Interleukin-13 and -4 induce death of activated microglia

Neuroprotective effect of L-DOPA-induced interleukin-13 on striatonigral degeneration in cerebral ischemia

Levodopa (L-DOPA) treatment is a clinically effective strategy for improving motor function in patients with ischemic stroke. However, the mechanisms by which modulating the dopamine system relieves the pathology of the ischemic brain remain unclear. Emerging evidence from an experimental mouse model of ischemic stroke, established by middle cerebral artery occlusion (MCAO), suggested that L-DOPA has the potential to modulate the inflammatory and immune response that occurs during a stroke. Here, we aimed to demonstrate the therapeutic effect of L-DOPA in regulating the systemic immune response and improving functional deficits in mice with ischemia. Transient MCAO led to progressive degeneration of nigrostriatal dopamine neurons and significant rotational behavior in mice. Exogenous L-DOPA treatment attenuated the striatonigral degeneration and reversed motor behavioral impairment. Notably, treatment with L-DOPA significantly increased IL-13 but reduced IFN-γ in infarct lesions. To investigate the role of IL-13 in motor behavior, we stereotaxically injected anti-IL-13 antibodies into the infarct area of the mouse brain one week after MCAO, followed by L-DOPA treatment. The intervention reduced dopamine, IL-13, and IL-10 levels and exacerbated motor function. IL-13 is potentially expressed on CD4 T cells, while IL-10 is mainly expressed on microglia rather than astrocytes. Finally, IL-13 activates the phagocytosis of microglia, which may contribute to neuroprotection by eliminating degenerating neurons. Our study provides evidence that the L-DOPA-activated dopamine system modulates peripheral immune cells, resulting in the expression of anti-inflammatory and neuroprotective cytokines in mice with ischemic stroke.

Differentiation and regulation of CD4+ T cell subsets in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its hallmark pathological features are the loss of dopaminergic (DA) neurons in the midbrain substantia nigra pars compacta (SNpc) and the accumulation of alpha-synuclein (α-syn). It has been shown that the integrity of the blood-brain barrier (BBB) is damaged in PD patients, and a large number of infiltrating T cells and inflammatory cytokines have been detected in the cerebrospinal fluid (CSF) and brain parenchyma of PD patients and PD animal models, including significant change in the number and proportion of different CD4+ T cell subsets. This suggests that the neuroinflammatory response caused by CD4+ T cells is an important risk factor for the development of PD. Here, we systematically review the differentiation of CD4+ T cell subsets, and focus on describing the functions and mechanisms of different CD4+ T cell subsets and their secreted cytokines in PD. We also summarize the current immunotherapy targeting CD4+ T cells with a view to providing assistance in the diagnosis and treatment of PD.

Behavior, synaptic mitochondria, and microglia are differentially impacted by chronic adolescent stress and repeated endotoxin exposure in male and female rats

Early life adversity and chronic inflammation have both been associated with cognitive impairment and neural compromise. In this study, we investigated the interactions between a history of chronic adolescent stress (CAS) and repeated endotoxin exposure on behavior, synaptic mitochondria, and microglia in adult male and female Wistar rats. Adult rats from chronic stress and control conditions were exposed to either repeated endotoxin (lipopolysaccharide; LPS) or saline injections every 3 days for 9 weeks. In both sexes, repeated LPS, regardless of stress history, impaired working memory in the Y maze. Regarding spatial memory, LPS impaired function for females; whereas, CAS altered function in males. Although males had an increase in anxiety-like behavior shortly after CAS, there were no long-term effects on anxiety-like behavior or social interaction observed in males or females. Stress did not alter synaptic mitochondrial function in either sex. Repeated LPS altered synaptic mitochondrial function such that ATP production was increased in females only. There were no observed increases in IBA-1 positive cells within the hippocampus for either sex. However, LPS and CAS altered microglia morphology in females. Impact of repeated LPS was evident at the terminal endpoint with increased spleen weight in both sexes and decreased adrenal weight in males only. Circulating cytokines were not impacted by repeated LPS at the terminal endpoint, but evidence of CAS effects on cytokines in females were evident. These data suggest a long-term impact of chronic stress and an impact of repeated endotoxin challenge in adulthood; however, not all physiological and behavioral metrics examined were impacted by the paradigm employed in this study and the two environmental challenges rarely interacted.

Maternal immune activation impairs endocannabinoid signaling in the mesolimbic system of adolescent male offspring

Prenatal infections can increase the risk of developing psychiatric disorders such as schizophrenia in the offspring, especially when combined with other postnatal insults. Here, we tested, in a rat model of prenatal immune challenge by the viral mimic polyriboinosinic-polyribocytidilic acid, whether maternal immune activation (MIA) affects the endocannabinoid system and endocannabinoid-mediated modulation of dopamine functions. Experiments were performed during adolescence to assess i) the behavioral endophenotype (locomotor activity, plus maze, prepulse inhibition of startle reflex); ii) the locomotor activity in response to Δ9-Tetrahydrocannabinol (THC) and iii) the properties of ventral tegmental area (VTA) dopamine neurons in vivo and their response to THC; iv) endocannabinoid-mediated synaptic plasticity in VTA dopamine neurons; v) the expression of cannabinoid receptors and enzymes involved in endocannabinoid synthesis and catabolism in mesolimbic structures and vi) MIA-induced neuroinflammatory scenario evaluated by measurements of levels of cytokine and neuroinflammation markers. We revealed that MIA offspring displayed an altered locomotor activity in response to THC, a higher bursting activity of VTA dopamine neurons and a lack of response to cumulative doses of THC. Consistently, MIA adolescence offspring showed an enhanced 2-arachidonoylglycerol-mediated synaptic plasticity and decreased monoacylglycerol lipase activity in mesolimbic structures. Moreover, they displayed a higher expression of cyclooxygenase 2 (COX-2) and ionized calcium-binding adaptor molecule 1 (IBA-1), associated with latent inflammation and persistent microglia activity. In conclusion, we unveiled neurobiological mechanisms whereby inflammation caused by MIA influences the proper development of endocannabinoid signaling that negatively impacts the dopamine system, eventually leading to psychotic-like symptoms in adulthood.

The Development of Systemic Inflammatory Diseases in Hidradenitis Suppurativa

It is understood that the skin is a peripheral lymphoid tissue that defends against external environmental stimuli. Continuous activation from these factors, on the other hand, promotes persistent inflammation at the local location and, occasionally, tissue damage. Hidradenitis suppurativa (HS) is a typical inflammatory skin disease and becomes a source of numerous inflammatory cytokines due to the chronic intractable repeated inflamed tissues. Because inflammatory cells and cytokines circulate throughout the body from the inflamed organ, it has been hypothesized that HS-mediated skin inflammation impacts the systemic functioning of numerous organs. Recent updates to clinical and experimental investigations revealed that HS has a significant connection with systemic inflammatory disorders. We provide the details and comprehensive molecular mechanisms associated with systemic inflammatory illnesses due to HS.

Interleukin-13 and its receptor are synaptic proteins involved in plasticity and neuroprotection

Immune system molecules are expressed by neurons, yet their functions are often unknown. We have identified IL-13 and its receptor IL-13Ra1 as neuronal, synaptic proteins in mouse, rat, and human brains, whose engagement upregulates the phosphorylation of NMDAR and AMPAR subunits and, in turn, increases synaptic activity and CREB-mediated transcription. We demonstrate that increased IL-13 is a hallmark of traumatic brain injury (TBI) in male mice as well as in two distinct cohorts of human patients. We also provide evidence that IL-13 upregulation protects neurons from excitotoxic death. We show IL-13 upregulation occurring in several cohorts of human brain samples and in cerebrospinal fluid (CSF). Thus, IL-13 is a physiological modulator of synaptic physiology of neuronal origin, with implications for the establishment of synaptic plasticity and the survival of neurons under injury conditions. Furthermore, we suggest that the neuroprotection afforded through the upregulation of IL-13 represents an entry point for interventions in the pathophysiology of TBI.

Innate lymphoid cells in depression: Current status and perspectives

The recent discovery of innate lymphoid cells (ILCs) has provided new insights into our understanding of the pathogenesis of many disease conditions with immune dysregulation. Type 1 innate lymphoid cells (ILC1s) induce type I immunity and are characterized by the expression of signature cytokine IFN-γ and the master transcription factor T-bet; ILC2s stimulate type II immune responses and are defined by the expression of signature cytokines IL-5 and IL-13, and transcription factors ROR-α and GATA3; ILC3s requires the transcription factor RORγt and produce IL-22 and IL-17. ILCs are largely tissue-resident and are enriched at barrier surfaces of the mammalian body. Increasing evidence shows that inflammation is involved in the pathogenesis of depression. Although few studies have directly investigated the role of ILCs in depression, several studies have examined the levels of cytokines produced by ILCs in depressed subjects. This review summarizes the potential roles of ILCs in depression. A better understanding of the biology of ILCs may lead to the development of new therapeutic strategies for the management of depression.

Tanshinone IIA-Loaded Nanoparticle and Neural Stem Cell Therapy Enhances Recovery in a Pig Ischemic Stroke Model

Induced pluripotent stem cell-derived neural stem cells (iNSCs) are a multimodal stroke therapeutic that possess neuroprotective, regenerative, and cell replacement capabilities post-ischemia. However, long-term engraftment and efficacy of iNSCs is limited by the cytotoxic microenvironment post-stroke. Tanshinone IIA (Tan IIA) is a therapeutic that demonstrates anti-inflammatory and antioxidative effects in rodent ischemic stroke models and stroke patients. Therefore, pretreatment with Tan IIA may create a microenvironment that is more conducive to the long-term survival of iNSCs. In this study, we evaluated the potential of Tan IIA drug-loaded nanoparticles (Tan IIA-NPs) to improve iNSC engraftment and efficacy, thus potentially leading to enhanced cellular, tissue, and functional recovery in a translational pig ischemic stroke model. Twenty-two pigs underwent middle cerebral artery occlusion (MCAO) and were randomly assigned to a PBS + PBS, PBS + iNSC, or Tan IIA-NP + iNSC treatment group. Magnetic resonance imaging (MRI), modified Rankin Scale neurological evaluation, and immunohistochemistry were performed over a 12-week study period. Immunohistochemistry indicated pretreatment with Tan IIA-NPs increased iNSC survivability. Furthermore, Tan IIA-NPs increased iNSC neuronal differentiation and decreased iNSC reactive astrocyte differentiation. Tan IIA-NP + iNSC treatment enhanced endogenous neuroprotective and regenerative activities by decreasing the intracerebral cellular immune response, preserving endogenous neurons, and increasing neuroblast formation. MRI assessments revealed Tan IIA-NP + iNSC treatment reduced lesion volumes and midline shift. Tissue preservation and recovery corresponded with significant improvements in neurological recovery. This study demonstrated pretreatment with Tan IIA-NPs increased iNSC engraftment, enhanced cellular and tissue recovery, and improved neurological function in a translational pig stroke model.

LncRNA, an Emerging Approach for Neurological Diseases Treatment by Regulating Microglia Polarization

Neurological disorders cause untold human disability and death each year. For most neurological disorders, the efficacy of their primary treatment strategies remains suboptimal. Microglia are associated with the development and progression of multiple neurological disorders. Targeting the regulation of microglia polarization has emerged as an important therapeutic strategy for neurological disorders. Their pro-inflammatory (M1)/anti-inflammatory (M2) phenotype microglia are closely associated with neuronal apoptosis, synaptic plasticity, blood-brain barrier integrity, resistance to iron death, and astrocyte regulation. LncRNA, a recently extensively studied non-coding transcript of over 200 nucleotides, has shown great value to intervene in microglia polarization. It can often participate in gene regulation of microglia by directly regulating transcription or sponging downstream miRNAs, for example. Through proper regulation, microglia can exert neuroprotective effects, reduce neurological damage and improve the prognosis of many neurological diseases. This paper reviews the progress of research linking lncRNAs to microglia polarization and neurological diseases.

Immune activation during Paenibacillus brain infection in African infants with frequent cytomegalovirus co-infection

Inflammation during neonatal brain infections leads to significant secondary sequelae such as hydrocephalus, which often follows neonatal sepsis in the developing world. In 100 African hydrocephalic infants we identified the biological pathways that account for this response. The dominant bacterial pathogen was a Paenibacillus species, with frequent cytomegalovirus co-infection. A proteogenomic strategy was employed to confirm host immune response to Paenibacillus and to define the interplay within the host immune response network. Immune activation emphasized neuroinflammation, oxidative stress reaction, and extracellular matrix organization. The innate immune system response included neutrophil activity, signaling via IL-4, IL-12, IL-13, interferon, and Jak/STAT pathways. Platelet-activating factors and factors involved with microbe recognition such as Class I MHC antigen-presenting complex were also increased. Evidence suggests that dysregulated neuroinflammation propagates inflammatory hydrocephalus, and these pathways are potential targets for adjunctive treatments to reduce the hazards of neuroinflammation and risk of hydrocephalus following neonatal sepsis.

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There is a characteristic immune response to Paenibacillus brain infection

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There is a characteristic immune response to CMV brain infection

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The matching immune response validates pathogen genomic presence

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The combined results support molecular infection causality

Interleukin-4-Mediated Oxidative Stress Is Harmful to Hippocampal Neurons of Prothrombin Kringle-2-Lesioned Rat In Vivo

The present study investigated the effects of reactive microglia/macrophages-derived interleukin-4 (IL-4) on hippocampal neurons in prothrombin kringle-2 (pKr-2)-lesioned rats. pKr-2 was unilaterally injected into hippocampus in the absence or presence of IL-4 neutralizing antibody (IL-4Nab). Immunohistochemical analysis showed a significant loss of Nissl⁺ and NeuN⁺ cells and activation of microglia/macrophages (increase in reactive OX-42⁺ and OX-6⁺ cells) in the hippocampus at 7 days after pKr-2 injection. The levels of IL-4 expression were upregulated in the reactive OX-42⁺ microglia/macrophages as early as 1 day, maximal at 3 days and maintained up to 7 days after pKr-2 injection. Treatment with IL-4Nab significantly increased neuronal survival in pKr-2-treated CA1 layer of hippocampus in vivo. Accompanying neuroprotection, IL-4 neutralization inhibited activation of microglia/macrophages, reactive oxygen species-derived oxidative damages, production of myeloperoxidase- and inducible nitric oxide synthase-derived reactive nitrogen species and nitrosative damages as analyzed by immunohistochemistry and hydroethidine histochemistry. These results suggest that endogenous IL-4 expressed on reactive microglia/macrophages mediates oxidative/nitrosative stress and play a critical role on neurodegeneration of hippocampal CA1 layer in vivo.

Neuroinflammation in Alzheimer's Disease: Microglia, Molecular Participants and Therapeutic Choices

Alzheimer's disease is the world's most common dementing illness. It is pathologically characterized by β-amyloid accumulation, extracellular senile plaques and intracellular neurofibrillary tangles formation, and neuronal necrosis and apoptosis. Neuroinflammation has been widely recognized as a crucial process that participates in AD pathogenesis. In this review, we briefly summarized the involvement of microglia in the neuroinflammatory process of Alzheimer's disease. Its roles in the AD onset and progression are also discussed. Numerous molecules, including interleukins, tumor necrosis factor alpha, chemokines, inflammasomes, participate in the complex process of AD-related neuroinflammation and they are selectively discussed in this review. In the end of this paper from an inflammation- related perspective, we discussed some potential therapeutic choices.

Murine induced pluripotent stem cell-derived neuroimmune cell culture models emphasize opposite immune-effector functions of interleukin 13-primed microglia and macrophages in terms of neuroimmune toxicity

Cellular models of induced pluripotent stem cell (iPSC)-derived microglia and macrophages are an emerging toolbox to investigate neuroinflammation in vitro. We previously demonstrated that murine iPSC-microglia and iPSC-macrophages display phenotypical activation properties highly comparable to microglia and macrophages in vivo. Here we extended the characterization of iPSC-microglia and iPSC-macrophages with the analysis of their transcriptome profile. Next, these cellular models were employed to evaluate neuroimmune toxicity in vitro and to investigate the immune-modulatory properties of interleukin 13 (IL13), a cytokine known for its ability to protect against neuroinflammation-induced pathology by modulating microglia and macrophage activation. iPSC-microglia and iPSC-macrophages, in co-culture with astrocyte-committed neural stem cells (NSC), were (pre)treated with IL13 and stimulated with lipopolysaccharide (LPS) and interferon γ (IFNγ), to assess how IL13 modulates their inflammatory response. Additionally, the use of luciferase-expressing NSC (Luc-NSC) allowed real-time monitoring of immune-mediated neurotoxicity. Despite the known anti-inflammatory properties of IL13, iPSC-microglia primed with IL13 before LPS + IFNγ stimulation significantly increased NO secretion. This was associated with a marked reduction of the luminescence signal produced by Luc-NSC. Interestingly, we observed that IL13 signaling has a divergent functional outcome in microglia as compared to macrophages, as for the latter no major alterations in NO release and Luc-NSC viability were observed upon IL13 (pre)treatment. Finally, the striking IL13-induced upregulation of NO secretion by microglia under pro-inflammatory conditions was confirmed in vivo, where intracerebral delivery of IL13 increased inducible nitric oxide synthase mRNA expression. Concluding, we applied iPSC-derived neuroimmune cell culture models to identify distinct neuroimmune (toxicity) responses of microglia and macrophages to IL13-based immune modulation.

Type 2 Innate Lymphoid Cells Accumulate in the Brain After Hypoxia-Ischemia but Do Not Contribute to the Development of Preterm Brain Injury

Background

The immune system of human and mouse neonates is relatively immature. However, innate lymphoid cells (ILCs), commonly divided into the subsets ILC1, ILC2, and ILC3, are already present in the placenta and other fetal compartments and exhibit higher activity than what is seen in adulthood. Recent reports have suggested the potential role of ILCs, especially ILC2s, in spontaneous preterm labor, which is associated with brain damage and subsequent long-term neurodevelopmental deficits. Therefore, we hypothesized that ILCs, and especially ILC2s, play a role in preterm brain injury.

Methods

C57Bl/6J mice at postnatal day 6 were subjected to hypoxia-ischemia (HI) insult induced by left carotid artery ligation and subsequent exposure to 10% oxygen in nitrogen. The presence of ILCs and ILC2s in the brain was examined at different time points after HI. The contribution of ILC2s to HI-induced preterm brain damage was explored using a conditionally targeted ILC2-deficient mouse strain (Rorα ^fl/fl IL7r ^Cre ), and gray and white-matter injury were evaluated at 7 days post-HI. The inflammatory response in the injured brain was assessed using immunoassays and immunochemistry staining.

Results

Significant increases in ILCs and ILC2s were observed at 24 h, 3 days, and 7 days post-HI in the injured brain hemisphere compared with the uninjured hemisphere in wild-type mice. ILC2s in the brain were predominantly located in the meninges of the injured ipsilateral hemispheres after HI but not in the brain parenchyma. Overall, we did not observe changes in cytokine/chemokine levels in the brains of Rorα ^fl/fl IL7r ^Cre mice compared with wild type animals apart from IL-13. Gray and white-matter tissue loss in the brain was not affected after HI in Rorα ^fl/fl IL7r ^Cre mice. Correspondingly, we did not find any differences in reactive microglia and astrocyte numbers in the brain in Rorα ^fl/fl IL7r ^Cre mice compared with wild-type mice following HI insult.

Conclusion

After HI, ILCs and ILC2s accumulate in the injured brain hemisphere. However, ILC2s do not contribute to the development of brain damage in this mouse model of preterm brain injury.

Laminarin Pretreatment Provides Neuroprotection against Forebrain Ischemia/Reperfusion Injury by Reducing Oxidative Stress and Neuroinflammation in Aged Gerbils

Laminarin is a polysaccharide isolated from brown algae that has various biological and pharmacological activities, such as antioxidant and anti-inflammatory properties. We recently reported that pretreated laminarin exerted neuroprotection against transient forebrain ischemia/reperfusion (IR) injury when we pretreated with 50 mg/kg of laminarin once a day for seven days in adult gerbils. However, there have been no studies regarding a neuroprotective effect of pretreated laminarin against IR injury in aged animals and its related mechanisms. Therefore, in this study, we intraperitoneally inject laminarin (50 mg/kg) once a day to aged gerbils for seven days before IR (5-min transient ischemia) surgery and examine the neuroprotective effect of laminarin treatment and the mechanisms in the gerbil hippocampus. IR injury in vehicle-treated gerbils causes loss (death) of pyramidal neurons in the hippocampal CA1 field at five days post-IR. Pretreatment with laminarin effectively protects the CA1 pyramidal neurons from IR injury. Regarding the laminarin-treated gerbils, production of superoxide anions, 4-hydroxy-2-nonenal expression and pro-inflammatory cytokines [interleukin(IL)-1β and tumor necrosis factor-α] expressions are significantly decreased in the CA1 pyramidal neurons after IR. Additionally, laminarin treatment significantly increases expressions of superoxide dismutase and anti-inflammatory cytokines (IL-4 and IL-13) in the CA1 pyramidal neurons before and after IR. Taken together, these findings indicate that laminarin can protect neurons from ischemic brain injury in an aged population by attenuating IR-induced oxidative stress and neuroinflammation.

Chronic Inflammatory Lameness Increases Cytokine Concentration in the Spinal Cord of Dairy Cows

Lameness in dairy cows is an extremely painful multifactorial condition that affects the welfare of animals and economically impacts the dairy industry worldwide. The aim of this study was to determine the profile of cytokines in the spinal cord dorsal horn of dairy cows with painful chronic inflammatory lameness. Concentrations of 10 cytokines were measured in the spinal cord of seven adult dairy cows with chronic lameness and seven adult dairy cows with no lameness. In all cows lameness was evaluated using a mobility scoring system and registered accordingly. Immediately after euthanasia the spinal cord was removed and 20 cm of lumbar segments (L2–L5) were obtained. After dorsal horn removal and processing, cytokine quantification of tumor necrosis factor-alpha (TNF-α), interleukin-1alpha (IL-1α), interleukin 13 (IL-13), chemokine-10 (CXCL10/IP-10), chemokine-9 (CXCL9/MIG), interferon-alpha (IFN-α), interferon-gamma (IFN-γ), interleukin-21 (IL-21), interleukin-36ra (IL-36ra), and macrophage inflammatory protein-1 beta (MIP-1β) was performed using a multiplex array. Lame cows had higher concentrations of TNF-α, IL-1-α, IL-13, CXCL10, CXCL9, IFN-α, and IFN-γ in their dorsal horn compared to non-lame cows, while IL-21 concentration was decreased. No differences in IL-36ra and MIP-1β concentrations between lame and non-lame cows were observed. Painful chronic inflammation of the hoof in dairy cows leads to a marked increase in cytokine concentration in the dorsal horn of the spinal cord, which could represent a state of neuroinflammation of the Central Nervous System (CNS).

IL-13 Ameliorates Neuroinflammation and Promotes Functional Recovery after Traumatic Brain Injury

Microglia play essential roles in neuroinflammatory responses after traumatic brain injury (TBI). Our previous studies showed that phenotypes of microglia, as well as infiltrating macrophages, altered at different stages after CNS injury, which was correlated to functional outcomes. IL-13 is an anti-inflammatory cytokine that has been reported to protect against demyelination and spinal cord injury through immunomodulation. The effects of IL-13 in microglia/macrophage-mediated immune responses after TBI remain unknown. In this study, we showed that intranasal administration of IL-13 in male C57BL/6J mice accelerated functional recovery in the controlled cortical impact model of TBI. IL-13 treatment increased the time to fall off in the Rotarod test, reduced the number of foot faults in the foot fault test, and improved the score in the wire hang test up to 28 d after TBI. Consistent with functional improvement, IL-13 reduced neuronal tissue loss and preserved white matter integrity 6 d after TBI. Furthermore, IL-13 ameliorated the elevation of proinflammatory factors and reduced the number of proinflammatory microglia/macrophages 6 d after TBI. Additionally, IL-13 enhanced microglia/macrophage phagocytosis of damaged neurons in the peri-lesion areas. In vitro studies confirmed that IL-13 treatment inhibited the production of proinflammatory cytokines in rat primary microglia in response to LPS or dead neuron stimulation and increased the ability of microglia to engulf fluorophore-labeled latex beads or dead neurons. Collectively, we demonstrated that IL-13 treatment improved neurologic outcomes after TBI through adjusting microglia/macrophage phenotypes and inhibiting inflammatory responses. IL-13 may represent a potential immunotherapy to promote long-term recovery from TBI.

Peripheral Administration of IL-13 Induces Anti-inflammatory Microglial/Macrophage Responses and Provides Neuroprotection in Ischemic Stroke

Neuroinflammation is strongly induced by cerebral ischemia. The early phase after the onset of ischemic stroke is characterized by acute neuronal injury, microglial activation, and subsequent infiltration of blood-derived inflammatory cells, including macrophages. Therefore, modulation of the microglial/macrophage responses has increasingly gained interest as a potential therapeutic approach for the ischemic stroke. In our study, we investigated the effects of peripherally administered interleukin 13 (IL-13) in a mouse model of permanent middle cerebral artery occlusion (pMCAo). Systemic administration of IL-13 immediately after the ischemic insult significantly reduced the lesion volume, alleviated the infiltration of CD45+ leukocytes, and promoted the microglia/macrophage alternative activation within the ischemic region, as determined by arginase 1 (Arg1) immunoreactivity at 3 days post-ischemia (dpi). Moreover, IL-13 enhanced the expression of M2a alternative activation markers Arg1 and Ym1 in the peri-ischemic (PI) area, as well as increased plasma IL-6 and IL-10 levels at 3 dpi. Furthermore, IL-13 treatment ameliorated gait disturbances at day 7 and 14 and sensorimotor deficits at day 14 post-ischemia, as analyzed by the CatWalk gait analysis system and adhesive removal test, respectively. Finally, IL-13 treatment decreased neuronal cell death in a coculture model of neuroinflammation with RAW 264.7 macrophages. Taken together, delivery of IL-13 enhances microglial/macrophage anti-inflammatory responses in vivo and in vitro, decreases ischemia-induced brain cell death, and improves sensory and motor functions in the pMCAo mouse model of cerebral ischemia.

Elevated Gestational IL-13 During Fetal Development Is Associated With Hyperactivity and Inattention in Eight-Year-Old Children

Maternal immune activation (MIA) during fetal development leads to behavioral and psychological disorders in the offspring. Concomitantly, insufficient supply of polyunsaturated fatty acids (PUFAs) is suspected to contribute to early neuronal maldevelopment due to the immune modulatory capabilities of PUFAs. However, human data are missing considering both of these aspects and their impact on children's behavioral outcomes. In line, this study aimed to elucidate the influence of gestational cytokines and PUFA-containing lipids during late pregnancy on behavioral sequelae in childhood, particularly focusing on an immune activation shaped by a history of maternal atopic diseases instead of a pathogen-mediated immune response. Based on the prospective mother-child cohort LINA we assessed the unstimulated blood cytokine profiles and concentrations of PUFA-containing lipids of 293 mothers at the 34th week of pregnancy. Maternal history of atopic diseases was obtained from questionnaires and behavior in eight-year-old children was assessed by the standardized Strength and Difficulties Questionnaires (SDQ) generating scores for hyperactivity/inattention, emotional symptoms, conduct problems, and peer relationship problems. Elevated IL-13 increased the risk for the child to show behavioral difficulties, in particular, hyperactive/inattentive behavior [adj. OR (95% CI): 2.47 (1.51-4.02), n = 255 vs. 38] at the age of eight years. Although the presence of maternal atopic dermatitis (AD) was associated with increased gestational IL-13 concentrations [adj. MR (95% CI): 1.17 (1.04-1.32)], no effect on children's behavioral difficulties was observed. However, a decrease in the PUFA containing lipid species PC aa C38:6 was not only associated with an increased gestational IL-13 concentration but also mediated the indirect effect of low PC aa C38:6 concentrations on children's abnormal behavior independent of maternal AD. We additionally assessed whether maternal IL-13 and PC aa C38:6 concentrations translate their effect by altering children's cord blood PC aa C38:6 and IL-13. While also the children's cord blood IL-13 was related to children's behavior, no effect of children's PC aa C38:6 was observed. This is the first study demonstrating that elevated gestational IL-13 increases the risk for children to develop behavioral difficulties. Analyses suggest that a reduced supply of gestational PC aa C38:6 contributes to elevated gestational IL-13 leading to behavioral sequelae in the offspring.

Interleukin-4 and Interleukin-13 Exacerbate Neurotoxicity of Prothrombin Kringle-2 in Cortex In Vivo via Oxidative Stress

The present study investigated the effects of activated microglia-derived interleukin-4 (IL-4) and IL-13 on neurodegeneration in prothrombin kringle-2 (pKr-2)-treated rat cortex. pKr-2 was unilaterally injected into the Sprague–Dawley rat cerebral cortex and IL-4 and IL-13 neutralizing antibody was used to block the function of IL-4 and IL-13. Immunohistochemical analysis showed a significant loss of NeuN⁺ and Nissl⁺ cells and an increase of OX-42⁺ cells in the cortex at seven days post pKr-2. The levels of IL-4 and IL-13 expression were upregulated in the activated microglia as early as 12 hours post pKr-2 and sustained up to seven days post pKr-2. Neutralization by IL-4 or IL-13 antibodies (NA) significantly increased neuronal survival in pKr-2-treated rat cortex in vivo by suppressing microglial activation and the production of reactive oxygen species, as analyzed by immunohisotochemistry and hydroethidine histochemistry. These results suggest that IL-4 and IL-13 that were endogenously expressed from reactive microglia may play a critical role on neuronal death by regulating oxidative stress during the neurodegenerative diseases, such as Alzheimer’s disease and dementia.

Pretreated Oenanthe Javanica extract increases anti-inflammatory cytokines, attenuates gliosis, and protects hippocampal neurons following transient global cerebral ischemia in gerbils

Recently, we have reported that Oenanthe javanica extract (OJE) displays strong neuroprotective effect against ischemic damage after transient global cerebral ischemia. However, neuroprotective mechanisms of OJE have not been fully identified. Thus, this study investigated the neuroprotection of OJE in the hippocampal CA1 area and its anti-inflammatory activity in gerbils subjected to 5 minutes of transient global cerebral ischemia. We treated the animals by intragastrical injection of OJE (100 and 200 mg/kg) once daily for 1 week prior to transient global cerebral ischemia. Neuroprotection of OJE was observed by immunohistochemistry for neuronal nuclear antigen and histofluorescence staining for Fluoro-Jade B. Immunohistochemistry of glial fibrillary acidic protein and ionized calcium-binding adapter molecule 1 was done for astrocytosis and microgliosis, respectively. To investigate the neuroprotective mechanisms of OJE, we performed immunohistochemistry of tumor necrosis factor-alpha and interleukin-2 for pro-inflammatory function and interleukin-4 and interleukin-13 for anti-inflammatory function. When we treated the animals by intragastrical administration of 200 mg/kg of OJE, hippocampal CA1 pyramidal neurons were protected from transient global cerebral ischemia and cerebral ischemia-induced gliosis was inhibited in the ischemic hippocampal CA1 area. We also found that interleukin-4 and -13 immunoreactivities were significantly increased in pyramidal neurons of the ischemic CA1 area after OJE pretreatment, and the increased immunoreactivities were sustained in the CA1 pyramidal neurons after transient global cerebral ischemia. However, OJE pretreatment did not increase interleukin-2 and tumor necrosis factor-alpha immunoreactivities in the CA1 pyramidal neurons. Our findings suggest that pretreatment with OJE can protect neurons and attenuate gliosis from transient global cerebral ischemia via increasing expressions of interleukin-4 and -13. The experimental plan of this study was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) in Kangwon National University (approval No. KW-160802-1) on August 10, 2016.

Myelination induction by a histamine H3 receptor antagonist in a mouse model of preterm white matter injury

Fifteen million babies are born preterm every year and a significant number suffer from permanent neurological injuries linked to white matter injury (WMI). A chief cause of preterm birth itself and predictor of the severity of WMI is exposure to maternal-fetal infection-inflammation such as chorioamnionitis. There are no neurotherapeutics for this WMI. To affect this healthcare need, the repurposing of drugs with efficacy in other white matter injury models is an attractive strategy. As such, we tested the efficacy of GSK247246, an H3R antagonist/inverse agonist, in a model of inflammation-mediated WMI of the preterm born infant recapitulating the main clinical hallmarks of human brain injury, which are oligodendrocyte maturation arrest, microglial reactivity, and hypomyelination. WMI is induced by mimicking the effects of maternal-fetal infection-inflammation and setting up neuroinflammation. We induce this process at the time in the mouse when brain development is equivalent to the human third trimester; postnatal day (P)1 through to P5 with i.p. interleukin-1β (IL-1β) injections. We initiated GSK247246 treatment (i.p at 7 mg/kg or 20 mg/kg) after neuroinflammation was well established (on P6) and it was administered twice daily through to P10. Outcomes were assessed at P10 and P30 with gene and protein analysis. A low dose of GSK247246 (7 mg/kg) lead to a recovery in protein expression of markers of myelin (density of Myelin Basic Protein, MBP & Proteolipid Proteins, PLP) and a reduction in macro- and microgliosis (density of ionising adaptor protein, IBA1 & glial fibrillary acid protein, GFAP). Our results confirm the neurotherapeutic efficacy of targeting the H3R for WMI seen in a cuprizone model of multiple sclerosis and a recently reported clinical trial in relapsing-remitting multiple sclerosis patients. Further work is needed to develop a slow release strategy for this agent and test its efficacy in large animal models of preterm infant WMI.

Cortical and hippocampal expression of inflammatory and intracellular signaling proteins in aged rats submitted to aerobic and resistance physical training

Aging is often accompanied by an increase in pro-inflammatory markers. This inflammatory process is directly related to cellular dysfunctions that induce events such as the exacerbated activation of cell death signaling pathways. In the aged brain, dysregulation of the normal activities of neuronal cells compromises brain functions, thereby favoring the onset of neurodegenerative diseases and cognitive deficits. Interactions between various stimuli, such as stress, are responsible for the modulation of cellular processes and activities. Physical exercise is a controllable model of stress, largely used as a strategy for studying the physiological mechanisms of inflammatory responses and their consequences. However, different types of physical exercise promote different responses in the organism. The present study was designed to investigate the expression of inflammatory cytokines and chemokines, and expression and activation of intracellular signaling proteins (CREB, ERK, Akt, p70S6k, STAT5, JNK, NFkB e p38) in the cerebral cortex and hippocampal formation of aged rats submitted to aerobic and resistance exercise. Inflammatory analysis showed that aged rats that underwent resistance training had decreased cortical levels of RANTES and a reduction in the hippocampal levels of MIP-2 when compared with control animals (sedentary). No significant difference was detected in the cortical and hippocampal inflammatory response between aerobic and sedentary groups. However, when comparing the two training models (aerobic vs resistance), it was observed that aerobic training increased the cortical levels of IL-13, IL-6, IL-17α compared with resistance training. Regarding the signaling proteins, a significant increase in cortical expression of the proteins JNK, ERK and p70S6k was found in the aerobic group in relation to the sedentary group. No significant change in the cortical and hippocampal expression of signaling proteins was detected between resistance training and sedentary groups. Nevertheless, when training models were compared, it was observed that aerobic training increased cortical expression of the total proteins p38, ERK, Akt and p70S6k in relation to resistance training. Taken together, these results show that changes in the brain expression of inflammatory and cell survival proteins in aged rats depend on the type of physical training.

Palmitate Induces an Anti-Inflammatory Response in Immortalized Microglial BV-2 and IMG Cell Lines that Decreases TNFα Levels in mHypoE-46 Hypothalamic Neurons in Co-Culture

BACKGROUND AND OBJECTIVES

Elevated levels of saturated fatty acids (SFA) induce a state of neuroinflammation in the hypothalamus. It has been suggested that microglia sense palmitate, a prevalent circulating SFA, and act as mediators of this inflammatory process by communicating with neurons, particularly those involved in appetite regulation. In this study, we examined the inflammatory response to palmitate in immortalized microglial cell lines, BV-2 and IMG, and the subsequent effects on inflammatory gene expression in a model of NPY/AgRP neurons, mHypoE-46.

METHODS

The BV-2 cells were treated with 50 µM palmitate for 4 and 24 h, and the transcriptional regulation of markers for inflammation and cellular stress was assessed using an RT2 Profiler PCR Array. Select genes were verified with qRT-PCR. The BV-2 and IMG cells were then co-cultured using 1.0-µm cell culture inserts with an immortalized hypothalamic cell line, mHypoE-46, to investigate potential intercellular communication between microglia and neurons.

RESULTS

We found that palmitate increased the mRNA levels of specific inflammatory genes, and a general anti-inflammatory profile was revealed in the microglia cells. The mRNA changes in TNFα at 4 and 24 h in BV-2 cells were abrogated with the toll-like receptor 4 (TLR4) inhibitor, TAK-242, indicating the involvement of TLR4. Co-culture of mHypoE-46 neurons with microglia pre-treated with palmitate resulted in repression of TNFα expression in the hypothalamic neurons. As palmitate significantly increased IL-13 expression in microglia, the effect of this cytokine was tested in mHypoE-46 neurons. The addition of IL-13 to neuronal cultures normalized the palmitate-mediated increase in IL-6 and AgRP expression, suggesting that microglia may protect surrounding neurons, at least in part, through the release of IL-13.

CONCLUSIONS

These results suggest a potential anti-inflammatory role of microglia towards the palmitate-induced neuroinflammation, and potentially energy homeostasis, in hypothalamic neurons.

Local and Systemic Immune Responses to Influenza A Virus Infection in Pneumonia and Encephalitis Mouse Models

OBJECTIVE

To compare local and systemic profiles between different disease pathologies (pneumonia and encephalitis) induced by influenza A virus (IAV).

METHODS

An IAV pneumonia model was created by intranasal inoculation of C57BL/6 mice with influenza A/WSN/33 (H1N1) virus. Lung lavage and blood collection were performed on day 3 after IAV inoculation. Similarly, an IAV encephalitis mouse model was created by direct intracranial IAV inoculation. Cerebrospinal fluid (CSF) and blood collection were conducted according to the same schedule. Cytokine/chemokine profiles were produced for each collected sample. Then the data were compared visually using radar charts.

RESULTS

Serum cytokine profiles were similar in pneumonia and encephalitis models, but local responses between the bronchoalveolar lavage fluid (BALF) in the pneumonia model and CSF in the encephalitis model differed. Moreover, to varying degrees, the profiles of local cytokines/chemokines differed from those of serum in both the pneumonia and encephalitis models.

CONCLUSION

Investigating local samples such as BALF and CSF is important for evaluating local immune responses, providing insight into pathology at the primary loci of infection. Serum data alone might be insufficient to elucidate local immune responses and might not enable clinicians to devise the most appropriate treatment strategies.

Acute ethanol administration results in a protective cytokine and neuroinflammatory profile in traumatic brain injury

Ethanol intoxication is a common comorbidity in traumatic brain injury. To date, the effect of ethanol on TBI pathogenic cascades and resulting outcomes remains debated. A closed blunt weight-drop murine TBI model has been implemented to investigate behavioral (by sensorimotor and neurological tests), and neuro-immunological (by tissue cytokine arrays and immuno-histology) effects of ethanol intoxication on TBI. The effect of the occurrence of traumatic intracerebral hemorrhage was also studied. The results indicate that ethanol pretreatment results in a faster and better recovery after TBI with reduced infiltration of leukocytes and reduced microglia activation. These outcomes correspond to reduced parenchymal levels of GM-CSF, IL-6 and IL-3 and to the transient upregulation of IL-13 and VEGF, indicating an early shift in the cytokine profile towards reduced inflammation. A significant difference in the cytokine profile was still observed 24h post injury in the ethanol pretreated mice, as shown by the delayed peak in IL-6 and by the suppression of GM-CSF, IFN-γ, and IL-3. Seven days post-injury, ethanol-pretreated mice displayed a significant decrease both in CD45+ cells infiltration and in microglial activation. On the other hand, in the case of traumatic intracerebral hemorrhage, the cytokine profile was dominated by KC, CCL5, M-CSF and several interleukins and ethanol pretreatment did not produce any modification. We can thus conclude that ethanol intoxication suppresses the acute neuro-inflammatory response to TBI, an effect which is correlated with a faster and complete neurological recovery, whereas, the presence of traumatic intracerebral hemorrhage overrides the effects of ethanol.

Intracerebral transplantation of interleukin 13-producing mesenchymal stem cells limits microgliosis, oligodendrocyte loss and demyelination in the cuprizone mouse model

Background

Promoting the neuroprotective and repair-inducing effector functions of microglia and macrophages, by means of M2 polarisation or alternative activation, is expected to become a new therapeutic approach for central nervous system (CNS) disorders in which detrimental pro-inflammatory microglia and/or macrophages display a major contribution to the neuropathology. In this study, we present a novel in vivo approach using intracerebral grafting of mesenchymal stem cells (MSC) genetically engineered to secrete interleukin 13 (IL13-MSC).

Methods

In the first experimental setup, control MSC and IL13-MSC were grafted in the CNS of eGFP⁺ bone marrow chimaeric C57BL/6 mice to histologically evaluate IL13-mediated expression of several markers associated with alternative activation, including arginase1 and Ym1, on MSC graft-recognising microglia and MSC graft-infiltrating macrophages. In the second experimental setup, IL13-MSC were grafted on the right side (or on both the right and left sides) of the splenium of the corpus callosum in wild-type C57BL/6 mice and in C57BL/6 CX₃CR1^eGFP/+CCR2^RFP/+ transgenic mice. Next, CNS inflammation and demyelination was induced by means of a cuprizone-supplemented diet. The influence of IL13-MSC grafting on neuropathological alterations was monitored by non-invasive T₂-weighted magnetic resonance imaging (MRI) and quantitative histological analyses, as compared to cuprizone-treated mice with control MSC grafts and/or cuprizone-treated mice without MSC injection.

Results

In the first part of this study, we demonstrate that MSC graft-associated microglia and MSC graft-infiltrating macrophages are forced into alternative activation upon grafting of IL13-MSC, but not upon grafting of control MSC. In the second part of this study, we demonstrate that grafting of IL13-MSC, in addition to the recruitment of M2 polarised macrophages, limits cuprizone-induced microgliosis, oligodendrocyte death and demyelination. Furthermore, we here demonstrate that injection of IL13-MSC at both sides of the splenium leads to a superior protective effect as compared to a single injection at one side of the splenium.

Conclusions

Controlled and localised production of IL13 by means of intracerebral MSC grafting has the potential to modulate cell graft- and pathology-associated microglial/macrophage responses, and to interfere with oligodendrocyte death and demyelinating events in the cuprizone mouse model.

Interleukin-13 immune gene therapy prevents CNS inflammation and demyelination via alternative activation of microglia and macrophages

Detrimental inflammatory responses in the central nervous system are a hallmark of various brain injuries and diseases. With this study we provide evidence that lentiviral vector-mediated expression of the immune-modulating cytokine interleukin 13 (IL-13) induces an alternative activation program in both microglia and macrophages conferring protection against severe oligodendrocyte loss and demyelination in the cuprizone mouse model for multiple sclerosis (MS). First, IL-13 mediated modulation of cuprizone induced lesions was monitored using T₂ -weighted magnetic resonance imaging and magnetization transfer imaging, and further correlated with quantitative histological analyses for inflammatory cell influx, oligodendrocyte death, and demyelination. Second, following IL-13 immune gene therapy in cuprizone-treated eGFP⁺ bone marrow chimeric mice, we provide evidence that IL-13 directs the polarization of both brain-resident microglia and infiltrating macrophages towards an alternatively activated phenotype, thereby promoting the conversion of a pro-inflammatory environment toward an anti-inflammatory environment, as further evidenced by gene expression analyses. Finally, we show that IL-13 immune gene therapy is also able to limit lesion severity in a pre-existing inflammatory environment. In conclusion, these results highlight the potential of IL-13 to modulate microglia/macrophage responses and to improve disease outcome in a mouse model for MS. GLIA 2016;64:2181-2200.

ROS-mediated apoptosis of HAPI microglia through p53 signaling following PFOS exposure

Perfluorooctane sulfonate (PFOS), the most extensively studied member of perfluoroalkyl and polyfluoroalkyl substances (PFASs), has been thought to be toxic to the central nervous system (CNS) of mammals. However, the neurotoxic effects of PFOS remain largely unknown. In this study, the effect of PFOS on microglial apoptosis was examined. The results showed that PFOS could significantly reduce the cell viability and mediate cell apoptosis in HAPI microglia, which was closely accompanied with ROS production and p53 overexpression. Moreover, p53 interference significantly ameliorated PFOS-triggered cytotoxic effects in HAPI microglia, including the downregulation of cleaved PARP and cleaved caspase 3. Interestingly, NAC, a ROS inhibitor, inhibited p53 expression, and decreased the apoptosis of HAPI microglia. Taken together, these findings suggest that upregulated production of ROS plays a vital role in PFOS-mediated apoptosis in HAPI microglia via the modulation of p53 signaling.

Safety of Striatal Infusion of siRNA in a Transgenic Huntington's Disease Mouse Model

BACKGROUND

The immune system In Huntington's disease (HD) is activated and may overreact to some therapies. RNA interference using siRNA lowers mutant huntingtin (mHTT) protein but could increase immune responses.

OBJECTIVE

To examine the innate immune response following siRNA infusion into the striatum of wild-type (WT) and HD transgenic (YAC128) mice.

METHODS

siRNAs (2'-O-methyl phosphorothioated) were infused unilaterally into striatum of four month-old WT and YAC128 mice for 28 days. Microglia number and morphology (resting (normal), activated, dystrophic), cytokine levels, and DARPP32-positive neurons were measured in striatum immediately or 14 days post-infusion. Controls included contralateral untreated striatum, and PBS and sham treated striata.

RESULTS

The striata of untreated YAC128 mice had significantly fewer resting microglia and more dystrophic microglia than WT mice, but no difference from WT in the proportion of activated microglia or total number of microglia. siRNA infusion increased the total number of microglia in YAC128 mice compared to PBS treated and untreated striata and increased the proportion of activated microglia in WT and YAC128 mice compared to untreated striata and sham treated groups. Cytokine levels were low and siRNA infusion resulted in only modest changes in those levels. siRNA infusion did not change the number of DARPP32-positive neurons.

CONCLUSION

Findings suggest that siRNA infusion may be a safe method for lowering mHTT levels in the striatum in young animals, since treatment does not produce a robust cytokine response or cause neurotoxicity. The potential long-term effects of a sustained increase in total and activated microglia after siRNA infusion in HD mice need to be explored.

Cytokine and Growth Factor Activation In Vivo and In Vitro after Spinal Cord Injury

Spinal cord injury results in a life-disrupting series of deleterious interconnected mechanisms encompassed by the primary and secondary injury. These events are mediated by the upregulation of genes with roles in inflammation, transcription, and signaling proteins. In particular, cytokines and growth factors are signaling proteins that have important roles in the pathophysiology of SCI. The balance between the proinflammatory and anti-inflammatory effects of these molecules plays a critical role in the progression and outcome of the lesion. The excessive inflammatory Th1 and Th17 phenotypes observed after SCI tilt the scale towards a proinflammatory environment, which exacerbates the deleterious mechanisms present after the injury. These mechanisms include the disruption of the spinal cord blood barrier, edema and ion imbalance, in particular intracellular calcium and sodium concentrations, glutamate excitotoxicity, free radicals, and the inflammatory response contributing to the neurodegenerative process which is characterized by demyelination and apoptosis of neuronal tissue.

Neuroimmunology of the Interleukins 13 and 4

The cytokines interleukin 13 and 4 share a common heterodimeric receptor and are important modulators of peripheral allergic reactions. Produced primarily by T-helper type 2 lymphocytes, they are typically considered as anti-inflammatory cytokines because they can downregulate the synthesis of T-helper type 1 pro-inflammatory cytokines. Their presence and role in the brain is only beginning to be investigated and the data collected so far shows that these molecules can be produced by microglial cells and possibly by neurons. Attention has so far been given to the possible role of these molecules in neurodegeneration. Both neuroprotective or neurotoxic effects have been proposed based on evidence that interleukin 13 and 4 can reduce inflammation by promoting the M2 microglia phenotype and contributing to the death of microglia M1 phenotype, or by potentiating the effects of oxidative stress on neurons during neuro-inflammation. Remarkably, the heterodimeric subunit IL-13Rα1 of their common receptor was recently demonstrated in dopaminergic neurons of the ventral tegmental area and the substantia nigra pars compacta, suggesting the possibility that both cytokines may affect the activity of these neurons regulating reward, mood, and motor coordination. In mice and man, the gene encoding for IL-13Rα1 is expressed on the X chromosome within the PARK12 region of susceptibility to Parkinson’s disease (PD). This, together with finding that IL-13Rα1 contributes to loss of dopaminergic neurons during inflammation, indicates the possibility that these cytokines may contribute to the etiology or the progression of PD.

Neuroprotection of Ischemic Preconditioning is Mediated by Anti-inflammatory, Not Pro-inflammatory, Cytokines in the Gerbil Hippocampus Induced by a Subsequent Lethal Transient Cerebral Ischemia

Ischemic preconditioning (IPC) induced by sublethal transient cerebral ischemia could reduce neuronal damage/death following a subsequent lethal transient cerebral ischemia. We, in this study, compared expressions of interleukin (IL)-2 and tumor necrosis factor (TNF)-α as pro-inflammatory cytokines, and IL-4 and IL-13 as anti-inflammatory cytokines in the gerbil hippocampal CA1 region between animals with lethal ischemia and ones with IPC followed by lethal ischemia. In the animals with lethal ischemia, pyramidal neurons in the stratum pyramidale (SP) of the hippocampal CA1 region were dead at 5 days post-ischemia; however, IPC protected the CA1 pyramidal neurons from lethal ischemic injury. Expressions of all cytokines were significantly decreased in the SP after lethal ischemia and hardly detected in the SP at 5 days post-ischemia because the CA1 pyramidal neurons were dead. IPC increased expressions of anti-inflammatory cytokines (IL-4 and IL-13) in the stratum pyramidale of the CA1 region following no lethal ischemia (sham-operation), and the increased expressions of IL-4 and IL-13 by IPC were continuously maintained is the SP of the CA1 region after lethal ischemia. However, pro-inflammatory cytokines (IL-2 and TNF-α) in the SP of the CA1 region were similar those in the sham-operated animals with IPC, and the IL-4 and IL-13 expressions in the SP were maintained after lethal ischemia. In conclusion, this study shows that anti-inflammatory cytokines significantly increased and longer maintained by IPC and this might be closely associated with neuroprotection after lethal transient cerebral ischemia.

EP2 Receptor Signaling Regulates Microglia Death

The timely resolution of inflammation prevents continued tissue damage after an initial insult. In the brain, the death of activated microglia by apoptosis has been proposed as one mechanism to resolve brain inflammation. How microglial death is regulated after activation is still unclear. We reported that exposure to lipopolysaccharide (LPS) and interleukin (IL)-13 together initially activates and then kills rat microglia in culture by a mechanism dependent on cyclooxygenase-2 (COX-2). We show here that activation of the E prostanoid receptor 2 (EP2, PTGER2) for prostaglandin E2 mediates microglial death induced by LPS/IL-13, and that EP2 activation by agonist alone kills microglia. Both EP2 antagonists and reactive oxygen scavengers block microglial death induced by either LPS/IL-13 or EP2 activation. By contrast, the homeostatic induction of heme oxygenase 1 (Hmox1) by LPS/IL-13 or EP2 activation protects microglia. Both the Hmox1 inducer cobalt protoporphyrin and a compound that releases the Hmox1 product carbon monoxide (CO) attenuated microglial death produced by LPS/IL-13. Whereas CO reduced COX-2 protein expression, EP2 activation increased Hmox1 and COX-2 expression at both the mRNA and protein level. Interestingly, caspase-1 inhibition prevented microglial death induced by either LPS/IL-13 or low (but not high) concentrations of butaprost, suggestive of a predominantly pyroptotic mode of death. Butaprost also caused the expression of activated caspase-3 in microglia, pointing to apoptosis. These results indicate that EP2 activation, which initially promotes microglial activation, later causes delayed death of activated microglia, potentially contributing to the resolution phase of neuroinflammation.

Alternatively activated microglia and macrophages in the central nervous system

Macrophages are important players in the fight against viral, bacterial, fungal and parasitic infections. From a resting state they may undertake two activation pathways, the classical known as M1, or the alternative known as M2. M1 markers are mostly mediators of pro-inflammatory responses whereas M2 markers emerge for resolution and cleanup. Microglia exerts in the central nervous system (CNS) a function similar to that of macrophages in the periphery. Microglia activation and proliferation occurs in almost any single pathology affecting the CNS. Often microglia activation has been considered detrimental and drugs able to stop microglia activation were considered for the treatment of a variety of diseases. Cumulative evidence shows that microglia may undergo the alternative activation pathway, express M2-type markers and contribute to neuroprotection. This review focuses on details about the role of M2 microglia and in the approaches available for its identification. Approaches to drive the M2 phenotype and data on its potential in CNS diseases are also reviewed.

Multiscale sensing of antibody-antigen interactions by organic transistors and single-molecule force spectroscopy

Antibody-antigen (Ab-Ag) recognition is the primary event at the basis of many biosensing platforms. In label-free biosensors, these events occurring at solid-liquid interfaces are complex and often difficult to control technologically across the smallest length scales down to the molecular scale. Here a molecular-scale technique, such as single-molecule force spectroscopy, is performed across areas of a real electrode functionalized for the immunodetection of an inflammatory cytokine, viz. interleukin-4 (IL4). The statistical analysis of force-distance curves allows us to quantify the probability, the characteristic length scales, the adhesion energy, and the time scales of specific recognition. These results enable us to rationalize the response of an electrolyte-gated organic field-effect transistor (EGOFET) operated as an IL4 immunosensor. Two different strategies for the immobilization of IL4 antibodies on the Au gate electrode have been compared: antibodies are bound to (i) a smooth film of His-tagged protein G (PG)/Au; (ii) a 6-aminohexanethiol (HSC6NH2) self-assembled monolayer on Au through glutaraldehyde. The most sensitive EGOFET (concentration minimum detection level down to 5 nM of IL4) is obtained with the first functionalization strategy. This result is correlated to the highest probability (30%) of specific binding events detected by force spectroscopy on Ab/PG/Au electrodes, compared to 10% probability on electrodes with the second functionalization. Specifically, this demonstrates that Ab/PG/Au yields the largest areal density of oriented antibodies available for recognition. More in general, this work shows that specific recognition events in multiscale biosensors can be assessed, quantified, and optimized by means of a nanoscale technique.

Distinctive responses of brain tumor cells to TLR2 ligands

Malignant brain tumor mass contains significant numbers of infiltrating glial cells that may intimately interact with tumor cells and influence cancer treatments. Understanding of characteristic discrepancies between normal GLIA and tumor cells would, therefore, be valuable for improving anticancer therapeutics. Here, we report distinct differences in toll-like receptors (TLR)-2-mediated responses between normal glia and primary brain tumor cell lines. We found that tyrosine phosphorylation of STAT1 by TLR2 ligands and its downstream events did not occur in mouse, rat, or human brain tumor cell lines, but were markedly induced in normal primary microglia and astrocytes. Using TLR2-deficient, interferon (IFN)-γ-deficient, and IFNγ-receptor-1-deficient mice, we revealed that the impaired phosphorylation of STAT1 might be linked with defective TLR2 system in tumor cells, and that a TLR2-dependent pathway, not IFNγ-receptor machinery, might be critical for tyrosine STAT1 phosphorylation by TLR2 ligands. We also found that TLR2 and its heterodimeric partners, TLR1 and 6, on brain tumor cells failed to properly respond to TLR2 ligands, and representative TLR2-dependent cellular events, such as inflammatory responses and cell death, were not detected in brain tumor cells. Similar results were obtained in in vitro and in vivo experiments using orthotopic mouse and rat brain tumor models. Collectively, these results suggest that primary brain tumor cells may exhibit a distinctive dysfunction of TLR2-associated responses, resulting in abnormal signaling and cellular events. Careful targeting of this distinctive property could serve as the basis for effective therapeutic approaches against primary brain tumors.

Central inflammatory response to experimental stroke is inhibited by a neuroprotective dose of dietary soy

Dietary soy and soy isoflavones are neuroprotective in experimental cerebral ischemia. Because the isoflavones in soy that are responsible for this neuroprotective effect act as phytoestrogens, we hypothesized that they would mimic the beneficial effects of estrogens on the innate inflammatory response to cerebral ischemia. Ovariectomized Sprague-Dawley rats were fed a soy free diet or a diet containing high dietary levels of soy for 5 weeks, after which they were subjected to transient middle cerebral artery occlusion (tMCAO) for 90min. Dietary soy was associated with a reduced inflammatory response in the cerebral cortex during the acute innate period 4 and 24h after tMCAO, including significant (>2-fold) reductions in interleukins 1 beta, 2, and 13, and the chemokine CXCL1. However, there was no effect of soy on tumor necrosis factor-alpha or interferon-gamma. Dietary soy was also associated with a 40 percent reduction in the nuclear translocation of p65 nuclear factor kappa B despite an increase in the expression of p65 RELA mRNA. In support of an early effect on the innate immune response to stroke, soy-fed rats had 44 percent fewer activated microglia in the infarct core than soy free rats. Interestingly, despite increased expression following injury, the steady state mRNA levels of inflammatory factors were not altered in soy-fed rats even though inflammatory proteins were. These data suggest that dietary soy isoflavones, like estrogens, inhibit of the innate immune response to injury. However, post-transcriptional mechanisms may play an important role in the mechanism of this action. Coupled with previously published data, these results support an early and rapid effect of dietary soy on the evolution of brain injury following stroke.

Traumatic brain injury causes selective, CD74-dependent peripheral lymphocyte activation that exacerbates neurodegeneration

Introduction

Traumatic brain injury (TBI), a significant cause of death and disability, causes, as in any injury, an acute, innate immune response. A key component in the transition between innate and adaptive immunity is the processing and presentation of antigen by professional antigen presenting cells (APCs). Whether an adaptive immune response to brain injury is beneficial or detrimental is not known. Current efforts to understand the contribution of the immune system after TBI have focused on neuroinflammation and brain-infiltrating immune cells. Here, we characterize and target TBI-induced expansion of peripheral immune cells that may act as potential APCs. Because MHC Class II-associated invariant peptide (CLIP) is important for antigen processing and presentation, we engineered a competitive antagonist (CAP) for CLIP, and tested the hypothesis that peptide competition could reverse or prevent neurodegeneration after TBI.

Results

We show that after fluid percussion injury (FPI), peripheral splenic lymphocytes, including CD4+ and CD8+ T cells, regulatory T cells (Tregs), and γδ T cells, are increased in number within 24 hours after FPI. These increases were reversed by CAP treatment and this antagonism of CLIP also reduced neuroinflammation and neurodegeneration after TBI. Using a mouse deficient for the precursor of CLIP, CD74, we observed decreased peripheral lymphocyte activation, decreased neurodegeneration, and a significantly smaller lesion size following TBI.

Conclusion

Taken together, the data support the hypothesis that neurodegeneration following TBI is dependent upon antigen processing and presentation that requires CD74.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0143-5) contains supplementary material, which is available to authorized users.

The immune response after hypoxia-ischemia in a mouse model of preterm brain injury

Background

Preterm brain injury consists primarily of periventricular leukomalacia accompanied by elements of gray-matter injury, and these injuries are associated with cerebral palsy and cognitive impairments. Inflammation is believed to be an important contributing factor to these injuries. The aim of this study was to examine the immune response in a postnatal day (PND) 5 mouse model of preterm brain injury induced by hypoxia-ischemia (HI) that is characterized by focal white and gray-matter injury.

Methods

C57Bl/6 mice at PND 5 were subjected to unilateral HI induced by left carotid artery ligation and subsequent exposure to 10% O₂ for 50 minutes, 70 minutes, or 80 minutes. At seven days post-HI, the white/gray-matter injury was examined. The immune responses in the brain after HI were examined at different time points after HI using RT-PCR and immunohistochemical staining.

Results

HI for 70 minutes in PND 5 mice induced local white-matter injury with focal cortical injury and hippocampal atrophy, features that are similar to those seen in preterm brain injury in human infants. HI for 50 minutes resulted in a small percentage of animals being injured, and HI for 80 minutes produced extensive infarction in multiple brain areas. Various immune responses, including changes in transcription factors and cytokines that are associated with a T-helper (Th)1/Th17-type response, an increased number of CD4+ T-cells, and elevated levels of triggering receptor expressed on myeloid cells 2 (TREM-2) and its adaptor protein DNAX activation protein of 12 kDa (DAP12) were observed using the HI 70 minute preterm brain injury model.

Conclusions

We have established a reproducible model of HI in PND 5 mice that produces consistent local white/gray-matter brain damage that is relevant to preterm brain injury in human infants. This model provides a useful tool for studying preterm brain injury. Both innate and adaptive immune responses are observed after HI, and these show a strong pro-inflammatory Th1/Th17-type bias. Such findings provide a critical foundation for future studies on the mechanism of preterm brain injury and suggest that blocking the Th1/Th17-type immune response might provide neuroprotection after preterm brain injury.

Anti-inflammatory effect of tanshinone I in neuroprotection against cerebral ischemia-reperfusion injury in the gerbil hippocampus

Tanshinone I (TsI) is an important lipophilic diterpene extracted from Danshen (Radix Salvia miltiorrhizae) and has been used in Asia for the treatment of cerebrovascular diseases such as ischemic stroke. In this study, we examined the neuroprotective effect of TsI against ischemic damage and its neuroprotective mechanism in the gerbil hippocampal CA1 region (CA1) induced by 5 min of transient global cerebral ischemia. Pre-treatment with TsI protected pyramidal neurons from ischemic damage in the stratum pyramidale (SP) of the CA1 after ischemia-reperfusion. The pre-treatment with TsI increased the immunoreactivities and protein levels of anti-inflammatory cytokines [interleukin (IL)-4 and IL-13] in the TsI-treated-sham-operated-groups compared with those in the vehicle-treated-sham-operated-groups; however, the treatment did not increase the immunoreactivities and protein levels of pro-inflammatory cytokines (IL-2 and tumor necrosis factor-α). On the other hand, in the TsI-treated-ischemia-operated-groups, the immunoreactivities and protein levels of all the cytokines were maintained in the SP of the CA1 after transient cerebral ischemia. In addition, we examined that IL-4 injection into the lateral ventricle did not protect pyramidal neurons from ischemic damage. In conclusion, these findings indicate that the pre-treatment with TsI can protect against ischemia-induced neuronal death in the CA1 via the increase or maintenance of endogenous inflammatory cytokines, and exogenous IL-4 does not protect against ischemic damage.

Interleukin-13/Interleukin-4-induced oxidative stress contributes to death of prothrombinkringle-2 (pKr-2)-activated microglia

The present study examined whether Interleukin-13 (IL-13) or IL-4, an anti-inflammatory cytokine, could induce cell death of activated microglia by prothrombin kringle-2 (pKr-2) which is a domain of prothrombin distinct from thrombin. Microglia cell death was detected at eight days after co-treatment of pKr-2 with IL-13/IL-4 in vitro. This cell death was assessed by live assay, dead assay, TUNEL and MTT assay. In parallel, reactive oxygen species (ROS) production was evident as assessed by superoxide assay, WST-1 and analyzing DCF in combination of pKr-2 and IL-13 or IL-4 treated microglia. The IL-13/IL-4-enhanced ROS production and cell death in pKr-2 activated microglia was partially inhibited by an NADPH oxidase inhibitor, apocynin and/or by several antioxidants. Moreover, Western blot analysis showed a significant increase in cyclooxygenase-2 (COX-2) expression in combination of pKr-2 and IL-13 or IL-4 treated microglia, which was partially inhibited by apocynin and an antioxidant, trolox. Additional studies demonstrated that microglia cell death was reversed by treatment with COX-2 inhibitor, NS398. Our data strongly suggest that oxidative stress and COX-2 activation through NADPH oxidase may contribute to IL-13/IL-4 induced cell death of pKr-2 activated microglia.

Sphingolipids and brain resident macrophages in neuroinflammation: an emerging aspect of nervous system pathology

Sphingolipid metabolism is deeply regulated along the differentiation and development of the central nervous system (CNS), and the expression of a peculiar spatially and temporarily regulated sphingolipid pattern is essential for the maintenance of the functional integrity of the nervous system. Microglia are resident macrophages of the CNS involved in general maintenance of neural environment. Modulations in microglia phenotypes may contribute to pathogenic forms of inflammation. Since defects in macrophage/microglia activity contribute to neurodegenerative diseases, it will be essential to systematically identify the components of the microglial cell response that contribute to disease progression. In such complex processes, the sphingolipid systems have recently emerged to play important roles, thus appearing as a key new player in CNS disorders. This review provides a rationale for harnessing the sphingolipid metabolic pathway as a potential target against neuroinflammation.

Vitamin B6 reduces hippocampal apoptosis in experimental pneumococcal meningitis

BACKGROUND

Bacterial meningitis caused by Streptococcus pneumoniae leads to death in up to 30% of patients and leaves up to half of the survivors with neurological sequelae. The inflammatory host reaction initiates the induction of the kynurenine pathway and contributes to hippocampal apoptosis, a form of brain damage that is associated with learning and memory deficits in experimental paradigms. Vitamin B6 is an enzymatic cofactor in the kynurenine pathway and may thus limit the accumulation of neurotoxic metabolites and preserve the cellular energy status. The aim of this study in a pneumococcal meningitis model was to investigate the effect of vitamin B6 on hippocampal apoptosis by histomorphology, by transcriptomics and by measurement of cellular nicotine amide adenine dinucleotide content.

METHODS AND RESULTS

Eleven day old Wistar rats were infected with 1x10(6) cfu/ml of S. pneumoniae and randomized for treatment with vitamin B6 or saline as controls. Vitamin B6 led to a significant (p > 0.02) reduction of hippocampal apoptosis. According to functional annotation based clustering, vitamin B6 led to down-regulation of genes involved in processes of inflammatory response, while genes encoding for processes related to circadian rhythm, neuronal signaling and apoptotic cell death were mostly up-regulated.

CONCLUSIONS

Our results provide evidence that attenuation of apoptosis by vitamin B6 is multi-factorial including down-modulation of inflammation, up-regulation of the neuroprotective brain-derived neurotrophic factor and prevention of the exhaustion of cellular energy stores. The neuroprotective effect identifies vitamin B6 as a potential target for the development of strategies to attenuate brain injury in bacterial meningitis.

Role of endoplasmic reticulum (ER) stress in cocaine-induced microglial cell death

While it has been well-documented that drugs of abuse such as cocaine can enhance progression of human immunodeficiency virus (HIV)-associated neuropathological disorders, the underlying mechanisms mediating these effects remain poorly understood. The present study was undertaken to examine the effects of cocaine on microglial viability. Herein we demonstrate that exposure of microglial cell line-BV2 or rat primary microglia to exogenous cocaine resulted in decreased cell viability as determined by MTS and TUNEL assays. Microglial toxicity of cocaine was accompanied by an increase in the expression of cleaved caspase-3 as demonstrated by western blot assays. Furthermore, increased microglial toxicity was also associated with a concomitant increase in the production of intracellular reactive oxygen species, an effect that was ameliorated in cells pretreated with NADPH oxidase inhibitor apocynin, thus emphasizing the role of oxidative stress in this process. A novel finding of this study was the involvement of endoplasmic reticulum (ER) signaling mediators such as PERK, Elf2α, and CHOP, which were up regulated in cells exposed to cocaine. Reciprocally, blocking CHOP expression using siRNA ameliorated cocaine-mediated cell death. In conclusion these findings underscore the importance of ER stress in modulating cocaine induced microglial toxicity. Understanding the link between ER stress, oxidative stress and apoptosis could lead to the development of therapeutic strategies targeting cocaine-mediated microglial death/dysfunction.

Inflammatory signalling associated with brain dead organ donation: from brain injury to brain stem death and posttransplant ischaemia reperfusion injury

Brain death is associated with dramatic and serious pathophysiologic changes that adversely affect both the quantity and quality of organs available for transplant. To fully optimise the donor pool necessitates a more complete understanding of the underlying pathophysiology of organ dysfunction associated with transplantation. These injurious processes are initially triggered by catastrophic brain injury and are further enhanced during both brain death and graft transplantation. The activated inflammatory systems then contribute to graft dysfunction in the recipient. Inflammatory mediators drive this process in concert with the innate and adaptive immune systems. Activation of deleterious immunological pathways in organ grafts occurs, priming them for further inflammation after engraftment. Finally, posttransplantation ischaemia reperfusion injury leads to further generation of inflammatory mediators and consequent activation of the recipient's immune system. Ongoing research has identified key mediators that contribute to the inflammatory milieu inherent in brain dead organ donation. This has seen the development of novel therapies that directly target the inflammatory cascade.