Pretreatment with Resveratrol Prevents Neuronal Injury and Cognitive Deficits Induced by Perinatal Hypoxia-Ischemia in Rats

Despite advances in neonatal care, hypoxic-ischemic brain injury is still a serious clinical problem, which is responsible for many cases of perinatal mortality, cerebral palsy, motor impairment and cognitive deficits. Resveratrol, a natural polyphenol with important anti-oxidant and anti-inflammatory properties, is present in grapevines, peanuts and pomegranates. The aim of the present work was to evaluate the possible neuroprotective effect of resveratrol when administered before or immediately after a hypoxic-ischemic brain event in neonatal rats by analyzing brain damage, the mitochondrial status and long-term cognitive impairment. Our results indicate that pretreatment with resveratrol protects against brain damage, reducing infarct volume, preserving myelination and minimizing the astroglial reactive response. Moreover its neuroprotective effect was found to be long lasting, as behavioral outcomes were significantly improved at adulthood. We speculate that one of the mechanisms for this neuroprotection may be related to the maintenance of the mitochondrial inner membrane integrity and potential, and to the reduction of reactive oxygen species. Curiously, none of these protective features was observed when resveratrol was administered immediately after hypoxia-ischemia.

Oxidative stress : emerging mitochondrial and cellular themes and variations in neuronal injury

Oxidative stress plays a central role in neuronal injury and cell death in acute and chronic pathological conditions. The cellular responses to oxidative stress embrace changes in mitochondria and other organelles, notably endoplasmic reticulum, and can lead to a number of cell death paradigms, which cover a spectrum from apoptosis to necrosis and include autophagy. In Alzheimer's disease, and other pathologies including Parkinson's disease, protein aggregation provides further cellular stresses that can initiate or feed into the pathways to cell death engendered by oxidative stress. Specific attention is paid here to mitochondrial dysfunction and programmed cell death, and the diverse modes of cell death mediated by mitochondria under oxidative stress. Novel insights into cellular responses to neuronal oxidative stress from a range of different stressors can be gained by detailed transcriptomics analyses. Such studies at the cellular level provide the key for understanding the molecular and cellular pathways whereby neurons respond to oxidative stress and undergo injury and death. These considerations underpin the development of detailed knowledge in more complex integrated systems, up to the intact human bearing the neuropathology, facilitating therapeutic advances.

Multifaceted role of nitric oxide in an in vitro mouse neuronal injury model: transcriptomic profiling defines the temporal recruitment of death signalling cascades

Nitric oxide is implicated in the pathogenesis of various neuropathologies characterized by oxidative stress. Although nitric oxide has been reported to be involved in the exacerbation of oxidative stress observed in several neuropathologies, existent data fail to provide a holistic description of how nitrergic pathobiology elicits neuronal injury. Here we provide a comprehensive description of mechanisms contributing to nitric oxide induced neuronal injury by global transcriptomic profiling. Microarray analyses were undertaken on RNA from murine primary cortical neurons treated with the nitric oxide generator DETA-NONOate (NOC-18, 0.5 mM) for 8–24 hrs. Biological pathway analysis focused upon 3672 gene probes which demonstrated at least a ±1.5-fold expression in a minimum of one out of three time-points and passed statistical analysis (one-way anova, P < 0.05). Numerous enriched processes potentially determining nitric oxide mediated neuronal injury were identified from the transcriptomic profile: cell death, developmental growth and survival, cell cycle, calcium ion homeostasis, endoplasmic reticulum stress, oxidative stress, mitochondrial homeostasis, ubiquitin-mediated proteolysis, and GSH and nitric oxide metabolism. Our detailed time-course study of nitric oxide induced neuronal injury allowed us to provide the first time a holistic description of the temporal sequence of cellular events contributing to nitrergic injury. These data form a foundation for the development of screening platforms and define targets for intervention in nitric oxide neuropathologies where nitric oxide mediated injury is causative.

Comparative microarray analysis identifies commonalities in neuronal injury: evidence for oxidative stress, dysfunction of calcium signalling, and inhibition of autophagy-lysosomal pathway

Mitochondrial dysfunction, ubiquitin-proteasomal system impairment and excitotoxicity occur during the injury and death of neurons in neurodegenerative conditions. The aim of this work was to elucidate the cellular mechanisms that are universally altered by these conditions. Through overlapping expression profiles of rotenone-, lactacystin- and N-methyl-D-aspartate-treated cortical neurons, we have identified three affected biological processes that are commonly affected; oxidative stress, dysfunction of calcium signalling and inhibition of the autophagic-lysosomal pathway. These data provides many opportunities for therapeutic intervention in neurodegenerative conditions, where mitochondrial dysfunction, proteasomal inhibition and excitotoxicity are evident.

Reactive oxygen intermediates contribute to necrotic and apoptotic neuronal injury in an infant rat model of bacterial meningitis due to group B streptococci.

Reactive oxygen intermediates (ROI) contribute to neuronal injury in cerebral ischemia and trauma. In this study we explored the role of ROI in bacterial meningitis. Meningitis caused by group B streptococci in infant rats led to two distinct forms of neuronal injury, areas of necrosis in the cortex and neuronal loss in the dentate gyrus of the hippocampus, the latter showing evidence for apoptosis. Staining of brain sections with diaminobenzidine after perfusion with manganese buffer and measurement of lipid peroxidation products in brain homogenates both provided evidence that meningitis led to the generation of ROI. Treatment with the radical scavenger alpha-phenyl-tert-butyl nitrone (PBN) (100 mg/kg q8h i.p.) beginning at the time of infection completely abolished ROI detection and the increase in lipidperoxidation. Cerebral cortical perfusion was reduced in animals with meningitis to 37.5+/-21.0% of uninfected controls (P < 0.05), and PBN restored cortical perfusion to 72.0+/-8.1% of controls (P < 0.05 vs meningitis). PBN also completely prevented neuronal injury in the cortex and hippocampus, when started at the time of infection (P < 0.02), and significantly reduced both forms of injury, when started 18 h after infection together with antibiotics (P < 0.004 for cortex and P < 0.001 for hippocampus). These data indicate that the generation of ROI is a major contributor to cerebral ischemia and necrotic and apoptotic neuronal injury in this model of neonatal meningitis.

Bok Is Not Pro-Apoptotic But Suppresses Poly ADP-Ribose Polymerase-Dependent Cell Death Pathways and Protects against Excitotoxic and Seizure-Induced Neuronal Injury.

UNLABELLED Bok (Bcl-2-related ovarian killer) is a Bcl-2 family member that, because of its predicted structural homology to Bax and Bak, has been proposed to be a pro-apoptotic protein. In this study, we demonstrate that Bok is highly expressed in neurons of the mouse brain but thatbokwas not required for staurosporine-, proteasome inhibition-, or excitotoxicity-induced apoptosis of cultured cortical neurons. On the contrary, we found thatbok-deficient neurons were more sensitive to oxygen/glucose deprivation-induced injuryin vitroand seizure-induced neuronal injuryin vivo Deletion ofbokalso increased staurosporine-, excitotoxicity-, and oxygen/glucose deprivation-induced cell death inbax-deficient neurons. Single-cell imaging demonstrated thatbok-deficient neurons failed to maintain their neuronal Ca(2+)homeostasis in response to an excitotoxic stimulus; this was accompanied by a prolonged deregulation of mitochondrial bioenergetics.bokdeficiency led to a specific reduction in neuronal Mcl-1 protein levels, and deregulation of both mitochondrial bioenergetics and Ca(2+)homeostasis was rescued by Mcl-1 overexpression. Detailed analysis of cell death pathways demonstrated the activation of poly ADP-ribose polymerase-dependent cell death inbok-deficient neurons. Collectively, our data demonstrate that Bok acts as a neuroprotective factor rather than a pro-death effector during Ca(2+)- and seizure-induced neuronal injuryin vitroandin vivo SIGNIFICANCE STATEMENT Bcl-2 proteins are essential regulators of the mitochondrial apoptosis pathway. The Bcl-2 protein Bok is highly expressed in the CNS. Because of its sequence similarity to Bax and Bak, Bok has long been considered part of the pro-apoptotic Bax-like subfamily, but no studies have yet been performed in neurons to test this hypothesis. Our study provides important new insights into the functional role of Bok during neuronal apoptosis and specifically in the setting of Ca(2+)- and seizure-mediated neuronal injury. We show that Bok controls neuronal Ca(2+)homeostasis and bioenergetics and, contrary to previous assumptions, exerts neuroprotective activitiesin vitroandin vivo Our results demonstrate that Bok cannot be placed unambiguously into the Bax-like Bcl-2 subfamily of pro-apoptotic proteins.

Heparin-binding growth-associated molecule (HB-GAM) in activity-dependent neuronal plasticity in hippocampus

Cell adhesion and extracellular matrix (ECM) molecules play a significant role in neuronal plasticity both during development and in the adult. Plastic changes in which ECM components are implicated may underlie important nervous system functions, such as memory formation and learning. Heparin-binding growthassociated molecule (HB-GAM, also known as pleiotrophin), is an ECM protein involved in neurite outgrowth, axonal guidance and synaptogenesis during perinatal period. In the adult brain HB-GAM expression is restricted to the regions which display pronounced synaptic plasticity (e.g., hippocampal CA3-CA1 areas, cerebral cortex laminae II-IV, olfactory bulb). Expression of HB-GAM is regulated in an activity-dependent manner and is also induced in response to neuronal injury. In this work mutant mice were used to study the in vivo function of HB-GAM and its receptor syndecan-3 in hippocampal synaptic plasticity and in hippocampus-dependent behavioral tasks. Phenotypic analysis of HBGAM null mutants and mice overexpressing HB-GAM revealed that opposite genetic manipulations result in reverse changes in synaptic plasticity as well as behavior in the mutants. Electrophysiological recordings showed that mice lacking HB-GAM have an increased level of long-term potentiation (LTP) in the area CA1 of hippocampus and impaired spatial learning, whereas animals with enhanced level of HB-GAM expression have attenuated LTP, but outperformed their wild-type controls in spatial learning. It was also found that GABA(A) receptor-mediated synaptic transmission is altered in the transgenic mice overexpressing HB-GAM. The results suggest that these animals have accentuated hippocampal GABAergic inhibition, which may contribute to the altered glutamatergic synaptic plasticity. Structural studies of HB-GAM demonstrated that this protein belongs to the thrombospondin type I repeat (TSR) superfamily and contains two β-sheet domains connected by a flexible linker. It was found that didomain structure is necessary for biological activity of HB-GAM and electrophysiological phenotype displayed by the HB-GAM mutants. The individual domains displayed weaker binding to heparan sulfate and failed to promote neurite outgrowth as well as affect hippocampal LTP. Effects of HB-GAM on hippocampal synaptic plasticity are believed to be mediated by one of its (co-)receptor molecules, namely syndecan-3. In support of that, HB-GAM did not attenuate LTP in mice deficient in syndecan-3 as it did in wild-type controls. In addition, syndecan-3 knockout mice displayed electrophysiological and behavioral phenotype similar to that of HB-GAM knockouts (i.e. enhanced LTP and impaired learning in Morris water-maze). Thus HB-GAM and syndecan-3 are important modulators of synaptic plasticity in hippocampus and play a role in regulation of learning-related behavior.

Perinatal hipoxic ischemic injury in the auditory pathway and the effect of several neuroprotective agents

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Donepezil attenuates hippocampal neuronal damage and cognitive deficits after global cerebral ischemia in gerbils.

Decreased cerebral blood flow causes cognitive impairments and neuronal injury in vascular dementia. In the present study, we reported that donepezil, a cholinesterase inhibitor, improved transient global cerebral ischemia-induced spatial memory impairment in gerbils. Treatment with 5mg/kg of donepezil for 21 consecutive days following a 10-min period of ischemia significantly inhibited delayed neuronal death in the hippocampal CA1 region. In Morris water maze test, memory impairment was significantly improved by donepezil treatment. Western blot analysis showed that donepezil treatment prevented reductions in p-CaMKII and p-CREB protein levels in the hippocampus. These results suggest that donepezil attenuates the memory deficit induced by transient global cerebral ischemia and this neuroprotection may be associated with the phosphorylation of CaMKII and CERB in the hippocampus.

Champagne wine polyphenols protect primary cortical neurons against peroxynitrite-induced injury

White wines are generally low in polyphenol content as compared to red wines. However, Champagne wines have been shown to contain relatively high amounts of phenolic acids that may exert protective cellular actions in vivo. In this study, we have investigated the potential neuroprotective effects of Champagne wine extracts, and individual phenolics present in these extracts, against peroxynitrite-induced injury. Organic and aqueous Champagne wine extracts exhibited potent neuroprotective activity against peroxynitrite-induced injury at low concentrations (0.1 mu g/mL). This protection appeared to be in part due to the cellular actions of individual components found in the organic extracts, notably tyrosol, caffeic acid, and gallic acid. These phenolics were observed to exert potent neuroprotection at concentrations between 0.1 and 10 mu M. Together, these data suggest that polyphenols present in Champagne wine may induce a neuroprotective effect against oxidative neuronal injury.

Multiple pathways of neuroprotection against oxidative stress and excitotoxic injury in immature primary hippocampal neurons

In the immature brain hydrogen peroxide accumulates after excitotoxic hypoxia-ischemia and is neurotoxic. Immature hippocampal neurons were exposed to N-methyl-D-aspartate (NMDA), a glutamate agonist, and hydrogen peroxide (H(2)O(2)) and the effects of free radical scavenging and transition metal chelation on neurotoxicity were studied. alpha-Phenyl-N-tert.-butylnitrone (PBN), a known superoxide scavenger, attenuated both H(2)O(2) and NMDA mediated toxicity. Treatment with desferrioxamine (DFX), an iron chelator, at the time of exposure to H(2)O(2) was ineffective, but pretreatment was protective. DFX also protected against NMDA toxicity. TPEN, a metal chelator with higher affinities for a broad spectrum of transition metal ions, also protected against H(2)O(2) toxicity but was ineffective against NMDA induced toxicity. These data suggest that during exposure to free radical and glutamate agonists, the presence of iron and other free metal ions contribute to neuronal cell death. In the immature nervous system this neuronal injury can be attenuated by free radical scavengers and metal chelators.

Brain injury in experimental neonatal meningitis due to group B streptococci

We have characterized the pattern of brain injury in a rat model of meningitis caused by group B streptococci (GBS). Infant rats (12-14 days old; n = 69) were infected intracisternally with 10 microliters of GBS (log10(2.3) to 4.5 colony-forming units). Twenty hours later, illness was assessed clinically and cerebrospinal fluid was cultured. Animals were either immediately euthanized for brain histopathology or treated with antibiotics and examined later. Early GBS meningitis was characterized clinically by severe obtundation and seizures, and histopathologically by acute inflammation in the subarachnoid space and ventricles, a vasculopathy characterized by vascular engorgement, and neuronal injury that was most prominent in the cortex and often followed a vascular pattern. Incidence of seizures, vasculopathy and neuronal injury correlated with the inoculum size (p < 0.01). Early injury was almost completely prevented by treatment with dexamethasone. Within days after meningitis, injured areas became well demarcated and showed new cellular infiltrates. Thirty days post-infection, brain weights of infected animals treated with antibiotics were decreased compared to uninfected controls (1.39 +/- 0.18 vs 1.64 +/- 0.1 g; p < 0.05). Thus, GBS meningitis in this model caused extensive cortical neuronal injury resembling severe neonatal meningitis in humans.

Mechanisms of brain injury in bacterial meningitis: workshop summary

Morbidity and mortality associated with bacterial meningitis remain high, although antibiotic therapy has improved during recent decades. The major intracranial complications of bacterial meningitis are cerebrovascular arterial and venous involvement, brain edema, and hydrocephalus with a subsequent increase of intracranial pressure. Experiments in animal models and cell culture systems have focused on the pathogenesis and pathophysiology of bacterial meningitis in an attempt to identify the bacterial and/or host factors responsible for brain injury during the course of infection. An international workshop entitled "Bacterial Meningitis: Mechanisms of Brain Injury" was organized by the Department of Neurology at the University of Munich and was held in Eibsee, Germany, in June 1993. This conference provided a forum for the exchange of current information on bacterial meningitis, including data on the clinical spectrum of complications, the associated morphological alterations, the role of soluble inflammatory mediators (in particular cytokines) and of leukocyte-endothelial cell interactions in tissue injury, and the molecular mechanisms of neuronal injury, with potential mediators such as reactive oxygen species, reactive nitrogen species, and excitatory amino acids. It is hoped that a better understanding of the pathophysiological events that take place during bacterial meningitis will lead to the development of new therapeutic regimens.

Brain-derived neurotrophic factor protects against multiple forms of brain injury in bacterial meningitis

BACKGROUND Brain-derived neurotrophic factor (BDNF) blocks activation of caspase-3, reduces translocation of apoptosis-inducing factor (AIF), attenuates excitotoxicity of glutamate, and increases antioxidant enzyme activities. The mechanisms of neuroprotection suggest that BDNF may be beneficial in bacterial meningitis. METHODS To assess a potentially beneficial effect of adjuvant treatment with BDNF in bacterial meningitis, 11-day-old infant rats with experimental meningitis due to Streptococcus pneumoniae or group B streptococci (GBS) were randomly assigned to receive intracisternal injections with either BDNF (3 mg/kg) or equal volumes (10 mu L) of saline. Twenty-two hours after infection, brains were analyzed, by histomorphometrical examination, for the extent of cortical and hippocampal neuronal injury. RESULTS Compared with treatment with saline, treatment with BDNF significantly reduced the extent of 3 distinct forms of brain cell injury in this disease model: cortical necrosis in meningitis due to GBS (median, 0.0% [range, 0.0%-33.7%] vs. 21.3% [range, 0.0%-55.3%]; P<.03), caspase-3-dependent cell death in meningitis due to S. pneumoniae (median score, 0.33 [range, 0.0-1.0] vs. 1.10 [0.10-1.56]; P<.05), and caspase-3-independent hippocampal cell death in meningitis due to GBS (median score, 0 [range, 0-2] vs. 0.88 [range, 0-3.25]; P<.02). The last form of injury was associated with nuclear translocation of AIF. CONCLUSION BDNF efficiently reduces multiple forms of neuronal injury in bacterial meningitis and may hold promise as adjunctive therapy for this disease.