Quan-Wei He

Astrocyte-Derived Sonic Hedgehog Contributes to Angiogenesis in Brain Microvascular Endothelial Cells via RhoA/ROCK Pathway After Oxygen–Glucose Deprivation

The human adult brain possesses intriguing plasticity, including neurogenesis and angiogenesis, which may be mediated by the activated sonic hedgehog (Shh). By employing a coculture system, brain microvascular endothelial cells (BMECs) cocultured with astrocytes, which were incubated under oxygen–glucose deprivation (OGD) condition, we tested the hypothesis that Shh secreted by OGD-activated astrocytes promotes cerebral angiogenesis following ischemia. The results of this study demonstrated that Shh was mainly secreted by astrocytes and the secretion was significantly upregulated after OGD. The proliferation, migration, and tube formation of BMECs cocultured with astrocytes after OGD were significantly enhanced, but cyclopamine (a Shh antagonist) or 5E1 (an antibody of Shh) reversed the change. Furthermore, silencing Ras homolog gene family, member A (RhoA) of BMECs by RNAi and blocking Rho-dependent kinase (ROCK) by Y27632, a specific antagonist of ROCK, suppressed the upregulation of proliferation, migration, and tube formation of BMECs after OGD. These findings suggested that Shh derived from activated astrocytes stimulated RhoA/ROCK pathway in BMECs after OGD, which might be involved in angiogenesis in vitro.

The protective effect of sonic hedgehog is mediated by the propidium iodide 3-kinase/AKT/Bcl-2 pathway in cultured rat astrocytes under oxidative stress

In our previous study, we found that the sonic hedgehog (Shh) signaling pathway is activated in neurons under oxidative stress and plays a neuro-protective role [Dai RL, et al. (2011) Neurochem Res 36:67-75]; we are led to postulate that the Shh might be released by astrocytes, thereby protecting neurons against oxidant injury. In primary cultured astrocytes of rats, we found that treatment with 100 μM H₂O₂ for 24 h induced a significant increase in the mRNA and protein levels of Shh, Patched1, and Gli-1, and the increase was substantially greater in astrocytes than in neurons. In the coculture systems of astrocytes and neurons under the H₂O₂ treatment, blocking the Shh signaling pathway with 5E1 (an antibody against the N-terminal domain of Shh) could block the neuroprotective activity of astrocytes on cocultured neurons. In this study, we found that treatment with H₂O₂ (100-800 μM) for 24 h caused cell death of astrocytes in a concentration-dependent manner. MTT reduction and Trypan Blue exclusion assay showed that exogenous Shh increased survival rate of the H₂O₂-treated astrocytes, whereas pretreatment with cyclopamine (a specific inhibitor of the Shh signaling pathway) or 5E1 decreased the survival rate of the H₂O₂-treated astrocytes. Shh also inhibited H₂O₂-induced apoptosis of astrocytes, and this effect could be partially reversed by cyclopamine. We also found that Shh promoted the phosphorylation of AKT, but had no significant effect on p38 or extracellular signal regulated kinases 1 and 2 (ERK 1/2) in H₂O₂-treated astrocytes. Blocking Shh or phosphoinositide 3-kinases (PI3-K)/AKT signaling pathway with cyclopamine or LY294002 decreased the survival rate of astrocytes, induced cell apoptosis, upregulated the expression of Bax, and downregulated the expression of Bcl-2. We are led to conclude that the oxidative stress induces astrocytes to secrete endogenous Shh and exogenous administration of Shh might protect the astrocytes from oxidative stress by activating PI3-K/AKT/Bcl-2 pathway.

Recombinant Human Sonic Hedgehog Protein Regulates the Expression of ZO-1 and Occludin by Activating Angiopoietin-1 in Stroke Damage

This study examines the regulating effect of Sonic Hedgehog (Shh) on the permeability of the blood-brain barrier (BBB) in cerebral ischemia. By employing permanent middle cerebral artery occlusion (pMCAO) model, we find that Shh significantly decreases brain edema and preserves BBB permeability. Moreover, Shh increases zonula occludens-1 (ZO-1), occludin and angiopiotetin-1 (Ang-1) expression in the ischemic penumbra. Blockage of Shh with cyclopamine abolishes the effects of Shh on brain edema, BBB permeability and ZO-1, occludin, Ang-1 expression. Primary brain microvessel endothelial cells (BMECs) and astrocytes were pre-treated with Shh, cyclopamine, Ang-1-neutralizing antibody, and subjected to oxygen-glucose deprivation (OGD). Results show that the Ang-1 protein level in the culture medium of Shh-treated astrocytes is significantly higher. Shh also increased ZO-1, occludin and Ang-1 expression in BMECs, while cyclopamine and Ang-1-neutralizing antibody inhibited the effects of Shh on the ZO-1 and occludin expression, respectively. This study suggests that, under ischemic insults, Shh triggers Ang-1 production predominantly in astrocytes, and the secreted Ang-1 acts on BMECs, thereby upregulating ZO-1 and occludin to repair the tight junction and ameliorate the brain edema and BBB leakage.

Endogenous Endothelial Progenitor Cells Participate in Neovascularization via CXCR4/SDF‐1 axis and Improve Outcome After Stroke

To study whether endogenous endothelial progenitor cells (EPCs) are involved in neovascularization after stroke.

MicroRNA-150 regulates blood-brain barrier permeability via Tie-2 after permanent middle cerebral artery occlusion in rats

The mechanism of blood‐brain barrier (BBB) disruption, involved in poststroke edema and hemorrhagic transformation, is important but elusive. We investigated microRNA‐150 (miR‐150)‐mediated mechanism in the disruption of BBB after stroke in rats. We found that up‐regulation of miR‐150 increased permeability of BBB as detected by MRI after permanent middle cerebral artery occlusion in vivo as well as increased permeability of brain microvascular endothelial cells after oxygen‐glucose deprivation in vitro. The expression of claudin‐5, a key tight junction protein, was decreased in the ischemic boundary zone after up‐regulation of miR‐150. We found in brain microvascular endothelial cells that overexpression of miR‐150 decreased not only cell survival rate but also the expression levels of claudin‐5 after oxygen‐glucose deprivation. With dual‐luciferase assay, we confirmed that miR‐150 could directly regulate the angiopoietin receptor Tie‐2. Moreover, silencing Tie‐2 with lentivirus‐delivered small interfering RNA reversed the effect of miR‐150 on endothelial permeability, cell survival, and claudin‐5 expression. Furthermore, poststroke treatment with antagomir‐150, a specific miR‐150 antagonist, contributed to BBB protection, infarct volume reduction, and amelioration of neurologic deficits. Collectively, our findings suggested that miR‐150 could regulate claudin‐5 expression and endothelial cell survival by targeting Tie‐2, thus affecting the permeability of BBB after permanent middle cerebral artery occlusion in rats, and that miR‐150 might be a potential alternative target for the treatment of stroke.—Fang, Z., He, Q.‐W., Li, Q., Chen, X.‐L., Baral, S., Jin, H.‐J., Zhu, Y.‐Y., Li, M., Xia, Y.‐P., Mao, L., Hu, B. MicroRNA‐150 regulates blood‐brain barrier permeability via Tie‐2 after permanent middle cerebral artery occlusion in rats. FASEB J. 30, 2097–2107 (2016). www.fasebj.org

Sonic Hedgehog (Shh) Regulates the Expression of Angiogenic Growth Factors in Oxygen–Glucose-Deprived Astrocytes by Mediating the Nuclear Receptor NR2F2

Sonic hedgehog (Shh) has been found to regulate the angiogenic growth factor such as VEGF, Ang-1, and Ang-2 during ischemic insults, but the underlying mechanism is not fully understood. In this study, we employed oxygen–glucose deprivation (OGD) in astrocytes to mimic the ischemia in vitro. We found that OGD could induce the expressions of VEGF, Ang-1, and Ang-2, with the expression of Shh signaling components increased. Moreover, inhibiting the Shh signaling pathway with 5EI, a specific antibody, could decrease the expressions of VEGF, Ang-1, and Ang-2. Furthermore, the administration of exogenous Shh could induce the expressions of VEGF, Ang-1, and Ang-2 in astrocytes. The results of silencing Gli-1, or NR2F2, exhibited that exogenous Shh could regulate the expressions of VEGF, Ang-1, and Ang-2 in astrocytes by activating the NR2F2, but not the Gli-1. These results suggested that Shh could regulate the angiogenic growth factor after ischemic insults in astrocytes, and the regulation was partially mediated by the NR2F2.

MiR-150 Regulates Poststroke Cerebral Angiogenesis via Vascular Endothelial Growth Factor in Rats

Angiogenesis is a harmonized target for poststroke recovery. Therefore, exploring the mechanisms involved in angiogenesis after stroke is vitally significant. In this study, we are reporting a miR‐150‐based mechanism underlying cerebral poststroke angiogenesis.

CYP2C19 polymorphism and clinical outcomes among patients of different races treated with clopidogrel: A systematic review and meta-analysis.

Several studies have investigated the association between CYP2C19 polymorphism and clinical outcomes of patients treated with clopidogrel, but few have noticed the difference in association between Westerners and Asians. We searched MEDLINE, EMBASE and Cochrane Library database and conducted a systematic review and meta-analysis. Thirty-six studies involving 44 655 patients with coronary artery disease (CAD) treated with clopidogrel were included, of which more than 68% had undergone percutaneous coronary intervention (PCI). The primary outcome of our interest was the recurrence of major adverse cardiovascular events (MACE) in those CAD patients. Firstly, we found that the distribution of reduced-function CYP2C19 allele varied between Westerners and Asians. Among Asians, 1 and 2 reduced-function CYP2C19 mutant allele carriers accounted for 42.5% and 10%, respectively. While among Westerners, 1 and 2 reduced-function CYP2C19 mutant allele carriers accounted for 25.5% and 2.4%, respectively. Secondly, the impact of CYP2C19 polymorphism on clinical outcomes of patients treated with clopidogrel varied with races. Among Asians, only 2 reduced-function CYP2C19 mutant allele carriers had the reduced effect of clopidogrel. And the reduced effect was significant only after the 30th day of treatment. While among Westerners, both 1 and 2 reduced-function CYP2C19 allele carriers had the reduced effect, and it mainly occurred within the first 30 days. Thirdly, the safety of clopidogrel was almost the same among races. Reduced-function allele non-carriers had higher risk for total bleeding but did not have higher risk for major bleeding. It is suggested that CYP2C19 polymorphism affects the efficacy of clopidogrel differently among Westerners and Asians.SummarySeveral studies have investigated the association between CYP2C19 polymorphism and clinical outcomes of patients treated with clopidogrel, but few have noticed the difference in association between Westerners and Asians. We searched MEDLINE, EMBASE and Cochrane Library database and conducted a systematic review and meta-analysis. Thirty-six studies involving 44 655 patients with coronary artery disease (CAD) treated with clopidogrel were included, of which more than 68% had undergone percutaneous coronary intervention (PCI). The primary outcome of our interest was the recurrence of major adverse cardiovascular events (MACE) in those CAD patients. Firstly, we found that the distribution of reduced-function CYP2C19 allele varied between Westerners and Asians. Among Asians, 1 and 2 reduced-function CYP2C19 mutant allele carriers accounted for 42.5% and 10%, respectively. While among Westerners, 1 and 2 reduced-function CYP2C19 mutant allele carriers accounted for 25.5% and 2.4%, respectively. Secondly, the impact of CYP2C19 polymorphism on clinical outcomes of patients treated with clopidogrel varied with races. Among Asians, only 2 reduced-function CYP2C19 mutant allele carriers had the reduced effect of clopidogrel. And the reduced effect was significant only after the 30th day of treatment. While among Westerners, both 1 and 2 reduced-function CYP2C19 allele carriers had the reduced effect, and it mainly occurred within the first 30 days. Thirdly, the safety of clopidogrel was almost the same among races. Reduced-function allele non-carriers had higher risk for total bleeding but did not have higher risk for major bleeding. It is suggested that CYP2C19 polymorphism affects the efficacy of clopidogrel differently among Westerners and Asians.

MicroRNA-493 regulates angiogenesis in a rat model of ischemic stroke by targeting MIF

MicroRNA‐493 (miR‐493) is known to suppress tumour metastasis and angiogenesis and its expression is decreased in stroke patients. In the present study, we investigated a role for miR‐493 in regulating post‐stroke angiogenesis. We found decreased expression of miR‐493 in the ischemic boundary zone (IBZ) of rats subjected to middle cerebral artery occlusion (MCAO), and in rat brain microvascular endothelial cells (RBMECs) exposed to oxygen glucose deprivation. Down‐regulating miR‐493 with a lateral ventricular injection of antagomir‐493, a synthetic miR‐493 inhibitor, increased capillary density in the IBZ, decreased focal infarct volume and ameliorated neurologic deficits in rats subjected to MCAO. Intriguingly, MCAO also increased the expression of macrophage migration inhibitory factor (MIF) in the IBZ of rats; MIF expression was also increased in RBMECs exposed to oxygen glucose deprivation. We found that miR‐493 directly targeted MIF, and that the protective effect of miR‐493 inhibition in angiogenesis was attenuated by knocking down MIF. This effect could then be rescued by administration of recombinant MIF. Our findings highlight the importance of miR‐493 in regulating angiogenesis after MCAO, and indicate that miR‐493 is a potential therapeutic target in the treatment of stroke.

Alleviative effects of fluoxetine on depressive - like behaviors by epigenetic regulation of BDNF gene transcription in mouse model of post-stroke depression

Fluoxetine, one of the selective serotonin reuptake inhibitor (SSRI) antidepressants, has been thought to be effective for treating post-stroke depression (PSD). Recent work has shown that fluoxetine may exert an antidepressive effect through increasing the level of brain-derived neurotrophic factor (BDNF), but the underlying mechanism still remains unclear. In the present study, we successfully established the PSD model using male C57BL/6 J mice by photothrombosis of the left anterior cortex combined with isolatied-housing conditions. In the process, we confirmed that fluoxetine could improve the depression-like behaviors of PSD mice and upregulate the expression of BDNF in the hippocampus. However, depletion of BDNF by transfecting lentivirus-derived shBDNF in hippocampus suppressed the effect of fluoxetine. Furthermore, we demonstrated the epigenetic mechanisms involved in regulation of BDNF expression induced by fluoxetine. We found a statistically significant increase in DNA methylation at specific CpG sites (loci 2) of Bdnf promoter IV in the hippocampus of PSD mice. We also found that fluoxetine treatment could disassociate the MeCP2-CREB-Bdnf promoter IV complex via phosphorylation of MeCP2 at Ser421 by Protein Kinase A (PKA). Our research highlighted the importance of fluoxetine in regulating BDNF expression which could represent a potential strategy for preventing PSD.