Neurotoxicology of the brain barrier system: new implications

Maternal prenatal lead levels and neonatal brain volumes: Testing moderations by maternal depressive symptoms and family income

There is considerable evidence that prenatal lead exposure is detrimental to child cognitive and socio-emotional development. Further evidence suggests that the effects of prenatal lead on developmental outcomes may be conditional upon exposure to social stressors, such as maternal depression and low socioeconomic status. However, no studies have examined associations between these co-occurring stressors during pregnancy and neonatal brain volumes. Leveraging a sample of 101 mother-infant dyads followed beginning in mid-pregnancy, we examined the main effects of prenatal urinary lead levels on neonatal lateralized brain volumes (left and right hippocampus, amygdala, cerebellum, frontal lobes) and total gray matter. We additionally tested for moderations between lead and depressive symptoms and between lead and family income relative to the federal poverty level (FPL) on the same neurodevelopmental outcomes. Analyses of main effects indicated that prenatal lead was significantly (ps < 0.05) associated with reduced right and left amygdala volumes (βs = -0.23- -0.20). The testing and probing of cross-product interaction terms using simple slopes indicated that the negative effect of lead on the left amygdala was conditional upon mothers having low depressive symptoms or high income relative to the FPL. We interpret the results in the context of trajectories of prenatal and postnatal brain development and susceptibility to low levels of prenatal lead in the context of other social stressors.

Blood-brain barrier transporters: An overview of function, dysfunction in Alzheimer's disease and strategies for treatment

The blood-brain-barrier (BBB) has a major function in maintaining brain homeostasis by regulating the entry of molecules from the blood to the brain. Key players in BBB function are BBB transporters which are highly expressed in brain endothelial cells (BECs) and critical in mediating the exchange of nutrients and waste products. BBB transporters can also influence drug delivery into the brain by inhibiting or facilitating the entry of brain targeting therapeutics for the treatment of brain disorders, such as Alzheimer's disease (AD). Recent studies have shown that AD is associated with a disrupted BBB and transporter dysfunction, although their roles in the development in AD are not fully understand. Modulation of BBB transporter activity may pose a novel approach to enhance the delivery of drugs to the brain for enhanced treatment of AD. In this review, we will give an overview of key functions of BBB transporters and known changes in AD. In addition, we will discuss current strategies for transporter modulation for enhanced drug delivery into the brain.

Macropinocytosis as a potential mechanism driving neurotropism of Cryptococcus neoformans

Cryptococcus neoformans can invade the central nervous system by crossing the blood-brain barrier via a transcellular mechanism that relies on multiple host factors. In this narrative, we review the evidence that a direct interplay between C. neoformans and brain endothelial cells forms the basis for invasion and transmigration across the brain endothelium. Adherence and internalization of C. neoformans is dependent on transmembrane proteins, including a hyaluronic acid receptor and an ephrin receptor tyrosine kinase. We consider the role of EphA2 in facilitating the invasion of the central nervous system by C. neoformans and highlight experimental evidence supporting macropinocytosis as a potential mechanism of internalization and transcytosis. How macropinocytosis might be conclusively demonstrated in the context of C. neoformans is also discussed.

Pediatric Posterior Reversible Encephalopathy Syndrome: A Review With Emphasis on Neuroimaging Characteristics

Posterior reversible encephalopathy syndrome (PRES) is a neurological disorder characterized by the sudden onset of seizures, headaches, and visual disturbances. Its exact cause is unknown, but several triggers and associated conditions are identified, including high blood pressure, kidney dysfunction, and various medications. Magnetic resonance imaging (MRI) plays a crucial role in diagnosis due to its high sensitivity and specificity for detecting characteristic features. Pediatric PRES exhibit age-dependent differences in triggers, radiological findings, and clinical course. The lesions typically involve the posterior cortical and subcortical white matter, but atypical locations and features are also observed. While generally reversible with appropriate treatment, PRES carries a risk of permanent neurological damage. Despite increasing cases, the current literature on pediatric PRES remains limited. This review highlights the need for further research to understand the mechanisms, delineate distinct clinical and radiological features, and develop precise diagnostic and management strategies for pediatric patients.

Biological activity and structure-activity relationship of dehydrodieugenol B analogues against visceral leishmaniasis

Visceral leishmaniasis is a neglected protozoan disease with high mortality. Existing treatments exhibit a number of limitations, resulting in a significant challenge for public health, especially in developing countries in which the disease is endemic. With a limited pipeline of potential drugs in clinical trials, natural products could offer an attractive source of new pharmaceutical prototypes, not least due to their high chemodiversity. In the present work, a study of anti-L. (L.) infantum potential was carried out for a series of 39 synthetic compounds based on the core scaffold of the neolignan dehydrodieugenol B. Of these, 14 compounds exhibited activity against intracellular amastigotes, with 50% inhibitory concentration (IC₅₀) values between 3.0 and 32.7 μM. A structure-activity relationship (SAR) analysis demonstrated a requirement for polar functionalities to improve activity. Lacking mammalian cytotoxicity and presenting the highest potency against the clinically relevant form of the parasite, compound 24 emerged as the most promising, fulfilling the hit criteria for visceral leishmaniasis defined by the Drugs for Neglected Diseases initiative (DNDi). This study emphasizes the potential of dehydrodieugenol B analogues as new candidates for the treatment of visceral leishmaniasis and suggests 24 to be a suitable compound for future optimization, including mechanism of action and pharmacokinetic studies.

Narirutin downregulates lipoxygenase-5 expression and induces G0/G1 arrest in triple-negative breast carcinoma cells

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 20% of breast cancer that does not express HER2, progesterone and estrogen receptors. It is associated with a high mortality rate, morbidity, metastasis, recurrence, poor prognosis and resistance to chemotherapy. Lipoxygenase-5 (LOX-5), cyclooxygenase-2 (COX-2), cathepsin-D (CATD), ornithine decarboxylase (ODC) and dihydrofolate reductase (DHFR) are involved in breast cancer carcinogenesis; hence, there is a pressing need to identify novel chemicals that targets these enzymes. Narirutin, a flavanone glycoside abundantly present in citrus fruits, is reported to have immune-modulatory, anti-allergic and antioxidant potential. Still, the cancer chemopreventive mechanism against TNBC has not been explored.

METHODS

In vitro experiments, enzyme activity, expression analysis, molecular docking and MD simulation were carried out.

RESULTS

Narirutin suppressed the growth of MDA-MB-231 and MCF-7 in a dose-proportional manner. The pronounced effect with >50% inhibition was observed in SRB and MTT assays for MDAMB-231 cells. Unexpectedly, narirutin suppressed the proliferation of normal cells (24.51%) at 100 μM. Further, narirutin inhibits the activity of LOX-5 in cell-free (18.18 ± 3.93 μM) and cell-based (48.13 ± 7.04 μM) test systems while moderately affecting COX-2, CATD, ODC and DHFR activity. Moreover, narirutin revealed a down-regulation of LOX-5 expression with a fold change of 1.23. Besides, MD simulation experiments confirm that narirutin binding forms a stable complex with LOX-5 and improves the stability and compactness of LOX-5. In addition, the prediction analysis demonstrates that narirutin could not cross the blood-brain barrier and did not act as an inhibitor of different CYPs.

CONCLUSIONS AND SIGNIFICANCE

Narirutin could be a potent cancer chemopreventive lead for TNBC, further paving the way for synthesizing novel analogues.

Delirium with Concurrent Use of Lithium and ECT and the Safety Implications: Case Reports and Review of the Literature

Using electroconvulsive treatment and lithium together to treat acute manic episodes is common, but the effects of combining these therapies vary according to the literature. Some studies have found severe adverse side effects, while others have found the combination of both medications safe and helpful. To investigate potential adverse side effects, this study reports on two cases where bipolar affective disorder patients developed delirium after receiving electroconvulsive therapy and lithium concurrently. The delirium was attributed only to the combined administration of these medicines after ruling out other potential causes. Additionally, alterations in blood-brain barrier permeability, such as those caused by electroconvulsive therapy and age, increased the likelihood of delirium. As a result, caution should be taken when using this combination of medicines, especially in those predisposed to delirium. This study established links between these medications and adverse effects, such as delirium. Further research is necessary to determine the efficacy and risks of combining these medications, establish causality, and develop prevention strategies.

Mechanism of action and neurotoxic effects of chronic exposure to bisphenol F in adult zebrafish

Although bisphenol F (BPF), the main replacement for bisphenol A, has been commonly used in polycarbonate production, its neurotoxicity and the underlying mechanisms remain poorly understood. To address this knowledge gap, this study aimed to assess the neurotoxicity caused by chronic exposure to BPF and to identify its underlying mechanisms. We exposed adult zebrafish chronically to BPF at environmentally relevant concentrations (0.001, 0.01, and 0.1 mg/L) for 4 weeks. The results revealed that with BPF crossing the blood-brain barrier and bioaccumulating in brain tissues, chronic exposure to BPF resulted in anxiety-like behaviors and disruptions in learning and memory function in adult zebrafish. Furthermore, BPF toxicity in the zebrafish brain involved the dysregulation of metabolic pathways for choline and kynurenine in neurotransmitter systems and for 17β-estradiol, cortisol, pregnenolone-sulfate, and Dehydroepiandrosterone (DHEA)-sulfate in neurosteroid systems. RNA-seq analysis revealed that BPF exposure affected metabolic pathways, calcium signaling pathways, neuroactive ligand-receptor interactions, tight junctions, gap junctions, and the gonadotropin-releasing hormone signaling pathway. Our results indicate that chronic exposure to BPF alters the neurochemical profile of the brain and causes neurobehavioral effects, such as anxiety and cognitive decline. Overall, the multimodal approach, including behavioral and neurochemical profiling technologies, has great potential for the comprehensive assessment of potential risks posed by environmental pollutants to human and ecosystem health.

Low glutamate diet improves working memory and contributes to altering BOLD response and functional connectivity within working memory networks in Gulf War Illness

Gulf War Illness is a chronic multi-symptom disorder with severe cognitive impairments which may be related to glutamate excitotoxicity and central nervous system dysfunction. The low glutamate diet has been proposed as a comprehensive intervention for Gulf War Illness. We examined the effects of the low glutamate diet on verbal working memory using a fMRI N-back task. Accuracy, whole-brain blood oxygen level dependency (BOLD) response, and task-based functional connectivity were assessed at baseline and after 1 month on the diet (N = 24). Multi-voxel pattern analysis identified regions of whole-brain BOLD pattern differences after the diet to be used as seeds for subsequent seed-to-voxel functional connectivity analyses. Verbal working memory accuracy improved after the diet (+ 13%; p = 0.006). Whole-brain BOLD signal changes were observed, revealing lower activation within regions of the frontoparietal network and default mode network after the low glutamate diet. Multi-voxel pattern analysis resulted in 3 clusters comprising parts of the frontoparietal network (clusters 1 and 2) and ventral attention network (cluster 3). The seed-to-voxel analyses identified significant functional connectivity changes post-diet for clusters 1 and 2 (peak p < 0.001, cluster FDR p < 0.05). Relative to baseline, clusters 1 and 2 had decreased functional connectivity with regions in the ventral attention and somatomotor networks. Cluster 2 also had increased functional connectivity with regions of the default mode and frontoparietal networks. These findings suggest that among veterans with Gulf War Illness, the low glutamate diet improves verbal working memory accuracy, alters BOLD response, and alters functional connectivity within two networks central to working memory.

Human tissue lead (Pb) levels and amyotrophic lateral sclerosis: a systematic review and meta-analysis of case–control studies

Aim

To combine the current scientific literature evidence and elucidate the differences of lead (Pb) bioaccumulation in human tissues by comparing amyotrophic lateral sclerosis (ALS) patients and healthy controls.

Methods

We systematically searched for case–control studies on the association of Pb levels with ALS, in human cells, tissues, and body fluids (nervous tissue, muscle, blood, cerebrospinal fluid, urine, skin appendages). Then, we performed a meta-analysis for all the tissues in which at least five case–control studies were available: whole blood (9 studies), serum/plasma (5 studies), and cerebrospinal fluid (CSF) (6 studies). Differences between cases and controls were evaluated using standardized mean difference, and combined estimates were derived using random effect maximum likelihood (REML) meta-analyses.

Results

Among 1734 records, we identified 46 full-text studies, of which 14 case–control studies met the meta-analysis inclusion criteria. We found higher Pb levels in ALS cases than controls in blood (standardized mean difference (SMD) = 0.61; 95% confidence interval (CI) 0.20, 1.01; p = 0.003), plasma/serum (SMD = 0.27; 95% CI − 0.16, 0.70; p = 0.26), and CSF (SMD = 0.53; 95% CI − 0.09, 1.15; p = 0.09).

Conclusions

This work provides further evidence of the association between Pb bioaccumulation and ALS in body fluids. The lack of association studies in solid tissues did not allow a robust meta-analysis. Future prospective studies are needed to clarify the causality in the association of Pb bioaccumulation with ALS.

Probable Reasons for Neuron Copper Deficiency in the Brain of Patients with Alzheimer’s Disease: The Complex Role of Amyloid

Alzheimer’s disease is a progressive neurodegenerative disorder that eventually leads the affected patients to die. The appearance of senile plaques in the brains of Alzheimer’s patients is known as a main symptom of this disease. The plaques consist of different components, and according to numerous reports, their main components include beta-amyloid peptide and transition metals such as copper. In this disease, metal dyshomeostasis leads the number of copper ions to simultaneously increase in the plaques and decrease in neurons. Copper ions are essential for proper brain functioning, and one of the possible mechanisms of neuronal death in Alzheimer’s disease is the copper depletion of neurons. However, the reason for the copper depletion is as yet unknown. Based on the available evidence, we suggest two possible reasons: the first is copper released from neurons (along with beta-amyloid peptides), which is deposited outside the neurons, and the second is the uptake of copper ions by activated microglia.

Age-dependent decline of copper clearance at the blood-cerebrospinal fluid barrier

The homeostasis of copper (Cu) in the central nervous system is regulated by the blood-brain barrier and blood-cerebrospinal (CSF) barrier (BCB) in the choroid plexus. While proteins responsible for Cu uptake, release, storage and intracellular trafficking exist in the choroid plexus, the influence of age on Cu clearance from the CSF via the choroid plexus and how Cu transporting proteins contribute to the process are unelucidated. This study was designed to test the hypothesis that the aging process diminishes Cu clearance from the CSF of rats by disrupting Cu transporting proteins in the choroid plexus. Data from ventriculo-cisternal perfusion experiments demonstrated greater ⁶⁴Cu radioactivity in the CSF effluents of older rats (18 months) compared to younger (1 month) and adult (2 months) rats, suggesting much slower removal of Cu by the choroid plexus in old animals. Studies utilizing qPCR and immunofluorescence revealed an age-specific expression pattern of Cu transporting proteins in the choroid plexus. Moreover, proteomic analyses unraveled age-specific proteomes in the choroid plexus with distinct pathway differences, particularly associated with extracellular matrix and neurodevelopment between young and old animals. Taken together, these findings support an age-dependent deterioration in CSF Cu clearance, which appears to be associated with altered subcellular distribution of Cu transporting proteins and proteomes in the choroid plexus.

The Protective Effects of Dexmedetomidine against Hypoxia/Reoxygenation-Induced Inflammatory Injury and Permeability in Brain Endothelial Cells Mediated by Sigma-1 Receptor

Cerebral ischemia-reperfusion injury (CIRI) mainly arises from the clinical treatment of ischemic stroke, induced by the blood-brain barrier (BBB) disruption and infiltrated inflammation. The Sigma-1 receptor (Sigma-1R) is a novel target for neuroprotection, and the α2-receptor agonist pain medication dexmedetomidine displays a neuroprotective effect through activating Sigma-1R. The present study aims to investigate the potential therapeutic effect of dexmedetomidine in a mouse stroke model and hypoxia/reoxygenation(OGD/R)-induced brain endothelial dysfunction. First, we found that Sigma-1R was significantly upregulated in middle cerebral artery occlusion (MCAO) mice by the administration of dexmedetomidine. In vivo experiments revealed that dexmedetomidine ameliorated hyperpermeability of the blood-brain barrier (BBB), lowered the expression level of Occludin, and impaired brain function as measured by neurological scores in MCAO mice. In vitro assays show that dexmedetomidine alleviated OGD/R-caused cytotoxicity, hyperpermeability, abnormal expression of Occludin, and inflammatory factors in human brain microvascular endothelial cells (HBMVECs). Moreover, blockage of Sigma-1R by its antagonist BD1047 abolished the neuroprotective property of dexmedetomidine in both animal and cell culture experiments. On the basis of these findings, we conclude that dexmedetomidine therapy shows neuroprotection in MCAO mice. Mechanistically, dexmedetomidine alleviated hypoxia/reoxygenation-induced cerebral endothelial dysfunction by activating the Sigma-1R-mediated signaling pathway.

Stem Cells for Next Level Toxicity Testing in the 21st Century

The call for a paradigm change in toxicology from the United States National Research Council in 2007 initiates awareness for the invention and use of human-relevant alternative methods for toxicological hazard assessment. Simple 2D in vitro systems may serve as first screening tools, however, recent developments infer the need for more complex, multicellular organotypic models, which are superior in mimicking the complexity of human organs. In this review article most critical organs for toxicity assessment, i.e., skin, brain, thyroid system, lung, heart, liver, kidney, and intestine are discussed with regards to their functions in health and disease. Embracing the manifold modes-of-action how xenobiotic compounds can interfere with physiological organ functions and cause toxicity, the need for translation of such multifaceted organ features into the dish seems obvious. Currently used in vitro methods for toxicological applications and ongoing developments not yet arrived in toxicity testing are discussed, especially highlighting the potential of models based on embryonic stem cells and induced pluripotent stem cells of human origin. Finally, the application of innovative technologies like organs-on-a-chip and genome editing point toward a toxicological paradigm change moves into action.

Caspase-1 has a critical role in blood-brain barrier injury and its inhibition contributes to multifaceted repair

Background

Excessive inflammation might activate and injure the blood-brain barrier (BBB), a common feature of many central nervous system (CNS) disorders. We previously developed an in vitro BBB injury model in which the organophosphate paraoxon (PX) affects the BBB endothelium by attenuating junctional protein expression leading to weakened barrier integrity. The objective of this study was to investigate the inflammatory cellular response at the BBB to elucidate critical pathways that might lead to effective treatment in CNS pathologies in which the BBB is compromised. We hypothesized that caspase-1, a core component of the inflammasome complex, might have important role in BBB function since accumulating evidence indicates its involvement in brain inflammation and pathophysiology.

Methods

An in vitro human BBB model was employed to investigate BBB functions related to inflammation, primarily adhesion and transmigration of peripheral blood mononuclear cells (PBMCs). Caspase-1 pathway was studied by measurements of its activation state and its role in PBMCs adhesion, transmigration, and BBB permeability were investigated using the specific caspase-1 inhibitor, VX-765. Expression level of adhesion and junctional molecules and the secretion of pro-inflammatory cytokines were measured in vitro and in vivo at the BBB endothelium after exposure to PX. The potential repair effect of blocking caspase-1 and downstream molecules was evaluated by immunocytochemistry, ELISA, and Nanostring technology.

Results

PX affected the BBB in vitro by elevating the expression of the adhesion molecules E-selectin and ICAM-1 leading to increased adhesion of PBMCs to endothelial monolayer, followed by elevated transendothelial-migration which was ICAM-1 and LFA-1 dependent. Blocking caspase-8 and 9 rescued the viability of the endothelial cells but not the elevated transmigration of PBMCs. Inhibition of caspase-1, on the other hand, robustly restored all of barrier insults tested including PBMCs adhesion and transmigration, permeability, and VE-cadherin protein levels. The in vitro inflammatory response induced by PX and the role of caspase-1 in BBB injury were corroborated in vivo in isolated blood vessels from hippocampi of mice exposed to PX and treated with VX-765.

Conclusions

These results shed light on the important role of caspase-1 in BBB insult in general and specifically in the inflamed endothelium, and suggest therapeutic potential for various CNS disorders, by targeting caspase-1 in the injured BBB.

Naringin attenuates Bisphenol-A mediated neurotoxicity in hypertensive rats by abrogation of cerebral nucleotide depletion, oxidative damage and neuroinflammation

We examined whether active fruit naringin can reduce the risk of BPA-mediated neurotoxicity in L-NAME induced hypertensive rats and whether the modulation could be linked to improvement of brain NO signaling. Male albino rats were randomly distributed into eight (n = 7) groups. Group I was control animals, Group II was orally-treated with L-NAME, Group III was orally treated with 100 mg/kg BPA, Group IV was orally-treated with L-NAME +100 mg/kg BPA. Group V was orally-administered with L-NAME +80 mg/kg NAR. Group VI was orally-administered with 100 mg/kg BPA +80 mg/kg NAR. Group VII was orally-administered with L-NAME+100 mg/kg BPA +80 mg/kg NAR. Lastly, group VIII was orally-treated with 80 mg/kg NAR. The treatment lasted for 14 days. Sub-acute exposure to L-NAME and BPA induced hypertension and mediated-neuroinflammation at CA-2 and CA-4 of hippocampus cells. It was evident by increase in PDE-5¹ and enzymes of ATP hydrolysis (ATPase, ADPase and AMPase) with corresponding upsurge in cholinergic (AChE and BuChE), dopaminergic (MAO-A) and adenosinergic (ADA) enzymes as well as movement disorder. The hypertensive-mediated neurotoxicity was related to alteration of NO signaling and higher release of pro-inflammatory cytokines (TNF-α and IL-1β), apoptotic proteins (P53 and caspace-9) and facilitated entry of T-lymphocytes (CD43⁺) into CNS through blood brain barrier potentiated by antigen presenting cells. Hence, these features of BPA-mediated neurotoxicity in L-NAME induced hypertensive rats were prohibited by co-administration of NAR through production of neuro-inflammatory mediators, stabilizing neurotransmitter enzymes, normalizing NO signaling and improving brain histology.

Mancozeb exposure during development and lactation periods results in decreased oocyte maturation, fertilization rates, and implantation in the first-generation mice pups: Protective effect of vitamins E and C

This study aimed to evaluate the mancozeb (MNZ) impact on oocyte maturation of first-generation mice pups as well as their fertilization rate, embryo development, and implantation along with the preventative effect of vitamins E and C. Pregnant mice were randomly divided into six groups: control, vehicle, and MNZ (500 mg/kg body weight (BW)), vitamin E (200 mg/kg BW), MNZ plus vitamin E, MNZ plus vitamin C (100 mg/kg BW), and MNZ plus two vitamins. All treatments were conducted by oral gavage every 2 days from the second day of gestation until the end of lactation. Vitamin treatment was initiated 30 min before receiving MNZ. After birth, first-generation mice pups were kept until adulthood (8-10 W). Adult female mice pups superovulated and then the collected oocytes were examined for nuclear maturity status. After in vitro fertilization of metaphase II oocytes with sperm of the first-generation male mice pups, fertilization rate and embryo development were evaluated over 24 h. Also, the fecundity rate and the number of implanted embryos in vivo were studied on the eighth day of pregnancy. MNZ exposure during embryo development and lactation significantly decreased the total number of collected oocytes, oocyte maturation, fertilization rate, implantation rate, fecundity rate, and embryo development compared with the control group in the first-generation pups. In contrast, vitamin treatments significantly increased these parameters compared to the MNZ group. Reduction in the quality of oocyte, the rate of fertilization, embryo implantation, and development following MNZ exposure could decrease female reproductive success, while coadministration of vitamins E and C could prevent these complications.

Brain–Barrier Regulation, Metal (Cu, Fe) Dyshomeostasis, and Neurodegenerative Disorders in Man and Animals

The neurodegenerative diseases (Alzheimers, Parkinsons, amyotrophic lateral sclerosis, Huntingtons) and the prion disorders, have in common a dysregulation of metalloprotein chemistry involving redox metals (Cu, Fe, Mn). The consequent oxidative stress is associated with protein plaques and neuronal cell death. An equilibrium exists between the functional requirement of the brain for Cu and Fe and their destructive potential with the production of reactive oxygen species. The importance of the brain barrier is highlighted in regulating the import of these metals. Upregulation of key transporters occurs in fetal and neonatal life when brain metal requirement is high, and is downregulated in adult life when need is minimal. North Ronaldsay sheep are introduced as an animal model in which a neonatal mode of CTR1 upregulation persists into adulthood and leads to the premise that metal regulation may return to this default setting in ageing, with implications for the neurodegenerative diseases.

Cytotoxic Lesions of the Corpus Callosum Caused by Thermogenic Dietary Supplements

Consumption of over-the-counter dietary supplements to reduce body weight is common among the population. Thermogenics are herbal combinations that claim to produce a fat-burning process through an increase in the cellular metabolic rate and greater cellular energy consumption, having a high risk for patients developing toxic leukoencephalopathy. We present a series of 6 patients with acute neurologic symptoms and MR imaging showing restricted diffusion and decreased apparent diffusion coefficient values (mean value, 400 mm²/s × 10^-6) in the entire corpus callosum compatible with a cytotoxic lesion of the corpus callosum. Although patients responded favorably to the product discontinuation with rapid recovery of neurologic symptoms, there was a more prolonged resolution on imaging alterations. Because of the widespread availability and unregulated nature of thermogenic dietary supplements, physicians must be aware of the clinical and radiologic characteristics of these potential complications of their use.

Amyloid Oligomers, Protofibrils and Fibrils

Amyloid diseases are of major concern all over the world due to a number of factors including: (i) aging population, (ii) increasing life span and (iii) lack of effective pharmacotherapy options. The past decade has seen intense research in discovering disease-modifying multi-targeting small molecules as therapeutic options. In recent years, targeting the amyloid cascade has emerged as an attractive strategy to discover novel neurotherapeutics. Formation of amyloid species, with different degrees of solubility and neurotoxicity is associated with the gradual decline in cognition leading to dementia/cell dysfunction. Here, in this chapter, we have described the recent scenario of amyloid diseases with a great deal of information about the structural features of oligomers, protofibrils and fibrils. Also, comprehensive details have been provided to differentiate the degree of toxicity associated with prefibrillar aggregates. Moreover, a review of the technologies that aid characterisation of oligomer, protofibrils and fibrils as well as various inhibition strategies to overcome protein fibrillation are also discussed.

Exposures of children to neonicotinoids in pine wilt disease control areas

Neonicotinoid insecticides that have been on the market since 1992 have been used globally including in Japan. Because they are sprayed over forests and agricultural areas, inadvertent toxicity in nontarget insects (especially honey bees) and humans is a matter of public concern. However, information on exposure levels and potential health impacts of neonicotinoids in children living around sprayed areas is scarce. Thus, we determined neonicotinoid exposure levels in children living in communities where thiacloprid was used to control pine wilt disease. A total of 46 children (23 males and 23 females) were recruited for the present study, and informed written consent was obtained from their guardians. Urine specimens were collected before, during, and after insecticide spraying events; and atmospheric particulate matter was also collected. Concentrations of thiacloprid and 6 other neonicotinoid compounds were determined in urine samples and in atmospheric particulate matter specimens using liquid chromatography-electrospray ionization-tandem mass spectrometry. In urine specimens, thiacloprid concentrations were <0.13 μg/L and were detectable in approximately 30% of all samples. Concentrations of the other neonicotinoids, N-dm-acetamiprid, thiamethoxam, dinotefuran, and clothianidin, were 18.7, 1.92, 72.3, and 6.02 µg/L, respectively. Estimated daily intakes of these neonicotinoids were then calculated from urinary levels; although the estimated daily intakes of the neonicotinoids were lower than current acceptable daily intake values, the children were found to be exposed to multiple neonicotinoids on a daily basis. Environ Toxicol Chem 2019;38:71-79. © 2018 SETAC.

Genistein Loaded Nanofibers Protect Spinal Cord Tissue Following Experimental Injury in Rats

Innovative drug-delivery systems offer a unique approach to effectively provide therapeutic drug dose over the needed time to achieve better tissue protection and enhanced recovery. The hypothesis of the current study was to test the antioxidant and anti-inflammatory effects of genistein and nanofibers on the spinal cord tissue following experimental spinal cord injury (SCI). Rats were treated post SCI with genistein that is loaded on chitosan/polyvinyl alcohol (CS/PVA) nanofibers as an implantable drug-delivery system. SCI caused marked oxidative damage and inflammation, as is evident by the reduction in the super oxide dismutase (SOD) activity and the level of interleukin-10 (IL-10) in injured spinal cord tissue, as well as the significant increase in the levels of nitric oxide (NO), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-α). Treatment of rats post SCI with genistein and CS/PVA nanofibers improved most of the above-mentioned biochemical parameters and shifted them toward the control group values. Genistein induced an increase in the activity of SOD and the level of IL-10, while causing a decrease in NO, MDA, and TNF-α in injured spinal cord tissue. Genistein and CS/PVA nanofibers provide a novel combination for treating inflammatory nervous tissue conditions, especially when combined as an implantable drug-delivery system.

Posterior Reversible Encephalopathy Syndrome Complicating Ruptured Appendicitis and Abscess Drainage in a Previously Healthy Pediatric Patient

In this study, we present the youngest reported case of posterior reversible encephalopathy syndrome (PRES) in the United States, which developed following perforated appendicitis with subsequent peritonitis and intra-abdominal abscess formation. Additionally, we discuss potential physiological factors contributing to her acute neurological deterioration and resultant cerebral vasogenic edema.

Lead, cadmium and mercury in cerebrospinal fluid and risk of amyotrophic lateral sclerosis: A case-control study

Exposure to neurotoxic chemicals such as pesticides, selenium, and heavy metals have been suggested to play a role in the etiology of amyotrophic lateral sclerosis (ALS). We assessed exposure to lead, cadmium, and mercury in 38 ALS patients (16 men and 22 females) and 38 hospital-admitted controls by using their cerebrospinal fluid (CSF) content as biomarker. We determined CSF heavy metal levels with inductively coupled plasma sector field mass spectrometry, according to a methodology specifically developed for this biological matrix. ALS patients had higher median values for Pb (155 vs. 132ng/L) but lower levels for Cd (36 vs. 72ng/L) and Hg (196 vs. 217ng/L). In the highest tertile of exposure, ALS odds ratio was 1.39 (95% CI 0.48-4.25) for Pb, 0.29 (0.08-1.04) for Cd and 3.03 (0.52-17.55) for Hg; however, no dose-response relation emerged. Results were substantially confirmed after conducting various sensitivity analyses, and after stratification for age and sex. Though interpretation of these results is limited by the statistical imprecision of the estimates, and by the possibility that CSF heavy metal content may not reflect long-term antecedent exposure, they do not lend support to a role of the heavy metals cadmium, lead and mercury in ALS etiology.

Clinical and radiological spectrum of posterior reversible encephalopathy syndrome: does age make a difference?--A retrospective comparison between adult and pediatric patients

Background

Posterior reversible encephalopathy syndrome (PRES) is a serious and increasingly recognized disorder, but data from observational studies on clinicoradiological differences between etiologies and age groups are limited. In this study, we aimed to investigate the clinical and imaging characteristics of PRES in children compared to adults in a large cohort.

Methods

We retrospectively reviewed the radiological report data bases between January 1999 and August 2012 for patients with PRES (total of 110 patients). Patients fulfilling the criteria for PRES after detailed investigation of clinical charts and imaging studies were separated into children (<18years) and adults (≥18years). Various imaging features at onset of symptoms and on follow-up as well as clinical and paraclinical data were analyzed.

Results

A total of 19 pediatric and 91 adult patients with PRES were included into the study. In pediatric PRES patients, seizures were significantly more frequent as initial PRES-related symptom (p = 0.01). In addition, in children the superior frontal sulcus topographic lesion pattern occurred as frequent as the parieto-occipital one and was significantly more prevalent than in adults (p = 0.02). In contrast, in adults visual disturbances tended to occur more frequently than in children (p = 0.05). Also, severity of edema tended to be greater in adults than in children (p = 0.07).

Conclusion

In our PRES cohort, we found relevant clinicoradiological differences between pediatric and adult PRES patients. However, prospective studies are warranted to establish factors that are specifically associated with pediatric PRES.

Toxic leukoencephalopathies, including drug, medication, environmental, and radiation-induced encephalopathic syndromes

Toxic leukoencephalopathies can be secondary to the exposure to a wide variety of exogenous agents, including cranial irradiation, chemotherapy, antiepileptic agents, drugs of abuse, and environmental toxins. There is no typical clinical picture, and patients can present with a wide array of signs and symptoms. Involvement of white matter is a key finding in this scenario, although in some circumstances other high metabolic areas of the central nervous system can also be affected. Magnetic resonance (MR) imaging usually discloses bilateral and symmetric white matter areas of hyperintense signal on T2-weighted and fluid-attenuated inversion recovery images, and signs of restricted diffusion are associated in the acute stage. In most cases, the changes are reversible, especially with prompt recognition of the disease and discontinuation of the noxious agent. Either the MR or clinical features may be similar to several nontoxic entities, such as demyelinating diseases, leukodystrophies, hepatic encephalopathy, vascular disease, hypoxic-ischemic states, and others. A high index of suspicion should be maintained whenever a patient presents recent onset of neurologic deficit, searching the risk of exposure to a neurotoxic agent. Getting to know the most frequent MR appearances and mechanisms of action of causative agents may help to make an early diagnosis and begin therapy, improving outcome. In this review, some of the most important causes of leukoencephalopathies are presented; as well as other 2 related conditions: strokelike migraine attacks after radiation therapy syndrome and reversible splenial lesions.

A histological study of toxic effects of aluminium sulfate on rat hippocampus

Aluminium has toxic effects on many organ systems of the human body. Aluminium toxicity also is a factor in many neurodegenerative diseases. We investigated changes in numbers of hippocampal neurons in rats exposed to aluminium using an optical fractionator and we investigated aluminium-induced apoptosis using the transferase mediated dUTP nick end labeling (TUNEL) assay. Twenty-four female rats were divided equally into control, sham and aluminium-exposed groups. The control group received no treatment. The two treatment groups were injected intraperitoneally with 1 ml 0.9% saline without (sham) and with 3 mg/ml aluminium sulfate every day for two weeks. Following the treatments, the brains were removed, the left hemisphere was used for hippocampal neuron counting using an optical fractionator and the right hemisphere was investigated using hippocampal TUNEL assay to determine the apoptotic index. The number of neurons in the stratum pyramidale of the hippocampus was significantly less in the aluminium group than in the control and sham groups; there was no significant difference between the control and sham groups. The apoptotic index also was significantly higher in the aluminium group than in the other two groups. We quantified the toxic effects of aluminium on the rat hippocampus and determined that apoptosis was the mechanism of aluminium-induced neuron death in the hippocampus.

Manganese accumulation in bone following chronic exposure in rats: steady-state concentration and half-life in bone

Literature data indicate that bone is a major storage organ for manganese (Mn), accounting for 43% of total body Mn. However, the kinetic nature of Mn in bone, especially the half-life (t(1/2)), remained unknown. This study was designed to understand the time-dependence of Mn distribution in rat bone after chronic oral exposure. Adult male rats received 50 mg Mn/kg (as MnCl2) by oral gavage, 5 days per week, for up to 10 weeks. Animals were sacrificed every 2 weeks during Mn administration for the uptake study, and on day 1, week 2, 4, 8, or 12 after the cessation at 6-week Mn exposure for the t(1/2) study. Mn concentrations in bone (MnBn) were determined by AAS analysis. By the end of 6-week's treatment, MnBn appeared to reach the steady state (T(ss)) level, about 2-3.2 fold higher than MnBn at day 0. Kinetic calculation revealed t(1/2)s of Mn in femur, tibia, and humerus bone of 77 (r=0.978), 263 (r=0.988), and 429 (r=0.994) days, respectively; the average t(1/2) in rat skeleton was about 143 days, equivalent to 8.5 years in human bone. Moreover, MnBn were correlated with Mn levels in striatum, hippocampus, and CSF. These data support MnBn to be a useful biomarker of Mn exposure.

Regulation of copper transport crossing brain barrier systems by Cu-ATPases: effect of manganese exposure

Regulation of cellular copper (Cu) homeostasis involves Cu-transporting ATPases (Cu-ATPases), i.e., ATP7A and ATP7B. The question as to how these Cu-ATPases in brain barrier systems transport Cu, i.e., toward brain parenchyma, cerebrospinal fluid (CSF), or blood, remained unanswered. This study was designed to characterize roles of Cu-ATPases in regulating Cu transport at the blood-brain barrier (BBB) and blood-CSF barrier (BCB) and to investigate how exposure to toxic manganese (Mn) altered the function of Cu-ATPases, thereby contributing to the etiology of Mn-induced parkinsonian disorder. Studies by quantitative real-time RT-PCR (qPCR), Western blot, and immunocytochemistry revealed that both Cu-ATPases expressed abundantly in BBB and BCB. Transport kinetic studies by in situ brain infusion and ventriculo-cisternal (VC) perfusion in Sprague Dawley rat suggested that the BBB was a major site for Cu entry into brain, whereas the BCB was a predominant route for Cu efflux from the CSF to blood. Confocal evidence showed that the presence of excess Cu or Mn in the choroid plexus cells led to ATP7A relocating toward the apical microvilli facing the CSF, but ATP7B toward the basolateral membrane facing blood. Mn exposure inhibited the production of both Cu-ATPases. Collectively, these data suggest that Cu is transported by the BBB from the blood to brain, which is mediated by ATP7A in brain capillary. By diffusion, Cu ions move from the interstitial fluid into the CSF, where they are taken up by the BCB. Within the choroidal epithelial cells, Cu ions are transported by ATP7B back to the blood. Mn exposure alters these processes, leading to Cu dyshomeostasis-associated neuronal injury.

Aluminum in the central nervous system (CNS): toxicity in humans and animals, vaccine adjuvants, and autoimmunity

We have examined the neurotoxicity of aluminum in humans and animals under various conditions, following different routes of administration, and provide an overview of the various associated disease states. The literature demonstrates clearly negative impacts of aluminum on the nervous system across the age span. In adults, aluminum exposure can lead to apparently age-related neurological deficits resembling Alzheimer's and has been linked to this disease and to the Guamanian variant, ALS-PDC. Similar outcomes have been found in animal models. In addition, injection of aluminum adjuvants in an attempt to model Gulf War syndrome and associated neurological deficits leads to an ALS phenotype in young male mice. In young children, a highly significant correlation exists between the number of pediatric aluminum-adjuvanted vaccines administered and the rate of autism spectrum disorders. Many of the features of aluminum-induced neurotoxicity may arise, in part, from autoimmune reactions, as part of the ASIA syndrome.

Hemodynamic and neuropathological analysis in rats with aluminum trichloride-induced Alzheimer's disease

BACKGROUND AND AIMS

Hemodynamic normality is crucial to maintaining the integrity of cerebral vessels and, therefore, preserving the cognitive functions of Alzheimer's disease patients. This study investigates the implications of the hemodynamic changes and the neuropathological diversifications of AlCl3-induced AD.

METHODS

The experimental animals were 8- to 12-wk-old male Wistar rats. The rats were randomly divided into 2 groups: a control group and a (+)control group. Food intake, water intake, and weight changes were recorded daily for 22 wk. Synchronously, the regional cerebral blood flow (rCBF) of the rats with AlCl3-induced AD were measured using magnetic resonance imaging (MRI). The hemorheological parameters were analyzed using a computerized auto-rotational rheometer. The brain tissue of the subjects was analyzed using immunohistological chemical (IHC) staining to determine the beta-amyloid (Aβ) levels.

RESULTS

The results of hemodynamic analysis revealed that the whole blood viscosity (WBV), fibrinogen, plasma viscosity and RBC aggregation index (RAI) in (+)control were significantly higher than that of control group, while erythrocyte electrophoresis (EI) of whole blood in (+)control were significantly lower than that of control group. The results of acetylcholinesterase-RBC (AChE-RBC)in the (+)control group was significantly higher than that of the control group. The results also show that the reduction of rCBF in rats with AlCl3-induced AD was approximately 50% to 60% that of normal rats. IHC stain results show that significantly more Aβ plaques accumulated in the hippocampus and cortex of the (+)control than in the control group.

CONCLUSION

The results accentuate the importance of hemorheology and reinforce the specific association between hemodynamic and neuropathological changes in rats with AlCl3-induced AD. Hemorheological parameters, such as WBV and fibrinogen, and AChE-RBC were ultimately proven to be useful biomarkers of the severity and progression of AD patients. In addition, the parameters can be substituted for invasive inspection in therapeutic intervention.

Extremely low-frequency magnetic exposure appears to have no effect on pathogenesis of Alzheimer's disease in aluminum-overloaded rat

Objective

Extremely low-frequency magnetic field (ELF-MF) has been reported to be of potential pathogenetic relevance to Alzheimer's disease (AD) for years. However, evidence confirming this function remains inconclusive. Chronic Al treatment has been identified as a contributing factor to cognitive function impairment in AD. This study aims to examine whether or not ELF-MF and Al have synergistic effects toward AD pathogenesis by investigating the effects of ELF-MF with or without chronic Al treatment on SD rats.

Methods

Sprague-Dawley (SD) rats were subjected one of the following treatments: sham (control group), oral Al (Al group), ELF-MF (100 µT at 50 Hz) with oral Al (MF+Al group), or ELF-MF (100 µT at 50 Hz) without oral Al (MF group).

Results

After 12 wk of treatment, oral Al treatment groups (Al and MF+Al groups) showed learning and memory impairment as well as morphological hallmarks, including neuronal cell loss and high density of amyloid-β (Aβ) in the hippocampus and cerebral cortex. ELF-MF without Al treatment showed no significant effect on AD pathogenesis. ELF-MF+Al treatment induced no more damage than Al treatment did.

Conclusions

Our results showed no evidence of any association between ELF-MF exposure (100 µT at 50 Hz) and AD, and ELF-MF exposure does not influence the pathogenesis of AD induced by Al overload.

Manganese in occupational arc welding fumes--aspects on physiochemical properties, with focus on solubility

Physicochemical properties, such as particle sizes, composition, and solubility of welding fumes are decisive for the bioaccessibility of manganese and thereby for the manganese cytotoxic and neurotoxic effects arising from various welding fumes. Because of the diverse results within the research on welding fume solubility, this article aims to review and discuss recent literature on physicochemical properties of gas metal arc welding, shielded metal arc welding, and flux-cored arc welding fumes, with focus on solubility properties. This article also presents a short introduction to the literature on arc welding techniques, health effects from manganese, and occupational exposure to manganese among welders.

Age and gender may affect posterior reversible encephalopathy syndrome in renal disease

It remains elusive what factors affect posterior reversible encephalopathy syndrome (PRES). Eleven PRES children, all with acute glomerulonephritis, Alport syndrome, and lupus nephritis, 5 with nephrosis, and 3 renal transplant recipients, were studied. PRES recurred in 1 patient. Neurological symptoms were graded as 1: mild (headache, nausea/vomiting, or tremor), 2: moderate (vision change), and 3: severe (mental dysfunction, cerebellar symptoms, seizures, recurrence of seizures, and coma). Magnetic resonance imaging was graded as 1: subtle change, 2: abnormal large areas, and 3: complete involvement of the regions. The common symptoms were seizures (100%), headache (82%), nausea/vomiting (73%), coma (55%), and vision change (46%). Seizures recurred in 7 (64%). All but one (91%) developed hypertension and 7 (64%) received calcineurin inhibitors (CNI). Edema occurred in 7 (64%) and renal insufficiency/end-stage renal disease (ESRD) in 4 (36%). Seizures recurred frequently in younger patients. Symptoms were severe in girls. Duration or severity of the condition with predisposing factors (hypertension, CNI, nephrosis or renal insufficiency/ERSD) did not make a difference in the symptoms and neuroimaging. Two patients developed chronic epilepsy. Age and gender may affect PRES symptoms. Our results are limited by small sample size and should be determined using larger numbers of patients.

Mechanisms of aluminum adjuvant toxicity and autoimmunity in pediatric populations

Immune challenges during early development, including those vaccine-induced, can lead to permanent detrimental alterations of the brain and immune function. Experimental evidence also shows that simultaneous administration of as little as two to three immune adjuvants can overcome genetic resistance to autoimmunity. In some developed countries, by the time children are 4 to 6 years old, they will have received a total of 126 antigenic compounds along with high amounts of aluminum (Al) adjuvants through routine vaccinations. According to the US Food and Drug Administration, safety assessments for vaccines have often not included appropriate toxicity studies because vaccines have not been viewed as inherently toxic. Taken together, these observations raise plausible concerns about the overall safety of current childhood vaccination programs. When assessing adjuvant toxicity in children, several key points ought to be considered: (i) infants and children should not be viewed as “small adults” with regard to toxicological risk as their unique physiology makes them much more vulnerable to toxic insults; (ii) in adult humans Al vaccine adjuvants have been linked to a variety of serious autoimmune and inflammatory conditions (i.e., “ASIA”), yet children are regularly exposed to much higher amounts of Al from vaccines than adults; (iii) it is often assumed that peripheral immune responses do not affect brain function. However, it is now clearly established that there is a bidirectional neuro-immune cross-talk that plays crucial roles in immunoregulation as well as brain function. In turn, perturbations of the neuro-immune axis have been demonstrated in many autoimmune diseases encompassed in “ASIA” and are thought to be driven by a hyperactive immune response; and (iv) the same components of the neuro-immune axis that play key roles in brain development and immune function are heavily targeted by Al adjuvants. In summary, research evidence shows that increasing concerns about current vaccination practices may indeed be warranted. Because children may be most at risk of vaccine-induced complications, a rigorous evaluation of the vaccine-related adverse health impacts in the pediatric population is urgently needed.

Regulation of brain iron and copper homeostasis by brain barrier systems: implication in neurodegenerative diseases

Iron (Fe) and copper (Cu) are essential to neuronal function; excess or deficiency of either is known to underlie the pathoetiology of several commonly known neurodegenerative disorders. This delicate balance of Fe and Cu in the central milieu is maintained by the brain barrier systems, i.e., the blood-brain barrier (BBB) between the blood and brain interstitial fluid and the blood-cerebrospinal fluid barrier (BCB) between the blood and cerebrospinal fluid (CSF). This review provides a concise description on the structural and functional characteristics of the brain barrier systems. Current understanding of Fe and Cu transport across the brain barriers is thoroughly examined, with major focuses on whether the BBB and BCB coordinate the direction of Fe and Cu fluxes between the blood and brain/CSF. In particular, the mechanism by which pertinent metal transporters in the barriers, such as the transferrin receptor (TfR), divalent metal transporter (DMT1), copper transporter (CTR1), ATP7A/B, and ferroportin (FPN), regulate metal movement across the barriers is explored. Finally, the detrimental consequences of dysfunctional metal transport by brain barriers, as a result of endogenous disorders or exogenous insults, are discussed. Understanding the regulation of Fe and Cu homeostasis in the central nervous system aids in the design of new drugs targeted on the regulatory proteins at the brain barriers for the treatment of metal's deficiency or overload-related neurological diseases.

Do aluminum vaccine adjuvants contribute to the rising prevalence of autism?

Autism spectrum disorders (ASD) are serious multisystem developmental disorders and an urgent global public health concern. Dysfunctional immunity and impaired brain function are core deficits in ASD. Aluminum (Al), the most commonly used vaccine adjuvant, is a demonstrated neurotoxin and a strong immune stimulator. Hence, adjuvant Al has the potential to induce neuroimmune disorders. When assessing adjuvant toxicity in children, two key points ought to be considered: (i) children should not be viewed as "small adults" as their unique physiology makes them much more vulnerable to toxic insults; and (ii) if exposure to Al from only few vaccines can lead to cognitive impairment and autoimmunity in adults, is it unreasonable to question whether the current pediatric schedules, often containing 18 Al adjuvanted vaccines, are safe for children? By applying Hill's criteria for establishing causality between exposure and outcome we investigated whether exposure to Al from vaccines could be contributing to the rise in ASD prevalence in the Western world. Our results show that: (i) children from countries with the highest ASD prevalence appear to have the highest exposure to Al from vaccines; (ii) the increase in exposure to Al adjuvants significantly correlates with the increase in ASD prevalence in the United States observed over the last two decades (Pearson r=0.92, p<0.0001); and (iii) a significant correlation exists between the amounts of Al administered to preschool children and the current prevalence of ASD in seven Western countries, particularly at 3-4 months of age (Pearson r=0.89-0.94, p=0.0018-0.0248). The application of the Hill's criteria to these data indicates that the correlation between Al in vaccines and ASD may be causal. Because children represent a fraction of the population most at risk for complications following exposure to Al, a more rigorous evaluation of Al adjuvant safety seems warranted.

Encephalopathy caused by lanthanum carbonate

Lanthanum carbonate is a nonaluminum, noncalcium phosphate-binding agent, which is widely used in patients with end-stage chronic kidney disease. Until now, no significant side-effects have been described for the clinical use of lanthanum carbonate, and there are no available clinical data regarding its tissue stores.

Here we report the case of a 59-year-old patient who was admitted with confusional syndrome. The patient received 3750 mg of lanthanum carbonate daily. Examinations were carried out, and the etiology of the encephalopathy of the patient could not be singled out. The lanthanum carbonate levels in serum and cerebrospinal fluid were high, and the syndrome eased after the drug was removed. The results of our study confirm that, in our case, the lanthanum carbonate did cross the blood-brain barrier (BBB).

Although lanthanum carbonate seems a safe drug with minimal absorption, this work reveals the problem derived from the increase of serum levels of lanthanum carbonate, and the possibility that it may cross the BBB. Further research is required on the possible pathologies that increase serum levels of lanthanum carbonate, as well as the risks and side-effects derived from its absorption.

Regulation of brain copper homeostasis by the brain barrier systems: effects of Fe-overload and Fe-deficiency

Maintaining brain Cu homeostasis is vital for normal brain function. The role of systemic Fe deficiency (FeD) or overload (FeO) due to metabolic diseases or environmental insults in Cu homeostasis in the cerebrospinal fluid (CSF) and brain tissues remains unknown. This study was designed to investigate how blood-brain barrier (BBB) and blood-SCF barrier (BCB) regulated Cu transport and how FeO or FeD altered brain Cu homeostasis. Rats received an Fe-enriched or Fe-depleted diet for 4 weeks. FeD and FeO treatment resulted in a significant increase (+55%) and decrease (-56%) in CSF Cu levels (p<0.05), respectively; however, neither treatment had any effect on CSF Fe levels. The FeD, but not FeO, led to significant increases in Cu levels in brain parenchyma and the choroid plexus. In situ brain perfusion studies demonstrated that the rate of Cu transport into the brain parenchyma was significantly faster in FeD rats (+92%) and significantly slower (-53%) in FeO rats than in controls. In vitro two chamber Transwell transepithelial transport studies using primary choroidal epithelial cells revealed a predominant efflux of Cu from the CSF to blood compartment by the BCB. Further ventriculo-cisternal perfusion studies showed that Cu clearance by the choroid plexus in FeD animals was significantly greater than control (p<0.05). Taken together, our results demonstrate that both the BBB and BCB contribute to maintain a stable Cu homeostasis in the brain and CSF. Cu appears to enter the brain primarily via the BBB and is subsequently removed from the CSF by the BCB. FeD has a more profound effect on brain Cu levels than FeO. FeD increases Cu transport at the brain barriers and prompts Cu overload in the CNS. The BCB plays a key role in removing the excess Cu from the CSF.

The potential of selected brominated flame retardants to affect neurological development

Various brominated flame retardants (BFR), including polybrominated diphenyl ether (PBDE) congeners, hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), are commonly used in household items and electronics and have been detected in the environment and/or the bodily fluids of people, including children. Some studies in animals suggest that exposure to PBDE congeners, HBCD, or TBBPA during the perinatal period may affect locomotor activity and/or memory and learning. Epidemiological studies showing similar effects in humans, however, are lacking. To assess whether an association exists between perinatal exposure and development of consistent neurobehavioral alterations, published animal studies investigating perinatal exposure to PBDE congeners, HBCD, or TBBPA with specific neurobehavioral evaluations-particularly, assessments of motor activity-were reviewed for consistency of results. Our analysis shows that although the majority of studies suggest that perinatal exposure affects motor activity, the effects observed were not consistent. This lack of consistency includes the type of motor activity (locomotion, rearing, or total activity) affected, the direction (increase or decrease) and pattern of change associated with exposure, the existence of a dose response, the permanency of findings, and the possibility of gender differences in response. Interestingly, Good Laboratory Practices (GLP)-compliant studies that followed U.S. Environmental Protection Agency (EPA)/Organization for Economic Cooperation and Development (OECD) guidelines for developmental neurotoxicity testing found no adverse effects associated with exposure to PBDE209, HBCD, or TBBPA at doses that were orders of magnitude higher and administered over longer durations than those used in the other studies examined herein. The lack of consistency across studies precludes establishment of a causal relationship between perinatal exposure to these substances and alterations in motor activity.

The elderly as a sensitive population in environmental exposures: making the case

The US population is aging. CDC has estimated that 20% of all Americans will be 65 or older by the year 2030. As a part of the aging process, the body gradually deteriorates and physiologic and metabolic limitations arise. Changes that occur in organ anatomy and function present challenges for dealing with environmental stressors of all kinds, ranging from temperature regulation to drug metabolism and excretion. The elderly are not just older adults, but rather are individuals with unique challenges and different medical needs than younger adults. The ability of the body to respond to physiological challenge presented by environmental chemicals is dependent upon the health of the organ systems that eliminate those substances from the body. Any compromise in the function of those organ systems may result in a decrease in the body's ability to protect itself from the adverse effects of xenobiotics. To investigate this issue, we performed an organ system-by-organ system review of the effects of human aging and the implications for such aging on susceptibility to drugs and xenobiotics. Birnbaum (1991) reported almost 20 years ago that it was clear that the pharmacokinetic behavior of environmental chemicals is, in many cases, altered during aging. Yet, to date, there is a paucity of data regarding recorded effects of environmental chemicals on elderly individuals. As a result, we have to rely on what is known about the effects of aging and the existing data regarding the metabolism, excretion, and adverse effects of prescription medications in that population to determine whether the elderly might be at greater risk when exposed to environmental substances. With increasing life expectancy, more and more people will confront the problems associated with advancing years. Moreover, although proper diet and exercise may lessen the immediate severity of some aspects of aging, the process will continue to gradually degrade the ability to cope with a variety of injuries and diseases. Thus, the adverse effects of long-term, low-level exposure to environmental substances will have a longer time to be manifested in a physiologically weakened elderly population. When such exposures are coupled with concurrent exposure to prescription medications, the effects could be devastating. Public health officials must be knowledgeable about the sensitivity of the growing elderly population, and ensure that the use of health guidance values (HGVs) for environmental contaminants and other substances give consideration to this physiologically compromised segment of the population.

Cholinergic stimulation improves autonomic and hemodynamic profile during dynamic exercise in patients with heart failure

BACKGROUND

Parasympathetic dysfunction is an independent risk factor for mortality in heart failure for which there is no specific pharmacologic treatment. This article aims to determine the effect of pyridostigmine, an anticholinesterase agent, on the integrated physiologic responses to dynamic exercise in heart failure.

METHODS AND RESULTS

Patients with chronic heart failure (n = 23; 9 female; age = 48 +/- 12 years) were submitted to 3 maximal cardiopulmonary exercise tests on treadmill in different days. The first test was used for adaptation and to determine exercise tolerance. The other tests were performed after oral administration of pyridostigmine (45 mg, 3 times/day, for 24 hours) or placebo, in random order. All patients were taking their usual medication. Pyridostigmine reduced cholinesterase activity by 30%, inhibited the chronotropic response throughout exercise, up to 60% of maximal effort (pyridostigmine = 108 +/- 3 beats/min vs. placebo = 113 +/- 3 beats/min; P = .040), and improved heart rate reserve (pyridostigmine = 73 +/- 5 beats/min vs. placebo = 69 +/- 5 beats/min; P = 0.035) and heart rate recovery in the first minute after exercise (pyridostigmine = 25 +/- 2 beats/min vs. placebo = 22 +/- 2 beats/min; P = .005), whereas peak heart rate was similar to placebo. Oxygen pulse, an indirect indicator of stroke volume, was higher under pyridostigmine during submaximal exercise.

CONCLUSIONS

Pyridostigmine was well tolerated by heart failure patients, leading to improved hemodynamic profile during dynamic exercise.

Copper transport to the brain by the blood-brain barrier and blood-CSF barrier

The mechanism of copper (Cu) transport into the brain is unclear. This study evaluated the main species and route of Cu transport into the brain using in situ brain perfusion technique, and assessed the levels of mRNA encoding Cu transporters using real time RT-PCR. Free (64)Cu uptake in rat choroid plexus (CP), where the blood-cerebrospinal fluid barrier (BCB) is primarily located, is about 50 and 1000 times higher than (64)Cu-albumin and (64)Cu-ceruloplasmin uptake, respectively. The unidirectional transport rate constants (K(in)) for Cu in the CP and brain capillaries of the blood-brain barrier (BBB) were 1034 and 319 microl/s/g, respectively, while K(in) in CSF and capillary-depleted parenchyma were much reduced, 0.8 and 112 microl/s/g, respectively. The K(in) in cerebellum was significantly lower than that in hippocampus. The mRNAs encoding Cu transporter-1 (Ctr1) and ATP7A were higher in the CP than those in brain capillaries and parenchyma, whereas ATP7B mRNA was higher in brain capillaries than those in the CP and brain parenchyma. Taken together, these data suggest that the expression of Cu transporters is higher in brain barriers than in brain parenchyma; the Cu transport into the brain is mainly achieved through the BBB as a free Cu ion and the BCB may serve as a main regulatory site of Cu in the CSF.

Manganese induces dopaminergic neurodegeneration via microglial activation in a rat model of manganism

Manganese is an essential trace element required for normal development and bodily functions. However, exposure of the brain to excessive amounts of manganese results in neurotoxicity. Although previous studies examining manganese neurotoxicity have focused on neuronal injury, especially direct injury to dopaminergic neurons, the effects of manganese-induced neurotoxicity on glial cells have not been reported. The current study was designed to examine the effect of manganese on microglial activation, and the underlying mechanism of manganese-induced dopaminergic neuronal injury in vivo. We established an animal model of manganism by intrastriatal injection of MnCl(2).4H(2)O into male Sprague-Dawley rats. One day after administration of manganese, a few microglial cells in the substantia nigra (SN) were activated, although the number of tyrosine hydroxylase (TH)-immunoreactive neurons in the SN was unaffected. Seven days after administration of manganese, a marked reduction in the number of TH-immunoreactive neurons was observed in the SN, and the majority of microglial cells were activated. We found that manganese upregulated inducible nitric oxide synthase (iNOS) and tumor necrosis factor alpha (TNF-alpha) gene expression, as well as iNOS, TNF-alpha, and interleukin-1beta (IL-1beta) protein levels in the SN. Furthermore, treatment with minocycline, an inhibitor of microglial activation, attenuated microglial activation and mitigated IL-1beta, TNF-alpha, and iNOS production as well as dopaminergic neurotoxicity induced by manganese. These results suggested that dopaminergic neurons could be damaged by manganese neurotoxicity, and that the activated microglial cells and their associated activation products played an important role in this neurodegenerative process.

Evidence for altered hippocampal volume and brain metabolites in workers occupationally exposed to lead: a study by magnetic resonance imaging and (1)H magnetic resonance spectroscopy

Environmental and occupational exposure to lead (Pb) remains to be a major public health issue. The purpose of this cross-sectional study was to use non-invasive magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy ((1)H MRS) techniques to investigate whether chronic exposure to Pb in an occupational setting altered brain structure and function of Pb-exposed workers. The Pb-exposed group consisted of 15 workers recruited from either a Pb-smelting factory or a Pb-battery manufacturer. The control group had 19 healthy volunteers who had no history of Pb exposure in working environment or at home. The average airborne Pb concentrations in fume and dust were 0.43 and 0.44 mg/m(3), respectively, in the smeltery, and 0.10 and 1.06 mg/m(3), respectively, in the Pb battery workshop. The average blood Pb concentrations (BPb) in Pb-exposed and control workers were 63.5 and 8.7 microg/dL, respectively. The MRI examination showed that brain hippocampal volume among Pb-exposed workers was significantly diminished in comparison to age-matched control subjects (p < 0.01), although the extent of this reduction was relatively small (5-6% of the control values). Linear regression analyses revealed significant inverse associations between BPb and the decreased hippocampal volume on both sides of brain hemisphere. Among five brain metabolites investigated by MRS, i.e., N-acetyl-aspartate (NAA), creatine (Cr), choline (Cho), inosine (mI), glutamate/glutamine (Glx) and lipids (Lip), a significant decrease in NAA/Cr ratio (7% of controls, p < 0.05) and a remarkable increase in Lip/Cr ratio (40%, p < 0.01) were observed in the brains of Pb-exposed workers as compared to controls. Furthermore, the increased Lip/Cr ratio was significantly associated with BPb (r = 0.46, p < 0.01). Taken together, this study suggests that occupational exposure to Pb may cause subtle structural and functional alteration in human brains. The MRI and MRS brain imaging techniques can be used as the non-invasive means to evaluate Pb-induced neurotoxicity.