Remote Ischemic Postconditioning Inhibits Hippocampal Neuronal Apoptosis and Mitophagy After Cardiopulmonary Resuscitation in Rats

The potential mechanism and clinical application value of remote ischemic conditioning in stroke

Some studies have confirmed the neuroprotective effect of remote ischemic conditioning against stroke. Although numerous animal researches have shown that the neuroprotective effect of remote ischemic conditioning may be related to neuroinflammation, cellular immunity, apoptosis, and autophagy, the exact underlying molecular mechanisms are unclear. This review summarizes the current status of different types of remote ischemic conditioning methods in animal and clinical studies and analyzes their commonalities and differences in neuroprotective mechanisms and signaling pathways. Remote ischemic conditioning has emerged as a potential therapeutic approach for improving stroke-induced brain injury owing to its simplicity, non-invasiveness, safety, and patient tolerability. Different forms of remote ischemic conditioning exhibit distinct intervention patterns, timing, and application range. Mechanistically, remote ischemic conditioning can exert neuroprotective effects by activating the Notch1/phosphatidylinositol 3-kinase/Akt signaling pathway, improving cerebral perfusion, suppressing neuroinflammation, inhibiting cell apoptosis, activating autophagy, and promoting neural regeneration. While remote ischemic conditioning has shown potential in improving stroke outcomes, its full clinical translation has not yet been achieved.

Hypothermia regulates mitophagy and apoptosis via PINK1/Parkin-VDAC 3 signaling pathway during oxygen-glucose deprivation/recovery injury

Post-cardiac arrest brain injury (PCABI), as the main cause of high mortality and long-term disability in patients, induces mitochondrial damage and cell apoptosis. Hypothermia is well-known as an effective neuroprotective therapy, but its underlying mechanisms deserve further exploration. Previous study has demonstrated that hypothermia provides neuroprotection via increasing PINK1/Parkin-mediated mitophagy. However, whether hypothermia can regulate both apoptosis and mitophagy through the PINK1/Parkin-VDAC3 signaling pathway or not. In this study, BV2 mouse microglial cells were cultured under oxygen-glucose deprivation for 6 h following reperfusion with or without hypothermia for 2-4 h. Cell viability was examined by trypan blue stain. Mitophagy was observed by transmission electron microscope. Mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (mPTP) opening were determined respectively by JC-1 staining and BBcellProbe M61 staining using a flow cytometer. Expression of mitophagy-related proteins (Cleaved PINK1, Parkin, SQSTM1/p62, Beclin-1, LC3B II/LC3B I), apoptosis-related proteins (Bcl-2, Cytochrome C, caspase-3, cleaved caspase3) and VDAC3 were assessed using western blot analysis and quantitative real-time PCR. The interaction between Parkin and VDAC3 was confirmed by immunofluorescence colocalization. The results showed that hypothermia alleviated MMP damage, inhibited mPTP opening, then decreased cell apoptosis and activated mitophagy at 2 h after temperature intervention, which might be mediated by the PINK1/Parkin-VDAC3 signaling pathway. Moreover, the effects of hypothermia were reduced or reversed at 4 h after temperature intervention. In conclusion, the potential mechanisms of hypothermia during oxygen-glucose deprivation/recovery could be summarized as follows:1) At 2 h after temperature intervention, hypothermia provided neuroprotective effects via promoting mitophagy and reducing apoptosis through activating the PINK1/Parkin-VDAC3 signaling pathway. 2) The curative effect of hypothermia was timeliness. At 4 h after temperature intervention, hypothermia aggravated apoptosis through inhibiting Parkin recruitment to mitochondria and aggravating the release of Cyt C through open mPTP.

Randomized feasibility trial of remote ischemic conditioning to enhance resuscitation (RICE)

RATIONALE

Restoration of blood flow after out-of-hospital cardiac arrest (OHCA) is associated with inflammation that causes cellular injury. The extent of this reperfusion injury (RI) is associated with the duration of ischemia and adequacy of resuscitation. Remote ischemic conditioning (RIC) consists of repeated application of non-lethal ischemia then reperfusion to a limb distal to the heart by inflating a blood pressure (BP) cuff. Trials in animal models in cardiac arrest and in humans with acute infarction show RIC reduces RI.

OBJECTIVE

We sought to demonstrate the feasibility and safety of RIC in patients resuscitated from OHCA and transported to hospital.

METHODS

This study was conducted under exception from informed consent (EFIC) for emergency research. Eligible subjects were randomized with masked allocation to control (standard care) versus intervention (standard care and RIC). Included were adults with non-traumatic OHCA. The primary outcome was attrition, the proportion of patients enrolled and not on allocated therapy for the study duration. Key secondary outcomes were survival to discharge, neurologic status at discharge, hospital-free survival, and adverse events. Results were summarized descriptively as recommended for pilot studies.

RESULTS

N = 30 patients were enrolled (n = 14 control, n = 16 intervention). Mean age of enrolled patients was 52.5 ± 16.2 years. Eight (27%) were female gender and 7 (23%) had a shockable first recorded rhythm. 100% of enrolled patients completed their allocated study intervention (i.e., 0% attrition). The RIC group had 7 (44%) survival to discharge and median Rankin score of 6 (IQR 1, 6) at discharge as compared to the standard care group which had 6 (43%) survival to discharge and median Rankin score of 6 (IQR 1.5, 6) at discharge. A single patient (6%) in the intervention group had transient occlusion of their upper extremity intravenous line, which immediately resolved on repositioning of the blood pressure cuff.

CONCLUSION

Application of RIC to patients resuscitated from CA and transported to an ED is feasible and safe. An adequately powered trial is required to assess whether RIC is effective at decreasing morbidity and mortality after CA.

Cerebral protective effect of in situ and remote ischemic postconditioning on ischemic stroke rat via the TGFβ1-Smad2/3 signaling pathway

Patients with acute ischemic stroke achieve inadequate benefit due to the short therapeutic window for thrombolysis and the risk of ischemia/reperfusion (IR) injury. Ischemic postconditioning induces endogenous cerebral protection for acute ischemic stroke, although the protective mechanisms associated with ischemic postconditioning haven't been well clarified. In present study, the rat models of ischemic cerebral stroke with in situ and remote ischemic postconditioning (ISP and RIP) were established successfully. The Zea Longa and the modified neurological severity scoring (mNSS) were carried out to evaluate neurological function in the rats, while the open field test was explored to estimate their autonomic athletic ability. The 2,3,5-riphenyltetrazolium chloride (TTC) staining method was used to measure the size of the infarcts. TUNEL and Nissl's staining were used to detect the apoptosis rate of cells in the ischemic penumbra, with the expression of TGFβ1, Smad2, and Smad3 in the ischemic penumbra and serum detected by immunohistochemical staining, qRT-PCR, Western blots, and ELISA analysis. We showed that application of both types of ischemic postconditioning had cerebral protective effects for the ischemic stroke rats, that included effective reduction in the volume of cerebral infarction, alleviation of apoptosis and inflammation in the ischemic penumbra, and promotion of recovery of neurological function. These effects included significantly enriched gene ontology (GO) terms after RIP intervention that were related to TGFβ1, increased protein levels of TGFβ1 and decreased levels of p-Smad2/3 and smad3 following RIP intervention. We showed that the TGFβ1-Smad2/3 signaling pathway was associated with the cerebral protection of ischemic postconditioning.

The Signaling Mechanism of Remote Postconditioning of the Heart: Prospects of the Use of Remote Postconditioning for the Treatment of Acute Myocardial Infarction

Acute myocardial infarction (AMI) remains the leading cause of mortality in the world, highlighting an urgent need for the development of novel, more effective approaches for the treatment of AMI. Remote postconditioning (RPost) of the heart could be a useful approach. It was demonstrated that RPost triggers infarct size reduction, improves contractile function of the heart in reperfusion, mitigates apoptosis, and stimulates autophagy in animals with coronary artery occlusion and reperfusion. Endogenous opioid peptides and adenosine could be involved in RPost. It was found that kinases and NO-synthase participate in RPost. KATP channels, MPT pore, and STAT3 could be hypothetical end-effectors of RPost. Metabolic syndrome and old age abolish the cardioprotective effect of RPost in rats. The data on the efficacy of RPost in clinical practice are inconsistent. These data are discussed in the review.

Neuroprotective Mechanism of Icariin on Hypoxic Ischemic Brain Damage in Neonatal Mice

Objective

Our previous results showed that icariin (ICA) could inhibit apoptosis and provide neuroprotection against hypoxic-ischemic brain damage (HIBD) in neonatal mice, but the specific mechanism of its neuroprotective effect remains unknown. This study aims at exploring whether ICA plays a neuroprotective role in apoptosis inhibition by regulating autophagy through the estrogen receptor α (ERα)/estrogen receptor β (ERβ) pathway in neonatal mice with HIBD.

Methods

A neonatal mouse model of HIBD was constructed in vivo, and an oxygen and glucose deprivation (OGD) model in HT22 cells from the hippocampal neuronal system was constructed in vitro. The effects of ICA pretreatment on autophagy and the expression of ERα and ERβ were detected in vitro and in vivo, respectively. ICA pretreatment was also supplemented with the autophagy inhibitor 3-methyladenine (3-MA), ERα inhibitor methylpiperidino pyrazole (MPP), and ERβ inhibitor 4-(2-phenyl-5,7-bis (trifluoromethyl) pyrazolo [1,5-a] pyramidin-3-yl) phenol (PHTPP) to further detect whether ICA pretreatment can activate the ERα/ERβ pathway to promote autophagy and reduce HIBD-induced apoptosis to play a neuroprotective role against HIBD in neonatal mice.

Results

ICA pretreatment significantly promoted autophagy in HIBD mice. Treatment with 3-MA significantly inhibited the increase in autophagy induced by ICA pretreatment, reversed the neuroprotective effect of ICA pretreatment, and promoted apoptosis. Moreover, ICA pretreatment significantly increased the expression levels of the ERα and ERβ proteins in HIBD newborn mice. Both MPP and PHTPP administration significantly inhibited the expression levels of the ERα and ERβ proteins activated by ICA pretreatment, reversed the neuroprotective effects of ICA pretreatment, inhibited the increase in autophagy induced by ICA pretreatment, and promoted apoptosis.

Conclusion

ICA pretreatment may promote autophagy by activating the ERα and ERβ pathways, thus reducing the apoptosis induced by HIBD and exerting a neuroprotective effect on neonatal mice with HIBD.

Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Mitochondria are the central target of ischemic preconditioning and postconditioning cardioprotective strategies, which consist of either the application of brief intermittent ischemia/reperfusion (I/R) cycles or the administration of pharmacological agents. Such strategies reduce cardiac I/R injury by activating protective signaling pathways that prevent the exacerbated production of reactive oxygen/nitrogen species, inhibit opening of mitochondrial permeability transition pore and reduce apoptosis, maintaining normal mitochondrial function. Cardioprotection also involves the activation of mitochondrial quality control (MQC) processes, which replace defective mitochondria or eliminate mitochondrial debris, preserving the structure and function of the network of these organelles, and consequently ensuring homeostasis and survival of cardiomyocytes. Such processes include mitochondrial biogenesis, fission, fusion, mitophagy and mitochondrial-controlled cell death. This review updates recent advances in MQC mechanisms that are activated in the protection conferred by different cardiac conditioning interventions. Furthermore, the role of extracellular vesicles in mitochondrial protection and turnover of these organelles will be discussed. It is concluded that modulation of MQC mechanisms and recognition of mitochondrial targets could provide a potential and selective therapeutic approach for I/R-induced mitochondrial dysfunction.

The molecular mechanism underlying mitophagy-mediated hippocampal neuron apoptosis in diabetes-related depression

Diabetes‐related depression (DD) is a major complication of diabetes mellitus. Our previous studies indicated that glutamate (Glu) and hippocampal neuron apoptosis are key signal and direct factor leading to diabetes‐related depression, respectively. However, the accurate pathogenesis remains to be unclear. We hypothesized that diabetes‐related depression might be associated with the mitophagy‐mediated hippocampal neuron apoptosis, triggered by aberrant Glu‐glutamate receptor2 (GluR2)‐Parkin pathway. To testify this hypothesis, here the rat model of DD in vivo and in vitro were both established so as to uncover the potential mechanism of DD based on mitophagy and apoptosis. We found that DD rats exhibit an elevated glutamate levels followed by monoamine neurotransmitter deficiency and depressive‐like behaviour, and DD modelling promoted autophagosome formation and caused mitochondrial impairment, eventually leading to hippocampal neuron apoptosis via aberrant Glu‐GluR2‐Parkin pathway. Further, in vitro study demonstrated that the simulated DD conditions resulted in an abnormal glutamate and monoamine neurotransmitter levels followed by autophagic flux increment, mitochondrial membrane potential reduction and mitochondrial reactive oxygen species and lactic dehydrogenase elevation. Interestingly, both GluR2 and mammalian target of rapamycin (mTOR) receptor blocker aggravated mitophagy‐induced hippocampal neuron apoptosis and abnormal expression of apoptotic protein. In contrast, both GluR2 and mTOR receptor agonist ameliorated those apoptosis in simulated DD conditions. Our findings revealed that mitophagy‐mediated hippocampal neuron apoptosis, triggered by aberrant Glu‐GluR2‐Parkin pathway, is responsible for depressive‐like behaviour and monoamine neurotransmitter deficiency in DD rats. This work provides promising molecular targets and strategy for the treatment of DD.