Aiguo Xuan

Guangzhou Medical University, Shengcheng, Guangdong, China

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Publications (6)20.27 Total impact

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    ABSTRACT: Neural stem cells (NSCs) are important pluripotent stem cells, which have potential applications in cell replacement therapy. Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have been demonstrated to exert a marked impact on the proliferation and differentiation of NSCs. The effects of NGF, BDNF, and BDNF combined with NGF on NSC neuronal differentiation and the possible mechanisms for these effects were investigated in this study. An adherent monolayer culture was employed to obtain highly homogeneous NSCs. The cells were divided into four groups: Control, NGF, BDNF and combination (BDNF + NGF) groups. Neuron differentiation was examined using immunocytochemistry and phospho-extracellular signal‑regulated kinase (p‑ERK) levels were analyzed using western blotting. Reverse transcription polymerase chain reaction was used to measure the mRNA expression levels of the HES1, HES5, MASH1, NGN1 and NeuroD transcription factors at different time intervals following neurotrophin‑induced differentiation. NGF and BDNF were observed to induce NSC neuronal differentiation, and β-tubulin III-positive cells and p-ERK expression levels were highest in the NGF + BDNF combination group at all time points. The proportion of β-tubulin Ⅲ‑positive neurons in each group was associated with the expression levels of MASH1, NGN1 and NeuroD in the group. In conclusion, BDNF combined with NGF significantly improved NSC neuronal differentiation, which may provide support for the practical application of NSCs in neurodegenerative diseases.
    Molecular Medicine Reports 07/2014; · 1.17 Impact Factor
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    ABSTRACT: Abstract Histone modifications are major post-translational mechanisms responsible for regulation of gene transcription involved in cellular senescence. By using immunofluorescence, we showed that the global acetylated levels of histone H3 and H4 were significantly reduced in both replicative and premature senescence of human embryonic lung fibroblasts. However the whole trimethylated level of histone H3 lysine 20 was higher in senescent cells. The alterations in the mRNA and protein levels of histone acetyltransferases (HATs), histone methyltransferase (HMT) and histone deacetylases (HDACs) indicate that differential expression exists between replicative and premature senescent cells. Meanwhile, the reduced activity of HDACs was accompanied by cellular senescence. By employing the quantitative chromatin immunoprecipitation assay detecting specific histone modifications in senescence related genes including p53 and p16, it was demonstrated that the mRNA expression of p53 was associated with increased H4 acetylation in replicative senescence and increased H4 acetylation and trimethylation of histone H3 at lysine 4 (H3K4me3) in premature senescence. Both acetylation and trimethylation of H3 were involved in replicative senescence, while the acetylation of histone H3 and H4 was predominant in premature senescence, contributing to the mRNA expression of p16. In summary, the global hypoacetylation of histone H3 and H4 and the hypertrimethylation of histone H4 lysine 20 account for epigenetic characteristics in senescence, controlled by HATs, HMT and HDACs differentially between replicative and premature senescence. Taken together, these findings suggest that the specific histone modifications are involved in regulating the expression of genes related to senescence of human embryonic lung fibroblasts.
    Free Radical Research 02/2014; · 3.28 Impact Factor
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    ABSTRACT: Abstract Foxa2 is one member of the Foxa subfamily of winged helix/forkhead box (Fox) transcription factors which has been found to play important roles in multiple stages of mammalian life, beginning with early development, continuing during organogenesis, and finally in metabolism and homeostasis in the adult. To explore the involvement of Foxa2 and its epigenetic regulations in cellular senescence, we established the premature senescence model induced by hydrogen peroxide in comparison with replicative senescence. The mRNA level of Foxa2 was downregulated in both replicative and premature senescent cells. We further found the increased DNA methylation level and new methylation at CpG sites in the promoter with 43.6% of methylated CpG islands in premature senescence, while only 5.7% and 17.1% in young cells and replicative senescence separately. Moreover, we noted the alterations of histone modifications including decreased histone H3 acetylation, increased H4 (Lys-20) trimethylation at the Foxa2 CpG islands in the promoter in replicative or premature senescence, while decreased histone H3 (Lys-4) trimethylation across the transcription start regions in cellular senescence. Taken together, epigenetic silencing of Foxa2 is associated with an increased DNA methylation level and histone H4 (Lys20) trimethylation, decreased histone H3 acetylation and histone H3 (Lys-4) trimethylation, involved in cellular replicative or premature senescence.
    Free Radical Research 02/2013; · 3.28 Impact Factor
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    ABSTRACT: Nickel (Ni) compounds are well-recognized human carcinogens, yet the molecular mechanism by which they cause human cancer are still not well understood. MicroRNAs (miRNAs), which are small noncoding RNAs, are involved in diverse biological functions and carcinogenesis. In previous study, we identified upregulation of DNA methyltransferase 1 (DNMT1) expression in NiS-transformed human bronchial epithelial cells. Here, we investigated whether some miRNAs are aberrantly expressed and targets DNMT1 in NiS-transformed cells. Our results showed that the expression of miRNA-152(miR-152) was specifically downregulated in NiS-transformed cells via promoter DNA hypermethylation. Whereas ectopic expression of miR-152 in NiS-transformed cells resulted in a marked reduction of DNMT1 expression. Further experiments revealed that miR-152 directly downregulated DNMT1 expression by targeting the 3'untranslated regions of its transcript. Interestingly, treatment of DNA methyltransferase inhibitor, DAC, or depletion of DNMT1 led to increased miR-152 expression by reversion of promoter hypermethylation, DNMT1 and MeCP2 binding to miR-152 promoter in NiS-transformed cells. Moreover, inhibition of miR-152 expression in 16HBE cells could increase DNMT1 expression, and result in an increase in DNA methylation, DNMT1 and MeCP2 binding to miR-152 promoter, indicating an interaction between miR-152 and DNMT1 is regulated by a double-negative circuit. Furthermore, ectopic expression of miR-152 in NiS-transformed cells led to a significant decrease of cell growth. Conversely, inhibition of miR-152 expression in 16HBE cells significantly increased cell growth. Taken together, these observations demonstrate a crucial functional crosstalk between miR-152 and the DNMT1 via a feedback loop involved in NiS-induced malignant transformation.
    Carcinogenesis 11/2012; · 5.64 Impact Factor
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    ABSTRACT: Endogenously produced hydrogen sulfide (H2S) may have multiple functions in brain. An increasing number of studies have demonstrated its anti-inflammatory effects. In the present study, we investigated the effect of sodium hydrosulfide (NaHS, a H2S donor) on cognitive impairment and neuroinflammatory changes induced by injections of Amyloid-β1-40 (Aβ1-40), and explored possible mechanisms of action. We injected Aβ1-40 into the hippocampus of rats to mimic rat model of Alzheimer's disease (AD). Morris water maze was used to detect the cognitive function. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay was performed to detect neuronal apoptosis. Immunohistochemistry analyzed the response of glia. The expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α was measured by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). The expression of Aβ1-40, phospho-p38 mitogen-activated protein kinase (MAPK), phospho-p65 Nuclear factor (NF)-κB, and phospho-c-Jun N-terminal Kinase (JNK) was analyzed by western blot. We demonstrated that pretreatment with NaHS ameliorated learning and memory deficits in an Aβ1-40 rat model of AD. NaHS treatment suppressed Aβ1-40-induced apoptosis in the CA1 subfield of the hippocampus. Moreover, the over-expression in IL-1β and TNF-α as well as the extensive astrogliosis and microgliosis in the hippocampus induced by Aβ1-40 were significantly reduced following administration of NaHS. Concomitantly, treatment with NaHS alleviated the levels of p38 MAPK and p65 NF-κB phosphorylation but not JNK phosphorylation that occurred in the Aβ1-40-injected hippocampus. These results indicate that NaHS could significantly ameliorate Aβ1-40-induced spatial learning and memory impairment, apoptosis, and neuroinflammation at least in part via the inhibition of p38 MAPK and p65 NF-κB activity, suggesting that administration of NaHS could provide a therapeutic approach for AD.
    Journal of Neuroinflammation 08/2012; 9:202. · 4.35 Impact Factor
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    ABSTRACT: A growing number of studies demonstrate that valproic acid (VPA), an anti-convulsant and mood-stabilizing drug, is neuroprotective against various insults. This study investigated whether treatment of ischemic stroke with VPA ameliorated hippocampal cell death and cognitive deficits. Possible mechanisms of action were also investigated. Global cerebral ischemia was induced to mimic ischemia/reperfusion (I/R) damage. The pyramidal cells within the CA1 field were stained with cresyl violet. Cognitive ability was measured 7 days after I/R using a Morris water maze. The anti-inflammatory effects of VPA on microglia were also investigated by immunohistochemistry. Pro-inflammatory cytokine production was determined using enzyme-linked immunosorbent assays (ELISA). Western blot analysis was performed to determine the levels of acetylated H3, H4 and heat shock protein 70 (HSP70) in extracts from the ischemic hippocampus. VPA significantly increased the density of neurons that survived in the CA1 region of the hippocampus on the 7th day after transient global ischemia. VPA ameliorated severe deficiencies in spatial cognitive performance induced by transient global ischemia. Post-insult treatment with VPA also dramatically suppressed the activation of microglia but not astrocytes, reduced the number of microglia, and inhibited other inflammatory markers in the ischemic brain. VPA treatment resulted in a significant increase in levels of acetylated histones H3 and H4 as well as HSP70 in the hippocampus. Our results indicated that VPA protected against hippocampal cell loss and cognitive deficits. Treatment with VPA following cerebral ischemia probably involves multiple mechanisms of action, including inhibition of ischemia-induced cerebral inflammation, inhibition of histone deacetylase (HDAC) and induction of HSP.
    Life sciences 03/2012; 90(11-12):463-8. · 2.56 Impact Factor