High-fat diet induces depression-like phenotype via astrocyte-mediated hyperactivation of ventral hippocampal glutamatergic afferents to the nucleus accumbens.

Comorbidity exists between metabolic disorders and depressive syndrome with unclear mechanisms. To characterize the causal relationship, we adopted a 12-week high-fat diet (HFD) to induce metabolic disorder and depressive phenotypes in mice. Initially, we identified an enhanced glutamatergic input in the nucleus accumbens of HFD mice. Retrograde tracing and chemogenetic inhibition showed that the hyperactive ventral hippocampal glutamatergic afferents to the nucleus accumbens determined the exhibition of depression-like behavior in HFD mice. Using lentiviral knockdown and overexpression approaches, we proved that HFD-induced downregulation of glial glutamate transporters, GLAST and GLT-1, contributed to the observed circuit maladaptations and subsequent depression-like behaviors. Finally, we identified a potential therapeutic agent, riluzole, which could mitigate the HFD-induced behavioral deficits by normalizing the expressions of GLAST and GLT-1 and ventral hippocampal glutamatergic afferents to the nucleus accumbens. Overall, astrocyte-mediated disturbance in glutamatergic transmission underlies the metabolic disorder-related depressive syndrome and represents a therapeutic target for this subtype of depressive mood disorders.

Behavioral and brain- transcriptomic synchronization between the two opponents of a fighting pair of the fish Betta splendens.

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.

Absence of the lectin-like domain of thrombomodulin reduces HSV-1 lethality of mice with increased microglia responses.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Overall, TM-LeD suppresses microglia responses to enhance HSV-1 infection.

Microglia Reduce Herpes Simplex Virus 1 Lethality of Mice with Decreased T Cell and Interferon Responses in Brains.

Herpes simplex virus 1 (HSV-1) infects the majority of the human population and can induce encephalitis, which is the most common cause of sporadic, fatal encephalitis. An increase of microglia is detected in the brains of encephalitis patients. The issues regarding whether and how microglia protect the host and neurons from HSV-1 infection remain elusive. Using a murine infection model, we showed that HSV-1 infection on corneas increased the number of microglia to outnumber those of infiltrating leukocytes (macrophages, neutrophils, and T cells) and enhanced microglia activation in brains. HSV-1 antigens were detected in brain neurons, which were surrounded by microglia. Microglia depletion increased HSV-1 lethality of mice with elevated brain levels of viral loads, infected neurons, neuron loss, CD4 T cells, CD8 T cells, neutrophils, interferon (IFN)-ß, and IFN-γ. In vitro studies demonstrated that microglia from infected mice reduced virus infectivity. Moreover, microglia induced IFN-ß and the signaling pathway of signal transducer and activator of transcription (STAT) 1 to inhibit viral replication and damage of neurons. Our study reveals how microglia protect the host and neurons from HSV-1 infection.

Intermittent peripheral exposure to lipopolysaccharide induces exploratory behavior in mice and regulates brain glial activity in obese mice.

BACKGROUND: Consecutive peripheral immune challenges can modulate the responses of brain resident microglia to stimuli. High-fat diet (HFD) intake has been reported to stimulate the activation of astrocytes and microglia in the arcuate nucleus (ARC) of the hypothalamus in obese rodents and humans. However, it is unknown whether intermittent exposure to additional peripheral immune challenge can modify HFD-induced hypothalamic glial activation in obese individuals. METHODS: In this study, we administered 1 mg/kg LPS (or saline) by intraperitoneal (i.p.) injection to 8-week-old male mice after 1, 2, or 8 weeks of a regular diet (show) or HFD. The level of interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) expression in the plasma and hypothalamic tissue was analyzed 24 h after each LPS injection. The behaviors of the animals in the four groups (the chow-saline, chow-LPS, HFD-saline, and HFD-LPS groups) were examined 5 months after exposure to chow or a HFD. Morphological examination of microglia in related brain regions was also conducted. RESULTS: The plasma levels and hypothalamic mRNA levels of IL-1ß and TNF-α were significantly upregulated 24 h after the first injection of LPS but not after the second or third injection of LPS. Chow-LPS mice displayed increased exploratory behavior 5 months after feeding. However, this LPS-induced abnormal exploratory behavior was inhibited in HFD-fed mice. Chronic HFD feeding for 5 months induced apparent increases in the number and cell body size of microglia, mainly in the ARC, and also increased the size of microglia in the nucleus accumbens (NAc) and insula. Moreover, microglial activation in the ARC, anterior cingulate cortex (ACC), insula, and basolateral amygdala (BLA) was observed in chow-LPS mice. However, microglial activation in the analyzed brain regions was suppressed in HFD-LPS mice. CONCLUSIONS: Altogether, the results indicate that intermittent peripheral challenge with LPS might prime microglia in the ARC and NAc to modify their response to chronic HFD feeding. Alternatively, chronic HFD feeding might mediate microglia in LPS-affected brain regions and subsequently suppress LPS-induced atypical exploratory behavior. Our findings suggest that the interaction of intermittent acute peripheral immune challenges with chronic HFD intake can drive microglia to amend the microenvironment and further modify animal behaviors in the later life.

The selective lipoprotein-associated phospholipase A2 inhibitor darapladib triggers irreversible actions on glioma cell apoptosis and mitochondrial dysfunction.

Although the development of a therapeutic strategy for glioblastoma multiforme (GBM), the most aggressive type of brain tumor in adults, is in progress, the prognosis is still limited. In this study, we evaluated the anti-glioma effects of darapladib, a selective reversible inhibitor of lipoprotein-associated phospholipase A2 (Lp-PLA2) that is encoded by the PLA2G7 gene and serves as a predictive biomarker of sub-clinical inflammation in cardiovascular diseases. The three glioma cell lines (rat C6 glioma cell line, human U87MG, and human U251MG) and an ex vivo brain tissue slice-glioma cell co-culture system were used to validate the inhibitory effect of darapladib on the expansion of glioma cells. Exposure to darapladib at doses higher than 5 µM induced profound cytotoxicity in C6, U87MG, and U251MG. Moreover, the colony formation ability of the glioma cell lines was significantly repressed after the addition of darapladib. Although darapladib did not reduce the generation of the Lp-PLA2 downstream molecule, arachidonic acid (AA), in the glioma cells, this small compound triggered mitochondrial membrane depolarization and cell apoptosis in these glioma cells. In addition, transient exposure to darapladib induced the upregulation of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) levels, but reduced phosphorylation of AKT/PKB (protein kinase B). The results from an ex vivo brain slice culture system further confirmed the effective inhibition of darapladib on the expansion of glioma cells. In conclusion, darapladib acts as a potential anti-glioma compound via the induction of mitochondrial membrane depolarization and cell apoptosis, and the inhibition of AKT signaling in glioma cells.

BRCA1/BRCA2-containing complex subunit 3 controls oligodendrocyte differentiation by dynamically regulating lysine 63-linked ubiquitination.

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.

Down-regulation of interleukin-33 expression in oligodendrocyte precursor cells impairs oligodendrocyte lineage progression.

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.

Chronic exposure to high fat diet triggers myelin disruption and interleukin-33 upregulation in hypothalamus.

BACKGROUND: Hypothalamic inflammation including astrogliosis and microglia activation occurs after intake of high fat diet (HFD) in rodent models or in obese individuals. However, the effect of chronic HFD feeding on oligodendrocytes (OLGs), a myelin-producing glial population in the central nervous system (CNS), remains unclear. In this study, we used 8-week old male C57BL/6 mice fed by HFD for 3-6 months to induce chronic obesity. RESULTS: The transmission electron microscopy imaging analysis showed that the integrity of hypothalamic myelin was disrupted after HFD feeding for 4 and 6 months. Moreover, the accumulation of Iba1+-microglia with an amoeboid hypertrophic form was continually observed in arcuate nucleus of HFD-fed mice during the entire feeding time period. Interleukin-33 (IL-33), a tissue alarmin upon injury to the CNS, was detected with an increased level in hypothalamus after HFD feeding for 3 and 4 months. Furthermore, the in vitro study indicated that exposure of mature OLGs to IL-33 impaired OLG cell structure along with a decline in the expression of myelin basic protein. CONCLUSIONS: Altogether, our findings demonstrate that chronic HFD feeding triggers hypothalamic myelin disruption in accompany with IL-33 upregulation and prolonged microglial activation in hypothalamus. Given that the addition of exogenous IL-33 was harmful for the maturation of OLGs, an increase in IL-33 by chronic HFD feeding might contribute to the induction of hypothalamic myelin disruption.

In Situ Click Reaction Coupled with Quantitative Proteomics for Identifying Protein Targets of Catechol Estrogens.

Catechol estrogens (CEs) are metabolic electrophiles that actively undergo covalent interaction with cellular proteins, influencing molecular function. There is no feasible method to identify their binders in a living system. Herein, we developed a click chemistry-based approach using ethinylestradiol (EE2) as the precursor probe coupled with quantitative proteomics to identify protein targets of CEs and classify their binding strengths. Using in situ metabolic conversion and click reaction in liver microsomes, CEs-protein complex was captured by the probe, digested by trypsin, stable isotope labeled via reductive amination, and analyzed by liquid chromatography-mass spectrometry (LC-MS). A total of 334 liver proteins were repeatedly identified ( n ≥ 2); 274 identified proteins were classified as strong binders based on precursor mass mapping. The binding strength was further scaled by D/H ratio (activity probe/solvent): 259 strong binders had D/H > 5.25; 46 weak binders had 5.25 > D/H > 1; 5 nonspecific binders (keratins) had D/H < 1. These results were confirmed using spiked covalent control (strong binder) and noncovalent control (weak binder), as well as in vitro testing of cytochrome c (D/H = 5.9), which showed covalent conjugation with CEs. Many identified strong binders, such as glutathione transferase, catechol-O-methyl transferase, superoxide dismutase, catalase, glutathione peroxidase, and cytochrome c, are involved in cellular redox processes or detoxification activities. CE conjugation was shown to suppress the superoxide oxidase activity of cytochrome c, suggesting that CEs modification may alter the redox action of cellular proteins. Due to structural similarity and inert alkyne group, EE2 probe is very likely to capture protein targets of CEs in general. Thus, this strategy can be adopted to explore the biological impact of CEs modification in living systems.

Stress Aggravates High-Fat-Diet-Induced Insulin Resistance via a Mechanism That Involves the Amygdala and Is Associated with Changes in Neuroplasticity.

BACKGROUND: The notion that exposure to chronic stress predisposes individuals to developing type 2 diabetes (T2D) has gained much attention in recent decades. Long-term stress induces neuroadaptation in the amygdala and increases corticosterone levels. Corticosterone, the major stress hormone in rodents, induces insulin resistance and obesity in mice. However, little is known about whether the stress-induced amygdalar neuroadaptation could promote the risk of T2D. METHODS: We used an 11-week high-fat diet (HFD) feeding paradigm to induce insulin dysfunction in mice, followed by implementation of a 10-day social defeat (SD) stress protocol. RESULTS: Mice receiving SD at the beginning of the HFD feeding aggravated HFD-induced insulin resistance and white adipose tissue expansion. HFD mice had higher levels of plasma corticosterone, which was not affected by the SD. The SD stress upregulated the expression of TrkB and synaptotagmin-4 in the amygdala of HFD mice. Bilateral lesions of the central amygdalae before SD stress inhibited the stress-induced aggravating effect without affecting the HFD-induced elevation of plasma corticosterone. CONCLUSIONS: Stress aggravates HFD-induced insulin resistance and neuroadaptation in the amygdala. The HFD-induced insulin resistance is amygdala-dependent. Understanding the role of stress-induced amygdalar adaptation in the development of T2D could inform therapies aimed at reducing chronic stressors to decrease the risk for T2D.

MicroRNA-212 inhibits oligodendrocytes during maturation by down-regulation of differentiation-associated gene expression.

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.

Reduction of CD200 expression in glioma cells enhances microglia activation and tumor growth.

CD200, a type I transmembrane glycoprotein, can interact with its receptor CD200R, which plays an inhibitory role in the activation of microglia-the resident macrophages of the central nervous system. In this study, the rat C6 glioma cell line (C6-1) that was previously characterized with high in vivo tumorigenicity was found to generate CD200 mRNA abundantly. However, CD200 expression was barely detected in another C6 glioma cell clone (C6-2) that was previously found to display low tumorigenic behavior. The results from CD200 immunohistochemistry on human glioma tissue array also showed that tumor cells in Grade I-II astrocytoma expressed a lower level of CD200 immunoreactivity than those detected in Grade III-IV glioblastoma multiforme. C6-1 transfectants with stable downregulation of CD200 gene expression using lentivirus knockdown approach were generated (C6-KD). Microglia and iNOS+ cells were increased when microglia were co-cultured with C6-KD cells. The colony formation of C6-KD was also augmented when those cells were co-cultured with microglia. Yet, increased colony formation of C6-KD transfectants in the co-culture with microglia was effectively suppressed by interleukin (IL)-4 and IL-10. The in vivo results indicated that the tumor formation of C6-1 cells in rat brain was promoted after CD200 gene knockdown. Moreover, CD11b+ activated microglia and iNOS+ microglia were highly accumulated in the tumor site formed by C6-KD. In conclusion, our findings demonstrate that the downregulation of CD200 expression in CD200-rich glioma cells could foster the formation of an activated microglia-associated tumor microenvironment, leading to glioma progression. © 2016 Wiley Periodicals, Inc.

MicroRNA-145 as one negative regulator of astrogliosis.

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.

Colchicine derivative as a potential anti-glioma compound.

Colchicine, an anti-microtubule and antimitotic drug, is a common therapeutically agent for gout, which is thought to have potential anti-tumor effects. Owing to concerns of colchicines poisoning, the development of derivatives with low dose efficacy and less side effects is of obvious interest. In this study, we characterized the inhibitory effects of a colchicine derivative named AD1 on the cell proliferation of human malignant glioblastoma (MG) cell lines, U87MG and U373MG. We found that 50 % of U87MG and U373MG cells were reduced in the cultures after exposure to AD1 for 24 h at 10 and 50 nM, respectively. Moreover, α-tubulin immunostaining indicated that AD1 induced the disruption of the microtubule polymerization in glioma cells with apoptotic features including membrane budding/blebbing or fragmented nuclei. Increased levels of reactive oxygen species (ROS) were also detected in AD1-treated U87MG and U373MG cells compared to that observed in the control culture. Moreover, examination of microtubule-associated protein 1A/1B-light chain 3 (LC3I)/LC3II conversion and acridine orange staining for autophagic vesicles, combined with flow cytometry, showed that treatment with AD1 induced the autophagic pathway in U87MG and U373MG cells. Furthermore, we found that the intermittent intravenous administration of AD1 suppressed glioma growth in rat brain receiving intracerebral injection with rat C6 glioma cells. Taken together, our findings reveal that treatment with AD1 at nanomolar scales can reduce glioma cell viability effectively, with the occurrence of a rise in ROS and cellular autophagy. In conjunction with the observations from in vivo study, the colchicine derivative AD1 has chemotherapeutic potential to suppress glioma progression.

Interleukin-33 has the protective effect on oligodendrocytes against impairment induced by cuprizone intoxication.

Our prior investigations have demonstrated the pivotal role of IL-33 in facilitating the maturation of oligodendrocytes (OLs), prompting our interest in exploring its potential therapeutic effects. In this study, our focus was directed towards deciphering the functions of interleukin-33 (IL-33) in established demyelinating mouse model induced by the feeding of cuprizone (CPZ)-containing diet. We observed the reduction in corpus callosal adenomatous polyposis coli (APC)+ OLs with IL-33 expression in mice subjected to CPZ feeding for durations of 6 and 8 weeks. In parallel, the levels of IL-33 in the corpus callosum declined after CPZ-containing diet. Furthermore, we conducted experiments utilizing primary oligodendrocyte precursor cells (OPCs) and mature OLs, which were exposed to CPZ. A decrease in the expression of myelin basic protein (MBP) was evident in the cultures of mature OLs after treatment with CPZ. Additionally, both IL-33 mRNA and protein levels exhibited downregulation. To counteract the diminished IL-33 levels induced by CPZ, we employed a lentiviral vector to overexpress IL-33 in OLs. Intriguingly, the overexpression of IL-33 (IL33OE) in OLs resulted in a more distinct membranous morphology following CPZ treatment when compared to that observed in OL Mock cultures. Moreover, MBP protein levels in the presence of CPZ were higher in IL33OE OLs than that detected in OL Mock cultures. These findings collectively indicate that IL-33 possesses the capability to mitigate CPZ-induced damage and bolster OL homeostasis. In summary, our study underscores the importance of IL-33 in the context of demyelinating diseases, shedding light on its potential therapeutic implications for fostering remyelination and preserving OL function.

Exposure to lipid mixture induces intracellular lipid droplet formation and impairs mitochondrial functions in astrocytes.

Astrocytes, the predominant glial cells in the central nervous system (CNS), play diverse roles including metabolic support for neurons, provision of neurotrophic factors, facilitation of synaptic neurotransmitter uptake, regulation of ion balance, and involvement in synaptic formation. The accumulation of lipids has been noted in various neurological conditions, yet the response of astrocytes to lipid-rich environments remains unclear. In this study, primary astrocytes isolated from the neonatal rat cortex were exposed to a lipid mixture (LM) comprising cholesterol and various fatty acids to explore their reaction. Our results showed that astrocyte viability remained unchanged following 24 h of 5% or 10% LM treatment. However, exposure to LM for 96 h resulted in reduced cell viability. In addition, LM treatment led to the accumulation of lipid droplets (LDs) in astrocytes, with LD size increasing over prolonged exposure periods. Following 24 h of LM treatment and then 48 h in fresh medium, a significant reduction in intracellular LD size was observed in cultures treated with 5% LM, while no change occurred in cultures exposed to 10% LM. Yet, exposure to 10% LM for 24 h significantly increased the expression of the cholesterol efflux regulatory protein/ATP-binding cassette transporter (ABCA1) gene, responsible for intracellular cholesterol efflux, resulting in reduced cholesterol content within astrocytes. Moreover, LM exposure led to decreased mitochondrial membrane potential (MMP) and increased levels of mature apoptosis-inducing factor (AIF). The smaller LDs were observed to co-localize with microtubule-associated protein 1A/1 B light chain 3 B (LC3) and lysosomal-associated membrane protein-1 (LAMP-1) in LM-treated astrocytes, coinciding with lysosomal acidification. These results indicate that the continuous buildup of LDs in astrocytes residing in lipid-enriched environments may be attributed to disruptions caused by LM in mitochondrial and lysosomal functions. Such disruptions could potentially impede the supportive role of astrocytes in neuronal function.

Interleukin-6 Inhibits Expression of miR-204-5p, a Regulator of Oligodendrocyte Differentiation: Involvement of miR-204-5p in the Prevention of Chemical-Induced Oligodendrocyte Impairment.

Oligodendrocytes (OLs) form myelin sheaths around axons in the central nervous system (CNS) facilitate the propagation of action potentials. The studies have shown that the differentiation and maturation of OLs involve microRNA (miR) regulation. The recent findings have addressed that miR-204 regulates OL differentiation in culture. In this study, through in situ hybridization in combination with immunohistochemistry, we showed that microRNA-204-5p in the corpus callosum was mainly expressed in OLs immunoreactive with adenomatous polyposis coli (APC), an OL marker. We also found miR-204-5p expression in mature OLs was suppressed by the addition of interleukin-6 (IL-6). Moreover, IL-6-induced inhibition of miR-204-5p expression was blocked by the addition of the inhibitors specific for p38 mitogen-activated protein kinase (p38MAPK) or phosphatidylinositol 3-kinase (PI3K) pathway. We further utilized a rat model by feeding cuprizone (CPZ)-containing diet for 3 weeks to induce demyelination and gliosis in the corpus callosum, as well as the upregulation of IL-6 gene expression significantly. Despite that miR-204-5p expression in the corpus callosum was not altered after feeding by CPZ for 3 weeks, its expression was increased and IL-6 transcription was decreased in the corpus callosum of the recovery group that was fed by CPZ for the first 2 weeks and by the regular diet for one more week. Our data demonstrate that miR-204-5p expression in OLs declined under the influence of the inflamed microenvironment. The findings that an increase in miR-204-5p and declined IL-6 expression observed in the recovery group might be involved with OL repair in the corpus callosum, and also shed light on a potential role for miR-204-5p in OL homeostasis following the white matter injury.

Erinacine S, a small active component derived from Hericium erinaceus, protects oligodendrocytes and alleviates mood abnormalities in cuprizone-exposed rodents.

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-1ß 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.

Enhanced cell growth and tumorigenicity of rat glioma cells by stable expression of human CD133 through multiple molecular actions.

CD133 (Prominin-1/AC133) is generally treated as a cell surface marker found on multipotent stem cells and tumor stem-like cells, and its biological function remains debated. Genetically modified rat glioma cell lines were generated by lentiviral gene delivery of human CD133 into rat C6 glioma cells (hCD133(+) -C6) or by infection of C6 cells with control lentivirus (mock-C6). Stable hCD133 expression promoted the self-renewal ability of C6-formed spheres with an increase in the expression of the stemness markers, Bmi-1 and SOX2. Akt phosphorylation, Notch-1 activation, and Notch-1 target gene expression (Hes-1, Hey1 and Hey2) were increased in hCD133(+) -C6 when compared to mock-C6. The inhibition of Akt phosphorylation, Notch-1 activation, and Hes-1 in hCD133(+) -C6 cells effectively suppressed their clonogenic ability, indicating that these factors are involved in expanding the growth of hCD133(+) -C6. An elevated expression of GTPase-activating protein 27 (Arhgap27) was detected in hCD133(+) -C6. A decline in the invasion of hCD133(+) -C6 by knockdown of Arhgap27 expression indicated the critical role of Arhgap27 in promoting cell migration of hCD133(+) -C6. In vivo study further showed that hCD133(+) -C6 formed aggressive tumors in vivo compared to mock-C6. Exposure of hCD133(+) -C6 to arsenic trioxide not only reduced Akt phosphorylation, Notch-1 activation and Hes-1 expression in vitro, but also inhibited their tumorigenicity in vivo. The results show that C6 glioma cells with stable hCD133 expression enhanced their stemness properties with increased Notch-1/Hes-1 signaling, Akt activation, and Arhgap27 action, which contribute to increased cell proliferation and migration of hCD133(+) -C6 in vitro, as well as progressive tumor formation in vivo.