Xiangpen Li

Remote ischemic conditioning for acute ischemic stroke: dawn in the darkness.

Abstract Stroke is a leading cause of disability with high morbidity and mortality worldwide. Of all strokes, 87% are ischemic. The only approved treatments for acute ischemic stroke are intravenous thrombolysis with alteplase within 4.5 h and thrombectomy within 8 h after symptom onset, which can be applied to just a few patients. During the past decades, ischemic preconditioning has been widely studied to confirm its neuroprotection against subsequent ischemia/reperfusion injury in the brain, including preconditioning in situ or in a remote organ (such as a limb) before onset of brain ischemia, the latter of which is termed as remote ischemic preconditioning. Because acute stroke is unpredicted, ischemic preconditioning is actually not suitable for clinical application. So remote ischemic conditioning performed during or after the ischemic duration of the brain was then designed to study its neuroprotection alone or in combination with alteplase in animals and patients, which is named as remote ischemic perconditioning or remote ischemic postconditioning. As expected, animal experiments and clinical trials both showed exciting results, indicating that an evolution in the treatment for acute ischemic stroke may not be far away. However, some problems or disputes still exist. This review summarizes the research progress and unresolved issues of remote ischemic conditioning (pre-, per-, and post-conditioning) in treating acute ischemic stroke, with the hope of advancing our understanding of this promising neuroprotective strategy for ischemic stroke in the near future.

The protective effect of astaxanthin on fetal alcohol spectrum disorder in mice.

Astaxanthin is a strong antioxidant with the ability of reducing the markers of inflammation. To explore the protective effect of astaxanthin on maternal ethanol induced embryonic deficiency, and to investigate the underlying mechanisms, we detected the morphology, expression of neural marker genes, oxidative stress indexes, and inflammatory factors in mice model of fetal alcohol spectrum disorder with or without astaxanthin pretreatment. Our results showed that astaxanthin blocked maternal ethanol induced retardation of embryonic growth, and the down-regulation of neural marker genes, Otx1 and Sox2. Moreover, astaxanthin also reversed the increases of malondialdehyde (MDA), hydrogen peroxide (H2O2), and the decrease of glutathione peroxidase (GPx) in fetal alcohol spectrum disorder. In addition, maternal ethanol induced up-regulation of toll-like receptor 4 (TLR4), and the down-streaming myeloid differentiation factor 88 (MyD88), NF-κB, TNF-α, and IL-1β in embryos, and this was inhibited by astaxanthin pretreatment. These results demonstrated a protective effect of astaxanthin on fetal alcohol spectrum disorder, and suggested that oxidative stress and TLR4 signaling associated inflammatory reaction are involved in this process.

VEGF induces angiogenesis in a zebrafish embryo glioma model established by transplantation of human glioma cells

Zebrafish (Danio rerio) is becoming an increasingly popular vertebrate cancer model. In this study, we established a xenotransplanted zebrafish embryo glioma model to further investigate the molecular mechanisms of tumor angiogenesis. We find that the glioma cell line U87 can survive, proliferate and induce additional SIV branches in zebrafish embryos. In addition, by the means of in situ hybridization and quantitive RT-PCR analyses we find that the transplanted U87 cells can induce the ectopic zebrafish vascular endothelial growth factor A (VEGF A) and its receptor VEGFR2/KDR mRNA expression and increase their expression levels, resulting in additional SIV branches.

A pH-sensitive hyaluronic acid prodrug modified with lactoferrin for glioma dual-targeted treatment.

Gliomas are the most common and lethal type of primary malignant brain tumor. But the existence of blood brain barrier (BBB) and blood-tumor barrier (BTB) hinder drug from reaching the tumor site. To address this problem, we developed a novel prodrug (Lf-HA-DOX) by conjugating hyaluronic acid with doxorubicin (HA-DOX) by an acid-labile hydrazone linkage, which is released in an acidic environment and accumulates in tumor tissues. Lactoferrin (Lf) was coupled for transporting across the BBB. In vitro, the release of DOX from Lf-HA-DOX was pH-dependent. At lower pH (5.0 and 6.0), the release of DOX was much quicker than that at pH7.4. In the cellular uptake studies, flow cytometry analyses and confocal laser scanning microscopy results showed significantly enhanced cellular uptake of Lf-HA-DOX and HA-DOX in C6 cells compared to DOX. In BALB/C mice bearing C6 glioma, enhanced accumulation of Lf-HA-DOX in the glioma was observed by real time fluorescence image. Correspondingly, glioma-bearing mice treated with Lf-HA-DOX displayed the longest median survival time, which was 2-fold longer than that of saline group. In conclusion, Lf-HA-DOX was able to significantly increase drug delivery to the glioma, which might provide a promising strategy for antiglioma therapy.

Relationship between Cerebral Hypoxic Tissue Volume and Prognosis after Stroke

Background/Aims: Between 50 and 70% of stroke survivors suffer from severe disabilities such as paralysis and aphasia. Poor stroke outcome is a reflection of our incomplete understanding of the underlying mechanisms, and hence the capacity to implement appropriate treatment(s). We evaluated hypoxic tissue after stroke and patient condition severity and prognosis. Methods: Hypoxic tissue volume was quantified within 14 days after stroke. Patients were classified as hypoxic positive or negative. Patients were evaluated at imaging and 21 days later. Prognosis was assessed at 30 and 90 days. Results: Significant improvement was shown in hypoxia-positive (vs. hypoxia-negative) patients (p < 0.05). There were significant positive relationships between the volume of hypoxic tissue and the improvement in specialized test scores at 90 days (p < 0.05 for both). Presence of hypoxic tissue within 14 days after cerebral stroke was related to recovery at 3 weeks and prognosis at 90 days. Conclusions: The assessment of hypoxic tissue volume after stroke may be useful in predicting patient recovery.

Tumor-associated macrophages induce vasculogenic mimicry of glioblastoma multiforme through cyclooxygenase-2 activation

Glioblastoma multiforme (GBM) is a malignant brain tumor with characteristics of strong aggressiveness which depend on vigorous microvascular supply. Vasculogenic mimicry (VM), a new microvascular circulation not involving endothelial cells, is reported as one part of the vascularization of GBM. Tumor-associated macrophages (TAMs), mostly present as immunosuppressive M2 phenotype in GBM, are well known as a promoter for tumor angiogenesis. However, whether TAMs can induce VM in GBM remains uncertain. In the present study, immunohistochemistry showed that higher numbers of macrophages infiltrating in the VM-positive area where tumor cells also highly express COX-2. By using the coculture model of U87 cell line and Interleukin-4-activated M2 macrophages, we found that the capability of VM formation was increased and COX-2 expression was up-regulated in U87 cells. Moreover, knockdown of COX-2 by siRNA Oligonucleotides or abrogating activity of COX-2 by specific inhibitors resulted in impairment of VM formation. Besides, in the process of VM formation, PGE2/EP1/PKC pathway was activated in U87 cells and inhibition of COX-2 led to down-regulation of PGE2 and PKC. In in vivo experiment, we found that COX-2 loss of function in the U87 xenograft model lead to less vascular mimicry. Collectively, our study demonstrates that M2 macrophages are capable of promoting generation of VM in GBM with COX-2 dependent, providing potential mechanisms of the interaction between inflammatory microenvironment and perivascular microenvironment.

Temporal pattern of Toll-like receptor 9 upregulation in neurons and glial cells following cerebral ischemia reperfusion in mice

Purpose: The family of Toll-like receptors (TLRs) has recently been reported to play a role in ischemic injury, but the time course and cell types of the post-stroke TLR9 upregulation remain unclear. In this study, we investigated the dynamic changes of TLR9 expression and the expression of TLR9 in neurons and glial cells after cerebral ischemia reperfusion in mice. Methods: Focal cerebral ischemia was induced by middle cerebral artery occlusion for 90 min in male C57BL/6 mice. The TLR9 expression levels in the tissue surrounding the infarct were detected by Western Blot at 6 h, 3 d, 7 d, 14 d, 21 d, and 28 d after reperfusion. The expression of TLR9 in neurons and glial cells was observed by immunofluorescence staining. Results: The expression of TLR9 protein first increased and then decreased, with the peak observed at 14 d–21 d. Only small punctate intracellular TLR9 was occasionally observed in the neurons at each time point, and the TLR9-positive rate showed no difference at different time points. By contrast, the activated microglia gathered at the margin of the infarct, and the intracellular TLR9 changed from scattered small punctate to coarse and lumpy. The TLR9-positive rate of microglia was first increased and then decreased with time, with the peak observed at 3 d. No positive TLR9 staining was found in the astrocytes and oligodendrocytes. Conclusions: TLR9 expression showed dynamic changes for a long period of time and microglias were the main brain cells to express TLR9 after cerebral ischemia and reperfusion.

Relationship between activated astrocytes and hypoxic cerebral tissue in a rat model of cerebral ischemia/reperfusion.

Following cerebral infarction, hypoxic tissues remains in the ischemic cortex for long periods of time. Glial fibrillary acidic protein (GFAP) is a specific marker of astrocytes, which is thought to be essential for neuronal survival. We aimed to clarify the relationship between hypoxic tissue and astrocytes following cerebral infarction. Rats with middle cerebral artery occlusion were randomly divided into a 1.5-hour ischemia-reperfusion(1.5-hour IR) group and a permanent ischemia (PI) group. Hypoxic tissue and GFAP fluorescence intensity in the ischemic cortex were observed postoperatively on days 1, 3, 7, and 14. Results showed that hypoxic tissue was present from day 1 to 14 in the 1.5-hour IR group and on days 1 and 3 in the PI group. The GFAP fluorescence intensity in the 1.5-hour IR group was stronger than that in the PI group at the same time point of observation. Over time, GFAP expression increased and peaked at 7 days in each group, followed by a decrease in signal. In hypoxic tissue, the GFAP fluorescence intensity was stronger than that in the surrounding tissue at all observation time points. These data indicate that astrocytes were strongly activated in hypoxic tissue induced by temporary ischemia followed by reperfusion. The activation of astrocytes may partially contribute to the survival and repair of hypoxic tissue following brain ischemia.

Identification of Potential Biomarkers for Artificial Cold Exposure–induced Hypertensive Stroke by Proteomic Analysis

BACKGROUND The effect of changing temperature on an individuals cerebrovascular risk is both biologically plausible and supported by epidemiologic evidence. We used a global proteomic-based approach to analyze the expression alterations of proteins in artificial cold exposure (ACE)-induced hypertensive stroke in renovascular hypertensive rats (RHR) and to identify the biomarker of ACE-induced hypertensive stroke. METHODS The RHR models were established by 2 kidney 2 clip methods. ACE treatment was achieved using an intelligent artificial climate cabinet. Blood pressure and neurologic symptoms were observed before and after ACE treatment. Hemorrhagic condition and infarction survey were examined using 2,3,5-triphenyltetrazolium chloride staining. The total number of proteins derived from the cerebral tissue of the RHR models were analyzed with 2-dimensional gel electrophoresis (2-DE), ImageMaster 2D Platinum software, and mass spectrometry. Significantly regulated proteins selected for further functional studies using the Search Tool for the Retrieval of Interacting Genes/Proteins system were verified by Western blot. RESULTS ACE-induced stroke in the RHR group (31.25%, 25 of 80 vs. 16.25%, 13 of 80; P < .05) but not in the sham-operated group. Following ACE treatment, we identified 37 differentially expressed proteins and 28 were unique. Two of the upregulated proteins, Syt1 and Idh3a, were obtained by bioinformatics analysis and verified by Western blot. CONCLUSIONS The rate of morbidity as a result of stroke in RHR was obviously elevated after ACE treatment. ACE might affect protein expression profile in cerebral tissues of RHR. Syt1 and Idh3a may play a vital role in ACE-induced hypertensive stroke.

EZH2 suppression in glioblastoma shifts microglia toward M1 phenotype in tumor microenvironment

BackgroundGlioblastoma multiforme (GBM) induces tumor immunosuppression through interacting with tumor-infiltrating microglia or macrophages (TAMs) with an unclear pathogenesis. Enhancer of zeste homolog 2 (EZH2) is abundant in GBM samples and cell lines and is involved in GBM proliferation, cell cycle, and invasion, whereas its association with innate immune response is not yet reported. Herein, the aim of this study was to investigate the role of EZH2 in GBM immune.MethodsCo-culturing models of human/murine GBM cells with PBMC-derived macrophages/primary microglia were employed. EZH2 mRNAs and function were suppressed by siEZH2 and DZNep. Real-time PCR and flow cytometry were used to determine levels of microglia/macrophages markers. The fluorescence-labeled latex beads and flow cytometry were utilized to evaluate phagocytic abilities of microglia. CCK8 assay was performed to assess microglia proliferation.ResultsEZH2 inhibition led to significant reduction of TGFβ1-3 and IL10 and elevation of IL1β and IL6 in human and murine GBM cells. More importantly, EZH2 suppression in GBM cells resulted in significant increase of M1 markers (TNFα and iNOS) and decrease of a pool of M2 markers in murine microglia. The proportion of CD206+ cells was decreased in PBMC-derived macrophages as co-incubated with EZH2-inhibited GBM cells. Functional researches showed that phagocytic capacities of microglia were significantly ameliorated after EZH2 inhibition in co-culturing GBM cells and microglia proliferation was declined after addition of TGFβ2 antibodies to co-incubated GBM cells with EZH2 inhibition. Besides, we found that EZH2 suppression in GBM cells enhanced co-culturing microglia engulfment through activation of iNOS.ConclusionsOur data demonstrates that EZH2 participates in GBM-induced immune deficient and EZH2 suppression in GBM can remodel microglia immune functions, which is beneficial for understanding GBM pathogenesis and suggests potential targets for therapeutic approaches.