Bis(N-Heterocyclic Carbene) Manganese(I) Complexes: Efficient and Simple Hydrogenation Catalysts

The use of bis(NHC) manganese(I) complexes 3 as catalysts for the hydrogenation of esters was investigated. For that purpose, a series of complexes has been synthesized via an improved two step procedure utilizing bis(NHC)-BEt3 adducts. By applying complexes 3 with KHBEt3 as additive, various aromatic and aliphatic esters were hydrogenated successfully at mild temperatures and low catalyst loadings, highlighting the efficiency of the novel catalytic system. The versatility of the developed catalytic system was further demonstrated by the hydrogenation of other substrate classes like ketones, nitriles, N-heteroarenes and alkenes. Mechanistic experiments and DFT calculations indicate an inner sphere mechanism with the loss of one CO ligand and reveal the role of BEt3 as cocatalyst.

Cable bacteria regulate sedimentary phosphorus release in freshwater sediments

Previous studies have demonstrated that e-SOx can regulate the sedimentary release of phosphorus (P) in brackish and marine sediments. When e-SOx is active, an iron (Fe) and manganese (Mn) oxide rich layer is formed near the sediment surface, which prevents P release. When e-SOx becomes inactive, the metal oxide layer is reduced via sulfide-mediated dissolution, and P is subsequently released to the water column. Cable bacteria have been shown to also occur in freshwater sediments. In these sediments, sulfide production is limited, and the metal oxide layer would thus dissolve less efficiently, leaving the P trapped at the sediment surface. This lack of an efficient dissolution mechanism implies that e-SOx could play an important role in the regulation of P availability in eutrophied freshwater streams. To test this hypothesis, we incubated sediments from a eutrophic freshwater river to investigate the impact of cable bacteria on sedimentary cycling of Fe, Mn and P. High-resolution depth profiling of pH, O2 and ΣH2S complemented with FISH analysis and high-throughput gene sequencing showed that the development of e-SOx activity was closely linked to the enrichment of cable bacteria in incubated sediments. Cable bacteria activity caused a strong acidification in the suboxic zone, leading to the dissolution of Fe and Mn minerals and consequently a strong release of dissolved Fe2+ and Mn2+ to the porewater. Oxidation of these mobilized ions at the sediment surface led to the formation of a metal oxide layer that trapped dissolved P, as shown by the enrichment of P-bearing metal oxides in the top layer of the sediment and low phosphate in the pore and overlying water. After e-SOx activity declined, the metal oxide layer did not dissolve and P remained trapped at the surface. Overall, our results suggested cable bacteria can play an important role to counteract eutrophication in freshwater systems.

Fe, Mn and me

In over 60 years of research, my team and I have focused on Fe/Mn removal and the application of KMnO4 in drinking water purification, and we have made several technological innovations during this period. In response to the basic need to remove Fe and Mn from groundwater sources in the early days of People's Republic of China, I firstly introduced a catalytic technology involving the application of natural manganese sand produced in China as one of the simplest, cost-effective techniques. During experiments, many phenomena that were inconsistent with conventional theories were observed and a new mechanism was proposed, indicating iron/manganese active films as a catalytic agent instead of MnO2. These films were found to be attached to the surface of natural manganese sand. Fe/Mn-containing compounds with special structures and catalytic features were identified by applying various analytical methods. Drinking water safety was also strengthened by applying KMnO4 as a new cost-effective chemical for source waters facing environmental pollution in China. Experiments showed that KMnO4 can effectively remove many pollutants, including trace organic micro-pollutants, by the combined effects of oxidation and adsorption, which were revealed and confirmed for the first time. Through the application of GC/MS analysis of water samples before and after KMnO4 treatment of samples from various surface water sources, the oxidation by-products from KMnO4 were found to be nontoxic. Therefore, KMnO4 is considered to be a safer chemical in comparison with other conventional oxidants (e.g. HOCl). Previous studies also showed several novel features of KMnO4, such as enhanced coagulation with chlorine, improved algae removal, and increased removal of organically bound manganese. In particular, the combined use of KMnO4 and chlorine could achieve the same disinfection effect at much lower (50%) chlorine dosages. In addition, there are various chemicals and substances that can be combined with KMnO4 to improve decontamination performance. Based on extensive experiments, permanganate compounds were found to be highly efficient in removing heavy metals, e.g., thallium. My research also found that both KMnO4 and powdered activated carbon were highly effective for removing odors and taste. Therefore, we developed a hybrid combination of these two technologies and successfully applied them in many water treatment plants, not only for taste and odor, but also to remove organic micro-pollutants in drinking water. This paper provides a summary of the aforementioned studies that were conducted by me, in collaboration with water treatment industry experts in China, and my graduate students. As a consequence of these studies, several techniques are now widely used in drinking water production in China.

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.

Spinel nanocomposite (nMnZnFe2O4) synchronously promotes grain yield and Fe-Zn biofortification in non-aromatic rice

Soils deficient in essential micro-nutrients produce nutritionally starved crops that do not fulfill human nutritional requirements. This is getting serious since progressively increasing nutritional disorders are being diagnosed in residents of third-world countries like Pakistan. During this study, we synthesized a spinel nanocomposite (nMnZnFe2O4) and investigated its effectiveness in improving the micronutrient status and yield traits of rice. The nMnZnFe2O4 exhibited a cubic structure at the most prominent peak (311); a crystallite size of 44 nm, and an average grain size ranging from 7 to 9 μm. Foliar application of this nanocomposite was performed to 45 days old plants at concentrations 0, 10, 20, 30, 40, and 50 mg L-1, and data from rice plant parts (straw, husk, and grain) was recorded at maturity. Agronomic traits like the number of tillers, straw dry weight, root dry biomass, and grain yield per plant were improved by nMnZnFe2O4 application (+34.4% yield). Whereas some biochemical traits like amino acids, soluble sugars, flavonoids, and phenolics varied significantly in rice plant parts compared to the control. Above all, the maximum Zn and Fe concentrations in rice grain were recorded through foliar application of spinel nanocomposite (40 and 50 mg L-1). Therefore, results indicated that micronutrient supply in the form of a nanocomposite could positively regulate nutritional quality and rice grain yield.

Room temperature X-ray absorption spectroscopy of metalloenzymes with drop-on-demand sample delivery at XFELs

X-ray crystallography and X-ray spectroscopy using X-ray free electron lasers plays an important role in understanding the interplay of structural changes in the protein and the chemical changes at the metal active site of metalloenzymes through their catalytic cycles. As a part of such an effort, we report here our recent development of methods for X-ray absorption spectroscopy (XAS) at XFELs to study dilute biological samples, available in limited volumes. Our prime target is Photosystem II (PS II), a multi subunit membrane protein complex, that catalyzes the light-driven water oxidation reaction at the Mn4CaO5 cluster. This is an ideal system to investigate how to control multi-electron/proton chemistry, using the flexibility of metal redox states, in coordination with the protein and the water network. We describe the method that we have developed to collect XAS data using PS II samples with a Mn concentration of <1 mM, using a drop-on-demand sample delivery method.

Insights into the regulation of cellular Mn2+ homeostasis via TMEM165

Golgi cation homeostasis is known to be crucial for many cellular processes including vesicular fusion events, protein secretion, as well as for the activity of Golgi glycosyltransferases and glycosidases. TMEM165 was identified in 2012 as the first cation transporter related to human glycosylation diseases, namely the Congenital Disorders of Glycosylation (CDG). Interestingly, divalent manganese (Mn) supplementation has been shown to suppress the observed glycosylation defects in TMEM165-deficient cell lines, thus suggesting that TMEM165 is involved in cellular Mn homeostasis. This paper demonstrates that the origin of the Golgi glycosylation defects arises from impaired Golgi Mn homeostasis in TMEM165-depleted cells. We show that Mn supplementation fully rescues the Mn content in the secretory pathway/organelles of TMEM165-depleted cells and hence the glycosylation process. Strong cytosolic and organellar Mn accumulations can also be observed in TMEM165- and SPCA1-depleted cells upon incubation with increasing Mn concentrations, thus demonstrating the crucial involvement of these two proteins in cellular Mn homeostasis. Interestingly, our results show that the cellular Mn homeostasis maintenance in control cells is correlated with the presence of TMEM165 and that the Mn-detoxifying capacities of cells, through the activity of SPCA1, rely on the Mn-induced degradation mechanism of TMEM165. Finally, this paper highlights that TMEM165 is essential in secretory pathway/organelles Mn homeostasis maintenance to ensure both Golgi glycosylation enzyme activities and cytosolic Mn detoxification.

Microglia Signaling Pathway Reporters Unveiled Manganese Activation of the Interferon/STAT1 Pathway and Its Mitigation by Flavonoids

Neuroinflammatory responses to neurotoxic manganese (Mn) in CNS have been associated with the Mn-induced Parkinson-like syndromes. However, the framework of molecular mechanisms contributing to manganism is still unclear. Using an in vitro neuroinflammation model based on the insulated signaling pathway reporter transposon constructs stably transfected into a murine BV-2 microglia line, we tested effects of manganese (II) together with a set of 12 metal salts on the transcriptional activities of the NF-κB, activator protein-1 (AP-1), signal transducer and activator of transcription 1 (STAT1), STAT1/STAT2, STAT3, Nrf2, and metal-responsive transcription factor-1 (MTF-1) via luciferase assay, while concatenated destabilized green fluorescent protein expression provided for simultaneous evaluation of cellular viability. This experiment revealed specific and strong responses to manganese (II) in reporters of the type I and type II interferon-induced signaling pathways, while weaker activation of the NF-κB in the microglia was detected upon treatment of cells with Mn(II) and Ba(II). There was a similarity between Mn(II) and interferon-γ in the temporal STAT1 activation profile and in their antagonism to bacterial LPS. Sixty-four natural and synthetic flavonoids differentially affected both cytotoxicity and the pro-inflammatory activity of Mn (II) in the microglia. Whereas flavan-3-ols, flavanones, flavones, and flavonols were cytoprotective, isoflavones enhanced the cytotoxicity of Mn(II). Furthermore, about half of the tested flavonoids at 10-50 μM could attenuate both basal and 100-200 μM Mn(II)-induced activity at the gamma-interferon activated DNA sequence (GAS) in the cells, suggesting no critical roles for the metal chelation or antioxidant activity in the protective potential of flavonoids against manganese in microglia. In summary, results of the study identified Mn as a specific elicitor of the interferon-dependent pathways that can be mitigated by dietary polyphenols.

Effect of mineral diets on the development of cartilage material properties

Vitamin D and minerals, including zinc (Zn) and manganese (Mn), are vital in the development of bones, but their roles in the development of articular cartilage material behavior are not well understood. In this study, articular cartilage material properties from a hypovitaminosis D porcine model were evaluated. Pigs were produced by sows fed vitamin D deficient diets during gestation and lactation, and the offspring were subsequently fed vitamin D deficient diets for 3 weeks during the nursery period. Pigs were then assigned to dietary treatment groups with inorganic minerals only or inorganic plus organic (chelated) minerals. Humeral heads were harvested from pigs at 24 weeks of age. Linear elastic modulus and dissipated energy were measured under compression to 15% engineering strain at 1 Hz. Anatomical location within the humeral head affected elastic modulus. Diet significantly affected linear modulus and dissipated energy. The largest modulus and highest energy dissipation was in the inorganic zinc and manganese group; the lowest modulus and the least energy dissipation was in the organic (chelated) zinc and manganese group. Pairwise results between the control group and all vitamin D deficient groups were not statistically significant. Overall, these results suggest that mineral availability during rapid growth subsequent to a vitamin-D deficiency during gestation and lactation had minimal effects on articular cartilage material properties in young growing pigs. Though not statistically significant, some of the numerical differences between mineral sources suggest the potential importance of mineral availability during cartilage formation and warrant further study.

Changes in the surface water quality of a tropical watershed in the southeastern amazon due to the environmental impacts of artisanal mining

The expansion of areas of human occupation and the increase in economic activity and deforestation are negatively impacting the Amazon ecosystem. Situated in the Carajás Mineral Province in the southeastern Amazon, the Itacaiúnas River Watershed (IRW) encompasses several active mines and has a historical record of intense deforestation primarily linked with the expansion of pasturelands, but also of urban areas, and mining activities. Industrial mining projects are subjected to strict environmental control, but artisanal mining (ASM; 'garimpos') sites have not been controlled, despite their known environmental impacts. In recent years, the opening and expansion of ASM in the IRW for the exploitation of mineral resources (Au, Mn, and Cu) have been remarkable. This study presents evidence of anthropogenic impacts, mainly caused by ASM, on the quality and hydrogeochemical characteristics of the IRW surface water. The hydrogeochemical data sets of two projects carried out in the IRW, during 2017 and from 2020 until present, were used to evaluate these impacts within the region. Water quality indices were calculated for the surface water samples. For the whole IRW, water collected during the dry season tended to yield better quality indicators in comparison to those collected during the rainy season. Two sampling sites at Sereno Creek showed very poor water quality and extremely high concentrations of Fe, Al, and potentially toxic elements over time. From 2016 to 2022, ASM sites increased markedly. Moreover, there are indications that Mn exploitation via ASM in Sereno hill is the main source of contamination in the area. New trends of ASM expansion were observed along the main watercourses, related to the exploitation of Au from alluvial deposits. Similar anthropogenic impacts are registered in other regions of the Amazon and environmental monitoring should be encouraged to assess the chemical safety of strategic areas.

In vitro studies of manganese transport and homeostasis

Manganese (Mn) is an essential micronutrient required for fundamental cell functions and vital physiological processes. More than a dozen putative Mn transporters have been described over the last two decades, but few have been thoroughly evaluated. Recent genetic studies have revealed vital roles for solute carrier family 39, member 8 (SLC39A8) in Mn homeostasis. SLC39A8 can mediate the cellular uptake of the essential metals zinc, iron, and Mn, as well as the non-essential metal cadmium. However, loss-of-function mutations in SLC39A8 have been found in patients with severe Mn deficiency in the blood without affecting other metals. An in vitro study from our laboratory showed that SLC39A8 is a cell-surface transporter that strongly stimulates 54Mn incorporation into cells (Choi, Nguyen, Gupta, Iwase, & Seo, 2018). By contrast, the disease-associated mutations completely abrogated the cellular uptake of 54Mn (Choi et al., 2018), thereby providing a causal link between SLC39A8 deficiency and Mn deficiency. The importance of SLC39A8 is now increasingly recognized in multiple disease processes, and SLC39A8 has emerged as a critical regulator of Mn homeostasis. Thus, exploring the function of SLC39A8 in cellular Mn homeostasis is of significant research interest. This chapter describes the advanced methods used in our laboratory to examine Mn homeostasis and transport. Specifically, genetic and molecular approaches are described in HeLa cells overexpressing SLC39A8 and disease-associated SLC39A8 mutants. These methods are useful for characterizing the roles of Mn in diverse cellular events.

A fungal functionalized magnetized solid phase extractor for preconcentrations of Pb(II), Mn(II), and Co(II) from real samples

Due to increasing industrialization and overpopulation, the amount of toxic metals is increasing in the environment, including air, soil, water, and food. Solid phase extraction is an efficient and ideal technique to preconcentrate the toxic metals before their measurements by analytical instruments. Russula brevipes was immobilized on γ-Fe₂O₃ magnetic nanoparticles and employed as a SPE sorbent to preconcentrate the trace level of Pb(II), Mn(II), and Co(II). To investigate the extraction conditions, significant experimental parameters were examined in details. LODs were calculated as 0.022, 0.015, and 0.024 ng mL^-1 for Pb(II), Mn(II), and Co(II), respectively. The biosorption capacities of R. brevipes immobilized γ-Fe₂O₃ were calculated as 43.1 mg g^-1 for Pb(II), 54.9 mg g^-1 for Mn(II), and 49.7 mg g^-1 for Co(II). Pb(II), Mn(II), and Co(II) in food samples at trace levels were preconcentrated by applying the developed method.

Early-Life Critical Windows of Susceptibility to Manganese Exposure and Sex-Specific Changes in Brain Connectivity in Late Adolescence

Background

Early-life environmental exposures during critical windows (CWs) of development can impact life course health. Exposure to neuroactive metals such as manganese (Mn) during prenatal and early postnatal CWs may disrupt typical brain development, leading to persistent behavioral changes. Males and females may be differentially vulnerable to Mn, presenting distinctive CWs to Mn exposure.

Methods

We used magnetic resonance imaging to investigate sex-specific associations between early-life Mn uptake and intrinsic functional connectivity in adolescence. A total of 71 participants (15-23 years old; 53% female) from the Public Health Impact of Manganese Exposure study completed a resting-state functional magnetic resonance imaging scan. We estimated dentine Mn concentrations at prenatal, postnatal, and early childhood periods using laser ablation-inductively coupled plasma-mass spectrometry. We performed seed-based correlation analyses to investigate the moderating effect of sex on the associations between Mn and intrinsic functional connectivity adjusting for age and socioeconomic status.

Results

We identified significant sex-specific associations between dentine Mn at all time points and intrinsic functional connectivity in brain regions involved in cognitive and motor function: 1) prenatal: dorsal striatum, occipital/frontal lobes, and middle frontal gyrus; 2) postnatal: right putamen and cerebellum; and 3) early childhood: putamen and occipital, frontal, and temporal lobes. Network associations differed depending on exposure timing, suggesting that different brain networks may present distinctive CWs to Mn.

Conclusions

These findings suggest that the developing brain is vulnerable to Mn exposure, with effects lasting through late adolescence, and that females and males are not equally vulnerable to these effects. Future studies should investigate cognitive and motor outcomes related to these associations.

Neuroinflammation and white matter alterations in occupational manganese exposure assessed by diffusion basis spectrum imaging

OBJECTIVE

To evaluate in-vivo neuroinflammation and white matter (WM) microstructural integrity in occupational manganese (Mn) exposure.

METHODS

We assessed brain inflammation using Diffusion Basis Spectrum Imaging (DBSI) in 26 Mn-exposed welders, 17 Mn-exposed workers, and 26 non-exposed participants. Cumulative Mn exposure was estimated from work histories and the Unified Parkinson's Disease Rating Scale motor subsection 3 (UPDRS3) scores were completed by a movement specialist. Tract-based Spatial Statistics allowed for whole-brain voxel-wise WM analyses to compare WM DBSI-derived measures between the Mn-exposed and non-exposed groups. Exploratory grey matter region of interest (ROI) analyses examined the presence of similar alterations in the basal ganglia. We used voxelwise general linear modeling and linear regression to evaluate the association between cumulative Mn exposure, WM or basal ganglia DBSI metrics, and UPDRS3 scores, while adjusting for age.

RESULTS

Mn-exposed welders had higher DBSI-derived restricted fraction (DBSI-RF), higher DBSI-derived nonrestricted fraction (DBSI-NRF), and lower DBSI-derived fiber fraction (DBSI-FF) in multiple WM tracts (all p < 0.05) in comparison to less-exposed workers and non-exposed participants. Basal ganglia ROI analyses revealed higher average caudate DBSI-NRF and DBSI-derived radial diffusion (DBSI-RD) values in Mn-exposed welders relative to non-exposed participants (p < 0.05). Caudate DBSI-NRF was also associated with greater cumulative Mn exposure and higher UPRDS3 scores.

CONCLUSIONS

Mn-exposed welders demonstrate greater DBSI-derived indicators of neuroinflammation-related cellularity (DBSI-RF), greater extracellular edema (DBSI-NRF), and lower apparent axonal density (DBSI-FF) in multiple WM tracts suggesting a neuroinflammatory component in the pathophysiology of Mn neurotoxicity. Caudate DBSI-NRF was positively associated with both cumulative Mn exposure and clinical parkinsonism, indicating a possible dose-dependent effect on extracellular edema with associated motor effects.

Risk factors and clinical features associated with basal ganglia manganese deposition in patients with hereditary hemorrhagic telangiectasia

BACKGROUND

T1-hyperintensity of the basal ganglia (BG) due to manganese deposition is a known radiologic finding in patients with hereditary hemorrhagic telangiectasia (HHT), but risk factors and associated clinical manifestations are unclear. This study conducted a quantitative analysis of the association of T1-hyperintensity in HHT patients with specific risk factors, signs, and symptoms.

METHODS

Patients seen at our center between 2005 and 2020 with a definitive diagnosis of HHT who had an available non-contrast T1-weighted brain MRI were included. Hyperintensity was evaluated using oval regions of interest measurements. The BG: thalamus intensity ratio was used to quantitatively evaluate T1-hyperintensity. Patient laboratory values and clinical findings were collected from electronic medical records. Hyperintensity was analyzed for its association with laboratory values, and clinical findings. Variables were analyzed through regression analysis.

RESULTS

A total of 239 patients were included in this study. On 1.5 T scanners, values that were significant on multivariable regression analysis were age (p < .001), hepatic AVMs (p < .001), iron deficiency anemia (p = .0021), and cirrhosis (p = .016). On 3 T scanners, values that were significant on multivariable analysis were hepatic AVMs (p = .0024) and cirrhosis (p = .0056). On 3 T scanners, hyperintensity was significantly associated with tremor (OR = 1.17, p = .033), restless leg syndrome (OR = 1.22, p = .0086), and memory problems (OR = 1.17, p = .046).

CONCLUSIONS

BG hyperintensity due to manganese deposition is significantly associated with hepatic risk factors on 1.5 T and 3 T scanners and iron deficiency anemia on 1.5 T scanners. On 3 T scanners, T1-hyperintensity is associated with neuropsychiatric signs and symptoms, such as tremor, restless leg syndrome, and memory problems.

Research progress in green synthesis of manganese and manganese oxide nanoparticles in biomedical and environmental applications - A review

Nanomaterials and nanotechnology have this unassailable position for environmental remediation and medicine. Currently, global environmental pollution and public health problems are increasing and need to be urgently addressed. Manganese (Mn) is one of the essential metal elements for plants and animals, it is necessary to integrate with nanotechnology. Mn and Mn oxide (MnO) nanoparticles (NPs) have applications in dye degradation, biomedicine, electrochemical sensors, plant and animal growth, and catalysis. However, the current research is limited, especially in terms of optimal synthesis of Mn and MnO NPs, separation, purification conditions, and the development of potential application areas is too basic and do not support by in-depth studies. Hence, this review comprehensively discusses the classification, green synthesis methods, and applications of Mn and MnO NPs in biomedical, environmental, and other fields and gives a perspective for the future.

AP10 harboured in Arabis paniculata mediates plant growth promotion and manganese detoxification

Phytoremediation of heavy metal-polluted soils assisted by plant-associated endophytes, is a suitable method for plant growth and manganese (Mn) removal in contaminated soils. This investigation was conducted to evaluate the Mn-resistant endophytic resources of the Mn hyperaccumulator Arabis paniculata and their functions in the phytoremediation of Mn²⁺ toxicity. This study isolated an endophytic bacterium with high Mn resistance and indole-3-acetic acid (IAA) production form A. paniculata and identified it as Bacillus sp. AP10 using 16 S rRNA gene sequencing analysis. The effects of Bacillus sp. AP10 on the alleviation of Mn²⁺ toxicity in Arabidopsis thaliana seedlings and the molecular mechanisms were further investigated using biochemical tests and RNA-seq analysis. Under Mn²⁺ stress, Bacillus sp. AP10 increased the biomass, chlorophyll content and the translocation factor (TF) values of Mn in the aerial parts, while decreased the malondialdehyde (MDA) content of A. thaliana seedlings compared with that of control plants. The differentially expressed genes (DEGs) and enrichment analysis showed that Bacillus sp. AP10 could significantly increase the expression of key genes involved in cell-wall loosening, which may improve plant growth under Mn stress. Superoxide dismutase (SOD)-encoding genes were detected as DEGs after AP10 treatment. Moreover, AP10 regulated the expression of genes responsible for phenylpropanoid pathway, which may promote antioxidant flavonoids accumulation for reactive oxygen species (ROS) scavenging to improve Mn tolerance. The activation of ATP-binding cassette (ABC) transporter gene expression especially ABCB1 after AP10 stimulation, explained the elevation of metal ion binding or transport related to enhanced Mn accumulation in plants. Futhermore, AP10 might alleviate Mn toxicity through enhancing abscisic acid (ABA) responsive gene expression and ABA biosynthesis. These findings provide new insights into the functions and regulatory mechanism of Bacillus sp. AP10 in promoting plant growth, and tolerance, improving Mn accumulation and alleviating Mn²⁺ toxicity in plants. The application of Bacillus sp. AP10 as potential phytoremediators may be a promising strategy in Mn²⁺ contaminated fields. AVAILABILITY OF DATA AND MATERIALS: The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Manganese-Catalyzed Redox-Neutral Thiolation of Alkyl Halides with Thioformates

Transition metal-catalyzed C-S cross-coupling has emerged as an important strategy to furnish thioethers; however, the dominant utilization of noble metal catalysts as well as the construction of challenging C(sp3)-S bonds by transition metal-catalysis remain highly problematic. Earth-abundant manganese has gathered increasing interest as an attractive catalyst for new reaction development; nevertheless, C(sp3)-S cross-coupling reaction by manganese catalysis has not been reported. Herein, we disclose a highly efficient manganese-catalyzed redox-neutral thiolation of a broad range of alkyl halides with thioformates as practical sulfuration agents. Strategically, employing easily synthesized thioformates as thiyl radical precursors allows access to various aryl and alkyl thioethers in good to excellent yields. Notably, this redox-neutral method avoids the utilization of strong bases, external ligands, forcing reaction conditions, and stoichiometric manganese, thus presenting apparent advantages, such as broad substrate scope, excellent functional group compatibility, and mild reaction conditions. Finally, the utilities of this method are also illustrated by downstream transformations and late-stage thiolation of structurally complex natural products and pharmaceuticals.

New insights into the pathogenicity of TMEM165 variants using structural modeling based on AlphaFold 2 predictions

TMEM165 is a Golgi protein playing a crucial role in Mn²⁺ transport, and whose mutations in patients are known to cause Congenital Disorders of Glycosylation. Some of those mutations affect the highly-conserved consensus motifs E-φ-G-D-[KR]-[TS] characterizing the CaCA2/UPF0016 family, presumably important for the transport of Mn²⁺ which is essential for the function of many Golgi glycosylation enzymes. Others, like the G>R³⁰⁴ mutation, are far away from these motifs in the sequence. Until recently, the classical membrane protein topology prediction methods were unable to provide a clear picture of the organization of TMEM165 inside the cell membrane, or to explain in a convincing manner the impact of patient and experimentally-generated mutations on the transporter function of TMEM165. In this study, AlphaFold 2 was used to build a TMEM165 model that was then refined by molecular dynamics simulation with membrane lipids and water. This model provides a realistic picture of the 3D protein scaffold formed from a two-fold repeat of three transmembrane helices/domains where the consensus motifs face each other to form a putative acidic cation-binding site at the cytosolic side of the protein. It sheds new light on the impact of mutations on the transporter function of TMEM165, found in patients and studied experimentally in vitro, formerly and within this study. More particularly and very interestingly, this model explains the impact of the G>R³⁰⁴ mutation on TMEM165's function. These findings provide great confidence in the predicted TMEM165 model whose structural features are discussed in the study and compared to other structural and functional TMEM165 homologs from the CaCA2/UPF0016 family and the LysE superfamily.

A comparative study of serum Zn, Cu, Mg, Mn, Cr, and Fe levels and their association with the vulnerability of Iraqi COVID-19 patients

BACKGROUND

For the immune system to protect the body from infectious diseases such as COVID-19, it needs the ideal amount of vital trace elements. Trace element levels, especially, zinc (Zn), copper (Cu), magnesium (Mg), manganese (Mn), chromium (Cr), and iron (Fe) levels, may affect how sensitive an individual is to COVID-19 and other viruses. The current study evaluated the level of those trace elements during stays in the isolation center and investigated their association with vulnerability to COVID-19.

METHODS

A total of 120 individuals, 49 males and 71 females aged between 20 and 60 years, were included in this study. Forty individuals infected with COVID-19, 40 individuals who had recovered from it, and 40 healthy individuals, were all evaluated and studied. By using a flame atomic absorption spectrophotometer, levels of Zn, Cu, and Mg were assessed for all samples, whereas levels of Mn, and Cr were determined by a flameless atomic absorption spectrophotometer.

RESULTS

The infected individuals had significantly lower levels of Zn, Mg, Mn, Cr, and Fe than recovered individuals and healthy control individuals (P < 0.0001). On the other hand, the total number of infected patients was found to have much higher levels of Cu than those in the recovered group and the control group. For the recovered and healthy control groups, no significant differences were observed in the levels of trace elements (P > 0.05), except for Zn (P < 0.01). Also, the findings indicated no association of trace elements with age and BMI (P > 0.05).

CONCLUSION

These results show that an imbalance in the levels of essential trace elements could be associated with increasing the risk of COVID-19 infection. However, additional thorough research of greater scope is required considering the severity of the infection.

Genome-wide identification of the NRAMP gene family in Populus trichocarpa and their function as heavy metal transporters

The natural resistance-associated macrophage protein (NRAMP) gene family plays a key role in essential mineral nutrient homeostasis, as well as toxic metal accumulation, translocation, and detoxification. Although the NRAMP family genes have been widely identified in various species, they still require to be analyzed comprehensively in tree species. In this study, a total of 11 NRAMP members (PtNRAMP1-11) were identified in Populus trichocarpa, a woody model plant, and further subdivided into three groups based on phylogenetic analysis. Chromosomal location analysis indicated that the PtNRAMP genes were unevenly distributed on six of the 19 Populus chromosomes. Gene expression analysis indicated that the PtNRAMP genes were differentially responsive to metal stress, including iron (Fe) and manganese (Mn) deficiency, as well as Fe, Mn, zinc (Zn), and cadmium (Cd) toxicity. Furthermore, the PtNRAMP gene functions were characterized using a heterologous yeast expression system. The results showed that PtNRAMP1, PtNRAMP2, PtNRAMP4, PtNRAMP9, PtNRAMP10, and PtNRAMP11 displayed the ability to transport Cd into yeast cells. In addition, PtNRAMP1, PtNRAMP6, and PtNRAMP7 complemented the Mn uptake mutant, while PtNRAMP1, PtNRAMP6, PtNRAMP7, and PtNRAMP9 complemented the Fe uptake mutant. In conclusion, our findings revealed the respective functions of PtNRAMPs during metal transport as well as their potential role in micronutrient biofortification and phytoremediation.

Synergistic effect of Mn-Si-COS on wound immune microenvironment by inhibiting excessive skin fibrosis mediated with ROS/TGF-β1/Smad7 signal

Excessive oxidative stress and inflammation often impede wound healing and ultimately lead to excessive skin fibrosis formation. It was known that the structural properties of biomaterials can affect the healing and immune response of surrounding tissues. In this work, a composite structure of Mn-Si-chitooligosaccharides (COS) was designed (COS@Mn-MSN) and the ability of regulating wound microenvironment for inhibiting skin fibrosis was investigated. In order to reduce the negative effects of Mn, the nano-level Mn was doped into MSN to minimize its content. The results show that Mn in COS@Mn-MSN showed significant ability of scavenging excess intracellular ROS within 1 d. The Si released from COS@Mn-MSN can shift M2 macrophage polarization in the later stage (1-3 d), showing anti-inflammatory effect. Macrophage (RAW264.7) were activated alternatively by COS released from COS@Mn-MSN, with upregulated expression of anti-inflammatory factors (IL-10 and CD206) and downregulated expression of pro-inflammatory factors (TNF-α, CD80, and IL-1β) in the whole time. The expression of fibrosis associated factor TGF-β1 and CD26 in fibroblast cells (L929) were inhibited by COS and Si. Besides, the inflammatory microenvironment mediated by COS@Mn-MSN downregulated Smad-7 gene expression and upregulated Col-1α gene expression. With the function of reducing oxidative stress (0-1 d), the TGF-β1 inhibition (1-3 d) and anti-inflammatory effects (0-3 d), COS@Mn-MSN could inhibit excessive skin fibrosis formation mediated with ROS/TGF-β1/Smad7 signal. Therefore, the prepared COS@Mn-MSN shows great potential to active scarless wound therapy.

Enhanced removal of phenanthrene and nutrients in wetland sediment with metallic biochar: Performance and mechanisms

Polycyclic aromatic hydrocarbon (PAHs) are persistent organic pollutants and pose high risk in aquatic environment. The utilization of biochar is a strategy for PAHs-contaminated remediation but is challenging due to the adsorption saturation and reoccurrence of PAHs desorbed back into water. In this study, iron (Fe) and manganese (Mn) were provided as electron acceptors for biochar modification to enhance anaerobic biodegradation of phenanthrene (Phe). Results revealed that, the Mn(Ⅳ) and Fe(Ⅲ) modification improved the removal of Phe by 24.2% and 31.4% than that of biochar, respectively. Additionally, nitrate removal was improved by 19.5% with Fe(Ⅲ) amendment. The Mn-and Fe-biochar decreased Phe contents by 8.7% and 17.4% in sediment, 10.3% and 13.8% in biochar than that of biochar. Much higher DOC contents were observed with Mn- and Fe-biochar, which provided bioavailable carbon source for microbes and contributed to microbial degradation of Phe. The greater degree of humification, higher proportions of humic and fulvic acid like components in metallic biochar participated in electron transport and further enhancing the degradation of PAHs. Microbial analysis proved the high abundance of Phe-degrading bacteria (e.g. PAH-RHD_α, Flavobacterium and Vibrio), nitrogen removal microbes (e.g. amoA, nxrA, and nir), Fe and Mn bioreduction or oxidation (e. g. Bacillus, Thermomonas, Deferribacter) with metallic biochar. Based on the results, the Fe and Mn modification, especially Fe-modified biochar provided well performance for PAHs removal in aquatic sediment.

Hair Trace Elements and Mineral Content in Moroccan Children with Autism Spectrum Disorder: a Case-Control Study

The prevalence of autism spectrum disorder (ASD) around the world continues to increase while the pathophysiology remains insufficiently elucidated. Genetics, environment, and epigenetic changes are often implicated. Abnormal level in trace elements and minerals is among environmental factors assumed to be involved. The purpose of this article is to assess hair concentrations of toxic and essential elements in children with ASD and children with neurotypical development in the city of Marrakech. Two hundred and twenty-seven children (107 with ASD and 120 controls) aged 3 to 14 years old were recruited. The results of analysis by ICP-MS showed a significant decrease in hair levels of copper, zinc, iron, and selenium (25%, 13%, 17%, 11%) of children with ASD. The most significantly reduced concentrations in children with ASD are that of manganese by 34%. Hair aluminum level was significantly elevated by 29% in ASD compared to controls. Multiple linear regression analysis revealed that copper, selenium, and iron content in hair were significantly inversely associated with ASD, similarly, hair aluminum content was significantly associated with ASD. Adjusted model for demographic parameters increased the predictive ability of the model, father's age was a significant predictor. In addition, ASD and gender were significant predictors of hair levels of aluminum, selenium, and manganese.These results support the hypothesis of the disparity of trace elements and minerals levels in children with ASD and highlight the potential interest of micronutrient supplementation in the eventual improvement of ASD symptoms. Future research should explore the pathophysiology of these micronutrient deficiencies.

A simple and highly reproducible method for the detection of erythrocyte membrane ZIP metal transporters by immunoblotting

Manganese is one of the essential trace elements found in erythrocytes. Metal transporters situated on the plasma membrane generally facilitate the movement of manganese into and out of cells. This study aims at determining whether two recently discovered manganese importers, ZIP8 and ZIP14, are located in the erythrocyte membrane. We outline a simple, effective and repeatable method for the isolation of erythrocyte membrane from a minimum of 50 µL mouse blood, followed by the identification of ZIP metal transporters using immunoblotting. Our results revealed that ZIP8 is expressed within the erythrocyte membrane, in contrast to ZIP14 which is not identified using immunoblotting approach. A direct measurement of the ZIP8 protein expression in erythrocyte membranes could provide valuable information for further analyzing its biological function.

Stabilization/solidification of Mn-contaminated clay slurry by using CaO-GGBS: Effects of anions

Clay sediment is removed by dredging, resulting in the disposal of enormous waste sediment clay slurries that consumes land space, as well as risks the human health and the environment. Manganese (Mn) is often identified in clay slurries. Quicklime (CaO)-activated ground granulated blast-furnace slag (GGBS) can be used to stabilize/solidify (S/S) contaminated soils; nevertheless, few studies have been published on the S/S of Mn-contaminated clay slurries using CaO-GGBS. Moreover, the anions contained in clay slurries may affect the S/S efficiency of CaO-GGBS in treating Mn-contaminated clay slurries, but this effect has hardly been investigated. Therefore, this study investigated the S/S efficiency of CaO-GGBS in treating MnSO₄-bearing and Mn(NO₃)₂-bearing clay slurries. The effect of anions (i.e. SO₄^2- and NO₃^-) on the strength, leachability, mineralogy, and microstructure of Mn-contaminated clay slurries treated with CaO-GGBS was explored. Results showed that CaO-GGBS could improve the strength of both Mn-contaminated slurries to meet the strength requirement for landfill waste outlined by United States Environmental Protection Agency (USEPA). The Mn leachabilities of both Mn-contaminated slurries were decreased to be less than the Euro limit for drinking water after cured for 56 days. The MnSO₄-bearing slurry generally produced higher UCS while lower Mn leachability than Mn(NO₃)₂-bearing slurry at the same CaO-GGBS addition. CSH and Mn(OH)₂ were formed, thereby enhancing strength and reducing leachability of Mn. Ettringite in CaO-GGBS-treated MnSO₄-bearing slurry, which was formed by the supply of SO₄^2- from MnSO₄, further contributed to the strength enhancement and the decrease of Mn leachability. Ettringite was the factor leading to the difference in strength and leaching properties between MnSO₄-bearing and Mn(NO₃)₂-bearing clay slurries. Hence, anions contained in Mn-contaminated slurries significantly affected the strength and the Mn leachability, and need to be identified before CaO-GGBS was used to treat such slurries.

Amorphous mixed-valent Mn-containing nanozyme with cocklebur-like morphology for specific colorimetric detection of cancer cells via Velcro effects

Designing nanozymes with excellent catalytic activity through valence state engineering and defect engineering is a widely applicable strategy. However, their development is hindered by the complexity of the design strategies. In this work, we employed a simple calcination method to regulate the valence of manganese and crystalline states in manganese oxide nanozymes. The oxidase-like activity of the nanozymes was found to benefit from a mixed valence state dominated by Mn (III). And the amorphous structure with more active defect sites significantly enhanced the catalytic efficiency. Moreover, we demonstrated that amorphous mixed-valent Mn-containing (amvMn) nanozymes with unique cocklebur-like biomimetic morphology achieved specific binding to cancer cells through the Velcro effects. Subsequently, the nanozymes mediated TMB coloration through their oxidase-like activity, enabling the colorimetric detection of cancer cells. This work not only provides guidance for optimizing nanozyme performance, but also inspire the development of equipment-free visual detection methods for cancer cells.

High-frequency sensor data capture short-term variability in Fe and Mn concentrations due to hypolimnetic oxygenation and seasonal dynamics in a drinking water reservoir

The biogeochemical cycles of iron (Fe) and manganese (Mn) in lakes and reservoirs have predictable seasonal trends, largely governed by stratification dynamics and redox conditions in the hypolimnion. However, short-term (i.e., sub-weekly) trends in Fe and Mn cycling are less well-understood, as most monitoring efforts focus on longer-term (i.e., monthly to yearly) time scales. The potential for elevated Fe and Mn to degrade water quality and impact ecosystem functioning, coupled with increasing evidence for high spatiotemporal variability in other biogeochemical cycles, necessitates a closer evaluation of the short-term Fe and Mn dynamics in lakes and reservoirs. We adapted a UV-visible spectrophotometer coupled with a multiplexor pumping system and partial least squares regression (PLSR) modeling to generate high spatiotemporal resolution predictions of Fe and Mn concentrations in a drinking water reservoir (Falling Creek Reservoir, Vinton, VA, USA) equipped with a hypolimnetic oxygenation (HOx) system. We quantified hourly Fe and Mn concentrations during two transitional periods: reservoir turnover (Fall 2020) and HOx initiation (Summer 2021). Our sensor system successfully predicted mean Fe and Mn concentrations and trends, ground-truthed by grab sampling and laboratory analysis. During fall turnover, hypolimnetic Fe and Mn concentrations began to decrease more than two weeks before complete mixing of the reservoir, with rapid equalization of epilimnetic and hypolimnetic Fe and Mn concentrations in less than 48 h after full water column mixing. During the initiation of HOx in Summer 2021, Fe and Mn displayed distinctly different responses to oxygenation, as indicated by the rapid oxidation of soluble Fe but not soluble Mn. This study demonstrates that Fe and Mn concentrations are sensitive to changes in redox conditions induced by stratification and oxygenation, although their responses to these changes differ. We also show that high spatio-temporal resolution predictions of Fe and Mn can improve drinking water monitoring programs and reservoir management practices.

Association of blood manganese concentrations with 24-h based brachial and central blood pressure, and pulse-wave velocity

Potential environmental determinants of BP and hypertension in older adults are far less known than their lifestyle risk factors. Manganese (Mn) is an essential element for life that may induce changes in blood pressure (BP), but the direction of the association is unclear. We aimed to examine the association of blood manganese (bMn) with 24-h-based brachial, central BP (cBP), and pulse-wave velocity (PWV). With this purpose, we analyzed data from 1009 community-living adults aged >65 years without BP medication. bMn was measured using inductively-coupled plasma-mass spectrometry and 24-h BP with validated devices. The association of bMn (median: 6.77 μg/L; IQR: 5.59-8.27) with daytime brachial and central systolic (SBP) and with diastolic BP (DBP) was non-linear, with BP increases up to around the median of Mn and then stabilization or slight rightward decrease. Mean BP differences (95% confidence interval) comparing Mn Q2 to Q5 (vs Q1 quintile) for brachial daytime SBP were 2.56 (0.22; 4.90), 3.59 (1.22; 5.96), 3.14 (0.77; 5.51) and 1.72 (-0.68; 4.11) mmHg, respectively; and 2.22 (0.70, 3.73), 2.55 (1.01, 4.08), 2.45 (0.91; 3.98), and 1.68 (0.13; 3.24), respectively, for DBP. Daytime central-pressures showed a similar dose-response relationship with bMn as daytime brachial-pressures. The association with nighttime BP was linearly positive for brachial BPs, and only increasing for Q5 for cBP. Regarding PWV, a tendency to significant linear increase along bMn levels was observed (p-trend = 0.042). The present findings extend the scarce evidence on the association between Mn and brachial BP to 2 other vascular parameters, suggesting Mn levels as a candidate risk factor for increasing levels of both brachial and cBPs in older adults, yet further research is needed with larger cohort studies in adults at all age ranges.

Manganese triggers persistent activation of the integrated stress response by inhibition of SIRT1 on deacetylation of GADD34

Overexposure to manganese (Mn) is conductive to neurodegenerative diseases and neuronal injury. Persistent activation of the integrated stress response (ISR) has a substantial impact on the etiology of neurodegenerative disorders by interfering with intracellular homeostasis. Nevertheless, the precise mechanism through which ISR engages in Mn-related neurotoxicity remains unclear. Sirtuin 1 (SIRT1), a typical NAD⁺-dependent protein deacetylase, which is known to participate in Mn-induced neuronal damage. Therefore, the aim of our study was to clarify how SIRT1 regulates persistent ISR activation in mouse hippocampal neuronal cells (HT-22 cells) exposed to various concentrations of Mn. We discovered that persistent ISR activation was engaged in Mn-triggered mitochondrial and exogenous apoptotic signaling pathways, which was attributed to the excessive phosphorylation of eukaryotic translation initiation factor 2α (eIF2α). Growth arrest and DNA damage-inducible protein 34 (GADD34) is known to be responsible for down-regulating the phosphorylation of eIF2α. However, Mn promoted GADD34 protein expression and its acetylation level. We further investigated the effect of SIRT1 on the acetylation of GADD34 by overexpressing and silencing SIRT1. We discovered that SIRT1 activation significantly declined the acetylation level of GADD34, thus alleviating persistent ISR activation-mediated neuronal apoptosis in HT-22 cells-treated with Mn. In summary, these results suggested that Mn induced persistent activation of the ISR by inhibition of SIRT1 on deacetylation of GADD34.

Deciphering the role of metal and non-metals in the treatment of epilepsy

Metals and non-metals have known to play a significant role in various physiological roles in the body including the central nervous system (CNS). The alterations in their concentration in the CNS leads to abnormalities in the normal functions which may lead to various neurological conditions including epilepsy. Manganese is a cofactor required for antioxidant enzymes such as Superoxide dismutase, Glutamine synthetase, etc. The accumulation of iron leads to formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) which have the potential to cause ferroptosis, one of the reasons for epileptogenesis. Zinc has biphasic response, both neurotoxic and neuroprotective, based on concentration levels in the CNS. Selenium is a main element for selenoproteins which is responsible for the regulation of oxidative state and antioxidant defence mechanism. The reduction in the phosphorous levels in the CNS is widely observed after generalised tonic clonic seizures (GTC), which can be a potential diagnostic biomarker. Copper acts in the CNS in an identical manner, i.e., by blocking both AMPA mediated and GABA mediated neuronal transmission. Magnesium blocks calcium channels in the NMDA receptor and prevents glutamatergic transmission, thus inhibiting excitotoxicity. Lithium acts as a proconvulsive agent and is used in combination with pilocarpine to induce seizures. The identified potential of metals and non-metals in epilepsy can be utilised in order to devise new adjuvant therapies for the management of epilepsy. The article summaries in depth the role of metals and non-metals in the treatment of epilepsy supported with special paragraph on author perspective on to the topic. Furthermore, an update of preclinical and clinical evidences are discussed in the review to give evidence on metal and non-metal based therapies in epilepsy.

Chemoselective α-Alkylation of Nitriles with Primary Alcohols by Manganese(I)-Catalysis

A sustainable and easy-to-use protocol for the alkylation of aryl nitriles with the earth-abundant manganese(I) catalyst is presented. The alkylation reaction employs readily available nitriles and naturally abundant alcohols as the coupling partners. The reaction proceeds chemoselectively and encompasses a broad substrate scope with good to excellent yields. The catalytic reaction yields selectively α-branched nitriles and water as the sole byproduct. Experimental studies were executed to understand the mechanism of the catalytic reaction.

Impacts of calcium peroxide on phosphorus and tungsten releases from sediments

In this study, CaO₂ was used as a capping material to control the release of Phosphate (P) and tungsten (W) from the sediment due to its oxygen-releasing and oxidative properties. The results revealed significant decreases in SRP and soluble W concentrations after the addition of CaO₂. The mechanisms of P and W adsorption by CaO₂ were mainly chemisorption and ligand exchange mechanisms. In addition, the results showed significant increases in HCl-P and amorphous and poorly crystalline(oxyhydr)oxides bound W after the addition of CaO₂. The highest reduction rates of sediment SRP and soluble W release were 37 and 43%, respectively. Furthermore, CaO₂ can promote the redox of iron (Fe) and manganese (Mn). On the other hand, a significant positive correlation was observed between SRP/soluble W and soluble Fe (II) and between SRP/soluble W and soluble Mn, indicating that the effects of CaO₂ on Fe and Mn redox play a crucial role in controlling P and W releases from sediments. However, the redox of Fe plays a key role in controlling sediment P and W release. Therefore, CaO₂ addition can simultaneously inhibit sediment internal P and W release.

Manganese uptake mediated by the NRAMP-type transporter MntH is required for acid tolerance in Listeria monocytogenes

Listeria monocytogenes is a foodborne pathogen that is characterized by its ability to withstand mild stresses (i.e. cold, acid, salt) often encountered in food products or food processing environments. In the previous phenotypic and genotypic characterization of a collection of L. monocytogenes strains, we have identified one strain 1381, originally obtained from EURL-lm, as acid sensitive (reduced survival at pH 2.3) and extremely acid intolerant (no growth at pH 4.9, which supports the growth of most strains). In this study, we investigated the cause of acid intolerance in strain 1381 by isolating and sequencing reversion mutants that were capable of growth at low pH (pH 4.8) to a similar extent as another strain (1380) from the same MLST clonal complex (CC2). Whole genome sequencing showed that a truncation in mntH, which encodes a homologue of an NRAMP (Natural Resistance-Associated Macrophage Protein) type Mn²⁺ transporter, is responsible for the acid intolerance phenotype observed in strain 1381. However, the mntH truncation alone was not sufficient to explain the acid sensitivity of strain 1381 at lethal pH values as strain 1381R1 (a mntH⁺ revertant) exhibited similar acid survival to its parental strain at pH 2.3. Further growth experiments demonstrated that Mn²⁺ (but not Fe²⁺, Zn²⁺, Cu²⁺, Ca²⁺, or Mg²⁺) supplementation fully rescues the growth of strain 1381 under low pH conditions, suggesting that a Mn²⁺ limitation is the likely cause of growth arrest in the mntH^- background. Consistent with the important role of Mn²⁺ in the acid stress response was the finding that mntH and mntB (both encoding Mn²⁺ transporters) had higher transcription levels following exposure to mild acid stress (pH 5). Taken together, these results provide evidence that MntH-mediated Mn²⁺ uptake is essential for the growth of L. monocytogenes under low pH conditions. Moreover, since strain 1381 was recommended for conducting food challenge studies by the European Union Reference Laboratory, the use of this strain in evaluating the growth of L. monocytogenes in low pH environments where Mn²⁺ is scarce should be reconsidered. Furthermore, since it is unknown when strain 1381 acquired the mntH frameshift mutation, the ability of the strains used for challenge studies to grow under food-related stresses needs to be routinely validated.

SIRT1/FOXO3-mediated autophagy signaling involved in manganese-induced neuroinflammation in microglia

Manganese (Mn), as one of the environmental risk factors for Parkinson's disease (PD), has been widely studied. Though autophagy dysfunction and neuroinflammation mainly are responsible for the causative issue of Mn neurotoxicity, the molecular mechanism of parkinsonism caused by Mn has not been explored clearly. The results of in vivo and in vitro experiments showed that overexposure to Mn caused neuroinflammation impairment and autophagy dysfunction, accompanied by the increase of IL-1β, IL-6, and TNF-α mRNA expression, and nerve cell apoptosis, microglia cell activation, NF-κB activation, poor neurobehavior performance. This is due to Mn-induced the downregulation of SIRT1. Upregulation of SIRT1 in vivo and in vitro could alleviate Mn-induced autophagy dysfunction and neuroinflammation, yet these beneficial effects were abolished following 3-MA administration. Furthermore, we found that Mn interfered with the acetylation of FOXO3 by SIRT1 in BV2 cells, leading to a decrease in the nuclear translocation of FOXO3, and its binding of LC3B promoter and transcription activity. This could be antagonized by the upregulation of SIRT1. Finally, it is proved that SIRT1/FOXO3-LC3B autophagy signaling involves in Mn-induced neuroinflammation impairment.

Associations of an industry-relevant metal mixture with verbal learning and memory in Italian adolescents: The modifying role of iron status

BACKGROUND

Biomarker concentrations of metals are associated with neurodevelopment, and these associations may be modified by nutritional status (e.g., iron deficiency). No prior study on associations of metal mixtures with neurodevelopment has assessed effect modification by iron status.

OBJECTIVES

We aimed to quantify associations of an industry-relevant metal mixture with verbal learning and memory among adolescents, and to investigate the modifying role of iron status on those associations.

METHODS

We used cross-sectional data from 383 Italian adolescents (10-14 years) living in proximity to ferroalloy industry. Verbal learning and memory was assessed using the California Verbal Learning Test for Children (CVLT-C), and metals were quantified in hair (manganese, copper, chromium) or blood (lead) using inductively coupled plasma mass spectrometry. Serum ferritin, a proxy for iron status, was measured using immunoassays. Covariate-adjusted associations of the metal mixture with CVLT subtests were estimated using Bayesian Kernel Machine Regression, and modification of the mixture associations by ferritin was examined.

RESULTS

Compared to the 50th percentile of the metal mixture, the 90th percentile was associated with a 0.12 standard deviation [SD] (95% CI = -0.27, 0.50), 0.16 SD (95% CI = -0.11, 0.44), and 0.11 SD (95% CI = -0.20, 0.43) increase in the number of words recalled for trial 5, long delay free, and long delay cued recall, respectively. For an increase from its 25th to 75th percentiles, copper was beneficially associated the recall trials when other metals were fixed at their 50th percentiles (for example, trial 5 recall: β = 0.31, 95% CI = 0.14, 0.48). The association between copper and trial 5 recall was stronger at the 75th percentile of ferritin, compared to the 25th or 50th percentiles.

CONCLUSIONS

In this metal mixture, copper was beneficially associated with neurodevelopment, which was more apparent at higher ferritin concentrations. These findings suggest that metal associations with neurodevelopment may depend on iron status, which has important public health implications.

The Optimized Homogenization Process of Cast 7Mo Super Austenitic Stainless Steel

Super austenitic stainless steels are expected to replace expensive alloys in harsh environments due to their superior corrosion resistance and mechanical properties. However, the ultra-high alloy contents drive serious segregation in cast steels, where the σ phase is difficult to eliminate. In this study, the microstructural evolution of 7Mo super austenitic stainless steels under different homogenization methods was investigated. The results showed that after isothermal treatment for 30 h at 1250 °C, the σ phase in steels dissolved, while the remelting morphologies appeared at the phase boundaries. Therefore, the stepped solution heat treatment was further conducted to optimize the homogenized microstructure. The samples were heated up to 1220 °C, 1235 °C and 1250 °C with a slow heating rate, and held at these temperatures for 2 h, respectively. The elemental segregation was greatly reduced without incipient remelting and the σ phase was eventually reduced to less than 0.6%. A prolonged incubation below the dissolution temperature will lead to a spontaneous compositional adjustment of the eutectic σ phase, resulting in uphill diffusion of Cr and Mn, and reducing the homogenization efficiency of ISHT, which is avoided by SSHT. The hardness reduced from 228~236 Hv to 220~232 Hv by adopting the cooling process of "furnace cooling + water quench". In addition, the study noticed that increasing the Ce content or decreasing the Mn content can both refine the homogenized grain size and accelerate diffusion processes. This study provides a theoretical and experimental basis for the process and composition optimization of super austenitic stainless steels.

Essential trace elements in patients with dyslipidemia: A meta-analysis

BACKGROUND

Lipid metabolism is a complex process that includes lipid uptake, transport, synthesis, and degradation. Trace elements are vital in maintaining normal lipid metabolism in the human body. This study explores the relationship between serum trace elements and lipid metabolism Methods: In this study, we reviewed articles on the relationship between alterations in somatic levels of zinc, iron, calcium, copper, chrome, manganese, selenium, and lipid metabolism. In this systematic review and mate-analysis, databases such as PubMed, Web of Science, and China National Knowledge Infrastructure (CNKI), Wanfang was searched for articles on the relationship published between January 1, 1900, and July 12, 2022. The meta-analysis was performed using Review Manager5.3 (Cochrane Collaboration).

RESULTS

No significant association was found between serum zinc and dyslipidemia, while other serum trace elements (Iron, selenium, copper, chromium, and manganese) were associated with hyperlipidemia.

CONCLUSION

The present study suggested that the human body's zinc, copper, and calcium content may be related to lipid metabolism. However, findings on lipid metabolism and Iron, Manganese have not been conclusive. In addition, the relationship between lipid metabolism disorders and selenium levels still needs to be further studied. Further research is needed on treating lipid metabolism diseases by changing trace elements.

Loss of hepatic manganese transporter ZIP8 disrupts serum transferrin glycosylation and the glutamate-glutamine cycle

BACKGROUND

ZIP8, encoded by SLC39A8, is a membrane transporter that facilitates the cellular uptake of divalent biometals including zinc (Zn), manganese (Mn), and iron (Fe). The hepatic system has long been accepted as the central modulator for whole-body biometal distribution. Earlier investigations suggest the propensity of ZIP8 to prioritize Mn influx, as opposed to Fe or Zn, in hepatocytes. Hepatic ZIP8 Mn transport is crucial for maintaining homeostasis of various Mn-dependent metalloenzymes and their associated pathways. Herein, we hypothesize that a drastic decrease in systemic Mn, via the loss of hepatic ZIP8, disrupts two unique cellular pathways, post-translational glycosylation and the glutamate-glutamine cycle.

METHODS

ZIP8 liver-specific knockout (LSKO) mice were chosen in an attempt to substantially decrease whole-body Mn levels. To further elucidate the role of Mn in serum glycosylation, a Mn-deficient diet was adopted in conjunction with the LSKO mice to model a near-complete loss of systemic Mn. After the treatment course, transferrin sialylation profiles were determined using imaged capillary isoelectric focusing (icIEF). We also investigated the role of Mn in the glutamate-glutamine cycle; the conversion of glutamate to glutamine in F/F and LSKO mice was assessed by the glutamine/glutamate ratio in cerebrospinal fluid (CSF) via HPLC-MS. An open-field study was ultimately conducted to check if these mice displayed atypical behavior.

RESULTS

Two major biological pathways were found to be significantly altered due to the loss of hepatic ZIP8. We identified a disparity between F/F and LSKO transferrin sialylation profiles that were exacerbated under a Mn-deficient diet. Additionally, we discovered a neurotransmitter imbalance between the levels of glutamine and glutamate, exclusive to LSKO mice. This was characterized by the decreased glutamine/glutamate ratio in CSF. Secondary to the neurotransmitter alteration, LSKO mice exhibited an increase in locomotor activity in an open-field.

CONCLUSION

Our model successfully established a connection between the loss of hepatic ZIP8 and two Mn-dependent cellular pathways, namely, protein glycosylation and the glutamate-glutamine cycle.

Association between blood manganese levels and depressive symptoms among US adults: A nationally representative cross-sectional study

BACKGROUND

Recent studies indicated that manganese (Mn) levels were inconsistently associated with the prevalence of depression. We aimed to evaluate whether blood Mn concentrations were associated with the risk of depression among US adults.

METHODS

Using the NHANES 2011-2019 datasets, we conducted a cross-sectional study in 16,572 eligible participants with complete data on blood Mn concentrations and depression diagnosis. A weighted multivariable logistic model and restricted cubic spline model were applied to explore the association and dose-response relationship of blood Mn concentrations with depression risk in the total population and subgroups.

RESULTS

In the total population, compared with the lowest reference group of blood Mn, participants in the second, third, and fourth quartile had an OR of 0.84 (95%CI: 0.66, 1.07), 0.93 (95%CI: 0.73, 1.19) and 0.91 (95%CI: 0.71, 1.15) for depression (p_trend = 0.640). In subgroup analyses, doubling of blood Mn concentrations was associated with a 0.83-fold (95%CI: 0.67, 1.02), 0.30 -fold (0.14, 0.65) decreased risk of depression in females and other ethnic groups, respectively. Significant modification effects of ethnicity on the association of blood Mn concentrations with depression risk were observed.

LIMITATIONS

cross-sectional study design and self-reported depressive symptoms.

CONCLUSIONS

Elevated blood Mn concentrations were associated with decreased depression risk in females and other specific subgroups. Mn supplementation could be a potential pathway for intervention and prevention of depression.

Manganese Relative Oral Bioavailability in Electric Arc Furnace Steel Slag is Influenced by High Iron Content and Low Bioaccessibility

Electric arc furnace (EAF) slag is a rock-like aggregate produced with carbon steel and used for construction, including residential ground cover. It is enriched with manganese (Mn) and other metals, including iron (Fe), but because metals are bound in mineral matrices, in vitro bioaccessibility is limited. We conducted a relative bioavailability (RBA) study using F344 rats to assess Mn RBA from EAF slag ingestion, compared to Mn in diet. Mn and Fe were measured in liver, and Mn in lung and striatum, the target tissue of the brain. Mn levels in each tissue were fit by dose to tissue concentration (D-TC) curves. The D-TC relationship was the most highly significant for the linear model using liver Mn, and the RBA was 48%. The D-TC relationship in lung showed a positive slope for chow, but that for EAF slag was slightly negative, and the RBA was 14%. In comparison, the striatum D-TC remained relatively constant, supporting that homeostasis was maintained. Increased Fe was observed in the liver of EAF slag-dosed groups, suggesting that Mn absorption was inhibited by the high Fe content of slag. Lung and striatum D-TC curves demonstrated that systemic delivery of Mn from EAF slag ingestion is limited and support an RBA of 14% for risk assessment. Although Mn levels in slag are elevated compared with health-based screening guidelines, this study supports that incidental ingestion of Mn in EAF slag is unlikely to pose a neurotoxicity hazard due to homeostatic controls, low bioaccessibility and high Fe content.

Meta-omics profiling of full-scale groundwater rapid sand filters explains stratification of iron, ammonium and manganese removals

Rapid sand filters (RSF) are an established and widely applied technology for groundwater treatment. Yet, the underlying interwoven biological and physical-chemical reactions controlling the sequential removal of iron, ammonia and manganese remain poorly understood. To resolve the contribution and interactions between the individual reactions, we studied two full-scale drinking water treatment plant configurations, namely (i) one dual-media (anthracite and quartz sand) filter and (ii) two single-media (quartz sand) filters in series. In situ and ex situ activity tests were combined with mineral coating characterization and metagenome-guided metaproteomics along the depth of each filter. Both plants exhibited comparable performances and process compartmentalization, with most of ammonium and manganese removal occurring only after complete iron depletion. The homogeneity of the media coating and genome-based microbial composition within each compartment highlighted the effect of backwashing, namely the complete vertical mixing of the filter media. In stark contrast to this homogeneity, the removal of the contaminants was strongly stratified within each compartment, and decreased along the filter height. This apparent and longstanding conflict was resolved by quantifying the expressed proteome at different filter heights, revealing a consistent stratification of proteins catalysing ammonia oxidation and protein-based relative abundances of nitrifying genera (up to 2 orders of magnitude difference between top and bottom samples). This implies that microorganisms adapt their protein pool to the available nutrient load at a faster rate than the backwash mixing frequency. Ultimately, these results show the unique and complementary potential of metaproteomics to understand metabolic adaptations and interactions in highly dynamic ecosystems.

Hematite-mediated Mn(II) abiotic oxidation under oxic conditions: pH effect and mineralization

Interactions between manganese (Mn) and iron (Fe) are widespread processes in soils and sediments, however, the abiotic transformation mechanisms are not fully understood. Herein, Mn(II) oxidation on hematite were investigated at various pH under oxic condition. Mn(II) oxidation rates increased from 3 × 10^-4 to 8 × 10^-2 h^-1 as pH increased from 7.0 to 9.0, whereas hematite enhanced Mn(II) oxidation rates to 1 h^-1. During oxidation process, high pH could promote the oxidation of Mn(II) into Mn minerals, resulting in the rapid consumption of the newly-formed H⁺, and high pH facilitated Mn(II) adsorption and oxidation by altering Mn(II) reactivity and speciation. Only granule-like hausmannite was found on the hematite surface at pH 7.0, whereas hausmannite particles and feitknechtite and manganite nanowires were formed at pH from 7.5 to 9.0. Moreover, a co-shell structured nanowire composed of manganite and feitknechtite was observed owing to autocatalytic reactions. Specifically, electron transfers between Mn(II) and O₂ occurred on the surface or through bulk phase of hematite, and direct electron transfers in the O₂-Mn(II) complex and indirect electron transfers in the O₂-Fe(II/III)-Mn(II) complex may both have contribution to the overall reactions. The findings provide a comprehensive interpretation of Fe-Mn interaction and have implications for the formation of soil Fe-Mn oxyhydroxides with unique properties in controlling element cycling.

Manganese and copper additions differently reduced cadmium uptake and accumulation in dwarf Polish wheat (Triticum polonicum L.)

This study investigated the effects of manganese (Mn) and copper (Cu) on dwarf Polish wheat under cadmium (Cd) stress by evaluating plant growth, Cd uptake, translocation, accumulation, subcellular distribution, and chemical forms, and the expression of genes participating in cell wall synthesis, metal chelation, and metal transport. Compared with the control, Mn deficiency and Cu deficiency increased Cd uptake and accumulation in roots, and Cd levels in root cell wall and soluble fractions, but inhibited Cd translocation to shoots. Mn addition reduced Cd uptake and accumulation in roots, and Cd level in root soluble fraction. Cu addition did not affect Cd uptake and accumulation in roots, while it caused a decrease and an increase of Cd levels in root cell wall and soluble fractions, respectively. The main Cd chemical forms (water-soluble Cd, pectates and protein integrated Cd, and undissolved Cd phosphate) in roots were differently changed. Furthermore, all treatments distinctly regulated several core genes that control the main component of root cell walls. Several Cd absorber (COPT, HIPP, NRAMP, and IRT) and exporter genes (ABCB, ABCG, ZIP, CAX, OPT, and YSL) were differently regulated to mediate Cd uptake, translocation, and accumulation. Overall, Mn and Cu differently influenced Cd uptake and accumulation; Mn addition is an effective treatment for reducing Cd accumulation in wheat.

High-efficiency oxygen evolution by photosystem II oxygen-evolving complex containing 3Mn per reaction center

Ca-depleted photosystem II membranes obtained by treatment with acidic buffer do not contain Ca²⁺ in the Mn₄CaO₅ cluster but contain all extrinsic proteins protecting this cluster (PSII(-Ca/low pH)). However, unlike native photosystem II, Mn cluster in PSII(-Ca/low pH) samples is available for small-sized reductants. Using this property, we investigated the substitution possibility of Mn cation(s) with Fe cation(s) to obtain a chimeric cluster in PSII(-Ca/low pH) samples containing extrinsic proteins. We found that Fe(II) cation replaces Mn cation at pH 6.5, however, PSII(-Ca/low pH) membranes with the 3Mn1Fe chimeric cluster in the oxygen-evolving complex evolve O₂ with high intensity in the presence of exogenous Ca²⁺. The O₂ evolution rate is about 80% of the same rate in PSII(-Ca/low pH) membranes.

Mn-Si-based nanoparticles-enhanced inhibitory effect on tumor growth and metastasis in photo-immunotherapy

The anticancer effect of phototherapy has been limited by some factors, including the easy degradation of photo agents, the complex tumor microenvironment, and the limited immune activation capacity, which impedes its efficiency in inhibiting tumor growth and tumor metastasis. Herein, Mn-doped mesoporous silica nanoparticles were synthesized to load the photo agent of IR 780, which were further coated with Mn (IMM). Notably, the combination of IMM and an 808 nm laser irradiation simultaneously inhibited the growth of primary tumors and distant untreated tumors in a bilateral animal model, which could be attributed to the protection of IMM to IR 780, the regulation functions to the tumor microenvironment, as well as the enhanced immune activation capacity. This work highlighted an alternative strategy for enhancing the inhibitory effect on both tumor growth and tumor metastasis in the combinational anticancer therapy of phototherapy and immunotherapy (photo-immunotherapy).

Exposure of preterm neonates to toxic metals during their stay in the Neonatal Intensive Care Unit and its impact on neurodevelopment at 2 months of age

BACKGROUND

Premature neonates might be exposed to toxic metals during their stay in the neonatal intensive care unit (NICU), which could adversely affect neurodevelopment; however, limited evidence is available. The present study was therefore designed to assess the exposure to mercury, lead, cadmium, arsenic, and manganese of preterm neonates who received total parenteral nutrition (TPN) and/or red blood cell (RBC) transfusions during their NICU stay and the risk of neurodevelopment delay at the age of 2 months.

METHODS

We recruited 33 preterm neonates who required TPN during their NICU admission. Blood samples were collected for metal analysis at two different time points (admission and before discharge). Metals in the daily TPN received by preterm neonates were analyzed. Neurodevelopment was assessed using the Ages and Stages Questionnaire Edition 3 (ASQ-3).

RESULTS

All samples of TPN had metal contamination: 96% exceeded the critical arsenic limit (0.3 μg/kg body weight/day); daily manganese intake from TPN for preterm neonates exceeded the recommended dose (1 µg/kg body weight) as it was added intentionally to TPN solutions, raising potential safety concerns. All samples of RBC transfusions exceeded the estimated intravenous reference dose for lead (0.19 µg/kg body weight). Levels of mercury, lead and manganese in preterm neonates at discharge decreased 0.867 µg/L (95% CI, 0.76, 0.988), 0.831 (95%CI, 0.779, 0.886) and 0.847 µg/L (95% CI, 0.775, 0.926), respectively. A decrease in ASQ-3-problem solving scores was associated with higher levels of blood lead in preterm neonates taken at admission (ß = -0.405, 95%CI = -0.655, -0.014), and with plasma manganese (ß = -0.562, 95%CI = -0.995, -0.172). We also observed an association between decreased personal social domain scores with higher blood lead levels of preterm neonates before discharge (ß = -0.537, 95%CI = -0.905, -0.045).

CONCLUSION

Our findings provide evidence to suggest negative impacts on the neurodevelopment at 2 months of preterm infants exposed to certain metals, possibly related to TPN intake and/or blood transfusions received during their NICU stay. Preterm neonates may be exposed to levels of metals in utero.

Bimetallic infinite coordination nanopolymers via phototherapy and STING activation for eliciting robust antitumor immunity

Phototherapy can trigger immunogenic cell death of tumors in situ, whereas it is virtually impossible to eradicate the tumor due to the intrinsic resistance and inefficient anti-tumor immunity. To overcome these limitations, novel bimetallic infinite coordination nanopolymers (TA-Fe/Mn-OVA@MB NPs) were synthesized using model antigen ovalbumin (OVA) as a template to assemble tannic acid (TA) and bi-metal, supplemented with methylene blue (MB) surface absorption. The formulated TA-Fe/Mn-OVA@MB NPs possess excellent photothermal and photodynamic therapy (PTT/PDT) performance, which is adequate to destroy tumor cells by physical and chemical attack. Especially, these TA-Fe/Mn-OVA@MB NPs are capability of promoting the dendritic cells (DCs) maturation and antigen presentation via manganese-mediated cGAS-STING pathway activation, finally activating cytotoxicity T lymphocyte and promoting memory T lymphocyte differentiation in the peripheral lymphoid organs. In conclusion, this research offers a versatile metal-polyphenol nanoplatform to integrate functional metals and therapeutic molecule for topical phototherapy and robust anti-tumor immune activation.

Evaluation of the oxidative toxicity induced by lead, manganese, and cadmium using genetically modified nrf2a-mutant zebrafish

Heavy metal pollution has become a serious environmental concern and a threat to public health. Three of the most common heavy metals are cadmium (Cd), lead (Pb), and manganese (Mn). Nuclear factor erythroid 2-related factor 2 (Nrf2) is an important transcription factor activated in the response to oxidative stress. In this study, mutant zebrafish with an nrf2a deletion of 7 bp were constructed by the CRISPR/Cas9 system to investigate the oxidative toxicity of these three heavy metals. The results of general toxicity tests showed that Pb exposure did not cause significant damage to mutant zebrafish compared with wild-type (WT) zebrafish. However, high Mn exposure increased mortality and malformation rates in mutant zebrafish. Of concern, Cd exposure caused significant toxic damage, including increased mortality and malformation rates, apoptosis of brain neurons, and severe locomotor behavior aberration in mutant zebrafish. The results of qRT-PCR indicated that Cd exposure could induce the activation of genes related to oxidative stress resistance in WT zebrafish, while the expression of these genes was inhibited in mutant zebrafish. This study showed that of the three heavy metals, Cd had the strongest oxidative toxicity, Mn had medium toxicity, and Pb had the weakest toxicity.

Synthesis and characterization of two piperazine containing macrocycles and their transition metal complexes

Rigidification of the ligand scaffolds has been a particular mechanism of interest employed to achieve properties suitable for MRI contrast, catalysis, or other applications of metal complexes. Towards the goal of targeting a 15-anePyN5Pip type ligand, a serendipitous isolation of a 30-anePy2N10Pip2 aza-macrocycle was achieved, instead. X-ray diffraction and determination of pKa events were carried out and compared to 17-anePyN5Pip. Furthermore, the X-ray diffraction of the Cu(II) and Zn(II) complexes of 17-anePyN5Pip was achieved and compared to previous reports of other first-row transition metal derivatives of this ligand. Determination of the log β with both 30-anePy2N10Pip2 and 17-anePyN5Pip with the divalent MnZn metal-ion series was used to demonstrate the impact that the piperazine ring plays compared to other, less rigid macrocycles reported to date.