Delayed Recanalization Promotes Functional Recovery in Rats Following Permanent Middle Cerebral Artery Occlusion

Delayed recanalization reduced neuronal apoptosis and neurological deficits by enhancing liver-derived trefoil factor 3-mediated neuroprotection via LINGO2/EGFR/Src signaling pathway after middle cerebral artery occlusion in rats

Delayed recanalization at days or weeks beyond the therapeutic window was shown to improve functional outcomes in acute ischemic stroke (AIS) patients. However, the underlying mechanisms remain unclear. Previous preclinical study reported that trefoil factor 3 (TFF3) was secreted by liver after cerebral ischemia and acted a distant neuroprotective factor. Here, we investigated the liver-derived TFF3-mediated neuroprotective mechanism enhanced by delayed recanalization after AIS. A total of 327 male Sprague-Dawley rats and the model of middle cerebral artery occlusion (MCAO) with permanent occlusion (pMCAO) or with delayed recanalization at 3 d post-occlusion (rMCAO) were used. Partial hepatectomy was performed within 5 min after MCAO. Leucine-rich repeat and immunoglobulin-like domain-containing nogo receptor-interacting protein 2 (LINGO2) siRNA was administered intracerebroventricularly at 48 h after MCAO. Recombinant rat TFF3 (rr-TFF3, 30 μg/Kg) or recombinant rat epidermal growth factor (rr-EGF, 100 μg/Kg) was administered intranasally at 1 h after recanalization, and EGFR inhibitor Gefitinib (75 mg/Kg) was administered intranasally at 30 min before recanalization. The evaluation of outcomes included neurobehavior, ELISA, western blot and immunofluorescence staining. TFF3 in hepatocytes and serum were upregulated in a similar time-dependent manner after MCAO. Compared to pMCAO, delayed recanalization increased brain TFF3 levels and attenuated brain damage with the reduction in neuronal apoptosis, infarct volume and neurological deficits. Partial hepatectomy reduced TFF3 levels in serum and ipsilateral brain hemisphere, and abolished the benefits of delayed recanalization on neuronal apoptosis and neurobehavioral deficits in rMCAO rats. Intranasal rrTFF3 treatment reversed the changes associated with partial hepatectomy. Delayed recanalization after MCAO increased the co-immunoprecipitation of TFF3 and LINGO2, as well as expressions of p-EGFR, p-Src and Bcl-2 in the brain. LINGO2 siRNA knockdown or EGFR inhibitor reversed the effects of delayed recanalization on apoptosis and brain expressions of LINGO2, p-EGFR, p-Src and Bcl-2 in rMCAO rats. EGFR activator abolished the deleterious effects of LINGO2 siRNA. In conclusion, our investigation demonstrated for the first time that delayed recanalization may enhance the entry of liver-derived TFF3 into ischemic brain upon restoring blood flow after MCAO, which attenuated neuronal apoptosis and neurological deficits at least in part via activating LINGO2/EGFR/Src pathway.

Melatonin Offers Dual-Phase Protection to Brain Vessel Endothelial Cells in Prolonged Cerebral Ischemia-Recanalization Through Ameliorating ER Stress and Resolving Refractory Stress Granule

Ischemic-reperfusion injury limits the time window of recanalization therapy in cerebral acute ischemic stroke (AIS). Brain vessel endothelial cells (BVECs) form the first layer of the blood-brain barrier (BBB) and are thus the first sufferer of ischemic-reperfusion disorder. The current study demonstrates that melatonin can reduce infarct volume, alleviate brain edema, ameliorate neurological deficits, and protect BBB integrity in prolonged-stroke mice. Here, we demonstrate that endoplasmic reticulum (ER)-associated injury contributes to BVEC death in the dural phase of reperfusion after prolonged ischemia. When encountering ischemia, ER stress arises, specifically activating PERK-EIF2α signaling and the subsequent programmed cell death. Prolonged ischemia leads stress granules (SGs) to be refractory, which remain unresolved and accumulate in ER during recanalization. During reperfusion, refractory SGs activate PKR-EIF2α and further exacerbate BVEC injury. We report that melatonin treatment downregulates ER stress in the ischemic period and enhances dissociation of the refractory SGs during reperfusion, thus offering dual-phase protection to BVECs in prolonged cerebral stroke. Mechanistically, melatonin enhances autophagy in BVECs, which preserves ER function and resolves refractory SGs. We, therefore, propose that melatonin is a potential treatment to extend the time window of delayed recanalization therapy in AIS.

A Microfluidics-Based Multiplex SERS Immunoassay Device for Analysis of Acute Ischemic Stroke Biomarkers

Sensitive and accurate methods for early detection of acute ischemic stroke (AIS) are essential for timely treatment and prognostic assessment of patients. In this study, we report a microfluidics-based ultrasensitive surface-enhanced Raman scattering (SERS) immunoassay device for the quantitative determination of multiplex biomarkers in AIS. By preparing 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) antibody-modified gold nanoparticles (AuNPs) on SERS devices as SERS probes, the biomarkers in whole blood of AIS were accurately captured and further visualized for SERS signal intensity quantitative analysis of six biomarkers in the blood samples. It is worth mentioning that the limit of detection (LOD) of the method can reach the level of fg/mL, with excellent sensitivity and selectivity. Meanwhile, the analytical comparison with ELISA method showed that the detection results of both methods were consistent, which verified the feasibility of the assembled device. The SERS immunoassay device detection provides a powerful strategy for the prediction, early diagnosis and dynamic monitoring of prognosis of AIS with a wide range of clinical practice prospects.

Three Days Delayed Recanalization Improved Neurological Function in pMCAO Rats by Increasing M2 Microglia-Possible Involvement of the IL-4R/STAT6/PPARγ Pathway

Current approved therapies for acute ischemic stroke have a restricted therapeutic time window. Delayed recanalization, which has been utilized clinically in patients who have missed the time window for administration, may be a promising alternative for stroke patients. However, the underlying molecular mechanisms remain undiscovered. Herein, we hypothesized that delayed recanalization would increase M2 microglial polarization through the IL-4R (interleukin-4 receptor)/STAT6 (signal transducer and activators of transcription 6)/PPARγ (peroxisome proliferator-activated receptor γ) pathway, subsequently promoting stroke recovery in rats. The permanent middle cerebral artery occlusion (pMCAO) model was induced via intravascular filament insertion. Recanalization was induced by withdrawing the filament at 3 days after MCAO (rMCAO). Interleukin (IL)-4 was administered intranasally at 3 days after pMCAO. AS1517499, a specific STAT6 inhibitor, was administered intranasally at 3 days after MCAO induction. Immunofluorescence staining, enzyme-linked immunosorbent assay (ELISA), western blot analysis, volumetric measurements of brain infarct, and neurological behavior tests were conducted. Delayed recanalization at 3 days after MCAO increased the polarization of M2 microglia, decreased inflammation, and improved neurological behavior. IL-4 treatment administered on the 3rd day after pMCAO increased M2 microglial polarization, improved neurological behavior, and reduced infarction volume of pMCAO rats. The inhibition of STAT6 decreased the level of p-STAT6 and PPARγ in rats treated with delayed recanalization. Delayed recanalization improved neurological function by increasing microglial M2 polarization, possibly involved with the IL-4R/STAT6/PPARγ pathway after MCAO in rats.

Delayed revascularization in acute ischemic stroke patients

Stroke shares a significant burden of global mortality and disability. A significant decline in the quality of life is attributed to the so-called post-stroke cognitive impairment including mild to severe cognitive alterations, dementia, and functional disability. Currently, only two clinical interventions including pharmacological and mechanical thrombolysis are advised for successful revascularization of the occluded vessel. However, their therapeutic effect is limited to the acute phase of stroke onset only. This often results in the exclusion of a significant number of patients who are unable to reach within the therapeutic window. Advances in neuroimaging technologies have allowed better assessment of salvageable penumbra and occluded vessel status. Improvement in diagnostic tools and the advent of intravascular interventional devices such as stent retrievers have expanded the potential revascularization window. Clinical studies have demonstrated positive outcomes of delayed revascularization beyond the recommended therapeutic window. This review will discuss the current understanding of ischemic stroke, the latest revascularization doctrine, and evidence from clinical studies regarding effective delayed revascularization in ischemic stroke.

Macrophage Infiltration Reduces Neurodegeneration and Improves Stroke Recovery after Delayed Recanalization in Rats

Background

Recent cerebrovascular recanalization therapy clinical trials have validated delayed recanalization in patients outside of the conventional window. However, a paucity of information on the pathophysiology of delayed recanalization and favorable outcomes remains. Since macrophages are extensively studied in tissue repair, we anticipate that they may play a critical role in delayed recanalization after ischemic stroke.

Methods

In adult male Sprague-Dawley rats, two ischemic stroke groups were used: permanent middle cerebral artery occlusion (pMCAO) and delayed recanalization at 3 days following middle cerebral artery occlusion (rMCAO). To evaluate outcome, brain morphology, neurological function, macrophage infiltration, angiogenesis, and neurodegeneration were reported. Confirming the role of macrophages, after their depletion, we assessed angiogenesis and neurodegeneration after delayed recanalization.

Results

No significant difference was observed in the rate of hemorrhage or animal mortality among pMCAO and rMCAO groups. Delayed recanalization increased angiogenesis, reduced infarct volumes and neurodegeneration, and improved neurological outcomes compared to nonrecanalized groups. In rMCAO groups, macrophage infiltration contributed to increased angiogenesis, which was characterized by increased vascular endothelial growth factor A and platelet-derived growth factor B. Confirming these links, macrophage depletion reduced angiogenesis, inflammation, neuronal survival in the peri-infarct region, and favorable outcome following delayed recanalization.

Conclusion

If properly selected, delayed recanalization at day 3 postinfarct can significantly improve the neurological outcome after ischemic stroke. The sanguineous exposure of the infarct/peri-infarct to macrophages was essential for favorable outcomes after delayed recanalization at 3 days following ischemic stroke.

Targeting upregulated RNA binding protein RCAN1.1: a promising strategy for neuroprotection in acute ischemic stroke

Aims

To explore the expression changes and roles of the RNA‐binding protein RCAN1.1 in acute ischemic stroke (AIS), and to preliminarily confirm the medicinal value of the RNA aptamer R1SR13 in AIS by targeting RCAN1.1.

Methods

Two mouse AIS models of middle cerebral artery occlusion (MCAO) and right common carotid artery ligation (R‐CCAL) and oxygen glucose deprivation (OGD) model of AIS in primary neurons and SH‐SY5Y were performed. The expression pattern of RCAN1.1 was assessed using real‐time quantitative PCR (RT‐qPCR) and western blotting (WB) in vivo and in vitro. The underlying mechanism for the elevation of RCAN1.1 in the upstream was investigated. Lentiviruses were administrated and the effect of RCAN1.1 in AIS was assessed by ATP level, caspase 3/7 assay, TUNEL and WB. The protective function of R1SR13 in AIS was evaluated both in vivo and in vitro.

Results

In two mouse models of AIS, RCAN1.1 mRNA and RCAN1.1 L protein were significantly upregulated in the ischemic brain tissue. The same results were detected in the OGD model of primary neurons and SH‐SY5Y. The mechanistic analysis proved that hypoxia‐inducible factor‐1α (HIF1α) could specifically activate the RCAN1.1 gene promoter through combining with the functional hypoxia‐responsive element (HRE) site (−325 to −322 bp). The increased expression of RCAN1.1 L markedly depleted ATP production and aggravated neuronal apoptosis under OGD condition. R1SR13, an antagonizing RNA aptamer of RCAN1.1, was demonstrated to reduce neuronal apoptosis caused by the elevated RCAN1.1 L in the cellular and animal models of AIS.

Conclusion

RCAN1.1 is a novel target gene of HIF1α and the functional HRE in the RCAN1.1 promoter region is −325 to −322 bp. The marked upregulation of RCAN1.1 in AIS promoted neuronal apoptosis, an effect that could be reversed by its RNA aptamer R1SR13 in vivo and in vitro. Thus, R1SR13 represents a promising strategy for neuroprotection in AIS and our study lays a theoretical foundation for it to become a clinically targeted drug.

Imaging Acute Stroke: From One-Size-Fit-All to Biomarkers

In acute stroke management, time window has been rigidly used as a guide for decades and the reperfusion treatment is only available in the first few limited hours. Recently, imaging-based selection of patients has successfully expanded the treatment window out to 16 and even 24 h in the DEFUSE 3 and DAWN trials, respectively. Recent guidelines recommend the use of imaging techniques to guide therapeutic decision-making and expanded eligibility in acute ischemic stroke. A tissue window is proposed to replace the time window and serve as the surrogate marker for potentially salvageable tissue. This article reviews the evolution of time window, addresses the advantage of a tissue window in precision medicine for ischemic stroke, and discusses both the established and emerging techniques of neuroimaging and their roles in defining a tissue window. We also emphasize the metabolic imaging and molecular imaging of brain pathophysiology, and highlight its potential in patient selection and treatment response prediction in ischemic stroke.

The Next Step in the Treatment of Stroke

Although many patients do not receive reperfusion therapy because of delayed presentation and/or severity and location of infarct, new reperfusion approaches are expanding the window of intervention. Novel application of neuroprotective agents in combination with the latest methods of reperfusion provide a path to improved stroke intervention outcomes. We examine why neuroprotective agents have failed to translate to the clinic and provide suggestions for new approaches. New developments in recanalization therapy in combination with therapeutics evaluated in parallel animal models of disease will allow for novel, intra-arterial deployment of therapeutic agents over a vastly expanded therapeutic time window and with greater likelihood success. Although the field of neuronal, endothelial, and glial protective therapies has seen numerous large trials, the application of therapies in the context of newly developed reperfusion strategies is still in its infancy. Given modern imaging developments, evaluation of the penumbra will likely play a larger role in the evolving management of stroke. Increasingly more patients will be screened with neuroimaging to identify patients with adequate collateral blood supply allowing for delayed rescue of the penumbra. These patients will be ideal candidates for therapies such as reperfusion dependent therapeutic agents that pair optimally with cutting-edge reperfusion techniques.

Selective brain cooling achieves peripheral organs protection in hemorrhagic shock resuscitation via preserving the integrity of the brain-gut axis

Background: Although whole-body cooling has been reported to improve the ischemic/reperfusion injury in hemorrhagic shock (HS) resuscitation, it is limited by its adverse reactions following therapeutic hypothermia. HS affects the experimental and clinical bowel disorders via activation of the brain-gut axis. It is unknown whether selective brain cooling achieves beneficial effects in HS resuscitation via preserving the integrity of the brain-gut axis. Methods: Male Sprague-Dawley rats were bled to hypovolemic HS and resuscitated with blood transfusion followed by retrograde jugular vein flush (RJVF) with 4 °C or 36 °C normal saline. The mean arterial blood pressure, cerebral blood flow, and brain and core temperature were measured. The integrity of intestinal tight junction proteins and permeability, blood pro-inflammatory cytokines, and multiple organs damage score were determined. Results: Following blood transfusion resuscitation, HS rats displayed gut barrier disruption, increased blood levels of pro-inflammatory cytokines, and peripheral vital organ injuries. Intrajugular-based infusion cooled the brain robustly with a minimal effect on body temperature. This brain cooling significantly reduced the HS resuscitation-induced gut disruption, systemic inflammation, and peripheral vital organ injuries in rats. Conclusion: Resuscitation with selective brain cooling achieves peripheral vital organs protection in hemorrhagic shock resuscitation via preserving the integrity of the brain-gut axis.

Hyperbaric oxygen therapy after acute ischemic stroke with large penumbra: a case report

Background

Hyperbaric oxygen therapy (HBOT) for the treatment of acute stroke has been under the radar for a long time. Previous studies have not been able to prove efficacy. Several factors might have contributed to such inconsistent results. The timing of delivering the hyperbaric oxygen in relation to the stage of stroke evolution may be an important factor. This was not taken into account in the previous studies as there was no feasible and standardized method to assess the penumbra in the acute phase. Now with the perfusion scan appearing as a key player in the acute stroke management, precise stroke patient selection for hyperbaric oxygen therapy deserves a second chance similar to mechanical thrombectomy.

Case presentation

A 62-year-old female patient who presented with acute large vessel stroke was not eligible for chemical or mechanical thrombectomy. There was a large penumbra on imaging. She got treated with several sessions of hyperbaric oxygen over a 2-week period immediately after stroke. The patient showed significant improvement on the follow-up perfusion imaging as well as some clinical improvement. The more impressive radiological improvement was probably due to the presence of relatively large core infarction at baseline affecting functional brain areas. The patient continued to improve clinically on her 6-month follow up visit.

Conclusion

Our case demonstrates immediate stroke-related penumbra improvement associated with HBOT. Based on that, we anticipate a potential role for HBOT in acute stroke management considering precise patient selection. Future randomized controlled trials are needed and should take that in consideration.

Valproate Sodium Protects Blood Brain Barrier Integrity in Intracerebral Hemorrhage Mice

Valproate sodium (VPA) is a traditional antiepileptic drug with a neuroprotective role in cerebrovascular disease. After intracerebral hemorrhage (ICH), mechanical compression by hematoma, neuroinflammation, oxidative stress, and cytotoxicity of hematoma lysates caused the destruction of the blood brain barrier (BBB). Targeting BBB is a major therapeutic method for patients with ICH. The purpose of the present study was to explore the role of VPA in preserving BBB integrity in the ICH model and investigate the underlying molecular mechanisms. One hundred and thirty-six adult male CD1 mice were randomly divided into five groups in the study. Mice subjected to ICH were administered intraperitoneally with VPA at 3, 24, and 48 h post-ICH, respectively. Neurobehavioral assessments, BBB permeability, Evans blue fluorescence, hematoma volume, and protein expression were evaluated. The administration of VPA reduced BBB permeability and improved the neurobehavior significantly post-ICH. VPA administration significantly decreased the expression of phosphorylated nuclear factor-kappa B (p-NFκB), matrix metalloproteinases 9 (MMP9), tumor necrosis factorα (TNFα), and interleukin-6 (IL-6), while it enhanced the expression of claudin 5 and occludin in the brain. In conclusion, VPA administration maintained the integrity of BBB after experimental ICH, thus reducing brain edema and improving the neurological outcomes. Therefore, VPA administration might be a new therapeutic method to protect BBB integrity for patients with ICH.

Edaravone-Loaded Macrophage-Derived Exosomes Enhance Neuroprotection in the Rat Permanent Middle Cerebral Artery Occlusion Model of Stroke

Edaravone (Edv) can inhibit tissue damage, cause cerebral edema, and delay neuronal death caused by acute cerebral infarction. Exosomes are considered as cargo carriers for intercellular communication and serve as important regulators in many pathological processes. Here, we developed macrophage-derived exosomes (Exo) containing Edv (Exo + Edv) to improve the bioavailability of Edv and enhance the neuroprotective effects in a rat model of permanent middle cerebral artery occlusion (PMCAO). The results showed that Exo + Edv significantly improved the bioavailability of Edv and prolonged half-life (t_1/2). At the same time, Exo + Edv made Edv more easily reach the ischemic side of rats with PMCAO and was localized with neuronal cells and microglia, thus reducing the death of neuronal cells and promoting the polarization of microglia from M1 to M2. Taken together, Exo + Edv may become a potential clinical treatment option for PMCAO.

Delayed recanalization after MCAO ameliorates ischemic stroke by inhibiting apoptosis via HGF/c-Met/STAT3/Bcl-2 pathway in rats

The activation of tyrosine kinase receptor c-Met by hepatocyte growth factor (HGF) showed an anti-apoptotic effect in numerous disease models. This study aimed to investigate the neuroprotective mechanism of the HGF/c-Met axis-mediated anti-apoptosis underlying the delayed recanalization in a rat model of middle cerebral artery occlusion (MCAO). Permanent MCAO model (pMCAO) was induced by intravascular filament insertion. Recanalization was induced by withdrawing the filament at 3 days after MCAO (rMCAO). HGF levels in the blood serum and brain tissue expressions of HGF, c-Met, phosphorylated-STAT3 (p-STAT3), STAT3, Bcl-2, Bax, cleaved caspase-3(CC3) were assessed using ELISA and western blot, respectively. To study the mechanism, HGF small interfering ribonucleic acid (siRNA) and c-Met inhibitor, su11274, were administered intracerebroventricularly (i.c.v.) or intranasally, respectively. The concentration of HGF in the serum was increased significantly after MCAO. Brain expression of HGF was increased after MCAO and peaked at 3 days after recanalization. HGF and c-Met were both co-localized with neurons. Compared to rats received permanent MCAO, delayed recanalization after MCAO decreased the infarction volume, inhibited neuronal apoptosis, and improved neurobehavioral function, increased expressions of p-STAT3 and its downstream Bcl-2. Mechanistic studies indicated that HGF siRNA and su11274 reversed the neuroprotection including anti-apoptotic effects provided by delayed recanalization. In conclusion, the delayed recanalization after MCAO increased the expression of HGF in the brain, and reduced the infarction and neuronal apoptosis after MCAO, partly via the activation of the HGF/c-Met/STAT3/Bcl-2 signaling pathway. The delayed recanalization may serve as a therapeutic alternative for a subset of ischemic stroke patients.

Knockdown of Arginyl-tRNA Synthetase Attenuates Ischemia-Induced Cerebral Cortex Injury in Rats After Middle Cerebral Artery Occlusion

Some researchers have previously shown that RNAi knockdown of arginyl-tRNA synthetase (ArgRS) before or after a hypoxic injury can rescue animals from death, based on the model organism, C. elegans. However, there has been no study on the application of arginyl-tRNA synthetase knockdown in treating mammalian ischemic stroke, and its potential mechanism and effect on ischemic brain damage are still unknown. Here, we focused on the Rars gene, which encodes an arginyl-tRNA synthetase, and examined the effects of Rars knockdown in a permanent middle cerebral artery occlusion model in rats. To achieve this aim, adult male Sprague-Dawley (SD) rats were given right cerebral cortex injections of short hairpin RNA (shRNA) adenovirus (AV) particles to knock down arginyl-tRNA synthetase, and a non-targeting control (NTC) vector or phosphate-buffered solution served as the controls. After 4 days, the rats were exposed to permanent middle cerebral artery occlusion (pMCAO). Then, the right cerebral cortex level of arginyl-tRNA synthetase was examined, and the effects of the Rars knockdown were evaluated by differences in infarction volume, oxidative stress, blood-brain barrier, mitochondrial function, and glucose metabolism at 1 day and 3 days after MCAO. The injection of shRNA adenovirus particles successfully suppressed the expression of arginyl-tRNA synthetase in the cerebral cortex. We observed an improvement in oxidative stress, mitochondrial function, and glucose utilization and a reduction in brain edema compared with the non-targeting control rats with suppressed expression of arginyl-tRNA synthetase mRNA in the ipsilateral ischemic cortex of the brain. Our findings indicate that knockdown of arginyl-tRNA synthetase in the cerebral cortex exerted neuroprotective effects, which were achieved not only by the improvement of oxidative stress and glucose utilization but also by the maintenance of mitochondrial morphological integrity and the preservation of mitochondrial function. Knockdown of ArgRS administration could be a promising approach to protect ischemic stroke.

Relation of Retinal Oxygen Measures to Electrophysiology and Survival Indicators after Permanent, Incomplete Ischemia in Rats

Studies in experimental ischemia models by permanent bilateral common carotid artery occlusion (BCCAO) have reported reduced retinal electrophysiological function, coupled with inner retinal degeneration and gliosis. In the current study, we tested the hypothesis that long-term (up to 14 days) BCCAO impairs oxygen delivery (DO₂), which affects oxygen metabolism (MO₂) and extraction fraction (OEF), electrophysiological function, morphology, and biochemical pathways. Twenty-one rats underwent BCCAO (N = 12) or sham surgery (N = 9) and were evaluated in separate groups after 3, 7, or 14 days. Electroretinography (ERG), optical coherence tomography, blood flow and vascular oxygen tension imaging, and morphological and biochemical evaluations were performed in both eyes. Reduced ERG b-wave amplitudes and delayed implicit times were reported at 3, 7, and 14 days following BCCAO. Total retinal blood flow, MO₂, and DO₂ were reduced in all BCCAO groups. OEF was increased in both 3- and 7-day groups, while no significant difference was observed in OEF at 14 days compared to the sham group. At 14 days following BCCAO, total and inner retinal layer thickness was reduced, while the outer nuclear layer thickness and gliosis were increased. There was an increase in nuclei containing fragmented DNA at 3 days following BCCAO. The compensatory elevation in OEF following BCCAO did not meet the tissue demand, resulting in the subsequent reduction of MO₂. The associations between retinal MO₂, DO₂, and retinal function were shown to be significant in the sequelae of persistent ischemia. In sum, measurements of DO₂, MO₂, and OEF may become useful for characterizing salvageable tissue in vision-threatening pathologies.

Ezetimibe Attenuates Oxidative Stress and Neuroinflammation via the AMPK/Nrf2/TXNIP Pathway after MCAO in Rats

Oxidative stress and neuroinflammation play essential roles in ischemic stroke-induced brain injury. Previous studies have reported that Ezetimibe (Eze) exerts antioxidative stress and anti-inflammatory properties in hepatocytes. In the present study, we investigated the effects of Eze on oxidative stress and neuroinflammation in a rat middle cerebral artery occlusion (MCAO) model. One hundred and ninety-eight male Sprague-Dawley rats were used. Animals assigned to MCAO were given either Eze or its control. To explore the downstream signaling of Eze, the following interventions were given: AMPK inhibitor dorsomorphin and nuclear factor erythroid 2-related factor 2 (Nrf2) siRNA. Intranasal administration of Eze, 1 h post-MCAO, further increased the endogenous p-AMPK expression, reducing brain infarction, neurologic deficits, neutrophil infiltration, microglia/macrophage activation, number of dihydroethidium- (DHE-) positive cells, and malonaldehyde (MDA) levels. Specifically, treatment with Eze increased the expression of p-AMPK, Nrf2, and HO-1; Romo-1, thioredoxin-interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3), Cleaved Caspase-1, and IL-1β were reduced. Dorsomorphin and Nrf2 siRNA reversed the protective effects of Eze. In summary, Eze decreases oxidative stress and subsequent neuroinflammation via activation of the AMPK/Nrf2/TXNIP pathway after MCAO in rats. Therefore, Eze may be a potential therapeutic approach for ischemic stroke patients.

Asymmetric Deep Medullary Veins in Patients With Occlusion of a Large Cerebral Artery: Association With Cortical Veins, Leptomeningeal Collaterals, and Prognosis

Objective: To explore the relationships of asymmetric deep medullary veins (ADMV) to asymmetric cortical veins (ACV), leptomeningeal collaterals and prognosis in patients with occlusion of a large cerebral artery. Methods: Clinical and imaging data of 56 patients with occlusion of a large cerebral artery were collected and reviewed. We assessed the time delayed between stroke onset and MR imaging (within 24 h of stroke onset), extension of cerebral infarction using the Alberta stroke program early CT score based on diffusion-weighted imaging (ASPECTs). ADMV and ACV were assessed using susceptibility-weighted imaging. The presence of ADMV (ACV) was defined as deep medullary veins (cortical veins) of the affected hemisphere that were greater in number and diameter than in the contralateral hemisphere. To evaluate leptomeningeal collaterals, the hyperintense vessel sign (HVS) was detected using T2 weighted fluid attenuated inversion recovery images. At 90 days, a modified Rankin scale score (mRS) was assessed to evaluate the clinical outcome. Results: Of 56 patients, 27 presented with ADMV. Those patients who presented with and without ADMV differed significantly in HVS and ACV (P < 0.05) but not in time delayed between stroke onset and MR imaging, age, gender, stroke risk factors, baseline NIHSS score, or modified Rankin scale score at 3 months (P > 0.05). Logistic regression analysis found that the presence of ADMV was independently related to HVS and ACV (ACV: OR 95% C.I., 1.287-4.368; HVS: OR 95% C.I., 1.132-4.887). Conclusions: The presence of ADMV on SWI was associated with prominent ACV and good leptomeningeal collateral flow but was not related to prognosis in patients with occlusion of a large cerebral artery.

Delayed recanalization in acute ischemic stroke patients: Late is better than never?

Successful recanalization of the occluded vessel as early as possible has been widely accepted as the key principle of acute ischemic stroke (AIS) treatment. Unfortunately, for many years, the vast majority of AIS patients were prevented from receiving effective recanalization therapy because of a narrow therapeutic window. Recently, a series of inspiring clinical trials have indicated that more patients may benefit from delayed recanalization during an expanded therapeutic window, even up to 24 h after symptom onset. However, could potentially salvageable brain tissue (penumbra) in patients who do not receive medication within 24 h still possible to be saved?

Therapeutic effects of JLX-001 on ischemic stroke by inducing autophagy via AMPK-ULK1 signaling pathway in rats

(3β,5α,16α,20S)-4,4,14-trimethyl-3,20-bis(methylamino)-9,19-cyclopregnan-16-ol-dihydrochloride (JLX-001), a structural analogue of cyclovirobuxine D (CVB-D), is a novel compound from synthesis. This study aims to confirm the therapeutic effects of JLX001 on ischemic stroke (IS) and research its induction of autophagy function via 5'-AMP-activated protein kinase (AMPK)-Human Serine/threonine-protein kinase (ULK1) signaling pathway activation. The therapeutic effects of JLX001 were evaluated by infarct sizes, brain edema, neurological scores and proportion of apoptotic neurons in Sprague-Dawley (SD) rats with middle cerebral artery occlusion/reperfusion (MCAO/R). The number of autophagosomes was obtained by transmission electron microscopy. The expression of LC3-II was measured by immunofluorescence. p-AMPK and activated ULK1 were detected by western blots. Results showed that JLX001 treatment markedly alleviated cerebral infarcts, edema, neurological scores and proportion of apoptotic neurons in MCAO/R rats. The number of autophagosomes was increased, accompanying with the increased expressions of LC3-II, p-AMPK and ULK1. In summary, JLX001 attenuates cerebral ischemia injury and the underlying mechanisms may relate to inducing autophagy via AMPK-ULK1 signaling pathway activation.

Delayed recanalization at 3 days after permanent MCAO attenuates neuronal apoptosis through FGF21/FGFR1/PI3K/Caspase-3 pathway in rats

Reperfusion exceeded time window may induce ischemia/reperfusion injury, increase hemorrhagic transformation, and deteriorate neurological outcomes in ischemic stroke models. However, the increasing clinical evidences supported that reperfusion even within 6-24 h may salvage ischemic tissue and improve neurological outcomes in selected large vessel occlusion patients, without inducing serious ischemia/reperfusion injury and hemorrhagic transformation. The underlying molecular mechanisms are less clear. In present study, we demonstrated that delayed recanalization at 3 days after permanent middle cerebral artery occlusion (MCAO) decreased infarct volumes and improved neurobehavioral deficits in rats, with no increasing animal mortality and intracerebral hemorrhage. Meanwhile, we observed that endogenous neuroprotective agent fibroblast growth factor 21 (FGF21) significantly increased in serum after MCAO, but which did not synchronously increase in penumbra due to permanent MCAO. Recanalization dramatically increased the endogenous FGF21 expression on neurons in penumbra after MCAO. We confirmed that FGF21 activated the FGFR1/PI3K/Caspase-3 signaling pathway, which attenuated neuronal apoptosis in penumbra. Conversely, knockdown of FGFR1 via FGFR1 siRNA abolished the anti-apoptotic effects of FGF21, and in part abrogated beneficial effects of recanalization on neurological outcomes. These findings suggested that delayed recanalization at 3 days after MCAO improved neurological outcomes in rats via increasing endogenous FGF21 expression and activating FGFR1/PI3K/Caspase-3 pathway to attenuate neuronal apoptosis in penumbra. Delayed recanalization at 3 days after ischemic stroke onset may be a promising treatment strategy in selected patients.

Chemerin reverses neurological impairments and ameliorates neuronal apoptosis through ChemR23/CAMKK2/AMPK pathway in neonatal hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a devastating neurological event that contributes to the prolonged neurodevelopmental consequences in infants. Therapeutic strategies focused on attenuating neuronal apoptosis in the penumbra appears to be promising. Given the increasingly recognized neuroprotective roles of adipokines in HIE, we investigated the potential anti-apoptotic roles of a novel member of adipokines, Chemerin, in an experimental model of HIE. In the present study, 10-day-old rat pups underwent right common carotid artery ligation followed by 2.5 h hypoxia. At 1 h post hypoxia, pups were intranasally administered with human recombinant chemerin (rh-chemerin). Here, we showed that rh-chemerin prevented the neuronal apoptosis and degeneration as evidenced by the decreased expression of the pro-apoptotic markers, cleaved caspase 3 and Bax, as well as the numbers of Fluoro-Jade C and TUNEL-positive neurons. Furthermore, rh-Chemerin reversed neurological and morphological impairments induced by hypoxia-ischemia in neonatal rats at 24 h and 4 weeks after HIE. In addition, chemerin-mediated neuronal survival correlated with the elevation of chemerin receptor 23 (chemR23), phosphorylated calmodulin-dependent protein kinase kinase 2 (CAMKK2), as well as phosphorylated adenosine monophosphate-activated protein kinase (AMPK). Specific inhibition of chemR23, CAMKK2, and AMPK abolished the anti-apoptotic effects of rh-chemerin at 24 h after HIE, demonstrating that rh-chemerin ameliorated neuronal apoptosis partially via activating chemR23/CAMKK2/AMPK signaling pathway. Neuronal apoptosis is a well-established contributing factor of pathological changes and the neurological impairment after HIE. These results revealed mechanisms of neuroprotection by rh-chemerin, and indicated that activation of chemR23 might be harnessed to protect from neuronal apoptosis in HIE.

Ezetimibe, a NPC1L1 inhibitor, attenuates neuronal apoptosis through AMPK dependent autophagy activation after MCAO in rats

Autophagy activation exerts neuroprotective effects in the ischemic stroke model. Ezetimibe (Eze), a Niemann-Pick disease type C1-Like 1 (NPC1L1) pharmacological inhibitor, has been reported to protect hepatocytes from apoptosis via autophagy activation. In this study, we explored whether Eze could attenuate neuronal apoptosis in the rat model of middle cerebral artery occlusion (MCAO), specifically via activation of the AMPK/ULK1/autophagy pathway. Two hundred and one male Sprague-Dawley rats were subjected to transient MCAO followed by reperfusion. Eze was administered 1 h after MCAO. To elucidate the underlying molecular mechanism, Dorsomorphin, a selective AMPK inhibitor, and 3-methyladenine (3-MA), an autophagy inhibitor, were injected intracerebroventricularly before MCAO. Infarct volume, neurological score, brain cholesterol levels, immunofluorescence staining, Western blot, and Fluoro-Jade C (FJC) staining were used to evaluate the effects of Eze. The endogenous NPC1L1 expression increased and mainly expressed in neurons after MCAO. Intranasal administration of Eze reduced brain infarct volume at 24 and 72 h after MCAO, with improved short and long-term neurological functions after MCAO. Eze reduced brain cholesterol levels (total cholesterol, free cholesterol and cholesteryl esters) and the number of FJC-positive neurons. The expression of phosphorylated AMPK (p-AMPK) and downstream ULK1, Beclin1, LC3BII, Bcl-2, and Bcl-xl increased, while P62 and proapoptotic Bax decreased after treatment with Eze. Pretreatment with Dorsomorphin and 3-MA reversed the beneficial effects of Eze. These findings suggest that intranasal administration of Eze plays neuroprotective role through autophagy activation after MCAO in rats. Lowered cholesterol levels and AMPK activation may act in conjunction to induce autophagy after treatment with Eze. Eze merits further investigation as a potential therapeutic agent in ischemic stroke patients.