Manuela Funke

The Lysophosphatidic Acid Receptor LPA1 Promotes Epithelial Cell Apoptosis after Lung Injury

Increased epithelial cell apoptosis in response to lung injury has been implicated in the development of idiopathic pulmonary fibrosis (IPF), but the molecular pathways promoting epithelial cell apoptosis in this disease have yet to be fully identified. Lysophosphatidic acid (LPA), which we have previously demonstrated to mediate bleomycin lung injury-induced fibroblast recruitment and vascular leak in mice and fibroblast recruitment in patients with IPF, is an important regulator of survival and apoptosis in many cell types. We now show that LPA signaling through its receptor LPA(1) promotes epithelial cell apoptosis induced by bleomycin injury. The number of apoptotic cells present in the alveolar and bronchial epithelia of LPA(1)-deficient mice was significantly reduced compared with wild-type mice at Day 3 after bleomycin challenge, as was lung caspase-3 activity. Consistent with these in vivo results, we found that LPA signaling through LPA(1) induced apoptosis in normal human bronchial epithelial cells in culture. LPA-LPA(1) signaling appeared to specifically mediate anoikis, the apoptosis of anchorage-dependent cells induced by their detachment. Similarly, LPA negatively regulated attachment of R3/1 rat alveolar epithelial cell line cells. In contrast, LPA signaling through LPA(1) promoted the resistance of lung fibroblasts to apoptosis, which has also been implicated in IPF. The ability of LPA-LPA(1) signaling to promote epithelial cell apoptosis and fibroblast resistance to apoptosis may therefore contribute to the capacity of this signaling pathway to regulate the development of pulmonary fibrosis after lung injury.

Lysophosphatidic Acid Signaling through the Lysophosphatidic Acid-1 Receptor Is Required for Alveolarization

Lysophosphatidic acid (LPA) signaling through one of its receptors, LPA1, contributes to both the development and the pathological remodeling after injury of many organs. Because we found previously that LPA-LPA1 signaling contributes to pulmonary fibrosis, here we investigated whether this pathway is also involved in lung development. Quantitative assessment of lung architecture of LPA1-deficient knock-out (KO) and wild-type (WT) mice at 3, 12, and 24 weeks of age using design-based stereology suggested the presence of an alveolarization defect in LPA1 KO mice at 3 weeks, which persisted as alveolar numbers increased in WT mice into adulthood. Across the ages examined, the lungs of LPA1 KO mice exhibited decreased alveolar numbers, septal tissue volumes, and surface areas, and increased volumes of the distal airspaces. Elastic fibers, critical to the development of alveolar septa, appeared less organized and condensed and more discontinuous in KO alveoli starting at P4. Tropoelastin messenger RNA expression was decreased in KO lungs, whereas expression of matrix metalloproteinases degrading elastic fibers was either decreased or unchanged. These results are consistent with the abnormal lung phenotype of LPA1 KO mice, being attributable to reduced alveolar septal formation during development, rather than to increased septal destruction as occurs in the emphysema of chronic obstructive pulmonary disease. Peripheral septal fibroblasts and myofibroblasts, which direct septation in late alveolarization, demonstrated reduced production of tropoelastin and matrix metalloproteinases, and diminished LPA-induced migration, when isolated from LPA1 KO mice. Taken together, our data suggest that LPA-LPA1 signaling is critically required for septation during alveolarization.

Idiopathic pulmonary fibrosis: the turning point is now!

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease with poor survival. Recent studies have improved understanding of IPF and new discoveries have led to novel treatment options, which now have become available for patients. In face of the newly available therapies we present an update on the pathophysiology and epidemiology of IPF. We discuss the typical clinical findings and elaborate diagnostic procedures according to current guidelines and our daily practice approach. The role of biomarkers will briefly be outlined. Finally, we discuss novel antifibrotic treatment options for IPF (pirfenidone, nintedanib) and the management of patients regarding to comorbidities and complications. Both pirfenidone and nintedanib were shown to reduce the progression of IPF and therefore represent novel therapeutic strategies in this so far untreatable chronic lung disease.

Toll-like receptor 4 activation attenuates profibrotic response in control lung fibroblasts but not in fibroblasts from patients with IPF

Idiopathic pulmonary fibrosis (IPF) is a devastating lung disease with a median survival of 3 yr. IPF deteriorates upon viral or bacterial lung infection although pulmonary infection (pneumonia) in healthy lungs rarely induces fibrosis. Bacterial lipopolysaccharide (LPS) activates Toll-like receptor 4 (TLR4), initiating proinflammatory pathways. As TLR4 has already been linked to hepatic fibrosis and scleroderma, we now investigated the role of TLR4 in IPF fibroblasts. Lung tissue sections from patients with IPF were analyzed for TLR4 expression. Isolated normal human lung fibroblasts (NL-FB) and IPF fibroblasts (IPF-FB) were exposed to LPS and transforming growth factor-β (TGF-β) before expression analysis of receptors, profibrotic mediators, and cytokines. TLR4 is expressed in fibroblast foci of IPF lungs as well as in primary NL-FB and IPF-FB. As a model for a gram-negative pneumonia in the nonfibrotic lung, NL-FB and IPF-FB were coexposed to LPS and TGF-β. Whereas NL-FB produced significantly less connective tissue growth factor upon costimulation compared with TGF-β stimulation alone, IPF-FB showed significantly increased profibrotic markers compared with control fibroblasts after costimulation. Although levels of antifibrotic prostaglandin E2 were elevated after costimulation, they were not responsible for this effect. However, significant downregulation of TGF-β receptor type 1 in control fibroblasts seems to contribute to the reduced profibrotic response in our in vitro model. Normal and IPF fibroblasts thus differ in their profibrotic response upon LPS-induced TLR4 stimulation.

Surfactant replacement therapy reduces acute lung injury and collapse induration-related lung remodeling in the bleomycin model

Bleomycin-induced lung injury leads to surfactant dysfunction and permanent loss of alveoli due to a remodeling process called collapse induration. Collapse induration also occurs in acute interstitial lung disease and idiopathic pulmonary fibrosis in humans. We hypothesized that surfactant dysfunction aggravates lung injury and early remodeling resulting in collapse induration within 7 days after lung injury. Rats received bleomycin to induce lung injury and either repetitive surfactant replacement therapy (SRT: 100 mg Curosurf/kg BW = surf group) or saline (0.9% NaCl = saline group). After 3 (D3) or 7 (D7) days, invasive pulmonary function tests were performed to determine tissue elastance (H) and static compliance (Cst). Bronchoalveolar lavage (BAL) was taken for surfactant function, inflammatory markers, and protein measurements. Lungs were fixed by vascular perfusion for design-based stereology and electron microscopic analyses. SRT significantly improved minimum surface tension of alveolar surfactant as well as H and Cst at D3 and D7. At D3 decreased inflammatory markers including neutrophilic granulocytes, IL-1β, and IL-6 correlated with reduced BAL-protein levels after SRT. Numbers of open alveoli were significantly increased at D3 and D7 in SRT groups whereas at D7 there was also a significant reduction in septal wall thickness and parenchymal tissue volume. Septal wall thickness and numbers of open alveoli highly correlated with improved lung mechanics after SRT. In conclusion, reduction in surface tension was effective to stabilize alveoli linked with an attenuation of parameters of acute lung injury at D3 and collapse induration at D7. Hence, SRT modifies disease progression to collapse induration.

Pulmonary hypertension associated with chronic lung diseases.

In 2015, the international guidelines for diagnosis and treatment of pulmonary hypertension (PH) were updated. Group 3 of the current classification includes PH associated with chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD), other pulmonary diseases with restrictive and obstructive pattern, sleep-disordered breathing, alveolar hypoventilation disorders, chronic exposure to high altitude, and developmental lung diseases [1]. PH associated with COPD and ILD is common but difficult to manage, as no long-term randomised controlled trial (RCT) has been conducted with specific pulmonary arterial hypertension (PAH) drugs in PH associated with COPD, and the one recent RCT in PH associated with ILD had to be stopped early due to a possible increased risk of death and side effects in the treatment group. Specific treatment may thus be harmful and may worsen gas exchange as a result of possible recruitment of less oxygenised areas, i.e. by increasing ventilation-perfusion mismatch. Management of PH patients with chronic lung diseases requires careful evaluation and understanding of pathophysiological mechanisms. Interestingly, mediators in PAH and in fibrotic lung disease show some overlaps. Several drugs effective in PAH have been evaluated for anti-fibrotic treatment in ILD, but until today without consistent success. While new drugs with anti-fibrotic effects are now accessible, a specific evidence-based treatment for PH in ILD or COPD with or without emphysema is not yet available.

Multiple breath washout: A new and promising lung function test for patients with idiopathic pulmonary fibrosis: Multiple breath washout in IPF

Idiopathic pulmonary fibrosis (IPF) is a devastating progressive lung disease affecting the parenchyma. Nitrogen multiple‐breath washout (N2‐MBW) is a lung function test that measures ventilation inhomogeneity, a biomarker of small airway disease. We assessed clinical properties of N2‐MBW in IPF.

Increased Expiratory Computed Tomography Density Reveals Possible Abnormalities in Radiologically Preserved Lung Parenchyma in Idiopathic Pulmonary Fibrosis

Objectives Idiopathic pulmonary fibrosis (IPF) is a progressive lethal chronic lung disease with unclear pathogenesis. Radiological hallmark is the pattern of usual interstitial pneumonia accentuated in peripheral and basal areas with otherwise preserved lung structure. One hypothesis is that alveolar collapse and consequent induration lead to fibrotic transformation of lung tissue. The aim of the study was to investigate normal-appearing tissue during expiration for signs of collapsibility and differences from other diseases or controls. Materials and Methods We retrospectively assessed a total of 43 patients (15 IPFs, 13 chronic obstructive pulmonary diseases, and 15 controls) with nonenhanced computed tomography (CT) in inspiration and expiration, performed for routine clinical workup. Densitometry of visually unaffected lung tissue was conducted in all lung lobes with a region of interest of 15-mm in diameter on soft tissue kernel reconstruction (slice thickness, 1 mm) during inspiration and expiration. Results One-factor analysis of variance analysis yielded significant difference in attenuation changes between inspiration and expiration of unaffected lung parenchyma among all subject groups in all lung lobes. For IPF patients, the highest differences in densities were observed in the lower lobes, which is the predominantly affected site of usual interstitial pneumonia. In the chronic obstructive pulmonary disease group, the density remained rather equal in the entire lung. Conclusions High CT attenuation changes between inspiration and expiration in IPF patients might suggest altered lung parenchyma in normal-appearing tissue on CT. Density changes during the respiratory cycle might be explained by alveolar collapse of radiologically unaffected lung tissue possibly preceding fibrosis. These results support the concept of alveolar collapse preceding lung fibrosis in IPF.

Contents Vol. 92, 2016

P.J. Barnes, London X. Basagana Flores, Barcelona (Statistical Consultant) S. Bilaceroglu, Izmir E. Brambilla, Grenoble P. Camus, Dijon M. Cazzola, Rome P.N. Chhajed, Mumbai U. Costabel, Essen H. Dutau, Marseille S. Fernandez-Bussy, Santiago de Chile A. Foresi, Sesto San Giovanni M.E. Froudarakis, Alexandroupolis G. Hoheisel, Leipzig M. Humbert, Clamart G. Izbicki, Jerusalem M. Kneussl, Vienna M. Kreuter, Heidelberg N. Künzli, Basel S. Li, Guangzhou W. Li, Chengdu P.N. Mathur, Indianapolis, Ind. A.R.L. Medford, Bristol A. Mehta, Boston, Mass. T. Nakajima, Chiba V. Poletti, Forlì H.-B. Ris, Lausanne F. Rodriguez-Panadero, Sevilla I. Rubinstein, Chicago, Ill. T. Schaberg, Rotenburg F.C. Sciurba, Pittsburgh, Pa. M. Solèr, Basel S. Spiro, London A. Valipour, Vienna A. Warth, Heidelberg H. Wirtz, Leipzig E.F.M. Wouters, Maastricht European Association for Bronchology and Interventional Pulmonology EABIP

Oxygen Saturation of 75%, but No Symptoms!

At the age of 30, a young father noticed a low oxygen saturation while playing with the finger pulse oximeter of his child awaiting surgery. Since he was completely asymptomatic, he did not seek medical attention. At the age of 51, he was referred to the outpatient clinic of our pulmonary department after detection of a severe nocturnal “hypoxemia”. Previous evaluation for obstructive sleep apnea by nocturnal respiratory polygraphy because of snoring revealed a significantly decreased average oxygen saturation (SpO 2 71%). The former smoker (25 packyears) was known for allergic/seasonal bronchial asthma with occasional use of an inhaled short-acting β-2selective adrenergic agonist (terbutalin) preceding physical activity. He denied having respiratory symptoms like dyspnea, cough, thoracic pain, or infections, and did not experience a decline of his physical performance. The patient presented to our outpatient clinic with a significantly decreased peripheral O 2 saturation of 76– 82% while breathing ambient air, which was measured by different pulse oximeters ( Fig. 1 ). SpO 2 rose only to 86% while breathing 7 L/min supplemental oxygen via nasal cannula. Other vital signs were normal (blood pressure 124/68 mm Hg, heart rate 86 beats/min, respiratory rate 16/min) and the patient showed no signs of respiratory Received: March 17, 2016 Accepted after revision: September 24, 2016 Published online: October 20, 2016