Cerebral Ischemic Postconditioning Research Articles

Differential Expression of CXCL1, CXCL10, and CXCL12 in Response to Cerebral Ischemic Postconditioning in Rat Brain

Objectives: Cerebral ischemic preconditioning lessens stroke-induced injuries, but it is clinically feasible only when the occurrence of stroke is predictable. Reperfusion plays a critical role against cerebral injury after stroke; we tested the hypothesis that interrupting ischemia during early reperfusion, i.e. Postconditioning (POCO) affects CXC chemokine expression and further reduce inflammation in rat model of ischemia/reperfusion. Materials & Methods: Adult male Wistar rats (250-300 g) were used in this experiment. Using 4-vessel occlusion method, global cerebral ischemia was induced and POCO was performed by applying 3 cycles of 15-s/15-s reperfusion/reocclusion after a 45-s reperfusion (POCO-45-15/15). Western blotting analysis was used to investigate CXCL1, CXCL10 and CXCL12 expression 24 h, 48 h and one week after ischemic postconditioning (iPOCO). Results: Based on the results, iPOCO attenuates the expression of inflammatory chemokines CXCL1 and CXCL10 in hippocampus area of postconditioned rats, while the CXCL12 was not affected by iPOCO. Conclusion: Current findings may support chemokines role in iPOCO via reduction of inflammation. Also there could be a link between postconditioning, stress and inflammation through chemokines.

Cerebral Ischemic Postconditioning Plays a Neuroprotective Role through Regulation of Central and Peripheral Glutamate.

Following cerebral ischemia/reperfusion (I/R) injury, a series of pathophysiological processes are stimulated in both the central nervous system (CNS) and the periphery, including, but not limited to, the peripheral immune and endocrine systems and underregulation of the neuroendocrine-immune network. Glutamate (Glu) is an important excitatory neurotransmitter in the CNS; its excitotoxicity following cerebral ischemia has been a focus of study for several decades. In addition, as a novel immunoregulator, Glu also regulates immune activity in both the CNS and periphery and may connect the CNS and periphery through regulation of the neuroendocrine-immune network. Ischemic postconditioning (IPostC) is powerful and activates various endogenous neuroprotective mechanisms following cerebral I/R, but only a few studies have focused on the mechanisms associated with Glu to date. Given that Glu plays an important and complex pathophysiological role, the understanding of Glu-related mechanisms of IPostC is an interesting area of research, which we review here.

Effect of inhibition of P38MAPK phosphorylation on learning and memory and autophagy in hippocampus of rats after cerebral ischemic postconditioning

Objective To investigate the effect of ischemic postconditioning on autophagy and learning and memory impairment in rats with ischemia-reperfusion injury by P38MAPK. Methods Ninty-six rats were randomly divided into sham group (Sham group), cerebral ischemia reperfusion group (CIR group), cerebral ischemic postconditioning group (CIP group) and cerebral ischemic postconditioning combined with SB203580 group (CIP + SB203580 group), and 24 rats in each group. The rat model of cerebral ischemia was established by Pulsinelli four-vessel occlusion. The learning and memory abilities of rats were measured by Morris water maze. HE staining were used to detect the morphological changes of hippocampal neurons. The phosphorylation of P38MAPK and Beclin-1, LC3-Ⅱexpression were observed by immunohistochemistry. Results Compared with the Sham group, the number of crossing the platform decreased(24 h: (3.04±0.20)times), and the escape latency was longer in CIR group(24 h: (58.38±1.52) s) (all P<0.05). The number of survival neurons reduced (24 h: 70.93±1.86), and the expression of P38MAPK, LC3-II, Beclin-1 in immunohistochemistry were increased in CIR group(all P<0.05). Compared with CIR group, the number of crossing the platform at each time point increased (24 h: (5.46±0.50)times), the escape latency was shorter (24 h: (52.42±1.53)s), the number of survival neurons increased at each time point(24 h: (83.07±5.30)) and the expression level of P38MAPK decreased in the CIP group, while the expression level of LC3-II, Beclin-1 increased (all P<0.05). Compared with the CIP group, the number of crossing the platform((24 h: (7.13±0.33)times), the escape latency was shorter (24 h: (48.04±1.39)s), the number of survival neurons increased at each time point(24 h: (91.40±1.74)), and the expression of P38MAPK was down-regulated, while the expression of LC3-II, Beclin-1 were up-regulated in CIP + SB203580 group(all P<0.05). Conclusion Ischemic postconditioning can improve learning and memory impairment in rats with ischemia-reperfusion injury by P38MAPK regulating autophagy. Key words: P38MAPK; Ischemic postconditioning; Learning and memory; Autophagy; Rat

Overview of Experimental and Clinical Findings regarding the Neuroprotective Effects of Cerebral Ischemic Postconditioning.

Research on attenuating the structural and functional deficits observed following ischemia-reperfusion has become increasingly focused on the therapeutic potential of ischemic postconditioning. In recent years, various methods and animal models of ischemic postconditioning have been utilized. The results of these numerous studies have indicated that the mechanisms underlying the neuroprotective effects of ischemic postconditioning may involve reductions in the generation of free radicals and inhibition of calcium overload, as well as the release of endogenous active substances, alterations in membrane channel function, and activation of protein kinases. Here we review the novel discovery, mechanism, key factors, and clinical application of ischemic postconditioning and discuss its implications for future research and problem of clinical practice.

Cerebral ischemic post‑conditioning induces autophagy inhibition and a HMGB1 secretion attenuation feedback loop to protect against ischemia reperfusion injury in an oxygen glucose deprivation cellular model.

Cerebral ischemic postconditioning (IPOC) has been demonstrated to be neuroprotective against cerebral ischemia reperfusion injury. The present study aimed to determine whether IPOC could inhibit autophagy and high mobility group box 1 (HMGB1) release in a PC12 cell oxygen glucose deprivation/reperfusion (OGD/R) model. An 8 h OGD and 24 h reperfusion cellular model was developed to mimic cerebral ischemia reperfusion injury, with 3 cycles of 10 min OGD/5 min reperfusion treatment to imitate IPOC. Cell viability was determined to demonstrate the efficiency of OGD/R, IPOC and autophagy activator, rapamycin (RAP), treatment. Transmission electron microscopy was performed to observe the formation of autophagosomes, and immunofluorescence, western blot and co-immunoprecipitation were used to examine the expression of autophagy-associated proteins and HMGB1. Enzyme-linked immunosorbent assay analysis was conducted to examine the level of HMGB1 in cell supernatants. Additionally, PC12 cells were treated with RAP to examine the effect of autophagy on HMGB1 release, and the effect of recombinant human HMGB1 and Beclin1 small interfering RNA on autophagy was investigated. The present study confirmed that IPOC inhibited autophagy and HMGB1 secretion, autophagy inhibition induced a decrease in HMGB1 secretion, and HMGB1 secretion attenuation caused autophagy inhibition in return, as demonstrated by immunofluorescence and western blot analyses. Autophagy inhibition and HMGB1 secretion attenuation were, therefore, demonstrated to form a feedback loop under IPOC. These mechanisms illustrated the protective effects of IPOC and may accelerate the clinical use of IPOC.

A Combination of Remote Ischemic Perconditioning and Cerebral Ischemic Postconditioning Inhibits Autophagy to Attenuate Plasma HMGB1 and Induce Neuroprotection Against Stroke in Rat.

Remote ischemic perconditioning (RIPerC) and ischemic postconditioning (IPOC) are well-acknowledged neuroprotective procedures during ischemic injury. The present study established a combined RIPerC and IPOC (RIPerC + IPOC) model in rats and studied how it would regulate the autophagy process and affect HMGB1 levels in a rat model of middle cerebral artery occlusion (MCAO). Rats with MCAO were treated with RIPerC by fastening and release of the left hind limb to achieve 4 cycles of 5 min remote ischemia reperfusion, 40 min prior to cerebral reperfusion, and then treated with IPOC by exposing the cerebral middle artery to 3 cycles of 30 s reperfusion/30 s occlusion at the onset of cerebral reperfusion. Infarction volumes, neurological deficits, and pathological changes were assessed 24 h after ischemia. The autophagy activator rapamycin (RAP) and the autophagy inhibitor 3-methyladenine (3-MA) were administrated for further mechanism. The expression and location of HMGB1 and the autophagy-related proteins like LC3, Beclin1, and P62 as well as plasma HMGB1 levels were measured. Our results suggested that RIPerC + IPOC attenuated plasma HMGB1 levels to intensify its neuroprotective effect against cerebral ischemic reperfusion injury via inhibiting the autophagy process.

The role of AMPA-receptors in mechanisms of neuroprotective effect of cerebral ischemic postconditioning

Objective. The purpose of the study is to explore the role of AMPA receptors in the neuroprotective effect of ischemic postconditioning (IРost) in the model of reversible global forebrain ischemia in Mongolian gerbils. Design and methods. Reversible global cerebral ischemia was induced by bilateral occlusion of common carotid arteries in Mongolian gerbils for 7 minutes. IРost was induced by three 15-s episodes of reperfusion/reocclusion. Antagonist of AMPA receptors NBQX was administered intraperitoneally at 2 nd minute of ischemia at a dose of 30 mg/kg. In the early and delayed reperfusion period, the number of viable neurons in the CA1, CA2, CA, and CA4 fields of the hippocampus was estimated. Results. Reversible 7 minutes ischemia followed by 48 hours of reperfusion resulted in a significant reduction in the number of viable neurons in the fields CA1 and СА3 of the hippocampus, while in the late reperfusion period a significant reduction in the number of viable neurons was observed in fields CA1, СА3 and CA4. Application of IРost has led to an increase in the number of viable neurons in fields CA1 and CA3 in the early reperfusion period and in fields CA1, CA3 and CA4 — in delayed period. AMPA receptor antagonist NBQX attenuated neuroprotective effect of IPost to a level comparable with the effect of a separate application of NBQX for neurons in the CA1 and CA3 fields of the hippocampus. Conclusions . Along with other mechanisms, the activation of AMPA receptors might be implicated in the mechanisms of cerebral IPost.

Ischemic Postconditioning Protects the Neurovascular Unit after Focal Cerebral Ischemia/Reperfusion Injury

Recently, cerebral ischemic postconditioning (Postcond) has been shown to reduce infarction volume in cerebral ischemia/reperfusion (I/R) injury. However, it is unclear if ischemic Postcond offers more extensive neuroprotection than current therapies. The aim of this study was to investigate the neuroprotective effects of ischemic Postcond on the neurovascular unit (NVU). A middle cerebral artery occlusion rat model was used; cerebral infarct volumes, neurologic scores, and transmission electron microscopy were evaluated 24 h after reperfusion. We used Evans blue extravasation, immunohistochemistry, and Western blot analyses to evaluate the integrity of the blood brain barrier (BBB) and the distribution and expression of the tight junction (TJ)-associated proteins of claudin-5 and occludin in brain microvessel endothelium. The Postcond group showed significantly reduced infarct volumes and decreased neurologic impairment scores compared to the I/R group. Also, injuries to the cerebral microvascular endothelial cells, astrocytes, and neurons were minimized in the Postcond group. The permeability of the BBB increased in both the I/R and Postcond groups, but the Postcond group showed a significant decrease in permeability than the I/R group. Expression of both claudin-5 and occludin were higher in the Postcond groups compared to the I/R group, but expression of both proteins decreased in the I/R and Postcond groups compared to the sham group. The results of our study suggest that ischemic Postcond is an effective way to reduce injury to neurons, astrocytes, and endothelial cells, to increase protein expressions of TJ-associated proteins, and to improve BBB intergrity affected by focal I/R. Ischemic Postcond could protect the NVU from I/R injury.

A Novel Neuroprotective Strategy for Ischemic Stroke: Transient Mild Acidosis Treatment by CO2 Inhalation at Reperfusion

Acidosis is one of the key components in cerebral ischemic postconditioning that has emerged recently as an endogenous strategy for neuroprotection. We set out to test whether acidosis treatment at reperfusion can protect against cerebral ischemia/reperfusion injury. Adult male C57BL/6 J mice were subjected to 60-minute middle cerebral arterial occlusion followed by 24-hour reperfusion. Acidosis treatment by inhaling 10%, 20%, or 30% CO2 for 5 or 10 minutes at 5, 50, or 100 minutes after reperfusion was applied. Our results showed that inhaling 20% CO2 for 5 minutes at 5 minutes after reperfusion-induced optimal neuroprotection, as revealed by reduced infarct volume. Attenuating brain acidosis with NaHCO3 significantly compromised the acidosis or ischemic postconditioning-induced neuroprotection. Consistently, both acidosis-treated primary cultured cortical neurons and acute corticostriatal slices were more resistant to oxygen-glucose deprivation/reperfusion insult. In addition, acidosis inhibited ischemia/reperfusion-induced apoptosis, caspase-3 expression, cytochrome c release to cytoplasm, and mitochondrial permeability transition pore (mPTP) opening. The neuroprotection of acidosis was inhibited by the mPTP opener atractyloside both in vivo and in vitro. Taken together, these findings indicate that transient mild acidosis treatment at reperfusion protects against cerebral ischemia/reperfusion injury. This neuroprotection is likely achieved, at least partly, by inhibiting mPTP opening and mitochondria-dependent apoptosis.

Transient Lack of Glucose but not O2 is Involved in Ischemic Postconditioning‐Induced Neuroprotection

Cerebral ischemic postconditioning has emerged recently as a kind of endogenous strategy for neuroprotection. We set out to test whether hypoxia or glucose deprivation (GD) would substitute for ischemia in postconditioning. Adult male C57BL/6J mice were treated with postconditioning evoked by ischemia (bilateral common carotid arteries occlusion) or hypoxia (8% O(2) ) after 45-min middle cerebral arterial occlusion. Corticostriatal slices from mice were subjected to 1-min oxygen-glucose deprivation (OGD), GD, or oxygen deprivation (OD) postconditioning at 5 min after 15-min OGD. Hypoxic postconditioning did not decrease infarct volume or improve neurologic function at 24 h after reperfusion, while ischemic postconditioning did. Similarly, OGD and GD but not OD postconditioning attenuated the OGD/reperfusion-induced injury in corticostriatal slices. The effective duration of low-glucose (1 mmol/L) postconditioning was longer than that of OGD postconditioning. Moreover, OGD and GD but not OD postconditioning reversed the changes of glutamate, GABA, glutamate transporter-1 protein expression, and glutamine synthetase activity induced by OGD/reperfusion. These results suggest that the transient lack of glucose but not oxygen plays a key role in ischemic postconditioning-induced neuroprotection, at least partly by regulating glutamate metabolism. Low-glucose postconditioning might be a clinically safe and feasible therapeutic approach against cerebral ischemia/reperfusion injury.

Ischemic postconditioning protects brain from ischemia/reperfusion injury by attenuating endoplasmic reticulum stress-induced apoptosis through PI3K-Akt pathway

Endoplasmic reticulum (ER) stress has been implicated in the pathology of cerebral ischemia. During prolonged period of stress or when the adaptive response fails, apoptotic cell death ensues. Cerebral ischemic postconditioning (Postcond) has been shown to reduce cerebral ischemia/reperfusion (I/R) injury in both focal and global cerebral ischemia model. However, the mechanism remains to be understood. This study aimed to elucidate whether Postcond attenuates brain I/R damage by suppressing ER stress-induced apoptosis and if the phosphatidylinositol-3kinase/Akt (PI3K/Akt) pathway is involved. A focal cerebral ischemia rat model was used in the study. Rat brain infarct size and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) positive cells in ischemic penumbra were assessed after reperfusion of the brain. The expressions of C/EBP-homologous protein (CHOP), caspase-12, glucose-regulated protein 78 (GRP78) and the phosphorylation of Akt (Ser473) in ischemic penumbra were measured after reperfusion. Our results showed that Postcond significantly attenuated brain I/R injury, as shown by reduction in infarct size, cell apoptosis, CHOP expression, caspase-12 activation and increase in GRP78 expression. LY294002, a phosphoinositide 3-kinase inhibitor, increased the number of TUNEL-positive cells suppressed by Postcond in penumbra. In addition, LY294002 diminished the effect of Postcond on the activation of CHOP, caspase-12 and GRP78. These results suggest that Postcond protects brain from I/R injury by suppressing ER stress-induced apoptosis and PI3K/Akt pathway is involved.