Hydrogen ameliorates chronic intermittent hypoxia-induced neurocognitive impairment via inhibiting oxidative stress

GLP-1 analogue liraglutide attenuates CIH-induced cognitive deficits by inhibiting oxidative stress, neuroinflammation, and apoptosis via the Nrf2/HO-1 and MAPK/NF-κB signaling pathways

Obstructive sleep apnea (OSA) is a common clinical condition linked to cognitive impairment, mainly characterized by chronic intermittent hypoxia (CIH). GLP-1 receptor agonist, known for promoting insulin secretion and reducing glucose levels, has demonstrated neuroprotective effects in various experimental models such as stroke, Alzheimer's disease, and Parkinson's disease. This study aims to investigate the potential role and mechanisms of the GLP-1 receptor agonist liraglutide in ameliorating OSA-induced cognitive deficits. CIH exposure, a well-established and mature OSA pathological model, was used both in vitro and in vivo. In vitro, CIH significantly activated oxidative stress, inflammation, and apoptosis in SH-SY5Y cells. Liraglutide enhanced the nuclear translocation of Nrf2, activating its downstream pathways, thereby mitigating CIH-induced injury in SH-SY5Y cells. Additionally, liraglutide modulated the MAPK/NF-κB signaling pathway, reducing the expression of inflammatory factors and proteins. In vivo, we subjected mice to an intermittent hypoxia incubator to mimic the pathogenesis of human OSA. The Morris water maze test revealed that CIH exposure substantially impaired spatial memory. Subsequent western blot analyses and histopathological examinations indicated that liraglutide could activate the Nrf2/HO-1 axis and inhibit the MAPK/NF-κB signaling pathway, thereby alleviating OSA-associated cognitive dysfunction in mice. These findings suggest that GLP-1 receptor agonists may offer a promising preventive strategy for OSA-associated cognitive impairment. By refining these findings, we provide new insights into GLP-1's protective mechanisms in combating cognitive deficits associated with CIH, underscoring its potential as a therapeutic agent for conditions linked to OSA.

ELK4 ameliorates cognitive impairment and neuroinflammation induced by obstructive sleep apnea

Intermittent hypoxia (IH) in patients with obstructive sleep apnea (OSA) syndrome elicited neuron injury (especially in the hippocampus and cortex), contributing to cognitive dysfunction. This study investigated the effects and clarified the mechanisms of ETS domain-containing protein Elk-4 (ELK4) on the cognitive function and neuroinflammation of mice with IH. Mouse microglia BV2 cells were induced with IH by exposure to fluctuating O2 concentrations (alternating from 5 % to 21 % every 30 min), and mice with OSA were developed and subjected to lentivirus-mediated gene intervention. ELK4 expression was significantly reduced in IH-induced microglia and brain tissues of mice with OSA. Overexpression of ELK4 attenuated oxidative stress, decreased the pro-inflammatory factors IL-1β, IL-6, and TNF-α, and increased the level of the anti-inflammatory factors IL-10 and TGF-β1, as well as the neuroprotective factor BDNF. ELK4 promoted the transcription of fibronectin type III domain-containing protein 5 (FNDC5) by binding to the promoter of FNDC5. Knockdown of FNDC5 in IH-induced microglia and animals reversed the protective effects of ELK4 on OSA-associated neuroinflammation and cognitive dysfunction. Overall, the results demonstrated that ELK4 overexpression repressed microglial activation by inducing the transcription of FNDC5, thus attenuating neuroinflammation and cognitive dysfunction induced by OSA.

Role of Oxidative Stress in the Occurrence and Development of Cognitive Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) causes recurrent apnea and intermittent hypoxia at night, leading to several complications such as cognitive dysfunction. However, the molecular mechanisms underlying cognitive dysfunction in OSAS are unclear, and oxidative stress mediated by intermittent hypoxia is an important mechanism. In addition, the improvement of cognitive dysfunction in patients with OSAS varies by different treatment regimens; among them, continuous positive airway pressure therapy (CPAP) is mostly recognized for improving cognitive dysfunction. In this review, we discuss the potential mechanisms of oxidative stress in OSAS, the common factors of affecting oxidative stress and the Links between oxidative stress and inflammation in OSAS, focusing on the potential links between oxidative stress and cognitive dysfunction in OSAS and the potential therapies for neurocognitive dysfunction in patients with OSAS mediated by oxidative stress. Therefore, further analysis on the relationship between oxidative stress and cognitive dysfunction in patients with OSAS will help to clarify the etiology and discover new treatment options, which will be of great significance for early clinical intervention.

Cytosolic Escape of Mitochondrial DNA Triggers cGAS-STING Pathway-Dependent Neuronal PANoptosis in Response to Intermittent Hypoxia

Intermittent hypoxia (IH) is the predominant pathophysiological disturbance in obstructive sleep apnea (OSA), characterized by neuronal cell death and neurocognitive impairment. We focus on the accumulated mitochondrial DNA (mtDNA) in the cytosol, which acts as a damage-associated molecular pattern (DAMP) and activates the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, a known trigger for immune responses and neuronal death in degenerative diseases. However, the specific role and mechanism of the mtDNA-cGAS-STING axis in IH-induced neural damage remain largely unexplored. Here, we investigated the involvement of PANoptosis, a novel type of programmed cell death linked to cytosolic mtDNA accumulation and the cGAS-STING pathway activation, in neuronal cell death induced by IH. Our study found that PANoptosis occurred in primary cultures of hippocampal neurons and HT22 cell lines exposed to IH. In addition, we discovered that during IH, mtDNA released into the cytoplasm via the mitochondrial permeability transition pore (mPTP) activates the cGAS-STING pathway, exacerbating PANoptosis-associated neuronal death. Pharmacologically inhibiting mPTP opening or depleting mtDNA significantly reduced cGAS-STING pathway activation and PANoptosis in HT22 cells under IH. Moreover, our findings indicated that the cGAS-STING pathway primarily promotes PANoptosis by modulating endoplasmic reticulum (ER) stress. Inhibiting or silencing the cGAS-STING pathway substantially reduced ER stress-mediated neuronal death and PANoptosis, while lentivirus-mediated STING overexpression exacerbated these effects. In summary, our study elucidates that cytosolic escape of mtDNA triggers cGAS-STING pathway-dependent neuronal PANoptosis in response to IH, mainly through regulating ER stress. The discovery of the novel mechanism provides theoretical support for the prevention and treatment of neuronal damage and cognitive impairment in patients with OSA.

Shengmaisan combined with Liuwei Dihuang Decoction alleviates chronic intermittent hypoxia-induced cognitive impairment by activating the EPO/EPOR/JAK2 signaling pathway

Chronic intermittent hypoxia (CIH), a principal pathophysiological aspect of obstructive sleep apnea (OSA), is associated with cognitive deficits. Clinical evidence suggests that a combination of Shengmaisan and Liuwei Dihuang Decoctions (SMS-LD) can enhance cognitive function by nourishing yin and strengthening the kidneys. This study aimed to assess the efficacy and underlying mechanisms of SMS-LD in addressing cognitive impairments induced by CIH. We exposed C57BL/6N mice to CIH for five weeks (20%-5% O2, 5 min/cycle, 8 h/day) and administered SMS-LD intragastrically (15.0 or 30 g·kg-1·day) 30 min before each CIH session. Additionally, AG490, a JJanus kinase 2 (JAK2) inhibitor, was administered via intracerebroventricular injection. Cognitive function was evaluated using the Morris water maze, while synaptic and mitochondrial structures were examined by transmission electron microscopy. Oxidative stress levels were determined using DHE staining, and the activation of the erythropoietin (ER)/ER receptor (EPOR)/JAK2 signaling pathway was analyzed through immunohistochemistry and Western blotting. To further investigate molecular mechanisms, HT22 cells were treated in vitro with either SMS-LD medicated serum alone or in combination with AG490 and then exposed to CIH for 48 h. Our results indicate that SMS-LD significantly mitigated CIH-induced cognitive impairments in mice. Specifically, SMS-LD treatment enhanced dendritic spine density, ameliorated mitochondrial dysfunction, reduced oxidative stress, and activated the EPO/EPOR/JAK2 signaling pathway. Conversely, AG490 negated SMS-LD's neuroprotective and cognitive improvement effects under CIH conditions. These findings suggest that SMS-LD's beneficial impact on cognitive impairment and synaptic and mitochondrial integrity under CIH conditions may predominantly be attributed to the activation of the EPO/EPOR/JAK2 signaling pathway.

NLRP3-GSDMD-dependent IL-1β Secretion from Microglia Mediates Learning and Memory Impairment in a Chronic Intermittent Hypoxia-induced Mouse Model

Hypoxia/reoxygenation caused by chronic intermittent hypoxia (CIH) plays an important role in cognitive deficits in patients with obstructive sleep apnea. However, the precise underlying mechanism remains unclear. This study investigated whether the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is involved in CIH-induced spatial learning and memory impairment in mice, and the possible underlying upstream and downstream mechanisms. The C57BL/6 male mice were exposed to CIH (21% O2-6% O2, 4 min/cycle, 8 h/day) for 9 weeks to investigate the role of NLRP3 in CIH-induced spatial learning and memory impairment in mice. BV2 cells were exposed to intermittent hypoxia (21% O2-1% O2, 90 min/cycle) for 48 h to investigate the possible mechanisms in vitro. We found that: 1) inhibition of NLRP3 inflammasome activation improved CIH-induced spatial learning and memory impairment in mice. 2) CIH damaged hippocampal neurons but increased the number of microglia in mice hippocampi; CIH activated microglia-specific NLRP3 inflammasome, leading to upregulation of matured IL-1β and N-GSDMD. 3) intermittent hypoxia activated NLRP3 inflammasome via the ROS-NF-κB signaling pathway to promote the release of matured IL-1β from microglia in a GSDMD-dependent manner without pyroptosis. 4) The IL-1β released from microglia might impair the synaptic plasticity of hippocampal CA3-CA1 synapses by acting on IL-1 receptors in hippocampal neurons. Our findings reveal that ROS-NF-κB-NLRP3 inflammasome-GSDMD dependent IL-1β release from microglia may participate in CIH-induced spatial learning and memory impairment by acting on hippocampal neuronal IL-1 receptor, leading to synaptic plasticity impairment.

The role of ferroptosis in chronic intermittent hypoxia-induced cognitive impairment

PURPOSE

Obstructive sleep apnea (OSA) is a sleep disorder that may lead to cognitive impairment. The primary pathophysiological feature of OSA is chronic intermittent hypoxia (CIH), but the underlying mechanisms of CIH are not known. There have been few studies on the role of ferroptosis, a novel form of programmed cell death, during CIH-induced cognitive impairment. Therefore, this paper examined ferroptosis' effect on CIH-mediated cognitive impairment.

METHODS

The study randomized twenty-four Sprague-Dawley (SD) male rats to control or CIH group. CIH rats were subjected to intermittent hypoxia for 4 weeks. Rat learning and memory were analyzed by the Morris water maze (MWM) test. Alterations of hippocampal neuronal ultrastructure were observed by transmission electron microscopy (TEM). Malondialdehyde (MDA) and ferrous iron (Fe2+) levels and superoxide dismutase (SOD) and reduced glutathione (GSH) contents were determined. Ferroptosis-associated protein levels were examined by Western blotting.

RESULTS

The MWM test indicated that rats in the CIH group exhibited neurocognitive impairment. TEM showed that CIH induced mitochondrial damage. Significant increases in Fe2+ and MDA levels were observed in the CIH group, and GSH and SOD levels were decreased. Expression of Acyl-CoA synthetase long-chain family member 4 (ACSL4) increased, and glutathione peroxidase 4 (GPX4) protein levels were decreased, suggesting that ferroptosis was induced in CIH model rats. The NF-E2-related factor 2 (Nrf2) protein level in the CIH group was decreased.

CONCLUSION

Ferroptosis had an essential effect on CIH-mediated cognitive impairment, and it may occur via Nrf2 dysregulation. These findings lay a solid foundation for the subsequent study of OSA-associated cognitive impairment offering potential evidence for the development of therapeutic strategies.

Solriamfetol enhances wakefulness and improves cognition and anxiety in a murine model of OSA

BACKGROUND

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH). Excessive daytime sleepiness (EDS) is a common consequence of OSA and is associated with cognitive deficits and anxiety. Modafinil (MOD) and Solriamfetol (SOL) are potent wake-promoting agents clinically used to improve wakefulness in OSA patients with EDS.

METHODS

Male C57Bl/6J mice were exposed to either IH or room air (RA) controls during the light phase for 16 weeks. Both groups were then randomly assigned to receive once-daily intraperitoneal injections of SOL (200 mg/kg), MOD (200 mg/kg) or vehicle (VEH) for 9 days while continuing IH exposures. Sleep/wake activity was assessed during the dark (active) phase. Novel object recognition (NOR), elevated-plus maze test (EPMT), and forced swim test (FST) were performed before and after drug treatment.

RESULTS

IH exposure increased dark phase sleep percentage and reduced wake bouts lengths and induced cognitive deficits and anxiogenic effects. Both SOL and MOD treatments decreased sleep propensity under IH conditions, but only SOL promoted improvements in NOR performance (explicit memory) and reduced anxiety-like behaviors.

CONCLUSION

Chronic IH, a hallmark feature of OSA, induces EDS in young adult mice that is ameliorated by both SOL and MOD. SOL, but not MOD, significantly improves IH-induced cognitive deficits and promotes anxiolytic effects. Thus, SOL could potentially benefit OSA patients beyond EDS management.

Tanshinone IIA inhibited intermittent hypoxia induced neuronal injury through promoting autophagy via AMPK-mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic intermittent hypoxia (CIH) is the primary pathophysiological process of obstructive sleep apnea (OSA) and is closely linked to neurocognitive dysfunction. Tanshinone IIA (Tan IIA) is extracted from Salvia miltiorrhiza Bunge and used in Traditional Chinese Medicine (TCM) to improve cognitive impairment. Studies have shown that Tan IIA has anti-inflammatory, anti-oxidant, and anti-apoptotic properties and provides protection in intermittent hypoxia (IH) conditions. However, the specific mechanism is still unclear.

AIM OF THE STUDY

To assess the protective effect and mechanism of Tan IIA treatment on neuronal injury in HT22 cells exposed to IH.

MATERIALS AND METHODS

The study established an HT22 cell model exposed to IH (0.1% O₂ 3 min/21% O₂ 7 min for six cycles/h). Cell viability was determined using the Cell Counting Kit-8, and cell injury was determined using the LDH release assay. Mitochondrial damage and cell apoptosis were observed using the Mitochondrial Membrane Potential and Apoptosis Detection Kit. Oxidative stress was assessed using DCFH-DA staining and flow cytometry. The level of autophagy was assessed using the Cell Autophagy Staining Test Kit and transmission electron microscopy (TEM). Western blot was used to detect the expressions of the AMPK-mTOR pathway, LC3, P62, Beclin-1, Nrf2, HO-1, SOD2, NOX2, Bcl-2/Bax, and caspase-3.

RESULTS

The study showed that Tan IIA significantly improved HT22 cell viability under IH conditions. Tan IIA treatment improved mitochondrial membrane potential, decreased cell apoptosis, inhibited oxidative stress, and increased autophagy levels in HT22 cells under IH conditions. Furthermore, Tan IIA increased AMPK phosphorylation and LC3II/I, Beclin-1, Nrf2, HO-1, SOD2, and Bcl-2/Bax expressions, while decreasing mTOR phosphorylation and NOX2 and cleaved caspase-3/caspase-3 expressions.

CONCLUSION

The study suggested that Tan IIA significantly ameliorated neuronal injury in HT22 cells exposed to IH. The neuroprotective mechanism of Tan IIA may mainly be related to inhibiting oxidative stress and neuronal apoptosis by activating the AMPK/mTOR autophagy pathway under IH conditions.

TGF-β3 Protects Neurons Against Intermittent Hypoxia-Induced Oxidative Stress and Apoptosis Through Activation of the Nrf-2/KEAP1/HO-1 Pathway via Binding to TGF-βRI

Intermittent hypoxia (IH) is the primary pathological manifestation of obstructive sleep apnea (OSA) and the main cause of OSA-induced cognitive impairment. Hippocampal neurons are considered to be critical cells affected by IH. Transforming growth factor-β3 (TGF-β3) is a cytokine with a neuroprotective effect, which plays a crucial role in resisting hypoxic brain injury, while its role in IH-induced neuronal injury is still unclear. Here, we aimed to clarify the mechanism of TGF-β3 protecting IH-exposed neurons by regulating oxidative stress and secondary apoptosis. Morris water maze results revealed that IH exposure was unable to affect the vision and motor ability of rats, but significantly affected their spatial cognition. Second-generation sequencing (RNA-seq) and subsequent experiments supported that IH decreased TGF-β3 expression and stimulated reactive oxygen species (ROS)-induced oxidative stress and apoptosis in rat hippocampus. In vitro, IH exposure significantly activated oxidative stress within HT-22 cells. Exogenous administration of Recombinant Human Transforming Growth Factor-β3 (rhTGF-β3) prevented ROS surge and secondary apoptosis in HT-22 cells caused by IH, while TGF-β type receptor I (TGF-βRI) inhibitor SB431542 blocked the neuroprotective effect of rhTGF-β3. Nuclear factor erythroid 2-related factor 2 (Nrf-2) is a transcription factor preserving intracellular redox homeostasis. rhTGF-β3 improved the nuclear translocation of Nrf-2 and activated downstream pathway. However, Nrf-2 inhibitor ML385 suppressed the activation of the Nrf-2 mechanism by rhTGF-3 and restored the effects of oxidative stress damage. These results indicate that TGF-β3 binding to TGF-βRI activates the intracellular Nrf-2/KEAP1/HO-1 pathway, reduces ROS creation, and attenuates oxidative stress and apoptosis in IH-exposed HT-22 cells.

Shashen-Maidong Decoction inhibited cancer growth under intermittent hypoxia conditions by suppressing oxidative stress and inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Lung cancer is one of the most common malignant tumours and has become the leading cause of cancer-related deaths worldwide. Abnormal microcirculation during tumour growth leads to intermittent hypoxia (IH), which is responsible for promoting cancer cell proliferation and migration. Patients with advanced lung cancers show deficiency of both Qi and Yin Syndrome (DQYS) in TCM, and studies have confirmed that IH exposure is related to DQYS. Shashen-Maidong Decoction (SMD), has been widely applied clinically targeting DQYS and has a long history for treating lung cancer by nourishing the body's "zheng qi" and resisting "xie qi". However, whether SMD could be beneficial to lung cancer under IH conditions remains unclear.

AIM OF THE STUDY

This study aimed to clarify the effects and mechanism of SMD on non-small cell lung cancer (NSCLC) growth under IH conditions.

MATERIALS AND METHODS

C57 mice were injected subcutaneously into the right axilla with Lewis lung cancer (LLC) cells and exposed to IH conditions (21%-5% O2, 5 min/cycle, 8 h/day) for 21 days. SMDs were orally treated with different concentrations (2.6, 5.2 or 10.4 g/kg/day) 30 min before IH exposure. Tumour proliferation and migration were assessed by HE and IHC staining, and oxidative stress was assessed by DHE staining and MDA or SOD detection. IL-6, IL-1β and TNF-α levels were assessed by IHC staining, and the IL-6/JAK2/STAT3 signalling pathway was detected by western blotting.

RESULTS

Our results showed that SMD treatment inhibited tumour growth and liver metastasis in LLC-bearing mice exposed to IH, decreased Ki67, CD31, VEGF, and MMP-2, and increased E-cadherin expression in tumourt tissue. SMD reduced ROS production, increased SOD levels and SOD-2 expression, and decreased MDA levels and NOX-2 expression. SMD decreased IL-6, IL-1β and TNF-α levels, reduced IL-6 expression and inhibited JAK2 and STAT3 phosphorylation. Additionally, SMD treatment improved DQYS and liver and kidney function in LLC-bearing mice under IH conditions.

CONCLUSION

Our research suggests that SMD treatment can inhibit tumour growth in mice exposed to IH. The antitumour effect of SMD may be related to attenuated oxidative stress and inflammation through inactivation of the IL-6/JAK2/STAT3 signalling pathway under IH conditions.

Insight into the Effects of High-Altitude Hypoxic Exposure on Learning and Memory

The earth land area is heterogeneous in terms of elevation; about 45% of its land area belongs to higher elevation with altitude above 500 meters compared to sea level. In most cases, oxygen concentration decreases as altitude increases. Thus, high-altitude hypoxic stress is commonly faced by residents in areas with an average elevation exceeding 2500 meters and those who have just entered the plateau. High-altitude hypoxia significantly affects advanced neurobehaviors including learning and memory (L&M). Hippocampus, the integration center of L&M, could be the most crucial target affected by high-altitude hypoxia exposure. Based on these points, this review thoroughly discussed the relationship between high-altitude hypoxia and L&M impairment, in terms of hippocampal neuron apoptosis and dysfunction, neuronal oxidative stress disorder, neurotransmitters and related receptors, and nerve cell energy metabolism disorder, which is of great significance to find potential targets for medical intervention. Studies illustrate that the mechanism of L&M damaged by high-altitude hypoxia should be further investigated based on the entire review of issues related to this topic.

Sulforaphane Attenuates Chronic Intermittent Hypoxia-Induced Brain Damage in Mice via Augmenting Nrf2 Nuclear Translocation and Autophagy

Obstructive sleep apnea–hypopnea syndrome (OSAHS), typically characterized by chronic intermittent hypoxia (CIH), is associated with neurocognitive dysfunction in children. Sulforaphane (SFN), an activator of nuclear factor E2-related factor 2 (Nrf2), has been demonstrated to protect against oxidative stress in various diseases. However, the effect of SFN on OSAHS remains elusive. In this research, we investigated the neuroprotective role of SFN in CIH-induced cognitive dysfunction and underlying mechanisms of regulation of Nrf2 signaling pathway and autophagy. CIH exposures for 4 weeks in mice, modeling OSAHS, contributed to neurocognitive dysfunction, manifested as increased working memory errors (WMEs), reference memory errors (RMEs) and total memory errors (TEs) in the 8-arm radial maze test. The mice were intraperitoneally injected with SFN (0.5 mg/kg) 30 min before CIH exposure everyday. SFN treatment ameliorated neurocognitive dysfunction in CIH mice, which demonstrates less RME, WME, and TE. Also, SFN effectively alleviated apoptosis of hippocampal neurons following CIH by decreased TUNEL-positive cells, downregulated cleaved PARP, cleaved caspase 3, and upregulated Bcl-2. SFN protects hippocampal tissue from CIH-induced oxidative stress as evidenced by elevated superoxide dismutase (SOD) activities and reduced malondialdehyde (MDA). In addition, we found that SFN enhanced Nrf2 nuclear translocation to hold an antioxidative function on CIH-induced neuronal apoptosis in hippocampus. Meanwhile, SFN promoted autophagy activation, as shown by increased Beclin1, ATG5, and LC3II/LC3I. Overall, our findings indicated that SFN reduced the apoptosis of hippocampal neurons through antioxidant effect of Nrf2 and autophagy in CIH-induced brain damage, which highlights the potential of SFN as a novel therapy for OSAHS-related neurocognitive dysfunction.

Blockade of adenosine A2A receptor alleviates cognitive dysfunction after chronic exposure to intermittent hypoxia in mice

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is widely known for its multiple systems damage, especially neurocognitive deficits in children. Since their discovery, adenosine A_2A receptors (A_2ARs) have been considered as key elements in signaling pathways mediating neurodegenerative diseases such as Huntington's and Alzheimer's, as well as cognitive function regulation. Herein, we investigated A_2AR role in cognitive impairment induced by chronic intermittent hypoxia (CIH). Mice were exposed to CIH 7 h every day for 4 weeks, and intraperitoneally injected with A_2AR agonist CGS21680 or A_2AR antagonist SCH58261 half an hour before IH exposure daily. The 8-arm radial arm maze was utilized to assess spatial memory after CIH exposures.To validate findings using pharmacology, the impact of intermittent hypoxia was investigated in A_2AR knockout mice. CIH-induced memory dysfunction was manifested by increased error rates in the radial arm maze test. The behavioral changes were associated with hippocampal pathology, neuronal apoptosis, and synaptic plasticity impairment. The stimulation of adenosine A_2AR exacerbated memory impairment with more serious neuropathological damage, attenuated long-term potentiation (LTP), syntaxin down-regulation, and increased BDNF protein. Moreover, apoptosis-promoting protein cleaved caspase-3 was upregulated while anti-apoptotic protein Bcl-2 was downregulated. Consistent with these findings, A_2AR inhibition with SCH58261 and A_2AR deletion exhibited the opposite result. Overall, these findings suggest that A_2AR plays a critical role in CIH-induced impairment of learning and memory by accelerating hippocampal neuronal apoptosis and reducing synaptic plasticity. Blockade of adenosine A_2A receptor alleviates cognitive dysfunction after chronic exposure to intermittent hypoxia in mice.

Shashen-Maidong Decoction improved chronic intermittent hypoxia-induced cognitive impairment through regulating glutamatergic signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Obstructive sleep apnea (OSA) is characterized by chronic intermittent hypoxia (CIH), which is associated with cognitive impairment. Previous study suggested CIH exposure could induce similar symptoms and signs to the clinical features of Deficiency of both Qi and Yin Syndrome (DQYS) in Traditional Chinese Medicine (TCM). Shashen-Maidong Decoction (SMD) has been applied clinically for DQYS for hundred years. However, SMD treatment could be beneficial to CIH induced cognitive impairment is still unclear.

AIM OF THE STUDY

Therefore, the aim of this study was to investigate the effect of SMD treatment on CIH induced cognitive impairment, and to explore the related neuroprotective mechanism.

MATERIALS AND METHODS

Mice were exposed to CIH for 5 weeks (8 h/day) and were orally treated with either vehicle or SMD (5.265 g/kg/day) 30 min before CIH exposure. Spatial memory was evaluated by Morris Water Maze and Y-Maze test. Synaptic morphology in hippocampus was observed by Golgi-Cox staining and Electron microscope, and NR2B-ERK signaling pathway were detected by western blotting.

RESULTS

Our results showed that SMD treatment improved performance in either Morris Water Maze or Y-Maze test in mice exposed to CIH, increased spine density and postsynaptic density (PSD) thickness in hippocampus. SMD treatment suppressed the over-activation of NR2B/CaMKII/SynGAP induced by CIH exposure, enhanced ERK/CREB phosphorylation and increased PSD-95 and BDNF expression.

CONCLUSION

SMD attenuates the CIH-induced cognitive impairment through regulating NR2B-ERK signaling pathway. Additionally, our findings provided that DQYS may be the potential therapeutic target for neurocognitive diseases in patients with OSA.

Neuroprotective Effects of Molecular Hydrogen: A Critical Review

Molecular hydrogen (H2) is a physiologically inert gas. However, during the last 10 years, increasing evidence has revealed its biological functions under pathological conditions. More specifically, H2 has protective effects against a variety of diseases, particularly nervous system disorders, which include ischemia/reperfusion injury, traumatic injury, subarachnoid hemorrhage, neuropathic pain, neurodegenerative diseases, cognitive dysfunction induced by surgery and anesthesia, anxiety, and depression. In addition, H2 plays protective roles mainly through anti-oxidation, anti-inflammation, anti-apoptosis, the regulation of autophagy, and preservation of mitochondrial function and the blood-brain barrier. Further, H2 is easy to use and has neuroprotective effects with no major side-effects, indicating that H2 administration is a potential therapeutic strategy in clinical settings. Here we summarize the H2 donors and their pharmacokinetics. Meanwhile, we review the effectiveness and safety of H2 in the treatment of various nervous system diseases based on preclinical and clinical studies, leading to the conclusion that H2 can be a simple and effective clinical therapy for CNS diseases such as ischemia-reperfusion brain injury, Parkinson's disease, and diseases characterized by cognitive dysfunction. The potential mechanisms involved in the neuroprotective effect of H2 are also analyzed.

Sesamol alleviates chronic intermittent hypoxia-induced cognitive deficits via inhibiting oxidative stress and inflammation in rats

Chronic intermittent hypoxia (CIH) is a major pathophysiological feature of obstructive sleep apnea (OSA), which can cause oxidative stress and inflammation which can further impair the nervous system. Cognitive impairment is a common complication of the nervous system in OSA. Sesamol, a natural extract from Sesamum plants, is believed to have strong antioxidant and anti-inflammation capacity, which has a powerful neuroprotective function. But whether sesamol can improve CIH-induced cognitive impairment is unclear. This study aimed to explore whether sesamol can improve CIH-induced cognitive impairment and its relative mechanism in the model rats with OSA. Rats were exposed to CIH for 8 h a day for 2, 4, 6, and 8 weeks separately and concurrently were treated with sesamol (20 mg/kg/day, intraperitoneal). The Morris water maze (MWM) test was used to evaluate their learning and memory function. The activity of the superoxide dismutase (SOD) and the level of malondialdehyde were measured to evaluate the oxidative stress in the hippocampus of the rats. The levels of tumour necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in the hippocampus were quantified to analyse neuroinflammation by ELISA. The MWM test showed that sesamol improved learning and memory impairment in CIH-exposed rats. We also found that the sesamol-treated CIH-exposed rats had significantly increased the activity of SOD, as well as reduced the level of malondialdehyde in the hippocampus. In addition, sesamol also reduced the levels of TNF-α and IL-1β in the hippocampus. These data show that sesamol is able to alleviate cognitive impairments in CIH-exposed rats, with its neuroprotective effects likely inhibiting oxidative stress and inflammation.

A narrative review of hydrogen-oxygen mixture for medical purpose and the inhaler thereof

Recent development regarding mixture of H₂ (concentration of ~66%) with O₂ (concentration of ~34%) for medical purpose, such as treatment of coronavirus disease-19 (COVID-19) patients, is introduced. Furthermore, the design principles of a hydrogen inhaler which generates mixture of hydrogen (~66%) with oxygen (~34%) for medical purpose are proposed. With the installation of the liquid blocking module and flame arresters, the air pathway of the hydrogen inhaler is divided by multiple isolation zones to prevent any unexpected explosion propagating from one zone to the other. An integrated filtering/cycling module is utilized to purify the impurity, and cool down the temperature of the electrolytic module to reduce the risk of the explosion. Moreover, a nebulizer is provided to selectively atomize the water into vapor which is then mixed with the filtered hydrogen-oxygen mix gas, such that the static electricity of a substance hardly occurs to reduce the risk of the explosion. Furthermore, hydrogen concentration detector is installed to reduce the risk of hydrogen leakage. Result shows that the hydrogen inhaler implementing the aforesaid design rules could effectively inhibit the explosion, even ignition at the outset of the hydrogen inhaler which outputs hydrogen-oxygen gas (approximately 66% hydrogen: 34% oxygen).

Silencing of the long non-coding RNA MEG3 suppresses the apoptosis of aortic endothelial cells in mice with chronic intermittent hypoxia via downregulation of HIF-1α by competitively binding to microRNA-135a

BACKGROUND

Chronic intermittent hypoxia (CIH) involves substantial cortico-hippocampal injury, causing impairments of neurocognitive, respiratory, and cardiovascular functions. Long non-coding RNAs (lncRNAs) participate in CIH functions and development. Therefore, we explored the mechanisms involving lncRNA maternally expressed gene 3 (MEG3) regulating the aortic endothelial function of CIH mice via regulation of microRNA-135a (miR-135a) and the hypoxia-inducible factor (HIF)-1α.

METHODS

Expression of MEG3, miR-135a, and HIF-1α in CIH mice and CIH-treated cells was detected. Then, the apoptosis and proliferation of the aortic endothelial cells were examined to verify whether miR-135a and HIF-1α participated in CIH. Next, the interactions between MEG3, miR-135a, and HIF-1α were explored. Later, the effects of MEG3/miR-135a/HIF-1α on the expression of proliferation- and apoptosis-related factors and aortic injury were investigated via gain- and loss-of function studies both in vivo and in vitro.

RESULTS

MEG3 and HIF-1α were highly expressed while miR-135a was poorly expressed in CIH mice and CIH-modeled cells. Moreover, miR-135a targeted HIF-1α to promote cell proliferation and inhibit apoptosis. MEG3 regulated HIF-1α expression by competitively binding to miR-135a. More importantly, we found that the silencing of MEG3/HIF-1α and the overexpression of miR-135a inhibited the apoptosis and injury of aortic endothelial cells while promoting cell proliferation in CIH mice.

CONCLUSIONS

Altogether, silencing of MEG3 suppressed the aortic endothelial injury and cell apoptosis in CIH mice by downregulating HIF-1α through sponging miR-135a, providing evidence of a potential therapeutic target for CIH.

Huperzine A, reduces brain iron overload and alleviates cognitive deficit in mice exposed to chronic intermittent hypoxia

Chronic intermittent hypoxia (CIH) is a consequence of obstructive sleep apnea (OSA), which increases reactive oxygen species (ROS) generation, resulting in oxidative damage and neurocognitive impairment. This study was designed to determine whether abnormal iron metabolism occurs in the brain under conditions of CIH and whether Huperzine A (HuA) could improve abnormal iron metabolism and neurological damage. The mouse model of CIH was established by reducing the percentage of inspired O₂ (FiO₂) from 21% to 9% 20 times/h for 8 h/day, and Huperzine A (HuA, 0.1 mg/kg, i.p.) was administered during CIH exposure for 21 days. HuA significantly improved cognitive impairment and neuronal damage in the hippocampus of CIH mice via increasing the ratio of Bcl-2/Bax and inhibiting caspase-3 cleavage. HuA considerably decreased ROS levels by downregulating the high levels of NADPH oxidase (NOX 2, NOX 4) mediated by CIH. There was an overload of iron, which was characterized by high levels of ferritin (FTL and FTH) and transferrin receptor 1 (TfR1) and low levels of ferroportin 1 (FPN1) in the hippocampus of CIH mice. Decreased levels of TfR1 and FTL proteins observed in HuA treated CIH group, could reduce iron overload in hippocampus. HuA increased PSD 95 protein expression, CREB activation and BDNF protein expression to protect against synaptic plasticity impairment induced by CIH. HuA acts as an effective iron chelator to attenuate apoptosis, oxidative stress and synaptic plasticity mediated by CIH.

Therapeutic effects and modulatory mechanism of Alpiniae oxyphyllae Fructus in chronic intermittent hypoxia induced enuresis in rats

OBJECTIVE

The objective of this study was to explore the effect of Alpiniae oxyphyllae Fructus (AOF) on a rat model of chronic intermittent hypoxia (CIH)-induced enuresis. Findings of this study may help identify therapeutic targets in children with nocturnal enuresis (NE).

METHODS

Female rats were randomly divided into a control group (saline gavage, 4 weeks of normal air), CIH group (saline gavage, 4 weeks of CIH), and AOF group (AOF gavage, 4 weeks of CIH). The variables measured in this study included water intake, urine output, bladder leak point pressure (BLPP), malondialdehyde (MDA) levels, and superoxide dismutase (SOD) activity. The expression levels of the purinergic P₂X₃ receptor, muscarinic M₃ receptor, and ß₃-adrenergic receptor (ß₃-AR) in the bladder were also measured. The bladder was subjected to haematoxylin and eosin (HE) and Weigert staining, and histological changes were observed under a light microscope to evaluate the morphological changes in the bladder in each group.

RESULTS

Compared with the control group, urine output was increased, and the BLPP was decreased in the CIH group, but AOF administration decreased urine output and increased BLPP. In addition, the serum MDA level increased and the SOD activity decreased in the CIH group compared with the control group. Administration of AOF decreased the MDA level and increased the SOD activity. Additionally, compared with the control group, HE and Weigert staining in the CIH group showed that the bladder detrusor muscle bundles were disordered and loose, some muscle bundles were broken, the content of collagen fibres in the gap was reduced, and the gap was significantly widened. However, following the administration of AOF, the bladder detrusor muscle bundles were neatly arranged, and the content of collagen fibres in the gap was increased. Furthermore, compared with the control group, the purinergic P₂X₃ receptor and muscarinic M₃ receptor were expressed at higher levels, and ß₃-AR was expressed at lower levels in the CIH group, but AOF administration decreased the expression of the purinergic P₂X₃ receptor and muscarinic M₃ receptor and increased the expression of the ß₃-AR.

CONCLUSIONS

AOF improves enuresis by inhibiting oxidative stress and regulating the expression of the purinergic P₂X₃ receptor, muscarinic M₃ receptor, and ß₃ adrenergic receptor.

Hydrogen protects against chronic intermittent hypoxia induced renal dysfunction by promoting autophagy and alleviating apoptosis

AIMS

Hydrogen gas (H₂) has a diversity of effects such as anti-apoptotic, anti-inflammatory and anti-oxidative properties. However, molecular mechanism underlying the potential effect of H₂ on chronic intermittent hypoxia (CIH) induced renal injury remains obscure.

MATERIALS AND METHODS

In the present study, adult male Sprague-Dawley rats were randomly allocated into four groups: control (CON) group, CIH group, CIH with H₂ treatment (CIH + H₂) group, and control with H₂ treatment (CON + H₂) group. Oxidative stress, autophagy and endoplasmic reticulum (ER) stress were detected to determine how H₂ affected the renal function of CIH exposed rats.

KEY FINDINGS

We demonstrated that rats who inhale hydrogen gas showed improved renal function, alleviated pathological damage, oxidative stress and apoptosis in CIH rats. Meanwhile, CIH-induced endoplasmic reticulum stress was decreased by H₂ as the expressions of CHOP, caspase-12, and GRP78 were down-regulated. Furthermore, relative higher levels of LC3-II/I ratio and Beclin-1, with decreased expression of p62, were found after H₂ administrated. Inhibition of mTOR may be involved in the upregulation of autophagy by H₂. Finally, increased phosphorylation of p38 and JNK was involved in the CIH-induced pathological process. H₂ could inhibit the activation of p38 and JNK, suggesting H₂ played an active part in resisting renal injury via MAPK.

SIGNIFICANCE

Taken together, our study reveals that H₂ can ameliorate CIH-induced kidney injury by decreasing endoplasmic reticulum stress and activating autophagy through inhibiting oxidative stress-dependent p38 and JNK MAPK activation.

Hydrogen Gas Alleviates Chronic Intermittent Hypoxia-Induced Renal Injury through Reducing Iron Overload

Iron-induced oxidative stress has been found to be a central player in the pathogenesis of kidney injury. Recent studies have indicated H₂ can be used as a novel antioxidant to protect cells. The present study was designed to investigate the protective effects of H₂ against chronic intermittent hypoxia (CIH)-induced renal injury and its correlation mechanism involved in iron metabolism. We found that CIH-induced renal iron overloaded along with increased apoptosis and oxidative stress. Iron accumulates mainly occurred in the proximal tubule epithelial cells of rats as showed by Perl’s stain. Moreover, we found that CIH could promote renal transferrin receptor and divalent metal transporter-1 expression, inhibit ceruloplasmin expression. Renal injury, apoptosis and oxidative stress induced by CIH were strikingly attenuated in H₂ treated rats. In conclusion, hydrogen may attenuate CIH-induced renal injury at least partially via inhibiting renal iron overload.