Manganese-Induced Parkinsonism and Parkinson's Disease: Shared and Distinguishable Features

Daidzein ameliorates nonmotor symptoms of manganese-induced Parkinsonism in zebrafish model: Behavioural and biochemical approach

BACKGROUND AND PURPOSE

Parkinson's disease (PD) is a prevalent neurodegenerative movement disorder characterized by motor dysfunction. Environmental factors, especially manganese (Mn), contribute significantly to PD. Existing therapies are focused on motor coordination, whereas nonmotor features such as neuropsychiatric symptoms are often neglected. Daidzein (DZ), a phytoestrogen, has piqued interest due to its antioxidant, anti-inflammatory, and anxiolytic properties. Therefore, we anticipate that DZ might be an effective drug to alleviate the nonmotor symptoms of Mn-induced Parkinsonism.

EXPERIMENTAL APPROACH

Naïve zebrafish were exposed to 2 mM of Mn for 21 days and intervened with DZ. Nonmotor symptoms such as anxiety, social behaviour, and olfactory function were assessed. Acetylcholinesterase (AChE) activity and antioxidant enzyme status were measured from brain tissue through biochemical assays. Dopamine levels and histology were performed to elucidate neuroprotective mechanism of DZ.

KEY RESULTS

DZ exhibited anxiolytic effects in a novel environment and also improved intra and inter fish social behaviour. DZ improved the olfactory function and response to amino acid stimuli in Mn-induced Parkinsonism. DZ reduced brain oxidative stress and AChE activity and prevented neuronal damage. DZ increased DA level in the brain, collectively contributing to neuroprotection.

CONCLUSION AND IMPLICATIONS

DZ demonstrated a promising effect on alleviating nonmotor symptoms such as anxiety and olfactory dysfunction, through the mitigation of cellular damage. These findings underscore the therapeutic potential of DZ in addressing nonmotor neurotoxicity induced by heavy metals, particularly in the context of Mn-induced Parkinsonism.

Experimental models of Parkinson's disease: Challenges and Opportunities

Parkinson's disease (PD) is a widespread neurodegenerative disorder occurs due to the degradation of dopaminergic neurons present in the substantia nigra pars compacta (SNpc). Millions of people are affected by this devastating disorder globally, and the frequency of the condition increases with the increase in the elderly population. A significant amount of progress has been made in acquiring more knowledge about the etiology and the pathogenesis of PD over the past decades. Animal models have been regarded to be a vital tool for the exploration of complex molecular mechanisms involved in PD. Various animals used as models for disease monitoring include vertebrates (zebrafish, rats, mice, guinea pigs, rabbits and monkeys) and invertebrate models (Drosophila, Caenorhabditis elegans). The animal models most relevant for study of PD are neurotoxin induction-based models (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 6-Hydroxydopamine (6-OHDA) and agricultural pesticides (rotenone, paraquat), pharmacological models (reserpine or haloperidol treated rats), genetic models (α-synuclein, Leucine-rich repeat kinase 2 (LRRK2), DJ-1, PINK-1 and Parkin). Several non-mammalian genetic models such as zebrafish, Drosophila and Caenorhabditis elegance have also gained popularity in recent years due to easy genetic manipulation, presence of genes homologous to human PD, and rapid screening of novel therapeutic molecules. In addition, in vitro models (SH-SY5Y, PC12, Lund human mesencephalic (LUHMES) cells, Human induced pluripotent stem cell (iPSC), Neural organoids, organ-on-chip) are also currently in trend providing edge in investigating molecular mechanisms involved in PD as they are derived from PD patients. In this review, we explain the current situation and merits and demerits of the various animal models.

The protective role of sesame oil against Parkinson's-like disease induced by manganese in rats

Chronic exposure to manganese (Mn) results in motor dysfunction, biochemical and pathological alterations in the brain. Oxidative stress, inflammation, and dysfunction of dopaminergic and GABAergic systems stimulate activating transcription factor-6 (ATF-6) and protein kinase RNA-like ER kinase (PERK) leading to apoptosis. This study aimed to investigate the protective effect of sesame oil (SO) against Mn-induced neurotoxicity. Rats received 25 mg/kg MnCl2 and were concomitantly treated with 2.5, 5, or 8 ml/kg of SO for 5 weeks. Mn-induced motor dysfunction was indicated by significant decreases in the time taken by rats to fall during the rotarod test and in the number of movements observed during the open field test. Also, Mn resulted in neuronal degeneration as observed by histological staining. The striatal levels of lipid peroxides and reduced glutathione (oxidative stress markers), interleukin-6 and tumor necrosis factor-α (inflammatory markers) were significantly elevated. Mn significantly reduced the levels of dopamine and Bcl-2, while GABA, PERK, ATF-6, Bax, and caspase-3 were increased. Interestingly, all SO doses, especially at 8 ml/kg, significantly improved locomotor activity, biochemical deviations and reduced neuronal degeneration. In conclusion, SO may provide potential therapeutic benefits in enhancing motor performance and promoting neuronal survival in individuals highly exposed to Mn.

A Unique Combination of Mn2+ and Aluminum Adjuvant Acted the Synergistic Effect

Introduction

The development of combinatorial adjuvants is a promising strategy to boost vaccination efficiency. Accumulating evidence indicates that manganese exerts strong immunocompetence and will become an enormous potential adjuvant. Here, we described a novel combination of Mn2+ plus aluminum hydroxide (AH) adjuvant that significantly exhibited the synergistic immune effect. Methodology. Initially, IsdB3 proteins as the immune-dominant fragment of IsdB proteins derived from Staphylococcus aureus (S. aureus) were prepared. IsdB3 proteins were identified by western blotting. Furthermore, we immunized C57/B6 mice with IsdB3 proteins plus Mn2+ and AH adjuvant. After the second immunization, the proliferation of lymphocytes was measured by the cell counting kit-8 (CCK-8) and the level of IFN-γ, IL-4, IL-10, and IL-17 cytokine from spleen lymphocytes in mice and generation of the antibodies against IsdB3 in serum was detected with ELISA, and the protective immune response was assessed through S. aureus challenge.

Results

IsdB3 proteins plus Mn2+ and AH obviously stimulated the proliferation of spleen lymphocytes and increased the secretion of IFN-γ, IL-4, IL-10, and IL-17 cytokine in mice, markedly enhanced the generation of the antibodies against IsdB3 in serum, observably decreased bacterial load in organs, and greatly improved the survival rate of mice.

Conclusion

These data showed that the combination of Mn2+ and AH significantly acted a synergistic effect, reinforced the immunogenicity of IsdB3, and offered a new strategy to increase vaccine efficiency.

A partial Drp1 knockout improves autophagy flux independent of mitochondrial function

BACKGROUND

Dynamin-related protein 1 (Drp1) plays a critical role in mitochondrial dynamics. Partial inhibition of this protein is protective in experimental models of neurological disorders such as Parkinson's disease and Alzheimer's disease. The protective mechanism has been attributed primarily to improved mitochondrial function. However, the observations that Drp1 inhibition reduces protein aggregation in such neurological disorders suggest the involvement of autophagy. To investigate this potential novel protective mechanism of Drp1 inhibition, a model with impaired autophagy without mitochondrial involvement is needed.

METHODS

We characterized the effects of manganese (Mn), which causes parkinsonian-like symptoms in humans, on autophagy and mitochondria by performing dose-response studies in two cell culture models (stable autophagy HeLa reporter cells and N27 rat immortalized dopamine neuronal cells). Mitochondrial function was assessed using the Seahorse Flux Analyzer. Autophagy flux was monitored by quantifying the number of autophagosomes and autolysosomes, as well as the levels of other autophagy proteins. To strengthen the in vitro data, multiple mouse models (autophagy reporter mice and mutant Drp1+/- mice and their wild-type littermates) were orally treated with a low chronic Mn regimen that was previously reported to increase α-synuclein aggregation and transmission via exosomes. RNAseq, laser captured microdissection, immunofluorescence, immunoblotting, stereological cell counting, and behavioural studies were used. RESULTS IN VITRO: data demonstrate that at low non-toxic concentrations, Mn impaired autophagy flux but not mitochondrial function and morphology. In the mouse midbrain, RNAseq data further confirmed autophagy pathways were dysregulated but not mitochondrial related genes. Additionally, Mn selectively impaired autophagy in the nigral dopamine neurons but not the nearby nigral GABA neurons. In cells with a partial Drp1-knockdown and Drp1+/- mice, Mn induced autophagic impairment was significantly prevented. Consistent with these observations, Mn increased the levels of proteinase-K resistant α-synuclein and Drp1-knockdown protected against this pathology.

CONCLUSIONS

This study demonstrates that improved autophagy flux is a separate mechanism conferred by Drp1 inhibition independent of its role in mitochondrial fission. Given that impaired autophagy and mitochondrial dysfunction are two prominent features of neurodegenerative diseases, the combined protective mechanisms targeting these two pathways conferred by Drp1 inhibition make this protein an attractive therapeutic target.

In situ Raman spectral observation of succinimide intermediates in amyloid fibrillation kinetics

Succinimide intermediates play the crucial role in the nucleation process for protein amyloid fibril formation, as they can usually induce a non-native conformation in a fraction of soluble proteins to render amyloidogenicity and neurotoxicity. Thus, in situ detection of succinimide intermediates during amyloid fibrillation kinetics is of considerable importance, albeit challenging, because these succinimides are generally unstable in physiological conditions. Here, we found an in situ Raman spectral fingerprint to trace the succinimide intermediates in amyloid fibril formation, wherein the carbonyl symmetric stretching of cyclic imide in the succinimide derivative is located at ca. 1790 cm-1. Using its intensity as an indicator of succinimide intermediates, we have in situ detected and unravelled the role of succinimide intermediates during the oligomer formation from the Bz-Asp-Gly-NH2 dipeptide or the amyloid fibrillation kinetics of lysozyme with thermal/acid treatment.

A homologous-targeting cGAS-STING agonist multimodally activates dendritic cells for enhanced cancer immunotherapy

Herein, we developed a doxorubicin (Dox)-loaded and 4T1 cancer cell membrane-modified hydrogenated manganese oxide nanoparticles (mHMnO-Dox) to elicit systemic antitumor immune responses. The results revealed that mHMnO-Dox actively recognized tumor cells and then effectively delivered Dox into the cells. Upon entering tumor cells, the mHMnO-Dox underwent rapid degradation and abundant release of Mn2+ and chemotherapeutic drugs. The released Mn2+ not only catalysed a Fenton-type reaction to produce excessive reactive oxygen species (ROS) but also activated the cGAS-STING pathway to boost dendritic cell (DC) maturation. This process increased cytotoxic T lymphocyte infiltration as well as natural killer cell recruitment into the tumor site. In addition, the released Dox could contribute to a chemotherapeutic effect, while activating DC cells and subsequently intensifying immune responses through immunogenic cell death (ICD) of tumor cells. Consequently, the mHMnO-Dox suppressed the primary and distal tumor growth and inhibited tumor relapse and metastasis, as well as prolonged the lifespan of tumor-bearing mice. Thus, the mHMnO-Dox multimodally activated DC cells to demonstrate synergistic antitumor activity, which was mediated via the activation of the cGAS-STING signalling pathway to regulate tumor microenvironment, ICD-mediated immunotherapy and ROS-mediated CDT. These findings suggest the therapeutic potential of mHMnO-Dox in cancer immunotherapy. STATEMENT OF SIGNIFICANCE: A cancer cell membrane-camouflaged hydrogenated mesoporous manganese oxide (mHMnO) has been developed as a cGAS-STING agonist and ICD inducer. The mHMnO effectively induced abundance of ROS production in cancer cells, which caused cancer cell death and then promoted DC maturation via tumour-associated antigen presentation. Meanwhile, the mHMnO significantly activated cGAS-STING pathway to facilitate DC maturation and cytotoxic T lymphocyte infiltration as well as natural killer cell recruitment, which further enhanced tumour immune response. In addition, the combination of the mHMnO and Dox could synergistically promote tumour ICD and then multimodally induce DC maturation, achieving an enhanced CIT. Overall, this study provides a potential strategy to design novel immunologic adjuvant for enhanced CIT.

Neurotoxic effects of heavy metal pollutants in the environment: Focusing on epigenetic mechanisms

The pollution of heavy metals (HMs) in the environment is a significant global environmental issue, characterized by its extensive distribution, severe contamination, and profound ecological impacts. Excessive exposure to heavy metal pollutants can damage the nervous system. However, the mechanisms underlying the neurotoxicity of most heavy metals are not completely understood. Epigenetics is defined as a heritable change in gene function that can influence gene and subsequent protein expression levels without altering the DNA sequence. Growing evidence indicates that heavy metals can induce neurotoxic effects by triggering epigenetic changes and disrupting the epigenome. Compared with genetic changes, epigenetic alterations are more easily reversible. Epigenetic reprogramming techniques, drugs, and certain nutrients targeting specific epigenetic mechanisms involved in gene expression regulation are emerging as potential preventive or therapeutic tools for diseases. Therefore, this review provides a comprehensive overview of epigenetic modifications encompassing DNA/RNA methylation, histone modifications, and non-coding RNAs in the nervous system, elucidating their association with various heavy metal exposures. These primarily include manganese (Mn), mercury (Hg), lead (Pb), cobalt (Co), cadmium (Cd), nickel (Ni), sliver (Ag), toxic metalloids arsenic (As), and etc. The potential epigenetic mechanisms in the etiology, precision prevention, and target therapy of various neurodevelopmental disorders or different neurodegenerative diseases are emphasized. In addition, the current gaps in research and future areas of study are discussed. From a perspective on epigenetics, this review offers novel insights for prevention and treatment of neurotoxicity induced by heavy metal pollutants.

Manganese-induced neurological pyroptosis: Unveiling the mechanism through the ROS activaed Caspase-3/GSDME signaling pathway

Manganese (Mn) is an essential micronutrient in maintaining homeostasis in the human body, while excessive Mn exposure can lead to neurological disorders. To investigate whether there is an association between elevated ROS and pyroptosis caused by Mn exposure using both in vitro and in vivo models. We exposed BV2 and N2a, which represent microglial cells and Neuroblastoma cells in the brain, respectively, to different concentrations of Mn for 24 h. Following Mn exposure, we assessed cell morphology, levels of lactate dehydrogenase, and cellular ROS levels. C57BL/6 male mice were exposed to 0-100 mg/kg MnCl2·4H2O for 12 weeks through gavage. The expression level of pyroptosis proteins including caspase3 and GSDME in the hippocampus was examined. We found that Mn exposure resulted in elevated levels of cellular ROS and protein expression of Caspase3 and GSDME in both N2a and BV2 cells. The pyroptosis levels were blunted by either inhibiting Caspase3 expression or ROS production. In the in vivo model, protein levels of Caspase3 and GSDME also increased dependent of Mn concentrations. These findings suggested that neuronal pyroptosis induced by Mn exposure may occur through the ROS-stimulated Caspase3-GSDME pathway. Moreover, utilizing inhibitors targeting Caspase3 or ROS may provide protection against Mn-induced toxicity.

Mechanism of action and treatment of type I interferon in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) caused by HBV, HCV infection, and other factors is one of the most common malignancies in the world. Although, percutaneous treatments such as surgery, ethanol injection, radiofrequency ablation, and transcatheter treatments such as arterial chemoembolization are useful for local tumor control, they are not sufficient to improve the prognosis of patients with HCC. External interferon agents that induce interferon-related genes or type I interferon in combination with other drugs can reduce the recurrence rate and improve survival in HCC patients after surgery. Therefore, in this review, we focus on recent advances in the mechanism of action of type I interferons, emerging therapies, and potential therapeutic strategies for the treatment of HCC using IFNs.

Effects of mixed metal exposures on MRI diffusion features in the medial temporal lobe

Background

Environmental exposure to metal mixtures is common and may be associated with increased risk for neurodegenerative disorders including Alzheimer's disease.

Objective

This study examined associations of mixed metal exposures with medial temporal lobe (MTL) MRI structural metrics and neuropsychological performance.

Methods

Metal exposure history, whole blood metal, and neuropsychological tests were obtained from subjects with/without a history of mixed metal exposure from welding fumes (42 exposed subjects; 31 controls). MTL structures (hippocampus, entorhinal and parahippocampal cortices) were assessed by morphologic (volume, cortical thickness) and diffusion tensor imaging [mean (MD), axial (AD), radial diffusivity (RD), and fractional anisotropy (FA)] metrics. In exposed subjects, correlation, multiple linear, Bayesian kernel machine regression, and mediation analyses were employed to examine effects of single- or mixed-metal predictor(s) and their interactions on MTL structural and neuropsychological metrics; and on the path from metal exposure to neuropsychological consequences.

Results

Compared to controls, exposed subjects had higher blood Cu, Fe, K, Mn, Pb, Se, and Zn levels (p's<0.026) and poorer performance in processing/psychomotor speed, executive, and visuospatial domains (p's<0.046). Exposed subjects displayed higher MD, AD, and RD in all MTL ROIs (p's<0.040) and lower FA in entorhinal and parahippocampal cortices (p's<0.033), but not morphological differences. Long-term mixed-metal exposure history indirectly predicted lower processing speed performance via lower parahippocampal FA (p=0.023). Higher whole blood Mn and Cu predicted higher entorhinal diffusivity (p's<0.043) and lower Delayed Story Recall performance (p=0.007) without overall metal mixture or interaction effects.

Discussion

Mixed metal exposure predicted MTL structural and neuropsychological features that are similar to Alzheimer's disease at-risk populations. These data warrant follow-up as they may illuminate the path for environmental exposure to Alzheimer's disease-related health outcomes.

Astrocytic transcription factors REST, YY1, and putative microRNAs in Parkinson's disease and advanced therapeutic strategies

Transcription factors (TF) and microRNAs are regulatory factors in astrocytes and are linked to several Parkinson's disease (PD) progression causes, such as disruption of glutamine transporters in astrocytes and concomitant disrupted glutamine uptake and inflammation. REST, a crucial TF, has been documented as an epigenetic repressor that limits the expression of neuronal genes in non-neural cells. REST activity is significantly linked to its corepressors in astrocytes, specifically histone deacetylases (HDACs), CoREST, and MECP2. Another REST-regulating TF, YY1, has been studied in astrocytes, and its interaction with REST has been investigated. In this review, the molecular processes that support the astrocytic control of REST and YY1 in terms of the regulation of glutamate transporter EAAT2 were addressed in a more detailed and comprehensive manner. Both TFs' function in astrocytes and how astrocyte abnormalities cause PD is still a mystery. Moreover, microRNAs (short non-coding RNAs) are key regulators that have been correlated to the expression and regulation of numerous genes linked to PD. The identification of numerous miRs that are engaged in astrocyte dysfunction that triggers PD has been shown. The term "Gut-brain axis" refers to the two systems' mutual communication. Gut microbial dysbiosis, which mediates an imbalance of the gut-brain axis, might contribute to neurodegenerative illnesses through altered astrocytic regulation. New treatment approaches to modify the gut-brain axis and prevent astrocytic repercussions have also been investigated in this review.

ATP13A2 (PARK9) and basal ganglia function

ATP13A2 is a lysosomal protein involved in polyamine transport with loss of function mutations associated with multiple neurodegenerative conditions. These include early onset Parkinson's disease, Kufor-Rakeb Syndrome, neuronal ceroid lipofuscinosis, hereditary spastic paraplegia, and amyotrophic lateral sclerosis. While ATP13A2 mutations may result in clinical heterogeneity, the basal ganglia appear to be impacted in the majority of cases. The basal ganglia is particularly vulnerable to environmental exposures such as heavy metals, pesticides, and industrial agents which are also established risk factors for many neurodegenerative conditions. Not surprisingly then, impaired function of ATP13A2 has been linked to heavy metal toxicity including manganese, iron, and zinc. This review discusses the role of ATP13A2 in basal ganglia function and dysfunction, potential common pathological mechanisms in ATP13A2-related disorders, and how gene x environment interactions may contribute to basal ganglia dysfunction.

Manganese and IL-12 treatment alters the ovarian tumor microenvironment

Metal immunotherapy is a novel adjuvant immunotherapy. Mn2+ can activate STING-a type I IFN response protein-that promotes innate immunity and increases anti-tumor activity by promoting macrophage phagocytosis. IL-12, a cytokine that increases the antigen-presenting ability to promote effector T-cell activation, has potent antitumor activity, albeit with severe adverse effects. In this study, we observed that the combination of Mn2+ and IL-12 has a better antitumor effect and possibly reflects a better safety profile, providing a novel approach and theoretical basis for safe and rapid cancer treatment.

Ion Channels and Metal Ions in Parkinson's Disease: Historical Perspective to the Current Scenario

Parkinson's disease (PD) is a neurodegenerative condition linked to the deterioration of motor and cognitive performance. It produces degeneration of the dopaminergic neurons along the nigrostriatal pathway in the central nervous system (CNS), which leads to symptoms such as bradykinesias, tremors, rigidity, and postural instability. There are several medications currently approved for the therapy of PD, but a permanent cure for it remains elusive. With the aging population set to increase, a number of PD cases are expected to shoot up in the coming times. Hence, there is a need to look for new molecular targets that could be investigated both preclinically and clinically for PD treatment. Among these, several ion channels and metal ions are being studied for their effects on PD pathology and the functioning of dopaminergic neurons. Ion channels such as N-methyl-D-aspartate (NMDA), γ-aminobutyric acid A (GABAA), voltage-gated calcium channels, potassium channels, HCN channels, Hv1 proton channels, and voltage-gated sodium channels and metal ions such as mercury, zinc, copper, iron, manganese, calcium, and lead showed prominent involvement in PD. Pharmacological agents have been used to target these ion channels and metal ions to prevent or treat PD. Hence, in the present review, we summarize the pathophysiological events linked to PD with an emphasis on the role of ions and ion channels in PD pathology, and pharmacological agents targeting these ion channels have also been listed.

13C and 15N resonance assignments of alpha synuclein fibrils amplified from Lewy Body Dementia tissue

Fibrils of the protein α-synuclein (Asyn) are implicated in the pathogenesis of Parkinson Disease, Lewy Body Dementia, and Multiple System Atrophy. Numerous forms of Asyn fibrils have been studied by solid-state NMR and resonance assignments have been reported. Here, we report a new set of 13C, 15N assignments that are unique to fibrils obtained by amplification from postmortem brain tissue of a patient diagnosed with Lewy Body Dementia.

Environmental chemical exposures and mental health outcomes in children: a narrative review of recent literature

Background: Mental health is an important factor for children's overall wellbeing. National health statistics show that millions of children are diagnosed with mental health disorders every year, and evidence from studies on chemical pollutants like lead and bisphenols indicate that environmental exposures are linked to mental health illnesses in youth. However, the relationship between children's mental health and the environment is not well understood. This paper aims to review recent literature on prenatal and/or childhood environmental chemical exposures and mental health problems related to mood, anxiety, and behavior. This work also identifies areas of insufficient data and proposes suggestions to fill the data gaps. Methods: A narrative review was performed by searching Google Scholar and PubMed for literature published in the last 6 years (2017-2022), using search terms related to children, mental health, and environmental chemical exposure. Additional relevant studies were identified by screening the references in these papers. Results: A total of 29 studies are included in this review and results are summarized by chemical category: heavy metals, endocrine-disrupting chemicals, and pesticides. The majority of studies reported positive and significant associations between chemical exposures and child mental health outcomes including internalizing and externalizing behaviors. Conclusion: This review demonstrates that there is a growing body of literature that suggests developmental exposure to some environmental chemicals increases a child's risk of mood, anxiety, and behavior problems. Future research should expand on these findings to understand cumulative impacts, chemical mixtures, neurotoxic mechanisms, sex differences, and windows of vulnerability.

Towards multimodal cellular imaging: optical and X-ray fluorescence

Imaging techniques permit the study of the molecular interactions that underlie health and disease. Each imaging technique collects unique chemical information about the cellular environment. Multimodal imaging, using a single probe that can be detected by multiple imaging modalities, can maximise the information extracted from a single cellular sample by combining the results of different imaging techniques. Of particular interest in biological imaging is the combination of the specificity and sensitivity of optical fluorescence microscopy (OFM) with the quantitative and element-specific nature of X-ray fluorescence microscopy (XFM). Together, these techniques give a greater understanding of how native elements or therapeutics affect the cellular environment. This review focuses on recent studies where both techniques were used in conjunction to study cellular systems, demonstrating the breadth of biological models to which this combination of techniques can be applied and the potential for these techniques to unlock untapped knowledge of disease states.

Probucol neuroprotection against manganese-induced damage in adult Wistar rat brain slices

Manganese (Mn) is an abundant element used for commercial purposes and is essential for the proper function of biological systems. Chronic exposure to high Mn concentrations causes Manganism, a Parkinson's-like neurological disorder. The pathophysiological mechanism of Manganism remains unknown; however, it involves mitochondrial dysfunction and oxidative stress. This study assessed the neuroprotective effect of probucol, a hypolipidemic agent with anti-inflammatory and antioxidant properties, on cell viability and oxidative stress in slices of the cerebral cortex and striatum from adult male Wistar rats. Brain structure slices were kept separately and incubated with manganese chloride (MnCl2) and probucol to evaluate the cell viability and oxidative parameters. Probucol prevented Mn toxicity in the cerebral cortex and striatum, as evidenced by the preservation of cell viability observed with probucol (10 and 30 μM) pre-treatment, as well as the prevention of mitochondrial complex I inhibition in the striatum (30 μM). These findings support the protective antioxidant action of probucol, attributed to its ability to prevent cell death and mitigate Mn-induced mitochondrial dysfunction.

Manganese Mineralization of Pathogenic Viruses as a Universal Vaccine Platform

Biomimetic viral mineralization improves viral vaccine stability and immunogenicity using inorganic metals such as Ca, Al, or Fe. Mn is a metal found in high concentrations in mammalian tissues; however, under natural or laboratory conditions, Mn mineralization by medical viruses has yet to be established. Herein, a single IAV particle is successfully encapsulated with manganese phosphate (MnP) under specific conditions using the human influenza A virus (IAV). MnP-mineralized IAVs (IAV@Mn) exhibited physiochemical and in vitro properties similar to Ca-mineralized IAVs. In animal models, IAV@Mn shows limited replication in immune-competent cells and a significant attenuation compared to naïve cells. Moreover, a single-dose vaccination with IAV@Mn induced robust humoral and cellular immune responses and conferred significant protection against a wild-type IAV challenge in mice. Thus, Mn mineralization in pathogenic viruses provides a rapid and universal strategy for generating an emergency vaccine in response to emerging viruses.

Common and Trace Metals in Alzheimer's and Parkinson's Diseases

Trace elements and metals play critical roles in the normal functioning of the central nervous system (CNS), and their dysregulation has been implicated in neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). In a healthy CNS, zinc, copper, iron, and manganese play vital roles as enzyme cofactors, supporting neurotransmission, cellular metabolism, and antioxidant defense. Imbalances in these trace elements can lead to oxidative stress, protein aggregation, and mitochondrial dysfunction, thereby contributing to neurodegeneration. In AD, copper and zinc imbalances are associated with amyloid-beta and tau pathology, impacting cognitive function. PD involves the disruption of iron and manganese levels, leading to oxidative damage and neuronal loss. Toxic metals, like lead and cadmium, impair synaptic transmission and exacerbate neuroinflammation, impacting CNS health. The role of aluminum in AD neurofibrillary tangle formation has also been noted. Understanding the roles of these elements in CNS health and disease might offer potential therapeutic targets for neurodegenerative disorders. The Codex Alimentarius standards concerning the mentioned metals in foods may be one of the key legal contributions to safeguarding public health. Further research is needed to fully comprehend these complex mechanisms and develop effective interventions.

A Non-Nucleotide STING Agonist MSA-2 Synergized with Manganese in Enhancing STING Activation to Elicit Potent Anti-RNA Virus Activity in the Cells

Both Manganese (Mn2+) and MSA-2 can activate the downstream signal pathway through stimulator of interferon genes (STING) and induce the expression of type I interferon, which is important for hosts to protect against DNA viruses. However, its effect on RNA viruses remains unknown. In this study, we used Seneca Valley virus (SVV) as a model RNA virus to investigate the inhibitory effects of Mn2+ and MSA-2 on the virus replication in the porcine cells (PK-15 cells). The results showed that both MSA-2 and Mn2+ were able to inhibit the SVV replication in PK-15 cells. The combination of MAS-2 and Mn2+ could confer better protection against SVV. Further studies showed that MSA-2 and Mn2+ could activate TBK1, IRF3 and NFκB through STING and induce the expression of IFN-β, IL-6 and TNF-α. The present study confirmed that MSA-2 synergized with Mn2+ in STING activation to generate a better antiviral effect in vitro, which would be helpful for the further development of effective antiviral drugs in the future.

Consequences of Disturbing Manganese Homeostasis

Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.

REST in the Road Map of Brain Development

Repressor element-1 silencing transcription factor (REST) or also known as neuron-restrictive silencing factor (NRSF), is the key initiator of epigenetic neuronal gene-expression modification. Identification of a massive number of REST-targeted genes in the brain signifies its broad involvement in maintaining the functionality of the nervous system. Additionally, REST plays a crucial role in conferring neuroprotection to the neurons against various stressors or insults during injuries. At the cellular level, nuclear localisation of REST is a key determinant for the functional transcriptional regulation of REST towards its target genes. Emerging studies reveal the implication of REST nuclear mislocalisation or dysregulation in several neurological diseases. The expression of REST varies depending on different types of neurological disorders, which has created challenges in the discovery of REST-targeted interventions. Hence, this review presents a comprehensive summary on the physiological roles of REST throughout brain development and its implications in neurodegenerative and neurodevelopmental disorders, brain tumours and cerebrovascular diseases. This review offers valuable insights to the development of potential therapeutic approaches targeting REST to improve pathologies in the brain. The important roles of REST as a key player in the nervous system development, and its implications in several neurological diseases.

Impact of manganese accumulation on Na,K-ATPase expression and function in the cerebellum and striatum of C57Bl/6 mice

Overexposure to Mn causes a neurological disorder-manganism-with motor symptoms that overlap closely with disorders associated with haploinsufficiency in the gene encoding for α3 isoform of Na+,K+-ATPase (NKA). The present study was designed to test the hypothesis that behavioral changes in the mouse model of manganism may be associated with changes in the expression and activity of α3 NKA in the cerebellum (CB) and striatum (STR)-the key brain structures responsible for motor control in adult mice. C57Bl/6 mice were exposed to MnCl2 at 0.5 g/L (in drinking water) for up to eight weeks. After four weeks of Mn consumption, Mn levels were increased in the CB only. Behavioral tests demonstrated decreased performance of Mn-treated mice in the shuttle box test (third through sixth weeks), and the inclined grid walking test (first through sixth weeks), suggesting the development of learning impairment, decreased locomotion, and motor discoordination. The activity of NKA significantly decreased, and the expression of α1-α3 isoforms of NKA increased in the second week in the CB only. Thus, signs of learning and motor disturbances developing in this model of manganism are unlikely to be directly linked to disturbances in the expression or activity of NKA in the CB or STR. Whether these early changes may contribute to the pathogenesis of later behavioral deficits remains to be determined.

Hepatic and intestinal manganese excretion are both required to regulate brain manganese during elevated manganese exposure

Manganese (Mn) is essential but neurotoxic at elevated levels. Under physiological conditions, Mn is primarily excreted by the liver, with the intestines playing a secondary role. Recent analyses of tissue-specific Slc30a10 or Slc39a14 knockout mice (SLC30A10 and SLC39A14 are Mn transporters) revealed that, under physiological conditions: 1) excretion of Mn by the liver and intestines is a major pathway that regulates brain Mn; and surprisingly, 2) the intestines compensate for loss of hepatic Mn excretion in controlling brain Mn. The unexpected importance of the intestines in controlling physiological brain Mn led us to determine the role of hepatic and intestinal Mn excretion in regulating brain Mn during elevated Mn exposure. We used liver- or intestine-specific Slc30a10 knockout mice as models to inhibit hepatic or intestinal Mn excretion. Compared with littermates, both knockout strains exhibited similar increases in brain Mn after elevated Mn exposure in early or later life. Thus, unlike physiological conditions, both hepatic and intestinal Mn excretion are required to control brain Mn during elevated Mn exposure. However, brain Mn levels of littermates and both knockout strains exposed to elevated Mn only in early life were normalized in later life. Thus, hepatic and intestinal Mn excretion play compensatory roles in clearing brain Mn accumulated by early life Mn exposure. Finally, neuromotor assays provided evidence consistent with a role for hepatic and intestinal Mn excretion in functionally modulating Mn neurotoxicity during Mn exposure. Put together, these findings substantially enhance understanding of the regulation of brain Mn by excretion.NEW & NOTEWORTHY This article shows that, in contrast with expectations from prior studies and physiological conditions, excretion of manganese by the intestines and liver is equally important in controlling brain manganese during human-relevant manganese exposure. The results provide foundational insights about the interorgan mechanisms that control brain manganese homeostasis at the organism level and have important implications for the development of therapeutics to treat manganese-induced neurological disease.

Smouldering Lesion in MS: Microglia, Lymphocytes and Pathobiochemical Mechanisms

Multiple sclerosis (MS) is an immune-mediated, chronic inflammatory, demyelinating, and neurodegenerative disease of the central nervous system (CNS). Immune cell infiltration can lead to permanent activation of macrophages and microglia in the parenchyma, resulting in demyelination and neurodegeneration. Thus, neurodegeneration that begins with acute lymphocytic inflammation may progress to chronic inflammation. This chronic inflammation is thought to underlie the development of so-called smouldering lesions. These lesions evolve from acute inflammatory lesions and are associated with continuous low-grade demyelination and neurodegeneration over many years. Their presence is associated with poor disease prognosis and promotes the transition to progressive MS, which may later manifest clinically as progressive MS when neurodegeneration exceeds the upper limit of functional compensation. In smouldering lesions, in the presence of only moderate inflammatory activity, a toxic environment is clearly identifiable and contributes to the progressive degeneration of neurons, axons, and oligodendrocytes and, thus, to clinical disease progression. In addition to the cells of the immune system, the development of oxidative stress in MS lesions, mitochondrial damage, and hypoxia caused by the resulting energy deficit and iron accumulation are thought to play a role in this process. In addition to classical immune mediators, this chronic toxic environment contains high concentrations of oxidants and iron ions, as well as the excitatory neurotransmitter glutamate. In this review, we will discuss how these pathobiochemical markers and mechanisms, alone or in combination, lead to neuronal, axonal, and glial cell death and ultimately to the process of neuroinflammation and neurodegeneration, and then discuss the concepts and conclusions that emerge from these findings. Understanding the role of these pathobiochemical markers would be important to gain a better insight into the relationship between the clinical classification and the pathomechanism of MS.

Uncovering the Molecular Link Between Lead Toxicity and Parkinson's Disease

Significance: Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects millions around the world. The etiology of PD remains unknown, but environmental and occupational exposures to heavy metals are likely at play, and may impact the severity of the disease. Lead is a toxin known to affect many organs in the body throughout life, particularly the central nervous system. Recent Advances: In this study, we summarize and examine the evidence for such environmental and/or occupational exposures, with a focus on the molecular mechanisms associated with lead exposure and its potential contribution to the onset of parkinsonism in PD. In particular, populational studies suggest higher bone and blood lead levels are associated with increased risk of PD. Interestingly, low levels of lead exposure in the very early stages of life cause increase the production of alpha-synuclein protein in animal models. Critical Issues: Although the specific mechanisms underlying this association have not been fully assessed, oxidative stress and mitochondrial dysfunction are likely implicated and may explain the toxic effects that connect lead exposure to parkinsonism. Future Directions: Additional pre-clinical and clinical studies should be performed in order to further document the molecular link between lead toxicity and PD, as this may open novel perspectives in terms of disease prevention. Antioxid. Redox Signal. 39, 321-335.

Associations of ambient manganese exposure with brain gray matter thickness and white matter hyperintensities

Manganese (Mn) exposure is associated with increased risks of dementia and cerebrovascular disease. However, evidence regarding the impact of ambient Mn exposure on brain imaging markers is scarce. We aimed to investigate the association between ambient Mn exposure and brain imaging markers representing neurodegeneration and cerebrovascular lesions. We recruited a total of 936 adults (442 men and 494 women) without dementia, movement disorders, or stroke from the Republic of Korea. Ambient Mn concentrations were predicted at each participant's residential address using spatial modeling. Neurodegeneration-related brain imaging markers, such as the regional cortical thickness, were estimated using 3 T brain magnetic resonance images. White matter hyperintensity volume (an indicator of cerebrovascular lesions) was also obtained from a certain number of participants (n = 397). Linear regression analyses were conducted after adjusting for potential confounders. A log-transformed ambient Mn concentration was associated with thinner parietal (β = -0.02 mm; 95% confidence interval [CI], -0.05 to -0.01) and occipital cortices (β = -0.03 mm; 95% CI, -0.04 to -0.01) after correcting for multiple comparisons. These associations remained statistically significant in men. An increase in the ambient Mn concentration was also associated with a greater volume of deep white matter hyperintensity in men (β = 772.4 mm3, 95% CI: 36.9 to 1508.0). None of the associations were significant in women. Our findings suggest that ambient Mn exposure may induce cortical atrophy in the general adult population.

Manganese-Induced Parkinsonism: Evidence from Epidemiological and Experimental Studies

Manganese (Mn) exposure has evolved from acute, high-level exposure causing manganism to low, chronic lifetime exposure. In this latter scenario, the target areas extend beyond the globus pallidus (as seen with manganism) to the entire basal ganglia, including the substantia nigra pars compacta. This change of exposure paradigm has prompted numerous epidemiological investigations of the occurrence of Parkinson's disease (PD), or parkinsonism, due to the long-term impact of Mn. In parallel, experimental research has focused on the underlying pathogenic mechanisms of Mn and its interactions with genetic susceptibility. In this review, we provide evidence from both types of studies, with the aim to link the epidemiological data with the potential mechanistic interpretation.

A partial Drp1 knockout improves autophagy flux independent of mitochondrial function

Dynamin-related protein 1 (Drp1) is typically known for its role in mitochondrial fission. A partial inhibition of this protein has been reported to be protective in experimental models of neurodegenerative diseases. The protective mechanism has been attributed primarily to improved mitochondrial function. Herein, we provide evidence showing that a partial Drp1-knockout improves autophagy flux independent of mitochondria. First, we characterized in cell and animal models that at low non-toxic concentrations, manganese (Mn), which causes parkinsonian-like symptoms in humans, impaired autophagy flux but not mitochondrial function and morphology. Furthermore, nigral dopaminergic neurons were more sensitive than their neighbouring GABAergic counterparts. Second, in cells with a partial Drp1-knockdown and Drp1 +/- mice, autophagy impairment induced by Mn was significantly attenuated. This study demonstrates that autophagy is a more vulnerable target than mitochondria to Mn toxicity. Furthermore, improving autophagy flux is a separate mechanism conferred by Drp1 inhibition independent of mitochondrial fission.

Defective Mitochondrial Dynamics and Protein Degradation Pathways Underlie Cadmium-Induced Neurotoxicity and Cell Death in Huntington's Disease Striatal Cells

Exposure to heavy metals, including cadmium (Cd), can induce neurotoxicity and cell death. Cd is abundant in the environment and accumulates in the striatum, the primary brain region selectively affected by Huntington's disease (HD). We have previously reported that mutant huntingtin protein (mHTT) combined with chronic Cd exposure induces oxidative stress and promotes metal dyshomeostasis, resulting in cell death in a striatal cell model of HD. To understand the effect of acute Cd exposure on mitochondrial health and protein degradation pathways, we hypothesized that expression of mHTT coupled with acute Cd exposure would cooperatively alter mitochondrial bioenergetics and protein degradation mechanisms in striatal STHdh cells to reveal novel pathways that augment Cd cytotoxicity and HD pathogenicity. We report that mHTT cells are significantly more susceptible to acute Cd-induced cell death as early as 6 h after 40 µM CdCl₂ exposure compared with wild-type (WT). Confocal microscopy, biochemical assays, and immunoblotting analysis revealed that mHTT and acute Cd exposure synergistically impair mitochondrial bioenergetics by reducing mitochondrial potential and cellular ATP levels and down-regulating the essential pro-fusion proteins MFN1 and MFN2. These pathogenic effects triggered cell death. Furthermore, Cd exposure increases the expression of autophagic markers, such as p62, LC3, and ATG5, and reduces the activity of the ubiquitin-proteasome system to promote neurodegeneration in HD striatal cells. Overall, these results reveal a novel mechanism to further establish Cd as a pathogenic neuromodulator in striatal HD cells via Cd-triggered neurotoxicity and cell death mediated by an impairment in mitochondrial bioenergetics and autophagy with subsequent alteration in protein degradation pathways.

SLC30A10 manganese transporter in the brain protects against deficits in motor function and dopaminergic neurotransmission under physiological conditions

Loss-of-function mutations in SLC30A10 induce hereditary manganese (Mn)-induced neuromotor disease in humans. We previously identified SLC30A10 to be a critical Mn efflux transporter that controls physiological brain Mn levels by mediating hepatic and intestinal Mn excretion in adolescence/adulthood. Our studies also revealed that in adulthood, SLC30A10 in the brain regulates brain Mn levels when Mn excretion capacity is overwhelmed (e.g. after Mn exposure). But, the functional role of brain SLC30A10 under physiological conditions is unknown. We hypothesized that, under physiological conditions, brain SLC30A10 may modulate brain Mn levels and Mn neurotoxicity in early postnatal life because body Mn excretion capacity is reduced in this developmental stage. We discovered that Mn levels of pan-neuronal/glial Slc30a10 knockout mice were elevated in specific brain regions (thalamus) during specific stages of early postnatal development (postnatal day 21), but not in adulthood. Furthermore, adolescent or adult pan-neuronal/glial Slc30a10 knockouts exhibited neuromotor deficits. The neuromotor dysfunction of adult pan-neuronal/glial Slc30a10 knockouts was associated with a profound reduction in evoked striatal dopamine release without dopaminergic neurodegeneration or changes in striatal tissue dopamine levels. Put together, our results identify a critical physiological function of brain SLC30A10-SLC30A10 in the brain regulates Mn levels in specific brain regions and periods of early postnatal life, which protects against lasting deficits in neuromotor function and dopaminergic neurotransmission. These findings further suggest that a deficit in dopamine release may be a likely cause of early-life Mn-induced motor disease.

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.

African Walnut (Tetracarpidium conophorum) Extract upregulates Glococerebrosidase activity and circumvents Parkinsonian changes in the Hippocampus via theActivation of Heatshock Proteins

BACKGROUND

Neurodegenerative illnesses like Parkinson's and Alzheimer's are largely caused by the accumulation of aggregated proteins. Heat shock proteins (HSPs), which are molecular chaperons, have been linked with the modulation of β-glucocerebrosidase (GCase) function encoded by GBA1 and Synucleinopathies. Herein, the chaperonic properties of African walnut ethanolic extract (WNE) in manganese-induced Parkinsonian neuropathology in the hippocampus was examined.

METHODOLOGY

48 adult male rats weighing 185g±10g were randomly assigned into 6 (A - F) groups (n=8) and treated orally as follows: A-PBS (1ml daily for 28 days), B-WNE (200mg/kg daily for 28 days), C- WNE (400mg/kg daily for 28 days), D-Mn (100mg/kg daily for 28 days), E-Mn plus WNE (100mg/kg Mn + 200mg/kg WNE daily concomitantly for 28 days), F-Mn plus WNE (100mg/kg Mn + 400mg/kg WNE daily concomitantly for 28 days).

RESULTS

Rats treated with WNE showed increased levels of HSP70 and HSP90 in comparison with the Mn-intoxicated group. GCase activity also increased significantly in animals treated with WNE. Our results further revealed the therapeutic tendencies of WNE against Mn toxicity by modulating oligomeric α-synuclein levels, redox activity, and glucose bioenergetics. Furthermore, immunohistochemical evaluation revealed reduced expression of neurofibrillary tangles, and reactive astrogliosis following WNE treatment.

CONCLUSION

The ethanolic extract of African Walnut induced the activation of HSPs and increased the expression of GBA1 gene in the hippocampus. Activated heat shock proteins suppressed neurodegenerative changes due to Manganese toxicity. WNE was also shown to modulate neuroinflammatory, bioenergetics and neural redox balance in Parkinson-like neuropathology. This study was limited to the use of crude walnut extract and the evaluation of non-motor cascades of Parkinson's disease.

Manganese Mediates Its Antiviral Functions in a cGAS-STING Pathway Independent Manner

The innate immune system is the first line of host defense sensing viral infection. Manganese (Mn) has recently been found to be involved in the activation of the innate immune DNA-sensing cGAS-STING pathway and subsequent anti-DNA virus function. However, it is still unclear whether Mn2+ mediates host defense against RNA viruses. In this study, we demonstrate that Mn2+ exhibited antiviral effects against various animal and human viruses, including RNA viruses such as PRRSVs and VSV, as well as DNA viruses such as HSV1, in a dose-dependent manner. Moreover, cGAS and STING were both investigated in the Mn2+ mediated antiviral roles using the knockout cells made by the CRISPR-Cas9 approach. Unexpectedly, the results revealed that neither cGAS knockout nor STING knockout had any effect on Mn2+-mediated antiviral functions. Nevertheless, we verified that Mn2+ promoted the activation of the cGAS-STING signaling pathway. These findings suggest that Mn2+ has broad-spectrum antiviral activities in a cGAS-STING pathway independent manner. This study also provides significant insights into redundant mechanisms participating in the Mn2+ antiviral functions, and also indicates a new target for Mn2+ antiviral therapeutics.

13C and 15N Resonance Assignments of Alpha Synuclein Fibrils Amplified from Lewy Body Dementia Tissue

Fibrils of the protein α-synuclein (Asyn) are implicated in the pathogenesis of Parkinson Disease, Lewy Body Dementia, and Multiple System Atrophy. Numerous forms of Asyn fibrils have been studied by solid-state NMR and resonance assignments have been reported. Here, we report a new set of 13C, 15N assignments that are unique to fibrils obtained by amplification from postmortem brain tissue of a patient diagnosed with Lewy Body Dementia.

pH-Sensitive and Biodegradable Mn3(PO4)2·3H2O Nanoparticles as an Adjuvant of Protein-Based Bivalent COVID-19 Vaccine to Induce Potent and Broad-Spectrum Immunity

Developing a novel and potent adjuvant with great biocompatibility for immune response augmentation is of great significance to enhance vaccine efficacy. In this work, we prepared a long-term stable, pH-sensitive, and biodegradable Mn3(PO4)2·3H2O nanoparticle (nano-MnP) by simply mixing MnCl2/NaH2PO4/Na2HPO4 solution for the first time and employed it as an immune stimulant in the bivalent COVID-19 protein vaccine comprised of wild-type S1 (S1-WT) and Omicron S1 (S1-Omicron) proteins as antigens to elicit a broad-spectrum immunity. The biological experiments indicated that the nano-MnP could effectively activate antigen-presenting cells through the cGAS-STING pathway. Compared with the conventional Alum-adjuvanted group, the nano-MnP-adjuvanted bivalent vaccine elicited approximately 7- and 8-fold increases in IgG antibody titers and antigen-specific IFN-γ secreting T cells, respectively. Importantly, antisera of the nano-MnP-adjuvanted group could effectively cross-neutralize the SARS-CoV-2 and its five variants of concern (VOCs) including Alpha, Beta, Gamma, Delta, and Omicron, demonstrating that this bivalent vaccine based on S1-WT and S1-Omicron proteins is an effective vaccine design strategy to induce broad-spectrum immune responses. Collectively, this nano-MnP material may provide a novel and efficient adjuvant platform for various prophylactic and therapeutic vaccines and provide insights for the development of the next-generation manganese adjuvant.

Antiviral Effect of Manganese against Foot-and-Mouth Disease Virus Both in PK15 Cells and Mice

Foot-and-mouth disease (FMD) is an acute contagious disease of cloven-hoofed animals such as cattle, pigs, and sheep. Current emergency FMD vaccines are of limited use for early protection because their protective effect starts 7 days after vaccination. Therefore, antiviral drugs or additives are used to rapidly stop the spread of the virus during FMD outbreaks. Manganese (Mn²⁺) was recently found to be an important substance necessary for the host to protect against DNA viruses. However, its antiviral effect against RNA viruses remains unknown. In this study, we found that Mn²⁺ has antiviral effects on the FMD virus (FMDV) both in PK15 cells and mice. The inhibitory effect of Mn²⁺ on FMDV involves NF-κB activation and up-regulation of interferon-stimulated genes. Animal experiments showed that Mn²⁺ can be highly effective in protecting C57BL/6N mice from being infected with FMDV. Overall, we suggest Mn²⁺ as an effective antiviral additive for controlling FMDV infection.

Manganese efflux transporter SLC30A10 missense polymorphism T95I associated with liver injury retains manganese efflux activity

The activity of the manganese (Mn) efflux transporter SLC30A10 in the liver and intestines is critical for Mn excretion and preventing Mn toxicity. Homozygous loss-of-function mutations in SLC30A10 are a well-established cause of hereditary Mn toxicity. But, the relationship between more common SLC30A10 polymorphisms, Mn homeostasis, and disease is only recently emerging. In 2021, the first coding SNP in SLC30A10 (T95I) was associated with liver disease raising the hypothesis that the T95I substitution may induce disease by inhibiting the Mn efflux function of SLC30A10. Here, we test this hypothesis using structural, viability, and metal quantification approaches. Analyses of a predicted structure of SLC30A10 revealed that the side chain of T95 pointed away from the putative Mn-binding cavity, raising doubts about the impact of the T95I substitution on SLC30A10 function. In HeLa or HepG2 cells, overexpression of SLC30A10-WT or T95I resulted in comparable reductions of intracellular Mn levels and protection against Mn-induced cell death. Furthermore, ΔSLC30A10 HepG2 cells, generated using CRISPR/Cas9, exhibited elevated Mn levels and heightened sensitivity to Mn-induced cell death, and these phenotypic changes were similarly rescued by expression of SLC30A10-WT or T95I. Finally, turnover rates of SLC30A10-WT or T95I were also comparable. In summary, our results indicate that the Mn transport activity of SLC30A10-T95I is essentially comparable to the WT protein. Our findings imply that SLC30A10-T95I either has a complex association with liver injury that extends beyond the simple reduction in SLC30A10 activity or alternatively the T95I mutation lacks a causal role in liver disease.NEW & NOTEWORTHY This study demonstrates that the T95I polymorphism in the manganese transporter SLC30A10, which has been associated with liver disease in human GWAS studies, does not impact transporter function in cell culture. These findings raise doubts about the causal relationship of the T95I polymorphism with human disease and highlight the importance of validating GWAS findings using mechanistic approaches.

Microglial immune regulation by epigenetic reprogramming through histone H3K27 acetylation in neuroinflammation

Epigenetic reprogramming is the ability of innate immune cells to form memories of environmental stimuli (priming), allowing for heightened responses to secondary stressors. Herein, we explored microglial epigenetic marks using the known inflammagen LPS as a memory priming trigger and Parkinsonian-linked environmental neurotoxic stressor manganese (Mn) as the secondary environmental trigger. To mimic physiological responses, the memory priming trigger LPS treatment was removed by triple-washing to allow the cells' acute inflammatory response to reset back before applying the secondary insult. Our results show that after the secondary Mn insult, levels of key proinflammatory markers, including nitrite release, iNOS mRNA and protein expression, Il-6, Il-α and cytokines were exaggerated in LPS-primed microglia. Our paradigm implies primed microglia retain immune memory that can be reprogrammed to augment inflammatory response by secondary environmental stress. To ascertain the molecular underpinning of this neuroimmune memory, we further hypothesize that epigenetic reprogramming contributes to the retention of a heightened immune response. Interestingly, Mn-exposed, LPS-primed microglia showed enhanced deposition of H3K27ac and H3K4me3 along with H3K4me1. We further confirmed the results using a PD mouse model (MitoPark) and postmortem human PD brains, thereby adding clinical relevance to our findings. Co-treatment with the p300/H3K27ac inhibitor GNE-049 reduced p300 expression and H3K27ac deposition, decreased iNOS, and increased ARG1 and IRF4 levels. Lastly, since mitochondrial stress is a driver of environmentally linked Parkinson's disease (PD) progression, we examined the effects of GNE-049 on primary trigger-induced mitochondrial stress. GNE-049 reduced mitochondrial superoxide, mitochondrial circularity and stress, and mitochondrial membrane depolarization, suggesting beneficial consequences of GNE-049 on mitochondrial function. Collectively, our findings demonstrate that proinflammatory primary triggers can shape microglial memory via the epigenetic mark H3K27ac and that inhibiting H3K27ac deposition can prevent primary trigger immune memory formation and attenuate subsequent secondary inflammatory responses.

Immunomodulatory activity of manganese dioxide nanoparticles: Promising for novel vaccines and immunotherapeutics

Manganese (Mn), a nutrient inorganic trace element, is necessary for a variety of physiological processes of animal body due to their important roles in oxidative regulation effects and other aspects of activities. Moreover, manganese ion (Mn²⁺) has widely reported to be crucial for the regulations of different immunological responses, thus showing promising application as potential adjuvants and immunotherapeutics. Taking the advantages of Mn-based biological and immunological activities, Manganese dioxide nanoparticles (MnO₂ NPs) are a new type of inorganic nanomaterials with numerous advantages, including simple preparation, low cost, environmental friendliness, low toxicity, biodegradable metabolism and high bioavailability. MnO₂ NPs, as a kind of drug carrier, have also shown the ability to catalyze hydrogen peroxide (H₂O₂) to produce oxygen (O₂) under acidic conditions, which can enhance the efficacy of radiotherapy, chemotherapy and other therapeutics for tumor treatment by remodeling the tumor microenvironment. More importantly, MnO₂ NPs also play important roles in immune regulations both in innate and adaptive immunity. In this review, we summarize the biological activities of Manganese, followed by the introduction for the biological and medical functions and mechanisms of MnO₂ NPs. What's more, we emphatically discussed the immunological regulation effects and mechanisms of MnO₂ NPs, as well as their potentials to serve as adjuvants and immunomodulators, which might benefit the development of novel vaccines and immunotherapies for more effective disease control.

Small noncoding RNA dysregulation is implicated in manganism in a rat model of methylcyclopentadienyl manganese tricarbonyl-induced unrepaired striatum damage

The accumulation of excessively high manganese levels within the brain can contribute to a series of Parkinsonian symptoms referred to as manganism. The gasoline antiknock additive Methylcyclopentadienyl Manganese Tricarbonyl (MMT) is an environmental source of manganese exposure and can induce manganism in rats. While some prior reports have demonstrated the differential expression of small noncoding RNAs (sncRNAs) in patients with Parkinson's disease (PD), the degree of sncRNA dysfunction in manganism has yet to be clearly documented. As sncRNAs such as transfer RNA-derived small RNAs (tsRNAs) and ribosomal RNA-derived small RNAs (rsRNAs) exhibit high levels of modifications such as 3' terminal 3'-phosphate and 2',3'-cyclic phosphate modifications that disrupt the process of adapter ligation and m1A, m3C, m1G, and m22G RNA methylation, these transcripts are not detected in traditional small RNA-sequencing studies. Here, differential sncRNA expression was analyzed by comparing a rat model of MMT-induced unrepaired striatum damage to appropriate control samples via PANDORA-Seq, which can detect highly modified sncRNAs. Following the removal of sncRNA modifications, this approach identified 599 sncRNAs that were differentially expressed in the striatum of MMT-exposed rats relative to controls, as well as 1155 sncRNAs that were differentially expressed in Mn-treated and control rats. Additional functional analyses were performed to predict the putative targets of these sncRNAs, implicating a role for such sncRNA dysregulation in the pathogenesis of manganism in this rat model system.

Serum zinc deficiency could be associated with dementia conversion in Parkinson's disease

Background

Association between heavy metals and Parkinson's disease (PD) is well noted, but studies regarding heavy metal levels and non-motor symptoms of PD, such as PD's dementia (PD-D), are lacking.

Methods

In this retrospective cohort study, we compared five serum heavy metal levels (Zn, Cu, Pb, Hg, and Mn) of newly diagnosed PD patients (n = 124). Among 124 patients, 40 patients were later converted to Parkinson's disease dementia (PD-D), and 84 patients remained without dementia during the follow-up time. We collected clinical parameters of PD and conducted correlation analysis with heavy metal levels. PD-D conversion time was defined as the initiation time of cholinesterase inhibitors. Cox proportional hazard models were used to identify factors associated with dementia conversion in PD subjects.

Results

Zn deficiency was significant in the PD-D group than in the PD without dementia group (87.53 ± 13.20 vs. 74.91 ± 14.43, p < 0.01). Lower serum Zn level was significantly correlated with K-MMSE and LEDD at 3 months (r = -0.28, p < 0.01; r = 0.38, p < 0.01). Zn deficiency also contributed to a shorter time to dementia conversion (HR 0.953, 95% CI 0.919 to 0.988, p < 0.01).

Conclusion

This clinical study suggests that a low serum Zn level can be a risk factor for developing PD-D and could be used as a biological marker for PD-D conversion.

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.

The cGAS-STING-autophagy pathway: Novel perspectives in neurotoxicity induced by manganese exposure

Chronic high-level heavy metal exposure increases the risk of developing different neurodegenerative diseases. Chronic excessive manganese (Mn) exposure is known to lead to neurodegenerative diseases. In addition, some evidence suggests that autophagy dysfunction plays an important role in the pathogenesis of various neurodegenerative diseases. Over the past decade, the DNA-sensing receptor cyclic GMP-AMP synthase (cGAS) and its downstream signal-efficient interferon gene stimulator (STING), as well as the molecular composition and regulatory mechanisms of this pathway have been well understood. The cGAS-STING pathway has emerged as a crucial mechanism to induce effective innate immune responses by inducing type I interferons in mammalian cells. Moreover, recent studies have found that Mn²⁺ is the second activator of the cGAS-STING pathway besides dsDNA, and inducing autophagy is a primitive function for the activation of the cGAS-STING pathway. However, overactivation of the immune response can lead to tissue damage. This review discusses the mechanism of neurotoxicity induced by Mn exposure from the cGAS-STING-autophagy pathway. Future work exploiting the cGAS-STING-autophagy pathway may provide a novel perspective for manganese neurotoxicity.

Neuroprotective Effects of Some Nutraceuticals against Manganese-Induced Parkinson's Disease in Rats: Possible Modulatory Effects on TLR4/NLRP3/NF-κB, GSK-3β, Nrf2/HO-1, and Apoptotic Pathways

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting the substantia nigra where functions controlling body movement take place. Manganese (Mn) overexposure is linked to a neurologic syndrome resembling PD. Sesamol, thymol, wheat grass (WG), and coenzyme Q10 (CoQ10) are potent antioxidants, anti-inflammatory, and anti-apoptotic nutraceuticals. We investigated the potential protective effects of these nutraceuticals alone or in combinations against MnCl₂-induced PD in rats. Seven groups of adult male Sprague Dawley rats were categorized as follows: group (I) was the control, while groups 2-7 received MnCl₂ either alone (Group II) or in conjunction with oral doses of sesamol (Group III), thymol (Group IV), CoQ10 (Group V), WG (Group VI), or their combination (Group VII). All rats were subjected to four behavioral tests (open-field, swimming, Y-maze, and catalepsy tests). Biochemical changes in brain levels of monoamines, ACHE, BDNF, GSK-3β, GABA/glutamate, as well as oxidative stress, and apoptotic and neuroinflammatory biomarkers were evaluated, together with histopathological examinations of different brain regions. Mn increased catalepsy scores, while decreasing neuromuscular co-ordination, and locomotor and exploratory activity. It also impaired vigilance, spatial memory, and decision making. Most behavioral impairments induced by Mn were improved by sesamol, thymol, WG, or CoQ10, with prominent effect by sesamol and thymol. Notably, the combination group showed more pronounced improvements, which were confirmed by biochemical, molecular, as well as histopathological findings. Sesamol or thymol showed better protection against neuronal degeneration and some behavioral impairments induced by Mn than WG or CoQ10, partly via interplay between Nrf2/HO-1, TLR4/NLRP3/NF-κB, GSK-3β and Bax/Bcl2 pathways.

Manganese Pollution and Its Remediation: A Review of Biological Removal and Promising Combination Strategies

Manganese (Mn), as a cofactor of multiple enzymes, exhibits great significance to the human body, plants and animals. It is also a critical raw material and alloying element. However, extensive employment for industrial purposes leads to its excessive emission into the environment and turns into a significant threat to the ecosystem and public health. This review firstly introduces the essentiality, toxicity and regulation of Mn. Several traditional physicochemical methods and their problems are briefly discussed as well. Biological remediation, especially microorganism-mediated strategies, is a potential alternative for remediating Mn-polluted environments in a cost-efficient and eco-friendly manner. Among them, microbially induced carbonate precipitation (MICP), biosorption, bioaccumulation, bio-oxidation are discussed in detail, including their mechanisms, pivotal influencing factors along with strengths and limitations. In order to promote bioremediation efficiency, the combination of different techniques is preferable, and their research progress is also summarized. Finally, we propose the future directions of Mn bioremediation by microbes. Conclusively, this review provides a scientific basis for the microbial remediation performance for Mn pollution and guides the development of a comprehensive competent strategy towards practical Mn remediation.

An Overview of the Relationship Between Occupational Manganese Exposure and Parkinsonism

Manganese (Mn) is an essential element used in many industries, such as welding, foundries, the production of metal alloys, especially stainless steel, and the production of dry batteries, pesticides, paints, and explosives. Individuals are exposed to Mn through inhalation of fumes, dermal absorption, and ingestion. This metal is an essential trace element required for normal growth, development, and cellular homeostasis. It has also toxic effects on the central nervous system and can cause Parkinsonism symptoms in exposed patients. Studies on human and animal models reveal that neurons of the globus pallidus, the cerebellum, pons, red nucleus, the thalamus, cortex, and the anterior horn of the spinal cord could be affected by Mn toxicity. Although the diagnosis of manganese-induced Parkinsonism is primarily clinical, there are some supporting features on brain MRI images that may be helpful to objectively distinguish it. This study was designed to review the ways of exposure to Mn, clinical symptoms in case of exposure, and discover the relationship between exposure to Mn and Parkinsonism in the working population.