Effects of Intermittent Hypoxia Exposure on Symptoms of Chronic Fatigue Syndrome in Repeated Restraint Stress and Forced Swimming Induced-Mouse Model

Background: Chronic fatigue syndrome (CFS) shows as its main symptoms debilitating fatigue that is not relieved by physiological rest, depression, inflammation, learning disability and memory impairment. But, intermittent hypoxia, consisting of alternating exposure to hypoxia and normoxia, plays a very important role in improving CFS. However, the essential components for improving learning and memory in CFS patients as well as their mechanism are largely unknown. Objectives: This study aims to analyze the effects of 12% and 15% hypoxia on the expression of alpha tumor necrosis factor (TNF-α) and nuclear factor kappa B (NF-κB) in CFS induced-mouse model for clarifying the effects on the learning and memory function. Methods: A total of 48 type IC mice were used. The CFS mouse model was established using restrained stress and repeated forced swimming. Treatment of CFS was done by exposing CFS mice to intermittent hypoxia at 12% and 15%. The effects of intermittent hypoxia on learning and memory as well as its mechanism of action on inflammation were tested respectively with the Morris test, the SDS page, the immunohistochemistry technique and the Nissl staining. Results: We found that 12% and 15% intermittent hypoxia exposure improved learning capacity and memory of CFS induced-mice. SDS page showed that CFS caused higher TNF-α expression. By exposing CFS mice to 12% and 15% intermittent hypoxia, TNF-α expression decreased significantly, with a much better effect at 15%. Both TNF-α and NF-κB increased in CFS state and decreased after treatment with intermittent hypoxia. Conclusion: Intermittent hypoxia improves learning capacity and memory. It acted by decreasing NF-κB come to down-regulating TNF-α and ameliorates learning capacity and memory impairment in CFS mice.

Intermittent hypoxia attenuates ischemia/reperfusion induced apoptosis in cardiac myocytes via regulating Bcl-2/Bax expression

Intermittent hypoxia has been shown to provide myocardial protection against ishemia/reperfusion-induced injury.Cardiac myocyte loss through apoptosis has been reported in ischemia/reperfusion injury. Our aim was to investigate whether intermittent hypoxia could attenuate ischemia/reperfusion-induced apoptosis in cardiac myocytes and its potential mechanisms. Adult male Sprague-Dawley rats were exposed to hypoxia simulated 5000 m in a hypobaric chamber for 6 h/day, lasting 42 days. Normoxia group rats were kept under normoxic conditions. Isolated perfused hearts from both groups were subjected to 30 min of global ischemia followed by 60 min reperfusion.Incidence of apoptosis in cardiac myocytes was determined by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) and DNA agarose gel electrophoresis. Expressions of apoptosis related proteins,Bax and Bcl-2, in cytosolic and membrane fraction were detected by Western Blotting. After ischemia/reperfusion,enhanced recovery of cardiac function was observed in intermittent hypoxia hearts compared with normoxia group.Ischemia/reperfusion-induced apoptosis, as evidenced by TUNEL-positive nuclei and DNA fragmentation, was significantly reduced in intermittent hypoxia group compared with normoxia group. After ischemia/reperfusion,expression of Bax in both cytosolic and membrane fractions was decreased in intermittent hypoxia hearts compared with normoxia group. Although ischemia/reperfusion did not induce changes in the level of Bcl-2 expression in cytosolic fraction between intermittent hypoxia and normoxia groups, the expression of Bcl-2 in membrane fraction was upregulated in intermittent hypoxia group compared with normoxia group. These results indicated that the cardioprotection of intermittent hypoxia against ischemia/reperfusion injury appears to be in part due to reduce myocardial apoptosis. Intermittent hypoxia attenuated ischemia/reperfusion-induced apoptosis via increasing the ratio of Bcl-2/Bax, especially in membrane fraction.

Intermittent hypoxia is involved in gut microbial dysbiosis in type 2 diabetes mellitus and obstructive sleep apnea-hypopnea syndrome

BACKGROUND Obstructive sleep apnea(OSA)-hypopnea syndrome(OSAHS)has been recognized as a comorbidity of type 2 diabetes mellitus(T2DM);more than half of T2DM patients suffer from OSAHS.Intermittent hypoxia(IH)plays an important role in metabolic diseases,such as obesity and OSAHS,through various mechanisms,including altering the gut microecological composition and function.Therefore,it is important to study the role of gut microbiota in T2DM patients with OSAHS,which has a high incidence and is prone to several complications.AIM To assess whether IH is involved in altering the fecal microbiome in T2DM patients with OSAHS.METHODS Seventy-eight participants were enrolled from Henan Province People’s Hospital and divided into healthy control(HC,n=26),T2DM(n=25),and T2DM+OSA(n=27)groups based on their conditions.The fecal bacterial DNA of the research participants was extracted and subjected to 16S ribosomal RNA sequencing.The clinical indices,such as insulin resistance index,homocysteine(HCY)concentration,and the concentrations of inflammatory factors in the peripheral blood,were assessed and recorded.RESULTS Group T2DM+OSA had the highest apnea-hypopnea index(AHI)(2.3 vs 3.7 vs 13.7),oxygen desaturation index(0.65 vs 2.2 vs 9.1),HCY concentration(9.6μmol/L vs 10.3μmol/L vs 13.81μmol/L)and C-reactive protein(CRP)concentrations(0.3 mg/L vs 1.43 mg/L vs 2.11 mg/L),and lowest mean oxygen saturation(97.05%vs 96.6%vs 94.7%)among the three groups.Twelve and fifteen key differences in amplicon sequence variants were identified when comparing group T2DM+OSA with groups T2DM and HC,respectively.We found progressively decreased levels of Faecalibacterium,Eubacterium,and Lachnospiraceae,and an increase in the level of Actinomyces,which strongly correlated with the HCY,CRP,fasting plasma glucose,and hemoglobin A1c concentrations,AHI,mean oxygen saturation,and insulin resistance index in group T2DM+OSA(P<0.05).CONCLUSION For T2DM patients with OSAHS,IH may be involved in selective alterations of the gut microbiota,which may affect the pathophysiological development of T2DM and DM-related complications.

Influence of chronic intermittent hypoxia on growth associated protein 43 expression in the hippocampus of young rats

This study aimed to explore the pathological change to hippocampal neurons and the expression of growth associated protein 43 in 21-day-old young rats following chronic intermittent hypoxia. Hematoxylin-eosin staining results showed varying degrees of degeneration and necrosis in hippocampal neurons depending on the modeling time. Immunohistochemistry revealed that growth associated protein 43 expression in young rats following chronic intermittent hypoxia decreased, but that levels were still higher than those of normal rats at each time point, especially 4 weeks after modeling. During 1 5 weeks after modeling, a slow growth in rat weight was observed. Experimental findings indicate that chronic intermittent hypoxia may induce growth dysfunction and necrosis of hippocampal neurons, as well as increase the expression of growth associated protein 43 in young rats.

Atorvastatin Attenuates Myocardial Hypertrophy Induced by Chronic Intermittent Hypoxia In Vitro Partly through miR-31/PKCε Pathway

Atorvastatin is proven to ameliorate cardiac hypertrophy induced by chronic intermittent hypoxia （CIH）. However, little is known about the mechanism by which atorvastatin modulates CIH-induced cardiac hypertrophy, and whether specific hypertrophyrelated microRNAs are involved in the modulation. MiR-31 plays key roles in the development of cardiac hypertrophy induced by ischemia/hypoxia. This study examined whether miR-31 was involved in the protective role of atorvastatin against CIH-induced myocardial hypertrophy. H9c2 cells were subjected to 8-h intermittent hypoxia per day in the presence or absence of atorvastatin for 5 days. The size of cardiomyocytes, and the expression of caspase 3 and miR-31 were determined by Western blotting and RT-PCR, respectively. MiR-31 mimic or Ro 31-8220, a specific inhibitor of protein kinase C epsilon （PKCε）, was used to determine the role of miR-31 in the anti-hypertrophic effect of atorvastatin on cardiomyocytes. PKCε in the cardiomyocytes with miR-31 upregulation or downregulation was detected using RT-PCR and Western blotting. The results showed that CIH induced obvious enlargement of cardiomyocytes, which was paralleled with increased atrial natriuretic peptide （ANP）, brain natriuretic peptide （BNP）, and slow/beta cardiac myosin heavy-chain （MYHT） mRNA levels. All these changes were reversed by the treatment with atorvastatin. Meanwhile, miR-31 was increased by CIH in vitro. Of note, the atorvastatin pretreatment significantly increased the mRNA and protein expression of PKCε and decreased that of miR-31. Moreover, overexpression of miR-31 abolished the anti-hypertrophic effect of atorvastatin on cardiomyocytes. Upregulation and downregulation of miR-31 respectively decreased and increased the mRNA and protein expression of PKCε. These results suggest that atorvastatin provides the cardioprotective effects against CIH probably via up-regulating PKCε and down-regulating miR-31.

Adiponectin Ameliorated Pancreatic Islet Injury Induced by Chronic Intermittent Hypoxia through Inhibiting the Imbalance in Mitochondrial Fusion and Division

Objective This study aimed to assess the protective value of adiponectin(APN)in pancreatic islet injury induced by chronic intermittent hypoxia(CIH).Methods Sixty rats were randomly divided into three groups:normal control(NC)group,CIH group,and CIH with APN supplement(CIH+APN)group.After 5 weeks of CIH exposure,we conducted oral glucose tolerance tests(OGTT)and insulin released test(IRT),examined and compared the adenosine triphosphate(ATP)levels,mitochondrial membrane potential(MMP)levels,reactive oxygen species(ROS)levels,enzymes gene expression levels of Ant1,Cs,Hmox1,and Cox4 i1 which represented mitochondrial tricarboxylic acid cycle function,the protein and gene expression levels of DRP1,FIS1,MFN1,and OPA1 which represented mitochondrial fusion and division,and the protein expression levels of BAX,BCL-2,cleaved Caspase-3,and cleaved PARP which represented mitochondrial associated apoptosis pathway of pancreatic islet.Results OGTT and IRT showed blood glucose and insulin levels had no differences among the NC,CIH and CIH+APN groups(both P>0.05)at 0 min,20 min,30 min,60 min,120 min.However,we found that compared to NC group,CIH increased the ROS level,reduced ATP level and MMP level.The islets of CIH exposed rats showed reduced gene expression levels of Ant1,Cs,Hmox1,and Cox4 i1,decreased protein and gene expression levels of MFN1 and OPA1,increased protein and gene expression levels of DRP1 and FIS1,increased protein expression levels of cleaved Caspase-3 and cleaved PARP,with lower ratio of BCL-2/BAX at protein expression level.All the differences among three groups were statistically significant.APN treated CIH rats showed mitigated changes in the above measurements associated with islet injuries.Conclusion APN may ameliorate the pancreatic islet injury induced by CIH via inhibiting the imbalance in mitochondrial fusion and division.

Chronic intermittent hypoxia induces cardiac inflammation and dysfunction in a rat obstructive sleep apnea model

Chronic intermittent hypoxia is considered to play an important role in cardiovascular pathogenesis during the development of obstructive sleep apnea（OSA）.We used a well-described OSA rat model induced with simultaneous intermittent hypoxia.Male Sprague Dawley rats were individually placed into plexiglass chambers with air pressure and components were electronically controlled.The rats were exposed to intermittent hypoxia 8 hours daily for 5weeks.The changes of cardiac structure and function were examined by ultrasound.The cardiac pathology,apoptosis,and fibrosis were analyzed by H＆E staining,TUNNEL assay,and picosirius staining,respectively.The expression of inflammation and fibrosis marker genes was analyzed by quantitative real-time PCR and Western blot.Chronic intermittent hypoxia/low pressure resulted in significant increase of left ventricular internal diameters（LVIDs）,endsystolic volume（ESV）,end-diastolic volume（EDV）,and blood lactate level and marked reduction in ejection fraction and fractional shortening.Chronic intermittent hypoxia increased TUNNEL-positive myocytes,disrupted normal arrangement of cardiac fibers,and increased Sirius stained collagen fibers.The expression levels of hypoxia induced factor（HIF）-l α,NF-κB,IL-6,and matrix metallopeptidase 2（MMP-2） were significantly increased in the heart of rats exposed to chronic intermittent hypoxia.In conclusion,the left ventricular function was adversely affected by chronic intermittent hypoxia,which is associated with increased expression of HIF-lα and NF-κB signaling molecules and development of cardiac inflammation,apoptosis and fibrosis.

Effect of NADPH Oxidase Inhibitor Apocynin on the Expression of Hypoxia-induced Factor-1α and Endothelin-1 in Rat Carotid Body Exposed to Chronic Intermittent Hypoxia

The effects of nicotinamide adenine dinucleotide phosphate （NADPH） oxidase inhibitor apocynin on the enhanced hypoxia induced factor-let （HIF-lct） and endothelin-1 （ET-1） expression, elevated systolic blood pressure under chronic intermittent hypoxia （CIH） condition and its action mechanism were investigated. Thirty healthy 8-week old Sprague-Dawley （SD） male rats were randomly divided into three groups （n=10 each）： sham group, CIH group, and apocynin-treated CIH group. Tail artery systolic blood pressure was measured by tail-cuff method. Real-time fluorescence quantitative polymerase chain reaction （PCR） was used to detect the mRNA expression of HIF-lu and ET-1 in the carotid body, and the HIF-1a protein expression was examined by using Western blotting. The levels of malondialdehyde （MDA） and superoxide dismutase （SOD） were determined by using colorimetric method. In addition, the plasma ET-1 and HIF-1a levels were measured by using enzyme-linked immunosorbent assay. It was found that CIH exposure was associated with increased MDA levels, and apo- cynin-treated CIH animals showed reduction in MDA levels. Apocynin treatment prevented CIH-induced hypertension as well as CIH-induced decrease in SOD. The increases of HIF-1a and ET-1 mRNA along with HIF-la protein expression in the carotid body, and elevated circulating HIF-1a and ET-1 levels were observed in CIH-exposed animals. Treatment with apocynin significantly decreased the ET-1 mRNA, HIF-lct protein expression and circulating HIF-la level in CIH-exposed animals, and there was no statistically significant difference in the HIF-lu mRNA expression between CIH group and apo- cynin-treated group. These results indicated that apocynin alleviated CIH-induced hypertension by inhibiting NADPH oxidase, further leading to the reduced vasoconstrictor ET-1 level and oxidative stress. HIF-1a/ET-1 system signal pathway may interact with CIH-induced NADPH oxidase-dependent oxidative stress. Inhibition of NADPH oxidase activity may hopefully serve as a useful strategy for prevention and treatment of obstructive sleep apnea hypopnea syndrome-induced hypertension.

Impairment of cognitive function and reduced hippocampal cholinergic activity in a rat model of chronic intermittent hypoxia

The present study established a rat model of chronic intermittent hypoxia （CIH） to simulate obstructive sleep apnea syndrome. CIH rats were evaluated for cognitive function using the Morris water maze, and neuronal pathology in the hippocampus was observed using hematoxylin-eosin staining. In addition, hippocampal choline acetyl transferase （CHAT） and nicotinic acetylcholine receptor （nAChR） expression was determined by immunohistochemistry. Our results revealed necrotic hippocampal neurons, decreased ChAT and nAChR expression, as well as cognitive impairment in CIH rats. These results suggest that hippocampal neuronal necrosis and decreased cholinerqic activity may be involved in CIH-induced cognitive impairment in rats.

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%O_(2),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.

Ginsenoside Rb1 alleviates chronic intermittent hypoxia-induced diabetic cardiomyopathy in db/db mice by regulating the adenosine monophosphate-activated protein kinase/Nrf2/heme oxygenase-1 signaling pathway

OBJECTIVE:To examine the protective effect of ginsenoside Rb1(Rb1),the main component of Renshen(Radix Ginseng),on cardiomyopathy in db/db mice exposed to chronic intermittent hypoxia(CIH)and explore the potential underlying mechanism of Rb1 in treating diabetic cardiomyopathy(DCM).METHODS:The db/db mice were randomly separated into five groups:normal control group,model group,Rb120 mg/kg group,Rb140 mg/kg group,and glucagon-like peptide-1(GLP-1)group.Mice were exposed to aircondition or CIH for 8 weeks,and Rb1 and GLP-1 were administrated before CIH exposure every day.Oral glucose tolerance test(OGTT),intraperitoneal insulin tolerance test(IPITT),total cholesterol(TC),triglyceride(TG),and high-density lipoprotein cholesterol(HDL-C)were detected to evaluate glycolipid metabolism.The level of insulin was detected by a mouse enzyme-linked immunosorbent assay(ELISA).Cardiac function was detected by echocardiography,and myocardial pathology was observed by hematoxylin-eosin and Masson staining.The expression of collagenⅠand collagenⅢwas detected by immunohistochemistry.Adenosine monophosphate-activated protein kinase(AMPK)/Nrf2/heme oxygenase-1(HO-1)signaling pathway was detected by Western blot and immunofluorescence.RESULTS:Rb1 treatment could improve glucose tolerance and the level of cardiac function indexes,and inhibit the level of oxidative stress indexes and the expression of collagenⅠand collagenⅢ.Moreover,Rb1 treatment enhanced AMPK phosphorylation and increased Nrf2 and HO-1 expression.CONCLUSION:Rb1 treatment alleviated CIH-induced diabetic cardiomyopathy and glycolipid metabolism disorders in db/db mice by inhibiting oxidative stress and regulating the AMPK/Nrf2/HO-1 signaling pathway.

Hippocampal impairments are associated with intermittent hypoxia of obstructive sleep apnea

Obstructive sleep apnea （OSA）,which is the most common sleep-related breathing disorder,is characterized as frequent upper airway collapse and obstruction.It is a treatable disorder but if left untreated is associated with complications in several organ systems.The health risk to OSA patients shows a strong association with acute cardiovascular events,and with chronic conditions.To the central nervous system,OSA causes behavioral and neuropsychologic deficits including daytime sleepiness,depression,impaired memory,mood disorders,cognition deficiencies,language comprehension and expression deficiencies,all of which are compatible with impaired hippocampal function.Furthermore,there exists a significant correlation between disease severity and cognitive deficits in OSA.Children with severe OSA have significantly lower intelligence quotient （IQ） and executive control functions compared to normal children matched for age,gender and ethnicity.This corroborates the findings of several pediatric studies of cognition in childhood OSA,where deficits are reported in general intelligence and some measures of executive function.In studies of OSA,it is difficult to differentiate the effects of its two main pathologic traits,intermittent hypoxia （IH） and sleep fragmentation.Many OSA studies,utilize IH as the only exposure factor in OSA studies.These approaches simplify research process and attain most of the academic goals.IH,continuous hypoxia and intermittent continuous hypoxia can all result in decreases in arterial O2.There are striking differences to them in the response of physiological systems.There are multiple studies showing that IH treatment in a rodent model of OSA can impair performance of standard water maze tests associated with deficits in spatial learning and memory which most likely are hippocampal-dependent.Cellular damage to the hippocampal cornuammonis 1 （CA1） region likely contributes to neuropsychological impairment among OSA patients,since neural circuits in the hippocampus are important in learning and memory.In this article,studies of hippocampal impairments from IH are reviewed for elucidating the mechanisms and relationships between hippocampal impairments and IH of OSA.

The effect of oxidative stress in myocardial cell injury in mice exposed to chronic intermittent hypoxia

Background Obstructive sleep apnea syndrome （OSAS） is an important risk factor for cardiovascular diseases. Chronic intermittent hypoxia （CIH） is considered to be one of the most important causes of cardiovascular diseases in OSA patients. This repeated hypoxia and reoxygenation cycle is similar to hypoxia-reperfusion injury, which initiates oxidative stress. In this study, we observed cardiocytes injury induced by CIH and the effect of N-acetylcysteine （NAC）. Methods Thirty ICR mice were randomly assigned to 3 groups： control, CIH and NAC （CIH＋NAC） groups. Malondialdehyde （MDA） and superoxide dismutase （SOD） of cardiocyte homogenates were measured. Serum lipids were measured by an instrument method. Serum cardiac troponin I （cTnl） was detected by enzyme-linked immunosorbent assays （ELISA）. Myocardium pathological sections were observed. Results （1） The SOD activity and MDA concentration of cardiocyte homogenates in the CIH group were significantly higher than in other groups （P 〈0.005）. The MDA concentration of the NAC group was lower than that of the control group （P 〈0.01）. （2） The serum cTnl concentration of the CIH and NAC groups was significantly higher than that of the control group （P 〈0.01）. （3） Serum triglyceride levels in the NAC group were lower than in the other groups （P 〈0.01）, while there were no significant differences in low density lipoprotein and high density lipoprotein among the three groups. （4） The degeneration of myocardium, transverse striation blurred, and fabric effusion were observed in tissue sections in the CIH and NAC groups. However, normal tissue was found in the control group. Conclusion The oxidative stress induced by CIH can injure cardiocytes and the injury effect can be partially inhibited by NAC.

Chronic Intermittent Hypoxia and Hypertension:A Review of Systemic Inflammation and Chinese Medicine

Obstructive sleep apnea syndrome （OSAS） and hypertension commonly coexist. Clinical studies indicate that OSAS plays a key role in increasing the risk of prevalent hypertension. Chronic intermittent hypoxia （CIH） is the core pathological mechanism of OSAS, and has a close relationship with systemic inflammation. Growing evidence shows that CIH and hypertension are strongly related, involving markers or pathways indicative of systemic inflammation, such as high-sensitivity C-reactive protein （hs-CRP）, interteukin-6, nuclear factor-kappa B, tumor necrosis factor-α, interleukin-8 and p38 mitogen-activated protein kinase （MAPK）dependent pathways. Oxidative stress also plays an important role in this process, including in the activation of polymorphonuclear neutrophils. However, the pathophysiological and clinical significance of systemic inflammation in CIH and hypertension is not proven. This review article highlights the relationship between CIH and hypertension through systemic inflammation and the current interventions available in Chinese medicine, to offer a background for the future treatment of OSAS-related hypertension with integrative medicine.

Altered Wnt Signaling Pathway in Cognitive Impairment Caused by Chronic Intermittent Hypoxia： Focus on Glycogen Synthase Kinase-3β and β-catenin

Background： Cognitive impairment is a severe complication caused by obstructive sleep apnea （OSA）. The mechanisms of causation are still unclear. The Wntβ-catenin signaling pathway is involved in cognition, and abnormalities in it are implicated in neurological disorders. Here, we explored the Wntβ-catenin signaling pathway abnormalities caused by chronic intermittent hypoxia （CIH）, the most characteristic pathophysiological component of OSA. Methods： We divided 32 4-week-old male C57/BL mice into four groups of eight each： a CIH ＋ normal saline （NS） group, CIH ＋ LiCI group, sham CIH ＋ NS group, and a sham CIH ＋ LiCI group. The spatial learning performance of each group was assessed by using the Morris water maze （MWM）. Protein expressions of glycogen synthase kinase-β （GSK-β） and β-catenin in the hippocampus were examined using the Western blotting test. EdU labeling and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling staining methods were used, respectively, to determine the proliferation and apoptosis of neurons in the hippocampal dentate gyrus region. Results： Mice exposed to CIH showed impaired spatial learning performance in the MWM, including increased mean escape latencies to reach the target platform, decreased mean times passing through the target platform and mean duration in the target quadrant. The GSK-313 activity increased, and expression of β-catenin decreased significantly in the hippocampus of the CIH-exposed mice. Besides, CIH significantly increased hippocampal neuronal apoptosis, with an elevated apoptosis index. Meanwhile, LiCI decreased the activity of GSK-β and increased the expression of β-catenin and partially reversed the spatial memory deficits in MWM and the apoptosis caused by CIH. Conclusions： Wntβ-catenin signaling pathway abnormalities possibly play an important role in the development of cognitive deficits among mice exposed to CIH and that LiCI might attenuate CIH-induced cognitive impairment via Wntβ-catenin signaling pathway.

Changes in genioglossus and their association with serum adiponectin levels in rats subjected to chronic intermittent hypoxia

Background The genioglossus （GG） is involved in the maintenance of an open airway for effective breathing.Although the pathogenesis of obstructive sleep apnea hypopnea syndrome （OSAHS） was closely associated with GG dysfunction,its causes and possible treatment have not been elucidated.The aim of the study was to investigate the effects of chronic intermittent hypoxia （CIH） on serum adiponectin levels, electromyograph （EMG） activity and ultrastructure of GG, as well as the effect of an adiponectin supplement in anesthetized rats.Methods Forty-two healthy male Wistar rats were randomly divided into normal control （A）, CIH （B） and adiponectin treatment （C） groups, 14 rats in each group.CIH was performed eight hours per day for five weeks in both groups B and C.Group C received transvenous injection of adiponectin at the dosage of 10 μg per injection, twice a week for five weeks.At the end of the 5th week the GG EMG voltage was measured and compared among the three groups.Transmission electron microscope was used to observe the ultrastructure of the GG.Results CIH caused significant hypoadiponectinemia, weakened activity of GG EMG at both baseline and hypoxia stimulation, and induced ultrastructural pathological changes, such as, myofibril discontinuities, lysis of myofilament,edema of mitochondria and disruption of cristae, vacuolus and lysis of some mitochondria.Venous supplement of adiponectin improved the above pathological changes resulting from CIH.Conclusion CIH resulted in pathological changes in GG＇s EMG and ultrastructure, which could be improved by supplement of adiponectin and be associated with hypoadiponectinemia caused by ClH.

Thioredoxin and impaired spatial learning and memory in the rats exposed to intermittent hypoxia

Background Obstructive sleep apnea （OSA） can cause cognitive dysfunction and may be a reversible cause of cognitive loss in patients with Alzheimer＇s disease （AD）. Chronic exposure to intermittent hypoxia （IH）, such as encountered in OSA, is marked by neurodegenerative changes in rat brain. We investigated the change of thioredoxin （Trx）, spatial learning and memory in rats exposed to chronic intermittent hypoxia （CIH）. Methods Forty healthy male Sprague-Dawley （SD） rats were randomly divided into four groups of ten each： a CIH＋normal saline （CIH＋NS group）, a N-acetylcystein-treated CIH （CIH＋NAC） group, a sham CIH group （sham CIH＋NS）, and a sham NAC-treated sham CIH （CIH＋NAC） group. Spatial learning and memory in each group was assessed with the Morris water maze. Real-time PCR and Western blotting were used to examine mRNA and protein expression of Trx in the hippocampus tissue. The terminal deoxynucleotidyl transferase-mediated dUTP-nick end-labeling （TUNEL） method was used to detect the apoptotic cells of the hippocampus CA1 region. Results CIH-rats showed impaired spatial learning and memory in the Morris water maze, including longer mean latencies for the target platform, reduced numbers of passes over the previous target platform and a smaller percentage of time spent in the target quadrant. Trx mRNA and protein levels were significantly decreased in the CIH-hippocampus, meanwhile, an elevated apoptotic index revealed apoptosis of hippocampal neurons of rats exposed to CIH. The rats, which acted better in the Morris water maze, showed higher levels of the Trx mRNA and protein in the hippocampus; apoptotic index of the neurons in the hippocampus of each group was negatively correlated with the Trx mRNA and protein levels. Conclusion The Trx deficit likely plays an important role in the impaired spatial learning and memory in the rats exposed to CIH and may work through the apoptosis of neurons in the hippocampus.

Ang II type 1 receptor expression in rat aorta exposed to chronic intermittent hypoxia： effects of p38MAPK and ERK1/2 signaling

Background Obstructive sleep apnea is a frequent medical condition consisting of repetitive sleep-related episodes of upper air ways obstruction and can lead to hypertension. Ang II type 1 receptor （AT1R） played important roles in hypertension since it binds with Ang II, controlling salt-water and blood pressure homeostasis. This study explores rat aorta AT1R expression during intermittent hypoxia （IH） and the signaling pathways involved. Methods A rat model and a cell model used a BioSpherix-OxyCycler A84 system and a ProOx C21 system respectively. The arterial blood pressure was recorded by a Nihon Kohden Polygraph System. Immunohistochemic was used to focus and analyze the expression of AT1R in rat aorta. Real-time PCR and Western blotting were used to explore the signaling pathways that participated in AT1R expression. Results In this study, we found that chronic intermittent hypoxia （CIH） induced AT1R transcription which increased the blood pressure in rat aorta compared to normoxia and to sustained hypoxia. The AT1R protein expression in the aorta was similar to the real-time PCR results. We explored the signaling mechanisms involved in the AT1R induction in both rat aorta and the aortic endothelial cells by real-time PCR and Western blotting. Compared to normoxia, CIH increased ERK1 mRNA transcription but not ERK2 or p38MAPK in the aorta; whereas sustained hypoxia （SH） upregulated ERK2 but not ERK1 or p38MAPK mRNA. In cells, IH induced AT1R expression with ERK1/2 phosphorylation but reduced p38MAPKs phosphorylation, whereas SH induced only ERK1/2 phosphorylation. The ERK1/2 inhibitor PD98059 attenuated the IH- induced AT1R increase but the p38MAPK inhibitor SB203580 did not. Conclusions Our results indicate that CIH induced the elevation of rat blood pressure and aorta AT1R expression. Moreover, ATIR expression in IH and sustained hypoxia might be regulated by different signal transduction pathways, highlighting a novel regulatory function through ERK1/2 signaling in IH.

Chronic intermittent hypoxia aggravates cardiomyocyte apoptosis in rat ovariectomized model

Background The prevalence of obstructive sleep apnea （OSA） increases after menopause in women, but remains under diagnosed because of social or lifestyle factors. It is important to evaluate the hazards of OSA on cardiovascular disease in menopausal women. We tested the hypothesis that chronic intermittent hypoxia （CIH） may aggravate cardiomyocyte apoptosis in ovariectomized （OVX） Sprague Dawley （SD） rats; the changes of anti-oxidation ability in cardiac muscles may be one of the reasons for cardiomyocyte apoptosis. Methods Forty-eight 60-day old female SD rats were randomly divided into a CIH group, OVX group, OVX±CIH （OC） group, and handled control （HC） group, and the rats were exposed either to CIH （nadir 02 6%） or handled normoxic controls. The changes of body weight and whole heart weight were measured. Super oxide dismutase （SOD） and malonaldehyde （MDA） were used to evaluate the level of oxidative stress. TdT-mediated dUTP nick end labeling （TUNEL） was used to measure apoptosis in each rat. Western blotting was used to measure apoptosis associated proteins in cardiac muscle samples from each rat. Results When compared with the HC and CIH groups, the levels of oxidative stress in the OC and OVX groups were significantly higher. The levels of SOD in the HC, CIH, OC, and OVX groups were （47.99±4.89）, （53.60±4.47）, （20.99±2.72）, and （30.64±3.79） mmol/mg protein; significantly increased in the CIH group （P 〈0.05） and significantly decreased in the OC （P 〈0.01） and OVX （P 〈0.05） groups. The levels of MDA in the HC, CIH, OVX, and OC groups were （1.63±0.20）, （1.93±0.77）, （3.30±0.39）, and （1.95_±0.20） mmol/mg protein; it significantly increased in the CIH （P 〈0.05）, OC （P 〈0.01）, and OVX （P 〈0.05） groups compared with the HC group. Bax protein expression was significantly increased and bcl-2 protein expression was significantly reduced after CIH compared with HC rats （P 〈0.05）. The protein expression of bax and bcl-2 in the OC group was not significantly different from the CIH group, but the ratio of bax/bcl-2 was significantly increased in the OC group （P 〈0.05）; this was associated with severe cardiomycyte apoptosis in the OC group. TUNEL confirmed this observation. Conclusions This study found that CIH may induce oxidative stress in OVX rats but not in CIH rats, and cause more severe cardiomyocyte apoptosis in OVX rats compared with CIH rats. This means that OVX rats exposed to CIH suffered more severe cardiac injury compared with CIH rats due to reduced antioxidation. These findings may partly explain the reason why OSA has a worse cardiovascular impact on menopausal women, and emphasize the importance of detection and early treatment of OSA in menopausal patients.

Adiponectin protects the genioglossus of rats against chronic intermittent hypoxia-induced injury via inhibition of endoplasmic reticulum stress

Background Obstructive sleep apnea hypopnea syndrome, characterized by chronic intermittent hypoxia （CIH）, is closely correlated with genioglossus dysfunction. CIH has been identified to mediate mitochondrial damage in genioglossus. It has been reported that endoplasmic reticulum stress （ERS） could be induced by mitochondrial dysfunction. This study aimed to investigate the role of ERS in CIH-induced genioglossus injury, as well as the possible intervention effect of adiponectin （Ad） supplement in rats. Methods Forty-five male Wistar rats were randomly divided into three groups and submitted to room air （group A, n=15） as a control or CIH （groups B and C, n=15, respectively）. Throughout the exposure period, intravenous Ad was given in group C; while intravenous normal saline was simultaneously given in groups A and B. After 35-day exposure, genioglossus samples were obtained from the pentobarbital-anaesthetized rats via surgical dissection, following blood sampling. Western blotting was applied to detect expressions of ERS signals and associated apoptotic pathways in genioglossus. Serum adiponectin levels were assessed via enzyme-linked immunosorbent assay （ELISA）. Results Significant hypoadiponectinemia was revealed in group B only （P 〈0.05）. Compared to those in groups A and C, expressions of markers involved in ERS, such as glucose regulated protein 78 （GRP78）, p-PERK, phosphorylated eukaryotic initiation factor 2α （p-elF2α）, phosphorylated inositol-requiring transmembrane kinase/endoribonuclease 1α （p-IRE1α）, spliced X-Box binding protein 1 （XBPls） and activating transcription factor 6 （ATF6）, were significantly enhanced in group B （all P 〈0.01）; while no significant difference was shown between groups A and C （all P 〉0.05）. ERS- associated apoptotic pathways were remarkably activated in group B. The involved markers detected as the expression of CCAAT/enhancer binding protein homologous protein （CHOP）, B-cell lymphoma/leukemia associatied X protein （BAX） and caspase-12 were significantly elevated （all P 〈0.01）. Transvenous adiponectin supplement improved the above CIH- induced pathological changes in group C. Conclusion Beyond hypoadiponectinemia, CIH could enhance ERS and induce activation of ERS-associated apoptotic pathways in genioglossus, which could be significantly improved by adiponectin supplement.