Study of potential transfer of aluminum to the brain via the olfactory pathway

Ethanol extract of Andrographis paniculata alleviates aluminum-induced neurotoxicity and cognitive impairment through regulating the p62-keap1-Nrf2 pathway

BACKGROUND

Alzheimer's disease (AD) is the most prevalent neurodegenerative and remains incurable. Aluminum is a potent neurotoxin associated with AD. The main pathological features of AD are extracellular amyloid-β protein deposition and intracellular hyperphosphorylated Tau protein. A body of evidence suggest that oxidative stress and autophagy are involved in the pathogenesis of AD. Andrographis paniculata (AP) is a native plant with anti-inflammatory, anti-oxidative stress, and regulation of autophagy properties. AP significantly alleviated cognitive impairments, reduced Aβ deposition and has neuroprotective effect. However, its effects on aluminum-induced AD model have not been studied much. In this study, we investigated whether AP protect against aluminum-induced neurotoxicity through regulation of p62-Kelch-like ECH-associated protein 1(Keap1)-Nuclear factor E2 related factor 2 (Nrf2) pathway and activation autophagy in vivo and in vitro.

METHODS

UPLC-ESI-qTOF-MS/MS was used to identify the chemical constituents of AP ethanol extract. The mice with cognitive deficit were established by injecting aluminum chloride and D-galactose, and treated with either AP extract (200, 400, or 600 mg/kg/d) or andrographolide (2 mg/kg/2d).The spatial memory ability was detected by Morris water maze, HE staining were used to detect in brain tissue,Oxidative stress indexs and SOD activity in both serum and brain tissue were detected by kit.The expression of p62-Nrf2 pathway proteins were measured via western blotting. Furthermore, the neurotoxicity model was induced by aluminum maltolate (700 µM) in PC12 cells. Following AP and andrographolide treatment, the cell viability was detected. The relevant mRNA and protein expressions were detected in cells transfected with the p62 siRNA.

RESULTS

The main active components of AP included andrographolide, neoandrographolide and deoxyandrographolide as identified. AP and andrographolide significantly improved the spatial memory ability of mice, attenuated pathological changes of hippocampal cells, reduced the level of malondialdehyde, and increased superoxide dismutase activity in serum or brain tissue as compared to model control. In addition, the Nrf2, p62 and LC3B-II proteins expression were increased, and p-Tau and Keap1 proteins were decreased in the hippocampus after AP and andrographolide treatment.Furthermore, AP increased aluminum maltolate-induced cell viability in PC12 cells. Silencing p62 could reverse the upregulation expression of Nrf2 and downregulation of Keap1 and Tau proteins induced by AP in aluminum maltolate-treated cells.

CONCLUSIONS

AP had neuroprotective effects against aluminum -induced cognitive dysfunction or cytotoxicity, which was involved in the activation of the p62-keap1-Nrf2 pathway and may develop as therapeutic drugs for the treatment of AD. However, this study has certain limitations, further optimize the protocol or model and study the molecular mechanism of AP improving AD.

Scanning Electron Microscopy and EDX Spectroscopy of Commercial Swabs Used for COVID-19 Lateral Flow Testing

The chemical composition of COVID test swabs has not been examined beyond the manufacturer's datasheets. The unprecedented demand for swabs to conduct rapid lateral flow tests and nucleic acid amplification tests led to mass production, including 3D printing platforms. Manufacturing impurities could be present in the swabs and, if so, could pose a risk to human health. We used scanning electron microscopy and energy dispersive X-ray (EDX) spectroscopy to examine the ultrastructure of seven assorted brands of COVID test swabs and to identify and quantify their chemical elements. We detected eight unexpected elements, including transition metals, such as titanium and zirconium, the metalloid silicon, as well as post-transition metals aluminium and gallium, and the non-metal elements sulphur and fluorine. Some of the elements were detected as trace amounts, but for others, the amount was close to reported toxicological thresholds for inhalation routes. Experimental studies have shown that the detrimental effects of unexpected chemical elements include moderate to severe inflammatory states in the exposed epithelium as well as proliferative changes. Given the massive testing still being used in the context of the COVID pandemic, we urge caution in continuing to recommend repeated and frequent testing, particularly of healthy, non-symptomatic, individuals.

Renal toxicity and biokinetics models after repeated uranium instillation

During nuclear fuel processing, workers can potentially be exposed to repeated inhalations of uranium compounds. Uranium nephrotoxicity is well documented after acute uranium intake, but it is controversial after long-term or protracted exposure. This study aims to analyze the nephrotoxicity threshold after repeated uranium exposure through upper airways and to investigate the resulting uranium biokinetics in comparison to reference models. Mice (C57BL/6J) were exposed to uranyl nitrate (0.03-3 mg/kg/day) via intranasal instillation four times a week for two weeks. Concentrations of uranium in urines and tissues were measured at regular time points (from day 1 to 91 post-exposure). At each exposure level, the amount of uranium retained in organs/tissues (kidney, lung, bone, nasal compartment, carcass) and excreta (urine, feces) reflected the two consecutive weeks of instillation except for renal uranium retention for the highest uranium dose. Nephrotoxicity biomarkers, KIM-1, clusterin and osteopontin, are induced from day 4 to day 21 and associated with changes in renal function (arterial fluxes) measured using non-invasive functional imaging (Doppler-ultrasonography) and confirmed by renal histopathological analysis. These results suggest that specific biokinetic models should be developed to consider altered uranium excretion and retention in kidney due to nephrotoxicity. The threshold is between 0.25 and 1 mg/kg/day after repeated exposure to uranium via upper airways.

Lithium administered to pregnant, lactating and neonatal rats: entry into developing brain

Background

Little is known about the extent of drug entry into developing brain, when administered to pregnant and lactating women. Lithium is commonly prescribed for bipolar disorder. Here we studied transfer of lithium given to dams, into blood, brain and cerebrospinal fluid (CSF) in embryonic and postnatal animals as well as adults.

Methods

Lithium chloride in a clinically relevant dose (3.2 mg/kg body weight) was injected intraperitoneally into pregnant (E15–18) and lactating dams (birth-P16/17) or directly into postnatal pups (P0–P16/17). Acute treatment involved a single injection; long-term treatment involved twice daily injections for the duration of the experiment. Following terminal anaesthesia blood plasma, CSF and brains were collected. Lithium levels and brain distribution were measured using Laser Ablation Inductively Coupled Plasma-Mass Spectrometry and total lithium levels were confirmed by Inductively Coupled Plasma-Mass Spectrometry.

Results

Lithium was detected in blood, CSF and brain of all fetal and postnatal pups following lithium treatment of dams. Its concentration in pups’ blood was consistently below that in maternal blood (30–35%) indicating significant protection by the placenta and breast tissue. However, much of the lithium that reached the fetus entered its brain. Levels of lithium in plasma fluctuated in different treatment groups but its concentration in CSF was stable at all ages, in agreement with known stable levels of endogenous ions in CSF. There was no significant increase of lithium transfer into CSF following application of Na⁺/K⁺ ATPase inhibitor (digoxin) in vivo, indicating that lithium transfer across choroid plexus epithelium is not likely to be via the Na⁺/K⁺ ATPase mechanism, at least early in development. Comparison with passive permeability markers suggested that in acute experiments lithium permeability was less than expected for diffusion but similar in long-term experiments at P2.

Conclusions

Information obtained on the distribution of lithium in developing brain provides a basis for studying possible deleterious effects on brain development and behaviour in offspring of mothers undergoing lithium therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12987-021-00285-w.

Brain accumulation of inhaled uranium in the rat depends on aerosol concentration, exposure repetitions, particle size and solubility

A rostro-caudal gradient of uranium (U) in the brain has been suggested after its inhalation. To study the factors influencing this mapping, we first used 30-min acute inhalation at 56 mg/m³ of the relatively soluble form UO₄ in the rat. These exposure parameters were then used as a reference in comparison with the other experimental conditions. Other groups received acute inhalation at different concentrations, repeated low dose inhalation of UO₄ (10 exposures) or acute low dose inhalation of the insoluble form UO₂. At 24 h after the last exposure, all rats showed a brain U accumulation with a rostro-caudal gradient as compared to controls. However, the total concentration to the brain was greater after repeated exposure than acute exposure, demonstrating an accumulative effect. In comparison with the low dose soluble U exposure, a higher accumulation in the front of the brain was observed after exposure to higher dose, to insoluble particles and following repetition of exposures, thus demonstrating a dose effect and influences of solubility and repetition of exposures. In the last part, exposure to ultrafine U particles made it possible to show 24 h after exposure the presence of U in the brain according to a rostro-caudal gradient. Finally, the time-course after exposure to micronic or nanometric U particles has revealed greater residence times for nanoparticles.

Intranasal administration of dauricine loaded on graphene oxide: multi-target therapy for Alzheimer's disease

Alzheimer's disease (AD) is a degenerative disease of the central nervous system characterized by progressive cognitive and memory-related impairment. However, current therapeutic treatments have not proved sufficiently effective, mainly due to the complicated pathogenesis of the disease. In this study, a nano-formulation of graphene oxide (GO) loaded with dauricine (Dau) was investigated in terms of the combined anti-inflammatory and anti-oxidative stress effects of Dau and the inhibition of misfolding and aggregation of the amyloid-β (Aβ) protein by GO. Both in vivo and in vitro models were induced using Aβ_1-42, and the formulation was administered nasally in mice. The results showed that GO loaded with Dau greatly reduced oxidative stress through increasing superoxide dismutase levels and decreasing reactive oxygen species and malondialdehyde levels in vitro; it also alleviated the cognitive memory deficits and brain glial cell activation in mice with Aβ_1-42-induced AD. This proved that GO loaded with Dau could protect against Aβ_1-42-induced oxidative damage and apoptosis in both in vitro and in vivo AD models; therefore, GO loaded with Dau has the potential to be an effective and agent for the rapid treatment of AD.

Pomegranate juice rescues developmental, neurobehavioral and biochemical disorders in aluminum chloride-treated male mice

PURPOSE

Aluminum (Al) is a harmful metal to organisms and is capable of entering the human body in multiple ways, such as through drinking, breathing, deodorant use, and vaccination. This study examined the prospective toxicity of Al and the protective attributes of pomegranate juice (PJ) on neurobehavioral and biochemical parameters of male mice.

METHODS

Six groups of male mice were treated for 35 days with 20 % PJ (group II), 40 % PJ (group III), 400 mg/kg Al (group IV), Al + 20 % PJ (group V), Al + 40 % PJ (group VI) or tap water (control, group I). Behavioral assessments were conducted for learning and memory evaluations at the end of experiment. In addition, the forebrain was isolated for biochemical analysis.

RESULTS

The exposure of male mice to Al decreased learning and memory retention in the shuttle box, Morris water-maze and T-Maze tests. Biochemical analysis revealed significant depletions in neurotransmitters including DA, 5-HT and AChE and oxidative proteins including GSH, GST, CAT and SOD and increased TBARES levels in Al-treated mice compared to untreated mice. Pomegranate juice provided protection against these effects after Al exposure by ameliorating learning and memory retention and oxidative state in a dose-independent manner.

CONCLUSION

Our data demonstrated that Al exposure caused behavioral and biochemical disorders. Pomegranate juice in lower dose has beneficial properties for health and can be used as a source of antioxidants to reduce the toxicity of Al and other substances.

The REACH registration process: A case study of metallic aluminium, aluminium oxide and aluminium hydroxide

The European Union's REACH Regulation requires determination of potential health and environmental effects of chemicals in commerce. The present case study examines the application of REACH guidance for health hazard assessments of three high production volume (HPV) aluminium (Al) substances: metallic aluminium, aluminium oxide, and aluminium hydroxide. Among the potential adverse health consequences of aluminium exposure, neurotoxicity is one of the most sensitive targets of Al toxicity and the most critical endpoint. This case study illustrates integration of data from multiple lines of evidence into REACH weight of evidence evaluations. This case study then explains how those results support regulatory decisions on classification and labelling. Challenges in the REACH appraisal of Al compounds include speciation, solubility and bioavailability, application of assessment factors, read-across rationale and differences with existing regulatory standards. Lessons learned from the present case study relate to identification and evaluation of toxicologic and epidemiologic data; assessing data relevance and reliability; development of derived no-effect levels (DNELs); addressing data gaps and preparation of chemical safety reports.

Neurotoxicology of Nanomaterials

The remarkable advances coming about through nanotechnology promise to revolutionize many aspects of modern life; however, these advances come with a responsibility for due diligence to ensure that they are not accompanied by adverse consequences for human health or the environment. Many novel nanomaterials (having at least one dimension <100 nm) could be highly mobile if released into the environment and are also very reactive, which has raised concerns for potential adverse impacts including, among others, the potential for neurotoxicity. Several lines of evidence led to concerns for neurotoxicity, but perhaps none more than observations that inhaled nanoparticles impinging on the mucosal surface of the nasal epithelium could be internalized into olfactory receptor neurons and transported by axoplasmic transport into the olfactory bulbs without crossing the blood-brain barrier. From the olfactory bulb, there is concern that nanomaterials may be transported deeper into the brain and affect other brain structures. Of course, people will not be exposed to only engineered nanomaterials, but rather such exposures will occur in a complex mixture of environmental materials, some of which are incidentally generated particles of a similar inhalable size range to engineered nanomaterials. To date, most experimental studies of potential neurotoxicity of nanomaterials have not considered the potential exposure sources and pathways that could lead to exposure, and most studies of nanomaterial exposure have not considered potential neurotoxicity. Here, we present a review of potential sources of exposures to nanoparticles, along with a review of the literature on potential neurotoxicity of nanomaterials. We employ the linked concepts of an aggregate exposure pathway (AEP) and an adverse outcome pathway (AOP) to organize and present the material. The AEP includes a sequence of key events progressing from material sources, release to environmental media, external exposure, internal exposure, and distribution to the target site. The AOP begins with toxicant at the target site causing a molecular initiating event and, like the AEP, progress sequentially to actions at the level of the cell, organ, individual, and population. Reports of nanomaterial actions are described at every key event along the AEP and AOP, except for changes in exposed populations that have not yet been observed. At this last stage, however, there is ample evidence of population level effects from exposure to ambient air particles that may act similarly to engineered nanomaterials. The data give an overall impression that current exposure levels may be considerably lower than those reported experimentally to be neurotoxic. This impression, however, is tempered by the absence of long-term exposure studies with realistic routes and levels of exposure to address concerns for chronic accumulation of materials or damage. Further, missing across the board are "key event relationships", which are quantitative expressions linking the key events of either the AEP or the AOP, making it impossible to quantitatively project the likelihood of adverse neurotoxic effects from exposure to nanomaterials or to estimate margins of exposure for such relationships.

Neurotoxic effects of aluminum are associated with its interference with estrogen receptors signaling

Aluminum compounds have been observed in various brain regions, and their accumulation has been associated with many neurodegenerative disorders. Neurotoxic effects of aluminum are attributed to reactive oxygen species generation, induction of apoptosis and inflammatory reactions activation. Metalloestrogen activity of aluminum has also been linked to breast cancer progression and metastasis. In this study, taking into account the anti-apoptotic and anti-oxidant activities of estrogens in neuronal cells, which are mediated by estrogen receptors, the possible estrogenic activity of aluminum in SH-SY5Y neuroblastoma cells was studied. Our results showed that aluminum in the form of aluminum chlorohydrate (ACH) exhibited no effect on estrogen receptors transcriptional activation, and differential effect on estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) protein levels. ACH caused reduction in ERβ protein levels, and increase in its mitochondrial localization. ACH-induced reduction in ERβ protein level may be linked, at least in part, to the ACH-induced increase in ERα protein level. This statement is based on our observations showing aluminum-induced reduction in the E2-induced increase in ERα S118 phosphorylation, in MCF-7 and SH-SH5Y cells. Phosphorylation at S118 residue is known to be associated with inhibition of the ubiquitin-induced proteolytic degradation of ERα, leading to its accumulation. Since it is known that ERα negatively regulate ERβ expression, increase in ERα, may contribute to reduction in ERβ levels and subsequent weakening of its anti-apoptotic and anti-oxidant activity, justified by the observed reduction in procaspase 9, mitochondrial cytochrome c, Bcl-2, Bcl-xL and mitochondrial thioredoxin protein level, as well as by the increase in proapoptotic BAX level, in ACH treated SH-SY5Y cells. In addition, increase in mitochondrial ERβ localization may also trigger mitochondrial metabolism, suppress biosynthetic process of gluconeogenesis, as indicated by the observed reduction in the phosphoenolpyruvate carboxykinase protein level, and eventually lead to increase in reactive oxygen species (ROS) generation, known to be implicated in aluminum induced neurodegeneration. This statement was verified by the observed ACH-induced increase in ERβ mitochondrial localization, induction of the mitochondrial membrane depolarization and increase in ROS production, in neuronal-like differentiated SH-SY5Y cells.

Evaluation of the Nose-to-Brain Transport of Different Physicochemical Forms of Uranium after Exposure via Inhalation of a UO4 Aerosol in the Rat

BACKGROUND

Health-risk issues are raised concerning inhalation of particulate pollutants that are thought to have potential hazardous effects on the central nervous system. The brain is presented as a direct target of particulate matter (PM) exposure because of the nose-to-brain pathway involvement. The main cause of contamination in nuclear occupational activities is related to exposure to aerosols containing radionuclides, particularly uranium dust. It has been previously demonstrated that instilled solubilized uranium in the rat nasal cavity is conveyed to the brain via the olfactory nerve.

OBJECTIVE

The aim of this study was to analyze the anatomical localization of uranium compounds in the olfactory system after in vivo exposure to a polydisperse aerosol of uranium tetraoxide (UO4) particles.

METHODS

The olfactory neuroepithelium (OE) and selected brain structures-olfactory bulbs (OB), frontal cortex (FC), hippocampus (HIP), cerebellum (Cer), and brainstem (BS)-were microdissected 4 h after aerosol inhalation via a nose-only system in adult rats. Tissues were subjected to complementary analytical techniques.

RESULTS

Uranium concentrations measured by inductively coupled plasma mass spectrometry (ICP-MS) were significantly higher in all brain structures from exposed animals compared with their respective controls. We observed that cerebral uranium concentrations followed an anteroposterior gradient with typical accumulation in the OB, characteristic of a direct olfactory transfer of inhaled compounds. Secondary ion mass spectrometry (SIMS) microscopy and transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (TEM-EDX) were used in order to track elemental uranium in situ in the olfactory epithelium. Elemental uranium was detected in precise anatomical regions: olfactory neuron dendrites, paracellular junctions of neuroepithelial cells, and olfactory nerve tracts (around axons and endoneural spaces).

CONCLUSION

These neuroanatomical observations in a rat model are consistent with the transport of elemental uranium in different physicochemical forms (solubilized, nanoparticles) along olfactory nerve bundles after inhalation of UO4 microparticles. This work contributes to knowledge of the mechanistic actions of particulate pollutants on the brain. https://doi.org/10.1289/EHP4927.

Influence of intranasal exposure of MPTP in multiple doses on liver functions and transition from non-motor to motor symptoms in a rat PD model

Besides the effects on the striatum, the impairment of visceral organs including liver functions has been reported in Parkinson's disease (PD) patients. However, it is yet unclear if liver functions are affected in the early stage of the disease before the motor phase has appeared. The aim of our present study was thus to assess the effect of intranasal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in different doses on striatum and liver functions. Deterioration of non-motor activities appeared on single exposure to MPTP along with rise in striatum oxidative stress and decline in antioxidant levels. Decreases in dopamine, noradrenaline, and GABA and increase in serotonin were detected in striatum. Motor coordination was impaired with a single dose of MPTP, and with repeated MPTP exposure, there was further significant impairment. Locomotor activity was affected from second exposure of MPTP, and the impairment increased with third MPTP exposure. Impairment of liver function through increase in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels was observed after first MPTP insult, and it worsened with second and third administrations. First administration of MPTP triggered systemic inflammation showing significant increase in inflammatory markers in the liver. Our data shows for the first time that an intranasal route of entry of MPTP affects liver from the non-motor phase of PD itself, occurring concomitantly with the reduction of striatal dopamine. It also suggests that a single dose is not enough to bring about progression of the disease from non-motor to locomotor deficiency, and a repeated dose is needed to establish the motor severity phase in the rat intranasal MPTP model.

A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III)

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al³⁺ with colorimetric and fluorescent responses. Upon addition of Al³⁺ to compound MCIH2 solution, compound MCIH2 could respond to Al³⁺ with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye. Furthermore, a remarkable fluorescence emission enhancement with an "OFF-ON" signal by over 700-fold was triggered, but other various metal ions had no such significant effects on the fluorescence emission. In addition, the detection limit of compound MCIH2 for recognizing Al³⁺ was evaluated to be as low as 1 × 10^-7 M level, which was sufficiently low for sensing Al³⁺ widely distributed in various environmental and biological systems.