Improving Microcirculatory Reperfusion Reduces Parenchymal Oxygen Radical Formation and Provides Neuroprotection

A new insight into the role of pericytes in ischemic stroke

The functional structure of the blood-brain barrier (BBB) deteriorates after stroke by developing diffuse microvascular and neurovascular dysfunction and loss of white matter integrity. This causes nervous tissue injury and causes sensory and motor disabilities in stroke patients. Improving the integrity of the BBB and neurovascular remodeling after stroke can promote post-stroke injury conditions. Pericytes are contractile cells abundant in the BBB and sandwiched between astrocytes and endothelial cells of the microvessels. Stroke could lead to the degeneration of pericytes in the BBB. However, recent evidence shows that promoting pericytes enhances BBB integrity and neurovascular remodeling. Furthermore, pericytes achieve multipotent properties under hypoxic conditions, allowing them to transdifferentiate into the brain resident cells such as microglia. Microglia regulate immunity and inflammatory response after stroke. The current review studies recent findings in the intervening mechanisms underlying the regulatory effect of pericytes in BBB recovery after stroke.

No-reflow after recanalization in ischemic stroke: From pathomechanisms to therapeutic strategies

Endovascular reperfusion therapy is the primary strategy for acute ischemic stroke. No-reflow is a common phenomenon, which is defined as the failure of microcirculatory reperfusion despite clot removal by thrombolysis or mechanical embolization. It has been reported that up to 25% of ischemic strokes suffer from no-reflow, which strongly contributes to an increased risk of poor clinical outcomes. No-reflow is associated with functional and structural alterations of cerebrovascular microcirculation, and the injury to the microcirculation seriously hinders the neural functional recovery following macrovascular reperfusion. Accumulated evidence indicates that pathology of no-reflow is linked to adhesion, aggregation, and rolling of blood components along the endothelium, capillary stagnation with neutrophils, astrocytes end-feet, and endothelial cell edema, pericyte contraction, and vasoconstriction. Prevention or treatment strategies aim to alleviate or reverse these pathological changes, including targeted therapies such as cilostazol, adhesion molecule blocking antibodies, peroxisome proliferator-activated receptors (PPARs) activator, adenosine, pericyte regulators, as well as adjunctive therapies, such as extracorporeal counterpulsation, ischemic preconditioning, and alternative or complementary therapies. Herein, we provide an overview of pathomechanisms, predictive factors, diagnosis, and intervention strategies for no-reflow, and attempt to convey a new perspective on the clinical management of no-reflow post-ischemic stroke.

Advanced age and female sex protect cerebral arteries from mitochondrial depolarization and apoptosis during acute oxidative stress

Aging increases reactive oxygen species (ROS) which can impair vascular function and contribute to brain injury. However, aging can also promote resilience to acute oxidative stress. Therefore, we tested the hypothesis that advanced age protects smooth muscle cells (SMCs) and endothelial cells (ECs) of posterior cerebral arteries (PCAs; diameter, ∼80 μm) during exposure to H2O2. PCAs from young (4-6 months) and old (20-26 months) male and female C57BL/6 mice were isolated and pressurized (~70 mm Hg) to evaluate cell death, mitochondrial membrane potential (ΔΨm), ROS production, and [Ca2+]i in response to H2O2 (200 μM, 50 min). SMC death and ΔΨm depolarization were greater in PCAs from males vs. females. Aging increased ROS in PCAs from both sexes but increased SMC resilience to death only in males. Inhibiting TRPV4 channels with HC-067047 (1 μM) or Src kinases with SU6656 (10 μM) reduced Ca2+ entry and SMC death to H2O2 most effectively in PCAs from young males. Activating TRPV4 channels with GSK1016790A (50 nM) evoked greater Ca2+ influx in SMCs and ECs of PCAs from young vs. old mice but did not induce cell death. However, when combined with H2O2, TRPV4 activation exacerbated EC death. Activating Src kinases with spermidine (100 μM) increased Ca2+ influx in PCAs from males vs. females with minimal cell death. We conclude that in males, chronic oxidative stress during aging increases the resilience of cerebral arteries, which contrasts with inherent protection in females. Findings implicate TRP channels and Src kinases as targets to limit vascular damage to acute oxidative injury.

Effects of the New Thrombolytic Compound LT3001 on Acute Brain Tissue Damage After Focal Embolic Stroke in Rats

LT3001 is a novel synthetic small molecule with thrombolytic and free radical scavenging activities. In this study, we tested the effects of LT3001 as a potential alternative thrombolytic in focal embolic ischemic stroke rat model. Stroked rats received intravenous injection of 10 mg/kg LT3001 or tPA at 1.5, 3, or 4.5 h after stroke, respectively, and the outcomes were measured at different time points after stroke by performing multi-parametric MRI, 2,3,5-triphenyltetrazolium chloride (TTC) staining, and modified neurological severity score. Lastly, we assessed the effect of LT3001 on the tPA activity in vitro, the international normalized ratio (INR), and the serum levels of active tPA and plasminogen activator inhibitor-1 (PAI-1). LT3001 treated at 1.5 h after stroke is neuroprotective by reducing the CBF lesion size and lowering diffusion and T2 lesion size measured by MRI, which is consistent with the reduction in TTC-stained infarction. When treated at 3 h after stroke, LT3001 had significantly better therapeutic effects regarding reduction of infarct size, swelling rate, and hemorrhagic transformation compared to tPA. When treated at 4.5 h after stroke, tPA, but not LT3001, significantly increased brain swelling and intracerebral hemorrhagic transformation. Lastly, LT3001 did not interfere with tPA activity in vitro, or significantly alter the INR and serum levels of active tPA and PAI-1 in vivo. Our data suggests that LT3001 is neuroprotective in focal embolic stroke rat model. It might have thrombolytic property, not interfere with tPA/PAI-1 activity, and cause less risk of hemorrhagic transformation compared to the conventional tPA. Taken together, LT3001 might be developed as a novel therapy for treating thrombotic ischemic stroke.

"No-reflow" phenomenon in acute ischemic stroke

Acute ischemic stroke (AIS) afflicts millions of individuals worldwide. Despite the advancements in thrombolysis and thrombectomy facilitating proximal large artery recanalization, the resultant distal hypoperfusion, referred to "no-reflow" phenomenon, often impedes the neurological function restoration in patients. Over half a century of scientific inquiry has validated the existence of cerebral "no-reflow" in both animal models and human subjects. Furthermore, the correlation between "no-reflow" and adverse clinical outcomes underscores the necessity to address this phenomenon as a pivotal strategy for enhancing AIS prognoses. The underlying mechanisms of "no-reflow" are multifaceted, encompassing the formation of microemboli, microvascular compression and contraction. Moreover, a myriad of complex mechanisms warrant further investigation. Insights gleaned from mechanistic exploration have prompted advancements in "no-reflow" treatment, including microthrombosis therapy, which has demonstrated clinical efficacy in improving patient prognoses. The stagnation in current "no-reflow" diagnostic methods imposes limitations on the timely application of combined therapy on "no-reflow" post-recanalization. This narrative review will traverse the historical journey of the "no-reflow" phenomenon, delve into its underpinnings in AIS, and elucidate potential therapeutic and diagnostic strategies. Our aim is to equip readers with a swift comprehension of the "no-reflow" phenomenon and highlight critical points for future research endeavors.

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.

Contribution and therapeutic value of mitophagy in cerebral ischemia-reperfusion injury after cardiac arrest

Cardiopulmonary resuscitation and related life support technologies have improved substantially in recent years; however, mortality and disability rates from cardiac arrest (CA) remain high and are closely associated with the high incidence of cerebral ischemia-reperfusion injury (CIRI), which is explained by a "double-hit" model (i.e., resulting from both ischemia and reperfusion). Mitochondria are important power plants in the cell and participate in various biochemical processes, such as cell differentiation and signaling in eukaryotes. Various mitochondrial processes, including energy metabolism, calcium homeostasis, free radical production, and apoptosis, are involved in several important stages of the progression and development of CIRI. Mitophagy is a key mechanism of the endogenous removal of damaged mitochondria to maintain organelle function and is a critical target for CIRI treatment after CA. Mitophagy also plays an essential role in attenuating ischemia-reperfusion in other organs, particularly during post-cardiac arrest myocardial dysfunction. Regulation of mitophagy may influence necroptosis (a programmed cell death pathway), which is the main endpoint of organ ischemia-reperfusion injury. In this review, we summarize the main signaling pathways related to mitophagy and their associated regulatory proteins. New therapeutic methods and drugs targeting mitophagy in ischemia-reperfusion animal models are also discussed. In-depth studies of the mechanisms underlying the regulation of mitophagy will enhance our understanding of the damage and repair processes in CIRI after CA, thereby contributing to the development of new therapeutic strategies.

Effect of prolonged microcirculation time after thrombectomy on the outcome of acute stroke

BACKGROUND

Although recanalization can be successful, microcirculatory dysfunction is common in acute large vessel occlusive stroke (LVOS). We assessed the microcirculation time by postprocessing software and analyzed its impact on prognosis in patients treated with mechanical thrombectomy (MT).

METHODS

Patients with acute LVOS treated with MT were retrospectively enrolled consecutively. We measured the time to peak (TTP) and cerebral circulation time (CCT) in regions of interest on digital subtraction angiography using syngo iFlow software (Siemens Healthineers, Forchheim, Germany). A modified Rankin score ≤2 at 90 days was defined as a favorable outcome. Logistic regression was used to analyze the effect of each time parameter on prognosis. Then, we included time parameters in the baseline model to construct receiver operating characteristic (ROC) curves to assess the predictive ability for prognosis.

RESULTS

A total of 215 patients were finally included. Of them, 118 (54.9%) had a favourable outcome at 90 days. Multivariate analysis showed that the microvascular cerebral circulation time (mCCT) was significantly associated with poor outcomes (odds ratio (OR) 2.061, 95% confidence interval (CI) 1.414 to 3.005 p<0.001). The area under the ROC curve was significantly enhanced by including mCCT in the baseline model (0.859 vs 0.829, p=0.016, DeLong test).

CONCLUSIONS

The mCCT immediately after recanalization is a powerful predictive factor for 90-day functional prognosis.

Crocetin Regulates Functions of Neural Stem Cells to Generate New Neurons for Cerebral Ischemia Recovery

Many neurons undergo apoptosis after ischemic stroke. In the brain, neurogenesis has the potential for neuronal replacement and can be activated by external conditions to repair the injury. Crocetin (CRO), naturally extracted from the plant saffron, acts as a neuroprotective agent for ischemic stroke. However, the underlying mechanism remains unknown. In this work, the effect of CRO on neural stem cell (NSC) behaviors and subventricular zone neurogenesis is investigated. Initially, NSCs are incubated with different concentrations of CRO to detect the cell proliferation and differentiation in vitro. Second, ischemic stroke induced rats are treated with CRO using nimodipine (NMDP) as a comparison. The behavioral functions, infarcted volume, and apoptotic Nissl bodies of rats are noticeably improved after CRO-treatment, comparable to those of NMDP. In addition, the increased regional cerebral blood flow and promoted neuronal differentiation are achieved by CRO-treatment. Brain tissue examination shows significantly increased neuronal regeneration in the focal ischemic injury area. Meanwhile, the length of neurites is prolonged, indicating that CRO could potentially promote neurite extension to enhance cell-cell communication. These findings demonstrate that CRO facilitated the neuronal differentiation of NSCs by activating subventricular zone neurogenesis in damaged cortex and striatum sites to repair ischemic stroke.

Inhaled nitric oxide improves post-cardiac arrest outcomes via guanylate cyclase-1 in bone marrow-derived cells

RATIONALE

Nitric oxide (NO) exerts its biological effects primarily via activation of guanylate cyclase (GC) and production of cyclic guanosine monophosphate. Inhaled NO improves outcomes after cardiac arrest and cardiopulmonary resuscitation (CPR). However, mechanisms of the protective effects of breathing NO after cardiac arrest are incompletely understood.

OBJECTIVE

To elucidate the mechanisms of beneficial effects of inhaled NO on outcomes after cardiac arrest.

METHODS

Adult male C57BL/6J wild-type (WT) mice, GC-1 knockout mice, and chimeric WT mice with WT or GC-1 knockout bone marrow were subjected to 8 min of potassium-induced cardiac arrest to determine the role of GC-1 in bone marrow-derived cells. Mice breathed air or 40 parts per million NO for 23 h starting at 1 h after CPR.

RESULTS

Breathing NO after CPR prevented hypercoagulability, cerebral microvascular occlusion, an increase in circulating polymorphonuclear neutrophils and neutrophil-to-lymphocyte ratio, and right ventricular dysfunction in WT mice, but not in GC-1 knockout mice, after cardiac arrest. The lack of GC-1 in bone marrow-derived cells diminished the beneficial effects of NO breathing after CPR.

CONCLUSIONS

GC-dependent signaling in bone marrow-derived cells is essential for the beneficial effects of inhaled NO after cardiac arrest and CPR.

Central Nervous System Pericytes Contribute to Health and Disease

Successful neuroprotection is only possible with contemporary microvascular protection. The prevention of disease-induced vascular modifications that accelerate brain damage remains largely elusive. An improved understanding of pericyte (PC) signalling could provide important insight into the function of the neurovascular unit (NVU), and into the injury-provoked responses that modify cell–cell interactions and crosstalk. Due to sharing the same basement membrane with endothelial cells, PCs have a crucial role in the control of endothelial, astrocyte, and oligodendrocyte precursor functions and hence blood–brain barrier stability. Both cerebrovascular and neurodegenerative diseases impair oxygen delivery and functionally impair the NVU. In this review, the role of PCs in central nervous system health and disease is discussed, considering their origin, multipotency, functions and also dysfunction, focusing on new possible avenues to modulate neuroprotection. Dysfunctional PC signalling could also be considered as a potential biomarker of NVU pathology, allowing us to individualize therapeutic interventions, monitor responses, or predict outcomes.

The Role of Pericytes in Ischemic Stroke: Fom Cellular Functions to Therapeutic Targets

Ischemic stroke (IS) is a cerebrovascular disease causing high rates of disability and fatality. In recent years, the concept of the neurovascular unit (NVU) has been accepted by an increasing number of researchers and is expected to become a new paradigm for exploring the pathogenesis and treatment of IS. NVUs are composed of neurons, endothelial cells, pericytes, astrocytes, microglia, and the extracellular matrix. As an important part of the NVU, pericytes provide support for other cellular components and perform a variety of functions, including participating in the maintenance of the normal physiological function of the blood–brain barrier, regulating blood flow, and playing a role in inflammation, angiogenesis, and neurogenesis. Therefore, treatment strategies targeting pericyte functions, regulating pericyte epigenetics, and transplanting pericytes warrant exploration. In this review, we describe the reactions of pericytes after IS, summarize the potential therapeutic targets and strategies targeting pericytes for IS, and provide new treatment ideas for ischemic stroke.

P2RY2 Alleviates Cerebral Ischemia-Reperfusion Injury by Inhibiting YAP Phosphorylation and Reducing Mitochondrial Fission

P2Y purinoceptor 2 (P2RY2) is involved in the regulation of cell proliferation and apoptosis. The aim of this study was to explore the effects of P2RY2 on cerebral ischemia/reperfusion (I/R) injury and its molecular mechanism. Middle cerebral artery occlusion (MCAO) model in rats and OXYGEN and oxygen-glucose deprivation/reoxygenation (OGD/R) model in PC12 cells were established. P2RY2 expressions in I/R injury model in vitro and in vivo were up-regulated. In the OGD/R group, ROS level, cyto-CytC and mitochondrial fission factors expressions and cell apoptosis were increased, while SOD activity, mito-CytC and mitochondrial fusion factors expressions were decreased. P2RY2 overexpression could reverse these results. Up-regulated P2RY2 expression decreased Yes-associated protein (YAP) phosphorylation level, promote the nuclear translocation of YAP, and inhibit cell apoptosis, which can be reversed by YAP inhibitor verteporfin. The addition of PI3K/AKT inhibitor LY294002 could reverse the decrease of YAP phosphorylation level and cell apoptosis, and the increase of nuclear translocation caused by P2RY2 overexpression. Further in vivo studies validated that interference with P2RY2 increased the cerebral infarction area, decreased AKT expression, enhanced YAP phosphorylation, and inhibited the nuclear translocation of YAP. In conclusion, P2RY2 can alleviate cerebral I/R injury by inhibiting YAP phosphorylation and reducing mitochondrial fission.

The critical roles of histone deacetylase 3 in the pathogenesis of solid organ injury

Histone deacetylase 3 (HDAC3) plays a crucial role in chromatin remodeling, which, in turn, regulates gene transcription. Hence, HDAC3 has been implicated in various diseases, including ischemic injury, fibrosis, neurodegeneration, infections, and inflammatory conditions. In addition, HDAC3 plays vital roles under physiological conditions by regulating circadian rhythms, metabolism, and development. In this review, we summarize the current knowledge of the physiological functions of HDAC3 and its role in organ injury. We also discuss the therapeutic value of HDAC3 in various diseases.

Addition of Popular Exogenous Antioxidant Agent, PBN, to Culture Media May Be an Important Step to Optimization of Myogenic Stem/Progenitor Cell Preparation Protocol

The aim of the study was to modify human skeletal muscle-derived stem/progenitor cells (SkMDS/PCs) and demonstrate the optimal cell preparation protocol for application in post-infarction hearts. We used conditioned SkMDS/PC culture medium with α-phenyl-N-tert-butyl nitrone (PBN). SkMDS/PCs were cultured under hypoxic conditions and the results were compared to the standard ones. We observed a significant increase of CD-56 positive phenotypic marker the ability to form functional myotubes, increase in the proportion of young cells in cell primary suspensions, and a decrease in the percentage of apoptotic cells among PBN-conditioned cells in normoxia an hypoxia. We also observed significantly higher levels of SOD3 expression; maintained expression of SOD1, SOD2, and CAT; a higher level of BCL2 gene expression; and a rather significant decrease in Hsp70 gene expression in PBN-conditioned SkMDS/PCs compared to the WT population under hypoxic conditions. In addition, significant increase of myogenic genes expression was observed after PBN addition to culture medium, compared to WT population under hypoxia. Interestingly, PBN addition significantly increased the lengths of telomeres under hypoxia. Based on the data obtained, we can postulate that PBN conditioning of human SkMDS/PCs could be a promising step in improving myogenic cell preparation protocol for pro-regenerative treatment of post-infarction hearts.

Ischemic-hypoxic preconditioning enhances the mitochondrial function recovery of transplanted olfactory mucosa mesenchymal stem cells via miR-181a signaling in ischemic stroke

Cerebral ischemia/reperfusion injury causes a series of intricate cascade reactions in brain tissue causing apoptosis and proinflammatory programmed cell death known as pyroptosis of nerve cells. The dysfunction of target organelle mitochondria plays a key role in the process of neuronal apoptosis and pyroptosis. Mesenchymal stem cells (MSCs) have been widely used in the experimental or clinical treatment of various ischemic diseases, but the therapeutic efficacy of MSCs on cerebral ischemia-reperfusion injury need to be improved. We successfully cultured olfactory mucosa MSCs (OM-MSCs) to obtain a better source of seed cells. In this way, the therapeutic potential of OM-MSCs transplantation has been evaluated for ischemic stroke using an optimized culture scheme in vitro. Ischemic-hypoxic preconditioned OM-MSCs (IhOM-MSCs) were used to treat a neuron model of oxygen-glucose deprivation/reperfusion and the middle cerebral artery occlusion in rats. These results demonstrated that IhOM-MSCs mediated the upregulation of the downstream target genes GRP78 and Bcl-2 by miR-181a to protect mitochondrial function and inhibit apoptosis and pyroptosis of neurons in the ischemia/reperfusion injury model. Thus, IhOM-MSCs transplantation may be an effective therapy of ischemic stroke in the future.

Dynamic capillary stalls in reperfused ischemic penumbra contribute to injury: A hyperacute role for neutrophils in persistent traffic jams

Ever since the introduction of thrombolysis and the subsequent expansion of endovascular treatments for acute ischemic stroke, it remains to be identified why the actual outcomes are less favorable despite recanalization. Here, by high spatio-temporal resolution imaging of capillary circulation in mice, we introduce the pathological phenomenon of dynamic flow stalls in cerebral capillaries, occurring persistently in salvageable penumbra after reperfusion. These stalls, which are different from permanent cellular plugs of no-reflow, were temporarily and repetitively occurring in the capillary network, impairing the overall circulation like small focal traffic jams. In vivo microscopy in the ischemic penumbra revealed leukocytes traveling slowly through capillary lumen or getting stuck, while red blood cell flow was being disturbed in the neighboring segments under reperfused conditions. Stall dynamics could be modulated, by injection of an anti-Ly6G antibody specifically targeting neutrophils. Decreased number and duration of stalls were associated with improvement in penumbral blood flow within 2-24 h after reperfusion along with increased capillary oxygenation, decreased cellular damage and improved functional outcome. Thereby, dynamic microcirculatory stall phenomenon can be a contributing factor to ongoing penumbral injury and is a potential hyperacute mechanism adding on previous observations of detrimental effects of activated neutrophils in ischemic stroke.

The rise of pericytes in neurovascular research

The popularity of pericyte research is increasing, and this was not more evident than at the recent 2019 Brain meeting in Yokohama which featured a large number of presentations focused on brain pericyte research, including the Presidential Symposium. In this article, we will provide a history of brain pericyte research, present the results of our analysis showing a substantial increase in brain pericyte research presented at Brain meetings since 2005, suggest reasons for their increased popularity, and comment on what the future holds for brain pericyte research.

Neutrophil-Related Oxidants Drive Heart and Brain Remodeling After Ischemia/Reperfusion Injury

The inflammatory response associated with myocardial and brain ischemia/reperfusion injury (IRI) is a critical determinant of tissue necrosis, functional organ recovery, and long-term clinical outcomes. In the post-ischemic period, reactive oxygen species (ROS) are involved in tissue repair through the clearance of dead cells and cellular debris. Neutrophils play a critical role in redox signaling due to their early recruitment and the large variety of released ROS. Noteworthy, ROS generated during IRI have a relevant role in both myocardial healing and activation of neuroprotective pathways. Anatomical and functional differences contribute to the responses in the myocardial and brain tissue despite a significant gene overlap. The exaggerated activation of this signaling system can result in adverse consequences, such as cell apoptosis and extracellular matrix degradation. In light of that, blocking the ROS cascade might have a therapeutic implication for cardiomyocyte and neuronal loss after acute ischemic events. The translation of these findings from preclinical models to clinical trials has so far failed because of differences between humans and animals, difficulty of agents to penetrate into specific cellular organs, and specifically unravel oxidant and antioxidant pathways. Here, we update knowledge on ROS cascade in IRI, focusing on the role of neutrophils. We discuss evidence of ROS blockade as a therapeutic approach for myocardial infarction and ischemic stroke.

A Systems Pharmacology Approach for Identifying the Multiple Mechanisms of Action for the Rougui-Fuzi Herb Pair in the Treatment of Cardiocerebral Vascular Diseases

Cardiocerebral vascular diseases (CCVDs) are the main reasons for high morbidity and mortality all over the world, including atherosclerosis, hypertension, myocardial infarction, stroke, and so on. Chinese herbs pair of the Cinnamomum cassia Presl (Chinese name, rougui) and the Aconitum carmichaelii Debx (Chinese name, fuzi) can be effective in CCVDs, which is recorded in the ancient classic book Shennong Bencao Jing, Mingyibielu and Thousand Golden Prescriptions. However, the active ingredients and the molecular mechanisms of rougui-fuzi in treatment of CCVDs are still unclear. This study was designed to apply a system pharmacology approach to reveal the molecular mechanisms of the rougui-fuzi anti-CCVDs. The 163 candidate compounds were retrieved from Traditional Chinese Medicine System Pharmacology Database and Analysis Platform (TCMSP). And 84 potential active compounds and the corresponding 42 targets were obtained from systematic model. The underlying mechanisms of the therapeutic effect for rougui-fuzi were investigated with gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Then, component-target-disease (C-T-D) and target-pathway (T-P) networks were constructed to further dissect the core pathways, potential targets, and active compounds in treatment of CCVDs for rougui-fuzi. We also constituted protein-protein in interaction (PPI) network by the reflect target protein of the crucial pathways against CCVDs. As a result, 21 key compounds, 8 key targets, and 3 key pathways were obtained for rougui-fuzi. Afterwards, molecular docking was performed to validate the reliability of the interactions between some compounds and their corresponding targets. Finally, UPLC-Q-Exactive-MS^E and GC-MS/MS were analyzed to detect the active ingredients of rougui-fuzi. Our results may provide a new approach to clarify the molecular mechanisms of Chinese herb pair in treatment with CCVDs at a systematic level.

Small Vessels Are a Big Problem in Neurodegeneration and Neuroprotection

The cerebral microcirculation holds a critical position to match the high metabolic demand by neuronal activity. Functionally, microcirculation is virtually inseparable from other nervous system cells under both physiological and pathological conditions. For successful bench-to-bedside translation of neuroprotection research, the role of microcirculation in acute and chronic neurodegenerative disorders appears to be under-recognized, which may have contributed to clinical trial failures with some neuroprotectants. Increasing data over the last decade suggest that microcirculatory impairments such as endothelial or pericyte dysfunction, morphological irregularities in capillaries or frequent dynamic stalls in blood cell flux resulting in excessive heterogeneity in capillary transit may significantly compromise tissue oxygen availability. We now know that ischemia-induced persistent abnormalities in capillary flow negatively impact restoration of reperfusion after recanalization of occluded cerebral arteries. Similarly, microcirculatory impairments can accompany or even precede neural loss in animal models of several neurodegenerative disorders including Alzheimer's disease. Macrovessels are relatively easy to evaluate with radiological or experimental imaging methods but they cannot faithfully reflect the downstream microcirculatory disturbances, which may be quite heterogeneous across the tissue at microscopic scale and/or happen fast and transiently. The complexity and size of the elements of microcirculation, therefore, require utilization of cutting-edge imaging techniques with high spatiotemporal resolution as well as multidisciplinary team effort to disclose microvascular-neurodegenerative connection and to test treatment approaches to advance the field. Developments in two photon microscopy, ultrafast ultrasound, and optical coherence tomography provide valuable experimental tools to reveal those microscopic events with high resolution. Here, we review the up-to-date advances in understanding of the primary microcirculatory abnormalities that can result in neurodegenerative processes and the combined neurovascular protection approaches that can prevent acute as well as chronic neurodegeneration.

Uric acid therapy for vasculoprotection in acute ischemic stroke

Uric acid (UA) is a product of the catabolism of purine nucleotides, the principal constituents of DNA, RNA, and cellular energy stores, such as adenosine triphosphate. The main properties of UA include scavenging of hydroxyl radicals, superoxide anion, hydrogen peroxide, and peroxynitrite that make this compound to be the most potent antioxidant in the human plasma. As the result of two silencing mutations in the gene of the hepatic enzyme uricase which degrades UA to allantoin, humans have higher levels of UA than most mammals. However, these levels rapidly decrease following an acute ischemic stroke (AIS), and this decrement has been associated to worse stroke outcomes. This review highlights the safety and potential clinical value of UA therapy in AIS, particularly in patients more exposed to redox-mediated mechanism following the onset of ischemia, such as women, hyperglycemic patients, or patients treated with mechanical thrombectomy. The clinical findings are supported by preclinical data gathered in different laboratories, and in assorted animal species which include male and female individuals or animals harboring comorbidities frequently encountered in patients with AIS, such as hyperglycemia or hypertension. A remarkable finding in these studies is that UA targets its main effects in the brain vasculature since available evidence suggests that does not seem to cross the blood–brain barrier. Altogether, the available data with UA therapy extend the importance of vasculoprotection for effective neuroprotection at the bedside and reinforce the role of endothelial cells after brain ischemia for an increased survival of the whole neurovascular unit.

Microthrombus-Targeting Micelles for Neurovascular Remodeling and Enhanced Microcirculatory Perfusion in Acute Ischemic Stroke

Reperfusion injury exists as the major obstacle to full recovery of neuron functions after ischemic stroke onset and clinical thrombolytic therapies. Complex cellular cascades including oxidative stress, neuroinflammation, and brain vascular impairment occur within neurovascular units, leading to microthrombus formation and ultimate neuron death. In this work, a multitarget micelle system is developed to simultaneously modulate various cell types involved in these events. Briefly, rapamycin is encapsulated in self-assembled micelles that are consisted of reactive oxygen species (ROS)-responsive and fibrin-binding polymers to achieve micelle retention and controlled drug release within the ischemic lesion. Neuron survival is reinforced by the combination of micelle facilitated ROS elimination and antistress signaling pathway interference under ischemia conditions. In vivo results demonstrate an overall remodeling of neurovascular unit through micelle polarized M2 microglia repair and blood-brain barrier preservation, leading to enhanced neuroprotection and blood perfusion. This strategy gives a proof of concept that neurovascular units can serve as an integrated target for ischemic stroke treatment with nanomedicines.

Reactive species-induced microvascular dysfunction in ischemia/reperfusion

Vascular endothelial cells line the inner surface of the entire cardiovascular system as a single layer and are involved in an impressive array of functions, ranging from the regulation of vascular tone in resistance arteries and arterioles, modulation of microvascular barrier function in capillaries and postcapillary venules, and control of proinflammatory and prothrombotic processes, which occur in all segments of the vascular tree but can be especially prominent in postcapillary venules. When tissues are subjected to ischemia/reperfusion (I/R), the endothelium of resistance arteries and arterioles, capillaries, and postcapillary venules become dysfunctional, resulting in impaired endothelium-dependent vasodilator and enhanced endothelium-dependent vasoconstrictor responses along with increased vulnerability to thrombus formation, enhanced fluid filtration and protein extravasation, and increased blood-to-interstitium trafficking of leukocytes in these functionally distinct segments of the microcirculation. The number of capillaries open to flow upon reperfusion also declines as a result of I/R, which impairs nutritive perfusion. All of these pathologic microvascular events involve the formation of reactive species (RS) derived from molecular oxygen and/or nitric oxide. In addition to these effects, I/R-induced RS activate NLRP3 inflammasomes, alter connexin/pannexin signaling, provoke mitochondrial fission, and cause release of microvesicles in endothelial cells, resulting in deranged function in arterioles, capillaries, and venules. It is now apparent that this microvascular dysfunction is an important determinant of the severity of injury sustained by parenchymal cells in ischemic tissues, as well as being predictive of clinical outcome after reperfusion therapy. On the other hand, RS production at signaling levels promotes ischemic angiogenesis, mediates flow-induced dilation in patients with coronary artery disease, and instigates the activation of cell survival programs by conditioning stimuli that render tissues resistant to the deleterious effects of prolonged I/R. These topics will be reviewed in this article.

Pericytes in Ischemic Stroke

Recent stroke research has shifted the focus to the microvasculature from neuron-centric views. It is increasingly recognized that a successful neuroprotection is not feasible without microvascular protection. On the other hand, recent studies on pericytes, long-neglected cells on microvessels have provided insight into the regulation of microcirculation. Pericytes play an essential role in matching the metabolic demand of nervous tissue with the blood flow in addition to regulating the development and maintenance of the blood-brain barrier (BBB), leukocyte trafficking across the BBB and angiogenesis. Pericytes appears to be highly vulnerable to injury. Ischemic injury to pericytes on cerebral microvasculature unfavorably impacts the stroke-induced tissue damage and brain edema by disrupting microvascular blood flow and BBB integrity. Strongly supporting this, clinical imaging studies show that tissue reperfusion is not always obtained after recanalization. Therefore, prevention of pericyte dysfunction may improve the outcome of recanalization therapies by promoting microcirculatory reperfusion and preventing hemorrhage and edema. In the peri-infarct tissue, pericytes are detached from microvessels and promote angiogenesis and neurogenesis, and hence positively effect stroke outcome. Expectedly, we will learn more about the place of pericytes in CNS pathologies including stroke and devise approaches to treat them in the next decades.