Proinflammatory microglial response is a common mechanism of Aroclor 1254- and Tetrabromobisphenol-A-induced neurotoxicity in immature chronically exposed rats.

Polychlorinated biphenyls (PCBs) and brominated flame retardants (BFRs) are dominant environmental and food contaminants. Tetrabromobisphenol A (TBBPA) is the most widely used BFR in the world to improve the fire safety of laminates in electrical and electronic equipment. Aroclor 1254, one of the PCBs, is widely distributed in the environment due to its extensive use in industrial applications around the world. Both groups of substances are potent toxicants. There is also increasing evidence that they have neurotoxic effects. In this study we tested the pro-inflammatory effects of Aroclor 1254 and TBBPA based on markers of microglial reactivity and levels of pro-inflammatory factors in the brain of immature rats. Aroclor 1254 or TBBPA were administered to the rats by oral gavage for two weeks at a dose of 10 mg/kg b.w. Both light and electron microscopy studies revealed features indicative of microglia activation in brains of exposed rats. Morphological changes were associated with overexpression of pro-inflammatory enzymes such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Analysis of cytokine/chemokine array revealed significant secretion of inflammatory mediators following exposure to both TBBPA and Aroclor 1254, which was stronger in the cerebellum than in the forebrain of exposed immature rats. The results indicate a pro-inflammatory profile of microglia activation as one of the neurotoxic mechanisms of both examined toxicants.

Memantine Improves the Disturbed Glutamine and γ-Amino Butyric Acid Homeostasis in the Brain of Rats Subjected to Experimental Autoimmune Encephalomyelitis.

Glutamine (Gln), glutamate (Glu), and γ-amino butyric acid (GABA) are essential amino acids for brain metabolism and function. Astrocyte-derived Gln is the precursor for the two most important neurotransmitters in the central nervous system (CNS), which are the excitatory neurotransmitter Glu and the inhibitory neurotransmitter GABA. In addition to their roles in neurotransmission, these amino acids can be used as alternative substrates in brain metabolism that enable metabolic coupling between astrocytes and neurons in the glutamate-glutamine cycle (GGC). The disturbed homeostasis of these amino acids within the tripartite synapse may be involved in the pathogenesis of various neurological diseases. Interactions between astrocytes and neurons in terms of Gln, Glu, and GABA homeostasis were studied in different phases of experimental allergic encephalomyelitis (EAE) in Lewis rats. The results of the study showed a decrease in the transport (uptake and release) of Gln and GABA in both neuronal and astrocyte-derived fractions. These effects were fully or partially reversed when the EAE rats were treated with memantine, a NMDA receptor antagonist. Changes in the expression and activity of selected glutamine/glutamate metabolizing enzymes, such as glutamine synthase (GS) and phosphate-activated glutaminase (PAG), which were affected by memantine, were observed in different phases of EAE. The results suggested perturbed homeostasis of Gln, Glu, and GABA during EAE, which may indicate alterations in neuron-astrocyte coupling and dysfunction of the tripartite synapse. Memantine appears to partially regulate the disturbed relationships between Gln, Glu, and GABA.

Mutant Tau protein-induced abnormalities in the Na+-dependent glutamine translocation and recycling and their impact on astrocyte-neuron integrity in vitro.

Tau-dependent neurodegeneration is accompanied by astrocytosis in a mouse trans-genic model, which replicates the neuropathological characteristic of tauopathy and other human neurodegenerative disorders where astrocyte activation precedes neuronal loss and is associated with disease progression. This indicates an important role of astrocytes in the development of the disease. Astrocytes derived from a transgenic mouse model expressing human Tau, exhibit changes in cellular markers of astrocyte neuroprotective function related to the glutamate-glutamine cycle (GGC), representing a key part of astrocyte-neuron integrity. Here, we focused on investigating the functional properties of key GGC components involved in the astrocyte-neuron network associated with Tau pathology in vitro. Mutant recombinant Tau (rTau) carrying the P301L mutation was added to the neuronal cultures, with or without control astrocyte-conditioned medium (ACM), to study glutamine translocation through the GGC. We demonstrated that mutant Tau in vitro induces neuronal degeneration, while control astrocytes response in neuroprotective way by preventing neurodegeneration. In parallel with this observation, we noticed the Tau-dependent decline of neuronal microtubule associated protein 2 (MAP2), followed by changes in glutamine (Gln) transport. Exposure to rTau decreases sodium-dependent Gln uptake in neurons and that effect was reversed when cells were co-incubated with control ACM after induction of rTau dependent pathology. Further, we found that neuronal Na+-dependent system A is the most specific system that is affected under rTau exposure. In addition, in rTau-treated astrocytes total Na+-dependent uptake of Gln, which is mediated by the N system, increases. Altogether, our study suggest mechanisms operating in Tau pathology may be related to the alterations in glutamine transport and recycling that affect neuronal-astrocytic integrity.

Endoplasmic Reticulum Stress Underlies Nanosilver-Induced Neurotoxicity in Immature Rat Brain.

The growing production of silver nanoparticles (AgNPs), and their widespread use in medical and consumer products, poses a potential threat to the environment and raises questions about biosafety. Immature organisms are particularly susceptible to various insults during development. The biological characteristics of immature organisms are different from those of adults, and dictate the consequences of exposure to various toxic substances, including AgNPs. Nanoparticles are highly reactive and can easily cross the blood-brain barrier (BBB) to accumulate in brain tissues. It is therefore important to investigate the molecular mechanisms of AgNP-induced neurotoxicity in the developing brain. Immature 2-week-old rats were exposed to a low dose of AgNPs (0.2 mg/kg b.w.) over a long period. Subsequently, brain tissues of the animals were subjected to ultrastructural and molecular analyses to determine endoplasmic reticulum (ER) stress. Ultrastructural markers of ER stress, such as pathological alterations in the ER and elongated forms of mitochondria accompanied by autophagy structures, were confirmed to be present in AgNP-exposed rat brain. Evidence for induction of ER stress in neurons was also provided by molecular markers. Upregulation of genes related to the ER-stress-induced unfolded protein response (UPR) pathway, such as GRP78, PERK, and CHOP ATF-6, was observed at the transcriptional and translational levels. The results show that prolonged exposure of immature rats to a low dose of AgNPs during the developmental period leads to induction of ER stress in the neurons of the developing brain. Simultaneously, in response to AgNP-induced ER stress, neurons promote protective mechanisms that partially compensate for ER stress by regulating the biodynamic processes of mitochondria and autophagy.

Developmental neurotoxicity of silver nanoparticles: the current state of knowledge and future directions.

The increasing production and use of silver nanoparticles (AgNPs) as an antimicrobial agent in an array of medical and commercial products, including those designed for infants and children, poses a substantial risk of exposure during the developmental period. This review summarizes current knowledge on developmental neurotoxicity of AgNPs in both pre- and post-natal stages with a focus on the biological specificity of immature organisms that predisposes them to neurotoxic insults as well as the molecular mechanisms underlying AgNP-induced neurotoxicity. The current review revealed that AgNPs increase the permeability of the blood-brain barrier (BBB) and selectively damage neurons in the brain of immature rats exposed pre and postnatally. Among the AgNP-induced molecular mechanisms underlying toxic insult is cellular stress, which can consequently lead to cell death. Glutamatergic neurons and NMDAR-mediated neurotransmission also appear to be a target for AgNPs during the postnatal period of exposure. Collected data indicate also that our current knowledge of the impact of AgNPs on the developing nervous system remains insufficient and further studies are required during different stages of development with investigation of environmentally-relevant doses of exposure.

Alterations in the transcriptional profile of genes related to glutamatergic signalling in animal models of Alzheimer's disease. The effect of fingolimod.

Alzheimer's disease (AD) is a multi-factorial illness that leads to progressive cognitive impairment. A glutamatergic system dysfunction has been reported to be implicated in the pathomechanism of AD. Therefore, in the current study we characterized the transcriptional profile of glutamate-related genes in transgenic AbPP V717I (TgAD) and sporadic (SAD, streptozotocin-induced) models of AD. Genes encoding glutamate membrane-bound (GLAST, GLT1, EAAC1) and vesicular (VGLUT1-3) transporters as well as ionotropic (AMPA, NMDA) and metabotropic (mGluR3, mGluR5) receptors were analysed. Based on qPCR analysis, we observed a discrepancy between TgAD and SAD mice in the profile of targeted genes. We noticed age-dependent upregulation of genes encoding VGLUT1, NMDAR1 and mGluR3 in 12-month-old TgAD mice. In the SAD model upregulation of genes encoding AMPAR1 and NMDAR1 as well as downregulation of GLAST, VGLUT3 and mGluR5 were found. Next, the effect of fingolimod (FTY720) was indicated. In the TgAD model, the drug reversed altered transcription of the mGluR3 glutamate receptor to the control level, whereas in the SAD model it downregulated the genes encoding VGLUT1, AMPAR2 and mGluR3. Interestingly, FTY720 influenced mGluR3 mRNA in both examined models. Observed alterations of gene transcription and the effects of FTY720 may potentially constitute an interesting target for further pharmacological studies.

Memantine Modulates Oxidative Stress in the Rat Brain following Experimental Autoimmune Encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is an animal model most commonly used in research on the pathomechanisms of multiple sclerosis (MS). The inflammatory processes, glutamate excitotoxicity, and oxidative stress have been proposed as determinants accompanying demyelination and neuronal degeneration during the course of MS/EAE. The aim of the current study was to characterize the role of NMDA receptors in the induction of oxidative stress during the course of EAE. The effect of memantine, the uncompetitive NMDA receptor antagonist, on modulation of neurological deficits and oxidative stress in EAE rats was analyzed using several experimental approaches. We demonstrated that the expression of antioxidative enzymes (superoxide dismutases SOD1 and SOD2) were elevated in EAE rat brains. Under the same experimental conditions, we observed alterations in oxidative stress markers such as increased levels of malondialdehyde (MDA) and decreased levels of sulfhydryl (-SH) groups, both protein and non-protein (indicating protein damage), and a decline in reduced glutathione. Importantly, pharmacological inhibition of ionotropic NMDA glutamate receptors by their antagonist memantine improved the physical activity of EAE rats, alleviated neurological deficits such as paralysis of tail and hind limbs, and modulated oxidative stress parameters (MDA, -SH groups, SOD's). Furthermore, the current therapy aiming to suppress NMDAR-induced oxidative stress was partially effective when NMDAR's antagonist was administered at an early (asymptomatic) stage of EAE.

Nanosystems and exosomes as future approaches in treating multiple sclerosis.

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system which leads to neurological dysfunctions and severe disabilities. MS pathology is characterised by damage of the blood-brain barrier and infiltration of autoreactive T cells that overactivate glial cells, thereby initiating neuroinflammation accompanied by the formation of demyelinating plaques and neurodegeneration. Clinical deficits in this multifactorial disease depend on the progression of myelin loss, the stage of inflammation, the status of axons and the activity of oligodendrocyte precursor cells (OPCs). Despite significant progress in the treatment of MS, current therapies remain limited and new approaches are highly desirable. Nanosystems based on liposomes and nanoparticles are among some of the more noteworthy therapeutic strategies being investigated. Applications of nanosystems alone or as drug carriers in animal models of MS have been found to successfully alleviate the symptoms of the disease and exert anti-inflammatory potential. Exosomes are a specific type of nanosystem based on nanometre-sized extracellular vesicles released by different cells which exhibit important healing features. Exosomes contain an array of anti-inflammatory and neuroprotective agents which may contribute to modulation of the immune system as well as promoting remyelination and tissue repair. In this review, opportunities to use nanosystems against progression of MS will be discussed in context of cell-specific pathologies associated with MS.

Early and Delayed Impact of Nanosilver on the Glutamatergic NMDA Receptor Complex in Immature Rat Brain.

Silver nanoparticles (AgNPs) are the one of the most extensively used nanomaterials. The strong antimicrobial properties of AgNPs have led to their use in a wide range of medical and consumer products. Although the neurotoxicity of AgNPs has been confirmed, the molecular mechanisms have not been extensively studied, particularly in immature organisms. Based on information gained from previous in vitro studies, in the present work, we examine whether ionotropic NMDA glutamate receptors contribute to AgNP-induced neurotoxicity in an animal model of exposure. In brains of immature rats subjected to a low dose of AgNPs, we identified ultrastructural and molecular alterations in the postsynaptic region of synapses where NMDA receptors are localized as a multiprotein complex. We revealed decreased expression of several NMDA receptor complex-related proteins, such as GluN1 and GluN2B subunits, scaffolding proteins PSD95 and SynGAP, as well as neuronal nitric oxide synthase (nNOS). Elucidating the changes in NMDA receptor-mediated molecular mechanisms induced by AgNPs, we also identified downregulation of the GluN2B-PSD95-nNOS-cGMP signaling pathway which maintains LTP/LTD processes underlying learning and memory formation during development. This observation is accompanied by decreased density of NMDA receptors, as assessed by a radioligand binding assay. The observed effects are reversible over the post-exposure time. This investigation reveals that NMDA receptors in immature rats are a target of AgNPs, thereby indicating the potential health hazard for children and infants resulting from the extensive use of products containing AgNPs.

Response of immature rats to a low dose of nanoparticulate silver: Alterations in behavior, cerebral vasculature-related transcriptome and permeability.

The increasing production and use of silver nanoparticles (AgNPs) as antimicrobial agents in medicinal and commercial products creates a substantial risk of exposure, especially for infants and children. Our current knowledge concerning the impact of AgNPs on developing brain is insufficient. Therefore we investigated the temporal profile of transcriptional changes in cellular components of the neurovascular unit in immature rats exposed to a low dose of AgNPs. The behavior of animals under these conditions was also monitored. Significant deposition of AgNPs in brain of exposed rats was identified and found to persist over the post-exposure time. Substantial changes were noted in the transcriptional profile of tight junction proteins such as occludin and claudin-5, and pericyte-related molecules such as angiopoietin-1. Moreover, downregulation of platelet-derived growth factor (PDGFß) and its receptor (PDGFßR) which constitute the main signaling pathway between endothelial cells and pericytes was observed. These were long-lasting effects, accompanied by overexpression of astroglial-specific GFAP mRNA and endothelial cell adhesion molecule, ICAM-1, involved in the pathomechanism of neuroinflammation. The profile of changes indicates that even low doses of AgNPs administered during the early stage of life induce dysregulation of neurovascular unit constituents which may lead to disintegration of the blood-brain barrier. This was confirmed by ultrastructural analysis that revealed enhanced permeability of cerebral microvessels resulting in perivascular edema. Changes in the behavior of exposed rats indicating pro-depressive and anti-anxiety impacts were also identified. The results show a high risk of using AgNPs in medical and consumer products dedicated for infants and children.

Early Postnatal Exposure to a Low Dose of Nanoparticulate Silver Induces Alterations in Glutamate Transporters in Brain of Immature Rats.

Due to strong antimicrobial properties, silver nanoparticles (AgNPs) are used in a wide range of medical and consumer products, including those dedicated for infants and children. While AgNPs are known to exert neurotoxic effects, current knowledge concerning their impact on the developing brain is scarce. During investigations of mechanisms of neurotoxicity in immature rats, we studied the influence of AgNPs on glutamate transporter systems which are involved in regulation of extracellular concentration of glutamate, an excitotoxic amino acid, and compared it with positive control-Ag citrate. We identified significant deposition of AgNPs in brain tissue of exposed rats over the post-exposure time. Ultrastructural alterations in endoplasmic reticulum (ER) and Golgi complexes were observed in neurons of AgNP-exposed rats, which are characteristics of ER stress. These changes presumably underlie substantial long-lasting downregulation of neuronal glutamate transporter EAAC1, which was noted in AgNP-exposed rats. Conversely, the expression of astroglial glutamate transporters GLT-1 and GLAST was not affected by exposure to AgNPs, but the activity of the transporters was diminished. These results indicate that even low doses of AgNPs administered during an early stage of life create a substantial risk for health of immature organisms. Hence, the safety of AgNP-containing products for infants and children should be carefully considered.

A Low Dose of Nanoparticulate Silver Induces Mitochondrial Dysfunction and Autophagy in Adult Rat Brain.

Extensive incorporation of silver nanoparticles (AgNPs) into many medical and consumer products has raised concerns about biosafety. Since nanosilver accumulates persistently in the central nervous system, it is important to assess its neurotoxic impacts. We investigated a model of prolonged exposure of adult rats to a low environmentally relevant dose of AgNPs (0.2 mg/kg b.w.). Ultrastructural analysis revealed pathological alterations in mitochondria such as swelling and cristolysis. Besides, elongated forms of mitochondria were present. Level of adenosine triphosphate was not altered after exposure, although a partial drop of mitochondrial membrane potential was noted. Induction of autophagy with only early autophagic forms was observed in AgNP-exposed rat brains as evidenced by ultrastructural markers. Increased expression of two protein markers of autophagy, beclin 1 and microtubule-associated proteins 1A/1B light chain 3B (MAP LC3-II), was observed, indicating induction of autophagy. Expression of lysosome-related Rab 7 protein and cathepsin B did not change, suggesting inhibition of physiological flux of autophagy. Our results show that exposure to a low, environmentally relevant dose of AgNPs leads to induction of autophagy in adult rat brain in response to partial mitochondrial dysfunction and to simultaneous interfering with an autophagic pathway. The cell compensates for the defective autophagy mechanism via development of enhanced mitochondrial biodynamic.

Prolonged inflammation leads to ongoing damage after spinal cord injury.

The pathogenesis of spinal cord injury (SCI) remains poorly understood and treatment remains limited. Emerging evidence indicates that post-SCI inflammation is severe but the role of reactive astrogliosis not well understood given its implication in ongoing inflammation as damaging or neuroprotective. We have completed an extensive systematic study with MRI, histopathology, proteomics and ELISA analyses designed to further define the severe protracted and damaging inflammation after SCI in a rat model. We have identified 3 distinct phases of SCI: acute (first 2 days), inflammatory (starting day 3) and resolution (>3 months) in 16 weeks follow up. Actively phagocytizing, CD68+/CD163- macrophages infiltrate myelin-rich necrotic areas converting them into cavities of injury (COI) when deep in the spinal cord. Alternatively, superficial SCI areas are infiltrated by granulomatous tissue, or arachnoiditis where glial cells are obliterated. In the COI, CD68+/CD163- macrophage numbers reach a maximum in the first 4 weeks and then decline. Myelin phagocytosis is present at 16 weeks indicating ongoing inflammatory damage. The COI and arachnoiditis are defined by a wall of progressively hypertrophied astrocytes. MR imaging indicates persistent spinal cord edema that is linked to the severity of inflammation. Microhemorrhages in the spinal cord around the lesion are eliminated, presumably by reactive astrocytes within the first week post-injury. Acutely increased levels of TNF-alpha, IL-1beta, IFN-gamma and other pro-inflammatory cytokines, chemokines and proteases decrease and anti-inflammatory cytokines increase in later phases. In this study we elucidated a number of fundamental mechanisms in pathogenesis of SCI and have demonstrated a close association between progressive astrogliosis and reduction in the severity of inflammation.

Prolonged Exposure to Silver Nanoparticles Results in Oxidative Stress in Cerebral Myelin.

Currently, silver nanoparticles (AgNPs) are frequently used in a wide range of medical and consumer products. Substantial usage of AgNPs is considered to create substantive risks to both the environment and the human health. Since there is increasing evidence that the main mechanism of toxicity of AgNPs relates to oxidative stress, in the current study we investigate oxidative stress-related biochemical parameters in myelin isolated from adult rat brain subjected to a low dose of AgNPs. Animals were exposed for 2 weeks to 0.2 mg/kg b.w. of small (10 nm) AgNPs stabilized in citrate buffer or silver citrate established as a control to compare the effects of particulate and ionic forms of silver. We observe enhanced peroxidation of lipids and decreased concentrations of protein and non-protein -SH groups in myelin membranes. Simultaneously, expression of superoxide dismutase, a free radical scavenger, is increased whereas the process of protein glutathionylation, being a cellular protective mechanism against irreversible oxidation, is found to be inefficient. Results indicate that oxidative stress-induced alterations in myelin membranes may be the cause of ultrastructural disturbances in myelin sheaths.

Administration of an antagonist of P2X7 receptor to EAE rats prevents a decrease of expression of claudin-5 in cerebral capillaries.

Purinergic P2X receptors, when activated under pathological conditions, participate in induction of the inflammatory response and/or cell death. Both neuroinflammation and neurodegeneration represent hallmarks of multiple sclerosis (MS), an autoimmune disease of the central nervous system. In the current study, we examined whether P2X7R is expressed in brain microvasculature of rats subjected to experimental autoimmune encephalomyelitis (EAE) and explore possible relationships with blood-brain barrier (BBB) protein-claudin-5 after administration of P2X7R antagonist-Brilliant Blue G (BBG). Capillary fraction isolated from control and EAE rat brains was subjected to immunohistochemical and Western blot analyses. We document the presence of P2X7R in brain capillaries isolated from brain tissue of EAE rats. P2X7R is found to be localized on the abluminal surface of the microvessels and is co-expressed with PDGFßR, a marker of pericytes. We also show over-expression of this receptor in isolated capillaries during the course of EAE, which is temporally correlated with a lower protein level of PDGFßR, as well as claudin-5, a tight junction-building protein. Administration of a P2X7R antagonist to the immunized rats significantly reduced clinical signs of EAE and enhances protein expression of both claudin-5 and PDGFßR. These results indicate that P2X7 receptor located on pericytes may contribute to pathological mechanisms operated during EAE in cerebral microvessels influencing the BBB integrity.

Ultrastructural and biochemical features of cerebral microvessels of adult rat subjected to a low dose of silver nanoparticles.

The widespread use of silver nanoparticles (AgNPs) in medicine and in multiple commercial products has motivated researchers to investigate their potentially hazardous effects in organisms. Since AgNPs may easily enter the brain through the blood-brain barrier (BBB), characterization of their interactions with cellular components of the neurovascular unit (NVU) is of particular importance. Therefore, in an animal model of prolonged low-dose exposure, we investigate the extent and mechanisms of influence of AgNPs on cerebral microvessels. Adult rats were treated orally with small (10 nm) AgNPs in a dose of 0.2 mg/kg b.w. over a 2-week period. A silver citrate-exposed group was established as a positive control of ionic silver effects. Alterations in the expression of tight junction proteins claudin-5, ZO-1, and occludin, were observed. These effects are accompanied by ultrastructural features indicating enhanced permeability of microvessels such as focal edema of perivascular astrocytic processes and surrounding neuropil. We did not identify changes in the expression of PDGFßR which is a marker of pericytes. Ultrastructural alterations in these cells were not identified. The results show that altered integrity of cerebral vessels under a low-dose of AgNP-exposure may be the consequence of dysfunction of endothelial cells caused by disruption of tight junction proteins.

Effects of IFN-ß1a and IFN-ß1b treatment on the expression of cytokines, inducible NOS (NOS type II), and myelin proteins in animal model of multiple sclerosis.

The aim of this study was to investigate the effects of interferon (IFN)-ß1a and IFN-ß1b treatment on inflammatory factors and myelin protein levels in the brain cortex of the Lewis rat experimental autoimmune encephalomyelitis (EAE), animal model of multiple sclerosis. To induce EAE, rat were immunized with inoculums containing spinal cord guinea pig homogenized in phosphate-buffered saline and emulsified in Freund's complete adjuvant containing 110 µg of the appropriate antigen in 100 µl of an emulsion and additionally 4-mg/ml Mycobacterium tuberculosis (H37Ra). The rats were treated three times per week with subcutaneous applications of 300,000 units IFN-ß1a or IFN-ß1b. The treatments were started 8 days prior to immunization and continued until day 14 after immunization. The rats were killed on the 14th day of the experiment. EAE induced dramatic increase in interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF)-concentrations and inducible nitric oxide synthase (iNOS) expression in the brain, which closely corresponded to the course of neurological symptoms and the loss of weight. Both IFN-ß1b and IFN-ß1a treatments inhibited the pro-inflammatory cytokines (IL-6, IL-1ß, TNF-α and IFN-γ), decreased the activation of astrocytes, increased the myelin protein level in the brain cortex, and improved the neurological status of EAE rats by different mechanisms; IFN-ß1a reduced iNOS expression, at least in part, by the enhancement of IL-10, while IFN-ß1b diminished IL-10 concentration and did not decrease EAE-induced iNOS expression.

Blockade of the kinin B1 receptor affects the cytokine/chemokine profile in rat brain subjected to autoimmune encephalomyelitis.

Kinins are bioactive peptides which provide multiple functions, including critical regulation of the inflammatory response. Released during tissue injury, kinins potentiate the inflammation which represents a hallmark of numerous neurological disorders, including those of autoimmune origin such as multiple sclerosis (MS). In the present work, we assess the expression of B1 receptor (B1R) in rat brain during the course of experimental autoimmune encephalomyelitis (EAE) which is an animal model of MS. We apply pharmacological inhibition to investigate the role of this receptor in the development of neurological deficits and in shaping the cytokine/chemokine profile during the course of the disease. Overexpression of B1R is observed in brain tissue of rats subjected to EAE, beginning at the very early asymptomatic phase of the disease. This overexpression is suppressed by a specific antagonist known as DALBK. The involvement of B1R in the progression of neurological symptoms in immunized rats is confirmed. Analysis of an array of cytokines/chemokines identified a sub-group as being B1R-dependent. Increase of the protein levels for the proinflammatory cytokines (Il-6, TNF-α but not IL-1ß), chemokines attracting immune cells into nervous tissue (MCP-1, MIP-3α, LIX), and protein levels of fractalkine and vascular endothelial growth factor observed in EAE rats, were significantly diminished after DALBK administration. This may indicate the protective potential of pharmacological inhibition of B1R. However, simultaneously reduced protein levels of anti-inflammatory and neuroprotective factors (IL-10, IL-4, and CNTF) was noticed. The results show that B1R-mediated signaling regulates the cellular response profile following neuroinflammation in EAE.

Oxidative stress in rat brain but not in liver following oral administration of a low dose of nanoparticulate silver.

While it is known that silver nanoparticles (AgNPs) can enter the brain, our knowledge of AgNP-induced neurotoxicity remains incomplete. We investigated the ability of 10 nm citrate-stabilized AgNPs to generate oxidative stress in brain and liver of adult male Wistar rats after repeated oral exposure for 14 days, using a low dose of 0.2 mg/kg b.w. as compared with the same dose of ionic silver (silver citrate). In AgNP-exposed animals, the level of reactive oxygen species (ROS), lipid peroxidation (MDA) and glutathione peroxidase (GPx) activity were found to be significantly higher in brain relative to the control group receiving saline. Administration of ionic silver (silver citrate) increased ROS and MDA levels in both tissues. Activities of GPx in brain so as superoxide dismutase (SOD) and catalase (CAT) in liver of exposed animals were also elevated. Besides, AgNPs and silver ions were both found to cause statistically significant decrease in the reduced-to-oxidized glutathione ratio (GSH/GSSG) in brain. The results show that exposure to a very low dose of particulate silver generates mild oxidative stress in the brain but not in the liver of rats, indicating a role of oxidative stress in AgNP-induced neurotoxicity.

Influence of a low dose of silver nanoparticles on cerebral myelin and behavior of adult rats.

Nanoscale particles have large surface to volume ratio that significantly enhances their chemical and biological reactivity. Although general toxicity of nano silver (nanoAg) has been intensively studied in both in vitro and in vivo models, its neurotoxic effects are poorly known, especially those of low-dose exposure. In the present study we assess whether oral administration of nanoAg influences behavior of exposed rats and induces changes in cerebral myelin. We examine the effect of prolonged exposure of adult rats to small (10nm) citrate-stabilized nanoAg particles at a low dose of 0.2mg/kg b.w. (as opposed to the ionic silver) in a comprehensive behavioral analysis. Myelin ultrastructure and the expression of myelin-specific proteins are also investigated. The present study reveals slight differences with respect to behavioral effects of Ag(+)- but not nanoAg-treated rats. A weak depressive effect and hyperalgesia were observed after Ag(+) exposure whereas administration of nanoAg was found to specifically increase body weight and body temperature of animals. Both nanoAg and Ag(+) induce morphological disturbances in myelin sheaths and alter the expression of myelin-specific proteins CNP, MAG and MOG. These results suggest that the CNS may be a target of low-level toxicity of nanoAg.