Chronic Intermittent Hypoxia Group Research Articles

Transient upregulation of TASK-1 expression in the hypoglossal nucleus during chronic intermittent hypoxia is reduced by serotonin 2A receptor antagonist.

Hypoglossal motoneurons innervate genioglossus muscle, the contraction of which is critical in the maintenance of upper airway patency in patients with obstructive sleep apnea. As a potassium channel distributed in hypoglossal motoneurons, TWIK-related acid-sensitive K+ channel-1 (TASK-1) could be inhibited by 5-HT. This study aimed to investigate if TASK-1 expression in hypoglossal nucleus could be influenced by chronic intermittent hypoxia (CIH) and 5-HT2A receptors antagonist. Two hundred twenty-eight rats were exposed to CIH or normoxia (NO) in the presence and absence of 5-HT 2A receptor antagonist (MDL-100907) microinjected into the hypoglossal nucleus. The expression of 5-HT and TASK-1 in the hypoglossal nucleus were detected by immunohistochemistry and reverse transcription quantitative polymerase chain reaction on the 1st, 3rd, 7th, 14th and 21st day of CIH exposure. The mean optical density (MOD) of 5-HT in the XII nucleus was significantly increased in the CIH and CIH + MDL group than the NO group on the 7th and 21st day ( p < 0.05). Compared with the NO group, the MOD and gene expression of TASK-1 in the CIH group was significantly increased on the 7th and 14th day ( p < 0.05), then normalized on the 21st day. The TASK-1 expression in the CIH + MDL group was significantly lower than the CIH + PBS and CIH group on the 7th and 14th day ( p < 0.05). The CIH-induced transiently upregulation of the TASK-1 expression in the hypoglossal nucleus could be reversed by 5-HT 2A receptor antagonist, indicating that the modulation of the TASK-1 expression in response to CIH involves 5-HT and 5-HT 2A receptors, and this CIH effect might be 5-HT 2A receptor-dependent.

Maternal chronic intermittent hypoxia in rats causes early atherosclerosis with increased expression of Caveolin-1 in offspring.

The objective of our research was to explore the effects of maternal and postpartum chronic intermittent hypoxia (CIH) exposure on atherosclerosis in adulthood offspring of rats, and the role of Caveolin-1 in the course. Sixteen rats were assigned to two groups (n = 8), maternal normoxia and CIH group. After delivery, two male pups per litter were selected and breastfed for 1month, which then randomly received postpartum normoxia or CIH. Thus, 4 groups were created as follows (n = 8): (1) maternal normoxia and postpartum normoxia group, (2) maternal CIH and postpartum normoxia group, (3) maternal CIH and postpartum CIH group, and (4) maternal normoxia and postpartum CIH group. The offspring were weighed at birth and weaning. After the duration of 12-week experiment, morphological changes, the expression of Caveolin-1 and NF-κB p65 in the aorta were detected. Maternal CIH resulted in significantly lower body weight and thicker intima (P < 0.001). CIH upregulated the expression of Caveolin-1 and NF-κB p65 significantly (P < 0.01). There was a synergistic effect of maternal and postpartum CIH on the thickening of intima (P < 0.05), also on the expression of Caveolin-1 and NF-κB p65 (P < 0.01). The results demonstrate that maternal CIH exposure causes a postpartum catch-up growth and early atherosclerotic changes followed by upregulating Caveolin-1 expression. Besides, maternal CIH enhances the atherosclerotic changes caused by postpartum CIH. Oxidative stress probably implicates in above effects.

Renal cortical oxygen tension is decreased following exposure to long-term but not short-term intermittent hypoxia in the rat.

Chronic kidney disease (CKD) occurs in more than 50% of patients with obstructive sleep apnea (OSA). However, the impact of intermittent hypoxia (IH) on renal function and oxygen homeostasis is unclear. Male Sprague-Dawley rats were exposed to IH (270 s at 21% O2; 90 s hypoxia, 6.5% O2 at nadir) for 4 h [acute IH (AIH)] or to chronic IH (CIH) for 8 h/day for 2 wk. Animals were anesthetized and surgically prepared for the measurement of mean arterial pressure (MAP), and left renal excretory function, renal blood flow (RBF), and renal oxygen tension (Po2). AIH had no effect on MAP (123 ± 14 vs. 129 ± 14 mmHg, means ± SE, sham vs. IH). The CIH group was hypertensive (122 ± 9 vs. 144 ± 15 mmHg, P < 0.05). Glomerular filtration rate (GFR) (0.92 ± 0.27 vs. 1.33 ± 0.33 ml/min), RBF (3.8 ± 1.5 vs. 7.2 ± 2.4 ml/min), and transported sodium (TNa) (132 ± 39 vs. 201 ± 47 μmol/min) were increased in the AIH group (all P < 0.05). In the CIH group, GFR (1.25 ± 0.28 vs. 0.86 ± 0.28 ml/min, P < 0.05) and TNa (160 ± 39 vs. 120 ± 40 μmol/min, P < 0.05) were decreased, while RBF (4.13 ± 1.5 vs. 3.08 ± 1.5 ml/min) was not significantly different. Oxygen consumption (QO2) was increased in the AIH group (6.76 ± 2.60 vs. 13.60 ± 7.77 μmol/min, P < 0.05), but it was not significantly altered in the CIH group (3.97 ± 2.63 vs. 6.82 ± 3.29 μmol/min). Cortical Po2 was not significantly different in the AIH group (46 ± 4 vs. 46 ± 3 mmHg), but it was decreased in the CIH group (44 ± 5 mmHg vs. 38 ± 2 mmHg, P < 0.05). For AIH, renal oxygen homeostasis was preserved through a maintained balance between O2 supply (RBF) and consumption (GFR). For CIH, mismatched TNa and QO2 reflect inefficient O2 utilization and, thereby, sustained decrease in cortical Po2.

Intervention effects and mechanism of Chinese herbal medicine of supplementing Qi and activating blood circulation on chronic intermittent hypoxia composite insulin resistance ApoE~(-/-) mice model

This study aims to observe the intervention effects of Chinese herbal medicine of supplementing Qi and activating blood circulation on chronic intermittent hypoxia(CIH) composite insulin resistance(IR) mediated atherosclerosis(AS) mice model,and to observe the mechanism of SREBP-1 c signaling molecule.IR Apo E-/-mice model was induced by high-fat diet combined with STZ injection.Then the mice were treated with hypoxic animal incubator for 8 h per day and 8 weeks to establish a CIH+IR-ApoE-/-mouse model.Model mice were randomly and averagely divided into normoxic control group(NC),model group(CIH) and SREBPs inhibitor group(betulin),atorvastatin group(WM),TCM low-dose group(TCM-L),TCM middle-dose group(TCM-M) and TCM high-dose group(TCM-H) group.Chinese herbal medicine of supplementing Qi and activating blood circulation including ginsenosides combined with ligustrazine(TMP) were used as intervention drugs.The study observed the effect of drugs on IR,serum lipid,inflammation,stress,AS and SREBP-1 c related molecules.The results showed that fasting blood glucose in TCM-H group decreased compared with other experimental groups(P<0.05).HDL-C level in betulin group,WM group,TCM-H group was higher than that in CIH group(P<0.05).LDL-C level in TCM-M group,TCM-H group is lower than that in CIH group(P<0.05).The level of CRP in CIH group was higher than that in other groups(P<0.05).The level of SOD in TCM-H group was higher than that in CIH group(P<0.05).NC group and CIH group showed obvious AS aortic plaque,while betulin group,WM group,TCM-H group showed reduction in AS plaque(P<0.05).For descending aorta,AS plaque in CIH group was multiple and large,while less and smaller in WM group and TCM-H(P<0.05).The expression of SREBP-1 c and FAS in aorta and skeletal muscle in TCM-H group was lower than that in CIH group(P<0.05).In aorta,the expression of TNF-α and CD106(VCAM-1) was lower in TCM-H group than that in CIH group(P<0.05).In aorta,skeletal muscle and liver,the level of p-IRS-1 in TCM-H group was significantly higher than that in CIH group(P<0.05).In aorta and liver,the expression of HIF-1α in TCM-H group was lower than that in CIH group(P<0.05).The study demonstrated that combination ginsenosides with TMP could improve IR and serum lipid level and inhibit inflammation and oxidative stress as well as ultimately alleviate AS to some extent.And the mechanism of its interventional effects might be related to the inhibition of CIH-induced upregulation of SREBP-1 c related molecules.

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 Cox4i1 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 Cox4i1, 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.

Changes and Significance of SYP and GAP-43 Expression in the Hippocampus of CIH Rats.

Synaptophysin (SYP) and growth-associated binding protein 43 (GAP-43) have been shown to be closely related to hippocampal synaptic plasticity in recent years. They are important molecular markers associated with synaptic plasticity. However, the role of SYP and GAP-43 in chronic intermittent hypoxic injury of the central nervous system needs to be further clarified. In this study, 25 adult male sprague dawley (SD) rats were randomly divided into a normal control group (CON) and a chronic intermittent hypoxia group (CIH) with four time points as follows: 1 W, 2 W, 3 W, and 4 W. The behavioural changes (primarily learning and memory abilities) were observed by the Morris water maze in each group, consisting of 5 rats per group.The localization of SYP and GAP-43 in hippocampal CA1 neurons was observed, and the expression of SYP and GAP-43 in the hippocampus was detected by Western blotting. The results showed that the mean oxygen saturation of the tail artery in CIH rats was less than that in normal rats (P < 0.05). The escape latency of CIH rats was longer than that of normal rats, and the number of space exploration platform crossings was less than that of normal rats. SYP-positive stained cells were yellow or brown and were mainly expressed on the cell membrane, while the GAP-43-positive staining was brown and was mainly expressed on the cell membrane and in the cytoplasm. The expression of SYP in plasma decreased gradually at the four time points for the CIH group (P < 0.05), while the expression of GAP-43 in the CIH 1W group increased (P < 0.05) and decreased gradually in the CIH 2 W, CIH 3 W and CIH 4 W groups (P < 0.05).

Endothelin-1-Mediated Mechanisms in the Carotid Body Modulates Cardiovascular Responses in Rats Exposed to Chronic Intermittent Hypoxia

Chronic intermittent hypoxia (CIH), the main feature of obstructive sleep apnea (OSA), is associated with hypertension. The increased of carotid body (CB) sensitivity due to enhanced sympathetic efferent may be mainly responsible for the elevation of blood pressure. Accordingly, we studied this effect of Endothelin-1 (ET-1)-induced CB chemosensory response to CIH, as a vasoactive peptide expressed in CB. The purpose of this study was to investigate the mean arterial blood pressure (MAP) and renal sympathetic nerve activity (RSNA) responses in CIH group by injecting ET-1 to directly stimulate CB chemoreceptor. Furthermore, whether ET receptor-mediated PKC and p38MAPK signaling pathway was involved in CIH-induced CB activation was also studied. Male Sprague–Dawley rats were exposed to CIH (8 h/day for 3 weeks) and the MAP and RSNA were recorded in CIH rats and Sham rats. Our results demonstrated that ET-1-induced MAP and RSNA increase were mainly mediated by ETA receptor activation in CB chemosensory after CIH exposure. Moreover, P38MAPK and PKC signaling pathway might be involved in ET-1-induced increase of MAP and RSNA in CIH group, which provided a potential therapeutic target of OSA.

The role of NF-κB-mediated JNK pathway in cognitive impairment in a rat model of sleep apnea.

The aim of this study is to determine the role of nuclear factor kappa B (NF-κB)-mediated c-Jun N-terminal kinase (JNK) pathway in cognitive impairment induced by chronic intermittent hypoxia (CIH). Ninety-six male Sprague-Dawley rats were randomly divided into 8 groups: sham group, sustained hypoxia (SH) group, CIH group, CIH + melatonin group, CIH + vitamin E group, CIH + DMSO group, CIH + BAY 11-7082 group and CIH + normal saline (NS) group. Rats were exposed to normoxia, CIH (21% O2 for 60 s and 10% O2 for 60 s, cyclically repeated for 10 h/day) or SH (10% O2 for 10 h/day) for 14 days. Afterwards, Morris water maze test was conducted, and serum and hippocampus tissues were subjected to molecular biological and biochemical analyses. Compared with the Sham and SH group, oxidative stress was induced by CIH in rat hippocampus with the high level of malondialdehyde (MDA) and 8-iso-PGF2α and the low level of superoxide dismutase (SOD) and glutathione (GSH). Activated NF-κB and its downstream products including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS) were highly expressed in CIH rats. These changes were attenuated by pretreatment of the rats with melatonin and vitamin E. CIH also resulted in hippocampus neuron apoptosis with increased caspase 3 level, dUIP nick end labeling (TUNEL)-positive neurons number and cognitive impairment verified by prolonged latency and shortened time in the target quadrant in Morris water maze test. JNK and its downstream transcriptional factors including c-Jun, activating transcription factor 2 (ATF2), and JunD were all significantly phosphorylated in CIH rats. However, pretreatment of NF-κB inhibitor BAY 11-7082 inhibited the activation of NF-κB under CIH condition and also significantly reduced the phosphorylation of JNK as well as c-Jun, ATF2, and JunD. Moreover, hippocampus neuron apoptosis and cognitive impairment were significantly improved with the pretreatment of BAY 11-7082 in rats subjected to CIH. These findings suggest that NF-κB-mediated JNK pathway is at least partially implicated in CIH-induced hippocampus neuron apoptosis and cognitive impairment. Inhibition of NF-κB activation provided a therapeutic potential for cognitive impairment in sleep apnea (SA).

Effect of doxycycline on chronic intermittent hypoxia-induced atrial remodeling in rats.

Atrial remodeling in the form of fibrosis is considered the basis in the development of atrial fibrillation (AF). The aim of this study was to investigate the effects of doxycycline on atrial remodeling induced by chronic intermittent hypoxia (CIH) and the mechanisms underlying such changes. Atotal of 45Sprague-Dawley rats were randomized into threegroups: control group, CIH group, CIH with doxycycline treatment (CIH-D) group. Arat model of atrial remodeling was established by CIH and Masson staining was used to evaluate the extent of atrial fibrosis. We studied the expression levels of microRNA-1 (miR-1), microRNA-21 (miR-21), microRNA-29b (miR-29b), microRNA-30 (miR-30), microRNA-133a (miR-133a), microRNA-328 (miR-328), transforming growth factor-β1 (TGF-β1), and connective tissue growth factor (CTGF). Atrial effective refractory period and AF inducibility were examined via isolated heart models of cardiac electrophysiology. Compared with the control rats, CIH rats showed higher atrial interstitial collagen deposition, increased AF inducibility, and increased miR-1, miR-21, miR-133a, miR-328, TGF-β1, and CTGF levels. Treatment with doxycycline significantly attenuated CIH-induced atrial fibrosis, improved AF inducibility, and reduced miR-1, miR-21, miR-133a, miR-328, TGF-β1, and CTGF. CIH induced significant atrial remodeling, which was attenuated by doxycycline in our rat model. These changes can be explained by the alterations initiated in the miR-133a/TGF-β1/CTGF pathway by doxycycline.

PO-080 Effect of Aerobic Exercise on Myocardial Mitochondria Fusion-Fission in Chronic Intermittent Hypoxia Mice

Objective Obstructive sleep apnea hypopnea syndrome (OSAHS) could impair the function of multiple organs because of repeated chronic intermittent hypoxia(CIH)/reoxygenation during sleep. Which is harmful to the health and economy of patients. It is found that exercise can protect the function of multiple organs in OSAHS patients, especially the heart function, while the specific mechanism is not clear. The purpose of this paper is to investigate the effects of aerobic exercise on cardiac contractile function and mitochondrial fusion-division of CIH mice.&#x0D; Methods C57/BL6 mice of 6 weeks old were used in this experiment. The mice were divided into 3 groups randomly: control group (C), intermittent hypoxia group (CIH), intermittent hypoxia plus exercise group (CIH+E), 10 mice in each group. A self-designed computer controlled chronic intermittent hypoxia device was used. Group C was treated with normal feeding for 5 weeks. The CIH group was treated with intermittent hypoxia for 8 hours a day for 5 weeks. The CIH+E group were treated with suitability running on treadmill after CIH treatment at the first week. Starting from week 2, this group were treated with 60 minutes of running stage after 8 hours of CIH treatment, total 5 weeks.&#x0D; After the experiment, the cardiac function of each group was measured by two- dimensional echocardiography. The interventricular septal thickness (IVS), left ventricular posterior wall thickness (LVPW), ejection fraction (EF) were measured. Ultrastructure and morphology of mitochondria in cardiomyocytes were observed by transmission electron microscopy (TEM). The expression of mitochondrial fusion (Mitofusin 1 (Mfn1), Mitofusin 2 (Mfn2), Op-ticatrophylopa (Opa1)) and fission (dynamic in-related protein 1(Drp1), mitogen 1, Fission1 (Fis1)) related genes were detected by RT-PCR.&#x0D; Results Intermittent hypoxia reduced IVS and EF in mice, suggesting that CIH caused the loss of cardiac myocytes. Compared with C group, LVPWd+IVSd in CIH+E group was significantly lower than that in C group (P&lt;0.01) and EF was significantly lower than that in CIH E group. The cardiomyocyte loss and cardiac contractile function of CIH+E mice were improved by aerobic exercise for 4 weeks.LVPWd+IVSd in CIH+E group was better than that in CIH group. The EF value of(P&lt;0.01) in group A was significantly higher than that in group CIH (P&lt;0.01).Intermittent hypoxia decreased heart weight/body weight ratio (HW/BW) and left ventricular weight/tibia length left ventricular weight/tibia (LVW/TL). Compared with the C group, the HW/BW in the CIH group was significantly lower than that in the C group, and the HW/BW in the CIH group was significantly higher than that in the CIH group. LVW/TL also increased significantly (P&lt;0.05), suggesting that intermittent hypoxia could lead to necrosis and decrease in number and weight of myocardial cells. (2)The results of mitochondrial electron microscope showed that compared with group C, the number of mitochondria decreased, the structure of mitochondria changed, and the number of myocardial mitochondria in CIH+E group increased after 4 weeks of aerobic exercise. Mitochondrial membrane and mitochondrial crest were repaired to improve the structure of myocardial mitochondria. (3) compared with C group, the mitochondrial fusion related gene Mfn2/OPA1 in CIH group was significantly lower than that in C group (P&lt;0.05, P&lt;0.05). Aerobic exercise significantly increased Mfn1,mfn2,OPA1 in CIH+E group than that in CIH group. Compared with C group, Mfn2,OPA1 in CIH group was significantly higher than that in CIH group. The Drp1 of the CIH+E group was significantly lower than that of the CIH group, and the Drp1 of the CIH+E group was significantly lower than that of the CIH group. 1 compared with CIH group, P&lt;0.01 was significantly lower than that of CIH group.&#x0D; Conclusions (1) aerobic exercise has protective effect on cardiac contractile function in intermittent hypoxia mice. (2) aerobic exercise can promote mitochondrial fusion in CIH mice, inhibit mitochondrial division, and protect myocardium by mediating mitochondrial function.

Beneficial effects of tolvaptan on atrial remodeling induced by chronic intermittent hypoxia in rats.

Atrial remodeling in the form of fibrosis is considered as the substrate for the development of atrial fibrillation (AF). The aim of this study was to investigate the effects of tolvaptan on chronic intermittent hypoxia (CIH) induced atrial remodeling and the mechanisms underlying such changes. A total of 45 Sprague-Dawley rats were randomized into three groups: Control group, CIH group, CIH with tolvaptan treatment (CIH-T) group (n=15). CIH rats were subjected to CIH 6hour/d for 30days, and CIH-T rats were administrated tolvaptan while they received CIH. After the echocardiography examination, rats were sacrificed in the 31days. In each group, 5 rats were randomly selected for isolated heart electrophysiology testing, for other 10 rats, the tissues of atria were sampled for histological and molecular biological experiments, Masson's trichrome staining was used to evaluate the extent of atrial fibrosis, expression levels of microRNA-21 (miR-21), Sprouty-1 (Spry1), phosphatase, and tensin homolog (PTEN), extracellular regulated protein kinase (ERK), phospho-extracellular regulated protein kinase (p-ERK), matrix metalloprotein 9 (MMP-9), phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), phospho-protein kinase B (p-AKT), nuclear factor-k-gene binding (NF-κB), phosphor-nuclear factor-k-gene binding (p-NF-κB) were measured. Compared to the Control rats, CIH rats showed higher atrial interstitial collagen deposition and AF inducibility, mRNA levels of miR-21, MMP-9, PI3K, AKT, and protein levels of ERK, p-ERK, MMP-9, NF-κB, p-NF-κB were significantly increased, whereas mRNA levels of Spry1, ERK, and protein levels of Spry1, PTEN, PI3K, AKT, p-AKT were significantly decreased. Treatment with tolvaptan attenuated CIH-induced atrial fibrosis, reduced AF inducibility, expression levels of miR-21 and its downstream factors were also improved. CIH-induced significant atrial remodeling in our rat model, which was attenuated by tolvaptan. These changes may be explained due to alterations in miR-21/Spry1/ERK/MMP-9, miR-21/PTEN/PI3K/AKT, and NF-κB pathways by tolvaptan.

MicroRNA-1249 regulates the apoptosis of myocardial cells in rats with chronic intermittent hypoxia by autophagy

Objective: To investigate the regulation and possible mechanism of microRNA (miR)-1249 on myocardial apoptosis in chronic intermittent hypoxia rats. Methods: A total of 16male SD rats aged 8 weeks were randomly divided into 2 groups by the random number table: normoxia control group and chronic intermittent hypoxia group (CIH) (n=8 each). The CIH group was exposed to intermittent hypoxia every day from 9: 00 to 17: 00 for 8 consecutive weeks, while the control group received the same frequency of pulse air. Hemodynamic values were measured via a cannula inserted into right common carotid artery. The expressions of miR-1249 and microtubule-associated protein light chain 3 (LC3) mRNA were observed by real-time PCR. The expressions of LC3 and Cleaved Caspase-3 were detected by Western bolt. TUNEL staining was performed to detect myocardial apoptosis. The rat cardiomyocyte cell H9C2 was divided into normoxia group, intermittent hypoxia (IH) group and miR-1249 inhibitor transfected and IH treatment group (inhibitor group). At the end of the experiment, the activation of LC3 protein in each group of cells was determined. Results: Compared with normoxia control group, left ventricle end diastolic pressure (LVEDP) increased [(4.6±0.4) vs (2.2±0.1) mmHg (1 mmHg=0.133 kPa)], left ventricular systolic pressure (LVSP) , maximal rate of pressure decline (-dp/dtmax), and maximal rate of pressure development (+ dp/dtmax) decreased in CIH group [(92.7±4.1) vs (135.3±3.2) mmHg, (4 247±108) vs (7 626±235) mmHg/s, and (3 168±105) vs (6 028±81) mmHg/s] (all P<0.001). The expression of miR-1249 and LC3 mRNA were significantly higher in CIH group than that in normoxia control group (all P<0.001), and a positive correlation was found between the expression of LC3 mRNA and miR-1249. The expression of LC3 and Cleaved Caspase-3 protein in myocardial tissue of CIH rats were significantly higher than that of the normoxia control group (all P<0.001). The proportion of myocardial cell apoptosis in CIH rats was significantly higher than that in the normoxia control group [(23.84±4.94)% vs (2.93±0.73)%] (P<0.001). The activation of LC3 in myocardial cells of inhibitor group was significantly lower than that of IH group, but higher than that in normoxia group. Conclusions: CIH could induce LC3 by raising the expression of miR-1249, and then induce the activation of apoptosis protein Caspase3. It ultimately induces myocardial apoptosis.

Telmisartan attenuates kidney apoptosis and autophagy-related protein expression levels in an intermittent hypoxia mouse model

PurposeObstructive sleep apnea (OSA) is associated with renal impairs. As a novel pathophysiological hallmark of OSA, chronic intermittent hypoxia (CIH) enhances apoptosis and autophagy. The present study aims to evaluate the effect of telmisartan on CIH-induced kidney apoptosis and autophagy in a mouse model of OSA.Materials and methodsMice were randomly allocated to normoxia, CIH, and CIH+telmisartan groups (n = 12 in each group). The CIH exposure duration was 12 weeks. Mice in the CIH+telmisartan group received telmisartan administration. The terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and western blotting of Bax and cleaved caspase-3 were conducted for evaluating apoptosis in kidney tissue. While the autophagy-related proteins, beclin-1 and LC3, were also observed via western blotting.ResultsThe percentage of apoptotic cell in the CIH group was significantly higher than that of normoxia group; meanwhile, Bax and cleaved caspase-3 protein levels were increased in the CIH group than those of normoxia group (all p < 0.05). Compared with the normoxia group, mice in the CIH group had greater autophagy-related proteins (beclin-1 and LC3) expression. When compared to the CIH group, both the renal apoptosis and autophagy in the CIH+telmisartan group were decreased.ConclusionThe CIH accelerates renal apoptosis and autophagy levels. Telmisartan ameliorating those levels suggests that it might prevent renal impairs from the CIH in OSA patients.

Overexpression of filamin c in chronic intermittent hypoxia-induced cardiomyocyte apoptosis is a potential cardioprotective target for obstructive sleep apnea.

Chronic intermittent hypoxia (CIH) is key pathological mechanism of obstructive sleep apnea (OSA), which induced cardiac dysfunction. Filamin c (FLNC) is a muscle-restricted isoform and predominantly expressed in muscle tissue. In this study, we utilized a recently developed CIH rat model to mimic OSA, investigated the expression of FLNC in cardiomyocytes, and examined the correlations of FLNC with active caspase-3 to ascertain whether FLNC regulates the survival of cardiomyocytes. Forty Sprague-Dawley rats were randomly divided into normoxia and CIH groups. All rats were exposed either to normoxia or CIH 8h daily for 6weeks. Echocardiogram and HE staining were used to examine cardiac pathology, structure, and function. Body weight, heart weight, and blood gas values were recorded, respectively. The FLNC, Bax, Bcl-2, BNIP 3, and active caspase-3 proteins were detected by western blot; FLNC was examined by immunohistochemistry and immunofluorescence. Association of FLNC with cardiomyocyte apoptosis was detected by immunofluorescence. CIH induced cardiac injuries and caused arterial blood gas disorder. FLNC significantly increased in CIH-induced cardiomyocytes than that in normoxia tissues. Pro-apoptotic BNIP 3 and Bax proteins were significantly increased in CIH, whereas anti-apoptotic member Bcl-2 was decreased. Active caspase-3, a universal marker of apoptosis, was significantly increased in CIH group. Co-localizations of FLNC and active caspase-3 were observed in CIH group. These results suggested FLNC is implicated in the pathogenesis of CIH-induced cardiomyocyte apoptosis, and FLNC may serve as a novel cardioprotective target for OSA patients.

Doxycycline Attenuates Atrial Remodeling by Interfering with MicroRNA-21 and Downstream Phosphatase and Tensin Homolog (PTEN)/Phosphoinositide 3-Kinase (PI3K) Signaling Pathway.

BackgroundAtrial remodeling especially in the form of fibrosis is the most important substrate of atrial fibrillation (AF). The aim of this study was to investigate the effects of doxycycline on chronic intermittent hypoxia (CIH)-induced atrial remodeling and the pathophysiological mechanisms underlying such changes.Material/MethodsA total of 30 Sprague-Dawley rats were randomized into 3 groups: Control group, CIH group, and CIH with doxycycline treatment group. CIH rats were subjected to CIH 6 h/d for 30 days and treatment rats were administrated doxycycline while they received CIH. After the echocardiography examination, rats were sacrificed at 31 days. The tissues of atria were collected for histological and molecular biological experiments, Masson staining was used to evaluate the extent of atrial fibrosis, microRNA-21, and its downstream target phosphatase and tensin homolog (PTEN), phosphoinositide 3-kinase (PI3K) were assessed.ResultsCompared to the control group, the CIH rats showed higher atrial interstitial collagen fraction, increased microRNA-21, PI3K levels, and decreased PTEN levels. Doxycycline treatment attenuated CIH-induced atrial fibrosis, reduced microRNA-21 and PI3K, and increased PTEN.ConclusionsCIH induced significant atrial remodeling, which was attenuated by doxycycline in our rat model. These changes may be explained due to alterations in the microRNA-21-related signaling pathways by doxycycline.

Telmisartan protects chronic intermittent hypoxic mice via modulating cardiac renin-angiotensin system activity

BackgroundTo explore the effects of chronic intermittent hypoxia (CIH), which mimics sleep apnea syndrome, on the cardiac renin angiotensin system (RAS), and to investigate the cardiac protection of an angiotensin receptor blocker (ARB)telmisartan (TERT) against CIH.Methods32 healthy male C57B6J mice were randomly divided into CIH, ARB, blank and air control groups. CIH lasted for 12 weeks. Cardiac angiotensin converting enzyme (ACE), angiotensin converting enzyme 2 (ACE 2) and angiotensin II (Ang II) were evaluated by immunohistochemistry. Myocardial apoptosis were assessed by TUNEL assay and myocardial cell ultrastructure were observed under transmission electron microscope.ResultsCardiac ACE expression was higher in the CIH group than in blank and air control groups, which was decreased with TERT treatment. TERT treatment elevated the expression of cardiac ACE 2 and Ang II compared with CIH group. Myocardial cell and capillary endothelial cell apoptosis, mitochondrial injury were most severe in CIH groups, which were mitigated with TERT treatment.ConclusionsCIH changes the expression of cardiac ACE, ACE2 and Ang II, which may cause myocardial damage. TERT protects mice from CIH-linked cardiac damage via modulating the activity of RAS in the hearts.

Abstract 4019: The chronic intermittent hypoxia enhances cancer progression in lung cancer mouse model

Abstract Background: Obstructive sleep apnoea (OSA) is a very prevalent disorder charaterized by chronic intermittent hypoxia (CIH) and some reports suggested that OSA is related to increased incidence of cancer as well as cancer progression. The purpose of this study was to evaluate whether intermittent hypoxia with a time course similar to that found in OSA influence lung cancer development and progression in metastatic lung cancer animal model. Methods: C57/BL6 mice were divided into two groups; control condition (room air) or CIH. The mice of CIH group were exposed to IH for 2 weeks before and immediately for 2 weeks after tumour induction by tail vein injection of carcinoma cells. At day 14, the mice were sacrificed and measured cancer growth. Hypoxia inducible factor (HIF-1α), vascular endothelial growth factor (VEGF) and metastasis related matrix metalloproteinases (MMP) were measured by ELISA and gelatin zymography in lung tissue and serum, respectively. The mRNA expressions of epithelial mesenchymal transition markers were measured by real-time PCR in lung tissue. Results: The marked increase in tumor number and volume was found in CIH group (p &amp;lt; 0.05). The accumulation of total cell and neutrophils in BAL fluids and the activation of MMP -2 and -9 in serum were also increased by CIH. The level of HIF-1α in the nuclear fraction of pneumocytes and the expression of VEGF were increased significantly in CIH group compared to the control (p &amp;lt; 0.05). The mRNA expression of E-cadherin was decreased in CIH group compared to the control group while vimentin was increased. Conclusions: Our data shows that CIH is associated with enhanced proliferative and migratory properties of cancer. These results suggest evidence for the causal link between OSA and lung cancer progression. Key words: chronic intermittent hypoxia, obstructive sleep apnea, lung cancer Citation Format: SangHaak Lee, In Kyoung Kim, Hyeon Hui Kang, Hee Young Kwon, Hye Sun Kang, Chang Dong Yeo. The chronic intermittent hypoxia enhances cancer progression in lung cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4019.

Long-Term Chronic Intermittent Hypobaric Hypoxia Induces Glucose Transporter (GLUT4) Translocation Through AMP-Activated Protein Kinase (AMPK) in the Soleus Muscle in Lean Rats.

Background: In chronic hypoxia (CH) and short-term chronic intermittent hypoxia (CIH) exposure, glycemia and insulin levels decrease and insulin sensitivity increases, which can be explained by changes in glucose transport at skeletal muscles involving GLUT1, GLUT4, Akt, and AMPK, as well as GLUT4 translocation to cell membranes. However, during long-term CIH, there is no information regarding whether these changes occur similarly or differently than in other types of hypoxia exposure. This study evaluated the levels of AMPK and Akt and the location of GLUT4 in the soleus muscles of lean rats exposed to long-term CIH, CH, and normoxia (NX) and compared the findings.Methods: Thirty male adult rats were randomly assigned to three groups: a NX (760 Torr) group (n = 10), a CIH group (2 days hypoxia/2 days NX; n = 10) and a CH group (n = 10). Rats were exposed to hypoxia for 30 days in a hypobaric chamber set at 428 Torr (4,600 m). Feeding (10 g daily) and fasting times were accurately controlled. Measurements included food intake (every 4 days), weight, hematocrit, hemoglobin, glycemia, serum insulin (by ELISA), and insulin sensitivity at days 0 and 30. GLUT1, GLUT4, AMPK levels and Akt activation in rat soleus muscles were determined by western blot. GLUT4 translocation was measured with confocal microscopy at day 30.Results: (1) Weight loss and increases in hematocrit and hemoglobin were found in both hypoxic groups (p < 0.05). (2) A moderate decrease in glycemia and plasma insulin was found. (3) Insulin sensitivity was greater in the CIH group (p < 0.05). (4) There were no changes in GLUT1, GLUT4 levels or in Akt activation. (5) The level of activated AMPK was increased only in the CIH group (p < 0.05). (6) Increased GLUT4 translocation to the plasma membrane of soleus muscle cells was observed in the CIH group (p < 0.05).Conclusion: In lean rats experiencing long-term CIH, glycemia and insulin levels decrease and insulin sensitivity increases. Interestingly, there is no increase of GLUT1 or GLUT4 levels or in Akt activation. Therefore, cellular regulation of glucose seems to primarily involve GLUT4 translocation to the cell membrane in response to hypoxia-mediated AMPK activation.

DL-Propargylglycine protects against myocardial injury induced by chronic intermittent hypoxia through inhibition of endoplasmic reticulum stress.

Chronic intermittent hypoxia (CIH), an important basis of the pathogenesis of organ damage induced by obstructive sleep apnea syndrome (OSAS), is associated with myocardial injury, such as left ventricular dysfunction, apoptosis, and oxidative stress. Endogenous hydrogen sulfide (H2S) plays an important role in maintaining cardiovascular functions. Many studies have demonstrated that exogenous H2S has protective effects against myocardial injury induced by various cardiovascular diseases, and inhibiting the generation of endogenous H2S has opposite effects. However, the effect of DL-propargylglycine (PAG), an effective inhibitor of cystathionine γ-lyase (CSE)-synthesized H2S, on the regulation myocardial injury remains controversial. The present study was aimed to explore the influence of PAG on myocardial injury induced in rats by CIH. Sprague-Dawley rats were randomly divided into a normal control (NC) group, a CIH group, a NC + PAG group, and a CIH + PAG group. After establishing the CIH model in rats, blood pressure, left ventricular function, oxidative stress, apoptosis, and the level of endoplasmic reticulum (ER) stress were detected. In NC rats, PAG had no effect on blood pressure, but induced myocardial dysfunction and up-regulated oxidative stress and apoptosis of the myocardium. In the CIH + PAG group, pretreatment with PAG significantly reduced blood pressure and improved the left ventricular ejection fraction (LVEF) and the left ventricular fractional shortening (LVFS) compared to the CIH group. Significantly lower levels of oxidative stress, apoptosis, and the ER stress were detected in the CIH + PAG group than in the CIH group. These results suggest that PAG can protect the myocardium against CIH-induced injury through inhibition of endoplasmic reticulum stress.

A Role for Hypoxia‐inducible Factor 1‐alpha (HIF1a) Signaling in Suppressing Synaptic Plasticity and Spatial Memory During Intermittent Hypoxia

Although HIF1a signaling is commonly identified as a mediator of positive homeostatic responses to hypoxia, during intermittent hypoxia (IH), a primary effect of sleep apnea, HIF1a signaling can cause oxidative stress in the body. IH‐dependent oxidative stress can lead to pathophysiological changes throughout the nervous system associated with sleep apnea. The objective of this study is to determine whether HIF1a signaling during IH opposes or facilitates IH‐dependent suppression in synaptic plasticity and spatial memory. Both adult wildtype mice (WT) and mice heterozygous for HIF1a (HIF1a+/−) were either unexposed (control) or exposed to chronic intermittent hypoxia (CIH) for 10 days. Hippocampal brain slices (350 microns thick) were prepared from mice of each group. Extracellular recordings of the field excitatory postsynaptic potential (fEPSP) were made before and after the induction of long‐term potentiation (LTP) in area CA1. While LTP occurred in brain slices of WT from both groups, the magnitude of LTP was larger in the control group (164±6% of baseline, n=5) as compared to the CIH group (115±10% of baseline, n=5). LTP in the brain slices from the HIF1a+/− exposed to CIH was 152±10% of baseline (n=5), which was greater in magnitude compared to WT LTP in the CIH group. Ongoing experiments suggest spatial memory in the Barnes Maze is unaffected by CIH in HIF1a+/−. These findings show that IH‐dependent HIF1a signaling disrupts hippocampal synaptic plasticity and spatial memory, which may contribute to cognitive impairment associated with sleep apnea.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.