Neuroprotective effects and mechanisms of ischemic/hypoxic preconditioning on neurological diseases

Remote ischemic conditioning-induced shift from a vulnerable to a tolerant penumbra: A proteomic perspective

The concept of the ischaemic penumbra - stroke tissue with the potential to survive - has opened the door to a wide range of experimental strategies that could benefit the recovery of patients after a stroke. In this study, we used proteomic analysis to examine how remote ischaemic postconditioning (RIPC) mediates a shift from a vulnerable to a tolerant penumbra. We identified 450 differentially abundant proteins between the control group and the groups subjected to ischaemia via middle cerebral artery occlusion with or without RIPC during infarct expansion. The majority of proteins were downregulated following RIPC. Based on Gene Ontology enrichment analysis, we uncovered 24 gene sets significantly influenced during the reprogramming from a vulnerable to a tolerant penumbra. RIPC treatment positively impacted the synthesis of proteins enriched in the cytosol (GO:0005829) but inhibited the abundance of proteins belonging to the cytoskeleton (GO:0005874 microtubule) and the glutamatergic synapse (GO:0098978). The shift to a tolerant phenotype involved overexpression of aminopeptidases (GO:0004177) related to proteolysis (GO:0006508). RIPC also downregulated proteins involved in the tricarboxylic acid cycle (GO:0006099), adenosine triphosphate (ATP) binding (GO:0005524), and ATP hydrolysis (GO:0016887). We validated our proteomic findings by selecting two candidate genes (Map2 and Tubb3) for immunofluorescence. We identified the low-molecular-weight Map2 isoform as a potential marker of the shift from a vulnerable to a tolerant penumbra. In summary, our findings have revealed novel avenues for multimodal investigation of reprogramming the penumbra as part of recovery from stroke.

Conserved components of the macroautophagy machinery in Caenorhabditis elegans

Macroautophagy involves the sequestration of cytoplasmic contents in a double-membrane autophagosome and its subsequent delivery to lysosomes for degradation and recycling. In Caenorhabditis elegans, autophagy participates in diverse processes such as stress resistance, cell fate specification, tissue remodeling, aging, and adaptive immunity. Genetic screens in C. elegans have identified a set of metazoan-specific autophagy genes that form the basis for our molecular understanding of steps unique to the autophagy pathway in multicellular organisms. Suppressor screens have uncovered multiple mechanisms that modulate autophagy activity under physiological conditions. C. elegans also provides a model to investigate how autophagy activity is coordinately controlled at an organismal level. In this chapter, we will discuss the molecular machinery, regulation, and physiological functions of autophagy, and also methods utilized for monitoring autophagy during C. elegans development.

Neuroprotective effect of remote ischemic preconditioning in MRI-guided focused ultrasound treatment

Introduction — Magnetic resonance imaging-guided focused ultrasound (MRgFUS) is used for ablation of various solid tumors and treatment of neurological diseases. During ablation, brain tissue is injured, resulting in the formation of necrosis and edema zones. Therefore, strategies to minimize brain damage are highly relevant. The goal of our research was to study the neuroprotective effect of remote ischemic preconditioning (RIPC) in the treatment of movement disorders using MRgFUS. Material and Methods — The study design was blinded randomized controlled 2-group trial. Patients were randomly assigned to the IPC group (systolic blood pressure +50 mm Hg, n=42) or sham IPC (sIPC) group (diastolic pressure, n=39) prior to MRgFUS in the mode of 3 cycles of 5 min of preconditioning on the forearm with 5 min of rest between cycles. Results — Following MRgFUS ablation of the ventralis intermediate (VIM) nucleus (gray matter), no differences in lesion size or tremor severity were detected after 2 h between the IPC and sIPC groups. When affecting the pallidothalamic tract (PTT, white matter), in the IPC group, in contrast to the sIPC, the main sizes of the necrotic lesion were significantly smaller after 2 h (frontal dimension, p=0.001; vertical dimension, p=0.037; necrosis lesion volume, p=0.007). Also, after 24 h in the IPC group, the dimensions of the lesion in the PTT were smaller (frontal dimension, p<0.001; vertical dimension, p=0.021; lesion volume, p=0.001). Conclusion — RIPC preceding MRgFUS has a neuroprotective effect on PTT (white matter).

The Epileptiogenic Modified Therapy: Regulating the Dynamic of Microglia via ROS-Responsive Cascade Nano-Formulation

Pharmacological treatment of epilepsy presents several challenges, particularly the ineffectiveness of antiseizure medicines (ASMs) in modifying disease. In fact, the removal of reactive oxygen species (ROS) and preconditioning with tolerable dose of nitric oxide (NO) can activate neuroprotective mechanisms during latency and enhance tolerance to oxidative stress during seizures. To address this, a ROS-responsive cascade Nano-formulation (RRCN) is developed, which will transform ROS into NO. Remarkably, RRCN significantly reduces seizure severity, prolongs seizure latency, and extends inter-seizure intervals, though it does not increase the latency of generalized seizures. Microglia, the primary immune cells of the brain, play a crucial role in the initiation and progression of epilepsy. In the kainic acid (KA) epilepsy model, microglial processes elongate, branching increases, and interactions between microglia and neurons are strengthened in the CA1 and CA3 regions of the hippocampus compared to the Vehicle group. RRCN reverses these dynamic changes in microglia and their interactions with neurons, which are mediated by the NO/HIF/ErBb2 pathway. Thus, RRCN can inhibit seizures generalization by preconditioning the dynamic changes of microglia.

The role of H3K27 acetylation in oxygen-glucose deprivation-induced spinal cord injury and potential for neuroprotective therapies

OBJECTIVE

Spinal cord injury (SCI) is a debilitating condition that often results in paralysis and lifelong medical challenges. Research has shown that epigenetic modifications, particularly histone acetylation, play a role in neuroprotection following hypoxic-ischemic events in SCI. The objective of this study was to explore the effects of histone H3K27 acetylation, along with its underlying mechanisms, on the tolerance to hypoxia and ischemia in SCI.

METHODS

This study employed an organotypic spinal cord slice culture model subjected to oxygen-glucose deprivation (OGD). We assessed cell apoptosis and changes in cellular type patterns under these conditions. Following hypoxia and ischemia, we analyzed the expression and distribution of H3K27ac across various nerve cell types. To identify key downstream genes, we integrated ChIP-seq and RNA-seq analyses, investigating molecular mechanisms driving the response to OGD in this model.

RESULTS

OGD stimulation increased cell apoptosis and induced time-dependent changes in the expression patterns of neurons, astrocytes, microglia, and oligodendrocytes in organotypic spinal cord slices, accompanied by a significant reduction in H3K27ac levels. Integrated ChIP-seq and RNA-seq analyses revealed that H3K27ac downregulation under hypoxic and ischemic conditions contributes to spinal cord damage by promoting neuroinflammation and disrupting gene regulation. Furthermore, we identified key downstream targets, including Apoc1, Spp1, Aff1, Brd4, KCNN3, and Rgma, which may represent promising therapeutic targets for SCI.

CONCLUSION

Our data underscore the pivotal role of H3K27ac in the organotypic spinal cord slice culture model following OGD exposure, offering promising avenues for neuroprotective therapies via epigenetic-immune regulation.

Acute Three-Dimensional Hypoxia Regulates Angiogenesis

Hypoxia elicits a multitude of tissue responses depending on the severity and duration of the exposure. While chronic hypoxia is shown to impact development, regeneration, and cancer, the understanding of the threats of acute (i.e., short-term) hypoxia is limited mainly due to its transient nature. Here, a novel gelatin-dextran (Gel-Dex) hydrogel is established that decouples hydrogel formation and oxygen consumption and thus facilitates 3D sprouting from endothelial spheroids and, subsequently, induces hypoxia "on-demand." The Gel-Dex platform rapidly achieves acute moderate hypoxic conditions without compromising its mechanical properties. Acute exposure to hypoxia leads to increased endothelial cell migration and proliferation, promoting the total length and number of vascular sprouts. This work finds that the enhanced angiogenic response is mediated by reactive oxygen species, independently of hypoxia-inducible factors. Reactive oxygen species-dependent matrix metalloproteinases activity mediated angiogenic sprouting is observed following acute hypoxia. Overall, the Gel-Dex hydrogel offers a novel platform to study how "on-demand" acute moderate hypoxia impacts angiogenesis, with broad applicability to the development of novel sensing technologies.

Protective effect of sub-hypothermic mechanical perfusion combined with membrane lung oxygenation on a yorkshire model of brain injury after traumatic blood loss

PURPOSE

To investigate the protective effect of sub-hypothermic mechanical perfusion combined with membrane lung oxygenation on ischemic hypoxic injury of yorkshire brain tissue caused by traumatic blood loss.

METHODS

This article performed a random controlled trial. Brain tissue of 7 yorkshire was selected and divided into the sub-low temperature anterograde machine perfusion group (n = 4) and the blank control group (n = 3) using the random number table method. A yorkshire model of brain tissue injury induced by traumatic blood loss was established. Firstly, the perfusion temperature and blood oxygen saturation were monitored in real-time during the perfusion process. The number of red blood cells, hemoglobin content, NA+, K+, and Ca2+ ions concentrations and pH of the perfusate were detected. Following perfusion, we specifically examined the parietal lobe to assess its water content. The prefrontal cortex and hippocampus were then dissected for histological evaluation, allowing us to investigate potential regional differences in tissue injury. The blank control group was sampled directly before perfusion. All statistical analyses and graphs were performed using GraphPad Prism 8.0 Student t-test. All tests were two-sided, and p value of less than 0.05 was considered to indicate statistical significance.

RESULTS

The contents of red blood cells and hemoglobin during perfusion were maintained at normal levels but more red blood cells were destroyed 3 h after the perfusion. The blood oxygen saturation of the perfusion group was maintained at 95% - 98%. NA+ and K+ concentrations were normal most of the time during perfusion but increased significantly at about 4 h. The Ca2+ concentration remained within the normal range at each period. Glucose levels were slightly higher than the baseline level. The pH of the perfusion solution was slightly lower at the beginning of perfusion, and then gradually increased to the normal level. The water content of brain tissue in the sub-low and docile perfusion group was 78.95% ± 0.39%, which was significantly higher than that in the control group (75.27% ± 0.55%, t = 10.49, p < 0.001), and the difference was statistically significant. Compared with the blank control group, the structure and morphology of pyramidal neurons in the Prefrontal cortex and CA1 region of the hippocampal gyrus were similar, and their integrity was better. The structural integrity of granulosa neurons was destroyed and cell edema increased in the perfusion group compared with the blank control group. Immunofluorescence staining for glail fibrillary acidic protein and Iba1, markers of glial cells, revealed well-preserved cell structures in the perfusion group. While there were indications of abnormal cellular activity, the analysis showed no significant difference in axon thickness or integrity compared to the 1-h blank control group.

CONCLUSIONS

Mild hypothermic machine perfusion can improve ischemia and hypoxia injury of yorkshire brain tissue caused by traumatic blood loss and delay the necrosis and apoptosis of yorkshire brain tissue by continuous oxygen supply, maintaining ion homeostasis and reducing tissue metabolism level.

MALAT1 and NEAT1 are Neuroprotective During Hypoxic Preconditioning in the Mouse Hippocampus Possibly by Regulation of NR2B

Wang, Liping, Gang Fu, Ruijuan Han, Peijia Fan, Jing Yang, Kerui Gong, Zhijun Zhao, Chunyang Zhang, Kai Sun, and Guo Shao. MALAT1 and NEAT1 are neuroprotective during hypoxic preconditioning in the mouse hippocampus possibly by regulation of NR2B. High Alt Med Biol. 25:285-294, 2024. Background: The regulation of noncoding ribonucleic acid (ncRNA) has been shown to be involved in cellular and molecular responses to hypoxic preconditioning (HPC), a situation created by the induction of sublethal hypoxia in the brain. The ncRNAs metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and nuclear paraspeckle assembly transcript 1 (NEAT1) are abundantly expressed in the brain, where they regulate the expression of various genes in nerve cells. However, the exact roles of MALAT1 and NEAT1 in HPC are not fully understood. Methods: A mouse model of acute repeated hypoxia was used as a model of HPC, and MALAT1 and NEAT1 levels in the hippocampus were measured using real-time polymerase chain reaction (PCR). The mRNA and protein levels of N-methyl-d-aspartate receptor subunit 2 B (NR2B) in the mouse hippocampus were measured using real-time PCR and western blotting, respectively. HT22 cells knocked-down for MALAT1 and NEAT1 were used for in vitro testing. Expression of NR2B, which is involved in nerve cell injury under ischemic and hypoxic conditions, was also evaluated. The levels of spectrin and cleaved caspase-3 in MALAT1 and NEAT1 knockdown HT22 cells under oxygen glucose deprivation/reperfusion (OGD/R) were determined by western blotting. Results: HPC increased the expression of MALAT1 and NEAT1 and decreased the expression of NR2B mRNA in the mouse hippocampus (p < 0.05). Knockdown of MALAT1 and NEAT1 increased both NR2B mRNA and protein levels nearly twofold and caused damage under OGD/R conditions in HT22 cells (p < 0.05). Conclusion: MALAT1 and NEAT1 exert neuroprotective effects by influencing the expression of NR2B.

Effect of remote ischemic preconditioning on cerebral circulation time in severe carotid artery stenosis: Results from the RIC-CCT trial

In patients with severe internal carotid artery stenosis (sICAS), cerebral circulation time (CCT) is associated with cerebral hyperperfusion syndrome. This study aims to investigate the effect of remote ischemic preconditioning (RIC) on CCT in patients with sICAS. Patients are randomly assigned to the RIC group (RIC twice daily, for 2-4 days before carotid artery stenting [CAS] as an adjunct to standard medical therapy) and the control group. The results show that RIC produces a significant decrease in CCT of the stenosis side (sCCT) from baseline to pre-CAS, and the occurrence of contrast staining on brain computed tomography (CT) is lower in RIC versus control group after CAS. In addition, significant changes in some serum biomarkers suggest that anti-neuroinflammation, anti-oxidative stress, protecting endothelial injury, and improving cerebral autoregulation may be associated with the effect of RIC. These findings provide supporting evidence that RIC can modulate cerebral circulation in patients with sICAS. This study was registered at ClinicalTrials.gov (NCT05451030).

Remote ischemic preconditioning plays a neuroprotective role in cerebral ischemia-reperfusion mice by inhibiting mitophagy

Remote ischemic preconditioning (RIPC) represents a clinically feasible method for safeguarding vital organs against ischemic injury. However, its specific role in cerebral ischemia-reperfusion (I/R) injury remains to be definitively elucidated. In this study, we investigated the neuroprotective effects of RIPC on mice at 7 days post-cerebral I/R and its involvement in mitophagy and mitochondrial dysfunction. Cerebral I/R led to impaired brain function, as well as structural and functional damage to mitochondria. Notably, RIPC treatment ameliorated the neurological dysfunction induced by cerebral I/R. Compared with the I/R group, the expression levels of NeuN, MBP, PDH, and Tom20 were significantly elevated in the RIPC + I/R group. Furthermore, mitochondria in the RIPC + I/R group exhibited more intact structure compared to those in the I/R group. In mice subjected to I/R injury, RIPC treatment markedly increased ATP content, ADP content, TAN level and glucose uptake while upregulating expression levels of Parkin, Pink1 and P62 proteins; it also reduced both the volume of ischemic foci and the number of mitochondrial autophagosomes along with decreasing LC3B II/I ratio. In conclusion, RIPC may exert a neuroprotective role by inhibiting excessive mitophagy during subacute stages following an ischemic stroke.

Investigation of preconditioning and the protective effects of nicotinamide against cerebral ischemia-reperfusion injury in rats

This study investigated the antioxidant and neuroprotective effects of nicotinamide combined with ischemic preconditioning against cerebral ischemia reperfusion (CIR) injury. Thirty-five Wistar albino male rats were randomly divided into five groups: sham, preconditioned ischemia/reperfusion (IP+IR), ischemia/reperfusion (IR), preconditioned ischemia/reperfusion + nicotinamide (IP+IR+N), and ischemia/reperfusion + nicotinamide (IR+N). CIR was achieved with bilateral common carotid artery occlusion. IP+IR and IP+IR+N groups 30 min before ischemia; Three cycles of 10 sec ischemia/30 sec reperfusion followed by 20 min IR were applied. The IP+IR+N and IR+N groups received 500 mg/kg nicotinamide intraperitoneally. After 24 h of reperfusion, a neurological evaluation was performed and vertıcal pole test. Biochemically, malondialdehyde (MDA), glutathione (GSH) levels and catalase (CAT) activity were measured in blood and brain tissue samples. Rates of red neurons, sateliosis and spongiosis were determined histopathologically in the prefrontal cortex areas. After CIR, MDA levels increased significantly in serum and brain tissue in the IR group compared to the sham group, while GSH and CAT activity decreased in the brain tissue (p < 0.05). MDA levels in the tissues were found significantly decreased in the IR+N group compared to the IR group (p < 0.05). Administration of nicotinamide together with IP significantly decreased MDA levels in brain tissue and increased GSH and CAT activity (p < 0.05). Compared to the IR group, the morphological and neurological damage in the prefrontal cortex areas decreased in the IP+IR, IP+IR+N, and IR+N groups (p < 0.05). In addition, red neuron, sateliosis and spongiosis rates increased significantly in the IR group compared to the Sham, IP+IR+N, IR+N groups (p < 0.001 for all). In neurological evaluation, while the neurological score increased and the time on the vertical pole decreased significantly in the IR group, preconditioning, and nicotinamide groups reversed (p < 0.05). The study's results show that nicotinamide administration with ischemic preconditioning alleviates cerebral ischemia/reperfusion injury.

Assessing the importance and safety of hypoxia conditioning for patients with occupational pulmonary diseases: A recent clinical perspective

Occupational pulmonary diseases (OPDs) pose a significant global health challenge, contributing to high mortality rates. This review delves into the pathophysiology of hypoxia and the safety of intermittent hypoxic conditioning (IHC) in OPD patients. By examining sources such as PubMed, Relemed, NLM, Scopus, and Google Scholar, the review evaluates the efficacy of IHC in clinical outcomes for OPD patients. It highlights the complexities of cardiovascular and respiratory regulation dysfunctions in OPDs, focusing on respiratory control abnormalities and the impact of intermittent hypoxic exposures. Key areas include the physiological effects of hypoxia, the role of hypoxia-inducible factor-1 alpha (HIF-1α) in occupational lung diseases, and the links between brain ischemia, stroke, and OPDs. The review also explores the interaction between intermittent hypoxic exposures, mitochondrial energetics, and lung physiology. The potential of IHE to improve clinical manifestations and underlying pathophysiology in OPD patients is thoroughly examined. This comprehensive analysis aims to benefit molecular pathologists, pulmonologists, clinicians, and physicians by enhancing understanding of IHE's clinical benefits, from research to patient care, and improving clinical outcomes for OPD patients.

Alternation of gene expression in brain-derived exosomes after cerebral ischemic preconditioning in mice

Aims

Cerebral ischemic preconditioning is a neuroprotective therapy against cerebral ischemia and ischemia-reperfusion injury. This study aims to demonstrate the alternation of gene expression in exosomes from brain tissue of mice after ischemic preconditioning and their potential functions.

Methods

Ten mice were divided into the sham and the cerebral ischemic preconditioning groups. Their brain tissues were harvested, from which the exosomes were extracted. The characteristics and protective effects of exosomes were evaluated. Whole transcriptome sequencing was used to demonstrate the gene expression discrepancy between the exosomes from the two groups of mice brains. Volcano graphs and heatmaps were used to picture the difference in expression quantity of mRNA, lncRNA, and circRNA. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to demonstrate the functions of differentially expressed RNAs.

Results

Exosomes were successfully extracted, and those from the cerebral ischemic preconditioning group had better protective effects on cells that received oxygen-glucose deprivation and restoration injury. A total of 306 mRNAs and 374 lncRNAs were significantly upregulated, and 320 mRNAs and 405 lncRNAs were significantly downregulated in the preconditioning group. No circRNAs were differentially expressed between the two groups. GO and KEGG pathway analysis indicated that the functions of differentially expressed RNAs were related to both neural protective and injurious effects.

Conclusion

The brain-derived exosomes may participate in the neuroprotective effect of cerebral ischemic preconditioning. Thorough research is necessary to investigate exosome functions derived from the ischemic preconditioned brain.

The role of cellular senescence in neurodegenerative diseases

Increasing evidence has revealed that cellular senescence drives NDs, including Alzheimer's disease (AD) and Parkinson's disease. Different senescent cell populations secrete senescence-associated secretory phenotypes (SASP), including matrix metalloproteinase-3, interleukin (IL)-1α, IL-6, and IL-8, which can harm adjacent microglia. Moreover, these cells possess high expression levels of senescence hallmarks (p16 and p21) and elevated senescence-associated β-galactosidase activity in in vitro and in vivo ND models. These senescence phenotypes contribute to the deposition of β-amyloid and tau-protein tangles. Selective clearance of senescent cells and SASP regulation by inhibiting p38/mitogen-activated protein kinase and nuclear factor kappa B signaling attenuate β-amyloid load and prevent tau-protein tangle deposition, thereby improving cognitive performance in AD mouse models. In addition, telomere shortening, a cellular senescence biomarker, is associated with increased ND risks. Telomere dysfunction causes cellular senescence, stimulating IL-6, tumor necrosis factor-α, and IL-1β secretions. The forced expression of telomerase activators prevents cellular senescence, yielding considerable neuroprotective effects. This review elucidates the mechanism of cellular senescence in ND pathogenesis, suggesting strategies to eliminate or restore senescent cells to a normal phenotype for treating such diseases.

Therapeutic approaches targeting the gut microbiota in ischemic stroke: current advances and future directions

Ischemic stroke (IS) is the predominant form of stroke pathology, and its clinical management remains constrained by therapeutic time frame. The gut microbiota (GM), comprising a multitude of bacterial and archaeal cells, surpasses the human cell count by approximately tenfold and significantly contributes to the human organism's growth, development, and overall well-being. The microbiota-gut-brain axis (MGBA) in recent years has established a strong association between gut microbes and the brain, demonstrating their intricate involvement in the progression of IS. The regulation of IS by the GM, encompassing changes in composition, abundance, and distribution, is multifaceted, involving neurological, endocrine, immunological, and metabolic mechanisms. This comprehensive understanding offers novel insights into the therapeutic approaches for IS. The objective of this paper is to examine the mechanisms of interaction between the GM and IS in recent years, assess the therapeutic effects of the GM on IS through various interventions, such as dietary modifications, probiotics, fecal microbiota transplantation, and antibiotics, and offer insights into the potential clinical application of the GM in stroke treatment.

Up-regulation of miR-126 via DNA methylation in hypoxia-preconditioned endothelial cells may contribute to hypoxic tolerance of neuronal cells

BACKGROUND

Endothelial cells (ECs) can confer neuroprotection by secreting molecules. This study aimed to investigate whether DNA methylation contributes to the neuroprotective gene expression induced by hypoxia preconditioning (HPC) in ECs and to clarify that the secretion of molecules from HPC ECs may be one of the molecular mechanisms of neuroprotection.

METHODS

Human microvascular endothelial cell-1 (HMEC-1) was cultured under normal conditions (C), hypoxia(H), and hypoxia preconditioning (HPC), followed by the isolation of culture medium (CM). SY5Y cell incubated with the isolated CM from HMEC-1 was exposed to oxygen-glucose deprivation (OGD). The DNA methyltransferases (DNMTs), global methylation level, miR-126 and its promotor DNA methylation level in HMEC-1 were measured. The cell viability and cell injury in SY5Y were detected.

RESULTS

HPC decreased DNMTs level and global methylation level as well as increased miR-126 expression in HMEC-1. CM from HPC treated HMEC-1 also relieved SY5Y cell damage, while CM from HMEC-1 which over-expression of miR-126 can reduce injury in SY5Y under OGD condition.

CONCLUSIONS

These findings indicate EC may secrete molecules, such as miR-126, to execute neuroprotection induced by HPC through regulating the expression of DNMTs.

MiR-18a affects hypoxia induced glucose metabolism transition in HT22 hippocampal neuronal cell line through the Hif1a gene

Hypoxia can cause a variety of diseases, including ischemic stroke and neurodegenerative diseases. Within a certain range of partial pressure of oxygen, cells can respond to changes in oxygen. Changes in oxygen concentration beyond a threshold will cause damage or even necrosis of tissues and organs, especially for the central nervous system. Therefore, it is very important to find appropriate measures to alleviate damage. MiRNAs can participate in the regulation of hypoxic responses in various types of cells. MiRNAs are involved in regulating hypoxic responses in many types of tissues by activating the hypoxia-inducible factor (HIF) to affect angiogenesis, glycolysis and other biological processes. By analyzing differentially expressed miRNAs in hypoxia and hypoxia-related studies, as well as the HT22 neuronal cell line under hypoxic stress, we found that the expression of miR-18a was changed in these models. MiR-18a could regulate glucose metabolism in HT22 cells under hypoxic stress by directly regulating the 3'UTR of the Hif1a gene. As a small molecule, miRNAs are easy to be designed into small nucleic acid drugs, so this study can provide a theoretical basis for the research and treatment of nervous system diseases caused by hypoxia.

Electroacupuncture pretreatment alleviates rats cerebral ischemia-reperfusion injury by inhibiting ferroptosis

Objective

To explore the preventive effect of electroacupuncture pretreatment on stroke in rats by inhibiting ferroptosis and oxidative stress.

Methods

Rats were randomly assigned to the sham, middle cerebral artery occlusion/reperfusion (MCAO/R), MCAO/R + EP, MCAO/R + EP + erastin, and MCAO/R + EP + ferrostatin 1 groups. Daily electroacupuncture was performed 2 weeks before establishing the MCAO/R model utilizing the modified Zea Longa suture method. Rats were sacrificed 1 day after reperfusion, and brain tissues were collected. They were prepared for hematoxylin and eosin staining, prussian blue staining, transmission electron microscope. Measurement of total iron levels using a commercial kit, detection of malondialdehyde (MDA) and superoxide dismutase (SOD) levels by ELISA, and examination of 15-lox2, GPX4, SLC7A11, ACSL4, and TFR1 by western blotting.

Results

Compared with sham rats, cerebral infarction size was dramatically larger in MCAO/R rats. Moreover, the MCAO/R group displayed damaged mitochondria with a disarranged structure of cristae; free iron, total iron levels, and oxidative stress were significantly higher. Cerebral pathological lesions, oxidative stress, total iron levels, and protein levels of ACSL4, TFR1, and 15-lox2 were significantly reduced in the MCAO/R + EP and MCAO/R + EP + ferrostatin 1 groups, while the protective effect of electroacupuncture pretreatment on cerebral ischemia-reperfusion injury was inhibited by treatment with the ferroptosis activator erastin.

Conclusion

Electroacupuncture pretreatment can protect rats from cerebral ischemia-reperfusion injury by reducing the area of cerebral infarction and inhibiting ferroptosis and oxidative stress.

Research hotspots and frontiers of preconditioning in cerebral ischemia: A bibliometric analysis

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.

Exosomes-Mediated Signaling Pathway: A New Direction for Treatment of Organ Ischemia-Reperfusion Injury

Ischemia reperfusion (I/R) is a common pathological process which occurs mostly in organs like the heart, brain, kidney, and lung. The injury caused by I/R gradually becomes one of the main causes of fatal diseases, which is an urgent clinical problem to be solved. Although great progress has been made in therapeutic methods, including surgical, drug, gene therapy, and transplant therapy for I/R injury, the development of effective methods to cure the injury remains a worldwide challenge. In recent years, exosomes have attracted much attention for their important roles in immune response, antigen presentation, cell migration, cell differentiation, and tumor invasion. Meanwhile, exosomes have been shown to have great potential in the treatment of I/R injury in organs. The study of the exosome-mediated signaling pathway can not only help to reveal the mechanism behind exosomes promoting reperfusion injury recovery, but also provide a theoretical basis for the clinical application of exosomes. Here, we review the research progress in utilizing various exosomes from different cell types to promote the healing of I/R injury, focusing on the classical signaling pathways such as PI3K/Akt, NF-κB, Nrf2, PTEN, Wnt, MAPK, toll-like receptor, and AMPK. The results suggest that exosomes regulate these signaling pathways to reduce oxidative stress, regulate immune responses, decrease the expression of inflammatory cytokines, and promote tissue repair, making exosomes a competitive emerging vector for treating I/R damage in organs.

Resveratrol Preconditioning Downregulates PARP1 Protein to Alleviate PARP1-Mediated Cell Death Following Cerebral Ischemia

Stroke remains a leading cause of mortality; however, available therapeutics are limited. The study of ischemic tolerance, in paradigms such as resveratrol preconditioning (RPC), provides promise for the development of novel prophylactic therapies. The heavily oxidative environment following stroke promotes poly-ADP-ribose polymerase 1 (PARP1)-overactivation and parthanatos, both of which are major contributors to neuronal injury. In this study, we tested the hypothesis that RPC instills ischemic tolerance through decreasing PARP1 overexpression and parthanatos following in vitro and in vivo cerebral ischemia. To test this hypothesis, we utilized rat primary neuronal cultures (PNCs) and middle cerebral artery occlusion (MCAO) in the rat as in vitro and in vivo models, respectively. RPC was administered 2 days preceding ischemic insults. RPC protected PNCs against oxygen and glucose deprivation (OGD)-induced neuronal loss, as well as increases in total PARP1 protein, implying protection against PARP1-overactivation. Twelve hours following OGD, we observed reductions in NAD+/NADH as well as an increase in AIF nuclear translocation, but RPC ameliorated NAD+/NADH loss and blocked AIF nuclear translocation. MCAO in the rat induced AIF nuclear translocation in the ischemic penumbra after 24 h, which was ameliorated with RPC. We tested the hypothesis that RPC's neuroprotection was instilled through long-term downregulation of nuclear PARP1 protein. RPC downregulated nuclear PARP1 protein for at least 6 days in PNCs, likely contributing to RPC's ischemic tolerance. This study describes a novel mechanism by which RPC instills prophylaxis against ischemia-induced PARP1 overexpression and parthanatos, through a long-term reduction of nuclear PARP1 protein.

Hypoxic acclimatization training improves the resistance to motion sickness

Objective

Vestibular provocation is one of the main causes of flight illusions, and its occurrence is closely related to the susceptibility of motion sickness (MS). However, existing training programs have limited effect in improving the resistance to motion sickness. In this study, we investigated the effects of hypoxia acclimatization training (HAT) on the resistance to motion sickness.

Methods

Healthy military college students were identified as subjects according to the criteria. MS model was induced by a rotary chair. Experimental groups included control, HAT, 3D roller training (3DRT), and combined training.

Results

The Graybiel scores were decreased in the HAT group and the 3DRT group and further decreased in the combined training group in MS induced by the rotary chair. Participants had a significant increase in blood pressure after the rotary chair test and a significant increase in the heart rate during the rotary chair test, but these changes disappeared in all three training groups. Additionally, LFn was increased, HFn was decreased, and LF/HF was increased accordingly during the rotary chair test in the control group, but the changes of these three parameters were completely opposite in the three training groups during the rotary chair test. Compared with the control group, the decreasing changes in pupillary contraction velocity (PCV) and pupillary minimum diameter (PMD) of the three training groups were smaller. In particular, the binocular PCV changes were further attenuated in the combined training group.

Conclusion

Our research provides a possible candidate solution for training military pilots in the resistance to motion sickness.

Immune mechanisms of depression in rheumatoid arthritis

Depression is a common and disabling comorbidity in rheumatoid arthritis that not only decreases the likelihood of remission and treatment adherence but also increases the risk of disability and mortality in patients with rheumatoid arthritis. Compelling data that link immune mechanisms to major depressive disorder indicate possible common mechanisms that drive the pathology of the two conditions. Preclinical evidence suggests that pro-inflammatory cytokines, which are prevalent in rheumatoid arthritis, have various effects on monoaminergic neurotransmission, neurotrophic factors and measures of synaptic plasticity. Neuroimaging studies provide insight into the consequences of inflammation on the brain (for example, on neural connectivity), and clinical trial data highlight the beneficial effects of immune modulation on comorbid depression. Major depressive disorder occurs more frequently in patients with rheumatoid arthritis than in the general population, and major depressive disorder also increases the risk of a future diagnosis of rheumatoid arthritis, further highlighting the link between rheumatoid arthritis and major depressive disorder. This Review focuses on interactions between peripheral and central immunobiological mechanisms in the context of both rheumatoid arthritis and major depressive disorder. Understanding these mechanisms will provide a basis for future therapeutic development, not least in depression.

The multifaceted roles of activating transcription factor 3 (ATF3) in inflammatory responses - Potential target to regulate neuroinflammation in acute brain injury

Activating transcription factor 3 (ATF3) is one of the most important transcription factors that respond to and exert dual effects on inflammatory responses. Recently, the involvement of ATF3 in the neuroinflammatory response to acute brain injury (ABI) has been highlighted. It functions by regulating neuroimmune activation and the production of neuroinflammatory mediators. Notably, recent clinical evidence suggests that ATF3 may serve as a potential ideal biomarker of the long-term prognosis of ABI patients. This mini-review describes the essential inflammation modulatory roles of ATF3 in different disease contexts and summarizes the regulatory mechanisms of ATF3 in the ABI-induced neuroinflammation.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Intermittent Hypoxia Conditioning: A Potential Multi-Organ Protective Therapeutic Strategy

Severe hypoxia can induce a range of systemic disorders; however, surprising resilience can be obtained through sublethal adaptation to hypoxia, a process termed as hypoxic conditioning. A particular form of this strategy, known as intermittent hypoxia conditioning hormesis, alternates exposure to hypoxic and normoxic conditions, facilitating adaptation to reduced oxygen availability. This technique, originally employed in sports and high-altitude medicine, has shown promise in multiple pathologies when applied with calibrated mild to moderate hypoxia and appropriate hypoxic cycles. Recent studies have extensively investigated the protective role of intermittent hypoxia conditioning and its underlying mechanisms using animal models, demonstrating its potential in organ protection. This involves a range of processes such as reduction of oxidative stress, inflammation, and apoptosis, along with enhancement of hypoxic gene expression, among others. Given that intermittent hypoxia conditioning fosters beneficial physiological responses across multiple organs and systems, this review presents a comprehensive analysis of existing studies on intermittent hypoxia and its potential advantages in various organs. It aims to draw attention to the possibility of clinically applying intermittent hypoxia conditioning as a multi-organ protective strategy. This review comprehensively discusses the protective effects of intermittent hypoxia across multiple systems, outlines potential procedures for implementing intermittent hypoxia, and provides a brief overview of the potential protective mechanisms of intermittent hypoxia.

Ischemic preconditioning attenuates endoplasmic reticulum stress-dependent apoptosis of hepatocytes by regulating autophagy in hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (HIRI) usually occurs during subtotal hepatectomy and severely damages liver function during the perioperative period. Endoplasmic reticulum stress (ERS) dependent apoptosis has been suggested to play a crucial role in HIRI progression. The present study focused on the regulatory effect of autophagy activation induced by ischemic preconditioning (IPC) on ERS-dependent apoptosis of hepatocytes in HIRI. A HIRI mouse model and oxygen-glucose deprivation/reperfusion (OGD/R) AML-12 hepatocyte cell lines were constructed to evaluate the protective effect of IPC in vivo and in vitro. The protein levels of p-eIF2α, CHOP, and cleaved caspase-12 were used to evaluate the ERS-dependent apoptosis, whereas LC3-II and p62 were considered as the autophagy activation markers. The beneficial molecular chaperones GRP78, HSP60, and HSP70 were also tested to evaluate autophagy. HIRI significantly increased ERS-dependent apoptosis markers and the number of apoptotic cells and damaged liver function. The ERS inhibitor salubrinal significantly alleviated liver injury in HIRI and OGD/R hepatocytes. Furthermore, both remote IPC and direct IPC significantly alleviated liver injury and inflammatory cell infiltration. IPC also upregulated LC3-II, downregulated p62 expression, and increased the mRNA levels of GRP78, HSP60, and HSP70 in HIRI mice and OGD/R hepatocytes, indicating the activation of autophagy by IPC. The autophagy inhibitor 3-methyladenine significantly attenuated the protective effects of IPC on ERS-dependent apoptosis and liver function, whereas the autophagy activator rapamycin mimicked the protective effects of IPC on ERS-dependent apoptosis in vivo and in vitro, suggesting a regulatory role of autophagy in ERS-dependent apoptosis. These results demonstrated that IPC could induce moderate autophagy and upregulate a few molecular chaperones to strengthen endogenous defense mechanisms, which is beneficial for alleviating ERS-dependent apoptosis and protecting hepatocytes from HIRI.

Hypoxic Preconditioning Modulates BDNF and Its Signaling through DNA Methylation to Promote Learning and Memory in Mice

Hypoxic preconditioning (HPC) as an endogenous mechanism can resist hypoxia/ischemia injury and exhibit protective effects on neurological function including learning and memory. Although underlying molecular mechanisms remain unclear, HPC probably regulates the expression of protective molecules by modulating DNA methylation. Brain-derived neurotrophic factor (BDNF) activates its signaling upon binding to the tropomyosin-related kinase B (TrkB) receptor, which is involved in neuronal growth, differentiation, and synaptic plasticity. Therefore, this study focused on the mechanism by which HPC regulates BDNF and BDNF/TrkB signaling through DNA methylation to influence learning and memory. Initially, the HPC model was established by hypoxia stimulations on ICR mice. We found that HPC downregulated the expression of DNA methyltransferase (DNMT) 3A and DNMT3B. Then, the upregulation of BDNF expression in HPC mice was generated from a decrease in DNA methylation of the BDNF gene promoter detected by pyrophosphate sequencing. Subsequently, upregulation of BDNF activated BDNF/TrkB signaling and ultimately improved learning and spatial memory in HPC mice. Moreover, after mice were intracerebroventricularly injected with the DNMT inhibitor, the restraint of DNA methylation accompanied by an increase of BDNF and BDNF/TrkB signaling was also discovered. Finally, we observed that the inhibitor of BDNF/TrkB signaling prevented HPC from ameliorating learning and memory in mice. However, the DNMT inhibitor promoted spatial cognition in mice. Thus, we suggest that HPC may upregulate BDNF by inhibiting DNMTs and decreasing DNA methylation of the BDNF gene and then activate BDNF/TrkB signaling to improve learning and memory in mice. This may provide theoretical guidance for the clinical treatment of cognitive dysfunction caused by ischemia/hypoxia disease.

Parkinson's disease in a patient with GBA and LRRK2 covariants after acute hypoxic insult: a case report

BACKGROUND

The glucocerebrosidase (GBA) and leucine-rich repeat kinase 2 (LRRK2) genes are associated with the risk of sporadic Parkinson's disease (PD). As an environmental factor, hypoxic insults may impair dopamine neurons in the substantia nigra and exacerbate PD symptoms. However, covariants of GBA and LRRK2 combined with hypoxic insults in clinical cases of Parkinsonism have not yet been reported.

CASE PRESENTATION

A 69-year-old male patient with PD and his relatives were clinically characterized and sequenced using the whole-exome technique. A novel covariant, c.1448 T > C (p. L483P, rs421016) on GBA and c.691 T > C (p. S231P, rs201332859) on LRRK2 were identified in this patient who first developed bradykinesia and rigidity in the neck at one month after an acute hypoxic insult during mountaineering. The patient presented with a mask-like face, festinating gait, asymmetric bradykinesia, and moderate rigidity. These symptoms were treated with levodopa and pramipexole, resulting in a 65% improvement in the Unified Parkinson's Disease Rating Scale (UPDRS) motor score. These parkinsonian symptoms persisted and developed with hallucinations, constipation, and rapid eye movement sleep behavior disorder. After 4 years, the patient exhibited a wearing-off phenomenon and died from pulmonary infection 8 years after disease onset. His parents, wife, and siblings were not diagnosed with PD, and his son carried p. L483P without Parkinsonism-like symptoms.

CONCLUSIONS

This is a case report of PD after hypoxic insult in a patient carrying a covariant of GBA and LRRK2. This study may help us understand the interaction between genetic and environmental factors in clinical PD.

Exercise preconditioning attenuates cerebral ischemia-induced neuronal apoptosis, Th17/Treg imbalance, and inflammation in rats by inhibiting the JAK2/STAT3 pathway

BACKGROUND

Exercise preconditioning (EP) is essential for preventing ischemic stroke. Recent studies have shown that EP exerts neuroprotective effects in the cerebral ischemia-reperfusion injury model. Nonetheless, there have been few reports on the relationship between EP and the Th17/Treg balance. Moreover, it is unclear whether the JAK2/STAT3 pathway is responsible for the neuroprotective effect of EP. Therefore, we aimed to explore the impact of EP, other than the anti-inflammatory and antiapoptotic functions, on the Th17/Treg balance via the JAK2/STAT3 pathway in a middle cerebral artery occlusion (MCAO)-induced model.

RESULTS

Fifty rats were randomly allocated into five groups, including the sham group (n = 10), EP+sham group (n = 10), MCAO group (n = 10), EP+MCAO group (n = 10), and EP+MCAO+JAK2/STAT3 pathway agonist (coumermycin A1, CA1) group (n = 10). The results indicated that EP alleviated neurological deficits, reduced infarct volume, and ameliorated neuronal apoptosis induced by MCAO. Additionally, the MCAO-induced Th17/Treg imbalance could be rectified by EP. The decreased levels of IL-10 and Foxp3 and increased IL-17 and RORα in the MCAO group were reversed by EP treatment. Regarding inflammation, EP reduced the concentrations of IL-6 and IL-17 and elevated those of IL-10 and TGF-β. The neuroprotective effects of EP were accompanied by decreased phosphorylation of JAK2 and STAT3. Furthermore, CA1 pretreatment diminished all the beneficial effects of EP partially.

CONCLUSION

Our findings suggest that EP contributes to attenuating neuronal apoptosis, Th17/Treg imbalance, and inflammation induced by MCAO via inhibiting the JAK2/STAT3 pathway, indicating its therapeutic potential in ischemic stroke.

The Notch pathway regulates autophagy after hypoxic-ischemic injury and affects synaptic plasticity

Following neonatal hypoxic-ischemia (HI) injury, it is crucial factor to reconstruct neural circuit and maintain neural network homeostasis for neurological recovery. A dynamic balance between the synthesis and degradation of synaptic protein is required for maintaining synaptic plasticity. Protein degradation is facilitated by autophagy. This study aimed to investigate the regulation of synaptic structural plasticity by the Notch pathway, by assessing changes in Notch pathway activation and their effects on synaptic proteins and autophagy after HI injury. The study involved 48 male newborn Yorkshire piglets, each weighing 1.0-1.5 kg and 3 days old. They were randomly assigned to two groups: the HI group and the Notch pathway inhibitor + HI group (n = 24 per group). Each group was further divided into six subgroups according to HI duration (n = 4 per group): a control subgroup, and 0-6, 6-12, 12-24, 24-48, and 48-72 h subgroups. The expression of Notch pathway-related proteins, including Notch1, Hes1, and Notch intracellular domains, increased following HI injury. The expression of autophagy proteins increased at 0-6 h and 6-12 h post-HI. The expression of synaptic proteins, such as postsynaptic density protein 95 (PSD95) and synaptophysin, increased 6-12 h and 12-24 h after HI, respectively. Notably, the increased expression of these proteins was reversed by a Notch pathway inhibitor. Transmission electron microscopy revealed the presence of autophagosome structures in synapses. These findings shed light on the underlying mechanisms of neurological recovery after HI injury and may provide insights into potential therapeutic targets for promoting neural circuit reconstruction and maintaining neural network homeostasis.

Mitochondria hormesis delays aging and associated diseases in Caenorhabditis elegans impacting on key ferroptosis players

Excessive iron accumulation or deficiency leads to a variety of pathologies in humans and developmental arrest in the nematode Caenorhabditis elegans. Instead, sub-lethal iron depletion extends C. elegans lifespan. Hypoxia preconditioning protects against severe hypoxia-induced neuromuscular damage across species but it has low feasible application. In this study, we assessed the potential beneficial effects of genetic and chemical interventions acting via mild iron instead of oxygen depletion. We show that limiting iron availability in C. elegans through frataxin silencing or the iron chelator bipyridine, similar to hypoxia preconditioning, protects against hypoxia-, age-, and proteotoxicity-induced neuromuscular deficits. Mechanistically, our data suggest that the beneficial effects elicited by frataxin silencing are in part mediated by counteracting ferroptosis, a form of non-apoptotic cell death mediated by iron-induced lipid peroxidation. This is achieved by impacting on different key ferroptosis players and likely via gpx-independent redox systems. We thus point to ferroptosis inhibition as a novel potential strategy to promote healthy aging.

The Critical Role of Sirt1 in Subarachnoid Hemorrhages: Mechanism and Therapeutic Considerations

The subarachnoid hemorrhage (SAH) is an important cause of death and long-term disability worldwide. As a nicotinamide adenine dinucleotide-dependent deacetylase, silent information regulator 1 (Sirt1) is a multipotent molecule involved in many pathophysiological processes. A growing number of studies have demonstrated that Sirt1 activation may exert positive effects on SAHs by regulating inflammation, oxidative stress, apoptosis, autophagy, and ferroptosis. Thus, Sirt1 agonists may serve as potential therapeutic drugs for SAHs. In this review, we summarized the current state of our knowledge on the relationship between Sirt1 and SAHs and provided an updated overview of the downstream molecules of Sirt1 in SAHs.

Associations of Lung Function Decline with Risks of Cognitive Impairment and Dementia: A Meta-Analysis and Systematic Review

BACKGROUND

There are controversies surrounding the effects of lung function decline on cognitive impairment and dementia.

OBJECTIVE

We conducted a meta-analysis and systematic review to explore the associations of lung function decline with the risks of cognitive impairment and dementia.

METHODS

The PubMed, EMBASE, and the Cochrane Library were searched to identify prospective studies published from database inception through January 10, 2023. We pooled relative risk (RR) and 95% confidence intervals (CI) using random-effects models. The Egger test, funnel plots, meta-regression, sensitivity, and subgroup analyses were conducted to detect publication bias and investigate the source of heterogeneity.

RESULTS

Thirty-three articles with a total of 8,816,992 participants were subjected to meta-analysis. Poorer pulmonary function was associated with an increased risk of dementia (FEV: RR = 1.25 [95% CI, 1.17-1.33]; FVC: RR = 1.40 [95% CI, 1.16-1.69]; PEF: RR = 1.84 [95% CI, 1.37-2.46]). The results of the subgroup analyses were similar to the primary results. Individuals with lung diseases had a higher combined risk of dementia and cognitive impairment (RR = 1.39 [95% CI, 1.20-1.61]). Lung disease conferred an elevated risk of cognitive impairment (RR = 1.37 [95% CI, 1.14-1.65]). The relationship between lung disease and an increased risk of dementia was only shown in total study participants (RR = 1.32 [95% CI, 1.11-1.57]), but not in the participants with Alzheimer's disease (RR = 1.39 [95% CI, 1.00-1.93]) or vascular dementia (RR = 2.11 [95% CI, 0.57-7.83]).

CONCLUSION

Lung function decline was significantly associated with higher risks of cognitive impairment and dementia. These findings might provide implications for the prevention of cognitive disorders and the promotion of brain health.

Role of ferroptosis in hypoxic preconditioning to reduce propofol neurotoxicity

Background: An increasing number of studies have reported that neurotoxicity of propofol may cause long-term learning and cognitive dysfunction. Hypoxic preconditioning has been shown to have neuroprotective effects, reducing the neurotoxicity of propofol. Ferroptosis is a new form of death that is different from apoptosis, necrosis, autophagy and pyroptosis. However, it is unclear whether hypoxic preconditioning reduces propofol neurotoxicity associated with ferroptosis. Thus, we aimed to evaluate the effect of propofol on primary hippocampal neurons in vitro to investigate the neuroprotective mechanism of hypoxic preconditioning and the role of ferroptosis in the reduction of propofol neurotoxicity by hypoxic preconditioning. Methods: Primary hippocampal neurons were cultured for 8 days in vitro and pretreated with or without propofol, hypoxic preconditioning, agonists or inhibitors of ferroptosis. Cell counting kit-8, Calcein AM, Reactive oxygen species (ROS), Superoxide dismutase (SOD), Ferrous iron (Fe²⁺), Malondialdehyde (MDA) and Mitochondrial membrane potential assay kit with JC-1 (JC-1) assays were used to measure cell viability, Reactive oxygen species level, Superoxide dismutase content, Fe²⁺ level, MDA content, and mitochondrial membrane potential. Cell apoptosis was evaluated using flow cytometry analyses, and ferroptosis-related proteins were determined by Western blot analysis. Results: Propofol had neurotoxic effects that led to decreased hippocampal neuronal viability, reduced mitochondrial membrane potential, decreased SOD content, increased ROS level, increased Fe²⁺ level, increased MDA content, increased neuronal apoptosis, altered expression of ferroptosis-related proteins and activation of ferroptosis. However, hypoxic preconditioning reversed these effects, inhibited ferroptosis caused by propofol and reduced the neurotoxicity of propofol. Conclusion: The neurotoxicity of propofol in developing rats may be related to ferroptosis. Propofol may induce neurotoxicity by activating ferroptosis, while hypoxic preconditioning may reduce the neurotoxicity of propofol by inhibiting ferroptosis.

Hypoxic stress accelerates the propagation of pathological alpha-synuclein and degeneration of dopaminergic neurons

AIMS

The etiology of Parkinson's disease (PD) is complex and the mechanism is unclear. It has become a top priority to find common factors that induce and affect PD pathology. We explored the key role of hypoxia in promoting the pathological propagation of α-synuclein (α-syn) and the progression of PD.

METHODS

We performed PD modeling by conducting intracranial stereotaxic surgery in the unilateral striatum of mice. We then measured protein aggregation in vitro. The rotarod and pole tests were employed next to measure the damage of the phenotype. Pathological deposition and autophagy were also observed by immunofluorescence staining and protein levels measured by western blotting.

RESULTS

We demonstrated that short-term hypoxia activated phosphorylated (p)-α-syn in mice. We confirmed that p-α-syn was more readily formed aggregates than α-syn in vitro. Furthermore, we found that hypoxia promoted the activation and propagation of endogenous α-syn, contributing to the earlier degeneration of dopaminergic neurons in the substantia nigra and the deposition of p-α-syn in our animal model. Finally, autophagy inhibition contributed to the above pathologies.

CONCLUSION

Hypoxia was shown to accelerate the pathological progression and damage phenotype in PD model mice. The results provided a promising research target for determining common interventions for PD in the future.

Chronic hypoxia leads to cognitive impairment by promoting HIF-2α-mediated ceramide catabolism and alpha-synuclein hyperphosphorylation

Chronic hypoxia leads to irreversible cognitive impairment, primarily due to hippocampal neurodegeneration, for which the underlying mechanism remains poorly understood. We administered hypoxia (13%) to C57BL mice for 1-14 days in this study. Chronic hypoxia for 7 or 14 d, but not 1 or 3 d, resulted in alpha-synuclein hyperphosphorylation at serine129 (α-Syn p-S129) and protein aggregation, hippocampal neurodegeneration, and cognitive deficits, whereas the latter could be prevented by alpha-synuclein knockdown or an administered short peptide competing at α-Syn S129. These results suggest that α-Syn p-S129 mediates hippocampal degeneration and cognitive impairment following chronic hypoxia. Furthermore, we found that chronic hypoxia enhanced ceramide catabolism by inducing hypoxia-inducible factor (HIF)-2α and HIF-2α-dependent transcriptional activation of alkaline ceramidase 2 (Acer2). Thus, the enzymatic activity of protein phosphatase 2A (PP2A), a specific phosphatase for α-syn, is inhibited, leading to the sustained induction of α-Syn p-S129. Finally, we found that intermittent hypoxic preconditioning protected against subsequent chronic hypoxia-induced hippocampal neurodegeneration and cognitive impairment by preventing α-Syn p-S129. These results proved the critical role of α-syn pathology in chronic hypoxia-afforded cognitive impairment and revealed a novel mechanism underlying α-syn hyperphosphorylation during chronic hypoxia. The findings bear implications in developing novel therapeutic interventions for chronic hypoxia-related brain disorders.

Intermittent hypoxia conditioning as a potential prevention and treatment strategy for ischemic stroke: Current evidence and future directions

Ischemic stroke (IS) is the leading cause of disability and death worldwide. Owing to the aging population and unhealthy lifestyles, the incidence of cerebrovascular disease is high. Vascular risk factors include hypertension, diabetes, dyslipidemia, and obesity. Therefore, in addition to timely and effective reperfusion therapy for IS, it is crucial to actively control these risk factors to reduce the incidence and recurrence rates of IS. Evidence from human and animal studies suggests that moderate intermittent hypoxia (IH) exposure is a promising therapeutic strategy to ameliorate common vascular risk factors and comorbidities. Given the complex pathophysiological mechanisms underlying IS, effective treatment must focus on reducing injury in the acute phase and promoting repair in the recovery phase. Therefore, this review discusses the preclinical perspectives on IH conditioning as a potential treatment for neurovascular injury and highlights IH pre and postconditioning strategies for IS. Hypoxia conditioning reduces brain injury by increasing resistance to acute ischemic and hypoxic stress, exerting neuroprotective effects, and promoting post-injury repair and regeneration. However, whether IH produces beneficial effects depends not only on the hypoxic regimen but also on inter-subject differences. Therefore, we discuss the factors that may influence the effectiveness of IH treatment, including age, sex, comorbidities, and circadian rhythm, which can be used to help identify the optimal intervention population and treatment protocols for more accurate, individualized clinical translation. In conclusion, IH conditioning as a non-invasive, non-pharmacological, systemic, and multi-targeted intervention can not only reduce brain damage after stroke but can also be applied to the prevention and functional recovery of IS, providing brain protection at different stages of the disease. It represents a promising therapeutic strategy. For patients with IS and high-risk groups, IH conditioning is expected to develop as an adjunctive clinical treatment option to reduce the incidence, recurrence, disability, and mortality of IS and to reduce disease burden.

Cobalt chloride has beneficial effects across species through a hormetic mechanism

Severe oxygen and iron deficiencies have evolutionarily conserved detrimental effects, leading to pathologies in mammals and developmental arrest as well as neuromuscular degeneration in the nematode Caenorhabditis elegans. Yet, similar to the beneficial effects of mild hypoxia, non-toxic levels of iron depletion, achieved with the iron chelator bipyridine or through frataxin silencing, extend C. elegans lifespan through hypoxia-like induction of mitophagy. While the positive health outcomes of hypoxia preconditioning are evident, its practical application is rather challenging. Here, we thus test the potential beneficial effects of non-toxic, preconditioning interventions acting on iron instead of oxygen availability. We find that limiting iron availability through the iron competing agent cobalt chloride has evolutionarily conserved dose-dependent beneficial effects: while high doses of cobalt chloride have toxic effects in mammalian cells, iPS-derived neurospheres, and in C. elegans, sub-lethal doses protect against hypoxia- or cobalt chloride-induced death in mammalian cells and extend lifespan and delay age-associated neuromuscular alterations in C. elegans. The beneficial effects of cobalt chloride are accompanied by the activation of protective mitochondrial stress response pathways.

Determination of significant parameters in remote ischemic postconditioning for ischemic stroke in experimental models: A systematic review and meta-analysis study

Objectives

To systematically review studies using remote ischemia postconditioning (RIPostC) for ischemic stroke in experimental models and obtain factors that significantly influence treatment outcomes.

Materials and Methods

Peer‐reviewed studies were identified and selected based on the eligibility criteria, followed by extraction of data on potentially influential factors related to model preparation, postconditioning, and measure time based on outcome measures including infarct size, neurological scales, and cell tests with autophagy, apoptosis, normal‐neuron, and damaged‐neuron counting. Then, all data were preprocessed, grouped, and meta‐analyzed with the indicator of the standardized mean difference.

Results

Fifty‐seven studies with 224 experiments (91 for infarct size, 92 for neurological scales, and 41 for cell‐level tests) were included. There was little statistical difference between different model preparations, treated body parts, number of treatments, and sides. And treatment effect was generally a positive correlation with the duration of conditioning time to stroke onset with exceptions at some time points. Based on infarct size, the number of cycles per treatment, duration of occlusion, and release per cycle showed significant differences. Combined with the effect sizes by other measures, the occlusion/release duration of 8–10 min per cycle is better than 5 min, and three cycles per treatment were most frequently used with good effects. Effect also varied when measuring at different times, showing statistical differences in infarct size and most neurological scales. RIPostC is confirmed as an effective therapeutic intervention for ischemic stroke, while the RIPostC‐mediated autophagy level being activated or inhibited remained conflicting.

Conclusions

Conditioning time, number of cycles per treatment, duration of occlusion, and release per cycle were found to influence the treatment effects of RIPostC significantly. More studies on the relevant influential factors and autophagy mechanisms are warranted.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Dehydroepiandrosterone alleviates hypoxia-induced learning and memory dysfunction by maintaining synaptic homeostasis

AIMS

Hypoxia causes plenty of pathologies in the central nervous system (CNS) including impairment of cognitive and memory function. Dehydroepiandrosterone (DHEA) has been proved to have therapeutic effects on CNS injuries by maintaining the homeostasis of synapses, yet its effect on hypoxia-induced CNS damage remains unknown.

METHODS

In vivo and in vitro models were established. Concentrations of glutamate and γ GABA were tested by ELISA. Levels of synapse-associated proteins were measured by western blotting. Density of dendritic protrusions of hippocampal neurons was assessed by Golgi staining. Immunofluorescence was adopted to observe the morphology of primary neurons. The novel object recognition test (NORT) and shuttle box test were used to evaluate cognition.

RESULTS

Dehydroepiandrosterone reversed abnormal elevation of glutamate levels, shortenings of neuronal processes, decreases in the density of dendritic protrusions, downregulation of synaptosome-associated protein (SNAP25), and impaired cognition caused by hypoxia. Hypoxia also resulted in notably downregulation of syntaxin 1A (Stx-1A). Overexpression of Stx-1A dramatically attenuated hypoxia-induced elevation of glutamate. Treatment with DHEA reversed the Stx-1A downregulation caused by hypoxic exposure.

CONCLUSION

Dehydroepiandrosterone may exert a protective effect on hypoxia-induced memory impairment by maintaining synaptic homeostasis. These findings offer a novel understanding of the therapeutic effect of DHEA on hypoxia-induced cognitive dysfunction.

Perioperative stroke: A perspective on challenges and opportunities for experimental treatment and diagnostic strategies

Perioperative stroke is an ischemic or hemorrhagic cerebral event during or up to 30 days after surgery. It is a feared condition due to a relatively high incidence, difficulties in timely detection, and unfavorable outcome compared to spontaneously occurring stroke. Recent preclinical data suggest that specific pathophysiological mechanisms such as aggravated neuroinflammation contribute to the detrimental impact of perioperative stroke. Conventional treatment options are limited in the perioperative setting due to difficult diagnosis and medications affecting coagulation in may cases. On the contrary, the chance to anticipate cerebrovascular events at the time of surgery may pave the way for prevention strategies. This review provides an overview on perioperative stroke incidence, related problems, and underlying pathophysiological mechanisms. Based on this analysis, we assess experimental stroke treatments including neuroprotective approaches, cell therapies, and conditioning medicine strategies regarding their potential use in perioperative stroke. Interestingly, the specific aspects of perioperative stroke might enable a more effective application of experimental treatment strategies such as classical neuroprotection whereas others including cell therapies may be of limited use. We also discuss experimental diagnostic options for perioperative stroke augmenting classical clinical and imaging stroke diagnosis. While some experimental stroke treatments may have specific advantages in perioperative stroke, the paucity of established guidelines or multicenter clinical research initiatives currently limits their thorough investigation.

Insight Into the Mechanism of Exercise Preconditioning in Ischemic Stroke

Exercise preconditioning has attracted extensive attention to induce endogenous neuroprotection and has become the hotspot in neurotherapy. The training exercise is given multiple times before cerebral ischemia, effectively inducing ischemic tolerance and alleviating secondary brain damage post-stroke. Compared with other preconditioning methods, the main advantages of exercise include easy clinical operation and being readily accepted by patients. However, the specific mechanism behind exercise preconditioning to ameliorate brain injury is complex. It involves multi-pathway and multi-target regulation, including regulation of inflammatory response, oxidative stress, apoptosis inhibition, and neurogenesis promotion. The current review summarizes the recent studies on the mechanism of neuroprotection induced by exercise, providing the theoretical basis of applying exercise therapy to prevent and treat ischemic stroke. In addition, we highlight the various limitations and future challenges of translational medicine from fundamental study to clinical application.

Ischemic Preconditioning Modulates the Peripheral Innate Immune System to Promote Anti-Inflammatory and Protective Responses in Mice Subjected to Focal Cerebral Ischemia

The development of tolerance triggered by a sublethal ischemic episode (preconditioning, PC) involves a complex crosstalk between neurons, astrocytes and microglia, although the role of the peripheral immune system in this context is largely unexplored. Here, we report that severe cerebral ischemia caused by transient middle cerebral artery occlusion (MCAo) in adult male mice elevates blood counts of inflammatory neutrophils and monocytes, and plasma levels of miRNA-329-5p. These inflammatory responses are prevented by ischemic PC induced by 15 min MCAo, 72h before the severe insult (1h MCAo). As compared with sham-operated animals, mice subjected to either ischemic PC, MCAo or a combination of both (PC+MCAo) display spleen contraction. However, protein levels of Ym1 (a marker of polarization of myeloid cells towards M2/N2 protective phenotypes) are elevated only in spleen from the experimental groups PC and PC+MCAo, but not MCAo. Conversely, Ym1 protein levels only increase in circulating leukocytes from mice subjected to 1h MCAo, but not in preconditioned animals, which is coincident with a dramatic elevation of Ym1 expression in the ipsilateral cortex. By immunofluorescence analysis, we observe that expression of Ym1 occurs in amoeboid-shaped myeloid cells, mainly representing inflammatory monocytes/macrophages and neutrophils. As a result of its immune-regulatory functions, ischemic PC prevents elevation of mRNA levels of the pro-inflammatory cytokine interleukin (IL)-1β in the ipsilateral cortex, while not affecting IL-10 mRNA increase induced by MCAo. Overall, the elevated anti-inflammatory/pro-inflammatory ratio observed in the brain of mice pre-exposed to PC is associated with reduced brain infarct volume and ischemic edema, and with amelioration of functional outcome. These findings reaffirm the crucial and dualistic role of the innate immune system in ischemic stroke pathobiology, extending these concepts to the context of ischemic tolerance and underscoring their relevance for the identification of novel therapeutic targets for effective stroke treatment.

Introducing the brain erythropoietin circle to explain adaptive brain hardware upgrade and improved performance

Executive functions, learning, attention, and processing speed are imperative facets of cognitive performance, affected in neuropsychiatric disorders. In clinical studies on different patient groups, recombinant human (rh) erythropoietin (EPO) lastingly improved higher cognition and reduced brain matter loss. Correspondingly, rhEPO treatment of young rodents or EPO receptor (EPOR) overexpression in pyramidal neurons caused remarkable and enduring cognitive improvement, together with enhanced hippocampal long-term potentiation. The 'brain hardware upgrade', underlying these observations, includes an EPO induced ~20% increase in pyramidal neurons and oligodendrocytes in cornu ammonis hippocampi in the absence of elevated DNA synthesis. In parallel, EPO reduces microglia numbers and dampens their activity and metabolism as prerequisites for undisturbed EPO-driven differentiation of pre-existing local neuronal precursors. These processes depend on neuronal and microglial EPOR. This novel mechanism of powerful postnatal neurogenesis, outside the classical neurogenic niches, and on-demand delivery of new cells, paralleled by dendritic spine increase, let us hypothesize a physiological procognitive role of hypoxia-induced endogenous EPO in brain, which we imitate by rhEPO treatment. Here we delineate the brain EPO circle as working model explaining adaptive 'brain hardware upgrade' and improved performance. In this fundamental regulatory circle, neuronal networks, challenged by motor-cognitive tasks, drift into transient 'functional hypoxia', thereby triggering neuronal EPO/EPOR expression.

The role of hypoxia in stem cell regulation of the central nervous system: From embryonic development to adult proliferation

Hypoxia is involved in the regulation of various cell functions in the body, including the regulation of stem cells. The hypoxic microenvironment is indispensable from embryonic development to the regeneration and repair of adult cells. In addition to embryonic stem cells, which need to maintain their self-renewal properties and pluripotency in a hypoxic environment, adult stem cells, including neural stem cells (NSCs), also exist in a hypoxic microenvironment. The subventricular zone (SVZ) and hippocampal dentate gyrus (DG) are the main sites of adult neurogenesis in the brain. Hypoxia can promote the proliferation, migration, and maturation of NSCs in these regions. Also, because most neurons in the brain are non-regenerative, stem cell transplantation is considered as a promising strategy for treating central nervous system (CNS) diseases. Hypoxic treatment also increases the effectiveness of stem cell therapy. In this review, we firstly describe the role of hypoxia in different stem cells, such as embryonic stem cells, NSCs, and induced pluripotent stem cells, and discuss the role of hypoxia-treated stem cells in CNS diseases treatment. Furthermore, we highlight the role and mechanisms of hypoxia in regulating adult neurogenesis in the SVZ and DG and adult proliferation of other cells in the CNS.