MyD88-TLR4-dependent choroid plexus activation precedes perilesional inflammation and secondary brain edema in a mouse model of intracerebral hemorrhage

miRNA506 Activates Sphk1 Binding with Sirt1 to Inhibit Brain Injury After Intracerebral Hemorrhage via PI3K/AKT Signaling Pathway

Intracerebral hemorrhage (ICH) is an acute neurological disorder characterized by high mortality and disability rates. Previous studies have shown that 75% of patients who survive ICH experience varying degrees of neurological deficits. Sphk1 has been implicated in a multitude of phylogenetic processes, including innate immunity and cell proliferation. An in vivo rat model of ICH and an in vitro model of neuronal oxyhemoglobin (OxyHb) were constructed. The expression level of Sphk1 was assessed using western blotting and immunofluorescence, whereas cell death following ICH was evaluated using fluoro-Jade B and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Immunofluorescence facilitated the examination of microglial phenotypic alterations, while enzyme-linked immunosorbent assays were used to determine the concentrations of inflammatory markers. Behavioral assays were employed to assess the overall behavioral modifications of animals. Neuronal Sphk1/Sirt1 protein levels gradually increased following the induction of ICH. Elevated Sphk1 expression resulted in increased levels of anti-inflammatory microglia and reduced levels of pro-inflammatory factors. In contrast, suppression of Sphk1 expression resulted in an increased number of dead cells, thereby exacerbating neurological deficits. In vitro findings indicated that the levels of phosphorylated PI3K and AKT proteins increased in conjunction with Sphk1 expression. This study established that after ICH, Sphk1 interacts with Sirt1 to mitigate neuroinflammation, cell death, oxidative stress, and brain edema via the PI3K/AKT signaling pathway. Augmenting expression of Sphk1 significantly can ameliorate neurological impairments induced by ICH, offering novel targets and perspectives for therapeutic interventions in ICH treatment.

Paclitaxel triggers molecular and cellular changes in the choroid plexus

Paclitaxel is a widely used chemotherapeutic agent for treating various solid tumors. However, resulting neuropathic pain, often a lifelong side effect of paclitaxel, can limit dosing and compromise optimal treatment. The choroid plexus, located in the brain ventricles, spreads peripheral inflammatory reactions into the brain. Our study is the first to analyze the effects of paclitaxel on inflammatory alterations in the choroid plexus. We hypothesized that the choroid plexus could respond directly to paclitaxel and simultaneously be indirectly altered via circulating damage-associated molecular patterns (DAMPs) produced by paclitaxel application. Using immunohistochemical and Western blot analysis, we examined the levels of toll-like receptor 9 (TLR9) and formyl peptide receptor 2 (FPR2), along with the pro-inflammatory cytokines interleukin 6 (IL6) and tumor necrosis factor α (TNFα) in choroid plexus epithelial cells of male Wistar rats following paclitaxel treatment. Moreover, we utilized an in vitro model of choroid plexus epithelial cells, the Z310 cells, to investigate the changes in these cells in response to paclitaxel and DAMPs (CpG ODN). Our results demonstrate that paclitaxel increases TLR9 and FPR2 levels in the choroid plexus while inducing IL6 and TNFα upregulation in both acute and chronic manners. In vitro experiments further revealed that paclitaxel directly interacts with epithelial cells of the choroid plexus, leading to increased levels of TLR9, FPR2, IL6, and TNFα. Additionally, treatment of cells with CpG ODN, an agonist of TLR9, elicited upregulation of IL6 and TNFα. Our findings determined that paclitaxel influences the choroid plexus through both direct and indirect mechanisms, resulting in inflammatory profile alterations. Given the pivotal role of the choroid plexus in brain homeostasis, a compromised choroid plexus following chemotherapy may facilitate the spread of peripheral inflammation into the brain, consequently exacerbating the development of neuropathic pain.

C1-inhibitor to prevent intracerebral hemorrhage-related secondary brain injury

BACKGROUND

Preclinical studies indicate that the systemic application of C1-inhibitor, clinically used to treat hereditary angioedema, reduces secondary brain injury after ischemic stroke. This study assessed the effect of C1-inhibitor on secondary brain injury after hemorrhagic stroke.

METHODS

We used an established striatal whole-blood injection mouse model to mimic intracerebral hemorrhage-related secondary brain injury. Based on the spatiotemporal dynamics in our model, we calculated the necessary sample size (n = 24) and determined the most sensitive time point to detect potential group differences (48 h) prior to the experiments. The experimental setup, tissue processing and image analysis adhered to our published protocol. We randomized mice into three groups: C1-inhibitor treatment, placebo, and sham. Histology was standardized by taking eight anatomically predefined slices across the entire lesion. Lesion size, vascular leakage, and inflammatory responses were assessed using automated thresholding and dextran/ICAM1/CD45 intensity mapping. Investigators were blinded to group allocation during the experiment, tissue processing, and image analysis.

RESULTS

Whole blood injection resulted in significantly larger lesion size and more pronounced vascular leakage and cellular inflammation compared to the sham group. However, there was no difference in lesion size or inflammatory markers between the C1-inhibitor and placebo groups. In addition, there was no difference in the inflammatory response of the choroid plexus, which has been identified as a central organ orchestrating inflammation after intracerebral hemorrhage.

CONCLUSION

The protective effect of C1-inhibitor might be isolated to pathophysiological processes with a predominant thromboinflammatory component, as in ischemia-reperfusion, but less so in permanent ischemia or intracerebral hemorrhage.

Perihematomal Neurovascular Protection: Blocking HSP90 Reduces Blood Infiltration Associated with Inflammatory Effects Following Intracerebral Hemorrhage in Rates

The active hemorrhage surrounding the hematoma is caused by the infiltration of blood into the cerebral parenchyma through the ruptured vessel, including the compromised blood-brain barrier (BBB). This process is thought to be mainly driven by inflammation and serves as a significant pathological characteristic that contributes to the neurological deterioration observed in individuals with intracerebral hemorrhage (ICH). Heat shock protein 90 (HSP90) exhibits abnormally high expression levels in various diseases and is closely associated with the onset of inflammation. Here, we found that blocking HSP90 effectively alleviates the inflammatory damage to BBB and subsequent bleeding around the hematoma. We have observed increased HSP90 levels in the serum of patients with ICH and the perihematoma region in ICH rats. Treatment with anti-HSP90 drugs (Geldanamycin and radicicol) effectively reduced HSP90 levels, resulting in enhanced neurological outcomes, decreased hematoma volume, and prevented peripheral immune cells from adhering to the BBB and infiltrating the brain parenchyma surrounding the hematoma in ICH rats. Mechanistically, anti-HSP90 therapy alleviated BBB injury caused by ICH-induced inflammation by suppressing TLR4 signaling. The study highlights the potential of anti-HSP90 therapy in mitigating BBB disruption and hemorrhage surrounding the hematoma, providing new insights into the management of ICH by targeting HSP90.

The association between TLR2/4 and clinical outcome in intracerebral hemorrhage

BACKGROUND AND PURPOSE

Toll-like receptors (TLRs) are involved in innate immunity and inflammatory responses in various diseases. Our study aimed to investigate the association between the levels of soluble TLR4 (sTLR4) and soluble TLR2 (sTLR2) and clinical outcomes following intracerebral hemorrhage (ICH).

METHODS

Patients admitted to department of Neurology with acute ICH were included. Plasma levels of sTLR4 and sTLR2 after ICH were measured by enzyme-linked immunosorbent assay. Poor clinical outcome was defined as a modified Rankin score (mRS) of 3-6 at 3-month and 12-month after onset.

RESULTS

All 207 patients with ICH and 100 non-stroke controls were included in our analysis. The mean sTLR4 level was 4.53±1.51 ng/ml and mean sTLR2 level was 3.65±0.72 ng/ml. There was significant trend towards worse clinical outcomes with increasing sTLR4 and sTLR2 terciles at 3 and 12 months. According to receiver operating curve (ROC), the sTLR4 was reliable predictor for poor clinical outcome at 3 months (ROC=0.75) and 12 months (ROC=0.74). The sTLR2 was less reliable predictor for poor clinical outcome at 3 months (ROC=0.64) and 12 months (ROC=0.65). The level of sTLR4 was an independent predictor of poor clinical outcome at 12-month (OR 1.24, 95 % CI 1.16-1.80; P=0.019).

CONCLUSIONS

The sTLR4 quantification may provide accurate prognostic information after ICH.

Transient ischemic stroke triggers sustained damage of the choroid plexus blood-CSF barrier

Neuroinflammation is a pathological event associated with many neurological disorders, including dementia and stroke. The choroid plexus (ChP) is a key structure in the ventricles of the brain that secretes cerebrospinal fluid (CSF), forms a blood-CSF barrier, and responds to disease conditions by recruiting immune cells and maintaining an immune microenvironment in the brain. Despite these critical roles, the exact structural and functional changes to the ChP over post-stroke time remain to be elucidated. We induced ischemic stroke in C57BL/6J mice via transient middle cerebral artery occlusion which led to reduction of cerebral blood flow and infarct stroke. At 1-7 days post-stroke, we detected time-dependent increase in the ChP blood-CSF barrier permeability to albumin, tight-junction damage, and dynamic changes of SPAK-NKCC1 protein complex, a key ion transport regulatory system for CSF production and clearance. A transient loss of SPAK protein complex but increased phosphorylation of the SPAK-NKCC1 complex was observed in both lateral ventricle ChPs. Most interestingly, stroke also triggered elevation of proinflammatory Lcn2 mRNA and its protein as well as infiltration of anti-inflammatory myeloid cells in ChP at day 5 post-stroke. These findings demonstrate that ischemic strokes cause significant damage to the ChP blood-CSF barrier, contributing to neuroinflammation in the subacute stage.

Clinical potential of automated convolutional neural network-based hematoma volumetry after aneurysmal subarachnoid hemorrhage

OBJECTIVES

Cerebrospinal fluid hemoglobin has been positioned as a potential biomarker and drug target for aneurysmal subarachnoid hemorrhage-related secondary brain injury (SAH-SBI). The maximum amount of hemoglobin, which may be released into the cerebrospinal fluid, is defined by the initial subarachnoid hematoma volume (ISHV). In patients without external ventricular or lumbar drain, there remains an unmet clinical need to predict the risk for SAH-SBI. The aim of this study was to explore automated segmentation of ISHV as a potential surrogate for cerebrospinal fluid hemoglobin to predict SAH-SBI.

METHODS

This study is based on a retrospective analysis of imaging and clinical data from 220 consecutive patients with aneurysmal subarachnoid hemorrhage collected over a five-year period. 127 annotated initial non-contrast CT scans were used to train and test a convolutional neural network to automatically segment the ISHV in the remaining cohort. Performance was reported in terms of Dice score and intraclass correlation. We characterized the associations between ISHV and baseline cohort characteristics, SAH-SBI, ventriculoperitoneal shunt dependence, functional outcome, and survival. Established clinical (World Federation of Neurosurgical Societies, Hunt & Hess) and radiological (modified Fisher, Barrow Neurological Institute) scores served as references.

RESULTS

A strong volume agreement (0.73 Dice, range 0.43 - 0.93) and intraclass correlation (0.89, 95% CI, 0.81-0.94) were shown. While ISHV was not associated with the use of antithrombotics or cardiovascular risk factors, there was strong evidence for an association with a lower Glasgow Coma Scale at hospital admission. Aneurysm size and location were not associated with ISHV, but the presence of intracerebral or intraventricular hemorrhage were independently associated with higher ISHV. Despite strong evidence for a positive association between ISHV and SAH-SBI, the discriminatory ability of ISHV for SAH-SBI was insufficient. The discriminatory ability of ISHV was, however, higher regarding ventriculoperitoneal shunt dependence and functional outcome at three-months follow-up. Multivariate survival analysis provided strong evidence for an independent negative association between survival probability and both ISHV and intraventricular hemorrhage.

CONCLUSIONS

The proposed algorithm demonstrates strong performance in volumetric segmentation of the ISHV on the admission CT. While the discriminatory ability of ISHV for SAH-SBI was similar to established clinical and radiological scores, it showed a high discriminatory ability for ventriculoperitoneal shunt dependence and functional outcome at three-months follow-up.

A year in review: brain barriers and brain fluids research in 2022

This aim of this editorial is to highlight progress made in brain barrier and brain fluid research in 2022. It covers studies on the blood-brain, blood-retina and blood-CSF barriers (choroid plexus and meninges), signaling within the neurovascular unit and elements of the brain fluid systems. It further discusses how brain barriers and brain fluid systems are impacted in CNS diseases, their role in disease progression and progress being made in treating such diseases.