Ceramide decreases surfactant protein B gene expression via downregulation of TTF-1 DNA binding activity

University of Texas Health Science Center at Tyler, Tyler, Texas, United States
AJP Lung Cellular and Molecular Physiology (Impact Factor: 4.08). 03/2006; 290(2):L351-8. DOI: 10.1152/ajplung.00275.2005
Source: PubMed


Ceramide, a sphingolipid, is an important signaling molecule in the inflammatory response. Mediators of acute lung injury such as TNF-alpha, platelet-activating factor, and Fas/Apo ligand stimulate sphingomyelin hydrolysis to increase intracellular ceramide levels. Surfactant protein B (SP-B), a hydrophobic protein of pulmonary surfactant, is essential for surfactant function and lung stability. In this study we investigated the effects of ceramide on SP-B gene expression in H441 lung epithelial cells. Ceramide decreased SP-B mRNA levels in control and dexamethasone-treated cells after 24-h incubation and inhibition of SP-B mRNA was associated with inhibition of immunoreactive SP-B. In transient transfections assays, ceramide inhibited SP-B promoter activity, indicating that the inhibitory effects are exerted at the transcriptional level. Deletion mapping experiments showed that the ceramide-responsive region is located within the -233/-80-bp region of human SP-B promoter. Electrophoretic mobility shift and reporter assays showed that ceramide reduced the DNA binding activity and transactivation capability of thyroid transcription factor 1 (TTF-1/Nkx2.1), a key factor for SP-B promoter activity. Collectively these data showed that ceramide inhibits SP-B gene expression by reducing the DNA biding activity of TTF-1/Nkx2.1 transcription factor. Protein kinase C inhibitor bisindolylmaleimide and the protein tyrosine kinase inhibitor genistein partially reversed ceramide inhibition, indicating that protein kinases play important roles in the ceramide inhibition of SP-B gene expression. Chemical inhibitors of de novo ceramide synthesis and sphingomyelin hydrolysis had no effect on TNF-alpha inhibition of SP-B promoter activity and mRNA levels, suggesting that ceramide does not play a role in the inhibition.

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Available from: Vijayakumar Boggaram,
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    • "Ceramide has been shown to trigger apoptosis in an experimental mouse model of emphysema [22], and increased levels of apoptosis have been found in the lungs of patients with severe cigarette-induced emphysema [23]. Increased ceramide levels have also been shown to influence surfactant production [24] and activity [25]. Since ceramide levels are increased in the lungs of patients with smoke-induced emphysema [22] ceramide upregulation might be an important pathogenetic element in emphysema development. "
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    ABSTRACT: The aim of this manuscript was to characterize airway ceramide profiles in a rodent model of elastase-induced emphysema and to examine the effect of pharmacological intervention directed towards ceramide metabolism. Adult mice were anesthetized and treated with an intratracheal instillation of elastase. Lung function was measured, broncho-alveolar lavage fluid collected and histological and morphometrical analysis of lung tissue performed within 3 weeks after elastase injection, with and without sphingomyelinase inhibitors or serine palmitoyltransferase inhibitor. Ceramides in broncho-alveolar lavage (BAL) fluid were quantified by tandem mass spectrometry. BAL fluid showed a transient increase in total protein and IgM, and activated macrophages and neutrophils. Ceramides were transiently upregulated at day 2 after elastase treatment. Histology showed persistent patchy alveolar destruction at day 2 after elastase installation. Acid and neutral sphingomyelinase inhibitors had no effect on BAL ceramide levels, lung function or histology. Addition of a serine palmitoyltransferase inhibitor ameliorated lung function changes and reduced ceramides in BAL. Ceramides were increased during the acute inflammatory phase of elastase-induced lung injury. Since addition of a serine palmitoyltransferase inhibitor diminished the rise in ceramides and ameliorated lung function, ceramides likely contributed to the early phase of alveolar destruction and are a potential therapeutic target in the elastase model of lung emphysema.
    Respiratory research 10/2013; 14(1):96. DOI:10.1186/1465-9921-14-96 · 3.09 Impact Factor
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    • "These results suggest that there may be a decrease in phospholipase A2 activity that would degrade both cell membranes and surfactant to increase levels of these lipid species [35]. High levels of these lipids are known to increase the sensitivity to protein inhibition that decreases surfactant bioactivity and is observed in respiratory distress syndromes and lung injury [34], [35], [36]. "
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    ABSTRACT: Cyclic AMP Response Element-Binding Protein 1 (Creb1) is a transcription factor that mediates cyclic adenosine 3', 5'-monophosphate (cAMP) signalling in many tissues. Creb1(-/-) mice die at birth due to respiratory failure and previous genome-wide microarray analysis of E17.5 Creb1(-/-) fetal mouse lung identified important Creb1-regulated gene targets during lung development. The lipogenic enzymes stearoyl-CoA desaturase 1 (Scd1) and fatty acid synthase (Fasn) showed highly reduced gene expression in Creb1(-/-) lungs. We therefore hypothesized that Creb1 plays a crucial role in the transcriptional regulation of genes involved in pulmonary lipid biosynthetic pathways during lung development. In this study we confirmed that Scd1 and Fasn mRNA levels were down regulated in the E17.5 Creb1(-/-) mouse lung while the lipogenic-associated transcription factors SrebpF1, C/ebpα and Pparγ were increased. In vivo studies using germline (Creb1(-/-) ) and lung epithelial-specific (Creb1(EpiΔ/Δ) ) Creb1 knockout mice showed strongly reduced Scd1, but not Fasn gene expression and protein levels in lung epithelial cells. In vitro studies using mouse MLE-15 epithelial cells showed that forskolin-mediated activation of Creb1 increased both Scd1 gene expression and protein synthesis. Additionally, MLE15 cells transfected with a dominant-negative ACreb vector blocked forskolin-mediated stimulation of Scd1 gene expression. Lipid profiling in MLE15 cells showed that dominant-negative ACreb suppressed forskolin-induced desaturation of ether linked lipids to produce plasmalogens, as well as levels of phosphatidylethanolamine, ceramide and lysophosphatidylcholine. Taken together these results demonstrate that Creb1 is essential for the induction and maintenance of Scd1 in developing fetal mouse lung epithelial cells.
    PLoS ONE 04/2013; 8(4):e59763. DOI:10.1371/journal.pone.0059763 · 3.23 Impact Factor
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    ABSTRACT: Surfactant proteins maintain lung function through their actions to reduce alveolar surface tension and control of innate immune responses in the lung. The ubiquitin proteasome pathway is responsible for the degradation of majority of intracellular proteins in eukaryotic cells, and proteasome dysfunction has been linked to the development of neurodegenerative, cardiac, and other diseases. Proteasome function is impaired in interstitial lung diseases associated with surfactant protein C (SP-C) mutation mapping to the BRICHOS domain located in the proSP-C protein. In this study we determined the effects of proteasome inhibition on surfactant protein expression in H441 and MLE-12 lung epithelial cells to understand the relationship between proteasome dysfunction and surfactant protein gene expression. Proteasome inhibitors lactacystin and MG132 reduced the levels of SP-A, SP-B, and SP-C mRNAs in a concentration-dependent manner in H441 and MLE-12 cells. In H441 cells, lactacystin and MG132 inhibition of SP-B mRNA was associated with similar decreases in SP-B protein, and the inhibition was due to inhibition of gene transcription. Proteasome inhibitors decreased thyroid transcription factor-1 (TTF-1)/Nkx2.1 DNA binding activity, and the reduced TTF-1 DNA binding activity was due to reduced expression levels of TTF-1 protein. These data indicated that the ubiquitin proteasome pathway is essential for the maintenance of surfactant protein gene expression and that disruption of this pathway inhibits surfactant protein gene expression via reduced expression of TTF-1 protein.
    AJP Lung Cellular and Molecular Physiology 02/2007; 292(1):L74-84. DOI:10.1152/ajplung.00103.2006 · 4.08 Impact Factor
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