Postnatal hypoxic-ischemic brain injury alters mechanisms mediating neuronal glucose transport

Therapeutic implications of glucose transporters (GLUT) in cerebral ischemia

Cerebral ischemia is a leading cause of death in the globe, with a large societal cost. Deprivation of blood flow, together with consequent glucose and oxygen shortage, activates a variety of pathways that result in permanent brain damage. As a result, ischemia raises energy demand, which is linked to significant alterations in brain energy metabolism. Even at the low glucose levels reported in plasma during ischemia, glucose transport activity may adjust to assure the supply of glucose to maintain normal cellular function. Glucose transporters in the brain are divided into two groups: sodium-independent glucose transporters (GLUTs) and sodium-dependent glucose cotransporters (SGLTs).This review assess the GLUT structure, expression, regulation, pathobiology of GLUT in cerebral ischemia and regulators of GLUT and it also provides the synopsis of the literature exploring the relationship between GLUT and the various downstream signalling pathways for e.g., AMP-activated protein kinase (AMPK), CREB (cAMP response element-binding protein), Hypoxia-inducible factor 1 (HIF)-1, Phosphatidylinositol 3-kinase (PI3-K), Mitogen-activated protein kinase (MAPK) and adenylate-uridylate-rich elements (AREs). Therefore, the aim of the present review was to elaborate the therapeutic implications of GLUT in the cerebral ischemia.

Effect of chronic alcohol consumption on myocardial apoptosis in the rat model of isoproterenol-induced myocardial injury and investigation on the cardioprotective role of calpain inhibitor 1

We investigated the presence of myocardial apoptosis on isoproterenol (ISO)-induced myocardial injury (MI) after long-term high dose alcohol consumption and examined the antiapoptotic role of calpain inhibitor 1. Male Wistar Albino rats (n = 108) were divided into six groups: Control, alcohol (ethanol was given during 30 days for chronic alcohol consumption), MI (150 mg/kg ISO injection at last two days of alcohol consumption), alcohol + MI, alcohol + MI + calpain inhibitor 1 (10 mg/kg inhibitor was injected at 15 min before ISO injections) and Dimethyl Sulfoxide (DMSO) groups. Biochemical, histological, and morphometric methods determined apoptosis levels in the heart tissue of rats. Cytochrome c, caspase 3, and calpain levels were significantly high in alcohol, MI, and alcohol + MI groups. In contrast, mitochondrial cardiolipin content was found to be low in alcohol, MI, and alcohol + MI groups. These parameters were close to the control group in the therapy group. Histological and morphometric data have supported biochemical results. As a result of our biochemical data, myocardial apoptosis was seen in the alcohol, MI, and especially alcohol after MI groups. Calpain inhibitor 1 reduced apoptotic cell death and prevented myocardial tissue injury in these groups. The efficiency of calpain inhibitor was very marked in MI after long-term high dose alcohol consumption.

Crossing the blood-brain barrier with carbon dots: uptake mechanism and in vivo cargo delivery

The blood-brain barrier (BBB) is a major obstacle for drug delivery to the central nervous system (CNS) such that most therapeutics lack efficacy against brain tumors or neurological disorders due to their inability to cross the BBB. Therefore, developing new drug delivery platforms to facilitate drug transport to the CNS and understanding their mechanism of transport are crucial for the efficacy of therapeutics. Here, we report (i) carbon dots prepared from glucose and conjugated to fluorescein (GluCD-F) cross the BBB in zebrafish and rats without the need of an additional targeting ligand and (ii) uptake mechanism of GluCDs is glucose transporter-dependent in budding yeast. Glucose transporter-negative strain of yeast showed undetectable GluCD accumulation unlike the glucose transporter-positive yeast, suggesting glucose-transporter-dependent GluCD uptake. We tested GluCDs' ability to cross the BBB using both zebrafish and rat models. Following the injection to the heart, wild-type zebrafish showed GluCD-F accumulation in the central canal consistent with the transport of GluCD-F across the BBB. In rats, following intravenous administration, GluCD-F was observed in the CNS. GluCD-F was localized in the gray matter (e.g. ventral horn, dorsal horn, and middle grey) of the cervical spinal cord consistent with neuronal accumulation. Therefore, neuron targeting GluCDs hold tremendous potential as a drug delivery platform in neurodegenerative disease, traumatic injury, and malignancies of the CNS.

Longitudinal in vivo imaging of acute neuropathology in a monkey model of Ebola virus infection

Ebola virus (EBOV) causes neurological symptoms yet its effects on the central nervous system (CNS) are not well-described. Here, we longitudinally assess the acute effects of EBOV on the brain, using quantitative MR-relaxometry, 18F-Fluorodeoxyglucose PET and immunohistochemistry in a monkey model. We report blood-brain barrier disruption, likely related to high cytokine levels and endothelial viral infection, with extravasation of fluid, Gadolinium-based contrast material and albumin into the extracellular space. Increased glucose metabolism is also present compared to the baseline, especially in the deep gray matter and brainstem. This regional hypermetabolism corresponds with mild neuroinflammation, sporadic neuronal infection and apoptosis, as well as increased GLUT3 expression, consistent with increased neuronal metabolic demands. Neuroimaging changes are associated with markers of disease progression including viral load and cytokine/chemokine levels. Our results provide insight into the pathophysiology of CNS involvement with EBOV and may help assess vaccine/treatment efficacy in real time.

Adult glut3 homozygous null mice survive to demonstrate neural excitability and altered neurobehavioral responses reminiscent of neurodevelopmental disorders

Since GLUT3 is vital for fueling neurotransmission, we examined in-vivo the adult phenotype carrying the conditional homozygous glut3 gene mutation (KO) in glutamate-excitatory neurons. These KO mice demonstrated sex-specific differences in brain and body weights (p = 0.0001 and p = 0.01 each) with reduced GLUT3 protein in cerebral cortices and brain stem (p = 0.005). In patch clamp studies the glut3 KO mice displayed a shorter latency to and enhanced paroxysmal activity (p = 0.01 and p = 0.015 each) in pyramidal neurons upon application of a GABA_A antagonist, supporting hyperexcitability. Further, associated changes in neurobehavior consisted of reduced latency to fall in the rotorod motor test related to incoordination, increased distance traveled in total and periphery versus center in open field testing suggesting hyperactivity with anxiety (p = 0.0013 in male, p = 0.045 in female), reduced time freezing reminiscent of disrupted contextual fear conditioning (p = 0.0033), decreased time in target quadrant seen with spatial cognitive memory water maze testing (p = 0.034), and enhanced sociability particularly for novelty reflecting a lack of inhibition/impulsivity (p = 0.038). Some of these features were equally pronounced in males and females (cognitive) while others were seen in females (anxiety and impulsivity). We conclude that GLUT3 in adult glutamate-excitatory neurons is essential for maintaining neurotransmitory equipoise regulating excitation with maintenance of motor coordination and activity, cognition, spatial memory and normal fear for both contextual events and novelty with tempered sociability. While sex-specificity was forthcoming for some of these behaviors, our findings collectively suggest that loss-of-function glut3 gene mutations or polymorphisms may underlie an endophenotype of attention deficit-hyperactivity disorder.

Energy Metabolism Decline in the Aging Brain-Pathogenesis of Neurodegenerative Disorders

There is a growing body of evidencethat indicates that the aging of the brain results from the decline of energy metabolism. In particular, the neuronal metabolism of glucose declines steadily, resulting in a growing deficit of adenosine triphosphate (ATP) production-which, in turn, limits glucose access. This vicious circle of energy metabolism at the cellular level is evoked by a rising deficiency of nicotinamide adenine dinucleotide (NAD) in the mitochondrial salvage pathway and subsequent impairment of the Krebs cycle. A decreasing NAD level also impoverishes the activity of NAD-dependent enzymes that augments genetic errors and initiate processes of neuronal degeneration and death.This sequence of events is characteristic of several brain structures in which neurons have the highest energy metabolism. Neurons of the cerebral cortex and basal ganglia with long unmyelinated axons and these with numerous synaptic junctions are particularly prone to senescence and neurodegeneration. Unfortunately, functional deficits of neurodegeneration are initially well-compensated, therefore, clinical symptoms are recognized too late when the damages to the brain structures are already irreversible. Therefore, future treatment strategies in neurodegenerative disorders should focus on energy metabolism and compensation age-related NAD deficit in neurons. This review summarizes the complex interrelationships between metabolic processes on the systemic and cellular levels and provides directions on how to reduce the risk of neurodegeneration and protect the elderly against neurodegenerative diseases.

Environmental Tobacco Smoke During the Early Postnatal Period of Mice Interferes With Brain 18 F-FDG Uptake From Infancy to Early Adulthood - A Longitudinal Study

Exposure to environmental tobacco smoke (ETS) is associated with high morbidity and mortality, mainly in childhood. Our aim was to evaluate the effects of postnatal ETS exposure in the brain 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (¹⁸F-FDG) uptake of mice by positron emission tomography (PET) neuroimaging in a longitudinal study. C57BL/6J mice were exposed to ETS that was generated from 3R4F cigarettes from postnatal day 3 (P3) to P14. PET analyses were performed in male and female mice during infancy (P15), adolescence (P35), and adulthood (P65). We observed that ETS exposure decreased ¹⁸F-FDG uptake in the whole brain, both left and right hemispheres, and frontal cortex in both male and female infant mice, while female infant mice exposed to ETS showed decreased ¹⁸F-FDG uptake in the cerebellum. In addition, all mice showed reduced ¹⁸F-FDG uptake in infancy, compared to adulthood in all analyzed VOIs. In adulthood, ETS exposure during the early postnatal period decreased brain ¹⁸F-FDG uptake in adult male mice in the cortex, striatum, hippocampus, cingulate cortex, and thalamus when compared to control group. ETS induced an increase in ¹⁸F-FDG uptake in adult female mice when compared to control group in the brainstem and cingulate cortex. Moreover, male ETS-exposed animals showed decreased ¹⁸F-FDG uptake when compared to female ETS-exposed in the whole brain, brainstem, cortex, left amygdala, striatum, hippocampus, cingulate cortex, basal forebrain and septum, thalamus, hypothalamus, and midbrain. The present study shows that several brain regions are vulnerable to ETS exposure during the early postnatal period and these effects on ¹⁸F-FDG uptake are observed even a long time after the last exposure. This study corroborates our previous findings, strengthening the idea that exposure to tobacco smoke in a critical period interferes with brain development of mice from late infancy to early adulthood.

Neural Deletion of Glucose Transporter Isoform 3 Creates Distinct Postnatal and Adult Neurobehavioral Phenotypes

We created a neural-specific conditional murine glut3 (Slc2A3) deletion (glut3 ^{flox/flox/nestin-Cre+}) to examine the effect of a lack of Glut3 on neurodevelopment. Compared with age-matched glut3 ^flox/flox = WT and heterozygotes (glut3 ^{flox/+/nestin-Cre+}), we found that a >90% reduction in male and female brain Glut3 occurred by postnatal day 15 (PN15) in glut3 ^{flox/flox/nestin-Cre+} This genetic manipulation caused a diminution in brain weight and cortical thickness at PN15, a reduced number of dendritic spines, and fewer ultrasonic vocalizations. Patch-clamp recordings of cortical pyramidal neurons revealed increased frequency of bicuculline-induced paroxysmal discharges as well as reduced latency, attesting to a functional synaptic and cortical hyperexcitability. Concomitant stunting with lower glucose concentrations despite increased milk intake shortened the lifespan, failing rescue by a ketogenic diet. This led to creating glut3 ^{flox/flox/CaMK2α-Cre+} mice lacking Glut3 in the adult male limbic system. These mice had normal lifespan, displayed reduced IPSCs in cortical pyramidal neurons, less anxiety/fear, and lowered spatial memory and motor abilities but heightened exploratory and social responses. These distinct postnatal and adult phenotypes, based upon whether glut3 gene is globally or restrictively absent, have implications for humans who carry copy number variations and present with neurodevelopmental disorders.SIGNIFICANCE STATEMENT Lack of the key brain-specific glucose transporter 3 gene found in neurons during early postnatal life results in significant stunting, a reduction in dendritic spines found on neuronal processes and brain size, heightened neuronal excitability, along with a shortened lifespan. When occurring in the adult and limited to the limbic system alone, lack of this gene in neurons reduces the fear of spatial exploration and socialization but does not affect the lifespan. These features are distinct heralding differences between postnatal and adult phenotypes based upon whether the same gene is globally or restrictively lacking. These findings have implications for humans who carry copy number variations pertinent to this gene and have been described to present with neurodevelopmental disorders.

Sex-Specific Life Course Changes in the Neuro-Metabolic Phenotype of Glut3 Null Heterozygous Mice: Ketogenic Diet Ameliorates Electroencephalographic Seizures and Improves Sociability

We tested the hypothesis that exposure of glut3+/- mice to a ketogenic diet ameliorates autism-like features, which include aberrant behavior and electrographic seizures. We first investigated the life course sex-specific changes in basal plasma-cerebrospinal fluid (CSF)-brain metabolic profile, brain glucose transport/uptake, glucose and monocarboxylate transporter proteins, and adenosine triphosphate (ATP) in the presence or absence of systemic insulin administration. Glut3+/- male but not female mice (5 months of age) displayed reduced CSF glucose/lactate concentrations with no change in brain Glut1, Mct2, glucose uptake or ATP. Exogenous insulin-induced hypoglycemia increased brain glucose uptake in glut3+/- males alone. Higher plasma-CSF ketones (β-hydroxybutyrate) and lower brain Glut3 in females vs males proved protective in the former while enhancing vulnerability in the latter. As a consequence, increased synaptic proteins (neuroligin4 and SAPAP1) with spontaneous excitatory postsynaptic activity subsequently reduced hippocampal glucose content and increased brain amyloid β1-40 deposition in an age-dependent manner in glut3+/- males but not females (4 to 24 months of age). We then explored the protective effect of a ketogenic diet on ultrasonic vocalization, sociability, spatial learning and memory, and electroencephalogram seizures in male mice (7 days to 6 to 8 months of age) alone. A ketogenic diet partially restored sociability without affecting perturbed vocalization, spatial learning and memory, and reduced seizure events. We conclude that (1) sex-specific and age-dependent perturbations underlie the phenotype of glut3+/- mice, and (2) a ketogenic diet ameliorates seizures caused by increased cortical excitation and improves sociability, but fails to rescue vocalization and cognitive deficits in glut3+/- male mice.

Prenatal alcohol-induced neuroapoptosis in rat brain cerebral cortex: protective effect of folic acid and betaine

PURPOSE

Alcohol consumption in pregnancy may cause fetal alcohol syndrome (FAS) in the infant. This study aims to investigate prenatal alcohol exposure related neuroapoptosis on the cerebral cortex tissues of newborn rats and possible neuroprotective effects of betaine, folic acid, and combined therapy.

METHODS

Pregnant rats were divided into five experimental groups: control, ethanol, ethanol + betaine, ethanol + folic acid, and ethanol + betaine + folic acid combined therapy groups. We measured cytochrome c release, caspase-3, calpain and cathepsin B and L. enzyme activities. In order to observe apoptotic cells in the early stages, TUNEL method was chosen together with histologic methods such as assessing the diameters of the apoptotic cells, their distribution in unit volume and volume proportion of cortical intact neuron nuclei.

RESULTS

Calpain, caspase-3 activities, and cytochrome c levels were significantly increased in alcohol group while cathepsin B and L. activities were also found to be elevated albeit not statistically significant. These increases were significantly reversed by folic acid and betaine + folic acid treatments. While ethanol increased the number of apoptotic cells, this increase was prevented in ethanol + betaine and ethanol + betaine + folic acid groups. Morphometric examination showed that the mean diameter of apoptotic cells was increased with ethanol administration while this increase was reduced by betaine and betaine + folic acid treatments.

CONCLUSION

We observed that ethanol is capable of triggering apoptotic cell death in the newborn rat brains. Furthermore, folic acid, betaine, and combined therapy of these supplements may reduce neuroapoptosis related to prenatal alcohol consumption, and might be effective on preventing fetal alcohol syndrome in infants.

Glucose metabolism and neurogenesis in the gerbil hippocampus after transient forebrain ischemia

Recent evidence exists that glucose transporter 3 (GLUT3) plays an important role in the energy metabolism in the brain. Most previous studies have been conducted using focal or hypoxic ischemia models and have focused on changes in GLUT3 expression based on protein and mRNA levels rather than tissue levels. In the present study, we observed change in GLUT3 immunoreactivity in the adult gerbil hippocampus at various time points after 5 minutes of transient forebrain ischemia. In the sham-operated group, GLUT3 immunoreactivity in the hippocampal CA1 region was weak, in the pyramidal cells of the CA1 region increased in a time-dependent fashion 24 hours after ischemia, and in the hippocampal CA1 region decreased significantly between 2 and 5 days after ischemia, with high level of GLUT3 immunoreactivity observed in the CA1 region 10 days after ischemia. In a double immunofluorescence study using GLUT3 and glial-fibrillary acidic protein (GFAP), we observed strong GLUT3 immunoreactivity in the astrocytes. GLUT3 immunoreactivity increased after ischemia and peaked 7 days in the dentate gyrus after ischemia/reperfusion. In a double immunofluorescence study using GLUT3 and doublecortin (DCX), we observed low level of GLUT3 immunoreactivity in the differentiated neuroblasts of the subgranular zone of the dentate gyrus after ischemia. GLUT3 immunoreactivity in the sham-operated group was mainly detected in the subgranular zone of the dentate gyrus. These results suggest that the increase in GLUT3 immunoreactivity may be a compensatory mechanism to modulate glucose level in the hippocampal CA1 region and to promote adult neurogenesis in the dentate gyrus.

The investigation of the prenatal and postnatal alcohol exposure-induced neurodegeneration in rat brain: protection by betaine and/or omega-3

PURPOSE

We aim to study the effect of neurodegeneration on the brain of rat pups caused by prenatal and postnatal ethanol exposure with modified liquid diet to elucidate protective effects of betaine and omega-3 supplementation. When ethanol is consumed during prenatal and postnatal periods, it may result in fetal alcohol syndrome (FAS) in the offspring.

METHODS

Rats were divided into control, ethanol, ethanol + betaine, ethanol + omega-3, ethanol + omega-3 + betaine groups. The effect of betaine and omega-3 in response to ethanol-induced changes on the brain, by biochemical analyses cytochrome c, caspase-3, calpain, cathepsin B and L, DNA fragmentation, histological and morfometric methods were evaluated.

RESULTS

Caspase-3, calpain, cathepsin B, and cytochrome c levels in ethanol group were significantly higher than control. Caspase-3, calpain levels were decreased in ethanol + betaine, ethanol + omega-3, and ethanol + omega-3 + betaine groups compared to ethanol group. Cathepsin B in ethanol + omega-3 + betaine group was decreased compared to ethanol, ethanol + betaine groups. Cathepsin L and DNA fragmentation were found not statistically significant. We found similar results in histological and morfometric parameters.

CONCLUSION

We found that pre- and postnatal ethanol exposure is capable of triggering necrotic cell death in rat brains, omega-3, and betaine reduce neurodegeneration. Omega-3 and betaine may prove beneficial for neurodegeneration, particularly in preventing FAS.

Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery

Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.

Effects of N-butylphthalide on the activation of Keap1/Nrf-2 signal pathway in rats after carbon monoxide poisoning

Carbon monoxide (CO) is the leading cause of death by poisoning all over the world and may result in neuropathologic changes and cognitive and neurologic sequelae, yet little is known regarding its outcomes. The present study aimed to evaluate the neuroprotective effects of N-butylphthalide (NBP) against brain damage after acute CO poisoning. The animal model of CO poisoning was established by exposed to 1000 ppm CO in air for 40 min and then to 3000 ppm for another 20 min. RT-PCR was used to assess the expressions of apoptosis-associated genes Bcl-2 mRNA and Bax mRNA. Mitochondrial membrane potential (MMP) was detected by fluorescent probe JC-1. Immunohistochemistry stain and Western blot assay were used to evaluate the expression levels of Kelch-like ECH-associated protein 1 (Keapl), nuclear factor erythroid 2-related factor 2 (Nrf-2) and

NAD(P)H

quinone oxidoreductase 1(NQO-1). CO poisoning could increase the levels of Bcl-2 mRNA and Bax mRNA expressions, and obviously decrease the MMP of cells. NBP treatment could maintain the high MMP, significantly up-regulate Bcl-2 mRNA and down-regulate Bax mRNA expression, and the ratio of Bcl-2 mRNA/Bax mRNA expressions was higher than that in the CO poisoning group (P<0.05). CO poisoning could start oxidative stress response. The expressions of Keap1, Nrf-2 and NQO-1 proteins significantly increased at 1, 3 and 7 day after NBP administration as compared with the CO poisoning group (P<0.01). These findings suggest that N-butylphthalide may protect mitochondrial function, balance the expressions of anti-apoptosis genes and pro-apoptosis genes, be in part associated with activation of Keap1-Nrf-2/antioxidant response element (ARE) signaling pathway, and play a neuroprotective role in brain damage after acute CO poisoning.

Anoxia-induced changes in optimal substrate for peripheral nerve

Hyperglycemia accentuates the injury produced by anoxia both in the central and peripheral nervous system. To understand whether this is a consequence of changes in metabolic pathways produced by anoxia, the effect of the metabolic substrate used by the rat peripheral nerve on the nerve action potential (NAP) was studied in the presence and absence of anoxia. In the continuously oxygenated state, the NAP was well preserved with glucose, lactate, as well as with high concentrations of sorbitol and fructose but not β-hydroxybutyrate, acetate or galactose. With intermittent anoxia, the pattern of substrate effects on the NAP changed markedly so that low concentrations of fructose became able to support neurophysiologic activity but not high concentrations of glucose. These alterations occurred gradually with repeated episodes of anoxia as reflected by the progressive increase in the time needed for the NAP to disappear during anoxia when using glucose as substrate. This "preconditioning" effect was not seen with other substrates and an opposite effect was seen with lactate. In fact, the rate at which the NAP disappeared during anoxia was not simply related to degree of recovery after anoxia. These are distinct phenomena. For example, the NAP persisted longest during anoxia in the setting of hyperglycemia but this was the state in which the anoxic damage was most severe. Correlating the results with existing literature on the metabolic functions of Schwann cells and axons generates testable hypotheses for the mechanism of hyperglycemic damage during anoxia and lead to discussions of the role for a metabolic shuttle between Schwann cells and axons as well as a potential important role of glycogen.

Upregulation of Hsp72 mediates anoxia/reoxygenation neuroprotection in the freshwater turtle via modulation of ROS

The neuroprotective role of Hsp72 has been demonstrated in several ischemic/stroke models to occur primarily through mediation of apoptotic pathways, and a number of heat shock proteins are upregulated in animal models capable of extended anoxic survival. In the present study, we investigated the role of Hsp72 on cell death and apoptotic regulators in one anoxia tolerant model system, the freshwater turtle Trachemys scripta. Since Hsp72 is known to regulate apoptosis through interactions with Bcl-2, we manipulated the levels of Hsp72 and Bcl-2 with siRNA in neuronally enriched primary cell cultures and examined downstream effects. The knockdown of either Hsp72 or Bcl-2 induced cell death during anoxia and reoxygenation. Knockdown of Bcl-2 resulted in increases in apoptotic markers and increased ROS levels 2-fold. However, significant knockdown of Hsp72 did not have any effect on the expression of key mitochondrial apoptotic regulators such as Cytochrome c and caspase-3. Hsp72 knockdown however significantly increased apoptosis inducing factor in both anoxia and reoxygenation and resulted in a six-fold induction of hydrogen peroxide levels. These findings suggest that the neuroprotection offered by Hsp72 in the anoxia/reoxygenation tolerant turtle is through the mediation of ROS levels and not through modulation of caspase-dependent pathways.

Consumption of Coprinus comatus polysaccharide extract causes recovery of alcoholic liver damage in rats

CONTEXT

Excess use of alcohol is known to be associated with liver diseases such as fatty liver, alcoholic hepatitis, and cirrhosis. Various practices may be applied to prevent or treat the damage caused by chronic alcoholism. Coprinus comatus (O.F. Müll.) Pers. (Agaricaceae) is a macrofungus that has been reported to aid the recovery of murine livers damaged by benzopyrene.

OBJECTIVE

In this study, the possible therapeutic effects of three different doses (50, 100, and 150 mg/kg) of C. comatus polysaccharide (PS) extract were studied in rats subjected to an alcoholic diet. The histological and biochemical results were compared between the control and experimental groups.

MATERIALS AND METHODS

Modified Lieber-Decarli's calorie-adjusted liquid alcohol diet was given orally for 60 d. In addition to histopathology, alanine transaminase (ALT), aspartate transaminase (AST), mitochondrial membrane integrity, total cytochrome-c oxidase activity (TotalStCox), total mitochondrial cytochrome-c oxidase activity (TotalMtStCox), and caspase-3 values were used as liver parameters, and liver sections from all experimental groups were examined by electron microscopy.

RESULTS

Using histopathological assessment, it was observed that there was a decline in liver hepatocyte vacuolization in the treatment group fed 50 mg PS/kg. The TotalStCox and TotalMtStCox values of this group differed from the EtOH control group (p < 0.05).

DISCUSSION AND CONCLUSION

Daily administration of 50 mg/kg of C. comatus PS extract considerably reduced the negative effects of alcohol on liver structure and function.

A novel prolyl hydroxylase inhibitor protects against cell death after hypoxia

Hypoxia-inducible factor 1 (HIF-1) is regulated by the oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHDs). We recently developed a novel PHD inhibitor, TM6008, that suppresses the activity of PHDs, inducing continuous HIF-1α activation. In this study, we investigated how TM6008 affects cell survival after hypoxic conditions capable of inducing HIF-1α expression and how TM6008 regulates PHDs and genes downstream of HIF-1α. After SHSY-5Y cells had been subjected to hypoxia, TM6008 was added to the cell culture medium under normoxic conditions. Apoptotic cell death was significantly augmented just after the hypoxic conditions, compared with cell death under normoxic conditions. Notably, when TM6008 was added to the media after the cells had been subjected to hypoxia, the expression level of HIF-1α increased and the number of cell deaths decreased, compared with the results for cells cultured in media without TM6008 after hypoxia, during the 7-day incubation period under normoxic conditions. Moreover, the protein expression levels of heme oxygenase 1, erythropoietin, and glucose transporter-3, which were genes downstream of HIF-1α, were elevated in media to which TM6008 had been added, compared with media without TM6008, during the 7-day incubation period under normoxic conditions. However, the protein expression levels of PHD2 and p53 which suppressed cell proliferation were suppressed in the media to which TM6008 had been added. Thus, TM6008, which suppresses the protein expressions of PHD2 and p53, might play an important role in cell survival after hypoxic conditions, with possible applications as a new compound for treatment after ischemic stroke.

Effect of Harderian adenectomy on the statistical analyses of mouse brain imaging using positron emission tomography

Positron emission tomography (PET) using 2-deoxy-2-[¹⁸F] fluoro-D-glucose (FDG) as a radioactive tracer is a useful technique for in vivo brain imaging. However, the anatomical and physiological features of the Harderian gland limit the use of FDG-PET imaging in the mouse brain. The gland shows strong FDG uptake, which in turn results in distorted PET images of the frontal brain region. The purpose of this study was to determine if a simple surgical procedure to remove the Harderian gland prior to PET imaging of mouse brains could reduce or eliminate FDG uptake. Measurement of FDG uptake in unilaterally adenectomized mice showed that the radioactive signal emitted from the intact Harderian gland distorts frontal brain region images. Spatial parametric measurement analysis demonstrated that the presence of the Harderian gland could prevent accurate assessment of brain PET imaging. Bilateral Harderian adenectomy efficiently eliminated unwanted radioactive signal spillover into the frontal brain region beginning on postoperative Day 10. Harderian adenectomy did not cause any post-operative complications during the experimental period. These findings demonstrate the benefits of performing a Harderian adenectomy prior to PET imaging of mouse brains.

Effect of kefir and low-dose aspirin on arterial blood pressure measurements and renal apoptosis in unhypertensive rats with 4 weeks salt diet

Abstract We aim to study the effect of low-dose aspirin and kefir on arterial blood pressure measurements and renal apoptosis in unhypertensive rats with 4 weeks salt diet. Forty adult male Sprague-Dawley rats were divided into five groups: control, high-salt (HS) (8.0% NaCl), HS+aspirin (10 mg/kg), HS+kefir (10.0%w/v), HS+aspirin +kefir. We measured sistolic blood pressure (SBP), mean arterial pressure (MAP), diastolic pressure, pulse pressure in the rats. Cathepsin B, L, DNA fragmentation and caspase-3 activities were determined from rat kidney tissues and rats clearance of creatinine calculated. Although HS diet increased significantly SBP, MAP, diastolic pressure, pulse pressure parameters compared the control values. They were not as high as accepted hypertension levels. When compared to HS groups, kefir groups significantly decrease Cathepsin B and DNA fragmentation levels. Caspase levels were elevated slightly in other groups according to control group. While, we also found that creatinine clearance was higher in HS+kefir and HS+low-dose aspirin than HS group. Thus, using low-dose aspirin had been approximately decreased of renal function damage. Kefir decreased renal function damage playing as Angiotensin-converting enzyme inhibitor. But, low-dose aspirin together with kefir worsened rat renal function damage. Cathepsin B might play role both apoptosis and prorenin-processing enzyme. But not caspase pathway may be involved in the present HS diet induced apoptosis. In conclusion, kefir and low-dose aspirin used independently protect renal function and renal damage induced by HS diet in rats.

Age-related alteration in cerebral blood flow and energy failure is correlated with cognitive impairment in the senescence-accelerated prone mouse strain 8 (SAMP8)

Cerebrovascular dysfunction is an early pathogenic event in Alzheimer's disease (AD) and plays a key role in the disease process. Cerebral hypoperfusion, brain glucose hypometabolism and disrupted blood-brain barrier (BBB) integrity contributed to the onset and progression of AD. However, the relationships between the age-related cognitive impairment and cerebral blood flow (CBF), energy metabolism and BBB have not been clearly explained. In this study, we investigated the cognitive function, CBF, BBB damage and expression level of glucose transporter (GLUT) 1 and 3 of senescence-accelerated mouse prone 8 (SAMP8), and the correlations between each of them were analyzed. When compared with SAMR1 (senescence-accelerated mouse resistant 1), the cognitive abilities of SAMP8 were damaged apparently even at 4 months of age, showing up a slower and more capricious acquisition in Morris water maze tasks. In both SAMP8 and SAMR1, reduced CBF and increased BBB leakage were observed with increasing age, but an earlier and more severe impairment was detected in SAMP8. In addition, alterations of GLUT1 and GLUT3 protein expression in cortex and hippocampus were more prominent in SAMP8. Correlation analysis demonstrated that the increased escape latency was correlated negatively with CBF and expression of glucose transporters; and positively with BBB permeability in the hippocampus. These results suggested that CBF, BBB integrity, the expression of GLUT1 and GLUT3 were significantly affected by age and strain, which were also closely associated with cognitive ability. The alteration in CBF and energy failure induced by aging and vascular insults resulted in cognitive decline in SAMP8.

Hypoxic adaptation engages the CBP/CREST-induced coactivator complex of Creb-HIF-1α in transactivating murine neuroblastic glucose transporter

We have shown in vitro a hypoxia-induced time-dependent increase in facilitative glucose transporter isoform 3 (GLUT3) expression in N2A murine neuroblasts. This increase in GLUT3 expression is partially reliant on a transcriptional increase noted in actinomycin D and cycloheximide pretreatment experiments. Transient transfection assays in N2A neuroblasts using murine glut3-luciferase reporter constructs mapped the hypoxia-induced enhancer activities to -857- to -573-bp and -203- to -177-bp regions. Hypoxia-exposed N2A nuclear extracts demonstrated an increase in HIF-1α and p-Creb binding to HRE (-828 to -824 bp) and AP-1 (-187 to -180 bp) cis-elements, respectively, in electromobility shift and supershift assays, which was confirmed by chromatin immunoprecipitation assays. In addition, the interaction of CBP with Creb and HIF-1α and CREST with CBP in hypoxia was detected by coimmunoprecipitation. Furthermore, small interference (si)RNA targeting Creb in these cells decreased endogenous Creb concentrations that reduced by twofold hypoxia-induced glut3 gene transcription. Thus, in N2A neuroblasts, phosphorylated HIF-1α and Creb mediated the hypoxia-induced increase in glut3 transcription. Coactivation by the Ca⁺⁺-dependent CREST and CBP proteins may enhance cross-talk between p-Creb-AP-1 and HIF-1α/HRE of the glut3 gene. Collectively, these processes can facilitate an adaptive response to hypoxic energy depletion targeted at enhancing glucose transport and minimizing injury while fueling the proliferative potential of neuroblasts.

Temporal and spatial distribution of murine placental and brain GLUT3-luciferase transgene as a readout of in vivo transcription

To investigate in vivo transcription of the facilitative glucose transporter isoform-GLUT3 gene, we created GLUT3-firefly luciferase transgenic mouse lines that demonstrate tissue-specific [adult: brain > testis ≥ skeletal muscle > placenta; postnatal (PN): skeletal muscle > brain = skin], temporal, and spatial distribution of the reporter gene/enzyme activity that is unique from endogenous GLUT3 mRNA/protein. In this mouse model, luciferase expression/activity serving as a readout of in vivo transcription peaked at 12 days gestation along with proliferating cell nuclear antigen (cell replication) in placenta and embryonic brain preceding peak GLUT3 protein expression at 18-19 days gestation. In contrast, a postnatal increase in brain luciferase mRNA peaked with endogenous GLUT3 mRNA, but after that of NeuroD6 protein (neurogenesis) at PN7. Luciferase activity paralleled GLUT3 protein expression with Na(+)-K(+)-ATPase (membrane expansion) and synaptophysin (synaptogenesis) proteins, peaking at PN14 and lasting until 60 days in the adult. Thus GLUT3 transcription in placenta and embryonic brain coincided with cell proliferation and in postnatal brain with synaptogenesis. Longitudinal noninvasive bioluminescence (BLI) monitoring of in vivo brain GLUT3 transcription reflected cross-sectional ex vivo brain luciferase activity only between PN7 and PN21. Hypoxia/reoxygenation at PN7 revealed transcriptional increase in brain GLUT3 expression reflected by in vivo BLI and ex vivo luciferase activity. These observations collectively support a temporal contribution by transcription toward ensuring adequate tissue-specific, developmental (placenta and embryonic brain), and postnatal hypoxic brain GLUT3 expression.

The neuroprotective effect of acute moderate alcohol consumption on caspase-3 mediated neuroapoptosis in traumatic brain injury: the role of lysosomal cathepsin L and nitric oxide

Our aim in this study was to investigate the effect of moderate acute alcohol administration on cysteine protease mediated neuronal apoptosis and nitric oxide production in the traumatic brain injury. A total of 29 adult Sprague-Dawley male rats weighing 250-300 g were used. The rats were allocated into four groups. The first group was the control (sham-operated) group in which only a craniotomy was performed, the others were alcohol, trauma and trauma+alcohol groups. Caspase-3 enzyme activity in the trauma group increased significantly in comparison with the control group. The alcohol given group showed a decreased caspase-3 enzyme activity compared to the trauma group. The level of caspase-3 enzyme activity in the alcohol+trauma group decreased in comparison to the trauma group. SF/FEL ratio of cathepsin-L enzyme activity in the trauma group was significantly higher than in the control group. Our results indicate that moderate alcohol consumption may have protective effects on apoptotic cell death after traumatic brain injury. Protective effects of moderate ethanol consumption might be related to inhibition of lysosomal protease release and nitric oxide production.

Superimposition of postnatal calorie restriction protects the aging male intrauterine growth- restricted offspring from metabolic maladaptations

Intrauterine growth restriction (IUGR) results in dysregulated glucose homeostasis and adiposity in the adult. We hypothesized that with aging, these perturbations will wane, and superimposition of postnatal growth restriction (PNGR) on IUGR [intrauterine and postnatal growth restriction (IPGR)] will reverse the residual IUGR phenotype. We therefore undertook hyperinsulinemic-euglycemic clamp, energy balance, and physical activity studies during fed, fasted, and refed states, in light and dark cycles, on postweaned chow diet-fed more than 17-month aging male IUGR, PNGR, and IPGR vs. control (CON) rat offspring. Hyperinsulinemic-euglycemic clamp revealed similar whole-body insulin sensitivity and physical activity in the nonobese IUGR vs. CON, despite reduced heat production and energy expenditure. Compared with CON and IUGR, IPGR mimicking PNGR was lean and growth restricted with increased physical activity, O(2) consumption (VO(2)), energy intake, and expenditure. Although insulin sensitivity was no different in IPGR and PNGR, skeletal muscle insulin-induced glucose uptake was enhanced. This presentation proved protective against the chronologically earlier (5.5 months) development of obesity and dysregulated energy homeostasis after 19 wk on a postweaned high-fat diet. This protective role of PNGR on the metabolic IUGR phenotype needs future fine tuning aimed at minimizing unintended consequences.

Changes of positron emission tomography in newborn infants at different gestational ages, and neonatal hypoxic-ischemic encephalopathy

Cerebral glucose metabolism was measured by (18)F-fluorodeoxyglucose position emission tomography in infants at different gestational ages and with neonatal hypoxic-ischemic encephalopathy. Thirty-six preterm and term infants at different gestational ages without brain injury were divided into four subgroups: ≤32 weeks (n = 4), 33-34 weeks (n = 5), 35-36 weeks (n = 12), and ≥37 weeks (n = 15). Twenty-four newborn infants with hypoxic-ischemic encephalopathy were divided into three subgroups: mild (n = 13), moderate (n = 7), and severe (n = 4). Cerebral glucose metabolism manifested a trend toward increase, and the structure of cranial (18)F-fluorodeoxyglucose positron emission tomography images became clear with increased gestational age, especially at ≥37 weeks. Uptakes of (18)F-fluorodeoxyglucose in the ≥37-week group were significantly higher than in the ≤32-week group (P < 0.01). Cerebral glucose metabolism changed significantly in neonatal hypoxic-ischemic encephalopathy, and was either unbalanced bilaterally or relatively low at all sites. Moreover, uptakes of (18)F-fluorodeoxyglucose were significantly lower in severe than in mild and medium hypoxic-ischemic encephalopathy (P < 0.05). Cerebral glucose metabolism, as measured by (18)F-fluorodeoxyglucose positron emission tomography, may prove useful for estimating brain development and injury in newborn infants, and its clinical values need further investigation.

Hypoxic-ischemic brain injury exacerbates neuronal apoptosis and precipitates spontaneous seizures in glucose transporter isoform 3 heterozygous null mice

We examined the effects of 45-min hypoxia (FiO(2) 0.08; Hx) vs. normoxia (FiO(2) 0.21; Nx) on the ipsilateral (Ipsi) and contralateral (Ctrl) sides of the brain in neuronal glucose transporter isoform 3 (Glut3) heterozygous null mice (glut3(+/-)) and their wild-type littermates (WT), undergoing unilateral carotid artery ligation. Glut3(+/-) mice, under Nx, demonstrated a compensatory increase in blood-brain barrier/glial Glut1 protein concentration and a concomitant increase in neuronal nitric oxide synthase (nNOS) enzyme activity and Bax protein, with a decrease in procaspase 3 protein (P < 0.05 each). After Hx, reoxygenation in FiO(2) of 0.21 led to no comparable adaptive up-regulation of the ipsilateral brain Glut3 or Glut1 protein at 4 hr and Glut1 at 24 hr in glut3(+/-) vs. WT. These brain Glut changes in glut3(+/-) but not WT mice were associated with an increase in proapoptotic Bax protein and caspase-3 enzyme activity (P < 0.01 each) and a decline in the antiapoptotic Bcl-2 and procaspase-3 proteins (P < 0.05 each). Glut3(+/-) mice after Hx demonstrated TUNEL-positive neurons with nuclear pyknosis in most ipsilateral (hypoxic-ischemia) brain regions. A subset (∼55%) of glut3(+/-) mice developed spontaneous seizures after hypoxic-ischemia, confirmed by electroencephalography, but the WT mice remained seizure-free. Pentylenetetrazole testing demonstrated an increased occurrence of longer lasting clinical seizures at a lower threshold in glut3(+/-) vs. WT mice, with no detectable differences in monamine neurotransmitters. We conclude that hypoxic-ischemic brain injury in glut3(+/-) mice exacerbates cellular apoptosis and necrosis and precipitates spontaneous seizures.

Increased expression of glucose transporter 3 in gerbil brains following magnesium sulfate treatment and focal cerebral ischemic injury

Glucose is the primary energy substrate for neurons. Glucose transporter 3 (Glut3) localizes at the neuronal cellular membrane, which transports glucose from the extracelluar space into neurons. Ischemia results in an increased energy demand that is associated with profound changes in brain energy metabolism. Magnesium sulfate (MgSO(4)) ameliorates ischemia-induced neuronal death in the rat and gerbil model. We investigated the effects of MgSO(4) administration on the expression of Glut3 in cortex and hippocampus of gerbils during ischemia. The focal cerebral ischemia was produced by unilateral occlusion of the right common carotid artery and right middle cerebral artery. Following ischemia, Glut3 expression increased significantly versus non-ischemic (contra-lateral) cortex and hippocampus. MgSO(4) treatment significantly increased the level of Glut3 expression in the non-ischemic and ischemic cortex and hippocampus. We found that the MgSO(4)-induced increase in Glut3 expression was not reversed by administration of U0126, a MEK kinase inhibitor. These results suggest that other factors may function to modulate the MgSO(4)-induced Glut3 response. In all, our data showed that MgSO(4) increases the expression of Glut3 in the cortex and hippocampus of gerbil brains both in non-ischemia and ischemia status. However, the MEK signaling pathway might not be involved in MgSO(4)-induced Glut3 expression following focal ischemia.

Enhanced expression of the sweet taste receptors and alpha-gustducin in reactive astrocytes of the rat hippocampus following ischemic injury

The heterodimeric sweet taste receptors, T1R2 and T1R3, have recently been proposed to be associated with the brain glucose sensor. To identify whether sweet taste signaling is regulated in response to an ischemic injury inducing acute impairment of glucose metabolism, we investigated the spatiotemporal expression of the sweet taste receptors and their associated taste-specific G-protein α-gustducin in the rat hippocampus after ischemia. The expression profiles of both receptor subunits and α-gustducin shared overlapping expression patterns in sham-operated and ischemic hippocampi. Constitutive expression of both receptors and α-gustducin was localized in neurons of the pyramidal cell and granule cell layers, but their upregulation was detected in reactive astrocytes in ischemic hippocampi. Immunoblot analysis confirmed the immmunohistochemically determined temporal patterns of sweet-taste signaling proteins. These results suggest that the expression of sweet taste signaling proteins in astrocytes might be regulated in response to altered extracellular levels of glucose following an ischemic insult.

Neuronal glucose transporter isoform 3 deficient mice demonstrate features of autism spectrum disorders

Neuronal glucose transporter (GLUT) isoform 3 deficiency in null heterozygous mice led to abnormal spatial learning and working memory but normal acquisition and retrieval during contextual conditioning, abnormal cognitive flexibility with intact gross motor ability, electroencephalographic seizures, perturbed social behavior with reduced vocalization and stereotypies at low frequency. This phenotypic expression is unique as it combines the neurobehavioral with the epileptiform characteristics of autism spectrum disorders. This clinical presentation occurred despite metabolic adaptations consisting of an increase in microvascular/glial GLUT1, neuronal GLUT8 and monocarboxylate transporter isoform 2 concentrations, with minimal to no change in brain glucose uptake but an increase in lactate uptake. Neuron-specific glucose deficiency has a negative impact on neurodevelopment interfering with functional competence. This is the first description of GLUT3 deficiency that forms a possible novel genetic mechanism for pervasive developmental disorders, such as the neuropsychiatric autism spectrum disorders, requiring further investigation in humans.

Neuroprotective role of lactate after cerebral ischemia

It is well established that lactate can be used as an energy substrate by the brain by conversion to pyruvate and a subsequent oxidation in the mitochondria. Knowing the need for readily metabolizable substrates directly after ischemia and the protective effect of lactate after excitotoxicity, the aim of this study was to investigate whether lactate administration directly after ischemia could be neuroprotective. In vitro, the addition of 4 mmol/L L-lactate to the medium of rat organotypic hippocampal slices, directly after oxygen and glucose deprivation (OGD), protected against neuronal death, whereas a higher dose of 20 mmol/L was toxic. In vivo, after middle cerebral artery occlusion in the mouse, an intracerebroventricular injection of 2 microL of 100 mmol/L L-lactate, immediately after reperfusion, led to a significant decrease in lesion size, which was more pronounced in the striatum, and an improvement in neurologic outcome. A later injection 1 h after reperfusion did not reduce lesion size, but significantly improved neurologic outcome, which is an important point in the context of a potential clinical application. Therefore, a moderate increase in lactate after ischemia may be a therapeutic tool.

A novel class of prolyl hydroxylase inhibitors induces angiogenesis and exerts organ protection against ischemia

OBJECTIVE

Hypoxia inducible factor (HIF) plays a pivotal role in the adaptation to ischemic conditions. Its activity is modulated by an oxygen-dependent hydroxylation of proline residues by prolyl hydroxylases (PHD).

METHODS AND RESULTS

We discovered 2 unique compounds (TM6008 and TM6089), which inhibited PHD and stabilized HIF activity in vitro. Our docking simulation studies based on the 3-dimensional structure of human PHD2 disclosed that they preferentially bind to the active site of PHD. Whereas PHD inhibitors previously reported inhibit PHD activity via iron chelation, TM6089 does not share an iron chelating motif and is devoid of iron chelating activity. In vitro Matrigel assays and in vivo sponge assays demonstrated enhancement of angiogenesis by local administration of TM6008 and TM6089. Their oral administration stimulated HIF activity in various organs of transgenic rats expressing a hypoxia-responsive reporter vector. No acute toxicity was observed up to 2 weeks after a single oral dose of 2000 mg/kg for TM6008. Oral administration of TM6008 protected neurons in a model of cerebrovascular disease. The protection was associated with amelioration of apoptosis but independent of enhanced angiogenesis.

CONCLUSIONS

The present study uncovered beneficial effects of novel PHD inhibitors preferentially binding to the active site of PHD.

Prostaglandin transporter expression in mouse brain during development and in response to hypoxia

Prostaglandins (PGs) are bioactive lipid mediators released following brain hypoxic-ischemic injury. Clearance and re-uptake of these prostaglandins occur via a transmembrane prostaglandin transporter (PGT), which exchanges PG for lactate. We used Western blot analyses to examine the PGT developmental profile and its regional distribution as well as changes in transporter expression during chronic hypoxia in the neonatal mouse brain. Microsomal preparations from four brain regions (cortex, hippocampus, cerebellum and brainstem/diencephalon) showed gradual increases in prostaglandin transporter expression in all brain regions examined from postnatal day 1 till day 30. There was a significant regional heterogeneity in the prostaglandin transporter expression with highest expression in the cortex, followed by cerebellum and hippocampus, and least expressed in the brainstem/diencephalon. To further delineate the pattern of prostaglandin transporter expression, separate astrocytic and neuronal microsomal preparations were also examined. In contrast to neurons, which had a robust expression of prostaglandin transporters, astrocytes had very little PGT expression under basal conditions. In response to chronic hypoxia, there was a significant decline in PGT expression in vivo and in neurons in vitro, whereas cultured astrocytes increased their PGT expression. This is the first report on PGT expression in the CNS and our studies suggest that PGTs have 1) a widespread distribution in the CNS; 2) a gradual increase and a differential expression in various regions during brain development; and 3) striking contrast in expression between glia and neurons, especially in response to hypoxia. Since PGTs play a role as prostaglandin-lactate exchangers, we hypothesize that PGTs are important in the CNS during stress such as hypoxia.

Down-regulation of Phospholipase D2 mRNA in Neonatal Rat Brainstem and Cerebellum after Hypoxia-Ischemia

Phospholipase D (PLD) and phosphatidylcholine (PC) were implicated in apoptosis and cancer. However, direct evidence on the role of PLD in the cause of apoptosis remains obscure. It was recently reported that apoptosis and necrosis could be induced in the cerebellum and brainstem after focal cerebral hypoxic-ischemic (HI) injury. It was found that apoptosis could be enhanced by farnesol inhibition of PLD signal transduction. Whereas it was shown that highly invasive cancer cell line depends on PLD activity for survival when deprived of serum growth factors. Based on these reports, it is postulated that apoptosis in the cerebellum and brainstem induced after focal cerebral HI treatment may be caused by faulty PLD expression. This is consistent with a report that PLD1 activity and mRNA levels were down-regulated during apoptosis. To test this hypothesis, Northern blotting was used to examine PLD2 mRNA expression after focal cerebral HI. The results show that both PLD2 mRNA 10.8 and 3.9 kb transcripts were significantly decreased by as much as 37% in the brainstem and cerebellum areas 3 h after HI compared to the control, concur with previous report of decreasing PLD activity after ischemia. These PLD2 transcripts, however, were not significantly different from the control 3 days after HI, indicating that the decrease in PLD2 transcription after HI maybe a transient phenomenon. This is the first report to show that the loss of membrane integrity resulting from deprivation of energy and growth factors after HI could cause decrease in PLD2 transcription that promotes apoptosis. The hypothetic role of PLD2 and the mechanism leading to apoptosis remains to be further elucidated.

Induction of Monocarboxylate Transporter 2 Expression and Ketone Transport following Traumatic Brain Injury in Juvenile and Adult Rats

Based on recent work demonstrating age-dependent ketogenic neuroprotection after traumatic brain injury (TBI), it was hypothesized that the neuroprotection among early post-weaned animals was related to induced cerebral transport of ketones after injury. Regional changes in monocarboxylate transporter 2 (MCT2) were acutely examined with immunohistochemistry after sham surgery or controlled cortical impact injury among postnatal day 35 and adult rats. Both ages showed elevated MCT2 expression in the ipsilateral cerebral vasculature after TBI. Using Western blotting, MCT2 expression was 80-88% greater in microvessels isolated from postnatal day 35 rats at all time points relative to adults. The increased MCT2 expression was temporally correlated with an age-related increase in cerebral uptake of ketones, when ketones were made available after injury.

Erythropoietin Downregulates Bax and DP5 ProApoptotic Gene Expression in Neonatal Hypoxic-Ischemic Brain Injury

BACKGROUND

Perinatal asphyxia is an important cause of neonatal mortality and subsequent serious sequelae such as motor and cognitive deficits and seizures. The ameliorative effect of erythropoietin (Epo) on experimental hypoxic-ischemic brain injury in neonatal rats has been recently reported. Recent studies also confirm the antiapoptotic effect of Epo in a variety of in vitro and in vivo neuronal injury models including hypoxic-ischemic brain injury. However, molecular mechanisms of Epo protection and antiapoptotic effect in this model are unclear. Epo may exert its antiapoptotic effect via the differential regulation of the expression of genes involved in the apoptotic process.

OBJECTIVES

Thus, in the present study, we studied the effects of systemically administered Epo on antiapoptotic (bcl-2, bcl-XL), proapoptotic (bax and DP5) gene expression following hypoxic-ischemic brain injury in neonatal rats.

METHODS

Seven- day-old Wistar rat pups were divided into three groups: control group (n=15), saline-treated group (n=17), and Epo-treated group (n=18). Rat pups were subjected to left carotid artery occlusion followed by 2.5 h of hypoxic exposure. Epo-treated group received an intraperitoneal injection of recombinant human Epo at a dose of 1,000 units/kg, saline-treated group received an intraperitoneal injection of saline at the same volume of Epo. Forty-eight hours after hypoxia, 3 animals in each group were killed for histopathological evaluation. To detect DNA fragmentation in cell nuclei, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling reaction was applied. Bcl-2 and bax protein expression were also analyzed with immunohistochemistry. For reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, rats were sacrificed 4, 12, and 24 h after hypoxia. Bcl-2, bcl-XL, bax, and DP5 mRNA expression were analyzed by RT-PCR.

RESULTS

Epo significantly prevented hypoxia-ischemia-induced bax and DP5 mRNA upregulation in brain tissue. Epo did not show any effect on bcl-XL transcription altered by injury. However, Epo reversed injury-induced downregulation in bcl-2 transcription. Modulating effects of Epo on bcl-2 and bax protein expression were also revealed by immunohistochemistry.

CONCLUSIONS

These results suggest that Epo exerts a neuroprotective effect against hypoxic-ischemic brain injury, at least partially, via the differential regulation of the expression of genes involved in apoptotic process.

Intensive insulin therapy reduces microdialysis glucose values without altering glucose utilization or improving the lactate/pyruvate ratio after traumatic brain injury*

OBJECTIVE

To determine that intensive glycemic control does not reduce microdialysis glucose concentration brain metabolism of glucose.

DESIGN

Prospective monitoring followed by retrospective data analysis of cerebral microdialysis and global brain metabolism.

SETTING

Single center, academic neurointensive care unit.

PATIENTS

Forty-seven moderate to severe traumatic brain injury patients.

INTERVENTIONS

A nonrandomized, consecutive design was used for glycemic control with loose insulin (n=33) for the initial 2 yrs or intensive insulin therapy (n=14) for the last year.

MEASUREMENTS AND MAIN RESULTS

In 14 patients treated with intensive insulin therapy, there was a reduction in microdialysis glucose by 70% of baseline concentration compared with a 15% reduction in 33 patients treated with a loose insulin protocol. Despite this reduction in microdialysis glucose, the global metabolic rate of glucose did not change. However, intensive insulin therapy was associated with increased incidence of microdialysis markers of cellular distress, namely elevated glutamate (38+/-37% vs. 10+/-17%, p<.01), elevated lactate/pyruvate ratio (38+/-37% vs. 19+/-26%, p<.03) and low glucose (26+/-17% vs. 11+/-15%, p<.05, and increased global oxygen extraction fraction. Mortality was similar in the intensive and loose insulin treatment groups (14% vs. 15%, p=.9), as was 6-month clinical outcome (p=.3).

CONCLUSIONS

Intensive insulin therapy results in a net reduction in microdialysis glucose and an increase in microdialysis glutamate and lactate/pyruvate without conveying a functional outcome advantage.

Glucose transport to the brain: a systems model

Glucose transport to the brain involves sophisticated interactions of solutes, transporters, enzymes, and cell signaling processes, within an intricate spatial architecture. The dynamics of the transport are influenced by the adaptive nature of the blood-brain barrier (BBB), the semi-impermeable membranes of brain capillaries. As both the gate and the gatekeeper between blood-borne nutrients and brain tissue, the BBB helps govern brain homeostasis. Glucose in the blood must cross the BBB's luminal and abluminal membranes to reach neural tissue. A robust representation of the glucose transport mechanism can highlight a target for brain therapeutic intervention, help characterize mechanisms behind several disease phenotypes, or suggest a new delivery route for drugs. The challenge for researchers is understanding the relationships between influential physiological variables in vivo, and using that knowledge to predict how alterations or interventions affect glucose transport. This paper reviews factors influencing glucose transport and approaches to representing blood-to-brain glucose transport including in vitro, in vivo, and kinetic models. Applications for different models are highlighted, while their limitations in answering arising questions about the human in vivo BBB lead to a discussion of an alternate approach. A developing complex systems simulation is introduced, initiating a single platform to represent the dynamics of glucose transport across the adapting human blood-brain barrier.

Mechanisms of hypoxic-ischemic injury in the term infant

The pathogenesis of hypoxic-ischemic brain injury in the term infant is multifactorial and complex. Over the past decade the investigative emphasis has turned to cellular and molecular mechanisms of injury, and it has been increasingly recognized that the neonatal brain differs vastly from the adult brain in terms of response to hypoxia-ischemia. This review will discuss the initiation and evolution of brain injury in the term neonate, and the inherent biochemical and physiologic qualities of the neonatal brain that make its response to hypoxia-ischemia unique. Attention will be given to specific areas of investigation including excitotoxicity, oxidative stress, and inflammation. The coalescence of these entities to a final common pathway of hypoxic-ischemic brain injury will be emphasized.

Pyruvate kinase activity in cerebral hemispheres and cerebellum-brainstem of normal and hypoxic-ischemic newborn rats

Energy metabolism is affected in hypoxia-ischemia. Changes in the tissue concentrations of the high-energy phosphate reserves occur early during the course of the metabolic insult and with concurrent increases in cellular ADP and AMP leading glycolysis. It has been shown that enzymes of glycolysis tend to be regulated in hypoxia and ischemia. In this study we determined pyruvate kinase (PK) activity, one of the main enzymes in glycolysis, in brain tissues of healthy (n = 15) and hypoxic-ischemic (n = 18) 7-day-old newborn rats. Left common carotid artery was ligated in the hypoxic-ischemic group and after 2 hours rats were exposed to hypoxia in a chamber at 34-36 degrees C with 8% oxygen in nitrogen. The rats were decapitated after 2 hours of hypoxia and right and left cerebral hemispheres (CH) and cerebellum-brain stem (C-BS) were removed. Pyruvate kinase activity was significantly higher in C-BSs than CHs in both groups (p < 0.00005). There was no significant difference in enzyme activities of either CHs or C-BS of hypoxic-ischemic group compared to control healthy group (p > 0.05). In conclusion, brain pyruvate kinase activity did not change in hypoxia-ischemia and suggests that PK of brain differs from other tissues where it usually increases in hypoxiaischemia.