Journal of Neuroinflammation - Latest Articles

Innate immunity in the Grid2 Lc/+ mouse model of cerebellar neurodegeneration: glial CD95/CD95L plays a non-apoptotic role in persistent neuron loss-associated inflammatory reactions in the cerebellum

Béatrice Garabedian — 2013-05-15T00:00:00Z

Background: There is growing evidence that the death receptor CD95 has a wider role in non-apoptotic functions. In the brain, it may contribute to neural death and to the associated inflammatory reaction via a non-apoptotic pathway. Brain injury triggers an inflammatory reaction in which the CD95/CD95L system acts principally through peripheral cells recruited to the lesion. In cases of inflammation within the brain, with no blood–brain barrier leakage, the role of the CD95/CD95L system is thus unclear. We investigated the possible role of CD95 and CD95L in such conditions, by studying the relationships between glial cell activation, neuron death and CD95/CD95L expression in the cerebellum of the Lurcher (Grid2 Lc/+ ) mutant mouse, a model of cerebellar neurodegeneration. Methods: Glial cells in slices of wild-type and Lurcher mouse cerebella were observed by light microscopy at various ages overlapping periods of neuron loss and of pre- and post-neurodegeneration. Subcellular organization was studied by electron microscopy. We assessed CD95 levels by western blotting, RT-PCR and glial cell cultures. The levels of CD95L and IL-6 were studied by ELISA and a biological assay, respectively. Results: In the Grid2 Lc/+ cerebellum, neuron loss triggers a typical, but abnormally persistent, inflammatory reaction. We identified two phases of astrogliosis: an early burst of large glial cell activation, peaking at postnatal days 25 to 26, coinciding with peak cerebellar neuron loss, followed by a long period of slow decline indicating that the strength of the glial reaction is modulated by neuron mortality rates. Comparisons of time-courses of glial cell activation, cytokine production and neuron loss revealed that the number of surviving neurons decreased as CD95 increased. Thus, CD95 cannot be directly involved in neuron death, and its role must be limited to a contribution to the inflammatory reaction. The upregulation of CD95 likely on astrocytes coincides with increases in the levels of IL-6, a cytokine produced principally by astrocytes, and soluble CD95L. Conclusions: These results suggest that CD95 and soluble CD95L contribute, via non-apoptotic signaling, to the inflammatory reaction initiated early in neuron death within the Grid2 Lc/+ cerebellum.

Neurogenic factor-induced Langerhans cell activation in diabetic mice with mechanical allodynia

Jacqueline Dauch — 2013-05-14T00:00:00Z

Background: Langerhans cells (LCs) are antigen-presenting dendritic cells located in the skin. It has been reported that LC activation is associated with painful diabetic neuropathy (PDN); however, the mechanism of LC activation is still unclear. Methods: The db/db mouse, a rodent model of PDN, was used to study the roles of LCs in the development of PDN in type 2 diabetes. Hind foot pads from db/db and control db/+ mice from 5 to 24 weeks of age (encompassing the period of mechanical allodynia development and its abatement) were collected and processed for immunohistochemistry studies. LCs were identified with immunohistochemistry using an antibody against CD207 (Langerin). The intraepidermal nerve fibers and subepidermal nerve plexus were identified by immunohistochemistry of protein gene product 9.5 (PGP 9.5) and tropomyosin-receptor kinase (Trk) A, the high affinity nerve growth factor receptor. Results: CD207-positive LCs increased in the db/db mouse during the period of mechanical allodynia, from 8 to 10 weeks of age, in both the epidermis and subepidermal plexus. At 16 weeks of age, when mechanical allodynia diminishes, LC populations were reduced in the epidermis and subepidermal plexus. Epidermal LCs (ELCs) were positive for Trk A. Subepidermal LCs (SLCs) were positive for CD68, suggesting that they are immature LCs. Additionally, these SLCs were positive for the receptor of advanced glycation end products (RAGE) and were in direct contact with TNF-alpha-positive nerve fibers in the subepidermal nerve plexus during the period of mechanical allodynia. Intrathecal administration of SB203580, a p38 kinase inhibitor, significantly reduced mechanical allodynia, TNF-alpha expression in the subepidermal plexus, and increased both ELC and SLC populations during the period of mechanical allodynia. Conclusions: Our data support the hypothesis that increased LC populations in PDN are activated by p38-dependent neurogenic factors and may be involved in the pathogenesis of PDN.

Delayed brain ischemia tolerance induced by electroacupuncture pretreatment is mediated via MCP-induced protein 1

Zhuqing Jin — 2013-05-10T00:00:00Z

Background: Emerging studies have demonstrated that pretreatment with electroacupuncture (EA) induces significant tolerance to focal cerebral ischemia. The present study seeks to determine the involvement of monocyte chemotactic protein-induced protein 1 (MCPIP1), a recently identified novel modulator of inflammatory reactions, in the cerebral neuroprotection conferred by EA pretreatment in the animal model of focal cerebral ischemia and to elucidate the mechanisms of EA pretreatment-induced ischemic brain tolerance. Methods: Twenty-four hours after the end of the last EA pretreatment, focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 90 minutes in male C57BL/6 mice and MCPIP1 knockout mice. Transcription and expression of MCPIP1 gene was monitored by qRT-PCR, Western blot and immunohistochemistry. The neurobehavioral scores, infarction volumes, proinflammatory cytokines and leukocyte infiltration in brain and NF-kappaB signaling were evaluated after ischemia/reperfusion. Results: MCPIP1 protein and mRNA levels significantly increased specifically in mouse brain undergoing EA pretreatment. EA pretreatment significantly attenuated the infarct volume, neurological deficits, upregulation of proinflammatory cytokines and leukocyte infiltration in the brain of wild-type mice after MCAO compared with that of the non-EA group. MCPIP1-deficient mice failed to evoke EA pretreatment-induced tolerance compared with that of the control MCPIP1 knockout group without EA treatment. Furthermore, the activation of NF-kappaB signaling was significantly reduced in EA-pretreated wild-type mice after MCAO compared to that of the non-EA control group and MCPIP1-deficient mice failed to confer the EA pretreatment-induced inhibition of NF-kappaB signaling after MCAO. Conclusions: Our data demonstrated that MCPIP1 deficiency caused significant lack of EA pretreatment-induced cerebral protective effects after MCAO compared with the control group and that MCPIP1 is involved in EA pretreatment-induced delayed brain ischemia tolerance.

Cerebrospinal fluid neopterin decay characteristics after initiation of antiretroviral therapy

Aylin Yilmaz — 2013-05-10T00:00:00Z

Background: Neopterin, a biomarker of macrophage activation, is elevated in the cerebrospinal fluid (CSF) of most HIV-infected individuals and decreases after initiation of antiretroviral therapy (ART). We studied decay characteristics of neopterin in CSF and blood after commencement of ART in HIV-infected subjects and estimated the set-point levels of CSF neopterin after ART-mediated viral suppression. Methods: CSF and blood neopterin were longitudinally measured in 102 neurologically asymptomatic HIV-infected subjects who were treatment-naïve or had been off ART for ≥ 6 months. We used a non-linear model to estimate neopterin decay in response to ART and a stable neopterin set-point attained after prolonged ART. Seven subjects with HIV-associated dementia (HAD) who initiated ART were studied for comparison. Results: Non-HAD patients were followed for a median 84.7 months. Though CSF neopterin concentrations decreased rapidly after ART initiation, it was estimated that set-point levels would be below normal CSF neopterin levels (<5.8 nmol/L) in only 60/102 (59%) of these patients. Pre-ART CSF neopterin was the primary predictor of set-point (P <0.001). HAD subjects had higher baseline median CSF neopterin levels than non-HAD subjects (P <0.0001). Based on the non-HAD model, only 14% of HAD patients were predicted to reach normal levels. Conclusions: After virologically suppressive ART, abnormal CSF neopterin levels persisted in 41% of non-HAD and the majority of HAD patients. ART is not fully effective in ameliorating macrophage activation in CNS as well as blood, especially in subjects with higher pre-ART levels of immune activation.

Exercise-induced hippocampal anti-inflammatory response in aged rats

Sérgio Gomes da Silva — 2013-05-10T00:00:00Z

Aging is often accompanied by cognitive decline, memory impairment and an increased susceptibility to neurodegenerative disorders. Most of these age-related alterations have been associated with deleterious processes such as changes in the expression of inflammatory cytokines. Indeed, higher levels of pro-inflammatory cytokines and lower levels of anti-inflammatory cytokines are found in the aged brain. This perturbation in pro- and anti-inflammatory balance can represent one of the mechanisms that contribute to age-associated neuronal dysfunction and brain vulnerability. We conducted an experimental study to investigate whether an aerobic exercise program could promote changes in inflammatory response in the brains of aged rats. To do so, we evaluated the levels of tumor necrosis factor alpha (TNFα), interleukin 1 beta (IL1β), interleukin 6 (IL6) and interleukin 10 (IL10) in the hippocampal formation of 18 month old rats that underwent treadmill training over 10 consecutive days. Quantitative immunoassay analyses showed that the physical exercise increased anti-inflammatory cytokine levels IL10 in the hippocampal formation of aged rats, when compared to the control group. The hippocampal levels of pro-inflammatory cytokines IL1β, IL6 and TNFα were not statistically different between the groups. However, a significant reduction in IL1β/IL10, IL6/IL10 and TNFα/IL10 ratio was observed in the exercised group in relation to the control group. These findings indicate a favorable effect of physical exercise in the balance between hippocampal pro- and anti-inflammatory during aging, as well as reinforce the potential therapeutic of exercise in reducing the risk of neuroinflammation-linked disorders.

Genetic variability in the rat Aplec C-type lectin gene cluster regulates lymphocyte trafficking and motor neuron survival after traumatic nerve root injury

Rickard Lindblom — 2013-05-08T00:00:00Z

Background: C-type lectin (CLEC) receptors are important for initiating and shaping immune responses; however, their role in inflammatory reactions in the central nervous system after traumatic injuries is not known. The antigen-presenting lectin-like receptor gene complex (Aplec) contains a few CLEC genes, which differ genetically among inbred rat strains. It was originally thought to be a region that regulates susceptibility to autoimmune arthritis, autoimmune neuroinflammation and infection. Methods: The inbred rat strains DA and PVG differ substantially in degree of spinal cord motor neuron death following ventral root avulsion (VRA), which is a reproducible model of localized nerve root injury. A large F2 (DAxPVG) intercross was bred and genotyped after which global expressional profiling was performed on spinal cords from F2 rats subjected to VRA. A congenic strain, Aplec, created by transferring a small PVG segment containing only seven genes, all C-type lectins, ontoDA background, was used for further experiments together with the parental strains. Results: Global expressional profiling of F2 (DAxPVG) spinal cords after VRA and genome-wide eQTL mapping identified a strong cis-regulated difference in the expression of Clec4a3 (Dcir3), a C-type lectin gene that is a part of the Aplec cluster. Second, we demonstrate significantly improved motor neuron survival and also increased T-cell infiltration into the spinal cord of congenic rats carrying Aplec from PVG on DA background compared to the parental DA strain. In vitro studies demonstrate that the Aplec genes are expressed on microglia and upregulated upon inflammatory stimuli. However, there were no differences in expression of general microglial activation markers between Aplec and parental DA rats, suggesting that the Aplec genes are involved in the signaling events rather than the primary activation of microglia occurring upon nerve root injury. Conclusions: In summary, we demonstrate that a genetic variation in Aplec occurring among inbred strains regulates both survival of axotomized motor neurons and the degree of lymphocyte infiltration. These results demonstrate a hitherto unknown role for CLECs for intercellular communication that occurs after damage to the nervous system, which is relevant for neuronal survival.

Acute and subacute IL-1beta administrations differentially modulate neuroimmune and neurotrophic systems: possible implications for neuroprotection and neurodegeneration

Cai Song — 2013-05-07T00:00:00Z

Background: In Alzheimer’s disease, stroke and brain injuries, activated microglia can release proinflammatory cytokines, such as interleukin (IL)-1β. These cytokines may change astrocyte and neurotrophin functions, which influences neuronal survival and induces apoptosis. However, the interaction between neuroinflammation and neurotrophin functions in different brain conditions is unknown. The present study hypothesized that acute and subacute elevated IL-1β differentially modulates glial and neurotrophin functions, which are related to their role in neuroprotection and neurodegeneration.MethodRats were i.c.v. injected with saline or IL-1β for 1 or 8 days and tested in a radial maze. mRNA and protein expressions of glial cell markers, neurotrophins, neurotrophin receptors, β-amyloid precursor protein (APP) and the concentrations of pro- and anti-inflammatory cytokines were measured in the hippocampus. Results: When compared to controls, memory deficits were found 4 days after IL-1 administrations, however the deficits were attenuated by IL-1 receptor antagonist (RA). Subacute IL-1 administrations increased expressions of APP, microglial active marker CD11b, and p75 neurotrophin receptor, and the concentration of tumor necrosis factor (TNF)-α and IL-1β, but decreased expressions of astrocyte active marker glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF) and TrK B. By contrast, up-regulations of NGF, BDNF and TrK B expressions were found after acute IL-1 administration, which are associated with the increase in both glial marker expressions and IL-10 concentrations. However, TrK A was down-regulated by acute and up-regulated by subacute IL-1 administrations. Subacute IL-1-induced changes in the glial activities, cytokine concentrations and expressions of BDNF and p75 were reversed by IL-1RA treatment. Conclusion: These results indicate that acute and subacute IL-1 administrations induce different changes toward neuroprotection after acute IL-1 administrations but neurodegeneration after subacute ones.

Microglial activation decreases retention of the protease inhibitor saquinavir: implications for HIV treatment

Shannon Dallas — 2013-05-04T00:00:00Z

Background: Active HIV infection within the central nervous system (CNS) is confined primarily to microglia. The glial cell compartment acts as a viral reservoir behind the blood-brain barrier. It provides an additional roadblock to effective pharmacological treatment via expression of multiple drug efflux transporters, including P-glycoprotein. HIV/AIDS patients frequently suffer bacterial and viral co-infections, leading to deregulation of glial cell function and release of pro-inflammatory mediators including cytokines, chemokines, and nitric oxide. Methods: To better define the role of inflammation in decreased HIV drug accumulation into CNS targets, accumulation of the antiretroviral saquinavir was examined in purified cultures of rodent microglia exposed to the prototypical inflammatory mediator lipopolysaccharide (LPS). Results: [3H]-Saquinavir accumulation by microglia was rapid, and was increased up to two-fold in the presence of the specific P-glycoprotein inhibitor, PSC833. After six or 24 hours of exposure to 10 ng/ml LPS, saquinavir accumulation was decreased by up to 45%. LPS did not directly inhibit saquinavir transport, and did not affect P-glycoprotein protein expression. LPS exposure did not alter RNA and/or protein expression of other transporters including multidrug resistance-associated protein 1 and several solute carrier uptake transporters. Conclusions: The decrease in saquinavir accumulation in microglia following treatment with LPS is likely multi-factorial, since drug accumulation was attenuated by inhibitors of NF-κβ and the MEK1/2 pathway in the microglia cell line HAPI, and in primary microglia cultures from toll-like receptor 4 deficient mice. These data provide new pharmacological insights into why microglia act as a difficult-to-treat viral sanctuary site.

Cognitive and cerebrovascular improvements following kinin B1 receptor blockade in Alzheimer's disease mice

Baptiste Lacoste — 2013-05-04T00:00:00Z

Background: Recent evidence suggests that the inducible kinin B1 receptor (B1R) contributes to pathogenic neuroinflammation induced by amyloid-beta (Abeta) peptide. The present study aims at identifying the cellular distribution and potentially detrimental role of B1R on cognitive and cerebrovascular functions in a mouse model of Alzheimer's disease (AD). Methods: Transgenic mice overexpressing a mutated form of the human amyloid precursor protein (APPSwe,Ind, line J20) were treated with a selective and brain penetrant B1R antagonist (SSR240612, 10 mg/kg/day for 5 or 10 weeks) or vehicle. The impact of B1R blockade was measured on i) spatial learning and memory performance in the Morris water maze, ii) cerebral blood flow (CBF) responses to sensory stimulation using laser Doppler flowmetry, and iii) reactivity of isolated cerebral arteries using online videomicroscopy. Abeta burden was quantified by ELISA and immunostaining, while other AD landmarks were measured by western blot and immunohistochemistry. Results: B1R protein levels were increased in APP mouse hippocampus and, prominently, in reactive astrocytes surrounding Abeta plaques. In APP mice, B1R antagonism with SSR240612 improved spatial learning, memory and normalized protein levels of the memory-related early gene Egr-1 in the dentate gyrus of the hippocampus. B1R antagonism restored sensory-evoked CBF responses, endothelium-dependent dilations, and normalized cerebrovascular protein levels of endothelial nitric oxide synthase and B2R. In addition, SSR240612 reduced (approximately 50%) microglial, but not astroglial, activation, brain levels of soluble Abeta1-42, diffuse and dense-core Abeta plaques, and it increased protein levels of the Abeta brain efflux transporter lipoprotein receptor-related protein-1 in cerebral microvessels. Conclusion: These findings show a selective upregulation of astroglial B1R in the APP mouse brain, and the capacity of the B1R antagonist to abrogate amyloidosis, cerebrovascular and memory deficits. Collectively, these findings provide convincing evidence for a role of B1R in AD pathogenesis.

Differential expression of interferon-¿ and chemokine genes distinguishes Rasmussen encephalitis from cortical dysplasia and provides evidence for an early Th1 immune response

Geoffrey Owens — 2013-05-02T00:00:00Z

Background: Rasmussen encephalitis (RE) is a rare complex inflammatory disease, primarily seen in young children, that is characterized by severe partial seizures and brain atrophy. Surgery is currently the only effective treatment option. To identify genes specifically associated with the immunopathology in RE, RNA transcripts of genes involved in inflammation and autoimmunity were measured in brain tissue from RE surgeries and compared with those in surgical specimens of cortical dysplasia (CD), a major cause of intractable pediatric epilepsy. Methods: Quantitative polymerase chain reactions measured the relative expression of 84 genes related to inflammation and autoimmunity in 12 RE specimens and in the reference group of 12 CD surgical specimens. Data were analyzed by consensus clustering using the entire dataset, and by pairwise comparison of gene expression levels between the RE and CD cohorts using the Harrell-Davis distribution-free quantile estimator method. Results: Consensus clustering identified six RE cases that were clearly distinguished from the CD cases and from other RE cases. Pairwise comparison showed that seven mRNAs encoding interferon-γ, CCL5, CCL22, CCL23, CXCL9, CXCL10, and Fas ligand were higher in the RE specimens compared with the CD specimens, whereas the mRNA encoding hypoxanthine-guanine phosphoribosyltransferase was reduced. Interferon-γ, CXCL5, CXCL9 and CXCL10 mRNA levels negatively correlated with time from seizure onset to surgery (P <0.05), whereas CCL23 and Fas ligand transcript levels positively correlated with the degree of tissue destruction and inflammation, respectively (P <0.05), as determined from magnetic resonance imaging (MRI) T2 and FLAIR images. Accumulation of CD4+ lymphocytes in leptomeninges and perivascular spaces was a prominent feature in RE specimens resected within a year of seizure onset. Conclusions: Active disease is characterized by a Th1 immune response that appears to involve both CD8+ and CD4+ T cells. Our findings suggest therapeutic intervention targeting specific chemokine/chemokine receptors may be useful in early stage RE.