Xuefeng Ding

miR-210 suppresses BNIP3 to protect against the apoptosis of neural progenitor cells.

MiR-210 is a hypoxia-inducible factor (HIF)-1 target gene and is the most consistently and predominantly upregulated miRNA in response to hypoxia in various cancer cell lines. Our recent study shows that hypoxia increased miR-210 expression in neural progenitor cells (NPCs) in a time-dependent manner. However, the role of miR-210 in NPCs remains unknown. Following the identification of the miR-210 putative target genes, we demonstrated that the Bcl-2 adenovirus E1B 19kDa-interacting protein 3 (BNIP3), which is regulated by HIF-1 and activates cell death, is regulated by miR-210 in NPCs under hypoxia. Moreover, the over-expression of miR-210 decreased apoptosis in NPCs, and the inhibition of miR-210 expression remarkably increased the number of TUNEL-positive NPCs by 30% in response to hypoxia. Importantly, miR-210 mimics reduced both BNIP3 protein expression and the translocation of AIF into the nucleus, which reduced cell death, whereas miR-210 inhibitors reversed this process, leading to cell death during hypoxia. Taken together, we report a novel feedback loop of BNIP3 regulation in NPCs under hypoxia. HIF-1 is activated under hypoxia and then induces the expression of both BNIP3 and miR-210. The upregulation of miR-210 then directly suppresses BNIP3 expression to maintain the survival of NPCs under hypoxia. This negative feedback regulation might partially contribute to protection against hypoxia-induced cell death via the inhibition of AIF nuclear translocation.

DNA demethylation regulates the expression of miR‐210 in neural progenitor cells subjected to hypoxia

Several studies have identified a set of hypoxia‐regulated microRNAs, among which is miR‐210, whose expression is highly induced by hypoxia in various cancer cell lines. Recent studies have highlighted the importance of miR‐210 and its transcriptional regulation by the transcription factor hypoxia‐inducible factor‐1 (HIF‐1). We report here that the expression of miR‐210 was highly induced in neural progenitor cells (NPCs) subjected to hypoxia. Specifically, treating hypoxic NPCs with the DNA demethylating agent 5‐aza‐2′‐deoxycytidine significantly increased the expression of miR‐210, even under normoxia; however, the activity of hypoxia‐inducible factor‐1 was unaffected. Further analysis of the miR‐210 sequence revealed that it is embedded in a CpG island. Bisulfite sequencing of the miR‐210 CpG island from NPCs grown under hypoxic conditions showed 24% CpG methylation in NPCs exposed to 20% O2, 18% in NPCs exposed to 3% O2, and 12% in NPCs exposed to 0.3% O2. In addition, the activity of DNA methyltransferases (DNMTs) in NPCs decreased after exposure to hypoxia. Specifically, the expression of DNMT3b decreased significantly after exposure to 0.3% O2. Thus, these results demonstrate that DNA demethylation regulates miR‐210 expression in NPCs under both normoxia and hypoxia.

DIXDC1 Promotes Retinoic Acid-Induced Neuronal Differentiation and Inhibits Gliogenesis in P19 Cells

Human DIXDC1 is a member of Dishevelled-Axin (DIX) domain containing gene family which plays important roles in Wnt signaling and neural development. In this report, we first confirmed that expression of Ccd1, a mouse homologous gene of DIXDC1, was up-regulated in embryonic developing nervous system. Further studies showed that Ccd1 was expressed specifically in neurons and colocalized with early neuronal marker Tuj1. During the aggregation induced by RA and neuronal differentiation of embryonic carcinoma P19 cells, expressions of Ccd1 as well as Wnt-1 and N-cadherin were dramatically increased. Stable overexpression of DIXDC1 in P19 cells promoted the neuronal differentiation. P19 cells overexpressing DIXDC1 but not the control P19 cells could differentiate into Tuj1 positive cells with RA induction for only 2 days. Meanwhile, we also found that overexpression of DIXDC1 facilitated the expression of Wnt1 and bHLHs during aggregation and differentiation, respectively, while inhibited gliogenesis by down-regulating the expression of GFAP in P19 cells. Thus, our finding suggested that DIXDC1 might play an important role during neurogenesis, overexpression of DIXDC1 in embryonic carcinoma P19 cells promoted neuronal differentiation, and inhibited gliogenesis induced by retinoic acid.

5-HMF prevents against oxidative injury via APE/Ref-1

Abstract Oxidative injury is involved in many diseases, including ischemic and neurodegenerative diseases. Antioxidant drugs can be used to relieve the oxidative injury caused by these diseases; however, there are very few antioxidant drugs available for clinical use. In this study, we found that 5-(hydroxymethyl)-2-furfural (5-HMF) protects against the oxidative damage induced by cerebral ischemia in rats or by hydrogen peroxide (H2O2) in PC12 cells. We demonstrated that 5-HMF performs this function via apurinic/apyrimidinic endonuclease/redox factor-1 (APE/Ref-1). APE/Ref-1 is a multifunctional protein involved in oxidative DNA damage repair through the base excision repair (BER) pathway and in the regulation of the DNA-binding activity of several transcription factors. The current study focused on the role of APE/Ref-1 in the antioxidative properties of 5-HMF. The results show that 5-HMF inhibited the reduction of APE/Ref-1 protein level caused by cerebral ischemia–reperfusion injury in rats or H2O2 treatment in PC12 cells. Treatment with an APE/Ref-1 inhibitor blocked 5-HMF-induced protection, suggesting that APE/Ref-1s DNA repair function contributes to antioxidation. In conclusion, this study suggests that APE/Ref-1 may be a potential target for antioxidant drugs.

Expression and Functional Roles of Smad1 and BMPR-IB in Glioma Development

Here we report the negative correlation of phosphorylation of Smad1 and BMPR-IB expression with the development of human glioma. Western blot analysis showed that expression of both phospho-Smad1/5/8 and BMPR-IB were decreased in malignant glioma tissues compared with normal brain tissues. Kaplan–Meier survival curves revealed that lower expression ratio of phospho-Smad1/5/8 to Smad1 expression significantly correlates with poor patient survival. Transient transfection of BMPR-IB activates Smad1 signaling and induces differentiation and apoptosis of U251 and U87 glioblastoma cells. The effects could be blocked by cotransfection of Smad6. These results might provide new molecular marker and target for glioma diagnosis and therapy.

DIXDC1 co-localizes and interacts with γ-tubulin in HEK293 cells

DIXDC1 is a Dishevelled‐Axin (DIX) domain‐containing protein involved in neural development and Wnt signaling pathway. Besides the DIX domain, DIXDC1 also contains a coiled‐coil domain (MTH domain), which is a common feature of centrosomal proteins. We have demonstrated that exogenously expressed GFP‐tag fused DIXDC1 co‐localize with γ‐tubulin both at interphase and mitotic phase in HEK293 cells. By immunostaining with anti‐DIXDC1 and anti‐γ‐tubulin antibody, endogenous DIXDC1 was also co‐localized with γ‐tubulin at the centrosomes in HEK293 cells. We confirmed this interaction of DIXDC1 with γ‐tubulin by co‐immunoprecipitation. The findings suggest that DIXDC1 might play an important role in chromosome segregation and cell cycle regulation.

Localization and cellular distribution of CPNE5 in embryonic mouse brain.

CPNE5 is one of the ubiquitous Ca(2+)-dependent, phospholipid-binding proteins that are highly conserved in animals. It was cloned in the fetal human brain with no exact functions identified yet. We have examined the distribution pattern of CPNE5 mRNA and protein in the developing murine brain by using in situ hybridization, western blotting and immunocytochemistry. Expression of CPNE5 mRNA remains high from embryonic day 9.5 (E9.5) to E15.5 in the developing murine brain. Whole-mount in situ hybridization with the E11.5 and E12.5 embryos showed the strong positive signals in the central nervous system. Western-blot analysis showed that CPNE5 protein is expressed in the developing but not in the adult murine brain. In situ hybridization and immunohistochemistry analysis on the embryonic brain sections indicated that both at RNA and protein levels CPNE5 is mainly expressed in frontal cortex, medial nasal prominence, ganglionic eminence and medulla, particularly in the ventricular zones. Further investigation revealed the co-localization of CPNE5 with Tuj1 and Nestin on embryonic brain sections. In addition to the slight expression in primary cultured neural progenitor cells, CPNE5 is found in soma and neurite projections of primary cultured neurons where Tuj1 is co-localized. Our results demonstrate that CPNE5 is expressed in both neural progenitor cells and the differentiated neurons during the neural development, which suggests that CPNE5 might play an important role in the development of murine central nervous system.

A method for establishing the high-altitude cerebral edema (HACE) model by acute hypobaric hypoxia in adult mice.

BACKGROUND Exposure to acute hypobaric hypoxia (AHH) during ascent to high altitudes (>3500 m) is one of the main causes of acute mountain sickness (AMS) and high-altitude cerebral edema (HACE). Therefore, the aim of this study was to develop a model of HACE. NEW METHODS We developed a model of HACE in mice using a decompression chamber with rapid ascent speed. RESULTS Healthy male C57BL/6 mice were randomly divided into the control group and the AHH group. The AHH group was housed in a decompression chamber (at a velocity of 50 m/s within 5 min to 6000 m). Compared with the controls, brain water content was increased in the early stage (within 24 h) in the AHH group. After 72 h of exposure to AHH, there was a higher BBB permeability observed. In addition, the brain structure showed significant widening of the pericellular spaces and a dilatation of the cortical blood vessels after exposure to AHH, and some of the neurons appeared shrunken with darkly stained pyknotic nuclei, resulting in neuronal structural damage. Further, exposure to AHH also decreased cognitive function in the mice. COMPARISON WITH EXISTING METHODS At present, there are no simple and rapid mouse models to study this syndrome in terms of its genetic basis, gene polymorphisms and susceptibility. CONCLUSION Our findings show that AHH can increase BBB permeability and lead to cerebral edema in mice; thus, we provide an effective and stable model of HACE in mice.

Enhanced Hypoxia-Inducible Factor (HIF)-1α Stability Induced by 5-Hydroxymethyl-2-Furfural (5-HMF) Contributes to Protection against Hypoxia

We first reported the role of 5-hydroxymethyl-2-furfural (5-HMF) against hypoxia. Here, we studied the mechanism by using oxygen-dependent degradation domain (ODD)-Luc mice, which are a useful model to probe the stabilization of hypoxia-inducible factor 1α (HIF-1α). Compared with three other compounds that have been reported to have a role in stabilizing HIF-1α, 5-HMF caused stronger bioluminescence, which is indicative of HIF-1α stability in the brain and kidney of ODD-Luc mice. We further demonstrated that the HIF-1α protein accumulated in response to 5-HMF in the brains and kidneys of these mice, as well as in PC12 cells. Additionally, 5-HMF promoted the nuclear translocation of HIF-1α and the transcriptional activity of HIF-1, which was evaluated by detecting vascular endothelial growth factor (VEGF) mRNA expression. These results suggest that 5-HMF stabilized HIF-1α and increased its activity. Considering the role of proline hydroxylases (PHDs) in negatively regulating HIF-1α stability, we explored whether 5-HMF interacts with the substrates and cofactors of PHDs, such as 2-oxoglutarate (2-OG), Fe2+ and vitamin C (VC), which affects the activity of PHDs. The result revealed that 5-HMF did not interact with Fe2+ or 2-OG but interacted with VC. This interaction was confirmed by subsequent experiments, in which 5-HMF entered into cells and reduced the VC content. The enhanced stability of HIF-1α by 5-HMF was reversed by VC supplementation, and the improved survival of mice caused by 5-HMF under hypoxia was abrogated by VC supplementation. Thus, we demonstrated for the first time that 5-HMF increases HIF-1α stability by reducing the VC content, which mediates the protection against hypoxia.

Nerve growth factor promotes human sperm motility in vitro by increasing the movement distance and the number of A grade spermatozoa

Nerve growth factor (NGF) was first found in the central nervous system and is now well known for its multiple pivotal roles in the nervous system and immune system. However, more and more evidences showed that NGF and its receptors TrkA and p75 were also found in the head and tail of spermatozoa, which indicate the possible effect of NGF on the sperm motility. Nevertheless, the exact role of NGF in the human sperm motility remains unclear until now. In this study, we investigated the effect of NGF on human sperm motility, and the results showed that NGF could promote human sperm motility in vitro by increasing the movement distance and the number of A grade spermatozoa. Further analysis demonstrated that NGF promoted the sperm motility in a dose‐dependent manner in vitro. These results may facilitate the further studies on human fertility and assisted reproduction techniques.