Inflammatory Response In Brain Research Articles

Expression profiling of Rab GTPases reveals the involvement of Rab20 and Rab32 in acute brain inflammation in mice

Rab GTPases have emerged as central regulators of vesicle trafficking and are essential for cytokine production during the pathogenesis of neuroinflammation. To characterize the roles of different Rab proteins in brain inflammation, we used quantitative PCR (qPCR) to examine the expression profiles of all members of the Rab family in an experimental model of brain inflammation in mice. We found that Rab20 and Rab32 were substantially up-regulated during the acute phase of inflammation. The increased expression of Rab20 was also confirmed by immunostaining of inflamed brains at different timepoints. The concomitant overexpression of Rabs (Rab20 and Rab32) and early response proinflammatory cytokines (TNF-α and IL-1β) suggested that these Rabs may be important for subsequent inflammatory responses in brain. Furthermore, we found that the expression of certain Rabs was dramatically reduced in cultured primary microglia, which was not observed in the in vivo profiling. In N9, a microglial cell line, however, there was no increase in the expression of Rab20 or Rab32, but Rab3c was significantly overexpressed. These results collectively indicate that Rabs may participate in inflammatory response in microglia during brain inflammation. The differential regulation of individual Rabs in different experimental systems is a caveat for the analysis of Rab functions.

The Impact of Intermittent Umbilical Cord Occlusions on the Inflammatory Response in Pre-Term Fetal Sheep

Fetal hypoxic episodes may occur antepartum with the potential to induce systemic and cerebral inflammatory responses thereby contributing to brain injury. We hypothesized that intermittent umbilical cord occlusions (UCOs) of sufficient severity but without cumulative acidosis will lead to a fetal inflammatory response. Thirty-one chronically instrumented fetal sheep at ∼0.85 of gestation underwent four consecutive days of hourly UCOs from one to three minutes duration for six hours each day. Maternal and fetal blood samples were taken for blood gases/pH and plasma interleukin (IL)-1β and IL-6 levels. Animals were euthanized at the end of experimental study with brain tissue processed for subsequent counting of microglia and mast cells. Intermittent UCOs resulted in transitory fetal hypoxemia with associated acidemia which progressively worsened the longer umbilical blood flow was occluded, but with no cumulative blood gas or pH changes over the four days of study. Fetal arterial IL-1β and IL-6 values showed no significant change regardless of the severity of the UCOs, nor was there any evident impact on the microglia and mast cell counts for any of the brain regions studied. Accordingly, intermittent UCOs of up to three minutes duration with severe, but limited fetal hypoxemia and no cumulative acidemia, do not result in either a systemic or brain inflammatory response in the pre-term ovine fetus. However, fetal IL-1B and IL-6 values were found to be well correlated with corresponding maternal values supporting the placenta as a primary source for these cytokines with related secretion into both circulations. Female fetuses were also found to have higher IL-1β levels than males, indicating that gender may impact on the fetal inflammatory response to various stimuli.

Maternal N-acetyl-cysteine (NAC) protects the rat fetal brain from inflammatory cytokine responses to lipopolysaccharide (LPS)

Objective: Inflammatory cytokines, play a central role in the genesis of preterm parturition and fetal brain injury. Lipopolysaccharide (LPS) may activate cytokine pathways via induction of oxidative stress pathways. We hypothesized that enhanced maternal antioxidant activity may blunt fetal brain inflammatory responses to maternal LPS injection in pregnant rats. Methods: Pregnant Sprague-Dawley rats at 18 and 20 days gestation received intraperitoneal (ip) LPS injection and pre- and post-treatment with the antioxidant N-acetyl-cysteine (NAC) or saline. Six hours after the LPS injection, rats were sacrificed, interleukin (IL)-6 and IL-10 mRNA expression in the fetal brains was determined by real time polymerase chain reaction. Results: Maternal ip LPS induced significant increase in fetal brain IL-6 mRNA expression at E18 (3.1 ± 0.6 vs 1.0 ± 0.10 AU) and E20 (29.01 + 13.06 vs 0.95 + 0.05 AU; p < 0.05) compared to Control, only at E20 maternal LPS induced increase in fetal brain IL-10 compared to control. NAC administered prior to and after LPS significantly reduced fetal brain IL-6 at E18 and E20 and IL-10 at E20. Conclusion: Maternal NAC can protect the fetal brain from inflammatory cytokine responses to maternal LPS injection. These results suggest that NAC may potentially protect fetus from inflammation-associated brain injury and potential long term sequelae.

Transcriptomic profile of host response in mouse brain after exposure to plant toxin abrin

Abrin toxin is a plant glycoprotein, which is similar in structure and properties to ricin and is obtained from the seeds of Abrus precatorius (jequirity bean). Abrin is highly toxic, with an estimated human fatal dose of 0.1–1μg/kg, and has caused death after accidental and intentional poisoning. Abrin is a potent biological toxin warfare agent. There are no chemical antidotes available against the toxin. Neurological symptoms like delirium, hallucinations, reduced consciousness and generalized seizures were reported in human poisoning cases. Death of a patient with symptoms of acute demyelinating encephalopathy with gastrointestinal bleeding due to ingestion of abrin seeds was reported in India. The aim of this study was to examine both dose and time-dependent transcriptional responses induced by abrin in the adult mouse brain. Mice (n=6) were exposed to 1 and 2 LD50 (2.83 and 5.66μg/kg respectively) dose of abrin by intraperitoneal route and observed over 3 days. A subset of animals (n=3) were sacrificed at 1 and 2 day intervals for microarray and histopathology analysis. None of the 2 LD50 exposed animals survived till 3 days. The histopathological analysis showed the severe damage in brain and the infiltration of inflammatory cells in a dose and time dependent manner. The abrin exposure resulted in the induction of rapid immune and inflammatory response in brain. Clinical biochemistry parameters like lactate dehydrogenase, aspartate aminotransferase, urea and creatinine showed significant increase at 2-day 2 LD50 exposure. The whole genome microarray data revealed the significant regulation of various pathways like MAPK pathway, cytokine-cytokine receptor interaction, calcium signaling pathway, Jak-STAT signaling pathway and natural killer cell mediated toxicity. The comparison of differential gene expression at both the doses showed dose dependent effects of abrin toxicity. The real-time qRT-PCR analysis of selected genes supported the microarray data. This is the first report on host-gene response using whole genome microarray in an animal model after abrin exposure. The data generated provides leads for developing suitable medical counter measures against abrin poisoning.

Brain Inflammatory Mediators induced by high fat diet are significantly blunted with the deletion of MCP‐1

Consumption of a high fat diet (HFD) can lead to central nervous system (CNS) inflammation. Monocyte chemoattractant protein (MCP‐1) is fundamental in the release of inflammatory mediators, but its role in HFD induced CNS inflammation has not yet been determined. The purpose of this study was to determine the role of MCP‐1 on brain inflammation following 15 weeks of HFD feedings. C57BL/6 wildtype mice (n=20) and MCP‐1 −/− mice (n=32), 4 weeks of age were randomly assigned to one of four groups: normal diet wildtype (ND‐WT), HFD wildtype (HFD‐WT), normal diet MCP‐1−/− (ND‐MCP‐1−/−) or HFD MCP‐1 −/− (HFD‐MCP‐1−/−). The mice were fed the HFD (41% of total caloric intake from fat) or normal diet (11.5% of total caloric intake from fat) for 15 weeks. Mice were sacrificed at 19 weeks of age and the brainstem was dissected and analyzed for mRNA gene expression of TLR4, F4/80, CD11c and TNF‐α using real time RT‐PCR. Gene expression of TLR4, CD11c and TNF‐α was increased in the brainstem of HFD‐WT relative to ND‐WT (p&lt;0.05), whereas HFD‐MCP‐1−/− was not different from ND‐WT. A similar effect was observed for F4/80, but this did not reach statistical significance. No differences were found among the other groups. These data support a necessary role of MCP‐1 on the brain inflammatory response following HFD feedings. MCP‐1 may be an important therapeutic target in HFD‐induced brain inflammation.

Fibromyalgia, mood disorders, and intense creative energy: A1AT polymorphisms are not always silent

Persons with single copies of common alpha-1-antitrypsin polymorphisms such as S and Z are often considered “silent carriers”. Published evidence however supports a complex behavioral phenotype or trait – intense creative energy (“ICE”)-associated with A1AT polymorphisms. We now confirm that phenotype and present an association of fibromyalgia syndrome (FMS) and A1AT in a consecutive series of neurological patients.This is a retrospective case control series of 3176 consecutive patients presenting to Duke University Memory Clinic (747 patients) and to regional community-based Caldwell Hospital Neurology and Memory center (2429 patients). Work-up included medical history and examination, psychological evaluation, and genetic analysis. Chronic widespread pain (CWP) or FMS were diagnosed according to clinical guidelines, mostly as secondary diagnoses. Neurological patients carrying A1AT polymorphisms were common (ca 16% prevalence) and carriers had significantly higher use of inhaler and anxiolytic medications. Patients with ICE phenotype had a significantly higher proportion of A1AT polymorphisms (42%) compared to non-ICE patients (13%). Presence of CWP or FMS was common (14–22%) with average age at presentation of 56 years old and mostly female gender (82%). Patients with CWP/FMS had again significantly higher proportion of A1AT polymorphisms (38%) compared to other neurological patients (13%). Patients with anxiety disorders, bipolar I or bipolar II disorders or PTSD also had increased proportion of A1AT polymorphisms and significant overlap with ICE and FMS phenotype. Significant reductions in CWP/FMS prevalence are seen in apolipoprotein E4 carriers and methylene tetrahydrofolate reductase (MTHFR) mutation homozygotes. Since ICE phenotype is reported as a lifelong behavioral attribute, the presumption is that A1AT carriers have fundamental differences in brain development and inflammatory response. In support of this concept is finding those persons reporting a diagnosis of juvenile rheumatoid or idiopathic arthritis (JRA, JIA) had a significantly high proportion of A1AT polymorphisms (63%), suggesting a spectrum for JRA to later FMS presentations. Likewise, persons reporting a history of attention deficit disorder (ADD) had an increased proportion of A1AT polymorphisms (26%) compared to non-ADD persons (13%). Toxic environmental exposures are common (23%) and associated with diagnoses of PSP, PPA, FTD, FTD-PD, PD and ADVD. A1AT carriers were increased in cases of toxic exposure and PSP, PPA and FTD-PD.Our findings support the ICE behavioral phenotype for A1AT polymorphism carriers and the reported association with anxiety and bipolar spectrum disorders. We now extend that phenotype to apparent vulnerability to inflammatory muscle disease in a spectrum from JRA to fibromyalgia (FMS) and specific behavioral subsets of ADD, PTSD, and specific late onset neurological syndromes (FTD-PD and PPA). High and low risk FMS subsets can be defined using A1AT, MTHFR and APOE genotyping. Clinical diagnoses associated with A1AT polymorphisms included fibromyalgia, JRA/JIA, bipolar disorder, PTSD, primary progressive aphasia and FTDPD, but not most Alzheimer Disease subtypes. These results support an extended phenotype for A1AT mutation carriers beyond liver and lung vulnerability to selective advantages: ICE phenotype and disadvantages: fibromyalgia, affective disorders, and selected late onset neurological syndromes.

Intracerebral lipopolysaccharide induces neuroinflammatory change and augmented brain injury in growth-restricted neonatal rats

IntroductionIntrauterine growth-restriction (IUGR) alters fetal development and is associated with neurodevelopmental abnormalities. We hypothesized that growth-restriction from reduced intrauterine perfusion would predispose neonatal rats to subsequent inflammatory brain injury.MethodsIn the current study, IUGR was achieved by induced placental insufficiency in pregnant rats at 14 days of gestation. IUGR offspring and sham-operated control pups were subsequently injected with intracerebral lipopolysaccharide (LPS) as a model of PVL (perventricular leukomalacia).ResultsLPS similarly elevates proinflammatory cytokines in the brains of both IUGR and control rat pups. However, the chemokines cytokine-induced neutrophil chemoattractant-1 (CINC-1) and macrophage chemoattractant protein-1 (MCP-1), as well as microglia activation, were significantly higher in LPS-treated IUGR rat pups compared to LPS-treated controls. In addition to the unique brain inflammatory response, IUGR rat pups demonstrated enhanced brain damage with an increased number of apoptotic cells, larger lateral ventricular size, and more severe impairment of myelination.DiscussionThis study provides evidence that placental insufficiency may sensitize the innate immune system in the immature brain, and reveals a possible link between brain inflammation and injury.

Characterization of Seizures Induced by Acute and Repeated Exposure to Tetramethylenedisulfotetramine

Tetramethylenedisulfotetramine (tetramine; TETS) is a potent convulsant poison that is considered to be a chemical threat agent. To provide a basis for the investigation of antidotes for TETS-induced seizures, we characterized the convulsant activity of TETS in mice and rats when administered by the intraperitoneal, intravenous, oral, and intraventricular routes as a single acute dose and with repeated sublethal doses. In mice, parenteral and oral TETS caused immobility, myoclonic body jerks, clonic seizures of the forelimbs and/or hindlimbs, tonic seizures, and death. The CD₅₀ values for clonic and tonic seizures after oral administration were 0.11 and 0.22 mg/kg, respectively. Intraventricular administration of TETS (5-100 μg) in rats also caused clonic-tonic seizures and death. In mice, repeated sublethal doses of TETS at intervals of 2, 24, and 48 h failed to result in the development of persistent enhanced seizure responsivity ("kindling") as was observed with repeated pentylenetetrazol treatment. In mice, sublethal doses of TETS that produced clonic seizures did not cause observable structural brain damage as assessed with routine histology and Fluoro-Jade B staining 7 days after treatment. However, 1 to 3 days after a single convulsant dose of TETS the expression of glial fibrillary acidic protein, an astrocyte marker, and ionized calcium binding adaptor molecule 1, a microglia marker, were markedly increased in cortex and hippocampus. Although TETS doses that are compatible with survival are not associated with overt evidence of cellular injury or neurodegeneration, there is transient reactive astrocytosis and microglial activation, indicating that brain inflammatory responses are provoked.

Dexamethasone and betamethasone protect against lipopolysaccharide-induced brain damage in neonatal rats

The aim of this study is to test whether dexamethasone (Dex) and betamethasone (Beta), two of the most commonly used corticosteroids, protect against lipopolysaccharide (LPS)-induced white matter damage and neurobehavioral dysfunction. LPS or sterile saline was injected into the brain white matter of rat pups at postnatal day 5 (P5) and Dex or Beta was given intraperitoneally to the rat pups 1 h before the LPS microinjection. Brain inflammatory response, brain damage, and myelination were examined at P6, P8 and P14. Neurobehavioral tests were performed from P3 through P22. Our results demonstrate that Dex and Beta markedly diminish the LPS-induced brain inflammatory response, restore myelin basic protein (MBP) expression and alleviate lateral ventricle dilation. Both corticosteroids demonstrate significant protection against most of LPS-induced behavioral deficits, including those in rearing, vibrissa-elicited forelimb-placing, beam walking, learning and elevated plus-maze test. Notably, only Beta improved the locomotion and stereotype dysfunction. In contrast to their beneficial effects, neither drug prevented LPS-induced delay in body weight gain from P6 through P21. Our study suggests that if their adverse effects are minimized, corticosteroids may be the potential candidate drugs to prevent brain damage in premature infants.

Inflammatory Effects of Highly Pathogenic H5N1 Influenza Virus Infection in the CNS of Mice

The A/VN/1203/04 strain of the H5N1 influenza virus is capable of infecting the CNS of mice and inducing a number of neurodegenerative pathologies. Here, we examined the effects of H5N1 on several pathological aspects affected in parkinsonism, including loss of the phenotype of dopaminergic neurons located in the substantia nigra pars compacta (SNpc), expression of monoamines and indolamines in brain, alterations in SNpc microglia number and morphology, and expression of cytokines, chemokines, and growth factors. We find that H5N1 induces a transient loss of the dopaminergic phenotype in SNpc and now report that this loss recovers by 90 d after infection. A similar pattern of loss and recovery was seen in monoamine levels of the basal ganglia. The inflammatory response in lung and different regions of the brain known to be targets of the H5N1 virus (brainstem, substantia nigra, striatum, and cortex) were examined at 3, 10, 21, 60, and 90 d after infection. In each of these brain regions, we found a significant increase in the number of activated microglia that lasted at least 90 d. We also quantified expression of IL-1α, IL-1β, IL-2, IL-6, IL-9, IL-10, IL-12(p70), IL-13, TNF-α, IFN-γ, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, macrophage colony-stimulating factor, eotaxin, interferon-inducible protein 10, cytokine-induced neutrophil chemoattractant, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP) 1α, MIP-1β, and VEGF, and found that the pattern and levels of expression are dependent on both brain region and time after infection. We conclude that H5N1 infection in mice induces a long-lasting inflammatory response in brain and may play a contributing factor in the development of pathologies in neurodegenerative disorders.

Abstract 3676: MyD88-Dependent Pathway Has a Dual Effect on Brain Injury after Cerebral Ischemia/Reperfusion in Mouse

Myeloid differentiation primary-response protein-88 (MyD88) is one of the intracellular adaptors in Toll-like receptor (TLR) signaling pathways, which regulates the activation of nuclear factor kappa B (NF-kappa-B) and transcription of other proinflammatory cytokines. We assessed the hypothesis that MyD88-dependent signaling mediates the inflammatory responses in ischemic brain and is implicated in the process of brain injury. A mouse model of cerebral ischemia/reperfusion (I/R) was induced by transient middle cerebral artery occlusion (tMCAO). MyD88 knockout (KO) mice and wild type control mice (WT, C57BL/6J) were assigned to I/R or sham-operated groups. The mice were killed at 4 hrs or 24 hrs after reperfusion following 60 minutes of MCAO. Using Nissl staining, brain infarct areas were evaluated and expressed as a percentage of the whole brain. Brain edema was evaluated and presented as the percentage of water content in the total weight of the brain tissue. The expression of mRNA was detected by real-time PCR, and the levels of inflammatory cytokines were measured by ELISA and Western Blots. The infarct size was analyzed by t-test. Brain edema and inflammatory response were analyzed by one way ANOVA with post hoc comparisons. Our results showed that the brain infarct size was not significantly different in MyD88KO mice compared with WT mice 24 hrs after cerebral I/R. However, brain edema (water content) significantly increased in MyD88KO mice compared with WT 24 hrs after ischemia (p&lt;0.05). The data also showed that the levels of mRNA of CD14, Pellino-1, cyclooxygenase-2 (COX-2), and Interferon beta-1 (INFb1) increased significantly 4 hrs after cerebral I/R in WT mice compared to sham-operated controls (p&lt;0.05). MyD88 deficiency inhibited the increased expression of Pellino-1 (p&lt;0.05) and COX-2 (p&lt;0.05), but not CD14. Twenty-four hrs after cerebral I/R, the protein levels of Interleukin - 1-beta, Interleukin - 6 (IL-6), p-IkappaB alpha, and the activity of NFkappaB, significantly increased in the ischemic brain in WT mice, and were inhibited in MyD88KO mice. Interestingly, VEGF significantly increased in MyD88KO mice compared with WT mice (p&lt;0.05). In addition, ZO-1, a tight-junction protein on the blood-brain barrier (BBB) decreased in MyD88KO mice compared with WT mice subjected to cerebral I/R. Our data demonstrates that MyD88 contributes to the activation of inflammatory responses after cerebral I/R. However, MyD88 reduces brain edema by mediating the expression of VEGF, and tight-junction proteins, which are important for maintaining BBB integrity. We concluded that the MyD88-dependent pathway has a dual effect on brain injury induced by cerebral I/R. Interpreting the results for the role of MyD88 dependent pathway based on brain injury from whole animal experiments is cautioned.

Intracerebroventricularly delivered VEGF promotes contralesional corticorubral plasticity after focal cerebral ischemia via mechanisms involving anti-inflammatory actions

Vascular endothelial growth factor (VEGF) has potent angiogenic and neuroprotective effects in the ischemic brain. Its effect on axonal plasticity and neurological recovery in the post-acute stroke phase was unknown. Using behavioral tests combined with anterograde tract tracing studies and with immunohistochemical and molecular biological experiments, we examined effects of a delayed i.c.v. delivery of recombinant human VEGF165, starting 3days after stroke, on functional neurological recovery, corticorubral plasticity and inflammatory brain responses in mice submitted to 30min of middle cerebral artery occlusion. We herein show that the slowly progressive functional improvements of motor grip strength and coordination, which are induced by VEGF, are accompanied by enhanced sprouting of contralesional corticorubral fibres that branched off the pyramidal tract in order to cross the midline and innervate the ipsilesional parvocellular red nucleus. Infiltrates of CD45+ leukocytes were noticed in the ischemic striatum of vehicle-treated mice that closely corresponded to areas exhibiting Iba-1+ activated microglia. VEGF attenuated the CD45+ leukocyte infiltrates at 14 but not 30days post ischemia and diminished the microglial activation. Notably, the VEGF-induced anti-inflammatory effect of VEGF was associated with a downregulation of a broad set of inflammatory cytokines and chemokines in both brain hemispheres. These data suggest a link between VEGF's immunosuppressive and plasticity-promoting actions that may be important for successful brain remodeling. Accordingly, growth factors with anti-inflammatory action may be promising therapeutics in the post-acute stroke phase.

Blocking IL-1 signaling rescues cognition, attenuates tau pathology, and restores neuronal β-catenin pathway function in an Alzheimer's disease model.

Inflammation is a key pathological hallmark of Alzheimer's disease (AD), although its impact on disease progression and neurodegeneration remains an area of active investigation. Among numerous inflammatory cytokines associated with AD, IL-1β in particular has been implicated in playing a pathogenic role. In this study, we sought to investigate whether inhibition of IL-1β signaling provides disease-modifying benefits in an AD mouse model and, if so, by what molecular mechanisms. We report that chronic dosing of 3xTg-AD mice with an IL-1R blocking Ab significantly alters brain inflammatory responses, alleviates cognitive deficits, markedly attenuates tau pathology, and partly reduces certain fibrillar and oligomeric forms of amyloid-β. Alterations in inflammatory responses correspond to reduced NF-κB activity. Furthermore, inhibition of IL-1 signaling reduces the activity of several tau kinases in the brain, including cdk5/p25, GSK-3β, and p38-MAPK, and also reduces phosphorylated tau levels. We also detected a reduction in the astrocyte-derived cytokine, S100B, and in the extent of neuronal Wnt/β-catenin signaling in 3xTg-AD brains, and provided in vitro evidence that these changes may, in part, provide a mechanistic link between IL-1 signaling and GSK-3β activation. Taken together, our results suggest that the IL-1 signaling cascade may be involved in one of the key disease mechanisms for AD.

Hypothalamic inflammation: a double‐edged sword to nutritional diseases

The hypothalamus is one of the master regulators of various physiological processes, including energy balance and nutrient metabolism. These regulatory functions are mediated by discrete hypothalamic regions that integrate metabolic sensing with neuroendocrine and neural controls of systemic physiology. Neurons and nonneuronal cells in these hypothalamic regions act supportively to execute metabolic regulations. Under conditions of brain and hypothalamic inflammation, which may result from overnutrition-induced intracellular stresses or disease-associated systemic inflammatory factors, extracellular and intracellular environments of hypothalamic cells are disrupted, leading to central metabolic dysregulations and various diseases. Recent research has begun to elucidate the effects of hypothalamic inflammation in causing diverse components of metabolic syndrome leading to diabetes and cardiovascular disease. These new understandings have provocatively expanded previous knowledge on the cachectic roles of brain inflammatory response in diseases, such as infections and cancers. This review describes the molecular and cellular characteristics of hypothalamic inflammation in metabolic syndrome and related diseases as opposed to cachectic diseases, and also discusses concepts and potential applications of inhibiting central/hypothalamic inflammation to treat nutritional diseases.

Fever, sickness behavior, and expression of inflammatory genes in the hypothalamus after systemic and localized subcutaneous stimulation of rats with the toll-like receptor 7 agonist imiquimod

The Toll-like receptor 7 (TLR7) agonist imiquimod is used for topical treatment of skin cancers. We studied the consequences of injections of imiquimod into a subcutaneous (s.c.) air pouch or of intraperitoneal (i.p.) injections on the manifestation of fever, sickness behavior, and the peripheral and brain-intrinsic induction of a variety of inflammatory molecules. Rats were given imiqimod s.c. or i.p. (1 or 5 mg/kg). Body temperature, motor activity, and food and water intake were recorded by telemetric devices. Peripheral and brain-intrinsic induction of inflammatory mediators was analyzed by real-time polymerase chain reaction (RT-PCR), bioassays, enzyme-linked immunosorbent assays (ELISAs), and immunohistochemistry. Imiquimod is the first TLR-agonist to produce more potent effects with s.c. than i.p. administration. Peripheral induction of interferons (IFNs) and putative circulating pyrogens corresponded to the magnitude of the illness responses. In the brain, an expression of cytokines (TNFα, IL-1β, and IL-6) and inducible forms of enzymes for prostaglandin E2 synthesis (COX-2 and mPGES) occurred, which was accompanied by a moderate activation of the transcription factors NFκB and STAT3, and a strong activation of the transcription factor NF-IL6, in cells of specific areas with an open blood–brain barrier. These inflammatory responses noted within the brain were more marked after s.c. administration, than i.p. administration of imiquimod. At a dose of 5 mg/kg, imiquimod causes rather moderate brain-inflammatory responses, which are related to peripheral IFN-expression and possibly mediated by brain-intrinsic activation of NF-IL6 and induction of a proinflammatory cocktail. The lack of a septic-like state in imiquimod-treated rats reinforces the therapeutic use of this drug.

Parthenolide attenuates LPS-induced fever, circulating cytokines and markers of brain inflammation in rats

Parthenolide, a sesquiterpene lactone, has been reported to exhibit a variety of anti-inflammatory and immunomodulatory effects. To test the effect of parthenolide on brain inflammatory responses, brain oxidative stress and fever, we treated rats with parthenolide (1mg/kg), simultaneously or 1h prior to a systemic (i.p.) challenge with a moderate dose (100μg/kg) of lipopolysaccharide (LPS). The initial hypothermia was exaggerated; the second phase of the biphasic LPS-induced fever and circulating interleukin-6 (IL-6) and tumor necrosis factor α (TNFα) were significantly attenuated only in parthenolide-pretreated animals. In the hypothalamus, markers of NFκB/NF-IL6 pathway activation (inhibitor κBα, NF-IL6 and the serin/threonin kinase-like protein mRNA expression) and markers of oxidative stress (including nuclear respiratory factor 1) and NFκB immunoreactivity were significantly reduced while NF-IL6 immunoreactivity and suppressor of cytokine signaling 3 mRNA expression remained unaltered, 8h after LPS-stimulation with parthenolide-pretreatment. Importantly, this response was accompanied by decreased mRNA expression of the rate limiting enzyme in prostaglandin synthesis, cyclooxygenase 2 (COX2), known for its critical role in fever induction pathways. A direct action of parthenolide on brain cells was also confirmed in a primary neuro-glial cell culture of the vascular organ of the lamina terminalis a pivotal brain structure for fever manifestation with a leaky blood–brain barrier. In summary, pretreatment with parthenolide attenuates the febrile response during LPS-induced systemic inflammation by reducing circulating IL-6 and TNFα and decreasing hypothalamic NFκB/NF-IL6 activation, oxidative stress and expression of COX2. Thus parthenolide appears to have the potential to reduce brain inflammation.

Ursolic acid improves high fat diet-induced cognitive impairments by blocking endoplasmic reticulum stress and IκB kinase β/nuclear factor-κB-mediated inflammatory pathways in mice

Evidence suggests that obesity-induced cognitive impairments are driven by in brain inflammatory responses and inflammation-mediated brain insulin resistance. Ursolic acid (UA), a triterpenoid compound, has many important biological functions, including antioxidant and anti-inflammatory activities. Here, we evaluated the effect of UA on cognitive impairment induced by a high-fat diet (HFD), and we explored the potential mechanisms mediating this effect. Results showed that UA administration significantly improved the behavioral performance of C57/BL6J mice fed a HFD in both the step-through test and the Morris water maze task. These results were associated with the inhibition of endoplasmic reticulum stress and IκB kinase β/nuclear factor-κB-mediated inflammatory signaling and the restoration of insulin signaling and phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway. UA administration also increased memory-related protein expression in the hippocampus of mice given a HFD. However, the neuroprotective effects of UA were blocked by an intracerebroventricular (i.c.v.) injection of PI-103, a specific PI3K 110α inhibitor. These results suggest that UA may be a potent candidate for the prevention and treatment of cognitive deficits caused by type 2 diabetes.

Traffic of leukocytes and cytokine up-regulation in the central nervous system in sepsis

To evaluate the effects of sepsis on brain microvasculature leukocyte rolling and adherence, myeloperoxidase (MPO) activity, cytokine and chemokine concentrations, and behavioral screening 6, 12, and 24 h after sepsis induction. C57BL/6 mice or Wistar rats underwent cecal ligation and perforation (CLP) or sham operation. At 6, 12, and 24 h after sepsis induction, intravital microscopy was performed in the mice brain microvasculature to evaluate leukocyte rolling and adherence. Animals were killed and had the brain removed to determine MPO activity and the levels of cytokines and chemokines. A behavioral screening was also performed in a separate cohort of animals. Blood-brain barrier (BBB) permeability and cytokines and chemokines were determined in different brain regions in Wistar rats. There was a decrease in circulating leukocyte levels at 6, 12, and 24 h, an increase in rolling and adhesion of leukocytes in the brain microvasculature, followed by an increase in brain MPO activity. In addition, there was an increase in both brain cytokines and chemokines at different times. There was a decrease in the neuropsychiatric state muscle tone and strength only at 6 h, and a decrease in the autonomous function at 6 and 12 h. The pattern of brain cytokines and chemokines, and BBB permeability between the analyzed regions seemed to be similar with minor differences. During sepsis the brain's production of cytokines and chemokines is an early event and it seemed to participate both in central nervous system (CNS) dysfunction and BBB permeability alterations, reinforcing the role of brain inflammatory response in the acute CNS dysfunction associated with sepsis.

Mutant presenilin-1 deregulated peripheral immunity exacerbates Alzheimer-like pathology

Mutations in the presenilin-1 (PS1) gene are independent causes of familial Alzheimer's disease (AD). AD patients have dysregulated immunity, and PS1 mutant mice exhibit abnormal systemic immune responses. To test whether immune function abnormality caused by a mutant human PS1 gene (mhPS1) could modify AD-like pathology, we reconstituted immune systems of AD model mice carrying a mutant human amyloid precursor protein gene (mhAPP; Tg2576 mice) or both mhAPP and mhPS1 genes (PSAPP mice) with allo-geneic bone marrow cells. Here, we report a marked reduction in amyloid-β (Aβ) levels, β-amyloid plaques and brain inflammatory responses in PSAPP mice following strain-matched wild-type PS1 bone marrow reconstitution. These effects occurred with immune switching from pro-inflammatory T helper (Th) 1 to anti-inflammatory Th2 immune responses in the periphery and in the brain, which likely instructed microglia to phagocytose and clear Aβ in an ex vivo assay. Conversely, Tg2576 mice displayed accelerated AD-like pathology when reconstituted with mhPS1 bone marrow. These data show that haematopoietic cells bearing the mhPS1 transgene exacerbate AD-like pathology, suggesting a novel therapeutic strategy for AD based on targeting PS1 in peripheral immune cells.

Mechanism of inflammatory responses in brain and impairment of spatial memory of mice caused by titanium dioxide nanoparticles

Although it is known that titanium dioxide nanoparticles (TiO 2 NPs) or other nanoparticles can induce brain toxicities, the mechanisms and the molecular pathogenesis are still unclear. In this study, TiO 2 NPs were injected into the abdominal cavity of ICR mice for consecutive 14 days, and the inflammatory responses of brain of mice and spatial memory were investigated. The results showed the obvious titanium accumulation in brain, neuroinflammation and impairment of spatial memory of mice. TiO 2 NPs can significantly promote the expressions of tumor necrosis factor-α, nucleic IκB kinase, factor-κB-inducible kinase, nucleic factor-κB, P52, P65, and significantly inhibit the expressions of IκB and interleukin-2. Our results also implied that the inflammatory responses and brain function injury may be involved in TiO 2 NPs-induced brain toxicity. The signaling pathway of brain injury in the TiO 2 NPs-stimulated mouse brain was discussed.