[Chronic fibrosing lung diseases : Idiopathic pulmonary fibrosis from the perspective of its differential diagnosis]. / Chronisch-fibrosierende Lungenerkrankungen : Die idiopathische pulmonale Fibrose im Spiegel ihrer Differenzialdiagnosen.

Fibrosing lung diseases describe a heterogeneous group of interstitial lung diseases (ILD) of highly variable etiology, but with a unifying terminal process of irreversible, fibroproliterative destruction of the alveolar surface, loss of compliance and progressive impairment of gas exchange. In view of the heterogeneity, the disastrous prognoses in some cases and the treatment consequences, a thorough differential diagnosis is essential in all patients. Antifibrotic therapies are currently only indicated in idiopathic pulmonary fibrosis (IPF). The only curative therapeutic option is lung transplantation. Therefore, suitable patients should be promptly evaluated.

[Disseminated osteolytic lesions in a 28-year-old refugee]. / Disseminierte osteolytische Läsionen bei einem 28-jährigen Flüchtling.

A 28-year-old Syrian refugee presented with right-sided knee pain and progressive deterioration of the general condition over the past months. Laboratory diagnostics revealed severe hypercalcemia due to primary hyperparathyroidism, and computed tomography (CT) scanning demonstrated disseminated osteolytic lesions throughout the skeleton. Histologically, these lesions were characterized by multinuclear giant cells (defining these lesions as so-called brown tumors). Finally, surgical removal of a jugular mass allowed the histopathologic diagnosis of a sporadic parathyroid carcinoma. In the patient, this condition was associated with a mutation in the HPRT2 gene locus.

Co-incubation of PMN and CaCo-2 cells modulates inflammatory potential.

Polymorphonuclear granulocytes (PMN) are activated in inflammatory reactions. Intestinal epithelial cells are relevant for maintaining the intestinal barrier. We examined interactions of PMN and intestinal epithelial cell-like CaCo-2 cells to elucidate their regulation of inflammatory signalling and the impact of cyclooxygenase (COX), nitric oxide (NO) and platelet-activating factor (PAF). Human PMN and CaCo-2 cells, separately and in co-incubation, were stimulated with the calcium ionophore A23187 or with N-Formyl-methionyl-leucyl-phenylalanin (fMLP) that activates PMN only. Human neutrophil elastase (HNE) and respiratory Burst were measured. To evaluate the modulation of inflammatory crosstalk we applied inhibitors of COX (acetyl salicylic acid; ASA), NO-synthase (N-monomethyl-L-arginin; L-NMMA), and the PAF-receptor (WEB2086). Unstimulated, co-incubation of CaCo-2 cells and PMN led to significantly reduced Burst and elevated HNE as compared to PMN. After stimulation with A23187, co-incubation resulted in an inhibition of Burst and HNE. Using fMLP co-incubation failed to modulate Burst but increased HNE. Without stimulation, all three inhibitors abolished the effect of co-incubation on Burst but did not change HNE.  ASA partly prevented modulation of Burst L-NMMA and WEB2086 did not change Burst but abolished mitigation of HNE. Without stimulation, co-incubation reduced Burst and elevated HNE. Activation of PMN and CaCo-2 cells by fMLP as compared to A23187 resulted in a completely different pattern of Burst and HNE, possibly due to single vs. dual cell activation. Anti-inflammatory effect of co-incubation might in part be due to due to COX-signalling governing Burst whereas NO- and PAF-dependent signalling seemed to control HNE release.

[Update pulmonary arterial hypertension : Definitions, diagnosis, therapy]. / Update pulmonalarterielle Hypertonie : Definitionen, Diagnose, Therapie.

The term pulmonary arterial hypertension comprises a group of pulmonary vascular diseases of different etiologies that are characterized by similar precapillary vascular remodeling processes and result in exertional dyspnea and right heart insufficiency. The specific pharmacological treatment approach considers the risk of mortality and phenotypical properties and includes treatment with phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostanoids, as well as with more novel substances, such as a soluble guanylyl cyclase stimulator and an oral prostacyclin receptor agonist. The prognosis of the disease is mainly determined by the right heart insufficiency for which there is currently no specific pharmacological treatment. Lung transplantation may be offered as a last option. This review provides an overview of the current European guidelines from 2015 and the recommendations of the Cologne Consensus Conference for pulmonary hypertension from 2016.

[Pulmonary hypertension : What is new in therapy?]. / Pulmonale Hypertonie : Was ist neu in der Therapie?

Pulmonary hypertension (PH) comprises a group of pulmonary vascular diseases that are characterized by progressive exertional dyspnea and right heart insufficiency ultimately resulting in right heart decompensation. The classification is into five clinical subgroups that form the absolutely essential basis for decisions on the indications for different pharmacological and non-pharmacological forms of treatment. The guidelines were updated in 2015 and in addition to the hitherto existing pharmacological treatment options of phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostacyclins, the soluble guanylate cyclase stimulator riociguat has now been incorporated for treatment of certain forms of PH. This article provides an overview of the new treatment recommendations in the current guidelines, e. g. for PH patients who are in intensive care units due to surgical interventions or progressive right heart insufficiency.

[Medical treatment of pulmonary hypertension: what's new?]. / Medikamentöse Therapie der pulmonalen Hypertonie: Was ist neu?

Pulmonary hypertension (PH) is a chronic progressive disease of the pulmonary circulation of multifactorial causes. The current diagnostic classification of PH distinguishes five main groups, which have as a common feature an increased pulmonary arterial pressure and pulmonary resistance. The classification differentiates pulmonary arterial hypertension (PAH), PH due to left heart disease, PH in lung diseases and/or hypoxia, chronic thromboembolic pulmonary hypertension (CTEPH), and PH with unclear/multifactorial mechanisms. Recent advances in basic research with the approval of new drugs and the establishment of therapeutic strategies, mainly in PAH and CTEPH, require a differentiated view of the disease, a careful diagnosis and initiation of therapy, and regular follow-ups. In this article, we provide an overview of the complex drug therapy currently available for PAH patients.

[Panniculitis of the thigh and lung emphysema in a 54-year-old patient]. / Pannikulitis des Oberschenkels und Lungenemphysem bei einem 54-jährigen Patienten.

This article reports a case of febrile, symmetrical and painful soft tissue swelling on both thighs in a 54-year-old otherwise healthy male patient. Histologically, necrotizing panniculitis of subcutaneous adipose tissue was described as a marker manifestation of a previously unknown alpha-1-antitrypsin (A1AT) deficiency with pulmonary emphysema and low plasma A1AT levels. The PiZZ homozygous form of A1AT could be diagnosed by gene sequencing. Complete remission of panniculitis could be achieved by A1AT replacement therapy.

[Dynamic hyperinflation in pulmonary arterial hypertension: "hyperinflator" and "non-hyperinflator"]. / Dynamische Hyperinflation bei der pulmonal arteriellen Hypertonie: "Hyperinflator" und "Non-Hyperinflator".

BACKGROUND: The dynamic decrease in inspiratory capacity (IC) during exercise with restriction of tidal volume (VT) is known as dynamic hyperinflation (DH) and is described mostly in patients with COPD differentiating between a "hyperinflator" and a "non-hyperinflator". Recent studies have revealed DH in patients with idiopathic pulmonary arterial hypertension (iPAH), but the influence of the DH on the reduced exercise capacity with exertional dyspnoae is still being debated. METHODS: We analysed flow-volume curves during cardiopulmonary exercise testing (CPET) in idiopathic PAH (n = 19), in COPD (n = 17), in idiopathic pulmonary fibrosis (IPF) (n = 19) and a control group (n = 30). We measured IC at rest and during maximal exercise and furthermore ventilation, VT and oxygen uptake (VO2 peak). In iPAH a right heart catheter test and a 6-minute walk test (6MWT) were performed, also the B-type naturetic peptide (BNP) and the NYHA/WHO functional class were determined. RESULTS: The IC decreased significantly in 11 PAH "hyperinflators" (PAH-H) (Δ IC: - 0.34 ± 0.14 L, p < 0.001) compared to 8 PAH "non-hyperinflators" (PAH-NH) (Δ IC: 0.08 ± 0.2 L). COPD patients exhibited a characteristic hyperinflation pattern with a decrease in IC throughout exercise (Δ IC: - 0.61 ± 0.3 L, p < 0.001), while patients with IPF (Δ IC: 0.03 ± 0.15 L) and the control group responsed to exercise with a non-hyperinflator pattern (Δ IC: 0.1 ± 0.2 L). Both PAH collectives showed a reduced IC/TLC, while VT/IC was elevated with a decreased peak VO2 and max. performance compared to the control group. Correlations of the IC rest/max (L) were shown in PAH-H and PAH-NH with the VO2 peak, max. performance and VT. CONCLUSION: The analysis of flow-volume curves during CPET can indentify DH in a subgroup of patients with iPAH. The DH contributes significantly but slightly to the development of exertional limitations and dyspnoe in a subgroup of iPAH. Further studies with a larger sample size will be required to definitively measure the impact of the DH seen in these patients.

Diagnosis of CTEPH versus IPAH using capillary to end-tidal carbon dioxide gradients.

Chronic thromboembolic pulmonary hypertension (CTEPH) represents an important differential diagnosis to idiopathic pulmonary arterial hypertension (IPAH). We hypothesised that the capillary to end-tidal carbon dioxide gradient at rest and during exercise might help differentiate CTEPH from IPAH. Patients who presented with unequivocal IPAH or CTEPH according to ventilation/perfusion scanning, pulmonary angiography, computed tomography and right heart catheterisation were included in this retrospective study and compared with healthy controls. 21 IPAH patients and 16 CTEPH patients fulfilled the inclusion criteria. Haemodynamics and peak oxygen uptake were comparable, but respiratory rates at rest and during exercise were significantly higher in CTEPH than in IPAH. End-tidal carbon dioxide was significantly lower in CTEPH versus IPAH at rest and during exercise, while capillary carbon dioxide values were similar. Correspondingly, capillary to end-tidal carbon dioxide gradients were significantly increased in CTEPH versus IPAH at rest and during exercise (median (range) 8.6 (3.0-13.7) versus 4.4 (0.9-9.0) (p<0.001) and 9.3 (3.3-13.1) versus 4.1 (0.0-8.8) mmHg (p<0.001), respectively). Although these values were closer to normal in IPAH they were still significantly elevated compared with healthy controls (2.3 (-4.8-8.1) and -1.9 (-5.7-6.2) mmHg, respectively). Capillary to end-tidal carbon dioxide gradients may help to distinguish CTEPH from IPAH based on resting and exercise values.

[The German centre for lung research - translational research for the prevention, diagnosis and treatment of respiratory diseases]. / Das Deutsche Zentrum für Lungenforschung - Translationale Forschung für Prävention, Diagnose und Therapie von Atemwegserkrankungen.

Respiratory diseases are one of the most important causes of mortality with tremendous costs for health care systems, not only in Germany, but worldwide. Up to now treatment options for most of these chronic diseases are limited. The German Ministry for Research and Education (BMBF) - following the example of the US National Institute of Health have supported the foundation of a German Centre for Lung Research (DZL) to speed up the development of preventive, diagnostic and therapeutic measures. Not only universities, but also non-university based research institutes are part of the DZL. To allow the translation from basic research experience into clinical practice to improve patient care, basic research orientated approaches will be combined with disease and patient focused approaches. The DZL is one of six German Centres for Health Care Research (neurological diseases, diabetes, cardiovascular diseases, infectious diseases, cancer, and lung diseases) for the optimisation of translational processes to overcome the burden of major diseases.

Terguride ameliorates monocrotaline-induced pulmonary hypertension in rats.

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterised by vasoconstriction and remodelling of the pulmonary vasculature. The serotonin (5-hydroxytryptamine (5-HT)) pathway has been shown to play a major role in the pathogenesis of PAH, but pharmacological modulation of this pathway for treatment of PAH is, to date, at a pre-clinical level. Terguride is a 5-HT receptor (5-HTR) antagonist that is well tolerated and clinically approved for ovulation disorders. Immunohistochemistry against 5-HTR(2A/B) on human lungs revealed their localisation to the vascular smooth muscle layer and quantitative RT-PCR showed 5-HTR(2B) upregulation in pulmonary artery smooth muscle cells (PASMC) isolated from PAH patients. Proliferation and migration of cultured primary human PASMC were dose-dependently blocked by terguride. Therapeutic 5-HT signalling inhibition was 1) demonstrated in isolated, ventilated and perfused rat lungs and 2) by chronic terguride treatment of rats with monocrotaline (MCT)-induced pulmonary hypertension in a preventive or curative approach. Terguride inhibited proliferation of PASMCs and abolished 5-HT-induced pulmonary vasoconstriction. Chronic terguride treatment prevented dose-dependently the development and progression of MCT-induced PAH in rats. Thus, terguride represents a valuable novel therapeutic approach in PAH.

Real-time quantitative RT-PCR after laser-assisted cell picking.

The present study describes a technique for quantitation of mRNA in a few isotypic cells obtained from an intact organ structure by combining laser-assisted cell picking and real-time PCR. The microscopically controlled lasering of selected cells in stained tissue sections was applied to lung alveolar macrophages, which are unique in that they can alternatively be gathered as a pure cell population from intact lungs by bronchoalveolar lavage as a reference technique. TNF-alpha was chosen as the transcriptionally inducible target gene to be quantified in alveolar macrophages of control rat lung, as well as low- and high-challenge lungs stimulated by endotoxin and IFN-gamma nebulization. Online fluorescence detection for quantitation of the number of amplified copies was based on 5' nuclease activity of Taq polymerase cleaving a sequence-specific dual-labeled fluorogenic hybridization probe. A pseudogene-free sequence of PBGD served as an internal calibrator for comparative quantitation of target. A quick procedure and minimized loss of template were achieved by avoiding RNA extraction, DNase digestion and nested-PCR. Using this approach, we demonstrated dose-dependent manifold upregulation of the ratio of TNF-alpha mRNA copies per one copy of PBGD mRNA in alveolar macrophages of the challenged lungs. The quantitative data obtained from laser-picked alveolar macrophages were well matched with those of lavaged alveolar macrophages carried out in parallel. We suggest that this new combination of laser-assisted cell picking and real-time PCR has great promise for quantifying mRNA expression in a few single cells or oligocellular clusters in intact organs, allowing assessment of transcriptional regulation in defined cell populations.

Inflammatory lipid mediator generation elicited by viable hemolysin-forming Escherichia coli in lung vasculature.

Escherichia coli hemolysin, a transmembrane pore-forming exotoxin, is considered an important virulence factor for E. coli-related extraintestinal infections and sepsis. The possible significance of hemolysin liberation for induction of inflammatory lipid mediators was investigated in isolated rabbit lungs infused with viable bacteria (concentration range, 10(4)-10(7)/ml). Hemolysin-secreting E. coli (E. coli-Hly+), but not an E. coli strain that releases an inactive form of the exotoxin, induced marked lung leukotriene (LT) generation with predominance of cysteinyl LTs. Eicosanoid synthesis was not inhibited in the presence of plasma with toxin-neutralizing capacity. Pre-application of 2 x 10(8) human granulocytes, which sequestered in the lung microvasculature, caused a severalfold increase in leukotriene generation in response to E. coli-Hly+ challenge both in the absence and presence of plasma. Data are presented indicating neutrophil-endothelial cell cooperation in arachidonic acid lipoxygenase metabolism as an underlying mechanism. We conclude that liberation of hemolysin from viable E. coli induces marked lipid mediator generation in lung vasculature, which is potentiated in the presence of neutrophil sequestration and may contribute to microcirculatory disturbances during the course of severe infections.

Neutrophil activation by anti-proteinase 3 antibodies in Wegener's granulomatosis: role of exogenous arachidonic acid and leukotriene B4 generation.

Among the anti-neutrophil cytoplasmic antibodies (ANCA), those targeting proteinase 3 (PR3) have a high specificity for Wegener's granulomatosis (WG). It is known that a preceding priming of neutrophils with cytokines is a prerequisite for membrane surface expression of PR3, which is then accessible to autoantibody binding. Employing a monoclonal antibody directed against human PR3 and ANCA-positive serum from WG patients with specificity for PR3, we now investigated the role of free arachidonic acid (AA) in autoantibody-related human neutrophil activation. Priming of neutrophils with tumor necrosis factor (TNF-alpha) for 15 min or exposure to anti-PR3 antibodies or incubation with free AA (10 microM) as sole events did not provoke superoxide generation, elastase secretion or generation of 5-lipoxygenase products of AA. Similarly, the combination of TNF-alpha-priming and AA incubation was ineffective. When TNF-alpha-primed neutrophils were stimulated by anti-PR3 antibodies, superoxide and elastase secretion was provoked in the absence of lipid mediator generation. However, when free AA was additionally provided, a strong activation of the 5-lipoxygenase pathway was demasked, with the appearance of excessive quantities of leukotriene (LT)B4, LTA4, and 5-hydroxyeicosatetraenoic acid. Moreover, superoxide and elastase secretion were markedly amplified, and studies with 5-lipoxygenase inhibitors and a LTB4-antagonist demonstrated this was due to an LTB4-related autocrine loop of cell activation. In contrast, the increased synthesis of platelet-activating factor in response to TNF-alpha-priming and anti-PR3 stimulation did not contribute to the amplification loop of neutrophil activation under the given conditions. We conclude that anti-PR3 antibodies are potent inductors of the 5-lipoxygenase pathway in primed human neutrophils, and extracellular free AA, as provided at an inflammatory focus, synergizes with the autoantibodies to evoke full-blown lipid mediator generation, granule secretion and respiratory burst. Such events may be enrolled in the pathogenesis of focal necrotizing vascular injury in Wegener's granulomatosis.

Endotoxin "priming" potentiates lung vascular abnormalities in response to Escherichia coli hemolysin: an example of synergism between endo- and exotoxin.

The pore-forming hemolysin of Escherichia coli (HlyA), an important virulence factor in extraintestinal E. coli infections, causes thromboxane generation and related vasoconstriction in perfused rabbit lungs (Seeger, W., H. Walter, N. Suttorp, M. Muhly, and S. Bhakdi. 1989. J. Clin. Invest. 84:220). We investigated the influence of pulmonary vascular "priming" with endotoxin on the responsiveness of the lung to a low-dose HlyA challenge. Rabbit lungs were perfused with Krebs Henseleit buffer containing 0.1-100 ng/ml Salmonella abortus equii lipopolysaccharide (LPS) for 60-180 min. This treatment caused protracted release of tumor necrosis factor into the recirculating medium, but did not induce significant alterations of pulmonary hemodynamics and fluid balance. At a dose of 1 ng/ml, HlyA elicited only moderate thromboxane release (< 200 pg/ml) and pulmonary artery pressure increase (< or = 6 mmHg) in control lungs. Acceleration and potentiation of both the metabolic and vasoconstrictor response occurred in lungs primed with LPS. This priming effect displayed dose (threshold integral of 0.1-1 ng/ml LPS) and time dependencies (threshold integral of 60-90 min LPS incubation). Maximum thromboxane release and pulmonary artery pressure increase surpassed the responses to HlyA in nonprimed lungs by more than 15-fold. Cyclooxygenase inhibition and thromboxane-receptor antagonism blocked these effects. These data demonstrate that LPS priming synergizes with HlyA challenge to provoke vascular abnormalities that are possibly relevant to the pathogenesis of organ failure in severe local and systemic infections.

Wegener's granulomatosis: anti-proteinase 3 antibodies are potent inductors of human endothelial cell signaling and leakage response.

Anti-neutrophil cytoplasmic antibodies (ANCAs) targeting proteinase 3 (PR3) have a high specifity for Wegener's granulomatosis (WG), and their role in activating leukocytes is well appreciated. In this study, we investigated the influence of PR3-ANCA and murine monoclonal antibodies on human umbilical vascular endothelial cells (HUVECs). Priming of HUVECs with tumor necrosis factor alpha induced endothelial upregulation of PR3 message and surface expression of this antigen, as measured by Cyto-ELISA, with a maximum occurrence after 2 h. Primed cells responded to low concentrations of both antibodies (25 ng-2.5 microg/ml), but not to control immunoglobulins, with pronounced, dose-dependent phosphoinositide hydrolysis, as assessed by accumulation of inositol phosphates. The signaling response peaked after 20 min, in parallel with the appearance of marked prostacyclin and platelet-activating factor synthesis. The F(ab)2 fragment of ANCA was equally potent as ANCA itself. Disrupture of the endothelial F-actin content by botulinum C2 toxin to avoid antigen-antibody internalization did not affect the response. In addition to the metabolic events, anti-PR3 challenge, in the absence of plasma components, provoked delayed, dose-dependent increase in transendothelial protein leakage. We conclude that anti-PR3 antibodies are potent inductors of the preformed phosphoinositide hydrolysis-related signal tranduction pathway in human endothelial cells. Associated metabolic events and the loss of endothelial barrier properties suggest that anti-PR3-induced activation of endothelial cells may contribute to the pathogenetic sequelae of autoimmune vasculitis characterizing WG.

Comparative gene expression profiling of post-natal and post-pneumonectomy lung growth.

Although increasing numbers of patients suffer from chronic destructive lung diseases, there are no effective therapeutic options apart from transplantation. Understanding the mechanisms of physiological and regenerative alveolar septation is prerequisite for the development of regenerative therapies for the lung. We compared lung gene expression in the phase of induction of post-natal and post-pneumonectomy alveolarisation to identify regulatory genes involved in both processes. We performed genome-wide microarray screenings of newborn and pneumonectomised mouse lungs 1 and 3 days after birth or surgery. Selected candidates were validated by real-time PCR, Western blot and in situ hybridisation. We found 58 genes to be regulated in both models with 40 candidates being changed likewise. Many of these genes participated in growth and differentiation processes. Additionally, immune system, structural molecules, respiratory chain, signal transduction and metabolism were involved. Some candidates were not yet linked to specific functions. The highest regulatory concordance was observed for various isoforms of (pro-)collagen molecules, elastin and the elastin-associated protein fibrillin1 being corporately upregulated. Our findings do not definitively support a common regulating mechanism for induction of post-natal and adult alveolarisation, but some candidates in the intersection of both models are promising for further investigations.

Epoxyeicosatrienoates are the dominant eicosanoids in human lungs upon microbial challenge.

Lipoxygenase, cyclo-oxygenase and cytochrome P450 (CYP) products of arachidonic acid (AA) are implicated in pulmonary vasoregulation. The CYP-mediated epoxyeicosatrienoates (EETs) have been described previously as the predominant eicosanoids in human lungs upon stimulation with the Ca(2+) ionophore A23187. In this study, we challenged perfused human lungs with two microbial agents: Escherichia coli haemolysin (ECH) and formyl-methionyl-leucyl-phenylalanine (fMLP). Both stimuli elicited pronounced generation of leukotrienes (LTs), hydroxyeicosatetraenoic acids (HETEs), prostanoids (PTs) and EETs/dihydroxyeicosatrienoic acids (DHETs), as assessed by liquid chromatography-mass spectrometry, paralleled by pulmonary artery pressor response and lung oedema formation. The maximum buffer concentrations of EETs/DHETs surpassed those of LTs plus HETEs and PTs by a factor of four (ECH) or three (AA/fMLP). Dual 5-lipoxygenase/cyclo-oxygenase inhibition caused pronounced reduction of AA/fMLP-induced LT/PT synthesis and oedema formation but only limited attenuation of pulmonary vasoconstriction, while inhibition of CYP epoxygenase clearly attenuated AA/fMLP-induced EET/DHET synthesis and vasoconstriction but not oedema formation, suggesting a major contribution of LTs/PTs to vascular leakage and of EETs/DHETs to pressor response. Consequently, generation of EETs/DHETs is greater than that of LTs plus HETEs and PTs in ex vivo perfused human lungs upon microbial challenge suggesting a substantial contribution of these mediators to inflammatory-infectious pulmonary injury.

Treprostinil inhibits the recruitment of bone marrow-derived circulating fibrocytes in chronic hypoxic pulmonary hypertension.

A unique subpopulation of peripheral blood mononuclear cells that exhibit a parallel expression of haematopoietic and mesenchymal markers has been described as "circulating fibrocytes". These cells were demonstrated to obtain a fibroblastic phenotype in tissues or cell culture and contribute to pulmonary fibrotic disorders and tissue remodelling processes. The aim of our study was to characterise the recruitment of circulating fibrocytes in vivo in the model of chronic hypoxic pulmonary hypertension in mice and to analyse the therapeutic effect of the stable prostacyclin analogue trepostinil with respect to this cell population. To track circulating fibrocytes in vivo, we transplanted wild-type mice with bone marrow from ubiquitously eGFP expressing mice and subjected them to chronic hypoxia. We observed significantly increased recruitment of circulating fibrocytes to the remodelled pulmonary resistance arteries in response to hypoxia. Treatment with treprostinil significantly reduced the recruitment of these cells compared to normoxic mice. Treprostinil also reduced right ventricular systolic pressure and slightly reduced the vascular remodelling but failed to reverse the right ventricular hypertrophy. In summary, we show that circulating fibrocytes contribute to hypoxic pulmonary vascular remodelling and may be specifically targeted by a prostacyclin analogue. Further investigations of cellular and paracrine mechanisms are warranted to decipher their role in pulmonary hypertension.

Mitochondrial cytochrome redox states and respiration in acute pulmonary oxygen sensing.

Hypoxic pulmonary vasoconstriction (HPV) is an essential mechanism to optimise lung gas exchange. We aimed to decipher the proposed oxygen sensing mechanism of mitochondria in HPV. Cytochrome redox state was assessed by remission spectrophotometry in intact lungs and isolated pulmonary artery smooth muscle cells (PASMC). Mitochondrial respiration was quantified by high-resolution respirometry. Alterations were compared with HPV and hypoxia-induced functional and molecular readouts on the cellular level. Aortic and renal arterial smooth muscle cells (ASMC and RASMC, respectively) served as controls. The hypoxia-induced decrease of mitochondrial respiration paralleled HPV in isolated lungs. In PASMC, reduction of respiration and mitochondrial cytochrome c and aa3 (complex IV), but not of cytochrome b (complex III) matched an increase in matrix superoxide levels as well as mitochondrial membrane hyperpolarisation with subsequent cytosolic calcium increase. In contrast to PASMC, RASMC displayed a lower decrease in respiration and no rise in superoxide, membrane potential or intracellular calcium. Pharmacological inhibition of mitochondria revealed analogous kinetics of cytochrome redox state and strength of HPV. Our data suggest inhibition of complex IV as an essential step in mitochondrial oxygen sensing of HPV. Concomitantly, increased superoxide release from complex III and mitochondrial membrane hyperpolarisation may initiate the cytosolic calcium increase underlying HPV.