Intermittent hypoxic conditioning restores neurological dysfunction of mice induced by long-term hypoxia

Decreased levels of phosphorylated synuclein in plasma are correlated with poststroke cognitive impairment

JOURNAL/nrgr/04.03/01300535-202509000-00022/figure1/v/2024-11-05T132919Z/r/image-tiff Poststroke cognitive impairment is a major secondary effect of ischemic stroke in many patients; however, few options are available for the early diagnosis and treatment of this condition. The aims of this study were to (1) determine the specific relationship between hypoxic and α-synuclein during the occur of poststroke cognitive impairment and (2) assess whether the serum phosphorylated α-synuclein level can be used as a biomarker for poststroke cognitive impairment. We found that the phosphorylated α-synuclein level was significantly increased and showed pathological aggregation around the cerebral infarct area in a mouse model of ischemic stroke. In addition, neuronal α-synuclein phosphorylation and aggregation were observed in the brain tissue of mice subjected to chronic hypoxia, suggesting that hypoxia is the underlying cause of α-synuclein-mediated pathology in the brains of mice with ischemic stroke. Serum phosphorylated α-synuclein levels in patients with ischemic stroke were significantly lower than those in healthy subjects, and were positively correlated with cognition levels in patients with ischemic stroke. Furthermore, a decrease in serum high-density lipoprotein levels in stroke patients was significantly correlated with a decrease in phosphorylated α-synuclein levels. Although ischemic stroke mice did not show significant cognitive impairment or disrupted lipid metabolism 14 days after injury, some of them exhibited decreased cognitive function and reduced phosphorylated α-synuclein levels. Taken together, our results suggest that serum phosphorylated α-synuclein is a potential biomarker for poststroke cognitive impairment.

Effects of hypoxia stress on the milk synthesis in bovine mammary epithelial cells

BACKGROUND

Milk synthesis is an energy-intensive process influenced by oxygen availability. This study investigates how hypoxia affects milk synthesis in BMECs, focusing on key genes involved in lactation and energy metabolism.

METHODS

BMECs were cultured in a normoxic environment and then transferred to a hypoxia chamber with 1% O2 for specified durations. The study evaluated cellular responses through various molecular experiments and RNA sequencing. Small interfering RNA was employed to knock down HIF-1α to investigate whether the lactation-related phenotype alteration depends on HIF-1α.

RESULTS

Hypoxia disrupted milk protein production by reducing mTOR/P70S6K/4EBP1 signaling and downregulating genes critical for amino acid transport and protein synthesis. Triglyceride synthesis increased due to enhanced fatty acid uptake and the upregulation of regulatory proteins, including FASN and PPARγ. Although glucose uptake was elevated under hypoxia, key enzymes for lactose synthesis were downregulated, suggesting a redirection of glucose toward energy production. Mitochondrial function was impaired under hypoxia, with reduced gene expression in TCA cycle, ETC, cytosol-mitochondrial transport, decreased ATP levels, increased ROS levels, and structural alterations. Additionally, lipid synthesis and glucose uptake depend on HIF-1α, while milk protein synthesis alterations occurred independently of HIF-1α.

CONCLUSIONS

Hypoxia alters milk synthesis in BMECs by disrupting milk protein synthesis, enhancing lipid metabolism, and impairing energy production. These findings provide valuable insights into the molecular mechanisms underlying the effect of oxygen deprivation on lactation efficiency, offering potential targets for mitigating hypoxic stress in the mammary glands of dairy animals.

A2-Astrocyte Activation by Short-Term Hypoxia Rescues α-Synuclein Pre-Formed-Fibril-Induced Neuronal Cell Death

Background/Objectives: Parkinson's disease (PD) is a neuro-degenerative disease for which a radical cure is not available, only symptomatic control. Studies have shown that hypoxia may have disease-modifying effects on PD. Methods: Herein, we investigated whether short-term hypoxia activates astrocytes and whether it has a protective effect on pre-formed fibril (PFF)-treated primary cortical neurons. Results: Long-term hypoxia suppresses astrocyte activation and induces cell death, whereas short-term hypoxia activates astrocytes without affecting cellular apoptosis or viability. Short-term hypoxia restored the cellular apoptosis and viability of PFF-treated neurons and reduced toxic phospho-α-synuclein (p-α-syn) aggregation. Similarly, the short-term hypoxia-exposed astrocyte-conditioned medium rescued cellular apoptosis and the viability of PFF-treated neurons and p-α-syn expression. Quantitative polymerase chain reaction revealed that short-term hypoxia promotes protective A2 astrocytes and suppresses toxic A1 astrocytes. Conclusions: Our findings suggest that short-term hypoxia has a neuro-protective effect against PD by activating protective A2 astrocytes, which rescue PFF-induced neuronal cell death. This provides insights into the clinical implications of short-term hypoxia as a disease-modifying PD strategy.

Big data for neuroscience in the context of predictive, preventive, and personalized medicine

Accurate and precise diagnosis made the medicine the hallmark of evidence-based medicine. While attaining absolute patient satisfaction may seem impossible in the aspect of disease recurrent, personalized their mecidal conditions to their responsive treatment approach may save the day. The last generation approaches in medicine require advanced technologies that will lead to evidence-based medicine. One of the trending fields in this is the use of big data in predictive, preventive, and personalized medicine (3PM). This review dwelled through the practical examples in which big data tools harness neuroscience to add more individualized apporahes to the medical conditions in a bid to confer a more personalized treatment strategies. Moreover, the known breakthroughs of big data in 3PM, big data and 3PM in neuroscience, AI and neuroscience, limitations of big data with 3PM in neuroscience, and the challenges are thoroughly discussed. Finally, the prospects of incorporating big data in 3PM are as well discussed. The review could point out that the implications of big data in 3PM are still in their infancy and will require a holistic approach. While there is a need to carefully sensitize the community, convincing them will come under interdisciplinary and, to some extent, inter-professional collaborations, capacity building for professionals, and optimal coordination of the joint systems.

The Role of Hypoxia in Longevity

Aging is marked by a progressive decrease in physiological function and reserve capacity, which results in increased susceptibility to diseases. Understanding the mechanisms of driving aging is crucial for extending health span and promoting human longevity. Hypoxia, marked by reduced oxygen availability, has emerged as a promising area of study within aging research. This review explores recent findings on the potential of oxygen restriction to promote healthy aging and extend lifespan. While the role of hypoxia-inducible factor 1 (HIF-1) in cellular responses to hypoxia is well-established, its impact on lifespan remains complex and context-dependent. Investigations in invertebrate models suggest a role for HIF-1 in longevity, while evidence in mammalian models is limited. Hypoxia extends the lifespan independent of dietary restriction (DR), a known intervention underlying longevity. However, both hypoxia and DR converge on common downstream effectors, such as forkhead box O (FOXO) and flavin-containing monooxygenase (FMOs) to modulate the lifespan. Further work is required to elucidate the molecular mechanisms underlying hypoxia-induced longevity and optimize clinical applications. Understanding the crosstalk between HIF-1 and other longevity-associated pathways is crucial for developing interventions to enhance lifespan and healthspan. Future studies may uncover novel therapeutic strategies to promote healthy aging and longevity in human populations.

Curcumin reverses cognitive deficits through promoting neurogenesis and synapse plasticity via the upregulation of PSD95 and BDNF in mice

Following prolonged exposure to hypoxic conditions, for example, due to ascent to high altitude, aging or stroke, cognitive deficits can develop. The exact nature and genesis of hypoxia-induced cognitive deficits remain unresolved. Curcumin has been reported to stimulate neurogenesis and reduce neuronal degeneration. This study aimed to investigate the effect of curcumin on cognitive deficits in hypoxic-brain injury mice and its potential mechanism. Eight-week-old male C57BL/6J mice were exposure to normobaric-hypoxia (13%O2) 14 days to establish hypoxic-brain injury models. Morris water maze and novel object recognition were used to detect the cognitive function of each mouse. Immunofluorescence assays, including Fluoro-Jade C (FJC) and bromodeoxyuridine (BrdU), were used to detect neuronal degeneration and neurogenesis. Thy1-YFP transgenic mice were used to detect synapse plasticity. Our results showed that curcumin administration rescued the impaired cognition of mice, shown as enhanced BrdU+ and dendritic spine in hippocampus. At the molecular level, curcumin was found to promote the expression of brain-derived neurotrophic factor (BDNF) and postsynaptic density protein 95 (PSD95). The results of primary hippocampal neuron detection showed that curcumin could promote dendritic growth. In conclusion, our study indicates that curcumin, increased BDNF and PSD95 expression and contacted with interneurons, salvaged of interneurons may normalize ambient neuroplasticity, resulting in the preservation of neurogenesis processes as well as contributing to improve cognitive performance.

Hypoxia adaptation mechanism in rats' peripheral auditory system in high altitude migration: a time series transcriptome analysis

High altitude is characterized by low oxygen, low pressure, and high radiation. When migrates from low to high altitudes, the body's tissues and organs experience hypoxic stress and will present acoustic adaptation as the protective response. However, the mechanisms of acoustic adaptation at high altitudes remain unclear. In this study, cochlear tissues from Wistar rats were collected at 15, 30, 60, 120, and 180 days after high-altitude migration. Transcriptome sequencing was conducted and DESeq algorithm revealed expression patterns of Differentially Expressed Genes(DEGs) after high altitude migration. Day 60 is a critical stage for cochlear tissue "damage" and "repair" in high-altitude conditions. Transmission Electron Microscopy (TEM) observations of structures also support the findings. A time-series gene co-expression network algorithm was used to investigate gene regulatory patterns and key genes after migration. Immunofluorescence, immunohistochemistry, and qPCR were per-formed for key gene validation and localization. At Day 60, the peak DEG count occurs in rats migrating to high altitude, aligning with the critical phase for cochlear tissue damage and repair at high altitudes. Repair hinges on synaptic plasticity and myelination-linked processes, influencing modules M4 to M6. Module M4's activation gradually diminishes from its peak. However, the 'damage' effect is orchestrated by inflammation-related processes in modules M3 to M5, with module M3's activation also waning. Key gene module M4, pivotal for repair during this pivotal phase, encompasses Sptbn5, Cldn1, Gfra2, and Lims2 as its core genes. Immunohistochemistry reveals Sptbn5's presence in cochlear neurons, hair cells, Schwann cells and stria vascularis tissue. Cldn1 and Gfra2 predominantly localize within the cochlear neuron region. These results may suggest new directions for future research on acoustic acclimatization to high altitude.

Mechanisms underlying the health benefits of intermittent hypoxia conditioning

Intermittent hypoxia (IH) is commonly associated with pathological conditions, particularly obstructive sleep apnoea. However, IH is also increasingly used to enhance health and performance and is emerging as a potent non-pharmacological intervention against numerous diseases. Whether IH is detrimental or beneficial for health is largely determined by the intensity, duration, number and frequency of the hypoxic exposures and by the specific responses they engender. Adaptive responses to hypoxia protect from future hypoxic or ischaemic insults, improve cellular resilience and functions, and boost mental and physical performance. The cellular and systemic mechanisms producing these benefits are highly complex, and the failure of different components can shift long-term adaptation to maladaptation and the development of pathologies. Rather than discussing in detail the well-characterized individual responses and adaptations to IH, we here aim to summarize and integrate hypoxia-activated mechanisms into a holistic picture of the body's adaptive responses to hypoxia and specifically IH, and demonstrate how these mechanisms might be mobilized for their health benefits while minimizing the risks of hypoxia exposure.

Dual Approach to Depression: The Combined Efficacy of Intermittent Hypoxia and Fluoxetine in Modulating Behavioral and Inflammatory Responses

Background/Objectives: Mental disorders pose a significant public health challenge, affecting millions worldwide. Given the limitations of current therapies, many patients experience inadequate responses and adverse effects. Intermittent hypoxia (IH) has demonstrated anxiolytic, antidepressant, and neuroprotective properties in various protocols. This study investigated the effects of acute IH (13% O2, 1 h), fluoxetine (FLX) and their combination on depression-like behavior, serum corticosterone, and inflammatory cytokine levels induced by acute restraint stress in C57BL/6 female mice. Methods: Behavioral assessments included the tail suspension test, forced swim test, and open field test. Results: The combined IH + FLX treatment exhibited a synergistic effect, reducing immobility time and increasing latency time, respectively, in the tail suspension test (46%, p = 0.0014; 73%, p = 0.0033) and forced swim test (56%, p = 0.0082; 48%, p = 0.0322) compared to the ARS group. Biochemical analysis revealed that individual and combined treatments significantly reduced most inflammatory interleukins by up to 96%. Corticosterone levels were reduced by 30% only in the IH group. Conclusions: These findings highlight the potential of a one-hour IH session, particularly when combined with fluoxetine, to alleviate depressive-like behaviors and exert anti-inflammatory effects, suggesting a promising therapeutic approach for depression.

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.

Randomized controlled trial of intermittent hypoxia in Parkinson's disease: study rationale and protocol

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disease for which no disease-modifying therapies exist. Preclinical and clinical evidence suggest that repeated exposure to intermittent hypoxia might have short- and long-term benefits in PD. In a previous exploratory phase I trial, we demonstrated that in-clinic intermittent hypoxia exposure is safe and feasible with short-term symptomatic effects on PD symptoms. The current study aims to explore the safety, tolerability, feasibility, and net symptomatic effects of a four-week intermittent hypoxia protocol, administered at home, in individuals with PD.

METHODS/DESIGN

This is a two-armed double-blinded randomized controlled trial involving 40 individuals with mild to moderate PD. Participants will receive 45 min of normobaric intermittent hypoxia (fraction of inspired oxygen 0.16 for 5 min interspersed with 5 min normoxia), 3 times a week for 4 weeks. Co-primary endpoints include nature and total number of adverse events, and a feasibility-tolerability questionnaire. Secondary endpoints include Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part II and III scores, gait tests and biomarkers indicative of hypoxic dose and neuroprotective pathway induction.

DISCUSSION

This trial builds on the previous phase I trial and aims to investigate the safety, tolerability, feasibility, and net symptomatic effects of intermittent hypoxia in individuals with PD. Additionally, the study aims to explore induction of relevant neuroprotective pathways as measured in plasma. The results of this trial could provide further insight into the potential of hypoxia-based therapy as a novel treatment approach for PD.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05948761 (registered June 20th, 2023).

The Hypoxia Response Pathway: A Potential Intervention Target in Parkinson's Disease?

Parkinson's disease (PD) is a progressive neurodegenerative disorder for which only symptomatic treatments are available. Both preclinical and clinical studies suggest that moderate hypoxia induces evolutionarily conserved adaptive mechanisms that enhance neuronal viability and survival. Therefore, targeting the hypoxia response pathway might provide neuroprotection by ameliorating the deleterious effects of mitochondrial dysfunction and oxidative stress, which underlie neurodegeneration in PD. Here, we review experimental studies regarding the link between PD pathophysiology and neurophysiological adaptations to hypoxia. We highlight the mechanistic differences between the rescuing effects of chronic hypoxia in neurodegeneration and short-term moderate hypoxia to improve neuronal resilience, termed "hypoxic conditioning". Moreover, we interpret these preclinical observations regarding the pharmacological targeting of the hypoxia response pathway. Finally, we discuss controversies with respect to the differential effects of hypoxia response pathway activation across the PD spectrum, as well as intervention dosing in hypoxic conditioning and potential harmful effects of such interventions. We recommend that initial clinical studies in PD should focus on the safety, physiological responses, and mechanisms of hypoxic conditioning, as well as on repurposing of existing pharmacological compounds. © 2023 International Parkinson and Movement Disorder Society.

Influence of hypoxia on retinal progenitor and ganglion cells in human induced pluripotent stem cell-derived retinal organoids

AIM

To observe the effect of low oxygen concentration on the neural retina in human induced pluripotent stem cell (hiPSC)-derived retinal organoids (ROs).

METHODS

The hiPSC and a three-dimensional culture method were used for the experiments. Generated embryoid bodies (EBs) were randomly and equally divided into hypoxic and normoxic groups. Photographs of the EBs were taken on days 38, 45, and 52, and the corresponding volume of EBs was calculated. Simultaneously, samples were collected at these three timepoints, followed by fixation, sectioning, and immunofluorescence.

RESULTS

The proportion of Ki67-positive proliferating cells increased steadily on day 38; this proliferation-promoting effect tended to increase tissue density rather than tissue volume. On days 45 and 52, the two groups had relatively similar ratios of Ki67-positive cells. Further immunofluorescence analysis showed that the ratio of SOX2-positive cells significantly increased within the neural retina on day 52 (P<0.05). In contrast, the percentage of PAX6- and CHX10-positive cells significantly decreased following hypoxia treatment at all three timepoints (P<0.01), except for CHX10 at day 45 (P>0.05). Moreover, the proportion of PAX6-/TUJ1+ cells within the neural retinas increased considerably (P<0.01, <0.05, <0.05 respectively).

CONCLUSION

Low oxygen promotes stemness and proliferation of neural retinas, suggesting that hypoxic conditions can enlarge the retinal progenitor cell pool in hiPSC-derived ROs.

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.