Heme regulation in traumatic brain injury: relevance to the adult and developing brain

Silica Nanoparticles from Melon Seed Husk Abrogated Binary Metal(loid) Mediated Cerebellar Dysfunction by Attenuation of Oxido-inflammatory Response and Upregulation of Neurotrophic Factors in Male Albino Rats

Silica nanoparticles (SiNPs) have been touted for their role in the management of non-communicable diseases. Their neuroprotective benefits against heavy metal-induced neurotoxicity remain largely unexplored. This is a comparative evaluation of the oxido-inflammatory and neurotrophic effects of Ni, Al, and Ni/Al mixture on the cerebellum of male albino rats with or without treatment with SiNPs generated from melon seed husk. The study complied with the ARRIVE guidelines for reporting in vivo experiments. A total of 91, 7-9 week-old weight-matched male Sprague rats (to avoid sex bias) were randomly divided into 13 different dosing groups where Group 1 served as the control. Other groups received 0.2 mg/kg Ni, 1 mg/kg Al, and 0.2 mg/kg Ni + 1 mg/kg Al mixture with or without different doses of SiNP for 90 days. Rotarod performance was carried out. Oxidative stress markers, Ni, Al, Ca, Fe, Mg, neurotrophic factors, amyloid beta (Aβ-42), cyclooxygenase-2 (COX-2), and acetylcholinesterase (AChE) were determined in the cerebellum. SiNPs from melon seed husk caused a significant decrease in Aβ-42 level and activities of AChE and COX-2 and a significant increase in brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) mediated by Ni, Al, and Ni/Al mixture exposure in rats. Neurotoxicity of the Ni/Al mixture is via heightened neuronal lipoperoxidative damage, decreased Mg, and increased Fe, and co-administration of SiNPs from melon seed husk with the Ni/Al mixture attenuated some of these biochemical changes in the cerebellum.

Evaluating the therapeutic effect of LIPUS in the early stage of traumatic brain injury using FA and T2* in rats

To evaluate the protective effect of LIPUS at the early stage of brain trauma in rats, 45 rats were randomly divided into 3 groups: sham (n = 15), TBI (n = 15) and LIPUS treatment groups (n = 15). Ipsilateral and contralateral cortical and thalamic parameters obtained by diffusion tensor imaging (DTI) and fast low-angle shot magnetic resonance imaging (FLASH-MRI) were measured at different times after trauma. For fractional anisotropy (FA) and T2* values, two-way repeated measures ANOVA with Tukey's post hoc was used for intergroup comparisons. With observation time prolonged, the FA values of the ipsilateral cortex in the TBI group gradually increased and were significantly higher than those in the LIPUS treatment group on Day 7 (adjusted P = 0.0067). FA values in the contralateral cortex decreased at this time and were significantly lower than those in the LIPUS treatment group (adjusted P = 0.0192). Meanwhile, compared with LIPUS group, FA values were significantly higher in the injured thalamus (adjusted P = 0.0025). Combined with correlation analysis, FA values were positively correlated with neuronal damage (P = 0.0148, r2 = 0.895). At 7 days after trauma, T2* values in the ipsilateral cortex of the TBI group were significantly lower. After analysis of ferritin content and correlation, we found that T2* values were negatively correlated with ferritin (P = 0.0259, r2 = -0.849). By measuring post-traumatic changes in FA and T2* values, it is possible to demonstrate a neuronal protective effect of LIPUS in the early phase of TBI rats and promote brain rehabilitation.

Heme: The Lord of the Iron Ring

Heme is an iron-protoporphyrin complex with an essential physiologic function for all cells, especially for those in which heme is a key prosthetic group of proteins such as hemoglobin, myoglobin, and cytochromes of the mitochondria. However, it is also known that heme can participate in pro-oxidant and pro-inflammatory responses, leading to cytotoxicity in various tissues and organs such as the kidney, brain, heart, liver, and in immune cells. Indeed, heme, released as a result of tissue damage, can stimulate local and remote inflammatory reactions. These can initiate innate immune responses that, if left uncontrolled, can compound primary injuries and promote organ failure. In contrast, a cadre of heme receptors are arrayed on the plasma membrane that is designed either for heme import into the cell, or for the purpose of activating specific signaling pathways. Thus, free heme can serve either as a deleterious molecule, or one that can traffic and initiate highly specific cellular responses that are teleologically important for survival. Herein, we review heme metabolism and signaling pathways, including heme synthesis, degradation, and scavenging. We will focus on trauma and inflammatory diseases, including traumatic brain injury, trauma-related sepsis, cancer, and cardiovascular diseases where current work suggests that heme may be most important.

Bilirubin-biliverdin concentration measurement using photoacoustic spectroscopic analysis for determining hemorrhage age

The onset of intracerebral hemorrhage and its progression toward acute brain injury have been correlated with the concentration of unconjugated bilirubin (BR). In addition, BR has been considered a novel predictor of outcome from intracranial hemorrhage. Since the existing invasive approach for determining localized BR and biliverdin (BV) concentration within the hemorrhagic brain lesion is not feasible, the predictive capability of BR in terms of determining the onset of hemorrhage and understanding the consequences of its progression (age) is unknown. In this study, we have demonstrated a photoacoustic (PA) approach to the noninvasive measurement of BR-BV ratio that can be utilized longitudinally to approximate the onset of the hemorrhage. The PA imaging-based measurements of BV and BR in tissues and fluids can potentially be used to determine hemorrhage "age," quantitatively evaluate the hemorrhage resorption or detect a rebleeding, and assess responses to therapy and prognosis.

Multi-Omic Admission-Based Prognostic Biomarkers Identified by Machine Learning Algorithms Predict Patient Recovery and 30-Day Survival in Trauma Patients

Admission-based circulating biomarkers for the prediction of outcomes in trauma patients could be useful for clinical decision support. It is unknown which molecular classes of biomolecules can contribute biomarkers to predictive modeling. Here, we analyzed a large multi-omic database of over 8500 markers (proteomics, metabolomics, and lipidomics) to identify prognostic biomarkers in the circulating compartment for adverse outcomes, including mortality and slow recovery, in severely injured trauma patients. Admission plasma samples from patients (n = 129) enrolled in the Prehospital Air Medical Plasma (PAMPer) trial were analyzed using mass spectrometry (metabolomics and lipidomics) and aptamer-based (proteomics) assays. Biomarkers were selected via Least Absolute Shrinkage and Selection Operator (LASSO) regression modeling and machine learning analysis. A combination of five proteins from the proteomic layer was best at discriminating resolvers from non-resolvers from critical illness with an Area Under the Receiver Operating Characteristic curve (AUC) of 0.74, while 26 multi-omic features predicted 30-day survival with an AUC of 0.77. Patients with traumatic brain injury as part of their injury complex had a unique subset of features that predicted 30-day survival. Our findings indicate that multi-omic analyses can identify novel admission-based prognostic biomarkers for outcomes in trauma patients. Unique biomarker discovery also has the potential to provide biologic insights.

Neuroprotective Role of α-Lipoic Acid in Iron-Overload-Mediated Toxicity and Inflammation in In Vitro and In Vivo Models

Hemoglobin and iron overload is considered the major contributor to intracerebral hemorrhage (ICH)-induced brain injury. Accumulation of iron in the brain leads to microglia activation, inflammation and cell loss. Current available treatments for iron overload-mediated disorders are characterized by severe adverse effects, making such conditions an unmet clinical need. We assessed the potential of α-lipoic acid (ALA) as an iron chelator, antioxidant and anti-inflammatory agent in both in vitro and in vivo models of iron overload. ALA was found to revert iron-overload-induced toxicity in HMC3 microglia cell line, preventing cell apoptosis, reactive oxygen species generation and reducing glutathione depletion. Furthermore, ALA regulated gene expression of iron-related markers and inflammatory cytokines, such as IL-6, IL-1β and TNF. Iron toxicity also affects mitochondria fitness and biogenesis, impairments which were prevented by ALA pre-treatment in vitro. Immunocytochemistry assay showed that, although iron treatment caused inflammatory activation of microglia, ALA treatment resulted in increased ARG1 expression, suggesting it promoted an anti-inflammatory phenotype. We also assessed the effects of ALA in an in vivo zebrafish model of iron overload, showing that ALA treatment was able to reduce iron accumulation in the brain and reduced iron-mediated oxidative stress and inflammation. Our data support ALA as a novel approach for iron-overload-induced brain damage.

Emerging Applications for Quantitative Susceptibility Mapping in the Detection of Traumatic Brain Injury Pathology

Traumatic brain injury (TBI) is a common but heterogeneous injury underpinned by numerous complex and interrelated pathophysiological mechanisms. An essential trace element, iron is abundant within the brain and involved in many fundamental neurobiological processes, including oxygen transportation, oxidative phosphorylation, myelin production and maintenance, as well as neurotransmitter synthesis and metabolism. Excessive levels of iron are neurotoxic and thus iron homeostasis is tightly regulated in the brain, however, many details about the mechanisms by which this is achieved are yet to be elucidated. A key mediator of oxidative stress, mitochondrial dysfunction and neuroinflammatory response, iron dysregulation is an important contributor to secondary injury in TBI. Advances in neuroimaging that leverage magnetic susceptibility properties have enabled increasingly comprehensive investigations into the distribution and behaviour of iron in the brain amongst healthy individuals as well as disease states such as TBI. Quantitative Susceptibility Mapping (QSM) is an advanced neuroimaging technique that promises quantitative estimation of local magnetic susceptibility at the voxel level. In this review, we provide an overview of brain iron and its homeostasis, describe recent advances enabling applications of QSM within the context of TBI and summarise the current state of the literature. Although limited, the emergent research suggests that QSM is a promising neuroimaging technique that can be used to investigate a host of pathophysiological changes that are associated with TBI.

Chorioamnionitis Precipitates Perinatal Alterations of Heme-Oxygenase-1 (HO-1) Homeostasis in the Developing Rat Brain

Chorioamnionitis (CHORIO), placental insufficiency, and preterm birth are well-known antecedents of perinatal brain injury (PBI). Heme-oxygenase-1 (HO-1) is an important inducible enzyme in oxidative and inflammatory conditions. In the brain, HO-1 and the iron regulatory receptor, transferrin receptor-1 (TfR1), are known to be involved in iron homeostasis, oxidative stress, and cellular adaptive mechanisms. However, the role of HO pathway in the pathophysiology of PBI has not been previously studied. In this study, we set out to define the ontogeny of the HO pathway in the brain and determine if CHORIO changed its normal developmental regulation. We also aimed to determine the role of HO-1/TfR1 in CHORIO-induced neuroinflammation and peripheral inflammation in a clinically relevant rat model of PBI. We show that HO-1, HO-2, and TfR1 expression are developmentally regulated in the brain during the perinatal period. CHORIO elevates HO-1 and TfR1 mRNA expression in utero and in the early postnatal period and results in sustained increase in HO-1/TfR1 ratios in the brain. This is associated with neuroinflammatory and peripheral immune phenotype supported by a significant increase in brain mononuclear cells and peripheral blood double negative T cells suggesting a role of HO-1/TfR1 pathway dysregulation in CHORIO-induced neuroinflammation.

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.

Serum bilirubin level correlates with mortality in patients with traumatic brain injury

As a catabolic product of hemoglobin, bilirubin has been confirmed playing an important role in the development of various central nervous system disease. The aim of this study is to explore the correlation between serum bilirubin level and mortality in patients with traumatic brain injury (TBI).Patients admitted with traumatic brain injury (TBI) in our hospital between January 2015 and January 2018 were enrolled in this study. Clinical and laboratory data of 361 patients were retrospectively collected to explore the independent risk factors of mortality.The comparison of baseline characteristics showed that non-survivors had lower Glasgow Coma Scale (GCS) (P < .001) and higher level of serum total bilirubin (TBIL) (P < .001) and direct bilirubin (DBIL) (P < .001). We found that only GCS (P < .001), glucose (P < .001), lactate dehydrogenase (LDH) (P = .042) and DBIL (P = .005) were significant risk factors in multivariate logistic regression analysis. GCS and DBIL had comparable AUC value (0.778 vs 0.750, P > .05) on predicting mortality in TBI patients. The AUC value of the combination of GCS and DBIL is higher than the single value of these two factors (P < .05). Moreover, predictive model 1 consisted of GCS, glucose, LDH and DBIL had the highest AUC value of 0.894.DBIL is a significant risk factor of mortality in TBI patients. Assessing the level of DBIL is beneficial for physicians to evaluate severity and predict outcome for TBI patients.

Modelling heme-mediated brain injury associated with cerebral malaria in human brain cortical organoids

Human cerebral malaria (HCM), a severe encephalopathy associated with Plasmodium falciparum infection, has a 20-30% mortality rate and predominantly affects African children. The mechanisms mediating HCM-associated brain injury are difficult to study in human subjects, highlighting the urgent need for non-invasive ex vivo human models. HCM elevates the systemic levels of free heme, which damages the blood-brain barrier and neurons in distinct regions of the brain. We determined the effects of heme on induced pluripotent stem cells (iPSCs) and a three-dimensional cortical organoid system and assessed apoptosis and differentiation. We evaluated biomarkers associated with heme-induced brain injury, including a pro-inflammatory chemokine, CXCL-10, and its receptor, CXCR3, brain-derived neurotrophic factor (BDNF) and a receptor tyrosine-protein kinase, ERBB4, in the organoids. We then tested the neuroprotective effect of neuregulin-1 (NRG-1) against heme treatment in organoids. Neural stem and mature cells differentially expressed CXCL-10, CXCR3, BDNF and ERBB4 in the developing organoids and in response to heme-induced neuronal injury. The organoids underwent apoptosis and structural changes that were attenuated by NRG-1. Thus, cortical organoids can be used to model heme-induced cortical brain injury associated with HCM pathogenesis as well as for testing agents that reduce brain injury and neurological sequelae.

Blood-Related Toxicity after Traumatic Brain Injury: Potential Targets for Neuroprotection

Emergency visits, hospitalizations, and deaths due to traumatic brain injury (TBI) have increased significantly over the past few decades. While the primary early brain trauma is highly deleterious to the brain, the secondary injury post-TBI is postulated to significantly impact mortality. The presence of blood, particularly hemoglobin, and its breakdown products and key binding proteins and receptors modulating their clearance may contribute significantly to toxicity. Heme, hemin, and iron, for example, cause membrane lipid peroxidation, generate reactive oxygen species, and sensitize cells to noxious stimuli resulting in edema, cell death, and increased morbidity and mortality. A wide range of other mechanisms such as the immune system play pivotal roles in mediating secondary injury. Effective scavenging of all of these pro-oxidant and pro-inflammatory metabolites as well as controlling maladaptive immune responses is essential for limiting toxicity and secondary injury. Hemoglobin metabolism is mediated by key molecules such as haptoglobin, heme oxygenase, hemopexin, and ferritin. Genetic variability and dysfunction affecting these pathways (e.g., haptoglobin and heme oxygenase expression) have been implicated in the difference in susceptibility of individual patients to toxicity and may be target pathways for potential therapeutic interventions in TBI. Ongoing collaborative efforts are required to decipher the complexities of blood-related toxicity in TBI with an overarching goal of providing effective treatment options to all patients with TBI.

Time-dependent hemeoxygenase-1, lipocalin-2 and ferritin induction after non-contusion traumatic brain injury

Traumatic brain injury (TBI) often presents with focal contusion and parenchymal bleeds, activating heme oxygenase (HO) to degrade released hemoglobin. Here we show that diffuse, midline fluid percussion injury causes time-dependent induction of HO-1 and iron binding proteins within both hemorrhagic neocortex and non-hemorrhagic hippocampus. Rats subjected to midline fluid percussion injury (FPI) survived 1-15d postinjury and tissue was collected for Western blot and immunohistochemical assays. HO-1 was elevated 1d after FPI, peaked at 3d, and returned to control baseline 7-15d. Iron management proteins lipocalin 2 (LCN2) and ferritin (FTL) exhibited distinct postinjury time courses, where peak LCN2 response preceded, and FTL followed that of HO-1. LCN2 elevation supported not only its role in iron transport, but also mediation of matrix metalloproteinase 9 (MMP9) activity. Upregulation of FTL for intracellular iron sequestration was delayed relative to both HO-1 and LCN2 induction. In the neocortex IBA-1+ microglia around the injury core expressed HO-1, but astrocytes co-localized with HO-1 in perilesional parenchyma. Non-hemorrhagic dentate gyrus showed predominant HO-1 labeling in hilar microglia and in molecular layer astrocytes. At 1d postinjury, LCN2 and HO-1 co-localized in a subpopulation of reactive glia within both brain regions. Notably, FTL was distributed within cells around injured vessels, damaged subcortical white matter, and along vessels of the hippocampal fissure. Together these results confirm that even the moderate, non-contusional insult of diffuse midline FPI can significantly activate postinjury HO-1 heme processing pathways and iron management proteins. Moreover, this activation is time-dependent and occurs in the absence of overt hemorrhage.

Iron accentuated reactive oxygen species release by NADPH oxidase in activated microglia contributes to oxidative stress in vitro

BACKGROUND

Excessive iron contributes to oxidative stress after central nervous system injury. NADPH oxidase (NOX) enzymes are upregulated in microglia after pro-inflammatory activation and contribute to oxidative stress. The relationship between iron, microglia, NOX, and oxidative stress is currently unclear.

METHODS

We evaluated the effects of iron on lipopolysaccharide (LPS)-activated microglia and its secondary effect within neuronal co-cultures. Further, NOX2 and four specific inhibitors were tested to evaluate the relationship with the reactive oxygen species (ROS)-producing enzymes.

RESULTS

An iron dose-dependent increase in ROS production among microglia treated with LPS was identified. Interestingly, despite this increase in ROS, inflammatory polarization alterations were not detected among the microglia after exposure to iron and LPS. Co-culture experimentation between primary neurons and exposed microglia (iron and LPS) significantly reduced neuronal cell number at 24 h, suggesting a profound neurotoxic effect despite the lack of a change in polarization phenotype. NOX2 and NOX4 inhibition significantly reduced ROS production among microglia exposed to iron and LPS and reduced neuronal damage and death in response to microglial co-culture.

CONCLUSIONS

In conclusion, iron significantly increased ROS production and neurotoxicity without exacerbating LP-activated microglia phenotype in vitro, suggesting that iron contributes to microglia-related oxidative stress, and this may be a viable therapeutic target for injury or neurodegeneration. Further, this study highlights both NOX2 and NOX4 as potential therapeutic targets in the treatment of iron-induced microglia-related inflammation and neurotoxicity.

Role of mitochondrial calcium uniporter-mediated Ca2+ and iron accumulation in traumatic brain injury

Previous studies have suggested that the cellular Ca²⁺ and iron homeostasis, which can be regulated by mitochondrial calcium uniporter (MCU), is associated with oxidative stress, apoptosis and many neurological diseases. However, little is known about the role of MCU‐mediated Ca²⁺ and iron accumulation in traumatic brain injury (TBI). Under physiological conditions, MCU can be inhibited by ruthenium red (RR) and activated by spermine (Sper). In the present study, we used RR and Sper to reveal the role of MCU in mouse and neuron TBI models. Our results suggested that the Ca²⁺ and iron concentrations were obviously increased after TBI. In addition, TBI models showed a significant generation of reactive oxygen species (ROS), decrease in adenosine triphosphate (ATP), deformation of mitochondria, up‐regulation of deoxyribonucleic acid (DNA) damage and increase in apoptosis. Blockage of MCU by RR prevented Ca²⁺ and iron accumulation, abated the level of oxidative stress, improved the energy supply, stabilized mitochondria, reduced DNA damage and decreased apoptosis both in vivo and in vitro. Interestingly, Sper did not increase cellular Ca²⁺ and iron concentrations, but suppressed the Ca²⁺ and iron accumulation to benefit the mice in vivo. However, Sper had no significant impact on TBI in vitro. Taken together, our data demonstrated for the first time that blockage of MCU‐mediated Ca²⁺ and iron accumulation was essential for TBI. These findings indicated that MCU could be a novel therapeutic target for treating TBI.

The Involvement of Iron in Traumatic Brain Injury and Neurodegenerative Disease

Traumatic brain injury (TBI) consists of acute and long-term pathophysiological sequelae that ultimately lead to cognitive and motor function deficits, with age being a critical risk factor for poorer prognosis. TBI has been recently linked to the development of neurodegenerative diseases later in life including Alzheimer’s disease, Parkinson’s disease, chronic traumatic encephalopathy, and multiple sclerosis. The accumulation of iron in the brain has been documented in a number of neurodegenerative diseases, and also in normal aging, and can contribute to neurotoxicity through a variety of mechanisms including the production of free radicals leading to oxidative stress, excitotoxicity and by promoting inflammatory reactions. A growing body of evidence similarly supports a deleterious role of iron in the pathogenesis of TBI. Iron deposition in the injured brain can occur via hemorrhage/microhemorrhages (heme-bound iron) or independently as labile iron (non-heme bound), which is considered to be more damaging to the brain. This review focusses on the role of iron in potentiating neurodegeneration in TBI, with insight into the intersection with neurodegenerative conditions. An important implication of this work is the potential for therapeutic approaches that target iron to attenuate the neuropathology/phenotype related to TBI and to also reduce the associated risk of developing neurodegenerative disease.

Oxidized phospholipid signaling in traumatic brain injury

Oxidative stress is a major contributor to secondary injury signaling cascades following traumatic brain injury (TBI). The role of lipid peroxidation in the pathophysiology of a traumatic insult to neural tissue is increasingly recognized. As the methods to quantify lipid peroxidation have gradually improved, so has the understanding of mechanistic details of lipid peroxidation and related signaling events in the injury pathogenesis. While free-radical mediated, non-enzymatic lipid peroxidation has long been studied, recent advances in redox lipidomics have demonstrated the significant contribution of enzymatic lipid peroxidation to TBI pathogenesis. Complex interactions between inflammation, phospholipid peroxidation, and hydrolysis define the engagement of different cell death programs and the severity of injury and outcome. This review focuses on enzymatic phospholipid peroxidation after TBI, including the mechanism of production, signaling roles in secondary injury pathology, and temporal course of production with respect to inflammatory response. In light of the newly identified phospholipid oxidation mechanisms, we also discuss possible therapeutic targets to improve neurocognitive outcome after TBI. Finally, we discuss current limitations in identifying oxidized phospholipids and possible methodologic improvements that can offer a deeper insight into the region-specific distribution and subcellular localization of phospholipid oxidation after TBI.

Unique Properties Associated with the Brain Penetrant Iron Chelator HBED Reveal Remarkable Beneficial Effects after Brain Trauma

Iron is postulated to contribute to secondary injury after brain trauma through various pathways including oxidative stress and inflammation. Therefore, one goal is to limit iron toxicity by either directly limiting iron activity, or limiting the secondary cascade mediated by iron, therefore rescuing the brain from damage after trauma. The N,N'-Di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid monohydrochloride (HBED) is a unique iron chelator that has the ability to cross the intact blood-brain barrier; it has a higher affinity to iron, and it has a longer half-life than most commonly used chelators. A controlled-cortical impact model of traumatic brain injury (TBI) was induced in mice. Mice were subcutaneously injected with HBED immediately after TBI, then at 12 h after, followed by a twice-a-day regimen until an end-point of 3 days. Neurobehavioral tests were performed daily. Cortical injury volume, hemispheric enlargement, and hippocampal swelling were quantified. Perls' iron immunostaining along with markers of gliosis, oxidative stress, and aquaporin (AQP) 4 were also performed. Data revealed that HBED treatment significantly decreases motor deficits and improves recovery after TBI. It also reduces cortical injury volume by 36.6 ± 6.8% (p < 0.001), hippocampal swelling by 23.4 ± 3.8% (p < 0.05), and total hemispheric volume by 13.3 ± 2.7% (p < 0.01). These effects are related to a reduction in microgliosis and oxidiative stress markers in the impacted corpus callosum area by 39.8 ± 7.3%, and by 80.5 ± 0.8% (p < 0.05), respectively. AQP4 staining is also attenuated in the hippocampus of HBED-treated mice. Therefore, our results suggest that HBED should be considered as a therapeutic tool to facilitate the recovery process following brain trauma.

Impact & Blast Traumatic Brain Injury: Implications for Therapy

Traumatic brain injury (TBI) is one of the most frequent causes of combat casualties in Operations Iraqi Freedom (OIF), Enduring Freedom (OEF), and New Dawn (OND). Although less common than combat-related blast exposure, there have been significant numbers of blast injuries in civilian populations in the United States. Current United States Department of Defense (DoD) ICD-9 derived diagnoses of TBI in the DoD Health Care System show that, for 2016, severe and moderate TBIs accounted for just 0.7% and 12.9%, respectively, of the total of 13,634 brain injuries, while mild TBIs (mTBIs) accounted for 86% of the total. Although there is a report that there are differences in the frequency of long-term complications in mTBI between blast and non-blast TBIs, clinical presentation is classified by severity score rather than mechanism because severity scoring is associated with prognosis in clinical practice. Blast TBI (bTBI) is unique in its pathology and mechanism, but there is no treatment specific for bTBIs-these patients are treated similarly to TBIs in general and therapy is tailored on an individual basis. Currently there is no neuroprotective drug recommended by the clinical guidelines based on evidence.

Neurodevelopment at Age 10 Years of Children Born <28 Weeks With Fetal Growth Restriction

OBJECTIVES

We sought to evaluate the relationships between fetal growth restriction (FGR) (both severe and less severe) and assessments of cognitive, academic, and adaptive behavior brain function at age 10 years.

METHODS

At age 10 years, the Extremely Low Gestational Age Newborns Cohort Study assessed the cognitive function, academic achievement, social-communicative function, psychiatric symptoms, and overall quality of life of 889 children born before 28 weeks' gestation. A pediatric epileptologist also interviewed parents as part of a seizure evaluation. The 52 children whose birth weight z scores were <-2 were classified as having severe FGR, and the 113 whose birth weight z scores were between -2 and -1 were considered to have less severe FGR.

RESULTS

The more severe the growth restriction in utero, the lower the level of function on multiple cognitive and academic achievement assessments performed at age 10 years. Growth-restricted children were also more likely than their extremely preterm peers to have social awareness impairments, autistic mannerisms, autism spectrum diagnoses, difficulty with semantics and speech coherence, and diminished social and psychosocial functioning. They also more frequently had phobias, obsessions, and compulsions (according to teacher, but not parent, report).

CONCLUSIONS

Among children born extremely preterm, those with severe FGR appear to be at increased risk of multiple cognitive and behavioral dysfunctions at age 10 years, raising the possibility that whatever adversely affected their intrauterine growth also adversely affected multiple domains of cognitive and neurobehavioral development.

Traumatic hemorrhagic brain injury: impact of location and resorption on cognitive outcome

OBJECTIVE

Hemorrhagic contusions are often the most visible lesions following traumatic brain injury. However, the incidence, location, and natural history of traumatic parenchymal hemorrhage and its impact on neurological outcome have been understudied. The authors sought to examine the location and longitudinal evolution of traumatic parenchymal hemorrhage and its association with cognitive outcome.

METHODS

Sixteen patients with hemorrhagic contusions due to acceleration-deceleration injuries underwent MRI in the acute (mean 6.3 days postinjury) and chronic (mean 192.9 days postinjury) phases. ImageJ was used to generate GRE and FLAIR volumes. To account for the effect of head-size variability across individuals, the authors calculated each patient's total brain tissue volume using SIENAX. GRE and FLAIR volumes were normalized to the total brain tissue volume, and values for absolute and percent lesion volume and total brain volume change were generated. Spearman's rank correlations were computed to determine associations between neuroimaging and 6-month postinjury neuropsychological testing of attention (Symbol Digit Modalities Test [SDMT], oral [O] and written [W] versions), memory (Selective Reminding Test, total learning and delayed recall), and executive function (Trail Making Test Part B [TMT-B]).

RESULTS

The patients' mean age was 31.4 ± 14.0 years and their mean Glasgow Coma Scale score at admission was 7.9 ± 2.8. Lesions were predominantly localized to the frontal (11 lesions) and temporal (9 lesions) lobes. The average percent reductions in GRE and FLAIR volumes were 44.2% ± 46.1% and 80.5% ± 26.3%, respectively. While total brain and frontal lesion volumes did not correlate with brain atrophy, larger temporal lobe GRE and FLAIR volumes were associated with larger volumes of atrophy (GRE: acute, −0.87, p < 0.01, chronic, −0.78, p < 0.01; FLAIR: acute, −0.81, p < 0.01, chronic, −0.88, p < 0.01). Total percent volume change of GRE lesions correlated with TMT-B (0.53, p < 0.05) and SDMT-O (0.62, p < 0.05) scores. Frontal lobe lesion volume did not correlate with neuropsychological outcome. However, robust relationships were seen in the temporal lobe, with larger acute temporal lobe GRE volumes were associated with worse scores on both oral and written versions of the SDMT (SDMT-W, −0.85, p < 0.01; SDMT-O, −0.73, p < 0.05). Larger absolute change in temporal GRE volume was strongly associated with worse SDMT scores (SDMT-W, 0.88, p < 0.01; SDMT-O, 0.75, p < 0.05). The same relationships were also seen between temporal FLAIR lesion volumes and neuropsychological outcome.

CONCLUSIONS

Traumatic parenchymal hemorrhages are largely clustered in the frontal and temporal lobes, and significant residual blood products are present at 6 months postinjury, a potential source of ongoing secondary brain injury. Neuropsychological outcome is closely tied to lesion volume size, particularly in the temporal lobe, where larger GRE and FLAIR volumes are associated with more brain atrophy and worse SDMT scores. Interestingly, larger volumes of hemorrhage resorption were associated with worse SDMT and TMT-B scores, suggesting that the initial tissue damage had a lasting impact on attention and executive function.

Pediatric Rodent Models of Traumatic Brain Injury

Due to a high incidence of traumatic brain injury (TBI) in children and adolescents, age-specific studies are necessary to fully understand the long-term consequences of injuries to the immature brain. Preclinical and translational research can help elucidate the vulnerabilities of the developing brain to insult, and provide model systems to formulate and evaluate potential treatments aimed at minimizing the adverse effects of TBI. Several experimental TBI models have therefore been scaled down from adult rodents for use in juvenile animals. The following chapter discusses these adapted models for pediatric TBI, and the importance of age equivalence across species during model development and interpretation. Many neurodevelopmental processes are ongoing throughout childhood and adolescence, such that neuropathological mechanisms secondary to a brain insult, including oxidative stress, metabolic dysfunction and inflammation, may be influenced by the age at the time of insult. The long-term evaluation of clinically relevant functional outcomes is imperative to better understand the persistence and evolution of behavioral deficits over time after injury to the developing brain. Strategies to modify or protect against the chronic consequences of pediatric TBI, by supporting the trajectory of normal brain development, have the potential to improve quality of life for brain-injured children.

Traumatic Brain Injury by a Closed Head Injury Device Induces Cerebral Blood Flow Changes and Microhemorrhages

OBJECTIVES

Traumatic brain injury is a poly-pathology characterized by changes in the cerebral blood flow, inflammation, diffuse axonal, cellular, and vascular injuries. However, studies related to understanding the temporal changes in the cerebral blood flow following traumatic brain injury extending to sub-acute periods are limited. In addition, knowledge related to microhemorrhages, such as their detection, localization, and temporal progression, is important in the evaluation of traumatic brain injury.

MATERIALS AND METHODS

Cerebral blood flow changes and microhemorrhages in male Sprague Dawley rats at 4 h, 24 h, 3 days, and 7 days were assessed following a closed head injury induced by the Marmarou impact acceleration device (2 m height, 450 g brass weight). Cerebral blood flow was measured by arterial spin labeling. Microhemorrhages were assessed by susceptibility-weighted imaging and Prussian blue histology.

RESULTS

Traumatic brain injury rats showed reduced regional and global cerebral blood flow at 4 h and 7 days post-injury. Injured rats showed hemorrhagic lesions in the cortex, corpus callosum, hippocampus, and brainstem in susceptibility-weighted imaging. Injured rats also showed Prussian blue reaction products in both the white and gray matter regions up to 7 days after the injury. These lesions were observed in various areas of the cortex, corpus callosum, hippocampus, thalamus, and midbrain.

CONCLUSIONS

These results suggest that changes in cerebral blood flow and hemorrhagic lesions can persist for sub-acute periods after the initial traumatic insult in an animal model. In addition, microhemorrhages otherwise not seen by susceptibility-weighted imaging are present in diverse regions of the brain. The combination of altered cerebral blood flow and microhemorrhages can potentially be a source of secondary injury changes following traumatic brain injury and may need to be taken into consideration in the long-term care of these cases.

Levels of F2-isoprostanes, F4-neuroprostanes, and total nitrate/nitrite in plasma and cerebrospinal fluid of patients with traumatic brain injury

Several events occurring during the secondary damage of traumatic brain injury (TBI) can cause oxidative stress. F(2)-isoprostanes (F(2)-IsoPs) and F(4)-neuroprostanes (F(4)-NPs) are specific lipid peroxidation markers generated from arachidonic acid and docosahexaenoic acid, respectively. In this study, we evaluated oxidative stress in patients with moderate and severe TBI. Since sedatives are routinely used to treat TBI patients and propofol has been considered an antioxidant, TBI patients were randomly treated with propofol or midazolam for 72 h postoperation. We postoperatively collected cerebrospinal fluid (CSF) and plasma from 15 TBI patients for 6-10 d and a single specimen of CSF or plasma from 11 controls. Compared with the controls, the TBI patients exhibited elevated levels of F(2)-IsoPs and F(4)-NPs in CSF throughout the postsurgery period regardless of the sedative used. Compared with the group of patients who received midazolam, those who received propofol exhibited markedly augmented levels of plasma F(2)-IsoPs, which were associated with higher F(4)-NPs levels and lower total nitrate/nitrite levels in CSF early in the postsurgery period. Furthermore, the higher CSF F(2)-IsoPs levels correlated with 6-month and 12-month worse outcomes, which were graded according to the Glasgow Outcome Scale. The results demonstrate enhanced oxidative damage in the brain of TBI patients and the association of higher CSF levels of F(2)-IsoPs with a poor outcome. Moreover, propofol treatment might promote lipid peroxidation in the circulation, despite possibly suppressing nitric oxide or peroxynitrite levels in CSF, because of the increased loading of the lipid components from the propofol infusion.

Cerebrospinal Fluid Markers of Macrophage and Lymphocyte Activation After Traumatic Brain Injury in Children

OBJECTIVES

The magnitude and role of the cellular immune response following pediatric traumatic brain injury remains unknown. We tested the hypothesis that macrophage/microglia and T-cell activation occurs following pediatric traumatic brain injury by measuring cerebrospinal fluid levels of soluble cluster of differentiation 163 and ferritin and soluble interleukin-2 receptor α, respectively, and determined whether these biomarkers were associated with relevant clinical variables and outcome.

DESIGN

Retrospective analysis of samples from an established, single-center cerebrospinal fluid bank.

SETTING

PICU in a tertiary children's hospital.

PATIENTS

Sixty-six pediatric patients after severe traumatic brain injury (Glasgow Coma Scale score < 8) who were 1 month to 16 years old and 17 control patients who were 1 month to 14 years old.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cerebrospinal fluid levels of soluble cluster of differentiation 163, ferritin, and soluble interleukin-2 receptor α were determined by enzyme-linked immunosorbent assay at two time points (t1 = 17 ± 10 hr; t2 = 72 ± 15 hr) for each traumatic brain injury patient. Cerebrospinal fluid levels of soluble cluster of differentiation 163, ferritin, and soluble interleukin-2 receptor α after traumatic brain injury were compared with controls and analyzed for associations with age, patient sex, initial Glasgow Coma Scale score, diagnosis of abusive head trauma, the presence of hemorrhage on CT scan, and Glasgow Outcome Scale score. Cerebrospinal fluid level of soluble cluster of differentiation 163 was increased in traumatic brain injury patients at t2 versus t1 and controls (median, 95.4 ng/mL [interquartile range, 21.8-134.0 ng/mL] vs 31.0 ng/mL [5.7-77.7 ng/mL] and 27.8 ng/mL [19.1-43.1 ng/mL], respectively; p < 0.05). Cerebrospinal fluid level of ferritin was increased in traumatic brain injury patients at t2 and t1 versus controls (8.3 ng/mL [<7.5-19.8 ng/mL] and 8.9 ng/mL [<7.5-26.7 ng/mL] vs <7.5 ng/mL below lower limit of detection, respectively; p < 0.05). Cerebrospinal fluid levels of soluble interleukin-2 receptor α in traumatic brain injury patients at t2 and t1 were not different versus controls. Multivariate regression revealed associations between high ferritin and age 4 years or younger, lower Glasgow Coma Scale score, abusive head trauma, and unfavorable Glasgow Outcome Scale score.

CONCLUSIONS

Children with traumatic brain injury demonstrate evidence for macrophage activation after traumatic brain injury, and in terms of cerebrospinal fluid ferritin, this appears more prominent with young age, initial injury severity, abusive head trauma, and unfavorable outcome. Further study is needed to determine whether biomarkers of macrophage activation may be used to discriminate between aberrant and adaptive immune responses and whether inflammation represents a therapeutic target after traumatic brain injury.

Neutrophil elastase mediates acute pathogenesis and is a determinant of long-term behavioral recovery after traumatic injury to the immature brain

While neutrophil elastase (NE), released by activated neutrophils, is a key mediator of secondary pathogenesis in adult models of brain ischemia and spinal cord injury, no studies to date have examined this protease in the context of the injured immature brain, where there is notable vulnerability resulting from inadequate antioxidant reserves and prolonged exposure to infiltrating neutrophils. We thus reasoned that NE may be a key determinant of secondary pathogenesis, and as such, adversely influence long-term neurological recovery. To address this hypothesis, wild-type (WT) and NE knockout (KO) mice were subjected to a controlled cortical impact at post-natal day 21, approximating a toddler-aged child. To determine if NE is required for neutrophil infiltration into the injured brain, and whether this protease contributes to vasogenic edema, we quantified neutrophil numbers and measured water content in the brains of each of these genotypes. While leukocyte trafficking was indistinguishable between genotypes, vasogenic edema was markedly attenuated in the NE KO. To determine if early pathogenesis is dependent on NE, indices of cell death (TUNEL and activated caspase-3) were quantified across genotypes. NE KO mice showed a reduction in these markers of cell death in the injured hippocampus, which corresponded to greater preservation of neuronal integrity as well as reduced expression of heme oxygenase-1, a marker of oxidative stress. WT mice, treated with a competitive inhibitor of NE at 2, 6 and 12h post-injury, likewise showed a reduction in cell death and oxidative stress compared to vehicle-treated controls. We next examined the long-term behavioral and structural consequences of NE deficiency. NE KO mice showed an improvement in long-term spatial memory retention and amelioration of injury-induced hyperactivity. However, volumetric and stereological analyses found comparable tissue loss in the injured cortex and hippocampus independent of genotype. Further, WT mice treated acutely with the NE inhibitor showed no long-term behavioral or structural improvements. Together, these findings validate the central role of NE in both acute pathogenesis and chronic functional recovery, and support future exploration of the therapeutic window, taking into account the prolonged period of neutrophil trafficking into the injured immature brain.

Sociosexual and communication deficits after traumatic injury to the developing murine brain

Despite the life-long implications of social and communication dysfunction after pediatric traumatic brain injury, there is a poor understanding of these deficits in terms of their developmental trajectory and underlying mechanisms. In a well-characterized murine model of pediatric brain injury, we recently demonstrated that pronounced deficits in social interactions emerge across maturation to adulthood after injury at postnatal day (p) 21, approximating a toddler-aged child. Extending these findings, we here hypothesized that these social deficits are dependent upon brain maturation at the time of injury, and coincide with abnormal sociosexual behaviors and communication. Age-dependent vulnerability of the developing brain to social deficits was addressed by comparing behavioral and neuroanatomical outcomes in mice injured at either a pediatric age (p21) or during adolescence (p35). Sociosexual behaviors including social investigation and mounting were evaluated in a resident-intruder paradigm at adulthood. These outcomes were complemented by assays of urine scent marking and ultrasonic vocalizations as indices of social communication. We provide evidence of sociosexual deficits after brain injury at p21, which manifest as reduced mounting behavior and scent marking towards an unfamiliar female at adulthood. In contrast, with the exception of the loss of social recognition in a three-chamber social approach task, mice that received TBI at adolescence were remarkably resilient to social deficits at adulthood. Increased emission of ultrasonic vocalizations (USVs) as well as preferential emission of high frequency USVs after injury was dependent upon both the stimulus and prior social experience. Contrary to the hypothesis that changes in white matter volume may underlie social dysfunction, injury at both p21 and p35 resulted in a similar degree of atrophy of the corpus callosum by adulthood. However, loss of hippocampal tissue was greater after p21 compared to p35 injury, suggesting that a longer period of lesion progression or differences in the kinetics of secondary pathogenesis after p21 injury may contribute to observed behavioral differences. Together, these findings indicate vulnerability of the developing brain to social dysfunction, and suggest that a younger age-at-insult results in poorer social and sociosexual outcomes.

Increased expression of ferritin in cerebral cortex after human traumatic brain injury

Despite numerous researches and improvements in the past few years, the precise mechanisms underlying secondary brain injury after trauma remain obscure. Iron is essential for almost all types of cells, including nerve cells. However, excess of iron has been proved to contribute to the brain injury following trauma in animal models. As a key iron-handling protein in the brain, ferritin might be involved in iron-induced pathophysiological process of various brain disorders. Therefore, the current study was aimed to investigate the expression of ferritin in the human contused brain. Nineteen contused brain samples were obtained from 19 patients undergoing surgery for brain contusions 3 h-17 d after trauma, and three normal temporal pole samples from 3 patients with petroclival meningioma were collected as controls. Expression of ferritin-H-chain was measured by quantitative real-time polymerase chain reaction (PCR), western blot and immunohistochemistry, respectively. Perl's reaction was taken for iron staining. The results showed that human traumatic brain injury (TBI) could up-regulate ferritin-H-chain in pericontusional cortex. A marked increase of ferritin was detected in the early group (≤12 h), and remained elevated for a long time till after 48 h post-injury. The location of ferritin-H-chain was found mainly at the neuron-like cells and seldom at glia-like cells. Perl's reaction showed that most of the iron-positive cells were glia-like cells. These findings suggested that iron and ferritin might be involved in the secondary brain injury and could be therapeutic targets for patients with TBI.

Evaluating the beneficial and detrimental effects of bile pigments in early and later life

The heme degradation pathway has been conserved throughout phylogeny and allows for the removal of a pro-oxidant and the generation of unique molecules including bile pigments with important cellular functions. The impact of bile pigments on health and disease are reviewed, as is the special circumstance of neonatal hyperbilirubinemia. In addition, the importance of promoter polymorphisms in the UDP-glucuronosyl transferase gene (UGTA1), which is key to the elimination of excess bilirubin and to the prevention of its toxicity, are discussed. Overall, the duality of bile pigments as either cytoprotective or toxic molecules is highlighted.

Selective brain cooling in rats ameliorates intracerebral hemorrhage and edema caused by penetrating brain injury: possible involvement of heme oxygenase-1 expression

Brain edema formation associated with trauma-induced intracerebral hemorrhage (ICH) is a clinical complication with high mortality. Studies have shown that heme oxygenase-1 (HO-1) plays an important role in ICH-induced brain edema. In order to understand the role of HO-1 in the protective effect of selective brain cooling (SBC), we investigated the time course of HO-1 changes following penetrating ballistic-like brain injury (PBBI) in rats. Samples were collected from injured and control animals at 6, 24, 48, and 72 h, and 7 days post-injury to evaluate HO-1 expression, heme concentration, brain water content, and immunohistochemistry (IHC). Following a 10% frontal PBBI, HO-1 mRNA and protein was increased at all time points studied, reaching maximum expression levels at 24-48 h post-injury. An increase in the heme concentration and the development of brain edema coincided with the upregulation of HO-1 mRNA and protein during the 7-day post-injury period. SBC significantly decreased PBBI-induced heme concentration, attenuated HO-1 upregulation, and concomitantly reduced brain water content. These results suggest that the neuroprotective effects of SBC may be partially mediated by reducing the heme accumulation, which reduced injury-mediated upregulation of HO-1, and in turn ameliorated edema formation. Collectively, these results suggest a potential value of HO-1 as a diagnostic and/or therapeutic biomarker in hemorrhagic brain injury.

Lesional accumulation of CD163+ macrophages/microglia in rat traumatic brain injury

A robust neuroinflammation, contributing to the development of secondary injury, is a common histopathological feature of traumatic brain injury (TBI). Characterization of leukocytic subpopulations contributing to the early infiltration of the damaged tissue might aid in further understanding of lesion development. Reactive macrophages/microglia can exert protective or damaging effects in TBI. CD163 is considered a marker of M2 (alternatively activated) macrophages. Therefore we investigated the accumulation of CD163(+) macrophages/microglia in the brain of TBI rats. TBI was induced in rats using an open skull weight-drop contusion model and the accumulation of CD163(+) cells was analyzed by immunohistochemistry. In normal rat brains, CD163 was expressed by meningeal, choroid plexus and perivascular macrophages. Significant parenchymal CD163(+) cell accumulation was observed two days post TBI and continuously increased in the investigated survival time. The accumulated CD163(+) cells were mainly distributed to the lesional areas and exhibited macrophage phenotypes with amoeboid morphologic characteristics but not activated microglial phenotypes with hypertrophic morphology and thick processes. Double-labeling experiments showed that most CD163(+) cells co-expressed heme oxygenase-1 (HO-1). In addition, in vitro incubating of macrophage RAW264.7 cells or primary peritoneal macrophages with hemoglobin- haptoglobin (Hb-Hp) complex suppressed LPS-induced inflammatory macrophages phenotype and induced CD163 and HO-1 upregulation, indicating that CD163(+) macrophages/microglia in TBI might have anti-inflammatory effects. And further study is necessary to identify functions of these cells in TBI.

Intracranial hemorrhage: mechanisms of secondary brain injury

ICH is a disease with high rates of mortality and morbidity, with a substantial public health impact. Spontaneous ICH (sICH) has been extensively studied, and a large body of data has been accumulated on its pathophysiology. However, the literature on traumatic ICH (tICH) is limited, and further investigations of this important topic are needed. This review will highlight some of the cellular pathways in ICH with an emphasis on the mechanisms of secondary injury due to heme toxicity and to events in the coagulation process that are common to both sICH and tICH.

Towards a unifying, systems biology understanding of large-scale cellular death and destruction caused by poorly liganded iron: Parkinson's, Huntington's, Alzheimer's, prions, bactericides, chemical toxicology and others as examples

Exposure to a variety of toxins and/or infectious agents leads to disease, degeneration and death, often characterised by circumstances in which cells or tissues do not merely die and cease to function but may be more or less entirely obliterated. It is then legitimate to ask the question as to whether, despite the many kinds of agent involved, there may be at least some unifying mechanisms of such cell death and destruction. I summarise the evidence that in a great many cases, one underlying mechanism, providing major stresses of this type, entails continuing and autocatalytic production (based on positive feedback mechanisms) of hydroxyl radicals via Fenton chemistry involving poorly liganded iron, leading to cell death via apoptosis (probably including via pathways induced by changes in the NF-κB system). While every pathway is in some sense connected to every other one, I highlight the literature evidence suggesting that the degenerative effects of many diseases and toxicological insults converge on iron dysregulation. This highlights specifically the role of iron metabolism, and the detailed speciation of iron, in chemical and other toxicology, and has significant implications for the use of iron chelating substances (probably in partnership with appropriate anti-oxidants) as nutritional or therapeutic agents in inhibiting both the progression of these mainly degenerative diseases and the sequelae of both chronic and acute toxin exposure. The complexity of biochemical networks, especially those involving autocatalytic behaviour and positive feedbacks, means that multiple interventions (e.g. of iron chelators plus antioxidants) are likely to prove most effective. A variety of systems biology approaches, that I summarise, can predict both the mechanisms involved in these cell death pathways and the optimal sites of action for nutritional or pharmacological interventions.

Interactions of multiple gas-transducing systems: hallmarks and uncertainties of CO, NO, and H2S gas biology

The diverse physiological actions of the "biologic gases," O2, CO, NO, and H2S, have attracted much interest. Initially viewed as toxic substances, CO, NO, and H2S play important roles as signaling molecules. The multiplicity of gas actions and gas targets and the difficulty in measuring local gas concentrations obscures detailed mechanisms whereby gases exert their actions, and many questions remain unanswered. It is now readily apparent, however, that heme-based proteins play central roles in gas-generation/reception mechanisms and provide a point where multiple gases can interact. In this review, we consider a number of key issues related to "gas biology," including the effective tissue concentrations of these gases and the importance and significance of the physical proximity of gas-producing and gas-receptor/sensors. We also take an integrated approach to the interaction of gases by considering the physiological significance of CO, NO, and H2S on mitochondrial cytochrome c oxidase, a key target and central mediator of mitochondrial respiration. Additionally, we consider the effects of biologic gases on mitochondrial biogenesis and "suspended animation." By evaluating gas-mediated control functions from both in vitro and in vivo perspectives, we hope to elaborate on the complex multiple interactions of O2, NO, CO, and H2S.

Sulforaphane protects immature hippocampal neurons against death caused by exposure to hemin or to oxygen and glucose deprivation

Oxidative stress is a mediator of cell death following cerebral ischemia/reperfusion and heme toxicity, which can be an important pathogenic factor in acute brain injury. Induced expression of phase II detoxification enzymes through activation of the antioxidant response element (ARE)/Nrf2 pathway has emerged as a promising approach for neuroprotection. Little is known, however, about the neuroprotective potential of this strategy against injury in immature brain cells. In this study, we tested the hypothesis that sulforaphane (SFP), a naturally occurring isothiocyanate that is also a known activator of the ARE/Nrf2 antioxidant pathway, can protect immature neurons from oxidative stress-induced death. The hypothesis was tested with primary mouse hippocampal neurons exposed to either O(2) and glucose deprivation (OGD) or hemin. Treatment of immature neurons with SFP immediately after the OGD during reoxygenation was effective in protecting immature neurons from delayed cell death. Exposure of immature hippocampal neurons to hemin induced significant cell death, and both pre- and cotreatment with SFP were remarkably effective in blocking cytotoxicity. RT-PCR analysis indicated that several Nrf2-dependent cytoprotective genes, including NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase 1 (HO1), and glutamate-cysteine ligase modifier subunit (GCLM), which is involved in glutathione biosynthesis, were up-regulated following SFP treatment both in control neurons and following exposure to OGD and hemin. These results indicate that SFP activates the ARE/Nrf2 pathway of antioxidant defense and protects immature neurons from death caused by stress paradigms relevant to those associated with ischemic and traumatic injury to the immature brain.

Heme oxygenase-2 modulates early pathogenesis after traumatic injury to the immature brain

We determined if heme oxygenase-2 (HO-2), an enzyme that degrades the pro-oxidant heme, confers neuroprotection in the developing brain after traumatic brain injury (TBI). Male HO-2 wild-type (WT) and homozygous knockout (KO) mice at postnatal day 21 were subjected to TBI and euthanized 1, 7, and 14 days later. Relative cerebral blood flow, measured by laser Doppler, cortical and hippocampal pathogenesis, and motor recovery were evaluated at all time points. Cerebral blood flow was found to be similar between experimental groups. Blood flow significantly decreased immediately after injury, returned to baseline by 1 day, and was significantly elevated by 7 days, post-injury. Nonheme iron preferentially accumulated in the ipsilateral cortex, hippocampus, and external capsule in both WT and KO brain-injured genotypes. There were, however, a significantly greater number of TUNEL-positive cells in the hippocampal dentate gyrus and a significantly greater cortical lesion volume in KOs relative to WTs within the first week post-injury. By 14 days post-injury, however, cortical lesion volume and cell density in the hippocampal CA3 region and dorsal thalamus were similar between the two groups. Assays of fine motor function (grip strength) over the first 2 weeks post-injury revealed a general pattern of decreased strength in the contralateral forelimbs of KOs as compared to WTs. Together, these findings demonstrate that deficiency in HO-2 alters both the kinetics of secondary damage and fine motor recovery after TBI.

Shorter GT repeat polymorphism in the heme oxygenase-1 gene promoter has protective effect on ischemic stroke in dyslipidemia patients

Background

The microsatellite polymorphism of heme oxygenase (HO)-1 gene promoter has been shown to be associated with the susceptibility to ischemic event, including coronary artery disease (CAD), myocardial infarction, and peripheral vascular disease. We aimed to examine whether the length of (GT)_n repeats in HO-1 gene promoter is associated with ischemic stroke in people with CAD risk factors, especially low level of HDL.

Methods

A total of 183 consecutive firstever ischemic stroke inpatients and 164 non-stroke patients were screened for the length of (GT)_n repeats in HO-1 promoter. The long (L) and short (S) genotype are defined as the averaged repeat number >26 and ≦26, respectively.

Results

Stroke patients tended to have more proportions of hypertension, diabetics and genotype L, than those of genotype S. Patients with genotype L of HO-1 gene promoter have higher stroke risk in comparison with genotype S especially in dyslipidemia individuals. The significant differences on stroke risk in multivariate odds ratios were found especially in people with low HDL-C levels.

Conclusions

Subjects carrying longer (GT)_n repeats in HO-1 gene promoter may have greater susceptibility to develop cerebral ischemic only in the presence of low HDL-C, suggesting the protective effects in HO-1 genotype S in the process of ischemic stroke, particularly in subjects with poor HDL-C status.

Shorter GT repeat polymorphism in the heme oxygenase-1 gene promoter has protective effect on ischemic stroke in dyslipidemia patients

BACKGROUND

The microsatellite polymorphism of heme oxygenase (HO)-1 gene promoter has been shown to be associated with the susceptibility to ischemic event, including coronary artery disease (CAD), myocardial infarction, and peripheral vascular disease. We aimed to examine whether the length of (GT)(n) repeats in HO-1 gene promoter is associated with ischemic stroke in people with CAD risk factors, especially low level of HDL.

METHODS

A total of 183 consecutive firstever ischemic stroke inpatients and 164 non-stroke patients were screened for the length of (GT)(n) repeats in HO-1 promoter. The long (L) and short (S) genotype are defined as the averaged repeat number >26 and <==26, respectively.

RESULTS

Stroke patients tended to have more proportions of hypertension, diabetics and genotype L, than those of genotype S. Patients with genotype L of HO-1 gene promoter have higher stroke risk in comparison with genotype S especially in dyslipidemia individuals. The significant differences on stroke risk in multivariate odds ratios were found especially in people with low HDL-C levels.

CONCLUSIONS

Subjects carrying longer (GT)(n) repeats in HO-1 gene promoter may have greater susceptibility to develop cerebral ischemic only in the presence of low HDL-C, suggesting the protective effects in HO-1 genotype S in the process of ischemic stroke, particularly in subjects with poor HDL-C status.

Evidence for oxidative stress in the developing cerebellum of the rat after chronic mild carbon monoxide exposure (0.0025% in air)

BACKGROUND

The present study was designed to test the hypothesis that chronic very mild prenatal carbon monoxide (CO) exposure (25 parts per million) subverts the normal development of the rat cerebellar cortex. Studies at this chronic low CO exposure over the earliest periods of mammalian development have not been performed to date. Pregnant rats were exposed chronically to CO from gestational day E5 to E20. In the postnatal period, rat pups were grouped as follows: Group A: prenatal exposure to CO only; group B: prenatal exposure to CO then exposed to CO from postnatal day 5 (P5) to P20; group C: postnatal exposure only, from P5 to P20, and group D, controls (air without CO). At P20, immunocytochemical analyses of oxidative stress markers, and structural and functional proteins were assessed in the cerebellar cortex of the four groups. Quantitative real time PCR assays were performed for inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) nitric oxide synthases.

RESULTS

Superoxide dismutase-1 (SOD1), SOD2, and hemeoxygenase-1 (HO-1) immunoreactivity increased in cells of the cerebellar cortex of CO-exposed pups. INOS and nitrotyrosine immunoreactivity also increased in blood vessels and Purkinje cells (PCs) of pups from group-A, B and C. By contrast, nNOS immunoreactivity decreased in PCs from group-B. Endothelial NOS immunoreactivity showed no changes in any CO-exposed group. The mRNA levels for iNOS were significantly up-regulated in the cerebellum of rats from group B; however, mRNA levels for nNOS and eNOS remained relatively unchanged in groups A, B and C. Ferritin-H immunoreactivity increased in group-B. Immunocytochemistry for neurofilaments (structural protein), synapsin-1 (functional protein), and glutamic acid decarboxylase (the enzyme responsible for the synthesis of the inhibitory neurotransmitter GABA), were decreased in groups A and B. Immunoreactivity for two calcium binding proteins, parvalbumin and calbindin, remained unchanged. The immunoreactivity of the astrocytic marker GFAP increased after prenatal exposure.

CONCLUSION

We conclude that exogenously supplied CO during the prenatal period promotes oxidative stress as indicated by the up-regulation of SOD-1, SOD-2, HO-1, Ferritin-H, and iNOS with increased nitrotyrosine in the rat cerebella suggesting that deleterious and protective mechanisms were activated. These changes correlate with reductions of proteins important to cerebellar function: pre-synaptic terminals proteins (synapsin-1), proteins for the maintenance of neuronal size, shape and axonal quality (neurofilaments) and protein involved in GABAergic neurotransmission (GAD). Increased GFAP immunoreactivity after prenatal CO-exposure suggests a glial mediated response to the constant presence of CO. There were differential responses to prenatal vs. postnatal CO exposure: Prenatal exposure seems to be more damaging; a feature exemplified by the persistence of markers indicating oxidative stress in pups at P20, following prenatal only CO-exposure. The continuation of this cellular environment up to day 20 after CO exposure suggests the condition is chronic. Postnatal exposure without prenatal exposure shows the least impact, whereas prenatal followed by postnatal exposure exhibits the most pronounced outcome among the groups.

Molecular mechanisms of traumatic brain injury in children. A review

Despite advances in molecular biology and genetics, the precise pathophysiology of traumatic brain injury (TBI) in children is unknown. In this paper the authors review what is currently known about intra- and extracellular responses to pediatric TBI and relate these factors to future investigations. Although hyperemia and vascular congestion have long been thought to be the hallmarks of pediatric TBI, on a cellular level, calcium influx as well as modulation of local neurotransmitters appears to play a major role in its onset. Recent genetic and proteomic research has identified specific neurotrophic factors as well as apoptotic and antiapoptotic genes that appear to control the progression of inflammation and neuronal damage. The search for a therapeutic target will ultimately require a thorough understanding of these factors and their interplay on a proteomic, genomic, and neuromic level.

Oxidative stress and the deleterious consequences to the rat cochlea after prenatal chronic mild exposure to carbon monoxide in air

Pregnant rats (starting on E5) were exposed chronically to carbon monoxide (CO) from gestational days 5-20. In the postnatal period, rat pups were grouped as follows: group A: prenatal exposure to CO only; group B: prenatal exposure to CO then exposed to CO from postnatal day (P) 5 to P20; group C, control (air without CO). Groups A and B showed similar deleterious effects after CO exposure. At P3, rat pup cochlea from group A showed a normal organization of the organ of Corti. There was no morphological deterioration, or loss of inner or outer hair cells. At P20, animals from group A and B showed vacuolization on the afferent terminals at the basal portion of the cochlea. We found synapsin-1 immunoreactivity (IR) to be decreased in efferent nerve terminals in CO-exposed pups at P3. From P12 to P20, synapsin-1-IR is low in efferent terminals. At P20, type I spiral ganglia neurons and afferent nerve fibers showed decreased neurofilament-IR in CO-exposed groups when compared with controls. Heme oxygenase-1 and superoxide dismutase-1-IR were elevated in the stria vascularis and blood vessels from CO-exposed rat pups at P12 and P20 in group B; in contrast group A showed a comparable expression to controls. Inducible nitric oxide synthase (iNOS) and nitrotyrosine-IR were increased in blood vessels of the cochlea in CO-exposed groups, from P3 to P20. iNOS up-regulation and the presence of nitrotyrosine in blood vessels of the cochlea indicated that CO exposure activates the production of nitric oxide via increased iNOS activity. Prenatal chronic CO exposure promotes oxidative stress in the cochlea blood vessels that in turn is reflected in damage to spiral ganglia neurons and inner hair cells, suggesting for the first time that prenatal exposure to CO at concentrations expected in poorly ventilated environments impairs the development of the inner ear.

Influence of the heme-oxygenase pathway on cerebrocortical blood flow

Heme-oxygenase (HO)-derived carbon monoxide (CO) is generated in the cardiovascular and in the central nervous systems. Endogenous CO exerts direct vascular effects and has also been shown to inhibit nitric oxide synthase (NOS). In the current study, the heme-oxygenase blockade [zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG), 45 micromol/kg intraperitoneally] decreased cerebral CO production and increased cerebrocortical blood flow (CBF) in anesthetized rats. This latter effect was abrogated by the NOS blockade (50 mg/kg L-NAME intravenously). Furthermore, inhibition of CO production had no effect on stepwise hypoxia/hypercapnia-stimulated increases in CBF. Our results indicate that endogenous CO reduces the resting CBF via inhibition of NOS but fails to influence the CBF response to hypoxia and hypercapnia in adult rats.

Astrocyte-specific heme oxygenase-1 hyperexpression attenuates heme-mediated oxidative injury

In prior studies, we have observed that HO activity protects astrocytes from heme-mediated injury, but paradoxically increases neuronal injury. In this study, we tested the hypothesis that an adenovirus encoding the human HO-1 gene driven by an enhanced glial fibrillary acidic protein promoter (Ad-GFAP-HO-1) would increase HO-1 expression selectively in astrocytes, and provide cytoprotection. Treatment with 100 MOI Ad-GFAP-HO-1 for 24 h resulted in HO-1 expression that was 6.4-fold higher in cultured primary astrocytes than in neurons. Astrocyte HO activity was increased by approximately fourfold over baseline, which was sufficient to reduce cell death after 24-h hemin exposure by 60%, as assessed by both MTT and LDH release assays. A similar reduction in cell protein oxidation, quantified by carbonyl assay, was also observed. These results suggest that HO-1 transgene expression regulated by an enhanced GFAP promoter selectively increases HO-1 expression in astrocytes, and is cytoprotective. Further investigation of this strategy in vivo is warranted.

Is being plastic fantastic? Mechanisms of altered plasticity after developmental traumatic brain injury

Traumatic brain injury (TBI) is predominantly a clinical problem of young persons, resulting in chronic cognitive and behavioral deficits. Specifically, the physiological response to a diffuse biomechanical injury in a maturing brain can clearly alter normal neuroplasticity. To properly evaluate and investigate developmental TBI requires an understanding of normal principles of cerebral maturation, as well as a consideration of experience-dependent changes. Changes in neuroplasticity may occur through many age-specific processes, and our understanding of these responses at a basic neuroscience level is only beginning. In this article, we will particularly discuss mechanisms of TBI-induced altered developmental plasticity such as altered neurotransmission, distinct molecular responses, cell death, perturbations in neuronal connectivity, experience-dependent 'good plasticity' enhancements and chronic 'bad plasticity' sequelae. From this summary, we can conclude that 'young is not always better' and that the developing brain manifests several crucial vulnerabilities to TBI.

Oxidative stress in immature brain after traumatic brain injury

High oxygen demand along with the abundance of readily oxidizable substrates yielding productive oxidative metabolism are required for the normal function of the brain. This necessitates the existence of the complex and multicomponent antioxidant system in the brain for protection against oxidative damage. However, during development, individual components of the antioxidant system are not equally expressed and not always sufficient to fulfill their tasks in a coordinated way. As a result, the developing brain may be more vulnerable to oxidative insults than the adult brain. Traumatic brain injury is one of the damaging acute impacts that challenge the brain antioxidant reserves by exposing them to a number of decompartmentalized prooxidant molecules. This review focuses on the sources and assessment of oxidative stress and the link between oxidative stress and cell death pathways in the immature brain after experimental and clinical traumatic brain injury.

Heme oxygenase 1 in cerebrospinal fluid from infants and children after severe traumatic brain injury

Heme oxygenase 1 (HO-1) is an enzyme important in the catabolism of heme that is induced under conditions of oxidative stress. HO-1 degradation of heme yields biliverdin, bilirubin, carbon monoxide and iron. HO-1 is thought to serve a protective antioxidant function, and upregulation of HO-1 has been demonstrated in experimental models of neurodegeneration, subarachnoid hemorrhage, cerebral ischemia and traumatic brain injury (TBI). We measured HO-1 concentration in cerebral spinal fluid samples from 48 infants and children following TBI and 7 control patients by ELISA. Increased HO-1 was seen in TBI versus control patients--mean 2.75+/-0.63, peak 4.17+/-0.96 ng/ml versus control (<0.078 ng/ml, not detectable) (p<0.001). Increased HO-1 concentration was associated with increased injury severity and unfavorable neurological outcome (both p<0.05). Increased HO-1 concentration was independently associated with younger age; however, statistical analysis could not rule out the possibility that the effect of age was related to inflicted TBI from child abuse. HO-1 increases after TBI and appears to be more prominent in infants compared with older children after injury.

Oxidative stress and neurodegeneration: where are we now?

The brain and nervous system are prone to oxidative stress, and are inadequately equipped with antioxidant defense systems to prevent 'ongoing' oxidative damage, let alone the extra oxidative damage imposed by the neurodegenerative diseases. Indeed, increased oxidative damage, mitochondrial dysfunction, accumulation of oxidized aggregated proteins, inflammation, and defects in protein clearance constitute complex intertwined pathologies that conspire to kill neurons. After a long lag period, therapeutic and other interventions based on a knowledge of redox biology are on the horizon for at least some of the neurodegenerative diseases.