Dectin-1/Syk signaling triggers neuroinflammation after ischemic stroke in mice.

BACKGROUND: Dendritic cell-associated C-type lectin-1 (Dectin-1) receptor has been reported to be involved in neuroinflammation in Alzheimer's disease and traumatic brain injury. The present study was designed to investigate the role of Dectin-1 and its downstream target spleen tyrosine kinase (Syk) in early brain injury after ischemic stroke using a focal cortex ischemic stroke model. METHODS: Adult male C57BL/6 J mice were subjected to a cerebral focal ischemia model of ischemic stroke. The neurological score, adhesive removal test, and foot-fault test were evaluated on days 1, 3, 5, and 7 after ischemic stroke. Dectin-1, Syk, phosphorylated (p)-Syk, tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) expression was analyzed via western blotting in ischemic brain tissue after ischemic stroke and in BV2 microglial cells subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) injury in vitro. The brain infarct volume and Iba1-positive cells were evaluated using Nissl's and immunofluorescence staining, respectively. The Dectin-1 antagonist laminarin (LAM) and a selective inhibitor of Syk phosphorylation (piceatannol; PIC) were used for the intervention. RESULTS: Dectin-1, Syk, and p-Syk expression was significantly enhanced on days 3, 5, and 7 and peaked on day 3 after ischemic stroke. The Dectin-1 antagonist LAM or Syk inhibitor PIC decreased the number of Iba1-positive cells and TNF-α and iNOS expression, decreased the brain infarct volume, and improved neurological functions on day 3 after ischemic stroke. In addition, the in vitro data revealed that Dectin-1, Syk, and p-Syk expression was increased following the 3-h OGD and 0, 3, and 6 h of reperfusion in BV2 microglial cells. LAM and PIC also decreased TNF-α and iNOS expression 3 h after OGD/R induction. CONCLUSION: Dectin-1/Syk signaling plays a crucial role in inflammatory activation after ischemic stroke, and further investigation of Dectin-1/Syk signaling in stroke is warranted.

Astrocytic Lrp4 (Low-Density Lipoprotein Receptor-Related Protein 4) Contributes to Ischemia-Induced Brain Injury by Regulating ATP Release and Adenosine-A2AR (Adenosine A2A Receptor) Signaling.

BACKGROUND AND PURPOSE: Lrp4 (low-density lipoprotein receptor-related protein 4) is predominantly expressed in astrocytes, where it regulates glutamatergic neurotransmission by suppressing ATP release. Here, we investigated Lrp4's function in ischemia/stroke-induced brain injury response, which includes glutamate-induced neuronal death and reactive astrogliosis. METHODS: The brain-specific Lrp4 conditional knockout mice (Lrp4GFAP-Cre), astrocytic-specific Lrp4 conditional knockout mice (Lrp4GFAP-creER), and their control mice (Lrp4f/f) were subjected to photothrombotic ischemia and the transient middle cerebral artery occlusion. After ischemia/stroke, mice or their brain samples were subjected to behavior tests, brain histology, immunofluorescence staining, Western blot, and quantitative real-time polymerase chain reaction. In addition, primary astrocytes and neurons were cocultured with or without oxygen and glucose deprivation and in the presence or absence of the antagonist for adenosine-A2AR (adenosine A2A receptor) or ATP-P2X7R (P2X purinoceptor 7) signaling. Gliotransmitters, such as glutamate, d-serine, ATP, and adenosine, in the condition medium of cultured astrocytes were also measured. RESULTS: Lrp4, largely expressed in astrocytes, was increased in response to ischemia/stroke. Both Lrp4GFAP-Cre and Lrp4GFAP-creER mice showed less brain injury, including reduced neuronal death, and impaired reactive astrogliosis. Mechanistically, Lrp4 conditional knockout in astrocytes increased ATP release and the production of ATP derivative, adenosine, which were further elevated by oxygen and glucose deprivation. Pharmacological inhibition of ATP-P2X7R or adenosine-A2AR signaling diminished Lrp4GFAP-creER's protective effect. CONCLUSIONS: The astrocytic Lrp4 plays an important role in ischemic brain injury response. Lrp4 deficiency in astrocytes seems to be protective in response to ischemic brain injury, likely because of the increased ATP release and adenosine-A2AR signaling.

High bioavailable testosterone levels increase the incidence of isolated REM sleep behavior disorder: Results from multivariable and network Mendelian randomization analysis.

OBJECTIVES: To explore the causal relationships between sex hormone levels and incidence of isolated REM sleep behavior disorder (iRBD). METHODS: In our study, we utilized Genome-Wide Association Studies (GWAS) data for iRBD, including 9447 samples with 1061 cases of iRBD provided by the International RBD Study Group. Initially, we conducted a two-sample univariate MR analysis to explore the impact of sex hormone-related indicators on iRBD. This was followed by the application of multivariable MR methods to adjust for other hormone levels and potential confounders. Finally, we undertook a network MR analysis, employing brain structure Magnetic Resonance Imaging (MRI) characteristics as potential mediators, to examine whether sex hormones could indirectly influence the incidence of iRBD by affecting brain structure. RESULTS: Bioavailable testosterone (BioT) is an independent risk factor for iRBD (Odds Ratio [95 % Confidence Interval] = 2.437 [1.308, 4.539], P = 0.005, corrected-P = 0.020), a finding that remained consistent even after adjusting for other sex hormone levels and potential confounders. Additionally, BioT appears to indirectly increase the risk of iRBD by reducing axial diffusivity and increasing the orientation dispersion index in the left cingulum and cingulate gyrus. CONCLUSIONS: Our research reveals that elevated levels of BioT contribute to the development of iRBD. However, the specific impact of BioT on different sexes remains unclear. Furthermore, high BioT may indirectly lead to iRBD by impairing normal pathways in the left cingulum and cingulate gyrus and fostering abnormal pathway formation.

Damage mechanism and therapy progress of the blood-brain barrier after ischemic stroke.

The blood-brain barrier (BBB) serves as a defensive line protecting the central nervous system, while also maintaining micro-environment homeostasis and inhibiting harmful materials from the peripheral blood. However, the BBB's unique physiological functions and properties make drug delivery challenging for patients with central nervous system diseases. In this article, we briefly describe the cell structure basis and mechanism of action of the BBB, as well as related functional proteins involved. Additionally, we discuss the various mechanisms of BBB damage following the onset of an ischemic stroke, and lastly, we mention several therapeutic strategies accounting for impairment mechanisms. We hope to provide innovative ideas for drug delivery research via the BBB.

Construction of circRNA-Mediated Immune-Related ceRNA Network and Identification of Circulating circRNAs as Diagnostic Biomarkers in Acute Ischemic Stroke.

Background and Purpose: Accumulating evidence suggests that circular RNAs (circRNAs) are involved in immune and inflammatory processes after acute ischemic stroke (AIS). However, the roles of circRNA-mediated competing endogenous RNA (ceRNA) in modulating immune inflammation of AIS have not yet been determined. This study aimed to construct a circRNA-mediated immune-related ceRNA network and identify novel circRNAs in AIS. Methods: Microarray data were downloaded from the GEO database and further analysed by R software. Then, we constructed a circRNA-mediated ceRNA network based on interaction information from the bioinformatics database. A topological property analysis of the ceRNA network was conducted to screen novel circRNAs. Finally, we further applied quantitative real-time polymerase chain reaction (qRT-PCR) to two independent sets. Results: We constructed an AIS immune-related ceRNA (AISIRC) network containing immune-related genes (IRGs), miRNAs, and circRNAs. Additionally, we extracted the subnetwork from the AISIRC network and screened six immune-related circRNAs. After identification and validation, we finally confirmed that plasma levels of circPTP4A2 and circTLK2 were significantly increased in AIS patients compared with both healthy control subjects (HCs) and transient ischemic attack (TIA) patients. Logistic regression and receiver-operating characteristic (ROC) curve analyses demonstrated that these two circRNAs may function as predictive and discriminative biomarkers for AIS. We also confirmed that plasma levels of circPTP4A2 were elevated in TIA patients compared with HCs and might be an independent risk factor for predicting TIA. Longitudinal analysis of circRNA expression up to 90 days after AIS indicated that the ability of circPTP4A2 and circTLK2 to monitor AIS dynamics was highly desirable. Conclusion: In summary, the circRNA-mediated immune-related ceRNA network was successfully constructed, and two circulating circRNAs (circPTP4A2 and circTLK2) improved sensitivity for the diagnosis of AIS and could be considered diagnostic biomarkers.

Macrophage migration inhibitory factor (MIF) acetylation protects neurons from ischemic injury.

Ischemia-induced neuronal death leads to serious lifelong neurological deficits in ischemic stroke patients. Histone deacetylase 6 (HDAC6) is a promising target for neuroprotection in many neurological disorders, including ischemic stroke. However, the mechanism by which HDAC6 inhibition protects neurons after ischemic stroke remains unclear. Here, we discovered that genetic ablation or pharmacological inhibition of HDAC6 reduced brain injury after ischemic stroke by increasing macrophage migration inhibitory factor (MIF) acetylation. Mass spectrum analysis and biochemical results revealed that HDAC6 inhibitor or aspirin treatment promoted MIF acetylation on the K78 residue. MIF K78 acetylation suppressed the interaction between MIF and AIF, which impaired MIF translocation to the nucleus in ischemic cortical neurons. Moreover, neuronal DNA fragmentation and neuronal death were impaired in the cortex after ischemia in MIF K78Q mutant mice. Our results indicate that the neuroprotective effect of HDAC6 inhibition and aspirin treatment results from MIF K78 acetylation; thus, MIF K78 acetylation may be a therapeutic target for ischemic stroke and other neurological diseases.

Ischemic postconditioning confers cerebroprotection by stabilizing VDACs after brain ischemia.

Ischemic postconditioning provides robust neuroprotection, therefore, determining the molecular events may provide promising targets for stroke treatment. Here, we showed that the expression of functional mitochondrial voltage-dependent anion channel proteins (VDAC1, VDAC2, and VDAC3) reduced in rat vulnerable hippocampal CA1 subfield after global ischemia. Ischemic postconditioning restored VDACs to physiological levels. Stabilized VDACs contributed to the benefits of postconditioning. VDAC1 was required for maintaining neuronal Ca2+ buffering capacity. We found that microRNA-7 (miR-7) was responsible for postischemic decline of VDAC1 and VDAC3. Notably, miR-7 was more highly expressed in the peripheral blood of patients with acute ischemic stroke compared to healthy controls. Inhibition of miR-7 attenuated neuronal loss and ATP decline after global ischemia, but also diminished the infarct volume with improved neurological functions after focal ischemia. Thus, ischemic postconditioning protects against mitochondrial damage by stabilizing VDACs. MiR-7 may be a potential therapeutic target for ischemic stroke.

The action of thrombin in intracerebral hemorrhage induced brain damage is mediated via PKCα/PKCδ signaling.

The present study investigates the role of protein kinase C alpha/delta (PKCα/PKCδ) in brain injury induced by intracerebral hemorrhage (ICH) by utilizing a rat model that received intracerebral injections of autologous blood and thrombin (TM). The activation and expression of PKC and PKCδ were analyzed by Western blot and immunohistochemistry. A PKC inhibitor, dihydrochloride (H7), was administrated intraperitoneally after injury to evaluate the effect of inhibition of PKC on ICH and TM induced brain damage. Our data indicate that both ICH and TM increased the expression of PKCα/PKCδ in the brain tissue, and PKCα expression peaked at 6h, while PKCδ expression reached its maximum value at 72h post-injury. Administration of H7 significantly reduced the inflammatory cells infiltrate, permeability of brain-blood barrier (BBB), brain edema, and neuronal death. We conclude that both PKCα and PKCδ play important roles in ICH and TM-induced brain injury, and dihydrochloride (H7) can attenuate brain damage after ICH.