KDM4C promotes mouse hippocampal neural stem cell proliferation through modulating ApoE expression

KDM4C is implicated in the regulation of cell proliferation, differentiation, and maintenance in various stem cell types. However, its function in neural stem cells (NSCs) remains poorly understood. Therefore, this study aims to investigate the role and regulatory mechanism of KDM4C in NSCs. Primary hippocampal NSCs were isolated from neonatal mice, and both in vivo and in vitro lentivirus-mediated overexpression of KDM4C were induced in these hippocampal NSCs. Staining results revealed a significant increase in BrdU- and Ki-67-positive cells, along with an elevated number of cells in S phases due to KDM4C overexpression. Subsequently, RNA-seq was employed to analyze gene expression changes following KDM4C upregulation. GO enrichment analysis, KEGG analysis, and GSEA highlighted KDM4C-regulated genes associated with development, cell cycle, and neurogenesis. Protein-protein interaction analysis uncovered that ApoE protein interacts with several genes (top 10 upregulated and downregulated) regulated by KDM4C. Notably, knocking down ApoE mitigated the proliferative effect induced by KDM4C overexpression in NSCs. Our study demonstrates that KDM4C overexpression significantly upregulates ApoE expression, ultimately promoting proliferation in mouse hippocampal NSCs. These findings provide valuable insights into the molecular mechanisms governing neurodevelopment, with potential implications for therapeutic strategies in neurological disorders.

CCN3/NOV Regulates Proliferation and Neuronal Differentiation in Mouse Hippocampal Neural Stem Cells via the Activation of the Notch/PTEN/AKT Pathway

Neural stem cells (NSCs) persist in the subgranular zone (SGZ) throughout the lifespan and hold immense potential for the repair and regeneration of the central nervous system, including hippocampal-related diseases. Several studies have demonstrated that cellular communication network protein 3 (CCN3) regulates multiple types of stem cells. However, the role of CCN3 in NSCs remains unknown. In this study, we identified CCN3 expression in mouse hippocampal NSCs and observed that supplementing CCN3 improved cell viability in a concentration-dependent manner. Additionally, in vivo results showed that the injection of CCN3 in the dentate gyrus (DG) increased Ki-67- and SOX2-positive cells while decreasing neuron-specific class III beta-tubulin (Tuj1) and doublecortin (DCX)-positive cells. Consistently with the in vivo results, supplementing CCN3 in the medium increased the number of BrdU and Ki-67 cells and the proliferation index but decreased the number of Tuj1 and DCX cells. Conversely, both the in vivo and in vitro knockdown of the Ccn3 gene in NSCs had opposite effects. Further investigations revealed that CCN3 promoted cleaved Notch1 (NICD) expression, leading to the suppression of PTEN expression and eventual promotion of AKT activation. In contrast, Ccn3 knockdown inhibited the activation of the Notch/PTEN/AKT pathway. Finally, the effects of changes in CCN3 protein expression on NSC proliferation and differentiation were eliminated by FLI-06 (a Notch inhibitor) and VO-OH (a PTEN inhibitor). Our findings imply that while promoting proliferation, CCN3 inhibits the neuronal differentiation of mouse hippocampal NSCs and that the Notch/PTEN/AKT pathway may be a potential intracellular target of CCN3. Our findings may help develop strategies to enhance the intrinsic potential for brain regeneration after injuries, particularly stem cell treatment for hippocampal-related diseases.

Luteolin Enhances Choroid Plexus 5-MTHF Brain Transport to Promote Hippocampal Neurogenesis in LOD Rats

Folates, provided by food, are commonly used antidepressant synergists in late-onset depression (LOD). However, increased intake of folic acid in the elderly population might lead to the accumulation of unmetabolized folic acid in the systemic circulation, leading to enhanced deterioration of the central nervous system function. In addition, folates cannot access the brain directly because of the blood-brain barrier. Choroid plexus (CP) 5-methyltetrahydrofolate (5-MTHF) brain transport plays a critical role in regulating the cerebrospinal fluid (CSF) 5-MTHF content. Luteolin is a natural flavonoid that has antidepressant effects and is involved in the anti-folate resistance pathway. It remains unclear whether the antidepressant effects of luteolin are associated with the CP 5-MTHF brain transport. In this study, 20-21-month-old Wistar rats were exposed to the chronic unpredictable mild stress (CUMS) protocol for 6 consecutive weeks to explore the long-term effects of luteolin on behavior, 5-MTHF levels, hippocampal neurogenesis, and folate brain transport of the CP. In vitro primary hippocampal neural stem cells (NSCs) cultured in media containing 10% CSF from each group of rats and choroid plexus epithelial cells (CPECs) cultured in media containing 20 μM luteolin were treated with 100 μM corticosterone and 40 mg/ml D-galactose. We found that aged rats exposed to CUMS showed a significantly reduced sucrose preference, decreased locomotion activity in the open field test and accuracy of the Morris water maze test, increased immobility time in the forced swimming test, accelerated dysfunctional neurogenesis and neuronal loss in the dentate gyrus of LOD rats, as well as decreased CSF and hippocampus 5-MTHF levels, and zona occludens protein 1 (ZO-1), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC) protein levels. In vitro assays showed media containing 10% aged CSF or LOD+ Luteolin-CSF significantly increased the viability of CORT + D-gal-injured NSCs and alleviated dysfunctional neurogenesis and neuronal loss compared with the CORT + D-gal medium. However, media containing 10% LOD-CSF had no such effect. In the meantime, induction of CORT + D-gal significantly decreased the ZO-1, PCFT, RFC, and folate receptor alpha (FR-α) protein levels and transepithelial electrical resistance in rat CPECs. As expected, luteolin treatment was effective in improving these abnormal changes. These findings suggested that luteolin could ameliorate CUMS-induced LOD-like behaviors by enhancing the folate brain transport.

HNSC exosome-derived MIAT improves cognitive disorders in rats with vascular dementia via the miR-34b-5p/CALB1 axis

OBJECTIVE

To explore the molecular mechanism by which hippocampal neural stem cell (HNSC) exosome (exo)-derived MIAT improves cognitive disorders in rats with vascular dementia (VD).

METHODS

Rat hippocampal tissues were collected, and HNSCs and hippocampal neuronal cells (HNCs) were isolated, purified, and identified. Then the exosomes (exo) of the HNSCs were extracted and identified. A VD rat model was constructed. HE staining was used to evaluate the hippocampal pathology in each group. The expressions of the RNAs in the HNSCs were intervened, and the cells were then grouped. ELISA was used to measure the of TNF-α, IL-1, and Aβ1-42 expression levels. The kits were used to determine the oxidative stress factor levels. The targeting relationships among MIAT, miR-34b-5p, and CALB1 were measured using dual-luciferase assays. The MIAT expressions in exo were measured using qRT-PCR. The proliferation and apoptosis of the HNCs were determined using CCK-8 and Annexin V-FITC/PI staining, respectively. The CALB1, TH, and Bcl-2 protein expressions were determined using Western blot. The Morris water maze test was used for the spatial learning and memory testing.

RESULTS

The hippocampal tissues in the model group were clearly damaged, but the pathological characteristics were significantly improved in the exo group. The exo group also showed an increased SOD level, decreased MDA and ROS levels, and down-regulated TNF-α, IL-1, and Aβ1-42 expressions (all P<0.05). MiR-34b-5p had a targeting relationship with both MIAT and CALB1, and MIAT was found to be expressed in exo. The oe-MIAT-exo group and the miR-34b-5p inhibitor group showed significantly up-regulated CALB1, TH, and Bcl-2 protein expressions in the HNCs, increased cell viability, as well as reduced apoptosis, but the si-MIAT-exo group showed the opposite results (all P<0.05). The MiR-34b-5p inhibitor partially reversed the effect on the si-MIAT-exo group. The miR-34b-5p mimic group showed significantly down-regulated CALB1, TH, and Bcl-2 protein expressions in the HNCs, inhibited cell viability, as well as increased apoptosis, but the oe-CALB1 group showed the opposite results (all P<0.05). Oe-CALB1 partially reversed the effect on the miR-34b-5p mimic group. The memory and learning abilities of the rats in the oe-MIAT-exo group and the model + exo group were significantly improved but not as much as they were in the normal rats.

CONCLUSION

MIAT-containing exo from HNSCs can improve cognitive disorders in VD rats via the miR-34b-5p/CALB1 axis.

Parkin Promotes Mitophagic Cell Death in Adult Hippocampal Neural Stem Cells Following Insulin Withdrawal

Regulated cell death (RCD) plays a fundamental role in human health and disease. Apoptosis is the best-studied mode of RCD, but the importance of other modes has recently been gaining attention. We have previously demonstrated that adult rat hippocampal neural stem (HCN) cells undergo autophagy-dependent cell death (ADCD) following insulin withdrawal. Here, we show that Parkin mediates mitophagy and ADCD in insulin-deprived HCN cells. Insulin withdrawal increased the amount of depolarized mitochondria and their colocalization with autophagosomes. Insulin withdrawal also upregulated both mRNA and protein levels of Parkin, gene knockout of which prevented mitophagy and ADCD. c-Jun is a transcriptional repressor of Parkin and is degraded by the proteasome following insulin withdrawal. In insulin-deprived HCN cells, Parkin is required for Ca2+ accumulation and depolarization of mitochondria at the early stages of mitophagy as well as for recognition and removal of depolarized mitochondria at later stages. In contrast to the pro-death role of Parkin during mitophagy, Parkin deletion rendered HCN cells susceptible to apoptosis, revealing distinct roles of Parkin depending on different modes of RCD. Taken together, these results indicate that Parkin is required for the induction of ADCD accompanying mitochondrial dysfunction in HCN cells following insulin withdrawal. Since impaired insulin signaling is implicated in hippocampal deficits in various neurodegenerative diseases and psychological disorders, these findings may help to understand the mechanisms underlying death of neural stem cells and develop novel therapeutic strategies aiming to improve neurogenesis and survival of neural stem cells.

Sevoflurane anesthesia represses neurogenesis of hippocampus neural stem cells via regulating microRNA-183-mediated NR4A2 in newborn rats

Sevoflurane has been commonly utilized in nonobstetric surgeries in pregnant women, and its impacts on fetal brain are still not completely known. Ectopic NR4A2 expression has been reported to be related with familial Parkinson disease, and through dual luciferase we found that NR4A2 is a target gene of microRNA-183 (miR-183). We proposed a hypothesis that miR-183 may participate in the process by targeting NR4A2 in neurons after sevoflurane anesthesia. To verify the effect of sevoflurane on hippocampal neural stem cells (NSCs) proliferation and differentiation, we conducted EdU assay and immunofluorescence staining. Next, for better understanding of the impact of miR-183, we altered the miR-183 expression using mimic and inhibitor. Meanwhile, the targeting relationship between miR-183 and NR4A2 was validated by a bioinformatics website and dual-luciferase reporter gene assay. Finally, expressions of miR-184, NR4A2, SRY (sex-determining region Y)-box 2 (Sox2), and brain-derived neurotrophic factor (BDNF) were determined and evaluated by reverse transcription quantitative polymerase chain reaction and western blot analysis. First, sevoflurane was determined a crucial factor in biological behaviors of hippocampal NSCs. Moreover, upregulated miR-183 expression by mimic inhibited the proliferation and differentiation of NSCs. Sevoflurane negatively regulated NR4A2 and Sox2 expressions but positively regulated miR-183 and BDNF expressions. Our findings revealed the underlying novel mechanism by which sevoflurane inhibits hippocampal NSC proliferation and differentiation through interaction with miR-183 and NR4A2. The study provides reliable reference for safe application of sevoflurane anesthesia in neonates.

Effect of NMDA on proliferation and apoptosis in hippocampal neural stem cells treated with MK-801

The purpose of the present study was to investigate effects of N-methyl-D-aspartate (NMDA) on proliferation and apoptosis of hippocampal neural stem cells (NSCs) treated with dizocilpine (MK-801). Cultures of hippocampal NSCs were randomly divided into four groups consisting of an untreated control, cells treated with MK-801, NMDA and a combination of MK801 and NMDA (M+N). Proliferative and apoptotic responses for each of the experimental groups were determined by MTS and flow cytometry. The results revealed that MK-801 and NMDA exerted significant effects on hippocampal NSCs proliferation. Cell survival rates decreased in MK-801, NMDA and M+N treated groups compared with the control group. Cells survival rates in NMDA and M+N treated groups increased compared with the MK-801 treated group. MK-801 and NMDA were demonstrated to significantly affect apoptosis in hippocampal NSCs. Total and early stages of apoptosis in MK-801 and NMDA groups significantly increased compared with the control group. Total and early apoptosis of NSCs in the M+N group significantly decreased compared with MK-801 and NMDA groups. Late apoptosis of NSCs in MK-801 and NMDA groups significantly decreased compared with the control group. Late apoptosis of NSCs in the M+N group significantly increased compared with MK-801 and NMDA groups. The present study revealed that MK-801 inhibited proliferation and increased apoptosis in hippocampal NSCs. NMDA may reduce the neurotoxicity induced by MK-801, which may be associated with its activity towards NMDA receptors and may describe a novel therapeutic target for the treatment of schizophrenia.