Risk of neurodegenerative disease due to tau phosphorylation changes and arsenic exposure via drinking water

EDXRF and the relative presence of K, Ca, Fe and as in amyloidogenic tissues

Trace and minor elements play crucial roles in a variety of biological processes, including amyloid fibrils formation. Mechanisms include activation or inhibition of enzymatic reactions, competition between elements and metal proteins for binding positions, also changes to the permeability of cellular membranes. These may influence carcinogenic processes, with trace and minor element concentrations in normal and amyloid tissues potentially aiding in cancer diagnosis and etiology. With the analytical capability of the spectroscopic technique X-ray fluorescence (XRF), this can be used to detect and quantify the presence of elements in amyloid characterization, two of the trace elements known to be associated with amyloid fibrils. In present work, involving samples from a total of 22 subjects, samples of normal and amyloid-containing tissues of heart, kidney, thyroid, and other tissue organs were obtained, analyzed via energy-dispersive X-ray fluorescence (EDXRF). The elemental distribution of potassium (K), calcium (Ca), arsenic (As), and iron (Fe) was examined in both normal and amyloidogenic tissues using perpetual thin slices. In amyloidogenic tissues the levels of K, Ca, and Fe were found to be less than in corresponding normal tissues. Moreover, the presence of As was only observed in amyloidogenic samples; in a few cases in which there was an absence of As, amyloid samples were found to contain Fe. Analysis of arsenic in amyloid plaques has previously been difficult, often producing contradictory results. Using the present EDXRF facility we could distinguish between amyloidogenic and normal samples, with potential correlations in respect of the presence or concentration of specific elements.

Arsenic and Tau Phosphorylation: a Mechanistic Review

Arsenic poisoning can affect the peripheral nervous system and cause peripheral neuropathy. Despite different studies on the mechanism of intoxication, the complete process is not explained yet, which can prevent further intoxication and produce effective treatment. In the following paper, we would like to consider the idea that arsenic might cause some diseases via inflammation induction, and tauopathy in neurons. Tau protein, one of the microtubule-associated proteins expressed in neurons, contributes to neuronal microtubules structure. Arsenic may be involved in cellular cascades involved in modulating tau function or hyperphosphorylation of tau protein, which ultimately leads to nerve destruction. For proof of this assumption, some investigations have been planned to measure the association between arsenic and quantities of phosphorylation of tau protein. Additionally, some researchers have investigated the association between microtubule trafficking in neurons and the levels of tau protein phosphorylation. It should be noticed that changing tau phosphorylation in arsenic toxicity may add a new feature to understanding the mechanism of poisonousness and aid in discovering novel therapeutic candidates such as tau phosphorylation inhibitors for drug development.

Metals in Alzheimer's Disease

The role of metals in the pathogenesis of Alzheimer's disease (AD) is still debated. Although previous research has linked changes in essential metal homeostasis and exposure to environmental heavy metals to the pathogenesis of AD, more research is needed to determine the relationship between metals and AD. In this review, we included human studies that (1) compared the metal concentrations between AD patients and healthy controls, (2) correlated concentrations of AD cerebrospinal fluid (CSF) biomarkers with metal concentrations, and (3) used Mendelian randomization (MR) to assess the potential metal contributions to AD risk. Although many studies have examined various metals in dementia patients, understanding the dynamics of metals in these patients remains difficult due to considerable inconsistencies among the results of individual studies. The most consistent findings were for Zn and Cu, with most studies observing a decrease in Zn levels and an increase in Cu levels in AD patients. However, several studies found no such relation. Because few studies have compared metal levels with biomarker levels in the CSF of AD patients, more research of this type is required. Given that MR is revolutionizing epidemiologic research, additional MR studies that include participants from diverse ethnic backgrounds to assess the causal relationship between metals and AD risk are critical.

The protective effect of natural or chemical compounds against arsenic-induced neurotoxicity: Cellular and molecular mechanisms

Arsenic is a notorious metalloid that exists in the earth's crust and is considered toxic for humans and the environment. Both cancerous and non-cancerous complications are possible after arsenic exposure. Target organs include the liver, lungs, kidney, heart, and brain. Arsenic-induced neurotoxicity, the main focus of our study, can occur in central and peripheral nervous systems. Symptoms can develop in a few hours, weeks, or years depending on the quantity of arsenic and the duration of exposure. In this review, we aimed to gather all the compounds, natural and chemical, that have been studied as protective agents in cellular, animal, and human reports. Oxidative stress, apoptosis, and inflammation are frequently described as destructive mechanisms in heavy metal toxicity. Moreover, reduced activity of acetylcholinesterase, the altered release of monoamine neurotransmitters, down-regulation of N-methyl-D-aspartate receptors, and decreased brain-derived neurotrophic factor are important underlying mechanisms of arsenic-induced neurotoxicity. As for neuroprotection, though some compounds have yet limited data, there are others, such as curcumin, resveratrol, taurine, or melatonin which have been studied more deeply and might be closer to a reliable protective agent. We collected the available information on all protective agents and the mechanisms by which they fight against arsenic-induced neurotoxicity.

Heavy Metals and Essential Metals Are Associated with Cerebrospinal Fluid Biomarkers of Alzheimer's Disease

Various metals have been associated with the pathogenesis of Alzheimer's disease (AD), principally heavy metals that are environmental pollutants (such as As, Cd, Hg, and Pb) and essential metals whose homeostasis is disturbed in AD (such as Cu, Fe, and Zn). Although there is evidence of the involvement of these metals in AD, further research is needed on their mechanisms of toxicity. To further assess the involvement of heavy and essential metals in AD pathogenesis, we compared cerebrospinal fluid (CSF) AD biomarkers to macro- and microelements measured in CSF and plasma. We tested if macro- and microelements' concentrations (heavy metals (As, Cd, Hg, Ni, Pb, and Tl), essential metals (Na, Mg, K, Ca, Fe, Co, Mn, Cu, Zn, and Mo), essential non-metals (B, P, S, and Se), and other non-essential metals (Al, Ba, Li, and Sr)) are associated with CSF AD biomarkers that reflect pathological changes in the AD brain (amyloid β1-42, total tau, phosphorylated tau isoforms, NFL, S100B, VILIP-1, YKL-40, PAPP-A, and albumin). We used inductively coupled plasma mass spectroscopy (ICP-MS) to determine macro- and microelements in CSF and plasma, and enzyme-linked immunosorbent assays (ELISA) to determine protein biomarkers of AD in CSF. This study included 193 participants (124 with AD, 50 with mild cognitive impairment, and 19 healthy controls). Simple correlation, as well as machine learning algorithms (redescription mining and principal component analysis (PCA)), demonstrated that levels of heavy metals (As, Cd, Hg, Ni, Pb, and Tl), essential metals (Ca, Co, Cu, Fe, Mg, Mn, Mo, Na, K, and Zn), and essential non-metals (P, S, and Se) are positively associated with CSF phosphorylated tau isoforms, VILIP-1, S100B, NFL, and YKL-40 in AD.

Effects of Asparagus officinalis on immune system mediated EAE model of multiple sclerosis

Background

About 5 to 10 percent of the population in developed countries are affected by autoimmune diseases. One of the most important autoimmune disease with high prevalence rate is Multiple sclerosis in which there is currently no definitive cure for it, and most medications such as interferons are used only to limit the disease. The present study aims to investigate the effect of using Asparagus Officinalis fractions in an immune system mediated model of multiple sclerosis.

Material and Methods

Fractionation was performed by maceration using n-hexane, chloroform, chloroform-methanol (9: 1), n-Butanol and methanol solvents from aerial parts of Asparagus Officinalis. Thin layer chromatography, NMR and phenolic component measurement were done and two fractions were selected for checking in MS induced in vivo model.

Results

It was observed that chloroform-methanolic and N-Butanol fractions had higher content of saponin in comparison of other extracts. Also, it was showed that the methanolic and n-Butanol extracts contains the highestportion of glycosylic steroid saponins in comparison to other fractions. Regarding experimental autoimmune encephalomyelitis (EAE) score, Butanolic and methanolic fractions with doses higher that 100mg/kg showed a potent supportive effects as long as locomotor activity protection even in lower dose in comparison to phosphate buffered saline (PBS) group.

Conclusion

Considering the proved different effects of saponin compounds on the immune system we observed that those fractions altered the circulatory peripheral blood cells and also remit the clinical signs after EAE induction along with enhanced myelin sheath content in the median region of corpus callusom. It could be inferred that this fractions are promising candidates for further investigation as dose-dependent immune system regulating compounds in multiple sclerosis patients.

Correlative study on heavy metal-induced oxidative stress and hypertension among the rural population of Malwa Region of Punjab, India

Heavy metal-induced toxicity contributes to the progression of various metabolic disorders and possible mechanisms involved in disease progression are not well established. In this study, the correlation of  heavy metal exposure and  hypertension have been demonstrated. The results showed that in hypertensive subjects, the lipid profiles (triglycerides, LDL-C, HDL-C, and total cholesterol) and cardiac markers (CK-MB and LDH) were altered abruptly. As a consequence of heavy- induced oxidative stress, the oxidants (TBARS and protein carbonyls) and antioxidants (SOD, GSH, and TAC) were significantly increased and decreased, respectively in hypertension subjects. The concentrations of heavy metals (Pb, Cd, and As) exceeded the permissible limits in hypertensive subjects. The Nrf-2 genotyping indicated that heavy metals may induce mutations at molecular level. The results of correlation analysis revealed that the heavy metals interact with cellular components and interfere with metabolic processes which then results in disturbed lipid profile, enhanced oxidative stress, and reduced antioxidant status. The current study systematically estimated the association of hair and nail heavy metal concentrations with hypertension among the population residing in the Malwa region of Punjab. The proposed study highlighted that heavy metals act as a silent risk factor in the hypertension progression in the population of Malwa region. Future studies are required to confirm current findings and further scrutinize the effect of heavy metals exposure in early adulthood, early, and late mid-life to develop metabolic complications such as hypertension.

Contemporary Comprehensive Review on Arsenic-Induced Male Reproductive Toxicity and Mechanisms of Phytonutrient Intervention

Arsenic (As) is a poisonous metalloid that is toxic to both humans and animals. Drinking water contamination has been linked to the development of cancer (skin, lung, urinary bladder, and liver), as well as other disorders such as diabetes and cardiovascular, gastrointestinal, neurological, and developmental damage. According to epidemiological studies, As contributes to male infertility, sexual dysfunction, poor sperm quality, and developmental consequences such as low birth weight, spontaneous abortion, and small for gestational age (SGA). Arsenic exposure negatively affected male reproductive systems by lowering testicular and accessory organ weights, and sperm counts, increasing sperm abnormalities and causing apoptotic cell death in Leydig and Sertoli cells, which resulted in decreased testosterone synthesis. Furthermore, during male reproductive toxicity, several molecular signalling pathways, such as apoptosis, inflammation, and autophagy are involved. Phytonutrient intervention in arsenic-induced male reproductive toxicity in various species has received a lot of attention over the years. The current review provides an in-depth summary of the available literature on arsenic-induced male toxicity, as well as therapeutic approaches and future directions.

The 28-day repeated arsenic exposure increases tau phosphorylation in the rat brain

Herein, we examined whether prolonged arsenic exposure altered tau phosphorylation in the brain of Sprague Dawley rats expressing endogenous wild-type tau. The results showed that daily intraperitoneal injections of 2.5 mg/kg BW sodium arsenite over 28 days caused arsenic accumulation in the rat brain. Interestingly, we found an increase in tau phosphorylation at the Tau 1 region (189-207) and S202 in the hippocampus, S404 in the cerebral cortex, and S396 and S404 in the cerebellum of arsenic-treated rats. Additionally, arsenic increased active ERK1/2 phosphorylation at T202/Y204 in the hippocampus, cerebral cortex, and cerebellum. Meanwhile, we detected increasing active JNK phosphorylation at T183/Y185 in the hippocampus and cerebellum. Moreover, p35, a neuron-specific activator of CDK5, was also elevated in the cerebellum of arsenic-treated rats, suggesting that CDK5 activity may be increased by arsenic. These results suggested that arsenic may induce tau phosphorylation through the activation of tau kinases, ERK1/2, JNK, and CDK5. Together, the findings from this study demonstrated that prolonged arsenic exposure is implicated in neurodegeneration by promoting tau phosphorylation in the rat brain and points toward a possible prevention strategy against neurodegeneration induced by environmental arsenic exposure.

Arsenic Induces GSK3β-dependent p-tau, neuronal apoptosis and cognitive impairment via an interdependent hippocampal ERα and IL-1/IL-1R1 mechanism in female rats

Arsenic is an environmental contaminant with potential neurotoxicity. We previously reported that arsenic promoted hippocampal neuronal apoptosis, inducing cognitive loss. Here, we correlated it with tau pathology. We observed that environmentally relevant arsenic exposure increased tau phosphorylation and the principal tau kinase, glycogen synthase kinase-3 beta (GSK3β), in the female rat hippocampal neurons. We detected the same in primary hippocampal neurons. Since a regulated estrogen receptor (ER) level and inflammation contributed to normal hippocampal functions, we examined their levels following arsenic exposure. Our ER screening data revealed that arsenic down-regulated hippocampal neuronal ERα. We also detected an up-regulated hippocampal interleukin-1 (IL-1) and its receptor, IL-1R1. Further, co-treating arsenic with the ERα agonist, 4,4',4''-(4-Propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT), or IL-1R antagonist (IL-1Ra) resulted in reduced GSK3β and p-tau, indicating involvement of decreased ERα and increased IL-1/IL-1R1 in tau hyperphosphorylation. We then checked whether ERα and IL-1/IL-1R1 had linkage, and detected that while PPT reduced IL-1 and IL-1R1, the IL-1Ra restored ERα, suggesting their arsenic-induced interdependence. We finally correlated this pathway with apoptosis and cognition. We observed that PPT, IL-1Ra and the GSK3β inhibitor, LiCl, reduced hippocampal neuronal cleaved caspase-3 and TUNEL+ve apoptotic count, and decreased the number of errors during learning and increased the saving-memory for Y-Maze Test and retention performance for Passive avoidance test in arsenic-treated rats. Thus, our study reveals a novel mechanism of arsenic-induced GSK3β-dependent tau pathology via interdependent ERα and IL-1/IL-1R1 signaling. It also envisages the protective role of ERα agonist and IL-1 inhibitor against arsenic-induced neurotoxicity.

Arsenic Exposure through Dietary Intake and Associated Health Hazards in the Middle East

Dietary arsenic (As) contamination is a major public health issue. In the Middle East, the food supply relies primarily on the import of food commodities. Among different age groups the main source of As exposure is grains and grain-based food products, particularly rice and rice-based dietary products. Rice and rice products are a rich source of core macronutrients and act as a chief energy source across the world. The rate of rice consumption ranges from 250 to 650 g per day per person in South East Asian countries. The source of carbohydrates through rice is one of the leading causes of human As exposure. The Gulf population consumes primarily rice and ready-to-eat cereals as a large proportion of their meals. Exposure to arsenic leads to an increased risk of non-communicable diseases such as dysbiosis, obesity, metabolic syndrome, diabetes, chronic kidney disease, chronic heart disease, cancer, and maternal and fetal complications. The impact of arsenic-containing food items and their exposure on health outcomes are different among different age groups. In the Middle East countries, neurological deficit disorder (NDD) and autism spectrum disorder (ASD) cases are alarming issues. Arsenic exposure might be a causative factor that should be assessed by screening the population and regulatory bodies rechecking the limits of As among all age groups. Our goals for this review are to outline the source and distribution of arsenic in various foods and water and summarize the health complications linked with arsenic toxicity along with identified modifiers that add heterogeneity in biological responses and suggest improvements for multi-disciplinary interventions to minimize the global influence of arsenic. The development and validation of diverse analytical techniques to evaluate the toxic levels of different As contaminants in our food products is the need of the hour. Furthermore, standard parameters and guidelines for As-containing foods should be developed and implemented.

Association of urinary arsenic and sleep disorder in the US population: NHANES 2015-2016

Arsenic is a known carcinogen and neurotoxin and is found in the natural earth crust. Arsenic exposure can develop depression, memory dysfunction, and neurodegenerative disorder. The mechanism of arsenic toxicity on the nervous system is not known. There is a lack of research on the association between arsenic exposure and sleep disturbance in humans. This study aims to investigate the relationship between six types of urinary speciated arsenic exposure and sleep disturbance in adults from the general population using the National Health and Nutrition Examination Survey (NHANES) 2015-2016 dataset. Sleep disturbance was measured using self-reported questionnaires, asking participants if they had ever told a doctor they had trouble sleeping. We utilized multivariate logistic regression analysis using complex survey procedures to examine the association between six types of urinary arsenic concentration and trouble sleeping. The total sample included 1,611 adults who were 20 years and older. Of the study participants, 30.0% had trouble sleeping. Compared to individuals with urinary arsenous acid below the lower level of detection (LLOD), those with urinary arsenous acid at or above the detection limit had lower odds of trouble sleeping [odds ratio: 0.72 (95% confidence interval 0.51-1.00, p-value: 0.05)]. The other five types of urinary speciated arsenic studied (arsenic acid, arsenobetaine, arsenocholine, dimethylarsinic acid, monomethylarsonic acid) were not associated with a sleep disorder. More studies are required to confirm or refute these findings.

Apamin as a BBB Shuttle and Its Effects on T Cell Population During the Experimental Autoimmune Encephalomyelitis-Induced Model of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system presented by autoimmune manifestations. This study aimed at investigating the effects of apamin administration on the activated T cell population in an experimental autoimmune encephalomyelitis (EAE) MS model. Thirty mice underwent EAE induction and were then randomly divided into 5 groups. Three groups received 10, 50, and 100 µg/kg apamin; the fourth group received 1 mg/kg dexamethasone; and the fifth group received the equivalent amount of PBS (phosphate-buffered saline) intraperitoneally. Peripheral CD4 + cell and memory T cell distribution was measured with a flow cytometer every week. Also, CD4 + and CD8 + cell infiltration to the brain was assessed with immunohistochemistry. It was observed that the group receiving 50 µg/kg apamin had a lower EAE score in comparison with the groups receiving 100 µg/kg apamin (p 0.014). Also, peripheral blood memory cells with CD44 + , CD62L - , and CD4 + markers were decreased in apamin-administered groups. Regarding the infiltrated CD8 + cells, a significant decrease (p 0.002) was observed in the group receiving 50 µg/kg apamin compared with the control group. These results indicate that 50-µg/kg doses of apamin had an effective treatment over 14 days; it reduced both the severity of symptoms and the infiltration of CD8 + cells into the CNS. Moreover, it increased myelin density and decreased the circulation of CD62L - , CD44L - , and CD44 + memory T cells. So, it appears that apamin plays a critical role in regulating immunity and reducing the complications of autoimmune MS.

Bee Venom-Derived BBB Shuttle and its Correlation with Oligodendrocyte Proliferation Markers in Mice Model of Multiple Sclerosis

Multiple sclerosis is a chronic demyelinating disease with a functional disturbance in the immune system and axonal damages. It was shown that Apamin as a blood-brain barrier shuttle acts as a Ca2+ activated K+ channels (SK channels) blocker. In this study, the effects of Apamin on oligodendrocyte differentiation markers were evaluated on an induced model of MS. Briefly, C57BL/6 male mice (22 ± 5 g) except the control group were fed with 0.2% (w/w) cuprizone pellets for 6 weeks. After cuprizone withdrawal, mice were divided randomly into six groups. Apamin (100 µg/kg/BW) was administered intraperitoneally as a co-treatment during phase I (demyelination) or post-treatment phase II (remyelination) twice a week. Mice were anesthetized, perfused with phosphate-buffered saline, then fixed brains were coronally sectioned and the changes in oligodendrocytes markers such as Olig2, PDGFR-α, and BrdU incorporation were assessed by immunohistochemistry assay. Apamin administration increased Olig2+ cells in phase I as compared to the control group (p < 0.0001). Also, a decreasing trend in PDGFRa+ cells observed after cuprizone withdrawal (p < 0.001). 5-Bromo-2'-deoxyuridine (BrdU) incorporation test was confirmed stimulation of oligodendrocyte progenitor cell proliferation in phase I in the Apamin exposed group (p < 0.0001), especially at the subventricular zone. This study highlights the potential therapeutic effects of Apamin as a bee venom-derived peptide on oligodendrocyte precursor proliferation and elevation in myelin content in an oxidative induced multiple sclerosis model due to cuprizone exposure.