Enhanced pulmonary leptin expression in patients with severe COPD and asymptomatic smokers.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterised by an abnormal inflammatory reaction of the lungs involving activation of epithelial cells. Leptin is a pleiotropic cytokine important in the regulation of immune responses via its functional receptor Ob-Rb. This study was undertaken to test the hypothesis that severe COPD is associated with increased leptin expression in epithelial cells. METHODS: Immunohistochemistry for leptin was performed on peripheral lung specimens from 20 patients with COPD (GOLD stage 4), 14 asymptomatic ex-smokers and 13 never smokers. Leptin and Ob-Rb mRNA expression were determined by rtPCR in cultured primary bronchial epithelial cells and primary type II pneumocytes. NCI-H292 and A549 cell lines were used to study functional activation of leptin signalling. RESULTS: Leptin immunoreactivity in lung tissue was observed in bronchial epithelial cells, type II pneumocytes, macrophages (tissue/alveolar) and interstitial lymphocytic infiltrates. rtPCR analysis confirmed pulmonary leptin and Ob-Rb mRNA expression in primary bronchial epithelial cells and pneumocytes. Leptin-expressing bronchial epithelial cells and alveolar macrophages were markedly higher in patients with severe COPD and ex-smokers than in never smokers (p<0.02). Exposure of cultured primary bronchial epithelial cells to smoke resulted in increased expression of both leptin and Ob-Rb (p<0.05). Leptin induced phosphorylation of STAT3 in both NCI-H292 and A549 cells. CONCLUSIONS: Leptin expression is increased in bronchial epithelial cells and alveolar macrophages of ex-smokers with or without severe COPD compared with never smokers. A functional leptin signalling pathway is present in lung epithelial cells.

Myeloperoxidase modulates lung epithelial responses to pro-inflammatory agents.

During extensive inflammation, neutrophils undergo secondary necrosis causing myeloperoxidase (MPO) release that may damage resident lung cells. Recent observations suggest that MPO has pro-inflammatory properties, independent of its enzymatic activity. The aims of the present study were to characterise MPO internalisation by lung epithelial cells and to investigate the effect of MPO on oxidative stress, DNA damage and cytokine production by lung epithelial cells. Human alveolar and bronchial epithelial cells were stimulated with MPO, with or without priming the cells with pro-inflammatory stimuli. MPO protein was detected in the cell cytoplasm. Expression of haemoxygenase (HO)-1 and DNA strand breakage were determined. The production of interleukin (IL)-8 and -6 were measured. Analyses of MPO-stimulated cells demonstrated MPO presence in the cells. HO-1 expression was increased after MPO stimulation and increased further when cells were primed before MPO stimulation. MPO exposure also induced DNA strand breakage. Interestingly, MPO inhibited IL-8 production in bronchial, but not alveolar epithelium. In conclusion, alveolar and bronchial epithelial cells can internalise myeloperoxidase. Stimulation with myeloperoxidase increases haemoxygenase-1 expression and DNA strand breakage, suggesting cell damaging capacity of myeloperoxidase. In addition, myeloperoxidase inhibited interleukin-8 production by bronchial epithelial cells, indicating a negative feedback loop for neutrophil recruitment.

Increased levels of enzymes involved in local estradiol synthesis in chronic obstructive pulmonary disease.

INTRODUCTION: Steroid hormones are involved in lung development, pulmonary inflammation, and lung cancer. Estrogen signaling and exposure may play a role in pulmonary disorders, including COPD. In both genders, estrogens can be generated locally in the lungs and this contributes importantly to the tissue exposure to these steroids. OBJECTIVE: To characterize and assess differences in localization of estrogen receptors and enzymes involved in the local generation of estrogens in COPD. METHODS: Estrogen Receptor alpha (ERα/ESR1), Estrogen Receptor beta (ERß/ESR2) and G-protein-coupled estrogen receptor 1 (GPER) were explored by real-time (RT)-PCR analysis (mRNA expression), immunohistochemistry and western blotting in controls and COPD patients. mRNA expression of the enzymes involved in the local estrogen generation - i.e. aromatase (CYP19A1), 17beta-hydroxysteroid dehydrogenases (17ß-HSDs) 1, 2, 4, 5, 7 and 12, steroid sulfatase (STS) and sulfotransferase (SULT1E1) - were analyzed by RT-PCR. RESULTS: ERα, ERß and GPER were expressed in lung tissue, but no differences were observed between patients and controls. The main enzymes involved in local estrogen generation were also present in both normal and COPD lung tissue. In lungs of COPD patients compared with controls, we observed increased expression of the enzymes 17ß-HSD type 1 and aromatase (positive association), both involved in the local synthesis of active estrogens. CONCLUSION: All ER subtypes are present in the lung. The shift in local mRNA level of estrogen metabolic enzymes suggests that exposure to estrogens is involved in the pathogenesis of COPD.

Leptin as local inflammatory marker in COPD.

INTRODUCTION: Chronic inflammation of the lung is a characteristic finding in chronic obstructive pulmonary disease (COPD). Leptin is a pleiotropic cytokine thought to play a role in host response to inflammation. As recent studies have shown that leptin receptors are present in the lung, this study aimed to determine if leptin is detectable in induced sputum of COPD patients and if there is a relationship between leptin and other inflammatory markers in sputum. METHODS: Sputum was induced in 14 male patients with moderate COPD (FEV1: 56 (15) % pred.). Leptin, total tumour necrosis factor (TNF)-alpha, and C-reactive protein (CRP) were analyzed in induced sputum supernatant by ELISA. Leptin was also determined in EDTA plasma. RESULTS: Leptin was detectable in induced sputum of 10 COPD patients. A significant relationship was found between sputum leptin and CRP (r = 0.943, P < 0.001) and total TNF-alpha (r = 0.690, P < 0.01). Plasma leptin and sputum leptin were inversely correlated (r = -0.643, P < 0.01). CONCLUSION: The present study demonstrated that leptin is detectable in induced sputum of patients with moderate COPD and is related to other inflammatory markers. The observed correlations between leptin and inflammatory markers in sputum may indicate that leptin is involved in the local inflammatory response in COPD.

Enhanced levels of hyaluronan in lungs of patients with COPD: relationship with lung function and local inflammation.

BACKGROUND: Chronic inflammation and airway remodelling are characteristics of chronic obstructive pulmonary disease (COPD). Hyaluronan (HA) is an extracellular matrix compound with proinflammatory activity. HA levels in induced sputum from patients with COPD were measured and related to local inflammation. The expression of hyaluronan synthase 2 (HAS2) and hyaluronidase 2 (HYAL2) was analysed in lung tissue. METHODS: Sputum was obtained from 18 patients with COPD (forced expiratory volume in 1 second (FEV(1)) 62% predicted (range 20-76)) and 14 healthy smokers. HA and inflammatory markers were measured using ELISA assays. Lung sections were obtained from five patients with severe COPD (FEV(1) <30%) and from five smokers, and mRNA levels of HAS2 and HYAL2 were analysed by polymerase chain reaction. RESULTS: HA levels were significantly higher in the sputum from patients with COPD than controls. The COPD population appeared to consist of two subpopulations with either high or moderate HA levels. The subgroup of patients with high HA levels had lower FEV(1) than the moderate HA group. In addition, neutrophil influx and levels of interleukin-8, and the soluble tumour necrosis factor receptors R55 and R75 were significantly higher in patients with high HA levels than in those with moderate HA levels and controls. Semiquantitative analysis revealed enhanced expression of HYAL2 in lung tissue of patients with severe COPD compared with control subjects. CONCLUSION: These data indicate a relationship between HA levels, local inflammation and severity of disease, and suggest enhanced breakdown of HA in the lungs of patients with COPD.