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Liu G, Li M, Zeng Z, Fan Q, Ren X, Wang Z, Sun Y, He Y, Sun L, Deng Y, Liu S, Zhong C, Gao J. Tyrosine hydroxylase inhibits HCC progression by downregulating TGFβ/Smad signaling. Eur J Med Res 2024; 29:228. [PMID: 38610044 PMCID: PMC11015545 DOI: 10.1186/s40001-024-01703-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/31/2024] [Indexed: 04/14/2024] Open
Abstract
The alteration of metabolic processes has been found to have significant impacts on the development of hepatocellular carcinoma (HCC). Nevertheless, the effects of dysfunction of tyrosine metabolism on the development of HCC remains to be discovered. This research demonstrated that tyrosine hydroxylase (TH), which responsible for the initial and limiting step in the bio-generation of the neuro-transmitters dopamine and adrenaline, et al. was shown to be reduced in HCC. Increased expression of TH was found facilitates the survival of HCC patients. In addition, decreased TH indicated larger tumor size, much more numbers of tumor, higher level of AFP, and the presence of cirrhosis. TH effectively impairs the growth and metastasis of HCC cells, a process dependent on the phosphorylation of serine residues (S19/S40). TH directly binds to Smad2 and hinders the cascade activation of TGFβ/Smad signaling with the treatment of TGFβ1. In summary, our study uncovered the non-metabolic functions of TH in the development of HCC and proposes that TH might be a promising biomarker for diagnosis as well as an innovative target for metastatic HCC.
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Affiliation(s)
- Guoqian Liu
- Key Laboratory of Molecular Radiation Oncology Hunan Province, Changsha, 410008, Hunan, China
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Mengwei Li
- Key Laboratory of Molecular Radiation Oncology Hunan Province, Changsha, 410008, Hunan, China
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Zimei Zeng
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Qi Fan
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Xinxin Ren
- Cancer Center, Department of Pathology, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, 310014, Zhejiang, China
| | - Zhexin Wang
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Yaoqi Sun
- Department of Obstetrics and Gynecology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China
- Institute of Gynecological Minimally Invasive Medicine, Tongji University School of Medicine, Shanghai, 200072, China
| | - Yulin He
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China
| | - Lunquan Sun
- Key Laboratory of Molecular Radiation Oncology Hunan Province, Changsha, 410008, Hunan, China
| | - Yuezhen Deng
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China.
| | - Shupeng Liu
- Department of Obstetrics and Gynecology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, 200072, China.
- Institute of Gynecological Minimally Invasive Medicine, Tongji University School of Medicine, Shanghai, 200072, China.
| | - Chenxi Zhong
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China.
| | - Jie Gao
- Key Laboratory of Molecular Radiation Oncology Hunan Province, Changsha, 410008, Hunan, China.
- Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, China.
- Xiangya Cancer Center, Xiangya Hospital, Central South University, 87th of Xiangya Road, Changsha, 410008, China.
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2
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Li L, Shen S, Bickler P, Jacobson MP, Wu LF, Altschuler SJ. Searching for molecular hypoxia sensors among oxygen-dependent enzymes. eLife 2023; 12:e87705. [PMID: 37494095 PMCID: PMC10371230 DOI: 10.7554/elife.87705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 07/09/2023] [Indexed: 07/27/2023] Open
Abstract
The ability to sense and respond to changes in cellular oxygen levels is critical for aerobic organisms and requires a molecular oxygen sensor. The prototypical sensor is the oxygen-dependent enzyme PHD: hypoxia inhibits its ability to hydroxylate the transcription factor HIF, causing HIF to accumulate and trigger the classic HIF-dependent hypoxia response. A small handful of other oxygen sensors are known, all of which are oxygen-dependent enzymes. However, hundreds of oxygen-dependent enzymes exist among aerobic organisms, raising the possibility that additional sensors remain to be discovered. This review summarizes known and potential hypoxia sensors among human O2-dependent enzymes and highlights their possible roles in hypoxia-related adaptation and diseases.
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Affiliation(s)
- Li Li
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Susan Shen
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Department of Psychiatry, University of California, San FranciscoSan FranciscoUnited States
| | - Philip Bickler
- Hypoxia Research Laboratory, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Center for Health Equity in Surgery and Anesthesia, University of California San Francisco, San FranciscoSan FranciscoUnited States
- Anesthesia and Perioperative Care, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Matthew P Jacobson
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Lani F Wu
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
| | - Steven J Altschuler
- Department of Pharmaceutical Chemistry, University of California San Francisco, San FranciscoSan FranciscoUnited States
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3
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Zhang Q, Huang R, Hu H, Yu L, Tang Q, Tao Y, Liu Z, Li J, Wang G. Integrative Analysis of Hypoxia-Associated Signature in Pan-Cancer. iScience 2020; 23:101460. [PMID: 32861996 PMCID: PMC7476856 DOI: 10.1016/j.isci.2020.101460] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 07/18/2020] [Accepted: 08/12/2020] [Indexed: 02/06/2023] Open
Abstract
Hypoxia is serving crucial roles in cancers. This study aims to comprehensively analyze the molecular features and clinical relevance of a well-defined hypoxia-associated signature in pan-cancer using multi-omics data. Data were acquired from TCGA, CCLE, GDSC, and GEO. RNA expression pattern, copy number variation (CNV), methylation, and mutation of the signature were analyzed. The majority of the 15 genes were upregulated in cancer tissues compared with normal tissue, and RNA expression was negatively associated with methylation level. CNV occurred in almost all the cancers, whereas mutation frequency was low across different cancer types. The signature was also closely related to cancer hallmarks and cancer-related metabolism pathways. NDRG1 was upregulated in kidney cancer tissues as indicated by immunohistochemistry. Besides, most of the 15 genes were risk factors for patients' overall survival. Our results provide a valuable resource that will guide both mechanistic and therapeutic analyses of the hypoxia signature in cancers.
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Affiliation(s)
- Qian Zhang
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Rui Huang
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Hanqing Hu
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Lei Yu
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Qingchao Tang
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Yangbao Tao
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Zheng Liu
- Department of Colorectal Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing 100000, China
| | - Jiaying Li
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
| | - Guiyu Wang
- Department of Colorectal Surgery, the Second Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang Province 150086, China
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4
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Bechmann N, Poser I, Seifert V, Greunke C, Ullrich M, Qin N, Walch A, Peitzsch M, Robledo M, Pacak K, Pietzsch J, Richter S, Eisenhofer G. Impact of Extrinsic and Intrinsic Hypoxia on Catecholamine Biosynthesis in Absence or Presence of Hif2α in Pheochromocytoma Cells. Cancers (Basel) 2019; 11:cancers11050594. [PMID: 31035382 PMCID: PMC6562431 DOI: 10.3390/cancers11050594] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 01/10/2023] Open
Abstract
Pheochromocytomas and paragangliomas (PPGLs) with activated pseudohypoxic pathways are associated with an immature catecholamine phenotype and carry a higher risk for metastasis. For improved understanding of the underlying mechanisms we investigated the impact of hypoxia and pseudohypoxia on catecholamine biosynthesis in pheochromocytoma cells naturally lacking Hif2α (MPC and MTT) or expressing both Hif1α and Hif2α (PC12). Cultivation under extrinsic hypoxia or in spheroid culture (intrinsic hypoxia) increased cellular dopamine and norepinephrine contents in all cell lines. To distinguish further between Hif1α- and Hif2α-driven effects we expressed Hif2α in MTT and MPC-mCherry cells (naturally lacking Hif2α). Presence of Hif2α resulted in similarly increased cellular dopamine and norepinephrine under hypoxia as in the control cells. Furthermore, hypoxia resulted in enhanced phosphorylation of tyrosine hydroxylase (TH). A specific knockdown of Hif1α in PC12 diminished these effects. Pseudohypoxic conditions, simulated by expression of Hif2α under normoxia resulted in increased TH phosphorylation, further stimulated by extrinsic hypoxia. Correlations with PPGL tissue data led us to conclude that catecholamine biosynthesis under hypoxia is mainly mediated through increased phosphorylation of TH, regulated as a short-term response (24–48 h) by HIF1α. Continuous activation of hypoxia-related genes under pseudohypoxia leads to a HIF2α-mediated phosphorylation of TH (permanent status).
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Affiliation(s)
- Nicole Bechmann
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
| | - Isabel Poser
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
| | - Verena Seifert
- Department of Radiopharmaceutical and Chemical Biology, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328 Dresden, Germany.
| | - Christian Greunke
- Research Unit Analytical Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
| | - Martin Ullrich
- Department of Radiopharmaceutical and Chemical Biology, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328 Dresden, Germany.
| | - Nan Qin
- Division of Pediatric Neuro-Oncogenomics, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany.
- German Consortium for Translational Cancer Research (DKTK), partner site Essen/Düsseldorf, 45147 Düsseldorf, Germany.
- Department of Pediatric Oncology, Hematology, and Clinical Immunology, Medical Faculty, University Hospital Düsseldorf, 40225 Düsseldorf, Germany.
- Department of Neuropathology, Medical Faculty, Heinrich-Heine University Düsseldorf, 40225 Düsseldorf, Germany.
| | - Axel Walch
- Research Unit Analytical Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany; Ingolstädter Landstraße 1, 85764 Neuherberg, Germany.
| | - Mirko Peitzsch
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
| | - Mercedes Robledo
- Hereditary Endocrine Cancer Group, CNIO, Madrid, Spain and Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), 28029 Madrid, Spain.
| | - Karel Pacak
- Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jens Pietzsch
- Department of Radiopharmaceutical and Chemical Biology, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiopharmaceutical Cancer Research, Bautzner Landstrasse 400, 01328 Dresden, Germany.
- Department of Chemistry and Food Chemistry, School of Science, Technische Universität Dresden, Mommsenstrasse 9, 01062 Dresden, Germany.
| | - Susan Richter
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
| | - Graeme Eisenhofer
- Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
- Department of Medicine III, University Hospital Carl Gustav Carus, Technische Universität Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
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5
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Dunkley PR, Dickson PW. Tyrosine hydroxylase phosphorylation
in vivo. J Neurochem 2019; 149:706-728. [DOI: 10.1111/jnc.14675] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 01/23/2019] [Accepted: 01/29/2019] [Indexed: 12/31/2022]
Affiliation(s)
- Peter R. Dunkley
- The School of Biomedical Sciences and Pharmacy and The Hunter Medical Research Institute The University of Newcastle University Drive Callaghan NSW Australia
| | - Phillip W. Dickson
- The School of Biomedical Sciences and Pharmacy and The Hunter Medical Research Institute The University of Newcastle University Drive Callaghan NSW Australia
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6
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Roy K, Chauhan G, Kumari P, Wadhwa M, Alam S, Ray K, Panjwani U, Kishore K. Phosphorylated delta sleep inducing peptide restores spatial memory and p-CREB expression by improving sleep architecture at high altitude. Life Sci 2018; 209:282-290. [PMID: 30107169 DOI: 10.1016/j.lfs.2018.08.026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 08/07/2018] [Accepted: 08/10/2018] [Indexed: 12/27/2022]
Abstract
AIMS Sleep loss at high altitude (HA) play major role in worsening of neuropsychological functions, such as attention, memory and decision making. This study investigates the role of phosphorylated delta sleep inducing peptide (p-DSIP) in improving sleep architecture during chronic hypobaric hypoxia (HH) exposure and restoration of spatial navigational memory. METHODS Morris water maze (MWM) trained rats were exposed to HH at 7620 m. p-DSIP was injected intra-peritoneally (10 μg/Kg bw) during HH exposure as an intervention against sleep alteration. Sleep architecture was recorded telemetrically before and during HH exposure. Monoamines were estimated by high performance liquid chromatography from brain stem (BS) and hypothalamus. CREB and p-CREB level in hippocampus was studied by western blotting and expression of different monoamine regulatory enzymes in BS was measured by flow cytometry. Naloxone (1 mg/kg bw), a μ opioid receptor antagonist of sleep inducing effect of DSIP was also studied. KEY FINDINGS p-DSIP injection daily in circadian active period (18.30 h) during chronic HH enhanced non rapid eye movement sleep, rapid eye movement sleep as well as improved MWM performance of rats. p-DSIP treatment showed lower monoamine level and tyrosine hydroxylase (TH) expression and increased monoamine oxidase A (MAO A), glutamic acid decarboxylase (GAD) and Choline acetyltransferase (ChAT) expression. Further, naloxone altered navigational memory by decreasing the CREB and p-CREB level in hippocampus suggesting suppression of sleep inducing effect of p-DSIP. SIGNIFICANCE Our study demonstrates that improvement of sleep quality by p-DSIP restores spatial memory by up regulating CREB phosphorylation during simulated high altitude hypoxia.
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Affiliation(s)
- Koustav Roy
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Garima Chauhan
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Punita Kumari
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Meetu Wadhwa
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Shahnawaz Alam
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Koushik Ray
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Usha Panjwani
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India
| | - Krishna Kishore
- Defence Institute of Physiology and Allied Sciences (DIPAS), Defence Research and Development Organization (DRDO), Lucknow Road, Timarpur, Delhi 110 054, India.
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7
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Luo Y, Liu B, Yang X, Ma X, Zhang X, Bragin DE, Yang XO, Huang W, Liu M. Myeloid adrenergic signaling via CaMKII forms a feedforward loop of catecholamine biosynthesis. J Mol Cell Biol 2018; 9:422-434. [PMID: 29087480 DOI: 10.1093/jmcb/mjx046] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Accepted: 10/25/2017] [Indexed: 11/13/2022] Open
Abstract
Type 2 immune response has been shown to facilitate cold-induced thermogenesis and browning of white fat. However, whether alternatively activated macrophages produce catecholamine and substantially promote adaptive thermogenesis in adipose tissue remains controversial. Here, we show that tyrosine hydroxylase (TyrH), a rate-limiting enzyme of catecholamine biosynthesis, was expressed and phosphorylated in adipose-resident macrophages. In addition, the plasma level of adrenaline was increased by cold stress in mice, and treatment of macrophages with adrenaline stimulated phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and TyrH. Genetic and pharmacological inhibition of CaMKII or PKA signaling diminished adrenaline-induced phosphorylation of TyrH in primary macrophages. Consistently, overexpression of constitutively active CaMKII upregulated basal TyrH phosphorylation, while suppressing the stimulatory effect of adrenaline on TyrH in macrophages. Myeloid-specific disruption of CaMKIIγ suppressed both the cold-induced production of norepinephrine and adipose UCP1 expression in vivo and the stimulatory effect of adrenaline on macrophage-dependent activation of brown adipocytes in vitro. Lack of CaMKII signaling attenuated catecholamine production mediated by cytokines IL-4 and IL-13, key inducers of type 2 immune response in primary macrophages. Taken together, these results suggest a feedforward mechanism of adrenaline in adipose-resident macrophages, and that myeloid CaMKII signaling plays an important role in catecholamine production and subsequent beige fat activation.
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Affiliation(s)
- Yan Luo
- Department of Endocrinology and Metabolism, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, China.,Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
| | - Bilian Liu
- Department of Endocrinology and Metabolism, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Xin Yang
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
| | - Xiaoxiao Ma
- Department of Diabetes Complications & Metabolism Research, City of Hope, Duarte, CA, USA
| | - Xing Zhang
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA.,Department of Microbiology and Molecular Genetics, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
| | - Denis E Bragin
- Department of Neurosurgery, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
| | - Xuexian O Yang
- Department of Microbiology and Molecular Genetics, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
| | - Wendong Huang
- Department of Diabetes Complications & Metabolism Research, City of Hope, Duarte, CA, USA
| | - Meilian Liu
- Department of Endocrinology and Metabolism, Metabolic Syndrome Research Center, Key Laboratory of Diabetes Immunology, National Clinical Research Center for Metabolic Diseases, The Second Xiangya Hospital, Central South University, Changsha, China.,Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center School of Medicine, Albuquerque, NM, USA
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8
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Hunyor I, Cook KM. Models of intermittent hypoxia and obstructive sleep apnea: molecular pathways and their contribution to cancer. Am J Physiol Regul Integr Comp Physiol 2018; 315:R669-R687. [PMID: 29995459 DOI: 10.1152/ajpregu.00036.2018] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Obstructive sleep apnea (OSA) is common and linked to a variety of poor health outcomes. A key modulator of this disease is nocturnal intermittent hypoxia. There is striking epidemiological evidence that patients with OSA have higher rates of cancer and cancer mortality. Small-animal models demonstrate an important role for systemic intermittent hypoxia in tumor growth and metastasis, yet the underlying mechanisms are poorly understood. Emerging data indicate that intermittent hypoxia activates the hypoxic response and inflammatory pathways in a manner distinct from chronic hypoxia. However, there is significant heterogeneity in published methods for modeling hypoxic conditions, which are often lacking in physiological relevance. This is particularly important for studying key transcriptional mediators of the hypoxic and inflammatory responses such as hypoxia-inducible factor (HIF) and NF-κB. The relationship between HIF, the molecular clock, and circadian rhythm may also contribute to cancer risk in OSA. Building accurate in vitro models of intermittent hypoxia reflective of OSA is challenging but necessary to better elucidate underlying molecular pathways.
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Affiliation(s)
- Imre Hunyor
- Department of Cardiology, Royal Prince Alfred Hospital , Sydney, New South Wales , Australia.,Faculty of Medicine and Health, University of Sydney School of Medicine , Sydney, New South Wales , Australia
| | - Kristina M Cook
- Faculty of Medicine and Health, University of Sydney School of Medicine , Sydney, New South Wales , Australia.,Charles Perkins Centre, University of Sydney , Sydney, New South Wales , Australia
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9
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Phenylethanolamine N-methyltransferase gene expression in PC12 cells exposed to intermittent hypoxia. Neurosci Lett 2018; 666:169-174. [DOI: 10.1016/j.neulet.2017.12.056] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 12/23/2017] [Accepted: 12/26/2017] [Indexed: 11/22/2022]
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10
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Minoves M, Morand J, Perriot F, Chatard M, Gonthier B, Lemarié E, Menut JB, Polak J, Pépin JL, Godin-Ribuot D, Briançon-Marjollet A. An innovative intermittent hypoxia model for cell cultures allowing fast Po2 oscillations with minimal gas consumption. Am J Physiol Cell Physiol 2017; 313:C460-C468. [DOI: 10.1152/ajpcell.00098.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 07/20/2017] [Accepted: 07/20/2017] [Indexed: 01/13/2023]
Abstract
Performing hypoxia-reoxygenation cycles in cell culture with a cycle duration accurately reflecting what occurs in obstructive sleep apnea (OSA) patients is a difficult but crucial technical challenge. Our goal was to develop a novel device to expose multiple cell culture dishes to intermittent hypoxia (IH) cycles relevant to OSA with limited gas consumption. With gas flows as low as 200 ml/min, our combination of plate holders with gas-permeable cultureware generates rapid normoxia-hypoxia cycles. Cycles alternating 1 min at 20% O2 followed by 1 min at 2% O2 resulted in Po2 values ranging from 124 to 44 mmHg. Extending hypoxic and normoxic phases to 10 min allowed Po2 variations from 120 to 25 mmHg. The volume of culture medium or the presence of cells only modestly affected the Po2 variations. In contrast, the nadir of the hypoxia phase increased when measured at different heights above the membrane. We validated the physiological relevance of this model by showing that hypoxia inducible factor-1α expression was significantly increased by IH exposure in human aortic endothelial cells, murine breast carcinoma (4T1) cells as well as in a blood-brain barrier model (2.5-, 1.5-, and 6-fold increases, respectively). In conclusion, we have established a new device to perform rapid intermittent hypoxia cycles in cell cultures, with minimal gas consumption and the possibility to expose several culture dishes simultaneously. This device will allow functional studies of the consequences of IH and deciphering of the molecular biology of IH at the cellular level using oxygen cycles that are clinically relevant to OSA.
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Affiliation(s)
- Mélanie Minoves
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
| | - Jessica Morand
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
| | - Frédéric Perriot
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
| | - Morgane Chatard
- Université de Lyon and Université Jean Monnet, Saint-Etienne, France
| | - Brigitte Gonthier
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
| | - Emeline Lemarié
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
| | | | - Jan Polak
- Center for Research on Diabetes, Metabolism and Nutrition Third Faculty of Medicine, Charles University, Prague, Czech Republic; and
| | - Jean-Louis Pépin
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
- Centre Hospitalier Universitaire, Grenoble, France
| | - Diane Godin-Ribuot
- HP2 Laboratory, Université Grenoble Alpes, Grenoble, France
- INSERM, U1042, Grenoble, France
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11
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Campillo N, Falcones B, Montserrat JM, Gozal D, Obeso A, Gallego-Martin T, Navajas D, Almendros I, Farré R. Frequency and magnitude of intermittent hypoxia modulate endothelial wound healing in a cell culture model of sleep apnea. J Appl Physiol (1985) 2017. [PMID: 28642292 DOI: 10.1152/japplphysiol.00077.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Intermittent hypoxia (IH) has been implicated in the cardiovascular consequences of obstructive sleep apnea (OSA). However, the lack of suitable experimental systems has precluded assessment as to whether IH is detrimental, protective, or both for the endothelium. The aim of the work was to determine the effects of frequency and amplitude of IH oxygenation swings on aortic endothelial wound healing. Monolayers of human primary endothelial cells were wounded and subjected to constant oxygenation (1%, 4%, 13%, or 20% O2) or IH at different frequencies (0.6, 6, or 60 cycles/h) and magnitude ranges (13-4% O2 or 20-1% O2), using a novel well-controlled system, with wound healing being measured after 24 h. Cell monolayer repair was similar at 20% O2 and 13% O2, but was considerably increased (approximately twofold) in constant hypoxia at 4% O2 The magnitude and frequency of IH considerably modulated wound healing. Cycles ranging 13-4% O2 at the lowest frequency (0.6 cycles/h) accelerated endothelial wound healing by 102%. However, for IH exposures consisting of 20% to 1% O2 oscillations, wound closure was reduced compared with oscillation in the 13-4% range (by 74% and 44% at 6 cycles/h and 0.6 cycles/h, respectively). High-frequency IH patterns simulating severe OSA (60 cycles/h) did not significantly modify endothelial wound closure, regardless of the oxygenation cycle amplitude. In conclusion, the frequency and magnitude of hypoxia cycling in IH markedly alter wound healing responses and emerge as key factors determining how cells will respond in OSA.NEW & NOTEWORTHY Intermittent hypoxia (IH) induces cardiovascular consequences in obstructive sleep apnea (OSA) patients. However, the vast array of frequencies and severities of IH previously employed in OSA-related experimental studies has led to controversial results on the effects of IH. By employing an optimized IH experimental system here, we provide evidence that the frequency and magnitude of IH markedly alter human aortic endothelial wound healing, emerging as key factors determining how cells respond in OSA.
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Affiliation(s)
- Noelia Campillo
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain
| | - Bryan Falcones
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain
| | - Josep M Montserrat
- Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Sleep Lab, Hospital Clinic Barcelona, Barcelona, Spain
| | - David Gozal
- Section of Pediatric Sleep Medicine, Department of Pediatrics, Pritzker School of Medicine, Biological Sciences Division, The University of Chicago, Chicago, Illinois
| | - Ana Obeso
- Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid, El Instituto de Biología y Genética Molecular/Consejo Superior de Investigaciones Científicas, Valladolid, Spain
| | - Teresa Gallego-Martin
- Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid, El Instituto de Biología y Genética Molecular/Consejo Superior de Investigaciones Científicas, Valladolid, Spain
| | - Daniel Navajas
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Institut de Bioenginyeria de Catalunya, Barcelona, Spain; and
| | - Isaac Almendros
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Institut d'Investigacions Biomediques August Pi Sunyer, Barcelona, Spain
| | - Ramon Farré
- Unitat de Biofísica i Bioenginyeria, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Barcelona, Spain; .,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias, Madrid, Spain.,Institut d'Investigacions Biomediques August Pi Sunyer, Barcelona, Spain
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12
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Kumar GK, Nanduri J, Peng YJ, Prabhakar NR. Neuromolecular mechanisms mediating the effects of chronic intermittent hypoxia on adrenal medulla. Respir Physiol Neurobiol 2015; 209:115-9. [PMID: 25583660 DOI: 10.1016/j.resp.2015.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 01/01/2015] [Indexed: 10/24/2022]
Abstract
Sleep disordered breathing (SDB) with recurrent apnea is a major health problem affecting several million adult men and women. Humans with SDB are prone to develop hypertension. Studies on rodents established that exposure to chronic intermittent hypoxia (CIH) alone is sufficient to induce hypertension similar to that seen in patients with SDB. Available evidence from studies on experimental animals suggests that catecholamines secreted from adrenal medulla (AM), an end-organ of the sympathetic nervous system is a major contributor to CIH-induced hypertension. In this article, we present an overview of our current understanding on how CIH reconfigures AM function and highlight recent findings on the underlying cellular and molecular mechanisms.
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Affiliation(s)
- Ganesh K Kumar
- Institute for Integrative Physiology and Center for Systems Biology of O(2) Sensing, Biological Sciences Division, University of Chicago, IL, USA.
| | - Jayasri Nanduri
- Institute for Integrative Physiology and Center for Systems Biology of O(2) Sensing, Biological Sciences Division, University of Chicago, IL, USA
| | - Ying-Jie Peng
- Institute for Integrative Physiology and Center for Systems Biology of O(2) Sensing, Biological Sciences Division, University of Chicago, IL, USA
| | - Nanduri R Prabhakar
- Institute for Integrative Physiology and Center for Systems Biology of O(2) Sensing, Biological Sciences Division, University of Chicago, IL, USA
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13
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Diogo LN, Monteiro EC. The efficacy of antihypertensive drugs in chronic intermittent hypoxia conditions. Front Physiol 2014; 5:361. [PMID: 25295010 PMCID: PMC4170135 DOI: 10.3389/fphys.2014.00361] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 09/03/2014] [Indexed: 12/22/2022] Open
Abstract
Sleep apnea/hypopnea disorders include centrally originated diseases and obstructive sleep apnea (OSA). This last condition is renowned as a frequent secondary cause of hypertension (HT). The mechanisms involved in the pathogenesis of HT can be summarized in relation to two main pathways: sympathetic nervous system stimulation mediated mainly by activation of carotid body (CB) chemoreflexes and/or asphyxia, and, by no means the least important, the systemic effects of chronic intermittent hypoxia (CIH). The use of animal models has revealed that CIH is the critical stimulus underlying sympathetic activity and hypertension, and that this effect requires the presence of functional arterial chemoreceptors, which are hyperactive in CIH. These models of CIH mimic the HT observed in humans and allow the study of CIH independently without the mechanical obstruction component. The effect of continuous positive airway pressure (CPAP), the gold standard treatment for OSA patients, to reduce blood pressure seems to be modest and concomitant antihypertensive therapy is still required. We focus this review on the efficacy of pharmacological interventions to revert HT associated with CIH conditions in both animal models and humans. First, we explore the experimental animal models, developed to mimic HT related to CIH, which have been used to investigate the effect of antihypertensive drugs (AHDs). Second, we review what is known about drug efficacy to reverse HT induced by CIH in animals. Moreover, findings in humans with OSA are cited to demonstrate the lack of strong evidence for the establishment of a first-line antihypertensive regimen for these patients. Indeed, specific therapeutic guidelines for the pharmacological treatment of HT in these patients are still lacking. Finally, we discuss the future perspectives concerning the non-pharmacological and pharmacological management of this particular type of HT.
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Affiliation(s)
- Lucilia N Diogo
- Centro de Estudos de Doenças Crónicas, CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa Lisboa, Portugal
| | - Emília C Monteiro
- Centro de Estudos de Doenças Crónicas, CEDOC, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa Lisboa, Portugal
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14
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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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15
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Nobiletin treatment improves motor and cognitive deficits seen in MPTP-induced Parkinson model mice. Neuroscience 2014; 259:126-41. [DOI: 10.1016/j.neuroscience.2013.11.051] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 11/21/2013] [Accepted: 11/22/2013] [Indexed: 02/07/2023]
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16
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Chen RC, Chuang LY, Tseng WL, Tyan YC, Lu CY. Determination of phosphoserine/threonine by nano ultra-performance liquid chromatography-tandem mass spectrometry coupled with microscale labeling. Anal Biochem 2013; 443:187-96. [PMID: 23994561 DOI: 10.1016/j.ab.2013.08.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Revised: 08/17/2013] [Accepted: 08/21/2013] [Indexed: 11/18/2022]
Abstract
Protein phosphorylation is an important regulatory post-translational modification in many biochemical processes. The phosphopeptide analysis strategies developed in this study were all at microscale. After using a standard microwave oven to assist protein digestion, phosphoserine and phosphothreonine were tagged with chemical analogues, such as 2-mercaptoethanol and 3-mercapto-1-propanol, to enable simultaneously relative quantitation and identification. This method enabled the use of thio alcohols for direct labeling of phosphorylated sites (not labeled at the mercapto, amino, hydroxyl, or carboxyl groups) of phosphopeptides. Various digestion parameters (e.g., microwave power, reaction time, NH4HCO3 concentration) and derivatization efficiency parameters (e.g., reaction time, labeling tag concentration) were studied and optimized. In both control and experimental samples, microwave-assisted digestion coupled with relative quantitation using analogue tags enabled calculation of phosphopeptide ratios in the same sequence. A non-labeling method was also established for quantifying phosphopeptides in human plasma by using the abundant protein albumin as an internal control for normalizing relative quantities of phosphopeptides. Nano ultra-performance liquid chromatography (nanoUPLC) was combined with LTQ Orbitrap to enable simultaneous protein relative quantitation and identification. These strategies proved to be effective for quantifying phosphopeptides in biological samples.
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Affiliation(s)
- Rong-Chun Chen
- Department of Biochemistry, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
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17
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Jenei-Lanzl Z, Capellino S, Kees F, Fleck M, Lowin T, Straub RH. Anti-inflammatory effects of cell-based therapy with tyrosine hydroxylase-positive catecholaminergic cells in experimental arthritis. Ann Rheum Dis 2013; 74:444-51. [PMID: 24297380 DOI: 10.1136/annrheumdis-2013-203925] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES Studies in rheumatoid arthritis (RA), osteoarthritis (OA) and mice with arthritis demonstrated tyrosine hydroxylase-positive (TH(+)) cells in arthritic synovium and parallel loss of sympathetic nerve fibres. The exact function of TH(+) cells and mode of TH induction are not known. METHODS Synovial cells of RA/OA were isolated and cultured under normoxic/hypoxic conditions with/without stimulating enzyme cofactors of TH and inhibitors of TH. We studied TH expression and release of cytokines/catecholamines. In vivo function was tested by cell therapy with TH(+) neuronal precursor cells (TH(+) neuronal cells) in DBA/1 mice with collagen type II-induced arthritis (CIA). RESULTS Compared with normoxic conditions, hypoxia increased TH protein expression and catecholamine synthesis and decreased release of tumour necrosis factor (TNF) in OA/RA synovial cells. This inhibitory effect on TNF was reversed by TH inhibition with α-methyl-para-tyrosine (αMPT), which was particularly evident under hypoxic conditions. Incubation with specific TH cofactors (tetrahydrobiopterin and Fe(2+)) increased hypoxia-induced inhibition of TNF, which was also reversed by αMPT. To address a possible clinical role of TH(+) cells, murine TH(+) neuronal cells were generated from mesenchymal stem cells. TH(+) neuronal cells exhibited a typical catecholaminergic phenotype. Adoptive transfer of TH(+) neuronal cells markedly reduced CIA in mice, and 6-hydroxydopamine, which depletes TH(+) cells, reversed this effect. CONCLUSIONS The anti-inflammatory effect of TH(+) neuronal cells on experimental arthritis has been presented for the first time. In RA/OA, TH(+) synovial cells have TH-dependent anti-inflammatory capacities, which are augmented under hypoxia. Using generated TH(+) neuronal cells might open new avenues for cell-based therapy.
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Affiliation(s)
- Zsuzsa Jenei-Lanzl
- Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Bavaria, Germany
| | - Silvia Capellino
- Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Bavaria, Germany Division of Endocrinology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Frieder Kees
- Department of Pharmacology and Toxicology, University Regensburg, Regensburg, Bavaria, Germany
| | - Martin Fleck
- Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Bavaria, Germany
| | - Torsten Lowin
- Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Bavaria, Germany
| | - Rainer H Straub
- Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Bavaria, Germany
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18
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Meiser J, Weindl D, Hiller K. Complexity of dopamine metabolism. Cell Commun Signal 2013; 11:34. [PMID: 23683503 PMCID: PMC3693914 DOI: 10.1186/1478-811x-11-34] [Citation(s) in RCA: 396] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 05/10/2013] [Indexed: 01/15/2023] Open
Abstract
: Parkinson's disease (PD) coincides with a dramatic loss of dopaminergic neurons within the substantia nigra. A key player in the loss of dopaminergic neurons is oxidative stress. Dopamine (DA) metabolism itself is strongly linked to oxidative stress as its degradation generates reactive oxygen species (ROS) and DA oxidation can lead to endogenous neurotoxins whereas some DA derivatives show antioxidative effects. Therefore, DA metabolism is of special importance for neuronal redox-homeostasis and viability.In this review we highlight different aspects of dopamine metabolism in the context of PD and neurodegeneration. Since most reviews focus only on single aspects of the DA system, we will give a broader overview by looking at DA biosynthesis, sequestration, degradation and oxidation chemistry at the metabolic level, as well as at the transcriptional, translational and posttranslational regulation of all enzymes involved. This is followed by a short overview of cellular models currently used in PD research. Finally, we will address the topic from a medical point of view which directly aims to encounter PD.
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Affiliation(s)
- Johannes Meiser
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7, avenue des Hauts-Fourneaux, L-4362 Esch-Belval, Luxembourg
| | - Daniel Weindl
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7, avenue des Hauts-Fourneaux, L-4362 Esch-Belval, Luxembourg
| | - Karsten Hiller
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 7, avenue des Hauts-Fourneaux, L-4362 Esch-Belval, Luxembourg
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Differential regulation of tyrosine hydroxylase by continuous and intermittent hypoxia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 758:381-5. [PMID: 23080186 DOI: 10.1007/978-94-007-4584-1_51] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
Although continuous hypoxia (CH) and intermittent hypoxia (IH) cause reduction in oxygen availability, organisms adapt to the effects of chronic CH whereas IH adversely impacts autonomic functions. Catecholamines are expressed both in the central and peripheral nervous systems and they play important roles in the regulation of cardio-respiratory functions during hypoxia. Tyrosine hydroxylase (TH) is the rate-limiting enzyme for catecholamine synthesis. Several studies have examined the effects of hypoxia on catecholamines by focusing on the regulation of TH. In this article, we present a brief overview of the impact of chronic CH and IH on TH expression, activity and the associated cellular mechanism(s).
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20
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Fung SJ, Xi M, Zhang J, Sampogna S, Chase MH. Apnea produces excitotoxic hippocampal synapses and neuronal apoptosis. Exp Neurol 2012; 238:107-13. [PMID: 22921462 DOI: 10.1016/j.expneurol.2012.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/27/2012] [Accepted: 08/03/2012] [Indexed: 12/20/2022]
Abstract
Obstructive sleep apnea (OSA) results in the degeneration of neurons in the hippocampus that eventuates in neurocognitive deficits. We were therefore interested in determining the effects of apnea on monosynaptic excitatory processes in a hippocampal pathway (cornu ammonis 3-cornu ammonis 1, CA3-CA1) that has been shown to mediate the processing of cognitive information. In addition, to substantiate an anatomical basis for the cognitive dysfunction that occurs in OSA patients, we examined the effects of apnea with respect to neurodegenerative changes (apoptosis) in the same hippocampal pathway. In order to determine the effects of apnea, an automated system for the generation and analysis of single and recurrent periods of apnea was developed. Utilizing this system, the field excitatory postsynaptic potential (fEPSP) generated by pyramidal neurons in the CA1 region of the hippocampus was monitored in α-chloralose anesthetized rats following stimulation of glutamatergic afferents in the CA3 region. A stimulus-response (input-output) curve for CA3-CA1 synaptic activity was determined. In addition, a paired-pulse paradigm was employed to evaluate, electrophysiologically, the presynaptic release of glutamate. Changes in the synaptic efficacy were assessed following single episodes of apnea induced by ventilatory arrest (60 to 80 s duration, mean=72 s; mean oxygen desaturation was 53% of normoxia level). Apnea resulted in a significant potentiation of the amplitude (mean=126%) and slope (mean=117%) of the baseline CA1 fEPSP. This increase in the fEPSP was accompanied by a significant decrease in the amplitude (71%) and slope (81%) of normalized paired-pulse facilitation (PPF) ratios. Since the potentiation of the fEPSP is inversely proportional to changes in PPF ratio, the potentiated fEPSP accompanied by the reduced PPF reveals that apnea produces an abnormal increase in the preterminal release of glutamate that results in the over-activation (and calcium overloading) of hippocampal CA1 neurons. Thus, we conclude that individual episodes of apnea result in the development of excitotoxic processes in the hippocampal CA3-CA1 pathway that is critically involved in the processing of cognitive information. Morphologically, the deleterious effect of recurrent apnea was substantiated by the finding of apoptosis in CA1 neurons of apneic (but not normoxic) animals.
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Affiliation(s)
- Simon J Fung
- VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA.
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21
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Abstract
Central and peripheral neurons as well as neuroendocrine cells express a variety of neurotransmitters/modulators that play critical roles in regulation of physiological systems. The synthesis of several neurotransmitters/modulators is regulated by O(2)-requiring rate-limiting enzymes. Consequently, hypoxia resulting from perturbations in O(2) homeostasis can affect neuronal functions by altering neurotransmitter synthesis. Two broad categories of hypoxia are frequently encountered: continuous hypoxia (CH) and intermittent hypoxia (IH). CH is often seen during high altitude sojourns, whereas IH is experienced in sleep-disordered breathing with recurrent apneas (i.e., brief, repetitive cessations of breathing). This article presents what is currently known on the effects of both forms of hypoxia on neurotransmitter levels and neurotransmitter synthesizing enzymes in the central and peripheral nervous systems.
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Affiliation(s)
- Ganesh K Kumar
- Institute for Integrative Physiology and Center for Systems Biology of O(2) Sensing, Biological Sciences Division, University of Chicago, Illinois, USA.
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22
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Raghuraman G, Prabhakar NR, Kumar GK. Post-translational modification of glutamic acid decarboxylase 67 by intermittent hypoxia: evidence for the involvement of dopamine D1 receptor signaling. J Neurochem 2010; 115:1568-78. [PMID: 20969567 DOI: 10.1111/j.1471-4159.2010.07063.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intermittent hypoxia (IH) associated with sleep apnea leads to cardio-respiratory morbidities. Previous studies have shown that IH alters the synthesis of neurotransmitters including catecholamines and neuropeptides in brainstem regions associated with regulation of cardio-respiratory functions. GABA, a major inhibitory neurotransmitter in the CNS, has been implicated in cardio-respiratory control. GABA synthesis is primarily catalyzed by glutamic acid decarboxylase (GAD). In this study, we tested the hypothesis that IH like its effect on other transmitters also alters GABA synthesis. The impact of IH on GABA synthesis was investigated in pheochromocytoma 12 cells, a neuronal cell line which is known to express active form of GAD67 in the cytosolic fraction and also assessed the underlying mechanisms contributing to IH-evoked response. Exposure of cell cultures to IH decreased GAD67 activity and GABA level. IH-evoked decrease in GAD67 activity was caused by increased cAMP - protein kinase A (PKA) - dependent phosphorylation of GAD67, but not as a result of changes in either GAD67 mRNA or protein expression. PKA inhibitor restored GAD67 activity and GABA levels in IH treated cells. Pheochromocytoma 12 cells express dopamine 1 receptor (D1R), a G-protein coupled receptor whose activation increased adenylyl cyclase activity. Treatment with either D1R antagonist or adenylyl cyclase inhibitor reversed IH-evoked GAD67 inhibition. Silencing D1R expression with siRNA reversed cAMP elevation and GAD67 inhibition by IH. These results provide evidence for the role of D1R-cAMP-PKA signaling in IH-mediated inhibition of GAD67 via protein phosphorylation resulting in down-regulation of GABA synthesis.
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Affiliation(s)
- Gayatri Raghuraman
- Department of Medicine, Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois 60637-1470, USA
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Ray K, Dutta A, Panjwani U, Thakur L, Anand JP, Kumar S. Hypobaric hypoxia modulates brain biogenic amines and disturbs sleep architecture. Neurochem Int 2010; 58:112-8. [PMID: 21075155 DOI: 10.1016/j.neuint.2010.11.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 10/29/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022]
Abstract
Sojourners to high altitude experience poor-quality of sleep due to hypobaric hypoxia (HH). Brain neurotransmitters are the key regulators of sleep wakefulness. Scientific literature has limited information on the role of brain neurotransmitters involved in sleep disturbance in HH. The present study aimed to investigate the time dependent changes in neurotransmitter levels and enzymes involved in the biosynthesis of brain neurotransmitters in frontal cortex, brain stem, cerebellum, pons and medulla and the effect of these alterations on sleep architecture in HH. Thirty adult Sprague-Dawley rats, body weight of 230-250 g were exposed to simulated altitude ∼7620 m, 282 mm Hg, partial pressure of O(2) 59 mm Hg for 7 and 14 days continuously in an animal decompression chamber. After 7 and 14 days of HH, brain nor-epinephrine and dopamine levels were significantly increased in frontal cortex, brain stem, cerebellum and pons and medulla whereas serotonin level was significantly reduced in frontal cortex and pons and medulla after 14 days of HH. Tyrosine hydroxylase level in locus coeruleus (LC) was significantly increased whereas Choline Acetyl Transferase and Glutamic Acid Decarboxylase (GAD) levels were significantly reduced in laterodorsal-tegmentum and pedunculopontine-tegmentum after 7 days of HH. GAD was also reduced in LC after 7 days HH. Alteration in these neurotransmitters and enzyme levels was accompanied with reduction in quality and quantity of sleep. There was a significant increase in sleep latency, rapid eye movement (REM) latency, duration of active awake, quiet awake, quiet sleep and a significant decrease in duration of REM sleep and deep sleep on day 7 and 14 of HH. It was concluded that HH alters the expression of enzymes linked to sleep neurotransmitter synthesis pathway and subsequent loss of homeostasis at neurotransmitter level disrupts the sleep pattern in hypobaric hypoxia.
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Affiliation(s)
- Koushik Ray
- Neurophysiology Division, Department of Physiology, Defence Institute of Physiology & Allied Sciences, Defence Research and Development Organization, Timarpur, Delhi, India
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Johansen JL, Sager TN, Lotharius J, Witten L, Mørk A, Egebjerg J, Thirstrup K. HIF prolyl hydroxylase inhibition increases cell viability and potentiates dopamine release in dopaminergic cells. J Neurochem 2010; 115:209-19. [PMID: 20649842 DOI: 10.1111/j.1471-4159.2010.06917.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Hypoxia-inducible factor (HIF) controls the expression of genes that adapts the cellular condition to accommodate oxidative stress. The potential beneficial effect of HIF up-regulation in ischemia has recently gained interest substantiated by the known HIF-regulation of erythropoietin and other hypoxia accommodating genes. So far the perspectives for HIF up-regulation has been focused on anemia and ischemia related diseases but little information is available about the relevance of HIF biology for neurodegenerative disease like Parkinson's disease. We therefore sought out to characterize the effect of HIF-up-regulation on survival and dopamine homeostasis in dopaminergic cells. We used a low molecular weight HIF prolyl hydroxylase (HPH) inhibitor and lentiviral based shRNA knockdown of HPH subtypes as molecular tools to increase HIF protein level and downstream HIF-regulated genes. We show that HIF induction results in protection against oxidative stress in cellular models based on PC12 cells and LUHMES cells. In addition, HPH inhibition elevates tyrosine hydroxylase expression and activity, which causes increased dopamine synthesis and release in both PC12 cells and a primary rat ventral mesencephalic cell culture. All together these findings suggest that prolyl hydroxylases may represent novel targets for therapeutic intervention in disorders characterized by dopamine homeostasis dysregulation like Parkinson's disease.
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Matsuo T, Izumi Y, Wakita S, Kume T, Takada-Takatori Y, Sawada H, Akaike A. Haloperidol, spiperone, pimozide and aripiprazole reduce intracellular dopamine content in PC12 cells and rat mesencephalic cultures: Implication of inhibition of vesicular transport. Eur J Pharmacol 2010; 640:68-74. [DOI: 10.1016/j.ejphar.2010.04.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2009] [Revised: 04/13/2010] [Accepted: 04/24/2010] [Indexed: 10/19/2022]
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Zhang YL, Tavakoli H, Chachisvilis M. Apparent PKA activity responds to intermittent hypoxia in bone cells: a redox pathway? Am J Physiol Heart Circ Physiol 2010; 299:H225-35. [PMID: 20453101 DOI: 10.1152/ajpheart.01073.2009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We studied hypoxia-induced dynamic changes in the balance between PKA and PKA-counteracting phosphatases in the microfluidic environment in single cells using picosecond fluorescence spectroscopy and intramolecular fluorescence resonance energy transfer (FRET)-based sensors of PKA activity. First, we found that the apparent PKA activity in bone cells (MC3T3-E1 cells) and endothelial cells (bovine aortic endothelial cells) is rapidly and sensitively modulated by the level of O(2) in the media. When the O(2) concentration in the glucose-containing media was lowered due to O(2) consumption by the cells in the microfluidic chamber, the apparent PKA activity increases; the reoxygenation of cells under hypoxia leads to a rapid ( approximately 2 min) decrease of the apparent PKA activity. Second, lack of glucose in the media led to a lower apparent PKA activity and to a reversal of the response of the apparent PKA activity to hypoxia and reoxygenation. Third, the apparent PKA activity in cells under hypoxia was predominantly regulated via a cAMP-independent pathway since 1) changes in the cAMP level in the cells were not detected using a cAMP FRET sensor, 2) the decay of cAMP levels was too slow to account for the fast decrease in PKA activity levels in response to reoxygenation, and 3) the response of the apparent PKA activity due to hypoxia/reoxygenation was not affected by an adenylate cyclase inhibitor (MDL-12,330A) at 1 mM concentration. Fourth, the immediate onset of ROS accumulation in MC3T3-E1 cells subjected to hypoxia and the sensitivity of the apparent PKA activity to redox levels suggest that the apparent PKA activity change during hypoxia and reoxygenation in this study can be linked to a redox potential change in response to intermittent hypoxia through the regulation of activities of PKA-counteracting phosphatases such as protein phosphatase 1. Finally, our results suggest that the detection of PKA activity could be used to monitor responses of cells to hypoxia in real time.
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Affiliation(s)
- Yan-Liang Zhang
- La Jolla Bioengineering Institute, 505 Coast Blvd. S., La Jolla, CA 92037, USA
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Raghuraman G, Rai V, Peng YJ, Prabhakar NR, Kumar GK. Pattern-specific sustained activation of tyrosine hydroxylase by intermittent hypoxia: role of reactive oxygen species-dependent downregulation of protein phosphatase 2A and upregulation of protein kinases. Antioxid Redox Signal 2009; 11:1777-89. [PMID: 19335094 PMCID: PMC2848511 DOI: 10.1089/ars.2008.2368] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We investigated the role of protein phosphatases (PP) and protein kinases in tyrosine hydroxylase (TH) activation by two patterns of intermittent hypoxia (IH) in rat brainstem. Rats exposed to either IH(15s) (15 s, 5% O(2); 5 min, 21%O(2)) or IH(90s) (90 s each of 10% O(2) & 21%O(2)) for 10 days were used. IH(15s) but not IH(90s) caused a robust increase in TH activity, dopamine (DA) level, and TH phosphorylation at Ser-31 and Ser-40 in the medulla but not in the pons. Likewise, IH(15s) but not IH(90s) decreased activity and expression of protein phosphatase 2A (PP2A) and increased activity of multiple protein kinases. In vitro dephosphorylation with PP2A nearly abolished IH(15s)-induced increase in TH activity. IH(15s) increased generation of reactive oxygen species (ROS) in brainstem medullary regions which was nearly threefold higher than that evoked by IH(90s). Antioxidants prevented IH(15s)-induced downregulation of PP2A and increases in multiple protein kinase activity with subsequent reversal of serine phosphorylation of TH, TH activity, and DA to control levels. These findings demonstrate that IH in a pattern-specific manner activates TH involving ROS-mediated sustained increase in TH phosphorylation via downregulation of PP2A and upregulation of protein kinases.
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Affiliation(s)
- Gayatri Raghuraman
- Center for Systems Biology of Oxygen Sensing, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
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28
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Post-translational modification of proteins during intermittent hypoxia. Respir Physiol Neurobiol 2009; 164:272-6. [PMID: 18602876 DOI: 10.1016/j.resp.2008.05.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 05/22/2008] [Accepted: 05/24/2008] [Indexed: 12/14/2022]
Abstract
Post-translational modification (PTM) is one of the mechanisms by which protein function is regulated by chronic hypoxia. This article presents an overview of recent findings on PTM of proteins induced by chronic intermittent hypoxia (CIH) which is experienced by humans with sleep disordered breathing resulting in autonomic abnormalities. The analysis of PTM of proteins involves electrophoretic separation of tissue or cellular proteins followed by immunolabeling using antibodies specific to native and post-translationally modified forms. Recent results demonstrate that CIH, depending on the pattern, duration and severity of hypoxia, alters the state of phosphorylation of a subset of proteins associated with transcriptional factor activation, signaling pathways and neurotransmitter synthesis via activation of appropriate enzymatic machinery that catalyzes specific phosphorylation reactions. Investigation pertaining to PTMs associated with CIH is at its infant stage and future application of high throughput proteomics techniques are necessary to unravel other important PTMs associated with various critical metabolic and signaling pathways that are activated by intermittent hypoxia.
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Souvannakitti D, Kumar GK, Fox A, Prabhakar NR. Neonatal intermittent hypoxia leads to long-lasting facilitation of acute hypoxia-evoked catecholamine secretion from rat chromaffin cells. J Neurophysiol 2009; 101:2837-46. [PMID: 19339466 DOI: 10.1152/jn.00036.2009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The objective of the present study was to examine the effects of intermittent hypoxia (IH) and sustained hypoxia (SH) on hypoxia-evoked catecholamine (CA) secretion from chromaffin cells in neonatal rats and assess the underlying mechanism(s). Experiments were performed on rat pups exposed to either IH (15-s hypoxia/5-min normoxia; 8 h/day) or SH (hypobaric hypoxia, 0.4 atm) or normoxia (controls) from P0 to P5. IH treatment facilitated hypoxia-evoked CA secretion and elevations in the intracellular calcium ion concentration ([Ca(2+)](i)) and these responses were attenuated, but not abolished, by treatments designed to eliminate Ca(2+) flux into cells (Ca(2+)-free medium or Cd(2+)), indicating that intracellular Ca(2+) stores were augmented by IH. Norepinephrine (NE) and epinephrine (E) levels of adrenal medullae were elevated in IH-treated pups. IH treatment increased reactive oxygen species (ROS) production in adrenal medullae and antioxidant treatment prevented IH-induced facilitation of CA secretion, elevations in [Ca(2+)](i) by hypoxia, and the up-regulation of NE and E. The effects of neonatal IH treatment on hypoxia-induced CA secretion and elevation in [Ca(2+)](i), CA, and ROS levels persisted in rats reared under normoxia for >30 days. In striking contrast, chromaffin cells from SH-treated animals exhibited attenuated hypoxia-evoked CA secretion. In SH-treated cells hypoxia-evoked elevations in [Ca(2+)](i), NE and E contents, and ROS levels were comparable with controls. These observations demonstrate that: 1) neonatal IH and SH evoke opposite effects on hypoxia-evoked CA secretion from chromaffin cells, 2) ROS signaling mediates the faciltatory effects of IH, and 3) the effects of neonatal IH on chromaffin cells persist into adult life.
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Affiliation(s)
- Dangjai Souvannakitti
- Department of Medicine, The Center for Systems Biology of O2Sensing, University of Chicago, MC 5068, Chicago, IL 60637, USA
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Sharma SD, Raghuraman G, Lee MS, Prabhakar NR, Kumar GK. Intermittent hypoxia activates peptidylglycine alpha-amidating monooxygenase in rat brain stem via reactive oxygen species-mediated proteolytic processing. J Appl Physiol (1985) 2008; 106:12-9. [PMID: 18818385 DOI: 10.1152/japplphysiol.90702.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intermittent hypoxia (IH) associated with sleep apneas leads to cardiorespiratory abnormalities that may involve altered neuropeptide signaling. The effects of IH on neuropeptide synthesis have not been investigated. Peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3) catalyzes the alpha-amidation of neuropeptides, which confers biological activity to a large number of neuropeptides. PAM consists of O(2)-sensitive peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) activities. Here, we examined whether IH alters neuropeptide synthesis by affecting PAM activity and, if so, by what mechanisms. Experiments were performed on the brain stem of adult male rats exposed to IH (5% O(2) for 15 s followed by 21% O(2) for 5 min; 8 h/day for up to 10 days) or continuous hypoxia (0.4 atm for 10 days). Analysis of brain stem extracts showed that IH, but not continuous hypoxia, increased PHM, but not PAL, activity of PAM and that the increase of PHM activity was associated with a concomitant elevation in the levels of alpha-amidated forms of substance P and neuropeptide Y. IH increased the relative abundance of 42- and 35-kDa forms of PHM ( approximately 1.6- and 2.7-fold, respectively), suggesting enhanced proteolytic processing of PHM, which appears to be mediated by an IH-induced increase of endoprotease activity. Kinetic analysis showed that IH increases V(max) but has no effect on K(m). IH increased generation of reactive oxygen species in the brain stem, and systemic administration of antioxidant prevented IH-evoked increases of PHM activity, proteolytic processing of PHM, endoprotease activity, and elevations in substance P and neuropeptide Y amide levels. Taken together, these results demonstrate that IH activates PHM in rat brain stem via reactive oxygen species-dependent posttranslational proteolytic processing and further suggest that PAM activation may contribute to IH-mediated peptidergic neurotransmission in rat brain stem.
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Murphy KL, Zhang X, Gainetdinov RR, Beaulieu JM, Caron MG. A regulatory domain in the N terminus of tryptophan hydroxylase 2 controls enzyme expression. J Biol Chem 2008; 283:13216-24. [PMID: 18339632 PMCID: PMC2442358 DOI: 10.1074/jbc.m706749200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Revised: 03/12/2008] [Indexed: 01/10/2023] Open
Abstract
Serotonin is involved in a variety of physiological processes in the central nervous system and the periphery. As the rate-limiting enzyme in serotonin synthesis, tryptophan hydroxylase plays an important role in modulating these processes. Of the two variants of tryptophan hydroxylase, tryptophan hydroxylase 2 (TPH2) is expressed predominantly in the central nervous system, whereas tryptophan hydroxylase 1 (TPH1) is expressed mostly in peripheral tissues. Although the two enzymes share considerable sequence homology, the regulatory domain of TPH2 contains an additional 41 amino acids at the N terminus that TPH1 lacks. Here we show that the extended TPH2 N-terminal domain contains a unique sequence involved in the regulation of enzyme expression. When expressed in cultured mammalian cells, TPH2 is synthesized less efficiently and is also less stable than TPH1. Removal of the unique portion of the N terminus of TPH2 results in expression of the enzyme at a level similar to that of TPH1, whereas protein chimeras containing this fragment are expressed at lower levels than their wild-type counterparts. We identify a region centered on amino acids 10-20 that mediates the bulk of this effect. We also demonstrate that phosphorylation of serine 19, a protein kinase A consensus site located in this N-terminal domain, results in increased TPH2 stability and consequent increases in enzyme output in cell culture systems. Because this domain is unique to TPH2, these data provide evidence for selective regulation of brain serotonin synthesis.
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Affiliation(s)
- Karen L Murphy
- Department of Neurobiology and Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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Abstract
Hypoxia, i.e. decreased availability of oxygen occurs under many different circumstances and can be either continuous or intermittent. Continuous hypoxia such as that experienced during periods of high altitude leads to physiological adaptations, whereas chronic IH (intermittent hypoxia) associated with sleep-disordered breathing manifested as recurrent apneas leads to morbidity. The purpose of the present chapter is to highlight recent findings on cellular responses to IH. Studies on cell culture models of IH revealed that for a given duration and intensity, IH is more potent than continuous hypoxia in evoking transcriptional activation. IH activates HIF-1 (hypoxia-inducible factor-1), the immediate early gene c-fos, activator protein-1, nuclear factor kappaB and cAMP-response-element-binding protein. Physiological studies showed that HIF-1 plays an important role in chronic IH-induced autonomic abnormalities in mice. IH affects expression of proteins associated with neuronal survival and apoptosis, as well as post-translational modifications of proteins resulting in increased biological activity. Comparisons between continuous hypoxia and IH revealed notable differences in the kinetics of protein kinase activation, type of protein kinase being activated and the downstream targets of protein kinases. IH increases ROS (reactive oxygen species) generation both in cell culture and in intact animals, and ROS-mediated signalling mechanisms contribute to cellular and systemic responses to IH. Future studies utilizing genomic and proteomic approaches may provide important clues to the mechanisms by which IH leads to morbidity as opposed to continuous hypoxia-induced adaptations. Cellular mechanisms associated with IH (other than recurrent apneas) such as repetitive, brief ascents to altitude, however, remain to be studied.
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Affiliation(s)
- Jayasri Nanduri
- Center for Systems Biology, Department of Medicine, The University of Chicago, Chicago, IL 60637, USA.
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Prabhakar NR, Kumar GK, Nanduri J, Semenza GL. ROS signaling in systemic and cellular responses to chronic intermittent hypoxia. Antioxid Redox Signal 2007; 9:1397-403. [PMID: 17627465 DOI: 10.1089/ars.2007.1732] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Chronic intermittent hypoxia (CIH) is a common and life-threatening condition that occurs in many different diseases, including sleep-disordered breathing manifested as recurrent apneas. Reactive oxygen species (ROS) have been identified as one of the causative factors in a variety of morbidities. The purpose of this article is to present a brief overview of recent studies implicating a critical role of ROS in evoking phenotypic adverse effects in experimental models of CIH and in patients with recurrent apneas. In experimental models, CIH activates ROS signaling that contributes to several systemic and cellular responses that include (a) altered carotid body function, the primary chemoreceptor for sensing changes in arterial blood O2; (b) elevated blood pressures; (c) enhanced release of transmitters and neurotrophic factors; (d) altered sleep and cognitive behaviors; and (e) activation of second-messenger pathways and transcriptional factors. Considerable evidence indicates elevated ROS levels in patients experiencing CIH as a consequence of recurrent apneas. Antioxidants not only prevent many of the CIH-evoked physiologic and cellular responses in experimental settings, but more important, they also offer protection against certain phenotypic adverse effects in patients with recurrent apneas, suggesting their potential therapeutic value in alleviating certain morbidities associated with recurrent apneas.
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Affiliation(s)
- Nanduri R Prabhakar
- Center for Systems Biology, Department of Medicine, The University of Chicago, Chicago, Illinois 60637, USA.
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35
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Lam SY, Tipoe GL, Liong EC, Fung ML. Hypoxia-inducible factor (HIF)-1alpha and endothelin-1 expression in the rat carotid body during intermittent hypoxia. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 580:21-7; discussion 351-9. [PMID: 16683693 DOI: 10.1007/0-387-31311-7_4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Siu-Yin Lam
- Department of Physiology, The University of Hong Kong, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong, China
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Cooper C, Liu GY, Niu YL, Santos S, Murphy LC, Watson PH. Intermittent hypoxia induces proteasome-dependent down-regulation of estrogen receptor alpha in human breast carcinoma. Clin Cancer Res 2005; 10:8720-7. [PMID: 15623657 DOI: 10.1158/1078-0432.ccr-04-1235] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Hypoxia may influence gene expression to promote malignancy, and acute hypoxia has been shown to transiently repress estrogen receptor (ER)-alpha expression in breast cell lines. However, the effect of intermittent hypoxia, which is likely more prevalent in breast cancers, remains to be determined. EXPERIMENTAL DESIGN ER-alpha expression was assessed by Western blot and immunohistochemistry in a selected cohort of 51 ER-alpha-positive breast carcinomas, in relation to markers of hypoxia. The effect of acute and intermittent hypoxia on ER-alpha expression was also determined in MCF7 and ZR-75 breast cell lines, together with the role of proteasome function with the proteasome inhibitor bortezomib. RESULTS Regional loss of ER-alpha expression occurs in breast tumors and is consistently present in hypoxic regions defined by the proximity of necrosis and induction of hypoxia-induced genes carbonic anhydrase IX (CA-IX) and glucose transporter 1 (Glut-1), in both in situ (n = 29; P < 0.0001) and invasive (n = 20; P = 0.0001) carcinomas. In MCF7 and ZR-75 cells, ER-alpha is transiently down-regulated by acute hypoxia and rapidly restored by reoxygenation. However, intermittent, acute hypoxia can cause a similar down-regulation of ER-alpha that is not attributable to decreased mRNA and persists in MCF7 cells despite reoxygenation for up to 14 days. This effect occurs with no change in cell viability but a corresponding reduction in growth response to estradiol. However, ER-alpha expression can be restored by bortezomib. CONCLUSIONS Intermittent hypoxia can cause persistent changes in proteasome function that may contribute to reduced ER-alpha expression in breast tumors and consequently to diminished response and development of resistance to endocrine therapy.
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Affiliation(s)
- Charlton Cooper
- Manitoba Institute of Cell Biology and Department of Pathology, University of Manitoba, Faculty of Medicine, Winnipeg, Manitoba, Canada
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Gozal E, Shah ZA, Pequignot JM, Pequignot J, Sachleben LR, Czyzyk-Krzeska MF, Li RC, Guo SZ, Gozal D. Tyrosine hydroxylase expression and activity in the rat brain: differential regulation after long-term intermittent or sustained hypoxia. J Appl Physiol (1985) 2005; 99:642-9. [PMID: 15817718 DOI: 10.1152/japplphysiol.00880.2004] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Tyrosine hydroxylase, a hypoxia-regulated gene, may be involved in tissue adaptation to hypoxia. Intermittent hypoxia, a characteristic feature of sleep apnea, leads to significant memory deficits, as well as to cortex and hippocampal apoptosis that are absent after sustained hypoxia. To examine the hypothesis that sustained and intermittent hypoxia induce different catecholaminergic responses, changes in tyrosine hydroxylase mRNA, protein expression, and activity were compared in various brain regions of male rats exposed for 6 h, 1 day, 3 days, and 7 days to sustained hypoxia (10% O2), intermittent hypoxia (alternating room air and 10% O2), or normoxia. Tyrosine hydroxylase activity, measured at 7 days, increased in the cortex as follows: sustained > intermittent > normoxia. Furthermore, activity decreased in the brain stem and was unchanged in other brain regions of sustained hypoxia-exposed rats, as well as in all regions from animals exposed to intermittent hypoxia, suggesting stimulus-specific and heterotopic catecholamine regulation. In the cortex, tyrosine hydroxylase mRNA expression was increased, whereas protein expression remained unchanged. In addition, significant differences in the time course of cortical Ser40tyrosine hydroxylase phosphorylation were present in the cortex, suggesting that intermittent and sustained hypoxia-induced enzymatic activity differences are related to different phosphorylation patterns. We conclude that long-term hypoxia induces site-specific changes in tyrosine hydroxylase activity and that intermittent hypoxia elicits reduced tyrosine hydroxylase recruitment and phosphorylation compared with sustained hypoxia. Such changes may not only account for differences in enzyme activity but also suggest that, with differential regional brain susceptibility to hypoxia, recruitment of different mechanisms in response to hypoxia will elicit region-specific modulation of catecholamine response.
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Affiliation(s)
- Evelyne Gozal
- Kosair Children's Hospital Research Institute, 570 S. Preston Street, Suite 321, Louisville, KY 40202, USA.
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Nemoto T, Mano-Otagiri A, Shibasaki T. Urocortin 2 induces tyrosine hydroxylase phosphorylation in PC12 cells. Biochem Biophys Res Commun 2005; 330:821-31. [PMID: 15809070 DOI: 10.1016/j.bbrc.2005.03.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Indexed: 10/25/2022]
Abstract
Urocotins (Ucns) are newly discovered members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn 2 is expressed in the adrenal medulla, and its receptor, CRF2 receptor, is also expressed in the adrenal gland. To predict the physiological significance of Ucn 2 expression in the adrenal medulla, we examined the effects of Ucn 2 on catecholamine secretion and intracellular signaling using PC12 cells, a rat pheochromocytoma cell line. PC12 cells were found to express CRF2 receptor, but not CRF1 receptor. Treatment with Ucn 2 increased noradrenaline secretion and induced phosphorylation of PKA and Erk1/2. Tyrosine hydroxylase (TH), a rate-limiting enzyme for catecholamine synthesis, was also phosphorylated by Ucn 2. Pretreatment with a PKA inhibitor blocked Ucn 2-induced NA secretion, and Erk1/2 and TH phosphorylation. Pretreatment with a MEK inhibitor did not block Ucn 2-induced noradrenaline secretion or PKA phosphorylation, although TH phosphorylation was blocked. Thus, Ucn 2 induces noradrenaline secretion and TH phosphorylation through the PKA pathway and the PKA-Erk1/2 pathway, respectively. These results suggest Ucn 2 in the adrenal gland may be involved in the regulation of catecholamine release and synthesis.
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Affiliation(s)
- Takahiro Nemoto
- Department of Physiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
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Chaube R, Joy KP. Cyclic AMP-protein kinase a and protein kinase C mediate in vitro T activation of brain tyrosine hydroxylase in the female catfish Heteropneustes fossilis. J Neuroendocrinol 2005; 17:91-6. [PMID: 15796759 DOI: 10.1111/j.1365-2826.2005.01282.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The present in vitro study demonstrates an involvement of both cAMP-dependent protein kinase A (PKA) and protein kinase C (PKC) signal transduction mechanisms in the triiodothyronone (T(3))-activation of forebrain (telencephalon and hypothalamus) tyrosine hydroxylase (TH) activity in the female catfish Heteropneustes fossilis. Incubations of the enzyme preparations with different concentrations of T(3) (0.15-2.4 ng/ml) stimulated TH activity over the concentrations. Similarly, coincubations of the enzyme preparations with T(3) and cAMP (1.0 mM) or cAMP-elevating drugs such as 1-methyl-3-isobutylxanthine (1.5 mM) or theophylline (1.5 mM) increased TH activity significantly over that of T(3). The stimulatory effect of TH activity with T(3) or cAMP was coincident with a low apparent K(m) and high V(max) for the cofactor, suggesting a higher affinity of the enzyme. Incubation of the enzyme preparations with PKA (H-89) and PKC (calphostin-C) inhibitors decreased basal enzyme activity significantly, with the inhibition being greater in the former group. The incubations of the enzyme preparations with T(3) or T(3) + cAMP, followed by the different inhibitors, also decreased enzyme activity. Although T(3) could not reverse the inhibitory effect of H-89, it could over-ride the effect of calphostin-C to some extent. The suppressive effect of the inhibitors could be related to a high apparent K(m) and low V(max) for the cofactor. The evidence strongly suggests a nongenomic action of T(3) on TH activity via the cell signalling pathways, for which the cAMP-dependent PKA appears to be the major regulatory mechanism.
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Affiliation(s)
- R Chaube
- Department of Zoology, Banaras Hindu University, Varanasi, India
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40
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Yuan G, Nanduri J, Bhasker CR, Semenza GL, Prabhakar NR. Ca2+/calmodulin kinase-dependent activation of hypoxia inducible factor 1 transcriptional activity in cells subjected to intermittent hypoxia. J Biol Chem 2004; 280:4321-8. [PMID: 15569687 DOI: 10.1074/jbc.m407706200] [Citation(s) in RCA: 181] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Intermittent hypoxia (IH) occurs in many pathological conditions. However, very little is known about the molecular mechanisms associated with IH. Hypoxia-inducible factor 1 (HIF-1) mediates transcriptional responses to continuous hypoxia. In the present study, we investigated whether IH activates HIF-1 and, if so, which signaling pathways are involved. PC12 cells were exposed to either to 20% O2 (non-hypoxic control) or to 60 cycles consisting of 30 s at 1.5% O2, followed by 4 min at 20% O2 (IH). Western blot analysis revealed significant increases in HIF-1alpha protein in nuclear extracts of cells subjected to IH. Expression of a HIF-1-dependent reporter gene was increased 3-fold in cells subjected to IH. Although IH induced the activation of ERK1, ERK2, JNK, PKC-alpha, and PKC-gamma, inhibitors of these kinases and of phosphatidylinositol 3-kinase did not block HIF-1-mediated reporter gene expression induced by IH, indicating that signaling via these kinases was not required. In contrast, addition of the intracellular Ca2+ chelator BAPTA-AM or the Ca2+/calmodulin-dependent (CaM) kinase inhibitor KN93 blocked reporter gene activation in response to IH. CaM kinase activity was increased 5-fold in cells subjected to IH. KN 93 prevented IH-induced transactivation mediated by HIF-1alpha, and its coactivator p300, which was phosphorylated by CaM kinase II in vitro. Expression of the HIF-1-regulated gene encoding tyrosine hydroxylase was induced by IH and this effect was blocked by KN93. These observations suggest that IH induces HIF-1 transcriptional activity via a novel signaling pathway involving CaM kinase.
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Affiliation(s)
- Guoxiang Yuan
- Department of Physiology & Biophysics, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA
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Gozal E, Sachleben LR, Rane MJ, Vega C, Gozal D. Mild sustained and intermittent hypoxia induce apoptosis in PC-12 cells via different mechanisms. Am J Physiol Cell Physiol 2004; 288:C535-42. [PMID: 15537711 DOI: 10.1152/ajpcell.00270.2004] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Episodic hypoxia, a characteristic feature of obstructive sleep apnea, induces cellular changes and apoptosis in brain regions associated with neurocognitive function. To investigate whether mild, intermittent hypoxia would induce more extensive neuronal damage than would a similar degree of sustained hypoxia, rat pheochromocytoma PC-12 neuronal cells were subjected to either sustained (5% O(2)) or intermittent (alternating 5% O(2) 35 min, 21% O(2) 25 min) hypoxia for 2 or 4 days. Quantitative assessment of apoptosis showed that while mild sustained hypoxia did not significantly increase cell apoptosis at 2 days (1.31 +/- 0.29-fold, n = 8; P = NS), a significant increase in apoptosis occurred after 4 days (2.25 +/- 0.4-fold, n = 8; P < 0.002), without increased caspase activation. Furthermore, caspase inhibition with the general caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) did not modify sustained hypoxia-induced apoptosis. In contrast, mild, intermittent hypoxia induced significant increases in apoptosis at 2 days (3.72 +/- 1.43-fold, n = 8; P < 0.03) and at 4 days (4.57 +/- 0.82-fold, n = 8; P < 0.001) that was associated with enhanced caspase activity and attenuated by Z-VAD-FMK pretreatment. We conclude that intermittent hypoxia induces an earlier and more extensive apoptotic response than sustained hypoxia and that this response is at least partially dependent on caspase-mediated pathways. In contrast, caspases do not seem to play a role in sustained hypoxia-induced apoptosis. These findings suggest that different signaling pathways are involved in sustained and intermittent hypoxia-induced cell injury and may contribute to the understanding of differential brain susceptibility to sustained and intermittent hypoxia.
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Affiliation(s)
- Evelyne Gozal
- Kosair Children's Hospital Research Institute, Department of Pediatrics, University of Louisville, 570 South Preston St., Suite 321, Louisville, KY 40202, USA.
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Yuan G, Adhikary G, McCormick AA, Holcroft JJ, Kumar GK, Prabhakar NR. Role of oxidative stress in intermittent hypoxia-induced immediate early gene activation in rat PC12 cells. J Physiol 2004; 557:773-83. [PMID: 15107478 PMCID: PMC1665161 DOI: 10.1113/jphysiol.2003.058503] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Intermittent hypoxia (IH) occurs in many pathophysiological conditions. The molecular mechanisms associated with IH, however, have received little attention. Previous studies have reported that the c-fos gene via formation of activator protein-1 (AP-1) transcription factor contributes to adaptive responses to continuous hypoxia. In the present study, using a cell culture model we examined whether IH activates c-fos and AP-1 and if so, by what mechanisms. Experiments were performed on rat phaeochromocytoma cells exposed to 21% O(2) (normoxia) or 60 and 120 cycles of IH, each cycle consisting 15 s of hypoxia followed by 4 min of normoxia. IH resulted in a significant elevation of c-fos mRNA as well as transcriptional activation. IH was more potent and induced a longer lasting activation of c-fos than comparable cumulative duration of continuous hypoxia. IH increased AP-1 activity and tyrosine hydroxylase (TH) mRNA, an AP-1-regulated downstream gene, and these effects were prevented by antisense c-fos. Superoxide dismutase mimetic, a potent scavenger of superoxide anions, prevented IH-induced c-fos, AP-1 and TH activations. IH increased superoxide anion levels in mitochondria as evidenced by decreased aconitase enzyme activity and increased levels of hydrogen peroxide, a stable dismutated product of superoxide anions. Complex I of the mitochondrial electron transport chain was markedly inhibited in IH exposed cells. Pharmacological inhibitors of complex I mimicked the effects of IH during normoxia and occluded the effects of IH on c-fos activation, suggesting the involvement of the mitochondrial electron transport chain in the generation of superoxide anions during IH. These results suggest IH-induced c-fos-mediated transcriptional activation involves oxidative stress.
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Affiliation(s)
- Guoxiang Yuan
- Department of Physiology, Case Western Reserve, University, Cleveland, OH 44106, USA
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Kumar GK, Klein JB. Analysis of expression and posttranslational modification of proteins during hypoxia. J Appl Physiol (1985) 2004; 96:1178-86; discussion 1170-2. [PMID: 14766768 DOI: 10.1152/japplphysiol.00818.2003] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cellular responses to hypoxia are complex and characterized by alterations in the expression of a number of genes, including stress-related genes and corresponding proteins that are necessary to maintain homeostasis. The purpose of this article is to review previous and recent studies that have examined the changes in the expression and posttranslational modification of proteins in response to chronic sustained and intermittent forms of hypoxia. A large number of studies focused on the analysis of either the single protein or a subset of related proteins using one-dimensional gel electrophoresis to separate a complex set of proteins from solubilized tissues or cell extracts, followed by immunostaining of proteins using antibodies that are specific to either native or posttranslationally modified forms. On the other hand, only a limited number of studies have examined the global perturbations on protein expression by hypoxia using proteomics approach involving two-dimensional electrophoresis coupled with mass spectrometry. Results derived from specific protein analysis of a variety of tissues and cells showed that hypoxia, depending on the duration and severity of the stimulus, affects the level and the state of posttranslational modification of a subset of proteins that are associated with energy metabolism, stress response, cell injury, development, and apoptosis. Some of these earlier findings are further corroborated by recent studies that utilize a global proteomics approach, and, more importantly, results from these proteomics investigations on the effects of hypoxia provide new protein targets for further functional analysis. The anticipated new information stems from the analysis of expression, and posttranslational modification of these novel protein targets, along with gene expression profiles, offers exciting new opportunities to further define the mechanisms of cellular responses to hypoxia and to control more effectively the clinical consequences of prolonged or periodic lack of oxygen.
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Affiliation(s)
- Ganesh K Kumar
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4935, USA.
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Prabhakar NR, Kumar GK. Oxidative stress in the systemic and cellular responses to intermittent hypoxia. Biol Chem 2004; 385:217-21. [PMID: 15134334 DOI: 10.1515/bc.2004.015] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Patients with chronic intermittent hypoxia (IH) caused by recurrent apneas have a greatly increased risk for developing hypertension, myocardial infarctions, and stroke. The purpose of this article is to highlight some of the recent studies focusing on the mechanisms associated with systemic and cellular effects of IH in experimental animals and cell culture models. Rats exposed to chronic IH exhibited elevated blood pressures and increased sympathetic nerve activity, partly due to enhanced reflexes arising from carotid bodies. Direct recordings of the carotid body sensory activity showed that chronic IH selectively augmented hypoxic sensitivity, and induced a novel form of functional plasticity manifested as sensory long-term facilitation. In cell culture models, prior exposure to IH resulted in facilitation of hypoxia-induced transmitter release and activation of several protein kinases. IH caused activation of c-Fos and activator protein-1 (AP-1) transcription factor and tyrosine hydroxylase, an AP-regulated downstream gene. For a given duration and intensity of hypoxia, IH was more potent and caused longer-lasting activation than continuous hypoxia. Scavengers of reactive oxygen species (ROS) prevented IH-induced systemic and cellular responses. Inhibition of complex I of the mitochondrial electron transport chain appears to be one of the sources for IH-induced generation of ROS. The persistent oxidative stress may contribute to the progression of morbidity associated with chronic IH caused by recurrent apneas, and antioxidants might be of considerable therapeutic value in preventing the progression of disease associated with chronic IH.
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Affiliation(s)
- Nanduri R Prabhakar
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH 44106, USA.
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Kim DK, Natarajan N, Prabhakar NR, Kumar GK. Facilitation of dopamine and acetylcholine release by intermittent hypoxia in PC12 cells: involvement of calcium and reactive oxygen species. J Appl Physiol (1985) 2003; 96:1206-15; discussion 1196. [PMID: 14657041 DOI: 10.1152/japplphysiol.00879.2003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have investigated the effects of preconditioning pheochromocytoma (PC12) cells with intermittent hypoxia (IH) on transmitter release during acute hypoxia. Cell cultures were exposed to either alternating cycles of hypoxia (1% O(2) + 5% CO(2); 30 s/cycle) and normoxia (21% O(2) + 5% CO(2); 3 min/cycle) for 15 or 60 cycles or normoxia alone (control) for similar durations. Control and IH cells were challenged with either hyperoxia (basal release) or acute hypoxia (Po(2) of approximately 35 Torr) for 5 min, and the amounts of dopamine (DA) and acetylcholine (ACh) released in the medium were determined by HPLC combined with electrochemical detection. Hypoxia augmented DA (approximately 80%) but not ACh release in naive cells, whereas, in IH-conditioned cells, it further enhanced DA release (ranging from 120 to approximately 145%) and facilitated ACh release (approximately 30%). Hypoxia-evoked augmentation of transmitter release was not seen in cells conditioned with sustained hypoxia. IH-induced increase in DA but not IH-induced ACh release during hypoxia was partially inhibited by cadmium chloride (100 microM), a voltage-gated Ca(2+) channel blocker. By contrast, 2-aminoethoxydiphenylborate (75 microM), a blocker of inositol 1,4,5-trisphosphate (IP(3)) receptors, and N-acetyl-L-cysteine (300 microM), a potent scavenger of reactive oxygen species, either attenuated or abolished IH-evoked augmentation of transmitter release during hypoxia. Together, the above results demonstrate that IH conditioning increases hypoxia-evoked neurotransmitter release from PC12 cells via mechanisms involving mobilization of Ca(2+) from intracellular stores through activation of IP(3) receptors. Our findings also suggest that oxidative stress plays a central role in IH-induced augmentation of transmitter release from PC12 cells during acute hypoxia.
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Affiliation(s)
- Dong-Kyu Kim
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106-4935, USA
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