1
|
Koc C, Cakir A, Salman B, Ocalan B, Alkan T, Kafa IM, Cetinkaya M, Cansev M. Preventive effects of antenatal CDP-choline in a rat model of neonatal hyperoxia-induced lung injury. Can J Physiol Pharmacol 2023; 101:65-73. [PMID: 36524681 DOI: 10.1139/cjpp-2022-0321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Antenatal steroid administration to pregnant women at risk of prematurity provides pulmonary maturation in infants, while it has limited effects on incidence of bronchopulmonary dysplasia (BPD), the clinical expression of hyperoxia-induced lung injury (HILI). Cytidine-5'-diphosphate choline (CDP-choline) was shown to alleviate HILI when administered to newborn rats. Therefore, we investigated effects of maternal administration of CDP-choline, alone or in combination with betamethasone, on lung maturation in neonatal rats subjected to HILI immediately after birth. Pregnant rats were randomly assigned to one of the four treatments: saline (1 mL/kg), CDP-choline (300 mg/kg), betamethasone (0.4 mg/kg), or CDP-choline plus betamethasone (combination therapy). From postnatal day 1 to 11, pups born to mothers in the same treatment group were pooled and randomly assigned to either normoxia or hyperoxia group. Biochemical an d histopathological effects of CDP-choline on neonatal lung tissue were evaluated. Antenatal CDP-choline treatment increased levels of phosphatidylcholine and total lung phospholipids, decreased apoptosis, and improved alveolarization. The outcomes were further improved with combination therapy compared to the administration of CDP-choline or betamethasone alone. These results demonstrate that antenatal CDP-choline treatment provides benefit in experimental HILI either alone or more intensively when administered along with a steroid, suggesting a possible utility for CDP-choline against BPD.
Collapse
Affiliation(s)
- Cansu Koc
- Department of Pharmacology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Aysen Cakir
- Department of Physiology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Berna Salman
- Department of Pharmacology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Busra Ocalan
- Department of Physiology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Tulin Alkan
- Department of Physiology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Ilker Mustafa Kafa
- Department of Anatomy, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| | - Merih Cetinkaya
- Department of Neonatology, Basaksehir Cam and Sakura City Hospital, University of Health Sciences, Istanbul, Turkey
| | - Mehmet Cansev
- Department of Pharmacology, Faculty of Medicine, Bursa Uludag University, Bursa, Turkey
| |
Collapse
|
2
|
Glucocorticoids, sodium transport mediators, and respiratory distress syndrome in preterm infants. Pediatr Res 2021; 89:1253-1260. [PMID: 32663837 PMCID: PMC7372212 DOI: 10.1038/s41390-020-1061-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/09/2020] [Accepted: 06/22/2020] [Indexed: 11/23/2022]
Abstract
BACKGROUND Antenatal glucocorticoids (GCs) reduce respiratory distress syndrome (RDS) in preterm infants and are associated with reduced lung liquid content. Our aim was to assess whether airway gene expression of mediators of pulmonary epithelial sodium and liquid absorption, and further, respiratory morbidity, associate with cord blood GC concentrations. METHODS The study included 64 infants delivered <32 weeks gestation. Cortisol and betamethasone in umbilical cord blood were quantified with liquid chromatography-tandem mass spectrometry. The total GC concentration was calculated. Gene expression of the epithelial sodium channel (ENaC), Na,K-ATPase, and serum- and GC-inducible kinase 1 at <2 h and at 1 day postnatally in nasal epithelial cell samples was quantified with reverse transcription-polymerase chain reaction. The mean oxygen supplementation during the first 72 h was calculated. RESULTS Concentrations of cord blood betamethasone and total GC were significantly lower in infants with RDS and correlated with mean oxygen supplementation. Expression of αENaC and α1- and β1Na,K-ATPase at <2 h correlated with betamethasone and total GC concentrations. Expression of Na,K-ATPase was lower in infants with RDS. CONCLUSION Enhancement of lung liquid absorption via increased expression of sodium transporters may contribute to the beneficial pulmonary effects of antenatal GCs. IMPACT RDS is related to lower umbilical cord blood GC concentrations and lower airway expression of sodium transporters. In addition to the timing of antenatal GC treatment, resulting concentrations may be of importance in preventing RDS. Induction of sodium transport may be a factor contributing to the pulmonary response to antenatal GCs.
Collapse
|
3
|
Li Z, Langhans SA. Transcriptional regulators of Na,K-ATPase subunits. Front Cell Dev Biol 2015; 3:66. [PMID: 26579519 PMCID: PMC4620432 DOI: 10.3389/fcell.2015.00066] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 10/05/2015] [Indexed: 12/20/2022] Open
Abstract
The Na,K-ATPase classically serves as an ion pump creating an electrochemical gradient across the plasma membrane that is essential for transepithelial transport, nutrient uptake and membrane potential. In addition, Na,K-ATPase also functions as a receptor, a signal transducer and a cell adhesion molecule. With such diverse roles, it is understandable that the Na,K-ATPase subunits, the catalytic α-subunit, the β-subunit and the FXYD proteins, are controlled extensively during development and to accommodate physiological needs. The spatial and temporal expression of Na,K-ATPase is partially regulated at the transcriptional level. Numerous transcription factors, hormones, growth factors, lipids, and extracellular stimuli modulate the transcription of the Na,K-ATPase subunits. Moreover, epigenetic mechanisms also contribute to the regulation of Na,K-ATPase expression. With the ever growing knowledge about diseases associated with the malfunction of Na,K-ATPase, this review aims at summarizing the best-characterized transcription regulators that modulate Na,K-ATPase subunit levels. As abnormal expression of Na,K-ATPase subunits has been observed in many carcinoma, we will also discuss transcription factors that are associated with epithelial-mesenchymal transition, a crucial step in the progression of many tumors to malignant disease.
Collapse
Affiliation(s)
- Zhiqin Li
- Nemours Center for Childhood Cancer Research, Nemours/Alfred I. duPont Hospital for Children Wilmington, DE, USA
| | - Sigrid A Langhans
- Nemours Center for Childhood Cancer Research, Nemours/Alfred I. duPont Hospital for Children Wilmington, DE, USA
| |
Collapse
|
4
|
Huynh TP, Barwe SP, Lee SJ, McSpadden R, Franco OE, Hayward SW, Damoiseaux R, Grubbs SS, Petrelli NJ, Rajasekaran AK. Glucocorticoids suppress renal cell carcinoma progression by enhancing Na,K-ATPase beta-1 subunit expression. PLoS One 2015; 10:e0122442. [PMID: 25836370 PMCID: PMC4383530 DOI: 10.1371/journal.pone.0122442] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 02/21/2015] [Indexed: 11/28/2022] Open
Abstract
Glucocorticoids are commonly used as palliative or chemotherapeutic clinical agents for treatment of a variety of cancers. Although steroid treatment is beneficial, the mechanisms by which steroids improve outcome in cancer patients are not well understood. Na,K-ATPase beta-subunit isoform 1 (NaK-β1) is a cell-cell adhesion molecule, and its expression is down-regulated in cancer cells undergoing epithelial-to mesenchymal-transition (EMT), a key event associated with cancer progression to metastatic disease. In this study, we performed high-throughput screening to identify small molecules that could up-regulate NaK-β1 expression in cancer cells. Compounds related to the glucocorticoids were identified as drug candidates enhancing NaK-β1 expression. Of these compounds, triamcinolone, dexamethasone, and fluorometholone were validated to increase NaK-β1 expression at the cell surface, enhance cell-cell adhesion, attenuate motility and invasiveness and induce mesenchymal to epithelial like transition of renal cell carcinoma (RCC) cells in vitro. Treatment of NaK-β1 knockdown cells with these drug candidates confirmed that these compounds mediate their effects through up-regulating NaK-β1. Furthermore, we demonstrated that these compounds attenuate tumor growth in subcutaneous RCC xenografts and reduce local invasiveness in orthotopically-implanted tumors. Our results strongly indicate that the addition of glucocorticoids in the treatment of RCC may improve outcome for RCC patients by augmenting NaK-β1 cell-cell adhesion function.
Collapse
MESH Headings
- Animals
- Carcinoma, Renal Cell/drug therapy
- Carcinoma, Renal Cell/enzymology
- Carcinoma, Renal Cell/pathology
- Cell Adhesion/drug effects
- Cell Line, Tumor
- Dexamethasone/pharmacology
- Disease Progression
- Fluorometholone/pharmacology
- Glucocorticoids/pharmacology
- HeLa Cells
- High-Throughput Screening Assays
- Humans
- Kidney Neoplasms/drug therapy
- Kidney Neoplasms/enzymology
- Kidney Neoplasms/pathology
- Male
- Mice
- Mice, Hairless
- Mice, SCID
- Neoplasm Invasiveness/prevention & control
- Promoter Regions, Genetic/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- Sodium-Potassium-Exchanging ATPase/genetics
- Sodium-Potassium-Exchanging ATPase/metabolism
- Triamcinolone/pharmacology
- Up-Regulation/drug effects
- Xenograft Model Antitumor Assays
Collapse
Affiliation(s)
- Thu P. Huynh
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Nemours Center for Childhood Cancer Research, A. I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Sonali P. Barwe
- Nemours Center for Childhood Cancer Research, A. I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Seung J. Lee
- Nemours Center for Childhood Cancer Research, A. I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Ryan McSpadden
- Nemours Center for Childhood Cancer Research, A. I. DuPont Hospital for Children, Wilmington, Delaware, United States of America
| | - Omar E. Franco
- Department of Urologic Surgery, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Simon W. Hayward
- Department of Urologic Surgery, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Robert Damoiseaux
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Stephen S. Grubbs
- Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, United States of America
| | - Nicholas J. Petrelli
- Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, United States of America
| | - Ayyappan K. Rajasekaran
- Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, United States of America
- Department of Biological Sciences, University of Delaware, Newark, Delaware, United States of America
- Therapy Architects, 2700 Silverside Road, Wilmington, Delaware, United States of America
| |
Collapse
|
5
|
Keller-Wood M, von Reitzenstein M, McCartney J. Is the fetal lung a mineralocorticoid receptor target organ? Induction of cortisol-regulated genes in the ovine fetal lung, kidney and small intestine. Neonatology 2009; 95:47-60. [PMID: 18787337 PMCID: PMC2654587 DOI: 10.1159/000151755] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2007] [Accepted: 01/28/2008] [Indexed: 01/29/2023]
Abstract
BACKGROUND Lung, kidney and small intestine are involved in fetal volume regulation and amniotic fluid secretion and play a pivotal role in the transition from intrauterine to extrauterine life. OBJECTIVE This study was performed to determine the ontogeny of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR), and of MR- and GR-regulated genes and proteins, serum and glucocorticoid-induced kinase (Sgk-1), epithelial sodium channel (ENaC alpha), and Na,K-ATPase alpha1. METHODS Lung, renal cortex and medulla, and small intestine were collected from fetuses at 80, 100, 120, 130 and 145 days' gestation and from day 1 and 7 neonatal lambs. Real-time PCR was performed to determine mRNA concentration for MR, GR, the 11 beta-hydroxysteroid dehydrogenases (11 beta-HSD1 and 2), Sgk-1, ENaC alpha, and Na,K-ATPase alpha1. Protein expression of ENaC alpha and Na,K-ATPase alpha1 in whole cell and membrane fractions was determined by immunoblotting. RESULTS Expression of corticosteroid-induced genes in renal cortex increases at term; in small intestine the induction occurs postnatally. In contrast, in lung expression of MR and GR mRNAs were greater at 100 days to term than postnatally and 11 beta-HSD1 peaked at 145 days; the corticosteroid-induced genes also increased prenatally: Sgk-1 and ENaC alpha increased by 120 days, peaking at 145 days, and Na,K-ATPase alpha1 was greatest at 130 days. CONCLUSIONS The expression of high levels of MR and 11 beta-HSD1 in preterm fetal lung suggest low endogenous fetal cortisol may exert actions at the high affinity MR in vivo, leading to increases in expression of sodium channels important in the regulation of lung liquid secretion and reabsorption.
Collapse
Affiliation(s)
- Maureen Keller-Wood
- Department of Pharmacodynamics, University of Florida, Gainesville, FL 32610, USA.
| | | | | |
Collapse
|
6
|
Otulakowski G, Rafii B, Harris M, O'Brodovich H. Oxygen and glucocorticoids modulate alphaENaC mRNA translation in fetal distal lung epithelium. Am J Respir Cell Mol Biol 2005; 34:204-12. [PMID: 16210692 DOI: 10.1165/rcmb.2005-0273oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Glucocorticoid hormones play an important role in fetal lung maturation. It is unknown how they interact with changes in O2 tension, which play an important role in converting the lung from a fluid-secreting to a fluid-absorbing organ at birth. Airspace fluid absorption arises from active transepithelial Na+ transport with the amiloride-sensitive epithelial Na channel (ENaC), consisting of alpha, beta, and gamma subunits, representing the rate-limiting step under nonpathologic conditions. We investigated the individual and combined effects of dexamethasone (DEX) and PO2 on alphaENaC mRNA levels, rate of alphaENaC protein synthesis, and amiloride-sensitive short-circuit current in primary cultures of rat fetal distal lung epithelial cells. DEX significantly induced alphaENaC mRNA in fetal (3%) and postnatal (21%) O2, but increases in alphaENaC protein synthesis and function occurred only when epithelia were grown under a postnatal PO2. Sucrose density gradient analyses showed that DEX treatment of cells cultured at 3% O2 decreased the association of alphaENaC mRNA with large polysomes and enhanced the association with small polysomes. Conversely, incubation of DEX-treated cells in 21% O2 restored alphaENaC mRNA association with large polysomes. No significant changes were seen in the overall polyribosome profiles or in the distribution of mRNAs encoding beta and gamma subunits of ENaC or cytokeratin 18, indicating specific modulation of alphaENaC mRNA translation. These data suggest that postnatal O2 exposure may be important for efficient translation of the alphaENaC mRNA.
Collapse
Affiliation(s)
- Gail Otulakowski
- Programme in Lung Biology Research, Hospital for Sick Children Research Institute, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
| | | | | | | |
Collapse
|
7
|
Otulakowski G, Rafii B, O'Brodovich H. Differential translational efficiency of ENaC subunits during lung development. Am J Respir Cell Mol Biol 2003; 30:862-70. [PMID: 14672917 DOI: 10.1165/rcmb.2003-0381oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The amiloride-sensitive epithelial Na(+) channel (ENaC), the rate-limiting step in epithelial Na(+) transport, consists of three subunits: alpha, beta, and gamma. The abundance of mRNA encoding the alpha-subunit far surpasses the amount for other subunits, and considerably exceeds the predicted subunit protein stoichiometry. We evaluated 5'-untranslated region (UTR) expression and found that fetal rat lung uses alternative 5'UTRs for alpha-ENaC during development. Sucrose density gradient analysis of postnuclear supernatants from fetal rat lung homogenates demonstrated that all three ENaC subunits were associated with high molecular weight polysomes, indicating active translation of the mRNAs, but translational efficiency was much lower for the alpha-subunit. Sucrose density gradient distributions were comparable for the endogenously expressed alpha-ENaC 5'UTRs in rat lung at Fetal Day 20 or Postnatal Day 1 using Northern analysis. Although birth resulted in a global decrease in lung mRNA translation, the loading of ribosomes on ENaC subunit mRNAs was largely unaffected. Evaluation of cytokeratin 18 and vimentin mRNAs in these gradients suggested a cell-specific effect. We conclude that there are different translational efficiencies for ENaC subunits and that perinatal processes globally modulate lung mRNA translation.
Collapse
Affiliation(s)
- Gail Otulakowski
- CIHR Group in Lung Development, Research Institute of the Hospital for Sick Children, Programme in Lung Biology Research, 555 University Avenue, Toronto, ON, M5G 1X8 Canada.
| | | | | |
Collapse
|
8
|
Hao H, Wendt CH, Sandhu G, Ingbar DH. Dexamethasone stimulates transcription of the Na+-K+-ATPase beta1 gene in adult rat lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 2003; 285:L593-601. [PMID: 12754184 DOI: 10.1152/ajplung.00037.2003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Na+-K+-ATPase plays an essential role in active alveolar epithelial fluid resorption. In fetal and adult alveolar epithelial cells, glucocorticoids (GC) increase Na+-K+-ATPase activity and mRNA levels. We sought to define the mechanism of Na+-K+-ATPase gene upregulation by GC. In a rat alveolar epithelial cell line (RLE), dexamethasone (Dex) increased beta1-subunit Na+-K+-ATPase mRNA expression two- to threefold within 3 h after exposure to the GC. The increased gene expression was due to increased transcription as demonstrated by nuclear run-on assays, whereas mRNA stability remained unchanged. Transient transfection of 5' deletion mutants of a beta1 promoter-reporter construct demonstrated a 1.5- to 2.2-fold increase in promoter activity by Dex. All of the 5' deletion constructs contained partial or palindromic GC regulatory elements (GRE) and responded to GC. The increased expression of promoter reporter was inhibited by RU-486, a GC receptor (GR) antagonist, suggesting the involvement of GR. The palindromic GRE at -631 demonstrated Dex induction in a heterologous promoter construct. Gel mobility shift assays using RLE nuclear extracts demonstrated specific binding to this site and the presence of GR. We conclude that GC directly stimulate transcription of Na+-K+-ATPase beta1 gene expression in adult rat lung epithelial cells through a GR-dependent mechanism that can act at multiple sites.
Collapse
Affiliation(s)
- Hong Hao
- Pulmonary and Critical Care Div., Dept. of Medicine, MMC 276, Univ. of Minnesota, Minneapolis, MN 55455, USA
| | | | | | | |
Collapse
|
9
|
O'Grady SM, Lee SY. Chloride and potassium channel function in alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2003; 284:L689-700. [PMID: 12676759 DOI: 10.1152/ajplung.00256.2002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electrolyte transport across the adult alveolar epithelium plays an important role in maintaining a thin fluid layer along the apical surface of the alveolus that facilitates gas exchange across the epithelium. Most of the work published on the transport properties of alveolar epithelial cells has focused on the mechanisms and regulation of Na(+) transport and, in particular, the role of amiloride-sensitive Na(+) channels in the apical membrane and the Na(+)-K(+)-ATPase located in the basolateral membrane. Less is known about the identity and role of Cl(-) and K(+) channels in alveolar epithelial cells, but studies are revealing important functions for these channels in regulation of alveolar fluid volume and ionic composition. The purpose of this review is to examine previous work published on Cl(-) and K(+) channels in alveolar epithelial cells and to discuss the conclusions and speculations regarding their role in alveolar cell transport function.
Collapse
Affiliation(s)
- Scott M O'Grady
- Department of Physiology, University of Minnesota, St. Paul, Minnesota 55108, USA.
| | | |
Collapse
|
10
|
Beneke S, Rooney SA. Glucocorticoids regulate expression of the fatty acid synthase gene in fetal rat type II cells. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1534:56-63. [PMID: 11750887 DOI: 10.1016/s1388-1981(01)00178-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Fatty acids are integral components of pulmonary surfactant, a mixture of phospholipids and specific proteins that lines the alveolar surface and is essential for normal lung function. There are developmental increases in fatty acid biosynthesis and surfactant production in late-gestation fetal lung, and both processes are accelerated by glucocorticoids. Fatty acid synthase (FAS) is a key enzyme in de novo fatty acid biosynthesis, and increased FAS activity is responsible for the developmental and hormone-induced increases in fatty acid biosynthesis in fetal lung. Using cultured fetal lung explants, it has been reported that dexamethasone (Dex) increases FAS activity, protein content, mRNA content and rate of transcription. However, FAS expression has not been measured in isolated type II cells, the cellular source of surfactant within the lung. In the present study we measured parameters of FAS expression in type II cells isolated from the lungs of Dex-treated rats. Pregnant rats were injected with Dex or saline on days 18 and 19 of gestation and the fetuses delivered on day 20. Type II cells and fibroblasts were then isolated from the fetal lungs. Dex increased FAS activity, protein content, mRNA content and rate of transcription in the type II cells but not in the fibroblasts. Increased FAS expression in fetal type II cells in response to Dex is consistent with a critical role for FAS in the biosynthesis of lung surfactant.
Collapse
Affiliation(s)
- S Beneke
- Division of Perinatal Medicine, Department of Pediatrics, Yale University School of Medicine, P.O. Box 208064, New Haven, CT 06520-8064, , USA
| | | |
Collapse
|
11
|
Dagenais A, Denis C, Vives MF, Girouard S, Massé C, Nguyen T, Yamagata T, Grygorczyk C, Kothary R, Berthiaume Y. Modulation of alpha-ENaC and alpha1-Na+-K+-ATPase by cAMP and dexamethasone in alveolar epithelial cells. Am J Physiol Lung Cell Mol Physiol 2001; 281:L217-30. [PMID: 11404265 DOI: 10.1152/ajplung.2001.281.1.l217] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
cAMP and dexamethasone are known to modulate Na+ transport in epithelial cells. We investigated whether dibutyryl cAMP (DBcAMP) and dexamethasone modulate the mRNA expression of two key elements of the Na+ transport system in isolated rat alveolar epithelial cells: alpha-, beta-, and gamma-subunits of the epithelial Na+ channel (ENaC) and the alpha1- and beta1-subunits of Na+-K+-ATPase. The cells were treated for up to 48 h with DBcAMP or dexamethasone to assess their long-term impact on the steady-state level of ENaC and Na+-K+-ATPase mRNA. DBcAMP induced a twofold transient increase of alpha-ENaC and alpha1-Na+-K+-ATPase mRNA that peaked after 8 h of treatment. It also upregulated beta- and gamma-ENaC mRNA but not beta1-Na+-K+-ATPase mRNA. Dexamethasone augmented alpha-ENaC mRNA expression 4.4-fold in cells treated for 24 h and also upregulated beta- and gamma-ENaC mRNA. There was a 1.6-fold increase at 8 h of beta1-Na+-K+-ATPase mRNA but no significant modulation of alpha1-Na+-K+-ATPase mRNA expression. Because DBcAMP and dexamethasone did not increase the stability of alpha-ENaC mRNA, we cloned 3.2 kb of the 5' sequences flanking the mouse alpha-ENaC gene to study the impact of DBcAMP and dexamethasone on alpha-ENaC promoter activity. The promoter was able to drive basal expression of the chloramphenicol acetyltransferase (CAT) reporter gene in A549 cells. Dexamethasone increased the activity of the promoter by a factor of 5.9. To complete the study, the physiological effects of DBcAMP and dexamethasone were investigated by measuring transepithelial current in treated and control cells. DBcAMP and dexamethasone modulated transepithelial current with a time course reminiscent of the profile observed for alpha-ENaC mRNA expression. DBcAMP had a greater impact on transepithelial current (2.5-fold increase at 8 h) than dexamethasone (1.8-fold increase at 24 h). These results suggest that modulation of alpha-ENaC and Na+-K+-ATPase gene expression is one of the mechanisms that regulates Na+ transport in alveolar epithelial cells.
Collapse
Affiliation(s)
- A Dagenais
- Département de Médecine, Centre Hospitalier de l'Université de Montréal-Hôtel-Dieu, Université de Montréal, Montreal, Quebec H2W 1T8, Canada.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Isohama Y, Rooney SA. Glucocorticoid enhances the response of type II cells from newborn rats to surfactant secretagogues. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1531:241-50. [PMID: 11325615 DOI: 10.1016/s1388-1981(01)00107-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
There is a developmental increase in agonist-induced surfactant secretion in type II cells. The response to the P2Y(2) agonist UTP is negligible in early newborn cells but increases with age. The response to terbutaline, N-ethylcarboxyamidoadenosine (NECA), and ATP also increases with age. As glucocorticoids are known to accelerate several aspects of lung maturation we examined the effect of dexamethasone (Dex) on the response of 1-day-old rat type II cells to surfactant secretagogues. Freshly isolated cells were cultured +/-10(-6) M Dex for 18--20 h after which phosphatidylcholine secretion was measured. Dex slightly decreased the basal secretion rate. However, it significantly increased the response to terbutaline, NECA, ATP and UTP. This effect was dependent on Dex concentration (EC(50)=2-6 x 10(-9) M) and blocked by the glucocorticoid receptor antagonist RU-486. It is unlikely to be due to increased receptor content as Dex had no effect on adenylate cyclase, phospholipase C or phospholipase D activation and the response to cAMP, forskolin and phorbol ester, secretagogues acting downstream from receptors, was also increased by Dex. These data show that Dex acts directly on the type II cell to enhance the response to surfactant secretagogues, that the effect of the hormone is mediated by the glucocorticoid receptor and suggest induction of a common downstream signaling step(s). Regulation of surfactant secretion may be an important function of glucocorticoids in the developing lung.
Collapse
Affiliation(s)
- Y Isohama
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520-8064, USA
| | | |
Collapse
|
13
|
Abstract
The Na(+) pump and its regulation is important for maintaining membrane potential and transmembrane Na(+) gradient in all mammalian cells and thus is essential for cell survival and function. Vascular smooth muscle cells (VSMC) have a relatively low number of pump sites on their membrane compared with other cells. We wished to determine the mechanisms for regulating the number of pump sites in these cells. We used canine saphenous vein VSMC cultured in 10% serum and passaged one time. These cells were subcultured in 5% serum media with low K(+) (1 mM vs. control of 5 mM), and their pump expression was assessed. These VSMC upregulated their pump sites as early as 4 h after treatment (measured by [(3)H]ouabain binding). At this early time point, there was no detectable increase in protein expression of either alpha(1)- or beta(1)-subunits of the pump shown by Western blots. When the cells were treated with the phosphoinositide 3-kinase (PI-3-K) inhibitor LY-294002 (which is known to inhibit cytoplasmic transport processes) in low-K(+) media, the pump site upregulation was inhibited. These data suggest that the low-K(+)-induced upregulation of Na(+) pump number can occur by translocation of preformed pumps from intracellular stores.
Collapse
Affiliation(s)
- A Aydemir-Koksoy
- Cardiovascular Sciences Section, Department of Molecular Physiology, Baylor College of Medicine, Houston, Texas 77030, USA
| | | |
Collapse
|
14
|
Lazrak A, Samanta A, Venetsanou K, Barbry P, Matalon S. Modification of biophysical properties of lung epithelial Na(+) channels by dexamethasone. Am J Physiol Cell Physiol 2000; 279:C762-70. [PMID: 10942727 DOI: 10.1152/ajpcell.2000.279.3.c762] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is considerable interest in identifying the basic mechanisms by which dexamethasone alters ion transport across the adult alveolar epithelium. Herein, we incubated synchronized A549 cells, a human alveolar epithelial cell line, with dexamethasone (1 microM) for 24-48 h. When normalized to HPRT (a housekeeping gene), A549 beta- and gamma-subunit mRNA levels for the human amiloride-sensitive epithelial sodium channel (hENaC), assessed by RT-PCR, increased by 1.6- and 17-fold respectively, compared with control values (P < 0.05). These changes were abolished by actinomycin D, indicating transcriptional regulation. Western blotting studies revealed that dexamethasone also increased expression of beta- and gamma-hENaC protein levels. In contrast, alpha-hENaC mRNA increased by onefold (P > 0.05) and alpha-hENaC protein level was unchanged. Incubation of A549 cells with dexamethasone increased their whole cell amiloride-sensitive sodium currents twofold and decreased the K(0.5) for amiloride from 833 +/- 69 to 22 +/- 5.4 nM (mean +/- SE; P < 0.01). Single channel recordings in the cell-attached mode showed that dexamethasone treatment increased single channel open time and open probability threefold and decreased channel conductance from 8.63 +/- 0.036 to 4. 4 +/- 0.027 pS (mean +/- SE; P < 0.01). We concluded that dexamethasone modulates the amiloride-sensitive Na(+) channels by differentially regulating the expression of beta- and gamma-subunits at the mRNA and protein levels in the human A549 cell line, with little effect on alpha-hENaC subunit.
Collapse
Affiliation(s)
- A Lazrak
- Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA
| | | | | | | | | |
Collapse
|