Current Neurovascular Research - Volume 14, Issue 4, 2017

Background: The regulation of cerebral arterial vasomotor tone involves several mechanisms. The role of sympathetic nerves and the adrenergic neurotransmitter, noradrenaline (NA), has been the subject of debate for decades. Moreover, the specific role of endothelin-1 (ET-1) in cerebral arterial vasoconstriction has not been elucidated to date. In this study, we evaluated the contribution of NA and ET-1 to cerebral artery vasoconstriction. Methods: Arterial responses of rat middle cerebral arteries, and human pial cerebral arteries to cumulative concentrations of NA and ET-1, and to Electrical Field Stimulation (EFS), were evaluated. To assess the role of NA and ET-1 when EFS was applied, experiments were performed in the presence of adrenergic, neurogenic, and endothelin-1 receptor modulators. Results: We found that vasoconstriction of cerebral arteries following EFS requires the application of exogenous NA, whereas neither EFS nor NA alone induced vasoconstriction. The observed vasoconstriction was abolished by α-adrenoreceptor antagonist, catecholamine-release inhibitor, blockade of the perivascular neurons, and by the endothelin-2 receptor antagonist (BQ123). Conclusion: Based on our results, cerebral artery vasoconstriction requires simultaneous neurogenic and adrenergic activation and is ET-1 dependent. We hypothesize that NA modulates the release of ET-1. Upon release, ET-1 binds to the ETA-receptor on smooth muscle cells inducing cerebral artery vasoconstriction.

Background: High prevalence of valve absence was found in the internal jugular vein (IJV) of healthy volunteers by means of M-mode high-resolution Echo Colour Doppler (ECD). However, the prevalence of valve in neurovascular disorders linked to Chronic Cerebrospinal Venous Insufficiency (CCSVI) is still unknown. Methods: A cohort of 83 Healthy Controls (HC), 71 Multiple Sclerosis (MS), 99 Inner Ear Disorders (IED) underwent ECD investigation of the IJV valve, including M-mode evaluation and related hemodynamics. The primary outcome measure was characterization of valve presence, morphology and motility, whereas the secondary outcome was the rate of flow alteration. Results: Bilateral valve presence was found in 38% of HC, 58% of MS and 25% of IED, whereas, bilateral valve absence was recorded in 16% of HC, 10% of MS and 31% of IED (p<0.003). Bicuspid morphology was more prevalent in HC 56%, while monocusp was more prevalent in patients: 75% MS and 57% IED (p<0.0001). The main finding was the presence of mobile valve leaflets in 98% of HC, contrarily fixed valve leaflets were recorded in 82% of MS and in 41% of IED, p< 0.0001. Finally, by stratifying the entire cohort according to the presence of mobile and not mobile valve leaflets, normal monodirectional and phasic flow were commonly found in the mobile leaflets subgroup, p<0.0001. Conclusion: In patients with miscellaneous neurological disorders, a significant higher rate of defective valves was found with respect to HC. The latter condition is strongly associated to brain outflow abnormalities described in CCSVI condition.

Background: Recent studies have provided evidence that microRNAs (miRNAs), as a potential biomarker, were involved in the regulation of gene expression in Myocardial Infarction (MI). This study aimed to highlight the role of salvianolate on cardiomyocyte apoptosis in MI. Methods: Anterior descending branch of left coronary artery was ligated to set up MI model. MiR- 122-5p mimic was transfected into cardiomyocytes and verified by quantitative real-time PCR (qRT-PCR). Cell viability and apoptotic rate were measured by MTT assay and flow cytometry together with TUNEL method, respectively. Changes in the expression of caspase-3, Bax and Bcl-2 were quantified by qRT-PCR and western blot. Results: After treatment with salvianolate, miR-122-5p expression and caspases-3 activity significantly decreased in rat myocardial tissues. Furthermore, cardiomyocytes apoptosis rate was obviously suppressed while cell viability dramatically increased in H9C2 cardiomyocytes. However, overexpression of miR-122-5p reversed the aforementioned trends. Simultaneously, it could also mitigate the anti-apoptosis effect of salvianolate on the upregulation of caspases-3 viability and Bax expression and downregulation of Bcl-2 expression. Conclusion: Salvianolate induces the anti-apoptosis mechanism of cardiomyocytes via downregulation of miR-122-5p, Bax expression and caspases-3 as well as upregulation of Bcl-2 expression. In contrast, overexpression of miR-122-5p inhibits the effect of salvianolate.

Background: MircroRNA (MiRNA) levels are associated with disease pathophysiology and are high in plasma exosomes. Plasma exosomal miRNAs serve as potential therapeutic targets and diagnosis biomarkers in some diseases but few studies have examined them in Ischemic Stroke (IS). Therefore, we explored the potential predictive value of plasma exosomal miR-422a and miR-125b-2-3p in different IS phases (acute and subacute phases). Methods: Fifty-five IS patients and 25 age and sex matched healthy controls were recruited. Patients were classified into two groups: 27 patients in acute phase (days 1-3) and 28 patients in subacute phase (days 4-14). The plasma exosomal levels of miR-422a and miR-125b-2-3p were examined via quantitative real-time polymerase chain reaction (qRT-PCR). The Areas Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve were constructed to evaluate the diagnostic accuracy of these miRNAs in IS. Results: The expression levels of plasma exosomal miR-422a and miR-125b-2-3p were significantly decreased in the subacute phase group (P&<0.001, P&<0.001, respectively), and the miR-422a levels were increased in the acute phase group (P&<0.005) as compared to the controls. Additionally, the expression levels of plasma exosomal miR-422a and miR-125b-2-3p were significantly decreased in the subacute phase group than in the acute phase group (P&<0.001, P&<0.005, respectively). ROC analysis showed high AUC values for miR-422a and miR-125b-2-3p in the subacute phase group as compared to those in healthy controls: 0.971 and 0.889, respectively, and miR-422a in the acute phase group as compared to healthy controls were 0.769. Conclusion: Plasma exosomal miR-422a and miR-125b-2-3p may serve as blood-based biomarkers for monitoring and diagnosing in IS patients, with plasma exosomal miR-422a showing the best diagnostic value. The use of these two plasma exosomal miRNAs in combination may be powerful for determining IS stage.

Background: Acute Ischemic Stroke (AIS) represents an economic challenge for health systems all over the globe. Changes of neuroactive steroids have been found in different neurological diseases. We have previously demonstrated that old patients with AIS show changes of plasma cortisol and estradiol concentrations, in that increased steroid levels are associated with a deterioration of neurological status and a worse cognitive decline. Objective: The present study assessed in patients with AIS if changes of behavior, Brain-Derived Neurotrophic Factor (BDNF) and Nitrites (NO-2) bear a relationship with the degree of hypercortisolism. Methods: We recruited patients hospitalized within the first 24 hours of AIS. Subjects were divided into two groups, each one composed of 40 control subjects and 40 AIS patients, including men and women. The neurological condition was assessed using the National Institute of Health Stroke Scale (NIHSS) and the cognitive status with the Montreal Cognitive Assessment (MoCA). The emotional status was evaluated using the Montgomery-Asberg Depression Rating Scale (MADRS), whereas the Modified Rankin Scale (MRS) was used to determine the functional condition. BDNF and NO-2 plasma levels were measured by ELISA and the Griess reaction method, respectively. Results: We found that in AIS patients, increased plasma cortisol was negatively correlated with plasma BDNF and NO-2 levels, neurological condition, cognition, functional responses and emotional status, suggesting a relationship between the declines of clinical, behavioral and blood parameters with stress-induced cortisol elevation. Conclusion: Nitrites and BDNF may represent potential biomarkers for cortisol negative effects on the area of cerebral ischemia and penumbra, potentiating ischemic cell damage.

Background: The time to maximum of the residue function (TMax) has been employed to identify the penumbra in acute ischemic stroke. Cognitive impairment in patients with Carotid Artery Stenosis (CAS) has been attributed to chronic cerebral hypoperfusion. The study aimed to examine whether cognitive impairment can be detected based on a preliminary TMax cutoff in patients with unilateral CAS. Methods: Fifty unilateral CAS patients underwent dynamic susceptibility contrast MR perfusion. The preliminary TMax cutoff (3 seconds) was derived on the basis of the upper limit of 95% confidence interval of TMax in the Middle Cerebral Artery (MCA) contralateral to the CAS side. All patients were allocated to the Right-delayed group (n=18), Left-delayed group (n=12), and Nondelayed group (n=20) by the cutoff. Cognitive assessment was also administered on all patients and 22 healthy volunteers. Results: No significant interhemispheric mean TMax differences of the Non-delayed group were noted (p=0.75), but the mean TMax of ipsilateral MCA was significantly longer than that of the contralateral MCA of the Left- and Right-delayed groups (ps&<0.001), respectively. Compared to healthy volunteers, the Right-delayed group performed significantly worse on most of the visuospatial tests (ps&<0.04), while the Left-delayed group performed significantly worse on most of the verbal tests (ps&<0.05). The performance of the Non-delayed group on all cognitive domains was similar to that of healthy volunteers (ps>0.07). Conclusion: TMax can be used to differentiate the chronic hypoperfusion state in unilateral CAS patients. Prolonged TMax in the MCA of either hemisphere may lead to lateralized impairment in cognition functions in patients with unilateral CAS.

Background: Postoperative Cognitive Dysfunction (POCD) has received considerable attention as one of the main postoperative complications. The underlying mechanism of POCD in elderly subjects has not been fully elucidated to date. The Central Nervous System (CNS) is isolated from the bloodstream by the Blood Brain Barrier (BBB) that consists of endothelial cells, capillary blood vessels and tight junctions. The tight junctions carry out significant biological functions that are associated with the CNS and blood circulation. Methods: In this review, I present a hypothesis that blood-brain barrier disruption leads to postoperative cognitive dysfunction. A total of 81 healthy male Wistar rats were used for the present study. All the experimental animals were randomly divided into 3 groups: normal control group, isoflurane group and splenectomy group. The control group was not subjected to any form of treatment. The rats in isoflurane group were given 1.5-2% isoflurane under intubation and mechanical ventilation. The rats in splenectomy group underwent splenectomy under the same anesthesia as the isoflurane group. The Morris water maze was used to examine the learning and memory ability of the animals. The expression of the Tight Junctions Proteins (TJPs) in the hippocampus was analyzed using Western blotting. The concentration of Evans Blue (EB) in the supernatant was analyzed using UV spectroscopy. Ultrastructure changes in the basal laminas, the Tight Junctions (TJs), mitochondria and the endoplasmic reticulum surrounding the capillaries were assessed by Transmission Electron Microscopy (TEM). Results: Following splenectomy, the rats displayed concomitant significant cognitive deficits in the Morris water maze test. Taken together, the results indicate that the expression levels of occludin (65KD) following splenectomy were reduced on days one and three in aged rats. No significant difference was noted in the expression levels of claudin-5, except for a reduction after surgery on day one. The leakage of EB was higher following splenectomy than control group and isoflurane group. The ultrastructure of the neurovascular unit was monitored on the day prior to surgery and on the 1st, 3rd and 7th day following surgery using a transmission electronmicroscope. Conclusion: The alterations in the levels of tight junction proteins following splenectomy may contribute to the BBB permeability increase, which in turn will induce postoperative cognitive dysfunction.

Background: Constraint-Induced Movement Therapy (CIMT) is one efficient approach to improve functional recovery after ischemic stroke. The underlying molecular mechanism remains unclear. In the current study, we investigated the effects of CIMT on angiogenesis and neurogenesis. To start linking our findings to molecular mediators, we further examined the expression of Hypoxia-Inducible Factor-1α (HIF-1α), Factor Inhibiting HIF-1 (FIH-1) and Vascular Endothelial Growth Factor (VEGF). Methods: Rats were randomly assigned into three groups: a Middle Cerebral Artery Occlusion group (MCAO), a therapeutic group (CIMT+MCAO), and a sham middle cerebral artery occlusion group (Sham). Seven days after surgery, a plaster cast was placed around the unimpaired upper limb of the rats in the CIMT+MCAO group for 14 days. CIMT was performed on a horizontal ladder. Neurobehavioral consequences were evaluated using the Open-Field Test (OFT) and the Foot-Fault Test (FFT). The number of new neurons, the length of vessels as well as the expression of HIF-1α, FIH-1, and VEGF were examined before and after 14 days of CIMT. Results: The CIMT+MCAO group showed a significant increase in the total length of microvessels and increased number of Bromodeoxyuridine+ (BrdU+)/NeuN+ double-labeled cells. These changes were correlated with an increase in HIF-1α and VEGF expressions and a decrease in FIH-1expression. FFT showed that the CIMT+MCAO group exhibited marked improvement in neurobehavioral outcome when compared to the MCAO group. Adverse effects on total activities or anxiety were not observed using open field analysis. Conclusion: CIMT-induced neuroprotection and functional recovery following cerebral ischemia were possibly mediated by an increase in endogenous HIF-1α and VEGF expression with subsequent neurogenesis and angiogenesis.

Background: Cerebral Small Vessel Disease (SVD) can cause cognitive impairment, disability and dementia. While it is still unclear about the pathogenesis of SVD, several risk factors of SVD have been identified, and studies suggested that hypertension may play a critical role in SVD. Furthermore, studies have demonstrated that CYP2J2 isoform, 50 G>T variant, is associated with increasing the risk of ischemic stroke. Thus, we hypothesized that CYP2J2 50 G>T variant is associated with increased risk of cerebral SVD. Methods: Thus, in this case-control study, we evaluated the association of CYP2J2 polymorphisms with the susceptibility to cerebral SVD in a population of Chinese Han adults. Results: We found that CYP2J2 50 G>T genotype was significantly higher in SVD patients compared to healthy control group. Furthermore, 50 G>T genotype of CYP2J2 was associated with a significantly higher risk of SVD. Additionally, this polymorphism was significantly associated with WMH volume and a number of impaired cognitive domains in SVD patients. Conclusion: In conclusion, our study demonstrated that CYP2J2 50 G>T polymorphism is associated with increased risk of cerebral SVD in Han Chinese.

Background: Chronic Cerebral Hypoperfusion (CCH) is an important vascular risk factor for vascular-related dementia cognitive impairment and there are no effective measures for the prevention and treatment of cognitive deficit by CCH and the underlying mechanisms are still poorly understood. Methyl cytidine-phosphate-guanosine (CpG) binding protein 2 (MeCP2), regulated by microRNA 132 (miR-132), is as a transcriptional repressor in high concentrations in the brain, which regulates the expression of synaptic proteins and neuroplasticity, and may be involved in the cognitive deficit after CCH. But no relevant studies have been reported. The aim of this study is to investigate the status of MeCP2 expression after CCH and explore whether MeCP2 changes is associated with cognitive deficits after CCH. Methods: We investigated MeCP2 expression after CCH using Western blotting, quantitative Real- Time Polymerase Chain Reaction (qRT-PCR) analysis and immunofluorescence technique in a rat model of permanent bilateral common carotid artery occlusion (2VO) to mimic CCH. We determined the effect of MeCP2 expression on cognitive deficits and neuroplasticity after CCH through lenti-virus stereotaxic injection, the Morris water maze and electrophysiology. Results: CCH contributed to the down-regulation of MeCP2 and mecp2 expressions in the hippocampus and cortex. miR-132 up-regulated by 2VO was distinctly negatively correlated with MeCP2 down-regulation by miR-132 inhibitors. MeCP2 over-expression improved learning and memory impairment, as well as neuroplasticity after 2VO. Brain-Derived Neurotrophic Factor (BDNF) and the activities of its downstream pathways moleculars, tropomyosin receptor kinase B (TrkB) and the cAMP Response Element Binding Protein (CREB) were down-regulated by 2VO and rescued by MeCP2 over-expression. Conclusion: Our study found that miR-132 may participate in the down-regulation of MeCP2 after CCH and MeCP2 down-regulation was possibly involved in the cognitive deficit through regulation of BDNF and its downstream pathways after 2VO. Our findings expounded the underlying mechanisms of cognition deficit after CCH, which contributes to understanding the mechanisms of vascular dementia.

Background: Although the neuroprotective effect of sodium hydrosulfide (NaHS, a hydrogen sulfide donor) pretreatment has been revealed, the effect of NaHS post-conditioning remains largely unknown. Objective: We aimed to investigate the neuroprotective effect of NaHS post-conditioning against transient Global Cerebral Ischemia (tGCI)-induced hippocampal CA1 injury and its underlying molecular mechanism. Methods: A tGCI rat model was established using the four-vessel occlusion method for 15 min of ischemia. The survival of hippocampal neurons was determined by Nissl staining and NeuN immunostaining. Protein expression of potassium voltage-gated channel subfamily D member 2 (Kv4.2) and potassium channel interacting protein 3 (KChIP3) was assessed by Immunohistochemistry (IHC) and Western blot. Results: Decreased concentrations (12 and 24 μmol/kg) of NaHS post-conditioning significantly increased the numbers of survival neurons and NeuN-positive neurons in the hippocampal CA1 region at 7 days post-tGCI (all P&<0.05). NaHS post-conditioning (24 μmol/kg) at 12 and 24 hr posttGCI can achieve the best protective effect (both P&<0.05). IHC data demonstrated that NaHS postconditioning (24 μmol/kg) markedly attenuated tGCI-induced down-regulation of Kv4.2 protein in the hippocampal CA1 region at 26 hr post-tGCI. Confocal images showed that Kv4.2 did not express in the neuronal nuclei but predominantly express in the neuronal dendrites. In addition, NaHS post-conditioning significantly up-regulated Kv4.2 and down-regulated KChIP3 in tGCI rats at 26 and 168 hr post- tGCI (all P&<0.05). Conclusion: Decreased concentrations of NaHS post-conditioning at 12-24 hr post-tGCI effectively protected hippocampal CA1 neurons from tGCI-induced injury, which may be through regulating the expression of Kv4.2 and KChIP3.

Cystatin C (CysC), a cysteine protease inhibitor, has been widely proven to be a highly sensitive biomarker to predict the kidney function. The similarity of the renal and cerebral small vessels has awakened a surge of studies suggesting that CysC plays a key role in various cerebrovascular disorders. This review focuses on four major mechanisms of CysC in a variety of cerebrovascular diseases. (1) The property of the CysC Leu-68-Gln (L68Q) variant to aggregate and the property of the wild type CysC protein to co-aggregate with Amyloid-β (Aβ); (2) The disruption of equilibrium between CysC and related cysteine proteases; (3) The function of CysC as an inflammatory inducing factor; (4) The ability of CysC to induce autophagy. The combination of these CysC properties provides a well-supported novel biomarker for cerebrovascular diseases.

Background: With almost 47 million individuals worldwide suffering from some aspect of dementia, it is clear that cognitive loss impacts a significant proportion of the global population. Unfortunately, definitive treatments to resolve or prevent the onset of cognitive loss are limited. In most cases such care is currently non-existent prompting the need for novel treatment strategies. Methods: Mammalian forkhead transcription factors of the O class (FoxO) are one such avenue of investigation that offer an exciting potential to bring new treatments forward for disorders that involve cognitive loss. Here we examine the background, structure, expression, and function of FoxO transcription factors and their role in cognitive loss, programmed cell death in the nervous system with apoptosis and autophagy, and areas to target FoxOs for dementia and specific disorders such as Alzheimer's disease. Results: FoxO proteins work in concert with a number of other cell survival pathways that involve growth factors, such as erythropoietin and neurotrophins, silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), Wnt1 inducible signaling pathway protein 1 (WISP1), Wnt signaling, and cancer-related pathways. FoxO transcription factors oversee proinflammatory pathways, affect nervous system amyloid (Aβ) production and toxicity, lead to mitochondrial dysfunction, foster neuronal apoptotic cell death, and accelerate the progression of degenerative disease. However, under some scenarios such as those involving autophagy, FoxOs also can offer protection in the nervous system and reduce toxic intracellular protein accumulations and potentially limit Aβ toxicity. Conclusion: Given the ability of FoxOs to not only promote apoptotic cell death in the nervous system, but also through the induction of autophagy offer protection against degenerative disease that can lead to dementia, a fine balance in the activity of FoxOs may be required to target cognitive loss in individuals. Future work should yield exciting new prospects for FoxO proteins as new targets to treat the onset and progression of cognitive loss and dementia.