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Lu B, Chen X, Ma Y, Gui M, Yao L, Li J, Wang M, Zhou X, Fu D. So close, yet so far away: the relationship between MAM and cardiac disease. Front Cardiovasc Med 2024; 11:1353533. [PMID: 38374992 PMCID: PMC10875081 DOI: 10.3389/fcvm.2024.1353533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 01/22/2024] [Indexed: 02/21/2024] Open
Abstract
Mitochondria-associated membrane (MAM) serve as crucial contact sites between mitochondria and the endoplasmic reticulum (ER). Recent research has highlighted the significance of MAM, which serve as a platform for various protein molecules, in processes such as calcium signaling, ATP production, mitochondrial structure and function, and autophagy. Cardiac diseases caused by any reason can lead to changes in myocardial structure and function, significantly impacting human health. Notably, MAM exhibits various regulatory effects to maintain cellular balance in several cardiac diseases conditions, such as obesity, diabetes mellitus, and cardiotoxicity. MAM proteins independently or interact with their counterparts, forming essential tethers between the ER and mitochondria in cardiomyocytes. This review provides an overview of key MAM regulators, detailing their structure and functions. Additionally, it explores the connection between MAM and various cardiac injuries, suggesting that precise genetic, pharmacological, and physical regulation of MAM may be a promising strategy for preventing and treating heart failure.
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Affiliation(s)
- Bo Lu
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, United States
| | - Xiaozhe Chen
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Yulong Ma
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Mingtai Gui
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Lei Yao
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Jianhua Li
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Mingzhu Wang
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Xunjie Zhou
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Shanghai University of Traditional Chinese Medicine, Shanghai, China
| | - Deyu Fu
- Department of Cardiology, Yueyang Hospital of Integrated Traditional Chinese and Western Medicine, Shanghai University of Traditional Chinese Medicine, Shanghai, China
- Shanghai University of Traditional Chinese Medicine, Shanghai, China
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Cetin-Atalay R, Meliton AY, Ozcan C, Woods PS, Sun KA, Fang Y, Hamanaka RB, Mutlu GM. Loss of heme oxygenase 2 causes reduced expression of genes in cardiac muscle development and contractility and leads to cardiomyopathy in mice. PLoS One 2023; 18:e0292990. [PMID: 37844118 PMCID: PMC10578579 DOI: 10.1371/journal.pone.0292990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 10/03/2023] [Indexed: 10/18/2023] Open
Abstract
Obstructive sleep apnea (OSA) is a common breathing disorder that affects a significant portion of the adult population. In addition to causing excessive daytime sleepiness and neurocognitive effects, OSA is an independent risk factor for cardiovascular disease; however, the underlying mechanisms are not completely understood. Using exposure to intermittent hypoxia (IH) to mimic OSA, we have recently reported that mice exposed to IH exhibit endothelial cell (EC) activation, which is an early process preceding the development of cardiovascular disease. Although widely used, IH models have several limitations such as the severity of hypoxia, which does not occur in most patients with OSA. Recent studies reported that mice with deletion of hemeoxygenase 2 (Hmox2-/-), which plays a key role in oxygen sensing in the carotid body, exhibit spontaneous apneas during sleep and elevated levels of catecholamines. Here, using RNA-sequencing we investigated the transcriptomic changes in aortic ECs and heart tissue to understand the changes that occur in Hmox2-/- mice. In addition, we evaluated cardiac structure, function, and electrical properties by using echocardiogram and electrocardiogram in these mice. We found that Hmox2-/- mice exhibited aortic EC activation. Transcriptomic analysis in aortic ECs showed differentially expressed genes enriched in blood coagulation, cell adhesion, cellular respiration and cardiac muscle development and contraction. Similarly, transcriptomic analysis in heart tissue showed a differentially expressed gene set enriched in mitochondrial translation, oxidative phosphorylation and cardiac muscle development. Analysis of transcriptomic data from aortic ECs and heart tissue showed loss of Hmox2 gene might have common cellular network footprints on aortic endothelial cells and heart tissue. Echocardiographic evaluation showed that Hmox2-/- mice develop progressive dilated cardiomyopathy and conduction abnormalities compared to Hmox2+/+ mice. In conclusion, we found that Hmox2-/- mice, which spontaneously develop apneas exhibit EC activation and transcriptomic and functional changes consistent with heart failure.
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Affiliation(s)
- Rengul Cetin-Atalay
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Angelo Y. Meliton
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Cevher Ozcan
- Department of Medicine, Section of Cardiology, University of Chicago, Chicago, Illinois, United States of America
| | - Parker S. Woods
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Kaitlyn A. Sun
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Yun Fang
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Robert B. Hamanaka
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
| | - Gökhan M. Mutlu
- Department of Medicine, Section of Pulmonary and Critical Care Medicine, University of Chicago, Chicago, Illinois, United States of America
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Yang X, Sha X, Cao Y, Wang W, Shi J. Cx43 overexpression reduce the incidence of obstructive sleep apnea associated atrial fibrillation via the CaMKⅡγ/HIF-1 axis. Biochem Biophys Res Commun 2023; 659:62-71. [PMID: 37037067 DOI: 10.1016/j.bbrc.2023.03.084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 03/26/2023] [Accepted: 03/31/2023] [Indexed: 04/03/2023]
Abstract
BACKGROUND Previous studies by our group have demonstrated chronic intermittent hypoxia (CIH) can decrease connexin 43 (Cx43) protein expression and thus increase atrial fibrillation (AF) inducibility. Cardiac sympathetic denervation (CSD) can reduce AF and increase Cx43 expression, however, the underlying molecular mechanisms and signaling pathways are still unclear. METHODS AND RESULTS An obstructive sleep apnea (OSA) rat model in vivo experiments and CIH H9c2 cells model in vitro experiments were used to figure out the roles and underlying mechanisms of Cx43 on OSA-associated AF. In this study, we examined the expression of Cx43, CaMKⅡγ, Bax, Caspase 3, HIF-1 Bcl-2, Tunel, and CPB/p300, to discover the association between proteins and the mechanism of regulatory changes. The downstream proteins of Cx43 were calculated by gene sequencing and data analysis. We found Cx43 expression was significantly downregulated after CIH exposure in rat and H9c2 cells. Active caspase-3 and Bax at CIH+8 h group are high, but decreased at OE+8 h group. The Bcl-2 expression was higher in the N and OE+8 h group than CIH+8 h group. TUNEL-positive cells from the CIH+8 h group was markedly higher. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated Cx43 overexpression inhibited the CaMKIIγ expression, and CaMKIIγ was involved in the HIF-1 signaling pathway. In addition, we also found Cx43 overexpression remarkably decreased the HIF-1 protein and p300 mRNA expression, which inhibits the CaMKIIγ/HIF-1 signaling pathway. CONCLUSIONS Taken together, these results suggested Cx43 overexpression inhibits the expression of calcium/calmodulin dependent protein CaMKⅡγ via the Cx43/CaMKIIγ/HIF-1 axis, which finally reduces the myocardial apoptosis and incidence of AF.
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Intermittent Hypoxia-Induced Cardiomyocyte Death Is Mediated by HIF-1 Dependent MAM Disruption. Antioxidants (Basel) 2022; 11:antiox11081462. [PMID: 36009181 PMCID: PMC9405320 DOI: 10.3390/antiox11081462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 07/19/2022] [Accepted: 07/20/2022] [Indexed: 12/04/2022] Open
Abstract
Rationale: Intermittent hypoxia (IH) is one of the main features of sleep-disordered breathing (SDB). Recent findings indicate that hypoxia inducible factor-1 (HIF-1) promotes cardiomyocytes apoptosis during chronic IH, but the mechanisms involved remain to be elucidated. Here, we hypothesize that IH-induced ER stress is associated with mitochondria-associated ER membrane (MAM) alteration and mitochondrial dysfunction, through HIF-1 activation. Methods: Right atrial appendage biopsies from patients with and without SDB were used to determine HIF-1α, Grp78 and CHOP expressions. Wild-type and HIF-1α+/− mice were exposed to normoxia (N) or IH (21–5% O2, 60 cycles/h, 8 h/day) for 21 days. Expressions of HIF-1α, Grp78 and CHOP, and apoptosis, were measured by Western blot and immunochemistry. In isolated cardiomyocytes, we examined structural integrity of MAM by proximity ligation assay and their function by measuring ER-to-mitochondria Ca2+ transfer by confocal microscopy. Finally, we measured mitochondrial respiration using oxygraphy and calcium retention capacity (CRC) by spectrofluorometry. MAM structure was also investigated in H9C2 cells incubated with 1 mM CoCl2, a potent HIF-1α inducer. Results: In human atrial biopsies and mice, IH induced HIF-1 activation, ER stress and apoptosis. IH disrupted MAM, altered Ca2+ homeostasis, mitochondrial respiration and CRC. Importantly, IH had no effect in HIF-1α+/− mice. Similar to what observed under IH, HIF-1α overexpression was associated with MAM alteration in H9C2. Conclusion: IH-induced ER stress, MAM alterations and mitochondrial dysfunction were mediated by HIF-1; all these intermediate mechanisms ultimately inducing cardiomyocyte apoptosis. This suggests that HIF-1 modulation might limit the deleterious cardiac effects of SDB.
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Chen TI, Chen MYC. Zinc Is Indispensable in Exercise-Induced Cardioprotection against Intermittent Hypoxia-Induced Left Ventricular Function Impairment in Rats. PLoS One 2016; 11:e0168600. [PMID: 27977796 PMCID: PMC5158066 DOI: 10.1371/journal.pone.0168600] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 12/03/2016] [Indexed: 01/19/2023] Open
Abstract
In obstructive sleep apnea (OSA), recurrent obstruction of the upper airway leads to intermittent hypoxia (IH) during sleep, which can result in impairment of cardiac function. Although exercise can have beneficial effects against IH-induced cardiac dysfunction, the mechanism remains unclear. This study aimed to investigate the interactions of zinc and exercise on IH-triggered left ventricular dysfunction in a rat model that mimics IH in OSA patients. Nine-week-old male Sprague-Dawley rats were randomly assigned to either a control group (CON) or to a group receiving 10 weeks of exercise training (EXE). During weeks 9 and 10, half the rats in each group were subjected to IH for 8 h per day for 14 days (IHCON, IHEXE), whereas the remainder continued to breathe room air. Rats within each of the CON, IHCON, EXE, and IHEXE groups were further randomly assigned to receive intraperitoneal injections of either zinc chloride, the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), or injection vehicle only. IH induced a lower left ventricular fractional shortening, reduced ejection fraction, higher myocardial levels of inflammatory factors, increased levels oxidative stress, and lower levels of antioxidative capacity, all of which were abolished by zinc treatment. IHEXE rats exhibited higher levels of cardiac function and antioxidant capacity and lower levels of inflammatory factors and oxidative stress than IHCON rats; however, IHEXE rats receiving TPEN did not exhibit these better outcomes. In conclusion, zinc is required for protecting against IH-induced LV functional impairment and likely plays a critical role in exercise-induced cardioprotection by exerting a dual antioxidant and anti-inflammatory effect.
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Affiliation(s)
- Tsung-I Chen
- Center of Physical Education, Office of General and Basic Education, Tzu Chi University, Hualien, Taiwan
- * E-mail:
| | - Michael Yu-Chih Chen
- Department of Cardiology, Buddhist Tzu Chi General Hospital, Hualien, Taiwan
- PhD Program in Institute of Medicine, Tzu Chi University, Hualien, Taiwan
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Chen TI, Tu WC. Exercise Attenuates Intermittent Hypoxia-Induced Cardiac Fibrosis Associated with Sodium-Hydrogen Exchanger-1 in Rats. Front Physiol 2016; 7:462. [PMID: 27790155 PMCID: PMC5064604 DOI: 10.3389/fphys.2016.00462] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 09/26/2016] [Indexed: 12/22/2022] Open
Abstract
Purpose: To investigate the role of sodium–hydrogen exchanger-1 (NHE-1) and exercise training on intermittent hypoxia-induced cardiac fibrosis in obstructive sleep apnea (OSA), using an animal model mimicking the intermittent hypoxia of OSA. Methods: Eight-week-old male Sprague–Dawley rats were randomly assigned to control (CON), intermittent hypoxia (IH), exercise (EXE), or IH combined with exercise (IHEXE) groups. These groups were randomly assigned to subgroups receiving either a vehicle or the NHE-1 inhibitor cariporide. The EXE and IHEXE rats underwent exercise training on an animal treadmill for 10 weeks (5 days/week, 60 min/day, 24–30 m/min, 2–10% grade). The IH and IHEXE rats were exposed to 14 days of IH (30 s of hypoxia—nadir of 2–6% O2—followed by 45 s of normoxia) for 8 h/day. At the end of 10 weeks, rats were sacrificed and then hearts were removed to determine the myocardial levels of fibrosis index, oxidative stress, antioxidant capacity, and NHE-1 activation. Results: Compared to the CON rats, IH induced higher cardiac fibrosis, lower myocardial catalase, and superoxidative dismutase activities, higher myocardial lipid and protein peroxidation and higher NHE-1 activation (p < 0.05 for each), which were all abolished by cariporide. Compared to the IH rats, lower cardiac fibrosis, higher myocardial antioxidant capacity, lower myocardial lipid, and protein peroxidation and lower NHE-1 activation were found in the IHEXE rats (p < 0.05 for each). Conclusion: IH-induced cardiac fibrosis was associated with NHE-1 hyperactivity. However, exercise training and cariporide exerted an inhibitory effect to prevent myocardial NHE-1 hyperactivity, which contributed to reduced IH-induced cardiac fibrosis. Therefore, NHE-1 plays a critical role in the effect of exercise on IH-induced increased cardiac fibrosis.
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Affiliation(s)
- Tsung-I Chen
- Center of Physical Education, Office of General and Basic Education, Tzu Chi University Hualien, Taiwan
| | - Wei-Chia Tu
- Master program in Physiological and Anatomical Medicine, School of Medicine, Tzu Chi University Hualien, Taiwan
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Pai P, Lai CJ, Lin CY, Liou YF, Huang CY, Lee SD. Effect of superoxide anion scavenger on rat hearts with chronic intermittent hypoxia. J Appl Physiol (1985) 2016; 120:982-90. [PMID: 26769958 DOI: 10.1152/japplphysiol.01109.2014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 01/08/2016] [Indexed: 12/18/2022] Open
Abstract
Only very limited information regarding the protective effects of the superoxide anion scavenger on chronic intermittent hypoxia-induced cardiac apoptosis is available. The purpose of this study is to evaluate the effects of the superoxide anion scavenger on cardiac apoptotic and prosurvival pathways in rats with sleep apnea. Forty-two Sprague-Dawley rats were divided into three groups, rats with normoxic exposure (Control, 21% O2, 1 mo), rats with chronic intermittent hypoxia exposure (Hypoxia, 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo), and rats with pretreatment of the superoxide anion scavenger and chronic intermittent hypoxia exposure (Hypoxia-O2 (-)-Scavenger, MnTMPyP pentachloride, 1 mg/kg ip per day; 3-7% O2vs. 21% O2per 40 s cycle, 8 h per day, 1 mo) at 5-6 mo of age. After 1 mo, the protein levels and apoptotic cells of excised hearts from three groups were measured by Western blotting and terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay. The superoxide anion scavenger decreased hypoxia-induced myocardial architecture abnormalities, left ventricular hypertrophy, and TUNEL-positive apoptosis. The superoxide anion scavenger decreased hypoxia-induced Fas ligand, Fas death receptors, Fas-associated death domain (FADD), activated caspase-8, and activated caspase-3 (Fas-dependent apoptotic pathway) as well as Bad, activated caspase-9 and activated caspase-3 (mitochondria-dependent apoptotic pathway), endonuclease G (EndoG), apoptosis-inducing factor (AIF), and TUNEL-positive apoptosis. The superoxide anion scavenger increased IGF-1, IGF-1R, p-PI3k, p-Akt, p-Bad, Bcl-2, and Bcl-xL (survival pathway). Our findings imply that the superoxide anion scavenger might prevent cardiac Fas-mediated and mitochondrial-mediated apoptosis and enhance the IGF-1-related survival pathway in chronic intermittent hypoxia. The superoxide anion scavenger may prevent chronic sleep apnea-enhanced cardiac apoptotic pathways and enhances cardiac survival pathways.
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Affiliation(s)
- Peiying Pai
- China Medical University, Graduate Institute of Clinical Medical Science, Taichung, Taiwan; Division of Cardiology, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Ching Jung Lai
- Department of Physiology, Tzu Chi University, Hualien, Taiwan
| | - Ching-Yuang Lin
- China Medical University, Graduate Institute of Clinical Medical Science, Taichung, Taiwan; Clinical Immunology Center, China Medical University Hospital, Taichung, Taiwan
| | - Yi-Fan Liou
- Division of Cardiology, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan
| | - Chih-Yang Huang
- Graduate Institute of Chinese Medical Science, China Medical University, Taichung, Taiwan; Institute of Basic Medical Science, China Medical University, Taichung, Taiwan; Department of Health and Nutrition Biotechnology, Asia University, Taichung, Taiwan
| | - Shin-Da Lee
- School of Rehabilitation Science, Shanghai University of Traditional Chinese Medicine, Shanghai, China; Department of Occupational Therapy, Asia University, Taichung, Taiwan; and Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, Taichung, Taiwan
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Chen TI, Chiu HW, Pan YC, Hsu ST, Lin JH, Yang KT. Intermittent hypoxia-induced protein phosphatase 2A activation reduces PC12 cell proliferation and differentiation. J Biomed Sci 2014; 21:46. [PMID: 24885237 PMCID: PMC4058715 DOI: 10.1186/1423-0127-21-46] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 11/26/2013] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Intermittent hypoxia (IH) plays a critical role in sleep breathing disorder-associated hippocampus impairments, including neurocognitive deficits, irreversible memory and learning impairments. IH-induced neuronal injury in the hippocampus may result from reduced precursor cell proliferation and the relative numbers of postmitotic differentiated neurons. However, the mechanisms underlying IH-induced reactive oxygen species (ROS) generation effects on cell proliferation and neuronal differentiation remain largely unknown. RESULTS ROS generation significantly increased after 1-4 days of IH without increased pheochromocytoma-12 (PC12) cell death, which resulted in increased protein phosphatase 2A (PP2A) mRNA and protein levels. After 3-4 days of IH, extracellular signal-regulated kinases 1/2 (ERK1/2) protein phosphorylation decreased, which could be reversed by superoxide dismutase (SOD), 1,10-phenanthroline (Phe), the PP2A phosphorylation inhibitors, okadaic acid (OKA) and cantharidin, and the ERK phosphorylation activator nicotine (p < 0.05). In particular, the significantly reduced cell proliferation and increased proportions of cells in the G0/G1 phase after 1-4 days of IH (p < 0.05), which resulted in decreased numbers of PC12 cells, could be reversed by treatment with SOD, Phe, PP2A inhibitors and an ERK activator. In addition, the numbers of nerve growth factor (NGF)-induced PC12 cells with neurite outgrowths after 3-4 days of IH were less than those after 4 days of RA, which was also reversed by SOD, Phe, PP2A inhibitors and an ERK activator. CONCLUSIONS Our results suggest that IH-induced ROS generation increases PP2A activation and subsequently downregulates ERK1/2 activation, which results in inhibition of PC12 cell proliferation through G0/G1 phase arrest and NGF-induced neuronal differentiation.
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Affiliation(s)
| | | | | | | | | | - Kun-Ta Yang
- Master program, Physiology and Anatomical Medicine, School of Medicine, Tzu Chi University, Hualien, Taiwan.
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Metallothionein prevents intermittent hypoxia-induced cardiac endoplasmic reticulum stress and cell death likely via activation of Akt signaling pathway in mice. Toxicol Lett 2014; 227:113-23. [PMID: 24680926 DOI: 10.1016/j.toxlet.2014.03.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 03/17/2014] [Accepted: 03/17/2014] [Indexed: 12/22/2022]
Abstract
Endoplasmic reticulum (ER) stress, an adaptive response normally, causes apoptotic cell death under pathological conditions. Cardiac ER stress and associated cell death involve in the inflammatory responses that often cause cardiac remodeling and dysfunction. Here we examined whether chronic intermittent hypoxia (IH) induces cardiac ER stress and associated cell death along with inflammatory response and if so, whether these effects can be affected by transgenic overexpression or deletion of metallothionein gene (MT-TG or MT-KO). IH exposures for 3 days to 4 weeks significantly increased cardiac ER stress and apoptosis, shown by the increased expression of GRP78, ATF6 and CHOP, the activation of caspase-12 and capase-3, and the decreased Bcl2/Bax expression ratio, predominantly in the 3rd week of IH exposures. These effects were significantly exacerbated in MT-KO mice, but completely prevented in MT-TG mice. In vitro mechanistic study with H9c2 cardiac and primary neonatal cardiomyocytes showed that MT protection from ER stress-induced apoptosis was mediated by up-regulating Akt phosphorylation since inhibition of Akt phosphorylation abolished MT's protection MT from ER stress and apoptosis. These findings suggest that chronic IH is able to induce cardiac ER stress, cell death and inflammation can be prevented by MT, probably via up-regulation of Akt function.
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Death by a thousand cuts in Alzheimer's disease: hypoxia--the prodrome. Neurotox Res 2013; 24:216-43. [PMID: 23400634 DOI: 10.1007/s12640-013-9379-2] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 01/10/2013] [Accepted: 01/21/2013] [Indexed: 12/30/2022]
Abstract
A wide range of clinical consequences may be associated with obstructive sleep apnea (OSA) including systemic hypertension, cardiovascular disease, pulmonary hypertension, congestive heart failure, cerebrovascular disease, glucose intolerance, impotence, gastroesophageal reflux, and obesity, to name a few. Despite this, 82 % of men and 93 % of women with OSA remain undiagnosed. OSA affects many body systems, and induces major alterations in metabolic, autonomic, and cerebral functions. Typically, OSA is characterized by recurrent chronic intermittent hypoxia (CIH), hypercapnia, hypoventilation, sleep fragmentation, peripheral and central inflammation, cerebral hypoperfusion, and cerebral glucose hypometabolism. Upregulation of oxidative stress in OSA plays an important pathogenic role in the milieu of hypoxia-induced cerebral and cardiovascular dysfunctions. Strong evidence underscores that cerebral amyloidogenesis and tau phosphorylation--two cardinal features of Alzheimer's disease (AD), are triggered by hypoxia. Mice subjected to hypoxic conditions unambiguously demonstrated upregulation in cerebral amyloid plaque formation and tau phosphorylation, as well as memory deficit. Hypoxia triggers neuronal degeneration and axonal dysfunction in both cortex and brainstem. Consequently, neurocognitive impairment in apneic/hypoxic patients is attributable to a complex interplay between CIH and stimulation of several pathological trajectories. The framework presented here helps delineate the emergence and progression of cognitive decline, and may yield insight into AD neuropathogenesis. The global impact of CIH should provide a strong rationale for treating OSA and snoring clinically, in order to ameliorate neurocognitive impairment in aged/AD patients.
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Quintessential Risk Factors: Their Role in Promoting Cognitive Dysfunction and Alzheimer’s Disease. Neurochem Res 2012; 37:2627-58. [DOI: 10.1007/s11064-012-0854-6] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 07/21/2012] [Indexed: 12/13/2022]
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Role of leptin as antioxidant in obstructive sleep apnea: an in vitro study using electron paramagnetic resonance method. Sleep Breath 2012; 17:105-10. [PMID: 22307865 DOI: 10.1007/s11325-012-0656-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 01/11/2012] [Accepted: 01/16/2012] [Indexed: 01/18/2023]
Abstract
INTRODUCTION As in obstructive sleep apnea (OSA), the chronic cycles of hypoxia and reoxygenation are thought to be conducive of oxidative stress (OS) with generation of reactive oxygen species, identifying effective mechanisms of protection against oxidant-mediated tissue damage becomes of outmost importance. Leptin's role had been recently extended into that of participant to OS; while its exact role in this process is yet to be defined, elevated leptin levels correlate significantly with several indices of OSA disease severity such as nocturnal hypoxemia, possibly acting as a counteractive mechanism against the chronic intermittent hypoxia-related OS and serving as a marker of future risk of atherosclerotic disease. We therefore investigated leptin's antioxidant mechanism on superoxide (O (2) (-•) ) anions using spectrophotometry and electron paramagnetic resonance (EPR). METHODS The O (2) (-•) was generated by oxidation of xanthine (XAN) by xanthine oxidase (XO) in the presence of spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide with various concentrations of leptin (0.001, 0.01, 0.1, and 1 mg/ml) and without leptin. Signal intensity between 3,440 and 3,540 G was expressed as standard means ± SD. The activity of leptin on XO was determined by monitoring the conversion of XAN to uric acid at 293 nm using a Beckman DU 800 UV-visible spectrophotometer. RESULTS Leptin added to aqueous solutions at 0.1 and 1 mg/ml concentrations was associated with a statistically significant decrease in the EPR signal due to leptin's direct scavenging activity towards the O (2) (-•) . CONCLUSION Leptin is an antioxidant agent of possible use as a marker of OS and future risk of atherosclerotic disease in OSA.
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Liu CF, Tung YT, Wu CL, Lee BH, Hsu WH, Pan TM. Antihypertensive effects of Lactobacillus-fermented milk orally administered to spontaneously hypertensive rats. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2011; 59:4537-4543. [PMID: 21446645 DOI: 10.1021/jf104985v] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Products fermented with lactic acid bacteria may show antihypertensive effects via substances such as angiotensin I-converting enzyme inhibitor (ACEI) and γ-aminobutyric acid (GABA). It was previously found that milk fermented with Lactobacillus paracasei subsp. paracasei NTU 101 (101FM) or Lactobacillus plantarum NTU 102 (102FM) has ACEI and GABA activities. This study aimed to investigate the antihypertensive effects of 101FM and 102FM orally administered to spontaneously hypertensive rats (SHRs). Eight hours after a single oral administration or after 8 weeks of weekly (chronic) administration, 101FM and 102FM significantly decreased systolic and diastolic blood pressures in the SHRs. Microscopic examination of aortic tissue demonstrated that 101FM and 102FM reduced the disorganization of the media layer. These findings suggest that orally administered 101FM and 102FM have antihypertensive effects, possibly via ACEI and GABA activity, in SHRs. Therefore, 101FM and 102FM may be useful ingredients in physiologically functional foods to prevent hypertension.
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Affiliation(s)
- Chin Feng Liu
- Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei, Taiwan
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