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Heinzinger CM, Lapin B, Thompson NR, Li Y, Milinovich A, May AM, Pena Orbea C, Faulx M, Van Wagoner DR, Chung MK, Foldvary-Schaefer N, Mehra R. Novel Sleep Phenotypic Profiles Associated With Incident Atrial Fibrillation in a Large Clinical Cohort. JACC Clin Electrophysiol 2024:S2405-500X(24)00451-1. [PMID: 39023484 DOI: 10.1016/j.jacep.2024.05.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Accepted: 05/02/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND While sleep disorders are implicated in atrial fibrillation (AF), the interplay of physiologic alterations and symptoms remains unclear. Sleep-based phenotypes can account for this complexity and translate to actionable approaches to identify at-risk patients and therapeutic interventions. OBJECTIVES This study hypothesized discrete phenotypes of symptoms and polysomnography (PSG)-based data differ in relation to incident AF. METHODS Data from the STARLIT (sleep Signals, Testing, And Reports LInked to patient Traits) registry on Cleveland Clinic patients (≥18 years of age) who underwent PSG from November 27, 2004, to December 30,2015, were retrospectively examined. Phenotypes were identified using latent class analysis of symptoms and PSG-based measures of sleep-disordered breathing and sleep architecture. Phenotypes were included as the primary predictor in a multivariable-adjusted Cox proportional hazard models for incident AF. RESULTS In our cohort (N = 43,433, age 51.8 ± 14.5 years, 51.9% male, 74.9% White), 7.3% (n = 3,166) had baseline AF. Over a 7.6- ± 3.4-year follow-up period, 8.9% (n = 3,595) developed incident AF. Five phenotypes were identified. The hypoxia subtype (n = 3,245) had 48% increased incident AF (HR: 1.48; 95% CI: 1.34-1.64), the apneas + arousals subtype (n = 4,592) had 22% increased incident AF (HR: 1.22; 95% CI: 1.10-1.35), and the short sleep + nonrapid eye movement subtype (n = 6,126) had 11% increased incident AF (HR: 1.11; 95% CI: 1.01-1.22) compared with long sleep + rapid eye movement (n = 26,809), the reference group. The hypopneas subtype (n = 2,661) did not differ from reference (HR: 0.89; 95% CI: 0.77-1.03). CONCLUSIONS Consistent with prior evidence supporting hypoxia as an AF driver and cardiac risk of the sleepy phenotype, this constellation of symptoms and physiologic alterations illustrates vulnerability for AF development, providing potential value in enhancing our understanding of integrated sleep-specific symptoms and physiologic risk of atrial arrhythmogenesis.
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Affiliation(s)
| | - Brittany Lapin
- Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA; Neurological Institute Center for Outcomes Research and Evaluation, Cleveland Clinic, Cleveland, Ohio, USA
| | - Nicolas R Thompson
- Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA; Neurological Institute Center for Outcomes Research and Evaluation, Cleveland Clinic, Cleveland, Ohio, USA
| | - Yadi Li
- Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA; Neurological Institute Center for Outcomes Research and Evaluation, Cleveland Clinic, Cleveland, Ohio, USA
| | - Alex Milinovich
- Department of Quantitative Health Sciences, Cleveland Clinic, Cleveland, Ohio, USA
| | - Anna M May
- Geriatric Research Education and Clinical Center, VA Northeast Ohio Healthcare System, Cleveland, Ohio, USA
| | - Cinthya Pena Orbea
- Sleep Disorders Center, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Michael Faulx
- Heart, Vascular, and Thoracic Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | | | - Mina K Chung
- Heart, Vascular, and Thoracic Institute, Cleveland Clinic, Cleveland, Ohio, USA; Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | | | - Reena Mehra
- Division of Pulmonary, Critical Care, and Sleep Medicine, University of Washington, Seattle, Washington, USA.
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Heinzinger CM, Thompson NR, Milinovich A, Diniz Araujo ML, Orbea CP, Foldvary‐Schaefer N, Haouzi P, Faulx M, Van Wagoner DR, Chung MK, Mehra R. Sleep-Disordered Breathing, Hypoxia, and Pulmonary Physiologic Influences in Atrial Fibrillation. J Am Heart Assoc 2023; 12:e031462. [PMID: 37947123 PMCID: PMC10727289 DOI: 10.1161/jaha.123.031462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 09/07/2023] [Indexed: 11/12/2023]
Abstract
Background We leverage a large clinical cohort to elucidate sleep-disordered breathing and sleep-related hypoxia in incident atrial fibrillation (AF) development given the yet unclear contributions of sleep-related hypoxia and pulmonary physiology in sleep-disordered breathing and AF. Methods and Results Patients who underwent sleep studies at Cleveland Clinic January 2, 2000, to December 30, 2015, comprised this retrospective cohort. Cox proportional hazards models were used to examine apnea hypopnea index, percentage time oxygen saturation <90%, minimum and mean oxygen saturation, and maximum end-tidal carbon dioxide on incident AF adjusted for age, sex, race, body mass index, cardiopulmonary disease and risk factors, antiarrhythmic medications, and positive airway pressure. Those with spirometry were additionally adjusted for forced expiratory volume in 1 second, forced vital capacity, and forced expiratory volume in 1 second/forced vital capacity. This cohort (n=42 057) was 50.7±14.1 years, 51.3% men, 74.1% White individuals, had median body mass index 33.2 kg/m2, and 1947 (4.6%) developed AF over 5 years. A 10-unit apnea hypopnea index increase was associated with 2% higher AF risk (hazard ratio [HR], 1.02 [95% CI, 1.00-1.03]). A 10-unit increase in percentage time oxygen saturation <90% and 10-unit decreases in mean and minimum oxygen saturation were associated with 6% (HR, 1.06 [95% CI, 1.04-1.08]), 30% (HR, 1.30 [95% CI, 1.18-1.42]), and 9% (HR, 1.09 [95% CI, 1.03-1.15]) higher AF risk, respectively. After adjustment for spirometry (n=9683 with available data), only hypoxia remained significantly associated with incident AF, although all coefficients were stable. Conclusions Sleep-related hypoxia was associated with incident AF in this clinical cohort, consistent across 3 measures of hypoxia, persistent after adjustment for pulmonary physiologic impairment. Findings identify a strong role for sleep-related hypoxia in AF development without pulmonary physiologic interdependence.
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Affiliation(s)
| | - Nicolas R. Thompson
- Department of Quantitative Health SciencesCleveland ClinicClevelandOH
- Neurological Institute Center for Outcomes Research & EvaluationCleveland ClinicClevelandOH
| | - Alex Milinovich
- Department of Quantitative Health SciencesCleveland ClinicClevelandOH
| | | | - Cinthya Pena Orbea
- Sleep Disorders Center, Neurological InstituteCleveland ClinicClevelandOH
| | | | | | - Michael Faulx
- Heart, Vascular, and Thoracic InstituteCleveland ClinicClevelandOH
| | | | - Mina K. Chung
- Heart, Vascular, and Thoracic InstituteCleveland ClinicClevelandOH
- Lerner Research InstituteCleveland ClinicClevelandOH
| | - Reena Mehra
- Sleep Disorders Center, Neurological InstituteCleveland ClinicClevelandOH
- Respiratory InstituteCleveland ClinicClevelandOH
- Heart, Vascular, and Thoracic InstituteCleveland ClinicClevelandOH
- Lerner Research InstituteCleveland ClinicClevelandOH
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Lee H, Kim IK, Im J, Jin BS, Kim HH, Kim SW, Yeo CD, Lee SH. Effects of aging on accompanying intermittent hypoxia in a bleomycin-induced pulmonary fibrosis mouse model. Korean J Intern Med 2023; 38:934-944. [PMID: 37793985 PMCID: PMC10636542 DOI: 10.3904/kjim.2023.090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 05/26/2023] [Accepted: 05/30/2023] [Indexed: 10/06/2023] Open
Abstract
BACKGROUND/AIMS Obstructive sleep apnea (OSA) is prevalent in older patients with idiopathic pulmonary fibrosis (IPF); however, it is underrecognized. OSA is characterized by intermittent hypoxia (IH) and sleep fragmentation. In this study, we evaluated the effects of IH in an older mouse model of bleomycin-induced lung fibrosis. METHODS Bleomycin-induced mice (C57BL/6, female) were randomly divided into four groups of young vs. old and room air (RA)-exposed vs. IH-exposed. Mice were exposed to RA or IH (20 cycles/h, FiO2 nadir 7 ± 0.5%, 8 h/day) for four weeks. The mice were sacrificed on day 28, and blood, bronchoalveolar lavage (BAL) fluid, and lung tissue samples were obtained. RESULTS The bleomycin-induced IH-exposed (EBI) older group showed more severe inflammation, fibrosis, and oxidative stress than the other groups. The levels of inflammatory cytokines in the serum and BAL fluid increased in the EBI group. Hydroxyproline levels in the lung tissue increased markedly in the EBI group. CONCLUSION This study demonstrates the possible harmful impact of OSA in an elderly mouse model of lung fibrosis. This study further suggests that older patients with IPF and OSA may be more of a concern than younger patients with IPF. Further research is required in this area.
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Affiliation(s)
- Heayon Lee
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - In Kyoung Kim
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
- Cancer Research Institute, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Jeonghyeon Im
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Bae Suk Jin
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Hwan Hee Kim
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Sei Won Kim
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Chang Dong Yeo
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
| | - Sang Haak Lee
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
- Cancer Research Institute, College of Medicine, The Catholic University of Korea, Seoul, Korea
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Gao H, Nepovimova E, Heger Z, Valko M, Wu Q, Kuca K, Adam V. Role of hypoxia in cellular senescence. Pharmacol Res 2023; 194:106841. [PMID: 37385572 DOI: 10.1016/j.phrs.2023.106841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/25/2023] [Accepted: 06/25/2023] [Indexed: 07/01/2023]
Abstract
Senescent cells persist and continuously secrete proinflammatory and tissue-remodeling molecules that poison surrounding cells, leading to various age-related diseases, including diabetes, atherosclerosis, and Alzheimer's disease. The underlying mechanism of cellular senescence has not yet been fully explored. Emerging evidence indicates that hypoxia is involved in the regulation of cellular senescence. Hypoxia-inducible factor (HIF)- 1α accumulates under hypoxic conditions and regulates cellular senescence by modulating the levels of the senescence markers p16, p53, lamin B1, and cyclin D1. Hypoxia is a critical condition for maintaining tumor immune evasion, which is promoted by driving the expression of genetic factors (such as p53 and CD47) while triggering immunosenescence. Under hypoxic conditions, autophagy is activated by targeting BCL-2/adenovirus E1B 19-kDa interacting protein 3, which subsequently induces p21WAF1/CIP1 as well as p16Ink4a and increases β-galactosidase (β-gal) activity, thereby inducing cellular senescence. Deletion of the p21 gene increases the activity of the hypoxia response regulator poly (ADP-ribose) polymerase-1 (PARP-1) and the level of nonhomologous end joining (NHEJ) proteins, repairs DNA double-strand breaks, and alleviates cellular senescence. Moreover, cellular senescence is associated with intestinal dysbiosis and an accumulation of D-galactose derived from the gut microbiota. Chronic hypoxia leads to a striking reduction in the amount of Lactobacillus and D-galactose-degrading enzymes in the gut, producing excess reactive oxygen species (ROS) and inducing senescence in bone marrow mesenchymal stem cells. Exosomal microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) play important roles in cellular senescence. miR-424-5p levels are decreased under hypoxia, whereas lncRNA-MALAT1 levels are increased, both of which induce cellular senescence. The present review focuses on recent advances in understanding the role of hypoxia in cellular senescence. The effects of HIFs, immune evasion, PARP-1, gut microbiota, and exosomal mRNA in hypoxia-mediated cell senescence are specifically discussed. This review increases our understanding of the mechanism of hypoxia-mediated cellular senescence and provides new clues for anti-aging processes and the treatment of aging-related diseases.
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Affiliation(s)
- Haoyu Gao
- College of Life Science, Yangtze University, Jingzhou 434025, China
| | - Eugenie Nepovimova
- Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové 500 03, Czech Republic
| | - Zbynek Heger
- Department of Chemistry and Biochemistry, Mendel University in Brno, Brno 613 00, Czech Republic
| | - Marian Valko
- Faculty of Chemical and Food Technology, Slovak University of Technology, Bratislava 812 37, Slovakia
| | - Qinghua Wu
- College of Life Science, Yangtze University, Jingzhou 434025, China; Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové 500 03, Czech Republic.
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové 500 03, Czech Republic; Biomedical Research Center, University Hospital Hradec Kralove, Hradec Kralove 500 05, Czech Republic; Andalusian Research Institute in Data Science and Computational Intelligence (DaSCI), University of Granada, Granada, Spain.
| | - Vojtech Adam
- Department of Chemistry and Biochemistry, Mendel University in Brno, Brno 613 00, Czech Republic.
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Ifedili I, Ingram E, Blount C, Kayali S, Heckle M, Levine YC. Vagal milieu or electrophysiologic substrate? The link between atrial fibrillation and obstructive sleep apnea. Exp Biol Med (Maywood) 2022; 247:1827-1832. [PMID: 36112833 PMCID: PMC9679354 DOI: 10.1177/15353702221120289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Atrial fibrillation is the most common cardiac arrhythmia with its prevalence expected to increase to 12.1 million people in the United States by 2030. Chronic underlying conditions that affect the heart and lungs predispose patients to develop atrial fibrillation. Obstructive sleep apnea is strongly associated with atrial fibrillation. Several pathophysiological mechanisms have been proposed to elucidate this relationship which includes electrophysiological substrate modification and the contribution of the autonomic nervous system. In this comprehensive review, we highlight important relationships and plausible causality between obstructive sleep apnea and atrial fibrillation which will improve our understanding in the evaluation, management, and prevention of atrial fibrillation. This is the most updated comprehensive review of the relationship between obstructive sleep apnea and atrial fibrillation.
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Affiliation(s)
- Ikechukwu Ifedili
- Division of Cardiovascular Diseases, Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Eva Ingram
- Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Courtland Blount
- Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Sharif Kayali
- Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
| | - Mark Heckle
- Division of Cardiovascular Diseases, Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
- Methodist Le Bonheur Healthcare, Memphis, TN 38104, USA
| | - Yehoshua C Levine
- Division of Cardiovascular Diseases, Department of Internal Medicine, University of Tennessee Health Science Center, Memphis, TN 38163, USA
- Methodist Le Bonheur Healthcare, Memphis, TN 38104, USA
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Baby SM, Tanner LH, Discala JF, Gruber RB, Hsieh YH, Lewis SJ. Systemic Administration of Tempol, a Superoxide Dismutase Mimetic, Augments Upper Airway Muscle Activity in Obese Zucker Rats. Front Pharmacol 2022; 13:814032. [PMID: 35222029 PMCID: PMC8864283 DOI: 10.3389/fphar.2022.814032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 01/24/2022] [Indexed: 12/28/2022] Open
Abstract
Obstructive sleep apnea (OSA) is characterized by repetitive partial/complete collapse of the pharynx during sleep, which results in apnea/hypopnea leading to arterial oxygen desaturations and arousals. Repetitive apnea/hypopnea-arousal episodes cause hypoxia/reoxygenation cycles, which increase free radical generation and oxidative stress that cause motor/sensory nerve impairments and muscle damage. We hypothesize that antioxidants may protect and/or reverse from oxidative stress-induced damage in OSA patients. To understand the acute protective effects of antioxidants on respiratory muscles, we studied the systemic effects of a membrane permeable superoxide dismutase mimetic, Tempol, on genioglossus (EMGGG) and diaphragmatic (EMGDIA) electro-myographic activities, hypoglossal motoneuron (HMN) nerve activity and cardiorespiratory parameters (mean arterial blood pressure, heart rate) in adult isoflurane-anesthetized obese Zucker rats (OZR) and age-matched lean Zucker rats (LZR). Tempol dose-dependently (1-100 mg/kg) increased EMGGG without changing EMGDIA in OZR and LZR. Tempol increased respiratory rate and tidal volume in OZR and LZR. Tempol (1-25 mg/kg) dose-dependently increased HMN nerve activity in healthy Sprague Dawley rats. Tempol (100 mg/kg) increased EMGGG output by 189% in OZR and 163% in LZR. With respect to mechanisms of effect, Tempol (100 mg/kg) did not augment EMGGG after bilateral HMN transection in Sprague Dawley rats. Although future studies are warranted, available data suggest that in addition to its antioxidant and antihypertensive properties, Tempol can selectively augment EMGGG through modulating HMN and this effect may prevent collapsibility and/or improve stability of the upper airway pharyngeal dilator muscles during episodes of partial and/or complete collapse of the upper airway in OSA human subjects.
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Affiliation(s)
- Santhosh M Baby
- Department of Drug Discovery, Galleon Pharmaceuticals, Inc., Horsham, PA, United States
| | - Lisa H Tanner
- Department of Drug Discovery, Galleon Pharmaceuticals, Inc., Horsham, PA, United States
| | - Joseph F Discala
- Department of Drug Discovery, Galleon Pharmaceuticals, Inc., Horsham, PA, United States
| | - Ryan B Gruber
- Department of Drug Discovery, Galleon Pharmaceuticals, Inc., Horsham, PA, United States
| | - Yee-Hsee Hsieh
- Division of Pulmonary, Critical Care and Sleep Medicine, University Hospitals Case Medical Center, Case Western Reserve University, Cleveland, OH, United States
| | - Stephen J Lewis
- Department of Pediatrics, Division of Pulmonology, Allergy and Immunology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States.,Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States
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Ventrikuläre Arrhythmien bei obstruktiver und zentraler Schlafapnoe. SOMNOLOGIE 2021. [DOI: 10.1007/s11818-021-00319-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Zusammenfassung
Hintergrund
Ventrikuläre Arrhythmien treten mit einer hohen Prävalenz auf und sind mit einer hohen Morbidität und Mortalität assoziiert. Sowohl die obstruktive (OSA) als auch die zentrale (ZSA) Schlafapnoe können auf Grund ihrer Pathophysiologie zu vermehrten ventrikulären Arrhythmien beitragen.
Ziel
Dieser Artikel soll die komplexen Zusammenhänge und Erkenntnisse jüngster Forschungen bezüglich schlafbezogenen Atmungsstörungen (SBAS) und ventrikulärer Arrhythmien und deren Therapiemöglichkeiten beleuchten.
Material und Methoden
Es erfolgte eine Literaturrecherche basierend auf prospektiven, retrospektiven, klinischen und experimentellen Studien sowie Reviews, Metaanalysen und aktuellen Leitlinien, die seit 2014 in der Medline-Datenbank gelistet wurden.
Ergebnisse
Es besteht ein bidirektionaler Zusammenhang zwischen der SBAS und ventrikulären Arrhythmien. Intermittierende Hypoxie, oxidativer Stress, wiederkehrende Arousals, intrathorakale Druckschwankungen und kardiales Remodeling tragen im Rahmen der SBAS zu einer erhöhten ventrikulären Arrhythmieneigung bei. Der Schweregrad der OSA, gemessen mittels Apnoe-Hypopnoe-Index, ist mit der Prävalenz ventrikulärer Arrhythmien assoziiert. Ähnliche Ergebnisse liegen für Patienten mit ZSA und Herzinsuffizienz vor. Studien zu ventrikulären Arrhythmien bei ZSA-Patienten ohne Herzinsuffizienz fehlen. Eine Positivdrucktherapie (PAP) bei OSA- oder ZSA-Patienten führte in verschiedenen Studien zu einer reduzierten Anzahl an ventrikulären Arrhythmien. Dieser Zusammenhang konnte jedoch nicht in allen Studien bestätigt werden. Ventrikuläre Arrhythmien treten bei der OSA gehäuft nachts auf, bei der ZSA gleichmäßig über den Tag verteilt.
Diskussion
Bisherige Studien weisen einen Zusammenhang zwischen der OSA bzw. der ZSA und ventrikulären Arrhythmien trotz unterschiedlicher Pathophysiologie nach. Hinsichtlich des Effektes der PAP auf ventrikuläre Arrhythmien bei Patienten mit OSA und ZSA sind weitere Studien erforderlich.
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Guo H, Ding H, Yan Y, Chen Q, Zhang J, Chen B, Cao J. Intermittent hypoxia-induced autophagy via AMPK/mTOR signaling pathway attenuates endothelial apoptosis and dysfunction in vitro. Sleep Breath 2021; 25:1859-1865. [PMID: 33483906 DOI: 10.1007/s11325-021-02297-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 07/10/2020] [Accepted: 01/05/2021] [Indexed: 02/06/2023]
Abstract
PURPOSE The aim of this study was to examine whether or not intermittent hypoxia (IH) upregulated autophagy and the contributions of autophagy to endothelial apoptosis and dysfunction in human umbilical vein endothelial cells (HUVECs). METHOD HUVECs were incubated under normoxia and IH conditions. After 3-, 6-, 12-, and 24-h exposure, the autophagic vacuoles and autophagosomes were observed by transmission electron microscopy and monodansylcadaverine staining. The protein levels of autophagy-related biomarkers and AMPK/mTOR pathway were measured by Western blot. The apoptosis-related proteins and the percentage of apoptotic cells were evaluated by Western blot and flow cytometry, respectively, while the levels of endothelial function biomarkers were assessed by ELISA. RESULTS IH induced autophagy, as determined by the increased numbers of the autophagic vacuoles, autophagosomes, and by the elevated levels of Beclin-1 protein, the LC3II/LC3I ratio, and p62 degradation. IH-induced autophagic flux peaked at 12-h duration and weakened at 24 h. IH increased the ratio of p-AMPK/AMPK and decreased the ratio of p-mTOR/mTOR, while compound C restored the alteration. A significant decrease in the Bcl-2 level and the Bcl-2/Bax ratio and a significant increase in the protein expression levels of Bax and cleaved caspase 3 and in the percentage of apoptosis were observed under IH exposure. Moreover, the NO level was reduced, while the ET-1 and VEGF levels were raised under IH condition. These alterations were suppressed by the pretreatment of 3-methyladenine. CONCLUSIONS IH upregulates autophagy through AMPK/mTOR pathway in HUVECs in vitro, which might be protective against endothelial apoptosis and dysfunction caused by IH.
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Affiliation(s)
- Hengjuan Guo
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Hui Ding
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Yuxia Yan
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Qianqian Chen
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Jing Zhang
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Baoyuan Chen
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China
| | - Jie Cao
- Department of Respiratory and Critical Care, Tianjin Medical University General Hospital, 154 Anshan Road, Heping District, Tianjin, 300052, China.
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Abstract
Zusammenfassung
Hintergrund
Vorhofflimmern (VHF) ist die häufigste Herzrhythmusstörung. Sowohl die zentrale als auch die obstruktive Schlafapnoe interagieren mit dieser Erkrankung. Intermittierende Hypoxie, oxidativer Stress, wiederkehrende Aufwachreaktionen, intrathorakale Druckveränderungen und atriales Remodeling können im Rahmen einer schlafbezogenen Atmungsstörung (SBAS) zu VHF führen.
Ziel
Dieser Artikel stellt die komplexen Zusammenhänge und Erkenntnisse jüngster Forschungen bezüglich SBAS und VHF sowie die Therapiemöglichkeiten dar.
Material und Methoden
Es erfolgten eine Literaturrecherche von Original- und Übersichtsartikeln sowie Metaanalysen, die zwischen 1963 und 2020 in der PubMed-Datenbank veröffentlicht wurden.
Ergebnisse
Die Erkenntnisse der Studien weisen auf einen bidirektionalen kausalen Zusammenhang zwischen SBAS und VHF hin. Die pathophysiologischen Auswirkungen der obstruktiven und zentralen Schlafapnoe auf VHF sind unterschiedlich. Die Studien, die die Effekte einer Therapie der SBAS auf das Rezidivrisiko von VHF nach Intervention (Kardioversion oder Pulmonalvenenisolation) untersuchen, ergeben bisher kein eindeutiges Bild.
Diskussion
Bisherige Studien bestätigen multiple Interaktionen zwischen SBAS und VHF. Aufgrund widersprüchlicher Ergebnisse hinsichtlich der Effekte einer positiven Atemwegsdrucktherapie auf das Rezidivrisiko von VHF nach Interventionen sind weitere Studien nötig.
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10
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Eisenstein A, Chitalia SV, Ravid K. Bone Marrow and Adipose Tissue Adenosine Receptors Effect on Osteogenesis and Adipogenesis. Int J Mol Sci 2020; 21:E7470. [PMID: 33050467 PMCID: PMC7589187 DOI: 10.3390/ijms21207470] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/01/2020] [Accepted: 10/06/2020] [Indexed: 12/12/2022] Open
Abstract
Adenosine is an extracellular signaling molecule that is particularly relevant in times of cellular stress, inflammation and metabolic disturbances when the levels of the purine increase. Adenosine acts on two G-protein-coupled stimulatory and on two G-protein-coupled inhibitory receptors, which have varying expression profiles in different tissues and conditions, and have different affinities for the endogenous ligand. Studies point to significant roles of adenosine and its receptors in metabolic disease and bone health, implicating the receptors as potential therapeutic targets. This review will highlight our current understanding of the dichotomous effects of adenosine and its receptors on adipogenesis versus osteogenesis within the bone marrow to maintain bone health, as well as its relationship to obesity. Therapeutic implications will also be reviewed.
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Affiliation(s)
- Anna Eisenstein
- Department of Dermatology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Shlok V. Chitalia
- Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA; (S.V.C.); (K.R.)
| | - Katya Ravid
- Department of Medicine and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA; (S.V.C.); (K.R.)
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11
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Zou F, Su X, Pan P. Toll-Like Receptor-4-Mediated Inflammation is Involved in Intermittent Hypoxia-Induced Lung Injury. Lung 2020; 198:855-862. [PMID: 32785858 DOI: 10.1007/s00408-020-00384-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 07/31/2020] [Indexed: 01/03/2023]
Abstract
PURPOSE Intermittent hypoxia (IH) is a recognized risk factor for multiple organs damage, resulting in lung injury. Its pathophysiology is still poorly understood. Toll-like receptor 4 (TLR4) signaling plays a critical role in host immune response to invading pathogen and non-infectious tissue injury. The role of TLR4-mediated inflammation in IH-induced lung injury was investigated in this study. METHODS Lean adult male TLR4-deficient (TLR4-/-) mice and their controls (C57BL/6 mice) were exposed to either IH (FiO2 6-8% for 25 s, 150 s/cycle, 8 h/day) or air (normoxic mice) for 6 weeks. Animals were sacrificed after 6-week exposure, and the lung tissues were harvested for morphological and inflammatory analyses. The expression of TLR4 and nuclear factor kappa-B (NF-κB) P65 were examined by real-time quantitative polymerase chain reaction and immunohistochemical method. Serum cytokine levels of interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-α) were analyzed by enzyme-linked immunosorbent assay. RESULTS IH induced morphological and inflammation changes in the lung. IH for 6 weeks induced higher expression of TLR4 (C57BL/6-N vs C57BL/6-IH, P < 0.05) and resulted in higher release of TNF-α, IL-6 (P < 0.05), and NF-κB P65 (P < 0.05). These alterations were remitted by TLR4 deletion. CONCLUSIONS TLR4-mediated inflammation plays an important role in the development of IH-induced lung injury in mice, possibly through mechanisms involving nuclear factor-κB. Targeting TLR4/NF-κB pathway could represent a further therapeutic option for sleep apnea patients.
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Affiliation(s)
- Fangfang Zou
- Department of Internal Medicine, Hunan Chest Hospital, Changsha, 410013, Hunan, People's Republic of China
| | - Xiaoli Su
- Department of Respiratory Medicine, Xiangya Hospital, Key Cite of National Clinical Research Center for Respiratory Disease, Central South University, Changsha, 410008, Hunan, People's Republic of China.
| | - Pinhua Pan
- Department of Respiratory Medicine, Xiangya Hospital, Key Cite of National Clinical Research Center for Respiratory Disease, Central South University, Changsha, 410008, Hunan, People's Republic of China
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12
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Turhan M, Bostanci A. Robotic Tongue-Base Resection Combined With Tongue-Base Suspension for Obstructive Sleep Apnea. Laryngoscope 2019; 130:2285-2291. [PMID: 31782809 DOI: 10.1002/lary.28443] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 10/07/2019] [Accepted: 11/11/2019] [Indexed: 11/11/2022]
Abstract
OBJECTIVES/HYPOTHESIS Our primary objective was to evaluate the feasibility, morbidity, and efficacy of transoral robotic surgery (TORS) tongue-base resection (TBR) combined with tongue-base suspension (TBS) for obstructive sleep apnea (OSA) with tongue-base collapse. Our secondary objective included evaluation of factors influencing treatment success. STUDY DESIGN Single-arm, prospective, observational cohort study. METHODS Patients were eligible if they had moderate-to-severe OSA (apnea hypopnea index [AHI] > 15) or positional OSA, had a tongue-base collapse and glossoptosis identified by drug-induced sleep endoscopy (DISE), and failed continuous positive airway pressure. All patients underwent TORS-TBR combined with TBS. Additionally, concomitant epiglottoplasty, uvulopalatopharyngoplasty, or expansion pharyngoplasty were performed based on DISE findings. RESULTS In total, 64 patients were enrolled in the trial. The mean age was 45.9 years, mean body mass index was 30.5 kg/m2 , and mean AHI was 41.7 events/hour. The mean robotic surgical time, total volume of tongue-base tissue removed, and the length of hospital stay were 21.4 minutes, 15.16 mL, and 6.5 days, respectively. Postoperatively, almost all polysomnographic metrics improved significantly (AHI = 41.72 vs. 18.82 events/hour, lowest oxygen saturation = 80.43% vs. 85.14%, Epworth Sleepiness Scale = 10.49 vs. 4.09). The procedure provided an overall success rate of 75%, with minor morbidity. All patients experienced varying degrees of temporary lingual edema postoperatively. Tracheotomy was not required for any patient. Although no independent predictor of treatment success was determined, patients with more severe disease tend to exhibit lower response to the treatment. CONCLUSIONS TORS-TBR combined with TBS is a feasible, safe, and efficient procedure for OSA with tongue-base collapse. LEVEL OF EVIDENCE 4 Laryngoscope, 130:2285-2291, 2020.
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Affiliation(s)
- Murat Turhan
- Department of Otolaryngology-Head and Neck Surgery, Akdeniz University School of Medicine, Antalya, Turkey
| | - Asli Bostanci
- Department of Otolaryngology-Head and Neck Surgery, Akdeniz University School of Medicine, Antalya, Turkey
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13
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Cho YD, Park SJ, Choi SH, Yoon YH, Kim JY, Lee SW, Lim CS. The inflammatory response of neutrophils in an in vitro model that approximates the postcardiac arrest state. Ann Surg Treat Res 2017; 93:217-224. [PMID: 29094032 PMCID: PMC5658304 DOI: 10.4174/astr.2017.93.4.217] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 03/14/2017] [Accepted: 03/30/2017] [Indexed: 11/30/2022] Open
Abstract
Purpose Postcardiac arrest syndrome (PCAS) shares many features with sepsis including plasma cytokine elevation with dysregulation of cytokine production, and the presence of endotoxin in plasma. PCAS is closely related to ischemia-reperfusion injury. During ischemia-reperfusion injury, neutrophil, which is the first line of innate immunity, plays a major role. In this study, we investigated the inflammatory response of human neutrophils in an in vitro model which we simulated with hypoxia-normoxia and hypoxia-hyperoxia environments. Methods After separation of neutrophils from the whole blood, they were divided into 3 experimental groups: normoxia-normoxia, hypoxia-normoxia, and hypoxia-hyperoxia groups. The production of H2O2, the expression of Toll-like receptor 4 (TLR4) receptor, and the extent of apoptosis of the neutrophils were checked. Results The in vitro hypoxia-normoxia and -hyperoxia models, which simulated the PCAS, showed initiation of the neutrophils' inflammatory reaction by hypoxia insult. Lipopolysaccharide amplifies such inflammation; therefore, prevention of secondary infection may be critical in postresuscitation patients. Temporary hyperoxia following hypoxic insult showed no difference in inflammatory reaction compared with hypoxia-normoxia. Rather, temporary hyperoxia may suppress or minimize inflammation by attenuation of TLR4 receptor. Conclusion It is well known that continuous hyperoxygenation after successful cardiac arrest harms patients, but temporary hyperoxygenation with 100% O2 in a clinical situation may be helpful.
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Affiliation(s)
- Young-Duck Cho
- Department of Emergency Medicine, Korea University College of Medicine, Seoul, Korea
| | - Sung-Jun Park
- The institute for Trauma Research, Korea University, Seoul, Korea
| | - Sung-Hyuk Choi
- The institute for Trauma Research, Korea University, Seoul, Korea
| | - Young-Hoon Yoon
- Department of Emergency Medicine, Korea University College of Medicine, Seoul, Korea
| | - Jung-Youn Kim
- Department of Emergency Medicine, Korea University College of Medicine, Seoul, Korea
| | - Sung-Woo Lee
- Department of Emergency Medicine, Korea University College of Medicine, Seoul, Korea
| | - Chae-Seung Lim
- Department of Laboratory Medicine, Korea University College of Medicine, Seoul, Korea
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14
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Bostanci A, Bozkurt S, Turhan M. Impact of age on intermittent hypoxia in obstructive sleep apnea: a propensity-matched analysis. Sleep Breath 2017; 22:317-322. [PMID: 28849299 DOI: 10.1007/s11325-017-1560-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2017] [Revised: 07/25/2017] [Accepted: 08/22/2017] [Indexed: 11/30/2022]
Abstract
PURPOSE To determine independent relationship of aging with chronic intermittent hypoxia, we compared hypoxia-related polysomnographic variables of geriatric patients (aged ≥ 65 years) with an apnea-hypopnea index (AHI)-, gender-, body mass index (BMI)-, and neck circumference-matched cohort of non-geriatric patients. METHODS The study was conducted using clinical and polysomnographic data of 1280 consecutive patients who underwent complete polysomnographic evaluation for suspected sleep-disordered breathing (SDB) at a single sleep disorder center. A propensity score-matched analysis was performed to obtain matched cohorts of geriatric and non-geriatric patients, which resulted in successful matching of 168 patients from each group. RESULTS Study groups were comparable for gender (P = 0.999), BMI (P = 0.940), neck circumference (P = 0.969), AHI (P = 0.935), and severity of SDB (P = 0.089). The oximetric variables representing the duration of chronic intermittent hypoxia such as mean (P = 0.001), the longest (P = 0.001) and total apnea durations (P = 0.003), mean (P = 0.001) and the longest hypopnea durations (P = 0.001), and total sleep time with oxygen saturation below 90% (P = 0.008) were significantly higher in the geriatric patients as compared with younger adults. Geriatric patients had significantly lower minimum (P = 0.013) and mean oxygen saturation (P = 0.001) than non-geriatric patients. CONCLUSIONS The study provides evidence that elderly patients exhibit more severe and deeper nocturnal intermittent hypoxia than the younger adults, independent of severity of obstructive sleep apnea, BMI, gender, and neck circumference. Hypoxia-related polysomnographic variables in geriatric patients may in fact reflect a physiological aging process rather than the severity of a SDB.
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Affiliation(s)
- Asli Bostanci
- Department of Otolaryngology, Head and Neck Surgery, Akdeniz University School of Medicine, Antalya, Turkey. .,Akdeniz University Hospital, Dumlupinar Boulevard, H Blok K: 1, Konyaalti, 07058, Antalya, Turkey.
| | - Selen Bozkurt
- Department of Biostatistics and Medical Informatics, Akdeniz University School of Medicine, Antalya, Turkey
| | - Murat Turhan
- Department of Otolaryngology, Head and Neck Surgery, Akdeniz University School of Medicine, Antalya, Turkey
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Zhang LC, Jin X, Huang Z, Yan ZN, Li PB, Duan RF, Feng H, Jiang JH, Peng H, Liu W. Protective effects of choline against hypoxia-induced injuries of vessels and endothelial cells. Exp Ther Med 2017; 13:2316-2324. [PMID: 28565844 PMCID: PMC5443310 DOI: 10.3892/etm.2017.4276] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 01/06/2017] [Indexed: 01/08/2023] Open
Abstract
The current study aimed to lay a theoretical foundation for further development of choline as an anti-hypoxia damage drug. Wild-type, 3- to 5-month-old male Sprague-Dawley rats, weighing 180-220 g, were used in this study. The rats were randomly divided into a normoxic control group (n=16) and a chronic intermittent hypoxia (CIH) group (n=16). The effects of CIH on acetylcholine (ACh)-mediated endothelium-dependent vasodilatation in the rat cerebral basilar arterioles and mesenteric arterioles, as well as the protective effects of choline on the arterioles damaged by hypoxia were observed. Moreover, the effects of choline on endothelial cell proliferation during hypoxia were observed, and choline's functional mechanism further explored. The ACh-mediated vasodilatation of rat cerebral basilar and mesenteric arterioles significantly reduced during hypoxia (P<0.01). Choline significantly increased dilation in the rat cerebral basilar (P<0.01) and mesenteric arterioles (P<0.05) damaged by CIH compared with those in the control group. In addition, under hypoxic conditions, choline significantly promoted the proliferation of rat aortic endothelial cells (P<0.05) and significantly reduced lactate dehydrogenase activity in the cell culture supernatant in vitro (P<0.05). Furthermore, the effect of choline could be related to its ability to significantly increase the secretion of vascular endothelial growth factor (P<0.01) and activation of α7 non-neuronal nicotinic acetylcholine receptors under hypoxia (P<0.01). This study demonstrated that choline could have protective effects against hypoxic injuries.
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Affiliation(s)
- Lian-Cheng Zhang
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Xin Jin
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Zhao Huang
- Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Tianjin University of Sport, Tianjin 300381, P.R. China
| | - Zhen-Nan Yan
- Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Tianjin University of Sport, Tianjin 300381, P.R. China
| | - Pei-Bing Li
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Rui-Feng Duan
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Hong Feng
- Tianjin Key Laboratory of Exercise Physiology and Sports Medicine, Tianjin University of Sport, Tianjin 300381, P.R. China
| | - Jian-Hua Jiang
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Hui Peng
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
| | - Wei Liu
- Department of Environment and Pharmacy, Tianjin Institute of Health and Environmental Medicine, Tianjin 300050, P.R. China
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16
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Korkmaz A, Yıldız A, Türker Duyuler P, Duyuler S, Yılmaz S, Basyigit F, Elalmis OU, Guray U, Ileri M. Combination of change in hematological parameters with exercise stress test to predict coronary artery disease. J Clin Lab Anal 2017; 32. [PMID: 28317171 DOI: 10.1002/jcla.22205] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 02/21/2017] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE Treadmill exercise stress testing for identifying patients with a higher likelihood of coronary artery disease (CAD) before elective coronary angiography is recommended in the current guidelines. In this study, we aimed to evaluate the changes in the hematological parameters before and after exercise stress test in relation with the presence of CAD. METHODS A total of 113 patients with chest pain who underwent treadmill exercise testing and coronary angiography were included in this study. RESULTS Neutrophil count (4.38±0.99 vs 5.19±0.93, P<.001), and neutrophil to lymphocyte ratio (NLR) (2.04±0.63 vs 2.41±0.78, P<.001) were significantly elevated after treadmill exercise test in all the patients. Increase in the NLR after exercise test was significantly higher in patients with positive exercise test (n=68) than negative exercise test (n=45) (0.49±0.58 vs 0.19±0.44, P=.016). The sensitivity and specificity of treadmill exercise testing according to coronary angiography was 79% and 64%, respectively. A cut-off point of 0.2 for the change in the NLR in addition to positive treadmill exercise testing had 91% sensitivity and 92% specificity in predicting significant coronary artery stenosis (AUC:0.913, 95% CI: 0.805-1.000, P<.001). CONCLUSIONS Neutrophil to lymphocyte ratio is an important inflammatory marker that can contribute to treadmill ECG testing in predicting CAD.
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Affiliation(s)
- Ahmet Korkmaz
- Cardiology Clinic, Ankara Numune Training Hospital, Ankara, Turkey
| | | | | | - Serkan Duyuler
- Cardiology Clinic, Acıbadem Ankara Hospital, Ankara, Turkey
| | - Samet Yılmaz
- Cardiology Clinic, Yozgat State Hospital, Yozgat, Turkey
| | - Funda Basyigit
- Cardiology Clinic, Ankara Numune Training Hospital, Ankara, Turkey
| | | | - Umit Guray
- Cardiology Clinic, Ankara Numune Training Hospital, Ankara, Turkey
| | - Mehmet Ileri
- Cardiology Clinic, Ankara Numune Training Hospital, Ankara, Turkey
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17
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May AM, Van Wagoner DR, Mehra R. OSA and Cardiac Arrhythmogenesis: Mechanistic Insights. Chest 2017; 151:225-241. [PMID: 27693594 PMCID: PMC5989643 DOI: 10.1016/j.chest.2016.09.014] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 09/14/2016] [Accepted: 09/16/2016] [Indexed: 12/13/2022] Open
Abstract
A surge of data has reproducibly identified strong associations of OSA with cardiac arrhythmias. As an extension of epidemiologic and clinic-based findings, experimental investigations have made strides in advancing our understanding of the putative OSA and cardiac arrhythmogenesis mechanistic underpinnings. Although most studies have focused on the links between OSA and atrial fibrillation (AF), relationships with ventricular arrhythmias have also been characterized. Key findings implicate OSA-related autonomic nervous system fluctuations typified by enhanced parasympathetic activation during respiratory events and sympathetic surges subsequent to respiratory events, which contribute to augmented arrhythmic propensity. Other more immediate pathophysiologic influences of OSA-enhancing arrhythmogenesis include intermittent hypoxia, intrathoracic pressure swings leading to atrial stretch, and hypercapnia. Intermediate pathways by which OSA may trigger arrhythmia include increased systemic inflammation, oxidative stress, enhanced prothrombotic state, and vascular dysfunction. Long-term OSA-associated sequelae such as hypertension, atrial enlargement and fibrosis, ventricular hypertrophy, and coronary artery disease also predispose to cardiac arrhythmia. These factors can lead to a reduction in atrial effective refractory period, triggered and abnormal automaticity, and promote slowed and heterogeneous conduction; all of these mechanisms increase the persistence of reentrant arrhythmias and prolong the QT interval. Cardiac electrical and structural remodeling observed in OSA animal models can progress the arrhythmogenic substrate to further enhance arrhythmia generation. Future investigations clarifying the contribution of specific OSA-related mechanistic pathways to arrhythmia generation may allow targeted preventative therapies to mitigate OSA-induced arrhythmogenicity. Furthermore, interventional studies are needed to clarify the impact of OSA pathophysiology reversal on cardiac arrhythmogenesis and related adverse outcomes.
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Affiliation(s)
- Anna M May
- Division of Pulmonary, Critical Care, and Sleep Medicine, University Hospitals Cleveland Medical Center, Cleveland, OH.
| | - David R Van Wagoner
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
| | - Reena Mehra
- Neurologic Institute, Respiratory Institute, Heart and Vascular Institute and Molecular Cardiology Department, Lerner Research Institute, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH
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18
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Manukhina EB, Downey HF, Mallet RT. Role of Nitric Oxide in Cardiovascular Adaptation to Intermittent Hypoxia. Exp Biol Med (Maywood) 2016; 231:343-65. [PMID: 16565431 DOI: 10.1177/153537020623100401] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Hypoxia is one of the most frequently encountered stresses in health and disease. The duration, frequency, and severity of hypoxic episodes are critical factors determining whether hypoxia is beneficial or harmful. Adaptation to intermittent hypoxia has been demonstrated to confer cardiovascular protection against more severe and sustained hypoxia, and, moreover, to protect against other stresses, including ischemia. Thus, the direct and cross protective effects of adaptation to intermittent hypoxia have been used for treatment and prevention of a variety of diseases and to increase efficiency of exercise training. Evidence is mounting that nitric oxide (NO) plays a central role in these adaptive mechanisms. NO-dependent protective mechanisms activated by intermittent hypoxia include stimulation of NO synthesis as well as restriction of NO overproduction. In addition, alternative, nonenzymic sources of NO and negative feedback of NO synthesis are important factors in optimizing NO concentrations. The adaptive enhancement of NO synthesis and/or availability activates or increases expression of other protective factors, including heat shock proteins, antioxidants and prostaglandins, making the protection more robust and sustained. Understanding the role of NO in mechanisms of adaptation to hypoxia will support development of therapies to prevent and treat hypoxic or ischemic damage to organs and cells and to increase adaptive capabilities of the organism.
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19
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Pamenter ME, Powell FL. Time Domains of the Hypoxic Ventilatory Response and Their Molecular Basis. Compr Physiol 2016; 6:1345-85. [PMID: 27347896 DOI: 10.1002/cphy.c150026] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Ventilatory responses to hypoxia vary widely depending on the pattern and length of hypoxic exposure. Acute, prolonged, or intermittent hypoxic episodes can increase or decrease breathing for seconds to years, both during the hypoxic stimulus, and also after its removal. These myriad effects are the result of a complicated web of molecular interactions that underlie plasticity in the respiratory control reflex circuits and ultimately control the physiology of breathing in hypoxia. Since the time domains of the physiological hypoxic ventilatory response (HVR) were identified, considerable research effort has gone toward elucidating the underlying molecular mechanisms that mediate these varied responses. This research has begun to describe complicated and plastic interactions in the relay circuits between the peripheral chemoreceptors and the ventilatory control circuits within the central nervous system. Intriguingly, many of these molecular pathways seem to share key components between the different time domains, suggesting that varied physiological HVRs are the result of specific modifications to overlapping pathways. This review highlights what has been discovered regarding the cell and molecular level control of the time domains of the HVR, and highlights key areas where further research is required. Understanding the molecular control of ventilation in hypoxia has important implications for basic physiology and is emerging as an important component of several clinical fields. © 2016 American Physiological Society. Compr Physiol 6:1345-1385, 2016.
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Affiliation(s)
| | - Frank L Powell
- Physiology Division, Department of Medicine, University of California San Diego, La Jolla, California, USA
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20
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Gonzalez-Rothi EJ, Lee KZ, Dale EA, Reier PJ, Mitchell GS, Fuller DD. Intermittent hypoxia and neurorehabilitation. J Appl Physiol (1985) 2015; 119:1455-65. [PMID: 25997947 DOI: 10.1152/japplphysiol.00235.2015] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/18/2015] [Indexed: 02/05/2023] Open
Abstract
In recent years, it has become clear that brief, repeated presentations of hypoxia [i.e., acute intermittent hypoxia (AIH)] can boost the efficacy of more traditional therapeutic strategies in certain cases of neurologic dysfunction. This hypothesis derives from a series of studies in animal models and human subjects performed over the past 35 yr. In 1980, Millhorn et al. (Millhorn DE, Eldridge FL, Waldrop TG. Respir Physiol 41: 87-103, 1980) showed that electrical stimulation of carotid chemoafferent neurons produced a persistent, serotonin-dependent increase in phrenic motor output that outlasts the stimulus for more than 90 min (i.e., a "respiratory memory"). AIH elicits similar phrenic "long-term facilitation" (LTF) by a mechanism that requires cervical spinal serotonin receptor activation and de novo protein synthesis. From 2003 to present, a series of studies demonstrated that AIH can induce neuroplasticity in the injured spinal cord, causing functional recovery of breathing capacity after cervical spinal injury. Subsequently, it was demonstrated that repeated AIH (rAIH) can induce recovery of limb function, and the functional benefits of rAIH are greatest when paired with task-specific training. Since uncontrolled and/or prolonged intermittent hypoxia can elicit pathophysiology, a challenge of intermittent hypoxia research is to ensure that therapeutic protocols are well below the threshold for pathogenesis. This is possible since many low dose rAIH protocols have induced functional benefits without evidence of pathology. We propose that carefully controlled rAIH is a safe and noninvasive modality that can be paired with other neurorehabilitative strategies including traditional activity-based physical therapy or cell-based therapies such as intraspinal transplantation of neural progenitors.
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Affiliation(s)
- Elisa J Gonzalez-Rothi
- Department of Physical Therapy College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - Kun-Ze Lee
- Department of Biological Sciences, College of Science, National Sun Yat-sen University, Kaohsiung City, Taiwan
| | - Erica A Dale
- Department of Integrative Biology and Physiology, University of California-Los Angeles, Los Angeles, California; and
| | - Paul J Reier
- Department of Neuroscience, College of Medicine, University of Florida, Gainesville, Florida
| | - Gordon S Mitchell
- Department of Physical Therapy College of Public Health and Health Professions, University of Florida, Gainesville, Florida
| | - David D Fuller
- Department of Physical Therapy College of Public Health and Health Professions, University of Florida, Gainesville, Florida;
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Aubrecht TG, Jenkins R, Magalang UJ, Nelson RJ. Influence of gonadal hormones on the behavioral effects of intermittent hypoxia in mice. Am J Physiol Regul Integr Comp Physiol 2014; 308:R489-99. [PMID: 25552660 DOI: 10.1152/ajpregu.00379.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Obstructive sleep apnea (OSA) is characterized by repetitive upper airway obstruction resulting in cyclic intermittent hypoxia (IH) during sleep in affected individuals. OSA occurs more frequently in postmenopausal than premenopausal women and the severity of OSA increases after menopause. Gonadal hormones can influence brain and behavior; testosterone and estrogens in particular can enhance spatial learning and memory. We hypothesized that estrogens may protect mice from IH-induced hippocampal morphological and behavioral changes. To test this hypothesis we exposed intact or gonadectomized male and female mice to room air or IH [15 cycles/h, 8 h/day, fraction of inspired oxygen (FiO 2) nadir of 5%] for a total of 30 days. During the final 4 days of IH, mice were tested for anxiety- and depressive-like behaviors. After cessation of IH exposure mice were tested on the Barnes maze and passive avoidance tests to assess learning and memory. Ovariectomy paired with IH treatment, impaired spatial learning and memory compared to all other female groups. Intact male mice receiving IH treatment also had impaired learning and memory compared with intact or castrated male mice exposed to room air. Learning and memory changes were mirrored by changes in basilar dendritic length of the CA1 region of the hippocampus. These data suggest that estrogens provide protection against IH-induced deficits, whereas androgens partially exacerbate IH-induced deficits on learning and memory.
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Affiliation(s)
- Taryn G Aubrecht
- Department of Neuroscience and Neuroscience Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio; and
| | - Richelle Jenkins
- Department of Neuroscience and Neuroscience Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio; and
| | - Ulysses J Magalang
- Department of Neuroscience and Neuroscience Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio; and Division of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Wexner Medical Center, The Ohio State University, Columbus, Ohio
| | - Randy J Nelson
- Department of Neuroscience and Neuroscience Research Institute, Wexner Medical Center, The Ohio State University, Columbus, Ohio; and
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Bostanci A, Turhan M, Bozkurt S. Factors influencing sleep time with oxygen saturation below 90% in sleep-disordered breathing. Laryngoscope 2014; 125:1008-12. [DOI: 10.1002/lary.24942] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 08/05/2014] [Accepted: 08/29/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Asli Bostanci
- Department of Otolaryngology-Head and Neck Surgery; Akdeniz University School of Medicine; Antalya Turkey
| | - Murat Turhan
- Department of Otolaryngology-Head and Neck Surgery; Akdeniz University School of Medicine; Antalya Turkey
| | - Selen Bozkurt
- Department of Biostatistics and Medical Informatics; Akdeniz University School of Medicine; Antalya Turkey
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Pathogenic roles of the carotid body inflammation in sleep apnea. Mediators Inflamm 2014; 2014:354279. [PMID: 25276055 PMCID: PMC4170702 DOI: 10.1155/2014/354279] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 08/15/2014] [Accepted: 08/27/2014] [Indexed: 11/30/2022] Open
Abstract
Breathing difficulties in sleep are a hallmark of sleep-disordered breathing commonly observed in patients with sleep disorders. The pathophysiology of sleep apnea is in part due to an augmented activity of the carotid body chemoreflex. Arterial chemoreceptors in the carotid body are sensitive to inflammatory cytokines and immunogenic molecules in the circulation, because cytokine receptors are expressed in the carotid body in experimental animals and human. Intriguingly, proinflammatory cytokines are also locally produced and released in the carotid body. Also, there are significant increases in the expression of proinflammatory cytokines, cytokine receptors, and inflammatory mediators in the carotid body under hypoxic conditions, suggesting an inflammatory response of the carotid body. These upregulated cytokine signaling pathways could enhance the carotid chemoreceptor activity, leading to an overactivity of the chemoreflex adversely effecting breathing instability and autonomic imbalance. This review aims to summarize findings of the literature relevant to inflammation in the carotid body, with highlights on the pathophysiological impact in sleep apnea. It is concluded that local inflammation in the carotid body plays a pathogenic role in sleep apnea, which could potentially be a therapeutic target for the treatment of the pathophysiological consequence of sleep apnea.
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Fung ML. The role of local renin-angiotensin system in arterial chemoreceptors in sleep-breathing disorders. Front Physiol 2014; 5:336. [PMID: 25249981 PMCID: PMC4155775 DOI: 10.3389/fphys.2014.00336] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/15/2014] [Indexed: 11/23/2022] Open
Abstract
The renin-angiotensin system (RAS) plays pivotal roles in the regulation of cardiovascular and renal functions to maintain the fluid and electrolyte homeostasis. Experimental studies have demonstrated a locally expressed RAS in the carotid body, which is functional significant in the effect of angiotensin peptides on the regulation of the activity of peripheral chemoreceptors and the chemoreflex. The physiological and pathophysiological implications of the RAS in the carotid body have been proposed upon recent studies showing a significant upregulation of the RAS expression under hypoxic conditions relevant to altitude acclimation and sleep apnea and also in animal model of heart failure. Specifically, the increased expression of angiotensinogen, angiotensin-converting enzyme and angiotensin AT1 receptors plays significant roles in the augmented carotid chemoreceptor activity and inflammation of the carotid body. This review aims to summarize these results with highlights on the pathophysiological function of the RAS under hypoxic conditions. It is concluded that the maladaptive changes of the RAS in the carotid body plays a pathogenic role in sleep apnea and heart failure, which could potentially be a therapeutic target for the treatment of the pathophysiological consequence of sleep apnea.
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Affiliation(s)
- Man Lung Fung
- Department of Physiology, University of Hong Kong Pokfulam, Hong Kong
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Shin MK, Yao Q, Jun JC, Bevans-Fonti S, Yoo DY, Han W, Mesarwi O, Richardson R, Fu YY, Pasricha PJ, Schwartz AR, Shirahata M, Polotsky VY. Carotid body denervation prevents fasting hyperglycemia during chronic intermittent hypoxia. J Appl Physiol (1985) 2014; 117:765-76. [PMID: 25103977 DOI: 10.1152/japplphysiol.01133.2013] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Obstructive sleep apnea causes chronic intermittent hypoxia (IH) and is associated with impaired glucose metabolism, but mechanisms are unknown. Carotid bodies orchestrate physiological responses to hypoxemia by activating the sympathetic nervous system. Therefore, we hypothesized that carotid body denervation would abolish glucose intolerance and insulin resistance induced by chronic IH. Male C57BL/6J mice underwent carotid sinus nerve dissection (CSND) or sham surgery and then were exposed to IH or intermittent air (IA) for 4 or 6 wk. Hypoxia was administered by decreasing a fraction of inspired oxygen from 20.9% to 6.5% once per minute, during the 12-h light phase (9 a.m.-9 p.m.). As expected, denervated mice exhibited blunted hypoxic ventilatory responses. In sham-operated mice, IH increased fasting blood glucose, baseline hepatic glucose output (HGO), and expression of a rate-liming hepatic enzyme of gluconeogenesis phosphoenolpyruvate carboxykinase (PEPCK), whereas the whole body glucose flux during hyperinsulinemic euglycemic clamp was not changed. IH did not affect glucose tolerance after adjustment for fasting hyperglycemia in the intraperitoneal glucose tolerance test. CSND prevented IH-induced fasting hyperglycemia and increases in baseline HGO and liver PEPCK expression. CSND trended to augment the insulin-stimulated glucose flux and enhanced liver Akt phosphorylation at both hypoxic and normoxic conditions. IH increased serum epinephrine levels and liver sympathetic innervation, and both increases were abolished by CSND. We conclude that chronic IH induces fasting hyperglycemia increasing baseline HGO via the CSN sympathetic output from carotid body chemoreceptors, but does not significantly impair whole body insulin sensitivity.
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Affiliation(s)
- Mi-Kyung Shin
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Qiaoling Yao
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Jonathan C Jun
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Shannon Bevans-Fonti
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Doo-Young Yoo
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Woobum Han
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Omar Mesarwi
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Ria Richardson
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Ya-Yuan Fu
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; and
| | - Pankaj J Pasricha
- Division of Gastroenterology and Hepatology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland; and
| | - Alan R Schwartz
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Machiko Shirahata
- Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland
| | - Vsevolod Y Polotsky
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland;
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Hayes HB, Jayaraman A, Herrmann M, Mitchell GS, Rymer WZ, Trumbower RD. Daily intermittent hypoxia enhances walking after chronic spinal cord injury: a randomized trial. Neurology 2013; 82:104-13. [PMID: 24285617 PMCID: PMC3897437 DOI: 10.1212/01.wnl.0000437416.34298.43] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Objectives: To test the hypothesis that daily acute intermittent hypoxia (dAIH) and dAIH combined with overground walking improve walking speed and endurance in persons with chronic incomplete spinal cord injury (iSCI). Methods: Nineteen subjects completed the randomized, double-blind, placebo-controlled, crossover study. Participants received 15, 90-second hypoxic exposures (dAIH, fraction of inspired oxygen [Fio2] = 0.09) or daily normoxia (dSHAM, Fio2 = 0.21) at 60-second normoxic intervals on 5 consecutive days; dAIH was given alone or combined with 30 minutes of overground walking 1 hour later. Walking speed and endurance were quantified using 10-Meter and 6-Minute Walk Tests. The trial is registered at ClinicalTrials.gov (NCT01272349). Results: dAIH improved walking speed and endurance. Ten-Meter Walk time improved with dAIH vs dSHAM after 1 day (mean difference [MD] 3.8 seconds, 95% confidence interval [CI] 1.1–6.5 seconds, p = 0.006) and 2 weeks (MD 3.8 seconds, 95% CI 0.9–6.7 seconds, p = 0.010). Six-Minute Walk distance increased with combined dAIH + walking vs dSHAM + walking after 5 days (MD 94.4 m, 95% CI 17.5–171.3 m, p = 0.017) and 1-week follow-up (MD 97.0 m, 95% CI 20.1–173.9 m, p = 0.014). dAIH + walking increased walking distance more than dAIH after 1 day (MD 67.7 m, 95% CI 1.3–134.1 m, p = 0.046), 5 days (MD 107.0 m, 95% CI 40.6–173.4 m, p = 0.002), and 1-week follow-up (MD 136.0 m, 95% CI 65.3–206.6 m, p < 0.001). Conclusions: dAIH ± walking improved walking speed and distance in persons with chronic iSCI. The impact of dAIH is enhanced by combination with walking, demonstrating that combinatorial therapies may promote greater functional benefits in persons with iSCI. Classification of evidence: This study provides Class I evidence that transient hypoxia (through measured breathing treatments), along with overground walking training, improves walking speed and endurance after iSCI.
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Affiliation(s)
- Heather B Hayes
- From the Department of Rehabilitation Medicine (H.B.H., R.D.T.), Emory University, Atlanta, GA; Department of Physical Medicine and Rehabilitation (A.J., M.H., W.Z.R.), Northwestern University, Chicago; Sensory Motor Performance Program (A.J., W.Z.R.), Rehabilitation Institute of Chicago, IL; Department of Comparative Biosciences (G.S.M.), University of Wisconsin, Madison; Department of Biomedical Engineering (R.D.T.), Georgia Institute of Technology, Atlanta; and The Shepherd Center (R.D.T.), Atlanta, GA
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Lam SY, Liu Y, Ng KM, Liong EC, Tipoe GL, Leung PS, Fung ML. Upregulation of a local renin-angiotensin system in the rat carotid body during chronic intermittent hypoxia. Exp Physiol 2013; 99:220-31. [PMID: 24036592 DOI: 10.1113/expphysiol.2013.074591] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The carotid body (CB) plays an important role in the alteration of cardiorespiratory activity in chronic intermittent hypoxia (IH) associated with sleep-disordered breathing, which may be mediated by local expression of the renin-angiotensin system (RAS). We hypothesized a pathogenic role for IH-induced RAS expression in the CB. The CB expression of RAS components was examined in rats exposed to IH resembling a severe sleep-apnoeic condition for 7 days. In situ hybridization showed an elevated expression of angiotensinogen in the CB glomus cells in the hypoxic group when compared with the normoxic control group. Immunohistochemical studies and Western blot analysis revealed increases in the protein level of both angiotensinogen and angiotensin II type 1 (AT1) receptors in the hypoxic group, which were localized to the glomic clusters containing tyrosine hydroxylase. RT-PCR studies confirmed that levels of the mRNA expression of angiotensinogen, angiotensin-converting enzyme, AT1a and AT2 receptors were significantly increased in the CBs of the hypoxic rats. Functionally, the [Ca(2+)]i response to exogenous angiotensin II was enhanced in fura-2-loaded glomus cells dissociated from hypoxic rats when compared with those of the normoxic control animals. Pretreatment with losartan, but not PD123319, abolished the angiotensin II-induced [Ca(2+)]i response, suggesting an involvement of AT1 receptors. Moreover, daily treatment of the IH group of rats with losartan attenuated the levels of oxidative stress, gp91(phox) expression and macrophage infiltration in the CB. Collectively, the upregulated local RAS expression could play a pathogenic role in the augmented CB activity and local inflammation via AT1 receptor activation during IH conditions in patients with sleep-disordered breathing.
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Affiliation(s)
- Siu-Yin Lam
- M. L. Fung: Department of Physiology, University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong.
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Serebrovskaya TV, Nosar VI, Bratus LV, Gavenauskas BL, Mankovska IM. Tissue oxygenation and mitochondrial respiration under different modes of intermittent hypoxia. High Alt Med Biol 2013; 14:280-8. [PMID: 24028642 DOI: 10.1089/ham.2013.1012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We compared the results of five modes of intermittent hypoxia training (IHT) on gastrocnemius muscle Po2 and heart and liver mitochondrial respiration in rats. Minutes of hypoxia, %O2, and recovery minutes on air in each mode were: 1) 5, 12%, 5; 2) 15, 12%, 15; 3) 5, 12%, 15; 4) 5, 7%, 5; and 5) 5, 7%, 15. Mode 1 proved best in that Pmo2 dropped minimally at the end of every hypoxic bout and recovered quickly after each bout. One, 2, and 3 week IHT in mode 1 each increased tissue PO2 in both normoxic and 30 min severe hypoxic (7% O2) tests. Adaptation to IHT in Mode 1 caused the substrate-dependent reorganization of liver and heart mitochondrial energy metabolism favoring NADH-dependent oxidation and improving the efficiency of oxidative phosphorylation. Mitochondrial adaptation occurred after 14 days of IHT in liver tissue, but after 21 days in myocardium, and was preserved during the 3 months following IHT termination. When using Mode 2, positive changes were also registered, but were less pronounced. Other IHT modes provoked negative effects on Pmo2 levels, both during hypoxic periods and reoxygenation. In conclusion, the most effective IHT regimen is 5 min 12% O2 with 5 min breaks, five cycles per day during 2 or 3 weeks depending on the task of IHT.
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Absolute hypoxic exercise training enhances in vitro thrombin generation by increasing procoagulant platelet-derived microparticles under high shear stress in sedentary men. Clin Sci (Lond) 2013; 124:639-49. [DOI: 10.1042/cs20120540] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
HS (high shear) stress associated with artery stenosis facilitates TG (thrombin generation) by increasing the release of procoagulant PDMPs (platelet-derived microparticles). Physical exercise and hypoxia may paradoxically modulate vascular thrombotic risks. The aim of the present study was to investigate how exercise training with/without hypoxia affected TG mediated by PDMPs under physio-pathological shear flows. A total of 75 sedentary males were randomly divided into five groups (n=15 in each group): 21% O2 [NC (normoxic control)] or 15% O2 [HC (hypoxic control)] at rest or were trained at 50% of peak work rate under 21% O2 [NT (normoxic training)] or 15% O2 [HAT (hypoxic-absolute training)], or 50% of HR (heart rate) reserve under 15% O2 [HRT (hypoxic-relative training)] for 30 min/day, 5 days/week for 4 weeks. The PDMP characteristics and dynamic TG were measured by flow cytometry and thrombinography respectively. Before the intervention, strenuous exercise markedly increased the PDMP count (14.8%) and TG rate (19.5%) in PDMP-rich plasma at 100 dynes/cm2 of shear stress (P<0.05). After the interventions, both NT and HRT significantly attenuated the enhancement of HS-induced PDMPs (4.7 and 4.9%) and TG rate (3.8 and 3.0%) (P<0.05) by severe exercise. Conversely, HAT notably promoted the PDMP count (37.3%) and TG rate (38.9%) induced by HS (P<0.05), concurrent with increasing plasma TF (tissue factor) and coagulation factor V levels at rest or following exercise. We conclude that both HRT and NT depress similarly HS-mediated TG during exercise, but HAT accelerates the prothrombotic response to vigorous exercise. These findings provide new insights into how exercise training under a hypoxic condition influences the risk of thrombosis associated with stenotic arteries.
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Cerebral white matter oxidation and nitrosylation in young rodents with kaolin-induced hydrocephalus. J Neuropathol Exp Neurol 2012; 71:274-88. [PMID: 22437339 DOI: 10.1097/nen.0b013e31824c1b44] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Hydrocephalus is associated with reduced blood flow in periventricular white matter. To investigate hypoxic and oxidative damage in the brains of rats with hydrocephalus, kaolin was injected into the cisterna magna of newborn 7- and 21-day-old Sprague-Dawley rats, and ventricle size was assessed by magnetic resonance imaging at 7, 21, and 42 days of age. In-situ evidence of hypoxia in periventricular capillaries and glial cells was shown by pimonidazole hydrochloride binding. Biochemical assay of thiobarbituric acid reaction and immunohistochemical detection of malondialdehyde and 4-hydroxy-2-nonenal indicated the presence of lipid peroxidation in white matter. Biochemical assay of nitrite indicated increased nitric oxide production. Nitrotyrosine immunohistochemistry showed nitrosylated proteins in white matter reactive microglia and astrocytes. Activities of the antioxidant enzymes catalase and glutathione peroxidase were not increased, and altered hypoxia-inducible factor 1α was not detected by quantitative reverse transcription-polymerase chain reaction. Cerebral vascular endothelial growth factor expression determined by quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay was not changed, but vascular endothelial growth factor immunoreactivity was increased in reactive astrocytes of hydrocephalic white matter. To determine if nitric oxide synthase is involved in the pathogenesis, we induced hydrocephalus in 7-day-old wild-type and neuronal nitric oxide synthase-deficient mice. At 7 days, the wild-type and mutant mice exhibited equally severe ventriculomegaly and no behavioral differences, although increased glial fibrillary acidic protein was less in the mutant mice. We conclude that hypoxia, via peroxidation and nitrosylation, contributes to brain changes in young rodents with hydrocephalus and that compensatory mechanisms are negligible.
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Fenik VB, Singletary T, Branconi JL, Davies RO, Kubin L. Glucoregulatory consequences and cardiorespiratory parameters in rats exposed to chronic-intermittent hypoxia: effects of the duration of exposure and losartan. Front Neurol 2012; 3:51. [PMID: 22509173 PMCID: PMC3321439 DOI: 10.3389/fneur.2012.00051] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 03/20/2012] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Obstructive sleep apnea (OSA) is associated with glucose intolerance. Both chronic sleep disruption and recurrent blood oxygen desaturations (chronic-intermittent hypoxia, CIH) may cause, or exacerbate, metabolic derangements. METHODS To assess the impact of CIH alone, without accompanying upper airway obstructions, on the counter-regulatory response to glucose load and cardiorespiratory parameters, we exposed adult male Sprague-Dawley rats to CIH or sham room air exchanges for 10 h/day for 7, 21, or 35 days and then, 1 day after conclusion of CIH exposure, conducted intravenous glucose-tolerance tests (ivgtt) under urethane anesthesia. Additional rats underwent 35 days of CIH followed by 35 days of regular housing, or had 35 day-long CIH exposure combined with daily administration of the type 1 angiotensin II receptor antagonist, losartan (15 mg/kg, p.o.), and then were also subjected to ivgtt. RESULTS Compared with the corresponding control groups, CIH rats had progressively reduced glucose-stimulated insulin release and impaired glucose clearance, only mildly elevated heart rate and/or arterial blood pressure and slightly reduced respiratory rate. The differences in insulin release between the CIH and sham-treated rats disappeared in the rats normally housed for 35 days after 35 days of CIH/sham exposure. The losartan-treated rats had improved insulin sensitivity, with no evidence of suppressed insulin release in the CIH group. CONCLUSION In adult rats, the glucose-stimulated insulin release is gradually suppressed with the duration of exposure to CIH, but the effect is reversible. Elimination of the detrimental effect of CIH on insulin release by losartan suggests that CIH disrupts glucoregulation through angiotensin/catecholaminergic pathways. Accordingly, treatment with continuous positive airway pressure may ameliorate pre-diabetic conditions in OSA patients, in part, by reducing sympathoexcitatory effects of recurrent nocturnal hypoxia.
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Affiliation(s)
- Victor B Fenik
- Department of Animal Biology 209E/VET, School of Veterinary Medicine, University of Pennsylvania Philadelphia, PA, USA
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Lovett-Barr MR, Satriotomo I, Muir GD, Wilkerson JER, Hoffman MS, Vinit S, Mitchell GS. Repetitive intermittent hypoxia induces respiratory and somatic motor recovery after chronic cervical spinal injury. J Neurosci 2012; 32:3591-600. [PMID: 22423083 PMCID: PMC3349282 DOI: 10.1523/jneurosci.2908-11.2012] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 12/06/2011] [Accepted: 01/14/2012] [Indexed: 12/14/2022] Open
Abstract
Spinal injury disrupts connections between the brain and spinal cord, causing life-long paralysis. Most spinal injuries are incomplete, leaving spared neural pathways to motor neurons that initiate and coordinate movement. One therapeutic strategy to induce functional motor recovery is to harness plasticity in these spared neural pathways. Chronic intermittent hypoxia (CIH) (72 episodes per night, 7 nights) increases synaptic strength in crossed spinal synaptic pathways to phrenic motoneurons below a C2 spinal hemisection. However, CIH also causes morbidity (e.g., high blood pressure, hippocampal apoptosis), rendering it unsuitable as a therapeutic approach to chronic spinal injury. Less severe protocols of repetitive acute intermittent hypoxia may elicit plasticity without associated morbidity. Here we demonstrate that daily acute intermittent hypoxia (dAIH; 10 episodes per day, 7 d) induces motor plasticity in respiratory and nonrespiratory motor behaviors without evidence for associated morbidity. dAIH induces plasticity in spared, spinal pathways to respiratory and nonrespiratory motor neurons, improving respiratory and nonrespiratory (forelimb) motor function in rats with chronic cervical injuries. Functional improvements were persistent and were mirrored by neurochemical changes in proteins that contribute to respiratory motor plasticity after intermittent hypoxia (BDNF and TrkB) within both respiratory and nonrespiratory motor nuclei. Collectively, these studies demonstrate that repetitive acute intermittent hypoxia may be an effective and non-invasive means of improving function in multiple motor systems after chronic spinal injury.
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Affiliation(s)
- Mary R. Lovett-Barr
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
| | - Irawan Satriotomo
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
| | - Gillian D. Muir
- Department of Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5B4
| | - Julia E. R. Wilkerson
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
| | - Michael S. Hoffman
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
| | - Stéphane Vinit
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
| | - Gordon S. Mitchell
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin, 53706, and
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Cheng L, Khoo MCK. Modeling the autonomic and metabolic effects of obstructive sleep apnea: a simulation study. Front Physiol 2012; 2:111. [PMID: 22291654 PMCID: PMC3250672 DOI: 10.3389/fphys.2011.00111] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Accepted: 12/09/2011] [Indexed: 01/12/2023] Open
Abstract
Long-term exposure to intermittent hypoxia and sleep fragmentation introduced by recurring obstructive sleep apnea (OSA) has been linked to subsequent cardiovascular disease and Type 2 diabetes. The underlying mechanisms remain unclear, but impairment of the normal interactions among the systems that regulate autonomic and metabolic function is likely involved. We have extended an existing integrative model of respiratory, cardiovascular, and sleep-wake state control, to incorporate a sub-model of glucose-insulin-fatty acid regulation. This computational model is capable of simulating the complex dynamics of cardiorespiratory control, chemoreflex and state-related control of breath-to-breath ventilation, state-related and chemoreflex control of upper airway potency, respiratory and circulatory mechanics, as well as the metabolic control of glucose-insulin dynamics and its interactions with the autonomic control. The interactions between autonomic and metabolic control include the circadian regulation of epinephrine secretion, epinephrine regulation on dynamic fluctuations in glucose and free-fatty acid in plasma, metabolic coupling among tissues and organs provided by insulin and epinephrine, as well as the effect of insulin on peripheral vascular sympathetic activity. These model simulations provide insight into the relative importance of the various mechanisms that determine the acute and chronic physiological effects of sleep-disordered breathing. The model can also be used to investigate the effects of a variety of interventions, such as different glucose clamps, the intravenous glucose tolerance test, and the application of continuous positive airway pressure on OSA subjects. As such, this model provides the foundation on which future efforts to simulate disease progression and the long-term effects of pharmacological intervention can be based.
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Affiliation(s)
- Limei Cheng
- Biomedical Engineering Department, University of Southern California Los Angeles, CA, USA
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Trumbower RD, Jayaraman A, Mitchell GS, Rymer WZ. Exposure to acute intermittent hypoxia augments somatic motor function in humans with incomplete spinal cord injury. Neurorehabil Neural Repair 2011; 26:163-72. [PMID: 21821826 DOI: 10.1177/1545968311412055] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Neural plasticity may contribute to motor recovery following spinal cord injury (SCI). In rat models of SCI with respiratory impairment, acute intermittent hypoxia (AIH) strengthens synaptic inputs to phrenic motor neurons, thereby improving respiratory function by a mechanism known as respiratory long-term facilitation. Similar intermittent hypoxia-induced facilitation may be feasible in somatic motor pathways in humans. OBJECTIVE Using a randomized crossover design, the authors tested the hypothesis that AIH increases ankle strength in people with incomplete SCI. METHODS Ankle strength was measured in 13 individuals with chronic, incomplete SCI before and after AIH. Voluntary ankle strength was estimated using changes in maximum isometric ankle plantar flexion torque generation and plantar flexor electromyogram activity following 15 low oxygen exposures (Fio(2) = 0.09, 1-minute intervals). Results were compared with trials where subjects received sham exposure to room air. RESULTS AIH increased plantar flexion torque by 82 ± 33% (P < .003) immediately following AIH and was sustained above baseline for more than 90 minutes (P < .007). Increased ankle plantar flexor electromyogram activity (P = .01) correlated with increased torque (r(2) = .5; P < .001). No differences in plantar flexion strength or electromyogram activity were observed in sham experiments. CONCLUSIONS AIH elicits sustained increases in volitional somatic motor output in persons with chronic SCI. Thus, AIH has promise as a therapeutic tool to induce plasticity and enhance motor function in SCI patients.
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Affiliation(s)
- Randy D Trumbower
- Emory University, School of Medicine, Department of Rehabilitation Medicine, Atlanta, GA 30322, USA.
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Almendros I, Farré R, Planas AM, Torres M, Bonsignore MR, Navajas D, Montserrat JM. Tissue oxygenation in brain, muscle, and fat in a rat model of sleep apnea: differential effect of obstructive apneas and intermittent hypoxia. Sleep 2011; 34:1127-33. [PMID: 21804675 DOI: 10.5665/sleep.1176] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
STUDY OBJECTIVES To test the hypotheses that the dynamic changes in brain oxygen partial pressure (PtO(2)) in response to obstructive apneas or to intermittent hypoxia differ from those in other organs and that the changes in brain PtO(2) in response to obstructive apneas is a source of oxidative stress. DESIGN Prospective controlled animal study. SETTING University laboratory. PARTICIPANTS 98 Sprague-Dawley rats. INTERVENTIONS Cerebral cortex, skeletal muscle, or visceral fat tissues were exposed in anesthetized animals subjected to either obstructive apneas or intermittent hypoxia (apneic and hypoxic events of 15 s each and 60 events/h) for 1 h. MEASUREMENTS AND RESULTS Arterial oxygen saturation (SpO(2)) presented a stable pattern, with similar desaturations during both stimuli. The PtO(2) was measured by a microelectrode. During obstructive apneas, a fast increase in cerebral PtO(2) was observed (38.2 ± 3.4 vs. 54.8 ± 5.9 mm Hg) but not in the rest of tissues. This particular cerebral response was not found during intermittent hypoxia. The cerebral content of reduced glutathione was decreased after obstructive apneas (46.2% ± 15.2%) compared to controls (100.0% ± 14.7%), but not after intermittent hypoxia. This antioxidant consumption after obstructive apneas was accompanied by increased cerebral lipid peroxidation under this condition. No changes were observed for these markers in the other tissues. CONCLUSIONS These results suggest that cerebral cortex could be protected in some way from hypoxic periods caused by obstructive apneas. The increased cerebral PtO(2) during obstructive apneas may, however, cause harmful effects (oxidative stress). The obstructive apnea model appears to be more adequate than the intermittent hypoxia model for studying brain changes associated with OSA.
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Should we standardize protocols and preparations used to study respiratory plasticity? Respir Physiol Neurobiol 2011; 177:93-7. [DOI: 10.1016/j.resp.2011.03.021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 03/20/2011] [Accepted: 03/22/2011] [Indexed: 11/19/2022]
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Chai C, Kou J, Zhu D, Yan Y, Yu B. Mice Exposed to Chronic Intermittent Hypoxia Simulate Clinical Features of Deficiency of both Qi and Yin Syndrome in Traditional Chinese Medicine. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2011; 2011:356252. [PMID: 20047893 PMCID: PMC3136371 DOI: 10.1093/ecam/nep226] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2009] [Accepted: 12/01/2009] [Indexed: 02/07/2023]
Abstract
Deficiency of both Qi and Yin Syndrome (DQYS) is one of the common syndromes in traditional Chinese medicine (TCM), mainly characterized by tiredness, emaciation, anorexia, fidget, palpitation and rapid pulse, and so forth. Currently, there is no available animal model which can reflect the clinical features of this syndrome. In the present paper, we observed the time-course changes of whole behavior, body weight, food intake, locomotive activity and electrocardiogram in mice exposed to chronic intermittent hypoxia for 6 weeks, and measured bleeding time at last according to the clinical features of DQYS and one key pathological factor. The results showed that the mice exposed to intermittent hypoxia for certain time presented lackluster hair, dull looking hair, resistance, attacking, body weight loss, food intake decline, locomotive activity decrease, heart rate quickening and T wave elevating, which were similar to the major clinical features of DQYS. Meanwhile, bleeding time shortening was also found, which was consistent with the clinical fact that DQYS often accompanied with blood stasis. The possible explanation was also outlined according to the available literature. Such findings suggested chronic intermittent hypoxia could induce similar symptoms and signs in mice accorded with the clinical features of DQYS, which provided a suitable animal model for evaluation of drugs for the treatment of this syndrome and further exploration of pathological process or correlation of the syndrome and related diseases.
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Affiliation(s)
- Chengzhi Chai
- Department of Complex Prescription of TCM, China Pharmaceutical University, Nanjing, Jiangsu 211198, China
| | - Junping Kou
- Department of Complex Prescription of TCM, China Pharmaceutical University, Nanjing, Jiangsu 211198, China
| | - Danni Zhu
- Department of Complex Prescription of TCM, China Pharmaceutical University, Nanjing, Jiangsu 211198, China
| | - Yongqing Yan
- Department of Complex Prescription of TCM, China Pharmaceutical University, Nanjing, Jiangsu 211198, China
| | - Boyang Yu
- Department of Complex Prescription of TCM, China Pharmaceutical University, Nanjing, Jiangsu 211198, China
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Impact of short-term systemic hypoxia on phagocytosis, cytokine production, and transcription factor activation in peripheral blood cells. Mediators Inflamm 2011; 2011:429501. [PMID: 21765619 PMCID: PMC3134261 DOI: 10.1155/2011/429501] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Accepted: 04/14/2011] [Indexed: 11/17/2022] Open
Abstract
Hypoxia frequently associated with certain physiologic and pathologic conditions influences numerous cellular functions. Because the effects of short-term hypoxia are incompletely understood, we examined phagocytosis and cytokine production as well as the activation of the transcription factors HIF-1 and NFκB in peripheral blood cells of healthy volunteers exposed to an oxygen concentration equivalent to that found at a height of 5500 m. Furthermore, we analysed plasma HIF-1 and serum concentrations of various HIF-1-dependent genes. Results showed that short-term hypoxia increased phagocytosis in neutrophils without affecting monocyte phagocytosis. Hypoxia decreased basal TNFα concentration in monocytes and basal interferon γ concentration in CD4(+) T lymphocytes. In contrast, plasma HIF and serum VEGF concentrations were not affected by hypoxia, although serum EPO concentration was raised. In PBMC, hypoxia increased cytosolic HIF-1 concentration without affecting nuclear HIF-1 concentration and led to a rise in the nuclear NFκB in PBMC. Our results show that short-term hypoxia affects immune functions in healthy individuals. Furthermore, we speculate that the effects of hypoxia are not due to HIF-1, but are caused by the activation of NFκB .
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MacFarlane PM, Vinit S, Mitchell GS. Serotonin 2A and 2B receptor-induced phrenic motor facilitation: differential requirement for spinal NADPH oxidase activity. Neuroscience 2011; 178:45-55. [PMID: 21223996 DOI: 10.1016/j.neuroscience.2011.01.011] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2010] [Revised: 12/08/2010] [Accepted: 01/05/2011] [Indexed: 10/18/2022]
Abstract
Acute intermittent hypoxia (AIH) facilitates phrenic motor output by a mechanism that requires spinal serotonin (type 2) receptor activation, NADPH oxidase activity and formation of reactive oxygen species (ROS). Episodic spinal serotonin (5-HT) receptor activation alone, without changes in oxygenation, is sufficient to elicit NADPH oxidase-dependent phrenic motor facilitation (pMF). Here we investigated: (1) whether serotonin 2A and/or 2B (5-HT2A/B) receptors are expressed in identified phrenic motor neurons, and (2) which receptor subtype is capable of eliciting NADPH-oxidase-dependent pMF. In anesthetized, artificially ventilated adult rats, episodic C4 intrathecal injections (3×6 μl injections, 5 min intervals) of a 5-HT2A (DOI) or 5-HT2B (BW723C86) receptor agonist elicited progressive and sustained increases in integrated phrenic nerve burst amplitude (i.e. pMF), an effect lasting at least 90 min post-injection for both receptor subtypes. 5-HT2A and 5-HT2B receptor agonist-induced pMF were both blocked by selective antagonists (ketanserin and SB206553, respectively), but not by antagonists to the other receptor subtype. Single injections of either agonist failed to elicit pMF, demonstrating a need for episodic receptor activation. Phrenic motor neurons retrogradely labeled with cholera toxin B fragment expressed both 5-HT2A and 5-HT2B receptors. Pre-treatment with NADPH oxidase inhibitors (apocynin and diphenylenodium (DPI)) blocked 5-HT2B, but not 5-HT2A-induced pMF. Thus, multiple spinal type 2 serotonin receptors elicit pMF, but they act via distinct mechanisms that differ in their requirement for NADPH oxidase activity.
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Affiliation(s)
- P M MacFarlane
- Department of Comparative Biosciences, University of Wisconsin, Madison; School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706, USA.
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McGovern NN, Cowburn AS, Porter L, Walmsley SR, Summers C, Thompson AAR, Anwar S, Willcocks LC, Whyte MKB, Condliffe AM, Chilvers ER. Hypoxia selectively inhibits respiratory burst activity and killing of Staphylococcus aureus in human neutrophils. THE JOURNAL OF IMMUNOLOGY 2010; 186:453-463. [PMID: 21135168 DOI: 10.4049/jimmunol.1002213] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Neutrophils play a central role in the innate immune response and a critical role in bacterial killing. Most studies of neutrophil function have been conducted under conditions of ambient oxygen, but inflamed sites where neutrophils operate may be extremely hypoxic. Previous studies indicate that neutrophils sense and respond to hypoxia via the ubiquitous prolyl hydroxylase/hypoxia-inducible factor pathway and that this can signal for enhanced survival. In the current study, human neutrophils were shown to upregulate hypoxia-inducible factor (HIF)-1α-dependent gene expression under hypoxic incubation conditions (3 kPa), with a consequent substantial delay in the onset of apoptosis. Despite this, polarization and chemotactic responsiveness to IL-8 and fMLP were entirely unaffected by hypoxia. Similarly, hypoxia did not diminish the ability of neutrophils to phagocytose serum-opsonized heat-killed streptococci. Of the secretory functions examined, IL-8 generation was preserved and elastase release was enhanced by hypoxia. Hypoxia did, however, cause a major reduction in respiratory burst activity induced both by the soluble agonist fMLP and by ingestion of opsonized zymosan, without affecting expression of the NADPH oxidase subunits. Critically, this reduction in respiratory burst activity under hypoxia was associated with a significant defect in the killing of Staphylococcus aureus. In contrast, killing of Escherichia coli, which is predominantly oxidase independent, was fully preserved under hypoxia. In conclusion, these studies suggest that although the NADPH oxidase-dependent bacterial killing mechanism may be compromised by hypoxia, neutrophils overall appear extremely well adapted to operate successfully under severely hypoxic conditions.
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Affiliation(s)
- Naomi N McGovern
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Andrew S Cowburn
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Linsey Porter
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Sarah R Walmsley
- Academic Unit of Respiratory Medicine, Department of Infection and Immunity, University of Sheffield, Sheffield, United Kingdom
| | - Charlotte Summers
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Alfred A R Thompson
- Academic Unit of Respiratory Medicine, Department of Infection and Immunity, University of Sheffield, Sheffield, United Kingdom
| | - Sadia Anwar
- Academic Unit of Respiratory Medicine, Department of Infection and Immunity, University of Sheffield, Sheffield, United Kingdom
| | - Lisa C Willcocks
- Cambridge Institute of Medical Research, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom
| | - Moira K B Whyte
- Academic Unit of Respiratory Medicine, Department of Infection and Immunity, University of Sheffield, Sheffield, United Kingdom
| | - Alison M Condliffe
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom.,Addenbrooke's amd Papworth Hospital Trusts, Cambridge, United Kingdom
| | - Edwin R Chilvers
- Department of Medicine, University of Cambridge School of Clinical Medicine, Cambridge, United Kingdom.,Addenbrooke's amd Papworth Hospital Trusts, Cambridge, United Kingdom
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Kuo TBJ, Yuan ZF, Lin YS, Lin YN, Li WS, Yang CCH, Lai CJ. Reactive oxygen species are the cause of the enhanced cardiorespiratory response induced by intermittent hypoxia in conscious rats. Respir Physiol Neurobiol 2010; 175:70-9. [PMID: 20863915 DOI: 10.1016/j.resp.2010.09.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/15/2010] [Accepted: 09/15/2010] [Indexed: 11/19/2022]
Abstract
This study was carried out to investigate the role of reactive oxygen species (ROS) in the elevation of cardiorespiratory responses during the development of intermittent hypoxia (IH)-induced hypertension. Rats were exposed to either 30 days of IH [(30s N₂)+(45 s room air (RA)] or RA for 6 h/day. After 5 days of exposure, stable mean arterial pressure, normalized low-frequency power of pulses interval spectrogram (a marker of cardiac sympathetic outflow), and minute ventilation (an index for arterial chemoreflex activation) were significantly increased throughout the observation period in IH-exposed rats, but not in RA-exposed rats. FosB expression in rostral ventrolateral medulla was elevated after IH exposure for 5 days. Intraperitoneal injection of MnTMPyP (a superoxide scavenger) or N-acetylcysteine (an antioxidant) prevented IH-induced elevation of the cardiorespiratory responses and lipid peroxidation of lung tissues. These results suggest that ROS are essential for IH-induced elevation of arterial chemoreflex activation and sympathetic outflow, which may, in turn, contribute to IH-induced hypertension.
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Affiliation(s)
- Terry B J Kuo
- Institute of Brain Science, National Yang-Ming University, Taipei, Taiwan
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Velez-Pardo C, Jimenez-Del-Rio M, Lores-Arnaiz S, Bustamante J. Protective Effects of the Synthetic Cannabinoids CP55,940 and JWH-015 on Rat Brain Mitochondria upon Paraquat Exposure. Neurochem Res 2010; 35:1323-32. [DOI: 10.1007/s11064-010-0188-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/04/2010] [Indexed: 10/19/2022]
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Almendros I, Montserrat JM, Torres M, González C, Navajas D, Farré R. Changes in oxygen partial pressure of brain tissue in an animal model of obstructive apnea. Respir Res 2010; 11:3. [PMID: 20078851 PMCID: PMC2817656 DOI: 10.1186/1465-9921-11-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 01/15/2010] [Indexed: 12/03/2022] Open
Abstract
Background Cognitive impairment is one of the main consequences of obstructive sleep apnea (OSA) and is usually attributed in part to the oxidative stress caused by intermittent hypoxia in cerebral tissues. The presence of oxygen-reactive species in the brain tissue should be produced by the deoxygenation-reoxygenation cycles which occur at tissue level during recurrent apneic events. However, how changes in arterial blood oxygen saturation (SpO2) during repetitive apneas translate into oxygen partial pressure (PtO2) in brain tissue has not been studied. The objective of this study was to assess whether brain tissue is partially protected from intermittently occurring interruption of O2 supply during recurrent swings in arterial SpO2 in an animal model of OSA. Methods Twenty-four male Sprague-Dawley rats (300-350 g) were used. Sixteen rats were anesthetized and non-invasively subjected to recurrent obstructive apneas: 60 apneas/h, 15 s each, for 1 h. A control group of 8 rats was instrumented but not subjected to obstructive apneas. PtO2 in the cerebral cortex was measured using a fast-response oxygen microelectrode. SpO2 was measured by pulse oximetry. The time dependence of arterial SpO2 and brain tissue PtO2 was carried out by Friedman repeated measures ANOVA. Results Arterial SpO2 showed a stable periodic pattern (no significant changes in maximum [95.5 ± 0.5%; m ± SE] and minimum values [83.9 ± 1.3%]). By contrast, brain tissue PtO2 exhibited a different pattern from that of arterial SpO2. The minimum cerebral cortex PtO2 computed during the first apnea (29.6 ± 2.4 mmHg) was significantly lower than baseline PtO2 (39.7 ± 2.9 mmHg; p = 0.011). In contrast to SpO2, the minimum and maximum values of PtO2 gradually increased (p < 0.001) over the course of the 60 min studied. After 60 min, the maximum (51.9 ± 3.9 mmHg) and minimum (43.7 ± 3.8 mmHg) values of PtO2 were significantly greater relative to baseline and the first apnea dip, respectively. Conclusions These data suggest that the cerebral cortex is partially protected from intermittently occurring interruption of O2 supply induced by obstructive apneas mimicking OSA.
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Abstract
Sleep-induced apnea and disordered breathing refers to intermittent, cyclical cessations or reductions of airflow, with or without obstructions of the upper airway (OSA). In the presence of an anatomically compromised, collapsible airway, the sleep-induced loss of compensatory tonic input to the upper airway dilator muscle motor neurons leads to collapse of the pharyngeal airway. In turn, the ability of the sleeping subject to compensate for this airway obstruction will determine the degree of cycling of these events. Several of the classic neurotransmitters and a growing list of neuromodulators have now been identified that contribute to neurochemical regulation of pharyngeal motor neuron activity and airway patency. Limited progress has been made in developing pharmacotherapies with acceptable specificity for the treatment of sleep-induced airway obstruction. We review three types of major long-term sequelae to severe OSA that have been assessed in humans through use of continuous positive airway pressure (CPAP) treatment and in animal models via long-term intermittent hypoxemia (IH): 1) cardiovascular. The evidence is strongest to support daytime systemic hypertension as a consequence of severe OSA, with less conclusive effects on pulmonary hypertension, stroke, coronary artery disease, and cardiac arrhythmias. The underlying mechanisms mediating hypertension include enhanced chemoreceptor sensitivity causing excessive daytime sympathetic vasoconstrictor activity, combined with overproduction of superoxide ion and inflammatory effects on resistance vessels. 2) Insulin sensitivity and homeostasis of glucose regulation are negatively impacted by both intermittent hypoxemia and sleep disruption, but whether these influences of OSA are sufficient, independent of obesity, to contribute significantly to the "metabolic syndrome" remains unsettled. 3) Neurocognitive effects include daytime sleepiness and impaired memory and concentration. These effects reflect hypoxic-induced "neural injury." We discuss future research into understanding the pathophysiology of sleep apnea as a basis for uncovering newer forms of treatment of both the ventilatory disorder and its multiple sequelae.
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Affiliation(s)
- Jerome A Dempsey
- The John Rankin Laboratory of Pulmonary Medicine, Departments of Population Health Sciences and of Orthopedics and Rehabilitation, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706, USA.
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Systemic hypoxia promotes lymphocyte apoptosis induced by oxidative stress during moderate exercise. Eur J Appl Physiol 2009; 108:371-82. [PMID: 19816709 DOI: 10.1007/s00421-009-1231-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2009] [Indexed: 01/01/2023]
Abstract
Blood undergoes oxidative stress during severe hypoxia or intense exercise. Excessive exposure to oxidative stress induces replicative senescence and apoptosis of lymphocytes. This study determines how various exercises with/without hypoxia affect lymphocyte subset mobilization and oxidative stress-induced lymphocyte apoptosis. Eighteen sedentary males randomly engaged in two normoxic exercise bouts [severe exercise (SE) (up to VO(2max)) and moderate-intensity exercise (ME) (50%VO(2max)) while exposed to 21%O(2)], two hypoxic exercise bouts (ME while exposed to 12%O(2) and 15%O(2)) and two hypoxic resting conditions (resting while exposed to 12%O(2) and 15%O(2)) in a normobaric hypoxia chamber. Under normoxic conditions, SE but not ME (1) increased the percentages of senescent (CD28(-) and CD57(+))/activated (CD62L(-) and CD11a(+))-form lymphocytes mobilized into the peripheral blood compartment; (2) decreased the levels of surface thiol and intracellular total (t-GSH) and reduced-form glutathione (r-GSH) of lymphocytes in blood; and (3) further enhanced the extents of H(2)O(2)-induced mitochondria trans-membrane potential diminishing, caspases 3/8/9 activation, poly(ADP-ribose) polymerase cleavage and phosphotidyl serine exposure in blood lymphocytes. However, no significant change occurred in the subset mobilization, antioxidant levels or apoptosis of lymphocytes following exposure to either 12%O(2) or 15%O(2). Although both 12%O(2) and 15%O(2) ME increased the mobilization of senescent/activated-form lymphocytes, only 12%O(2) ME enhanced H(2)O(2)-induced lymphocyte thiol, t-GSH and r-GSH consumption and apoptotic responses. Therefore, we conclude that the 12%O(2) exposure increases the mobilization of senescent/activated-form lymphocytes into the peripheral blood compartment and simultaneously enhances oxidative stress-induced lymphocyte apoptosis by diminishing cellular antioxidant levels during exercise.
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Abstract
Obstructive sleep apnea is characterized by repeated upper airway obstruction during sleep and affects between 5% and 20% of the population. Epidemiological studies reveal that sleep apnea and associated intermittent hypoxemia increase the risk for hypertension and vascular disease but the mechanisms underlying these effects are incompletely understood. This review reports the results of rodent models of intermittent hypoxia (IH) and relates them to the observed hemodynamic and vascular consequences of sleep apnea. These animal studies have demonstrated that IH exposure in the absence of any other comorbidity causes hypertension, endothelial dysfunction, and augmented constrictor sensitivity, all due at least in part to increased vascular oxidative stress. Animal studies have used a variety of exposure paradigms to study intermittent hypoxia and these different exposure protocols can cause hypocapnia or hypercapnia-or maintain eucapnia-with accompanying alterations in plasma pH. It appears that these different profiles of arterial blood gases can lead to divergent results but the impact of these differences is still being investigated. Overall, the studies in rodents have clearly demonstrated that the vascular and hemodynamic impact of intermittent hypoxia provides a strong rationale for treating clinical sleep apnea to prevent the resulting cardiovascular morbidity and mortality.
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Affiliation(s)
- Nancy L Kanagy
- Vascular Physiology Group, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.
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Expression of signal transduction genes differs after hypoxic or isoflurane preconditioning of rat hippocampal slice cultures. Anesthesiology 2009; 111:258-66. [PMID: 19568165 DOI: 10.1097/aln.0b013e3181a8647f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Preconditioning neurons with noninjurious hypoxia (hypoxic preconditioning, HPC) or the anesthetic isoflurane (APC) induces tolerance of severe ischemic stress. The mechanisms of both types of preconditioning in the hippocampus require moderate increases in intracellular Ca and activation of protein kinase signaling. The authors hypothesized that the expression of signal transduction genes would be similar after APC and HPC. METHODS Hippocampal slice cultures prepared from 9-day-old rats were preconditioned with hypoxia (5 min of 95% nitrogen/5% carbon dioxide) or 1% isoflurane in air/5% carbon dioxide for 1 h. A day later, cultures were subjected to 10 min oxygen and glucose deprivation (simulated ischemia). Intracellular Ca, measured in CA1 neurons at the completion of preconditioning, and cell death in CA1, CA3, and dentate regions was assessed 48 h after simulated ischemia. Message RNA encoding 119 signal transduction genes was quantified with rat complimentary DNA microarrays from pre-oxygen-glucose deprivation samples. RESULTS Both APC and HPC increased intracellular Ca approximately 50 nm and decreased CA1, CA3, and dentate neuron death by about 50% after simulated ischemia. Many signaling genes were increased after preconditioning, with hypoxia increasing more apoptosis/survival genes (8 of 10) than isoflurane (0 of 10). In contrast, isoflurane increased more cell cycle/development/growth genes than did hypoxia (8 of 14 genes, vs. 1 of 14). CONCLUSIONS Despite sharing similar upstream signaling and neuroprotective outcomes, the genomic response to APC and HPC is different. Increased expression of antiapoptosis genes after HPC and cell development genes after APC has implications both for neuroprotection and long-term effects of anesthetics.
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Weissmann N, Hackemack S, Dahal BK, Pullamsetti SS, Savai R, Mittal M, Fuchs B, Medebach T, Dumitrascu R, Eickels MV, Ghofrani HA, Seeger W, Grimminger F, Schermuly RT. The soluble guanylate cyclase activator HMR1766 reverses hypoxia-induced experimental pulmonary hypertension in mice. Am J Physiol Lung Cell Mol Physiol 2009; 297:L658-65. [PMID: 19617308 DOI: 10.1152/ajplung.00189.2009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Severe pulmonary hypertension (PH) is a disabling disease with high mortality, characterized by pulmonary vascular remodeling and right heart hypertrophy. In mice with PH induced by chronic hypoxia, we examined the acute and chronic effects of the soluble guanylate cyclase (sGC) activator HMR1766 on hemodynamics and pulmonary vascular remodeling. In isolated perfused mouse lungs from control animals, HMR1766 dose-dependently inhibited the pressor response of acute hypoxia. This dose-response curve was shifted leftward when the effects of HMR1766 were investigated in isolated lungs from chronic hypoxic animals for 21 days at 10% oxygen. Mice exposed for 21 or 35 days to chronic hypoxia developed PH, right heart hypertrophy, and pulmonary vascular remodeling. Treatment with HMR1766 (10 mg x kg(-1) x day(-1)), after full establishment of PH from day 21 to day 35, significantly reduced PH, as measured continuously by telemetry. In addition, right ventricular (RV) hypertrophy and structural remodeling of the lung vasculature were reduced. Pharmacological activation of oxidized sGC partially reverses hemodynamic and structural changes in chronic hypoxia-induced experimental PH.
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Affiliation(s)
- Norbert Weissmann
- Univ. of Giessen Lung Center Medical Clinic II/V, Klinikstr. 36, 35392 Giessen, Germany
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Systemic hypoxia enhances bactericidal activities of human polymorphonuclear leuocytes. Clin Sci (Lond) 2009; 116:805-17. [DOI: 10.1042/cs20080224] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
ROS (reactive oxygen species) generated by hypoxia facilitate the vascular inflammatory response, but whether systemic hypoxia influences leucocyte bactericidal activity by modulating circulatory redox status remains unclear. The present study elucidates how various hypoxic interventions influence the bactericidal activity of PMNs (polymorphonuclear leucocytes) following treatment with an antioxidant, vitamin E (D-α-tocopheryl acetate). Forty healthy sedentary men were randomly assigned to vitamin E (n=20) and placebo (n=20) groups. At 1 h following oral administration of 1000 i.u. of vitamin E or placebo, each subject in the two groups was randomly exposed to 12%, 15%, 18% and 21% O2 for 2 h in a normobaric hypoxia chamber. The results demonstrated that exposure to 12% O2 in the placebo group increased urinary 8-isoprostane and plasma malondialdehyde levels and decreased plasma total antioxidant content and superoxide dismutase activity, but did not alter plasma complement-C3a desArg/C4a desArg/C5a concentrations. Moreover, this hypoxic exposure also increased the chemotaxis of PMNs by exposure to N-formyl-Met-Leu-Phe, the phagocytosis of PMNs to Escherichia coli and the release of PMN oxidant products by E. coli, processes which were accompanied by increased expressions of L-selectin, LFA-1 (lymphocyte function-associated antigen 1), Mac-1, FcγIIIBR, C1qRp and C5aR on PMNs. However, exposure to 12% O2 in the vitamin E group did not influence expression of the opsonic/complement receptors on PMNs, and the chemotactic, phagocytic or oxidative burst activities of PMN, whereas the circulatory redox status and complement fragment levels were unaltered following this hypoxic exposure and pretreatment with vitamin E. Additionally, the circulatory redox status, complement systems, PMN-mediated bactericidal processes and the opsonic/complement receptors on PMNs were constant following exposure to 15%, 18% or 21% O2 in the two groups. We conclude that exposure to 12% O2 promotes the chemotactic, phagocytic and oxidative burst activities of PMNs, possibly by increasing lipid peroxidation and decreasing antioxidative capacity. However, this hypoxic effect on PMN bactericidal activity is ameliorated by pretreatment with vitamin E.
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HIF-1 and ventilatory acclimatization to chronic hypoxia. Respir Physiol Neurobiol 2009; 164:282-7. [PMID: 18708172 DOI: 10.1016/j.resp.2008.07.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Revised: 07/17/2008] [Accepted: 07/18/2008] [Indexed: 12/18/2022]
Abstract
Ventilatory acclimatization to hypoxia (VAH) is a time-dependent increase in ventilation and ventilatory O2-sensitivity that involves plasticity in carotid body chemoreceptors and CNS respiratory centers. Hypoxia inducible factor-1alpha (HIF-1alpha) controls the expression of several genes that increase physiological O2 supply. Studies using transgenic mice show HIF-1alpha expression in the carotid bodies and CNS with chronic sustained and intermittent hypoxia is important for VAH. Other O2-sensitive transcription factors such as HIF-2alpha may be important for VAH by reducing metabolic O2 demands also. Specific gene targets of HIF-1alpha shown to be involved in VAH include erythropoietin, endothelin-1, neuronal nitric oxide synthase and tyrosine hydroxylase. Other HIF-1alpha targets that may be involved in VAH include vascular endothelial growth factor, heme oxygenase 1 and cytoglobin. Interactions between these multiple pathways and feedback control of HIF-1alpha expression from some of the targets support a complex and powerful role for HIF-1alpha in neural plasticity of physiological control circuits with chronic hypoxia.
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