Neurotoxicity of hemoglobin in cortical cell culture

Surgical closure of spinal cerebrospinal fluid leaks improves symptoms in patients with superficial siderosis

BACKGROUND AND PURPOSE

Spinal cerebrospinal fluid (CSF) leaks may cause a myriad of symptoms, most common being orthostatic headache. In addition, ventral spinal CSF leaks are a possible etiology of superficial siderosis (SS), a rare condition characterized by hemosiderin deposits in the central nervous system (CNS). The classical presentation of SS involves ataxia, bilateral hearing loss, and myelopathy. Unfortunately, treatment options are scarce. This study was undertaken to evaluate whether microsurgical closure of CSF leaks can prevent further clinical deterioration or improve symptoms of SS.

METHODS

This cohort study was conducted using data from a prospectively maintained database in two large spontaneous intracranial hypotension (SIH) referral centers in Germany and Switzerland of patients who meet the modified International Classification of Headache Disorders, 3rd edition criteria for SIH. Patients with spinal CSF leaks were screened for the presence of idiopathic infratentorial symmetric SS of the CNS.

RESULTS

Twelve patients were included. The median latency between the onset of orthostatic headaches and symptoms attributed to SS was 9.5 years. After surgical closure of the underlying spinal CSF leak, symptoms attributed to SS improved in seven patients and remained stable in three. Patients who presented within 1 year after the onset of SS symptoms improved, but those who presented in 8-12 years did not improve. We could show a significant association between patients with spinal longitudinal extrathecal collections and SS.

CONCLUSIONS

Long-standing untreated ventral spinal CSF leaks can lead to SS of the CNS, and microsurgical sealing of spinal CSF leaks might stop progression and improve symptoms in patients with SS in a time-dependent manner.

The Haptoglobin Response after Aneurysmal Subarachnoid Haemorrhage

Haptoglobin is the body's first line of defence against the toxicity of extracellular haemoglobin released following a subarachnoid haemorrhage (SAH). We investigated the haptoglobin response after SAH in cerebrospinal fluid (CSF) and serum. Paired CSF and serum samples from 19 controls and 92 SAH patients were assayed as follows: ultra-performance liquid chromatography for CSF haemoglobin and haptoglobin, immunoassay for serum haptoglobin and multiplexed CSF cytokines, and colorimetry for albumin. There was marked CSF haptoglobin deficiency: 99% of extracellular haemoglobin was unbound. The quotients for both CSF/serum albumin (qAlb) and haptoglobin (qHp) were used to compute the CSF haptoglobin index (qHp/qAlb). CSF from SAH patients had a significantly lower haptoglobin index compared to controls, especially in Haptoglobin-1 allele carriers. Serum haptoglobin levels increased after SAH and were correlated with CSF cytokine levels. Haptoglobin variables were not associated with long-term clinical outcomes post-SAH. We conclude that: (1) intrathecal haptoglobin consumption occurs after SAH, more so in haptoglobin-1 allele carriers; (2) serum haptoglobin is upregulated after SAH, in keeping with the liver acute phase response to central inflammation; (3) haptoglobin in the CSF is so low that any variation is too small for this to affect long-term outcomes, emphasising the potential for therapeutic haptoglobin supplementation.

Functional effects of haemoglobin can be rescued by haptoglobin in an in vitro model of subarachnoid haemorrhage

During subarachnoid haemorrhage, a blood clot forms in the subarachnoid space releasing extracellular haemoglobin (Hb), which causes oxidative damage and cell death in surrounding tissues. High rates of disability and cognitive decline in SAH survivors are attributed to loss of neurons and functional connections during secondary brain injury. Haptoglobin sequesters Hb for clearance, but this scavenging system is overwhelmed after a haemorrhage. Whilst exogenous haptoglobin application can attenuate cytotoxicity of Hb in vitro and in vivo, the functional effects of sub-lethal Hb concentrations on surviving neurons and whether cellular function can be protected with haptoglobin treatment remain unclear. Here we use cultured neurons to investigate neuronal health and function across a range of Hb concentrations to establish the thresholds for cellular damage and investigate synaptic function. Hb impairs ATP concentrations and cytoskeletal structure. At clinically relevant but sub-lethal Hb concentrations, we find that synaptic AMPAR-driven currents are reduced, accompanied by a reduction in GluA1 subunit expression. Haptoglobin co-application can prevent these deficits by scavenging free Hb to reduce it to sub-threshold concentrations and does not need to be present at stoichiometric amounts to achieve efficacy. Haptoglobin itself does not impair measures of neuronal health and function at any concentration tested. Our data highlight a role for Hb in modifying synaptic function in surviving neurons, which may link to impaired cognition or plasticity after SAH and support the development of haptoglobin as a therapy for subarachnoid haemorrhage.

Deferoxamine in intracerebral hemorrhage: Systematic review and meta-analysis

BACKGROUND

Intracerebral hemorrhage (ICH) is a stroke with a high morbidity and mortality rate. Deferoxamine (DFX) is thought to be effective in treating Intracerebral Hemorrhage. In our study, we performed a meta-analysis to evaluate the treatment effects of DFX.

METHODS

We systematically searched PubMed, Embase, Web of Science, the Cochrane Central Register of Controlled Trials, and Chinese Biomedical Literature Database in Jan 2022 for studies on DFX for ICH patients. Outcome measures included relative hematoma volume, relative edema volume, good neurological functional outcome and adverse events. Odds risk (OR) and weighted mean difference (WMD) were used to evaluate clinical outcomes.

RESULTS

After searching 636 articles, 4 RCTs, 2 NRCTs, and 1cohort study were included. We found that DFX was effective in hematoma absorption on day 7 after onset, but the difference was not significant on day 14. DFX could suppress edema expansion on days 3, 7, and 14 after onset. DFX did not contribute to better outcomes after 3 and 6 months when used the modified Rankin Scale and the Glasgow Outcome Scale to evaluate neurological prognosis. The pooled results showed no statistically significant difference in Serious adverse events between the experimental and control groups.

CONCLUSIONS

DFX could limit edema expansion on days 3, 7, and 14 after commencement and facilitate hematoma absorption at week 1 without significantly increasing the risk of adverse events, but it did not improve neurological prognosis.

Protecting the injured central nervous system: Do anesthesia or hypothermia ameliorate secondary injury?

Traumatic injury to the central nervous system (CNS) and stroke initiate a cascade of processes that expand the area of tissue loss. The current review considers recent studies demonstrating that the induction of an anesthetic state or cooling the affected tissue (hypothermia) soon after injury can have a therapeutic effect. We first provide an overview of the neurobiological processes that fuel tissue loss after traumatic brain injury (TBI), spinal cord injury (SCI) and stroke. We then examine the rehabilitative effectiveness of therapeutic anesthesia across a variety of drug categories through a systematic review of papers in the PubMed database. We also review the therapeutic benefits hypothermia, another treatment that quells neural activity. We conclude by considering factors related to the safety, efficacy and timing of treatment, as well as the mechanisms of action. Clinical implications are also discussed.

The amyotrophic lateral sclerosis-linked protein TDP-43 regulates interleukin-6 cytokine production by human brain pericytes

Amyotrophic lateral sclerosis (ALS) is a fatal movement disorder involving degeneration of motor neurons through dysfunction of the RNA-binding protein TDP-43. Pericytes, the perivascular cells of the blood-brain, blood-spinal cord, and blood-CSF barriers also degenerate in ALS. Indeed, pericytes are among the earliest cell types to show gene expression changes in pre-symptomatic animal models of ALS. This suggests that pericyte degeneration precedes neurodegeneration and may involve pericyte cell-autonomous TDP-43 dysfunction. Here we determined the effect of TDP-43 dysfunction in human brain pericytes on interleukin 6 (IL-6), a critical secreted inflammatory mediator reported to be regulated by TDP 43. Primary human brain pericytes were cultured from biopsy tissue from epilepsy surgeries and TDP-43 was silenced using siRNA. TDP-43 silencing of pericytes stimulated with pro-inflammatory cytokines, interleukin-1β or tumour necrosis factor alpha, robustly suppressed the induction of IL-6 transcript and protein. IL-6 regulation by TDP-43 did not involve the assembly of TDP-43 nuclear splicing bodies, and did not occur via altered splicing of IL6. Instead, transcriptome-wide analysis by RNA-Sequencing identified a poison exon in the IL6 destabilising factor HNRNPD (AUF1) as a splicing target of TDP-43. Our data support a model whereby TDP-43 silencing favours destabilisation of IL6 mRNA, via enhanced AU-rich element-mediated decay by HNRNP/AUF1. This suggests that cell-autonomous deficits in TDP-43 function in human brain pericytes would suppress their production of IL-6. Given the importance of the blood-brain and blood-spinal cord barriers in maintaining motor neuron health, TDP-43 in human brain pericytes may represent a cellular target for ALS therapeutics.

The Role of Circadian Clock Genes in Critical Illness: The Potential Role of Translational Clock Gene Therapies for Targeting Inflammation, Mitochondrial Function, and Muscle Mass in Intensive Care

The Earth's 24-h planetary rotation, with predictable light and heat cycles, has driven profound evolutionary adaptation, with prominent impacts on physiological mechanisms important for surviving critical illness. Pathways of interest include inflammation, mitochondrial function, energy metabolism, hypoxic signaling, apoptosis, and defenses against reactive oxygen species. Regulation of these by the cellular circadian clock (BMAL-1 and its network) has an important influence on pulmonary inflammation; ventilator-associated lung injury; septic shock; brain injury, including vasospasm; and overall mortality in both animals and humans. Whether it is cytokines, the inflammasome, or mitochondrial biogenesis, circadian medicine represents exciting opportunities for translational therapy in intensive care, which is currently lacking. Circadian medicine also represents a link to metabolic determinants of outcome, such as diabetes and cardiovascular disease. More than ever, we are appreciating the problem of circadian desynchrony in intensive care. This review explores the rationale and evidence for the importance of the circadian clock in surviving critical illness.

Myelinated axons are the primary target of hemin-mediated oxidative damage in a model of the central nervous system

Iron released from oligodendrocytes during demyelination or derived from haemoglobin breakdown products is believed to amplify oxidative tissue injury in multiple sclerosis (MS). However, the pathophysiological significance of iron-containing haemoglobin breakdown products themselves is rarely considered in the context of MS and their cellular specificity and mode of action remain unclear. Using myelinating cell cultures, we now report the cytotoxic potential of hemin (ferriprotoporphyrin IX chloride), a major degradation product of haemoglobin, is 25-fold greater than equimolar concentrations of free iron in myelinating cultures; a model that reproduces the complex multicellular environment of the CNS. At low micro molar concentrations (3.3 - 10 μM) we observed hemin preferentially binds to myelin and axons to initiate a complex detrimental response that results in targeted demyelination and axonal loss but spares neuronal cell bodies, astrocytes and the majority of oligodendroglia. Demyelination and axonal loss in this context are executed by a combination of mechanisms that include iron-dependent peroxidation by reactive oxygen species (ROS) and ferroptosis. These effects are microglial-independent, do not require any initiating inflammatory insult and represent a direct effect that compromises the structural integrity of myelinated axons in the CNS. Our data identify hemin-mediated demyelination and axonal loss as a novel mechanism by which intracerebral degradation of haemoglobin may contribute to lesion development in MS.

DNA Double-Strand Breaks as Pathogenic Lesions in Neurological Disorders

The damage and repair of DNA is a continuous process required to maintain genomic integrity. DNA double-strand breaks (DSBs) are the most lethal type of DNA damage and require timely repair by dedicated machinery. DSB repair is uniquely important to nondividing, post-mitotic cells of the central nervous system (CNS). These long-lived cells must rely on the intact genome for a lifetime while maintaining high metabolic activity. When these mechanisms fail, the loss of certain neuronal populations upset delicate neural networks required for higher cognition and disrupt vital motor functions. Mammalian cells engage with several different strategies to recognize and repair chromosomal DSBs based on the cellular context and cell cycle phase, including homologous recombination (HR)/homology-directed repair (HDR), microhomology-mediated end-joining (MMEJ), and the classic non-homologous end-joining (NHEJ). In addition to these repair pathways, a growing body of evidence has emphasized the importance of DNA damage response (DDR) signaling, and the involvement of heterogeneous nuclear ribonucleoprotein (hnRNP) family proteins in the repair of neuronal DSBs, many of which are linked to age-associated neurological disorders. In this review, we describe contemporary research characterizing the mechanistic roles of these non-canonical proteins in neuronal DSB repair, as well as their contributions to the etiopathogenesis of selected common neurological diseases.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

Elevated intraspinal pressure in traumatic spinal cord injury is a promising therapeutic target

The currently recommended management for acute traumatic spinal cord injury aims to reduce the incidence of secondary injury and promote functional recovery. Elevated intraspinal pressure (ISP) likely plays an important role in the processes involved in secondary spinal cord injury, and should not be overlooked. However, the factors and detailed time course contributing to elevated ISP and its impact on pathophysiology after traumatic spinal cord injury have not been reviewed in the literature. Here, we review the etiology and progression of elevated ISP, as well as potential therapeutic measures that target elevated ISP. Elevated ISP is a time-dependent process that is mainly caused by hemorrhage, edema, and blood-spinal cord barrier destruction and peaks at 3 days after traumatic spinal cord injury. Duraplasty and hypertonic saline may be promising treatments for reducing ISP within this time window. Other potential treatments such as decompression, spinal cord incision, hemostasis, and methylprednisolone treatment require further validation.

MSC Secretome as a Promising Tool for Neuroprotection and Neuroregeneration in a Model of Intracerebral Hemorrhage

Multipotent mesenchymal stromal cells (MSCs) are considered to be critical contributors to injured tissue repair and regeneration, and MSC-based therapeutic approaches have been applied to many peripheral and central neurologic disorders. It has been demonstrated that the beneficial effects of MSC are mainly mediated by the components of their secretome. In the current study, we have explored the neuroprotective potential of the MSC secretome in a rat model of intracerebral hemorrhage and shown that a 10-fold concentrated secretome of human MSC and its combination with the brain-derived neurotrophic factor (BDNF) provided a better survival and neurological outcome of rats within 14 days of intracerebral hemorrhage compared to the negative (non-treated) and positive (BDNF) control groups. We found that it was due to the ability of MSC secretome to stimulate neuron survival under conditions of glutamate-induced neurotoxicity. However, the lesion volume did not shrink in these rats, and this also correlated with prominent microglia activation. We hypothesize that this could be caused by the species-specificity of the used MSC secretome and provide evidence to confirm this. Thus, we have found that allogenic rat MSC secretome was more effective than xenogenic human MSC secretome in the rat intracerebral hemorrhage model: it reduced the volume of the lesion and promoted excellent survival and neurological outcome of the treated rats.

Role of endolysosome function in iron metabolism and brain carcinogenesis

Iron, the most abundant metal in human brain, is an essential microelement that regulates numerous cellular mechanisms. Some key physiological roles of iron include oxidative phosphorylation and ATP production, embryonic neuronal development, formation of iron-sulfur clusters, and the regulation of enzymes involved in DNA synthesis and repair. Because of its physiological and pathological importance, iron homeostasis must be tightly regulated by balancing its uptake, transport, and storage. Endosomes and lysosomes (endolysosomes) are acidic organelles known to contain readily releasable stores of various cations including iron and other metals. Increased levels of ferrous (Fe2+) iron can generate reactive oxygen species (ROS) via Fenton chemistry reactions and these increases can damage mitochondria and genomic DNA as well as promote carcinogenesis. Accumulation of iron in the brain has been linked with aging, diet, disease, and cerebral hemorrhage. Further, deregulation of brain iron metabolism has been implicated in carcinogenesis and may be a contributing factor to the increased incidence of brain tumors around the world. Here, we provide insight into mechanisms by which iron accumulation in endolysosomes is altered by pH and lysosome membrane permeabilization. Such events generate excess ROS resulting in mitochondrial DNA damage, fission, and dysfunction, as well as DNA oxidative damage in the nucleus; all of which promote carcinogenesis. A better understanding of the roles that endolysosome iron plays in carcinogenesis may help better inform the development of strategic therapeutic options for cancer treatment and prevention.

Cerebrospinal fluid hemoglobin drives subarachnoid hemorrhage-related secondary brain injury

Secondary brain injury after aneurysmal subarachnoid hemorrhage (SAH-SBI) contributes to poor outcomes in patients after rupture of an intracranial aneurysm. The lack of diagnostic biomarkers and novel drug targets represent an unmet need. The aim of this study was to investigate the clinical and pathophysiological association between cerebrospinal fluid hemoglobin (CSF-Hb) and SAH-SBI. In a cohort of 47 patients, we collected daily CSF-samples within 14 days after aneurysm rupture. There was very strong evidence for a positive association between spectrophotometrically determined CSF-Hb and SAH-SBI. The accuracy of CSF-Hb to monitor for SAH-SBI markedly exceeded that of established methods (AUC: 0.89 [0.85-0.92]). Temporal proteome analysis revealed erythrolysis accompanied by an adaptive macrophage response as the two dominant biological processes in the CSF-space after aneurysm rupture. Ex-vivo experiments on the vasoconstrictive and oxidative potential of Hb revealed critical inflection points overlapping CSF-Hb thresholds in patients with SAH-SBI. Selective depletion and in-solution neutralization by haptoglobin or hemopexin efficiently attenuated the vasoconstrictive and lipid peroxidation activities of CSF-Hb. Collectively, the clinical association between high CSF-Hb levels and SAH-SBI, the underlying pathophysiological rationale, and the favorable effects of haptoglobin and hemopexin in ex-vivo experiments position CSF-Hb as a highly attractive biomarker and potential drug target.

Impaired meningeal lymphatic vessels exacerbate early brain injury after experimental subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Blood that enters the subarachnoid space (SAS) and its breakdown products are neurotoxic and are the principal inducers of brain injury after subarachnoid hemorrhage (SAH). Recently, meningeal lymphatic vessels (MLVs) have been proven to play an important role in clearing erythrocytes that arise from SAH, as well as other macromolecular solutes. However, evidence demonstrating the relationship between MLVs and brain injury after SAH is still limited. Therefore, we performed this study to observe the effects of meningeal lymphatic impairment on early brain injury (EBI) after experimental SAH.

METHODS

The MLVs of C57BL/6 male adult mice were ablated by injecting Visudyne into the cisterna magna and transcranially photoconverting it with laser light. The MLVs were then examined by immunofluorescence staining for lyve-1. Next, both the MLV-ablated group and the control group (normal mice) underwent filament perforation to model SAH or sham operation. We assessed the cortical perfusion of all the mice before SAH induction, 5 min after SAH and 24 h after SAH. In addition, we evaluated neurological function deficits by Garcia scores and measured brain water content at 24 h post SAH. Then, neuroinflammation and neural apoptosis in the mouse brain were also examined.

RESULTS

Visudyne and transcranial photoconversion treatment notably ablated mouse MLVs. Five minutes after SAH induction, cortical perfusion was significantly impaired, and after 24 h, this impairment was ameliorated considerably in the control group but ameliorated only slightly or worsened in the MLV-ablated group. Additionally, the MLVablated group presented worse neurological function deficits and more severe brain edema than the control group. More notably, neuroinflammation and neural apoptosis were also observed.

CONCLUSION

Ablation of MLVs by Visudyne treatment exacerbated EBI after experimental SAH in mice. The worsening of EBI may have arisen from limited drainage of blood and other breakdown products, which are thought to cause brain edema, neuroinflammation, neuronal apoptosis and other pathological processes.

When the Blood Hits Your Brain: The Neurotoxicity of Extravasated Blood

Hemorrhage in the central nervous system (CNS), including intracerebral hemorrhage (ICH), intraventricular hemorrhage (IVH), and aneurysmal subarachnoid hemorrhage (aSAH), remains highly morbid. Trials of medical management for these conditions over recent decades have been largely unsuccessful in improving outcome and reducing mortality. Beyond its role in creating mass effect, the presence of extravasated blood in patients with CNS hemorrhage is generally overlooked. Since trials of surgical intervention to remove CNS hemorrhage have been generally unsuccessful, the potent neurotoxicity of blood is generally viewed as a basic scientific curiosity rather than a clinically meaningful factor. In this review, we evaluate the direct role of blood as a neurotoxin and its subsequent clinical relevance. We first describe the molecular mechanisms of blood neurotoxicity. We then evaluate the clinical literature that directly relates to the evacuation of CNS hemorrhage. We posit that the efficacy of clot removal is a critical factor in outcome following surgical intervention. Future interventions for CNS hemorrhage should be guided by the principle that blood is exquisitely toxic to the brain.

Treatment Response of Deferiprone in Infratentorial Superficial Siderosis: a Systematic Review

Superficial siderosis describes haemosiderin deposition on the surface of the brain. When present on infratentorial structures, it can cause ataxia, sensorineural hearing loss and pyramidal signs. There is no proven treatment and patients experience slow progression of symptoms. Iron-chelating agents have been suggested as a therapeutic option and deferiprone is suited as it crosses the blood-brain barrier. However, deferiprone is reported to have a 1–2% risk of agranulocytosis. We performed a systematic review on treatment of infratentorial superficial siderosis with deferiprone based on PRISMA guidelines. Studies were included if in English or an English language translation was available, were about human subjects and referred to patients with ataxia. Studies were excluded if they did not possess an English translation, included animal studies or did not have ataxia. Studies were excluded if they discussed cerebral amyloid angiopathy or siderosis of other regions. Eleven papers were included. We identified 69 patients. Seventeen patients (25%) discontinued the drug. The most encountered adverse effect was anaemia (21.7%). Neutropaenia was observed in 8.7% and agranulocytosis in 5.8% of patients. Clinically, response varied, and stability or improvement was seen across neurological domains in 6 studies while 5 showed a mixed response. On imaging, 13 (28.9%) patients improved, 24 (53.3%) stabilised and 8 (17.8%) deteriorated. A prospective international centralised register of patients should be developed to inform the design and conduct of a multicentre, placebo-controlled, randomised clinical trial to evaluate the efficacy of deferiprone. The evidence from this systematic review is that deferiprone is a promising intervention.

Optimized lactoferrin as a highly promising treatment for intracerebral hemorrhage: Pre-clinical experience

Intracerebral hemorrhage (ICH) is the deadliest form of stroke for which there is no effective treatment, despite an endless number of pre-clinical studies and clinical trials. The obvious therapeutic target is the neutralization of toxic products of red blood cell (RBC) lysis that lead to cytotoxicity, inflammation, and oxidative damage. We used rigorous approaches and translationally relevant experimental ICH models to show that lactoferrin-(LTF)-based monotherapy is uniquely robust in reducing brain damage after ICH. Specifically, we designed, produced, and pharmacokinetically/toxicologically characterized an optimized LTF, a fusion of human LTF and the Fc domain of human IgG (FcLTF) that has a 5.8-fold longer half-life in the circulation than native LTF. Following dose-optimization studies, we showed that FcLTF reduces neurological injury caused by ICH in aged male/female mice, and in young male Sprague Dawley (SD) and spontaneously hypertensive rats (SHR). FcLTF showed a remarkably long 24-h therapeutic window. In tissue culture systems, FcLTF protected neurons from the toxic effects of RBCs and promoted microglia toward phagocytosis of RBCs and dead neurons, documenting its pleotropic effect. Our findings indicate that FcLTF is safe and effective in reducing ICH-induced damage in animal models used in this study.

Subarachnoid Hemorrhage Increases Level of Heme Oxygenase-1 and Biliverdin Reductase in the Choroid Plexus

Subarachnoid hemorrhage is a specific, life-threatening form of hemorrhagic stroke linked to high morbidity and mortality. It has been found that the choroid plexus of the brain ventricles forming the blood-cerebrospinal fluid barrier plays an important role in subarachnoid hemorrhage pathophysiology. Heme oxygenase-1 and biliverdin reductase are two of the key enzymes of the hemoglobin degradation cascade. Therefore, the aim of present study was to investigate changes in protein levels of heme oxygenase-1 and biliverdin reductase in the rat choroid plexus after experimental subarachnoid hemorrhage induced by injection of non-heparinized autologous blood to the cisterna magna. Artificial cerebrospinal fluid of the same volume as autologous blood was injected to mimic increased intracranial pressure in control rats. Immunohistochemical and Western blot analyses were used to monitor changes in the of heme oxygenase-1 and biliverdin reductase levels in the rat choroid plexus after induction of subarachnoid hemorrhage or artificial cerebrospinal fluid application for 1, 3, and 7 days. We found increased levels of heme oxygenase-1 and biliverdin reductase protein in the choroid plexus over the entire period following subarachnoid hemorrhage induction. The level of heme oxygenase-1 was the highest early (1 and 3 days) after subarachnoid hemorrhage indicating its importance in hemoglobin degradation. Increased levels of heme oxygenase-1 were also observed in the choroid plexus epithelial cells at all time points after application of artificial cerebrospinal fluid. Biliverdin reductase protein was detected mainly in the choroid plexus epithelial cells, with levels gradually increasing during subarachnoid hemorrhage. Our results suggest that heme oxygenase-1 and biliverdin reductase are involved not only in hemoglobin degradation but probably also in protecting choroid plexus epithelial cells and the blood-cerebrospinal fluid barrier from the negative effects of subarachnoid hemorrhage.

Therapeutic Potential of Heme Oxygenase-1 in Aneurysmal Diseases

Abdominal aortic aneurysm (AAA) and intracranial aneurysm (IA) are serious arterial diseases in the aorta and brain, respectively. AAA and IA are associated with old age in males and females, respectively, and if rupture occurs, they carry high morbidity and mortality. Aneurysmal subarachnoid hemorrhage (SAH) due to IA rupture has a high rate of complication and fatality. Despite these severe clinical outcomes, preventing or treating these devastating diseases remains an unmet medical need. Inflammation and oxidative stress are shared pathologies of these vascular diseases. Therefore, therapeutic strategies have focused on reducing inflammation and reactive oxygen species levels. Interestingly, in response to cellular stress, the inducible heme oxygenase-1 (HO-1) is highly upregulated and protects against tissue injury. HO-1 degrades the prooxidant heme and generates molecules with antioxidative and anti-inflammatory properties, resulting in decreased oxidative stress and inflammation. Therefore, increasing HO-1 activity is an attractive option for therapy. Several HO-1 inducers have been identified and tested in animal models for preventing or alleviating AAA, IA, and SAH. However, clinical trials have shown conflicting results. Further research and the development of highly selective HO-1 regulators may be needed to prevent the initiation and progression of AAA, IA, or SAH.

Pharmacological Transection of Brain-Spinal Cord Communication Blocks Pain-Induced Hemorrhage and Locomotor Deficits after Spinal Cord Injury in Rats

Spinal cord injury (SCI) is often accompanied by additional tissue damage (polytrauma), which engages pain (nociceptive) fibers. Prior research has shown that nociceptive input can increase cell death, expand the area of hemorrhage, and impair long-term recovery. The current study shows that these adverse effects can be blocked by the sodium channel blocker lidocaine applied rostral to a contusion injury. Rats received a lower thoracic (T12) contusion injury, and noxious electrical stimulation (shock) was applied to the tail 24 h later. Immediately before shock treatment, a pharmacological transection was performed by slowly infusing lidocaine at T2. Long-term locomotor recovery was assessed over the next 21 days. Noxious electrical stimulation impaired locomotor recovery, and this effect was blocked by rostral lidocaine. Next, the acute effect of lidocaine was assessed. Tissue was collected 3 h after noxious stimulation, and the extent of hemorrhage was evaluated by assessing hemoglobin content using Western blotting. Nociceptive stimulation increased the extent of hemorrhage. Lidocaine applied at T2 before, but not immediately after, stimulation blocked this effect. A similar pattern of results was observed when lidocaine was applied at the site of injury by means of a lumbar puncture. The results show that a pharmacological transection blocks nociception-induced hemorrhage and exacerbation of locomotor deficits.

Haptoglobin administration into the subarachnoid space prevents hemoglobin-induced cerebral vasospasm

Delayed ischemic neurological deficit (DIND) is a major driver of adverse outcomes in patients with aneurysmal subarachnoid hemorrhage (aSAH), defining an unmet need for therapeutic development. Cell-free hemoglobin that is released from erythrocytes into the cerebrospinal fluid (CSF) is suggested to cause vasoconstriction and neuronal toxicity, and correlates with the occurrence of DIND. Cell-free hemoglobin in the CSF of patients with aSAH disrupted dilatory NO signaling ex vivo in cerebral arteries, which shifted vascular tone balance from dilation to constriction. We found that selective removal of hemoglobin from patient CSF with a haptoglobin-affinity column or its sequestration in a soluble hemoglobin-haptoglobin complex was sufficient to restore physiological vascular responses. In a sheep model, administration of haptoglobin into the CSF inhibited hemoglobin-induced cerebral vasospasm and preserved vascular NO signaling. We identified 2 pathways of hemoglobin delocalization from CSF into the brain parenchyma and into the NO-sensitive compartment of small cerebral arteries. Both pathways were critical for hemoglobin toxicity and were interrupted by the large hemoglobin-haptoglobin complex that inhibited spatial requirements for hemoglobin reactions with NO in tissues. Collectively, our data show that compartmentalization of hemoglobin by haptoglobin provides a novel framework for innovation aimed at reducing hemoglobin-driven neurological damage after subarachnoid bleeding.

Deferoxamine deconditioning increases neuronal vulnerability to hemoglobin

Concomitant treatment with deferoxamine (DFO) protects neural cells from iron and heme-mediated oxidative injury, but also disrupts cell responses to iron loading that may be protective. We hypothesized that DFO treatment and withdrawal would subsequently increase neuronal vulnerability to hemoglobin. Pretreatment with DFO followed by its washout increased neuronal loss after subsequent hemoglobin exposure by 3-4-fold compared with control vehicle-pretreated cultures. This was associated with reduced ferritin induction by hemoglobin; expression of heme oxygenase-1, which catalyzes iron release from heme, was not altered. Increased neuronal loss was prevented by exogenous apoferritin or by continuing DFO or antioxidants throughout the experimental course. Cell nonheme iron levels after hemoglobin treatment were similar in DFO-pretreated and control cultures. These results indicate that DFO deconditions neurons and subsequently increases their vulnerability to heme-mediated injury. Its net effect after CNS hemorrhage may be highly dependent on the timing and duration of its administration. Withdrawal of DFO while heme or iron levels remain elevated may be deleterious, and may negate any benefit of prior concomitant therapy.

Haemoglobin causes neuronal damage in vivo which is preventable by haptoglobin

After subarachnoid haemorrhage, prolonged exposure to toxic extracellular haemoglobin occurs in the brain. Here, we investigate the role of haemoglobin neurotoxicity in vivo and its prevention. In humans after subarachnoid haemorrhage, haemoglobin in cerebrospinal fluid was associated with neurofilament light chain, a marker of neuronal damage. Most haemoglobin was not complexed with haptoglobin, an endogenous haemoglobin scavenger present at very low concentration in the brain. Exogenously added haptoglobin bound most uncomplexed haemoglobin, in the first 2 weeks after human subarachnoid haemorrhage, indicating a wide therapeutic window. In mice, the behavioural, vascular, cellular and molecular changes seen after human subarachnoid haemorrhage were recapitulated by modelling a single aspect of subarachnoid haemorrhage: prolonged intrathecal exposure to haemoglobin. Haemoglobin-induced behavioural deficits and astrocytic, microglial and synaptic changes were attenuated by haptoglobin. Haptoglobin treatment did not attenuate large-vessel vasospasm, yet improved clinical outcome by restricting diffusion of haemoglobin into the parenchyma and reducing small-vessel vasospasm. In summary, haemoglobin toxicity is of clinical importance and preventable by haptoglobin, independent of large-vessel vasospasm.

Subarachnoid Hemorrhage-Related Epilepsy

Epilepsy is a significant worldwide public health problem that leads to reduced quality of life and negative psychosocial consequences and significantly increases mortality rates in those who are affected. The development of epilepsy from subarachnoid hemorrhage (SAH) has an important negative impact on long-term survival, functional status, and cognitive recovery in patients following aneurysmal rupture. Anticonvulsant medication (AED) administration to prevent the development of epilepsy following SAH is controversial, and studies to date have not shown effectiveness of AED use as prophylaxis. This paper reviews the pathophysiology of SAH in the development of epilepsy, the scope of the problem of epilepsy related to SAH, and the studies that have evaluated AED administration as prophylaxis for seizures and epilepsy.

Growth Hormone and Neuronal Hemoglobin in the Brain-Roles in Neuroprotection and Neurodegenerative Diseases

In recent years, evidence for hemoglobin (Hb) synthesis in both animal and human brains has been accumulating. While circulating Hb originating from cerebral hemorrhage or other conditions is toxic, there is also substantial production of neuronal Hb, which is influenced by conditions such as ischemia and regulated by growth hormone (GH), insulin-like growth factor-I (IGF-I), and other growth factors. In this review, we discuss the possible functions of circulating and brain Hb, mainly the neuronal form, with respect to the neuroprotective activities of GH and IGF-I against ischemia and neurodegenerative diseases. The molecular pathways that link Hb to the GH/IGF-I system are also reviewed, although the limited number of reports on this topic suggests a need for further studies. In summary, GH and/or IGF-I appear to be significant determinants of systemic and local brain Hb concentrations through mediating responses to oxygen and metabolic demand, as part of the neuroprotective effects exerted by GH and IGF-I. The nature and quantity of the latter deserve further exploration in specific experiments.

Biomimetic drug-delivery systems for the management of brain diseases

Acting as a double-edged sword, the blood-brain barrier (BBB) is essential for maintaining brain homeostasis by restricting the entry of small molecules and most macromolecules from blood. However, it also largely limits the brain delivery of most drugs. Even if a drug can penetrate the BBB, its accumulation in the intracerebral pathological regions is relatively low. Thus, an optimal drug-delivery system (DDS) for the management of brain diseases needs to display BBB permeability, lesion-targeting capability, and acceptable safety. Biomimetic DDSs, developed by directly utilizing or mimicking the biological structures and processes, provide promising approaches for overcoming the barriers to brain drug delivery. The present review summarizes the biological properties and biomedical applications of the biomimetic DDSs including the cell membrane-based DDS, lipoprotein-based DDS, exosome-based DDS, virus-based DDS, protein template-based DDS and peptide template-based DDS for the management of brain diseases.

Intracerebral Hemorrhage: Blood Components and Neurotoxicity

Intracerebral hemorrhage (ICH) is a subtype of stroke which is associated with the highest mortality and morbidity rates of all strokes. Although it is a major public health problem, there is no effective treatment for ICH. As a consequence of ICH, various blood components accumulate in the brain parenchyma and are responsible for much of the secondary brain damage and ICH-induced neurological deficits. Therefore, the strategies that could attenuate the blood component-induced neurotoxicity and improve hematoma resolution are highly needed. The present article provides an overview of blood-induced brain injury after ICH and emphasizes the need to conduct further studies elucidating the mechanisms of hematoma resolution after ICH.

Haemoglobin scavenging in intracranial bleeding: biology and clinical implications

Haemoglobin is released into the CNS during the breakdown of red blood cells after intracranial bleeding. Extracellular free haemoglobin is directly neurotoxic. Haemoglobin scavenging mechanisms clear haemoglobin and reduce toxicity; these mechanisms include erythrophagocytosis, haptoglobin binding of haemoglobin, haemopexin binding of haem and haem oxygenase breakdown of haem. However, the capacity of these mechanisms is limited in the CNS, and they easily become overwhelmed. Targeting of haemoglobin toxicity and scavenging is, therefore, a rational therapeutic strategy. In this Review, we summarize the neurotoxic mechanisms of extracellular haemoglobin and the peculiarities of haemoglobin scavenging pathways in the brain. Evidence for a role of haemoglobin toxicity in neurological disorders is discussed, with a focus on subarachnoid haemorrhage and intracerebral haemorrhage, and emerging treatment strategies based on the molecular pathways involved are considered. By focusing on a fundamental biological commonality between diverse neurological conditions, we aim to encourage the application of knowledge of haemoglobin toxicity and scavenging across various conditions. We also hope that the principles highlighted will stimulate research to explore the potential of the pathways discussed. Finally, we present a consensus opinion on the research priorities that will help to bring about clinical benefits.

Iron-induced energy supply deficiency and mitochondrial fragmentation in neurons

Iron dyshomeostasis and mitochondrial impairments are both vitally important for the progression of many neurodegenerative diseases, including Parkinson's disease and Alzheimer's disease. Nevertheless, how these two pathological phenomena are linked with one another remains unclear, especially in neurons. To address the question, a model of iron overload was established with exposure of rat primary cortical neurons to excessive iron. We first verified that iron overload resulted in a decrease in adenosine triphosphate (ATP) production in neurons. Meanwhile, the release of mitochondrial cytochrome c was significantly increased after iron overload and consequently triggered an apoptosis signal, as revealed by Caspase 3 cleavage. To explore the potential underlying molecular mechanisms, an unlabeled quantitative proteomics approach was applied to primary neurons. Gene Ontology enrichment analysis revealed that 58 mitochondria-associated proteins were significantly altered, including three subunits of mitochondrial complex I and optic atrophy 1(OPA1). Increased NADH-ubiquinone oxidoreductase 75 kDa subunit and decreased NADH-ubiquinone oxidoreductase subunit A10 levels were further validated by a western blot, and more importantly, complex I activity markedly declined. Iron-induced down-regulation on the OPA1 level was also validated by a western blot, which was not reversed by the anti-oxidant but was reversed by the iron chelator. Moreover, an OPA1-associated key downstream effect, mitochondrial fragmentation, was found to be aggravated in neurons exposed to excessive iron, which is consistent with the down-regulation of OPA1. Furthermore, the protein level of PTEN-induced putative kinase 1, an important protein closely related to complex I activity and mitochondrial fragmentation, also significantly declined in neurons by iron overload. Thus, our findings may shed new light on the linkage between iron toxicity and mitochondrial impairments, such as energy supply deficiency and mitochondrial fragmentation, and further expand the toxic repertoire of iron in the central nerve system. Cover Image for this issue: doi: 10.1111/jnc.14205.

Protective effect of vitreous against hemoglobin neurotoxicity

Hemorrhage into the brain parenchyma or subarachnoid space is associated with edema and vascular injury that is likely mediated at least in part by the toxicity of hemoglobin. In contrast, extravascular blood appears to be less neurotoxic when localized to the retina or adjacent vitreous, the gel filling the posterior segment of the eye. In this study, the hypothesis that vitreous protects neurons from hemoglobin toxicity was investigated in a primary cortical cell culture model. Consistent with prior observations, hemoglobin exposure for 24 h resulted in death of most neurons without injury to co-cultured glia. Neuronal loss was reduced in a concentration-dependent fashion by bovine vitreous, with complete protection produced by 3% vitreous solutions. This effect was associated with a reduction in malondialdehyde but an increase in cell iron. At low vitreous concentrations, its ascorbate content was sufficient to account for most neuroprotection, as equivalent concentrations of ascorbate alone had a similar effect. However, other vitreous antioxidants provided significant protection when applied at concentrations present in undiluted vitreous, and prevented all neuronal loss when combined in the absence of ascorbate. These results indicate that vitreous is an antioxidant cocktail that robustly protects neurons from hemoglobin toxicity, and may contribute to the relative resistance of retinal neurons to hemorrhagic injury.

Subarachnoid hemorrhage - Induced block of cerebrospinal fluid flow: Role of brain coagulation factor III (tissue factor)

Subarachnoid hemorrhage (SAH) in 95% of cases results in long-term disabilities due to brain damage, pathogenesis of which remains uncertain. Hindrance of cerebrospinal fluid (CSF) circulation along glymphatic pathways is a possible mechanism interrupting drainage of damaging substances from subarachnoid space and parenchyma. We explored changes in CSF circulation at different time following SAH and possible role of brain tissue factor (TF). Fluorescent solute and fluorescent microspheres injected into cisterna magna were used to track CSF flow in mice. SAH induced by perforation of circle of Willis interrupted CSF flow for up to 30 days. Block of CSF flow did not correlate with the size of hemorrhage. Following SAH, fibrin deposits were observed on the brain surface including areas without visible blood. Block of astroglia-associated TF by intracerebroventricular administration of specific antibodies increased size of hemorrhage, decreased fibrin deposition and facilitated spread of fluorophores in sham/naïve animals. We conclude that brain TF plays an important role in localization of hemorrhage and also regulates CSF flow under normal conditions. Targeting of the TF system will allow developing of new therapeutic approaches to the treatment of SAH and pathologies related to CSF flow such as hydrocephalus.

Hemopexin increases the neurotoxicity of hemoglobin when haptoglobin is absent

Hemopexin (Hpx) binds heme with extraordinary affinity, and after haptoglobin may provide a second line of defense against the toxicity of extracellular hemoglobin (Hb). In this series of experiments, the hypothesis that Hpx protects neurons from Hb neurotoxicity was evaluated in murine primary cultures containing neurons and glial cells. Contrary to hypothesis, Hpx increased neuronal loss due to micromolar concentrations of Hb by 4- to 12-fold, as measured by LDH release assay; conversely, the neurotoxicity of hemin was completely prevented. The endogenous fluorescence of Hpx was quenched by Hb, consistent with transfer of Hb-bound heme to Hpx. This was associated with precipitation of globin chains, as detected by immunostaining and fluorescent Hb labeling. A portion of this precipitate attached firmly to cells and could not be removed by multiple washes. Concomitant treatment with haptoglobin (Hp) prevented globin precipitation and most of the increase in neuronal loss. Hpx weakly attenuated the increase in culture non-heme iron produced by Hb treatment, quantified by ferrozine assay. However, Hb-Hpx toxicity was iron-dependent, and was blocked by deferoxamine and ferrostatin-1. Up-regulation of cell ferritin expression, a primary cell defense against Hb toxicity, was not observed on western blots of culture lysates that had been concomitantly treated with Hpx. These results suggest that Hpx destabilizes Hb in the absence of haptoglobin, leading to globin precipitation and exacerbation of iron-dependent oxidative cell injury. Combined therapy with hemopexin plus haptoglobin may be preferable to hemopexin alone after CNS hemorrhage.

Mechanisms of Endogenous Neuroprotective Effects of Astrocytes in Brain Injury

Astrocytes, once believed to serve only as "glue" for the structural support of neurons, have been demonstrated to serve critical functions for the maintenance and protection of neurons, especially under conditions of acute or chronic injury. There are at least seven distinct mechanisms by which astrocytes protect neurons from damage; these are (1) protection against glutamate toxicity, (2) protection against redox stress, (3) mediation of mitochondrial repair mechanisms, (4) protection against glucose-induced metabolic stress, (5) protection against iron toxicity, (6) modulation of the immune response in the brain, and (7) maintenance of tissue homeostasis in the presence of DNA damage. Astrocytes support these critical functions through specialized responses to stress or toxic conditions. The detoxifying activities of astrocytes are essential for maintenance of the microenvironment surrounding neurons and in whole tissue homeostasis. Improved understanding of the mechanisms by which astrocytes protect the brain could lead to the development of novel targets for the development of neuroprotective strategies.

Injury mechanisms in acute intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the most common hemorrhagic stroke subtype, and rates are increasing with an aging population. Despite an increase in research and trials of therapies for ICH, mortality remains high and no interventional therapy has been demonstrated to improve outcomes. We review known mechanisms of injury, recent clinical trial results, and newly discovered signaling pathways involved in hematoma clearance. Enthusiasm remains high for methods of minimally invasive clot removal as well as pharmacologic strategies to improve recovery after ICH, both of which are currently being evaluated in clinical trials. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

CD163 Expression in Neurons After Experimental Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

CD163, a receptor for hemoglobin, is involved in hemoglobin clearance after intracerebral hemorrhage (ICH). In contrast to microglial/macrophage CD163, neuronal CD163 hemoglobin has not been well studied. This study examined the expression of neuronal CD163 in a pig model of ICH and in vitro rat cortical neurons and the impact of deferoxamine on that expression.

METHODS

There were 2 parts to this study. In the in vivo part, piglets had injection of autologous blood into the right frontal lobe. The time course of CD163 expression and the effect of deferoxamine on the expression of CD163 after ICH were determined in the grey matter. In the in vitro part, the levels of CD163 and neuronal death and the effect of deferoxamine were examined in rat cortical neurons culture treated with hemoglobin.

RESULTS

CD163-positive cells were found, and the CD163 protein levels were upregulated in the ipsilateral grey matter after ICH. The CD163 levels peaked at days 1 and 3. The CD163-positive cells were colocated with NeuN-positive, heme oxygenase-2-positive, and terminal deoxynucleatidyl transferase dUTP nick end labeling-positive cells. Deferoxamine treatment attenuated ICH-induced CD163 upregulation and significantly reduced both brain CD163 and hemoglobin levels at day 3. Treating neuronal cultures with hemoglobin for 24 hours resulted in CD163 upregulation and increased cell death. Deferoxamine significantly attenuated the hemoglobin-induced neuronal death and CD163 upregulation.

CONCLUSIONS

CD163 is expressed in neurons and upregulated after ICH. Deferoxamine reduced ICH-induced CD163 upregulation and brain cell death in vivo and hemoglobin-induced CD163 upregulation and neuronal death in vitro.

Neuronal Death After Hemorrhagic Stroke In Vitro and In Vivo Shares Features of Ferroptosis and Necroptosis

BACKGROUND AND PURPOSE

Intracerebral hemorrhage leads to disability or death with few established treatments. Adverse outcomes after intracerebral hemorrhage result from irreversible damage to neurons resulting from primary and secondary injury. Secondary injury has been attributed to hemoglobin and its oxidized product hemin from lysed red blood cells. The aim of this study was to identify the underlying cell death mechanisms attributable to secondary injury by hemoglobin and hemin to broaden treatment options.

METHODS

We investigated cell death mechanisms in cultured neurons exposed to hemoglobin or hemin. Chemical inhibitors implicated in all known cell death pathways were used. Identified cell death mechanisms were confirmed using molecular markers and electron microscopy.

RESULTS

Chemical inhibitors of ferroptosis and necroptosis protected against hemoglobin- and hemin-induced toxicity. By contrast, inhibitors of caspase-dependent apoptosis, protein or mRNA synthesis, autophagy, mitophagy, or parthanatos had no effect. Accordingly, molecular markers of ferroptosis and necroptosis were increased after intracerebral hemorrhage in vitro and in vivo. Electron microscopy showed that hemin induced a necrotic phenotype. Necroptosis and ferroptosis inhibitors each abrogated death by >80% and had similar therapeutic windows in vitro.

CONCLUSIONS

Experimental intracerebral hemorrhage shares features of ferroptotic and necroptotic cell death, but not caspase-dependent apoptosis or autophagy. We propose that ferroptosis or necroptotic signaling induced by lysed blood is sufficient to reach a threshold of death that leads to neuronal necrosis and that inhibition of either of these pathways can bring cells below that threshold to survival.

Increased Expression of Caspase-12 After Experimental Subarachnoid Hemorrhage

Convincing evidences have proved that apoptosis plays a vital role in the pathogenesis of early and delayed brain injury following subarachnoid hemorrhage (SAH). Recently, a novel caspase-12-mediated apoptotic pathway has been reported to be induced by excess endoplasmic reticulum (ER) stress. Extensive protein damage occurs after SAH, which may trigger ER stress-associated apoptotic pathway. Thus, we hypothesized that caspase-12, as the major molecular marker of this novel apoptotic pathway, may be activated and involved in the pathogenesis of apoptotic injury after SAH. This study sought to investigate the changes of caspase-12 expressions in both in vitro and in vivo SAH models. Western blot analysis found significantly increased protein expressions of both pro- and active forms of caspase-12 after SAH. Quantitative real-time PCR and immunohistochemistry assays confirmed elevated caspase-12 level after SAH in vivo. Further, double immunofluorescence staining revealed obvious caspase-12 over-expression in both cortical neurons and astrocytes. Moreover, immunofluorescent co-staining in vivo demonstrated that neural cells with high immunoreactivity of caspase-12 also expressed caspase-3, and dual-immunofluorescent staining for caspase-12 and TUNEL in vitro showed that TUNEL-positive cells were more likely to exhibit higher caspase-12 immunoreactivity, indicating a potential contribution of caspase-12 activation to apoptosis in SAH. Collectively, our results showed significant upregulation of caspase-12 expression after experimental SAH. These findings also offer important implications for further investigations of the therapeutic potential of caspase-12 associated apoptosis in SAH.

Longitudinal profile of iron accumulation in good-grade subarachnoid hemorrhage

OBJECTIVE

MRI parameters of iron concentration (R2*, transverse relaxation rate), microstructural integrity (mean diffusivity and fractional anisotropy), as well as gray and white matter volumes were analyzed in patients with subarachnoid hemorrhage (SAH) and uncomplicated clinical course to detect the evolution of brain tissue changes 3 weeks and 12 months after ictus.

METHODS

MRI scans of 14 SAH patients (aneurysm of the anterior communicating artery, n = 5; no aneurysm n = 9) were compared with 14 age-matched healthy control subjects. Statistical parametric mapping (SPM) was applied to objectively identify focal changes of MRI parameters throughout the entire brain and to correlate image parameters with neuropsychological measures.

RESULTS

SPM localized significant bilateral increases in R2* signal within the white matter compartment of the temporal and parietal lobe and the cingulate gyrus (P < 0.001) which did not change significantly at 12 months. Significant gray matter volume reduction of the left insula and superior temporal gyrus (P < 0.001), as well as decreases in fractional anisotropy of the cingulate gyrus (P < 0.01) were also evident at 12 months. Significant correlations were found between fractional anisotropy signal alterations adjacent to the left middle and superior frontal gyrus and cognitive parameters of executive dysfunction (P < 0.001).

INTERPRETATION

The study indicates that iron is trapped predominantly throughout large portions of the white matter compartment in SAH patients at 12 months postbleeding. Increased disintegration of fiber tracts colocalizing with iron overload and correlating with lower executive function performance suggests that the white matter compartment is primarily susceptible toward long-term damage in patients with good clinical grade SAH.

Haptoglobin increases the vulnerability of CD163-expressing neurons to hemoglobin

Haptoglobin (Hp) binds hemoglobin (Hb) with high affinity and provides the primary defense against its toxicity after intravascular hemolysis. Neurons are exposed to extracellular Hb after CNS hemorrhage, and a therapeutic effect of Hp via Hb sequestration has been hypothesized. In this study, we tested the hypothesis that Hp protects neurons from Hb in primary mixed cortical cell cultures. Treatment with low micromolar concentrations of human Hb for 24 h resulted in loss of 10-20% of neurons without injuring glia. Concomitant treatment with Hp surprisingly increased neuronal loss five-sevenfold, with similar results produced by Hp 1-1 and 2-2 phenotypes. Consistent with a recent in vivo observation, neurons expressed the CD163 receptor for Hb and the Hb-Hp complex in these cultures. Hp reduced overall Hb uptake, directed it away from the astrocyte-rich CD163-negative glial monolayer, and decreased induction of the iron-binding protein ferritin. Hb-Hp complex neuronal toxicity, like that of Hb per se, was iron-dependent and reduced by deferoxamine and 2,2' bipyridyl. These results suggest that Hp increases the vulnerability of CD163+ neurons to Hb by permitting Hb uptake while attenuating the protective response of ferritin induction by glial cells. Cover Image for this issue: doi: 10.1111/jnc.13342.

Age-Dependent Effects of Haptoglobin Deletion in Neurobehavioral and Anatomical Outcomes Following Traumatic Brain Injury

Cerebral hemorrhages are common features of traumatic brain injury (TBI) and their presence is associated with chronic disabilities. Recent clinical and experimental evidence suggests that haptoglobin (Hp), an endogenous hemoglobin-binding protein most abundant in blood plasma, is involved in the intrinsic molecular defensive mechanism, though its role in TBI is poorly understood. The aim of this study was to investigate the effects of Hp deletion on the anatomical and behavioral outcomes in the controlled cortical impact model using wildtype (WT) C57BL/6 mice and genetically modified mice lacking the Hp gene (Hp(-∕-)) in two age cohorts [2-4 mo-old (young adult) and 7-8 mo-old (older adult)]. The data obtained suggest age-dependent significant effects on behavioral and anatomical TBI outcomes and recovery from injury. Moreover, in the adult cohort, neurological deficits in Hp(-∕-) mice at 24 h were significantly improved compared to WT, whereas there were no significant differences in brain pathology between these genotypes. In contrast, in the older adult cohort, Hp(-∕-) mice had significantly larger lesion volumes compared to WT, but neurological deficits were not significantly different. Immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) revealed significant differences in microglial and astrocytic reactivity between Hp(-∕-) and WT in selected brain regions of the adult but not the older adult-aged cohort. In conclusion, the data obtained in the study provide clarification on the age-dependent aspects of the intrinsic defensive mechanisms involving Hp that might be involved in complex pathways differentially affecting acute brain trauma outcomes.

Hemoglobin-induced neuronal degeneration in the hippocampus after neonatal intraventricular hemorrhage

Neuronal degeneration following neonatal intraventricular hemorrhage (IVH) is incompletely understood. Understanding the mechanisms of degeneration and cell loss may point toward specific treatments to limit injury. We evaluated the role of hemoglobin (Hb) in cell death after intraventricular injection in neonatal rats. Hb was injected into the right lateral ventricle of post-natal day 7 rats. Rats exposed to anesthesia were used for controls. The CA-1 region of the hippocampus was analyzed via immunohistochemistry, hematoxylin and eosin (H&E) staining, Fluoro-Jade C staining, Western blots, and double-labeling stains. Compared to controls, intraventricular injection of Hb decreased hippocampal volume (27% decrease; p<0.05), induced neuronal loss (31% loss; p<0.01), and increased neuronal degeneration (2.7 fold increase; p<0.01), which were all significantly reduced with the iron chelator, deferoxamine. Hb upregulated p-JNK (1.8 fold increase; p<0.05) and increased expression of the Hb/haptoglobin endocytotic receptor CD163 in neurons in vivo and in vitro (cultured cortical neurons). Hb induced expression of the CD163 receptor, which co-localized with p-JNK in hippocampal neurons, suggesting a potential pathway by which Hb enters the neuron to result in cell death. There were no differences in neuronal loss or degenerating neurons in Hb-injected animals that developed hydrocephalus versus those that did not. Intraventricular injection of Hb causes hippocampal neuronal degeneration and cell loss and increases brain p-JNK levels. p-JNK co-localized with the Hb/haptoglobin receptor CD163, suggesting a novel pathway by which Hb enters the neuron after IVH to result in cell death.

Oxidative Stress in Intracerebral Hemorrhage: Sources, Mechanisms, and Therapeutic Targets

Intracerebral hemorrhage (ICH) is associated with the highest mortality and morbidity despite only constituting approximately 10–15% of all strokes. Complex underlying mechanisms consisting of cytotoxic, excitotoxic, and inflammatory effects of intraparenchymal blood are responsible for its highly damaging effects. Oxidative stress (OS) also plays an important role in brain injury after ICH but attracts less attention than other factors. Increasing evidence has demonstrated that the metabolite axis of hemoglobin-heme-iron is the key contributor to oxidative brain damage after ICH, although other factors, such as neuroinflammation and prooxidases, are involved. This review will discuss the sources, possible molecular mechanisms, and potential therapeutic targets of OS in ICH.

Blue light-induced retinal lesions, intraretinal vascular leakage and edema formation in the all-cone mouse retina

Little is known about the mechanisms underlying macular degenerations, mainly for the scarcity of adequate experimental models to investigate cone cell death. Recently, we generated R91W;Nrl(-/-) double-mutant mice, which display a well-ordered all-cone retina with normal retinal vasculature and a strong photopic function that generates useful vision. Here we exposed R91W;Nrl(-/-) and wild-type (wt) mice to toxic levels of blue light and analyzed their retinas at different time points post illumination (up to 10 days). While exposure of wt mice resulted in massive pyknosis in a focal region of the outer nuclear layer (ONL), the exposure of R91W;Nrl(-/-) mice led to additional cell death detected within the inner nuclear layer. Microglia/macrophage infiltration at the site of injury was more pronounced in the all-cone retina of R91W;Nrl(-/-) than in wt mice. Similarly, vascular leakage was abundant in the inner and outer retina in R91W;Nrl(-/-) mice, whereas it was mild and restricted to the subretinal space in wt mice. This was accompanied by retinal swelling and the appearance of cystoid spaces in both inner and ONLs of R91W;Nrl(-/-) mice indicating edema in affected areas. In addition, basal expression levels of tight junction protein-1 encoding ZO1 were lower in R91W;Nrl(-/-) than in wt retinas. Collectively, our data suggest that exposure of R91W;Nrl(-/-) mice to blue light not only induces cone cell death but also disrupts the inner blood-retinal barrier. Macular edema in humans is a result of diffuse capillary leakage and microaneurysms in the macular region. Blue light exposure of the R91W;Nrl(-/-) mouse could therefore be used to study molecular events preceding edema formation in a cone-rich environment, and thus potentially help to develop treatment strategies for edema-based complications in macular degenerations.

Ischemia-reperfusion injury in stroke

Despite ongoing advances in stroke imaging and treatment, ischemic and hemorrhagic stroke continue to debilitate patients with devastating outcomes at both the personal and societal levels. While the ultimate goal of therapy in ischemic stroke is geared towards restoration of blood flow, even when mitigation of initial tissue hypoxia is successful, exacerbation of tissue injury may occur in the form of cell death, or alternatively, hemorrhagic transformation of reperfused tissue. Animal models have extensively demonstrated the concept of reperfusion injury at the molecular and cellular levels, yet no study has quantified this effect in stroke patients. These preclinical models have also demonstrated the success of a wide array of neuroprotective strategies at lessening the deleterious effects of reperfusion injury. Serial multimodal imaging may provide a framework for developing therapies for reperfusion injury.

The role of hemorrhage following spinal-cord injury

Spinal-cord injury is characterized by primary damage as a direct consequence of mechanical insult, and secondary damage that is partly due to the acute inflammatory response. The extent of any hemorrhage within the injured cord is also known to be associated with the formation of intraparenchymal cavities and has been anecdotally linked to secondary damage. This study was designed to examine the contribution of blood components to the outcome of spinal-cord injury. We stereotaxically microinjected collagenase, which causes localized bleeding, into the spinal cord to model the hemorrhage associated with spinal cord injury in the absence of significant mechanical trauma. Tissue damage was observed at the collagenase injection site over time, and was associated with localized disruption of the blood-spinal-cord barrier, neuronal cell death, and the recruitment of leukocytes. The magnitude of the bleed was related to neutrophil mobilization. Interestingly, the collagenase-induced injury also provoked extended axonal damage. With this model, the down-stream effects of hemorrhage are easily discernible, and the impact of treatment strategies for spinal-cord injury on hemorrhage-related injury can be evaluated.

Brain alpha- and beta-globin expression after intracerebral hemorrhage

Our recent study has demonstrated that hemoglobin (Hb) is present in cerebral neurons and neuronal Hb is inducible after cerebral ischemia. In the present study, we examined the effects of intracerebral hemorrhage (ICH) on the mRNA levels of the α-globin (HbA) and the β-globin (HbB) components of Hb and Hb protein in the brain in vivo and in vitro. In vivo, male Sprague-Dawley rats received either a needle insertion (sham) or an infusion of autologous whole blood into the basal ganglia and were killed at different time points. In vitro, cultured rat brain cells were used for HbA, HbB and Hb determination. Cultured neurons were exposed to 50 or 100 μM hemin for 24 h. Some neurons also were treated with deferoxamine, an iron chelator, or vehicle. Levels of HbA and HbB, Hb and hemopexin, a transporter of heme, were measured. We found that HbA, HbB and Hb are primarily expressed in neurons, with much lower expression in astrocytes and microglia. HbA, HbB and Hb expression in the perihematomal zone was increased after ICH and Hb was localized in neurons and glia. Hemin increased HbA, HbB and hemopexin mRNA levels in cultured neurons. Deferoxamine reduced hemin-induced neuronal Hb expression. ICH increased HbA and HbB expression in the brain, which may potentially serve to buffer the heme released during clot resolution.