Taurine Reduces tPA (Tissue-Type Plasminogen Activator)-Induced Hemorrhage and Microvascular Thrombosis After Embolic Stroke in Rat

The role of amino acid metabolism alterations in acute ischemic stroke: From mechanism to application

Acute ischemic stroke (AIS) is the most prevalent type of stroke, and due to its high incidence, disability rate, and mortality rate, it imposes a significant burden on the health care system. Amino acids constitute one of the most crucial metabolic products within the human body, and alterations in their metabolic pathways have been identified in the microenvironment of AIS, thereby influencing the pathogenesis, severity, and prognosis of AIS. The amino acid metabolism characteristics in AIS are complex. On one hand, the dynamic progression of AIS continuously reshapes the amino acid metabolism pattern. Conversely, changes in the amino acid metabolism pattern also exert a double-edged effect on AIS. This interaction is bidirectional, dynamic, heterogeneous, and dose-specific. Therefore, the distinctive metabolic reprogramming features surrounding amino acids during the AIS process are systematically summarized in this paper, aiming to provide potential investigative strategies for the early diagnosis, treatment approaches, and prognostic enhancement of AIS.

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.

The p75 neurotrophin receptor inhibitor, LM11A-31, ameliorates acute stroke injury and modulates astrocytic proNGF

The precursor form of nerve growth factor (proNGF) is essential to maintain NGF survival signaling. ProNGF is also among endogenous ligands for p75 neurotrophin receptor (p75ntr). Mounting evidence implies that p75ntr signaling contributes to neural damage in ischemic stroke. The present study examines the therapeutic effect of the p75ntr modulator LM11A-31. Adult mice underwent transient distal middle cerebral artery occlusion (t-dMCAO) followed by LM11A-31 treatment (25 mg/kg, i.p., twice daily) either for 72 h post-injury (acute phase) or afterward till two weeks post-stroke (subacute phase). LM11A-31 reduced blood-brain barrier permeability, cerebral tissue injury, and sensorimotor function in the acute phase of stroke. Ischemic brain samples showed repressed proNGF/P75ntr signaling and Caspase 3 activation in LM11A-31 treated mice, where we observed less reactive microglia and IL-1β production. LM11A-31 (20-80 nM) also mitigated neural injury induced by oxygen-glucose deprivation (OGD) in sandwich co-cultures of primary cortical neurons (PCN) and astrocytes. This concurred with JNK/PARP downregulation and reduced caspase-3 cleavage in the PCNs and was associated with repressed proNGF generation in astrocytes. Further in vitro experiments indicated human proNGF suppresses the pro-inflammatory phenotype in microglial cultures, as determined by a sharp decline in HMGB-1 production and moderate arginase-1 upregulation. Despite significant protection in acute stroke, LM11A-31 treatment did not improve cortical atrophy and sensorimotor function in the subacute phase. Our findings provide preclinical evidence supporting LM11A-31 as a promising therapy for acute stroke injury. Further investigations may elucidate if reduced astrocytic proNGF, an endogenous reservoir of pro-neurotrophins, may restrict the therapeutic window.

Remote ischemic conditioning attenuates blood-brain barrier disruption after recombinant tissue plasminogen activator treatment via reducing PDGF-CC

Treatment of acute ischemic stroke with the recombinant tissue plasminogen activator (rtPA) is associated with increased blood-brain barrier (BBB) disruption and hemorrhagic transformation. Remote ischemic conditioning (RIC) has demonstrated neuroprotective effects against acute ischemic stroke. However, whether and how RIC regulates rtPA-associated BBB disruption remains unclear. Here, a rodent model of thromboembolic stroke followed by rtPA thrombolysis at different time points was performed with or without RIC. Brain infarction, neurological outcomes, BBB permeability, and intracerebral hemorrhage were assessed. The platelet-derived growth factor CC (PDGF-CC)/PDGFRα pathway in the brain tissue, PDGF-CC levels in the skeletal muscle and peripheral blood were also measured. Furthermore, impact of RIC on serum PDGF-CC levels were measured in healthy subjects and AIS patients. Our results showed that RIC substantially reduced BBB injury, intracerebral hemorrhage, cerebral infarction, and neurological deficits after stroke, even when rtPA was administrated in a delayed therapeutic time window. Mechanistically, RIC significantly decreased PDGFRα activation in ischemic brain tissue and reduced blood PDGF-CC levels, which partially resulted from PDGF-CC reduction in the skeletal muscle of RIC-applied hindlimbs and platelets. Intravenous or intraventricular recombinant PDGF-CC supplementation abolished RIC protective effects on BBB integrity. Moreover, similar changes of PDGF-CC in serum by RIC were also observed in healthy humans and acute ischemic stroke patients. Together, our study demonstrates that RIC can attenuate rtPA-aggravated BBB disruption after ischemic stroke via reducing the PDGF-CC/PDGFRα pathway and thus supports RIC as a potential approach for BBB disruption prevention or treatment following thrombolysis.

Versatile Triad Alliance: Bile Acid, Taurine and Microbiota

Taurine is the most abundant free amino acid in the body, and is mainly derived from the diet, but can also be produced endogenously from cysteine. It plays multiple essential roles in the body, including development, energy production, osmoregulation, prevention of oxidative stress, and inflammation. Taurine is also crucial as a molecule used to conjugate bile acids (BAs). In the gastrointestinal tract, BAs deconjugation by enteric bacteria results in high levels of unconjugated BAs and free taurine. Depending on conjugation status and other bacterial modifications, BAs constitute a pool of related but highly diverse molecules, each with different properties concerning solubility and toxicity, capacity to activate or inhibit receptors of BAs, and direct and indirect impact on microbiota and the host, whereas free taurine has a largely protective impact on the host, serves as a source of energy for microbiota, regulates bacterial colonization and defends from pathogens. Several remarkable examples of the interaction between taurine and gut microbiota have recently been described. This review will introduce the necessary background information and lay out the latest discoveries in the interaction of the co-reliant triad of BAs, taurine, and microbiota.

J147 Reduces tPA-Induced Brain Hemorrhage in Acute Experimental Stroke in Rats

Background and purpose

J147, a novel neurotrophic compound, was originally developed to treat aging-associated neurological diseases. Based on the broad spectrum of cytoprotective effects exhibited by this compound, we investigated whether J147 has cerebroprotection for acute ischemic stroke and whether it can enhance the effectiveness of thrombolytic therapy with tissue plasminogen activator (tPA).

Methods

Rats were subjected to transient occlusion of the middle cerebral artery (tMCAO) by insertion of an intraluminal suture or embolic middle cerebral artery occlusion (eMCAO), and treated intravenously with J147 alone or in combination with tPA.

Results

We found that J147 treatment significantly reduced infarct volume when administered at 2 h after stroke onset in the tMCAO model, but had no effect in eMCAO without tPA. However, combination treatment with J147 plus tPA at 4 h after stroke onset significantly reduced infarct volume and neurological deficits at 72 h after stroke compared with saline or tPA alone groups in the eMCAO model. Importantly, the combination treatment significantly reduced delayed tPA-associated brain hemorrhage and secondary microvascular thrombosis. These protective effects were associated with J147-mediated inhibition of matrix metalloproteinase-9 (MMP9), 15-lipoxygenase-1, and plasminogen activator inhibitor (PAI) expression in the ischemic hemispheres (predominantly in ischemic cerebral endothelium). Moreover, the combination treatment significantly reduced circulating platelet activation and platelet-leukocyte aggregation compared with saline or tPA alone groups at 24 h after stroke, which might also contribute to reduced microvascular thrombosis and neuroinflammation (as demonstrated by reduced neutrophil brain infiltration and microglial activation).

Conclusion

Our results demonstrate that J147 treatment alone exerts cerebral cytoprotective effects in a suture model of acute ischemic stroke, while in an embolic stroke model co-administration of J147 with tPA reduces delayed tPA-induced intracerebral hemorrhage and confers cerebroprotection. These findings suggest that J147-tPA combination therapy could be a promising approach to improving the treatment of ischemic stroke.

Resveratrol Alleviates Ischemic Brain Injury by Inhibiting the Activation of Pro-Inflammatory Microglia Via the CD147/MMP-9 Pathway

OBJECTIVE

Ischemic stroke is one of the most common diseases with high mortality and disability. This study was intended to investigate the mechanism of resveratrol (RES) regulating microglia activation through the CD147/matrix metalloproteinase-9 (MMP-9) pathway on ischemic stroke.

METHODS

The middle cerebral artery occlusion (MCAO) mouse model and oxygen and glucose deprivation (OGD) cell model were established. The behavioral defects, neuronal damage, cerebral infarction volume, and histopathological changes were assessed in MCAO mice. The activation of pro-inflammatory microglia CD86⁺/Iba-1⁺ and anti-inflammatory microglia CD206⁺/Iba-1⁺ was detected. The expressions of pro-inflammatory microglia markers (CD11b, CD16) and cytokines (TNF-α, IL-1β, and IL-6) were measured. The activation of the CD147/MMP-9 pathway was detected and its effect on microglia activation was assessed.

RESULTS

After RES administration, the neuronal dysfunction, infarct volume, and morphological changes of neurons were improved in MCAO mice. Meanwhile, the motivation of pro-inflammatory microglia and the release of inflammatory factors were repressed. RES suppressed the stimulation of OGD/R microglia and the release of inflammatory factors. The expression of CD147 and MMP-9 in primary microglia was up-regulated. Inhibition of CD147 can reduce pro-inflammatory microglia activation by inhibiting MMP-9 expression. RES inhibited the CD147/MMP-9 axis in OGD/R microglia, and overexpression of CD147 partially reversed the inhibitory effect of RES on the activation and release of inflammatory factors in OGD/R microglia.

CONCLUSION

RES restrained the stimulation of pro-inflammatory microglia by down-regulating the CD147/MMP-9 axis, and thus protected against ischemic brain injury.

Taurine and Its Derivatives: Analysis of the Inhibitory Effect on Platelet Function and Their Antithrombotic Potential

Taurine is a semi-essential, the most abundant free amino acid in the human body, with a six times higher concentration in platelets than any other amino acid. It is highly beneficial for the organism, has many therapeutic actions, and is currently approved for heart failure treatment in Japan. Taurine has been repeatedly reported to elicit an inhibitory action on platelet activation and aggregation, sustained by in vivo, ex vivo, and in vitro animal and human studies. Taurine showed effectiveness in several pathologies involving thrombotic diathesis, such as diabetes, traumatic brain injury, acute ischemic stroke, and others. As human prospective studies on thrombosis outcome are very difficult to carry out, there is an obvious need to validate existing findings, and bring new compelling data about the mechanisms underlying taurine and derivatives antiplatelet action and their antithrombotic potential. Chloramine derivatives of taurine proved a higher stability and pronounced selectivity for platelet receptors, raising the assumption that they could represent future potential antithrombotic agents. Considering that taurine and its analogues display permissible side effects, along with the need of finding new, alternative antithrombotic drugs with minimal side effects and long-term action, the potential clinical relevance of this fascinating nutrient and its derivatives requires further consideration.

Investigation of Taurine Derivative Magnesium-Bis-(2-Aminoethanesulfonic)-Butadioateon Alleviation of Neurological Defects in Simulated Hemorrhagic Stroke in Rats

Stroke or ischemia is caused by a blockage in a specific blood vessel that partially or completely reduces the blood flow to the brain. Nutritional factors such as antioxidants and healthy eating patterns are important variables in preventing stroke. Molecular composition properties such as molecular binding and screening can be used to evaluate the specific activity and morphological changes. The present study aimed to evaluate the effectiveness of pharmacological correction of the consequences of a hemorrhagic stroke in rats with a new derivative of taurine magnesium-bis-(2-aminoethanesulfonic)-butadioate. The animals (n=170) were divided into four groups as follows: 1) control group (n=20), 2) group 2 suffered a hemorrhagic stroke without pharmacological correction (n=50), 3) group 3 (n=50) underwent simulation of hemorrhagic stroke received Taurine at the dose of 50 mg/kg, 4) Group 4 underwent simulation of hemorrhagic stroke with correction of hemorrhagic stroke with magnesium-bis-(2-aminoethanesulfonic)-butadioate at the dose of 150 mg/kg (LKHT 3-17) (n=50). Hemorrhagic stroke was induced by transfusing autologous blood into the parietal lobe of the right hemisphere of the brain. Lethality, neurological status, locomotor, and exploratory behavior, as well as the morphological pattern of the brain damage, were assessed on the 1st, 3rd, and 7th days after the pathology simulation. Neurological deficit was determined in animals by the McGrow stroke index scale. The locomotor and exploratory behavior was evaluated using the Acti-track software and hardware complex. Two criteria were considered when assessing morphological changes in the brain: the average thickness of the cerebral cortex (in micrometers) and the number of neurons without degenerative changes. LKHT 3-17 (150 mg/kg) and taurine (50 mg/kg) reduced lethality by 1.7 and 1.36 times, respectively, on the 3rd day after stroke compared to that of the control (p<0.05). In parallel, a neurological deficit was effectively corrected LKHT 3-17 and taurine to 5.3±0.8 and 6.5±0.9, respectively, on the 1st day in contrast to the control of 8.1±0.7 points. The locomotor and exploratory behavior was significantly different on the 7th day and was accompanied by a significant increase in total activity under the influence of LKHT 3-17 to 491 conventional units (CU) compared to the control of 110 conventional units. On the 1st day, the thickness of the cortex was 1943.7±44.08 µm, and 1491.0±38.61 µm in the control and LKHT 3-17 groups, respectively. The number of neurons without neurodegenerative changes prevailed in LKHT 3-17 group (18.7±4.32), and the lowest number was observed in the group without pharmacological correction of the pathology (14.3±3.78). The taurine derivative magnesium-bis-(2-aminoethanesulfonic)-butadioate, which is a combination of the amino acid, magnesium ion, and succinic acid, decreases the neurological deficits, lethality, and enhances the locomotor and exploratory behavior in experimental hemorrhagic stroke in rats. The effect of the studied medication on the dynamics of molecular pathophysiological mechanisms occurring in the cell requires additional research.

Notoginsenoside R1 intervenes degradation and redistribution of tight junctions to ameliorate blood-brain barrier permeability by Caveolin-1/MMP2/9 pathway after acute ischemic stroke

BACKGROUND

The leakage of blood-brain barrier (BBB) is main pathophysiological change in acute stage of ischemic stroke, which not only deteriorates neurological function, but also increases the risk of hemorrhagic transformation after thrombolysis.

PURPOSE/STUDY DESIGN

This article investigates the efficacy of Notoginsenoside R1, an active ingredient of Panax notoginseng, on BBB permeability and explores related mechanisms after acute ischemic stroke.

METHODS

In vivo, male Sprague-Dawley rats (260-280 g) were selected and randomly divided into 6 groups: sham group, model group, low, middle and high doses of Notoginsenoside R1 groups and positive drug Dl-3-n-Butylphthalide group. Except for sham group, rats were performed with permanent middle cerebral artery occlusion model in each group. Twelve hours later, rats were evaluated for Bederson neurological function, and BBB integrity by Evans blue leak imaging; Triphenyltetrazolium chloride staining was used to detect the volume of cerebral infarction. Frozen sections of rats' brain tissue were prepared for detection of MMPs activity in situ zymography. Peripheral tissue of cerebral infarction was collected and tested the expression of MMP2, 9 and tight junction proteins (zo1, claudin5, occludin) by western blot. In vitro, transwell endothelial barrier model was established by bEnd.3 cells. Oxygen glucose deprivation (OGD) was chosen to simulate the hypoxic environment. Suitable OGD stimulation time as well as Notoginsenoside R1 and Dl-3-n-Butylphthalide optimal dose concentrations were determined through transwell leakage and CCK8 assay. Furthermore, endothelial subcellular component proteins were extracted. The change of zo1, claudin5, occludin and caveolin1 was detected by western blot.

RESULTS

Notoginsenoside R1 treatment significantly reduced BBB leakage and cerebral infarction volume, weakened neurological deficits in post-stroke rats. Moreover, it inhibited the activity of MMPs in infarcted cortex and striatum, down-regulated MMP2, 9 and up-regulated zo1 and claudin5 expressions in penumbra. In vitro, Notoginsenoside R1 treatment decreased OGD-induced endothelial barrier permeability, restored expressions of zo1, claudin5 on cellular membrane and cytoplasm, as well as mediated membrane redistribution of occludin and caveolin1 from actin cytoskeletal fraction.

CONCLUSIONS

Notoginsenoside R1 treatment attenuates BBB permeability, cerebral infarction volume and neurological impairments in rats with acute cerebral ischemia. The mechanisms might be related to intervening degradation and redistribution of zo1, caludin5 and occludin by caveolin1/ MMP2/9 pathway. More effects and mechanisms of Notoginsenoside R1 on rehabilitation of stroke are worthy to be explored in the future.

Influence of prior intravenous thrombolysis on outcome after failed mechanical thrombectomy: ETIS registry analysis

BACKGROUND

Despite constant improvements in recent years, sufficient reperfusion after mechanical thrombectomy (MT) is not reached in up to 15% of patients with large vessel occlusion stroke (LVOS). The outcome of patients with unsuccessful reperfusion after MT especially after intravenous thrombolysis (IVT) use is not known. We investigated the influence of initial IVT in this particular group of patients with failed intracranial recanalization.

METHODS

We conducted a retrospective analysis of the Endovascular Treatment in Ischemic Stroke (ETIS) registry from January 2015 to December 2019. Patients presenting with LVOS of the anterior circulation and final modified Thrombolysis in Cerebral Infarction score (mTICI) of 0, 1 or 2a were included. Posterior circulation, isolated cervical carotid occlusions and successful reperfusions (mTICI 2b, 2c or 3) were excluded. The primary endpoint was favorable outcome (modified Rankin Scale score of 0-2) after 3 months. Secondary endpoints were safety outcomes including mortality, any intracranial hemorrhage (ICH), parenchymal hematoma (PH) and symptomatic intracranial hemorrhage (sICH) rates.

RESULTS

Among 5076 patients with LVOS treated with MT, 524 patients with insufficient recanalization met inclusion criteria, of which 242 received IVT and 282 did not. Functional outcome was improved in the MT+IVT group compared with the MT alone group, although the difference did not reach statistical significance (23.0% vs 12.9%; adjusted OR=1.82; 95% CI 0.98 to 3.38; p=0.058). However, 3 month mRS shift analysis showed a significant benefit of IVT (adjusted OR=1.68; 95% CI 1.56 to 6.54). ICH and sICH rates were similar in both groups, although PH rate was higher in the MT+IVT group (adjusted OR=3.20; 95% CI 1.56 to 6.54).

CONCLUSIONS

Among patients with LVOS in the anterior circulation and unsuccessful MT, IVT was associated with improved functional outcome even after unsuccessful MT. Despite recent trials questioning the place of IVT in the LVOS reperfusion strategy, these findings emphasize a subgroup of patients still benefiting from IVT.

Pinocembrin attenuates hemorrhagic transformation after delayed t-PA treatment in thromboembolic stroke rats by regulating endogenous metabolites

Hemorrhagic transformation (HT) is a common serious complication of stroke after thrombolysis treatment, which limits the clinical use of tissue plasminogen activator (t-PA). Since early diagnosis and treatment for HT is important to improve the prognosis of stroke patients, it is urgent to discover the potential biomarkers and therapeutic drugs. Recent evidence shows that pinocembrin, a natural flavonoid compound, exerts anti-cerebral ischemia effect and expands the time window of t-PA. In this study, we investigated the effect of pinocembrin on t-PA-induced HT and the potential biomarkers for HT after t-PA thrombolysis, thereby improving the prognosis of stroke. Electrocoagulation-induced thrombotic focal ischemic rats received intravenous infusion of t-PA (10 mg/kg) 6 h after ischemia. Administration of pinocembrin (10 mg/kg, iv) prior t-PA infusion significantly decreased the infarct volume, ameliorated t-PA-induced HT, and protected blood-brain barrier. Metabolomics analysis revealed that 5 differential metabolites in the cerebral cortex and 16 differential metabolites in serum involved in amino acid metabolism and energy metabolism were significantly changed after t-PA thrombolysis, whereas pinocembrin administration exerted significant intervention effects on these metabolites. Linear regression analysis showed that lactic acid was highly correlated to the occurrence of HT. Further experiments confirmed that t-PA treatment significantly increased the content of lactic acid and the activity of lactate dehydrogenase in the cerebral cortex and serum, and the expression of monocarboxylate transporter 1 (MCT 1) in the cerebral cortex; pinocembrin reversed these changes, which was consistent with the result of metabolomics. These results demonstrate that pinocembrin attenuates HT after t-PA thrombolysis, which may be associated with the regulation of endogenous metabolites. Lactic acid may be a potential biomarker for HT prediction and treatment.

Lactulose Improves Neurological Outcomes by Repressing Harmful Bacteria and Regulating Inflammatory Reactions in Mice After Stroke

Background and Objective

Gut microbiota dysbiosis following stroke affects the recovery of neurological function. Administration of prebiotics to counteract post-stroke dysbiosis may be a potential therapeutic strategy to improve neurological function. We aim to observe the effect of lactulose on neurological function outcomes, gut microbiota composition, and plasma metabolites in mice after stroke.

Methods

Male C57BL/6 mice (20–25 g) were randomly divided into three groups: healthy control, photothrombotic stroke + triple-distilled water, and photothrombotic stroke + lactulose. After 14 consecutive days of lactulose administration, feces, plasma, and organs were collected. 16S rDNA sequencing, plasma untargeted metabolomics, qPCR, flow cytometry and Elisa were performed.

Results

Lactulose supplementation significantly improved the functional outcome of stroke, downregulated inflammatory reaction, and increased anti-inflammatory factors in both the brain and gut. In addition, lactulose supplementation repaired intestinal barrier injury, improved gut microbiota dysbiosis, and partially amended metabolic disorder after stroke.

Conclusion

Lactulose promotes functional outcomes after stroke in mice, which may be attributable to repressing harmful bacteria, and metabolic disorder, repairing gut barrier disruption, and reducing inflammatory reactions after stroke.

Pseudoginsenoside-F11 ameliorates thromboembolic stroke injury in rats by reducing thromboinflammation

Pseudoginsenoside-F11 (PF11), an ocotillol-type ginsenoside, has been reported to exert neuroprotective effects on ischemic stroke induced by permanent and transient middle cerebral artery occlusion in experimental animals. The aim of the present study was to investigate the effect of PF11 on thromboembolic stroke in rats and its possible mechanisms on thromboinflammation. PF11 (4, 12, 36 mg/kg) was injected intravenously (i.v.) once a day for 3 consecutive days to male Wistar rats followed by embolic middle cerebral artery occlusion (eMCAO). The results showed that PF11 significantly reduced the cerebral infarction volume, brain edema and neurological deficits induced by eMCAO. Meanwhile, the thromboinflammation in the ischemic hemisphere was observed at 24 h after eMCAO, as indicated by the increased number of microvascular thrombus and inflammatory response. Moreover, eMCAO resulted in the up-regulation of platelet glycoprotein Ibα (GPIbα) and VI (GPVI), as well as the activation of contact-kinin pathway. Notably, PF11 significantly reversed all these changes. Furthermore, PF11 prevented the eMCAO-induced loss of tight junction proteins and up-regulation of matrix metalloproteinase-9 (MMP-9), thus leading to the alleviation of blood-brain barrier (BBB) damage. In conclusion, the present study revealed that thromboinflammation was induced in the ischemic hemisphere of rats after eMCAO and PF11 exerted marked protective effects against thromboembolic stroke by attenuating thromboinflammation and preventing BBB damage. This research further identifies the potential therapeutic role of PF11 for ischemic stroke.

Taurine Protects against Postischemic Brain Injury via the Antioxidant Activity of Taurine Chloramine

Taurine is ubiquitously distributed in mammalian tissues and is highly concentrated in the heart, brain, and leukocytes. Taurine exerts neuroprotective effects in various central nervous system diseases and can suppress infarct formation in stroke. Taurine reacts with myeloperoxidase (MPO)-derived hypochlorous acid (HOCl) to produce taurine chloramine (Tau-Cl). We investigated the neuroprotective effects of taurine using a rat middle cerebral artery occlusion (MCAO) model and BV2 microglial cells. Although intranasal administration of taurine (0.5 mg/kg) had no protective effects, the same dose of Tau-Cl significantly reduced infarct volume and ameliorated neurological deficits and promoted motor function, indicating a robust neuroprotective effect of Tau-Cl. There was neutrophil infiltration in the post-MCAO brains, and the MPO produced by infiltrating neutrophils might be involved in the taurine to Tau-Cl conversion. Tau-Cl significantly increased the levels of antioxidant enzymes glutamate-cysteine ligase, heme oxygenase-1, NADPH:quinone oxidoreductase 1, and peroxiredoxin-1 in BV2 cells, whereas taurine slightly increased some of them. Antioxidant enzyme levels were increased in the post-MCAO brains, and Tau-Cl further increased the level of MCAO-induced antioxidant enzymes. These results suggest that the neutrophils infiltrate the area of ischemic injury area, where taurine is converted to Tau-Cl, thus protecting from brain injury by scavenging toxic HOCl and increasing antioxidant enzyme expression.

Development and Testing of Thrombolytics in Stroke

Despite recent advances in recanalization therapy, mechanical thrombectomy will never be a treatment for every ischemic stroke because access to mechanical thrombectomy is still limited in many countries. Moreover, many ischemic strokes are caused by occlusion of cerebral arteries that cannot be reached by intra-arterial catheters. Reperfusion using thrombolytic agents will therefore remain an important therapy for hyperacute ischemic stroke. However, thrombolytic drugs have shown limited efficacy and notable hemorrhagic complication rates, leaving room for improvement. A comprehensive understanding of basic and clinical research pipelines as well as the current status of thrombolytic therapy will help facilitate the development of new thrombolytics. Compared with alteplase, an ideal thrombolytic agent is expected to provide faster reperfusion in more patients; prevent re-occlusions; have higher fibrin specificity for selective activation of clot-bound plasminogen to decrease bleeding complications; be retained in the blood for a longer time to minimize dosage and allow administration as a single bolus; be more resistant to inhibitors; and be less antigenic for repetitive usage. Here, we review the currently available thrombolytics, strategies for the development of new clot-dissolving substances, and the assessment of thrombolytic efficacies in vitro and in vivo.

The Protective Role of Immunomodulators on Tissue-Type Plasminogen Activator-Induced Hemorrhagic Transformation in Experimental Stroke: A Systematic Review and Meta-Analysis

Background: Recanalization with tissue plasminogen activator (tPA) is the only approved agent available for acute ischemic stroke. But delayed treatment of tPA may lead to lethal intracerebral hemorrhagic transformation (HT). Numerous studies have reported that immunomodulators have good efficacy on tPA-induced HT in ischemic stroke models. The benefits of immunomodulators on tPA-associated HT are not clearly defined. Here, we sought to conduct a systematic review and meta-analysis of preclinical studies to further evaluate the efficacy of immunomodulators.

Methods: The PubMed, Web of Science, and Scopus electronic databases were searched for studies. Studies that reported the efficacy of immunomodulators on tPA-induced HT in animal models of stroke were included. Animals were divided into two groups: immunomodulators plus tPA (intervention group) or tPA alone (control group). The primary outcome was intracerebral hemorrhage, and the secondary outcomes included infarct volume and neurobehavioral score. Study quality was assessed by the checklist of CAMARADES. We used standardized mean difference (SMD) to assess the impact of interventions. Regression analysis and subgroup analysis were performed to identify potential sources of heterogeneity and evaluate the impact of the study characteristics. The evidence of publication bias was evaluated using trim and fill method and Egger’s test.

Results: We identified 22 studies that met our inclusion criteria involving 516 animals and 42 different comparisons. The median quality checklist score was seven of a possible 10 (interquartile range, 6–8). Immunomodulators improved cerebral hemorrhage (1.31 SMD, 1.09–1.52); infarct volume (1.35 SMD, 0.95–1.76), and neurobehavioral outcome (0.9 SMD, 0.67–1.13) in experimental stroke. Regression analysis and subgroup analysis indicated that control of temperature and time of assessment were important factors that influencing the efficacy of immunomodulators.

Conclusion: Our findings suggested that immunomodulators had a favorable effect on tPA-associated intracerebral hemorrhage, cerebral infarction, and neurobehavioral impairments in animal models of ischemic stroke.

Study on the therapeutic material basis and effect of Acanthopanax senticosus (Rupr. et Maxim.) Harms leaves in the treatment of ischemic stroke by PK-PD analysis based on online microdialysis-LC-MS/MS method

Leaves of Acanthopanax senticosus (Rupr. et Maxim.) Harms (ASL) have revealed significant biological activity in the treatment of ischemic stroke diseases. However, there was no in-depth study of the therapeutic material basis and effect of ASL from the pharmacokinetics-pharmacodynamics (PK-PD) analysis level. In this study, a method based on microdialysis coupled with ultra-performance liquid chromatography combined with triple quadruple mass spectrometry (MD-UPLC-QQQ-MS) was established to simultaneously and continuously collect and quantify the active compounds and endogenous neuroactive substances related to therapeutic effect in plasma and hippocampus of fully awake ischemic stroke rats. The acquired data were analyzed by the PK-PD analysis method. It was found that hyperoside, quercitrin, quercetin, and caffeic acid could pass through the blood-brain barrier, and quercetin needed a longer intake time than quercitrin and hyperoside, but the passage rate was higher. The exposure of the four compounds in the hippocampus affected the contents of seven neuroactive substances in different ways and was depicted graphically (concentration-time effect). In addition, the study found that the brain index and brain water content of ischemic stroke rats were significantly reduced after the oral administration of ASL. ASL observably regulated the content or activity of six important biochemical indexes in rats. On the one hand, this study verified that ASL could regulate ischemic stroke in many aspects. On the other hand, a visualized method to express the relationship between pharmacokinetics and pharmacodynamics in the hippocampus of cerebral ischemic areas was established. This research gives a hand to the study on the therapeutic material basis and effect of traditional Chinese medicine mechanism.

Diabetes Mellitus/Poststroke Hyperglycemia: a Detrimental Factor for tPA Thrombolytic Stroke Therapy

Intravenous administration of tissue-type plasminogen activator (IV tPA) therapy has long been considered a mainstay in ischemic stroke management. However, patients respond to IV tPA therapy unequally with some subsets of patients having worsened outcomes after treatment. In particular, diabetes mellitus (DM) is recognized as a clinically important vascular comorbidity that leads to lower recanalization rates and increased risks of hemorrhagic transformation (HT). In this short-review, we summarize the recent advances in understanding of the underlying mechanisms involved in post-IV tPA worsening of outcome in diabetic stroke. Potential pathologic factors that are related to the suboptimal tPA recanalization in diabetic stroke include higher plasma plasminogen activator inhibitor (PAI)-1 level, diabetic atherogenic vascular damage, glycation of the tPA receptor annexin A2, and alterations in fibrin clot density. While factors contributing to the exacerbation of HT in diabetic stroke include hyperglycemia, vascular oxidative stress, and inflammation, tPA neurovascular toxicity and imbalance in extracellular proteolysis are discussed. Besides, impaired collaterals in DM also compromise the efficacy of IV tPA therapy. Additionally, several tPA combination approaches developed from experimental studies that may help to optimize IV tPA therapy are also briefly summarized. In summary, more research efforts are needed to improve the safety and efficacy of IV tPA therapy in ischemic stroke patients with DM/poststroke hyperglycemia.

Inhibition of PI3Kγ by AS605240 plus low-dose tissue plasminogen activator (tPA) combination improves thrombolytic therapy in a rat model of embolic stroke

Our previous study showed that PI3Kγ inhibition with AS605240 plus a standard rat-dose tPA (10 mg/kg) combination attenuates delayed tPA-induced brain hemorrhage and ameliorates acute stroke injury 3 days after ischemic stroke in rats. The purpose of this study was to investigate whether combining AS605240 with tPA can enhance thrombolytic efficacy, so that lower doses of tPA can be applied to improve long-term outcome after ischemic stroke. The results showed that AS605240 plus low-dose tPA (5 mg/kg) combination therapy at 4 h after stroke onset significantly reduced infarct volume and neurological deficits at 24 h after stroke compared with saline, AS605240 or low-dose tPA alone group. Importantly, the combination therapy significantly reduced the delayed tPA-associated brain hemorrhage. Moreover, the combination therapy significantly decreased the size of the residual embolus within the middle cerebral artery, which was associated with a decrease in plasma plasminogen activator inhibitor-1 (PAI-1) activity compared with saline and tPA alone. Finally, AS605240 plus low-dose tPA combination improved long-term outcome for at least 35 days after stroke compared with the saline-treated group. Taken together, these findings suggest that PI3Kγ inhibition with AS605240 might act as an adjunct approach for enhancing tPA thrombolytic efficacy in acute ischemic stroke.

Alterations of gut microbiota contribute to the progression of unruptured intracranial aneurysms

Unruptured intracranial aneurysm (UIA) is a life-threatening cerebrovascular condition. Whether changes in gut microbial composition participate in the development of UIAs remains largely unknown. We perform a case-control metagenome-wide association study in two cohorts of Chinese UIA patients and control individuals and mice that receive fecal transplants from human donors. After fecal transplantation, the UIA microbiota is sufficient to induce UIAs in mice. We identify UIA-associated gut microbial species link to changes in circulating taurine. Specifically, the abundance of Hungatella hathewayi is markedly decreased and positively correlated with the circulating taurine concentration in both humans and mice. Consistently, gavage with H. hathewayi normalizes the taurine levels in serum and protects mice against the formation and rupture of intracranial aneurysms. Taurine supplementation also reverses the progression of intracranial aneurysms. Our findings provide insights into a potential role of H. hathewayi-associated taurine depletion as a key factor in the pathogenesis of UIAs.

Unruptured intracranial aneurysm (UIA) is a life-threatening cerebrovascular condition. Here the authors report altered gut microbiota including low abundance of Hungatella hathewayi in patients with UIAs, and show that supplementation with Hungatella hathewayi or the metabolite taurine prevents UIAs in mice.

Time Course of Metabolomic Alterations in Cerebrospinal Fluid After Aneurysmal Subarachnoid Hemorrhage

Object: The aim of this study was to investigate metabolite levels in cerebrospinal fluid (CSF) in their time-dependent course after aneurysmal subarachnoid hemorrhage (aSAH) comparing them to patients harboring unruptured intracranial aneurysms. Methods: Eighty CSF samples of 16 patients were analyzed. The study population included patients undergoing endovascular/microsurgical treatment of ruptured intracranial aneurysms (n = 8), which were assessed for 9 days after aSAH. Control samples were collected from the basal cisterns in elective aneurysm surgery (n = 8). The CSF samples were consecutively collected with extraventricular drain (EVD) placement/intraoperatively, 6 h later, and daily thereafter (day 1-9). The endogenous metabolites were analyzed with a targeted quantitative and quality controlled metabolomics approach using the AbsoluteIDQ®p180Kit. Differences inbetween timepoints and compared to the control group were evaluated. Results: Numerous alterations of amino acid (AA) levels were detected within the first hours after bleeding. The highest mean concentrations occurred 1 week after aSAH. AA levels were continuously increasing over time starting 6 h after aSAH. Taurine concentration was highest briefly after aSAH starting to decrease already after 6 h (vs. day 1-9, p = 0.02). The levels of sphingomyelins/ phosphatidylcholines/ lysophosphatidylcholines/mono-unsaturated fatty acid chain were highly elevated on day 0 (compared to other timepoints or controls, p < 0.01) and decreased over the next several days to concentrations comparable to the control group. Carnitine concentrations were decreased after SAH (vs. day 7, p < 0.01), while they recovered within the next day. The Fischer ratio of branched-chain AA to aromatic AA was lowest immediately after SAH and increased in 7 days (p < 0.001). Conclusion: AA levels in CSF increased overtime and often differ from patients without SAH. There was a peak concentration of structural AA within the first 6 h after aneurysm treatment. Time-dependent alterations of CSF metabolites and compounds may elucidate pathophysiological processes after aSAH, providing potential predictors assessed non-invasively by routine lab testing.

Combined Treatment With 2-(2-Benzofu-Ranyl)-2-Imidazoline and Recombinant Tissue Plasminogen Activator Protects Blood-Brain Barrier Integrity in a Rat Model of Embolic Middle Cerebral Artery Occlusion

Recombinant tissue plasminogen activator (rt-PA) is used to treat acute ischemic stroke but is only effective if administered within 4.5 h after stroke onset. Delayed rt-PA treatment causes blood-brain barrier (BBB) disruption and hemorrhagic transformation. The compound 2-(-2-benzofuranyl)-2-imidazoline (2-BFI), a newly discovered antagonist of high-affinity postsynaptic N-methyl-D-aspartate (NMDA) receptors, has been shown to have neuroprotective effects in ischemia. Here, we investigated whether combining 2-BFI and rt-PA can ameliorate BBB disruption and prolong the therapeutic window in a rat model of embolic middle cerebral artery occlusion (eMCAO). Ischemia was induced in male Sprague Dawley rats by eMCAO, after which they were treated with 2-BFI (3 mg/kg) at 0.5 h in combination with rt-PA (10 mg/kg) at 6 or 8 h. Control rats were treated with saline or 2-BFI or rt-PA. Combined therapy with 2-BFI and rt-PA (6 h) reduced the infarct volume, denatured cell index, BBB permeability, and brain edema. This was associated with increased expression of aquaporin 4 (AQP4) and tight junction proteins (occludin and ZO-1) and downregulation of intercellular adhesion molecule 1 (ICAM-1) and matrix metalloproteinases 2 and 9 (MMP2 and MMP9). We conclude that 2-BFI protects the BBB from damage caused by delayed rt-PA treatment in ischemia. 2-BFI may therefore extend the therapeutic window up to 6 h after stroke onset in rats and may be a promising therapeutic strategy for humans. However, mechanisms to explain the effects oberved in the present study are not yet elucidated.

Nanoparticle Delivery of CD147 Antagonistic Peptide-9 Protects against Acute Ischemic Brain Injury and tPA-Induced Intracerebral Hemorrhage in Mice

CD147 has emerged as a potential therapeutic target in many human diseases. We have demonstrated that inhibition of CD147 using its function-blocking antibody ameliorates acute ischemic brain injury and promotes long-term functional recovery in mice. Recently, peptide-nanoparticle conjugates have emerged as powerful tools for biomedical applications. The present study aimed to investigate the therapeutic potential of CD147 antagonist peptide-9 (AP9) in acute ischemic stroke in mice using nanomaterial as the drug delivery vehicles. AP9-conjugated nanoparticles (APN), with an average size of about 40 nm, were fabricated by maleimide linkage and characterized using dynamic light scattering and transmission electron microscopy. We found that APN specifically bound to CD147 in cultured mouse brain endothelial cells (bEnd.3) and to ischemia-induced CD147 in mouse cerebral microvessels. Using a mouse model of transient middle cerebral artery occlusion (tMCAO), we demonstrated, for the first time, that systemic delivery of APN (2.5 mg/kg, I.V.) initiated at 1 h after tMCAO significantly reduced brain infarct size, improved functional outcome, and attenuated delayed (5 h after tMCAO) tPA-induced intracerebral hemorrhage in acute ischemic stroke. These protective effects were associated with profound inhibition of MMP-9 and MMP-3 in both ischemic brain and plasma. In conclusion, the CD147 antagonist peptide-9 represents a potentially promising therapeutic candidate for the treatment of ischemic stroke.

PI3Kγ (Phosphoinositide 3-Kinase-γ) Inhibition Attenuates Tissue-Type Plasminogen Activator-Induced Brain Hemorrhage and Improves Microvascular Patency After Embolic Stroke

Genetic and pharmacological inhibition of the PI3Kγ (phosphoinositide 3-kinase-γ) exerts anti-inflammatory and protective effects in a number of inflammatory and autoimmune diseases. SHRs (spontaneously hypertensive rats) subjected to embolic middle cerebral occlusion were treated with AS605240 (30 mg/kg) at 2 or 4 hours, tPA (tissue-type plasminogen activator; 10 mg/kg) at 2 or 6 hours, or AS605240 at 4 hours plus tPA at 6 hours. Infarct volume, brain hemorrhage, neurological function, microvascular thrombosis, and cerebral microvessel patency were examined. We found that treatment with AS605240 alone at 2 hours or the combination treatment with AS605240 at 4 hours and tPA at 6 hours significantly reduced infarct volume and neurological deficits at 3 days after stroke compared with ischemic rats treated with saline, AS605240 alone at 4 hours, and tPA alone at 6 hours. Moreover, the combination treatment effectively prevented the delayed tPA-induced cerebral hemorrhage. These protective effects are associated with reduced disruption of the blood-brain barrier, reduced downstream microvascular thrombosis, and improved microvascular patency by AS605240. Inhibition of the NF-κB (nuclear transcription factor-κB)-dependent MMP (matrix metalloproteinase)-9 and PAI-1 (plasminogen activator inhibitor-1) in the ischemic brain endothelium may underlie the neurovascular protective effect of AS605240. In addition, the combination treatment significantly reduced circulating platelet P-selectin expression and platelet-leukocyte aggregation compared with ischemic rats treated with saline or tPA alone at 6 hours. In conclusion, inhibition of PI3Kγ with AS605240 reduces delayed tPA-induced intracerebral hemorrhage and improves microvascular patency, which likely contributes to neuroprotective effect of the combination treatment.

Taurine and its analogs in neurological disorders: Focus on therapeutic potential and molecular mechanisms

Taurine is a sulfur-containing amino acid and known as semi-essential in mammals and is produced chiefly by the liver and kidney. It presents in different organs, including retina, brain, heart and placenta and demonstrates extensive physiological activities within the body. In the several disease models, it attenuates inflammation- and oxidative stress-mediated injuries. Taurine also modulates ER stress, Ca2+ homeostasis and neuronal activity at the molecular level as part of its broader roles. Different cellular processes such as energy metabolism, gene expression, osmosis and quality control of protein are regulated by taurine. In addition, taurine displays potential ameliorating effects against different neurological disorders such as neurodegenerative diseases, stroke, epilepsy and diabetic neuropathy and protects against injuries and toxicities of the nervous system. Several findings demonstrate its therapeutic role against neurodevelopmental disorders, including Angelman syndrome, Fragile X syndrome, sleep-wake disorders, neural tube defects and attention-deficit hyperactivity disorder. Considering current biopharmaceutical limitations, developing novel delivery approaches and new derivatives and precursors of taurine may be an attractive option for treating neurological disorders. Herein, we present an overview on the therapeutic potential of taurine against neurological disorders and highlight clinical studies and its molecular mechanistic roles. This article also addresses the neuropharmacological potential of taurine analogs.