Differential response to lead toxicity in rat primary microglia and astrocytes

M1 polarization induction by lead and amyloid peptides in microglial cells: Implications for neurodegeneration process

Neurodegeneration in conditions like Alzheimer's and Parkinson's disease is influenced by genetic and environmental factors. This study explores the potential neurodegenerative effects of lead (Pb) toxicity and amyloid beta peptides (Aβp 1-40 and Aβp 25-35) by promoting M1 polarization in microglial cells. To this end, we investigated and observed that IC50 concentrations of Pb (22.8 μM) and Aβp 25-35(29.6 μM). Our results demonstrated significant Pb uptake (31.13% at 25 μM Pb) and increased intracellular ROS levels (77.1%) upon treatment with Pb in combination of both Aβp 1-40 and Aβp 25-35. Protein carbonylation significantly increased (73.12 nmol/mL) upon treatment with Pb in combination of both Aβp 1-40 and Aβp 25-35, indicating oxidative damage and compromised cellular defenses against oxidative stress along with elevated DNA oxidative damage (164.9 pg/mL of 8-OH-dG) upon treatment with Pb in combination with both Aβp 1-40 and Aβp 25-35. Microglial polarization showed elevated M1 markers (inducible nitric oxide synthase and cyclooxygenase 2) and reduced M2 markers (arginase-1 and cluster of differentiation 206), suggesting Pb's role in inducing neurodegenerative microglial polarization. These findings provide insights into the complex molecular events contributing to Pb-induced neurotoxicity and neurodegenerative diseases.

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.

Magnesium-lithium thin films for neurological applications-An in vitro investigation of glial cytocompatibility and neuroinflammatory response

Lithium (Li), a widely used drug for bipolar disorder management, is associated with many side effects due to systemic exposure. The localized delivery of lithium through implants could be an approach to overcome this challenge, for which biodegradable magnesium (Mg)-based materials are a promising choice. In this study, we focus on Mg-Li thin film alloys as potential Li-releasing implants. Therefore, we investigated the in vitro short-term corrosion behavior and cytocompatibility of two alloys, Mg-1.6wt%Li and Mg-9.5wt%Li. As glial cells are the key players of foreign body responses to implants, we used human glial cell lines for cytocompatibility studies, and a murine brain slice model for a more holistic view at the neuroinflammatory response. We found that Mg-1.6wt%Li corrodes approximately six times slower than Mg-9.5wt%Li. Microscopic analysis showed that the material surface (Mg-1.6wt%Li) is suitable for cell adhesion. The cytocompatibility test with Mg-1.6wt%Li and Mg-9.5wt%Li alloy extracts revealed that both cell types proliferated well up to 10 mM Mg concentration, irrespective of the Li concentration. In the murine brain slice model, Mg-1.6wt%Li and Mg-9.5wt%Li alloy extracts did not provoke a significant upregulation of glial inflammatory/ reactivity markers (IL-1β, IL-6, FN1, TNC) after 24 h of exposure. Furthermore, the gene expression of IL-1β (up to 3-fold) and IL-6 (up to 16-fold) were significantly downregulated after 96 h, and IL-6 downregulation showed a Li concentration dependency. Together, these results indicate the acute cytocompatibility of two Mg-Li thin film alloys and provide basis for future studies to explore promising applications of the material. STATEMENT OF SIGNIFICANCE: We propose the idea of lithium delivery to the brain via biodegradable implants to reduce systemic side effects of lithium for bipolar disorder therapy and other neurological applications. This is the first in vitro study investigating Mg-xLi thin film degradation under physiological conditions and its influence on cellular responses such as proliferation, viability, morphology and inflammation. Utilizing human brain-derived cell lines, we showed that the material surface of such a thin film alloy is suitable for normal cell attachment. Using murine brain slices, which comprise a multicellular network, we demonstrated that the material extracts did not elicit a pro-inflammatory response. These results substantiate that degradable Mg-Li materials are biocompatible and support the further investigation of their potential as neurological implants.

Screening and Identification of Probiotic Lactobacilli from the Infant Gut Microbiota to Alleviate Lead Toxicity

Lead (Pb2+) exposure cause a potential hazard to human health and the ecological environment; however, prevention and treatment of Pb2+ toxicity remain problems. The aim of this study is to isolate a novel probiotic lead (Pb2+)-resistant Lactobacillus strain from the infant gut microbiota and to determine whether they have the probiotic properties and investigate its preventive and therapeutic effects in the early-life Pb2+ exposure mouse model. In the present study, a total of 64 Pb2+-resistant colonies were isolated from the infant gut microbiota. Of these colonies, SYF-08, identified as Lacticaseibacillus casei, exhibited a Pb2+-binding capacity and Pb2+ tolerance. The in vivo study showed that SYF-08 treatment could effectively reduce Pb2+ levels in the blood, alleviate Pb2+ enrichment in bone and brain tissues, and recover the intestinal and brain damage in both dams and offspring. SYF-08 treatment also improved the antioxidant index in the liver and kidney tissues, while increasing the diversity of the intestinal microbiota of the offspring. The results of the in vitro and in vivo studies suggest that SYF-08, isolated from infant fecal samples, is a promising candidate probiotic against Pb2+ toxicity.

Dietary fiber ameliorates lead-induced gut microbiota disturbance and alleviates neuroinflammation

Dietary fiber (DF) is a carbohydrate from the edible part of plants and has the functions of promoting gastrointestinal motility, regulating gut microbiota (GM) and improving health. Lead is a non-essential toxic heavy metal that can accumulate in the environment over time and enter the body through the respiratory tract, skin and gastrointestinal tract. Lead not only causes disturbances in GM but also leads to loss of homeostasis of immune functions, causes neuronal damage and results in neuroinflammation. The scientific literature has reported that DF had anti-inflammatory activity as a natural product. This review highlights the role of DF and its metabolic products in alleviating lead-induced neuroinflammation by inducing changes in the species and quantity of GM and regulating the immune system, providing a potential dietary protective strategy for lead-induced disease. © 2022 Society of Chemical Industry.

Lead-induced neurodevelopmental lesion and epigenetic landscape: Implication in neurological disorders

Lead (Pb) was implicated in multiple genotoxic, neuroepigenotoxic, and chromosomal-toxic mechanisms and interacted with varying synaptic plasticity pathways, likely underpinning previous reports of links between Pb and cognitive impairment. Epigenetic changes have emerged as a promising biomarker for neurological disorders, including cognitive disorders, Alzheimer's disease (AD), and Parkinson's disease (PD). In the present review, special attention is paid to neural epigenetic features and mechanisms that can alter gene expression patterns upon environmental Pb exposure in rodents, primates, and zebrafish. Epigenetic modifications have also been discussed in population studies and cell experiment. Further, we explore growing evidence of potential linkage between Pb-induced disruption of regulatory pathway and neurodevelopmental and neurological disorders both in vivo and in vitro. These findings uncover how epigenome in neurons facilitates the development and function of the brain in response to Pb insult.

N,N'bis-(2-mercaptoethyl) isophthalamide (NBMI) exerts neuroprotection against lead-induced toxicity in U-87 MG cells

N,N'-bis(2-mercaptoethyl)isophthalamide (NBMI) is a novel lipophilic heavy metal chelator and thiol redox antioxidant. This study was designed to investigate the neuroprotective activity of NBMI in U-87 MG cells exposed to lead acetate (PbAc). Cells were pretreated with NBMI for 24 h prior to a 48 h exposure to PbAc. Cell death (55%, p < 0.0001) and reduction of intracellular GSH levels (0.70-fold, p < 0.005) induced by 250 µM Pb were successfully attenuated by NBMI pretreatment at concentrations as low as 10 µM. A similar pretreatment with the FDA-approved Pb chelator dimercaptosuccinic acid (DMSA) proved ineffective, indicating a superior PKPD profile for NBMI. Pretreatment with NBMI successfully counteracted Pb-induced neuroinflammation by reducing IL-1β (0.59-fold, p < 0.05) and GFAP expression levels. NBMI alone was also found to significantly increase ferroportin expression (1.97-fold, p < 0.05) thereby enhancing cellular ability to efflux heavy metals. While no response was observed on the apoptotic pathway, this study demonstrated for the first time that necrotic cell death induced by Pb in U-87 MG cells is successfully attenuated by NBMI. Collectively these data demonstrate NBMI to be a promising neuroprotective compound in the realm of Pb poisoning.

Detoxification modification of coal-tar pitch by ultraviolet & microwave radiation-enhanced chemical reaction and toxicity evaluation by chemical index and cytotoxicity assay in vitro

Although coal tar pitch (CTP) has a large yield in China, its large-scale and effective utilization is significantly hindered because of existing and possibly releasing polycyclic aromatic hydrocarbons (PAHs). Therefore, it is an imminent problem how to prepare an environmentally friendly CTP by detoxification modification. In the investigation, a typical CTP was subjected to structural characterization via solid-state ¹³C NMR and gas chromatograph/mass spectrometer, which confirmed the existence of dominant PAHs such as fluoranthene, pyrene, as well as benzo[a]pyrene, and few heterocyclic compounds. Subsequently, the CTP was modified using 10-undecenal via alkylation reaction enhanced by ultraviolet & microwave radiation. Compared with the original CTP, the total content of 16 toxic PAHs in the modified CTP decreased with a reduction efficiency of above 90%. According to different environmental standards, toxic equivalent quotient of CTP after modification was reduced by above 90%. In order to veritably and fully evaluate the toxicity of CTP, a living vascular smooth muscle cell (A-10 cell) in vitro was used in the cell counting kit-8 assay. The viability of A-10 cell was always higher when exposed to modified CTP than the original CTP. These results powerfully indicated that the enhanced modification was actually effective and efficient for reducing the toxicity of CTP.

MOLECULAR MECHANISMS OF LEAD NEUROTOXICITY

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

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.

Interaction of Microglia and Astrocytes in the Neurovascular Unit

The interaction between microglia and astrocytes significantly influences neuroinflammation. Microglia/astrocytes, part of the neurovascular unit (NVU), are activated by various brain insults. The local extracellular and intracellular signals determine their characteristics and switch of phenotypes. Microglia and astrocytes are activated into two polarization states: the pro-inflammatory phenotype (M1 and A1) and the anti-inflammatory phenotype (M2 and A2). During neuroinflammation, induced by stroke or lipopolysaccharides, microglia are more sensitive to pathogens, or damage; they are thus initially activated into the M1 phenotype and produce common inflammatory signals such as IL-1 and TNF-α to trigger reactive astrocytes into the A1 phenotype. These inflammatory signals can be amplified not only by the self-feedback loop of microglial activation but also by the unique anatomy structure of astrocytes. As the pathology further progresses, resulting in local environmental changes, M1-like microglia switch to the M2 phenotype, and M2 crosstalk with A2. While astrocytes communicate simultaneously with neurons and blood vessels to maintain the function of neurons and the blood-brain barrier (BBB), their subtle changes may be identified and responded by astrocytes, and possibly transferred to microglia. Although both microglia and astrocytes have different functional characteristics, they can achieve immune "optimization" through their mutual communication and cooperation in the NVU and build a cascaded immune network of amplification.

Effects of Gastrodin against Lead-Induced Brain Injury in Mice Associated with the Wnt/Nrf2 Pathway

Gastrodin (GAS), the main phenolic glycoside extracted from Gastrodia elata Blume, exhibited potential neuroprotective properties. Here we examined the protective effects of GAS against lead(Pb)-induced nerve injury in mice, and explores its underlying mechanisms. Our research findings revealed that GAS improved behavioral deficits in Pb-exposed mice. GAS reduced the accumulation of p-tau and amyloid-beta (Aβ). GAS inhibited Pb-induced inflammation in the brain, as indicated by the decreased levels of pro-inflammatory cytokines, including tumor necrosis factor-a (TNF-α), cyclooxygenase-2 (COX-2). GAS increased the expression levels of NR2A and neurotrophin brain-derived neurotrophic factor (BDNF). GAS inhibited Pb-induced apoptosis of neurons in hippocampus tissue, as indicated by the decreased levels of pro-apoptotic proteins Bax and cleaved caspase-3. Furthermore, the neuroprotective effects of GAS were associated with inhibiting oxidative stress by modulating nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated antioxidant signaling. GAS supplement activated the Wnt/β-catenin signaling pathway and reduced the expression of Wnt inhibitor Dickkopf-1 (Dkk-1). Collectively, this study clarified that GAS exhibited neuroprotective property by anti-oxidant, anti-inflammatory and anti-apoptosis effects and its ability to regulate the Wnt/Nrf2 pathway.