[Show abstract][Hide abstract] ABSTRACT: Pulmonary vascular remodeling, the pathological hallmark of pulmonary arterial hypertension, is attributed to proliferation, apoptosis resistance, and migration of vascular cells. A role of dysregulated matrix cross-linking and stability as a pathogenic mechanism has received little attention. We aimed to assess whether matrix cross-linking enzymes played a causal role in experimental pulmonary hypertension (PH).
All 5 lysyl oxidases were detected in concentric and plexiform vascular lesions of patients with idiopathic pulmonary arterial hypertension. Lox, LoxL1, LoxL2, and LoxL4 expression was elevated in lungs of patients with idiopathic pulmonary arterial hypertension, whereas LoxL2 and LoxL3 expression was elevated in laser-capture microdissected vascular lesions. Lox expression was hypoxia-responsive in pulmonary artery smooth muscle cells and adventitial fibroblasts, whereas LoxL1 and LoxL2 expression was hypoxia-responsive in adventitial fibroblasts. Lox expression was increased in lungs from hypoxia-exposed mice and in lungs and pulmonary artery smooth muscle cells of monocrotaline-treated rats, which developed PH. Pulmonary hypertensive mice exhibited increased muscularization and perturbed matrix structures in vessel walls of small pulmonary arteries. Hypoxia exposure led to increased collagen cross-linking, by dihydroxylysinonorleucine and hydroxylysinonorleucine cross-links. Administration of the lysyl oxidase inhibitor β-aminopropionitrile attenuated the effect of hypoxia, limiting perturbations to right ventricular systolic pressure, right ventricular hypertrophy, and vessel muscularization and normalizing collagen cross-linking and vessel matrix architecture.
Lysyl oxidases are dysregulated in clinical and experimental PH. Lysyl oxidases play a causal role in experimental PH and represent a candidate therapeutic target. Our proof-of-principle study demonstrated that modulation of lung matrix cross-linking can affect pulmonary vascular remodeling associated with PH.
Arteriosclerosis Thrombosis and Vascular Biology 05/2014; · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acute respiratory distress syndrome (ARDS) is a major cause of mortality in intensive care units. Patients with ARDS often require parenteral nutrition with lipid emulsions as essential components. Besides energy supply these lipid emulsions might display differential modulatory effects on lung integrity and inflammation.
In a pre-emptive strategy, we investigated the impact of three different intravenously infused lipid emulsions on lung morphology, leukocyte invasion, protein leakage and cytokines in a murine model of ARDS. Mice received an infusion of normal saline solution, pure long-chain triglycerides (LCT) emulsion, a medium-chain triglycerides (MCT) containing mixed emulsion (LCT/MCT), or a fish-oil (FO) containing mixed emulsion (LCT/MCT/FO) before lipopolysaccharide (LPS) challenge.
Mice pre-infused with fish-oil containing lipid emulsion showed decreased leukocyte invasion, protein leakage, myeloperoxidase activity, and cytokine production in their alveolar space after LPS challenge compared to mice receiving LCT or LCT/MCT. In line with these findings lung morphology assessed by histological staining after LPS-induced lung injury improved faster in the LCT/MCT/FO group. Concerning above mentioned parameters no significant difference was observed between mice infused with LCT or the combination of LCT and MCT.
Fish oil-containing lipid emulsions might exert anti-inflammatory and pro-resolving effects in the murine model of acute lung injury. Partial replacement of n-6 fatty acids with n-3 fatty acids may thus be of benefit for critically ill patients at risk for ARDS which require parenteral nutrition.
Critical care (London, England) 04/2014; 18(2):R85. · 4.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Castleman's disease, also known as angiofollicular lymph node hyperplasia, is a rare disease with two known expansion types, unicentric and multicentric, which play a major role in determining therapy. We focus here on the unicentric type, which can be treated and cured by surgery. To date, approximately 1000 cases of Castleman's disease have been reported in the literature.
A 50-year-old Caucasian woman presented to our Department of Hematology and Internal Oncology with increasing fatigue as her sole symptom. Diagnostic investigations including laboratory studies, ultrasound, computed tomography and magnetic resonance imaging were performed. These revealed an interaortocaval, retroperitoneal tumor mass in her upper abdomen as the only manifestation of the disease. No enlarged lymph nodes were detected. We conducted a laparotomy with radical extirpation of the tumor mass (10x9x5.7cm). Complete tumor resection with clear margins was achieved. A pathological analysis of the resected sample showed atypical lymphoid tissue of small to medium cells with some clearly visible nucleoli, enlarged sinusoidal vessels, pleomorphic calcifications and focally preserved germinal-center-like structures. Histological and immunohistochemical analysis confirmed the diagnosis of Castleman's disease: staining for CD3, CD5, CD10, CD20, CD23, CD79 and Ki-67 was strongly positive in the germinal-center-like structures. Histological findings clearly showed the disease to be the hyaline vascular subtype. Staining for cyclin D1 and CD30 was negative. Expression of CD15 was positive in the enlarged sinusoidal vessels. A supplementary clonality analysis was without pathological findings. Tests for human immunodeficiency virus and human herpes virus 8 were negative and results from a bone marrow biopsy were normal. Our patient recovered well from surgery and was discharged from our hospital. To date, no recurrence of the disease has been detected.
Castleman's disease is a rare disorder that remains a diagnostic challenge. Radical surgical resection is considered to be the gold standard for treating the unicentric variant of this disease.
[Show abstract][Hide abstract] ABSTRACT: Aberrant remodelling of the extracellular matrix in the developing lung may underlie arrested alveolarisation associated with bronchopulmonary dysplasia (BPD). Transglutaminases are regulators of extracellular matrix remodelling. Therefore, the expression and activity of transglutaminases were assessed in lungs from human neonates with BPD and in a rodent model of BPD.Transglutaminase expression and localisation were assessed by RT-PCR, immunoblotting, activity assay and immunohistochemical analyses of human and mouse lung tissues. Transglutaminase regulation by transforming growth factor (TGF)-β was investigated in lung cells by luciferase-based reporter assay and RT-PCR. TGF-β signalling was neutralised in vivo in an animal model of BPD, to determine whether TGF-β mediated the hyperoxia-induced changes in transglutaminase expression.Transglutaminase 2 expression was upregulated in the lungs of preterm infants with BPD and in the lungs of hyperoxia-exposed mouse pups, where lung development was arrested. Transglutaminase 2 localised to the developing alveolar septa. TGF-β was identified as a regulator of transglutaminase 2 expression in human and mouse lung epithelial cells. In vivo neutralisation of TGF-β signalling partially restored normal lung structure and normalised lung transglutaminase 2 mRNA expression.Our data point to a role for perturbed transglutaminase 2 activity in the arrested alveolarisation associated with BPD.
European Respiratory Journal 03/2014; · 6.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Arrested alveolarization is the pathological hallmark of bronchopulmonary dysplasia (BPD), a complication of premature birth. Here, the impact of systemic application of hydrogen sulfide (H2S) on post-natal alveolarization was assessed in a mouse BPD model. Exposure of newborn mice to 85% O2 for 10 days reduced the total lung alveoli number by 56% and increased alveolar septal wall thickness by 29%, as assessed by state-of-the-art stereological analysis. Systemic application of H2S using the slow-release H2S donor GYY4137 for 10 days resulted in pronounced improvement in lung alveolarization in pups breathing 85% O2, compared with vehicle-treated littermates. Although without impact on lung oxidative status, systemic H2S blunted leukocyte infiltration into alveolar airspaces provoked by hyperoxia, and restored normal lung interleukin 10 levels that were otherwise depressed by 85% O2. Treatment of primary mouse alveolar type II (ATII) cells with the rapid-release H2S donor NaHS had no impact on cell viability; however, NaHS promoted ATII cell migration. While exposure of ATII cells to 85% O2 caused dramatic changes in mRNA expression, exposure to either GYY4137 or NaHS had no impact on ATII cell mRNA expression, as assessed by microarray, suggesting that the effects observed were independent of changes in gene expression. The impact of NaHS on ATII cell migration was attenuated by glibenclamide, implicating ion channels; and was accompanied by activation of Akt, hinting at two possible mechanisms of H2S action. These data support further investigation of H2S as a candidate interventional strategy to limit the arrested alveolarization associated with BPD.
[Show abstract][Hide abstract] ABSTRACT: Influenza virus is a paradigm for a pathogen that frequently crosses the species barrier from animals to humans, causing severe disease in the human population. This ranges from frequent epidemics to occasional pandemic outbreaks with millions of death. All previous pandemics in humans were caused by animal viruses or virus reassortants carrying animal virus genes, underlining that the fight against influenza requires a One Health approach integrating human and veterinary medicine. Furthermore, the fundamental question of what enables a flu pathogen to jump from animals to humans can only be tackled in a transdisciplinary approach between virologists, immunologists and cell biologists. To address this need the German FluResearchNet was established as a first nationwide influenza research network that virtually integrates all national expertise in the field of influenza to unravel viral and host determinants of pathogenicity and species transmission and to explore novel avenues of antiviral intervention. Here we focus on the various novel anti-flu approaches that were developed as part of the FluResearchNet activities.
International Journal of Medical Microbiology. 01/2014;
[Show abstract][Hide abstract] ABSTRACT: The lung mesenchyme consists of a widely heterogeneous population of cells that play crucial roles during development and homeostasis after birth. These cells belong to myogenic, adipogenic, chondrogenic, neuronal and other lineages. Yet, no clear hierarchy for these lineages has been established. We have previously generated a novel Fgf10(iCre) knock-in mouse line that allows lineage tracing of Fgf10-positive cells during development and postnatally. Using these mice, we hereby demonstrate the presence of two waves of Fgf10 expression during embryonic lung development: the first wave, comprising Fgf10-positive cells residing in the submesothelial mesenchyme at early pseudoglandular stage (as well as their descendants); and the second wave, comprising Fgf10-positive cells from late pseudoglandular stage (as well as their descendants). Our lineage-tracing data reveal that the first wave contributes to the formation of parabronchial and vascular smooth muscle cells as well as lipofibroblasts at later developmental stages, whereas the second wave does not give rise to smooth muscle cells but to lipofibroblasts as well as an Nkx2.1Ð E-CadÐ Epcam(+) Pro-Spc(+) lineage that requires further in-depth analysis. During alveologenesis, Fgf10-positive cells give rise to lipofibroblasts rather than alveolar myofibroblasts, and during adult life, a subpopulation of Fgf10-expressing cells represents a pool of resident mesenchymal stromal (stem) cells (MSCs) (Cd45Ð Cd31Ð Sca-1(+)). Taken together, we show for the first time that Fgf10-expressing cells represent a pool of mesenchymal progenitors in the embryonic and postnatal lung. Our findings suggest that Fgf10-positive cells could be useful for developing stem cell-based therapies for treating interstitial lung diseases.
[Show abstract][Hide abstract] ABSTRACT: Glucocorticoids represent the mainstay therapy for many lung diseases, providing outstanding management of asthma, but performing surprisingly poorly in patients with acute respiratory distress syndrome, chronic obstructive pulmonary disease, lung fibrosis, and blunted lung development associated with bronchopulmonary dysplasia in pre-term infants. Transforming growth factor (TGF)-β is a pathogenic mediator of all four of these diseases, prompting us to explore glucocorticoid/TGF-β signaling cross-talk. Glucocorticoids, including dexamethasone, methylprednisolone, budesonide, and fluticasone, potentiated TGF-β signaling by the Acvrl1/Smad1/5/8 signaling axis, and blunted signaling by the Tgfbr1/Smad2/3 axis in NIH/3T3 cells, as well as primary lung fibroblasts, smooth muscle cells, and endothelial cells. Dexamethasone drove expression of the accessory type III TGF-β receptor Tgfbr3, also called betaglycan. Tgfbr3 was demonstrated to be a switch that blunted Tgfbr1/Smad2/3 and potentiated Acvrl1/Smad1 signaling in lung fibroblasts. The Acvrl1/Smad1 axis, which was stimulated by dexamethasone, was active in lung fibroblasts, and antagonized Tgfbr1/Smad2/3 signaling. Dexamethasone acted synergistically with TGF-β to drive differentiation of primary lung fibroblasts to myofibroblasts, revealed by acquisition of smooth muscle actin and smooth muscle myosin, which are exclusively Smad1-dependent processes in fibroblasts. Administration of dexamethasone to live mice recapitulated these observations, and revealed a lung-specific impact of dexamethasone on lung Tgfbr3 expression and phospho-Smad1 levels in vivo. These data point to an interesting and hitherto unknown impact of glucocorticoids on TGF-β signaling in lung fibroblasts, and other constituent cell-types of the lung, that may be relevant to lung physiology, as well as lung pathophysiology, in terms of drug-disease interactions.
Journal of Biological Chemistry 12/2013; · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: TGF-β is a pathogenic factor in patients with acute respiratory distress syndrome (ARDS), a condition characterized by alveolar edema. A unique TGF-β pathway is described, which rapidly promoted internalization of the αβγ epithelial sodium channel (ENaC) complex from the alveolar epithelial cell surface, leading to persistence of pulmonary edema. TGF-β applied to the alveolar airspaces of live rabbits or isolated rabbit lungs blocked sodium transport and caused fluid retention, which-together with patch-clamp and flow cytometry studies-identified ENaC as the target of TGF-β. TGF-β rapidly and sequentially activated phospholipase D1, phosphatidylinositol-4-phosphate 5-kinase 1α, and NADPH oxidase 4 (NOX4) to produce reactive oxygen species, driving internalization of βENaC, the subunit responsible for cell-surface stability of the αβγENaC complex. ENaC internalization was dependent on oxidation of βENaC Cys(43). Treatment of alveolar epithelial cells with bronchoalveolar lavage fluids from ARDS patients drove βENaC internalization, which was inhibited by a TGF-β neutralizing antibody and a Tgfbr1 inhibitor. Pharmacological inhibition of TGF-β signaling in vivo in mice, and genetic ablation of the nox4 gene in mice, protected against perturbed lung fluid balance in a bleomycin model of lung injury, highlighting a role for both proximal and distal components of this unique ENaC regulatory pathway in lung fluid balance. These data describe a unique TGF-β-dependent mechanism that regulates ion and fluid transport in the lung, which is not only relevant to the pathological mechanisms of ARDS, but might also represent a physiological means of acutely regulating ENaC activity in the lung and other organs.
Proceedings of the National Academy of Sciences 12/2013; · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bronchopulmonary dysplasia (BPD) is a common and serious complication of premature birth, characterized by a pronounced arrest of alveolar development. The underlying pathophysiological mechanisms are poorly understood, although perturbations to the maturation and remodeling of the extracellular matrix (ECM) are emerging as candidate disease pathomechanisms. In this study, the expression and regulation of three members of the lysyl hydroxylase family of ECM remodeling enzymes (Plod1, Plod2, and Plod3) in clinical BPD, as well as in an experimental animal model of BPD, were addressed. All three enzymes were localized to the septal walls in developing mouse lungs, with Plod1 also expressed in the vessel walls of the developing lung, and Plod3 expressed uniquely at the base of developing septa. The expression of plod1, plod2, and plod3 was up-regulated in the lungs of mouse pups exposed to 85% O2, an experimental animal model of BPD. Transforming growth factor (TGF)-β increased plod2 mRNA levels and activated the plod2 promoter in vitro in lung epithelial cells and in lung fibroblasts. Using in vivo neutralization of TGF-β signaling in the experimental animal model of BPD, TGF-β was identified as the regulator of aberrant plod2 expression. PLOD2 mRNA expression was also elevated in human neonates who died with BPD or at risk for BPD, compared with neonates matched for gestational age at birth or chronological age at death. These data point to potential roles for lysyl hydroxylases in normal lung development, as well as in perturbed late lung development associated with BPD.
[Show abstract][Hide abstract] ABSTRACT: Primary alveolar epithelial cells play a pivotal role in lung research, particularly when focusing on gas exchange, barrier function and transepithelial transport processes. However, efficient transfection of primary alveolar epithelial cells continues to be a major challenge. In the present study, we applied nucleofection, a novel method of gene and oligonucleotide delivery to the nucleus of cells by electroporation, to achieve highly efficient transfection of primary alveolar epithelial type II (ATII) cells. To quantify the amount of ATII cells effectively transfected, we applied a plasmid expressing GFP and assessed the amount of GFP expressing cells by flow cytometry. Analysis of the nucleofected ATII cells revealed a concentration-dependent transfection efficiency of up to 50% when using 3 to 8 µg plasmid DNA without affecting cell viability. Nucleofection of cultured A549 and H441 cells yielded similar transfection rates. Importantly, nucleofection of ATII cells did not interfere with the integrity of ATII monolayers even when using relatively high concentrations of plasmid DNA. In subsequent studies, we also efficiently delivered small interfering RNAs to ATII cells by nucleofection, thereby silencing Akt and the multi-ligand receptor megalin, that has been recently shown to play a key role in removal of excess protein from the alveolar space, and effectively inhibited megalin-driven uptake and transcellular transport of albumin in ATII cells. Thus, we report successful transfection of primary rat alveolar epithelial cells both with plasmids and oligonucleotides via nucleofection with high viability and consistently good transfection rates without impairing key physiological properties of the cells.
[Show abstract][Hide abstract] ABSTRACT: Klebsiella pneumoniae is a leading cause of severe hospital-acquired respiratory tract infections and death but little is known regarding the modulation of respiratory dendritic cell (DC) subsets. Plasmacytoid DC (pDC) are specialized type 1 interferon producing cells and considered to be classical mediators of antiviral immunity.
By using multiparameter flow cytometry analysis we have analysed the modulation of respiratory DC subsets after intratracheal Klebsiella pneumonia infection.
Data indicate that pDCs and MoDC were markedly elevated in the post acute pneumonia phase when compared to mock-infected controls. Analysis of draining mediastinal lymph nodes revealed a rapid increase of activated CD103+ DC, CD11b+ DC and MoDC within 48 h post infection. Lung pDC identification during bacterial pneumonia was confirmed by extended phenotyping for 120G8, mPDCA-1 and Siglec-H expression and by demonstration of high Interferon-alpha producing capacity after cell sorting. Cytokine expression analysis of ex vivo-sorted respiratory DC subpopulations from infected animals revealed elevated Interferon-alpha in pDC, elevated IFN-gamma, IL-4 and IL-13 in CD103+ DC and IL-19 and IL-12p35 in CD11b+ DC subsets in comparison to CD11c+ MHC-class IIlow cells indicating distinct functional roles. Antigen-specific naive CD4+ T cell stimulatory capacity of purified respiratory DC subsets was analysed in a model system with purified ovalbumin T cell receptor transgenic naive CD4+ responder T cells and respiratory DC subsets, pulsed with ovalbumin and matured with Klebsiella pneumoniae lysate. CD103+ DC and CD11b+ DC subsets represented the most potent naive CD4+ T helper cell activators.
These results provide novel insight into the activation of respiratory DC subsets during Klebsiella pneumonia infection. The detection of increased respiratory pDC numbers in bacterial pneumonia may indicate possible novel pDC functions with respect to lung repair and regeneration.
Respiratory research 09/2013; 14(1):91. · 3.64 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this review we summarize recent major advances in our understanding on the molecular mechanisms, mediators and biomarkers of ALI and alveolo-capillary barrier dysfunction, highlighting the role of immune cells, inflammatory and non-inflammatory signaling events, mechanical noxae, and the affected cellular and molecular entities and functions. Furthermore, we address novel aspects of resolution and repair of ALI, as well as putative candidates for treatment of ALI, including pharmacological and cellular therapeutic means.
[Show abstract][Hide abstract] ABSTRACT: Background: Sepsis is a severe inflammatory disorder with a high mortality in intensive care units mostly due to multiorgan failure. Mitochondrial dysfunction is regarded as a key factor involved in the pathogenesis of septic disorders, leading to a decline in energy supply. The aim of the present study was to evaluate whether application of short-chain fatty acids (SCFAs) and medium-chain fatty acids (MCFAs) could improve mitochondrial function and thus might serve as a potential energy source under inflammatory conditions. Materials and Methods: As an experimental approach, starved human endothelial cells and monocytes were incubated with hexanoic acid, heptanoic acid, octanoic acid, or glucose and subsequently subjected to high-resolution respirometry to assess mitochondrial function under baseline conditions. In a second set of experiments, cells were pretreated with tumor necrosis factor-α to mimic inflammation and sepsis. Results: We demonstrated that addition of SCFAs and MCFAs increases mitochondrial respiratory capacity at baseline and inflammatory conditions in both cell types. None of the fatty acids induced changes in mitochondrial DNA content or the generation of proinflammatory cytokines, indicating a beneficial safety profile. Conclusion: We deduce that SCFAs and MCFAs are suitable and safe sources of energy under inflammatory conditions with the capability to partly restore mitochondrial respiration.
Journal of Parenteral and Enteral Nutrition 05/2013; · 2.49 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Influenza viruses (IV) cause pneumonia in humans with progression to lung failure and fatal outcome. Dysregulated release of cytokines including type I interferons (IFNs) has been attributed a crucial role in immune-mediated pulmonary injury during severe IV infection. Using and IV infection models, we demonstrate that alveolar macrophage (AM)-expressed IFN-β significantly contributes to IV-induced alveolar epithelial cell (AEC) injury by autocrine induction of the pro-apoptotic factor TNF-related apoptosis-inducing ligand (TRAIL). Of note, TRAIL was highly upregulated in and released from AM of patients with pandemic H1N1 IV-induced acute lung injury. Elucidating the cell-specific underlying signalling pathways revealed that IV infection induced IFN-β release in AM in a protein kinase R- (PKR-) and NF-κB-dependent way. Bone marrow chimeric mice lacking these signalling mediators in resident and lung-recruited AM and mice subjected to alveolar neutralization of IFN-β and TRAIL displayed reduced alveolar epithelial cell apoptosis and attenuated lung injury during severe IV pneumonia. Together, we demonstrate that macrophage-released type I IFNs, apart from their well-known anti-viral properties, contribute to IV-induced AEC damage and lung injury by autocrine induction of the pro-apoptotic factor TRAIL. Our data suggest that therapeutic targeting of the macrophage IFN-β-TRAIL axis might represent a promising strategy to attenuate IV-induced acute lung injury.
[Show abstract][Hide abstract] ABSTRACT: Influenza viruses (IVs) cause pneumonia in humans with progression to lung failure. Pulmonary DCs are key players in the antiviral immune response, which is crucial to restore alveolar barrier function. The mechanisms of expansion and activation of pulmonary DC populations in lung infection remain widely elusive. Using mouse BM chimeric and cell-specific depletion approaches, we demonstrated that alveolar epithelial cell (AEC) GM-CSF mediates recovery from IV-induced injury by affecting lung DC function. Epithelial GM-CSF induced the recruitment of CD11b+ and monocyte-derived DCs. GM-CSF was also required for the presence of CD103+ DCs in the lung parenchyma at baseline and for their sufficient activation and migration to the draining mediastinal lymph nodes (MLNs) during IV infection. These activated CD103+ DCs were indispensable for sufficient clearance of IVs by CD8+ T cells and for recovery from IV-induced lung injury. Moreover, GM-CSF applied intratracheally activated CD103+ DCs, inducing increased migration to MLNs, enhanced viral clearance, and attenuated lung injury. Together, our data reveal that GM-CSF-dependent cross-talk between IV-infected AECs and CD103+ DCs is crucial for effective viral clearance and recovery from injury, which has potential implications for GM-CSF treatment in severe IV pneumonia.
The Journal of clinical investigation 09/2012; 122(10):3652-64. · 15.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Key points • Under physiological conditions the lung alveoli are impermeable to protein. • In patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) protein-rich oedema fluid accumulates in the distal airspaces and leads to a life-threatening impairment of alveolar gas exchange. • Albumin is a ligand of megalin, a member of the low-density lipoprotein (LDL)-receptor family. • We show that clearance of albumin from the distal air spaces is facilitated by active megalin-mediated transport across the alveolar epithelium. • Understanding of protein clearance mechanisms in the lung may ultimately lead to novel therapeutic approaches for the treatment of ALI/ARDS.
The Journal of Physiology 07/2012; 590(Pt 20):5167-81. · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Influenza A viruses (IV) can cause primary viral pneumonia in humans resulting in acute lung injury (ALI/ARDS) with fatal outcome. One of the hallmarks of IV-induced ALI is the accumulation of edema fluid in the alveolar compartment, which under normal conditions is cleared along a sodium gradient established by basolateral Na,K-ATPase and the apical epithelial sodium channel (ENaC). IV-infection was found to be associated with a decrease in alveolar fluid clearance (AFC). Therefore we aim to investigate the regulation of ENaC and Na,K-ATPase in IV-infection by viral and host factors to characterize the molecular mechanisms affecting AFC.
The effects of IV-infection on ENaC and Na,K-ATPase have been studied in primary murine alveolar epithelial cells (AEC) in monoculture and in co-culture with primary murine alveolar macrophages. AEC and/or macrophages were infected with A/PR/8/1934 (H1N1) and were lysed 6hpi, 16hpi and 24hpi. Cell lysates were subjected to real-time PCR or Western blot analysis. Cellular localization of Na,K-ATPase was analysed by immunofluorescence and by pulldown of surface exposed proteins.
Real-time PCR revealed the presence of Na,K-ATPase subunit isoforms α1, α2, α3, β1 and γ in murine AEC, none of which was regulated on mRNA levels upon IV-infection. ENaC subunits were regulated on gene expression level 12hpi and 24hpi in a dose-dependent manner. Na,K-ATPase α1 and β1 subunit protein levels were significantly decreased by IV-infection in AEC monoculture at 6hpi and 16hpi, but returned to basal levels at 24hpi. Cocultivation of AEC with infected alveolar macrophages, which have been shown to be key players in modulation of IV-induced disease progression, further enhanced the degradation of Na,K-ATPase protein levels. Both surface fraction analysis and immunofluorescence data revealed distinct changes in cellular localization patterns with a decrease of basolaterally located Na,K-ATPase in the time-course of infection.
We provide evidence that edema clearance in IV-induced ALI is directly impaired by viral and host factors during IV-pneumonia by affecting ENaC and Na,K-ATPase expression levels and localisation. Defining the molecular pathways underlying these effects might provide potential targets for new treatment strategies to increase edema clearance in IV-induced ALI.
[Show abstract][Hide abstract] ABSTRACT: Programmed cell death is a crucial cellular response frequently observed in IV-infected tissue. This article reviews the current knowledge on the molecular virus-host interactions that induce apoptosis pathways in an IV-infected cell and the functional implications of these cellular signaling events on viral propagation at distinct steps during the viral replication cycle. Furthermore, it summarizes the role of IV-induced apoptosis pathways in equilibrating the host's antiviral immune response between effective viral clearance and development of severe apoptotic lung injury.
Journal of leukocyte biology 02/2012; 92(1):75-82. · 4.99 Impact Factor