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AIM: To explore whether free radicals participate in cerebral ischemic tolerance and the up-regula-tion of p38 MAPK and ERK signaling pathways in rats induced by limb ischemic preconditioning (LIP). METHODS: A total of 128 Wistar rats with permanent occlusion of bilateral vertebral arteries were randomly divided into sham group (n=16), cerebral ischemia (CI) group (n=16), LIP+CI group (n=16), DMTU (a free radical scavenger)+LIP+CI group (n=64) and DMTU+sham group (n=16). Six rats in each group were used to observe the delayed neuronal death (DND) in hippocampal CA1 region by thionin staining at 7 d after the end of operation. Other 10 rats in each group were used to de-tect the expression of p38 MAPK and ERK in hippocampal CA1 region by immunohistochemistry and Western blot. RE-SULTS: Lethal CI resulted in obvious DND in hippocampal CA1 region. However, LIP reversed the above injurious changes, represented by the decrease in histological grade and the increase in neuronal density compared with CI group (P<0. 01). Moreover, LIP significantly up-regulated the expression of p38 MAPK and ERK in hippocampal CA1 region com-pared with CI group (P<0. 01). Administration of free radical scavenger DMTU via femoral vein before LIP partially re-versed the neuroprotective effect of LIP, and blocked the up-regulation of p38 MAPK and ERK expression in hippocampal CA1 region in rats compared with LIP+CI group (P<0. 01). CONCLUSION: Free radicals are involved in the neuropro-tection and up-regulation of p38 MAPK and ERK expression induced by LIP in rats.
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Electroacupuncture preconditioning can alleviate the nerve defect after cerebral ischemia injury, induce cerebral ischemic tolerance and exert the certain protective effect on brain, which may be involved in regulating endocannabinoid system, inhibiting exitotoxicity, inhibiting oxidative stress, inhibiting endoplasmic reticulum stress, inhibiting inflammatory response, protecting blood-brain barrier, inhibiting apoptosis and regulating autophagy, etc.
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A 74-year-old male presented to us with a history of vision loss for 36 hours in the right eye (RE). The RE had a visual acuity of hand movements. The fundus revealed a pale retina, cattle tracking in the retinal vessels, and a cherry-red spot at the macula. The patient was a known case of pyoderma gangrenosum (PG) and had received intravenous methylprednisolone and cyclophosphamide at the onset of visual symptoms. An emergency anterior chamber paracentesis was performed following unsuccessful attempts of ocular massage. The patient improved to 6/9 in the RE 4 months after paracentesis. The patient had an aggressive course of PG, for which he needed a combination of oral steroid, immunomodulator therapy and biologicals. An association between central retinal arterial occlusion and PG has not been reported before, according to the best of authors' knowledge.
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Ischemic preconditioning (IP) is one of the most important endogenous mechanisms that protect the cells against ischemia-reperfusion (I/R) injury. However, the exact molecular mechanisms remain unclear. In this study, we showed that changes in the level of agmatine were correlated with ischemic tolerance. Changes in brain edema, infarct volume, level of agmatine, and expression of arginine decarboxylase (ADC) and nitric oxide synthases (NOS; inducible NOS [iNOS] and neural NOS [nNOS]) were analyzed during I/R injury with or without IP in the rat brain. After cerebral ischemia, brain edema and infarct volume were significantly reduced in the IP group. The level of agmatine was increased before and during ischemic injury and remained elevated in the early reperfusion phase in the IP group compared to the experimental control (EC) group. During IP, the level of plasma agmatine was increased in the early phase of IP, but that of liver agmatine was abruptly decreased. However, the level of agmatine was definitely increased in the ipsilateral and contralateral hemisphere of brain during the IP. IP also increased the expression of ADC—the enzyme responsible for the synthesis of endogenous agmatine—before, during, and after ischemic injury. In addition, ischemic injury increased endogenous ADC expression in the EC group. The expression of nNOS was reduced in the I/R injured brain in the IP group. These results suggest that endogenous increased agmatine may be a component of the ischemic tolerance response that is induced by IP. Agmatine may have a pivotal role in endogenous ischemic tolerance.
Subject(s)
Animals , Rats , Agmatine , Arginine , Brain , Brain Edema , Brain Ischemia , Ischemic Preconditioning , Liver , Neuroprotection , Nitric Oxide , Nitric Oxide Synthase , Plasma , Reperfusion , Reperfusion InjuryABSTRACT
The mice models of blood stasis were established by injecting dexamethasone into the intramuscular of side the thigh for successive 15 days, and giving related drugs via an intragastric administration. Firstly, the method of blocking the bilateral common carotid artery (CCA) was used for 10 minutes, and then perfusion restore for 5 days. Secondly, the method of CCA was used for 30 minutes, and then reperfusion for 24 hours. The whole blood viscosity and plasma viscosity, the activity of NOS and ATPase and the level of NOS, and the content of Glu in the ischemic brain were measured. The morphological changes of brain tissue were observed by eosin (HE) staining technique. The results showed that compared with IPC model group the large doses of the flavonoids could reduce the viscosity of whole blood significantly (P<0.01). The small and medium doses of flavonoids could reduce the whole blood viscosity low-shear obviously (P<0.01). The medium doses of flavonoids could reduce the midst-shear obviously (P<0.05). The large and medium dose of flavonoids could significantly improve the ATP activity (P<0.01). The medium dose of flavonoids could improve the Na⁺-K⁺-ATPase activity significantly (P<0.01). The small dose of flavonoids could improve the Na⁺-K⁺-ATPase activity obviously (P<0.05). The large doses of flavonoids could reduce the content of gluin the ischemic brain significantly (P<0.01). And the others does of flavonoids could reduce the content of gluin the ischemic brain obviously (P<0.05). The large doses of flavonoids could reduce the activity of TNOS and iNOS significantly (P<0.01). The medium doses of flavonoids could reduce the activity of TNOS and iNOS obviously (P<0.05). The small doses of flavonoids could reduce the activity of iNOS obviously (P<0.05). Total flavonoids could obviously or significantly decrease the whole blood viscosity, the activity of NOS and the content of gluin the ischemic brain, increase the activity of ATPase significantly or obviously, could significantly relieve the degree of pathological injury of brain tissue of animal models.
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Brain ischemic tolerance refers to endogenous brain protective mechanism during severe ischemic injury of the body. Ischemia preconditioning is an effective mean to induce brain ischemic tolerance. However, the invasive and ethical limitation made the application of ischemic preconditioning difficult in the clinical practice. Studies found that extracellular signal regulated kinase (ERK) signaling pathway played an important role in the formation of brain ischemic tolerance. Meanwhile, brain ischemic tolerance induced by traditional Chinese medicine (TCM) had its unique advantages. This article reviewed effects of ERK signaling pathway in the inducing of brain ischemic tolerance and TCM intervention in recent years.
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Objective To explore the role of brief ischemia pretreatment in the induction of renal ischemic tolerance,and investigate its effects on tubular cell necrosis,apoptosis and proliferation. Methods Male Sprague-Dawley rats were randomly divided into three groups,including sham-operated group (Sham),ischemia/reperfusion injured group subjected to theocclusion of both renal pedicles for 40 min followed by reperfusion(I/R),and preconditioned group with 20-min ischemia pretreatment induced 4 days before I/R(IPC).Histological changes were evaluated by PAS staining.The ultra-structure of tubular cells was observed by transmission electron microscopy(TEM).Apoptosis was confirmed by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL).The proliferation of tubular cells was evaluated with proliferating cell nuclear antigen(PCNA). Results Twenty-minites ischemia pretreatment offered both promising functional and histological protection against 40-min ischemia/reperfusion injury (P<0.01).The mortality rate wag reduced from 33%in I/R group to 0 in IPC group.The renopmtection offered by 20-min ischemia pretreatment was accompanied with reduced postischemic tubular cell apoptosis and necrosis (P<0.05), and increased cell proliferation (PCNA positive) (P< 0.01). Conclusions Brief and sublethal prior ischemia can render the kidney more tolerant to subsequent prolonged I/R injury. Its ability to tilt the balance of tubular cell fate toward survival, reducing postischemic cell death and enhancing cell proliferation, may play an important role in renal protection of ischemic preconditioning.
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Objective: To study the effect of ischemic preconditioning on heat-shock protein 70 (HSP70) expression and the learning,memory functions after forebrain ischemia-reperfusion injury in gerbils. Methods: Gerbils (n=100) were evenly randomized into four groups: Sham group, ischemia-reperfusion (I/R) group, ischemia preconditioning (IP) group, and Cycloheximide + IP group (Cycloheximide was administered 30 min before IP). Transient forebrain ischemia-reperfusion model was established by bilateral common carotid artery occlusion according to the method described previously, and ischemia preconditioning model was established as described by Kitagawa. Changes of neuron morphous in hippocampus CA1 region were observed by H-E staining 1, 2, and 3 days after reperfusion. The expression of HSP70 was examined by immunohistochemistry and Western blotting assay. Neuron apoptosis was detected by TUNEL method. The learning/memory functions of gerbils were examined using 4-PTT dry path maze 3, 4, 5, 6, and 7 days after reperfusion. Results: Compared with Sham group, I/R group had significantly decreased survival neurons(P<0. 05), increased neuron apoptosis(P<0. 05), increased expression of HSP70 (P<0. 05), and decreased learning/memory functions(P<0. 05). Compared with I/R group, IP group had significantly increased survival neurons(P<0. 05), decreased neuron apoptosis (P<0. 05), and increased expression of HSP70 (P<0. 05), and improved learning/memory functions (P < 0. 05). However, cycloheximide almost totally abolished the effect of ischemia preconditioning, with the neuron morphology, density, apoptosis, HSP70 expression, and learning/memory functions similar to those of I/R group. Conclusion: Ischemic preconditioning can protect against cerebral ischemia injury and improve the learning/ memory functions after forebrain ischemia-reperfusion damage, which is possibly through promoting HSP70 expression and starting endogenous neuroprotective mechanism, subsequently reinforcing the protective effect against ischemia.
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In the brain, brief episodes of ischemia induce tolerance against a subsequent severe episode of ischemia. This phenomenon of endogenous neuroprotection is known as preconditioning-induced ischemic tolerance. The purpose of this review is to summarize the current state of knowledge about mechanisms and potential applications of cerebral preconditioning and ischemic tolerance. Articles related to the terms ischemic preconditioning and ischemic tolerance were systematically searched via MEDLINE/PubMed, and articles published in English related to the nervous system were selected and analyzed. The past two decades have provided interesting insights into the molecular mechanisms of this neuroprotective phenomenon. Although both rapid and delayed types of tolerance have been documented in experimental settings, the delayed type has been found to be more prominent in the case of neuronal ischemic tolerance. Many intracellular signaling pathways have been implicated regarding ischemic preconditioning. Most of these are associated with membrane receptors, kinase cascades, and transcription factors. Moreover, ischemic tolerance can be induced by exposing animals or cells to diverse types of endogenous and exogenous stimuli that are not necessarily hypoxic or ischemic in nature. These cross-tolerances raise the hope that, in the future, it will be possible to pharmacologically activate or mimic ischemic tolerance in the human brain. Another promising approach is remote preconditioning in which preconditioning of one organ or system leads to the protection of a different (remote) organ that is difficult to target, such as the brain. The preconditioning strategy and related interventions can confer neuroprotection in experimental ischemia, and, thus, have promise for practical applications in cases of vascular neurosurgery and endo-vascular therapy.
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Animals , Humans , Brain , Brain Ischemia , Hydrazines , Ischemia , Ischemic Preconditioning , Membranes , Nervous System , Neurons , Neurosurgery , Phosphotransferases , Transcription FactorsABSTRACT
@#Objective To observe the effects of Tongxinluo on cerebral ischemic tolerance and expression of Bcl-2 and Bax in rats with cerebral infarction.Methods The neurophysical assessment and the volume of the cerebral infarction in Tongxinluo group,middle cerebral artery occlusion(MCAO)group,preconditioning and MCAO(PC-MCAO)group were determined at different time point.The expression of Bcl-2 and Bax were measured with immunohistochemitry and the apoptosis of the nerve cells were detected with TUNEL.Results Among these groups in the corresponding time,the neurophysical marks of Tongxinluo group was the lowest and the cerebral infarction volume was the smallest at 24 h,3 d and 5 d points.The Bcl-2 positive neurons were the highest,while the Bax positive neurons and the apoptosis rate of nerve cells were the lowest around the necrotic areas in Tongxinluo group(P<0.05).Conclusion Tongxinluo can improve the cerebral ischemic tolerance and increase the expression of Bcl-2 and decrease that of Bax around the necrotic area after cerebral ischemia in rats.
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Objective To study ischemic tolerance induced by acanthopannx senticosus saponins(ASS) on ischemia in PC12 cells and involve expression of hypoxia inducible factor-1?(HIF-1?).Methods An ischemic model was developed in PC12 cell line with treatment of oxygen glucose deprivation(OGD).The protective effects of ASS pretreatment on ischemic tolerance of PC12 cells and whether protective effects of ASS could be inhibited by LY294002(PI3K inhibitor) were analyzed through MTT assay.The induction of phospho-glycogen synthesis kinase-3?(p-GSK-3?) and HIF-1? after pretreatment of ASS and possible blocking effects of LY294002 were detected by Western-blot.Results MTT results showed that after 9 h ischemia,the viability of PC12 cells decreased dramatically(P
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Hypoxia inducible factor 1 (HIF-1), a nuclear protein with transcription activity, can make the body produce adaptive response to hypoxia/ischemia by binding to target gene, transcription and post-transcriptional control. Ischemic tolerance refers to the adaptive response to transient ischemia and reperfusion, which can improve tissue tolerance during the following damage caused by more severe ischemic events. The recent studies have found that the expression of HIF-1 has an important significance in ischemic tolerance. HIF-1 may be a key factor of the oxygen signal transduction pathway in the development of cerebral ischemic tolerance.
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To systematically evaluate the importance of protein synthesis in ischemic preconditioning (PC)-induced ischemic tolerance (IT), temporary middle cerebral artery occlusion (MCAO)by Longa (20 min) was used for PC (ischemic precondioning). Twenty-four hours of reperfusion was allowed after PC and before permanent MCAO to establish ischemic tolerance (IT) to compare with non-PC (sham-operated) rats (n=5 for each group). Infarct size and neurological deficits were measured 24 h after PMCAO. Samples of brain were taken for the determination of HSP70 expression by Western blot analysis. The effects of the protein synthesis inhibitor cycloheximide administered just before PC or administered long after PC but just before PMCAO on IT were also determined (n=5 for each group). Our results showed that hemispheric infarct was significantly reduced (P＜0.01) only if PC was performed after 24 h, and PC significantly (P＜0.05) reduced neurological deficits (similar to reductions in infarct size). Cycloheximide eliminated ischemic PC-induced IT effects on both brain injury and neurological deficits if administered before PC but not if administered long after PC but before PMCAO. PC produced no brain injury but did increase HSP70 protein 24 h after PC. Cycloheximide eliminated that effect. The results suggest that PC is a powerful inducer of ischemic brain tolerance as reflected by the preservation of brain tissue and motor function. PC induces IT that is dependent on de novo protein synthesis.
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Objective To investigate the influence of focal ischemic preconditioning on the expression of heat shock protein 70(HSP70) and ischemic tolerance Methods 42 SD rats were divided into 3 groups in which control group received sham operation only, and the other two groups received 2 hours of middle cerebral artery occlusion(MCAO) followed by 22 hours of reperfusion with or without 10 minutes of ischemic preconditioning 3 days before Infarct volume and HSP70 immunoreactivity were evaluated in each group Results Compared with the sham operated group, there was a smaller infarct volume( P
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Objective To research the expression and correlation between erythropoietin(EPO)mRNA and hypoxia inducible factor-1?(HIF-1?)mRNA in rats with brain ischemic tolerance induced by ischemic preconditioning.Methods Models of cerebral ischemic preconditioning and ischemic-reperfusion(preconditioning group)were made by twice suture method,after the short ischemic preconditioning 1 d,3 d,7 d,14 d and 21 d respectively,the models were underwent ischemic-reperfusion again.The infarct volume was measured by tetrazolium chloride(TTC)staining,the expressions of HIF-1? mRNA and EPO mRNA in the different time(1～21 d)of ischemic-reperfusion were detected by reverse transcriptase polymerase chain reaction(RT-PCR)and compared with non-preconditioning group.Results The infarct volume in the 1 d,3 d and 7 d subgroups of preconditioning group were significantly smaller compared with non-preconditioning group(all P
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BACKGROUND: Although reperfusion certainly prevents tissue ischemia from possible cardiac death, several lines of evidence suggest that reperfusion may paradoxically aggravate the frequency of serious reperfusion-induced lethal arrhythmias. It has been reported that acute administration of estrogen at physiological concentrations reduced with myocardial ischemic injury in women with coronary heart disease. In studies with canines, acute administration by either the intra-muscular or the intra-coronary route similarly prevented ischemia and reperfusion dysrhythmias and also reduced the infarct size because the estrogen increased the distal coronary perfusion pressure, scavenged free radicals and had other effects during both ischemia and reperfusion. However, the canine heart is notoriously well collateralized. 17beta-estradiol induces very little vasorelaxation in cat coronary rings, suggesting that increased ischemic myocardial blood flow dose not contribute to the protective effect. In the present study, employing a cat model of regional cardiac ischemia, we examined whether reperfusion rendered after acute administration of 17beta-estradiol could lower the incidence of reperfusion-induced lethal arrhythmia and the death rate. METHOD: Adult mongrel male cats(n=31, 2.7~4.5 kg) were anesthetized under positive-pressure artificial ventilation with room air. Electrocardiograms were recorded. The animals of the control group(n=15) were subjected to 20-minute left anterior descending coronary artery(LAD) occlusion followed by abrupt reperfusion. The animals in the experimental 17beta-estradiol(2 or 20 microgram/kg) group were subjected to ischemia/reperfusion insult following drug treatment: 17beta-estradiol was applied intravenously within the 60 seconds just before LAD ligation followed by abrupt reperfusion. The Fisher's exact test was used to compare the data from different animal groups(p<0.05). RESULTS: The number of arrhythmias(ventricular premature beat, ventricular tachycardia and ventricular fibrillation) emerging during the reperfusion phase were not statistically different from that in the control group. The death rate in the 17beta-estradiol 20 microgram/kg group was lower from that in the control group(P value = 0.039). CONCLUSION: Acute administration of 17beta-estradiol at a supraphysiological concentration might produce cardioprotective effects, not by modificating the coronary blood flow into the threatened myocardial region, but by other mechanisms that directly or indirectly increase the intrinsic myocardial ischemic tolerance in the cat during the reperfusion phase.
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Adult , Animals , Cats , Female , Humans , Male , Arrhythmias, Cardiac , Cardiac Complexes, Premature , Coronary Disease , Death , Electrocardiography , Estrogens , Free Radicals , Heart , Incidence , Ischemia , Ligation , Mortality , Perfusion , Reperfusion , Tachycardia, Ventricular , Vasodilation , VentilationABSTRACT
AIM: To investigate the relationship between astroglial activation state and ischemic tolerance induced by low dose of 3 nitropropionic acid (3 NPA) in gerbil hippocampus. METHODS: Transient forebrain ischemic model was induced by bilateral common carotid arteries occlution. HE staining and immunohistochemistry were used to identify neuronal and astrocyte response. RESULTS: Preconditioning with 3 NPA produced protective effects of CA 1neurons. The number of glial fibrillary acidic protein positive astrocyte in hippocampal CA 1 region increased slightly in control group, but increased significantly in preconditioning of the brain with 3 nitropropionic acid. CONCLUSION: The state of astroglial activation is related to neuronal survival in ischemic tolerance induced by low dose of 3 nitropropionic acid.
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A brief period of cerebral ischemia produces neuronal damage in the vulnerable regions of the brain, such as the CA1 area of the hippocampus. However, mild ischemic episodes may limit damage from subsequent ischemic insults, the phenomenon known as ischemic tolerance or preconditioning. We used hippocampal slices as an experimental model to investigate the possible utilization of ischemic tolerance, and to determine the effects of various drugs acting on glutamate and adenosine receptors following a conditioned ischemic insult. Preconditioning ischemic insult was induced in hippocampal slices of 450nm thickness for 60-70 seconds. Glutamate and adenosine receptors were pretreated 1 hour later with D,L-2-amino-5-phosphonovaleric acid(AP-5, 50nM), propentofylline(PPF, 200nM), 6-cyano-7-nitroquinoxaline-2,3-dione(CNQX, 10nM), 8-cyclopentyl-3,7-dihydro-1,3-dipropyl-1H-purine-2,6-dione(DPCPX, 1, 10nM) and 2-chloro-N6-cyclopentyl-adenosine (CCPA, 1, 10, 50nM). The slices were reoxygenated for 3 hours, after then a second ischemic insult was induced by substituting 95% O2, 5% CO2 and glucose for 95% N2, 5% CO2 and sucrose for 10 minutes. Population spikes(PS) were estimated from extracellular electrophysiological recordings of the hippocampal CA3-CA1 synaptic conduction 1 hour following the second ischemic insult. The PS(mV) was 2.69+/-0.06 in the normal hippocampal slice, while it was reduced to 1.21+/-0.05 in the hippocampal slice induced with 10 minutes of ischemia. The effects of the A1 selective agonist CPPA revealed a reduction of PS to 0.98+/-0.06 with low concentration(1nM), similar PS as the control group with a concentration of 10nM, and an increase in ischemic tolerance of 1.78+/-0.05 at a higher concentration(50nM). The selective A1 antagonist DPCPX(1nM) showed minimal reduction in PS of 1.10+/-0.04, while the NMDA antagonist AP-5(5nM) had a more profound weakening effect(1.05+/-0.04). The adenosine uptake inhibitor profentophylline(200nM) augmented the PS to 1.56+/-0.06; this effect was not influenced by 1nM DPCPX(1.60+/-0.07), but was abolished by a higher concentration of 10nM(1.36+/-0.05). These results confirmed ischemic tolerance in the hippocampal experimental model. We conclude that adenosine plays an important role in ischemic tolerance as activation of adenosine receptors or adenosine uptake inhibition enhances ischemic tolerance.
Subject(s)
Adenosine , Brain , Brain Ischemia , Glucose , Glutamic Acid , Hippocampus , Ischemia , Models, Theoretical , N-Methylaspartate , Neurons , Receptors, Purinergic P1 , SucroseABSTRACT
BACKGROUND: The term 'ischemic preconditioning', which implies the first, brief, sublethal ischemia before the next ischemia, is widely accepted to have protective effect in the myocardium, and recently with a specified circumstances, in the brain also. However, the existence of this 'ischemic tolerance' phenomenon is not yet clarified in the repeated transient focal cerebral ischemia model. This study was performed to test whether the ischemic preconditiong has protective effect also in this TIA-mimicking condition. METHODS: Using intraluminar suture technique, initial transient focal ischemia was maintained for 30 minutes in the rat brain. After this ischemic preconditioning, second ischemia of 120 minutes duration was performed using the same method at 1, 3, 5, and 7 days after the 1st ischemia (n=20). The resulting brain infarct volume was assessed and compared to that of previously sham-operated paired controls(n=20). RESULTS: Using the infarct volume as parameters, there was no significant difference between the ischemia and control group in all pairs. But when the percent of infarct volume compared to the hemispheric volume was used instead, neocortical infarct percent was significantly smaller at day 3 after preconditiong (p<0.05). But such difference was not found at 1, 5, and 7th day in the neocotex. Neither the percent of total infarct nor the subcortical infarct showed any statistical difference. CONCLUSION: It could be concluded that transient focal cerebral ischemic preconditioning have neuroprotective effect. The optimal interval between ischemia for this 'ischemic tolerance' to happen is 3 days, and this phenomenon seems to be the function of cerebral cortex, but not the subcortex.
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Animals , Rats , Brain , Brain Ischemia , Cerebral Cortex , Ischemia , Ischemic Preconditioning , Models, Animal , Myocardium , Neuroprotective Agents , Suture TechniquesABSTRACT
Objective To investigate the role of apoptosis and apoptotic proteins p53,p21 and Bax in mechanisms of brain ischemic tolerance in rats.Methods In our study the models of focal-focal type brain ischemic preconditioning were maded by occlusion middle cerebral artery using an intraluminal filament method. Infarct sizes were measured by image analysis system.Neuronal apoptosis was identified by TUNEL staining and expressions of p53, p21 and Bax were analyzed by immunohistochemistry.Results Compared with the lethal ischemic group, the volume of infarct was greatly reduced when MCAO 20 minutes was performed as ischemic preconditioning( P