Lanthanum chloride impairs spatial learning and memory and downregulates NF-κB signalling pathway in rats

Effects of arsenic exposure on the PI3K/Akt/NF-κB signaling pathway in the hippocampus of offspring mice at different developmental stages

The primary purpose of present study was to explore the effects of arsenic exposure on the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/nuclear transcription factor-κB (NF-κB) signaling pathway in the hippocampus of offspring mice at different developmental stages. Sodium arsenite (NaAsO2) at doses of 0, 15, 30 or 60 mg/L administered to female mice and their pups. The nuclear translocation levels of NF-κB were assessed by EMSA. Real-time RT-PCR was used to measure Akt, NF-κB and PI3K mRNA levels. Protein expressions of PI3K, p-Akt, inhibitor kappa B kinase (IKK), p-NF-κB, protein kinase A (PKA), inhibitor kappa B (IκB), and cAMP response element-binding protein (CREB) were measured by Western blot. Results disclosed that exposure to 60 mg/L NaAsO2 could suppress NF-κB levels of nuclear translocation of postnatal day (PND) 20 and PND 40 mice. Arsenic downregulated the transcriptional and translational levels of PI3K, Akt and NF-κB. Additionally, protein expressions of p-IKK, p-IκB, PKA and p-CREB also reduced. Taken together, results of present study indicated that arsenic could downregulate the PI3K/Akt/NF-κB signaling pathway, particularly on PND 40, which might be involved in the cognitive impairments.

Rare Earth Element Content in Hair Samples of Children Living in the Vicinity of the Kola Peninsula Mining Site and Nervous System Diseases

The aim of this study is to assess the rare earth element (REE) content in hair samples of children living in Lovozero village, near an REE mining site, and the possible effects of REEs on the prevalence of nervous system diseases in Lovozersky District (Murmansk region, Kola Peninsula). Fifty-three school-age children were recruited for the analysis of REE content in hair samples. REE (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) content was estimated by means of inductively coupled plasma mass spectrometry (ICP-MS). The analysis of REE content in the hair of children living in Russia, Kazakhstan, and China indicated REE intake from the environment. The possible contribution of REEs to nervous system disorders is supported by the link between the REE content in hair samples of children living near REE mining areas (China) and the manifestation of cognitive disorders in these children. It is also found that the prevalence of nervous system diseases in children aged 15-17 years is higher in Lovozersky District compared to the other districts of the Murmansk region. In this paper, the possible contribution of REEs to the prevalence of episodic paroxysmal disorders (G40-G47), cerebral palsy (G80-G83), and epilepsy and status epilepticus (G40-G41) is discussed.

Lanthanum nitrate demonstrated no genotoxicity in the conducted tests

Given the widespread applications in industrial and agricultural production, the health effects of rare earth elements (REEs) have garnered public attention, and the genotoxicity of REEs remains unclear. In this study, we evaluated the genetic effects of lanthanum nitrate, a typical representative of REEs, with guideline-compliant in vivo and in vitro methods. Genotoxicity assays, including the Ames test, comet assay, mice bone marrow erythrocyte micronucleus test, spermatogonial chromosomal aberration test, and sperm malformation assay were conducted to assess mutagenicity, chromosomal damage, DNA damage, and sperm malformation. In the Ames test, no statistically significant increase in bacterial reverse mutation frequencies was found as compared with the negative control. Mice exposed to lanthanum nitrate did not exhibit a statistically significant increase in bone marrow erythrocyte micronucleus frequencies, spermatogonial chromosomal aberration frequencies, or sperm malformation frequencies compared to the negative control (P > 0.05). Additionally, after a 24-h treatment with lanthanum nitrate at concentrations of 1.25, 5, and 20 μg/ml, no cytotoxicity was observed in CHL cells. Furthermore, the comet assay results indicate no significant DNA damage was observed even after exposure to high doses of lanthanum nitrate (20 μg/ml). In conclusion, our findings suggest that lanthanum nitrate does not exhibit genotoxicity.

Association between prenatal exposure to rare earth elements and the neurodevelopment of children at 24-months of age: A prospective cohort study

The increasing consumption of rare earth elements (REEs) has resulted in a considerable risk of environmental exposure. However, the adverse effects of prenatal REEs exposure on children's neurodevelopment are not yet fully recognized. Therefore, we investigated the individual and joint effects of prenatal exposure to 13 REEs on children's neurocognitive development based on 809 mother-child pairs from a large birth cohort in Wuhan, China. Maternal urinary concentrations of 13 REEs were repeatedly measured by inductively coupled plasma mass spectrometry. Children's neurodevelopment [e.g., mental and psychomotor development index (MDI/PDI)] at 24-months was assessed using Bayley Scales of Infant Development of Chinese Revision. GEE and BKMR models were applied to estimate the individual and joint effects of prenatal REE exposure on child neurodevelopment level. After controlling for typical confounders, we observed that exposure to 9 REEs during the first trimester were significantly associated with decreased MDI scores [βs and 95% confidence intervals (CIs) ranging from -2.24 (-3.86 ∼ -0.63) to -1.44 (-2.26∼ -0.26)], and 7 REEs during third trimester were significantly associated decreased PDI scores [β and 95% CIs ranging from -1.95 (-3.19 ∼ -0.71) to -1.25 (-2.34 ∼ -0.16)]. Higher quantiles of REE mixture in first and third trimester were associated with decreased MDI and PDI score. Thulium, erbium in the first trimester and cerium, lanthanum in the third trimester accounted most importance to joint effects on MDI and PDI, respectively. In conclusion, prenatal exposure to higher concentrations of REEs during the first and third trimester were negative associated with children's neurodevelopment.

Lanthanum Chloride Induces Axon Abnormality Through LKB1-MARK2 and LKB1-STK25-GM130 Signaling Pathways

Lanthanum (La) is a natural rare-earth element that can damage the central nervous system and impair learning and memory. However, its neurotoxic mechanism remains unclear. In this study, adult female rats were divided into 4 groups and given distilled water solution containing 0%, 0.125%, 0.25%, and 0.5% LaCl3, respectively, and this was done from conception to the end of the location. Their offspring rats were used to establish animal models to investigate LaCl3 neurotoxicity. Primary neurons cultured in vitro were treated with LaCl3 and infected with LKB1 overexpression lentivirus. The results showed that LaCl3 exposure resulted in abnormal axons in the hippocampus and primary cultured neurons. LaCl3 reduced the expression of LKB1, p-LKB1, STRAD and MO25 proteins, and directly or indirectly affected the expression of LKB1, leading to decreased activity of LKB1-MARK2 and LKB1-STK25-GM130 pathways. This study indicated that LaCl3 exposure could interfere with the normal effects of LKB1 in the brain and downregulate LKB1-MARK2 and LKB1-STK25-GM130 signaling pathways, resulting in abnormal axon in offspring rats.

Dietary Exposure Assessment of Rare Earth Elements in the Chinese Population

Rare earth elements (REEs) are widely found in foods. A high intake of REEs may have associations with adverse effects on human health. This study aimed to investigate the concentrations of REEs in foods in China and to assess the risk of dietary REEs exposure in the Chinese population. The mean concentrations of the total REEs in 27,457 food samples from 11 food categories ranged from 0.04 to 1.41 mg/kg. The daily mean dietary exposure of the total REEs was 1.62 μg/kg BW in the general Chinese population and ranged from 1.61 to 2.80 μg/kg BW in different sex-age groups. The high consumer exposure (95th percentile, P95) was 4.83 μg/kg BW, 9.38% of the temporary ADI (tADI) of REEs (51.5 μg/kg BW). None of the P95 exposure exceeded the tADI in all of the sub-groups. Lanthanum, cerium, and yttrium accounted for approximately 63% of the total exposure of the 16 REEs. The hazard index of 16 REEs was far below 1. Therefore, the health risk of dietary REEs exposure in the general Chinese population was low. No cumulative risk was found for the 16 REEs in China. The results indicate there was no need to stipulate the limits of REEs in foods.

Effects of lanthanum nitrate on behavioral disorder, neuronal damage and gene expression in different developmental stages of Caenorhabditis elegans

Rare earth elements (REEs) are widely used in the industry, agriculture, biomedicine, aerospace, etc, and have been shown to pose toxic effects on animals, as such, studies focusing on their biomedical properties are gaining wide attention. However, environmental and population health risks of REEs are still not very clear. Also, the REEs damage to the nervous system and related molecular mechanisms needs further research. In this study, the L1 and L4 stages of the model organism Caenorhabditis elegans were used to evaluate the effects and possible neurotoxic mechanism of lanthanum(III) nitrate hexahydrate (La(NO₃)₃·6H₂O). For the L1 and L4 stage worms, the 48-h median lethal concentrations (LC₅₀s) of La(NO₃)₃·6H₂O were 93.163 and 648.0 mg/L respectively. Our results show that La(NO₃)₃·6H₂O induces growth inhibition and defects in behavior such as body length, body width, body bending frequency, head thrashing frequency and pharyngeal pumping frequency at the L1 and L4 stages in C. elegans. The L1 stage is more sensitive to the toxicity of lanthanum than the L4 stage worms. Using transgenic strains (BZ555, EG1285 and NL5901), we found that La(NO₃)₃·6H₂O caused the loss or break of soma and dendrite neurons in L1 and L4 stages; and α-synuclein aggregation in L1 stage, indicating that Lanthanum can cause toxic damage to dopaminergic and GABAergic neurons. Mechanistically, La(NO₃)₃·6H₂O exposure inhibited or activated the neurotransmitter transporters and receptors (glutamate, serotonin and dopamine) in C. elegans, which regulate behavior and movement functions. Furthermore, significant increase in the production of reactive oxygen species (ROS) was found in the L4 stage C. elegans exposed to La(NO₃)₃·6H₂O. Altogether, our data show that exposure to lanthanum can cause neuronal toxic damage and behavioral defects in C. elegans, and provide basic information for understanding the neurotoxic effect mechanism and environmental health risks of rare earth elements.

Lanthanum chloride induces autophagy in primary cultured rat cortical neurons through Akt/mTOR and AMPK/mTOR signaling pathways

Autophagy is a lysosome dependent degradation pathway occurring in eukaryotic cells. Autophagy ensures balance and survival mechanism of cells during harmful stress. Excessive or weak autophagy leads to abnormal function and death in some cases. Lanthanum (La), a rare earth element (REE), damages the central nervous system (CNS) and promotes learning and memory dysfunction. However, underlying mechanism has not been fully elucidated. La induces oxidative stress, inhibits Nrf2/ARE and Akt/mTOR signaling pathways, and activates JNK/c-Jun and JNK/Foxo signaling pathways, resulting in abnormal induction of autophagy in rat hippocampus. In addition, La activates PINK1- Parkin signaling pathway and induces mitochondrial autophagy. However, the relationship between La and autophagy in rat neurons at the cellular level has not been explored previously. The aim of this study was to explore adverse effects of La. Primary culture of rat neurons were exposed to 0 mmol/L, 0.025 mmol/L, 0.05 mmol/L and 0.1 mmol/L lanthanum chloride (LaCl₃). The results showed that La upregulates p-AMPK, inhibits levels of p-Akt and p-mTOR, increases levels of autophagy related proteins (Beclin1 and LC3B-II), and downregulates expression of p-Bcl-2 and p62. Upstream and downstream intervention agents of autophagy were used to detect autophagy flux to verify accuracy of our results. Electron microscopy results showed significant increase in the number of autophagosomes in LaCl₃ exposed groups. These findings imply that LaCl₃ inhibits Akt/mTOR signaling pathway and activates AMPK/mTOR signaling pathway, resulting in abnormal autophagy in primary cultured rat cortical neurons. In addition, LaCl₃ induces neuronal damage through excessive autophagy.

Cell and molecular toxicity of lanthanum nanoparticles: are there possible risks to humans?

Lanthanum nanoparticles are widely used in industry, agriculture, and biomedicine. Over 900 kg of lanthanum is annually released into the environment only in Europe, 50 times higher than the metals, mercury, and cadmium's environmental spread. Human health risk associated with long-term exposure to the abundant lanthanum nanoparticles is a concerning environmental issue. Due to lanthanum's ability to disrupt the main biological barriers and interrupt various cells' hemostasis, they seem to cause severe disruptions to various tissues. This review opens a new perspective regarding the cellular and molecular interaction of nanosized and ionic lanthanum with the possible toxicity on the nervous system and other tissues that would show lanthanum nanoparticles' potential danger to follow in toxicological science.

Effects of PI3K/AKT/mTOR pathway regulation of HIF-1α on Lanthanum-induced neurotoxicity in rats

This study examined the effects of the AKT/mTOR/HIF-1α signaling pathway on learning and memory in offspring rats induced by lanthanum from neuroethology and molecular biology perspectives. 32 pregnant adult Wistar rats were divided into four groups randomly: control group (NC), 0.25%, 0.5% and 1.0% LaCl3 groups (n = 8). All rats were poisoned through free drinking from day 0 of pregnancy to postnatal day 21 (suckling period). All offspring rats were poisoned through free drinking from delactation to postnatal day 48. Offspring rats aged 49-days-old were used as sampling objects to construct an LaCl3 poisoning model of offspring rats. Changes in hippocampal neurons, apoptosis of hippocampal neurons, learning and memory abilities of LaCl3-poisoned animals were measured by Nissl staining, TUNEL method and the shuttle box test, respectively. Expressions of PI3K, AKT, and mTOR, HIF-1α, and VEGF in the hippocampus were tested by qPCR and Western blot. Distributions of PI3K and p-AKT in hippocampal neurons were observed through the immunohistochemical method. With increasing LaCl3 dose, lightning strike time and active avoidance incubation period of offspring rats in the different LaCl3 groups were significantly prolonged. The Nissl body positive neurons of hippocampal neurons gradually declined while apoptosis in cells increased. The expressions of both mRNA (PI3K, AKT, mTOR, HIF-1α, VEGF) and proteins (PI3K, p-AKT, p-mTOR, HIF-1α, VEGF) in the hippocampus of the LaCl3 groups were significantly lower than those of NC group (p < 0.05). LaCl3 poisoning can induce developmental injuries in hippocampal neurons and can increase cell apoptosis. As a result, learning and memory abilities of offspring rats, as well as the expressions of PI3K/AKT/mTOR, are decreased, thus inhibiting activation of HIF-1α and influencing the expression of the downstream VEGF gene.

Rare earth element lanthanum protects against atherosclerosis induced by high-fat diet via down-regulating MAPK and NF-κB pathways

Rare earth elements, which are extensively used in environmental protection, medicine, food, aerospace and other fields, have attracted widespread attention in recent years. However, the effect on atherosclerosis and its biological mechanism remains unclear. To elucidate these problems, here we performed a study that Apolipoprotein E-deficient mice were fed with high-fat diet to promote the development of atherosclerosis, meanwhile, mice were received 0.1, 0.2, 1.0, 2.0 mg/kg lanthanum nitrate (La(NO₃)₃) for 12 weeks. The results showed that La(NO₃)₃ prominently inhibited aorta morphological alternations by histopathological examination. Meanwhile, La(NO₃)₃ regulated serum lipids, including reducing total cholesterol and increasing high-density lipoprotein. Moreover, the oxidative stress was alleviated by La(NO₃)₃ intervention through enhancing superoxide dismutase and glutathione, and decreasing malondialdehyde levels. In addition, enzyme-linked immunosorbent assay analysis showed La(NO₃)₃ could ameliorate the dysfunction of vascular endothelium with declined endothelin-1 and increased prostacyclin. Furthermore, Western blot analysis indicated that La(NO₃)₃ significantly down-regulated inflammation-mediated proteins including phosphorylated p38 mitogen-activated protein kinases (p-p38 MAPK), monocyte chemo-attractant protein, intercellular adhesion molecule-1, nuclear factor-kappa B p65 (NF-κB p65), tumor necrosis factor-α, interleukin-6 and interleukin-1β, whereas up-regulated the inhibitor of NF-κB protein. In conclusion, La(NO₃)₃ ameliorates atherosclerosis by regulating lipid metabolism, oxidative stress, endothelial dysfunction and inflammatory response in mice. The potential mechanism associates with the inhibition of MAPK and NF-κB signaling pathways.

Postweaning exposure to lanthanum alters neurological behavior during early adulthood in rats

Lanthanum is a rare-earth element that has been used in various fields including medicine, agriculture and industry. Previously, in utero lanthanum exposure to dams was shown to alter neurobehavior and neurotransmitter levels in rat offspring; however, the effects of postweaning exposure to lanthanum on neurological behavior is still limited. The purpose of this study was to investigate the effects of postweaning exposure to lanthanum on neurological behavior during early adulthood in rats. Rats were orally exposed to 0, 2, 20, 60 mg/kg BW of lanthanum nitrate from postnatal day (PND) 24 to PND60. Our results indicated that lanthanum treatment significantly decreased body weight and food intake. Morris water maze test results showed that lanthanum significantly decreased escape latency and travel distance. Lanthanum treatment also significantly decreased grip strength, hindlimb strength, and running time & distance in motor activity test. Further results showed that lanthanum treatment significantly decreased plasma neurotransmitter levels of acetylcholine and norepinephrine as well as the number of neurons in the CA1 area of the hippocampus. These results suggest that postweaning exposure to lanthanum have adverse effects on neurobehaviors and the central nervous system, with no-observed-adverse-effect level at 2 mg/kg BW and benchmark dose lower confidence limit at 1.7 mg/kg BW.

Association of prenatal exposure to rare earth elements with newborn mitochondrial DNA content: Results from a birth cohort study

BACKGROUND

Rare earth elements (REE) have been widely used in industry and agriculture. Mitochondria are susceptible to environmental exposure and the change of mitochondrial DNA (mtDNA) content is a proxy indicator of mitochondrial response to damage. However, no study has explored the associations between prenatal repeated REE exposure and newborn mtDNA content.

OBJECTIVES

We aimed to investigate the trimester-specific associations between prenatal REE exposure and newborn mtDNA content.

METHODS

A total of 587 mother-newborn pairs were recruited from Wuhan Children's Hospital between November 2013 and March 2015 in Wuhan, China. Urinary concentrations of REE collected during 3 trimesters were measured by inductively coupled plasma mass spectrometry (ICP-MS). Quantitative real-time polymerase chain reaction (qPCR) was used to measure relative cord blood mtDNA content. We evaluated the trimester-specific associations between prenatal REE exposure and relative cord blood mtDNA content with multiple informant models. False discovery rate (FDR) was used to correct for multiple testing.

RESULTS

After adjustment for potential confounders, prenatal exposure to REE [gadolinium (Gd), dysprosium (Dy), erbium (Er), praseodymium (Pr)] during the third trimester were positively related to cord blood mtDNA content, and the positive associations with cord blood mtDNA content were still observed in Dy, Er, and Pr after FDR correction.

CONCLUSIONS

This prospective study demonstrated that maternal REE exposure during the third trimester was associated with the increased newborn mtDNA content, and the third trimester might be a potential window for sensitivity of newborn mtDNA content to REE exposure. The results might provide evidence of the potential health effects of environmental REE exposure.

Baseline characteristics, diagnostic efficacy, and peri-examinational safety of IV gadoteric acid MRI in 148,489 patients

BACKGROUND

Magnetic resonance imaging (MRI) examinations with intravenous (IV) contrast are performed worldwide in routine daily practice. In order to detect and enumerate even rare adverse events (AE) and serious adverse events (SAE), and to relate them with patients' baseline characteristics and diagnostic effectiveness, high quantity sample size is necessary.

PURPOSE

To assess safety, diagnostic effectiveness, and baseline characteristics of patients undergoing IV gadoteric acid (Dotarem®) MRI in routine practice.

MATERIAL AND METHODS

Data from two observational post-marketing surveillance (PMS) databases compiled by 139 and 52 German centers in 2004-2011 and 2011-2013, respectively, were pooled, yielding data on a total of 148,489 patients examined over a 10-year period. Radiologists used a standardized questionnaire to report data including patient demographics, characteristics of MR examinations, and results in terms of diagnosis and patient safety.

RESULTS

Overall, 712 AEs were reported in 467 (0.3%) patients, mainly nausea (n = 224, 0.2%), vomiting (n = 29, <0.1%), urticaria (n = 20, <0.1%), and feeling hot (n = 13, <0.1%). AEs were considered related to gadoteric acid in 362 (0.2%) patients. Higher frequencies of AEs were observed among patients with a previous reaction to a contrast agent (2.0%), liver dysfunction (0.7%), bronchial asthma (0.7%), and a history of allergies (0.6%). There were 49 SAEs in 18 (<0.1%) patients, including two children. No fatal SAE was reported. Examinations were diagnostic in 99.8% of all patients, and image quality was excellent or good in 97.7% of the patients.

CONCLUSION

Gadoteric acid is a safe peri-examinational and effective contrast agent for MRI in routine practice.

Action of Akt Pathway on La-Induced Hippocampal Neuron Apoptosis of Rats in the Growth Stage

This study investigated the influences of lanthanum (La) exposure on learning and memory and the expression of apoptosis-related proteins in offspring rats. Wistar female rats were randomly divided into a control group (NC) and 0.25%, 0.5% and 1.0% LaCl₃ treatment groups, with eight per group. La dye was transmitted to offspring rats through parental blood circulation and breast milk before delactation and through water drinking after delectation. Offspring rats were killed at 14, 28 and 42 days after birth. Hippocampal neurons were observed by microscope, and apoptosis and necrosis were tested. The expression levels of apoptosis-related proteins were detected by Western blot, and Morris water maze experiments were used to measure learning and memory abilities. LaCl₃ groups showed longer escape latency periods and swimming distances than the NC group (p < 0.05). The 1.0% LaCl₃ group passed across the target quadrants and platforms more times and stayed in the target quadrants for less time, than the NC group (p < 0.05). At 42 days, the apoptosis rate and necrosis in the hippocampus of the 1.0% LaCl₃ group were significantly higher than those of other groups. There was a significant difference among LaCl₃ groups in terms of protein expressions measured in the hippocampus. In LaCl₃ groups, caspase-3 and caspase-9 were significantly higher than in the NC group (p < 0.05). Therefore, La exposure can promote neuronal apoptosis by regulating the protein expressions of Akt, Bcl-2, Bcl-xl, Bax, Bad, caspase-3 and caspase-9, thus damaging learning and memory and the hippocampal neurons of offspring rats.

Lanthanum Chloride Causes Neurotoxicity in Rats by Upregulating miR-124 Expression and Targeting PIK3CA to Regulate the PI3K/Akt Signaling Pathway

Background

Lanthanum (La) exposure can cause central nervous system (CNS) damage and dysfunction in children, seriously affecting intellectual development. miR-124 plays an important role in the development of the nervous system. We exposed rats to a La environment then observed the rats' learning and memory damage and neurotoxicity and the relationship with miR-124.

Methods

Rats were exposed to LaCl₃ via drinking water. The rats' offspring were exposed to LaCl₃ from their mother before weaning, then from La water for 28 days. A Morris water maze was used to observe spatial memory capabilities. H&E staining and TUNEL assays were used to observe pathological changes and apoptosis in the hippocampus. miR-124 was detected by RT-qPCR, and its targeting was confirmed by luciferase assay. The HT22 cell line was cultured with LaCl₃ and treated with miR-124 mimics or inhibitors; then, expression of PI3K/Akt-related proteins was detected by western blot.

Results

La exposure can lead to impaired learning and memory ability in offspring. Offspring with La accumulations in the hippocampus showed severe damage, disordered cells, and increased neurocyte apoptosis. In vitro, the postsynaptic density protein 95 was downregulated under La exposure and apoptosis increased. This effect of La can be attenuated by miR-124 inhibitors and enhanced by miR-124 mimics. LaCl₃ exposure increased miR-124 expression and targeting on PIK3CA, downregulating PI3K, p-Akt, and p-NF-κB p65.

Conclusion

La causes neurotoxicity by upregulating miR-124 expression and targeting PIK3CA through the PI3K/Akt signaling pathway.

Lanthanum Chloride Impairs Learning and Memory and Induces Dendritic Spine Abnormality by Down-Regulating Rac1/PAK Signaling Pathway in Hippocampus of Offspring Rats

Lanthanum (La) is a natural rare earth element. It has neurotoxic effects which can impair learning and memory in humans. However, its mechanism of neurotoxicity is unclear. Learning and memory are coordinated by dendritic spines which form tiny protruding structures on the dendritic branches of neurons. This study investigated the effect of LaCl3 exposure to pregnant and lactating rats on the offspring rats' learning and memory ability. In this study, rats were divided into 4 groups and given distilled water solution containing 0%, 0.125%, 0.25%, 0.5% LaCl3, respectively, and this was done from conception to the end of the location. The effects of LaCl3 on spatial learning and memory ability in offspring rats and in the development of dendritic spines in CA1 pyramidal cells were investigated. The results showed that LaCl3 impaired spatial learning and memory ability in offspring rats, and decreased dendritic spine density during development. In addition, LaCl3 can affect the expression of CaMKII, miRNA132, p250GAP, Tiam1, PARD3, and down-regulated the activation of Rac1 which led to a decrease in the expression of Rac1/PAK signaling pathway and downstream regulatory proteins Cortactin and actin-related protein 2/3 complex (Arp2/3 complex). This study indicated that the learning and memory impairment and the decrease of dendritic spine density in the offspring of LaCl3 exposure may be related to the down-regulation of the Rac1/PAK signaling pathway regulated by Tiam1 and p250GAP.

Lanthanum chloride causes blood–brain barrier disruption through intracellular calcium-mediated RhoA/Rho kinase signaling and myosin light chain kinase

Lanthanum caused endothelial barrier hyperpermeability, loss of VE-cadherin and rearrangement of the actin cytoskeleton, though intracellular Ca²⁺-mediated RhoA/ROCK and MLCK pathways.

Use of lanthanum for water treatment A matter of concern?

Among several other eutrophication management tools, Phoslock®, a lanthanum modified bentonite (LMB) clay, is now frequently used. Concerns have been raised as to whether exposure to Phoslock®-treated water may lead to lanthanum accumulation/toxicity in both animals and humans. In the present experimental study, rats were administered lanthanum orally as either lanthanum carbonate, lanthanum chloride or Phoslock® at doses of either 0.5 or 17 mg/L during 10 weeks. Controls received vehicle. The gastrointestinal absorption and tissue distribution of lanthanum was investigated. Extremely strict measures were implemented to avoid cross-contamination between different tissues or animals. Results showed no differences in gastrointestinal absorption between the different compounds under study as reflected by the serum lanthanum levels and concentrations found in the brain, bone, heart, spleen, lung, kidney and testes. At sacrifice, significant but equally increased lanthanum concentrations versus vehicle were observed in the liver for the highest dose of each compound which however, remained several orders of magnitude below the liver lanthanum concentration previously measured after long-term therapeutic administration of lanthanum carbonate and for which no hepatotoxicity was noticed in humans. In conclusion, (i) the use of LMB does not pose a toxicity risk (ii) gastrointestinal absorption of lanthanum is minimal and independent on the type of the compound, (iii) with exception of the liver, no significant increase in lanthanum levels is observed in the various organs under study, (iv) based on previous studies, the slightly increased liver lanthanum levels observed in a worst case scenario do not hold any risk of hepatotoxicity.

Lanthanum chloride impairs spatial learning and memory by inducing [Ca2+]m overload, mitochondrial fission–fusion disorder and excessive mitophagy in hippocampal nerve cells of rats

Lanthanum chloride damages hippocampal nerve cells of rats through inducing [Ca²⁺]_m overload, mitochondrial fission–fusion disorder, and excessive mitophagy.

Effects of in utero exposure to lanthanum on neurological behavior in rat offspring

The increasing use of rare-earth elements in various fields has raised concern from public heath perspective regarding their accumulation in human body. Long-term exposure to lanthanum, one of the frequently used rare-earth elements in biomedicine and agriculture, has been previously shown to exert neurotoxicity during development in rats; however, the effects of short-term exposure to lanthanum during gestation on neurobehavioral development in rat offspring is still not clear. The purpose of this study is to investigate the effects of intrauterine exposure to lanthanum on neurobehavioral development in rat offspring. Dams were orally exposed to 0, 2, 20, & 60 mg/kg BW of lanthanum nitrate from gestation day 7 to day 16. Morris water maze test, hindlimb strength test, nociceptive perception test, and grip strength test were conducted during postnatal day 61 to 66 in rat offspring. Blood lanthanum concentration and plasma neurotransmitters were measured after sacrifice. The results showed that intrauterine exposure to lanthanum nitrate significantly impaired memory and spatial learning in Morris water maze test. Lanthanum treatment dose-dependently increased blood lanthanum concentration in dams and pups. Lanthanum treatment significantly decreased hindlimb and grip strength and increased delay time in nociceptive response. Plasma neurotransmitter results showed that lanthanum treatment significantly decreased the level of acetylcholine and serotonin while increased the level of glutamate in rat offspring. These results suggest that short-term in utero exposure to lanthanum has potential adverse effects on neurodevelopment in rat offspring.

Prenatal exposure of rare earth elements cerium and ytterbium and neonatal thyroid stimulating hormone levels: Findings from a birth cohort study

BACKGROUND

Prior studies have suggested exposure to heavy metals and endocrine disrupting chemicals could disturb the homeostasis of thyroid stimulating hormone (TSH), but no epidemiology study concerning the influence of rare earth elements (REE) exposure during pregnancy on neonatal TSH levels. The present study aimed to investigate the relationships between prenatal REE exposure and neonatal TSH levels.

METHODS

A total of 7367 pregnant women were recruited from Wuhan Children's Hospital between September 2012 and October 2014 in Wuhan, China. Urinary concentrations of cerium (Ce), and ytterbium (Yb) were measured by inductively coupled plasma mass spectrometry (ICP-MS). Immunofluorescence assay was used to detect neonatal TSH levels. The associations between REE exposure and neonatal TSH levels were evaluated using multivariate linear regression models.

RESULTS

The geometric means of maternal urinary Ce and Yb concentrations were 0.060 μg/g creatinine and 0.025 μg/g creatinine, respectively. The results showed that per doubling of maternal urinary Ce and Yb were associated with 4.07% (95% CI: -5.80%, -2.31%), 5.13% (95% CI: -6.93%, -3.30%) decreased neonatal TSH levels respectively in the adjusted model. Sex stratified analysis demonstrated that the decreased neonatal TSH levels were observed both in male infants and female infants, and the decrease was greater in male infants in urinary Ce. There were no significant interactions between maternal urinary Ce, Yb and infant sex (Ce: P for interaction = 0.173, Yb: P for interaction = 0.967).

CONCLUSIONS

Our findings demonstrated that increased maternal urinary Ce and Yb were associated with decreased neonatal TSH levels. Further researches from different populations are warranted to verify the association and to explore the mechanisms.

Conditioned medium from overly excitatory primary astrocytes induced by La3+ increases apoptosis in primary neurons via upregulating the expression of NMDA receptors

Lanthanum (La) can accumulate in the brain and impair learning and memory. However, the underlying mechanism of La-induced neurotoxicity has remained elusive. Under physiological conditions, it has been reported that moderately excitatory astrocytes play an important role in the regulation of neuronal signals and synaptic plasticity. However, under pathological conditions, overly excitatory astrocytes can release excess excitatory transmitters, such as glutamate (Glu) and d-serine, and induce the over-activation of NMDA receptors (NMDAR) in neurons, ultimately leading to neuronal excitotoxicity. To date, limited work has been performed with respect to whether La can induce neuronal excitotoxicity by inducing astrocytes to become overexcited. In this study, in vitro models of primary culture rat cortical astrocytes and neurons were established. First, the astrocytes were treated with 0.125 mM, 0.25 mM and 0.5 mM lanthanum chloride (LaCl3) for 24 h, and the supernatants were collected as a conditioned medium (CM) which is denoted as CM (La3+); then, the neurons were treated with CM (La3+) for 48 h. The results illustrate that LaCl3 treatment significantly upregulated the mRNA and protein expression levels of metabotropic glutamate receptor 5 (mGLUR5), phospholipase C (PLC), connexin 43 (Cx43) and Cx30, increased the concentrations of inositol trisphosphate (IP3) and [Ca2+]i, and promoted the synthesis and release of Glu and d-serine in astrocytes. Moreover, the CM (La3+) could increase the mRNA and protein expression levels of NMDAR subunits (NR1, NR2A, NR2B), the concentration of [Ca2+]i and the rate of apoptosis in neurons. Furthermore, after removal of La, CM (La-free) had a similar effect on neurons which could be antagonized by MK-801, DCKA and DAAO. These results suggest that the neuron apoptosis induced by La is closely related to the excessive release of Glu and d-serine from overly excitatory astrocytes.

Lanthanum Chloride Impairs the Blood-Brain Barrier Integrity by Reduction of Junctional Proteins and Upregulation of MMP-9 in Rats

Lanthanum could cause cognitive impairment in children and rodent animals. The normal blood-brain barrier (BBB) integrity is essential for protecting the brain from systemic toxins and maintaining the homeostasis for proper neuronal function. BBB dysfunction has been implicated as a potential mechanism of heavy metal-induced neurotoxicity. The present study was aimed to investigate effects of lanthanum on BBB integrity and endothelial junctional complexes in the cerebral cortex of young rats. Animals were exposed to lanthanum chloride (LaCl₃) through drinking water under 0, 0.25, 0.5, and 1.0% concentrations from postnatal day 0 until 30 days after weaning. LaCl₃-exposure increased BBB permeability, caused ultrastructure changes in cerebral capillaries, and reduced protein expression of claudin-5, occludin, and VE-cadherin. Due to the critical role of matrix metalloproteinases (MMPs) in BBB integrity, we further examined alterations in MMPs activity and expression. Enhanced gelatinase activity and upregulated MMP-9 expression were observed after LaCl₃-exposure, concurrently with decreased expression of endogenous inhibitor tissue inhibitors of metalloproteinase (TIMP)-1. Taken together, this study demonstrated that postnatal lanthanum exposure caused leakage of BBB in young rats, partially attributed to upregulation of MMP-9 and reduction of junctional proteins expression.

Lanthanum chloride induces autophagy in rat hippocampus through ROS-mediated JNK and AKT/mTOR signaling pathways

Lanthanum (La) can cause central nervous system damage in rats and lead to learning and memory impairment, but the relevant mechanisms have not been fully elucidated.

Lanthanum chloride induces neuron damage by activating the nuclear factor-kappa B signaling pathway in activated microglia

Lanthanum is a rare earth element which can have adverse effects on the central nervous system (CNS).

Gadolinium deposition and the potential for toxicological sequelae - A literature review of issues surrounding gadolinium-based contrast agents

Every year, approximately 30 million magnetic resonance imaging scans are enhanced with gadolinium-based contrast agents (GBCAs) worldwide. Although the development of nephrogenic systemic fibrosis in patients with renal impairment is well-documented, over recent years it has become apparent that exposure to GBCAs can potentially result in gadolinium deposition within human bone and brain tissue even in the presence of normal renal function. This review will address some of the controversies surrounding the safety of GBCA administration based on evidence from in vivo experiments, animal studies and clinical studies. We additionally evaluate the potential risk of toxicity from exposure to gadolinium in light of new guidance published by the US Food and Drug Administration and the European Medicines Agency, and discuss whether gadolinium deposition disease exists as a new diagnosis.

The Toxic Effect of Lanthanum on Planaria Is Mediated by a Variety of Ion Channels

The effect of toxic concentrations of La³⁺ on the Ca, K, Na, Mg, and Cl channels of planaria was investigated through the use of various agonists and antagonists to those channels. It was demonstrated that La exerts its toxic effects through L-type, but not T-type, Ca channels. La also demonstrated activity at Na, K, Mg, and Cl channels, but, these effects were most likely mediated by other effects of La on Ca activity. However, these interactions appear to be very complex and confounded by oxidative stresses. The study also introduces a planaria stress scale which allows the effects of toxic substances to be examined on a continuum.

The effect of nuclear factor erythroid 2-related factor/antioxidant response element signalling pathway in the lanthanum chloride-induced impairment of learning and memory in rats

Lanthanum exerts adverse effects on the central nervous system. However, the mechanism underlying these adverse effects has not been clarified. It is known that oxidative stress plays an important role in neurological injuries induced by harmful factors. Nuclear factor erythroid 2-related factor (Nrf2) is very important in the response to oxidative stress in tissues and cells. The purpose of this study was to explore the effect of lanthanum chloride (LaCl₃ ) on the spatial learning and memory of rats and to determine whether the Nrf2/antioxidant response element pathway acts in the hippocampus. Four groups of Wistar rats were exposed to 0 mM, 9 mM, 18 mM or 36 mM LaCl₃ through their drinking water from the day of birth to 2 months after weaning. The results showed that LaCl₃ impaired the spatial learning and memory of the rats, damaged the neuronal ultrastructure, increased reactive oxygen species levels and significantly down-regulated Nrf2 as well as the mRNA and protein expression of Nrf2-regulated genes, including NADP(H): dehydrogenase quinone 1, haeme oxygenase-1, superoxide dismutase 2, glutathione peroxidase 1, glutathione-S-transferase, γ-glutamine cysteine synthase and glutathione reductase, in the hippocampus. This study suggests that LaCl₃ can impair the spatial learning and memory of rats, possibly by perturbing the Nrf2/antioxidant response element signalling pathway.

Activation of Nrf2/ARE signaling pathway attenuates lanthanum chloride induced injuries in primary rat astrocytes

Lanthanum (La) exposure can lead to learning and memory disorder in animals; however, the underlying mechanism of La induced neurotoxicity is still unknown.

Lanthanum chloride impairs spatial memory through ERK/MSK1 signaling pathway of hippocampus in rats

Rare earth elements (REEs) are used in many fields for their diverse physical and chemical properties. Surveys have shown that REEs can impair learning and memory in children and cause neurobehavioral defects in animals. However, the mechanism underlying these impairments has not yet been completely elucidated. Lanthanum (La) is often selected to study the effects of REEs. The aim of this study was to investigate the spatial memory impairments induced by lanthanum chloride (LaCl3) and the probable underlying mechanism. Wistar rats were exposed to LaCl3 in drinking water at 0 % (control, 0 mM), 0.25 % (18 mM), 0.50 % (36 mM), and 1.00 % (72 mM) from birth to 2 months after weaning. LaCl3 considerably impaired the spatial learning and memory of rats in the Morris water maze test, damaged the synaptic ultrastructure and downregulated the expression of p-MEK1/2, p-ERK1/2, p-MSK1, p-CREB, c-FOS and BDNF in the hippocampus. These results indicate that LaCl3 exposure impairs the spatial learning and memory of rats, which may be attributed to disruption of the synaptic ultrastructure and inhibition of the ERK/MSK1 signaling pathway in the hippocampus.

Roles for NF-κB and gene targets of NF-κB in synaptic plasticity, memory, and navigation

Although traditionally associated with immune function, the transcription factor nuclear factor kappa B (NF-κB) has garnered much attention in recent years as an important regulator of memory. Specifically, research has found that NF-κB, localized in both neurons and glia, is activated during the induction of long-term potentiation (LTP), a paradigm of synaptic plasticity and correlate of memory. Further, experimental manipulation of NF-κB activation or its blockade results in altered memory and spatial navigation abilities. Genetic knockout of specific NF-κB subunits in mice results in memory alterations. Collectively, such data suggest that NF-κB may be a requirement for memory, although the direction of the response (i.e., memory enhancement or deficit) is inconsistent. A limited number of gene targets of NF-κB have been recently identified in neurons, including neurotrophic factors, calcium-regulating proteins, other transcription factors, and molecules associated with neuronal outgrowth and remodeling. In turn, several key molecules are activators of NF-κB, including protein kinase C and [Ca(++)]i. Thus, NF-κB signaling is complex and under the regulation of numerous proteins involved in activity-dependent synaptic plasticity. The purpose of this review is to highlight the literature detailing a role for NF-κB in synaptic plasticity, memory, and spatial navigation. Secondly, this review will synthesize the research evaluating gene targets of NF-κB in synaptic plasticity and memory. Although there is ample evidence to suggest a critical role for NF-κB in memory, our understanding of its gene targets in neurons is limited and only beginning to be appreciated.