Astrogliosis occurs at the lesion site within days to weeks after spinal cord injury (SCI) and involves the proliferation and hypertrophy of astrocytes, leading to glia scar formation. Changes in ...gene expression by deregulated microRNAs (miRNAs) are involved in the process of central nervous system neurodegeneration. Here, we report that mir‐145, a miRNA enriched in rat spinal neurons and astrocytes, was downregulated at 1 week and 1 month after SCI. Our in vitro studies using astrocytes prepared from neonatal spinal cord tissues indicated that potent inflammagen lipopolysaccharide downregulated mir‐145 expression in astrocytes, suggesting that SCI‐triggered inflammatory signaling pathways could play the inhibitory role in astrocytic mir‐145 expression. To induce overexpression of mir‐145 in astrocytes at the spinal cord lesion site, we developed a lentivirus‐mediated pre‐miRNA delivery system using the promoter of glial fibrillary acidic protein (GFAP), an astrocyte‐specific intermediate filament. The results indicated that astrocyte‐specific overexpression of mir‐145 reduced astrocytic cell density at the lesion border of the injured spinal cord. In parallel, overexpression of mir‐145 reduced the size of astrocytes and the number of related cell processes, as well as cell proliferation and migration. Through a luciferase reporter system, we found that GFAP and c‐myc were the two potential targets of mir‐145 in astrocytes. Together, the findings demonstrate the novel role of mir‐145 in the regulation of astrocytic dynamics, and reveal that the downregulation of mir‐145 in astrocytes is a critical factor inducing astrogliosis after SCI. GLIA 2015;63:194–205
Main Points
mir‐145 expression is reduced in the spinal cord after a traumatic injury.
Increased expression of mir-145 in astrocytes reduces astrocytic migration and hypertrophy.
GFAP and c‐myc are two potential targets of mir-145 in astrocytes.
Oligodendrocytes (OLs) provide the myelin sheath surrounding axons that propagates action potentials in the central nervous system (CNS). The metabolism of myelinated membranes and proteins is ...strictly regulated in the OLs and is closely associated with OL differentiation and maturation. The ubiquitination‐associated proteasome and endosomal system have not yet been well studied during OL differentiation and maturation. Here, we determined the functions of the Lys63‐linked ubiquitination (K63Ub) and K63‐specific deubiquitination (DUB) systems regulated by BRCA1/BRCA2‐containing complex subunit 3 (BRCC3) during OL differentiation. The competitive inhibition of K63Ub by overexpression of mutant ubiquitin (K63R) in oligodendrocyte precursor cells (OPCs) indicated that the two major CNS myelin proteins, myelin basic protein (MBP) and proteolipid protein (PLP), were upregulated in OLs derived from K63R OPCs. In contrast, the knockdown of BRCC3 (BRCC3‐KD) through the application of lentivirus‐mediated shRNA delivery system into OPCs suppressed OL differentiation by decreasing MBP expression and PLP production. Further immunoprecipitation assays revealed higher levels of sphingolipid GalC, MBP, and PLP, which were associated with K63Ub‐immunoprecipitants and detected in endosome/lysosomal compartments, in BRCC3‐KD OLs than those in OLs transfected with the scrambled shRNA (scramble OLs). The differentiation of OLs from BRCC3‐KD OPCs was impaired in the demyelinating corpus callosum of rats receiving a cuprizone‐containing diet. In the demyelinating tissues from human patients suffering from multiple sclerosis, we detected a decreased number of BRCC3‐expressing OLs at the lesion site, accompanied by a greater number of OLs expressing EEA1 and K63Ub at high levels. Altogether, the counterbalance of the K63Ub machinery and BRCC3‐triggered DUB machinery are important for the cellular trafficking of myelin proteins and OL differentiation.
• Reduced expression of BRCC3 inhibited OL differentiation by an increase in Lys63‐linked ubiquitination to promote endocytosis of myelin proteins.
• Decline in BRCC3 with an increase in K63Ub and EEA1 was detected in the lesion sites of multiple sclerosis patients.
MicroRNA‐212 (mir‐212) has been reported to regulate neuronal development and functioning. However, its expression and function in glia are not yet known. Here, we demonstrate that the level of ...microRNA‐212 (mir‐212) was reduced in spinal cord lesion site at 1 week and 1 month after a contusive spinal cord injury. In addition to its expression in neurons, mir‐212 expression was detected in oligodendrocytes (OLGs) and glial progenitor cells (GPCs) in adult CNS. The addition of antagomir‐212 to reduce mir‐212 expression enabled to improve the cell process outgrowth of OLGs along with the up‐regulation of the genes associated with OLG differentiation and maturation, including OLIG1, SOX10, myelin basic protein (MBP), and proteolipid protein 1 (PLP1). In contrast, these genes were significantly down‐regulated by an increased expression of mir‐212 in GPCs or in OLG progenitor cells (OPCs) through lentivirus‐mediated gene delivery approach. Moreover, we found that PLP1 was the direct target molecule of mir‐212. Furthermore, mir‐212 over‐expression diminished the protein production of OLGs markers including 2′,3′‐cyclic‐nucleotide 3′‐phosphodiesterase (CNPase), MBP, and PLP. Additionally, mir‐212 over‐expression decreased the number of mature OLGs expressing MBP, and the expression of galactocerebroside (GC). Complementary studies in a hippocampal neuron‐OLG co‐culture model and an ex vivo cerebellar slice system indicated that OLGs derived from GPCs with mir‐212 over‐expression exhibited decreased ability to interact with neuronal axons. Collectively, our findings demonstrate that mir‐212 repressed the expression of OLG maturation‐associated proteins and inhibited OLG cell process extension, indicating that mir‐212 has negative regulatory effect on OLG lineage progression.
MicroRNA‐212 (mir‐212) can regulate neuronal development and functioning. However, its expression and function in glia are not yet known. This report shows that spinal cord injury and interferon‐γ (other undefined molecules) can reduce mir‐212 expression in oligodendrocytes. Furthermore, mir‐212 can suppress oligodendrocyte maturation with the reduction in oligodendrocyte differentiation‐associated genes (OLIG1, OLIG2, and SOX10) and maturation proteins (MBP and PLP).
Interleukin‐33 (IL‐33), a member of the IL1 family, has been found to be expressed in oligodendrocytes (OLGs) and released as an alarmin from injured OLGs to work on other glial cell‐types in the ...central nervous system. However, its functional role in OLGs remains unclear. Herein, we present that IL‐33 was mainly expressed in the nucleus of CC1+‐oligodendrocytes (OLGs) in mouse and rat corpus callosum, as well as NG2+‐oligodendrocyte precursor cells (OPCs). The in vitro study indicated that the amount of IL‐33 expressing in OPCs was higher when compared to that detected in OLGs. Results from the experiments using lentivirus‐mediated shRNA delivery against IL‐33 expression (IL33‐KD) in OPCs showed that IL33‐KD reduced the differentiation of OLGs into mature OLGs along with the down‐regulation of OLG differentiation‐related genes and mature OLG marker proteins, myelin basic protein (MBP) and proteolipid protein (PLP). Alternatively, we observed reduced differentiation of OLGs that were prepared from the brains of IL‐33 gene knockout (IL33‐KO) mice with anxiolytic‐like behavior. Observations were correlated with the results showing lower levels of MBP and PLP in IL33‐KO cultures than those detected in the control cultures prepared from wildtype (WT) mice. Transmission Electron Microscopy (TEM) analysis revealed that the myelin structures in the corpus callosum of the IL33‐KO mice were impaired compared to those observed in the WT mice. Overall, this study provides important evidence that declined expression of IL‐33 in OPCs suppresses the maturation of OLGs. Moreover, gene deficiency of IL‐33 can disrupt OLG maturation and interfere with myelin compaction.
Cover Image for this issue: doi: 10.1111/jnc.14522
Our study demonstrates that declined expression of IL‐33 (IL33‐KD) or IL‐33 gene ablation (IL33‐KO) in oligodendrocyte precursor cells (OPCs) reduced oligodendrocyte (OLG) maturation along with the down‐regulation of Olig2, Myrf, and Sox10, as well as OLG lineage markers (MBP, PLP, and CNPase). The findings also implicate that loss of IL‐33 function in OPCs might impair myelin integrity in the white matter.
Open Science: This manuscript was awarded with the Open Materials Badge
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Cover Image for this issue: doi: 10.1111/jnc.14522
Oligodendrocytes (OLs), myelin-producing glia in the central nervous system (CNS), produce a myelin extension that enwraps axons to facilitate action potential propagation. An effective approach to ...induce oligodendrogenesis and myelination is important to foster CNS development and promote myelin repair in neurological diseases. Hericium (H.) erinaceus, an edible and culinary-medicinal mushroom, has been characterized as having neuroprotective activities. However, its effect on OL differentiation has not yet been uncovered. In this study using oligodendrocyte precursor cell (OPC) cultures and an ex vivo cerebellar slice system, we found that the extract from H. erinaceus mycelium (HEM) not only promoted the differentiation of OPCs to OLs in the differentiation medium, but also increased the level of myelin basic protein (MBP) on neuronal fibers. Moreover, daily oral administration of HEM into neonatal rat pups for 7 days enhanced MBP expression and OLs in the corpus callosum of the postnatal rat brain. The effect of HEM-derived bioactive compounds, the diterpenoid xylosides erinacine A (HeA) and HeC and a sesterterpene with 5 isoprene units called HeS, were further evaluated. The results showed that HeA and HeS more potently stimulated MBP expression in OLs and increased the number of OLs. Moreover, overlap between MBP immunoreactivity and neuronal fibers in cultured cerebellar tissue slices was significantly increased in the presence of HeA and HeS. In summary, our findings indicate that HEM extract and its ingredients HeA and HeS display promising functional effects and promote OL maturation, providing insights into their potential for myelination in neurodevelopmental disorders.
•HFD induces astrocyte activation in the hippocampus.•HFD represses the process arborization of the hippocampal astrocytes.•HFD downregulates the hippocampal expression of astrocytic glutamate ...transporters.•HFD induces depression-like behaviors in mice.
Metabolic disorders induce adverse effects on brain functions. The hippocampus is one of the most vulnerable regions to metabolic disorders. Disrupted neuroplasticity is a major cause of hippocampus-related behavioral impairments, including memory loss, anxiety, and depression. Astrocytes support processes of neuroplasticity. However, whether metabolic disorders induce changes in astrocytes and their roles in affective disorders is relatively unclear. To answer this question, we fed 8-week-old male C57BL/6 mice with a high-fat diet (HFD) for 12 weeks to induce metabolic disruption and then examined their performance of hippocampus-related memory, and anxiety- and depression-like behaviors. The morphology of astrocytes and the expression of astrocytic neuroplasticity-related proteins in the hippocampus were also assessed. The results showed that HFD led to obesity, systemic insulin resistance and dysregulated lipid metabolism in mice. HFD induced depression-like behaviors, but not anxiety or memory impairment. Furthermore, HFD increased the expression of GFAP, shortened the processes of GFAP+ cells, and downregulated the expression of astrocytic neuroplasticity-related protein, GLAST, GLT-1, and connexin-43 in the hippocampi. In conclusion, HFD disturbs the function of hippocampal astrocytes and induces depression-like behaviors in mice. A decrease of hippocampal glutamate transporters may play a critical role in the pathogenesis of metabolic disorder-related depression.
Background and purpose: Natural compounds obtained from marine organisms have received considerable attention as potential sources of novel drugs for treatment of human inflammatory diseases. ...Capnellene, isolated from the marine soft coral Capnella imbricate, 4,4,6a‐trimethyl‐3‐methylene‐decahydro‐cyclopentapentalene‐2,3a‐diol (GB9) exhibited anti‐inflammatory actions on activated macrophages in vitro. Here we have assessed the anti‐neuroinflammatory properties of GB9 and its acetylated derivative, acetic acid 3a‐hydroxy‐4,4,6a‐trimethyl‐3‐methylene‐decahydro‐cyclopentapentalen‐2‐yl ester (GB10).
Experimental approach: Effects of GB9 or GB10 on the expression of inducible nitric oxide synthase (iNOS), and cyclooxygenase‐2 (COX‐2) in interferon‐γ (IFN‐γ)‐stimulated mouse microglial BV2 cells were measured by Western blot. The in vivo effects of these compounds were examined in the chronic constriction injury (CCI) rat model of neuropathic pain, measuring thermal hyperalgesia, and microglial activation and COX‐2 protein in lumbar spinal cord, by immunohistochemistry.
Key results: In BV2 cells, GB9 and GB10 inhibited the expression of iNOS and COX‐2, stimulated by IFN‐γ. Intrathecal administration of GB9 and GB10 inhibited CCI‐induced nociceptive sensitization and thermal hyperalgesia in a dose‐dependent manner. Intraperitoneal injection of GB9 inhibited CCI‐induced thermal hyperalgesia and also inhibited CCI‐induced activation of microglial cells and up‐regulation of COX‐2 in the dorsal horn of the lumbar spinal cord ipsilateral to the injury.
Conclusion and implications: Taken together, these data indicate that the marine‐derived capnellenes, GB9 and GB10, had anti‐neuroinflammatory and anti‐nociceptive properties in IFN‐γ‐stimulated microglial cells and in neuropathic rats respectively. Therefore, capnellene may serve as a useful lead compound in the search for new therapeutic agents for treatment of neuroinflammatory diseases.
Hericium erinaceus mycelium extract (HEM), containing erinacine A (HeA) and erinacine S (HeS), has shown promise in promoting the differentiation of oligodendrocyte precursor cells (OPCs) into mature ...oligodendrocytes (OLs), crucial for myelin production in the central nervous system (CNS). The main aim of this study was to characterize the protective effects of HEM and its components on OLs and myelin in demyelinating rodents by exposure to cuprizone (CPZ), a copper chelating agent commonly used to induce demyelination in the corpus callosum of the brain. Rats were fed by CPZ-containing diet and simultaneously orally administered HEM, HeA, or HeS on a daily basis for three weeks. We found that HEM and HeS preserved myelin and OLs in the corpus callosum of CPZ-fed rats, along with reduced microglia and astrocyte activation, and downregulated IL-1β expression. Furthermore, post-treatment with HeS, in mouse models with acute (6 weeks) or chronic (12 weeks) CPZ-induced demyelination demonstrated oral administration during the final 4 weeks (HeS4/6 or HeS4/12) effectively preserved myelin in the corpus callosum. Additionally, HeS4/6 and HeS4/12 inhibited anxious and depressive-like behaviors in CPZ-fed mice. In summary, simultaneous administration of HEM and HeS in rats during short-term CPZ intoxication preserved OLs and myelin. Furthermore, post-administration of HeS not only inhibited demyelination and gliosis but also alleviated anxiety and depression in both acute and chronic CPZ-fed mice. This study presents compelling evidence supporting the potential of HeS as a promising small active compound for protecting OLs and preserving myelin in demyelinating diseases associated with emotional disorders.
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•H. erinaceus mycelium extract or erinacine S prevent loss of oligodendrocytes and myelin during acute demyelination.•Post treatment with erinacine S preserves myelin amount during chronic demyelination.•Erinacine S exhibits an alleviating effect on depression and anxiety associated with chronic demyelination.
Conspecific male animals fight for resources such as food and mating opportunities but typically stop fighting after assessing their relative fighting abilities to avoid serious injuries. ...Physiologically, how the fighting behavior is controlled remains unknown. Using the fighting fish Betta splendens, we studied behavioral and brain-transcriptomic changes during the fight between the two opponents. At the behavioral level, surface-breathing, and biting/striking occurred only during intervals between mouth-locking. Eventually, the behaviors of the two opponents became synchronized, with each pair showing a unique behavioral pattern. At the physiological level, we examined the expression patterns of 23,306 brain transcripts using RNA-sequencing data from brains of fighting pairs after a 20-min (D20) and a 60-min (D60) fight. The two opponents in each D60 fighting pair showed a strong gene expression correlation, whereas those in D20 fighting pairs showed a weak correlation. Moreover, each fighting pair in the D60 group showed pair-specific gene expression patterns in a grade of membership analysis (GoM) and were grouped as a pair in the heatmap clustering. The observed pair-specific individualization in brain-transcriptomic synchronization (PIBS) suggested that this synchronization provides a physiological basis for the behavioral synchronization. An analysis using the synchronized genes in fighting pairs of the D60 group found genes enriched for ion transport, synaptic function, and learning and memory. Brain-transcriptomic synchronization could be a general phenomenon and may provide a new cornerstone with which to investigate coordinating and sustaining social interactions between two interacting partners of vertebrates.
Herpes simplex virus 1 (HSV-1) can induce fatal encephalitis. Cellular factors regulate the host immunity to affect the severity of HSV-1 encephalitis. Recent reports focus on the significance of ...thrombomodulin (TM), especially the domain 1, lectin-like domain (TM-LeD), which modulates the immune responses to bacterial infections and toxins and various diseases in murine models. Few studies have investigated the importance of TM-LeD in viral infections, which are also regulated by the host immunity.
In vivo studies comparing wild-type and TM-LeD knockout mice were performed to determine the role of TM-LeD on HSV-1 lethality. In vitro studies using brain microglia cultured from mice or a human microglia cell line to investigate whether and how TM-LeD affects microglia to reduce HSV-1 replication in brain neurons cultured from mice or in a human neuronal cell line.
Absence of TM-LeD decreased the mortality, tissue viral loads, and brain neuron apoptosis of HSV-1-infected mice with increases in the number, proliferation, and phagocytic activity of brain microglia. Moreover, TM-LeD deficiency enhanced the phagocytic activity of brain microglia cultured from mice or of a human microglia cell line. Co-culture of mouse primary brain microglia and neurons or human microglia and neuronal cell lines revealed that TM-LeD deficiency augmented the capacity of microglia to reduce HSV-1 replication in neurons.
Overall, TM-LeD suppresses microglia responses to enhance HSV-1 infection.
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