Cerebral microvessel responses to focal ischemia

Coupled pulsatile vascular and paravascular fluid dynamics in the human brain

BACKGROUND

Cardiac pulsation propels blood through the cerebrovascular network to maintain cerebral homeostasis. The cerebrovascular network is uniquely surrounded by paravascular cerebrospinal fluid (pCSF), which plays a crucial role in waste removal, and its flow is suspected to be driven by arterial pulsations. Despite its importance, the relationship between vascular and paravascular fluid dynamics throughout the cardiac cycle remains poorly understood in humans.

METHODS

In this study, we developed a non-invasive neuroimaging approach to investigate the coupling between pulsatile vascular and pCSF dynamics within the subarachnoid space of the human brain. Resting-state functional MRI (fMRI) and dynamic diffusion-weighted imaging (dynDWI) were retrospectively cardiac-aligned to represent cerebral hemodynamics and pCSF motion, respectively. We measured the time between peaks (∆TTP) ind d ϕ f M R I and dynDWI waveforms and measured their coupling by calculating the waveforms correlation after peak alignment (correlation at aligned peaks). We compared the ∆TTP and correlation at aligned peaks between younger [mean age: 27.9 (3.3) years, n = 9] and older adults [mean age: 70.5 (6.6) years, n = 20], and assessed their reproducibility within subjects and across different imaging protocols.

RESULTS

Hemodynamic changes consistently precede pCSF motion. ∆TTP was significantly shorter in younger adults compared to older adults (-0.015 vs. -0.069, p < 0.05). The correlation at aligned peaks were high and did not differ between younger and older adults (0.833 vs. 0.776, p = 0.153). The ∆TTP and correlation at aligned peaks were robust across fMRI protocols (∆TTP: -0.15 vs. -0.053, p = 0.239; correlation at aligned peaks: 0.813 vs. 0.812, p = 0.985) and demonstrated good to excellent within-subject reproducibility (∆TTP: intraclass correlation coefficient = 0.36; correlation at aligned peaks: intraclass correlation coefficient = 0.89).

CONCLUSION

This study proposes a non-invasive technique to evaluate vascular and paravascular fluid dynamics. Our findings reveal a consistent and robust cardiac pulsation-driven coupling between cerebral hemodynamics and pCSF dynamics in both younger and older adults.

The relationship between ischemic penumbra progression and the oxygen content of cortex microcirculation in acute ischemic stroke

The precise oxygen content thresholds of ischemic deep parenchymal (OCIDP) and that in cortical microcirculation (OCCM), which leads to ischemic penumbra converting into the infarcted core, remain uncertain. This study employed an invasive fiber-optic oxygen meter and a newly developed oxygen-responsive probe called RuA3-Cy5-rtPA (RC-rtPA) based on recombinant tissue-type plasminogen activator (rtPA) to examine the oxygen content thresholds. A mouse model of middle cerebral artery occlusion was generated and animals were randomly divided into a sham, 24-h reperfusion after 3-h ischemia (IR 3-h), and IR 6-h groups, all of which were sacrificed following reperfusion. Stroke severity was evaluated based on the infarction area, neurological symptoms, microcirculation perfusion, and microemboli in microcirculation. OCIDP was characterized based on its extent and distribution, whereas OCCM was measured using RC-rtPA. During ischemia, stroke severity escalation manifested as increasing infarction area, severe neurologic symptoms, and poorer microcirculation perfusion with more microthrombi depositions. OCIDP presented rapid decline following artery occlusion along with a gradual increase in the hypoxic area. Within 3 ​h following ischemia induction, the ischemic tissue that experienced hypoxia could be rescued, and this reversibility would disappear after 6 ​h. Within 6 ​h, OCCM continued to decrease. A significant decrease in oxygen content in cortical venules and cortical parenchyma was observed. These findings assist in establishing the extent of the ischemic penumbra at the microcirculation level and offer a foundation for assessing the ischemic penumbra that could respond positively to reperfusion therapy beyond the typical time window.

Reprint of: Fibrinolytic and Non-fibrinolytic Roles of Tissue-type Plasminogen Activator in the Ischemic Brain

The neurovascular unit (NVU) is assembled by endothelial cells (ECs) and pericytes, and encased by a basement membrane (BM) surveilled by microglia and surrounded by perivascular astrocytes (PVA), which in turn are in contact with synapses. Cerebral ischemia induces the rapid release of the serine proteinase tissue-type plasminogen activator (tPA) from endothelial cells, perivascular astrocytes, microglia and neurons. Owning to its ability to catalyze the conversion of plasminogen into plasmin, in the intravascular space tPA functions as a fibrinolytic enzyme. In contrast, the release of astrocytic, microglial and neuronal tPA have a plethora of effects that not always require the generation of plasmin. In the ischemic brain tPA increases the permeability of the NVU, induces microglial activation, participates in the recycling of glutamate, and has various effects on neuronal survival. These effects are mediated by different receptors, notably subunits of the N-methyl-D-aspartate receptor (NMDAR) and the low-density lipoprotein receptor-related protein-1 (LRP-1). Here we review data on the role of tPA in the NVU under non-ischemic and ischemic conditions, and analyze how this knowledge may lead to the development of potential strategies for the treatment of acute ischemic stroke patients.

Near-Infrared II Photobiomodulation Preconditioning Ameliorates Stroke Injury via Phosphorylation of eNOS

BACKGROUND

The current management of patients with stroke with intravenous thrombolysis and endovascular thrombectomy is effective only when it is timely performed on an appropriately selected but minor fraction of patients. The development of novel adjunctive therapy is highly desired to reduce morbidity and mortality with stroke. Since endothelial dysfunction is implicated in the pathogenesis of stroke and is featured with suppressed endothelial nitric oxide synthase (eNOS) with concomitant nitric oxide deficiency, restoring endothelial nitric oxide represents a promising approach to treating stroke injury.

METHODS

This is a preclinical proof-of-concept study to determine the therapeutic effect of transcranial treatment with a low-power near-infrared laser in a mouse model of ischemic stroke. The laser treatment was performed before the middle cerebral artery occlusion with a filament. To determine the involvement of eNOS phosphorylation, unphosphorylatable eNOS S1176A knock-in mice were used. Each measurement was analyzed by a 2-way ANOVA to assess the effect of the treatment on cerebral blood flow with laser Doppler flowmetry, eNOS phosphorylation by immunoblot analysis, and stroke outcomes by infarct volumes and neurological deficits.

RESULTS

Pretreatment with a 1064-nm laser at an irradiance of 50 mW/cm2 improved cerebral blood flow, eNOS phosphorylation, and stroke outcomes.

CONCLUSIONS

Near-infrared II photobiomodulation could offer a noninvasive and low-risk adjunctive therapy for stroke injury. This new modality using a physical parameter merits further consideration to develop innovative therapies to prevent and treat a wide array of cardiovascular diseases.

The Role of Neutrophils in Multiple Sclerosis and Ischemic Stroke

Inflammation plays an important role in numerous central nervous system (CNS) disorders. Its role is ambiguous-it can induce detrimental effects, as well as repair and recovery. In response to injury or infection, resident CNS cells secrete numerous factors that alter blood-brain barrier (BBB) function and recruit immune cells into the brain, like neutrophils. Their role in the pathophysiology of CNS diseases, like multiple sclerosis (MS) and stroke, is highly recognized. Neutrophils alter BBB permeability and attract other immune cells into the CNS. Previously, neutrophils were considered a homogenous population. Nowadays, it is known that various subtypes of these cells exist, which reveal proinflammatory or immunosuppressive functions. The primary goal of this review was to discuss the current knowledge regarding the important role of neutrophils in MS and stroke development and progression. As the pathogenesis of these two disorders is completely different, it gives the opportunity to get insight into diverse mechanisms of neutrophil involvement in brain pathology. Our understanding of the role of neutrophils in CNS diseases is still evolving as new aspects of their activity are being unraveled. Neutrophil plasticity adds another level to their functional complexity and their importance for CNS pathophysiology.

Fibrinolytic and Non-fibrinolytic Roles of Tissue-type Plasminogen Activator in the Ischemic Brain

The neurovascular unit (NVU) is assembled by endothelial cells (ECs) and pericytes, and encased by a basement membrane (BM) surveilled by microglia and surrounded by perivascular astrocytes (PVA), which in turn are in contact with synapses. Cerebral ischemia induces the rapid release of the serine proteinase tissue-type plasminogen activator (tPA) from endothelial cells, perivascular astrocytes, microglia and neurons. Owning to its ability to catalyze the conversion of plasminogen into plasmin, in the intravascular space tPA functions as a fibrinolytic enzyme. In contrast, the release of astrocytic, microglial and neuronal tPA have a plethora of effects that not always require the generation of plasmin. In the ischemic brain tPA increases the permeability of the NVU, induces microglial activation, participates in the recycling of glutamate, and has various effects on neuronal survival. These effects are mediated by different receptors, notably subunits of the N-methyl-D-aspartate receptor (NMDAR) and the low-density lipoprotein receptor-related protein-1 (LRP-1). Here we review data on the role of tPA in the NVU under non-ischemic and ischemic conditions, and analyze how this knowledge may lead to the development of potential strategies for the treatment of acute ischemic stroke patients.

Progressive microvascular failure in acute ischemic stroke: A systematic review, meta-analysis, and time-course analysis

This systematic review, meta-analysis, and novel time course analysis examines microvascular failure in the treatment of acute ischemic stroke (AIS) patients undergoing endovascular therapy (EVT) and/or thrombolytic administration for stroke management. A systematic review and meta-analysis following PRIMSA-2020 guidelines was conducted along with a novel curve-of-best fit analysis to elucidate the time-course of microvascular failure. Scopus and PubMed were searched using relevant keywords to identify studies that examine recanalization and reperfusion assessment of AIS patients following large vessel occlusion. Meta-analysis was conducted using a random-effects model. Curve-of-best-fit analysis of microvascular failure rate was performed with a negative exponential model. Twenty-seven studies with 1151 patients were included. Fourteen studies evaluated patients within a standard stroke onset-to-treatment time window (≤6 hours after last known normal) and thirteen studies had an extended time window (>6 hours). Our analysis yields a 22% event rate of microvascular failure following successful recanalization (95% CI: 16-30%). A negative exponential curve modeled a microvascular failure rate asymptote of 28.5% for standard time window studies, with no convergence of the model for extended time window studies. Progressive microvascular failure is a phenomenon that is increasingly identified in clinical studies of AIS patients undergoing revascularization treatment.

Probiotics Show Promise as a Novel Natural Treatment for Neurological Disorders

Probiotics are beneficial microorganisms shown to improve human health when consumed regularly and in sufficient quantities. Numerous health benefits can be attained by possessing important metabolites with nutritional and medicinal qualities. It has been shown through scientific research that these living microbial consortiums can influence a variety of mental health outcomes, including but not limited to anxiety, depression, cognitive processes, stress responses, and behavioral patterns. Selected strains of bacteria and yeasts control how the central nervous system (CNS) communicates with the gut-brain axis (GBA) through neuronal, humoral, and metabolic pathways to ease mood. Psychobiotics are substances that can affect the digestive system as well as mood and anxiety. There is scant evidence to validate the beneficial effects of psychiatric drugs in treating neurological diseases or disorders. The therapeutic method of research into psychobiotics opens exciting prospects for the future of the field of development. This review compiles the current evidence available in the scientific literature on the use of probiotics to influence neurological disorders.

No-reflow phenomenon in stroke patients: A systematic literature review and meta-analysis of clinical data

BACKGROUND

The no-reflow phenomenon refers to the absence of microvascular reperfusion despite macrovascular reperfusion.

AIM

The aim of this analysis was to summarize the available clinical evidence on no-reflow in patients with acute ischemic stroke.

METHODS

A systematic literature review and a meta-analysis of clinical data on definition, rates, and impact of the no-reflow phenomenon after reperfusion therapy was carried out. A predefined research strategy was formulated according to the Population, Intervention, Comparison, and Outcome (PICO) model and was used to screen for articles in PubMed, MEDLINE, and Embase up to 8 September 2022. Whenever possible, quantitative data were summarized using a random-effects model.

RESULTS

Thirteen studies with a total of 719 patients were included in the final analysis. Most studies (n = 10/13) used variations of the Thrombolysis in Cerebral Infarction scale to evaluate macrovascular reperfusion, whereas microvascular reperfusion and no-reflow were mostly assessed on perfusion maps (n = 9/13). In one-third of stroke patients with successful macrovascular reperfusion (29%, 95% confidence interval (CI), 21-37%), the no-reflow phenomenon was observed. Pooled analysis showed that no-reflow was consistently associated with reduced rates of functional independence (odds ratio (OR), 0.21, 95% CI, 0.15-0.31).

CONCLUSION

The definition of no-reflow varied substantially across studies, but it appears to be a common phenomenon. Some of the no-reflow cases may simply represent remaining vessel occlusions, and it remains unclear whether no-reflow is an epiphenomenon of the infarcted parenchyma or causes infarction. Future studies should focus on standardizing the definition of no-reflow with more consistent definitions of successful macrovascular reperfusion and experimental set-ups that could detect the causality of the observed findings.

Risk Factors, Pathophysiologic Mechanisms, and Potential Treatment Strategies of Futile Recanalization after Endovascular Therapy in Acute Ischemic Stroke

Endovascular therapy is the first-line treatment for acute ischemic stroke. However, studies have shown that, even with the timely opening of occluded blood vessels, nearly half of all patients treated with endovascular therapy for acute ischemic stroke still have poor functional recovery, a phenomenon called "futile recanalization.". The pathophysiology of futile recanalization is complex and may include tissue no-reflow (microcirculation reperfusion failure despite recanalization of the occluded large artery), early arterial reocclusion (reocclusion of the recanalized artery 24-48 hours post endovascular therapy), poor collateral circulation, hemorrhagic transformation (cerebral bleeding following primary ischemic stroke), impaired cerebrovascular autoregulation, and large hypoperfusion volume. Therapeutic strategies targeting these mechanisms have been attempted in preclinical research; however, translation to the bedside remains to be explored. This review summarizes the risk factors, pathophysiological mechanisms, and targeted therapy strategies of futile recanalization, focusing on the mechanisms and targeted therapy strategies of no-reflow to deepen the understanding of this phenomenon and provide new translational research ideas and potential intervention targets for improving the efficacy of endovascular therapy for acute ischemic stroke.

Universal method for the isolation of microvessels from frozen brain tissue: A proof-of-concept multiomic investigation of the neurovasculature

The neurovascular unit, comprised of vascular cell types that collectively regulate cerebral blood flow to meet the needs of coupled neurons, is paramount for the proper function of the central nervous system. The neurovascular unit gatekeeps blood-brain barrier properties, which experiences impairment in several central nervous system diseases associated with neuroinflammation and contributes to pathogenesis. To better understand function and dysfunction at the neurovascular unit and how it may confer inflammatory processes within the brain, isolation and characterization of the neurovascular unit is needed. Here, we describe a singular, standardized protocol to enrich and isolate microvessels from archived snap-frozen human and frozen mouse cerebral cortex using mechanical homogenization and centrifugation-separation that preserves the structural integrity and multicellular composition of microvessel fragments. For the first time, microvessels are isolated from postmortem ventromedial prefrontal cortex tissue and are comprehensively investigated as a structural unit using both RNA sequencing and Liquid Chromatography with tandem mass spectrometry (LC-MS/MS). Both the transcriptome and proteome are obtained and compared, demonstrating that the isolated brain microvessel is a robust model for the NVU and can be used to generate highly informative datasets in both physiological and disease contexts.

Two-photon microscopy: application advantages and latest progress for in vivo imaging of neurons and blood vessels after ischemic stroke

Two-photon microscopy (TPM) plays an important role in the study of the changes of the two important components of neurovascular units (NVU) - neurons and blood vessels after ischemic stroke (IS). IS refers to sudden neurological dysfunction caused by focal cerebral ischemia, which is one of the leading causes of death and disability worldwide. TPM is a new and rapidly developing high-resolution real-time imaging technique used in vivo that has attracted increasing attention from scientists in the neuroscience field. Neurons and blood vessels are important components of neurovascular units, and they undergo great changes after IS to respond to and compensate for ischemic injury. Here, we introduce the characteristics and pre-imaging preparations of TPM, and review the common methods and latest progress of TPM in the neuronal and vascular research for injury and recovery of IS in recent years. With the review, we clearly recognized that the most important advantage of TPM in the study of ischemic stroke is the ability to perform chronic longitudinal imaging of different tissues at a high resolution in vivo. Finally, we discuss the limitations of TPM and the technological advances in recent years.

Angiogenesis after ischemic stroke

Owing to its high disability and mortality rates, stroke has been the second leading cause of death worldwide. Since the pathological mechanisms of stroke are not fully understood, there are few clinical treatment strategies available with an exception of tissue plasminogen activator (tPA), the only FDA-approved drug for the treatment of ischemic stroke. Angiogenesis is an important protective mechanism that promotes neural regeneration and functional recovery during the pathophysiological process of stroke. Thus, inducing angiogenesis in the peri-infarct area could effectively improve hemodynamics, and promote vascular remodeling and recovery of neurovascular function after ischemic stroke. In this review, we summarize the cellular and molecular mechanisms affecting angiogenesis after cerebral ischemia registered in PubMed, and provide pro-angiogenic strategies for exploring the treatment of ischemic stroke, including endothelial progenitor cells, mesenchymal stem cells, growth factors, cytokines, non-coding RNAs, etc.

Impaired intracranial venous outflow profiles are associated with poor outcome in stroke after reperfusion therapy: A hypoperfusion-matched intracranial venous scale

PURPOSE

Arterial blood flow provided prognostic information in acute ischemic stroke (AIS). However, part of the patients with favorable arterial blood flow still suffered from poor outcomes after reperfusion therapy. We aimed to verify the hypothesis that intracranial venous outflow profiles (both cortical and deep) within the hypoperfusion area were associated with clinical outcome in AIS patients who received reperfusion therapy.

METHOD

We performed a retrospective analysis of prospectively collected data from anterior circulation AIS patients. All patients underwent pretreatment CTP and received reperfusion therapy. We constructed a 5-point hypoperfusion-matched Intracranial Venous Scale (hypo-IVS) from the sum of the contrast enhancement degree (1, attenuated contrast enhancement; 0, complete contrast enhancement) of 4 typical veins (superficial middle cerebral vein, vein of Labbé, vein of Trolard, and internal cerebral vein) whose outflow territories had matched hypoperfusion. Logistic and ordinal regression were used to analyze the association between hypo-IVS and clinical outcome.

RESULTS

A total of 751 patients were included. Higher Hypo-IVS was significantly associated with poor outcome (3-month mRS of >2; OR = 1.194; 95 % CI: 1.014-1.407; p = 0.033). The adjusted ORs for poor outcome and high 24-hour NIHSS were 1.172 (95 %CI: 1.035-1.328; p = 0.012) and 1.176 (95 %CI: 1.030-1.330; p = 0.010) in ordinal regression, respectively. Hypo-IVS > 2 was an independent risk factor of poor outcome (75.2 % vs 40.8 %; OR = 1.932; 95 %CI: 1.158-3.224; p = 0.012).

CONCLUSIONS

Intracranial venous outflow profiles deliver prognostic information in AIS and the hypo-IVS is a helpful tool to predict clinical outcomes after reperfusion therapy.

Blocking of PI3-kinase beta protects against cerebral ischemia/reperfusion injury by reducing platelet activation and downstream microvascular thrombosis in rats

Phosphoinositide 3-kinase beta (PI3Kβ) plays an important role in platelet activation and thrombosis, but its role in stroke pathology remains unknown. In this study, we investigated whether inhibition of PI3Kβ protects against cerebral ischemia/reperfusion (I/R) injury by preventing circulating platelet activation and downstream microvascular thrombosis. We used a rat intraluminal filament model of transient middle cerebral artery occlusion (tMCAO) because the rapid restoration of cerebral blood flow to the ischemic area in both tMCAO and endovascular thrombectomy provides clinical relevance for this model. The results showed that TGX221, a selective PI3Kβ inhibitor, treatment immediately before the onset of reperfusion dose-dependently reduced infarct volume and improved neurological function. The protective effects were associated with blocking platelet activation and thrombotic response, thereby reducing downstream microvascular thrombosis, and maintaining reperfusion efficiency. These results suggest that PI3Kβ might be a promising target for treating downstream microvascular thrombosis induced by cerebral I/R injury and offer a novel adjunctive treatment to improve reperfusion therapy for acute ischemic stroke.

Impact of leukoaraiosis in patients with acute ischemic stroke treated with thrombectomy: a post hoc analysis of the DIRECT-MT trial

BACKGROUND

The influence of leukoaraiosis in patients with acute ischemic stroke (AIS) given intra-arterial treatment (IAT) with or without preceding intravenous thrombolysis (IVT) remains unknown.

OBJECTIVE

To assess the clinical and radiological outcomes of IAT in patients with or without leukoaraiosis.

METHODS

Patients of the direct mechanical thrombectomy trial (DIRECT-MT) whose leukoaraiosis grade could be assessed were included. DIRECT-MT was a randomized clinical trial performed in China to assess the effect of direct IAT compared with intravenous thrombolysis plus IAT. We employed the Age-Related White Matter Changes Scale for grading leukoaraiosis (ARWMC, 0 indicates no leukoaraiosis, 1-2 indicates mild-to-moderate leukoaraiosis, and 3 indicates severe leukoaraiosis) based on brain CT. The primary outcome was the score on the modified Rankin Scale (mRS) assessed at 90 days.

RESULTS

There were 656 patients in the trial, 649 patients who were included, with 432 patients without leukoaraiosis, and 217 (33.4%) patients with leukoaraiosis divided into mild-to-moderate (n=139) and severe groups (n=78). Leukoaraiosis was a predictor of a worse mRS score (adjusted OR (aOR)=0.7 (95% CI 0.5 to 0.8)) and higher mortality (aOR=1.4 (1.1 to 1.9)), but it was not associated with symptomatic intracranial hemorrhage (sICH) (aOR=0.9 (0.5 to 1.5)). IVT preceding IAT did not increase sICH risk for patients with no (aOR=1.4 (0.6 to 3.4)), mild-to-moderate (aOR=1.5 (0.3 to 7.8)), or severe (aOR=1.5 (0.1 to 21.3)) leukoaraiosis.

CONCLUSION

Patients with leukoaraiosis with AIS due to large vessel occlusion are at increased risk of a poor functional outcome after IAT but demonstrate similar sICH rates, and IVT preceding IAT does not increase the risk of sICH in Chinese patients with leukoaraiosis.

A review of stress-induced hyperglycaemia in the context of acute ischaemic stroke: Definition, underlying mechanisms, and the status of insulin therapy

The transient elevation of blood glucose produced following acute ischaemic stroke (AIS) has been described as stress-induced hyperglycaemia (SIH). SIH is common even in patients with AIS who have no previous diagnosis of diabetes mellitus. Elevated blood glucose levels during admission and hospitalization are strongly associated with enlarged infarct size and adverse prognosis in AIS patients. However, insulin-intensive glucose control therapy defined by admission blood glucose for SIH has not achieved the desired results, and new treatment ideas are urgently required. First, we explore the various definitions of SIH in the context of AIS and their predictive value in adverse outcomes. Then, we briefly discuss the mechanisms by which SIH arises, describing the dual effects of elevated glucose levels on the central nervous system. Finally, although preclinical studies support lowering blood glucose levels using insulin, the clinical outcomes of intensive glucose control are not promising. We discuss the reasons for this phenomenon.

Protective Effect of Beta-Carotene against Myeloperoxidase- Mediated Oxidative Stress and Inflammation in Rat Ischemic Brain Injury

Oxidative stress and inflammatory reaction play critical roles in ischemia/reperfusion (I/R) injury in the brain. β-carotene (βCAR) is a naturally occurring pigment present in fruits and vegetables that expresses antioxidant and anti-inflammatory activities. This study was conducted to investigate the involvement of Bcl2/Bax and NF-κB signaling pathways in the potential protective role of βCAR against brain injury in a middle cerebral artery occlusion (MCAO) rat model. A focal brain ischemia model was created for 2 h, followed by reperfusion. Rats were given 10 and 20 mg/kg of βCAR for 7 days orally before induction of ischemia, at the start of reperfusion, and 3 days after ischemia. Scores of neurological deficit were rated 24 h after induction of ischemia. Motor coordination and spontaneous coordinate activities were assessed using rotarod and activity cage, respectively. After 2 h of the last dose, the animals were killed and their brains were extracted for further examinations. The results of the study show that βCAR diminished the score of neurological deficits and ameliorated motor coordination, balance, and locomotor activity in the I/R control group. Further, βCAR resulted in diminution of malondialdehyde (MDA) and augmentation of reduced glutathione (GSH) contents, as well as the elevation of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) enzyme activities in the brain homogenates of I/R rats. βCAR treatment significantly reduced nuclear factor kappa B (NF-κB) brain content and myeloperoxidase (MPO) activity and ameliorated the histological alterations in the brain tissues. βCAR significantly suppressed Bcl-2-associated X protein (Bax) and caspase-3 expression, as well as upregulated B-cell lymphoma-2 (Bcl-2) expression, suggesting a neuroprotective potential via downregulating NF-kB and protecting the rat brain against the I/R-associated apoptotic injury.

The role of TIGAR in nervous system diseases

TP53-induced glycolysis and apoptosis regulator (TIGAR) mainly regulates pentose phosphate pathway by inhibiting glycolysis, so as to synthesize ribose required by DNA, promote DNA damage repair and cell proliferation, maintain cell homeostasis and avoid body injury. Its physiological functions include anti-oxidative stress, reducing inflammation, maintaining mitochondrial function, inhibiting apoptosis, reducing autophagy etc. This paper reviews the research of TIGAR in neurological diseases, including stroke, Parkinson’s disease (PD), Alzheimer’s disease (AD), seizures and brain tumors, aiming to provide reference for the development of new therapeutic targets.

Ischemic stroke: From pathological mechanisms to neuroprotective strategies

Ischemic stroke (IS) has complex pathological mechanisms, and is extremely difficult to treat. At present, the treatment of IS is mainly based on intravenous thrombolysis and mechanical thrombectomy, but they are limited by a strict time window. In addition, after intravenous thrombolysis or mechanical thrombectomy, damaged neurons often fail to make ideal improvements due to microcirculation disorders. Therefore, finding suitable pathways and targets from the pathological mechanism is crucial for the development of neuroprotective agents against IS. With the hope of making contributions to the development of IS treatments, this review will introduce (1) how related targets are found in pathological mechanisms such as inflammation, excitotoxicity, oxidative stress, and complement system activation; and (2) the current status and challenges in drug development.

Delayed CTP-Derived Deep Venous Outflow: A Novel Predictor of Striatocapsular Infarction after M1 Thrombectomy

BACKGROUND AND PURPOSE

Isolated striatocapsular infarction occurs commonly in patients with ischemic stroke following M1 thrombectomy. We aimed to explore the correlation between CTP-derived parameters of deep venous outflow at presentation and subsequent striatocapsular infarction in a retrospective cohort of such patients.

MATERIALS AND METHODS

TTP and peak enhancement were measured on CTP-derived time-attenuation curves of the internal cerebral and thalamostriate veins bilaterally. The difference in TTP (ΔTTP) and the relative decrease in venous enhancement between the ischemic and normal sides were calculated. NCCT performed 24 (SD, 12) hours postthrombectomy was used to determine tissue fate in the caudate head, caudate body, lentiform nucleus, and internal capsule. Striatocapsular ischemia (striatocapsular infarction-positive) was defined as infarction and striatocapsular injury as either infarction, contrast enhancement, or hemorrhagic transformation in ≥1 of these regions. A striatocapsular ischemia score was calculated (0 = no ischemic region, 1 = 1 ischemic region, 2 = ≥2 ischemic regions).

RESULTS

One hundred sixteen patients were included in the analysis. Sixty-one patients had striatocapsular infarction (striatocapsular infarction-positive). The mean thalamostriate ΔTTP was 1.95 (SD, 1.9) seconds for patients positive for striatocapsular infarction and 0.79 (SD, 2.1) for patients negative for it (P = .010). Results were similar for striatocapsular injury. The mean thalamostriate ΔTTP was 0.79 (SD, 2.1), 1.68 (SD, 1.4), and 2.05 (SD, 2) for striatocapsular infarction scores of 0, 1, and 2, respectively (P = .030).

CONCLUSIONS

CTP-derived thalamostriate ΔTTP is an excellent surrogate marker for striatocapsular infarction in patients post-M1 thrombectomy. The novel approach of extracting venous outflow parameters from CTP has numerous potential applications and should be further explored.

Endothelial caveolin-1 regulates cerebral thrombo-inflammation in acute ischemia/reperfusion injury

BACKGROUND

Thrombo-inflammation is an important checkpoint that orchestrates infarct development in ischemic stroke. However, the underlying mechanism remains largely unknown. Here, we explored the role of endothelial Caveolin-1 (Cav-1) in cerebral thrombo-inflammation.

METHODS

The correlation between serum Cav-1 level and clinical outcome was analyzed in acute ischemic stroke patients with successful recanalization. Genetic manipulations by endothelial-specific adeno-associated virus (AAV) and siRNA were applied to investigate the effects of Cav-1 in thrombo-inflammation in a transient middle cerebral artery occlusion (tMCAO) model. Thrombo-inflammation was analyzed by microthrombosis formation, myeloid cell infiltration, and endothelial expression of adhesion molecules as well as inflammatory factors.

FINDINGS

Reduced circulating Cav-1, with the potential to predict microembolic signals, was more frequently detected in recanalized stroke patients without early neurological improvement. At 24 h after tMCAO, serum Cav-1 was consistently reduced in mice. Endothelial Cav-1 was decreased in the peri-infarct region. Cav-1^-/- endothelium, with prominent barrier disruption, displayed extensive microthrombosis, accompanied by increased myeloid cell inflammatory infiltration after tMCAO. Specific enhanced expression of endothelial Cav-1 by AAV-Tie1-Cav-1 remarkably reduced infarct volume, attenuated vascular hyper-permeability and alleviated thrombo-inflammation in both wild-type and Cav-1^-/- tMCAO mice. Transcriptome analysis after tMCAO further designated Rxrg as the most significantly changed molecule resulting from the knockdown of Cav-1. Supplementation of RXR-γ siRNA reversed AAV-Tie1-Cav-1-induced amelioration of thrombo-inflammation without affecting endothelial tight junction.

INTERPRETATION

Endothelial Cav-1/RXR-γ may regulate infarct volume and neurological impairment, possibly through selectively controlling thrombo-inflammation coupling, in cerebral ischemia/reperfusion.

FUNDING

This work was supported by National Natural Science Foundation of China.

High neutrophil counts before endovascular treatment for acute basilar artery occlusion predict worse outcomes

Background and purpose

Ischemic stroke is related to inflammation. We investigated leukocyte counts, neutrophil counts, and NLR (neutrophil-to-lymphocyte ratio) to explore their prognostic potential and determine if high neutrophil counts before endovascular treatment (EVT) in patients with acute basilar artery occlusion (BAO) are associated with worse outcomes at 90 days post-EVT.

Methods

Leukocyte and neutrophil counts and NLR were determined in eligible patients from the Acute Basilar Artery Occlusion Study (BASILAR). Patients were divided into four groups according to leukocyte and neutrophil counts and NLR quartiles. The primary outcome was a favorable outcome based on the modified Rankin Scale (mRS: 0–3). The secondary outcome was functional independence (mRS 0–2). The safety outcome was mortality, and an unfavorable outcome was mRS 4–6. Successful reperfusion was mTICI (modified Thrombolysis in Cerebral Infarction) of 2b or 3. All the data were collected within 90 days after EVT.

Results

We enrolled 586 patients in the study. The leukocyte and neutrophil counts and NLR were significantly associated with clinical outcomes in all patients though no effects were seen in some intervals. Of these three parameters, the neutrophil count had the most significant impact, negatively affecting the outcome. The findings were similar in patients who were successfully recanalized.

Conclusion

Higher neutrophil counts predicted worse clinical outcomes 90 days after EVT. This finding supports the deleterious role of inflammation in patients with acute BAO despite EVT or successful recanalization.

ASPECTS-based net water uptake predicts poor reperfusion and poor clinical outcomes in patients with ischemic stroke

OBJECTIVE

To investigate the value of automated Alberta Stroke Program Early CT Score (ASPECTS)-based net water uptake (NWU) to predict tissue-level reperfusion status and 90-day functional outcomes in acute ischemic stroke (AIS) patients after reperfusion therapy.

METHODS

One hundred and twelve patients with AIS who received reperfusion therapy were enrolled. ASPECTS-NWU was calculated from admission CT (NWU_admission) and follow-up CT (NWU_FCT), and the difference (ΔNWU) was calculated. Tissue-level reperfusion status was evaluated via follow-up arterial spin labeling imaging. The relationship between ASPECTS-NWU and tissue-level reperfusion was evaluated. Predictors of 90-day unfavorable outcomes (modified Rankin Scale score > 2) were assessed by multivariate logistic regression analysis and receiver operating characteristic (ROC) curves.

RESULTS

Poor reperfusion was observed in 40 patients (35.7%) after therapy. Those patients had significantly elevated NWU_FCT (median, 14.15% vs. 8.08%, p = 0.018) and higher ΔNWU (median, 4.12% vs. -2.03%, p < 0.001), compared to patients with good reperfusion. High ΔNWU was a significant marker of poor reperfusion despite successful recanalization. National Institutes of Health Stroke Scale score at admission (odds ratio [OR], 1.11; 95% confidence interval [CI] 1.03-1.20, p = 0.007) and ΔNWU (OR, 1.07; 95% CI 1.02-1.13, p = 0.008) were independently associated with unfavorable outcomes. An outcome prediction model including both parameters yields an area under the curve of 0.762 (sensitivity 70.3%, specificity, 84.2%).

CONCLUSIONS

Elevated NWU_FCT and higher ΔNWU were associated with poor tissue-level reperfusion after therapy. Higher ΔNWU was an independent predictor of poor reperfusion and unfavorable neurological outcomes despite successful recanalization.

KEY POINTS

• ASPECTS-NWU may provide pathophysiological information about tissue-level reperfusion status and offer prognostic benefits for patients with AIS after reperfusion therapy. • Elevated NWU_FCT and higher ΔNWU were correlated with poor tissue-level reperfusion after therapy. • A higher ΔNWU is an independent predictor of poor reperfusion and 90-day unfavorable outcomes despite successful recanalization.

Polyphenols for the Treatment of Ischemic Stroke: New Applications and Insights

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Currently, the main therapeutic strategy involves the use of intravenous thrombolysis to restore cerebral blood flow to prevent the transition of the penumbra to the infarct core. However, due to various limitations and complications, including the narrow time window in which this approach is effective, less than 10% of patients benefit from such therapy. Thus, there is an urgent need for alternative therapeutic strategies, with neuroprotection against the ischemic cascade response after IS being one of the most promising options. In the past few decades, polyphenolic compounds have shown great potential in animal models of IS because of their high biocompatibility and ability to target multiple ischemic cascade signaling pathways, although low bioavailability is an issue that limits the applications of several polyphenols. Here, we review the pathophysiological changes following cerebral ischemia and summarize the research progress regarding the applications of polyphenolic compounds in the treatment of IS over the past 5 years. Furthermore, we discuss several potential strategies for improving the bioavailability of polyphenolic compounds as well as some essential issues that remain to be addressed for the translation of the related therapies to the clinic.

Intravenous tPA (Tissue-Type Plasminogen Activator) Correlates With Favorable Venous Outflow Profiles in Acute Ischemic Stroke

BACKGROUND

Intravenous tPA (tissue-type plasminogen activator) is often administered before endovascular thrombectomy (EVT). Recent studies have questioned whether tPA is necessary given the high rates of arterial recanalization achieved by EVT, but whether tPA impacts venous outflow (VO) is unknown. We investigated whether tPA improves VO profiles on baseline computed tomography (CT) angiography (CTA) images before EVT.

METHODS

Retrospective multicenter cohort study of patients with acute ischemic stroke due to large vessel occlusion undergoing EVT triage. Included patients underwent CT, CTA, and CT perfusion before EVT. VO profiles were determined by opacification of the vein of Labbé, sphenoparietal sinus, and superficial middle cerebral vein on CTA as 0, not visible; 1, moderate opacification; and 2, full. Pial arterial collaterals were graded on CTA, and tissue-level collaterals were assessed on CT perfusion using the hypoperfusion intensity ratio. Clinical and demographic data were determined from the electronic medical record. Using multivariable regression analysis, we determined the correlation between tPA administration and favorable VO profiles.

RESULTS

Seven hundred seventeen patients met inclusion criteria. Three hundred sixty-five patients received tPA (tPA+), while 352 patients were not treated with tPA (tPA-). Fewer tPA+ patients had atrial fibrillation (n=128 [35%] versus n=156 [44%]; P=0.012) and anticoagulants/antiplatelet treatment before acute ischemic stroke due to large vessel occlusion onset (n=130 [36%] versus n=178 [52%]; P<0.001) compared with tPA- patients. One hundred eighty-five patients (51%) in the tPA+ and 100 patients (28%) in the tPA- group exhibited favorable VO (P<0.001). Multivariable regression analysis showed that tPA administration was a strong independent predictor of favorable VO profiles (OR, 2.6 [95% CI, 1.7-4.0]; P<0.001) after control for favorable pial arterial CTA collaterals, favorable tissue-level collaterals on CT perfusion, age, presentation National Institutes of Health Stroke Scale, antiplatelet/anticoagulant treatment, history of atrial fibrillation and time from symptom onset to imaging.

CONCLUSIONS

In patients with acute ischemic stroke due to large vessel occlusion undergoing thrombectomy triage, tPA administration was strongly associated with the presence of favorable VO profiles.

Roles of Polymorphonuclear Neutrophils in Ischemic Brain Injury and Post-Ischemic Brain Remodeling

Following ischemic stroke, polymorphonuclear neutrophils (PMNs) are rapidly recruited to the ischemic brain tissue and exacerbate stroke injury by release of reactive oxygen species (ROS), proteases and proinflammatory cytokines. PMNs may aggravate post-ischemic microvascular injury by obstruction of brain capillaries, contributing to reperfusion deficits in the stroke recovery phase. Thus, experimental studies which specifically depleted PMNs by delivery of anti-Ly6G antibodies or inhibited PMN brain entry, e.g., by CXC chemokine receptor 2 (CXCR2) or very late antigen-4 (VLA-4) blockade in the acute stroke phase consistently reduced neurological deficits and infarct volume. Although elevated PMN responses in peripheral blood are similarly predictive for large infarcts and poor stroke outcome in human stroke patients, randomized controlled clinical studies targeting PMN brain infiltration did not improve stroke outcome or even worsened outcome due to serious complications. More recent studies showed that PMNs have decisive roles in post-ischemic angiogenesis and brain remodeling, most likely by promoting extracellular matrix degradation, thereby amplifying recovery processes in the ischemic brain. In this minireview, recent findings regarding the roles of PMNs in ischemic brain injury and post-ischemic brain remodeling are summarized.

Metabolic Contribution and Cerebral Blood Flow Regulation by Astrocytes in the Neurovascular Unit

The neurovascular unit (NVU) is a conceptual framework that has been proposed to better explain the relationships between the neural cells and blood vessels in the human brain, focused mainly on the brain gray matter. The major components of the NVU are the neurons, astrocytes (astroglia), microvessels, pericytes, and microglia. In addition, we believe that oligodendrocytes should also be included as an indispensable component of the NVU in the white matter. Of all these components, astrocytes in particular have attracted the interest of researchers because of their unique anatomical location; these cells are interposed between the neurons and the microvessels of the brain. Their location suggests that astrocytes might regulate the cerebral blood flow (CBF) in response to neuronal activity, so as to ensure an adequate supply of glucose and oxygen to meet the metabolic demands of the neurons. In fact, the adult human brain, which accounts for only 2% of the entire body weight, consumes approximately 20–25% of the total amount of glucose and oxygen consumed by the whole body. The brain needs a continuous supply of these essential energy sources through the CBF, because there are practically no stores of glucose or oxygen in the brain; both acute and chronic cessation of CBF can adversely affect brain functions. In addition, another important putative function of the NVU is the elimination of heat and waste materials produced by neuronal activity. Recent evidence suggests that astrocytes play pivotal roles not only in supplying glucose, but also fatty acids and amino acids to neurons. Loss of astrocytic support can be expected to lead to malfunction of the NVU as a whole, which underlies numerous neurological disorders. In this review, we shall focus on historical and recent findings with regard to the metabolic contributions of astrocytes in the NVU.

Protection of Vasoactive Intestinal Peptide on the Blood-Brain Barrier Dysfunction Induced by Focal Cerebral Ischemia in Rats

OBJECTIVE

To investigate the effects of vasoactive intestinal peptide on the blood brain barrier function after focal cerebral ischemia in rats.

MATERIALS AND METHODS

Rats were intracerebroventricular injected with vasoactive intestinal peptide after a two hours middle cerebral artery occlusion. Functional outcome was studied with the neurological severity score. The brain edema and the infarction were evaluated via histology. The blood brain barrier permeability was assessed using Evans Blue dye injection method. We also measure the apoptosis of brain microvascular endothelial cells and brain levels of B-cell leukemia-2 protein by immunohistochemical analysis and western blotting, respectively.

RESULTS

In contrast to the cases treated with vehicle at 72 h after middle cerebral artery occlusion, the treatment with vasoactive intestinal peptide significantly (P < 0.05) reduced the neurological severity score, the brain edema and infarct volume. The Evans Blue leakage and brain water content were obviously reduced (P < 0.05) in vasoactive intestinal peptide-treated rats compared with those of control rats at 72 and 96 h after stroke. In addition, vasoactive intestinal peptide decreased the numbers of terminal deoxynucleotidyl transferase-mediated dUTP-nick end labeling positive endothelial cells and increased the protein levels of B-cell leukemia-2 in the ischemic hemisphere at 72 h after ischemia.

CONCLUSIONS

Our data suggest that treatment with vasoactive intestinal peptide ameliorates the blood brain barrier function, contributing to reduce in brain damage both morphologically and functionally in the ischemic rat. This amelioration may be associated with attenuation in apoptosis of brain microvascular endothelial cells by increased B-cell leukemia-2 expression.

Effects of Natural Polyphenols on Oxidative Stress-Mediated Blood–Brain Barrier Dysfunction

The blood-brain barrier (BBB), which consists mainly of brain microvascular endothelial cells and astrocytes connected by tight junctions (TJs) and adhesion molecules (AMs), maintains the homeostatic balance between brain parenchyma and extracellular fluid. Accumulating evidence shows that BBB dysfunction is a common feature of neurodegenerative diseases, including stroke, traumatic brain injury, and Alzheimer’s disease. Among the various pathological pathways of BBB dysfunction, reactive oxygen species (ROS) are known to play a key role in inducing BBB disruption mediated via TJ modification, AM induction, cytoskeletal reorganization, and matrix metalloproteinase activation. Thus, antioxidants have been suggested to exert beneficial effects on BBB dysfunction-associated brain diseases. In this review, we summarized the sources of ROS production in multiple cells that constitute or surround the BBB, such as BBB endothelial cells, astrocytes, microglia, and neutrophils. We also reviewed various pathological mechanisms by which BBB disruption is caused by ROS in these cells. Finally, we summarized the effects of various natural polyphenols on BBB dysfunction to suggest a therapeutic strategy for BBB disruption-related brain diseases.

Borneol enhances the protective effect against cerebral ischemia/reperfusion injury by promoting the access of astragaloside IV and the components of Panax notoginseng saponins into the brain

BACKGROUND

Astragalus and Panax notoginseng are significant traditional Chinese medicines for treating ischemic stroke, with astragaloside IV (AST IV) and Panax notoginseng saponins (PNS) being the major effective compounds, respectively. These compounds can also be used in combination. We have previously shown that AST IV and PNS have an antagonistic effect on cerebral ischemia/reperfusion (I/R) injury, and the combination of these two drugs can elevate this effect; unfortunately, AST IV and PNS cannot easily enter the brain tissues through the blood brain barrier (BBB). Previous studies have confirmed that the combination of borneol with other agents could promote the penetration of the drug components through the BBB. However, it remains unclear whether borneol can promote entry of the active components of AST IV and PNS into the brain tissues and enhance their effect against cerebral ischemia.

OBJECTIVE

This study aimed to investigate the effects of a combination of borneol with AST IV and PNS against I/R injury and explore the mechanisms of borneol-promoting penetration of drug components into the BBB based on the drug transport of brain tissues.

METHODS

A rat model of focal cerebral I/R injury was established, and drugs, including borneol, AST IV, and PNS, as well as their combinations were intragastrically administered. Subsequently, drug efficacy was assessed, and the condition of AST IV and PNS active components (Rg1, Rb1, R1) delivered into the brain was analyzed. Moreover, BBB permeability was determined, and the expression of related drug transporters and their genes were evaluated.

RESULTS

After treatment with borneol, AST IV, PNS, AST Ⅳ+PNS, and borneol+AST Ⅳ+PNS after cerebral I/R, the neurological function deficit scores, cerebral infarct rate, and brain water content markedly decreased. The effects of the three-drug-combination were better than those of the drugs used alone and those of AST Ⅳ+PNS. Moreover, after I/R in rats, AST IV and the components of PNS (Rg1, Rb1, R1) were mainly found in the cerebral cortex and in the cerebellum, respectively, when used alone. Borneol combined with AST IV and PNS increased the contents of AST IV, Rb1, Rg1, and R1 in the cerebral cortex and in the cerebellum, thus, promoting the enrichment of active components to the cerebral cortex, especially to the affected side. In addition, following I/R, diffuse distribution of lanthanum particles in the basement membrane, intercellular and intracellular locations of rat brain tissues indicated BBB destruction and increase in permeability, which were alleviated in each drug group. The effects of borneol combined with AST IV and PNS were stronger than those of the drug single-used and those of the AST IV+PNS group. Finally, the expression of effluent transporters (ET) and their genes, including P-glycoprotein (P-gp), multidrug resistance protein (MRP)-1, MRP-2, MRP-4, and MRP-5 in brain tissues, strikingly increased after I/R. Borneol remarkedly down-regulated the protein expression of P-gp, MRP-2, and MRP-4 in the brain, whereas PNS down-regulated MRP-4 and MRP-5 protein expression. AST IV, AST IV+PNS, and bornoel+AST IV+PNS effectively decreased the expression of P-gp, MRP-2, MRP-4, and MRP-5 proteins. The effects of the three-drug combination were significantly greater than those of the drug single-used and AST IV+PNS groups. The expression of each ET gene manifested corresponding results. Meanwhile, PNS, AST IV+PNS, and bornoel+AST IV+PNS significantly inhibited the down-regulation of the uptake transporter organic anion transporting polypeptide (OATP)-2 expression, and the effect of bornoel+AST IV+PNS was stronger than that of other groups.

CONCLUSION

After I/R, the brain tissues were injured, BBB permeability increased, expression of critical ET and their genes were markedly up-regulated, and the main uptake transporters were down-regulated. We propose that the combination of borneol, AST IV and PNS could enhance the effect against cerebral I/R injury and protect BBB integrity. The potential mechanism might be the delivery of AST IV and active components of PNS to the brain tissues after treatment in combination with borneol, which could be effectively promoted by down-regulating the expression of ETs and up-regulating the expression of uptake transporters in the brain tissues. This study was the first to demonstrate that borneol combined with AST IV+PNS enhanced the effect against cerebral I/R injury through promoting the entry of AST and PNS active components to the brain tissues. Thus, this study proposes an instructive role in developing effective active ingredients combination of Chinese medicine with clear ingredients and synergistic effects in terms of the characteristic of borneol.

Research Progress on the Ability of Astragaloside IV to Protect the Brain Against Ischemia-Reperfusion Injury

Stroke, a disease with a sudden onset and high morbidity and mortality rates, is difficult to treat in the clinic. Traditional Chinese medicine has become increasingly widely used in clinical practice. Modern pharmacological studies have found that Radix Astragali has a variety of medicinal properties, i.e., immunoregulatory, antioxidative, anti-cancer, anti-diabetes, myocardial protective, hepatoprotective, and antiviral functions. This article reviews the protective effect and mechanism of astragaloside IV, which is extracted from Radix Astragali, on stroke, discusses the cerebroprotective effect of astragaloside IV against ischemia-reperfusion-related complications, offers insight into research prospects, and expands the idea of integrating traditional Chinese and Western medicine treatment strategies and drugs to provide a theoretical reference for the clinical treatment of cerebral ischemia-reperfusion injury and the improvement of stroke prognosis.

Infarct growth precedes cerebral thrombosis following experimental stroke in mice

Ischemic stroke is among the leading causes of disability and death worldwide. In acute ischemic stroke, successful recanalization of occluded vessels is the primary therapeutic aim, but even if it is achieved, not all patients benefit. Although blockade of platelet aggregation did not prevent infarct progression, cerebral thrombosis as cause of secondary infarct growth has remained a matter of debate. As cerebral thrombi are frequently observed after experimental stroke, a thrombus-induced impairment of the brain microcirculation is considered to contribute to tissue damage. Here, we combine the model of transient middle cerebral artery occlusion (tMCAO) with light sheet fluorescence microscopy and immunohistochemistry of brain slices to investigate the kinetics of thrombus formation and infarct progression. Our data reveal that tissue damage already peaks after 8 h of reperfusion following 60 min MCAO, while cerebral thrombi are only observed at later time points. Thus, cerebral thrombosis is not causative for secondary infarct growth during ischemic stroke.

Pattern Recognition Molecules of Lectin Complement Pathway in Ischemic Stroke

Purpose

The current study aimed to investigate in an Armenian population the levels of pattern recognition molecules (PRMs) of lectin complement pathway (LCP), MBL (mannan-binding lectin) and M-ficolin in plasma in ischemic stroke (IS), and the possible association of 11 single nucleotide polymorphisms (SNPs) in MBL2, FCN1 and FCN2 genes.

Patients and Methods

A total of 122 patients with IS and 150 control subjects were included in this study. Immunofluorometric assays (TRIFMAs) and real-time polymerase chain reactions with TaqMan probes were conducted.

Results

According to the results, the levels of M-ficolin in IS patients are significantly higher than in control subjects, and the MBL2 rs11003125 and rs12780112 SNPs, as well as MBL2 rs12780112*T and FCN1 rs10120023*T minor alleles (MAs) are negatively associated with the risk of IS. Further, MBL2 rs11003125 and rs1800450 SNPs and the carriage of their MAs, as well as FCN1 rs2989727 SNP and the carriage of FCN1 rs10120023*T MA significantly alter plasma MBL and M-ficolin levels in IS patients, respectively. Five common haplotypes in MBL2 gene and three common haplotypes in FCN1 and FCN2 genes were revealed, among which CGTC was negatively associated with IS and decreasing MBL plasma levels in IS.

Conclusion

In conclusion, we suggest that LCP PRMs are associated with the risk of developing IS, and may also participate in pathological events leading to post-ischemic brain damage. This study emphasizes the important contribution of alterations of LCP PRMs on genomic and proteomic levels to the pathomechanisms of ischemic stroke, at least in an Armenian population.

Neutrophils Obstructing Brain Capillaries Are a Major Cause of No-Reflow in Ischemic Stroke

Despite successful clot retrieval in large vessel occlusion stroke, ∼50% of patients have an unfavorable clinical outcome. The mechanisms underlying this functional reperfusion failure remain unknown, and therapeutic options are lacking. In the thrombin-model of middle cerebral artery (MCA) stroke in mice, we show that, despite successful thrombolytic recanalization of the proximal MCA, cortical blood flow does not fully recover. Using in vivo two-photon imaging, we demonstrate that this is due to microvascular obstruction of ∼20%-30% of capillaries in the infarct core and penumbra by neutrophils adhering to distal capillary segments. Depletion of circulating neutrophils using an anti-Ly6G antibody restores microvascular perfusion without increasing the rate of hemorrhagic complications. Strikingly, infarct size and functional deficits are smaller in mice treated with anti-Ly6G. Thus, we propose neutrophil stalling of brain capillaries to contribute to reperfusion failure, which offers promising therapeutic avenues for ischemic stroke.

Brain vulnerability and viability after ischaemia

The susceptibility of the brain to ischaemic injury dramatically limits its viability following interruptions in blood flow. However, data from studies of dissociated cells, tissue specimens, isolated organs and whole bodies have brought into question the temporal limits within which the brain is capable of tolerating prolonged circulatory arrest. This Review assesses cell type-specific mechanisms of global cerebral ischaemia, and examines the circumstances in which the brain exhibits heightened resilience to injury. We suggest strategies for expanding such discoveries to fuel translational research into novel cytoprotective therapies, and describe emerging technologies and experimental concepts. By doing so, we propose a new multimodal framework to investigate brain resuscitation following extended periods of circulatory arrest.

Contribution of Extracellular Matrix Component Landscapes in the Adult Subventricular Zone to the Positioning of Neural Stem/Progenitor Cells

Neurogenesis persists in restricted regions of the adult brain, including the subventricular zone (SVZ). Adult neural stem cells (NSCs) in the SVZ proliferate and give rise to new neurons and glial cells depending on intrinsic and environmental cues. Among the multiple factors that contribute to the chemical, physical, and mechanical components of the neurogenic niche, we focused on the composition of the extracellular matrix (ECM) of vasculature and fractones in the SVZ. The SVZ consists of ECM-rich blood vessels and fractones during development and adulthood, and adult neural stem/progenitor cells (NS/PCs) preferentially attach to the laminin-rich basal lamina. To examine the ECM preference of adult NS/PCs, we designed a competition assay using cell micropatterning. Although both laminin and collagen type IV, which are the main components of basal lamina, act as physical scaffolds, adult NS/PCs preferred to adhere to laminin over collagen type IV. Interestingly, the ECM preference of adult NS/PCs could be manipulated by chemokines such as stromal-derived factor 1 (SDF1) and α6 integrin. As SDF1 re-routes NSCs and their progenitors toward the injury site after brain damage, these results suggest that the alteration in ECM preferences may provide a molecular basis for context-dependent NS/PC positioning.

Cognitive Dysfunction after Heart Disease: A Manifestation of the Heart-Brain Axis

The functions of the brain and heart, which are the two main supporting organs of human life, are closely linked. Numerous studies have expounded the mechanisms of the brain-heart axis and its related clinical applications. However, the effect of heart disease on brain function, defined as the heart-brain axis, is less studied even though cognitive dysfunction after heart disease is one of its most frequently reported manifestations. Hypoperfusion caused by heart failure appears to be an important risk factor for cognitive decline. Blood perfusion, the immune response, and oxidative stress are the possible main mechanisms of cognitive dysfunction, indicating that the blood-brain barrier, glial cells, and amyloid-β may play active roles in these mechanisms. Clinicians should pay more attention to the cognitive function of patients with heart disease, especially those with heart failure. In addition, further research elucidating the associated mechanisms would help discover new therapeutic targets to intervene in the process of cognitive dysfunction after heart disease. This review discusses cognitive dysfunction in relation to heart disease and its potential mechanisms.

Evolution of blood-brain barrier in brain diseases and related systemic nanoscale brain-targeting drug delivery strategies

Blood–brain barrier (BBB) strictly controls matter exchange between blood and brain, and severely limits brain penetration of systemically administered drugs, resulting in ineffective drug therapy of brain diseases. However, during the onset and progression of brain diseases, BBB alterations evolve inevitably. In this review, we focus on nanoscale brain-targeting drug delivery strategies designed based on BBB evolutions and related applications in various brain diseases including Alzheimer's disease, Parkinson's disease, epilepsy, stroke, traumatic brain injury and brain tumor. The advances on optimization of small molecules for BBB crossing and non-systemic administration routes (e.g., intranasal treatment) for BBB bypassing are not included in this review.

β2 glycoprotein I participates in phagocytosis of apoptotic neurons and in vascular injury in experimental brain stroke

Beta-2 Glycoprotein I (β2-GPI) is the main target of anti-phospholipid antibodies (aPL) in the autoimmune anti-phospholipid syndrome, characterized by increased risk of stroke. We here investigated the antibody independent role of β2-GPI after ischemia/reperfusion, modeled in vivo by transient middle cerebral artery occlusion (tMCAo) in male C57Bl/6J mice; in vitro by subjecting immortalized human brain microvascular endothelial cells (ihBMEC) to 16 h hypoxia and 4 h re-oxygenation. ApoH (coding for β2-GPI) was upregulated selectively in the liver at 48 h after tMCAo. At the same time β2-GPI circulating levels increased. β2-GPI was detectable in brain parenchyma and endothelium at all time points after tMCAo. Parenchymal β2-GPI recognized apoptotic neurons (positive for annexin V, C3 and TUNEL) cleared by CD68+ brain macrophages. Hypoxic ihBMEC showed increased release of IL-6, over-expression of thrombomodulin and IL-1α after re-oxygenation with β2-GPI alone. β2-GPI interacted with mannose-binding lectin in mouse plasma and ihBMEC medium, potentially involved in formation of thrombi. We show for the first time that brain ischemia triggers the hepatic production of β2-GPI. β2-GPI is present in the ischemic endothelium, enhancing vascular inflammation, and extravasates binding stressed neurons before their clearance by phagocytosis. Thus β2-GPI may be a new mediator of brain injury following ischemic stroke.

Ligands of the Neuropeptide Y Y2 Receptors as a Potential Multitarget Therapeutic Approach for the Protection of the Neurovascular Unit Against Acute Ischemia/Reperfusion: View from the Perspective of the Laboratory Bench

Ischemic stroke is the third leading cause of death and disability worldwide, with no available satisfactory prevention or treatment approach. The current treatment is limited to the use of “reperfusion methods,” i.e., an intravenous or intra-arterial infusion of a fibrinolytic agent, mechanical removal of the clot by thrombectomy, or a combination of both methods. It should be stressed, however, that only approximately 5% of all acute strokes are eligible for fibrinolytic treatment and fewer than 10% for thrombectomy. Despite the tremendous progress in understanding of the pathomechanisms of cerebral ischemia, the promising results of basic research on neuroprotection are not currently transferable to human stroke. A possible explanation for this failure is that experiments on in vivo animal models involve healthy young animals, and the experimental protocols seldom consider the importance of protecting the whole neurovascular unit (NVU), which ensures intracranial homeostasis and is seriously damaged by ischemia/reperfusion. One of the endogenous protective systems activated during ischemia and in neurodegenerative diseases is represented by neuropeptide Y (NPY). It has been demonstrated that activation of NPY Y2 receptors (Y2R) by a specific ligand decreases the volume of the postischemic infarction and improves performance in functional tests of rats with arterial hypertension subjected to middle cerebral artery occlusion/reperfusion. This functional improvement suggests the protection of the NVU. In this review, we focus on NPY and discuss the potential, multidirectional protective effects of Y2R agonists against acute focal ischemia/reperfusion injury, with special reference to the NVU.

New Insight Into Neutrophils: A Potential Therapeutic Target for Cerebral Ischemia

Ischemic stroke is one of the main issues threatening human health worldwide, and it is also the main cause of permanent disability in adults. Energy consumption and hypoxia after ischemic stroke leads to the death of nerve cells, activate resident glial cells, and promote the infiltration of peripheral immune cells into the brain, resulting in various immune-mediated effects and even contradictory effects. Immune cell infiltration can mediate neuronal apoptosis and aggravate ischemic injury, but it can also promote neuronal repair, differentiation and regeneration. The central nervous system (CNS), which is one of the most important immune privileged parts of the human body, is separated from the peripheral immune system by the blood-brain barrier (BBB). Under physiological conditions, the infiltration of peripheral immune cells into the CNS is controlled by the BBB and regulated by the interaction between immune cells and vascular endothelial cells. As the immune response plays a key role in regulating the development of ischemic injury, neutrophils have been proven to be involved in many inflammatory diseases, especially acute ischemic stroke (AIS). However, neutrophils may play a dual role in the CNS. Neutrophils are the first group of immune cells to enter the brain from the periphery after ischemic stroke, and their exact role in cerebral ischemia remains to be further explored. Elucidating the characteristics of immune cells and their role in the regulation of the inflammatory response may lead to the identification of new potential therapeutic strategies. Thus, this review will specifically discuss the role of neutrophils in ischemic stroke from production to functional differentiation, emphasizing promising targeted interventions, which may promote the development of ischemic stroke treatments in the future.