Acute ischemic stroke therapy

Intermittent Fasting on Neurologic Diseases: Potential Role of Gut Microbiota

As the global population ages, the prevalence of neurodegenerative diseases is surging. These disorders have a multifaceted pathogenesis, entwined with genetic and environmental factors. Emerging research underscores the profound influence of diet on the development and progression of health conditions. Intermittent fasting (IF), a dietary pattern that is increasingly embraced and recommended, has demonstrated potential in improving neurophysiological functions and mitigating pathological injuries with few adverse effects. Although the precise mechanisms of IF's beneficial impact are not yet completely understood, gut microbiota and their metabolites are believed to be pivotal in mediating these effects. This review endeavors to thoroughly examine current studies on the shifts in gut microbiota and metabolite profiles prompted by IF, and their possible consequences for neural health. It also highlights the significance of dietary strategies as a clinical consideration for those with neurological conditions.

Advances in Acute Ischemic Stroke Therapy

The treatment of acute ischemic stroke continues to advance. The mainstay of treatment remains intravenous thrombolysis with alteplase. Recent studies demonstrated that later treatment with alteplase is beneficial in patients selected with advanced imaging techniques. Tenecteplase has been evaluated as an alternative thrombolytic drug and evidence suggests that it is as least as effective as alteplase and may lyse large vessel clots more effectively. Endovascular therapy with mechanical thrombectomy has now been shown to be beneficial up to 24 hours after stroke onset in carefully selected patients with proximal, large vessel occlusions. Ongoing studies are evaluating the effectiveness of thrombectomy in patients with more distal vessel occlusions and patients with proximal large vessel occlusions with larger ischemic core volumes and also in patients with milder neurological deficits. Cytoprotection is another potential acute stroke therapy that has not demonstrated efficacy in prior clinical trials. It should be reconsidered as an adjunct to reperfusion and a variety of new clinical trials can be envisioned to evaluate the potential benefits of cytoprotection in patients before and after reperfusion.

Pharmacological brain cytoprotection in acute ischaemic stroke — renewed hope in the reperfusion era

For over 40 years, attempts to develop treatments that protect neurons and other brain cells against the cellular and biochemical consequences of cerebral ischaemia in acute ischaemic stroke (AIS) have been unsuccessful. However, the advent of intravenous thrombolysis and endovascular thrombectomy has taken us into a new era of treatment for AIS in which highly effective reperfusion therapy is widely available. In this context, cytoprotective treatments should be revisited as adjunctive treatment to reperfusion therapy. Renewed efforts should focus on developing new drugs that target multiple aspects of the ischaemic cascade, and previously developed drugs should be reconsidered if they produced robust cytoprotective effects in preclinical models and their safety profiles were reasonable in previous clinical trials. Several development pathways for cytoprotection as an adjunct to reperfusion can be envisioned. In this Review, we outline the targets for cytoprotective therapy and discuss considerations for future drug development, highlighting the recent ESCAPE-NA1 trial of nerinetide, which produced the most promising results to date. We review new types of clinical trial to evaluate whether cytoprotective drugs can slow infarct growth prior to reperfusion and/or ameliorate the consequences of reperfusion, such as haemorrhagic transformation. We also highlight how advanced brain imaging can help to identify patients with salvageable ischaemic tissue who are likely to benefit from cytoprotective therapy.

In this Review, Fisher and Savitz consider how the era of reperfusion therapy in ischaemic stroke provides new hope for the development of cytoprotective therapies to further improve outcomes, highlighting how promising recent findings can be built on to benefit patients.

Highly successful reperfusion therapy with intravenous thrombolysis and endovascular thrombectomy is now widely available for the treatment of acute ischaemic stroke, making cytoprotective therapy a viable additional treatment approach.

Previous attempts to develop cytoprotective therapy have been unsuccessful, but this approach should now be reconsidered as an adjunctive therapy to thrombolysis and thrombectomy.

New cytoprotective drugs should be developed to target multiple aspects of the ischaemic cascade, and previously developed drugs should be reconsidered.

Trials should be conducted to evaluate the effects of cytoprotective drugs when administered before or after reperfusion therapy or both.

Advanced brain imaging should be used to select patients who are most likely to benefit from cytoprotective treatment for enrolment in new trials.

HDAC3 Downregulation Improves Cerebral Ischemic Injury via Regulation of the SDC1-Dependent JAK1/STAT3 Signaling Pathway Through miR-19a Upregulation

Histone deacetylase (HDAC) inhibitors can protect the brain from ischemic injury. This study aimed to identify the regulation of HDAC3 in cerebral ischemic injury. Middle cerebral artery occlusion (MCAO) was performed to establish a mouse model with cerebral ischemic injury, in which expression of HDAC3 and miR-19a was evaluated using RT-qPCR. In MCAO mice with silencing of HDAC3, infarct volume was determined using 2,3,5-triphenyl tetrazolium chloride (TTC) staining, and serum levels of TNF-α, IL-6, and IL-8 were measured using ELISA. An in vitro model was constructed in human umbilical vein endothelial cells (HUVECs) with oxygen-glucose deprivation/reoxygenation (OGD/R), followed by gain- and loss-of-function experiments. Relationships among miR-19a, HDAC3, and syndecan-1 (SDC1) were explored using RIP, ChIP, and dual-luciferase reporter assays. The expression of HDAC3, SDC1, JAK1, and STAT3 along with the extent of JAK1 and STAT3 phosphorylation was measured by Western blot analysis. HUVEC viability, apoptosis, and angiogenesis were assessed by CCK-8, flow cytometry, and angiogenesis assays in vitro separately. We found elevated HDAC3 and downregulated miR-19a expression in the MCAO mice. Decreased TNF-α, IL-6, and IL-8 serum levels were observed in response to silencing of HDAC3. HDAC3 inhibited the expression of miR-19a, which in turn targeted SDC1, leading to JAK1/STAT3 signaling pathway activation. HDAC3 overexpression or miR-19a inhibition repressed HUVEC viability and angiogenesis but enhanced HUVEC apoptosis. Our data unraveled the mechanism whereby HDAC3 inhibition ameliorated cerebral ischemic injury by activating the JAK1/STAT3 signaling pathway through miR-19a-mediated SDC1 inhibition.

Nucleic Acid Therapies for Ischemic Stroke

Stroke remains a leading cause of disability and death worldwide despite significant scientific and therapeutic advances. Therefore, there is a critical need to improve stroke prevention and treatment. In this review, we describe several examples that leverage nucleic acid therapeutics to improve stroke care through prevention, acute treatment, and recovery. Aptamer systems are under development to increase the safety and efficacy of antithrombotic and thrombolytic treatment, which represent the mainstay of medical stroke therapy. Antisense oligonucleotide therapy has shown some promise in treating stroke causes that are genetically determined and resistant to classic prevention approaches such as elevated lipoprotein (a) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Targeting microRNAs may be attractive because they regulate factors involved in neuronal cell death and reperfusion-associated injury, as well as neurorestorative pathways. Lastly, microRNAs may aid reliable etiologic classification of stroke subtypes, which is important for effective secondary stroke prevention.

ZL006 promotes migration and differentiation of transplanted neural stem cells in male rats after stroke

New strategies must be developed to resolve the problems of stroke treatment. In recent years, stem cell-based therapy after stroke has come into the public and academic lens. Previously we have shown that uncoupling neuronal nitric oxide synthase (nNOS) from the postsynaptic density protein-95 (PSD-95) by ZL006, a small molecular compound, can ameliorate ischemic damage and promote neuronal differentiation of endogenous neural stem cells (NSCs) in focal cerebral ischemic male rats. In this study, we transplanted exogenous NSCs into the ipsilateral hemisphere of male rats in combination with ZL006 treatment after ischemic stroke. We show that ZL006 treatment facilitates the migration of transplanted NSCs into the ischemia-injured area and promotes neuronal differentiation of these cells, which is not due to a direct effect of ZL006 on exogenous NSCs but is associated with increased phosphorylation of cAMP response element-binding protein (CREB) in neurons and favorable microenvironment. Moreover, improved functional outcome in the ZL006-treated group was also found. Taken together, our data indicate that ZL006, uncoupling nNOS-PSD-95 in neurons, positively regulates the fate of transplanted NSCs and benefits the functional outcome after stroke in male rats.

Commensal microbiota affects ischemic stroke outcome by regulating intestinal γδ T cells

Commensal gut bacteria impact the host immune system and can influence disease processes in several organs, including the brain. However, it remains unclear whether the microbiota has an impact on the outcome of acute brain injury. Here we show that antibiotic-induced alterations in the intestinal flora reduce ischemic brain injury in mice, an effect transmissible by fecal transplants. Intestinal dysbiosis alters immune homeostasis in the small intestine, leading to an increase in regulatory T cells and a reduction in interleukin (IL)-17-positive γδ T cells through altered dendritic cell activity. Dysbiosis suppresses trafficking of effector T cells from the gut to the leptomeninges after stroke. Additionally, IL-10 and IL-17 are required for the neuroprotection afforded by intestinal dysbiosis. The findings reveal a previously unrecognized gut-brain axis and an impact of the intestinal flora and meningeal IL-17(+) γδ T cells on ischemic injury.

Endothelial CD36 Contributes to Postischemic Brain Injury by Promoting Neutrophil Activation via CSF3

The scavenger receptor CD36 is a critical factor initiating ischemic brain injury, but the cell type(s) expressing CD36 and responsible for its harmful effects remain unknown. Using bone marrow (BM) chimeras subjected to transient middle cerebral artery occlusion, we found that CD36(-/-) mice transplanted with wild-type (WT) BM (WT→CD36(-/-)) have smaller infarcts (-67%), comparable with those of mice lacking CD36 both in brain and hematogenous cells (CD36(-/-) →CD36(-/-); - 72%). Conversely, WT mice receiving CD36(-/-) BM (CD36(-/-) →WT) have infarcts similar to WT→WT mice, suggesting that CD36 in the host brain (i.e., in microglia and endothelial cells), and not in hematogenous cells is involved in the damage. As anticipated, postischemic neutrophil infiltration in CD36(-/-) →CD36(-/-) mice was attenuated. Surprisingly, however, in WT→CD36(-/-) mice, in which infarcts were small, neutrophil infiltration was large and similar to that of CD36(-/-) →WT mice, in which infarcts were not reduced. Postischemic neutrophil free radical production was attenuated in WT→CD36(-/-) mice compared with CD36(-/-) →WT mice, whereas expression of the neutrophil activator colony-stimulating factor 3 (CSF3) was suppressed in CD36(-/-) cerebral endothelial cells, but not microglia. In CD36(-/-) cerebral endothelial cultures exposed to extracts from stroke brains, the upregulation of CSF3, but not neutrophil attractant chemokines, was suppressed. Intracerebroventricular administration of CSF3, 24 h after stroke, reconstituted neutrophil radical production and increased infarct volume in WT→CD36(-/-) mice. The findings identify endothelial cells as a key player in the deleterious effects of CD36 in stroke, and unveil a novel role of endothelial CD36 in enabling neutrophil neurotoxicity through CSF3.

SIGNIFICANCE STATEMENT

Ischemic stroke is a leading cause of death and disability worldwide with limited therapeutic options. The inflammatory response initiated by cerebral ischemia-reperfusion contributes to ischemic brain injury and is a potential therapeutic target. Here we report that CD36, an innate immunity receptor involved in the initiation of postischemic inflammation, is a previously unrecognized regulator of neutrophil cytotoxicity. The effect is mediated by endothelial CD36 via upregulation of the neutrophil activator CSF3 in cerebral endothelial cells. Therefore, approaches to modulate cerebral endothelial CD36 signaling or to neutralize CSF3 may provide novel therapeutic opportunities to ameliorate postischemic inflammatory injury.

Unraveling the ischemic brain transcriptome in a permanent middle cerebral artery occlusion mouse model by DNA microarray analysis

Brain ischemia, also termed cerebral ischemia, is a condition in which there is insufficient blood flow to the brain to meet metabolic demand, leading to tissue death (cerebral infarction) due to poor oxygen supply (cerebral hypoxia). Our group is interested in the protective effects of neuropeptides for alleviating brain ischemia, as well as the underlying mechanisms of their action. The present study was initiated to investigate molecular responses at the level of gene expression in ischemic brain tissue. To achieve this, we used a mouse permanent middle cerebral artery occlusion (PMCAO) model in combination with high-throughput DNA microarray analysis on an Agilent microarray platform. Briefly, the right (ipsilateral) and left (contralateral) hemispheres of PMCAO model mice were dissected at two time points, 6 and 24 hours post-ischemia. Total RNA from the ischemic (ipsilateral) hemisphere was subjected to DNA microarray analysis on a mouse whole genome 4x44K DNA chip using a dye-swap approach. Functional categorization using the gene ontology (GO, MGD/AMIGO) of numerous changed genes revealed expression pattern changes in the major categories of cellular process, biological regulation, regulation of biological process, metabolic process and response to stimulus. Reverse-transcriptase PCR (RT-PCR) analysis on randomly selected highly up- or downregulated genes validated, in general, the microarray data. Using two time points for this analysis, major and minor trends in gene expression and/or functions were observed in relation to early- and late-response genes and differentially regulated genes that were further classified into specific pathways or disease states. We also examined the expression of these genes in the contralateral hemisphere, which suggested the presence of bilateral effects and/or differential regulation. This study provides the first ischemia-related transcriptome analysis of the mouse brain, laying a strong foundation for studies designed to elucidate the mechanisms regulating ischemia and to explore the neuroprotective effects of agents such as target neuropeptides.