The p53 transcription factor modulates microglia behavior through microRNA-dependent regulation of c-Maf

Glial 'omics in ischemia: Acute stroke and chronic cerebral small vessel disease

Vascular injury and pathologies underlie common diseases including ischemic stroke and cerebral small vessel disease (CSVD). Prior work has identified a key role for glial cells, including microglia, in the multifaceted and temporally evolving neuroimmune response to both stroke and CSVD. Transcriptional profiling has led to important advances including identification of distinct gene expression signatures in ischemia-exposed, flow cytometrically sorted microglia and more recently single cell RNA sequencing-identified microglial subpopulations or clusters. There is a reassuring degree of overlap in the results from these two distinct methodologies with both identifying a proliferative and a separate type I interferon responsive microglial element. Similar patterns were later seen using multimodal and spatial transcriptomal profiling in ischemia-exposed microglia and astrocytes. Methodological advances including enrichment of specific neuroanatomic/functional regions (such as the neurovascular unit) prior to single cell RNA sequencing has led to identification of novel cellular subtypes and generation of new credible hypotheses as to cellular function based on the enhanced cell sub-type specific gene expression patterns. A ribosomal tagging strategy focusing on the cellular translatome analyses carried out in the acute phases post stroke has revealed distinct inflammation-regulating roles for microglia and astrocytes in this setting. Early spatial transcriptomics experiments using cerebral ischemia models have identified regionally distinct microglial cell clusters in ischemic core versus penumbra. There is great potential for combination of these methods for multi-omics approaches to further elucidate glial responses in the context of both acute ischemic stroke and chronic CSVD.

Interpretable identification of cancer genes across biological networks via transformer-powered graph representation learning

Graph representation learning has been leveraged to identify cancer genes from biological networks. However, its applicability is limited by insufficient interpretability and generalizability under integrative network analysis. Here we report the development of an interpretable and generalizable transformer-based model that accurately predicts cancer genes by leveraging graph representation learning and the integration of multi-omics data with the topologies of homogeneous and heterogeneous networks of biological interactions. The model allows for the interpretation of the respective importance of multi-omic and higher-order structural features, achieved state-of-the-art performance in the prediction of cancer genes across biological networks (including networks of interactions between miRNA and proteins, transcription factors and proteins, and transcription factors and miRNA) in pan-cancer and cancer-specific scenarios, and predicted 57 cancer-gene candidates (including three genes that had not been identified by other models) among 4,729 unlabelled genes across 8 pan-cancer datasets. The model's interpretability and generalization may facilitate the understanding of gene-related regulatory mechanisms and the discovery of new cancer genes.

Alzheimer's disease and diabetes-associated cognitive dysfunction: the microglia link?

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) plaques and the aggregation of tau protein, resulting in intense memory loss and dementia. Diabetes-associated cognitive dysfunction (DACD) is a complication of diabetes mellitus, which is associated with decreased cognitive function and impaired memory. A growing body of literature emphasize the involvement of microglia in AD and DACD. Although AD and DACD share some common features related to symptomatology and pathophysiology, the characteristics and heterogeneity of microglia remain largely unknown in these two diseases. In this study, multiple bioinformatics analyses were performed to analyze the frequency, altered genes, cell-cell communication, and subtypes of microglia in AD and DACD mouse models based on two publicly single-nucleus RNA sequencing (snRNA-Seq) datasets. The results revealed that the frequency of microglia was increased in both AD and DACD mouse models when compared with control mice. After analyzing the differentially expressed genes of microglia from the two mouse models, only six common upregulated genes were found. The CellChat analysis revealed the complex cell-cell communication network (microglia clusters with other cell types) in 5XFAD vs. control mice and db/db vs. control mice. The microglia subtypes and their transcription factor activity profile in 5XFAD mice were different from that in db/db mice. In summary, this study provided some insights into the alterations of microglia in 5XFAD and db/db mice, which might open up potential avenues for the microglial-targeted therapy in AD and DACD.

Pharmaceutical-mediated neuroimmune modulation in psychiatric/psychological adverse events

The therapeutic use of many pharmaceuticals, including small molecules and biological therapies, has been associated with the onset of psychiatric and psychological adverse events (PPAEs), posing substantial concerns to patients' health and safety. These events, which encompass mood (e.g., depression, schizophrenia, suicidal ideation) and cognitive changes (e.g., learning and memory impairment, dementia) often remain undetected until advanced stages of clinical trials or pharmacovigilance, mostly because the mechanisms underlying the onset of PPAEs remain poorly understood. In recent years, the role of neuroimmune modulation (comprising an intricate interplay between various cell types and signaling pathways) in PPAEs has garnered substantial interest. Indeed, understanding these complex interactions would substantially contribute to increase the ability to predict the potential onset of PPAEs during preclinical stages of a new drug's R&D. This review provides a comprehensive summary of the most recent advances in neuroimmune modulation-related mechanisms contributing to the onset of PPAEs and their association with specific pharmaceuticals. Reported data strongly support an association between neuroimmune modulation and the onset of PPAEs. Pharmaceuticals may target specific molecular pathways and pathway elements (e.g., cholinergic and serotonergic systems), which in turn may directly or indirectly impact the inflammatory status and the homeostasis of the brain, regulating inflammation and neuronal function. Also, modulation of the peripheral immune system by pharmaceuticals that do not permeate the blood-brain barrier (e.g., monoclonal antibodies) may alter the neuroimmunomodulatory status of the brain, leading to PPAEs. In summary, this review underscores the diverse pathways through which drugs can influence brain inflammation, shedding light on potential targeted interventions.

Role of transcription factors, noncoding RNAs, epitranscriptomics, and epigenetics in post-ischemic neuroinflammation

Post-stroke neuroinflammation is pivotal in brain repair, yet persistent inflammation can aggravate ischemic brain damage and hamper recovery. Following stroke, specific molecules released from brain cells attract and activate central and peripheral immune cells. These immune cells subsequently release diverse inflammatory molecules within the ischemic brain, initiating a sequence of events, including activation of transcription factors in different brain cell types that modulate gene expression and influence outcomes; the interactive action of various noncoding RNAs (ncRNAs) to regulate multiple biological processes including inflammation, epitranscriptomic RNA modification that controls RNA processing, stability, and translation; and epigenetic changes including DNA methylation, hydroxymethylation, and histone modifications crucial in managing the genic response to stroke. Interactions among these events further affect post-stroke inflammation and shape the depth of ischemic brain damage and functional outcomes. We highlighted these aspects of neuroinflammation in this review and postulate that deciphering these mechanisms is pivotal for identifying therapeutic targets to alleviate post-stroke dysfunction and enhance recovery.

Research progress on immune-related therapeutic targets of brain injury caused by cerebral ischemia

Stroke is the second leading cause of death worldwide and a leading cause of disability. The innate immune response occurs immediately after cerebral ischemia, resulting in adaptive immunity. More and more experimental evidence has proved that the immune response caused by cerebral ischemia plays an important role in early brain injury and later the recovery of brain injury. Innate immune cells and adaptive cells promote the occurrence of cerebral ischemic injury but also protect brain cells. A large number of studies have shown that cytokines and immune-related substances also have dual functions of promoting injury, reducing injury, or promoting injury recovery in the later stage of cerebral ischemia. They can be an important target for treating cerebral ischemic recovery. Therefore, this study discussed the immune cells, cytokines, and immune-related substances with dual roles in cerebral ischemia and summarized the therapeutic targets of cerebral ischemia. To explore more effective methods to treat cerebral ischemia, promote the recovery of brain function, and improve the prognosis of patients.

Loss of miR-145 promotes remyelination and functional recovery in a model of chronic central demyelination

Strategies for treating progressive multiple sclerosis (MS) remain limited. Here, we found that miR-145-5p is overabundant uniquely in chronic lesion tissues from secondary progressive MS patients. We induced both acute and chronic demyelination in miR-145 knockout mice to determine its contributions to remyelination failure. Following acute demyelination, no advantage to miR-145 loss could be detected. However, after chronic demyelination, animals with miR-145 loss demonstrated increased remyelination and functional recovery, coincident with altered presence of astrocytes and microglia within the corpus callosum relative to wild-type animals. This improved response in miR-145 knockout animals coincided with a pathological upregulation of miR-145-5p in wild-type animals with chronic cuprizone exposure, paralleling human chronic lesions. Furthermore, miR-145 overexpression specifically in oligodendrocytes (OLs) severely stunted differentiation and negatively impacted survival. RNAseq analysis showed altered transcriptome in these cells with downregulated major pathways involved in myelination. Our data suggest that pathological accumulation of miR-145-5p is a distinctive feature of chronic demyelination and is strongly implicated in the failure of remyelination, possibly due to the inhibition of OL differentiation together with alterations in other glial cells. This is mirrored in chronic MS lesions, and thus miR-145-5p serves as a potential relevant therapeutic target in progressive forms of MS.

Doxorubicin induced epigenetic regulation of dendritic cell maturation in association with T cell activation facilitates tumor protective immune response in non-small cell lung cancer (NSCLC)

BACKGROUND

NSCLC is one of the leading causes of death and is often diagnosed at late stages with no alternative therapeutic approach. DCs are professional antigen-presenting cells and DC-based immunotherapy has been under the spotlight for its anti-cancer properties. Epigenetic modifications including DNA methylation and histone modification in DCs play a crucial role in regulating their functions such as maturation and activation,innate immune responses, T cell priming, antigen presentation, and cytokine production. In the current study, we investigated the anti-cancer properties of Doxorubicin at a noncytotoxic concentration that could be extrapolated as an epigenetic regulator for DC maturation to elicit anti-tumor activity.

METHODOLOGIES

PBMCs from normal and NSCLC blood samples were isolated and treated with growth factors. DCs were matured with low dose Doxorubicin and the DC maturation markers were checked by using flow-cytometry. Further, ELISA was performed and low dose Doxorubicin-induced DCs were pulsed with LCA (Lung Cancer Antigen) and primed with CD4 +T helper (Th) cells for cytotoxicity assessment. Further, epigenetic markers of T: DC conjugation were immunofluorescently visualized under a microscope. ChIP-qPCR and Invitro assays such as histone methylation, DNA methylation, and m6A methylation were performed to study the epigenetic changes under low dose Dox treatment. IL-12 neutralization assay was performed to check for the IL-12 dependency of DCs and their effect under Dox at low dose treatment. This was further followed by a Western Blotting analysis for histone and non-histone proteins.

RESULTS

Low dose Doxorubicin induces epigenetic changes in DCs to elicit an anti-tumor response in NSCLC through the generation of CTLs with a concomitant increase in the extracellular secretions of anti-inflammatory cytokines. We also found that low dosage of Doxorubicin matured DCs when pulsed with LCA and primed with CD4 +T helper cells, secrete IFN-γ which is important in orchestrating adaptive immunity by activating CD8 + cytotoxic T-lymphocytes. Also, the secretions of IL-12 help us infer that protective immunity is also induced via Th1 response which triggered selectively the translocation of PKCθ to immunological synapse in between DC and Th. Further, methylation and acetylation markers H3K4me3 and H3K14Ac respectively upregulated whereas levels of STAT5, NFkB, NOTCH1, and DNAPKcs were downregulated. DNA and RNA methylation assays then lead to confirmations about the epigenetic changes caused by low dose Dox treatment. DNA methylation was reduced which resulted in the activation of tumor suppressor gene p53 and Th1-associated transcription factor TBX21. On the other hand, both absolute and relative RNA methylation quantification increased in the presence of Dox at a low dose.

CONCLUSION

From this study, we understand that non-cytotoxic concentration of Doxorubicin increases the Ag-presenting ability of DCs via an IL-12-dependent mechanism and causes epigenetic modifications in NSCLC.

The miRNA neuroinflammatory biomarkers in COVID-19 patients with different severity of illness

INTRODUCTION

The expression of specific miRNAs and their mRNA targets are changed in infectious disease. The aim of this study was to analyze the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their mRNA targets in the serum of COVID-19 patients with different grades.

METHODS

COVID-19 patients with different grades were enrolled in this study and the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their target mRNAs was analyzed by q-PCR.

RESULTS

The relative expression of anti- neuroinflammatory miRNAs (mir-21, mir-124, and mir-146a) was decreased and the relative expression of their target mRNAs (IL-12p53, Stat3, and TRAF6) was increased. Also, the relative expression of pro-neuroinflammatory miRNAs (mir-326, mir-155, and mir-27b) was increased and the relative expression of their target mRNA (PPARS, SOCS1, and CEBPA) was decreased in COVID-19 patients with increase of disease grade. A negative significant correlation was seen between mir-21 and IL-12p53 mRNA, mir-124 and Stat3 mRNA, mir-146a and TRAF6 mRNA, mir-27b and PPARS mRNA, mir-155 and SOCS1 mRNA, and between mir-326 and CEBPA mRNA in COVID-19 patients (P<0.05).

CONCLUSIONS

This study showed that the relative expression of anti- neuroinflammatory miRNAs was decreased and the relative expression of their targeted mRNAs was increased in COVID-19 patients from asymptomatic to critical illness. Also, this study showed that the relative expression of pro-neuroinflammatory miRNAs was increased and the relative expression of their targeted mRNA was decreased in COVID-19 patients from asymptomatic to critical illness.

Targeting p53 for neuroinflammation: New therapeutic strategies in ischemic stroke

Ischemic stroke (IS) is characterized by high incidence, high recurrence, and high mortality and places a heavy burden on society and families. The pathological mechanisms of IS are complex, among which secondary neurological impairment mediated by neuroinflammation is considered to be the main factor in cerebral ischemic injury. At present, there is still a lack of specific therapies to treat neuroinflammation. The tumor suppressor protein p53 has long been regarded as a key substance in the regulation of the cell cycle and apoptosis in the past. Recently, studies have found that p53 also plays an important role in neuroinflammatory diseases, such as IS. Therefore, p53 may be a crucial target for the regulation of the neuroinflammatory response. Here, we provide a comprehensive review of the potential of targeting p53 in the treatment of neuroinflammation after IS. We describe the function of p53, the major immune cells involved in neuroinflammation, and the role of p53 in inflammatory responses mediated by these cells. Finally, we summarize the therapeutic strategies of targeting p53 in regulating the neuroinflammatory response after IS to provide new directions and ideas for the treatment of ischemic brain injury.

Tumor-suppressive role of the musculoaponeurotic fibrosarcoma gene in colorectal cancer

Somatic cell reprogramming using the microRNAs miR-200c, miR-302s, and miR-369s leads to increased expression of cyclin-dependent kinase inhibitors in human colorectal cancer (CRC) cells and suppressed tumor growth. Here, we investigated whether these microRNAs inhibit colorectal tumorigenesis in CPC;Apc mice, which are prone to colon and rectal polyps. Repeated administration of microRNAs inhibited polyp formation. Microarray analysis indicated that c-MAF, which reportedly shows oncogene-like behavior in multiple myeloma and T cell lymphoma, decreased in tumor samples but increased in microRNA-treated normal mucosa. Immunohistochemistry identified downregulation of c-MAF as an early tumorigenesis event in CRC, with low c-MAF expression associated with poor prognosis. Of note, c-MAF expression and p53 protein levels were inversely correlated in CRC samples. c-MAF knockout led to enhanced tumor formation in azoxymethane/dextran sodium sulfate-treated mice, with activation of cancer-promoting genes. c-MAF may play a tumor-suppressive role in CRC development.

Microglia specific deletion of miR-155 in Alzheimer's disease mouse models reduces amyloid-β pathology but causes hyperexcitability and seizures

Alzheimer's Disease (AD) is characterized by the accumulation of extracellular amyloid-β (Aβ) as well as CNS and systemic inflammation. Microglia, the myeloid cells resident in the CNS, use microRNAs to rapidly respond to inflammatory signals. MicroRNAs (miRNAs) modulate inflammatory responses in microglia, and miRNA profiles are altered in Alzheimer's disease (AD) patients. Expression of the pro-inflammatory miRNA, miR-155, is increased in the AD brain. However, the role of miR-155 in AD pathogenesis is not well-understood. We hypothesized that miR-155 participates in AD pathophysiology by regulating microglia internalization and degradation of Aβ. We used CX3CR1CreER/+ to drive-inducible, microglia-specific deletion of floxed miR-155 alleles in two AD mouse models. Microglia-specific inducible deletion of miR-155 in microglia increased anti-inflammatory gene expression while reducing insoluble Aβ1-42 and plaque area. Yet, microglia-specific miR-155 deletion led to early-onset hyperexcitability, recurring spontaneous seizures, and seizure-related mortality. The mechanism behind hyperexcitability involved microglia-mediated synaptic pruning as miR-155 deletion altered microglia internalization of synaptic material. These data identify miR-155 as a novel modulator of microglia Aβ internalization and synaptic pruning, influencing synaptic homeostasis in the setting of AD pathology.

The role and regulation of Maf proteins in cancer

The Maf proteins (Mafs) belong to basic leucine zipper transcription factors and are members of the activator protein-1 (AP-1) superfamily. There are two subgroups of Mafs: large Mafs and small Mafs, which are involved in a wide range of biological processes, such as the cell cycle, proliferation, oxidative stress, and inflammation. Therefore, dysregulation of Mafs can affect cell fate and is closely associated with diverse diseases. Accumulating evidence has established both large and small Mafs as mediators of tumor development. In this review, we first briefly describe the structure and physiological functions of Mafs. Then we summarize the upstream regulatory mechanisms that control the expression and activity of Mafs. Furthermore, we discuss recent studies on the critical role of Mafs in cancer progression, including cancer proliferation, apoptosis, metastasis, tumor/stroma interaction and angiogenesis. We also review the clinical implications of Mafs, namely their potential possibilities and limitations as biomarkers and therapeutic targets in cancer.

Role of MicroRNAs, Aptamers in Neuroinflammation and Neurodegenerative Disorders

Exploring the microRNAs and aptamers for their therapeutic role as biological drugs has expanded the horizon of its applicability against various human diseases, explicitly targeting the genetic materials. RNA-based therapeutics are widely being explored for the treatment and diagnosis of multiple diseases, including neurodegenerative disorders (NDD). Latter includes microRNA, aptamers, ribozymes, and small interfering RNAs (siRNAs), which control the gene expression mainly at the transcriptional strata. One RNA transcript translates into different protein types; hence, therapies targeted at the transcriptional sphere may have prominent and more extensive effects than alternative therapeutics. Unlike conventional gene therapy, RNAs, upon delivery, can either altogether abolish or alter the synthesis of the protein of interest, therefore, regulating their activities in a controlled and diverse manner. NDDs like Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, Prion disease, and others are characterized by deposition of misfolded protein such as amyloid-ß, tau, α-synuclein, huntingtin and prion proteins. Neuroinflammation, one of the perquisites for neurodegeneration, is induced during neurodegenerative pathogenesis. In this review, we discuss microRNAs and aptamers' role as two different RNA-based approaches for their unique ability to regulate protein production at the transcription level, hence offering many advantages over other biologicals. The microRNA acts either by alleviating the malfunctioning RNA expression or by working as a replacement to lost microRNA. On the contrary, aptamer act as a chemical antibody and forms an aptamer-target complex.

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

Molecular Mechanisms Driving IL-10- Producing B Cells Functions: STAT3 and c-MAF as Underestimated Central Key Regulators?

Regulatory B cells (Bregs) have been highlighted in very different pathology settings including autoimmune diseases, allergy, graft rejection, and cancer. Improving tools for the characterization of Bregs has become the main objective especially in humans. Transitional, mature B cells and plasma cells can differentiate into IL-10 producing Bregs in both mice and humans, suggesting that Bregs are not derived from unique precursors but may arise from different competent progenitors at unrestricted development stages. Moreover, in addition to IL-10 production, regulatory B cells used a broad range of suppressing mechanisms to modulate the immune response. Although Bregs have been consistently described in the literature, only a few reports described the molecular aspects that control the acquisition of the regulatory function. In this manuscript, we detailed the latest reports describing the control of IL-10, TGFβ, and GZMB production in different Breg subsets at the molecular level. We focused on the understanding of the role of the transcription factors STAT3 and c-MAF in controlling IL-10 production in murine and human B cells and how these factors may represent an important crossroad of several key drivers of the Breg response. Finally, we provided original data supporting the evidence that MAF is expressed in human IL-10- producing plasmablast and could be induced in vitro following different stimulation cocktails. At steady state, we reported that MAF is expressed in specific human B-cell tonsillar subsets including the IgD⁺ CD27⁺ unswitched population, germinal center cells and plasmablast.

Sporadic Alzheimer's Disease- and Neurotoxicity-Related microRNAs Affecting Key Events of Tau-Driven Adverse Outcome Pathway Toward Memory Loss

BACKGROUND

A complex network of aging-related homeostatic pathways that are sensitive to further deterioration in the presence of genetic, systemic, and environmental risk factors, and lifestyle, is implicated in the pathogenesis of progressive neurodegenerative diseases, such as sporadic (late-onset) Alzheimer's disease (sAD).

OBJECTIVE

Since sAD pathology and neurotoxicity share microRNAs (miRs) regulating common as well as overlapping pathological processes, environmental neurotoxic compounds are hypothesized to exert a risk for sAD initiation and progression.

METHODS

Literature search for miRs associated with human sAD and environmental neurotoxic compounds was conducted. Functional miR analysis using PathDip was performed to create miR-target interaction networks.

RESULTS

The identified miRs were successfully linked to the hypothetical starting point and key events of the earlier proposed tau-driven adverse outcome pathway toward memory loss. Functional miR analysis confirmed most of the findings retrieved from literature and revealed some interesting findings. The analysis identified 40 miRs involved in both sAD and neurotoxicity that dysregulated processes governing the plausible adverse outcome pathway for memory loss.

CONCLUSION

Creating miR-target interaction networks related to pathological processes involved in sAD initiation and progression, and environmental chemical-induced neurotoxicity, respectively, provided overlapping miR-target interaction networks. This overlap offered an opportunity to create an alternative picture of the mechanisms underlying sAD initiation and early progression. Looking at initiation and progression of sAD from this new angle may open for new biomarkers and novel drug targets for sAD before the appearance of the first clinical symptoms.

Cerebrospinal Fluid Extracellular Vesicles with Distinct Properties in Autoimmune Encephalitis and Herpes Simplex Encephalitis

Encephalitis mediated by autoantibodies against neuronal antigens and herpes simplex encephalitis (HSE) are seemingly separate causes of encephalopathy in adults. Autoimmune encephalitis (AE) is autoimmune in origin, and herpes simplex encephalitis is infectious. The purpose of this study was to examine the role of cerebrospinal fluid (CSF) exosomes from patients with antibody-positive AE and HSE. Towards this, exosomes were isolated from CSF from 13 patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, 11 patients with anti-gamma-aminobutyric acid-B (GABAB) receptor encephalitis, 9 patients with anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis, and 8 patients with anti-contactin-associated protein-like 2 (CASPR2) encephalitis, and 12 control individuals negative of antibodies against neuronal autoantigens. There were ten miRNAs highly expressed in patients with anti-NMDAR encephalitis compared to those in control subjects. Eight miRNAs were found to be lower expressed in anti-NMDAR encephalitis CSF-derived exosomes. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enriched by AE differential expressed exosomic miRNAs demonstrated that AE-related exosomic miRNAs may participate as a feedback regulation in cancer development. In addition, the exosome concentration in CSF of 9 HSE patients was significantly higher compared to those from 9 HSV( −) patients. This observation was consistent with the results that exosome concentration was found to be higher in the animal model which was inoculated intranasally with HSV-1 compared to controls. Furthermore, western blot demonstrated that the subunits of NMDAR, GABA_BR, and AMPAR were detected highly expressed in exosomes derived from sera of HSV-1-treated animal model compared to controls. More importantly, exosomes isolated from CSF of HSE patients contained higher expression levels of two miRNAs encoded by HSV, miR-H2-3p, and miR-H4-3p compared to those from HSV( −) patients. In summary, HSV may trigger brain autoimmunity in HSE by presentation of surface autoantigens via exosomes.

MiR-155: An Important Regulator of Neuroinflammation

MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression at the post-transcriptional level and that play an important role in many cellular processes, including modulation of inflammation. MiRNAs are present in high concentrations in the central nervous system (CNS) and are spatially and temporally expressed in a specific way. Therefore, an imbalance in the expression pattern of these small molecules can be involved in the development of neurological diseases. Generally, CNS responds to damage or disease through the activation of an inflammatory response, but many neurological disorders are characterized by uncontrolled neuroinflammation. Many studies support the involvement of miRNAs in the activation or inhibition of inflammatory signaling and in the promotion of uncontrolled neuroinflammation with pathological consequences. MiR-155 is a pro-inflammatory mediator of the CNS and plays an important regulatory role. The purpose of this review is to summarize how miR-155 is regulated and the pathological consequences of its deregulation during neuroinflammatory disorders, including multiple sclerosis, Alzheimer's disease and other neuroinflammatory disorders. Modulation of miRNAs' expression could be used as a therapeutic strategy in the treatment of pathological neuroinflammation.

Differential and Common Signatures of miRNA Expression and Methylation in Childhood Central Nervous System Malignancies: An Experimental and Computational Approach

Epigenetic modifications are considered of utmost significance for tumor ontogenesis and progression. Especially, it has been found that miRNA expression, as well as DNA methylation plays a significant role in central nervous system tumors during childhood. A total of 49 resected brain tumors from children were used for further analysis. DNA methylation was identified with methylation-specific MLPA and, in particular, for the tumor suppressor genes CASP8, RASSF1, MGMT, MSH6, GATA5, ATM1, TP53, and CADM1. miRNAs were identified with microarray screening, as well as selected samples, were tested for their mRNA expression levels. CASP8, RASSF1 were the most frequently methylated genes in all tumor samples. Simultaneous methylation of genes manifested significant results with respect to tumor staging, tumor type, and the differentiation of tumor and control samples. There was no significant dependence observed with the methylation of one gene promoter, rather with the simultaneous presence of all detected methylated genes' promoters. miRNA expression was found to be correlated to gene methylation. Epigenetic regulation appears to be of major importance in tumor progression and pathophysiology, making it an imperative field of study.

Anti-Oxidative, Anti-Inflammatory and Anti-Apoptotic Effects of Flavonols: Targeting Nrf2, NF-κB and p53 Pathways in Neurodegeneration

Neurodegenerative diseases are one of the leading causes of disability and death worldwide. Intracellular transduction pathways that end in the activation of specific transcription factors are highly implicated in the onset and progression of pathological changes related to neurodegeneration, of which those related to oxidative stress (OS) and neuroinflammation are particularly important. Here, we provide a brief overview of the key concepts related to OS- and neuroinflammation-mediated neuropathological changes in neurodegeneration, together with the role of transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB). This review is focused on the transcription factor p53 that coordinates the cellular response to diverse genotoxic stimuli, determining neuronal death or survival. As current pharmacological options in the treatment of neurodegenerative disease are only symptomatic, many research efforts are aimed at uncovering efficient disease-modifying agents. Natural polyphenolic compounds demonstrate powerful anti-oxidative, anti-inflammatory and anti-apoptotic effects, partially acting as modulators of signaling pathways. Herein, we review the current understanding of the therapeutic potential and limitations of flavonols in neuroprotection, with emphasis on their anti-oxidative, anti-inflammatory and anti-apoptotic effects along the Nrf2, NF-κB and p53 pathways. A better understanding of cellular and molecular mechanisms of their action may pave the way toward new treatments.

[The miRNA neuroinflammatory biomarkers in COVID-19 patients with different severity of illness]

INTRODUCTION

The expression of specific miRNAs and their mRNA targets are changed in infectious disease. The aim of this study was to analyze the expression of pro-neuroinflammatory miRNAs, anti- neuroinflammatory miRNAs, and their mRNA targets in the serum of COVID-19 patients with different grades.

METHODS

COVID-19 patients with different grades were enrolled in this study and the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their target mRNAs was analyzed by q-PCR.

RESULTS

The relative expression of anti- neuroinflammatory miRNAs (mir-21, mir-124, and mir-146a) was decreased and the relative expression of their target mRNAs (IL-12p53, Stat3, and TRAF6) was increased. Also, the relative expression of pro-neuroinflammatory miRNAs (mir-326, mir-155, and mir-27b) was increased and the relative expression of their target mRNA (PPARS, SOCS1, and CEBPA) was decreased in COVID-19 patients with increase of disease grade. A negative significant correlation was seen between mir-21 and IL-12p53 mRNA, mir-124 and Stat3 mRNA, mir-146a and TRAF6 mRNA, mir-27b and PPARS mRNA, mir-155 and SOCS1 mRNA, and between mir-326 and CEBPA mRNA in COVID-19 patients (P<0.05).

CONCLUSIONS

This study showed that the relative expression of anti- neuroinflammatory miRNAs was decreased and the relative expression of their targeted mRNAs was increased in COVID-19 patients from asymptomatic to critical illness. Also, this study showed that the relative expression of pro-neuroinflammatory miRNAs was increased and the relative expression of their targeted mRNA was decreased in COVID-19 patients from asymptomatic to critical illness.

The pro-inflammatory microRNA miR-155 influences fibrillar β-Amyloid1-42 catabolism by microglia

Microglia are the innate immune cells of the central nervous system that adopt rapid functional changes in response to Damage Associated Molecular Patterns, including aggregated β-Amyloid (Aβ) found in Alzheimer's disease (AD). microRNAs (miRNAs) are post-transcriptional modulators that influence the timing and magnitude of microglia inflammatory responses by downregulating the expression of inflammatory effectors. Recent studies implicate miR-155, a miRNA known to regulate inflammatory responses, in the pathogenesis of neurodegenerative disorders including multiple sclerosis, ALS, familial Parkinson's disease, and AD. In this work, we asked if miR-155 expression in microglia modifies cellular behaviors in response to fibrillar Aβ1-42 (fAβ1-42 ), in vitro. We hypothesized that in microglia, miR-155 expression would impact the internalization and catabolism of extracellular fAβ1-42 . Primary microglia stimulated with lipopolysaccharide demonstrate fast upregulation of miR-155 followed by delayed upregulation of miR-146a, an anti-inflammatory miRNA. Conditional overexpression of miR-155 in microglia resulted in significant upregulation of miR-146a. Conditional deletion of miR-155 promoted transit of fAβ1-42 to low-pH compartments where catabolism occurs, while miR-155 overexpression decreases fAβ1-42 catabolism. Uptake of fAβ1-42 across the plasma membrane increased with both up and downregulation of miR-155 expression. Taken together, our results support the hypothesis that inflammatory signaling influences the ability of microglia to catabolize fAβ1-42 through interconnected mechanisms modulated by miR-155. Understanding how miRNAs modulate the ability of microglia to catabolize fAβ1-42 will further elucidate the role of cellular players and molecular crosstalk in AD pathophysiology.

miR-155 as an Important Regulator of Multiple Sclerosis Pathogenesis. A Review

Multiple sclerosis (MS) is a chronic, immune-mediated disease and the leading cause of disability among young adults. MicroRNAs (miRNAs) are involved in the post-transcriptional regulation of gene expression. Of them, miR-155 is a crucial regulator of inflammation and plays a role in modulating the autoimmune response in MS. miR-155 is involved in blood–brain barrier (BBB) disruption via down-regulation of key junctional proteins under inflammatory conditions. It drives demyelination processes by contributing to, e.g., microglial activation, polarization of astrocytes, and down-regulation of CD47 protein and affecting crucial transcription factors. miR-155 has a huge impact on the development of neuropathic pain and indirectly influences a regulatory T (Treg) cell differentiation involved in the alleviation of pain hypersensitivity. This review also focused on neuropsychiatric symptoms appearing as a result of disease-associated stressors, brain atrophy, and pro-inflammatory factors. Recent studies revealed the role of miR-155 in regulating anxiety, stress, inflammation in the hippocampus, and treatment-resistant depression. Inhibition of miR-155 expression was demonstrated to be effective in preventing processes involved in the pathophysiology of MS. This review aimed to support the better understanding the great role of miR-155 dysregulation in various aspects of MS pathophysiology and highlight future perspectives for this molecule.

Altered microRNAs in cerebrospinal fluid exosomes in paraneoplastic and autoimmune encephalitis: A possible feedback in cancer development

AIMS

The purpose of this study was to examine the role of cerebrospinal fluid (CSF) exosomes from patients with paraneoplastic and autoimmune encephalitis (AE).

MAIN METHODS

Towards this, microRNA profiling in the exosomes which were isolated from cerebrospinal fluid of 12 patients with anti-N-methyl-d-aspartate (NMDA) receptor encephalitis, 12 patients with anti-gamma-aminobutyric acid-B (GABAB) receptor encephalitis, 12 patients with anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis, and 12 patients with anti-contactin-associated protein-like 2 (CASPR2) encephalitis, and 12 control individuals negative of antibodies against neuronal auto-antigens. Selected findings were validated with quantitative RT-PCR. DIANA-mirPath was chosen for bioinformatic analysis.

KEY FINDINGS

There were ten miRNAs higher expressed in AE patients with anti-NMDAR encephalitis compared to those in healthy controls. Further, eight miRNAs were found to be lower expressed in anti-NMDAR encephalitis CSF derived exosomes. In addition, Endometrial cancer, p53 signaling pathway, Non-small cell lung cancer, Small cell lung cancer, Transcriptional misregulation in cancer, Basal cell carcinoma, Acute myeloid leukemia, Renal cell carcinoma, Colorectal cancer, Choline metabolism in cancer, Melanoma, Pancreatic cancer, Prostate cancer, Ras signaling pathway, Glioma, Pathways in cancer, and Proteoglycans in cancer (all p < 0.01) were significantly enriched in differentially expressed miRNAs.

SIGNIFICANCES

Exosomes expressing specific miRNAs in antibody positive AE may participate as a feedback regulation in cancer development.

Fetal-Derived Immune Cells at the Roots of Lifelong Pathophysiology

Tissue-resident innate immune cells exert a wide range of functions in both adult homeostasis and pathology. Our understanding of when and how these cellular networks are established has dramatically changed with the recognition that many lineages originate at least in part from fetal sources and self-maintain independently from hematopoietic stem cells. Indeed, fetal-derived immune cells are found in most organs and serous cavities of our body, where they reside throughout the entire lifespan. At the same time, there is a growing appreciation that pathologies manifesting in adulthood may be caused by adverse early life events, a concept known as “developmental origins of health and disease” (DOHaD). Yet, whether fetal-derived immune cells are mechanistically involved in DOHaD remains elusive. In this review, we summarize our knowledge of fetal hematopoiesis and its contribution to adult immune compartments, which results in a “layered immune system.” Based on their ontogeny, we argue that fetal-derived immune cells are prime transmitters of long-term consequences of prenatal adversities. In addition to increasing disease susceptibility, these may also directly cause inflammatory, degenerative, and metabolic disorders. We explore this notion for cells generated from erythro-myeloid progenitors (EMP) produced in the extra-embryonic yolk sac. Focusing on macrophages and mast cells, we present emerging evidence implicating them in lifelong disease by either somatic mutations or developmental programming events resulting from maternal and early environmental perturbations.

Neuroinflammation in Ischemic Stroke: Focus on MicroRNA-mediated Polarization of Microglia

Ischemic stroke is one of the most common causes of death and disability worldwide. Neuroinflammation is a major pathological event involved in the process of ischemic injury and repair. In particular, microglia play a dual role in neuroinflammation. During the acute phase of stroke onset, M2 microglia are the dominant phenotype and exert protective effects on neuronal cells, whereas permanent M1 microglia contribute to prolonged inflammation and are detrimental to brain tissue. Emerging evidence indicates that microRNAs (miRNAs) may have regulatory effects on microglia-associated inflammation. Thus, we briefly reviewed the dynamic response of microglia after a stroke and assessed how specific miRNAs affect the behavior of reactive microglia. We concluded that miRNAs may be useful novel therapeutic targets to improve stroke outcomes and modulate neuroinflammation.

MicroRNA-155 contributes to plexiform neurofibroma growth downstream of MEK

MicroRNAs (miRs) are small non-coding RNAs that can have large impacts on oncogenic pathways. Possible functions of dysregulated miRs have not been studied in neurofibromatosis type 1 (NF1) plexiform neurofibromas (PNFs). In PNFs, Schwann cells (SCs) have biallelic NF1 mutations necessary for tumorigenesis. We analyzed a miR-microarray comparing to normal and PNF SCs and identified differences in miR expression, and we validated in mouse PNFs versus normal mouse SCs by qRT-PCR. Among these, miR-155 was a top overexpressed miR, and its expression was regulated by RAS/MAPK signaling. Overexpression of miR-155 increased mature Nf1^−/− mouse SC proliferation. In SC precursors, which model tumor initiating cells, pharmacological and genetic inhibition of miR-155 decreased PNF-derived sphere numbers in vitro and we identified Maf as a miR-155 target. In vivo, global deletion of miR-155 significantly decreased tumor number and volume, increasing mouse survival. Fluorescent nanoparticles entered PNFs, suggesting that an anti-miR might have therapeutic potential. However, treatment of established PNFs using anti-miR-155 peptide nucleic acid-loaded nanoparticles marginally decreased tumor numbers and did not reduce tumor growth. These results suggest that miR-155 plays a functional role in PNF growth and/or SC proliferation, and that targeting neurofibroma miRs is feasible, and might provide novel therapeutic opportunities.

SIRT1 activation by minocycline on regulation of microglial polarization homeostasis

Sirtuin 1 (SIRT1) has been reported to be involved in the mechanisms underlying longevity and has also been indicated as a valuable regulator of age-related neurological disorders. Some natural products increase SIRT1 activity and stimulate deacetylation of various proteins. In the present study, SIRT1 overexpression by genetic modification or treatment with SIRT1 activators significantly inhibited the secretion of nitric oxide and expression of inducible nitric oxide synthase, cyclooxygenase 2, and proinflammatory mediator-interleukin 1β-in microglia. SIRT1 activation also decreased the levels of K379 acetyl-p53 and the protein inhibitor of activated Stat 1 expression in microglial cells. In addition, it dramatically promoted M2 polarization of microglia, which enhanced cell motility and altered phagocytic ability. We also used minocycline, a well-known inhibitor of microglial activation, to study the mechanism of SIRT1 signaling. Minocycline treatment decreased neuroinflammatory responses and promoted M2 polarization of microglia. It also reduced the acetyl-p53 level in the brain tissues in an inflammatory mouse model. Our findings demonstrated that SIRT1 participates in the maintenance of microglial polarization homeostasis and that minocycline exerts regulatory effects on SIRT1 activation. Therefore, our results indicate that SIRT1 activation may be a useful therapeutic target for the treatment of neuroinflammation-associated disorders.

microRNAs: key modulators of disease-modifying therapies in multiple sclerosis

There is a high level of heterogeneity in symptom manifestations and response to disease-modifying therapies (DMTs) in multiple sclerosis (MS), an immune-based neurodegenerative disease with ever-increasing prevalence in recent decades. Because of unknown aspects of the etiopathology of MS and mechanism of action of DMTs, the reason for this variability is undetermined, and much remains to be understood. Traditionally, physicians consider switching to other DMTs based on the exacerbation of symptoms and/or change in the results of magnetic resonance imaging and biochemical factors. Therefore, identifying biological treatment response markers that help us recognizing non-responders rapidly and subsequently choosing another DMTs is necessary. microRNAs (miRNAs) are micromanagers of gene expression which have been profiled in different samples of MS patients, highlighting their role in pathogenetic of MS. Recent studies have investigated expression profiling of miRNAs after treatment with DMTs to clarify possible DMTs-mediated mechanism and obtaining response to therapy biomarkers. In this review, we will discuss the modulation of miRNAs by DMTs in cells and pathways involved in MS.

Trp53 regulates platelets in bone marrow via the PI3K pathway

The p53 gene is well known as a key tumor suppressor gene; it is vital for hematopoietic stem cell differentiation and growth. In the present study, the change of platelets (PLTs) in p53 knockout mice (p53^-/- mice) was investigated. The peripheral blood cell subsets and PLT parameters in p53^-/-mice were compared with those in age-matched p53^+/+ mice. Bleeding time as well as the alteration of PLT levels, were analyzed with the PLT marker CD41 antibody using flow cytometry. The results revealed that the number of PLTs in p53^-/- mice was significantly lower than that in p53^+/+ mice. Bleeding time was prolonged in the peripheral blood of p53^-/- mice compared with that of p53^+/+ mice. Furthermore, the related gene expression of the PI3K signaling pathway in the bone marrow of p53^-/- mice was shown to be associated with plateletogenesis. PI3K inhibitor (LY294002) was also used to treat p53^-/- mice, and the results demonstrated that LY294002 revert the change of PLTs in these mice. In summary, PLTs were altered in p53^-/- mice, and the PI3K signaling pathway was involved in that process, suggesting that the p53-dependent PI3K signaling pathway is involved in thrombocytopenia or PLT diseases. PLT number is reduced in p53 deficiency; however, this reduction could be reverted by inhibiting the PI3K pathway.

microRNA-367-3p regulation of GPRC5A is suppressed in ischemic stroke

Ischemic stroke is a major cause of mortality and long-term disability with limited treatment options, and a greater understanding of the gene regulatory mechanisms underlying ischemic stroke-associated neuroinflammation is required for new therapies. To study ischemic stroke in vivo, mice were subjected to sustained ischemia by intraluminal filament-induced middle cerebral artery occlusion (MCAo) for 24 h without reperfusion or transient ischemia for 30 min followed by 23.5 h reperfusion, and brain miRNA and mRNA expression changes were quantified by TaqMan OpenArrays and gene (mRNA) expression arrays, respectively. Sustained ischemia resulted in 18 significantly altered miRNAs and 392 altered mRNAs in mouse brains compared to Sham controls; however, the transient ischemic condition was found to impact only 6 miRNAs and 126 mRNAs. miR-367-3p was found to be significantly decreased in brain homogenates with sustained ischemia. G protein-coupled receptor, family C, group 5, member A (Gprc5a), a miR-367-3p target gene, was found to be significantly increased with sustained ischemia. In primary neurons, inhibition of endogenous miR-367-3p resulted in a significant increase in Gprc5a expression. Moreover, miR-367-3p was found to be co-expressed with GPRC5A in human neurons. Results suggest that loss of miR-367-3p suppression of GPRC5A may contribute to neuroinflammation associated with ischemic stroke.

Aggravated brain injury after neonatal hypoxic ischemia in microglia-depleted mice

Background

Neuroinflammation plays an important role in neonatal hypoxic-ischemic encephalopathy (HIE). Although microglia are largely responsible for injury-induced inflammatory response, they play beneficial roles in both normal and disease states. However, the effects of microglial depletion on neonatal HIE remain unclear.

Methods

Tamoxifen was administered to Cx3cr1^CreER/+Rosa26^DTA/+ (microglia-depleted model) and Cx3cr1^CreER/+Rosa26^DTA/− (control) mice at P8 and P9 to assess the effect of microglial depletion. The density of microglia was quantified using Iba-1 staining. Moreover, the proportion of resident microglia after the HI insult was analyzed using flow cytometric analysis. At P10, the HI insult was conducted using the Rice-Vannucci procedure at P10. The infarct size and apoptotic cells were analyzed at P13. Cytokine analyses were performed using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) at P13.

Results

At P10, tamoxifen administration induced > 99% microglial depletion in DTA⁺ mice. Following HI insult, there was persisted microglial depletion over 97% at P13. Compared to male DTA⁻ mice, male DTA⁺ mice exhibited significantly larger infarct volumes; however, there were no significant differences among females. Moreover, compared to male DTA⁻ mice, male DTA⁺ mice had a significantly higher density of TUNEL⁺ cells in the caudoputamen, cerebral cortex, and thalamus. Moreover, compared to female DTA⁻ mice, female DTA⁺ mice showed a significantly greater number of TUNEL⁺ cells in the hippocampus and thalamus. Compared to DTA⁻ mice, ELISA revealed significantly lower IL-10 and TGF-β levels in both male and female DTA⁺ mice under both normal conditions and after HI (more pronounced).

Conclusion

We established a microglial depletion model that aggravated neuronal damage and apoptosis after the HI insult, which was predominantly observed in males.

c-MAF, a Swiss Army Knife for Tolerance in Lymphocytes

Beyond its well-admitted role in development and organogenesis, it is now clear that the transcription factor c-Maf has owned its place in the realm of immune-related transcription factors. Formerly introduced solely as a Th2 transcription factor, the role attributed to c-Maf has gradually broadened over the years and has extended to most, if not all, known immune cell types. The influence of c-Maf is particularly prominent among T cell subsets, where c-Maf regulates the differentiation as well as the function of multiple subsets of CD4 and CD8 T cells, lending it a crucial position in adaptive immunity and anti-tumoral responsiveness. Recent research has also revealed the role of c-Maf in controlling Th17 responses in the intestine, positioning it as an essential factor in intestinal homeostasis. This review aims to present and discuss the recent advances highlighting the particular role played by c-Maf in T lymphocyte differentiation, function, and homeostasis.

Endothelial Cell-Specific Transcriptome Reveals Signature of Chronic Stress Related to Worse Outcome After Mild Transient Brain Ischemia in Mice

Vascular mechanisms underlying the adverse effects that depression and stress-related mental disorders have on stroke outcome are only partially understood. Identifying the transcriptomic signature of chronic stress in endothelium harvested from the ischemic brain is an important step towards elucidating the biological processes involved. Here, we subjected male 129S6/SvEv mice to a 28-day model of chronic stress. The ischemic lesion was quantified after 30 min filamentous middle cerebral artery occlusion (MCAo) and 48 h reperfusion by T2-weighted MRI. RNA sequencing was used to profile transcriptomic changes in cerebrovascular endothelial cells (ECs) from the infarct. Mice subjected to the stress procedure displayed reduced weight gain, increased adrenal gland weight, and increased hypothalamic FKBP5 mRNA and protein expression. Chronic stress conferred increased lesion volume upon MCAo. Stress-exposed mice showed a higher number of differentially expressed genes between ECs isolated from the ipsilateral and contralateral hemisphere than control mice. The genes in question are enriched for roles in biological processes closely linked to endothelial proliferation and neoangiogenesis. MicroRNA-34a was associated with nine of the top 10 biological process Gene Ontology terms selectively enriched in ECs from stressed mice. Moreover, expression of mature miR-34a-5p and miR-34a-3p in ischemic brain tissue was positively related to infarct size and negatively related to sirtuin 1 (Sirt1) mRNA transcription. In conclusion, this study represents the first EC-specific transcriptomic analysis of chronic stress in brain ischemia. The stress signature uncovered relates to worse stroke outcome and is directly relevant to endothelial mechanisms in the pathogenesis of stroke.

Ischemic preconditioning induces cortical microglial proliferation and a transcriptomic program of robust cell cycle activation

Ischemic preconditioning (IPC) is an experimental phenomenon in which a subthreshold ischemic insult applied to the brain reduces damage caused by a subsequent more severe ischemic episode. Identifying key molecular and cellular mediators of IPC will provide critical information needed to develop novel therapies for stroke. Here we report that the transcriptomic response of acutely isolated preconditioned cortical microglia is dominated by marked upregulation of genes involved in cell cycle activation and cellular proliferation. Notably, this transcriptional response occurs in the absence of cortical infarction. We employed ex vivo flow cytometry, immunofluorescent microscopy, and quantitative stereology methods on brain tissue to evaluate microglia proliferation following IPC. Using cellular colocalization of microglial (Iba1) and proliferation (Ki67 and BrdU) markers, we observed a localized increase in the number of microglia and proliferating microglia within the preconditioned hemicortex at 72, but not 24, hours post-IPC. Our quantification demonstrated that the IPC-induced increase in total microglia was due entirely to proliferation. Furthermore, microglia in the preconditioned hemisphere had altered morphology and increased soma volumes, indicative of an activated phenotype. Using transgenic mouse models with either fractalkine receptor (CX3CR1)-haploinsufficiency or systemic type I interferon signaling loss, we determined that microglial proliferation after IPC is dependent on fractalkine signaling but independent of type I interferon signaling. These findings suggest there are multiple distinct targetable signaling pathways in microglia, including CX3CR1-dependent proliferation that may be involved in IPC-mediated protection.

The role of microglia in ischemic preconditioning

Ischemic preconditioning (IPC) is an experimental phenomenon in which a brief ischemic stimulus confers protection against a subsequent prolonged ischemic event. Initially thought to be due to mechanistic changes in neurons, our understanding of IPC has evolved to encompass a global reprogramming of the Central Nervous System (CNS) after transient ischemia/reperfusion that requires innate immune signaling pathways including Toll-like receptors (TLRs) and Type I interferons. Microglia are the CNS resident neuroimmune cells that express these key innate immune receptors. Studies suggest that microglia are required for IPC-mediated neuronal and axonal protection. Multiple paradigms targeting TLRs have converged on a distinctive Type I interferon response in microglia that is critical for preconditioning-mediated protection against ischemia. These pathways can be targeted through administration of TLR agonists, cytokines including interferon-β, and pharmaceutical agents that induce preconditioning through cross-tolerance mechanisms. Transcriptomic analyses and single cell RNA studies point to specific gene expression signatures in microglia that functionally shift these mutable cells to an immunomodulatory or protective phenotype. Although there are technological challenges and gaps in knowledge to overcome, the targeting of specific molecular signaling pathways in microglia is a promising direction for development of novel and effective pharmacotherapies for stroke. Studies on preconditioning in animal models, including nonhuman primates, show promise as prophylactic preconditioning treatments for selected at risk patient populations. In addition, our growing understanding of the mechanisms of IPC-mediated protection is identifying novel cellular and molecular targets for therapeutic interventions that could apply broadly to both acute stroke and chronic vascular cognitive impairment patients.

Prioritizing target-disease associations with novel safety and efficacy scoring methods

Biological target (commonly genes or proteins) identification is still largely a manual process, where experts manually try to collect and combine information from hundreds of data sources, ranging from scientific publications to omics databases. Targeting the wrong gene or protein will lead to failure of the drug development process, as well as incur delays and costs. To improve this process, different software platforms are being developed. These platforms rely strongly on efficacy estimates based on target-disease association scores created by computational methods for drug target prioritization. Here novel computational methods are presented to more accurately evaluate the efficacy and safety of potential drug targets. The proposed efficacy scores utilize existing gene expression data and tissue/disease specific networks to improve the inference of target-disease associations. Conversely, safety scores enable the identification of genes that are essential, potentially susceptible to adverse effects or carcinogenic. Benchmark results demonstrate that our transcriptome-based methods for drug target prioritization can increase the true positive rate of target-disease associations. Additionally, the proposed safety evaluation system enables accurate predictions of targets of withdrawn drugs and targets of drug trials prematurely discontinued.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

Neuroinvasive Listeria monocytogenes Infection Triggers IFN-Activation of Microglia and Upregulates Microglial miR-155

MicroRNA (miR) miR-155 modulates microglial activation and polarization, but its role in activation of microglia during bacterial brain infection is unclear. We studied miR-155 expression in brains of C57BL/6 (B6.WT) mice infected i.p. with the neuro-invasive bacterial pathogen Listeria monocytogenes (L. monocytogenes). Infected mice were treated with ampicillin starting 2 days (d) post-infection (p.i.) and analyzed 3d, 7d, and 14d p.i. Virulent L. monocytogenes strains EGD and 10403s upregulated miR-155 in whole brain 7 d p.i. whereas infection with avirulent, non-neurotropic Δhly or ΔactA L. monocytogenes mutants did not. Similarly, infection with virulent but not mutated bacteria upregulated IFN-γ mRNA in the brain at 7 d p.i. Upregulation of miR-155 in microglia was confirmed by qPCR of flow cytometry-sorted CD45^intCD11b^pos brain cells. Subsequently, brain leukocyte influxes and gene expression in sorted microglia were compared in L. monocytogenes-infected B6.WT and B6.Cg-Mir155tm1.1Rsky/J (B6.miR-155^−/−) mice. Brain influxes of Ly-6C^high monocytes and upregulation of IFN-related genes in microglia were similar to B6.WT mice at 3 d p.i. In contrast, by d 7 p.i. expressions of microglial IFN-related genes, including markers of M1 polarization, were significantly lower in B6.miR-155^−/− mice and by 14 d p.i., influxes of activated T-lymphocytes were markedly reduced. Notably, CD45^highCD11b^pos brain cells from B6.miR-155^−/− mice isolated at 7 d p.i. expressed 2-fold fewer IFN-γ transcripts than did cells from B6.WT mice suggesting reduced IFN-γ stimulation contributed to dampened gene expression in B6.miR-155^−/− microglia. Lastly, in vitro stimulation of 7 d p.i. brain cells with heat-killed L. monocytogenes induced greater production of TNF in B6.miR-155^−/− microglia than in B6.WT microglia. Thus, miR-155 affects brain inflammation by multiple mechanisms during neuroinvasive L. monocytogenes infection. Peripheral miR-155 promotes brain inflammation through its required role in optimal development of IFN-γ-secreting lymphocytes that enter the brain and activate microglia. Microglial miR-155 promotes M1 polarization, and also inhibits inflammatory responses to stimulation by heat-killed L. monocytogenes, perhaps by targeting Tab2.

A lincRNA-p21/miR-181 family feedback loop regulates microglial activation during systemic LPS- and MPTP- induced neuroinflammation

The role of microglial-mediated sustained neuroinflammation in the onset and progression of Parkinson’s disease (PD) is well established, but the mechanisms contributing to microglial activation remain unclear. LincRNA-p21, a well studied long intergenic noncoding RNA (lincRNA), plays pivotal roles in diverse biological processes and diseases. Its role in microglial activation and inflammation-induced neurotoxicity, however, has not yet been fully elucidated. Here, we report that lincRNA-p21 promotes microglial activation through a p53-dependent transcriptional pathway. We further demonstrate that lincRNA-p21 competitively binds to the miR-181 family and induces microglial activation through the miR-181/PKC-δ pathway. Moreover, PKC-δ induction further increases the expression of p53/lincRNA-p21 and thus forms a circuit. Taken together, our results suggest that p53/lincRNA-p21, together with miR-181/PKC-δ, form a double-negative feedback loop that facilitates sustained microglial activation and the deterioration of neurodegeneration.

Increased expression of matrix metalloproteinase 3 can be attenuated by inhibition of microRNA-155 in cultured human astrocytes

Background

Temporal lobe epilepsy (TLE) is a chronic neurological disease, in which about 30% of patients cannot be treated adequately with anti-epileptic drugs. Brain inflammation and remodeling of the extracellular matrix (ECM) seem to play a major role in TLE. Matrix metalloproteinases (MMPs) are proteolytic enzymes largely responsible for the remodeling of the ECM. The inhibition of MMPs has been suggested as a novel therapy for epilepsy; however, available MMP inhibitors lack specificity and cause serious side effects. We studied whether MMPs could be modulated via microRNAs (miRNAs). Several miRNAs mediate inflammatory responses in the brain, which are known to control MMP expression. The aim of this study was to investigate whether an increased expression of MMPs after interleukin-1β (IL-1β) stimulation can be attenuated by inhibition of the inflammation-associated miR-155.

Methods

We investigated the expression of MMP2, MMP3, MMP9, and MMP14 in cultured human fetal astrocytes after stimulation with the pro-inflammatory cytokine IL-1β. The cells were transfected with miR-155 antagomiR, and the effect on MMP3 expression was investigated using real-time quantitative PCR and Western blotting. Furthermore, we characterized MMP3 and miR-155 expression in brain tissue of TLE patients with hippocampal sclerosis (TLE-HS) and during epileptogenesis in a rat TLE model.

Results

Inhibition of miR-155 by the antagomiR attenuated MMP3 overexpression after IL-1β stimulation in astrocytes. Increased expression of MMP3 and miR-155 was also evident in the hippocampus of TLE-HS patients and throughout epileptogenesis in the rat TLE model.

Conclusions

Our experiments showed that MMP3 is dynamically regulated by seizures as shown by increased expression in TLE tissue and during different phases of epileptogenesis in the rat TLE model. MMP3 can be induced by the pro-inflammatory cytokine IL-1β and is regulated by miR-155, suggesting a possible strategy to prevent epilepsy via reduction of inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1245-y) contains supplementary material, which is available to authorized users.

The p53 Family in Brain Disease

SIGNIFICANCE

The p53 family of transcription factors, including p53, p63, and p73, plays key roles in both biological and pathological processes, including cancer and neural development. Recent Advances: In recent years, a growing body of evidence has indicated that the entire p53 family is involved in the regulation of the central nervous system (CNS) functions as well as in the pathogenesis of several neurological disorders. Mechanistically, the p53 proteins control neuronal cell fate, terminal differentiation, and survival, via a complex interplay among the family members.

CRITICAL ISSUES

In this article, we discuss the involvement of the p53 family in neurobiology and in pathological conditions affecting the CNS, including neuroinflammation.

FUTURE DIRECTIONS

Understanding the molecular mechanism(s) underlying the function of the p53 family could improve our general knowledge of the pathogenesis of brain disorders and potentially pave the road for new therapeutic intervention. Antioxid. Redox Signal. 29, 1-14.

Correction to: Neuroimmune Response in Ischemic Preconditioning

Ischemic preconditioning (IPC) is a robust neuroprotective phenomenon in which a brief period of cerebral ischemia confers transient tolerance to subsequent ischemic challenge. Research on IPC has implicated cellular, molecular, and systemic elements of the immune response in this phenomenon. Potent molecular mediators of IPC include innate immune signaling pathways such as Toll-like receptors and type 1 interferons. Brain ischemia results in release of pro- and anti-inflammatory cytokines and chemokines that orchestrate the neuroinflammatory response, resolution of inflammation, and transition to neurological recovery and regeneration. Cellular mediators of IPC include microglia, the resident central nervous system immune cells, astrocytes, and neurons. All of these cell types engage in cross-talk with each other using a multitude of signaling pathways that modulate activation/suppression of each of the other cell types in response to ischemia. As the postischemic neuroimmune response evolves over time there is a shift in function toward provision of trophic support and neuroprotection. Peripheral immune cells infiltrate the central nervous system en masse after stroke and are largely detrimental, with a few subtypes having beneficial, protective effects, though the role of these immune cells in IPC is largely unknown. The role of neural progenitor cells in IPC-mediated neuroprotection is another active area of investigation as is the role of microglial proliferation in this setting. A mechanistic understanding of these molecular and cellular mediators of IPC may not only facilitate more effective direct application of IPC to specific clinical scenarios, but also, more broadly, reveal novel targets for therapeutic intervention in stroke.

Neuroprotective effects of pifithrin-α against traumatic brain injury in the striatum through suppression of neuroinflammation, oxidative stress, autophagy, and apoptosis

Cortical and hippocampal neuronal damages caused by traumatic brain injury (TBI) are associated with motor and cognitive impairments; however, only little attention paid to the striatal damage. It is known that the p53 tumor-suppressor transcription factor participated in TBI-induced secondary brain damage. We investigated how the p53 inactivator pifithrin (PFT)-α affected TBI-induced striatal neuronal damage at 24 h post-injury. Sprague-Dawley rats subjected to a controlled cortical impact were used as TBI models. We observed that p53 mRNA significantly increased, whereas p53 protein expression was distributed predominantly in neurons but not in glia cells in striatum after TBI. PFT-α improved motor deficit following TBI. PFT-α suppressed TBI-induced striatal glial activation and expression of proinflammatory cytokines. PFT-α alleviated TBI-induced oxidative damage TBI induced autophagy was evidenced by increased protein expression of Beclin-1 and shift of microtubule-associated light chain (LC)3-I to LC3-II, and decreased p62. These effects were reduced by PFT-α. Post-injury PFT-α treatment reduced the number of degenerating (FJC-positive) and apoptotic neurons. Our results suggest that PFT-α may provide neuroprotective effects via p53-dependent or -independent mechanisms depending on the cell type and timing after the TBI and can possibly be developed into a novel therapy to ameliorate TBI-induced neuronal damage.

Bridging Autism Spectrum Disorders and Schizophrenia through inflammation and biomarkers - pre-clinical and clinical investigations

In recent years, evidence supporting a link between inflammation and neuropsychiatric disorders has been mounting. Autism spectrum disorders (ASD) and schizophrenia share some clinical similarities which we hypothesize might reflect the same biological basis, namely, in terms of inflammation. However, the diagnosis of ASD and schizophrenia relies solely on clinical symptoms, and to date, there is no clinically useful biomarker to diagnose or monitor the course of such illnesses.

The focus of this review is the central role that inflammation plays in ASD and schizophrenia. It spans from pre-clinical animal models to clinical research and excludes in vitro studies. Four major areas are covered: (1) microglia, the inflammatory brain resident myeloid cells, (2) biomarkers, including circulating cytokines, oxidative stress markers, and microRNA players, known to influence cellular processes at brain and immune levels, (3) effect of anti-psychotics on biomarkers and other predictors of response, and (4) impact of gender on response to immune activation, biomarkers, and response to anti-psychotic treatments.

miR-146a-Traf6 regulatory axis controls autoimmunity and myelopoiesis, but is dispensable for hematopoietic stem cell homeostasis and tumor suppression

microRNA-146a (miR-146a) has been previously implicated as an essential molecular brake, preventing immune overreaction and malignant transformation by attenuating NF-κB signaling, putatively via repression of the Traf6 and Irak1 genes. The exact contribution of miR-146a-mediated silencing of these genes to the control of immune activation is currently unknown. Therefore, we defined the role of the miR-146a-Traf6 signaling axis in the regulation of immune homeostasis using a genetic epistasis analysis in miR-146a^-/- mice. We have uncovered a surprising separation of functions at the level of miR-146a targets. Lowering the Traf6 gene dose and consequent attenuation of NF-κB activation rescued several significant miR-146a^-/- phenotypes, such as splenomegaly, aberrant myeloproliferation, and excessive inflammatory responses. In contrast, decreasing Traf6 expression had no effect on the development of the progressive bone marrow failure phenotype, as well as lymphomagenesis in miR-146a^-/- mice, indicating that miR-146a controls these biological processes through different molecular mechanisms.