Person:

Wang, Xiaoying

Brain neurons and tissues respond to sublethal injury by activating endogenous protective pathways. Recently, following the failure of a large number of clinical trials for protective strategies against stroke that aim to inhibit a specific ischemia response pathway, endogenous neuroprotection has emerged as a more promising and hopeful strategy for development of therapeutics against stroke and neurodegenerative disorders. Neuroglobin (Ngb) is an oxygen-binding globin protein that is highly and specifically expressed in brain neurons. Accumulating evidence have clearly demonstrated that Ngb is an endogenous neuroprotective molecule against hypoxic/ischemic and oxidative stress-related insults in cultured neurons and animals, as well as neurodegenerative disorders such as Alzheimer’s disease, thus any pharmacological strategy that can up-regulate endogenous Ngb expression may lead to novel therapeutics against these brain disorders. In this review, we summarize recent studies about the biological function, regulation of gene expression, and neuroprotective mechanisms of Ngb. Furthermore, strategies for identification of chemical compounds that can up-regulate endogenous Ngb expression for neuroprotection against stroke and neurodegenerative disorders are discussed.

Objective: Diabetes is an independent risk factor for stroke. However, the underlying mechanism of how diabetes confers that this risk is not fully understood. We hypothesize that secretion of neurotrophic factors by the cerebral endothelium, such as brain-derived neurotrophic factor (BDNF), is suppressed in diabetes. Consequently, such accrued neuroprotective deficits make neurons more vulnerable to injury. Research Design and Methods: We examined BDNF protein levels in a streptozotocin-induced rat model of diabetes by Western blotting and immunohistochemistry. Levels of total and secreted BDNF protein were quantified in human brain microvascular endothelial cells after exposure to advanced glycation end product (AGE)-BSA by enzyme-linked immunosorbent assay and immunocytochemistry. In media transfer experiments, the neuroprotective efficacy of conditioned media from normal healthy endothelial cells was compared with AGE-treated endothelial cells in an in vitro hypoxic injury model. Results: Cerebrovascular BDNF protein was reduced in the cortical endothelium in 6-month diabetic rats. Immunohistochemical analysis of 6-week diabetic brain sections showed that the reduction of BDNF occurs early after induction of diabetes. Treatment of brain microvascular endothelial cells with AGE caused a similar reduction in BDNF protein and secretion in an extracellular signal–related kinase-dependent manner. In media transfer experiments, conditioned media from AGE-treated endothelial cells were less neuroprotective against hypoxic injury because of a decrease in secreted BDNF. Conclusions: Taken together, our findings suggest that a progressive depletion of microvascular neuroprotection in diabetes elevates the risk of neuronal injury for a variety of central nervous system diseases, including stroke and neurodegeneration.

Magnetic resonance imaging (MRI) and spectroscopy (MRS) are versatile diagnostic techniques capable of characterizing the complex stroke pathophysiology, and hold great promise for guiding stroke treatment. Particularly, tissue viability and salvageability are closely associated with its metabolic status. Upon ischemia, ischemic tissue metabolism is disrupted including altered metabolism of glucose and oxygen, elevated lactate production/accumulation, tissue acidification and eventually, adenosine triphosphate (ATP) depletion and energy failure. Whereas metabolism impairment during ischemic stroke is complex, it may be monitored non-invasively with magnetic resonance (MR)-based techniques. Our current article provides a concise overview of stroke pathology, conventional and emerging imaging and spectroscopy techniques, and data analysis tools for characterizing ischemic tissue damage.

Background: Accumulating evidence has demonstrated that over-expression of Neuroglobin (Ngb) is neuroprotective against hypoxic/ischemic brain injuries. In this study we tested the neuroprotective effects of Ngb over-expression against traumatic brain injury (TBI) in mice. Results: Both Ngb over-expression transgenic (Ngb-Tg) and wild-type (WT) control mice were subjected to TBI induced by a controlled cortical impact (CCI) device. TBI significantly increased Ngb expression in the brains of both WT and Ngb-Tg mice, but Ngb-Tg mice had significantly higher Ngb protein levels at the pre-injury baseline and post-TBI. Production of oxidative tissue damage biomarker 3NT in the brain was significantly reduced in Ngb-Tg mice compared to WT controls at 6 hours after TBI. The traumatic brain lesion volume was significantly reduced in Ngb Tg mice compared to WT mice at 3 weeks after TBI; however, there were no significant differences in the recovery of sensorimotor and spatial memory functional deficits between Ngb-Tg and WT control mice for up to 3 weeks after TBI. Conclusion: Ngb over-expression reduced traumatic lesion volume, which might partially be achieved by decreasing oxidative stress.

Background: Amyloid-beta (Aβ) accumulation is a hallmark of Alzheimer’s disease (AD) that can lead to neuronal dysfunction and apoptosis. Tumor necrosis factor, alpha-induced protein 1 (TNFAIP1) is an apoptotic protein that was robustly induced in the transgenic C. elegans AD brains. However, the roles of TNFAIP1 in AD have not been investigated. Results: We found TNFAIP1 protein and mRNA levels were dramatically elevated in primary mouse cortical neurons and Neuro2a (N2a) cells exposed to Aβ25–35. Knockdown and overexpression of TNFAIP1 significantly attenuated and exacerbated Aβ25–35-induced neurotoxicity in N2a cells, respectively. Further studies showed that TNFAIP1 knockdown significantly blocked Aβ25–35-induced cleaved caspase 3, whereas TNFAIP1 overexpression enhanced Aβ25–35-induced cleaved caspase 3, suggesting that TNFAIP1 plays an important role in Aβ25–35-induced neuronal apoptosis. Moreover, we observed that TNFAIP1 was capable of inhibiting the levels of phosphorylated Akt and CREB, and also anti-apoptotic protein Bcl-2. TNFAIP1 overexpression enhanced the inhibitory effect of Aβ25–35 on the levels of p-CREB and Bcl-2, while TNFAIP1 knockdown reversed Aβ25–35-induced attenuation in the levels of p-CREB and Bcl-2. Conclusion: These results suggested that TNFAIP1 contributes to Aβ25–35-induced neurotoxicity by attenuating Akt/CREB signaling pathway, and Bcl-2 expression.

Tissue plasminogen activator (tPA) is the only FDA-approved treatment for reperfusing ischemic strokes. But widespread use of tPA is still limited by fears of inadvertently administering tPA in patients with intracerebral hemorrhage (ICH). Surprisingly, however, the assumption that tPA will worsen ICH has never been biologically tested. Here, we assessed the effects of tPA in two models of ICH. In a mouse model of collagenase-induced ICH, hemorrhage volumes and neurological deficits after 24 hrs were similar in saline controls and tPA-treated mice, whereas heparin-treated mice had 3-fold larger hematomas. In a model of laser-induced vessel rupture, tPA also did not worsen hemorrhage volumes, while heparin did. tPA is known to worsen neurovascular injury by amplifying matrix metalloproteinases during cerebral ischemia. In contrast, tPA did not upregulate matrix metalloproteinases in our mouse ICH models. In summary, our experimental data do not support the assumption that intravenous tPA has a deleterious effect in acute ICH. However, due to potential species differences and the inability of models to fully capture the dynamics of human ICH, caution is warranted when considering the implications of these findings for human therapy.

Immuno-inflammation has been shown to play a pivotal role in the pathogenesis of moyamoya disease (MMD). However, how did circulating Treg/Th17 cells involve in MMD patients remains unclear. 26 MMD, 21 atherothrombotic stroke, and 32 healthy controls were enrolled in this study. MMD patients have a significantly higher percentage of circulating Treg and Th17 cells as well as their dominantly secreting cytokines than other groups (P < 0.0001), whereas no difference was found in the ratio of Treg/Th17 between patients in MMD and atherothrombotic stroke group or control subjects (P = 0.244). However, the increased Treg in MMD patients which were enriched with FrIII Treg cells had deficient suppressive functions (P = 0.0017) compared to healthy volunteers. There was a positive correlation between Treg or TGF-β and MMD Suzuki’s stage. And the level of circulating Treg was as an independent factor associated with MMD stage. Besides, TGF-β was also correlated with the increased expression of VEGF in MMD patients. Our findings indicated an important involvement of circulating Treg in the pathogenic development of MMD and TGF-β in Treg induced VEGF.

Background: Microglial cultures comprise a critically important model system for investigating inflammatory mechanisms in almost all CNS disorders. Mild trypsinization and shaking are the two most commonly used methods to isolate primary microglia from mixed glial cultures. In this study, we characterized and compared microglia obtained using these two methods. Methods: Primary rat microglia cultures were prepared from cerebral cortices of 1–2-day-old neonatal Sprague-Dawley rats. After achieving confluency at about 14 days in vitro, microglia were isolated from mixed glial cultures via either mild trypsinization or shaking. The purity of microglia was estimated by flow cytometry. Quantitative real-time PCR was used to measure mRNA expression. TNFα, IL-1β, IL-10, and IGF-1 in cell culture supernatant were measured using ELISA kits. Phagocytic function was assessed using fluorescein-labeled Escherichia coli K-12 BioParticles. Results: Mild trypsinization generated a higher yield and purity than shaking. Microglia isolated by mild trypsinization appeared to be in a quiescent state with ramified morphology. Microglia isolated by shaking showed a more heterogenous morphology, including cells with rounded shapes suggestive of activation. Compared with shaking, microglia isolated by trypsinization also had lower baseline phenotype markers (iNOS, CD86, CD206, and arginase 1) and lower levels of cytokines (TNFα, IL-1β, IL-10, and IGF-1) as well as reduced phagocytic capability. Both methods yielded microglia that were responsive to various stimuli such as IL-4, lipopolysaccharide (LPS), or interferon-γ (IFNγ). Although stimulated patterns of gene expression and cytokine release were generally similar, there were also significant differences in terms of absolute response. LPS treatment induced significantly higher levels of TNFα and IL-10 in microglia isolated by mild trypsinization versus shaking. IFNγ induced a lower response in TNFα in microglia obtained by mild trypsinization versus shaking. Conclusions: Our results suggest that isolating microglia with the shaking method may induce slight activation even at baseline, and this may affect stimulus responses in subsequent experiments. Caution and attention should be warranted when choosing isolation protocols for primary microglia cultures.

Risk of hemorrhagic transformation, incomplete reperfusion, neurotoxicity, and a short treatment time window comprises major challenges for tissue plasminogen activator (tPA) thrombolytic stroke therapy. Improving tPA therapy has become one of the highest priorities in the stroke field. This mini review article focuses on our recent efforts aimed at evaluating a novel combination approach of low-dose tPA plus recombinant annexin A2 (rA2, a tPA, and plasminogen co-receptor), which might enhance tPA thrombolytic efficacy, while reducing its associated complications related to intracerebral hemorrhagic transformation. Results of our experimental studies using a focal embolic stroke model in rats support the feasibility of the combination approach and suggest the potential for successful clinical translation.

Infections occur commonly after stroke and are strongly associated with an unfavourable functional outcome of these patients. Approaches for effective management of poststroke infection remain scarce, presenting an urgent need for preventive anti-infection strategies for patients who have suffered a stroke. Emerging evidence indicates that stroke impairs systemic immune responses and increases the susceptibility to infections, suggesting that the modification of impaired immune defence could be beneficial. In this review, we summarised previous attempts to prevent poststroke infections using prophylactic antibiotics and the current understanding of stroke-induced immunosuppression. Further elucidation of the immune mechanisms of stroke will pave the way to tailored design of new treatment to combat poststroke infection via modifying the immune system.