Mn Treatment Research Articles

The Effect of Foliar and Ground-Applied Essential Nutrients on Huanglongbing-Affected Mature Citrus Trees.

The fate of foliar and ground-applied essential nutrients is the least studied topic under citrus greening or Huanglongbing (HLB)-affected citrus, which is inherently suffering from severe root decline because of HLB-associated problems. The objective of this study was to evaluate if ground-applied coupled with foliar spray of essential nutrients can reverse the decline in tree growth and understand the fate of the nutrients in the soil-root-tree interfaces. The treatments were arranged in a split-split plot design in which nitrogen (N) was ground-applied in 20 splits biweekly and Mn, Zn, and B were foliar and /or ground-applied in three splits following the spring, summer, and late summer flush seasons. Soil nutrients in three depths (0–15, 15–30, and 30–45 cm), root, and leaf nutrient concentrations of the essential nutrients, leaf area index (LAI), and tree canopy volume (TCV) data were studied twice (spring and summer) for two years. A significantly higher soil NH4-N and NO3-N concentrations were detected in the topsoil depth than the two lower soil depths (15–30 and 30–45 cm) indicating lesser nutrient leaching as trees received moderate (224 kg ha−1) N rate. Except for soil zinc (Zn) concentration, all the nutrient concentrations were significantly higher in the topsoil (0–15 cm), compared with two lower soil depths indicating that Zn was intricate by changes in soil environmental conditions, root acquisition, and/or leaching to lower soil depth. Leaf N concentration significantly increased over time following seasonal environmental fluctuations, tree growth, and development. Thus, leaf N concentration remained above the optimum nutrient range implying lower N requirement under irrigation scheduling with SmartIrrigation, an App used to determine the daily irrigation duration to meet tree water requirement and split fertigation techniques. Root Manganese (Mn) and Zn concentrations were significantly higher in the root tissues of the treated than the control trees and translocated to the leaves accordingly. Meanwhile, a significantly higher LAI for trees budded on Swingle (Swc) rootstock however, larger TCV for trees budded on Volkameriana (Volk) rootstocks. The trees had significantly larger TCV when the trees received a moderate N rate during early study years and under foliar 9 kg ha−1 coupled with the ground 9 kg ha−1 Mn and Zn treatments during the late study years. Therefore, split ground application of 224 kg ha−1 of N, foliar applied 9 kg ha−1 coupled with ground-applied 9 kg ha−1 Mn and Zn were the suggested rates to sustain the essential leaf nutrient concentration within the optimum ranges and improve the deterioration of vegetative growth associated with HLB-induced problems of citrus trees.

Hepatic oxidative damage and Nrf2 pathway protein changes in rats following long-term manganese exposure.

This study investigated hepatic oxidative damage in rats following long-term manganese (Mn) exposure and clarified the underlying mechanisms. Forty-eight rats (SPF, male) were randomly assigned to receive low (10 mg/kg, n = 16) or high doses of Mn (50 mg/kg, n = 16) or sterilized distilled water (control group, n = 16). Rats were euthanized after 12 months, and liver Mn levels and histopathological changes were determined. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and liver malondialdehyde (MDA), glutathione peroxidase (GSH-PX), nuclear factor E2-related factor-2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H quinine oxidoreductase-1 (NQO1) levels were also determined. The Mn concentration and relative liver weights were significantly higher in the high-dose Mn group than in the control and low-dose Mn exposure groups. Low-dose Mn exposure resulted in mild expansion of hepatic sinuses and intact nuclei, whereas high-dose exposure led to pathological alterations in hepatocytes. High-dose Mn treatment significantly increased AST, ALT, and MDA activities and decreased GSH-PX activity. Additionally, liver Nrf2, HO-1, and NQO1 protein expression were markedly reduced by Mn exposure. Under the study conditions, long-term low-dose Mn exposure resulted in slight pathological changes in liver structure, but high-dose Mn exposure affected both liver structure and function, which might be related to the inhibition of Nrf2 expression, suppression of the transcription of its underlying antioxidant genes, and down regulation of the corresponding proteins. Consequently, the antioxidant capacity in the rat liver was weakened.

Determination of The Optimal Dosage of Chemical Compounds in the Wastewater Treatment Process in Trang Bach Coal Mine: the Laboratory Scale

The pH index of Trang Bach coal mine wastewater ranges from 2,8 to 6, meanwhile, the content of Fe, Mn, and turbidity & suspendedsolids (TSS) are rather high and it is impossible to discharge the wastewater directly to the environment. In order to achievethe requirement of QCVN 40:2011/BTNMT standard – The national standard for industrial wastewater quality after treatment ofVietnam and other purposes, the wastewater need to be treated by several methods such as coagulation-flocculation or sedimentation.In this article, we intend to find the optimal dosages of chemical compounds for the TSS, pH, Fe and Mn treatment processfor Trang Bach coal mine wastewater in the laboratory modular.

The Effect of Foliar Fertilization with Micronutrients on Disease Severity and Mycotoxin Concentrations in the Grain of Winter Spelt (Triticum aestivum spp. spelta L.): A Case Study

The effect of mineral fertilization (NPK), foliar fertilization with micronutrients (Cu, Zn and Mn) and the NanoGro biostimulant on the severity of leaf, spike, stem base and root diseases in winter spelt cv. Schwabenkorn was evaluated in a field-plot experiment. A mycological analysis was performed and the content of Fusarium mycotoxins in grain was determined. Mineral fertilization (NPK), foliar fertilization with micronutrients and the NanoGro biostimulant exerted varied effects on the severity of Septoria leaf blotch and Septoria glume blotch, they promoted the spread of brown rust (excluding the NPK + NanoGro treatment) and inhibited the spread of black head mold (excluding the NPK treatment), eyespot and Fusarium foot and root rot (excluding the NPK + Mn treatment). Fertilization had no influence on grain yield or the content of Fusarium mycotoxins in grain. The concentrations of deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA) and fumonisins FB1 + FB2 did not exceed the maximum permissible levels (except for DON in NPK + Cu + Zn + Mn and NPK + NanoGro treatments). Throughout the experiment, ergosterol (ERG) concentrations were highest in the grain of unfertilized spelt plants.

Dendrobium nobile Lindl. alkaloids alleviate Mn-induced neurotoxicity via PINK1/Parkin-mediated mitophagy in PC12 cells

Modern pharmacological studies have demonstrated that Dendrobium nobile Lindl. Alkaloids (DNLA), the main active ingredients of Dendrobium nobile, is valuable as an anti-aging and neuroprotective herbal medicine. The present study was designed to determine whether DNLA confers protective function over neurotoxicant manganese (Mn)-induced cytotoxicity and the mechanism involved. Our results showed that pretreatment of PC12 cells with DNLA alleviated cell toxicity induced by Mn and improved mitochondrial respiratory capacity and oxidative status. Mn treatment increased apoptotic cell death along with a marked increase in the protein expression of Bax and a decrease in the expression of Bcl-2 protein, all of which were noticeably reversed by DNLA. Furthermore, DNLA significantly abolished the decrease in protein levels of both PINK1 and Parkin, and mitigated the increased expression of autophagy marker LC3-II and accumulation of p62 caused by Mn. These results demonstrate that DNLA inhibits Mn induced cytotoxicity, which may be mediated through modulating PINK1/Parkin-mediated autophagic flux and improving mitochondrial function.

Exogenous application of Mn significantly increased Cd accumulation in the Cd/Zn hyperaccumulator Sedum alfredii.

Sedum alfredii is a Cd/Zn hyperaccumulator native to China, which was collected from a mined area where Mn content in soil was extremely high, together with Zn and Cd content. We investigated the tolerance and accumulation ability of Mn and its possible association with Cd hyperaccumulation in this plant species by using MP-AES, SR-μ-XRF, and RT-PCR. The results showed that the hyperaccumulating ecotype (HE) S.alfredii exhibited high tolerance to Mn and accumulating around 10,000 and 12,000mgkg-1 Mn in roots and shoots, respectively, without exhibiting toxicity under 5000mgkg-1 Mn treatment for 4 weeks. Exposure to Cd significantly reduced plant uptake of Mn. In contrast, exogenous Mn application significantly improved root uptake and root-to-shoot translocation of Cd, resulting in the increased Cd accumulation in the shoots of HE S.alfredii. SR-μ-XRF analysis demonstrated that high Mn (20μM) exposure resulted in higher intensities of Cd localized in both stem vascular bundles and cortex, as well as leaf mesophyll cells, than in those treated with low Mn levels (0.2μM or 2.0μM). RT-PCR analysis of several genes possibly involved in Mn/Cd transportation showed that expression of SaNramp3 in roots was significantly reduced under high Mn exposure. These results suggested a significant interaction between Cd and Mn in the HE S.alfredii plants, possibly through their competition for transporters and theoretically provided a strategy to improve the efficiency of Cd extraction from polluted soils by this plant species, after using appropriate nutrient management of Mn.

Exogenous Application of 24-Epibrassinolide Improves Manganese Tolerance in Arabidopsis thaliana L. via the Modulation of Antioxidant System

The goal of the present study was to investigate the role of 24-Epibrassinolide (EBL) hormone in supporting adaptation of plant to manganese (Mn) stress. For this purpose, changes in antioxidant system and stress-related gene expression were determined in rosette leaves of Arabidopsis thaliana following 24-h exposure to Mn (0.5 and 1.0 mM) and/or EBL (1 µM). Decreased chlorophyll level in the rosette leaves of seedlings due to Mn stress increased consequent to exogeneous EBL application. Superoxide dismutase (SOD) and catalase (CAT) enzyme activities alongside transcript level of copper/zinc superoxide dismutase 1 (CSD1), copper/zinc superoxide dismutase 2 (CSD2), copper/zinc superoxide dismutase 3 (CSD3), Fe superoxide dismutase 2 (FSD2), Fe superoxide dismutase 3 (FSD3), and catalase 2 (CAT2) genes were found to increase depending on Mn concentration; however, co-exposure of EBL and Mn led to a further improvement in enzyme activities and gene expressions (except CSD1 and CSD2 genes). The mRNA level of Fe superoxide dismutase 1 (FSD1) gene was downregulated following Mn and/or EBL treatments. Exogenous treatment of EBL improved the total antioxidant and proline level, while it decreased the lipid peroxidation under Mn stress. EBL treatment upregulated transcript level of delta 1-pyrroline-5-carboxylate synthase 1 (P5CS1) and delta 1-pyrroline-5-carboxylate synthase 2 (P5CS2) genes in seedlings treated with Mn. Co-treatment of Mn and EBL enhanced expression level of A. thaliana detoxification 1 (AtDTX1) and A. thaliana detoxification 3 (AtDTX3) genes when compared to the seedlings treated with Mn. Biochemical and molecular results from the current study revealed that EBL regulates antioxidant system in a coordinated manner under A. thaliana Mn stress.

A novel role of sulfate in promoting Mn phytoextraction efficiency and alleviating Mn stress in Polygonum lapathifolium Linn

A hydroponic method was performed to explore the effects of sulfate supply on the growth, manganese (Mn) accumulation efficiency and Mn stress alleviation mechanisms of Polygonum lapathifolium Linn. Three Mn concentrations (1, 8 and 16 mmol L−1, representing low (Mn1), medium (Mn8) and high (Mn16) concentrations, respectively) were used. Three sulfate (S) levels (0, 200, and 400 μmol L−1, abbreviated as S0, S200 and S400, respectively) were applied for each Mn concentration. (1) The average biomass (g plant−1) of P. lapathifolium was ordered as Mn8 (6.36) > Mn1 (5.25) > Mn16 (4.16). Under Mn16 treatment, S addition increased (P < 0.05) biomass by 29.96% (S200) and 53.07% (S400) compared to that S0. The changes in the net photosynthetic rate and mean daily increase in biomass were generally consistent with the changes in biomass. (2) Mn accumulation efficiency (g plant−1) was ordered as Mn8 (99.66) > Mn16 (58.33) > Mn1 (27.38); and S addition increased (p < 0.05) plant Mn accumulation and Mn transport, especially under Mn16 treatment. (3) In general, antioxidant enzyme activities (AEAs) and malondialdehyde (MDA) in plant leaves were ordered in Mn16 > Mn8 > Mn1. Sulfate addition decreased (P < 0.05) AEAs and MDA under Mn16 treatment, while the changes were minor under Mn1 and Mn8 treatments. (4) Amino acid concentrations generally increased with increasing Mn concentration and S level. In summary, the medium Mn treatment promoted plant growth and Mn bioaccumulation; sulfate, especially at 400 µmol L−1 S, can effectively promote plant growth and Mn accumulation efficiency. The most suitable bioremediation strategy was Mn16 with 400 µmol L−1 S.

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

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

Protective Effects of Sodium Para-aminosalicylic Acid on Manganese-Induced Damage in Rat Pancreas.

Sodium p-aminosalicylic acid (PAS-Na) has been previously shown to protect the brain from manganese (Mn)-induced toxicity. However, the efficacy of PAS-Na in protecting other organs from Mn toxicity and the mechanisms associated with this protection have yet to be addressed. Therefore, here, we assessed pancreatic damage in response to Mn treatment and the efficacy of PAS-Na in limiting this effect, along with specific mechanisms that mediate PAS-Na's protection. Mn exposure led to increased blood Mn content in dose- and time-dependent manner. Furthermore, subchronic Mn exposure (20 mg/kg for 8 weeks) led to pancreatic damage in a dose-dependent manner. In addition, the elevated Mn levels increased iron and decreased zinc and magnesium content in the pancreas. These effects were noted even 8 weeks after Mn exposure cessation. Mn exposure also affected the levels of amylase, lipase, and inflammatory factors such as tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β). PAS-Na significantly inhibited the increase in Mn concentration in both blood and pancreas, restored Mn-induced pancreatic damage, reversed the Mn-induced alterations in metal levels, and restored amylase and lipase concentrations. Taken together, we conclude that in rats, PAS-Na shows pharmacological efficacy in protecting the pancreas from Mn-induced damage.

Effects of organic manure partial substitution for chemical fertilizer on the photosynthetic rate, nitrogen use efficiency and yield of rice

Rational application of organic fertilizers is an effective approach to improve soil fertility, crop yield, and zero growth of chemical fertilizer in agricultural production. The rice variety 'Shennong9816' was planted in Shenyang, Liaoning Province, under seven different treatments: zero nitrogen fertilizer (CK), low nitrogen, 150 kg·hm-2(LN), medium nitrogen, 240 kg·hm-2 (MN), high nitrogen, 330 kg·hm-2(HN), medium nitrogen with replacement of chemical N by 10% organic manure (OMN10), medium nitrogen with replacement of chemical N by 20% organic manure (OMN20), and medium nitrogen with replacement of chemical N by 30% organic manure (OMN30). The effects of different treatments on photosynthetic rate, nitrogen absorption, nitrogen use efficiency, and yield were examined and the optimal fertilization scheme was determined. The results showed that the photosynthetic rate, biomass and yield were increased with the increases of nitrogen application rate, while the nitrogen use efficiency was decreased significantly. Compared with the MN treatment, the photosynthetic rate of OMN10 and OMN20 in filling stage was increased by 22.9% and 9.9%, respectively. The yield of OMN20 was increased by 3.8% compared to that of MN. The nitrogen agronomic efficiency and physiological efficiency of OMN20 were significantly improved by 8.1% and 13.3%, respectively. Moreover, the nitrogen agronomic efficiency and physiological efficiency of OMN20 were improved by 27.2% and 37.2% compared with the HN treatment. Thus, we concluded that the organic fertilizer replacement treatment could conserve soil fertility, achieve high yield and high nitrogen use efficiency, while reduce chemical nitrogen fertilizer application. The OMN20 treatment was recommended as a fertilizer application model due to its superior performance among the seven treatments.

Physiological and transcriptomic analyses reveal the roles of secondary metabolism in the adaptive responses of Stylosanthes to manganese toxicity

BackgroundAs a heavy metal, manganese (Mn) can be toxic to plants. Stylo (Stylosanthes) is an important tropical legume that exhibits tolerance to high levels of Mn. However, little is known about the adaptive responses of stylo to Mn toxicity. Thus, this study integrated both physiological and transcriptomic analyses of stylo subjected to Mn toxicity.ResultsResults showed that excess Mn treatments increased malondialdehyde (MDA) levels in leaves of stylo, resulting in the reduction of leaf chlorophyll concentrations and plant dry weight. In contrast, the activities of enzymes, such as peroxidase (POD), phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO), were significantly increased in stylo leaves upon treatment with increasing Mn levels, particularly Mn levels greater than 400 μM. Transcriptome analysis revealed 2471 up-regulated and 1623 down-regulated genes in stylo leaves subjected to Mn toxicity. Among them, a set of excess Mn up-regulated genes, such as genes encoding PAL, cinnamyl-alcohol dehydrogenases (CADs), chalcone isomerase (CHI), chalcone synthase (CHS) and flavonol synthase (FLS), were enriched in secondary metabolic processes based on gene ontology (GO) analysis. Numerous genes associated with transcription factors (TFs), such as genes belonging to the C2H2 zinc finger transcription factor, WRKY and MYB families, were also regulated by Mn in stylo leaves. Furthermore, the C2H2 and MYB transcription factors were predicted to be involved in the transcriptional regulation of genes that participate in secondary metabolism in stylo during Mn exposure. Interestingly, the activation of secondary metabolism-related genes probably resulted in increased levels of secondary metabolites, including total phenols, flavonoids, tannins and anthocyanidins.ConclusionsTaken together, this study reveals the roles of secondary metabolism in the adaptive responses of stylo to Mn toxicity, which is probably regulated by specific transcription factors.

Variation of Cicer Germplasm to Manganese Toxicity Tolerance.

After aluminum, manganese toxicity is the most limiting factor for crops grown in acidic soils worldwide. But overall, research on Mn toxicity is still limited. The poor acid tolerance of chickpea may be related to Mn toxicity, but there has been no previous screening of chickpea germplasm (nor in its wild Cicer relatives, Cicer reticulatum and Cicer echinospermum) for tolerance to Mn toxicity. A screening technique was developed for tolerance to Mn toxicity using three released cultivars of chickpea (Cicer arietinum L), Ambar, PBA HatTrick, and PBA Striker; one accession each of C. reticulatum and C. echinospermum; and lupin (Lupinus angustifolius) as a Mn-tolerant check, with eight Mn concentrations of 2, 25, 50, 100, 150, 200, 250, and 500 μM Mn as MnSO4 in a low-ionic-strength nutrient solution. The plants were harvested at 14 and 28 days after Mn treatments. The nutrient uptake in shoots (young, old leaves, and the rest of the shoot) and roots was investigated. The best discrimination between tolerant and intolerant Cicer genotypes based on relative shoot dry weight, root dry weight, total root length, and scoring of toxicity symptoms was achieved at 150 μM Mn after 14 days of growth in Mn solution. Among the chickpea cultivars, the greater relative plant growth (both shoot and root) of Ambar and PBA Striker at 100–200 μM Mn contrasted with that of PBA HatTrick, while the C. echinospermum accession was more tolerant to Mn toxicity than C. reticulatum. Manganese tolerance in both domestic cultivars and wild accessions was associated with internal tolerance to excess Mn following greater uptake of Mn and translocation of Mn from roots to shoots.

Differential mechanisms between traditionally established and new highbush blueberry (Vaccinium corymbosum L.) cultivars reveal new insights into manganese toxicity resistance

In acid soils, manganese (Mn) concentration increases, becoming toxic to plants. Mn toxicity differentially affects physiological processes in highbush blueberry (Vaccinium corymbosum L.) cultivars. However, the mechanisms involved in Mn toxicity of the new and traditionally established cultivars are unknown. To understand Mn toxicity mechanisms, four traditionally established (Legacy, Brigitta, Duke, and Star) cultivars and two recently introduced to Chile (Camellia and Cargo) were grown under hydroponic conditions subjected to control Mn (2 μM) and Mn toxicity (1000 μM). Physiological, biochemical, and molecular parameters were evaluated at 0, 7, 14, and 21 days. We found that the relative growth rate was reduced in almost all blueberry cultivars under Mn toxicity, except Camellia, with Star being the most affected. The photosynthetic parameters were reduced only in Star by Mn treatment. Leaf Mn concentrations increased in all cultivars, exhibiting the lowest levels in Camellia and Cargo. Brigitta and Duke exhibited higher β-carotene levels, while Cargo exhibited a reduction under toxic Mn. In Legacy, lutein levels increased under Mn toxicity. Traditionally established cultivars exhibited higher antioxidant activity than the new cultivars under Mn toxicity. The Legacy and Duke cultivars increased VcMTP4 expression with Mn exposure time. A multivariate analysis separated Legacy and Duke from Camellia; Star and Cargo; and Brigitta. Our study demonstrated that Mn toxicity differentially affects physiological, biochemical, and molecular features in the new and traditionally established cultivars, with Legacy, Duke, Camellia, and Cargo as the Mn-resistant cultivars differing in their Mn-resistance mechanisms and Star as the Mn-sensitive cultivar.

Effects of Excess Manganese on the Xylem Sap Protein Profile of Tomato (Solanum lycopersicum) as Revealed by Shotgun Proteomic Analysis.

Metal toxicity is a common problem in crop species worldwide. Some metals are naturally toxic, whereas others such as manganese (Mn) are essential micro-nutrients for plant growth but can become toxic when in excess. Changes in the composition of the xylem sap, which is the main pathway for ion transport within the plant, is therefore vital to understanding the plant’s response(s) to metal toxicity. In this study we have assessed the effects of exposure of tomato roots to excess Mn on the protein profile of the xylem sap, using a shotgun proteomics approach. Plants were grown in nutrient solution using 4.6 and 300 µM MnCl2 as control and excess Mn treatments, respectively. This approach yielded 668 proteins reliably identified and quantified. Excess Mn caused statistically significant (at p ≤ 0.05) and biologically relevant changes in relative abundance (≥2-fold increases or ≥50% decreases) in 322 proteins, with 82% of them predicted to be secretory using three different prediction tools, with more decreasing than increasing (181 and 82, respectively), suggesting that this metal stress causes an overall deactivation of metabolic pathways. Processes most affected by excess Mn were in the oxido-reductase, polysaccharide and protein metabolism classes. Excess Mn induced changes in hydrolases and peroxidases involved in cell wall degradation and lignin formation, respectively, consistent with the existence of alterations in the cell wall. Protein turnover was also affected, as indicated by the decrease in proteolytic enzymes and protein synthesis-related proteins. Excess Mn modified the redox environment of the xylem sap, with changes in the abundance of oxido-reductase and defense protein classes indicating a stress scenario. Finally, results indicate that excess Mn decreased the amounts of proteins associated with several signaling pathways, including fasciclin-like arabinogalactan-proteins and lipids, as well as proteases, which may be involved in the release of signaling peptides and protein maturation. The comparison of the proteins changing in abundance in xylem sap and roots indicate the existence of tissue-specific and systemic responses to excess Mn. Data are available via ProteomeXchange with identifier PXD021973.

Sodium para-aminosalicylic acid inhibits manganese-induced NLRP3 inflammasome-dependent pyroptosis by inhibiting NF-\u03baB pathway activation and oxidative stress

BackgroundThe activation of NOD-like receptor protein 3 (NLRP3) inflammasome-dependent pyroptosis has been shown to play a vital role in the pathology of manganese (Mn)-induced neurotoxicity. Sodium para-aminosalicylic acid (PAS-Na) has a positive effect on the treatment of manganism. However, the mechanism is still unclear. We hypothesized that PAS-Na might act through NLRP3.MethodsThe microglial cell line BV2 and male Sprague-Dawley rats were used to investigate the impacts of PAS-Na on Mn-induced NLRP3 inflammasome-dependent pyroptosis. The related protein of the NF-κB pathway and NLRP3-inflammasome-dependent pyroptosis was detected by western blot. The reactive oxygen species and mitochondrial membrane potential were detected by immunofluorescence staining and flow cytometry. The activation of microglia and the gasdermin D (GSDMD) were detected by immunofluorescence staining.ResultsOur results showed that Mn treatment induced oxidative stress and activated the NF-κB pathway by increasing the phosphorylation of p65 and IkB-α in BV2 cells and in the basal ganglia of rats. PAS-Na could alleviate Mn-induced oxidative stress damage by inhibiting ROS generation, increasing mitochondrial membrane potential and ATP levels, thereby reducing the phosphorylation of p65 and IkB-α. Besides, Mn treatment could activate the NLRP3 pathway and promote the secretion of IL-18 and IL-1β, mediating pyroptosis in BV2 cells and in the basal ganglia and hippocampus of rats. But an inhibitor of NF-κb (JSH-23) treatment could significantly reduce LDH release, the expression of NLRP3 and Cleaved CASP1 protein and IL-1β and IL-18 mRNA level in BV2 cells. Interestingly, the effect of PAS-Na treatment in Mn-treated BV2 cells is similar to those of JSH-23. Besides, immunofluorescence results showed that PAS-Na reduced the increase number of activated microglia, which stained positively for GSDMD.ConclusionPAS-Na antagonized Mn-induced NLRP3 inflammasome dependent pyroptosis through inhibiting NF-κB pathway activation and oxidative stress.

Manganese Exposure Aggravates β-Amyloid Pathology by Microglial Activation

Human epidemiological evidence and animal experimental data suggest that chronic manganese (Mn) exposure increases the risk of Alzheimer’s disease (AD) and amyloid plaques, a hallmark of AD brain pathology, but the underlying mechanisms were not fully understood. Using the transgenic APP/PS1/Tau triple transgenic AD (3×Tg-AD) mouse model and mouse-derived microglia and neuroblastoma cell lines, we found that chronic 5-month Mn treatment increased beta amyloid peptide (Aβ) expression and Aβ plaques in the cerebral cortex and hippocampus in these 3×Tg-AD mice. Furthermore, we found that the β- and γ-secretase cleavage activities were markedly increased, while α-secretase cleavage activity was reduced in the brain of Mn-treated AD mice; these effects increase Aβ production and thus are amyloidogenic. Equally important, Mn treatment alone did not alter β-secretase 1 (BACE1) gene expression or Aβ production in amyloidogenic mutant amyloid precursor protein (APP) gene hAPPsw-transfected N2a cells (APPsw-N2a), but in APPsw-N2a cells either co-cultured with microglia or cultured with microglia-conditioned media, Mn exposure increased BACE1 expression and amyloidogenesis. We further determined that Mn exposure promoted the activation of microglia both in 3×Tg-AD mouse brains and in cultured microglia cells, and increased the secretion of the inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Taken together, these results suggest that Mn may increase the release of IL-1β and TNF-α from microglia that in turn stimulates the expression of BACE1 gene and protein and consequently Aβ production; this novel molecular mechanism not only advances our understanding about the amyloidogenic effect of chronic Mn exposure reported for special human populations but also indicates Mn dyshomeostasis as a potential contributor to AD pathogenesis.

Influence of manganese availability on switchgrass and pearl millet biomass production

AbstractManganese is an essential nutrient and plays key roles in photosynthetic processes, including in NAD‐malic enzyme (NAD‐ME)‐type C4 plants as an activator of NAD‐ME. However, little is known about the Mn requirements of switchgrass (Panicum virgatum L.). To study Mn requirements for optimum growth and biomass production, a lowland (‘Alamo’) and an upland (‘Cave‐in‐Rock’) switchgrass ecotype were grown with either washed sand, vermiculite, or perlite and fertilized with nutrient solutions ranging in [Mn] from 0 to 200 μM. In the perlite experiment, pearl millet [Pennisetum glaucum (L.) R. Br. ‘KGraze’] was also grown. Shoot [Mn] was highly responsive to increasing Mn in the nutrient solution. When grown in washed sand and vermiculite, tissue [Mn] remained above those normally considered deficient, even in the 0 μM Mn treatment, and no Mn treatment effects on biomass production were found. In perlite, end‐of‐season shoot [Mn] were &lt;5 mg kg−1 in all entries when no Mn was supplied, and a decrease in biomass production compared with 10–25 μM Mn treatments was observed for Alamo and KGraze, but not for Cave‐in‐Rock. Relative chlorophyll contents of switchgrass were lower in the 0 μM Mn treatment than in other treatments late in the season, but in KGraze, they were low early in the season and increased throughout the season, resulting in less pronounced (but still significant) differences at late stages. Overall, results indicated that switchgrass and pearl millet respond differently to low Mn availability and that even low levels of shoot tissue [Mn] allow switchgrass to maintain biomass production.

Manganese-induced oxidative stress, ultrastructural changes, and proteomics studies in rice plants.

Manganese (Mn) is an essential element for plant growth but it becomes phytotoxic at higher concentrations. The effect of Mn-excess in hydroponics medium was examined on growth, oxidative stress, and ultrastructural changes in chloroplasts and mitochondria as well proteomic alterations in rice (Oryza sativa L.) seedlings. Seedlings grown with 1mM and 2mM Mn in nutrient medium for 8days showed decline in length and fresh biomass, and decline in net photosynthetic rate, transpiration rate, and stomatal conductance. Shoots of the seedlings had higher Mn content than roots. Mn-treated seedlings showed increased production of O2·-, H2O2, and .OH, increased lipid peroxidation, increased carbonylation of proteins, and increased proteolytic activity compared to untreated seedlings. Mn-treated seedlings showed disorganization and swelling of chloroplasts with appearance of plastoglobuli in TEM images and deformity in shape of mitochondria. Using confocal microscopy depolarization of mitochondrial membrane was observed marked by green fluorescence of JC-1 dye monomers in Mn-treated roots. Proteomics studies from leaves of Mn-treated seedlings involving 2DE and PDQuest analysis showed differential expression of 23 proteins, among which MALDI-TOF/TOF mass spectrometry analysis revealed Mn-led downregulation of photosynthesis-related proteins, namely oxygen-evolving complex protein associated with PSII, PAP-3, enzyme involved in protein folding peptidyl-prolyl cis-trans isomerase (PPIase) and carbohydrate metabolizing enzymes hydrolase, fructose-bisphosphate aldolase, transketolase, and isocitrate dehydrogenase, whereas ATP-dependent Clp protease, peroxidase, and nucleic acid-binding proteins were downregulated due to Mn treatment. Results indicate that Mn-excess inhibits growth of rice plants with induction of oxidative stress, causing structural alterations in chloroplasts, mitochondria, inhibiting photosynthesis, and downregulating many photosynthesis and carbohydrate metabolism-related proteins.

The effects of foliar-applied manganese on major cell wall polysaccharide fractions and soluble sugar composition of cucumber leaves

Increasing evidence shows that micronutrients can induce changes in cell wall (CW) properties in plants. A detailed knowledge of these changes will contribute to understand the beneficial and detrimental impacts of trace elements on plant development and defence. In the present work, the influence of foliar spray of manganese (Mn) on the composition of CW polysaccharides and soluble sugars was investigated in cucumber leaves using spectrophotometric and chromatographic techniques. Cucumber seedlings were hydroponically cultured under controlled situations for 21 days. At the two-leaf stage, the above facade of cucumber leaves was fertilized with MnSO4 solutions at various dosages (1.8, 4.5 and 7.2 mM). Results showed that the foliar Mn spray decreased the galacturonic acid (GalA) content, while it increased the degree-of-methyl-esterification (DM) of pectin. The amounts of fucose, arabinose and galactose diminished upon Mn application. The contents of rhamnose and xylose decreased or did not change by Mn treatment. The glucose level enhanced at low concentration of Mn (1.8 mM), but it decreased at medium and high concentrations of Mn (4.5 and 7.2 mM). The increase of mannose content was significant only at medium concentration of Mn. Overall, the amount of total hemicellulose increased at 1.8 mM concentration of Mn, while a decrease was observed at 4.5 and 7.2 mM concentrations of Mn. The cellulose content decreased at low and high concentrations of Mn, although it remained unchanged at medium concentration of Mn. Generally, the total contents of CW polysaccharides increased at low concentration of Mn, but they decreased at the higher concentrations of Mn. Such changes can be important in plant resistance to environmental stresses via reduction of permeability against fungal pathogens and decrease of water loss from tissues under stresses such as drought and salinity.