The mechanisms by which the exposure of mice to Cl2 decreases vectorial Na+ transport and fluid clearance across their distal lung spaces have not been elucidated. We examined the biophysical, biochemical, and physiological changes of rodent lung epithelial Na+ channels (ENaCs) after exposure to Cl2, and identified the mechanisms involved. We measured amiloride-sensitive short-circuit currents (Iamil) across isolated alveolar Type II (ATII) cell monolayers and ENaC single-channel properties by patching ATII and ATI cells in situ. α-ENaC, γ-ENaC, total and phosphorylated extracellular signal-related kinase (ERK)1/2, and advanced products of lipid peroxidation in ATII cells were measured by Western blot analysis. Concentrations of reactive intermediates were assessed by electron spin resonance (ESR). Amiloride-sensitive Na+ channels with conductances of 4.5 and 18 pS were evident in ATI and ATII cells in situ of air-breathing mice. At 1 hour and 24 hours after exposure to Cl2, the open probabilities of these two channels decreased. This effect was prevented by incubating lung slices with inhibitors of ERK1/2 or of proteasomes and lysosomes. The exposure of ATII cell monolayers to Cl2 increased concentrations of reactive intermediates, leading to ERK1/2 phosphorylation and decreased Iamil and α-ENaC concentrations at 1 hour and 24 hours after exposure. The administration of antioxidants to ATII cells before and after exposure to Cl2 decreased concentrations of reactive intermediates and ERK1/2 activation, which mitigated the decrease in Iamil and ENaC concentrations. The reactive intermediates formed during and after exposure to Cl2 activated ERK1/2 in ATII cells in vitro and in vivo, leading to decreased ENaC concentrations and activity.
lung slices; patch clamp; radicals
The effects of acute hyperglycemia on lung ischemia–reperfusion (IR) injury and the role of receptor for advanced glycation end-products (RAGE) signaling in this process are unknown. The objective of this study was twofold: (1) evaluate the impact of acute hyperglycemia on lung IR injury; and (2) determine if RAGE signaling is a mechanism of hyperglycemia-enhanced IR injury. We hypothesized that acute hyperglycemia worsens lung IR injury through a RAGE signaling mechanism. C57BL/6 wild-type (WT) and RAGE knockout (RAGE −/−) mice underwent sham thoracotomy or lung IR (1-h left hilar occlusion and 2-h reperfusion). Acute hyperglycemia was established by dextrose injection 30 minutes before ischemia. Lung injury was assessed by measuring lung function, cytokine expression in bronchoalveolar lavage fluid, leukocyte infiltration, and microvascular permeability via Evans blue dye. Mean blood glucose levels doubled in hyperglycemic mice 30 minutes after dextrose injection. Compared with IR in normoglycemic mice, IR in hyperglycemic mice significantly enhanced lung dysfunction, cytokine expression (TNF-α, keratinocyte chemoattractant, IL-6, monocyte chemotactic protein-1, regulated upon activation, normal T cell expressed and secreted), leukocyte infiltration, and microvascular permeability. Lung injury and dysfunction after IR were attenuated in normoglycemic RAGE −/− mice, and hyperglycemia failed to exacerbate IR injury in RAGE −/− mice. Thus, this study demonstrates that acute hyperglycemia exacerbates lung IR injury, whereas RAGE deficiency attenuates IR injury and also prevents exacerbation of IR injury in an acute hyperglycemic setting. These results suggest that hyperglycemia-enhanced lung IR injury is mediated, at least in part, by RAGE signaling, and identifies RAGE as a potential, novel therapeutic target to prevent post-transplant lung IR injury.
lung transplant; receptor for advanced glycation end-products; hyperglycemia; inflammation
Many phytochemicals possess antioxidant and cancer-preventive properties, some putatively through antioxidant response element–mediated phase II metabolism, entailing mutagen/oxidant quenching. In our recent studies, however, most candidate phytochemical agents were not potent in inducing phase II genes in normal human lung cells. In this study, we applied a messenger RNA (mRNA)–specific gene expression–based high throughput in vitro screening approach to discover new, potent plant-derived phase II inducing chemopreventive agents. Primary normal human bronchial epithelial (NHBE) cells and immortalized human bronchial epithelial cells (HBECs) were exposed to 800 individual compounds in the MicroSource Natural Products Library. At a level achievable in humans by diet (1.0 μM), 2,3-dihydroxy-4-methoxy-4′-ethoxybenzophenone (DMEBP), triacetylresveratrol (TRES), ivermectin, sanguinarine sulfate, and daunorubicin induced reduced nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase 1 (NQO1) mRNA and protein expression in NHBE cells. DMEBP and TRES were the most attractive agents as coupling potency and low toxicity for induction of NQO1 (mRNA level, ≥3- to 10.8-fold that of control; protein level, ≥ two- to fourfold that of control). Induction of glutathione S-transferase pi mRNA expression was modest, and none was apparent for glutathione S-transferase pi protein expression. Measurements of reactive oxygen species and glutathione/oxidized glutathione ratio showed an antioxidant effect for DMEBP, but no definite effect was found for TRES in NHBE cells. Exposure of NHBE cells to H2O2 induced nuclear translocation of nuclear factor erythroid 2–related factor 2, but this translocation was not significantly inhibited by TRES and DMEBP. These studies show that potency and low toxicity may align for two potential NQO1-inducing agents, DMEBP and TRES.
GSTP1; NQO1; phytochemicals; high-throughput screening; gene expression
Experimental asthma increases eosinophil and collagen deposition in the lungs of sickle cell disease (SCD) mice to a greater extent than in control mice. However, the effects of asthma on inflammation and airway physiology remain unclear. To determine effects of asthma on pulmonary inflammation and airway mechanics in SCD mice, hematopoietic stem cell transplantation was used to generate chimeric SCD and hemoglobin A mice. Experimental asthma was induced by sensitizing mice with ovalbumin (OVA). Airway mechanics were assessed using forced oscillation techniques. Mouse lungs were examined histologically and physiologically. Cytokine, chemokine, and growth factors in bronchoalveolar lavage fluid were determined by multiplex. IgE was quantified by ELISA. LDH was quantified using a colorimetric enzymatic assay. At baseline (nonsensitized), chimeric SCD mice developed hemolytic anemia with sickled red blood cells, mild leukocytosis, and increased vascular endothelial growth factor and IL-13 compared with chimeric hemoglobin A mice. Experimental asthma increased perialveolar eosinophils, plasma IgE, and bronchoalveolar lavage fluid IL-1β, IL-4, IL-6, and monocyte chemotactic protein 1 in chimeric hemoglobin A and SCD mice. IFN-γ levels were reduced in both groups. IL-5 was preferentially increased in chimeric SCD mice but not in hemoglobin A mice. Positive end-expiratory pressures and methacholine studies revealed that chimeric SCD mice had greater resistance in large and small airways compared with hemoglobin A mice at baseline and after OVA sensitization. SCD alone induces a baseline lung pathology that increases large and small airway resistance and primes the lungs to increased inflammation and airway hyperresponsiveness after OVA sensitization.
sickle cell disease; OVA sensitization; IgE; IL-5; airway hyperresponsiveness
It is widely held that exposure to pathogens such as fungi can be an agent of comorbidity, such as exacerbation of asthma or chronic obstructive pulmonary disease. Although many studies have examined allergic responses to fungi and their effects on pulmonary function, the possible pathologic implications of the early innate responses to fungal pathogens have not been explored. We examined early responses to the atypical fungus Pneumocystis in two common strains of mice in terms of overall immunological response and related pathology, such as cell damage and airway hyperresponsiveness (AHR). We found a strong strain-specific response in BALB/c mice that included recruitment of neutrophils, NK, NKT, and CD4 T cells. This response was accompanied by elevated indicators of lung damage (bronchoalveolar lavage fluid albumin and LDH) and profound AHR. This early response was absent in C57BL/6 mice, although both strains exhibited a later response associated with the clearance of Pneumocystis. We found that this AHR could not be attributed exclusively to the presence of recruited neutrophils, NKT, NK, or CD4 cells or to the actions of IFN-γ or IL-4. However, in the absence of STAT6 signaling, AHR and inflammatory cell recruitment were virtually absent. Gene expression analysis indicated that this early response included activation of several transcription factors that could be involved in pulmonary remodeling. These results show that exposure to a fungus such as Pneumocystis can elicit pulmonary responses that may contribute to morbidity, even without prior sensitization, in the context of certain genetic backgrounds.
STAT6; airway hyperresponsiveness; Pneumocystis; pulmonary inflammation; strain-specific
We previously reported that hypoxia attenuates nitric oxide–cyclic guanosine monophosphate (NO-cGMP)–mediated fetal pulmonary vessel relaxation by inhibiting cGMP-dependent protein kinase 1 (PKG1) activity, but not all the mechanisms by which acute hypoxia inhibits PKG1 activity have been delineated. Here we demonstrate for the first time, to the best of our knowledge, that acute hypoxia induces an accumulation of ubiquitinated PKG1 in ovine fetal and newborn pulmonary artery smooth muscle cells. Such a modification was not evident in ovine fetal systemic (cerebral) artery smooth muscle cells. The accumulation of polyubiquitinated PKG1 observed after 4 hours of hypoxia was affected neither by the activation of PKG1 kinase activity with the cell-permeable cGMP analogue 8-bromo-cGMP, nor by its inhibition with DT-3 in fetal pulmonary artery smooth muscle cells. Ubiquitinated PKG1α was unable to bind the cGMP analogue 8-(2-aminoethyl)thioguanosine-3′,5′ (AET)-cGMP, a ligand for the unmodified protein. Inhibition of the proteasomal complex with MG132 led to the accumulation of polyubiquitinated PKG1 in normoxia, indicating the involvement of the ubiquitin-26S proteasomal system in degradation and clearance of this protein under normoxic conditions. The ubiquitinated PKG1 under hypoxic conditions, however, was not predominantly targeted for proteasomal degradation. Importantly, reoxygenation reversed the acute hypoxia-induced accumulation of ubiquitinated PKG1. Our results suggest that the PKG1 ubiquitination induced by acute hypoxia plays a unique role in the regulation of the pulmonary vascular smooth muscle cell vasoreactivity and relaxation mediated by the NO-cGMP–PKG1 pathway.
cGMP-dependent protein kinase; proteasome; ubiquitin conjugation; vascular smooth muscle; hypoxia
Pulmonary fibrosis remains a significant public health burden with no proven therapies. The mitogen-activated protein kinase (MAPK)/MAPK kinase (MEK)/extracellular signal–regulated kinase (ERK) signaling cascade is a major pathway controlling cellular processes associated with fibrogenesis, including growth, proliferation, and survival. Activation of the MAPK/ERK pathway is detected in the lungs of human fibrosis samples; however, the effect of modulating the pathway in vivo is unknown. Overexpression of transforming growth factor (TGF)-α in the lung epithelium of transgenic mice causes a progressive pulmonary fibrosis associated with increased MEK/ERK activation localized primarily in mesenchymal cells. To determine the role of the MEK pathway in the induction of TGF-α–induced lung fibrosis, TGF-α was overexpressed for 4 weeks while mice were simultaneously treated with the specific MEK inhibitor, ARRY-142886 (ARRY). Treatment with ARRY prevented increases in lung cell proliferation and total lung collagen, attenuated production of extracellular matrix genes, and protected mice from changes in lung function. ARRY administered as a rescue treatment after fibrosis was already established inhibited fibrosis progression, as assessed by lung histology, changes in body weights, extracellular matrix gene expression, and lung mechanics. These findings demonstrate that MEK inhibition prevents progression of established fibrosis in the TGF-α model, and provides proof of concept of targeting the MEK pathway in fibrotic lung disease.
pulmonary fibrosis; transforming growth factor-α; epidermal growth factor receptor; mitogen-activated protein kinase/mitogen-activated protein kinase kinase/extracellular signal–regulated kinase; ARRY-142886
In many species, pneumonectomy triggers compensatory lung growth that results in an increase not only in lung volume, but also in alveolar number. Whether the associated alveolar angiogenesis involves the contribution of blood-borne progenitor cells is unknown. To identify and characterize blood-borne progenitor cells contributing to lung growth after pneumonectomy in mice, we studied wild-type and wild-type/green fluorescence protein (GFP) parabiotic mice after left pneumonectomy. Within 21 days of pneumonectomy, a 3.2-fold increase occurred in the number of lung endothelial cells. This increase in total endothelial cells was temporally associated with a 7.3-fold increase in the number of CD34+ endothelial cells. Seventeen percent of the CD34+ endothelial cells were actively proliferating, compared with only 4.2% of CD34− endothelial cells. Using wild-type/GFP parabiotic mice, we demonstrated that 73.4% of CD34+ cells were derived from the peripheral blood. Furthermore, lectin perfusion studies demonstrated that CD34+ cells derived from peripheral blood were almost uniformly incorporated into the lung vasculature. Finally, CD34+ endothelial cells demonstrated a similar profile, but had enhanced transcriptional activity relative to CD34− endothelial cells. We conclude that blood-borne CD34+ endothelial progenitor cells, characterized by active cell division and an amplified transcriptional signature, transition into resident endothelial cells during compensatory lung growth.
endothelial progenitor cells; CD31+ CD34+ cell; lung angiogenesis; lung regeneration
The generation of phospholipid oxidation products in atherosclerosis, sepsis, and lung pathologies affects endothelial barrier function, which exerts significant consequences on disease outcomes in general. Our group previously showed that oxidized 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine (OxPAPC) at low concentrations increases endothelial cell (EC) barrier function, but decreases it at higher concentrations. In this study, we determined the mechanisms responsible for the pulmonary endothelial cell barrier dysfunction induced by high OxPAPC concentrations. OxPAPC at a range of 5–20 μg/ml enhanced EC barriers, as indicated by increased transendothelial electrical resistance. In contrast, higher OxPAPC concentrations (50–100 μg/ml) rapidly increased EC permeability, which was accompanied by increased total cell protein tyrosine (Tyr) phosphorylation, phosphorylation at Tyr-418, the activation of Src kinase, and the phosphorylation of adherens junction (AJ) protein vascular endothelial cadherin (VE-cadherin) at Tyr-731 and Tyr-658, which was not observed in ECs stimulated with low OxPAPC doses. The early tyrosine phosphorylation of VE-cadherin was linked to the dissociation of VE-cadherin–p120-catenin/β-catenin complexes and VE-cadherin internalization, whereas low OxPAPC doses promoted the formation of VE-cadherin–p120-catenin/β-catenin complexes. High but not low doses of OxPAPC increased the production of reactive oxygen species (ROS) and protein oxidation. The inhibition of Src by PP2 and ROS production by N-acetyl cysteine inhibited the disassembly of VE-cadherin–p120-catenin complexes, and attenuated high OxPAPC-induced EC barrier disruption. These results show the differential effects of OxPAPC doses on VE-cadherin–p120-catenin complex assembly and EC barrier function. These data suggest that the rapid tyrosine phosphorylation of VE-cadherin and other potential targets mediated by Src and ROS-dependent mechanisms plays a key role in the dissociation of AJ complexes and EC barrier dysfunction induced by high OxPAPC doses.
endothelium; oxidized phospholipids; protein tyrosine phosphorylation; VE-cadherin; permeability
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 LPA1 promotes epithelial cell apoptosis induced by bleomycin injury. The number of apoptotic cells present in the alveolar and bronchial epithelia of LPA1–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 LPA1 induced apoptosis in normal human bronchial epithelial cells in culture. LPA-LPA1 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 LPA1 promoted the resistance of lung fibroblasts to apoptosis, which has also been implicated in IPF. The ability of LPA-LPA1 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.
pulmonary fibrosis; apoptosis; epithelial cells, lysophosphatidic acid; LPA1
Mutations in the SFTPC gene, encoding surfactant protein–C (SP-C), are associated with interstitial lung disease (ILD). Knowledge of the intracellular fate of mutant SP-C is essential in the design of therapies to correct trafficking/processing of the proprotein, and to prevent the formation of cytotoxic aggregates. We assessed the potential of a chemical chaperone to correct the trafficking and processing of three disease-associated mutant SP-C proteins. HEK293 cells were stably transfected with wild-type (SP-CWT) or mutant (SP-CL188Q, SP-CΔexon4, or SP-CI73T) SP-C, and cell lines with a similar expression of SP-C mRNA were identified. The effects of the chemical chaperone 4-phenylbutyric acid (PBA) and lysosomotropic drugs on intracellular trafficking to the endolysosomal pathway and the subsequent conversion of SP-C proprotein to mature peptide were assessed. Despite comparable SP-C mRNA expression, proprotein concentrations varied greatly: SP-CI73T was more abundant than SP-CWT and was localized to the cell surface, whereas SP-CΔexon4 was barely detectable. In contrast, SP-CL188Q and SP-CWT proprotein concentrations were comparable, and a small amount of SP-CL188Q was localized to the endolysosomal pathway. PBA treatment restored the trafficking and processing of SP-CL188Q to SP-CWT concentrations, but did not correct the mistrafficking of SP-CI73T or rescue SP-CΔexon4. PBA treatment also promoted the aggregation of SP-C proproteins, including SP-CL188Q. This study provides proof of the principle that a chemical chaperone can correct the mistrafficking and processing of a disease-associated mutant SP-C proprotein.
pulmonary surfactant protein–C; interstitial lung disease; 4-phenylbutyric acid; chemical chaperone
Eosinophils function in murine allergic airways inflammation as professional antigen-presenting cells (APCs). In murine professional APC cell types, optimal functioning of MHC Class II depends on its lateral association in plasma membranes and colocalization with the tetraspanin CD9 into detergent-resistant membrane microdomains (DRMs). With human eosinophils, we evaluated the localization of MHC Class II (HLA-DR) to DRMs and the functional significance of such localization. In granulocyte-macrophage colony-stimulating factor–stimulated human eosinophils, antibody cross-linked HLA-DR colocalized by immunofluorescence microscopy focally on plasma membranes with CD9 and the DRM marker ganglioside GM1. In addition, HLA-DR coimmunoprecipitates with CD9 after chemical cross-linking of CD9. HLA-DR and CD9 were localized by Western blotting in eosinophil DRM subcellular fractions. DRM disruption with the cholesterol-depleting agent methyl-β-cyclodextrin decreased eosinophil surface expression of HLA-DR and CD9. We show that CD9 is abundant on the surface of eosinophils, presenting the first electron microscopy data of the ultrastructural immunolocalization of CD9 in human eosinophils. Disruption of HLA-DR–containing DRMs decreased the ability of superantigen-loaded human eosinophils to stimulate CD4+ T-cell activation (CD69 expression), proliferation, and cytokine production. Our results, which demonstrate that eosinophil MHC Class II localizes to DRMs in association with CD9 in a functionally significant manner, represent a novel insight into the organization of the antigen presentation complex of human eosinophils.
eosinophils; antigen presentation; HLA-DR; CD9; immunoelectron microscopy
Fibroblasts are the major mesenchymal cells present within the interstitium of the lung and are a major source of vascular endothelial growth factor (VEGF), which modulates the maintenance of pulmonary microvasculature. Prostaglandin E2 (PGE2) acts on a set of E-prostanoid (EP) receptors that activate multiple signal transduction pathways leading to downstream responses. We investigated the modulation by PGE2 of VEGF release by human lung fibroblasts. Human lung fibroblasts were cultured until reaching 90% confluence in tissue culture plates, after which the culture media were changed to serum-free Dulbecco's modified Eagle's medium, with or without PGE2, and with specific agonists or antagonists for each EP receptor. After 2 days, culture media were assayed for VEGF by ELISA. The results demonstrated that PGE2 and the EP2 agonist ONO-AE1-259-01 significantly stimulated the release of VEGF in a concentration-dependent manner. Agonists for other EP receptors did not stimulate the release of VEGF. The stimulatory effect of PGE2 was blocked by the EP2 antagonist AH6809, but was not blocked by antagonists for other EP receptors. The protein kinase–A (PKA) inhibitor KT-5720 also blocked the stimulatory effect of PGE2. The increased release of VEGF induced by PGE2 was accompanied by a transient increase in the concentration of VEGF mRNA. These findings demonstrate that PGE2 can modulate the release of VEGF by human lung fibroblasts through its actions in the EP2 receptor/PKA pathway. This activity may contribute to the maintenance of pulmonary microvasculature in the alveolar wall.
prostaglandin E2; vascular endothelial growth factor; human lung fibroblasts; tissue repair
Histone deacetylase (HDAC) inhibitors may offer novel approaches in the treatment of asthma. We postulate that trichostatin A (TSA), a Class 1 and 2 inhibitor of HDAC, inhibits airway hyperresponsiveness in antigen-challenged mice. Mice were sensitized and challenged with Aspergillus fumigatus antigen (AF) and treated with TSA, dexamethasone, or vehicle. Lung resistance (RL) and dynamic compliance were measured, and bronchial alveolar lavage fluid (BALF) was analyzed for numbers of leukocytes and concentrations of cytokines. Human precision-cut lung slices (PCLS) were treated with TSA and their agonist-induced bronchoconstriction was measured, and TSA-treated human airway smooth muscle (ASM) cells were evaluated for the agonist-induced activation of Rho and intracellular release of Ca2+. The activity of HDAC in murine lungs was enhanced by antigen and abrogated by TSA. TSA also inhibited methacholine (Mch)-induced increases in RL and decreases in dynamic compliance in naive control mice and in AF-sensitized and -challenged mice. Total cell counts, concentrations of IL-4, and numbers of eosinophils in BALF were unchanged in mice treated with TSA or vehicle, whereas dexamethasone inhibited the numbers of eosinophils in BALF and concentrations of IL-4. TSA inhibited the carbachol-induced contraction of PCLS. Treatment with TSA inhibited the intracellular release of Ca2+ in ASM cells in response to histamine, without affecting the activation of Rho. The inhibition of HDAC abrogates airway hyperresponsiveness to Mch in both naive and antigen-challenged mice. TSA inhibits the agonist-induced contraction of PCLS and mobilization of Ca2+ in ASM cells. Thus, HDAC inhibitors demonstrate a mechanism of action distinct from that of anti-inflammatory agents such as steroids, and represent a promising therapeutic agent for airway disease.
HDAC; asthma; allergen; mice; trichostatin A
T-box expressed in T cells (T-bet) is a critical transcription factor for T helper (Th) 1 responses. Although Th1 cells are thought to contribute to certain alloimmune responses, their role in pulmonary graft-versus-host disease (GVHD) is uncertain. We have established a murine model of acute pulmonary GVHD after hematopoietic cell transplant (HCT) and inhaled LPS exposure. We tested the hypothesis that pulmonary GVHD can occur independent of Th1 cells using T-bet–deficient donors. B10.BR(H2k) mice underwent allogeneic (Allo) or syngeneic (Syn) HCT with cells from either C57Bl/6J(H2b) mice (Allo wild-type [WT] or SynWT) or C57Bl/6J mice lacking T-bet (AlloTbet−/− or SynTbet−/−). After HCT, mice were exposed daily to aerosolized LPS and subsequently bronchoalveolar lavage and lung tissue were analyzed for cytokines, lymphocytic inflammation, pathology, and fibrosis. Independent of LPS exposure, AlloTbet−/− mice developed pulmonary GVHD manifested by lymphocytic inflammation. Furthermore, AlloTbet−/− mice developed features of chronic pulmonary GVHD, including increased peribronchiolar fibrosis and collagen content. LPS exposure increased neutrophil recruitment and decreased static compliance in AlloTbet−/− mice as compared with LPS-exposed AlloWT mice or LPS-exposed SynTbet−/− mice. In addition, LPS-exposed AlloTbet−/− mice had increased pulmonary IL-17, IL-13, and Th17 cells, and diminished regulatory T cells compared with the other groups. Our results demonstrate that Th1 cytokines are dispensable in pulmonary GVHD. In the absence of T-bet, there is increased production of Th17 and Th2 cytokines that is associated with peribronchiolar fibrosis and is further enhanced by LPS. These results suggest that the interplay between local innate immunity and non-Th1 T cell subsets contribute to chronic pulmonary GVHD.
pulmonary graft-versus-host disease; T helper cell type 1; IL-17; LPS; peribronchiolar fibrosis
Malignant pleural mesothelioma (MPM) is a rare cancer that is refractory to current treatments. It is characterized by a robust deposition of transitional fibrin that is in part promoted by tumor cells. MPM cells express tissue factor (TF) and the tissue factor pathway inhibitor (TFPI), but their contribution to the pathogenesis of MPM has been unclear. We found that REN MPM cells fail to express TFPI. Based on the tumor growth–promoting properties of TF, we hypothesized that the stable transfection of TFPI into REN MPM cells would decrease their aggressiveness. We tested our hypothesis using in vitro, in vivo, and ex vivo analyses. TFPI knock-in decreased the proliferation, invasion, and TF activity of REN cells in vitro. REN TFPI knock-in cells, empty vector, and naive control cells were next injected intrapleurally into nude mice. The expression of TFPI significantly decreased tissue invasion, inflammation, and the deposition of fibrin and collagen associated with tumor tissue, pleural effusions, and tumor burden. In ex vivo analyses, REN cells were cultured from harvested tumors. The overexpression of TFPI was maintained in cells propagated from TFPI knock-in tumors, and attenuated the activation of Factor X and the invasiveness of tumor cells. These analyses demonstrate that TFPI reduces the aggressiveness of MPM in vitro and in vivo, and that its effect involves the inhibition of TF procoagulant activity. These observations suggest that the interactions of TF and TFPI represent a novel therapeutic target in the treatment of MPM.
malignant pleural mesothelioma; tissue factor pathway inhibitor; proliferation; invasion; tumorigenesis
Urokinase plasminogen activator receptor–associated protein (uPARAP, or Endo180) is a transmembrane endocytic receptor that mediates collagen internalization and degradation. uPARAP may be a novel pathway for collagen turnover and matrix remodeling in the lung. The function of uPARAP in lung injury has not been described. We analyzed the pulmonary mechanics of uPARAP−/− and wild-type mice at baseline and examined their response after bleomycin instillation. We compared collagen internalization in primary mouse lung fibroblasts (MLFs) from wild-type and uPARAP−/− mice using flow cytometry and fluorescent microscopy, and we examined the role of cytokines in regulating uPARAP expression and collagen internalization. We show that uPARAP is highly expressed in the lung, and that uPARAP−/− mice have increased lung elastance at baseline and after injury. uPARAP−/− mice are protected from changes in lung permeability after acute lung injury and have increased collagen content after bleomycin injury. uPARAP is the primary pathway for internalization of collagens in MLFs. Furthermore, collagen internalization through uPARAP does not require matrix metalloproteinase digestion and is independent of integrins. Mediators of lung injury, including transforming growth factor-β, TNF-α, and IL-1, down-regulate both uPARAP expression and collagen internalization. uPARAP is highly expressed in the murine lung, and loss of uPARAP leads to differences in lung mechanics, lung permeability, and collagen content after injury. uPARAP is required for collagen internalization by MLFs. Thus, uPARAP is a novel pathway that regulates matrix remodeling in the lung after injury.
urokinase plasminogen activator receptor–associated protein; Endo180; collagen internalization; lung fibroblasts; matrix remodeling
The low-density lipoprotein receptor–related protein 1 (LRP-1) binds and can internalize a diverse group of ligands, including members of the fibrinolytic pathway, urokinase plasminogen activator (uPA), and its receptor, uPAR. In this study, we characterized the role of LRP-1 in uPAR processing, collagen synthesis, proteolysis, and migration in pleural mesothelial cells (PMCs). When PMCs were treated with the proinflammatory cytokines TNF-α and IL-1β, LRP-1 significantly decreased at the mRNA and protein levels (70 and 90%, respectively; P < 0.05). Consequently, uPA-mediated uPAR internalization was reduced by 80% in the presence of TNF-α or IL-1β (P < 0.05). In parallel studies, LRP-1 neutralization with receptor-associated protein (RAP) significantly reduced uPA-dependent uPAR internalization and increased uPAR stability in PMCs. LRP-1–deficient cells demonstrated increased uPAR t1/2 versus LRP-1–expressing PMCs. uPA enzymatic activity was also increased in LRP-1–deficient and neutralized cells, and RAP potentiated uPA-dependent migration in PMCs. Collagen expression in PMCs was also induced by uPA, and the effect was potentiated in RAP-treated cells. These studies indicate that TNF-α and IL-1β regulate LRP-1 in PMCs and that LRP-1 thereby contributes to a range of pathophysiologically relevant responses of these cells.
pleural mesothelial cells; uPAR; LRP-1; internalization; half-life
MUC1 (or Muc1 in nonhuman species) is a membrane-tethered mucin expressed on the apical surface of mucosal epithelia (including those of the airways) that suppresses Toll-like receptor (TLR) signaling. We sought to determine whether the anti-inflammatory effect of MUC1 is operative during infection with nontypeable Haemophilus influenzae (NTHi), and if so, which TLR pathway was affected. Our results showed that: (1) a lysate of NTHi increased the early release of IL-8 and later production of MUC1 protein by A549 cells in dose-dependent and time-dependent manners, compared with vehicle control; (2) both effects were attenuated after transfection of the cells with a TLR2-targeting small interfering (si) RNA, compared with a control siRNA; (3) the NTHi-induced release of IL-8 was suppressed by an overexpression of MUC1, and was enhanced by the knockdown of MUC1; (4) the TNF-α released after treatment with NTHi was sufficient to up-regulate MUC1, which was completely inhibited by pretreatment with a soluble TNF-α receptor; and (5) primary murine tracheal surface epithelial (MTSE) cells from Muc1 knockout mice exhibited an increased in vitro production of NTHi-stimulated keratinocyte chemoattractant compared with MTSE cells from Muc1-expressing animals. These results suggest a hypothetical feedback loop model whereby NTHi activates TLRs (mainly TLR2) in airway epithelial cells, leading to the increased production of TNF-α and IL-8, which subsequently up-regulate the expression of MUC1, resulting in suppressed TLR signaling and decreased production of IL-8. This report is the first, to the best of our knowledge, demonstrating that the inflammatory response in airway epithelial cells during infection with NTHi is controlled by MUC1 mucin, mainly through the suppression of TLR2 signaling.
bacteria; innate immunity; inflammation; TNF-α
Asthma affects an estimated 300 million people worldwide and accounts for 1 of 250 deaths and 15 million disability-adjusted life years lost annually. Plastic-adherent bone marrow–derived cell (BMC) administration holds therapeutic promise in regenerative medicine. However, given the low cell engraftment in target organs, including the lung, cell replacement cannot solely account for the reported therapeutic benefits. This suggests that BMCs may act by secreting soluble factors. BMCs also possess antiinflammatory and immunomodulatory properties and may therefore be beneficial for asthma. Our objective was to investigate the therapeutic potential of BMC-secreted factors in murine asthma. In a model of acute and chronic asthma, intranasal instillation of BMC conditioned medium (CdM) prevented airway hyperresponsiveness (AHR) and inflammation. In the chronic asthma model, CdM prevented airway smooth muscle thickening and peribronchial inflammation while restoring blunted salbutamol-induced bronchodilation. CdM reduced lung levels of the TH2 inflammatory cytokines IL-4 and IL-13 and increased levels of IL-10. CdM up-regulated an IL-10–induced and IL-10–secreting subset of T regulatory lymphocytes and promoted IL-10 expression by lung macrophages. Adiponectin (APN), an antiinflammatory adipokine found in CdM, prevented AHR, airway smooth muscle thickening, and peribronchial inflammation, whereas the effect of CdM in which APN was neutralized or from APN knock-out mice was attenuated compared with wild-type CdM. Our study provides evidence that BMC-derived soluble factors prevent murine asthma and suggests APN as one of the protective factors. Further identification of BMC-derived factors may hold promise for novel approaches in the treatment of asthma.
cellular therapy; bone marrow stromal cells; hypersensitivity; paracrine
Microbial communities in the lungs of patients with cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD) have been shown to be spatially heterogeneous. Viral communities may also vary spatially, leading to localized viral populations and infections. Here, we characterized viral communities from multiple areas of the lungs of two patients with late-stage CF using metagenomics, that is, the explanted lungs from a transplant patient and lungs acquired postmortem. All regions harbored eukaryotic viruses that may infect the human host, notably herpesviruses, anelloviruses, and papillomaviruses. In the highly diseased apical lobes of explant lungs, viral diversity was extremely low, and only eukaryotic viruses were present. The absence of phage suggests that CF-associated microbial biofilms may escape top-down controls by phage predation. The phages present in other lobes of explant lungs and in all lobes of postmortem lungs comprised distinct communities, and encoded genes for clinically important microbial phenotypes, including small colony variants and antibiotic resistance. Based on the these observations, we postulate that viral communities in CF lungs are spatially distinct and contribute to CF pathology by augmenting the metabolic potential of resident microbes, as well as by directly damaging lung tissue via carcinomas and herpesviral outbreaks.
cystic fibrosis; viruses; metagenomics; antibiotic resistance
Although empyema affects more than 65,000 people each year in the United States and in the United Kingdom, there are limited data on the pathogenesis of pleural infection. We investigated the pathogenesis of empyema using animal and cell culture models of Streptococcus pneumoniae infection. The pathological processes during the development of empyema associated with murine pneumonia due to S. pneumoniae (strain D39) were investigated. Lungs were examined using histology, and pleural fluid and blood bacterial colony-forming units, cytokine levels, and cellular infiltrate were determined over time. Bacterial migration across mesothelial monolayers was investigated using cell culture techniques, flow cytometry, and confocal microscopy. After intranasal inoculation with 107
S. pneumoniae D39 strain, mice developed pneumonia associated with rapid bacterial invasion of the pleural space; raised intrapleural IL-8, VEGF, MCP-1, and TNF-α levels; and caused significant intrapleural neutrophilia followed by the development of fibrinous pleural adhesions. Bacterial clearance from the pleural space was poor, and in vitro assays demonstrated that S. pneumoniae crossed mesothelial layers by translocation through cells rather than by a paracellular route. This study describes key events during the development of S. pneumoniae empyema using a novel murine model of pneumonia-associated empyema that closely mimics human disease. The model allows for future assessment of molecular mechanisms involved in the development of empyema and evaluation of potential new therapies. The data suggest that transmigration of bacteria through mesothelial cells could be important in empyema development. Furthermore, upon entry the pleural cavity offers a protected compartment for the bacteria.
Streptoccocus pneumoniae; empyema; animal models; translocation; mesothelial cells
The activator protein–1 (AP-1) transcription factor, comprising Jun and Fos family proteins, distinctly regulates various cellular processes, including those involved in inflammation. FOS like antigen 1 (Fra-1), a member of the Fos family, dimerizes with members of the Jun family and regulates gene expression in a context-dependent manner. Although respiratory toxicants are known to stimulate the expression of Fra-1 in the lung, whether Fra-1 promotes or decreases susceptibility to the development and progression of toxicant-induced lung disease in vivo is not well established. To determine the role of Fra-1 in LPS-induced acute lung injury and mortality, we administered LPS either intraperitoneally or intratracheally to Fra-1–sufficient (Fra-1+/+) and Fra-1–deficient (Fra-1Δ/Δ) mice. LPS-induced mortality, lung injury, inflammation, cytokine measurements, and AP-1 and NF-κB activities were then assessed in these mice. Fra-1Δ/Δ mice showed a greater resistance to LPS-induced mortality than did their Fra-1+/+counterparts. Consistent with this result, LPS-induced lung injury and inflammatory responses were markedly lower in Fra-1Δ/Δ mice than in Fra-1+/+ mice. Compared with Fra-1+/+ mice, Fra-1Δ/Δ mice showed a reduced influx of neutrophils into the lungs, accompanied by a decreased expression of proinflammatory cytokines in response to treatment with LPS. The decreased inflammatory responses in Fra-1Δ/Δ mice coincided with diminished and increased levels of NF-κB and c-Jun/AP-1 binding, respectively. These results demonstrate that Fra-1/AP-1 plays a key role in promoting LPS-induced injury and mortality in mice, and they suggest that targeting (i.e., inhibiting) this transcription factor may be a useful approach to dampening the adverse effects of exposure to endotoxins.
acute lung injury; inflammation; Fra-1; cytokines; host defense
The expression of β-catenin–dependent genes can be increased through the Cre recombinase (Cre)–mediated elimination of the exon 3–encoded sequence. This mutant β-catenin is termed DE3, and promotes the expression of β-catenin–dependent genes. Our previous study used the DE3 model to demonstrate that persistent β-catenin activity inhibited bronchiolar Clara-to-ciliated cell differentiation. The present study was designed to evaluate the roles of β-catenin in regulating the tracheal progenitor cell hierarchy. However, initial experiments demonstrated that the tetracycline-responsive element–Cre transgene (TRE-Cre) was active in the absence of a reverse tetracycline transactivator driver or inducer, doxycycline (Dox). This spurious TRE-Cre transgene activity was not detected using the ROSA26-floxed STOP-LacZ reporter. To determine if the phenotype was a consequence of genotype or treatment with Dox, tracheal and lung specimens were evaluated using quantitative histomorphometric techniques. Analyses of uninduced mice demonstrated a significant effect of genotype on tracheal epithelial cell mass, involving basal, Clara-like cell types. The bronchial and bronchiolar Clara cell mass was also decreased. Paradoxically, an effect on ciliated cell mass was not detected. Activation of the β-catenin reporter transgene TOPGal demonstrated that β-catenin–dependent gene expression led to the genotype-dependent tracheal and bronchiolar phenotype. Comparative analyses of wild-type or keratin 14-rtTA+/0/TRE-cre+/0/DE3+/+ mice receiving standard or Dox chow demonstrated an effect of treatment with Dox on basal, Clara-like, and Clara cell masses. We discuss these results in terms of cautionary notes and with regard to alterations of progenitor cell hierarchies in response to low-level injury.
Clara cell; doxycycline; Cre recombinase; β-catenin; stereology
Stimulation by the ephrin-A1 ligand of the EphA2 receptor increases endothelial permeability. Lung injury increases the expression of EphA2, but the role of EphA2 in such injury is not well understood. To determine whether EphA2 contributes to changes in permeability and inflammation in the injured lung, we studied wild-type (WT) and EphA2 knockout (KO) mice, using isolated, perfused lung (IPL) preparations and a model of bleomycin-induced lung injury. We also studied the response of endothelial cells to ephrin-A1. In the IPL preparations, ephrin-A1 increased the filtration coefficient in WT mice, but not in EphA2 KO mice, demonstrating that EphA2 regulates vascular permeability. In early bleomycin injury in WT mice, the expression of both EphA2 and ephrin-A1 increased. EphA2 KO animals were protected from lung injury, showing less water and alveolar protein in the lungs than WT mice, consistent with reduced permeability. Bleomycin caused less accumulation of lung leukocytes in EphA2 KO animals than in WT animals, suggesting that EphA2 regulates inflammation. To determine whether EphA2 deficiency alters the production of chemokines, CXCL1 and CCL2 in the lungs were measured. After bleomycin injury, EphA2 KO animals produced less CXCL1 and CCL2 than WT animals. Because NF-κβ mediates the production of chemokines, the effect of the ephrin-A1 ligand on the activation of NF-κβ and the expression of chemokines was measured in endothelial cells. Ephrin-a1 significantly increased NF-κβ nuclear translocation and the expression of chemokine mRNA. This study demonstrates that the expression of EphA2 increases in the injured lung, and not only contributes to changes in permeability, but also plays a previously unrecognized role in promoting inflammatory responses.
chemokine; ephrin-A1; inflammation; vascular leak