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Evidence indicates that erythrocyte-derived iron and inflammation both play a role in intraventricular hemorrhage-induced brain injury including hydrocephalus. Many immune-associated cells, primarily stromal macrophages, reside at the choroid plexus where they are involved in inflammatory responses and antigen presentation. However, whether intraventricular iron impacts those stromal cells is unknown. The aim of this study was to evaluate the relationship between choroid plexus stromal macrophages and iron-induced hydrocephalus in rats and the impact of minocycline and clodronate liposomes on those changes. Aged (18-month-old) and young (3-month-old) male Fischer 344 rats were used to study choroid plexus stromal macrophages. Rats underwent intraventricular iron injection to induce hydrocephalus and treated with either minocycline, a microglia/macrophage inhibitor, or clodronate liposomes, a macrophage depleting agent. Ventricular volume was measured using magnetic resonance imaging, and stromal macrophages were quantified by immunofluorescence staining. We found that stromal macrophages accounted for about 10% of the total choroid plexus cells with more in aged rats. In both aged and young rats, intraventricular iron injection resulted in hydrocephalus and increased stromal macrophage number. Minocycline or clodronate liposomes ameliorated iron-induced hydrocephalus and the increase in stromal macrophages. In conclusion, stromal macrophages account for ~10% of all choroid plexus cells, with more in aged rats. Treatments targeting macrophages (minocycline and clodronate liposomes) are associated with reduced iron-induced hydrocephalus. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Cerebrospinal Fluid from Aneurysmal Subarachnoid Hemorrhage Patients Leads to Hydrocephalus in Nude Mice" published in the journal Neurocritical Care. The authors have identified an error in Figure 1A of the manuscript, where one MRI image was inadvertently duplicated. The corrected version of Figure 1A is provided in the document. The error does not affect any of the data analysis in the paper. The publisher, Springer Nature, maintains a neutral stance on jurisdictional claims and institutional affiliations. [Extracted from the article]

After a cerebral hemorrhage (intracerebral, subarachnoid, and intraventricular), extravasated blood contributes to both initial brain injury, via physical disruption and mass effect, and secondary injury, through the release of potentially neurotoxic and pro-inflammatory factors such as hemoglobin, iron, and peroxiredoxin-2. Erythrocytes are a major blood component and are a source of such damaging factors. Erythrolysis after cerebral hemorrhage releases potential neurotoxins, contributing to brain injury and edema. Alternatively, erythrocyte phagocytosis via microglia or macrophages may limit the spill of neurotoxins therefore limiting subsequent brain injury. The aim of this review is to discuss the process of phagocytosis of erythrocytes by microglia or macrophages after cerebral hemorrhage, the effect of erythrolysis on brain injury, novel mechanisms of erythrocyte and phagocyte egress from the brain, and exciting new targets in this pathway to attenuate brain injury. Understanding the fate of erythrocytes after cerebral hemorrhage may uncover additional potential interventions for clinical translational research. [ABSTRACT FROM AUTHOR]

Subarachnoid hemorrhage (SAH) is associated with a high incidence of morbidity and mortality, particularly within the first 72 h after aneurysm rupture. We recently found ultra-early cerebral thrombosis, detectable on T2* magnetic resonance imaging (MRI), in a mouse SAH model at 4 h after onset. The current study examined whether such changes also occur in rat at 24 h after SAH, the vessels involved, whether the degree of thrombosis varied with SAH severity and brain injury, and if it differed between male and female rats. Adult Sprague Dawley rats were subjected to an endovascular perforation SAH model or sham surgery and underwent T2 and T2* MRI 24 h later. Following SAH, increased numbers of T2* hypointense vessels were detected on MRI. The number of such vessels correlated with SAH severity, as assessed by MRI-based grading of bleeding. Histologically, thrombotic vessels were found on hematoxylin and eosin staining, had a single layer of smooth muscle cells on alpha-smooth muscle actin immunostaining, and had laminin 2α/fibrinogen double labeling, suggesting venule thrombosis underlies the T2*-positive vessels on MRI. Capillary thrombosis was also detected which may follow the venous thrombosis. In both male and female rats, the number of T2*-positive thrombotic vessels correlated with T2 lesion volume and neurological function, and the number of such vessels was significantly greater in female rats. In summary, this study identified cerebral venous thrombosis 24 h following SAH in rats that could be detected with T2* MRI imaging and may contribute to SAH-induced brain injury. [ABSTRACT FROM AUTHOR]

Intracerebral hemorrhage (ICH) is a stroke subtype with high mortality and severe morbidity. Hemorrhages frequently develop within the white matter, but whether white matter fibers within the hematoma survive after ICH has not been well studied. The current study examines whether white matter fibers persist in the hematoma after ICH, fibers that might be impacted by evacuation, and their relationship to macrophage infiltration in a porcine model. Male piglets had 2.5 ml blood with or without CD47 blocking antibody injected into the right frontal lobe. Brains were harvested from 3 days to 2 months after ICH for brain histology. White matter fibers were detected within the hematoma 3 and 7 days after hemorrhage by brain histology and myelin basic protein immunohistochemistry. White matter still remained in the hematoma cavity at 2 months after ICH. Macrophage scavenger receptor-1 positive macrophages/microglia and heme oxygenase-1 positive cells infiltrated into the hematoma along the intra-hematomal white matter fibers at 3 and 7 days after ICH. Treatment with CD47 blocking antibody enhanced the infiltration of these cells. In conclusion, white matter fibers exist within the hematoma after ICH and macrophages/microglia may use such fibers as a scaffold to infiltrate into the hematoma and aid in hematoma clearance. [ABSTRACT FROM AUTHOR]

Thrombin is increased in the brain after hemorrhagic and ischemic stroke primarily due to the prothrombin entry from blood either with a hemorrhage or following blood-brain barrier disruption. Increasing evidence indicates that thrombin and its receptors (protease-activated receptors (PARs)) play a major role in brain pathology following ischemic and hemorrhagic stroke (including intracerebral, intraventricular, and subarachnoid hemorrhage). Thrombin and PARs affect brain injury via multiple mechanisms that can be detrimental or protective. The cleavage of prothrombin into thrombin is the key step of hemostasis and thrombosis which takes place in every stroke and subsequent brain injury. The extravascular effects and direct cellular interactions of thrombin are mediated by PARs (PAR-1, PAR-3, and PAR-4) and their downstream signaling in multiple brain cell types. Such effects include inducing blood-brain-barrier disruption, brain edema, neuroinflammation, and neuronal death, although low thrombin concentrations can promote cell survival. Also, thrombin directly links the coagulation system to the immune system by activating interleukin-1α. Such effects of thrombin can result in both short-term brain injury and long-term functional deficits, making extravascular thrombin an understudied therapeutic target for stroke. This review examines the role of thrombin and PARs in brain injury following hemorrhagic and ischemic stroke and the potential treatment strategies which are complicated by their role in both hemostasis and brain. [ABSTRACT FROM AUTHOR]

Objective: Our prior studies have found that intracerebroventricular injection of blood components can cause hydrocephalus and choroid plexus epiplexus cell activation in rats. To minimize the cross-species reaction, the current study examines whether intraventricular injection of acellular components of cerebrospinal fluid (CSF) from subarachnoid hemorrhage patients can cause hydrocephalus and epiplexus macrophage activation in nude mice which lack a T cell inflammatory response. Methods: Adult male nude mice received intraventricular injections of acellular CSF from subarachnoid hemorrhage patients or a control patient. All mice had preoperative magnetic resonance imaging as baseline and postoperative scans at 24 h after CSF injection to determine ventricular volume. Brains were harvested at 24 h for brain histology, immunohistochemistry, and electron microscopy. Results: Intraventricular injection of CSF from two of five subarachnoid hemorrhage patients obtained < 48 h from ictus resulted in ventricular enlargement at 24 h. CSF-related hydrocephalus was associated with activation of epiplexus macrophages and ependymal injury. Conclusions: Components of the acellular CSF of subarachnoid hemorrhage patients can cause epiplexus macrophage activation, ependymal cell damage, and ventricular enlargement in nude mice. This may serve as a unique model to study mechanisms of hydrocephalus development following subarachnoid hemorrhage. [ABSTRACT FROM AUTHOR]

Macrophage phagocytosis plays an important role in hematoma clearance after intracerebral hemorrhage (ICH). This study examined the characteristics of multinucleated giant cells (MGCs), a group of macrophages with multiple nuclei, in a mouse ICH model. Whether MGCs could be increased by treatment with a CD47 blocking antibody and decreased by treatment with clodronate liposomes were also examined. ICH was induced via autologous blood injection. Male adult C57BL/6 mice in different groups had (1) ICH alone; (2) ICH with anti-CD47 blocking antibody or control IgG; and (3) ICH with anti-CD47 antibody combined with clodronate liposomes or control liposomes. The effect of anti-CD47 antibody on MGC formation was also tested in females. Brains were harvested at days 3 or 7 for brain histology. Many MGCs were found at day 3 post-ICH, but were reduced at day 7. MGCs phagocytosed many red blood cells and were heme oxygenase-1, ferritin, YM-1, and iNOS positive. CD47 blocking antibody injection increased MGC numbers in the peri-hematomal zone and in the hematoma in both sexes. Co-injection of clodronate liposomes depleted MGCs in both the hematoma core and the peri-hematomal area. In conclusion, MGCs represent a macrophage/microglia subtype with strong phagocytosis capacity. MGCs exhibited not only an M2 but also an M1 phenotype and appeared involved in hemoglobin degradation. Anti-CD47 antibody boosted the number of MGCs, which may contribute to enhance hematoma clearance. Understanding the exact roles of MGCs in ICH may reveal novel targets for ICH treatment. [ABSTRACT FROM AUTHOR]

Both experimental studies and surgical clinical trials suggest that hematoma clearance is a therapeutic target in intracerebral hemorrhage (ICH). We have investigated effects of CD47, a "don't eat me" signal expressed on erythrocytes, on hematoma resolution after ICH in young mice. This study expands those findings by examining the effects on a CD47 blocking antibody in aged rats. First, male Fischer 344 rats (18 months old) received an intracaudate injection of 50 μL autologous whole blood or saline. Hematoma features of magnetic resonance imaging (MRI) and neurological deficits were evaluated within 3 days. Second, rats had an intracaudate co-injection of 50 μL autologous blood with either CD47 blocking antibody or IgG. MRI was used to quantify hematoma/iron volume, hemolysis, brain swelling, and atrophy at different time points, behavioral tests to assess neurological deficits, and immunohistochemistry to assess brain injury and neuroinflammation. The CD47 blocking antibody significantly promoted hematoma clearance, attenuated brain swelling, hemolysis, and neuronal loss and increased the number of phagocytic macrophages in and around hematoma 3 days after ICH. Moreover, CD47 blockade reduced neuronal loss, brain atrophy, and neurobehavioral deficits at day 28. These results indicate that a CD47 blocking antibody can accelerate hematoma clearance and alleviate short- and long-term brain injury after ICH in aged rats and that it might be a therapeutic strategy for ICH. [ABSTRACT FROM AUTHOR]

Red blood cell (RBC) lysis within the hematoma causes brain injury following intracerebral hemorrhage. Peroxiredoxin 2 (PRX-2) is the third most abundant protein in RBCs and this study examined the potential role of PRX-2 in inducing brain injury in rats. First, adult male Sprague-Dawley rats had an intracaudate injection of lysed RBCs or saline. Brains were harvested at 1 h to measure PRX-2 levels. Second, rats had an intracaudate injection of either recombinant PRX-2, heat-inactivated PRX-2, or saline. Third, rats had intracaudate co-injection of lysed RBCs with conoidin A, a PRX-2 inhibitor, or vehicle. For the second and third parts of studies, behavioral tests were performed and all rats had magnetic resonance imaging prior to euthanasia for brain immunohistochemistry and Western blotting. We found that brain PRX-2 levels were increased after lysed RBC injection. Intracaudate injection of PRX-2 resulted in blood-brain barrier disruption, brain swelling, neutrophil infiltration, microglia activation, neuronal death, and neurological deficits. Intracerebral injection of lysed RBCs induced brain injury, which was reduced by conoidin A. These results suggest that extracellular PRX-2 released from hematoma can cause brain injury following brain hemorrhage and could be a potential therapeutic target. [ABSTRACT FROM AUTHOR]

Ceruloplasmin (CP) is an essential ferroxidase that is involved in maintaining iron homeostasis by oxidizing toxic ferrous iron (Fe2+) to less-toxic ferric iron (Fe3+). CP has been well studied in many neurodegenerative diseases, but there has not been an in-depth investigation in intracerebral hemorrhage (ICH). This research investigated brain CP expression in rats after ICH and the effect of CP on Fe2+-induced brain injury. This study had two parts: first, rats had injection of autologous blood into the right basal ganglia and the time course of CP expression in the brain examined (protein and mRNA). Second, rats had an injection of either Fe2+ in saline, Fe2+ plus CP in saline, or saline alone into the right basal ganglia. All rats in the second part had T2-weighted magnetic resonance imaging, and behavioral tests before the brains were harvested for immunohistochemistry and Western blotting. We found that CP was expressed on neurons and astrocytes in both cortex and basal ganglia after ICH. The time course showed that ICH induced CP expression increased from 4 h to 7 days, peaking at day 3. Whether the brain itself can produce CP was confirmed by RT-PCR. Exogenous CP reduced Fe2+-induced T2 lesions, blood-brain barrier disruption, brain cell death, and neurological deficits. These results suggest a role of CP in potentially reducing ICH-induced brain injury. [ABSTRACT FROM AUTHOR]

Early hemolysis occurs in the hematoma within 24 h in rat model of intracerebral hemorrhage (ICH). The present study investigated the prevalence of early hemolysis in ICH patients using MRI and the relationship between early hemolysis and perihematomal edema. Thirty ICH patients were prospectively enrolled within 24 h of onset. All patients had cranial CT on admission. Cranial MRI with T2 FLAIR-weighted imaging and T2*-weighted imaging were undertaken at days 1 and 14. The evolution of a non-hypointense lesion on T2*-weighted images and the relationship between the volume of that non-hypointense lesion and perihematomal edema volume were investigated. MRI images of 15 patients were analyzed. The median hematoma volume was 16.3 ml on admission. All patients underwent a baseline MRI within 24 h of ICH onset and showed a non-hypointense lesion within the hematoma on T2*-weighted images. The volume of non-hypointense lesion on T2*-weighted image was 6.0 (8.9) ml at day 1 and 8.6 (17.3) ml at day 14. The absolute perihematomal edema volume was 16.0 (17.9) ml and 24.8 (27.5) ml at days 1 and 14, respectively. There was a linear correlation between non-hypointense T2* lesion and perihematomal edema volume at day 1 and day 14 (p < 0.01). Early hemolysis in the hematoma occurs in humans and contributes to the development of perihematomal edema. [ABSTRACT FROM AUTHOR]

Erythrolysis occurs in the clot after intracerebral hemorrhage (ICH), and the release of hemoglobin causes brain injury, but it is unclear when such lysis occurs. The present study examined early erythrolysis in rats. ICH rats had an intracaudate injection of 100 μl autologous blood, and sham rats had a needle insertion. All rats had T2 and T2* magnetic response imaging (MRI) scanning, and brains were used for histology and CD163 (a hemoglobin scavenger receptor) and DARPP-32 (a neuronal marker) immunohistochemistry. There was marked heterogeneity within the hematoma on T2* MRI, with a hyperintense or isointense core and a hypointense periphery. Hematoxylin and eosin staining in the same animals showed significant erythrolysis in the core with the formation of erythrocyte ghosts. The degree of erythrolysis correlated with the severity of perihematomal neuronal loss. Perihematomal CD163 was increased by day 1 after ICH and may be involved in clearing hemoglobin caused by early hemolysis. Furthermore, ICH resulted in more severe erythrolysis, neuronal loss, and perihematomal CD163 upregulation in spontaneously hypertensive rats compared to Wistar-Kyoto rats. In conclusion, T2*MRI-detectable early erythrolysis occurred in the clot after ICH and activated CD163. Hypertension is associated with enhanced erythrolysis in the hematoma. [ABSTRACT FROM AUTHOR]

Polarized microglia play a dual (beneficial/detrimental) role in neurological diseases. However, the status and the factors that modulate microglia polarization in intracerebral hemorrhage (ICH) remain unclear. In the present study, we investigated the role of protease-activated receptor-1 (PAR-1, a thrombin receptor) in ICH-induced microglia polarization in mice. Male wild-type (WT) and PAR-1 knockout (PAR-1 KO) mice received an infusion of 30-μL autologous blood or saline into the right basal ganglia. Mice were euthanized at different time points and the brains were used for Western blotting and immunohistochemistry. Some mice had magnetic resonance imaging. We found that ICH induced microglia activation and polarization. M1 phenotypic markers were markedly increased and reached a peak as early as 4 h, remained high at 3 days and decreased 7 days after ICH. M2 phenotypic markers were upregulated later than M1 markers reaching a peak at day 1 and declining by day 7 after ICH. PAR-1 was upregulated after ICH and expressed in the neurons and microglia. ICH induced less brain swelling and neuronal death in PAR-1 KO mice, and this was associated with less M1 polarization and reduced proinflammatory cytokine levels in the brain. In conclusion, these results suggest that polarized microglia occur dynamically after ICH and that PAR-1 plays a role in the microglia activation and polarization. [ABSTRACT FROM AUTHOR]

Sphingolipids are a series of cell membrane-derived lipids which act as signaling molecules and play a critical role in cell death and survival, proliferation, recognition, and migration. Sphingosine-1-phosphate acts as a key signaling molecule and regulates lymphocyte trafficking, glial cell activation, vasoconstriction, endothelial barrier function, and neuronal death pathways which plays a critical role in numerous neurological conditions. Stroke is a second leading cause of death all over the world and effective therapies are still in great demand, including ischemic stroke and hemorrhagic stroke as well as poststroke repair. Significantly, sphingolipid activities change after stroke and correlate with stroke outcome, which has promoted efforts to testify whether the sphingolipid pathway could be a novel therapeutic target in stroke. The sphingolipid metabolic pathway, the connection between the pathway and stroke, as well as therapeutic interventions to manipulate the pathway to reduce stroke-induced brain injury are discussed in this review. [ABSTRACT FROM AUTHOR]

Early brain injury (EBI) plays a significant role in poor outcomes for subarachnoid hemorrhage (SAH) patients. Further investigations are required to characterize the cellular metabolic and related histological changes that may contribute to EBI following SAH. We investigated the image patterns of 18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) during EBI and correlated histopathological changes utilizing a rat SAH model. SAH was induced in six adult male Sprague-Dawley rats by endovascular perforation, and animals were randomly assigned to receive FDG PET-CT imaging at either 3 or 12 h post-procedure. Mean FDG standard uptake value (SUV) of the brain was calculated. Animals were euthanized 48 h post-procedure, and brain samples were used for heme oxygenase-1 (HO-1) and dopamine- and cAMP-regulated phosphoprotein (DARPP-32) Mr 32 kDa immunohistochemistry. Rats within the SAH group had higher mean whole brain FDG SUV (2.349 ± 0.376 g/ml in the 3-h group and 2.453 ± 0.495 g/ml in the 12-h group) compared to that of sham ( n = 3; mean SUV = 2.030 ± 0.247 g/ml; P < 0.05) or control groups ( n = 3; mean SUV = 1.800 ± 0.484 g/ml; P < 0.05). Whole brain FDG SUV did not vary significantly between rats imaged at 3 h vs. those imaged at 12 h post-SAH ( P > 0.05). Regions of decreasing SUV in SAH rats correlated with neuronal death and increased expression of HO-1. Higher FDG PET SUV was evident in rats post-SAH compared to sham and control groups. Regions of decreasing SUV in SAH rats correlated with neuronal death and increased HO-1 expression as evaluated by histopathology. [ABSTRACT FROM AUTHOR]

Brain iron overload has a key role in brain injury after intracerebral hemorrhage (ICH). Our recent study demonstrated that ICH-induced brain injury was greater in low capacity runner (LCR) than in high capacity runner (HCR) rats. The present study examines whether iron-induced brain injury differs between LCRs and HCRs. Adult male LCR and HCR rats had an intracaudate injection of iron or saline. Rats were euthanized at 2 and at 24 h after T2 magnetic resonance imaging, and the brains were used for immunostaining and Western blotting. LCRs had more hemispheric swelling, T2 lesion volumes, blood-brain barrier disruption, and neuronal death at 24 h after iron injection ( p < 0.05). Many propidium iodide (PI)-positive cells, indicative of necrotic cell death, were observed in the ipsilateral basal ganglia of both HCRs and LCRs at 2 h after iron injection. PI fluorescence intensity was higher in LCRs than in HCRs. In addition, membrane attack complex (MAC) expression was increased at 2 h after iron injection and was higher in LCRs than in HCRs. The PI-positive cells co-localized with MAC-positive cells in the ipsilateral basal ganglia. Iron induces more severe necrotic brain cell death, brain swelling, and blood-brain barrier disruption in LCR rats, which may be related with complement activation and MAC formation. [ABSTRACT FROM AUTHOR]