The roles of transforming growth factor-ß1 and vascular endothelial growth factor in the tracheal granulation formation.

BACKGROUND: Acquired tracheal stenosis is common in patients with a long-term tracheostomy and granulation is one of the most commonly observed lesions in benign airway stenosis. The aim of this study was to investigate the mechanisms of tracheal granulation formation and find the potential therapeutic targets to prevent the granulation formation. RESULTS: In granulation tissue obtained from patients during interventional bronchoscopy for the relief of airway obstruction, increased expression of transforming growth factor (TGF)-ß1 and vascular endothelial growth factor (VEGF), as well as increased numbers of fibroblasts, was found by immunohistochemical staining. TGF-ß1 expression was detected in both the epithelial and submucosal layers. The highest levels of VEGF and vimentin expression occurred in the submucosal layers. In comparison with the control, significantly increased numbers of small vessels were observed in the submucosal layers of the granulation tissue. In vitro, TGF-ß1 stimulated production of VEGF by cultured fibroblasts at both the mRNA and protein level. VEGF siRNA treatment resulted in a significant decrease of TGF-ß1-induced VEGF production. SIS3, a selective Smad3 inhibitor, and UO126 both inhibited p44/42 MAP kinase phosphorylation and attenuated subsequent VEGF production by fibroblasts. A low concentration of erythromycin (1 µg/ml), but not dexamethasone (100 µM), inhibited TGF-ß1-induced VEGF production. CONCLUSION: This study provides important information that facilitates an understanding, at least in part, of the mechanisms of granulation formation. Targeting these mediators and cells may help to prevent the formation of granulation tissue in long-term tracheostomy or prolonged endotracheal intubation patients.

Bile acid aspiration in suspected ventilator-associated pneumonia.

AIMS: The aims of this study were to measure the levels of bile acids in patients with suspected ventilator-associated pneumonia (VAP) and provide a possible pathway for neutrophilic inflammation to explain its proinflammatory effect on the airway. METHODS: Bile acid levels were measured by spectrophotometric enzymatic assay, and liquid chromatography mass spectrometry was used to quantify the major bile acids. Alveolar cells were grown on modified air-liquid interface culture inserts, and bile acids were then employed to stimulate the cells. Reverse transcriptase polymerase chain reaction and Western blots were used to determine the involved gene expression and protein levels. RESULTS: The mean (+/- SE) concentration of total bile acids in tracheal aspirates was 6.2 +/- 2.1 and 1.1 +/- 0.4 mumol/L/g sputum, respectively, for patients with and without VAP (p < 0.05). The interleukin (IL)-8 level was significantly higher in the VAP group (p < 0.05). The major bile acid, chenodeoxycholic acid, stimulated alveolar epithelial cells to increase IL-8 production at both the messenger RNA and protein level through p38 and c-Jun N-terminal kinase (JNK) activation. The selective p38 and JNK inhibitors, as well as dexamethasone, successfully inhibited IL-8 production. CONCLUSION: These data suggest that early intervention to prevent bile acid aspiration may reduce the intensity of neutrophilic inflammation in intubated and mechanically ventilated patients in the ICU.

Bile acids induce CCN2 production through p38 MAP kinase activation in human bronchial epithelial cells: a factor contributing to airway fibrosis.

BACKGROUND AND OBJECTIVE: Bile acid aspiration occurs in a variety of acute and chronic airway disorders. The consequence of bile acid aspiration and lung disease remains unclear. It was hypothesized that airway epithelium exposure to bile acids would induce fibrosis via production of connective tissue growth factor (CCN2), CCN2 is essential for transforming growth factor-beta (TGFbeta)-induced fibrogenesis and functions as a downstream mediator of TGF-beta action on fibroblasts. METHODS: Human bronchial epithelial cells were grown on air-liquid interface culture inserts. Cells were stimulated with the major components of bile acids, chenodeoxycholic acid (CD) and glycochenodeoxycholic acid (GCD). RT-PCR and real-time quantitative PCR were used to detect mRNA expression. ELISA and western blotting were used to measure protein. RESULTS: CD-stimulated airway epithelial cells produce CCN2 at both mRNA and protein levels in a dose-dependent manner. GCD failed to increase CCN2 production. CCN2 expression occurred via activation of p38 mitogen-activated protein (MAP) kinase and the downstream transcription factor ATF-2. Dexamethasone and the selective p38 MAP kinase inhibitor SB203580 successfully inhibited p38 MAP kinase, ATF-2 phosphorylation and subsequent CCN2 production. CD induced TGF-beta1 release from airway epithelium via the same signalling pathway. TGF-beta1 therefore enhanced CCN2production in an autocrine manner. CONCLUSION: Early intervention to stop these processes may be useful in preventing fibrogenesis in chronic airway diseases associated with bile acid exposure.