Induction of Ischemic Stroke and Ischemia-reperfusion in Mice Using the Middle Artery Occlusion Technique and Visualization of Infarct Area

Neuronal and Astrocyte Insulin-like Growth Factor-1 Signaling Differentially Modulates Ischemic Stroke Damage

Ischemic stroke is a leading cause of death and disability, as therapeutic options for mitigating the long-term deficits precipitated by the event remain limited. Acute administration of the neuroendocrine modulator insulin-like growth factor-1 (IGF-1) attenuates ischemic stroke damage in preclinical models, and clinical studies suggest IGF-1 can reduce the risk of stroke and improve overall outcomes. The cellular mechanism by which IGF-1 exerts this protection is poorly defined, as all cells within the neurovascular unit express the IGF-1 receptor. We hypothesize that the functional regulation of both neurons and astrocytes by IGF-1 is critical in minimizing damage in ischemic stroke. To test this, we utilized inducible astrocyte-specific or neuron-specific transgenic mouse models to selectively reduce IGF-1R in the adult mouse brain prior to photothrombotic stroke. Acute changes in blood brain barrier permeability, microglial activation, systemic inflammation, and biochemical composition of the brain were assessed 3 hours following photothrombosis, and significant protection was observed in mice deficient in neuronal and astrocytic IGF-1R. When the extent of tissue damage and sensorimotor dysfunction was assessed for 3 days following stroke, only the neurological deficit score continued to show improvements, and the extent of improvement was enhanced with additional IGF-1 supplementation. Overall, results indicate that neuronal and astrocytic IGF-1 signaling influences stroke damage but IGF-1 signaling within these individual cell types is not required for minimizing tissue damage or behavioral outcome.

NLRP3 inflammasome activation increases brain oxidative stress after transient global cerebral ischemia in rats

Pupurpose of the study: Oxidative stress has been reported to be an important mechanism for brain damage following ischemic stroke. Recently, the involvement of cytosolic receptors capable of forming protein complexes called inflammasomes has been demonstrated to perpetuate oxidative stress. Herein, we report the effect of NLRP3 inhibition with MCC950 on brain oxidative stress in an animal model of transient global cerebral ischemia.Materials and methods: Male Wistar rats received an intracerebroventricularly (icv) injection of MCC950 (140 ng/kg) or saline and were subjected to sham procedure or ischemia/reperfusion (I/R). Twenty-four hours after I/R, myeloperoxidase (MPO) activity, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the prefrontal cortex, hippocampus, cortex, cerebellum and striatum. Results: After I/R, MPO activity increased in the prefrontal cortex, hippocampus, cortex and cerebellum and N/N concentration elevated in the prefrontal cortex, hippocampus and cortex, while MCC950 decreased this level except in hippocampus. After I/R, lipid peroxidation enhanced in the prefrontal cortex and cerebellum and increased the oxidative protein damage in both structures and hippocampus. MCC950 decreased lipid peroxidation in the prefrontal cortex and decreased protein oxidative damage in all brain structures except in the striatum. SOD activity decreased in the cortex after I/R and MCC950 reestablished these levels. CAT activity decreased in the prefrontal cortex, hippocampus and cerebellum after I/R and MCC950 reestablished these levels in the prefrontal cortex.Conclusion: Our data provide novel demonstration that inhibiting NLRP3 activation with MCC950 reduces brain oxidative damage after cerebral I/R in rats.

Platelet Endothelial Cell Adhesion Molecule (PECAM/CD31) Blockade Modulates Neutrophil Recruitment Patterns and Reduces Infarct Size in Experimental Ischemic Stroke

The infiltration of polymorphonuclear leukocytes (PMNs) in ischemia-reperfusion injury (I/RI) has been implicated as a critical component of inflammatory damage following ischemic stroke. However, successful blockade of PMN transendothelial migration (TEM) in preclinical studies has not translated to meaningful clinical outcomes. To investigate this further, leukocyte infiltration patterns were quantified, and these patterns were modulated by blocking platelet endothelial cell adhesion molecule-1 (PECAM), a key regulator of TEM. LysM-eGFP mice and microscopy were used to visualize all myeloid leukocyte recruitment following ischemia/reperfusion. Visual examination showed heterogeneous leukocyte distribution across the infarct at both 24 and 72 hours after I/RI. A semiautomated process was designed to precisely map PMN position across brain sections. Treatment with PECAM function-blocking antibodies did not significantly affect total leukocyte recruitment but did alter their distribution, with more observed at the cortex at both early and later time points (24 hours: 89% PECAM blocked vs. 72% control; 72 hours: 69% PECAM blocked vs. 51% control). This correlated with a decrease in infarct volume. These findings suggest that TEM, in the setting of I/RI in the cerebrovasculature, occurs primarily at the cortical surface. The reduction of stroke size with PECAM blockade suggests that infiltrating PMNs may exacerbate I/RI and indicate the potential therapeutic benefit of regulating the timing and pattern of leukocyte infiltration after stroke.

Integrated Bioinformatics Analysis of Potential mRNA and miRNA Regulatory Networks in Mice With Ischemic Stroke Treated by Electroacupuncture

Background: The complicated molecular mechanisms underlying the therapeutic effect of electroacupuncture (EA) on ischemic stroke are still unclear. Recently, more evidence has revealed the essential role of the microRNA (miRNA)–mRNA networks in ischemic stroke. However, a systematic analysis of novel key genes, miRNAs, and miRNA–mRNA networks regulated by EA in ischemic stroke is still absent.

Methods: We established a middle cerebral artery occlusion (MCAO) mouse model and performed EA therapy on ischemic stroke mice. Behavior tests and measurement of infarction area were applied to measure the effect of EA treatment. Then, we performed RNA sequencing to analyze differentially expressed genes (DEGs) and functional enrichment between the EA and control groups. In addition, a protein–protein interaction (PPI) network was built, and hub genes were screened by Cytoscape. Upstream miRNAs were predicted by miRTarBase. Then hub genes and predicted miRNAs were verified as key biomarkers by RT-qPCR. Finally, miRNA–mRNA networks were constructed to explore the potential mechanisms of EA in ischemic stroke.

Results: Our analysis revealed that EA treatment could significantly alleviate neurological deficits in the affected limbs and reduce infarct area of the MCAO model mice. A total of 174 significant DEGs, including 53 upregulated genes and 121 downregulated genes, were identified between the EA and control groups. Functional enrichment analysis showed that these DEGs were associated with the FOXO signaling pathway, NF-kappa B signaling pathway, T-cell receptor signaling pathway, and other vital pathways. The top 10 genes with the highest degree scores were identified as hub genes based on the degree method, but only seven genes were verified as key genes according to RT-qPCR. Twelve upstream miRNAs were predicted to target the seven key genes. However, only four miRNAs were significantly upregulated and indicated favorable effects of EA treatment. Finally, comprehensive analysis of the results identified the miR-425-5p-Cdk1, mmu-miR-1186b-Prc1, mmu-miR-434-3p-Prc1, and mmu-miR-453-Prc1 miRNA–mRNA networks as key networks that are regulated by EA and linked to ischemic stroke. These networks might mainly take place in neuronal cells regulated by EA in ischemic stroke.

Conclusion: In summary, our study identified key DEGs, miRNAs, and miRNA–mRNA regulatory networks that may help to facilitate the understanding of the molecular mechanism underlying the effect of EA treatment on ischemic stroke.

Circular RNA 0025984 Ameliorates Ischemic Stroke Injury and Protects Astrocytes Through miR-143-3p/TET1/ORP150 Pathway

MiR-143-3p is aberrantly expressed in patients with ischemic stroke and associated with ischemic brain injury. However, the underlying mechanisms are largely unknown. Here, we confirmed circ_0025984 and TET1 as a sponge and target of miR-143-3p, respectively, by luciferase reporter assay. In astrocytes, OGD significantly decreased circ_0025984 and TET1 levels but increased miR-143-3p levels, which was also observed in brains of mice with MCAO. Treatment with miR-143-3p inhibitor or circ_0025984 significantly decreased astrocyte apoptosis and autophagy, as well as cerebral injury and neuron loss in mice with MCAO. Notably, TET1 overexpression decreased astrocyte apoptosis and autophagy and induced promoter hypomethylation and expression of ORP150. Our results demonstrated for the first time that circ_0025984 protects astrocytes from ischemia-induced autophagy and apoptosis by targeting the miR-143-3p/TET1 pathway and might inhibit cerebral injury induced by ischemic stroke. Furthermore, our data revealed the important positive regulation of ORP150 by TET1, which could be associated with its neuroprotective role. Graphical abstract Model for signaling pathway of circ_0025984/miR-143-3p/TET1 inastrocytes cultured under OGD. In astrocytes, circ_0025984 acts as a sponge of miR-143-3p, which directly targets TET1 and decreases its expression (A). After translocatinginto the nucleus, TET1 binds to the promoter of ORP150, converts 5mC into 5hmC,leading to DNA demethylation and increased expression of ORP150 (B). In astrocytescultured under OGD, ER stress is induced and eventually leads to apoptosis andautophagy mediated by ATG7, which is regulated by circ_0025984 via ORP150 andGRP78 (C).

Methamphetamine Enhances HIV-Induced Aberrant Proliferation of Neural Progenitor Cells via the FOXO3-Mediated Mechanism

Maintaining an intact pool of neural progenitor cells (NPCs) is crucial for generating new and functionally active neurons. Methamphetamine (METH) can exacerbate the HIV-induced deficit of adult neurogenesis; however, potential mechanisms of this influence are still poorly understood. In the present study, we present evidence that chronic exposure to METH combined with brain infection by EcoHIV results in enhanced proliferation of NPCs in the subventricular zone (SVZ) in mice. This effect was long-lasting as it was preserved ex vivo in NPCs isolated from the exposed mice over several passages in the absence of additional treatments. Increased proliferation in response to METH plus HIV was associated with dysregulation of cyclin B1 and cyclin D. Transcriptomic studies indicated that 27 out of the top 30 differentially expressed genes in response to METH plus EcoHIV were targets of the forkhead box O transcriptional factor (FOXO) and primarily FOXO3. Additional ex vivo studies and in vitro experiments using human NPCs exposed to METH and infected with HIV revealed upregulation of the CXCL12-CXCR4 axis, leading to activation of downstream pAkt and pErk, the pathways that can phosphorylate FOXO3 and force its exports from the nuclei into the cytoplasm. Indeed, nuclear expulsion of FOXO3 was demonstrated both in mice exposed to METH and infected with EcoHIV and in cell cultures of human NPCs. These results provide novel information that exposure to METH combined with HIV infection can induce aberrant proliferation of SVZ-derived NPCs and identifies CXCL12-CXCR4-Akt-1-mediated phosphorylation of FOXO3 as the mechanism responsible for this effect.

DSIP-Like KND Peptide Reduces Brain Infarction in C57Bl/6 and Reduces Myocardial Infarction in SD Rats When Administered during Reperfusion

A structural analogue of the DSIP, peptide KND, previously showed higher detoxification efficacy upon administration of the cytotoxic drug cisplatin, compared to DSIP. DSIP and KND were investigated using the model of acute myocardial infarction in male SD rats and the model of acute focal stroke in C57Bl/6 mice. A significant decrease in the myocardial infarction area was registered in KND-treated animals relative to saline-treated control animals (19.1 ± 7.3% versus 42.1 ± 9.2%). The brain infarction volume was significantly lower in animals intranasally treated with KND compared to the control saline-treated animals (7.4 ± 3.5% versus 12.2 ± 5.6%). Injection of KND in the first minute of reperfusion in the models of myocardial infarction and cerebral stroke reduced infarction of these organs, indicating a pronounced cardioprotective and neuroprotective effect of KND and potentiality for the treatment of ischemia-reperfusion injuries after transient ischemic attacks on the heart and brain, when administered during the reperfusion period. A preliminary pilot study using the model of myocardial infarction with the administration of DSIP during occlusion, and the model of cerebral stroke with the administration of KND during occlusion, resulted in 100% mortality in animals. Thus, in the case of ischemia-reperfusion injuries of the myocardium and the brain, use of these peptides is only possible during reperfusion.

LncRNA DANCR attenuates brain microvascular endothelial cell damage induced by oxygen-glucose deprivation through regulating of miR-33a-5p/XBP1s

Brain microvascular endothelial cell (BMEC) survival and angiogenesis after ischemic stroke has great significance for improving the prognosis of stroke. Abnormal variants of lncRNAs are closely associated with stroke. In this study, we examined the effects and molecular mechanisms of differentiation antagonizing non-protein coding RNA (DANCR) on apoptosis, migration, and angiogenesis of oxygen-glucose deprivation (OGD)-treated BMECs. We found that DANCR expression significantly increased at 2, 4, 6, 8, and 10 h after OGD. DANCR overexpression promoted cell viability, migration, and angiogenesis in OGD-treated BMECs. Additionally, we found that X-box binding protein l splicing (XBP1s) expression was positively correlated with DANCR expression. DANCR overexpression promoted XBP1s expression in OGD-treated BMECs. Silenced XBP1s reversed the effect of DANCR in OGD-treated BMECs. Furthermore, we found that microRNA (miR)-33a-5p bound to DANCR and the 3'-UTR of XBP1. miR-33a-5p overexpression inhibited proliferation, migration, angiogenesis, and XBP1s expression in OGD-treated DANCR-overexpressing BMECs, reversing the protective effect of DANCR. Finally, we found that XBP1s expression promoted proliferation, migration, and angiogenesis, reversing the damaging effect of miR-33a-5p. In conclusion, DANCR enhanced survival and angiogenesis in OGD-treated BMECs through the miR-33a-5p/XBP1s axis.

Targeting the HIV-infected brain to improve ischemic stroke outcome

HIV-associated cerebrovascular events remain highly prevalent even in the current era of antiretroviral therapy (ART). We hypothesize that low-level HIV replication and associated inflammation endure despite antiretroviral treatment and affect ischemic stroke severity and outcomes. Using the EcoHIV infection model and the middle cerebral artery occlusion as the ischemic stroke model in mice, we present in vivo analysis of the relationship between HIV and stroke outcome. EcoHIV infection increases infarct size and negatively impacts tissue and functional recovery. Ischemic stroke also results in an increase in EcoHIV presence in the affected regions, suggesting post-stroke reactivation that magnifies pro-inflammatory status. Importantly, ART with a high CNS penetration effectiveness (CPE) is more beneficial than low CPE treatment in limiting tissue injury and accelerating post-stroke recovery. These results provide potential insight for treatment of HIV-infected patients that are at risk of developing cerebrovascular disease, such as ischemic stroke.

Antiretroviral Treatment with Efavirenz Disrupts the Blood-Brain Barrier Integrity and Increases Stroke Severity

The introduction of antiretroviral drugs (ARVd) changed the prognosis of HIV infection from a deadly disease to a chronic disease. However, even with undetectable viral loads, patients still develop a wide range of pathologies, including cerebrovascular complications and stroke. It is hypothesized that toxic side effects of ARVd may contribute to these effects. To address this notion, we evaluated the impact of several non-nucleoside reverse transcriptase inhibitors (NNRTI; Efavirenz, Etravirine, Rilpivirine and Nevirapine) on the integrity of the blood-brain barrier, and their impact on severity of stroke. Among studied drugs, Efavirenz, but not other NNRTIs, altered claudin-5 expression, increased endothelial permeability, and disrupted the blood-brain barrier integrity. Importantly, Efavirenz exposure increased the severity of stroke in a model of middle cerebral artery occlusion in mice. Taken together, these results indicate that selected ARVd can exacerbate HIV-associated cerebrovascular pathology. Therefore, careful consideration should be taken when choosing an anti-retroviral therapy regimen.