Genetic Disorders of Manganese Metabolism

Data- and knowledge-derived functional landscape of human solute carriers

The human solute carrier (SLC) superfamily of ~460 membrane transporters remains the largest understudied protein family despite its therapeutic potential. To advance SLC research, we developed a comprehensive knowledgebase that integrates systematic multi-omics data sets with selected curated information from public sources. We annotated SLC substrates through literature curation, compiled SLC disease associations using data mining techniques, and determined the subcellular localization of SLCs by combining annotations from public databases with an immunofluorescence imaging approach. This SLC-centric knowledge is made accessible to the scientific community via a web portal featuring interactive dashboards and visualization tools. Utilizing this systematically collected and curated resource, we computationally derived an integrated functional landscape for the entire human SLC superfamily. We identified clusters with distinct properties and established functional distances between transporters. Based on all available data sets and their integration, we assigned biochemical/biological functions to each SLC, making this study one of the largest systematic annotations of human gene function and a potential blueprint for future research endeavors.

Consensus of Expert Opinion for the Diagnosis and Management of Hypermanganesaemia With Dystonia 1 and 2

Hypermanganesaemia with Dystonia 1 and 2 (HMNDYT1 and 2) are inherited, autosomal recessive disorders caused by pathogenic variants in the genes encoding the manganese transporters SLC30A10 and SLC39A14, respectively. Impaired hepatic and enterocytic manganese uptake (SLC39A14) and excretion (SLC30A10) lead to deposition of manganese in the basal ganglia resulting in childhood-onset dystonia-parkinsonism. HMNDYT1 is characterized by additional features due to manganese accumulation in the liver causing cirrhosis, polycythaemia, and depleted iron stores. High blood manganese levels and pathognomonic MRI brain appearances of manganese deposition resulting in T1 hyperintensity of the basal ganglia are diagnostic clues. Treatment is limited to chelation therapy and iron supplementation that can prevent disease progression. Due to their rarity, the awareness of the inherited manganese transporter defects is limited. Here, we provide consensus expert recommendations for the diagnosis and treatment of patients with HMNDYT1 and 2 in order to facilitate early diagnosis and optimize clinical outcome. These recommendations were developed through an evidence and consensus-based process led by a group of 13 international experts across the disciplines of metabolic medicine, neurology, hematology, genetics, and radiology, and address the clinical presentation, diagnostic investigations, principles of treatment, and monitoring of patients with HMNDYT1 and 2.

Role of manganese in brain health and disease: Focus on oxidative stress

Manganese (Mn) is an essential trace element crucial for various physiological processes, but excessive exposure can lead to significant health concerns, particularly neurotoxicity. This review synthesizes current knowledge on Mn-induced oxidative stress and its role in cellular dysfunction and disease. We discuss how Mn promotes toxicity through multiple mechanisms, primarily through reactive oxygen species (ROS) generation, which leads to oxidative stress and disruption of cellular processes. The review examines key pathways affected by Mn toxicity, including mitochondrial dysfunction, endoplasmic reticulum stress, inflammasome activation, and epigenetic modifications. Recent studies have identified promising therapeutic compounds, including both synthetic and natural substances such as probucol, metformin, curcumin, resveratrol, and daidzein, which demonstrate protective effects through various mechanisms, including antioxidant enhancement, mitochondrial function preservation, and epigenetic pathway modulation. Understanding these mechanisms provides new insights into potential therapeutic strategies for Mn-induced disorders. This review also highlights future research directions, emphasizing the need for developing targeted therapies and investigating combination approaches to address multiple aspects of Mn toxicity simultaneously.

Manganese Neurotoxicity: A Comprehensive Review of Pathophysiology and Inherited and Acquired Disorders

Manganese (Mn) is an essential trace element and a cofactor for several key enzymes, such as mitochondrial superoxide dismutase. Consequently, it plays an important defense role against reactive oxygen species. Despite this, Mn chronic overexposure can result in a neurological disorder referred to as manganism, which shares some similarities with Parkinson's disease. Mn levels seem regulated by many transporters responsible for its uptake and efflux. These transporters play an established role in many inherited disorders of Mn metabolism and neurotoxicity. Some inherited Mn metabolism disorders, caused by mutations of SLC30A10 and SLC39A14, assume crucial importance since earlier treatment results in a better prognosis. Physicians should be familiar with the clinical presentation of these disorders as the underlying cause of dystonia/parkinsonism and look for other accompanying features, such as liver disease and polycythemia, which are typically associated with SLC30A10 mutations. This review aims to highlight the currently known Mn transporters, Mn-related neurotoxicity, and its consequences, and it provides an overview of inherited and acquired disorders of Mn metabolism. Currently available treatments are also discussed, focusing on the most frequently encountered presentations.

Human genetic variants in SLC39A8 impact uptake and steady-state metal levels within the cell

The human SLC39A8 (hSLC39A8) gene encodes a plasma membrane protein SLC39A8 (ZIP8) that mediates the specific uptake of the metals Cd2+, Mn2+, Zn2+, Fe2+, Co2+, and Se4+ Pathogenic variants within hSLC39A8 are associated with congenital disorder of glycosylation type 2 (CDG type II) or Leigh-like syndrome. However, numerous mutations of uncertain significance are also linked to different conditions or benign traits. Our study characterized 21 hSLC39A8 variants and measured their impact on protein localization and intracellular levels of Cd2+, Zn2+, and Mn2+ We identified four variants that disrupt protein expression, five variants with high retention in the endoplasmic reticulum, and 12 variants with localization to the plasma membrane. From the 12 variants with plasma membrane localization, we identified three with complete loss of detectable ion uptake by the cell and five with differential uptake between metal ions. Further in silico analysis on protein stability identified variants that may affect the stability of homodimer interfaces. This study elucidates the variety of effects of hSLC39A8 variants on ZIP8 and on diseases involving disrupted metal ion homeostasis.

Impact of blood lead and manganese levels on metabolic dysfunction-associated steatotic liver disease prevalence: insights from NHANES (2017-2020)

BACKGROUND

The metabolic dysfunction-associated steatotic liver disease (MASLD) paradigm represents a significant departure from the previous nonalcoholic fatty liver disease (NAFLD) framework, offering a non-stigmatizing approach that enhances awareness and accelerates patient understanding. Our primary aim was to investigate the potential relationship between blood lead and manganese exposure and the onset of MASLD.

METHODS

Using data from the National Health and Nutrition Examination Survey (NHANES) database spanning from 2017 to 2020, a cross-sectional study included 4,475 participants was performed to assess the relationship. The statistical analysis used throughout the study included multivariable linear regression and multiple logistic regression models, adjusted for potential confounders to ensure robust and reliable results. We applied a thorough multivariable analysis, examining various factors including age, sex, and ethnicity to enhance the robustness of our findings.

RESULTS

Employing linear regression models in our study, we observed a clear positive correlation between elevated levels of blood lead and manganese and Controlled attenuation parameter (CAP). Additionally, employing multiple logistic regression models for detailed analysis, we noted a significant increase in the likelihood of MASLD with higher levels of blood lead and manganese.

CONCLUSION

The findings of this study strongly suggest a notable correlation between increased levels of blood lead and manganese with both CAP and the presence of MASLD. This study represents a population-based approach, enhancing the generalizability of the findings to the broader U.S.

POPULATION

Studies of Slc30a10 Deficiency in Mice Reveal That Intestinal Iron Transporters Dmt1 and Ferroportin Transport Manganese

BACKGROUND & AIMS

SLC11A2 (DMT1) and SLC40A1 (ferroportin) are essential for dietary iron absorption, but their role in manganese transport is debated. SLC30A10 deficiency causes severe manganese excess due to loss of gastrointestinal manganese excretion. Patients are treated with chelators but also respond to oral iron, suggesting that iron can outcompete manganese for absorption in this disease. Here, we determine if divalent metal transport 1 (Dmt1) and ferroportin can transport manganese using Slc30a10-deficient mice as a model.

METHODS

Manganese absorption and levels and other disease parameters were assessed in Slc30a10-/- mice with and without intestinal Dmt1 and ferroportin deficiency using gastric gavage, surgical bile collections, multiple metal assays, and other techniques. The contribution of intestinal Slc30a10 deficiency to ferroportin-dependent manganese absorption was explored by determining if intestinal Slc30a10 deficiency increases manganese absorption in a mouse model of hereditary hemochromatosis, a disease of iron excess due to ferroportin upregulation.

RESULTS

Manganese absorption was increased in Slc30a10-deficient mice despite manganese excess. Intestinal Dmt1 and ferroportin deficiency attenuated manganese absorption and excess in Slc30a10-deficient mice. Intestinal Slc30a10 deficiency increased manganese absorption and levels in the hemochromatosis mouse model.

CONCLUSIONS

Aberrant absorption contributes prominently to SLC30A10 deficiency, a disease previously attributed to impaired excretion, and is dependent upon intestinal Dmt1 and ferroportin and exacerbated by loss of intestinal Slc30a10. This work expands our understanding of overlaps between manganese and iron transport and the mechanisms by which the body regulates absorption of 2 nutrients that can share transport pathways. We propose that a reconsideration of the role of Dmt1 and ferroportin in manganese homeostasis is warranted.

Mitochondrially Transcribed dsRNA Mediates Manganese-induced Neuroinflammation

Manganese (Mn) is an essential trace element required for various biological functions, but excessive Mn levels are neurotoxic and lead to significant health concerns. The mechanisms underlying Mn-induced neurotoxicity remain poorly understood. Neuropathological studies of affected brain regions reveal astrogliosis, and neuronal loss, along with evidence of neuroinflammation. Here, we present a novel Mn-dependent mechanism linking mitochondrial dysfunction to neuroinflammation. We found that Mn disrupts mitochondrial transcriptome processing, resulting in the accumulation of complementary RNAs that form double-stranded RNA (dsRNA). This dsRNA is released to the cytoplasm, where it activates cytosolic sensor pathways, triggering type I interferon responses and inflammatory cytokine production. This mechanism is present in 100-day human cerebral organoids, where Mn-induced inflammatory responses are observed predominantly in mature astrocytes. Similar effects were observed in vivo in a mouse model carrying mutations in the SLC30A10 gene, which results in Mn accumulation. These findings highlight a previously unrecognized role for mitochondrial dsRNA in Mn-induced neuroinflammation and provide insights into the molecular basis of manganism. We propose that this mitochondrial dsRNA-induced inflammatory pathway has broad implications in for neurodegenerative diseases caused by environmental or genetic insults.

Association of blood manganese and selenium levels with hepatic steatosis among adolescents: a nationwide cross-sectional analysis

Objective

This study aimed to investigate the association between blood manganese and selenium levels and hepatic steatosis among adolescents, using data from the National Health and Nutrition Examination Survey (NHANES) 2017-2023.

Methods

A cross-sectional analysis was conducted using data from 2,459 adolescents (aged 12-19 years) with complete data on liver ultrasound transient elastography, blood manganese, and selenium levels. Hepatic steatosis was defined as a controlled attenuation parameter (CAP) score of ≥248 dB/m, a measure of liver steatosis, which is a primary characteristic and a less severe stage of hepatic steatosis, assessed by vibration-controlled transient elastography (VCTE). Multivariate logistic regression models were used to assess the associations between blood manganese and selenium levels and hepatic steatosis, while restricted cubic splines (RCS) were employed to examine the dose-response relationships.

Results

The mean age of the participants was 15.37 years, with 52.22% boy. Higher blood manganese and selenium levels were significantly associated with an increased prevalence of hepatic steatosis. In the fully adjusted model, adolescents in the highest quartile of blood manganese had more than twice the odds of hepatic steatosis compared to those in the lowest quartile (OR = 2.41, 95% CI: 1.55-3.75, P < 0.01). Similarly, the highest quartile of blood selenium was associated with a 57% increase in hepatic steatosis prevalence compared to the lowest quartile (OR = 1.57, 95% CI: 1.19-2.08, P < 0.01). RCS analysis confirmed a linear association between both blood manganese and selenium levels and hepatic steatosis prevalence. Subgroup analyses did not reveal statistically significant interactions by age, sex, or obesity status, although associations appeared stronger in younger adolescents.

Conclusion

Elevated blood manganese and selenium levels are associated with a higher prevalence of hepatic steatosis in adolescents. These findings suggest a potential role of trace elements in the development of hepatic steatosis, highlighting the need for further research to better understand the underlying mechanisms involved in liver fat accumulation in this population.

Association of dietary manganese intake and the IL1R1 rs3917225 polymorphism with thyroid cancer risk: a prospective cohort study in Korea

Dietary Mn intake may have a beneficial effect in reducing cancer risk; however, its association with thyroid cancer (TC) risk remains inadequately understood. Additionally, Mn was associated with inflammation markers. Thus, we examined whether dietary Mn intake emerges a protective role against TC and whether this preventative effect has an interaction with IL1 receptor type 1 (IL1R1) rs3917225. The prospective study was designed at National Cancer Center in Korea between October 2007 and December 2020 including 17 754 participants. We identified TC cases by following participants until December 2020. Mn intake was collected using a semiquantitative food frequency questionnaire (SQFFQ). Genotyping was performed to determine IL1R1 rs3917225. The hazard ratios (HR) and 95 % confidence interval (CI) were calculated with a Cox proportional hazards model. We ascertained 108 incident TC cases throughout follow-up duration. Dietary Mn intake was found to be inversely associated with TC risk (HR (95 % CI)=0·64 (0·44, 0·95)). However, IL1R1 rs3917225 seemed to modify this association; the protective effect was limited to G-allele carriers (HR = 0·30 (0·11, 0·86), P interaction=0·028). A higher dietary Mn was suggested to be a protective factor against TC. Additionally, we drew a potential biological interaction between Mn intake and IL1R1 rs3917225 with a greater effect among individuals with a minor allele. This implies that when considering the cancer-preventive role of Mn, it is important to account for the influence of inflammatory gene participation.

Welding techniques and manganese concentrations in blood and brain: Results from the WELDFUMES study

This study used whole-brain mapping to investigate the effect of different welding processes on manganese (Mn) accumulation in the brain. Exposure measurements were performed at the welders' workplaces about 3 weeks before a magnetic resonance imaging (MRI) examination. The welders were categorized into three main groups based on welding method, and the T1-relaxation rate (R1) was measured using quantitative MRI (qMRI). Welders using shielded metal arc welding (SMAW) were found to have lower accumulations of total Mn in clusters encompassing white matter, thalamus, putamen, pallidum, and substantia nigra compared with welders using inert gas tungsten arc welding (GTAW) or continuous consumable electrode arc welding (CCEAW). A positive correlation was found between Mn in red blood cells (Mn-RBC) and R1 in a region encompassing pre-and post-central gyri. The results of this study show that the accumulation of free, bound, or compartmentalized Mn ions in the brain differed depending on the welding method used. These differences were predominately located in the basal ganglia but were also found in regions encompassing white matter. The level of Mn-RBC was correlated to the deposition of Mn in the left primary somatosensory and motor cortex and may therefore be linked to neurological and neurobehavioral symptoms.

Cotinine exposure enhances the association of blood manganese and non-alcoholic fatty liver disease in American children: a cross-sectional study

This cross-sectional survey aims to determine whether cotinine exposure would enhance the relationship between blood manganese (Mn) and non-alcoholic fatty liver disease (NAFLD) in children using the NHANES database. Restricted cubic spline (RCS) and logistic regression analyses were adopted to determine the potential relationship. Besides, we tested the robustness of the results by performing trend tests and subgroup analyses. The study finally enrolled 866 children aged 18 years and below. Blood Mn was linearly linked to NAFLD and the risk of NAFLD was increased with the blood Mn elevation (P < 0.05). There was a notable relationship between blood Mn and NAFLD in crude model 1, which was still significant upon adjustment of all the identified covariates (all P < 0.05). Under Mn exposure, the cotinine-exposed group had a higher risk of NAFLD than the cotinine-unexposed group. In conclusion, blood Mn level is an independent risk factor for pediatric NAFLD, and cotinine exposure can enhance this relationship to some degree. Therefore, reducing cotinine exposure may alleviate detrimental consequences related to exposure to heavy metals in children.

Signal Transduction Associated with Mn-induced Neurological Dysfunction

Manganese (Mn) is a heavy metal that occurs widely in nature and has a vital physiological role in growth and development. However, excessive exposure to Mn can cause neurological damage, especially cognitive dysfunction, such as learning disability and memory loss. Numerous studies on the mechanisms of Mn-induced nervous system damage found that this metal targets a variety of metabolic pathways, for example, endoplasmic reticulum stress, apoptosis, neuroinflammation, cellular signaling pathway changes, and neurotransmitter metabolism interference. This article reviews the latest research progress on multiple signaling pathways related to Mn-induced neurological dysfunction.

Manganese transporter SLC30A10 and iron transporters SLC40A1 and SLC11A2 impact dietary manganese absorption

SLC30A10 deficiency is a disease of severe manganese excess attributed to loss of SLC30A10-dependent manganese excretion via the gastrointestinal tract. Patients develop dystonia, cirrhosis, and polycythemia. They are treated with chelators but also respond to oral iron, suggesting that iron can outcompete manganese for absorption in this disease. Here we explore the latter observation. Intriguingly, manganese absorption is increased in Slc30a10-deficient mice despite manganese excess. Studies of multiple mouse models indicate that increased dietary manganese absorption reflects two processes: loss of manganese export from enterocytes into the gastrointestinal tract lumen by SLC30A10, and increased absorption of dietary manganese by iron transporters SLC11A2 (DMT1) and SLC40A1 (ferroportin). Our work demonstrates that aberrant absorption contributes prominently to SLC30A10 deficiency and expands our understanding of biological interactions between iron and manganese. Based on these results, we propose a reconsideration of the role of iron transporters in manganese homeostasis is warranted.

Elevated thyroid manganese reduces thyroid iodine to induce hypothyroidism in mice, but not rats, lacking SLC30A10 transporter

Elevated manganese (Mn) accumulates in the brain and induces neurotoxicity. SLC30A10 is an Mn efflux transporter that controls body Mn levels. We previously reported that full-body Slc30a10 knockout mice (1) recapitulate the body Mn retention phenotype of humans with loss-of-function SLC30A10 mutations and (2) unexpectedly develop hypothyroidism induced by Mn accumulation in the thyroid, which reduces intra-thyroid thyroxine. Subsequent analyses of National Health and Nutrition Examination Survey data identified an association between serum Mn and subclinical thyroid changes. The emergence of thyroid deficits as a feature of Mn toxicity suggests that changes in thyroid function may be an underappreciated, but critical, modulator of Mn-induced disease. To better understand the relationship between thyroid function and Mn toxicity, here we further defined the mechanism of Mn-induced hypothyroidism using mouse and rat models. Slc30a10 knockout mice exhibited a profound deficit in thyroid iodine levels that occurred contemporaneously with increases in thyroid Mn levels and preceded the onset of overt hypothyroidism. Wild-type Mn-exposed mice also exhibited increased thyroid Mn levels, an inverse correlation between thyroid Mn and iodine levels, and subclinical hypothyroidism. In contrast, thyroid iodine levels were unaltered in newly generated Slc30a10 knockout rats despite an increase in thyroid Mn levels, and the knockout rats were euthyroid. Thus, Mn-induced thyroid dysfunction in genetic or Mn exposure-induced mouse models occurs due to a reduction in thyroid iodine subsequent to an increase in thyroid Mn levels. Moreover, rat and mouse thyroids have differential sensitivities to Mn, which may impact the manifestations of Mn-induced disease in these routinely used animal models.

Interaction and competition for intestinal absorption by zinc, iron, copper, and manganese at the intestinal mucus layer

Trace elements such as zinc, manganese, copper, or iron are essential for a wide range of physiological functions. It is therefore crucial to ensure an adequate supply of these elements to the body. Many previous investigations have dealt with the role of transport proteins, in particular their selectivity for, and competition between, different ions. Another so far less well investigated major factor influencing the absorption of trace elements seems to be the intestinal mucus layer. This gel-like substance covers the entire gastrointestinal tract and its physiochemical properties can be mainly assigned to the glycoproteins it contains, so-called mucins. Interaction with mucins has already been demonstrated for some metals. However, knowledge about the impact on the respective bioavailability and competition between those metals is still sketchy. This review therefore aims to summarize the findings and knowledge gaps about potential effects regarding the interaction between gastrointestinal mucins and the trace elements iron, zinc, manganese, and copper. Mucins play an indispensable role in the absorption of these trace elements in the neutral to slightly alkaline environment of the intestine, by keeping them in a soluble form that can be absorbed by enterocytes. Furthermore, the studies so far indicate that the competition between these trace elements for uptake already starts at the intestinal mucus layer, yet further research is required to completely understand this interaction.

Manganese-derived biomaterials for tumor diagnosis and therapy

Manganese (Mn) is widely recognized owing to its low cost, non-toxic nature, and versatile oxidation states, leading to the emergence of various Mn-based nanomaterials with applications across diverse fields, particularly in tumor diagnosis and therapy. Systematic reviews specifically addressing the tumor diagnosis and therapy aspects of Mn-derived biomaterials are lacking. This review comprehensively explores the physicochemical characteristics and synthesis methods of Mn-derived biomaterials, emphasizing their role in tumor diagnostics, including magnetic resonance imaging, photoacoustic and photothermal imaging, ultrasound imaging, multimodal imaging, and biodetection. Moreover, the advantages of Mn-based materials in tumor treatment applications are discussed, including drug delivery, tumor microenvironment regulation, synergistic photothermal, photodynamic, and chemodynamic therapies, tumor immunotherapy, and imaging-guided therapy. The review concludes by providing insights into the current landscape and future directions for Mn-driven advancements in the field, serving as a comprehensive resource for researchers and clinicians.

Manganese Overexposure Alters Neurogranin Expression and Causes Behavioral Deficits in Larval Zebrafish

Manganese (Mn), a cofactor for various enzyme classes, is an essential trace metal for all organisms. However, overexposure to Mn causes neurotoxicity. Here, we evaluated the effects of exposure to Mn chloride (MnCl2) on viability, morphology, synapse function (based on neurogranin expression) and behavior of zebrafish larvae. MnCl2 exposure from 2.5 h post fertilization led to reduced survival (60%) at 5 days post fertilization. Phenotypical changes affected body length, eye and olfactory organ size, and visual background adaptation. This was accompanied by a decrease in both the fluorescence intensity of neurogranin immunostaining and expression levels of the neurogranin-encoding genes nrgna and nrgnb, suggesting the presence of synaptic alterations. Furthermore, overexposure to MnCl2 resulted in larvae exhibiting postural defects, reduction in motor activity and impaired preference for light environments. Following the removal of MnCl2 from the fish water, zebrafish larvae recovered their pigmentation pattern and normalized their locomotor behavior, indicating that some aspects of Mn neurotoxicity are reversible. In summary, our results demonstrate that Mn overexposure leads to pronounced morphological alterations, changes in neurogranin expression and behavioral impairments in zebrafish larvae.

Hepatic HIF2 is a key determinant of manganese excess and polycythemia in SLC30A10 deficiency

Manganese is an essential yet potentially toxic metal. Initially reported in 2012, mutations in SLC30A10 are the first known inherited cause of manganese excess. SLC30A10 is an apical membrane protein that exports manganese from hepatocytes into bile and from enterocytes into the lumen of the gastrointestinal tract. SLC30A10 deficiency results in impaired gastrointestinal manganese excretion, leading to manganese excess, neurologic deficits, liver cirrhosis, polycythemia, and erythropoietin excess. Neurologic and liver disease are attributed to manganese toxicity. Polycythemia is attributed to erythropoietin excess. The goal of this study was to determine the basis of erythropoietin excess in SLC30A10 deficiency. Here, we demonstrate that transcription factors hypoxia-inducible factor 1a (Hif1a) and 2a (Hif2a), key mediators of the cellular response to hypoxia, are both upregulated in livers of Slc30a10-deficient mice. Hepatic Hif2a deficiency corrected erythropoietin expression and polycythemia and attenuated aberrant hepatic gene expression in Slc30a10-deficient mice, while hepatic Hif1a deficiency had no discernible impact. Hepatic Hif2a deficiency also attenuated manganese excess, though the underlying cause of this is not clear at this time. Overall, our results indicate that hepatic HIF2 is a key determinant of pathophysiology in SLC30A10 deficiency and expand our understanding of the contribution of HIFs to human disease.

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.

AAV-mediated hepatic expression of SLC30A10 and the Thr95Ile variant attenuates manganese excess and other phenotypes in Slc30a10-deficient mice

The manganese (Mn) export protein SLC30A10 is essential for Mn excretion via the liver and intestines. Patients with SLC30A10 deficiency develop Mn excess, dystonia, liver disease, and polycythemia. Recent genome-wide association studies revealed a link between the SLC30A10 variant T95I and markers of liver disease. The in vivo relevance of this variant has yet to be investigated. Using in vitro and in vivo models, we explore the impact of the T95I variant on SLC30A10 function. While SLC30A10 I95 expressed at lower levels than T95 in transfected cell lines, both T95 and I95 variants protected cells similarly from Mn-induced toxicity. Adeno-associated virus 8-mediated expression of T95 or I95 SLC30A10 using the liver-specific thyroxine binding globulin promoter normalized liver Mn levels in mice with hepatocyte Slc30a10 deficiency. Furthermore, Adeno-associated virus-mediated expression of T95 or I95 SLC30A10 normalized red blood cell parameters and body weights and attenuated Mn levels and differential gene expression in livers and brains of mice with whole body Slc30a10 deficiency. While our in vivo data do not indicate that the T95I variant significantly compromises SLC30A10 function, it does reinforce the notion that the liver is a key site of SLC30A10 function. It also supports the idea that restoration of hepatic SLC30A10 expression is sufficient to attenuate phenotypes in SLC30A10 deficiency.

Anticancer Metallocenes and Metal Complexes of Transition Elements from Groups 4 to 7

With the progression in the field of bioinorganic chemistry, the role of transition metal complexes as the most widely used therapeutics is becoming a more and more attractive research area. The complexes of transition metals possess a great variety of attractive pharmacological properties, including anticancer, anti-inflammatory, antioxidant, anti-infective, etc., activities. Transition metal complexes have proven to be potential alternatives to biologically active organic compounds, especially as antitumor agents. The performance of metal coordination compounds in living systems is anticipated to differ generally from the action of non-metal-containing drugs and may offer unique diagnostic and/or therapeutic opportunities. In this review, the rapid development and application of metallocenes and metal complexes of elements from Groups 4 to 7 in cancer diagnostics and therapy have been summarized. Most of the heavy metals discussed in the current review are newly discovered metals. That is why the use of their metal-based compounds has attracted a lot of attention concerning their organometallic and coordination chemistry. All of this imposes more systematic studies on their biological activity, biocompatibility, and toxicity and presupposes further investigations.

Loss of SLC30A10 manganese transporter alters expression of neurotransmission genes and activates hypoxia-inducible factor signaling in mice

The essential metal manganese (Mn) induces neuromotor disease at elevated levels. The manganese efflux transporter SLC30A10 regulates brain Mn levels. Homozygous loss-of-function mutations in SLC30A10 induce hereditary Mn neurotoxicity in humans. Our prior characterization of Slc30a10 knockout mice recapitulated the high brain Mn levels and neuromotor deficits reported in humans. But, mechanisms of Mn-induced motor deficits due to SLC30A10 mutations or elevated Mn exposure are unclear. To gain insights into this issue, we characterized changes in gene expression in the basal ganglia, the main brain region targeted by Mn, of Slc30a10 knockout mice using unbiased transcriptomics. Compared with littermates, >1000 genes were upregulated or downregulated in the basal ganglia sub-regions (i.e. caudate putamen, globus pallidus, and substantia nigra) of the knockouts. Pathway analyses revealed notable changes in genes regulating synaptic transmission and neurotransmitter function in the knockouts that may contribute to the motor phenotype. Expression changes in the knockouts were essentially normalized by a reduced Mn chow, establishing that changes were Mn dependent. Upstream regulator analyses identified hypoxia-inducible factor (HIF) signaling, which we recently characterized to be a primary cellular response to elevated Mn, as a critical mediator of the transcriptomic changes in the basal ganglia of the knockout mice. HIF activation was also evident in the liver of the knockout mice. These results: (i) enhance understanding of the pathobiology of Mn-induced motor disease; (ii) identify specific target genes/pathways for future mechanistic analyses; and (iii) independently corroborate the importance of the HIF pathway in Mn homeostasis and toxicity.

Shared Proteins and Pathways of Cardiovascular and Cognitive Diseases: Relation to Vascular Cognitive Impairment

One of the primary goals of systems medicine is the detection of putative proteins and pathways involved in disease progression and pathological phenotypes. Vascular cognitive impairment (VCI) is a heterogeneous condition manifesting as cognitive impairment resulting from vascular factors. The precise mechanisms underlying this relationship remain unclear, which poses challenges for experimental research. Here, we applied computational approaches like systems biology to unveil and select relevant proteins and pathways related to VCI by studying the crosstalk between cardiovascular and cognitive diseases. In addition, we specifically included signals related to oxidative stress, a common etiologic factor tightly linked to aging, a major determinant of VCI. Our results show that pathways associated with oxidative stress are quite relevant, as most of the prioritized vascular cognitive genes and proteins were enriched in these pathways. Our analysis provided a short list of proteins that could be contributing to VCI: DOLK, TSC1, ATP1A1, MAPK14, YWHAZ, CREB3, HSPB1, PRDX6, and LMNA. Moreover, our experimental results suggest a high implication of glycative stress, generating oxidative processes and post-translational protein modifications through advanced glycation end-products (AGEs). We propose that these products interact with their specific receptors (RAGE) and Notch signaling to contribute to the etiology of VCI.

EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck D, Bohn T, Castenmiller J, de Henauw S, Hirsch‐Ernst K, Knutsen HK, Maciuk A, Mangelsdorf I, McArdle HJ, Pentieva K, Siani A, Thies F, Tsabouri S, Vinceti M, Bornhorst J, Cubadda F, Dopter A, FitzGerald R, de Sesmaisons Lecarré A, das Neves Ferreira P, Fabiani L, Horvath Z, Matijević L, Naska A. Scientific opinion on the tolerable upper intake level for manganese

Following a request from the European Commission (EC), the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for manganese. Systematic reviews of the literature of human and animal data were conducted to assess evidence regarding excess manganese intake (including authorised manganese salts) and the priority adverse health effect, i.e. manganese-induced neurotoxicity. Available human and animal studies support neurotoxicity as a critical effect, however, data are not sufficient and suitable to characterise a dose-response relationship and identify a reference point for manganese-induced neurotoxicity. In the absence of adequate data to establish an UL, estimated background dietary intakes (i.e. manganese intakes from natural dietary sources only) observed among high consumers (95th percentile) were used to provide an indication of the highest level of intake where there is reasonable confidence on the absence of adverse effects. A safe level of intake of 8 mg/day was established for adults ≥ 18 years (including pregnant and lactating women) and ranged between 2 and 7 mg/day for other population groups. The application of the safe level of intake is more limited than an UL because the intake level at which the risk of adverse effects starts to increase is not defined.

Trace elements dyshomeostasis in liver and brain of weanling mice under altered dietary selenium conditions

BACKGROUND

A balanced diet containing selenium (Se) and other trace elements is essential for normal development and growth. Se has been recognized as an essential trace element; however, its interaction with other elements has not been fully investigated. In the present study, sodium (Na), magnesium (Mg), potassium (K), calcium (Ca), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), Se and rubidium (Rb), were analysed in liver and brain regions under altered dietary Se intake in weanling mice to identify major discriminatory elements.

METHODS

The study investigated the effects of different levels of Se intake on the elemental composition in liver and brain tissues of weaned mice. After 24 weeks of feeding with Se adequate, deficient, and excess diets, elemental analysis was performed on the harvested tissues using Inductively coupled plasma mass spectrometry (ICP-MS). Statistical analysis that included analysis of covariance (ANCOVA), correlation coefficient analysis, principal component analysis, and partial least squares discriminant analysis were performed.

RESULTS

The ANCOVA showed statistically significant changes and correlations among the analysed elements under altered dietary Se status. The multivariate analysis showed differential changes in elements in liver and brain regions. The results suggest that long-term dietary Se alternations lead to dyshomeostasis in trace elements that are required in higher concentrations compared to Se. It was observed that changes in the Fe, Co, and Rb levels were similar in all the tissues studied, whereas the changes in Mg, Cr, and Mn levels were different among the tissues under altered dietary Se status. Additionally, the changes in Rb levels correlated with the dietary Se intake but had no relation with the tissue Se levels.

CONCLUSIONS

The findings suggest interactions between Mg, Cr, Mn, Fe, Co, and Se under altered Se status may impact cellular functions during postnatal development. However, the possible biological significance of alterations in Rb levels under different dietary Se paradigms needs to be further explored.

Association of genes in hereditary metabolic diseases with diagnosis, prognosis, and treatment outcomes in gastric cancer

Background

Aberrant metabolism is a major hallmark of cancers and hereditary diseases. Genes associated with inborn metabolic errors may also play roles in cancer development. This study evaluated the overall impact of these genes on gastric cancer (GC).

Methods

In total, 162 genes involved in 203 hereditary metabolic diseases were identified in the Human Phenotype Ontology database. Clinical and multi-omic data were acquired from the GC cohort of the Affiliated Hospital of Jiangsu University and other published cohorts. A 4-gene and 32-gene signature was established for diagnosis and prognosis or therapeutic prediction, respectively, and corresponding abnormal metabolism scores (AMscores) were calculated.

Results

The diagnostic AMscore showed high sensitivity (0.88-1.00) and specificity (0.89-1.00) to distinguish between GC and paired normal tissues, with area under the receiver operating characteristic curve (AUC) ranging from 0.911 to 1.000 in four GC cohorts. The prognostic or predictive AMscore was an independent predictor of overall survival (OS) in five GC cohorts and a predictor of the OS and disease-free survival benefit of postoperative chemotherapy or chemoradiotherapy in one GC cohort with such data. The AMscore adversely impacts immune biomarkers, including tumor mutation burden, tumor neoantigen burden, microsatellite instability, programmed death-ligand 1 protein expression, tumor microenvironment score, T cell receptor clonality, and immune cell infiltration detected by multiplex immunofluorescence staining. The AUC of the AMscore for predicting immunotherapy response ranging from 0.780 to 0.964 in four cohorts involving GC, urothelial cancer, melanoma, and lung cancer. The objective response rates in the low and high AMscore subgroups were 78.6% and 3.2%, 40.4% and 7%, 52.6% and 0%, and 72.7% and 0%, respectively (all p<0.001). In cohorts with survival data, a high AMscore was hazardous for OS or progression-free survival, with hazard ratios ranged from 5.79 to 108.59 (all p<0.001). Importantly, the AMscore significantly improved the prediction of current immune biomarkers for both response and survival, thus redefining the advantaged and disadvantaged immunotherapy populations.

Conclusions

Signatures based on genes associated with hereditary metabolic diseases and their corresponding scores could be used to guide the diagnosis and treatment of GC. Therefore, further validation is required.

Blood manganese and non-alcoholic fatty liver disease in a high manganese exposure area in China

BACKGROUND AND AIMS

Manganese (Mn) deficiency and intoxication may affect nonalcoholic fatty liver disease (NAFLD) risk differently. We aimed to explore the association between blood Mn and NAFLD in an area with high Mn exposure in drinking water.

METHODS

We conducted a case-control study among 1407 patients with NAFLD and 1774 sex- and age-matched healthy controls in a physical examination population in Zhoushan hospital, Zhejiang province in China. We used the restricted cubic splines method to investigate the dose-response relationship. Logistic regression models were applied to determine the risk of NAFLD, and severity of NAFLD.

RESULTS

The blood Mn concentration was higher in the NAFLD group than in the control group in women (16.1 ± 6.2 μg/L vs. 14.7 ± 6.4 μg/L, P = 0.022) and men (14.5 ± 6.3 μg/L vs. 13.6 ± 6.8 μg/L, P < 0.001). We found an inverted L shape relationship between blood Mn and NAFLD in both women and men. Compared to the lowest quartile, the adjusted odds ratio (OR) and 95% confidence interval (CI) of NAFLD for the highest quartile group was 1.646(1.222,2.217), 1.494(1.082,2.061), and 3.146(1.285,7.701) for the total population, men, and women. The positive relationship was only observed in those with fibrosis-4 score < 1.30 and normal alanine transaminase. Stratified analysis showed an interaction between smoking (P = 0.073), alcohol drinking (P = 0.013), and Mn, with a more prominent effect on the NAFLD in the never-smokers (OR = 2.153, 95% CI 1.408-3.290) and drinkers (OR = 2.596, 95% CI 1.608-4.191).

CONCLUSION

Higher blood Mn is associated with an elevated NAFLD risk in the high Mn exposure areas, especially in nonsmokers and drinkers. Further studies are needed to verify this result in the areas with high Mn exposure.

Structural basis for binding of the renal carcinoma target hypoxia-inducible factor 2α to prolyl hydroxylase domain 2

The hypoxia-inducible factor (HIF) prolyl-hydroxylases (human PHD1-3) catalyze prolyl hydroxylation in oxygen-dependent degradation (ODD) domains of HIFα isoforms, modifications that signal for HIFα proteasomal degradation in an oxygen-dependent manner. PHD inhibitors are used for treatment of anemia in kidney disease. Increased erythropoietin (EPO) in patients with familial/idiopathic erythrocytosis and pulmonary hypertension is associated with mutations in EGLN1 (PHD2) and EPAS1 (HIF2α); a drug inhibiting HIF2α activity is used for clear cell renal cell carcinoma (ccRCC) treatment. We report crystal structures of PHD2 complexed with the C-terminal HIF2α-ODD in the presence of its 2-oxoglutarate cosubstrate or N-oxalylglycine inhibitor. Combined with the reported PHD2.HIFα-ODD structures and biochemical studies, the results inform on the different PHD.HIFα-ODD binding modes and the potential effects of clinically observed mutations in HIFα and PHD2 genes. They may help enable new therapeutic avenues, including PHD isoform-selective inhibitors and sequestration of HIF2α by the PHDs for ccRCC treatment.

Trace metal elements: a bridge between host and intestinal microorganisms

Trace metal elements, such as iron, copper, manganese, and zinc, are essential nutrients for biological processes. Although their intake demand is low, they play a crucial role in cell homeostasis as the cofactors of various enzymes. Symbiotic intestinal microorganisms compete with their host for the use of trace metal elements. Moreover, the metabolic processes of trace metal elements in the host and microorganisms affect the organism's health. Supplementation or the lack of trace metal elements in the host can change the intestinal microbial community structure and function. Functional changes in symbiotic microorganisms can affect the host's metabolism of trace metal elements. In this review, we discuss the absorption and transport processes of trace metal elements in the host and symbiotic microorganisms and the effects of dynamic changes in the levels of trace metal elements on the intestinal microbial community structure. We also highlight the participation of trace metal elements as enzyme cofactors in the host immune process. Our findings indicate that the host uses metal nutrition immunity or metal poisoning to resist pathogens and improve immunity.

Manganese-induced apoptosis through the ROS-activated JNK/FOXO3a signaling pathway in CTX cells, a model of rat astrocytes

Manganese (Mn) is an essential trace element that maintains many normal physiological functions. However, multi-system disorders would occur once overexposure to Mn, especially neurotoxicity. Despite evidence demonstrating the critical role of ROS-activated JNK/FOXO3a signaling pathway in neuronal survival, the specific mechanisms by which it contributes to Mn-induced neurotoxicity are still unclear. The objectives of this study was to examine the modulation of the JNK/FOXO3a signaling pathway, which is activated by ROS, in Mn-induced apoptosis, using a rat brain astrocyte cell line (CTX cells). This study found that a dose-dependent decrease in cell viability of CTX cells was observed with 150, 200, 250, 300 μmol/L Mn. The results of apoptosis-related protein assay showed that Mn decreased the expression of anti-apoptotic protein Bcl-2 and enhanced the expression of apoptosis-related proteins like Bax and Cleaved-Caspase3. In addition, treatment with Mn resulted in elevated ROS levels and increased phosphorylation levels of JNK. Conversely, phosphorylation of nuclear transcription factors FOXO3a, which regulates expression of transcription factors including Bim and PUMA, was decreased. Depletion of ROS by N-acetyl-L-cysteine (NAC) and inhibition of the JNK pathway by SP600125 prevented Mn-induced JNK/FOXO3a pathway activation and, more importantly, the level of apoptosis was also significantly reduced. Confirmation of Mn-induced apoptosis in CTX cells through ROS generation and activation of the JNK/FOXO3a signaling pathway was the outcome of this study. These findings offer fresh insights into the neurotoxic mechanisms of Mn and therapeutic targets following Mn exposure.

Metal-ion transporter SLC39A8 is required for brain manganese uptake and accumulation

Manganese (Mn) is an essential nutrient, but is toxic in excess. Whole-body Mn levels are regulated in part by the metal-ion influx transporter SLC39A8, which plays an essential role in the liver by reclaiming Mn from bile. Physiological roles of SLC39A8 in Mn homeostasis in other tissues, however, remain largely unknown. To screen for extrahepatic requirements for SLC39A8 in tissue Mn homeostasis, we crossed Slc39a8-inducible global-KO (Slc39a8 iKO) mice with Slc39a14 KO mice, which display markedly elevated blood and tissue Mn levels. Tissues were then analyzed by inductively coupled plasma-mass spectrometry to determine levels of Mn. Although Slc39a14 KO; Slc39a8 iKO mice exhibited systemic hypermanganesemia and increased Mn loading in the bone and kidney due to Slc39a14 deficiency, we show Mn loading was markedly decreased in the brains of these animals, suggesting a role for SLC39A8 in brain Mn accumulation. Levels of other divalent metals in the brain were unaffected, indicating a specific effect of SLC39A8 on Mn. In vivo radiotracer studies using 54Mn in Slc39a8 iKO mice revealed that SLC39A8 is required for Mn uptake by the brain, but not most other tissues. Furthermore, decreased 54Mn uptake in the brains of Slc39a8 iKO mice was associated with efficient inactivation of Slc39a8 in isolated brain microvessels but not in isolated choroid plexus, suggesting SLC39A8 mediates brain Mn uptake via the blood-brain barrier. These findings establish SLC39A8 as a candidate therapeutic target for mitigating Mn uptake and accumulation in the brain, the primary organ of Mn toxicity.

Manganese-induced PINK1 S-nitrosylation exacerbates nerve cell damage by promoting ZNF746 repression of mitochondrial biogenesis

Occupational exposure and non-occupational exposure to excessive levels of manganese (Mn) result in neuronal cell damage through mitochondrial dysfunction. The functional integrity of mitochondria is maintained by mitophagy and mitochondrial biogenesis. Although Mn-induced S-nitrosylation of PTEN-induced putative kinase 1 (PINK1) can interfere with mitophagy, its effect on mitochondrial biogenesis remains unclear. In this study, we established a rat model of Mn poisoning or "manganism" to examine the relationship between PINK1 S-nitrosylation and impairment of mitochondrial biogenesis, and found that treatment with 60 mg/kg Mn induced marked neurobehavioral abnormalities in rats and significantly increased the S-nitrosylation level of PINK1. We also found that the nuclear-encoded peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PPARGC1A)-mediated mitochondrial biogenesis was significantly upregulated in rats treated with 15 and 30 mg/kg Mn, and downregulated in rats treated with 60 mg/kg Mn. We further investigated the role of S-nitrosylated PINK1 and its molecular mechanism in the high-dose Mn-mediated impairment of mitochondrial biogenesis in primary cultured neurons treated with the nitric oxide synthase 2 (NOS2) inhibitor 1400 W. Our results revealed that the PPARGC1A-mediated mitochondrial biogenesis was upregulated in neurons treated with 100 μM, but downregulated in neurons treated with 200 μM Mn, which was similar to the in vivo results. However, treatment with 1400W could effectively prevent the 200 μM Mn-mediated impairment of mitochondrial biogenesis by suppressing nitric oxide (NO)-mediated PINK1 S-nitrosylation and rescuing Parkin-interacting substrate (PARIS, ZNF746) degradation, thereby upregulating mitochondrial biogenesis via PPARGC1A. These findings demonstrated that S-nitrosylation of PINK1 and subsequent prevention of ZNF746 degradation were crucial signaling processes involved in the Mn-mediated impairment of mitochondrial biogenesis, which might serve as an underlying mechanism of Mn-induced neurotoxicity. Furthermore, this study provided a reliable target for the prevention and treatment of manganism.

The Role of Selected Trace Elements in Oxidoreductive Homeostasis in Patients with Thyroid Diseases

Impaired levels of selenium (Se), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn) and iodine (I) in the organism may adversely affect the thyroid endocrine system. These trace elements play a role in the fight against oxidative stress as components of enzymes. Oxidative-antioxidant imbalance is considered a possible factor in many pathological conditions, including various thyroid diseases. In the available literature, there are few scientific studies showing a direct correlation of the effect of supplementation of trace elements on slowing down or preventing the occurrence of thyroid diseases in combination with the improvement of the antioxidant profile, or through the action of these elements as antioxidants. Among the available studies, it has been shown that an increase in lipid peroxidation levels and a decrease in the overall antioxidant defense status occur during such thyroid diseases as thyroid cancer, Hashimoto's thyroiditis and dysthyroidism. In studies in which trace elements were supplemented, the following were observed: a decrease in the level of malondialdehyde after supplementation with Zn during hypothyroidism and reduction in the malondialdehyde level after Se supplementation with a simultaneous increase in the total activity status and activity of antioxidant defense enzymes in the course of autoimmune thyroiditis. This systematic review aimed to present the current state of knowledge about the relationship between trace elements and thyroid diseases in terms of oxidoreductive homeostasis.

Hypoxia-inducible factor 2 is a key determinant of manganese excess and polycythemia in SLC30A10 deficiency

Manganese is an essential yet potentially toxic metal. Initially reported in 2012, mutations in SLC30A10 are the first known inherited cause of manganese excess. SLC30A10 is an apical membrane transport protein that exports manganese from hepatocytes into bile and from enterocytes into the lumen of the gastrointestinal tract. SLC30A10 deficiency results in impaired gastrointestinal manganese excretion, leading to severe manganese excess, neurologic deficits, liver cirrhosis, polycythemia, and erythropoietin excess. Neurologic and liver disease are attributed to manganese toxicity. Polycythemia is attributed to erythropoietin excess, but the basis of erythropoietin excess in SLC30A10 deficiency has yet to be established. Here we demonstrate that erythropoietin expression is increased in liver but decreased in kidneys in Slc30a10-deficient mice. Using pharmacologic and genetic approaches, we show that liver expression of hypoxia-inducible factor 2 (Hif2), a transcription factor that mediates the cellular response to hypoxia, is essential for erythropoietin excess and polycythemia in Slc30a10-deficient mice, while hypoxia-inducible factor 1 (HIF1) plays no discernible role. RNA-seq analysis determined that Slc30a10-deficient livers exhibit aberrant expression of a large number of genes, most of which align with cell cycle and metabolic processes, while hepatic Hif2 deficiency attenuates differential expression of half of these genes in mutant mice. One such gene downregulated in Slc30a10-deficient mice in a Hif2-dependent manner is hepcidin, a hormonal inhibitor of dietary iron absorption. Our analyses indicate that hepcidin downregulation serves to increase iron absorption to meet the demands of erythropoiesis driven by erythropoietin excess. Finally, we also observed that hepatic Hif2 deficiency attenuates tissue manganese excess, although the underlying cause of this observation is not clear at this time. Overall, our results indicate that HIF2 is a key determinant of pathophysiology in SLC30A10 deficiency.

Mechanisms of manganese-induced neurotoxicity and the pursuit of neurotherapeutic strategies

Chronic exposure to elevated levels of manganese via occupational or environmental settings causes a neurological disorder known as manganism, resembling the symptoms of Parkinson's disease, such as motor deficits and cognitive impairment. Numerous studies have been conducted to characterize manganese's neurotoxicity mechanisms in search of effective therapeutics, including natural and synthetic compounds to treat manganese toxicity. Several potential molecular targets of manganese toxicity at the epigenetic and transcriptional levels have been identified recently, which may contribute to develop more precise and effective gene therapies. This review updates findings on manganese-induced neurotoxicity mechanisms on intracellular insults such as oxidative stress, inflammation, excitotoxicity, and mitophagy, as well as transcriptional dysregulations involving Yin Yang 1, RE1-silencing transcription factor, transcription factor EB, and nuclear factor erythroid 2-related factor 2 that could be targets of manganese neurotoxicity therapies. This review also features intracellular proteins such as PTEN-inducible kinase 1, parkin, sirtuins, leucine-rich repeat kinase 2, and α-synuclein, which are associated with manganese-induced dysregulation of autophagy/mitophagy. In addition, newer therapeutic approaches to treat manganese's neurotoxicity including natural and synthetic compounds modulating excitotoxicity, autophagy, and mitophagy, were reviewed. Taken together, in-depth mechanistic knowledge accompanied by advances in gene and drug delivery strategies will make significant progress in the development of reliable therapeutic interventions against manganese-induced neurotoxicity.

Clinical Profile and Treatment Outcomes of Hypermanganesemia with Dystonia 1 and 2 among 27 Indian Children

Background

Hypermanganesemia with dystonia 1 and 2 (HMNDYT1 and 2) are rare, inherited disorders of manganese transport.

Objectives

We aimed to describe clinical, laboratory features, and outcomes among children with HMNDYT.

Methods

We conducted a retrospective multicenter study involving tertiary centers across India. We enrolled children between 1 month to 18 years of age with genetically confirmed/clinically probable HMNDYT. Clinical, laboratory profile, genetic testing, treatment details, and outcomes scored by treating physicians on a Likert scale were recorded.

Results

We enrolled 27 children (19 girls). Fourteen harbored SLC30A10 mutations; nine had SLC39A14 mutations. The SLC39A14 cohort had lower median age at onset (1.3 [interquartile range (IQR), 0.7-5.5] years) versus SLC30A10 cohort (2.0 [IQR, 1.5-5.1] years). The most frequent neurological features were dystonia (100%; n = 27), gait abnormality (77.7%; n = 21), falls (66.7%; n = 18), and parkinsonism (59.3%; n = 16). Median serum manganese (Mn) levels among SLC39A14 (44.9 [IQR, 27.3-147.7] mcg/L) cohort were higher than SLC30A10 (29.4 [17.1-42.0] mcg/L); median hemoglobin was higher in SLC30A10 (16.3 [IQR, 15.2-17.5] g/dL) versus SLC39A14 cohort (12.5 [8.8-13.2] g/dL). Hepatic involvement and polycythaemia were observed exclusively in SLC30A10 variants. A total of 26/27 children underwent chelation with disodium calcium edetate. Nine demonstrated some improvement, three stabilized, two had marked improvement, and one had normalization. Children with SLC39A14 mutations had poorer response. Two children died and nine were lost to follow-up.

Conclusions

We found female predominance. Children with SLC39A14 mutations presented at younger age and responded less favorably to chelation compared to SLC30A10 mutations. There is emerging need to better define management strategies, especially in low resource settings.

Exposing the role of metals in neurological disorders: a focus on manganese

Metals are ubiquitous chemical entities involved in a myriad of biological processes. Despite their integral role in sustaining life, overexposure can lead to deleterious neurological outcomes posing a public health concern. Excess exposure to metals has been associated with aberrant neurodevelopmental and neurodegenerative diseases and prominently contributes to environmental risk for neurological disorders. Here, we use manganese (Mn) to exemplify the gap in our understanding of the mechanisms behind acute metal toxicity and their relationship to chronic toxicity and disease. This challenge frustrates understanding of how individual exposure histories translate into preventing and treating brain diseases from childhood through old age. We discuss ways to enhance the predictive value of preclinical models and define mechanisms of chronic, persistent, and latent neurotoxicity.

Impact of Zinc Transport Mechanisms on Embryonic and Brain Development

The trace element zinc (Zn) binds to over ten percent of proteins in eukaryotic cells. Zn flexible chemistry allows it to regulate the activity of hundreds of enzymes and influence scores of metabolic processes in cells throughout the body. Deficiency of Zn in humans has a profound effect on development and in adults later in life, particularly in the brain, where Zn deficiency is linked to several neurological disorders. In this review, we will summarize the importance of Zn during development through a description of the outcomes of both genetic and early dietary Zn deficiency, focusing on the pathological consequences on the whole body and brain. The epidemiology and the symptomology of Zn deficiency in humans will be described, including the most studied inherited Zn deficiency disease, Acrodermatitis enteropathica. In addition, we will give an overview of the different forms and animal models of Zn deficiency, as well as the 24 Zn transporters, distributed into two families: the ZIPs and the ZnTs, which control the balance of Zn throughout the body. Lastly, we will describe the TRPM7 ion channel, which was recently shown to contribute to intestinal Zn absorption and has its own significant impact on early embryonic development.

M. de Rosales R. Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.

A rare genetic variant in the manganese transporter SLC30A10 and elevated liver enzymes in the general population

BACKGROUND

A genetic variant in the manganese transporter SLC30A10 (rs188273166, p.Thr95Ile) was associated with increased plasma alanine transaminase (ALT) in a recent genome-wide association study in the UK Biobank (UKB). The aims of the present study were to test the association of rs188273166 with ALT in an independent cohort, and to begin to assess the clinical, hepatic, and biochemical phenotypes associated with the variant.

METHODS

We included n = 334,886 white participants from UKB, including 14,462 with hepatic magnetic resonance imaging (MRI), and n = 113,612 individuals from the Copenhagen City Heart Study and the Copenhagen General Population Study combined.

RESULTS

Genotyping SLC30A10 p.Thr95Ile identified 816 heterozygotes in the UKB and 111 heterozygotes in the Copenhagen cohort. Compared to noncarriers, heterozygotes had 4 and 5 U/L higher levels of ALT in the UKB and Copenhagen cohort, respectively, and 3 U/L higher plasma aspartate transaminase and gamma-glutamyl transferase in the UKB. Heterozygotes also had higher corrected T1 on liver MRI, a marker of hepatic inflammation (p = 4 × 10-7), but no change in MRI-quantified steatosis (p = 0.57). Plasma manganese was within the normal range in nine heterozygotes that provided new blood samples. SLC30A10 p.Thr95Ile heterozygotes had an eightfold increased risk of biliary tract cancer in UKB (p = 4 × 10-7), but this association was not replicated in the Copenhagen cohort.

CONCLUSIONS

SLC30A10 p.Thr95Ile was associated with elevated liver enzymes in two large general population cohorts, and with MRI-quantified hepatic inflammation. A rare genetic variant (p.Thr95Ile) in the manganese transporter SLC30A10 is associated with elevated plasma alanine transaminase (ALT) and higher corrected T1 on liver MRI, markers of liver inflammation. These data support that the variant may increase the risk of liver disease.

Effect of Chelation Therapy on a Korean Patient With Brain Manganese Deposition Resulting From a Compound Heterozygous Mutation in the SLC39A14 Gene

Mutations in the manganese transporter gene SLC39A14 lead to inherited disorders of manganese metabolism. Chelation therapy with edetate calcium disodium (CaNa2EDTA) is known to effectively reduce manganese deposition. We describe the first identified Korean case of SLC39A14-associated manganism and the treatment response to a 5-year chelation therapy. An 18-year-old female presented with childhood-onset dystonia. Magnetic resonance imaging showed T1 hyperintensity throughout the basal ganglia, brainstem, cerebellum, cerebral and cerebellar white matter, and pituitary gland. Blood manganese levels were elevated, and whole-exome sequencing revealed compound heterozygous mutations in SLC39A14. Treatment with intravenous CaNa2EDTA led to a significant reduction in serum manganese levels and T1 hyperintensities. However, her dystonia improved insignificantly. Hence, early diagnosis of this genetic disorder is essential because it is potentially treatable. Even though our treatment did not significantly reverse the establish deficits, chelation therapy could have been more effective if it was started at an earlier stage of the disease.

Role of excretion in manganese homeostasis and neurotoxicity: a historical perspective

The essential metal manganese (Mn) induces incurable neurotoxicity at elevated levels that manifests as parkinsonism in adults and fine motor and executive function deficits in children. Studies on Mn neurotoxicity have largely focused on the role and mechanisms of disease induced by elevated Mn exposure from occupational or environmental sources. In contrast, the critical role of excretion in regulating Mn homeostasis and neurotoxicity has received less attention although 1) studies on Mn excretion date back to the 1920s; 2) elegant radiotracer Mn excretion assays in the 1940s to 1960s established the routes of Mn excretion; and 3) studies on patients with liver cirrhosis in the 1990s to 2000s identified an association between decreased Mn excretion and the risk of developing Mn-induced parkinsonism in the absence of elevated Mn exposure. Notably, the last few years have seen renewed interest in Mn excretion largely driven by the discovery that hereditary Mn neurotoxicity due to mutations in SLC30A10 or SLC39A14 is caused, at least in part, by deficits in Mn excretion. Quite remarkably, some of the recent results on SLC30A10 and SLC39A14 provide explanations for observations made ∼40-50 years ago. The goal of the current review is to integrate the historic studies on Mn excretion with more contemporary recent work and provide a comprehensive state-of-the-art overview of Mn excretion and its role in regulating Mn homeostasis and neurotoxicity. A related goal is to discuss the significance of some of the foundational studies on Mn excretion so that these highly consequential earlier studies remain influential in the field.

Manganese transport in mammals by zinc transporter family proteins, ZNT and ZIP

Manganese (Mn) is an essential trace element required for various biological processes. However, excess Mn causes serious side effects in humans, including parkinsonism. Thus, elucidation of Mn homeostasis at the systemic, cellular, and molecular levels is important. Many metal transporters and channels can be involved in the transport and homeostasis of Mn, and an increasing body of evidence shows that several zinc (Zn) transporters belonging to the ZIP and ZNT families, specifically, ZNT10, ZIP8, and ZIP14, play pivotal roles in Mn metabolism. Mutations in the genes encoding these transporter proteins are associated with congenital disorders related to dysregulated Mn homeostasis in humans. Moreover, single nucleotide polymorphisms of ZIP8 are associated with multiple clinical phenotypes. In this review, we discuss the recent literature on the structural and biochemical features of ZNT10, ZIP8, and ZIP14, including transport mechanisms, regulation of expression, and pathophysiological functions. Because a disturbance in Mn homeostasis is closely associated with a variety of phenotypes and risk of human diseases, these transporters constitute a significant target for drug development. An understanding of the roles of these key transporters in Mn metabolism should provide new insights into pharmacological applications of their inhibitors and enhancers in human diseases.

Atypical presentation of SLC30A10 gene mutation with hypermanganesemia, seizures and polycythemia

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Seizure was the sole neurological symptom of hereditary hypermanganesemia. In this case.

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Absence of pyramidal and extrapyramidal signs or liver failure were other outstanding features.

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Treatment with chelation therapy led to resolution of seizures and T1 hyperintensity on brain MRI.

Manganese is an essential element that is ubiquitously present in our diet and water supply. It is a cofactor for several critical physiological processes. Elevated blood levels of Manganese secondary to SLC30A10 gene mutation presents distinctly with dystonia, polycythemia, chronic liver disease and a characteristic high T1 signal in basal ganglia on brain MRI. The primary treatment for this condition is chelation along with iron therapy. We report a previously healthy boy with compound heterozygous SLC30A10 gene mutations who had a unique clinical presentation with prominent seizures, polycythemia, and characteristic T1 hyperintensity in basal ganglia. Seizures have not been previously reported to be associated with this specific mutation.

Sodium P-aminosalicylic Acid Attenuates Manganese-Induced Neuroinflammation in BV2 Microglia by Modulating NF-κB Pathway

Exposure to high levels of manganese (Mn) leads to brain Mn accumulation, and a disease referred to as manganism. Activation of microglia plays an important role in Mn-induced neuroinflammation. Sodium p-aminosalicylic acid (PAS-Na) is a non-steroidal anti-inflammatory drug that inhibits Mn-induced neuroinflammation. The aim of the current study was to explore the role of NF-κB in the protective mechanism of PAS-Na on Mn-induced neuroinflammation in BV2 microglial experimental model. We treated BV2 microglia with 200 μM Mn for 24 h followed by 48 h treatment with graded concentrations of PAS-Na, using an NF-kB inhibitor, JSH-23, as a positive control. MTT results established that 200 and 400 μM PAS-Na treatment increased the Mn-induced cell viability reduction. NF-κB (P65) mRNA expression and the phosphorylation of p65 were increased in Mn-treated BV2 cell, and suppressed by PAS-Na, analogous to the effect of JSH-23 pretreatment. Furthermore, PAS-Na significantly reduced the contents of the inflammatory cytokine TNF-α and IL-1β, both of which were increased by Mn treatment. The current results show that PAS-Na attenuated Mn-induced inflammation by abrogating the activation of the NF-κB signaling pathways and reduced the release of pro-inflammatory cytokines.