Exercise preconditioning reduces neuronal apoptosis in stroke by up-regulating heat shock protein-70 (heat shock protein-72) and extracellular-signal-regulated-kinase 1/2

Cerebral Ischemic Preconditioning: the Road So Far…

Cerebral preconditioning constitutes the brain's adaptation to lethal ischemia when first exposed to mild doses of a subtoxic stressor. The phenomenon of preconditioning has been largely studied in the heart, and data from in vivo and in vitro models from past 2-3 decades have provided sufficient evidence that similar machinery exists in the brain as well. Since preconditioning results in a transient protective phenotype labeled as ischemic tolerance, it can open many doors in the medical warfare against stroke, a debilitating cerebrovascular disorder that kills or cripples thousands of people worldwide every year. Preconditioning can be induced by a variety of stimuli from hypoxia to pharmacological anesthetics, and each, in turn, induces tolerance by activating a multitude of proteins, enzymes, receptors, transcription factors, and other biomolecules eventually leading to genomic reprogramming. The intracellular signaling pathways and molecular cascades behind preconditioning are extensively being investigated, and several first-rate papers have come out in the last few years centered on the topic of cerebral ischemic tolerance. However, translating the experimental knowledge into the clinical scaffold still evades practicality and faces several challenges. Of the various preconditioning strategies, remote ischemic preconditioning and pharmacological preconditioning appears to be more clinically relevant for the management of ischemic stroke. In this review, we discuss current developments in the field of cerebral preconditioning and then examine the potential of various preconditioning agents to confer neuroprotection in the brain.

Voluntary Exercise Preconditioning Activates Multiple Antiapoptotic Mechanisms and Improves Neurological Recovery after Experimental Traumatic Brain Injury

Physical activity can attenuate neuronal loss, reduce neuroinflammation, and facilitate recovery after brain injury. However, little is known about the mechanisms of exercise-induced neuroprotection after traumatic brain injury (TBI) or its modulation of post-traumatic neuronal cell death. Voluntary exercise, using a running wheel, was conducted for 4 weeks immediately preceding (preconditioning) moderate-level controlled cortical impact (CCI), a well-established experimental TBI model in mice. Compared to nonexercised controls, exercise preconditioning (pre-exercise) improved recovery of sensorimotor performance in the beam walk task, as well as cognitive/affective functions in the Morris water maze, novel object recognition, and tail-suspension tests. Further, pre-exercise reduced lesion size, attenuated neuronal loss in the hippocampus, cortex, and thalamus, and decreased microglial activation in the cortex. In addition, exercise preconditioning activated the brain-derived neurotrophic factor pathway before trauma and amplified the injury-dependent increase in heat shock protein 70 expression, thus attenuating key apoptotic pathways. The latter include reduction in CCI-induced up-regulation of proapoptotic B-cell lymphoma 2 (Bcl-2)-homology 3-only Bcl-2 family molecules (Bid, Puma), decreased mitochondria permeabilization with attenuated release of cytochrome c and apoptosis-inducing factor (AIF), reduced AIF translocation to the nucleus, and attenuated caspase activation. Given these neuroprotective actions, voluntary physical exercise may serve to limit the consequences of TBI.

Protective effect of geranylgeranylacetone against hydrogen peroxide-induced oxidative stress in human neuroblastoma cells

AIMS

Heat shock protein 70 (HSP70), one of the major HSPs, has been reported to suppress apoptosis and formation of pathogenic proteins in neurodegenerative disorders. Geranylgeranylacetone (GGA), an anti-ulcer drug, induces HSP70 and thereby protects against cellular damage in various diseases. We investigated the effect of GGA on hydrogen peroxide (H2O2)-induced neurotoxicity in human neuroblastoma SH-SY5Y cells.

MAIN METHODS

H2O2-induced neuronal toxicity was measured by a CCK-8 assay and Hoechst 33342 staining. We also assessed oxidative stress and apoptosis by measuring reactive oxygen species (ROS) generation with 2′,7′-dichlorofluorescein diacetate (DCFH-DA), caspase-3 activity, and mitogen-activated protein kinase (MAPK) pathway.

KEY FINDINGS

GGA showed a concentration-dependent inhibition on H2O2-induced apoptotic cell death. H2O2-induced induction of HSP70 was enhanced by GGA pretreatment. GGA effectively suppressed the up-regulation of Bax and down-regulation of Bcl-2. GGA also blocked the H2O2-induced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). In addition, GGA attenuated H2O2-induced ROS generation and caspase-3 activity.

SIGNIFICANCE

These results demonstrate that GGA protects SH-SY5Y cells from H2O2-induced apoptosis, at least in part by enhancing HSP70 production. Neuroprotective properties of GGA indicate that this compound may be a potential therapeutic agent for the treatment and prevention of neurodegenerative diseases.

HIF1α is necessary for exercise-induced neuroprotection while HIF2α is needed for dopaminergic neuron survival in the substantia nigra pars compacta

Exercise reduces the risk of developing a number of neurological disorders and increases the efficiency of cellular energy production. However, overly strenuous exercise produces oxidative stress. Proper oxygenation is crucial for the health of all tissues, and tight regulation of cellular oxygen is critical to balance O2 levels and redox homeostasis in the brain. Hypoxia Inducible Factor (HIF)1α and HIF2α are transcription factors regulated by cellular oxygen concentration that initiate gene regulation of vascular development, redox homeostasis, and cell cycle control. HIF1α and HIF2α contribute to important adaptive mechanisms that occur when oxygen and ROS homeostasis become unbalanced. It has been shown that preconditioning by exposure to a stressor prior to a hypoxic event reduces damage that would otherwise occur. Previously we reported that 3 months of exercise protects SNpc dopaminergic (DA) neurons from toxicity caused by Complex I inhibition. Here, we identify the cells in the SNpc that express HIF1α and HIF2α and show that running exercise produces hypoxia in SNpc DA neurons, and alters the expression of HIF1α and HIF2α. In mice carrying a conditional knockout of Hif1α in postnatal neurons we observe that exercise alone produces SNpc TH+ DA neuron loss. Loss of HIF1α also abolishes exercise-induced neuroprotection. In mice lacking Hif2α in postnatal neurons, the number of TH+ DA neurons in the adult SNpc is diminished, but 3months of exercise rescues this loss. We conclude that HIF1α is necessary for exercise-induced neuroprotection and both HIF1α and HIF2α are necessary for the survival and function of adult SNpc DA neurons.

High-altitude pulmonary edema can be prevented by heat shock protein 70-mediated hyperbaric oxygen preconditioning

BACKGROUND

The primary goal of this study was to test whether high-altitude exposure (HAE of 9.7% O2 at 0.47 absolute atmosphere [ATA] for 3 days) was capable of increasing lung edema, neutrophil, and hemorrhage scores as well as decreasing lung levels of both aquaporin 1 (AQP1) and AQP5 proteins and messenger RNA (mRNA) expression in rats, with a secondary goal to test whether a preinduction of heat shock protein 70 (HSP70) by hyperbaric oxygen preconditioning (HBO2P of 100% O2 at 2.0 ATA for 1 hour per day for 5 consecutive days) attenuated the HAE-induced increased lung injury scores and decreased lung AQP1 and AQP5 protein and mRNA expressions.

METHODS

Rats were assigned to (1) non-HBO2P (21% O2 at 1.0 ATA) + non-HAE (21% O2 at 1.0 ATA) group; (2) non-HBO2P + HAE group; (3) HBO2P + HAE group; and HBO2P + HSP70 antibodies (Ab) + HAE group. For the HSP70 Ab group, a neutralizing HSP70 Ab was injected intravenously at 24 hours before HAE. All the physiologic and biochemical parameters were obtained at the end of HAE or the equivalent period of non-HAE. The cardiovascular and blood gas parameters were monitored for all experiments. Bronchoalveolar lavage (BAL) was performed to determine proinflammatory cytokines (interleukin 6, interleukin 1β, and tumor necrosis factor α). Parts of the lung were excised for myeloperoxidase activity measurement, whereas the rest was collected for lung damage score assessments. AQP1 and AQP5 protein and mRAN expressions were also determined in the lung tissues.

RESULTS

In the non-HBO2P + HAE group, the animals displayed higher values of lung myeloperoxidase activity, BAL proinflammatory cytokines, lung water weight, and acute lung injury scores compared with those of the non-HBO2P + non-HAE controls. In contrast, the non-HBO2P + HAE group rats had lower values of lung AQP1 and AQP5 protein and mRNA expressions, mean arterial pressure, heart rate, SO2, Paco2, HCO3, and pH compared with those of non-HBO2P + non-HAE group rats. The increased acute lung edema, neutrophil, and hemorrhage scores; increased BAL levels of proinflammatory cytokines; decreased lung AQP1 and AQP5 protein and mRNA expressions; and hypotension, bradycardia, hypoxia, and acidosis caused by HAE were all significantly attenuated by HBO2P.

CONCLUSION

Our data indicate that HBO2P may attenuate high-altitude acute lung injury by a preinduction of lung HSP70 in rats.

Exercise preconditioning protects against spinal cord injury in rats by upregulating neuronal and astroglial heat shock protein 72

The heat shock protein 72 (HSP 72) is a universal marker of stress protein whose expression can be induced by physical exercise. Here we report that, in a localized model of spinal cord injury (SCI), exercised rats (given pre-SCI exercise) had significantly higher levels of neuronal and astroglial HSP 72, a lower functional deficit, fewer spinal cord contusions, and fewer apoptotic cells than did non-exercised rats. pSUPER plasmid expressing HSP 72 small interfering RNA (SiRNA-HSP 72) was injected into the injured spinal cords. In addition to reducing neuronal and astroglial HSP 72, the (SiRNA-HSP 72) significantly attenuated the beneficial effects of exercise preconditioning in reducing functional deficits as well as spinal cord contusion and apoptosis. Because exercise preconditioning induces increased neuronal and astroglial levels of HSP 72 in the gray matter of normal spinal cord tissue, exercise preconditioning promoted functional recovery in rats after SCI by upregulating neuronal and astroglial HSP 72 in the gray matter of the injured spinal cord. We reveal an important function of neuronal and astroglial HSP 72 in protecting neuronal and astroglial apoptosis in the injured spinal cord. We conclude that HSP 72-mediated exercise preconditioning is a promising strategy for facilitating functional recovery from SCI.

Autophagy suppression by exercise pretreatment and p38 inhibition is neuroprotective in cerebral ischemia

Autophagy is a degradative mechanism for cellular proteins and organelles, but its role in the nervous system is still not clear. In the present study, we found that exercise pretreatment and p38 inhibition had influence on autophagic process after cerebral ischemia, contributing to their neuroprotective effects. We examined the levels of p62 and phosphorylated ERK1/2 as an autophagic marker and cell-survival marker respectively after cerebral ischemic injury. The brain infarction volume after ischemia was measured as well. Both treadmill training pretreatment and p38 inhibition decreased the degradation of p62, promoted the phosphorylation of ERK1/2, and alleviated the brain infarction, indicating that these treatments could provide neuroprotection in cerebral ischemic injury via autophagy suppression.

The effects of exercise preconditioning on cerebral blood flow change and endothelin-1 expression after cerebral ischemia in rats

Stroke is an acute cerebrovascular disease with high incidence, morbidity, and mortality. Preischemic treadmill training has been shown to be effective in improving behavioral and neuropathologic indices after cerebral ischemia. However, the exact neuroprotective mechanism of preischemic treadmill training against ischemic injury has not been elucidated clearly. The present study investigated whether preischemic treadmill training could protect the brain from ischemic injury via regulating cerebral blood flow (CBF) and endothelin 1 (ET-1). We analyzed the CBF by laser speckle imaging and ET-1 expression by an enzyme-linked immunosorbent assay using an ischemic rat model with preischemic treadmill training. Generally speaking, ET-1 expression decreased and CBF increased significantly in the pretreadmill group. It is worth noting that ET-1 expression is increased at 24 hours of reperfusion in the pretreadmill group compared with the level of the time after middle cerebral artery occlusion. These changes were followed by significant changes in neurologic deficits and cerebral infarct volume. This study indicated that preconditioning exercise protected brain from ischemic injury through the improvement of CBF and regulation of ET-1 expression, which may be a novel component of the neuroprotective mechanism of preischemic treadmill training against brain injury.

Physical exercise training and neurovascular unit in ischemic stroke

Physical exercise could exert a neuroprotective effect in both clinical studies and animal experiments. A series of related studies have indicated that physical exercise could reduce infarct volume, alleviate neurological deficits, decrease blood-brain barrier dysfunction, promote angiogenesis in cerebral vascular system and increase the survival rate after ischemic stroke. In this review, we summarized the protective effects of physical exercise on neurovascular unit (NVU), including neurons, astrocytes, pericytes and the extracellular matrix. Furthermore, it was demonstrated that exercise training could decrease the blood-brain barrier dysfunction and promote angiogenesis in cerebral vascular system. An awareness of the exercise intervention benefits pre- and post stroke may lead more stroke patients and people with high-risk factors to accept exercise therapy for the prevention and treatment of stroke.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

Forced exercise before or after induction of 6-OHDA-mediated nigrostriatal insult does not mitigate behavioral asymmetry in a hemiparkinsonian rat model

Studies on exercise before and after toxin-induced hemiparkinsonism have reported promising findings in terms of amelioration of motor asymmetry in adult, 6-hydroxydopamine (6-OHDA) rats. However, recent studies have had more mixed results. Therefore, the purpose of this study was to further explore the notion of exercise, in particular forced exercise, as a potential neuroprotective therapy when implemented before and after 6-OHDA hemiparkinsonism. To explore this, two experiments were conducted: Experiment 1 - exercise before a 6-OHDA lesion; and, Experiment 2 - exercise after a 6-OHDA lesion. In Experiment 1, rats were randomly assigned into one of the two 4-week experimental conditions, a forced exercise condition and a non-exercise control condition. Then, after the experimental conditions rats were injected with 6-OHDA into the right medial forebrain bundle. In Experiment 2, rats were first injected with 6-OHDA and were then randomly assigned into one of the two 4-week experimental groups, a forced exercise group and a non-exercise control group. Outcomes in both experiments did not show any differences in terms of motor behavioral tests (i.e., apomorphine rotations, forelimb placement asymmetry, exploratory rearing) between the forced exercise and sedentary control groups. Based on our results and in light of the body of literature, it is possible that the stress of shock-motivated forced running utilized in this study may have canceled beneficial behavioral effects. Additionally, it is possible that the one-week delay in the forced exercise protocol implementation in Experiment 2 may have prevented behavioral rescue.

Increased expression of heat shock protein 70 in chronic obstructive pulmonary disease

BACKGROUND

Heat shock protein 70 (HSP70) plays a critical role in the process of inflammation and innate immunity response under environmental stress.

OBJECTIVES

This study was to investigate HSP70 expression in the peripheral lung tissues of chronic obstructive pulmonary disease (COPD) patients and in human bronchial epithelial cells (16-HBE) exposed to cigarette smoke extract (CSE).

METHODS

Peripheral lung tissues were collected after lung cancer resection from 26 patients without COPD, 20 with mild COPD and 15 with advanced COPD, classified by lung function criteria. Among these cases, 37 were smokers and 24 non-smokers. Lung tissues were examined for histopathological changes and levels of HSP70 and IL-8. Cultured 16-HBE cells were stimulated with CSE in the absence or presence of HSP70 neutralizing antibody and the expressions of IL-8 and phospho-EGFR protein were determined.

RESULTS

Compared to patients without COPD, the levels of HSP70 and IL-8 were significantly increased in the lung tissues of COPD patients and positively correlated with the severity of the disease. The HSP70 expression was significantly higher in current smokers than that in non-smokers. Moreover, CSE-induced HSP70 significantly enhanced IL-8 production and EGFR phosphorylation in 16-HBE cells. The increases in IL-8 and phospho-EGFR were blocked by anti-HSP70 antibody.

CONCLUSIONS

Our study clarified that increased expression of HSP70 is closely related to COPD disease severity and smoking status. Extracellular HSP70 regulated chemokine productions and EGFR phosphorylation and plays an important role in the CSE-induced inflammatory and innate immunity responses in bronchial epithelia cells.

Neuroprotective effects of prior exposure to enriched environment on cerebral ischemia/reperfusion injury in rats: the possible molecular mechanism

Increasing evidence shows that exposure to an enriched environment (EE) after cerebral ischemia/reperfusion injury is neuroprotective in animal models. Recent studies have demonstrated that animals housed in an enriched environment condition after an experimental stroke obtained a better functional outcome than those housed in a standard condition. However, little is known about the underlying mechanisms of neuroprotective effects of enriched environment exposure prior to injury. The current study examined the neuroprotective effects of prior enriched environment exposure after transient middle cerebral artery occlusion (MCAO) in rats. Male Sprague Dawley (SD) rats, weighing 55-65g at the beginning of the experiment, were randomly assigned to a pre-ischemic enriched environment (PIEE) or pre-ischemic standard condition (PISC) group for 1 month. They were weighed on days1, 7, 18, and 28, and their locomotor activity was tracked during the period between 9:00am and 3:00pm daily. After 1 month, ischemia was induced by occluding the middle cerebral artery for 90min, followed by reperfusion. After approximately 24h of the operation, functional outcomes were assessed using the beam-walking test and a neurological evaluation scale in all rats. We measured the expression of extracellular signal regulated protein kinases1/2 (ERK1/2) by western blotting and gene expression levels of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthasen (iNOS) by Real-Time PCR in the cortical area affected by ischemia. Finally, we measured the level of malondialdehyde (MDA) content, which is a biomarker of oxidative stress. The results showed that rats in the PIEE group had lighter weight than those in the PISC group. The functional outcomes of rats in the PIEE group were better than those in the PISC group, and substances associated with inflammation, such as MDA, nNOS, iNOS, and phospho-ERK1/2, were lower in the PIEE group compared with the PISC group. These results indicate that enriched environment may provide neuroprotection via ischemic preconditioning and enhance resilience to cerebral ischemia.

Inhibition of C2C12 myotube atrophy by a novel HSP70 inducer, celastrol, via activation of Akt1 and ERK1/2 pathways

Celastrol (CEL) is known as a potent inducer of heat shock protein (HSP) in non-muscle cells and exhibits cytoprotective function and inhibitory effects on proteasome and glucocorticoid receptor activities. To investigate an anti-atrophic effect of CEL on skeletal muscle cells, C2C12 myotubes were treated with 150 μM dexamethasone (DEX) for 24h and 1.5 μM CEL was added for the last 6h during the 24h DEX treatment. Compared to the control, the myotube diameter was reduced by a factor of 0.30 by DEX, but CEL treatment almost abrogated the DEX-induced atrophy. CEL treatment also increased expression of HSP72 and phosphorylation of heat shock transcription factor 1 (p-HSF1) 11-fold and 3.4-fold, respectively, as well as accumulation of p-HSF1 in the nucleus. Furthermore, CEL treatment elevated activities of Akt1, p70/S6K and ERK1/2 2.0- to 4.4-fold whereas DEX had no effect on these signaling activities. Inhibition of Akt1 and ERK1/2 pathways by specific inhibitors confirmed CEL-induced anti-atrophic effect. Moreover, DEX-mediated downregulation of FoxO3 phosphorylation and upregulation of MuRF1 expression and proteasome activity were abrogated by CEL treatment. These results demonstrate a novel anti-atrophic function of CEL in muscle cells via both activation of protein anabolic signals and suppression of catabolic signaling activities.

Attenuating heatstroke-induced acute lung inflammation, edema, and injury in rats by exercise preconditioning

BACKGROUND

This study aimed to ascertain whether heat-induced acute lung edema, inflammation, and ischemic damage can be affected by heat shock protein 70 (HSP-70)-mediated exercise preconditioning (EP) in rats.

METHODS

Wistar rats were assigned to one of the following four groups: the non-EP + nonheated group, the non-EP + heated group, the EP + heated group, and the EP + HSP-70 antibodies + heated group. EP groups of animals were subjected to a protocol of running on a treadmill for 30 minutes at 20 m/min, 30 minutes at 30 m/min, and 60 minutes at 30 m/min after 1, 2, and 3 weeks of training, respectively. Heated group of animals, under general anesthesia, were put in a folded heating pad of 43°C for 68 minutes. Then, the heated animals were allowed to recover at room temperature. HSP-70 antibodies were injected intravenously 24 hours before heat exposure.

RESULTS

As compared with the non heated + non-EP rats, the heated + non-EP rats had significantly higher scores of alveolar edema, neutrophil infiltration, and hemorrhage, acute pleurisy, and increased bronchoalveolar fluid levels of proinflammatory cytokines and ischemic and oxidative damage markers. EP, in addition to inducing overexpression of HSP-70 in lung tissues, significantly attenuated heat-induced acute pulmonary edema, inflammation, and ischemic and oxidative damage in the lungs. HSP-70 antibodies, in addition to reducing HSP-70 expression in the lungs, significantly attenuated the beneficial effects of EP in reducing acute lung inflammation and injury.

CONCLUSION

EP may attenuate the occurrence of pulmonary edema, inflammation, as well as ischemic and oxidative damage caused by heatstroke by up-regulating HSP-70 in the lungs.

Method parameters' impact on mortality and variability in rat stroke experiments: a meta-analysis

Background

Even though more than 600 stroke treatments have been shown effective in preclinical studies, clinically proven treatment alternatives for cerebral infarction remain scarce. Amongst the reasons for the discrepancy may be methodological shortcomings, such as high mortality and outcome variability, in the preclinical studies. A common approach in animal stroke experiments is that A) focal cerebral ischemia is inflicted, B) some type of treatment is administered and C) the infarct sizes are assessed. However, within this paradigm, the researcher has to make numerous methodological decisions, including choosing rat strain and type of surgical procedure. Even though a few studies have attempted to address the questions experimentally, a lack of consensus regarding the optimal methodology remains.

Methods

We therefore meta-analyzed data from 502 control groups described in 346 articles to find out how rat strain, procedure for causing focal cerebral ischemia and the type of filament coating affected mortality and infarct size variability.

Results

The Wistar strain and intraluminal filament procedure using a silicone coated filament was found optimal in lowering infarct size variability. The direct and endothelin methods rendered lower mortality rate, whereas the embolus method increased it compared to the filament method.

Conclusions

The current article provides means for researchers to adjust their middle cerebral artery occlusion (MCAo) protocols to minimize infarct size variability and mortality.

Early Exercise Protects against Cerebral Ischemic Injury through Inhibiting Neuron Apoptosis in Cortex in Rats

Early exercise is an effective strategy for stroke treatment, but the underlying mechanism remains poorly understood. Apoptosis plays a critical role after stroke. However, it is unclear whether early exercise inhibits apoptosis after stroke. The present study investigated the effect of early exercise on apoptosis induced by ischemia. Adult SD rats were subjected to transient focal cerebral ischemia by middle cerebral artery occlusion model (MCAO) and were randomly divided into early exercise group, non-exercise group and sham group. Early exercise group received forced treadmill training initiated at 24 h after operation. Fourteen days later, the cell apoptosis were detected by TdT-mediated dUTP-biotin nick-end labeling (TUNEL) and Fluoro-Jade-B staining (F-J-B). Caspase-3, cleaved caspase-3 and Bcl-2 were determined by western blotting. Cerebral infarct volume and motor function were evaluated by cresyl violet staining and foot fault test respectively. The results showed that early exercise decreased the number of apoptotic cells (118.74 ± 6.15 vs. 169.65 ± 8.47, p < 0.05, n = 5), inhibited the expression of caspase-3 and cleaved caspase-3 (p < 0.05, n = 5), and increased the expression of Bcl-2 (p < 0.05, n = 5). These data were consistent with reduced infarct volume and improved motor function. These results suggested that early exercise could provide neuroprotection through inhibiting neuron apoptosis.

Enriched environment preconditioning induced brain ischemic tolerance without reducing infarct volume and edema: the possible role of enrichment-related physical activity increase

External stimuli, including environmental enrichment (EE) and physical activity, have been shown to significantly facilitate recovery from brain injury. However, whether EE can be used as a preconditioning method to induce cerebral ischemic tolerance has never been investigated. Furthermore, whether, and to what extent, such environmental stimuli regulate physical activity to promote neuroprotection is largely unclear. To examine the neuroprotective effects of pre-ischemic EE (PIEE) and to investigate the relationship between these effects and EE-induced physical activity, we tested neurobehavioral and morphological recovery of rats following transient focal cerebral ischemia. Our study showed that PIEE improved the recovery of motor function, spatial learning and memory without reduction in brain edema or infarct volume. We also found that PIEE robustly increased the level of physical activity of rats that positively correlated with the extent of neurobehavioral recovery. Our results suggest that PIEE may induce brain ischemic tolerance through, at least partially, increasing physical activity.

Hypobaric hypoxia preconditioning attenuates experimental heatstroke syndromes via preinduction of heat shock protein 70

INTRODUCTION

Heatstroke has been defined as a form of hyperthermia associated with a systemic inflammatory response that leads to multiple organ dysfunction syndrome (MODS). It has also been documented that heat shock protein 70 (HSP70) preconditioning is able to induce thermotolerance. Here, the authors further investigated whether hypobaric hypoxia preconditioning (HHP) improved the MODS in heatstroke by up-regulation of HSP70.

METHODS

Anesthetized rats were randomly assigned to (a) non-HHP + nonheated group, (b) non-HHP + heated group, (c) HHP + heated group and (d) HHP + HSP70 antibodies (Abs) + heated groups. All heated groups were exposed to heat stress (43°C, 70 minutes) to induce heatstroke. For HHP, animals were exposed to 0.66 atmosphere absolute (18.3% O2) for 5 hours daily for consecutive 5 days per week for 2 weeks before the start of heat exposure.

RESULTS

HHP significantly (i) attenuated hypotension, (ii) reduced plasma index of the toxic oxidizing radicals and the organ injury indicator, (iii) attenuated plasma systemic inflammatory response molecules, (iv) reduced an index of infiltration of polymorphonuclear neutrophils in the lung like myeloper-oxidase activity, (v) promoted plasma levels of an anti-inflammatory cytokine, interleukin-10, (vi) promoted the survival time to fourfold compared with non-HHP group and (vii) promoted the overexpression of HSP70 in different organs (eg, the lung) during heatstroke. The beneficial effects of HHP could be significantly attenuated by HSP70 Ab preconditioning.

CONCLUSION

Our results show that HHP protects rats from heat-induced MODS via up-regulating HSP70. Thus, HHP could be a novel strategy for the prevention of heatstroke animals or patients before heat exposure.

Energy intake and exercise as determinants of brain health and vulnerability to injury and disease

Evolution favored individuals with superior cognitive and physical abilities under conditions of limited food sources, and brain function can therefore be optimized by intermittent dietary energy restriction (ER) and exercise. Such energetic challenges engage adaptive cellular stress-response signaling pathways in neurons involving neurotrophic factors, protein chaperones, DNA-repair proteins, autophagy, and mitochondrial biogenesis. By suppressing adaptive cellular stress responses, overeating and a sedentary lifestyle may increase the risk of Alzheimer's and Parkinson's diseases, stroke, and depression. Intense concerted efforts of governments, families, schools, and physicians will be required to successfully implement brain-healthy lifestyles that incorporate ER and exercise.

Physical activity in the prevention of ischemic stroke and improvement of outcomes: a narrative review

Physical activity is an integral component of stroke prevention. Although approximately 80% of strokes are due to cerebral ischemia, the mechanisms linking physical activity to the incidence of and recovery from ischemic stroke are not completely understood. This review summarizes evidence from human and animal studies regarding physical activity in the prevention of overt and covert ischemic stroke and associated injury. In cohort studies, people who are physically active have reduced rates of overt ischemic stroke and ischemic stroke mortality. However, few human studies have examined physical activity and the incidence of covert stroke. Evidence from animal models of ischemic stroke indicates that physical activity reduces injury after ischemic stroke by reducing infarct size and apoptotic cell death. Accordingly, physical activity may reduce the magnitude of injury from ischemic stroke so that there are fewer or less severe symptoms. Future research should investigate physical activity and incidence of covert stroke prospectively, ascertain the optimal dose and type of exercise to prevent ischemic injury, and identify the underlying neuroprotective mechanisms.

Preconditioning for traumatic brain injury

Traumatic brain injury (TBI) treatment is now focused on the prevention of primary injury and reduction of secondary injury. However, no single effective treatment is available as yet for the mitigation of traumatic brain damage in humans. Both chemical and environmental stresses applied before injury have been shown to induce consequent protection against post-TBI neuronal death. This concept termed "preconditioning" is achieved by exposure to different pre-injury stressors to achieve the induction of "tolerance" to the effect of the TBI. However, the precise mechanisms underlying this "tolerance" phenomenon are not fully understood in TBI, and therefore even less information is available about possible indications in clinical TBI patients. In this review, we will summarize TBI pathophysiology, and discuss existing animal studies demonstrating the efficacy of preconditioning in diffuse and focal type of TBI. We will also review other non-TBI preconditioning studies, including ischemic, environmental, and chemical preconditioning, which maybe relevant to TBI. To date, no clinical studies exist in this field, and we speculate on possible future clinical situations, in which pre-TBI preconditioning could be considered.

Salvinorin A administration after global cerebral hypoxia/ischemia preserves cerebrovascular autoregulation via kappa opioid receptor in piglets

Background

Cerebral hypoxia/ischemia (HI) is not uncommon during the perinatal period. If occurring, it can result in severe neurologic disabilities that persist throughout life. Salvinorin A, a non-opioid Kappa opioid receptors (KOR) selective agonist, has the potential to address this devastating situation. We have demonstrated that salvinorin A administration before HI, preserves pial artery autoregulative function through both the KOR and extracellular signal-regulated kinases (ERK) pathways. In the present study, we tested the hypothesis that administration of salvinorin A after HI could preserve cerebral autoregulation via KOR and ERK pathway.

Methodology/Principal Findings

The response of the pial artery to hypercapnia, hypotension and isoproterenol were monitored before and 1 hour after HI in piglets equipped with a cranial window. Four groups of drug administration were performed after HI. The control group had DMSO (1 µl/kg, i.v.) administrated immediately after HI. Two salvinorin A treated groups had salvinorin A (10 µg/kg, i.v.) administrated 0 and 30 min after HI, respectively. The 4^th group had salvinorin A and the KOR antagonist norbinaltorphimine (Nor-BIN, 1 µM topical) co-administrated 0 min after HI (n = 5). The dilation responses of the pial artery to hypercapnia and hypotension were impaired after global HI and were preserved with salvinorin A administration immediately or 30 min after HI. The preservation of autoregulation was abolished when nor-BIN was administered. Levels of phosphor-ERK(pERK)/ERK in the cerebrospinal fluid (CSF) were measured before and 1 hour after HI. After HI, the pERK/ERK levels significantly increased in both DMSO control group and salvinorin A and nor-BIN co-administration group. The elevated levels of pERK/ERK were not observed with salvinorin A only groups.

Conclusions

Salvinorin A administration 0 and 30 min after HI preserves autoregulation of pial artery to hypercapnia and hypotension via kappa opioid receptor and ERK pathway.

Salvinorin A pretreatment preserves cerebrovascular autoregulation after brain hypoxic/ischemic injury via extracellular signal-regulated kinase/mitogen-activated protein kinase in piglets

BACKGROUND

Cerebral hypoxia/ischemia during infant congenital heart surgery is not uncommon and may induce devastating neurologic disabilities persistent over the lifespan. Hypoxia/ischemia-induced cerebrovascular dysfunction is thought to be an important contributor to neurological damage. No pharmacological agents have been found to prevent this. Mitogen activated protein kinase (MAPK), including extracellular signal regulated kinase (ERK), c-Jun-N-terminal kinase, and p38, is thought to contribute to ischemic preconditioning. We investigated whether pretreatment with salvinorin A, the only natural nonopioid κ receptor agonist, could preserve autoregulation of the pial artery via MAPK.

METHODS

The response of the pial artery to hypotension and hypercapnia was monitored in piglets equipped with a closed cranial window before and after hypoxia and ischemia in the presence or absence of U0126, an inhibitor for the protein kinase upstream of ERK, sp600125, an inhibitor of c-Jun-N-terminal kinase or sb203580, an inhibitor of p38. Salvinorin A (10 μg/kg IV) was administered 30 minutes before hypoxia/ischemia in salvinorin-treated animals. Cerebrospinal fluid samples were collected before and 30 minutes after salvinorin A administration for the measurement of MAPK. Data (n = 5) were analyzed by repeated-measures analysis of variance.

RESULTS

Pial artery dilation to hypercapnia and hypotension was blunted after hypoxia/ ischemia but preserved well by pretreatment with salvinorin A. U0126, but not sp600125 or sb203580, abolished the preservative effects of salvinorin A on cerebral vascular autoregulation to hypotension and hypercapnia. The ratio of pERK/ERK in cerebrospinal fluid increased significantly in salvinorin-treated animals, which was inhibited by U0126.

CONCLUSIONS

Salvinorin A pretreatment preserves autoregulation of the pial artery to hypotension and hypercapnia after hypoxia/ischemia via ERK in a piglet model.

Evaluation of peripheral nerve regeneration via in vivo serial transcutaneous imaging using transgenic Thy1-YFP mice

This study uses the saphenous nerve crush model in Thy1-YFP mice and serial transcutaneous imaging to evaluate the rate of nerve regeneration under various FK-506 (tacrolimus) dosing regimens and in the presence of transgenic overexpression of glial cell line-derived neurotrophic factor (GDNF). Thy1-YFP transgenic mice received saphenous nerve crush and were monitored for axonal regeneration via transcutaneous imaging for 7 days. Group A received no FK-506. Groups B and C received FK-506 at 2 or 0.5 mg/kg/day, starting three days before injury (preload). Groups D and E received FK-506 at 2 or 0.5 mg/kg/day, starting on the day of injury. Group F consisted of double transgenic mice with central overexpression of GDNF by CNS astrocytes (GFAP-GDNF/Thy1-YFP). Length and rate of axonal regeneration were measured and calculated over time. Regardless of concentration, FK-506 preload (Groups B and C) improved length and rate of axonal outgrowth compared with controls (Group A) and no preload (Groups D and E). Surprisingly, central overexpression of GDNF (GFAP-GDNF) delayed and stunted axonal outgrowth. Saphenous nerve crush in Thy1-YFP mice represents a viable model for timely evaluation of therapeutic strategies affecting the rate of nerve regeneration. FK-506 administered three days prior to injury accelerates axonal regeneration beyond injury conditioned regeneration alone and may serve as a reliable positive control for the model. GDNF overexpression in the CNS impedes early axonal outgrowth.

Exercise inhibits neuronal apoptosis and improves cerebral function following rat traumatic brain injury

Exercise is reported to inhibit neuronal apoptotic cell death in the hippocampus and improve learning and memory. However, the effect of exercise on inhibition of neuronal apoptosis surrounding the area of damage after traumatic brain injury (TBI) and the improvement of cerebral dysfunction following TBI are unknown. Here, we investigate the effect of exercise on morphology and cerebral function following TBI in rats. Wistar rats received TBI by a pneumatic controlled injury device were randomly divided into two groups: (1) non-exercise group and (2) exercise group. The exercise group ran on a treadmill for 30 min/day at 22 m/min for seven consecutive days. Immunohistochemical and behavioral studies were performed following TBI. The number of single-stranded DNA (ssDNA)-positive cells around the damaged area early after TBI was significantly reduced in the exercise group compared with the non-exercise group (P < 0.05). Furthermore, most ssDNA-positive cells in the non-exercise group co-localized with neuronal cells. However, in the exercise group, a few ssDNA-positive cells co-localized with neurons. In addition, there was a significant increase in neuronal cell number and improvement in cerebral dysfunction after TBI in the exercise group compared with the non-exercise group (P < 0.05). These results indicate that exercise following TBI inhibits neuronal degeneration and apoptotic cell death around the damaged area, which results in improvement of cerebral dysfunction. In summary, treadmill running improved cerebral dysfunction following TBI, indicating its potential as an effective clinical therapy. Therefore, exercise therapy (rehabilitation) in the early phase following TBI is important for recuperation from cerebral dysfunction.

Exercise preconditioning and brain ischemic tolerance

It is well established that physical exercise can exert neuroprotection both in clinical settings and animal experiments. A series of studies have demonstrated that physical exercise may be a promising preconditioning method to induce brain ischemic tolerance through the promotion of angiogenesis, mediation of the inflammatory response, inhibition of glutamate over-activation, protection of the blood brain barrier (BBB) and inhibition of apoptosis. Through these mechanisms, exercise preconditioning may reduce the neural deficits associated with ischemia and the development of brain infarction and thus provide brain ischemic tolerance. An awareness of the benefits of exercise preconditioning may lead more patients to accept exercise therapy in cases of ischemic stroke.

Extracellular heat shock proteins (eHSP70) in exercise: Possible targets outside the immune system and their role for neurodegenerative disorders treatment

The intracellular heat shock protein 70kDa (iHSP70) is a universal marker of stress protein whose expression is induced by different cell stressors, such as heat, metabolite deprivation, redox imbalances and also during physical exercise. The activation of the iHSP70 is sine qua non for the promotion of tissue repair, since the expression of this chaperone confers cytoprotection and also exerts anti-inflammatory effects. On the other hand, exercise also induces the appearance of HSP70 in the extracellular medium (eHSP70) but, so far, the eHSP70 function has been mainly attributed to the activation of the immune system, seeming to perform an opposite function from the iHSP70. Since a moderate intensity exercise bout induces a general anti-inflammatory response even in the presence of an elevated eHSP70, this protein could carry out other functions rather than immune activation. Because exercise generates heat and metabolic challenges (especially on glucose metabolism) we suggests that the motoneurons, a very active (possibly one of the most stressed cells during exercise) and also very sensitive cells to heat and glucose metabolism imbalances, could be the major sites for the eHSP70 function. Due to the importance of the iHSP70 for repair and stress adaptation, this protein must be present in abundance on the site of stress and, because of its intrinsic inability response to stress [low heat shock factor 1 (HSF-1) activation] and the structure of the motoneurons (very long cells), the iHSP70, produced on the very far nucleus, is not appropriately transported through the axon to the axon terminal, were it is required. Then, during the exercise, the released eHSP70 can be internalized by the motoneurons and act as intracellular chaperons, protecting this cell against oxidative damage, protein denaturation and many others. Since a decreased iHSP70 expression capacity is associated with neurodegeneration diseases (such as Parkinson, polyglutamine, Amyotrophic lateral sclerosis, Alzheimer's, Huntington's and many others), the understanding of the physiological function of the extracellular HSP70 could be helpful on the treatment of neurodegenerative and other neuronal diseases. Besides that, it could explain some of the beneficial effects of the pharmacological HSP70 activators and also the beneficial effects of the exercise among neuronal cells during neurodegenerative-inducing diseases.

Combined effect of tumor necrosis factor (TNF)-alpha and heat shock protein (HSP)-70 in reducing apoptotic injury in hypoxia: a cell culture study

Studies have demonstrated neuroprotective effects of either TNF-alpha or HSP-70 in ischemia/reperfusion injury following exercise. However, the protective mechanisms involving combined effect of the two proteins, particularly in neuronal apoptosis, remain unclear. This study aims to elucidate the beneficial role of TNF-alpha and HSP-70 in the regulation of apoptotic proteins and ERK signaling in hypoxic injury. Cortical neurons from 20 Sprague-Dawley rat embryos were isolated and cultured in five groups with or without pretreatment with recombinant TNF-alpha, HSP-70 protein or both prior to hypoxic conditions: (1) control; (2) control/hypoxia; (3) TNF-alpha/hypoxia; (4) HSP-70/hypoxia and (5) TNF-alpha/HSP-70/hypoxia. Western blotting was used to detect pro- and anti-apoptotic proteins, including Bax, AIF, Bcl-xL, Bcl-2, and pERK1/2 protein. TNF-alpha and HSP-70 significantly (p<0.05) reduced the levels of pro-apoptotic proteins, Bax and AIF. Also, pretreatment of hypoxic brain tissue with TNF-alpha and HSP-70 significantly (p<0.05) enhanced the levels of anti-apoptotic protein, Bcl-xL. TNF-alpha and HSP-70 together increased Bcl-2 levels by 70%. Hypoxia caused a significant (p<0.05) increase in ERK1/2 phosphorylation levels by 224%. The most effective inhibition of ERK levels was obtained by the combined administration of TNF-alpha and HSP-70. This study suggested that TNF-alpha and HSP-70 together enhance the decrease in pro-apoptotic protein levels and the increase in anti-apoptotic protein levels in the event of neuronal hypoxia through ERK1/2 signal transduction.

Pre-ischemic treadmill training induces tolerance to brain ischemia: involvement of glutamate and ERK1/2

Physical exercise has been shown to be beneficial in stroke patients and animal stroke models. However, the exact mechanisms underlying this effect are not yet very clear. The present study investigated whether pre-ischemic treadmill training could induce brain ischemic tolerance (BIT) by inhibiting the excessive glutamate release and event-related kinase 1/2 (ERK1/2) activation observed in rats exposed to middle cerebral artery occlusion (MCAO). Sprague–Dawley rats were divided into three groups (n = 12/group): sham surgery without prior exercise, MCAO without prior exercise and MCAO following three weeks of exercise. Pre-MCAO exercise significantly reduced brain infarct size (103.1 ± 6.7 mm³) relative to MCAO without prior exercise (175.9 ± 13.5 mm³). Similarly, pre-MCAO exercise significantly reduced neurological defects (1.83 ± 0.75) relative to MCAO without exercise (3.00 ± 0.63). As expected, MCAO increased levels of phospho-ERK1/2 (69 ± 5%) relative to sham surgery (40 ± 5%), and phospho-ERK1/2 levels were normalized in rats exposed to pre-ischemic treadmill training (52 ± 6%) relative to MCAO without exercise (69% ± 5%). Parallel effects were observed on striatal glutamate overflow. This study suggests that pre-ischemic treadmill training might induce neuroprotection by inhibiting the phospho-ERK1/2 over-activation and reducing excessive glutamate release