1
|
Tan J, Gao C, Wang C, Ma L, Hou X, Liu X, Li Z. Expression of Aquaporin-1 and Aquaporin-5 in a Rat Model of High-Altitude Pulmonary Edema and the Effect of Hyperbaric Oxygen Exposure. Dose Response 2020; 18:1559325820970821. [PMID: 33192205 PMCID: PMC7607770 DOI: 10.1177/1559325820970821] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 09/24/2020] [Accepted: 10/08/2020] [Indexed: 11/29/2022] Open
Abstract
Objective: To investigate the therapeutic roles of hyperbaric oxygen exposure on high-altitude pulmonary edema and to determine whether aquaporin-1 and aquaporin-5 were involved in the pathogenesis of HAPE in rats. Methods: Rats were divided into 5 groups: The control group, the HAPE group (HAPE model), the HBO group (hyperbaric oxygen exposure), the NBO group (normobaric oxygen exposure), and the NA group (normal air exposure). Western blot and real-time PCR were used to analyze the pulmonary expressions of AQP1 and AQP5. The wet-to-dry (W/D) weight ratio and the morphology of the lung were also examined. Results: The lung W/D weight ratio in the HAPE group was increased compared with the control group. The injury score in the HBO group was noticeably lower than that in the control group. The mRNA and proteins expressions of AQP1 and AQP5 were significantly downregulated in the HAPE group. Conclusions: Oxygen exposure alleviated high-altitude hypobaric hypoxia-induced lung injury in rats. Additionally, HBO therapy had significant advantage on interstitial HAPE.
Collapse
Affiliation(s)
- Jiewen Tan
- Department of Rehabilitation Medicine, XinHua College, Sun Yat-Sen University, Guangzhou, China
| | - Chunjin Gao
- Department of Hyperbaric Oxygen, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Cong Wang
- Department of Hyperbaric Oxygen, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Linlin Ma
- Department of Hyperbaric Oxygen, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Xiaomin Hou
- Department of Hyperbaric Oxygen, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Xuehua Liu
- Department of Hyperbaric Oxygen, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, China
| | - Zhuo Li
- Department of Rehabilitation Medicine, XinHua College, Sun Yat-Sen University, Guangzhou, China
| |
Collapse
|
2
|
Kuzmenko NV. Seasonal Variations in Atmospheric Pressure, Partial Oxygen Density, and Geomagnetic Activity as Additional Synchronizers of Circannual Rhythms. Biophysics (Nagoya-shi) 2019. [DOI: 10.1134/s0006350919040080] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
3
|
Mahalanobish S, Saha S, Dutta S, Sil PC. Mangiferin alleviates arsenic induced oxidative lung injury via upregulation of the Nrf2-HO1 axis. Food Chem Toxicol 2019; 126:41-55. [PMID: 30769048 DOI: 10.1016/j.fct.2019.02.022] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/15/2019] [Accepted: 02/08/2019] [Indexed: 01/12/2023]
Abstract
Arsenic contaminated drinking water consumption is a serious health issue around the world. Chronic inorganic arsenic exposure has been associated with respiratory dysfunctions. It exerts various detrimental effects, disrupting normal cellular homeostasis and turning on severe pulmonary complications. This study elucidated the role of mangiferin, a natural xanthone, against arsenic induced lung toxicity. Chronic exposure of sodium arsenite (NaAsO2) at 10 mg/kg bw for 3 months abruptly increased the LDH release in broncho-alveolar lavage fluid, generated reactive oxygen species (ROS), impaired the antioxidant defense and distorted the alveoli architecture. It caused significant inflammatory outburst and promoted the apoptotic mode of cell death via upregulating the expressions of various proapoptotic molecules related to mitochondrial, extra-mitochondrial and ER stress mediated apoptotic pathway. Activation of inflammatory cascade led to disruption of alveolar capillary barrier and impaired Na+/K+-ATPase function that led to detaining of alveolar fluid clearance activity. Mangiferin due to its anti-inflammatory activity suppressed this inflammation and reduced inflammatory cell infiltration in lung tissue. It significantly restored the antioxidant balance and inhibited apoptosis in lung via upregulating Nrf2-HO1 axis.
Collapse
Affiliation(s)
- Sushweta Mahalanobish
- Division of Molecular Medicine, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata, 700054, India
| | - Sukanya Saha
- Division of Molecular Medicine, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata, 700054, India
| | - Sayanta Dutta
- Division of Molecular Medicine, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata, 700054, India
| | - Parames C Sil
- Division of Molecular Medicine, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata, 700054, India.
| |
Collapse
|
4
|
Clifford RJ, Kaplan JH. Regulation of Na,K-ATPase subunit abundance by translational repression. J Biol Chem 2009; 284:22905-15. [PMID: 19553675 PMCID: PMC2755698 DOI: 10.1074/jbc.m109.030536] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 06/22/2009] [Indexed: 01/10/2023] Open
Abstract
The Na,K-ATPase is an alphabeta heterodimer responsible for maintaining fluid and electrolyte homeostasis in mammalian cells. We engineered Madin-Darby canine kidney cell lines expressing alpha(1)FLAG, beta(1)FLAG, or beta(2)MYC subunits via a tetracycline-regulated promoter and a line expressing both stable beta(1)MYC and tetracycline-regulated beta(1)FLAG to examine regulatory mechanisms of sodium pump subunit expression. When overexpression of exogenous beta(1)FLAG increased total beta subunit levels by >200% without changes in alpha subunit abundance, endogenous beta(1) subunit (beta(1)E) abundance decreased. beta(1)E down-regulation did not occur during beta(2)MYC overexpression, indicating isoform specificity of the repression mechanism. Measurements of RNA stability and content indicated that decreased beta subunit expression was not accompanied by any change in mRNA levels. In addition, the degradation rate of beta subunits was not altered by beta(1)FLAG overexpression. Cells stably expressing beta(1)MYC, when induced to express beta(1)FLAG subunits, showed reduced beta(1)MYC and beta(1)E subunit abundance, indicating that these effects occur via the coding sequences of the down-regulated polypeptides. In a similar way, Madin-Darby canine kidney cells overexpressing exogenous alpha(1)FLAG subunits exhibited a reduction of endogenous alpha(1) subunits (alpha(1)E) with no change in alpha mRNA levels or beta subunits. The reduction in alpha(1)E compensated for alpha(1)FLAG subunit expression, resulting in unchanged total alpha subunit abundance. Thus, regulation of alpha subunit expression maintained its native level, whereas beta subunit was not as tightly regulated and its abundance could increase substantially over native levels. These effects also occurred in human embryonic kidney cells. These data are the first indication that cellular sodium pump subunit abundance is modulated by translational repression. This mechanism represents a novel, potentially important mechanism for regulation of Na,K-ATPase expression.
Collapse
Affiliation(s)
- Rebecca J. Clifford
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607
| | - Jack H. Kaplan
- From the Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60607
| |
Collapse
|
5
|
Matchett GA, Martin RD, Zhang JH. Hyperbaric oxygen therapy and cerebral ischemia: neuroprotective mechanisms. Neurol Res 2009; 31:114-21. [PMID: 19298750 DOI: 10.1179/174313209x389857] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
INTRODUCTION Numerous studies have demonstrated a protective effect of hyperbaric oxygen therapy in experimental ischemic brain injury, and many physiological and molecular mechanisms of hyperbaric oxygen therapy-related neuroprotection have been identified. METHODS Review of articles pertaining to hyperbaric oxygen therapy and cerebral ischemia in the National Library of Medicine and National Institutes of Health database, emphasizing mechanisms of hyperbaric oxygen therapy-related neuroprotection. RESULTS Hyperbaric oxygen therapy has been shown to ameliorate brain injury in a variety of animal models including focal cerebral ischemia, global cerebral ischemia, neonatal hypoxia-ischemia and subarachnoid hemorrhage. Small human trials of hyperbaric oxygen therapy in focal ischemia have not shown benefit, although one trial of hyperbaric oxygen therapy before cardiopulmonary bypass demonstrated improved neuropsychological and inflammatory outcomes with hyperbaric oxygen therapy. Hyperbaric oxygen therapy is associated with improved cerebral oxygenation, reduced blood-brain barrier breakdown, decreased inflammation, reduced cerebral edema, decreased intracranial pressure, reduced oxidative burden, reduced metabolic derangement, decreased apoptotic cell death and increased neural regeneration. CONCLUSION On a molecular level, hyperbaric oxygen therapy leads to activation of ion channels, inhibition of hypoxia inducible factor-1alpha, up-regulation of Bcl-2, inhibition of MMP-9, decreased cyclooxygenase-2 activity, decreased myeloperoxidase activity, up-regulation of superoxide dismutase and inhibition of Nogo-A (an endogenous growth-inhibitory factor). Ongoing research will continue to describe the mechanisms of hyperbaric oxygen therapy-related neuroprotection, and possibly expand hyperbaric oxygen therapy use clinically.
Collapse
Affiliation(s)
- Gerald A Matchett
- Department of Anesthesiology, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA
| | | | | |
Collapse
|
6
|
Thome UH, Davis IC, Nguyen SV, Shelton BJ, Matalon S. Modulation of sodium transport in fetal alveolar epithelial cells by oxygen and corticosterone. Am J Physiol Lung Cell Mol Physiol 2003; 284:L376-85. [PMID: 12533313 DOI: 10.1152/ajplung.00218.2002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Regulation of active Na(+) transport across fetal distal lung epithelial cells (FDLE) by corticosterone (CST), corticotropin-releasing hormone (CRH), and oxygen tension may be crucial for postnatal adaptation. FDLE isolated from 19-day rat fetuses (term: 22 days) were grown on permeable supports to confluent monolayers (duration 3 days) in 2.5, 5, 12, or 20% O(2) with 5% CO(2)-balance N(2) and mounted in Ussing chambers for measurement of short-circuit currents (I(sc)). FDLE monolayers grown in 20% O(2) had significantly higher levels of total I(sc) and of their amiloride-sensitive (I(amil)) and ouabain-sensitive (I(ouab)) components than hypoxic cells. Values (microA/cm(2) +/- SE) for 2.5-5% O(2) and 20% O(2) were, respectively, I(sc) 5.3 +/- 0.2 vs. 8.4 +/- 0.3 (P < 0.001), I(amil) 3.4 +/- 0.2 vs. 4.3 +/- 0.2 (P < 0.01), and I(ouab) 3.4 +/- 0.6 vs. 9.1 +/- 0.6 (P < 0.001). Addition of CST but not CRH to the culture medium at any O(2) concentration increased I(amil). FDLE cells grown at 5% O(2) expressed significantly lower levels of alpha-, beta-, and gamma-epithelial Na(+) channel (ENaC), and of the alpha(1)-Na(+)-K(+)-ATPase, as determined by Western blotting. We conclude that higher O(2) concentrations increased total vectorial Na(+) transport, and the function of Na(+)-K(+)-ATPase and apical amiloride-sensitive Na(+) conductance, whereas CST only increased ENaC function.
Collapse
Affiliation(s)
- Ulrich H Thome
- Department of Pediatrics, University of Alabama at Birmingham, 901 19th Street South, Birmingham, AL 35226, USA
| | | | | | | | | |
Collapse
|
7
|
Matthay MA, Folkesson HG, Clerici C. Lung epithelial fluid transport and the resolution of pulmonary edema. Physiol Rev 2002; 82:569-600. [PMID: 12087129 DOI: 10.1152/physrev.00003.2002] [Citation(s) in RCA: 490] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The discovery of mechanisms that regulate salt and water transport by the alveolar and distal airway epithelium of the lung has generated new insights into the regulation of lung fluid balance under both normal and pathological conditions. There is convincing evidence that active sodium and chloride transporters are expressed in the distal lung epithelium and are responsible for the ability of the lung to remove alveolar fluid at the time of birth as well as in the mature lung when pathological conditions lead to the development of pulmonary edema. Currently, the best described molecular transporters are the epithelial sodium channel, the cystic fibrosis transmembrane conductance regulator, Na+-K+-ATPase, and several aquaporin water channels. Both catecholamine-dependent and -independent mechanisms can upregulate isosmolar fluid transport across the distal lung epithelium. Experimental and clinical studies have made it possible to examine the role of these transporters in the resolution of pulmonary edema.
Collapse
Affiliation(s)
- Michael A Matthay
- Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, California 94143-0624, USA.
| | | | | |
Collapse
|
8
|
Clerici C, Uchida T, Planès C, Matthay MA. Regulation of Gene Expression by Hypoxia in Lung Alveolar Epithelial Cells. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1568-1254(02)80004-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
|
9
|
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
|
10
|
Crandall ED, Matthay MA. Alveolar epithelial transport. Basic science to clinical medicine. Am J Respir Crit Care Med 2001; 163:1021-9. [PMID: 11282783 DOI: 10.1164/ajrccm.163.4.2006116] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- E D Crandall
- Department of Medicine, University of Southern California, Los Angeles, USA
| | | |
Collapse
|
11
|
Wendt CH, Gick G, Sharma R, Zhuang Y, Deng W, Ingbar DH. Up-regulation of Na,K-ATPase beta 1 transcription by hyperoxia is mediated by SP1/SP3 binding. J Biol Chem 2000; 275:41396-404. [PMID: 10988288 DOI: 10.1074/jbc.m004759200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sodium pump, Na,K-ATPase, is an important protein for maintaining intracellular ion concentration, cellular volume, and ion transport and is regulated both transcriptionally and post-transcriptionally. We previously demonstrated that hyperoxia increased Na,K-ATPase beta(1) gene expression in Madin-Darby canine kidney (MDCK) cells. In this study, we identify a DNA element necessary for up-regulation of the Na,K-ATPase beta(1) transcription by hyperoxia and evaluate the nuclear proteins responsible for this up-regulation. Transient transfection experiments in MDCK cells using sequential 5'-deletions of the rat Na,K-ATPase beta(1) promoter-luciferase fusion gene demonstrated promoter activation by hyperoxia between -102 and +151. The hyperoxia response was localized to a 7-base pair region between -62 and -55, which contained a GC-rich region consistent with a consensus sequence for the SP1 family, that was sufficient for up-regulation by hyperoxia. This GC element exhibited both basal and hyperoxia-induced promoter activity and bound both transcription factors SP1 and SP3 in electrophoretic mobility shift assays. In addition, electrophoretic mobility shift assays demonstrated increased binding of SP1/SP3 in cells exposed to hyperoxia while mutation of this element eliminated protein binding. Other GC sites within the proximal promoter also demonstrated up-regulation of transcription by hyperoxia, however, the site at -55 had higher affinity for SP proteins.
Collapse
Affiliation(s)
- C H Wendt
- University of Minnesota, Department of Medicine, Minneapolis, Minnesota 55455, USA.
| | | | | | | | | | | |
Collapse
|
12
|
Factor P, Dumasius V, Saldias F, Brown LA, Sznajder JI. Adenovirus-mediated transfer of an Na+/K+-ATPase beta1 subunit gene improves alveolar fluid clearance and survival in hyperoxic rats. Hum Gene Ther 2000; 11:2231-42. [PMID: 11084680 DOI: 10.1089/104303400750035753] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Pulmonary edema is cleared via active Na(+) transport by alveolar epithelial Na(+)/K(+)-ATPases and Na(+) channels. Rats exposed to acute hyperoxia have a high mortality rate, decreased Na(+)/K(+)-ATPase function, and decreased alveolar fluid clearance (AFC). We hypothesized that Na(+)/K(+)-ATPase subunit gene overexpression could improve AFC in rats exposed to hyperoxia. We delivered 4 x 10(9) PFU of recombinant adenoviruses containing rat alpha(1) and beta(1) Na(+)/K(+)-ATPase subunit cDNAs (adalpha(1) and adbeta(1), respectively) to rat lungs 7 days prior to exposure to 100% O(2) for 64 hr. As compared with controls and ad alpha(1), AFC in the adbeta(1) rats was increased by >300%. Permeability for large solutes was less in the ad beta(1) than in the other hyperoxia groups. Glutathione oxidation, but not superoxide dismutase activity, was increased only in the adbeta(1) group. Survival through 14 days of hyperoxia was 100% in the adbeta(1) group but was not different from hyperoxic controls in animals given adalpha(1). Our data show that overexpression of a beta(1) Na(+)/K(+)-ATPase subunit augments AFC and improves survival in this model of acute lung injury via antioxidant-independent mechanisms. Conceivably, restoration of AFC via gene transfer of Na(+)/K(+)-ATPase subunit genes may prove useful for the treatment of acute lung injury and pulmonary edema.
Collapse
Affiliation(s)
- P Factor
- Pulmonary and Critical Care Medicine, Evanston Northwestern Healthcare, Evanston, IL 60201, USA.
| | | | | | | | | |
Collapse
|
13
|
Wendt CH, Sharma R, Towle H, Gick G, Ingbar DH. Hyperoxia upregulated Na,K-adenosine triphosphatase beta1 gene transcription. Chest 1999; 116:87S-88S. [PMID: 10424606 DOI: 10.1378/chest.116.suppl_1.87s] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Affiliation(s)
- C H Wendt
- University of Minnesota Medical School, Minneapolis 55455, USA.
| | | | | | | | | |
Collapse
|
14
|
Acarregui MJ, Kumar AR, Penisten ST, Snyder JM. O2 regulates surfactant protein A mRNA transcription and stability in human fetal lung in vitro. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L343-50. [PMID: 9530169 DOI: 10.1152/ajplung.1998.274.3.l343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The effect of O2 on surfactant protein (SP) A mRNA transcription and half-life was determined in midtrimester human fetal lung tissue cultured in either 20 (control) or 70% O2. Incubation of tissues in 70% O2 resulted in a 133% increase in SP-A mRNA transcription rate compared with control tissues. The SP-A mRNA half-life was increased by 54% in lung tissues cultured in 70% O2 vs. control tissues. Western blot analysis indicated a threefold increase in SP-A in the 70% O2 condition, demonstrating that O2 regulation of SP-A mRNA levels results in corresponding changes in SP-A levels. Primer extension assays were performed to determine whether the observed increase in SP-A mRNA levels is secondary to the preferential expression of one of the human SP-A genes, SP-A1 or SP-A2. Transcripts of both the SP-A1 and SP-A2 genes were increased approximately 100% in tissues maintained in 70% O2 compared with control tissues. These data demonstrate that O2 regulates human SP-A mRNA levels by both transcriptional and posttranscriptional mechanisms. Furthermore, because there is no differential effect of O2 on the expression of SP-A1 vs. SP-A2 mRNA, the properties of these genes that mediate regulation by O2 must be conserved between the two genes.
Collapse
Affiliation(s)
- M J Acarregui
- Department of Pediatrics, University of Iowa College of Medicine, Iowa City 52242, USA
| | | | | | | |
Collapse
|
15
|
Wendt CH, Towle H, Sharma R, Duvick S, Kawakami K, Gick G, Ingbar DH. Regulation of Na-K-ATPase gene expression by hyperoxia in MDCK cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C356-64. [PMID: 9486124 DOI: 10.1152/ajpcell.1998.274.2.c356] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Na-K-ATPase plays a central role in a variety of physiological processes, including ion transport and regulation of cell volume. Our previous data showed that hyperoxia increased the expression of Na-K-ATPase alpha 1 and beta 1 mRNA in lung type II cells. We similarly show that hyperoxia (> or = 95% O2 for 24-48 h) increased steady-state mRNA levels in both Na-K-ATPase subunits in Madin-Darby canine kidney (MDCK) cells. The mechanism of gene regulation by hyperoxia was assessed. Stability of the Na-K-ATPase mRNA levels of both subunits was unchanged in hyperoxia-exposed MDCK cells. To determine whether gene transcription was augmented by hyperoxia, MDCK cells were transfected with a beta 1-subunit promoter-reporter construct. Transfection with the wild-type promoter (beta 1-817) revealed a 1.9 +/- 0.2-fold increase in promoter activity. Transfection with 5' deletion constructs identified a 61-base pair (bp) region between -102 and -41 that was necessary for this increase in promoter activity by hyperoxia. Incorporation of this 61-bp region into a minimal promoter (mouse mammary tumor virus) similarly increased promoter activity 2.3-fold in the presence of hyperoxia. This increase in promoter activity was not seen when MDCK cells were incubated with various concentrations of hydrogen peroxide. In summary, hyperoxia increased Na-K-ATPase beta 1-subunit mRNA steady-state level due to increased transcription in MDCK cells. A region necessary for this hyperoxic effect on beta 1 transcription is located between base pairs -102 and -41 on the promoter.
Collapse
Affiliation(s)
- C H Wendt
- University of Minnesota Medical School, Minneapolis 55455, USA
| | | | | | | | | | | | | |
Collapse
|