inflammatory response in the rat brain and explored the potential mechanism of its action. The results showed that PCs administration significantly improved behavioral performance of lead-exposed rats. One of the potential mechanisms was that PCs decreased reactive oxygen species production and increased the total antioxidant capacity in the brains of lead-exposed rats. Furthermore, the results also showed that PCs significantly decreased the levels of tumor necrosis factor-α, interleukin 1β and cyclooxygenase-2 in the brains of lead-exposed rats. Moreover, PCs significantly decreased the levels of beta amyloid and phosphorylated tau in the brains of lead-treated rats, which in turn inhibited endoplasmic reticulum (ER) stress. PCs also decreased the phosphorylation of protein kinase RNA-like ER kinase, eukaryotic translation initiation factor-2, inositol-requiring protein-1, c-Jun N-terminal kinase, p38 and inhibited nuclear factor-κB nuclear translocation in the brains of lead-exposed rats. In conclusion, these results suggested that PCs could improve cognitive impairments by inhibiting brain oxidative stress and inflammatory response.

Effects of lead exposure on the expression of amyloid β and phosphorylated tau proteins in the C57BL/6 mouse hippocampus at different life stages

The objective of this study was to investigate the effects of lead exposure on spatial learning and memory capacity and the expression of amyloid β and phosphorylated tau proteins in the mouse hippocampus. A total of 24 adult C57BL/6 mice (12 of each sex) were mated at a 1:1 ratio. After delivery, the litters were normalised to 6 pups per litter. During the lactation period, the pups were randomly separated into four groups: control, early exposure, late exposure, or long-term exposure. These groups were not exposed to lead, exposed to lead from birth to week 24, exposed to lead from week 24 to week 48, or exposed to lead from birth to 48 weeks of age, respectively. Lead exposure was induced by providing Pb-contaminated drinking water at a concentration of 0.1%. All of the pups were fed until 72 weeks of age, at which time their spatial learning and memory capacity was evaluated via the Morris water maze test. Then, the lead levels in their blood and hippocampus were measured via graphite furnace atomic absorption spectrometry. The protein expression of amyloid β and phosphorylated tau in the hippocampus was detected via Western blot. The results revealed that the hippocampal and blood lead levels were significantly higher in all of the groups exposed to lead than the control group (P<0.05). The spatial learning and memory performances of the lead-exposed groups were much poorer than those of the control group (P<0.05). The expression levels of amyloid β and phosphorylated tau proteins were increased in the lead-exposed groups compared to the control group (P<0.05). The enhanced expressions of amyloid β and phosphorylated tau proteins might contribute to the impairment in spatial learning and memory in the lead-exposed mice.