Expression of TNF and TNF Receptors (p55 and p75) in the Rat Brain after Focal Cerebral Ischemia

After Ischemic Stroke, Minocycline Promotes a Protective Response in Neurons via the RNA-Binding Protein HuR, with a Positive Impact on Motor Performance

Ischemic stroke is the most common cause of adult disability and one of the leading causes of death worldwide, with a serious socio-economic impact. In the present work, we used a new thromboembolic model, recently developed in our lab, to induce focal cerebral ischemic (FCI) stroke in rats without reperfusion. We analyzed selected proteins implicated in the inflammatory response (such as the RNA-binding protein HuR, TNFα, and HSP70) via immunohistochemistry and western blotting techniques. The main goal of the study was to evaluate the beneficial effects of a single administration of minocycline at a low dose (1 mg/kg intravenously administered 10 min after FCI) on the neurons localized in the penumbra area after an ischemic stroke. Furthermore, given the importance of understanding the crosstalk between molecular parameters and motor functions following FCI, motor tests were also performed, such as the Horizontal Runway Elevated test, CatWalk™ XT, and Grip Strength test. Our results indicate that a single administration of a low dose of minocycline increased the viability of neurons and reduced the neurodegeneration caused by ischemia, resulting in a significant reduction in the infarct volume. At the molecular level, minocycline resulted in a reduction in TNFα content coupled with an increase in the levels of both HSP70 and HuR proteins in the penumbra area. Considering that both HSP70 and TNF-α transcripts are targeted by HuR, the obtained results suggest that, following FCI, this RNA-binding protein promotes a protective response by shifting its binding towards HSP70 instead of TNF-α. Most importantly, motor tests showed that reduced inflammation in the brain damaged area after minocycline treatment directly translated into a better motor performance, which is a fundamental outcome when searching for new therapeutic options for clinical practice.

Bibliometric analysis of tumor necrosis factor in post-stroke neuroinflammation from 2003 to 2021

Objective

Tumor necrosis factor (TNF), a crucial cytokine, has important research value in post-stroke neuroinflammation (PSN). We analyzed the studies that have been conducted in this area and used bibliometric methods to predict research hotspots and identify trends regarding TNF in PSN.

Methods

Publications were accessed at the Science Citation Index Expanded 1975-2021 (SCI expanded), Web of Science Core Collection (WoSCC), on May 1, 2022. Additionally, software such as CiteSpace and VOSviewer were utilized for bibliometric analyses.

Results

In total, 1391 original articles and reviews on TNF in PSN published from 2003 to 2021 were identified. An upward trend was observed in the number of publications on TNF in PSN. These publications were primarily from 57 countries and 1446 institutions, led by China and the United States with China leading the number of publications (NP) and the US with the number of citations (NC). The League of European Research Universities (LERU) and Journal of Neuroinflammation, respectively were the most prolific branches and journals. Zhang, John H. published the most papers and Finsen, Bente had the most cited papers. One paper by Kettenmann, H. published in 2011 reached the highest level of Global Citation Score (GCS). The keyword co-occurrence and reference co-citation analyses suggest that poststroke therapy and potential mechanistic pathways are important topics related to PSN in recent years. Reference burst detection suggests new burst hotspots after 2015, focusing on pathway modulation and discovery of therapeutic targets, suggesting a substantial development in the study of TNF in PSN research.

Conclusion

The present bibliometric analysis shows a continuous trend of increasing literature related to TNF in PSN, and shows that TNF plays an important role in PSN involves multiple immune mechanisms and may contribute as a potential target for neuroprotective therapeutics after stroke. Prior to 2011, most of the research was focused on discovering the specific role of TNF in PSN, and in recent years studies have mainly targeted the exploration of the signaling pathways. Future research prospects may lie in finding key therapeutic targets in pathway of TNF in PSN.

Characterization of Astrocytes in the Minocycline-Administered Mouse Photothrombotic Ischemic Stroke Model

Astrocytes, together with microglia, play important roles in the non-infectious inflammation and scar formation at the brain infarct during ischemic stroke. After ischemia occurs, these become highly reactive, accumulate at the infarction, and release various inflammatory signaling molecules. The regulation of astrocyte reactivity and function surrounding the infarction largely depends on intercellular communication with microglia. However, the mechanisms involved remain unclear. Furthermore, recent molecular biological studies have revealed that astrocytes are highly divergent under both resting and reactive states, whereas it has not been well reported how the communication between microglia and astrocytes affects astrocyte divergency during ischemic stroke. Minocycline, an antibiotic that reduces microglial activity, has been used to examine the functional roles of microglia in mice. In this study, we used a mouse photothrombotic ischemic stroke model to examine the characteristics of astrocytes after the administration of minocycline during ischemic stroke. Minocycline increased astrocyte reactivity and affected the localization of astrocytes in the penumbra region. Molecular characterization revealed that the induced expression of mRNA encoding the fatty acid binding protein 7 (FABP7) by photothrombosis was enhanced by the minocycline administration. Meanwhile, minocycline did not significantly affect the phenotype or class of astrocytes. The expression of Fabp7 mRNA was well correlated with that of tumor-necrosis factor α (TNFα)-encoding Tnf mRNA, indicating that a correlated expression of FABP7 from astrocytes and TNFα is suppressed by microglial activity.

Tumor necrosis factor (TNF) induces astrogliosis, microgliosis and promotes survival of cortical neurons

Objectives

Neuro-inflammation occurs as a sequence of brain injury and is associated with production of cytokines. Cytokines can modulate the function and survival of neurons, microglia and astrocytes. The objective of this study is to examine the effect of TNF on the neurons, microglia and astrocytes in normal brain and stab wound brain injury.

Methods

Normal BALB/c male mice (N) without any injury were subdivided into NA and NB groups. Another set mouse was subjected to stab wound brain injury (I) and were subdivided into IA and IB. NA and IA groups received intraperitoneal injections of TNF (1 µg/kg body weight/day) for nine days, whereas NB and IB groups received intraperitoneal injections of PBS. Animals were killed on 1^st, 2^nd, 3^rd, 7^th, and 9^th day. Frozen brain sections through the injury site in IA and IB or corresponding region in NA and NB groups were stained for neurodegeneration, immunostained for astrocytes, microglia and neurons. Western blotting for GFAP and ELISA for BDNF were done from the tissues collected from all groups.

Results

The number of degenerating neurons significantly decreased in TNF treated groups. There was a significant increase in the number of astrocytes and microglia in TNF treated groups compared to PBS treated groups. In addition, it was found that TNF stimulated the expression of GFAP and BDNF in NA and IA groups.

Conclusions

TNF induces astrogliosis and microgliosis in normal and injured brain and promotes the survival of cortical neurons in stab wound brain injury, may be by upregulating the BDNF level.

Innate immune responses after stimulation with Toll-like receptor agonists in ex vivo microglial cultures and an in vivo model using mice with reduced microglia

Background

Past experiments studying innate immunity in the central nervous system (CNS) utilized microglia obtained from neonatal mouse brain, which differ developmentally from adult microglia. These differences might impact our current understanding of the role of microglia in CNS development, function, and disease.

Methods

Cytokine protein secretion was compared in ex vivo P3 and adult microglial cultures after exposure to agonists for three different toll-like receptors (TLR4, lipopolysaccharide [LPS]; TLR7, imiquimod [IMQ]; and TLR9, CpG Oligodeoxynucleotide [CpG-ODN] 1585). In addition, changes in inflammatory gene expression in ex vivo adult microglia in response to the TLR agonists was assessed. Furthermore, in vivo experiments evaluated changes in gene expression associated with inflammation and TLR signaling in brains of mice with or without treatment with PLX5622 to reduce microglia.

Results

Ex vivo adult and P3 microglia increased cytokine secretion when exposed to TLR4 agonist LPS and to TLR7 agonist IMQ. However, adult microglia decreased expression of numerous genes after exposure to TLR 9 agonist CpG-ODN 1585. In contrast, in vivo studies indicated a core group of inflammatory and TLR signaling genes increased when each of the TLR agonists was introduced into the CNS. Reducing microglia in the brain led to decreased expression of various inflammatory and TLR signaling genes. Mice with reduced microglia showed extreme impairment in upregulation of genes after exposure to TLR7 agonist IMQ.

Conclusions

Cultured adult microglia were more reactive than P3 microglia to LPS or IMQ exposure. In vivo results indicated microglial influences on neuroinflammation were agonist specific, with responses to TLR7 agonist IMQ more dysregulated in mice with reduced microglia. Thus, TLR7-mediated innate immune responses in the CNS appeared more dependent on the presence of microglia. Furthermore, partial responses to TLR4 and TLR9 agonists in mice with reduced microglia suggested other cell types in the CNS can compensate for their absence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02240-w.

The progress of research on histone methylation in ischemic stroke pathogenesis

Stroke, also known as cerebral stroke or cerebrovascular accident, refers to acute ischemic or hemorrhagic encephalopathy caused by a disturbance to cerebral blood flow. Ischemic stroke is the most common type of cerebral stroke, accounting for approximately 80% of the total incidence of clinical stroke. High morbidity, disability, and mortality rates place heavy burdens on the families of patients and society. An increasing number of studies have shown that histone modification plays an important role in the pathogenesis of ischemic stroke, but most studies on histone modification focus on acetylation, and studies on the role of histone methylation in the pathogenesis of ischemic stroke are limited. Here, we review the role of histone methylation and related histone methyltransferase (HMT) inhibitors in the pathogenesis of ischemic stroke and related HMT inhibitors in the treatment of ischemic stroke, which may open up a new avenue to the study of ischemic stroke.

A cell-penetrating CD40-TRAF2,3 blocking peptide diminishes inflammation and neuronal loss after ischemia/reperfusion

While the administration of anti‐CD154 mAbs in mice validated the CD40‐CD154 pathway as a target against inflammatory disorders, this approach caused thromboembolism in humans (unrelated to CD40 inhibition) and is expected to predispose to opportunistic infections. There is a need for alternative approaches to inhibit CD40 that avoid these complications. CD40 signals through TRAF2,3 and TRAF6‐binding sites. Given that CD40‐TRAF6 is the pathway that stimulates responses key for cell‐mediated immunity against opportunistic pathogens, we examined the effects of pharmacologic inhibition of CD40‐TRAF2,3 signaling. We used a model of ischemia/reperfusion (I/R)‐induced retinopathy, a CD40‐driven inflammatory disorder. Intravitreal administration of a cell‐penetrating CD40‐TRAF2,3 blocking peptide impaired ICAM‐1 upregulation in retinal endothelial cells and CXCL1 upregulation in endothelial and Müller cells. The peptide reduced leukocyte infiltration, upregulation of NOS2/COX‐2/TNF‐α/IL‐1β, and ameliorated neuronal loss, effects that mimic those observed after I/R in Cd40−/− mice. While a cell‐penetrating CD40‐TRAF6 blocking peptide also diminished I/R‐induced inflammation, this peptide (but not the CD40‐TRAF2,3 blocking peptide) impaired control of the opportunistic pathogen Toxoplasma gondii in the retina. Thus, inhibition of the CD40‐TRAF2,3 pathway is a novel and potent approach to reduce CD40‐induced inflammation, while likely diminishing the risk of opportunistic infections that would otherwise accompany CD40 inhibition.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

LPS Preconditioning Attenuates Apoptosis Mechanism by Inhibiting NF-κB and Caspase-3 Activity: TLR4 Pre-activation in the Signaling Pathway of LPS-Induced Neuroprotection

Neuroinflammation, an inflammatory response within the nervous system, has been shown to be implicated in the progression of various neurodegenerative diseases. Recent in vivo studies showed that lipopolysaccharide (LPS) preconditioning provides neuroprotection by activating Toll-like receptor 4 (TLR4), one of the members for pattern recognition receptor (PRR) family that play critical role in host response to tissue injury, infection, and inflammation. Pre-exposure to low dose of LPS could confer a protective state against cellular apoptosis following subsequent stimulation with LPS at higher concentration, suggesting a role for TLR4 pre-activation in the signaling pathway of LPS-induced neuroprotection. However, the precise molecular mechanism associated with this protective effect is not well understood. In this article, we provide an overall review of the current state of our knowledge about LPS preconditioning in attenuating apoptosis mechanism and conferring neuroprotection via TLR4 signaling pathway.

Roadmap for Stroke: Challenging the Role of the Neuronal Extracellular Matrix

Stroke is a major challenge in modern medicine and understanding the role of the neuronal extracellular matrix (NECM) in its pathophysiology is fundamental for promoting brain repair. Currently, stroke research is focused on the neurovascular unit (NVU). Impairment of the NVU leads to neuronal loss through post-ischemic and reperfusion injuries, as well as coagulatory and inflammatory processes. The ictal core is produced in a few minutes by the high metabolic demand of the central nervous system. Uncontrolled or prolonged inflammatory response is characterized by leukocyte infiltration of the injured site that is limited by astroglial reaction. The metabolic failure reshapes the NECM through matrix metalloproteinases (MMPs) and novel deposition of structural proteins continues within months of the acute event. These maladaptive reparative processes are responsible for the neurological clinical phenotype. In this review, we aim to provide a systems biology approach to stroke pathophysiology, relating the injury to the NVU with the pervasive metabolic failure, inflammatory response and modifications of the NECM. The available data will be used to build a protein–protein interaction (PPI) map starting with 38 proteins involved in stroke pathophysiology, taking into account the timeline of damage and the co-expression scores of their RNA patterns The application of the proposed network could lead to a more accurate design of translational experiments aiming at improving both the therapy and the rehabilitation processes.

TNF Production and Release from Microglia via Extracellular Vesicles: Impact on Brain Functions

Tumor necrosis factor (TNF) is a pleiotropic cytokine powerfully influencing diverse processes of the central nervous system (CNS) under both physiological and pathological conditions. Here, we analyze current literature describing the molecular processes involved in TNF synthesis and release from microglia, the resident immune cells of the CNS and the main source of this cytokine both in brain development and neurodegenerative diseases. A special attention has been given to the unconventional vesicular pathway of TNF, based on the emerging role of microglia-derived extracellular vesicles (EVs) in the propagation of inflammatory signals and in mediating cell-to-cell communication. Moreover, we describe the contribution of microglial TNF in regulating important CNS functions, including the neuroinflammatory response following brain injury, the neuronal circuit formation and synaptic plasticity, and the processes of myelin damage and repair. Specifically, the available data on the functions mediated by microglial EVs carrying TNF have been scrutinized to gain insights on possible novel therapeutic strategies targeting TNF to foster CNS repair.

Repeated Application of Autologous Bone Marrow-Derived Lineage-Negative Stem/Progenitor Cells-Focus on Immunological Pathways in Patients with ALS

Therapeutic interventions in amyotrophic lateral sclerosis (ALS) are still far from satisfying. Immune modulating procedures raise hopes for slowing the disease progression. Stem cell therapies are believed to possess the ability to regulate innate and adaptive immune response and inflammation processes. Hence, three intrathecal administrations of autologous bone marrow-derived lineage-negative (Lin^–) cells were performed every six weeks in 40 sporadic ALS patients. The concentrations of inflammatory-related proteins and expression profiles of selected miRNA in the cerebrospinal fluid (CSF) and plasma at different timepoints post-transplantation were quantified by multiplex Luminex and qRT-PCR. The global gene expression in nucleated blood cells was assessed using the gene microarray technique. According to the ALS Functional Rating Scale (FRSr), the study population was divided into responders (group I, n = 17) and non-responders (group II, n = 23). A thorough analysis of the pro-inflammatory expression profiles, regulated miRNA pathways, and global gene expression profiles at the RNA level revealed the local and systemic effects of Lin^– cell therapy on the immune system of patients with ALS. The autologous application of Lin^– cells in CSF modulates immune processes and might prevent the progression of neurodegeneration. However, further in-depth studies are necessary to confirm the findings, and prolonged intervention is needed to maintain therapeutic effects.

G-CSF attenuates neuroinflammation and neuronal apoptosis via the mTOR/p70SK6 signaling pathway in neonatal Hypoxia-Ischemia rat model

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is an important cause of permanent damage to the central nervous system, associated with long-lasting neurological disabilities and neurodevelopmental impairment in neonates. Granulocyte-colony stimulating factor (G-CSF) has been shown to have neuroprotective activity in a variety of experimental brain injury models and G-CSF is a standard treatment in chemotherapeutic-induced neutropenia. The underlying mechanisms are still unclear. The mTOR (mammalian target of rapamycin) signaling pathway is a master regulator of cell growth and proliferation in the nervous system. However, the effects of G-CSF treatment on the mTOR signaling pathway have not been elucidated in neonates with hypoxic-ischemic (HI) brain injury. Our study investigated the neuroprotective effect of G-CSF on neonates with hypoxic-ischemic (HI) brain injury and the possible mechanism involving the mTOR/p70S6K pathway.

METHODS

Sprague-Dawley rat pups at postnatal day 7 (P7) were subjected to right unilateral carotid artery ligation followed by hypoxic (8% oxygen and balanced nitrogen) exposure for 2.5 h or sham surgery. Pups received normal saline, G-CSF, G-CSF combined with rapamycin or ethanol (vehicle for rapamycin) intraperitoneally. On postnatal day 9 (P9), TTC staining for infarct volume, and Nissl and TUNEL staining for neuronal cell injury were conducted. Activation of mTOR/p70S6K pathway, cleaved caspase-3 (CC3), Bax and Bcl-2 and cytokine expression levels were determined by western blotting.

RESULTS

The G-CSF treated group was associated with significantly reduced infarction volume and decreased TUNEL positive neuronal cells compared to the HI group treated with saline. The expression levels of TNF-α and IL-1ß were significantly decreased in the G-CSF treated group, while IL-10 expression level was increased. The relative immunoreactivity of p-mTOR and p-p70S6K was significantly reduced in the HI group compared to sham. The HI group treated with G-CSF showed significant upregulated protein expression for p-mTOR and p-p70S6K levels compared to the HI group treated with saline. Furthermore, G-CSF treatment increased Bcl-2 expression levels and decreased CC3 and Bax expression levels in the ipsilateral hemispheres of the HI brain. The effects induced by G-CSF were all reversed by rapamycin.

CONCLUSION

Treatment with G-CSF decreases inflammatory mediators and apoptotic factors, attenuating neuroinflammation and neuronal apoptosis via the mTOR/p70S6K signalling pathway, which represents a potential target for treating HI induced brain damage in neonatal HIE.

Differential Thermoregulatory and Inflammatory Patterns in the Circadian Response to LPS-Induced Septic Shock

Sepsis is caused by a dysregulated host response to infection, and characterized by uncontrolled inflammation together with immunosuppression, impaired innate immune functions of phagocytes and complement activation. Septic patients develop fever or hypothermia, being the last one characteristic of severe cases. Both lipopolysaccharide (LPS) and Tumor Necrosis Factor (TNF)-α- induced septic shock in mice is dependent on the time of administration. In this study, we aimed to further characterize the circadian response to high doses of LPS. First, we found that mice injected with LPS at ZT11 developed a higher hypothermia than those inoculated at ZT19. This response was accompanied by higher neuronal activation of the preoptic, suprachiasmatic, and paraventricular nuclei of the hypothalamus. However, LPS-induced Tnf-α and Tnf-α type 1 receptor (TNFR1) expression in the preoptic area was time-independent. We also analyzed peritoneal and spleen macrophages, and observed an exacerbated response after ZT11 stimulation. The serum of mice inoculated with LPS at ZT11 induced deeper hypothermia in naïve animals than the one coming from ZT19-inoculated mice, related to higher TNF-α serum levels during the day. We also analyzed the response in TNFR1-deficient mice, and found that both the daily difference in the mortality rate, the hypothermic response and neuronal activation were lost. Moreover, mice subjected to circadian desynchronization showed no differences in the mortality rate throughout the day, and developed lower minimum temperatures than mice under light-dark conditions. Also, those injected at ZT11 showed increased levels of TNF-α in serum compared to standard light conditions. These results suggest a circadian dependency of the central thermoregulatory and peripheral inflammatory response to septic-shock, with TNF-α playing a central role in this circadian response.

Topical Administration of a Soluble TNF Inhibitor Reduces Infarct Volume After Focal Cerebral Ischemia in Mice

Background

Tumor necrosis factor, which exists both as a soluble (solTNF) and a transmembrane (tmTNF) protein, plays an important role in post-stroke inflammation. The objective of the present study was to test the effect of topical versus intracerebroventricular administration of XPro1595 (a solTNF inhibitor) and etanercept (a solTNF and tmTNF inhibitor) compared to saline on output measures such as infarct volume and post-stroke inflammation in mice.

Methods

Adult male C57BL/6 mice were treated topically (2.5 mg/ml/1μl/h for 3 consecutive days) or intracerebroventricularly (1.25 mg/kg/0.5 ml, once) with saline, XPro1595, or etanercept immediately after permanent middle cerebral artery occlusion (pMCAO). Mice were allowed to survive 1 or 3 days. Infarct volume, microglial and leukocyte profiles, and inflammatory markers were evaluated.

Results

We found that topical, and not intracerebroventricular, administration of XPro1595 reduced infarct volume at both 1 and 3 days after pMCAO. Etanercept showed no effect. We observed no changes in microglial or leukocyte populations. XPro1595 increased gene expression of P2ry12 at 1 day and Trem2 at 1 and 3 days, while decreasing Cx3cr1 expression at 1 and 3 days after pMCAO, suggesting a change in microglial activation toward a phagocytic phenotype.

Conclusion

Our data demonstrate that topical administration of XPro1595 for 3 consecutive days decreases infarct volumes after ischemic stroke, while modifying microglial activation and the inflammatory response post-stroke. This suggests that inhibitors of solTNF hold great promise for future neuroprotective treatment in ischemic stroke.

Evaluation of the effects of erythropoietin and interleukin-6 in rats submitted to acute spinal cord injury

OBJECTIVE

To evaluate the effects of interleukin-6 (IL-6) and erythropoietin (EPO) in experimental acute spinal cord injury (SCI) in rats.

METHODS

Using standardized equipment, namely, a New York University (NYU) Impactor, a SCI was produced in 50 Wistar rats using a 10-g weight drop from a 12.5-mm height. The rats were divided into the following 5 groups of 10 animals each: "Group EPO", treated with erythropoietin only; "Group EPO + IL-6", treated with both substances; "Group IL-6", receiving IL-6 administration only; "Group Placebo", receiving a placebo solution; and "Group Sham", submitted to an incomplete procedure (only laminectomy, without SCI). All drugs and the placebo solution were administered intraperitoneally for three weeks. The animals were followed up for 42 days. Functional motor recovery was monitored by the Basso, Beattie, and Bresnahan (BBB) scale on days 2, 7, 14, 21, 28, 35 and 42. Motor-evoked potential tests were performed on the 42nd day. Histological analysis was performed after euthanasia.

RESULTS

The group receiving EPO exhibited superior functional motor results on the BBB scale. IL-6 administration alone was not superior to the placebo treatment, and the IL-6 combination with EPO yielded worse results than did EPO alone.

CONCLUSIONS

Using EPO after acute SCI in rats yielded benefits in functional recovery. The combination of EPO and IL-6 showed benefits, but with inferior results compared to those of isolated EPO; moreover, isolated use of IL-6 resulted in no benefit.

Role of immune responses for extracellular matrix remodeling in the ischemic brain

Neuroinflammation is one of the key components contributing to the devastating outcome of ischemic stroke. Starting with stroke onset, inflammatory processes contribute both to cell damage and tissue remodeling. The early release of alarmins triggers the upregulation of multiple proinflammatory cytokines, resulting in the compromised integrity of the blood–brain barrier. From this moment on, the infiltration of peripheral immune cells, reactive gliosis and extracellular matrix (ECM) alterations become intricately intertwined and act as one unit during the tissue remodeling. While the mechanisms of leukocyte and glia activation are amply reviewed, the field of ECM modification remains as yet under explored. In this review, we focus on the interplay between neuroinflammatory cascades and ECM in the ischemic brain. By summarizing the currently available evidence obtained by in vitro research, animal experimentation and human studies, we aim to propose a new direction for the future investigation of stroke recovery.

Psychoneuroimmunology and immunopsychiatry of zebrafish

Despite the high prevalence of neural and immune disorders, their etiology and molecular mechanisms remain poorly understood. As the zebrafish (Danio rerio) is increasingly utilized as a powerful model organism in biomedical research, mounting evidence suggests these fish as a useful tool to study neural and immune mechanisms and their interplay. Here, we discuss zebrafish neuro-immune mechanisms and their pharmacological and genetic modulation, the effect of stress on cytokines, as well as relevant models of microbiota-brain interplay. As many human brain diseases are based on complex interplay between the neural and the immune system, here we discuss zebrafish models, as well as recent successes and challenges, in this rapidly expanding field. We particularly emphasize the growing utility of zebrafish models in translational immunopsychiatry research, as they improve our understanding of pathogenetic neuro-immune interactions, thereby fostering future discovery of potential therapeutic agents.

Tumor necrosis factor receptor 2 is required for ischemic preconditioning-mediated neuroprotection in the hippocampus following a subsequent longer transient cerebral ischemia

Tumor Necrosis Factor-α (TNF-α) is a proinflammatory cytokine implicated in neuronal damage in response to cerebral ischemia. Ischemic preconditioning (IPC) provides neuroprotection against a subsequent severer or longer transient ischemia by ischemic tolerance. Here, we focused on the role of TNF-α in IPC-mediated neuroprotection against neuronal death following a subsequent longer transient cerebral ischemia (TCI). Gerbils used in this study were randomly assigned to eight groups; sham group, TCI operated group, IPC plus (+) sham group, IPC + TCI operated group, sham + etanercept (an inhibitor of TNF-a) group, TCI + etanercept group, IPC + sham + etanercept group, and IPC + TCI + etanercept group. IPC was induced by a 2-min sublethal transient ischemia, which was operated 1 day prior to a longer (5-min) TCI. A significant death of neurons was found in the stratum pyramidale (SP) in the CA1 area (CA1) of the hippocampus 5 days after TCI; however, IPC protected SP neurons from TCI. We found that TNF-α immunoreactivity was significantly increased in CA1 pyramidal neurons in the TCI and IPC + TCI groups compared to the sham group. TNF-R1 expression in CA1 pyramidal neurons of the TCI group was also increased 1 and 2 days after TCI; however, in the IPC + TCI group, TNF-R1 expression was significantly lower than that in the TCI group. On the other hand, we did not detect TNF-R2 immunoreactivity in CA1 pyramidal neurons 1 and 2 days after TCI; meanwhile, in the IPC + TCI group, TNF-R2 expression was significantly increased compared to TNF-R2 expression at 1 and 2 days after TCI. In addition, in this group, TNF-R2 was newly expressed in pericytes, which are important cells in the blood brain barrier, from 1 day after TCI. When we treated etanercept to the IPC + TCI group, IPC-induced neuroprotection was significantly weakened. In brief, this study indicates that IPC confers neuroprotection against TCI by TNF-α signaling through TNF-R2 and suggests that the enhancement of TNF-R2 expression by IPC may be a legitimate strategy for a therapeutic intervention of TCI.

Tumor necrosis factor alpha in sleep regulation

This review details tumor necrosis factor alpha (TNF) biology and its role in sleep, and describes how TNF medications influence sleep/wake activity. Substantial evidence from healthy young animals indicates acute enhancement or inhibition of endogenous brain TNF respectively promotes and inhibits sleep. In contrast, the role of TNF in sleep in most human studies involves pathological conditions associated with chronic elevations of systemic TNF and disrupted sleep. Normalization of TNF levels in such patients improves sleep. A few studies involving normal healthy humans and their TNF levels and sleep are consistent with the animal studies but are necessarily more limited in scope. TNF can act on established sleep regulatory circuits to promote sleep and on the cortex within small networks, such as cortical columns, to induce sleep-like states. TNF affects multiple synaptic functions, e.g., its role in synaptic scaling is firmly established. The TNF-plasticity actions, like its role in sleep, can be local network events suggesting that sleep and plasticity share biochemical regulatory mechanisms and thus may be inseparable from each other. We conclude that TNF is involved in sleep regulation acting within an extensive tightly orchestrated biochemical network to niche-adapt sleep in health and disease.

Intra-cerebral cannabidiol infusion-induced neuroprotection is partly associated with the TNF-α/TNFR1/NF-кB pathway in transient focal cerebral ischaemia

BACKGROUND

Stroke is a neurological disease, which, in addition to high mortality, imposes many financial and mental burdens on families and the society. The main objective of this study was to investigate the effect of cannabidiol (CBD) on one of the major inflammatory pathways in cerebral ischaemia.

METHOD

Using stereotaxic surgery, the cannula was implanted into the right lateral ventricle of rats. CBD (50, 100, and 200 ng/rat; i.c.v.) was administrated for five consecutive days. After pretreatment, the rats were subjected to 60 min of right middle cerebral artery occlusion (MCAO). After 24 h, neurological deficits score, infarct volume, brain oedema, and blood-brain barrier (BBB) permeability in total, core, and penumbra areas were assessed. The expression of tumour necrosis factor alfa (TNF-α), tumour necrosis factor receptor 1 (TNFR1), and nuclear factor-kappa B (NF-кB) in the mentioned regions was also studied.

RESULTS

Administration of CBD (100 and 200 ng/rat) caused a significant reduction in infarction, brain oedema, and BBB permeability compared with the vehicle-received group. Down-regulation of TNF-α, TNFR1, and NF-кB expression was also observed by CBD.

CONCLUSION

The results achieved in this study support the idea that CBD has a cerebroprotective effect (partly through suppression of TNF-α, TNFR1, and NF-кB) on ischaemic injury.

ABBREVIATIONS

CBD, cannabidiol; ANOVA, analysis of variance; PVDF, polyvinylidene difluoride; SDS-PAGE, sodium dodecyl sulphate polyacrylamide gel electrophoresis; SEM, standard error of mean.

Nutrients, neurogenesis and brain ageing: From disease mechanisms to therapeutic opportunities

Appreciation of the physiological relevance of mammalian adult neurogenesis has in recent years rapidly expanded from a phenomenon of homeostatic cell replacement and brain repair to the current view of a complex process involved in high order cognitive functions. In parallel, an array of endogenous or exogenous triggers of neurogenesis has also been identified, among which metabolic and nutritional cues have drawn significant attention. Converging evidence from animal and in vitro studies points to nutrient sensing and energy metabolism as major physiological determinants of neural stem cell fate, and modulators of the whole neurogenic process. While the cellular and molecular circuitries underlying metabolic regulation of neurogenesis are still incompletely understood, the key role of mitochondrial activity and dynamics, and the importance of autophagy have begun to be fully appreciated; moreover, nutrient-sensitive pathways and transducers such as the insulin-IGF cascade, the AMPK/mTOR axis and the transcription regulators CREB and Sirt-1 have been included, beside more established "developmental" signals like Notch and Wnt, in the molecular networks that dictate neural-stem-cell self-renewal, migration and differentiation in response to local and systemic inputs. Many of these nutrient-related cascades are deregulated in the contest of metabolic diseases and in ageing, and may contribute to impaired neurogenesis and thus to cognition defects observed in these conditions. Importantly, accumulating knowledge on the metabolic control of neurogenesis provides a theoretical framework for the trial of new or repurposed drugs capable of interfering with nutrient sensing as enhancers of neurogenesis in the context of neurodegeneration and brain senescence.

Adult neurogenesis and neurodegenerative diseases: A systems biology perspective

New neurons are generated throughout adulthood in two regions of the brain, the olfactory bulb and dentate gyrus of the hippocampus, and are incorporated into the hippocampal network circuitry; disruption of this process has been postulated to contribute to neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. Known modulators of adult neurogenesis include signal transduction pathways, the vascular and immune systems, metabolic factors, and epigenetic regulation. Multiple intrinsic and extrinsic factors such as neurotrophic factors, transcription factors, and cell cycle regulators control neural stem cell proliferation, maintenance in the adult neurogenic niche, and differentiation into mature neurons; these factors act in networks of signaling molecules that influence each other during construction and maintenance of neural circuits, and in turn contribute to learning and memory. The immune system and vascular system are necessary for neuronal formation and neural stem cell fate determination. Inflammatory cytokines regulate adult neurogenesis in response to immune system activation, whereas the vasculature regulates the neural stem cell niche. Vasculature, immune/support cell populations (microglia/astrocytes), adhesion molecules, growth factors, and the extracellular matrix also provide a homing environment for neural stem cells. Epigenetic changes during hippocampal neurogenesis also impact memory and learning. Some genetic variations in neurogenesis related genes may play important roles in the alteration of neural stem cells differentiation into new born neurons during adult neurogenesis, with important therapeutic implications. In this review, we discuss mechanisms of and interactions between these modulators of adult neurogenesis, as well as implications for neurodegenerative disease and current therapeutic research. © 2016 Wiley Periodicals, Inc.

A Model for Spheroid versus Monolayer Response of SK-N-SH Neuroblastoma Cells to Treatment with 15-Deoxy-PGJ2

Researchers have observed that response of tumor cells to treatment varies depending on whether the cells are grown in monolayer, as in vitro spheroids or in vivo. This study uses data from the literature on monolayer treatment of SK-N-SH neuroblastoma cells with 15-deoxy-PGJ₂ and couples it with data on growth rates for untreated SK-N-SH neuroblastoma cells grown as multicellular spheroids. A linear model is constructed for untreated and treated monolayer data sets, which is tuned to growth, death, and cell cycle data for the monolayer case for both control and treatment with 15-deoxy-PGJ₂. The monolayer model is extended to a five-dimensional nonlinear model of in vitro tumor spheroid growth and treatment that includes compartments of the cell cycle (G₁, S, G₂/M) as well as quiescent (Q) and necrotic (N) cells. Monolayer treatment data for 15-deoxy-PGJ₂ is used to derive a prediction of spheroid response under similar treatments. For short periods of treatment, spheroid response is less pronounced than monolayer response. The simulations suggest that the difference in response to treatment of monolayer versus spheroid cultures observed in laboratory studies is a natural consequence of tumor spheroid physiology rather than any special resistance to treatment.

The Anti-Inflammatory Activity of Eucommia ulmoides Oliv. Bark. Involves NF-κB Suppression and Nrf2-Dependent HO-1 Induction in BV-2 Microglial Cells

In the present study, we investigated the anti-inflammatory properties of Eucommia ulmoides Oliv. Bark. (EUE) in lipopolysaccharide (LPS)-stimulated microglial BV-2 cells and found that EUE inhibited LPS-mediated up-regulation of pro-inflammatory response factors. In addition, EUE inhibited the elevated production of pro-inflammatory cytokines, mediators, and reactive oxygen species (ROS) in LPS-stimulated BV-2 microglial cells. Subsequent mechanistic studies revealed that EUE suppressed LPS-induced phosphorylation of mitogen-activated protein kinases (MAPKs), phosphoinositide-3-kinase (PI3K)/Akt, glycogen synthase kinase-3β (GSK-3β), and their downstream transcription factor, nuclear factor-kappa B (NF-κB). EUE also blocked the nuclear translocation of NF-κB and inhibited its binding to DNA. We next demonstrated that EUE induced the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and upregulated heme oxygenase-1 (HO-1) expression. We determined that the significant up-regulation of HO-1 expression by EUE was a consequence of Nrf2 nuclear translocation; furthermore, EUE increased the DNA binding of Nrf2. In contrast, zinc protoporphyrin (ZnPP), a specific HO-1 inhibitor, blocked the ability of EUE to inhibit NO and PGE₂ production, indicating the vital role of HO-1. Overall, our results indicate that EUE inhibits pro-inflammatory responses by modulating MAPKs, PI3K/Akt, and GSK-3β, consequently suppressing NF-κB activation and inducing Nrf2-dependent HO-1 activation.

Help-me signaling: Non-cell autonomous mechanisms of neuroprotection and neurorecovery

Self-preservation is required for life. At the cellular level, this fundamental principle is expressed in the form of molecular mechanisms for preconditioning and tolerance. When the cell is threatened, internal cascades of survival signaling become triggered to protect against cell death and defend against future insults. Recently, however, emerging findings suggest that this principle of self-preservation may involve not only intracellular signals; the release of extracellular signals may provide a way to recruit adjacent cells into an amplified protective program. In the central nervous system where multiple cell types co-exist, this mechanism would allow threatened neurons to "ask for help" from glial and vascular compartments. In this review, we describe this new concept of help-me signaling, wherein damaged or diseased neurons release signals that may shift glial and vascular cells into potentially beneficial phenotypes, and help remodel the neurovascular unit. Understanding and dissecting these non-cell autonomous mechanisms of self-preservation in the CNS may lead to novel opportunities for neuroprotection and neurorecovery.

TNF-α/TNFR2 Regulatory Axis Stimulates EphB2-Mediated Neuroregeneration Via Activation of NF-κB

HIV-1 infected individuals are at high risk of developing HIV-associated neurocognitive disorders (HAND) as HIV infection leads to neuronal injury and synaptic loss in the central nervous system (CNS). The neurotoxic effects of HIV-1 are primarily a result of viral replication leading to the production of inflammatory chemokines and cytokines, including TNF-α. Given an important role of TNF-α in regulating synaptic plasticity, we investigated the effects of TNF-α on the development of neuronal processes after mechanical injury, and we showed that TNF-α treatment stimulates the regrowth of neuronal processes. To investigate transcriptional effects of TNF-α on synaptic plasticity, we analyzed both human neurosphere and isolated neuronal cultures for the regulation of genes central to synaptic alterations during learning and memory. TNF-α treatment upregulated Ephrin receptor B2 (EphB2), which is strongly involved in dendritic arborization and synaptic integrity. TNF-α strongly activates the NF-κB pathway, therefore, we propose that TNF-α-induced neurite regrowth occurs primarily through EphB2 signaling via stimulation of NF-κB. EphB2 promoter activity increased with TNF-α treatment and overexpression of NF-κB. Direct binding of NF-κB to the EphB2 promoter occurred in the ChIP assay, and site-directed mutagenesis identified binding sites involved in TNF-α-induced EphB2 activation. TNF-α induction of EphB2 was determined to occur specifically through TNF-α receptor 2 (TNFR2) activation in human primary fetal neurons. Our observations provide a new avenue for the investigation on the impact of TNF-α in the context of HIV-1 neuronal cell damage as well as providing a potential therapeutic target in TNFR2 activation of EphB2.

Increased levels of tumour necrosis factor alpha (TNFα) but not transforming growth factor-beta 1 (TGFβ1) are associated with the severity of congenital hydrocephalus in the hyh mouse

AIMS

Here, we tested the hypothesis that glial responses via the production of cytokines such as transforming growth factor-beta 1 (TGFβ1) and tumour necrosis factor alpha (TNFα), which play important roles in neurodegenerative diseases, are correlated with the severity of congenital hydrocephalus in the hyh mouse model. We also searched for evidence of this association in human cases of primary hydrocephalus.

METHODS

Hyh mice, which exhibit either severe or compensated long-lasting forms of hydrocephalus, were examined and compared with wild-type mice. TGFβ1, TNFα and TNFαR1 mRNA levels were quantified using real-time PCR. TNFα and TNFαR1 were immunolocalized in the brain tissues of hyh mice and four hydrocephalic human foetuses relative to astroglial and microglial reactions.

RESULTS

The TGFβ1 mRNA levels were not significantly different between hyh mice exhibiting severe or compensated hydrocephalus and normal mice. In contrast, severely hydrocephalic mice exhibited four- and two-fold increases in the mean levels of TNFα and TNFαR1, respectively, compared with normal mice. In the hyh mouse, TNFα and TNFαR1 immunoreactivity was preferentially detected in astrocytes that form a particular periventricular reaction characteristic of hydrocephalus. However, these proteins were rarely detected in microglia, which did not appear to be activated. TNFα immunoreactivity was also detected in the glial reaction in the small group of human foetuses exhibiting hydrocephalus that were examined.

CONCLUSIONS

In the hyh mouse model of congenital hydrocephalus, TNFα and TNFαR1 appear to be associated with the severity of the disease, probably mediating the astrocyte reaction, neurodegenerative processes and ischaemia.

Rapid mitochondrial dysfunction mediates TNF-alpha-induced neurotoxicity

Tumor necrosis factor alpha (TNF-α) is known to exacerbate ischemic brain injury; however, the mechanism is unknown. Previous studies have evaluated the effects of TNF-α on neurons with long exposures to high doses of TNF-α, which is not pathophysiologically relevant. We characterized the rapid effects of TNF-α on basal respiration, ATP production, and maximal respiration using pathophysiologically relevant, post-stroke concentrations of TNF-α. We observed a reduction in mitochondrial function as early as 1.5 h after exposure to low doses of TNF-α, followed by a decrease in cell viability in HT-22 cells and primary neurons. Subsequently, we used the HT-22 cell line to determine the mechanism by which TNF-α causes a rapid and profound reduction in mitochondrial function. Pre-treating with TNF-R1 antibody, but not TNF-R2 antibody, ameliorated the neurotoxic effects of TNF-α, indicating that TNF-α exerts its neurotoxic effects through TNF-R1. We observed an increase in caspase 8 activity and a decrease in mitochondrial membrane potential after exposure to TNF-α which resulted in a release of cytochrome c from the mitochondria into the cytosol. These novel findings indicate for the first time that an acute exposure to pathophysiologically relevant concentrations of TNF-α has neurotoxic effects mediated by a rapid impairment of mitochondrial function. This study focuses on the neurotoxic mechanism of a pro-inflammatory cytokine, tumor necrosis factor alpha (TNF-α). We demonstrate a prompt mitochondrial dysfunction followed by nerve cell loss after exposure to TNF-α. These studies may provide evidence that the immune system can rapidly and adversely affect brain function and that TNF-α signaling may be a target for neuroprotection.

Genetic deletion of TNFR2 augments inflammatory response and blunts satellite-cell-mediated recovery response in a hind limb ischemia model

We have previously shown that TNF-tumor necrosis factor receptor-2/p75 (TNFR2/p75) signaling plays a critical role in ischemia-induced neovascularization in skeletal muscle and heart tissues. To determine the role of TNF-TNFR2/p75 signaling in ischemia-induced inflammation and muscle regeneration, we subjected wild-type (WT) and TNFR2/p75 knockout (p75KO) mice to hind limb ischemia (HLI) surgery. Ischemia induced significant and long-lasting inflammation associated with considerable decrease in satellite-cell activation in p75KO muscle tissue up to 10 d after HLI surgery. To determine the possible additive negative roles of tissue aging and the absence of TNFR2/p75, either in the tissue or in the bone marrow (BM), we generated 2 chimeric BM transplantation (BMT) models where both young green fluorescent protein (GFP)-positive p75KO and WT BM-derived cells were transplanted into adult p75KO mice. HLI surgery was performed 1 mo after BMT, after confirming complete engraftment of the recipient BM with GFP donor cells. In adult p75KO with the WT-BMT, proliferative (Ki67(+)) cells were detected only by d 28 and were exclusively GFP(+), suggesting significantly delayed contribution of young WT-BM cell to adult p75KO ischemic tissue recovery. No GFP(+) young p75KO BM cells survived in adult p75KO tissue, signifying the additive negative roles of tissue aging combined with decreased/absent TNFR2/p75 signaling in postischemic recovery.

Biochanin A attenuates LPS-induced pro-inflammatory responses and inhibits the activation of the MAPK pathway in BV2 microglial cells

Inflammation in the brain, characterized by the activation of microglia, is believed to participate in the pathogenesis of Parkinson's disease. Biochanin A, an O-methylated isoflavone, is a natural organic compound and is classified as a phytoestrogen. In this study, using murine BV2 microglial cells, we investigated the anti-inflammatory effects of biochanin A and the possible mechanisms involved. BV2 microglial cells were treated with lipopolysaccharide (LPS) to induce pro-inflammatory responses and the cells were then treated with biochanin A. Cell viability was examined by MTT assay. The production of nitric oxide (NO) was examined using Griess reagent and intracellular reactive oxygen species (ROS production) was measured by DCFH-DA assay. The mRNA expression of interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS) and tumor necrosis factor-α (TNF-α) was examined by RT-PCR. The expression of p-ERK, p-JNK, p-p38 and iNOS was measured by western blot analysis. In addition, the protein and mRNA and phosphorylation levels of pro-inflammatory cytokines were determined by western blot analysis and RT-PCR, respectively. The results revealed that biochanin A attenuated LPS-induced microglial activation and the production of TNF‑α, IL-1β, nitric oxide and reactive oxygen species in a dose-dependent manner. Biochanin A significantly decreased the LPS-induced mRNA expression of TNF-α and IL-1β, and inhibited iNOS mRNA and protein expression. Furthermore, biochanin A significantly inhibited the LPS-induced phosphorylation of c-Jun NH2-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38. These findings suggest that the inhibitory effects of biochanin A on LPS-induced proinflammatory responses may be associated with the inhibition of mitogen-activated protein kinase (MAPK) signaling pathways in BV2 microglial cells.

Tumor necrosis factor-α promotes the expression of excitatory amino-acid transporter 2 in astrocytes: Optimal concentration and incubation time

The aim of the present study was to determine whether tumor necrosis factor (TNF)-α regulates the expression levels of excitatory amino-acid transporters (EAATs) in primary astrocytes and its roles in brain ischemia. Exogenous TNF-α was administered to pure cultured astrocytes and the expression levels of EAAT1, EAAT2 and glial fibrillary acidic protein (GFAP) were evaluated. The results showed that TNF-α at 10 ng/ml enhanced the expression of EAAT2 in a time-dependent manner, while the expression levels of EAAT1 and GFAP did not change. To determine whether the elevation in the levels of the EAAT2 protein induced by TNF-α had a beneficial effect on ischemic insult, TNF-α was applied to in vitro models of cerebral ischemia; the treatment was observed to increase neuronal viability. The present results suggest that a relatively short-term application of an optimal concentration of TNF-α may protect neurons against ischemic injury by elevating the expression of EAAT2 in astrocytes.

Peripheral noxious stimulation reduces withdrawal threshold to mechanical stimuli after spinal cord injury: role of tumor necrosis factor alpha and apoptosis

We previously showed that peripheral noxious input after spinal cord injury (SCI) inhibits beneficial spinal plasticity and impairs recovery of locomotor and bladder functions. These observations suggest that noxious input may similarly affect the development and maintenance of chronic neuropathic pain, an important consequence of SCI. In adult rats with a moderate contusion SCI, we investigated the effect of noxious tail stimulation, administered 1 day after SCI on mechanical withdrawal responses to von Frey stimuli from 1 to 28 days after treatment. In addition, because the proinflammatory cytokine tumor necrosis factor alpha (TNFα) is implicated in numerous injury-induced processes including pain hypersensitivity, we assessed the temporal and spatial expression of TNFα, TNF receptors, and several downstream signaling targets after stimulation. Our results showed that unlike sham surgery or SCI only, nociceptive stimulation after SCI induced mechanical sensitivity by 24h. These behavioral changes were accompanied by increased expression of TNFα. Cellular assessments of downstream targets of TNFα revealed that nociceptive stimulation increased the expression of caspase 8 and the active subunit (12 kDa) of caspase 3, indicative of active apoptosis at a time point consistent with the onset of mechanical allodynia. In addition, immunohistochemical analysis revealed distinct morphological signs of apoptosis in neurons and microglia at 24h after stimulation. Interestingly, expression of the inflammatory mediator NFκB was unaltered by nociceptive stimulation. These results suggest that noxious input caudal to the level of SCI can increase the onset and expression of behavioral responses indicative of pain, potentially involving TNFα signaling.

Biochemical and inflammatory biomarkers in ischemic stroke: translational study between humans and two experimental rat models

Background

our objective was to examine the plasma levels of three biological markers involved in cerebral ischemia (IL-6, glutamate and TNF-alpha) in stroke patients and compare them with two different rat models of focal ischemia (embolic stroke model- ES and permanent middle cerebral artery occlusion ligation model-pMCAO) to evaluate which model is most similar to humans. Secondary objectives: 1) to analyze the relationship of these biological markers with the severity, volume and outcome of the brain infarction in humans and the two stroke models; and 2) to study whether the three biomarkers are also increased in response to damage in organs other than the central nervous system, both in humans and in rats.

Methods

Multi-center, prospective, case-control study including acute stroke patients (n = 58) and controls (n = 19) with acute non-neurological diseases Main variables: plasma biomarker levels on admission and at 72 h; stroke severity (NIHSS scale) and clinical severity (APACHE II scale); stroke volume; functional status at 3 months (modified Rankin Scale [mRS] and Barthel index [BI]). Experimental groups: ES (n = 10), pMCAO (n = 6) and controls (tissue stress by leg compression) (n = 6). Main variables: plasma biomarker levels at 3 and 72 h; volume of ischemic lesion (H&E) and cell death (TUNEL).

Results

in stroke patients, IL-6 correlated significantly with clinical severity (APACHE II scale), stroke severity (NIHSS scale), infarct volume (cm³) and clinical outcome (mRS) (r = 0.326, 0.497, 0.290 and 0.444 respectively; P < 0.05). Glutamate correlated with stroke severity, but not with outcome, and TNF-alpha levels with infarct volume. In animals, The ES model showed larger infarct volumes (median 58.6% vs. 29%, P < 0.001) and higher inflammatory biomarkers levels than pMCAO, except for serum glutamate levels which were higher in pMCAO. The ES showed correlations between the biomarkers and cell death (r = 0.928 for IL-6; P < 0.001; r = 0.765 for TNF-alpha, P < 0.1; r = 0.783 for Glutamate, P < 0.1) and infarct volume (r = 0.943 for IL-6, P < 0.0001) more similar to humans than pMCAO. IL-6, glutamate and TNF-α levels were not higher in cerebral ischemia than in controls.

Conclusions

Both models, ES and pMCAO, show differences that should be considered when conducting translational studies. IL-6, Glutamate and TNF-α are not specific for cerebral ischemia either in humans or in rats.

Tumor necrosis factor reduces the amplitude of rat cortical spreading depression in vivo

OBJECTIVE

Brain damage and ischemia often trigger cortical spreading depression (CSD), which aggravates brain damage. The proinflammatory cytokine tumor necrosis factor (TNF) is significantly upregulated during brain damage, but it is unknown whether TNF influences spreading depression in cerebral cortex in vivo. This question is important because TNF not only furthers inflammatory reactions but might also be neuroprotective. Here we tested the hypothesis that TNF affects CSD, and we explored the direction in which CSD is modified by TNF.

METHODS

CSD, elicited by pressure microinjection of KCl, was recorded in anesthetized rats and mice. TNF was administered locally into a trough, providing local TNF treatment of a cortical area. For further analysis, antibodies to TNF receptor (TNFR) 1 or 2 were applied, or CSD was monitored in TNFR1 and TNFR2 knockout mice. γ-Aminobutyric acid (GABA)A receptors were blocked by bicuculline. Immunohistochemistry localized the cortical expression of TNFR1 and TNFR2.

RESULTS

Local application of TNF to the cortex reduced dose-dependently the amplitude of CSD. This effect was prevented by blockade or knockout of TNFR2 but not by blockade or knockout of TNFR1. TNFR2 was localized at cortical neurons including parvalbumin-positive inhibitory interneurons, and blockade of GABAA receptors by bicuculline prevented the reduction of CSD amplitudes by TNF.

INTERPRETATION

We identified a functional link between TNF and CSD. TNF activates TNFR2 in cortical inhibitory interneurons. The resulting release of GABA reduces CSD amplitudes. In this manner, TNF might be neuroprotective in pathological conditions.

Inhibition of soluble tumor necrosis factor is therapeutic in Huntington's disease

Neuroinflammation is a common feature of many neurodegenerative diseases, including Huntington's disease (HD). HD is an autosomal dominant genetic disease caused by an expanded CAG repeat in exon 1 of the huntingtin (HTT) gene. Previous studies demonstrated that levels of several proinflammatory cytokines, including tumor necrosis factor (TNF)-α, were higher in the plasma and brain tissues of mice and patients with HD, suggesting that inflammation may contribute to HD progression. To evaluate the pathological role of TNF-α in HD pathogenesis, we blocked TNF-α signaling using a dominant negative inhibitor of soluble TNF-α (XPro1595). XPro1595 effectively suppressed the inflammatory responses of primary astrocytes-enriched culture isolated from a transgenic mouse model (R6/2) and human astrocytes-enriched culture derived from induced pluripotent stem cells (iPSCs) of HD patients evoked by lipopolysaccharide and cytokines, respectively. Moreover, XPro1595 protected the cytokine-induced toxicity of primary R6/2 neurons and human neurons derived from iPSCs of HD patients. To assess the beneficial effect of XPro1595 in vivo, an intracerebroventricular (i.c.v.) infusion was provided with an osmotic minipump. ELISA analyses showed that i.c.v. infusion of XPro1595 decreased elevated levels of TNFα in the cortex and striatum, improved motor function, reduced caspase activation, diminished the amount of mutant HTT aggregates, increased neuronal density and decreased gliosis in brains of R6/2 mice. Moreover, reducing the peripheral inflammatory response by a systemic injection of XPro1595 improved the impaired motor function of R6/2 mice but did not affect caspase activation. Collectively, our findings suggest that an effective and selective anti-inflammatory treatment targeting the abnormal brain inflammatory response is a potential therapeutic strategy for HD.

Therapeutic non-toxic doses of TNF induce significant regression in TNFR2-p75 knockdown Lewis lung carcinoma tumor implants

Tumor necrosis factor-alpha (TNF) binds to two receptors: TNFR1/p55-cytotoxic and TNFR2/p75-pro-survival. We have shown that tumor growth in p75 knockout (KO) mice was decreased more than 2-fold in Lewis lung carcinoma (LLCs). We hypothesized that selective blocking of TNFR2/p75 LLCs may sensitize them to TNF-induced apoptosis and affect the tumor growth. We implanted intact and p75 knockdown (KD)-LLCs (>90%, using shRNA) into wild type (WT) mice flanks. On day 8 post-inoculation, recombinant murine (rm) TNF-α (12.5 ng/gr of body weight) or saline was injected twice daily for 6 days. Tumor volumes (tV) were measured daily and tumor weights (tW) on day 15, when study was terminated due to large tumors in LLC+TNF group. Tubular bones, spleens and peripheral blood (PB) were examined to determine possible TNF toxicity. There was no significant difference in tV or tW between LLC minus (-) TNF and p75KD/LLC-TNF tumors. Compared to 3 control groups, p75KD/LLC+TNF showed >2-5-fold decreases in tV (p<0.001) and tW (p<0.0001). There was no difference in tV or tW end of study vs. before injections in p75KD/LLC+TNF group. In 3 other groups tV and tW were increased 2.7-4.5-fold (p<0.01, p<0.0002 and p<0.0001). Pathological examination revealed that 1/3 of p75KD/LLC+rmTNF tumors were 100% necrotic, the remaining revealed 40-60% necrosis. No toxicity was detected in bone marrow, spleen and peripheral blood. We concluded that blocking TNFR2/p75 in LLCs combined with intra-tumoral rmTNF injections inhibit LLC tumor growth. This could represent a novel and effective therapy against lung neoplasms and a new paradigm in cancer therapeutics.

PI3Kδ inhibition reduces TNF secretion and neuroinflammation in a mouse cerebral stroke model

Stroke is a major cause of death worldwide and the leading cause of permanent disability. Although reperfusion is currently used as treatment, the restoration of blood flow following ischaemia elicits a profound inflammatory response mediated by proinflammatory cytokines such as tumour necrosis factor (TNF), exacerbating tissue damage and worsening the outcomes for stroke patients. Phosphoinositide 3-kinase delta (PI3Kδ) controls intracellular TNF trafficking in macrophages and therefore represents a prospective target to limit neuroinflammation. Here we show that PI3Kδ inhibition confers protection in ischaemia/reperfusion models of stroke. In vitro, restoration of glucose supply following an episode of glucose deprivation potentiates TNF secretion from primary microglia-an effect that is sensitive to PI3Kδ inhibition. In vivo, transient middle cerebral artery occlusion and reperfusion in kinase-dead PI3Kδ (p110δ(D910A/D910A)) or wild-type mice pre- or post-treated with the PI3Kδ inhibitor CAL-101, leads to reduced TNF levels, decreased leukocyte infiltration, reduced infarct size and improved functional outcome. These data identify PI3Kδ as a potential therapeutic target in ischaemic stroke.

7,8-Dihydroxyflavone attenuates the release of pro-inflammatory mediators and cytokines in lipopolysaccharide-stimulated BV2 microglial cells through the suppression of the NF-κB and MAPK signaling pathways

7,8-Dihydroxyflavone (7,8-DHF), a member of the flavonoid family, has received considerable attention as a selective tyrosine kinase receptor B agonist. However, the pharmacological mechanisms responsible for its anti-inflammatory activities in microglial cells have yet to be elucidated. In this study, we evaluated the anti-inflammatory effects of this compound on the production of inflammatory mediators and cytokines in lipopolysaccharide (LPS)-stimulated murine BV2 microglial cells. At non-toxic concentrations, 7,8-DHF attenuated the production of nitric oxide (NO) and prostaglandin E2 (PGE2), by inhibiting inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, respectively. Furthermore, the release and expression of inflammatory cytokines, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), were inhibited by 7,8-DHF. In addition, 7,8-DHF suppressed nuclear factor-κB (NF-κB) translocation and its transcriptional activity by blocking IκB (IκB)-α degradation; in addition, it exerted suppressive effects on the phosphorylation of mitogen-activated protein kinases (MAPKs). These results indicate that 7,8-DHF possesses therapeutic potential against neurodegenerative diseases that involve microglial activation.

Minocycline attenuates brain tissue levels of TNF-α produced by neurons after prolonged hypothermic cardiac arrest in rats

Neuro-cognitive disabilities are a well-recognized complication of hypothermic circulatory arrest. We and others have reported that prolonged cardiac arrest (CA) produces neuronal death and microglial proliferation and activation that are only partially mitigated by hypothermia. Microglia, and possibly other cells, are suggested to elaborate tumor necrosis factor alpha (TNF-α), which can trigger neuronal death cascades and exacerbate edema after CNS insults. Minocycline is neuroprotective in some brain ischemia models in part by blunting the microglial response. We tested the hypothesis that minocycline would attenuate neuroinflammation as reflected by brain tissue levels of TNF-α after hypothermic CA in rats. Rats were subjected to rapid exsanguination, followed by a 6 min normothermic CA. Hypothermia (30 °C) was then induced by an aortic saline flush. After a total of 20 min CA, resuscitation was achieved via cardiopulmonary bypass (CPB). After 5 min reperfusion, minocycline (90 mg kg−1; n = 6) or vehicle (PBS; n = 6) was given. Hypothermia (34 °C) was maintained for 6 h. Rats were sacrificed at 6 or 24 h. TNF-α was quantified (ELISA) in four brain regions (cerebellum, CEREB; cortex, CTX; hippocampus, HIP; striatum, STRI). Naïve rats (n = 6) and rats subjected to the same anesthesia and CPB but no CA served as controls (n = 6). Immunocytochemistry was used to localize TNF-α. Naïve rats and CPB controls had no detectable TNF-α in any brain region. CA markedly increased brain TNF-α. Regional differences were seen, with the highest TNF-α levels in striatum in CA groups (10-fold higher, P < 0.05 vs. all other brain regions). TNF-α was undetectable at 24 h. Minocycline attenuated TNF-α levels in CTX, HIP and STRI (P < 0.05). TNF-α showed unique co-localization with neurons. In conclusion, we report region-dependent early increases in brain TNF-α levels after prolonged hypothermic CA, with maximal increases in striatum. Surprisingly, TNF-α co-localized in neurons and not microglia. Minocycline attenuated TNF-α by approximately 50% but did not totally ablate its production. That minocycline decreased brain TNF-α levels suggests that it may represent a therapeutic adjunct to hypothermia in CA neuroprotection. University of Pittsburgh IACUC 0809278B-3.

TNF-α/NF-κB signaling in the CNS: possible connection to EPHB2

Tumor necrosis factor-alpha, TNF-α, is a cytokine that is a well-known factor in multiple disease conditions and is recognized for its major role in central nervous system signaling. TNF-α signaling is most commonly associated with neurotoxicity, but in some conditions it has been found to be neuroprotective. TNF-α has long been known to induce nuclear factor-kappa B, NF-κB, signaling by, in most cases, translocating the p65 (RelA) DNA binding factor to the nucleus. p65 is a key member of NF-κB, which is well established as a family of transcription factors that regulates many signaling events, including growth and process development, in neuronal cell populations. NF-κB has been shown to affect both the receiving aspect of neuronal signaling events in dendritic development as well as the sending of neuronal signals in axonal development. In both cases, NK-κB functions as a promoter and/or inhibitor of growth, depending on the environmental conditions and signaling cascade. In addition, NF-κB is involved in memory formation or neurogenesis, depending on the region of the brain in which the signaling occurs. The ephrin (Eph) receptor family represents a subfamily of receptor tyrosine kinases, RTKs, which received much attention due to its potential involvement in neuronal cell health and function. There are two subsets of ephrin receptors, Eph A and Eph B, each with distinct functions in cardiovascular and skeletal development and axon guidance and synaptic plasticity. The presence of multiple binding sites for NF-κB within the regulatory region of EphB2 gene and its potential regulation by NF-κB pathway suggests that TNF-α may modulate EphB2 via NF-κB and that this may contribute to the neuroprotective activity of TNF-α.

The specific PKR inhibitor C16 prevents apoptosis and IL-1β production in an acute excitotoxic rat model with a neuroinflammatory component

The double-stranded RNA-dependent protein kinase (PKR), an apoptotic inducer, regulates much pro-inflammatory cytokine production. The purpose of this study was to evaluate in vivo the effects of the specific PKR inhibitor C16 in the striatum in an acute excitotoxic rat model with an important neuroinflammatory component. Inflammation was induced by unilateral striatal injection of quinolinic acid (QA) in 10-week-old normotensive rats. Animals were separated into groups receiving either vehicle or C16 for both sham and QA rats. The effects were assessed in ipsi- and contralateral striata by immunoblotting for PKR activation, by Luminex assay for cytokine levels and by immunofluorescent staining for cleaved caspase-3 to detect neuronal apoptosis. The highest dose of C16 (600μg/kg; C16-2) in QA rats reduced expression of the active catalytic domain of the PKR vs. that in vehicle-injected QA rats. A robust increase of IL-1β levels on the contralateral side of QA rats was prevented by C16-2 (97% inhibition). Macroscopic and microscopic observation of cerebral tissue (Hematoxylin & Eosin staining) revealed that tissue integrity was more preserved with C16-2 treatment than its vehicle in QA rats. Furthermore, C16-2 treatment decreased by 47% the neuronal loss and by 37% the number of positive cleaved caspase-3 neurons induced by QA injection. In conclusion, C16 prevented not only the PKR-induced neuronal loss but also the inflammatory response in this acute excitotoxic in vivo model, highlighting its promising neuroprotective properties to rescue acute brain lesions.

TNF-α type 2 receptor mediates renal inflammatory response to chronic angiotensin II administration with high salt intake in mice

Tumor necrosis factor-alpha (TNF-α) has been implicated in salt-sensitive hypertension and renal injury (RI) induced by angiotensin II (ANG II). To determine the receptor type of TNF-α involved in this mechanism, we evaluated the responses to chronic ANG II infusion (25 ng/min by implanted minipump) given with high-salt diet (HS; 4% NaCl) for 2 wk in gene knockout mice for TNF-α receptor type 1 (TNFR1KO; n = 6) and type 2 (TNFR2KO; n = 6) and compared the responses with those in wild-type (WT; C57BL/6; n = 6) mice. Blood pressure in these mice was measured by implanted radiotelemetry as well as by tail-cuff plethysmography. RI responses were assessed by measuring macrophage cell infiltration (CD68(+) immunohistochemistry), glomerulosclerosis (PAS staining), and interstitial fibrosis (Gomori's trichrome staining) in renal tissues at the end of the treatment period. The increase in mean arterial pressure induced by ANG II + HS treatment was not different in these three groups of mice (TNFR1KO, 114 ± 1 to 161 ± 7 mmHg; TNFR2KO, 113 ± 1 to 161 ± 3 mmHg; WT, 110 ± 3 to 154 ± 3 mmHg). ANG II + HS-induced RI changes were similar in TNFR1KO mice but significantly less in TNFR2KO mice (macrophage infiltration, 0.02 ± 0.01 vs. 1.65 ± 0.45 cells/mm(2); glomerulosclerosis, 26.3 ± 2.6 vs. 35.7 ± 2.2% area; and interstitial fibrosis, 5.2 ± 0.6 vs. 8.1 ± 1.1% area) compared with the RI changes in WT mice. The results suggest that a direct activation of TNF-α receptors may not be required in inducing hypertensive response to chronic ANG II administration with HS intake, but the induction of inflammatory responses leading to renal injury are mainly mediated by TNF-α receptor type 2.

TLR9 bone marrow chimeric mice define a role for cerebral TNF in neuroprotection induced by CpG preconditioning

Systemic preconditioning with the TLR9 ligand CpG induces neuroprotection against brain ischemic injury through a tumor necrosis factor (TNF)-dependent mechanism. It is unclear how systemic administration of CpG engages the brain to induce the protective phenotype. To address this, we created TLR9-deficient reciprocal bone marrow chimeric mice lacking TLR9 on either hematopoietic cells or radiation-resistant cells of nonhematopoietic origin. We report that wild-type mice reconstituted with TLR9-deficient hematopoietic cells failed to show neuroprotection after systemic CpG preconditioning. Further, while hematopoietic expression of TLR9 is required for CpG-induced neuroprotection it is not sufficient to restore protection to TLR9-deficient mice that are reconstituted with hematopoietic cells bearing TLR9. To determine whether the absence of protection was associated with TNF, we examined TNF levels in the systemic circulation and the brain. We found that although TNF is required for CpG preconditioning, systemic TNF levels did not correlate with the protective phenotype. However, induction of cerebral TNF mRNA required expression of TLR9 on both hematopoietic and nonhematopoietic cells and correlated with neuroprotection. In accordance with these results, we show the therapeutic potential of intranasal CpG preconditioning, which induces brain TNF mRNA and robust neuroprotection with no concomitant increase in systemic levels of TNF.

Cytokines in radiobiological responses: a review

Cytokines function in many roles that are highly relevant to radiation research. This review focuses on how cytokines are structurally organized, how they are induced by radiation, and how they orchestrate mesenchymal, epithelial and immune cell interactions in irradiated tissues. Pro-inflammatory cytokines are the major components of immediate early gene programs and as such can be rapidly activated after tissue irradiation. They converge with the effects of ionizing radiation in that both generate free radicals including reactive oxygen and nitrogen species (ROS/RNS). "Self" molecules secreted or released from cells after irradiation feed the same paradigm by signaling for ROS and cytokine production. As a result, multilayered feedback control circuits can be generated that perpetuate the radiation tissue damage response. The pro-inflammatory phase persists until such times as perceived challenges to host integrity are eliminated. Antioxidant, anti-inflammatory cytokines then act to restore homeostasis. The balance between pro-inflammatory and anti-inflammatory forces may shift to and fro for a long time after radiation exposure, creating waves as the host tries to deal with persisting pathogenesis. Individual cytokines function within socially interconnected groups to direct these integrated cellular responses. They hunt in packs and form complex cytokine networks that are nested within each other so as to form mutually reinforcing or antagonistic forces. This yin-yang balance appears to have redox as a fulcrum. Because of their social organization, cytokines appear to have a considerable degree of redundancy and it follows that an elevated level of a specific cytokine in a disease situation or after irradiation does not necessarily implicate it causally in pathogenesis. In spite of this, "driver" cytokines are emerging in pathogenic situations that can clearly be targeted for therapeutic benefit, including in radiation settings. Cytokines can greatly affect intrinsic cellular radiosensitivity, the incidence and type of radiation tissue complications, bystander effects, genomic instability and cancer. Minor and not so minor, polymorphisms in cytokine genes give considerable diversity within populations and are relevant to causation of disease. Therapeutic intervention is made difficult by such complexity; but the potential prize is great.