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‘Ischemic tolerance’ phenomenon found in the brain
Abstract
We investigated the possibility that neuronal cells given a mild ischemic treatment sufficient to perturb the cellular metabolism acquired tolerance to a subsequent, and what would be lethal, ischemic stress in vivo. Cerebral ischemia was produced in the gerbils by occlusion of both common carotids for 5 min, which consistently resulted in delayed neuronal death in the CA1 region of the hippocampus. Minor 2-min ischemia in this model depletes high-energy phosphate compounds and perturbs the protein synthesis, but never causes neuronal necrosis, and therefore was chosen as mild ischemic treatment. Single 2-min ischemia 1 day or 2 days before 5 min ischemia exhibited only partial protective effects against delayed neuronal death. However, two 2-min ischemic treatments at 1 day intervals 2 days before 5 min ischemia exhibited drastically complete protection against neuronal death. The duration and intervals of ischemic treatment, enough to perturb cellular metabolism and cause protein synthesis, were needed respectively, because neither 1-min ischemia nor 2-min ischemia received twice at short intervals exhibited protective effects. This 'ischemic tolerance' phenomenon induced by ischemic stress--which is unquestionably important--and frequent stress in clinical medicine, is intriguing and may open a new approach to investigate the pathophysiology of ischemic neuronal damage.
... They occluded left circumflex artery in repetitive cycles prior to prolonged occlusion of the same artery reducing myocardial infarct size. In neural tissue the same concept of ischemic tolerance was introduced in a gerbil model [27]. Further studies found ischemic preconditioning to be similarly effective when applied at a distance along with another non-target tissue referring to a method of remote ischemic preconditioning [28,29] (RIPC). ...
... Ã Three articles were included in the analysis through reference list search. together with cytoskeleton elements and their signaling pathways or tissue architecture elements [27,44,48,49,57,68,69]. Catecholamine and its metabolites by Fan et al. [46], as well as, copper, calcium, magnesium, zinc by Yu et al. [61], oxidative stress by Lee et al. [63], proliferative, degenerating and ependymal cells by Orend a cov a et al. [55,59] were also evaluated as possible mechanisms. ...
Objectives. Paraplegia is devastating complication associated with thoracic and thoracoabdominal aortic aneurysm repair. Vast evidence has been gathered on pre-, peri- and postoperative protective adjuncts aiming to minimize spinal cord ischemia. This review focuses on the pretreatment phase of open surgical or endovascular aortic procedures and gathers the experimental data on the interventional preconditioning and priming methods that increase the spinal cord ischemic tolerance. Design. By the start of March 2021, a systematic review was performed in PubMed, Scopus and Web of Science core collection to identify the articles that reported (i) either an ischemic preconditioning, remote ischemic preconditioning or priming method prior to (ii) experimental spinal cord ischemia performed in endovascular or open surgical fashion mimicking either thoracic, abdominal or thoracoabdominal aortic aneurysm procedures. (iii) The outcomes were reported via neurological, motor-evoked potential, somatosensory-evoked potential, histopathological, immunohistochemical, physiological analysis, or in different combinations of these measurements. Results. The search yielded 7802 articles, and 57 articles were included in the systematic review. The articles were assessed by the evaluated species, the utilized pretreatment, the measured protective effects, and the suggested underlying mechanisms. Conclusions. The reviewed articles showed several possible mechanisms in ischemic and remote ischemic preconditioning for prevention of spinal cord ischemia. The main suggested method for priming was arteriogenetic stimulus. Future studies should confirm these hints of arteriogenetic stimulus with more precise quantification of the protective recruitment process.
... Preexposure to a brief period of ischemia (brief ischemia) induces a neuroprotective mechanism in which neurons acquire tolerance to ischemia (termed ischemic tolerance or ischemic preconditioning) (18,19). We hypothesized that neural depolarization under both EE and brief ischemia conditions would trigger expression of common genes underlying the protective mechanism that blocks death induced by excitotoxicity (Fig. 2B). ...
... It is well known that a patient who either had a recent transient ischemic attack or recovered from a mild stroke is at high risk of recurrence (36). Although pretreatment with brief ischemia induces a neuroprotective mechanism (18,19), it is difficult to apply this to patients. Interestingly, animal experiments reveal that exercise preconditioning (walking on a treadmill) provides significant neuroprotection against stroke (37), although at least 2 or 3 wk of pretraining is necessary to induce ischemic tolerance. ...
Significance
Stroke is the second leading cause of death and the most frequent cause of disability in adults. After stroke, most ischemic neurons die and a few neurons live, leading to brain dysfunction; yet, genes involved in both neuronal survival and death remain poorly understood. Here, we found that the activity-dependent transcription factor Npas4 is essential for acquisition of neuronal tolerance to ischemia. Moreover, a systematic search for Npas4-downstream genes identified Gem , which encodes Ras-related small GTPase that mediates neuroprotective effects of Npas4. Gem suppresses the membrane localization of voltage-gated Ca ²⁺ channels to inhibit excess Ca ²⁺ influx, thereby protecting neurons from excitotoxic death. Our findings suggest that Gem expression via Npas4 promotes neuroprotection and neuroplasticity in injured and healthy brains, respectively.
... Ischemic preconditioning (IPC) refers to a phenomenon that a sublethal ischemic stimulation induces ischemic tolerance toward subsequent severe ischemia (Murry et al. 1986). This phenomenon has been reported in multiple organs, including the brain (Murry et al. 1986;Kitagawa et al. 1990). The underlying mechanisms for IPC-mediated neuroprotection are mainly related to neurons, including membrane stabilization, inhibition of excitability/apoptosis, and de novo protein synthesis (Bell et al. 2011;Yang et al. 2017;Kirino 2002;Ara and De Montpellier 2013). ...
... Previous animal studies have suggested that IPC promotes endogenous neurogenesis and angiogenesis, in addition to protect against subsequent stroke (Stetler et al. 2014;Kitagawa et al. 1990;Lee et al. 2007), while there is no study showing the effects of IPC on oligodendrogenesis. Here, we demonstrate that IPC enhanced cell proliferation in the SVZ and peri-ischemic area in mice for the first time and further explore whether IPC affects oligodendrogenesis in mice. ...
Ischemic preconditioning (IPC) is an approach of protection against cerebral ischemia by inducing endogenous cytoprotective machinery. However, few studies in neurogenesis and oligodendrogenesis after IPC have been reported, especially the latter. The purpose of this study is to test our hypothesis that IPC may also induce cell proliferation and oligodendrogenesis in the subventricular zone and striatum, as well as to investigate the effect of nuclear factor erythroid 2-related factor 2 (Nrf2) on oligodendrogenesis. IPC was induced in mice by 12-min ischemia through the occlusion of the middle cerebral artery. Newly generated cells were labeled with 5-bromo-2′-deoxyuridine. Our findings demonstrated that IPC stimulated the proliferation of neural stem cells in the subventricular zone, promoted the generation of oligodendrocyte precursor cells in the striatum and corpus callosum/external capsule (CC/EC), and stimulated oligodendrocyte precursor cells differentiation into oligodendrocytes in the striatum and the CC/EC. Furthermore, we describe a crucial role for Nrf2 in IPC-induced oligodendrogenesis in the subventricular zone, striatum, and CC/EC and show for the first time that Nrf2 promoted the migration and differentiation of oligodendrocyte precursor cells into oligodendrocytes in the striatum and CC/EC. Our data imply that IPC stimulates the oligodendrogenesis in the brain and that Nrf2 signaling may contribute to the oligodendrogenesis.
... After exposed the atlas carefully, a preheated electrocautery needle was used to electro-coagulate bilateral vertebral arteries permanently via the alar foramen. After two days recovery, the rats' bilateral common carotid arteries were exposed under anesthesia of isoflurane and clamped by clips for 8 min to occlude the blood flow in them to produce global cerebral ischemia, which usually result in DND of pyramidal neurons of hippocampus CA1 region 15 . Because it has been reported that systemic anesthesia can protect cerebral neurons against ischemic insult 16 , to exclude the effect of the anesthetic on the neuronal survival after ischemic insult and to evaluate the occurrence of global cerebral ischemia, the clamping of the bilateral common carotid arteries was performed when the rats awaked from the anesthesia of isoflurane. ...
... Paraffin brain sections with thionin stain were prepared as usual. Using the methods established by Kitagawa et al. and Kato et al 15,19 , conditions of the pyramidal neurons in CA1 subfield of hippocampus were assessed by histological grade (HG) and neuronal density (ND). HG including the following 4 grades: ① grade 0, without neuronal death; ② grade I, only scattered neuronal death; ③ grade II, massive neuronal death; ④ grade III, practically all neurons dead. ...
Our previous studies have shown that sulbactam can play a neuroprotection role in hippocampal neurons by upregulating the expression and function of glial glutamate transporter-1 (GLT-1) during ischemic insult. Here, using rat global cerebral ischemia model, we studied in vivo the role of p38 mitogen-activated protein kinases (MAPK) in the sulbactam-induced GLT-1 upregulation and neuroprotection against ischemia. The hippocampal CA1 field was selected as observing target. The expressions of phosphorylated-p38 MAPK and GLT-1 were assayed with western blot analysis and immunohistochemistry. The condition of delayed neuronal death (DND) was assayed with neuropathological evaluation under thionin staining. It was shown that administration of sulbactam protected CA1 hippocampal neurons against ischemic insult accompanied with significantly upregulation in the expressions of phosphorylated-p38 MAPK and GLT-1. The time course analysis showed that sulbactam activated p38 MAPK before the GLT-1 upregulation in either normal or global cerebral ischemic rats. Furthermore, inhibiting p38 MAPK activation by SB203580 blocked the GLT-1 upregulation and neuroprotection induced by sulbactam. The above results suggested that p38 MAPK, at least partly, participated in the sulbactam-induced brain tolerance to ischemia mediated by GLT-1 upregulation in rats.
... Indeed, it has recently received particular attention due to its similarity to some pathological conditions, such as brief ischemic TIA, which appears to protect the brain against a subsequent lethal stroke [89,90]. It was described for the first time in the heart [91] and then in many other irrorated organs, including the brain [92]. It is a phenomenon that can be induced by a sublethal anoxic insult that improves tissue tolerance to a subsequent and possibly fatal ischemic event. ...
Brain ischemia is one of the major causes of chronic disability and death worldwide. It is related to insufficient blood supply to cerebral tissue, which induces irreversible or reversible intracellular effects depending on the time and intensity of the ischemic event. Indeed, neuronal function may be restored in some conditions, such as transient ischemic attack (TIA), which may be responsible for protecting against a subsequent lethal ischemic insult. It is well known that the brain requires high levels of oxygen and glucose to ensure cellular metabolism and energy production and that damage caused by oxygen impairment is tightly related to the brain’s low antioxidant capacity. Oxygen is a key player in mitochondrial oxidative phosphorylation (OXPHOS), during which reactive oxygen species (ROS) synthesis can occur as a physiological side-product of the process. Indeed, besides producing adenosine triphosphate (ATP) under normal physiological conditions, mitochondria are the primary source of ROS within the cell. This is because, in 0.2–2% of cases, the escape of electrons from complex I (NADPH-dehydrogenase) and III of the electron transport chain occurring in mitochondria during ATP synthesis leads to the production of the superoxide radical anion (O2•−), which exerts detrimental intracellular effects owing to its high molecular instability. Along with ROS, reactive nitrosative species (RNS) also contribute to the production of free radicals. When the accumulation of ROS and RNS occurs, it can cause membrane lipid peroxidation and DNA damage. Here, we describe the intracellular pathways activated in brain tissue after a lethal/sub lethal ischemic event like stroke or ischemic tolerance, respectively, highlighting the important role played by oxidative stress and mitochondrial dysfunction in the onset of the two different ischemic conditions.
... The duration of hypoxia has a major effect on nerve injury, more so than the frequency of occurrences. An animal study investigating cerebral damage due to ischemia found that neuronal death occurred after 5 min of bilateral common carotid blood ow obstruction and not under 2 min, suggesting that short-term hypoxia may protect against subsequent long-term hypoxia exposure 32 . Moreover, peripheral nerves are more resistant to ischemia than the brain tissue [33][34][35] . ...
The relationship between obstructive sleep apnea (OSA) and hearing loss (HL) remains uncertain. We examined this association by retrospectively reviewing 90 patients diagnosed with OSA who underwent overnight polysomnography (PSG) and pure-tone audiometry. Patients with OSA were compared with non-OSA individuals, identified via the STOP-BANG questionnaire (SBQ) and age-sex 1:1 matching. The results indicated elevated hearing thresholds across all frequencies in the OSA group. Further categorization of patients with OSA into HL and non-HL groups revealed a significant increase in apnea duration in the HL group for all-frequency and high-frequency cases (p=0.038, 0.006). Multiple linear regression, adjusting for age and sex, revealed a significant influence of apnea duration on HL in both all-frequency and high-frequency cases (ß=0.404, p=0.002; ß=0.425, p=0.001). These findings underscore the reduced auditory function in patients with OSA and highlight the potential of apnea duration as a marker of chronic hypoxic damage linked to OSA.
... The recovery of function in neurons damaged by ischemia could thus be limited, even though reperfusion represents the main treatment for acute ischemic stroke (AIS). Conversely, the phenomenon leading to the acquisition of ischemic tolerance called "ischemic preconditioning" is known to provide marked neuroprotective effects against I/R injury, triggered by placing mild intermittent ischemic loads on the brain prior to fatal ischemic assault (Kitagawa et al. 1990;Nakagawa et al. 2002;Yin et al. 2005). However, predicting when AIS will occur is very difficult in clinical situations and provision of ischemic preconditioning for patients before AIS onset is not feasible. ...
The phenomenon of ischemic postconditioning (PostC) is known to be neuroprotective against ischemic reperfusion (I/R) injury. One of the key processes in PostC is the opening of the mitochondrial ATP-dependent potassium (mito-KATP) channel and depolarization of the mitochondrial membrane, triggering the release of calcium ions from mitochondria through low-conductance opening of the mitochondrial permeability transition pore. Mitochondrial calcium uniporter (MCU) is known as a highly sensitive transporter for the uptake of Ca²⁺ present on the inner mitochondrial membrane. The MCU has attracted attention as a new target for treatment in diseases, such as neurodegenerative diseases, cancer, and ischemic stroke. We considered that the MCU may be involved in PostC and trigger its mechanisms. This research used the whole-cell patch-clamp technique on hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca²⁺ concentration, mitochondrial membrane potential, and N-methyl-d-aspartate receptor (NMDAR) currents under inhibition of MCU by ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased the occurrence of sEPSCs (p = 0.014), NMDAR currents (p < 0.001), intracellular Ca²⁺ concentration (p < 0.001), and dead cells (p < 0.001) significantly after reperfusion, reflecting removal of the neuroprotective effects in PostC. Moreover, mitochondrial depolarization in PostC with Ru265 was weakened, compared to PostC (p = 0.004). These results suggest that MCU affects mitochondrial depolarization in PostC to suppress NMDAR over-activation and prevent elevation of intracellular Ca²⁺ concentrations against I/R injury.
Graphical Abstract
... Three images per section were taken using light microscopy (Olympus, BX63, Japan). The neuronal density (ND) in the hippocampal CA1 region was calculated as described earlier [29,30]. The ND of the hippocampal CA1 subfield was represented by the number of surviving pyramidal neurons with intact cell membrane, full nucleus, and clear nucleolus within 1 mm linear length of the CA1 subfield. ...
Cerebral ischemic preconditioning (CIP) has been shown to improve brain ischemic tolerance against subsequent lethal ischemia. Reactive astrocytes play important roles in cerebral ischemia–reperfusion. Recent studies have shown that reactive astrocytes can be polarized into neurotoxic A1 phenotype (C3d) and neuroprotective A2 phenotype (S100A10). However, their role in CIP remains unclear. Here, we focused on the role of N-myc downstream-regulated gene 2 (NDRG2) in regulating the transformation of A1/A2 astrocytes and promoting to brain ischemic tolerance induced by CIP. A Sprague Dawley rat model of middle cerebral artery occlusion/reperfusion (MCAO/R) was used. Rats were divided into the following six groups: (1) sham group; (2) CIP group: left middle cerebral artery was blocked for 10 min; (3) MCAO/R group: left middle cerebral artery was blocked for 90 min; (4) CIP + MCAO/R group: CIP was performed 72 h before MCAO/R; (5) AAV-NDRG2 + CIP + MCAO/R group: adeno-associated virus (AAV) carrying NDRG2 was administered 14 days before CIP + MCAO/R; (6) AAV-Ctrl + CIP + MCAO/R group: empty control group. The rats were subjected to neurological evaluation 24 h after the above treatments, and then were sacrificed for 2, 3, 5-triphenyltetraolium chloride staining, thionin staining, immunofluorescence and western blot analysis. In CIP + MCAO/R group, the neurological deficit scores decreased, infarct volume reduced, and neuronal density increased compared with MCAO/R group. Notably, CIP significantly increased S100A10 expression and the number of S100A10⁺/GFAP⁺ cells, and also increased NDRG2 expression. MCAO/R significantly decreased S100A10 expression and the number of S100A10⁺/GFAP⁺ cells yet increased C3d expression and the number of C3d⁺/GFAP⁺ cells and NDRG2 expression, and these trends were reversed by CIP + MCAO/R. Furthermore, over-expression of NDRG2 before CIP + MCAO/R, the C3d expression and the number of C3d⁺/GFAP⁺ cells increased, while S100A10 expression and the number of S100A10⁺/GFAP⁺ cells decreased. Meanwhile, over-expression of NDRG2 blocked the CIP-induced brain ischemic tolerance. Taken together, these results suggest that CIP exerts neuroprotective effects against ischemic injury by suppressing A1 astrocyte polarization and promoting A2 astrocyte polarization via inhibiting NDRG2 expression.
... Acute ischemic stroke can be treated by clot busting and clot removal, but main failure of this treatment is the short time interval from stroke onset within which it has to be used ( Researchers have also directed their focus from time to time so as to develop processes in order to salvage ischemic injury. Ischemic preconditioning (IPC) is a potent protective strategy introduced by Murry et al for the ischemic myocardium, which was later applied by Kitagawa et al to the ischemic neuronal injury (Murry, Jennings et al. 1986, Kitagawa, Matsumoto et al. 1990). IPC has been demonstrated in other organ systems as well including skeletal muscle, spinal cord, kidney, intestine, and liver (Goadsby and Edvinsson 1993, Pang, Yang et al. 1995, Hotter, Closa et al. 1996, Matsuyama, Chiba et al. 1997, Turman and Bates 1997. ...
... Furthermore, Mun et al. (2010) found that administering agmatine to a global ischemia model increased endothelial NOS (eNOS) expression but decreased iNOS expression, suggesting that agmatine protects the microvasculature in the brain by activation of eNOS and reduces extracellular matrix degradation by inhibition of iNOS and other proteins (e.g., MMMP-9; see below) during the early phase of ischemia 46 . In addition, it has been observed that the occurrence of several transient ischemic events induces the appearance of a phenomenon called ischemic preconditioning (IP), which protects the brain from a lethal ischemic event; for example, it has been described that IP protects hippocampal pyramidal cells from subsequent fatal ischemic events 55 . However, the mechanism behind this phenomenon has not been fully elucidated, so it is interesting to note that after several subsequently induced transient ischemic events, an increase in the synthesis and release of endogenous cerebral and hepatic agmatine has been reported. ...
Ischemic cerebrovascular diseases are leading cause of mortality and disability worldwide. Given the need for a pharmacological treatment for these diseases, agmatine has gained great interest due to its neuroprotective properties. This article explores these properties of agmatine in ischemic events and their underlying mechanisms. Agmatine, considered as a neuromodulator, exerts its effects through its interaction with various molecular targets, including glutamate receptors, nitric oxide synthase, and metalloproteinases. Its ability to cross the blood-brain barrier and its role in neurotransmission processes postulate agmatine as a potential candidate for neuroprotection. Agmatine has a positive effect in the central nervous system to counteract excitotoxicity, oxidative stress, inflammation, alteration of the blood-brain barrier and energy disorders during ischemic events. This review describes the multiple interactions of agmatine within the ischemic cascade known to date, showing its ability to mitigate free radical formation, attenuate excitotoxicity, modulate inflammatory responses, stabilize the blood-brain barrier, and preserve mitochondrial function. These properties position agmatine as a promising therapeutic agent for ischemic cerebrovascular diseases.
... This phenomenon was first discovered by Murry et al. in 1986 in a study of the heart [34]. The cardioprotective effect of ischemic tolerance is very strong and it has been observed in many organs other than the heart, including the lungs, kidneys, liver, skeletal muscle, and brain [35][36][37]. Therefore, many studies have attempted to elucidate the molecular mechanisms of ischemic tolerance as a key to therapeutic strategies for stroke. ...
Peripheral infection induces inflammation in peripheral tissues and the brain, impacting brain function. Glial cells are key players in this process. However, the effects of peripheral infection on glial activation and brain function remain unknown. Here, we showed that varying degrees of peripheral infection had different effects on the regulation of brain functions by microglia-dependent and -independent mechanisms. Acute mild infection (one-day LPS challenge: 1LPS) exacerbated middle cerebral artery occlusion (MCAO) injury, and severe infection (four-day LPS challenge: 4LPS) for one week suppressed it. MCAO injury was assessed by triphenyltetrazolium chloride staining. We observed early activation of microglia in the 1LPS and 4LPS groups. Depleting microglia with a colony-stimulating factor-1 receptor (CSF1R) antagonist had no effect on 1LPS-induced brain injury exacerbation but abolished 4LPS-induced protection, indicating microglial independence and dependence, respectively. Microglia-independent exacerbation caused by 1LPS involved peripheral immune cells including macrophages. RNA sequencing analysis of 4LPS-treated microglia revealed increased factors related to anti-inflammatory and neuronal tissue repair, suggesting their association with the protective effect. In conclusion, varying degrees of peripheral inflammation had contradictory effects (exacerbation vs. protection) on MCAO, which may be attributed to microglial dependence. Our findings highlight the significant impact of peripheral infection on brain function, particularly in relation to glial cells.
... Consequently, the recovery of the function in neurons damaged by ischemia could be limited even though reperfusion is the main treatment for acute ischemic stroke (AIS). On the contrary, the phenomenon of acquiring the ischemic tolerance called "ischemic preconditioning" is known for the remarkable neuroprotective effect against I/R injury, which is triggered by giving a mild intermittent ischemic load to brain before fatal ischemic assault (Kitagawa et al., 1990;Nakagawa et al., 2002;Yin et al., 2005). However, in the clinical situation, it is very di cult to predict when AIS occurs and impossible to make the application of ischemic preconditioning for patient before the onset. ...
Ischemic postconditioning (PostC) phenomenon is known as the neuroprotection against ischemic reperfusion (I/R) injury. One of the key processes in PostC is opening of mitochondrial ATP dependent potassium (mito-K ATP ) channel and depolarization of mitochondrial membrane potential, which triggers the release of calcium ion from mitochondria through the low conductance opening of mitochondrial permeability transition pore (mPTP). Mitochondrial calcium uniporter (MCU) is known as the highly sensitive transporter for uptake of Ca ²⁺ inwardly existed on the inner mitochondrial membrane. Furthermore, it has attracted attention as a new target of treatments in disease such as neurodegenerative disease, cancer and ischemic stroke. Thus, we considered that MCU may involve in PostC and trigger its mechanism. In this research, we used the whole-cell patch clamp technique to hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca ²⁺ concentration, mitochondrial membrane potential and N-methyl-D-aspartate receptor (NMDAR) currents under the inhibition of MCU by Ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased sEPSCs occurrence (p = 0.008), NMDAR currents (p < 0.001), intracellular Ca ²⁺ concentration (p < 0.001) and dead cells (p < 0.001) significantly after reperfusion, indicating the removal of the neuroprotective effects in PostC. Moreover, the mitochondrial depolarization in PostC with Ru265 was weakened, compared to it in PostC (p = 0.03). These results suggest that MCU affects the mitochondrial depolarization in the PostC mechanism to suppress NMDAR over-activation and prevent the elevation of intracellular Ca ²⁺ concentration against I/R injury.
... Also of note in the present study, cerebral ischemic tolerance has a profound effect on AIS. Repeated, transient ischemic burden induced greater ischemic tolerance than a single ischemic burden, as shown by Kitagawa et al. (1990) in a model of cerebral ischemia, who showed significant interhemispheric differences in ischemic tolerance in ipsilateral versus contralateral cerebral tissue. With stenosis or even occlusion of extracranial segments of the ICA, the ipsilateral hemisphere is in a prolonged low-flow state, and the tolerance of corresponding brain tissue increases. ...
Background
Previous studies on unilateral internal carotid artery occlusive disease have focused on the mechanisms of ipsilateral hemispheric stroke, and contralateral stroke is considered to be an accidental phenomenon. Little is known about the relationship between severe stenosis (including occlusion) of the unilateral extracranial segment of the internal carotid artery and contralateral cerebral stroke, and the infarct patterns and pathogenesis require further study. The purpose of this study was to investigate the clinical characteristics and pathogenesis of contralateral acute stroke with unilateral extracranial internal carotid artery stenosis (including occlusion).
Methods
Thirty‐four patients were enrolled in this study, and all patients underwent routine clinical evaluation, including medical history, physical examination, laboratory tests, and various imaging evaluations. The morphological characteristics of diffusion‐weighted magnetic resonance imaging were applied to determine infarct patterns. The etiological classification was confirmed according to the TOAST classification.
Results
There were six distinctive lesion patterns: small subcortical infarcts (six patients), large subcortical infarcts (one patient), diffuse infarcts (eight patients), multiple anterior circulation infarcts (eight patients), multiple posterior circulation infarcts (two patients), and multiple anterior and posterior circulation infarcts (nine patients).
Conclusion
Diffuse and multiple infarcts were the most common topographic patterns in ischemic stroke contralateral to internal carotid artery stenosis or occlusion. Hemodynamic impairment of the contralateral hemisphere due to hypoperfusion and blood theft is regarded as the basis of stroke occurrence. Low ischemic tolerance and embolism are the main causes of acute ischemic stroke.
... [120][121][122] Experiments in gerbils were the first to explore ischemic tolerance in the brain, demonstrating that ischemic damage after global ischemia could be reduced by prior brief ischemic challenges. 123,124 Roger Simon and colleagues later characterized the spatio-temporal profile of ischemic tolerance in a rat intraluminal filament model of stroke. These studies showed a window of tolerance where reduced brain injury followed a prolonged MCA occlusion lasted at least four days after the brief MCA occlusion. ...
In recent years, medical developments have resulted in an increase in human life expectancy. Some developed countries now have a larger population of individuals aged over 64 than those under 14. One consequence of the ageing population is a higher incidence of certain neurodegenerative disorders. In order to prevent these, we need to learn more about them. This book provides up-to-date information on the use of transgenic mouse models in the study of neurodegenerative disorders such as Alzheimer's and Huntington's disease. By reproducing some of the pathological aspects of the diseases, these studies could reveal the mechanism for their onset or development. Some of the transgenic mice can also be used as targets for testing new compounds with the potential to prevent or combat these disorders. The editors have extensive knowledge and experience in this field and the book is aimed at undergraduates, postgraduates and academics. The chapters cover disorders including: Alzheimer's disease, Parkinson's disease, Huntington's and other CAG diseases, amyotrophic lateral sclerosis (ALS), recessive ataxias, disease caused by prions, and ischemia.
... Исследования, начатые еще в XIX веке, к 60-м годам XX века сформировали представления о гипоксии, как о важнейшем проявлении патологии тканей и клеток, вызываемом комплексом физических, химических и биологических факторов. К концу века сформировались представления не о патогенных, а об адаптогенных свойствах гипоксии умеренной силы, которую можно использовать в качестве прекондиционирующего (упреждающего, защитного) воздействия для снижения повреждающего эффекта последующей, более тяжелой формы гипоксии на мозг [1]. Главным патогенетическим элементом при гипоксии любой этиологии выступает не пониженный уровень кислорода как таковой, а ограничение возможности клетки производить достаточное количество макроэргических соединений для обеспечения комплекса своих эндергонических процессов (энергодефицит). ...
02.09.2022 г. После доработки 07.11.2022 г. Принята к публикации 07.11.2022 г.
В настоящее время наблюдается новый всплеск интереса к проблеме гипоксии, почти утраченный в последние десятилетия. В связи с тем, что когорта компетентных специалистов в этой области существенно сократилась, необходимо осуществлять интенсивный обмен знаниями. С целью проинформировать широкий круг заинтересованных исследователей и врачей, в настоящем обзоре обобщено современное понимание гипоксии, ее патогенных и адаптогенных последствий, а также ключевых физиологических и молекулярных механизмов, которые реализуют реакцию на гипоксию на различных уровнях-от клеточного до организменного. В обзоре приведена современная классификация форм гипоксии, понимание которой необходимо для формирования научно обоснованного подхода к экспериментальному моделированию гипоксических состояний. Про-веден анализ литературы, освещающий историю и современный уровень моделирования гипоксии в экспериментах на млекопитающих животных и человеке, в том числе способов создания умеренной гипоксии, применяемой для повыше-ния резистентности нервной системы к тяжелым формам гипоксии и другим экстремальным факторам. Отдельное внимание уделяется обсуждению особенностей и ограничений различных подходов к созданию гипоксии, а также раскрытию потенциала практического применения умеренных гипоксических воздействий в лечебной и профилактической медицине. Ключевые слова: гипоксия, классификация форм, экспериментальные модели гипоксии/ишемии, гипоксическая толерантность, мозг
... By the 1960s, the studies that began as early as the 19th century had formed the concept of hypoxia as the most important manifestation of tissue and cell pathology caused by a complex of physical, chemical and biological factors. By the end of the century ideas were formed not about pathogenic, but about the adaptogenic properties of moderate hypoxia, which can be used as a pre conditioning (preventive, protective) procedure to reduce the damaging effect of the subsequent, more severe form of hypoxia on the brain [1]. The main pathogenetic element in hypoxia of any eti ology is not the reduced oxygen level as such, but the limitation of the cell ability to produce a suffi cient amount of macroergic compounds to ensure the complex of its endergonic processes (energy deficiency). ...
Currently, there is a new surge of interest in the problem of hypoxia, almost lost in recent decades. Due to the fact that the circle of competent specialists in this field has significantly narrowed, it is necessary to carry out an intensive exchange of knowledge. In order to inform a wide range of interested researchers and doctors, this review summarizes the current understanding of hypoxia, its pathogenic and adaptogenic consequences, as well as key physiological and molecular mechanisms that implement the response to hypoxia at various levels-from cellular to organismic. The review presents a modern classification of forms of hypoxia, the understanding of which is necessary for the formation of a scientifically based approach to experimental modeling of hypoxic states. An analysis of the literature covering the history and current level of hypoxia modeling in mammals and human experiments, including methods for creating moderate hypoxia used to increase the resistance of the nervous system to severe forms of hypoxia and other extreme factors, is carried out. Special attention is paid to the discussion of the features and limitations of various approaches to the creation of hypoxia, as well as the disclosure of the potential for the practical application of moderate hypoxic effects in medicine.
... Stroke is extremely harmful to human health. Previous studies have shown that preconditioning stimuli had a neuroprotective effect, which has been referred as "cerebral ischemic tolerance" (Kitagawa et al., 1990). Interestingly, a series of subsequent studies have found that in addition to ischemic preconditioning, other drug and nondrug cerebral ischemia preconditioning also can benefit patients with severe cerebral ischemia events (Chang et al., 2018;Han et al., 2019;Zhang et al., 2020a). ...
Ischemic stroke (IS) has been associated with an impairment in glymphatic function. Xuefu Zhuyu Decoction (XFZYD) is widely used in the prevention and treatment of ischemic stroke. We hypothesized that Xuefu Zhuyu decoction pretreatment could attenuate early neurological deficits after ischemic stroke by enhancing the function of the glymphatic system. To prove our hypothesis, we carried out temporary middle cerebral artery occlusion and reperfusion surgery on C57BL/6 mice and then measured neurological score, infarct size and performed hematoxylin-eosin staining to assess stroke outcomes after 24 h of reperfusion. Subsequently, we injected fluorescent tracers in to the cisterna magna and evaluated tracer distribution in coronal brain sections. The polarization of aquaporin-4 (AQP4), colocalization of aquaporin-4, α-dystroglycan, β-dystroglycan and agrin were determined by immunofluorescence. Our research showed that pretreatment with Xuefu Zhuyu decoction significantly alleviated neurological scores, neurological deficits and pathological abnormalities in a mouse model of ischemic stroke. Importantly, Xuefu Zhuyu decoction pretreatment enhanced cerebrospinal fluid influx, protected aquaporin-4 depolarization and promoted the colocalization of aquaporin-4 with its anchoring proteins in the brain. Our findings highlight novel mechanisms underlying the neuroprotective effect of Xuefu Zhuyu decoction pretreatment on ischemic stroke-induced brain damage through the glymphatic system. Xuefu Zhuyu decoction pretreatment may offer a promising approach to slow the onset and progression of ischemic stroke.
... Tissues with a high sensitivity of ischemia such as the myocardium and brain, are the most promising targets for therapeutic use of IPC. The IPC was first identified in the heart by Murry et al. (Murry et al. 1986) and then was subsequently found to occur in the brain (Kitagawa et al. 1990). IPC in the brain followed the delayed pattern and it induced two phases of protection against the deleterious effects of prolonged ischemia and reperfusion. ...
Stroke is one of the leading causes of death and long-term serious disability. Current therapeutic strategy is limited to thrombolytic agents, consequently, boosting endogenous neuroprotective mechanisms of the brain to protect itself against harmful stimuli and restore from damages are widely studied. Preconditioned brain to tolerate cerebral ischemia/reperfusion injury could be initiated by several different pharmacological and mechanical strategies, such as ischemic preconditioning, ethanol pharmacological preconditioning and other pre- and post-conditions, such as remote ischemic preconditioning and exercise preconditioning. In this article, we will discuss the major mechanism of ischemia/reperfusion injury and provide an overview of preconditioning in all its various forms, describe the underlying mechanisms and review the recent clinical application of this emerging neuroprotective strategy.
... In several subsequent studies, it has been confirmed that ischemic preconditioning can reduce myocardial infarct size and coronary vascular injury and improve the clinical prognosis of patients with myocardial infarction (4,5). Kitagawa et al. showed that ischemic preconditioning of the gerbil brain prior to ischemia had a protective effect on the post-ischemic brain and reduced neuronal death in the C1 region of the hippocampus (6). However, ischemic preconditioning requires intervention before the onset of an ischemic event, which is difficult to achieve in clinical practice because we may not be able to anticipate sudden events. ...
Background
There is evidence that remote limb ischemic postconditioning (RIPostC) can reduce ischemia-reperfusion injury (IRI) and improve the prognosis of patients with ischemic stroke. However, so far, only few relevant clinical studies have been conducted. Therefore, we carried out a meta-analysis of eligible randomized controlled trials to compare the RIPostC group with a control group (no intervention or sham surgery) in patients with ischemic stroke.
Methods
Four English-language publication databases, PubMed, Cochrane, Embase, and Web of Science, were systematically searched up to March 2022. The data were analyzed using Review Manager fixed-effects and random-effects models.
Results
A total of 12 studies were included, and 11 of those were analyzed quantitatively. Compared to controls, The RIPostC group showed significantly reduced NIHHS scores in patients with ischemic stroke, (MD: −1.09, 95% confidence interval [CI]: −1.60, −0.57, P < 0.0001) and improved patients' Montreal Cognitive Assessment (MoCA) scores, (MD: 1.89, 95% CI: 0.78, 3.00, P = 0.0009), Our results showed that RIPostC is safe, (RR = 0.81, 95%CI: 0.61, 1.08, P = 0.15).
Conclusion
Our meta-analysis showed that RIPostC is safe and effective and has a positive cerebral protective effect in patients with ischemic stroke, which is safe and effective, and future large-sample, multicenter trials are needed to validate the cerebral protective effect of RIPostC.
... Because the cardioprotective effect of ischemic tolerance is very strong and ischemic tolerance has been observed in many organs other than the heart, including the lung, kidney, liver, skeletal muscle, and the brain, which is the organ most vulnerable to ischemia, basic research on ischemic tolerance as well as practical research for clinical applications has been very active. The finding that ischemic tolerance was observed in vivo in the brain was first demonstrated in a Japanese study using a gerbil model of cerebral ischemia, and since then, many Japanese researchers have contributed to the development of this field [14] [15] [16]. The preceding stimulus to induce Ischemic tolerance (A) Brain tissues exposed to invasive ischemia (Lethal ischemia) develop severe neuronal damage and cell death (white area surrounded by dotted line). ...
Ischemic tolerance is a phenomenon in which resistance to subsequent invasive ischemia is acquired by a preceding noninvasive ischemic application, and is observed in many organs, including the brain, the organ most vulnerable to ischemic insult. To date, much research has been conducted on cerebral ischemic tolerance as a cell-autonomous action of neurons. In this article, we review the essential roles of microglia and astrocytes in the acquisition of ischemic tolerance through neuron-non-autonomous mechanisms, where the two types of glial cells function in a concerted manner to induce ischemic tolerance.
... Following paraffin embedding, 5 μm sections of the brain were cut and stained with thionine. The number of surviving pyramidal neurons in the hippocampal CA1 region within a 1 mm linear length was counted as described previously (Kitagawa et al. 1990;Kato et al. 1991) and was used to assess neuronal density. Experimenters were blinded to the treatments. ...
Cerebral ischemic preconditioning (CIP)-induced brain ischemic tolerance protects neurons from subsequent lethal ischemic insult. However, the specific mechanisms underlying CIP remain unclear. In the present study, we explored the hypothesis that peroxisome proliferator-activated receptor gamma (PPARγ) participates in the upregulation of Klotho during the induction of brain ischemic tolerance by CIP. First we investigated the expression of Klotho during the brain ischemic tolerance induced by CIP. Lethal ischemia significantly decreased Klotho expression from 6 h to 7 days, while CIP significantly increased Klotho expression from 12 h to 7 days in the hippocampal CA1 region. Inhibition of Klotho expression by its shRNA blocked the neuroprotection induced by CIP. These results indicate that Klotho participates in brain ischemic tolerance by CIP. Furthermore, we tested the role of PPARγ in regulating Klotho expression after CIP. CIP caused PPARγ protein translocation to the nucleus in neurons in the CA1 region of the hippocampus. Pretreatment with GW9962, a PPARγ inhibitor, significantly attenuated the upregulation of Klotho protein and blocked the brain ischemic tolerance induced by CIP. Taken together, it can be concluded that Klotho upregulation via PPARγ contributes to the induction of brain ischemic tolerance by CIP.
... This ischemic tolerance is commonly observed clinically and experimentally. The endogenous neuroprotective effects by PC were originally reported in the heart [3,4], but were also observed in the kidneys [5], liver [6], skeletal muscle [7], and the brain [8,9]. Since the discovery of ischemic tolerance [3], it has received tremendous attention because it shows robust neuroprotective effects. ...
A sub-lethal ischemic episode (preconditioning [PC]) protects neurons against a subsequent lethal ischemic injury. This phenomenon is known as ischemic tolerance. PC itself does not cause brain damage, but affects glial responses, especially astrocytes, and transforms them into an ischemia-resistant phenotype. P2X7 receptors (P2X7Rs) in astrocytes play essential roles in PC. Although P2X7Rs trigger inflammatory and toxic responses, PC-induced P2X7Rs in astrocytes function as a switch to protect the brain against ischemia. In this review, we focus on P2X7Rs and summarize recent developments on how astrocytes control P2X7Rs and what molecular mechanisms they use to induce ischemic tolerance.
... In a dog heart model, they were able to prove that this phenomenon could reduce the infarct size by 75%. Four years later Kitagawa et al. described ischaemic preconditioning in the brain of gerbils (Kitagawa et al., 1990). ...
... In a dog heart model, they were able to prove that this phenomenon could reduce the infarct size by 75%. Four years later Kitagawa et al. described ischaemic preconditioning in the brain of gerbils (Kitagawa et al., 1990). ...
Preconditioning is complex, strong, evolutionary conserved cellular survival mechanism that is exhibited by different species as well as in different organs. A focused approach on microarray evaluation of precon-ditioning will be used to highlight the lack of clarity in investigating this complex phenomenon, exacerbated by the absence of a standardised terminology. This paper is an extensive review of the scientific literature on the investigation of preconditioning by means of a microarray approach. It dissects the design of the experiments used to investigate such phenomenon and classifies the complex factors in investigating preconditioning. It presents an attention to detail to the lexicon with a suggested classification and terminology that describes precondi-tioning that may help stratify and clarify research in this field.
... The phenomenon of acquiring ischemic tolerance by intermittent ischemic stress before fatal ischemia is called ischemic preconditioning and has been shown to have marked neuroprotective effects on cerebral ischemia-reperfusion injury [1][2][3]. However, the clinical application of ischemic preconditioning to acute ischemic strokes (AIS) is not realistic unless the onset of an AIS can be predicted. ...
Mitochondrial membrane potential regulation through the mitochondrial permeability transition pore (mPTP) is reportedly involved in the ischemic postconditioning (PostC) phenomenon. Melatonin is an endogenous hormone that regulates circadian rhythms. Its neuroprotective effects via mitochondrial melatonin receptors (MTs) have recently attracted attention. However, details of the neuroprotective mechanisms associated with PostC have not been clarified. Using hippocampal CA1 pyramidal cells from C57BL mice, we studied the involvement of MTs and the mPTP in melatonin-induced PostC mechanisms similar to those of ischemic PostC. We measured changes in spontaneous excitatory postsynaptic currents (sEPSCs), intracellular calcium concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents after ischemic challenge, using the whole-cell patch-clamp technique. Melatonin significantly suppressed increases in sEPSCs and intracellular calcium concentrations. The NMDAR currents were significantly suppressed by melatonin and the MT agonist, ramelteon. However, this suppressive effect was abolished by the mPTP inhibitor, cyclosporine A, and the MT antagonist, luzindole. Furthermore, both melatonin and ramelteon potentiated depolarization of mitochondrial membrane potentials, and luzindole suppressed depolarization of mitochondrial membrane potentials. This study suggests that melatonin-induced PostC via MTs suppressed the NMDAR that was induced by partial depolarization of mitochondrial membrane potential by opening the mPTP, reducing excessive release of glutamate and inducing neuroprotection against ischemia-reperfusion injury.
... Ischemic tolerance has been primarily described in experimental studies as a process during which the brain is subjected to a short period of ischemia which might enable the brain to be more tolerant when exposed to a more persistent ischemic event (15)(16)(17)(18)(19). Therefore, it has been proposed that pre-stroke exposure to Transient ischemic attacks (TIAs) might have a potential neuroprotective role when persistent ischemia affects the same exposed region. ...
Stroke is a leading cause of mortality and disability worldwide. Transient ischemic attack (TIA) is defined as transient brain ischemia with temporary neurological deficits. In animal models, prior TIA seems to enhance brain ischemic tolerance to withstand further ischemic events, which might be explained by brain preconditioning. Thus, this review aims to formulate evidence of whether TIAs can induce positive preconditioning and enhance the functional outcomes in patients suffering from subsequent ischemic strokes. Five databases were searched (PubMed, Embase, SAGE, Web of Science, and Scopus), and twelve studies were included in the quantitative analysis. Studies were eligible when comparing patients with acute ischemic stroke (AIS) and previous TIA with those with AIS without TIA. Comparisons included the National Institute of Health Stroke Scale (NIHSS) score at admission and 7 days from the stroke event, modified Rankin score (mRS), and Trial of ORG 10,172 in Acute Stroke Treatment (TOAST) classification. Odds ratio (OR), mean difference (MD), and 95% confidence interval (CI) were used to describe our results using the random effect model. Our results revealed that patients with stroke and prior TIAs had lower NIHSS scores at admission than those without prior TIAs. However, the NIHSS score was not significantly different between the two groups at 7 days. Furthermore, there was no statistically significant difference between both groups in terms of mortality. Despite the differences in the admission mRS score groups, patients with prior TIAs had lower mRS scores at discharge.
... In a nutshell, the brain ischemia is formed by the complex mechanisms where participate wide range of signalling pathways resulting in disruption of the cell membranes and neuron loss. On the other hand, neural cells are able to enhance tolerance against stroke mediated damage through the phenomenon known as ischemic tolerance (IT) [24][25][26]. Progression of this adaptive protective reaction induced with the conditioning has two phases (early and delayed), while each of them is specific by the expression of the effectors molecules in the complex activating mechanism [27]. ...
BackgroundA stroke is an acute damage to a certain area of a nerve tissue of the brain. In developed countries, it ranks second among the most often causes of death and is also the leading cause of disability. Recent findings emphasize the significant neuroprotective effect of conditioning on the course and rate of recovery after ischemic attack; however the molecular mechanism of ischemic tolerance induced by conditioning is still not completely explored.Methods and resultsThe purpose of this study is an identification of changes in gene expression induced by stimulation of reaction cascades after activation of the neuroprotective mechanism using an experimental rat model of global ischemia. The induction of neuroprotective cascades was stimulated by the application of early and delayed form of remote ischemic postconditioning. The quantitative qRT-PCR method was used to assess the rate of change in ADM, BDNF, CDKN1A, CREB, GADD45G, IL6, nNOS, and TM4SF1 gene expression levels 72 h after ischemic attack. The detected results confirm the neuroprotective effect of both forms of postconditioning. Participation of neuroprotection-related gene expression changes was observed once as an early one (CREB, GADD45G), once as a delayed one (ADM, IL6), or both (BDNF, CDKN1A, nNOS, TM4SF1) postconditioning forms, depending on the particular gene.Conclusions
Our results characterize impact of ischemic tolerance on the molecular level. We predict ischemic tolerance to be consisted of complex combination of early and delayed remote postconditioning.
... The delayed neuronal death in the hippocampal CA1 region was evaluated based on the neuronal density (ND) and histological grade (HG), as previously reported (Kato et al. 1991;Kitagawa et al. 1990). Briefly, the ND value was assessed by counting the number of intact pyramidal neurons at every 1-mm linear length in the hippocampal CA1 area using light microscopy. ...
Glutamate transporter-1 (GLT-1) removes most glutamate in the synaptic cleft. Sulbactam confers neuronal protection against ischemic insults in the hippocampal CA1 region accompanied by the upregulation of GLT-1 expression in rats. The present study further investigates the effect of sulbactam on the binding property and uptake capacity of GLT-1 for glutamate, and the change in extracellular glutamate concentration in the hippocampal CA1 region of rats with global brain ischemia. The binding property and uptake capacity of GLT-1 were measured using a radioligand binding and uptake assay, respectively, with L-3H-glutamate. The extracellular glutamate concentration was detected using microdialysis and high-performance liquid chromatography–mass spectrometry. Neuropathological evaluation was performed based on thionin staining. It was shown that sulbactam pre-treatment changed GLT-1 binding property, including increased Bmax and decreased Kd values, increased GLT-1 uptake capacity for glutamate, and inhibited the elevation of extracellular glutamate concentration in rats with global cerebral ischemia. These effects of sulbactam were accompanied by its neuronal protection on the hippocampal CA1 neurons against delayed neuronal death resulted from ischemic insult. Furthermore, administration of GLT-1 antisense oligodeoxynucleotides, which inhibited the expression of GLT-1, blocked the aforementioned sulbactam-related effects, which suggested that GLT-1 upregulation mediated the above effect although other mechanisms independent of the upregulation of GLT-1 expression could not be excluded. It could be concluded that sulbactam improves the binding property and uptake capacity of GLT-1 for glutamate and then reduces the glutamate concentration and excitotoxicity during global cerebral ischemia, which contributes to the neuroprotection of sulbactam against brain ischemia.
... In experimental models of limb post-RIC, reduced infarction was observed after 2 days when RIC was applied up to 3 h after stroke, but not if RIC was applied after 6 h or 2 months later when only behavioral outcome was ameliorated [23]. In the gerbil brain, for example, induction of ischemic tolerance was shown to require at least 2 min of ischemic preconditioning, at least 1 day before a damaging cerebral ischemic event [81], with a 2-day interval providing even more neuroprotection. This early study also showed that two episodes of preconditioning on consecutive days provided complete tolerance to 5-min cerebral ischemia after 2 days. ...
Stroke is one of the main causes of neurological disability worldwide and the second cause of death in people over 65 years old, resulting in great economic and social burden. Ischemic stroke accounts for 85% of total cases, and the approved therapies are based on re-establishment of blood flow, and do not directly target brain parenchyma. Thus, novel therapies are urgently needed. In this review, limb remote ischemic conditioning (RIC) is revised and discussed as a potential therapy against ischemic stroke. The review targets both (i) fundamental research based on experimental models and (ii) clinical research based on clinical trials and human interventional studies with healthy volunteers. Moreover, it also presents two approaches concerning RIC mechanisms in stroke: (i) description of the underlying cerebral cellular and molecular mechanisms triggered by limb RIC that promote neuroprotection against stroke induced damage and (ii) the identification of signaling factors involved in inter-organ communication following RIC procedure. Limb to brain remote signaling can occur via circulating biochemical factors, immune cells, and/or stimulation of autonomic nervous system. In this review, these three hypotheses are explored in both humans and experimental models. Finally, the challenges involved in translating experimentally generated scientific knowledge to a clinical setting are also discussed.
... Ischemic tolerance (IT) induction or ischemic preconditioning (PC) consists of reducing the damage caused in a severe ischemic episode by provoking a previous mild ischemic insult and has recently appeared as an exciting therapeutic approach for I/R injury [173]. Astrocytic activation seems to be essential for induction of ischemic tolerance as previously preconditioned brains of GFAP −/− Vim −/− mice show greater infarct volume upon ischemia compared with preconditioned brains of WT mice [153]. ...
Abstract
Ischemic stroke is the second cause of mortality and the first cause of long-term disability constituting a serious socioeconomic burden worldwide. Approved treatments include thrombectomy and rtPA intravenous administration, which, despite their efficacy in some cases, are not suitable for a great proportion of patients. Glial cell-related therapies are progressively overcoming inefficient neuron-centered approaches in the preclinical phase. Exploiting the ability of microglia to naturally switch between detrimental and protective phenotypes represents a promising therapeutic treatment, in a similar way to what happens with astrocytes. However, the duality present in many of the roles of these cells upon ischemia poses a notorious difficulty in disentangling the precise pathways to target. Still, promoting M2/A2 microglia/astrocyte protective phenotypes and inhibiting M1/A1 neurotoxic profiles is globally rendering promising results in different in vivo models of stroke. On the other hand, described oligodendrogenesis after brain ischemia seems to be strictly beneficial, although these cells are the less studied players in the stroke paradigm and negative effects could be described for oligodendrocytes in the next years. Here, we review recent advances in understanding the precise role of mentioned glial cell types in the main pathological events of ischemic stroke, including inflammation, blood brain barrier integrity, excitotoxicity, reactive oxygen species management, metabolic support, and neurogenesis, among others, with a special attention to tested therapeutic approaches.
Keywords: ischemic stroke; glia; neuroprotection; microglia; astrocytes; oligodendrocytes; therapy
... Secondary brain injury results from tissue ischemia induced by increased vascular resistance in the at-risk brain tissue due to compression by traumatic hematomas and development of cytotoxic and vasogenic tissue edema (Bouma et al., 1991). While traumatic hematomas may be managed surgically, cytotoxic and vasogenic edema with resulting perfusion impairment perpetuates brain ischemia and injury (Kitagawa et al., 1990). There is a new technique for protection against ischemic-reperfusion injury called the remote ischemic conditioning (RIC). ...
Cerebral impairment caused by an external force to the head is known as Traumatic Brain Injury (TBI). The aim of this study was to determine the role of local hypothermia and Remote Ischemic Conditioning (RIC) on oxidative stress, inflammatory response after TBI, and other involved variables. The present study is a clinical trial on 84 TBI patients who were divided into 4 groups. The Head Cooling for 1.5 to 6 hours was performed in the first three days after TBI. RIC intervention was performed within the Golden Time after TBI in the form of four 5-minute cycles with full cuff and 5 minutes of emptying of cuff. The group receiving the head cooling technique recovered better than the group receiving the RIC technique. Generally, combination of the two interventions of head cooling and RIC techniques is more effective on the improvement of clinical status of patients than each separate technique.
... apoptosis by different pathways [2]. Moreover, the relative expression levels of HS-induced HSPs are correlated with cell viability [5,[36][37][38]. The results presented in this study demonstrate that different HS conditions induce distinct HSP expression profiles, which effect the cell viability of a homogeneous population of proliferating NSCs cultured in proliferative conditions. ...
Cells have a regulatory mechanism known as heat shock (HS) response, which induces the expression of HS genes and proteins in response to heat and other cellular stresses. Exposure to moderate HS results in beneficial effects, such as thermotolerance and promotes survival, whereas excessive HS causes cell death. The effect of HS on cells depends on both exogenous factors, including the temperature and duration of heat application, and endogenous factors, such as the degree of cell differentiation. Neural stem cells (NSCs) can self-renew and differentiate into neurons and glial cells, but the changes in the HS response of symmetrically proliferating NSCs in culture are unclear. We evaluated the HS response of homogeneous proliferating NSCs derived from mouse embryonic stem cells during the proliferative phase and its effect on survival and cell death in vitro . The number of adherent cells and the expression ratios of HS protein ( Hsp ) 40 and Hsp70 genes after exposure to HS for 20 min at temperatures above 43°C significantly increased with the extension of the culture period before exposure to HS. In contrast, caspase activity was significantly decreased by extension of the culture period before exposure to HS and suppressed the decrease in cell viability. These results suggest that the culture period before HS remarkably affects the HS response, influencing the expression of HS genes and cell survival of proliferating NSCs in culture.
... In a dog heart model, they were able to prove that this phenomenon could reduce the infarct size by 75%. Four years later Kitagawa et al. described ischaemic preconditioning in the brain of gerbils (Kitagawa et al., 1990). ...
Preconditioning is complex, strong, evolu- tionary conserved cellular survival mechanism that is ex- hibited by different species as well as in different organs. A focused approach on microarray evaluation of precon- ditioning will be used to highlight the lack of clarity in investigating this complex phenomenon, exacerbated by the absence of a standardised terminology. This paper is an extensive review of the scientific literature on the in- vestigation of preconditioning by means of a microarray approach. It dissects the design of the experiments used to investigate such phenomenon and classifies the com- plex factors in investigating preconditioning. It presents an attention to detail to the lexicon with a suggested classification and terminology that describes precondi- tioning that may help stratify and clarify research in this field.
... The experiment in cerebral did in 4 years later using a brief (2 minutes) bilateral carotid occlusions, and could protect from neuronal death due to the subsequent 5 minutes bilateral carotid in gerbils. (67) Ischemic pre-and postconditioning complex signaling pathways involve ligands released from ischemic myocardium, G-protein-linked receptors, membrane growth factor receptors, phospholipids, signaling kinases, NO, protein kinase C (PKC) and cGMP-dependent protein kinase or protein kinase G (PKG), mitochondrial ATP-sensitive potassium channels, reactive oxygen species (ROS), tumor necrosis factor (TNF-α and sphingosine-1-phosphate. The mitochondrial permeability transition pore (mtPTP) is probably the final effector, together with the signal to prevent pore formation. ...
BACKGROUND: Hormesis was initially defined as a phenomenon where a small dose of harmful agent exposure to living organisms gives beneficial effects. The dose and time of this ‘tress’ exposure has become the object of investigation across the broad range of biomedical studies.
CONTENT: Hormesis characterized by the biphasic dose-effect or time-effect relationship for any substance. Some hormetic mechanisms performed biological plasticity, involve oxidative damage which instead induce antioxidant enzyme production in various cells. Early-life stress can increase resilience in later life and lack of stress can lead to vulnerability. Many stressors like dietary factors and natural environmental toxins can be occupied for healthy growth or homeostasis, which exemplifies how illness is the doorway to health.
SUMMARY: Hormesis reconcile many paradoxical phenomena exert opposite effects of the same substance, either a xenobiotic or an endogenous substance, a hormone or a metabolite, a genetic manipulation or an epigenetic alteration, an experimental intervention or a natural event. Human bodies are highly adaptive. A resilient body would be resulted after the ‘training’. In this review, we will elucidate the hormesis’ definition, mechanisms and pathways, and also how hormesis impacts in human health and lifespan.
KEYWORDS: biphasic, cell signaling, dose response, hormesis, preconditioning
... A phenomenon whereby ischemic tolerance can be obtained by intermittently applying ischemic loads prior to lethal ischemia has been called ischemic preconditioning (IPC; Kitagawa et al. 1990;Nakagawa et al. 2002;Yin et al. 2005). Although IPC has been proven to have a remarkable neuroprotective effect for cerebral I/R injury, clinical application of the IPC mechanism for AIS is impractical unless the onset of AIS can be predicted. ...
Ischemic postconditioning (PostC) is known to reduce cerebral ischemia/reperfusion (I/R) injury; however, whether the opening of mitochondrial ATP-dependent potassium (mito-KATP) channels and mitochondrial permeability transition pore (mPTP) cause the depolarization of the mitochondrial membrane that remains unknown. We examined the involvement of the mito-KATP channel and the mPTP in the PostC mechanism. Ischemic PostC consisted of three cycles of 15 s reperfusion and 15 s re-ischemia, and was started 30 s after the 7.5 min ischemic load. We recorded N-methyl-d-aspartate receptors (NMDAR)-mediated currents and measured cytosolic Ca²⁺ concentrations, and mitochondrial membrane potentials in mouse hippocampal pyramidal neurons. Both ischemic PostC and the application of a mito-KATP channel opener, diazoxide, reduced NMDAR-mediated currents, and suppressed cytosolic Ca²⁺ elevations during the early reperfusion period. An mPTP blocker, cyclosporine A, abolished the reducing effect of PostC on NMDAR currents. Furthermore, both ischemic PostC and the application of diazoxide potentiated the depolarization of the mitochondrial membrane potential. These results indicate that ischemic PostC suppresses Ca²⁺ influx into the cytoplasm by reducing NMDAR-mediated currents through mPTP opening. The present study suggests that depolarization of the mitochondrial membrane potential by opening of the mito-KATP channel is essential to the mechanism of PostC in neuroprotection against anoxic injury.
... The phenomenon of preconditioning or ischemic tolerance was described in several previous studies [17][18][19]. In the study of Anrather et al., authors pointed that this phenomenon might alter the tolerance of the entire organism to a more lethal stimulus by previously applying stressful but sublethal stimulus probably by a cascade of molecular and biochemical events [19]. ...
Genetic determinants play important role in the complex processes of inflammation and immune response in stroke and could be studied in different ways. Inflammation and immunomodulation are associated with repair processes in ischemic stroke, and together with the concept of preconditioning are promising modes of stroke treatment. One of the important aspects to be considered in the recovery of patients after the stroke is a genetic predisposition, which has been studied extensively. Polymorphisms in a number of candidate genes, such as IL-6, BDNF, COX2, CYPC19, and GPIIIa could be associated with stroke outcome and recovery. Recent GWAS studies pointed to the variant in genesPATJ and LOC as new genetic markers of long term outcome. Epigenetic regulation of immune response in stroke is also important, with mechanisms of histone modifications, DNA methylation, and activity of non-coding RNAs. These complex processes are changing from acute phase over the repair to establishing homeostasis or to provoke exaggerated reaction and death. Pharmacogenetics and pharmacogenomics of stroke cures might also be evaluated in the context of immuno-inflammation and brain plasticity. Potential novel genetic treatment modalities are challenged but still in the early phase of the investigation.
Background
Preconditioning is a promising strategy against ischemic brain injury, and numerous studies in vitro and in vivo have demonstrated its neuroprotective effects. However, at present there is no bibliometric analysis of preconditioning in cerebral ischemia. Therefore, a comprehensive overview of the current status, hot spots, and emerging trends in this research field is necessary.
Materials and methods
Studies on preconditioning in cerebral ischemia from January 1999–December 2022 were retrieved from the Web of Science Core Collection (WOSCC) database. CiteSpace was used for data mining and visual analysis.
Results
A total of 1738 papers on preconditioning in cerebral ischemia were included in the study. The annual publications showed an upwards and then downwards trend but currently remain high in terms of annual publications. The US was the leading country, followed by China, the most active country in recent years. Capital Medical University published the largest number of articles. Perez-Pinzon, Miguel A contributed the most publications, while KITAGAWA K was the most cited author. The focus of the study covered three areas: (1) relevant diseases and experimental models, (2) types of preconditioning and stimuli, and (3) mechanisms of ischemic tolerance. Remote ischemic preconditioning, preconditioning of mesenchymal stem cells (MSCs), and inflammation are the frontiers of research in this field.
Conclusion
Our study provides a visual and scientific overview of research on preconditioning in cerebral ischemia, providing valuable information and new directions for researchers.
Ischemic postconditioning (PostC) phenomenon is known as the neuroprotection against ischemic reperfusion (I/R) injury. One of the key processes in PostC is opening of mitochondrial ATP dependent potassium (mito-K ATP ) channel and depolarization of mitochondrial membrane potential, which triggers the release of calcium ion from mitochondria through the low conductance opening of mitochondrial permeability transition pore (mPTP). Mitochondrial calcium uniporter (MCU) is known as the highly sensitive transporter for uptake of Ca ²⁺ inwardly existed on the inner mitochondrial membrane. Furthermore, it has attracted attention as a new target of treatments in disease such as neurodegenerative disease, cancer, and ischemic stroke. Thus, we considered that MCU may involve in PostC and trigger its mechanism. In this research, we used the whole-cell patch clamp technique to hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca ²⁺ concentration, mitochondrial membrane potential and N-methyl-D-aspartate receptor (NMDAR) currents under the inhibition of MCU by Ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased sEPSCs occurrence (p = 0.008), NMDAR currents (p < 0.001), intracellular Ca ²⁺ concentration (p < 0.001) and dead cells (p < 0.001) significantly after reperfusion, indicating the removal of the neuroprotective effects in PostC. Moreover, mitochondrial depolarization in PostC with Ru265 was gradually decreased after reperfusion (p < 0.001). These results suggest that MCU plays an important role in PostC by maintaining mitochondrial depolarization, which suppresses hyperactivation of NMDARs and prevents the elevation of intracellular Ca ²⁺ concentration against I/R injury.
Ischemic stroke (IS) has become the second leading cause of morbidity and mortality worldwide, and the prevention of IS should be given high priority. Recent studies have indicated that hyperbaric oxygen preconditioning (HBO-PC) may be a protective nonpharmacological method, but its underlying mechanisms remain poorly defined. This study comprehensively reviewed the pathophysiology of IS and revealed the underlying mechanism of HBO-PC in protection against IS. The preventive effects of HBO-PC against IS may include inducing antioxidant, anti-inflammation, and anti-apoptosis capacity; activating autophagy and immune responses; upregulating heat shock proteins, hypoxia-inducible factor-1, and erythropoietin; and exerting protective effects upon the blood-brain barrier. In addition, HBO-PC may be considered a safe and effective method to prevent IS in combination with stem cell therapy. Although the benefits of HBO-PC on IS have been widely observed in recent research, the implementation of this technique is still controversial due to regimen differences. Transferring the results to clinical application needs to be taken carefully, and screening for the optimal regimen would be a daunting task. In addition, whether we should prescribe an individualized preconditioning regimen to each stroke patient needs further exploration.
Ischemic stroke is one of the leading causes of death and disability worldwide. The inhibition of cerebral blood flow triggers intertwined pathological events, resulting in cell death and loss of brain function. Interestingly, animals pre-exposed to short-term ischemia can tolerate subsequent severe ischemia. This phenomenon is called ischemic tolerance and is also triggered by other noxious stimuli. However, whether short-term exposure to non-noxious stimuli can induce ischemic tolerance remains unknown. Recently, we found that pre-exposing mice to an enriched environment for 40minutes is sufficient to facilitate cell survival after a subsequent stroke. The neuroprotective process depends on the neuronal activity soon before stroke, of which the activity-dependent transcription factor Npas4 is essential. Excessive Ca2+ influx triggers Npas4 expression in ischemic neurons, leading to the activation of neuroprotective programs. Pre-induction of Npas4 in the normal brain effectively supports cell survival after stroke. Furthermore, our study revealed that Npas4 regulates L-type voltage-gated Ca2+ channels through expression of the small Ras-like GTPase Gem in ischemic neurons. Ischemic tolerance is a good model for understanding how to promote neuroprotective mechanisms in the normal and injured brain. Here, we highlight activity-dependent ischemic tolerance and discuss its role in promoting neuroprotection against stroke.
Being a major cause of mortality and disability worldwide, stroke represents a serious unmet medical need. In fact, currently approved therapies for acute ischemic episodes only rely on tissue reperfusion through pharmacological thrombolysis and/or endovascular thrombectomy. Recent innovative imaging approaches have revolutionized the standard care, by widening the time-window for the intervention (up to 24h after stroke onset), thus increasing the number of patients that can actually benefit from reperfusive therapies. Nevertheless, removing the original cause of ischemia is not sufficient to fully restore cerebral function, while blocking the progression of brain damage through effective neuroprotective strategies represents a desirable aim. However, during the last three decades, virtually all the strategies aimed at targeting the processes involved in the ‘ischemic cascade’, including excitotoxicity, oxidative stress and inflammation, have failed in clinical trials for excess toxicity or lack of efficacy. Recent advances in our understanding of ischemic stroke pathobiology, together with a critical re-assessment of failed trials, have led to the development of novel encouraging approaches that include pharmacological agents (e.g., memantines, uric acid, minocycline, fingolimod, citicoline, etc.) and non-pharmacological interventions (e.g., hypothermia, post-conditioning, brain stimulation). Clinical trials are currently ongoing to assess the benefits of these promising strategies that have revitalized the potential of neuroprotection in stroke.
Oxygen levels are key regulators of virtually every living mammalian cell, both under physiological and pathological conditions. Starting from embryonic and fetal development, through growth, onset and progression of diseases, oxygen is a subtle, although pivotal, mediator of key processes such as differentiation, proliferation, autophagy, necrosis and apoptosis. Hypoxia-driven modifications of cellular physiology are deeply investigated for the clinical and translational relevance, especially in the ischemic scenario. The mild or severe lack of oxygen is undoubtedly related to cell death although abundant evidence points at oscillating oxygen levels, instead of permanent low pO2, as the most detrimental factor. Different cell types can consume oxygen at different rates and, most interestingly, some cells can shift from low to high consumption according to the metabolic demand. Hence, we can assume that, in the intracellular compartment, oxygen tension varies from low to high levels depending on both supply and consumption. The positive balance between supply and consumption leads to a pro-oxidative environment, with some cell types facing hypoxia/hyperoxia cycles, while some others are under fairly constant oxygen tension. Within this frame, the alterations of oxygen levels (dysoxia) are critical in two paradigmatic organs, heart the brain, under physiological and pathological conditions and the interactions of oxygen with other physiologically relevant gases, such as nitric oxide, can alternatively contribute to the worsening or protection of ischemic organs. Furthermore, the effects of dysoxia is of pivotal importance for iron metabolism.
Stroke Warning Syndrome (SWS) is a form of early recurrent transient ischemic attack (TIA) which carries a high risk of infarction. It is characterized by repeated stereotypical sensorimotor symptoms affecting the face, arm, and leg without associated cortical involvement occurring within a seven-day period after an index TIA. In this systematic review, we identified that that 1.5 to 4.5% of TIAs present as SWS and despite this occurrence, little is known about management strategies and treatment outcomes. Various mechanisms including small vessel disease, artery to artery embolism, hemodynamic instability and periinfarct depolarization may account for its nature. There are no specific guidelines on treatment, but thrombolysis appears safe but does not necessarily provide an advantage over antiplatelet and/or anticoagulation in preventing recurrences. Regardless of treatment, SWS is associated with excellent clinical outcomes.
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Cerebral conditioning is defined as the mild harmful stimuli applied to the brain before ischemia (preconditioning), during ischemia (perconditioning), immediately, a few hours or days after reperfusion (postconditioning). Various noxious stimuli can precondition, precondition or postcondition the brain, including ischemia, hypoxia or anesthetics to induce tolerance to lethal ischemia/reperfusion injury. The mechanisms underlying cerebral conditioning range from sensors and transducers including extracellular neurotransmitters and receptors, intracellular signals, transcription factors and epigenetic regulation, to effectors involving physiological protection, stem cells, heat shock proteins, Bcl-2, mitochondria, ubiquitin - proteasome pathway and autophagy pathway. Based on the large number of studies conducted in animal models, researchers explore the clinical application of cerebral conditioning. Remote ischemic conditioning is considered the most applicable and clinically relevant form of cerebral conditioning. The translational research also involves development of the biomarkers of conditioning and optimization of organ transplantation. The present review summarized the recent progress in signaling pathways and clinical applications of cerebral conditioning to explore the possibility to develop a potential therapeutic strategy for the prevention and treatment of ischemic stroke.
Our previous findings suggest that p38 MAPK contributes to the GLT-1 upregulation during induction of brain ischemic tolerance by cerebral ischemic preconditioning (CIP), however, the underlying mechanism is still unclear. Here, we investigated the molecular mechanisms underlying the CIP-induced GLT-1 upregulation by using Western blotting, Co-immunoprecipitation (Co-IP), electrophoretic mobility shift assay (EMSA) and thionin staining in rat hippocampus CA1 subset. We found that application of BAY11-7082 (an inhibitor of NF-κB), or dihydrokainate (an inhibitor of GLT-1), or SB203580 (an inhibitor of p38 MAPK) could attenuate the CIP-induced neuronal protection in hippocampus CA1 region of rats. Moreover, CIP caused rapid activation of NF-κB, as evidenced by nuclear translocation of NF-κB p50 protein, which led to active p50/p65 dimer formation and increased DNA binding activity. GLT-1 was also increased after CIP. Pretreatment with BAY11-7082 blocked the CIP-induced GLT-1 upregulation. The above results suggest that NF-κB participates in GLT-1 up-regulation during the induction of brain ischemic tolerance by CIP. We also found that pretreatment with SB203580 caused significant reduction of NF-κB p50 protein in nucleus, NF-κB p50/p65 dimer nuclear translocation and DNA binding activity of NF-κB. Together, we conclude that p38 MAPK/NF-κB pathway participates in the mediation of GLT-1 up-regulation during the induction of brain ischemic tolerance induced by CIP.
As the organ with the highest demand for oxygen, the brain has a poor tolerance to ischemia and hypoxia. Despite severe ischemia/hypoxia induces the occurrence and development of various central nervous system (CNS) diseases, sublethal insult may induce strong protection against subsequent fatal injuries by improving tolerance. Searching for potential measures to improve brain ischemic/hypoxic is of great significance for treatment of ischemia/hypoxia related CNS diseases. Ischemic/hypoxic preconditioning (I/HPC) refers to the approach to give the body a short period of mild ischemic/hypoxic stimulus which can significantly improve the body's tolerance to subsequent more severe ischemia/hypoxia event. It has been extensively studied and been considered as an effective therapeutic strategy in CNS diseases. Its protective mechanisms involved multiple processes, such as activation of hypoxia signaling pathways, anti‐inflammation, antioxidant stress, and autophagy induction, etc. As a strategy to induce endogenous neuroprotection, I/HPC has attracted extensive attention and become one of the research frontiers and hotspots in the field of neurotherapy. In this review, we discuss the basic and clinical research progress of I/HPC on CNS diseases, and summarize its mechanisms. Furthermore, we highlight the limitations and challenges of their translation from basic research to clinical application.
Herkinorin is a novel opioid receptor agonist. Activation of opioid receptors, a member of G protein coupled receptors (GPCRs), may play an important role in Herkinorin neuroprotection. GPCRs may modulate NOD‐like receptor protein 3 (NLRP3)‐mediated inflammatory responses in the mechanisms of inflammation‐associated disease and pathological processes. In this study, we investigated the effects of Herkinorin on NLRP3 and the underlying receptor and molecular mechanisms in oxygen‐glucose deprivation/reperfusion (OGD/R)‐treated rat cortex neurons. First, Western blot analysis showed that Herkinorin can inhibit the activation of NLRP3 and Caspase‐1, decrease the expression of interleukin (IL)‐1β, and decrease the secretion of IL‐6 and tumour necrosis factor α detected by enzyme‐linked immunosorbent assay in OGD/R‐treated neurons. Then we found that Herkinorin downregulated NLRP3 levels by inhibiting the activation of nuclear factor kappa B (NF‐κB) pathway, reducing the phosphorylation level of p65 and IκBα in OGD/R‐treated neurons (p < .05 or .01, n = 3 per group). Instead, both the mu opioid receptor (MOR) inhibitor, β‐funaltrexamine, and MOR knockdown reversed the effects of Herkinorin on NLRP3 (p < .05 or .01, n = 3 per group). Further, we found that the level of β‐arrestin2 decreased in the cell membrane and increased in the cytoplasm after Herkinorin pretreatment in OGD/R‐treated neurons. In co‐immunoprecipitation experiments, Herkinorin increased the binding of IκBα with β‐arrestin2, decreased the ubiquitination level of IκBα, and β‐arrestin2 knockdown reversed the effects of Herkinorin on IκBα in OGD/R‐treated neurons (p < .05 or .01, n = 3 per group). Our data demonstrated that Herkinorin negatively regulated NLRP3 inflammasome to alleviate neuronal ischemic injury through inhibiting NF‐κB pathway mediated primarily by MOR activation. Inhibition of the NF‐κB pathway by Herkinorin may be achieved by decreasing the ubiquitination level of IκBα, in which β‐arrestin2 may play an important role. In this manuscript, at the first time, we reported that Herkinorin negatively regulated NOD‐like receptor protein 3‐mediated inflammatory response to alleviate cerebral ischemic injury through activating mu opioid receptor and inhibiting the nuclear factor kappa B pathway, in which β‐arrestin2 may play an important role. Such findings may provide potential drug targets for the prevention and treatment of ischemic stroke.
The neuroprotective effects of MK-801, a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors, were evaluated in models of cerebral ischemia using Mongolian gerbils. Bilateral occlusion of the carotid arteries for a period of 5 min resulted in a consistent pattern of degeneration of hippocampal CA1 and CA2 pyramidal neurons, which was quantified using an image analyzer. Systemic administration of MK-801 (0.01-10 mg/kg, i.p.) 1 hr prior to the occlusion caused a dose-dependent protection of the CA1 and CA2 neurons. The ED50 value for neuroprotection by MK-801 was calculated to be 0.3 mg/kg, and at doses greater than or equal to 3 mg/kg the majority of animals were completely protected against the ischemic insult. Systemic administration of MK-801 (1 or 10 mg/kg, i.p.) 1 hr prior to unilateral occlusion of the right carotid artery resulted in significant protection against hippocampal neurodegeneration following 10 min of occlusion, and increased the survival rate after 30 min of occlusion. The potent neuroprotective effects of MK-801 in these cerebral ischemia models add further weight to the evidence that NMDA receptors are involved in the mechanism of ischemia-induced neuronal degeneration.
The present study was undertaken to correlate calcium accumulation with the development of neuronal necrosis following transient ischemia. After 10 min of forebrain ischemia in the rat--a period that leads to reproducible damage of CA1 pyramidal cells--determination of calcium concentration and evaluation of morphological signs of cell body necrosis in the dorsal hippocampus were performed at various recirculation times. Tissue calcium concentration was not different from control at the end of ischemic period and did not change after 3, 6, 12, or 24 h of recirculation. However, after 48 h, calcium content increased significantly, with a further increase being seen after 72 h. At early recovery periods, only scattered necrotic neurons were observed. After 48 h, only 2 of 12 hemispheres showed more than 25 necrotic cells per section. More conspicuous neuronal death was observed after 72 h. The results thus demonstrate that net accumulation of calcium in regio superior of the hippocampus precedes marked necrosis of CA1 pyramidal cells. The results suggest that one primary event in the delayed death of these cells is membrane dysfunction with increased calcium cycling.
Morris hepatoma 7777 cells, heat conditioned at 43 degrees for 0.5 hr, become gradually thermoresistant during an incubation at 37 degrees as judged by their ability to form colonies following a second heat challenge. Pulse incorporation of [35S]methionine into proteins at various times after the conditioning treatment and subsequent fractionation of the proteins by polyacrylamide gel electrophoresis indicate that the gradual putative modifications occurring at the cellular level and leading to the thermotolerance state are accompanied by an elevated synthesis above the normal level of a small set of polypeptides with apparent molecular weights of 27,000, 65,000, 68,000, 70,000, 89,000, and 107,000. Both thermotolerance development and protein induction are completed after a 6- to 8-hr period. At the end of this period, thermotolerance is at its maximum level and heat shock protein synthesis is returned to normal. This acquired thermal resistance eventually disappears between 60 and 80 hr following conditioning treatment. In a parallel manner, the heat shock-induced proteins synthesized during the first 4 hr following the conditioning treatment are maintained in the cells at a high level for several hr but become undetectable by 82 hr. The results provide strong circumstantial evidence that heat shock proteins are involved in the acquisition, maintenance, and decay of thermotolerance.
Michael Ashburner* and J. Jose Bonnert Department of Biochemistry and Biophysics University of California, San Francisco San Francisco, California 94143 During the normal development of the larval salivary gland of Drosophila melanogaster, considerable changes occur in the patterns of puffing activity. These can be seen as changes in the puffs of the gland’s polytene chromosomes, and occur as a con- sequence of changes in the titer of the insect’s growth and moulting hormone, ecdysone (for review see Ash- burner and Richards, 1976). In addition to the changes in gene activity normal to development, there are changes in the activities of a set of genes that occur as a direct consequence of subjecting animals to a wide variety of experimental insults, for example, a brief heat shock. The discovery of the induction of a unique set of puffs by heat shock (Ritossa, 1962) has led the way to an analysis of gene function and structure in Drosophila that is, so far, unique. The cytological facts can be summarized briefly (Ritossa, 1962, 1963, 1964a; Berendes and Holt, 1964; Berendes, Van Breugel and Holt, 1965; van Breugel, 1966; Ashburner, 1970; Ellgaard, 1972; Lewis, Helmsing and Ashburner, 1975). If Drosophila larvae or their excised tissues are subjected to a brief heat shock (for example, 40 min at 37”C, the normal culture temperature being 25”C), puffs are induced at a few specific sites (Figure 1). In D. melanogaster there are nine heat-inducible puffs, (33B, 63C, 64F, 678, 70A. 87A, 87C, 93D and 95D); in D. hydei there are six (32A, 36A, 48BC and 81 B; 31 C and 858 are small and variable in their response). The in vivo induction of the puffs by the heat shock is very rapid; it occurs within 1 min of the temperature increase although the puffs continue to increase in size for some 30-40 min (at 37°C) before regressing. The maximum sizes of the induced puffs are a function of the severity of the temperature shock, at least until lethal temperatures are met (Figure 2). The induction requires RNA, but not protein synthesis. In the ab- sence of protein synthesis, however, the induced puffs fail to regress unless the temperature is returned to normal (puff 48BC of D. hydei is an exception; Leen- ders and Beckers, 1972). Prolonged (for example, more than 1 hr) temperature shock results in addi- tional changes in puffing activity; most remarkable is the fact that all other puffs, puffs active at the time the temperature shock began, regress. It was the discovery that heat shock also results in the induction of the synthesis of a set of polypeptides ’ Permanent
HEAT can induce a transient state of thermal tolerance so that mammalian cells surviving one exposure to hyperthermia are much more resistant to a subsequent heat exposure1,2. Studies of the combined and sequential cytotoxic effects of hyperthermia and adriamycin (ADM) show that cells exposed to heat could then also develop considerable resistance to ADM3. The most reasonable explanation for the latter finding is that prolonged heat exposure modifies the cell membrane permeability to ADM. No precise mechanisms were postulated as being responsible for either type of tolerance. We report here that ethanol induces tolerance to heat and also tolerance to ADM. The qualitative patterns of cellular survival closely resemble those induced by heat exposure. These results reinforce the hypothesis that one of the prime targets of inactivation of mammalian cells by heat is the cellular membrane.
IN mammalian cells, hyperthermia causes temperature-dependent changes in
cell growth parameters1, reduces DNA and protein synthesis
rates2 and cell metabolism3, and leads to a loss
of proliferative capacity4,5. Harris6 has shown
that temperature-resistant pig kidney cells can be obtained after
multiple exposures to very high thermal doses (colony-forming ability
reduced to 10-5-10-6 of controls). The purpose of
our experiments was to determine whether a single hyperthermic treatment
(44 °C for 1 h) could induce a state of thermotolerance in cells,
and if so, what was the mode of origin of the thermal resistant cells.
We investigated the pathogenic role of free radical formation in ischemic neuronal death using radical scavenger, superoxide dismutase. Cerebral ischemia was produced in the gerbil by bilateral common carotid occlusion for 5 min, which consistently resulted in delayed neuronal death in the CA1 region of the hippocampus. The effects of free superoxide dismutase and a derivatized superoxide dismutase, pyran copolymer conjugated superoxide dismutase, on early ischemic damages, detected sensitively by the immunohistochemical reaction for microtubule associated protein 2, and a subsequent delayed neuronal death after restoration of blood flow were investigated. Preischemic treatment by pyran conjugated superoxide dismutase showed clear protective effects against both the neuronal damages detected by immunohistochemistry after 5 min ischemia and the delayed neuronal necrosis after one week of recovery, although no clear beneficial effects were observed when this drug was administered just before the recirculation or free superoxide dismutase was used. These results strongly suggest that free radical generation during brief period of ischemia plays a pivotal role in triggering the ischemic neuronal damages causing delayed neuronal death at the selectively vulnerable areas of the brain.
We used a gerbil model of cerebral ischemia to study the effects of ion channel blockers on neuronal death resulting from enhanced glutamate release and calcium ion influx. The common carotid arteries of gerbils were occluded for 5 minutes and injected intraperitoneally immediately after ischemia with an alkylene iminopropylene derivative (glutamate blocker) or a piperazinyl ethanol derivative (calcium blocker) given at high or low doses. Two vehicle groups received saline or 0.2% methyl cellulose solution. Seven days later, the gerbils were perfusion-fixed and their brains were processed for histologic study. The number of neurons per millimeter (neuronal density) of the CA1 region was calculated, and the neuronal density in each group was statistically compared using the Mann-Whitney U test. Compared with a control group not subjected to carotid ligation, neurons of the two vehicle groups and the low-dose calcium blocker group were almost nonexistent in the CA1 region. Neuronal densities of the glutamate blocker group and the high-dose calcium blocker group were similar and were found to be within normal limits by statistical analysis. Our study shows that detrimental membrane phenomena and the incidence of delayed neuronal death may be counteracted by the systemic administration of these ion channel blockers after ischemic insult.
The relative levels of c-fos mRNA in individual neurons of the hippocampal formation of rats is dramatically increased following 20 min of cerebral ischemia induced by 4-vessel occlusion. After 24 h of recirculation, a number of scattered neurons in the dentate hilus became hybridization positive. This effect appeared to peak between 24 and 48 h. A few neurons in the pyramidal cell layer of CA1 expressed c-fos as early as 24 h, but the most intense labeling in this region was seen at 72 h of recirculation. These results correlate well with the known distribution of delayed ischemic necrosis in the brain.
We investigated the neuronal distribution of microtubule-associated protein 2 in gerbil brain and monitored the progression of ischemic damage immunohistochemically by using this protein as a dendritic marker. The reaction for microtubule-associated protein 2 in normal gerbil brain clearly visualized neuronal soma and dendrites but other structures such as axonal bundles, glia and endothelial cells exhibited little immunoreactivity. In a reproducible gerbil model of unilateral cerebral ischemia, we could detect the ischemic lesions as early as 3 min after right common carotid occlusion at the subiculum-CA1 region of the ipsilateral hippocampus as faint loss of the reaction in the dendrites. After ischemia for 30 min, the ischemic lesions were clearly detected as loss of the reaction in the nerve cell bodies, dendrites and the neuropil in the hippocampus, cerebral cortex, thalamus and the caudoputamen. Although the mechanism for prompt disappearance of the immunohistochemical reaction for microtubule-associated protein 2 is not clear, the present investigation suggests that dendrites in the vulnerable regions may be quite susceptible to ischemic stress and that the immunohistochemical procedure for microtubule-associated protein 2 may be very useful for demonstration of dendritic damage in various pathophysiological states of the central nervous system.
The effect of repetition of brief ischemia, which causes no morphological brain damage when given as a single insult, was studied. Two-minute forebrain ischemia was induced in gerbils singly and 3 or 5 times at 60-min intervals. Although 2-min ischemia induced no neuronal damage, 3 or 5 repeated ischemic insults caused neuronal damage in the selectively vulnerable regions, the severity being dependent on the number of episodes.
The failure of adult rats to survive prolonged exposure to greater than 95% O2 is generally ascribed to the inability of their lungs to increase antioxidant enzyme synthesis in response to the oxidant challenge. We studied the synthesis rate of the antioxidant enzyme CuZn superoxide dismutase (CuZn SOD) in lungs of adult and neonatal rats exposed to conditions that alter the lung's oxidant-to-antioxidant balance. Lung CuZn SOD synthesis in the adult was significantly increased after 24 h of hyperoxia but fell to control levels after further exposure, whereas in neonatal lungs an increased rate of synthesis of CuZn SOD was found only after 72 h of hyperoxia. The adult lung responded to two in vitro oxidant stresses, [diethyldithiocarbamate exposure and heat (42 degrees C)] with increases in CuZn SOD synthesis twice the magnitude of those in the neonatal lung. These data indicate that the adult lung is at least as capable as the neonatal lung of increasing its synthesis of CuZn SOD in response to an oxidative stress. However, the inability of the adult lung to maintain an increased rate of CuZn SOD synthesis during in vivo hyperoxia may contribute to the poor tolerance of the adult lung to greater than 95% O2.
Synthesis of a small group of highly conserved proteins in response to elevated temperature and other agents that induce stress is a universal feature of prokaryotic and eukaryotic cells. Although correlative evidence suggests that these proteins play a role in enhancing survival during and after stress, there is no direct evidence to support this in mammalian cells. To assess the role of the most highly conserved heat shock protein (hsp) family during heat shock, affinity-purified monoclonal antibodies to hsp70 were introduced into fibroblasts by needle microinjection. In addition to impairing the heat-induced translocation of hsp70 proteins into the nucleus after mild heat shock treatment, injected cells were unable to survive a brief incubation at 45 degrees C. Cells injected with control antibodies survived a similar heat shock. These results indicate that functional hsp70 is required for survival of these cells during and after thermal stress.
An increase in the synthesis of heat shock proteins that is induced in cells in vitro by hyperthermia or other types of metabolic
stress correlates with enhanced cell survival upon further stress. To determine if a similar increase in stress tolerance
could be elicited in vivo, rats were made hyperthermic, and then their retinas were tested for sensitivity to light damage.
This treatment resulted in a marked decrease in photoreceptor degeneration after exposure to bright light as compared to normothermic
animals. Concomitant with such protection was an increase in retinal synthesis of three heat shock proteins. Thus, a physiological
rise in body temperature enhances the stress tolerance of nerve tissue, perhaps by increasing heat shock protein production.
Twenty mongolian gerbils were anesthetized (1.5% halothane) and severe forebrain ischemia was produced in 15 animals by occluding both common carotid arteries. After 5 min ischemia brains were recirculated spontaneously. Immediately after ischemia nimodipine (1.5 mg/kg) or pentobarbital (50 mg/kg) was injected intraperitoneally into five animals. Four days later animals were reanesthetized (1.5% halothane); the brains were frozen with liquid nitrogen and cut in a cryostat. Ten-micrometer-thick coronal cryostat sections were stained with cresyl violet to assess the extent of ischemic cell damage in the lateral striatum, the CA1-layer of the hippocampus, and the thalamus. In addition, tissue samples (about 4 mg each) were taken from the lateral striatum, CA1 layer of the hippocampus and the thalamus. Putrescine levels were measured in these samples using reversed-phase high performance liquid chromatography and fluorescence detection. Reversible cerebral ischemia produced a significant increase in putrescine in the lateral striatum (from 11.15 +/- 0.79 to 44.83 +/- 11.76 nmol/g, P less than or equal to 0.05), the CA1 subfield of the hippocampus (from 11.27 +/- 0.64 to 41.80 +/- 3.62 nmol/g, P less than or equal to 0.05) and less so in the thalamus (from 11.28 +/- 0.70 to 16.50 +/- 1.71 nmol/g).(ABSTRACT TRUNCATED AT 250 WORDS)
We investigated progression and recovery of neuronal damage during and after global cerebral ischemia in gerbils after bilateral occlusion of the common carotid arteries, using the immunohistochemical method (reaction for tubulin and creatine kinase BB-isoenzyme). The earliest, but reversible, ischemic lesions occurred after 3 minutes' ischemia in the subiculum-CA1 and CA2 regions of the hippocampus. The lesions became irreversible after 4 minutes' ischemia. The ischemic and postischemic lesions in the cerebral cortex, thalamus, and caudoputamen were partially or completely reversible if the ischemic period was 5 minutes, whereas delayed degeneration occurred in the pyramidal cells of the medial CA1 region after reperfusion for 48 hours (delayed neuronal death). After 10 minutes' ischemia and subsequent reperfusion, delayed neuronal death extended from the medial to the lateral CA1 region; the ischemic and postischemic lesions in the cerebral cortex, thalamus, and caudoputamen also expanded during reperfusion. Our investigation demonstrates that selective vulnerability existed in global cerebral ischemia as in incomplete or regional ischemia and suggests that neurons in many areas of the brain possessed the potential for recovery, progressive deterioration, and even delayed neuronal death depending on the severity and duration of cerebral ischemia.
Living organisms are known to react to a heat stress by the selective induction in the synthesis of several polypeptides. In this review we list the major stress proteins of mammalian cells that are induced by heat shock and other environments and categorize these proteins into specific subgroups: the major heat shock proteins, the glucose-regulated proteins, and the low-molecular-weight heat shock proteins. Characteristics of the localization and expression of proteins in each of these subgroups are presented. Specifically, the nuclear/nucleolar locale of certain of the major heat shock proteins is considered with respect to their association with RNA and the recovery of cells after a heat exposure. The induction of these major heat shock proteins and the repression of the glucose-regulated proteins as a result of reoxygenation of anoxic cells or by the addition of glucose to glucose-deprived cultures is described. Changes in the expression of these protein systems during embryogenesis and differentiation in mammalian and nonmammalian systems is summarized, and the protective role that some of these proteins appear to play in protecting the animal against the lethal effects of a severe heat treatment and against teratogenesis is critically examined.
An experimental model for repeated ischemic attacks, which allows easy induction of cerebral ischemia of any desired duration and frequency, has been developed in the gerbil. With this procedure, a pronounced cumulative effect on development of edema and tissue injury was observed using 3 separate, 5-min bilateral occlusions of the common carotid arteries spaced at various time intervals. This effect was most evident when the occlusions were carried out at 1-h intervals, i.e., during the period of marked postischemic hypoperfusion. Such animals, killed after 24 h of recirculation, showed significantly more severe edema and brain tissue injury in the areas exposed to ischemia than was observed in animals killed 24 h after single 5- or 15-min occlusions. The changes of regional CBF, assayed with a [3H]nicotine method, indicated a relatively rapid onset of hypoperfusion of similar degree after each release of arterial occlusion. The hypoperfusion recovered significantly within 6 h of recirculation following either single or multiple occlusions, and no residual hypoperfusion was observed in animals which, when killed at 24 h, showed severe edema and brain tissue injury. This model should prove useful in elucidating the pathophysiological mechanisms operative in repetitive cerebral ischemia.
This study examined the pattern of protein synthesis in the neocortex, caudate-putamen, and the hippocampus following transient forebrain ischemia in rats. The animal model of temporary ischemia used in this study causes permanent damage to vulnerable neurons with a time course of injury that varies from hours (caudate nucleus) to days (hippocampus). To examine the spectrum of proteins synthesized in these regions at 3 and 18 h after recirculation, cerebral proteins were pulse-labeled in vivo by an intravenous injection of [35S]methionine. Newly synthesized (35S-labeled) and constitutive (unlabeled) proteins were analyzed by two-dimensional gel electrophoresis and fluorography. In all three brain regions, specific proteins underwent preferential synthesis (Mr approximately 27,000, approximately 65,000, approximately 70,000, approximately 110,000), while others showed decreased synthesis (neuron-specific enolase, alpha- and beta-tubulin). There was an early (3 h post ischemia) induction of the Mr approximately 70,000 mammalian "stress" protein; at 18 h post ischemia, its synthesis remained high in the hippocampus but was diminished in the neocortex and had largely subsided in the caudate-putamen. All regions at 18 h showed increased synthesis of an Mr approximately 50,000 protein, tentatively identified as glial fibrillary acidic protein. The results show that temporary forebrain ischemia induces changes in protein synthesis that include features similar to those observed in other eukaryotic cells subjected to injurious stress. These postischemic changes in protein synthesis are qualitatively similar in all brain regions examined despite regional differences in the severity of subsequent neuronal damage. The persistent synthesis of the Mr approximately 70,000 stress protein in the hippocampus, however, may reflect continued metabolic injury long after the ischemic episode has passed.
The time course of the reduction in brain protein synthesis following transient bilateral ischemia in the gerbil was characterized and compared with changes in a number of metabolites related to brain energy metabolism. The recovery of brain protein synthesis was similar following ischemic periods of 5, 10, or 20 min; in vitro incorporation activity of brain supernatants was reduced to approximately 10% of control at 10 or 30 min recirculation, showed slight recovery at 60 min, and returned to 60% of control activity by 4 h. Protein synthesis activity was indistinguishable from control at 24 h. One minute of ischemia produced no detectable effect on protein synthesis measured after 30 min reperfusion; longer periods of ischemia resulted in progressive inhibition, with 5 min producing the maximal effect. Pentobarbital (50 mg/kg) increased by 1-2 min the threshold ischemic duration required to produce a given effect. Whereas most metabolites recovered quickly following 5 min ischemia, glycogen showed a delayed recovery comparable to that seen for protein synthesis. These results are discussed in relation to possible mechanisms for the coordinate regulation of brain energy metabolism and protein synthesis. An improved method for the fluorimetric measurement of guanine nucleotides is described.
In vitro translation products of gerbil brain preparations, obtained from animals killed during recirculation following transient ischemia, showed increased synthesis of a 70-kilodalton stress protein, identified by two-dimensional gel electrophoresis. Stimulation of stress protein synthesis was evident as early as 2 h after recirculation, at which time overall translation activity remained low. Expression of the 70-kilodalton protein reached a maximum at 8 h recirculation, when incorporation into other translation products had returned to essentially control levels. Increased incorporation into the stress protein was still detectable after 24 h recirculation. Although the functional consequences of increased expression of this stress protein remain unknown, these results suggest that the gerbil ischemia model may provide a useful experimental system in which to study the involvement of this phenomenon in processes related to postischemic cell damage and recovery.
Carbohydrate substrates, organic phosphates, amino acids and ammonia were studied in the rat brain during complete ischemia of 1–15 min duration utilising an ischemic model with increase of the intracranial CSF pressure. Depletion of glucose occurred in 1 min and accumulation of lactate was maximal at 3 min. Measurements of phosphocreatine, ATP, ADP and AMP and calculations of energy use showed that no useful energy remained after 5 min of ischemia. The results indicate that tissue Pco2 increased to over 100 mm Hg and that cell pH fell by 0.5 units.Depletion of α-ketoglutarate occurred in 1 min and there was no pyruvate left with prolonged ischemia. Since decreases were observed also in citrate, malate and oxaloacetate the results either suggest that citric acid cycle intermediates in general were diverted towards amino acid formation, or that ischemia is associated with a redistribution of carbon atoms within the cycle with accumulation of other (unmeasured) intermediates. With 1 min of ischemia, ammonia increased although the adenine nucleotide sum remained constant. Prolonged ischemia was associated with unchanged levels of glutamate and aspartate but there was a moderate fall in glutamine.
In rats ischemia of the forebrain induced by a 30-minute occlusion of the carotid artery, followed by 120 minutes of arterial reperfusion, produced ischemic lesions of selectively vulnerable pyramidal cells in both hippocampi. Focal microinfusion into the dorsal hippocampus of 2-amino-7-phosphonoheptanoic acid, an antagonist of excitation at the N-methyl-D-aspartate-preferring receptor, before ischemia was induced protected against the development of ischemic damage. It is proposed that excitatory neurotransmission plays an important role in selective neuronal loss due to cerebral ischemia.
Light and electron microscopy has been used to study the cytopathological changes in the rat hippocampus directly after a 30-min period of forebrain ischemia and after 30 or 120 min of reperfusion. The fine structural localization of calcium has been demonstrated using the oxalate/pyroantimonate procedure. Cellular changes considered typical of ischemia (swelling of astrocytic processes, distention of mitochondria, condensation of cytoplasm, "ischemic cell change") are most prominent after 30 min of reperfusion. At this time, dense calcium pyroantimonate deposits are evident in swollen mitochondria in pyramidal and hilar neurons. After 120 min of reperfusion, substantial restitution has occurred; most mitochondria appear normal and there are few calcium deposits. However, a small number of selectively vulnerable neurons (hilar and pyramidal neurons) show dense condensation (ischemic cell change) with multiple vacuoles containing calcium deposits. The role of excessive calcium entry and mitochondrial calcium overload during the reperfusion period in determining the death of selectively vulnerable neurons is discussed.
The possibility that the exposure of organisms to whole-body hyperthermia may provide protection against subsequent thermal exposures is intriguing and may play an important role in the clinical scheduling of fractionated hyperthermia. We used C3H mice to investigate whether whole-body heating can be used as a conditioning treatment to induce protection of mice against thermal death from a subsequent heat treatment. Our data clearly show that a conditioning whole-body heat dose (41 degrees for 40 min), by itself nonlethal, can give substantial protection to animals against a later heat treatment. The heat-induced protection is transient in nature: it reaches a maximum by 6 to 24 hr following the 41 degrees conditioning dose and decays by approximately 60% by 72 hr. The data presented do not shed any light on the cause of death following whole-body hyperthermia. Our results show clearly that the response of a complex organism to heat can be altered by previous heat exposure.
Synthesis of a family of proteins called "heat shock" proteins is induced or enhanced in cells in response to various environmental stresses, suggesting that these proteins may perform functions essential to cell survival. Because a brief, nonlethal heat treatment can dramatically induce a transient resistance to a subsequent lethal heat treatment (thermotolerance), we examined the effect of heat treatment (41-46 degrees C) on protein synthesis and cell survival in plateau-phase Chinese hamster fibroblast (HA-1) cells. After heat treatments that either drastically inhibited total protein synthesis (46 degrees C) or did not suppress it (41 degrees C), the synthesis of heat shock proteins was greatly enhanced over that in unheated cells, and cell survival was increased 10(2)- to 10(6)-fold when cells were challenged by a subsequent lethal heat treatment. The synthesis of heat shock proteins correlated well with the development of thermotolerance, and the stability of these proteins correlated well with the persistence of thermotolerance up to 36 hr. Sodium arsenite, hypoxia, and ethanol also induced both the synthesis of heat shock proteins and transient thermotolerance. A qualitative analysis of individual proteins suggests that the synthesis and persistence of polypeptides of Mr 70,000 or 87,000 most closely conformed to the kinetics of thermotolerance.
In the CA1 subfield of the gerbil hippocampus, an unusual series of changes were noticed after ischemia. Mongolian gerbils were subjected to bilateral carotid occlusion for 5 min. Perfusion fixation was performed 3, 6 and 12 h or 1, 2, 4, 7 and 21 days afterwards. Specimens obtained from the dorsal hippocampus were processed for light and electron microscopy. Three different types of changes were observed in the CA4, CA2 and CA1 subfields. In CA4, the change was rapid and corresponded to ischemic cell change. The alteration in CA2 was relatively slow, and identical to what has been called reactive change. On the contrary, the change in the CA1 pyramidal cells was very slow, only becoming apparent by light microscopy 2 days following ischemia. The CA1 subfield was selected for electron microscopic observation. The lamellar alignment of proliferated cisterns of the endoplasmic reticulum was the most conspicuous finding in these cells. Four days following ischemia, almost all of the pyramidal cells in CA1 were destroyed. In the CA1 neuropil, numerous presynaptic terminals remained without being apposed to normal postsynaptic sites. These changes in CA1, called here 'delayed neuronal death', may differ from those thought to be typical of ischemic neuronal damage. It was unlikely that the disturbance of local blood vessels was the cause of these changes.