Acute Brain Diseases Research Articles

Prognostication of outcome after cardiac arrest and targeted temperature management

The vast majority of cardiac arrest (CA) survivors remain comatose at hospital arrival. Around one-half of these patients suffer from severe hypoxic encephalopathy leading to death or unresponsive wakefulness. Early outcome prognostication may reduce futile intensive care and suffering for next of kin. Several early prognostic markers have shown high positive predictive value for poor outcome in patients treated at normothermia, but results may be altered by targeted temperature management (TTM). Most prominently, absent motor response to painful stimuli 3 days after CA and a serum concentration of neuron-specific enolase (NSE) above 33 ng/ml do not predict poor outcome reliably in these patients [1,2]. Sedation during TTM is a relevant confounder for motor response and corneal reflexes [3]. Bilaterally absent pupillary light reaction 3 days after CA is a reliable predictor of poor outcome (sensitivity 20%) [1]. Eye diseases and medication are potential confounders. A threshold for poor outcome prediction by NSE has not been established after TTM. Above a level of 80 to 100 ng/ml 72 hours after CA good outcome has rarely been reported. The NSE levels may vary with different test kits, and NSE producing tumors, acute brain diseases and severe hematological diseases/hemolysis are confounders. Bilateral absence of cortical median nerve SSEP remains a reliable predictor, but single cases with recovery were reported [4] and inter-rater reliability is not perfect. Preserved spinal SSEP and low cortical noise levels are important prerequisites. The sensitivity of absent SSEP for poor outcome prediction is around 40% [1]. EEG can be a valuable predictive tool when interpreted by experienced neurophysiologists and indicates (subclinical) status epilepticus [5]. The influence of medication on EEG needs to be considered. Recently, a revised EEG classification has been proposed [6]. A reduced contrast between gray and white matter in brain computed tomography is associated with poor outcome. It can be quantified as gray–white-matter ratio and values below 1.1 predict poor outcome with high specificity [7]. Additional studies are needed to establish this threshold more firmly. MRI emerges as a prognostic parameter because of high spatial resolution and high sensitivity for cytotoxic brain edema with DWI/ADC imaging [8]. However, access is limited and quantification of early changes needs to be established in larger cohorts. To date, most authors argue for a multiparameter prognostication approach including repeated neurological examination, SSEP, NSE, EEG and imaging (CT or MRI) combined with a waiting period for potential recovery of several days after cardiac arrest.

Robust Low-Dose CT Perfusion Deconvolution via Tensor Total-Variation Regularization.

Acute brain diseases such as acute strokes and transit ischemic attacks are the leading causes of mortality and morbidity worldwide, responsible for 9% of total death every year. "Time is brain" is a widely accepted concept in acute cerebrovascular disease treatment. Efficient and accurate computational framework for hemodynamic parameters estimation can save critical time for thrombolytic therapy. Meanwhile the high level of accumulated radiation dosage due to continuous image acquisition in CT perfusion (CTP) raised concerns on patient safety and public health. However, low-radiation leads to increased noise and artifacts which require more sophisticated and time-consuming algorithms for robust estimation. In this paper, we focus on developing a robust and efficient framework to accurately estimate the perfusion parameters at low radiation dosage. Specifically, we present a tensor total-variation (TTV) technique which fuses the spatial correlation of the vascular structure and the temporal continuation of the blood signal flow. An efficient algorithm is proposed to find the solution with fast convergence and reduced computational complexity. Extensive evaluations are carried out in terms of sensitivity to noise levels, estimation accuracy, contrast preservation, and performed on digital perfusion phantom estimation, as well as in vivo clinical subjects. Our framework reduces the necessary radiation dose to only 8% of the original level and outperforms the state-of-art algorithms with peak signal-to-noise ratio improved by 32%. It reduces the oscillation in the residue functions, corrects over-estimation of cerebral blood flow (CBF) and under-estimation of mean transit time (MTT), and maintains the distinction between the deficit and normal regions.

Dynamin-Related Protein 1 Inhibitors Protect against Ischemic Toxicity through Attenuating Mitochondrial Ca2+ Uptake from Endoplasmic Reticulum Store in PC12 Cells

Intracellular calcium homeostasis disorder and mitochondrial dysfunction are involved in many acute and chronic brain diseases, including ischemic brain injury. An imbalance in mitochondrial fission and fusion is one of the most important structural abnormalities found in a large number of mitochondrial dysfunction related diseases. Here, we investigated the effects of mitochondrial division inhibitor A (mdivi A) and mdivi B, two small molecule inhibitors of mitochondrial fission protein dunamin-related protein 1 (Drp-1), in neuronal injury induced by oxygen-glucose deprivation (OGD) in PC12 cells. We found that mdivi A and mdivi B inhibited OGD-induced neuronal injury through attenuating apoptotic cell death. These two inhibitors also preserved mitochondrial function, as evidenced by reduced reactive oxygen species (ROS) generation and cytochrome c release, as well as prevented loss of mitochondrial membrane potential (MMP). Moreover, mdivi A and mdivi B significantly suppressed mitochondrial Ca2+ uptake, but had no effect on cytoplasmic Ca2+ after OGD injury. The results of calcium imaging and immunofluorescence staining showed that Drp-1 inhibitors attenuated endoplasmic reticulum (ER) Ca2+ release and prevented ER morphological changes induced by OGD. These results demonstrate that Drp-1 inhibitors protect against ischemic neuronal injury through inhibiting mitochondrial Ca2+ uptake from the ER store and attenuating mitochondrial dysfunction.

Downregualtion of dynamin-related protein 1 attenuates glutamate-induced excitotoxicity via regulating mitochondrial function in a calcium dependent manner in HT22 cells

Glutamate-mediated excitotoxicity is involved in many acute and chronic brain diseases. Dynamin related protein 1 (Drp-1), one of the GTPase family of proteins that regulate mitochondrial fission and fusion balance, is associated with apoptotic cell death in cancer and neurodegenerative diseases. Here we investigated the effect of downregulating Drp-1 on glutamate excitotoxicity-induced neuronal injury in HT22 cells. We found that downregulation of Drp-1 with specific small interfering RNA (siRNA) increased cell viability and inhibited lactate dehydrogenase (LDH) release after glutamate treatment. Downregulation of Drp-1 also inhibited an increase in the Bax/Bcl-2 ratio and cleavage of caspase-9 and caspase-3. Drp-1 siRNA transfection preserved the mitochondrial membrane potential (MMP), reduced cytochrome c release, enhanced ATP production, and partly prevented mitochondrial swelling. In addition, Drp-1 knockdown attenuated glutamate-induced increases of cytoplasmic and mitochondrial Ca2+, and preserved the mitochondrial Ca2+ buffering capacity after excitotoxicity. Taken together, these results suggest that downregulation of Drp-1 protects HT22 cells against glutamate-induced excitatory damage, and this neuroprotection may be dependent at least in part on the preservation of mitochondrial function through regulating intracellular calcium homeostasis.

SiRNA Treatment: “A Sword-in-the-Stone” for Acute Brain Injuries

Ever since the discovery of small interfering ribonucleic acid (siRNA) a little over a decade ago, it has been highly sought after for its potential as a therapeutic agent for many diseases. In this review, we discuss the promising possibility of siRNA to be used as a drug to treat acute brain injuries such as stroke and traumatic brain injury. First, we will give a brief and basic overview of the principle of RNA interference as an effective mechanism to decrease specific protein expression. Then, we will review recent in vivo studies describing siRNA research experiments/treatment options for acute brain diseases. Lastly, we will discuss the future of siRNA as a clinical therapeutic strategy against brain diseases and injuries, while addressing the current obstacles to effective brain delivery.

Proteinase 3 induces oxidative stress-mediated neuronal death in rat primary cortical neuron

The recruitment of neutrophils into the cerebral microcirculation occurs, especially, in acute brain diseases like a focal cerebral ischemia and plays important role in pathological processes. Proteinase 3 is one of the three major proteinases expressed in neutrophils but no reports are available whether proteinase 3 can modulate neuronal survival. In this study, treatment of cultured rat primary cortical neuron with proteinase 3 induced overt reactive oxygen species production and decreased total glutathione contents as well as disruption of mitochondrial transmembrane potential. Proteinase 3 induced neuronal cell death as evidenced by MTT analysis as well as propidium iodide staining, which was prevented by pretreatment with an antioxidant, N-acetyl cysteine. Proteinase 3 increased activation of procaspase-3 and altered expression level of apoptotic regulator proteins, such as Bcl-2, Bax, and Bcl-xL. Similar to in vitro data, a direct microinjection of proteinase 3 into striatum of rat brain induced neuronal death, which was mediated by reactive oxygen species. These results suggest that proteinase 3 is new essential regulator of neuronal cell death pathway in a condition of excess neutrophil encounter in neuroinflammatory conditions.

Outcome and frequency of sodium disturbances in neurocritically ill patients

Sodium disturbances are frequent and serious complications in neurocritically ill patients. Hyponatremia is more common than hypernatremia, which is, however, prognostically worse. The aim of this study was to analyse outcome and frequency of sodium disturbances in relation to measured serum osmolality in neurologic-neurosurgical critically ill patients. A 5-year retrospective collection of patients (pts) and laboratory data were made from the Laboratory Information System database in the Clinical Biochemistry Department. The criteria for patients' inclusion was acute brain disease and serum sodium (SNa(+)) <135mmol/l (hyponatremia) or SNa(+) >150mmol/l (hypernatremia). Hypoosmolality was defined as measured serum osmolality (SOsm) <275mmol/kg, hyperosmolality as SOsm >295mmol/kg. We performed analysis of differences between hyponatremia and hypernatremia and subanalysis of differences between hypoosmolal hyponatremia and hypernatremia. From 1,440 pts with acute brain diseases there were 251 (17%) pts with hyponatremia (mean SNa(+) 131.78±2.89mmol/l, SOsm 279.46±11.84mmol/kg) and 75 (5%) pts with hypernatremia (mean SNa(+) 154.38±3.76mmol/l, SOsm 326.07±15.93mmol/kg). Hypoosmolal hyponatremia occurred in 50 (20% of hyponatremic patients) pts (mean SNa(+) 129.62±4.15mmol/l; mean SOsm 267.35± 6.28mmol/kg). Multiple logistic regression analysis showed that hypernatremia is a significant predictor of mortality during neurologic-neurosurgical intensive care unit (NNICU) stay (OR 5.3, p=0.002) but not a predictor of bad outcome upon discharge from NNICU, defined as Glasgow Coma Scale 1-3. These results showed that hypernatremia occurred less frequently than all hyponatremias, but more often than hypoosmolal hyponatremia. Hypernatremia was shown to be a significant predictor of NNICU mortality compared to hyponatremia.

Disappearance of a deadly disease acute hepatomyoencephalopathy syndrome from Saharanpur

Sir, Apropos our earlier correspondence1, there has been a drastic reduction of the deadly disease affecting young children of Saharanpur district of western Uttar Pradesh (UP). The outbreaks of this unexplained acute brain disease in children was recurring every year, with very high (70-80%) fatality for over two decades. It was earlier known as “Saharanpur encephalitis” or “acute viral encephalitis of unknown origin”. However, it was later found not encephalitis, but a multi-system disease affecting liver, muscle and brain and re-named “acute hepatomyoencephalopathy (HME) syndrome” caused by phytotoxins2. Later, the source of toxicity was found to be to the consumption of beans of a ubiquitous herb Cassia occidentalis by unsupervised young children of poor families3,4. Cases occurred only in September through December every year coinciding with the poding season of this annual plant. After publication of these studies, a meeting of all stakes-holders that comprised paediatricians, general physicians, local health and district administrations, health agencies, and media representatives was conducted in 2007 at the district headquarter city of Saharanpur, the worst affected district. Later, the local unit of Indian Academy of Pediatrics, with support from the health agencies [mainly UNICEF and National Polio Surveillance Project (NPSP)], district administration, and media launched a massive educational campaign in and around Saharanpur district to educate people about the poisonous nature of the weed. Pamphlets in local language were printed and distributed; the ‘live weed’ was exhibited/displayed at the registration counters of all hospitals and nursing homes, frequently-visited government offices, and at other public places. The task of massive uprooting of the weed was taken by the forest and Public Works departments. Instructions were given to village ‘Pradhans’ to employ labourers for destroying the weed from the neighbourhoods. Regular meetings were organized with ‘Gram Panchayat’ members and villagers were educated regarding the toxic nature of the plant. Media played a significant role in creating awareness among rural population. The entire operation was supervised by the district magistrate of Saharanpur. This massive campaign, sustained over 2 years led to drastic reduction in the number of cases in the district. As evident from the Table, the total number of admissions in Saharanpur district hospital which has a special ‘encephalitis ward’ to admit these cases, fell from 100-200 cases admitted annually up to 2007 to 15-30 in 2008 and 2009 and to nil in 2010. Table Numbers of admitted cases and deaths in Saharanpur District Hospital, 2002-2010 There is an urgent need to carry out similar awareness/education campaigns in all other affected districts of western UP and Uttarakhand. The lessons learnt are that there is no substitute to systematic and professional investigation of any outbreak of unknown cause2–4. This experience deserves wider publicity and public understanding. Healthcare professionals both in private and public sectors should have inquisitive mind and motivation to solve local problems by team approach. Public-private partnership in health sector can help achieving some difficult, unattainable targets. And, media can also play a very important constructive role in raising awareness among general public.

Expression of tissue transglutaminase on primary olfactory ensheathing cells cultures exposed to stress conditions

Tissue transglutaminase (TG2), a multifunctional enzyme implicated in cellular proliferation and differentiation processes, plays a modulatory role in the cell response to stressors. Herein, we used olfactory ensheathing cells (OECs), representing an unusual population of glial cells to promote axonal regeneration and to provide trophic support, as well as to assess whether the effect of some Growth Factors (GFs), NGF, bFGF or GDNF, on TG2 overexpression induced by stress conditions, such as glutamate or lipopolysaccaride (LPS). Glial Fibrillary Acidic Protein (GFAP) and vimentin were used as markers of astroglial differentiation and cytoskeleton component, respectively. Glutamate or LPS treatment induced a particular increase of TG2 expression. A pre-treatment of the cells with the GFs restored the levels of the protein to that of untreated ones. Our results demonstrate that the treatment of OECs with the GFs was able to restore the OECs oxidative status as modified by stress, also counteracting TG2 overexpression. It suggests that, in OECs, TG2 modulation or inhibition induced by GFs might represent a therapeutic target to control the excitotoxicity and/or inflammation, which are involved in several acute and chronic brain diseases.

Down-regulation of Homer1b/c attenuates glutamate-mediated excitotoxicity through endoplasmic reticulum and mitochondria pathways in rat cortical neurons

Glutamate-mediated excitotoxicity is involved in many acute and chronic brain diseases. Homer proteins, a new member of the postsynaptic scaffolding proteins, regulate glutamatergic signaling and intracellular calcium mobilization in the central nervous system. Here we investigated the effects of down-regulating Homer1b/c, a constitutively expressed long form of Homer proteins, on glutamate excitotoxicity-induced neuronal injury. In our in vitro excitotoxic models, we demonstrated that glutamate insults led to a dose-dependent neuronal injury, which was mediated by the intracellular calcium-dependent reactive oxygen species (ROS) production. We found that down-regulation of Homer1b/c with specific small interfering RNA (siRNA) improved neuronal survival, inhibited intracellular ROS production, and reduced apoptotic cell death after neurotoxicity. Homer1b/c knockdown decreased the intracellular calcium overload through inhibition of the group I metabotropic glutamate receptor (mGluR)/inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca2+ release from the endoplasmic reticulum (ER) in injured neurons. In addition, Homer1b/c siRNA transfection attenuated the activation of eukaryotic initiation factor 2α (eIF2α), RNA-dependent protein kinase-like ER kinase (PERK) and caspase-12, and inhibited the up-regulation of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) after glutamate treatment. Homer1b/c knockdown also preserved the mitochondrial membrane potential (MMP), reduced cytochrome c (Cyt. c) release, and partly blocked the increase of capase-9 activity and Bax/Bcl-2 ratio. Taken together, these results suggest that down-regulation of Homer1b/c protects cortical neurons against glutamate-induced excitatory damage, and this neuroprotection may be dependent at least in part on the inhibition of calcium-dependent ROS production and the preservation of the ER and mitochondrial function.

Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum

The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex.

Effects of 3 weeks GMP oral administration on glutamatergic parameters in mice neocortex

Overstimulation of the glutamatergic system (excitotoxicity) is involved in various acute and chronic brain diseases. Several studies support the hypothesis that guanosine-5'-monophosphate (GMP) can modulate glutamatergic neurotransmission. The aim of this study was to evaluate the effects of chronically administered GMP on brain cortical glutamatergic parameters in mice. Additionally, we investigated the neuroprotective potential of the GMP treatment submitting cortical brain slices to oxygen and glucose deprivation (OGD). Moreover, measurements of the cerebrospinal fluid (CSF) purine levels were performed after the treatment. Mice received an oral administration of saline or GMP during 3weeks. GMP significantly decreases the cortical brain glutamate binding and uptake. Accordingly, GMP reduced the immunocontent of the glutamate receptors subunits, NR2A/B and GluR1 (NMDA and AMPA receptors, respectively) and glutamate transporters EAAC1 and GLT1. GMP treatment significantly reduced the immunocontent of PSD-95 while did not affect the content of Snap 25, GLAST and GFAP. Moreover, GMP treatment increased the resistance of neocortex to OGD insult. The chronic GMP administration increased the CSF levels of GMP and its metabolites. Altogether, these findings suggest a potential modulatory role of GMP on neocortex glutamatergic system by promoting functional and plastic changes associated to more resistance of mice neocortex against an in vitro excitotoxicity event.

Sequences of the non-coding RNA, NTAB, are contained within the 3'-UTR of human and rat EAAT2/GLT-1 transcripts and act as transcriptional enhancers.

In the CNS, extracellular glutamate is predominantly cleared by astroglial cells through the high-affinity glutamate transporter subtype, EAAT2/GLT-1. Expression of EAAT2/GLT-1 is perturbed in various acute and chronic brain diseases eventually allowing for the onset of neurotoxic extracellular glutamate concentrations and subsequent excitotoxic neuronal cell death. The idea that glutamate-induced brain damage could be prevented by restoring glutamate homeostasis in the injured brain, spurred considerable interest in identifying the mechanisms controlling EAAT2/GLT-1 expression. Since to date most of this study was done with rat astrocytes, an emerging issue is to whether these findings would also apply to humans. While so far it is known that the promoter region of the EAAT2/GLT-1 gene is strikingly similar in rat and man, little information is available on the function of the EAAT2/GLT-1 3'-UTR in the control of EAAT2/GLT-1 expression in general as well as across both species. We now report on the presence of a homologous sequence within the 3'-UTR of the human and rat EAAT2/GLT-1 gene which we identified as a partial sequence of the putative non-coding RNA, Ntab. We further demonstrate that fragments of Ntab act as enhancers of EAAT2/GLT-1 transcription. Finally, we unravel that partial Ntab sequences are selectively present in the vicinity of the EAAT2/GLT-1 gene in several other mammalians, implying a conserved function of this sequence in the vertebrate CNS.

Brain-Penetrating Tumor Necrosis Factor Decoy Receptor in the Mouse

Biologic tumor necrosis factor inhibitors (TNFIs) include TNF decoy receptors (TNFRs). TNFα plays a pathologic role in both acute and chronic brain disease. However, biologic TNFIs cannot be developed as brain therapeutics because these large molecule drugs do not cross the blood-brain barrier (BBB). To enable penetration of the brain via receptor-mediated transport, the human TNFR type II was re-engineered as an IgG fusion protein, where the IgG part is a chimeric monoclonal antibody (MAb) against the mouse transferrin receptor (TfR), and this fusion protein is designated cTfRMAb-TNFR. The cTfRMAb part of the fusion protein acts as a molecular Trojan horse to ferry the TNFR across the BBB via transport on the endogenous BBB TfR. cTfRMAb-TNFR was expressed by stably transfected Chinese hamster ovary cells and purified by affinity chromatography to homogeneity on electrophoretic gels. The fusion protein reacted with antibodies to both mouse IgG and the human TNFR and bound TNFα with high affinity (K(d) = 96 ± 34 pM). cTfRMAb-TNFR was rapidly transported into mouse brain in vivo after intravenous administration, and the brain uptake of the fusion protein was 2.8 ± 0.5% of injected dose per gram of brain, which is >45-fold higher than the brain uptake of an IgG that does not recognize the mouse TfR. This new IgG-TNFR fusion protein can be tested in mouse models of brain diseases in which TNFα plays a pathologic role.

Treating Hyperglycemia in Neurocritical Patients: Benefits and Perils

There is growing debate over the value of intensive insulin therapy (IIT) in critically ill patients. Available trials have been performed in general medical or surgical intensive care units, and the results may not be directly applicable to patients with severe acute brain disease because these patients may have heightened susceptibility to hyperglycemia (HyperG) and hypoglycemia. Our objective was to review the pathophysiology and effects of HyperG and hypoglycemia in neurocritical patients and to analyze the potential role of IIT in this population. Source data were obtained from a PubMed search of the medical literature combining the terms HyperG, hypoglycemia, insulin, stroke, intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), traumatic brain injury (TBI), spinal cord injury (SCI), and related diagnoses. Brain metabolism is highly dependent on constant supply of glucose. As a consequence, the acutely injured brain is particularly sensitive to hypoglycemia, which can induce a state of energy failure (metabolic crisis). Meanwhile, neurocritical patients have a high prevalence of HyperG, and its occurrence is associated with poor outcome after acute ischemic stroke, ICH, SAH, and TBI. It is unclear whether this association is due to direct detrimental effects exerted by HyperG or simply represents a marker of severe brain injury. Insulin has been shown to have various potentially pleiotropic neuroprotective properties in experimental models. However, the safety and efficacy of IIT in patients with critical brain disease have not been well studied. Available results do not support the use of IIT to maintain strict normoglycemia in this population. Patients with critical brain disease should have frequent glucose monitoring because severe HyperG and even modest hypoglycemia may be detrimental. Careful use of insulin infusion protocols appears advisable, but maintenance of strict normoglycemia cannot be recommended. Rigorous studies must be conducted to assess the value of insulin therapy and to determine the optimal blood glucose targets in patients with the most common acute vascular and traumatic brain insults.

Prevention of Urinary Tract Infection in Patients with Acute Brain Disease

Prevention of Urinary Tract Infection in Patients with Acute Brain Disease

Prognosticating after severe acute brain disease

As neurologists, one of the toughest tasks we face when caring for patients with severe acute brain insults is answering the question, How will they do? In the neurologic intensive care unit, we interact every day with families asking this question. The answer depends on many factors, and we know that in most cases it is not exact. The stakes cannot be higher, as often the decision by families to continue or withdraw intensive care and life-sustaining measures hinges on what we say and how they hear it. Estimating prognosis is an essential part of our practice in the intensive care unit, and many studies have been performed that identify clinical, imaging, and laboratory predictors of patient outcome. However, little is known regarding what factors determine the way we prognosticate and the accuracy of our actual prognoses. This is a critical distinction: the difference between predictors of outcome and how physicians use this information to predict outcome. The study reported by Finley Caulfield et al.1 in this issue of Neurology ® provides valuable information on the challenges and variability of prognostication in patients with critical brain disease. We congratulate the investigators for their commitment to examine this difficult topic and encourage our colleagues to read the study in detail and interpret its findings carefully. The main results are that neurointensivists participating in …

Comparative structural and functional analysis of the GLT‐1/EAAT‐2 promoter from man and rat

In the vertebrate CNS, glutamate transport predominantly occurs through the glutamate transporter subtype, GLT-1/EAAT-2, which prevails in astrocytes. GLT-1/EAAT-2 expression is impaired in many acute and chronic brain diseases, leading to increases in extracellular glutamate and subsequent excitotoxic neuronal cell death. An obvious therapeutical approach to prevent glutamate-induced brain damage would be targeting GLT-1/EAAT-2 expression. Since so far, insights into the mechanisms modulating GLT-1/EAAT-2 expression mostly originated from work with rat astrocytes, we now sought to determine whether this modulatory network would also apply to humans. To this end, we have cloned the previously unknown rat GLT-1/EAAT-2 promoter and compared it to the human promoter sequence. In reporter assays, the cloned 2.7-kb region immediately flanking the 5'-end of the rat GLT-1/EAAT-2 gene allowed for similar increases in constitutive gene expression as the human promoter sequence. Sequence analysis demonstrated the presence of highly conserved regions on the rat and human GLT-1/EAAT-2 promoters, which turned out to be likewise essential for constitutive GLT-1/EAAT-2 expression, stimulation of gene transcription by EGF, TGFalpha, and PACAP as well as inhibition of gene transcription by TNFalpha. Intriguingly, endothelin-1 which inhibits endogenous GLT-1/EAAT-2 expression, promoted activity of both rat and human reporter constructs, indicating the existence of (an) inhibitory mechanism(s) not operational in the reporter gene assay. Our findings establish close similarities in the regulation of GLT-1/EAAT-2 expression in rat and man and, hence, validate rat astrocytes as an assay system for studying the molecular mechanisms affecting glutamate homeostasis in the healthy and diseased human brain.

Encapsulated living choroid plexus cells: potential long-term treatments for central nervous system disease and trauma

In neurodegenerative disease and in acute brain injury, there is often local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable neurotrophin-producing cells close to the trauma lesion, or site of degenerative disease, might provide a novel means for continuous delivery of these molecules directly to the site of injury or to a degenerative region. The aim of this paper is to summarize recent published information and present new experimental data that indicate that long-lasting therapeutic implants of choroid plexus (CP) neuroepithelium may be used to treat brain disease. CP produces and secretes numerous biologically active neurotrophic factors (NT). New gene microarray and proteomics data presented here indicate that many other anti-oxidant, anti-toxin and neuronal support proteins are also produced and secreted by CP cells. In the healthy brain, these circulate in the cerebrospinal fluid through the brain and spinal cord, maintaining neuronal networks and associated cells. Recent publications describe how transplanted CP cells and tissue, either free or in an immunoprotected encapsulated form, can effectively deliver therapeutic molecules when placed near the lesion or site of degenerative disease in animal models. Using simple techniques, CP neuroepithelial cell clusters in suspension culture were very durable, remaining viable for 6 months or more in vitro. The cell culture conditions had little effect on the wide range and activity of genes expressed and proteins secreted. Recently, completed experiments show that implanting CP within alginate–poly-ornithine capsules effectively protected these xenogeneic cells from the host immune system and allowed their survival for 6 months or more in the brains of rats, causing no adverse effects. Previously reported evidence demonstrated that CP cells support the survival and differentiation of neuronal cells in vitro and effectively treat acute brain injury and disease in rodents and non-human primates in vivo. The accumulated preclinical data together with the long-term survival of implanted encapsulated cells in vivo provide a sound base for the investigation of these treatments for chronic inherited and established neurodegenerative conditions.

Growth factors improve neurogenesis and outcome after focal cerebral ischemia

Stem cells have been proposed as a new form of cell-based therapy in a variety of disorders, including acute and degenerative brain diseases. Endogenous neural stem cells (eNSC) reside in the subventricular zone and in the subgranular zone of the hippocampus. eNSC are capable of self-renewal and differentiation into functional glia and neurons. Unfortunately, spontaneous brain regeneration is inefficient for clinically significant improvement following brain injury. However, eNSC responses may be augmented considerably by perturbing the pathways governing cell proliferation, migration and differentiation by application of exogenous growth factors. Importantly, current evidence suggests that such perturbations may lead to better functional outcome after stroke. This article summarizes the progress made in this field.