Upregulation of the secretory pathway Ca2+/Mn2+-ATPase isoform 1 in LPS-stimulated microglia and its involvement in Mn2+-induced Golgi fragmentation.

Microglia play an important protective role in the healthy nervous tissue, being able to react to a variety of stimuli that induce different intracellular cascades for specific tasks. Ca2+ signaling can modulate these pathways, and we recently reported that microglial functions depend on the endoplasmic reticulum as a Ca2+ store, which involves the Ca2+ transporter SERCA2b. Here, we investigated whether microglial functions may also rely on the Golgi, another intracellular Ca2+ store that depends on the secretory pathway Ca2+/Mn2+-transport ATPase isoform 1 (SPCA1). We found upregulation of SPCA1 upon lipopolysaccharide stimulation of microglia BV2 cells and primary microglia, where alterations of the Golgi ribbon were also observed. Silencing and overexpression experiments revealed that SPCA1 affects cell morphology, Golgi apparatus integrity, and phagocytic functions. Since SPCA1 is also an efficient Mn2+ transporter and considering that Mn2+ excess causes manganism in the brain, we addressed the role of microglial SPCA1 in Mn2+ toxicity. Our results revealed a clear effect of Mn2+ excess on the viability and morphology of microglia. Subcellular analysis showed Golgi fragmentation and subsequent alteration of SPCA1 distribution from early stages of toxicity. Removal of Mn2+ by washing improved the culture viability, although it did not effectively reverse Golgi fragmentation. Interestingly, pretreatment with curcumin maintained microglia cultures viable, prevented Mn2+-induced Golgi fragmentation, and preserved SPCA Ca2+-dependent activity, suggesting curcumin as a potential protective agent against Mn2+-induced Golgi alterations in microglia.

Biomarkers for occupational manganese exposure.

Long-term inhalation exposure to manganese (Mn) metal or its inorganic compounds can result in manganism or subclinical neurofunctional deficits. Studies have described affected workers in Mn dioxide mining, Mn-containing ore crushing and milling facilities, manufacturing of dry-cell batteries, Mn steel and alloy production plants, and in welders. The objective of this study was to critically review existing evidence on the reliability of potential biomarkers of Mn exposure, specifically the relationship between inhalation exposure to Mn particulates in different occupational settings and Mn concentrations in blood and other biological fluids and tissues, with a particular focus on whole blood as a potentially useful medium for measuring internal tissue dose. We also examined available evidence on the relationship between Mn levels in blood and adverse clinical and subclinical neurotoxic outcomes. Three bibliographic databases were searched for relevant studies and identified references were screened by two independent reviewers. Of the 6338 unique references identified, 76 articles were retained for data abstraction. Findings indicate that the relationships between Mn in blood and both external Mn exposure indices and neurofunctional impairments are limited and inconsistent. Different sources of exposure to Mn compounds, heterogeneity in the methodological approaches, and inadequate reporting of essential information limited direct comparison of the reported findings. Among the Mn-exposure biomarkers considered in this review - including biomarkers in blood, plasma, serum, erythrocytes, urine, bone, toenails, fingernails, hair, saliva - biomarkers in whole blood may provide to be most useful in Mn biomonitoring and risk assessment.

Protective effect of calpain inhibitors against manganese-induced toxicity in rats.

Development of manganism is a major complication of manganese exposure in which neurological dysfunction is linked to accumulation of metal in the brain. Current therapies do not prevent progression of the disease. Therefore, development of effective therapeutic strategies for treatment of manganism is of utmost importance. Since the hyperactivation of calpain family proteases in CNS during manganism in an animal model is observed, we assumed that inhibition of calpains can suppress the development of Mn-induced neurological disturbances. The goal of this study is to delineate protective effect and the mechanism of neuroprotection of calpain inhibitor in rat model of Mn-induced neurological symptoms. Using the Gait analysis test, we found that chronic intranasal administration of the calpain inhibitor Cast (184-210) (peptide, which is corresponding to the 184-210 amino acid of the endogenous inhibitor of calpains-human calpastatin) to Mn-treated rats contributed to a significant decrease in the severity of gait disorders, although it did not lead to a decrease in the Mn deposition in the striatum and hippocampus. Accordingly to the results of PCR-RT, this effect was accompanied by a partial reduction in the content of neuro-inflammatory markers (IL-1ß, TNF-α, NFκB mRNA in the hippocampus and, additionally, IBA-1 mRNA in the striatum), as well as normalization of the content of dopamine and its metabolites in the hippocampus and striatum, which was assessed by HPLC. In striatum cells, the application of Cast (184-210) also led to a significant increase in the production of tyrosine hydroxylase, which was analyzed by immunoblotting method. These findings suggest that calpain inhibitors may be a valid therapeutic agent in manganism.

Hereditary Disorders of Manganese Metabolism: Pathophysiology of Childhood-Onset Dystonia-Parkinsonism in SLC39A14 Mutation Carriers and Genetic Animal Models.

Over the last decade, several clinical reports have outlined cases of childhood-onset manganese (Mn)-induced dystonia-parkinsonism, resulting from loss-of-function mutations in the Mn influx transporter gene SLC39A14. These clinical cases have provided a wealth of knowledge on Mn toxicity and homeostasis. However, our current understanding of the underlying neuropathophysiology is severely lacking. The recent availability of Slc39a14 knockout (KO) murine and zebrafish animal models provide a powerful platform to investigate the neurological effects of elevated blood and brain Mn concentrations in vivo. As such, the objective of this review was to organize and summarize the current clinical literature and studies utilizing Slc39a14-KO animal models and assess the validity of the animal models based on the clinical presentation of the disease in human mutation carriers.

[Curcumin alleviates the manganese-induced neurotoxicity by promoting autophagy in rat models of manganism].

OBJECTIVE: To investigate the protective effects of curcumin(CUR) and its mechanism on a rat model of neurotoxicity induced by manganese chloride (MnCl2), which mimics mangnism. METHODS: Sixty male SD rats were randomly divided into 5 groups, with 12 rats in each group. Control group received 0.9% saline solution intraperitoneally (ip) plus double distilled water (dd) H2O intragastrically (ig), MnCl2 group received 15 mg/kg MnCl2(Mn2+ 6.48 mg/kg) intraperitoneally plus dd H2O intragastrically, CUR group received 0.9% saline solution intraperitoneally plus 300 mg/kg CUR intragastrically, MnCl2+ CUR1 group received 15 mg/kg MnCl2 intraperitoneally plus 100 mg/kg curcumin intragastrically, MnCl2+ CUR2 group received 15 mg/kg MnCl2 intraperitoneally plus 300 mg/kg CUR intragastrically, 5 days/week, 4 weeks. Open-field and rotarod tests were used to detect animals' exploratory behavior, anxiety, depression, movement and balance ability. Morris water maze (MWM) experiment was used to detect animals' learning and memory ability. ICP-MS was used to investigate the Mn contents in striata. The rats per group were perfused in situ, their brains striata were removed by brains model and fixed for transmission electron microscope (TEM), histopathological and immunohistochemistry (ICH) analyses. The other 6 rats per group were sacrificed. Their brains striata were removed and protein expression levels of transcription factor EB (TFEB), mammalian target of rapamycin (mTOR), p-mTOR, Beclin, P62, microtubule-associated protein light chain-3 (LC3) were detected by Western blotting. Terminal deoxynucleotidyl transterase-mediated dUTP nick end labeling (TUNEL) staining was used to determine neurocyte apoptosis of rat striatum. RESULTS: After exposure to MnCl2 for four weeks, MnCl2-treated rats showed depressive-like behavior in open-field test, the impairments of movement coordination and balance in rotarod test and the diminishment of spatial learning and memory in MWM (P < 0.05). The striatal TH+ neurocyte significantly decreased, eosinophilic cells, aggregative α-Syn level and TUNEL-positive neurocyte significantly increased in the striatum of MnCl2 group compared with control group (P < 0.05). Chromatin condensation, mitochondria tumefaction and autophagosomes were observed in rat striatal neurocytes of MnCl2 group by TEM. TFEB nuclear translocation and autophagy occurred in the striatum of MnCl2 group. Further, the depressive behavior, movement and balance ability, spatial learning and memory ability of MnCl2+ CUR2 group were significantly improved compared with MnCl2 group (P < 0.05). TH+ neurocyte significantly increased, the eosinophilic cells, aggregative α-Syn level significantly decreased in the striatum of MnCl2+ CUR2 group compared with MnCl2 group. Further, compared with MnCl2 group, chromatin condensation, mitochondria tumefaction was alleviated and autophagosomes increased, TFEB-nuclear translocation, autophagy was enhanced and TUNEL-positive neurocyte reduced significantly in the striatum of MnCl2+ CUR2 group (P < 0.05). CONCLUSION: Curcumin alleviated the MnCl2-induced neurotoxicity and α-Syn aggregation probably by promoting TFEB nuclear translocation and enhancing autophagy.

Manganese exposure causes movement deficit and changes in the protein profile of the external globus pallidus in Sprague Dawley rats.

Manganese (Mn) is required for normal brain development and function. Excess Mn may trigger a parkinsonian movement disorder but the underlying mechanisms are incompletely understood. We explored changes in the brain proteomic profile and movement behavior of adult Sprague Dawley (SD) rats systemically treated with or without 1.0 mg/mL MnCl2 for 3 months. Mn treatment significantly increased the concentration of protein-bound Mn in the external globus pallidus (GP), as demonstrated by inductively coupled plasma mass spectrometry. Behavioral study showed that Mn treatment induced movement deficits, especially of skilled movement. Proteome analysis by two-dimensional fluorescence difference gel electrophoresis coupled with mass spectrometry revealed 13 differentially expressed proteins in the GP of Mn-treated versus Mn-untreated SD rats. The differentially expressed proteins were mostly involved in glycolysis, metabolic pathways, and response to hypoxia. Selected pathway class analysis of differentially expressed GP proteins, which included phosphoglycerate mutase 1 (PGAM1), primarily identified enrichment in glycolytic process and innate immune response. In conclusion, perturbation of brain energy production and innate immune response, in which PGAM1 has key roles, may contribute to the movement disorder associated with Mn neurotoxicity.

Intestine-specific deletion of metal transporter Zip14 (Slc39a14) causes brain manganese overload and locomotor defects of manganism.

Impaired manganese (Mn) homeostasis can result in excess Mn accumulation in specific brain regions and neuropathology. Maintaining Mn homeostasis and detoxification is dependent on effective Mn elimination. Specific metal transporters control Mn homeostasis. Human carriers of mutations in the metal transporter ZIP14 and whole body Zip14-knockout (WB-KO) mice display similar phenotypes, including spontaneous systemic and brain Mn overload and motor dysfunction. Initially, it was believed that Mn accumulation due to ZIP14 mutations was caused by impaired hepatobiliary Mn elimination. However, liver-specific Zip14-KO mice did not show systemic Mn accumulation or motor deficits. ZIP14 is highly expressed in the small intestine and is localized to the basolateral surface of enterocytes. Thus, we hypothesized that basolaterally localized ZIP14 in enterocytes provides another route for the elimination of Mn. Using wild-type and intestine-specific Zip14-KO (I-KO) mice, we have shown that ablation of intestinal Zip14 is sufficient to cause systemic and brain Mn accumulation. The lack of intestinal ZIP14-mediated Mn excretion was compensated for by the hepatobiliary system; however, it was not sufficient to maintain Mn homeostasis. When supplemented with extra dietary Mn, I-KO mice displayed some motor dysfunctions and brain Mn accumulation based on both MRI imaging and chemical analysis, thus demonstrating the importance of intestinal ZIP14 as a route of Mn excretion. A defect in intestinal Zip14 expresssion likely could contribute to the Parkinson-like Mn accumulation of manganism.NEW & NOTEWORTHY Mn-induced parkinsonism is recognized as rising in frequency because of both environmental factors and genetic vulnerability; yet currently, there is no cure. We provide evidence in an integrative animal model that basolaterally localized ZIP14 regulates Mn excretion and detoxification and that deletion of intestinal ZIP14 leads to systemic and brain Mn accumulation, providing robust evidence for the indispensable role of intestinal ZIP14 in Mn excretion.

Neuropathological Findings in Ephedrone Encephalopathy.

BACKGROUND: A number of cases of severe parkinsonism-dystonia have been recognized and reported following the illicit use of ephedrone prepared from pseudoephedrine and potassium permanganate. The pathology associated with ephedrone neurotoxicity has not been described yet in the scientific literature. OBJECTIVES: To report the first neuropathological study of ephedrone toxicity. METHODS: The brain of a 33-year-old Ukrainian female ex-ephedrone addict with a long history of l-dopa-unresponsive parkinsonism with dysarthria, dystonia, profound postural instability, cock-gait, and frequent falls, and on antiretroviral treatment, was examined using routine stains and immunohistochemistry. RESULTS: Neuropathological findings included diffuse pallidal astrogliosis without neuronal depletion. There was also widespread vascular pathology with small vessels occluded by foreign material, associated with giant cell response without any evidence of consequent focal infarction and a cerebellar abscess. CONCLUSIONS: Clinical findings of l-dopa-unresponsive parkinsonism with dystonia, caused by illicit use of ephedrone, are fully consistent with neuropathological changes in the pallidum, lack of change in the SN, and preserved tyrosine hydroxylase activity. The findings in the basal ganglia are compatible with manganese toxicity. The vascular pathology is likely a joint effect of infection and the ephedrone toxicity on the vessels. © 2020 International Parkinson and Movement Disorder Society.

Chronic Manganese Administration with Longer Intervals Between Injections Produced Neurotoxicity and Hepatotoxicity in Rats.

Subacute exposure to manganese (Mn) produced Parkinson's disease-like syndrome called Manganism. Chronic onset and progression are characteristics of Manganism, therefore, this study aimed to examine Mn toxicity following chronic exposures. Male Sprague-Dawley rats were injected Mn2+ 1 and 5 mg/kg, every 10 days for 150 days (15 injections). Animal body weight and behavioral activities were recorded. At the end of experiments, the brain and liver were collected for morphological and molecular analysis. Chronic Mn exposure did not affect animal body weight gain, but the high dose of Mn treatment caused 20% mortality after 140 days of administration. Motor activity deficits were observed in a dose-dependent manner at 148 days of Mn administration. Immunofluorescence double staining of substantia nigra pars compacta (SNpc) revealed the activation of microglia and loss of dopaminergic neurons. The chronic neuroinflammation mediators TNFα, inflammasome Nlrp3, Fc fragment of IgG receptor IIb, and formyl peptide receptor-1 were increased, implicating chronic Mn-induced neuroinflammation. Chronic Mn exposure also produced liver injury, as evidenced by hepatocyte degeneration with pink, condensed nuclei, indicative of apoptotic lesions. The inflammatory cytokines TNFα, IL-1ß, and IL-6 were increased, alone with stress-related genes heme oxygenase-1, NAD(P)H:quinone oxidoreductase-1 and metallothionein. Hepatic transporters, such as multidrug resistant proteins (Abcc1, Abcc2, and Abcc3) and solute carrier family proteins (Slc30a1, Slc39a8 and Slc39a14) were increased in attempt to eliminate Mn from the liver. In summary, chronic Mn exposure produced neuroinflammation and dopaminergic neuron loss in the brain, but also produced inflammation to the liver, with upregulation of hepatic transporters.

The neuroprotective properties of carnosine in a mouse model of manganism is mediated via mitochondria regulating and antioxidative mechanisms.

Objective(s): Manganese (Mn) is an essential trace element physiologically incorporated in the structure of several vital enzymes. Despite its essentiality, excessive Mn exposure is toxic with brain tissue as the primary target organ. There is no specific and clinically available therapeutic/preventive option against Mn neurotoxicity. Carnosine is a neuropeptide with several physiological roles. The neuroprotective properties of this peptide have been evaluated in different experimental models. The current study was designed to investigate the effect of carnosine supplementation and its potential mechanisms of action in an animal model of Mn-induced neurotoxicity. Materials and Methods: Male C57BL/6 mice received Mn (100 mg/kg, s.c) alone and/or in combination with carnosine (10, 50, and 100 mg/kg, i.p). Several locomotor activity indices were monitored. Moreover, biomarkers of oxidative stress and mitochondrial function were assessed in the brain tissue of Mn-exposed animals. Results: Significant locomotor dysfunction was revealed in Mn-exposed animals. Furthermore, brain tissue biomarkers of oxidative stress were significantly increased, and mitochondrial indices of functionality were impaired in Mn-treated animals. It was found that carnosine supplementation (10, 50, and 100 mg/kg, i.p) alleviated the Mn-induced locomotor deficit. Moreover, this peptide mitigated oxidative stress biomarkers and preserved brain tissue mitochondrial functionality in the animal model of manganism. Conclusion: These data indicate that carnosine is a potential neuroprotective agent against Mn neurotoxicity. Antioxidative and mitochondria protecting effects of carnosine might play a fundamental role in its neuroprotective properties against Mn toxicity.

Glial-neuronal signaling mechanisms underlying the neuroinflammatory effects of manganese.

BACKGROUND: Exposure to increased manganese (Mn) causes inflammation and neuronal injury in the cortex and basal ganglia, resulting in neurological symptoms resembling Parkinson's disease. The mechanisms underlying neuronal death from exposure to Mn are not well understood but involve inflammatory activation of microglia and astrocytes. Expression of neurotoxic inflammatory genes in glia is highly regulated through the NF-κB pathway, but factors modulating neurotoxic glial-glial and glial-neuronal signaling by Mn are not well understood. METHODS: We examined the role of NF-κB in Mn-induced neurotoxicity by exposing purified microglia, astrocytes (from wild-type and astrocyte-specific IKK knockout mice), and mixed glial cultures to varying Mn concentrations and then treating neurons with the conditioned media (GCM) of each cell type. We hypothesized that mixed glial cultures exposed to Mn (0-100 µM) would enhance glial activation and neuronal death compared to microglia, wild-type astrocytes, or IKK-knockout astrocytes alone or in mixed cultures. RESULTS: Mixed glial cultures treated with 0-100 µM Mn for 24 h showed the most pronounced effect of increased expression of inflammatory genes including inducible nitric oxide synthase (Nos2), Tnf, Ccl5, Il6, Ccr2, Il1b, and the astrocyte-specific genes, C3 and Ccl2. Gene deletion of IKK2 in astrocytes dramatically reduced cytokine release in Mn-treated mixed glial cultures. Measurement of neuronal viability and apoptosis following exposure to Mn-GCM demonstrated that mixed glial cultures induced greater neuronal death than either cell type alone. Loss of IKK in astrocytes also decreased neuronal death compared to microglia alone, wild-type astrocytes, or mixed glia. CONCLUSIONS: This suggests that astrocytes are a critical mediator of Mn neurotoxicity through enhanced expression of inflammatory cytokines and chemokines, including those most associated with a reactive phenotype such as CCL2 but not C3.

Novel founder intronic variant in SLC39A14 in two families causing Manganism and potential treatment strategies.

Congenital disorders of manganese metabolism are rare occurrences in children, and medical management of these disorders is complex and challenging. Homozygous exonic mutations in the manganese transporter SLC39A14 have recently been associated with a pediatric-onset neurodegenerative disorder characterized by brain manganese accumulation and clinical signs of manganese neurotoxicity, including parkinsonism-dystonia. We performed whole exome sequencing on DNA samples from two unrelated female children from the United Arab Emirates with progressive movement disorder and brain mineralization, identified a novel homozygous intronic mutation in SLC39A14 in both children, and demonstrated that the mutation leads to aberrant splicing. Both children had consistently elevated serum manganese levels and were diagnosed with SLC39A14-associated manganism. Over a four-year period, we utilized a multidisciplinary management approach for Patient 1 combining decreased manganese dietary intake and chelation with symptomatic management of dystonia. Our treatment strategy appeared to slow disease progression, but did not lead to a cure or reversal of already established deficits. Clinicians should consider testing for noncoding mutations in the diagnosis of congenital disorders of manganese metabolism and utilizing multidisciplinary approaches in the management of these disorders.

Taurine prevents mitochondrial membrane permeabilization and swelling upon interaction with manganese: Implication in the treatment of cirrhosis-associated central nervous system complications.

Brain tissue manganese (Mn) accumulation is a cirrhosis-associated complication. Cellular mitochondria are among the potential targets for Mn-induced cytotoxicity. Taurine is one of the most abundant amino acids with high concentrations in human brain tissue. Several pharmacological properties including regulation of mitochondrial function are attributed to taurine. The current investigation was designed to evaluate the effect of taurine on Mn-induced mitochondrial impairment in isolated mice brain mitochondria. The brain mitochondria were exposed to increasing concentrations of Mn (0.1-10 mM). Taurine (0.1, 1, and 10 mM) was added as the protective agent. The severe collapse of mitochondrial membrane potential, decreased mitochondrial dehydrogenases activity, mitochondrial swelling, and depleted mitochondrial adenosine triphosphate (ATP) were evident in Mn-exposed mitochondria. It was found that taurine administration preserved mitochondrial ATP, prevented mitochondrial depolarization and swelling, and increased mitochondrial dehydrogenases activity. These data suggest mitochondrial protection as an underlying mechanism for the protective effects of taurine against Mn toxicity.

Microglia amplify inflammatory activation of astrocytes in manganese neurotoxicity.

BACKGROUND: As the primary immune response cell in the central nervous system, microglia constantly monitor the microenvironment and respond rapidly to stress, infection, and injury, making them important modulators of neuroinflammatory responses. In diseases such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and human immunodeficiency virus-induced dementia, activation of microglia precedes astrogliosis and overt neuronal loss. Although microgliosis is implicated in manganese (Mn) neurotoxicity, the role of microglia and glial crosstalk in Mn-induced neurodegeneration is poorly understood. METHODS: Experiments utilized immunopurified murine microglia and astrocytes using column-free magnetic separation. The effect of Mn on microglia was investigated using gene expression analysis, Mn uptake measurements, protein production, and changes in morphology. Additionally, gene expression analysis was used to determine the effect Mn-treated microglia had on inflammatory responses in Mn-exposed astrocytes. RESULTS: Immunofluorescence and flow cytometric analysis of immunopurified microglia and astrocytes indicated cultures were 97 and 90% pure, respectively. Mn treatment in microglia resulted in a dose-dependent increase in pro-inflammatory gene expression, transition to a mixed M1/M2 phenotype, and a de-ramified morphology. Conditioned media from Mn-exposed microglia (MCM) dramatically enhanced expression of mRNA for Tnf, Il-1ß, Il-6, Ccl2, and Ccl5 in astrocytes, as did exposure to Mn in the presence of co-cultured microglia. MCM had increased levels of cytokines and chemokines including IL-6, TNF, CCL2, and CCL5. Pharmacological inhibition of NF-κB in microglia using Bay 11-7082 completely blocked microglial-induced astrocyte activation, whereas siRNA knockdown of Tnf in primary microglia only partially inhibited neuroinflammatory responses in astrocytes. CONCLUSIONS: These results provide evidence that NF-κB signaling in microglia plays an essential role in inflammatory responses in Mn toxicity by regulating cytokines and chemokines that amplify the activation of astrocytes.

Subchronic, Low-Level Intraperitoneal Injections of Manganese (IV) Oxide and Manganese (II) Chloride Affect Rat Brain Neurochemistry.

Manganese (Mn) is neurotoxic and can induce manganism, a Parkinson-like disease categorized as being a serious central nervous system irreversible neurodegenerative disease. An increased risk of developing symptoms of Parkinson disease has been linked to work-related exposure, for example, for workers in agriculture, horticulture, and people living near areas with frequent use of Mn-containing pesticides. In this study, the focus was placed on neurochemical effects of Mn. Rats were dosed intraperitoneally with 0.9% NaCl (control), 1.22 mg Mn (as MnO2)/kg bodyweight (bw)/day, or 2.5 mg Mn (as MnCl2)/kg bw/day for 7 d/wk for 8 or 12 weeks. This dosing regimen adds relevant new knowledge about Mn neurotoxicity as a consequence of low-dose subchronic Mn dosing. Manganese concentrations increased in the striatum, the rest of the brain, and in plasma, and regional brain neurotransmitter concentrations, including noradrenaline, dopamine (DA), 5-hydroxytrytamine, glutamate, taurine, and γ-amino butyric acid, and the activity of acetylcholinesterase changed. Importantly, a target parameter for Parkinson disease and manganism, the striatal DA concentration, was reduced after 12 weeks of dosing with MnCl2. Plasma prolactin concentration was not significantly affected due to a potentially reduced dopaminergic inhibition of the prolactin release from the anterior hypophysis. No effects on the striatal α-synuclein and synaptophysin protein levels were detected.

Quercetin Attenuates Manganese-Induced Neuroinflammation by Alleviating Oxidative Stress through Regulation of Apoptosis, iNOS/NF-κB and HO-1/Nrf2 Pathways.

Manganese (Mn) is an essential trace element required for the development of human body and acts as an enzyme co-factor or activator for various reactions of metabolism. While essential in trace amounts, excessive Mn exposure can result in toxic accumulations in human brain tissue and resulting extrapyramidal symptoms called manganism similar to idiopathic Parkinson's disease (PD). Quercetin (QCT) has been demonstrated to play an important role in altering the progression of neurodegenerative diseases by protecting against oxidative stress. This study aimed to investigate the protective effect of QCT on Mn-induced neurotoxicity and the underlying mechanism in SK-N-MC human neuroblastoma cell line and Sprague-Dawley (SD) male rat brain. The results showed that Mn treatment significantly decreased the cell viability of SK-N-MC cell and increased the release of lactate dehydrogenase (LDH), which was attenuated by QCT pretreatment at 10 and 20 µg/mL. Compared to the Mn alone group, QCT pretreatment significantly attenuated Mn-induced oxidative stress, mitochondrial dysfunction and apoptosis. Meanwhile, QCT pretreatment markedly downregulated the NF-κB but upregulated the heme oxygenase-1 (HO-1) and Nrf2 proteins, compared to the Mn alone group. Our result showed the beneficial effect of QCT on hematological parameters against Mn in rat brain. QCT decrease reactive oxygen species (ROS) and protein carbonyl levels and increased Cu/Zn-superoxide dismutase (SOD) activity induced in Mn-treated rats. QCT administration caused a significant reduction in the Mn-induced neuroinflammation by inhibiting the expression of inflammatory markers such as tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), interleukin-6 (IL-6) cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). QCT lowered the Mn elevated levels of various downstream apoptotic markers, including Bax, cytochrome c, cleaved caspase-3 and polymerase-1 (PARP-1), while QCT treatment upregulated anti-apoptotic Bcl-2 proteins and prevented Mn-induced neurodegeneration. Furthermore, administration of QCT (25 and 50 mg/kg) to Mn-exposed rats showed improvement of histopathological alteration in comparison to Mn-treated rats. Moreover, administration of QCT to Mn-exposed rats showed significant reduction of 8-hydroxy-2'-deoxyguanosine (8-OHdG), Bax, activated caspase-3 and PARP-1 immunoreactivity. These results indicate that QCT could effectively inhibit Mn induced apoptosis and inflammatory response in SK-N-MC cells and SD rats, which may involve the activation of HO-1/Nrf2 and inhibition of NF-κB pathway.

Magnetic Resonance Imaging and Manganism: A Narrative Review and Laboratory Recommendations.

In recent years, a series of articles has been published concerning magnetic resonance imaging (MRI) studies in a group of patients exposed to manganism, specifically factory workers, welders, and individuals with liver diseases, as well as those abusing home-produced ephedrone. Some potential symptoms of manganese toxicity include motor disturbances, neurocognitive problems, sleep disorders, and psychosocial changes. Despite various publications on MRI research in individuals with an elevated risk of manganism, there is a noticeable absence of a comprehensive review in this field. The detection of the accumulation of manganese in the brain through MRI can confirm the diagnosis and guide appropriate treatment. Due to the high cost of determining manganese ion levels in biological material, an additional aim of the manuscript was to identify simple medical laboratory parameters that, when performed concurrently with MRI, could assist in the diagnosis of manganism. Among these types of parameters are the levels of bilirubin, magnesium, liver enzymes, creatinine, hemoglobin, and hematocrit.

Diagnosis of manganism and manganese neurotoxicity: A workshop report.

With declining exposures to manganese (Mn) in occupational settings, there is a need for more sensitive exposure assessments and clinical diagnostic criteria for manganism and Mn neurotoxicity. To address this issue, a workshop was held on November 12-13, 2020, with international experts on Mn toxicity. The workshop discussions focused on the history of the diagnostic criteria for manganism, including those developed by the Institut de Recherche Robert-Sauvé en Santé et en Sécurité du Travail (IRSST) in Quebec in 2005 and criteria developed by the Chinese government in 2002 and updated in 2006; the utility of biomarkers of exposure; recent developments in magnetic resonance imaging (MRI) for assessing Mn accumulation in the brain and diagnosing manganism; and potential future applications of metabolomics. The suggestions of the participants for updating manganism diagnostic criteria included the consideration of: i) A history of previous occupational and environmental exposure to Mn; ii) relevant clinical symptoms such as dystonia; iii) MRI imaging to document Mn accumulation in the neural tissues, including the basal ganglia; and iv) criteria for the differential diagnosis of manganism and other neurological conditions. Important research gaps include the characterization of Mn exposure and other co-exposures, exploration of the roles of different brain regions with MRI, understanding the complexity of metal ion transporters involved in Mn homeostasis, and a need for information on other neurotransmitter systems and brain regions underlying the pathophysiology of manganism.

Manganism due to occupational welding fume exposure: a case report.

Occupational exposure to manganese (Mn) primarily occurs through the inhalation of manganese-containing fumes and dust, with welding environments being significant sources of such exposure. Elevated levels of Mn in welding fumes can lead to a neurological syndrome known as manganism. A 28-yr-old male welder with 14 yr of experience, is presenting with complaints of forgetfulness, reasoning disorder, and decreased mental functions persisting for 10 yr. Three months ago, when he started working at the new workplace, he underwent employment screening conducted by the workplace physician. During this screening process, the physician identified a high whole blood Mn level of 25.9 µg/l. The diagnosis of manganism in this patient was established based on exposure to Mn and its compounds, high levels of Mn detected in the whole blood, hyperactive patellar reflexes observed during the physical examination, cranial Magnetic Resonance Imaging (MRI) findings consistent with manganism and complaints reported by the patient that are characteristic of manganism. In this report, the aim is to emphasize the significance of taking a comprehensive occupational history and to draw attention the potential health hazards associated with Mn and its compounds.

Manganese Neurotoxicity as a Stroke Mimic: A Case Report.

Manganese (Mn)-induced cerebral toxicity is a rare neurological condition that can present as a stroke mimic in high-risk populations. We present a case of a 40-year-old male with no known comorbidities who was brought to the emergency department with complaints of nonprogressive slurred speech and left facial weakness for eight days. Further history revealed that he had been working as a welder in a steel factory for the past seven years without using proper personal protective equipment (PPE). On physical examination, an upper motor neuron (UMN) type weakness on the left side of his face and spastic dysarthria could be appreciated. Following a brain computed tomography (CT) scan that showed ill-defined hypodensities in the basal ganglia without any signs of a hemorrhage, he was admitted to the stroke unit for conservative management and further investigations. A magnetic resonance imaging (MRI) scan of the brain done later showed features of manganese deposition and absorption in the globus pallidus and corticospinal tracts, indicating a diagnosis of manganese-induced cerebral toxicity. His serum manganese levels obtained during admission were normal. He was managed conservatively with intravenous rehydration and was discharged after symptomatic improvement. He was counseled and educated regarding the importance of wearing protective equipment while at work to reduce further exposure to the metal. During his follow-up visit, his symptoms had considerably improved with proper adherence to workplace safety measures.