Endothelial nitric oxide synthase regulates white matter changes via the BDNF/TrkB pathway after stroke in mice

Perspective insights into versatile hydrogels for stroke: From molecular mechanisms to functional applications

As the leading killer of life and health, stroke leads to limb paralysis, speech disorder, dysphagia, cognitive impairment, mental depression and other symptoms, which entail a significant financial burden to society and families. At present, physiology, clinical medicine, engineering, and materials science, advanced biomaterials standing on the foothold of these interdisciplinary disciplines provide new opportunities and possibilities for the cure of stroke. Among them, hydrogels have been endowed with more possibilities. It is well-known that hydrogels can be employed as potential biosensors, medication delivery vectors, and cell transporters or matrices in tissue engineering in tissue engineering, and outperform many traditional therapeutic drugs, surgery, and materials. Therefore, hydrogels become a popular scaffolding treatment option for stroke. Diverse synthetic hydrogels were designed according to different pathophysiological mechanisms from the recently reported literature will be thoroughly explored. The biological uses of several types of hydrogels will be highlighted, including pro-angiogenesis, pro-neurogenesis, anti-oxidation, anti-inflammation and anti-apoptosis. Finally, considerations and challenges of using hydrogels in the treatment of stroke are summarized.

Enriched environment enhanced the astrocyte-derived BDNF and VEGF expression and alleviate white matter injuries of rats with ischemic stroke

OBJECTIVES

Numerous studies have shown that an enriched environment can promote ischemic stroke and improve cognitive function. In addition, white matter is closely related to cognitive function. The effects and mechanisms of the enriched environment on white matter recovery after stroke have not been elucidated. This study will analyse the effects of the enriched environment on white matter and cognitive function in the post-stroke brain from the perspective of astrocytes and their secretions.

METHODS

Stroke models were used for middle cerebral artery occlusion model. post-operative rats were divided into sham-operated, standard and enriched environment groups. The degree of cerebral infarction was assessed by TTC staining and the degree of white matter damage was assessed by Luxol-Fast Blue staining. The prognosis after stroke was assessed using the longa score and Morris water maze test. Western Blot and immunofluorescence were used to quantify and localize astrocytes and their associated secretory factors and myelin protein markers.

RESULTS

We found that ischemic stroke can cause severe demyelination. After EE treatment, there was a significant increase in cerebral remyelination and a significant improvement in neurological and cognitive functions. Astrocyte, BDNF, and VEGF expression were significantly higher than in rats in the standard circumstances of stroke model.

CONCLUSION

These data suggest that the enriched environment contributes to brain white matter recovery and improvement of cognitive function after stroke. The mechanism is related to astrocytes and their secretions. EE can activate astrocytes to secrete BDNF and VEGF, which may be crucial to promote white matter recovery.

Altered cerebrovascular regulation in low birthweight swine

Full-term low birthweight (LBW) offspring exhibit peripheral vascular dysfunction in the postnatal period; however, whether such impairments extend to the cerebrovasculature remains to be elucidated. We used a swine model to test the hypothesis that LBW offspring would exhibit cerebrovascular dysfunction at later stages of life. Offspring from 14 sows were identified as normal birthweight (NBW) or LBW and were assessed at 28 (similar to end of infancy) and 56 (similar to childhood) days of age. LBW swine had lower absolute brain mass, but demonstrated evidence of brain sparing (increased brain mass scaled to body mass) at 56 days of age. The cerebral pulsatility index, based on transcranial Doppler, was increased in LBW swine. Moreover, arterial myography of isolated cerebral arteries revealed impaired vasoreactivity to bradykinin and reduced contribution of nitric oxide (NO) to vasorelaxation in the LBW swine. Immunoblotting demonstrated a lower ratio of phosphorylated-to-total endothelial NO synthase in LBW offspring. This impairment in NO signaling was greater at 28 vs. 56 days of age. Vasomotor responses to sodium nitroprusside (NO-donor) were unaltered, while Leu³¹, Pro³⁴ neuropeptide Y-induced vasoconstriction was enhanced in LBW swine. Increases in total Y1 receptor protein content in the LBW group were not significant. In summary, LBW offspring displayed signs of cerebrovascular dysfunction at 28 and 56 days of age, evidenced by altered cerebral hemodynamics (reflective of increased impedance) coupled with endothelial dysfunction and altered vasomotor control. Overall, the data reveal that normal variance in birthweight of full-term offspring can influence cerebrovascular function later in life.

The Potential Impact of Neuroimaging and Translational Research on the Clinical Management of Lacunar Stroke

Lacunar infarcts represent one of the most frequent subtypes of ischemic strokes and may represent the first recognizable manifestation of a progressive disease of the small perforating arteries, capillaries, and venules of the brain, defined as cerebral small vessel disease. The pathophysiological mechanisms leading to a perforating artery occlusion are multiple and still not completely defined, due to spatial resolution issues in neuroimaging, sparsity of pathological studies, and lack of valid experimental models. Recent advances in the endovascular treatment of large vessel occlusion may have diverted attention from the management of patients with small vessel occlusions, often excluded from clinical trials of acute therapy and secondary prevention. However, patients with a lacunar stroke benefit from early diagnosis, reperfusion therapy, and secondary prevention measures. In addition, there are new developments in the knowledge of this entity that suggest potential benefits of thrombolysis in an extended time window in selected patients, as well as novel therapeutic approaches targeting different pathophysiological mechanisms involved in small vessel disease. This review offers a comprehensive update in lacunar stroke pathophysiology and clinical perspective for managing lacunar strokes, in light of the latest insights from imaging and translational studies.

Delayed rFGF21 Administration Improves Cerebrovascular Remodeling and White Matter Repair After Focal Stroke in Diabetic Mice

Type 2 diabetes mellitus (T2DM) is a major comorbidity exacerbating ischemic brain injury and impairing post-stroke recovery. Our previous study suggested that recombinant human fibroblast growth factor (rFGF) 21 might be a potent therapeutic targeting multiple aspects of pathophysiology in T2DM stroke. This study aims to evaluate the potential effects of rFGF21 on cerebrovascular remodeling after T2DM stroke. Permanent distal middle cerebral artery occlusion was performed in heterozygous non-diabetic db/ + and homozygous diabetic db/db mice. Daily rFGF21 administration was initiated 1 week after stroke induction and maintained for up to 2 weeks thereafter. Multiple markers associated with post-stroke recovery, including angiogenesis, oligodendrogenesis, white matter integrity, and neurogenesis, were assessed up to 3 weeks after stroke. Our results showed an impairment in post-stroke vascular remodeling under T2DM condition, reflected by the decreased expression of trophic factors in brain microvessels and impairments of angiogenesis. The defected cerebrovascular remodeling was accompanied by the decreased oligodendrogenesis and neurogenesis. However, delayed rFGF21 administration normalized post-stroke hyperglycemia and improved neurological outcomes, which may partially be via the promotion of pro-angiogenic trophic factor expression in brain microvessels and cerebrovascular remodeling. The better cerebrovascular remodeling may also contribute to oligodendrogenesis, white matter integrity, and neurogenesis after T2DM stroke. Therefore, delayed rFGF21 administration may improve neurological outcomes in T2DM stroke mice, at least in part by normalizing the metabolic abnormalities and promoting cerebrovascular remodeling and white matter repair.

Deficiency of Endothelial Nitric Oxide Synthase (eNOS) Exacerbates Brain Damage and Cognitive Deficit in A Mouse Model of Vascular Dementia

Vascular Dementia (VaD) accounts for nearly 20% of all cases of dementia. eNOS plays an important role in neurovascular remodeling, anti-inflammation, and cognitive functional recovery after stroke. In this study, we investigated whether eNOS regulates brain damage, cognitive function in mouse model of bilateral common carotid artery stenosis (BCAS) induced VaD. Late-adult (6-8 months) C57BL/6J and eNOS knockout (eNOS-/-) mice were subjected to BCAS (n=12/group) or sham group (n=8/group). BCAS was performed by applying microcoils to both common carotid arteries. Cerebral blood flow (CBF) and blood pressure were measured. A battery of cognitive functional tests was performed, and mice were sacrificed 30 days after BCAS. Compared to corresponding sham mice, BCAS in wild-type (WT) and eNOS-/- mice significantly: 1) induces short term, long term memory loss, spatial learning and memory deficits; 2) decreases CBF, increases ischemic cell damage, including apoptosis, white matter (WM) and axonal damage; 3) increases blood brain barrier (BBB) leakage, decreases aquaporin-4 (AQP4) expression and vessel density; 4) increases microglial, astrocyte activation and oxidative stress in the brain; 5) increases inflammatory factor interleukin-1 receptor-associated kinase-1(IRAK-1) and amyloid beta (Aβ) expression in brain; 6) increases IL-6 and IRAK4 expression in brain. eNOS-/-sham mice exhibit increased blood pressure, decreased iNOS and nNOS in brain compared to WT-sham mice. Compared to WT-BCAS mice, eNOS-/-BCAS mice exhibit worse vascular and WM/axonal damage, increased BBB leakage and inflammatory response, increased cognitive deficit, decreased iNOS, nNOS in brain. eNOS deficit exacerbates BCAS induced brain damage and cognitive deficit.

The Roles of Nitric Oxide Synthase/Nitric Oxide Pathway in the Pathology of Vascular Dementia and Related Therapeutic Approaches

Vascular dementia (VaD) is the second most common form of dementia worldwide. It is caused by cerebrovascular disease, and patients often show severe impairments of advanced cognitive abilities. Nitric oxide synthase (NOS) and nitric oxide (NO) play vital roles in the pathogenesis of VaD. The functions of NO are determined by its concentration and bioavailability, which are regulated by NOS activity. The activities of different NOS subtypes in the brain are partitioned. Pathologically, endothelial NOS is inactivated, which causes insufficient NO production and aggravates oxidative stress before inducing cerebrovascular endothelial dysfunction, while neuronal NOS is overactive and can produce excessive NO to cause neurotoxicity. Meanwhile, inflammation stimulates the massive expression of inducible NOS, which also produces excessive NO and then induces neuroinflammation. The vicious circle of these kinds of damage having impacts on each other finally leads to VaD. This review summarizes the roles of the NOS/NO pathway in the pathology of VaD and also proposes some potential therapeutic methods that target this pathway in the hope of inspiring novel ideas for VaD therapeutic approaches.

Diabetes, stroke, and neuroresilience: looking beyond hyperglycemia

Ischemic stroke is a leading cause of morbidity and mortality among type 2 diabetic patients. Preclinical and translational studies have identified critical pathophysiological mediators of stroke risk, recurrence, and poor outcome in diabetic patients, including endothelial dysfunction and inflammation. Most clinical trials of diabetes and stroke have focused on treating hyperglycemia alone. Pioglitazone has shown promise in secondary stroke prevention for insulin-resistant patients; however, its use is not yet widespread. Additional research into clinical therapies directed at diabetic pathophysiological processes to prevent stroke and improve outcome for diabetic stroke survivors is necessary. Resilience is the process of active adaptation to a stressor. In patients with diabetes, stroke recovery is impaired by insulin resistance, endothelial dysfunction, and inflammation, which impair key neuroresilience pathways maintaining cerebrovascular integrity, resolving poststroke inflammation, stimulating neural plasticity, and preventing neurodegeneration. Our review summarizes the underpinnings of stroke risk in diabetes, the clinical consequences of stroke in diabetic patients, and proposes hypotheses and new avenues of research for therapeutics to stimulate neuroresilience pathways and improve stroke outcome in diabetic patients.

Hydroalcoholic Extract of Anchusa Italica Protects Global Cerebral Ischemia-Reperfusion Injury Via a Nitrergic Mechanism

INTRODUCTION

In stroke models, Inducible Nitric Oxide Synthase (iNOS) expression initiates cellular toxicity due to excessive Nitric Oxide (NO) generation. Anchusa italica is a medicinal herb with anti-inflammatory, antioxidant and neuroprotective properties. This study evaluated the antioxidant activity and NOS mRNA expression of the Hydroalcoholic Extract Of Anchusa Italica (HEAI) in an experimental stroke model in rats.

METHODS

The stroke model was induced by bilateral occlusion of both common carotid arteries for 60 min. Twenty-four hours after surgery, HEAI (50 and 100 mg/kg i.p.) was injected daily for 10 consecutive days. mRNA expression levels of NOS subtypes and hippocampal Brain-Derived Neurotrophic Factor (BDNF) were studied using real-time PCR. Besides, hippocampal tissue plus serum concentrations of NO and Malondialdehyde (MDA) were measured.

RESULTS

HEAI decreased MDA in both serum and hippocampal tissue and also reduced serum NO levels. Additionally, in the HEAI-treated groups, a down-regulation of iNOS mRNA expression, and an up-regulation of BDNF mRNA expression were observed.

CONCLUSION

The results indicated that the administration of HEAI even after the onset of ischemia protects the brain from free radical injury and inflammation via a down-regulation of iNOS expression inhibiting NO production and an up-regulation of BDNF mRNA.

Brain-Derived Neurotrophic Factor and Its Potential Therapeutic Role in Stroke Comorbidities

With the rise in the aging global population, stroke comorbidities have become a serious health threat and a tremendous economic burden on human society. Current therapeutic strategies mainly focus on protecting neurons from cytotoxic damage at the acute phase upon stroke onset, which not only is a difficult way to ameliorate stroke symptoms but also presents a challenge for the patients to receive effective treatment in time. The brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain, which possesses a remarkable capability to repair brain damage. Recent promising preclinical outcomes have made BDNF a popular late-stage target in the development of novel stroke treatments. In this review, we aim to summarize the latest progress in the understanding of the cellular/molecular mechanisms underlying stroke pathogenesis, current strategies and difficulties in drug development, the mechanism of BDNF action in poststroke neurorehabilitation and neuroplasticity, and recent updates in novel therapeutic methods.

Caveolin-1 in Stroke Neuropathology and Neuroprotection: A Novel Molecular Therapeutic Target for Ischemic-Related Injury

Cardiovascular disease and associated cerebral stroke are a global epidemic attributed to genetic and epigenetic factors, such as diet, life style and an increasingly sedentary existence due to technological advances in both the developing and developed world. There are approximately 5.9 million stroke-related deaths worldwide annually. Current epidemiological data indicate that nearly 16.9 million people worldwide suffer a new or recurrent stroke yearly. In 2014 alone, 2.4% of adults in the United States (US) were estimated to experience stroke, which is the leading cause of adult disability and the fifth leading cause of death in the US There are 2 main types of stroke: Hemorrhagic (HS) and ischemic stroke (IS), with IS occurring more frequently. HS is caused by intra-cerebral hemorrhage mainly due to high blood pressure, while IS is caused by either embolic or thrombotic stroke. Both result in motor impairments, numbness or abnormal sensations, cognitive deficits, and mood disorders (e.g. depression). This review focuses on the 1) pathophysiology of stroke (neuronal cell loss, defective blood brain barrier, microglia activation, and inflammation), 2) the role of the membrane protein caveolin- 1 (Cav-1) in normal brain physiology and stroke-induced changes, and, 3) we briefly discussed the potential therapeutic role of Cav-1 in recovery following stroke.

Impaired Cognitive Performance in Endothelial Nitric Oxide Synthase Knockout Mice After Ischemic Stroke: A Pilot Study

OBJECTIVES

Cognitive dysfunction and dementia are common following ischemic stroke. Endothelial nitric oxide synthase (eNOS) has been found to play an important role in neurologic function and cognition. The purpose of the present study was to assess the specific role of eNOS in cognitive performance after stroke.

DESIGN

Male wild-type and mice lacking eNOS (eNOS) underwent middle cerebral artery occlusion or sham-surgery. Primary outcomes were repeated measures of neurologic score, limb asymmetry, sensory/motor function, and spatial memory/learning assessed at intervals up to 28 days postsurgery. Group differences in brain microglia activation and infiltration and levels of interferon-gamma were examined.

RESULTS

There was no genotype × surgery interaction effect on the pattern of change in neurologic score, limb asymmetry, or sensory motor function across the 28 days postsurgery. In the Morris water maze, eNOS-/- middle cerebral artery occlusion mice displayed learning and memory deficits not evident in wild-type middle cerebral artery occlusion mice. Poorer spatial memory and learning in eNOS-/- middle cerebral artery occlusion mice was associated with a reduction in the number of activated microglia in the striatum on the lesion side and decreased brain tissue levels of interferon-gamma.

CONCLUSIONS

This study's data support a role for eNOS in cognitive performance after stroke. This finding may lead to the development of novel interventions to treat poststroke cognitive deficits.

The Level of proBDNF in Blood Lymphocytes Is Correlated with that in the Brain of Rats with Photothrombotic Ischemic Stroke

Stroke is accompanied by severe inflammation in the brain. The role of mature brain-derived neurotrophic factor (mBDNF) in ischemic stroke has received intensive attention, but the function of its precursor proBDNF is less understood. Recent studies showed that mBDNF and proBDNF in the ischemic brain are upregulated, but the significance of mBDNF and proBDNF in the lymphocytes in ischemic stroke is not known. Here, we propose that the expression levels of mBDNF and proBDNF in lymphocytes correlate with those in the brain after ischemic stroke and therefore can be surrogate markers for the ischemic brain. Using a photothrombotic model in rats and ELISA assay technique, we found that proBDNF and mBDNF in peripheral lymphocytes were upregulated but produced differential time courses after ischemia. The levels of mBDNF and proBDNF in lymphocytes at early stages of stroke (1 day), showed a strong positive correlation with those in the brain. The levels of p75, sortilin, were also increased in a time-dependent manner after ischemic stroke; however, the levels of p-TrkB in the ischemic brain at 6 h, 1 and 3 days were significantly reduced in the brain. The present study suggests that the levels of proBDNF and mBDNF in the blood lymphocytes in acute ischemic stroke reflect those in the brain at early stages.

BDNF, endurance activity, and mechanisms underlying the evolution of hominin brains

OBJECTIVES

As a complex, polygenic trait, brain size has likely been influenced by a range of direct and indirect selection pressures for both cognitive and non-cognitive functions and capabilities. It has been hypothesized that hominin brain expansion was, in part, a correlated response to selection acting on aerobic capacity (Raichlen & Polk, 2013). According to this hypothesis, selection for aerobic capacity increased the activity of various signaling molecules, including those involved in brain growth. One key molecule is brain-derived neurotrophic factor (BDNF), a protein that regulates neuronal development, survival, and plasticity in mammals. This review updates, partially tests, and expands Raichlen and Polk's (2013) hypothesis by evaluating evidence for BDNF as a mediator of brain size.

DISCUSSION

We contend that selection for endurance capabilities in a hot climate favored changes to muscle composition, mitochondrial dynamics and increased energy budget through pathways involving regulation of PGC-1α and MEF2 genes, both of which promote BDNF activity. In addition, the evolution of hairlessness and the skin's thermoregulatory response provide other molecular pathways that promote both BDNF activity and neurotransmitter synthesis. We discuss how these pathways contributed to the evolution of brain size and function in human evolution and propose avenues for future research. Our results support Raichlen and Polk's contention that selection for non-cognitive functions has direct mechanistic linkages to the evolution of brain size in hominins.

Involvement of brain-derived neurotrophic factor in exercise‑induced cardioprotection of post-myocardial infarction rats

Exercise induces a number of benefits, including angiogenesis in post‑myocardial infarction (MI); however, the underlying mechanisms have not been fully clarified. Neurotrophic brain‑derived neurotrophic factor (BDNF) serves a protective role in certain adult cardiac diseases through its specific receptor, BDNF/NT‑3 growth factors receptor (TrkB). The present study explored the mechanisms by which exercise improves cardiac function, with a focus on the involvement of the BDNF/TrkB axis. MI rats were assigned to Sham, sedentary, exercise, exercise with K252a (a TrkB inhibitor), and exercise with NG‑nitro‑L‑arginine methyl ester (L‑NAME) groups. The exercise group was subjected to 8 weeks of treadmill running. The results demonstrated that the rats in the exercise group exhibited increased myocardial angiogenesis and improved cardiac function, which was attenuated by K252a. Exercise induced activation of the BDNF/TrkB axis in the ischaemic myocardium and increased serum BDNF levels were abated by exposure to L‑NAME. Improvements in angiogenesis and left ventricular function exhibited a positive association, with changes in serum BDNF. In the in vitro experiments, human umbilical vein endothelial cells were exposed to shear stress (SS) of 12 dyn/cm2 to mimic the effects of exercise training on vascular tissue. An increased tube‑forming capacity, and a nitric oxide (NO)‑dependent prolonged activation of the BDNF/TrkB‑full‑length axis over 12 h, but not the TrkB‑truncated axis, was observed. The SS‑related angiogenic response was attenuated by TrkB inhibition. Overall, these results demonstrate that exercise confers certain aspects of its cardioprotective effects through the activation of the BDNF/TrkB axis in an NO‑dependent manner, a process in which fluid‑induced SS may serve a crucial role.

Engineered 3D vascular and neuronal networks in a microfluidic platform

Neurovascular coupling plays a key role in the pathogenesis of neurodegenerative disorders including motor neuron disease (MND). In vitro models provide an opportunity to understand the pathogenesis of MND, and offer the potential for drug screening. Here, we describe a new 3D microvascular and neuronal network model in a microfluidic platform to investigate interactions between these two systems. Both 3D networks were established by co-culturing human embryonic stem (ES)-derived MN spheroids and endothelial cells (ECs) in microfluidic devices. Co-culture with ECs improves neurite elongation and neuronal connectivity as measured by Ca2+ oscillation. This improvement was regulated not only by paracrine signals such as brain-derived neurotrophic factor secreted by ECs but also through direct cell-cell interactions via the delta-notch pathway, promoting neuron differentiation and neuroprotection. Bi-directional signaling was observed in that the neural networks also affected vascular network formation under perfusion culture. This in vitro model could enable investigations of neuro-vascular coupling, essential to understanding the pathogenesis of neurodegenerative diseases including MNDs such as amyotrophic lateral sclerosis.

Bone marrow mesenchymal stromal cells alleviate brain white matter injury via the enhanced proliferation of oligodendrocyte progenitor cells in focal cerebral ischemic rats

The effects of transplanting bone marrow mesenchymal stromal cells (BMSCs) for the treatment of white matter damage are not well understood, nor are the underlying mechanisms. Recent studies showed that endogenous oligodendrocyte progenitor cells (OPCs) can be stimulated to proliferate. Therefore, we explore the effects of BMSCs transplantation on white matter damage and the proliferation of OPCs in transient focal cerebral ischemic rats. BMSCs were transplanted into a group of rats that had undergone middle cerebral artery occlusion (MCAO) 24 h after reperfusion. The ratswere examined by MRI-T2 and DTI sequencesdynamically. The proliferating cells were labeled by 5-Bromo-2'-deoxyuridine (BrdU). The effects of BMSC transplantation on neurons, axons, myelination, and proliferating OPCs were examined by Nissl staining, MBP/NF-H and BrdU/NG2 immunofluorescence staining7 days after transplantation. More Nissl-stained neuronswere found and the FA value of MRI-DTI was significantly higher in the MCAO + BMSCs group than in the MCAOgroup (both P < .01). The fold change of MBP protein was significantly higher in the MCAO + BMSCs group than in the MCAO group (P < .01); the same was true of NF-H protein. Additionally, there were more BrdU⁺NG2⁺ cells in the SVZ areas of the MCAO + BMSCs group than in the MCAO group (P < .01). BMSCs thus were shown to alleviate neuronal/axonal injury and promote the proliferation of OPCs and formation of myelin sheath, significantly alleviating white matter damage in focal cerebral ischemic rats.

Whole Body Periodic Acceleration (pGz) as a non-invasive preconditioning strategy for pediatric cardiac surgery

We hypothesized that pGz has cardio and neuroprotective effects due to upregulation of pathways which include eNOS, anti-apoptotic, and anti-inflammatory pathways. We analyze protein expression of these pathways in the brain of neonatal piglets, as well as report on the myocardial function after Deep Hypothermic Circulatory Arrest (DHCA) and pGz preconditioning. Animal data affirms both a cardio and neuroprotective role for pGz. These findings suggest that pGz can be a simple, non-invasive cardio and neuroprotective strategy preconditioning strategy in children requiring surgical intervention.

Brain-Derived Neurotrophic Factor Attenuates Septic Myocardial Dysfunction via eNOS/NO Pathway in Rats

Sepsis-induced myocardial dysfunction increases mortality in sepsis, yet the underlying mechanism is unclear. Brain-derived neurotrophic factor (BDNF) has been found to enhance cardiomyocyte function, but whether BDNF has a beneficial effect against septic myocardial dysfunction is unknown. Septic shock was induced by cecal ligation and puncture (CLP). BDNF was expressed in primary cardiomyocytes, and its expression was significantly reduced after sepsis. In rats with sepsis, a sharp decline in survival was observed after CLP, with significantly reduced cardiac BDNF expression, enhanced myocardial fibrosis, elevated oxidative stress, increased myocardial apoptosis, and decreased endothelial nitric oxide (NO) synthase (eNOS) and NO. Supplementation with recombined BDNF protein (rhBDNF) enhanced myocardial BDNF and increased survival rate with improved cardiac function, reduced oxidative stress, and myocardial apoptosis, which were associated with increased eNOS expression, NO production, and Trk-B, a BDNF receptor. Pretreatment with NOS inhibitor, N (omega)-nitro-L-arginine methyl ester, abolished the abovementioned BDNF cardioprotective effects without affecting BDNF and Trk-B. It is concluded that BDNF protects the heart against septic cardiac dysfunction by reducing oxidative stress and apoptosis via Trk-B, and it does so through activation of eNOS/NO pathway. These findings provide a new treatment strategy for sepsis-induced myocardial dysfunction.

Molecular mechanisms of brain-derived neurotrophic factor in neuro-protection: Recent developments

Neuronal cell injury, as a consequence of acute or chronic neurological trauma, is a significant cause of mortality around the world. On a molecular level, the condition is characterized by widespread cell death and poor regeneration, which can result in severe morbidity in survivors. Potential therapeutics are of major interest, with a promising candidate being brain-derived neurotrophic factor (BDNF), a ubiquitous agent in the brain which has been associated with neural development and may facilitate protective and regenerative effects following injury. This review summarizes the available information on the potential benefits of BDNF and the molecular mechanisms involved in several pathological conditions, including hypoxic brain injury, stroke, Alzheimer's disease and Parkinson's disease. It further explores the methods in which BDNF can be applied in clinical and therapeutic settings, and the potential challenges to overcome.

Tyrosine Kinase Inhibitor as a new Therapy for Ischemic Stroke and other Neurologic Diseases: is there any Hope for a Better Outcome?

The relevance of tyrosine kinase inhibitors (TKIs) in the treatment of malignancies has been already defined. Aberrant activation of tyrosine kinase signaling pathways has been causally linked not only to cancers but also to other non-oncological diseases. This review concentrates on the novel plausible usage of this group of drugs in neurological disorders, such as ischemic brain stroke, subarachnoid hemorrhage, Alzheimer’s disease, multiple sclerosis. The drugs considered here are representatives of both receptor and non-receptor TKIs. Among them imatinib and masitinib have the broadest spectrum of therapeutic usage. Both drugs are effective in ischemic brain stroke and multiple sclerosis, but only imatinib produces a therapeutic effect in subarachnoid hemorrhage. Masitinib and dasatinib reduce the symptoms of Alzheimer’s disease. In the case of multiple sclerosis several TKIs are useful, including apart from imatinib and masitinib, also sunitinib, sorafenib, lestaurtinib. Furthermore, the possible molecular targets for the drugs are described in connection with the underlying pathophysiological mechanisms in the diseases in question. The most frequent target for the TKIs is PDGFR which plays a pivotal role particularly in ischemic brain stroke and subarachnoid hemorrhage. The collected data indicates that TKIs are very promising candidates for new therapeutic interventions in neurological diseases.

Brain BDNF levels are dependent on cerebrovascular endothelium-derived nitric oxide

Scientific evidence continues to demonstrate a link between endothelial function and cognition. Besides, several studies have identified a complex interplay between nitric oxide (NO) and brain-derived neurotrophic factor (BDNF), a neurotrophin largely involved in cognition. Therefore, this study investigated the link between cerebral endothelium-derived NO and BDNF signaling. For this purpose, levels of BDNF and the phosphorylated form of endothelial NO synthase at serine 1177 (p-eNOS) were simultaneously measured in the cortex and hippocampus of rats subjected to either bilateral common carotid occlusion (n = 6), physical exercise (n = 6) or a combination of both (n = 6) as experimental approaches to modulate flow-induced NO production by the cerebrovasculature. Tropomyosin-related kinase type B (TrkB) receptors and its phosphorylated form at tyrosine 816 (p-TrkB) were also measured. Moreover, we investigated BDNF synthesis in brain slices exposed to the NO donor glyceryl trinitrate. Our results showed increased p-eNOS and BDNF levels after exercise and decreased levels after vascular occlusion as compared to corresponding controls, with a positive correlation between changes in p-eNOS and BDNF (r = 0.679). Exercise after vascular occlusion did not change levels of these proteins. Gyceryl trinitrate increased proBDNF and BDNF levels in brain slices, thus suggesting a possible causal relationship between NO and BDNF. Moreover, vascular occlusion, like exercise, resulted in increased TrkB and p-TrkB levels, whereas no change was observed with the combination of both. These results suggest that brain BDNF signaling may be dependent on cerebral endothelium-derived NO production.

Compound 21 is pro-angiogenic in the brain and results in sustained recovery after ischemic stroke

INTRODUCTION

Angiotensin II type 2 receptor (AT2R) stimulation is neuroprotective after experimental stroke. However, the therapeutic utility of AT2R stimulation has been hampered by the lack of a specific agonist with favourable bioavailability. Compound 21 (C21) - the first non-peptide AT2R agonist - offers a potential option to enhance stroke recovery. This study aimed to investigate the effect of C21 administration on early and late stroke outcomes, and the molecular mediators involved.

METHODS

Rats were subjected to 3 h or 90 min of middle cerebral artery occlusion (MCAO) and randomized to intraperitoneal C21 (0.03 mg/kg) or saline at reperfusion. Animals were sacrificed at 24 h or 7 days and brains were collected for molecular analysis and immunostaining, respectively. Functional outcome at days 1, 4 and 7 was assessed blindly. C21 angiogenic potential was assessed in vitro.

RESULTS

After 3 h of MCAO, C21 treatment reduced infarct size and improved behavioural outcome at 24 h without affecting blood pressure. Co-administration of the AT2R antagonist (PD123319) blocked these effects. On the molecular level, C21 decreased brain haemoglobin content, down-regulated apoptotic and oxidative markers, and increased pro-survival molecules in the brain. After 90 min of MCAO, C21 treatment resulted in sustained functional improvement at 7 days, together with increased vascular density in the ischemic penumbra. In vitro, C21 showed a pro-angiogenic effect that was blocked with brain-derived neurotrophic factor neutralization.

CONCLUSION

These findings demonstrate that a single dose of C21 is neurovascular-protective and improves stroke outcome possibly through increasing neurotrophin activity, mitigating brain inflammation, and promoting antioxidant and pro-angiogenic effects.

Atorvastatin treatment is associated with increased BDNF level and improved functional recovery after atherothrombotic stroke

BACKGROUND

Statins have a positive impact on ischemic stroke outcome. It has been reported that statin have neuroprotective function after ischemic stroke in addition to lipid-lowering effect in animal model. However, the neuroprotective function of statin after stroke has not been confirmed in clinical studies. The aim of this study was to evaluate in a clinical model if statins induce neuroprotection after stroke. We, therefore, assessed serum brain-derived neurotrophic factor (BDNF) levels and functional recovery in atherothrombotic stroke patients and investigated their relationship with atorvastatin treatment.

METHODS

Seventy-eight patients with atherothrombotic stroke were enrolled and randomly assigned to atorvastatin treatment group or placebo control group. Neurological function after stroke was assessed with the National Institutes of Health Stroke Scale, modified Rankin Scale (mRS) and Barthel Index (BI). The serum BDNF levels were both measured at 1 day and 6 weeks after stroke. Linear regression was used to assess the association between BDNF levels and neurological function scores.

RESULTS

The mRS and BI were markedly improved in the atorvastatin group when compared to placebo at 6 weeks after stroke. The serum BDNF levels in atorvastatin group were significantly elevated by 6 weeks after stroke and higher than the BDNF levels in controls. In addition, the serum BDNF levels significantly correlated with mRS and BI after stroke. Our results demonstrated that atorvastatin treatment was associated with the increased BDNF level and improved functional recovery after atherothrombotic stroke.

CONCLUSION

This study indicates that atorvastatin-related elevation in the BDNF level may promote functional recovery in stroke patients.

14,15-epoxyeicosatrienoic acid promotes production of brain derived neurotrophic factor from astrocytes and exerts neuroprotective effects during ischaemic injury

AIMS

14,15-Epoxyeicosatrienoic acid (14,15-EET) is abundantly expressed in brain and exerts protective effects against ischaemia. 14,15-EET is hydrolysed by soluble epoxide hydrolase (sEH). sEH^-/- mice show a higher level of 14,15-EET in the brain. Astrocytes play a pivotal role in neuronal survival under ischaemic conditions. However, it is unclear whether the neuroprotective effect of 14,15-EET is associated with astrocytes.

METHODS

A mouse model of focal cerebral ischaemia was induced by middle cerebral artery occlusion. Oxygen-glucose deprivation/reoxygenation (OGD/R) was performed on cultured murine astrocytes, neurons and a human cell line. Cell viabilities were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The mRNA expressions were quantified by real-time PCR. Brain derived neurotrophic factor (BDNF) concentration was measured by ELISA. Protein expressions were quantified by Western blotting. BDNF and peroxisome proliferators-activated receptor gamma (PPAR-γ) expressions were analysed by confocal microscopy.

RESULTS

Decreased infarct volumes, elevated BDNF expression and increased numbers of BDNF/GFAP Glial Fibrillary Acidic Protein double-positive cells were observed in the ischaemic penumbra of sEH^-/- mice. The decreased infarct volumes of sEH^-/- mice were diminished by intracerebroventricular injection of a blocker of BDNF receptor. 14,15-EET increases BDNF expression and cell viability of murine astrocytes and U251 cells by BDNF-TrkB Tyrosine receptor kinase-B-extracellular signal-regulated kinase 1/2 signalling during OGD/R. 14,15-EET protects neurons from OGD/R by stimulating the production of astrocyte-derived BDNF. 14,15-EET stimulates the production of astrocyte-derived BDNF through PPAR-γ/p-cAMP-response element binding protein signal pathways.

CONCLUSIONS

Our study demonstrates the importance of 14,15-EET-mediated production of astrocyte-derived BDNF for enhancing viability of astrocytes and protecting neurons from the ischaemic injury and provides insights into the mechanism by which 14,15-EET is involved in neuroprotection.

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.

Considerations for the Optimization of Induced White Matter Injury Preclinical Models

White matter (WM) injury in relation to acute neurologic conditions, especially stroke, has remained obscure until recently. Current advances in imaging technologies in the field of stroke have confirmed that WM injury plays an important role in the prognosis of stroke and suggest that WM protection is essential for functional recovery and post-stroke rehabilitation. However, due to the lack of a reproducible animal model of WM injury, the pathophysiology and mechanisms of this injury are not well studied. Moreover, producing selective WM injury in animals, especially in rodents, has proven to be challenging. Problems associated with inducing selective WM ischemic injury in the rodent derive from differences in the architecture of the brain, most particularly, the ratio of WM to gray matter in rodents compared to humans, the agents used to induce the injury, and the location of the injury. Aging, gender differences, and comorbidities further add to this complexity. This review provides a brief account of the techniques commonly used to induce general WM injury in animal models (stroke and non-stroke related) and highlights relevance, optimization issues, and translational potentials associated with this particular form of injury.

Neuroprotective role of an N-acetyl serotonin derivative via activation of tropomyosin-related kinase receptor B after subarachnoid hemorrhage in a rat model

N-[2-(5-hydroxy-1H-indol-3-yl) ethyl]-2-oxopiperidine-3-carboxamide (HIOC), an N-acetyl serotonin derivative, selectively activates tropomyosin-related kinase receptor B (TrkB). This study is to investigate a potential role of HIOC on ameliorating early brain injury after experimental subarachnoid hemorrhage (SAH). One hundred and fifty-six adult male Sprague-Dawley rats were used. SAH model was induced by endovascular perforation. TrkB small interfering RNA (siRNA) or scramble siRNA was injected intracerebroventricularly 24h before SAH. HIOC was administrated intracerebroventricularly 3h after SAH and compared with brain-derived neurotrophic factor (BDNF). SAH grade and neurologic scores were evaluated for the outcome study. For the mechanism study, the expression of TrkB, phosphorylated TrkB (p-TrkB), phosphorylated extracellular signal regulated kinase (p-ERK), B-cell lymphoma 2 (Bcl-2) and cleaved caspase 3 (CC3) was detected by Western blots, and neuronal injury was determined by double immunofluorescence staining of neuronal nuclei and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling. Knocking down of TrkB decreased the expression of Bcl-2 and aggravated neurologic deficits 24h after SAH. HIOC activated TrkB/ERK pathway, decreased neuronal cell death, and improved neurobehavioral outcome, and these effects were abolished by TrkB siRNA. HIOC was more potent than BDNF in reduction of apoptosis 24h post-SAH. Thus, we conclude that administration of HIOC activated TrkB/ERK signaling cascade and attenuated early brain injury after SAH. HIOC may be a promising agent for further treatment for SAH and other stroke events.

Neuroinflammation and white matter pathology in schizophrenia: systematic review

BACKGROUND

Neuroinflammation and white matter pathology have each been independently associated with schizophrenia, and experimental studies have revealed mechanisms by which the two can interact in vitro, but whether these abnormalities simultaneously co-occur in people with schizophrenia remains unclear.

METHOD

We searched MEDLINE, EMBASE, PsycINFO and Web of Science from inception through 12 January 2014 for studies reporting human data on the relationship between microglial or astroglial activation, or cytokines and white matter pathology in schizophrenia.

RESULTS

Fifteen studies totaling 792 subjects (350 with schizophrenia, 346 controls, 49 with bipolar disorder, 37 with major depressive disorder and 10 with Alzheimer's disease) met all eligibility criteria. Five neuropathological and two neuroimaging studies collectively yielded consistent evidence of an association between schizophrenia and microglial activation, particularly in white rather than gray matter regions. Ultrastructural analysis revealed activated microglia near dystrophic and apoptotic oligodendroglia, demyelinating and dysmyelinating axons and swollen and vacuolated astroglia in subjects with schizophrenia but not controls. Two neuroimaging studies found an association between carrier status for a functional single nucleotide polymorphism in the interleukin-1β gene and abnormal white as well as gray matter volumes in schizophrenia but not controls. A neuropathological study found that orbitofrontal white matter neuronal density was increased in schizophrenia cases exhibiting high transcription levels of pro-inflammatory cytokines relative to those exhibiting low transcription levels and to controls. Schizophrenia was associated with decreased astroglial density specifically in subgenual cingulate white matter and anterior corpus callosum, but not other gray or white matter areas. Astrogliosis was consistently absent. Data on astroglial gene expression, mRNA expression and protein concentration were inconsistent.

CONCLUSION

Neuroinflammation is associated with white matter pathology in people with schizophrenia, and may contribute to structural and functional disconnectivity, even at the first episode of psychosis.

Hydrogen sulfide-releasing cyclooxygenase inhibitor ATB-346 enhances motor function and reduces cortical lesion volume following traumatic brain injury in mice

BACKGROUND

Traumatic brain injury (TBI) induces secondary injury mechanisms, including dynamic interplay between ischemic, inflammatory and cytotoxic processes. We recently reported that administration of ATB-346 (2-(6-methoxynapthalen- 2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester), a hydrogen sulfide-releasing cyclooxygenase inhibitor, showed marked beneficial effects in an animal model of spinal cord injury, significantly enhancing recovery of motor function and reducing the secondary inflammation and tissue injury.

METHODS

Here we evaluated the neuroprotective potential of ATB-346, a hydrogen sulfide-releasing derivative of naproxen, using the controlled cortical impact (CCI) injury model in mice, one of the most common models of TBI. Moreover, the aim of the present study was to carefully investigate molecular pathways and subtypes of glial cells involved in the protective effect of ATB-346 on inflammatory reaction associated with an experimental model of TBI. In these studies, TBI was induced in mice by CCI and mice were orally administered ATB-346, naproxen (both at 30 μmol/kg) or vehicle (dimethylsulfoxide:1% carboxymethylcellulose [5:95] suspension) one and six hours after brain trauma and once daily for 10 days.

RESULTS

Results revealed that ATB-346 attenuated TBI-induced brain edema, suppressed TBI-induced neural cell death and improved neurological function. ATB-346 also significantly reduced the severity of inflammation and restored neurotrophic factors that characterized the secondary events of TBI.

CONCLUSIONS

These data demonstrate that ATB-346 can be efficacious in a TBI animal model by reducing the secondary inflammation and tissue injury. Therefore, ATB-346 could represent an interesting approach for the management of secondary damage following CNS diseases, counteracting behavioral changes and inflammatory process.

Biological basis of neuroprotection and neurotherapeutic effects of Whole Body Periodic Acceleration (pGz)

Exercise is a well known neuroprotective and neurotherapeutic strategy in animal models and humans with brain injury and cognitive dysfunction. In part, exercise induced beneficial effects relate to endothelial derived nitric oxide (eNO) production and induction of the neurotrophins; Brain Derived Neurotrophic Factor (BDNF) and Glial Derived Neurotrophic Factor (GDNF). Whole Body Periodic Acceleration (WBPA (pGz), is the motion of the supine body headward to footward in a sinusoidal fashion, at frequencies of 100-160 cycles/min, inducing pulsatile shear stress to the vascular endothelium. WBPA (pGz) increases eNO in the cardiovascular system in animal models and humans. We hypothesized that WBPA (pGz) has neuroprotective and neurotherapeutic effects due to enhancement of biological pathways that include eNOS, BDNF and GDNF. We discuss protein expression analysis of these in brain of rodents. Animal and observational human data affirm a neuroprotective and neurotherapeutic role for WBPA (pGz). These findings suggest that WBPA (pGz) in addition to its well known beneficial cardiovascular effects can be a simple non-invasive neuroprotective and neurotherapeutic strategy with far reaching health benefits.