Interleukin-1β orchestrates underlying inflammatory responses in microglia via Krüppel-like factor 4

The effects of different types of exercises on cognition in older persons with mild cognitive impairment: A systematic review and meta-analysis

PURPOSE

This systematic review with meta-analysis aims to analyze the effects of different types of exercise on cognition, neuroprotective and neuroinflammatory blood markers in older adults with mild cognitive impairment (MCI).

METHODS

Relevant studies were identified using PubMED, SPORTDiscuss, Web of Science, Scopus, and PsycInfo databases. Methodological quality assessment of the studies was done with modified Downs and Black checklist. Data obtained from the included studies was analyzed using Comprehensive Meta-Analysis 4.0 software and results were reported using the random effects method.

RESULTS

A total of twenty-three studies were identified. The findings were summarized as change in cognitive function after the exercise interventions in general and after each type of exercise. On average, the exercise intervention revealed an effect size (ES): 1.165; 0.741 to 1.589 (95% Confidence Interval (CI); p < 0.001); aerobic exercise ES: 1.442; 0.624 to 2.260 (95 %CI); p = 0.001; Multimodal ES: 0,856; 0.366 to 1.346 (95 % CI); p = 0.001 and resistance exercise ES: 1.229; 0.339 to 2.120 (95 % CI); p = 0.007. In addition, we observed significant small ES: -0.475; -0.817 to -0.134 (95 %CI); p = 0.006, I2= 0 %; τ2 = 0 of exercise effects on Tumor Necrosis Factor-α (TNF-α) and non-significant large ES:0.952; -0.238 to 2.142 (95 %CI); p = 0.117 on Brain Derived Neurotrophic Factor (BDNF) in persons with MCI.

CONCLUSION

The present study revealed the existence of a large positive effect of overall exercise intervention on cognitive function and a small effect on TNF-α in old people with MCI. Additionally, this study demonstrates that aerobic and resistance exercises had similar larger positive effects and were better than multimodal exercise on increasing cognition in older persons with MCI.

A review of KLF4 and inflammatory disease: Current status and future perspective

Inflammation is the response of the human body to injury, infection, or other abnormal states, which is involved in the development of many diseases. As a member of the Krüppel-like transcription factors (KLFs) family, KLF4 plays a crucial regulatory role in physiological and pathological processes due to its unique dual domain of transcriptional activation and inhibition. A growing body of evidence has demonstrated that KLF4 plays a pivotal role in the pathogenesis of various inflammatory disorders, including inflammatory bowel disease, osteoarthritis, renal inflammation, pneumonia, neuroinflammation, and so on. Consequently, KLF4 has emerged as a promising new therapeutic target for inflammatory diseases. This review systematically generalizes the molecular regulatory network, specific functions, and mechanisms of KLF4 to elucidate its complex roles in inflammatory diseases. An in-depth study on the biological function of KLF4 is anticipated to offer a novel research perspective and potential intervention strategies for inflammatory diseases.

Krüppel-like factors: potential roles in blood-brain barrier dysfunction and epileptogenesis

Epilepsy is a chronic and debilitating neurological disorder, known for the occurrence of spontaneous and recurrent seizures. Despite the availability of antiseizure drugs, 30% of people with epilepsy experience uncontrolled seizures and drug resistance, evidencing that new therapeutic options are required. The process of epileptogenesis involves the development and expansion of tissue capable of generating spontaneous recurrent seizures, during which numerous events take place, namely blood-brain barrier (BBB) dysfunction, and neuroinflammation. The consequent cerebrovascular dysfunction results in a lower seizure threshold, seizure recurrence, and chronic epilepsy. This suggests that improving cerebrovascular health may interrupt the pathological cycle responsible for disease development and progression. Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors, encountered in brain endothelial cells, glial cells, and neurons. KLFs are known to regulate vascular function and changes in their expression are associated with neuroinflammation and human diseases, including epilepsy. Hence, KLFs have demonstrated various roles in cerebrovascular dysfunction and epileptogenesis. This review critically discusses the purpose of KLFs in epileptogenic mechanisms and BBB dysfunction, as well as the potential of their pharmacological modulation as therapeutic approach for epilepsy treatment.

Development and characterisation of mgTHP-1, a novel in vitro model for neural macrophages with microglial characteristics

Neuroinflammation is primarily characterised by activation of the brain's resident macrophages - the microglia. However, other central nervous system (CNS) cells also contribute to this response, including the astrocytes and endothelial cells. In addition, there is infiltration into the CNS of peripherally derived immune cells. Together these cells mediate inflammation by the production of cytokines, chemokines, reactive oxygen species, and secondary messengers, and enacting of the appropriate response to those signals. However, deciphering the specific contributions of each cell type has been challenging. Studying CNS cell biology is often challenging, as the isolation of primary cells is not always feasible, and differentiation towards microglia-like cells is complex. Here, we demonstrate a novel method whereby THP-1 monocytic cells are differentiated into neural macrophage cells with microglia-like cell characteristics. The cells, designated mgTHP-1, show typical morphological and gene expression patterns of resident CNS macrophages and functionally respond to inflammatory stimuli by producing inflammatory cytokines. Furthermore, with the addition of Vicenin-2 (an anti-inflammatory flavonoid) such responses can be reversed. This novel cell model will allow further investigations, and hence insights, into the neuroinflammatory mechanisms associated with CNS diseases.

Hair and cord blood element levels and their relationship with air pollution, dietary intake, gestational diabetes mellitus, and infant neurodevelopment

BACKGROUND & AIMS

Exposure to a range of elements, air pollution, and specific dietary components in pregnancy has variously been associated with gestational diabetes mellitus (GDM) risk or infant neurodevelopmental problems. We measured a range of pregnancy exposures in maternal hair and/or infant cord serum and tested their relationship to GDM and infant neurodevelopment.

METHODS

A total of 843 pregnant women (GDM = 224, Non-GDM = 619) were selected from the Complex Lipids in Mothers and Babies cohort study. Forty-eight elements in hair and cord serum were quantified using inductively coupled plasma-mass spectrometry analysis. Binary logistic regression was used to estimate the associations between hair element concentrations and GDM risk, while multiple linear regression was performed to analyze the relationship between hair/cord serum elements and air pollutants, diet exposures, and Bayley Scales of infant neurodevelopment at 12 months of age.

RESULTS

After adjusting for maternal age, BMI, and primiparity, we observed that fourteen elements in maternal hair were associated with a significantly increased risk of GDM, particularly Ta (OR = 9.49, 95% CI: 6.71, 13.42), Re (OR = 5.21, 95% CI: 3.84, 7.07), and Se (OR = 5.37, 95% CI: 3.48, 8.28). In the adjusted linear regression model, three elements (Rb, Er, and Tm) in maternal hair and infant cord serum were negatively associated with Mental Development Index scores. For dietary exposures, elements were positively associated with noodles (Nb), sweetened beverages (Rb), poultry (Cs), oils and condiments (Ca), and other seafood (Gd). In addition, air pollutants PM2.5 (LUR) and PM10 were negatively associated with Ta and Re in maternal hair.

CONCLUSIONS

Our findings highlight the potential influence of maternal element exposure on GDM risk and infant neurodevelopment. We identified links between levels of these elements in both maternal hair and infant cord serum related to air pollutants and dietary factors.

Systemic administration of Shikonin ameliorates cognitive impairment and neuron damage in NPSLE mice

Shikonin is an anti-inflammatory natural herbal drug extracted from Lithospermum erythrorhizon and its therapeutic effect on neuropsychiatric systemic lupus erythematosus (NPSLE) is yet unknown. In our study, Shikonin significantly reversed the cognitive impairment and alleviated the brain tissue damage in NPSLE mice. The permeability of blood-brain barrier was also verified to be repaired in Shikonin-treated NPSLE mice. In particular, we found that Shikonin alleviated neuroinflammation through inhibiting β-catenin signaling pathway, thereby depressing the activation of microglia and the loss of neuronal synapses. Overall, Shikonin may be a promising candidate drug for NPSLE through diminishing neuroinflammation and repairing neuron damage.

GKLF, a transcriptional activator of Txnip, drives microglia activation in kainic acid-induced murine models of epileptic seizures

Neuroinflammation is a major component of epilepsy. Gut-enriched Kruppel-like factor (GKLF), a transcription factor of Kruppel-like factor family, has been reported to promote microglia activation and mediate neuroinflammation. However, the role of GKLF in epilepsy remains poorly characterized. This study focused on the function of GKLF in neuron loss and neuroinflammation in epilepsy and the molecular mechanism underlying microglia activation induced by GKLF upon lipopolysaccharides (LPS) treatment. An experimental epileptic model was induced by an intraperitoneal injection of 25 mg/kg kainic acid (KA). Lentivirus vectors (Lv) carrying Gklf CDS or short hairpin RNA targeting Gklf (shGKLF) was injected into the hippocampus, resulting in Gklf overexpression or knockdown in the hippocampus. BV-2 cells were co-infected with Lv-shGKLF or/and Lv carrying thioredoxin interacting protein (Txnip) CDS for 48 h and treated with 1 μg/mL LPS for 24 h. Results showed that GKLF enhanced KA-induced neuronal loss, pro-inflammatory cytokine secretion, activation of NOD-like receptor protein-3 (NLRP3) inflammasomes and microglia, and TXNIP expression in the hippocampus. GKLF inhibition showed negative effects on LPS-induced microglia activation, as evidenced by reduced pro-inflammatory cytokine secretion and activation of NLRP3 inflammasomes. GKLF bound to Txnip promoter and increased TXNIP expression in LPS-activated microglia. Interestingly, Txnip overexpression reversed the inhibitory effect of Gklf knockdown on microglia activation. These findings indicated that GKLF was involved in microglia activation via TXNIP. This study demonstrates the underlying mechanism of GKLF in the pathogenesis of epilepsy and uncovers that GKLF inhibition may be a therapeutic strategy for epilepsy treatment.

Integrated transcriptomics and lipidomics investigation of the mechanism underlying the gastrointestinal mucosa damage of Loropetalum chinense (R.Br.) and its representative component

BACKGROUND

Loropetalum chinensis (R.Br) Oliv (Bhjm), a Chinese folk herbal medicine, was traditionally used in the treatment of wound bleeding and skin ulcers. A new drug named JIMUSAN granules used for gastrosia was developed by our group, and clinical trials have been approved. However, as the principal herb, the material basis and underlying mechanisms of Bhjm in attenuating gastrointestinal mucosa damage (GMD) remain to be systemically illuminated.

PURPOSE

An integrated strategy was used to explore the therapeutic effects and mechanisms of Bhjm and ellagic acid (EA) on GMD zebrafish, using network pharmacology, transcriptomics, lipidomics, and real-time quantitative PCR (RT-qPCR) verification.

METHODS

First, network pharmacological analysis was used to infer the major effective constituents and targets of Bhjm. Ultra high performance liquid chromatography-linear ion trap/orbitrap high resolution mass spectrometry (UHPLC-LTQ-Orbitrap HRMS) and ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) were employed to identify the chemical constituents and quantify the different types of constituents. Second, zebrafish model of GMD was established by using 2,4,6-trinitrobenzenesulfonic acid (TNBS) to evaluate the efficacy of Bhjm and EA. The potential mechanism was examined by integrated transcriptomics and lipidomics analysis. Finally, validation tests were implemented using RT-qPCR.

RESULTS

In this study, targets indentified by network pharmacology were related to inflammation and mucosal damage. Ten representative components that interacted with these targets were simultaneously determined by UHPLC-MS/MS. Sixty four compounds were identified or tentatively characterized, most of which were flavonoids and polyphenols. Bhjm and EA alleviated mucosal damage and reduced inflammation in a TNBS-induced zebrafish GMD model, indicating that EA was the main active compounds. Eight common differentially expressed genes were downregulated by Bhjm and EA, as determined by transcriptomics analysis. Lipidomics analysis confirmed 12 differential lipids, including phosphatidylcholine (PC) and triglyceride (TG). Further network enrichment analysis demonstrated that differential lipid metabolism was regulated by klf4 and hist1h2ba, and were validated by RT-qPCR.

CONCLUSION

In our study, the chemical profile of Bhjm was clarified. Moreover, the GMD repair effect and the mechanism of Bhjm and EA was comprehensively analyzed for the first time, involving inflammation and lipid metabolism. Collectively, these findings will be significantly helpful for deeply exploring the clinical application value of Bhjm.

Small molecule inhibiting microglial nitric oxide release could become a potential treatment for neuroinflammation

Microglia are the immune effector cells of the central nervous system (CNS) and react to pathologic events with a complex process including the release of nitric oxide (NO). NO is a free radical, which is toxic for all cells at high concentrations. To target an exaggerated NO release, we tested a library of 16 544 chemical compounds for their effect on lipopolysaccharide (LPS)-induced NO release in cell line and primary neonatal microglia. We identified a compound (C1) which significantly reduced NO release in a dose-dependent manner, with a low IC50 (252 nM) and no toxic side effects in vitro or in vivo. Target finding strategies such as in silico modelling and mass spectroscopy hint towards a direct interaction between C1 and the nitric oxide synthase making C1 a great candidate for specific intra-cellular interaction with the NO producing machinery.

Genetic deletion of Krüppel-like factor 11 aggravates traumatic brain injury

BACKGROUND

The long-term functional recovery of traumatic brain injury (TBI) is hampered by pathological events, such as parenchymal neuroinflammation, neuronal death, and white matter injury. Krüppel-like transcription factor 11 (KLF 11) belongs to the zinc finger family of transcription factors and actively participates in various pathophysiological processes in neurological disorders. Up to now, the role and molecular mechanisms of KLF11 in regulating the pathogenesis of brain trauma is poorly understood.

METHODS

KLF11 knockout (KO) and wild-type (WT) mice were subjected to experimental TBI, and sensorimotor and cognitive functions were evaluated by rotarod, adhesive tape removal, foot fault, water maze, and passive avoidance tests. Brain tissue loss/neuronal death was examined by MAP2 and NeuN immunostaining, and Cresyl violet staining. White matter injury was assessed by Luxol fast blue staining, and also MBP/SMI32 and Caspr/Nav1.6 immunostaining. Activation of cerebral glial cells and infiltration of blood-borne immune cells were detected by GFAP, Iba-1/CD16/32, Iba-1/CD206, Ly-6B, and F4/80 immunostaining. Brian parenchymal inflammatory cytokines were measured with inflammatory array kits.

RESULTS

Genetic deletion of KLF11 worsened brain trauma-induced sensorimotor and cognitive deficits, brain tissue loss and neuronal death, and white matter injury in mice. KLF11 genetic deficiency in mice also accelerated post-trauma astrocytic activation, promoted microglial polarization to a pro-inflammatory phenotype, and increased the infiltration of peripheral neutrophils and macrophages into the brain parenchyma. Mechanistically, loss-of-KLF11 function was found to directly increase the expression of pro-inflammatory cytokines in the brains of TBI mice.

CONCLUSION

KLF11 acts as a novel protective factor in TBI. KLF11 genetic deficiency in mice aggravated the neuroinflammatory responses, grey and white matter injury, and impaired long-term sensorimotor and cognitive recovery. Elucidating the functional importance of KLF11 in TBI may lead us to discover novel pharmacological targets for the development of effective therapies against brain trauma.

Normalization of Neuroinflammation: A New Strategy for Treatment of Persistent Pain and Memory/Emotional Deficits in Chronic Pain

Chronic pain, which affects around 1/3 of the world population and is often comorbid with memory deficit and mood depression, is a leading source of suffering and disability. Studies in past decades have shown that hyperexcitability of primary sensory neurons resulting from abnormal expression of ion channels and central sensitization mediated pathological synaptic plasticity, such as long-term potentiation in spinal dorsal horn, underlie the persistent pain. The memory/emotional deficits are associated with impaired synaptic connectivity in hippocampus. Dysregulation of numerous endogenous proteins including receptors and intracellular signaling molecules is involved in the pathological processes. However, increasing knowledge contributes little to clinical treatment. Emerging evidence has demonstrated that the neuroinflammation, characterized by overproduction of pro-inflammatory cytokines and glial activation, is reliably detected in humans and animals with chronic pain, and is sufficient to induce persistent pain and memory/emotional deficits. The abnormal expression of ion channels and pathological synaptic plasticity in spinal dorsal horn and in hippocampus are resulting from neuroinflammation. The neuroinflammation is initiated and maintained by the interactions of circulating monocytes, glial cells and neurons. Obviously, unlike infectious diseases and cancer, which are caused by pathogens or malignant cells, chronic pain is resulting from alterations of cells and molecules which have numerous physiological functions. Therefore, normalization (counterbalance) but not simple inhibition of the neuroinflammation is the right strategy for treating neuronal disorders. Currently, no such agent is available in clinic. While experimental studies have demonstrated that intracellular Mg²⁺ deficiency is a common feature of chronic pain in animal models and supplement Mg²⁺ are capable of normalizing the neuroinflammation, activation of upregulated proteins that promote recovery, such as translocator protein (18k Da) or liver X receptors, has a similar effect. In this article, relevant experimental and clinical evidence is reviewed and discussed.

The protective effect of Palmatine on depressive like behavior by modulating microglia polarization in LPS-induced mice

The purpose of the present study was to evaluate the protective effect of Palmatine on LPS-induced depressive like behavior and explore its potential mechanism. The mice were intragastrically treated with Fluoxetine or Palmatine once daily for 1 week. After the last drug administration, the mice were intraperitoneally challenged with LPS and suffered for Sucrose preference test, Tail suspension test, Forced swimming test and Open field test. The pro-inflammatory biomarkers were measured by ELISA, qPCR, WB and immunofluorescence. As a result, the administration of Palmatine effectively lessened depressive-like behavior. Palmatine could decrease the levels of pro-inflammatory cytokines TNF-α, IL-6, the expressions of CD68, iNOS mRNA, as well as increase the levels of anti-inflammatory cytokines IL-4, IL-10, the expressions of CD206, Arg1 mRNA, Ym1 mRNA both in LPS-induced mice and in LPS-induced BV2 cells. The beneficial effect of Palmatine might be attributed to the suppression of M1 microglia polarization and the promotion of M2 microglia polarization via PDE4B/KLF4 signaling. The similar results were observed in CUMS-induced depressive mice. The transfection with PDE4B SiRNA or KLF4 SiRNA indicated that PDE4B and KLF4 were both involved in the Palmatine-mediated microglia polarization. Molecular docking indicated that Palmatine could interact with PDE4B. In conclusion, this research demonstrated that Palmatine attenuated depressive like behavior by modulating microglia polarization via PDE4B/KLF4 signaling.

Neuroinflammation as an etiological trigger for depression comorbid with inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) suffer from depression at higher rates than the general population. An etiological trigger of depressive symptoms is theorised to be inflammation within the central nervous system. It is believed that heightened intestinal inflammation and dysfunction of the enteric nervous system (ENS) contribute to impaired intestinal permeability, which facilitates the translocation of intestinal enterotoxins into the blood circulation. Consequently, these may compromise the immunological and physiological functioning of distant non-intestinal tissues such as the brain. In vivo models of colitis provide evidence of increased blood–brain barrier permeability and enhanced central nervous system (CNS) immune activity triggered by intestinal enterotoxins and blood-borne inflammatory mediators. Understanding the immunological, physiological, and structural changes associated with IBD and neuroinflammation may aid in the development of more tailored and suitable pharmaceutical treatment for IBD-associated depression.

The Causal Role of Magnesium Deficiency in the Neuroinflammation, Pain Hypersensitivity and Memory/Emotional Deficits in Ovariectomized and Aged Female Mice

Purpose

Postmenopausal women often suffer from chronic pain, memory decline and mood depression. The mechanisms underlying the neuronal disorders are not fully understood, and effective treatment is still lacking.

Methods

Oral administration of magnesium-L-threonate was tested to treat the neuronal disorders in ovariectomized and aged female mice. The pain hypersensitivity, memory function and depression-like behaviors were measured with a set of behavioral tests. Western blots, immunochemistry and in situ hybridization were used to assess molecular changes.

Results

Chronic oral administration of magnesium-L-threonate substantially prevented or reversed the chronic pain and memory/emotional deficits in both ovariectomized and aged female mice. We found that phospho-p65, an active form of nuclear factor-kappaB, tumor necrosis factor-alpha and interleukin-1 beta were significantly upregulated in the neurons of dorsal root ganglion, spinal dorsal horn and hippocampus in ovariectomized and aged mice. The microglia and astrocytes were activated in spinal dorsal horn and hippocampus. Calcitonin gene–related peptide, a marker for peptidergic C-fibers, was upregulated in dorsal horn, which is associated with potentiation of C-fiber-mediated synaptic transmission in the model mice. In parallel with neuroinflammation and synaptic potentiation, free Mg²⁺ levels in plasma, cerebrospinal fluid and in dorsal root ganglion neurons were significantly reduced. Oral magnesium-L-threonate normalized the neuroinflammation, synaptic potentiation and Mg²⁺ deficiency, but did not affect the estrogen decline in ovariectomized and aged mice. Furthermore, in cultured dorsal root ganglion neurons, estrogen at physiological concentration elevated intracellular Mg²⁺, and downregulated phospho-p65, tumor necrosis factor-alpha and interleukin-1 beta exclusively in the presence of extracellular Mg²⁺.

Conclusion

Estrogen decline in menopause may cause neuroinflammation by reducing intracellular Mg²⁺ in neurons, leading to chronic pain, memory/emotional deficits. Supplement Mg²⁺ by oral magnesium-L-threonate may be a novel approach for treating menopause-related neuronal disorders.

Zinc Finger Proteins in Neuro-Related Diseases Progression

Zinc finger proteins (ZNF) are among the most abundant proteins in eukaryotic genomes. It contains several zinc finger domains that can selectively bind to certain DNA or RNA and associate with proteins, therefore, ZNF can regulate gene expression at the transcriptional and translational levels. In terms of neurological diseases, numerous studies have shown that many ZNF are associated with neurological diseases. The purpose of this review is to summarize the types and roles of ZNF in neuropsychiatric disorders. We will describe the structure and classification of ZNF, then focus on the pathophysiological role of ZNF in neuro-related diseases and summarize the mechanism of action of ZNF in neuro-related diseases.

Magnolol attenuates depressive-like behaviors by polarizing microglia towards the M2 phenotype through the regulation of Nrf2/HO-1/NLRP3 signaling pathway

PURPOSE

Magnolol (MA) exhibits anti-depressant effect by inhibiting inflammation. However, its effect on microglia polarization remains not fully understood. Herein, our study was performed to evaluate the effect of MA on microglia polarization in chronic unpredictable mild stress (CUMS)-induced depression and explore its potential mechanism.

STUDY DESIGN

The CUMS procedure was conducted, and the mice were intragastrically treated with MA. BV2 cells were pretreated with MA prior to LPS/ATP challenge.

METHODS

The levels of TNF-α, IL-1β, IL-6 and IL-4, IL-10 in brain and BV2 cells were examined by ELISA. The mRNA expressions of Arg1, Ym1, Fizz1 and Klf4 in brains were measured. ROS content was determined using flow cytometry. Immunofluorescence was employed to evaluate Iba-1 level, Nrf2 nuclear translocation, Iba-1⁺CD16/32⁺ and Iba-1⁺CD206⁺ cell population. The protein expressions of Nrf2, HO-1, NLRP3, caspase-1 p20 and IL-1β in brains and BV2 cells were investigated by western blot. Nrf2 siRNA was induced in experiments to explore the role of Nrf2 in MA-mediated microglia polarization. The ubiquitination of Nrf2 was visualized by Co-IP.

RESULTS

The treatment with MA notably relieved depressive like behaviors, suppressed pro-inflammatory cytokines, promoted anti-inflammatory cytokines and the transcription of M2 phenotype microglia-specific indicators. MA upregulated the expression of Nrf2, HO-1, downregulated the expression of NLRP3, caspase-1 p20, IL-1β both in vivo and in vitro. MA also reduced ROS concentration, promoted Nrf2 nucleus translocation and prevented Nrf2 ubiquitination. Nrf2 Knockdown by siRNA abolished the MA-mediated microglia polarization.

CONCLUSION

The present research demonstrated that MA attenuated CUMS-stimulated depression by inhibiting M1 polarization and inducing M2 polarization via Nrf2/HO-1/NLRP3 signaling.

IL-1β induces expression of proinflammatory cytokines and migration of human colon cancer cells through upregulation of SIRT1

SIRT1 is a mammalian NAD⁺-dependent deacetylase, which is known to be involved in various physiological events, such as adaptive response to environmental stresses including caloric restriction, as well as in aging and cellular senescence. However, recent studies have revealed overexpression of SIRT1 in many different types of human malignancies, particularly colon cancer. Interleukin-1β (IL-1β) is a proinflammatory cytokine that plays a major role in invasiveness, stemness and progression of colon cancer. However, the interaction between IL-1β and SIRT1 in the tumor development and progression remains elusive. In this study, we found that IL-1β induces SIRT1 protein expression in human colon cancer HCT-116 cells. IL-1β-induced SIRT1 upregulation led to enhanced expression of mRNA transcripts of pro-inflammatory cytokines, IL-6 and IL-8 as well as that of IL-1β. Knockdown of SIRT1 prevented IL-1β-induced phosphorylation and nuclear accumulation of c-Jun. Furthermore, pharmacologic inhibition of SIRT1 abrogated clonogenicity and migrative capability of human colon cancer cells stimulated with IL-1β. In summary, IL-1β-induced SIRT1 upregulation stimulates production of proinflammatory cytokines via a nuclear accumulation of c-Jun, leadng to colon cancer growth and progression.

Crosstalk between nonclassical monocytes and alveolar macrophages mediates transplant ischemia-reperfusion injury through classical monocyte recruitment

Primary graft dysfunction (PGD) is the predominant cause of early graft loss following lung transplantation. We recently demonstrated that donor pulmonary intravascular nonclassical monocytes (NCM) initiate neutrophil recruitment. Simultaneously, host-origin classical monocytes (CM) permeabilize the vascular endothelium to allow neutrophil extravasation necessary for PGD. Here, we show that a CCL2-CCR2 axis is necessary for CM recruitment. Surprisingly, although intravital imaging and multichannel flow cytometry revealed that depletion of donor NCM abrogated CM recruitment, single cell RNA sequencing identified donor alveolar macrophages (AM) as predominant CCL2 secretors. Unbiased transcriptomic analysis of murine tissues combined with murine KOs and chimeras indicated that IL-1β production by donor NCM was responsible for the early activation of AM and CCL2 release. IL-1β production by NCM was NLRP3 inflammasome dependent and inhibited by treatment with a clinically approved sulphonylurea. Production of CCL2 in the donor AM occurred through IL-1R-dependent activation of the PKC and NF-κB pathway. Accordingly, we show that IL-1β-dependent paracrine interaction between donor NCM and AM leads to recruitment of recipient CM necessary for PGD. Since depletion of donor NCM, IL-1β, or IL-1R antagonism and inflammasome inhibition abrogated recruitment of CM and PGD and are feasible using FDA-approved compounds, our findings may have potential for clinical translation.

De novo Neurosteroidogenesis in Human Microglia: Involvement of the 18 kDa Translocator Protein

Neuroactive steroids are potent modulators of microglial functions and are capable of counteracting their excessive reactivity. This action has mainly been ascribed to neuroactive steroids released from other sources, as microglia have been defined unable to produce neurosteroids de novo. Unexpectedly, immortalized murine microglia recently exhibited this de novo biosynthesis; herein, de novo neurosteroidogenesis was characterized in immortalized human microglia. The results demonstrated that C20 and HMC3 microglial cells constitutively express members of the neurosteroidogenesis multiprotein machinery-in particular, the transduceosome members StAR and TSPO, and the enzyme CYP11A1. Moreover, both cell lines produce pregnenolone and transcriptionally express the enzymes involved in neurosteroidogenesis. The high TSPO expression levels observed in microglia prompted us to assess its role in de novo neurosteroidogenesis. TSPO siRNA and TSPO synthetic ligand treatments were used to reduce and prompt TSPO function, respectively. The TSPO expression downregulation compromised the de novo neurosteroidogenesis and led to an increase in StAR expression, probably as a compensatory mechanism. The pharmacological TSPO stimulation the de novo neurosteroidogenesis improved in turn the neurosteroid-mediated release of Brain-Derived Neurotrophic Factor. In conclusion, these results demonstrated that de novo neurosteroidogenesis occurs in human microglia, unravelling a new mechanism potentially useful for future therapeutic purposes.

Preeclampsia and Neurodevelopmental Outcomes: Potential Pathogenic Roles for Inflammation and Oxidative Stress?

Preeclampsia (PE) is a common and serious hypertensive disorder of pregnancy that occurs in approximately 3-5% of first-time pregnancies and is a well-known leading cause of maternal and neonatal mortality and morbidity. In recent years, there has been accumulating evidence that in utero exposure to PE acts as an environmental risk factor for various neurodevelopmental disorders, particularly autism spectrum disorder and ADHD. At present, the mechanism(s) mediating this relationship are uncertain. In this review, we outline the most recent evidence implicating a causal role for PE exposure in the aetiology of various neurodevelopmental disorders and provide a novel interpretation of neuroanatomical alterations in PE-exposed offspring and how these relate to their sub-optimal neurodevelopmental trajectory. We then postulate that inflammation and oxidative stress, two prominent features of the pathophysiology of PE, are likely to play a major role in mediating this association. The increased inflammation in the maternal circulation, placenta and fetal circulation in PE expose the offspring to both prenatal maternal immune activation-a risk factor for neurodevelopmental disorders, which has been well-characterised in animal models-and directly higher concentrations of pro-inflammatory cytokines, which adversely affect neuronal development. Similarly, the exaggerated oxidative stress in the mother, placenta and foetus induces the placenta to secrete factors deleterious to neurons, and exposes the fetal brain to directly elevated oxidative stress and thus adversely affects neurodevelopmental processes. Finally, we describe the interplay between inflammation and oxidative stress in PE, and how both systems interact to potentially alter neurodevelopmental trajectory in exposed offspring.

Microglial Activation Modulates Neuroendocrine Secretion During Experimental Sepsis

Sepsis promotes an inflammatory state in the central nervous system (CNS) that may cause autonomic, cognitive, and endocrine changes. Microglia, a resident immune cell of the CNS, is activated in several brain regions during sepsis, suggesting its participation in the central alterations observed in this disease. In this study, we aimed to investigate the role of microglial activation in the neuroendocrine system functions during systemic inflammation. Wistar rats received an intracerebroventricular injection of the microglial activation inhibitor minocycline (100 μg/animal), shortly before sepsis induction by cecal ligation and puncture. At 6 and 24 h after surgery, hormonal parameters, central and peripheral inflammation, and markers of apoptosis and synaptic function in the hypothalamus were analyzed. The administration of minocycline decreased the production of inflammatory mediators and the expression of cell death markers, especially in the late phase of sepsis (24 h). With respect to the endocrine parameters, microglial inhibition caused a decrease in oxytocin and an increase in corticosterone and vasopressin plasma levels in the early phase of sepsis (6 h), while in the late phase, we observed decreased oxytocin and increased ACTH and corticosterone levels compared to septic animals that did not receive minocycline. Prolactin levels were not affected by minocycline administration. The results indicate that microglial activation differentially modulates the secretion of several hormones and that this process is associated with inflammatory mediators produced both centrally and peripherally.

Pertussis Toxin Ameliorates Microglial Activation Associated With Ischemic Stroke

Objective: To investigate the effect and the underlying mechanism of Pertussis toxin (PTX) on microglia in the setting of cerebral ischemia. Methods: We tested the effect of PTX 400 ng/days on middle cerebral artery occlusion stroke model by evaluating the neurologic function, infarct size, microglial distribution, and activation. In parallel, we also tested the effect of PTX on primary cultured microglia by evaluating microglial proliferation, activation, cytokine release, and CX3CR1 expression. Results: PTX reduced the poststroke infarct size, improved the neurologic function as evaluated by Longa score, and reduced microglial aggregation and activation in the infarcted area. Further, PTX significantly decreased lipopolysaccharide-stimulated microglial proliferation, the release of interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α), and the expression of CX3CR1. Interpretation: PTX treatment in stroke reduced microglial accumulation and activation in the infarct zone, resulting in a better functional outcome. The benefits of PTX treatment may be attributed to the reduced production of proinflammatory cytokine such as IL-1β and TNF-α and reduced expression of chemokine CX3CR1.

Human-Induced Neurons from Presenilin 1 Mutant Patients Model Aspects of Alzheimer's Disease Pathology

Traditional approaches to studying Alzheimer’s disease (AD) using mouse models and cell lines have advanced our understanding of AD pathogenesis. However, with the growing divide between model systems and clinical therapeutic outcomes, the limitations of these approaches are increasingly apparent. Thus, to generate more clinically relevant systems that capture pathological cascades within human neurons, we generated human-induced neurons (HiNs) from AD and non-AD individuals to model cell autonomous disease properties. We selected an AD patient population expressing mutations in presenilin 1 (mPS1), which is linked to increased amyloid production, tau pathology, and calcium signaling abnormalities, among other features. While these AD components are detailed in model systems, they have yet to be collectively identified in human neurons. Thus, we conducted molecular, immune-based, electrophysiological, and calcium imaging studies to establish patterns of cellular pathology in this patient population. We found that mPS1 HiNs generate increased Aβ₄₂ and hyperphosphorylated tau species relative to non-AD controls, and exaggerated ER calcium responses that are normalized with ryanodine receptor (RyR) negative allosteric modulators. The inflammasome product, interleukin-18 (IL-18), also increased PS1 expression. This work highlights the potential for HiNs to model AD pathology and validates their role in defining cellular pathogenesis and their utility for therapeutic screening.

Iron potentiates microglial interleukin-1β secretion induced by amyloid-β

Alzheimer's disease (AD) is characterized by accumulation of amyloid-beta (Aβ) senile plaques in patients' brain tissues. Elevated levels of interleukin-1beta (IL-1β) have been identified in cerebrospinal fluid of living AD patients and in animal models of AD. Increased expression of IL-1β and iron accumulation have been identified in microglial cells that cluster around amyloid plaques in AD mouse models and post-mortem brain tissues of AD patients. The goals of this study were to determine the effects of Aβ on the secretion of IL-1β by microglial cells and whether iron status influences this pro-inflammatory signaling cue. Immortalized microglial (IMG) cells were incubated with Aβ with or without iron. qRT-PCR and western blot analyses showed that Aβ induces biosynthesis of IL-1β by IMG cells. IMG cells secrete the mature form of IL-1β in a caspase 1-dependent manner. Incubation with iron provoked a greater pro-inflammatory response. Inhibition of the iron transporter divalent metal transporter 1 protected IMG cells against Aβ-induced inflammation. Potentiation of Aβ-elicited IL-1β induction by iron was also antagonized by ROS inhibitors, supporting the model that divalent metal transporter 1-mediated iron loading and subsequent increase in ROS contribute to the inflammatory effects of Aβ in microglia. Immunoblotting and immunofluorescence microscopy indicate that iron enhances Aβ activation of NF-κB signaling to promote IL-1β synthesis. These results support the hypothesis that Aβ stimulates IL-1β expression by activating NF-κB signaling in microglia cells. Most importantly, iron appears to exacerbate the pro-inflammatory effects of Aβ to increase IL-1β levels.

Neurotoxicity to dopamine neurons after the serial exposure to alcohol and methamphetamine: Protection by COX-2 antagonism

A significant co-morbidity exists between alcohol and methamphetamine (Meth) in humans but the consequences and mechanisms underlying their co-morbid effects remain to be identified. A consequence associated with the abuse of either alcohol or Meth involves inflammation but little is known about the role of inflammation in a possible neurotoxicity arising from their co-exposure. Sprague Dawley rats were allowed 28 days of intermittent, voluntary access to 10% ethanol (EtOH) followed by a neurotoxic binge administration of Meth. EtOH drinking followed by Meth increased microglial cell counts and produced morphological changes in microglia of the substantia nigra pars compacta 2 h after Meth administration that were distinct from those produced by either EtOH or Meth alone. These effects preceded the activation of cleaved caspase-3 in dopamine cell bodies, as well as decreases in tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra and dopamine transporter (DAT) immunoreactivity in the striatum measured at 7 days after Meth. Intervention with a selective COX-2 inhibitor during EtOH drinking prevented the changes in microglia, and attenuated the increase in cleaved caspase-3, and decreases in TH and DAT after Meth administration. Furthermore, motor dysfunction measured by a rotarod test was evident but only in rats that were exposed to both EtOH and Meth. The motor dysfunction was ameliorated by prior inhibition of COX-2 during EtOH drinking. The exaggerated neurochemical and behavioral deficits indicate that the comorbidity of EtOH and Meth induces a degeneration of the nigrostriatal pathway and support the role of inflammation produced by EtOH drinking that primes and mediates the neurotoxic consequences associated with the common co-morbidity of these drugs.

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.

Microglial Pro-Inflammatory and Anti-Inflammatory Phenotypes Are Modulated by Translocator Protein Activation

A key role of the mitochondrial Translocator Protein 18 KDa (TSPO) in neuroinflammation has been recently proposed. However, little is known about TSPO-activated pathways underlying the modulation of reactive microglia. In the present work, the TSPO activation was explored in an in vitro human primary microglia model (immortalized C20 cells) under inflammatory stimulus. Two different approaches were used with the aim to (i) pharmacologically amplify or (ii) silence, by the lentiviral short hairpin RNA, the TSPO physiological function. In the TSPO pharmacological stimulation model, the synthetic steroidogenic selective ligand XBD-173 attenuated the activation of microglia. Indeed, it reduces and increases the release of pro-inflammatory and anti-inflammatory cytokines, respectively. Such ligand-induced effects were abolished when C20 cells were treated with the steroidogenesis inhibitor aminoglutethimide. This suggests a role for neurosteroids in modulating the interleukin production. The highly steroidogenic ligand XBD-173 attenuated the neuroinflammatory response more effectively than the poorly steroidogenic ones, which suggests that the observed modulation on the cytokine release may be influenced by the levels of produced neurosteroids. In the TSPO silencing model, the reduction of TSPO caused a more inflamed phenotype with respect to scrambled cells. Similarly, during the inflammatory response, the TSPO silencing increased and reduced the release of pro-inflammatory and anti-inflammatory cytokines, respectively. In conclusion, the obtained results are in favor of a homeostatic role for TSPO in the context of dynamic balance between anti-inflammatory and pro-inflammatory mediators in the human microglia-mediated inflammatory response. Interestingly, our preliminary results propose that the TSPO expression could be stimulated by NF-κB during activation of the inflammatory response.

KLF4 activates NFκB signaling and esophageal epithelial inflammation via the Rho-related GTP-binding protein RHOF

Understanding the regulatory mechanisms within esophageal epithelia is essential to gain insight into the pathogenesis of esophageal diseases, which are among the leading causes of morbidity and mortality throughout the world. The zinc-finger transcription factor Krüppel-like factor (KLF4) is implicated in a large number of cellular processes, such as proliferation, differentiation, and inflammation in esophageal epithelia. In murine esophageal epithelia, Klf4 overexpression causes chronic inflammation which is mediated by activation of NFκB signaling downstream of KLF4, and this esophageal inflammation produces epithelial hyperplasia and subsequent esophageal squamous cell cancer. Yet, while NFκB activation clearly promotes esophageal inflammation, the mechanisms by which NFκB signaling is activated in esophageal diseases are not well understood. Here, we demonstrate that the Rho-related GTP-binding protein RHOF is activated by KLF4 in esophageal keratinocytes, leading to the induction of NFκB signaling. Moreover, RHOF is required for NFκB activation by KLF4 in esophageal keratinocytes and is also important for esophageal keratinocyte proliferation and migration. Finally, we find that RHOF is upregulated in eosinophilic esophagitis, an important esophageal inflammatory disease in humans. Thus, RHOF activation of NFκB in esophageal keratinocytes provides a potentially important and clinically-relevant mechanism for esophageal inflammation and inflammation-mediated esophageal squamous cell cancer.

Macrophage-Associated PGK1 Phosphorylation Promotes Aerobic Glycolysis and Tumorigenesis

Macrophages are a dominant leukocyte population in the tumor microenvironment and actively promote cancer progression. However, the molecular mechanism underlying the role of macrophages remains poorly understood. Here we show that polarized M2 macrophages enhance 3-phosphoinositide-dependent protein kinase 1 (PDPK1)-mediated phosphoglycerate kinase 1 (PGK1) threonine (T) 243 phosphorylation in tumor cells by secreting interleukin-6 (IL-6). This phosphorylation facilitates a PGK1-catalyzed reaction toward glycolysis by altering substrate affinity. Inhibition of PGK1 T243 phosphorylation or PDPK1 in tumor cells or neutralization of macrophage-derived IL-6 abrogates macrophage-promoted glycolysis, proliferation, and tumorigenesis. In addition, PGK1 T243 phosphorylation correlates with PDPK1 activation, IL-6 expression, and macrophage infiltration in human glioblastoma multiforme (GBM). Moreover, PGK1 T243 phosphorylation also correlates with malignance and prognosis of human GBM. Our findings demonstrate a novel mechanism of macrophage-promoted tumor growth by regulating tumor cell metabolism, implicating the therapeutic potential to disrupt the connection between macrophages and tumor cells by inhibiting PGK1 phosphorylation.

The Role of KLF4 in Alzheimer's Disease

Krüppel-like factor 4 (KLF₄), a member of the family of zinc-finger transcription factors, is widely expressed in range of tissues that play multiple functions. Emerging evidence suggest KLF₄’s critical regulatory effect on the neurophysiological and neuropathological processes of Alzheimer’s disease (AD), indicating that KLF₄ might be a potential therapeutic target of neurodegenerative diseases. In this review, we will summarize relevant studies and illuminate the regulatory role of KLF₄ in the neuroinflammation, neuronal apoptosis, axon regeneration and iron accumulation to clarify KLF₄’s status in the pathogenesis of AD.

LncRNA SNHG5 enhances astrocytes and microglia viability via upregulating KLF4 in spinal cord injury

This study aims to explore the role and mechanism of lncRNA SNHG5 in spinal cord injury (SCI). The interaction between SNHG5 and Krüppel-like factor 4 (KLF4) was verified by RNA pull-down and RNA immunoprecipitation (RIP) assay. Rat neural function was evaluated by BBB and BMS scores. Results showed that GFAP and Iba-1 (specific proteins for astrocytes and microglia respectively) were upregulated in spinal cord of SCI rats. Simultaneously, spinal cord also expressed substantially higher levels of SNHG5, KLF4 and eNOS (endothelial Nitric Oxide Synthase) than sham group. In traumatically injured astrocytes and microglia, SNHG5 overexpression increased cells viability, which was significantly inhibited by SNHG5 knockdown. KLF4 is a directly target for SNHG5 and is positively regulated by SNHG5. The knockdown of KLF4 effectively decreased astrocytes and microglia viability induced by SHNG5 overexpression and attenuated the pcDNA-SNHG5-mediated repression of the apoptosis. In SCI rats, the injection of Lenti-SNHG5 reduced BBB and BMS scores and also enhanced the protein expression of KLF4, eNOS, GFAP and Iba-1. In summary, our data suggested that SNHG5 promotes SCI via increasing the viability of astrocytes and microglia. The mechanism by which SNHG5 works is its directive interaction to KLF4 and contribution to eNOS upregulation.

Neuroinflammation in Amyotrophic Lateral Sclerosis: Role of Redox (dys)Regulation

SIGNIFICANCE

Amyotrophic lateral sclerosis (ALS) is due to degeneration of upper and lower motor neurons in the anterior horn of the spinal cord and in the motor cortex. Mechanisms leading to motor neuron death are complex and currently the disease is untreatable. Recent Advances: Work in genetic models of ALS indicates that an imbalance in the cross talk that physiologically exists between motor neurons and the surrounding cells is eventually detrimental to motor neurons. In particular, the cascade of events collectively known as neuroinflammation and mainly characterized by a reactive phenotype of astrocytes and microglia, moderate infiltration of peripheral immune cells, and elevated levels of inflammatory mediators has been consistently observed in motor regions of the central nervous system (CNS) in sporadic and familial ALS, constituting a hallmark of the disease. Resident glial cells and infiltrated immune cells are considered among the major producers of reactive species of oxygen and nitrogen in pathological conditions of the CNS, including motor neuron diseases.

CRITICAL ISSUES

The timing and exact role of oxidative stress-mediated neuroinflammation and damage to motor neurons in ALS are still not fully elucidated.

FUTURE DIRECTIONS

It is clear that a major challenge in the next future will be to envisage effective strategies to modulate the neuroinflammatory response in the symptomatic stage of disease, to prevent progression of neurodegeneration through the propagation of oxidative damage. Antioxid. Redox Signal. 29, 15-36.

HSP60 critically regulates endogenous IL-1β production in activated microglia by stimulating NLRP3 inflammasome pathway

Background

Interleukin-1β (IL-1β) is one of the most important cytokine secreted by activated microglia as it orchestrates the vicious cycle of inflammation by inducing the expression of various other pro-inflammatory cytokines along with its own production. Microglia-mediated IL-1β production is a tightly regulated mechanism which involves the activation of nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing 3 (NLRP3) inflammasome pathway. Our previous study suggests the critical role of heat shock protein 60 (HSP60) in IL-1β-induced inflammation in microglia through TLR4-p38 MAPK axis. However, whether HSP60 regulates endogenous IL-1β production is not known. Therefore, to probe the underlying mechanism, we elucidate the role of HSP60 in endogenous IL-1β production.

Methods

We used in vitro (N9 murine microglial cells) and in vivo (BALB/c mouse) models for our study. HSP60 overexpression and knockdown experiment was done to elucidate the role of HSP60 in endogenous IL-1β production by microglia. Western blotting and quantitative real-time PCR was performed using N9 cells and BALB/c mice brain, to analyze various proteins and transcript levels. Reactive oxygen species levels and mitochondrial membrane depolarization in N9 cells were analyzed by flow cytometry. We also performed caspase-1 activity assay and enzyme-linked immunosorbent assay to assess caspase-1 activity and IL-1β production, respectively.

Results

HSP60 induces the phosphorylation and nuclear localization of NF-κB both in vitro and in vivo. It also induces perturbation in mitochondrial membrane potential and enhances reactive oxygen species (ROS) generation in microglia. HSP60 further activates NLRP3 inflammasome by elevating NLRP3 expression both at RNA and protein levels. Furthermore, HSP60 enhances caspase-1 activity and increases IL-1β secretion by microglia. Knockdown of HSP60 reduces the IL-1β-induced production of IL-1β both in vitro and in vivo. Also, we have shown for the first time that knockdown of HSP60 leads to decreased IL-1β production during Japanese encephalitis virus (JEV) infection, which eventually leads to decreased inflammation and increased survival of JEV-infected mice.

Conclusion

HSP60 mediates microglial IL-1β production by regulating NLRP3 inflammasome pathway and reduction of HSP60 leads to reduction of inflammation in JEV infection.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1214-5) contains supplementary material, which is available to authorized users.

Exploitation of microRNAs by Japanese Encephalitis virus in human microglial cells

JEV infection in CNS leads to the JE neuroinflammation. Children and old age individual have been reported to be more prone to JEV infection. MicroRNAs are endogenous, small non-coding RNAs, which regulate the gene expression. These are ∼22 nucleotide long, conserved RNA sequence that binds at the 3'UTR of a target mRNA and regulate the post-transcriptional gene expression. The role of microRNAs has been reported in several diseases like cancer, viral infection, neuro-degeneration, diabetes etc. In the present study, the human microglial cells were infected with JEV (JaOArS982). The control and infected samples were subject to microarray profiling for microRNA expression. The microarray profile yielded differentially expressed microRNAs from JEV infected samples. The microRNA gene targets, gene ontology, annotations, and pathways were identified through various bioinformatics tools. Additionally, the pathways were mostly found common to "ubiquitin mediated proteolysis," "cytokine signaling," "maintenance of barrier function/cell junctions," JAK/STAT pathway" "Toll-like receptor signaling," "Wnt-signaling," "adhesion molecules," "apoptosis," "endocytosis," "vesicle mediated transport" etc.

Physiological stress-induced corticosterone increases heme uptake via KLF4-HCP1 signaling pathway in hippocampus neurons

Iron overload has attracted much attention because of its adverse effect in increasing the risk of developing several neurodegenerative disorders. Under various pathologic conditions, a lot of heme are released. The aggregation of heme is more neurotoxic than that of iron released from the heme breakdown. Our previous studies demonstrated that psychological stress (PS) is a risk factor of cerebral iron metabolism disorders, thus causing iron accumulation in rat brains. In the present study, we found PS could increase heme uptake via heme carrier protein 1 (HCP1) in rat brains. We demonstrated that Glucocorticoid (GC), which is largely secreted under stress, could up-regulate HCP1 expression, thus promoting heme uptake in neurons. We also ascertained that HCP1 expression can be induced by GC through a transcription factor, Krüppel-like factor 4 (KLF4). These results may gain new insights into the etiology of heme uptake and iron accumulation in PS rats, and find new therapeutic targets of iron accumulation in Parkinson’s disease or Alzheimer’s disease.

Cocaine-Mediated Downregulation of miR-124 Activates Microglia by Targeting KLF4 and TLR4 Signaling

Cocaine is known to activate microglia both in vitro and in vivo. High expression of microglial Toll-like receptors (TLRs) and their downstream signal transducers play critical roles in determining microglial activation status. Emerging reports have also demonstrated that cocaine can enhance the strength of TLR signaling. Detailed molecular mechanisms underlying this phenomenon, however, remain elusive. In this study, we investigated the role(s) of miR-124 in regulating microglial TLR4 signaling in the context of cocaine. Herein, we found a dose- and time-dependent upregulation of KLF4 in cocaine-exposed BV-2 cells and rat primary microglial cells (rPMs). KLF4 also identified as a novel 3'-UTR target directly regulated by miR-124. In parallel, miR-124 regulated multiple TLR4 signaling molecules including TLR4, MyD88, TRAF6, and IRAK1. Repeated doses of cocaine (20 mg/kg; i.p.) administration in mice for 7 days further validated the in vitro key findings. Also, miR-124 overexpression significantly blocked the cocaine-mediated upregulation of pro-inflammatory cytokines. In contrast, miR-124 overexpression notably increased the expression of anti-inflammatory mediators in cocaine-exposed microglial cells. Intriguingly, stereotactic administration of lentivirus-miR-124 in the striatum significantly inhibited cocaine-mediated microglial activation and locomotor hyperactivity in vivo. In summary, these findings implicate the role of miR-124 in regulating TLR4 signaling, thereby indicating a new pathway responsible for cocaine-mediated microglial activation.

Differential Neuroprotective Effects of Interleukin-1 Receptor Antagonist on Spinal Cord Neurons after Excitotoxic Injury

Secondary damage following spinal cord injury (SCI) induces neuronal damage through inflammatory and excitotoxic pathways. We hypothesized that the interleukin-1 receptor antagonist (IL1RA) protects neuronal populations and suppresses apoptosis and gliosis after injury. Spinal cord slice cultures (SCSCs) were subjected to excitotoxic injury with N-methyl-D-aspartate (NMDA) and treated with IL1RA. Immunohistochemistry for neuronal nuclei (NeuN), MacII, glial fibrillary acidic protein, and TdT-mediated dUTP nick end labelling stains were used to evaluate neuronal survival, glial activation, and apoptosis. Treatment with IL1RA significantly reduced the number of apoptotic cells in both NMDA-lesioned and unlesioned cultures. Experimental injury with NMDA reduced the number of NeuN-positive ventral horn neurons, and IL1RA treatment counteracted this loss 1 day after injury. However, IL1RA had no effect on the number of presumable Renshaw cells, identified by their selective expression of the cholinergic nicotinic α2-receptor subunit (Chrna2). Activated microglial cells were more numerous in NMDA-lesioned cultures 1 day after injury, and IL1RA significantly reduced their numbers. We conclude that IL1RA modulates neuronal apoptosis and microglial activation in excitotoxically injured SCSCs. Renshaw cells were more susceptible to excitotoxic injury than other neurons and were not rescued by IL1RA treatment. Modulation of IL-1-mediated pathways may thus be effective in reducing excitotoxically induced neuronal damage after SCI, however only in specific neuronal populations, such as ventral horn neurons. These findings motivate further investigations of the possibility to antagonize inflammatory pathways after SCI.

Antidepressant-like effect of pramipexole in an inflammatory model of depression

Pramipexole (PPX), a dopamine D2/3 receptor preferring agonist, is currently in use for the treatment of Parkinson's disease symptoms and restless legs syndrome. Recently, anti-inflammatory properties of PPX have been shown in an autoimmune model of multiple sclerosis, and case reports indicate PPX ameliorates depressive symptoms. Since peripheral inflammation is known to induce depression-like behavior in rodents, we assessed the potential antidepressant effect of PPX in an inflammatory model of depression induced by LPS. Repeated (daily for 7days, 1mg/kg, i.p.), but not acute (1h before LPS) treatment with PPX abolished the depression-like behavior induced by LPS (0.1mg/kg, i.p.) in the forced swim test, and the anhedonic behavior in the splash test. Interestingly, PPX per se decreased interleukin 1β levels and reversed LPS-induced increase in its content in mice hippocampus⋅ Repeated PPX treatment also prevented the increase in hippocampal levels of the 3-nitrotyrosine protein adducts induced by LPS. Haloperidol (0.2mg/kg, i.p.) and sulpiride (50mg/kg, i.p.) were unable to prevent the antidepressant-like effect of PPX in LPS-treated mice. Altogether, these results suggest that the observed antidepressant-like effect of PPX in LPS-treated mice may be dependent on its anti-inflammatory properties and may not be related to dopamine D2 receptor activation.

MicroRNA-7 Deficiency Ameliorates the Pathologies of Acute Lung Injury through Elevating KLF4

Recent evidence showed that microRNA-7 (miR-7) played an important role in the pathologies of lung-related diseases. However, the potential role of miR-7 in acute lung injury (ALI) still remains poorly understood. Here, we assessed the effect of miR-7 deficiency on the pathology of ALI. We, first, found that the expression of miR-7 was upregulated in lung tissue in murine LPS-induced ALI model. Notably, we generated miR-7 knock down mice by using miRNA-Sponge technique and found that miR-7 deficiency could ameliorate the pathologies of lung as evidenced by accelerated body weight recovery, reduced level of bronchoalveolar lavage (BAL) proinflammatory cytokines and decreased number of BAL cells in ALI mice. Moreover, the proportion and number of various immune cells in BAL, including innate immune cell F4/80⁺ macrophages, γδT cells, NK1.1⁺ T cells, and CD11c⁺DCs, as well as adaptive immune cell CD4⁺ T cells and CD8⁺ T cells, also significantly changed, respectively. Mechanistic evidence showed that KLF4, a target molecule of miR-7, was upregulated in lung tissues in ALI model, accompanied by altered transduction of NF-κB, AKT, and ERK pathway. These data provided a previously unknown role of miR-7 in pathology of ALI, which could ultimately aid the understanding of development of ALI and the development of new therapeutic strategies against clinical inflammatory lung diseases.

1400W, a highly selective inducible nitric oxide synthase inhibitor is a potential disease modifier in the rat kainate model of temporal lobe epilepsy

Status epilepticus (SE) initiates epileptogenesis to transform normal brain to epileptic state which is characterized by spontaneous recurrent seizures (SRS). Prior to SRS, progressive changes occur in the brain soon after SE, for example, loss of blood-brain barrier (BBB) integrity, neuronal hyper-excitability (epileptiform spiking), neuroinflammation [reactive gliosis, high levels of reactive oxygen/nitrogen species (ROS/RNS)], neurodegeneration and synaptic re-organization. Our hypothesis was that modification of early epileptogenic events will alter the course of disease development and its progression. We tested the hypothesis in the rat kainate model of chronic epilepsy using a novel disease modifying drug, 1400W, a highly selective inhibitor of inducible nitric oxide synthase (iNOS/NOS-II). In an in vitro mouse brain slice model, using a multi-electrode array system, co-application of 1400W with kainate significantly suppressed kainate-induced epileptiform spiking. In the rats, in vivo, 4h after the induction of SE with kainate, 1400W (20mg/kg, i.p.) was administered twice daily for three days to target early events of epileptogenesis. The rats were subjected to continuous (24/7) video-EEG monitoring, remotely, for six months from epidurally implanted cortical electrodes. The 1400W treatment significantly reduced the epileptiform spike rate during the first 12-74h post-SE, which resulted in >90% reduction in SRS in long-term during the six month period when compared to the vehicle-treated control group (257±113 versus 19±10 episodes). Immunohistochemistry (IHC) of brain sections at seven days and six months revealed a significant reduction in; reactive astrogliosis and microgliosis (M1 type), extravascular serum albumin (a marker for BBB leakage) and neurodegeneration in the hippocampus, amygdala and entorhinal cortex in the 1400W-treated rats when compared to the vehicle control. In the seven day group, hippocampal Western blots revealed downregulation of inwardly-rectifying potassium (Kir 4.1) channels and glutamate transporter-1 (GLT-1) levels in the vehicle group, and 1400W treatment partially reversed Kir 4.1 levels, however, GLT-1 levels were unaffected. In the six month group, a significant reduction in mossy fiber staining intensity in the inner molecular layer of the dentate gyrus was observed in the 1400W-treated group. Overall these findings demonstrate that 1400W, by reducing the epileptiform spike rate during the first three days of post-insult, potentially modifies epileptogenesis and the severity of chronic epilepsy in the rat kainate model of TLE.

Interleukin-1β overproduction is a common cause for neuropathic pain, memory deficit, and depression following peripheral nerve injury in rodents

BACKGROUND

Chronic pain is often accompanied by short-term memory deficit and depression. Currently, it is believed that short-term memory deficit and depression are consequences of chronic pain. Here, we test the hypothesis that the symptoms might be caused by overproduction of interleukin-1beta (IL-1β) in the injured nerve independent of neuropathic pain following spared nerve injury in rats and mice.

RESULTS

Mechanical allodynia, a behavioral sign of neuropathic pain, was not correlated with short-term memory deficit and depressive behavior in spared nerve injury rats. Spared nerve injury upregulated IL-1β in the injured sciatic nerve, plasma, and the regions in central nervous system closely associated with pain, memory and emotion, including spinal dorsal horn, hippocampus, prefrontal cortex, nucleus accumbens, and amygdala. Importantly, the spared nerve injury-induced memory deficits, depressive, and pain behaviors were substantially prevented by peri-sciatic administration of IL-1β neutralizing antibody in rats or deletion of IL-1 receptor type 1 in mice. Furthermore, the behavioral abnormalities induced by spared nerve injury were mimicked in naïve rats by repetitive intravenous injection of re combinant rat IL-1β (rrIL-1β) at a pathological concentration as determined from spared nerve injury rats. In addition, microglia were activated by both spared nerve injury and intravenous injection of rrIL-1β and the effect of spared nerve injury was substantially reversed by peri-sciatic administration of anti-IL-1β.

CONCLUSIONS

Neuropathic pain was not necessary for the development of cognitive and emotional disorders, while the overproduction of IL-1β in the injured sciatic nerve following peripheral nerve injury may be a common mechanism underlying the generation of neuropathic pain, memory deficit, and depression.

Krüpple-like factors in the central nervous system: novel mediators in stroke

Transcription factors play an important role in the pathophysiology of many neurological disorders, including stroke. In the past three decades, an increasing number of transcription factors and their related gene signaling networks have been identified, and have become a research focus in the stroke field. Krüppel-like factors (KLFs) are members of the zinc finger family of transcription factors with diverse regulatory functions in cell growth, differentiation, proliferation, migration, apoptosis, metabolism, and inflammation. KLFs are also abundantly expressed in the brain where they serve as critical regulators of neuronal development and regeneration to maintain normal brain function. Dysregulation of KLFs has been linked to various neurological disorders. Recently, there is emerging evidence that suggests KLFs have an important role in the pathogenesis of stroke and provide endogenous vaso-or neuro-protection in the brain's response to ischemic stimuli. In this review, we summarize the basic knowledge and advancement of these transcriptional mediators in the central nervous system, highlighting the novel roles of KLFs in stroke.

Distribution of mesenchymal stem cells and effects on neuronal survival and axon regeneration after optic nerve crush and cell therapy

Bone marrow-derived cells have been used in different animal models of neurological diseases. We investigated the therapeutic potential of mesenchymal stem cells (MSC) injected into the vitreous body in a model of optic nerve injury. Adult (3–5 months old) Lister Hooded rats underwent unilateral optic nerve crush followed by injection of MSC or the vehicle into the vitreous body. Before they were injected, MSC were labeled with a fluorescent dye or with superparamagnetic iron oxide nanoparticles, which allowed us to track the cells in vivo by magnetic resonance imaging. Sixteen and 28 days after injury, the survival of retinal ganglion cells was evaluated by assessing the number of Tuj1- or Brn3a-positive cells in flat-mounted retinas, and optic nerve regeneration was investigated after anterograde labeling of the optic axons with cholera toxin B conjugated to Alexa 488. Transplanted MSC remained in the vitreous body and were found in the eye for several weeks. Cell therapy significantly increased the number of Tuj1- and Brn3a-positive cells in the retina and the number of axons distal to the crush site at 16 and 28 days after optic nerve crush, although the RGC number decreased over time. MSC therapy was associated with an increase in the FGF-2 expression in the retinal ganglion cells layer, suggesting a beneficial outcome mediated by trophic factors. Interleukin-1β expression was also increased by MSC transplantation. In summary, MSC protected RGC and stimulated axon regeneration after optic nerve crush. The long period when the transplanted cells remained in the eye may account for the effect observed. However, further studies are needed to overcome eventually undesirable consequences of MSC transplantation and to potentiate the beneficial ones in order to sustain the neuroprotective effect overtime.

Interleukin-1 receptor antagonist promotes survival of ventral horn neurons and suppresses microglial activation in mouse spinal cord slice cultures

Secondary damage after spinal cord injury (SCI) induces neuronal demise through neurotoxicity and inflammation, and interleukin (IL)-1β is a key inflammatory mediator. We hypothesized that IL-1β is released in spinal cord slice cultures (SCSC) and aimed at preventing the potentially neurotoxic effects of IL-1β by using interleukin-1 receptor antagonist (IL1RA). We hypothesized that IL1RA treatment enhances neuronal survival and suppresses microglial activation. SCSC were cultured up to 8 days in vitro (DIV) in the presence of IL1RA or without, either combined with trophic support using neurotrophin (NT)-3 or not. Four groups were studied: negative control, IL1RA, NT-3, and IL1RA + NT-3. IL-1β concentrations in supernatants were measured by ELISA. SCSC were immunohistochemically stained for NeuN and α-neurofilament, and microglial cells were visualized with isolectin B4 . After 8 DIV, ventral horn neurons were significantly more numerous in the IL1RA, NT-3, and IL1RA + NT-3 groups compared with negative controls. Activated microglial cells were significantly less numerous in the IL1RA, NT-3, and IL1RA + NT-3 groups compared with negative controls. Axons expanded into the collagen matrix after treatment with IL1RA, NT-3, or IL1RA + NT-3, but not in negative controls. IL-1β release from cultures peaked after 6 hr and was lowest in the IL1RA + NT-3 group. We conclude that IL-1β is released in traumatized spinal cord tissue and that IL1RA could exert its neuroprotective actions by blocking IL-1-receptors. IL1RA thereby sustains neuronal survival irrespective of the presence of additional trophic support. Microglial activation is suppressed in the presence of IL1RA, suggesting decreased inflammatory activity. IL1RA treatment approaches may have substantial impact following SCI.

Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury

Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.