Gas exchange in the lung occurs within alveoli, air-filled sacs composed of type 2 and type 1 epithelial cells (AEC2s and AEC1s), capillaries, and various resident mesenchymal cells. Here, we use a combination of in vivo clonal lineage analysis, different injury/repair systems, and in vitro culture of purified cell populations to obtain new information about the contribution of AEC2s to alveolar maintenance and repair. Genetic lineage-tracing experiments showed that surfactant protein C–positive (SFTPC-positive) AEC2s self renew and differentiate over about a year, consistent with the population containing long-term alveolar stem cells. Moreover, if many AEC2s were specifically ablated, high-resolution imaging of intact lungs showed that individual survivors undergo rapid clonal expansion and daughter cell dispersal. Individual lineage-labeled AEC2s placed into 3D culture gave rise to self-renewing “alveolospheres,” which contained both AEC2s and cells expressing multiple AEC1 markers, including HOPX, a new marker for AEC1s. Growth and differentiation of the alveolospheres occurred most readily when cocultured with primary PDGFRα+ lung stromal cells. This population included lipofibroblasts that normally reside close to AEC2s and may therefore contribute to a stem cell niche in the murine lung. Results suggest that a similar dynamic exists between AEC2s and mesenchymal cells in the human lung.
Christina E. Barkauskas, Michael J. Cronce, Craig R. Rackley, Emily J. Bowie, Douglas R. Keene, Barry R. Stripp, Scott H. Randell, Paul W. Noble, Brigid L.M. Hogan
Atopic asthma is a chronic inflammatory disease of the lungs generally marked by excessive Th2 inflammation. The role of allergen-specific IgG in asthma is still controversial; however, a receptor of IgG–immune complexes (IgG-ICs), FcγRIII, has been shown to promote Th2 responses through an unknown mechanism. Herein, we demonstrate that allergen-specific IgG-ICs, formed upon reexposure to allergen, promoted Th2 responses in two different models of IC-mediated inflammation that were independent of a preformed T cell memory response. Development of Th2-type airway inflammation was shown to be both FcγRIII and TLR4 dependent, and T cells were necessary and sufficient for this process to occur, even in the absence of type 2 innate lymphoid cells. We sought to identify downstream targets of FcγRIII signaling that could contribute to this process and demonstrated that bone marrow–derived DCs, alveolar macrophages, and respiratory DCs significantly upregulated IL-33 when activated through FcγRIII and TLR4. Importantly, IC-induced Th2 inflammation was dependent on the ST2/IL-33 pathway. Our results suggest that allergen-specific IgG can enhance secondary responses by ligating FcγRIII on antigen-presenting cells to augment development of Th2-mediated responses in the lungs via an IL-33–dependent mechanism.
Melissa Y. Tjota, Jesse W. Williams, Tiffany Lu, Bryan S. Clay, Tiara Byrd, Cara L. Hrusch, Donna C. Decker, Claudia Alves de Araujo, Paul J. Bryce, Anne I. Sperling
Increased airway smooth muscle (ASM) contractility and the development of airway hyperresponsiveness (AHR) are cardinal features of asthma, but the signaling pathways that promote these changes are poorly understood. Tyrosine phosphorylation is tightly regulated by the opposing actions of protein tyrosine kinases and phosphatases, but little is known about whether tyrosine phosphatases influence AHR. Here, we demonstrate that genetic inactivation of receptor-like protein tyrosine phosphatase J (
Tamiko R. Katsumoto, Makoto Kudo, Chun Chen, Aparna Sundaram, Elliott C. Callahan, Jing W. Zhu, Joseph Lin, Connor E. Rosen, Boryana N. Manz, Jae W. Lee, Michael A. Matthay, Xiaozhu Huang, Dean Sheppard, Arthur Weiss
Matrix stiffening and myofibroblast resistance to apoptosis are cardinal features of chronic fibrotic diseases involving diverse organ systems. The interactions between altered tissue biomechanics and cellular signaling that sustain progressive fibrosis are not well defined. In this study, we used ex vivo and in vivo approaches to define a mechanotransduction pathway involving Rho/Rho kinase (Rho/ROCK), actin cytoskeletal remodeling, and a mechanosensitive transcription factor, megakaryoblastic leukemia 1 (MKL1), that coordinately regulate myofibroblast differentiation and survival. Both in an experimental mouse model of lung fibrosis and in human subjects with idiopathic pulmonary fibrosis (IPF), we observed activation of the Rho/ROCK pathway, enhanced actin cytoskeletal polymerization, and MKL1 cytoplasmic-nuclear shuttling. Pharmacologic disruption of this mechanotransduction pathway with the ROCK inhibitor fasudil induced myofibroblast apoptosis through a mechanism involving downregulation of BCL-2 and activation of the intrinsic mitochondrial apoptotic pathway. Treatment with fasudil during the postinflammatory fibrotic phase of lung injury or genetic ablation of
Yong Zhou, Xiangwei Huang, Louise Hecker, Deepali Kurundkar, Ashish Kurundkar, Hui Liu, Tong-Huan Jin, Leena Desai, Karen Bernard, Victor J. Thannickal
Chemically modified mRNA is capable of inducing therapeutic levels of protein expression while circumventing the threat of genomic integration often associated with viral vectors. We utilized this novel therapeutic tool to express the regulatory T cell transcription factor, FOXP3, in a time- and site-specific fashion in murine lung, in order to prevent allergic asthma in vivo. We show that modified
Lauren E. Mays, Susanne Ammon-Treiber, Benedikt Mothes, Mohammed Alkhaled, Jennifer Rottenberger, Eva Sophie Müller-Hermelink, Melanie Grimm, Markus Mezger, Sandra Beer-Hammer, Esther von Stebut, Nikolaus Rieber, Bernd Nürnberg, Matthias Schwab, Rupert Handgretinger, Marco Idzko, Dominik Hartl, Michael S.D. Kormann
Hypoxic pulmonary vasoconstriction (HPV) is a physiological mechanism by which pulmonary arteries constrict in hypoxic lung areas in order to redirect blood flow to areas with greater oxygen supply. Both oxygen sensing and the contractile response are thought to be intrinsic to pulmonary arterial smooth muscle cells. Here we speculated that the ideal site for oxygen sensing might instead be at the alveolocapillary level, with subsequent retrograde propagation to upstream arterioles via connexin 40 (Cx40) endothelial gap junctions. HPV was largely attenuated by Cx40-specific and nonspecific gap junction uncouplers in the lungs of wild-type mice and in lungs from mice lacking Cx40 (Cx40–/–). In vivo, hypoxemia was more severe in Cx40–/– mice than in wild-type mice. Real-time fluorescence imaging revealed that hypoxia caused endothelial membrane depolarization in alveolar capillaries that propagated to upstream arterioles in wild-type, but not Cx40–/–, mice. Transformation of endothelial depolarization into vasoconstriction involved endothelial voltage-dependent α1G subtype Ca2+ channels, cytosolic phospholipase A2, and epoxyeicosatrienoic acids. Based on these data, we propose that HPV originates at the alveolocapillary level, from which the hypoxic signal is propagated as endothelial membrane depolarization to upstream arterioles in a Cx40-dependent manner.
Liming Wang, Jun Yin, Hannah T. Nickles, Hannes Ranke, Arata Tabuchi, Julia Hoffmann, Christoph Tabeling, Eduardo Barbosa-Sicard, Marc Chanson, Brenda R. Kwak, Hee-Sup Shin, Songwei Wu, Brant E. Isakson, Martin Witzenrath, Cor de Wit, Ingrid Fleming, Hermann Kuppe, Wolfgang M. Kuebler
Alveolar capillary dysplasia (ACD) is a congenital, lethal disorder of the pulmonary vasculature. Phosphatase and tensin homologue deleted from chromosome 10 (Pten) encodes a lipid phosphatase controlling key cellular functions, including stem/progenitor cell proliferation and differentiation; however, the role of PTEN in mesodermal lung cell lineage formation remains unexamined. To determine the role of mesodermal PTEN in the ontogeny of various mesenchymal cell lineages during lung development, we specifically deleted Pten in early embryonic lung mesenchyme in mice. Pups lacking Pten died at birth, with evidence of failure in blood oxygenation. Analysis at the cellular level showed defects in angioblast differentiation to endothelial cells and an accompanying accumulation of the angioblast cell population that was associated with disorganized capillary beds. We also found decreased expression of Forkhead box protein F1 (Foxf1), a gene associated with the ACD human phenotype. Analysis of human samples for ACD revealed a significant decrease in PTEN and increased activated protein kinase B (AKT). These studies demonstrate that mesodermal PTEN has a key role in controlling the amplification of angioblasts as well as their differentiation into endothelial cells, thereby directing the establishment of a functional gas exchange interface. Additionally, these mice could serve as a murine model of ACD.
Caterina Tiozzo, Gianni Carraro, Denise Al Alam, Sheryl Baptista, Soula Danopoulos, Aimin Li, Maria Lavarreda-Pearce, Changgong Li, Stijn De Langhe, Belinda Chan, Zea Borok, Saverio Bellusci, Parviz Minoo
Asthma is a chronic condition with unknown pathogenesis, and recent evidence suggests that enhanced airway epithelial chloride (Cl–) secretion plays a role in the disease. However, the molecular mechanism underlying Cl– secretion and its relevance in asthma pathophysiology remain unknown. To determine the role of the solute carrier family 26, member 9 (SLC26A9) Cl– channel in asthma, we induced Th2-mediated inflammation via IL-13 treatment in wild-type and Slc26a9-deficient mice and compared the effects on airway ion transport, morphology, and mucus content. We found that IL-13 treatment increased Cl– secretion in the airways of wild-type but not Slc26a9-deficient mice. While IL-13–induced mucus overproduction was similar in both strains, treated Slc26a9-deficient mice exhibited airway mucus obstruction, which did not occur in wild-type controls. In a study involving healthy children and asthmatics, a polymorphism in the 3′ UTR of SLC26A9 that reduced protein expression in vitro was associated with asthma. Our data demonstrate that the SLC26A9 Cl– channel is activated in airway inflammation and suggest that SLC26A9-mediated Cl– secretion is essential for preventing airway obstruction in allergic airway disease. These results indicate that SLC26A9 may serve as a therapeutic target for airway diseases associated with mucus plugging.
Pinelopi Anagnostopoulou, Brigitte Riederer, Julia Duerr, Sven Michel, Aristea Binia, Raman Agrawal, Xuemei Liu, Katrin Kalitzki, Fang Xiao, Mingmin Chen, Jolanthe Schatterny, Dorothee Hartmann, Thomas Thum, Michael Kabesch, Manoocher Soleimani, Ursula Seidler, Marcus A. Mall
There is emerging evidence that platelets are major contributors to inflammatory processes through intimate associations with innate immune cells. Here, we report that activated platelets induce the formation of neutrophil extracellular traps (NETs) in transfusion-related acute lung injury (TRALI), which is the leading cause of death after transfusion therapy. NETs are composed of decondensed chromatin decorated with granular proteins that function to trap extracellular pathogens; their formation requires the activation of neutrophils and release of their DNA in a process that may or may not result in neutrophil death. In a mouse model of TRALI that is neutrophil and platelet dependent, NETs appeared in the lung microvasculature and NET components increased in the plasma. We detected NETs in the lungs and plasma of human TRALI and in the plasma of patients with acute lung injury. In the experimental TRALI model, targeting platelet activation with either aspirin or a glycoprotein IIb/IIIa inhibitor decreased NET formation and lung injury. We then directly targeted NET components with a histone blocking antibody and DNase1, both of which protected mice from TRALI. These data suggest that NETs contribute to lung endothelial injury and that targeting NET formation may be a promising new direction for the treatment of acute lung injury.
Axelle Caudrillier, Kai Kessenbrock, Brian M. Gilliss, John X. Nguyen, Marisa B. Marques, Marc Monestier, Pearl Toy, Zena Werb, Mark R. Looney
Chronic obstructive pulmonary disease/emphysema (COPD/emphysema) is characterized by chronic inflammation and premature lung aging. Anti-aging sirtuin 1 (SIRT1), a NAD+-dependent protein/histone deacetylase, is reduced in lungs of patients with COPD. However, the molecular signals underlying the premature aging in lungs, and whether SIRT1 protects against cellular senescence and various pathophysiological alterations in emphysema, remain unknown. Here, we showed increased cellular senescence in lungs of COPD patients. SIRT1 activation by both genetic overexpression and a selective pharmacological activator, SRT1720, attenuated stress-induced premature cellular senescence and protected against emphysema induced by cigarette smoke and elastase in mice. Ablation of Sirt1 in airway epithelium, but not in myeloid cells, aggravated airspace enlargement, impaired lung function, and reduced exercise tolerance. These effects were due to the ability of SIRT1 to deacetylate the FOXO3 transcription factor, since Foxo3 deficiency diminished the protective effect of SRT1720 on cellular senescence and emphysematous changes. Inhibition of lung inflammation by an NF-κB/IKK2 inhibitor did not have any beneficial effect on emphysema. Thus, SIRT1 protects against emphysema through FOXO3-mediated reduction of cellular senescence, independently of inflammation. Activation of SIRT1 may be an attractive therapeutic strategy in COPD/emphysema.
Hongwei Yao, Sangwoon Chung, Jae-woong Hwang, Saravanan Rajendrasozhan, Isaac K. Sundar, David A. Dean, Michael W. McBurney, Leonard Guarente, Wei Gu, Mikko Rönty, Vuokko L. Kinnula, Irfan Rahman