56 research outputs found
Identification of CNS Injury-Related microRNAs as Novel Toll-Like Receptor 7/8 Signaling Activators by Small RNA Sequencing
Toll-like receptors (TLRs) belong to pattern recognition receptors, which respond to danger signals such as pathogen-associated molecular patterns or damage-associated molecular patterns. Upon TLR activation in microglia, the major immune cells in the brain, distinct signaling cascades trigger the production of inflammatory molecules, being a critical feature in neuroinflammation and neurodegenerative processes. Recently, individual microRNAs (miRNAs) were shown to act as endogenous TLR ligands. Here, we conducted systematic screening for miRNAs as potential TLR7/8 ligands by small RNA sequencing of apoptotic neurons and their corresponding supernatants. Several miRNA species were identified in both supernatants and injured neurons, and 83.3% of the media-enriched miRNAs activated murine and/or human TLR7/8 expressed in HEK293-derived TLR reporter cells. Among the detected extracellular miRNAs, distinct miRNAs such as miR-340-3p and miR-132-5p induced cytokine and chemokine release from microglia and triggered neurotoxicity in vitro. Taken together, our systematic study establishes miRNAs released from injured neurons as new TLR7/8 activators, which contribute to inflammatory and neurodegenerative responses in the central nervous system (CNS)
Intrathecal heat shock protein 60 mediates neurodegeneration and demyelination in the CNS through a TLR4- and MyD88-dependent pathway
Background Toll-like receptors (TLR) constitute a highly conserved class of
receptors through which the innate immune system responds to both pathogen-
and host-derived factors. Although TLRs are involved in a wide range of
central nervous system (CNS) disorders including neurodegenerative diseases,
the molecular events leading from CNS injury to activation of these innate
immune receptors remain elusive. The stress protein heat shock protein 60
(HSP60) released from injured cells is considered an endogenous danger signal
of the immune system. In this context, the main objective of the present study
was to investigate the impact of extracellular HSP60 on the brain in vivo.
Results We show here that HSP60 injected intrathecally causes neuronal and
oligodendrocyte injury in the CNS in vivo through TLR4-dependent signaling.
Intrathecal HSP60 results in neuronal cell death, axonal injury, loss of
oligodendrocytes, and demyelination in the cerebral cortex of wild-type mice.
In contrast both mice lacking TLR4 and the TLR adaptor molecule MyD88 are
protected against deleterious effects induced by HSP60. In contrast to the
exogenous TLR4 ligand, lipopolysaccharide, intrathecal HSP60 does not induce
such a considerable inflammatory response in the brain. In the CNS, endogenous
HSP60 is predominantly expressed in neurons and released during brain injury,
since the cerebrospinal fluid (CSF) from animals of a mouse stroke model
contains elevated levels of this stress protein compared to the CSF of sham-
operated mice. Conclusions Our data show a direct toxic effect of HSP60
towards neurons and oligodendrocytes in the CNS. The fact that these harmful
effects involve TLR4 and MyD88 confirms a molecular pathway mediated by the
release of endogenous TLR ligands from injured CNS cells common to many forms
of brain diseases that bi-directionally links CNS injury and activation of the
innate immune system to neurodegeneration and demyelination in vivo
Оптимизация работы установок электроцентробежных насосов в процессе добычи нефти на Снежном нефтегазоконденсатном месторождении (Томская область)
Объектом исследования является Снежное нефтегазоконденсатное месторождение.
Цель работы – изучить оптимизацию работы установок электроцентробежных насосов в процессе добычи нефти на Снежном нефтегазоконденсатном месторождении.
В процессе работы были рассмотрены причины отказов в работе установок электроцентробежных насосов, выполнен статистический анализ отказов в работе скважин, оборудованных УЭЦН, показавший, что большая доля причин проведения подземных ремонтов (до 15%) связана с рассогласованием гидравлических характеристик центробежного насоса и пласта.The object of research is the Snezhnoye oil and gas condensate field.
The purpose of the work is to study the optimization of the operation of electric centrifugal pump installations in the process of oil production at the Snezhnoye oil and gas condensate field.
During the work, the reasons for failures in the operation of electric centrifugal pump installations were considered, a statistical analysis of failures in the operation of wells equipped with ESP was performed, which showed that a large share of the reasons for underground repairs (up to 15%) is associated with a mismatch in the hydraulic characteristics of the centrifugal pump and the formation
MicroRNA-100-5p and microRNA-298-5p released from apoptotic cortical neurons are endogenous Toll-like receptor 7/8 ligands that contribute to neurodegeneration
Background: MicroRNA (miRNA) expression in the brain is altered in neurodegenerative diseases. Recent studies demonstrated that selected miRNAs conventionally regulating gene expression at the post-transcriptional level can act extracellularly as signaling molecules. The identity of miRNA species serving as membrane receptor ligands involved in neuronal apoptosis in the central nervous system (CNS), as well as the miRNAs' sequence and structure required for this mode of action remained largely unresolved.
Methods. Using a microarray-based screening approach we analyzed apoptotic cortical neurons of C56BL/6 mice and their supernatant with respect to alterations in miRNA expression/presence. HEK-Blue Toll-like receptor (TLR) 7/8 reporter cells, primary microglia and macrophages derived from human and mouse were employed to test the potential of the identified miRNAs released from apoptotic neurons to serve as signaling molecules for the RNA-sensing receptors. Biophysical and bioinformatical approaches, as well as immunoassays and sequential microscopy were used to analyze the interaction between candidate miRNA and TLR. Immunocytochemical and -histochemical analyses of murine CNS cultures and adult mice intrathecally injected with miRNAs, respectively, were performed to evaluate the impact of miRNA-induced TLR activation on neuronal survival and microglial activation.
Results: We identified a specific pattern of miRNAs released from apoptotic cortical neurons that activate TLR7 and/or TLR8, depending on sequence and species. Exposure of microglia and macrophages to certain miRNA classes released from apoptotic neurons resulted in the sequence-specific production of distinct cytokines/chemokines and increased phagocytic activity. Out of those miRNAs miR-100-5p and miR-298-5p, which have consistently been linked to neurodegenerative diseases, entered microglia, located to their endosomes, and directly bound to human TLR8. The miRNA-TLR interaction required novel sequence features, but no specific structure formation of mature miRNA. As a consequence of miR-100-5p- and miR-298-5p-induced TLR activation, cortical neurons underwent cell-autonomous apoptosis. Presence of miR-100-5p and miR-298-5p in cerebrospinal fluid led to neurodegeneration and microglial accumulation in the murine cerebral cortex through TLR7 signaling.
Conclusion: Our data demonstrate that specific miRNAs are released from apoptotic cortical neurons, serve as endogenous TLR7/8 ligands, and thereby trigger further neuronal apoptosis in the CNS. Our findings underline the recently discovered role of miRNAs as extracellular signaling molecules, particularly in the context of neurodegeneration
The impact of single and pairwise Toll-like receptor activation on neuroinflammation and neurodegeneration
Background Toll-like receptors (TLRs) enable innate immune cells to respond to
pathogen- and host-derived molecules. The central nervous system (CNS)
exhibits most of the TLRs identified with predominant expression in microglia,
the major immune cells of the brain. Although individual TLRs have been shown
to contribute to CNS disorders, the consequences of multiple activated TLRs on
the brain are unclear. We therefore systematically investigated and compared
the impact of sole and pairwise TLR activation on CNS inflammation and injury.
Methods Selected TLRs expressed in microglia and neurons were stimulated with
their specific TLR ligands in varying combinations. Cell cultures were then
analyzed by immunocytochemistry, FlowCytomix, and ELISA. To determine neuronal
injury and neuroinflammation in vivo, C57BL/6J mice were injected
intrathecally with TLR agonists. Subsequently, brain sections were analyzed by
quantitative real-time PCR and immunohistochemistry. Results Simultaneous
stimulation of TLR4 plus TLR2, TLR4 plus TLR9, and TLR2 plus TLR9 in microglia
by their respective specific ligands results in an increased inflammatory
response compared to activation of the respective single TLR in vitro. In
contrast, additional activation of TLR7 suppresses the inflammatory response
mediated by the respective ligands for TLR2, TLR4, or TLR9 up to 24 h,
indicating that specific combinations of activated TLRs individually modulate
the inflammatory response. Accordingly, the composition of the inflammatory
response pattern generated by microglia varies depending on the identity and
combination of the activated TLRs engaged. Likewise, neuronal injury occurs in
response to activation of only selected TLRs and TLR combinations in vitro.
Activation of TLR2, TLR4, TLR7, and TLR9 in the brain by intrathecal injection
of the respective TLR ligand into C57BL/6J mice leads to specific expression
patterns of distinct TLR mRNAs in the brain and causes influx of leukocytes
and inflammatory mediators into the cerebrospinal fluid to a variable extent.
Also, the intensity of the inflammatory response and neurodegenerative effects
differs according to the respective activated TLR and TLR combinations used in
vivo. Conclusions Sole and pairwise activation of TLRs modifies the pattern
and extent of inflammation and neurodegeneration in the CNS, thereby enabling
innate immunity to take account of the CNS diseases’ diversity
Expression of Toll-Like Receptors in the Developing Brain
Toll-like receptors (TLR) are key players of the innate and adaptive immune response in vertebrates. The original protein Toll in Drosophila melanogaster regulates both host defense and morphogenesis during development. Making use of real-time PCR, in situ hybridization, and immunohistochemistry we systematically examined the expression of TLR1–9 and the intracellular adaptor molecules MyD88 and TRIF during development of the mouse brain. Expression of TLR7 and TLR9 in the brain was strongly regulated during different embryonic, postnatal, and adult stages. In contrast, expression of TLR1–6, TLR8, MyD88, and TRIF mRNA displayed no significant changes in the different phases of brain development. Neurons of various brain regions including the neocortex and the hippocampus were identified as the main cell type expressing both TLR7 and TLR9 in the developing brain. Taken together, our data reveal specific expression patterns of distinct TLRs in the developing mouse brain and lay the foundation for further investigation of the pathophysiological significance of these receptors for developmental processes in the central nervous system of vertebrates
The role of Toll-like receptors in neuronal and glial injury in the CNS
Der primäre Vorteil einer inflammatorischen Reaktion im Zentralen Nervensystem
(ZNS) ist der Schutz vor eindringenden Pathogenen und Neoplasmen sowie die
Beseitigung zellulären Abfalls. Der Nachteil eines solchen inflammatorischen
Prozesses im ZNS ist die Möglichkeit einer beschleunigten Neurodegeneration.
Wir haben die durch Pathogene induzierte Aktivierung des angeborenen
Immunsystems und die hierdurch ausgelöste Inflammation im ZNS untersucht und
die in diesem Zusammenhang existierende Literatur analysiert. Der Hauptfokus
lag auf der Rolle des Toll-like Rezeptor (TLR) 4 bei der Schädigung von
Oligodendrozyten und Neuronen. Darüberhinaus wurde die Rolle des Toll-like
Rezeptor 2 bei der Schädigung und dem Zelltod von Mikroglia und Neuronen
beleuchtet. Im letzten Teil der Arbeit wurde die Rolle endogener Liganden von
Rezeptoren der angeborenen Immunität bei der Schädigung des ZNS untersucht.
Mit Hilfe des Schlaganfallmodells der Maus wurde eine kritische Rolle für TLR2
bei der nicht-infektiösen Schädigung des ZNS nachgewiesen. Der in diesem
Kontext verantwortliche Ligand des TLR2 wurde bisher nicht identifiziert.
Hingegen wurde Heat shock protein 60 (HSP60), ein ubiquitär exprimiertes
Chaperon, als endogener Ligand für TLR4 in Mikroglia identifiziert. Die
Bindung an diesen Rezeptor und die anschliessende Aktivierung der Zelle führt
zu neuronaler Schädigung. In der vorliegenden Arbeit wurden die oben
aufgeführten Resultate diskutiert und zusammengefasst.The predictable advantage of an inflammatory response in the central nervous
system (CNS) is protection from pathogens and neoplasms and clearing of non-
viable cellular remains. However, an unanticipated disadvantage of
inflammation may be the possibility of accelerated neurodegeneration. We have
investigated and reviewed the field of pathogen-induced activation of the
innate immune system and subsequent inflammation in the CNS. A major focus has
been on the role of Toll-like receptor (TLR) 4 in oligodendrocyte and neuronal
injury. Furthermore, the role of Toll-like receptor 2 in neuronal and
microglial cell death has been elucidated. Finally, the role of endogenous
ligands of innate immune receptors in CNS injury has been investigated. In the
context of stroke, TLR2 plays a critical role in non-infectious CNS injury.
Whereas in this context the endogenous ligand of TLR2 remains unknown, heat
shock protein 60 (HSP60), a ubiquitously expressed chaperone molecule, has
been identified as an endogenous ligand of TLR4 in microglia inducing neuronal
injury. In this work the above-named results have been discussed and
summarized
Human endogenous retrovirus HERV-K(HML-2) RNA causes neurodegeneration through Toll-like receptors
Although human endogenous retroviruses (HERVs) represent a substantial proportion of the human genome and some HERVs, such as HERV-K(HML-2), are reported to be involved in neurological disorders, little is known about their biological function. We report that RNA from an HERV-K(HML-2) envelope gene region binds to and activates human Toll-like receptor (TLR) 8, as well as murine Tlr7, expressed in neurons and microglia, thereby causing neurodegeneration. HERV-K(HML-2) RNA introduced into the cerebrospinal fluid (CSF) of either C57BL/6 wild-type mice or APPPS1 mice, a mouse model for Alzheimer\u27s disease (AD), resulted in neurodegeneration and microglia accumulation. Tlr7-deficient mice were protected against neurodegenerative effects but were resensitized toward HERV-K(HML-2) RNA when neurons ectopically expressed murine Tlr7 or human TLR8. Transcriptome data sets of human AD brain samples revealed a distinct correlation of upregulated HERV-K(HML-2) and TLR8 RNA expression. HERV-K(HML-2) RNA was detectable more frequently in CSF from individuals with AD compared with controls. Our data establish HERV-K(HML-2) RNA as an endogenous ligand for species-specific TLRs 7/8 and imply a functional contribution of human endogenous retroviral transcripts to neurodegenerative processes, such as AD
miR-154-5p Is a Novel Endogenous Ligand for TLR7 Inducing Microglial Activation and Neuronal Injury
Toll-like receptors (TLRs) are a collection of pattern recognition sensors that form a first line of defence by detecting pathogen- or damage-associated molecular patterns and initiating an inflammatory response. TLR activation in microglia, the major immune cells in the brain, can trigger the release of inflammatory molecules, which may contribute to various CNS diseases including Alzheimer’s disease. Recently, some microRNAs were shown to serve as signalling molecules for TLRs. Here, we present miR-154-5p as a novel TLR7 ligand. Exposing microglia to miR-154-5p results in cytokine release and alters expression of the TLR signalling pathway dependent on TLR7. Additionally, miR-154-5p causes neuronal injury in enriched cortical neuron cultures and additive toxicity in the presence of microglia. Finally, intrathecal injection of miR-154-5p into mice leads to neuronal injury and accumulation of microglia in the cerebral cortex dependent on TLR7 expression. In conclusion, this study establishes miR-154-5p as a direct activator of TLR7 that can cause neuroinflammation and neuronal injury, which may contribute to CNS disease
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