A silent agonist of α7 nicotinic acetylcholine receptors modulates inflammation ex vivo and attenuates EAE.

Nicotinic acetylcholine receptors (nAChRs) are best known to function as ligand-gated ion channels in the nervous system. However, recent evidence suggests that nicotine modulates inflammation by desensitizing non-neuronal nAChRs, rather than by inducing channel opening. Silent agonists are molecules that selectively induce the desensitized state of nAChRs while producing little or no channel opening. A silent agonist of α7 nAChRs has recently been shown to reduce inflammation in an animal model of inflammatory pain. The objective of this study was to determine whether a silent agonist of α7 nAChRs can also effectively modulate inflammation and disease manifestation in an animal model of multiple sclerosis. We first evaluated the effects of various nAChR ligands and of an α7 nAChR-selective silent agonist, 1-ethyl-4-(3-(bromo)phenyl)piperazine (m-bromo PEP), on the modulation of mouse bone marrow-derived monocyte/macrophage (BMDM) numbers, phenotype and cytokine production. The non-competitive antagonist mecamylamine and the silent agonist m-bromo PEP reduced pro-inflammatory BMDM numbers by affecting their viability and proliferation. Both molecules also significantly reduced cytokine production by mouse BMDMs and significantly ameliorated disease in experimental autoimmune encephalomyelitis. Finally, m-bromo PEP also reduced chronic inflammatory pain in mice. Taken together, our results further support the hypothesis that nAChRs may modulate inflammation via receptor desensitization rather than channel opening. α7 nAChR-selective silent agonists may thus be a novel source of anti-inflammatory compounds that could be used for the treatment of inflammatory disorders.

Infiltration of CCR2+Ly6Chigh Proinflammatory Monocytes and Neutrophils into the Central Nervous System Is Modulated by Nicotinic Acetylcholine Receptors in a Model of Multiple Sclerosis.

Myeloid cells, including proinflammatory monocytes and neutrophils, have important roles in the pathology of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). These cells infiltrate the CNS in the early stages of disease development and contribute to the inflammatory response that is associated with symptom severity. It is thus crucial to identify and understand new mechanisms that can regulate the CNS infiltration of proinflammatory myeloid cells. Nicotinic acetylcholine receptors (nAChRs) have been increasingly studied for their immune-regulatory properties. In this study, we assessed the ability of nicotine, an nAChR ligand, to modulate proinflammatory myeloid cell numbers within the bone marrow, spleen, blood, and CNS of EAE mice. We found that nicotine significantly inhibits the infiltration of proinflammatory monocytes and neutrophils into the CNS at time points where these cells are known to play critical roles in disease pathology. In contrast, nicotine does not affect the expansion of other monocytes. We also show that nicotine exerts these effects by acting on α7 and α9 nAChR subtypes. Finally, mRNA transcript levels for CCL2 and CXCL2, chemokines involved in the chemotaxis of proinflammatory monocytes and neutrophils, respectively, are reduced in the brain of nicotine-treated EAE mice before the massive infiltration of these cells. Taken together, our data provide evidence that nAChRs can regulate proinflammatory cell infiltration into the CNS, which could be of significant value for the treatment of neuroinflammatory disorders.

Non-neuronal cholinergic activity is potentiated in myasthenia gravis.

BACKGROUND: Non-neuronal acetylcholine (ACh) restricts autoimmune responses and attenuates inflammation by cholinergic anti-inflammation pathway. To date, the implication of ACh in myasthenia gravis (MG) remained unexplored. This study aimed to investigate the possible relationship between ACh levels, anti-muscle-specific tyrosine kinase (MuSK) antibody titers, main clinical features and outcomes of MG patients. METHODS: We successfully measured ACh levels in human peripheral blood mononuclear cells (PBMCs) from 125 MG patients and 50 matched healthy controls by using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). We assessed the quantitative MG (QMG) scores for each patient and titered anti-MuSK antibody. RESULTS: We found that PBMC-derived ACh level was significantly higher in MG patients, especially in patients of class III, IV-V, compared with that in controls (0.142 ± 0.108 vs. 0.075 ± 0.014 ng/million cells, p = 0.0003) according to the Myasthenia Gravis Foundation of America clinical classification. Importantly, we also found that ACh levels were positively correlated with QMG scores (r = 0.83, p < 0.0001) and anti-MuSK Ab levels (r = 0.85, p < 0.0001). CONCLUSIONS: Our demonstration of elevated ACh levels in PBMCs of MG patients foreshadows potential new avenues for MG research and treatment.

Differential modulation of EAE by α9*- and ß2*-nicotinic acetylcholine receptors.

Nicotine is a potent inhibitor of the immune response and is protective against experimental autoimmune encephalomyelitis (EAE). Initial studies suggested that the cholinergic system modulates inflammation via the α7-nicotinic acetylcholine receptor (nAChR) subtype. We recently have shown that effector T cells and myeloid cells constitutively express mRNAs encoding nAChR α9 and ß2 subunits and found evidence for immune system roles for non-α7-nAChRs. In the present study, we assessed the effects of nAChR α9 or ß2 subunit gene deletion on EAE onset and severity, with or without nicotine treatment. We report again that disease onset is delayed and severity is attenuated in nicotine-treated, wild-type mice, an effect that also is observed in α9 subunit knock-out (KO) mice irrespective of nicotine treatment. On the other hand, ß2 KO mice fail to recover from peak measures of disease severity regardless of nicotine treatment, despite retaining sensitivity to nicotine's attenuation of disease severity. Prior to disease onset, we found significantly less reactive oxygen species production in the central nervous system (CNS) of ß2 KO mice, elevated proportions of CNS myeloid cells but decreased ratios of CNS macrophages/microglia in α9 or ß2 KO mice, and some changes in iNOS, TNF-α and IL-1ß mRNA levels in α9 KO and/or ß2 KO mice. Our data thus suggest that ß2*- and α9*-nAChRs, in addition to α7-nAChRs, have different roles in endogenous and nicotine-dependent modulation of immune functions and could be exploited as therapeutic targets to modulate inflammation and autoimmunity.

Comparison of the Anti-inflammatory Properties of Two Nicotinic Acetylcholine Receptor Ligands, Phosphocholine and pCF3-diEPP.

Activation of nicotinic acetylcholine receptors (nAChRs) expressed by innate immune cells can attenuate pro-inflammatory responses. Silent nAChR agonists, which down-modulate inflammation but have little or no ionotropic activity, are of outstanding clinical interest for the prevention and therapy of numerous inflammatory diseases. Here, we compare two silent nAChR agonists, phosphocholine, which is known to interact with nAChR subunits α7, α9, and α10, and pCF3-N,N-diethyl-N'-phenyl-piperazine (pCF3-diEPP), a previously identified α7 nAChR silent agonist, regarding their anti-inflammatory properties and their effects on ionotropic nAChR functions. The lipopolysaccharide (LPS)-induced release of interleukin (IL)-6 by primary murine macrophages was inhibited by pCF3-diEPP, while phosphocholine was ineffective presumably because of instability. In human whole blood cultures pCF3-diEPP inhibited the LPS-induced secretion of IL-6, TNF-α and IL-1ß. The ATP-mediated release of IL-1ß by LPS-primed human peripheral blood mononuclear leukocytes, monocytic THP-1 cells and THP-1-derived M1-like macrophages was reduced by both phosphocholine and femtomolar concentrations of pCF3-diEPP. These effects were sensitive to mecamylamine and to conopeptides RgIA4 and [V11L; V16D]ArIB, suggesting the involvement of nAChR subunits α7, α9 and/or α10. In two-electrode voltage-clamp measurements pCF3-diEPP functioned as a partial agonist and a strong desensitizer of classical human α9 and α9α10 nAChRs. Interestingly, pCF3-diEPP was more effective as an ionotropic agonist at these nAChRs than at α7 nAChR. In conclusion, phosphocholine and pCF3-diEPP are potent agonists at unconventional nAChRs expressed by monocytic and macrophage-like cells. pCF3-diEPP inhibits the LPS-induced release of pro-inflammatory cytokines, while phosphocholine is ineffective. However, both agonists signal via nAChR subunits α7, α9 and/or α10 to efficiently down-modulate the ATP-induced release of IL-1ß. Compared to phosphocholine, pCF3-diEPP is expected to have better pharmacological properties. Thus, low concentrations of pCF3-diEPP may be a therapeutic option for the treatment of inflammatory diseases including trauma-induced sterile inflammation.

Lasting Effects of Low to Non-Lethal Radiation Exposure during Late Gestation on Offspring's Cardiac Metabolism and Oxidative Stress.

Ionizing radiation (IR) is known to cause fetal programming, but the physiological effects of low-dose IR are not fully understood. This study examined the effect of low (50 mGy) to non-lethal (300 and 1000 mGy) radiation exposure during late gestation on cardiac metabolism and oxidative stress in adult offspring. Pregnant C57BL/6J mice were exposed to 50, 300, or 1000 mGy of gamma radiation or Sham irradiation on gestational day 15. Sixteen weeks after birth, 18F-Fluorodeoxyglucose (FDG) uptake was examined in the offspring using Positron Emission Tomography imaging. Western blot was used to determine changes in oxidative stress, antioxidants, and insulin signaling related proteins. Male and female offspring from irradiated dams had lower body weights when compared to the Sham. 1000 mGy female offspring demonstrated a significant increase in 18F-FDG uptake, glycogen content, and oxidative stress. 300 and 1000 mGy female mice exhibited increased superoxide dismutase activity, decreased glutathione peroxidase activity, and decreased reduced/oxidized glutathione ratio. We conclude that non-lethal radiation during late gestation can alter glucose uptake and increase oxidative stress in female offspring. These data provide evidence that low doses of IR during the third trimester are not harmful but higher, non-lethal doses can alter cardiac metabolism later in life and sex may have a role in fetal programming.

Bone marrow-derived microglia play a critical role in restricting senile plaque formation in Alzheimer's disease.

Microglia are the immune cells of the brain. Here we show a massive infiltration of highly ramified and elongated microglia within the core of amyloid plaques in transgenic mouse models of Alzheimer's disease (AD). Many of these cells originate from the bone marrow, and the beta-amyloid-40 and -42 isoforms are able to trigger this chemoattraction. These newly recruited cells also exhibit a specific immune reaction to both exogenous and endogenous beta-amyloid in the brain. Creation of a new AD transgenic mouse that expresses the thymidine kinase protein under the control of the CD11b promoter allowed us to show that blood-derived microglia and not their resident counterparts have the ability to eliminate amyloid deposits by a cell-specific phagocytic mechanism. These bone marrow-derived microglia are thus very efficient in restricting amyloid deposits. Therapeutic strategies aiming to improve their recruitment could potentially lead to a new powerful tool for the elimination of toxic senile plaques.

A novel nicotinic acetylcholine receptor subtype in basal forebrain cholinergic neurons with high sensitivity to amyloid peptides.

Nicotinic acetylcholine receptors (nAChRs) containing alpha7 subunits are thought to assemble as homomers. alpha7-nAChR function has been implicated in learning and memory, and alterations of alpha7-nAChR have been found in patients with Alzheimer's disease (AD). Here we report findings consistent with a novel, naturally occurring nAChR subtype in rodent, basal forebrain cholinergic neurons. In these cells, alpha7 subunits are coexpressed, colocalize, and coassemble with beta2 subunit(s). Compared with homomeric alpha7-nAChRs from ventral tegmental area neurons, functional, presumably heteromeric alpha7beta2-nAChRs on cholinergic neurons freshly dissociated from medial septum/diagonal band (MS/DB) exhibit relatively slow kinetics of whole-cell current responses to nicotinic agonists and are more sensitive to the beta2 subunit-containing nAChR-selective antagonist, dihydro-beta-erythroidine (DHbetaE). Interestingly, presumed, heteromeric alpha7beta2-nAChRs are highly sensitive to functional inhibition by pathologically relevant concentrations of oligomeric, but not monomeric or fibrillar, forms of amyloid beta(1-42) (Abeta(1-42)). Slow whole-cell current kinetics, sensitivity to DHbetaE, and specific antagonism by oligomeric Abeta(1-42) also are characteristics of heteromeric alpha7beta2-nAChRs, but not of homomeric alpha7-nAChRs, heterologously expressed in Xenopus oocytes. Moreover, choline-induced currents have faster kinetics and less sensitivity to Abeta when elicited from MS/DB neurons derived from nAChR beta2 subunit knock-out mice rather than from wild-type mice. The presence of novel, functional, heteromeric alpha7beta2-nAChRs on basal forebrain cholinergic neurons and their high sensitivity to blockade by low concentrations of oligomeric Abeta(1-42) suggests possible mechanisms for deficits in cholinergic signaling that could occur early in the etiopathogenesis of AD and might be targeted by disease therapies.

Medroxyprogesterone acetate impairs memory and alters the GABAergic system in aged surgically menopausal rats.

In women, medroxyprogesterone acetate (MPA) is the most commonly used progestin component of hormone therapy (HT). In vitro, MPA negatively impacts markers of neuronal health and exacerbates experimentally-induced neurotoxicity. There is in vitro evidence that these factors are driven by GABAergic and neurotrophic systems. Whether these effects translate to a negative impact on brain function has not been tested in vivo, clinically or preclinically. Here we evaluate the mnemonic and neurobiological effects of MPA in the surgically menopausal rat. Aged ovariectomized (OVX) rats were given subcutaneous vehicle, natural progesterone, low-dose MPA or high-dose MPA. Multiple cognitive domains were analyzed via the water radial-arm maze (WRAM) and Morris maze (MM). Cognitive brain regions were assayed for changes in the GABAergic system by evaluating GAD protein, the synthesizing enzyme for GABA, and neurotrophins. On the WRAM, both progestin types impaired learning. Further, high-dose MPA impaired delayed memory retention on the WRAM, and exacerbated overnight forgetting on the MM. While neurotrophins were not affected by progesterone or MPA treatment, both progestin types altered GAD levels. MPA significantly and progesterone marginally decreased GAD levels in the hippocampus, and both MPA and progesterone significantly increased GAD levels in the entorhinal cortex. These findings suggest that MPA, the most commonly used progestin in HT, is detrimental to learning and two types of memory, and modulates the GABAergic system in cognitive brain regions, in aged surgically menopausal rats. These findings, combined with in vitro evidence that MPA is detrimental to neuronal health, indicates that MPA has negative effects for brain health and function.

A component of Premarin(®) enhances multiple cognitive functions and influences nicotinic receptor expression.

In women, ovarian hormone loss at menopause has been related to cognitive decline, and some studies suggest that estrogen-containing hormone therapy (HT) can mitigate these effects. Recently, the Women's Health Initiative study found that conjugated equine estrogens, the most commonly prescribed HT, do not benefit cognition. Isolated components of conjugated equine estrogens (tradename Premarin(®)) have been evaluated in vitro, with delta(8,9)-dehydroestrone (∆(8)E1) and equilin showing the strongest neuroprotective profiles. It has not been evaluated whether ∆(8)E1 or equilin impact cognition or the cholinergic system, which is affected by other estrogens and known to modulate cognition. Here, in middle-aged, ovariectomized rats, we evaluated the effects of ∆(8)E1 and equilin treatments on a cognitive battery and cholinergic nicotinic receptors (nAChR). Specifically, we used (125)I-labeled epibatidine binding to assay brain nicotinic receptor containing 4α and 2ß subunits (α4ß2-nAChR), since this nicotinic receptor subtype has been shown previously to be sensitive to other estrogens. ∆(8)E1 enhanced spatial working, recent and reference memory. ∆(8)E1 also decreased hippocampal and entorhinal cortex α4ß2-nAChR expression, which was related to spatial reference memory performance. Equilin treatment did not affect spatial memory or rat α4ß2-nAChR expression, and neither estrogen impacted (86)Rb(+) efflux, indicating lack of direct action on human α4ß2 nAChR function. Both estrogens influenced vaginal smear profiles, uterine weights, and serum luteinizing hormone levels, analogous to classic estrogens. The findings indicate that specific isolated Premarin(®) components differ in their ability to affect cognition and nAChR expression. Taken with the works of others showing ∆(8)E1-induced benefits on several dimensions of health-related concerns associated with menopause, this body of research identifies ∆(8)E1 as a new avenue to be investigated as a potential component of HT that may benefit brain health and function during aging.

Selective ablation of proliferating microglial cells exacerbates ischemic injury in the brain.

Here we report in vivo evidence of a neuroprotective role of proliferating microglial cells in cerebral ischemia. Using transgenic mice expressing a mutant thymidine kinase form of herpes simplex virus driven by myeloid-specific CD11b promoter and ganciclovir treatment as a tool, we selectively ablated proliferating (Mac-2 positive) microglia after transient middle cerebral artery occlusion. The series of experiments using green fluorescent protein-chimeric mice demonstrated that within the first 72 h after ischemic injury, the Mac-2 marker [unlike Iba1 (ionized calcium-binding adapter molecule 1)] was preferentially expressed by the resident microglia. Selective ablation of proliferating resident microglia was associated with a marked alteration in the temporal dynamics of proinflammatory cytokine expression, a significant increase in the size of infarction associated with a 2.7-fold increase in the number of apoptotic cells, predominantly neurons, and a 1.8-fold decrease in the levels of IGF-1. A double-immunofluorescence analysis revealed a approximately 100% colocalization between IGF-1 positive cells and Mac-2, a marker of activated/proliferating resident microglia. Conversely, stimulation of microglial proliferation after cerebral ischemia by M-CSF (macrophage colony stimulating factor) resulted in a 1.9-fold increase in IGF-1 levels and a significant increase of Mac2+ cells. Our findings suggest that a postischemic proliferation of the resident microglial cells may serve as an important modulator of a brain inflammatory response. More importantly, our results revealed a marked neuroprotective potential of proliferating microglia serving as an endogenous pool of neurotrophic molecules such as IGF-1, which may open new therapeutic avenues in the treatment of stroke and other neurological disorders.

Neuroprotective effects of resident microglia following acute brain injury.

Microglia quickly react to various neurodegenerative processes by producing cytokines and eliminating cellular debris via phagocytosis. These events are also associated with an increased proliferation of microglia, which derive from resident progenitors and those present in the bone marrow. However, it is not clear whether the innate immune response by resident or newly differentiated microglia is beneficial or detrimental to the central nervous system. The aim of this study was to determine the impact of an altered immune response following acute excitotoxicity. Sodium nitroprusside (SNP) or kainic acid (KA) was administered in the brain of various groups of mice, and the extent of neurodegeneration, myelin damage, and inflammation was evaluated within a period of 2 weeks. We used synthetic glucocorticoid (GC), myeloid differentiation factor 88 (MyD88)-deficient mice to suppress nuclear factor kappaB (NF-kappaB) signaling and transgenic mice that express the thymidine kinase (TK) protein under the control of the CD11b promoter to determine the role of proliferating and infiltrating microglia in acute models of brain injury. Neurodegeneration was more extensive in GC-treated and MyD88-deficient mice, suggesting that NF-kappaB signaling and microglia activation are potent neuroprotective mechanisms in the presence of SNP. KA was also highly toxic to neurons of the amygdala in MyD88 knockout mice but not in their WT littermates. Although bone marrow-derived cells are clearly attracted to neurodegenerative areas, preventing their infiltration and differentiation did not affect the extent of SNP-related damage. These data indicate that MyD88/NF-kappaB signaling in resident non-proliferating microglia plays a critical role by restricting damage during acute excitotoxicity.

Expression Profile of Long Noncoding RNAs in Peripheral Blood Mononuclear Cells from Multiple Sclerosis Patients.

AIMS: Long noncoding RNAs (lncRNAs) play a key role in regulating immunological functions. Their impact on the chronic inflammatory disease multiple sclerosis (MS), however, remains unknown. We investigated the expression of lncRNAs in peripheral blood mononuclear cells (PBMCs) of patients with MS and attempt to explain their possible role in the process of MS. METHODS: For this study, we recruited 26 patients with MS according to the revised McDonald criteria. Then, we randomly chose 6 patients for microarray analysis. Microarray assays identified outstanding differences in lncRNA expression, which were verified through real-time PCR. LncRNA functions were annotated for target genes using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, and regulatory relationships between lncRNAs and target genes were analyzed using the "cis" and "trans" model. RESULTS: There were 2353 upregulated lncRNAs, 389 downregulated lncRNAs, 1037 upregulated mRNAs, and 279 downregulated mRNAs in patients with MS compared to healthy control subjects (fold change >2.0). Real-time PCR results of six aberrant lncRNAs were consistent with the microarray data. The coexpression network comprised 864 lncRNAs and 628 mRNAs. Among differentially expressed lncRNAs, 10 lncRNAs were predicted to have 10 cis-regulated target genes, and 33 lncRNAs might regulate their trans target genes. CONCLUSIONS: We identified a subset of dysregulated lncRNAs and mRNAs. The differentially expressed lncRNAs may be important in the process of MS. However, the specific molecular mechanisms and biological functions of these lncRNAs in the pathogenesis of MS need further study.

Nicotinic Acetylcholine Receptors Modulate Bone Marrow-Derived Pro-Inflammatory Monocyte Production and Survival.

It is increasingly clear that nicotinic acetylcholine receptors (nAChRs) are involved in immune regulation, and that their activation can protect against inflammatory diseases. Previous data have shown that nicotine diminishes the numbers of peripheral monocytes and macrophages, especially those of the pro-inflammatory phenotype. The goal of the present study was to determine if nicotine modulates the production of bone marrow -derived monocytes/macrophages. In this study, we first found that murine bone marrow cells express multiple nAChR subunits, and that the α7 and α9 nAChRs most predominant subtypes found in immune cells and their precursors. Using primary cultures of murine bone marrow cells, we then determined the effect of nicotine on monocyte colony-stimulating factor and interferon gamma (IFNγ)-induced monocyte production. We found that nicotine lowered the overall number of monocytes, and more specifically, inhibited the IFNγ-induced increase in pro-inflammatory monocytes by reducing cell proliferation and viability. These data suggested that nicotine diminishes the ratio of pro-inflammatory versus anti-inflammatory monocyte produced in the bone marrow. We thus confirmed this hypothesis by measuring cytokine expression, where we found that nicotine inhibited the production of the pro-inflammatory cytokines TNFα, IL-1ß and IL-12, while stimulating the secretion of IL-10, an anti-inflammatory cytokine. Finally, nicotine also reduced the number of pro-inflammatory monocytes in the bone marrow of LPS-challenged mice. Overall, our data demonstrate that both α7 and α9 nAChRs are involved in the regulation of pro-inflammatory M1 monocyte numbers.

Differentially expressed lncRNAs and mRNAs identified by microarray analysis in GBS patients vs healthy controls.

The aim of our present study was to determine whether message RNAs (mRNAs) and long noncoding RNAs (lncRNAs) are expressed differentially in patients with Guillain-Barré syndrome (GBS) compared with healthy controls. The mRNA and lncRNA profiles of GBS patients and healthy controls were generated by using microarray analysis. From microarray analysis, we listed 310 mRNAs and 114 lncRNAs with the mRMR software classed into two sample groups, GBS patients and healthy controls. KEGG mapping demonstrated that the top seven signal pathways may play important roles in GBS development. Several GO terms, such as cytosol, cellular macromolecular complex assembly, cell cycle, ligase activity, protein catabolic process, etc., were enriched in gene lists, suggesting a potential correlation with GBS development. Co-expression network analysis indicated that 113 lncRNAs and 303 mRNAs were included in the co-expression network. Our present study showed that these differentially expressed mRNAs and lncRNAs may play important roles in GBS development, which provides basic information for defining the mechanism(s) that promote GBS.

Bone marrow stem cells have the ability to populate the entire central nervous system into fully differentiated parenchymal microglia.

Pluripotent stem cells can differentiate into a variety of cell types during tissue development and regeneration. However, it is still unclear whether bone marrow-derived stem cells can migrate across the blood-brain barrier in many regions of the central nervous system (CNS) and if these cells can readily differentiate into functional parenchymal microglia. We thus studied the differentiation fate of bone marrow stem cells upon immigration into the CNS. To this end, we systemically transplanted stem cells that express green fluorescent protein (GFP) into lethally irradiated mice and found that these cells immigrated into the brain parenchyma of many regions of the CNS. Nearly all of the infiltrating cells had a highly ramified morphology and colocalized with the microglial marker iba1. Moreover, these cells expressed high levels of the protein CD11c, indicating that microglia of bone marrow origin may be potent antigen presenting cells. These data suggest that microglia of blood origin could activate cells of the adaptive immune system and cause harm to the CNS. Therefore, these results may have great clinical relevance for both immune-derived neuronal disorders and cancer patients undergoing allogeneic hematopoietic stem-cell transplantation.

Do pathogen exposure and innate immunity cause brain diseases?

It had long been thought that the central nervous system was isolated from the immune system owing to the blood-brain barrier and that this organ was unable to mount an immune reaction of its own when challenged by invading pathogens. It is now clear that the immune system has a profound impact on the central nervous system, because immune molecules found in the blood stream are able to stimulate cells within the brain. Moreover, recent studies have demonstrated that cells within the central nervous system have the capacity to produce molecules of the innate immune system and that this organ is able to generate a proper immune reaction. This topic has been extensively studied in recent years, and it is becoming clear that the innate immune system is an important modulator of the fate of neurons. Indeed, the precise role(s) of the innate immune response in neurodegenerative diseases is currently under intensive debate. In this review paper, we present evidence either supporting or opposing a role for the innate immune response in these events. The mechanisms by which pathogens interact with the brain and whether such an interaction leads to neurodegenerative disorders are also discussed.

Role of inflammation in the neurobiology of stem cells.

Unlike most organs, tissue regeneration and repair are not very efficient in the CNS, which explains the severity of neurodegenerative diseases. Many have hoped that stem cells would provide an effective mean to solve this problem. Unfortunately, evidence supporting this approach remains controversial. In this review, we discuss the capacity of stem cells to generate the cells that reside in the brain. Neural stem cells are able to generate new neurons, astrocytes and oligodendrocytes, but not microglia. The latter are instead replenished by self-replication and monocyte recruitment across the blood-brain barrier. The fact that blood-derived monocytes can enter the brain and differentiate into microglial cells has many implications for neurodegenerative diseases. They are more efficient antigen-presenting cells and produce proinflammatory molecules that can be both detrimental to the brain and beneficial to recovery and repair after insults. It is therefore very important to better understand the role of these newly differentiated microglia before devising therapeutic strategies to either inhibit or improve their recruitment at diseased and injured sites.

New strategies in the management of Guillain-Barré syndrome.

Guillain-Barré syndrome (GBS) is an acute and usually monophasic, neurological, demyelinating disease. Although most patients have good outcomes without sequelae after conventional plasma exchange and intravenous immunoglobulin therapy, 20% of patients continue to have severe disease and 5% die of their disease. Therefore, there is an obvious need for more acceptable and efficacious therapies. Experimental autoimmune neuritis (EAN) is the classical animal model for GBS. As there is no specific drug for GBS, several drugs targeting the humoral and cellular components of the immune response have been used to treat EAN in the endeavour to find new treatment alternatives for GBS. This review focused on some new strategies for GBS, which have been reported but have not yet been widely used, and on the main drugs which have been investigated in EAN.