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Osuru HP, Lavallee M, Thiele RH. Molecular and Cellular Response of the Myocardium (H9C2 Cells) Towards Hypoxia and HIF-1α Inhibition. Front Cardiovasc Med 2022; 9:711421. [PMID: 35928940 PMCID: PMC9343679 DOI: 10.3389/fcvm.2022.711421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 06/21/2022] [Indexed: 11/30/2022] Open
Abstract
Introduction Oxidative phosphorylation is an essential feature of Animalian life. Multiple adaptations have developed to protect against hypoxia, including hypoxia-inducible-factors (HIFs). The major role of HIFs may be in protecting against oxidative stress, not the preservation of high-energy phosphates. The precise mechanism(s) of HIF protection is not completely understood. Materials and Methods To better understand the role of hypoxia-inducible-factor-1, we exposed heart/myocardium cells (H9c2) to both normoxia and hypoxia, as well as cobalt chloride (prolyl hydroxylase inhibitor), echniomycin (HIF inhibitor), A2P (anti-oxidant), and small interfering RNA to beclin-1. We measured cell viability, intracellular calcium and adenosine triphosphate, NADP/NADPH ratios, total intracellular reactive oxidative species levels, and markers of oxidative and antioxidant levels measured. Results Hypoxia (1%) leads to increased intracellular Ca2+ levels, and this response was inhibited by A2P and echinomycin (ECM). Exposure of H9c2 cells to hypoxia also led to an increase in both mRNA and protein expression for Cav 1.2 and Cav 1.3. Exposure of H9c2 cells to hypoxia led to a decrease in intracellular ATP levels and a sharp reduction in total ROS, SOD, and CAT levels. The impact of hypoxia on ROS was reversed with HIF-1 inhibition through ECM. Exposure of H9c2 cells to hypoxia led to an increase in Hif1a, VEGF and EPO protein expression, as well as a decrease in mitochondrial DNA. Both A2P and ECM attenuated this response to varying degrees. Conclusion Hypoxia leads to increased intracellular Ca2+, and inhibition of HIF-1 attenuates the increase in intracellular Ca2+ that occurs with hypoxia. HIF-1 expression leads to decreased adenosine triphosphate levels, but the role of HIF-1 on the production of reactive oxidative species remains uncertain. Anti-oxidants decrease HIF-1 expression in the setting of hypoxia and attenuate the increase in Ca2+ that occurs during hypoxia (with no effect during normoxia). Beclin-1 appears to drive autophagy in the setting of hypoxia (through ATG5) but not in normoxia. Additionally, Beclin-1 is a powerful driver of reactive oxidative species production and plays a role in ATP production. HIF-1 inhibition does not affect autophagy in the setting of hypoxia, suggesting that there are other drivers of autophagy that impact beclin-1.
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Abstract
Oxygen (O2) is essential for life and therefore the supply of sufficient O2 to the tissues is a major physiological challenge. In mammals, a deficit of O2 (hypoxia) triggers rapid cardiorespiratory reflexes (e.g. hyperventilation and increased heart output) that within a few seconds increase the uptake of O2 by the lungs and its distribution throughout the body. The prototypical acute O2-sensing organ is the carotid body (CB), which contains sensory glomus cells expressing O2-regulated ion channels. In response to hypoxia, glomus cells depolarize and release transmitters which activate afferent fibers terminating at the brainstem respiratory and autonomic centers. In this review, we summarize the basic properties of CB chemoreceptor cells and the essential role played by their specialized mitochondria in acute O2 sensing and signaling. We focus on recent data supporting a "mitochondria-to-membrane signaling" model of CB chemosensory transduction. The possibility that the differential expression of specific subunit isoforms and enzymes could allow mitochondria to play a generalized adaptive O2-sensing and signaling role in a wide variety of cells is also discussed.
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Affiliation(s)
- José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, Seville, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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Mukherjee S, Sikdar SK. Intracellular activation of full-length human TREK-1 channel by hypoxia, high lactate, and low pH denotes polymodal integration by ischemic factors. Pflugers Arch 2020; 473:167-183. [PMID: 33025137 DOI: 10.1007/s00424-020-02471-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/18/2020] [Accepted: 09/30/2020] [Indexed: 10/23/2022]
Abstract
TREK-1, a two-pore domain potassium channel, responds to ischemic levels of intracellular lactate and acidic pH to provide neuroprotection. There are two splice variants of hTREK1: the shorter splice variant having a shorter N-terminus compared with the full-length hTREK1 with similar C-terminus sequence that is widely expressed in the brain. The shorter variant was reported to be irresponsive to hypoxia-a condition attributed to ischemia, which has put the neuroprotective role of hTREK-1 channel into question. Since interaction between N- and C-terminus of different ion channels shapes their gating, we re-examined the sensitivity of the full-length as well as the shorter hTREK-1 channel to intracellular hypoxia along with lactate. Single-channel data obtained from the excised inside-out patches of the full-length channel expressed in HEK293 cells indicated an increase in activity as opposed to a decrease in activity in the shorter isoform. However, both the isoforms showed an increase in activity under combined hypoxia, 20mM lactate, and low pH 6 condition, albeit with subtle differences in their individual actions, confirming the neuroprotective role played by hTREK-1 irrespective of the differences in the N-terminus among the splice variants. Furthermore, E321A mutant that disrupts the interaction of the C-terminus with the membrane showed a decrease in activity with hypoxia indicating the importance of the C-terminus in the hypoxic response of the full-length hTREK-1. We propose an increase in activity of both the splice variants of hTREK-1 in combined hypoxia, high lactate, and low pH conditions typically associated with ischemia provides neuroprotection.
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Affiliation(s)
- Sourajit Mukherjee
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India
| | - Sujit Kumar Sikdar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, 560012, India.
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López-Barneo J, González-Rodríguez P, Gao L, Fernández-Agüera MC, Pardal R, Ortega-Sáenz P. Oxygen sensing by the carotid body: mechanisms and role in adaptation to hypoxia. Am J Physiol Cell Physiol 2016; 310:C629-42. [PMID: 26764048 DOI: 10.1152/ajpcell.00265.2015] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Oxygen (O2) is fundamental for cell and whole-body homeostasis. Our understanding of the adaptive processes that take place in response to a lack of O2(hypoxia) has progressed significantly in recent years. The carotid body (CB) is the main arterial chemoreceptor that mediates the acute cardiorespiratory reflexes (hyperventilation and sympathetic activation) triggered by hypoxia. The CB is composed of clusters of cells (glomeruli) in close contact with blood vessels and nerve fibers. Glomus cells, the O2-sensitive elements in the CB, are neuron-like cells that contain O2-sensitive K(+)channels, which are inhibited by hypoxia. This leads to cell depolarization, Ca(2+)entry, and the release of transmitters to activate sensory fibers terminating at the respiratory center. The mechanism whereby O2modulates K(+)channels has remained elusive, although several appealing hypotheses have been postulated. Recent data suggest that mitochondria complex I signaling to membrane K(+)channels plays a fundamental role in acute O2sensing. CB activation during exposure to low Po2is also necessary for acclimatization to chronic hypoxia. CB growth during sustained hypoxia depends on the activation of a resident population of stem cells, which are also activated by transmitters released from the O2-sensitive glomus cells. These advances should foster further studies on the role of CB dysfunction in the pathogenesis of highly prevalent human diseases.
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Affiliation(s)
- José López-Barneo
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Patricia González-Rodríguez
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Lin Gao
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - M Carmen Fernández-Agüera
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Ricardo Pardal
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Patricia Ortega-Sáenz
- Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío, CSIC, Universidad de Sevilla, Seville, Spain; Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain; and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
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Prasad M, Zachar V, Fink T, Pennisi CP. Moderate hypoxia influences potassium outward currents in adipose-derived stem cells. PLoS One 2014; 9:e104912. [PMID: 25115627 PMCID: PMC4130641 DOI: 10.1371/journal.pone.0104912] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 07/15/2014] [Indexed: 01/23/2023] Open
Abstract
Moderate hypoxic preconditioning of adipose-derived stem cells (ASCs) enhances properties such as proliferation and secretion of growth factors, representing a valuable strategy to increase the efficiency of cell-based therapies. In a wide variety of cells potassium (K+) channels are key elements involved in the cellular responses to hypoxia, suggesting that ASCs cultured under low oxygen conditions may display altered electrophysiological properties. Here, the effects of moderate hypoxic culture on proliferation, whole-cell currents, and ion channel expression were investigated using human ASCs cultured at 5% and 20% oxygen. Although cell proliferation was greatly enhanced, the dose-dependent growth inhibition by the K+ channel blocker tetraethylammonium (TEA) was not significantly affected by hypoxia. Under both normoxic and hypoxic conditions, ASCs displayed outward K+ currents composed by Ca2+-activated, delayed rectifier, and transient components. Hypoxic culture reduced the slope of the current-voltage curves and caused a negative shift in the voltage activation threshold of the whole-cell currents. However, the TEA-mediated shift of voltage activation threshold was not affected by hypoxia. Semiquantitative real-time RT-PCR revealed that expression of genes encoding for various ion channels subunits related to oxygen sensing and proliferation remained unchanged after hypoxic culture. In conclusion, outward currents are influenced by moderate hypoxia in ASCs through a mechanism that is not likely the result of modulation of TEA-sensitive K+ channels.
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Affiliation(s)
- Mayuri Prasad
- Laboratory for Stem Cell Research, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Vladimir Zachar
- Laboratory for Stem Cell Research, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Trine Fink
- Laboratory for Stem Cell Research, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Cristian Pablo Pennisi
- Laboratory for Stem Cell Research, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
- * E-mail:
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Wang JB, Wang DL, Wang HT, Wang ZH, Wen Y, Sun CM, Zhao YT, Wu J, Liu P. Tumor necrosis factor-alpha-induced reduction of glomerular filtration rate in rats with fulminant hepatic failure. J Transl Med 2014; 94:740-51. [PMID: 24887412 DOI: 10.1038/labinvest.2014.71] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2013] [Revised: 04/11/2014] [Accepted: 04/20/2014] [Indexed: 12/16/2022] Open
Abstract
The mechanism of renal failure during fulminant hepatic failure (FHF) or end-stage of liver disease is not fully understood. The present study aims to delineate the mechanisms of decreased glomerular filtration rate (GFR) in acute hepatic failure. A rat model of renal insufficiency in severe liver injury was established by lipopolysaccharide (LPS) plus D-galactosamine (GalN) exposure. GFR was evaluated by continuous infusion of fluorescein isothiocyanate-inulin with implanted micro-osmotic pumps. GalN/LPS intoxication resulted in severe hepatocyte toxicity as evidenced by liver histology and biochemical tests, whereas renal morphology remained normal. GFR was reduced by 33% of the controls 12 h after GalN/LPS exposure, accompanied with a decreased serum sodium levels, a marked increase in serum TNF-α and ET-1 levels as well as significantly upregulated renal type 1 inositol 1,4,5-trisphosphate receptor (IP3R1) expression. The upregulated IP3R1 expression was abrogated by the treatment of anti-TNF-α antibodies, but not by 2-aminoethoxydiphenylborate (2-APB), which blocks the inositol 1,4,5-trisphosphate signaling pathway. Treatments with either TNF-α antibodies or 2-APB also significantly improved the compromised GFR, elevated serum urea nitrogen and creatinine levels, and reversed the decrease in glomerular inulin space and the increase in glomerular calcium content in GalN/LPS-exposed rats. The extent of acute liver injury as reflected by serum ALT levels was much more attenuated by anti-TNF-α antibodies than by 2-APB. Liver histology further confirmed that anti-TNF-α antibodies conferred better protection than 2-APB in GalN/LPS-exposed rats. LPS-elicited TNF-α over-production is responsible for decreased GFR through IP3R1 overexpression, and the compromised GFR resulted in the development of acute renal failure in rats with FHF.
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Affiliation(s)
- Jing-Bo Wang
- 1] Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China [2] Division of Gastroenterology, Department of Internal Medicine, The Sixth People's Hospital of Shenyang, Shenyang City, People's Republic of China
| | - Dong-Lei Wang
- Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China
| | - Hai-Tao Wang
- Division of Hepatobiliary Diseases, Department of Surgery, The Affiliated Shenzhou Hospital of Shenyang Medical College, Shenyang City, People's Republic of China
| | - Zhao-Han Wang
- Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China
| | - Ying Wen
- Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China
| | - Cui-Ming Sun
- Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China
| | - Yi-Tong Zhao
- Division of Gastroenterology, Department of Internal Medicine, The Sixth People's Hospital of Shenyang, Shenyang City, People's Republic of China
| | - Jian Wu
- 1] Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of California, Davis Medical Center, Sacramento, CA, USA [2] Key Laboratory of Molecular Virology, Fudan University College of Basic Medical Sciences, Shanghai, People's Republic of China
| | - Pei Liu
- Department of Infectious Diseases, The First Affiliated Hospital, China Medical University, Shenyang City, People's Republic of China
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Revuelta-López E, Castellano J, Roura S, Gálvez-Montón C, Nasarre L, Benitez S, Bayes-Genis A, Badimon L, Llorente-Cortés V. Hypoxia Induces Metalloproteinase-9 Activation and Human Vascular Smooth Muscle Cell Migration Through Low-Density Lipoprotein Receptor–Related Protein 1–Mediated Pyk2 Phosphorylation. Arterioscler Thromb Vasc Biol 2013; 33:2877-87. [DOI: 10.1161/atvbaha.113.302323] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Elena Revuelta-López
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - José Castellano
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Santiago Roura
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Carolina Gálvez-Montón
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Laura Nasarre
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Sonia Benitez
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Antoni Bayes-Genis
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Lina Badimon
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
| | - Vicenta Llorente-Cortés
- From the Cardiovascular Research Center, CSIC-ICCC, IIB-Sant Pau, Barcelona, Spain (E.R.-L., J.C., L.N., L.B.); ICREC Research Program, Fundació Institut d´Investigació en Ciències de la Salut Germans Trias i Pujol (IGTP), Badalona, Spain (S.R., C.G.-M., A.B.-G.); and Cardiovascular Biochemistry Group, Biomedical Research Institute Sant Pau, IIB-Sant Pau, Barcelona, Spain (S.B.)
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Roy A, Derakhshan F, Wilson RJA. Stress peptide PACAP engages multiple signaling pathways within the carotid body to initiate excitatory responses in respiratory and sympathetic chemosensory afferents. Am J Physiol Regul Integr Comp Physiol 2013; 304:R1070-84. [PMID: 23594614 DOI: 10.1152/ajpregu.00465.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Consistent with a critical role in respiratory and autonomic stress responses, the carotid bodies are strongly excited by pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide implicated in stress responses throughout the sympathetic nervous system. PACAP excites isolated carotid body glomus cells via activation of PAC1 receptors, with one study suggesting PAC1-induced excitation is due entirely to protein kinase A (PKA)-mediated inhibition of TASK channels. However, in other systems, PAC1 is known to be coupled to multiple intracellular signaling pathways, including PKA, phospholipase C (PLC), phospholipase D (PLD), and protein kinase C (PKC), that trigger multiple downstream effectors including increased Ca²⁺ mobilization, inhibition of various K⁺ channels, and activation of nonselective cation channels. This study tests if non-PKA/TASK channel signaling helps mediate the stimulatory effects of PACAP on the carotid body. Using an ex vivo arterially perfused rat carotid body preparation, we show that PACAP-38 stimulates carotid sinus nerve activity in a biphasic manner (peak response, falling to plateau). PKA blocker H-89 only reduced the plateau response (~41%), whereas the TASK-1-like K⁺ channel blocker/transient receptor potential vanilloid 1 channel agonist anandamide only inhibited the peak response (~48%), suggesting involvement of additional pathways. The PLD blocker CAY10594 significantly inhibited both peak and plateau responses. The PLC blocker U73122 decimated both peak and plateau responses. Brefeldin A, a blocker of Epac (cAMP-activated guanine exchange factor, reported to link Gs-coupled receptors with PLC/PLD), also reduced both phases of the response, as did blocking signaling downstream of PLC/PLD with the PKC inhibitors chelerythrine chloride and GF109203X. Suggesting the involvement of non-TASK ion channels in the effects of PACAP, the A-type K⁺ channel blocker 4-aminopyridine, and the putative transient receptor potential channel (TRPC)/T-type calcium channel blocker SKF96365 each significantly inhibited the peak and steady-state responses. These data suggest the stimulatory effect of PACAP-38 on carotid body sensory activity is mediated through multiple signaling pathways: the PLC-PKC pathways predominates, with TRPC and/or T-type channel activation and Kv channel inactivation; only partial involvement is attributable to PKA and PLD activation.
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Affiliation(s)
- Arijit Roy
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
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Gouriou Y, Bijlenga P, Demaurex N. Mitochondrial Ca2+ uptake from plasma membrane Cav3.2 protein channels contributes to ischemic toxicity in PC12 cells. J Biol Chem 2013; 288:12459-68. [PMID: 23508951 PMCID: PMC3642294 DOI: 10.1074/jbc.m112.428128] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
T-type Ca(2+) channel inhibitors protect hippocampal CA1 neurons from delayed death after global ischemia in rats, suggesting that Cav3.1, Cav3.2, or Cav3.3 channels generate cytotoxic Ca(2+) elevations during anoxia. To test this hypothesis, we measured the Ca(2+) concentration changes evoked by oxygen and glucose deprivation (OGD) in the cytosol and in the mitochondria of PC12 cells. OGD evoked long-lasting cytosolic Ca(2+) elevations that were reduced by Cav3.2 inhibition (50 μm Ni(2+)) and Cav3.1/Cav3.2 silencing and potentiated by Cav3.2 overexpression. The kinetics of the sustained cytosolic Ca(2+) elevations occurring during OGD directly correlated to the extent of cell death measured 20 h after reoxygenation, which was decreased by Ni(2+) and Cav3.1/Cav3.2 silencing and increased by Cav3.2 overexpression. Ni(2+) and Cav3.1/Cav3.2 silencing delayed the decline of cellular ATP during OGD, consistent with a reduction in the Ca(2+) load actively extruded by plasma membrane Ca(2+) pumps. The cytosolic Ca(2+) elevations were paralleled by mitochondrial Ca(2+) elevations that were also increased by Cav3.2 overexpression and decreased by Ni(2+) but not by Cav3.1/Cav3.2 silencing. Overexpression and silencing of the mitochondrial Ca(2+) uniporter, the major mitochondrial Ca(2+) uptake protein, revealed that the cytotoxicity was correlated to the amplitude of the mitochondrial, rather than the cytosolic, Ca(2+) elevations. Selective activation of T-type Ca(2+) channels evoked both cytosolic and mitochondrial Ca(2+) elevations, but only the mitochondrial responses were reduced by Cav3.1/Cav3.2 silencing. We conclude that the opening of Cav3.2 channels during ischemia contribute to the entry of Ca(2+) ions that are transmitted to mitochondria, resulting in a deleterious mitochondrial Ca(2+) overload.
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Affiliation(s)
- Yves Gouriou
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva CH-1211, Switzerland
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Numata T, Ogawa N, Takahashi N, Mori Y. TRP channels as sensors of oxygen availability. Pflugers Arch 2013; 465:1075-85. [DOI: 10.1007/s00424-013-1237-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/31/2013] [Accepted: 01/31/2013] [Indexed: 11/28/2022]
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Bae YJ, Yoo JC, Park N, Kang D, Han J, Hwang E, Park JY, Hong SG. Acute Hypoxia Activates an ENaC-like Channel in Rat Pheochromocytoma (PC12) Cells. Korean J Physiol Pharmacol 2013; 17:57-64. [PMID: 23440317 PMCID: PMC3579106 DOI: 10.4196/kjpp.2013.17.1.57] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Revised: 11/28/2012] [Accepted: 12/04/2012] [Indexed: 12/17/2022]
Abstract
Cells can resist and even recover from stress induced by acute hypoxia, whereas chronic hypoxia often leads to irreversible damage and eventually death. Although little is known about the response(s) to acute hypoxia in neuronal cells, alterations in ion channel activity could be preferential. This study aimed to elucidate which channel type is involved in the response to acute hypoxia in rat pheochromocytomal (PC12) cells as a neuronal cell model. Using perfusing solution saturated with 95% N(2) and 5% CO(2), induction of cell hypoxia was confirmed based on increased intracellular Ca(2+) with diminished oxygen content in the perfusate. During acute hypoxia, one channel type with a conductance of about 30 pS (2.5 pA at -80 mV) was activated within the first 2~3 min following onset of hypoxia and was long-lived for more than 300 ms with high open probability (P(o), up to 0.8). This channel was permeable to Na(+) ions, but not to K(+), Ca(+), and Cl(-) ions, and was sensitively blocked by amiloride (200 nM). These characteristics and behaviors were quite similar to those of epithelial sodium channel (ENaC). RT-PCR and Western blot analyses confirmed that ENaC channel was endogenously expressed in PC12 cells. Taken together, a 30-pS ENaC-like channel was activated in response to acute hypoxia in PC12 cells. This is the first evidence of an acute hypoxia-activated Na(+) channel that can contribute to depolarization of the cell.
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Affiliation(s)
- Yeon Ju Bae
- Department of Physiology, Institute of Health Sciences and Medical Research Center for Neural Dysfunction, Gyeongsang National University School of Medicine, Jinju 660-751, Korea
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Abstract
Even a short blockade of oxygen flow in brain may lead to the inhibition of oxidative phosphorylation and depletion of cellular ATP, which results in profound deficiencies in cellular function. Following ischemia, dying, injured, and hypoxic cells release soluble purine-nucleotide and -nucleoside pools. Growing evidence suggests that purine nucleosides might act as trophic factors in the CNS and PNS. In addition to equilibrative nucleoside transporters (ENTs) regulating purine nucleoside concentrations intra- and extracellularly, specific extracellular receptor subtypes for these compounds are expressed on neurons, glia, and endothelial cells, mediating stunningly diverse effects. Such effects range from induction of cell differentiation, apoptosis, mitogenesis, and morphogenetic changes, to stimulation of synthesis and/or release of cytokines and neurotrophic factors under both physiological and pathological conditions. Multiple signaling pathways regulate the critical balance between cell death and survival in hypoxia-ischemia. A convergent pathway for the regulation of multiple modalities involved in O₂ sensing is the mitogen activated protein kinase (p42/44 MAPK) or (ERK1/2 extracellular signal-regulated kinases) pathway terminating in a variety of transcription factors, for example, hypoxia-inducible factor 1α. In this review, the coherence of purine nucleoside-related pathways and MAPK activation in the endogenous neuroprotective regulation of the nervous system's development and neuroplasticity under hypoxic stress will be discussed.
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Affiliation(s)
- Bettina Thauerer
- Division of Neurobiochemistry, Biocenter Department, Medical University of Innsbruck, Innsbruck, Austria
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Brown ST, Buttigieg J, Nurse CA. Divergent roles of reactive oxygen species in the responses of perinatal adrenal chromaffin cells to hypoxic challenges. Respir Physiol Neurobiol 2010; 174:252-8. [PMID: 20804866 DOI: 10.1016/j.resp.2010.08.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 08/23/2010] [Accepted: 08/24/2010] [Indexed: 11/28/2022]
Abstract
The fetus and neonate experience variable patterns of low P(O)₂(hypoxia) ranging from acute, sustained, and intermittent. Adaptation to hypoxia involves activation of key transcription factors, known as hypoxia-inducible factors (e.g. HIF-1α, HIF-2α), which regulate a number of genes in different cell types. This review focuses on the signaling pathways that mediate proper physiological responses of perinatal adrenomedullary chromaffin cells (AMC) to varying patterns of hypoxic challenges, and particularly on the controversial role of reactive oxygen species (ROS). At birth, acute hypoxia (seconds to minutes) directly stimulates catecholamine release from AMC via K+ channel inhibition, mediated by a decrease in mitochondrial-derived ROS. By contrast, exposure to chronic sustained hypoxia (CSH) induces HIF-2α in a fetal-derived chromaffin cell line independently of changes in ROS. Exposure to chronic intermittent hypoxia (CIH) activates antioxidant responses via the regulator Nrf-2, in association with an increase in ROS and the induction of HIF-1α. We propose that the physiological responses of perinatal AMC to hypoxia and the ensuing directional changes in ROS are dependent on the pattern and duration of the hypoxic exposure.
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Affiliation(s)
- Stephen T Brown
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, Ontario, Canada L8S 4K1
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Guo Z, Shi F, Zhang L, Zhang H, Yang J, Li B, Jia J, Wang X, Wang X. Critical role of L-type voltage-dependent Ca2+ channels in neural progenitor cell proliferation induced by hypoxia. Neurosci Lett 2010; 478:156-60. [PMID: 20466036 DOI: 10.1016/j.neulet.2010.05.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2010] [Revised: 05/01/2010] [Accepted: 05/03/2010] [Indexed: 11/16/2022]
Abstract
Hypoxia can promote proliferation of neural progenitor cells in vitro and in vivo, however, the mechanisms underlying this phenomenon remain largely unknown. Calcium ions are important for the proliferation of progenitor cells. In this study, we reported that Ca(2+) influx through L-type voltage-dependent Ca(2+) channels mediated hypoxia-promoted proliferation of neural progenitor cells isolated from embryonic day 14.5 rat mesencephalon. Cell number was greatly increased in the cultured neural progenitor cells exposed to physiological hypoxia (3% O(2), 72 h) compared with normoxia exposure (20% O(2), 72 h). Increased intracellular Ca(2+) concentration was also observed when the cells were exposed to hypoxia. Moreover, removal of extracellular Ca(2+) or administration of nicardipine, an agent known to block L-type Ca(2+) channels, resulted in suppression of the hypoxia-induced increase in intracellular Ca(2+) and cell numbers. These results suggest that hypoxia promoted the proliferation of neural progenitor cells by increasing Ca(2+) influx, which was likely a result of upregulation of L-type voltage-dependent Ca(2+) channel function.
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Affiliation(s)
- Zixuan Guo
- Department of Physiology, Capital Medical University, Key Laboratory for Neurodegenerative Disorders of the Ministry of Education, Beijing, PR China
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15
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Thauerer B, zur Nedden S, Baier-Bitterlich G. Vital role of protein kinase C-related kinase in the formation and stability of neurites during hypoxia. J Neurochem 2010; 113:432-46. [PMID: 20132472 DOI: 10.1111/j.1471-4159.2010.06624.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Exposure of pheochromocytoma cells to hypoxia (1% O(2)) favors differentiation at the expense of cell viability. Additional incubation with nerve growth factor (NGF) and guanosine, a purine nucleoside with neurotrophin characteristics, rescued cell viability and further enhanced the extension of neurites. In parallel, an increase in the activity of protein kinase C-related kinase (PRK1), which is known to be involved in regulation of the actin cytoskeleton, was observed in hypoxic cells. NGF and guanosine further enhanced PRK1 in normoxic and hypoxic cells. To study the role of PRK1 during cellular stress response and neurotrophin-mediated signaling, pheochromocytoma cells were transfected with small interfering RNA directed against PRK1. Loss of functional PRK1 initiated a significant loss of viability and inhibited neurite formation. SiRNA-mediated knockdown of PRK1 also completely stalled guanosine-mediated neuroprotective effects. Additionally, the F-actin-associated cytoskeleton and the expression of the plasticity protein growth associated protein-43 were disturbed upon PRK1 knockdown. A comparable dependency of neurite formation and growth associated protein-43 immunoreactivity on functional PRK1 expression was observed in cerebellar granule neurons. Based on these data, a putative role of PRK1 as a key-signaling element for the successive NGF- and purine nucleoside-mediated protection of hypoxic neuronal cells is hypothesized.
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Affiliation(s)
- Bettina Thauerer
- Med. University of Innsbruck, Biocenter, Division of Neurobiochemistry, A-6020 Innsbruck, Austria
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17
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D'Agostino D, Mazza E, Neubauer JA. Heme oxygenase is necessary for the excitatory response of cultured neonatal rat rostral ventrolateral medulla neurons to hypoxia. Am J Physiol Regul Integr Comp Physiol 2009; 296:R102-18. [PMID: 18971354 PMCID: PMC2636982 DOI: 10.1152/ajpregu.90325.2008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2008] [Accepted: 10/21/2008] [Indexed: 12/17/2022]
Abstract
Heme oxygenase has been linked to the oxygen-sensing function of the carotid body, pulmonary vasculature, cerebral vasculature, and airway smooth muscle. We have shown previously that the cardiorespiratory regions of the rostral ventrolateral medulla are excited by local hypoxia and that heme oxygenase-2 (HO-2) is expressed in the hypoxia-chemosensitive regions of the rostral ventrolateral medulla (RVLM), the respiratory pre-Bötzinger complex, and C1 sympathoexcitatory region. To determine whether heme oxygenase is necessary for the hypoxic-excitation of dissociated RVLM neurons (P1) cultured on confluent medullary astrocytes (P5), we examined their electrophysiological responses to hypoxia (NaCN and low Po(2)) using the whole-cell perforated patch clamp technique before and after blocking heme oxygenase with tin protoporphyrin-IX (SnPP-IX). Following the electrophysiological recording, immunocytochemistry was performed on the recorded neuron to correlate the electrophysiological response to hypoxia with the expression of HO-2. We found that the responses to NaCN and hypoxia were similar. RVLM neurons responded to NaCN and low Po(2) with either depolarization or hyperpolarization and SnPP-IX blocked the depolarization response of hypoxia-excited neurons to both NaCN and low Po(2) but had no effect on the hyperpolarization response of hypoxia-depressed neurons. Consistent with this observation, HO-2 expression was present only in the hypoxia-excited neurons. We conclude that RVLM neurons are excited by hypoxia via a heme oxygenase-dependent mechanism.
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Affiliation(s)
- Dominic D'Agostino
- Div. of Pulmonary & Critical Care Medicine, Dept. of Medicine, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
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Liu X, He L, Stensaas L, Dinger B, Fidone S. Adaptation to chronic hypoxia involves immune cell invasion and increased expression of inflammatory cytokines in rat carotid body. Am J Physiol Lung Cell Mol Physiol 2008; 296:L158-66. [PMID: 18978039 DOI: 10.1152/ajplung.90383.2008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Exposure to chronic hypoxia (CH; 3-28 days at 380 Torr) induces adaptation in mammalian carotid body such that following CH an acute hypoxic challenge elicits an abnormally large increase in carotid sinus nerve impulse activity. The current study examines the hypothesis that CH initiates an immune response in the carotid body and that chemoreceptor hyperexcitability is dependent on the expression and action of inflammatory cytokines. CH resulted in a robust invasion of ED1(+) macrophages, which peaked on day 3 of exposure. Gene expression of proinflammatory cytokines, IL-1beta, TNFalpha, and the chemokine, monocyte chemoattractant protein-1, was increased >2-fold after 1 day of hypoxia followed by a >2-fold increase in IL-6 on day 3. After 28 days of CH, IL-6 remained elevated >5-fold, whereas expression of other cytokines recovered to normal levels. Cytokine expression was not restricted to immune cells. Studies of cultured type I cells harvested following 1 day of in vivo hypoxia showed elevated transcript levels of inflammatory cytokines. In situ hybridization studies confirmed expression of IL-6 in type I cells and also showed that CH induces IL-6 expression in supporting type II cells. Concurrent treatment of CH rats with anti-inflammatory drugs (ibuprofen or dexamethasone) blocked immune cell invasion and severely reduced CH-induced cytokine expression in carotid body. Drug treatment also blocked the development of chemoreceptor hypersensitivity in CH animals. Our findings indicate that chemoreceptor adaptation involves novel neuroimmune mechanisms, which may alter the functional phenotypes of type I cells and chemoafferent neurons.
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Affiliation(s)
- X Liu
- Dept. of Physiology, Univ. of Utah School of Medicine, Salt Lake City, UT 84108-6500, USA
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Meng F, To WKL, Gu Y. Role of TRP channels and NCX in mediating hypoxia-induced [Ca(2+)](i) elevation in PC12 cells. Respir Physiol Neurobiol 2008; 164:386-93. [PMID: 18822394 DOI: 10.1016/j.resp.2008.09.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 08/31/2008] [Accepted: 09/01/2008] [Indexed: 10/21/2022]
Abstract
Mammalian cells require a constant O2 supply to produce adequate energy, and sustained hypoxia can kill cells. Mammals therefore have evolved sophisticated mechanisms to allow their cells to adapt to hypoxia. In this study, we investigated the role of TRP channels and the Na+-Ca2+ exchanger (NCX) in mediating hypoxia-induced [Ca2+]i elevation in a model of the O2-sensing rat pheochromocytoma (PC12) cell line by using Ca2+ imaging and molecular biological approaches. Non-selective cation channels, such as TRPC1, 3 and 6, were found to be functionally expressed in PC12 cells. They mediated Ca2+ entry when cells were exposed to acute hypoxia (PO2 of 15 mmHg), in addition to Ca2+ entry via VGCCs. Blockage of TRPCs by 2APB and SKF96365 could significantly reduce hypoxia-mediated [Ca2+]i elevation. Suramin and U73122 attenuated the hypoxia-induced [Ca2+]i elevation, implying the involvement of the G-protein and PLC pathways in the hypoxic response. In addition to TRPCs and VGCCs, NCX also contributed to the hypoxia-induced [Ca2+]i elevation, and blockade of NCX by KBR7943 could significantly decrease the hypoxia-induced [Ca2+]i elevation. Our results suggest that the activation of TRP by hypoxia could lead to NCX reversal; furthermore, membrane depolarization and TRPCs may play a primary role in mediating the hypoxic response in PC12 cells.
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Affiliation(s)
- Fei Meng
- Department of Physiology, The Medical School, University of Birmingham, Vincent Drive, Edgbaston B15 2TT, Birmingham, UK
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20
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Tomaselli B, Nedden SZ, Podhraski V, Baier-Bitterlich G. p42/44 MAPK is an essential effector for purine nucleoside-mediated neuroprotection of hypoxic PC12 cells and primary cerebellar granule neurons. Mol Cell Neurosci 2008; 38:559-68. [DOI: 10.1016/j.mcn.2008.05.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 04/29/2008] [Accepted: 05/07/2008] [Indexed: 10/22/2022] Open
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21
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Meng F, To WKL, Gu Y. Inhibition effect of arachidonic acid on hypoxia-induced [Ca(2+)](i) elevation in PC12 cells and human pulmonary artery smooth muscle cells. Respir Physiol Neurobiol 2008; 162:18-23. [PMID: 18455484 DOI: 10.1016/j.resp.2008.03.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 03/13/2008] [Accepted: 03/17/2008] [Indexed: 11/29/2022]
Abstract
[Ca(2+)](i) elevation is a key event when O(2) sensitive cells, e.g. PC12 cells and pulmonary artery smooth muscle cells, face hypoxia. Ca(2+) entry pathways in mediating hypoxia-induced [Ca(2+)](i) elevation include: voltage-gated Ca(2+) channels (VGCCs), transient receptor potential (TRP) channel and Na(+)-Ca(2+) ex-changer (NCX). In the pulmonary artery, accumulated evidence strongly suggests that prostaglandins (PGs) are involved in pulmonary inflammation and cause vasoconstriction during hypoxia. In this study, we investigated the effect of arachidonic acid (AA), the upstream substrate for PGs, on hypoxia response in O(2) sensitive cells. Exogenous application of AA significantly inhibited hypoxia-induced [Ca(2+)](i) elevation. This effect was due to AA itself rather than its degenerative products. The pharmacological modulation of endogenous AA showed that the prevention of AA generation by blockage of cPLA2, diacylglycerol (DAG) lipase and fatty acid hydrolysis (FAAH), augments hypoxia-induced [Ca(2+)](i) elevation, whereas prevention of AA degeneration attenuates hypoxia-induced [Ca(2+)](i) elevation. Over-expression of COX2 enhances hypoxia-induced [Ca(2+)](i) elevation and this enhancement is reversed by exogenous AA. Our results suggest that AA inhibits hypoxia response. The dynamic alterations in cellular lipids might determine cell response to hypoxia.
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Affiliation(s)
- Fei Meng
- Department of Physiology, The Medical School, University of Birmingham, Vincent Drive, Birmingham, UK
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22
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zur Nedden S, Tomaselli B, Baier-Bitterlich G. HIF-1 alpha is an essential effector for purine nucleoside-mediated neuroprotection against hypoxia in PC12 cells and primary cerebellar granule neurons. J Neurochem 2008; 105:1901-14. [PMID: 18248612 DOI: 10.1111/j.1471-4159.2008.05275.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Hypoxia-inducible factor-1 alpha (HIF-1alpha) and purine nucleosides adenosine and inosine are critical mediators of physiological responses to acute and chronic hypoxia. The specific aim of this paper was to evaluate the potential role of HIF-1alpha in purine-mediated neuroprotection. We show that adenosine and inosine efficiently rescued clonal rat pheochromocytoma (PC12) cells (up to 43.6%) as well as primary cerebellar granule neurons (up to 25.1%) from hypoxic insult, and furthermore, that HIF-1alpha is critical for purine-mediated neuroprotection. Next, we studied hypoxia or purine nucleoside increased nuclear accumulation of HIF-1alpha in PC12 cells. As a possible result of increased protein stabilization or synthesis an up to 2.5-fold induction of HIF-1alpha accumulation was detected. In cerebellar granule neurons, purine nucleosides induced an up to 3.1-fold HIF-1alpha accumulation in cell lysates. Concomitant with these results, small interfering RNA-mediated reduction of HIF-1alpha completely abolished adenosine- and inosine-mediated protection in PC12 cells and severely hampered purine nucleoside-mediated protection in primary neurons (up to 94.2%). Data presented in this paper thus clearly demonstrate that HIF-1alpha is a key regulator of purine nucleoside-mediated rescue of hypoxic neuronal cells.
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Affiliation(s)
- Stephanie zur Nedden
- Division of Neurobiochemistry, Medical University of Innsbruck, Biocenter, Innsbruck, Austria
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Zhdanov AV, Ward MW, Prehn JHM, Papkovsky DB. Dynamics of intracellular oxygen in PC12 Cells upon stimulation of neurotransmission. J Biol Chem 2007; 283:5650-61. [PMID: 18086678 DOI: 10.1074/jbc.m706439200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurotransmission, synaptic plasticity, and maintenance of membrane excitability require high mitochondrial activity in neurosecretory cells. Using a fluorescence-based intracellular O2 sensing technique, we investigated the respiration of differentiated PC12 cells upon depolarization with 100 mm K+. Single cell confocal analysis identified a significant depolarization of the plasma membrane potential and a relatively minor depolarization of the mitochondrial membrane potential following K+ exposure. We observed a two-phase respiratory response: a first intense spike lasting approximately 10 min, during which average intracellular O2 was reduced from 85-90% of air saturation to 55-65%, followed by a second wave of smaller amplitude and longer duration. The fast rise in O2 consumption coincided with a transient increase in cellular ATP by approximately 60%, which was provided largely by oxidative phosphorylation and by glycolysis. The increase of respiration was orchestrated mainly by Ca2+ release from the endoplasmic reticulum, whereas the influx of extracellular Ca2+ contributed approximately 20%. Depletion of Ca2+ stores by ryanodine, thapsigargin, and 4-chloro-m-cresol reduced the amplitude of respiratory spike by 45, 63, and 71%, respectively, whereas chelation of intracellular Ca2+ abolished the response. Uncoupling of the mitochondria with the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone amplified the responses to K+; elevated respiration induced a profound deoxygenation without increasing the cellular ATP levels reduced by carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Cleavage of synaptobrevin 2 by tetanus toxin, known to reduce neurotransmission, did not affect the respiratory response to K+, whereas the general excitability of d PC12 cells increased.
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Affiliation(s)
- Alexander V Zhdanov
- Biochemistry Department, University College Cork, Cavanagh Pharmacy Building, Cork, Ireland
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Ortega-Sáenz P, Pascual A, Piruat JI, López-Barneo J. Mechanisms of acute oxygen sensing by the carotid body: Lessons from genetically modified animals. Respir Physiol Neurobiol 2007; 157:140-7. [PMID: 17360248 DOI: 10.1016/j.resp.2007.02.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2006] [Revised: 02/06/2007] [Accepted: 02/09/2007] [Indexed: 01/23/2023]
Abstract
We have studied carotid body (CB) glomus cell sensitivity to changes in O(2) tension in three different genetically engineered animals models using thin CB slices and monitoring the secretory response to hypoxia by amperometry. Glomus cells from partially HIF-1alpha deficient mice exhibited a normal sensitivity to hypoxia. Animals with complete deletion of the small membrane anchoring subunit of succinate dehydrogenase (SDHD) died during embryonic life but heterozygous SDHD +/- mice showed a normal CB response to low O(2) tension. SDHD +/- mice had, however, a clear CB phenotype characterized by a decrease of K(+) current amplitude, an increase of basal catecholamine release from glomus cells, and a slight organ growth. The lack of hemeoxygenase-2 (HO-2), a ubiquitous powerful antioxidant enzyme, produces a notable CB phenotype, characterized by hypertrophy and alteration in the level of CB expression of some stress-dependent genes (including down-regulation of the maxi-K(+) channel alpha-subunit). Nevertheless, in HO-2 deficient mice the exquisite intrinsic O(2) responsiveness of CB glomus cells remains unaltered. Therefore, HO-2 is not absolutely necessary for acute CB O(2) sensing. Although the nature of the CB acute O(2) sensor(s) is yet unknown, studies similar to those summarized here serve to test the existing hypothesis and help to distinguish between those that need to be explored further and those that definitively lack experimental support.
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Affiliation(s)
- Patricia Ortega-Sáenz
- Laboratorio de Investigaciones Biomédicas, Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Sevilla, Spain
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Shu HF, Wang BR, Bi H, Pei JM, Wang X, Fan J, Ju G. PC12 cells express IL-1 receptor type I and response to IL-1beta stimulation. Respir Physiol Neurobiol 2007; 157:187-95. [PMID: 17321804 DOI: 10.1016/j.resp.2007.01.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2006] [Revised: 12/26/2006] [Accepted: 01/15/2007] [Indexed: 11/29/2022]
Abstract
PC12 cell line has been widely used in a diverse array of neurophysiological studies including in exploration of oxygen-sensing mechanism. In present study, we first identified with immunocytochemistry and Western blot methods that interleukin-1 receptor type I was expressed in the PC12 cells. We then demonstrated with patch clamping technique that extracellular application of IL-1beta dose-dependently inhibited the outward voltage-dependent and TEA-sensitive potassium currents (I(K)) in the PC12 cells, and pre-incubation with the interleukin-1 receptor antagonist almost completely abolished this inhibitory effect. In addition, application of IL-1beta shifted steady-state inactivation of I(K) in hyperpolarizing direction, but did not alter its steady-state activation. Furthermore, IL-1beta-induced inhibition of I(K) led to a membrane depolarization and a transient increase of [Ca(2+)](i) in PC12 cells. Taking together, the present study elucidates that PC12 cells bear interleukin-1 receptor and response to IL-1beta stimulation.
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Affiliation(s)
- Hai-Feng Shu
- Institute of Neurosciences, The Fourth Military Medical University, Xi'an 710032, PR China
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Abstract
Hypoxia-inducible factors (HIFs) are ubiquitous transcription factors that mediate adaptation to hypoxia by inducing specific sets of target genes. It is well accepted that hypoxia induces accumulation and activity of HIFs by causing stabilization of their alpha subunits. We have demonstrated that hypoxia stimulates translation of HIF-1alpha and -2alpha proteins by distributing HIF-alpha mRNAs to larger polysome fractions. This requires influx of extracellular calcium, stimulation of classical protein kinase C-alpha (cPKC-alpha), and the activity of mammalian target of rapamycin, mTOR. The translational component contributes to approximately 40-50% of HIF-alpha proteins accumulation after 3 h of 1% O2. Hypoxia also inhibits general protein synthesis and mTOR activity; however, cPKC-alpha inhibitors or rapamycin reduce mTOR activity and total protein synthesis beyond the effects of hypoxia alone. These data show that during general inhibition of protein synthesis by hypoxia, cap-mediated translation of selected mRNAs is induced through the mTOR pathway. We propose that calcium-induced activation of cPKC-alpha hypoxia partially protects an activity of mTOR from hypoxic inhibition. These results provide an important physiologic insight into the mechanism by which hypoxia-stimulated influx of calcium selectively induces the translation of mRNAs necessary for adaptation to hypoxia under conditions repressing general protein synthesis.
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Affiliation(s)
- Anna S Hui
- Department of Genome Science, Genome Research Institute, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0505, USA
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Wang H, Yuan G, Prabhakar NR, Boswell M, Katz DM. Secretion of brain-derived neurotrophic factor from PC12 cells in response to oxidative stress requires autocrine dopamine signaling. J Neurochem 2005; 96:694-705. [PMID: 16390493 DOI: 10.1111/j.1471-4159.2005.03572.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Expression of brain-derived neurotrophic factor (BDNF) is sensitive to changes in oxygen availability, suggesting that BDNF may be involved in adaptive responses to oxidative stress. However, it is unknown whether or not oxidative stress actually increases availability of BDNF by stimulating BDNF secretion. To approach this issue we examined BDNF release from PC12 cells, a well-established model of neurosecretion, in response to hypoxic stimuli. BDNF secretion from neuronally differentiated PC12 cells was strongly stimulated by exposure to intermittent hypoxia (IH). This response was inhibited by N-acetyl-l-cysteine, a potent scavenger of reactive oxygen species (ROS) and mimicked by exogenous ROS. IH-induced BDNF release requires activation of tetrodotoxin sensitive Na+ channels and Ca2+ influx through N- and L-type channels, as well as mobilization of internal Ca2+ stores. These results demonstrate that oxidative stress can stimulate BDNF release and that underlying mechanisms are similar to those previously described for activity-dependent BDNF secretion from neurons. Surprisingly, we also found that IH-induced secretion of BDNF was blocked by dopamine D2 receptor antagonists or by inhibition of dopamine synthesis with alpha-methyl-p-tyrosine. These data indicate that oxidative stress can stimulate BDNF release through an autocrine or paracrine loop that requires dopamine receptor activation.
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Affiliation(s)
- Hong Wang
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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Affiliation(s)
- E Kenneth Weir
- Department of Medicine, Minneapolis Veterans Affairs Medical Center and University of Minnesota, Minneapolis 55417, USA.
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29
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Abstract
Oxygen is a major regulator of nuclear gene expression. However, although mitochondria consume almost all of the O2 available to the cells, little is known about how O2 tension influences the expression of the mitochondrial genome. We show in O2-sensitive excitable rat PC12 cells that, among the mtDNA-encoded genes, hypoxia produced a specific down-regulation of the transcripts encoding mitochondrial complex I NADH dehydrogenase (ND) subunits, particularly ND4 and ND5 mRNAs and a stable mRNA precursor containing the ND5 and cytochrome b genes. This unprecedented effect of hypoxia was fast (developed in <30 min) and fairly reversible and occurred at moderate levels of hypoxia (O2 tensions in the range of 20-70 mm Hg). Hypoxic down-regulation of the mitochondrial complex I genes was paralleled by the reduction of complex I activity and was retarded by iron chelation, suggesting that an iron-dependent post-transcriptional mechanism could regulate mitochondrial mRNA stability. It is known that cell respiration is under tight control by the amount of proteins in mitochondrial complexes of the electron transport chain. Therefore, regulation of the expression of the mitochondrial (mtDNA)-encoded complex I subunits could be part of an adaptive mechanism to adjust respiration rate to the availability of O2 and to induce fast adaptive changes in hypoxic cells.
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Affiliation(s)
- José I Piruat
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología, Seville, Spain
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30
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Abstract
1. Control of glucose uptake is distributed between three steps. These are the rate that glucose is delivered to cells, the rate of transport into cells, and the rate that glucose is phosphorylated within these same cells. The functional limitations to each one of these individual steps has been difficult to assess because they are so closely coupled to each other. Studies have been performed in recent years using complex isotopic techniques or transgenic mouse models to shed new light on the role that each step plays in overall control of muscle glucose uptake. 2. Membrane glucose transport is a major barrier and glucose delivery and glucose phosphorylation are minor barriers to muscle glucose uptake in the fasted, sedentary state. GLUT-4 is translocated to the muscle membrane during exercise and insulin-stimulation. The result of this is that it can become so permeable to glucose that it is only a minor barrier to glucose uptake. 3. In addition to increasing glucose transport, exercise and insulin-stimulation also increase muscle blood flow and capillary recruitment. This effectively increases muscle glucose delivery and by doing so, works to enhance muscle glucose uptake. 4. There is a growing body of data that suggests that insulin resistance to muscle glucose uptake can be because of impairments in any one or more of the three steps that comprise the process.
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Affiliation(s)
- David H Wasserman
- Department of Molecular Physiological and Biophysics, Mouse Metabolic Phenotyping Center, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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31
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Zakrzewska A, Schnell PO, Striet JB, Hui A, Robbins JR, Petrovic M, Conforti L, Gozal D, Wathelet MG, Czyzyk-Krzeska MF. Hypoxia-activated metabolic pathway stimulates phosphorylation of p300 and CBP in oxygen-sensitive cells. J Neurochem 2005; 94:1288-96. [PMID: 16000154 PMCID: PMC1411962 DOI: 10.1111/j.1471-4159.2005.03293.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transcription co-activators and histone acetyltransferases, p300 and cyclic AMP responsive element-binding protein-binding protein (CBP), participate in hypoxic activation of hypoxia-inducible genes. Here, we show that exposure of PC12 and cells to 1-10% oxygen results in hyperphosphorylation of p300/CBP. This response is fast, long lasting and specific for hypoxia, but not for hypoxia-mimicking agents such as desferioxamine or Co2+ ions. It is also cell-type specific and occurs in pheochromocytoma PC12 cells and the carotid body of rats but not in hepatoblastoma cells. The p300 hyperphosphorylation specifically depends on the release of intracellular calcium from inositol 1,4,5-triphosphate (IP3)-sensitive stores. However, it is not inhibited by pharmacological inhibitors of any of the kinases traditionally known to be directly or indirectly calcium regulated. On the other hand, p300 hyperphosphorylation is inhibited by several different inhibitors of the glucose metabolic pathway from generation of NADH by glyceraldehyde 3-phosphate dehydrogenase, through the transfer of NADH through the glycerol phosphate shuttle to ubiquinone and complex III of the mitochondrial respiratory chain. Inhibition of IP3-sensitive calcium stores decreases generation of ATP, and this inhibition is significantly stronger in hypoxia than in normoxia. We propose that the NADH glycerol phosphate shuttle participates in generating a pool of ATP that serves either as a co-factor or a modulator of the kinases involved in the phosphorylation of p300/CBP during hypoxia.
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Affiliation(s)
| | | | - Justin B. Striet
- Departments of Genome Science
- Molecular and Cellular Physiology and
| | - Anna Hui
- Departments of Genome Science
- Molecular and Cellular Physiology and
| | - Jennifer R. Robbins
- Medicine, Division of Nephrology and Hypertension, University of Cincinnati, Ohio, USA
| | - Milan Petrovic
- Medicine, Division of Nephrology and Hypertension, University of Cincinnati, Ohio, USA
| | - Laura Conforti
- Molecular and Cellular Physiology and
- Medicine, Division of Nephrology and Hypertension, University of Cincinnati, Ohio, USA
| | - David Gozal
- Departments of Pediatrics, Pharmacology, and Toxicology, Kosair Children’s Hospital Research Institute, University of Louisville, Kentucky, USA
| | | | - Maria F. Czyzyk-Krzeska
- Departments of Genome Science
- Molecular and Cellular Physiology and
- Address correspondence and reprint requests to Maria F. Czyzyk-Krzeska, Department of Genome Science, University of Cincinnati, College of Medicine, 2180 E Galbraith Road., Cincinnati, OH 45267–0505, USA. E-mail:
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32
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Hool LC. Acute hypoxia differentially regulates K+ channels. Implications with respect to cardiac arrhythmia. Eur Biophys J 2005; 34:369-76. [PMID: 15726346 DOI: 10.1007/s00249-005-0462-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Revised: 01/03/2005] [Accepted: 01/14/2005] [Indexed: 11/26/2022]
Abstract
The first ion channels demonstrated to be sensitive to changes in oxygen tension were K(+) channels in glomus cells of the carotid body. Since then a number of hypoxia-sensitive ion channels have been identified. However, not all K(+) channels respond to hypoxia alike. This has raised some debate about how cells detect changes in oxygen tension. Because ion channels respond rapidly to hypoxia it has been proposed that the channel is itself an oxygen sensor. However, channel function can also be modified by thiol reducing and oxidizing agents, implicating reactive oxygen species as signals in hypoxic events. Cardiac ion channels can also be modified by hypoxia and redox agents. The rapid and slow components of the delayed rectifier K(+) channel are differentially regulated by hypoxia and beta-adrenergic receptor stimulation. Mutations in the genes that encode the subunits for the channel are associated with Long QT syndrome and sudden cardiac death. The implications with respect to effects of hypoxia on the channel and triggering of cardiac arrhythmia will be discussed.
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Affiliation(s)
- Livia C Hool
- School of Biomedical and Chemical Sciences Australia and The Western Australian Institute of Medical Research, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
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33
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Robbins JR, Lee SM, Filipovich AH, Szigligeti P, Neumeier L, Petrovic M, Conforti L. Hypoxia modulates early events in T cell receptor-mediated activation in human T lymphocytes via Kv1.3 channels. J Physiol 2005; 564:131-43. [PMID: 15677684 PMCID: PMC1456048 DOI: 10.1113/jphysiol.2004.081893] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
T lymphocytes are exposed to hypoxia during their development and when they migrate to hypoxic pathological sites. Although it has been shown that hypoxia inhibits Kv1.3 channels and proliferation in human T cells, the mechanisms by which hypoxia regulates T cell activation are not fully understood. Herein we test the hypothesis that hypoxic inhibition of Kv1.3 channels induces membrane depolarization, thus modulating the increase in cytoplasmic Ca2+ that occurs during activation. Hypoxia causes membrane depolarization in human CD3+ T cells, as measured by fluorescence-activated cell sorting (FACS) with the voltage-sensitive dye DiBAC4(3). Similar depolarization is produced by the selective Kv1.3 channel blockers ShK-Dap22 and margatoxin. Furthermore, pre-exposure to such blockers prevents any further depolarization by hypoxia. Since membrane depolarization is unfavourable to the influx of Ca2+ through the CRAC channels (necessary to drive many events in T cell activation such as cytokine production and proliferation), the effect of hypoxia on T cell receptor-mediated increase in cytoplasmic Ca2+ was determined using fura-2. Hypoxia depresses the increase in Ca2+ induced by anti-CD3/CD28 antibodies in approximately 50% of lymphocytes. In the remaining cells, hypoxia either did not elicit any change or produced a small increase in cytoplasmic Ca2+. Similar effects were observed in resting and pre-activated CD3+ cells and were mimicked by ShK-Dap22. These effects appear to be mediated solely by Kv1.3 channels, as we find no influence of hypoxia on IKCa1 and CRAC channels. Our findings indicate that hypoxia modulates Ca2+ homeostasis in T cells via Kv1.3 channel inhibition and membrane depolarization.
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Affiliation(s)
- Jennifer R Robbins
- Department of Internal Medicine, University of CincinnatiCincinnati, OH 45267, USA
- Department of Biology, Xavier UniversityCincinnati, OH 45207, USA
| | - Susan Molleran Lee
- Division of Hematology/Oncology, Cincinnati Children's Hospital Medical CenterCincinnati, OH 45267, USA
| | - Alexandra H Filipovich
- Division of Hematology/Oncology, Cincinnati Children's Hospital Medical CenterCincinnati, OH 45267, USA
| | - Peter Szigligeti
- Department of Internal Medicine, University of CincinnatiCincinnati, OH 45267, USA
| | - Lisa Neumeier
- Department of Internal Medicine, University of CincinnatiCincinnati, OH 45267, USA
| | - Milan Petrovic
- Department of Internal Medicine, University of CincinnatiCincinnati, OH 45267, USA
| | - Laura Conforti
- Department of Internal Medicine, University of CincinnatiCincinnati, OH 45267, USA
- Department of Molecular and Cellular Physiology, University of CincinnatiCincinnati, OH 45267, USA
- Corresponding author L. Conforti: Department of Internal Medicine, 231 Albert Sabin Way, University of Cincinnati, Cincinnati, OH 45267-0585, USA.
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34
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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35
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Abstract
O(2) sensing is of critical importance for cell survival and adaptation of living organisms to changing environments or physiological conditions. O(2)-sensitive ion channels are major effectors of the cellular responses to hypoxia. These channels are preferentially found in excitable neurosecretory cells (glomus cells of the carotid body, cells in the neuroepithelial bodies of the lung, and neonatal adrenal chromaffin cells), which mediate fast cardiorespiratory adjustments to hypoxia. O(2)-sensitive channels are also expressed in the pulmonary and systemic arterial smooth muscle cells where they participate in the vasomotor responses to low O(2) tension (particularly in hypoxic pulmonary vasoconstriction). The mechanisms underlying O(2) sensing and how the O(2) sensors interact with the ion channels remain unknown. Recent advances in the field give different support to the various current hypotheses. Besides the participation of ion channels in acute O(2) sensing, they also contribute to the gene program developed under chronic hypoxia. Gene expression of T-type calcium channels is upregulated by hypoxia through the same hypoxia-inducible factor-dependent signaling pathway utilized by the classical O(2)-regulated genes. Alteration of acute or chronic O(2) sensing by ion channels could participate in the pathophysiology of human diseases, such as sudden infant death syndrome or primary pulmonary hypertension.
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Affiliation(s)
- José López-Barneo
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología, Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Seville, Spain.
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36
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Abstract
The responses of afferent chemosensory fibres of the carotid body to individual chemostimuli have long been established. However, the mechanisms underlying the multiplicative interactions of these stimuli (i.e. how the combined effects of hypoxia and hypercapnia exert a greater effect on afferent nerve discharge than the sum of their individual effects) have not been elucidated. Using the membrane hypothesis for carotid body chemoreception, in which chemostimuli inhibit type I cell K+ channels, leading to depolarization, voltage-gated Ca2+ entry and hence the triggering of exocytosis, this article considers data acquired in isolated type I carotid body cells and model chemoreceptor (PC12) cells to attempt to explain stimulus interactions. Whilst stimulus interactions are not clearly evident at the level of K+ channel inhibition or rises of [Ca2+]i, they are apparent at the level of transmitter release. Thus, it is clear that individual chemoreceptor cells can sense multiple stimuli, and that interactions of these stimuli can produce greater than additive effects in terms of transmitter release.
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Affiliation(s)
- Chris Peers
- Institute for Cardiovascular Research, University of Leeds, Leeds LS2 9JT, UK.
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37
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Thébaud B, Michelakis ED, Wu XC, Moudgil R, Kuzyk M, Dyck JRB, Harry G, Hashimoto K, Haromy A, Rebeyka I, Archer SL. Oxygen-sensitive Kv channel gene transfer confers oxygen responsiveness to preterm rabbit and remodeled human ductus arteriosus: implications for infants with patent ductus arteriosus. Circulation 2004; 110:1372-9. [PMID: 15353504 DOI: 10.1161/01.cir.0000141292.28616.65] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Oxygen (O2)-sensitive K+ channels mediate acute O2 sensing in many tissues. At birth, initial functional closure of the ductus arteriosus (DA) results from O2-induced vasoconstriction. This mechanism often fails in premature infants, resulting in persistent DA, a common form of congenital heart disease. We hypothesized that the basis for impaired O2 constriction in preterm DA is reduced expression and function of O2-sensitive, voltage-gated (Kv) channels. METHODS AND RESULTS Preterm rabbit DA rings have reduced O2 constriction (even after inhibition of prostaglandin and nitric oxide synthases), and preterm DA smooth muscle cells (DASMCs) display reduced O2-sensitive K+ current. This is associated with decreased mRNA and protein expression of certain O2-sensitive Kv channels (Kv1.5 and Kv2.1) but equivalent expression of the L-type calcium channel. Transmural Kv1.5 or Kv2.1 gene transfer "rescues" the developmental deficiency, conferring O2 responsiveness to preterm rabbit DAs. Targeted SMC Kv1.5 gene transfer also enhances O2 constriction in human DAs. CONCLUSIONS These data demonstrate a central role for developmentally regulated DASMC O2-sensitive Kv channels in the functional closure of the DA. Modulation of Kv channels may have therapeutic potential in diseases associated with impaired O2 responsiveness, including persistent DA.
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Affiliation(s)
- Bernard Thébaud
- Vascular Biology Group, University of Alberta, Edmonton, Alberta, Canada
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38
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Abstract
Several potentially life-threatening cardiovascular and respiratory disorders result in prolonged deprivation of oxygen, which in turn results in significant cellular adaptation, or remodelling. An important component of this functional adaptation arises as a direct consequence of altered ion channel expression by chronic hypoxia. In this review, we discuss current understanding of this hypoxic remodelling process, with particular reference to regulation of L-type Ca2+ channels and high-conductance, Ca2+-sensitive K+ (BK) channels. In systems where this remodelling occurs, changes in functional expression of these particular channels evokes marked alteration in, or responses to, Ca2+-dependent events. Evidence to date indicates that channel expression can be modulated at the transcriptional level but, additionally, that crucial post-transcriptional events are also regulated by chronic hypoxia. Importantly, such remodelling is, in some cases, strongly associated with production of amyloid peptides of Alzheimer's disease, implicating chronic hypoxia as a causative factor in the progression of specific pathology. Moreover, subtle changes in functional expression of BK channels implicates chronic hypoxia as an important regulator of cell excitability.
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Affiliation(s)
- Chris Peers
- School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
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39
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Seta KA, Yuan Y, Spicer Z, Lu G, Bedard J, Ferguson TK, Pathrose P, Cole-Strauss A, Kaufhold A, Millhorn DE. The role of calcium in hypoxia-induced signal transduction and gene expression. Cell Calcium 2004; 36:331-40. [PMID: 15261489 DOI: 10.1016/j.ceca.2004.02.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2004] [Accepted: 02/18/2004] [Indexed: 01/25/2023]
Abstract
Mammalian cells require a constant supply of oxygen in order to maintain adequate energy production, which is essential for maintaining normal function and for ensuring cell survival. Sustained hypoxia can result in cell death. Sophisticated mechanisms have therefore evolved which allow cells to respond and adapt to hypoxia. Specialized oxygen-sensing cells have the ability to detect changes in oxygen tension and transduce this signal into organ system functions that enhance the delivery of oxygen to tissue in a wide variety of different organisms. An increase in intracellular calcium levels is a primary response of many cell types to hypoxia/ischemia. The response to hypoxia is complex and involves the regulation of multiple signaling pathways and coordinated expression of perhaps hundreds of genes. This review discusses the role of calcium in hypoxia-induced regulation of signal transduction pathways and gene expression. An understanding of the molecular events initiated by changes in intracellular calcium will lead to the development of therapeutic approaches toward the treatment of hypoxic/ischemic diseases and tumors.
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Affiliation(s)
- Karen A Seta
- Department of Genome Science, Genome Research Institute, University of Cincinnati, 2180 E. Galbraith Rd., Cincinnati, OH 45237, USA
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40
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Gao L, Mejías R, Echevarría M, López-Barneo J. Induction of the glucose-6-phosphate dehydrogenase gene expression by chronic hypoxia in PC12 cells. FEBS Lett 2004; 569:256-60. [PMID: 15225644 DOI: 10.1016/j.febslet.2004.06.004] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Accepted: 06/03/2004] [Indexed: 12/01/2022]
Abstract
We studied the regulation of glucose-6-phosphate dehydrogenase (G6PD) gene expression by chronic hypoxia. G6PD mRNA level and activity were increased in PC12 cells by hypoxia in a dose- and time-dependent manner. Cobalt chloride and dimethyloxalylglycine, which can mimic hypoxia, also activated G6PD gene expression. Interestingly, hypoxia-induced G6PD expression followed a time course much slower than that of phosphoglycerate kinase 1 (PGK1), a hypoxia-inducible factor (HIF)-dependent glycolytic enzyme. Hypoxic-G6PD induction was almost negligible in non-excitable Buffalo rat liver cells, although in these cells PGK1 was strongly upregulated by low PO(2). Furthermore, G6PD but not PGK1 induction was blocked by the antioxidants glutathione and N-acetylcysteine. These results suggest the dependence of G6PD gene expression on HIF and intracellular redox status and the differential hypoxic regulation of glucose-metabolizing enzymes.
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Affiliation(s)
- Lin Gao
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología and Hospital Universitario Virgen del Rocío, Universidad de Sevilla, E-41013 Seville, Spain
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41
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Abstract
This mini-review summarizes the present knowledge regarding central oxygen-chemosensitive sites with special emphasis on their function in regulating changes in cardiovascular and respiratory responses. These oxygen-chemosensitive sites are distributed throughout the brain stem from the thalamus to the medulla and may form an oxygen-chemosensitive network. The ultimate effect on respiratory or sympathetic activity presumably depends on the specific neural projections from each of these brain stem oxygen-sensitive regions as well as on the developmental age of the animal. Little is known regarding the cellular mechanisms involved in the chemotransduction process of the central oxygen sensors. The limited information available suggests some conservation of mechanisms used by other oxygen-sensing systems, e.g., carotid body glomus cells and pulmonary vascular smooth muscle cells. However, major gaps exist in our understanding of the specific ion channels and oxygen sensors required for transducing central hypoxia by these central oxygen-sensitive neurons. Adaptation of these central oxygen-sensitive neurons during chronic or intermittent hypoxia likely contributes to responses in both physiological conditions (ascent to high altitude, hypoxic conditioning) and clinical conditions (heart failure, chronic obstructive pulmonary disease, obstructive sleep apnea syndrome, hypoventilation syndromes). This review underscores the lack of knowledge about central oxygen chemosensors and highlights real opportunities for future research.
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Affiliation(s)
- Judith A Neubauer
- Division of Pulmonary and Critical Care Medicine, Deparment of Medicine, Uversity of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08903-0019, USA.
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42
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Affiliation(s)
- Paul J Kemp
- School of Biomedical Sciences, University of Leeds, United Kingdom
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43
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Abstract
Mammalian cells require a constant supply of oxygen to maintain energy balance, and sustained hypoxia can result in cell death. It is therefore not surprising that sophisticated adaptive mechanisms have evolved that enhance cell survival during hypoxia. During the past few years, there have been a growing number of reports on hypoxia-induced transcription of specific genes. In this review, we describe a unique experimental approach that utilizes focused cDNA libraries coupled to microarray analyses to identify hypoxia-responsive signal transduction pathways and genes that confer the hypoxia-tolerant phenotype. We have used the subtractive suppression hybridization (SSH) method to create a cDNA library enriched in hypoxia-regulated genes in oxygen-sensing pheochromocytoma cells and have used this library to create microarrays that allow us to examine hundreds of genes at a time. This library contains over 300 genes and expressed sequence tags upregulated by hypoxia, including tyrosine hydroxylase, vascular endothelial growth factor, and junB. Hypoxic regulation of these and other genes in the library has been confirmed by microarray, Northern blot, and real-time PCR analyses. Coupling focused SSH libraries with microarray analyses allows one to specifically study genes relevant to a phenotype of interest while reducing much of the biological noise associated with these types of studies. When used in conjunction with high-throughput, dye-based assays for cell survival and apoptosis, this approach offers a rapid method for discovering validated therapeutic targets for the treatment of cardiovascular disease, stroke, and tumors.
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Affiliation(s)
- Karen A Seta
- Department of Genome Science, Genome Research Institute, University of Cincinnati, Cincinnati, Ohio 45237, USA
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44
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Abstract
Hypoxic inhibition of TASK-1, a tandem pore domain background K+ channel, provides a critical link between reduced O2 levels and physiological responses in various cell types. Here, we examined the expression and O2 sensitivity of TASK-1 in immortalized adrenomedullary chromaffin (MAH) cells. In physiological (asymmetrical) K+ solutions, 3 μM anandamide or 300 μM Zn2+ inhibited a strongly pH-sensitive current. Under symmetrical K+ conditions, the anandamide- and Zn2+-sensitive K+ currents were voltage independent. These data demonstrate the functional expression of TASK-1, and cellular expression of this channel was confirmed by RT-PCR and Western blotting. At concentrations that selectively inhibit TASK-1, anandamide and Zn2+ were without effect on the magnitude of the O2-sensitive current or the hypoxic depolarization. Thus TASK-1 does not contribute to O2 sensing in MAH cells, demonstrating the failure of a known O2-sensitive K+ channel to respond to hypoxia in an O2-sensing cell. These data demonstrate that, ultimately, the sensitivity of a particular K+ channel to hypoxia is determined by the cell, and we propose that this is achieved by coupling distinct hypoxia signaling systems to individual channels. Importantly, these data also reiterate the indirect O2 sensitivity of TASK-1, which appears to require the presence of an intracellular mediator.
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Affiliation(s)
- Rosalyn P Johnson
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, Canada L8S 4K1
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45
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Abstract
Since O(2) is the bare necessity for multicellular organisms, they develop multiple protective mechanisms against hypoxia. Mammals will adapt to hypoxia in short and long terms. The short-term responses include enhancement of the respiratory and cardiac functions, adrenaline secretion from adrenal medullary cells, and pulmonary vasoconstriction, whereas the long-term response is the increase in erythropoietin production with the consequent increase in red blood cells. Although much work has been done to elucidate molecular mechanisms for O(2)-sensing for the last ten years, the majority of the mechanisms remain unclear. We will review mechanisms proposed for hypoxia detection in carotid body type I cells, pulmonary artery smooth muscle, adrenal medullary cells, and liver cells, with the special focus on adrenal medullary cells.
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Affiliation(s)
- Naoji Fujishiro
- Department of Cell and System Physiology, University of Occupational and Environmental Health School of Medicine, Kitakyushu, 807-8555 Japan
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46
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Hui AS, Striet JB, Gudelsky G, Soukhova GK, Gozal E, Beitner-Johnson D, Guo SZ, Sachleben LR, Haycock JW, Gozal D, Czyzyk-Krzeska MF. Regulation of catecholamines by sustained and intermittent hypoxia in neuroendocrine cells and sympathetic neurons. Hypertension 2003; 42:1130-6. [PMID: 14597643 DOI: 10.1161/01.hyp.0000101691.12358.26] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chronic intermittent hypoxia, a characteristic feature of sleep-disordered breathing, induces hypertension through augmented sympathetic nerve activity and requires the presence of functional carotid body arterial chemoreceptors. In contrast, chronic sustained hypoxia does not alter blood pressure. We therefore analyzed the biosynthetic pathways of catecholamines in peripheral nervous system structures involved in the pathogenesis of intermittent hypoxia-induced hypertension, namely, carotid bodies, superior cervical ganglia, and adrenal glands. Rats were exposed to either intermittent hypoxia (90 seconds of room air alternating with 90 seconds of 10% O2) or to sustained hypoxia (10% O2) for 1 to 30 days. Dopamine, norepinephrine, epinephrine, dihydroxyphenylacetic acid, and 5-hydroxytyptamine contents were measured by high-performance liquid chromatography. Expression of tyrosine hydroxylase and its phosphorylated forms, dopamine beta-hydroxylase, phenylethanolamine N-methyltransferase, and GTP cyclohydrolase-1 were determined by Western blot analyses. Both sustained and intermittent hypoxia significantly increased dopamine and norepinephrine content in carotid bodies but not in sympathetic ganglia or adrenal glands. In carotid bodies, both types of hypoxia augmented total levels of tyrosine hydroxylase protein and its phosphorylation on serines 19, 31, 40, as well as levels of GTP cyclohydrolase-1. However, the effects of intermittent hypoxia on catecholaminergic pathways were significantly smaller and delayed than those induced by sustained hypoxia. Thus, attenuated induction of catecholaminergic phenotype by intermittent hypoxia in carotid body may play a role in development of hypertension associated with sleep-disordered breathing. The effects of both types of hypoxia on expression of catecholaminergic enzymes in superior cervical neurons and adrenal glands were transient and small.
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Affiliation(s)
- Anna S Hui
- Department of Genome Science, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0505, USA
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Kumar GK, Kim DK, Lee MS, Ramachandran R, Prabhakar NR. Activation of tyrosine hydroxylase by intermittent hypoxia: involvement of serine phosphorylation. J Appl Physiol (1985) 2003; 95:536-44. [PMID: 12692140 DOI: 10.1152/japplphysiol.00186.2003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulation of tyrosine hydroxylase (TH) by intermittent hypoxia (IH) was investigated in rat pheochromocytoma 12 (PC-12) cells by exposing them to alternating cycles of hypoxia (1% O2, 15 s) and normoxia (21% O2, 3 min) for up to 60 cycles; controls were exposed to normoxia for a similar duration. IH exposure increased dopamine content and TH activity by approximately 42 and approximately 56%, respectively. Immunoblot analysis revealed that comparable levels of TH protein were expressed in normoxic and IH cells. Removal of TH-bound catecholamines and in vitro phosphorylation of TH in cell-free extracts by the catalytic subunit of protein kinase A (PKA) increased TH activity in normoxic but not in IH cells, suggesting possible induction of TH phosphorylation and removal of endogenous inhibition of TH by IH. To assess the role of serine phosphorylation in IH-induced TH activation, TH immunoprecipitates and extracts derived from normoxic and IH cells were probed with anti-phosphoserine and anti-phospho-TH (Ser-40) antibody, respectively. Compared with normoxic cells, total serine and Ser-40-specific phosphorylation of TH were increased in IH cells. IH-induced activation of TH and the increase in total serine and Ser-40-specific phosphorylation of TH were inhibited by Ca2+/calmodulin-dependent protein kinase (CaMK) and PKA-specific inhibitors but not by inhibitors of the extracellular signal-regulated protein kinase pathway, suggesting that IH activates TH in PC-12 cells via phosphorylation of serine residues including Ser-40, in part, by CaMK and PKA. Our results also suggest that IH-induced phosphorylation of TH facilitates the removal of endogenous inhibition of TH, leading to increased synthesis of dopamine.
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Affiliation(s)
- Ganesh K Kumar
- Department of Biochemistry,Western Reserve University, Cleveland, OH 44106-4935, USA.
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Abstract
Cellular responses to hypoxia can be acute or chronic. Acute responses mainly depend on oxygen-sensitive ion channels, whereas chronic responses rely on the hypoxia-inducible transcription factors (HIFs), which up-regulate the expression of enzymes, transporters, and growth factors. It is unknown whether the expression of genes coding for ion channels is also influenced by hypoxia. We report here that the alpha1H gene of T-type voltage-gated calcium channels is highly induced by lowering oxygen tension in PC12 cells. Accumulation of alpha1H mRNA in response to hypoxia is time- and dose-dependent and paralleled by an increase in the density of T-type calcium channel current recorded in patch clamped cells. HIF appears to be involved in the response to hypoxia, since cobalt chloride, desferrioxamine, and dimethyloxalylglycine, compounds that mimic HIF-regulated gene expression, replicate the hypoxic effect. Moreover, functional inhibition of HIF-2alpha protein accumulation using antisense HIF-2alpha oligonucleotides reverses the effect of hypoxia on T-type Ca2+ channel expression. Importantly, regulation by oxygen tension is specific for T-type calcium channels, since it is not observed with the L-, N-, and P/Q-channel types. These findings show for the first time that hypoxia induces an ion channel gene via a HIF-dependent mechanism and define a new role for the T-type calcium channels as regulators of cellular excitability and calcium influx under chronic hypoxia.
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Affiliation(s)
- Raquel Del Toro
- Laboratorio de Investigaciones Biomédicas, Departamento de Fisiología and Hospital Universitario Virgen del Rocío, Universidad de Sevilla, E-41013 Seville, Spain
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Hyakukoku M, Higashiura K, Ura N, Murakami H, Yamaguchi K, Wang L, Furuhashi M, Togashi N, Shimamoto K. Tissue-specific impairment of insulin signaling in vasculature and skeletal muscle of fructose-fed rats. Hypertens Res 2003; 26:169-76. [PMID: 12627878 DOI: 10.1291/hypres.26.169] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The relation between insulin resistance/hyperinsulinemia and cardiovascular diseases has attracted much attention. Insulin affects not only glucose metabolism, but also protein synthesis and cell growth. Insulin stimulates both the phosphatidylinositol 3-kinase (PI3-K) and mitogen-activated protein kinase (MAPK) pathways, but the relationship between cardiovascular disease and selective insulin signal pathways is unclear. We investigated the tissue specificity and intracellular signal transduction selectivity of insulin resistance in the vasculature and skeletal muscle of fructose-fed rats (FFR). Sprague-Dawley rats were fed either normal rat chow (control rats) or fructose-rich chow. Normal saline with or without 1,000 (microg/kg) insulin was injected, and then the thoracic aorta or soleus muscle was removed under anesthetization. Insulin-induced tyrosine phosphorylation of insulin receptor beta subunit (IRbeta) and insulin receptor substrate-1 (IRS-1) and tyrosine/threonine phosphorylation of p44/42 MAPK (ERK-1/2) were evaluated. There were no significant differences in the degree of phosphorylation of IRbeta or ERK-1/2 in the thoracic aorta or in the soleus muscle between FFR and controls. However, tyrosine phosphorylation of IRS-1 in the soleus muscle of FFR was significantly reduced to 80% (p<0.001) of that in controls. The results suggest that PI3-K pathway in skeletal muscle is selectively impaired in FFR, and this impairment may induce hyperinsulinemia, which in turn may stimulate the MAPK pathway and lead to atherosclerosis. Thus PI3-K pathway may be one of the factors underlying the onset of cardiovascular disease in patients with insulin resistance.
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Affiliation(s)
- Masaya Hyakukoku
- Second Department of Internal Medicine, Sapporo Medical University School of Medicine, Sapporo, Japan.
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Rao SP, McRae C, Lapanowski K, Churchill M, Kurtz TW, Dunbar JC. Insulin mediated hemodynamic responses in spontaneous hypertensive rats (SHRs): effect of chromosome 4 gene transfer. Clin Exp Hypertens 2003; 25:131-42. [PMID: 12611424 DOI: 10.1081/ceh-120017933] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The spontaneous hypertensive rat (SHR) is a widely studied model of essential hypertension and has been reported to exhibit alterations in carbohydrate and lipid metabolism. Genetic linkage studies implicated that SHR carries deletion variant of Cd36 gene of chromosome 4, the gene that encodes fatty acid transporter. Thus it could be possible that primary genetic defect in SHR is compromised tissue utilization of fatty acid that would form the basis for the pathogenesis of hyperinsulinemia, insulin resistance and insulin-mediated responses. We measured both the hemodynamic and metabolic responses to insulin in SHR in comparison with the chromosome congenic spontaneous hypertensive rats (cSHRs) (rats in which piece of chromosome 4 containing wild type Cd36 was integrated into the SHR genome). A bolus infusion of insulin increased iliac conductance and decreased blood pressure in Wistar Kyoto (WKY) rats. However, in SHR insulin did not reduce blood pressure as in WKY but after about 15 min it significantly enhanced blood pressure and reduced iliac conductance. Whereas in cSHR insulin did not reduce blood pressure as in WKY rats. However, pressor responses to insulin were eliminated by chromosome 4 gene transfer. Glucose clearance was significantly slower in both SHR and cSHR. Glucose tolerance test revealed that SHR are hyperinsulinemic and insulin resistant. These findings indicate that transfer of segment of chromosome 4 from Brown Norway rats onto spontaneous hypertensive background eliminates hyperinsulinemia and pressor effects of insulin.
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Affiliation(s)
- Sumangala P Rao
- Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201-1928, USA
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