The role of mRNA stability in airway remodelling

Sirolimus-coated Eustachian tube balloon dilatation for treating Eustachian tube dysfunction in a rat model

Eustachian tube balloon dilatation (ETBD) has shown promising results in the treatment of ET dysfunction (ETD); however, recurrent symptoms after ETBD frequently occur in patients with refractory ETD. The excessive pressure of balloon catheter during ETBD may induce the tissue hyperplasia and fibrotic changes around the injured mucosa. Sirolimus (SRL), an antiproliferative agent, inhibits tissue proliferation. An SRL-coated balloon catheter was fabricated using an ultrasonic spray coating technique with a coating solution composed of SRL, purified shellac, and vitamin E. This study aimed to investigate effectiveness of ETBD with a SRL-coated balloon catheter to prevent tissue proliferation in the rat ET after ETBD. In 21 Sprague-Dawley rats, the left ET was randomly divided into the control (drug-free ETBD; n = 9) and the SRL (n = 9) groups. All rats were sacrificed for histological examination immediately after and at 1 and 4 weeks after ETBD. Three rats were used to represent the normal ET. The SRL-coated ETBD significantly suppressed tissue proliferation caused by mechanical injuries compared with the control group. ETBD with SRL-coated balloon catheter was effective and safe to maintain ET luminal patency without tissue proliferation at the site of mechanical injuries for 4 weeks in a rat ET model.

Serial histological changes in the cartilaginous eustachian tube in the rat following balloon dilation

Although balloon dilation has shown promising results in the treatment of dilatory Eustachian tube (ET) dysfunction, the histological effects of ET balloon dilation (ETBD) is unknown because histological examination of the whole human cartilaginous ET is impossible. Animal studies are needed to elucidate the effect of ETBD so we evaluated the histological changes after ETBD in a rat model. The left ET of 20 Wistar rats was dilated with a balloon catheter and the right ET was used as a control. Five rats were sacrificed immediately after ETBD, at 1, 4 and 12 weeks after the procedure for histological examination. The epithelial cells, presence of epithelial hyperplasia, and the proportion of the goblet cells in the epithelium; the vascular structures and dimensions of the submucosa; and presence of cartilage fracture and the area of the ET lumen were evaluated and compared between the groups. Desquamation of nearly all epithelial cells and the fracture of tubal cartilages were observed immediately after ETBD. At 1-week post-ETBD, the ciliated epithelial cells started to recover with epithelial hyperplasia. The goblet cells recovered by 4 weeks post-ETBD and epithelial hyperplasia decreased but was still present at 12 weeks post-ETBD. The depth of the submucosa increased and neovascularization in this region was observed at 1-week post-ETBD and persisted up to 12 weeks post-ETBD. The lumen of the cartilaginous ET increased immediately after ETBD but decreased at 1-week post-ETBD. The cartilaginous ET lumen recovered to the normal value at 4 weeks post-ETBD. This study is the first to describe the serial histological changes to the cartilaginous ET after ETBD and helps our understanding of the histological changes that occur after an ETBD intervention for intractable ET dysfunction.

A sodium binding system alleviates acute salt stress during seawater acclimation in eels

BACKGROUND

Teleosts transiting from freshwater (FW) to seawater (SW) environments face an immediate osmotic stress from ion influxes and water loss, but some euryhaline species such as eels can maintain a stable plasma osmolality during early SW exposure. The time course changes in the gene expression, protein abundance, and localization of key ion transporters suggested that the reversal of the ion transport systems was gradual, and we investigate how eels utilize a Na-binding strategy to slow down the ion invasion and complement the transporter-mediated osmoregulation.

RESULTS

Using an electron probe micro-analyzer, we localized bound Na in various eel tissues in response to SW transfer, suggesting that the Na-binding molecules were produced to sequester excess ionic Na⁺ to negate its osmotic potential, thus preventing acute cellular dehydration. Mucus cells were acutely activated in digestive tract, gill, and skin after SW transfer, producing Na-binding molecule-containing mucus layers that fence off high osmolality of SW. Using gel filtration HPLC, some molecules at 18 kDa were found to bind Na in the luminal secretion of esophagus and intestine, and higher binding was associated with SW transfer. Transcriptome and protein interaction results indicated that downregulation of Notch and β-catenin pathways, and dynamic changes in TGFβ pathways in intestine were involved during early SW transition, supporting the observed histological changes on epithelial desquamation and increased mucus production.

CONCLUSIONS

The timing for the activation of the Na-binding mechanism to alleviate the adverse osmotic gradient was temporally complementary to the subsequent remodeling of branchial ionocytes and transporting epithelia of the digestive tract. The strategy to manipulate the osmotic potential of Na⁺ by specific binding molecules is similar to the osmotically inactive Na described in human skin and muscle. The Na-binding molecules provide a buffer to tolerate the salinity changes, which is advantageous to the estuary and migrating fishes. Our data pave the way to identify this unknown class of molecules and open a new area of vertebrate osmoregulation research.

Tristetraprolin and its role in regulation of airway inflammation

Chronic inflammatory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are clinically and socioeconomically important diseases globally. Currently the mainstay of anti-inflammatory therapy in respiratory diseases is corticosteroids. Although corticosteroids have proven clinical efficacy in asthma, many asthmatic inflammatory conditions (e.g., infection, exacerbation, and severe asthma) are not responsive to corticosteroids. Moreover, despite an understanding that COPD progression is driven by inflammation, we currently do not have effective anti-inflammatory strategies to combat this disease. Hence, alternative anti-inflammatory strategies are required. p38 mitogen-activated protein kinase (MAPK) has emerged as an important signaling molecule driving airway inflammation, and pharmacological inhibitors against p38 MAPK may provide potential therapies for chronic respiratory disease. In this review, we discuss some of the recent in vitro and in vivo studies targeting p38 MAPK, but suggest that p38 MAPK inhibitors may prove less effective than originally considered because they may block anti-inflammatory molecules along with proinflammatory responses. We propose that an alternative strategy may be to target an anti-inflammatory molecule farther downstream of p38 MAPK, i.e., tristetraprolin (TTP). TTP is an mRNA-destabilizing, RNA-binding protein that enhances the decay of mRNAs, including those encoding proteins implicated in chronic respiratory diseases. We suggest that understanding the molecular mechanism of TTP expression and its temporal regulation will guide future development of novel anti-inflammatory pharmacotherapeutic approaches to combat respiratory disease.

Lentivirus mediated IL-17R blockade improves diastolic cardiac function in spontaneously hypertensive rats

BACKGROUND

Hypertension causes cardiac fibrosis characterized by low-grade inflammation. We hypothesized that proinflammatory cytokine, interleukin-17 (IL-17) is important in hypertensive cardiac fibrosis. The pre-ligand assembly domain (PLAD) of IL-17 receptor A (IL-17RA) mediates receptor-chain associations essential for signaling. This study was designed to explore the role of IL-17 RA PLAD in hypertension-induced cardiac fibrosis.

METHODS

Eight-week-old male spontaneously hypertensive rats (SHRs) were divided into 2 groups, depending on receiving IL-17RA PLAD-Ig or green fluorescent protein (GFP) lentivirus. Age-matched Wistar Kyoto rats served as controls. Cardiac function was determined by echocardiography. Cardiac hypertrophy and fibrosis were histopathologically examined. Matrix metalloproteinase (MMP) and tissue inhibitors of metalloproteinase (TIMP) expression were quantified by immunoblotting. Collagen content was quantified.

RESULTS

Both cardiac systolic and diastolic function and myocardial fibrosis in SHRs was improved significantly by the IL-17RA PLAD. Expression of MMP-2 and MMP-9, TIMP-1 and -2, type I and type III collagen were statistically decreased by IL-17RA PLAD-Ig treatment. Collagen quantitation, as well as collagen concentration and collagen cross-linking, were reduced by IL-17/IL-17R signal blockade.

CONCLUSIONS

IL-17/IL-17RA signaling plays an important role in myocardial collagen metabolism in hypertension-induced diastolic dysfunction.

Changes in the proteome of human bronchial epithelial cells following stimulation with leucotriene E4 and transforming growth factor-beta1

BACKGROUND AND OBJECTIVE

Activated bronchial epithelial cells exert considerable potential to maintain a microenvironment in the airway wall that promotes airway inflammation and remodelling. Cysteinyl leucotrienes (CysLT) and transforming growth factor-beta(1) (TGF-beta(1)) are both increased in asthmatic airways and may influence the pathophysiology of disease. However, the consequences of activation of bronchial epithelial cells by these mediators are not fully understood. A proteomic-based approach was used to characterize the inflammatory pathways in bronchial epithelial cells after stimulation with CysLT and TGF-beta(1).

METHODS

Human bronchial epithelial cells (BEAS-2B) were stimulated with 1 ng/mL TGF-beta(1) and 50 nmol/L leucotriene E(4) (LTE(4)) for 48 h and whole-cell lysates were subjected to two-dimensional gel electrophoresis. Proteins showing statistically significant differential expression were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and database searching.

RESULTS

Stimulation with LTE(4) increased the expression of three proteins and five proteins showed decreased expression. Of the latter group, two were definitively identified as heat shock protein (Hsp90 alpha) and stress-70 protein. Hsp90 alpha forms a heterocomplex with the glucocorticoid receptor (GR) and a significant decrease in GR following LTE(4) stimulation was confirmed. TGF-beta(1) downregulated 18 intracellular proteins, including lamin A/C, glyceraldehyde-3-phosphate dehydrogenase, protein DJ-1, voltage-dependent calcium channel gamma-7 subunit, heterogeneous nuclear ribonucleoprotein A2/B1 and stress-70 protein.

CONCLUSIONS

The current findings suggest that by downregulating GR and Hsp90 alpha, CysLT may interfere with the action of glucocorticoids. Overall, the results confirm the complex role of bronchial epithelium in aspects of airway inflammation and remodelling.

Molecular cloning and characterization of the Dicer-like 2 gene from Brassica rapa

Dicer-like proteins (DCLs) are involved in small RNA-mediated development and viral defense in plants. In model plants, at least four DCLs have been found and a number of studies have helped to understand their function. However, the function of the Dicer or DCLs in other plants is still unclear. Here, we report the full-length cDNA sequence of Brassica rapa ssp. chinensis DCL2 (BrDCL2) gene, which contains a 4,179 bp open reading frame (ORF) encoding a protein of 1,392 amino acids. At the 3' end of BrDCL2, clones with three different lengths of 3' untranslated region were found. An alternative splice variant of BrDCL2, BrDCL2sv, in which one intron was retained between exon9 and exon10, was also cloned. Because of a change in the coding sequence resulting in a premature terminal codon, BrDCL2sv was expected to translate a short peptide containing the whole DEXHc domain.

Corticosteroids reduce IL-6 in ASM cells via up-regulation of MKP-1

The mechanisms by which corticosteroids reduce airway inflammation are not completely understood. Traditionally, corticosteroids were thought to inhibit cytokines exclusively at the transcriptional level. Our recent evidence, obtained in airway smooth muscle (ASM), no longer supports this view. We have found that corticosteroids do not act at the transcriptional level to reduce TNF-alpha-induced IL-6 gene expression. Rather, corticosteroids inhibit TNF-alpha-induced IL-6 secretion by reducing the stability of the IL-6 mRNA transcript. TNF-alpha-induced IL-6 mRNA decays at a significantly faster rate in ASM cells pretreated with the corticosteroid dexamethasone (t(1/2) = 2.4 h), compared to vehicle (t(1/2) = 9.0 h; P < 0.05) (results are expressed as decay constants [k] [mean +/- SEM] and half-life [h]). Interestingly, the underlying mechanism of inhibition by corticosteroids is via the up-regulation of an endogenous mitogen-activated protein kinase (MAPK) inhibitor, MAPK phosphatase-1 (MKP-1). Corticosteroids rapidly up-regulate MKP-1 in a time-dependent manner (44.6 +/- 10.5-fold increase after 24 h treatment with dexamethasone; P < 0.05), and MKP-1 up-regulation was temporally related to the inhibition of TNF-alpha-induced p38 MAPK phosphorylation. Moreover, TNF-alpha acts via a p38 MAPK-dependent pathway to stabilize the IL-6 mRNA transcript (TNF-alpha, t(1/2) = 9.6 h; SB203580 + TNF-alpha, t(1/2) = 1.5 h), exogenous expression of MKP-1 significantly inhibits TNF-alpha-induced IL-6 secretion and MKP-1 siRNA reverses the inhibition of TNF-alpha-induced IL-6 secretion by dexamethasone. Taken together, these results suggest that corticosteroid-induced MKP-1 contributes to the repression of IL-6 secretion in ASM cells.

Bench-to-bedside review: the role of glycosaminoglycans in respiratory disease

The extracellular matrix (ECM) plays a significant role in the mechanical behaviour of the lung parenchyma. The ECM is composed of a three-dimensional fibre mesh that is filled with various macromolecules, among which are the glycosaminoglycans (GAGs). GAGs are long, linear and highly charged heterogeneous polysaccharides that are composed of a variable number of repeating disaccharide units. There are two main types of GAGs: nonsulphated GAG (hyaluronic acid) and sulphated GAGs (heparan sulphate and heparin, chondroitin sulphate, dermatan sulphate, and keratan sulphate). With the exception of hyaluronic acid, GAGs are usually covalently attached to a protein core, forming an overall structure that is referred to as proteoglycan. In the lungs, GAGs are distributed in the interstitium, in the sub-epithelial tissue and bronchial walls, and in airway secretions. GAGs have important functions in lung ECM: they regulate hydration and water homeostasis; they maintain structure and function; they modulate the inflammatory response; and they influence tissue repair and remodelling. Given the great diversity of GAG structures and the evidence that GAGs may have a protective effect against injury in various respiratory diseases, an understanding of changes in GAG expression that occur in disease may lead to opportunities to develop innovative and selective therapies in the future.