Perinatal exposure to lead (Pb) promotes Tau phosphorylation in the rat brain in a GSK-3β and CDK5 dependent manner: Relevance to neurological disorders

Lead exposure induces neurodysfunction through caspase-1-mediated neuronal pyroptosis

Chronic lead (Pb) exposure causes neurodysfunction and contributes to the development of neurodegenerative disease. However, the mechanism of Pb-induced neurological dysfunction have yet to be fully elucidated. This study determined the role pyroptosis plays in Pb-induced neurodysfunction in neurons. We used both in vitro and in vivo approaches to explore whether Pb exposure induces caspase-1-mediated pyroptosis in neurons and its relationship to Pb-induced neurological disorders. Our findings showed that caspase-1-mediated pyroptosis in Pb-exposed neurons activated glycogen synthase kinase 3 protease activity by disrupting Ca2+/calmodulin-dependent protein kinase II/cAMP-response element binding protein pathway, leading to neurological disorders. Moreover, the caspase-1 inhibition VX-765 or the non-steroidal anti-inflammatory drug sodium para-aminosalicylic acid (PAS-Na) attenuated the Pb-induced neurological disorders by alleviating caspase-1 mediated neuronal pyroptosis. Our novel studies suggest that caspase-1-mediated pyroptosis in neurons represents a potential mechanism for Pb-induced neurodysfunction, identifying a putative target for attenuating the neurodegenerative effects induced by this metal.

Environmental Toxins and Alzheimer's Disease: a Comprehensive Analysis of Pathogenic Mechanisms and Therapeutic Modulation

Alzheimer's disease is a leading cause of mortality worldwide. Inorganic and organic hazards, susceptibility to harmful metals, pesticides, agrochemicals, and air pollution are major environmental concerns. As merely 5% of AD cases are directly inherited indicating that these environmental factors play a major role in disease development. Long-term exposure to environmental toxins is believed to progress neuropathology, which leads to the development of AD. Numerous in-vitro and in-vivo studies have suggested the harmful impact of environmental toxins at cellular and molecular level. Common mechanisms involved in the toxicity of these environmental pollutants include oxidative stress, neuroinflammation, mitochondrial dysfunction, abnormal tau, and APP processing. Increased expression of GSK-3β, BACE-1, TNF-α, and pro-apoptotic molecules like caspases is observed upon exposure to these environmental toxins. In addition, the expression of neurotrophins like BDNF and GAP-43 have been found to be reduced as a result of toxicity. Further, modulation of signaling pathways involving PARP-1, PGC-1α, and MAPK/ERK induced by toxins have been reported to contribute in AD pathogenesis. These pathways are a promising target for developing novel AD therapeutics. Drugs like epigallocatechin-gallate, neflamapimod, salsalate, dexmedetomidine, and atabecestat are in different phases of clinical trials targeting the pathways for possible treatment of AD. This review aims to culminate the correlation between environmental toxicants and AD development. We emphasized upon the signaling pathways involved in the progression of the disease and the therapeutics under clinical trial targeting the altered pathways for possible treatment of AD.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

Insights into the mechanism of transcription factors in Pb2+-induced apoptosis

The health risks associated with exposure to heavy metals, such as Pb2+, are increasingly concerning the public. Pb2+ can cause significant harm to the human body through oxidative stress, autophagy, inflammation, and DNA damage, disrupting cellular homeostasis and ultimately leading to cell death. Among these mechanisms, apoptosis is considered crucial. It has been confirmed that transcription factors play a central role as mediators during the apoptosis process. Interestingly, these transcription factors have different effects on apoptosis depending on the concentration and duration of Pb2+ exposure. In this article, we systematically summarize the significant roles of several transcription factors in Pb2+-induced apoptosis. This information provides insights into therapeutic strategies and prognostic biomarkers for diseases related to Pb2+ exposure.

Preclinical Evidence for the Role of the Yin/Yang Angiotensin System Components in Autism Spectrum Disorder: A Therapeutic Target of Astaxanthin

Autism spectrum disorder (ASD) prevalence is emerging with an unclear etiology, hindering effective therapeutic interventions. Recent studies suggest potential renin-angiotensin system (RAS) alterations in different neurological pathologies. However, its implications in ASD are unexplored. This research fulfills the critical gap by investigating dual arms of RAS and their interplay with Notch signaling in ASD, using a valproic acid (VPA) model and assessing astaxanthin's (AST) modulatory impacts. Experimentally, male pups from pregnant rats receiving either saline or VPA on gestation day 12.5 were divided into control and VPA groups, with subsequent AST treatment in a subset (postnatal days 34-58). Behavioral analyses, histopathological investigations, and electron microscopy provided insights into the neurobehavioral and structural changes induced by AST. Molecular investigations of male pups' cortices revealed that AST outweighs the protective RAS elements with the inhibition of the detrimental arm. This established the neuroprotective and anti-inflammatory axes of RAS (ACE2/Ang1-7/MasR) in the ASD context. The results showed that AST's normalization of RAS components and Notch signaling underscore a novel therapeutic avenue in ASD, impacting neuronal integrity and behavioral outcomes. These findings affirm the integral role of RAS in ASD and highlight AST's potential as a promising treatment intervention, inviting further neurological research implications.

Lead exposure induces neuronal apoptosis via NFκB p65/RBBP4/Survivin signaling pathway

Lead (Pb), as a heavy metal that is easily exposed in daily life, can cause damage to various systems of body. Apoptosis is an autonomous cell death process regulated by genes in order to maintain the stability of internal environment, which plays an important role in the development of nervous system. RB binding protein 4 (RBBP4) is one of the core histone binding subunits and is closely related to the apoptosis process of nervous system cells. However, it is not known whether RBBP4 can regulate neuronal apoptosis in lead-exposed environments. We exposed PC12 cells to 0 μM (control group), 1 μM, and 100 μM PbAc for 24 h to obtain cell samples. The female rats ingested drinking water containing 0, 0.5 g/L, and 2.0 g/L PbAc from the first day of pregnancy to three weeks after delivery to obtain hippocampal tissue samples from mammary rats. The results of TUNEL showed that lead exposure promoted the onset of apoptosis in cells and hippocampus. The mRNA and protein levels of the apoptosis-related protein Survivin were significantly reduced in the lead-exposed group compared to the control group. In addition, we found that lead exposure reduces the mRNA and protein levels of RBBP4 in PC12 cells and hippocampus, and increases the mRNA and protein levels of NFκB p65. Moreover, inhibiting NFκB p65 can reverse the decrease in RBBP4 expression in the lead exposure model. Overexpression of RBBP4 increased Survivin expression and reduced apoptosis induced by lead exposure. This suggests that lead exposure induces apoptosis through the NFκB p65/RBBP4/Survivin signaling pathway.

Lithium Cholesterol Sulfate: A Novel and Potential Drug for Treating Alzheimer's Disease and Autism Spectrum Disorder

BACKGROUND AND OBJECTIVE

Recent studies have shown that lithium treatment can reduce symptoms of Alzheimer's disease (AD) and Autism Spectrum Disorder (ASD). However, the present lithium salts clinically available have serious short-term and long-term side effects which requires frequent monitoring of blood chemistry and plasma lithium levels so as to avoid toxicity. Consequently, there is a demand for a safer and more effective lithium formulation to treat these diseases.

METHODS

Hence, we firstly synthesized lithium cholesterol sulfate (LiCS) and compared its pharmacological effects with that of lithium chloride (LiCl) and sodium cholesterol sulfate (NaCS) on markers of neurodegenerative disease in cell cultures.

RESULTS

LiCS was more potent than LiCl in increasing inhibitory GSK3β (Ser9) phosphorylation (pGSK3β) in both CHO and SH-SY5Y cells. These agents dose-dependently increased pGSK3β, starting at 10 µM for LiCS and 60µM for LiCl and maximally by approximately 100% at 60 µM for LiCS and 1.25 mM for LiCl, without altering total GSK3β levels. In HEK293/tau cells, LiCS reduced tau (Thr231) phosphorylation (ptau) starting at 10 µM and maximally by 63% at 40 µM without altering total tau levels, but ptau levels were not altered by LiCl at any dose between 60 µM and 1.25 mM. In BV2 cells, LiCS and LiCl decreased LPS-induced TNFα levels, starting at 20 µM for LiCS and 5 mM for LiCl, and maximally by approximately 30% at 80 µM for LiCS and 20 mM for LiCl. NaCS at any dose between 5 and 90 µM did not alter pGSK3β, ptau or LPS-induced TNFα.

CONCLUSION

LiCS may become a new drug with good pharmacological potential for the treatment of neurodegenerative disorders such as AD and ASD by allowing lithium to more readily access intracellular pathological processes.

Lead Exposure in Developmental Ages Promotes Aβ Accumulation by Disturbing Aβ Transportation in Blood-Cerebrospinal Fluid Barrier/Blood-Brain Barriers and Impairing Aβ Clearance in the Liver

Environmental lead exposure is closely related to the progression of Alzheimer's disease (AD). Our previous study has shown that exposure to lead could result in the cholesterol unbalance and increase amyloid-beta (Aβ) generation in the brain. However, the potential effect of lead exposure on Aβ transportation is poorly reported. In this study, we sought to explore whether lead exposure in developmental ages impaired the integrity of BCSFB and BBB, two highly vascularized structures in the brain in a rat model. The Aβ clearance in the liver was also assessed. Our results showed that lead treatment in developmental ages increased the number of TUNEL-positive apoptotic cells in rat choroid plexus and microvessels. Moreover, lead exposure markedly increased pro-inflammatory factors expression including TNF-α and IL-1β in rat choroid plexus and microvessels. Interestingly, lead treatment increased the expression of AQP-1 and reduced the expression of TTR, two key proteins associated with the functions of choroid plexus and microvessels. Additionally, the expressions of ABCB1, LRP-1, and RAGE, three major receptors responsible for Aβ transportation, were disturbed by developmental lead exposure. All these pathologies resulted in Aβ_1-40 deposition within BCSFB and BBB and malfunctions of these two vascularized structures. Finally, we found that lead treatment remarkably inhibited the gene expression of LRP-1, which is responsible for Aβ endocytosis, in the liver tissue of the rat model. Collectively, our results provide the first evidence that developmental lead exposure induces Aβ deposition in BCSFB and BBB and impairs Aβ clearance in the liver, which would ultimately disturb Aβ transportation via choroid plexus/brain microvessels and facilitate Aβ deposition in the brain.

Acute lead acetate induces neurotoxicity through decreased synaptic plasticity-related protein expression and disordered dendritic formation in nerve cells

Lead (Pb) is a widespread environmental heavy metal that can damage the cerebral cortex and hippocampus, and reduce the learning and memory ability in humans and animals. In vivo and in vitro models of acute lead acetate exposure were established to further study the mechanism of neurons injury. In this study, 4-week-old female Kunming mice were randomly divided into four groups. Each group was treated with distilled water with different Pb concentrations (0, 2.4, 4.8 and 9.6 mM). Mice were killed, and brain tissues were collected to detect the changes in synaptic plasticity-related protein expression. Furthermore, Neuro-2A cells were treated with 0, 5, 25 and 50 μM lead acetate for 24 h to observe the changes in cell morphology and function. In in vivo experiment, results showed that the expression levels of cytoskeleton-associated and neural function-related proteins decreased in a dose-dependent manner in the mouse brain tissue. In in vitro experiment, compared with the control group, Pb treatment groups were observed with smaller and round cells, decreased cell density and number of synapses. In the Pb exposure group, the survival rate of nerve cells decreased evidently, and the permeability of the cell membrane was increased. Western blot results showed that the expression of cytoskeleton-associated and function-related proteins decreased gradually with increased Pb exposure dose. Confocal laser scanning microscopy results revealed the morphological and volumetric changes in Neuro-2A cells, and a dose-dependent reduction in the number of axon and dendrites. These results suggested that abnormal neural structures and inhibiting expression of synaptic plasticity-related proteins might be the possible mechanisms of Pb-induced mental retardation in human and animals, thereby laying a foundation for the molecular mechanism of Pb neurotoxicity.

Lead (Pb) exposure exacerbates behavioral and immune abnormalities by upregulating Th17 and NF-κB-related signaling in BTBR T+ Itpr3tf/J autistic mouse model

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder that are characterized by abnormal social interaction impairments in communication and repetitive and restricted activities or interests. Even though the exact etiology of ASD remains unknown. Lead (Pb) is a toxin known to harm many organs in the body, it is one of the most ubiquitous metal exposures which is associated with neurological deficits. Previous studies have shown that the exposure to Pb may play a role in ASD. BTBR T⁺ Itpr3^tf/J (BTBR) mouse model is commonly used as a preclinical model for ASD. In this study, we investigated the effects of Pb exposure on sociability, self-grooming and marble burying behaviors tests in BTBR mice. We further examined the effects of Pb on IL-17A- RORγT-, STAT3-, NF-κB p65-, iNOS-, TLR-2- and TLR-4-producing CD45⁺ cells in spleen using flow cytometry. We also explored the effects of Pb on IL-17A, RORγT, STAT3, NF-κB p65, and TLR-2 mRNA expression in the brain tissue using RT-PCR analysis. Our results demonstrated that Pb exposure substantially increased repetitive behavior, marble burying and decrease social interactions in BTBR mice. In addition, in spleen cells, Pb exposure exaggerated CD45⁺IL-17A⁺, CD45⁺RORγT⁺, CD45⁺STAT3⁺, CD45⁺NF-κB p65⁺, CD45⁺iNOS⁺, CD45⁺TLR-2⁺ and CD45⁺TLR-4⁺ in BTBR mice. We also found that Pb significantly increased IL-17A, RORγT, STAT3, NF-κB p65, and TLR-2 mRNA in the brain tissue. Therefore, Pb exposure exacerbates behavioral and neuroimmune function in BTBR mice, suggesting a potentially strong role for Pb in ASD.

Building a Network of Adverse Outcome Pathways (AOPs) Incorporating the Tau-Driven AOP Toward Memory Loss (AOP429)

The adverse outcome pathway (AOP) concept was first proposed as a tool for chemical hazard assessment facilitating the regulatory decision-making in toxicology and was more recently recommended during the BioMed21 workshops as a tool for the characterization of crucial endpoints in the human disease development. This AOP framework represents mechanistically based approaches using existing data, more realistic and relevant to human biological systems. In principle, AOPs are described by molecular initiating events (MIEs) which induce key events (KEs) leading to adverse outcomes (AOs). In addition to the individual AOPs, the network of AOPs has been also suggested to beneficially support the understanding and prediction of adverse effects in risk assessment. The AOP-based networks can capture the complexity of biological systems described by different AOPs, in which multiple AOs diverge from a single MIE or multiple MIEs trigger a cascade of KEs that converge to a single AO. Here, an AOP network incorporating a recently proposed tau-driven AOP toward memory loss (AOP429) related to sporadic (late-onset) Alzheimer’s disease is constructed. This proposed AOP network is an attempt to extract useful information for better comprehending the interactions among existing mechanistic data linked to memory loss as an early phase of sporadic Alzheimer’s disease pathology.

Early-Life Environment Influence on Late-Onset Alzheimer’s Disease

With the expand of the population’s average age, the incidence of neurodegenerative disorders has dramatically increased over the last decades. Alzheimer disease (AD) which is the most prevalent neurodegenerative disease is mostly sporadic and primarily characterized by cognitive deficits and neuropathological lesions such as amyloid -β (Aβ) plaques and neurofibrillary tangles composed of hyper- and/or abnormally phosphorylated Tau protein. AD is considered a complex disease that arises from the interaction between environmental and genetic factors, modulated by epigenetic mechanisms. Besides the well-described cognitive decline, AD patients also exhibit metabolic impairments. Metabolic and cognitive perturbations are indeed frequently observed in the Developmental Origin of Health and Diseases (DOHaD) field of research which proposes that environmental perturbations during the perinatal period determine the susceptibility to pathological conditions later in life. In this review, we explored the potential influence of early environmental exposure to risk factors (maternal stress, malnutrition, xenobiotics, chemical factors … ) and the involvement of epigenetic mechanisms on the programming of late-onset AD. Animal models indicate that offspring exposed to early-life stress during gestation and/or lactation increase both AD lesions, lead to defects in synaptic plasticity and finally to cognitive impairments. This long-lasting epigenetic programming could be modulated by factors such as nutriceuticals, epigenetic modifiers or psychosocial behaviour, offering thus future therapeutic opportunity to protect from AD development.

Mechanisms associated with the dysregulation of mitochondrial function due to lead exposure and possible implications on the development of Alzheimer's disease

Lead (Pb) is a multimedia contaminant with various pathophysiological consequences, including cognitive decline and neural abnormalities. Recent findings have reported an association of Pb toxicity with Alzheimer's disease (AD). Studies have revealed that mitochondrial dysfunction is a pathological characteristic of AD. According to toxicology reports, Pb promotes mitochondrial oxidative stress by lowering complex III activity in the electron transport chain, boosting reactive oxygen species formation, and reducing the cell's antioxidant defence system. Here, we review recent advances in the role of mitochondria in Pb-induced AD pathology, as well as the mechanisms associated with the mitochondrial dysfunction, such as the depolarisation of the mitochondrial membrane potential, mitochondrial permeability transition pore opening; mitochondrial biogenesis, bioenergetics and mitochondrial dynamics alterations; and mitophagy and apoptosis. We also discuss possible therapeutic options for mitochondrial-targeted neurodegenerative disease (AD).

Zeaxanthin Attenuates the Vicious Circle Between Endoplasmic Reticulum Stress and Tau Phosphorylation: Involvement of GSK-3β Activation

BACKGROUND

Alzheimer's disease (AD) characterized by neurofibrillary tangles caused by hyperphosphorylated tau is the most common cause of dementia. Zeaxanthin (Zea), derived from fruits and vegetables, may reduce the risk of AD. Endoplasmic reticulum stress (ERS) might cause memory impairment in AD.

OBJECTIVE

Here, we studied protective role of Zea on the relationship among ERS, activity of glycogen synthase kinase 3β (GSK-3β, tau phosphorylated kinase), and p-Tau (Ser 396 and Thr 231).

METHODS

The results were obtained in non-RA and RA group by using different treatment, such as 9-cis-retinoic acid (RA), TM (ERS inducer), Zea, 4-PBA (ERS inhibitor), and SB216763 (GSK-3β inhibitor). The methods included flow cytometry and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] for the detections of cell cycle and cell viability and western blot as a third measure of proteins in relation to ERS and tau phosphorylation. We have collected and analyzed all the data that suggested application of drugs for the treatment in non-RA and RA group.

RESULTS

Zea displays its protection on TM-induced cell injury, upregulation of GRP78 expression, and change of GSK-3β activity and tau phosphorylation when 4-PBA and SB216763 interfere with the process.

CONCLUSION

These studies indicated that Zea is in vicious circle in ERS, GSK-3β, and tau phosphorylation, and further reflect its potential value in AD.

The influence of erdosteine administration on lead-induced oxidative stress in rat muscle

Lead-exposure is known to disrupt the redox balance of tissues leading to oxidative stress. Due to the fact that a mucolytic drug, erdosteine, exerts also antioxidant properties, we decided to perform a pilot study on rats to evaluate its therapeutic potency in lead poisoning. Male Wistar rats were divided randomly into the following seven groups having 10 animals in each. Group I served as the control group. During 8-week period, rats in groups II-IV, except standard alimentation, received: erdosteine in a dose 350 mg/kg (collateral control group), 1200 ppm of lead acetate in drinking water and placebo, as well as the same doses of lead and erdosteine, respectively. Rats in group V-VII received 1200 ppm of lead acetate in drinking water for the initial 6-week period and then administered: placebo, erdosteine and EDTA for 2 weeks, respectively. The levels of malondialdehyde (MDA) were significantly higher in groups III and V compared to the control group. The activities of catalase (CAT) were significantly higher in groups IV, V, and VI compared to the control group. The activities of glutathione-S-transferase (GST) were significantly lower in group II and significantly higher in groups VI and VII compared to the control group, while the activities of glutathione reductase (GR) were significantly lower in group III and significantly higher in group VI. Erdosteine has an effect of protection against lead-induced oxidative stress which is not worse than that of EDTA.

Ratiometric G-Quadruplex Assay for Robust Lead Detection in Food Samples

Lead (Pb²⁺) pollution is a serious food safety issue, rapid detection of Pb²⁺ residual in food is vital to guarantee food quality and safety. Here we proposed ratiometric aptamer probes, allowing robust Pb²⁺ supervision in food samples. Pb²⁺ specific aptamer can bolster a transition of G-quadruplex structural response to Pb²⁺; this process can be monitored by N-methyl mesoporphyrin IX (NMM), which is highly specific to G-quadruplex. Particularly, the utilization of G-quadruplex specific dye and terminal-labeled fluorophore allowed to endue ratiometric signal outputs towards Pb²⁺, dramatically increase the robustness for lead detection. The ratiometric G-quadruplex assay allowed a facile and one-pot Pb²⁺ detection at room temperature using a single-stranded DNA aptamer. We demonstrated its feasibility for detecting lead pollution in fresh eggs and tap water samples. The ratiometric G-quadruplex design is expected to be used for on-site Pb²⁺ testing associated with food safety.

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

Perinatal Lead Exposure Alters Calsyntenin-2 and Calsyntenin-3 Expression in the Hippocampus and Causes Learning Deficits in Mice Post-weaning

Calsyntenin-2 (Clstn2) and calsyntenin-3 (Clstn3) are the members of the cadherin superfamily and function to regulate the postsynaptic activity. Both proteins are known to play an important role in memory and learning. This study was designed to test the hypothesis that exposure of mothers to Pb in drinking water may alter the expression of Clstn2 and Clstn3 in offspring, which contributes to the Pb-induced learning deficiency. Pregnant mice were exposed to Pb in drinking water as Pb acetate from gestation to weaning. At the postnatal day 21, the learning and memory ability of pups was tested by Morris water maze, and the blood and brain tissues from pups were collected for metal and protein analyses. Data showed that perinatal Pb exposure resulted in a dose-dependent increase of Pb concentrations in blood (6-20-fold), hippocampus (2-7-fold), and cerebral cortex (2-8-fold) in offspring, as compared to controls (p < 0.05).The ability of learning and memory was decreased in lead exposure group, as compared to controls (p < 0.05). Both immunofluorescence and Western blot analyses revealed a striking difference in the expression of Clstn2 vs. Clstn3 following perinatal Pb exposure. In pregnant mice exposed to 0.1%, 0.2%, and 0.5% Pb, the expression of Clstn2 in offspring showed a Pb dose-related decrease by 39.2%, 76.5%, and 96.1% in hippocampus and by12.5%, 59.4%, and 78.1% in cerebral cortex, respectively (p < 0.05). In contrast, Clstn3 expression in these offspring brain regions was significantly increased (p < 0.05), after perinatal Pb exposure. The nature of Pb differential effect on Clstn2 and Clstn3 remains unknown. These observations suggest that Clstn2 and Clstn3 may have different roles in synaptic development and differentiation. Pb-induced learning defects may partly relate to the altered expression of calsyntenin proteins.

Alterations in Tau Protein Level and Phosphorylation State in the Brain of the Autistic-Like Rats Induced by Prenatal Exposure to Valproic Acid

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficient social interaction and communication besides repetitive, stereotyped behaviours. A characteristic feature of ASD is altered dendritic spine density and morphology associated with synaptic plasticity disturbances. Since microtubules (MTs) regulate dendritic spine morphology and play an important role in spine development and plasticity the aim of the present study was to investigate the alterations in the content of neuronal α/β-tubulin and Tau protein level as well as phosphorylation state in the valproic acid (VPA)-induced rat model of autism. Our results indicated that maternal exposure to VPA induces: (1) decrease the level of α/β-tubulin along with Tau accumulation in the hippocampus and cerebral cortex; (2) excessive Tau phosphorylation and activation of Tau-kinases: CDK5, ERK1/2, and p70S6K in the cerebral cortex; (3) up-regulation of mTOR kinase-dependent signalling in the hippocampus and cerebral cortex of adolescent rat offspring. Moreover, immunohistochemical staining showed histopathological changes in neurons (chromatolysis) in both analysed brain structures of rats prenatally exposed to VPA. The observed changes in Tau protein together with an excessive decrease in α/β-tubulin level may suggest destabilization and thus dysfunction of the MT cytoskeleton network, which in consequence may lead to the disturbance in synaptic plasticity and the development of autistic-like behaviours.

Lead (Pb) Accumulation in Human THP-1 Monocytes/Macrophages In Vitro and the Influence on Cell Apoptosis

In this study, we investigated the ability of THP-1 monocytes and macrophages to accumulate lead (Pb) in vitro, relative to Pb concentration and length of exposure. Moreover, we also evaluated the effect of Pb accumulation on cell viability and apoptosis. THP-1 monocytes and macrophages were cultured in the presence of Pb at 1.25 μg/dL, 2.5 μg/dL, 5 μg/dL, and 10 μg/dL. Pb accumulation was examined by inductively coupled plasma and confocal microscopy. The influence of Pb on cell viability, apoptosis, and necrosis was assessed using flow cytometry. The results showed that Pb was toxic to THP-1 monocytes/macrophages even at very low environmental concentrations. Despite the use of low concentrations, both monocytes and macrophages showed dose-dependent and time-dependent decreases in viability, with a simultaneous increase in the percentage of early and late apoptotic cells. Macrophages reacted more strongly to Pb than monocytes. When exposed to the same Pb concentrations, they showed lower viability and a higher percentage of necrotic cells. The incubation time positively correlated with Pb accumulation in a dose-dependent manner. The obtained results indicate that environmental exposure to low Pb concentrations may significantly impair the function of macrophages, with the increased number of apoptotic cells potentially contributing to the development of many pathologies in the brain and whole body.

Signal transduction associated with lead-induced neurological disorders: A review

Lead is a heavy metal pollutant that is widely present in the environment. It affects every organ system, yet the nervous system appears to be the most sensitive and primary target. Although many countries have made significant strides in controlling Pb pollution, Pb poisoning continuous to be a major public health concern. Exposure to Pb causes neurotoxicity that ranges from neurodevelopmental disorders to severe neurodegenerative lesions, leading to impairments in learning, memory, and cognitive function. Studies on the mechanisms of Pb-induced nervous system injury have convincingly shown that this metal can affect a plethora of cellular pathways affecting on cell survival, altering calcium dyshomeostasis, and inducing apoptosis, inflammation, energy metabolism disorders, oxidative stress, autophagy and glial stress. This review summarizes recent knowledge on multiple signaling pathways associated with Pb-induced neurological disorders in vivo and in vitro.

Cognitive Impairment Induced by Lead Exposure during Lifespan: Mechanisms of Lead Neurotoxicity

Lead (Pb) is considered a strong environmental toxin with human health repercussions. Due to its widespread use and the number of people potentially exposed to different sources of this heavy metal, Pb intoxication is recognized as a public health problem in many countries. Exposure to Pb can occur through ingestion, inhalation, dermal, and transplacental routes. The magnitude of its effects depends on several toxicity conditions: lead speciation, doses, time, and age of exposure, among others. It has been demonstrated that Pb exposure induces stronger effects during early life. The central nervous system is especially vulnerable to Pb toxicity; Pb exposure is linked to cognitive impairment, executive function alterations, abnormal social behavior, and fine motor control perturbations. This review aims to provide a general view of the cognitive consequences associated with Pb exposure during early life as well as during adulthood. Additionally, it describes the neurotoxic mechanisms associated with cognitive impairment induced by Pb, which include neurochemical, molecular, and morphological changes that jointly could have a synergic effect on the cognitive performance.

The Synaptic Dysregulation in Adolescent Rats Exposed to Maternal Immune Activation

Maternal immune activation (MIA) is a risk factor for neurodevelopmental disorders in offspring, but the pathomechanism is largely unknown. The aim of our study was to analyse the molecular mechanisms contributing to synaptic alterations in hippocampi of adolescent rats exposed prenatally to MIA. MIA was evoked in pregnant female rats by i.p. administration of lipopolysaccharide at gestation day 9.5. Hippocampi of offspring (52-53-days-old rats) were analysed using transmission electron microscopy (TEM), qPCR and Western blotting. Moreover, mitochondrial membrane potential, activity of respiratory complexes, and changes in glutathione system were measured. It was found that MIA induced changes in hippocampi morphology, especially in the ultrastructure of synapses, including synaptic mitochondria, which were accompanied by impairment of mitochondrial electron transport chain and decreased mitochondrial membrane potential. These phenomena were in agreement with increased generation of reactive oxygen species, which was evidenced by a decreased reduced/oxidised glutathione ratio and an increased level of dichlorofluorescein (DCF) oxidation. Activation of cyclin-dependent kinase 5, and phosphorylation of glycogen synthase kinase 3β on Ser9 occurred, leading to its inhibition and, accordingly, to hypophosphorylation of microtubule associated protein tau (MAPT). Abnormal phosphorylation and dysfunction of MAPT, the manager of the neuronal cytoskeleton, harmonised with changes in synaptic proteins. In conclusion, this is the first study demonstrating widespread synaptic changes in hippocampi of adolescent offspring prenatally exposed to MIA.

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.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

The Effect of Whole Blood Lead (Pb-B) Levels on Changes in Peripheral Blood Morphology and Selected Biochemical Parameters, and the Severity of Depression in Peri-Menopausal Women at Risk of Metabolic Syndrome or with Metabolic Syndrome

The aim of our study was to assess the impact of whole blood lead (Pb-B) levels on changes in peripheral blood morphology and selected biochemical parameters, and the severity of depression in peri-menopausal women at risk of metabolic syndrome (pre-MetS) or with metabolic syndrome (MetS). The study involved 233 women from the general population of the West Pomeranian Province (Poland) aged 44–65 years. The intensity of menopausal symptoms and the severity of depression was examined using the Blatt–Kupperman Index (KI) and the Beck Depression Inventory (BDI). C-reactive protein (CRP), insulin, glucose, glycated hemoglobin (HbA1C), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglyceride levels (TG), cortisol, morphology of blood cells and homeostasis model assessment for insulin resistance (HOMA-IR) and Pb-B was measured. Women with MetS had higher levels of glucose, HbA1C, HDL, LDL, TG, cortisol, insulin and higher HOMA-IR. No significant differences in Pb-B were observed between pre-MetS and the control group, and between pre-MetS and the MetS group. A significant correlation was noticed between Pb-B vs. the percentage of monocytes in blood, and blood cortisol levels in women with MetS; Pb-B vs. lymphocyte count and HbA1C in the pre-MetS group, as well as in the BDI scores between the MetS and pre-MetS group. We cannot clearly state that exposure to Pb is an environmental factor that can be considered as a risk factor for MetS in this studied group.

Depression, changes in peripheral blood cell count, and changes in selected biochemical parameters related to lead concentration in whole blood (Pb-B) of women in the menopausal period

THE AIM

The aim of this study was to assess the severity of depression, vasomotor symptoms, changes in peripheral blood cell count, and selected biochemical parameters in relation to the concentration of lead in whole blood of women in the perimenopausal period.

METHODS

The study sample consisted of 233 women from the general population of the West Pomeranian Province (Poland) in age between 44-65 years. The intensity of menopausal symptoms was examined using the Blatt-Kupperman Index, and the severity of depression using the Beck Depression Inventory. The following biochemical data were evaluated: concentrations of glucose, triglycerides, HDL, C-reactive protein, glycated haemoglobin, cortisol, insulin, blood cell count, and lead concentration in whole blood (Pb-B).

RESULTS

A whole blood Pb concentration below 5 μg/dl was found in 55 subjects (23.61 %), in 142 women (60.94 %) it ranged from 5 to 10 μg/dl, while in 36 women (15.45 %) was higher than 10 μg/dl. There was a strong positive correlation between Pb concentration in the blood of the examined women and the severity of depressive symptoms (Rs=+0.60, p = 0.001). The lowest mean values for total leukocytes (5.07 ± 1.22 thousand/μl) and neutrophils (2.76 ± 0.86 thousand/μl) were found in women with Pb concentration above 10 μg/dl (p < 0.05). There was a significant negative correlation between the number of total leukocytes (r=-0.45, p = 0.002) and neutrophils (r=-0.50, p = 0.001) and blood Pb concentration. Analysis showed statistically significant differences in glucose concentration (p < 0.05) between groups. Blood glucose was higher in women with Pb-B <5 and between 5-10 μg/dl than in women with Pb-B >10 μg/dl.

CONCLUSION

Exposure to Pb may be a factor playing a significant role in the development of depressive symptoms in menopausal women. It may also be associated with glucose metabolism disorders and immunosuppression in women during this period of life.

Lead (Pb) as a Factor Initiating and Potentiating Inflammation in Human THP-1 Macrophages

The aim of this study was to assess the influence of lead (Pb) at low concentrations (imitating Pb levels in human blood in chronic environmental exposure to this metal) on interleukin 1β (IL-1β) and interleukin 6 (IL-6) concentrations and the activity and expression of COX-1 and COX-2 in THP-1 macrophages. Macrophages were cultured in vitro in the presence of Pb at concentrations of: 1.25 μg/dL; 2.5 μg/dL; 5 μg/dL; 10 μg/dL. The first two concentrations of Pb were selected on the basis of our earlier study, which showed that Pb concentration in whole blood (PbB) of young women living in the northern regions of Poland and in the cord blood of their newborn children was within this range (a dose imitating environmental exposure). Concentrations of 5 μg/dL and 10 μg/dL correspond to the previously permissible PbB concentrations in children or pregnant women, and adults. Our results indicate that even low concentrations of Pb cause an increase in production of inflammatory interleukins (IL-1β and IL-6), increases expression of COX-1 and COX-2, and increases thromboxane B2 and prostaglandin E2 concentration in macrophages. This clearly suggests that the development of inflammation is associated not only with COX-2 but also with COX-1, which, until recently, had only been attributed constitutive expression. It can be concluded that environmental Pb concentrations are able to activate the monocytes/macrophages similarly to the manner observed during inflammation.

Highly effective removal of Pb2+ in aqueous solution by Na-X zeolite derived from coal gangue

The present study aimed to synthesize Na-X zeolite from coal gangue powder (CGP) via the alkali fusion hydrothermal method. The optimal synthetic conditions were investigated, the mass ratio of CGP/NaOH(s) was 1:1.25, and crystallization reaction time was 12 h. X-ray powder diffraction, scanning electron microscopy energy-dispersive X-ray spectrum, and Fourier transform infrared spectrometer techniques were used to test the properties of resultant zeolite product, which was highly identical to that of commercial zeolite. The efficiencies of the synthetic zeolite for Pb²⁺ adsorption were analyzed on factors including solution pH, adsorbent dosage, temperature, and contact time. Compared with the pseudo-first-order, Elovich, Freundlich, and Temkin models, the pseudo-second-order and Langmuir models were fitted more satisfactorily with the dynamic data and adsorption equilibrium data, respectively. The maximum Pb²⁺ adsorption capacity of synthetic zeolite (457 mg/g) could be reached when the pH, contact time, temperature, and initial Pb²⁺ concentration was 6, 40 min, 45 °C, and 200 mg/L. The adsorption capacity was higher than many of the natural and synthetic zeolites reported in previous literature.

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.

Association between blood lead level and subsequent Alzheimer's disease mortality

Background:

Previous studies suggest that cumulative lead exposure is associated with cognitive decline, but its relation with Alzheimer’s disease (AD) remains unclear. Therefore, this study investigated the longitudinal association between blood lead level (BLL) and AD mortality.

Methods:

This study included 8,080 elders (60 years or older) with BLL data from the 1999 to 2008 US National Health and Nutrition Examination Survey. Mortality was determined from linked 1999–2014 National Death Index data. A causal diagram presented causal assumptions and identified a sufficient set of confounders: age, sex, poverty, race/ethnicity, and smoking. Cox proportional hazard models were used to determine the association between BLL and subsequent AD mortality. Impacts of competing risks and design effect were also assessed. Adjusted hazard rate ratio (HRR) and 95% confidence interval (CI) were reported.

Results:

Follow-up ranged from <1 to 152 months (median, 74). Eighty-one participants died from AD over 632,075 total person-months at risk. An increase in BLL was associated with an increase in AD mortality after adjusting for identified confounders. We estimated that those with BLL of 1.5 and 5 μg/dl had 1.2 (95% CI = 0.70, 2.1) and 1.4 (95% CI = 0.54, 3.8) times the rate of AD mortality compared to those with BLL of 0.3 μg/dl, respectively, after accounting for competing risks. Adjusted HRRs were 1.5 (95% CI = 0.81, 2.9) and 2.1 (95% CI = 0.70, 6.3), respectively, after considering design effect.

Conclusions:

This longitudinal study demonstrated a positive, albeit not statistically significant, association between BLL and AD mortality after adjustment for competing risks or design effect.

Hair Mineral and Trace Element Content in Children with Down's Syndrome

The objective of the present study was to assess the level of minerals and trace elements in 40 children with Down's syndrome and 40 controls aged 1-2 years old. Hair mineral and trace element analysis was performed using inductively coupled plasma mass spectrometry. The obtained data demonstrate that hair levels of Mg, P, I, Cr, Si, Zn, and Pb in Down's syndrome patients exceeded the respective control values by 36, 36, 93, 57, 45, 28, and 54%, whereas hair mercury was more than twofold lower in children with Down's syndrome. The observed difference in the levels of trace elements was age-dependent. In particular, in 1-year-olds, major differences were observed for essential elements (Cr, Si, Zn), whereas in 2-year-olds-for toxic elements (Hg, Pb). At the same time, hair P levels in Down's syndrome patients were 14 and 35% higher at the age of 1 and 2 years in comparison to the respective controls. Multiple regression analysis demonstrated that a model incorporating all elements, being characterized by a significant group difference, accounted for 42.5% of status variability. At the same time, only hair phosphorus was significantly interrelated with Down's syndrome status (β = 0.478; p < 0.001). Principal component analysis (PCA) used As, Ca, Cr, Fe, Hg, I, Mg, P, Pb, Se, Si, Sn, and Zn as predictors, with the resulting R² = 0.559. The OPLS-DA models also separated between Down's and health control groups. Therefore, 1-2-year-old patients with Down's syndrome are characterized by significant alterations of mineral and trace element status.

Potential Role of Fluoride in the Etiopathogenesis of Alzheimer's Disease

The etiopathogenesis of Alzheimer's disease has not been fully explained. Now, the disease is widely attributed both to genetic and environmental factors. It is believed that only a small percentage of new AD cases result solely from genetic mutations, with most cases attributed to environmental factors or to the interaction of environmental factors with preexistent genetic determinants. Fluoride is widespread in the environment and it easily crosses the blood⁻brain barrier. In the brain fluoride affects cellular energy metabolism, synthesis of inflammatory factors, neurotransmitter metabolism, microglial activation, and the expression of proteins involved in neuronal maturation. Finally, and of specific importance to its role in Alzheimer's disease, studies report fluoride-induced apoptosis and inflammation within the central nervous system. This review attempts to elucidate the potential relationship between the effects of fluoride exposure and the pathogenesis of Alzheimer's disease. We describe the impact of fluoride-induced oxidative stress and inflammation in the pathogenesis of AD and demonstrate a role for apoptosis in disease progression, as well as a mechanism for its initiation by fluoride. The influence of fluoride on processes of AD initiation and progression is complex and warrants further investigation, especially considering growing environmental fluoride pollution.

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.

Dihydromyricetin Inhibits Lead-Induced Cognitive Impairments and Inflammation by the Adenosine 5'-Monophosphate-Activated Protein Kinase Pathway in Mice

Dihydromyricetin (DHM), a natural flavonoid derived from the medicinal and edible plant Ampelopsis grossedentata, exhibits antioxidant, antiapoptosis, antitumor, and anti-inflammatory bioactivities. This study evaluated the effects of DHM on Pb-induced neurotoxicity and explored the underlying mechanisms. DHM significantly ameliorated behavioral impairments of Pb-induced mice. It decreased the levels of lipid peroxidation and protein carbonyl and increased the activities of superoxide dismutase and catalase in the brains. DHM suppressed Pb-induced apoptosis, as indicated by the decreased levels of Bax and cleaved caspase-3. DHM also decreased inflammatory cytokines in the brains of Pb-treated mice. DHM decreased amyloid-beta (Aβ) level and nuclear factor-κB nuclear translocation. Moreover, DHM induced the adenosine 5'-monophosphate-activated protein kinase (AMPK) phosphorylation and inhibited the activation of p38, Toll-like receptor 4, myeloid differentiation factor 88, and glycogen synthase kinase-3. Collectively, this is the first report indicating that DHM could improve Pb-induced cognitive functional impairment by preventing oxidative stress, apoptosis, and inflammation and that the protective effect was mediated partly through the AMPK pathway.

Psychiatric benefits of lithium in water supplies may be due to protection from the neurotoxicity of lead exposure

INTRODUCTION

Lithium is a medication used to treat bipolar disorder and may also prevent cognitive decline and suicide. Lithium is also found naturally, in levels well below clinical doses, in drinking water worldwide, and levels have been inversely associated with rates of psychiatric disorders. Lead (Pb) is another element in the environment but is a toxin of public health concern. Negative effects of chronic lead exposure and possible benefits of environmental lithium exposure appear complementary.

HYPOTHESIS

Exposure to environmental lithium has associated benefits, which may be due to the mitigation of lead toxicity by lithium.

METHODS

A series of reviews tested each element of the hypothesis. A systematic review clarified the psychiatric and medical correlates of lithium in drinking water. Non-systematic reviews clarified the harms of environmental lead, summarized experimental studies of lithium used to prevent lead toxicity, and explored overlapping biological mechanisms in lithium and lead exposure.

RESULTS

Higher levels of lithium in drinking water were associated with lower suicide rates in 13 of 15 identified studies. While fewer studies were available for other outcomes, lithium was associated with lower rates of homicide, crime, dementia, and mortality. Lead was reported to be ubiquitous in the environment, and chronic low-level exposure has been associated with adverse effects, including effects opposite to the outcomes associated with lithium. Animal studies demonstrated that lithium pre-treatment mitigates lead toxicity. Neurophysiological correlates of lead and lithium exposure overlap.

CONCLUSIONS

Microdose lithium is associated with better psychiatric and medical outcomes, which are complementary to harms of environmental lead exposure. Experimental animal evidence is supportive, and lead and lithium impact overlapping neurophysiologic pathways. Therefore, several lines of circumstantial evidence suggest that lithium protects against the neurotoxic effects of lead. Further studies are required to clarify the benefits and mechanisms of low-dose lithium. There are significant public health implications if this paper's hypothesis is true.

Lead-induced changes of cytoskeletal protein is involved in the pathological basis in mice brain

Lead poisoning is a geochemical disease. On the other hand, lead is highly carcinogenic and exhibits liver and kidney toxicity. This element can also cross the blood-brain barrier, reduce learning and memory ability and damage the structure of the cerebral cortex and hippocampus. To further investigate the mechanism of lead neurotoxicity, 4-week-old Kunming mice were used to explore the effects of different concentrations of Pb²⁺ (0, 2.4, 4.8 and 9.6 mM) for 9 days. In this study, pathological and ultrastructural changes in brain cells of the treated group were related to damages to mitochondria, chromatin and the nucleus. Lead content in blood was tested by atomic absorption spectroscopy, which showed high lead concentrations in the blood with increasing doses of lead. Distribution of lead in nerve cells was analysed by transmission electron microscopy with energy dispersive spectroscopy. Data showed the presence of lead in nucleopores, chromatin and nuclear membrane of nerve cells in the treatment groups, whereas lead content increased with increasing doses of lead acetate. Finally, microtubule-associated protein 2 (MAP2) mRNA and protein expression levels were detected by real-time PCR and Western blotting, which showed a reduction in MAP2 expression with increasing lead doses in the mouse brain. These findings suggest that acute lead poisoning can cause significant dose-dependent toxic effects on mouse brain function and can contribute to better understanding of lead-induced toxicity.

Metal Ion Effects on Aβ and Tau Aggregation

Amyloid and tau aggregation are implicated in manifold neurodegenerative diseases and serve as two signature pathological hallmarks in Alzheimer's disease (AD). Though aging is considered as a prominent risk factor for AD pathogenesis, substantial evidence suggests that an imbalance of essential biometal ions in the body and exposure to certain metal ions in the environment can potentially induce alterations to AD pathology. Despite their physiological importance in various intracellular processes, biometal ions, when present in excessive or deficient amounts, can serve as a mediating factor for neurotoxicity. Recent studies have also demonstrated the contribution of metal ions found in the environment on mediating AD pathogenesis. In this regard, the neuropathological features associated with biometal ion dyshomeostasis and environmental metal ion exposure have prompted widespread interest by multiple research groups. In this review, we discuss and elaborate on findings from previous studies detailing the possible role of both endogenous and exogenous metal ions specifically on amyloid and tau pathology in AD.

Glycogen metabolism in brain and neurons - astrocytes metabolic cooperation can be altered by pre- and neonatal lead (Pb) exposure

Lead (Pb) is an environmental neurotoxin which particularly affects the developing brain but the molecular mechanism of its neurotoxicity still needs clarification. The aim of this paper was to examine whether pre- and neonatal exposure to Pb (concentration of Pb in rat offspring blood below the "threshold level") may affect the brain's energy metabolism in neurons and astrocytes via the amount of available glycogen. We investigated the glycogen concentration in the brain, as well as the expression of the key enzymes involved in glycogen metabolism in brain: glycogen synthase 1 (Gys1), glycogen phosphorylase (PYGM, an isoform active in astrocytes; and PYGB, an isoform active in neurons) and phosphorylase kinase β (PHKB). Moreover, the expression of connexin 43 (Cx43) was evaluated to analyze whether Pb poisoning during the early phase of life may affect the neuron-astrocytes' metabolic cooperation. This work shows for the first time that exposure to Pb in early life can impair brain energy metabolism by reducing the amount of glycogen and decreasing the rate of its metabolism. This reduction in brain glycogen level was accompanied by a decrease in Gys1 expression. We noted a reduction in the immunoreactivity and the gene expression of both PYGB and PYGM isoform, as well as an increase in the expression of PHKB in Pb-treated rats. Moreover, exposure to Pb induced decrease in connexin 43 immunoexpression in all the brain structures analyzed, both in astrocytes as well as in neurons. Our data suggests that exposure to Pb in the pre- and neonatal periods results in a decrease in the level of brain glycogen and a reduction in the rate of its metabolism, thereby reducing glucose availability, which as a further consequence may lead to the impairment of brain energy metabolism and the metabolic cooperation between neurons and astrocytes.

SLM, a novel carbazole-based fluorophore attenuates okadaic acid-induced tau hyperphosphorylation via down-regulating GSK-3β activity in SH-SY5Y cells

Phosphorylated tau dissociates from microtubules and aggregates to form neurofibrillary tangles resulting in neuronal toxicity and cognitive deficits. Attenuating tau hyperphosphorylation is considered as an effective therapeutic approach for Alzheimer's disease (AD). From our previous study, SLM, a carbazole-based fluorophore prevents Aβ aggregation, reduced glycogen synthase kinase-3β (GSK-3β) activity and tau hyperphosphorylation in triple transgenic mouse model of AD. However, the mechanism by which SLM attenuates tau hyperphosphorylation warrants further investigation. In the current study, we intend to evaluate the effects of SLM against okadaic acid (OA)-induced tau hyperphosphorylation and microtubules instability in human neuroblastoma (SH-SY5Y) cells. The results showed that, SLM reduced the OA-induced cell neurotoxicity and tau hyperphosphorylation in SH-SY5Y cells. SLM treatment down-regulated GSK-3β activity. However, in the presence of GSK-3β inhibitor (SB216763, 10μM), SLM treatment could not reduce GSK-3β activity and tau hyperphosphorylation as compared with SB216763 treatment alone. Furthermore, SLM treatment also ameliorated OA-induced microtubules instability and cytoskeleton damage. Collectively, SLM attenuated OA-induced tau hyperphosphorylation via down-regulating GSK-3β activity in SH-SY5Y cells. Therefore, this study supports SLM as a potential compound for AD and other tau pathology-related neurodegenerative disorders.