Gene therapy with HSP72 is neuroprotective in rat models of stroke and epilepsy

NeuroD6 genomic signature bridging neuronal differentiation to survival via the molecular chaperone network

During neurogenesis, expression of the basic helix-loop-helix NeuroD6/Nex1/MATH-2 transcription factor parallels neuronal differentiation and is maintained in differentiated neurons in the adult brain. To dissect NeuroD6 differentiation properties further, we previously generated a NeuroD6-overexpressing stable PC12 cell line, PC12-ND6, which displays a neuronal phenotype characterized by spontaneous neuritogenesis, accelerated NGF-induced differentiation, and increased regenerative capacity. Furthermore, we reported that NeuroD6 promotes long-term neuronal survival upon serum deprivation. In this study, we identified the NeuroD6-mediated transcriptional regulatory pathways linking neuronal differentiation to survival, by conducting a genome-wide microarray analysis using PC12-ND6 cells and serum deprivation as a stress paradigm. Through a series of filtering steps and a gene-ontology analysis, we found that NeuroD6 promotes distinct but overlapping gene networks, consistent with the differentiation, regeneration, and survival properties of PC12-ND6 cells. By using a gene-set-enrichment analysis, we provide the first evidence of a compelling link between NeuroD6 and a set of heat shock proteins in the absence of stress, which may be instrumental in conferring stress tolerance on PC12-ND6 cells. Immunocytochemistry results showed that HSP27 and HSP70 interact with cytoskeletal elements, consistent with their roles in neuritogenesis and preserving cellular integrity. HSP70 also colocalizes with mitochondria located in the soma, growing neurites, and growth cones of PC12-ND6 cells prior to and upon stress stimulus, consistent with its neuroprotective functions. Collectively, our findings support the notion that NeuroD6 links neuronal differentiation to survival via the network of molecular chaperones and endows the cells with increased stress tolerance.

Ischemic tolerance in stroke treatment

Although outcome after stroke treatment has significantly improved over the last 30 years, there has been no revolutionary breakthrough. Among different combined approaches, systemic thrombolysis in combination with neuroprotection became a favorite research target. Recent studies suggest that transient ischemic attacks may represent a clinical model of such ischemic tolerance; thus, a new focus on this research has emerged. In this review, we show the parallels between ischemia and neuroprotection and discuss the potential therapeutic options that may be opened by this new molecular knowledge.

Influence of geranylgeranylacetone on the expression of HSP70 in retina of rats with chronic IOP elevation

AIM

To study the effects of geranylgeranylacetone (GGA) on the expression of heat shock protein70 (HSP70) on retinal ganglion cells (RGC) in rats with chronic intraocular pressure (IOP) elevation.

METHODS

Seventy Wistars were divided into blank control group (10 rats), chronic hypertension group (30 rats) and GGA group (30 rats). Chronic hypertension was created by cauterizing the superficial scleral veins. 800mg/kg/d GGA was given by oral daily after cauterization. Immunohistochemistry was used respectively to observe the changes of expression of HSP70 in the model rats and GGA interference rats at different time points during the course of chronic IOP elevation.

RESULTS

The successful model was identified as the IOP over 40% of normal rats. The retinal thickness was significantly reduced in model group and model+GGA group compared with normal rats from 21 days through 28 days after cauterization (P<0.05), and that of model rats was obviously decreased in comparison with model+GGA rats (P<0.05). The number of ganglion cells was significantly decreased in model rats and model+GGA rats compared with normal rats from 21 days and 28 days. The stronger expression intensity (IOD) value was seen for HSP70 in the model+GGA rats by immunochemistry (P<0.01).

CONCLUSION

Systemic administration of GGA protects retina from chronic IOP elevation by regulating the expression of HSP70.

Herpes Virus Amplicon Vectors

Since its emergence onto the gene therapy scene nearly 25 years ago, the replication-defective Herpes Simplex Virus Type-1 (HSV-1) amplicon has gained significance as a versatile gene transfer platform due to its extensive transgene capacity, widespread cellular tropism, minimal immunogenicity, and its amenability to genetic manipulation. Herein, we detail the recent advances made with respect to the design of the HSV amplicon, its numerous in vitro and in vivo applications, and the current impediments this virus-based gene transfer platform faces as it navigates a challenging path towards future clinical testing.

Protein ubiquitination in postsynaptic densities after hypoxia in rat neostriatum is blocked by hypothermia

Synaptic dysfunction has been associated with neuronal cell death following hypoxia. The lack of knowledge on the mechanisms underlying this dysfunction prompted us to investigate the morphological changes in the postsynaptic densities (PSDs) induced by hypoxia. The results presented here demonstrate that PSDs of the rat neostriatum are highly modified and ubiquitinated 6 months after induction of hypoxia in a model of perinatal asphyxia. Using both two dimensional (2D) and three dimensional (3D) electron microscopic analyses of synapses stained with ethanolic phosphotungstic acid (E-PTA), we observed an increment of PSD thickness dependent on the duration and severity of the hypoxic insult. The PSDs showed clear signs of damage and intense staining for ubiquitin. These morphological and molecular changes were effectively blocked by hypothermia treatment, one of the most effective strategies for hypoxia-induced brain injury available today. Our data suggest that synaptic dysfunction following hypoxia may be caused by long-term misfolding and aggregation of proteins in the PSD.

Antioxidant enzyme gene transfer for ischemic diseases

The balance of redox is pivotal for normal function and integrity of tissues. Ischemic insults occur as results of a variety of conditions, leading to an accumulation of reactive oxygen species (ROS) and an imbalanced redox status in the tissues. The oxidant stress may activate signaling mechanisms provoking more toxic events, and eventually cause tissue damage. Therefore, treatments with antioxidants, free radical scavengers and their mimetics, as well as gene transfer approaches to overexpress antioxidant genes represent potential therapeutic options to correct the redox imbalance. Among them, antioxidant gene transfer may enhance the production of antioxidant scavengers, and has been employed to experimentally prevent or treat ischemic injury in cardiovascular, pulmonary, hepatic, intestinal, central nervous or other systems in animal models. With improvements in vector systems and delivery approaches, innovative antioxidant gene therapy has conferred better outcomes for myocardial infarction, reduced restenosis after coronary angioplasty, improved the quality and function of liver grafts, as well as outcome of intestinal and cerebral ischemic attacks. However, it is crucial to be mindful that like other therapeutic armentarium, the efficacy of antioxidant gene transfer requires extensive preclinical investigation before it can be used in patients, and that it may have unanticipated short- or long-term adverse effects. Thus, it is critical to balance between the therapeutic benefits and potential risks, to develop disease-specific antioxidant gene transfer strategies, to deliver the therapy with an optimal time window and in a safe manner. This review attempts to provide the rationale, the most effective approaches and the potential hurdles of available antioxidant gene transfer approaches for ischemic injury in various organs, as well as the possible directions of future preclinical and clinical investigations of this highly promising therapeutic modality.

Blocking glucocorticoid and enhancing estrogenic genomic signaling protects against cerebral ischemia

Glucocorticoids (GCs) and estrogen can modulate neuron death and dysfunction during neurological insults. Glucocorticoids are adrenal steroids secreted during stress, and hypersecretion of GCs during cerebral ischemia compromises the ability of hippocampal and cortical neurons to survive. In contrast, estrogen can be neuroprotective after cerebral ischemia. Here we evaluate the protective potential of a herpes viral vector expressing a chimeric receptor (ER/GR), which is composed of the ligand-binding domain of the GC receptor (GR) and the DNA-binding domain of the estrogen receptor-alpha (ER). This novel receptor can transduce an endangering GC signal into a protective estrogenic one. Using an in vitro oxygen glucose deprivation model (OGD), GCs exacerbated neuron death in primary cortical cultures, and this worsening effect was completely blocked by ER/GR expression. Moreover, blocking GC actions with a vector expressing a dominant negative GC receptor promoted neuron survival during postischemia, but not preischemia. Thus, gene therapeutic strategies to modulate GC and estrogen signaling can be beneficial during an ischemic insult.

The development of gene therapy: from monogenic recessive disorders to complex diseases such as cancer

During the last 4 decades, gene therapy has moved from preclinical to clinical studies for many diseases ranging from monogenic recessive disorders such as hemophilia to more complex diseases such as cancer, cardiovascular disorders, and human immunodeficiency virus (HIV). To date, more than 1,340 gene therapy clinical trials have been completed, are ongoing, or have been approved in 28 countries, using more than 100 genes. Most of those clinical trials (66.5%) were aimed at the treatment of cancer. Early hype, failures, and tragic events have now largely been replaced by the necessary stepwise progress needed to realize clinical benefits. We now understand better the strengths and weaknesses of various gene transfer vectors; this facilitates the choice of appropriate vectors for individual diseases. Continuous advances in our understanding of tumor biology have allowed the development of elegant, more efficient, and less toxic treatment strategies. In this introductory chapter, we review the history of gene therapy since the early 1960s and present in detail two major recurring themes in gene therapy: (1) the development of vector and delivery systems and (2) the design of strategies to fight or cure particular diseases. The field of cancer gene therapy experienced an "awkward adolescence." Although this field has certainly not yet reached maturity, it still holds the potential of alleviating the suffering of many individuals with cancer.

Hippocampal transcriptome after status epilepticus in mice rendered seizure damage-tolerant by epileptic preconditioning features suppressed calcium and neuronal excitability pathways

Preconditioning brain with a sub-lethal stressor can temporarily generate a damage-refractory state. Microarray analyses have defined the changes in hippocampal gene expression that follow brief preconditioning seizures, but not the transcriptome after a prolonged and otherwise injurious seizure in previously preconditioned brain. Presently, microarray analysis was performed 24 h after status epilepticus in mice that had received previously either seizure preconditioning (tolerance) or sham-preconditioning (injury). Transcriptional changes in the hippocampal CA3 subfield of >or=2 fold were detected for 1357 genes in the tolerance group compared to a non-seizure control group, with 54% up-regulated. Of these regulated genes, 792 were also regulated in the injury group. Among the remaining 565 genes regulated only in tolerance, 73% were down-regulated. Analysis of the genes differentially suppressed in tolerance identified calcium signaling, ion channels and excitatory neurotransmitter receptors, and the synapse as over-represented among pathways, functions and compartments. Finally, 12 days continuous EEG recordings determined mice with induced tolerance had fewer spontaneous electrographic seizures compared to the injury group. Our data suggest the transcriptional phenotype of neuroprotection in tolerance may be dictated by the biology of the preconditioning stressor, functions by transcriptional reduction of vulnerability to excitotoxicity, and has anti-epileptogenic effects.

Transient 5-(4-phenylbutoxy)psoralen (PAP-1) treatment dissociates developing pathologies in autoimmune optic neuritis into two distinct pathology profiles

Discovery of treatments to protect axonal function of neurons and prevent permanent disability associated with progressive multiple sclerosis (MS) has faced the uphill challenge of assessing relatively small changes in accumulated axon damage within a background environment that is disorganized by CNS inflammation. We hypothesized that transient immunosuppression after initiation of MS-like autoimmune mechanisms would disassociate development of MS-like myelinated axon pathology from development of CNS inflammation in a rat model of autoimmune optic neuritis (AON). A rat model of myelin oligodendrocyte glycoprotein peptide-induced AON was transiently treated (on days 3-7 after antigen exposure) with 5-(4-phenylbutoxy)psoralen (PAP-1), an immunomodulatory drug previously shown specifically to suppress proliferation of effector memory T-cells and immunoglobulin class-switched B-cells. Thirteen days after antigen exposure, optic nerves were harvested for quantitative assessment of 12 MS-associated pathologies using microfluorimetry. With one exception, the immunoreactivities (-ir) for eight markers of MS-like neuroinflammation and immune infiltration were significantly reduced (P < 0.05) by transient PAP-1 treatment, often to levels significantly below those detected in normal control rat optic nerves. With one exception, four immunoreactive markers of MS-like myelinated axon pathology were detected at levels indicating increased axon/myelin pathology compared with vehicle-treated rats with AON (P < 0.05). These data suggest the conclusion that early causative mechanisms in CNS autoimmunity initiate signaling mechanisms that diverge into two separate pathways, one that is strongly associated with inflammatory responses and one that is associated predominantly with disturbed axon-myelin interactions and impaired fast axonal transport.

Gene therapy in epilepsy

Results from animal models suggest gene therapy is a promising new approach for the treatment of epilepsy. Several candidate genes such as neuropeptide Y and galanin have been demonstrated in preclinical studies to have a positive effect on seizure activity. For a successful gene therapy-based treatment, efficient delivery of a transgene to target neurons is also essential. To this end, advances have been made in the areas of cell transplantation and in the development of recombinant viral vectors for gene delivery. Recombinant adeno-associated viral (rAAV) vectors in particular show promise for gene therapy of neurological disorders due to their neuronal tropism, lack of toxicity, and stable persistence in neurons, which results in robust, long-term expression of the transgene. rAAV vectors have been recently used in phase I clinical trials of Parkinson's disease with an excellent safety profile. Prior to commencement of phase I trials for gene therapy of epilepsy, further preclinical studies are ongoing including evaluation of the therapeutic benefit in chronic models of epileptogenesis, as well as assessment of safety in toxicological studies.

Intracellular and extracellular expression of the major inducible 70kDa heat shock protein in experimental ischemia-reperfusion injury of the spinal cord

Inflammatory responses exacerbate ischemia-reperfusion (IR) injury of spinal cord, although understanding of mediators is incomplete. The major inducible 70kDa heat shock protein (hsp70) is induced by ischemia and extracellular hsp70 (e-hsp70) can modulate inflammatory responses, but there is no published information regarding e-hsp70 levels in the cerebrospinal fluid (CSF) or serum as part of any neurological disease state save trauma. The present work addresses this deficiency by examining e-hsp70 in serum and CSF of dogs in an experimental model of spinal cord IR injury. IR injury of spinal cord caused hind limb paraplegia within 2-3 h that was correlated to lumbosacral poliomalacia with T cell infiltrates at 3 d post-ischemia. In this context, we showed a 5.2-fold elevation of e-hsp70 in CSF that was induced by ischemia and was sustained for the following 3 d observation interval. Plasma e-hsp70 levels were unaffected by IR injury, indicating e-hsp70 release from within the central nervous system. A putative source of this e-hsp70 was ependymal cells in the ischemic penumbra, based upon elevated i-hsp70 levels detected within these cells. Results warrant further investigation of e-hsp70's potential to modulate spinal cord IR injury.

Molecular physiology of preconditioning-induced brain tolerance to ischemia

Ischemic tolerance describes the adaptive biological response of cells and organs that is initiated by preconditioning (i.e., exposure to stressor of mild severity) and the associated period during which their resistance to ischemia is markedly increased. This topic is attracting much attention because preconditioning-induced ischemic tolerance is an effective experimental probe to understand how the brain protects itself. This review is focused on the molecular and related functional changes that are associated with, and may contribute to, brain ischemic tolerance. When the tolerant brain is subjected to ischemia, the resulting insult severity (i.e., residual blood flow, disruption of cellular transmembrane gradients) appears to be the same as in the naive brain, but the ensuing lesion is substantially reduced. This suggests that the adaptive changes in the tolerant brain may be primarily directed against postischemic and delayed processes that contribute to ischemic damage, but adaptive changes that are beneficial during the subsequent test insult cannot be ruled out. It has become clear that multiple effectors contribute to ischemic tolerance, including: 1) activation of fundamental cellular defense mechanisms such as antioxidant systems, heat shock proteins, and cell death/survival determinants; 2) responses at tissue level, especially reduced inflammatory responsiveness; and 3) a shift of the neuronal excitatory/inhibitory balance toward inhibition. Accordingly, an improved knowledge of preconditioning/ischemic tolerance should help us to identify neuroprotective strategies that are similar in nature to combination therapy, hence potentially capable of suppressing the multiple, parallel pathophysiological events that cause ischemic brain damage.

Panax ginseng ginsenoside-Rg2 protects memory impairment via anti-apoptosis in a rat model with vascular dementia

ETHNOPHARMACOLOGICAL RELEVANCE

Ginsenosides, the major active ingredients of Panax ginseng, produce a variety of pharmacological or physiological responses with effects on the central and peripheral nervous systems.

AIM OF THE STUDY

In this report, we investigated the effects of ginsenoside Rg2 on cerebral ischemia-reperfusion induced impairment of neurological responses, memory and caudate-putamen neuronal apoptosis in a vascular dementia (VD) rat model.

MATERIALS AND METHODS

Neurological evaluation was performed 24h after reperfusion and Y-maze memory performance was assessed at 48 h after reperfusion. Immunocytochemical techniques were employed to check the protein expression of BCL-2, BAX, heat shock protein 70 and P53, which are related with cell apoptosis.

RESULTS

Neurological responses and memory ability of the ginsenoside Rg2 or nimodipine groups improved significantly compared with the VD group. The expression of BCL-2 and HSP70 were decreased, while BAX and P53 were increased in the VD model. The expression of BCL-2 and HSP70 proteins were increased, while BAX and P53 decreased after ginsenoside Rg2 (2.5, 5 and 10mg/kg) and nimodipine (50 microg/kg) treatment compared with the VD group. The study suggests that ginsenoside Rg2 improved neurological performance and memory ability of VD rats through mechanisms related to anti-apoptosis.

CONCLUSIONS

The capacity for ginsenoside Rg2 to modulate the expression of apoptotic related proteins suggests that ginsenoside Rg2 may represent a potential treatment strategy for vascular dementia or other ischemic insults.

Changes in the regulation of heat shock gene expression in neuronal cell differentiation

Neuronal differentiation of the NG108-15 neuroblastoma-glioma hybrid cells is accompanied by a marked attenuation in the heat shock induction of the Hsp70-firefly luciferase reporter gene activity. Analysis of the amount and activation of heat shock factor 1, induction of mRNA(hsp), and the synthesis and accumulation of heat shock proteins (HSPs) in the undifferentiated and differentiated cells suggest a transcriptional mechanism for this attenuation. Concomitant with a decreased induction of the 72-kDa Hsp70 protein in the differentiated cells, there is an increased abundance of the constitutive 73-kDa Hsc70, a protein known to function in vesicle trafficking. Assessment of sensitivity of the undifferentiated and differentiated cells against stress-induced cell death reveals a significantly greater vulnerability of the differentiated cells toward the cytotoxic effects of arsenite and glutamate/glycine. This study shows that changes in regulation of the HSP and HSC proteins are components of the neuronal cell differentiation program and that the attenuated induction of HSPs likely contributes to neuronal vulnerability whereas the increased expression of Hsc70 likely has a role in neural-specific functions.

Heat shock protein 70 expression in epilepsy suggests stress rather than protection

Although heat shock protein 70 (HSP70) has been suggested to be a stress marker or to play a protective role in brain injury, the relevance of its pathological expression in epilepsy is unclear. We investigated the expression of HSP70 in brain tissue from human temporal lobe epilepsy (TLE) patients and from kainic acid (KA)-induced seizure-related neuronal damage in vivo and in vitro. The human TLE tissue showed severe neuronal loss and gliosis in hippocampal CA3 area. The KA-induced neuronal damage was similar to pathological changes of the TLE hippocampus. An increased number of TUNEL-positive cells were observed at day 5 when compared with day 2 after seizure induction. Intense HSP70 immunofluorescence was observed in hippocampal CA3 pyramidal neurons of rat, 2 days following KA administration, which then declined in labeling by day 5. No HSP70 expression was found in Fluoro-Jade B positive dying neurons by double staining. Western blot analysis showed an increased level of p53 and Bax expression following KA treatment. In vitro, there was no apparent difference in the degree of apoptosis between HSP70 siRNA- and control empty vector-transfected primary neurons following KA treatment. Our results revealed that HSP70 was a useful indicator of stressed neurons in acute phase of epilepsy, but not associated with neuronal death, thereby suggesting that HSP70 played no role in neuroprotection during an epileptogenic state.

Anti-inflammatory effects of the 70 kDa heat shock protein in experimental stroke

The 70-kDa heat shock protein (Hsp70) is involved in protecting the brain from a variety of insults including stroke. Although the mechanism has been largely considered to be because of its chaperone functions, recent work indicates that Hsp70 also modulates inflammatory responses. To explore how and whether Hsp70 regulate immune responses in brain ischemia, mice overexpressing Hsp70 (Hsp Tg) were subjected to 2 h middle cerebral artery occlusion, followed by 24 h reperfusion. Parallel experiments were performed using a brain inflammation model. Hsp Tg microglia cocultured with astrocytes were used to evaluate the direct effects of Hsp70 on cytotoxicity of microglia. Compared with wild-type (Wt) littermates, Hsp Tg mice showed decreased infarct size and improved neurological deficits. The number of activated microglia/macrophages were also reduced in ischemic brains of Hsp Tg mice. Similar observations were made in a model of brain inflammation that does not result in brain cell death. Overexpression of Hsp70 in microglia completely prevented microglia-induced cytotoxicity to astrocytes. Activation of the inflammatory transcription factor, nuclear factor-kappaB (NF-kappaB) was inhibited significantly in Hsp Tg mice and microglia. This was associated with decreased phosphorylation of NF-kappaB inhibitor protein, IkappaBalpha, and decreased expression of several NFkappaB-regulated genes. Co-immunoprecipitation studies revealed an interaction of Hsp70 with NF-kappaB and IkappaBalpha, but not with IkappaB kinase, IKKgamma, suggesting that Hsp70 binds to the NF-kappaB:IkappaB complex preventing IkappaB phosphorylation by IKK. The findings of the present work establish an anti-inflammatory role for Hsp70 in the context of brain ischemia as a novel mechanism of protection.

Expression of heat shock transcription factors and heat shock protein 72 in rat retina after intravitreal injection of low dose N-methyl-D-aspartate

The heat shock response is a genetically well-ordered process for cell to generate heat shock protein (HSP). Various stressors can trigger the response through heat shock transcriptional factor (HSF) regulation. Recent studies demonstrated that preconditioning of N-methyl-d-aspartate (NMDA) at non-lethal levels has neuroprotective effects, but the exact mechanisms are unclear. We hypothesize that the protective mechanisms of NMDA preconditioning could involve HSP expression. To understand the regulatory mechanisms of HSP under stress, we examined the expression of Hsp72, HSF1 and HSF2 in the adult rat retina after intravitreal injection of NMDA. Retinal ganglion cell (RGC) counting with retrograde labeling showed that 8 nmol, but not 0.8 nmol, of intravitreal NMDA reduced RGC survival. Western blotting and immunohistochemistry showed that non-lethal (0.8 nmol) doses of NMDA induced a time-dependent expression of HSF1 and HSF2, and that the expression of HSF1 and HSF2 in the RGC layer peaked between 9 and 18 h after injection. Parallel to the increased HSF expression, immunohistochemistry and in situ hybridization demonstrated that Hsp72 mRNA and protein expression increased 9 and 12 h after non-lethal NMDA injection, respectively. Our findings suggest that the expression of HSF1 and HSF2 is associated with the Hsp72-related stress response.

Tat-Hsp70 protects dopaminergic neurons in midbrain cultures and in the substantia nigra in models of Parkinson's disease

Parkinson's disease is characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra. The heat-shock protein 70 (Hsp70) reduces protein misfolding and aggregation. It has been shown to protect cells against oxidative stress and apoptotic stimuli in various neurodegenerative disease models. To deliver Hsp70 across cellular membranes and into the brain, we linked it to a cell-penetrating peptide derived from the HIV trans-activator of transcription (Tat) protein. In vitro, Tat-Hsp70 transduced neuroblastoma cells and protected primary mesencephalic DA neurons and their neurites against MPP+-mediated degeneration. In vivo, the systemic application of cell-permeable Hsp70 protected DA neurons of the substantia nigra pars compacta against subacute toxicity of MPTP. Furthermore, Tat-Hsp70 diminished the MPTP induced decrease in DA striatal fiber density. Thus, we demonstrate that systemically applied Tat-Hsp70 effectively prevents neuronal cell death in in vitro and in vivo models of Parkinson's disease. The use of Tat-fusion proteins might therefore be a valuable tool to deliver molecular chaperones like Hsp70 into the brain and may be the starting point for new protective strategies in neurodegenerative diseases.

Viral caspase inhibitor p35, but not crmA, is neuroprotective in the ischemic penumbra following experimental stroke

Apoptosis, a predominant cause of neuronal death after stroke, can be executed in a caspase-dependent or apoptosis inducing factor (AIF)-dependent manner. Herpes simplex virus (HSV) vectors expressing caspase inhibitors p35 and crmA have been shown to be neuroprotective against various excitotoxic insults. Here we further evaluated the possible neuroprotective role of p35 and crmA in a rat stroke model. Overexpression of p35, but not crmA, significantly increased neuronal survival. Results of double immunofluorescence staining indicate that compared with neurons infected with crmA or control vectors, p35-infected neurons had less active caspase-3 expression, cytosolic cytochrome c and nuclear AIF translocation.

Evidence for a role of Hsp70 in the neuroprotection induced by heat shock pre-treatment against 3,4-methylenedioxymethamphetamine toxicity in rat brain

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') produces acute hyperthermia which increases the severity of the selective serotoninergic neurotoxicity produced by the drug in rats. Heat shock protein 70 (Hsp70) is a major inducible cellular protein expressed in stress conditions and which is thought to exert protective functions. MDMA (12.5 mg/kg, i.p.), given to rats housed at 22 degrees C, produced an immediate hyperthermia and increased Hsp70 in frontal cortex between 3 h and 7 days after administration. MDMA, given to rats housed at low ambient temperature (4 degrees C) produced transient hypothermia followed by mild hyperthermia but no increase in Hsp70 expression, while rats treated at elevated room temperature (30 degrees C) showed enhanced hyperthermia and similar expression of Hsp70 to that seen in rats housed at 22 degrees C. Fluoxetine-induced inhibition of 5-HT release and hydroxyl radical formation did not modify MDMA-induced Hsp70 expression 3 h later. Four- or 8-day heat shock (elevation of basal rectal temperature by 1.5 degrees C for 1 h) or geldanamycin pre-treatment induced Hsp70 expression and protected against MDMA-induced serotoninergic neurotoxicity without affecting drug-induced hyperthermia. Thus, MDMA-induced Hsp70 expression depends on the drug-induced hyperthermic response and not on 5-HT release or hydroxyl radical formation and pre-induction of Hsp70 protects against the long-term serotoninergic damage produced by MDMA.

Molecular targets in cerebral ischemia for developing novel therapeutics

Cerebral ischemia (stroke) triggers a complex series of biochemical and molecular mechanisms that impairs the neurologic functions through breakdown of cellular integrity mediated by excitotoxic glutamatergic signalling, ionic imbalance, free-radical reactions, etc. These intricate processes lead to activation of signalling mechanisms involving calcium/calmodulin-dependent kinases (CaMKs) and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The distribution of these transducers bring them in contact with appropriate molecular targets leading to altered gene expression, e.g. ERK and JNK mediated early gene induction, responsible for activation of cell survival/damaging mechanisms. Moreover, inflammatory reactions initiated at the neurovascular interface and alterations in the dynamic communication between the endothelial cells, astrocytes and neurons are thought to substantially contribute to the pathogenesis of the disease. The damaging mechanisms may proceed through rapid nonspecific cell lysis (necrosis) or by active form of cell demise (apoptosis or necroptosis), depending upon the severity and duration of the ischemic insult. A systematic understanding of these molecular mechanisms with prospect of modulating the chain of events leading to cellular survival/damage may help to generate the potential strategies for neuroprotection. This review briefly covers the current status on the molecular mechanisms of stroke pathophysiology with an endeavour to identify potential molecular targets such as targeting postsynaptic density-95 (PSD-95)/N-methyl-d-aspartate (NMDA) receptor interaction, certain key proteins involved in oxidative stress, CaMKs and MAPKs (ERK, p38 and JNK) signalling, inflammation (cytokines, adhesion molecules, etc.) and cell death pathways (caspases, Bcl-2 family proteins, poly (ADP-ribose) polymerase-1 (PARP-1), apoptosis-inducing factor (AIF), inhibitors of apoptosis proteins (IAPs), heat shock protein 70 (HSP70), receptor interacting protein (RIP), etc., besides targeting directly the genes itself. However, selecting promising targets from various signalling cascades, for drug discovery and development is very challenging, nevertheless such novel approaches may lead to the emergence of new avenues for therapeutic intervention in cerebral ischemia.

Differential expression of heat shock protein mRNAs under in vivo glutathione depletion in the mouse retina

Heat shock proteins (HSPs) are highly conserved proteins playing a protective role under deleterious conditions caused by a wide variety of pathophysiological, including environmental stresses. Glutathione (GSH) is known to play a critical role in the cellular defense against unregulated oxidative stress in mammalian cells including neurons. We previously demonstrated that GSH depletion induced cell death in the retina, but the mechanism(s) of cellular protection were not clear. Unregulated oxidative stress was induced by depletion of intracellular GSH by systematic administration of buthionine sulphoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase. After 0, 1, 4 and 7 days of BSO administration, we examined expression of both large and small HSP mRNAs (hsp90alpha, hsp90beta, hsp70, hsp60 and hsp25) in oxidative-stressed mouse retina. Of large HSPs, only hsp70 expression was significantly decreased from 1 day after BSO injection, whereas expression of other large hsps was not changed on day 1. Expression of hsp60 decreased on 4 days, whereas expression of hsp90 decreased on 7 days after BSO administration. Different from large HSPs, a small HSP, hsp25 increased its expression to a great extent from 1 day after BSO administration. Taken together, our results show that unregulated oxidative stress could induce differential expression of HSPs, which, in turn, may play distinct roles in the cellular defense. Targeting HSPs, therefore, may provide novel tools for treatment of retinal degenerative diseases such as glaucoma, retinopathy or age-related macular degeneration.

Novel antiseizure drug mechanisms

The amount of new knowledge being generated regarding brain mechanisms in general, and epileptic mechanisms in particular, is enormous. Anticonvulsant drugs are ineffective in approximately a third of people with epilepsy. To our knowledge, strategies for preventing epilepsy after an initial insult are nonexistent. In this review, we briefly examine some recent novel concepts for preventing seizures, which might lead to enhanced anticonvulsant drug therapy. We start with some known seizure mechanisms that have yet to yield widely used anticonvulsant drugs, including potassium channels, chloride cotransporters, extracellular space constriction, gap junctions and magnesium. Pharmacoresistance is then discussed, focusing on the upregulation of drug-resistance proteins (a concept with significant therapeutic appeal) and the drug-target hypothesis. Two further areas that hold great promise for future therapeutics are sex hormones and inflammatory processes. The genetics of epilepsy are currently being elaborated, providing potential novel anticonvulsant targets. Prevention being better than a cure, we discuss epileptogenesis and its treatment. Given the astounding progress of neuroscience research, one hopes for many new therapeutics for our intractable epileptic patients.

The HSV-2 protein ICP10PK prevents neuronal apoptosis and loss of function in an in vivo model of neurodegeneration associated with glutamate excitotoxicity

Excessive glutamate receptor activation results in neuronal death, a process known as excitotoxicity. Intrastriatal injection of N-methyl-d-aspartate (NMDA) is a model of excitotoxicity. We used this model to examine whether excitotoxic injury is inhibited by the anti-apoptotic herpes simplex virus type 2 (HSV-2) protein, ICP10PK, delivered by the replication incompetent HSV-2 vector, DeltaRR. Intrastriatal DeltaRR administration (2500 plaque forming units) was nontoxic and did not induce microglial activation 5 days after injection. Intrastriatal injection of DeltaRR with NMDA or 4 h after NMDA injection showed increased neuronal survival and decreased mitochondrial damage compared to injection of NMDA alone. Neuroprotection was due to the inhibition of NMDA-induced apoptosis through ERK activation. DeltaRR-treated mice did not develop NMDA-associated behavioral deficits. The data suggest that DeltaRR is a promising platform for treatment of acute neuronal injury.

Co-expression of heat shock transcription factors 1 and 2 in rat retinal ganglion cells

Heat shock protein (HSP) plays an important role in the maintenance of neuronal survival during harmful conditions. Previously, we reported that metabolic stress induces HSP72 in retinal ganglion cells (RGCs) and protects against excitotoxicity, hypoxia and experimental glaucoma. To understand heat shock protein transcriptional mechanisms, we examined the cellular expression of heat shock factors 1 (HSF1) and 2 (HSF2) in the unstressed adult rat retina. Western blotting, immunohistochemistry and RT-PCR showed that mRNA and protein of HSF1 and HSF2 were present in the rat retina and predominantly expressed in RGC layer cells. Western blotting of dissociated RGC suspensions harvested with Thy-1 immuno-labeled magnetic beads confirmed that RGCs expressed HSF1, HSF2 and HSP72. Our findings suggest that both heat shock transcription factors 1 and 2 are linked to the heat shock response in retinal ganglion cells.

Heat shock inhibits both aminoglycoside- and cisplatin-induced sensory hair cell death

Human hearing and balance impairments are often attributable to the death of sensory hair cells in the inner ear. These cells are hypersensitive to death induced by noise exposure, aging, and some therapeutic drugs. Two major classes of ototoxic drugs are the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Exposure to these drugs leads to hair cell death that is mediated by the activation of specific apoptotic proteins, including caspases. The induction of heat shock proteins (HSPs) in response to cellular stress is a ubiquitous and highly conserved response that can significantly inhibit apoptosis in some systems by inhibiting apoptotic proteins. Induction of HSPs occurs in hair cells in response to a variety of stimuli. Given that HSPs can directly inhibit apoptosis, we hypothesized that heat shock may inhibit apoptosis in hair cells exposed to ototoxic drugs. To test this hypothesis, we developed a method for inducing HSP expression in the adult mouse utricle in vitro. In vitro heat shock reliably produces a robust up-regulation of HSP-70 mRNA and protein, as well as more modest up-regulation of HSP-90 and HSP-27. The heat shock does not result in death of hair cells. Heat shock has a significant protective effect against both aminoglycoside- and cisplatin-induced hair cell death in the utricle preparation in vitro. These data indicate that heat shock can inhibit ototoxic drug-induced hair cell death, and that the utricle preparation can be used to examine the molecular mechanism(s) underlying this protective effect.

Sexual dimorphism of the intracellular heat shock protein 72 response

The majority of previous work examining stress responses has been done in males. Recently, it has become clear that the impact of stressor exposure is modulated by sex. One stress response that may be affected by sex is the induction of intracellular heat shock protein (HSP) 72, which is a stress- responsive molecular chaperone that refolds denatured proteins and promotes cellular survival. The following study compared HSP72 in males and females and also examined whether the estrous cycle altered HSP72 induction in females. We hypothesized that females compared with males would have a constrained HSP72 response after an acute stressor and that the stress-induced HSP72 response in females would fluctuate with the estrous cycle. Male and female F344 rats were either left in their home cage or exposed to acute tail-shock stress (8–10/group). Immediately following stressor, trunk blood was collected and tissues were flash frozen. Vaginal smear and estrogen enzyme immunoassay were used to categorize the phase of estrous. Results show that female rats had a greater corticosterone response than males, that both males and females exhibit a stress-induced release of progesterone, and that males and females had equal levels of stress-induced circulating norepinephrine. Sexual dimorphism of the HSP72 (ELISA) response existed in pituitary gland, mesenteric lymph nodes, and liver such that female rats had an attenuated HSP72 response compared with males after stress. The adrenal glands, spleen, and heart did not exhibit sexual dimorphism of the HSP72 response. The estrous cycle did not have a significant effect on basal or stress-induced HSP72 in females.

Postischemic Alterations of BDNF, NGF, HSP 70 and Ubiquitin Immunoreactivity in the Gerbil Hippocampus: Pharmacological Approach

1. We investigated the immunohistochemical alterations of BDNF, NGF, HSP 70 and ubiquitin in the hippocampus 1 h to 14 days after transient cerebral ischemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor pitavastatin against the changes of BDNF, NGF, HSP 70 and ubiquitin in the hippocampus after cerebral ischemia in the hippocampus after ischemia. 2. The transient cerebral ischemia was carried out by clamping the carotid arteries with aneurismal clips for 5 min. 3. In the present study, the alteration of HSP 70 and ubiquitin immunoreactivity in the hippocampal CA1 sector was more pronounced than that of BDNF and NGF immunoreactivity after transient cerebral ischemia. In double-labeled immunostainings, BDNF, NGF and ubiquitin immunostaining was observed both in GFAP-positive astrocytes and MRF-1-positive microglia in the hippocampal CA1 sector after ischemia. Furthermore, prophylactic treatment with pitavastatin prevented the damage of neurons with neurotrophic factor and stress proteins in the hippocampal CA1 sector after ischemia. 4. These findings suggest that the expression of stress protein including HSP 70 and ubiquitin may play a key role in the protection against the hippocampal CA1 neuronal damage after transient cerebral ischemia in comparison with the expression of neurotrophic factor such as BDNF and NGF. The present findings also suggest that the glial BDNF, NGF and ubiquitin may play some role for helping surviving neurons after ischemia. Furthermore, our present study indicates that prophylactic treatment with pitavastatin can prevent the damage of neurons with neurotrophic factor and stress proteins in the hippocampal CA1 sector after transient cerebral ischemia. Thus our study provides further valuable information for the pathogenesis after transient cerebral ischemia.

Neuroprotective effects of virally delivered HSPs in experimental stroke

Heat shock proteins (HSPs) are molecular chaperones with essential roles in modulating the proteolytic machinery and accelerating cell repair. Heat shock protein overexpression has been observed in vivo and in vitro under stresses including heat, nutrient deprivation and ischemia. Experiments in in vivo models of stroke indicate that transgenically overexpressed or virally delivered HSPs can enhance cell survival, but cannot always reduce lesion size. This study aims to assess the effects of virally delivered HSPs in a rat middle cerebral artery occlusion model of reversible focal cerebral ischemia using noninvasive magnetic resonance imaging. Attenuated herpes simplex virus carrying HSP27, HSP70, or a LacZ control was microinjected into the striatum 3 days before ischemia. Multislice T(2)-weighted images at 24 h after ischemia indicated that lesion volume was reduced by 44% in HSP27-treated animals compared with controls (P = 0.019). No significant differences were found between HSP70-treated and control animals (P = 0.88). Immunohistochemistry and Western blots revealed that HSP27 and HSP70 expression levels were equally high in injected hemispheres, but only the former had an effect on lesion size. This is the first evidence of the efficacy of gene therapy with any viral vector expressing HSP27 in an experimental model of stroke.

Expression profiling of p53-target genes in copper-mediated neuronal apoptosis

Copper toxicity associated with Wilson's disease is known to cause neuronal damage and death in the basal ganglia and frontal cortex leading to Parkinson-like symptoms and cognitive deficits. Our previous work in cultured human NTERA-2-N neurons showed that copper-induced neuronal apoptosis is dependent on the induction and nuclear translocation of the tumor suppressor protein, p53. Because p53 acts as a DNA-binding transcription factor, this work used an oligonucleotide array to identify p53 target genes that are differentially regulated in copper-loaded neurons. Arrays representing 145 human genes expressed downstream of p53 were hybridized with labeled mRNA from control and copper-treated neurons. Differentially regulated mRNAs included those involved in the regulation of the cell cycle, cytoprotective mechanisms, and apoptotic mechanisms. Transfection of cells with a dominant-negative p53 construct enabled us to determine which molecular events were dependent on p53 expression. Copper treatment resulted in the upregulation of p21, reprimo, stathmin, and Tp53INP1, all known to participate in cell cycle arrest. Protective mechanisms included the upregulation of stat-3, and the heat-shock proteins, heat-shock protein (Hsp) 70 and Hsp 27. Both p53-dependent and -independent mechanisms leading to apoptosis were identified including insulin-like growth factor binding protein-6, glutathione peroxidase, bcl-2, RB-1, PUMA, and several members of the redox active PIG family of proteins. Thus it appears that following copper-mediated neuronal DNA damage, the regulation of a variety of pro- and antiapoptotic genes are responsible for determining neuronal fate.

Ischemic tolerance in chemical preconditioning: Possible role of astrocytic glutamine synthetase buffering glutamate-mediated neurotoxicity

Glutamine synthetase (GS), localized to astrocyte is a key enzyme in the glutamate-glutamine pathway in the brain. 3-Nitropropionic acid (3-NPA) is an irreversible inhibitor of succinate dehydrogenase in the tricarboxylic-acid cycle, and provides ischemic tolerance to the brain. So far, there have been no reports on the relationship of astrocytic GS and ischemic tolerance by chemical preconditioning. In order to test the hypothesis that astrocytes serve a pivotal role in 3-NPA-induced chemical preconditioning, we have investigated the temporal profile of GS expression in astrocyte parallel with those of glial fibrillary acidic protein and heat-shock protein 70 (HSP70). In our rat model of permanent focal ischemia, preconditioning with 3-NPA singnificantly reduced the subsequent neurological deficits and infarct volume within 24-72 hours after treatment. Immunohistochemically, protoplasmic astrocytes in the cortex and striatum were activated in terms of upregulation of GS and more abundant protoplasmic processes with 3-NPA preconditioning, however, HSP70 expression could not be induced. Thus, the activation of astrocytes and upregulation of GS play an important role in 3-NPA-induced preconditioning but HSP70 does not. In view of glutamate being imposed on the cerebral ischemic damage, the astrocytic GS may contribute to 3-NPA-induced ischemic tolerance.

Ischemic preconditioning prevents protein aggregation after transient cerebral ischemia

Transient cerebral ischemia leads to protein aggregation mainly in neurons destined to undergo delayed neuronal death after ischemia. This study utilized a rat transient cerebral ischemia model to investigate whether ischemic preconditioning is able to alleviate neuronal protein aggregation, thereby protecting neurons from ischemic neuronal damage. Ischemic preconditioning was introduced by a sublethal 3 min period of ischemia followed by 48 h of recovery. Brains from rats with either ischemic preconditioning or sham-surgery were then subjected to a subsequent 7 min period of ischemia followed by 30 min, 4, 24, 48 and 72 h of reperfusion. Protein aggregation and neuronal death were studied by electron and confocal microscopy, as well as by biochemical analyses. Seven minutes of cerebral ischemia alone induced severe protein aggregation after 4 h of reperfusion mainly in CA1 neurons destined to undergo delayed neuronal death (which took place after 72 h of reperfusion). Ischemic preconditioning reduced significantly protein aggregation and virtually eliminated neuronal death in CA1 neurons. Biochemical analyses revealed that ischemic preconditioning decreased accumulation of ubiquitin-conjugated proteins (ubi-proteins) and reduced free ubiquitin depletion after brain ischemia. Furthermore, ischemic preconditioning also reduced redistribution of heat shock cognate protein 70 and Hdj1 from cytosolic fraction to protein aggregate-containing fraction after brain ischemia. These results suggest that ischemic preconditioning decreases protein aggregation after brain ischemia.

LateN-methyl-d-aspartate receptor blockade rescues hippocampal neurons from excitotoxic stress and death after 4-aminopyridine-induced epilepsy

The intrahippocampal perfusion of 4-aminopyridine (4-AP) in the rat produces immediate seizures and delayed neuronal death, due to the overactivation of N-methyl-D-aspartate (NMDA) receptors by endogenous glutamate released from nerve endings. With the same time course, 4-AP also induces the expression of the cell stress marker heat shock protein 70 (HSP70) in the contralateral non-damaged hippocampus. We have used this experimental model to study the mechanisms of the delayed neuronal stress and death. The NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate (MK-801), administered intraperitoneally 30 or 60 but not 120 min after 4-AP perfusion, when animals show intense electroencephalography epileptiform activity, prevented the delayed neurodegeneration whereas the seizures continued for about 3 h as in the control animals. With an identical time window, MK-801 treatment also modified the pattern of HSP70 expression; the protein was expressed in the protected perfused hippocampus but no longer in the undamaged contralateral hippocampus. The possible role of Ca2+ in the delayed cell death and HSP70 expression was also studied by coperfusing the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester) with 4-AP. This treatment resulted in protective and HSP70 effects very similar to those of MK-801. These results suggest that the seizures are not linked to neurodegeneration and that NMDA receptors need to be continuously overactivated by endogenous glutamate for at least 60 min in order to induce delayed neuronal stress and death, which are dependent on Ca2+ entry through the NMDA receptor channel.

New insights on brain stem death: From bedside to bench

As much as brain stem death is currently the clinical definition of death in many countries and is a phenomenon of paramount medical importance, there is a dearth of information on its mechanistic underpinnings. A majority of the clinical studies are concerned only with methods to determine brain stem death. Whereas a vast amount of information is available on the cellular and molecular mechanisms of cell death, rarely are these studies directed specifically towards the understanding of brain stem death. This review presents a framework for translational research on brain stem death that is based on systematically coordinated clinical and laboratory efforts that center on this phenomenon. It begins with the identification of a novel clinical marker from patients that is related specifically to brain stem death. After realizing that this "life-and-death" signal is related to the functional integrity of the brain stem, its origin is traced to the rostral ventrolateral medulla (RVLM). Subsequent laboratory studies on this neural substrate in animal models of brain stem death provide credence to the notion that both "pro-life" and "pro-death" programs are at work during the progression towards death. Those programs (mitochondrial functions, nitric oxide, peroxynitrite, superoxide anion, coenzyme Q10, heat shock proteins and ubiquitin-proteasome system) hitherto identified from the RVLM are presented, along with their cellular and molecular mechanisms. It is proposed that outcome of the interplay between the "pro-life" and "pro-death" programs (dying) in this neural substrate determines the final fate of the individual (being dead). Thus, identification of additional programs in the RVLM and delineation of their regulatory mechanisms should shed new lights on future directions for clinical management of life-and-death.

Neuroprotective potential of dietary restriction against kainate-induced excitotoxicity in adult male Wistar rats

The influence that dietary factors have on the nervous system and its susceptibility to disease, is an active area of biomedical research. Recent studies have shown that dietary restriction (DR) can have profound effect on brain function and vulnerability to injury and disease and can also enhance synaptic plasticity, which may increase the ability of brain to resist aging and restore function following injury. The dietary restriction may result in neuroprotection as suggested by marked reduction in neuronal cell death of the CA3 region of hippocampus after kainate administration in our study. We examined the effects of 3 months of DR (alternate day feeding regimen) on the antioxidants and antioxidant enzymes from different brain regions such as cerebral hemispheres, diencephalon, cerebellum and brain stem after kainate-induced excitotoxicity in adult male Wistar rats. The present study reports the beneficial effects of dietary restriction on different antioxidants and antioxidant enzymes against kainate-induced excitotoxicity in different brain regions of young adult male Wistar rats. The expression of stress response protein heat shock protein 70 (HSP 70) was also studied from discrete regions of rat brain under the same set of experimental conditions. DR significantly enhanced the expression of HSP 70 in kainic acid (KA)-treated rats, whereas KA treatment of ad libitum fed rats resulted in decreased HSP 70 expression. The DR was observed to exert neuroprotection by enhancing the expression of HSP 70 in kainic acid treated rats.

Heat shock proteins as emerging therapeutic targets

Chaperones (stress proteins) are essential proteins to help the formation and maintenance of the proper conformation of other proteins and to promote cell survival after a large variety of environmental stresses. Therefore, normal chaperone function is a key factor for endogenous stress adaptation of several tissues. However, altered chaperone function has been associated with the development of several diseases; therefore, modulators of chaperone activities became a new and emerging field of drug development. Inhibition of the 90 kDa heat shock protein (Hsp)90 recently emerged as a very promising tool to combat various forms of cancer. On the other hand, the induction of the 70 kDa Hsp70 has been proved to be an efficient help in the recovery from a large number of diseases, such as, for example, ischemic heart disease, diabetes and neurodegeneration. Development of membrane-interacting drugs to modify specific membrane domains, thereby modulating heat shock response, may be of considerable therapeutic benefit as well. In this review, we give an overview of the therapeutic approaches and list some of the key questions of drug development in this novel and promising therapeutic approach.

Neuroprotective effects of HSP70 overexpression after cerebral ischaemia--an MRI study

Heat shock proteins (HSPs) have been reported to increase cell survival in response to a wide range of cellular challenges. However, the role of HSP70 overexpression is still a matter of debate, with some reports showing protection and others not. In order to resolve these discrepancies and further investigate the action of these proteins in vivo, transgenic mice overexpressing HSP70 have been compared to wild-type mice in a middle cerebral artery occlusion model of permanent cerebral ischaemia. Previously, the effect of HSP70 was assessed histologically postmortem. In this report, magnetic resonance imaging (MRI) was used to assess the mice in vivo after the onset of stroke. The lesion volume, as measured at 24 h using T(2)-weighted MRI, was significantly smaller in HSP70 transgenic mice compared with wild-type mice. The smaller lesion size in HSP70 transgenic mice could not be attributed to differences in vascular anatomy or in cerebral blood flow during occlusion. Additionally, the apparent diffusion coefficient showed different spatial and temporal patterns between the groups, suggesting that the damage within the lesion may be less severe for HSP70 transgenic mice. Thus, we conclude that overexpression of HSP70 reduces the overall lesion size and may also limit the tissue damage within the lesion.

Nonsteroidal anti-inflammatory drugs differentially affect the heat shock response in cultured spinal cord cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to amplify the heat shock response in cell lines by increasing the binding of heat shock transcription factor-1 to heat shock elements within heat shock gene promoters. Because overexpression of the inducible heat shock protein 70 (Hsp70) was neuroprotective in a culture model of motor neuron disease, this study investigated whether NSAIDs induce Hsp70 and confer cytoprotection in motor neurons of dissociated spinal cord cultures exposed to various stresses. Two NSAIDs, sodium salicylate and niflumic acid, lowered the temperature threshold for induction of Hsp70 in glia but failed to do so in motor neurons. At concentrations that increased Hsp70 in heat shocked glial cells, sodium salicylate failed to delay death of motor neurons exposed to hyperthermia, paraquat-mediated oxidative stress, and glutamate excitotoxicity. Neither sodium salicylate nor the cyclooxygenase-2 inhibitor, niflumic acid, protected motor neurons from the toxicity of mutated Cu/Zn-superoxide dismutase (SOD-1) linked to a familial form of the motor neuron disease, amyotrophic lateral sclerosis. Thus, treatment with 2 types of NSAIDs failed to overcome the high threshold for the activation of heat shock response in motor neurons.

The therapeutic window of hypothermic neuroprotection in experimental ischemic neuropathy: Protection in ischemic phase and potential deterioration in later reperfusion phase

Hypothermia will neuroprotect peripheral nerve from ischemia-reperfusion (IR) injury, but the therapeutic window of hypothermic neuroprotection has not been defined. Unilateral IR injury was produced by the ligation and release of nooses tied around supplying arteries to the right sciatic-tibial nerve of the rat. Using this model, 114 rats were divided into 12 groups according to the delay (0, 1, 3, and 4 h) and the depth of hypothermia (28, 32, and 35 degrees C). All rats were subjected to 3 h ischemia and 7 days reperfusion followed by behavioral, electrophysiological, and pathological evaluations. We demonstrated significant hypothermic neuroprotection with both deep (28 degrees C) and mild (32 degrees C) hypothermia initiated during ischemia (0 and 1 h delay), but not hypothermia initiated during reperfusion (3 and 4 h delay) in both behavioral and electrophysiological evaluations. In addition, the pathologically significant differences were observed between deep hypothermia (28 degrees C) and normothermia (35 degrees C) initiated during ischemia. We conclude that the therapeutic window of hypothermic neuroprotection is optimal during the intraischemic period and that mild and deep hypothermia provide neuroprotection. Prolonged delay of hypothermic treatment results in worsening of IR injury.

Heat shock protein modulation of KATPand KCachannel cerebrovasodilation after brain injury

Fluid percussion brain injury (FPI) impairs pial artery dilation to activators of the ATP-sensitive (KATP) and calcium-activated (KCa) K+channels. This study investigated the role of heat shock protein (HSP) in the modulation of K+channel-induced pial artery dilation after FPI in newborn pigs equipped with a closed cranial window. Under nonbrain injury conditions, topical coadministration of exogenous HSP-27 (1 μg/ml) blunted dilation to cromakalim, CGRP, and NS-1619 (10−8and 10−6M; cromakalim and CGRP are KATPagonists and NS-1619 is a KCaagonist). In contrast, coadministration of exogenous HSP-70 (1 μg/ml) potentiated dilation to cromakalim, CGRP, and NS-1619. FPI increased the cerebrospinal fluid (CSF) concentration of HSP-27 from 0.051 ± 0.012 to 0.113 ± 0.035 ng/ml but decreased the CSF concentration of HSP-70 from 50.42 ± 8.96 to 30.9 ± 9.9 ng/ml at 1 h postinsult. Pretreatment with topical exogenous HSP-70 (1 μg/ml) before FPI fully blocked injury-induced impairment of cromakalim and CGRP dilation and partially blocked injury-induced impairment of dilation to NS-1619. These data indicate that HSP-27 and HSP-70 contribute to modulation of K+channel-induced pial artery dilation. These data suggest that HSP-70 is an endogenous protectant of which its actions may be unmasked and/or potentiated with exogenous administration before brain injury.

Heat stress induced histopathology and pathophysiology of the central nervous system

The number of reports on the effects of heat stress is still increasing on account of the temperature is one of the most encountered stressful factors on the different biological systems. Because the heat stress (HS) considered a model of thermal injury to the central nervous system (CNS), the purpose of this review was to assess the histopathological changes of HS on CNS. Also, this review emphasized that the heat stress may retard partially the degree of the postnatal neurogenesis and growth of CNS. Taken together, owing to one of the most important functions of heat shock protein is to protect the organisms from the deleterious effects of temperature, thus, it can be hypothesized that the formation of heat shock proteins may be related to the deleterious effect of HS. On the other hands, the alterations of neurotransmitters in the central nervous system might be involved in the physiological and biochemical responses that occur during heat stress. The hypothalamic monoaminergic systems play an important role in the thermoregulation through regulate the heat production and heat dissipation. In addition, the disturbance in the biochemical variables due to the high temperature may be the cause of the histopathological changes and the partial retardation in CNS and the reverse is true. Thus, further studies need to be done to emphasize this concept.

Hsp70 overexpression sequesters AIF and reduces neonatal hypoxic/ischemic brain injury

Apoptosis is implicated in neonatal hypoxic/ischemic (H/I) brain injury among various forms of cell death. Here we investigate whether overexpression of heat shock protein (Hsp) 70, an antiapoptotic protein, protects the neonatal brain from H/I injury and the pathways involved in the protection. Postnatal day 7 (P7) transgenic mice overexpressing rat Hsp70 (Tg) and their wild-type littermates (Wt) underwent unilateral common carotid artery ligation followed by 30 mins exposure to 8% O(2). Significant neuroprotection was observed in Tg versus Wt mice on both P12 and P21, correlating with a high level of constitutive but not inducible Hsp70 in the Tg. More prominent injury was observed in Wt and Tg mice on P21, suggesting its continuous evolution after P12. Western blot analysis showed that translocation of cytochrome c, but not the second mitochondria-derived activator of caspase (Smac)/DIABLO and apoptosis-inducing factor (AIF), from mitochondria into cytosol was significantly reduced in Tg 24 h after H/I compared with Wt mice. Coimmunoprecipitation detected more Hsp70 bound to AIF in Tg than Wt mice 24 h after H/I, inversely correlating with the amount of nuclear, but not cytosolic, AIF translocation. Our results suggest that interaction between Hsp70 and AIF might have reduced downstream events leading to cell death, including the reduction of nuclear AIF translocation in the neonatal brains of Hsp70 Tg mice after H/I.

Neuroprotective role of heat shock protein 70 in the rostral ventrolateral medulla during acute mevinphos intoxication in the rat

Heat shock protein (HSP) is a family of highly conserved proteins that respond to stress and participate actively in cytoprotection. Within the HSP family, HSP70 is the major inducible member that confers protection against cell death. This study investigated whether HSP70 plays a neuroprotective role at the rostral ventrolateral medulla (RVLM), the origin of sympathetic neurogenic vasomotor tone in the medulla oblongata where the organophosphate insecticide mevinphos (Mev) acts to elicit cardiovascular toxicity. Experiments were carried out in adult male Sprague-Dawley rats that were maintained under propofol anesthesia. Intravenous administration of Mev (960 microg/kg) induced a significant increase in the HSP70 level in the ventrolateral medulla during phase I ('pro-life' phase), and returned to baseline during phase II ('pro-death' phase) Mev intoxication. Compared to artificial cerebrospinal fluid, normal mouse serum (1:20), or sense hsp70 oligonucleotide (50 pmol) pretreatment, microinjection of an anti-HSP70 antiserum (1:20) or an antisense hsp70 oligonucleotide (50 pmol) bilaterally into the RVLM significantly increased mortality, shortened the duration of phase I intoxication and augmented the induced hypotension in rats that received Mev (960 microg/ kg, i.v.). These results suggest that HSP70 induced in the RVLM during Mev intoxication provides neuroprotection against the organophosphate poison via prevention of cardiovascular depression.