VEGF-induced neuroprotection, neurogenesis, and angiogenesis after focal cerebral ischemia

Bisperoxovandium (pyridin-2-squaramide) targets both PTEN and ERK1/2 to confer neuroprotection

BACKGROUND AND PURPOSE

We and others have shown that inhibiting phosphatase and tensin homolog deleted on chromosome 10 (PTEN) or activating ERK1/2 confer neuroprotection. As bisperoxovanadium compounds are well-established inhibitors of PTEN, we designed bisperoxovandium (pyridin-2-squaramide) [bpV(pis)] and determined whether and how bpV(pis) exerts a neuroprotective effect in cerebral ischaemia-reperfusion injury.

EXPERIMENTAL APPROACH

Malachite green-based phosphatase assay was used to measure PTEN activity. A western blot assay was used to measure the phosphorylation level of Akt and ERK1/2 (p-Akt and p-ERK1/2). Oxygen-glucose deprivation (OGD) was used to injure cultured cortical neurons. Cell death and viability were assessed by LDH and MTT assays. To verify the effects of bpV(pis) in vivo, Sprague-Dawley rats were subjected to middle cerebral artery occlusion, and brain infarct volume was measured and neurological function tests performed.

KEY RESULTS

bpV(pis) inhibited PTEN activity and increased p-Akt in SH-SY5Y cells but not in PTEN-deleted U251 cells. bpV(pis) also elevated p-ERK1/2 in both SH-SY5Y and U251 cells. These data indicate that bpV(pis) enhances Akt activation through PTEN inhibition but increases ERK1/2 activation independently of PTEN signalling. bpV(pis) prevented OGD-induced neuronal death in vitro and reduced brain infarct volume and promoted functional recovery in stroke animals. This neuroprotective effect of bpV(pis) was blocked by inhibiting Akt and/or ERK1/2.

CONCLUSIONS AND IMPLICATIONS

bpV(pis) confers neuroprotection in OGD-induced injury in vitro and in cerebral ischaemia in vivo by suppressing PTEN and activating ERK1/2. Thus, bpV(pis) is a bi-target neuroprotectant that may be developed as a drug candidate for stroke treatment.

A functional variant in the 3'-UTR of VEGF predicts the 90-day outcome of ischemic stroke in Chinese patients

Vascular endothelial growth factor (VEGF) plays critical roles in angiogenesis and vasculogenesis, which are associated with post-stroke functional recovery. However, the effects of the VEGFA polymorphisms on the outcome of ischemic stroke (IS) have been rarely reported. We therefore investigated the associations of +936C/T variant (rs3025039) with the susceptibilities and the 90-day outcomes from 494 IS patients and 337 healthy controls in Chinese population through the establishment of logistic multivariate regression model. Stroke severity at admission and outcome of 90 days were respectively assessed according to the National Institutes of Health Stroke Scale and the modified Rankin Scale. The analysis showed that there were no significant associations of the rs3025039 genotypes with the susceptibility (P = 0.229) and the severity (P = 0.734). However, when we divided the 308 IS patients into two groups according to the different outcomes, we found that the rs3025039 TC+TT genotype significantly increased the risk of poor recovery [adjusted odds ratio (OR), 1.99; 95% confidence interval (CI), 1.18–3.37]. Interestingly, we observed another 3ˈUTR variant, +1451C/T (rs3025040), exhibited strong linkage disequilibrium (r² = 1.0) with +936C/T and was located in a predicted microRNA-binding site. The rs3025040 T allele significantly decreased the luciferase activities in four cell lines, which indicated a potential disruption of the miRNA-mRNA interaction that would result in lower VEGF expression levels. Our data suggested that the +936C/T variants significantly increased the risk of poorer stroke outcome by affecting the bindings of miR-199a and miR-199b to VEGF mRNA at the rs30250340 polymorphic site.

Synergistic effect of therapeutic stem cells expressing cytosine deaminase and interferon-beta via apoptotic pathway in the metastatic mouse model of breast cancer

As an approach to improve treatment of breast cancer metastasis to the brain, we employed genetically engineered stem cells (GESTECs, HB1.F3 cells) consisting of neural stem cells (NSCs) expressing cytosine deaminase and the interferon-beta genes, HB1.F3.CD and HB1.F3.CD.IFN-β. In this model, MDA-MB-231/Luc breast cancer cells were implanted in the right hemisphere of the mouse brain, while pre-stained GESTECs with redfluorescence were implanted in the contralateral brain. Two days after stem cells injection, 5-fluorocytosine (5-FC) was administrated via intraperitoneal injection. Histological analysis of extracted brain confirmed the therapeutic efficacy of GESTECs in the presence of 5-FC based on reductions in density and aggressive tendency of breast cancer cells, as well as pyknosis, karyorrhexis, and karyolysis relative to a negative control. Additionally, expression of PCNA decreased in the stem cells treated group. Treatment of breast cancer cells with 5-fluorouracil (5-FU) increased the expression of pro-apoptotic and anti-proliferative factor, BAX and p21 protein through phosphorylation of p53 and p38. Moreover, analysis of stem cell migratory ability revealed that MDA-MB-231 cells endogenously secreted VEGF, and stem cells expressed their receptor (VEGFR2). To confirm the role of VEGF/VEGFR2 signaling in tumor tropism of stem cells, samples were treated with the VEGFR2 inhibitor, KRN633. The number of migrated stem cells decreased significantly in response to KRN633 due to Erk1/2 activation and PI3K/Akt inhibition. Taken together, these results indicate that treatment with GESTECs, particularly HB1.F3.CD.IFN-β co-expressing CD.IFN-β, may be a useful strategy for treating breast cancer metastasis to the brain in the presence of a prodrug.

Lack of collagen XV is protective after ischemic stroke in mice

Collagens are key structural components of basement membranes, providing a scaffold for other components or adhering cells. Collagens and collagen-derived active fragments contribute to biological activities such as cell growth, differentiation and migration. Here, we report that collagen XV knock-out (ColXV KO) mice are resistant to experimental ischemic stroke. Interestingly, the infarcts of ColXV KO mice were as small as those of wild-type (WT) mice thrombolysed with recombinant tissue plasminogen activator (rtPA), the actual treatment for ischemic stroke. Importantly, there were no differences in the architecture of cerebrovascular anatomy between WT and ColXV KO mice. We found a twofold increase of the most potent pro-angiogenic factor, type A vascular growth endothelial factor (VEGF-A) in the ipsilateral cortex of rtPA-treated ischemic WT mice compared with untreated ischemic and sham-operated counterparts. A similar increase of VEGF-A was also found in both rtPA and untreated ischemic ColXV KO mice compared with sham ColXV KO mice. Finally, we evidenced that the levels of ColXV were increased in the plasma of WT mice treated with rtPA compared with untreated ischemic counterparts. Altogether, this study indicates that the lack ColXV is protective after stroke and that the degradation of endothelial ColXV may contribute to the beneficial effect of rtPA after ischemic stroke. The neuroprotection observed in ColXV KO mice may be attributed to the increased VEGF-A production following stroke in the ischemic territory.

Neuronal HIF-1α and HIF-2α deficiency improves neuronal survival and sensorimotor function in the early acute phase after ischemic stroke

Hypoxia-inducible factors mediate adaptive responses to ischemia, among others, by induction of anti- and pro-survival genes. Thus, the impact of HIF on neuronal survival upon stroke is controversial. Therefore, neuron-specific knockout mice deficient for Hif1a and Hif2a were exposed to inspiratory hypoxia or ischemia-reperfusion injury. Both Hif1a- and Hif2a-deficient mice showed no altered infarct and edema size, suggesting that both HIF-α subunits might compensate for each other. Accordingly, hypoxic HIF-target gene regulation was marginally affected with exception of anti-survival Bnip3 and pro-survival erythropoietin. In the early acute stage upon stroke, Hif1a/Hif2a double knockout mice exhibited significantly reduced expression of the anti-survival Bnip3, Bnip3L, and Pmaip1 Accordingly, global cell death and edema were significantly reduced upon 24 h but not 72 h reperfusion. Behavioral assessment indicated that Hif1a/Hif2a-deficient mice initially performed better, but became significantly more impaired after 72 h accompanied by increased apoptosis and reduced angiogenesis. Our findings suggest that in neurons HIF-1 and HIF-2 have redundant functions for cellular survival under ischemic conditions. By contrast, lack of anti-survival factors in Hif1a/Hif2a-deficient mice might protect from early acute neuronal cell death and neurological impairment, indicating a benefit of HIF-pathway inhibition in neurons in the very acute phase after ischemic stroke.

[Influence of vascular endothelial growth factor on angiogenesis and neurogenesis]

Vascular endothelial growth factor (VEGF) is known as a key mediator of angiogenesis, but there is also evidence of its broad significance in neurogenesis and neuroprotection. Cytokines of the VEGF family affect neovascularization and neural development in the brain, particularly during cerebral ischemia, in which there is a coordinated interaction of angiogenesis and neurogenesis that contributes to rapid functional recovery. This review examines the involvement of VEGF family members and their receptors in physiological and pathophysiological processes as well as the relationship between VEGF-A plasma levels and ischemic stroke.

Characterization of meningeal type 2 innate lymphocytes and their response to CNS injury

The meningeal space is occupied by a diverse repertoire of immune cells. Central nervous system (CNS) injury elicits a rapid immune response that affects neuronal survival and recovery, but the role of meningeal inflammation remains poorly understood. Here, we describe type 2 innate lymphocytes (ILC2s) as a novel cell type resident in the healthy meninges that are activated after CNS injury. ILC2s are present throughout the naive mouse meninges, though are concentrated around the dural sinuses, and have a unique transcriptional profile. After spinal cord injury (SCI), meningeal ILC2s are activated in an IL-33–dependent manner, producing type 2 cytokines. Using RNAseq, we characterized the gene programs that underlie the ILC2 activation state. Finally, addition of wild-type lung-derived ILC2s into the meningeal space of IL-33R^−/− animals partially improves recovery after SCI. These data characterize ILC2s as a novel meningeal cell type that responds to SCI and could lead to new therapeutic insights for neuroinflammatory conditions.

Early VEGF inhibition attenuates blood-brain barrier disruption in ischemic rat brains by regulating the expression of MMPs

Vascular endothelial growth factor (VEGF) inhibition has been demonstrated to be an effective strategy in preserving the integrity of the blood-brain barrier (BBB) in patients with acute ischemic stroke. Loss of the BBB is the key event associated with morbidity and mortality in these patients. However, the underlying mechanisms remain poorly understood. In the present study, the effects of VEGF inhibition and the possible mechanism that underlies acute cerebral ischemia in rats was investigated. Following the induction of transient middle cerebral artery occlusion for a 90-min period, either an anti-VEGF neutralizing antibody (RB-222; 5 or 10 µg), or IgG (control), was administered by intracerebroventricular injection at 1 h following reperfusion. Functional outcomes, BBB leakage, brain edema, microvessel numbers and the relative protein levels of VEGF, matrix metalloproteinase (MMP)-2, MMP-9, occludin and collagen-IV were then determined using neurological assessments, Evans Blue staining, brain water content, CD31 staining and western blotting. Treatment with RB-222 at a dose of 5 and 10 µg significantly improved neurological functional outcomes and diminished infarct size, BBB leakage and brain edema compared with the MCAO and IgG groups at 24 h following reperfusion; 10 µg RB-222 was more effective than a 5 µg dose of the antibody. In addition, RB-222 reduced the number of immature microvessels, which subsequently attenuated BBB permeability. RB-222 significantly repressed VEGF expression as well as decreased MMP-2 and MMP-9 expression. However, it enhanced occludin and collagen-IV levels in the ischemic rat brain compared with the MCAO and IgG groups. Taken together, the results indicate that early inhibition of VEGF may have significant potential against cerebral ischemia, partly by regulating the expression of MMPs.

Ischemia reduces inter-alpha inhibitor proteins in the brain of the ovine fetus

Hypoxic-ischemic (HI) brain injury is a major cause of neurological abnormalities in the perinatal period. Inflammation contributes to the evolution of HI brain injury. Inter-alpha inhibitor proteins (IAIPs) are a family of proteins that are part of the innate immune system. We have reported that endogenous IAIPs exhibit developmental changes in ovine brain and that exogenous IAIP treatment reduces neuronal death in HI neonatal rats. However, the effects of HI on endogenous IAIPs in brain have not been previously examined. In this study, we examined the effects of ischemia-reperfusion on endogenous IAIPs levels in fetal sheep brain. Cerebral cortex, cerebellum, cervical spinal cord, choroid plexus, and CSF were snap frozen from sham control fetuses at 127 days gestation and after 30-min of carotid occlusion and 4-, 24-, and 48-h of reperfusion. IAIP levels were determined by Western immunoblot. IAIP expressions of the 250 kDa Inter-alpha inhibitor (IaI) and 125 kDa Pre-alpha inhibitor (PaI) in cerebral cortex and PaI in cerebellum were reduced (p < 0.05) 4-h after ischemia compared with controls and returned toward control levels 24- and 48-h after ischemia. CSF PaI and IaI were reduced 48 h after ischemia. We conclude that IAIPs in cerebral cortex and cerebellum are reduced by brain ischemia, and return toward control levels between 24 and 48 h after ischemia. However, changes in CSF IAIPs were delayed, exhibiting decreases 48 h after ischemia. We speculate that the decreases in endogenous IAIPs reflect increased utilization, potentially suggesting that they have endogenous neuroprotective properties. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 726-737, 2017.

Role of Hypoxia Inducible Factor 1 in Hyperglycemia-Exacerbated Blood-Brain Barrier Disruption in Ischemic Stroke

Diabetes is a major stroke risk factor and is associated with poor functional recovery after stroke. Accumulating evidence indicates that the worsened outcomes may be due to hyperglycemia-induced cerebral vascular complications, especially disruption of the blood-brain barrier (BBB). The present study tested a hypothesis that the activation of hypoxia inducible factor-1 (HIF-1) was involved in hyperglycemia-aggravated BBB disruption in an ischemic stroke model. Non-diabetic control and Streptozotocin-induced type I diabetic mice were subjected to 90min transient middle cerebral artery occlusion (MCAO) followed by reperfusion. Our results demonstrated that hyperglycemia induced higher expression of HIF-1α and vascular endothelial growth factor (VEGF) in brain microvessels after MCAO/reperfusion. Diabetic mice showed exacerbated BBB damage and tight junction disruption, increased infarct volume as well as worsened neurological deficits. Furthermore, suppressing HIF-1 activity by specific knock-out endothelial HIF-1α ameliorated BBB leakage and brain infarction in diabetic animals. Moreover, glycemic control by insulin abolished HIF-1α up-regulation in diabetic animals and reduced BBB permeability and brain infarction. These findings strongly indicate that HIF-1 plays an important role in hyperglycemia-induced exacerbation of BBB disruption in ischemic stroke. Endothelial HIF-1 inhibition warrants further investigation as a therapeutic target for the treatment of stroke patients with diabetes.

GSNO promotes functional recovery in experimental TBI by stabilizing HIF-1α

Traumatic brain injury (TBI) causes sustained disability due to compromised neurorepair mechanisms. Crucial to neurorepair and functional recovery following both TBI and stroke is hypoxia-inducible factor-1 alpha (HIF-1α). Based on reports that HIF-1α could be stabilized via S-nitrosylation, we tested the hypothesis that the S-nitrosylating agent S-nitrosoglutathione (GSNO) would stabilize HIF-1α, thereby stimulating neurorepair mechanisms and aiding in functional recovery. TBI was induced by controlled cortical impact (CCI) in adult rats. GSNO (0.05mg/kg) was administered at two hours after CCI. The treatment was repeated daily until the 14th day after CCI. Functional recovery was assessed by motor and cognitive functions, and the recovery was compared with the expression of HIF-1α. The mechanisms of GSNO-mediated S-nitrosylation of HIF-1α were determined using brain endothelial cells. While non-treated TBI animals showed sustained neurobehavioral deficits, GSNO treatment of TBI improved neurobehavioral functions. GSNO also increased the expression of HIF-1α and VEGF. The beneficial effects of GSNO on neurobehavioral functions in TBI animals were blocked by treatment with the HIF-1α inhibitor 2-methoxyestradiol (2-ME). The stimulatory effect of GSNO on VEGF was reversed not only by 2-ME but also by the denitrosylating agent dithiothreitol, confirming our hypothesis that GSNO's benefits are mediated by the stabilization of HIF-1α via S-nitrosylation. GSNO's S-nitrosylation of HIF-1α was further confirmed using a biotin switch assay in endothelial cells. The data provide evidence that GSNO treatment of TBI aids functional recovery through stabilizing HIF-1α via S-nitrosylation. GSNO is a natural component of the human brain/body, and its exogenous administration has not shown adverse effects in humans. Therefore, the translational potential of GSNO therapy in TBI is high.

Sphingolipids in spinal cord injury

Spinal cord injury (SCI) is a debilitating condition that affects millions of individuals worldwide. Despite progress over the last few decades, the molecular mechanisms of secondary SCI that continue to occur days and weeks after the original trauma remain poorly understood. As a result, current therapies for SCI are only marginally effective. Sphingolipids, a diverse class of bioactive lipids, have been shown to regulate SCI repair and key secondary injury processes such as apoptosis, ischemia and inflammation. This review will discuss the numerous roles of sphingolipids and highlight the potential of sphingolipid-targeted therapies for SCI.

Sodium ferulate and n-butylidenephthalate combined with bone marrow stromal cells (BMSCs) improve the therapeutic effects of angiogenesis and neurogenesis after rat focal cerebral ischemia

BACKGROUND

Studies have indicated that bone marrow stromal cell (BMSC) administration is a promising approach for stroke treatment. For our study, we chose sodium ferulate (SF) and n-butylidenephthalide (BP) combined with BMSC, and observed if the combination treatment possessed more significant effects on angiogenesis and neurogenesis post-stroke.

METHODS

We established rat permanent middle cerebral artery occlusion (MCAo) model and evaluated ischemic volumes of MCAo, BMSC, SF + BP, Simvastatin + BMSC and SF + BP + BMSC groups with TTC staining on the 7th day after ischemia. Immunofluorescence staining of vascular endothelial growth factor (VEGF) and brain derived neurotrophic factor (BDNF), as well as immunohistochemistry staining of von Willebrand factor (vWF) and neuronal class III β-tubulin (Tuj1) were performed in ischemic boundary zone (IBZ), furthermore, to understand the mechanism, western blot was used to investigate AKT/mammalian target of rapamycin (mTOR) signal pathway in ischemic cortex. We also tested BMSC derived-VEGF and BDNF expressions by western blot assay in vitro.

RESULTS

SF + BP + BMSC group obviously decreased infarction zone, and elevated the expression of VEGF and the density and perimeter of vWF-vessels as same as Simvastatin + BMSC administration; moreover, its effects on BDNF and Tuj1 expressions were superior to Simvastatin + BMSC treatment in IBZ. Meanwhile, it showed that SF and BP combined with BMSC treatment notably up-regulated AKT/mTOR signal pathway compared with SF + BP group and BMSC alone post-stroke. Western blot results showed that SF and BP treatment could promote BMSCs to synthesize VEGF and BDNF in vitro.

CONCLUSIONS

We firstly demonstrate that SF and BP combined with BMSC can significantly improve angiogenesis and neurogenesis in IBZ following stroke. The therapeutic effects are associated with the enhancement of VEGF and BDNF expressions via activation of AKT/mTOR signal pathway. Furthermore, triggering BMSC paracrine function of SF and BP might contribute to amplifying the synergic effects of the combination treatment.

Role of Hypoxia Inducible Factor 1 in Hyperglycemia-Exacerbated Blood-Brain Barrier Disruption in Ischemic Stroke

Diabetes is a major stroke risk factor and is associated with poor functional recovery after stroke. Accumulating evidence indicates that the worsened outcomes may be due to hyperglycemia-induced cerebral vascular complications, especially disruption of the blood-brain barrier (BBB). The present study tested a hypothesis that the activation of hypoxia inducible factor-1 (HIF-1) was involved in hyperglycemia-aggravated BBB disruption in an ischemic stroke model. Non-diabetic control and Streptozotocin-induced type I diabetic mice were subjected to 90min transient middle cerebral artery occlusion (MCAO) followed by reperfusion. Our results demonstrated that hyperglycemia induced higher expression of HIF-1α and vascular endothelial growth factor (VEGF) in brain microvessels after MCAO/reperfusion. Diabetic mice showed exacerbated BBB damage and tight junction disruption, increased infarct volume as well as worsened neurological deficits. Furthermore, suppressing HIF-1 activity by specific knock-out endothelial HIF-1α ameliorated BBB leakage and brain infarction in diabetic animals. Moreover, glycemic control by insulin abolished HIF-1α up-regulation in diabetic animals and reduced BBB permeability and brain infarction. These findings strongly indicate that HIF-1 plays an important role in hyperglycemia-induced exacerbation of BBB disruption in ischemic stroke. Endothelial HIF-1 inhibition warrants further investigation as a therapeutic target for the treatment of stroke patients with diabetes.

Comparative effect of immature neuronal or glial cell transplantation on motor functional recovery following experimental traumatic brain injury in rats

The present study evaluated the comparative effect of stereotaxically transplanted immature neuronal or glial cells in brain on motor functional recovery and cytokine expression after cold-induced traumatic brain injury (TBI) in adult rats. A total of 60 rats were divided into four groups (n=15/group): Sham group; TBI only group; TBI plus neuronal cells-transplanted group (NC-G); and TBI plus glial cells-transplanted group (GC-G). Cortical lesions were induced by a touching metal stamp, frozen with liquid nitrogen, to the dura mater over the motor cortex of adult rats. Neuronal and glial cells were isolated from rat embryonic and newborn cortices, respectively, and cultured in culture flasks. Rats received neurons or glia grafts (~1×10⁶ cells) 5 days after TBI was induced. Motor functional evaluation was performed with the rotarod test prior to and following glial and neural cell grafts. Five rats from each group were sacrificed at 2, 4 and 6 weeks post-cell transplantation. Immunofluorescence staining was performed on brain section to identify the transplanted neuronal or glial cells using neural and astrocytic markers. The expression levels of cytokines, including transforming growth factor-β, glial cell-derived neurotrophic factor and vascular endothelial growth factor, which have key roles in the proliferation, differentiation and survival of neural cells, were analyzed by immunohistochemistry and western blotting. A localized cortical lesion was evoked in all injured rats, resulting in significant motor deficits. Transplanted cells successfully migrated and survived in the injured brain lesion, and the expression of neuronal and astrocyte markers were detected in the NC-G and GC-G groups, respectively. Rats in the NC-G and GC-G cell-transplanted groups exhibited significant motor functional recovery and reduced histopathologic lesions, as compared with the TBI-G rats that did not receive neural cells (P<0.05, respectively). Furthermore, GC-G treatment induced significantly improved motor functional recovery, as compared with the NC-G group (P<0.05). Increased cytokine expression levels were detected in the NC-G and GC-G groups, as compared with the TBI-G; however, no differences were found between the two groups. These data suggested that transplanted immature neural cells may promote the survival of neural cells in cortical lesion and motor functional recovery. Furthermore, transplanted glial cells may be used as an effective therapeutic tool for TBI patients with abnormalities in motor functional recovery and cytokine expression.

Detrimental effects of physical inactivity on neurogenesis

Patients diagnosed with neurological disorders exhibit a variety of physical and psychiatric symptoms, including muscle atrophy, general immobility, and depression. Patients who participate in physical rehabilitation at times show unexpected clinical improvement, which includes diminished depression and other stress-related behaviors. Regenerative medicine has advanced two major stem cell-based therapies for central nervous system (CNS) disorders, transplantation of exogenous stem cells, and enhancing the endogenous neurogenesis. The latter therapy utilizes a natural method of re-innervating the injured brain, which may mend neurological impairments. In this study, we examine how inactivity-induced atrophy, using the hindlimb suspension model, alters neurogenesis in rats. The hypothesis is that inactivity inhibits neurogenesis by decreasing circulation growth or trophic factors, such as vascular endothelial growth or neurotrophic factors. The restriction modifies neurogenesis and stem cell differentiation in the CNS, the stem cell microenvironment is examined by the trophic and growth factors, including stress-related proteins. Despite growing evidence revealing the benefits of “increased” exercise on neurogenesis, the opposing theory involving “physical inactivity,” which simulates pathological states, continues to be neglected. This novel theory will allow us to explore the effects on neurogenesis by an intransigent stem cell microenvironment likely generated by inactivity. 5-bromo-2-deoxyuridine labeling of proliferative cells, biochemical assays of serum, cerebrospinal fluid, and brain levels of trophic factors, growth factors, and stress-related proteins are suggested identifiers of neurogenesis, while evaluation of spontaneous movements will give insight into the psychomotor effects of inactivity. Investigations devised to show how in vivo stimulation, or lack thereof, affects the stem cell microenvironment are necessary to establish treatment methods to boost neurogenesis in bedridden patients.

Over-Expression of Meteorin Drives Gliogenesis Following Striatal Injury

A number of studies have shown that damage to brain structures adjacent to neurogenic regions can result in migration of new neurons from neurogenic zones into the damaged tissue. The number of differentiated neurons that survive is low, however, and this has led to the idea that the introduction of extrinsic signaling factors, particularly neurotrophic proteins, may augment the neurogenic response to a level that would be therapeutically relevant. Here we report on the impact of the relatively newly described neurotrophic factor, Meteorin, when over-expressed in the striatum following excitotoxic injury. Birth-dating studies using bromo-deoxy-uridine (BrdU) showed that Meteorin did not enhance injury-induced striatal neurogenesis but significantly increased the proportion of new cells with astroglial and oligodendroglial features. As a basis for comparison we found under the same conditions, glial derived neurotrophic factor significantly enhanced neurogenesis but did not effect gliogenesis. The results highlight the specificity of action of different neurotrophic factors in modulating the proliferative response to injury. Meteorin may be an interesting candidate in pathological settings involving damage to white matter, for example after stroke or neonatal brain injury.

Vascular endothelial growth factor: a neurovascular target in neurological diseases

Brain function critically relies on blood vessels to supply oxygen and nutrients, to establish a barrier for neurotoxic substances, and to clear waste products. The archetypal vascular endothelial growth factor, VEGF, arose in evolution as a signal affecting neural cells, but was later co-opted by blood vessels to regulate vascular function. Consequently, VEGF represents an attractive target to modulate brain function at the neurovascular interface. On the one hand, VEGF is neuroprotective, through direct effects on neural cells and their progenitors and indirect effects on brain perfusion. In accordance, preclinical studies show beneficial effects of VEGF administration in neurodegenerative diseases, peripheral neuropathies and epilepsy. On the other hand, pathologically elevated VEGF levels enhance vessel permeability and leakage, and disrupt blood-brain barrier integrity, as in demyelinating diseases, for which blockade of VEGF may be beneficial. Here, we summarize current knowledge on the role and therapeutic potential of VEGF in neurological diseases.

Potential Roles of Adropin in Central Nervous System: Review of Current Literature

Adropin is a 4.9 kDa peptide that is important for maintenance of metabolic and non-metabolic homeostasis. It regulates glucose and fatty acid metabolism and is involved in endothelial cell function and endothelial nitric oxide (NO) synthase bioactivity as well as physical activity and motor coordination. Adropin is expressed in many tissues and organs including central nervous system (CNS). This peptide plays a crucial role in the development of various CNS disorders such as stroke, schizophrenia, bipolar disorder as well as Alzheimer's, Parkinson's, and Huntington's diseases. In this comprehensive review, the potential roles of adropin in cellular signaling pathways that lead to pathogenesis and/or treatment of CNS disorders will be discussed.

Angiogenesis in Ischemic Stroke and Angiogenic Effects of Chinese Herbal Medicine

Stroke is one of the major causes of death and adult disability worldwide. The underlying pathophysiology of stroke is highly complicated, consisting of impairments of multiple signalling pathways, and numerous pathological processes such as acidosis, glutamate excitotoxicity, calcium overload, cerebral inflammation and reactive oxygen species (ROS) generation. The current treatment for ischemic stroke is limited to thromolytics such as recombinant tissue plasminogen activator (tPA). tPA has a very narrow therapeutic window, making it suitable to only a minority of stroke patients. Hence, there is great urgency to develop new therapies that can protect brain tissue from ischemic damage. Recent studies have shown that new vessel formation after stroke not only replenishes blood flow to the ischemic area of the brain, but also promotes neurogenesis and improves neurological functions in both animal models and patients. Therefore, drugs that can promote angiogenesis after ischemic stroke can provide therapeutic benefits in stroke management. In this regard, Chinese herbal medicine (CHM) has a long history in treating stroke and the associated diseases. A number of studies have demonstrated the pro-angiogenic effects of various Chinese herbs and herbal formulations in both in vitro and in vivo settings. In this article, we present a comprehensive review of the current knowledge on angiogenesis in the context of ischemic stroke and discuss the potential use of CHM in stroke management through modulation of angiogenesis.

Comparison of Neuroprotective Effect of Bevacizumab and Sildenafil following Induction of Stroke in a Mouse Model

To evaluate the effect of bevacizumab and sildenafil on stroke parameters in a mouse model, middle cerebral artery occlusion was induced in male C57Bl/6 mice using an intra-arterial filament method. The filament was removed after 60 minutes, and the mice were immediately given a single intraperitoneal injection of saline, bevacizumab, or sildenafil. An additional group of mice (n = 7) received bevacizumab 6 h after MCAO induction. The mice were euthanized 24 hours later and evaluated for infarct area and brain edema using triphenyltetrazolium chloride staining and ImageJ. In the saline-treated mice (n = 16), total stroke volume was 19.20 ± 6.38 mm³, mean penumbra area was 4.5 ± 2.03 mm³, and hemispheric asymmetry was 106.5%. Corresponding values in the bevacizumab group (n = 19) were 17.79 ± 5.80 mm³, 7.3 ± 3.5 mm³, and 108.6%; in the delayed (6 h) bevacizumab injected mice (n = 7) they were 9.80 ± 8.00 mm³, 2.4 ± 2.0 mm³, and 98.2%; and in the sildenafil group (n = 16) they were 18.42 ± 5.41 mm³, 5.7 ± 2.02 mm³, and 109.9%. The bevacizumab group had a significantly larger mean penumbra area when given immediately and smaller total stroke area in both groups than the saline- (p = 0.03) and sildenafil-treated (p = 0.003) groups. Only delayed bevacizumab group had reduced edema. Bevacizumab, injected immediately or delayed after injury, exerts a neuroprotective/salvage effect, whereas immediate treatment with sildenafil does not. Inflammation may play a role in the neuroprotective effect.

Regenerative repair of Pifithrin-α in cerebral ischemia via VEGF dependent manner

Promoting regenerative repair, including neurogenesis and angiogenesis, may provide a new therapeutic strategy for treatment of stroke. P53, a well-documented transcription factor, has been reported to be involved in cerebral ischemia and also serves as an important regulator of vascular endothelial growth factor (VEGF). However, the role of p53 in endogenous regenerative repair after brain ischemia is poorly understood. In this study, we investigated the effects of PFT-α, a specific p53 inhibitor on neurogenesis and angiogenesis improvement and associated signal pathways in rats impaired by cerebral artery occlusion (MCAo). PFT-α induced neuroprotection, reduced infarct volume and neurological functional impairment after ischemic stroke. More importantly, neurogenesis and angiogenesis were greatly enhanced by PFT-α, and accompanied by increased expression of VEGF. Moreover, we got consistent results in neural stem cells (NSCs) isolated from fetal rats. In contrast, application of the anti-VEGF neutralizing antibody (RB-222) partially reversed PFT-α-induced neuroprotection and rescued p53 expression. Noteworthily, inhibition of p53 after ischemic stroke in these rats improved their outcomes via promotion of regenerative repair. In conclusion, PFT-α could serve as a promising therapeutic strategy for ischemic stroke by promoting regenerative repair.

Distal retinal ganglion cell axon transport loss and activation of p38 MAPK stress pathway following VEGF-A antagonism

There is increasing evidence that VEGF-A antagonists may be detrimental to neuronal health following ocular administration. Here we investigated firstly the effects of VEGF-A neutralization on retinal neuronal survival in the Ins2^Akita diabetic and JR5558 spontaneous choroidal neovascularization (CNV) mice, and then looked at potential mechanisms contributing to cell death. We detected elevated apoptosis in the ganglion cell layer in both these models following VEGF-A antagonism, indicating that even when vascular pathologies respond to treatment, neurons are still vulnerable to reduced VEGF-A levels. We observed that retinal ganglion cells (RGCs) seemed to be the cells most susceptible to VEGF-A antagonism, so we looked at anterograde transport in these cells, due to their long axons requiring optimal protein and organelle trafficking. Using cholera toxin B-subunit tracer studies, we found a distal reduction in transport in the superior colliculus following VEGF-A neutralization, which occurred prior to net RGC loss. This phenomenon of distal transport loss has been described as a feature of early pathological changes in glaucoma, Alzheimer's and Parkinson's disease models. Furthermore, we observed increased phosphorylation of p38 MAPK and downstream Hsp27 stress pathway signaling in the retinas from these experiments, potentially providing a mechanistic explanation for our findings. These experiments further highlight the possible risks of using VEGF-A antagonists to treat ocular neovascular disease, and suggest that VEGF-A may contribute to the maintenance and function of axonal transport in neurons of the retina.

The regulatory role of hepatoma-derived growth factor as an angiogenic factor in the eye

PURPOSE

Hepatoma-derived growth factor (HDGF) is a mitogen that promotes endothelial proliferation and neuronal survival. Using a unique technology of ligandomics, we recently identified HDGF as a retinal endothelial binding protein. The purpose of this study is to examine the role of HDGF in regulating ocular vasculature and the expression of HDGF in the retina.

METHODS

HDGF expression in the retinal was analyzed with western blot and immunohistochemistry. Angiogenic activity was investigated in human retinal microvascular endothelial cells (HRMVECs) with in vitro endothelial proliferation, migration, and permeability assays. In vivo angiogenic activity was quantified with a corneal pocket assay. The Evans blue assay and western blot using anti-mouse albumin were performed to detect the capacity of HDGF to induce retinal vascular leakage.

RESULTS

Immunohistochemistry revealed that HDGF is expressed in the retina with a distinct pattern. HDGF was detected in retinal ganglion cells and the inner nuclear layer but not in the inner plexiform layer, suggesting that HDGF is expressed in the nucleus, but not in the cytoplasm, of retinal neurons. In contrast to family member HDGF-related protein 3 (HRP-3) that has no expression in photoreceptors, HDGF is also present in the outer nuclear layer and the inner and outer segments of photoreceptors. This suggests that HDGF is expressed in the nucleus as well as the cytoplasm of photoreceptors. In vitro functional assays showed that HDGF induced the proliferation, migration, and permeability of HRMVECs. Corneal pocket assay indicated that HDGF directly stimulated angiogenesis in vivo. Intravitreal injection of HDGF significantly induced retinal vascular leakage.

CONCLUSIONS

These results suggest that HDGF is an angiogenic factor that regulates retinal vasculature in physiologic and pathological conditions. Identification of HDGF by ligandomics and its independent characterization in this study also support the validity of this new technology for systematic identification of cellular ligands, including angiogenic factors.

Help-me signaling: Non-cell autonomous mechanisms of neuroprotection and neurorecovery

Self-preservation is required for life. At the cellular level, this fundamental principle is expressed in the form of molecular mechanisms for preconditioning and tolerance. When the cell is threatened, internal cascades of survival signaling become triggered to protect against cell death and defend against future insults. Recently, however, emerging findings suggest that this principle of self-preservation may involve not only intracellular signals; the release of extracellular signals may provide a way to recruit adjacent cells into an amplified protective program. In the central nervous system where multiple cell types co-exist, this mechanism would allow threatened neurons to "ask for help" from glial and vascular compartments. In this review, we describe this new concept of help-me signaling, wherein damaged or diseased neurons release signals that may shift glial and vascular cells into potentially beneficial phenotypes, and help remodel the neurovascular unit. Understanding and dissecting these non-cell autonomous mechanisms of self-preservation in the CNS may lead to novel opportunities for neuroprotection and neurorecovery.

Neuroprotective effects of Ilexonin A following transient focal cerebral ischemia in rats

Ilexonin A is a compound isolated from the root of a plant commonly used in traditional Chinese medicine. The aim of the present study was to investigate the possible protective mechanism of Ilexonin A in rats subjected to occlusion of the middle cerebral artery (MCAO). Transient focal cerebral ischemia was induced by 2 h of MCAO, followed by reperfusion. Ilexonin A at doses of 20, 40 and 80 mg/kg were administered via intraperitoneal injection immediately following ischemia/reperfusion. The expression levels of glial fibrillary acidic protein (GFAP), ionized calcium‑binding adapter molecule‑1 (Iba‑1), vascular endothelial growth factor (VEGF), fetal liver kinase‑1 (Flk‑1) and Nestin were examined using immunostaining and Western blot analysis of the peri‑infarct region following ischemia/reperfusion. Ilexonin A significantly decreased the infarct volume and improved neurological deficits in a dose‑dependent manner. The expression levels of VEGF, Flk‑1 and Nestin were significantly increased in the rats treated with Ilexonin A, compared with the rats administered with saline. Following treatment with Ilexonin A, a higher number of GFAP‑positive astrocytes were found in the Ilexonin A‑treated rats at 1, 3 and 7 days, compared with the rats exposed to ischemia only, however, there were fewer astrocytes at 14 days, compared with the ischemia group. Ilexonin A significantly decreased the protein expression of Iba‑1. The results of the present study suggested that the protective effects of Ilexonin A were associated with revascularization, neuronal regeneration, and the regulation of astrocyte and microglia cell activation.

High-dose estrogen treatment at reperfusion reduces lesion volume and accelerates recovery of sensorimotor function after experimental ischemic stroke

Estrogens have previously been shown to protect the brain against acute ischemic insults, by potentially augmenting cerebrovascular function after ischemic stroke. The current study hypothesized that treatment with sustained release of high-dose 17β-estradiol (E2) at the time of reperfusion from middle cerebral artery occlusion (MCAO) in rats would attenuate reperfusion injury, augment post-stroke angiogenesis and cerebral blood flow, and attenuate lesion volume. Female Wistar rats underwent ovariectomy, followed two weeks later by transient, two-hour right MCAO (tMCAO) and treatment with E2 (n=13) or placebo (P; n=12) pellets starting at reperfusion. E2 treatment resulted in significantly smaller total lesion volume, smaller lesions within striatal and cortical brain regions, and less atrophy of the ipsilateral hemisphere after six weeks of recovery. E2-treated animals exhibited accelerated recovery of contralateral forelimb sensorimotor function in the cylinder test. Magnetic resonance imaging (MRI) showed that E2 treatment reduced the formation of lesion cysts, decreased lesion volume, and increased lesional cerebral blood flow (CBF). K(trans), a measure of vascular permeability, was increased in the lesions. This finding, which represents lesion neovascularization, was not altered by E2 treatment. Ischemic stroke-related angiogenesis and vessel formation was confirmed with immunolabeling of brain tissue and was not altered with E2 treatment. In summary, E2 treatment administered immediately following reperfusion significantly reduced lesion size, cyst formation, and brain atrophy while improving lesional CBF and accelerating recovery of functional deficits in a rat model of ischemic stroke.

Astrocytic response to cerebral ischemia is influenced by sex differences and impaired by aging

Ischemic stroke occurs more often among the elderly, and within this demographic, women are at an increased risk for stroke and have poorer functional recovery than men. This is also well replicated in animal studies where aging females are shown to have more extensive brain tissue loss as compared to adult females. Astrocytes provide nutrients for neurons, regulate glutamate levels, and release neurotrophins and thus play a key role in the events that occur following ischemia. In addition, astrocytes express receptors for gonadal hormones and synthesize several neurosteroids suggesting that the sex differences in stroke outcome may be mediated through astrocytes. This review discusses key astrocytic responses to ischemia including, reactive gliosis, excitotoxicity, and neuroinflammation. In light of the age and sex differences in stroke outcomes, this review highlights how aging and gonadal hormones influence these responses. Lastly, astrocyte specific changes in gene expression and epigenetic modifications during aging and following ischemia are discussed as possible molecular mechanisms for impaired astrocytic functioning.

Transplantation of vascular endothelial growth factor-modified neural stem/progenitor cells promotes the recovery of neurological function following hypoxic-ischemic brain damage

Neural stem/progenitor cell (NSC) transplantation has been shown to effectively improve neurological function in rats with hypoxic-ischemic brain damage. Vascular endothelial growth factor (VEGF) is a signaling protein that stimulates angiogenesis and improves neural regeneration. We hypothesized that transplantation of VEGF-transfected NSCs would alleviate hypoxic-ischemic brain damage in neonatal rats. We produced and transfected a recombinant lentiviral vector containing the VEGF₁₆₅ gene into cultured NSCs. The transfected NSCs were transplanted into the left sensorimotor cortex of rats 3 days after hypoxic-ischemic brain damage. Compared with the NSCs group, VEGF mRNA and protein expression levels were increased in the transgene NSCs group, and learning and memory abilities were significantly improved at 30 days. Furthermore, histopathological changes were alleviated in these animals. Our findings indicate that transplantation of VEGF-transfected NSCs may facilitate the recovery of neurological function, and that its therapeutic effectiveness is better than that of unmodified NSCs.

Tissue plasminogen activator followed by antioxidant-loaded nanoparticle delivery promotes activation/mobilization of progenitor cells in infarcted rat brain

Inherent neuronal and circulating progenitor cells play important roles in facilitating neuronal and functional recovery post stroke. However, this endogenous repair process is rather limited, primarily due to unfavorable conditions in the infarcted brain involving reactive oxygen species (ROS)-mediated oxidative stress and inflammation following ischemia/reperfusion injury. We hypothesized that during reperfusion, effective delivery of antioxidants to ischemic brain would create an environment without such oxidative stress and inflammation, thus promoting activation and mobilization of progenitor cells in the infarcted brain. We administered recombinant human tissue-type plasminogen activator (tPA) via carotid artery at 3 h post stroke in a thromboembolic rat model, followed by sequential administration of the antioxidants catalase (CAT) and superoxide dismutase (SOD), encapsulated in biodegradable nanoparticles (nano-CAT/SOD). Brains were harvested at 48 h post stroke for immunohistochemical analysis. Ipsilateral brain slices from animals that had received tPA + nano-CAT/SOD showed a widespread distribution of glial fibrillary acidic protein-positive cells (with morphology resembling radial glia-like neural precursor cells) and nestin-positive cells (indicating the presence of immature neurons); such cells were considerably fewer in untreated animals or those treated with tPA alone. Brain sections from animals receiving tPA + nano-CAT/SOD also showed much greater numbers of SOX2- and nestin-positive progenitor cells migrating from subventricular zone of the lateral ventricle and entering the rostral migratory stream than in t-PA alone treated group or untreated control. Further, animals treated with tPA + nano-CAT/SOD showed far fewer caspase-positive cells and fewer neutrophils than did other groups, as well as an inhibition of hippocampal swelling. These results suggest that the antioxidants mitigated the inflammatory response, protected neuronal cells from undergoing apoptosis, and inhibited edema formation by protecting the blood-brain barrier from ROS-mediated reperfusion injury. A longer-term study would enable us to determine if our approach would assist progenitor cells to undergo neurogenesis and to facilitate neurological and functional recovery following stroke and reperfusion injury.

Mechanisms and Functional Significance of Stroke-Induced Neurogenesis

Stroke affects one in every six people worldwide, and is the leading cause of adult disability. After stroke, some limited spontaneous recovery occurs, the mechanisms of which remain largely unknown. Multiple, parallel approaches are being investigated to develop neuroprotective, reparative and regenerative strategies for the treatment of stroke. For years, clinical studies have tried to use exogenous cell therapy as a means of brain repair, with varying success. Since the rediscovery of adult neurogenesis and the identification of adult neural stem cells in the late nineties, one promising field of investigation is focused upon triggering and stimulating this self-repair system to replace the neurons lost following brain injury. For instance, it is has been demonstrated that the adult brain has the capacity to produce large numbers of new neurons in response to stroke. The purpose of this review is to provide an updated overview of stroke-induced adult neurogenesis, from a cellular and molecular perspective, to its impact on brain repair and functional recovery.

Brain protection against ischemic stroke using choline as a new molecular bypass treatment

AIM

To determine whether administration of choline could attenuate brain injury in a rat model of ischemic stroke and the underlying mechanisms.

METHODS

A rat model of ischemic stroke was established through permanent middle cerebral artery occlusion (pMCAO). After the surgery, the rats were treated with choline or choline plus the specific α7 nAChR antagonist methyllycaconitine (MLA), or with the control drug nimodipine for 10 days. The neurological deficits, brain-infarct volume, pial vessel density and the number of microvessels in the cortex were assessed. Rat brain microvascular endothelial cells (rBMECs) cultured under hypoxic conditions were used in in vitro experiments.

RESULTS

Oral administration of choline (100 or 200 mg·kg(-1)·d(-1)) or nimodipine (20 mg·kg(-1)·d(-1)) significantly improved neurological deficits, and reduced infarct volume and nerve cell loss in the ischemic cerebral cortices in pMCAO rats. Furthermore, oral administration of choline, but not nimodipine, promoted the pial arteriogenesis and cerebral-cortical capillary angiogenesis in the ischemic regions. Moreover, oral administration of choline significantly augmented pMCAO-induced increases in the expression levels of α7 nAChR, HIF-1α and VEGF in the ischemic cerebral cortices as well as in the serum levels of VEGF. Choline-induced protective effects were prevented by co-treatment with MLA (1 mg·kg(-1)·d(-1), ip). Treatment of rBMECs cultured under hypoxic conditions in vitro with choline (1, 10 and 100 μmol/L) dose-dependently promoted the endothelial-cell proliferation, migration and tube formation, as well as VEGF secretion, which were prevented by co-treatment with MLA (1 μmol/L) or by transfection with HIF-1α siRNA.

CONCLUSION

Choline effectively attenuates brain ischemic injury in pMCAO rats, possibly by facilitating pial arteriogenesis and cerebral-cortical capillary angiogenesis via upregulating α7 nAChR levels and inducing the expression of HIF-1α and VEGF.

Ischemia-induced Angiogenesis is Attenuated in Aged Rats

To study whether focal angiogenesis is induced in aged rodents after permanent distal middle cerebral artery occlusion (MCAO), young adult (3-month-old) and aged (24-month-old) Fisher 344 rats underwent MCAO and sacrificed up to two months after MCAO. Immunohistochemistry and synchrotron radiation microangiography were performed to examine the number of newly formed blood vessels in both young adult and aged rats post-ischemia. We found that the number of capillaries and small arteries in aged brain was the same as young adult brain. In addition, we found that after MCAO, the number of blood vessels in the peri-infarct region of ipsilateral hemisphere in aged ischemic rats was significantly increased compared to the aged sham rats (p<0.05). We also confirmed that ischemia-induced focal angiogenesis occurred in young adult rat brain while the blood vessel density in young adult ischemic brain was significantly higher than that in the aged ischemic brain (p<0.05). Our data suggests that focal angiogenesis in aged rat brain can be induced in response to ischemic brain injury, and that aging impedes brain repairing and remodeling after ischemic stroke, possible due to the limited response of angiogenesis.

RNA sequencing of transcriptomes in human brain regions: protein-coding and non-coding RNAs, isoforms and alleles

Background

We used RNA sequencing to analyze transcript profiles of ten autopsy brain regions from ten subjects. RNA sequencing techniques were designed to detect both coding and non-coding RNA, splice isoform composition, and allelic expression. Brain regions were selected from five subjects with a documented history of smoking and five non-smokers. Paired-end RNA sequencing was performed on SOLiD instruments to a depth of >40 million reads, using linearly amplified, ribosomally depleted RNA. Sequencing libraries were prepared with both poly-dT and random hexamer primers to detect all RNA classes, including long non-coding (lncRNA), intronic and intergenic transcripts, and transcripts lacking poly-A tails, providing additional data not previously available. The study was designed to generate a database of the complete transcriptomes in brain region for gene network analyses and discovery of regulatory variants.

Results

Of 20,318 protein coding and 18,080 lncRNA genes annotated from GENCODE and lncipedia, 12 thousand protein coding and 2 thousand lncRNA transcripts were detectable at a conservative threshold. Of the aligned reads, 52 % were exonic, 34 % intronic and 14 % intergenic. A majority of protein coding genes (65 %) was expressed in all regions, whereas ncRNAs displayed a more restricted distribution. Profiles of RNA isoforms varied across brain regions and subjects at multiple gene loci, with neurexin 3 (NRXN3) a prominent example. Allelic RNA ratios deviating from unity were identified in > 400 genes, detectable in both protein-coding and non-coding genes, indicating the presence of cis-acting regulatory variants. Mathematical modeling was used to identify RNAs stably expressed in all brain regions (serving as potential markers for normalizing expression levels), linked to basic cellular functions. An initial analysis of differential expression analysis between smokers and nonsmokers implicated a number of genes, several previously associated with nicotine exposure.

Conclusions

RNA sequencing identifies distinct and consistent differences in gene expression between brain regions, with non-coding RNA displaying greater diversity between brain regions than mRNAs. Numerous RNAs exhibit robust allele selective expression, proving a means for discovery of cis-acting regulatory factors with potential clinical relevance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2207-8) contains supplementary material, which is available to authorized users.

Physical exercise-induced protection on ischemic cardiovascular and cerebrovascular diseases

Physical exercise is any bodily activity to enhance or maintain physical fitness and overall health and wellness. A series of associated studies have demonstrated that physical exercise could alleviate the infarct volume, increase the collateral circulation, promote endothelial progenitor cells, improve cerebral blood flow after cardiovascular and cerebrovascular diseases. In this review, we summed up the protective effects of physical exercise on cerebral blood flow (CBF), vascular endothelium, vascular vasodilation, endothelial progenitor cells and collateral circulation. An awareness of the exercise intervention benefits for cardiovascular and cerebrovascular diseases may encourage more patients with cerebral infarction and myocardial infarction and people with high risk factors to accept exercise interventions for the prevention and treatment of cardiovascular and cerebrovascular diseases.

Identification of neurotoxic cytokines by profiling Alzheimer's disease tissues and neuron culture viability screening

Alzheimer's disease (AD) therapeutics based on the amyloid hypothesis have shown minimal efficacy in patients, suggesting that the activity of amyloid beta (Aβ) represents only one aspect of AD pathogenesis. Since neuroinflammation is thought to play an important role in AD, we hypothesized that cytokines may play a direct role in promoting neuronal death. Here, we profiled cytokine expression in a small cohort of human AD and control brain tissues. We identified AD-associated cytokines using partial least squares regression to correlate cytokine expression with quantified pathologic disease state and then used neuron cultures to test whether cytokines up-regulated in AD tissues could affect neuronal viability. This analysis identified cytokines that were associated with the pathological severity. Of the top correlates, only TNF-α reduced viability in neuron culture when applied alone. VEGF also reduced viability when applied together with Aβ, which was surprising because VEGF has been viewed as a neuro-protective protein. We found that this synthetic pro-death effect of VEGF in the context of Aβ was commensurate with VEGFR-dependent changes in multiple signaling pathways that govern cell fate. Our findings suggest that profiling of tissues combined with a culture-based screening approach can successfully identify new mechanisms driving neuronal death.

Neurogenesis following Stroke Affecting the Adult Brain

A bulk of experimental evidence supports the idea that the stroke-damaged adult brain makes an attempt to repair itself by producing new neurons also in areas where neurogenesis does not normally occur (e.g., the striatum and cerebral cortex). Knowledge about mechanisms regulating the different steps of neurogenesis after stroke is rapidly increasing but still incomplete. The functional consequences of stroke-induced neurogenesis and the level of integration of the new neurons into existing neural circuitries are poorly understood. To have a substantial impact on the recovery after stroke, this potential mechanism for self-repair needs to be enhanced, primarily by increasing the survival and differentiation of the generated neuroblasts. Moreover, for efficient repair, optimization of neurogenesis most likely needs to be combined with promotion of other endogenous neuroregenerative responses (e.g., protection and sprouting of remaining mature neurons, transplantation of neural stem/progenitor cells [NSPC]-derived neurons and glia cells, and modulation of inflammation).

Enhanced brain release of erythropoietin, cytokines and NO during carotid clamping

Although effective and safe, carotid endarterectomy (CEA) implies a reduced blood flow to the brain and likely an ischemia/reperfusion event. The high rate of uneventful outcomes associated with CEA suggests the activation of brain endogenous protection mechanisms aimed at limiting the possible ischemia/reperfusion damage. This study aims at assessing whether CEA triggers protective mechanisms such as brain release of erythropoietin and nitric oxide. CEA was performed in 12 patients; blood samples were withdrawn simultaneously from the surgically exposed ipsilateral jugular and leg veins before, during (2 and 40 min) and after clamp removal (2 min). Plasma antioxidant capacity, carbonylated proteins, erythropoietin, nitrates and nitrites (NOx) were determined. No changes in intraoperative EEG, peripheral and transcranial blood oxygen saturation were detectable, and no patients showed any neurologic sign after the intervention. Antioxidant capacity and protein carbonylation in plasma were unaffected. Differently, erythropoietin, VEGF, TNF-α and NOx increased during clamping in the jugular blood (2 and 40 min), while no changes were observed in the peripheral circulation. These results show that blood erythropoietin, VEGF, TNF-α, and NOx increased in the brain during uncomplicated CEA. This may represent an endogenous self-activated neuroprotective mechanism aimed at the prevention of ischemia/reperfusion damage.

Mechanisms of cell-cell interaction in oligodendrogenesis and remyelination after stroke

White matter damage is a clinically important aspect of several central nervous system diseases, including stroke. Cerebral white matter primarily consists of axonal bundles ensheathed with myelin secreted by mature oligodendrocytes, which play an important role in neurotransmission between different areas of gray matter. During the acute phase of stroke, damage to oligodendrocytes leads to white matter dysfunction through the loss of myelin. On the contrary, during the chronic phase, white matter components promote an environment, which is favorable for neural repair, vascular remodeling, and remyelination. For effective remyelination to take place, oligodendrocyte precursor cells (OPCs) play critical roles by proliferating and differentiating into mature oligodendrocytes, which help to decrease the burden of axonal injury. Notably, other types of cells contribute to these OPC responses under the ischemic conditions. This mini-review summarizes the non-cell autonomous mechanisms in oligodendrogenesis and remyelination after white matter damage, focusing on how OPCs receive support from their neighboring cells. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Coupling of neurogenesis and angiogenesis after ischemic stroke

Stroke is a leading cause of mortality and severe long-term disability worldwide. Development of effective treatment or new therapeutic strategies for ischemic stroke patients is therefore crucial. Ischemic stroke promotes neurogenesis by several growth factors including FGF-2, IGF-1, BDNF, VEGF and chemokines including SDF-1, MCP-1. Stroke-induced angiogenesis is similarly regulated by many factors most notably, eNOS and CSE, VEGF/VEGFR2, and Ang-1/Tie2. Important findings in the last decade have revealed that neurogenesis is not the stand-alone consideration in the fight for full functional recovery from stroke. Angiogenesis has been also shown to be critical in improving post-stroke neurological functional recovery. More than that, recent evidence has shown a highly possible interplay or dependence between stroke-induced neurogenesis and angiogenesis. Moving forward, elucidating the underlying mechanisms of this coupling between stroke-induced neurogenesis and angiogenesis will be of great importance, which will provide the basis for neurorestorative therapy. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Astrocytes, therapeutic targets for neuroprotection and neurorestoration in ischemic stroke

Astrocytes are the most abundant cell type within the central nervous system. They play essential roles in maintaining normal brain function, as they are a critical structural and functional part of the tripartite synapses and the neurovascular unit, and communicate with neurons, oligodendrocytes and endothelial cells. After an ischemic stroke, astrocytes perform multiple functions both detrimental and beneficial, for neuronal survival during the acute phase. Aspects of the astrocytic inflammatory response to stroke may aggravate the ischemic lesion, but astrocytes also provide benefit for neuroprotection, by limiting lesion extension via anti-excitotoxicity effects and releasing neurotrophins. Similarly, during the late recovery phase after stroke, the glial scar may obstruct axonal regeneration and subsequently reduce the functional outcome; however, astrocytes also contribute to angiogenesis, neurogenesis, synaptogenesis, and axonal remodeling, and thereby promote neurological recovery. Thus, the pivotal involvement of astrocytes in normal brain function and responses to an ischemic lesion designates them as excellent therapeutic targets to improve functional outcome following stroke. In this review, we will focus on functions of astrocytes and astrocyte-mediated events during stroke and recovery. We will provide an overview of approaches on how to reduce the detrimental effects and amplify the beneficial effects of astrocytes on neuroprotection and on neurorestoration post stroke, which may lead to novel and clinically relevant therapies for stroke.

The effects of delayed reduction of tonic inhibition on ischemic lesion and sensorimotor function

To aid in development of chronic stage treatments for sensorimotor deficits induced by ischemic stroke, we investigated the effects of GABA antagonism on brain structure and fine skilled reaching in a rat model of focal ischemia induced via cortical microinjections of endothelin-1 (ET-1). Beginning 7 days after stroke, animals were administered a gamma-aminobutyric acid (GABAA) inverse agonist, L-655,708, at a dose low enough to afford α5-GABAA receptor specificity. A week after stroke, the ischemic lesion comprised a small hypointense necrotic core (6±1 mm(3)) surrounded by a large (62±11 mm(3)) hyperintense perilesional region; the skilled reaching ability on the Montoya staircase test was decreased to 34%±2% of the animals' prestroke performance level. On L-655,708 treatment, animals showed a progressive decrease in total stroke volume (13±4 mm(3) per week), with no change in animals receiving placebo. Concomitantly, treated animals' skilled reaching progressively improved by 9%±1% per week, so that after 2 weeks of treatment, these animals performed at 65%±6% of their baseline ability, which was 25%±11% better than animals given placebo. These data indicate beneficial effects of delayed, sustained low-dose GABAA antagonism on neuroanatomic injury and skilled reaching in the chronic stage of stroke recovery in an ET-1 rat model of focal ischemia.

Electroacupuncture modulated the inflammatory reaction in MCAO rats via inhibiting the TLR4/NF-κB signaling pathway in microglia

In this study, we aim to investigate the effects of electroacupuncture on the TLR4/NF-κB signaling pathway in microglia. Male Wistar rat of SPF grade (weighing 200 ± 20 g) were randomly divided into (i): sham control group, which was subjected to sham operation (ii) vehicle group, which underwent the occlusion of middle cerebral artery; (iii-v): acupuncture groups, which were subjected to the occlusion of middle cerebral artery and treated with acupuncture on the Neiguan acupoint (P6), Quchi acupoint (LI11), and Diji acupoint (SP8), respectively. HE staining was performed to detect the necrotic rate of neurons. Mediators of inflammation were measured using ELISA. Immunofluorescence was performed to measure the expression of TLR4, HMGB1, TRAF6, IKKβ and NF-κB p65 in microglia. Severe decrease was noticed in the neurological score, necrotic rates of neuron, expression of IL-1β, IL-6, TLR4, HMGB1, TRAF6, IKKβ and NF-κB p65 in microglia. Compared with the vehicle group, significant decrease was revealed in the neurological score, necrotic rate, IL-1β, TLR4, TRAF6, IKKβ and NF-κB p65 in Neiguan group and Quchi group, respectively. In addition, remarkable decrease was observed in the expression of TNF-α and IL-6 in Quchi group. Compared with the Diji group, the necrotic rate of neurons in hippocampus region was significantly decreased in the Quchi group (P < 0.05). In Neiguan group, the expression of TLR4 and IKKβ was significantly attenuated (P < 0.05). The expression of TRAF6 was remarkably decreased in the Neiguan group and Quchi group, respectively. Electroacupuncture on Neiguan and Quchi could improve the neurological injury, attenuate the inflammation, and inhibit the activity of TLR4/NF-κB signaling pathway in microglia.

Herbal Formula Danggui-Shaoyao-San Promotes Neurogenesis and Angiogenesis in Rat Following Middle Cerebral Artery Occlusion

Current studies demonstrated that traditional Chinese herbal formula Danggui-Shaoyao-San (DSS) is not only used for the treatment of menstrual disorder, but has also found its use in neurological diseases. However, the neuroprotective role of DSS on ischemia-induced brain injury is still unclear. The aim of the present study is to explore the effect of DSS in ischemic brain injury. Total 30 adult female Sprague-Dawley rats underwent 90 min transient middle cerebral artery occlusion (MCAO). DSS (600 mg/kg) was administered through the intragastric route at the time of reperfusion and then performed every day thereafter until sacrifice. Results showed that DSS treatment significantly improved neurobehavioral outcomes (N=10 per group, P<0.05). Immunohistochemical staining showed that microvessel density in the perifocal region of DSS-treated rats was significantly increased compared to the saline-treated group (N=4 per group, P<0.01). Similarly, the numbers of BrdU(+)/DCX(+) cells in the subventricular zone were increased in DSS-treated rats compared to the saline-treated group (P<0.05). Furthermore, we demonstrated that DSS treatment activated vascular endothelial growth factor (N=4 per group, P<0.05) and promoted eNOS phosphorylation (N=4 per group, P<0.05). Thus, we concluded that DSS promoted focal angiogenesis and neurogenesis, and attenuated ischemia-induced brain injury in rats after MCAO, suggesting that DSS is a potential drug for ischemic stroke therapy.

Ontogeny of inter-alpha inhibitor proteins in ovine brain and somatic tissues

Inter-alpha inhibitor proteins (IAIPs) found in relatively high concentrations in human plasma are important in inflammation. IAIPs attenuate brain damage in young and adult subjects, decrease during sepsis and necrotizing enterocolitis in premature infants, and attenuate sepsis-related inflammation in newborn rats. Although a few studies have reported adult organ-specific IAIP expression, information is not available on age-dependent IAIP expression. Given evidence suggesting IAIPs attenuate brain damage in young and adult subjects, and inflammation in newborns, we examined IAIP expression in plasma, cerebral cortex (CC), choroid plexus (CP), cerebral spinal fluid (CSF), and somatic organs in fetal, newborn, and adult sheep to determine the endogenous expression patterns of these proteins during development. IAIPs (enzyme-linked immunosorbent assay) were higher in newborn and adult than fetal plasma (P < 0.05). Western immunoblot detected 125 kDa PaI (Pre-alpha Inhibitor) and 250 kDa IaI (Inter-alpha Inhibitor) in plasma, CNS, and somatic organs. PaI expression in CC and CP was higher in fetuses than newborns and adults, but IaI expression was higher in adults than fetuses and newborns. Both PaI and IaI were higher in fetal than newborn CSF. IAIPs exhibited organ-specific ontogenic patterns in placenta, liver, heart, and kidney. These results provide evidence for the first time that plasma, brain, placenta, liver, heart, and kidney express IAIPs throughout ovine development and that expression patterns are unique to each organ. Although exact functions of IAIPs in CNS and somatic tissues are not known, their presence in relatively high amounts during development suggests their potential importance in brain and organ development.

Angiogenesis dysregulation in term asphyxiated newborns treated with hypothermia

BACKGROUND

Neonatal encephalopathy following birth asphyxia is a major predictor of long-term neurological impairment. Therapeutic hypothermia is currently the standard of care to prevent brain injury in asphyxiated newborns but is not protective in all cases. More robust and versatile treatment options are needed. Angiogenesis is a demonstrated therapeutic target in adult stroke. However, no systematic study examines the expression of angiogenesis-related markers following birth asphyxia in human newborns.

OBJECTIVE

This study aimed to evaluate the expression of angiogenesis-related protein markers in asphyxiated newborns developing and not developing brain injury compared to healthy control newborns.

DESIGN/METHODS

Twelve asphyxiated newborns treated with hypothermia were prospectively enrolled; six developed eventual brain injury and six did not. Four healthy control newborns were also included. We used Rules-Based Medicine multi-analyte profiling and protein array technologies to study the plasma concentration of 49 angiogenesis-related proteins. Mean protein concentrations were compared between each group of newborns.

RESULTS

Compared to healthy newborns, asphyxiated newborns not developing brain injury showed up-regulation of pro-angiogenic proteins, including fatty acid binding protein-4, glucose-6-phosphate isomerase, neuropilin-1, and receptor tyrosine-protein kinase erbB-3; this up-regulation was not evident in asphyxiated newborns eventually developing brain injury. Also, asphyxiated newborns developing brain injury showed a decreased expression of anti-angiogenic proteins, including insulin-growth factor binding proteins -1, -4, and -6, compared to healthy newborns.

CONCLUSIONS

These findings suggest that angiogenesis pathways are dysregulated following birth asphyxia and are putatively involved in brain injury pathology and recovery.

Endogenous repair signaling after brain injury and complementary bioengineering approaches to enhance neural regeneration

Traumatic brain injury (TBI) affects 5.3 million Americans annually. Despite the many long-term deficits associated with TBI, there currently are no clinically available therapies that directly address the underlying pathologies contributing to these deficits. Preclinical studies have investigated various therapeutic approaches for TBI: two such approaches are stem cell transplantation and delivery of bioactive factors to mitigate the biochemical insult affiliated with TBI. However, success with either of these approaches has been limited largely due to the complexity of the injury microenvironment. As such, this review outlines the many factors of the injury microenvironment that mediate endogenous neural regeneration after TBI and the corresponding bioengineering approaches that harness these inherent signaling mechanisms to further amplify regenerative efforts.

Evaluating the SERCA2 and VEGF mRNAs as Potential Molecular Biomarkers of the Onset and Progression in Huntington's Disease

Abnormalities of intracellular Ca²⁺ homeostasis and signalling as well as the down-regulation of neurotrophic factors in several areas of the central nervous system and in peripheral tissues are hallmarks of Huntington’s disease (HD). As there is no therapy for this hereditary, neurodegenerative fatal disease, further effort should be made to slow the progression of neurodegeneration in patients through the definition of early therapeutic interventions. For this purpose, molecular biomarker(s) for monitoring disease onset and/or progression and response to treatment need to be identified. In the attempt to contribute to the research of peripheral candidate biomarkers in HD, we adopted a multiplex real-time PCR approach to analyse the mRNA level of targeted genes involved in the control of cellular calcium homeostasis and in neuroprotection. For this purpose we recruited a total of 110 subjects possessing the HD mutation at different clinical stages of the disease and 54 sex- and age-matched controls. This study provides evidence of reduced transcript levels of sarco-endoplasmic reticulum-associated ATP2A2 calcium pump (SERCA2) and vascular endothelial growth factor (VEGF) in peripheral blood mononuclear cells (PBMCs) of manifest and pre-manifest HD subjects. Our results provide a potentially new candidate molecular biomarker for monitoring the progression of this disease and contribute to understanding some early events that might have a role in triggering cellular dysfunctions in HD.