Modification of biophysical properties of lung epithelial Na+ channels by dexamethasone

2000 ◽  
Vol 279 (3) ◽  
pp. C762-C770 ◽  
Author(s):  
A. Lazrak ◽  
A. Samanta ◽  
K. Venetsanou ◽  
P. Barbry ◽  
S. Matalon
Keyword(s):  
Cell Line ◽  
Single Channel ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Alveolar Epithelium ◽  
Housekeeping Gene ◽  
Epithelial Cell Line ◽  
Mrna Levels ◽  
Open Probability ◽  
Protein Levels

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 μM) for 24–48 h. When normalized to HPRT (a housekeeping gene), A549 β- and γ-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 β- and γ-hENaC protein levels. In contrast, α-hENaC mRNA increased by onefold ( P > 0.05) and α-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 β- and γ-subunits at the mRNA and protein levels in the human A549 cell line, with little effect on α-hENaC subunit.

Glucocorticoid-stimulated lung epithelial Na+ transport is associated with regulated ENaC andsgk1 expression

2002 ◽  
Vol 282 (4) ◽  
pp. L631-L641 ◽  
Author(s):  
Omar A. Itani ◽  
Scott D. Auerbach ◽  
Russell F. Husted ◽  
Kenneth A. Volk ◽  
Shana Ageloff ◽  
...  
Keyword(s):  
Cell Line ◽  
Single Channel ◽  
A549 Cells ◽  
Epithelial Cell Line ◽  
Alveolar Type ◽  
Xenopus Laevis Oocytes ◽  
Biophysical Properties ◽  
Transport Pathway ◽  
Slow Kinetics ◽  
Single Channel Currents

H441 cells, a bronchiolar epithelial cell line, develop a glucocorticoid-regulated amiloride-sensitive Na+ transport pathway on permeable supports (R. Sayegh, S. D. Auerbach, X. Li, R. Loftus, R. Husted, J. B. Stokes, and C. P. Thomas. J Biol Chem 274: 12431–12437, 1999). To understand its molecular basis, we examined the effect of glucocorticoids (GC) on epithelial Na+ channel (ENaC)-α, -β, and -γ and sgk1 expression and determined the biophysical properties of Na+ channels in these cells. GC stimulated the expression of ENac-α, -β, and -γ and sgk1 mRNA, with the first effect seen by 1 h. These effects were abolished by actinomycin D, but not by cycloheximide, indicating a direct stimulatory effect on ENaC and sgk1 mRNA synthesis. The GC effect on transcription of ENaC-α mRNA was accompanied by a significant increase in ENaC-α protein levels. GC also stimulated ENaC-α, -β, and -γ and sgk1 mRNA expression in A549 cells, an alveolar type II cell line. To determine the biophysical properties of the Na+channel, single-channel currents were recorded from cell-attached H441 membranes. An Na+-selective channel with slow kinetics and a slope conductance of 10.8 pS was noted, properties similar to ENaC-α, -β, and -γ expressed in Xenopus laevis oocytes. These experiments indicate that amiloride-sensitive Na+ transport is mediated through classic ENaC channels in human lung epithelia and that GC-regulated Na+ transport is accompanied by increased transcription of each of the component subunits and sgk1.

scholarly journals Anti-Fibrosis Effects of Magnesium Lithospermate B in Experimental Pulmonary Fibrosis: By Inhibiting TGF-βRI/Smad Signaling

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1715
Author(s):  
Xin Luo ◽  
Qiangqiang Deng ◽  
Yaru Xue ◽  
Tianwei Zhang ◽  
Zhitao Wu ◽  
...  
Keyword(s):  
Pulmonary Fibrosis ◽  
Cell Line ◽  
Molecular Mechanisms ◽  
Transforming Growth Factor ◽  
Salvia Miltiorrhiza ◽  
A549 Cells ◽  
Epithelial Cell Line ◽  
Human Lung Fibroblast ◽  
Magnesium Lithospermate B

Pulmonary fibrosis is a severe and irreversible interstitial pulmonary disease with high mortality and few treatments. Magnesium lithospermate B (MLB) is a hydrosoluble component of Salvia miltiorrhiza and has been reported to have antifibrotic effects in other forms of tissue fibrosis. In this research, we studied the effects of MLB on pulmonary fibrosis and the underlying mechanisms. Our results indicated that MLB treatment (50 mg/kg) for seven days could attenuate bleomycin (BLM)-induced pulmonary fibrosis by reducing the alveolar structure disruption and collagen deposition in the C57 mouse model. MLB was also found to inhibit transforming growth factor-beta (TGF-β)-stimulated myofibroblastic transdifferentiation of human lung fibroblast cell line (MRC-5) cells and collagen production by human type II alveolar epithelial cell line (A549) cells, mainly by decreasing the expression of TGF-β receptor I (TGF-βRI) and regulating the TGF-β/Smad pathway. Further studies confirmed that the molecular mechanisms of MLB in BLM-induced pulmonary fibrosis mice were similar to those observed in vitro. In summary, our results demonstrated that MLB could alleviate experimental pulmonary fibrosis both in vivo and in vitro, suggesting that MLB has great potential for pulmonary fibrosis treatment.

Effect of Steroids on the Synthesis of Complement C3 in a Human Alveolar Epithelial Cell Line

1993 ◽  
Vol 19 (5) ◽  
pp. 603-616 ◽  
Author(s):  
Terence L. Zach ◽  
Vicki A. Herrman ◽  
Laura D. Hill ◽  
M. Patricia Leuschen
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Alveolar Epithelial Cell ◽  
Complement C3 ◽  
Epithelial Cell Line ◽  
Alveolar Epithelial ◽  
Human Alveolar Epithelial Cell

A new rat type I-like alveolar epithelial cell line R3/1: bleomycin effects on caveolin expression

2004 ◽  
Vol 121 (6) ◽  
Author(s):  
Roland Koslowski ◽  
Kathrin Barth ◽  
Antje Augstein ◽  
Thomas Tschernig ◽  
Gerhard Bargsten ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Alveolar Epithelial Cell ◽  
Epithelial Cell Line ◽  
Type I ◽  
Alveolar Epithelial

scholarly journals Hepatocyte nuclear factor 4α regulates the expression of intestinal epithelial Na+/H+ exchanger isoform 3

2018 ◽  
Vol 314 (1) ◽  
pp. G14-G21 ◽  
Author(s):  
Saminathan Muthusamy ◽  
Jong Jin Jeong ◽  
Ming Cheng ◽  
Jessica A. Bonzo ◽  
Anoop Kumar ◽  
...  
Keyword(s):  
Promoter Activity ◽  
Core Promoter ◽  
Epithelial Cell Line ◽  
Mrna Levels ◽  
Nuclear Factor ◽  
Intestinal Epithelial ◽  
Hepatocyte Nuclear Factor ◽  
Mobility Shift ◽  
Protein Levels ◽  
Hepatocyte Nuclear Factor 4Α

Na+/H+ exchanger isoform 3 (NHE3) plays a key role in coupled electroneutral NaCl absorption in the mammalian intestine. Reduced NHE3 expression or function has been implicated in the pathogenesis of diarrhea associated with inflammatory bowel disease (IBD) or enteric infections. Our previous studies revealed transcriptional regulation of NHE3 by various agents such as TNF-α, IFN-γ, and butyrate involving transcription factors Sp1 and Sp3. In silico analysis revealed that the NHE3 core promoter also contains a hepatocyte nuclear factor 4α (HNF-4α) binding site that is evolutionarily conserved in several species suggesting that HNF-4α has a role in NHE3 regulation. Nhe3 mRNA levels were reduced in intestine-specific Hnf4α-null mice. However, detailed mechanisms of NHE3 regulation by HNF-4α are not known. We investigated the regulation of NHE3 gene expression by HNF-4α in vitro in the human intestinal epithelial cell line C2BBe1 and in vivo in intestine-specific Hnf4α-null ( Hnf4αΔIEpC) and control ( Hnf4αfl/fl) mice. HNF-4α knockdown by short interfering RNA in C2BBe1 cells significantly decreased NHE3 mRNA and NHE3 protein levels. Gel mobility shift and chromatin immunoprecipitation assays revealed that HNF-4α directly interacts with the HNF-4α motif in the NHE3 core promoter. Site-specific mutagenesis on the HNF-4α motif decreased, whereas ectopic overexpression of HNF-4α increased, NHE3 promoter activity. Furthermore, loss of HNF-4α in Hnf4αΔIEpC mice decreased colonic Nhe3 mRNA and NHE3 protein levels. Our results demonstrate a novel role for HNF-4α in basal regulation of NHE3 expression. These studies represent an important and novel target for therapeutic intervention in IBD-associated diarrhea. NEW & NOTEWORTHY Our studies for the first time show that hepatocyte nuclear factor 4α directly regulates NHE3 promoter activity and its basal expression in the intestine.

Effect of divalent heavy metals on epithelial Na+ channels in A6 cells

2007 ◽  
Vol 293 (1) ◽  
pp. F236-F244 ◽  
Author(s):  
Ling Yu ◽  
Douglas C. Eaton ◽  
My N. Helms
Keyword(s):  
Heavy Metal ◽  
Voltage Dependence ◽  
Transmembrane Domain ◽  
Single Channel ◽  
Epithelial Cell Line ◽  
Open Probability ◽  
Renal Epithelial Cell ◽  
Histidine Residues ◽  
Voltage Dependent ◽  
Renal Epithelial Cell Line

To better understand how renal Na+ reabsorption is altered by heavy metal poisoning, we examined the effects of several divalent heavy metal ions (Zn2+, Ni2+, Cu2+, Pb2+, Cd2+, and Hg2+) on the activity of single epithelial Na+ channels (ENaC) in a renal epithelial cell line (A6). None of the cations changed the single-channel conductance. However, ENaC activity [measured as the number of channels ( N) × open probability ( Po)] was decreased by Cd2+ and Hg2+ and increased by Cu2+, Zn2+, and Ni2+ but was not changed by Pb2+. Of the cations that induced an increase in Na+ channel function, Zn2+ increased N, Ni2+ increased Po, and Cu2+ increased both. The cysteine modification reagent [2-(trimethylammonium)ethyl]methanethiosulfonate bromide also increased N, whereas diethylpyrocarbonate, which covalently modifies histidine residues, affected neither Po nor N. Cu2+ increased N and stimulated Po by reducing Na+ self-inhibition. Furthermore, we observed that ENaC activity is slightly voltage dependent and that the voltage dependence of ENaC is insensitive to extracellular Na+ concentration; however, apical application of Ni2+ or diethylpyrocarbonate reduced the channel voltage dependence. Thus the voltage sensor of Xenopus ENaC is different from that of typical voltage-gated channels, since voltage appears to be sensed by histidine residues in the extracellular loops of ENaC, rather than by charged amino acids in a transmembrane domain.

Coordinate expression of amplified metallothionein I and II genes in cadmium-resistant Chinese hamster cells

1985 ◽  
Vol 5 (12) ◽  
pp. 3525-3531
Author(s):  
J K Griffith
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Recombinant Dna ◽  
Chinese Hamster ◽  
Single Copy ◽  
Ovary Cell ◽  
Gene Copy ◽  
Mrna Levels ◽  
Protein Levels ◽  
Copy Numbers

Recombinant DNA probes complementary to Chinese hamster metallothionein (MT)-1 and MT-2 mRNAs were used to compare MT gene copy numbers, zinc-induced MT mRNA levels, and uninduced MT mRNA levels in cadmium-resistant (Cdr) Chinese hamster ovary cell lines. Quantitative hybridization analyses determined that the MT-1 and MT-2 genes are each present at approximately single-copy levels in the genome of cell line Cdr2C10 and are coordinately amplified approximately 7, 3, and 12 times over the Cdr2C10 value in the genomes of cell lines Cdr20F4, Cdr30F9, and Cdr200T1, respectively. The maximum zinc-induced MT-1 mRNA concentrations in cell lines Cdr20F4, Cdr30F9, and Cdr200T1 were equal to 1, 3, and 15 times that measured in Cdr2C10, respectively. Similarly, the maximum zinc-induced MT-2 mRNA concentrations were equal to 1, 3, and 14 times that measured in Cdr2C10, respectively, and in each instance they were 90 to 150 times greater than their respective concentrations in uninduced cells. Thus, relative MT gene numbers are closely correlated with both zinc-induced and uninduced MT mRNA levels in Cdr2C10, Cdr30F9, and Cdr200T1, but not in Cdr20F4. Each of the latter two lines possesses structurally altered chromosomes whose breakpoints are near the MT locus. Nonetheless, the ratio of the levels of MT-1 to MT-2 mRNAs was constant in each of the four cell lines, including Cdr20F4. These results demonstrate that MT-1 and MT-2 mRNAs are induced coordinately in each Cdr cell line. Therefore, the coordination of the induction of MT-1 and MT-2 mRNA is independent of MT gene amplification, MT gene rearrangement, and the relative inducibilities of amplified MT genes. However, MT mRNA and protein levels each indicate that MT-1 and MT-2 expression is non-coordinate in uninduced cells. Thus, regulation of MT expression may involve two different mechanisms which are differentially operative in induced and uninduced cells.

Lactobacilli intra-tracheal administration protects from Pseudomonas aeruginosa pulmonary infection in mice – a proof of concept

2019 ◽  
Vol 10 (8) ◽  
pp. 893-900 ◽  
Author(s):  
M.S. Fangous ◽  
Y. Alexandre ◽  
N. Hymery ◽  
S. Gouriou ◽  
D. Arzur ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Murine Model ◽  
Alveolar Epithelial Cell ◽  
A549 Cells ◽  
Respiratory Pathogen ◽  
Public Health Issue ◽  
Epithelial Cell Line ◽  
High Morbidity ◽  
Respiratory Pathogens

The spreading of antibiotic resistance is a major public health issue, which requires alternative treatments to antibiotics. Lactobacilli have shown abilities to prevent pneumonia in clinical studies when given by oral route, certainly through the gut-lung axis involvement. Rationally, respiratory administration of lactobacilli has been developed and studied in murine model, to prevent from respiratory pathogens. It allows a direct effect of probiotics into the respiratory system. To our knowledge, no study has ever focused on the effect of probiotic intra-respiratory administration to prevent from Pseudomonas aeruginosa (PA) pneumonia, a major respiratory pathogen associated with high morbidity rates. In this study, we evaluated the beneficial activity of three Lactobacillus strains (Lactobacillus fermentum K.C6.3.1E, Lactobacillus zeae Od.76, Lactobacillus paracasei ES.D.88) previously screened by ourselves and known to be particularly efficient in vitro in inhibiting PAO1 virulence factors. Cytotoxic assays in alveolar epithelial cell line A549 were performed, followed by the comparison of two lactobacilli prophylactic protocols (one or two administrations) by intra-tracheal administration in a C57BL/6 murine model of PA pneumonia. A549 cells viability was improved from 23 to 75% when lactobacilli were administered before PAO1 incubation, demonstrating a protective effect (P<0.001). A significant decrease of 2 log of PAO1 was observed 4 h after PAO1 instillation (3×106 cfu/mouse) in both groups receiving lactobacilli (9×106 cfu/mouse) compared to PAO1 group (P<0.05). One single prophylactic administration of lactobacilli significantly decreased the secretion by 50% in bronchoalveolar lavages of interleukin (IL)-6 and tumour necrosis factor-α compared to PAO1. No difference of secretion was observed for the IL-10 secretion, whatever the prophylactic study design. This is the first study highlighting that direct lung administration of Lactobacillus strains protect against PA pneumonia. Next step will be to decipher the mechanisms involved before developing this novel approach for human applications.

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