Isoprenoid-Mediated Control of SMAD3 Expression in a Cultured Model of Cystic Fibrosis Epithelial Cells

Lee, Jenny Y.; Elmer, Heather L.; Ross, Kristie; Kelley, Thomas J.

doi:10.1165/rcmb.2003-0447oc

Cited by 27 publications

(20 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…AMPK activation has long been known to inhibit HMGCoA reductase (39), the rate-limiting enzyme in sterol biosynthesis and the production of isoprenoids, which are increased in the CF airway and may contribute to excessive inflammation there (40,41). Moreover, pharmacologic activation of AMPK has been reported to attenuate LPS-induced expression of proinflammatory cytokines through down-regulation of IkK activity and inhibition of NF-kB (42).…”

Section: Discussionmentioning

confidence: 99%

AMPK Agonists Ameliorate Sodium and Fluid Transport and Inflammation in Cystic Fibrosis Airway Epithelial Cells

Myerburg

King²,

Oyster³

et al. 2010

Am J Respir Cell Mol Biol

View full text Add to dashboard Cite

The metabolic sensor AMP-activated kinase (AMPK) inhibits both the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) Cl -channel and epithelial Na 1 channel (ENaC), and may inhibit secretion of proinflammatory cytokines in epithelia. Here we have tested in primary polarized CF and non-CF human bronchial epithelial (HBE) cells the effects of AMPK activators, metformin and 5-aminoimidazole-4-carboxamide-1-b-D-riboside (AICAR), on various parameters that contribute to CF lung disease: ENaC-dependent short-circuit currents (I sc ), airway surface liquid (ASL) height, and proinflammatory cytokine secretion. AMPK activation after overnight treatment with either metformin (2-5 mM) or AICAR (1 mM) substantially inhibited ENaC-dependent I sc in both CF and non-CF airway cultures. Live-cell confocal images acquired 60 minutes after apical addition of Texas Red-dextran-containing fluid revealed significantly greater ASL heights after AICAR and metformin treatment relative to controls, suggesting that AMPK-dependent ENaC inhibition slows apical fluid reabsorption. Both metformin and AICAR decreased secretion of various proinflammatory cytokines, both with and without prior LPS stimulation. Finally, prolonged exposure to more physiologically relevant concentrations of metformin (0.03-1 mM) inhibited ENaC currents and decreased proinflammatory cytokine levels in CF HBE cells in a dose-dependent manner. These findings suggest that novel therapies to activate AMPK in the CF airway may be beneficial by blunting excessive sodium and ASL absorption and by reducing excessive airway inflammation, which are major contributors to CF lung disease.Keywords: metformin; cystic fibrosis transmembrane conductance regulator; ENaC; airway surface liquid; inflammationThe serious genetic disease cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) Cl -channel expressed at the apical membrane in a variety of epithelial tissues, including the lung, where CF lung disease causes considerable morbidity and mortality (1). Defective CFTR function prevents airway epithelium from adequately regulating the airway surface liquid (ASL) volume, which has an adverse effect on mucus clearance from the lung. The CF airway invariably becomes colonized by bacteria such as Pseudomonas aeruginosa and develops excessive inflammation, which can cause extensive damage to lung architecture and eventuate in respiratory failure (2). There is growing evidence that a lack of functional CFTR promotes an exaggerated or prolonged inflammatory response to bacterial and other insults, although the underlying pathophysiologic mechanisms are unclear (3-5). Both up-regulation of proinflammatory mediators (e.g., IL-8, IL-6, TNF-a, and GM-CSF) and down-regulation of anti-inflammatory mediators (e.g., IL-10 and inducible nitric oxide synthase) in the CF airway may play an important role in this process (6-8).Excessive activity of the epithelial sodium channel (ENaC) on the luminal airway surface is a key factor involved in th...

show abstract

Section: Discussionmentioning

confidence: 99%

AMPK Agonists Ameliorate Sodium and Fluid Transport and Inflammation in Cystic Fibrosis Airway Epithelial Cells

Myerburg

King²,

Oyster³

et al. 2010

Am J Respir Cell Mol Biol

View full text Add to dashboard Cite

show abstract

“…Interestingly, the effects of this enhancer in HeLa and HepG2 cells are almost completely dependent on rs17293632C>T genotype because the presence of the (T) allele nearly fully disrupts enhancer activity. To further examine the contribution of the enhancer in the SMAD3 context, we cloned a 347-bp subset of this enhancer ( Figure 2A) with both alleles of rs17293632 into the SMAD3p-Luc plasmid containing the human SMAD3 promoter in the pGL3-Basic backbone 21 ( Figure 2D). The enhancer was inserted 3′ of both the SMAD3 promoter sequence and firefly luciferase gene to mimic the orientation in the genome.…”

Section: Rs17293632 (T) Disrupts the Function Of A Novel Enhancer In mentioning

confidence: 99%

Functional Analysis of a Novel Genome-Wide Association Study Signal in SMAD3 That Confers Protection From Coronary Artery Disease

Turner

Martinuk

Silva

et al. 2016

ATVB

View full text Add to dashboard Cite

Objective-A recent genome-wide association study meta-analysis identified an intronic single nucleotide polymorphism in SMAD3, rs56062135C>T, the minor allele (T) which associates with protection from coronary artery disease. Relevant to atherosclerosis, SMAD3 is a key contributor to transforming growth factor-β pathway signaling. Here, we seek to identify ≥1 causal coronary artery disease-associated single nucleotide polymorphisms at the SMAD3 locus and characterize mechanisms whereby the risk allele(s) contribute to coronary artery disease risk. Approach and Results-By genetic and epigenetic fine mapping, we identified a candidate causal single nucleotide polymorphism rs17293632C>T (D′, 0.97; r 2 , 0.94 with rs56062135) in intron 1 of SMAD3 with predicted functional effects. We show that the sequence encompassing rs17293632 acts as a strong enhancer in human arterial smooth muscle cells. The common allele (C) preserves an activator protein (AP)-1 site and enhancer function, whereas the protective (T) allele disrupts the AP-1 site and significantly reduces enhancer activity (P<0.001). Pharmacological inhibition of AP-1 activity upstream demonstrates that this allele-specific enhancer effect is AP-1 dependent (P<0.001). Chromatin immunoprecipitation experiments reveal binding of several AP-1 component proteins with preferential binding to the (C) allele. We show that rs17293632 is an expression quantitative trait locus for SMAD3 in blood and atherosclerotic plaque with reduced expression of SMAD3 in carriers of the protective allele. Finally, siRNA knockdown of SMAD3 in human arterial smooth muscle cells increases cell viability, consistent with an antiproliferative role. Phosphorylated SMAD3 then forms a complex with the common SMAD4 that subsequently translocates to the nucleus and regulates transcription. 6,7 Relevant to a role in atherosclerosis, in systems genetics analysis of multiple GWAS, we identified TGF-β signaling and SMAD transcriptional activities as enriched pathways for CAD association. 8 However, despite extensive data on the functions of TGF-β with respect to atherosclerosis, 9,10 the roles of SMAD proteins particularly SMAD3 and SMAD3 signaling are less well-understood. Conclusions-TheSMAD3 is expressed at low levels in healthy human aorta by immunohistochemistry and quantitative reverse transcription polymerase chain reaction (PCR).11 There is, however, a marked increase in SMAD3 and other SMAD proteins in fibrofatty lesions, with expression mostly limited to CD68-positive macrophages/macrophage-derived foam cells in these samples. Conversely, in fibrous atherosclerotic plaques, there are high levels of SMAD3 in vascular smooth muscle cells (SMCs), suggesting that the role of SMAD3 in atherosclerosis depends on cell type and stage of atherosclerosis.11 Higher SMAD3 expression in SMCs of the fibrous plaque coincides with TGF-β-mediated synthesis of collagen and other extracellular matrix proteins, which contribute to plaque stability.12 Rare SMAD3 mutations cause aneurysms-osteoarthritis syn...

show abstract

“…An additional mechanism by which AMPK may dampen inflammation is through its phosphorylation and inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase (59), the rate-limiting enzyme in sterol biosynthesis and the production of isoprenoids. Isoprenoids are increased in the CF airway and may contribute to excessive airway inflammation (17,60,61). Indeed, treatment with the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor mevastatin was recently found to confer anti-inflammatory effects by inducing nitric-oxide synthase 2 expression in models of CF epithelia, an effect that may be mediated through modulation of the RhoA and STAT1 (signal transducer and activator of transcription 1) signaling pathways (17).…”

Section: Potential Mechanisms Of Ampk-dependent Modulation Ofmentioning

confidence: 99%

Up-regulation of AMP-activated Kinase by Dysfunctional Cystic Fibrosis Transmembrane Conductance Regulator in Cystic Fibrosis Airway Epithelial Cells Mitigates Excessive Inflammation

Hallows

Fitch

Richardson

et al. 2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

AMP-activated kinase (AMPK) is a ubiquitous metabolic sensor that inhibits the cystic fibrosis (CF) transmembrane conductance regulator (CFTR).Further pharmacologic AMPK activation inhibited inflammatory mediator secretion in both wild type-and ⌬F508-expressing cells, suggesting that AMPK activation in CF airway cells is an adaptive response that reduces inflammation. We propose that therapies to activate AMPK in the CF airway may be beneficial in reducing excessive airway inflammation, a major cause of CF morbidity.

show abstract

Isoprenoid-Mediated Control of SMAD3 Expression in a Cultured Model of Cystic Fibrosis Epithelial Cells

Cited by 27 publications

References 35 publications

AMPK Agonists Ameliorate Sodium and Fluid Transport and Inflammation in Cystic Fibrosis Airway Epithelial Cells

AMPK Agonists Ameliorate Sodium and Fluid Transport and Inflammation in Cystic Fibrosis Airway Epithelial Cells

Functional Analysis of a Novel Genome-Wide Association Study Signal in SMAD3 That Confers Protection From Coronary Artery Disease

Up-regulation of AMP-activated Kinase by Dysfunctional Cystic Fibrosis Transmembrane Conductance Regulator in Cystic Fibrosis Airway Epithelial Cells Mitigates Excessive Inflammation

Contact Info

Product

Resources

About