Dexamethasone and salbutamol stimulate human lung fibroblast proliferation

Pharmacological Modulation of Endotoxin-Induced Release of IL-26 in Human Primary Lung Fibroblasts

Background: Interleukin (IL)-26 is a neutrophil-mobilizing and bactericidal cytokine that is enhanced in human airways in vivo in response to endotoxin from Gram-negative bacteria. This cytokine is also enhanced in the airways during exacerbations of chronic obstructive pulmonary disease (COPD). Here, we investigated whether human primary lung fibroblasts (HLF) release IL-26 constitutively and in response to TLR4 stimulation by endotoxin and characterized the effects of bronchodilatory and anti-inflammatory drugs utilized in COPD.

Methods: The HLF were stimulated with different concentrations of endotoxin. Cells were also treated with different concentrations of bronchodilatory and anti-inflammatory drugs, with and without endotoxin stimulation. Cytokine protein concentrations were quantified in the cell-free conditioned media [enzyme-linked immunosorbent assay (ELISA)], and the phosphorylation levels of intracellular signaling molecules were determined (phosphoELISA).

Results: Whereas HLF displayed constitutive release of IL-26 into the conditioned medium, endotoxin markedly enhanced this release, as well as that of IL-6 and IL-8. This cytokine release was paralleled by increased phosphorylation of the intracellular signaling molecules NF-κB, c-Jun N-terminal kinase (JNK) 1-3, p38, and extracellular signal-regulated kinase (ERK) 1/2. The glucocorticoid hydrocortisone caused substantial inhibition of the endotoxin-induced release of IL-26, IL-6, and IL-8, an effect paralleled by a decrease of the phosphorylation of NF-κB, p38, and ERK1/2. The muscarinic receptor antagonist (MRA) tiotropium, but not aclidinium, caused minor inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB. The β2-adrenoceptor agonist salbutamol caused modest inhibition of the endotoxin-induced release of IL-26 and IL-8, paralleled by a decreased phosphorylation of NF-κB, JNK1-3, and p38. Similar pharmacological effects were observed for the constitutive release of IL-26.

Conclusions: The HLF constitute an abundant source of IL-26 that may contribute to local host defense against Gram-negative bacteria. Among the tested drugs, the glucocorticoid displayed the most powerful inhibitory effect, affecting the NF-κB, p38, and ERK1/2 signaling pathways. Whether or not this inhibition of IL-26 contributes to an increased risk for local infections in COPD requires further evaluation.

Glucocorticoids and erythropoietin in chronic lung disease of prematurity: Proliferative potential in lung fibroblast and epithelial cells exposed to tracheal aspirates

BACKGROUND

We investigated the effects of glucocorticoids, erythropoietin (EPO) and spironolactone (SPL) n human fetal lung fibroblasts and human alveolar epithelial cells exposed to tracheal aspirate fluid (TAF) from extremely premature infants with chronic lung disease (CLD), characterized by fibrosis and changes in the alveolar epithelium.

METHODS

Fibroblasts and epithelial cells (FHs 738Lu and A549, respectively) were treated with different concentrations of hydrocortisone (HDC), dexamethasone (DEX), betamethasone (BET), SPL, and EPO in the absence or presence of TAF from infants with CLD (gestational age, 25.3 ± 0.8 weeks; birthweight, 658 ± 77 g; postnatal age, 0-28 days) and assayed for proliferation.

RESULTS

Exposure to TAF resulted in a concentration-dependent proliferation of fibroblasts and epithelial cells. Proliferation of TAF-exposed fibroblasts was suppressed most significantly by 100 μmol/L DEX (21%, P = 0.046) and 300 mIU/mL EPO (18%, P = 0.02) and promoted most significantly by 0.4 μmol/L HDC (10%, P = 0.04). Epithelial proliferation was promoted by 4 μmol/L HDC (15%, P = 0.04), 10 μmol/L DEX (53%, P < 0.01), 0.2 μmol/L BET (56%, P < 0.01), and 300 mIU/mL EPO (35%, P < 0.01) in the presence of TAF. Treatment with glucocorticoids alone did not significantly affect fibroblast proliferation.

CONCLUSIONS

Glucocorticoids and EPO reduced fibroproliferation while promoting epithelial cell growth in vitro within certain dose ranges. Appropriate doses of glucocorticoids and EPO may be useful in the prevention and resolution of CLD in extremely premature infants.

Concomitant inhibition of primary equine bronchial fibroblast proliferation and differentiation by selective β2-adrenoceptor agonists and dexamethasone

Altered airway cell proliferation plays an important role in the pathogenesis of human bronchial asthma and chronic obstructive pulmonary disease (COPD) as well as the equine recurrent airway obstruction (RAO) with consistent changes, i.e. narrowing the airway wall, explained by proliferation and differentiation of fibroblasts. In permanent cell lines, it has been suggested that β2-adrenoceptor agonists and glucocorticoids regulate cell proliferation via the β2-adrenoceptor pathway; indeed, no study was carried out in fresh isolated primary equine bronchial fibroblasts (EBF). We characterized the β-adrenoceptors in EBF, and compared effects of long-acting (clenbuterol) and short-acting (salbutamol and isoproterenol) β2-agonists and dexamethasone on proliferation, differentiation and collagen synthesis. High density (Bmax; 5037±494 sites/cell) of β2-adrenoceptor subtype was expressed in EBF. β2-agonists inhibited concentration-dependently EBF proliferation with potency of clenbuterol>salbutamol »isoproterenol which was inhibited by ICI 118.551 and propranolol but not by CGP 20712A. In contrast, dexamethasone alone inhibited less EBF proliferation, but the effect was high when dexamethasone was combined with β2-agonists. Transforming growth factor-β1 (TGF-β1) increased transformation of fibroblasts into myofibroblasts, which was inhibited by clenbuterol and dexamethasone alone and drug combination resulted in high inhibition rate. Collagen synthesis in EBF was rather hampered by dexamethasone than by β-agonists. Collectively, the expression of β2-adrenoceptor subtype in EBF and the anti-proliferative effect of clenbuterol suggest that β2-adrenoceptors are growth inhibitory and anti-fibrotic in EBF. These β2-agonist effects in EBF were synergistically enhanced by dexamethasone, providing the additive effects of glucocorticoids to counteract airway remodelling and morbidity of asthma and RAO.