1
|
Hsia CCW. Tissue Perfusion and Diffusion and Cellular Respiration: Transport and Utilization of Oxygen. Semin Respir Crit Care Med 2023; 44:594-611. [PMID: 37541315 DOI: 10.1055/s-0043-1770061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
This article provides an overview of the journey of inspired oxygen after its uptake across the alveolar-capillary interface, and the interplay among tissue perfusion, diffusion, and cellular respiration in the transport and utilization of oxygen. The critical interactions between oxygen and its facilitative carriers (hemoglobin in red blood cells and myoglobin in muscle cells), and with other respiratory and vasoactive molecules (carbon dioxide, nitric oxide, and carbon monoxide), are emphasized to illustrate how this versatile system dynamically optimizes regional convective transport and diffusive gas exchange. The rates of reciprocal gas exchange in the lung and the periphery must be well-matched and sufficient for meeting the range of energy demands from rest to maximal stress but not excessive as to become toxic. The mobile red blood cells play a vital role in matching tissue perfusion and gas exchange by dynamically regulating the controlled uptake of oxygen and communicating regional metabolic signals across different organs. Intracellular oxygen diffusion and facilitation via myoglobin into the mitochondria, and utilization via electron transport chain and oxidative phosphorylation, are summarized. Physiological and pathophysiological adaptations are briefly described. Dysfunction of any component across this integrated system affects all other components and elicits corresponding structural and functional adaptation aimed at matching the capacities across the entire system and restoring equilibrium under normal and pathological conditions.
Collapse
Affiliation(s)
- Connie C W Hsia
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
| |
Collapse
|
2
|
Andreyeva AY, Kladchenko ES, Sudnitsyna JS, Krivchenko AI, Mindukshev IV, Gambaryan S. Protein kinase A activity and NO are involved in the regulation of crucian carp (Carassius carassius) red blood cell osmotic fragility. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1105-1117. [PMID: 34052972 DOI: 10.1007/s10695-021-00971-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 05/18/2021] [Indexed: 06/12/2023]
Abstract
Activation of the cAMP pathway by β-adrenergic stimulation and cGMP pathway by activation of guanylate cyclase substantially affects red blood cell (RBC) membrane properties in mammals. However, whether similar mechanisms are involved in RBC regulation of lower vertebrates, especially teleosts, is not elucidated yet. In this study, we evaluated the effects of adenylate cyclase activation by epinephrine and forskolin, guanylate cyclase activation by sodium nitroprusside, and the role of Na+/H+-exchanger in the changes of osmotic fragility and regulatory volume decrease (RVD) response in crucian carp RBCs. Western blot analysis of protein kinase A and protein kinase G substrate phosphorylation revealed that changes in osmotic fragility were regulated via the protein kinase A, but not protein kinase G signaling pathway. At the same time, the RVD response in crucian carp RBCs was not affected either by activation of adenylate or guanylate cyclase. Adenylate cyclase/protein kinase A activation significantly decreased RBC osmotic fragility, i.e., increased cell rigidity. Inhibition of Na+/H+-exchanger by amiloride had no effect on the epinephrine-mediated decrease of RBC osmotic fragility. NO donor SNP did not activate guanylate cyclase, however affected RBCs osmotic fragility by protein kinase G-independent mechanisms. Taken together, our data demonstrated that the cAMP/PKA signaling pathway and NO are involved in the regulation of crucian carp RBC osmotic fragility, but not in RVD response. The authors confirm that the study has no clinical trial.
Collapse
Affiliation(s)
- Aleksandra Yu Andreyeva
- Department of Animal Physiology and Biochemistry, Moscow Representative Office A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Leninsky ave 38, Moscow, Russia, 119991.
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Toreza, 44, St-Petersburg, Russia, 194223.
| | - Ekaterina S Kladchenko
- Department of Animal Physiology and Biochemistry, Moscow Representative Office A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Leninsky ave 38, Moscow, Russia, 119991
| | - Julia S Sudnitsyna
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Toreza, 44, St-Petersburg, Russia, 194223
- Center for Theoretical Problems of Physicochemical Pharmacology, RAS, Srednyaya Kalitnikovskaya Str., 30, Moscow, Russia, 109029
| | - Aleksander I Krivchenko
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Toreza, 44, St-Petersburg, Russia, 194223
| | - Igor V Mindukshev
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Toreza, 44, St-Petersburg, Russia, 194223
| | - Stepan Gambaryan
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, pr. Toreza, 44, St-Petersburg, Russia, 194223
| |
Collapse
|
3
|
Zhu M, Gao Z, Fu Y, Qiu Y, Huang K, Zhu C, Wu Y, Zhu T, Wang Q, Yang L, Yin Y, Li P. Amorphous Selenium Nanoparticles Improve Vascular Function in Rats With Chronic Isocarbophos Poisoning via Inhibiting the Apoptosis of Vascular Endothelial Cells. Front Bioeng Biotechnol 2021; 9:673327. [PMID: 34249881 PMCID: PMC8266299 DOI: 10.3389/fbioe.2021.673327] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Accepted: 05/27/2021] [Indexed: 11/13/2022] Open
Abstract
Aim This study aimed to investigate the preventive effect and possible mechanism of amorphous selenium nanoparticles (A-SeQDs) on isocarbophos induced vascular dysfunction. Methods A-SeQDs was made by auto redox decomposition of selenosulfate precursor. Male rats were given isocarbophos (0.5 mg/kg/2 days) by intragastric administration for 16 weeks to induce vascular dysfunction. During the course, A-SeQDs (50 mg/kg/day) was added to the water from week 5. Then, the rats were killed to observe and test the influence of A-SeQDs on the vascular dysfunction induced by isocarbophos. Finally, human umbilical vein endothelial cells (HUVECs) were treated with 10% DMEM of isocarbophos (100 μM) for 5 days to detect the related indexes. Before the use of isocarbophos treatment, different drugs were given. Results A-SeQDs could reduce total carbon dioxide, MDA, VCAM-1, ICAM-1, IL-1, and IL-6 while increasing oxygen saturation, NO content, and SOD activity in rats. A-SeQDs also resulted in relatively normal vascular morphology, and the expression of sodium hydrogen exchanger 1 (NHE1) and caspase-3 decreased in rats. Furthermore, in HUVECs treated with isocarbophos, A-SeQDs maintained mitochondrial membrane potential, inhibited the cleaved caspase-3 expression, and released cytochrome c from mitochondria to cytosol. Conclusion A-SeQDs can inhibit the apoptosis of HUVECs through the mitochondrial pathway, and effectively treat the impairment of vascular endothelial function caused by isocarbophos, which is NHE1-dependent.
Collapse
Affiliation(s)
- Moli Zhu
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China.,Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, China.,Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, China
| | - Zhitao Gao
- School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, China
| | - Yutian Fu
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Yue Qiu
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Keke Huang
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Chaonan Zhu
- Department of Pharmacy, The First Affiliated Hospital of Xinxiang Medical University, Xinxiang, China
| | - Yinan Wu
- Sanquan Medical College, Xinxiang Medical University, Xinxiang, China
| | - Tiantian Zhu
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Qianqian Wang
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| | - Lin Yang
- Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, China.,Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, China
| | - Yaling Yin
- Basic Medical College, Xinxiang Medical University, Xinxiang, China
| | - Peng Li
- School of Pharmacy, Xinxiang Medical University, Xinxiang, China
| |
Collapse
|
4
|
Feng X, Yan J, Li G, Liu J, Fan R, Li S, Zheng L, Zhang Y, Zhu J. Source of dopamine in gastric juice and luminal dopamine-induced duodenal bicarbonate secretion via apical dopamine D 2 receptors. Br J Pharmacol 2020; 177:3258-3272. [PMID: 32154577 PMCID: PMC7312307 DOI: 10.1111/bph.15047] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 02/02/2020] [Accepted: 02/07/2020] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Dopamine protects the duodenal mucosa. Here we have investigated the source of dopamine in gastric juice and the mechanism underlying the effects of luminal dopamine on duodenal bicarbonate secretion (DBS) in rodents. EXPERIMENTAL APPROACH Immunofluorescence, UPLC-MS/MS, gastric incubation and perfusion were used to detect gastric-derived dopamine. Immunofluorescence and RT-PCR were used to examine the expression of dopamine receptors in the duodenal mucosa. Real-time pH titration and pHi measurement were performed to investigate DBS. KEY RESULTS H+ -K+ -ATPase was co-localized with tyrosine hydroxylase and dopamine transporters in gastric parietal cells. Dopamine was increased in in vivo gastric perfusate after intravenous infusion of histamine and in gastric mucosa incubated, in vitro, with bethanechol chloride or tyrosine. D2 receptors were the most abundant dopamine receptors in rat duodenum, mainly distributed on the apical membrane of epithelial cells. Luminal dopamine increased DBS in a concentration-dependent manner, an effect mimicked by a D2 receptor agonist quinpirole and inhibited by the D2 receptor antagonist L741,626, in vivo D2 receptor siRNA and in D2 receptor -/- mice. Dopamine and quinpirole raised the duodenal enterocyte pHi . Quinpirole-evoked DBS and PI3K/Akt activity were inhibited by calcium chelator BAPTA-AM or in D2 receptor-/- mice. CONCLUSION AND IMPLICATIONS Dopamine in the gastric juice is derived from parietal cells and is secreted along with gastric acid. On arrival in the duodenal lumen, dopamine increased DBS via an apical D2 receptor- and calcium-dependent pathway. Our data provide novel insights into the protective effects of dopamine on the duodenal mucosa.
Collapse
Affiliation(s)
- Xiao‐Yan Feng
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Jing‐Ting Yan
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Guang‐Wen Li
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Jing‐Hua Liu
- Grade 2017 Clinical Medicine, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Rui‐Fang Fan
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Shi‐Chao Li
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Li‐Fei Zheng
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Yue Zhang
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| | - Jin‐Xia Zhu
- Department of Physiology and Pathophysiology, School of Basic Medical ScienceCapital Medical UniversityBeijingChina
| |
Collapse
|
5
|
Zheng S, Krump NA, McKenna MM, Li YH, Hannemann A, Garrett LJ, Gibson JS, Bodine DM, Low PS. Regulation of erythrocyte Na +/K +/2Cl - cotransport by an oxygen-switched kinase cascade. J Biol Chem 2018; 294:2519-2528. [PMID: 30563844 DOI: 10.1074/jbc.ra118.006393] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 12/14/2018] [Indexed: 11/06/2022] Open
Abstract
Many erythrocyte processes and pathways, including glycolysis, the pentose phosphate pathway (PPP), KCl cotransport, ATP release, Na+/K+-ATPase activity, ankyrin-band 3 interactions, and nitric oxide (NO) release, are regulated by changes in O2 pressure that occur as a red blood cell (RBC) transits between the lungs and tissues. The O2 dependence of glycolysis, PPP, and ankyrin-band 3 interactions (affecting RBC rheology) are controlled by O2-dependent competition between deoxyhemoglobin (deoxyHb), but not oxyhemoglobin (oxyHb), and other proteins for band 3. We undertook the present study to determine whether the O2 dependence of Na+/K+/2Cl- cotransport (catalyzed by Na+/K+/2Cl- cotransporter 1 [NKCC1]) might similarly originate from competition between deoxyHb and a protein involved in NKCC1 regulation for a common binding site on band 3. Using three transgenic mouse strains having mutated deoxyhemoglobin-binding sites on band 3, we found that docking of deoxyhemoglobin at the N terminus of band 3 displaces the protein with no lysine kinase 1 (WNK1) from its overlapping binding site on band 3. This displacement enabled WNK1 to phosphorylate oxidative stress-responsive kinase 1 (OSR1), which, in turn, phosphorylated and activated NKCC1. Under normal solution conditions, the NKCC1 activation increased RBC volume and thereby induced changes in RBC rheology. Because the deoxyhemoglobin-mediated WNK1 displacement from band 3 in this O2 regulation pathway may also occur in the regulation of other O2-regulated ion transporters, we hypothesize that the NKCC1-mediated regulatory mechanism may represent a general pattern of O2 modulation of ion transporters in erythrocytes.
Collapse
Affiliation(s)
- Suilan Zheng
- From the Institute for Drug Discovery and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907
| | - Nathan A Krump
- the Hematopoiesis Section, National Human Genome Research Institute and
| | - Mary M McKenna
- the Hematopoiesis Section, National Human Genome Research Institute and
| | - Yen-Hsing Li
- From the Institute for Drug Discovery and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907
| | - Anke Hannemann
- the Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom
| | - Lisa J Garrett
- the National Human Genome Research Institute Embryonic Stem Cell and Transgenic Mouse Core Facility, National Institutes of Health, Bethesda, Maryland 20815, and
| | - John S Gibson
- the Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom
| | - David M Bodine
- the Hematopoiesis Section, National Human Genome Research Institute and
| | - Philip S Low
- From the Institute for Drug Discovery and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907,
| |
Collapse
|
6
|
Muzzachi S, Guerra L, Martino NA, Favia M, Punzi G, Silvestre F, Guaricci AC, Roscino MT, Pierri CL, Dell'Aquila ME, Casavola V, Lacalandra GM, Ciani E. Effect of cariporide on ram sperm pH regulation and motility: possible role of NHE1. Reproduction 2018; 155:433-445. [PMID: 29491124 DOI: 10.1530/rep-17-0456] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2017] [Accepted: 02/27/2018] [Indexed: 01/05/2023]
Abstract
Sperm motility, a feature essential for in vivo fertilization, is influenced by intracellular pH (pHi) homeostasis. Several mechanisms are involved in pHi regulation, among which sodium-hydrogen exchangers (NHEs), a family of integral transmembrane proteins that catalyze the exchange of Na+ for H+ across lipid bilayers. A preliminary characterization of NHE activity and kinetic parameters, followed by analysis of the expression and localization of the protein in ram spermatozoa was performed. NHE activity showed an apparent Km for external Na+ of 17.61 mM. Immunoblotting revealed a molecular mass of 85 kDa. Immunolocalization pattern showed some species-specific aspects, such as positive labeling at the equatorial region of the sperm head. Cariporide, a selective NHE1 inhibitor, significantly reduced pHi recovery (85%). Similarly, exposure to cariporide significantly inhibited different motility parameters, including those related to sperm capacitation. In vitro fertilization (IVF) was not affected by cariporide, possibly due to the non-dramatic, although significant, drop in motility and velocity parameters or due to prolonged exposure during IVF, which may have caused progressive loss of its inhibitory effect. In conclusion, this is the first study documenting, in a large animal model (sheep) of well-known translational relevance, a direct functional role of NHE on sperm pHi and motility. The postulated specificity of cariporide toward isoform 1 of the Na+/H+ exchanger seems to suggest that NHE1 may contribute to the observed effects on sperm cell functionality.
Collapse
Affiliation(s)
- Stefania Muzzachi
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Lorenzo Guerra
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Nicola Antonio Martino
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy.,Istituto Zooprofilattico Sperimentale della Puglia e della BasilicataFoggia, Italy
| | - Maria Favia
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Giuseppe Punzi
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Fabio Silvestre
- Section of Veterinary Clinics and Animal ProductionsDepartment of Emergency and Organ Transplantation, University of Bari 'Aldo Moro', Valenzano, Bari, Italy
| | - Antonio Ciro Guaricci
- Section of Veterinary Clinics and Animal ProductionsDepartment of Emergency and Organ Transplantation, University of Bari 'Aldo Moro', Valenzano, Bari, Italy
| | - Maria Teresa Roscino
- Section of Veterinary Clinics and Animal ProductionsDepartment of Emergency and Organ Transplantation, University of Bari 'Aldo Moro', Valenzano, Bari, Italy
| | - Ciro Leonardo Pierri
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Maria Elena Dell'Aquila
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Valeria Casavola
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| | - Giovanni Michele Lacalandra
- Section of Veterinary Clinics and Animal ProductionsDepartment of Emergency and Organ Transplantation, University of Bari 'Aldo Moro', Valenzano, Bari, Italy
| | - Elena Ciani
- Department of BiosciencesBiotechnologies and Biopharmaceutics, University of Bari 'Aldo Moro', Bari, Italy
| |
Collapse
|
7
|
Chao PC, Butt AG. cAMP-dependent secretagogues stimulate the NaHCO 3 cotransporter in the villous epithelium of the brushtail possum, Trichosurus vulpecula. J Comp Physiol B 2017; 187:1019-1028. [PMID: 28247055 DOI: 10.1007/s00360-017-1063-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 01/30/2017] [Accepted: 02/05/2017] [Indexed: 12/22/2022]
Abstract
In the ileum of the brushtail possum, Trichosurus vulpecula, fluid secretion appears to be driven by electrogenic HCO3- secretion. Consistent with this, the cystic fibrosis transmembrane conductance regulator is expressed in the apical membrane of the ileal epithelial cells and the pancreatic or secretory variant of the NaHCO3 cotransporter in the basolateral membrane. This suggests that in the possum ileum, electrogenic HCO3- secretion is driven by basolateral NaHCO3 cotransporter (NBC) activity. To determine if the NBC contributes to HCO3- secretion in the possum ileum, intracellular pH (pHi) measurements in isolated villi were used to demonstrate NBC activity in the ileal epithelial cells and investigate the effect of cAMP-dependent secretagogues. In CO2/HCO3--free solutions, recovery of the epithelial cells from an acid load was Na+-dependent and ≈80% inhibited by ethyl-isopropyl-amiloride (EIPA, 10 µmol L-1), indicative of the presence of an Na+/H+ exchanger, most likely NHE1. However, in the presence of CO2/HCO3-, EIPA only inhibited ≈ 50% of the recovery, the remainder was inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS, 500 µmol L-1), indicative of NBC activity. Under steady-state conditions, NHE1 inhibition by EIPA had little effect on pHi in the presence or absence of secretagogues, but NBC inhibition with DIDS resulted in a rapid acidification of the cells, which was increased fivefold by secretagogues. These data demonstrate the functional activity of an NaHCO3 cotransporter in the ileal epithelial cells. Furthermore, the stimulation of NBC activity by secretagogues is consistent with the involvement of an NaHCO3 cotransporter in electrogenic HCO3- secretion.
Collapse
Affiliation(s)
- Pin-Chun Chao
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand
| | - A Grant Butt
- Department of Physiology, School of Biomedical Sciences, University of Otago, PO Box 56, Dunedin, 9054, New Zealand.
| |
Collapse
|
8
|
Abstract
Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints.
Collapse
Affiliation(s)
- Connie C.W. Hsia
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Dallas M. Hyde
- California National Primate Research Center, University of California at Davis, Davis, California, USA
| | | |
Collapse
|
9
|
Role of NHE1 in Nociception. PAIN RESEARCH AND TREATMENT 2013; 2013:217864. [PMID: 23431433 PMCID: PMC3572692 DOI: 10.1155/2013/217864] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 01/02/2013] [Indexed: 12/14/2022]
Abstract
Intracellular pH is a fundamental parameter to cell function that requires tight homeostasis. In the absence of any regulation, excessive acidification of the cytosol would have the tendency to produce cellular damage. Mammalian Na(+)/H(+) exchangers (NHEs) are electroneutral Na(+)-dependent proteins that exchange extracellular Na(+) for intracellular H(+). To date, there are 9 identified NHE isoforms where NHE1 is the most ubiquitous member, known as the housekeeping exchanger. NHE1 seems to have a protective role in the ischemia-reperfusion injury and other inflammatory diseases. In nociception, NHE1 is found in neurons along nociceptive pathways, and its pharmacological inhibition increases nociceptive behavior in acute pain models at peripheral and central levels. Electrophysiological studies also show that NHE modulates electrical activity of primary nociceptive terminals. However, its role in neuropathic pain still remains controversial. In humans, NHE1 may be responsible for inflammatory bowel diseases since its expression is reduced in Crohn's disease and ulcerative colitis. The purpose of this work is to provide a review of the evidence about participation of NHE1 in the nociceptive processing.
Collapse
|
10
|
Bartnikas TB, Steinbicker AU, Campagna DR, Blevins S, Woodward LS, Herrera C, Bloch KD, Justice MJ, Fleming MD. Identification and characterization of a novel murine allele of Tmprss6. Haematologica 2013; 98:854-61. [PMID: 23300183 DOI: 10.3324/haematol.2012.074617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Mutagenesis screens can establish mouse models of utility for the study of critical biological processes such as iron metabolism. Such screens can produce mutations in novel genes or establish novel alleles of known genes, both of which can be useful tools for study. In order to identify genes of relevance to hematologic as well as other phenotypes, we performed N-ethyl-N-nitrosourea mutagenesis in C57BL/6J mice. An anemic mouse was identified and a putative mutation was characterized by mapping, sequencing and in vitro activity analysis. The mouse strain was backcrossed for ten generations then phenotypically characterized with respect to a previously established null mouse strain. Potential modifying loci were identified by quantitative trait locus analysis. Mapping and sequencing in an anemic mouse termed hem8 identified an I286F substitution in Tmprss6, a serine protease essential for iron metabolism; this substitution impaired in vitro protease activity. After backcrossing to C57BL6/J for ten generations, the hem8(-/-) strain exhibited a phenotype similar in some but not all aspects to that of Tmprss6(-/-) mice. The hem8 and Tmprss6-null mutations were allelic. Both hem8(-/-) and Tmprss6(-/-) mice responded similarly to pharmacological modulators of bone morphogenetic protein signaling, a key regulator of iron metabolism. Quantitative trait locus analysis in the hem8 strain identified potential modifying loci on chromosomes 2, 4, 7 and 10. In conclusion, the hem8 mouse model carries a novel allele of Tmprss6. Potential uses for this strain in the study of iron metabolism are discussed.
Collapse
Affiliation(s)
- Thomas B Bartnikas
- Department of Pathology and Laboratory Medicine, Brown University, Providence, RI, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Sun YM, Su Y, Li J, Tian Y, Wang LF. Role of the Na+/H+ exchanger on the development of diabetes mellitus and its chronic complications. Biochem Biophys Res Commun 2012; 427:229-31. [DOI: 10.1016/j.bbrc.2012.09.050] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Accepted: 09/08/2012] [Indexed: 11/28/2022]
|
12
|
Phosphorylation and activation of the plasma membrane Na+/H+ exchanger (NHE1) during osmotic cell shrinkage. PLoS One 2011; 6:e29210. [PMID: 22216214 PMCID: PMC3247252 DOI: 10.1371/journal.pone.0029210] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/22/2011] [Indexed: 11/19/2022] Open
Abstract
The Na(+)/H(+)Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na(+)/H(+) exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na(+)/H(+) exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na(+) transport capacity without affecting transport affinity (K(m)=44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ(32)P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na(+) transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events.
Collapse
|
13
|
Abstract
Cell volume homeostasis and its fine-tuning to the specific physiological context at any given moment are processes fundamental to normal cell function. The understanding of cell volume regulation owes much to August Krogh, yet has advanced greatly over the last decades. In this review, we outline the historical context of studies of cell volume regulation, focusing on the lineage started by Krogh, Bodil Schmidt-Nielsen, Hans-Henrik Ussing, and their students. The early work was focused on understanding the functional behaviour, kinetics and thermodynamics of the volume-regulatory ion transport mechanisms. Later work addressed the mechanisms through which cellular signalling pathways regulate the volume regulatory effectors or flux pathways. These studies were facilitated by the molecular identification of most of the relevant channels and transporters, and more recently also by the increased understanding of their structures. Finally, much current research in the field focuses on the most up- and downstream components of these paths: how cells sense changes in cell volume, and how cell volume changes in turn regulate cell function under physiological and pathophysiological conditions.
Collapse
Affiliation(s)
- E K Hoffmann
- Section of Cell and Developmental Biology, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | |
Collapse
|
14
|
Nørholm AB, Hendus-Altenburger R, Bjerre G, Kjaergaard M, Pedersen SF, Kragelund BB. The Intracellular Distal Tail of the Na+/H+ Exchanger NHE1 Is Intrinsically Disordered: Implications for NHE1 Trafficking. Biochemistry 2011; 50:3469-80. [DOI: 10.1021/bi1019989] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ann-Beth Nørholm
- Cell and Developmental Biology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Ruth Hendus-Altenburger
- Cell and Developmental Biology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Gabriel Bjerre
- Cell and Developmental Biology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
| | - Magnus Kjaergaard
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Stine F. Pedersen
- Cell and Developmental Biology, Department of Biology, University of Copenhagen, Universitetsparken 13, DK-2100 Copenhagen Ø, Denmark
| | - Birthe B. Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| |
Collapse
|
15
|
Wakabayashi S, Nakamura TY, Kobayashi S, Hisamitsu T. Novel phorbol ester-binding motif mediates hormonal activation of Na+/H+ exchanger. J Biol Chem 2010; 285:26652-61. [PMID: 20551318 DOI: 10.1074/jbc.m110.130120] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase C (PKC) is considered crucial for hormonal Na(+)/H(+) exchanger (NHE1) activation because phorbol esters (PEs) strongly activate NHE1. However, here we report that rather than PKC, direct binding of PEs/diacylglycerol to the NHE1 lipid-interacting domain (LID) and the subsequent tighter association of LID with the plasma membrane mainly underlies NHE1 activation. We show that (i) PEs directly interact with the LID of NHE1 in vitro, (ii) like PKC, green fluorescent protein (GFP)-labeled LID translocates to the plasma membrane in response to PEs and receptor agonists, (iii) LID mutations markedly inhibit these interactions and PE/receptor agonist-induced NHE1 activation, and (iv) PKC inhibitors ineffectively block NHE1 activation, except staurosporin, which itself inhibits NHE1 via LID. Thus, we propose a PKC-independent mechanism of NHE1 regulation via a PE-binding motif previously unrecognized.
Collapse
Affiliation(s)
- Shigeo Wakabayashi
- Department of Molecular Physiology, National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka, Japan.
| | | | | | | |
Collapse
|
16
|
Oxidative stress and intracellular pH in the young and old erythrocytes of rat. Biogerontology 2009; 10:659-69. [DOI: 10.1007/s10522-009-9212-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 01/20/2009] [Indexed: 10/21/2022]
|
17
|
Abstract
Cell volume perturbation initiates a wide array of intracellular signalling cascades, leading to protective and adaptive events and, in most cases, activation of volume-regulatory osmolyte transport, water loss, and hence restoration of cell volume and cellular function. Cell volume is challenged not only under physiological conditions, e.g. following accumulation of nutrients, during epithelial absorption/secretion processes, following hormonal/autocrine stimulation, and during induction of apoptosis, but also under pathophysiological conditions, e.g. hypoxia, ischaemia and hyponatremia/hypernatremia. On the other hand, it has recently become clear that an increase or reduction in cell volume can also serve as a specific signal in the regulation of physiological processes such as transepithelial transport, cell migration, proliferation and death. Although the mechanisms by which cell volume perturbations are sensed are still far from clear, significant progress has been made with respect to the nature of the sensors, transducers and effectors that convert a change in cell volume into a physiological response. In the present review, we summarize recent major developments in the field, and emphasize the relationship between cell volume regulation and organism physiology/pathophysiology.
Collapse
Affiliation(s)
- I H Lambert
- Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | | | | |
Collapse
|
18
|
Kristensen K, Berenbrink M, Koldkjaer P, Abe A, Wang T. Minimal volume regulation after shrinkage of red blood cells from five species of reptiles. Comp Biochem Physiol A Mol Integr Physiol 2008; 150:46-51. [PMID: 18424207 DOI: 10.1016/j.cbpa.2008.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Revised: 03/05/2008] [Accepted: 03/05/2008] [Indexed: 11/27/2022]
Abstract
Red blood cells (RBCs) from most vertebrates restore volume upon hypertonic shrinkage and the mechanisms underlying this regulatory volume increase (RVI) have been studied extensively in these cells. Despite the phylogenetically interesting position of reptiles, very little is known about their red cell function. The present study demonstrates that oxygenated RBCs in all major groups of reptiles exhibit no or a very reduced RVI upon approximately 25% calculated hyperosmotic shrinkage. Thus, RBCs from the snakes Crotalus durissus and Python regius, the turtle Trachemys scripta and the alligator Alligator mississippiensis showed no statistically significant RVI within 120 min after shrinkage, while the lizard Tupinambis merianae showed 22% volume recovery after 120 min. Amiloride (10(-4) M) and bumetanide (10(-5) M) had no effect on the RVI in T. merianae, indicating no involvement of the Na(+)/H(+) exchanger (NHE) or the Na(+)/K(+)/2Cl(-) co-transporter (NKCC) or insentive transporters. Deoxygenation of RBCs from A. mississippiensis and T. merianae did not significantly affect RVI upon shrinkage. Deoxygenation per se of red blood cells from T. merianae elicited a slow volume increase, but the mechanism was not characterized. It seems, therefore, that the RVI response based on NHE activation was lost among the early sauropsids that gave rise to modern reptiles and birds, while it was retained in mammals. An RVI response has then reappeared in birds, but based on activation of the NKCC. Alternatively, the absence of the RVI response may represent the most ancient condition, and could have evolved several times within vertebrates.
Collapse
|
19
|
Pedersen SF, Darborg BV, Rasmussen M, Nylandsted J, Hoffmann EK. The Na+/H+ exchanger, NHE1, differentially regulates mitogen-activated protein kinase subfamilies after osmotic shrinkage in Ehrlich Lettre Ascites cells. Cell Physiol Biochem 2007; 20:735-50. [PMID: 17982256 DOI: 10.1159/000110434] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2007] [Indexed: 11/19/2022] Open
Abstract
Osmotic stress modulates mitogen activated protein kinase (MAPK) activities, leading to altered gene transcription and cell death/survival balance, however, the mechanisms involved are incompletely elucidated. Here, we show, using a combination of biochemical and molecular biology approaches, that three MAPKs exhibit unique interrelationships with the Na(+)/H(+) exchanger, NHE1, after osmotic cell shrinkage: Extracellular Signal Regulated Kinase (ERK1/2) is inhibited in an NHE1-dependent, pH(i)-independent manner, c-Jun N-terminal kinase (JNK1/2) is stimulated, in part through NHE1-mediated intracellular alkalinization, and p38 MAPK is activated in an NHE1-independent manner, and contributes to NHE1 activation and ERK inhibition. Shrinkage-induced ERK1/2 inhibition was attenuated in Ehrlich Lettre Ascites cells by NHE1 inhibitors (EIPA, cariporide) or removal of extracellular Na(+), and mimicked by human (h) NHE1 expression in cells lacking endogenous NHE1 activity. The effect of NHE1 on ERK1/2 was pH(i)-independent and upstream of MEK1/2. Shrinkage-activation of JNK1/2 was attenuated by EIPA, augmented by hNHE1 expression, and abolished in the presence of HCO(3)(-). Basal JNK activity was augmented at alkaline pH(i). Shrinkage-activation of p38 MAPK was NHE1-independent, and p38 MAPK inhibition (SB203580) attenuated NHE1 activation and ERK1/2 inhibition. Long-term shrinkage elicited caspase-3 activation and a loss of cell viability, which was augmented by ERK1/2 or JNK1/2 inhibition, and attenuated by p38 MAPK inhibition.
Collapse
|
20
|
Tse WKF, Au DWT, Wong CKC. Effect of osmotic shrinkage and hormones on the expression of Na+/H+ exchanger-1, Na+/K+/2Cl- cotransporter and Na+/K+ -ATPase in gill pavement cells of freshwater adapted Japanese eel, Anguilla japonica. ACTA ACUST UNITED AC 2007; 210:2113-20. [PMID: 17562884 DOI: 10.1242/jeb.004101] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It is well-known that gill epithelial cells are important in fish osmoregulation. However, studies on the effect of osmotic stress on the direct cellular responses of the gill epithelial cells are limited. In this paper, we aimed to determine the effects of osmotic hypertonicity, hormones and cellular signaling molecules on the expression of ion transporters in the cultured primary freshwater pavement cells (PVCs), prepared from freshwater-adapted eels (Anguilla japonica). Our data demonstrated that the hypertonic (500 mOsmol l(-1)) treatment of the isolated PVCs induced cell shrinkage, followed by regulatory volume increase (RVI). Application of blockers (i.e. ouabain, bumetanide and EIPA) demonstrated that Na+/K+ -ATPase, Na+/K+/2Cl- cotransporter (NKCC) and Na+/H+ exchanger-1 (NHE-1) were involved in RVI. Western blot analysis of the hypertonic-treated cells revealed a significant induction of NHE-1, NKCC and, alpha and beta subunits of Na+/K+ -ATPase. In nonshrunken cultured PVCs, we found that dexamethasone and dibutyryl cAMP treatments significantly stimulated the expression levels of the three ion transporters. Both prolactin and insulin-like growth factor-1, can only induce the expression of NKCC. The effect of thyroid hormone (T3) and dibutyryl cGMP was negligible. In this study, the induction of ion transporter expression was found to be post-transcriptionally regulated as no significant change in mRNA levels was detected. This observation implies that the regulation is rapid and is probably induced via nongenomic actions.
Collapse
Affiliation(s)
- William K F Tse
- Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong
| | | | | |
Collapse
|
21
|
Kristensen K, Koldkjaer P, Berenbrink M, Wang T. Oxygen-sensitive regulatory volume increase and Na transport in red blood cells from the cane toad,Bufo marinus. J Exp Biol 2007; 210:2290-9. [PMID: 17575034 DOI: 10.1242/jeb.002824] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe red blood cells (RBCs) of cane toad, Bufo marinus, are only partially saturated with oxygen in most of the circulation due to cardiac shunts that cause desaturation of arterial blood. The present study examines the oxygen dependency of RBC ouabain-insensitive unidirectional Na transport,using 22Na, in control cells and in cells exposed to hyperosmotic shrinkage or the β-adrenergic agonist isoproterenol. Deoxygenation per se induced a slow, but significant Na influx, which was paralleled by a slow increase in RBC volume. Hyperosmotic shrinkage by a calculated 25% activated a robust Na influx that in the first 30 min had a strong PO2 dependency with maximal activation at low PO2 values and a P50of ∼5.5 kPa. This activation was completely abolished by the Na/H exchanger (NHE) inhibitor EIPA (10–4 mol l-1). Hyperosmotic shrinkage is particularly interesting in B. marinus as it withstands considerable elevation in extracellular osmolarity following dehydration. Parallel studies showed that deoxygenated B. marinusRBCs had a much faster regulatory volume increase (RVI) response than air-equilibrated RBCs, reflecting the difference in magnitude of Na influxes at the two PO2 values. The extent of RVI(∼60%) after 90 min, however, was similar under the two conditions,reflecting a more prolonged elevation of the shrinkage-induced Na influx in air-equilibrated RBCs. There were no significant differences in the ability to perform RVI between whole blood cells at a PCO2of 1 and 3 kPa or washed RBCs, and 10–4 mol l-1amiloride reduced the RVI under all conditions, whereas 10–5mol l-1 bumetanide had no effect. Isoproterenol(10–5 mol l-1) induced a significant and prolonged increase in an EIPA-sensitive and bumetanide-insensitive Na influx at low PO2 under iso-osmotic conditions, whilst there was no stimulation by isoproterenol for up to 45 min in air-equilibrated RBCs. The prolonged β-adrenergic activation of the Na influx at low PO2 is distinctly different from the rapid and transient stimulation in teleost RBCs, suggesting significant differences in the signal transduction pathways leading to transporter activation between vertebrate groups.
Collapse
|
22
|
Pedersen SF, King SA, Nygaard EB, Rigor RR, Cala PM. NHE1 inhibition by amiloride- and benzoylguanidine-type compounds. Inhibitor binding loci deduced from chimeras of NHE1 homologues with endogenous differences in inhibitor sensitivity. J Biol Chem 2007; 282:19716-27. [PMID: 17493937 DOI: 10.1074/jbc.m701637200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interaction of the ubiquitous Na(+)/H(+) exchanger, NHE1, with its commonly used inhibitors, amiloride- and benzoylguanidine (Hoechst type inhibitor (HOE))-type compounds, is incompletely understood. We previously cloned NHE1 from Amphiuma tridactylum (AtNHE1) and Pleuronectes americanus (PaNHE1). Although highly homologous to the amiloride- and HOE-sensitive human NHE1 (hNHE1), AtNHE1 is insensitive to HOE-type and PaNHE1 to both amiloride- and HOE-type compounds. Here we generated chimeras to "knock in" amiloride and HOE sensitivity to PaNHE1, and we thereby identified several NHE1 regions involved in inhibitor interaction. The markedly different inhibitor sensitivities of hNHE1, AtNHE1, and PaNHE1 could not be accounted for by differences in transmembrane (TM) region 9. Replacing TM10 through the C-terminal tail of PaNHE1 with the corresponding region of AtNHE1 partially restored sensitivity to amiloride and the related compound 5'-(N-ethyl-N-isopropyl)amiloride (EIPA) but not to HOE694. This effect was not due to the tail region, but it was dependent on TM10-11, because replacing only this region with that of AtNHE1 also partially restored amiloride and EIPA but not HOE sensitivity. The converse mutant (TM10-11 of AtNHE1 replaced with those of PaNHE1) exhibited even higher amiloride and EIPA sensitivity and was also HOE-sensitive. Replacing an LFFFY motif in TM region 4 of PaNHE1 with the corresponding residues of hNHE1 (VFFLF) or AtNHE1 (TFFLF) greatly increased sensitivity to both amiloride- and HOE-type compounds, despite the fact that AtNHE1 is HOE694-insensitive. Gain of amiloride sensitivity appeared to correlate with increased Na(+)/H(+) exchange rates. It is concluded that regions within TM4 and TM10-11 contribute to amiloride and HOE sensitivity, with both regions imparting partial inhibitor sensitivity to NHE1.
Collapse
Affiliation(s)
- Stine F Pedersen
- Department of Physiology and Membrane Biology, University of California, Davis, California 95616, USA
| | | | | | | | | |
Collapse
|
23
|
Lambert IH, Pedersen SF. Multiple PLA2 isoforms regulate taurine release in NIH3T3 mouse fibroblasts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2007; 583:99-108. [PMID: 17153593 DOI: 10.1007/978-0-387-33504-9_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Affiliation(s)
- Ian Henry Lambert
- Dept. of Biochemistry, Institute for Molecular Biology and Physiology, The August Krogh Building, 13, Universitetsparken, DK-2100 Copenhagen, Denmark.
| | | |
Collapse
|
24
|
Ivanova TI, Agalakova NI, Gusev GP. Activation of sodium transport in rat erythrocytes by inhibition of protein phosphatases 1 and 2A. Comp Biochem Physiol B Biochem Mol Biol 2006; 145:60-7. [PMID: 16875859 DOI: 10.1016/j.cbpb.2006.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Revised: 06/09/2006] [Accepted: 06/19/2006] [Indexed: 11/29/2022]
Abstract
Four structurally different protein phosphatases (PPs) inhibitors - fluoride, calyculin A, okadaic acid and cantharidin--were tested for their ability to modulate unidirectional Na(+) influx in rat red blood cells. Erythrocytes were incubated at 37 degrees C in isotonic and hypertonic media containing 1 mM ouabain and (22)Na in the absence or presence of PP inhibitors. Exposure of the cells to 20 mM fluoride or 50 nM calyculin A for 1 h under isosmotic conditions caused a significant stimulation of Na(+) influx, whereas addition of 200 microM cantharidin or 100 nM okadaic acid had no effect. After 2 h of treatment, however, all these PPs blockers significantly enhanced Na(+) transport in rat erythrocytes. Selective inhibitors of PP-1 and PP-2A types, calyculin A, cantharidin and okadaic acid, produced similar ( approximately 1.2-1.4-fold) stimulatory effects on Na(+) influx in the cells. Activation of Na(+) influx was unchanged with increasing calyculin A concentration from 50 to 200 nM. No additive stimulation of Na(+) influx was observed when the cells were treated with combination of 20 mM fluoride and 50 nM calyculin A. Na(+) influx induced by PPs blockers was inhibited by 1 mM amiloride and 200 muM bumetanide approximately in the equal extent, indicating the involvement of Na(+)/H(+) exchange and Na-K-2Cl cotransport in sodium transport through rat erythrocytes membrane. Activation of Na(+) transport in the cells induced by calyculin A and fluoride was associated with increase of intracellular Na(+) content. Shrinkage of the rat erythrocytes resulted in 2-fold activation of Na(+) influx. All tested PPs inhibitors additionally activated the Na(+) influx by 70-100% above basal shrinkage-induced level. Amiloride and bumetanide have diminished both the shrinkage-induced and PPs-inhibitors-induced Na(+) influxes. Thus, our observations clearly indicate that activities of Na(+)/H(+) exchanger and Na-K-2Cl cotransporter in rat erythrocytes are regulated by protein phosphatases and stimulated when protein dephosphorylation is inhibited.
Collapse
Affiliation(s)
- Tatiana I Ivanova
- Laboratory of Comparative Biochemistry of Inorganic Ions, Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez pr., 194223, St. Petersburg, Russia
| | | | | |
Collapse
|
25
|
De Vito P. The sodium/hydrogen exchanger: a possible mediator of immunity. Cell Immunol 2006; 240:69-85. [PMID: 16930575 DOI: 10.1016/j.cellimm.2006.07.001] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Revised: 06/30/2006] [Accepted: 07/05/2006] [Indexed: 10/24/2022]
Abstract
Immune cells such as macrophages and neutrophils provide the first line of defence of the immune system using phagocytosis, cytokine and chemokine synthesis and release, as well as Reactive Oxygen Species (ROS) generation. Many of these functions are positively coupled with cytoplasmic pH (pHi) and/or phagosomal pH (pHp) modification; an increase in pHi represents an important signal for cytokine and chemokine release, whereas a decrease in pHp can induce an efficient antigen presentation. However, the relationship between pHi and ROS generation is not well understood. In immune cells two main transport systems have been shown to regulate pHi: the Na+/H+ Exchanger (NHE) and the plasmalemmal V-type H+ ATPase. NHE is a family of proteins which exchange Na+ for H+ according to their concentration gradients in an electroneutral manner. The exchanger also plays a key role in several other cellular functions including proliferation, differentiation, apoptosis, migration, and cytoskeletal organization. Since not much is known on the relationship between NHE and immunity, this review outlines the contribution of NHE to different aspects of innate and adaptive immune responses such as phagosomal acidification, NADPH oxidase activation and ROS generation, cytokine and chemokine release as well as T cell apoptosis. The possibility that several pro-inflammatory diseases may be modulated by NHE activity is evaluated.
Collapse
Affiliation(s)
- Paolo De Vito
- Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, 00133 Rome, Italy.
| |
Collapse
|
26
|
Ahmed KH, Pelster B, Krumschnabel G. Signalling pathways involved in hypertonicity- and acidification-induced activation of Na+/H+ exchange in trout hepatocytes. J Exp Biol 2006; 209:3101-13. [PMID: 16888059 DOI: 10.1242/jeb.02357] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYIn trout hepatocytes, hypertonicity and cytosolic acidification are known to stimulate Na+/H+ exchanger (NHE) activity, which contributes to recovery of cell volume and intracellular pH (pHi),respectively. The present study investigated the signalling mechanisms underlying NHE activation under these conditions. Exposing trout hepatocytes to cariporide, a specific inhibitor of NHE-1, decreased baseline pHi,completely blocked the hypertonicity-induced increase of pHi and reduced the hypertonicity-induced proton secretion by 80%. Changing extracellular pH (pHe)above and below normal values, and allowing cells to adjust pHi accordingly,significantly delayed alkalinization during hypertonic exposure, whereas following an acid load an enhanced pHi recovery with increasing pHe was seen. Chelating Ca2+, and thereby preventing the hypertonicity-induced increase in intracellular Ca2+ ([Ca2+]i), significantly diminished hypertonic elevation of pHi, indicating that Ca2+signalling might be involved in NHE activation. A reduction in alkalinization and proton secretion was also observed in the presence of the protein kinase A(PKA) inhibitor H-89 or the calmodulin (CaM) inhibitor calmidazolium. A complete inhibition of hypertonic- and acidification-induced changes of pHi concurrent with an increase in hypertonically induced proton efflux was seen with the protein kinase C (PKC) inhibitor chelerythrine. Recovery of pHi following sodium propionate addition was reduced by more than 60% in the presence of cariporide, was sensitive to PKA inhibition, and tended to be reduced by CaM inhibition. In conclusion, we showed that NHE-1 is the main acid secretion mechanism during hypertonicity and recovery following acid loading. In addition, Ca2+-, PKA- and CaM-dependent pathways are involved in NHE-1 activation for recovery of cell volume and pHi. On the other hand, PKC appeared to have an impact on NHE-independent pathways affecting intracellular acid-base homeostasis.
Collapse
Affiliation(s)
- Khaled H Ahmed
- Institut für Zoologie and Center of Molecular Biosciences, Leopold Franzens Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | | | | |
Collapse
|
27
|
Pedersen SF. The Na+/H+ exchanger NHE1 in stress-induced signal transduction: implications for cell proliferation and cell death. Pflugers Arch 2006; 452:249-59. [PMID: 16586098 DOI: 10.1007/s00424-006-0044-y] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 12/27/2005] [Indexed: 10/24/2022]
Abstract
The ubiquitous plasma membrane Na+/H+ exchanger NHE1 is highly conserved across vertebrate species and is extensively characterized as a major membrane transport mechanism in the regulation of cellular pH and volume. In recent years, the understanding of the role of NHE1 in regulating cell function has expanded from one of a household protein involved in ion homeostasis to that of a multifaceted regulator and/or modulator of a wide variety of cell functions. NHE1 plays pivotal roles in response to a number of important physiological stress conditions which, in addition to cell shrinkage and acidification, include hypoxia and mechanical stimuli, such as cell stretch. It has recently become apparent that NHE1-mediated modulation of, e.g., cell migration, morphology, proliferation, and death results not only from NHE1-mediated changes in pHi, cell volume, and/or [Na+]i, but also from direct protein-protein interactions with, e.g., ezrin/radixin/moesin (ERM) proteins and regulation of cellular signaling events, including the activity of mitogen-activated protein kinases (MAPKs) and Akt/protein kinase B (PKB). The aim of this review is to present and discuss new findings implicating NHE1 activation as a central signaling event activated by stress conditions and modulating cell proliferation and death. The pathophysiological importance of NHE1 in modulating the balance between cell proliferation and cell death in cancer and in ischemia/severe hypoxia will also be briefly addressed.
Collapse
Affiliation(s)
- Stine Falsig Pedersen
- Department of Biochemistry, August Krogh Building, Institute for Molecular Biology and Physiology, University of Copenhagen, 13, Universitetsparken, Dk-2100, Copenhagen, Denmark.
| |
Collapse
|
28
|
Mizumori M, Meyerowitz J, Takeuchi T, Lim S, Lee P, Supuran CT, Guth PH, Engel E, Kaunitz JD, Akiba Y. Epithelial carbonic anhydrases facilitate PCO2 and pH regulation in rat duodenal mucosa. J Physiol 2006; 573:827-42. [PMID: 16556652 PMCID: PMC1779739 DOI: 10.1113/jphysiol.2006.107581] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The duodenum is the site of mixing of massive amounts of gastric H+ with secreted HCO3-, generating CO2 and H2O accompanied by the neutralization of H+. We examined the role of membrane-bound and soluble carbonic anhydrases (CA) by which H+ is neutralized, CO2 is absorbed, and HCO3- is secreted. Rat duodena were perfused with solutions of different pH and PCO2 with or without a cell-permeant CA inhibitor methazolamide (MTZ) or impermeant CA inhibitors. Flow-through pH and PCO2 electrodes simultaneously measured perfusate and effluent pH and PCO2. High CO2 (34.7 kPa) perfusion increased net CO2 loss from the perfusate compared with controls (pH 6.4 saline, PCO2 approximately 0) accompanied by portal venous (PV) acidification and PCO2 increase. Impermeant CA inhibitors abolished net perfusate CO2 loss and increased net HCO3- gain, whereas all CA inhibitors inhibited PV acidification and PCO2 increase. The changes in luminal and PV pH and [CO2] were also inhibited by the Na+-H+ exchanger-1 (NHE1) inhibitor dimethylamiloride, but not by the NHE3 inhibitor S3226. Luminal acid decreased total CO2 output and increased H+ loss with PV acidification and PCO2 increase, all inhibited by all CA inhibitors. During perfusion of a 30% CO2 buffer, loss of CO2 from the lumen was CA dependent as was transepithelial transport of perfused 13CO2. H+ and CO2 loss from the perfusate were accompanied by increases of PV H+ and tracer CO2, but unchanged PV total CO2, consistent with CA-dependent transmucosal H+ and CO2 movement. Inhibition of membrane-bound CAs augments the apparent rate of net basal HCO3- secretion. Luminal H+ traverses the apical membrane as CO2, is converted back to cytosolic H+, which is extruded via NHE1. Membrane-bound and cytosolic CAs cooperatively facilitate secretion of HCO3- into the lumen and CO2 diffusion into duodenal mucosa, serving as important acid-base regulators.
Collapse
Affiliation(s)
- Misa Mizumori
- Department of Medicine, School of Medicine, University of California, Los Angeles, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Amiloride and the regulation of NF-kappaB: an unsung crosstalk and missing link between fluid dynamics and oxidative stress-related inflammation--controversy or pseudo-controversy? Biochem Biophys Res Commun 2005; 327:373-81. [PMID: 15629126 DOI: 10.1016/j.bbrc.2004.11.166] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2004] [Indexed: 11/17/2022]
Abstract
Understanding the biophysics of fluid dynamics within the context of transcriptional regulation, mediated by nuclear factor (NF)-kappaB, is crucial to developing a consensus on the molecular basis of fluid mechanics and imbalance. Amiloride, an antikaliuretic-diuretic agent, has recently entered the realm of NF-kappaB as a key player in regulating the molecular association of fluid dynamics with inflammation and oxidative stress. With the identification of flanking regions encoding the amiloride-sensitive channels that are NF-kappaB-responsive, a new theme emerges which underlies the significance of this association. What is the role of NF-kappaB in regulating fluid mechanics-is it a physiologic or immunologic function? Conversely, amiloride is purported as a major regulator of this transcriptional pathway. It is the mainstream of this survey, therefore, to outline current advances on the biophysics and nature of the interaction existing between amiloride, amiloride-sensitive channels, and NF-kappaB, while searching for potential molecular mechanisms.
Collapse
|