Secondary Neuronal Injury Research Articles

Intracerebral Hemorrhage: A Brief Evidence-Based Review of Common Etiologies, Mechanisms of Secondary Injury, and Medical and Surgical Management

AbstractIntracerebral hemorrhage (ICH) accounts for only 10 to 15% of all strokes but remains a significant cause of morbidity and mortality. Despite lengthy stays in critical care units, only one-half of those experiencing an ICH survive after 30 days, and those who do are often left with considerable disability. Treatment has traditionally focused on minimizing the hemorrhage expansion and reducing clot volume through both medical and surgical means. Management of ICH is a complex and multidisciplinary process. This review will discuss a few common etiologies, explore the pathophysiology of secondary neuronal injury after ICH, review the basics of ICH imaging with computed tomography and magnetic resonance imaging, and highlight latest practices in medical and surgical management. Secondary injury mechanisms such as perihematomal edema and disordered cerebral autoregulation are discussed as potential targets for new treatment modalities. Emergent treatment in the “golden hour” after ictus provides a template of measures to adopt from initial contact with emergency medical services, to the emergency department, and thereafter, triage to the intensive care unit. Medical management including blood pressure control, hemostasis, and coagulopathy reversal are discussed and evidence from trials such as INTERACT 2, ATACH 2, and ANNEXA-4 are given a clinical context. Surgical management including intracranial pressure monitoring, surgical evacuation with open craniotomy, and minimally invasive approaches such as stereotactic-guided aspiration and thrombolysis, ultrasound-induced thrombolysis, image-guided stereotactic endoscopic aspiration, and stereotactic ICH underwater blood aspiration are enumerated. The outcomes and relevance of STICH, MISTIE, and CLEAR trials to present surgical care are elaborated. The review summarizes the current guidelines for the treatment of ICH and the latest literature in the field they are based upon. It aims to provide a concise article beneficial to the emergency physicians and neurointensivists/neuroanesthesiologists.

Adaptive immune cell activation in acute pediatric traumatic brain injury

Abstract Traumatic brain injury (TBI) is mediated by mechanical injury to the brain resulting in tissue shearing, and characterized by neuronal injury and inflammation. We hypothesize that TBI activates brain-targeting immune responses which can induce secondary neuronal injury. Blood and cerebral spinal fluid (external ventricular drain, EVD) were collected from pediatric TBI patients (pTBI, 1–18 yrs.) at days 1, 3 and 5 following TBI and EVD placement. The blood from sick controls (0–18 yrs, no CNS injury) were collected at day 1 post injury. pTBI patients exhibited a higher quantity of leukocytes (CD45+) relative to controls (p=0.01) on day 1 post-TBI, indicating an immediate and robust immune modulation due to CNS injury, that decreased at days 3 and 5, relative to day 1. Major subsets of adaptive immune cells (CD3, CD4, CD8, and CD19) did not exhibit altered cellularity relative to controls but activated adaptive T cells (CD4+CD161+and CD8+CD161+) were substantially higher at day 1 versus controls. Neuronal autoreactivity was evaluated by labeling peripheral blood mononuclear cells with carboxyfluorescein succinimidyl ester (CFSE) and culturing with neuronal and control antigens. Response to antigen was determined by dilution of CFSE (proliferation) and expression of CD25 (activation). Autoreactivity analysis of pTBI patients revealed a decrease in the CD4 T-cell responses to CNS antigens relative to sick control patients. Interestingly, the CD8 T-cell analysis revealed CNS-specific autoimmune responses absent in pTBI patients which were present in sick controls. Based on these initial observations, we hypothesize that the adaptive immune system is activated upon TBI and can potentially target CNS resident cells in young patients.

Neuroprotective effects of a catalytic antioxidant in a rat nerve agent model

Persistent inhibition of acetylcholinesterase resulting from exposure to nerve agents such as soman, is associated with prolonged seizure activity known as status epilepticus (SE). Without medical countermeasures, exposure to soman and resultant SE leads to high morbidity and mortality. Currently available therapeutics are effective in limiting mortality, however effects on morbidity are highly time-dependent and rely on the ability to suppress SE. We have previously demonstrated significant protection from secondary neuronal injury in surrogate nerve agent models by targeting oxidative stress. However, whether oxidative stress represents a relevant therapeutic target in genuine nerve agent toxicity is unknown. Here, we demonstrate that soman exposure results in robust region- and time-dependent oxidative stress. Targeting this oxidative stress in a post-exposure paradigm using a small molecular weight, broad spectrum catalytic antioxidant, was sufficient to attenuate brain and plasma oxidative stress, neuroinflammation and neurodegeneration. Thus, targeting of oxidative stress in a post-exposure paradigm can mitigate secondary neuronal injury following soman exposure.

Hepcidin Attenuates the Secondary Neuronal Injury after Intracerebral Hemorrhage in Rats

Iron plays a key role in secondary neuronal injury after intracerebral hemorrhage (ICH), and hepcidin is able to reduce brain iron in iron-overloaded rats by down-regulating iron transport proteins. These led us to hypothesize that hepcidin might reduce iron-mediated neurotoxicity by inhibiting iron accumulation in ICH brain. Here, we tested our hypothesis in 510 rats and demonstrated for the first time that hepcidin could significantly suppress the ICH-induced increase in iron and ferritin in brain tissues and cerebrospinal fluid by inhibiting expression of iron transport proteins, increase neuronal survival by attenuating ICH-induced apoptosis, neurodegeneration and brain edema, as well as effectively improve ICH-induced behavioral and cognitive deficit in rats. We concluded that hepcidin could effectively attenuate iron-mediated secondary neuronal injury after ICH in rats. This naturally existing protein which is biodegradable, nontoxic, and non-immunogenic can potentially be developed into a therapeutic drug for the treatment of ICH patients. Funding: The studies were supported by the National Natural Science Foundation of China (NSFC31330035-ZMQ, NSFC31571195-ZMQ), the Competitive Earmarked Grants of The Hong Kong Research Grants Council (GRF14111815-KY, GRF 14167817-KY, GRF14107616-KY), Hong Kong Health & Medical Research Fund (HMRF: 03141436-KY), Hong Kong Innovation and Technology Fund (ITS/163/16-KY), and the National 973 Programs (2014CB541604-ZMQ). Conflict of interest: The authors declare that they have no conflict of interest. Ethical Approval Statement: The Health Department of Hong Kong and Shanghai Government and the Animal Research Ethics Committee of The Chinese University of Hong Kong and Fudan University approved the experimental procedures of this study and the care and handling of the animals were in accord with National Institutes of Health guidelines.

Multimodal Approach to Decision to Treat Critically Ill Patients With Periodic or Rhythmic Patterns Using an Ictal-Interictal Continuum Spectral Severity Score.

We propose a comprehensive review of the subject of epileptiform and potentially harmful EEG patterns that lie on the interictal continuum (IIC) to help with therapeutic decision-making and target future research. This approach to "electro-physiological SE" encompasses five dimensions of the IIC: it characterizes a periodic or rhythmic pattern, not only regarding its ictal morphology and potential harm with secondary neuronal injury, but also addresses the "metabolic footprint," clinical repercussion, and epileptogenic potential. Recent studies have attempted to determine and qualify the ictal nature and the epileptogenic potential (i.e., risk of subsequent acute seizures) of particular IIC patterns and their intrinsic EEG characteristics. Others have correlated non-convulsive seizures with cognitive outcomes beyond mortality; non-convulsive seizures and sporadic, periodic, or rhythmic discharges to encephalopathy severity; and the spectrum of periodic or rhythmic patterns to measurable secondary brain injury. Equivocal periodic or rhythmic patterns on the IIC are frequently encountered in critical care neurology where clinicians often incorporate advanced neuroimaging, metabolic neuromonitoring, and anti-seizure drug short trials, in an effort to gauge these patterns. We propose portraying the IIC with a multiaxial graph to disambiguate each of these risks. Quantification along each axis may help calibrate therapeutic urgency. An adaptable scoring system assesses which quasi-ictal EEG patterns in this spectrum might reach the tipping point toward anti-seizure drug escalation, in neurocritically ill patients.

Use of Prophylactic Phenobarbitone for Prevention of Morbidity and Mortality in Term Neonates Following Perinatal Asphyxia

Background: Seizures are common following perinatal asphyxia and may exacerbate secondary neuronal injury. Barbiturate therapy has been used for infants with perinatal asphyxia in order to prevent seizures. However, barbiturate therapy may adversely affect neurodevelopment leading to concern regarding its aggressive use in neonates. The objective of the study was to determine the effect of administering prophylactic barbiturate therapy on seizure control and mortality in term neonates following perinatal asphyxia.Methodology: This was a randomized controlled trial (RCT) of prophylactic phenobarbitone therapy in term asphyxiated neonates without clinical evidence of seizures when compared to controls conducted in the neonatal ward of Sher-e-Bangla Medical College Barisal from 1st January 2016 to 30th June 2016.Results: Among the 100 neonates equally divided into two groups, there was no significant difference found in clinical outcome e.g. seizures (8% vs. 12%, p > 0.05), neurological abnormality at discharge (10% vs. 14%, p >0.05), mortality (12% vs. 14%, p >0.05) and major neurological disability (14% vs. 18%, p >0.05).Conclusion: In this study, prophylactic phenobarbitone therapy did not significantly prevent seizures in asphyxiated neonates.Bangladesh J Child Health 2017; VOL 41 (3) :165-169

Tissue and cellular rigidity and mechanosensitive signaling activation in Alexander disease

Glial cells have increasingly been implicated as active participants in the pathogenesis of neurological diseases, but critical pathways and mechanisms controlling glial function and secondary non-cell autonomous neuronal injury remain incompletely defined. Here we use models of Alexander disease, a severe brain disorder caused by gain-of-function mutations in GFAP, to demonstrate that misregulation of GFAP leads to activation of a mechanosensitive signaling cascade characterized by activation of the Hippo pathway and consequent increased expression of A-type lamin. Importantly, we use genetics to verify a functional role for dysregulated mechanotransduction signaling in promoting behavioral abnormalities and non-cell autonomous neurodegeneration. Further, we take cell biological and biophysical approaches to suggest that brain tissue stiffness is increased in Alexander disease. Our findings implicate altered mechanotransduction signaling as a key pathological cascade driving neuronal dysfunction and neurodegeneration in Alexander disease, and possibly also in other brain disorders characterized by gliosis.

Dexmedetomidine attenuates traumatic brain injury: action pathway and mechanisms.

Traumatic brain injury induces potent inflammatory responses that can exacerbate secondary blood-brain barrier (BBB) disruption, neuronal injury, and neurological dysfunction. Dexmedetomidine is a novel α2-adrenergic receptor agonist that exert protective effects in various central nervous system diseases. The present study was designed to investigate the neuroprotective action of dexmedetomidine in a mouse traumatic brain injury model, and to explore the possible mechanisms. Adult male C57BL/6J mice were subjected to controlled cortical impact. After injury, animals received 3 days of consecutive dexmedetomidine therapy (25 µg/kg per day). The modified neurological severity score was used to assess neurological deficits. The rotarod test was used to evaluate accurate motor coordination and balance. Immunofluorescence was used to determine expression of ionized calcium binding adapter molecule-1, myeloperoxidase, and zonula occluden-1 at the injury site. An enzyme linked immunosorbent assay was used to measure the concentration of interleukin-1β (IL-1β), tumor necrosis factor α, and IL-6. The dry-wet weight method was used to measure brain water content. The Evans blue dye extravasation assay was used to measure BBB disruption. Western blot assay was used to measure protein expression of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), caspase-1 p20, IL-1β, nuclear factor kappa B (NF-κB) p65, occluding, and zonula occluden-1. Flow cytometry was used to measure cellular apoptosis. Results showed that dexmedetomidine treatment attenuated early neurological dysfunction and brain edema. Further, dexmedetomidine attenuated post-traumatic inflammation, up-regulated tight junction protein expression, and reduced secondary BBB damage and apoptosis. These protective effects were accompanied by down-regulation of the NF-κB and NLRP3 inflammasome pathways. These findings suggest that dexmedetomidine exhibits neuroprotective effects against acute (3 days) post-traumatic inflammatory responses, potentially via suppression of NF-κB and NLRP3 inflammasome activation.

Neuroprotective Effects of AEOL10150 in a Rat Organophosphate Model.

Prolonged seizure activity or status epilepticus (SE) is one of the most critical manifestations of organophosphate exposure. Previous studies in our laboratory have demonstrated that oxidative stress is a critical mediator of SE-induced neuronal injury. The goal of this study was to determine if diisopropylflurorphoshate (DFP) exposure in rats resulted in oxidative stress and whether scavenging reactive oxygen species attenuated DFP-induced neurotoxicity. DFP treatment increased indices of oxidative stress in a time- and region- dependent manner. Neuronal loss measured by Fluoro-Jade B staining was significantly increased in the hippocampus, piriform cortex and amygdala following DFP. Similarly, levels of the proinflammatory cytokines, particularly TNF-α, IL-6, and KC/GRO were significantly increased in the piriform cortex and in the hippocampus following DFP treatment. The catalytic antioxidant AEOL10150, when treatment was initiated 5 min after DFP-induced SE, significantly attenuated indices of oxidative stress, neuroinflammation and neuronal damage. This study suggests that catalytic antioxidant treatment may be useful as a novel therapy to attenuate secondary neuronal injury following organophosphate exposure.

Hepcidin Protects Neuron from Hemin-Mediated Injury by Reducing Iron.

Hemin plays a key role in mediating secondary neuronal injury after intracerebral hemorrhage (ICH) and the cell toxicity of hemin is thought to be due to iron that is liberated when hemin is degraded. In a recent study, we demonstrated the iron regulatory hormone hepcidin reduces brain iron in iron-overloaded rats. Therefore, we hypothesized that hepcidin might be able to reduce iron and then protect neurons from hemin or iron-mediated neurotoxicity in hemin-treated neuronal cells. Here, we tested the hypothesis and demonstrated that ad-hepcidin and hepcidin peptide both have the ability to suppress the hemin-induced increase in LDH release and apoptotic cell numbers, to reduce cell iron and ferritin contents, and to inhibit expression of transferrin receptor 1, divalent metal transporter 1, and ferroportin 1 in hemin-treated neurons. We conclude that hepcidin protects neuron from hemin-mediated injury by reducing iron via inhibition of expression of iron transport proteins.

Neuroprotective pentapeptide CN-105 is associated with reduced sterile inflammation and improved functional outcomes in a traumatic brain injury murine model

At present, there are no proven pharmacological treatments demonstrated to improve long term functional outcomes following traumatic brain injury(TBI). In the setting of non-penetrating TBI, sterile brain inflammatory responses are associated with the development of cerebral edema, intracranial hypertension, and secondary neuronal injury. There is increasing evidence that endogenous apolipoprotein E(apoE) modifies the neuroinflammatory response through its role in downregulating glial activation, however, the intact apoE holoprotein does not cross the blood-brain barrier due to its size. To address this limitation, we developed a small 5 amino acid apoE mimetic peptide(CN-105) that mimics the polar face of the apoE helical domain involved in receptor interactions. The goal of this study was to investigate the therapeutic potential of CN-105 in a murine model of closed head injury. Treatment with CN-105 was associated with a durable improvement in functional outcomes as assessed by Rotarod and Morris Water Maze and a reduction in positive Fluoro-Jade B stained injured neurons and microglial activation. Administration of CN-105 was also associated with reduction in mRNA expression of a subset of inflammatory and immune-related genes.

Involvement of Toll Like Receptor 2 Signaling in Secondary Injury during Experimental Diffuse Axonal Injury in Rats.

Treatment of diffuse axonal injury (DAI) remains challenging in clinical practice due to the unclear pathophysiological mechanism. Uncontrolled, excessive inflammation is one of the most recognized mechanisms that contribute to the secondary injury after DAI. Toll like receptor 2 (TLR2) is highlighted for the initiation of a vicious self-propagating inflammatory circle. However, the role and detailed mechanism of TLR2 in secondary injury is yet mostly unknown. In this study, we demonstrated the expression of TLR2 levels in cortex, corpus callosum, and internal capsule and the localization of TLR2 in neurons and glial cells in rat DAI models. Intracerebral knockdown of TLR2 significantly downregulated TLR2 expression, attenuated cortical apoptosis, lessened glial response, and reduced the secondary axonal and neuronal injury in the cortex by inhibiting phosphorylation of mitogen-activated protein kinases (MAPK) including Erk, JNK, and p38, translocation of NF-κB p65 from the cytoplasm to the nucleus, and decreasing levels of proinflammatory cytokines including interleukin-6, interleukin-1β, and tumor necrosis factor-α. On the contrary, administration of TLR2 agonist to DAI rats achieved an opposite effect. Collectively, we demonstrated that TLR2 was involved in mediating secondary injury after DAI by inducing inflammation via the MAPK and NF-κB pathways.

Prophylactic barbiturate use for the prevention of morbidity and mortality following perinatal asphyxia.

Seizures are common following perinatal asphyxia and may exacerbate secondary neuronal injury. Barbiturate therapy has been used for infants with perinatal asphyxia in order to prevent seizures. However, barbiturate therapy may adversely affect neurodevelopment leading to concern regarding aggressive use in neonates. To determine the effect of administering prophylactic barbiturate therapy on death or neurodevelopmental disability in term and late preterm infants following perinatal asphyxia. We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL, 2015, Issue 11), MEDLINE via PubMed (1966 to 30 November 2015), EMBASE (1980 to 30 November 2015), and CINAHL (1982 to 30 November 2015). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomized controlled trials (RCT) and quasi-RCTs. We included all RCTs or quasi-RCTs of prophylactic barbiturate therapy in term and late preterm infants without clinical or electroencephalographic evidence of seizures compared to controls following perinatal asphyxia. Three review authors independently selected, assessed the quality of, and extracted data from the included studies. We assessed methodologic quality and validity of studies without consideration of the results. The review authors independently extracted data and performed meta-analyses using risk ratios (RR) and risk differences (RD) for dichotomous data and mean difference for continuous data with 95% confidence intervals (CI). For significant results, we calculated the number needed to treat for an additional beneficial outcome (NNTB) or for an additional harmful outcome (NNTH). In this updated review, we identified nine RCTs of any barbiturate therapy in term and late preterm infants aged less than three days old with perinatal asphyxia without evidence of seizures. Eight of these studies compared prophylactic barbiturate therapy to conventional treatment (enrolling 439 infants) and one study compared barbiturate therapy to treatment with phenytoin (enrolling 17 infants). Prophylactic barbiturate therapy versus conventional treatment: one small trial reported a decreased risk of death or severe neurodevelopmental disability for barbiturate therapy (phenobarbital) versus conventional treatment (RR 0.33, 95% CI 0.14 to 0.78; RD -0.55, 95% CI -0.84 to -0.25; NNTB 2, 95% CI 1 to 4; 1 study, 31 infants) (very low quality evidence).Eight trials comparing prophylactic barbiturate therapy with conventional treatment following perinatal asphyxia demonstrated no significant impact on the risk of death (typical RR 0.88, 95% CI 0.55 to 1.42; typical RD -0.02, 95% CI -0.08 to 0.05; 8 trials, 429 infants) (low quality evidence) and the one small trial noted above reported a significant decrease in the risk of severe neurodevelopmental disability (RR 0.24, 95% CI 0.06 to 0.92; RD -0.43, 95% CI -0.73 to -0.13; NNTB 2, 95% CI 1 to 8; 1 study, 31 infants) (very low quality evidence).A meta-analysis of the six trials reporting on seizures in the neonatal period demonstrated a statistically significant reduction in seizures in the prophylactic barbiturate group versus conventional treatment (typical RR 0.62, 95% CI 0.48 to 0.81; typical RD -0.18, 95% CI -0.27 to -0.09; NNTB 5, 95% CI 4 to 11; 6 studies, 319 infants) (low quality evidence). There were similar results in subgroup analyses based on type of barbiturate and Sarnat score. Prophylactic barbiturate therapy versus other prophylactic anticonvulsant therapy: one study reported on prophylactic barbiturate versus prophylactic phenytoin. There was no significant difference in seizure activity in the neonatal period between the two study groups (RR 0.89, 95% CI 0.07 to 12.00; 1 trial, 17 infants). We found only low or very low quality evidence addressing the use of prophylactic barbiturates in infants with perinatal asphyxia. Although the administration of prophylactic barbiturate therapy to infants following perinatal asphyxia did reduce the risk of seizures, there was no reduction seen in mortality and there were few data addressing long-term outcomes. The administration of prophylactic barbiturate therapy for late preterm and term infants in the immediate period following perinatal asphyxia cannot be recommended for routine clinical practice. If used at all, barbiturates should be reserved for the treatment of seizures. The results of the current review support the use of prophylactic barbiturate therapy as a promising area of research. Future studies should be of sufficient size and duration to detect clinically important reductions in mortality and severe neurodevelopmental disability and should be conducted in the context of the current standard of care, including the use of therapeutic hypothermia.

Advances in minimally invasive treatment of hemorrhagic and ischemic stroke.

Advances in minimally invasive treatment of hemorrhagic and ischemic stroke.

Abstract T P409: Experimental Chronic Cerebral Hypoperfusion Results in Decreased Pericyte Coverage and Increased Blood Brain Barrier Permeability in the Corpus Callosum

Murine chronic cerebral hypoperfusion (CCH) results in white matter (WM) injury and behavioral deficits. Underlying mechanisms remain unclear. Pericytes influence blood-brain barrier (BBB) integrity and cerebral blood flow. Under hypoxic conditions, perictyes detach from perivascular locations increasing blood vessel permeability and secondary neuronal injury. This study aims to characterize the time course of BBB dysfunction and pericyte coverage following murine experimental CCH. White matter injury and behavioral deficits have been reported consistently on post-operative day 30 in this model. C57BL/6J mice underwent either CCH (n=12) or sham operation (n=9). BBB permeability in the corpus callosum (CC) was characterized on post-procedure days 1, 3, 7, and 30 using Evans blue (EB) extravasation and IgG staining. Pericyte coverage (CD 13/CD31 ratio) in the paramedian region of the corpus callosum was calculated on post-procedure days 1, 3, 7, and 30. The CCH cohort demonstrated increased EB extravasation (integrate density) on postoperative days 1,3,7 and 30 when compared to the sham cohort (CCH: 583.58 ±98.28, 1529.32 ±448.87, 366.02 ±34.51, 5.85 ±1.80; SHAM: 44.51, 230.22, 24.03, 2.55 on postoperative days 1, 3, 7, and 30 respectively.) Further EB extravasation was significantly greater (p<0.05 ) at day 3 (peak level) than at days 7 and 30 in CCH mice. Positive IgG staining was seen at post-procedure days 3, 7, and 30 in the CCH group, but not in the sham operated mice. The CCH mice demonstrated a nadir in pericyte coverage on post-operative day 3 (30.88 ±10.27%). These values were significantly lower (p<0.05) than those on postoperative days 7 (89.36 ±5.11%), and 30 (74.97 ±2.39%). The post-operative day 3 pericyte coverage ratios were also significantly decreased compared to those in the sham mice (72.09 ±3.89%; p<0.01). Decreased pericyte coverage and increased BBB permeability are most pronounced on postoperative day 3 following murine experimental CCH. This precedes any notable WM injury or behavioral deficits (post-op. day 30). Morphologic pericyte changes are concordant with BBB breakdown. Neurotoxic macromolecule extravasation may contribute to the pathogenesis of WM lesions and resultant behavioral deficits in this model system.

Neuroinflammation and neuroimmune dysregulation after acute hypoxic-ischemic injury of developing brain.

Hypoxic-ischemic (HI) injury to developing brain results from birth asphyxia in neonates and from cardiac arrest in infants and children. It is associated with varying degrees of neurologic sequelae, depending upon the severity and length of HI. Global HI triggers a series of cellular and biochemical pathways that lead to neuronal injury. One of the key cellular pathways of neuronal injury is inflammation. The inflammatory cascade comprises activation and migration of microglia – the so-called “brain macrophages,” infiltration of peripheral macrophages into the brain, and release of cytotoxic and proinflammatory cytokines. In this article, we review the inflammatory and immune mechanisms of secondary neuronal injury after global HI injury to developing brain. Specifically, we highlight the current literature on microglial activation in relation to neuronal injury, proinflammatory and anti-inflammatory/restorative pathways, the role of peripheral immune cells, and the potential use of immunomodulators as neuroprotective compounds.

Knockdown of STIM1 improves neuronal survival after traumatic neuronal injury through regulating mGluR1-dependent Ca(2+) signaling in mouse cortical neurons.

Activation of glutamate receptors and followed increase of intracellular calcium concentration is a key pathological mechanism involved in secondary neuronal injury after traumatic brain injury (TBI). Stromal interaction molecule (STIM) proteins are considered to be important players in regulating neuronal Ca(2+) homeostasis under normal aging and pathological conditions. Here, we investigated the role of STIM1 in regulating metabotropic glutamate receptor 1 (mGluR1)-related Ca(2+) signaling and neuronal survival by using an in vitro traumatic neuronal injury (TNI) model. The expression of STIM1 was significantly increased at both mRNA and protein levels after TNI. Down-regulation of STIM1 by specific small interfere RNA significantly preserved neuronal viability, decreased lactate dehydrogenase release, and inhibited apoptotic cell death after traumatic injury. Moreover, knockdown of STIM1 significantly alleviated the mGluR1-related increase of cytoplasmic Ca(2+) levels after TNI. By analyzing Ca(2+) imaging in Ca(2+)-free conditions, we demonstrated that the mGluR1-dependent inositol trisphosphate receptor and/or ryanodine receptor-mediated Ca(2+) release from the endoplasmic reticulum after TNI is strongly attenuated in the absence of STIM1. Together, our results demonstrate that in the mammalian nervous system, STIM1 is a key regulator of mGluR1-dependent Ca(2+) signaling and knockdown of STIM1 might be an effective intervention target in TBI.

Attenuation of cerebral vasospasm and secondary injury by testosterone following experimental subarachnoid hemorrhage in rabbit.

The vasodilatator effects of testosterone have been widely studied and demonstrated. Based on previous studies of these vasodilatatory activities, we hypothesized that testosterone might have potential effects on subarachnoid hemorrhage-induced cerebral vasospasm. Thirty-two adult male New Zealand white rabbits were randomly divided into four groups of eight rabbits in each group: group 1 (control); group 2 (subarachnoid hemorrhage); group 3 (subarachnoid hemorrhage + vehicle); and group 4 (subarachnoid hemorrhage + testosterone). Testosterone (15 mg/kg, intraperitoneally) was administered 5 min after the intracisternal blood injection and continued for 72 h once per day in the same dose for group 4. Animals were killed 72 h after subarachnoid hemorrhage. Basilar artery cross-sectional areas, arterial wall thicknesses, and hippocampal degeneration scores were evaluated in all groups. Intraperitoneal administration of testosterone was found to attenuate cerebral vasospasm and provide neuroprotection after subarachnoid hemorrhage in rabbits. Testosterone treatment was determined to be effective at increasing the luminal area and reducing the wall thickness of the basilar artery. Our findings show that testosterone has some preventive effects on SAH-induced vasospasm and secondary neuronal injury in rabbits. We propose that the vasodilatatory activity of testosterone is due to its effects on inhibiting calcium channels, activating potassium channels, augmenting nitric oxide synthesis, and inhibiting oxidant stress and inflammation.

Perioperative measures to improve outcome after subarachnoid hemorrhage-revisiting the concept of secondary brain injury.

Progress in the management of aneurysmal subarachnoid hemorrhage (SAH) is reflected most clearly in a continuously decreasing case fatality rate over the last decades. The purpose of the present review is to identify the relevant factors responsible for this progress and to outline future possibilities of improvement. Although data on intracerebral hemorrhage and ischemic stroke are less homogeneous, the respective data suggest that reduction of case fatalities could also be achieved with these types of stroke. Therefore, advances of general neurocritical care may be the common denominator responsible for the decreasing case fatality rates. Additionally, a change in practice with regard to treatment of elderly patients that is more active may also be a factor. Regarding SAH, the majority of unfavorable outcomes is still related to early or delayed cerebral injury. Therefore, efforts to pharmacologically prevent secondary neuronal damage are likely to play a certain role in achieving improvement in overall outcome. However, the data from previous randomized clinical trials conducted during the last three decades does not strongly support this. A clear benefit has only been proven for oral nimodipine, whereas other calcium antagonists and the rho-kinase inhibitors were not conclusively shown to have a significant effect on functional outcome, and all other tested substances disappointed in clinical trials. Regarding ischemic stroke and traumatic brain injury, intensive clinical research has also been conducted during the last 30 years to improve outcome and to minimize secondary neuronal injury. For ischemic stroke, treatment focusing on reversal of the primary pathomechanism, such as thrombolysis, proved effective, but none of the pharmacological neuroprotective concepts resulted in any benefit. To date, decompressive hemicraniectomy has been the only effective effort focused at reducing secondary damage that resulted in a clear reduction of mortality. In the case of traumatic brain injury, none of the pharmacological or other efforts to limit secondary damage met our hopes. In summary, although limited, pharmacotherapy to limit delayed neuronal injury is more effective for SAH than for ischemic stroke and traumatic brain injury. The disappointing results of most trials addressing secondary damage force one to question the general concept of mechanisms of secondary damage that do not also have a positive side in the natural course of the disease. For example, in the case of SAH, the data from the Cooperative Study from the 1960s showed that vasospasm to some degree protects against rerupture of unsecured aneurysms. Thus, one could argue from an evolutionary standpoint that the purpose of vasospasm was not exclusively a detrimental or suicide pathomechanism, but an attempt to protect against life-threating aneurysm rerupture. Because of the above-discussed arguments, SAH may indeed differ from ischemic stroke and traumatic brain injury with regard to the usefulness of blocking secondary mechanisms pharmacologically. Further efforts to limit vasospasm should therefore be made, and the most promising drugs, calcium antagonists, deserve further development. Because, with various drugs, systemic side effects counteracted the local beneficial effect, future efforts should focus on topical administration of drugs instead of systemic administration. Furthermore, efforts for a better understanding of the variations of the calcium channels and the interplay between the different types of calcium channels should be made.

Perihemorrhagic ischemia occurs in a volume-dependent manner as assessed by multimodal cerebral monitoring in a porcine model of intracerebral hemorrhage.

Changes in the perihemorrhagic zone (PHZ) of intracerebral hemorrhage (ICH) are variable. Different mechanisms contribute to secondary neuronal injury after ICH. This multimodal monitoring study investigated early changes in the PHZ of ICH. Twenty-four swine were anesthetized, ventilated, and underwent monitoring of vital parameters. Next to an intracranial pressure-probe (ICP), microdialysis (MD), thermodiffusion cerebral blood flow (td-CBF), and oxygen probes (PbrO2) were placed into the gray white matter junction for 12h of monitoring. ICH was induced using the autologous blood injection model. Pre-defined volumes were 0ml (sham), 1.5ml ipsilateral (1.5ml), 3.0ml ipsilateral (3.0ml), and 3.0ml contralateral (3.0ml contra). ICP equally increased in all groups after ICH. In the 3.0ml group tissue oxygenation decreased to ischemic values of 9±7mmHg early after 6h of monitoring. This decrease was associated with a significant perfusion reduction from 36±8ml/100g/min to 20±10ml/100g/min. MD correlated with a threefold lactate/pyruvate ratio increase. Measurements in all other groups were unchanged. Multimodal monitoring demonstrates volume-dependent changes of tissue oxygenation, blood flow, and ischemic MD markers in the PHZ independent of increased ICP suggesting early moderate ischemia. No evidence was found for the existence of a perihemorrhagic ischemia in the small hematoma groups.