Yong-Qi Zhao

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.

Methylene Blue Reduces Acute Cerebral Ischemic Injury via the Induction of Mitophagy.

The treatment of stroke is limited by a short therapeutic window and a lack of effective clinical drugs. Methylene blue (MB) has been used in laboratories and clinics since the 1890s. Few studies have reported the neuroprotective role of MB in cerebral ischemia-reperfusion injury. However, whether and how MB protects against acute cerebral ischemia (ACI) injury was unclear. In this study, we investigated the effect of MB on this injury and revealed that MB protected against ACI injury by augmenting mitophagy. Using a rat middle cerebral artery occlusion (MCAO) model, we demonstrated that MB improved neurological function and reduced the infarct volume and necrosis after ACI injury. These improvements depended on the effect of MB on mitochondrial structure and function. ACI caused the disorder and disintegration of mitochondrial structure, while MB ameliorated the destruction of mitochondria. In addition, mitophagy was inhibited at 24 h after stroke and MB augmented mitophagy. In an oxygen-glucose deprivation (OGD) model in vitro, we further revealed that the elevation of mitochondrial membrane potential (MMP) by MB under OGD conditions mediated the augmented mitophagy. In contrast, exacerbating the decline of MMP during OGD abolished the MB-induced activation of mitophagy. Taken together, MB promotes mitophagy by maintaining the MMP at a relatively high level, which contributes to a decrease in necrosis and an improvement in neurological function, thereby protecting against ACI injury.

Reduced Cerebral Oxygen Content in the DG and SVZ In Situ Promotes Neurogenesis in the Adult Rat Brain In Vivo

Neurogenesis in the adult brain occurs mainly within two neurogenic structures, the dentate gyrus (DG) of the hippocampus and the sub-ventricular zone (SVZ) of the forebrain. It has been reported that mild hypoxia promoted the proliferation of Neural Stem Cells (NSCs)in vitro. Our previous study further demonstrated that an external hypoxic environment stimulated neurogenesis in the adult rat brain in vivo. However, it remains unknown how external hypoxic environments affect the oxygen content in the brain and result in neurogenesis. Here we use an optical fiber luminescent oxygen sensor to detect the oxygen content in the adult rat brain in situ under normoxia and hypoxia. We found that the distribution of oxygen in cerebral regions is spatiotemporally heterogeneous. The Po2 values in the ventricles (45∼50 Torr) and DG (approximately 10 Torr) were much higher than those of other parts of the brain, such as the cortex and thalamus (approximately 2 Torr). Interestingly, our in vivo studies showed that an external hypoxic environment could change the intrinsic oxygen content in brain tissues, notably reducing oxygen levels in both the DG and SVZ, the major sites of adult neurogenesis. Furthermore, the hypoxic environment also increased the expression of HIF-1α and VEGF, two factors that have been reported to regulate neurogenesis, within the DG and SVZ. Thus, we have demonstrated that reducing the oxygen content of the external environment decreased Po2 levels in the DG and SVZ. This reduced oxygen level in the DG and SVZ might be the main mechanism triggering neurogenesis in the adult brain. More importantly, we speculate that varying oxygen levels may be the physiological basis of the regionally restricted neurogenesis in the adult brain.

Hypoxia augments LPS-induced inflammation and triggers high altitude cerebral edema in mice

High altitude cerebral edema (HACE) is a life-threatening illness that develops during the rapid ascent to high altitudes, but its underlying mechanisms remain unclear. Growing evidence has implicated inflammation in the susceptibility to and development of brain edema. In the present study, we investigated the inflammatory response and its roles in HACE in mice following high altitude hypoxic injury. We report that acute hypobaric hypoxia induced a slight inflammatory response or brain edema within 24h in mice. However, the lipopolysaccharide (LPS)-induced systemic inflammatory response rapidly aggravated brain edema upon acute hypobaric hypoxia exposure by disrupting blood-brain barrier integrity and activating microglia, increasing water permeability via the accumulation of aquaporin-4 (AQP4), and eventually leading to impaired cognitive and motor function. These findings demonstrate that hypoxia augments LPS-induced inflammation and induces the occurrence and development of cerebral edema in mice at high altitude. Here, we provide new information on the impact of systemic inflammation on the susceptibility to and outcomes of HACE.

Geranylgeranylacetone preconditioning may attenuate heat-induced inflammation and multiorgan dysfunction in rats

Objectives Geranylgeranylacetone, an acyclic isoprenoid, is a non‐toxic inducer of heat shock protein (HSP)70. HSP70 overproduction is associated with heat tolerance in rats. This study aimed to investigate whether geranylgeranylacetone preconditioning of rats reduced heat‐induced inflammation and multiple organ dysfunction.

WIP1 Phosphatase Plays a Critical Neuroprotective Role in Brain Injury Induced by High-Altitude Hypoxic Inflammation

The hypobaric hypoxic environment in high-altitude areas often aggravates the severity of inflammation and induces brain injury as a consequence. However, the critical genes regulating this process remain largely unknown. The phosphatase wild-type p53-induced phosphatase 1 (WIP1) plays important roles in various physiological and pathological processes, including the regulation of inflammation in normoxia, but its functions in hypoxic inflammation-induced brain injury remain unclear. Here, we established a mouse model of this type of injury and found that WIP1 deficiency augmented the release of inflammatory cytokines in the peripheral circulation and brain tissue, increased the numbers of activated microglia/macrophages in the brain, aggravated cerebral histological lesions, and exacerbated the impairment of motor and cognitive abilities. Collectively, these results provide the first in vivo evidence that WIP1 is a critical neuroprotector against hypoxic inflammation-induced brain injury.

Quinacrine protects neuronal cells against heat-induced injury

The effects of quinacrine (QA) on heat‐induced neuronal injury have been explored, with the intention of understanding the mechanisms of QA protection. Primary cultivated striatum neurons from newborn rats were treated with QA 1 h before heat treatment at 43 °C which lasted for another 1 h, and necrosis and apoptosis were detected by Annexin‐V‐FITC and propidium iodide (PI) double staining. Neuronal apoptosis was determined using terminal deoxynucleotidyl transferase‐mediated biotinylated UTP nick end labeling (TUNEL) techniques. Cell membrane fluidity, activity of cytosolic phospholipase A2 (cPLA2) and the level of arachidonic acid (AA) were also examined. Membrane surface ultrastructure of striatum neurons was investigated by atomic force microscopy (AFM). Results showed that heat treatment induced great striatum neurons death, with many dying neurons undergoing necrosis rather than apoptosis. QA alone had little effect on the survival of striatum neurons, while QA pretreatment before heat treatment decreased necrosis. Heat treatment also resulted in decreased membrane fluidity and increased cPLA2 activity as well as arachidonic acid level; these effects were reversed by QA pretreatment. QA pretreatment also significantly prevented damage to the membrane surface ultrastructure of heat‐treated neurons. These results suggest that QA protects striatum neurons against heat‐induced neuronal necrosis, and also demonstrate that inhibition of cPLA2 activity and stabilization of membranes may contribute to protective effect of quinacrine.

An Improved Elevated Platform for Simultaneously Assessing Rodent Locomotor Activity and Anxiety

Elevated plus maze (EPM) has been the golden standard for assessing rodent anxiety, which consists of two enclosed arms and two open arms elevated 100 cm above the floor. The two closed arms are closed and dark space with high edges (>30 cm). The two open arms are open space with low edges (0.5 cm). Animals prefer exploring unknown environment but will feel fearful in the open arms; thus, the psychiatric conflict between intrinsic exploring desire and fearful challenge produced by the 100 cm height reflects the rodent anxiety level [1–3]. However, the existing EPM has some limitations. Firstly, time spent in the center zone was usually neglected for the much smaller area than the four arms, which may greatly decrease its sensitivity in assessing anxiety. Secondly, the route from the closed arm to open arm is not linear, and high walls of closed arm make the open arm invisible for animals in the closed arm, which may decrease the animal exploring activity and thus affect the sensitivity. This drawback even makes some animals stay in the closed arms during all the test duration in some experiment without entering the open arm. Thirdly, it is difficult to handle mouse/rat when test finish, which may increase animal stress and further affect the subsequent behavior test. Thus, a more sensitive method should be developed for better assessing animal anxiety.

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.