Synergistic dopaminergic neurotoxicity of manganese and lipopolysaccharide: differential involvement of microglia and astroglia

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Blockage of KHSRP-NLRP3 by MCC950 Can Reverse the Effect of Manganese-Induced Neuroinflammation in N2a Cells and Rat Brain

Manganese neurotoxicity has been reported to cause a neurodegenerative disease known as parkinsonism. Previous reports have shown that the expression of the KH-type splicing regulatory protein (KHSRP), a nucleic acid-binding protein, and NLRP3 is increased upon Mn exposure. However, the relation between these two during Mn toxicity has not been fully deduced. The mouse neuroblastoma (N2a) and SD rats are treated with LPS and MnCl2 to evaluate the expression of KHSRP and NLRP3. Further, the effect of the NLRP3 inhibitor MCC950 is checked on the expression of NLRP3, KHSRP and pro-inflammatory markers (TNFα, IL-18 and IL-1β) as well as the caspase-1 enzyme. Our results demonstrated an increment in NLRP3 and KHSRP expression post-MnCl2 exposure in N2a cells and rat brain, while on the other hand with LPS exposure only NLRP3 expression levels were elevated and KHSRP was found to be unaffected. An increased expression of KHSRP, NLRP3, pro-inflammatory markers and the caspase-1 enzyme was observed to be inhibited with MCC950 treatment in MnCl2-exposed cells and rats. Manganese exposure induces NLRP3 and KHSRP expression to induce neuroinflammation, suggesting a correlation between both which functions in toxicity-related pathways. Furthermore, MCC950 treatment reversed the role of KHSRP from anti-inflammatory to pro-inflammatory.

MiR-30a-5p and miR-153-3p regulate LPS-induced neuroinflammatory response and neuronal apoptosis by targeting NeuroD1

Neurogenic differentiation 1 (NeuroD1) is an essential transcription factor for neuronal differentiation, maturation, and survival, and is associated with inflammation in lipopolysaccharide (LPS)- induced glial cells; however, the concrete mechanisms are still ambiguous. Therefore, we investigated whether NeuroD1-targeting miRNAs affect inflammation and neuronal apoptosis, as well as the underlying mechanism. First, we confirmed that miR-30a-5p and miR-153-3p, which target NeuroD1, reduced NeuroD1 expression in microglia and astrocytes. In LPS-induced microglia, miR-30a-5p and miR-153-3p suppressed pro-inflammatory cytokines, reactive oxygen species, the phosphorylation of c-Jun N-terminal kinase, extracellular-signal-regulated kinase (ERK), and p38, and the expression of cyclooxygenase and inducible nitric oxide synthase (iNOS) via the NF-κB pathway. Moreover, miR-30a-5p and miR-153-3p inhibited the expression of NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasomes, NLRP3, cleaved caspase-1, and IL-1β, which are involved in the innate immune response. In LPS-induced astrocytes, miR-30a-5p and miR-153-3p reduced ERK phosphorylation and iNOS expression via the STAT-3 pathway. Notably, miR-30a-5p exerted greater anti-inflammatory effects than miR-153-3p. Together, these results indicate that miR-30a-5p and miR-153-3p inhibit MAPK/NF-κB pathway in microglia as well as ERK/STAT-3 pathway in astrocytes to reduce LPS-induced neuronal apoptosis. This study highlights the importance of NeuroD1 in microglia and astrocytes neuroinflammation and suggests that it can be regulated by miR-30a-5p and miR-153-3p. [BMB Reports 2022; 55(9): 447-452].

Molecular mechanisms involved in the effects of morin in experimental hepatic encephalopathy

This study aimed to investigate the possible usefulness of morin flavonoid in comparison to silymarin as a hepatic/neuronal-supportive agent with similar effects and higher bioavailability in a rat model of hepatic encephalopathy (HE). Morin effects on rat liver and brain were evaluated post-induction of HE by thioacetamide (TAA; 200 mg/kg/day for 3 successive days). Then, the serum activities of aspartate transaminase (AST) and alanine transaminase (ALT) together with ammonia concentration were estimated to assess the liver function. Also, the degree of brain effects was evaluated via the assessment of brain contents of reduced glutathione (GSH), malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and interleukin (IL-1β) together with glutathione peroxidase (GPx) activity. In addition, the apoptotic and inflammatory changes in brain and liver tissues were also assessed via immunohistochemical examination. Our findings revealed a promising effect of morin against HE complications; as it corrected the liver functions, attenuated the brain/liver tissue injuries, and reduced the apoptotic and inflammatory insults of HE on both organs. These effects are comparable to those of silymarin. Morin could be introduced as a promising hepato- and neuro-therapeutic adjuvant in HE-associated neuronal complications especially in cases like silymarin intolerance.

Role of p53 methylation in manganese-induced cyclooxygenase-2 expression in BV2 microglial cells

Manganese (Mn) is an essential cofactor for many enzymes and plays an important role in normal growth and development. However, excess exposure to manganese (Mn) may be an important environmental factor leading to neurodegeneration. The overexpression of microglial cyclooxygenase-2 (COX-2) plays a key role in neuroinflammation in neurodegenerative diseases. The existing data suggest that Mn can induce neuroinflammation by up-regulating COX-2 expression. However, the mechanisms involved in Mn-induced microglial COX-2 up-regulation remain to be determined. The aim of this study was to investigate the role of p53 in Mn-induced COX-2 expression in microglial cells. The results showed that Mn exposure induced the up-regulation of COX-2 and inhibited the expression of p53 in BV2 microglial cells. The addition of p53 activator and the over-expression of p53 blocked the expression of COX-2 and prostaglandin E2 (PGE2), a COX-2 downstream effector, induced by Mn. Further, Mn increased the methylation of p53 DNA in microglia, while the addition of demethylation reagent 5-Aza-dC enhanced the expression of p53 but decreased the expression of COX-2. These results suggested that Mn may inhibit p53 expression through induction of DNA methylation, which can further induce the expression of COX-2 in microglial cells.

Astrocytes and Microglia in Stress-Induced Neuroinflammation: The African Perspective

Background: Africa is laden with a youthful population, vast mineral resources and rich fauna. However, decades of unfortunate historical, sociocultural and leadership challenges make the continent a hotspot for poverty, indoor and outdoor pollutants with attendant stress factors such as violence, malnutrition, infectious outbreaks and psychological perturbations. The burden of these stressors initiate neuroinflammatory responses but the pattern and mechanisms of glial activation in these scenarios are yet to be properly elucidated. Africa is therefore most vulnerable to neurological stressors when placed against a backdrop of demographics that favor explosive childbearing, a vast population of unemployed youths making up a projected 42% of global youth population by 2030, repressive sociocultural policies towards women, poor access to healthcare, malnutrition, rapid urbanization, climate change and pollution. Early life stress, whether physical or psychological, induces neuroinflammatory response in developing nervous system and consequently leads to the emergence of mental health problems during adulthood. Brain inflammatory response is driven largely by inflammatory mediators released by glial cells; namely astrocytes and microglia. These inflammatory mediators alter the developmental trajectory of fetal and neonatal brain and results in long-lasting maladaptive behaviors and cognitive deficits. This review seeks to highlight the patterns and mechanisms of stressors such as poverty, developmental stress, environmental pollutions as well as malnutrition stress on astrocytes and microglia in neuroinflammation within the African context.

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

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

Gut Microbiota as a Potential Player in Mn-Induced Neurotoxicity

Manganese (Mn) is an essential metal, which at high exposures causes neurotoxic effects and neurodegeneration. The neurotoxic effects of Mn are mediated by neuroinflammation, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction, and other mechanisms. Recent findings have demonstrated the potential impact of Mn overexposure on gut microbiota dysbiosis, which is known to contribute to neurodegeneration via secretion of neuroactive and proinflammatory metabolites. Therefore, in this review, we discuss the existing data on the impact of Mn exposure on gut microbiota biodiversity, bacterial metabolite production, and gut wall permeability regulating systemic levels. Recent data have demonstrated that Mn exposure may affect gut microbiota biodiversity by altering the abundance of Shiegella, Ruminococcus, Dorea, Fusicatenibacter, Roseburia, Parabacteroides, Bacteroidetes, Firmicutes, Ruminococcaceae, Streptococcaceae, and other bacterial phyla. A Mn-induced increase in Bacteroidetes abundance and a reduced Firmicutes/Bacteroidetes ratio may increase lipopolysaccharide levels. Moreover, in addition to increased systemic lipopolysaccharide (LPS) levels, Mn is capable of potentiating LPS neurotoxicity. Due to the high metabolic activity of intestinal microflora, Mn-induced perturbations in gut microbiota result in a significant alteration in the gut metabolome that has the potential to at least partially mediate the biological effects of Mn overexposure. At the same time, a recent study demonstrated that healthy microbiome transplantation alleviates Mn-induced neurotoxicity, which is indicative of the significant role of gut microflora in the cascade of Mn-mediated neurotoxicity. High doses of Mn may cause enterocyte toxicity and affect gut wall integrity through disruption of tight junctions. The resulting increase in gut wall permeability further promotes increased translocation of LPS and neuroactive bacterial metabolites to the systemic blood flow, ultimately gaining access to the brain and leading to neuroinflammation and neurotransmitter imbalance. Therefore, the existing data lead us to hypothesize that gut microbiota should be considered as a potential target of Mn toxicity, although more detailed studies are required to characterize the interplay between Mn exposure and the gut, as well as its role in the pathogenesis of neurodegeneration and other diseases.

Functional Pathway Identification With CRISPR/Cas9 Genome-wide Gene Disruption in Human Dopaminergic Neuronal Cells Following Chronic Treatment With Dieldrin

Organochlorine pesticides, once widely used, are extremely persistent and bio-accumulative in the environment. Epidemiological studies have implicated that environmental exposure to organochlorine pesticides including dieldrin is a risk factor for the development of Parkinson's disease. However, the pertinent mechanisms of action remain poorly understood. In this study, we carried out a genome-wide (Brunello library, 19 114 genes, 76 411 sgRNAs) CRISPR/Cas9 screen in human dopaminergic SH-SY5Y neuronal cells exposed to a chronic treatment (30 days) with dieldrin to identify cellular pathways that are functionally related to the chronic cellular toxicity. Our results indicate that dieldrin toxicity was enhanced by gene disruption of specific components of the ubiquitin proteasome system as well as, surprisingly, the protein degradation pathways previously implicated in inherited forms of Parkinson's disease, centered on Parkin. In addition, disruption of regulatory components of the mTOR pathway which integrates cellular responses to both intra- and extracellular signals and is a central regulator for cell metabolism, growth, proliferation, and survival, led to increased sensitivity to dieldrin-induced cellular toxicity. This study is one of the first to apply a genome-wide CRISPR/Cas9-based functional gene disruption screening approach in an adherent neuronal cell line to globally decipher cellular mechanisms that contribute to environmental toxicant-induced neurotoxicity and provides novel insight into the dopaminergic neurotoxicity associated with chronic exposure to dieldrin.

N-Acetylcysteine Ameliorates Neurotoxic Effects of Manganese Intoxication in Rats: A Biochemical and Behavioral Study

Clinical and experimental evidences reveal that excess exposure to manganese is neurotoxic and leads to cellular damage. However, the mechanism underlying manganese neurotoxicity remains poorly understood but oxidative stress has been implicated to be one of the key pathophysiological features related to it. The present study investigates the effects associated with manganese induced toxicity in rats and further to combat these alterations with a well-known antioxidant N-acetylcysteine which is being used in mitigating the damage by its radical scavenging activity. The study was designed to note the sequential changes along with the motor and memory dysfunction associated with biochemical and histo-pathological alterations following exposure and treatment for 2 weeks. The results so obtained showed decrease in the body weights, behavioral deficits with increased stress markers and also neuronal degeneration in histo-pathological examination after manganese intoxication in rats. To overcome the neurotoxic effects of manganese, N-acetylcysteine was used in the current study due to its pleiotropic potential in several pathological ailments. Taken together, N-acetylcysteine helped in ameliorating manganese induced neurotoxic effects by diminishing the behavioral deficits, normalizing acetylcholinesterase activity, and augmentation of redox status.

Manganese Accumulation in the Brain via Various Transporters and Its Neurotoxicity Mechanisms

Manganese (Mn) is an essential trace element, serving as a cofactor for several key enzymes, such as glutamine synthetase, arginase, pyruvate decarboxylase, and mitochondrial superoxide dismutase. However, its chronic overexposure can result in a neurological disorder referred to as manganism, presenting symptoms similar to those inherent to Parkinson’s disease. The pathological symptoms of Mn-induced toxicity are well-known, but the underlying mechanisms of Mn transport to the brain and cellular toxicity leading to Mn’s neurotoxicity are not completely understood. Mn’s levels in the brain are regulated by multiple transporters responsible for its uptake and efflux, and thus, dysregulation of these transporters may result in Mn accumulation in the brain, causing neurotoxicity. Its distribution and subcellular localization in the brain and associated subcellular toxicity mechanisms have also been extensively studied. This review highlights the presently known Mn transporters and their roles in Mn-induced neurotoxicity, as well as subsequent molecular and cellular dysregulation upon its intracellular uptakes, such as oxidative stress, neuroinflammation, disruption of neurotransmission, α-synuclein aggregation, and amyloidogenesis.

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

Background

The 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.

Methods

The 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.

Results

Our 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.

Conclusion

PAS-Na antagonized Mn-induced NLRP3 inflammasome dependent pyroptosis through inhibiting NF-κB pathway activation and oxidative stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02018-6.

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.

The impact of manganese on neurotransmitter systems

BACKGROUND

Manganese (Mn) is a metal ubiquitously present in nature and essential for many living organisms. As a trace element, it is required in small amounts for the proper functioning of several important enzymes, and reports of Mn deficiency are indeed rare.

METHODS

This mini-review will cover aspects of Mn toxicokinetics and its impact on brain neurotransmission, as well as its Janus-faced effects on humans and other animal's health.

RESULTS

The estimated safe upper limit of intracellular Mn for physiological function is in anarrow range of 20-53 μM.Therefore, intake of higher levels of Mn and the outcomes, especially to the nervous system, have been well documented.

CONCLUSION

The metal affects mostly the brain by accumulating in specific areas, altering cognitive functions and locomotion, thus severely impacting the health of the exposed organisms.

Preventive impacts of PAS-Na on the slow growth and activated inflammatory responses in Mn-exposed rats

BACKGROUND

Sodium para-aminosalicylic acid (PAS-Na), an anti-tuberculosis drug, has been demonstrated its function in facilitating the Mn elimination in manganism patients and Mn-exposed models in vivo and improving the symptoms of Mn poisoning. But whether it can improve the growth retardation and inflammatory responses induced by Mn have not been reported.

OBJECTIVES

This study was designed to investigate the preventive effects of PAS-Na on the development of retardation and inflammatory responses in Mn-exposed rats.

METHODS

Male Sprague Dawley (SD) rats (8 weeks old, weighing 180 ± 20 g) were randomly divided into normal control group and Mn-exposed group in the 4 weeks experiment observation and normal control group, Mn-exposed group, PAS-Na preventive group and PAS-Na control group in the 8 weeks experiment observation. The Mn-exposed group received an intraperitoneal injection (i.p.) of 15 mg/kg MnCl₂ and the normal control group i.p. physiological Saline in the same volume once a day for 4 or 8 weeks, 5 days per week. The PAS-Na preventive group i.p. 15 mg/kg MnCl₂ along with back subcutaneous (s.c.) injection of 240 mg/kg PAS-Na once a day for 8 weeks, 5 days per week. PAS-Na control group received s.c. injection of 240 mg/kg PAS-Na along with i.p. injection of saline once daily. The body weight was determined once a week until the end of the experiment. The manganese contents in the blood were detected by graphite furnace atomic absorption spectrometry. The inflammatory factor levels (TNF-α, IL-1β, IL-6, and PGE2) in the blood were detected by using enzyme-linked immunosorbent assay (Elisa) and each organ taking from rats were weighed and recorded.

RESULTS

Mn exposure significantly suppressed the growth in rats and increased heart, liver, spleen and kidney coefficients as compared with the control group. The whole blood Mn level and serum levels of IL-1β, IL-6, PGE2, and TNF-α in sub-chronic Mn-exposure group were markedly higher than those in the control group. However, preventive treatment with PAS-Na obviously reduced the whole blood Mn level, the spleen and liver coefficients of the Mn-exposed rats. And serum levels of IL-1β and TNF-α were significantly reduced by 33.9% and 14.7% respectively in PAS-Na prevention group.

CONCLUSIONS

PAS-Na could improve the growth retardation and alleviate inflammatory responses in Mn-exposed rats.

Environmental neurotoxicant-induced dopaminergic neurodegeneration: a potential link to impaired neuroinflammatory mechanisms

With the increased incidence of neurodegenerative diseases worldwide, Parkinson's disease (PD) represents the second-most common neurodegenerative disease. PD is a progressive multisystem neurodegenerative disorder characterized by a marked loss of nigrostriatal dopaminergic neurons and the formation of Lewy pathology in diverse brain regions. Although the mechanisms underlying dopaminergic neurodegeneration remain poorly characterized, data from animal models and postmortem studies have revealed that heightened inflammatory responses mediated via microglial and astroglial activation and the resultant release of proinflammatory factors may act as silent drivers of neurodegeneration. In recent years, numerous studies have demonstrated a positive association between the exposure to environmental neurotoxicants and the etiology of PD. Although it is unclear whether neuroinflammation drives pesticide-induced neurodegeneration, emerging evidence suggests that the failure to dampen neuroinflammatory mechanisms may account for the increased vulnerability to pesticide neurotoxicity. Furthermore, recent studies provide additional evidence that shifts the focus from a neuron-centric view to glial-associated neurodegeneration following pesticide exposure. In this review, we propose to summarize briefly the possible factors that regulate neuroinflammatory processes during environmental neurotoxicant exposure with a focus on the potential roles of mitochondria-driven redox mechanisms. In this context, a critical discussion of the data obtained from experimental research and possible epidemiological studies is included. Finally, we hope to provide insights on the pivotal role of exosome-mediated intercellular transmission of aggregated proteins in microglial activation response and the resultant dopaminergic neurodegeneration after exposure to pesticides. Collectively, an improved understanding of glia-mediated neuroinflammatory signaling might provide novel insights into the mechanisms that contribute to neurodegeneration induced by environmental neurotoxicant exposure.

The effect of the source and dose of manganese on the performance, digestibility and distribution of selected minerals, redox, and immune status of turkeys

The aim of this study was to determine the effect of various levels of manganese added to the diet of growing turkeys in the conventional form of MnO or in the form of NP-Mn2O3 nanoparticles on growth performance, absorption, and accumulation of Mn, Zn, and Cu, and antioxidant and immune status. The experiment was conducted on 1080 one-day-old Hybrid Converter turkeys randomly assigned to 6 groups with 10 replications, in a two-factor design with three dosages of manganese - 100, 50, and 10 mg/kg, and two sources-manganese oxide (MnO) and manganese nanoparticles (NP-Mn2O3). Neither reducing the addition of Mn from 100 to 50 or even 10 mg/kg of the diet nor replacing MnO with NP-Mn2O3 had a negative effect on the growth performance of the turkeys. Replacing MnO with NP-Mn2O3 in the turkey diet improved ileal digestibility of Mn and decreased accumulation of Cu in the liver and breast muscle. The study showed that irrespective of the form used, reducing the level of Mn supplementation of the diet from the 100 mg/kg recommended by British United Turkey to 50 or 10 mg/kg decreased its ileal digestibility and increased its accumulation in the liver, breast muscle, and skin. Reducing the addition of Mn to the turkey diet increased intestinal absorption of Zn and reduced accumulation of Zn and Cu in the liver, breast muscle, and skin. It did not increase oxidation processes in the liver or breast muscle of the turkeys. Reducing the addition of Mn to the turkey diet stimulated the immune system, which was manifested by stimulation of B cells to produce immunoglobulin M and by the release of the cytokine IL-6, but did not intensify apoptosis. The results of the study indicate that the recommended manganese supplement in turkey diets can be reduced. The use of manganese nanoparticles in turkey feeding requires further study.

Trace element levels are associated with neuroinflammatory markers in children with autistic spectrum disorder

The objective of the present study was to estimate the association between brain inflammatory markers and serum trace element levels as assessed by inductively coupled plasma mass spectrometry at NexION 300D. Leukocyte elastase (LE), α1-proteinase inhibitor (α1-PI) activity, anti-nerve growth factor-antibodies (anti-NGF-Ab), and anti-myelin basic protein-antibodies (anti-MBP-Ab) levels were assessed as inflammatory markers. The obtained data demonstrate that the increase in LE and α1-PI activity is associated with higher serum Cr and Cu levels, respectively. The increase in Anti-NGF-Ab levels was associated with a nearly significant 16% increase in serum Mn levels. Autistic children with high MBP-Ab levels were characterized by 28% higher serum Mn and lower Mg concentration. The results of correlation analysis were generally in agreement with the outcome of group comparisons. Regression analysis demonstrated that serum Mg was significantly negatively associated with LE activity, whereas both serum Fe and V concentrations were characterized by a positive influence on the parameter. In turn, serum Cu was a significant predictor of α1-PI, as well as Cr levels. At the same time, the serum concentrations of Cd and Fe were found to be inversely associated with α1-PI levels. Serum Cd and Mn levels were significant positive predictors of anti-MBP-Ab levels, whereas Mg levels had a negative impact on anti-MBP-Ab values. Generally, the obtained data demonstrate the interrelationship between trace element homeostasis and neuroinflammation in autism. Hypothetically, modulation of trace element status may be used for reduction of neuroinflammatory response, although further studies are required to reveal the underlying mechanisms of the observed associations.

Regulated Necrosis Orchestrates Microglial Cell Death in Manganese-Induced Toxicity

Microglia, the brain resident immune cells, play prominent roles in immune surveillance, tissue repair and neural regeneration. Despite these pro-survival actions, the relevance of these cells in the progression of several neuropathologies has been established. In the context of manganese (Mn) overexposure, it has been proposed that microglial activation contributes to enhance the neurotoxicity. However, the occurrence of a direct cytotoxic effect of Mn on microglial cells remains controversial. In the present work, we investigated the potential vulnerability of immortalized mouse microglial cells (BV-2) toward Mn²⁺, focusing on the signaling pathways involved in cell death. Evidence obtained showed that Mn²⁺ induces a decrease in cell viability which is associated with reactive oxygen species (ROS) generation. In this report we demonstrated, for the first time, that Mn²⁺ triggers regulated necrosis (RN) in BV-2 cells involving two central mechanisms: parthanatos and lysosomal disruption. The occurrence of parthanatos is supported by several cellular and molecular events: (i) DNA damage; (ii) AIF translocation from mitochondria to the nucleus; (iii) mitochondrial membrane permeabilization; and (iv) PARP1-dependent cell death. On the other hand, Mn²⁺ induces lysosomal membrane permeabilization (LMP) and cathepsin D (CatD) release into the cytosol supporting the lysosomal disruption. Pre-incubation with CatB and D inhibitors partially prevented the Mn²⁺-induced cell viability decrease. Altogether these events point to lysosomes as players in the execution of RN. In summary, our results suggest that microglial cells could be direct targets of Mn²⁺ damage. In this scenario, Mn²⁺ triggers cell death involving RN pathways.

Recent Advances in Biomarkers for Parkinson's Disease

Parkinson's disease (PD) is one of the common progressive neurodegenerative disorders with several motor and non-motor symptoms. Most of the motor symptoms may appear at a late stage where most of the dopaminergic neurons have been already damaged. In order to provide better clinical intervention and treatment at the onset of disease, it is imperative to find accurate biomarkers for early diagnosis, including prodromal diagnosis and preclinical diagnosis. At the same time, these reliable biomarkers can also be utilized to monitor the progress of the disease. In this review article, we will discuss recent advances in the development of PD biomarkers from different aspects, including clinical, biochemical, neuroimaging and genetic aspects. Although various biomarkers for PD have been developed so far, their specificity and sensitivity are not ideal when applied individually. So, the combination of multimodal biomarkers will greatly improve the diagnostic accuracy and facilitate the implementation of personalized medicine.

The effect of manganese nanoparticles on apoptosis and on redox and immune status in the tissues of young turkeys

The aim of the study was to determine whether the use of Mn nanoparticles would make it possible to reduce the level of this micronutrient added to turkey diets without adversely affecting growth performance, antioxidant and immune status, or apoptosis. The experiment was conducted on 6 groups of turkeys with 10 replications in a two-factor design with 3 dosages of manganese, 100, 50 and 10 mg/kg, and 2 sources, manganese oxide (MnO) and manganese nanoparticles (NP-Mn₂O₃). The study showed that irrespective of the form of Mn used, reducing the Mn level recommended by British United Turkeys for supplementation of the diet of young turkeys from 100 mg/kg to 10 mg/kg increases the content of this element in the blood with no adverse effect on growth performance or the immune system. The reduction in Mn supplementation in the form of NP-Mn₂O₃ from 100 to 50 and even to 10 mg/kg of turkey diet has no negative effect on antioxidant defence in young turkeys. A 50% reduction of the recommended Mn level in the form of MnO enhances lipid oxidation processes. Replacing MnO with NP-Mn₂O₃ in the turkey diet probably can increase apoptosis in young turkeys. On the other hand, irrespective of the form of Mn used, reducing supplementation of the turkey diet with this element from 100 to 50 and even to 10 mg/kg probably can reduce apoptosis.

Effect of High Dietary Manganese on the Immune Responses of Broilers Following Oral Salmonella typhimurium Inoculation

Manganese (Mn) is an essential nutrient for both host and pathogen. Recent studies have demonstrated the nutritional immunity of Mn against Salmonella infection in mammals. To investigate the effect of high dietary Mn on immune responses of broilers following Salmonella challenge, 144 1-day-old male broilers were fed a basal diet (containing 20.04 mg Mn/kg) plus an additional 40 (the control group) or 400 mg Mn/kg (the H-Mn group) for 7 days. The 72 broilers in each group were then orally inoculated with 5 × 10⁷ CFUs of Salmonella typhimurium (ATCC#14028) or phosphate-buffered saline. Peripheral blood, spleens, cecal tonsils, and bursa of Fabricius were collected from Salmonella-inoculated and Salmonella-noninoculated broilers (n = 6) at 2 days post inoculation (2 DPI) and 7 days post inoculation (7 DPI). Peripheral blood lymphocyte subpopulations were determined by flow cytometry. The messenger RNA (mRNA) abundance of genes was determined by quantitative real-time polymerase chain reaction. Salmonella counts were higher (P < 0.05) in the H-Mn group than that in the control group at 2 DPI in the cecal contents of Salmonella-inoculated broilers. High dietary Mn increased CD3⁺CD4⁺ and CD3⁺CD8⁺ percentages in the peripheral blood of Salmonella-inoculated broilers at 2 DPI. Salmonella inoculation increased interleukin (IL)-6 mRNA expression in spleens and bursa of Fabricius at 2 DPI and increased IL-1β and IL-6 mRNA expression in cecal tonsils at 7 DPI in the H-Mn group. These changes were not observed in the control group. High dietary Mn increased interferon-γ (IFN-γ) in spleens and decreased IFN-γ and IL-12 mRNA expression in cecal tonsils of Salmonella-inoculated broilers at 2 DPI. High dietary Mn decreased IL-17 mRNA expression in the bursa of Fabricius at 7 DPI, but increased this expression in cecal tonsils at 2 and 7 DPI in Salmonella-inoculated broilers. These results suggested that dietary Mn level affected T helper (Th) 1-cytokine reaction in spleens and cecal tonsils, and Th17-mediated immunity in cecal tonsils and the bursa of Fabricius of broilers when challenged with Salmonella.

Deciphering variability in the role of interleukin-1β in Parkinson's disease

Although the role of inflammation in neurodegeneration has been well acknowledged, less is known on the issue of each cytokine in specific neurodegenerative diseases. In this review, we will present evidence elucidating that interleukin-1β (IL-1β) has a multi-faceted character in pathogenesis of Parkinson's disease, which is a progressive neurodegenerative disorder. Increased levels of IL-1β were found in PD patients. Besides, PD symptoms were observed in IL-1β wild-type, but not deficient, animals. These lines of evidence suggest that IL-1β may contribute to the initiation or progression of PD. On the other hand, some studies reported decreased levels of IL-1β in PD patients. Also, genetic studies provided evidence suggesting that IL-1β may protect individuals against PD. Presumably, the broad range of IL-1β role is due to its interaction with both upstream and downstream mediators. Differences in IL-1β levels could be because of glia population (i.e. microglia and astrocytes), mitogen-activated protein kinase and nuclear factor κ light-chain-enhancer of activated B cells signaling pathways, and several mediators (including cyclooxygenase, neurotrophic factors, reactive oxygen species, caspases, heme oxygenase-1, and matrix metalloproteinases). Although far from practice at this point, unraveling theoretical therapeutic targets based on the up-down IL-1β neuroweb could facilitate the development of strategies that are likely to be used for pharmaceutical designs of anti-neurodegenerative drugs of the future.

Ischemia-responsive protein 94 is a key mediator of ischemic neuronal injury-induced microglial activation

Neuroinflammation, especially activation of microglia, the key immune cells in the brain, has been proposed to contribute to the pathogenesis of ischemic stroke. However, the dynamics and the potential mediators of microglial activation following ischemic neuronal injury are not well understood. In this study, using oxygen/glucose deprivation and reoxygenation with neuronal and microglial cell cultures as an in vitro model of ischemic neuronal injury, we set out to identify neuronal factors released from injured neurons that are capable of inducing microglial activation. Conditioned media (CM) from hippocampal and cortical neurons exposed to oxygen/glucose deprivation and reoxygenation induced significant activation of microglial cells as well as primary microglia, evidenced by up-regulation of inducible nitric oxide synthase, increased production of nitrite and reactive oxygen species, and increased expression of microglial markers. Mechanistically, neuronal ischemia-responsive protein 94 (Irp94) was a key contributor to microglial activation since significant increase in Irp94 was detected in the neuronal CM following ischemic insult and immunodepletion of Irp94 rendered ischemic neuronal CM ineffective in inducing microglial activation. Ischemic insult-augmented oxidative stress was a major facilitator of neuronal Irp94 release, and pharmacological inhibition of NADPH oxidase significantly reduced the ischemic injury-induced neuronal reactive oxygen species production and Irp94 release. Taken together, these results indicate that neuronal Irp94 may play a pivotal role in the propagation of ischemic neuronal damage. Continued studies may help identify Irp94 and/or related proteins as potential therapeutic targets and/or diagnostic/prognostic biomarkers for managing ischemia-associated brain disorders.

Sodium P-aminosalicylic acid inhibits sub-chronic manganese-induced neuroinflammation in rats by modulating MAPK and COX-2

Excessive manganese (Mn) accumulation in the brain may induce an extrapyramidal disorder known as manganism. Inflammatory processes play a critical role in neurodegenerative diseases. Therapeutically, non-steroidal anti-inflammatory drugs or analogous anti-inflammatory therapies have neuroprotective effects. As a non-steroidal anti-inflammatory drug, p-aminosalicylic acid (PAS) has anti-inflammatory effects, which are mediated by decreased prostaglandins E2 (PGE2) levels. The aim of the current study was to investigate whether PAS-Na treatment prevents Mn-induced behavioral changes and neuroinflammation in vivo. Male Sprague-Dawley rats were intraperitoneally (i.p.) injected with MnCl₂·4H₂O (15mg/kg) for 12 weeks, followed by 6 weeks PAS-Na treatment. Sub-chronic Mn exposure increased Mn levels in the whole blood, cortex, hippocampus and thalamus, and induced learning and memory deficits, concomitant with astrocytes activation in the cortex, hippocampus and thalamus. Moreover inflammatory cytokine levels in serum and brain of Mn-treated group were increased, including IL-1β, IL-6, TNF-αand PGE2, especially in the hippocampus and thalamus. Furthermore, sub-chronic Mn exposure also increased inflammatory cytokines and COX-2 in transcription levels concomitant with increased MAPK signaling and COX-2 in the same selected brain regions. PAS-Na treatment at the highest doses also decreased Mn levels in the whole blood and selected brain tissues, and reversed the Mn-induced learning and memory deficits. PAS-Na inhibited astrocyte activation as well as the Mn-induced increase in inflammatory cytokine levels, reducing p38, ERK MAPK pathway and COX-2 activity. In contrast PAS-Na had no effects on the JNK MAPK pathway. These data establish the efficacy of PAS-Na not only as a chelating agent to mobilize whole blood Mn, but also as an anti-inflammatory agent.

De Novo and Uninterrupted SILAC Labeling of Primary Microglia

Microglia have increasingly been recognized as playing a wide spectrum of roles in various physiological and pathological processes in the central nervous system. Studies in the past have mostly associated individual microglial enzymes or soluble factors such as cytokines with specific functions of microglia. Stable isotope labeling with amino acids in cell culture (SILAC)-based proteomic analysis enables an unbiased, simultaneous, and global-scale analysis of the expression of thousands of proteins involved in key cellular pathways that regulate microglial activities. Primary microglia, characteristically, bear a much greater resemblance to microglia in vivo than immortalized microglial cell lines. In this chapter, we provide a detailed protocol for a de novo and uninterrupted primary culture SILAC labeling strategy (DUP-SILAC) for primary rat microglia that could be applied to the analysis of microglial involvement in various normal and disease processes.

Microglia amplify inflammatory activation of astrocytes in manganese neurotoxicity

BACKGROUND

As the primary immune response cell in the central nervous system, microglia constantly monitor the microenvironment and respond rapidly to stress, infection, and injury, making them important modulators of neuroinflammatory responses. In diseases such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and human immunodeficiency virus-induced dementia, activation of microglia precedes astrogliosis and overt neuronal loss. Although microgliosis is implicated in manganese (Mn) neurotoxicity, the role of microglia and glial crosstalk in Mn-induced neurodegeneration is poorly understood.

METHODS

Experiments utilized immunopurified murine microglia and astrocytes using column-free magnetic separation. The effect of Mn on microglia was investigated using gene expression analysis, Mn uptake measurements, protein production, and changes in morphology. Additionally, gene expression analysis was used to determine the effect Mn-treated microglia had on inflammatory responses in Mn-exposed astrocytes.

RESULTS

Immunofluorescence and flow cytometric analysis of immunopurified microglia and astrocytes indicated cultures were 97 and 90% pure, respectively. Mn treatment in microglia resulted in a dose-dependent increase in pro-inflammatory gene expression, transition to a mixed M1/M2 phenotype, and a de-ramified morphology. Conditioned media from Mn-exposed microglia (MCM) dramatically enhanced expression of mRNA for Tnf, Il-1β, Il-6, Ccl2, and Ccl5 in astrocytes, as did exposure to Mn in the presence of co-cultured microglia. MCM had increased levels of cytokines and chemokines including IL-6, TNF, CCL2, and CCL5. Pharmacological inhibition of NF-κB in microglia using Bay 11-7082 completely blocked microglial-induced astrocyte activation, whereas siRNA knockdown of Tnf in primary microglia only partially inhibited neuroinflammatory responses in astrocytes.

CONCLUSIONS

These results provide evidence that NF-κB signaling in microglia plays an essential role in inflammatory responses in Mn toxicity by regulating cytokines and chemokines that amplify the activation of astrocytes.

Inflammatory Activation of Microglia and Astrocytes in Manganese Neurotoxicity

Neurotoxicity due to excessive exposure to manganese (Mn) has been described as early as 1837 (Couper, Br Ann Med Pharm Vital Stat Gen Sci 1:41-42, 1837). Extensive research over the past two decades has revealed that Mn-induced neurological injury involves complex pathophysiological signaling mechanisms between neurons and glial cells. Glial cells are an important target of Mn in the brain, both for sequestration of the metal, as well as for activating inflammatory signaling pathways that damage neurons through overproduction of numerous reactive oxygen and nitrogen species and inflammatory cytokines. Understanding how these pathways are regulated in glial cells during Mn exposure is critical to determining the mechanisms underlying permanent neurological dysfunction stemming from excess exposure. The subject of this review will be to delineate mechanisms by which Mn interacts with glial cells to perturb neuronal function, with a particular emphasis on neuroinflammation and neuroinflammatory signaling between distinct populations of glial cells.

The biomarkers of immune dysregulation and inflammation response in Parkinson disease

Parkinson's disease (PD) is referring to the multi-systemic α-synucleinopathy with Lewy bodies deposited in midbrain. In ageing, the environmental and genetic factors work together and overactive major histocompatibility complex pathway to regulate immune reactions in central nerve system which resulting in neural degeneration, especially in dopaminergic neurons. As a series of biomarkers, the human leukocyte antigen genes with its related proteomics play cortical roles on the antigen presentation of major histocompatibility complex molecules to stimulate the differentiation of T lymphocytes and i-proteasome activities under their immune response to the PD-related environmental alteration and genetic variation. Furthermore, dopaminergic drugs change the biological characteristic of T lymphatic cells, affect the α-synuclein presentation pathway, and inhibit T lymphatic cells to release cytotoxicity in PD development. Taking together, the serum inflammatory factors and blood T cells are involved in the immune dysregulation of PD and inspected as the potential clinic biomarkers for PD prediction.

Manganism and Parkinson's disease: Mn(ii) and Zn(ii) interaction with a 30-amino acid fragment

A 30-amino acid fragment, Ac-SPDEKHELMIQLQKLDYTVGFCGDGANDCG-Am, from residues 1164 to 1193 in the encoded protein from Parkinson's disease gene Park9 (YPk9), was studied for manganese and zinc binding.

Interleukin-10 Protection against Lipopolysaccharide-Induced Neuro-Inflammation and Neurotoxicity in Ventral Mesencephalic Cultures

Interleukin (IL)-10, an anti-inflammatory cytokine, is expressed in the brain and can inhibit microglial activation. Herein, we utilized lipopolysaccharide (LPS)-induced inflammatory Parkinson’s disease (PD) cell model to determine whether microglia and astrocytes are necessary targets for IL-10 neuroprotection. Primary ventral mesencephalic (VM) cultures with different composition of neurons, microglia and astrocytes were prepared. The cells were exposed to IL-10 (15, 50 or 150 ng/mL) 1 h prior to LPS (50 ng/mL) treatment. LPS induced dopaminergic and non-dopaminergic neuronal loss in VM cultures, VM neuron-enriched cultures, and neuron-microglia co-cultures, but not in neuron-astrocyte co-cultures. IL-10 reduced LPS-induced neuronal loss particularly in single VM neuron cultures. Pro-inflammatory mediators (TNF-α, IL-1β, inducible nitric oxide synthase and cyclooxygenase-2) were upregulated in both neuron-microglia and neuron-astrocyte co-cultures by LPS. In contrast, neurotrophic factors (brain-derived neurotrophic factor, insulin-like growth factor-1 or glial cell-derived neurotrophic factor) were downregulated in neuron-microglia co-cultures, but upregulated in neuron-astrocyte co-cultures by LPS. IL-10 reduced both the increase in production of the pro-inflammatory mediators and the decrease in production of the neurotrophic factors induced by LPS. These results suggest that astrocytes can balance LPS neurotoxicity by releasing more neurotrophic factors and that IL-10 exerts neuroprotective property by an extensive action including direct on neurons and indirect via inhibiting microglial activation.

Manganese Is Essential for Neuronal Health

The understanding of manganese (Mn) biology, in particular its cellular regulation and role in neurological disease, is an area of expanding interest. Mn is an essential micronutrient that is required for the activity of a diverse set of enzymatic proteins (e.g., arginase and glutamine synthase). Although necessary for life, Mn is toxic in excess. Thus, maintaining appropriate levels of intracellular Mn is critical. Unlike other essential metals, cell-level homeostatic mechanisms of Mn have not been identified. In this review, we discuss common forms of Mn exposure, absorption, and transport via regulated uptake/exchange at the gut and blood-brain barrier and via biliary excretion. We present the current understanding of cellular uptake and efflux as well as subcellular storage and transport of Mn. In addition, we highlight the Mn-dependent and Mn-responsive pathways implicated in the growing evidence of its role in Parkinson's disease and Huntington's disease. We conclude with suggestions for future focuses of Mn health-related research.

Ceruloplasmin potentiates nitric oxide synthase activity and cytokine secretion in activated microglia

BACKGROUND

Ceruloplasmin is a ferroxidase expressed in the central nervous system both as soluble form in the cerebrospinal fluid (CSF) and as membrane-bound GPI-anchored isoform on astrocytes, where it plays a role in iron homeostasis and antioxidant defense. It has been proposed that ceruloplasmin is also able to activate microglial cells with ensuing nitric oxide (NO) production, thereby contributing to neuroinflammatory conditions. In light of the possible role of ceruloplasmin in neurodegenerative diseases, we were prompted to investigate how this protein could contribute to microglial activation in either its native form, as well as in its oxidized form, recently found generated in the CSF of patients with Parkinson's and Alzheimer's diseases.

METHODS

Primary rat microglial-enriched cultures were treated with either ceruloplasmin or oxidized-ceruloplasmin, alone or in combination with lipopolysaccharide (LPS). Production of NO and expression of inducible nitric oxide synthase (iNOS) were evaluated by Griess assay and Western blot analysis, respectively. The productions of the pro-inflammatory cytokine IL-6 and the chemokine MIP-1α were assessed by quantitative RT-PCR and ELISA.

RESULTS

Regardless of its oxidative status, ceruloplasmin by itself was not able to activate primary rat microglia. However, ceruloplasmin reinforced the LPS-induced microglial activation, promoting an increase of NO production, as well as the induction of IL-6 and MIP-1α. Interestingly, the ceruloplasmin-mediated effects were observed in the absence of an additional induction of iNOS expression. The evaluation of iNOS activity in primary glial cultures and in vitro suggested that the increased NO production induced by the combined LPS and ceruloplasmin treatment is mediated by a potentiation of the enzymatic activity.

CONCLUSIONS

Ceruloplasmin potentiates iNOS activity in microglial cells activated by a pro-inflammatory stimulus, without affecting iNOS expression levels. This action might be mediated by the activation of a yet unknown Cp receptor that triggers intracellular signaling that cross-talks with the response elicited by LPS or other pro-inflammatory stimuli. Therefore, ceruloplasmin might contribute to pathological conditions in the central nervous system by exacerbating neuroinflammation.

Oxidative induction of pro-inflammatory cytokine formation by human monocyte-derived macrophages following exposure to manganese in vitro

Manganese (as Mn(2+)), a superoxide dismutase mimetic, catalyzes the formation of the relatively stable membrane-permeable reactive oxygen species (ROS) hydrogen peroxide (H2O2), a mediator of intracellular redox signaling in immune and inflammatory cells. The goal of this study was to investigate the potential for Mn(2+), via its pro-oxidative properties, to activate production of pro-inflammatory cytokines/chemokines IL-1β, IL-6, IL-8, IFNγ, TNFα, and G-CSF by human monocyte-derived macrophages in vitro. For these studies, the cells were isolated from peripheral blood mononuclear leukocytes and matured to generate a population of large CD14/CD16 co-expressing cells. The monocyte-derived macrophages were then exposed to bacterial lipopolysaccharide (LPS, 1 μg/ml) or MnCl2 (25-100 μM)-alone or in combination-for 24 h at 37 °C, after which cell-free supernatants were analyzed using a multiplex cytokine assay procedure. Exposure of the cells to LPS caused modest statistically insignificant increases in cytokine production; MnCl2 caused dose-related increases in production of all six cytokines (achieving statistical significance of p < 0.0171- < 0.0005 for IL-1β, IL-6, IL-8, IFNγ, and TNFα). In the case of LPS and MnCl2 combinations, the observed increases in production of IL-1β, IL-6, IL-8, IFNγ, and G-CSF were greater than those seen with cells exposed to the individual agents. The Mn(2+)-mediated induction of cytokine production was associated with increased production of H2O2 and completely attenuated by inclusion of the H2O2-scavenger dithiothreitol, and partially by inhibitors of NF-κB and p38MAP kinase. The findings from the studies here help to further characterize the pro-inflammatory mechanisms that may underpin clinical disorders associated with excess exposure to Mn(2+), particularly those disorders seen in the central nervous and respiratory systems.

Protective role of sodium para-amino salicylic acid against manganese-induced hippocampal neurons damage

Manganese (Mn) is an essential trace element of human. However, excessive Mn can cause manganism. Mn selectively accumulated in Mn-exposed workers' hippocampus which is crucial for higher brain functions such as learning, memory, and motivation during our postnatal life. Studies suggested sodium para-aminosalicylic acid (PAS) appeared to be therapeutic for manganism. We aimed to explore whether PAS could block Mn-induced neuronal injury in hippocampus in vitro. Hippocampal neurons were exposed to 50 μM manganese chloride (MnCl(2)) for 24 h, following by 50, 500, or 5000 μM PAS treatment for 24 h. Cell viability, apoptosis rate, mean fluorescence intensity of mitochondrial and DNA damage were respectively performed. MnCl(2) significantly decreased neurons' viability and fluorescence intensity of comet head of DNA, while increasing the apoptosis rate, mean fluorescence intensity of mitochondrial, percentage of tail DNA, and Olive tail moment of DNA. PAS reduced the percentage of tail DNA and Olive tail moment of Mn-exposed neurons. These data suggested that Mn caused hippocampal neurons' injury, and 50-5000 μM PAS could inhibit Mn-induced DNA damage.

Perspectives on neuroinflammation and excitotoxicity: a neurotoxic conspiracy?

Emerging evidences underline the ability of several environmental contaminants to induce an inflammatory response within the central nervous system, named neuroinflammation. This can occur as a consequence of a direct action of the neurotoxicant to the CNS and/or as a response secondary to the activation of the peripheral inflammatory response. In both cases, neuroinflammation is driven by the release of several soluble factors among which pro-inflammatory cytokines. IL-1β and TNF-α have been extensively studied for their effects within the CNS and emerged for their role in the modulation of the neuronal response, which allow the immune response to integrate with specific neuronal functions, as neurotransmission and synaptic plasticity. In particular, it has been evidenced a potential detrimental link between these cytokines and the glutamatergic system that seems to be part of increased brain excitability and excitotoxicity occurring in different pathological conditions. Aim of this mini-review will be to present experimental evidence on the way IL-1β and TNF-α impact neurons, focusing on the glutamatergic signalling, to provide a perspective on novel pathways possibly involved in environmental contaminants neurotoxicity.

Study on the dynamic changes in synaptic vesicle-associated protein and axonal transport protein combined with LPS neuroinflammation model

Microglia activation is the major component of inflammation that constitutes the characteristic of neurodegenerative disease. A large amount of researches have demonstrated that inflammation involved in the pathogenesis of PD process activated microglia acting on the neurons through the release of a variety of inflammatory factors. However, the molecular mechanism underlying how it does work on neurons is still unclear. Here, we show that intracerebral injections of LPS induced Parkinson's disease pathology in C57BL/6J mice. Furthermore, study on the dynamic changes in Synaptic vesicle-associated protein and axonal transport Protein in this process. The results indicated that after administration of LPS in the brain, the inflammatory levels of TNF-α and IL-1β both are elevated, and have a time-dependent.

The liver-brain axis in liver failure: neuroinflammation and encephalopathy

Systemic inflammation is common in liver failure and its acquisition is a predictor of hepatic encephalopathy severity. New studies provide convincing evidence for a role of neuroinflammation (inflammation of the brain per se) in liver failure; this evidence includes activation of microglia, together with increased synthesis in situ of the proinflammatory cytokines TNF, IL-1β and IL-6. Liver-brain signalling mechanisms in liver failure include: direct effects of systemic proinflammatory molecules, recruitment of monocytes after microglial activation, brain accumulation of ammonia, lactate and manganese, and altered permeability of the blood-brain barrier. Ammonia and cytokines might act synergistically. Existing strategies to reduce ammonia levels (including lactulose, rifaximin and probiotics) have the potential to dampen systemic inflammation, as does albumin dialysis, mild hypothermia and N-acetylcysteine, the latter two agents acting at both peripheral and central sites. Minocycline, an agent with potent central anti-inflammatory properties, reduces neuroinflammation, brain oedema and encephalopathy in liver failure, as does the anti-TNF agent etanercept.

Manganese neurotoxicity: a focus on glutamate transporters

Manganese (Mn) is an essential element that is required in trace amount for normal growth, development as well maintenance of proper function and regulation of numerous cellular and biochemical reactions. Yet, excessive Mn brain accumulation upon chronic exposure to occupational or environmental sources of this metal may lead to a neurodegenerative disorder known as manganism, which shares similar symptoms with idiopathic Parkinson's disease (PD). In recent years, Mn exposure has gained public health interest for two primary reasons: continuous increased usage of Mn in various industries, and experimental findings on its toxicity, linking it to a number of neurological disorders. Since the first report on manganism nearly two centuries ago, there have been substantial advances in the understanding of mechanisms associated with Mn-induced neurotoxicity. This review will briefly highlight various aspects of Mn neurotoxicity with a focus on the role of astrocytic glutamate transporters in triggering its pathophysiology.

Naloxone inhibition of lipopolysaccharide-induced activation of retinal microglia is partly mediated via the p38 mitogen activated protein kinase signalling pathway

OBJECTIVES

To investigate the effects and underlying mechanism of action of naloxone on lipopolysaccharide (LPS)-induced activation of retinal microglia in vitro.

METHODS

Rat retinal microglia primary cultures were divided into four treatment groups: untreated; 1 μg/ml LPS for 12 h; 0.5, 1.0 or 2.0 μM naloxone for 30 min before LPS; 2.5 or 5.0 μM SB203580 for 12 h before LPS and naloxone. Levels of tumour necrosis factor (TNF)-α and interleukin (IL)-1β were determined by enzyme-linked immuno sorbent assay. Western blot analysis and double immunofluorescence were used to examine activation of the mitogen activated protein kinase (MAPK) signalling pathway.

RESULTS

LPS induced an increase in TNF-α and IL-1β in culture supernatants, which was dose-dependently inhibited by naloxone. Naloxone also dose-dependently inhibited LPS-induced increases in phosphorylated p38 MAPK. Pretreatment of cells with SB203580 attenuated the inhibitory effect of naloxone on TNF-α and IL-1β production.

CONCLUSIONS

Naloxone suppressed LPS-induced activation of cultured retinal microglia and this suppression appeared to occur partly through the p38 MAPK signalling pathway. Naloxone may have therapeutic potential in neuro degenerative diseases characterized by the activation of microglia.

Β-funaltrexamine inhibits chemokine (CXCL10) expression in normal human astrocytes

Neuroinflammation is an integral component of neurodegenerative disorders, CNS infection and trauma. Astroglial chemokines, such as CXCL10, are instrumental in neuroinflammatory signaling as well as neurotoxicity. We have utilized proinflammatory-induced CXCL10 expression in normal human astrocytes (NHA) as a model in which to assess the anti-inflammatory actions of the selective, mu-opioid receptor (MOR) antagonist, β-funaltrexamine (β-FNA). Interferon (IFN)γ+HIV-1 Tat-induced CXCL10 expression (secreted protein and mRNA) was inhibited by co-treatment with β-FNA. Neither the MOR-selective antagonist, D-Phe-Cys-Tyr-D-Trp-Arg-Pen-Thr-NH2 (CTAP) nor the nonselective opioid receptor antagonist, naltrexone inhibited IFNγ+HIV-1 Tat-induced CXCL10 expression. Furthermore, co-treatment with excess CTAP or naltrexone did not prevent β-FNA mediated inhibition of IFNγ+HIV-1 Tat-induced CXCL10 expression. Additionally, we utilized an inhibitor of NF-κB activation (SN50) to demonstrate that IFNγ+HIV-1 Tat-induced CXCL10 expression is NF-κB-dependent in NHA. Subsequent experiments revealed that β-FNA did not significantly affect NF-κB activation. Interestingly, we discovered that β-FNA inhibited p38 activation as indicated by decreased expression of phospho-p38. Together, these findings suggest that the inhibitory actions of β-FNA are MOR-independent and mediated, in part, via a transcriptional mechanism. These findings add to our understanding of the mechanism by which chemokine expression is inhibited by β-FNA. In conjunction with future investigations, these novel findings are expected to provide insights into the development of safe and effective treatments for neuroinflammation.

Complex II of the mitochondrial respiratory chain is the key mediator of divalent manganese-induced hydrogen peroxide production in microglia

Exposure to excessive levels of manganese (Mn) is associated with the development of movement disorders, with symptoms overlapping with Parkinson's disease. Oxidative damage has been implicated as a key contributor to Mn-induced neurotoxicity. We have recently reported that divalent Mn (Mn(2+)) stimulates brain microglia to produce and release hydrogen peroxide (H2O2), and microglial-free radical generation facilitates Mn(2+)-induced dopaminergic neurotoxicity. The goal of this study was to elucidate the underlying mechanism of the Mn(2+)-induced H2O2 production in microglia. Exposure to low micromolar concentrations of Mn(2+), but not divalent copper, cadmium, nickel, cobalt, zinc, and iron, induced a significant production of H2O2 from rat microglial but not astroglial cells. Subcellular fractionation studies revealed that Mn(2+) was capable of inducing significant H2O2 production in the mitochondrial but not the cytosolic or nuclear fraction prepared from microglia. Analysis of the relative contribution of mitochondrial respiratory chain complexes indicated that Mn(2+)-induced mitochondrial H2O2 production required the presence of complex II substrate succinate. In contrast, complex I substrates malate and glutamate failed to support H2O2 production in the presence of Mn(2+). Furthermore, the succinate-supported Mn(2+)-induced mitochondrial H2O2 production was abolished by pharmacological inhibition of complex II but not that of complexes I and III, suggesting that mitochondrial complex II is a key mediator in Mn(2+)-induced H2O2 production. These findings advance our knowledge on the mechanisms by which Mn induces oxidative stress and the potential contribution to Mn neurotoxicity.

Manganese homeostasis and transport

The review addresses issues pertinent to Mn accumulation and its mechanisms of transport, its neurotoxicity and mechanisms of neurodegeneration. The role of mitochondria and glia in this process is emphasized. We also discuss gene x environment interactions, focusing on the interplay between genes linked to Parkinson's disease (PD) and sensitivity to Mn.

Involvement of dopaminergic neuronal cystatin C in neuronal injury-induced microglial activation and neurotoxicity

Factors released from injured dopaminergic (DA) neurons may trigger microglial activation and set in motion a vicious cycle of neuronal injury and inflammation that fuels progressive DA neurodegeneration in Parkinson's disease. In this study, using proteomic and immunoblotting analysis, we detected elevated levels of cystatin C in conditioned media (CM) from 1-methyl-4-phenylpyridinium and dieldrin-injured rat DA neuronal cells. Immunodepletion of cystatin C significantly reduced the ability of DA neuronal CM to induce activation of rat microglial cells as determined by up-regulation of inducible nitric oxide synthase, production of free radicals and release of proinflammatory cytokines as well as activated microglia-mediated DA neurotoxicity. Treatment of the cystatin C-containing CM with enzymes that remove O- and sialic acid-, but not N-linked carbohydrate moieties markedly reduced the ability of the DA neuronal CM to activate microglia. Taken together, these results suggest that DA neuronal cystatin C plays a role in the neuronal injury-induced microglial activation and neurotoxicity. These findings from the rat DA neuron-microglia in vitro model may help guide continued investigation to define the precise role of cystatin C in the complex interplay among neurons and glia in the pathogenesis of Parkinson's disease.

The adverse effects of air pollution on the nervous system

Exposure to ambient air pollution is a serious and common public health concern associated with growing morbidity and mortality worldwide. In the last decades, the adverse effects of air pollution on the pulmonary and cardiovascular systems have been well established in a series of major epidemiological and observational studies. In the recent past, air pollution has also been associated with diseases of the central nervous system (CNS), including stroke, Alzheimer's disease, Parkinson's disease, and neurodevelopmental disorders. It has been demonstrated that various components of air pollution, such as nanosized particles, can easily translocate to the CNS where they can activate innate immune responses. Furthermore, systemic inflammation arising from the pulmonary or cardiovascular system can affect CNS health. Despite intense studies on the health effects of ambient air pollution, the underlying molecular mechanisms of susceptibility and disease remain largely elusive. However, emerging evidence suggests that air pollution-induced neuroinflammation, oxidative stress, microglial activation, cerebrovascular dysfunction, and alterations in the blood-brain barrier contribute to CNS pathology. A better understanding of the mediators and mechanisms will enable the development of new strategies to protect individuals at risk and to reduce detrimental effects of air pollution on the nervous system and mental health.

Role of glial cells in manganese neurotoxicity

The objectives of this focused review are to (i) provide a systematic overview of recent advances pertaining to the role of glia, namely microglia and astrocytes, in the neuropathology associated with excessive exposure to manganese (Mn), (ii) highlight possible mechanisms and factors involved in Mn-modulated, glia-derived neuroinflammation, and (iii) discuss the implications of excessive neuroinflammation on neuronal injury within the context of Mn overexposure. As this is not meant to be a comprehensive review on the topic of Mn neurotoxicity, the reader may wish to refer to several broader and more comprehensive reviews. After a brief introduction to Mn neurotoxicity, we first discuss the role of glial cells in neurodegeneration. Next, we review existing in vitro and in vivo studies that implicate Mn as a modulator of glial activation and ensuing neuroinflammation. This is followed by an examination of recognized and potential mechanisms that are involved in the modulation of glial inflammatory output by Mn; here the common pathways activated by Mn in glial and neuronal cells, including outcomes of such activation, are also addressed. We finish with a discussion of the implications of Mn-modulated glial activation for neuronal survival and with a list of data gaps in the topic that need to be filled in the future.